阅读说明：本技术 工程机械 (Construction machine ) 是由 斋藤哲平 高桥宏政 平工贤二 于 2019-11-05 设计创作，主要内容包括：本发明提供一种工程机械,其搭载驱动单杆式液压缸筒及回转液压马达的液压闭合回路,且回转减速响应性良好。在分别以闭合回路驱动单杆式液压缸筒及回转用液压马达的工程机械中,第二冲泄阀全开时的从上述第二冲泄阀到油罐的最小流路面积比第一冲泄阀全开时的从上述第一冲泄阀到上述油罐的最小流路面积小。(The invention provides a construction machine which carries a hydraulic closed circuit for driving a single-rod hydraulic cylinder and a rotary hydraulic motor and has good rotary deceleration response. In a construction machine in which a single-rod hydraulic cylinder and a hydraulic motor for rotation are driven in a closed circuit, the minimum flow path area from a second flushing valve to an oil tank when the second flushing valve is fully opened is smaller than the minimum flow path area from a first flushing valve to the oil tank when the first flushing valve is fully opened.)

1. A construction machine is provided with:

a lower traveling body;

an upper revolving structure which is rotatably attached to the lower traveling structure;

a working device provided in the upper slewing body;

an oil tank that stores working oil;

a single-rod hydraulic cylinder that drives the working device;

a hydraulic motor for rotation that drives the upper rotation body;

an operation device that instructs operations of the working device and the upper slewing body;

a first closed-circuit pump composed of two tilt pumps;

a second closed-circuit pump composed of two tilt pumps;

a cylinder closed circuit that connects the first closed circuit pump and the single rod hydraulic cylinder in a closed circuit shape;

a swing closed circuit connecting the second closed circuit pump and the swing hydraulic motor in a closed circuit form;

a first flushing/discharging valve that communicates a flow path on a low-pressure side of the cylinder closed circuit with the oil tank;

a second flushing/discharging valve for communicating a flow path on a low-pressure side of the slewing closed circuit with the oil tank;

a first switching valve that switches between connection and disconnection of the first closed circuit pump and the single rod hydraulic cylinder; and

a second switching valve that switches between connection and disconnection of the second closed circuit pump and the hydraulic motor for rotation,

opening and closing of the first and second switching valves and discharge flow rates of the first and second closed-circuit pumps are controlled in accordance with an operation signal input from the operation device,

the above-mentioned working machine is characterized in that,

the minimum flow path area from the second flushing valve to the oil tank when the second flushing valve is fully opened is smaller than the minimum flow path area from the first flushing valve to the oil tank when the first flushing valve is fully opened.

2. The work machine of claim 1,

the first flushing and discharging valve comprises: a first manifold; a first spool valve disposed in the first manifold; a first spring disposed in the first manifold and applying a force to the first spool; and a first gasket disposed between the first spool and the first spring,

the second flushing and discharging valve comprises: a second manifold; a second spool valve disposed in the second manifold; a second spring disposed in the second manifold and biasing the second spool; and a second gasket disposed between the second spool and the second spring,

the thickness of the second spacer in the axial direction of the spool is larger than the thickness of the first spacer in the axial direction of the spool.

3. The work machine of claim 1,

the first flushing and draining valve has a first manifold and a first slide valve arranged in the first manifold,

the second flushing and discharging valve has a second manifold and a second slide valve arranged in the second manifold,

a first tank connection passage for connecting a low-pressure-side passage of the closed cylinder circuit to the tank is formed in an intermediate portion of the first spool valve,

a second tank connection flow path for connecting a flow path on a low-pressure side of the slewing closed circuit to the tank is formed in an intermediate portion of the second spool valve,

the width of the second tank connection passage in the axial direction of the spool valve is smaller than the width of the first tank connection passage in the axial direction of the spool valve.

4. The work machine of claim 1,

further comprises a throttle part provided in a flow path connecting the second flush valve and the oil tank,

the second flushing and discharging valve has the same structure as the first flushing and discharging valve.

Technical Field

The present invention relates to a construction machine such as a hydraulic excavator, and more particularly to a construction machine in which a single-rod hydraulic cylinder and a hydraulic motor for rotation are driven by a hydraulic closed circuit.

Background

In recent years, energy saving has become an important research and development project in construction machines such as hydraulic excavators and wheel loaders. For energy saving of construction machines, energy saving of a hydraulic system itself is important, and a hydraulic closed circuit (hereinafter, a closed circuit) in which a hydraulic pump and a hydraulic actuator are connected in a closed circuit and the speed of the hydraulic actuator is directly controlled by flow rate control of the hydraulic pump is studied. This system has no pressure loss due to the conventional flow control valve, and the pump discharges only a required flow rate, so that the energy loss is small. Further, the potential energy of the hydraulic actuator and the kinetic energy at the time of deceleration can be regenerated. Therefore, energy can be further saved.

