JPS5944544B2 - Directional switching device that also functions as flow control - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a directional switching device equipped with a pressure-compensated flow rate control mechanism, and more particularly to a directional switching device that can effectively use power in simultaneous operation of two or more directional switching devices.

When conventional valves of this kind are used in multiple series and two or more series are operated simultaneously, the pressure fluid from the pump 1 is divided into two parts at the flow rate regulating valve 2, as shown in FIG. 4, for example. One of them passes through the supply passage 3 and is connected to the directional control valve 4.
through the actuator 5 and actuates the actuator 5, the return liquid is returned to the tank and the other is supplied to the supply passage 6 of the next valve section.

That is, in the upstream valve section of two or more valve sections, a flow rate proportional to the amount of movement of the flow rate adjustment valve 2 is sent to the actuator, and for the downstream valve section, the flow rate is calculated from the pump discharge amount of the upstream valve section. A method is used to utilize the surplus flow rate after deducting the amount used.

For this reason, even if the load on the actuator is small and there is surplus power, there is a drawback that the downstream valve section can only use the surplus flow from the upstream valve section.

The present invention eliminates the drawbacks of the above-mentioned conventional ones,
When the total load of each valve section that is operated simultaneously is small, a series circuit is configured in which multiple valve sections are connected in series, and the return flow rate from the actuator in the upstream valve section is converted into the surplus flow of the upstream valve section. By merging and supplying the downstream valve section, it is possible to use the downstream valve section at a flow rate close to the pump discharge flow rate during simultaneous operation, and even when the total load of each valve section is large. By returning the return flow rate from the actuator of the upstream valve section to the tank, the pump pressure is prevented from increasing.The purpose of the above operation is to use power efficiently and facilitate simultaneous operations. shall be.

To this end, in the present invention, a supply passage on the pump side that communicates with the pump, a return passage on the tank side that communicates with the tank, a supply passage and a return passage on the actuator side that communicate with the actuator, and a branch from the supply passage on the pump side. and a surplus flow path connected to the supply passage of the next load, a supply passage on the pump side and a return passage on the tank side, which are displaced in response to external operation, and a supply passage and a return passage on the tank side, and a supply passage and a return passage on the actuator side. a directional control valve that selectively communicates with the passage, and variably controls and shuts off the communication area; and a directional control valve that is interposed between the supply passage on the pump side and the surplus flow passage, and is arranged to branch the surplus flow passage by axial displacement. a flow control valve including a spool that variably controls passage area distribution between the supply passage and the surplus flow passage on the side of the pump downstream from the pump; A spring is interposed to guide the hydraulic pressure downstream of the directional control valve in the supply passage on the actuator side, and a hydraulic pressure upstream of the directional control valve in the supply passage on the pump side is introduced. Two pressure chambers adjust the displacement of the spool by the elastic force of the spring and the differential pressure before and after the directional control valve in each of the supply passages; a bypass valve device which opens a return passage on the tank side when a normally closed check valve that is interposed in a communication passage between the bypass valve device upstream side of the passage and the surplus flow path and opens when the hydraulic pressure on the upstream side of the bypass valve device is equal to or higher than a predetermined pressure. However, if the hydraulic pressure in the supply passage on the pump side is lower than a predetermined value, the bypass valve device is closed and the hydraulic pressure in the return passage on the tank side upstream from this device is increased, and the check valve is opened to prevent the actuator from flowing. The return liquid of the pump is merged into the excess flow path to form a series circuit. Conversely, if the fluid pressure in the supply path on the pump side becomes excessive than a predetermined value, the bypass valve device is opened and the check valve is activated at the same time. is closed and the return liquid from the actuator is returned to the tank, thereby forming a parallel circuit.

Hereinafter, one example of implementation of the present invention will be described based on the accompanying drawings.

FIG. 1 shows the granger section of a stacked valve according to the invention.

In the figure, 11 is a housing, 12 is a directional control valve, and 13
14 is a flow rate adjustment valve, and 14 is a bypass valve, which constitutes a bypass valve device together with an inlet section 83, which will be described later.

