JPH0310401Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial field of application) This invention is applicable to the case where three hydraulic pumps whose output is controlled to be constant are driven by a common prime mover.
The present invention relates to a power control device that allows a specific hydraulic pump to preferentially use the prime mover power, and controls the discharge amount of the other two hydraulic pumps to a minimum when the flow rate is not used, thereby saving the prime mover power.

(Prior art) Conventionally, for example, as shown in the first diagram, three variable displacement hydraulic pumps a, b, and c are connected to one common prime mover d, and the power consumption of a specific hydraulic pump a increases. When this happens, the power consumption of the other hydraulic pumps b and c is reduced accordingly, and the reduced power is preferentially consumed by the specific hydraulic pump a.

In this case, each hydraulic pump a, b, c is in principle controlled by a regulator g, h, i composed of a control cylinder e and a servo valve f.
In order to keep the power consumption of pumps b and c constant, each pump a,
The sum of the power consumption of b and c is controlled within the range of the prime mover power, but the discharge pressure of priority pump a increases,
When there is a request for increased power consumption, the discharge pressure of the priority pump a moves the on-off valve j against the spring k to its closing side. With this movement of on-off valve j, pumps b and c
The pressure in the pilot circuits n and o connected to the tank m from the discharge circuit through the throttle I and the throttle in the on-off valve j increases, and this pressure pushes the servo valve f through the pilot piston p, causing the control cylinder e to By reducing the pump capacities of pumps b and c, the power consumption of pumps b and c is reduced, and as a result, the priority pump a can use the power preferentially.

(Problem to be solved by the invention) However, in the power control device as described above, when there is no request to increase the output of priority pump a and the load of pump b or c is, for example, no load, the pilot Since the pressure acting on the piston p is low,
The servo valve f is pushed by the spring q, and the capacity of the pump b or c increases, resulting in a large amount of flow being wasted, which inconveniences the power loss of the prime mover.

An object of the present invention is to provide a power control device that prevents a follower pump from discharging wasteful flow when there is no request for an increase in the output of the priority pump.

(Means for Solving the Problems) In the present invention, in order to solve the above problems, one priority pump 2 and two variable displacement follower pumps 3 and 4 are connected to a common prime mover 1, A regulator 7 consisting of a control cylinder 5 that changes the pump capacity and a servo valve 6 that controls the pump discharge pressure acting on the cylinder 5 is provided for each of the following pumps 3 and 4 to control the output of each pump 3 and 4. The priority pump 2 controls the pump discharge pressure acting on the servo valve 6.
In a control device controlled by an on-off valve 8 that slides from a throttle position 8a to a closed position 8b according to the discharge pressure of . It is a piston, and one pressure-receiving surface has its own pump system bleed-off circuit 1.
The pressure generated by the throttles 28 and 29 of 1 and 12 is guided, and the pump discharge pressure of both follower pumps 3 and 4 controlled by the on-off valve 8 is guided to the other multi-stage pressure receiving surface, respectively, and the bleed Off circuit 1
1 and 12, the servo valve 6
An auxiliary piston 13 is provided to move the following pumps 3 and 4 in the direction of decreasing the pump capacity.

(Function) When the discharge pressure of the priority pump 2 increases, the discharge pressure causes the on-off valve 8 to close the discharge circuit 16 of the follower pump 3, 4.
The pilot circuits 22 and 23 connected to 17 are closed.
As a result, the pressure in the pilot circuits 22, 23 increases, and the increased pressure acts on the servo valve 6 of each follower pump 3, 4.
The discharge amount of No. 4 decreases. As a result, the output of each follower pump 3, 4 becomes smaller, and the surplus power generated in each pump 3, 4 can be preferentially used for the priority pump 2.

When the discharge pressure of the priority pump 2 is so low that it cannot operate to throttle the on-off valve 8, the pressure in the pilot circuits 22, 23 acting on the servo valves 6 of each follower pump 3, 4 is also low; , the discharge amount of each follower pump 3, 4 is determined by the bleed-off circuit 11,
12 to the tank, pressure is generated in the bleed-off circuits 11 and 12 due to the throttles 28 and 29 interposed therein, and this pressure is applied to each of the follower pumps 3 and 4. Auxiliary piston 13
in order to act on the pressure receiving surface 32 of the auxiliary piston 1.
3 pushes the servo valve 6, and as a result, the pump capacity of each follower pump 3, 4 is controlled to be reduced, and unnecessary flow rate is no longer discharged.

