JPS5918561B2 - Pressure control servo device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit pressure control servo device, and more specifically to a control pulp for pump flow rate control and an IJ in the circuit.
The present invention relates to a circuit pressure control servo device in which IJ-F valves are coaxially integrated and a pressure setting spring is shared.

In general, in open circuits and closed circuits that connect a variable flow rate pump and a load, it is necessary to adjust the pump's discharge flow rate each time to maintain the circuit internal pressure constant even when the load pressure increases or decreases. be.

For example, an example of this is disclosed in British Patent No. 1224266.

However, since the relief valve and control pulp are assembled separately in this product, it is necessary to adjust each spring installed in each of these valves and set the pressure separately, which requires a large number of parts. , has a complicated structure, poor processability, and poor economic efficiency.

On the other hand, the circuit pressure acts on the relief pulp through the restriction by the flat part provided in the control valve, and the control valve is operated by the differential pressure before and after the restriction by the flat part, for example. In an open circuit, when the flow from the pump to the load is interrupted and the circuit pressure rises, the relief pulp valve opens and a fluid flow is generated in the throttle area formed by the flat part of the control pulp. The control pulp is actuated by the differential pressure generated, and the servo device controls the pump discharge amount to zero.

However, when the pump discharge amount becomes zero with this value of 5,
The fluid that had been flowing through the throttle area created by the flat part of the control pulp disappears, and therefore the servo device operates to increase the pump discharge amount.

Then, the R+J-f valve opens again and the servo device controls the pump output amount to zero in the same way as above, and thus this servo device controls the circuit pressure to be constant when the pump output amount is controlled to zero. Since there is no mechanism, the circuit pressure becomes unstable and cannot be maintained at a controlled pressure (constant pressure).

Furthermore, since the control pulp is a differential pressure operated type that utilizes the differential pressure before and after the throttle, it is necessary to open the relief valve from the throttle to secure a certain amount of flow, which means that the flow rate that operates the control valve is decreases accordingly, and the switching speed of the control valve becomes slower.
Responsiveness is also poor.

Therefore, the object of the present invention is to reduce the number of parts and improve the structure! To provide a circuit pressure control servo device that is compact, has excellent workability and economic efficiency, can maintain circuit pressure constant even when the flow from a pump to a load is cut off, and has good responsiveness of a control valve. It is.

j In order to achieve this objective, the present invention operates a servo device using changes in circuit pressure due to load fluctuations as pilot pressure, controls the pump discharge amount, and maintains the circuit pressure at a constant value. Pressure control servo equipped with relief pulp to prevent sudden rise.In the device, a spool that serves as both a control valve and a relief valve is integrated into the main body of the servo device that controls the pump discharge amount, and can slide freely on the same axis. A spring inserted into the control valve and opposed to pilot pressure is provided at one end of the control valve, and the relief pulp is configured to provide a minute break flow rate at a neutral position of the control valve. be.

An embodiment of the present invention will be described below with reference to the drawings.

In the open circuit shown in FIG. 1, the variable displacement pump 1 is used.

and a load 2 are connected by a main circuit A, a control circuit B is connected to the main circuit A, and a servo device 6, an actuator I, and a reducer according to the present invention that integrate a control valve and a relief valve are connected to the main circuit A. singbalp 5
is provided.

or . An accumulator 3,
4 are connected.

In the above-mentioned open circuit, if the discharge amount of the pump 1 is Ql, the circuit pressure to the load is adjusted to the set value P1 of the servo device 6 consisting of the control valve 6a and the relief valve 6b. In this case, the control valve 6a is in the neutral position, and in this state, the relief pulp 6b discharges a minute break flow rate q1 from the pilot circuit to the tank side.

From this state, assume that the page change 2 changes and the circuit pressure increases, and the required flow rate to return this increased circuit pressure to the original set value P1 becomes Q2 (Ql > Q2). The break flow rate q of 6b increases and at the same time, the control valve 6a is switched to the left position.

Therefore, the reducing pressure of the reducing valve 5 flows into the actuator 7, reducing the pump flow rate and the load 2.
required flow rate.

Balance in Q2.

At this time, the relief break flow rate q has returned to the original ql.

Conversely, the circuit pressure decreases and the required flow rate becomes Q3 (Ql<Q3
), the relief break flow rate q becomes zero and at the same time the control valve 6a switches to the right position, so the pressure from the accumulator 4 enters the actuator 7, displacing the tilting angle of the pump 1 and increasing the pump flow rate to the required flow rate Q3. balance.

At this time, an accumulator 3 is included in the main circuit 3 to compensate for the circuit pressure.

