JPS60167012A - Pressure reducing valve circuit - Google Patents

Abstract

PURPOSE:To absorb surge pressure and to eliminate fluctuations of pressure by delaying the closing speed of a pressure reducing valve abruptly through the operation of a cushion mechanism right before the pressure reducing valve is closed completely, and preventing the mutual interference between the pressure reducing valve and by-pass valve. CONSTITUTION:The cushion mechanism 25 is provided to a pilot chamber 19 and this cushion mechanism 25 is so sized that the right end surface of a spool 17 abuts on the left end surface of a cushion cylinder 26 right before the spool 17 moves right to close a secondary port B completely, so the cushion cylinder 26 begins to move right before the port is closed completely and its speed is a slow speed corresponding to a slight flow rate of discharge from the chamber 33 between the cushion piston 27 and cushion cylinder 26 through a clearance 31. Therefore, the spool 17 is slowed down right before the port is closed fully. Consequently, a small amount oil is supplied continuously to the port B of the pressure reducing valve 5 even after surge pressure drops in case of transition and it is considered that the pressure response is only the pressure response of the by-pass valve 11.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a pressure reducing valve circuit including a pressure reducing valve, a bypass valve, and a pilot relief valve.

<Prior art> Conventionally, this type of pressure reducing valve circuit has been equipped with a normal oven type pressure reducing valve on the main line, connecting the pilot chamber of the pressure reducing valve to the main line on the secondary side of the pressure reducing valve, and A bypass valve is provided in a bypass line branched from the main line on the secondary side, and the spring chamber of the pressure reducing valve and the spring chamber of the bypass valve are connected to the pilot relief valve via a pilot line, and a throttle valve is connected to the pilot line. A method has been proposed in which the main line on the secondary side of the pressure reducing valve is connected through a valve (Japanese Patent Application Laid-Open No. 56-39308).

In the above pressure reducing valve circuit, the pilot pressure of the pressure reducing valve and the bypass valve is controlled by the pilot relief valve.
The set pressure of the bypass valve can be automatically set according to the set pressure of the pressure reducing valve, and since the surge pressure is absorbed by the bypass valve, which operates quickly, the surge pressure does not increase and the surge pressure absorption performance is improved. It has the advantage of being excellent.

However, in the conventional pressure reducing valve circuit described above, when surge pressure occurs, for example when an actuator suddenly stops or when a switching valve closes, the pressure reducing valve and bypass valve operate to reduce the pressure. Due to the mutual interference with the valve, the settling time of the secondary pressure of the pressure reducing valve becomes longer, and the stability becomes worse, resulting in large pressure fluctuations. This phenomenon of long settling time and poor stability also occurs when the set secondary pressure is increased or decreased by the pilot relief valve.

<Objective of the Invention> Therefore, an object of the present invention is to provide a pressure reducing valve circuit with excellent surge pressure absorption performance, short settling time, and excellent stability.

<Configuration of the Invention> In order to achieve the above object, the configuration of the present invention has a spring chamber at one end of the spool and a pilot chamber at the other end, and a spring chamber is provided in the pilot chamber just before the fully closed position of the spool. A normally closed type pressure reducing valve having a cushion mechanism that slows down the speed in the closing direction of the spool is provided on the main line, the spring chamber of the pressure reducing valve is connected to the main line on the secondary side of the pressure reducing valve, and further, the above-mentioned 2. A bypass valve is provided in a bypass line branched from the main line on the next side, and the pilot chamber of the pressure reducing valve and the spring chamber of the bypass valve are connected to the pilot relief valve via the pilot line, and It is characterized in that the main line on the primary side of the two pressure reducing valves is connected through a throttle means.

<Example> Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

In FIG. 1, 1 is a pressure source, 2 is a main line connecting the pressure source 1 and a hydraulic cylinder 3, which is an example of an actuator, 5 is a normally closed pressure reducing valve provided in the main line 2, and 6 is the above-mentioned A throttle valve is provided in the main line 2 between the pressure reducing valve 5 and the hydraulic cylinder 3, 7 is a bypass line branched from the main line 2 between the throttle valve 6 and the hydraulic cylinder 3 to the tank 8, and 11 is a bypass line. ” - This is a bypass valve provided in the bypass line 7.

