JPH07190006A - Pressure compensation type oil pressure control circuit - Google Patents

Abstract

PURPOSE:To surely operate each actuator without breaking a relative balance among actuators even when there is any shortage of a pump ejecting amount. CONSTITUTION:An oil pressure control circuit is provided with a plurality of control valves 4a to 4c connected to one oil pressure pump 1 via pressure compensatory valves 5a to 5c, electromagnetic proportional pressure control valves 6a to 6c for supplying pressure oil to the spool ends of the control valves connected to both ends thereof and actuators 3a to 3c connected to respective control valves. This circuit is further provided with shuttle valves 7 and 7' for detecting load pressure on respective actuators and detecting the maximum load pressure thereof, a unloading valve 13 for controlling the ejecting pressure of the oil pressure pump in accordance with this maximum load pressure and a pressure reducing valve 15 for controlling pressure applied to the spool ends of the control valves through the electromagnetic proportional control valves in accordance with the maximum load pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure compensation type hydraulic control circuit.

[0002]

2. Description of the Related Art Generally, a plurality of hydraulic actuators are connected to one hydraulic pump, and the hydraulic pump discharge pressure is automatically adjusted by using a pressure compensating valve according to the load pressure of each hydraulic actuator. A control circuit is known (see, for example, Japanese Patent Publication No. 51-14665).

This type has a control valve for supplying / discharging pressure oil to / from a hydraulic actuator, and when the control valve is operated individually or simultaneously, the pump discharge amount is in the oil amount range required by each actuator. Within the range, the pressure-compensated oil flows to each actuator through the control valve, so that there is an advantage that good control can be realized irrespective of load fluctuations.

[0004]

However, in the case where the pump discharge amount is insufficient due to the combined operation of the actuators requiring a large amount of oil, for example, when the boom is raised and lowered and the swing is simultaneously performed by the power shovel. However, the conventional configuration has a problem that pressure compensation cannot be performed. In this case, a large amount of oil flows to the actuator with a light load pressure, and a small amount of oil does not flow to the actuator with a large load pressure. Therefore, the movement becomes slow, and there is a problem that the controllability is deteriorated due to the irregular movement. .

As a countermeasure for this, it is sufficient to increase the pump capacity, but it is not appropriate to increase the pump capacity in terms of economy.

Therefore, an object of the present invention is to solve the problems of the above-mentioned conventional techniques and to operate two or more control valves with pressure compensation at the same time, so that the pump discharge amount can be accurately achieved. It is an object of the present invention to provide a pressure compensation type hydraulic control circuit capable of performing pressure compensation and operating each actuator without disturbing the relative balance of the plurality of actuators related to each control valve.

[0007]

In order to achieve the above object, the present invention relates to a plurality of control valves each connected to one hydraulic pump via a pressure compensating valve, and to both ends of each control valve. An electromagnetic proportional pressure control valve for supplying pressure oil to the spool end of the control valve, an actuator connected to each control valve, and a shuttle for detecting the load pressure of each actuator and detecting the maximum load pressure among them. Valve, an unload valve that controls the discharge pressure of the hydraulic pump according to this maximum load pressure, and a pressure reducing valve that controls the pressure applied to the spool end of the control valve through the electromagnetic proportional pressure control valve according to the maximum load pressure. It is characterized by having.

[0008]

According to the present invention, when the discharge amount of the hydraulic pump is insufficient, the spool opening amount of the control valve is automatically throttled via the pressure reducing valve, so that the discharge pressure of the hydraulic pump is automatically increased. As a result, the pressure of the oil on the outlet side of the pressure compensating valve rises, so that the pressure compensating valve operates properly and the flow rate of the oil flowing to the pressure oil side of each actuator is accurately controlled. Therefore, even if the pump discharge amount is insufficient, the pressure compensation can be accurately performed, so that the operability of each actuator is maintained well without breaking the relative balance of the plurality of actuators connected to each control valve. be able to.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, 1 is a hydraulic pump, and 2
Is an oil tank, 3a, 3b, 3c are hydraulic cylinders,
A plurality of actuators (three in the figure) are composed of hydraulic motors and the like. Further, 4a, 4b and 4c are spring center type hydraulic pilot type 4 port 3 position switching valves (hereinafter referred to as control valves) for controlling the flow rate and the flow direction of oil to the actuators 3a, 3b and 3c.
And each control valve has a throttle mechanism 40, 41.
Is built in.