Next, in the Clost forward/reverse circuit shown in Figure 2, boost pump 1
b The built-in variable discharge amount pump 1a and the load 2 are connected to the main circuit E,
The boost pump 1b is connected to the control circuit G and the main circuit E.

F is provided with a relief valve switching valve 9 and a lashing switching valve 10 in parallel, and a control circuit G is provided with a servo device 6, a switching pulp 8, and an actuator 1 according to the present invention in series.

The switching valves 8 and 9 are configured to switch in conjunction with each other.

The circuit H between the switching pulps 9 and 10 is connected to the IJ valve 6b and the 7 lashing relief valve 5a.

Note that 11 is a check valve, 12 is a boost relief valve, and 13 is an accumulator.

The operation in the above circuit is substantially the same as in FIG.

That is, if the pump 1a is now discharging hydraulic oil to the circuit E side and the circuit E side is at high pressure, the switching pulps 8 and 9 are held at the left position as shown in the figure, and the switching pulp 10 is in the circuit E side. .

It is switched to the upper position with a differential pressure of F.

For this reason, the hydraulic oil from the boost pump 1b opens the lower check valve 11 in the figure and enters the circuit F, and the same amount of hydraulic oil as the hydraulic oil that entered this circuit F flows from the circuit F to the switching valve 1.
0 and flushing relief valve 5a (low pressure relief valve)? In this way, part of the hydraulic oil in circuits E and F is sent to the boost pump 1 through Il- and returned to the tank.
The temperature rise in circuits E and F is prevented by replacing it with hydraulic oil from b.

When the load 2 changes from this state and the pressure in the circuit E rises, this pressure acts on the pilot circuit from the switching pulp 9, switching the control pulp 6a of the servo device 6 to the right position, and at the same time causing the minute break flow rate of the relief pulp 6b. q1 increases to flow rate q.

Thus, the hydraulic oil from the boost pump 1b enters the actuator 1 via the control pulp 6a and the switching valve 8, displacing the tilt angle of the pump 1a, and
balance by reducing the discharge amount to the required flow rate.

Similarly, when the pressure in circuit E decreases, the control valve 6 switches to the left position, and the minute break flow rate q1 of the relief pulp 6b becomes zero, increasing the discharge rate of the pump 1a to the required flow rate and increasing the pressure in circuit E to the set value. Balance by controlling to P1.

In addition, when the pump 1a is operated in the reverse rotation direction with circuit F on the reverse rotation side set to the high pressure side, the switching pulp 10 is switched to the lower position by the differential pressure between circuits F and E, and in this case, the boost Hydraulic oil from pump 1b flows through upper check valve 11
The signal flows into circuit E, and seven lashings of circuits E and F are performed in the same manner as described above.

On the other hand, the switching valves 8 and 9 are each switched to the right position, whereby the servo device 60 control circuit becomes a reverse flow circuit and similarly controls the pressure on the circuit F side to the set value P1.

Next, the servo device 6 of the present invention shown in FIG. 3 will be described in detail.

Servo device main body 14 and cylinder 15 of actuator 7
are integrally connected, and a passage 16 is provided in the lateral direction in the servo device main body 14, and a spool 11 that serves both as the control pulp 6a and the relief pulp 6b is integrated in the passage 16 and can freely slide on the same axis. A piston 18 is inserted into the cylinder 15 and connected to a slide arm 19.
is slidably inserted, the piston 18 is slid in one direction by switching the spool 17, and the slide arm 19
The tilt angles of the pumps 1 and 1a are changed through the pumps 1 and 1a.

Inside the servo device main body 14 are a relief valve inlet port 20 from the pilot circuit led opposite to the right end of the passage 16, a control valve entry port 21 and a control pulp drain port 22 that open on the side of the passage 16.
．． 23 and relief pulp drain port 24 are drilled,
The ports 21, 22, 23 are sealed by the land of the spool 17 when the spool 17 is in the neutral position, and similarly, in the neutral position, the tip 17a of the spool 17 allows the relief valve drain port 24 to open somewhat through a slight clearance around the spool 17. The small flow rate g1 of pressure oil from the port 20 breaks through this opening as a forward leak.

A spring seat 25 is connected to the back of the spool 17, a pressure setting spring 27 is interposed between the spring seat 25 and a spring piston 26 at the back, and a pressure setting bolt 28 abuts against the back of the spring piston 26. ing.

The pressure within the circuit is set by the pressure setting bolt 28 and spring 27.

Also, the main body 14 has port 2 by switching the spool 17.
Holes 30, 31 are drilled in selective communication with 1.

Next, liquid chambers 32 and 33 are formed in the cylinder 15 and are partitioned by the piston 18. The liquid chamber 32 is connected to the hole 30 of the main body 14 through the hole 34, and the liquid chamber 33 is connected to the hole
5, it communicates with the hole 31 of the main body 14.