The pressure reducing valve 5 has a spool 17 having two lands 17a and 17b slidably fitted into a cylinder chamber 16 in the main body 15, and a spring chamber 18 at one end of the spool 17 and a spring chamber 18 at the other end. Form one 7-pyro chamber. Above spring chamber 1
8 is compressed with a spool spring 21, and a pressure reducing valve 5 is installed.
Connect the main line 2 on the secondary side of the

On the other hand, a cushion mechanism 25 is provided in the pilot chamber 19. This cushion mechanism 25 includes a substantially cap-shaped cushion cylinder 26, a cushion piston 27 that is slidably fitted to the inner peripheral surface of the cushion cylinder 26 with a certain clearance 31, and a cushion piston 27 that is slidably fitted to the inner peripheral surface of the cushion cylinder 26, It consists of a cushion spring 28 compressed between the end face of the piston 27. The spring force of the cushion spring 28 is the spring force of the spool spring 21.
Set it much smaller than Neka. Then, the spool 17 is moving to the left in Figure 1, and the primary port) A
When the gap between the cushion cylinder 26 and the secondary port B is sufficiently opened, the spring force of the cushion spring 28 causes the flange 26a of the cushion cylinder 26 to come into contact with the stopper part 32. From this state, the spool 17 moves to the right as shown in FIG. Dimensions are set so that the right end surface of [Pool] 7 is in contact with the pool. Therefore, the spool 17 is moved to the first position by the spring 21.
The land 17a is moved to the right in the figure, and the land 17a is
Immediately before fully closing, the spool 17 presses against the cushion cylinder 26 and moves with it, or this cushion cylinder 26 passes through the clearance 31 from the chamber 33 between the cushion cylinder 26 and the cushion piston 27. It can only move at a slow speed corresponding to the small amount of fluid being expelled. Therefore, the closing speed of the spool 17 decreases rapidly just before it is fully closed.

Note that, at this time, the cushion piston 27 is of course in contact with the main body 15. Further, both left and right end surfaces of the cushion piston 27 are communicated through a passage 36 having a check valve 35, and when the cushion cylinder 26 moves to the left in FIG. However, oil is supplied to the chamber 33 in the forward direction of the check valve 35, and the spool 17 is braked via the cushion cylinder 26.
Since the sliding clearance between the cushion cylinder 6 and the inner circumferential surface of the main body 15 is sufficiently large, the cushion cylinder 26 quickly returns to the left.

On the other hand, the pilot chamber 19 of the pressure reducing valve 5 is connected to a pilot relief valve 41 via a pilot line 39 having a check throttle valve 38 in the middle. Also,
A pilot line 39 between the check throttle valve 38 and the pilot chamber 19 is connected to the annular groove 43 located on the outer peripheral side between the spool 17 and the cushion cylinder 26 of the pilot chamber 19 via a pilot line 44. By connecting, the movement of the spool 17 to the left in FIG. 1 and the opening operation of the spool 17 are quickly performed regardless of the operation of the cushion cylinder 26. Also, −[
- Checked throttle valve 38 and pilot relief valve 41
The pilot line 39 is connected to the main line 2 on the primary side of the pressure reducing valve 5 via a pilot line 52 having a pressure-compensated throttle valve 51 as an example of a throttle means in the middle.
is connected so that a constant amount of vent flow rate is always supplied to the pilot relief valve 41.

Further, a spring chamber 56 in which a spring 55 of the bypass valve 11 is compressed is connected to the pilot line 39 between the check throttle valve 38 and the pilot relief valve 41 via a pilot line 57. Therefore, the bypass valve 11 and the pressure reducing valve 5 are the same pilot relief valve 4.
1 will control the pilot pressure. The piston 58 of the bypass valve 11 is of a 100% balanced type in which the pressure receiving area on the spring chamber 56 side and the pressure receiving area on the primary Pony X side are exactly the same.

A tank 63 is connected to the bypass line 7 via a line 62 having a fixed throttle 61 in the middle, or the bypass line 7 and the pilot line 57 are connected via a line 67 having a fixed throttle 65 and a check valve 66 in the middle. Connected to stabilize the circuit system.

The pressure reducing valve circuit configured as described above operates as follows.

(During pressure reduction operation) At this time, due to the operation of the pressure reduction valve 5, the two people's urine P2 is reduced to P2 = + (Pilot line pressure Pp set by the pilot relief valve 41) - (Pressure equivalent to the spring force of the spool spring 21) )) ・・・・Controlled by ■.

In this state, the force F that tries to close the piston 58 of the bypass valve 11 is: F=Pressure equivalent to the spring force of the spring 55) - (Load pressure Pl downstream of the throttle valve 6)l... becomes.

By the way, during the stroke of the hydraulic cylinder 3, the throttle valve 6
Since oil is flowing through, (2 major pressure P2') > (load pressure PI) ......■
It is.

Therefore, from the above ■, ■, ■, p = ipp + (pressure equivalent to the spring force of the spring 55) - Pll>(
pp ten (pressure equivalent to the spring force of the spring 55) - p2+ = [Pp ten (pressure equivalent to the spring force of the spring 55) -1Pp- (pressure equivalent to the spring force of the spring 21)) 1 = (pressure equivalent to the spring force of the spring 55) + (spring equivalent pressure of spring 21)>0...■, the bypass valve 11 will not open and pressure control will be performed only by operating the pressure reducing valve 5.

