JP2553341B2 - Pressure control valve - Google Patents

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure control valve suitable for use in vehicle attitude control, for example, and more particularly to a pressure control valve capable of controlling pressure in proportion to current. (Prior Art) Nearly, there is a tendency that a high level of comfort is also required for a vehicle, and for example, vehicle height adjustment, vehicle body attitude control during cornering and braking, and the like are performed. When such various controls are performed by hydraulic pressure, a pressure control valve for generating hydraulic pressure proportional to the current value to the solenoid is often used. As a conventional pressure control valve of this type, for example, see FIG. There is something like the one shown. In FIG. 7, when the spool valve 2 housed in the body 1 is energized to the solenoid 3, the spool valve 2 is pushed rightward in the drawing by an electromagnetic force corresponding to the current value, and the supply port 4 And the cylinder port 5 communicate with each other, and the hydraulic pump 6
Pressure oil is supplied from the cylinder 7 to the piston 8 to move the piston 8 to change the vehicle height. At this time, the pressure oil of the cylinder port 5 is guided to the right chamber (spring chamber) 9 of the spool valve 2 through the oil passage 10 and acts as a balance force against the electromagnetic force of the solenoid 3. Without this balancing force, the solenoid 3
It is not possible to generate a control force (pressure on the cylinder 7) according to the electric current at. That is, in the pressure control valve of FIG. 7, by making the pressure receiving area of the spool valve 2 in the left-right movement direction the same and applying the cylinder pressure to the right side,
The mechanism is to perform proportional control of current-pressure. The left chamber 11 of the spool valve 2 communicates with the discharge port 12 through the oil passage 12, and the discharge port 13 communicates with the reservoir tank 14. The proportional control is performed by changing the passage area between the supply port 4 and the cylinder port 5 under the balance of the spool valve 2 according to the current value to the solenoid 3. (Problems to be Solved by the Invention) However, such a conventional pressure control valve is configured to guide the cylinder pressure to the right chamber 12 of the spool valve 2 in order to perform current proportional control. Therefore, a large electromagnetic force that opposes the cylinder pressure is applied to the solenoid 3
Required. Therefore, there were the following problems. (I) The solenoid 3 is upsized, and the installation space is restricted and the cost is high. When such a pressure control valve is used in a vehicle height adjusting device or the like, the above-mentioned problem becomes particularly remarkable. (II) Further, as will be described later in detail, compensation of the axial force of the spool valve 2 due to the hydraulic force R of the pressure oil is not taken into consideration, and the target control pressure changes or the responsiveness deteriorates. There are also problems. On the other hand, as a solution to the problem (I),
For example, a second type as shown in FIG. 8 has also been proposed. In FIG. 8, a piston hole 22 is formed inside the spool valve 21, and a small piston 23 is housed therein. The right chamber 24 and the left chamber 25 of the spool valve 21 communicate with each other through an oil passage 27 that communicates with the discharge port 26. In addition, 28 is a body, 29 is a supply port, and 30 is a cylinder port. Here, the cylinder pressure acts only on the end surface of the small piston 23 and the inside of the spool valve 21 on the opposite side, and the force pushing the spool 21 to the left becomes a balance force against the electromagnetic force of the solenoid 31. Therefore, the pressure oil can be supplied with a smaller electromagnetic force than the first pressure control valve described above, and the solenoid 31 can be downsized. However, even with this second pressure control valve, the above (I
The problem of I) is not resolved, and improvement is desired in this respect.
Next, the defect will be described in detail. When the piston 11 in the cylinder 9 does not operate, that is, when the pressure oil does not flow through the spool valve 21 (supply port 29
When the flow rate is not generated even though the cylinder port 30 communicates with the cylinder port 30, the spool valve 21 is balanced by the following equation, and the cylinder 9 is maintained at the control pressure Ps at that time. Fs = A × Ps ...... However, Fs: Electromagnetic force of solenoid 31 A: Pressure receiving area of small piston 23 in spool valve 21 From the above formula, control pressure Ps is determined according to the value of the current that generates the electromagnetic force of solenoid 31 Therefore, so-called current proportional control is performed. On the other hand, when the piston 11 in the cylinder 9 operates, the pressure oil having a flow rate according to the moving speed of the piston 11 passes through the spool valve 21, so that the spool valve
It is well known that the fluid force R is generated at 21. Here, the fluid force R is expressed by the following equation. R = ρ · Q · V · COS ψ, where ρ: operating oil density Q: flow rate V: flow velocity ψ: flow angle Therefore, when the piston 11 operates, the solenoid is calculated by the following equation, which is the fluid force R added to the above equation. 31 electromagnetic forces are balanced. Fs = A × Ps ± R In the formula, the sign (+) of R is the pressure oil supplied port 29.