(Example) An example of the present invention will be described based on FIG. 2 of the drawings.

In the embodiment shown in the figure, the priority pump 2 is also configured with a variable displacement hydraulic pump like the following pumps 3 and 4, and the priority pump 2 is also controlled in the same manner as the regulator 7 of each of the following pumps 3 and 4. A regulator 7a including a cylinder 5a and a servo valve 6a is provided. The priority pump 2 is connected to, for example, a swivel base of a power shovel, and in this case, the two follower pumps 3 and 4 include a traveling means, an arm, a boom,
An actuator that drives the bucket is connected. Control cylinder 5 of each regulator 7, 7a,
The piston rod 5a is connected to a means for varying the displacement of the pumps 2, 3, 4, such as a swash plate, so that the force due to the discharge pressure of each pump is increased and the spools of the servo valves 6, 6a are moved by the spring 14, 14a
When the valves are opened against the The piston rods of the cylinders 5, 5a move toward the rod side due to the difference in pressure receiving areas on both sides of the pistons. With this movement, the inclination angle of, for example, the swash plate of the pumps 2, 3, 4 is reduced, the pump capacity is reduced, and therefore the pump discharge amount is reduced. Also, during this movement, the springs 14, 14a
As the servo valves 6, 6a are bent, their elasticity changes, and when the force due to the pump discharge pressure acting on the servo valves 6, 6a becomes equal to the elasticity, the servo valves 6, 6a
remains between the original position and the switching position,
The movement of the control cylinders 5, 5a is stopped. As the force due to the discharge pressure of each pump decreases, the servo valves 6, 6a
When the spool of the control cylinder 5,5a enters the position connecting the head chamber of the control cylinder 5,5a to the tank by means of the spring 14, the piston of the control cylinder 5,5a absorbs the pump discharge pressure acting on its rod side chamber. Accordingly, the elasticity of the springs 14, 14a is weakened, the servo valves 6, 6a remain in the neutral position, and the control cylinders 5, 5a are stopped.

While repeating such movement and stopping, the pump capacity (pump discharge amount) is controlled in accordance with the pump discharge pressure, and the pump output expressed as the product of the pump discharge pressure and the pump capacity is controlled to be substantially constant.

Further, the servo valve 6a of the regulator 7a of the priority pump 2 operates against the spring 14a by the force of the discharge pressure of its own discharge circuit 15, and controls the output of the priority pump 2 to a constant level. Each servo valve 6 of the regulator 7 of the pumps 3, 4 is provided with a two-stage pilot piston 18, and both pistons 18 are connected to the discharge circuits 16, 17 of both pumps 3, 4
When pressure acts between the throttles 19, 20 and the shut-off valve 8 in the pilot circuits 22, 23 connected to the tank 21 via the throttles 19, 20 and the shut-off valve 8, each servo valve 6 resists the spring 14. The output of each follower pump 3, 4 was controlled to be constant by sliding as described above.

When the force due to the discharge pressure of the discharge circuit 15 of the priority pump 2 increases, the on-off valve 8 bends the spring 24 and slides from the throttle position 8a, which throttles the flow of the pilot circuits 23 and 24, to the closed position 8b. As the valves move, the pressure in each pilot circuit 22, 23 is gradually throttled down by the on-off valve 8, and is controlled to eventually increase to the discharge pressure of each discharge circuit 16, 17. Therefore, when the discharge pressure of the priority pump 2 is low, the pump discharge pressure of each follower pump 3, 4 acting on the spool of the servo valve 6 of each follower pump 3, 4 is weakened, and each follower pump 3, 4 is The pump capacity is controlled to be large by the above-described action of the regulator 7, and a large output is generated, and when the discharge pressure of the priority pump 2 is high, each follower pump 3, 4
is controlled so that the pump displacement is small and generates a small output. As a result, the outputs of the follower pumps 3 and 4 become smaller, and the resulting surplus power can be preferentially used by the priority pump 2.