(When surge pressure occurs) For example, due to a sudden stop of the hydraulic cylinder 3, the load pressure Pl
When the pressure rises rapidly, the spool 17 of the pressure reducing valve 5 moves to the right in FIG. 1 and tries to close, but due to the delay in response, the load pressure pl becomes higher than the set reduced pressure. And, pl > iPp+ (pressure equivalent to the spring force of the spring 55))...
...■, the bypass valve 11 opens and transfers the load pressure PI to the tank 8.
Relief force and suppress the generation of surge pressure.

During transient surge pressure absorption, when the surge pressure decreases and the two major pressures P2 become below the set pressure, the spool 17 of the pressure reducing valve 5
tries to close secondary boat B, but cushion mechanism 5
Due to this operation, the closing speed of the spool 17 suddenly slows just before the fully closed position, and even during transient times and after the surge pressure has decreased, a small amount of oil continues to be supplied to the secondary port (B) of the pressure reducing valve 5. More oil than is discharged into the tank through the throttles 61 and 65 is discharged into the tank through the bypass valve 11.

By doing so, the pressure response after the surge pressure decreases and during transient times can be made to be only the pressure response of the bypass valve 11, which essentially has a quick response, and the pressure response of both the pressure reducing valve 5 and the bypass valve 11 can be reduced. Mutual interference of responses can be eliminated, and therefore, surge pressure absorption performance can be improved, settling time can be shortened, stability can be increased, and fluctuations in pressure can be eliminated.

(When the set secondary pressure is lowered by the pilot relief valve 41 with the hydraulic cylinder 3 at the stroke end) When the pilot line pressure Pp starts to decrease by the pilot relief valve 41, the bar and varnish valve 11 opens, and the load Pressure PL decreases. The drop in the load pressure PL is faster than the drop in the pilot line pressure Pp, and instantaneously becomes P+, <f, Pp- (pressure equivalent to the spring force of the spring 21 of the pressure reducing valve 5), and the pressure reducing valve 5 opens. Pressure reducing valve 5 once opened
Even if the load pressure pl drops to the set pressure, the cushion mechanism 25 delays closing, so the fluctuation in pressure is eliminated, similar to when a surge pressure is generated, the settling time is shortened, and stability is increased.

(When the set secondary pressure is increased by the pilot relief valve 41 while the hydraulic cylinder 3 is at the stroke end) When the pilot line pressure Pρ starts to rise by the pilot relief valve 41, the pressure reducing valve 5 opens and the second maximum pressure P
2 rises. The pressure reducing valve 5 once opened is the cushion mechanism 2
5, the valve is closed even when the two major pressures P2 rise to the set value, so there is no pressure fluctuation like when a surge pressure occurs, the settling time is shortened, and stability is increased.

Note that the check throttle valve 38 includes the pressure reducing valve 5 and the bypass valve 1.
It is used to match the response of 1.

In the above embodiment, the throttle 61 and the line 62° or the throttle 65, the check valve 62, and the line 67 are provided so that a drain flow rate always exists. May be omitted.

Further, the cushion mechanism is not limited to the above embodiment, and various configurations are possible. For example, a convex portion may be integrally provided at the pilot chamber side end of the spool of the pressure reducing valve, and this convex portion may be fitted into four portions provided on the main body to provide a cushioning effect.

Further, the pilot relief valve may be a proportional pilot relief valve or a vent switching type pilot relief valve.

<Effects of the Invention> As is clear from the above description, the pressure reducing valve circuit of the present invention rapidly delays the closing speed by operating the cushion mechanism just before the pressure reducing valve completely closes, thereby connecting the pressure reducing valve and the bypass. Since mutual interference with the valve is prevented, surge pressure can be effectively absorbed, pressure fluctuations can be eliminated, settling time can be shortened, and stability can be increased.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention. 2... Main line, 5... Normally closed type pressure reducing valve, 7... Bypass line, 11... Bypass valve, 17... Spool, 18... Spring chamber, 19...
・Pilot room, 25...Cushion mechanism, 41...
・Pilot relief valve. Patent applicant Daikin Industries, Ltd. Representative patent attorney Haga Aoyama 2 people

Claims (1)

[Claims] (1) The spool (17) has a spring chamber on one end side and a pilot chamber on the other end side, and the pilot chamber has a spring chamber in the closing direction of the spool (17) immediately before the fully closed position of the spool (17). Normally closed pressure reducing valve (5) with a cushion mechanism (25) that slows down the speed
is installed in the main line (2), and the spring chamber of the pressure reducing valve (5) is connected to the main line (2) on the secondary side of the pressure reducing valve (5).
A bypass valve (11) is connected to the bypass line (7) branched from the main line (2) on the secondary side.
Further, the pilot chamber of the pressure reducing valve (5) and the spring chamber of the bypass valve (11) are connected to the pilot relief valve (41) via a pilot line,
A pressure reducing valve circuit characterized in that a main line (2) on the primary side of the pressure reducing valve (5) is connected to the pilot line via a throttle means (51).