The directional control valve 12 is provided with annular passages 16 to 24 along a plunger 15 which is slidable in the axial direction under the action of an operating portion (not shown).

Of these, the annular passages 16 and 24 communicate with the tank via return passages (tank side) 25 and 26, respectively, and the annular passages 18 and 22 communicate with the service ports (supply passage and return passage on the actuator side) 2γ and 28. It communicates with a supply port and a return port of an actuator (not shown) through it.

The annular passages 19 and 21 are interconnected by a passage 29.

The plunger 15 also has lands 3B, 39, 4 having small diameter portions 31, 32° 33 and orifices 34, 35, 36, 3γ formed by inching notches, respectively.
0 and 41 are provided, and each annular passage is selectively communicated through each orifice by axial displacement of the plunger 15, so that the fluid flow throttling effect differs according to the amount of displacement.

The flow rate adjustment valve 13 has a spool 43 that can freely slide in the axial direction, and an annular passage 44, an annular supply passage (pump side) 45, a surplus flow passage 46, and annular passages 47, 48 are provided along this spool 43. It is being

The annular passage 44 communicates with a supply passage (pump side) 49 that goes toward the annular passage 20 of the directional control valve 12, and the supply passage 45 communicates with a supply passage of an inlet section, which will be described later, to which pressurized liquid is supplied. Ru.

The surplus flow path 46 communicates with the supply passage 45 through a small diameter portion 51 provided on the spool 43, and also with the supply passage of the next plunger section as the next load circuit.

Further, the annular passage 47 communicates with a return passage (tank side) 52 from the directional switching valve 12, and the remaining annular passage 48 communicates with the annular passage 21 of the directional switching valve 12 via a passage 53.

Pressure chambers 54 and 55 are provided on both sides of the spool 43 in the axial direction.

An annular passage 44 is always in communication with one pressure chamber 54 through an orifice 56 provided in the spool 43, and an annular passage 48 is always in communication with the other pressure chamber 55 through a through hole 57 provided in the spool 43. It also communicates with the spring 58.
is arranged within this pressure chamber 55 so as to urge the spool 43 to the left in the figure.

Additionally, the spool 43 has lands 59 and 6 on both sides of the small diameter portion 510.
0, and the edge of one land 59 has a notch 6.
1 is provided to constantly communicate the supply passage 45 and the annular passage 44.

Therefore, the pressure on the upstream side of the orifice 35 or 36 of the pressure fluid flowing toward the directional control valve 12 through the notch 61 always enters the pressure chamber 54 through the orifice 56 and the spool 4.
3 to the right while orifice 36 or 35
The downstream pressure enters the pressure chamber 55 through the passage 53, the annular passage 48, and the through hole 5γ, and in combination with the biasing force of the spring 58, tends to move the spool 43 to the left in the figure, and the components of these forces in both directions The spool 43 comes to rest when it is balanced.

In this rest position, the cross-sectional area of the flow through the notch 61 of the spool 43 is determined, and therefore the flow rate from the supply passage 45 to the surplus flow passage 46 is also determined.

If the spring constant of the spring 58 is set small, the orifice 3
The spool 43 moves so that the differential pressure before and after the supply channel 5 or 36 is kept substantially constant.

When the plunger 15 of the directional control valve 12 is in the neutral position, a passage 62 is provided in the plunger 15 in order to relieve the pressure in the pressure chamber 55 on the side where the spring 58 of the flow rate adjustment valve 13 exists.
By forming the annular passage 21 and communicating with the annular passage 24, the pressure in the pressure chamber 55 is transferred to the through hole 51 and the annular passage 4.
8, the passage 53 and the passage 62 are opened to the tank via the return passage 26.

A check valve 63 is configured inside the spool 43.

That is, the valve hole 64 provided in the spool 43 communicates with the annular passage 47 that communicates with the return passage 52 from the directional control valve 12, and furthermore, the valve body 66 normally closes the valve hole 64 by the force of the spring 65. It communicates with the surplus flow path 46 via.