Specifically, when both follower pumps 3 and 4 are operated with output characteristics as shown by curve A in FIG. 4, the discharge pressure of priority pump 2 becomes Pb as shown in FIG.
When the on-off valve 8 is closed, the output characteristics of both follower pumps 3 and 4 are changed to the curve Amin shown in FIG. 4, and the reduced power is used to power the priority pump 2. In addition, the discharge pressure Pb of the priority pump 2
When it becomes below, both follower pumps 3 and 4 curve Amax
It is operated at an output close to .

The above structure and operation are almost the same as the conventional one, but in this case, when the follower pumps 3 and 4 are in a no-load state, for example, they discharge a flow rate corresponding to Q ₁ in Fig. 4, and the energy is There is a disadvantage that the loss is large.

Therefore, in the present invention, bleed-off circuits 11 and 12 are provided in the circuits to the actuators 9 and 10 driven by the following pumps 3 and 4, respectively.
The pressure generated by the throttles 28 and 29 provided in the piston and the discharge pressure of the pumps 3 and 4 controlled by the on-off valves 8 of the pilot circuits 22 and 23 is applied to each pressure-receiving surface of the end face of the spool-type auxiliary piston 13. When the pressure in the circuits 11 and 12 is predominant, the auxiliary piston 13 moves the servo valve 6 in a direction that reduces the pump capacity of each follower pump 3 and 4; The details are as follows.

The bleed-off circuits 11 and 12 are known ones that are provided in valve units 24 and 25 that include switching valves and the like for controlling the actuators 9 and 10, and the valve units 24 and 25 are connected to the follower pumps 3 and 25, respectively. Actuator 9,1 with full flow from 4
When operated to drive 0, all of the tank return flow flows to the tank via the tank circuits 26 and 27, but part of the flow of the pumps 3 and 4 drives the actuators 9 and 10, or , 10 to be stopped.
4 and 25 are operated, the remainder or all of the pump flow rate flows to the tank via the bleed-off circuits 11 and 12, and a resistance pressure corresponding to the bleed-off flow rate is generated at the throttles 28 and 29. 30 and 31 are safety valves. The pressure in each bleed-off circuit 11, 12 is applied to the circuit 3 by an auxiliary piston 13 provided to operate the servo valve 6 of its own follow-up pump 3, 4, respectively.
5,36.

As shown in the third diagram, each auxiliary piston 13 has a pressure receiving surface 32 on which the pressure of the bleed-off circuit 11 or 12 acts, and two pressure receiving surfaces 33, 34 on the opposite side.
The pressure of the pilot circuit 22, the part of which is omitted, acts on the pressure receiving surface 33, and
4 is acted upon by the pressure of the pilot circuit 23. If the force caused by the pressure in the bleed-off circuit is stronger than the force caused by the pressure in the pilot circuits 22, 23, the auxiliary piston 13 pushes the servo valve 6 via the pilot piston 18, causing the regulator 7 to reduce the pump displacement. Force operation. The area of the pressure receiving surfaces 33 and 34 of the auxiliary piston 13 is
For example, the pressure receiving surface 32 is formed to have the same area as each pressure receiving surface 18a, 18b of the corresponding pilot piston 18, and each pressure receiving surface 18a, 18b is also formed to have the same area, but the pressure receiving surface 32 may be formed on both pressure receiving surfaces depending on the usage conditions. 1
It is formed about 10 times as large as 8a and 18b. In this case, each servo valve 6 is operated by the auxiliary piston 1 when the pump discharge pressures of the pilot circuits 22 and 23 controlled by the on-off valve 8 are both at no-load pressure.
3, the pressure of the bleed-off circuits 11 and 12 multiplied by the area of the pressure receiving area 32 is used to reduce the volume of the pumps 3 and 4 to Q ₂ or less in FIG. 4, thereby eliminating wasted fluid. Discharge is prevented, but the sum of the pressures in the pilot circuits 22 and 23 is greater than the value obtained by multiplying the pressure in the bleed-off circuits 11 and 12 by the area of the pressure receiving surface 32 and dividing this by the total area of both pressure receiving surfaces 18a and 18b. Then, the auxiliary piston 13 separates from the pilot piston 18 and exerts no force on it, and the servo valve 6 closes the pilot circuits 22, 23.
controlled only by pressure.

