JPH0433049B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is suitable for use in controlling a hydraulic cylinder for a clutch in an automobile, for example, and is used to reduce the secondary pressure from zero pressure to a value equal to the primary pressure. This invention relates to a pressure reducing valve that can be controlled over a wide range.

<Prior art> Conventionally, as a pressure reducing valve, as shown in Fig. 7,
Poppet-type 3-port pilot valve 2 for main valve 1
(Hydraulic Technology, Vol. 24,
No. 4, p. 21). This pressure reducing valve is provided with a pilot passage 6 having a vent throttle 5 that forms a vent flow from the secondary port B side of the main valve 1 to the poppet 3 of the pilot valve 2.
The fluid pressure between the main valve 1 and the secondary port B of the main valve 1 is guided to the spring chamber 8 on one end side of the main spool 7
pressure in the pilot chamber 9 at the other end of the main spool 7.
is leading to In other words, the main spool 7 is opposed by the fluid pressure in the pilot chamber 9, the fluid pressure in the spring chamber 8, and the resultant force of the spring 10.
When the fluid pressure at the next port B reaches the set pressure of the pilot valve 2, the pilot valve 2 opens to form a vent flow. Therefore, a pressure difference is formed before and after the vent throttle 5, and when this pressure difference becomes equivalent to spring pressure, the main spool 7 is operated to narrow the opening degree of the variable orifice 4 and reduce the pressure at the secondary port B. . When the fluid pressure at the secondary port B becomes lower than the set pressure, the pilot valve 2 closes and the vent flow rate is reduced to zero, so the differential pressure across the vent throttle 5 is eliminated and the main spool 7 is opened by the force of the spring 10. The variable orifice 4 can be moved to the right in FIG. 5 to widen the opening degree of the variable orifice 4, supplying fluid from the primary port A to the secondary port B, increasing the pressure in the secondary port B, and setting the desired set pressure. is controlled. In addition, the relief operation occurs from the secondary port B to the tank port T <Problem to be solved by the invention> However, in the above conventional pressure reducing valve, the pilot pressure for operating the main spool 7 is guided from the secondary port B side. Therefore, there is a problem that the minimum control pressure becomes high. That is, even if the pressing force of the electromagnetic solenoid 11 of the pilot valve 2 is zero and the poppet 3 is fully opened, in order to overcome the spring force of the spring 10 pressing the main spool 7,
The pressure at next port B is generally 1.5 to 2 kg/
Since a pressure of cm ² is required, the minimum control pressure at secondary port B will inevitably be 1.5 to 2 Kg/cm ² or more.
There is a problem in that the secondary pressure cannot be controlled from approximately zero pressure.

In addition, in the conventional pressure reducing valve, a vent throttle 5 is connected from the secondary port B of the main valve 1 to the pilot valve 2.
By the pilot flow (vent flow) through the
Since pilot pressure is obtained to operate the main spool 7, a certain amount of vent flow rate is required to constantly generate a certain pressure difference across the vent throttle 5, and even at the lowest control pressure, a certain amount of vent flow is required. The disadvantage is that a large flow rate is required and the power loss is large.

Therefore, the main purpose of this invention is to be able to control the secondary pressure over the entire range from completely low pressure (zero pressure) to equal to the primary pressure, thereby controlling the hydraulic pressure for the clutch connected to the secondary port. Actuators such as cylinders can be started softly and smoothly from low pressure, and can also be operated at high pressure equal to the primary pressure.

Another object of the present invention is to eliminate the vent flow from the secondary port of the main valve and introduce pilot pressure from the primary port side of the main valve, thereby reducing the overall leakage flow rate (drain flow rate). The goal is to reduce

<Means for Solving the Problems> In order to achieve the above object, the pressure reducing valve of the present invention has the secondary port B connected to one
The secondary port B is passed through a chamber on the end surface on the spool portion side of the main spool 25, which has a spool portion that switches and communicates with the secondary port A and the tank port T, and a piston portion whose diameter is larger than the diameter of the spool portion. The 3-port main valve 21 communicates with the secondary port b
A chamber at one end of the pilot spool 41 which switches between the primary port a and the tank port t is connected to the secondary port b via a passage, and a pressing means is provided at the other end of the pilot spool 41. It consists of a 3-port pilot valve 22, with the primary port a of the pilot valve 22 connected to the primary port A of the main valve 21, and the secondary port b of the pilot valve 22 connected to the piston side of the main spool 25. It is characterized by being connected to each chamber.