This check valve 63 controls the pressure inside the valve hole 64, that is, the return flow path 5
2 opens only when the pressure inside the spring 650 becomes equal to or higher than the set load of the spring 650, and the return liquid flowing in the return flow path 52 passes through the valve hole 64 and merges with the surplus liquid flowing in the surplus flow path 46.

In the bypass valve 14 constituting a part of the bypass valve device, a valve body 70 which normally closes the valve hole 68 by receiving the restoring force of a spring 69 is provided so as to be freely displaceable in the axial direction.
A pressure chamber 71 in which a spring 69 of the valve body γ0 exists communicates with an inlet section, which will be described later, through a port 72.

An orifice 73 is provided in the valve body 70 to communicate the pressure chamber γ1 and the valve hole 68, and the valve hole 68 is connected to the passage 74 and the annular passage 75.
It communicates with the annular passage 47 of the flow rate regulating valve 13 via a return passage (tank side) 76, and further communicates with the annular passage 17 of the directional control valve 12 via a return passage (tank side) γ7.

That is, in the operating position of the directional control valve 12, the return liquid from the actuator flows from the service port 27 or 28 through the directional control valve 12 into the return passages 52, 76, γ7, and the return liquid pressure at this time maintains a constant pressure. In the above case, the flow always flows from the valve hole 64 to the surplus flow path 46 via the check valve 62 and merges with the surplus flow, but once the bypass valve 14 is opened, the check valve 62 is closed. The liquid in the return passage γθ is bypassed to the tank through the return passage 25 via the directional control valve 12.

The bypass circuit includes a downstream chamber 78 of the valve body 10 and a passage 79.
The annular passage 80 communicates with the annular passage 16 of the directional control valve 12 via a return passage 81.

FIG. 2 shows an inlet section forming part of the bypass valve arrangement.

The inlet section 83 includes a supply passage (pump side) 85 leading to a pump 84 (see FIG. 3) and a return passage 86 leading to the return passage 25 of the plunger section described above.
The return passage (tank side) 86 is equipped with a piston valve 87 that is operated by the hydraulic pressure of the supply passage 85, that is, the pump pressure.

This piston valve 81 has a structure in which a piston 89 that is freely slidable in the axial direction within a cylinder 88 closes a through hole 90 provided in the cylinder 88 by a repelling blade of a spring 91.

Since the opening area of this through hole 90 is smaller than the internal space cross-sectional area of the cylinder 88, that is, the effective pressure receiving area of the piston 89 when the through hole 90 is closed and opened is smaller in the former case. The pump pressure required to open the valve hole 90 by pushing the piston 89 against the spring 91 causes the piston 89 to open the valve hole 90 again by the restoring force of the spring 91.
Compared to the pump pressure that closes 0, it is higher in inverse proportion to the effective pressure receiving area.

The inlet selection 83 is further provided with an annular passage 92 surrounding the cylinder 88 , and the cylinder 88 is provided with a passage 93 communicating with the annular passage 92 and a passage 94 communicating with the return passage 86 .

The piston 89 has a spring 91 inside it.
When moving to the left in the figure, the passages 93, 9
A passage 95 communicating with 4 is provided.

Therefore, when the tank pressure becomes high and moves the piston 89 to the left, the pressure in the pressure chamber 71 of the bypass valve 14 of the plunger section in FIG. 94-Return passage 86-
Since the liquid falls into the tank via the return flow path 26 of the plunger section, the liquid pressure in the pressure chamber 71 drops rapidly, and the valve body 70
The differential pressure across the orifice 73 of the fluid flowing from the valve hole 65 to the pressure chamber γ1 through the orifice 73 of the spring 69
The valve body γ0 moves to the left in the figure against the spring 69, and the valve hole 68 communicates with the return passages 7γ, γ6, 52.
is opened to the downstream chamber γ8, the passage γ9, the annular passage 80, the return passage 81, the annular passage 16 of the directional control valve 12, the return passage 2.
8 and flows into the tank.

Therefore, the check valve 63 is closed, and the return liquid from the actuator does not join the surplus flow path 46.

Next, its operation will be explained.