Reference numerals 5a, 5b and 5c are pressure compensating valves, which are valves for controlling the amount of oil supplied to the actuator so as not to change even if the load changes in pressure. That is, the pressure compensating valves 5a, 5b and 5c are the control valves 4a and 4c.
It is connected to the upstream side of b and 4c, and is for flowing the amount of oil whose pressure is compensated according to the opening amount of the spool of each control valve, and is connected in parallel to the hydraulic pump 1, respectively. 6a, 6a ', 6b, 6b', 6c, 6
Reference character c'is an electromagnetic proportional pressure control valve which is arranged at both ends of each control valve 4a, 4b, 4c and controls the position of the spool of each control valve 4a, 4b, 4c.

That is, the solenoid proportional valves 6a, 6a ', 6b, 6
b ', 6c, 6c' are solenoids SoLa1, SoLa2, So
It has Lb1, SoLb2, SoLc1, and SoLc2, and by controlling each solenoid, oil from the hydraulic pump 1 is added to the pilot pressure chambers at both ends of the control valves 4a, 4b, 4c through the solenoid proportional valve, and the spool ends Pressure oil is added to.

Solenoid proportional valves 6a, 6a ', 6b, 6b',
6c, 6c 'solenoids SoLa1, SoLa2, SoLb1, So
Lb2, SoLc1 and SoLc2 are electrically connected to the controller 12 as shown in FIG.
Resistors a1, a2, b1, b2, c1, c on the input side of
Remote control levers 11a, 11b, 11c containing 2 are connected to the remote control levers 11a, 11b, 11c.
The SoLa1 and SoLa from the controller 12 according to the displacement of
2, The drive signal (voltage or current) sent to SoLb1, SoLb2, SoLc1 and SoLc2 is adjusted, and the pilot pressure sent to the spool end is controlled accordingly.

The remote control levers 11a, 11b, 11
c is a control lever mounted on, for example, a hydraulic power shovel.

7, 7'denotes actuators 3a, 3b,
3c is a shuttle valve for detecting the maximum pressure among the load pressures, and the shuttle valves 7 and 7'include the load pressure detection port shown in the center of each control valve 4a, 4b and 4c and the pressure compensation. The maximum load pressure PLS detected here is connected to the spring side of the valves 5a, 5b, 5c and the spring side of the unload valve 13 and the solenoid proportional valves 6a, 6a ', 6b, through the line 70. 6
It is adapted to be guided to a pressure reducing valve 15 for reducing the supply pressure of b ', 6c, 6c'.

In the unload valve 13, when the discharge pressure of the hydraulic pump 1 is PP, the maximum load pressure is PLS, and the spring pressure of the unload valve 13 is PS1, normally, PP = PS1 + PLS ...
The relationship of equation (1) is maintained.

Further, at one spool end of the pressure reducing valve 15, the maximum load pressure PLS and the electromagnetic proportional valves 6a, 6 are provided.
The supply pressure PA to a ', 6b, 6b', 6c, 6c 'is introduced, and the discharge pressure PP of the hydraulic pump 1 is introduced to the other spool end of the pressure reducing valve 15. In the pressure reducing valve 15, when the spring pressure of the pressure reducing valve 15 is PS2, PA = PP + PS2 -PLS ...
The relationship of equation (2) is maintained.

Next, the operation of this embodiment will be described.

The operator operates an arbitrary remote control lever 11
When a, 11b, 11c is operated, the built-in resistors a1, a2, b1, b2, c1, c according to the displacement
The resistance of 2 changes. This resistance change is the controller 1
The corresponding solenoid proportional valves 6a, 6a ', 6b, 6b', 6c, 6 as a change in the drive signal (eg voltage) via
c'Solenoids SoLa1, SoLa2, SoLb1, SoLb2, So
It is sent to Lc1 and SoLc2 and converted to changes in pilot pressure. Then, this pilot pressure is applied to the spool ends of the control valves 4a, 4b, 4c, the spool is displaced, and the control valves 4a, 4b, 4c are switched to positions I or III.

When the control valves 4a, 4b, 4c are switched to the position I or III, the load pressure detection ports of the control valves 4a, 4b, 4c are connected to the pressure oil side of the actuators 3a, 3b, 3c, and thereby the load is increased. The pressure is guided to the shuttle valve 7, 7 ', and in this shuttle valve 7, 7', the maximum load pressure PLS of the actuators 3a, 3b, 3c is selected, and this selected maximum load pressure PLS is Unload valve 13 through 70
Is transmitted to the spring side and one spool end of the pressure reducing valve 15.

This will be described step by step.

