JP3534854B2 - Unload valve for load-sensitive hydraulic circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an unload valve for a load-sensitive hydraulic circuit that connects a pump and a tank under certain conditions.

[0002]

2. Description of the Related Art In the load pressure sensitive hydraulic circuit shown in FIG.
The variable discharge pump P and the actuator 2 are connected via a directional control valve 3 of a closed center system.
The directional control valve 3 has three switching positions. Particularly, in the flow paths in the switching positions 3a and 3b, the throttle 39 is provided on the most upstream side.
Is provided. The port 37 of the directional control valve 3 is connected to the bottom side chamber A of the actuator 2 and
8 is connected to the rod side chamber B. On the other hand, the directional control valve 3
The pump port 34 is connected to the discharge pipe line 4 of the variable discharge pump P, and the tank ports 31 and 36 are connected to the tank T. Also, ports 32, 33, 3
5 is connected to the signal oil passage 5 and the signal oil passage 5
Is connected to the tank T via a relief valve 6. A spring 6a acts on one side of the relief valve 6 and the hydraulic pressure of the signal oil passage 5 is guided to the other side. When the oil pressure in the signal oil passage 5 rises and becomes larger than the set pressure determined by the spring 6a, the relief valve 6 opens and the signal oil passage 5 communicates with the tank T. The set pressure may be set in consideration of the maximum load pressure of the actuator 2.

The discharge pipe line 4 branches at an X point on the way and is connected to a regulator 9. Furthermore, the discharge pipe line 4 branches at a Y point downstream of the X point, and the branched unload oil passage 7 is connected to the tank T via the unload valve 1. Switching position 1a of unload valve 1
The hydraulic pressure in the unload oil passage 7 is guided to the second pilot pressure chamber 10 on the side. On the other hand, the signal oil passage 5 is branched midway and connected to the regulator 9 as the signal oil passage 5b. That is, the hydraulic pressure of the signal oil passage 5b and the discharge pressure of the pump P are guided to the regulator 9 as pilot pressures, and the pilots are regulated by the pilot pressures.
Controls the discharge pressure of the variable discharge pump P to be higher than the oil pressure of the signal oil passage 5b by a predetermined differential pressure. When the signal oil passage 5b has the tank pressure, the discharge amount of the pump P becomes the minimum amount.

Further, the signal oil passage 5 is branched, the branched signal passage 5a is connected to the first pilot pressure chamber 26 of the unload valve 1, and the first pilot pressure chamber 2 is connected.
6, a spring 8 is provided. Although not shown, a spool having equal pressure receiving areas at both ends is slidably incorporated in the unload valve 1. Then, as described above, the hydraulic pressure of the unload oil passage 7 acts on the spool end portion on the second pilot pressure chamber 10 side, and the signal oil passage 5a of the signal oil passage 5a is formed on the spool end portion on the first pilot pressure chamber 26 side. The hydraulic pressure and the spring force of the spring 8 act. The initial load held by the spring 8 will be described later.

Next, the operation of this conventional example will be described. When the directional control valve 3 is at the switching position 3a, the discharge oil from the variable discharge pump P is guided to the port 34. Switching position 3a
Since the port 34 and the port 33 communicate with each other through the throttle 39, the flow rate of the discharged oil is controlled through the throttle 39. The pressure oil on the downstream side of the throttle 39 is the port 32.
And is led to the bottom side chamber A through the port 37. Therefore, the hydraulic pressure on the downstream side of the throttle 39 is the actuator 2
It becomes equal to the load pressure of. At this time, since the port 38 communicates with the tank port 36, the pressure oil in the rod chamber side B is returned to the tank T.

The pressure oil on the downstream side of the throttle 39, that is, the load pressure of the actuator 2 is passed through the signal oil passage 5 to the relief valve 6
And to the first pilot pressure chamber 26 of the unload valve 1 via the signal oil passage 5a. At the same time, the load pressure is also guided to the regulator 9 via the signal oil passage 5b, and the regulator 9 controls the discharge pressure of the pump P to be higher than the load pressure by a predetermined differential pressure. The discharge pressure of the pump P acts on the spool end of the unload valve 1 on the side of the second pilot pressure chamber 10, while the load of the actuator 2 is applied to the spool end of the spool on the side of the first pilot pressure chamber 26 as described above. The pressure and the spring force of the spring 8 act.

