阅读说明：本技术 油压系统 (Oil pressure system ) 是由 近藤哲弘 村冈英泰 于 2018-06-14 设计创作，主要内容包括：油压系统具备调节泵的倾转角的调节器和以泵的吐出流量成为操作要求流量和马力控制流量中较小的一方的形式控制调节器的控制装置；控制装置中储存有第一马力控制线和比其低的第二马力控制线；控制装置在从操作装置输出的操作信号增加且操作要求流量大于马力控制流量的情况下,当工作点越过第一马力控制线时使泵的倾转角减少,当工作点低于第二马力控制线时使泵的倾转角增加,当越过第一马力控制线或低于第二马力控制线的工作点移动到第一马力控制线与第二马力控制线之间时维持泵的倾转角。(The hydraulic system includes a regulator for regulating a tilt angle of the pump, and a control device for controlling the regulator such that a discharge flow rate of the pump is smaller than a requested operation flow rate or a power control flow rate; the control device is stored with a first horsepower control line and a second horsepower control line lower than the first horsepower control line; the control device decreases the tilt angle of the pump when the operating point crosses over the first horsepower control line, increases the tilt angle of the pump when the operating point is lower than the second horsepower control line, and maintains the tilt angle of the pump when the operating point crosses over the first horsepower control line or lower than the second horsepower control line and moves between the first horsepower control line and the second horsepower control line, when the operating signal output from the operating device increases and the operation request flow rate is larger than the horsepower control flow rate.)

1. An oil pressure system, characterized in that,

the disclosed device is provided with:

an operation device that outputs an operation signal corresponding to an operation amount to the operation unit;

a variable capacity type pump;

an adjuster that adjusts a tilt angle of the pump;

a pressure sensor for detecting the discharge pressure of the pump; and

a control device that controls the regulator such that a discharge flow rate of the pump becomes a smaller one of an operation required flow rate corresponding to an operation signal output from the operation device and a horsepower control flow rate corresponding to a discharge pressure of the pump detected by the pressure sensor;

a first horsepower control line that defines a relationship between a discharge pressure of the pump and the horsepower control flow rate, and a second horsepower control line that is lower than the first horsepower control line are stored in the control device;

the control device sets a tilt angle of the pump to a tilt angle corresponding to the operation required flow rate until an operation point determined by a discharge pressure of the pump detected by the pressure sensor and a discharge flow rate of the pump exceeds the first horsepower control line, decreases the tilt angle of the pump until the operation point becomes the tilt angle determined by the first horsepower control line when the operation point crosses over the first horsepower control line, increases the tilt angle of the pump until the operation point becomes the tilt angle determined by the second horsepower control line when the operation point is lower than the second horsepower control line, and shifts to the first horsepower control line and the second horsepower control line when the operation point crosses over the first horsepower control line Maintaining a tilt angle of the pump when the operating point between horsepower control lines or below the second horsepower control line is shifted between the first and second horsepower control lines.

2. The oil hydraulic system of claim 1,

the control device reduces or increases the pump tilting angle using the first horsepower control line without using the second horsepower control line when the temperature of the working oil is lower than a prescribed value even when the operation signal output from the operation device increases and the operation required flow rate corresponding to the operation signal output from the operation device is larger than the horsepower control flow rate corresponding to the discharge pressure of the pump detected by the pressure sensor.

Technical Field

The present invention relates to an electric positive control type hydraulic system.

Background

Conventionally, an electrically positive control type hydraulic system has been adopted in construction machines, industrial machines, and the like (for example, see patent document 1). In general, in a hydraulic system, a hydraulic actuator is supplied with hydraulic oil from a variable displacement pump via a control valve, and a tilt angle of the pump is adjusted by a regulator. In an electric positive control type hydraulic system, a control device controls a regulator so that a discharge flow rate of a pump is increased as an operation amount of an operation device for operating a hydraulic actuator is increased.

In the hydraulic system of the electric positive control system, horsepower control is often performed to prevent an engine stall of the drive pump. In this case, the control device controls the regulator such that the discharge flow rate of the pump becomes the smaller of the operation required flow rate corresponding to the operation amount of the operation device and the horsepower control flow rate corresponding to the discharge pressure of the pump.

