JP2652791B2 - Flow control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a flow control device for driving a plurality of actuators with one load sensing pump.

(Prior Art) In the conventional flow control device shown in FIG. 7, a pair of actuators 1 and 2 are connected in parallel to a load sensing pump 3 and a pressure compensating valve is connected to the load sensing pump 3 from an upstream side thereof. 4 and 5 and variable apertures 6 and 7 are provided.

The load sensing pump 3 includes a variable discharge pump having a discharge pressure control unit 8.
One of the pilot chambers 9 is connected via a shuttle valve 10 to the downstream side of the two variable throttles 6 and 7. The other pilot chamber 11 of the discharge pressure control unit 8 is provided with the pump 3
Is connected to the discharge side. The discharge pressure control unit 8
Compares the maximum load pressure selected by the shuttle valve 10 with the discharge pressure of the pump 3, and controls the discharge pressure of the pump 3 so that the discharge pressure is always maintained higher than the maximum load pressure by a set amount. It controls the pressure.

Further, the pressure compensating valves 4 and 5 have springs 12 and 13 act on one side thereof, and normally, the pressure compensating valves 4 and 5 are kept in a fully opened state as shown. Further, the pilot chambers 14 and 15 on which the springs act are connected to the downstream side of the variable throttles 6 and 7, while the pilot chambers 16 and 17 on the other side of the pressure compensating valves 4 and 5 are connected to each other. The variable throttles 6 and 7 are connected to the upstream side.

Now, for example, it is assumed that the following normal operating conditions are set.

Actuator 1 Load pressure 50 kg Required flow rate 40 / min Actuator 2 Load pressure 100 kg Required flow rate 50 / min Pump 3 Maximum discharge rate 100 / min Load sensing differential pressure 10 kg Pressure compensating valves 4 and 5 Compensator differential pressure 5 kg The required flow rate of each of the actuators 1 and 2 is determined according to the opening of the variable throttles 6 and 7, and the opening of the variable throttles 6 and 7 is selected by the operator.

The load sensing differential pressure of 10 kg is equivalent to the shuttle valve 10
Means that the discharge pressure P _{OUT of the} pump P is controlled to P _OUT = P _LS +10 kg with respect to the load pressure P _LS selected in.

Furthermore, the compensator differential pressure of 5 kg means that the variable throttle 6
So that the differential pressure around 7 is 5 kg,
5 works.

When the required flow rates of the two actuators 1 and 2 are 40 and 50 as described above, the pressure compensating valves 4 and 5 function as follows because they are within the range of the maximum discharge capacity of the pump 3. .

That is, the load pressure of the actuator 2 selected by the shuttle valve 10 is stored in one pilot chamber 9 of the discharge pressure control unit 8.
Since 100 kg acts, the discharge pressure of the pump 3 is maintained at 110 kg, which is 10 kg higher than that.

Therefore, one pressure compensating valve 4 bears a 55 kg pressure drop to maintain the differential pressure across the variable throttle 6 at 5 kg.
Further, the other pressure compensating valve 5 also controls the differential pressure across the variable throttle 7.
In order to maintain the pressure at 5 kg, a pressure drop of 5 kg is borne, and the required flow rate is supplied to each of the actuators 1 and 2.

(Problems to be Solved by the Present Invention) In the conventional apparatus as described above, there is no problem if the total required flow rate of the actuators 1 and 2 is within the range of the maximum discharge capacity of the pump 3. When the total required flow rate exceeds the maximum discharge capacity, the following problem occurs.

For example, assuming that the opening degree of one of the variable throttles 6 is increased and the required flow rate of the actuator 1 is increased to 60 / min, the total required flow rate of both actuators 1 and 2 becomes 100 and exceeds the capacity of the pump 3. Would.

Therefore, when a pilot pressure of 100 kg acts on the pilot chamber 9, the pump 3 tries to maintain the discharge pressure at 110 kg, but cannot maintain it.

Therefore, assuming that the discharge pressure at this time is, for example, 104 kg, one pressure compensating valve 4 increases its opening degree to reduce its own pressure loss to 49 kg, and maintains a differential pressure of 5 kg before and after the variable throttle 6, and Maintain the flow rate 60 for the actuator 1.

On the other hand, the other pressure compensating valve 5 also attempts to reduce its own pressure loss by increasing its opening, but since the discharge pressure of the pump 3 decreases, the differential pressure across the variable throttle 7 is maintained at 5 kg. Can not do.

