JP2553345B2 - 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) Recently, there is a tendency that a high level of comfort is also required for automobiles, 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. 6, 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. 6, by making the pressure receiving areas of the spool valve 2 in the left-right movement direction the same and applying the cylinder pressure to the right side thereof,
The mechanism is to perform proportional control of current-pressure. The left chamber 11 of the spool valve 2 communicates with an exhaust port 13 through an oil passage 12, and the exhaust port 13 communicates with a 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 9 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. 7 has also been proposed. In FIG. 7, 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 valve 21 to the left serves as 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 8 in the cylinder 7 does not operate, that is, when the pressure oil does not flow through the spool valve 21, the spool valve 21
Are balanced by the following equation, and the cylinder 9 is maintained at the control pressure Ps at that time. Fs = F × Ps ...... However, Fs: Electromagnetic force of the solenoid 31 A: Pressure receiving area of the small piston 23 in the spool valve 21 From the above formula, the control pressure Ps is determined according to the value of the current that generates the electromagnetic force of the solenoid. That is, so-called current proportional control is performed. On the other hand, when the piston 8 in the cylinder 7 operates, the pressure oil having a flow rate corresponding to the moving speed of the piston 11 passes through the spool valve 21, so that the spool valve 21
It is well known that the fluid force R is generated in the. Here, the fluid force R is expressed by the following equation. R = ρ · Q · V · COS ψ, where ρ: hydraulic oil density Q: flow rate V: flow velocity ψ: flow angle Therefore, when the piston 11 operates, the solenoid is calculated by the following formula that adds the fluid force R to the above formula. 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 becomes high due to processing, or hardening of processing can be expected only within a predetermined flow rate and pressure plate, 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. 8 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 device 42 provided in the vehicle,
By 42, the attitude control of the vehicle as described above is performed. 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 set pressure P applied to the actuator 41 is constantly detected by the pressure sensor 45 and used for feedback control, so that the current i with respect to the control voltage Vc is appropriately corrected. That is, since the voltage Vp acts so as to cancel the fluid force R generated in the pressure control valve 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, resulting in a significant increase in cost. 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, in the present invention, a throttle is formed in the spool valve, and the cylinder side pressure of the throttle is applied to the pressure receiving surface of the spool valve which acts in the direction opposite to the direction in which the electromagnetic force of the solenoid acts,
By applying a pressure opposite to that on the cylinder side to the other pressure-receiving surface of the spool valve, an axial force that opposes the fluid force is generated in the spool valve to compensate for the fluid force and maintain a compact solenoid while maintaining a compact solenoid. It is an object of the present invention to provide a pressure control valve having a configuration and capable of improving the performance of current proportional control characteristics at low cost. (Means for Solving the Problems) In order to achieve the above object, a pressure control valve according to the present invention has a spool valve having pressure receiving portions in directions in which acting forces are opposite to each other and having different pressure receiving areas. The electromagnetic force of the solenoid is applied in the direction of movement of the solenoid, the control pressure of the cylinder is applied to the difference in the pressure receiving area in the other direction of movement opposite to the direction of the electromagnetic force, and the spool valve is moved to reduce the passage area of the pressure oil. Change
In a pressure control valve that proportionally controls the control pressure of pressure oil supplied to the cylinder from the cylinder port according to the solenoid current, a predetermined throttle is formed in the spool valve, and the pressure on the cylinder side of the throttle is changed by the electromagnetic force of the solenoid. It guides to one pressure receiving surface of the spool valve that acts in the direction opposite to the acting direction, and the other side of the spool valve that acts the pressure opposite to the cylinder side of the throttle in the same direction as the electromagnetic force of the solenoid acts. The axial force in the opposite direction is generated in the spool valve against the fluid force of the pressure oil generated in the spool valve and compensated for the fluid force. (Operation) In the present invention, the spool valve is provided with a throttle, the pressure on the cylinder side of the throttle acts in a direction opposite to the direction in which the solenoid electromagnetic force of the spool valve acts, and the pressure opposite to the cylinder side of the throttle acts on the spool. Acts in the opposite direction of the valve. Therefore, an 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, a current proportional control characteristic can be obtained with a simple configuration and at low cost.
Moreover, the responsiveness is remarkably 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 spring (not shown).
