阅读说明：本技术 作业车辆用的控制装置及作业车辆 (Control device for work vehicle and work vehicle ) 是由 加藤裕治 法田诚二 井本翼 武藤圣也 松原史明 池田博 于 2019-06-25 设计创作，主要内容包括：本发明提供一种作业车辆用的控制装置及作业车辆。所述作业车辆用的控制装置即便针对作业装置的负荷的急剧增大,也能够以良好的追随性降低机体的行驶速度。在减速率设定部(61)中,设定与发动机的负荷率是否超过基准值相应的减速率,在目标斜盘位置计算部(62)中,设定作为液压泵(33)的斜盘的目标位置的目标斜盘位置,以使机体的行驶速度从与变速杆的位置相应的速度与减速率相应地减速。而且,控制向HST的比例减压控制阀(52、53)供给的电流,以使液压泵的斜盘的位置与目标斜盘位置一致。(The invention provides a control device for a work vehicle and the work vehicle. The control device for the working vehicle can reduce the traveling speed of the machine body with good following performance even if the load of the working device is increased suddenly. A deceleration rate setting unit (61) sets a deceleration rate corresponding to whether or not the load factor of the engine exceeds a reference value, and a target swash plate position calculation unit (62) sets a target swash plate position as a target position of a swash plate of a hydraulic pump (33) so that the traveling speed of the engine body is decelerated from a speed corresponding to the position of a shift lever according to the deceleration rate. Then, the current supplied to the proportional pressure reduction control valves (52, 53) of the HST is controlled so that the position of the swash plate of the hydraulic pump coincides with the target swash plate position.)

1. A control device for a work vehicle, the work vehicle comprising: a body; an engine; a working device driven by power of the engine; a continuously variable transmission device including a swash plate type pump driven by power of the engine and a motor driven by fluid discharged from the pump, and outputting power of the motor; a pair of left and right traveling devices that support the machine body and are driven by power output from the continuously variable transmission; and an operation member operated to indicate a traveling speed of the machine body traveling by the traveling device,

wherein the control device includes:

a position detection mechanism that detects a position of the operation member;

deceleration rate setting means that sets a deceleration rate corresponding to whether or not a load corresponding value corresponding to a load of the engine exceeds a reference value;

target position setting means that sets a target position of a swash plate of the pump so that a traveling speed of the machine body is decelerated from a speed corresponding to the position detected by the position detecting means and the deceleration rate set by the deceleration rate setting means; and

a control means that controls the continuously variable transmission so that a position of a swash plate of the pump coincides with the target position set by the target position setting means.

2. The control device for a work vehicle according to claim 1,

the deceleration rate setting means sets the deceleration rate including a proportional term set by multiplying a proportional gain by a deviation of the load corresponding value from the reference value, when the load corresponding value exceeds the reference value.

3. The control device for a work vehicle according to claim 2,

the deceleration rate setting means sets the deceleration rate by adding an integral term, which is set by multiplying an integral gain by an integral value of a deviation of the load corresponding value from the reference value, to the proportional term in a case where the load corresponding value exceeds the reference value.

4. The control device for a work vehicle according to claim 3,

the deceleration rate setting means eliminates the proportional term in response to a change in the load corresponding value from a value exceeding the reference value to a value equal to or less than the reference value, and sets the deceleration rate including the integral term so that the traveling speed of the machine body is accelerated toward a speed corresponding to the position detected by the position detecting means.

5. The control device for a work vehicle according to claim 4,

the deceleration rate setting means sets the deceleration rate including the integral term after addition by adding the integral term to the deceleration rate of the proportional term that disappears when the proportional term disappears in accordance with a change in the load corresponding value from a value exceeding the reference value to a value equal to or less than the reference value.

6. The control device for the working vehicle according to any one of claims 1 to 5,

the target position setting means sets the target position based on a product obtained by multiplying the deceleration rate by a numerical value indicating the position detected by the position detecting means.

7. A work vehicle, comprising:

a body;

a continuously variable transmission device including a swash plate type pump and a motor to which a fluid is supplied from the pump, the continuously variable transmission device outputting power of the motor that is shifted in accordance with a flow direction and a flow rate of the fluid supplied from the pump to the motor;

a pair of left and right traveling devices that support the machine body and are driven by power output from the continuously variable transmission;

a brake operating member that is provided to the machine body in an operable manner;

a brake mechanically coupled to the brake operating member, the brake applying a braking force to the travel device in response to an operation of the brake operating member;

a brake operation detection mechanism that detects an operation of the brake operation member; and

a stop control mechanism that controls a position of a swash plate of the pump to a stop position side at which fluid is not discharged from the pump when the operation of the brake operation member is detected by the brake operation detection mechanism.

8. The work vehicle according to claim 7,

the work vehicle further includes a shift operation member provided in the machine body, and operated from a neutral position to one side to instruct forward movement of the machine body and operated from the neutral position to the other side to instruct reverse movement of the machine body,

the stop control mechanism does not change the position of the swash plate from the stop position until the shift operation member returns to the neutral position even if the operation of the brake operation member is released after the swash plate is located at the stop position.

9. The work vehicle according to claim 7 or 8,

the brake operation detection means is a sensor that detects an operation amount of the brake operation member,

the stop control means controls the position of the swash plate so that the swash plate approaches the stop position in conjunction with an increase in the operation amount detected by the brake operation detection means.

10. The work vehicle according to claim 7 or 8,

the brake operation detection means is a switch that switches from a first state to a second state when the amount of operation of the brake operating member reaches a certain amount,

the stop control mechanism controls the position of the swash plate so that the swash plate reaches the stop position over a certain time after the brake operation detection mechanism is switched from the first state to the second state.

Technical Field

The present invention relates to a control device used for a work vehicle such as a combine harvester.

The invention also relates to a working vehicle such as a harvester for harvesting grains.

Background

In relation to the first aspect, in a combine harvester, roots of grain stalks standing in a field are harvested by a harvesting device, the harvested grain stalks are transported from the harvesting device to a threshing device, the grain stalks are threshed by the threshing device, and grains are collected in a grain bin. In a combine harvester, an engine is mounted as a driving source, and power from the engine is transmitted to a working device such as a harvesting device and a threshing device, and power from the engine is transmitted to a traveling device including a pair of left and right crawler belts.

Therefore, the load of the engine varies depending on the state of work in the work machine. When the load on the work machine becomes large and the load on the engine becomes excessive (overload), the number of revolutions of the engine decreases, and the engine may be stopped. The power transmitted to the traveling device may be shifted by a continuously variable transmission device, and a shift lever operated to adjust the shifting by the continuously variable transmission device is provided on the driver's seat. Therefore, when the load of the engine exceeds a predetermined value, automatic control is executed to reduce the traveling speed of the machine body by operating the shift lever by the motor in order to reduce the load of the engine.

Prior art documents

Patent document

Patent document 1: japanese laid-open patent publication No. 10-259868

However, in the configuration in which the traveling speed is reduced via the motor, the speed cannot be sufficiently reduced when the load of the work machine is rapidly increased, and there is a possibility that the engine stop due to the reduction of the engine rotation cannot be avoided.

In a second aspect, for example, in a combine equipped with an HST (hydrostatic Transmission), a hydraulic pump of the HST is driven by power of an engine, a hydraulic motor is driven by oil discharged from the hydraulic pump, and power of the hydraulic motor is transmitted to left and right crawler belts. The left and right crawler belts are driven at the same speed, whereby the machine body moves straight forward and backward, and the left and right crawler belts are driven at a speed difference, whereby the machine body turns left and right.

