KR930010814B1 - Fluid operated pump displacement control system - Google Patents

Abstract

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Description

Control device of variable displacement fluid pump

1 schematically illustrates the overall membership of one preferred embodiment of the present invention.

2 is a circuit schematic diagram of a controller used in the embodiment of FIG.

3 is a cross-sectional view showing in detail the main part of the embodiment of FIG.

4 is a graph showing the relationship between the position of the control lever, the potentiometer output voltage, and the reference rotational speed of the prime mover.

5 is a graph showing the relationship between the rotational speed and the current value of the prime mover.

6 is a graph showing the relationship between the current value and the torque condition of the variable displacement pump.

7 is a graph showing the relationship between pressure and capacity per cycle of variable displacement pumps.

8 is a graph showing the relationship between the torque condition of the capacity and the torque curve of the prime mover.

* Explanation of symbols for the main parts of the drawings

P ₁ : first variable displacement pump P ₂ : second variable displacement pump

P ₃ : Control Pump E: Engine

1: discharge passage of the first variable displacement pump 3: discharge passage of the second variable displacement pump

2 ₁ , 2 ₂ , 2 ₃ , 2 ₄ , 2 ₅ , 2 ₆ : 1st ~ 6th valves 5,6: swash plate

7,8: control device 11: jet flow detector

12: NC valve 13: CO valve

14: rotational force control valve 16: discharge path

E ₁ : fuel injection pump 17: potentiometer

18: control lever 19: speed detector

20: controller.

The present invention relates to a fluid operated control device for a variable displacement pump driven by a prime mover such as an internal combustion engine. In particular, the present invention is to control the periodic capacity of a variable displacement pump for supplying pressurized fluid to a tool actuator, and to change the rotational force (torque) condition of the pump without changing the set output condition of the prime mover. The purpose is to provide a device that can.

In the control of the known variable displacement pump, for example, the discharge oil of the control hydraulic pump is supplied to a servo cylinder through a control valve to change the swash plate angle of the variable displacement pump, By controlling the depressurization action of the control valve in accordance with the discharge pressure of the pump, the capacity of the variable displacement pump is controlled in accordance with the discharge pressure of the variable displacement pump and the rotational force condition (capacity per cycle of the pump x pressure) of the variable displacement pump is fixed. Keep it. That is, the control apparatus which controls self pressure by a control signal is known.

In such a control device, since the rotational force conditions of the variable displacement pump are constant, the rotational force condition for efficiently utilizing the engine horsepower corresponds to the point calculated by the output condition (maximum load) set to the maximum of the engine. The torque conditions are usually dependent on the engine output conditions, ie the lever position of the engine's fuel injection pump.

In addition, if the engine's designated output condition is set to a partial load, that is, the lever position of the fuel injection pump is lowered, and the set output is decreased, the engine rotational speed is decreased, but the torque condition of the variable displacement pump does not change for a while. . However, if the rotational speed of the variable displacement pump is reduced, as a result, the rotational force condition of the variable displacement pump is also reduced, thereby reducing the capacity per unit time of the variable displacement pump. Therefore, the working speed of the tool actuator is lowered. For example, in a construction machine such as a power shovel, it is necessary to quickly operate a tool without having to use a large amount of power in light work and ground picking. In such light work, when the engine is operated at a low speed, the capacity per unit time of the variable displacement pump is reduced as described above, so that the operation speed of the tool actuator is lowered and the working efficiency is lowered. On the other hand, under the engine setting output conditions of some of these loads, the maximum rotational force of the engine is lower than that of the maximum load, so that the engine rotational force is lower than that of the variable displacement pump, which may cause the engine to stop.

Therefore, when the engine is operated at a high altitude where air density is low or when crude fuel is used, the engine power corresponding to the position of the lever cannot be obtained. Therefore, even if the engine is adjusted to the maximum load, the calculated torque can be obtained. You will not be able to. Therefore, the rotational force condition of the variable displacement pump increases with respect to the efficient rotational force of the engine, and the rotational speed of the engine decreases. In the worst case, the operation of the engine is stopped. To eliminate this drawback, the engine fuel consumption is unnecessarily increased if the engine is adjusted to the maximum load rotation speed so as to sufficiently maintain the variable amount per unit time of the variable displacement pump.

