JPH0130634Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for controlling a variable displacement hydraulic pump driven by an engine.

A variable displacement hydraulic pump discharges pressure oil by rotating, and the pressure of the discharged pressure oil changes depending on the load of the actuator, and the difference between that pressure and the discharge when the variable displacement hydraulic pump rotates once. The torque for driving the variable displacement hydraulic pump is determined by the displacement amount per rotation, and the magnitude of the torque is the displacement amount per rotation x discharge pressure. Expressed as.

Further, the value obtained by multiplying the above-mentioned absorption torque by the rotational speed becomes the horsepower for driving the variable displacement hydraulic pump, and if the rotational speed is constant and the absorption torque is constant, the horsepower also becomes constant.

A control device for a variable displacement hydraulic pump, for example, increases or decreases the discharge amount per rotation according to the pressure of the variable displacement hydraulic pump so that the absorbed torque remains constant, and then adjusts the absorbed torque to the engine's rated point. There is known a device that controls the absorption torque of a variable displacement hydraulic pump so that it always has the set value.

However, with this control device, when considering the matching with the torque characteristics of the engine, the absorption torque of the variable displacement hydraulic pump becomes equal to the torque at the rated point a of the engine torque curve, as shown in Figure 1. This is fine when the engine is at full load, but when the engine is at partial load, the engine torque curve differs from the torque curve at full load, as shown by symbol c in Figure 1. A line b parallel to the horizontal axis from the rated point a
The absorption torque of the variable displacement hydraulic pump is controlled in accordance with the torque at the intersection point d between the curve c and the torque curve c.

For this reason, it is not possible to utilize the torque in the shaded area in Figure 1, which becomes larger than the torque at rated point a when the engine speed decreases below the rated speed, that is, the engine's torque rise. It cannot be used effectively, and when the engine is set to low idle, the torque curve becomes as shown by symbol e in Figure 1, which is smaller than the torque at the rated point a.
The engine will stop.

The present invention was developed in view of the above circumstances, and its purpose is to make it possible to effectively utilize engine output in the entire engine speed range and to prevent engine stalling during low riding.

Embodiments of the present invention will be described below with reference to FIG. 2 and subsequent figures.

Figure 2 is an overall circuit diagram, in which the engine E operates 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-capacity fixed-capacity hydraulic pressure for control. A pump (hereinafter referred to as a control pump) P ₃ is driven, and first, second, and third operation valves 2 ₁ , 2 ₂ , 2 ₃ are connected to the discharge path 1 of the first variable pump P _{1 .}
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 the first to sixth actuators 4 _{1 to} 4 such as motors and cylinders. 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,
The control mechanisms 7 and 8 are controlled by jet sensors 11 and 10 provided in the drain passages 9 and 10 of the discharge passages 1 and 3 of the first and second variable pumps P ₁ and P ₂ , respectively.
12 and cut-off and negative control valve (hereinafter referred to as CO+NC valve) 13,1
4 and a valve 15 provided in the discharge passage 16 of the control pump _P3 .

A rotation sensor 17 detects the actual rotational speed of the engine E, and its detected value (signal voltage) is sent to a controller 18, which transmits a signal current to the variable torque control valve 15.

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.
The spring 33 is always held at the minimum swash plate angle position (minimum discharge amount position) shown in the figure, and the spring 33 is held down by a cover 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 first spring 39 ₁ , a spring receiver 40, and a second spring 39 ₂ are linearly arranged on the other side. There is.

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 into the inlet hole 59 of the case 30, and the first and second outlet ports 57 and 58 are formed in the case 30 and the first and second passages 60 and 58 are 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+NC valve 13 includes a cut-off valve section C and a negative control valve section D.

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 form a cut-off valve section C.

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
b faces the second pressure receiving chamber 115, and the third pressure receiving chamber 114 communicates with the port 117 through a passage 116.
Port 117 connects the spool 113 to the passage 106.
At the same time, the fourth pressure receiving chamber 115 is opened to the port 118, and the spool 113 is connected to the spring 1.
19, and its spring chamber 120 opens into a port 121, forming a negative valve section D.