From the cylinder 9 to the cylinder port 30, the symbol (-) is from the cylinder 9 to the reservoir tank 7. As is clear from the equation, when the pressure oil flows through the end portion (edge) in the spool valve 21, the control force Ps changes due to the generation of the fluid force R, which impairs the proportional characteristic and the responsiveness. On the other hand, in order to reduce the influence of such fluid force R,
For example, it is possible to process the end portion (edge) of the spool valve 21. However, according to this method, there is a new problem that the cost is high due to processing, or the effect of processing can be expected only within a predetermined flow rate and pressure range, and it is not an effective solution. On the other hand, in order to electrically cancel the influence of such a fluid force, the one shown in FIG. 9 has also been proposed. This is for detecting the pressure P of the pressure oil acting on the actuator 41, performing feedback control, and performing the above-mentioned proportional control. The actuator 41 is connected to a vehicle height adjusting mechanism 42 provided on the front, rear, left, and right of the vehicle, and the vehicle height adjusting mechanism 42 performs the attitude control of the vehicle as described above. Now, G is being applied to the vehicle by cornering and braking.
When the change of the voltage occurs, it is detected by the G sensor 43, and the voltage
Vs is input to the amplifier 44. On the other hand, the voltage Vp based on the pressure P applied to the actuator 41 is input to the amplifier 44 from the pressure sensor 45, and the control voltage Vc from a controller or the like (not shown) is also input to the amplifier 44. , Vp, Vc based on the current i is input to the solenoid (not shown) of the pressure control valve 46. The pressure control valve 46 controls the pressure of the pressure oil according to the current i, and gives the actuator 41 a set pressure P. At this time, the pressure P applied to the actuator 41 is constantly detected by the pressure sensor 45 and is used for feedback control, so that the current i with respect to the control voltage Vc is appropriately corrected. That is, the voltage Vp is the pressure control valve
Since it acts so as to cancel the fluid force R generated at 46, there is no change in the target pressure P with respect to the input voltage Vc, and the responsiveness is improved. However, although the influence of the fluid force R is canceled, it introduces the following new problems. (III) The entire configuration, that is, the sensor, the electronic circuit, and the like are complicated, and the cost is significantly increased. Especially when applied to a vehicle height adjusting device of a vehicle, it is difficult to realize. Although the above problems are examples when the pressure control valve is applied to the vehicle height adjusting device, etc., since the pressure control valve is applied in other wide range of control fields, the above-mentioned improvement may be made. desirable. (Object of the Invention) Therefore, the present invention provides a spool valve in which a throttle is provided midway in an oil passage connecting a spool valve and a cylinder, and the spool valve side pressure of the throttle acts in the same direction as the electromagnetic force of the solenoid. On the pressure receiving surface of the spool valve and the pressure on the cylinder side of the throttle on the other pressure receiving surface of the spool valve,
The axial force that opposes the fluid force is generated in the spool valve to compensate for the fluid force, and the performance of the current proportional control characteristic can be improved at a low cost with a simple configuration while maintaining the miniaturization of the solenoid. It is intended to provide a pressure control valve. (Means for Solving the Problems) In order to achieve the above object, the pressure control valve according to the present invention has a spool valve having pressure receiving portions whose directions of action are opposite to each other and whose pressure receiving areas are different from each other. Side, the electromagnetic force of the solenoid is applied, and the control pressure of the cylinder is applied to the difference of the pressure receiving area in the direction opposite to the direction of the electromagnetic force, and the spool valve is moved to change the passage area of the pressure oil. In a pressure control valve for proportionally controlling the control pressure of pressure oil supplied to a cylinder according to a solenoid current, a predetermined throttle is provided in the oil passage connecting the cylinder port and the cylinder, and a spool valve side of the throttle is provided. Guide the pressure to the pressure receiving surface of the spool valve that acts in the same direction as the electromagnetic force of the solenoid, and reverse the cylinder side pressure from the throttle to the direction in which the solenoid electromagnetic force acts. Is directed to the other pressure receiving surface of the spool valve that acts in the direction of, and an axial force in the opposite direction is generated in the spool valve against the hydraulic fluid force generated in the spool valve to compensate the fluid force. (Operation) In the present invention, the throttle is provided in the middle of the oil passage connecting the spool valve and the cylinder, and the spool valve side pressure of the throttle acts in the direction in which the solenoid electromagnetic force of the spool valve acts.