Patent document 1 discloses a conventional art of a construction machine having a closed circuit. Patent document 1 describes the following structure: the hydraulic pump is connected to an actuator (boom cylinder, rotary motor, etc.) in a closed circuit, and the operating speed of the actuator is controlled by swash plate control of the hydraulic pump.

The closed circuit described in patent document 1 is provided with a flush valve. The flushing/discharging valve is a valve for communicating a low-pressure-side flow path in the closed circuit with the oil tank in order to maintain the pressure oil in the closed circuit, and has a function of discharging excess oil on the low-pressure side to the oil tank.

In patent document 1, when the boom cylinder is contracted, the pump sucks the hydraulic oil from the head side of the boom cylinder and discharges the hydraulic oil to the rod side. At this time, the flush valve is switched to connect the rod side of the boom cylinder, which becomes the low pressure side, and the oil tank. As a result, the hydraulic oil discharged from the pump flows into the rod side of the boom cylinder, while the hydraulic oil having a difference in the pressure receiving area of the boom cylinder of the single-rod cylinder is discharged from the flush valve to the oil tank.

On the other hand, in the case of accelerating the rotary body, the pump sucks the hydraulic oil from one input/output side of the rotary motor and discharges the hydraulic oil to the other input/output side. At this time, the flush valve is switched to connect the suction side of the pump, which becomes the low pressure side, to the oil tank. Here, when the discharge flow rate of the pump is reduced to decelerate the rotation body, the rotation motor continues to discharge the working oil due to the inertial energy of the rotation body, so that the pump suction side becomes high pressure, and the flushing valve is switched so as to connect the pump discharge side, which is the low pressure side of the closed circuit, to the oil tank. Thereby, brake pressure acts on the rotary motor, and the rotary body is decelerated.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2016 + 017602

Disclosure of Invention

Problems to be solved by the invention

In the case of a normal single-rod cylinder, the ratio of the pressure-receiving area on the head side to the rod side is approximately 2: 1, therefore, in a closed circuit (hereinafter, a cylinder closed circuit) that drives the single rod cylinder, about half of the hydraulic oil discharged from the pump is discharged from the flushing valve to the tank. Therefore, in the closed cylinder circuit, in order to reduce the pressure loss of the flush valve, it is necessary to increase the size of the flush valve.

On the other hand, since the slewing motor does not have a pressure receiving area difference as in the case of a single-rod cylinder, the flow rate discharged from the flush valve to the tank in a closed circuit (hereinafter, slewing closed circuit) that drives the slewing motor is lower than 1/10 or less than that in a cylinder closed circuit. Here, in the case where the flush valve having the same shape is used for the cylinder closed circuit and the swing closed circuit from the viewpoint of cost and the like, the increase in the pressure on the pump suction side (low pressure side) is delayed at the start of the swing deceleration because the pressure loss of the flush valve in the swing closed circuit is small. This delays the timing of switching the flush valve, and takes time until the pressure on the pump suction side reaches the relief pressure (brake pressure). As a result, the response of the slewing deceleration is reduced, and the problem of deterioration in operability is caused.

The present invention has been made in view of the above problems, and an object thereof is to provide a construction machine equipped with a hydraulic closed circuit for driving a single-rod hydraulic cylinder and a turning hydraulic motor, and having good turning deceleration response.

Means for solving the problems

In order to achieve the above object, the present invention provides a construction machine including: a lower traveling body; an upper revolving structure which is rotatably attached to the lower traveling structure; a working device provided in the upper slewing body; an oil tank that stores working oil; a single-rod hydraulic cylinder that drives the working device; a hydraulic motor for rotation that drives the upper rotation body; an operation device that instructs operations of the working device and the upper slewing body; a first closed-circuit pump composed of two tilt pumps; a second closed-circuit pump composed of two tilt pumps; a cylinder closed circuit that connects the first closed circuit pump and the single rod hydraulic cylinder in a closed circuit shape; a swing closed circuit connecting the second closed circuit pump and the swing hydraulic motor in a closed circuit form; a first flushing/discharging valve that communicates a flow path on a low-pressure side of the cylinder closed circuit with the oil tank; a second flushing/discharging valve for communicating a flow path on a low-pressure side of the slewing closed circuit with the oil tank; a first switching valve that switches between connection and disconnection of the first closed circuit pump and the single rod hydraulic cylinder; and a second switching valve that switches communication and disconnection between the second closed circuit pump and the hydraulic motor for rotation, and controls opening and closing of the first switching valve and the second switching valve and discharge flow rates of the first closed circuit pump and the second closed circuit pump in accordance with an operation signal input from the operation device, wherein in the construction machine, a minimum flow path area from the second flushing valve to the oil tank when the second flushing valve is fully open is smaller than a minimum flow path area from the first flushing valve to the oil tank when the first flushing valve is fully open.

