JP2553342B2 - 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 aptitude is required also 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 the figure, a spool valve 2 housed in a body 1
When the solenoid 3 is turned on, the electromagnetic force corresponding to the current value pushes the spool valve 2 to the right in the figure to connect the supply port 4 and the cylinder port 5, thereby connecting the hydraulic pump 6 to the cylinder 7. Pressure oil is supplied, the piston 8 moves, and the vehicle height changes. 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
Control pressure (pressure to cylinder 7) according to current in
Cannot be generated. That is, in the pressure control valve of FIG. 1, the spool valve 2 has the same pressure-receiving area in the left-right movement direction, and the cylinder pressure is applied to the right side of the pressure-receiving area to perform current-pressure proportional control. . 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 fluid force R of the pressure oil is not taken into consideration, and the target control pressure fluctuates and the responsiveness deteriorates. There are also points. 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 the figure, a piston hole is provided inside the spool valve 21.
22 is formed, and the small piston 23 is housed therein. The right chamber 24 and the left chamber 25 of the spool valve 21 are oil passages connected to the discharge port 26.
It communicates through 27. 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 oil 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 7 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 8 in the cylinder 7 operates, the pressure oil having a flow rate according to the moving speed of the piston 8 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 8 operates, the solenoid is calculated according to 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 7 to the cylinder port 30, the symbol (-) is from the cylinder 7 to the reservoir tank 14. 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, this method is not an effective solution because there is a new problem that the cost becomes high due to processing, or the effect of processing can be expected only within a predetermined flow rate and pressure range. 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 the vehicle height adjusting device 42, and the vehicle height adjusting device 42 performs the posture 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 supplied 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 fluctuation with the target pressure P with respect to the control voltage Vc, and the response 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. The above problems are examples when the pressure control valve is applied to a vehicle height adjusting device and the like.However, since the pressure control valve is applied in a wide range of other control fields, the above-mentioned improvement should be made. Or desirable. In particular, the fluid force R is determined by the flow rate Q, the flow velocity v, etc. as shown in the above equation, and the fluid force R also changes if these conditions change. Further, since these various conditions are different when the control pressure is increased and when the control pressure is reduced, it is desirable that the influence of the fluid force R be appropriately reduced according to the magnitude of the fluid force R. (Object of the Invention) Therefore, the present invention provides a throttle valve having a throttle whose opening area changes in accordance with the increase or decrease of the control pressure in the middle of an oil passage connecting the spool valve and the cylinder for each passage direction of the pressure oil. The side pressure acts on the pressure receiving surface of the spool valve that acts in the same direction as the electromagnetic force of the solenoid, and the cylinder side pressure of the throttle acts on the other pressure receiving surface of the spool valve. A force proportional to the current proportional control characteristic over the entire control range of the cylinder control pressure is achieved at a low cost by compensating the fluid force by generating an axial force corresponding to the above in the spool valve and compensating for the fluid force, while maintaining the miniaturization of the solenoid. It is an object of the present invention to provide a pressure control valve capable of improving the performance of. (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 moving direction of the solenoid, and the control pressure of the cylinder is applied to the difference in the pressure receiving area in the other moving direction opposite to the direction of the electromagnetic force to move the spool valve to change the passage area of the pressure oil. In a pressure control valve that proportionally controls the control pressure of the pressure oil supplied to the cylinder from the cylinder port according to the solenoid current, the throttle amount of the throttle amount is changed in the direction of the pressure oil in the middle of the oil passage connecting the cylinder port