Here, the spring 8 holds an initial load larger than the acting force due to the difference between the discharge pressure of the pump and the load pressure of the actuator 2. Therefore, when the directional control valve 3 is in the switching position 3a, the unload valve 1
Keeps the switching position 1b. When the directional control valve 3 is at the switching position 3b, the rod chamber side B of the actuator 2 communicates with the pump P via the throttle 39, and the bottom side chamber A is connected to the tank, as opposed to when it is at the switching position 3a. Communicate. The fact that the hydraulic pressures of the signal oil passages 5 and 5a, 5b become the load pressure of the actuator 2 is the same as when it is in the switching position 3a, and the detailed description thereof is omitted. As described above, when the direction switching valve 3 is in the switching positions 3a and 3b, the regulator 9 changes the discharge amount of the variable discharge pump P according to the load pressure of the actuator 2.

When the directional control valve 3 is in the neutral position shown in FIG. 3, the ports 37 and 38 to which the bottom side chamber A and the rod side chamber B are connected are blocked. Therefore, the actuator 2 can be fixed. At the same time, since the ports 35 and 36 are in communication with each other in the neutral position, the ports 32, 33 and 35 are eventually in communication with the tank T through the tank port 36. Therefore, the signal oil passages 5 and 5a connected to the ports 32, 33 and 35,
5b is the tank pressure. Since the signal oil passage 5b is the tank pressure, the pump P has the minimum discharge amount, but the pump port 34
Is blocked, the hydraulic pressures of the discharge pipe line 4 and the unloading oil line 7 increase. Then, as the acting force of the discharge pressure on the spool end portion in the unload valve 1 increases, the unload valve 1 is switched to the switching position 1a side while resisting the spring 17, and depending on the opening degree at this time. Pump P and tank T communicate with each other. That is, the pump P discharge pressure when the directional control valve 3 is in the neutral position is the pressure required to open the unload valve 1, that is, the spring 8
The pressure is based on the spring force of.

[0009]

In the load-sensitive hydraulic hydraulic circuit as described above, the directional control valve 3 has the switching position 3a.
Alternatively, when the load pressure of the actuator 2 becomes larger than the set value when it is at 3b, the relief valve 6 connected to the signal oil passage 5 opens. And the relief valve 6
When is opened, a flow naturally occurs in the signal oil passages 5 and 5a, 5b. At this time, a pressure difference occurs between the signal oil passages 5 and 5a, 5b due to the line resistance, and the oil pressure of the signal oil passage 5a becomes smaller than the oil pressure of the signal oil passage 5b.
That is, the difference between the discharge pressure determined by the oil pressure in the signal oil passage 5b and the oil pressure in the signal oil passage 5a becomes large, and the unload valve 1 tries to switch to the switching position 1a against the spring 8. When the unload valve 1 is switched in this way, there is a problem that vibration occurs in the signal oil passage and the unload valve 1. As a means to prevent this problem,
It is conceivable to increase the initial load of the spring 8 of the unload valve 1. However, when the initial load is increased, when the directional control valve 3 is in the neutral position, the discharge pressure increases by this initial load, resulting in energy loss. At the same time, considering the strength of the spring 8, it is necessary to make the spring 8 large, which makes it difficult to incorporate it in the unload valve. An object of the present invention is to prevent the opening of the unload valve even if the fluid pressure on the first pilot pressure chamber side is reduced under a certain condition without increasing the initial load of the spring of the unload valve. It is to provide an unloading valve that can.

[0010]

According to a first aspect of the invention, slidably assembled the spool in the spool hole formed in the wafer Woojin <br/> the grayed
Insert one end of this spool into the first pilot pressure chamber.
So that the other end faces the second pilot pressure chamber and
A spring is installed in the first pilot pressure chamber,
The spring force of the ring acts on the spool, and the acting force of the pump discharge pressure introduced to the second pilot pressure chamber is equal to the acting force of the fluid pressure introduced to the first pilot pressure chamber and the spring force of the spring. It is premised on a load-sensitive hydraulic circuit unload valve that communicates between a pump and a tank at an opening that corresponds to the amount of movement of the spool when it becomes larger than the resultant force. In the first aspect of the present invention, the pressure receiving area of the spool facing the first pilot pressure chamber is made larger than the pressure receiving area on the second pilot pressure chamber side on the premise of the load-sensitive hydraulic circuit unload valve. It is characterized by points.
According to a second aspect of the present invention, in the first aspect, a small hole is formed in the spool end portion facing the second pilot pressure chamber in the axial direction and communicates with the through hole in the radial direction of the spool. When the spool moves against the spring force of the spring and the fluid pressure of the first pilot pressure chamber, the opening degree of the small hole and the passage communicating with the tank changes, and the opening degree changes depending on the opening degree. The feature is that the pump and the tank communicate with each other.