According to the present invention configured as described above, when the hydraulic oil is discharged from the pump suction side to the tank through the flushing/draining valve (second flushing/draining valve) for the swing closed circuit at the start of the swing deceleration, a large pressure loss occurs in the second flushing/draining valve, and the pressure in the flow passage on the pump suction side rapidly rises and the second flushing/draining valve rapidly switches. Accordingly, the time until the pressure of the pump suction side flow passage reaches the relief pressure can be shortened, and therefore, the slewing deceleration response is improved, and a good slewing operability can be obtained.

Effects of the invention

According to the present invention, in the construction machine in which the single-rod hydraulic cylinder and the swing hydraulic motor are driven by the hydraulic closed circuit, the swing deceleration response is improved, and the good swing operability can be obtained.

Drawings

Fig. 1 is a side view of a hydraulic excavator according to a first embodiment of the present invention.

Fig. 2 is a hydraulic circuit diagram showing a hydraulic drive apparatus according to a first embodiment of the present invention.

Fig. 3 is a schematic diagram showing an internal structure of a flush valve provided in a cylinder closed circuit according to a first embodiment of the present invention.

Fig. 4 is a schematic diagram showing an internal structure of a flush valve provided in a slewing closed circuit according to a first embodiment of the present invention.

Fig. 5 is a diagram showing an example of an operation of a conventional swing closed circuit.

Fig. 6 is a diagram showing an example of the operation of the swing closed circuit according to the first embodiment of the present invention.

Fig. 7 is a schematic diagram showing an internal structure of a flushing and discharging valve provided in a slewing closed circuit according to a second embodiment of the present invention.

Fig. 8 is a hydraulic circuit diagram showing a hydraulic drive apparatus according to a third embodiment of the present invention.

Detailed Description

Hereinafter, a hydraulic excavator will be described as an example of a construction machine according to an embodiment of the present invention with reference to the drawings. The present invention is applicable to all construction machines including a plurality of closed hydraulic circuits in which a closed circuit pump and a hydraulic cylinder are connected via a switching valve in a closed circuit form, and including a closed slewing circuit, and is not limited to hydraulic excavators.

Example 1

A hydraulic excavator according to a first embodiment of the present invention will be described.

(vehicle body main body)

Fig. 1 is a side view showing a hydraulic excavator according to the present embodiment.

In fig. 1, a hydraulic excavator 100 includes: a lower traveling structure 103 having crawler-type traveling devices 8a and 8b on both sides in the left-right direction; and an upper revolving structure 102 which is rotatably mounted on the lower traveling structure 103. The lower traveling structure 103 and the upper revolving structure 102 constitute a body main body of the hydraulic excavator 100.

The upper revolving structure 102 is provided with a cab 101 as an operation room on which an operator rides. The lower traveling structure 103 and the upper revolving structure 102 can revolve via a revolving motor 7 as a hydraulic motor for revolving. A base end portion of a front working machine 104 as a working device for performing, for example, excavation work is rotatably attached to the front side of the upper revolving structure 102. Here, the front side refers to a direction (left direction in fig. 1) in which an operator riding on cab 101 faces.

The front work implement 104 includes a boom 2 having a base end portion connected to the front side of the upper revolving structure 102 so as to be rotatable in the vertical direction. The boom 2 is operated via a boom cylinder 1 which is a single-rod hydraulic cylinder. The boom cylinder 1 has a boom rod 1b whose tip end is connected to the upper slewing body 102 and a boom head 1a whose base end is connected to the boom 2. A base end portion of the boom 4 is connected to a front end portion of the boom 2 so as to be rotatable in the vertical or front-rear direction. The boom 4 is operated via a boom cylinder 3 as a single rod hydraulic cylinder. The boom cylinder 3 has a boom rod 3b whose tip end is connected to the boom 4, and a boom head 3a whose base end is connected to the boom 2. A base end portion of the bucket 6 is connected to a front end portion of the boom 4 so as to be rotatable in the vertical or front-rear direction. The bucket 6 operates via a bucket cylinder 5 which is a single-rod hydraulic cylinder. The bucket cylinder 5 has a bucket rod 5b whose tip end is coupled to the bucket 6, and a bucket head 5a whose base end is coupled to the arm 4. An operation lever 30 (shown in fig. 2) as an operation member for operating the boom 2, the arm 4, the bucket 6, and the upper revolving structure 102 constituting the front work machine 104 is disposed in the cab 101.

(Hydraulic drive device)

Fig. 2 is a schematic diagram showing a hydraulic drive device for driving the hydraulic shovel 100. In fig. 2, only the parts related to the driving of the boom cylinder 1 and the swing motor 7 are illustrated, and the parts related to the driving of other actuators are omitted.