The pressure on the cylinder side of the throttle acts in the opposite direction of the spool valve. Therefore, the axial force that opposes the fluid force is generated in the spool valve to compensate the fluid force, and while maintaining the downsizing of the solenoid, the current proportional control characteristic can be obtained with a simple configuration and at low cost, and the responsiveness is high. Is significantly improved. (Example) Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a first embodiment of the pressure control valve according to the present invention. First, the configuration will be described. In the figure, 51 is a pressure control valve, and the pressure control valve 51 is a solenoid 52 and a spool valve 5.
It is composed of 3, body 54, etc. A plunger 55 is fitted in the solenoid 52, and the plunger 55 is biased in the direction of arrow A in the figure by a solenoid spring (not shown). The solenoid 52 is connected to the body 54
A substantially cylindrical spool valve 53 is slidably accommodated in 54. The spool valve 53 has a large diameter portion 56 at one end and a small diameter portion 57 at the center.
The large diameter portion 56 defines a right chamber 58 and an annular auxiliary chamber 59. Also, spool valve 53
The other end contacts the plunger 55 of the solenoid 52 and defines the left chamber 60. A spring 61 is provided in the right chamber 58, and the spring 61 biases the spool valve 53 in the direction of arrow B in the figure. That is, when the solenoid 52 is not energized, the spring of the solenoid 52 and the urging force of the spring 61 are balanced and the spool valve 53 is stationary. The small diameter portion 57 of the spool valve 53 defines an annular central chamber 62, and both ends of the central chamber 62 are provided with an annular supply chamber 63 and an exhaust chamber 64 that are open in contact with the periphery of the spool valve 53.
The pressure oil from the hydraulic pump 66 is guided to the supply chamber 63 via the oil passage 65, and the discharge chamber 64 communicates with the reservoir tank 68 via the oil passage 67. An oil passage 69 is provided between the discharge chamber 64 and the auxiliary chamber 59, and the oil passage 69 connects the discharge chamber 64 and the auxiliary chamber 59. An oil passage 71 is opened to the central chamber 62 via the cylinder port 70, and the oil passage 71 connects the central chamber 62 and the working chamber 73 of the cylinder 72. The cylinder 72 has a piston 74, which defines a working chamber 73 and is displaced according to the pressure in the working chamber 73. A piston rod 75 is connected to the piston 74, and the piston rod 75 is connected to, for example, a vehicle height adjusting mechanism or the like. The oil passage 71 is provided with a throttle 76 having an opening area smaller than the cross-sectional area of the oil passage 71 in the middle of the oil passage 71. Left chamber
The cylinder 72 side communicates with the right chamber 58 via an oil passage 78. Next, the operation will be described. The control of hydraulic pressure by the pressure control valve 51 for the cylinder 72 is performed as follows. When no current is supplied to the solenoid 52, the spool valve 53 is stationary at an arbitrary position where the solenoid spring and the spring 61 balance each other as described above. When a current is supplied to the solenoid 52, an electromagnetic force corresponding to the current is generated and the spool valve 53 slides in the direction of arrow A in the figure. At this time, the central chamber 62 and the supply chamber 63 communicate with each other, and the pressure oil from the hydraulic pump 66 is supplied to the cylinder 72 via the oil passage 65, the supply chamber 63, the central chamber 62, and the oil passage 71. That is, the piston 74 of the cylinder 72 is displaced in the direction of arrow C in the figure by the pressure oil from the hydraulic pump 66. Further, a fluid force corresponding to the flow rate of the pressure oil flowing from the supply chamber 63 to the central chamber 62 is generated and acts on the spool valve 53 in the direction of arrow B in FIG. On the other hand, a pressure difference ΔP corresponding to the flow rate Q of the pressure oil flowing through the oil passage 71 is generated before and after the throttle 76 provided in the oil passage 71. That is, since the pressure on the upstream side of the throttle 76 becomes higher than the pressure on the downstream side by ΔP,
The pressure on the spool valve 53 side of 76 is P _S1 , and the cylinder 72 of the throttle 76 is
If the pressure on the side is P _S2 , the pressure difference ΔP is expressed by the following equation. ΔP = P _S1 −P _S2 …… where the pressures P _S1 and P _S2 before and after the throttle 76 are the oil passages, respectively.