Disclosure of Invention

The problems to be solved by the invention are as follows:

however, when the operation device is rapidly and largely operated to control the horsepower, the discharge flow rate of the pump repeatedly increases and decreases as shown in fig. 5, and the behavior of the hydraulic actuator may oscillate (hunting). Specifically, when the operating point determined by the discharge pressure and the discharge flow rate of the pump is higher than the horsepower control line that defines the relationship between the discharge pressure and the horsepower control flow rate of the pump (point a in the figure), the tilt angle of the pump decreases. Accordingly, the discharge flow rate of the pump decreases, and the discharge pressure of the pump decreases. As a result, the operating point is lower than the horsepower control line (point b in the drawing), and therefore the tilt angle of the pump increases. As the discharge flow rate of the pump increases, the discharge pressure of the pump increases, and the operating point becomes higher than the horsepower control line again (point c in the figure). Such oscillation of the behavior of the hydraulic actuator due to the repeated increase and decrease in the discharge flow rate of the pump is generally likely to occur except when the temperature of the hydraulic oil is low to some extent (when the outside air temperature is low and the operation of warming up the machine is not completed).

In general, a technique of adding a restrictor to a hydraulic line of a regulator is often used to prevent oscillation of the behavior of the hydraulic actuator, but such a configuration is known to cause a problem of response delay when the temperature of the hydraulic oil is low.

Accordingly, an object of the present invention is to provide a hydraulic system capable of suppressing oscillation of behavior of a hydraulic actuator without causing a disadvantage when the temperature of hydraulic oil is low.

Means for solving the problems:

in order to solve the above problem, a hydraulic system according to the present invention includes: an operation device that outputs an operation signal corresponding to an operation amount to the operation unit; a variable capacity type pump; an adjuster that adjusts a tilt angle of the pump; a pressure sensor for detecting the discharge pressure of the pump; and a control device that controls the regulator such that a discharge flow rate of the pump becomes a smaller one of an operation required flow rate corresponding to an operation signal output from the operation device and a horsepower control flow rate corresponding to the discharge pressure of the pump detected by the pressure sensor; a first horsepower control line that defines a relationship between a discharge pressure of the pump and the horsepower control flow rate, and a second horsepower control line that is lower than the first horsepower control line are stored in the control device; the control device sets a tilt angle of the pump to a tilt angle corresponding to the operation required flow rate until an operation point determined by a discharge pressure of the pump detected by the pressure sensor and a discharge flow rate of the pump exceeds the first horsepower control line, decreases the tilt angle of the pump until the operation point becomes the tilt angle determined by the first horsepower control line when the operation point crosses over the first horsepower control line, increases the tilt angle of the pump until the operation point becomes the tilt angle determined by the second horsepower control line when the operation point is lower than the second horsepower control line, and shifts to the first horsepower control line and the second horsepower control line when the operation point crosses over the first horsepower control line Maintaining a tilt angle of the pump when the operating point between horsepower control lines or below the second horsepower control line is shifted between the first and second horsepower control lines.

According to the above configuration, a hysteresis (hystersis) is provided between the first horsepower control line as a criterion for determining when the tilting angle of the pump should be decreased and the second horsepower control line as a criterion for determining when the tilting angle of the pump should be increased in the case of performing the horsepower control. Therefore, when the tilt angle of the pump is changed and the operating point shifts between the first horsepower control line and the second horsepower control line, the tilt angle of the pump cannot be further changed. Therefore, repetition of increase and decrease in the discharge flow rate of the pump can be suppressed with a simple configuration without requiring an additional member, and oscillation of the behavior of the hydraulic actuator can be suppressed. Further, since the oscillation is suppressed by the electronic control of the control device without using a member such as an orifice whose characteristic greatly changes depending on the temperature (particularly, at a low temperature), there is no disadvantage in the case where the temperature of the hydraulic oil is low. Therefore, a hydraulic system having excellent stability from a low temperature to a normal operating temperature (after completion of warm-up) with respect to the temperature of the hydraulic oil can be realized.