(Cylinder barrel, motor)

The hydraulic drive device 105 includes a boom cylinder 1, a swing motor 7, a closed-circuit pump 11 that drives the boom cylinder 1, and a closed-circuit pump 12 that drives the swing motor 7. The turning motor 7 includes a pair of input/output ports 7a and 7 b.

(Pump)

The closed circuit pumps 11 and 12 are driven by receiving power from the engine 9 via the transmission device 10. The closed circuit pumps 11 and 12 are provided with a swash plate mechanism having a pair of input/output ports as a flow rate adjusting device, and regulators 11a and 12a for adjusting the pump displacement by adjusting the inclination angle of the swash plate. The regulators 11a, 12a control the discharge flow rates and the discharge directions of the closed-circuit pumps 11, 12 based on pump discharge flow rate command values received from the pump valve control device 40 via control signal lines.

(closed Circuit, switching valve)

The two discharge ports of the closed circuit pump 11 are connected to the boom cylinder 1 via the flow passages 21 and 22 and the switching valve 23, and constitute a cylinder closed circuit C1. The two discharge ports of the closed circuit pump 12 are connected to the swing motor 7 via the flow paths 24 and 25 and the switching valve 26, and constitute a swing closed circuit C2. The switching valve 23 switches between the flow paths 21 and 22 and blocks them in response to an opening/closing control command received from the pump valve control device 40 via a control signal line. The switching valve 26 switches between the flow paths 24 and 25 and blocks them in response to an opening/closing control command received from the pump valve control device 40 via a control signal line.

(flush valve)

The flush valve 31 is connected to the flow paths 21 and 22 and the oil tank 33. The flushing/discharging valve 31 is switched so as to communicate the lower pressure one of the flow paths 21 and 22 with the oil tank 33. The flush valve 32 is connected to the flow paths 24 and 25 and the oil tank 33. The flushing valve 32 is also switched so as to communicate the lower pressure one of the flow paths 24 and 25 with the oil tank 33.

(check valve, overflow valve)

The check valve 34a is provided to connect the oil tank 33 and the flow paths 21, 22. When the pressure of the flow passages 21, 22 is lower than the pressure of the oil tank 33, the working oil is supplied from the oil tank 33 to the flow passages 21, 22. The check valve 34b is provided to connect the oil tank 33 and the flow paths 24, 25. When the pressure of the flow passages 24 and 25 is lower than the pressure of the oil tank 33, the working oil is supplied from the oil tank 33 to the flow passages 24 and 25.

Relief valves 37a, 37b are provided to connect the oil tank 33 and the flow paths 21, 22. The relief valves 37a, 37b, 38a, and 38b function as relief valves that open when the pressure in the flow passages 21, 22, 24, and 25 exceeds a predetermined pressure, and discharge the hydraulic oil to the tank 33.

(Pump valve control device)

The pump valve control device 40 is connected to the boom 30a and the swing lever 30b as the operation lever 30 via signal lines, and is connected to the selector valves 23 and 26 and the regulators 11a and 12a of the closed-circuit pumps 11 and 12 via control signal lines. The pump valve control device 40 determines the discharge flow rate of the closed circuit pumps 11 and 12 based on the operation amounts of the boom lever 30a and the swing lever 30b, and outputs a control signal corresponding to the discharge flow rate to the regulators 11a and 12 a. When detecting that the boom lever 30a and the swing lever 30b are operated, the pump valve control device 40 opens the switching valves 23 and 26, and controls the drive of the boom cylinder 1 and the swing motor 7 by causing the hydraulic oil discharged from the closed-circuit pumps 11 and 12 to flow into the boom cylinder 1 and the swing motor 7, respectively. The discharge direction of the hydraulic oil of the closed circuit pumps 11 and 12 is determined by the operation direction of the boom lever 30a and the swing lever 30 b. In the present embodiment, the description is given by taking as an example a controller in which the pump valve control device 40 is configured by an electric circuit, but the pump valve control device 40 may be configured by a hydraulic circuit.

(Structure of the invention)

Next, the structure of the flush valve of the present embodiment will be described.

(flushing and discharging valve structure)

Fig. 3 shows an example of the internal structure of the flush valve 31 for the cylinder closed circuit C1. The manifold 31a is provided with channels 31b, 31c, and 31 d. The flow paths 21 and 22 and the oil tank 33 in fig. 2 are connected to the flow paths 31b, 31c, and 31d, respectively. A spool 31e having a flow path 31h formed therein, spacers 31g1, 31g2, a spring 31f1, and a spring 31f2 are disposed in the manifold 31 a. When pressure oil is introduced from the flow passages 31b and 31c to the oil chambers having the springs 31f1 and 31f2, the spool valve 31e moves to either the left or right depending on the magnitude of the pressure in the oil chambers. For example, when the pressure of the passage 31b is higher than that of the passage 31c, the oil chamber having the spring 31f1 becomes high pressure, and therefore, the spool valve 31e moves rightward. By moving the spool 31e rightward by the stroke amount 31i, the low-pressure side flow passage 32c is connected to the flow passage 32d via the flow passage 32 h.

