JPS6032041B2 - fluid control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fluid control device that alleviates shock during operation of an inertial load such as a turning base of a hydraulic excavator or the like.

<Prior art> This type of fluid control device suffers from circuit vibration caused by the interaction between the compression of the bottle in the circuit due to the inertial load and the delay in response of the pressure compensating means during paddy refilling of the directional control valve. In order to solve this problem, the foundation was constructed as shown in Figures 1 and 2.

For example, in the fluid control system shown in FIG. 1, a throttle valve 3 and an actuator 4 are sequentially connected to a pressure line 2 of a pump 1, and a pressure compensating means consisting of a bypass type pressure compensating valve 5 is provided on the primary side of the throttle valve 3. A throttle valve 6 is installed in the spring chamber of a bypass type pressure compensation valve 5 that communicates with the secondary side of the throttle valve 3, and a throttle 6 is installed in the middle. tank 8 via pent line 7
a to dampen the compression of oil in the circuit caused by the inertial load, thereby eliminating circuit vibration.

In addition, the fluid control device shown in FIG. 2 has the secondary side of the throttle valve 3
It is connected to the tank 8b via a pentline 7 with a throttle 6 installed in the middle, and is designed to eliminate circuit vibration by relaxing the compression of oil in the circuit. <Problems to be Solved by the Invention> However, in the fluid control device shown in FIGS. 1 and 2, since there is always a leakage flow rate from the pento line 7,
Not only does power loss and heat generation occur, but the maximum discharge flow rate of the pump 1 cannot be utilized, and even if the flow rate of the throttle valve 3 is controlled by the bypass type pressure compensation valve 5, it is not possible to use the flow rate of the throttle valve 3 at all. There was a problem in that the control became inaccurate because V could not be supplied to the motor.

Therefore, when these devices are used in a hydraulic excavator with an inertial load that is likely to cause circuit vibration, the following problems occur.

In other words, if these devices are used to drive a hydraulic motor for running a hydraulic excavator, etc., the constantly occurring leakage flow rate will cause the left and right wheels to rotate at different speeds, making it impossible to drive in a straight line, and the flow rate will be too low. There is a problem in that the maximum flow rate of the pump cannot be utilized if it is used to drive the required hydraulic motor for turning the turning table. Therefore, the purpose of this invention is to generate leakage flow from the load side to the tank at the beginning of turning or running of a hydraulic excavator to alleviate the shock, and to eliminate leakage flow during steady state to ensure a large flow rate. , and to obtain accurate flow control.

<Means for Solving the Problems> In the present invention, a spool is inserted into a main body having at least three boats P and T'A, and the pressure boat P and the load boat A are connected by the spool and the main body. In between, the first aperture,
A second throttle is formed between the load boat A and the tank boat T, and when the spool is in a neutral position, the first throttle is closed and the second throttle is open. a directional control valve that opens the first throttle and closes the second throttle, while opening the first and second throttle during the transition period from the neutral position to the switching position; This fluid control device includes pressure compensating means that maintains a constant writing pressure before and after the first throttle using a spool that responds to the pressure of the branched differential pressure passage.

(Function) With the above configuration, the present invention prevents the spool 23 of the directional control valve from flowing through the load boat A, the tank T, and the second throttle 51 when the spool 23 of the directional control valve is in operation, causing a leakage flow, thereby preventing circuit vibration and surge pressure. This is prevented, and after the switching of the spool 23 is completed, the first throttle 53 is closed and the leakage flow disappears, allowing accurate flow control without causing power loss or heat generation.

Embodiments> Hereinafter, the fluid control device according to the present invention will be described in detail with reference to illustrated embodiments.

As shown in FIG. 3, this fluid control device includes a directional control valve 20 in the upper stage and a pressure compensation means 60 in the lower stage.

The multi-directional control valve 20 is a 4-boat, 3-position light-cut sliding door valve, in which a spool 23 is slidably fitted into a subur chamber 22 provided in a main body 21. The spool chamber 22 is provided with five annular grooves 24, 25, 26, 27, and 28 in order from the left.
Suitable for pressure boat P, load boat A, tank boat T.