Therefore, in this conventional apparatus, when the total required flow rate of the actuators exceeds the maximum discharge capacity of the pump 3, the supply flow rate is preferentially supplied to the actuator with a small load, and the actuator with a large load is supplied. However, there is a problem in that a sufficient flow rate is not supplied, which hinders the operation of an actuator having a large load.

An object of the present invention is to make it possible to control the flow rate distribution according to a target ratio when the total required flow rate of the actuator exceeds the maximum discharge capacity of the pump. Is to be able to supply.

(Means for Solving the Problems) According to a first invention, a plurality of actuators are driven by one load sensing pump, and a flow path opening control unit is provided upstream of the actuator. Further on the upstream side, a flow control device is premised on which a pressure compensating valve for maintaining a constant differential pressure before and after the flow path opening control unit is connected.

On the premise of the above device, the first invention is for operating the pressure compensating valve in a direction to reduce the differential pressure before and after the flow path opening control unit when the load sensing differential pressure becomes equal to or less than the set pressure. It is characterized in that a pilot chamber is provided in the pressure compensating valve.

Further, the second invention controls the opening between the flow path opening control unit and the pressure compensating valve according to the load sensing differential pressure under the same preconditions as the first invention. It is characterized in that a flow control valve is provided.

The flow path opening control unit is used as a concept including a variable throttle and a direction switching valve. In the present invention, the number of actuators is not limited.

(Operation of the present invention) Since the first invention is configured as described above, when the total required flow rate of the actuator exceeds the maximum discharge capacity of the pump, the opening of the pressure compensating valve is made relatively small, The differential pressure across the flow path opening control unit is kept small. Therefore, a flow rate according to the target ratio is supplied to each actuator within the range of the maximum discharge capacity of the pump.

In the second invention, when the total required flow rate of the actuator exceeds the maximum discharge capacity of the pump, the flow control valve functions to control the flow rate in accordance with the target ratio.

(Effect of the Present Invention) According to the device of the present invention, even when the total required flow rate of the actuator exceeds the maximum discharge capacity of the pump, the working fluid is not supplied to the actuator with a small load.

(Embodiment of the present invention) The first embodiment shown in FIGS. 1 and 2 is the pressure compensating valves 4 and 5, which are located on the pilot chambers 16 and 17 side opposite to the springs 12 and 13, respectively. Pilot room 1 different from them
8 and 19 are provided, and these two pilot chambers 18 and 19 are connected to a pilot port 21 of a pilot pressure control valve 20.
The pilot pressure control valve 20 has an inflow port 22 connected to a pilot pump 23 and an outflow port 24.
Is connected to the tank 25.

Further, pilot chambers 26 and 27 are formed in the pilot pressure control valve 20, and a spring 28 is provided on one pilot chamber 26 side. The one pilot chamber 26 is connected to the shuttle valve 10 and the discharge pressure control unit 8
As in the case of the pilot chamber 9, the higher load pressure of the actuators 1 and 2 acts on the pilot chamber 26. The other pilot chamber 27 is connected to the discharge side of the load sensing pump 3.

Normally, the pilot pressure control valve 20 as described above is
Although the fully open position I is held by the action of the spring 28, when the acting force on the pilot chamber 27 side overcomes the acting force on the pilot chamber 26 side, the switch to the throttle position II or the fully closed position III is made. . Then, when switching to the fully closed position III, the other pilot chambers 18 and 19 of the pressure compensating valves 4 and 5 are connected to the tank 25.

Reference numeral 29 in the figure denotes a relief valve for controlling the discharge pressure of the pilot pump 23.

Therefore, assuming that both actuators are driven under the same conditions as the conventional one and that the total required flow rate of both the actuators 1 and 2 is maintained within the range of the maximum discharge capacity of the pump 3, the pump 3 becomes The discharge pressure is maintained higher than the load pressure of 100 kg by the load sensing differential pressure of 10 kg. Thus, when the load sensing differential pressure is maintained at 10 kg, the pilot chamber of the pilot pressure control valve 20
Since a differential pressure of 10 kg also occurs in 26 and 27, the pilot pressure control valve 20 switches to the fully closed position III.

When the pilot pressure control valve 20 is switched to the fully closed position III as described above, the pilot chambers 1 of the pressure compensating valves 4 and 5 are moved.
8 and 19 communicate with the tank 25.
8, 19 do not work at all. Therefore, in this case,
The operation is exactly the same as the conventional one described above, and one actuator 1 is supplied with a flow rate of 40 and the other actuator 2 is supplied with a flow rate of 50.