Accordingly, an object of the present invention is to provide a control device for a variable capacity fluid pump that can change the rotational output condition of a variable displacement pump according to the difference between each reference output rotational speed of the engine's set output conditions and the actual rotational speed of the engine. It is.

It is still another object of the present invention to add the second control signal arbitrarily taken to the first control signal with its own pressure as the first control signal without changing the set output condition of the engine, thereby adding the rotational force condition of the variable displacement pump to the second control signal. The present invention provides a variable displacement fluid pump control device capable of changing a rotational force condition of a variable displacement pump by adjusting the capacity corresponding to a control signal.

It is still another object of the present invention to provide a variable displacement fluid pump control device which can adjust the rotational force conditions of the variable displacement pump according to the use (work volume) of the tool to improve the work efficiency and reduce the engine fuel consumption. There is.

A variable displacement fluid pump control method according to the present invention which achieves this object has its own pressure as the first control signal and, unlike the first control signal, adds a second control signal which can be arbitrarily changed to the first control signal. Characterized in that the variable corresponding to the value of the second control signal. Here, the first control signal is the discharge fluid pressure of the variable displacement pump, and the second control signal corresponds to a signal corresponding to a difference between the set reference rotational speed of the prime mover and the actual rotational speed of the prime mover or to a working condition irrespective of the difference. Signal is set.

In addition, the variable displacement fluid pump control apparatus according to the present invention is connected to each capacity control device of the variable displacement pump to provide a control device to operate by the discharge hydraulic pressure of the separate control pump, the proportional correction electromagnet solenoid A rotational force control valve and a prime mover for moving a variable displacement pump, which are installed in a circuit connecting the control device and the control pump to reduce the pressure due to the discharge pressure of the variable displacement pump and the propulsion force of the proportional correction electromagnet solenoid. A device for detecting output conditions, and a device for supplying current to the proportional correction electromagnet solenoid according to the difference between the reference rotational speed and the actual rotational speed of the prime mover, respectively.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 schematically shows the overall membership, wherein the first and second variable displacement hydraulic pumps (hereinafter referred to as first and second variable displacement pumps) P ₁ and P ₂ and a constant capacity. The small capacity hydraulic control pump (hereinafter referred to as control pump) (P ₃ ) operates as an engine (E). The first, second and third action valves 2 ₁ , 2 ₂ and 2 ₃ are connected in parallel to the discharge path _{1 of} the first variable displacement pump P ₁ , and the second variable displacement pump P ₂ is connected in parallel. The fourth, fifth and sixth action valves 2 ₄ , 2 _5, and 2 ₆ are connected in parallel to the discharge path 3 of). Each of the actuation valves 2 ₁ to 2 ₆ is a well-known three-digit selection valve and supplies discharge oil to the first to sixth actuators 4 ₁ to 4 ₆ for motors, cylinders, and the like.

The capacity control members (hereinafter referred to as swash plates) 5 and 6 of the first and second variable displacement pumps P ₁ and P ₂ are controlled by the control devices 7 and 8, which control devices 7 and 8. Is controlled by the discharge oil from the control pump (P ₃ ). Those installed in the discharge path 16 are neutral control valves (hereinafter referred to as NC valves) 12, shut-off valves (hereinafter referred to as CO valves) 13, and rotational force regulating control valves 14, which are the rotational force. The regulating control valve is operated by a jet flow detector 11 installed in the discharge paths 9 and 1 from the discharge paths 1 and 3 of the first and second variable displacement pumps P ₁ and P ₂ . have.

The potentiometer 17 detects the position of the control lever 18 of the fuel injection pump E ₁ of the engine E, and the speed detector 19 detects the actual rotational speed of the engine E. The detected values (signal voltages) are all received by the controller 20 to send a signal current to the torque control valve 14.

Those indicated by symbols 21, 22 and 23 indicate the mode selector switch, the power source and the selector switch. The selector switch 23 normally connects the output circuit 20 'of the controller 20 to the circuit 14' facing the torque control valve 14, and the battery 22 when the controller 20 or the like fails. The circuit 14 'is connected to the auxiliary circuit 25 with the resistor 24 connected to the circuit.