The control device may be configured to decrease or increase the pump tilting angle using the first horsepower control line without using the second horsepower control line when the temperature of the hydraulic oil is lower than a predetermined value even when the operation signal output from the operation device increases and the operation required flow rate corresponding to the operation signal output from the operation device is larger than the horsepower control flow rate corresponding to the discharge pressure of the pump detected by the pressure sensor. According to this configuration, a simple control using the first horsepower control line can be performed except when the behavior of the hydraulic actuator is likely to oscillate due to a high temperature of the hydraulic oil, and the power of the engine or the like can be used in a larger amount.

The invention has the following effects:

according to the present invention, oscillation of behavior of the hydraulic actuator can be suppressed without taking the disadvantage that the temperature of the hydraulic oil is low.

Drawings

FIG. 1 is a schematic configuration diagram of a hydraulic system according to an embodiment of the present invention;

FIG. 2 is a graph showing operational demand flow;

FIG. 3 is a graph illustrating the behavior of an operating point relative to a first horsepower control line and a second horsepower control line;

fig. 4A shows a change with time in the operation amount of the operation device, and fig. 4B shows a change with time in the discharge flow rate of the pump;

fig. 5 is a graph showing an operation of an operating point with respect to a horsepower control line in the conventional hydraulic system.

Detailed Description

Fig. 1 shows a hydraulic system 1 according to an embodiment of the present invention. The hydraulic system 1 is mounted on a construction machine, a civil engineering machine, an agricultural machine, or an industrial machine such as a hydraulic excavator, a hydraulic crane, or the like.

Specifically, the oil pressure system 1 includes an oil pressure actuator 5 and a pump 2 that supplies working oil to the oil pressure actuator 5 through a control valve 4. In the illustrated example, the hydraulic actuator 5 and the control valve 4 are combined into one set, but a plurality of sets of the hydraulic actuator 5 and the control valve 4 may be provided.

The pump 2 is driven by the engine 21. However, the pump 2 may also be driven by an electric motor. The pump 2 is a variable displacement pump (swash plate pump or inclined shaft pump) whose tilt angle can be changed. The tilt angle of the pump 2 is adjusted by the adjuster 3.

The pump 2 is connected to the control valve 4 via a supply line 11. The discharge pressure of the pump 2 is kept at a pressure lower than the relief pressure by a relief valve, not shown.

In the present embodiment, the hydraulic actuator 5 is a cylinder, and the control valve 4 is connected to the hydraulic actuator 5 through a pair of supply and discharge lines 12. However, the hydraulic actuator 5 may be a single cylinder, and the control valve 4 may be connected to the hydraulic actuator 5 through one supply/discharge line 12. Alternatively, the hydraulic actuator 5 may be a hydraulic motor.

The control valve 4 is operated by the operating device 6 to switch from a neutral position to a first position (a position where the hydraulic actuator 5 is operated in one direction) or a second position (a position where the hydraulic actuator 5 is operated in the opposite direction). In the present embodiment, the control valve 4 is of a hydraulic pilot type and has a pair of pilot ports. However, the control valve 4 may be of an electromagnetic pilot type.

The operation device 6 includes an operation unit 61 and outputs an operation signal corresponding to an operation amount to the operation unit 61. That is, the operation signal output from the operation device 6 increases as the operation amount increases. The operation unit 61 is, for example, an operation lever, but may be a foot pedal or the like.

In the present embodiment, the operation device 6 is a pilot operation valve that outputs a pilot pressure as an operation signal. Therefore, the operation device 6 is connected to the pilot port of the control valve 4 through the pair of pilot lines 13. The control valve 4 increases the opening area of a passage through which the hydraulic oil is supplied to the hydraulic actuator 5 as the pilot pressure (operation signal) output from the operation device 6 increases.

The regulator 3 operates in response to an electrical signal. For example, when the pump 2 is a swash plate pump, the regulator 3 may be an electric actuator that electrically changes the hydraulic pressure acting on a servo piston coupled to a swash plate of the pump 2, or an electric actuator coupled to a swash plate of the pump 2.

The regulator 3 is controlled by a control device 7. For example, the control device 7 has a memory such as a ROM and a RAM, and a CPU, and the CPU executes a program stored in the ROM.

The control device 7 is electrically connected to a pressure sensor 8 provided on each of the pair of pilot lines 13. However, only a part of the signal lines is drawn in fig. 1 for simplicity of the drawing.