The shift lever is provided on the driver's seat so as to be displaceable from a neutral position to a forward position on the front side and a reverse position on the rear side. When the shift lever is operated from the neutral position to the forward position, the swash plate of the hydraulic pump tilts to one side from the neutral position, the oil supplied from the hydraulic pump to the hydraulic motor flows in one direction at a flow rate according to the tilt angle of the swash plate of the hydraulic pump, and the hydraulic motor rotates in the forward direction at a rotation speed according to the flow rate of the supplied oil. Thus, the power in the forward direction is transmitted to the left and right crawler belts, and the machine body moves forward. On the other hand, when the shift lever is operated from the neutral position to the reverse position, the swash plate of the hydraulic pump tilts from the neutral position to the other side, the oil supplied from the hydraulic pump to the hydraulic motor flows in the other direction at a flow rate corresponding to the tilt angle of the swash plate of the hydraulic pump, and the hydraulic motor rotates in the reverse direction at a rotation speed corresponding to the flow rate of the supplied oil. Thus, the power in the backward direction is transmitted to the left and right crawler belts, and the machine body moves backward. When the shift lever is returned from the forward position or the reverse position to the neutral position, the swash plate of the hydraulic pump is returned to the neutral position, the supply of oil from the hydraulic pump to the hydraulic motor is stopped, and the hydraulic motor is braked to stop the machine body.

In this combine harvester, there is a combine harvester including a parking brake operated by stepping on a parking brake pedal and a link mechanism for returning a shift lever to a neutral position in accordance with stepping on the parking brake pedal. The left and right crawler belts are braked by the operation of the parking brake, and the stopped state of the machine body is maintained. Further, when the parking brake pedal is depressed, the shift lever returns to the neutral position even when the shift lever is located at the forward position or the reverse position, and the hydraulic motor is braked, so that it is possible to prevent the body from suddenly moving in the forward direction or the reverse direction when the parking brake is released.

Prior art documents

Patent document

Patent document 2: japanese patent laid-open publication No. 2012-62973

However, in a state where the shift lever is in the forward position or the reverse position and power is transmitted from the hydraulic motor to the left and right crawler belts, if the parking brake pedal is depressed, if the return of the shift lever to the neutral position is slower than the operation of the parking brake, there is a possibility that a problem such as burnout of the parking brake may occur. Therefore, the link mechanism needs to be adjusted so that the shift lever is returned to the neutral position before the parking brake is actuated.

Further, since the link mechanism is connected to the shift lever, the operating load of the shift lever becomes large or the operator feels uncomfortable with the operation of the shift lever.

Disclosure of Invention

A first aspect of the present invention is directed to provide a control device for a work vehicle, which can reduce a traveling speed of a machine body with good following performance even when a load on a work device increases suddenly.

Means for solving the problems

In order to achieve the above object, a control device for a work vehicle according to the present invention includes: a body; an engine; a working device driven by power of the engine; a continuously variable transmission device including a swash plate pump driven by power of an engine and a motor driven by fluid discharged from the pump, and outputting power of the motor; a pair of left and right traveling devices which support the machine body and are driven by power output from the continuously variable transmission; and an operation member operated to instruct a travel speed of the machine body traveling by the traveling device, wherein the control device includes: a position detection mechanism that detects a position of the operation member; deceleration rate setting means that sets a deceleration rate corresponding to whether or not a load corresponding value corresponding to a load of the engine exceeds a reference value; target position setting means for setting a target position of a swash plate of the pump so that a traveling speed of the machine body is decelerated from a speed corresponding to the position detected by the position detecting means and a deceleration rate set by the deceleration rate setting means; and a control means for controlling the continuously variable transmission so that the position of the swash plate of the pump coincides with the target position set by the target position setting means.

According to this configuration, the deceleration rate is set according to whether or not the load corresponding value corresponding to the load of the engine exceeds the reference value, and the target position of the swash plate of the pump is set so that the traveling speed of the engine body is decelerated from the speed according to the position of the operation member according to the deceleration rate. Further, the continuously variable transmission is controlled such that the position of the swash plate of the pump coincides with the target position. Thus, compared to control in which the target position of the swash plate of the pump is changed by operating the operating member by an actuator such as a motor to reduce the traveling speed of the machine body, the responsiveness of the control is high, and the traveling speed of the machine body can be reduced with good follow-up performance even for a sudden increase in the load of the engine caused by a sudden increase in the load of the working device.

Preferably, the deceleration rate setting means sets the deceleration rate including a proportional term set by multiplying a deviation of the load corresponding value from the reference value by a proportional gain when the load corresponding value exceeds the reference value. Accordingly, the deceleration rate is set to a larger value as the deviation of the load corresponding value from the reference value is larger, and therefore, the traveling speed of the engine body can be reduced with better following ability against a sudden increase in the load of the engine.

The deceleration rate setting means may be configured to set the deceleration rate by adding an integral term, which is set by multiplying an integral value of a deviation of the load corresponding value from the reference value by an integral gain, to a proportional term, when the load corresponding value exceeds the reference value.

The deceleration rate setting means may be configured to eliminate the proportional term in response to a change in the load corresponding value from a value exceeding the reference value to a value equal to or less than the reference value, and set the deceleration rate including the integral term so that the traveling speed of the machine body is accelerated toward a speed corresponding to the position detected by the position detecting means.

In this case, preferably, the deceleration rate setting means adds the integral term to the deceleration rate of the proportional term that has disappeared when the proportional term disappears in response to the change in the load corresponding value from the value exceeding the reference value to the value equal to or less than the reference value, and sets the deceleration rate including the integral term after the addition. Thus, when the traveling speed of the machine body shifts from a state of deceleration to a state of returning to a normal speed by acceleration, a sudden change in the deceleration rate can be suppressed. Further, the deceleration rate changes with a slow change in the integral term, and the traveling speed of the body is slowly accelerated (increased) with the change in the deceleration rate, so that a rapid increase in the traveling speed, fluctuation, or the like of the body can be suppressed. Therefore, the riding comfort of the operator can be improved.

The target position setting means may set the target position based on a product obtained by multiplying the deceleration rate by a numerical value indicating the position detected by the position detecting means.

According to the present invention, even when the load on the working device increases rapidly, the traveling speed of the machine body can be reduced with good following performance.

A second aspect of the present invention is directed to provide a work vehicle that can satisfactorily stop a motor when a brake is actuated without using a conventional link mechanism.

Means for solving the problems

In order to achieve the above object, a work vehicle of the present invention includes: a body; a continuously variable transmission device including a swash plate type pump and a motor to which fluid is supplied from the pump, the continuously variable transmission device outputting power of the motor that is changed in speed in accordance with a flow direction and a flow rate of the fluid supplied from the pump to the motor; a pair of left and right traveling devices that support the machine body and are driven by power output from the continuously variable transmission; a brake operating member that is provided to the machine body in an operable manner; a brake mechanically coupled to the brake operating member, the brake applying a braking force to the travel device in response to an operation of the brake operating member; a brake operation detection mechanism that detects an operation of the brake operation member; and a stop control mechanism that controls a position of a swash plate of the pump to a stop position side at which fluid is not discharged from the pump, in a case where an operation of the brake operation member is detected by the brake operation detection mechanism.

According to this structure, the continuously variable transmission is configured as follows: the motor is provided with a swash plate type pump and a motor for supplying fluid from the pump, and outputs power of the motor which is changed in speed according to the flow direction and flow rate of the fluid supplied from the pump to the motor. A pair of left and right traveling devices supporting the machine body are driven by power output from the continuously variable transmission.

A brake operating member is provided to be operable on the machine body. The brake operating member is mechanically coupled to the brake, and a braking force generated by the brake acts on the travel device in response to an operation of the brake operating member. In addition, when the brake operating member is operated, the operation is detected by the brake operation detecting mechanism. When the operation of the brake operating member is detected, the position of the swash plate of the pump is controlled to a stop position side where fluid is not discharged from the pump. Therefore, without using the conventional link mechanism, the discharge of the fluid from the pump can be stopped and the motor can be stopped satisfactorily when the brake is operated. In addition, since the link mechanism is not used, the link mechanism does not need to be adjusted, and the time and labor required for adjusting the link mechanism can be saved.

The work vehicle may further include a shift operation member that is provided in the machine body, and that is operated from a neutral position to one side in order to instruct forward movement of the machine body and that is operated from the neutral position to the other side in order to instruct reverse movement of the machine body.

In a normal state, when the shift operating member is operated from the neutral position to one side or the other side, the swash plate position of the pump is controlled so that power in the forward direction or the reverse direction is output from the motor. Therefore, when the shift operation member is positioned at one side or the other side from the neutral position after the position of the swash plate of the pump is positioned at the stop position by the operation of the brake operation member, the power in the forward or reverse direction is output from the motor when the brake is released, and the machine body starts to move forward or reverse. When the operator forgets to return the shift operation member to the neutral position, the forward or backward movement of the machine body may not be expected by the operator.