The solenoid 52 is connected to a body 54, and a substantially cylindrical spool valve 53 is slidably accommodated in the body 54. The spool valve 53 has a large-diameter portion 56 at one end and a small-diameter portion 57 at the center, and the small-diameter portion 57 has an annular land 58 formed near the center thereof. The small diameter portion 57 and the land portion 58 define a supply chamber 59 on the large diameter portion 56 side and a cylinder chamber 60 on the solenoid 52 side with the land portion 58 as a boundary, and the large diameter portion 56 defines a right chamber 61. , An annular auxiliary chamber 62 is defined. Hole 63 in land 58
Is formed, and the hole 63 connects the supply chamber 59 and the cylinder chamber 60. The hole 63 has a function as a diaphragm. The other end of the spool valve 52 contacts the plunger 55 of the solenoid 52 and defines the left chamber 64. The spool valve 53 has an oil passage 65 therein, and the oil passage 65 connects the supply chamber 59 and the left chamber 64.
A spring 66 is provided in the right chamber 61, and the spring 66 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 66 are balanced and the spool valve 53 is stationary. Large diameter part 56 of supply chamber 59
An annular supply auxiliary chamber 67, which is opened in contact with the periphery of the spool valve 53, is defined at the side end portion, and pressure oil from a hydraulic pump 69 is guided to the supply auxiliary chamber 67 via an oil passage 68. Cylinder chamber
A discharge auxiliary chamber 70 that opens in contact with the periphery of the spool valve 53 is defined at the end of the solenoid 52 on the side of the solenoid 52, and the discharge auxiliary chamber 70 communicates with a reservoir tank 72 via an oil passage 71. Discharge auxiliary chamber
An oil passage 73 is provided between the 70 and the auxiliary chamber 62.
Connects the discharge auxiliary chamber 70 and the auxiliary chamber 62. The cylinder chamber
60 communicates with the right chamber 61 via the oil passages 74 and 75, and also communicates with the working chamber 77 of the cylinder 76 via the oil passage 74.
The cylinder 76 has a piston 78, which defines the working chamber 77 and is displaced according to the pressure in the working chamber 77. A piston rod 79 is connected to the piston 78,
The piston rod 79 is connected to, for example, a vehicle height adjusting device. Next, the operation will be described. The hydraulic pressure control for the oil passage 75 by the pressure control valve 51 is performed as follows. When current is not supplied to the solenoid 52, as described above, the spool valve 53 is stationary at an arbitrary position where the spring of the solenoid 52 and the spring 66 balance each other. Electromagnetic force is generated, and the spool valve 53 slides in the direction of arrow A in the figure. At this time, the supply auxiliary chamber 67 and the supply chamber 59 communicate with each other and the hydraulic pump 69
Pressure oil from the oil passage 68, supply auxiliary chamber 67, supply chamber 59, hole 63,
It is supplied to the cylinder 76 through the cylinder chamber 60 and the oil passage 74 in this order. That is, the piston 78 of the cylinder 76 is displaced in the direction of arrow C in the figure by the pressure oil from the hydraulic pump 69. Also,
A fluid force corresponding to the flow rate of the pressure oil flowing from the auxiliary supply chamber 67 to the supply chamber 59 is generated, and an arrow B in FIG.