The mode selector switch 21 manually selects the normal mode position I, the middle mode position II, and the low mode position III to send control signals to the controller 20.

In other words, as shown in FIG. 2, when the mode selection switch 21 is selected as the normal mode position I, the output condition of the engine (e.g., according to the position of the control lever 18 detected by the potentiometer 17) Maximum output condition, intermediate output condition, low output condition) is detected, and the detected value is input to the memory device 20a of the controller 20, where the reference rotational speed N _set of the set output condition is measured and operated. Input to device 20b. At the same time, the actual rotational speed N detected by the speed detector 19 is input to the operating device 20b. When the actual rotational speed N becomes lower than the reference rotational speed N _set , a current is supplied to the circuit 14 ′ of the rotational force regulating control valve 14 according to the difference value N _set -N.

When the mode selection switch 21 is selected to the intermediate mode position II, the current adjusted as the first adjusting device 26 of the controller 20 is supplied to the output circuit 20 '. On the other hand, when the mode selection switch 21 is selected as the low mode position III, the current adjusted as the second adjusting device 27 is supplied to the output circuit 20 ', in which case the control lever 18 The position and the actual rotation speed N are no longer relevant.

The torque control valve 14 adjusts the discharge pressure of the first and second variable displacement pumps P ₁ and P ₂ and the discharge pressure of the control pump P ₃ according to the first control signal supplied from the controller 20. It is to act to change. The control devices 7 and 8 change the inclination angles of the swash plates 5 and 6 to increase or decrease the capacity per cycle of the first and second pumps P ₁ and P ₂ , thereby changing the rotational force conditions. will be.

In this way, when the mode selector switch 21 is selected in the low mode position III, the discharge pressure of the torque control valve 14 is adjusted by the second regulator 27, i.e., the actual rotational speed of the engine. The rotational force condition is determined by controlling according to the second control signal regardless of the set output condition. The adjustment current adjusted by this second adjustment device 27 corresponds to a rotational force condition suitable for light work, and the rotational force condition in this case is shown as X in FIG. 8, and the engine speed is calculated as the maximum load. Increased per rotation time condition (Y), which is determined by the point at which it is determined, thus increasing the capacity per unit time of the first and second variable displacement pumps (P ₁ and P ₂ ), while reducing the discharge pressure so that the engine fuel consumption is reduced. At the same time, they are suitable for light work with high torque and low pressure.

Similarly, when the mode selection switch 21 is selected as the intermediate mode position II, the adjustment current in which the discharge pressure of the torque control valve 14 is adjusted by the first adjusting device 26, that is, another second control signal Is controlled according to the rotational force condition. The adjustment current adjusted by this first adjustment device 26 is a value corresponding to the rotational force condition suitable for normal operation, and the rotational force condition in this case is shown as Z in FIG. 8, between the rotational force conditions Y and X. This is the intermediate position in, indicating the median capacity and medium pressure per unit time for normal operation.

In addition, when the mode selection switch 21 is selected as the normal mode position I, the rotational force condition is set to a value corresponding to heavy work as shown by Y in FIG. The small capacity and high pressure per unit time fit.

When the normal mode position I is selected in this example, the output current is controlled according to the actual rotational speed and the reference output condition of the engine, so that the rotational force condition can be obtained according to the efficient rotational force of the engine. When operating the engine in the high altitude where the density of air is small and using crude fuel, even if the engine output corresponding to the engine's standard output condition cannot be obtained, the torque condition increases due to the effective torque of the engine. This reduces the risk of disruption of the engine in the worst case.

In this way, the rotational force condition can be controlled to a value corresponding to each working condition by applying another arbitrary second control signal to the first control signal by the mode selector switch 21, without increasing the fuel consumption of the engine. Various tasks can be performed efficiently.