and the cylinder. Different restricting means are provided, and the restricting means restricts the flow rate from the cylinder port to the cylinder, and the restricting amount is variable in accordance with the cylinder control pressure. Direction in which the electromagnetic force of the solenoid acts on the pressure on the spool valve side from the regulating means, which is constituted by second throttling means for throttling the flow rate from the cylinder to the cylinder port and varying the throttling amount according to the cylinder control pressure. Guides to one pressure receiving surface of the spool valve that acts in the same direction as, and a spool valve that acts on the cylinder side pressure from the throttle in the direction opposite to the direction in which the electromagnetic force of the solenoid acts, leads to the other pressure receiving surface, 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, a throttle whose opening area changes in accordance with the increase / decrease in control pressure is provided in the middle of the oil passage connecting the spool valve and the cylinder, and the pressure on the spool valve side of the throttle is reduced. Acts in the direction in which the solenoid electromagnetic force of the spool valve acts, and the cylinder side pressure of the throttle acts in the direction opposite to the spool valve. Therefore, regardless of the passage direction of the pressure oil, the opposing axial force corresponding to the magnitude of the fluid force is always appropriately generated in the spool valve to compensate the fluid force, and the solenoid can be downsized while maintaining a simple structure. In addition, the current proportional control characteristic over the entire control range of the cylinder control pressure can be obtained at low cost, and 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 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 in the central chamber 62 via a cylinder port 70, and the oil passage 71 is connected with an oil passage 72 and an oil passage 73. A check valve 74 and a throttle 75 are provided in the middle of the oil passage 72, and a check valve 76 and a throttle 77 are provided in the middle of the oil passage 73. Aperture 75 is first
The diaphragm 77 has a function as a diaphragm means, the diaphragm 77 has a function as a second diaphragm means, and the diaphragm 75 and the diaphragm 77 constitute a restricting means. The oil passage 72 and the oil passage 73 communicate with the oil passage 78, and the oil passage 78 communicates with the oil passages 71, 72 and 73, the central chamber 62 and the working chamber 80 of the cylinder 79. The cylinder 79 has a piston 81, which defines the working chamber 80 and is displaced according to the pressure in the working chamber 80. A piston rod 82 is connected to the piston 81, and the piston rod 82 is connected to, for example, a vehicle height adjusting device. The check valve 74 opens the oil passage 72 to guide the pressure oil from the central chamber 62 to the working chamber 80 of the cylinder 79 when the pressure on the central chamber 62 side of the check valve 74 is higher than the pressure on the cylinder 79 side. The check valve 76 is a check valve.
When the pressure on the cylinder 79 side of 76 is higher than the pressure on the central chamber 62 side, the oil passage 73 is opened to guide the pressure oil from the working chamber 80 of the cylinder 79 to the central chamber 62. In the throttles 75 and 77, the pressure in the central chamber 62 is the oil passage.
It is guided by the oil passage 83 and the oil passage 84 via 71, respectively.
The aperture area of the throttle 75 increases as the pressure in the central chamber 62 increases, and the aperture area of the throttle 77 decreases as the pressure in the central chamber 62 increases. The spool valve side pressure of each throttle 75, 77 is guided to the left chamber 60 via the oil passage 85, and the cylinder 79 side pressure is guided to the right chamber 58 via the flow path 86. Next, the operation will be described. The hydraulic pressure control of the pressure control valve 51 for the cylinder 79 is performed as follows. 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, since the central chamber 62 and the supply chamber 63 communicate with each other, the pressure oil from the hydraulic pump 66 passes through the oil passage 65, the supply chamber 63, the central chamber 62, and the oil passage 71, and the throttle 75, the check valve 74, and the oil passage 78. And is supplied to the cylinder 79. Therefore, the piston 81 of the cylinder 79 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 72 is generated before and after the throttle 75 provided in the oil passage 72. That is, since the pressure on the upstream side of the throttle 75 becomes higher than the pressure on the downstream side by ΔP,
75 Spool valve 53 side pressure is P _S1 , throttle 75 cylinder 79
If the pressure on the side is P _S2 , the pressure difference ΔP is expressed by the following equation. ΔP = P _S1 −P _S2 …… Here, the pressures P _S1 and P _S2 before and after the throttle 75 are oil passages, respectively.