Acts in the direction. On the other hand, a pressure difference ΔP corresponding to the flow rate Q of the pressure oil flowing through the hole 63 is generated before and after the hole 63 formed in the land portion 58 due to the function as a throttle. That is, since the pressure on the upstream side of the hole 63 is higher than the pressure on the downstream side by ΔP, if the pressure on the hydraulic pump 69 side of the hole 63 is P _S1 and the pressure on the cylinder 72 side of the hole 63 is P _S2 , The pressure difference ΔP is expressed by the following equation. ΔP = P _S1 −P _S2 …… where the pressure P _S1 on the hydraulic pump 69 side of the hole 63 is the supply chamber 5
9, led to the left chamber 64 via the oil passage 56, the cylinder chamber 76 of the hole 63
Since the pressure P _S2 on the side is guided to the right chamber 61 via the cylinder chamber 60, the oil passage 74, and the oil passage 75, the pressure receiving area of the solenoid valve end surface of the spool valve 53 is A ₁ , and the large diameter portion 56 side of the spool valve 53 side. If the pressure receiving area of the end surface is A ₂ , the balance equation of the forces acting on the spoo valve 53 is expressed 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 modified 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 ] represents the axial force F acting on the spool valve 53 due to the pressure difference ΔP generated before and after the hole 63, and since P _S1 > P _S2 , [(P _S2- P _S1 ) ・ A ₁ ]. <0. Therefore,
This axial force F acts in the opposite direction to the fluid force R, which makes it possible to cancel the fluid force R. Here, the relationship between the pressure difference ΔP generated before and after the hole 63 and the flow rate Q of the pressure oil flowing through the hole 63 has the following equation. However, C: flow rate coefficient a: aperture 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 are not exactly the same, 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 straight lines. 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. The response of the pressure control valve 51 is greatly improved. In this way, control pressure is applied to the cylinder 76 according to the current input to the solenoid, and the piston 78
To displace. When the piston 7 of the cylinder 76 is stationary, the flow rate Q of the pressure oil supplied from the hydraulic pump 69 to the working chamber 77 is

Since it becomes [0], the pressure difference ΔP generated before and after the hole 63 and the fluid force R are both

It becomes [0]. At this time, the same pressure Ps acting on the working chamber 77 of the cylinder is introduced into the right chamber 61 and the left chamber 64, and the spool valve 53
The force acting on is P _S1 = P _S2 = Ps, R = 0 in the above equation
Is expressed by the following equation. 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, but the control pressure is reduced as follows. When the current i of the solenoid 52 having the predetermined control pressure Ps is reduced to a predetermined value, the electromagnetic force Fs in the above equation is reduced. Therefore, the balance between the electromagnetic force Fs of the solenoid 52 and the hydraulic force is lost, the spool valve 53 slides in the direction of arrow B in FIG. 1, and the cylinder chamber 60 and the auxiliary discharge chamber 70 communicate with each other.
At this time, the pressure oil supplied to the working chamber 77 of the cylinder 76 is discharged to the reservoir tank 72 through the oil passage 74, the cylinder chamber 60, the discharge auxiliary chamber 70, and the oil passage 71, and the pressure of the working chamber 77 reaches a predetermined value. Decompressed to. In the first embodiment, since the compensation in the fluid at the time of increasing the pressure is almost perfect, it is suitable for use in, for example, a hoist or a robot for lifting a member to a predetermined position (height). This is because this robot or the like does not often require accuracy when depressurizing after lowering the members. 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 made different and the pressure supplied to the working chamber 77 of the cylinder 76 is guided to both end faces, the force required to slide the spool valve 53 is It is sufficient to resist the force represented by the product of the left side of the area and the pressure of the working chamber 77. 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 means that the conventional problem (I) can be solved. (B) Effect 2 A hole through which pressure oil passes through the land 58 provided on the spool valve 53
When the pressure difference is generated before and after 63 is provided, the axial force against the fluid force corresponding to the pressure difference is generated in the spool valve 53, so that 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. (C) Effect 3 Since the fluid force is canceled by providing the hole 63, the structure is simple and the hole 63 can be easily processed. Therefore, it is possible to provide the low-cost pressure control valve 51 while improving the characteristics of the current proportional control.
Solution of III). In addition to the above effects (solution of problems), there are the following effects. (D) Effect 4 Since the hole 63 is provided in the path of the pressure oil supplied from the hydraulic pump 69 to the cylinder 76, the flow rate loss of the pressure oil supplied from the hydraulic pump 69 does not occur at all. Also, the pressure difference generated before and after the hole 63 can be almost ignored (practically 3 k
g / cm ² or less). Therefore, the problem of pressure loss can be ignored. (E) Effect 5 Since the spool valve 53 itself is provided with a function as a throttle and only a few oil passages are provided in the body 54, the pressure control valve 51 of the pressure control valve 51 can be considered in consideration of fluid force compensation. The size can be reduced. Therefore, the degree of freedom in assembling can be expanded, and the range of application in various control fields can be expanded. In the above first embodiment, the spool valve 53 is provided with the hole 63 having a function as a throttle to compensate for the fluid force. Next, as a second embodiment, the function as a throttle is indirectly performed. The case where it is realized will be described. FIG. 4 is a diagram showing a second embodiment according to the present invention. In the figure, the same components as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. Reference numeral 81 is a pressure control valve, and the spool valve 82 housed in the body 54 has an annular land portion 83 near the center of the small diameter portion 57, and the land portion 83 forms an annular throttle between the inner wall of the body 54. 84 is formed. That is, when the pressure oil from the hydraulic pump 69 is supplied to the cylinder 76, the pressure difference Δ before and after the throttle 84 is increased.