It is guided to the left chamber 60 and the right chamber 58 by 77 and 78. If the pressure receiving area of the spool valve 53 on the solenoid side end surface is A ₁ , and the pressure receiving area of the spool valve 53 on the large diameter portion 56 side is A ₂ , The equation for balancing the forces acting on the spool valve 53 is represented by the following equation. Fs ＋ P _S1・ A ₁ ＝ P _S2・ A ₂ ＋ R ・ ・ ・ However, Fs: Electromagnetic force of solenoid R: Fluid force (force by spring is omitted) When the above formula is rearranged and transformed for electromagnetic force Fs, the following formula is obtained. To be Fs = P _S2・ (A ₂ −A ₁ ) + (P _S2 −P _S1 ) ・ A ₁ + R …… In the above formula, [(P _S2 −P _S1 ) ・ of the second term on the right side
A ₁ ] indicates that the pressure difference ΔP generated before and after the throttle 76 is the spool valve.
It represents the axial force F acting on 53, and since P _S1 > P _S2 , [(P _S2 −P _S1 ) · A ₁ ] <0. Therefore, the axial force F acts in the opposite direction to the fluid force R, and the fluid force R can be canceled. Here, the pressure difference ΔP generated before and after the throttle 76 and the throttle 76
There is a relationship of the following equation with the flow rate Q of the pressure oil flowing through. However, C: flow coefficient a opening area of throttle ρ: density of pressure oil As described above, since the pressure difference ΔP is proportional to the square of the flow rate Q, the axial force F is proportional to the square of the flow rate Q. On the other hand, it is known that the fluid force R has a proportional relationship with the flow rate Q as shown in the above equation. FIG. 2 shows the spool acting force with respect to the flow rate Q, that is, the magnitude of the axial force F proportional to the square of the fluid force R and the flow rate Q. As is clear from the figure, the fluid force R and the axial force F do not completely match, but they are approximate. Therefore, most of the fluid force R is canceled by the axial force F, and the force acting as the actual disturbance acting on the spool valve 53 corresponds to the portion sandwiched between the two curves. That is, it is [fluid force R-axial force F], and this value is extremely smaller than the fluid force R. Therefore, the following equation 'is obtained as an approximate equation from the above equation. Fs = P _S2 (A ₂ −A ₁ ) ... That is, since the cylinder pressure P _S2 is determined by the solenoid electromagnetic force Fs, it is possible to prevent the target control pressure from varying due to the influence of the fluid force R. At the same time, the responsiveness of the pressure control valve 51 is significantly improved. In this way, control pressure is applied to the cylinder 72 according to the current input to the solenoid, and the piston 74 of the cylinder 72
To displace. When the piston 74 of the cylinder 72 is stationary, the flow rate Q of the pressure oil in the oil passage 71 is

Since it becomes [0], the pressure difference ΔP and the fluid force R generated before and after the throttle 76 are both

It becomes [0]. That is, the same pressure as the pressure Ps acting on the working chamber 73 of the cylinder 72 is introduced to the right chamber 58 and the left chamber 60, and the force acting on the spool valve 53 is P _S1 = P _S2 = P in the above equation. _The following equation is obtained with _S and R = 0. Fs ＋ P _S1・ A ₁ ＝ P _S2・ A ₂ ∴Fs ＝ Ps ・ (A ₂ −A ₁ ) …… where the electromagnetic force Fs is generated in proportion to the current, the control pressure proportional to the current Ps occurs. FIG. 3 shows the relationship between the control pressure Ps and the current i flowing through the solenoid 52. The above has described the case where the control pressure is increased. Next, the case where the pressure is reduced will be described. When the electric current i that has obtained the above-mentioned control pressure Ps is reduced to a predetermined value, the electromagnetic force Fs in the above equation decreases. Therefore, the balance between the electromagnetic force and the hydraulic force of the spool valve 53 is lost, the spool valve 53 slides in the direction of arrow B in FIG. 1, and the central chamber 62 and the discharge chamber 64 communicate with each other. At this time, the pressure oil supplied to the working chamber 73 of the cylinder 72 is transferred to the oil passage 71, the central chamber 62,
Since it is discharged to the reservoir tank 68 through the discharge chamber 64 and the oil passage 67, the pressure difference according to the flow rate Q of the pressure oil in the oil passage 71 is reduced by the throttle 76.