FIG. 1 shows a state in which the plunger 15 of the directional control valve 12 is in a neutral state.

At this time, the pressure liquid from the pump 84 enters the annular supply passage 45, passes through the small diameter portion 51 of the spool 43 of the flow rate regulating valve 13, and enters the annular surplus flow passage 46.

The pressure liquid passing through this excess flow path 46 is sent to the supply circuit of the next load, that is, the supply passage of the next plunger section (a portion corresponding to the supply passage 45 in FIG. 1).

A pressure chamber 54 at the left end of the spool 43 is constantly provided with an annular passage 4.
4 is introduced through the orifice 56, and the pressure within the passage 29 is constantly introduced into the endless pressure chamber 55 via the passage 53 and the annular passage 48.

When the plunger 15 is in the neutral position, the passage 29 is communicated with the return passage 26 by the passage 62 in the granger 15, so that the pressure chamber 55 is at tank pressure.

Further, the pressure of the supply passage 45 is guided to the other pressure chamber 54 by a notch 61 provided in the spool 43.

Therefore, in the neutral state, the spool 43 pushes the spring 58 and moves to the right, and the pressurized liquid in the supply passage 45 flows through the annular surplus flow passage 46 toward the next plunger section.

Next, when the operating section is operated to move the plunger 15 to the right, communication between the passage 62 in the plunger 15 and the annular passage 21 is closed, and the orifice (inching notch) 36 closes the communication between the annular passage 20 and the annular passage 21. The annular passage 19 and the annular passage 18 communicate with each other.

Therefore, the pressure of the fluid before passing through the orifice 36 of the directional control valve 12 acts on the left end of the spool 43 of the flow rate adjustment valve 13, and the pressure of the fluid after passing through the orifice 36 acts on the right end of the spool 43. , a repelling force by the spring 58 acts.

Therefore, the spool 43 is located at a position where the differential pressure across the orifice 36 and the force of the spring 58 are balanced.

At this time, if the spool 43 moves to the left, the annular passage 44
Since the communication between the supply passage 45 and the supply passage 45 is increased, and the flow rate passing through the orifice 36 is increased, the differential pressure across the orifice 36 is increased.

If the spool 43 moves to the right, the communication between the supply passage 45 and the excess passage 46 will increase, so the flow rate through the orifice 36 will decrease, and the differential pressure across the orifice 36 will become smaller.

Therefore, if the spring constant of the spring 58 is set appropriately small, the spool 43 will move so that the differential pressure across the orifice 36 is kept approximately constant.

Due to the action of the spool 430 described above, a flow rate proportional to the opening degree of the orifice 36 is supplied from the annular passage 21 to the passage 29, through the annular passage 19, and further through the annular passage 18 to the actuator from the service port 27.

On the other hand, the return pressure fluid from the actuator is introduced into the plunger section through the service port 28 and enters the annular passage 22, and further passes through the small diameter portion of the plunger 15 from the annular passage 23 to the return passage 52 and the flow control valve 13. The annular passage 4γ enters the valve hole 68 of the spool 43.

Here, the piston valve 87 of the inlet section 83 (see FIG. 2) is closed, cutting off communication between the annular passage 92 and the return passage 86, so that the pressure chamber of the bypass valve 14 communicating with the annular passage 92 is closed. T1 pressure is orifice 73
Since the pressure in the valve hole 68 is the same as that in the valve hole 68 , the force of the spring 69 causes the valve body 70 to block communication between the valve hole 68 and the return passage 81 .

Therefore, the return liquid flowing into the valve hole 64 of the check valve 63 passes through the annular passage 47, the return passage 76, the annular passage γ5 of the bypass valve 14, the passage 74, the valve hole 68, the passage 74, and the return passage 17. , ends up in the annular passage 1γ of the directional control valve 12, and as a result, the pressure in the valve hole 64 in the check valve 63 increases, pushing the valve body 66 open to the left against the force of the spring 65, and the excess flow It joins the excess flow in channel 46 and is fed into the supply passage of the next plunger section.