When the total required flow rate of the two actuators 1 and 2 exceeds the maximum discharge capacity of the pump 3, as in the conventional case,
Since the pump discharge pressure cannot be maintained at 110 kg, the pressure difference between the pilot chambers 26 and 27 of the pilot pressure control valve 20 also decreases. Therefore, the pilot pressure control valve 20 is operated by the spring force of the spring 28 so that the throttle position II or the fully open position I
Switch to. When the pilot pressure control valve 20 is switched in this way, the discharge pressure of the pilot pump 23 acts on the pilot chambers 18 and 19 of the pressure compensating valves 4 and 5 via the pilot pressure control valve 20. And the pilot room at this time
The acting forces of 18 and 19 are determined according to the switching position of the pilot pressure control valve 20 determined by the load sensing differential pressure.

Now, assuming that the total required flow rate of the two actuators 1 and 2 exceeds the maximum discharge capacity of the pump 3 and that the discharge pressure of the pump 3 at this time is 109.545 kg, the control form is as follows. Become.

First, the output P _AS of the pilot pressure control valve 20 is a specified load sensing differential pressure− (P _OUT −P _LS ), and the output P _AS = 10−
(109.545-100) = 0.455.

Since the output P _AS of the pilot pressure control valve 20 is transmitted to the pilot chambers 18 and 19 of the pressure compensating valves 4 and 5, the compensator pressure ΔP is ΔP = (specified differential pressure by the springs 12 and 13). the (P _aS due to the pressure) = 5-0.455 = 4.545.

Therefore, the supply flow rate to the actuator 1 is the required flow rate 60 × (4.545 / 5) = 54.5.

The supply flow rate to the actuator 2 is the required flow rate 50
× (4.545 / 5) = 45.5, and the total flow rate of both is 100
become.

According to the first embodiment as described above, if the total required flow rate of the actuators 1 and 2 is within the range of the maximum discharge capacity of the pump 3 as shown in the graph of FIG. Is distributed along the characteristic line b.

However, when the required flow rate on the actuator 1 side is set to 60 as described above, the flow rate distribution is along the target ratio characteristic line a. That is, for example, approximately 90% of the required flow rate 60 of one actuator 1 is supplied, and the supply flow rate of the other actuator 2 side is also substantially 90%.

The second embodiment shown in FIG.
Port 22 of the pump 3 is directly connected to the discharge side of the pump 3,
This embodiment is different from the first embodiment in that the pilot pump 23 of the embodiment is omitted and a throttle 30 is provided in the connection process between the inflow port 22 and the pump 3. Note that this second
The throttle 30 in the embodiment may be replaced with a relief valve.

The third embodiment shown in FIG.
Is different from the first and second embodiments.
That is, the pilot pressure control valve 20 of the third embodiment
A spool 31 is provided inside the valve body, and pilot chambers 32 and 33 are formed on both sides of the spool 31, and the spool end further outside the pilot chamber 33 faces the pressure sensing chamber 34. And the pilot room
A spring 35 is interposed on the 32 side. Therefore, the control characteristic of the pilot pressure control valve 20 changes in accordance with the pressure change of the pilot chambers 18, 19 of the pressure compensating valves 4, 5.

The pressure compensating valves 4 and 5 in the third embodiment are
This is a specific example of the first embodiment, and is substantially the same as the first embodiment.

In the fourth embodiment shown in FIG. 5, the pilot chamber 33 of the third embodiment is connected to a pilot pump 36, and the other configuration is the same as that of the third embodiment.

The fifth embodiment shown in FIG. 6 is similar to the first embodiment,
Actuators 1 and 2 are connected in parallel to the downstream side of the load sensing pump 3, and between these pumps 3 and the actuators 1 and 2, pressure control valves 37 and 38, a flow control valve 39, 40 and the variable apertures 6 and 7 are connected in order.

The pressure control valves 37 and 38 are connected to the flow control valve 3
The differential pressure set by the springs 41 and 42 is maintained between the pressure on the upstream side of the variable throttles 9 and 40 and the pressure on the downstream side of the variable throttles 6 and 7.

The flow control valves 39 and 40 have upstream ports 45 and 46 and downstream ports 47 and 48 in their main bodies 43 and 44, respectively, and have poppet chambers 49 and 50 and control chambers 5 in the main bodies 43 and 44.
1 and 52 are divided.