<Function> With the above configuration, the pressing means 4 of the pilot valve 22 is used to adjust the secondary pressure P _B of the main valve 21 to approximately zero pressure.
8, the operation of the pilot spool 41 due to the balance between the pressure Pb in the chamber at one end of the pilot spool 41 and the pressing means 48 closes the space between the primary port a and the secondary port b of the pilot valve 22. , open the space between secondary port b and tank port t. And the main spool 2 of the main valve 21
The chamber on the side of the piston section 5 communicates with the tank port t of the pilot valve 22, and the pressure in the chamber on the side of the piston section is controlled to zero pressure. Therefore, the main spool 25 of the main valve 21 operates due to the balance between the chamber on the spool side and the chamber on the piston side, and the main spool 25 moves to the right in FIG. and the tank port T, and the pressure at the secondary port B of the main valve 21 is controlled to zero pressure. Further, the pressing means 48 of the pilot valve 22 is changed from zero pressure to the main valve 21.
When the pressing force is controlled to correspond to the pressure between the primary pressures PA of the pilot valves 22 and 2,
The next pressure Pb and the pressure in the chamber on the piston side of the main valve 21 are controlled, and the main spool 25 operates based on the balance between the pressure in the chamber on the piston side and the pressure in the spool side. The pressure P _B at the secondary port B is controlled to a desired reduced pressure. Main valve 21
When the secondary pressure P _B is controlled to be equal to the primary pressure PA, fluid acts on the end face of the piston part, which has a larger cross-sectional area than the end face of the spool part, and the main spool 25 is actuated by the increased force. Therefore, even if the spring 31 that presses the main spool 25 is used, the main spool 25 can compress the spring 31 and move until the space between the primary port A and the secondary port B is fully opened, and the main spool 25 can be moved by compressing the spring 31. The pressure can be controlled so that the primary pressure PA and the secondary pressure _PB of the valve 21 are equal.

When the secondary pressure P _B of the main valve 21 is controlled to be equal to the primary pressure PA, or when the secondary pressure P B of the main valve 21 is
When the next pressure P _B is controlled to zero pressure, the pilot spool 41 and the main spool 25 can be at the stroke end position, and at this time, from the primary port a of the pilot valve 22 and the main valve 21, There is almost no drain flow rate. Therefore, power loss is small.

Also, the main spool 2 is connected through the pilot valve 22.
Since the pressure fluid is supplied to the piston part 5 with a large pressure receiving area and is made to act on it, the main spool 25 can be operated with a large force against the axial thrust (flow force) acting on the main spool 25. Therefore, it is possible to resist axial thrust and increase the maximum flow rate.

<Examples> The present invention will be described in detail below with reference to illustrated examples.

In Fig. 1, 21 is a 3-port main valve;
2 is a 3-port pilot valve.

The main spool 25 of the main valve 21 is integrally formed with a spool portion 25a having three lands 25a-1, 25a-2, and 25a-3, and a pilot valve 25b having a larger diameter than the spool portion 25a. The above lands 25a-1, 25a-2, 25a
-3 and the piston portion 25b are slidably fitted into the main body 20. The diameter of the piston portion 25b is larger than the diameters of the lands 25a-a, 25a-2, and 25a-3. And the main spool section 2
5, the secondary port B is switched to communicate with the primary port A and the tank port T at the land 25a-2. A secondary port B is connected via a pilot passage 29 to a spring chamber 28 in which a spring 31 is compressed on one side of the spool portion 25a of the main spool 25. The dimensions of the main spool 25 are determined so that the opening 29a opening into the land 25a-2 of the pilot passage 29 always communicates with the secondary port B. Further, a pilot chamber 32 is provided at the other end of the main spool 25 on the piston portion 25b side. The piston portion 25b and land 25a
-3 is connected to the tank 6 through the passage 53.
Connected to 1. Therefore, the main valve 21 operates the main spool 25 so that the force due to the differential pressure between the pilot chamber 32 and the spring chamber 28 corresponds to the spring force of the spring 31, and the secondary port B and the primary port A
Variable orifice 2 between and tank port T
Controls the opening degree of 6 and 30.

On the other hand, the pilot valve 22 is of a normally closed type, and the operation of the pilot spool 41 switches the secondary port b to the primary port a and the tank port t at the land 41a.
A secondary port b is connected to the chamber 45 at one end of the pilot spool 41 via a pilot passage 46. A spring 47 is compressed in the chamber 45 of the pilot valve 22. On the other hand, on the other end side of the pilot spool 41, an electromagnetic proportional solenoid 48 as an example of adjustable pressing means is provided, and the center of the pilot spool 41 is set to a current energization value by a plunger 48a of the electromagnetic proportional solenoid 48. The pressure is applied with a force proportional to (i). The plunger 48a has a counterbalance spring 49 that presses the plunger 48a toward the pilot spool 41. The spring force of the spring 47 is made slightly stronger than the spring force of the spring 49. An engaging portion 41b is provided at the left end of the pilot spool 41 for engaging and positioning the surrounding body to close the space between the primary port a and the secondary port b in the normal position. . That is, the pilot valve 22 is of a normally closed type. Therefore,
The pilot spool 41 of the pilot valve 22 has the pressure of the plunger 48a and the pressure of the chamber 45, that is, 2.
It is designed to operate in such a way that the pressure at the next port b is balanced.

