JPH0612495B2 - Pressure control valve - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure control valve used in a hydraulic circuit.

[Prior Art] As shown in FIG. 3, the conventional pressure control valve 1A has an input pressure of
The spool 3A is fitted into the valve chamber 22A of the valve casing 2 having the annular groove 14 connected to the inlet 16 for supplying the pressure oil of P1 and the annular groove 15 connected to the outlet 17 for generating the output pressure P2, and the both ends are fitted. End chambers 13A and 19A are partitioned on the side. End chamber 13A,
19A are communicated with each other by a throttle passage 3c penetrating the spool 3A, the force of the spring 4 of the end chamber 13A acts on the end surface 3a of the spool 3A, and the pressure of the outlet 17 acts on the end surface 3b. The spool 3A is provided with a wide annular groove 18 that straddles the annular groove 14 and the annular groove 15.

The pressure control valve 1A is provided with a pilot valve 5A at its end. The poppet type valve body 8A, which is biased in the valve closing direction by the force of the spring 7, serves as a valve chamber 10 and an end chamber 13A of the pressure control valve 1A.
It is arranged in a passage 21 connecting to and. The valve chamber 10 accommodating the spring 7 and the valve body 8 </ b> A is communicated with the oil tank 20 via the drain 12.

When the pilot pressure Pc acting on the end chamber 13A from the outlet 17 through the passage 2a, the end chamber 19A and the throttle passage 3c becomes larger than the force of the spring 7 set by the dial 6, the valve body 8A opens the passage 21. The pilot pressure Pc acting on the end surface 3a of the spool 3A and the force of the spring 4 make the spool 3
The spool 3A is displaced to a position balanced with the output pressure P2 acting on the end face 3b of A, the input pressure P1 at the inlet 16 is reduced corresponding to the pilot pressure Pc, and the output pressure P2 at the outlet 17 is obtained.
(See FIG. 4) is generated.

In the above-mentioned pressure control valve, the output pressure P2 is set to a pressure equal to or lower than F / A0 (the ratio of the set load F of the spring 4 to the pressure receiving area A0 of the end face 3b of the spool 3A) as shown by a line 29 in FIG. Therefore, it is impossible to control the output pressure P2 between 0 and F / A0 in the low pressure region. If the set load of the spring 4 is reduced to control the output pressure P2 in the low pressure range, the output pressure
Stable control of P2 cannot be obtained.

[Problems to be Solved by the Invention] In view of the above problems, an object of the present invention is that the ratio of the spool displacement amount to the pilot pressure change amount is large, and the output pressure is stable against the pulsation of the input pressure. The purpose is to provide a pressure control valve capable of continuously controlling the output pressure from 0 to a required value.

[Means for Solving the Problem] In order to achieve the above object, the configuration of the present invention forms a stepped valve chamber having a large diameter cylindrical portion and a small diameter cylindrical portion in a valve box, and the stepped portion of the stepped valve chamber is formed. An annular groove connected to the outlet is provided to the large diameter cylindrical portion, an annular groove connected to the hydraulic pressure source via the inlet, and an annular groove connected to the oil tank via the drain is provided to the small diameter cylindrical portion, and a step having a large diameter portion and a small diameter portion A pilot pressure chamber that is fitted to the stepped valve chamber and is connected to the inlet via the internal throttle passage on the large diameter end side of the stepped spool, and is connected to the oil tank via the throttle passage on the small diameter end side of the stepped spool. A buffer chamber is divided into compartments, a spring for urging the stepped spool toward the pilot pressure chamber is housed in the buffer chamber, and a circumferential surface of a large diameter portion of the stepped spool enables communication between the inlet and the outlet. The annular groove of the stepped spool allows communication between the drain and the outlet on the peripheral surface of the small diameter portion of the stepped spool. The second annular groove is provided respectively, and the lands capable of alternately blocking between the inlet and the outlet and between the drain and the outlet are provided between the first and second annular grooves of the stepped spool. Insert and connect a normally open electromagnetic poppet valve into the passage that connects the chamber and the oil tank,
The electromagnetic poppet valve restricts the passage in proportion to the electromagnetic force that opposes the spring force.

