JP2005226741A - Flow control valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the supplied amount of a hydraulic oil to an actuator by controlling to reduce the flow rate of the hydraulic oil passed through an orifice passage when a pump discharge pressure is high. <P>SOLUTION: This flow control valve comprises a spool valve 3 moving according to a pressure difference between an operation chamber 4 and a back pressure chamber 10, a lead-in passage 5 leading a working fluid discharged from a pump into the operation chamber, a lead-out passage 6 leading the necessary working fluid led into the operation chamber to hydraulic equipment, a drain passage 7 for draining an excess fluid led into the operation chamber, and a variable orifice mechanism 8 varying the opening area of the orifice passage 18 formed in the lead-out passage by a needle valve 19. The needle valve is moved forward and backward independently of the spool valve, and moves in the axial direction by the pressure difference between a pressure on the drain passage side of a communication chamber 16 applied to a rear end part 19b and a pressure on the downstream side of the orifice passage applied to a tip part 19a to gradually vary the opening area of an orifice. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a flow rate control valve that controls a discharge flow rate of working liquid discharged from an engine-driven oil pump or the like to an actuator.

  In a power steering device and many other hydraulic devices mounted on an automobile, hydraulic fluid is introduced by, for example, a pump device using an engine as a drive source. In this case, since the rotational speed of the engine and the pump device driven by the engine varies greatly depending on the driving situation of the vehicle, it is necessary to control the flow rate of hydraulic fluid introduced between the discharge unit of the pump device and, for example, the hydraulic device. A flow control valve is provided.

  In this type of flow control valve, the spool valve is housed in a valve hole formed in the valve housing so as to be movable in the axial direction, and hydraulic oil discharged from the pump device is formed on the front end side of the spool valve. An introduction passage to be introduced into the working chamber, a lead-out passage through which hydraulic oil is led out from the working chamber to the hydraulic equipment side, an orifice passage formed in the middle of the lead-out passage, and a tip end side of the spool valve A needle valve that is integrally fixed in the axial direction and that changes the opening area of the orifice passage by a tapered outer peripheral surface of the tip.

  A back pressure chamber is formed on the opposite side of the working chamber across the spool valve. The back pressure chamber biases the spool valve toward the working chamber, that is, via a seal valve body. A valve spring that biases the drain passage in the closing direction is accommodated, and a signal hydraulic pressure downstream of the orifice passage is introduced through the signal passage.

  Therefore, the liquid pressure-fed from the pump device is introduced into the working chamber through the introduction passage, and the liquid pressure acts on the pressure receiving surface of the spool valve, while the liquid is sent from the outlet passage to the hydraulic equipment through the orifice passage. It is done.

  For example, when the rotational speed of the pump device is low, the differential pressure across the orifice passage is small, so the spool valve closes the drain passage, and all the working fluid in the working chamber is removed from the outlet passage through the orifice passage. Supply to hydraulic equipment.

On the other hand, when the number of rotations of the pump device increases, the pump discharge pressure in the working chamber increases, and the differential pressure across the orifice passage increases beyond the set pressure, the spool valve resists the spring force of the valve spring and the drain passage Is opened to discharge a part of the liquid in the working chamber to the drain passage, and the needle valve moves backward in the same direction together with the spool valve to narrow the opening area of the orifice passage. For this reason, it is controlled so that the flow rate of the liquid sent from the working chamber to the hydraulic device via the outlet passage is reduced.
Japanese Utility Model Publication No. 4-37075 (see FIG. 2)

  However, in the conventional flow rate control valve, the front-rear differential pressure acting before and after the spool valve is substantially constant regardless of the pump discharge pressure (pump rotation speed). As compared with this, the differential pressure across the spool valve with respect to the pump discharge pressure does not change.

  Therefore, as shown in FIG. 5, although the pump discharge pressure is increased to, for example, 1.8 MPa or 3.9 MPa, the spool valve does not move backward greatly, so that it is integrated with the spool valve. The needle valve cannot be moved backward sufficiently. For this reason, the opening area of the orifice passage cannot be narrowed down sufficiently. As a result, there is a possibility that the supply amount from the outlet passage to the hydraulic device becomes a flow rate larger than desired.

