JPH0553948B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a device for controlling the displacement of a variable displacement hydraulic pump that is driven by an engine and supplies pressure oil to an actuator.

Prior Art The discharge pressure oil of a control hydraulic pump is supplied to a servo cylinder that changes the discharge amount of a variable displacement hydraulic pump (hereinafter referred to as variable pump), for example, the swash plate angle, through a control valve, and the control valve is It has a structure that reduces pressure according to the discharge pressure of the variable pump, and controls the discharge volume of the variable pump according to the discharge pressure of the variable pump so that the absorption torque (discharge volume x pressure) of the variable pump remains constant. The device is known.

In such a control device, the absorption torque of the variable pump is a constant value, so in order to effectively utilize the engine horsepower, the absorption torque should be set to match the torque at the rated point of the engine's maximum set output state (full load). is normal.

Note that the set output state of the engine is determined by the lever position of the fuel injection pump of the engine.

For this reason, when the set output state of the engine is set to partial load, the maximum torque of the engine becomes smaller than the rated point torque of full load, and the engine may stop (engine stall).

In addition, when operating at high altitudes where the atmospheric density is low, or when using poor quality fuel, the engine output commensurate with the lever position cannot be obtained, so even if the engine is set to full load, it will not be possible to obtain the engine output commensurate with the rated point torque. Torque cannot be obtained, and the absorption torque of the variable pump becomes larger than the engine's effective torque, causing the engine rotation speed to drop, and in the worst case, the engine stalls.

OBJECTS OF THE INVENTION It is an object of the invention to enable the absorption torque of a variable displacement hydraulic pump to be changed depending on the set output state and actual rotation speed of the engine.

Structure of the Invention A variable torque control valve is provided between a control mechanism that drives a displacement control member of a variable displacement hydraulic pump and a control hydraulic pump, and this variable torque control valve is connected to the discharge pressure of the variable displacement hydraulic pump. The thrust force of the proportional electromagnetic solenoid is used to reduce the pressure, and the proportional electromagnetic solenoid is provided with means for supplying current according to the difference between each set standard rotation speed and the actual rotation speed in the set output state of the engine.

Embodiment Figure 1 is an overall circuit diagram, in which the engine E drives the first and second variable displacement hydraulic pumps (hereinafter referred to as the first and second variable pumps) P ₁ and P ₂ and a small fixed capacity for control. A type hydraulic pump (hereinafter referred to as a control pump) P ₃ is driven, and the discharge path 1 of the first variable pump P ₁ has first, second, and third operation valves 2 ₁ , 2 ₂ , 2 _{3 .}
are connected in parallel, and the discharge path 3 of the second variable pump _P2
The fourth, fifth, and sixth operating valves 2 ₄ , 2 ₅ , and 2 ₆ are connected in parallel, and each of the operating valves 2 ₁ to 2 ₆ is connected to a first to sixth actuator 4 _{1 to 4} such as a motor or cylinder. It is a known three-position switching valve that supplies discharge pressure oil to 4 _{and 6} .

The capacity control members (hereinafter referred to as swash plates) 5 and 6 of the first and second variable pumps P ₁ and P ₂ are controlled by a control mechanism 7,
8, and the control mechanisms 7 and 8 are controlled by the discharge pressure oil of the control pump _P3 , and the discharge passage 16 of the control pump P3 is connected to the discharge passage ₁ of the first and second variable pumps P1 and _P2 . A neutral control valve (hereinafter referred to as NC valve) 12, a cut-off valve (hereinafter referred to as CO valve) 13, and a variable torque control valve 14 are operated by jet sensors 11 and 11 provided in the drain passages 9 and 10 of , 3 and 3, respectively. It is provided.

17 is a potentiometer that detects the position of the control lever 18 of the fuel injection pump E ₁ of the engine E, 19 is a rotation sensor that detects the actual rotational speed of the engine E, and each detected value (signal voltage) is sent to the controller 20 The controller 20 sends a signal current to the variable torque control valve 14.

21 is a mode selection switch, 22 is a power supply, 23
is a changeover switch, and the changeover switch 23 normally connects the output circuit 20' of the controller 20 and the circuit 14' to the variable torque control valve 14, and has a resistor 24 connected to the battery 22 when the controller 20 or the like breaks down. The redundant circuit 25 and the circuit 14' are connected.

The mode changeover switch 21 is manually switched between a steady mode position, an intermediate mode position, and a low mode position, and outputs a control signal to the controller 20.

