JP2710770B2 - Switching valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a poppet type switching valve interposed in a hydraulic circuit and driven by a solenoid or pilot pressure.

[0002]

2. Description of the Related Art Conventionally, as a switching valve of a hydraulic circuit,
In general, a spool switching type is widely used, but a poppet type switching valve is used in a case where leakage of hydraulic oil is not desired. If a poppet type switching valve is used, the port can be almost certainly shut off. However, when the outer peripheral portion of the poppet is higher in pressure than the seat portion, the pressure difference is overcome when switching or returning the poppet. It is necessary to generate a driving force.

FIG. 4 shows a structure disclosed in FIG. 2 of Japanese Patent Application Laid-Open No. 6-185638 as a prior art regarding a poppet type switching valve. A spool 2 that is slidable and displaceable in the axial direction is housed in the body 1, and a poppet portion 3 having a large diameter is formed. In the body 1, valve seats 4, 5 whose diameters become smaller are arranged at positions facing the hydraulic oil passages 6, 7 of the spool 2, respectively. A solenoid 9 is attached to one end of the body 1 so that the plunger 8 contacts one end of the spool 2. A plurality of ports 10, 11, 12 are provided on the side surface of the body 1, and the oil chambers A,
B and C are formed. The hydraulic oil passage 6 can communicate between the oil chambers A and B, and the hydraulic oil passage 7 can communicate between the oil chambers B and C. Poppet part 3 facing hydraulic oil passage 6
Similarly, a poppet portion 13 is provided facing the hydraulic oil passage 7. Stopper 14 to prevent spool 2 from coming off
Is provided, and the stopper 14 is pressed by one end of the spring 15. A seal case 16 is attached to the other end of the spring 15 from the end face side of the body 1 with the valve seat 5 interposed therebetween. From the other end of the body 1
A seal case 17 is mounted. Seal case 1
Projections 20, 21 which are slidably displaced by seals 18, 19 project inside the spools 6, 17 so as to extend in the axial direction at both ends of the spool 2. Projection 2
The outer diameters of 0 and 21 are formed to be substantially equal to the inner diameters of the seat portions 4 and 5. As described above, since the similar projections 20 and 21 are provided on both sides in the axial direction, the switching pressure acting on the spool 2 is canceled on both sides in the axial direction, and the driving force required for sliding displacement of the spool 2 is reduced. Can be suppressed.

[0004]

In the prior art structure as shown in FIG. 4, the center portion of the spool 2 in the axial direction has a larger outer diameter than the protruding portions 20 and 21 due to the poppet portions 3 and 13. ing. For this reason, it is necessary to attach the seal cases 16 and 17 to the body 1 from both sides in the axial direction. Moreover, in order to hold the seals 18 and 19, the periphery of the oil chambers B and C needs to be formed separately. That is, it is necessary to cancel the pressure acting on the outer peripheral portion of the poppet by using a complicated nest structure in which the seal cases 16 and 17 are inserted from both sides of the body 1. With such a complicated structure, the components of the switching valve increase,
The time required for assembly and the cost of parts increase. In addition, miniaturization becomes difficult, and the installation location of the switching valve is likely to be restricted.

In order to suppress the driving force required for switching the poppet, a structure is also conceivable in which the switching pressure is guided to the driving portion to cancel the increase in the driving pressure due to the increase in the switching pressure. However, since a large pressure-resistant solenoid or the like provided in the driving portion is required, it is not possible to achieve a reduction in size and cost of the switching valve.

An object of the present invention is to provide a poppet type switching valve which can suppress the driving force with a simple structure and can be manufactured at low cost.

[0007]

According to the present invention, there is provided a valve body in which a plurality of ports are arranged along an axis, an annular seat portion formed between adjacent ports, and inserted into the valve body. In a switching valve that switches between adjacent ports in a communication state or a cutoff state by opening and closing with a poppet part formed on a spool that is slidably displaceable in the axial direction, a spool closer to an axial end than the poppet part A reaction chamber communicating with the port is formed, is housed in an insertion passage formed between the reaction chamber and the end face of the spool, one end faces the reaction chamber, and the other end faces the inner wall of the valve body. And a cross section perpendicular to the axial direction on the outer peripheral side of the seat portion of the poppet portion is set to be equal to a cross sectional area perpendicular to the axial direction of the reaction piston. Specially A switching valve to be. According to the present invention, in a state in which the poppet portion and the sheet portion are in close contact with each other and block the ports, the pressure of the port is applied to the poppet portion on the outer peripheral side of the sheet portion. Since a reaction force chamber communicating with the port is formed in the spool closer to the axial end than the poppet portion, the pressure of the port is also transmitted to the reaction force chamber. One end of the reaction force chamber faces the reaction force chamber, and the other end of the reaction force piston contacts the inner wall of the valve body. Pressure acts on the reaction chamber except for the pressure acting on the reaction chamber. Since the cross-sectional area perpendicular to the axial direction of the reaction piston is set to be equal to the cross-sectional area perpendicular to the axial direction on the outer peripheral side of the sheet portion of the poppet portion, the poppet portion is not contained in the reaction chamber. Forces acting in the opposite direction to the force acting on the outer peripheral side act and cancel each other out, so that the acting force of the pressure acting on the outer peripheral portion of the poppet is not included, and the force required to drive the spool is suppressed. Similarly, when the valve is closed when oil is conducted between the ports in a valve-open state where the poppet and the seat are separated, the force acting on the outer peripheral portion of the poppet is also affected. do not do.