85, is guided to the left chamber 60 and the right chamber 58 by the oil passage 86, and the pressure receiving area of the solenoid side end surface of the spool valve 53 is A ₁ ,
Assuming that the pressure receiving area of the end surface of the spool valve 53 on the large diameter portion 56 side is A ₂ , the force acting on the spool 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 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 equation, [(P _S2 −P _S1 ) ・
A ₁ ] indicates that the pressure difference ΔP generated before and after the throttle 75 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. By the way, the fluid force R changes according to the flow rate Q, the flow velocity v, etc. as shown in the above equation, and is proportional to the flow rate Q and the flow velocity v. Here, the flow velocity v is expressed by the following equation. However, Pp: Supply pressure of hydraulic pump P _S1 : Pressure on spool valve side of throttle Cv: Flow coefficient ρ: Density of pressure oil Therefore, if [Pp-P _S1 = ΔPc], then the differential pressure ΔPc Is large (that is, the control pressure P _S1 is small because the supply pressure Pp is constant), the flow velocity v increases and the fluid force R increases. Further, when the differential pressure ΔPc is small (the control pressure P _S1 is large), the flow velocity v becomes slow and the fluid force R
Becomes smaller. The sum of these is the fluid forces R ₁ , R ₂ , R ₃ (simply R ₁ , R ₂ , R _{3 in the} figure) shown by the solid lines in Fig. ₂ , which are proportional to the flow rate Q and the differential pressures. ΔP _C1 ,
It corresponds to ΔP _C2 and ΔP _C3 (simply ΔP _C1 , ΔP _C2 and ΔP _C3 in the figure). In this way, the fluid force R changes with the differential pressure Pc even if the flow rate Q is constant. On the other hand, the relationship between the pressure difference ΔP generated before and after the throttle 75 and the flow rate Q of the pressure oil flowing through the throttle 75 has the following equation. However, C: flow rate coefficient a: aperture area of the throttle. As described above, since the pressure difference ΔP is proportional to the square of the flow rate Q, the axial force F described above is proportional to the square of the flow rate Q. Also,
Even if the flow rate Q is constant, the pressure difference ΔP changes by changing the opening area of the throttle 75. That is, the axial force F described above can be changed by changing the opening area of the diaphragm 75. Therefore, when the differential pressure ΔPc changes and the fluid force R acting on the spool valve 53 changes, the throttle is changed according to the differential pressure ΔPc.
The fluid force R is effectively compensated by changing the opening area of 75. That is, the restriction 75 is provided to the restriction 75 by the oil passage 83.
The pressure on the spool valve 53 side (control pressure P _S1 ) is introduced, and the opening area of the throttle 75 changes according to the control pressure P _S1 . In this case, the relationship between the opening area a of the throttle 75 and the control pressure P _S1 is that the opening area a increases as the control pressure P _S1 increases, as indicated by the straight line T in FIG. In this way, when the control pressure P _S1 increases, the opening area a increases in accordance with the control pressure P _S1 , so the pressure difference ΔP = (P _S1 −P _S2 ) decreases. On the other hand, the fluid force R decreases as described above in accordance with the increase of the control pressure P _S1 , so that the difference between the supply pressure Pp and the control pressure P _S1 , that is, the fluid force R decreases as the differential pressure ΔPc decreases. The axial force F also decreases according to the differential pressure ΔPc. Fig. 2 shows such a relationship between the two. The differential pressure ΔP _C1 ,
The axial forces F ₁ , F ₂ , F ₃ (simply F ₁ , F ₂ , F _{3 in the} figure) corresponding to ΔP _C2 and ΔP _C3 , respectively, are indicated by broken lines. As is clear from the figure, the fluid force R and the axial force F associated with the change in the differential pressure ΔPc are not exactly the same, but
The axial force F corresponding to the change in the fluid force R is generated and is approximate. Therefore, most of the fluid force R is canceled by the axial force F, and the actual force acting on the spool valve 53 corresponds to the portion sandwiched between the two curves. That is, [fluid force R-
Axial force F], which is extremely smaller than the fluid force R. Therefore, the following expression 'is obtained as an approximate expression from the above expression. Fs ＝ P _S2・ (A ₂ −A ₁ ) …… ′ That is, the cylinder pressure P _S2 is the electromagnetic force Fs of the solenoid.