[0011]

According to the unloading valve V of the first invention, the spool pressure receiving area on the first pilot pressure chamber 24 side is made larger than the spool pressure receiving area on the second pilot pressure chamber 10 side. Therefore, the acting force by the hydraulic pressure introduced to the first pilot pressure chamber is large. That is, the differential pressure acting on both ends of the spool of the unload valve, which is required to open the unload valve, becomes larger than that in the conventional example. For example, in this embodiment, even if the relief valve 6 is opened and the hydraulic pressure introduced to the first pilot pressure chamber 24 is slightly reduced, the opening of the unload valve V can be prevented.
When the directional control valve 3 is in the neutral position, the first pilot pressure chamber 24 has the tank pressure, and therefore the unload valve V is opened even if the spool pressure receiving area on the first pilot pressure chamber side is large. There is almost no change in the condition. That is, even when the unloading valve V of the present invention is used, the discharge pressure of the pump P can be determined by the spring force of the spring 17 at the neutral position. According to the second aspect of the invention, when the spool is moved by the acting force of the pump discharge pressure guided to the second pilot pressure chamber, the opening degree of the small hole and the passage communicating with the tank changes, and the opening degree is changed according to the opening degree. The pump can communicate with the tank. Therefore, it is not necessary to form a pump port separately from the second pilot pressure chamber.

[0012]

1 and 2 show an embodiment of the present invention. Figure 1
As shown in the negative pressure sensitive circuit diagram in FIG. 2, the spool pressure receiving area of the unload valve V on the first pilot pressure chamber 24 side is
It is made larger than the spool pressure receiving area on the pilot pressure chamber 10 side. The rest of the configuration is the same as the circuit diagram described in the conventional example, and detailed description thereof is omitted. The specific configuration of the unload valve V of the present invention is shown below.
It is FIG. The unload valve V has a hole 12 in the body 11.
And the cylindrical sleeve 1 is formed in the hole 12.
3 is incorporated. Inside the sleeve 13, the tubular portion 13b
A large diameter cylindrical portion 13a is formed at one end and a small diameter cylindrical portion 13c is formed at the other end. And these cylinder parts comprise the spool hole. The spool 14 is a large land portion 14
a and a small land portion 14b, the large land portion 14a is slidably incorporated in the cylindrical portion 13b, and the small land portion 14b is exposed in the small cylindrical portion 13c.

On the other hand, the large cylinder portion 13a is provided with a pair of spring receivers 15 and 16, and both spring receivers 15 and 16 are provided.
A spring 17 is provided between 16. Then, when the cover 18 is attached to the body 11, the large tubular portion 13a and the cover 18 are combined to form the first pilot pressure chamber 24, and the spring 17 holds the initial load, and the spring force thereof is applied to the first pilot pressure chamber. It will act on the spool end on the chamber 24 side. In this embodiment, the housing is composed of the body 11, the cover 18 and the sleeve 13. The state of FIG. 2 is when the spring 17 is extended, and at this time, the spring receiver 15 is
9 and at the same time, the end of the small land 14b has a step 25
Touches. A signal oil passage 5a is connected to the oil passage 20 formed in the sleeve 13, and the signal oil passage 5a
The oil a is guided to the first pilot pressure chamber 24. And
The oil pressure of the signal oil passage 5a acts on the spool end portion on the first pilot pressure chamber 24 side. The pressure receiving area of the spool 14 is A1.

A second pilot pressure chamber 10 communicating with the unload oil passage 7 is formed in the sleeve 13 on the side opposite to the first pilot pressure chamber. Small land part 1 of spool 14
A through hole 21 is formed in the axial direction at the end of 4b. And
The through hole 21 communicates with the second pilot pressure chamber. Further, a small hole 23 communicating with the through hole 21 is formed in the radial direction of the small land portion 14b. The pressure receiving area of the spool 14 on which the hydraulic pressure of the unloading oil passage 7 acts is A2.
When the spool 14 moves in the upward direction in the figure against the spring 17 and the end of the small hole 23 exceeds the step 25, the hydraulic pressure in the second pilot pressure chamber 10 is changed according to the opening of the small hole 23 and the cylindrical portion 13b.
Then, the unloading oil passage 7 communicates with the tank T via the oil passage 22. It should be noted that the chamber 27 formed by the spool 14 and the cylindrical portion 13b being joined together, and the oil passage 2
It is assumed that 2 forms a passage.

Next, the operation of this embodiment will be described. When the directional control valve 3 is in the switching position 3a or 3b, the first
The load pressure of the actuator 2 is introduced into the pilot pressure chamber 24, and the load pressure and the spring force of the spring 17 act on the spool 14 on the first pilot pressure chamber 24 side. At the same time, the discharge pressure of the variable discharge pump P acts on the spool on the second pilot pressure chamber 10 side. Here, the discharge pressure of the pump P is made higher than the load pressure of the actuator 2 by a predetermined amount by the regulator 9, and the spring 17 holds an initial load larger than the acting force due to this differential pressure. There is. Therefore, at this time, the spool 14 is in the state shown in FIG. 2, and the unloading oil passage 7 and the tank do not communicate with each other. That is,
The unload valve V is at the switching position Vb.