3 is a detailed cross-sectional view of each member on the side of the first variable displacement pump P _{1. The} control device 7 includes a servo piston 31, an input signal portion A and a guide valve in the barrel 30. We have wealth (B). The servo piston 31 is connected to the swash plate 5 via the control rod 32 and is normally at the minimum swash plate inclination angle position by the pair of springs 33 by the end plates 34 and 35 as shown in the drawing. Keep at (minimum displacement).

The servo piston 31 provided in the input signal portion A provided with the first compartment 38 is provided, and the spring 39 is long supported on the other side thereof.

The guide valve portion B is configured by inserting a guide spool 42 into the sleeve 41, and into the cylinder 30, a space 43 communicating with the sleeve 41, and a control piston 36. And a servo piston 31. The support 44 contained in the space 43 is supported by the pin 45 at the center of the control piston 36. One end 44a of the support 44 engages the groove 31a of the servo piston 31, and the other end 44b passes through the groove 41a of the guide spool 42 through the hole 41a of the sleeve 41. 42a).

The inlet 56 and the first and second outlets 57 and 58 are formed in the sleeve 41. The inlet port 56 is connected to the inlet port 59, and the first and second outlet ports 57 and 58 are the servo pistons through the first and second passages 60 and 61 formed in the barrel 30, respectively. It communicates with the 1st and 2nd pressure chambers 62 and 63 of (31). One end of the sleeve 41 is placed against the adjustment plug 67 screwed into the cap 66 via the spring support 64 and the free piston 65, while the other end is through the free piston 68, Set against the adjustment plug 70 screwed in the cap 69. Reference numerals 71 and 72 denote the fastening nuts.

The guide spool 42 is provided with an annular groove 73 for closing or connecting the inlet 56 and the first and second outlets 57 and 58 to each other so that it is usually turned to the right by a spring 74. To keep the servo piston 31 at the minimum swash plate tilt angle position. In addition, the guide spool 42 forms the first and second annular flaws 75 and 76 so as to close or connect the first and second outlets 57 and 58 with the space 43. The side hole 77 is formed.

The CO valve 13 and the NC valve 12 are integrally formed with each other.

The CO valve 13 is configured as follows. That is, the spool 103 is provided long along with the sleeve 102 which couples the piston 101 to the valve body 100. The first pressure chamber 104 is formed by the jaw 101a of the piston 101 and the hole 102a of the sleeve 102. The small diameter portion 101b of the piston 101 places its free end in the second pressure chamber 105, and the second pressure chamber 105 is opened by the spool 103 through the passage 106. 109) and close or connect with each other. The first pressure chamber 104 is connected to the discharge path 1 through the hole 108. The spool 103 is pushed to the left by the spring 110 so as to close or connect the passage 106 and the hole 109.

On the other hand, the NC valve 12 is configured as follows. That is, the valve body 100 is provided with the sleeve 112 which couples the piston 111, and the spool 1130 is provided long each other. The third pressure chamber 114 is formed by the jaw 111a of the piston 111 and the hole 112a of the sleeve 112. The small diameter portion 111b of the piston 111 is positioned in the fourth pressure chamber 115. The third pressure chamber 114 communicates with the hole 117 through the passage 116, and the hole 117 communicates with the passage 106 by the spool 113. The fourth pressure chamber 115 is in communication with the hole 118. The spool 113 is pushed to the right by the spring 119, and the spring chamber 120 'communicates with the hole 121'.

The jet flow detector 11 is provided with a restricting portion 82 between the inlet 80 and the outlet 81, and the total pressure (stop pressure + dynamic pressure) at the first hole 83, the second hole 84 ) To detect the static pressure. The first hole 83 connects to the fourth pressure chamber 115 through the hole 118 while the second hole 84 communicates with the spring chamber 120 'through the hole 121'. The hole 117 is connected to the first chamber 38.

The rotational force regulating control valve 14 includes a spool 123 for closing or connecting the inlet 121 to the outlet 122 in the valve body 120, as well as the first, second, and third pistons 124, 125, and the like. 126 has sleeves 127 engaged in a row. The spool 123 connects the inlet 121 and the outlet 122 to each other by a spring 128 and pushes the pressure receiver 124a of the first piston 124 and the outlet 122 in a direction to connect each other to reduce pressure. To form a valve. The pressure receiving portion 125a of the second piston 125 is connected to the discharge path 1 through the hole 129 and pushes the spool 123 to the left side with respect to the spring 128 by the second piston 125. To do that. The pressure receiving portion 126a of the third piston 126 is connected to the discharge path 3 of the second variable displacement pump P ₂ through the hole 90.