The target control pressure can be prevented from fluctuating due to the influence of the fluid force R, and the responsiveness of the pressure control valve 51 is significantly improved. In this way, the control pressure according to the current input to the solenoid 52 is applied to the cylinder 79, which displaces the piston 81 of the cylinder 79 and causes the piston rod 82 to displace the piston 81.
When the force acting on 81 in the direction of arrow D in FIG. 1 becomes the same as the force acting on piston 81 in the direction of arrow C by the supplied pressure oil, piston 81 stops. At this time, oil passage
The flow rate Q of pressure oil in 71 is

Since it becomes [0], the pressure difference ΔP and the fluid force R generated before and after the throttle 75 are both

It becomes [0]. That is, the same pressure as the pressure Ps acting on the working chamber 80 of the cylinder 79 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 =
The following equation is obtained with Ps and R = 0. Fs + P _S1・ A ₁ = P _S2・ A ₂ ∴Fs = Ps ・ (A ₂ −A ₁ ) ... In the above formula, the electromagnetic force Fs is generated in proportion to the electric current. Since Ps is proportional to Ps, control pressure Ps proportional to the current supplied to the solenoid 52 is generated. The above has described the case where the cylinder control pressure is increased. Next, the case where the pressure is reduced will be described. When the current of the solenoid 52 that has obtained a predetermined cylinder control pressure 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, and the spool valve 53 moves in the direction of arrow B in FIG.
The central chamber 62 and the discharge chamber 64 communicate with each other by sliding in the direction. At this time, the pressure oil supplied into the working chamber 80 of the cylinder 79 passes through the throttle 77, the check valve 76, the oil passage 71, the central chamber 62, the discharge chamber.
64, it is discharged to the reservoir tank 68 via the oil passage 67,
A pressure difference ΔP occurs before and after the throttle 77. Also, the central room 62
A fluid force R corresponding to the flow rate of the pressure oil flowing from the discharge chamber 64 to the discharge chamber 64 is generated and 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 pressure increase, but the pressure generated before and after the throttle 77 is upstream on the cylinder 79 side, and therefore P _S1 <P _S2 . 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. By the way, the differential pressure ΔPc generated before and after the spool valve 53
The central chamber 62 has a large value at the beginning when the discharge chamber 64 communicates, but the control pressure P _S1 decreases and the differential pressure ΔPc also gradually decreases as the pressure oil is discharged. Therefore, the fluid force acting on the spool valve 53 also initially has a large value, but gradually decreases as the differential pressure ΔPc decreases. On the other hand, the opening area of the diaphragm 77 decreases as the control pressure P _S1 increases, as indicated by the straight line R in FIG. That is, when the control pressure P _S1 decreases, the aperture area a of the throttle 77 becomes [a ₁ ], [a ₂ ] and then [a ₃ ] and gradually increases. Therefore, the pressure difference ΔP generated before and after the throttle 77 decreases as the control pressure P _S1 decreases, and the axial force F acting on the spool valve 53 also decreases due to the pressure difference ΔP. As a result, the fluid force R acting on the spool valve 53
Axial force F is generated in the opposite direction with respect to, and of substantially the same magnitude. That is, 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 canceled as in the pressure increase. Therefore, the cylinder pressure is reduced to a predetermined pressure without changing by the fluid force R. Due to the operation of the pressure control valve 51 as described above, 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 When the throttles 75 and 77 are provided in the middle of the oil passage 71, and 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 the pressure difference. Therefore, the influence of the fluid force can be made extremely small. Therefore, the responsiveness of the pressure control valve 51 is greatly improved (problem II is solved). (C) Effect 3 Since the cancellation of the fluid force is performed by providing the throttle 75 and the throttle 77, the configuration is simple. Therefore, it is possible to provide the low-cost pressure control valve 51 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 throttles 75 and 77 are provided between the spool valve 53 and the cylinder 79, there is no loss of flow rate of the pressure oil supplied from the hydraulic pump 66. In addition, the pressure difference generated before and after each throttle 75, 77 can be almost ignored (3 kg / cm in practical use).