That is, as shown in FIG. 2, when the mode changeover switch 21 is set to the steady mode position, the position of the control lever 18 detected by the potentiometer 17 determines the set output state of the engine (for example, maximum output state, medium output state). , small output state)
is detected, this detected value is input to the storage section 20a of the controller 20, and the set standard rotational speed Nset in the set output state is read out from the storage section 20a and inputted to the calculation section 20b, and at the same time, the detected value is detected by the rotation sensor 19. The actual rotation speed N is input to the calculation unit 20b, and the actual rotation speed N is set as the reference rotation speed Nset.
circuit 1 of the variable torque control valve 14 according to the value of (Nset-N).
4'.

When the mode selector switch 21 is set to the intermediate mode position, the current set in the first setting device 26 of the controller 20 is supplied to the output circuit 20', and when it is set to the low mode position, the current set in the second setting device 27 of the controller 20 is supplied to the output circuit 20'. is supplied to the output circuit 20', and the position of the control lever 18,
The actual rotational speed N has no bearing whatsoever.

FIG. 3 is a detailed sectional view of each member only on the first variable pump _P1 side, and the control device 7 is connected to the case 30.
It has a servo piston 31, an input signal section A, and a guide valve section B provided therein, and the servo piston 31 is connected to the swash plate 5 by a rod 32.
A pair of springs 33, 33 always hold the swash plate at the minimum swash plate angle position (minimum discharge amount position) shown in the figure.
It is held at 4,35.

The input signal section A includes a control piston 36;
A protruding rod 37 is provided on one side of the control piston 36 to form a first chamber 38, and a second spring 39 is arranged linearly on the other side.

The guide valve part B has a guide spool 42 inserted into a sleeve 41, and the case 30 is formed with a notch 43 that is open across the sleeve 41, the control piston 36, and the servo piston 31. The central part of an arm 44 provided in the section 43 is pivotally connected to the control piston 36 by a pin 45, one end 44a engages with the recess 31a of the servo piston 31, and the other end 44b is inserted into the guide spool 42 from the notch 41a of the sleeve 41. It engages with the recess 42a.

The sleeve 41 has an inlet port 56 and a first,
Second outlet ports 57 and 58 are formed, the inlet port 56 opens to the inlet hole 59 of the case 30, and the first and second outlet ports 57 and 58 are formed in the first and second passages 60 and 58 formed in the case 30, respectively. 61 communicates with the first and second pressure chambers 62 and 63 of the servo piston 31, and a spring seat 6 is provided on one end surface of the sleeve 41.
4. An adjustment plug 67 screwed into the cap 66 via the free piston 65 is in contact with the other end surface, and an adjustment plug 70 screwed into the cap 69 through the free piston 68 is in contact with the other end surface. 71 and 72 are lock nuts.

The guide spool 42 is formed with an annular groove 73 that cuts through the inlet port 56 and the first and second outlet ports 57 and 58, and is constantly pushed to the right by a spring 74 to move the servo piston 31 to the minimum swash plate angle position. It is maintained so that In addition, the guide spool 4
2 have first and second annular grooves 75 and 7 that connect the first and second outlet ports 57 and 58 to the notch 43.
6. A shaft hole 77 is formed.

The CO valve 13 and NC valve 12 are integrated.

In other words, the valve body 100 has a piston 101.
A sleeve 102 and a spool 103 are disposed in a straight line, and the stepped portion 101 of the piston 101
a and the hole 102a of the sleeve 102.
A pressure receiving chamber 104 is configured, and the tip of the small diameter portion 101b of the piston 101 faces a second pressure receiving chamber 105. 1
The pressure receiving chamber 104 is connected to the discharge passage 1 through a port 108, and the spool 103 is pushed leftward by a spring 110 to connect to the port 109 and the passage 1.
06 to constitute a cut-off valve 13.

A sleeve 112 having a piston 111 therein and a spool 113 are arranged in a straight line in the valve body 100, and a third pressure receiving chamber 114 is formed by a stepped portion 111a of the piston 111 and a hole 112a of the sleeve 112. , small diameter portion 11 of piston 111
1b faces the second pressure receiving chamber 115, the third pressure receiving chamber 114 communicates with a port 117 through a passage 116, and the port 117 communicates with the passage 1 through a spool 113.
06, the fourth pressure receiving chamber 115 opens to the port 118, the spool 113 is pushed to the right by the spring 119, and the spring chamber 120'
constitutes the neutral control valve 12 by opening into the port 121'.