The load boat A is connected to an actuator (not shown) having an inertial load. Furthermore, a small annular groove 31 provided between the annular grooves 25 and 26, and a small annular groove 31 provided between the annular grooves 26 and 26,
The small annular grooves 32 provided between 7 and 7 are conveyed to the annular grooves 26 through passages (not shown). That is, the small annular grooves 31 and 32 always communicate with the pressure boat P. On the other hand, the spool 23 has four lands 35, 36.
, 37, 38.

The interaction between the lands 35, 36, 37, and 38 and the sliding surface of the spool chamber 22 switches and connects the pressure boat P to the load boat A or B, and the load boat A or B to the tank boat T. A first throttle 53 is formed between the pressure boat P and the load boat A by the interaction between the land 35 and the sliding surface of the spool chamber 22. Similarly, a first throttle is formed between the boat P and the loaded boat B. That is, in the neutral position of the spool 23 shown in the figure, the pressure boat P is closed, the load boats A and B pass through the tank boat T, and when the spool 23 is positioned to the left, the pressure boat P and the load boat A are closed. : When tank boat T and load boat B are in transit and spool 23 is positioned to the right, pressure boat P and load boat B; tank boat T and load boat A are suitable. A cover 41 is fixed to the left end of the main body 21 to form a spring chamber 42, and a spring 43 provided in the spring chamber 42 always urges the spool 23 to a neutral position.

A cover 58 is fixed to the upper part of the main body 21, and a passage 59 provided in the cover 58 connects the annular grooves 24 at both ends.
, 28 is passed through the lotus. On the other hand, each inner end of the emotional surfaces of the lands 35 and 38 at both ends of the spool 23 is provided with respective notch grooves 46''45 in the direction of the axis D.
When the above-mentioned notch grooves 45, 46 and the spool chamber 22 are displaced,
The sliding surfaces 22a, 22b of the second apertures 51, 5
2 are formed respectively. That is, when the spool 23 moves to the left, the second throttle 51 causes the central land 37 to move away from the sliding surface 22c of the spool chamber 22 so that the load boat A is applied to the pressure boat P. 38 comes into contact with the sliding surface 22a and tries to cut off the passage of the load boat A and the tank boat T.
2a. Therefore, the second aperture 5
1, when the flow rate from the pressure boat P to the load boat A is small immediately after the switching of the spool 23, the load boat A carries the tank boat T so that a leakage flow rate occurs. Further, when the second diaphragm 51 further moves the spool 23 to the left and has maximum displacement,
The notch groove 45 completely covers the sliding surface 22 of the spool chamber 22.
It is closed by being covered by a.

As a result, when the flow rate from pressure boat P to load boat A is large enough to prevent circuit vibration, load boat A
There is no leakage flow from the tank boat T to the tank boat T. The specific dimensional configuration of the opening and closing of the second throttle 51 and the opening and closing between the boats A and T with respect to the stroke displacement of the spool 23 is shown in FIG.

That is, the total stroke of the spool 23 from the neutral position is 13=8.5 ribs, and the pressure boat P and the load boat A are 1, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 2, 2 2.
Load boat A
and tank boat T remain selected through the second throttle 51 until the spool 23 is displaced leftward by 12=7.5 degrees from the neutral position, and the spool 23 is displaced by 7.5 degrees or more. Then, the second diaphragm 51 is closed and the lotus passage is cut off. On the other hand, the main body 21 is provided with a pilot passage 54, and the entrances 54a, 54b of the pilot passage 54 are connected to the sliding surfaces 22c, 22c of the spool chamber 22.
2d, respectively, and by displacing the land according to the spool 23, the load boat A or B is made to carry speed through the opening 54a or 54b. That is, the Sekiguchi 54a is provided between the annular groove 27 and the small annular groove 32, while the Sekiguchi 54b is provided between the annular groove 25 and the small annular groove 31. When it is displaced in the direction, the land 37
The sliding surface of the land 36 moves away from the opening 54a to allow the load boat A to move through the opening 54a, while the sliding surface of the land 36 closes the opening 54b, and when the spool 23 is displaced to the right, the land 37 The sliding surface of the land 36 closes the opening 54a, while the contact surface of the land 36 is separated from the closure 54b, allowing the core closure 54b to pass through to the load boat B. Therefore, the pilot passage 54 is suitable for the load boat A or B carried by the pressure boat P when the spool 23 is switched from the neutral position. Further, the main body 21 is vertically provided with a pent passage 55 which has one end communicating with the pilot passage 54 and the other end communicating with the passage 59 of the cover 58.