And the fluid force R corresponding to the flow rate of the pressure oil flowing from the central chamber 62 to the discharge chamber 64. This fluid force R acts on the spool valve 53 in the direction of arrow A in FIG. Therefore, the force acting on the spool valve 53 is expressed by the following equation. Fs + P _S1・ A ₁ ＝ P _S2・ A ₂ −R …… The following formula is obtained by rearranging and transforming the above formula for electromagnetic force Fs as in boosting. Fs = P _S2・ (A ₂ −A ₁ ) + (P _S2 −P _S1 ) ・ A ₁ −R …… In the above formula, [(P _S2 −P _S1 ) ・ of the second term on the right side
A ₁ ] represents the axial force F acting on the spool valve 53 as in the case of increasing the pressure, but the pressure generated before and after the throttle 76 is P _S1 <P _S2 because the cylinder 72 side is upstream. Therefore, [(P
_S2− P _S1 ) · A ₁ ]> 0, and this axial force F acts in the opposite direction to the fluid force R, so that the fluid force R is canceled. The relationship between the fluid force R and the axial force F does not completely match as described above, but the influence of the fluid force R is almost negated. Therefore, the cylinder pressure is reduced to a predetermined pressure without changing by the fluid force R. Due to the action of the pressure control valve 51, the conventional problems are solved as follows. (A) Effect 1 Since the pressure receiving areas of both end faces of the spool valve 53 are different and the pressure of the oil passage 71 is guided to both end faces, the force required to slide the spool valve 53 is the difference between the pressure receiving area and the oil receiving area. It is enough to resist the force represented by the product of the pressure of the passage 71. Therefore, the electromagnetic force required for the solenoid 52 may be small, so that the solenoid 52 can be downsized and the cost can be reduced. This is a conventional problem (I)
Means that can be solved. (B) Effect 2 A throttle 76 is provided in the middle of the oil passage 71, and when a pressure difference is generated before and after that, an axial force that opposes the fluid force acting on the spool valve 53 is generated according to this pressure difference. The influence of the fluid force can be made extremely small. Therefore, the current proportional control characteristic of the pressure control valve 51 is obtained, and the responsiveness is significantly improved without changing the target control pressure (solution of problem II). (C) Effect 3 Since the fluid force is canceled by providing the diaphragm 76, the structure is simple and the processing of the diaphragm 76 is easy. Therefore, it is possible to provide the low cost spool valve 53 while improving the characteristics of the current proportional control (solution of problem III). In addition to the above effects (solution of problems), there are the following effects. (D) Effect 4 Since the throttle 76 is provided in the middle of the oil passage 71, the hydraulic pump
There is no flow rate loss of the pressure oil supplied from 66. Further, the pressure difference generated before and after the throttle 76 is a value that can be almost ignored (practically 3 kg / cm ² or less). Therefore,
The problem of pressure loss can also be ignored. In the first embodiment described above, the aperture area of the diaphragm provided for compensating the fluid force is fixed, but as the second embodiment, the case where the aperture area of the diaphragm is made variable by external adjustment will be described. explain. FIGS. 4 and 5 are views showing a second embodiment of the present invention, FIG. 4 is a sectional view of a main part of a pressure control valve according to the present invention, and FIG. 5 is a sectional view taken along line XX '. FIG. The first
The same components as those in the embodiment are designated by the same reference numerals and the description thereof will be omitted. In FIG. 4, reference numeral 81 is a throttle provided in the middle of the oil passage 71, and the aperture area of the throttle 81 is adjustable by an adjusting bolt 82. A lock nut 83 is screwed onto the adjusting bolt 82,
Is fixed by a lock nut 83 so that the aperture area of the diaphragm 81 is fixed. On the other hand, the pressure on the spool valve 53 side of the throttle 81 is guided to the left chamber 60 by the oil passage 77, and the pressure on the other side is guided to the right chamber 58 by the oil passage 78. Here, in the present embodiment, the structure of the diaphragm 81 has its characteristics, which will be described in detail. In FIG. 5, the body 54
A spool valve 53 is housed therein, and a central chamber 62 is defined around the spool valve 53. The central chamber 62 communicates with the oil passage 84,
An oil passage 77 opens in the oil passage 84. One end of the oil passage 84 is the body 54
Has an opening at the top thereof, and an adjustment bolt 82 is screwed into this opening. A groove is provided at one end of the adjustment bolt 82.