Therefore, it is preferable that the stop control mechanism does not change the position of the swash plate from the stop position until the shift operation member returns to the neutral position even if the operation of the brake operation member is released after the swash plate is located at the stop position. Thus, when the operator releases the operation of the brake operating member, the body can be prevented from moving forward or backward, which is not intended by the operator.

The brake operation detection means is a sensor that detects the amount of operation of the brake operation member, and the stop control means controls the position of the swash plate so that the swash plate approaches the stop position in conjunction with an increase in the amount of operation detected by the brake operation detection means.

The brake operation detection means may be a switch that switches from the first state to the second state when the amount of operation of the brake operation member reaches a certain amount, and the stop control means may control the position of the swash plate so that the swash plate reaches the stop position after a certain period of time after the brake operation detection means switches from the first state to the second state.

According to the present invention, the discharge of the fluid from the pump can be stopped and the motor can be stopped satisfactorily when the brake is operated without using the conventional link mechanism. In addition, since the link mechanism is not used, the link mechanism does not need to be adjusted, and the time and labor required for adjusting the link mechanism can be saved.

Drawings

First embodiment

Fig. 1 is a right side view showing a front part of a combine harvester using a control device according to an embodiment of the present invention.

Fig. 2 is a block diagram showing a main part of an electrical structure of the combine harvester.

Fig. 3 is a block diagram showing a specific configuration for HST control.

Fig. 4 is a diagram for explaining a method of setting the deceleration rate by the deceleration rate setting unit.

Fig. 5 is a graph showing an example of temporal changes in the load factor, proportional term, integral term, and deceleration rate.

Second embodiment

Fig. 6 is a right side view showing a front portion of the combine harvester according to the embodiment of the present invention.

Fig. 7 is a view showing a partial structure of a drive transmission system of the combine harvester.

Fig. 8 is a cross-sectional view showing a part of the drive transmission system, and shows a configuration from the hydraulic motors of the left HST and the right HST to the middle of the travel device.

Fig. 9 is a side view showing a part of the internal structure of the cab.

Fig. 10 is a block diagram showing a main part of an electrical structure of the combine harvester.

Fig. 11 is a flowchart showing a flow of the brake control.

Fig. 12 is a flowchart showing another flow of the brake control.

Description of the reference numerals

First embodiment

1: combine harvester

11: machine body

12: traveling device

14: reaping apparatus (working device)

15: threshing device (working device)

19: gear lever (operating parts)

31: engine

32: HST (stepless speed change device)

33: hydraulic pump

34: hydraulic motor

41: main ECU

42: engine ECU

43: HSTECU (control device, position detection mechanism, deceleration rate setting mechanism, target position setting mechanism, control mechanism)

44: shift lever position sensor (position detection mechanism)

61: deceleration rate setting unit (deceleration rate setting means)

62: target swash plate position calculating unit (target position setting mechanism)

Second embodiment

1: combine harvester (working vehicle)

11: machine body

12: traveling device

21: main gear shift lever (Shift operating parts)

33: left side HST

34: right side HST

41: hydraulic pump

42: hydraulic motor

141: brake pedal

146: brake

152: running control ECU (stop control mechanism)

155: brake sensor (brake operation detection mechanism)

Detailed Description

First embodiment

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

< integral Structure of combine harvester >

Fig. 1 is a right side view showing a front part of a combine harvester 1 using a control device according to an embodiment of the present invention.

The combine harvester 1 is a work vehicle that harvests grain and straw and threshes grain from grain and straw while traveling in a field. The body 11 of the combine harvester 1 is supported by a pair of left and right traveling devices 12. In order to enable the combine harvester 1 to travel in the field, the travel device 12 employs a crawler having an uneven ground passing capability.

The machine body 11 is provided with a driving platform 13, a harvesting device 14, a threshing device 15 and a grain tank 16.

The cab 13 is disposed above the front end of the traveling device 12. A seat 17 on which an operator sits is provided on the cab 13. Further, an operation panel 18 operated by an operator is provided on the cab 13, for example, from the front of the seat 17 to the left.

The operation panel 18 is provided with a shift lever 19 and the like. The shift lever 19 is provided to be tiltable in the front-rear direction, for example. The operator can instruct the body 11 to advance by tilting the shift lever 19 forward, and can change the speed of advance by the amount of tilting. The operator can instruct the body 11 to retreat by tilting the shift lever 19 to the rear side, and can change the speed of retreat by using the amount of tilting.

The harvesting device 14 is disposed in front of the traveling device 12. The harvesting device 14 includes a divider 21 at a front end thereof, and a harvesting knife 22 at a rear of the divider 21. The crop divider 21 and the harvesting knife 22 are supported by a harvesting front frame 23. A harvesting cross frame 24 extending in the left-right direction is provided at the rear end of the harvesting front frame 23. One end of the harvesting main frame 25 is connected to the harvesting cross frame 24. The harvesting main frame 25 extends rearward from the harvesting cross frame 24, and the other end (disposed downward and forward, and the rear end) thereof is rotatably connected to the frame of the machine body 11. The harvesting main frame 25 is swung by the operation of a cylinder (not shown), and the divider 21 and the harvesting blade 22 are raised and lowered between a raised position where they are raised from the ground surface and a lowered position where the divider 21 and the harvesting blade 22 are lowered to the vicinity of the ground surface by the swing. When the machine body 11 moves forward with the grain divider 21 and the harvesting knife 22 positioned at the lowered position, the grain stalks are harvested by the harvesting knife 22 while the roots of the grain stalks standing in the field are divided by the grain divider 21.

The threshing device 15 and the grain tank 16 are arranged side by side above the traveling device 12 and behind the harvesting device 14. The harvested straw is transported to the threshing device 15 by the harvesting device 14. The threshing device 15 conveys the root side of the grain stalks backward by a threshing supply chain, and supplies the ear tip side of the grain stalks to a threshing chamber for threshing. The grains are transported from the threshing device 15 to the grain tank 16, and the grains are accumulated in the grain tank 16. The grain discharging auger 26 is connected with the grain box 16, and grains accumulated in the grain box 16 can be discharged outside the machine by the grain discharging auger 26.

< Electrical Structure of combine harvester >

Fig. 2 is a block diagram showing a main part of an electrical structure of the combine harvester 1.

The combine harvester 1 is equipped with an engine 31 and an HST (Hydro Static Transmission) 32. The HST32 shifts and outputs the power of the engine 31. Specifically, the HST32 includes a hydraulic pump 33 driven by power of the engine 31 and a hydraulic motor 34 driven by fluid discharged from the hydraulic pump 33. The hydraulic pump 33 is a variable displacement swash plate type piston pump. In the range where the inclination angle of the pump swash plate with respect to the axis of the pump rotating shaft of the hydraulic pump 33 is less than 90 °, the larger the inclination angle, the smaller the discharge amount of the hydraulic oil from the hydraulic pump 33. When the inclination angle of the pump swash plate is 90 °, the discharge of the hydraulic oil from the hydraulic pump 33 is stopped. When the inclination angle of the pump swash plate exceeds 90 °, the discharge direction of the hydraulic oil from the hydraulic pump 33 is reversed when the inclination angle is less than 90 °. The hydraulic motor 34 is a variable displacement swash plate type piston motor. When the inclination angle of the motor swash plate with respect to the axis of the motor rotary shaft of the hydraulic motor 34 is constant, the rotation speed of the motor rotary shaft increases as the amount of hydraulic oil supplied to the hydraulic motor 34, that is, the amount of hydraulic oil discharged from the hydraulic pump 33 increases.

The power of the engine 31 is transmitted to the left and right traveling devices 12 and the harvesting device 14 after being shifted in speed by the HST 32. Further, the power of the engine 31 is transmitted to the thresher 15 without being subjected to the shifting action of the HST 32. Power transmission mechanisms (not shown) including clutches and the like are interposed between the HST32 and the traveling device 12, between the HST32 and the harvesting device 14, and between the engine 31 and the threshing device 15, respectively.