The primary port a of the pilot valve 22 is connected to the primary port A of the main valve 21 via the pilot passage 51, and the secondary port b of the pilot valve 22 is connected to the pilot chamber on the piston portion 25b side of the main valve 21. 32 via a pilot passage 52. Tank port t of the pilot valve 22
A chamber 65 accommodating the plunger 48a is connected to the tank 61 via a drain passage 53.

Further, the secondary port B of the main valve 21 is connected to a clutch cylinder 55 of the automobile via a passage 56, the primary port A is connected to a pressure source 57 via a passage 58, and the tank port T is connected to a passage 71. It is connected to the tank 61 via.

In the above configuration, the current value of the current flowing through the electromagnetic proportional solenoid 48 of the pilot valve 22 is
When (i) is set to zero, the pilot spool 41 of the pilot valve 22 is pushed to the right in FIG. Closed, secondary port b
and tank port t is fully opened. Therefore, the pilot chamber 32 of the main valve 21 communicates with the tank 61 via the passage 52 and the tank port t, and the main spool 25 of the main valve 21 is pressed by the spring 31 of the spring chamber 28 and moves to the right in FIG. Move, land 25
At a-2, the space between the primary port A and the secondary port B is closed, the space between the secondary port B and the tank port T is fully opened, and the pressure of the secondary port B is controlled to zero pressure. At this time, the drain flow rate from the primary port A of the main valve 21 and the primary port A side of the pilot valve 22 is substantially less than during the pressure control described below.

Next, when the current applied to the electromagnetic proportional solenoid 48 of the pilot valve 22 is increased, as the current value (i) increases, the pressure in the pilot chamber 32 of the secondary port b and the main valve 21 increases due to the operation of the pilot spool 41. increase The main spool 25 of the main valve 21 receives a force due to a pressure difference between the fluid pressure acting on the pilot chamber 32 on the piston portion 25b side and the fluid pressure of the secondary port B acting on the spring chamber 28. It operates like a spring force, and 2
Next, control the pressure at port B. At this time, main valve 2
Drain fluid necessary for control is discharged from both the tank port T of the pilot valve 1 and the tank port t of the pilot valve 22.

Further, when the current value (i) applied to the electromagnetic proportional solenoid 48 of the pilot valve 22 is increased by a certain value or more, the pilot spool 4 of the pilot valve 22
1 moves to the left in FIG. The pressure of the primary port a is introduced into the chamber 32 via the passage 52. Therefore, the pressure of the primary port a acts on the piston portion 25b having a larger cross-sectional area, and the main spool 25 moves to the left in FIG. Fully open and completely close the space between secondary port B and tank port T. And the secondary pressure of secondary port B
P _B is controlled to be equal to the primary pressure PA of primary port A. At this time, the drain flow rate from the tank port T of the main valve 21 and the tank port t of the pilot valve 22 is substantially lower than during the pressure control described above, and therefore the power loss is reduced.

FIG. 2 is a graph showing the relationship between the current value (i) energized to the electromagnetic proportional solenoid 48 of the pilot valve 22 and the fluid pressure P _B of the secondary port B of the main valve 21.
It can be seen that the secondary pressure P _B increases almost linearly from 0 Kg/cm ² in proportion to the current value (i), and when the current value (i) exceeds a certain value, P _B =PA. Furthermore, Fig. 3 is a graph showing the relationship between the above current value (i) and the total leakage amount (drainage amount) from both tank ports T and t of the main valve 21 and pilot valve 22, and shows the relationship between the secondary pressure
It can be seen that the amount of leakage decreases when P _B is at the lowest control pressure (approximately zero pressure), at the highest control pressure (when P _B = PA), and in the areas connected thereto.