The jet sensor 11 has a restriction 82 provided between an inlet port 80 and an outlet port 81, and a first
The total pressure (static pressure + dynamic pressure) is detected by port 83,
The second port 84 is configured to detect static pressure, and the first port 83 communicates with the fourth pressure receiving chamber 115 via the port 118, and the second port 84 communicates with the spring chamber 120 via the port 121. communication,
Port 117 communicates with the first chamber 38 .

The variable torque control valve 14 is
A spool 123, a first,
A sleeve 127 with second and third pistons 124, 125, 126 inside is arranged linearly, and the spool 123 is connected to the inlet port 123 with a spring 128.
and the outlet port 122, the pressure receiving part 124a of the first piston 124 is communicated with the outlet port 122 to constitute a pressure reducing valve, and the pressure receiving part 125a of the second piston 125 is connected to the port 12.
The second piston 1 is connected to the discharge passage 1 through the
25, the spool 123 is pushed to the left against the spring 128, and the pressure receiving part 126a of the third piston 126 is connected to the discharge path ₃ of the second variable pump P2 through the port 90, and the spring An adjustment bolt 93 screwed into a cover 92 is provided facing the receiving plate 91 of the third piston 128, and a proportional electromagnetic solenoid 94 is provided facing the end surface 126b of the third piston 126.
An output plunger 95 is provided, the inlet port 121 is connected to the discharge passage 16 of the control pump _P3 , and the outlet port 122 is connected to the port 109 of the cut-off valve 13.

Next, the operation will be explained.

When the first to fourth operation valves 2 ₁ to 2 ₃ are in the neutral position, the flow rate in the drain path 9 becomes large, so the differential pressure between the total pressure of the jet sensor 11 and the static pressure becomes maximum, and the pressure of the neutral control valve 12 increases. Since the difference between the total pressure supplied to the fourth pressure receiving chamber 115 and the static pressure supplied to the spring chamber 120' is maximum, the force pushing the spool 113 to the right by the spring 119 is minimized, and the port 117 is supplied to the third pressure receiving chamber 114 and pushes the spool 113 to the left against the spring 119, so the output pressure of the neutral control valve 12 (output pressure from port 117) is the minimum pressure. Become.

On the other hand, since the pressure in the discharge passage 1 is at a minimum at this time, the pressure in the pressure receiving part 125a of the variable torque control valve 14 is at a minimum, and the second piston 1
Since the force of pushing the spool 123 by the spring 125 is the minimum, the spool 123 is pushed to the right by the spring 128 and the inlet port 121 and the outlet port 12 are pushed to the right.
The source pressure set by the relief valve 96 of the control pump P ₃ flows out from the outlet port 122 and is supplied to the port 106 of the cut-off valve 13 .

Since the pressure supplied to the first pressure receiving part 104 of the cut-off valve 13 is also the minimum, the piston 101
The pushing force to the right becomes minimum, and the spool 103 is pushed to the left by the spring 110, and the port 109 and the passage 106 are communicated, so that the source pressure of the control pump _P3 is transferred from the passage 106 to the neutral control valve. 12.

However, as mentioned above, the neutral control valve 12 is designed to minimize the output pressure, so the source pressure of the control pump P ₃ is reduced to the minimum discharge pressure, and the output pressure from the port 117 is reduced. It is supplied to the first chamber 38 of the input signal section A as control pressure.

Since this control pressure is the minimum, the spring 39
, the control spool 36 is pushed to the right and the protruding rod 37 comes into contact with the plug 73 as shown in the figure, and the swash plate 5 is moved with the servo piston 31 in the illustrated position.
is the minimum tilt angle position, and the discharge amount of the first variable pump _P1 is the minimum.

That is, the sleeve 41 is in the illustrated position, the inlet port 56 is blocked from the first and second outlet ports 57 and 58, and the pressures in the first and second pressure chambers 62 and 63 of the servo piston 31 are balanced.