First, all the control valves 4a, 4
When b, 4c are set to position II (when all actuators are stopped), pressure compensation valves 5a, 5b, 5
Since the pilot side pressure P6 of c becomes zero, the maximum load pressure PLS becomes zero. Therefore, when the hydraulic pump 1 is driven, the pump discharge pressure PP overcomes the spring pressure PS1 of the unload valve 13 to open, and the total discharge amount is returned to the tank 2. In this way, the pump discharge pressure PP when all are in position II, as is clear from the equation (1), only opposes the spring pressure PS1 and therefore is virtually unloaded.

Next, the control valves 4a, 4b, 4
If only one of c is set to position I or III and the other control valves are set to position II in the same manner as above (when only one of the actuators is operated), position I or III The pilot side pressure P6 in the above system becomes the same pressure as the pressure P4 or P5, and the pressure P6 is propagated into the pipe 70 through the shuttle valves 7, 7'as the maximum load pressure PLS.

When the load on the actuator increases and the maximum load pressure PLS increases, the discharge pressure PP of the hydraulic pump 1 increases at the unload valve 13 until the relationship of PP = PS1 + PLS (1) is established. When this pressure PP reaches the load pressure, oil starts to be fed into the actuator in the system set to position I or III. At this time, the flow rate supplied to the actuator depends on the pressure compensation valves 5a, 5
It is kept constant regardless of the load pressure by being compensated by b and 5c. When the maximum load pressure PLS rises and the discharge pressure PP of the hydraulic pump 1 rises accordingly, the pressure reducing valve 15 holds the electromagnetic proportional valve 6a, until the relation of PA = PP + PS2-PLS (2) is established. 6a ', 6b, 6b', 6
The supply pressure PA of c and 6c 'is controlled. In the case of this example, from the expressions (1) and (2), PA = PS1 + PS2 ...
Since it is the expression (3), the supply pressure PA is constant.

Further, control valves 4a, 4b, 4c
If two or more positions are set to position I or III at the same time (when a plurality of hydraulic cylinders are operated at the same time), position I or II is set in the same manner as in the above case.
The pilot side pressure P6 in all the systems designated as I becomes the same pressure as the respective pressure P4 or P5, and the shuttle valve 7,
7 ', the highest pilot side pressure P
6 is selected as the maximum load pressure PLS, which pressure is propagated in line 70.

Accordingly, the unload valve 13
PP = PS1 + PLS ... The discharge pressure PP of the hydraulic pump 1 rises until the relation of the formula (1) is established, and when this pressure PP reaches the load pressure, oil is fed into the actuator in the system set to position I or III. Start sending. At this time, the flow rate supplied to the actuator depends on the pressure compensation valves 5a, 5
It is kept constant regardless of the load pressure by being compensated by b and 5c. Up to this point, it is the same as the above case.

By the way, the actuators 3a, 3b, 3
The flow rate Q of the oil flowing to the pressure oil side of c is determined by the pressure compensating valves 5a, 5
Pressure difference ΔP = P3-P4 (or P5) between the oil pressure P3 on the outlet side of b and 5c and the oil pressure P4 or P5 on the pressure oil side.
It is determined by the equation (4) and the opening amounts of the spools of the actuators 3a, 3b, 3c.

In the pressure compensating valves 5a, 5b and 5c,
If the spring pressure is PS3, PS3 = P3-
P6 (= P4 or P5) ... Since the relationship of the equation (5) is established, the pressure compensating valves 5a, 5b, 5 are obtained from the equations (4), (5).
c always controls the differential pressure ΔP to be constant, and therefore the flow rate Q of the oil flowing to the pressure oil side of the actuators 3a, 3b, 3c is always controlled to be constant.

Here, for example, all the actuators 3
In the case where a, 3b, 3c are operated and the oil consumption amount there exceeds the discharge amount of the hydraulic pump 1, the unload valve 13 sets PP = PS1 + P
LS ... (1) relationship is no longer valid. That is, since the discharge amount of the hydraulic pump 1 is insufficient, the discharge pressure PP decreases, and if this is assumed to be PP ', the pressure PLS required on the actuator side does not change, so that PP'<PS1 + PLS.
... It becomes a relation of a formula (6).

If this is left as it is, PP '<PLS
When the relationship of the equation (7) is developed, and in this state, if the opening amounts of the spools of the control valves 4a, 4b, 4c are the same, an actuator requiring the maximum load pressure PLS (= P4 or P5) The discharge pressure PP 'of the hydraulic pump 1 will no longer operate, and the operation of each actuator will be inconsistent.