The adjustment bolt 93 screwed to the end cap 92 is provided with respect to the support 91 of the spring 128. A proportional correction electromagnetic solenoid is provided on the end face 126b of the third piston 126. The inlet 121 is connected to the discharge path 16 of the control pump P ₃ , while the outlet 122 is connected to the hole 109 of the CO valve 13.

When the first to third actuation valves 2 ₁ to 2 ₃ are placed in the neutral position during operation, the flow velocity of the discharge passage 9 increases, so that the pressure difference between the total pressure of the jet flow detector 11 and the stop pressure becomes maximum. The difference between the total pressure supplied to the fourth pressure chamber 115 of the NC valve 12 and the stop pressure supplied to the spring seal 120 'is maximized. Therefore, the force pushing the spool 113 to the left with respect to the spring 119 is maximized. At the same time, the pressure in the hole 117 is supplied to the third pressure chamber 114 to push the spool 113 to the left against the spring 119, so that the discharge pressure (pressure from the hole 117) of the NC valve is minimized. It becomes small.

At this time, when the pressure in the discharge path 1 is minimum, the pressure on the pressure receiving portion 125a of the rotational force control valve 14 is minimized, and the force pushing the second piston 125 against the spool 123 is reduced. It is minimum. Accordingly, the spool 123 is pushed to the right by the spring 128 to connect the inlet 121 with the outlet 122, and the initial pressure of adjusting the control pump P ₃ with the release valve 96 is the outlet ( It is discharged from 122 to be supplied to the hole 106 of the CO valve (13).

When the pressure supplied to the first pressure receiving part 104 of the CO valve 13 is also minimum, the force for pushing the piston 101 to the right is minimized so that the spool 103 is pushed to the left by the spring 110. The hole 109 and the passage 106 are connected so that the initial pressure of the control pump P ₃ is supplied to the NC valve 12 through the passage 106.

However, since the discharge pressure of the NC valve 12 is made to be outward as described above, the initial pressure of the control pump P ₃ is dropped to the minimum discharge pressure and the input signal portion (3) through the hole 117 as the control pressure ( It is supplied to the 1st compartment 38 of A).

As such, when the control pressure is minimized, the control piston 36 is pushed to the right by the spring 39 so that the protruding rod 37 comes into contact with the plug as shown. When the control piston 31 is in the position as shown, the inclination angle position of the swash plate 5 is minimized, and the capacity per cycle of the first variable displacement pump P ₁ is minimized.

In other words, if the sleeve 41 is adjusted to the position shown to block the passage between the inlet 56 and the first and second outlets 57 and 58, the first and second pressure chambers of the control piston 31 ( Pressure balance between 62 and 63).

When the first action valve (2 ₁ ) is adjusted to supply a part of oil discharged from the first variable displacement pump (P ₁ ) to the first actuator (4 ₁ ), the flow rate of the discharge passage (9) is reduced and ejected. Since the detected pressure difference of the flow detector 11 is reduced, the pressure difference between the spring chamber 120 'and the fourth pressure chamber 115 of the NC valve 12 is reduced. Therefore, the force pushing against the spool 113 to the right increases, increasing the pressure of the hole 117. Accordingly, when the pressure of the first compartment 38 increases, the control piston 36 is pushed to the left to rotate the support 44 to the left with the servo piston 31 as the station and the inlet 56 and the second outlet. (58) communicate with each other. Therefore, since the oil discharged from the control pump P ₃ is supplied to the second pressure chamber 63 of the servo piston 31 and pushes the servo piston 31 to the left, the inclination angle of the swash plate 8 is increased. The capacity per cycle of the first variable displacement pump P ₁ is increased.