P occurs, and the axial force F corresponding to the pressure difference ΔP is generated as in the first embodiment, and the fluid force R is compensated. Therefore,
The same operation and effect as those of the first embodiment can be obtained. Further, since the land portion 83 is formed only by providing the spool valve 82 on the pressure control valve 81, the pressure control valve 81 can be processed more easily. Therefore, the cost of the pressure control valve 51 can be further reduced. In the first and second embodiments described above, the fluid force is compensated when the cylinder pressure is increased.
As an example, a case will be described in which the fluid force generated at the time of pressure reduction is also compensated as at the time of pressure increase. FIG. 5 is a diagram showing a third embodiment according to the present invention. In the figure, members having the same configurations as those of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. Reference numeral 91 is a pressure control valve, and a small diameter portion 93 is formed near the center of the spool valve 92 housed in the body 54. Small diameter part 93
Are provided with land portions 94 and land portions 95 at substantially equal intervals, and the spool valve 92 and the land portions 94, 95 are provided in the supply chamber 96,
A cylinder chamber 97 and a discharge chamber 98 are defined. The supply chamber 96 and the discharge chamber 98 communicate with each other through an oil passage 99 provided in the pressure control valve 91 and also communicate with the left chamber 64, and each land portion 94, 95 is provided with a hole 100 and a hole 101, respectively. . The hole 100 connects the cylinder chamber 97 and the supply chamber 96, and the hole 101 connects the cylinder chamber 97 and the discharge chamber 98. Now, assuming that the pressure is being increased, the pressure oil from the hydraulic pump 69 is guided to the supply chamber 96 via the oil passage 68 and the supply auxiliary chamber 67. The pressure oil guided to the supply chamber 96 is guided to the cylinder chamber 97 via the hole 100, is guided to the cylinder chamber 97 via the oil passage 99, the discharge chamber 98, and the hole 101, and passes through the oil passage 74 to the cylinder 76. It is led to the working chamber 77. At this time, due to the holes 100 and 101, the pressure difference Δ between the supply chamber 96 (the same pressure in the discharge chamber 98) and the cylinder chamber 97
P is generated, the pressure on the upstream side of each hole 100, 101 is guided to the left chamber 64 via the oil passage 99, and the pressure on the downstream side is guided to the right chamber 61 via the oil passages 74 and 75. . Therefore, the axial force F corresponding to the pressure ΔP resisting the fluid force R generated in the spool valve 92 acts on the spool valve 92 to compensate the fluid force R. On the other hand, when the pressure is reduced, there is a feature of this embodiment, which will be described in detail. Now, the current i of the solenoid 52 that has obtained the predetermined control pressure Ps
Is reduced to a predetermined value, the electromagnetic force Fs in the above equation decreases. Therefore, the electromagnetic force Fs of the solenoid 52 and the hydraulic force (that is, [Ps · (A ₂ −
A ₁ ))) is lost and the spool valve 53 slides in the direction of arrow B in FIG. 5, and the discharge chamber 98 and the discharge auxiliary chamber 70 communicate with each other. At this time, the pressure oil supplied into the working chamber 77 of the cylinder 76 is guided to the cylinder chamber 97 through the oil passage 74, and the hole 101
Is led to the discharge chamber 98 through the hole 100, the supply chamber 9
6. It is guided to the discharge chamber 98 through the oil passage 99. The pressure oil guided to the discharge chamber 98 passes through the discharge auxiliary chamber 70 and the oil passage 71, and is stored in the reservoir tank.