According to this embodiment, however, when the oil consumption of the actuators 3a, 3b, 3c exceeds the discharge amount of the hydraulic pump 1, the pressure reducing valve 15 discharges the hydraulic pump 1. As the pressure PP 'decreases, PA also decreases to PA', so that all the solenoid proportional valves 6a, 6
The pressure supplied to a ', 6b, 6b', 6c, 6c 'decreases. Since the spools of the control valves 4a, 4b, 4c are pushed by the difference between the supply pressure PA and the spring pressure PS4, if the supply pressure PA is lowered to PA ', the spool is pushed back by the difference. The spool opening is reduced. In this case, the spool opening amounts of all the control valves 4a, 4b, 4c decrease at the same time.

When the amount of opening of the spool is decreased in this way, the flow rate Q of the oil flowing to the pressure oil side of all the actuators 3a, 3b, 3c is decreased and the discharge pressure PP of the hydraulic pump 1 is automatically increased. Therefore, the operation of each actuator becomes slower, but the discharge pressure PP is the oil pressure P4 or P on the pressure side of the actuators 3a, 3b, 3c.
It does not become lower than 5, and troubles such as the actuator not operating due to insufficient pressure can be resolved. After the discharge pressure PP of the hydraulic pump 1 is recovered, the unload valve 13 performs control based on the equation (1).

However, according to this embodiment, when the discharge amount of the hydraulic pump 1 becomes insufficient, the pressure reducing valve 15
Since the spool opening amounts of the control valves 4a, 4b, 4c are automatically throttled, the discharge pressure PP of the hydraulic pump 1
Automatically rises, which causes the pressure compensation valves 5a, 5b,
Since the oil pressure P3 on the outlet side of 5c rises, the pressure compensating valves 5a, 5b, 5c operate accurately, and the flow rate Q of the oil flowing to the pressure oil side of the actuators 3a, 3b, 3c is accurately controlled. It

Therefore, even if the pump discharge amount is insufficient, pressure compensation can be accurately performed, and the relative balance of the plurality of actuators 3a, 3b, 3c connected to the control valves 4a, 4b, 4c is lost. Without this, the operability of each actuator 3a, 3b, 3c can be favorably maintained.

FIG. 3 shows another embodiment.

In the figure, each solenoid proportional valve 6a, 6
The upstream side pressure of the solenoid proportional valve is introduced as pilot pressure to the solenoid-side spool ends of a ', 6b, 6b', 6c, 6c 'through the conduit 100.

However, according to this embodiment, the opening amount of the spool of each control valve 4a, 4b, 4c is adjusted according to the respective load pressure.

That is, when the supply pressure PA is controlled by the pressure reducing valve 15 to decrease to PA 'as in the above embodiment, the pressure PA' is supplied to the solenoid side of each solenoid proportional valve through each line 100. Is led to the spool end of. According to this, the spool opening amount of the control valve to which a load pressure higher than the reduced supply pressure PA 'is applied decreases, but the other spool opening amounts do not decrease, so that the movements of all actuators at once It does not become slow, but the spool opening amount decreases in accordance with the respective load pressures, so that it is possible to control the movement of the actuator stepwise.

[0039]

As is apparent from the above description, according to the present invention, in a hydraulic circuit in which the control valves for a plurality of actuators are pressure-compensated by one hydraulic pump, the control valves are simultaneously operated. In addition, when the pump discharge amount is insufficient with respect to the required oil amount of the actuator controlled by each control valve, the amount of oil that can perform pressure compensation in the circuit can be set. The effect is that good operability can be realized without losing the balance.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a pressure compensation type hydraulic control circuit according to the present invention.

FIG. 2 is a block diagram of a solenoid proportional valve.

FIG. 3 is a circuit diagram showing another embodiment.

[Explanation of symbols]

1 hydraulic pump 2 oil tank 3a, 3b, 3c actuator 4a, 4b, 4c control valve 5a, 5b, 5c pressure compensating valve 6a, 6a ', 6b, 6b', 6c, 6c 'electromagnetic proportional pressure control valve 7, 7' Shuttle valve 11a, 11b, 11c Remote control lever 12 Controller 13 Unload valve 15 Pressure reducing valve

Claims (1)

[Claims] 1. A plurality of control valves each connected to one hydraulic pump via a pressure compensating valve, and an electromagnetic proportional pressure connected to both ends of each control valve to supply pressure oil to spool ends of the control valves. A control valve, an actuator connected to each control valve, a shuttle valve that detects the load pressure of each actuator and detects the maximum load pressure among them, and the discharge pressure of the hydraulic pump according to this maximum load pressure. And a pressure reducing valve for controlling the pressure applied to the spool end of the control valve through the electromagnetic proportional pressure control valve according to the maximum load pressure. Control circuit.