Accordingly, the support 44 rotates clockwise about the pin 45 of the control piston 36, and the guide spool 42 is pushed to the right by the end 44b of the support 44 to inlet 56. By blocking the passage between the second outlet 58 and the first variable displacement pump P ₁ is variable only by the amount of reduction in the detected pressure difference of the jet flow detector (11).

That is, the movement of the servo piston 31 is returned to the guide spool 42 through the support 44.

At this time, since the control piston 36 moves to the left according to the characteristics of the spring 39, the increase in the capacity per cycle of the first variable displacement pump P ₁ can be arbitrarily changed according to the characteristics of the spring.

In addition, when the pressure in the discharge passage (1) increases, the pressure on the pressure receiving portion (125a) of the rotational force control valve 14 is increased to increase the force pushing the second piston (125). Therefore, the spool 123 is strongly pushed against the spring 128 to the left to increase the decompression effect, thereby lowering the discharge pressure of the outlet 122.

Therefore, the control pressure supplied to the first compartment 38 of the input signal portion A through the CO valve 13 and the NC valve 12 drops, and the control piston 36 moves to the right as opposed to the above case. By moving, the capacity per cycle of the first variable displacement pump P ₁ is reduced.

When the pressure in the discharge passage 1 increases near the designated pressure of the main release valve, the pressure in the first pressure chamber 104 of the CO valve 13 increases to spring the spool 103 to the right by the piston 101. By pushing against 110 to block between the hole 109 and the passage 106 to start the pressure-reducing action, the discharge pressure of the NC valve 12 is lowered.

Subsequently, if the pressure in the discharge passage 1 further increases, the decompression action proceeds further to minimize the discharge pressure of the NC valve 12. Therefore, since the control voltage of the first compartment 38 of the input signal portion A is minimized, the capacity per cycle of the first variable displacement pump P ₁ is also minimized, while only the discharge pressure is the release adjustment pressure of the circuit. Increases to and remains in that state. In summary, the variable displacement control valve 14 reduces or increases the capacity per cycle as the discharge pressures of the first and second variable displacement pumps P ₁ and P ₂ increase or decrease, respectively. Done.

The above operation is applicable when the control current is not supplied from the controller 20. The case where the control current is supplied from the controller 20 will be described below.

As shown in FIG. 4, the output voltage of the potentiometer 16 is minimum in the open position (maximum load), and gradually increases as the partial load is performed in the closed position. Therefore, it is possible to detect the reference rotational speed of the engine stored in the storage device 20a, that is, the designated output condition of the engine, for example, a maximum load or a partial load.

Subsequently, the reference rotational speed N _set is input to the operating device 20b of the controller 20 and compared with the actual rotational speed detected by the speed detector 19. As a result, as shown in FIG. 5, the output current to the output circuit 20 'is controlled in accordance with the value N _set -N.

Specifically, if the actual rotation speed N is 200 rpm less than the reference rotation speed N _set , the output current is controlled according to the value. When the reference rotational speed N _set is less than 1500rpm, the maximum output current is supplied.

On the other hand, when the value of the current supplied to the proportional correction electronic solenoid of the rotational force control valve 14 is increased, the pushing force to the spool 123 is increased, the discharge pressure of the outlet 122 is lowered, and conversely, the current value is reduced. When the pushing force drops, the discharge pressure of the outlet 122 is increased. In other words, as the current supply amount increases, the capacity per cycle of the variable displacement pump decreases, whereas when the current supply decreases, the capacity per cycle increases. Therefore, as shown in FIG. 6, the relationship between the rotational force condition and the current value is such that the rotational force condition drops when the current value increases while the rotational force condition increases when the current value drops.

Therefore, the relationship between the capacity per cycle of the variable displacement pump and its pressure varies depending on the reference rotational speed in the range I 'to II' as shown in FIG. 7, but is always constant at a constant reference rotational speed.

As described above, the rotational force condition changes according to the position of the control lever 18, i.e., the engine's designated output condition, and increases and decreases the capacity per cycle of the variable displacement pump in accordance with the discharge pressure, according to the reference output condition. The torque condition is obtained. Therefore, even when the engine's reference output condition is at the maximum load as well as the partial load, the capacity of the variable displacement pump can be controlled without stopping the engine operation.