The combine harvester 1 is mounted with a single main ECU (Electronic Control Unit) 41 for overall unified Control and a plurality of ECUs for individual specific Control. The ECUs used for individual specific control include, for example, the engine ECU42 and HSTECU 43. The main ECU41, the engine ECU42, and the HSTECU43 are each a structure including a Micro Controller Unit (MCU).

The main ECU41 is communicably connected to each ECU for individual specific control, that is, the engine ECU42 and the HSTECU 43. The main ECU41 receives information acquired from detection signals of various sensors and the like by each ECU for individual specific control, and transmits commands and information necessary for control of each ECU to each ECU.

The engine ECU42 receives commands from the main ECU41 and controls the engine 31.

A shift lever position sensor 44 that outputs a detection signal corresponding to the operation position of the shift lever 19 is connected to the HSTECU43, and the detection signal of the shift lever position sensor 44 is input to the HSTECU 43. A pump swash plate position sensor 45 that outputs a detection signal corresponding to the position of the pump swash plate of the hydraulic pump 33 of the HST32 (the inclination angle from the reference position) is connected to the HSTECU43, and the detection signal of the pump swash plate position sensor 45 is input to the HSTECU 43. The HSTECU43 receives a command from the main ECU41, and controls the HST32 (performs HST control) based on information obtained from the detection signals of the shift lever position sensor 44 and the swash plate position sensor 45.

< specific Structure for HST control >

Fig. 3 is a block diagram showing a specific configuration for HST control.

In the HST32, an electronically controlled servo cylinder 51 is additionally provided to change the inclination angle of the swash plate of the hydraulic pump 33. The servo hydraulic cylinder 51 has a first pressure chamber to which hydraulic pressure is supplied from a forward-side proportional pressure reduction control valve 52 and a second pressure chamber to which hydraulic pressure is supplied from a reverse-side proportional pressure reduction control valve 53. The servo cylinder 51 has a rod that moves linearly by a differential pressure between the first pressure chamber and the second pressure chamber, and the tilt angle of the pump swash plate is changed by the linear movement of the rod. The servo cylinder 51, the forward proportional pressure reduction control valve 52, and the reverse proportional pressure reduction control valve 53 constitute a servo mechanism 54 that controls the inclination angle of the swash plate of the hydraulic pump 33.

The HSTECU43 substantially includes a deceleration rate setting unit 61, a target swash plate position calculation unit 62, an actual swash plate position detection unit 63, a deviation calculation unit 64, and a PI (Proportional-Integral) calculation unit 65 as a processing unit for HST control. Each processing unit is realized by software through program processing, or by hardware such as a logic circuit.

Fig. 4 is a diagram for explaining a method of setting the deceleration rate by deceleration rate setting unit 61. Fig. 5 is a graph showing an example of temporal changes in the load factor, proportional term, integral term, and deceleration rate.

Deceleration rate setting unit 61 sets a deceleration rate according to the load of engine 31.

Specifically, information on the rotation speed of the engine 31 (hereinafter referred to as "engine rotation speed") is input from the engine ECU42 to the HSTECU43 via the main ECU 41. The combine harvester 1 is provided with an engine rotation sensor that outputs a pulse signal synchronized with the rotation of the engine 31 (the rotation of the crankshaft) as a detection signal, and the engine speed is determined from the detection signal of the engine rotation sensor.

The deceleration rate setting unit 61 determines the amount of decrease in the engine speed from the reference speed using the speed of the engine 31 in the no-load state as the reference speed, and determines the ratio of the amount of decrease to a predetermined reference amount of decrease as the load rate (%). Then, the deceleration rate setting unit 61 sets a deceleration rate according to whether or not the load rate, which is a load corresponding value corresponding to the load of the engine 31, exceeds a reference value. More specifically, when the load factor exceeds 100% as the reference value (time T1, T3), the deceleration rate setting unit 61 sets a proportional term and an integral term, and adds the sum of the proportional term and the integral term to 1000(‰) to set the deceleration rate in order to decelerate the traveling speed of the machine body 11. The proportional term is set by multiplying the proportional gain by the deviation of the load rate from a reference value. The integral term is set by multiplying an integral gain by an integral value of a deviation of the load factor from a reference value.

Referring to fig. 3, the target swash plate position calculation unit 62 sets a detection value obtained by digitizing a detection signal of the shift lever position sensor 44 to a value corresponding to the position of the shift lever 19, and calculates a value corresponding to a target swash plate position that is a target position of the pump swash plate of the hydraulic pump 33 according to a predetermined calculation formula based on a product obtained by multiplying the deceleration rate set by the deceleration rate setting unit 61 by the detection value. It should be noted that a map that specifies a relationship between a product obtained by multiplying the deceleration rate by the detection value of the shift lever position sensor 44 and a value corresponding to the target swash plate position may be stored in the memory of the HSTECU43, and the target swash plate position calculation unit 62 may set a value corresponding to the target swash plate position based on the product according to the map.

The actual swash plate position detecting unit 63 converts the detection value obtained by digitizing the detection signal of the pump swash plate position sensor 45 into a value corresponding to the actual swash plate position that is the actual position (inclination angle) of the pump swash plate of the hydraulic pump 33.

The deviation calculating section 64 calculates a swash plate position deviation, which is a deviation of the target swash plate position from the actual swash plate position, by subtracting a value corresponding to the actual swash plate position calculated by the actual swash plate position detecting section 63 from a value corresponding to the target swash plate position calculated by the target swash plate position calculating section 62.

The PI operation unit 65 performs PI (proportional integral) operation using the swash plate position deviation, and sets a target current value, which is a target of the current value supplied to each of the proportional pressure reduction control valves 52 and 53, based on the result of the PI operation.

In the HSTECU43, the currents supplied to the proportional pressure reduction control valves 52 and 53 are chopped at a duty ratio corresponding to the target current values so that the values of the currents supplied to the proportional pressure reduction control valves 52 and 53 match the target current values.

By setting the deceleration rate to be less than 1000(‰), the value corresponding to the target swash plate position of the hydraulic pump 33 is set to a smaller value than the case where the deceleration rate is set to 1000 (% o). As a result, the amount of hydraulic oil discharged from the hydraulic pump 33 decreases, the rotation speed of the hydraulic motor 34 transmitted to the traveling device 12 decreases, and the traveling speed of the machine body 11 is reduced. The load on the engine 31 is reduced by the reduction in the traveling speed of the machine body 11. When the load factor of engine 31 decreases from a value exceeding 100% as the reference value to a value equal to or less than the reference value (times T2 and T4) as shown in fig. 5, deceleration rate setting unit 61 sets an integral term so as to eliminate the proportional term set up so far as shown in fig. 4 in order to increase the traveling speed of machine body 11, and adds 1000(‰) to the integral term to set the deceleration rate. At this time, the deceleration rate setting unit 61 sets an integral gain by adding the deceleration rate of the vanished proportional term to the integral term, and multiplies the integral gain by the integral value of the deviation of the load factor from the reference value to set the integral term. This suppresses a sudden change in the deceleration rate when the traveling speed of the machine body 11 is switched from deceleration to acceleration.

< Effect >

As described above, the deceleration rate according to whether or not the load factor of the engine 31 exceeds the reference value is set, and the target swash plate position as the target position of the swash plate of the hydraulic pump 33 is set so that the traveling speed of the engine body 11 is decelerated from the speed according to the position of the shift lever 19 and the deceleration rate. Also, the HST32 is controlled in such a manner that the position of the swash plate of the hydraulic pump 33 coincides with the target swash plate position. Thus, compared to control in which the target position of the swash plate of the hydraulic pump 33 is changed by operating the shift lever 19 by an actuator such as a motor to reduce the traveling speed of the machine body 11, the responsiveness of the control is high, and the traveling speed of the machine body 11 can be reduced with good follow-up performance even for a sudden increase in the load of the engine 31 caused by a sudden increase in the load of the working devices such as the reaping apparatus 14 and the threshing apparatus 15.

In a state where the load factor of engine 31 exceeds a reference value, a deceleration rate including a proportional term is set by multiplying a proportional gain by a deviation of the load factor from the reference value. Accordingly, the deceleration rate is set to a larger value as the deviation of the load factor from the reference value is larger, and therefore, the traveling speed of the machine body 11 can be reduced with better following ability against a sudden increase in the load of the engine 31.