The present invention is further characterized in that the sectional area of the spool perpendicular to the axial direction at the end of the spool is set to be equal to the sectional area of the sheet perpendicular to the axial direction. I do. According to the present invention, the tank pressure acts on the end of the spool. Since the cross-sectional area perpendicular to the axial direction of the end of the spool is set to be equal to the cross-sectional area perpendicular to the axial direction of the seat portion, it is possible to suppress the force exerted by the tank pressure from both ends of the spool. it can.

Further, the present invention is characterized in that two ports are provided. According to the present invention, the switching valve is provided with two ports and operates as a two-port two-position switching valve. Since only one seat portion and one poppet portion may be formed between the ports, the switching valve can be realized with a simple structure.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a configuration of a solenoid-driven 2-port 2-position switching valve according to an embodiment of the present invention. The body 31 housed in the casing 30 constitutes a body main body, in which a spool 32 is housed so as to be slidable in the axial direction. A poppet portion 33 is formed on the spool 32 and can be in close contact with a sheet portion 34 on the body 31 side. The poppet portion 33 and the seat portion 34 perform switching for communicating or blocking a path from an oil chamber 35 formed in the body 31 to another oil chamber 37 via a hydraulic oil passage 36 formed in the spool 32. A plunger 3 is provided on the tip side of the body 31 on the right side in FIG.
8 is mounted, and a plunger 38 is mounted.
Is in contact with the tip of the spool 32 in the axial direction. The body 31 has ports 40, 41, 4 along the axial direction.
2 are formed. The port 41 that is closer to the center in the axial direction is connected to, for example, the primary side. The port 40 near the base end in the axial direction, which is the left side in FIG. 1, is connected to the secondary side. The port 42 near the axial end is connected to the tank. The poppet 33 and the seat 34 open and close between the port 40 and the port 41.

A reaction force chamber 43 is formed on the proximal end side of the spool 32. The reaction chamber 43 is connected to the oil chamber 3 through the communication hole 44.
7 communicates with port 40. A spring 45 is inserted into the distal end side of the spool 32. The proximal end of the spring 45 is supported by the body 31. The distal end side of the spring 45 in the axial direction is connected to the spool 32 via a spring receiver 47 and a retaining ring 48.
Is biased toward the front end in the axial direction. An O-ring 4 is provided at a portion of the spool 32 which is closer to the front end than the hydraulic oil passage 36.
9 is formed.

A reaction force piston 50 whose front end faces a reaction force chamber 43 formed on the base end side of the spool 32 in the axial direction, has an insertion hole 5 formed between the reaction force chamber 43 and the base end of the spool 32.
1 is inserted. The base end side of the reaction force piston 50 contacts the inner wall surface of the casing 30. On the proximal end side of the spool 32, the casing 30 communicates with the port 42 via the communication passage 52. Port 42 is connected to the tank and is typically at a lower pressure.

The outer diameter of the spool 32 is d1 equal to the inner diameter of the seat portion 34 at the portion where the O-ring 49 is inserted, the outer diameter of the reaction force piston 50 is d2, and the maximum diameter of the poppet portion 33 is d3.

FIG. 2 shows a simplified system of a hydraulic system using the solenoid-operated 2-port 2-position switching valve 53 of FIG. To the A port, for example, hydraulic oil projected from the hydraulic pump 54 is supplied. Port B has cylinder 55
Connect. The B port is in a state where oil leakage is extremely small when the poppet portion 33 in FIG. 1 is in close contact with the seat portion 34, so that even if a load is applied to the cylinder 55, leakage leaking through the hydraulic oil passage 36 is prevented. The displacement can be extremely reduced, and the displacement state of the cylinder 55 can be stably continued.

When the solenoid 39 is excited, the spool 3
2 slides to the right, that is, to the left in FIG. 1, and the space between the B port 41 and the A port 40 changes from the block state to the open state. When the excitation of the solenoid 39 is stopped, the spool 32 is slid and displaced rightward in FIG. 1 by the pressing force of the spring 45, and the poppet 33 blocks the seat 34. When switching between the B port 41 and the A port 40 in the open direction, under normal conditions, pressure is generated on the A port 40 side, and a force corresponding to the pressure is applied on the outer peripheral side of the sheet portion 34 of the poppet portion 3. Works.

FIG. 3 shows the poppet section 33 and the reaction force chamber 43.
Shows the force acting on the spool 32 in relation to. If the pressure at port A and P _A, the force F _A acting on the outer peripheral side of the poppet portion 33 is calculated as the first equation below.

[0017]

(Equation 1)

The tip of the reaction force piston 50 has the following second
Force F _P represented by the formula acts.