Specifically, when the control lever 18 is at its maximum position, that is, when the rotation speed of the engine is equal to or greater than the value calculated by the maximum load of 210 rpm (reference rotation speed N _set ), it is supplied to the proportional correction electronic solenoid 94. The current to become minimum (0.3A). Capacity per cycle (swash plate angle) is maximum until torque conditions reach the engine's calculated output. When the rotational speed of the engine is less than the calculated value, the current supplied to the proportional correction electronic solenoid 94 increases according to the value N _set -N to decrease the capacity per cycle. When the engine rotation speed is lower than 1900rpm, the supply current is maximized to minimize the rotational force conditions by minimizing the capacity per cycle.

In this example, the rotational force condition is controlled as described above when the engine's reference rotational speed (N _set ) becomes 1500 rpm or more, and is controlled in such a way as to minimize the capacity per cycle by maximizing the supply current value without interrupting the operation of the engine. However, even when the value of N _set is in the range of 1500 rpm or less, it can be controlled in the same manner as described above.

In addition, when the mode selection switch 21 is in the intermediate mode position II, the current regulated by the first adjusting device 26 is supplied from the controller 20 to the proportional correction electromagnet solenoid 94 and its spool ( When the force pushing 123 reaches a certain value, the rotational force condition exists corresponding to the supply current value regardless of the engine's designated output condition.

Similarly, when the current selected by the second adjusting device 27 is supplied from the controller 20 to the proportional correction electromagnet solenoid 94 when the mode selection switch 21 is in the low mode position III, the rotational force condition is It exists in correspondence with the supply current value regardless of the engine set output condition.

In this way, since the rotational force condition is arbitrarily present regardless of the engine set output condition by the selection of the mode selection switch 21, fuel consumption can be efficiently used because the engine output can be efficiently used in accordance with the operation of the actuator, that is, the workload. It can be improved.

If the controller 20 fails for some reason, no current is supplied to the coil 23a of the selector switch 23, so that the selector switch 23 connects the auxiliary circuit 25 and the circuit 14 '. . As a result, a current is supplied from the auxiliary circuit 25 to the proportional correction electromagnet solenoid 94, so that a constant rotational force condition can be obtained regardless of the engine's designated output condition to control the capacity per cycle of the variable displacement pump. .

Specifically, as shown in FIG. 8, the rotational force condition at the intermediate mode position is expressed as X when the relationship between the pressure and the capacity per cycle is shown as II 'in FIG. The rotational force condition is indicated by S in the state where the auxiliary circuit 25 is connected. The torque condition in the normal mode position is indicated by Y.

Further, since the discharge pressure of the variable displacement pump is introduced into the rotational force regulating control valve 14 to control the pressure of the discharge port 122, the variable displacement pump is supplied even if current is supplied to the proportional correction electromagnet solenoid 94. The capacity of can be controlled in a certain range.

Claims (4)

It is provided between the capacity control device of the variable displacement pump and a separate control pump, and has control means for controlling the capacity control device by the discharge fluid pressure of the control pump, and this control means is provided for the discharge fluid pressure of the variable displacement pump. The discharge fluid pressure of the control pump is controlled by a first control signal and a second control signal separate from the second control signal, and the second control signal is the reference rotational speed of the prime mover and the actual revolution speed of the prime mover. The control device for a variable displacement fluid pump, characterized in that the signal corresponding to the difference or the signal set in response to the working conditions irrespective of the difference. 2. A control torque control valve according to claim 1, wherein said control means has a variable torque control valve provided between said capacity control means and said control pump, said variable torque control valve being coupled to said first control signal and said second control signal. Controlling the discharge fluid pressure of the control pump by reducing the pressure. 3. The neutral control valve according to claim 2, wherein the neutral control valve acts as a jet sensor provided between the displacement control device and the variable torque control valve in the drain passage of the discharge passage of the variable displacement pump, and the discharge pressure of the variable displacement pump. Control device for a variable displacement fluid pump, characterized in that a cut-off valve to operate. The control device for a variable displacement fluid pump according to claim 1, wherein a mode changeover switch for selecting a type of said second control signal is provided.

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