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 15 is
A sleeve 27 having a spool 23 and first, second, and third pistons 24, 25, and 26 disposed inside the valve body 20 that connects the inlet port 21 and the outlet port 22 is linearly disposed, and the spool 23 The spring 28 urges the inlet port 21 and the outlet port 22 in a direction to communicate with each other, and the first piston 24
The pressure receiving part 24a of the second piston 25 is connected to the outlet port 22 to form a pressure reducing valve, and the pressure receiving part 25a of the second piston 25 is connected to the discharge passage 1 through the port 29, and the second piston 25 connects the spool 23 to the spring 28. At the same time, the third piston 26 is connected to the discharge passage 3 of the second variable pump P ₂ through the port 90, and is opposed to the receiving plate 91 of the spring 28. An output plunger 93 of the first proportional electromagnetic solenoid 92 is provided, and an output plunger 95 of the second proportional electromagnetic solenoid 94 is provided opposite the end surface 26b of the third piston 26. The inlet port 21 is connected to the control pump _P3 . The outlet port 22 is connected to the port 109 of the cut-off valve section C.

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 passage 9 is large, so the differential pressure between the total pressure of the jet sensor 11 and the static pressure becomes maximum, and the negative control valve D 4 Pressure receiving chamber 11
Since the difference between the total pressure supplied to spring 119 and the static pressure supplied to spring chamber 120 is maximum,
As a result, the force pushing the spool 113 to the right is minimized, and the pressure in the port 117 is reduced to the third pressure receiving chamber 1.
14 to connect the spool 113 to the spring 1
19, the output pressure of negative control valve D (output pressure from port 117) becomes the minimum pressure.

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 25a of the variable torque control valve 15 is at a minimum, and the pressure in the second piston 25 is at a minimum.
Since the force pushing the spool 23 by
The spool 23 is pushed to the right by the spring 28, the inlet port 21 and the outlet port 22 are communicated with each other, and the source pressure set by the relief valve 96 of the control pump _P3 flows out from the outlet port 22, and is cut off. It is supplied to port 109 of valve section C.

Since the pressure supplied to the first pressure receiving part 104 of the cut-off valve part C is also 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 to communicate with the control pump _P3.
The source pressure of is supplied to the negative control valve D from the passage 106.

However, as mentioned above, the output pressure of the negative control valve D is set to be the minimum, so the source pressure of the control pump _P3 is reduced to the minimum discharge pressure, and the input pressure is output from the port 117. It is supplied to the first chamber 38 of the signal section A as control pressure.

Since this control pressure is the minimum, the control spool 36 is pushed to the right by the first and second springs 39 ₁ and 39 ₂ to the illustrated position where the protruding rod 37 is in contact with the plug 113, and the servo piston 31 as the illustrated position and the swash plate 5 as the minimum tilt angle position.
Minimize the discharge amount of variable pump _P1 .

In other words, the guide spool 42 is in the illustrated position,
Inlet port 56 and first and second outlet ports 57,5
8 is shut off, and the pressures in the first and second pressure chambers 62 and 63 of the servo piston 31 are balanced.

When the first operation 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, so it is negative. The pressure difference between the spring chamber 120 and the fourth pressure receiving chamber 115 of the control valve section D becomes smaller, and the force pushing the spool 113 to the right increases, causing the port 1
17 pressure 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. The inlet port 56 and the second outlet port 58 communicate with each other, and 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 leftward to the swash plate 5. The displacement angle of the first variable pump P1 is increased to increase the discharge amount of the first 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. .

Further, when the pressure in the discharge passage 1 increases, the pressure in the pressure receiving part 25a of the variable torque control valve 15 increases, and the pushing force of the second piston 25 increases, so the spool 23 is strongly moved to the left against the spring 28. As a result, the pressure reduction effect increases and the output pressure of the outlet port 22 decreases.

For this purpose, the input signal section A is passed through the cut-off valve section C and the negative control valve section D.
The control pressure supplied to the first chamber 38 of is reduced, and 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.

Furthermore, 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 section C increases, 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 negative control valve D is reduced.

Then, when the pressure in the discharge passage 1 further increases, the pressure is further reduced to minimize the output pressure from the negative control valve D, and the first chamber 3 of the input signal section A
When the control pressure in 8 becomes the minimum, the first variable pump
The discharge amount of _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 18 is not being sent. Next, the case where the control current from the controller 18 is being sent will be described.

First, when the engine's fuel injection pump lever is in the full position (that is, when it is set to the maximum output state), the rotation sensor 17 detects the engine's maximum rotational speed under no-load conditions to detect that it is in the full position. and inputs this information to the controller 18.

As a result, the controller 18 does not output a control current to the first and second proportional electromagnetic solenoids 92 and 94, and no thrust acts on the output plungers 93 and 95, so the controller 18 operates in the same manner as described above.
The absorption torque of the variable pump corresponds to A in FIG. 4, and in terms of engine torque characteristics, it corresponds to the point (rated point) on the maximum torque curve 1 as shown in FIG.