Fig. 4 shows an example of the internal structure of the flushing valve 32 for the swing closed circuit C2. The manifold 32a is provided with channels 32b, 32c, and 32 d. The flow paths 24 and 25 and the oil tank 33 in fig. 2 are connected to the flow paths 32b, 32c, and 32d, respectively. A spool 32e having a flow path 32h formed therein, spacers 32g1, 32g2, a spring 32f1, and a spring 32f2 are disposed in the manifold 32 a. The flushing valve 32 operates in the same manner as the flushing valve 31 of fig. 3. In fig. 4, the amount of movement of the spool 32e from the neutral position is referred to as a stroke amount 32 i.

Here, in the flushing valve 32 for the swing closed circuit C2 of fig. 4, the thicknesses T2 of the shims 32g1 and 32g2 are made larger than the thicknesses T1 of the shims 31g1 and 31g2 of fig. 3 in order to make the throttle portion narrower than the flushing valve 31 (shown in fig. 3) for the cylinder closed circuit C1. Accordingly, the stroke amount 32i of the spool 32e in the case where a pressure difference occurs between the flow path 32b and the flow path 32c in fig. 4 is smaller than the stroke amount 31i in fig. 3, and therefore the maximum opening area between the flow path 32b or the flow path 32c and the flow path 32h becomes smaller.

(conventional swing action)

Next, the operation of the swing motor 7 driven by a conventional hydraulic drive device will be described with reference to fig. 2. Here, in the conventional hydraulic drive apparatus, the structure of the flushing valve 32 for the swing closed circuit C2 is the same as that of the flushing valve 31 (shown in fig. 3) for the cylinder closed circuit C1 in the hydraulic drive apparatus 105 shown in fig. 2.

(stop-lever input-rotation acceleration)

When the operator operates the swing lever 30b from the neutral position to a predetermined operation amount and applies an input for commanding the rotation drive of the swing motor 7, the pump valve control device 40 receives the operation amount of the swing lever 30b via the signal line. The pump valve control device 40 sets a control command value for switching the switching valve 26 to the open state in order to connect the closed circuit pump 12 to the swing motor 7, based on the received operation amount of the swing lever 30 b. The pump valve control device 40 sets the pump discharge flow rate command value of the closed circuit pump 12 to a value corresponding to the operation amount of the rotary lever 30 b. The pump valve control device 40 outputs a control command value and a pump discharge flow rate command value to the switching valve 26 and the regulator 12a of the closed-circuit pump 12 via a control signal line.

Thereby, the switching valve 26 is opened, and the hydraulic oil discharged from the closed circuit pump 12 flows into the input/output port 7a of the swing motor 7 via the switching valve 26 and the flow path 24, and drives the swing motor 7. The hydraulic oil that has flowed out of the input/output port 7b is sucked into the closed circuit pump 12 via the flow path 25 and the switching valve 26.

At this time, since the pressure oil discharged from the closed circuit pump 12 accelerates the inertial body connected to the upper revolving structure 102 (shown in fig. 1) of the revolving motor 7, the pressure of the flow path 24, which is the working oil discharge side of the closed circuit pump 12, is higher than the pressure of the flow path 25. The flush valve 32 is switched to connect the low-pressure-side flow path 25 and the oil tank 33.

(rotation center-rod center-rotation deceleration)

When the operator operates the swing lever 30b from a constant operation amount to the neutral position and inputs an instruction to stop the swing motor 7, the pump valve control device 40 receives the operation amount of the swing lever 30b via a signal line. The pump valve control device 40 sets a control command value for switching the switching valve 26 to the closed state in order to connect the closed circuit pump 12 to the swing motor 7, based on the received operation amount of the swing lever 30 b. The pump valve control device 40 sets the pump discharge flow rate command value of the closed circuit pump 12 to a value corresponding to the operation amount of the rotary lever 30 b. When the rotary lever 30b is in the neutral state, the pump discharge flow rate command value is 0. The pump valve control device 40 outputs a control command value and a pump discharge flow rate command value to the switching valve 26 and the regulator 12a of the closed-circuit pump 12 via a control signal line.