The flow rate is the sum of the surplus flow rate and the return flow rate from the actuator, and almost matches the pump discharge rate.

In this way, when two or more plunger sections shown in Figure 1 are used to configure two or more load circuits, the downstream plunger section not only receives the afterflow from the upstream plunger section, but also has a flow from the actuator. The combined pressure fluid with the return flow is used, forming a so-called series circuit.

By using this series circuit, it is very easy to operate two or more plunger sections simultaneously, and even the downstream plunger section has a flow rate close to the pump discharge amount (if the actuator is a cylinder, the ratio of the rond diameter to the cylinder diameter and the connection direction) (depending on the situation) can be used.

However, by using a series circuit, the load pressure of two or more actuators that are operated simultaneously is added to the pump, and this sometimes reaches the operating pressure of the main relief valve, causing the actuator to operate. There is a risk that you will not be able to.

Taking this into consideration, in the present invention, the set load of the spring 910 of the piston valve 87 of the inlet section 83 is set to be lower than the operating pressure of the main relief valve.

Then, when operating in the series circuit as described above, the pump discharge pressure will be the sum of the load pressures of two or more actuators, but if the load on the actuators is large and this total pressure exceeds the spring 910 set load, The pump discharge pressure in the supply passage 85 passes through the valve hole 90 to the piston 8.
9, moves the piston 89 to the left against the force of the spring 91, returns to the annular passage 92 via the passage 95, and returns to the passage 8.
6 and is connected to the tank.

For this purpose, the pilot flow passes through the orifice 73 of the bypass valve 14, passes from the valve hole 68 to the pressure chamber 71, through the port 72, through the annular passage 92 of the inlet section 83, through the passages 93, 95, 94, and from the return passage 86 to the tank. flows.

Therefore, the leftward force due to the differential pressure across the orifice 73 of the pilot flow overcomes the spring 69 and opens the valve body 70 .

This allows return passages 52, 76 from the actuator to
is the passage γ4, the valve hole 68, and the downstream chamber γ8 from the annular passage γ5.
, passage 79, return passage 81, annular passage 16, return passage 2
5 and flows into the tank.

Therefore, the pressure inside the valve hole 64 of the check valve 63 decreases, and the restoring force of the spring 65 causes the valve body 66 to move to the right.
Since the valve hole 64 is closed, the liquid returned from the actuator does not merge with the surplus flow and all flows to the tank.

Therefore, only the surplus flow of the pressure liquid used in the upstream plunger section flows through the surplus flow path 46 into the supply passage of the downstream next plunger section.
This constitutes a so-called parallel circuit.

In the case of a series circuit, the pump pressure was the sum of the load pressures of actuators operated simultaneously, but by operating the bypass valve 14 in this parallel circuit, the pump pressure becomes the highest pressure among each actuator,
This will be lower than that of a series circuit.

This becomes the operating pressure of the relief valve in the series circuit, and the parallel circuit prevents the actuator from becoming inoperable, and also prevents the pump from overloading.

Note that when the piston 87 is closed in the inlet section 83, the pressure receiving area of the piston 89 is equal to that of the through hole 90.
However, once opened, the effective pressure-receiving area becomes the cross-sectional area inside the cylinder 88.

Therefore, by changing the cross-sectional area of the through hole 90 and the internal space of the cylinder 88, the pump pressure when the piston 89 opens and the pump pressure when the piston 89 closes can be set to an arbitrary ratio.

A bypass valve device consisting of a combination of an inlet section 83 and a bypass valve '14 senses pressure in the supply passage 85 equal to or higher than a predetermined value, opens the bypass valve 14, and opens the return passage 76.
Of course, this can also be accomplished by other devices having the same effect.

FIG. 3 is a schematic explanatory diagram of two stacked devices of the present invention.

Each plunger section is identical to that shown in FIG. 1, and identical parts have the same reference numerals and suffixes as shown in FIG.