In accordance with a change in the load factor of the engine 31 from a value exceeding the reference value to a value equal to or less than the reference value, the proportional term disappears, and the deceleration rate of the disappeared proportional term is added to the integral term to set the deceleration rate including the added integral term. Thus, when the traveling speed of the machine body 11 shifts from a state of deceleration to a state of returning to a normal speed by acceleration, a sudden change in the deceleration rate can be suppressed. Further, since the integral term changes slowly with respect to the change in the load factor, the deceleration rate changes with the slow change in the integral term, and the traveling speed of the machine body 11 is accelerated (increased) slowly with the change in the deceleration rate. Therefore, a rapid increase in the traveling speed, fluctuation, or the like of the machine body 11 can be suppressed. Therefore, the riding comfort of the operator can be improved.

< modification example >

While the embodiments of the present invention have been described above, the present invention can be implemented in other embodiments.

For example, the deceleration rate setting unit 61 sets a proportional term and an integral term when the load rate exceeds 100% which is a reference value, and adds 1000 (#) to the sum of the proportional term and the integral term to set the deceleration rate, but may further set a differential term by multiplying a differential gain by a differential value of the load rate, and add 1000 (#) to set the deceleration rate.

Further, although the combine harvester 1 is proposed as an example of the work vehicle, the present invention is not limited to the combine harvester 1, and may be applied to a work vehicle other than the combine harvester 1, such as a harvester that harvests vegetables such as carrots, radishes, green beans, and cabbage.

In the above configuration, various design changes can be made within the scope of items described in the claims.

Second embodiment

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

< combine harvester >

Fig. 6 is a right side view showing a front part of the combine harvester 1 according to the embodiment of the present invention.

The combine harvester 1 is a work vehicle that harvests grain and straw and threshes grain from the grain and straw while traveling in a field. The body 11 of the combine harvester 1 is supported by a pair of left and right traveling devices 12. In the travel device 12, in order to enable the combine harvester 1 to travel in a field, a crawler having an uneven ground passing capability is employed.

The machine body 11 is provided with a driving platform 13, a harvesting device 14, a threshing device 15 and a grain tank 16.

The cab 13 is disposed above the front end of the traveling device 12. The driver's seat 17 on which the operator sits is provided on the driver's seat 13, and an operation panel 18 operated by the operator is provided, for example, from the front to the left of the driver's seat 17. The operation panel 18 includes a main shift lever 21, a steering lever 22, and the like.

The main shift lever 21 is provided to be displaceable from a neutral position to a forward position on the front side and a reverse position on the rear side. When the main shift lever 21 is operated from the neutral position to the forward position, power in the forward direction is transmitted to the right and left traveling devices 12, and the machine body 11 moves forward. On the other hand, when the main shift lever 21 is operated from the neutral position to the reverse position, the power in the reverse direction is transmitted to the left and right traveling devices 12, and the machine body 11 is reversed. When the main shift lever 21 returns to the neutral position from the forward position or the reverse position, the machine body 11 stops. The forward or reverse speed can be changed according to the operation amount of the main shift lever 21.

The steering rod 22 is provided to be tiltable in the right and left direction and in the front and rear direction. The straight advance, the left turn, and the right turn of the machine body 11 can be switched by the left-right tilting operation of the steering lever 22. In addition, the harvesting unit 14 can be raised and lowered by the forward and backward tilting operation of the steering lever 22.

The harvesting device 14 is disposed in front of the traveling device 12. The harvesting device 14 includes a crop divider 23 at a front end thereof, and a harvesting knife 24 at a rear of the crop divider 23. The crop divider 23 and the harvesting knife 24 are supported by the harvesting unit frame 25. A harvesting cross frame 26 extending in the left-right direction is provided at the rear end of the harvesting device frame 25. One end of the harvesting main frame 27 is connected to the harvesting cross frame 26. The harvesting main frame 27 extends rearward from the harvesting cross frame 26, and the other end (disposed downward and forward, and the rear end) thereof is rotatably connected to the frame of the machine body 11. The harvesting main frame 27 can be swung by operating a cylinder (not shown) by tilting operation of the steering rod 22 in the forward and backward direction, and the crop divider 23 and the harvesting knife 24 are raised and lowered between a raised position where they are raised from the ground surface and a lowered position where they are lowered to the vicinity of the ground surface by the swinging movement. When the machine body 11 moves forward with the grain divider 23 and the harvesting knife 24 positioned at the lowered position, the grain stalks are harvested by the harvesting knife 24 while the roots of the grain stalks standing in the field are divided by the grain divider 23.

The threshing device 15 and the grain tank 16 are arranged side by side above the traveling device 12 and behind the harvesting device 14. The harvested straw is transported to the threshing device 15 by the harvesting device 14. The threshing device 15 conveys the root side of the grain stalks backward by a threshing supply chain, and supplies the ear tip side of the grain stalks to a threshing chamber for threshing. The grains are transported from the threshing device 15 to the grain tank 16, and the grains are accumulated in the grain tank 16. The grain discharging auger 28 is connected with the grain box 16, and grains accumulated in the grain box 16 can be discharged outside the machine by the grain discharging auger 28.

< drive transmission System >

Fig. 7 is a view showing a partial structure of the drive transmission system 32 of the combine harvester 1. Fig. 7 schematically shows the structure from the engine 31 to the left HST33 and the right HST34, and the hydraulic circuit diagram shows the structure relating to the left HST33 and the right HST 34.

The combine harvester 1 is equipped with an engine 31 and a drive transmission system 32 for transmitting the power of the engine 31 to the traveling device 12.

The drive Transmission system 32 includes a left-side HST (Hydro Static Transmission) 33 and a right-side HST 34.

The left HST33 has a closed circuit structure in which the hydraulic pump 41 and the hydraulic motor 42 are connected by the first oil passage 43 and the second oil passage 44 so that the hydraulic oil circulates between the hydraulic pump 41 and the hydraulic motor 42. The first oil passage 43 is connected to a first port 45 of the hydraulic pump 41 and a first port 46 of the hydraulic motor 42. The second oil passage 44 is connected to a second port 47 of the hydraulic pump 41 and a second port 48 of the hydraulic motor 42.

Further, the left HST33 is provided with a supply pump 51. The feed pump 51 is a fixed displacement hydraulic pump, and discharges hydraulic oil to the feed oil passage 53 by rotation of the pump rotation shaft 52. The supply oil passage 53 is connected to the first oil passage 43 via a first check valve 54, and is connected to the second oil passage 44 via a second check valve 55. The supply oil passage 53 is connected to an oil tank 57 via a supply/release valve 56.

The hydraulic pressure of the supply oil passage 53 is maintained at a predetermined supply pressure by the function of the supply relief valve 56. When the hydraulic pressure of the first oil passage 43 is lower than the hydraulic pressure of the supply oil passage 53, that is, the supply pressure, the first check valve 54 opens, and the working oil is supplied from the supply oil passage 53 to the first oil passage 43 via the first check valve 54. When the hydraulic pressure in the second oil passage 44 is lower than the supply pressure, the second check valve 55 opens, and the hydraulic oil is supplied from the supply oil passage 53 to the second oil passage 44 via the second check valve 55. Thereby, the hydraulic pressures of the first oil passage 43 and the second oil passage 44 are maintained at the supply pressure or higher.

The left HST33 is configured as an integrated HST in which the hydraulic pump 41, the hydraulic motor 42, the first oil passage 43, the second oil passage 44, the first check valve 54, the second check valve 55, the supply/release valve 56, and the like are housed in a single housing.

The hydraulic pump 41 is a variable displacement swash plate type piston pump, and includes a cylinder block, a plurality of pistons radially arranged in the cylinder block, a pump swash plate on which the pistons slide, and the like. The hydraulic pump 41 and the feed pump 51 have a pump rotating shaft 52 in common, and the cylinder is provided so as to rotate integrally with the pump rotating shaft 52.

An electronically controlled servo piston 58 is provided to change the inclination angle of the swash plate of the hydraulic pump 41. The servo piston 58 has: a first pressure chamber 62 to which hydraulic pressure is supplied from the forward side pressure control valve 61, and a second pressure chamber 64 to which hydraulic pressure is supplied from the reverse side pressure control valve 63. The servo piston 58 has a rod 65 that moves linearly by a differential pressure between the first pressure chamber 62 and the second pressure chamber 64, and the tilt angle of the swash plate of the pump is changed by the linear movement of the rod 65.