[0019]

(Equation 2)

[0020] In the reaction chamber within 43, but the pressure P _A of the hydraulic oil acts uniformly over all directions, the force acting on the tip of the reaction piston 50 is balanced with the reaction force from the inner wall surface of the casing 30, It does not act on the spool 32. For this reason, the force of F _P is applied to the spool 3 in the reaction chamber 43.
2 acts only on the tip side in the axial direction, and forces in other directions cancel each other out in the reaction force chamber 43. Therefore, if the condition shown in the following formula (3) is satisfied, the driving force required to drive the spool 32 in the axial direction is suppressed, and the spring 4
5, etc., can be reduced. If the spring force of the spring 45 may be small, a small one can be used as the spring 45, and the spring receiver 47 and the seal case 46 in which the spring 45 is housed can be downsized, so that the body 31 can also be downsized. Further, the fact that the force of the spring 45 may be small means that the magnetic force of the solenoid 39 having a function of overcoming the spring force and moving the spool can be reduced, so that the solenoid 39 can be downsized. Due to these facts, the manufacturing cost can be reduced.

[0021] d ₃ ² - if ^{_{d 1 2 = d 2 2 ...}} (3) third equation condition is satisfied, the driving force for sliding displacement of the spool 32 due to pressure at port A can be suppressed.

Although the T port of FIG. 1 is connected to a tank, in some cases considerable pressure may be generated. As described above, even if pressure is generated in the tank passage, the driving force of the sliding displacement of the spool 32 can be suppressed. Therefore, the following fourth equation holds.

[0023]

(Equation 3)

Here, _PT indicates the pressure in the tank passage. From the fourth equation, the following fifth equation is obtained.

D ₃ ² −d ₂ ² = d ₁ ² (5) Equations 5 and 3 have a relationship in which d ₁ and d ₂ are interchanged. That is, the third formula and the fifth formula represent the same relationship, and if the tank pressure _{PT is applied} to both ends of the spool 32, A
It can be seen that as long as the condition for canceling the pressure on the port is satisfied, the condition for canceling the tank pressure is automatically satisfied.

In the embodiment shown in FIG. 1, although the spool 32 is driven by the solenoid 39, it may be driven by pilot pressure. Although the embodiment of FIG. 1 describes the two-port two-position switching valve, three or more ports related to switching may be formed so that switching is performed at both ends in the axial direction of the spool.

[0027]

As described above, according to the present invention, a reaction chamber is formed in the spool nearer to the axial end than the poppet, and the other end of the reaction piston whose one end faces the reaction chamber is valved. Since it is brought into contact with the inner wall surface of the main body, a pressure in a direction opposite to the pressure acting on the poppet acts in the reaction chamber in the axial direction of the spool. Since the cross-sectional area perpendicular to the axial direction of the poppet portion on the outer peripheral side of the seat portion is set equal to the cross-sectional area perpendicular to the axial direction of the reaction force piston, the force acting on the poppet portion and the reaction force chamber is: Since the directions are equal and the directions are opposite, they cancel each other out. For this reason, the force acting on the poppet does not cause an increase in the driving force when the spool is slid and displaced, and the increase in the driving force can be suppressed with a simple structure.

Further, according to the present invention, since the tank pressure and the like at both ends in the axial direction of the spool can be offset, the driving force required for the sliding displacement of the spool can be suppressed.

Further, according to the present invention, a two-port two-position switching valve having a poppet seat portion can be manufactured at a low cost with a simple structure.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a schematic configuration of an embodiment of the present invention.

FIG. 2 is a hydraulic system diagram using a 2-port 2-position switching valve according to the embodiment of FIG. 1;

FIG. 3 is a cross-sectional view illustrating an area relationship related to a poppet portion 33 and a reaction force chamber 43 in the switching valve of FIG.

FIG. 4 is a sectional view showing the structure of a switching valve according to the prior art.

[Explanation of symbols]

 Reference Signs List 30 casing 31 body 32 spool 33 poppet part 34 seat part 35, 37 oil chamber 36 hydraulic oil passage 39 solenoid 40, 41, 42 port 43 reaction force chamber 44 communication hole 45 spring 49 O-ring 50 reaction force piston 52 communication passage

Claims (3)

(57) [Claims] An annular seat portion formed between adjacent ports in a valve body in which a plurality of ports are arranged along an axis, and is inserted into the valve body and slidably displaceable in an axial direction. In a switching valve that switches between adjacent ports in a communicating state or a blocking state by opening and closing with a poppet part formed on a spool, a reaction force communicating with the port is provided in a spool closer to an axial end than the poppet part. A reaction force piston which is housed in an insertion passage formed between the reaction force chamber and the end face of the spool, one end of which faces the reaction force chamber, and the other end of which contacts the inner wall of the valve body. A switching valve characterized in that a cross-sectional area perpendicular to the axial direction on the outer peripheral side of the seat portion of the poppet portion is set to be equal to a cross-sectional area perpendicular to the axial direction of the reaction force piston. 2. The cross-sectional area of the spool perpendicular to the axial direction at the end of the spool is set to be equal to the cross-sectional area of the sheet portion perpendicular to the axial direction. 1. The switching valve according to 1. 3. The switching valve according to claim 1, wherein two ports are provided.