Thereby, the switching valve 26 is closed, and the closed circuit pump 12 stops the discharge of the hydraulic oil, but the rotation motor 7 continues to rotate due to the inertial force of the upper rotation body 102 (shown in fig. 1) connected to the rotation motor 7, and therefore the rotation motor 7 discharges the hydraulic oil from the input/output port 7b to the flow path 25. At this time, the flushing valve 32 is kept at the switching position at the start of rotation, and therefore, the flow path 25 and the oil tank 33 are connected. Therefore, the hydraulic oil flowing out of the input/output port 7b is discharged to the oil tank 33 via the flow path 25 and the flush valve 32.

The state in the swing closed circuit C2 at this time will be described with reference to fig. 5. When the operator operates the rotary lever 30b from a certain operation amount to the neutral position, the flow rate of the hydraulic oil flowing to the flush valve 32 increases. When the flow rate passing through the flush valve 32 increases, the pressure in the flow path 25 rises due to pressure loss. On the other hand, since the working oil in the flow path 24 is sucked into the input/output port 7a of the swing motor 7, the pressure in the flow path 24 is less likely to decrease. When the pressure of the flow path 24 becomes lower than the pressure of the flow path 25, the flush valve 32 is switched to connect the flow path 24 and the oil tank 33. Then, the hydraulic oil flowing out of the input/output port 7b of the swing motor 7 flows into the flow path 25, and the pressure in the flow path 25 further increases. When the pressure of the flow path 25 rises to a preset set pressure (hereinafter, relief pressure) of the relief valve 38b, the relief valve 38b opens, and the hydraulic oil is discharged to the oil tank 33. When the pressure in the flow path 25 exceeds the pressure in the flow path 24 and reaches the relief pressure, the rotation speed of the turning motor 7 is reduced, and after a certain time, the turning motor 7 is stopped.

(case of flush valve of the present invention)

Next, the operation of the swing motor 7 driven by the hydraulic drive device 105 according to the present embodiment will be described with reference to fig. 2.

(stop-lever input-rotation acceleration)

The operation of the swing motor 7 when the operator operates the swing lever 30b from the neutral position to a predetermined operation amount is the same as described above, and therefore, the description thereof is omitted.

(rotation center-rod center-rotation deceleration)

When the operator operates the swing lever 30b from a constant operation amount to the neutral position and inputs an instruction to stop the swing motor 7, the pump valve control device 40 receives the operation amount of the swing lever 30b via a signal line. The pump valve control device 40 sets a control command value for switching the switching valve 26 to the closed state in order to connect the closed circuit pump 12 to the swing motor 7, based on the received operation amount of the swing lever 30 b. The pump valve control device 40 sets the pump discharge flow rate command value of the closed circuit pump 12 to a value corresponding to the operation amount of the rotary lever 30 b. When the rotary lever 30b is in the neutral state, the pump discharge flow rate command value is 0. The pump valve control device 40 outputs a control command value and a pump discharge flow rate command value to the switching valve 26 and the regulator 12a of the closed-circuit pump 12 via a control signal line.

Thereby, the switching valve 26 is closed, and the closed circuit pump 12 stops the discharge of the hydraulic oil, but the rotation motor 7 continues to rotate due to the inertial force of the inertial body connected to the upper rotation body 102 (shown in fig. 1) of the rotation motor 7, and therefore the rotation motor 7 discharges the hydraulic oil from the input/output port 7b to the flow path 25. At this time, the flushing valve 32 is kept at the switching position at the start of rotation, and therefore the flow path 25 and the oil tank 33 are connected. Therefore, the hydraulic oil flowing out of the input/output port 7b is discharged to the oil tank 33 via the flow path 25 and the flush valve 32.

Next, a state in the swing closed circuit C2 will be described with reference to fig. 6. When the operator operates the rotary lever 30b from a certain operation amount to the neutral position, the flow rate of the flush valve 32 increases.

In the structure of the flush valve 32 shown in fig. 4, the stroke amount 32i is small and the throttle portion is narrow, compared to the structure of fig. 3 described above, and therefore, the pressure rise in the flow passage 25 due to the pressure loss is early relative to the increase in the flow rate passing through the flush valve 32. As a result, the flush valve 32 is switched earlier than in the case of applying the structure of fig. 3 with respect to the operation of the rotary rod 30 b.

Then, as shown in fig. 6, when the flow path 25 exceeds the pressure of the flow path 24 and reaches the relief pressure, the rotation speed of the swing motor 7 is reduced and is stopped after a certain time.

(effect of the invention)

In the structure of the flushing valve 32 shown in fig. 4, the throttling portion is narrower than the structure of fig. 3 applied to the flushing valve 31, and therefore, the pressure rise of the flow path 25 with respect to the flow rate passing through the flushing valve 32 shown in fig. 6 is larger than that of the conventional example shown in fig. 5. Accordingly, the timing of the pressure rise in the flow path 25 is earlier than in the conventional example (shown in fig. 5) and the start of deceleration of the swing motor 7 is also earlier than in the return operation of the swing lever 30b to the neutral position. That is, according to the present invention, the deceleration response of the swing motor 7 is improved.