  In particular, when the flow control valve is applied to a power steering device, the supply flow rate to the hydraulic equipment such as an actuator is large even when the pump device rotates at a high speed and the pump discharge pressure increases when the vehicle is traveling at high speed. Thus, the operation load is temporarily reduced during operation of the steering wheel, and the steering feeling may be deteriorated.

  The present invention has been devised in view of the actual state of the conventional flow control valve, and in particular, the variable orifice mechanism is connected to the spool valve so as to be relatively movable, and the opening area of the outlet passage is reduced. The spool valve is configured to change independently of the change of the opening area of the drain passage by the spool valve.

  According to the present invention, the spool valve moves backward by a predetermined amount due to the differential pressure before and after the pump discharge pressure rises, but if no further movement is obtained, the needle valve independent of the spool valve is By moving backward independently, the opening area of the orifice passage is narrowed down sufficiently. This makes it possible to limit the unnecessary supply flow rate of the hydraulic fluid to the hydraulic equipment.

  According to a second aspect of the present invention, the variable orifice mechanism is provided in an orifice passage provided in the outlet passage, and is movable in the axial direction in the orifice passage. The pressure on the drain passage side and the downstream of the orifice passage are provided. And a needle valve that changes the opening area of the orifice as it moves in the axial direction due to a differential pressure across the pressure on the side.

  According to the present invention, the independent moving structure of the needle valve with respect to the spool valve can be formed with a simple structure without almost changing the existing structure, so that an increase in cost can be suppressed.

According to a third aspect of the present invention, there is provided a first spring member that urges the spool valve in the closing direction of the drain passage, while urging the needle valve in a direction in which the opening area of the orifice passage is increased. Two spring members are provided, and the spring force of the second spring member is set larger than that of the first spring member;
When the spool valve moves in the opening direction of the drain passage against the spring force of the first spring member, the opening area of the orifice is increased by the spring force of the second spring member. When the spool valve is further moved in the opening direction of the drain passage, the needle valve has a small opening area against the spring force of the second spring member due to the differential pressure across the spool valve. It is characterized by controlling to become.

  According to this invention, in a region where the pump discharge pressure is low, the spool valve moves backward against the spring force of the first spring member due to the differential pressure across the pump and moves to a position where the drain passage is opened and closed. On the other hand, the needle valve is controlled so as to increase the opening area of the orifice passage without largely retreating by the spring force of the second spring member at such time. Therefore, in this region, it is possible to sufficiently secure the flow rate of the hydraulic fluid with respect to the hydraulic device.

  Next, when the pump discharge pressure increases as the pump rotation increases and exceeds the predetermined pressure, the spool valve does not move backward greatly due to a substantially constant differential pressure, but the drain passage is slightly opened. To discharge the excess liquid in the working chamber. On the other hand, in the needle valve, the hydraulic pressure that has passed through the orifice passage is sufficiently larger than the hydraulic pressure on the low-pressure drain passage side, so that the differential pressure across the needle valve resists the spring force of the second spring member. By moving backward, the opening area of the orifice passage is controlled to be small. Thereby, the supply flow rate to the hydraulic equipment can be controlled sufficiently small.

  Hereinafter, embodiments of a flow control valve according to the present invention will be described with reference to the drawings. In this embodiment, the flow control valve is applied to a power steering device.

  As shown in FIG. 1, this flow control valve is interposed in a passage that connects an oil pump (not shown) that is rotationally driven by the rotational force of the engine and an actuator that is a hydraulic device.

  That is, the oil pump is provided in a spool valve 3 slidably provided in a valve hole 2 formed along the axial direction inside the housing 1 and a working chamber 4 formed on the front end side of the spool valve 3. An introduction passage 5 for introducing the hydraulic oil pressure-fed from, a lead-out passage 6 for deriving the hydraulic pressure in the working chamber 4 to the actuator side, and surplus hydraulic oil in the working chamber 4 on the pump suction side (low pressure side) ) And a variable orifice mechanism 8 which is provided on the working chamber 4 side of the spool valve 3 and controls the flow rate of the hydraulic oil led out to the lead-out passage 6.