[Operation] The electromagnetic poppet valve exerts a force proportional to the exciting current of the electromagnetic coil on the valve body via the plunger to control the pilot pressure acting on the large-diameter end surface of the stepped spool of the pressure control valve.

The pilot pressure is proportional to the exciting current of the electromagnetic coil, and the displacement of the stepped spool is proportional to the pilot pressure. Therefore, when the exciting current is continuously increased from 0, the output pressure is also continuously increased from 0.

The stepped portion of the stepped spool (the difference between the areas of the large diameter portion and the small diameter portion) always faces the annular groove that connects to the outlet of the valve chamber, so that feedback pressure is applied to the stepped spool against a sudden change in the input pressure. , Suppresses the sudden displacement of the stepped spool and stabilizes the output pressure.

Since the buffer chamber on the small diameter end side of the stepped spool communicates with the oil tank through the throttle passage, vibration of the stepped spool is suppressed against pulsation of the input pressure and the output pressure is stabilized.

Embodiment of the Invention As shown in FIG. 1, the pressure control valve according to the present invention comprises a main pressure control valve 1 and an electromagnetic poppet valve 5 to which an electromagnetic actuator 25 is connected. The main pressure control valve 1 is provided with a stepped valve chamber including a large diameter cylindrical portion 22 and a small diameter cylindrical portion 22a in a valve box 2, and a stepped spool 3 is slidably fitted in the stepped valve chamber. In the stepped valve chamber, the pilot pressure chamber 55 is defined at the upper end of the large-diameter cylindrical portion 22, and the valve box 9 of the electromagnetic poppet valve 5 fitted with the seal ring 50 is fitted. The stepped valve chamber is provided with an annular groove 14 in the large-diameter cylindrical portion 22 and an annular groove 15 in the stepped portion. Entrance 1 of the annular groove 14
6 communicates with a hydraulic pressure source (a discharge port of a hydraulic pump), and an outlet 17 of the annular groove 15 communicates with a hydraulically operated device.

In the stepped valve chamber, the buffer chamber 19 is defined by fitting the lid 44 to the lower end of the small diameter cylindrical portion 22a. The lid 44 is fixed by a retaining ring 43. The small diameter cylindrical portion 22a is provided with an annular groove 48 and communicates with the oil tank 20 via a drain 49. Buffer chamber 1
9 is a cylindrical portion at the lower end of the stepped spool 3, the throttle passage 53,
It communicates with the oil tank 20 via the annular groove 48 and the drain 49.

The annular groove 15 is provided on both sides with a notched cylindrical portion 15a having a diameter slightly larger than the large diameter cylindrical portion 22 and a shorter axial dimension, and the annular groove 48 is provided with a similar notched cylindrical portion 48a on one end side.

The stepped spool 3 is provided with a wide annular groove 60 on the peripheral surface of the large diameter portion that fits into the large diameter cylindrical portion 22.

The annular groove 60 always communicates with the annular groove 14, and the annular groove 14 and the annular groove 15 can communicate with each other. A large diameter portion of the stepped spool 3 is provided inside with a throttle passage 40 that connects the annular groove 14 and the pilot pressure chamber 55.

The stepped spool 3 is provided with an annular groove 42 on the peripheral surface of the small diameter portion. The annular groove 42 always communicates with the annular groove 48, and the annular groove 48
And the annular groove 15 can communicate with each other.

The stepped spool 3 is provided with a land between the annular grooves 60 and 42. The land is divided into a large diameter land and a small diameter land by an annular groove 41, but the annular groove 41 is not essential. The land of the stepped spool 3 has an inlet 16 and an outlet 17.
And the drain 49 and the outlet 17 can be isolated from each other.

The lower end portion of the stepped spool 3 is provided with a split groove 46 and a cylindrical portion, and a spring 45 is interposed between the cylindrical portion and the lid 44. The large-diameter end surface of the stepped spool 3 having the split groove can be abutted against the lower end surface of the valve box 9 by the force of the spring 45.

The electromagnetic poppet valve 5 has a split groove 51 formed in the upper end surface of the valve box 9. The valve chamber 10 accommodates the valve body 8 which is biased by the spring 38 in the valve opening direction. The valve body 8 is driven by an electromagnetic actuator 25, which will be described later, and the ball connected to the end of the valve body 8 opens and closes the passage 21. The passage 21 communicates with the pilot pressure chamber 55. The valve chamber 10 is communicated with the oil tank 20 through the split groove 51 and the drain 12.