The pressure difference ΔP is generated between the cylinder chamber 97 and the discharge chamber 98 (the supply chamber 96 has the same pressure) by the holes 100 and 101, and the pressure difference ΔP corresponds to the flow rate of the pressure oil. In addition, the discharge chamber 98 to the discharge auxiliary chamber 70
A fluid force R is generated according to the flow rate of the pressure oil flowing to the spool valve 92, and acts on the spool valve 92 in the direction of arrow A in the figure contrary to the pressure increase. Here, if the pressure in the discharge chamber 98 is P _S1 and the pressure in the cylinder chamber 97 is P _S2 , the pressure in the supply chamber 96 is P _S1, and the pressure generated before and after each hole 100, 101. The difference ΔP is expressed by the following equation. ΔP = P _S2 −P _S1 ...... Therefore, if the pressure receiving area on the solenoid 52 side end surface of the spool valve 92 is A ₁ and the pressure receiving area on the large diameter portion 56 side end surface of the spool valve 92 is A ₂ , the spool valve 92 will be The acting force is expressed by the following equation. Fs + P _S1 · A ₁ = P _S2 · A ₂ −R ...... The following formula 'is obtained by rearranging and modifying the above formula for the electromagnetic force Fs as in the pressure boosting of the first embodiment. 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 92 as in the case of increasing the pressure in the first embodiment. However, since the pressure generated before and after each hole 100, 101 is on the cylinder 76 side, P _S1 < It becomes P _S2 .
Therefore, [(P _S2 −P _S1 ) · A ₁ ]> 0 holds, and this axial force F acts in the opposite direction to the fluid force R, and the fluid force R is canceled. Fluid force R and axial force F
However, the influence of the fluid force R is almost cancelled. Therefore, the cylinder pressure is reduced to a predetermined pressure without changing by the fluid force R. As described above, in this embodiment, the spool valve 92 is provided with the hole 100 and the hole 1
Since 01 is provided and the pressure oil at the time of pressure increase / decrease is configured to pass through the holes 100 and 101, in addition to the same operation and effect as those of the first and second embodiments, it is generated when the control pressure is decreased. Fluid force R
The effect of is reduced as well as when increasing pressure. Therefore, when increasing pressure,
The responsiveness of the current proportional control by the pressure control valve 91 is greatly improved regardless of the pressure reduction. The pressure control valve 51, the pressure control valve 81, and the pressure control valve 91 in the first, second, and third embodiments described above are different only in the shapes of the spool valves 53, 82, and 92, and the body 54 The solenoid 52 can be shared. Therefore, by selecting an appropriate one from the spool valves 53, 82, 92, it is possible to provide a pressure control valve according to the application. This means that when various pressure control valves are provided, the types of parts can be reduced and the cost can be reduced. (Effect) According to the present invention, the spool valve is provided with a throttle, and the pressure on the cylinder side of the throttle is applied to the pressure receiving surface of the spool valve that acts in the direction opposite to the direction of the electromagnetic force of the solenoid, and the pressure on the opposite side to the cylinder side is exerted. 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 which has a simple structure while maintaining the miniaturization of the solenoid and which has an improved current proportional control characteristic at a 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 the control pressure with respect to the current, and FIG. 4 is a sectional view of the essential parts showing the second embodiment of the pressure control valve according to the present invention.
FIG. 6 is a sectional view of a main part of a third embodiment of a pressure control valve according to the present invention, FIGS. 6 to 8 are views showing a conventional pressure control valve, and FIG. When the cylinder pressure is applied to the spool valve of the control valve so as to oppose the electromagnetic force, FIG. 7 is a cross-sectional view of the main part, and FIG. 7 shows the case where the electromagnetic force for sliding the spool valve of the second pressure control valve is reduced. FIG. 8 is a cross-sectional view of an essential part of FIG. 8, and FIG. 8 is a block diagram when the fluid force acting on the spool valve of the third pressure control valve is electrically compensated. 51, 51, 91 ... pressure control valve, 52 ... solenoid, 53, 82, 92 ... spool valve, 56 ... large diameter part, 58, 83, 94, 95 ... land part, 61 ... right chamber , 63, 100, 101 …… hole (throttle), 64 …… left chamber, 65,74,75,99 …… oil passage, 84 …… throttle.

Claims (1)

(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 to the cylinder is proportional to the solenoid current. In a pressure control valve to be controlled, a predetermined throttle is formed in the spool valve, and the pressure on the cylinder side of the throttle is guided to one 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. At the same time, the pressure opposite to the cylinder side of the throttle is guided to the other pressure receiving surface of the spool valve that acts in the same direction as the electromagnetic force of the solenoid, and opposes against the fluid force of the pressure oil generated in the spool valve. Directional The pressure control valve, characterized in that a force is generated in the spool valves so as to compensate for the flow strength.