  In the valve hole 2, a plug 9 is screwed into an opening, and the annular working chamber 4 is defined between the plug 9 and the front end of the spool valve 3. A back pressure chamber 10 is formed on the opposite side of the sandwiched working chamber 4.

  The plug 9 has a cylindrical projection 9a formed at the tip thereof facing the working chamber 4, and the lead-out passage 6 is formed in the inner axial direction. A signal passage 11 is formed inside the plug 9 and the housing 1 with one end connected to the lead-out passage 6 downstream of the variable orifice mechanism 8 and the other end connected to the back pressure chamber 10. The signal passage 11 causes the discharge pressure of the outlet passage 6 to act on the rear surface of the spool valve 3 via the back pressure chamber 10. A small-diameter restricting portion 11 a that restricts the signal pressure supplied to the back pressure chamber 10 is formed in the signal passage 11.

  The spool valve 3 is formed in a substantially cylindrical shape, and a check valve 12 is provided inside the rear end to release operating hydraulic pressure exceeding a predetermined pressure in the back pressure chamber 10, and the drain passage 7 is provided on the outer periphery of the front end. An annular seal valve body 13 for opening and closing the one end opening 7a is integrally provided.

  The seal valve body 13 is formed in the drain passage 7 according to the position where the entire spool valve 3 slides in the axial direction due to the differential pressure between the signal pressure in the back pressure chamber 10 and the pump discharge pressure in the working chamber 4. One end opening 7a is opened and closed. A pressure receiving surface 13 a that receives the hydraulic pressure (pump discharge pressure) in the working chamber 4 is formed on the end surface of the seal valve body 13 on the working chamber 4 side.

  Inside the back pressure chamber 10, the spool valve 3 is pressed toward the working chamber 4, and is urged by the seal valve body 13 in a direction (closing direction) that blocks the communication between the one end opening 7 a and the working chamber 4. A valve spring 14 as a first spring member is elastically mounted.

  Further, a communication chamber 16 communicating with the drain passage 7 and the radial passage 15 is formed inside the front end side of the spool valve 3.

  As shown in FIG. 3, the variable orifice mechanism 8 includes a substantially cylindrical orifice component 17 that is press-fitted and fixed inside a cylindrical projection 9 a of the plug 9, and an internal axial direction of the orifice component 17. An orifice passage 18 that is formed through and communicates with the working chamber 4 and the outlet passage 6; and a needle valve 19 that slides independently with respect to the spool valve 3 to change the opening area of the orifice passage 18; It has.

  The needle valve 19 is formed substantially in the shape of a rod having a small diameter, and the distal end side is inserted into the orifice passage 18. Further, the tip 19a facing the lead-out passage 6 is formed in a large diameter set to an outer diameter slightly smaller than the inner diameter of the orifice passage 18, and a tapered surface 19c that is widened forward at the base. Is formed. Further, the flat tip surface 19 d of the tip 19 a is formed as a pressure receiving portion that receives the hydraulic pressure in the outlet passage 6.

  When the tip 19a is positioned inside the orifice passage 18, an annular minute gap C is formed between the outer peripheral surface of the tip 19a and the inner peripheral surface of the orifice passage 18. Yes.

  On the other hand, the rear end side is slidably held in an axial hole 20a formed in the inner axial direction of a cylindrical retainer 20 screwed and fixed in the front end opening of the spool valve 3. An annular spring retainer 21 is fixed to the rear end 19 b facing the communication chamber 16. Between the spring retainer 21 and the inner end surface of the communication chamber 16, a spring 22 as a second spring member that urges the needle valve 19 toward the lead-out passage 6 is elastically mounted. The spring force is set larger than that of the valve spring 14.

  As a result, the needle valve 19 basically has a differential pressure between the combined pressure of the hydraulic pressure in the drain passage 7 and the spring force of the spring 22 and the hydraulic pressure that has passed through the orifice passage 18 via the communication chamber 16. It is designed to move forward and backward.