In the hydraulic excavator 100, the deceleration stop performance is important for the swing operation of the upper swing body 102. For example, when loading excavated soil into a vehicle such as a dump truck, the excavator 100 must be rotated after excavation to carry the soil onto the dump truck without scattering, but in this case, if the braking response, which is a deceleration response of the rotation, is poor, the rotation cannot be stopped on the dump truck, the rotation is excessive, and the work efficiency is reduced.

The present invention improves the braking responsiveness of the swing closed circuit, facilitates stopping the swing on the dump truck, and improves the work efficiency.

In a first embodiment of the present invention, a construction machine 100 includes: a lower traveling structure 103; an upper revolving structure 102 which is rotatably attached to a lower traveling structure 103; a working device 104 provided in the upper slewing body 102; an oil tank 33 for storing working oil; a single-rod hydraulic cylinder 1 that drives the working device 104; a turning hydraulic motor 7 that drives the upper turning body 102; an operation device 30 that instructs operations of the work implement 104 and the upper slewing body 102; a first closed-circuit pump 11 composed of two tilt pumps; a second closed-circuit pump 12 configured from two tilt pumps; a cylinder closed circuit C1 that connects the first closed circuit pump 11 and the single rod hydraulic cylinder 1 in a closed circuit; a swing closed circuit C2 that connects the second closed circuit pump 12 and the swing hydraulic motor 7 in a closed circuit; a first flush/drain valve 31 that communicates a low-pressure-side flow path of the cylinder closed circuit C1 with the oil tank 33; a second flushing/discharging valve 32 that communicates a low-pressure-side flow path of the swing closed circuit C2 with the oil tank 33; a first switching valve 23 that switches communication and disconnection of the first closed circuit pump 11 with the single rod hydraulic cylinder 1; and a second switching valve 26 that switches communication and disconnection between the second closed circuit pump 12 and the turning hydraulic motor 7, and controls opening and closing of the first switching valve 23 and the second switching valve 26 and discharge flow rates of the first closed circuit pump 11 and the second closed circuit pump 12 in accordance with an operation signal input from the operation device 30, wherein in the construction machine 100, a minimum flow path area from the second flushing valve 32 to the oil tank 33 when the second flushing valve 32 is fully opened is smaller than a minimum flow path area from the first flushing valve 31 to the oil tank 33 when the first flushing valve 31 is fully opened.

According to the present embodiment configured as described above, when the hydraulic oil is discharged from the pump suction side to the tank through the flushing/draining valve (second flushing/draining valve) 32 for the swing closed circuit C2 at the start of the swing deceleration, a large pressure loss occurs in the second flushing/draining valve 32, and the pressure in the flow passage on the pump suction side rapidly rises, and the second flushing/draining valve 32 rapidly switches. Accordingly, the time until the pressure of the flow passage on the pump suction side reaches the relief pressure can be shortened, and therefore, the slewing deceleration response is improved, and a good slewing operability can be obtained.

The first flushing/discharging valve 31 includes: the first manifold 31 a; a first spool valve 31e disposed in the first manifold 31 a; first springs 31f1, 31f2 disposed in the first manifold 31a and urging the first spool valve 31 e; and first shims 31g1 and 31g2 disposed between the first spool 31e and first springs 31f1 and 31f2, and the second flush valve 32 includes: a second manifold 32 a; a second spool valve 32e disposed in the second manifold 32 a; second springs 32f1, 32f2 disposed in the second manifold 32a and urging the second spool valve 32 e; and second shims 32g1 and 32g2 disposed between the second spool 32e and second springs 32f1 and 32f2, wherein the thickness T2 of the second shims 32g1 and 32g2 in the spool axial direction is greater than the thickness T1 of the first shims 31g1 and 31g2 in the spool axial direction. This makes it possible to reduce the maximum opening area of the flush valve 32 without changing the shape of the manifold 32a molded by the mold, and therefore, the cost of the flush valve 32 can be reduced.

Example 2

Fig. 7 shows the internal configuration of the flush valve 32 for the swing closed circuit C2 of the second embodiment of the present invention.

Fig. 7 is different from the flushing valve 32 (shown in fig. 4) for the swing closed circuit C2 of the first embodiment in that the thickness T2 of the shims 32g1 and 32g2 is equal to the thickness T1 of the shims 31g1 and 31g2 of the flushing valve 31 (shown in fig. 2) for the cylinder closed circuit C1, and the width W2 in the spool axial direction of the flow passage 32h formed in the spool 32e is smaller than the width W1 of the flow passage 31h of the flushing valve 31.