The pressure sensor 8 detects a pilot pressure output from the operation device 6. Then, as shown in fig. 2, the control device 7 determines the operation request flow rate Qa corresponding to the pilot pressure (operation signal) detected by the pressure sensor 8. That is, the operation required flow rate Qa increases as the pilot pressure increases. In the present embodiment, the operation required flow rate Qa is proportional to the pilot pressure. However, the line of the relation between the operation demand flow rate Qa and the operation signal is not necessarily a straight line, and may be an upward or downward convex curve as shown by a broken line in fig. 2.

The control device 7 is also electrically connected to a pressure sensor 9 provided in the supply line 11. The pressure sensor 9 detects the discharge pressure of the pump 2. The control device 7 determines a horsepower control flow rate Qb corresponding to the discharge pressure of the pump 2 detected by the pressure sensor 9.

Specifically, as shown in fig. 3, the control device 7 stores a first horsepower control line L1 that defines the relationship between the discharge pressure of the pump 2 and the horsepower control flow rate Qb. The control device 7 determines the horsepower control flow rate Qb based on the first horsepower control line L1.

In the present embodiment, the maximum value of the operation request flow rate Qa and the maximum value of the horsepower control flow rate Qb are substantially equal to each other, but may be different from each other. This relationship is also the same when each of the operation devices 6 is operated individually when a combination of a plurality of sets of the hydraulic actuator 5, the control valve 4, and the operation device 6 is provided.

After the operation request flow rate Qa and the horsepower control flow rate Qb are determined, the control device 7 controls the regulator 3 so that the discharge flow rate of the pump 2 becomes the smaller of the operation request flow rate Qa and the horsepower control flow rate Qb.

In the present embodiment, as shown in fig. 3, the control device 7 is stored with a second horsepower control line L2 that is lower than the first horsepower control line L1. In other words, the second horsepower control line L2 specifies the second type of horsepower control flow rate lower than the horsepower control flow rate Qb.

In the present embodiment, the second horsepower control line L2 has a similar shape to the first horsepower control line L1. For example, the second horsepower control line L2 specifies a discharge flow rate of 70 to 98% of the first horsepower control line L1. However, the second horsepower control line L2 need not be shaped similarly to the first horsepower control line L1. For example, the interval between the first horsepower control line L1 and the second horsepower control line L2 may be small on the low discharge pressure side and large on the high discharge pressure side.

In the present embodiment, the second horsepower control line L2 is used when the special acceleration condition is satisfied and the temperature of the hydraulic oil is higher than a predetermined value (for example, 40 to 50 ℃). The case where the special acceleration condition is satisfied is a case where the operation signal output from the operation device 6 is increased (a case where the operation amount of the operation device 6 is increased in order to accelerate the hydraulic actuator 5) and the operation request flow rate Qa corresponding to the operation signal output from the operation device 6 is larger than the horsepower control flow rate Qb corresponding to the discharge pressure of the pump 2 detected by the pressure sensor 9.

That is, even in the case where the special acceleration condition is satisfied, only the first horsepower control line L1 is used when the temperature of the working oil is lower than the prescribed value. Also, when the special acceleration condition is not satisfied, that is, when the operation signal output from the operation device 6 is constant or decreased, only the first horsepower control line L1 is used. However, it is also possible to always use the second horsepower control line L2 regardless of the temperature of the working oil in the case where the special acceleration condition is satisfied.

When the operation request flow rate Qa is larger than the horsepower control flow rate Qb in the case of using only the first horsepower control line L1, the control device 7 decreases or increases the tilt angle of the pump 2 so that the operating point determined by the discharge pressure of the pump 2 detected by the pressure sensor 9 and the discharge flow rate of the pump 2 is maintained at the first horsepower control line L1. The discharge flow rate of the pump 2 is obtained by multiplying the pump discharge capacity per revolution, which is obtained from the tilt angle of the pump 2, by the rotation speed of the engine 21.

The temperature of the hydraulic oil may be detected by a temperature sensor provided in a tank for storing the hydraulic oil. Alternatively, a temperature sensor that detects the atmospheric temperature may be used, and a case where the temperature detected by the temperature sensor is higher than a threshold may be regarded as a case where the temperature of the hydraulic oil is higher than a predetermined value. Further, the temperature of the cooling water of the engine 21 may be regarded as the temperature of the working oil.