  Therefore, according to this embodiment, in a region where the discharge pressure of the oil pump is low, such as when the vehicle is traveling at a low speed, the spool valve 3 has a differential pressure across the working chamber 4 and the back pressure chamber 10 as shown in FIG. Accordingly, the valve spring 14 moves backward against the spring force of the valve spring 14 and the seal valve body 13 moves to a position where the open end 7a of the drain passage 7 is to be opened, but is still in a closed state.

  On the other hand, as shown by the broken lines in FIGS. 1 and 3, the needle valve does not largely move backward due to the spring force of the spring 22 at such time, and the tip 19 a is positioned in front of the oil pump passage 18 and the orifice passage. The opening area of 18 is controlled to be large. Therefore, in this region, the flow rate of the hydraulic oil with respect to the actuator is sufficiently ensured.

  Next, when the pump discharge pressure increases with a rise in pump rotation when the vehicle is traveling at high speed or the like and exceeds a predetermined pressure, the spool valve 3 is moved to the pressure receiving surface 13a or the like as shown by the solid lines in FIGS. The pressure difference between the pressure of the working chamber 4 received by the front end surface of the retainer 20 and the pressure difference between the back pressure chamber 10 received by the rear end surface is maintained in a substantially constant state, so that there is no significant backward movement. Repeat with vibration. As a result, the seal valve body 13 repeatedly opens and closes the opening end 7 a slightly, and discharges excess oil in the working chamber 4 discharged from the oil pump into the drain passage 7.

  At this time, as shown in FIG. 2, the needle valve 19 moves backward together with the spool valve 3 so that the tip 19 a is not located in the orifice passage 18 and the tapered surface 19 c is located near the opening edge of the orifice passage 18. . However, since the inside of the drain passage 7 is in a low pressure state, the communication chamber 16 is also in a low pressure state via the radial passage 15, while the outlet passage 6 downstream of the orifice passage 18 is in a high pressure state. Therefore, the large differential pressure, that is, the high pressure of the outlet passage 6 is received by the pressure receiving portion 19d at the tip, and the spring 22 is moved backward independently against the spring force of the spring 22.

  Thereby, as shown by the solid line in FIG. 3, the needle valve 19 gradually enters the orifice passage 18 from the tapered surface 19c into the orifice passage 18 to narrow the opening area of the orifice passage 18 and finally opens the minute gap C. Control the area small.

  Therefore, as shown in FIG. 4, even if the pump discharge pressure in the working chamber 4 increases to 1.8 MPa, 3.9 MPa, or the like, only a small amount of hydraulic oil from the minute gap C is supplied to the actuator. Become.

  As a result, it is possible to solve the problem that the operation load is temporarily reduced during the operation of the steering wheel and the steering feeling is deteriorated.

  Moreover, as described above, when the opening area of the orifice passage 18 is sufficiently restricted by the needle valve 19, the hydraulic pressure in the working chamber 4 is further increased, and the high pressure is applied to the pressure receiving surface 13 a of the spool valve 3. As a result, the spool valve 3 further moves backward.

  Thereby, the opening area of the opening end 7a of the drain passage 7 is increased by the seal valve body 13, and the flow rate of the hydraulic oil from the working chamber 4 to the drain passage 7 is increased.

  As a result, since the flow rate of the hydraulic oil from the minute gap C to the outlet passage 6 is controlled to be smaller, it is possible to further suppress the deterioration of the steering feeling.

  Moreover, in this embodiment, since the needle valve 19 can be moved back and forth independently of the spool valve 3 without significantly changing the existing structure, an increase in manufacturing cost can be suppressed.

  The technical ideas other than the invention described in the claims, as grasped from the embodiment, will be described below.

  (1) The spool valve has a pressure receiving surface that receives a discharge pressure flowing into the working chamber from the introduction passage, and the spool valve moves greatly by the hydraulic pressure acting on the pressure receiving surface, so that the drain passage 4. The flow control valve according to claim 3, wherein when the opening area is increased, the needle valve is formed so as to restrict the orifice to a minimum as the spool valve moves.