When the first operating valve ₂₁ is switched to supply part of the discharge pressure oil of the first variable pump _P1 to the first actuator ₄₁ , the flow rate in the drain passage 9 is reduced and the differential pressure detected by the jet sensor 11 is reduced. , the pressure difference between the spring chamber 120' of the neutral control valve 12 and the fourth pressure receiving chamber 115 becomes smaller,
As the force pushing spool 113 to the right increases, the pressure in port 117 increases. For this reason, the pressure in the first chamber 38 increases and the control piston 36 is pushed to the left, the arm 44 swings to the left about the servo piston 31 and moves the guide spool 42 to the left. Inlet port 56 and second outlet port 58
The pressure oil discharged from the control pump P ₃ is supplied to the second pressure chamber 63 of the servo piston 31, and the servo piston 31 is moved to the left to increase the tilt angle of the swash plate 5 and the second pressure chamber 63 of the servo piston 31 is moved to the left. 1 Increase the discharge amount of variable pump _P1 .

As a result, the arm 44 swings clockwise about the pin 45 of the control piston 36, and the other end 44b pushes the guide spool 42 to the right to connect the inlet port 56 and the second outlet port 58. is shut off, and the discharge amount of the first variable pump _P1 increases in accordance with the decrease in the differential pressure detected by the jet sensor 11.

In other words, the servo piston 3 is
1 is fed back to the guide spool 42.

At this time, the control piston 36 moves to the left according to the spring characteristics of the first and second springs 39 ₁ and 39 ₂ , so the increase in the discharge amount of the first variable pump P ₁ can be arbitrarily changed according to the spring characteristics. can.

Furthermore, when the pressure in the discharge passage 1 increases, the pressure in the pressure receiving part 125a of the variable torque control valve 14 increases, and the pushing force of the second piston 125 increases, so the spool 123 is strongly moved to the left against the spring 128. As a result, the pressure reduction effect increases and the output pressure of the outlet port 122 decreases.

For this reason, the control pressure supplied to the first chamber 38 of the input signal section A via the cut-off valve 13 and the neutral control valve 12 decreases,
The control piston 36 is moved to the right, contrary to the above, and the discharge amount of the first variable pump _P1 is reduced.

Further, when the pressure in the discharge passage 1 rises close to the set pressure of the main relief valve, the pressure in the first pressure receiving chamber 104 of the cut-off valve 13 becomes large, and the piston 101 causes the spool 103 to move to the spring 11.
0 to the right to connect port 109 and passage 1.
06 and starts the pressure reducing action, the output pressure from the neutral control valve 12 is reduced.

When the pressure in the discharge passage 1 further increases, the pressure is further reduced and the neutral control valve 1
Minimize the output pressure from input signal section A.
The control pressure in the chamber 38 becomes the minimum, the discharge amount of the first variable pump _P1 becomes the minimum, and only the pressure rises to the relief set pressure of the circuit and is maintained.

The above operation is performed when the control current from the controller 20 is not being sent. Next, the case where the control current from the controller 20 is being sent will be described.

First, as shown in Fig. 4, the output voltage of the potentiometer 17 is at its minimum at the full position (full load) and gradually increases as it moves toward the slow position (partial load). Part 20
It is possible to detect the engine setting reference rotation speed stored in a, that is, the engine setting output state, for example, full load or partial load.

Then, this set standard rotation speed Nset is input to the calculation section 20b of the controller, and the rotation sensor 1
It is compared with the actual rotational speed N detected in step 9,
The output current to the output circuit 20' is controlled according to the value of (Nset-N) as shown in FIG.

Specifically, when the actual rotation speed N decreases by 200 rpm than the set reference rotation speed Nset (Nset−
The output current is controlled according to the value of N), and the maximum current is output when the set reference rotation speed Nset is 1500 rpm or less.

On the other hand, when the current value supplied to the proportional electromagnetic solenoid 94 of the variable torque control valve 14 increases, the force pushing the spool 23 increases and the discharge pressure of the outlet port 122 becomes high, and when it decreases, the force pushing the spool 23 becomes small. and exit port 122
Since the discharge pressure of the variable pump becomes low pressure, when the supply current increases, the discharge amount of the variable pump decreases, and when it decreases, the discharge amount increases, so the relationship between the absorption torque and the current value is as shown in FIG. 6.

As a result, the relationship between the discharge amount and pressure of the variable pump changes depending on the set reference rotational speed within the range of ~' in FIG. 7, and is always the same at one set reference rotational speed.

As described above, the absorption torque is changed according to the position of the control lever 18, that is, the set output state of the engine, and the discharge amount of the variable pump is controlled to increase or decrease according to the discharge pressure, so that the absorption torque matches the set output state. Since the operation is controlled in this manner, the displacement of the variable pump can be controlled without stalling even when the set output state of the engine is not only at full load but also at partial load.