Next, we will discuss its operation.

Now, when the circuit A in Figure 1 or the circuit E or F in Figure 2 is at the set value P1, if the spring 21 is set so that the spool 11 maintains the neutral position, the circuit pressure will be the set value P□ As long as the spool 17 is in the neutral position,
The piston 18 of the actuator 7 is in a stopped state, and the pump 1 or 1a discharges the necessary flow rate to maintain the circuit pressure at the set value P1.

At this time, the tip 17a of the spool 11 leaks pressure oil from the port 20 toward the lJ'J-7 valve drain port 24, giving a minute break flow rate q1 as a pre-leak.

When the pressure in the circuit increases in this state, this pressure acts on the tip 17a of the spool 1T from the pilot circuit through the relief valve inlet port 20, and moves the spool 17 to the left against the spring 27.

For this purpose, the hole 3o of the main body 14 communicates with the control valve entry port 21 through the passage 16, so that reducing pressure or boost pressure is transmitted to the cylinder 15 through the hole 30.34.
The liquid chamber 33 on the opposite side enters the liquid chamber 32 through the holes 35, 3.
1. It is opened to the drain side via the passage 16 and the port 22, so the piston 18 and the slide arm 19 move to the left to reduce the discharge flow rate of the pumps 1 and 1a.
When the pump flow rate matches the load flow rate, the spool 17 is activated again.
returns to neutral position.

Note that during this control, the amount of relief by the tip 17a of the spool 17 increases from ql to q because the circumferential clearance length of the tip 17a decreases or the annular groove portion opens slightly, but this increase amount is Simultaneously with the switching of the spool 17, the piston 18 operates to control the discharge amount of the pump 1 or 1a, and the increase in circuit pressure is kept within a minute range, so the amount of movement of the spool 17 is not very large, so the relief The break flow rate q flowing from the pulp inlet port 20 to the drain port 24 is kept to a minimum.

When the internal pressure of the circuit decreases, spool 1γ moves to the right,
As a result, the clearance length around the tip 17a of the spool 11 increases, so the relief amount decreases from ql to zero or approaches it, and the hole 31 of the main body 14 closes to the passage 16.
The control pulp enters the port 21 through the hole 30.
communicates with the control valve drain port 23, reducing pressure or boost pressure enters the liquid chamber 33 of the cylinder 15 through the hole 31.35, moves the piston 1B and the slide arm 19 to the right, and increases the pump discharge amount. Balance is achieved when the circuit pressure is set to the set value P1.

As described above, in the servo device 6 of the present invention, the spools 17 and 17a of the control pulse 7''6a to')')-7 valve 6b are integrally arranged on the same axis and the pressure setting spring 27 is shared. Fewer points, easy pressure setting, simple structure, fewer circuit configurations,
The main body is smaller and more compact, and it also has improved workability and
It is highly economical.

In addition, when the control valve is in the neutral position, the relief valve generates a small break flow rate q1, so even when the flow from pumps 1 and 1a toward the load is cut off, the servo device 6 is able to control pump 7''. The pumps 1 and 1a are controlled to a position where the discharge amount of 1 t 1 a compensates for the minute break flow rate from the IJ valve, and therefore the flow rate flowing toward the load is maintained at the same circuit pressure from zero to the maximum. control becomes possible.

Furthermore, when controlling the control pulp, the break flow rate from the relief valve can be reduced to the necessary minimum, so a sufficient control flow rate can be ensured, making it possible to increase the operating speed of the servo device and improve responsiveness. be.

[Brief explanation of drawings]

FIG. 1 shows an open circuit in which a servo device according to an embodiment of the present invention is installed, FIG. 2 shows a closed circuit, and a third
The figure is a longitudinal sectional side view of the servo device according to the present invention. 6a-#・Control pulp, 6b…IJ IJ −
7 valves, 7...actuator, 14...main body,
16... Passage, 17... Spool, 17a... Spool tip, 20... Relief valve inlet port, 2
1... Control valve entry port, 22, 23.
... Control valve drain port, 24... Relief valve drain port, 27... Pressure setting spring, 30.31... Hole.

Claims (1)

[Claims] 1 IJ- In a circuit pressure control servo device equipped with a leaf valve, a spool that also serves as a control valve and an IJ leaf valve is integrated into the main body of the servo device that controls the pump discharge amount, and is slidably inserted on the same axis. 1. A circuit pressure control servo device, characterized in that one end of the control valve is provided with a spring that opposes pilot pressure, and the relief pulp is configured to provide a minute break flow rate at the neutral position of the control valve.