The discharge amount of the hydraulic oil from the hydraulic pump 41 decreases as the inclination angle of the pump swash plate with respect to the axis of the pump rotary shaft 52 of the hydraulic pump 41 (the rotation axis of the cylinder block) increases, and when the inclination angle of the pump swash plate is 90 °, the discharge of the hydraulic oil from the hydraulic pump 41 is stopped. When the inclination angle of the pump swash plate exceeds 90 ° (at the time of inclination reversal), the discharge direction of the hydraulic oil from the hydraulic pump 41 is reversed when the inclination angle is less than 90 °.

The hydraulic motor 42 is a variable displacement swash plate type piston motor, and includes a motor rotary shaft 71, a cylinder block 72 (see fig. 8) that rotates integrally with the motor rotary shaft 71, a plurality of pistons 73 (see fig. 8) disposed radially in the cylinder block 72, a motor swash plate 74 (see fig. 8) that presses the pistons 73, and the like. When the inclination angle of the motor swash plate 74 with respect to the axis of the motor rotary shaft 71 of the hydraulic motor 42 (the rotation axis of the cylinder block 72) is constant, the rotation speed of the motor rotary shaft 71 increases as the amount of hydraulic oil supplied to the hydraulic motor 42, that is, the amount of hydraulic oil discharged from the hydraulic pump 41 increases.

When the amount of hydraulic oil supplied to the hydraulic motor 42 is constant, the rotation speed of the motor rotary shaft 71 decreases as the inclination angle of the motor swash plate 74 increases. A sub-transmission piston 75 is provided for changing the inclination angle of the motor swash plate 74 of the hydraulic motor 42. The low-speed switching valve 76 and the high-speed switching valve 77 are connected to the sub-transmission piston 75. When the low-speed switching valve 76 is turned on and the high-speed switching valve 77 is turned off, and hydraulic pressure is supplied from the low-speed switching valve 76 to the sub-transmission piston 75, the rod 78 of the sub-transmission piston 75 is positioned at the low-speed position, and the inclination angle of the motor swash plate 74 is relatively increased. On the other hand, the low-speed switching valve 76 is closed, the high-speed switching valve 77 is opened, and hydraulic pressure is supplied from the high-speed switching valve 77 to the sub-transmission piston 75, so that the rod 78 of the sub-transmission piston 75 is positioned at the high-speed position, and the inclination angle of the motor swash plate 74 is relatively decreased. Therefore, by switching on or off the low speed switching valve 76 and the high speed switching valve 77, it is possible to switch to two stages, i.e., a high speed stage in which the rotation speed of the motor rotary shaft 71 is relatively increased and a low speed stage in which the rotation speed of the motor rotary shaft 71 is relatively decreased.

Since the right HST34 has the same structure as the left HST33, the parts corresponding to the parts of the left HST33 in the right HST34 are denoted by the same reference numerals as the parts described above, and the description thereof is omitted.

The power of the engine 31 is input to the pump rotation shafts 52 of the left HST33 and the right HST 34. Specifically, a pulley 82 is provided on the output shaft 81 of the engine 31 so as not to be relatively rotatable. The drive transmission system 32 includes an input shaft 83 extending parallel to the output shaft 81 of the engine 31. A pulley 84 is provided on the input shaft 83 so as not to be rotatable relative thereto. An endless belt 85 is wound between the pulleys 82, 84. Further, an input gear 86 is provided on the input shaft 83 so as not to be relatively rotatable. The intermediate gear 87 meshes with the input gear 86, and the pump gear 88 provided on the pump rotating shaft 52 of the right HST34 so as not to be relatively rotatable meshes with the intermediate gear 87. The pump gear 88 is engaged with a pump gear 89 provided on the pump rotating shaft 52 of the left HST33 so as not to be relatively rotatable.

Thereby, the power of the engine 31 is transmitted from the output shaft 81 to the pulley 84 via the pulley 82 and the belt 85, and rotates the input shaft 83 integrally with the pulley 84. The power (rotation) of the input shaft 83 is transmitted from the input gear 86 to the pump gear 88 of the right HST34 via the intermediate gear 87, and the pump rotation shaft 52 of the right HST34 is rotated in a predetermined direction integrally with the pump gear 88. The power of the input shaft 83 is transmitted from the input gear 86 to the pump gear 88 of the right HST34 via the intermediate gear 87, and further transmitted from the pump gear 88 to the pump gear 89, and the pump rotary shaft 52 of the left HST33 is rotated in the direction opposite to the predetermined direction integrally with the pump gear 89. Therefore, when the inclination angles of the pump swash plates of the hydraulic pumps 41 of the left HST33 and the right HST34 are the same, the motor rotary shaft 71 of the hydraulic motor 42 of the left HST33 and the motor rotary shaft 71 of the hydraulic motor 42 of the right HST34 rotate in opposite directions to each other.

Fig. 8 is a cross-sectional view showing a part of the drive transmission system 32, and shows a structure from the hydraulic motor 42 of the left HST33 and the right HST34 to a point halfway through the travel device 12.

The hydraulic motors 42 of the left HST33 and the right HST34 are arranged in bilateral symmetry with each other such that the motor rotation shafts 71 are aligned on the same axis (have a common axis) and the axes thereof are parallel to the axes of the left and right axles.

In the following description, the motor rotation shaft 71 of the left HST33 is referred to as "motor rotation shaft 71L", and the motor rotation shaft 71 of the right HST34 is referred to as "motor rotation shaft 71R".

The motor rotary shafts 71L, 71R are rotatably supported at their outer ends in the left-right direction by a unit case 101 constituting the outer shell of the drive transmission system 32 via bearings 102L, 102R, respectively. The motor output gears 103L and 103R are supported by the left and right inner ends of the motor rotary shafts 71L and 71R, respectively, so as to be relatively non-rotatable.

First intermediate shaft 104 and second intermediate shaft 105 are provided between motor rotary shafts 71L, 71R and the axle. The respective axes of the first intermediate shaft 104 and the second intermediate shaft 105 are parallel to the axes of the motor rotary shafts 71L, 71R. The first intermediate shaft 104 is non-rotatably supported by the unit case 101. The left end portion of the second intermediate shaft 105 is rotatably supported by the unit case 101 via a bearing 106. A cylindrical sleeve 107 is fitted over the right portion 105R of the second intermediate shaft 105. The inner race of the bearing 108 is fitted to the sleeve 107 so as not to rotate relatively. The outer race of the bearing 108 is fixed to the unit case 101. Thereby, the second intermediate shaft 105 is rotatably held by the unit case 101.

The first left intermediate gear 111L and the first right intermediate gear 111R are aligned in the left-right direction and rotatably held by the first intermediate shaft 104. The left motor output gear 103L meshes with the first left intermediate gear 111L, and the right motor output gear 103R meshes with the first right intermediate gear 111R. The second left and right intermediate gears 112L and 112R are fixedly held in the left and right portions 105L and 105R of the second intermediate shaft 105, respectively, in a left-right arrangement. The first left intermediate gear 111L meshes with the second left intermediate gear 112L, and the first right intermediate gear 111R meshes with the second right intermediate gear 112R.

An annular groove 113L centered on the axis of the second intermediate shaft 105 is formed in the left side surface of the second left intermediate gear 112L. A plurality of internal teeth 114L protruding toward the rotation center side are formed in a circumferential direction at the left end portion of the groove portion 113L. A third left intermediate gear 115L is provided to the left of the second left intermediate gear 112L. The third left intermediate gear 115L is held on the left portion 105L of the second intermediate shaft 105 so as to be relatively non-rotatable and movable in the axial direction of the second intermediate shaft 105. The third left intermediate gear 115L has a plurality of external teeth 116L on the outer peripheral surface. A notch 117 notched over the entire circumference is formed in the right side portion of the outer tooth 116L.