The pressure liquid discharged from the pump 84 passes through the supply passage 85 of the inlet section 83 and is connected to the supply passage 45a of the first plunger section 99a.
5a communicates with the surplus flow path 46a through the small diameter part of the flow rate adjustment valve 13a, and this surplus flow path 46a is connected to the supply passage 45b of the second plunger section 99b, and the surplus flow path 46a of the flow rate adjustment valve 13b is connected to the supply passage 45b of the second plunger section 99b. Flow rate 46b enters return passage 97 of outlet 96 and is connected to tank 98.

In this case, if three or more plunger sections are used, the surplus flow path 46b of the second plunger section 99b
will be connected to the supply circuit of the next plunger section.

The low pressure return passage 86 of the inlet section 83 is connected to the first
The low pressure of the outlet 96 is connected via the return passage 25a of the plunger section 99a to the annular passage 16aK of the directional valve 12a, and further via the return passage 25b of the second plunger section 99b to the annular passage 16b of the directional valve 12b. It is connected to a tank 98 through a return passage 97 .

A pilot circuit as a bypass circuit is connected to the pressure chamber 71a from the annular passage 92 of the inlet section 83 through the port 72 of the bypass valve 14a in the first grunge section 99a, and at the same time is connected to the pressure chamber 71a in the second plunger section 99b. It is also connected to the pressure chamber 71b of the bypass valve 14b.

Also, the first and second plunger sections 99a, 99b
service ports 27a, 28a and 27b, 28
b communicates with the supply and return ports of respective actuators 82a and 82b.

In this configuration, the plungers 15a of the first plunger section 99a and the second plunger section 99b,
15b to the right at the same time. Pressure liquid from the pump 84 enters the supply passage 45a of the first plunger section 99a through the supply passage 85 of the inlet section 83, and the partial directional control valve 12a
Actuator 82 from service port 27a via
The liquid is supplied to the rond side chamber of a, and the return liquid from the base side chamber enters the service port 28a, passes through the direction switching valve 12a, pushes open the check valve 63a, and enters the surplus flow path 46a.

The remainder of the liquid discharged from the pump flows from the supply passage 45a into the surplus passage 46a, where the return liquid from the actuator joins and flows into the second plunger section 99b.
is supplied to the supply passage 45b.

The pressure fluid supplied to the second plunger section 99b is divided into the working fluid of the actuator 82b and its surplus fluid, as in the first plunger section. Road 9
7 to tank 98.

Furthermore, when the sum of the load pressures of the actuators 82 a t 82 b exceeds the bracket 910 set load of the piston valve 87 in the inlet section 83, the piston valve 8γ acts and the first and second plunger sections 99a, 99b The check valve 63a communicates the pressure chambers 71a, 7lb in the bypass valves 14a, 14b with the tank 98 via the return passage 86 of the inlet section 83.

63b is closed and each actuator 82 a t 82 b
The return liquid is transferred to the return passage 9 of the outlet 96 from the return passages 25a and 25b via the bypass valves 14a and 14b.
7, the first plunger section 99a returns the remaining surplus flow after subtracting the amount of working fluid from the actuator 82a from the pump discharge amount through the surplus flow path 46a to the second plunger section 99b.
Similarly, in the second plunger section 99b, only the surplus flow remaining after subtracting the operating flow rate of the actuator 82b from the surplus flow rate from the first plunger section 99a is returned to the tank 98 through the surplus flow path 46b. Also, the pressure of the pump 84 may be the higher pressure of the actuator 82a or 82b.

To explain this with an example, the pressure at which the piston valve 87 in Inlesotho opens is 200 k! il'/cr
A, and the main relief set pressure is slightly higher than this.

Also, the pressure when the piston valve 8γ closes is set to 90'i/c.
Let it be rA.

Assuming that two actuators 82a and 82b are operated simultaneously, each load pressure is 120 kg/C4 and 100 kl;
Consider the case where l/crA.

In this case, initially it is a series circuit and the pump pressure is 2
20 kg/cr;i will be required.

When the pump pressure increases and reaches 200 kg/crA, the piston valve 8γ opens and the return oil flows to the tank by operating the bypass valve 14a.

Then, the maximum pressure of the pump is 120 kg/crtt
Therefore, the remaining pump flow rate used upstream flows to the downstream actuator.