When the special acceleration condition is satisfied and the temperature of the hydraulic oil is higher than the predetermined value, the control device 7 sets the tilt angle of the pump 2 to the tilt angle corresponding to the operation required flow rate Qa until the operating point determined by the discharge pressure of the pump 2 and the discharge flow rate of the pump 2 detected by the pressure sensor 9 exceeds the first horsepower control line L1.

On the other hand, when the operating point crosses the first horsepower control line L1 (point a in fig. 3), the control device 7 decreases the tilt angle of the pump 2 until the tilt angle (the tilt angle corresponding to the point on the first horsepower control line L1 at the current discharge pressure) determined by the first horsepower control line L1. As a result, when the operating point crossing the first horsepower control line L1 is shifted between the first horsepower control line L1 and the second horsepower control line L2, the control device 7 maintains the tilt angle of the pump 2.

Alternatively, when the operating point is lower than the second horsepower control line L2 due to the decrease in the tilt angle of the pump 2 (point B in fig. 3), the control device 7 increases the tilt angle of the pump 2 until the tilt angle is determined by the second horsepower control line L2 (the tilt angle corresponding to the point on the second horsepower control line L2 at the current discharge pressure). As a result, when the operating point lower than the second horsepower control line L2 shifts between the first horsepower control line L1 and the second horsepower control line L2, the control device 7 maintains the tilt angle of the pump 2.

As described above, in the hydraulic system 1 according to the present embodiment, a hysteresis is provided between the first horsepower control line L1, which is a criterion for determining when the tilting angle of the pump 2 should be decreased when the horsepower control is performed, and the second horsepower control line L2, which is a criterion for determining when the tilting angle of the pump 2 should be increased. Therefore, when the tilt angle of the pump 2 is changed and the operating point shifts between the first horsepower control line L1 and the second horsepower control line L2, the tilt angle of the pump 2 is not further changed. Therefore, the repetition of increase and decrease in the discharge flow rate of the pump 2 can be suppressed with a simple configuration without requiring additional components, and the oscillation of the behavior of the hydraulic actuator 5 can be suppressed. Further, since the oscillation is suppressed by the electronic control of the control device without using a member such as an orifice whose characteristic greatly changes depending on the temperature (particularly, at a low temperature), there is no disadvantage in the case where the temperature of the hydraulic oil is low. Therefore, the hydraulic system 1 having excellent stability from a low temperature to a normal operating temperature (after completion of warm-up) with respect to the temperature of the hydraulic oil can be realized without sacrificing responsiveness even when the operation device 6 is suddenly operated.

For example, in the case where only the first horsepower control line L1 is used as in the related art, when the operation device is rapidly and largely operated as shown in fig. 4A after the warm-up operation is completed when the atmospheric temperature is low, the discharge flow rate of the pump 2 repeatedly increases and decreases as shown by a broken line in fig. 4B, and the behavior of the hydraulic actuator oscillates. In contrast, when the second horsepower control line L2 is used in addition to the first horsepower control line L1 as in the present embodiment, the repetition of increase and decrease in the discharge flow rate of the pump 2 can be suppressed as shown by the solid line in fig. 4B, and the oscillation of the behavior of the hydraulic actuator 5 can be suppressed.

In the present embodiment, even when the special acceleration condition is satisfied, the second horsepower control line L2 is not used when the temperature of the hydraulic oil is lower than the predetermined value, so that a simple control using the first horsepower control line L1 is possible except when the behavior of the hydraulic actuator 5 is likely to oscillate due to the high temperature of the hydraulic oil, and a larger amount of power of the engine 21 and the like can be used.

(modification example)

The present invention is not limited to the above-described embodiments, and various modifications can be made within a scope not departing from the gist of the present invention.

For example, the operation device 6 may be an electric joystick that outputs an electric signal as an operation signal to the control device 7. In this case, the pressure sensor 8 is not required, and each pilot port of the control valve 4 is connected to the secondary pressure port of the electromagnetic proportional valve.

Description of the symbols:

1 an oil pressure system;

2, pumping;

3, a regulator;

4a control valve;

5, an oil pressure actuator;

6 operating the device;

61 an operation section;

7 a control device;

8. 9 a pressure sensor.