An annular groove portion 113R centered on the axis of the second intermediate shaft 105 is formed on the right side surface of the second right intermediate gear 112R. A plurality of internal teeth 114R protruding toward the rotation center side are formed in a circumferential direction at the right end of the groove portion 113R. A third right intermediate gear 115R is provided on the right side of the second right intermediate gear 112R. The third right intermediate gear 115R is held by the sleeve 107 so as to be relatively non-rotatable and movable in the axial direction of the second intermediate shaft 105. The third right intermediate gear 115R has a plurality of external teeth 116R on the outer peripheral surface.

A shift rail 121 is provided at a position apart from the second intermediate shaft 105 in a direction orthogonal to the axial direction thereof. A center line of shift rail 121 extends parallel to the axis of second intermediate shaft 105, and shift rail 121 is held by unit case 101 so as to be movable in the center line direction. A recess 122L is formed on the outer peripheral surface of the third left intermediate gear 115L over the entire periphery. A left fork 123L projecting in the radial direction of shift rail 121 is fixed to shift rail 121, and a distal end portion of left fork 123L is fitted into recess 122L with a gap. Further, a recess 122R is formed on the outer peripheral surface of the third right idler gear 115R over the entire periphery. A right fork 123R projecting in the radial direction of shift rail 121 is fixed to shift rail 121, and a distal end portion of right fork 123R is fitted into recess 122R with a gap.

An operation groove 124 extending in the circumferential direction is formed at the left end portion of the shift rail 121. The distal end portion of operating member 126, which extends from the distal end portion of shift operating piece 125 toward shift rail 121, enters operating slot 124 from the radial direction of shift rail 121. A support shaft 127 that is orthogonal to both the center line direction of the shift rail 121 and the direction in which the shift operating piece 125 extends is fixedly provided at the base end portion of the shift operating piece 125. The support shaft 127 is rotatably supported by the unit case 101. An operating arm 128 extending in a direction orthogonal to both the axis of the support shaft 127 and the direction in which the shift operating piece 125 extends is supported by the support shaft 127 so as not to be rotatable relative thereto.

A coil-shaped spring 129 fitted around the shift fork shaft 121 is interposed in a compressed state between the unit case 101 and the right fork 123R. Thereby, the elastic force of spring 129 is applied to right fork 123R, and shift rail 121 is biased leftward by the elastic force.

In a state where the operating arm 128 is not operated, the shift rail 121 is located at the left end of the movable range, the external teeth 116L of the third left intermediate gear 115L mesh with the internal teeth 114L of the second left intermediate gear 112L, and the external teeth 116R of the third right intermediate gear 115R mesh with the internal teeth 114R of the second right intermediate gear 112R. Therefore, the power (rotation) transmitted from the motor rotating shaft 71 to the second left intermediate gear 112L via the first left intermediate gear 111L is transmitted from the second left intermediate gear 112L to the third left intermediate gear 115L, and is transmitted from the third left intermediate gear 115L to the left axle via a gear train (not shown), whereby the left travel device 12 is driven. The power (rotation) transmitted from the motor rotating shaft 71 to the second right intermediate gear 112R via the first right intermediate gear 111R is transmitted from the second right intermediate gear 112R to the third right intermediate gear 115R, and is transmitted from the third right intermediate gear 115R to the right axle via a gear train (not shown), whereby the right travel device 12 is driven.

When the operating arm 128 is operated to raise the tip, the shift operating piece 125 is pivoted about the support shaft 127 as a fulcrum in accordance with the pivoting of the operating arm 128, and the shift rail 121 moves to the right. In a state where the shift rail 121 is positioned at the right end of the movable range, the external teeth 116L of the third left intermediate gear 115L and the internal teeth 114L of the second left intermediate gear 112L are disengaged, and the external teeth 116R of the third right intermediate gear 115R and the internal teeth 114R of the second right intermediate gear 112R are disengaged. Therefore, the power (rotation) transmitted from the motor rotating shaft 71 to the second left intermediate gear 112L via the first left intermediate gear 111L is not transmitted from the second left intermediate gear 112L to the third left intermediate gear 115L and the third right intermediate gear 115R. That is, the drive transmission system 32 is in a neutral state in which the power from the engine 31 (the left HST33 and the right HST34) is not transmitted to the left and right axles. An arc-shaped locking recess 131 that is recessed upward is formed at the distal end of the operating arm 128. The neutral state of the drive transmission system 32 can be maintained by engaging the engaging recess 131 with the engaging projection 132 fixedly provided on the unit case 101.

< brake >

Fig. 9 is a side view showing a part of the internal structure of the cab 13.

A brake pedal 141 is provided in front of the driver seat 17 (see fig. 5) on the driver's seat 13. The brake pedal 141 includes a brake pedal arm 142 and a pedal body 143 supported by the brake pedal arm 142.

The brake pedal arm 142 extends in the front-rear direction. An arm support shaft 144 extending in the left-right direction is integrally provided at a base end portion, which is a distal end portion of the brake pedal arm 142. The brake pedal arm 142 is provided swingably about the arm support shaft 144 as a fulcrum by the arm support shaft 144 being rotatably supported by the body 11.

One end of the coil-shaped spring 145 is connected to the brake pedal arm 142. The other end of the spring 145 is fixed to the body 11. The brake pedal arm 142 is biased in a direction in which a distal end portion, which is a rear end portion thereof, is lifted by an elastic force of the spring 145.

The pedal body 143 has a rectangular plate shape and is attached to a distal end portion of the brake pedal arm 142.

When the pedal body 143 of the brake pedal 141 is stepped on by the foot of the operator, the brake pedal arm 142 rotates against the elastic force of the spring 145, and the brake 146 mechanically coupled to the brake pedal arm 142 operates. By the operation of the brake 146, for example, a braking force is applied from the brake 146 to the second intermediate shaft 105 (see fig. 8). Thereby, the second intermediate shaft 105 of the drive transmission system 32 is braked, the left and right traveling devices 12 are braked, and the stopped state of the machine body 11 is maintained.

< Electrical Structure >

Fig. 10 is a block diagram showing a main part of an electrical structure of the combine harvester 1.

The combine harvester 1 is mounted with a single main ECU (Electronic Control Unit) 151 for overall unified Control and a plurality of ECUs for individual specific Control. The ECU for individual specific control includes, for example, the travel control ECU152 for controlling the left HST33 and the right HST34, and the like. Each ECU including the main ECU151 and the travel control ECU152 is configured to include a Micro Controller Unit (MCU).

The main ECU151 is communicably connected to each ECU for individual specific control, i.e., the travel control ECU152 and the like.

The travel control ECU152 is connected to: a main shift operation amount sensor 153 that outputs a detection signal according to the operation amount (operation position) of the main shift lever 21, a steering lever sensor 154 that outputs a detection signal according to the operation position of the steering lever 22, and a brake sensor 155 that outputs a detection signal according to the operation amount of the brake pedal 141 are input to the travel control ECU 152.

Further, although not shown, the travel control ECU152 is connected to: a current sensor that outputs detection signals corresponding to the values of the currents supplied to the pressure control valves 61 and 63 included in the left HST33 and the right HST34, respectively, and a swash plate position sensor that outputs detection signals corresponding to the positions (inclination angles) of the swash plates of the hydraulic pumps 41 included in the left HST33 and the right HST34, respectively, are input to the travel control ECU 152.

The main ECU151 receives information acquired from detection signals of various sensors and the like by each ECU for individual specific control, and transmits commands and information necessary for control of each ECU to each ECU.

The travel control ECU152 controls the pressure control valves 61 and 63, the low-speed switching valve 76, the high-speed switching valve 77, and the like included in the left HST33 and the right HST34, respectively, in order to control the left HST33 and the right HST34 based on information obtained from the detection signals of the main shift operation amount sensor 153, the steering lever sensor 154, the brake sensor 155, the current sensor, and the swash plate position sensor.

< braking control >

Fig. 11 is a flowchart showing a flow of the brake control.

During driving of the left HST33 and the right HST34, the travel control ECU152 executes brake control.

In the braking control, it is determined whether or not an operation of depressing the brake pedal 141 (hereinafter, simply referred to as "braking operation") is performed (step S11). Until the braking operation is performed, the braking control does not proceed to the subsequent steps (no at step S11).