85 is formed, and the groove 85 is fitted with a predetermined fastening tool. An umbrella-shaped poppet 86 is formed at the other end of the adjusting bolt 82, and an O-ring 87 is fitted around the center of the adjusting bolt 82. On the other hand, an oil passage 88 having an inner diameter smaller than that of the oil passage 84 is connected to the other end of the oil passage 84, and an oil passage 78 opens in the oil passage 88. An oil passage 71 is connected to the oil passage 88 via an O-ring 89, and the oil passage 71 is connected to the cylinder 72. The opening ends of the poppet 86 and the oil passage 88 on the spool valve 53 side function as the throttle 81 described above, and the oil passage 84 and the oil passage are rotated by rotating the adjusting bolt 82.
The communication area between 88 can be changed. Therefore, in this embodiment, the following effects are obtained in addition to the effects of the first embodiment. That is, the fluid force acting on the spool valve 53 changes depending on the pressure of the pressure oil supplied to the pressure control valve 51 and the reference value of the cylinder pressure (that is, the steady value in the operating state), but the opening area of the throttle 81 is Since it can be changed by a predetermined adjusting mechanism, it is possible to cope with a wide range of changes in fluid force. As a result, the pressure control valve
The application range of 51 can be expanded. Specifically, it is possible to finely change the opening area of the throttle 81 of the pressure control valve 51 and adjust the compensation of the current proportional characteristic to the optimum one in the factory. Further, when the pressure control valve 51 is used in the vehicle body adjusting device, the user can change the opening area of the diaphragm 81 to perform fine adjustment, and this can also be performed by a dealer maintenance person. Further, also in other application fields such as hoists, rockets, and ships, it is possible to adjust the compensation of the fluid force so as to obtain the optimum characteristics suitable for each application. The first and second embodiments described above are examples in which the difference in pressure receiving area of the spool valve is configured as the area difference between both end surfaces of the spool valve. However, as a method for making a difference in pressure receiving area, attention is paid to both end surfaces. Not exclusively. The point is that it is only necessary to change the pressure receiving area depending on the moving direction. Therefore, a method of processing the end portion instead of the end surface to make the area difference may be used. An example of this will be described next. That is, in the first and second embodiments described above, the pressure difference generated before and after the restriction is applied to both end faces of the spool valve. A case where an auxiliary chamber for guiding a pressure difference is provided in the vicinity will be described. FIG. 6 is a diagram showing a third embodiment of the present invention, in which the same components as those in the first embodiment are designated by the same reference numerals and the description thereof is omitted. In the figure, 90 is a pressure control valve, 91 is a spool valve, and an annular auxiliary chamber 92 is formed on the 91 right chamber 58 side of the spool valve, and a piston hole 93 is formed at the center of the auxiliary chamber 92. The auxiliary chamber 92 communicates with the piston hole 93 via the flow passage 94, and the pressure on the cylinder 72 side of the throttle 76 is stored in the auxiliary chamber 92 through the flow passage 95.
Guided through. In addition, the piston hole 93 has a small piston.
96 is stored. On the other hand, an annular auxiliary chamber 97 is defined on the solenoid valve 52 side of the spool valve 91, and the auxiliary chamber 97 communicates with the central chamber 62 via a flow passage 98 formed in the spool valve 91.