The electromagnetic actuator 25 has the partition wall body 56 fitted to the upper end of the valve box 2 and pressed against the valve box 9. Partition body 56
The sleeve 37 made of a non-magnetic material and the sleeve 37a made of a magnetic material are abutted against each other, and the sleeves 37, 37a are fitted and supported inside the cylindrical core 59. Sleeve 3
Plunger 34 having a through hole 36 inside 7, 37a
Is slidably fitted, and the iron core 33 is fitted and fixed to the upper end of the sleeve 37a.

An electromagnetic coil 61 is wound around the core 59, and a cylindrical iron core 52 is fitted on the outside of the electromagnetic coil 61. Iron core 52
An annular iron core 58 is supported on the upper end of the. Iron core 52,5
8 and the end flange of the sleeve 37a are housed inside a cup-shaped case 32. The terminal conductor 31 of the electromagnetic coil 61 extends outward from the case 32. The opening end portion of the case 32 is externally fitted and supported by the partition wall body 56. In the cylindrical portion of the partition wall body 56, the spring 7 is interposed between the valve body 8 and the plunger 34, and the spring 35 for suppressing the fluttering of the plunger 34 is interposed between the plunger 34 and the iron core 33.

As shown in FIG. 2, the valve body 8 is integrally joined by fitting a ball 63 into a hemispherical recess 62 formed at the end and caulking an edge 62a of the recess 62.

Next, the operation of the pressure control valve according to the present invention will be described. When the electromagnetic coil 61 of the electromagnetic actuator 25 is demagnetized, the valve body 8 of the electromagnetic poppet valve 5 is pushed up by the force of the spring 38 to open the passage 21. Entrance 16
The pressure oil that has entered the annular groove 14 of the valve box 2 from the
After entering the pilot pressure chamber 55, pressure is exerted on the large-diameter end surface of the stepped spool 3, and the passage 21, the valve chamber 10, the split groove 5
It returns to the oil tank 20 through 1 and the drain 12.

Therefore, the pressure acting on the large-diameter end surface of the stepped spool 3 is extremely low, and even if the stepped spool 3 is slightly lowered, the large diameter portion (land) of the stepped spool 3 fits into the large diameter cylindrical portion 22. The pressure oil does not flow to the outlet 17 because the gap between the annular groove 14 and the annular groove 15 is cut off as they are fitted together. The output pressure at this time is 0.

When the electromagnetic coil 61 of the electromagnetic actuator 25 is excited, a magnetic circuit passing through the electromagnetic coil 61, the partition wall 56, the plunger 34, the sleeve 37a, the iron cores 58 and 52 is formed, and the plunger 34 descends in proportion to the exciting current. The valve body 8 is pushed toward the passage 21 and the passage 21 is narrowed. Therefore, the pressure oil at the inlet 16 is transferred to the annular groove 14, the throttle passage 40,
The pressure exerted on the large-diameter end surface of the stepped spool 3 via the pilot pressure chamber 55 is increased, and the stepped spool 3 is lowered against the force of the spring 45.

The large diameter portion (land) of the stepped spool 3 moves to the annular groove 15, and the annular groove 60 of the stepped spool 3 connects the annular groove 14 and the annular groove 15. At this time, the small diameter portion (land) of the stepped spool 3 moves to the small diameter cylindrical portion 22a, and the small diameter portion (land) blocks the gap between the annular groove 15 and the annular groove 48. The pressure oil that has entered the annular groove 14 from the inlet 16 is depressurized according to the passage area between the upper notched cylindrical portion 15a and the large diameter portion (land) of the stepped spool 3 and flows into the annular groove 15, It is supplied from the outlet 17 to hydraulically operated equipment.

When the stepped spool 3 descends, the oil in the buffer chamber 19 is replaced by the spring 4
The oil is returned to the oil tank 20 through the cylindrical portion that accommodates 5, the throttle passage 53, the annular groove 48, and the drain 49.