From this state, when a load pressure equal to or higher than a set value is applied to the actuator 2, the relief valve 6 opens and a flow occurs in the signal oil passages 5 and 5a, 5b. At this time, a pressure difference occurs in the signal oil passage due to the line resistance, and the oil pressure of the signal oil passage 5a becomes smaller than the oil pressure of the signal oil passage 5b. Therefore, the hydraulic pressure in the first pilot pressure chamber 24 decreases, and the hydraulic pressure relatively on the second pilot pressure chamber 10 side becomes a predetermined differential pressure or more than the hydraulic pressure on the first pilot pressure chamber 24 side. However, the first pilot pressure chamber 24
Since the spool 14 pressure receiving area A1 on the side is larger than the spool 14 pressure receiving area A2 on the second pilot pressure chamber 10 side,
The acting force due to the load pressure is increased by this pressure receiving area difference. Therefore, even if the spring holding the same initial load as the conventional one is used, it is possible to prevent the unload valve V from opening, that is, moving to the switching position Va side.

When the directional control valve 3 is in the neutral position, the first pilot pressure chamber 24 has the tank pressure. Therefore, even if the spool pressure receiving area on the first pilot pressure chamber side is increased, the action of the tank pressure is exerted. It has nothing to do with power. That is, even when the unloading valve V of this embodiment is used, the discharge pressure of the pump P is determined by the spring force of the spring 17 at the neutral time. The difference in the pressure receiving area may be determined according to the conduit resistance and the like. As described above, by using the unloading valve V of this embodiment, the opening of the unloading valve V can be prevented even when the relief valve 6 is opened when the directional control valve 3 is in the switching positions 3a and 3b. In addition, the discharge pressure of the pump P does not increase at the neutral position.

[0018]

According to the unload valve for a load-sensitive hydraulic circuit of the first invention, the discharge pressure of the variable pump, which is higher than the fluid pressure introduced into the first pilot pressure chamber by a predetermined pressure, is the second pilot pressure. For some reason, while being led to the room,
Even if the fluid pressure in the pilot pressure chamber drops to a certain extent, the opening of the unload valve can be prevented, and careless unloading can be prevented. Also used for the unload valve
You don't have to increase the spring initial load
The pump discharge pressure when the directional valve is in the neutral position.
It is possible to prevent the price from becoming higher than necessary. According to the second invention, the structure of the unload valve can be simplified.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a load-sensitive hydraulic circuit using an unload valve of the present invention.

FIG. 2 is a sectional view of the unload valve of the present invention.

FIG. 3 is a circuit diagram of a load-sensitive hydraulic circuit using a conventional unload valve.

[Explanation of symbols]

10 Second pilot pressure chamber 14 spool 17 spring 24 1st pilot pressure chamber V unload valve A1, A2 Pressure receiving area

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-163003 (JP, A) JP-A-3-153901 (JP, A) Actual opening Sho-59-149565 (JP, U) Actual opening Flat 6- 62204 (JP, U) JP-B 3-48361 (JP, B2) JP-B 5-4522 (JP, B2) JP-B 2-28244 (JP, Y2) (58) Fields surveyed (Int.Cl. ⁷ , DB name) F15B 11/00 F16K 17/04

Claims (2)

(57) [Claims] 1. A scan to the spool hole formed in the housings
The pool is slidably installed and one end of this spool is
One pilot pressure chamber, the other end is the second pilot pressure chamber
The first pilot pressure chamber
A ring is provided and the spring force of this spring is applied to the spool.
When the acting force of the pump discharge pressure introduced to the second pilot pressure chamber becomes larger than the resultant force of the fluid pressure introduced to the first pilot pressure chamber and the spring force of the spring, the spool moves. Load-sensitive that moves and moves the pump and tank in communication according to the amount of movement.
In the unloading valve for a hydraulic circuit, the pressure receiving area of the spool facing the first pilot pressure chamber is larger than the pressure receiving area on the second pilot pressure chamber side.
Unload valve for load sensitive hydraulic circuits . 2. A through hole is formed in the axial direction of the spool end portion facing the second pilot pressure chamber, and a small hole communicating with the through hole is formed in the radial direction of the spool. When moving against the spring force of the first pilot pressure chamber and the fluid pressure of the first pilot pressure chamber, the opening degree of the small hole and the passage communicating with the tank changes, and the pump communicates with the tank according to the opening degree. The load-sensitive type according to claim 1, wherein
Unload valve for hydraulic circuit .