Poppets 53 and 54 are placed in the poppet chambers 49 and 50, respectively.
And the poppet rooms 49, 50 and the control room 5
Push rods 55 and 56 are slidably inserted through 1 and 52.

And pistons 57 and 58 are provided in the control chambers 51 and 52,
This control room is divided into the first control rooms 51a, 52a and the second control rooms 51b, 5b.
2b, and springs 59, 60 act on the first control chambers 51a, 52a. The spring force of the springs 59, 60 is transmitted to the push rods 55, 56 via the pistons 57, 58, and the spring force acts on the poppets 53, 54.

By operating the springs 59, 60 on the poppets 53, 54 as described above, the poppets 53, 54 function as check valves that allow only the flow from the upstream ports 45, 46 to the downstream ports 47, 48. Like that.

The first control chambers 51a and 52a are connected to the load sensing pump 3, and the second control chambers 51b and 52b are connected to the shuttle valve 10.

Reference numerals 61 and 62 in the drawing denote pressure introduction passages for causing the pressures of the downstream ports 47 and 48 to act as back pressures of the poppets 53 and 54.

When the total required flow rate of the two actuators 1 and 2 is within the range of the maximum discharge flow rate of the pump 3, the load sensing differential pressure is sufficiently maintained, but the differential pressure is maintained in the first and second control chambers. Pressure difference. That is, the second control room
Since the pressure in the first control chambers 51a, 52a is maintained sufficiently higher than the pressure in the first control chambers 51a, 52a, the pistons 57, 58
Ascends against 59 and 60 and releases the pressing force of push rods 55 and 56. When the pressing force of the push rods 55 and 56 is released in this way, the poppets 53 and 54 become free, so that
The supply flow rate for the actuators 1 and 2 is controlled by a pressure control valve.
The control is performed by 37 and 38 and the variable apertures 6 and 7, and the control mode is the same as that of the first embodiment.

On the other hand, when the required flow rate on the actuator 1 side increases and the total required flow rate exceeds the maximum discharge capacity of the pump 3, the load sensing differential pressure decreases, as in the first embodiment. Therefore, in this case, the first,
2 Since the pressure difference in the control chamber is reduced, the piston 57,
58 is lowered by the action of the springs 59, 60, and the pressing force acts on the poppets 53, 54.

When the poppets 53 and 54 are pushed as described above, the opening of the upstream ports 45 and 46 is reduced according to the pressing force, and the supply flow rate to the actuators 1 and 2 is reduced by the reduced amount. Decrease. That is, in the fifth embodiment, the flow rate passing through the flow control valves 39 and 40 is relatively reduced, and the total flow rate required by both actuators is held within the range of the maximum discharge flow rate of the pump 3. Is used to distribute the required flow rate to the actuator.

[Brief description of the drawings]

FIGS. 1 and 2 show a first embodiment of the present invention. FIG. 1 is a circuit diagram, FIG. 2 is a graph showing distribution flow characteristics, and FIG. 3 is a second embodiment. FIG. 4 is a circuit diagram of the third embodiment, FIG. 5 is a schematic diagram of a main part of the fourth embodiment, FIG. 6 is a circuit diagram of the fifth embodiment, and FIG. 7 is a conventional circuit diagram. It is. 1, 2,... Actuator, 3,... Load sensing pump, 4, 5,... Pressure compensating valve, 6, 7,.
…… Flow control valve.

Claims (2)

(57) [Claims] A single load sensing pump drives a plurality of actuators, and a flow path opening control section is provided upstream of the actuator, and the flow path opening control section is further provided upstream of the flow path opening control section. In a flow control device connected to a pressure compensating valve that keeps the differential pressure before and after the road opening control unit constant, when the load sensing differential pressure falls below the set pressure, the differential pressure before and after the flow opening control unit is reduced. A flow control device provided with a pilot chamber for operating the pressure compensating valve in a direction in which the pressure compensating valve operates. 2. A plurality of actuators are driven by one load sensing pump, and a flow path opening control section is provided upstream of the actuator, and the flow path control section is further upstream of the flow path opening control section. In a flow control device connected with a pressure compensating valve for keeping a differential pressure before and after a road opening control unit constant, an opening degree according to a load sensing differential pressure is provided between the flow path opening control unit and the pressure compensating valve. A flow control device provided with a flow control valve for controlling the flow rate.