As described above, in the present embodiment, the first flushing valve 31 includes the first manifold 31a and the first spool valve 31e disposed in the first manifold 31a, the second flushing valve 32 includes the second manifold 32a and the second spool valve 32e disposed in the second manifold 32a, the first tank connection passage 31h for communicating the low-pressure side passage of the cylinder closed circuit C1 with the oil tank 33 is formed in the intermediate portion of the first spool valve 31e, the second tank connection passage 32h for communicating the low-pressure side passage of the swing closed circuit C2 with the oil tank 33 is formed in the intermediate portion of the second spool valve 32e, and the width W2 in the spool axial direction of the second tank connection passage 32h is smaller than the width W1 in the spool axial direction of the first tank connection passage 31 h.

In the present embodiment configured as described above, since the minimum flow path area from the flush valve 32 to the oil tank 33 when the flush valve 32 is fully opened is also smaller than the minimum flow path area from the flush valve 31 to the oil tank 33 when the flush valve 31 is fully opened, the slewing deceleration response is improved and good slewing operability is obtained as in the first embodiment.

Example 3

Fig. 8 shows a hydraulic drive apparatus 105 according to a third embodiment of the present invention.

Fig. 8 is different from the first embodiment (shown in fig. 2) in that the structure of the flushing valve 32 for the swing closed circuit C2 is the same as that of the flushing valve 31 (shown in fig. 3) for the cylinder closed circuit C1, and the throttle portion 41 is provided in the flow path connecting the flushing valve 31 and the oil tank 33. Here, the opening area of the throttle portion 41 is about the same as the maximum opening area between the flow passage 32b or the flow passage 32C and the flow passage 32h of the flushing valve 32 (shown in fig. 4) for the slewing closed circuit C2 in the first embodiment. Thus, as in the first embodiment, the minimum flow path area from the flush valve 32 to the oil tank 33 when the flush valve 32 is fully opened is smaller than the minimum flow path area from the flush valve 31 to the oil tank 33 when the flush valve 31 is fully opened.

As described above, the excavator 100 of the present embodiment further includes the throttle portion 41 provided in the flow path connecting the second flushing valve 32 and the tank 33, and the second flushing valve 32 has the same structure as the first flushing valve 31.

In the present embodiment configured as described above, since the minimum flow path area from the flush valve 32 to the oil tank 33 when the flush valve 32 is fully opened is smaller than the minimum flow path area from the flush valve 31 to the oil tank 33 when the flush valve 31 is fully opened, the slewing deceleration response is improved and good slewing operability is obtained as in the first embodiment.

Further, since the flushing valve (the second flushing valve 32) for the swing closed circuit C2 and the flushing valve (the first flushing valve 31) for the cylinder closed circuit C1 are of the same specification, the cost can be reduced.

The embodiments of the present invention have been described in detail, but the present invention is not limited to the above embodiments and includes various modifications. For example, the above-described embodiments are described in detail to explain the present invention easily and understandably, and are not limited to having all the configurations described. Further, a part of the structure of another embodiment may be added to the structure of one embodiment, or a part of the structure of one embodiment may be deleted or replaced with a part of another embodiment.

Description of the symbols

1-boom cylinder (single-rod hydraulic cylinder), 1 a-boom head, 1 b-boom lever, 2-boom, 3-boom cylinder, 3 a-boom head, 3 b-boom rod, 4-boom, 5-bucket cylinder, 5 a-bucket head, 5 b-bucket rod, 6-bucket, 7-swing motor (hydraulic motor for swing), 7a, 7 b-input/output port, 8a, 8 b-travel device, 9-engine, 10-transmission device, 11-closed-circuit pump (first closed-circuit pump), 12-closed-circuit pump (second closed-circuit pump), 11a, 12 a-regulator, 21, 22, 24, 25-flow path, 23-switching valve (first switching valve), 26-switching valve (second switching valve), 30-operation lever (operation device), 30 a-boom lever, 30 b-swing lever, 31-flush valve (first flush valve), 32-flush valve (second flush valve), 31b, 31c, 31 d-flow path, 31 e-spool (first spool valve), 31g1, 31g 2-shim (first shim), 31f1, 31f 2-spring (first spring), 31 h-flow path (first tank connection flow path), 31 i-stroke amount, 32b, 32c, 32 d-flow path, 32 e-spool (second spool valve), 32g1, 32g 2-shim (second shim), 32f1, 32f 2-spring (second spring), 32 h-flow path (second tank connection flow path), 32 i-stroke amount, 33-oil tank, 34a, 34 b-check valve, 37a, 37b, 38a, 38 b-overflow valve, 40-pump valve control device, 100-hydraulic excavator (construction machine), 101-cab, 102-upper revolving body, 104-front working machine (working device), 105-hydraulic drive device.