² or less). Therefore, the problem of pressure loss can be ignored. (E) Effect 5 Since the throttle 75 and the throttle 77 are provided according to the cylinder pressure increase and the cylinder pressure decrease, respectively, and the opening areas of the throttles 75 and 77 are changed according to the control pressure P _S1 , the control pressure It is possible to generate the axial force F according to the fluid force R accompanying the change of P _S1 . Therefore, it is possible to compensate the influence of the fluid force R over the entire control range due to the increase or decrease of the cylinder control pressure. In the first embodiment described above, the throttle for compensating the fluid force is integrally formed with the pressure control valve. Next, as the second and third embodiments, the throttle valve having a function as a throttle is used as a pressure control valve. The case where they are separately provided will be described. The same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. FIG. 4 is a diagram showing a second embodiment of the pressure control valve according to the present invention. In the figure, 90 is a pressure control valve, 91 is a throttle valve, and the throttle valve 91 comprises a housing 92, a piston 93 and a spring 94. The piston 93 is slidably accommodated in the housing 92 and defines a supply chamber 95, a main chamber 96, an auxiliary chamber 97 and a spring chamber 98, respectively. Spring chamber
A spring 94 is housed in 98, and the spring 94 urges the piston 93 in the direction of arrow A in the figure. When the pressure is increased, the pressure oil from the hydraulic pump 66 controlled by the pressure control valve 51 is guided to the supply chamber 95 by the oil passage 99, and the pressure oil guided to the supply chamber 95 is supplied to the main chamber 96 and the oil passage 100. Working chamber 8 of cylinder 79 via check valve 101 provided on the way
Supplied to 0. The pressure oil supplied to the working chamber 80 is the piston 8
1 is displaced in the direction of arrow C in the figure, and power is applied to, for example, a vehicle height adjusting mechanism connected to the piston rod 82. Supply room
95 and the main chamber 96 communicate with each other in a predetermined communication area, and the oil passage 10
When the pressure on the pressure oil control valve 51 side of the throttle valve 91 guided by 2 increases, the pressure in the auxiliary chamber 97 increases, and the piston 93 slides in the direction of arrow B in the drawing, increasing the communication area between the two. On the other hand, when the pressure is reduced, a force in the direction of the arrow D in the drawing is applied to the piston rod 82, and when the piston 81 is displaced, pressure oil is guided to the throttle valve 104 via the oil passage 103. The throttle valve 104 is a housing
An auxiliary chamber A108 is formed in the housing 105, which includes a piston 105, a piston 106, and a spring 107. Housing 1
The piston 106 is slidably stored in 05
The front end portion thereof projects into the auxiliary chamber A108 and defines the discharge chamber 109, the main chamber 110, the auxiliary chamber B111 and the spring chamber 112. A spring 107 is housed in the spring chamber 112, and the spring 107 biases the piston 106 in the direction of arrow B in the figure. The pressure guided to the throttle valve 104 via the oil passage 103 is guided to the main chamber 110, and to the reservoir tank 68 via the discharge chamber 109, the check valve 114 and the pressure control valve 90 provided in the middle of the oil passage 113. Return. The discharge chamber 109 and the main chamber 110 communicate with each other in a predetermined communication area. When the pressure control valve 90 side pressure of the check valve 114 guided by the oil passage 115 increases, the pressure in the auxiliary chamber A108 increases, and the piston 106 Slides in the direction of arrow A in the figure, and the communication area between the two becomes smaller. The pressure on the cylinder 79 side of each throttle valve 91, 104, that is, the pressure in the working chamber 80 of the cylinder 79 is guided to the right chamber 58 of the pressure control valve 90 by the oil passage 116, and each throttle valve 91, throttle valve 10 is connected.