When the brake operation is performed (yes in step S11), the operation amount of the brake operation, that is, the amount of depression of the brake pedal 141 is acquired from the detection signal of the brake sensor 155, and the target swash plate position, which is the target position of the pump swash plate of the hydraulic pump 41 according to the operation amount, is set according to a predetermined calculation formula (step S12). The target swash plate position is set such that the position of the pump swash plate of each hydraulic pump 41 of the left HST33 and the right HST34 approaches the stop position at the inclination angle of 90 ° as the operation amount of the brake operation becomes larger.

Note that a map in which the relationship between the operation amount of the brake pedal 141 and the target swash plate position is determined may be stored in the memory of the travel control ECU152, and the target swash plate position corresponding to the operation amount of the brake pedal 141 may be set based on the map.

When the target swash plate position of each hydraulic pump 41 is set, the current supplied to the pressure control valves 61 and 63 provided in association with each hydraulic pump 41 is feedback-controlled based on the deviation between the target swash plate position and the actual position of the swash plate of each hydraulic pump 41 obtained from the detection signal of the swash plate position sensor (step S13: HST stop control). As a result, the position of the swash plate of each hydraulic pump 41 approaches the stop position inclined at an angle of 90 °.

Thereafter, the position of the swash plate of each hydraulic pump 41 is at the stop position inclined at an angle of 90 °, and it is determined whether each hydraulic motor 42 of the left HST33 and the right HST34 is stopped (step S14). When the hydraulic motors 42 are not stopped (no in step S14), the operation amount of the brake operation is newly acquired, and the target swash plate position corresponding to the operation amount is set (S12). Then, the current supplied to the pressure control valves 61, 63 provided corresponding to the respective hydraulic pumps 41 is feedback controlled in accordance with the deviation between the target swash plate position and the actual position of the pump swash plate of the respective hydraulic pumps 41 (step S13).

When the discharge of the hydraulic pressure from each hydraulic pump 41 is stopped and the hydraulic motors 42 of the left HST33 and the right HST34 are stopped (yes in step S14), the position of the swash plate of each hydraulic pump 41 is at the position of the inclination angle of 90 °, it is determined whether or not the main shift lever 21 is at the neutral position (step S15).

When the main shift lever 21 is not located at the neutral position (no in step S15), the change of the position of the swash plate of each hydraulic pump 41 is prohibited (step S16). When the main shift lever 21 is at the neutral position (yes at step S15), the change of the position of the swash plate of each hydraulic pump 41 is permitted (step S17), and the brake control ends. Thus, when the main shift lever 21 is located at a position other than the neutral position, the position of the swash plate of each hydraulic pump 41 is held at the stop position inclined at an angle of 90 ° until the main shift lever 21 returns from the position to the neutral position, and each hydraulic motor 42 is not driven.

< Effect >

As described above, the left HST33 and the right HST34 are of the following structure: the hydraulic pump 41 of the swash plate type and the hydraulic motor 42 supplied with fluid from the hydraulic pump 41 are provided, and power of the hydraulic motor 42 is output, which is shifted in accordance with the flow direction and flow rate of the fluid supplied from the hydraulic pump 41 to the hydraulic motor 42. The pair of left and right traveling devices 12 supporting the machine body 11 are driven by power output from the left HST33 and the right HST 34.

A brake pedal 141 is provided to be operable on the body 11. The brake pedal 141 is mechanically coupled to the brake 146, and the braking force generated by the brake 146 acts on the traveling device 12 in response to the operation of the brake pedal 141. When the brake pedal 141 is operated, the operation is detected by the brake sensor 155. When the operation of the brake pedal 141 is detected, the position of the swash plate of the hydraulic pump 41 is controlled to the stop position side where the fluid is not discharged from the hydraulic pump 41. Therefore, without using the conventional link mechanism, the discharge of the fluid from the hydraulic pump 41 can be stopped and the hydraulic motor 42 can be stopped satisfactorily when the brake 146 is operated. In addition, since the link mechanism is not used, the link mechanism does not need to be adjusted, and the time and labor required for adjusting the link mechanism can be saved.

In a normal state, when the main shift lever 21 is operated from the neutral position to one side or the other side, the swash plate position of the hydraulic pump 41 is controlled so that power in the forward direction or the reverse direction is output from the hydraulic motor 42. Therefore, when the main shift lever 21 is positioned at one side or the other side from the neutral position after the position of the swash plate of the hydraulic pump 41 is positioned at the stop position by the operation of the brake pedal 141, the hydraulic motor 42 outputs power in the forward or reverse direction to start the forward or reverse movement of the machine body 11 when the brake 146 is released. When the operator forgets to return the main shift lever 21 to the neutral position, the forward or backward movement of the machine body 11 is not expected by the operator.

Therefore, even if the operation of the brake pedal 141 is released after the hydraulic motor 42 is stopped by the operation of the brake pedal 141, the position of the swash plate is not changed from the stop position until the main shift lever 21 returns to the neutral position. This can suppress the forward or backward movement of the body 11, which is not intended by the operator, when the operator releases the operation of the brake pedal 141.

< braking control >

Fig. 12 is a flowchart showing another flow of the brake control.

In the above embodiment, the brake sensor 155 that outputs a detection signal according to the operation amount of the brake operation is connected to the travel control ECU152, and the travel control ECU152 sets the target swash plate position according to the operation amount of the brake operation. For example, instead of the brake sensor 155, a brake switch may be used that outputs an on signal as a detection signal when the operation amount of the brake pedal 141 is equal to or greater than a certain amount and outputs an off signal as a detection signal when the operation amount of the brake pedal 141 is less than the certain amount.

In the case of using the brake switch, the brake control shown in fig. 12 may be executed instead of the brake control shown in fig. 11.

In the braking control shown in fig. 12, it is determined whether or not a braking operation is performed, that is, whether or not the brake switch is on (step S21). Until the brake switch is turned on, the brake control does not proceed to the subsequent steps (no at step S21).

When the brake switch is turned on by the brake operation (yes in step S21), the target swash plate positions of the pump swash plates of the hydraulic pumps 41 of the left HST33 and the right HST34 are set. The target swash plate position is updated at a fixed cycle, and is set at a position close to the stop position of the inclination angle 90 ° at each update. Then, the current supplied to the pressure control valves 61 and 63 provided corresponding to the respective hydraulic pumps 41 is feedback controlled based on the deviation between the target swash plate position and the actual position of the swash plate of the respective hydraulic pumps 41 obtained from the detection signal of the swash plate position sensor (step S22: HST scanning (sweep) stop control). As a result, the position of the swash plate of each hydraulic pump 41 approaches the stop position at the inclination angle of 90 ° after a certain time.

Thereafter, the position of the swash plate of each hydraulic pump 41 is at the stop position at the inclination angle of 90 °, and when each hydraulic motor 42 of the left HST33 and the right HST34 is stopped, it is determined whether the main shift lever 21 is at the neutral position (step S23).

When the main shift lever 21 is not located at the neutral position (no in step S23), the change of the position of the swash plate of each hydraulic pump 41 is prohibited (step S24). When the main shift lever 21 is at the neutral position (yes at step S23), the change of the position of the swash plate of each hydraulic pump 41 is permitted (step S25), and the brake control ends. Thus, when the main shift lever 21 is located at a position other than the neutral position, the position of the swash plate of each hydraulic pump 41 is held at the stop position inclined at an angle of 90 ° until the main shift lever 21 returns from the position to the neutral position, and each hydraulic motor 42 is not driven.

By executing this brake control, the same operational effects as in the case of the above-described embodiment can be obtained.

In the configuration using the brake sensor 155, the brake control shown in fig. 12 may be executed. In this case, if the operation amount of the braking operation obtained from the detection signal of the brake sensor 155 is a certain amount or more, it is determined that the braking operation (on) is performed, and if the operation amount is less than a predetermined amount, it is determined that the braking operation (off) is not performed.

< modification example >

While the embodiments of the present invention have been described above, the present invention can be implemented in other embodiments.

For example, although the combine harvester 1 is proposed as an example of a work vehicle, the present invention is not limited to the combine harvester 1, and may be applied to a work vehicle other than the combine harvester 1, such as a harvester that harvests vegetables such as carrots, radishes, green beans, and cabbage.

In the above configuration, various design changes can be made within the scope of items described in the claims.