When the fuel injection pump lever of the engine is set to the half position (when set to an intermediate output state), the rotation sensor 17 detects that it is in the half position and inputs it to the controller 18, and the controller 18 stores the engine Torque curve at half position in torque characteristics (Figure 5)
The current corresponding to (-) is the first
It is input to the proportional electromagnetic solenoid 92.

As a result, the output plunger 93 outputs a thrust proportional to the input current to push the catch 91 and increase the set load of the spring 28 by an amount corresponding to (-).

Therefore, the output pressure of the variable torque control valve 15 increases, and the control pressure in the first chamber 38 of the input signal section A increases as described above.
Similarly to the above, the discharge amount of the first variable pump _P1 increases.

At this time, the variable pump absorption torque becomes large as shown in FIG. 4, and the engine torque can be used effectively.

Furthermore, when the fuel injection pump lever of the engine is at the low idle position (when set to a low output state), the rotation sensor 17 detects the low idle position and inputs it to the controller 18.
8 is the torque curve at the low idle position in the memorized engine torque characteristics (Figure 5)
The current corresponding to (-) according to the second point
The current is input to the proportional electromagnetic solenoid 94, and the output plunger 95 generates a thrust proportional to the current.

As a result, the third, second, and first pistons 26,
The spool 23 is connected to the spring 2 through 25 and 24.
8 to the left to reduce the pressure, the output pressure of this outlet port 22 decreases, and the control pressure in the first chamber 38 of the input signal section A decreases as described above. , the discharge amount of the first variable pump _P1 decreases.

Therefore, the absorption torque of the first variable pump _P1 becomes small as shown in C in FIG. 4, so that engine stall can be prevented.

In addition, in the above embodiment, the pressure receiving part 2 of the third piston 26 of the variable torque control valve 15
Since the discharge pressure of the second variable pump P ₂ is supplied to 6a, the discharge amount can be controlled by the sum of the discharge amount and discharge pressure of the first and second variable pumps P ₁ and P ₂ .
The third piston 26 may be omitted.

The present invention is as described above, and when the set output state of the engine is at full load, the output pressure from the variable torque control valve 15 can be used to increase or decrease the discharge amount and control the absorption torque to be constant. When the set output state is at partial load, the output pressure of the variable torque control valve 15 is increased by the first proportional electromagnetic solenoid 92 and the discharge amount is increased, so the absorption torque can be made larger than at full load, and the engine setting When the output state is low idle, the output pressure of the variable torque control valve 15 is lowered by the second proportional electromagnetic solenoid 94, and the discharge amount is reduced, so that the absorption torque can be made smaller than when the load is full.

Therefore, the absorption torque of the variable displacement hydraulic pump should be set to a value commensurate with the torque at the rated point when the set output state of the engine is at full load, and set to a value larger than the torque at the rated point at partial load to increase the engine torque. At low idle, the torque value is smaller than the rated point torque so that the engine does not stop, and the variable displacement hydraulic pump can be controlled so that the engine output can be effectively used in the entire engine speed range. This can prevent the engine from stopping.

[Brief explanation of the drawing]

Fig. 1 is a table showing the matching state with the engine output in the conventional example, Fig. 2 is an explanatory overall diagram showing the embodiment of the present invention, Fig. 3 is a detailed sectional view of the main part, Fig. 4 5 is a table showing the absorption torque of the variable pump, and FIG. 5 is a table showing the matching state with the engine output in the present invention. P ₁ and P ₂ are variable displacement hydraulic pumps, P ₃ is a control pump, E is an engine, 4 is an actuator, 1
5 is a variable torque control valve.

Claims (1)

[Scope of utility model registration request] Variable displacement hydraulic pump driven by engine E
The discharge pressure oil of P ₁ and P ₂ is supplied to the actuator 4, and the discharge amount of the variable displacement hydraulic pumps P ₁ and P ₂ is controlled by the output pressure oil from the variable torque control valve 15, so that the output pressure is high. In a control device for a variable displacement hydraulic pump configured to control the discharge amount to increase when the discharge rate increases and to decrease when the discharge rate decreases, the variable control valve 15 is provided with a first proportional electromagnetic solenoid 92 that increases the output pressure.
and a means for detecting the set output state of the engine by arranging a second proportional electromagnetic solenoid 94 to reduce the output, and when the set output state of the engine is a partial load, inputting current to the first proportional electromagnetic solenoid 92 to reduce the engine output. When the set output state is low idle, the second
A control device for a variable displacement hydraulic pump, characterized in that a controller 18 for inputting current to a proportional electromagnetic solenoid 94 is provided.