In addition, 99 is a solenoid. Although not shown, the right chamber 58 and the left chamber 60 communicate with the reservoir tank 68. Thus, the pressure on the spool valve 91 side of the throttle 76 is
The pressure on the cylinder 72 side of the throttle 76 is guided to the piston hole 93 via the flow passage 95, the auxiliary chamber 92, and the flow passage 94. Therefore, in this embodiment, the following effects are obtained in addition to the effects of the first embodiment. That is, since the pressure of the spool valve 91 side of the central chamber 62 is guided to the auxiliary chamber 97 and the pressure of the reservoir tank 68 is guided to the left chamber 60, the pressure of the left chamber 60 is equal to the atmospheric pressure. Therefore, the oil sealability between the plunger 55 and the solenoid 99 can be facilitated, or the structure in which the low pressure oil is filled in the solenoid improves the durability of the solenoid 99 and improves the reliability. In addition, the solenoid 99 can be downsized. Further, in practice, it is troublesome to machine the spool valve with a different diameter from the viewpoint of ensuring accuracy, but it is easier to machine the inside of the spool valve while making the same diameter in this way. is there. (Effect) According to the present invention, a throttle is provided in the oil passage connecting the spool valve and the cylinder, and the spool valve side pressure of the throttle is used in the same direction as the electromagnetic force of the solenoid. Since the pressure is applied to the surface and the pressure on the cylinder side of the throttle is applied to the other pressure receiving surface of the spool valve, the axial force that opposes the fluid force can be generated in the spool valve to compensate the fluid force. As a result, it is possible to obtain a pressure control valve having a simple structure while maintaining the miniaturization of the solenoid and improving the performance of the current proportional control characteristic at low cost.

[Brief description of drawings]

1 to 3 are views showing a first embodiment of a pressure control valve according to the present invention, FIG. 1 is a sectional view of a main part thereof, and FIG. 2 is a view showing a relationship between a flow rate thereof and a spool acting force, FIG. 3 is a diagram showing the relationship of control pressure with respect to the current, FIGS. 4 and 5 are diagrams showing a second embodiment of the pressure control valve according to the present invention, and FIG. FIG. 5 is a sectional view taken along the line XX 'in FIG. 4, FIG. 6 is a sectional view of an essential part showing a third embodiment of the pressure control valve according to the present invention, and FIGS. FIG. 7 is a view showing a pressure control valve, FIG. 7 is a cross-sectional view of a main part when a cylinder pressure is applied to a spool valve of the first pressure control valve so as to oppose electromagnetic force, and FIG. 2 is a sectional view of an essential part when the electromagnetic force for sliding the spool valve of the second pressure control valve is reduced, and FIG. 9 shows the spool valve of the third pressure control valve. It is a block diagram of a case where the electrically compensate the fluid force. 51, 90 ... Pressure control valve, 52, 99 ... Solenoid, 53, 91 ... Spool valve, 56 ... Large diameter part, 58 ... Right chamber, 60 ... Left chamber, 70 ... Cylinder port, 76 , 81 …… throttle, 77, 78, 98 …… oil passage.

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-55-39991 (JP, A) JP-A-57-106910 (JP, A) JP-A-58-166184 (JP, A) JP-A-53- 73617 (JP, A)

Claims (2)

(57) [Claims] 1. A spool valve having pressure-receiving portions having different pressure-receiving areas in which the acting forces are opposite to each other, and the electromagnetic force of a solenoid is applied in one moving direction of the spool valve to reverse the direction of the electromagnetic force. The control pressure of the cylinder acts on the difference of the pressure receiving area in the other moving direction of the cylinder, the spool valve is moved to change the passage area of the pressure oil, and the control pressure of the pressure oil supplied from the cylinder port to the cylinder is converted to the solenoid current. In the pressure control valve for proportional control in accordance therewith, a predetermined throttle is provided in the middle of the oil passage connecting the cylinder port and the cylinder, and the pressure on the spool valve side from the throttle is the same as the direction in which the electromagnetic force of the solenoid acts. The pressure on the cylinder side from the throttle to the other pressure receiving surface of the spool valve that acts in the direction opposite to the direction in which the electromagnetic force of the solenoid acts. , The pressure control valve, characterized in that the axial force in the opposite direction against the fluid force of the pressure oil generated in the spool valve so as to compensate for the flow strength is generated in the spool valve. 2. The pressure control valve according to claim 1, wherein the throttle has a predetermined adjusting means, and the area of the throttle can be adjusted from the outside.