  According to the present invention, the needle valve passes through the differential pressure between the front and rear, that is, the pressure on the drain passage side and the orifice passage, while the spool valve is moved by a predetermined amount in the opening direction of the drain passage due to the discharge pressure applied to the pressure receiving surface. When moving in the direction of reducing the opening area of the orifice passage due to the difference from the hydraulic pressure, the working hydraulic pressure introduced into the working chamber further rises and is applied to the pressure receiving surface, and the spool valve increases the opening area of the drain passage. The amount of discharge from the drain passage is increased.

  For this reason, the flow volume discharged to the hydraulic equipment from the orifice passage through the outlet passage can be further reduced.

The spool valve includes an axial hole that movably guides the needle valve, a communication chamber that is formed inside and communicates with the drain passage, and a seal valve body that opens and closes the drain passage. While having
The needle valve has a pressure receiving portion that receives pressure on the downstream side of the orifice passage on the tip side, and moves in the axial direction by a differential pressure between the pressure acting on the pressure receiving portion and the pressure of the drain passage in the communication chamber. The flow control valve according to claim 1, wherein an opening area of the orifice passage is changed.

  According to the present invention, the needle valve is moved by a relative differential pressure between the hydraulic fluid pressure (pressure on the outlet passage side) applied to the pressure receiving portion on the front end side and the pressure on the drain passage side applied to the rear end side. Therefore, the opening area characteristic of the orifice passage, that is, the throttle characteristic can be obtained in accordance with the pressure change on the outlet passage side.

  The present invention is not limited to the configuration of the above-described embodiment. For example, the flow control valve can be applied to devices other than the power steering device.

It is a longitudinal section showing one embodiment of a flow control valve concerning the present invention. It is a longitudinal cross-sectional view of the flow control valve which shows the effect | action of this embodiment. It is a principal part expanded sectional view of this embodiment. It is an orifice flow rate characteristic figure by the flow control valve of this embodiment. It is an orifice flow rate characteristic figure by the conventional flow control valve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Housing 2 ... Valve hole 3 ... Spool valve 4 ... Working chamber 5 ... Inlet passage 6 ... Outlet passage 7 ... Drain passage 8 ... Variable orifice mechanism 10 ... Back pressure chamber 13 ... Seal valve body 14 ... Valve spring (1st spring) Element)
16 ... Communication chamber 18 ... Orifice passage 19 ... Needle valve 19a ... Tip 19b ... Rear end 19c ... Tapered surface C ... Minute gap

Claims (3)

A valve hole formed inside the housing;
A spool valve provided in the valve hole so as to be movable in the axial direction and moving in accordance with a differential pressure across the front and rear;
An introduction passage for introducing the hydraulic fluid discharged from the pump into the working chamber of the valve hole;
A lead-out passage for leading necessary hydraulic fluid introduced into the working chamber to the actuator;
A drain passage for discharging excess hydraulic fluid introduced into the working chamber;
A variable orifice mechanism for changing the opening area of the outlet passage as the spool valve moves, and changing the opening area of the drain passage by moving the spool valve back and forth to discharge hydraulic fluid to the outlet passage. In the flow control valve that controls the flow rate,
The variable orifice mechanism is connected to the spool valve so as to be movable relative to the spool valve, and is configured to change an opening area of the outlet passage independently of a change in the opening area of the drain passage by the spool valve. A flow control valve characterized by that. The variable orifice mechanism is provided in an orifice passage provided in the lead-out passage, and is movable in the axial direction in the orifice passage. By the differential pressure between the pressure on the drain passage side and the pressure on the downstream side of the orifice passage, The flow rate control valve according to claim 1, further comprising a needle valve that changes an opening area of the orifice with movement in an axial direction. A first spring member for urging the spool valve in the closing direction of the drain passage is provided, and a second spring member for urging the needle valve in a direction in which the opening area of the orifice passage increases is provided. The spring force of the spring member is set larger than that of the first spring member,
When the spool valve moves in the opening direction of the drain passage against the spring force of the first spring member, the opening area of the orifice is increased by the spring force of the second spring member. When the spool valve is further moved in the opening direction of the drain passage, the needle valve has a small opening area against the spring force of the second spring member due to the differential pressure across the spool valve. It controls so that it may become. The flow control valve of Claim 2 characterized by the above-mentioned.

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