Since the closing pressure of the piston valve 8γ is 90 kg/crA, these two actuators 82a.

During the simultaneous operation of 82b, the bypass valves 14a and 1
4b remains open.

When this operation is completed, the plungers of the directional control valves 12a and 12b are returned to their neutral positions, and when the pump pressure decreases, the piston valve 87 is also closed.

In the next work, the pump pressure will be 200 kg/crA.
The following is a series circuit.

The above explanation has been made only for the case where the plunger 15 of the directional control valve 12 is moved to the right, but also when the plunger 15 is moved to the left and the actuator is operated in the opposite direction.
Since substantially the same effect is performed except for the case where the flow direction of some fluids is reversed, the explanation in this case will be omitted.

As described above, the present invention is a multi-direction switching device equipped with a pressure-compensated flow control mechanism, and when operating multiple actuators at the same time, usually a series circuit is configured and the actuators of upstream devices are The return liquid of the upstream actuator is combined with the surplus flow and supplied to the downstream device, and when the load pressure of each actuator is large and the pump pressure exceeds a preset value, the return liquid of the upstream actuator is flowed downstream. Since the mechanism is such that the pump pressure is lowered by returning it to the tank through the suspension, in a series circuit, it is possible to use a large flow rate close to the pump discharge volume even in the downstream equipment, so the actuators can be operated simultaneously at relatively low pressure. It is possible to efficiently use the pump power when performing a This has a significant effect of avoiding circuit inconveniences.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a plunger section according to an embodiment of the present invention, Fig. 2 is a cross-sectional view of an inlet section according to an embodiment of the present invention, and Fig. 3 is a circuit explanatory diagram when plunger sections are installed in multiple series. , FIG. 4 is a schematic explanatory diagram of the conventional one. 12... Directional switching valve, 13... Flow rate adjustment valve, 14... Bypass valve, 15...
Plunger, 25°26.52, 76, γγ, 86...
...Return passage (tank side), 27, 28...-
・Service port (supply passage and return passage on the actuator side), 35° 36... Orifice, 43 ・
... Spool, 45°49.85 ... Supply passage (pump side), 46 ... Surplus flow path, 54
, 55... Pressure chamber, 56... Orifice, 58... Spring, 61...
Notch, 63... Check valve, 65, 69...
・Spring, 70... Valve body, γ1...
・Pressure chamber, γ meter... Orifice, 83...
- Inlet section, 87... Piston valve, 91... Spring.

Claims (1)

[Claims] 1. A supply passage on the pump side communicating with the pump, and b.
, a return passage on the tank side that communicates with the tank; C. a supply passage and a return passage on the actuator side that communicate with the actuator; d) an extra flow passage that branches off from the supply passage on the pump side and connects to the supply passage of the next load. and (e) selective communication between the supply passage on the pump side and the return passage on the tank side, and the supply passage and the return passage on the actuator side, which are displaced in response to external operation and responsive to the displacement; a directional switching valve that variably controls and shuts off a communication area; and f, a spool that variably controls passage area distribution between the supply passage on the pump side downstream of the surplus flow path branch part and the surplus flow path by axial displacement; g, facing both ends of the spool, one of which is interposed with a spring that imparts an elastic force to the spool, and a hydraulic pressure downstream of the directional control valve in the supply passage on the actuator side; is guided, and the other is guided by the hydraulic pressure upstream of the directional switching valve in the supply passage on the pump side, and the displacement of the spool is adjusted by the elastic force of the spring and the differential pressure across the directional switching valve in each of the supply passages. h, a bypass valve device that is interposed in the return passage on the tank side and opens the return passage on the tank side when the hydraulic pressure in the supply passage on the pump side is equal to or higher than a set value; a passageway that communicates the pressure chamber in which the spring is installed with the tank at the communication cutoff position of the directional control valve; A directional switching device that also functions as a flow rate control device, characterized in that the device includes: a normally closed check valve that is interposed and opens when the hydraulic pressure upstream of the bypass valve device is equal to or higher than a predetermined pressure.