Specifically, when the control lever 18 is in the full position, that is, at full load, and the engine rotation speed is 2100 rpm or more at the rated point (set reference rotation speed Nset), the current to the proportional electromagnetic solenoid 94 is the minimum (0.3A), The discharge amount (swash plate angle) is at its maximum until the absorbed torque reaches the engine rated point output.
When the engine speed falls below the rated point, the current is increased to the proportional electromagnetic solenoid 94 according to (Nset-N) to reduce the discharge amount, and when the engine speed falls below 1900 rpm, the supplied current reaches its maximum value. As a result, the discharge amount becomes the minimum and the absorption torque becomes the minimum.

In addition, in the embodiment, when the engine setting standard rotation speed Nset is up to 1500 rpm, control is performed in the same manner as described above, and when it is below 1500 rpm, the supply current value is maximized and the discharge amount is minimized to prevent the engine from stalling. Control may be performed in the same manner as described above even in the range of 1500 rpm or less.

Furthermore, when the mode changeover switch 21 is set to the intermediate mode position, the controller 20 selects the first setting device 2.
The current value set in step 6 is the proportional electromagnetic solenoid 94.
Since the force pushing the spool 123 becomes a predetermined value, the absorption torque becomes a value commensurate with the supplied current value regardless of the set output state of the engine.

Similarly, when the mode selector switch 21 is set to the low mode position, the second setting device 27
Since the current value set in is supplied to the proportional electromagnetic solenoid 94, the absorption torque becomes a value commensurate with the supplied current value regardless of the set output state of the engine.

In this way, by switching the mode changeover switch 21, the absorption torque can be set arbitrarily regardless of the set output state of the engine, so that the operation of the actuator 2, that is, the effective use of engine output suitable for the work content and the reduction of fuel consumption. You can improve your performance.

In addition, due to some circumstances, the controller 20
If the coil 2 of the changeover switch 23 is out of order,
Since no current flows through 3a, selector switch 23
is switched and the redundant circuit 25 and circuit 14' are connected, and the set current value is supplied from the redundant circuit 25 to the proportional electromagnetic solenoid 94, so that a predetermined absorption torque can be obtained regardless of the set output state of the engine. This allows the discharge amount of the variable pump to be controlled.

Specifically, the absorption torque at the intermediate mode position is X in Figure 8, and the pressure and flow rate are in Figure 7'.
The absorption torque at the low mode position is as shown in FIG. 8Y, the pressure and flow rate are as shown in FIG. 7', and the absorption torque when the redundant circuit 25 is connected is as shown in FIG. 8Z.

Further, the discharge pressure of the variable pump is introduced into the variable torque control valve 14, and the pressure at the outlet port 122 is controlled by the discharge pressure. The capacity of the variable pump can be controlled within a range.

Effects of the Invention Since the output pressure of the variable torque control valve can be controlled according to the difference between the set standard rotation speed and the actual rotation speed in each set output state of the engine,
The displacement of the variable displacement hydraulic pump can be controlled by changing the absorption torque depending on each set output state and the actual rotational speed so that the absorption torque is constant in each set output state.

Therefore, the displacement of the variable displacement hydraulic pump can be controlled by effectively utilizing the engine output without stalling even under full load or partial load.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which Fig. 1 is an explanatory overall diagram, Fig. 2 is an explanatory drawing of the controller, Fig. 3 is a detailed sectional view of main parts, and Fig. 4 is a control lever and potentiometer. Fig. 5 is a table showing the relationship between the engine rotation speed and the engine rotation speed, and Fig. 6 is the table showing the relationship between the current value and the absorbed torque. Table diagram, Figure 7 is a table diagram showing the relationship between pressure and flow rate,
FIG. 8 is a table showing the relationship between absorption torque and engine torque curve.

Claims (1)

[Claims] 1. The capacity control member of the variable displacement hydraulic pump is connected to a control mechanism operated by the discharge pressure oil of the control pump, and the connection circuit between this control mechanism and the control pump is connected to a control member that is proportional to the discharge pressure of the variable displacement hydraulic pump. A variable torque control valve that operates to reduce pressure by the thrust of an electromagnetic solenoid is provided, and a means for detecting a set output state of the engine that drives the variable displacement hydraulic pump, and a set reference rotation speed and actual speed for each set output state are provided. A control device for a variable displacement hydraulic pump, comprising means for supplying current to the proportional electromagnetic solenoid according to a difference between the rotational speed and the rotational speed.