The pent passage 55 is opened by the annular narrow groove 37a provided in the land 37 when the spool 23 is in the neutral position, and closed by the sliding surface of the land 37 when the spool 23 is displaced from the neutral position. It is now possible to do so. Therefore, the pilot passage 54 is fitted to the tank boat T via the vent passage 55 and the passage 59 when the spool 23 is in the neutral position. On the other hand, the pressure compensating means 60 is comprised of a bypass type pressure compensating valve. However, a pressure reduction type pressure compensation valve or a priority type pressure compensation valve may be used instead of the bypass type pressure compensation valve. The bypass type pressure compensation valve 60 has a main body 6
A spool 63 is slidably fitted with iron in a spool chamber 62 provided in 1.

The spool chamber 62 has an annular groove 65 from the left side.
, 66 and 67, the annular groove 65 is connected to the pump 9 and is also connected to the pressure boat P of the directional control valve 20 via a passage 69, while the annular groove 67 is connected to the tank 91 and Directional control valve 20 via passage 70
It is connected to tank boat T. On the other hand, the spool 63 is provided with lands 71, 72, 73, and the lands 71, 72, 73 are respectively connected to the sliding surface 6 of the spool chamber 62.
2a, 62b, and 62c are slidably fitted into the box.

Then, as the spool 63 moves left and right, the sliding surface 62b and the sliding surface of the land 72 come into contact with and separate from each other, opening and closing the passage between the annular grooves 65 and 67, and draining the oil from the pump 90 into the tank. I am trying to bypass it to 91. A spring chamber 76 provided at the other end of the main body 61 is connected to the pilot passage 54 of the directional control valve 20 via a pilot passage 81 which is a differential pressure passage, while a pilot chamber 78 provided at the right end of the main body 61 is connected to the annular groove 65 via a passage 83, which is a differential pressure passage provided at the center of the spool 63.

Therefore, the hydraulic pressure of the load boat A or B of the directional control valve 20 is applied to the spring chamber 76, while the hydraulic pressure of the pressure boat P of the directional control valve 20 is applied to the pilot chamber 78. The spool 63 of the pressure compensation valve 60 is operated so that the differential pressure across the directional control valve 20 becomes a value corresponding to the spring force of the spring 79 provided in the spring chamber 76. Note that FIG. 8 shows the structural diagram of FIG. 3 using circuit symbols. 53 indicates a first aperture.

The fluid control device configured as described above operates as follows.

When the spool 23 of the directional control valve 20 is in the neutral position shown, the pressure boat P is closed by the lands 36, 37, the load boats A, B are connected to the tank boat T, and the spring of the bypass type pressure compensation valve 60 is closed. The chamber 76 is connected to the tank 91 via a pilot passage 81, a pilot passage 54, and a vent passage 55, and the pump 90 performs an unload operation.

Now, when the spool 23 of the directional control valve 20 is displaced to the left from the position shown in the figure, the sliding surface of the land 37 moves into the spool chamber 2.
The pressure boat P is connected to the load boat A apart from the sliding surface 22c of No. 2.

At this time, the sliding surface of the land 38 comes into close contact with the emotional surface 22a of the spool chamber 22 and attempts to cut off the communication between the load boat A and the tank boat T, but the notch groove 45 provided on the sliding surface of the land 38 Due to the second throttle 51 formed by the sliding surface 22a and the sliding surface 22a, the load boat A and the tank boat T remain in operation. Therefore, oil leaks from the load boat A to the tank boat T through the second throttle 51, and this action causes a circuit caused by the intertwining of the response delay of the bypass type pressure compensation valve 60 and the compression of oil due to the inertial load. Prevents vibration and surge pressure. Furthermore, when the spool 23 is displaced more than 7.5 ribs to the left from the neutral position,
The sliding surface 22a of the Subur chamber 27 completely covers the notched groove 45 provided in the sliding surface of the land 38, and the second throttle 51 is sealed.