In the spring chamber 98 and the auxiliary chamber B111 of 4, the oil passage 11
7. It communicates with the reservoir tank 68 via the oil passage 118. As described above, the throttle valve 91 and the throttle valve 104 whose opening area changes in time according to the increase and decrease of the cylinder pressure.
Are independently provided, and the pressure difference across the throttle valves 91 and 104 acts on the spool valve 53 of the pressure control valve 51.
The fluid force acting on the spool valve 53 is compensated. Therefore, in addition to the effects of the first embodiment, the following effects can be obtained. That is, since the throttle valves 91 and 104 for compensating the fluid force are provided separately from the pressure control valve 90, the pressure control valve 90 can be downsized. In addition, each throttle valve
Since the 91 and the throttle valve 104 are also small in size, it is possible to increase the degree of freedom of attachment when these are assembled to the device. Further, in terms of compensation of fluid force, it is relatively easy to apply to the conventional pressure control valve. FIG. 5 is a diagram showing a third embodiment of the pressure control valve according to the present invention. In the figure, 120 is a pressure control valve, 121 is a throttle valve, the throttle valve 121 is a housing 122, a piston 123,
It is composed of a spring 124 and the like. The piston 123 is slidably accommodated in the housing 122 and defines a main chamber 125 and a spring chamber 126. Spring 12 in spring chamber 126
4, the spring 124 urges the piston 123 in the direction of arrow C in the figure. A rod 127 is fixed to the main chamber 125 side of the piston 123, and a spherical valve body 128 is fixed to the tip of the rod 127. When the pressure is increased, the pressure oil from the hydraulic pump 66 controlled by the pressure control valve 120 is guided to the main chamber 125 by the oil passage 129,
The pressure oil guided to the main chamber 125 is supplied to the working chamber 80 of the cylinder 79 via the port 130 provided at the position where the valve body 128 of the housing 122 faces and the check valve 132 provided in the middle of the oil passage 131. To be done. The pressure oil supplied to the working chamber 80 displaces the piston 81 in the direction of arrow C in the figure, and gives power to the vehicle height adjusting mechanism connected to the piston rod 82. The opening area of the port 130 with respect to the main chamber 125 increases as the pressure on the pressure oil control valve 120 side of the throttle valve 121 guided by the oil passage 129 increases, and the piston 123 slides in the direction of arrow D in the figure. As a result, the opening area becomes large. On the other hand, when the pressure is reduced, a force in the direction of the arrow D in the figure is applied to the piston rod 82, and when the piston 81 is displaced, pressure oil is guided to the throttle valve 134 via the oil passage 133. The throttle valve 134 is a housing
135, piston 136, spring 137, etc. A piston 136 is slidably accommodated in the housing 135, and the piston 136 defines a main chamber 138 and an auxiliary chamber 139. A spring 137 is stored in the main chamber 138.
137 urges the piston 136 in the direction of arrow D in the figure. A spherical valve element 140 is fixed to the end of the piston 136 on the main chamber 138 side, and a port is provided at a position facing the valve element 140 of the housing 135.
141 is provided. The pressure oil guided to the throttle valve 134 by the oil passage 133 returns to the reservoir tank 68 via the port 141, the main chamber 138, the check valve 143 provided in the middle of the oil passage 142, and the pressure control valve 120. The opening area of the port 141 with respect to the main chamber 138 (hereinafter, referred to as an effective opening area) is such that when the pressure control valve 120 side pressure of the throttle valve 134 guided by the oil passage 144 increases, the pressure in the auxiliary chamber 139 increases, and the piston 136 moves. Arrow C in the figure
Slide in the direction to reduce the effective opening area. The pressure on the cylinder 79 side of each throttle valve 121, 134, that is, the pressure in the working chamber 80 of the cylinder 79 is guided to the right chamber 58 of the pressure control valve 51 by the oil passage 145, and the spring chamber 126 of the throttle valve 121 is It communicates with the reservoir tank 68 via the oil passage 146. As described above, the throttle valve 121 and the throttle valve 134 whose opening area changes timely according to the increase and decrease of the cylinder pressure.