To explain the operation when the follower pumps 3 and 4 are operated under no load, in this case, the flow rate of the pumps 3 and 4 flows into the bleed-off circuits 11 and 12, so pressure is generated by the throttles 28 and 29. The pressure acts on the pressure receiving surface 32 of the auxiliary piston 13. At this time, the discharge pressure of the follower pumps 3, 4 is relatively small, and the pressure receiving surface 32 is large, so the auxiliary piston 13 pushes the servo valve 6 via the pilot piston 18, and as a result, the pump capacity of the pumps 3, 4 is Since the flow rate is controlled to be small and unnecessary flow rate is not discharged, the power of the prime mover 1 is saved. When the discharge pressure of the priority pump 2 increases, the on-off valve 8 is moved toward its closed position 8b, and the pilot circuit 22,
The pressure at 23 gradually approaches the discharge pressure of the follower pumps 3, 4, and that pressure acts on the servo valve 6 via the pilot piston 18, resulting in
The capacity of pump No. 4 is reduced to generate power to be transferred to priority pump No. 2.

In particular, when there is no variation in the discharge pressure of the priority pump 2, the follower pumps 3 and 4 are controlled to have a constant output by operating the regulator 7 in accordance with the discharge pressure.

(Effect of the invention) As described above, according to the invention, the bleed-off circuits 11 and 12 equipped with the throttles 28 and 29 are provided in the system of each follower pump 3 and 4, and each bleed-off circuit 1
1 and 12 are applied to one pressure-receiving surface of a spool-shaped auxiliary piston 13 attached to the servo valve 6, and the other multi-stage pressure-receiving surface is provided with two follower pumps 3 and 4 controlled by an on-off valve 8. Since the pump discharge pressures are applied to each, the power can be applied preferentially to the priority pump 2, and each follower pump 3, 4 can be applied preferentially.
The discharge amount can be reduced when the flow rate is not used, and the power of the prime mover 1 can be effectively used and saved with a simple configuration that includes one on-off valve 8 that is operated by the pressure of the auxiliary piston 13 attached to the servo valve 6 and the priority pump 2. This has the effect of making it possible to achieve this goal.

[Brief explanation of drawings]

Fig. 1 is a line diagram of a conventional example, Fig. 2 is a line diagram of an embodiment of the present invention, and Fig. 3 is a sectional view of a specific example of the main part thereof.
FIG. 4 is an output characteristic curve diagram of the following pump, and FIG. 5 is an output characteristic curve diagram of the priority pump. 1... Prime mover, 2... Priority pump, 3, 4...
Follow-up pump, 5... Control cylinder, 6... Servo valve, 7... Regulator, 8... Open/close valve, 8a...
...Aperture position, 8b...Closed position, 9,10...Actuator, 11,12...Bleed-off circuit,
13... Auxiliary piston, 28, 29... Throttle.

Claims (1)

[Scope of utility model registration request] One priority pump 2 and two variable displacement following pumps 3 and 4 are connected to a common prime mover 1, and each of the following pumps 3 and 4 has a control cylinder 5 and a control cylinder 5 for changing the pump displacement, respectively. A regulator 7 composed of a servo valve 6 that controls the pump discharge pressure that is applied is provided to control the output of each pump 3, 4,
The pump discharge pressure acting on the servo valve 6 is changed from the throttle position 8a to the closed position 8 according to the discharge pressure of the priority pump 2.
In the control device controlled by the on-off valve 8 that slides into the valve 8, the bleed-off circuits 11 and 12 have throttles 28 and 29 interposed in the circuits to the actuators 9 and 10 driven by the respective follower pumps 3 and 4, respectively. established,
Each servo valve 6 has a spool-shaped piston whose both ends are formed as pressure receiving surfaces and one pressure receiving surface is provided with a stepped portion to form a multistage pressure receiving surface, and one pressure receiving surface has its own pump. The pressure generated by the throttles 28 and 29 of the bleed-off circuits 11 and 12 of the system is guided, and the pump discharge pressure of both follower pumps 3 and 4 controlled by the on-off valve 8 is applied to the other multi-stage pressure receiving surface, respectively. The servo valve 6 is guided by the force of the bleed-off circuits 11 and 12.
A power control device for three hydraulic pumps driven by a common prime mover, which is provided with an auxiliary piston 13 that moves the following pumps 3 and 4 in the direction of decreasing pump capacity.