At this time, the land 37 is far away from the sliding surface 22c, and the controlled flow rate to the load boat A is larger than that of the pressure boat P, so the second throttle 51 is fully closed as described above to cause leakage oil. Even if you do not do so, circuit vibration will not occur. On the other hand, as described above, since leakage oil is not generated, a large flow rate can be ensured. In other words, all the flow rate controlled by the bypass type pressure compensating means 601 can be supplied to the actuator. FIG. 5 shows the controlled flow rate of the directional control valve 20 with respect to the load pressure, using the stroke displacement of the spool 23 of the directional control valve 20 as an auxiliary variable.

Each curve S,, S2, S3, S4, Flea, S6 has a stroke displacement of 3.5 ribs, 4.5 skin, 5.5 side, 6.5 willow,
Shows the condition of 7.5 skin and 8 fence. As is clear from this, when the stroke displacement is 7.5 ribs or more, no leakage flow occurs regardless of the load pressure. The first diaphragm 51a shown in FIG. 6 is a modification of the second diaphragm 51, and is
The amount of aperture is changed in accordance with the stroke displacement of No. 3.

The groove 49 provided in the land 38 to form the second aperture 51a is enlarged in a V-shape toward the end surface of the land 38.

Therefore, when circuit vibration is likely to occur immediately after switching, the second throttle 51a increases the cross-sectional area of the second throttle 51a to increase the leakage flow rate and prevent circuit vibration, while at the same time preventing circuit vibration due to an increase in stroke displacement. The cross-sectional area of the second throttle 51a is reduced to reduce the leakage flow rate. Further, the second diaphragm 51b shown in FIG. 7 is a second modification of the second diaphragm 51, and has a type in which the amount of diaphragm does not change much with the stroke displacement of the spool 23. Such aperture shape can be selected depending on the load situation. In each of the above embodiments, each of the first apertures 51, 51a, 51b connects each notch groove 45, 46 to the land 38 of the spool 23,
Although the cutout groove is provided on the sliding surface 222 of the spool chamber 22, the aperture may be formed.

<Effects of the Invention> As is clear from the above description, the fluid control device of the present invention has the following effects:
Leakage flow is generated only during switching transients, and leakage flow is eliminated after switching is completed, so it is possible to prevent circuit vibration and shock (surge pressure) at the beginning of startup, and furthermore, there is no leakage flow after switching is completed. This eliminates power loss and heat generation, and allows accurate flow control.

Furthermore, if the first and second throttles are structured so that the amount of throttle changes as the spool is displaced, it is more suitable for preventing circuit vibration and surge pressure.

[Brief explanation of the drawing]

1 and 2 are hydraulic circuit diagrams of a conventional fluid control device, and FIG. 3 is a sectional view of essential parts of a fluid control device according to an embodiment of the present invention.
Fig. 4 is a diagram showing the opening/closing relationship between each boat with respect to the stroke displacement of the fluid control device shown in Fig. 3, Fig. 5 is a load control flow characteristic diagram with the spool displaced, and Fig. 6 , FIG. 7 is a diagram showing a modified example of the throttle, and FIG. 8 is a circuit diagram of the fluid control device of FIG. 3. 20... Directional control valve, 21... Body,
23... Spool, 51... First throttle, 53... Second throttle, 60... Pressure compensation means, 63...
... Spools 81, 83... Differential pressure passage. Figure 1 Figure 2 Figure 4 Figure 5 Figure 6 Figure 7 Figure 3 Figure 8

Claims (1)

[Claims] 1 Body 2 with at least three ports P, T, A
1, a first throttle 53 is formed between the pressure port P and the load port A between the spool 23 and the main body 21, and a first throttle 53 is formed between the pressure port P and the load port A, and a first throttle 53 is formed between the pressure port P and the load port A, and
Second throttles 51, 51a, and 51b are respectively formed in between, and when the spool 23 is in its neutral position, the first throttle 53 is closed, the second throttles 51, 51a, and 51b are opened, and the spool 23 is closed. At the switching position, the first throttle 53 is opened and the second throttle 51, 51a, 51b is closed, while in the transition period from the neutral position to the switching position, the first and second throttles 53, 51, 51a are closed. , 51b, and the first throttle 51, 51a,
A fluid control device comprising a pressure compensation means 60 that maintains the differential pressure across the first throttle 53 constant by a spool 63 that responds to the pressure of differential pressure passages 81 and 83 branched from the front and rear of the first throttle 51b.