Are independently provided, and the pressure difference across the throttle valves 121 and 134 acts on the spool valve 53 of the pressure control valve 51, so that the fluid force acting on the spool valve 53 is appropriately compensated.
In addition, the function as a throttle is provided for each valve element 128, 140 and each port 13
Since it is realized by 0, 141, each piston 123, 136
The influence of the fluid force acting on is small. Therefore, in addition to the effects of the first and second embodiments, the following effects can be obtained. That is, the fluid force is generated when the area of the flow path of the fluid changes, and the fluid force also acts on the pistons 123 and 136 of the throttle valves 121 and 134.
However, the effective opening area of each port 130, 141 is
8 and 140, and since each valve element 128, 140 is spherical, the influence of fluid force can be reduced. Therefore, the pressure control valve 51 of each throttle valve 121, 134 is
The throttle area can be obtained according to the side pressure, and the pressure control valve
The compensation of the fluid force acting on the spool valve 53 of 51 can be made appropriate. (Effects) According to the present invention, a throttle whose opening area changes according to the increase or decrease of the control pressure in each passage direction of the pressure oil is provided in the middle of the oil passage connecting the spool valve and the cylinder, and the throttle valve side of the throttle is provided. The pressure acts on the pressure receiving surface of the spool valve that acts in the same direction as the electromagnetic force of the solenoid, and the cylinder side pressure of the throttle acts on the other pressure receiving surface of the spool valve. Regardless of this, it is always possible to appropriately generate an opposing axial force corresponding to the magnitude of the fluid force 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 has a low cost and which has an improved current proportional control characteristic over the entire control range of the cylinder control pressure.

[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 between the control pressure and the opening area of each throttle, FIG. 4 is a sectional view of the essential parts showing a second embodiment of the pressure control valve according to the present invention, and FIG. A principal part sectional view showing a third embodiment of such a pressure control valve, FIGS. 6 to 8 are views showing a conventional pressure control valve, and FIG. 6 is a spool valve of the first pressure control valve. Cross-sectional view of the main part when the cylinder pressure is applied to oppose the electromagnetic force, and FIG. 7 is a cross-sectional view of the main part when the electromagnetic force for sliding the spool valve of the second pressure control valve is reduced. 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, 90, 120 ... Pressure control valve, 52 ... Solenoid, 53 ... Spool valve, 56 ... Large diameter part, 58 ... Right chamber, 60 ... Left chamber, 70 ... Cylinder port, 72, 73 , 86, 116, 145 …… Oil passage, 74, 76, 101, 114, 132, 134 …… Check valve, 75, 77 …… Throttle, 91, 104, 121, 134 …… Throttle valve.

 ─────────────────────────────────────────────────── --- Continuation of the 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) JP 63-211005 (JP, A)

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 is applied to the difference of the pressure receiving area in the other moving direction to change the passage area of the pressure oil by moving the spool valve, and the control pressure of the pressure oil supplied from the cylinder port to the cylinder depends on the solenoid current. In a pressure control valve that performs proportional control by means of a proportional control, a regulating means having a different throttling amount in the passage direction of pressure oil is provided in the middle of an oil passage connecting the cylinder port and the cylinder, and the regulating means is a flow rate from the cylinder port to the cylinder. And a first throttling means for varying the throttling amount according to the cylinder control pressure, and throttling the flow rate from the cylinder to the cylinder port to control the throttling amount. It is composed of a second throttle means that is variable according to the pressure, and guides the pressure on the spool valve side from the regulating means to one pressure receiving surface of the spool valve which acts in the same direction as the electromagnetic force of the solenoid. At the same time, the pressure on the cylinder side from the throttle is guided 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, and the shaft in the opposite direction resists the hydraulic fluid force generated in the spool valve. A pressure control valve characterized in that a force is generated in a spool valve to compensate for the fluid force.