As described above, the input pressure at the inlet 16 is output as the output pressure to the outlet 17 via the annular groove 14, the large-diameter cylindrical portion 22, and the annular groove 15. The output pressure at the outlet 17 is the stepped spool 3.
Is determined by the pilot pressure Pc acting on the large-diameter end surface of.
The pilot pressure Pc is determined by the force exerted by the plunger 34 on the valve body 8 of the electromagnetic poppet valve 5 via the spring 7 based on the exciting current of the electromagnetic actuator 25.

As indicated by the solid line 30 in FIG. 4, the electromagnetic actuator 2
When the exciting current of 5 continuously increases from 0, the pilot pressure Pc increases in proportion to the exciting current,
The displacement of the stepped spool 3 increases in proportion to Pc, and the outlet 1
The output pressure of 7 continuously increases from 0.

[Advantages of the Invention] As described above, the present invention increases the displacement amount of the valve body of the electromagnetic poppet valve pushed by the plunger in proportion to the exciting current of the electromagnetic actuator, so that the large-diameter end surface of the stepped spool is Since the acting pilot pressure rises and the displacement amount of the stepped spool increases in proportion to the pilot pressure, the output pressure eventually rises continuously from 0 in proportion to the exciting current.

Since the electromagnetic poppet valve controls the pilot pressure acting on the stepped spool while allowing the input pressure to overflow into the oil tank through the throttle passage and the valve passage, it operates reliably and has excellent pilot pressure control performance.

The stepped portion of the stepped spool (the difference in area between the large diameter portion and the small diameter portion) always faces the annular groove that connects to the outlet of the valve chamber. (Pushing force) acts on the stepped portion of the stepped spool, suppressing abrupt displacement of the stepped spool and stabilizing the output pressure.

Since the throttle passage is provided between the buffer chamber of the valve box and the oil tank, vibration of the stepped spool can be suppressed even when the pilot pressure changes rapidly when the exciting current of the electromagnetic coil is constant. That is, the pulsation of the output pressure is suppressed with respect to the pulsation of the input pressure.

[Brief description of drawings]

FIG. 1 is a front sectional view of a pressure control valve according to the present invention, FIG. 2 is a front sectional view of a valve body of an electromagnetic poppet valve, FIG. 3 is a front sectional view of a conventional pressure control valve, and FIG. FIG. 6 is a diagram showing a comparison between the actions of the pressure control valve and the pressure control valve according to the present invention. 2: valve box, 3: stepped spool, 5: electromagnetic poppet valve,
8: valve body, 12, 49: drain, 15: annular groove, 16:
Inlet, 17: Exit, 19: Buffer chamber, 21: Passage, 22:
Large diameter cylindrical portion, 22a: Small diameter cylindrical portion, 38, 45: Spring,
40, 53: throttle passage, 42, 60: second and first annular grooves, 45: spring, 55: pilot pressure chamber

Claims (1)

[Claims] 1. A stepped valve chamber having a large diameter cylindrical portion and a small diameter cylindrical portion is formed in a valve box, an annular groove communicating with an outlet is provided at the stepped portion of the stepped valve chamber, and the large diameter cylindrical portion is passed through an inlet. An annular groove connected to the hydraulic pressure source and an annular groove connected to the oil tank through the drain are provided in the small diameter cylindrical part, and a stepped spool having a large diameter part and a small diameter part is fitted in the stepped valve chamber to increase the size of the stepped spool. The pilot pressure chamber is connected to the inlet via the internal throttle passage on the radial end side, and the buffer chamber is connected to the oil tank via the throttle passage on the small diameter end side.The stepped spool is attached to the pilot pressure chamber side. A first annular groove for accommodating an urging spring in the buffer chamber and allowing communication between the inlet and the outlet on the peripheral surface of the large diameter portion of the stepped spool,
A second annular groove that allows communication between the drain and the outlet is provided on the peripheral surface of the small diameter portion of the stepped spool, and between the inlet and the outlet between the first and second annular grooves of the stepped spool. Lands that can alternately shut off between the drain and the outlet are provided, and a normally open type electromagnetic poppet valve is inserted and connected in the passage that connects the pilot pressure chamber and the oil tank.The electromagnetic poppet valve has an electromagnetic force that resists the spring force. A pressure control valve characterized in that the passage is throttled in proportion to.