In this way, this pressure reducing valve diverts the pilot pressure that operates the main spool 25 of the main valve 21 to the primary port A.
Since it is led from the side, even if the pressure at the secondary port B is controlled to an extremely low pressure close to zero, the main spool 25 can be operated to control the pressure reduction, and the pressure at the secondary port B can be controlled to be low. Pressure can be controlled from zero pressure. Since the pressure at the secondary port B can be controlled from zero pressure in this manner, the clutch hydraulic cylinder 55 can be started very softly and without a shock. Further, by increasing the pressing force of the electromagnetic proportional solenoid 48, the pressure at the secondary port B can be controlled to a pressure equal to the pressure at the primary port A. In this way, this pressure reducing valve reduces the primary pressure at primary port A from an extremely low pressure close to zero pressure.
The secondary pressure P B at the secondary port _B can be controlled over a wide range up to a pressure equal to PA.

Moreover, since the main spool 25 of the main valve 21 is actuated by supplying fluid pressure to the piston portion 25b, the main spool 25 is actuated.
Against the axial thrust (flow force) acting on the
The main spool 25 can be actuated and the maximum flow rate of the main valve 21 can be increased.

FIG. 4 shows another embodiment, in which the primary port a and tank port t of the pilot valve 22 are replaced with the one shown in FIG. The pressure of the secondary port b is guided to the chamber 65 that accommodates the plunger 48a. The other configurations are the same as those shown in FIG. 1, so the same reference numerals are given to them and the explanation will be omitted.

In the case shown in FIG. 4, the spring 47 serves as a pressing means, and as the pressing force of the electromagnetic proportional solenoid 48 becomes stronger, the pressing force of the spring 47 against the pilot spool 41 becomes relatively weaker.
As shown in FIG. 5, as the current value (iv) increases, the secondary pressure P _B of the main valve 21 decreases. In addition, the current value (i)
Until it reaches the set value, the spring force of the spring 47 is much stronger than the spring force of the spring 47, so the space between the primary port a and the secondary port b of the pilot valve 22 is fully open, and the main valve 21 Primary pressure PA and secondary pressure P _B
are equal. Further, the characteristics of the amount of leakage with respect to the current value (i) in this example are shown in FIG. 6 and are similar to those in FIG. 3.

In the above embodiment, the spool portion 25a and the piston portion 25b of the main spool 25 of the main valve 21 are made into an integral structure, but the spool portion 25a and the piston portion 25b may have a separate structure.

<Effects of the Invention> As is clear from the above, the pressure reducing valve of the present invention has one of the main valves connected to the chamber on the piston side of the main spool of the three-port main valve through the three-port pilot valve.
Since the pressure on the secondary port A side is guided and the secondary port B side of the main valve is not communicated, it is possible to operate the main spool of the main valve even in a controlled state under extremely low pressure at the secondary port. Therefore, the pressure at the secondary port can be controlled to an extremely low pressure close to zero pressure, and can be controlled to a high pressure approximately equal to the pressure at the primary port, making it possible to control the pressure over a wide range. Therefore, the actuator connected to this pressure reducing valve is
The actuator can be activated very softly and without shock from a low pressure, and the actuator can also be operated at a high pressure approximately equal to the primary pressure.

Furthermore, since the pressure reducing valve of the present invention does not perform pressure control using a constant flow rate of vent flow from the secondary port side via a vent throttle as in the conventional art, the amount of leakage can be reduced overall. In addition, the main spool can be operated by applying the pressure of the fluid supplied from the primary port to the secondary port of the pilot valve to the piston portion of the main spool.
The main spool can be operated even with large axial thrust,
The maximum flow rate of the pressure reducing valve can be increased. In addition, since the piston section increases the force and operates the main spool,
The secondary pressure of the main valve can be controlled over a wide range from approximately zero pressure to a value equal to the primary pressure.

[Brief explanation of drawings]

Figures 1 and 4 are principle diagrams of an embodiment of the present invention, Figures 2, 3, 5, and 6 are characteristic diagrams of the above embodiment, respectively, and Figure 7 is a diagram of the conventional example. FIG. 21... Main valve, 22... Pilot valve, 25... Main spool, 25a... Spool portion, 25b... Piston portion, 41... Pilot spool, 48... Electromagnetic proportional solenoid.

Claims (1)

[Claims] 1. The spool portion side of the main spool 25, which has a spool portion that switches and communicates the secondary port B with the primary port A and the tank port T, and a piston portion whose diameter is larger than the diameter of the spool portion. A three-port main valve 21 whose end chamber is connected to the secondary port B through a passage, and the secondary port B is connected to the primary port a and the tank port t.
A three-port pilot valve 22 has a chamber at one end of the pilot spool 41 which communicates with the secondary port b via a passage, and a pressing means is provided at the other end of the pilot spool 41. , the primary port a of the pilot valve 22 communicates with the primary port A of the main valve 21, and the secondary port b of the pilot valve 22 communicates with the chamber on the piston side of the main spool 25 of the main valve 21, respectively. A pressure reducing valve characterized by: