JP2005162042A - Power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power steering device capable of heightening control accuracy of a flow rate of working fluid. <P>SOLUTION: This power steering device comprises a supply passage 2 introducing working fluid delivered from a pump 1 into a power steering output part 8; a supply port 34 interposed in the middle of the supply passage 2; a spool 11 returning the working fluid of the supply passage 2 to the pump intake side according to the difference between front and rear pressures of the supply port 34; and a taper rod 12 inserted in the supply port 34 and constituting a variable throttle valve 3. The taper rod 12 is connected with the spool 11. The device is equipped with a solenoid valve 6 interposed to the supply passage 2 in series with the variable throttle valve 3. The working fluid passing through the variable throttle valve 3 passes through the solenoid valve 6, and is directed to a power steering output part 8. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an improvement in a power steering device that assists the steering force of a wheel by fluid pressure.

  Conventionally, there is a fluid pressure source of this type of power steering apparatus as shown in FIG. 2 (see Patent Document 1).

  The power steering output unit 8 assists the steering force by operating with a power steering control valve (not shown) that controls the fluid pressure and the flow direction of the fluid according to various signals from the vehicle, and the controlled fluid pressure. A power cylinder (not shown) or the like is used.

  The flow control valve 9 houses the flow rate adjusting valve 4 and the variable throttle valve 3 in the valve body 21. The valve body 21 has a spool hole 26 into which the spool 11 is slidably inserted, a pump port 22 communicating with the discharge side of the pump, a return port 23 communicating with the pump suction side, and a supply port constituting the variable throttle valve 3 34, the upstream side chamber 20 and the downstream side chamber 32 constituting the supply passage are formed.

  The flow rate adjusting valve 4 includes a spool 11 that is biased by a spring 13, and a land portion 10 that is in sliding contact with the spool hole 26 is formed on the outer periphery of the spool 11. When the spool 11 moves to the left in the drawing against the spring 13, the tip of the land portion 10 faces the return port 23, communicates the pump port 22 and the return port 23, and the pump port according to the sliding position of the spool 11. The flow rate of the working fluid returned from 22 to the return port 23 is adjusted. An upstream chamber 20 that communicates with the upstream side of the variable throttle valve 3 is defined at one end of the spool 11. A spring chamber 27 in which a spring 13 is interposed is defined at the other end of the spool 11, and the spring chamber 27 communicates with the downstream side of the variable throttle valve 3 through the through hole 14. Thus, the flow regulating valve 4 is guided to the opposite ends of the spool 11 by the differential pressure across the variable throttle valve 3, and the spool 11 moves to a position where the differential pressure across the variable throttle valve 3 and the spring force of the spring 13 are balanced.

  The variable throttle valve 3 includes a taper rod 12 protruding from one end of the spool 11 and a supply port 34 into which the taper rod 12 is inserted, and the supply port is provided in a predetermined stroke region as the taper rod 12 moves together with the spool 11. The opening area of 34 gradually decreases. In this way, the flow rate adjusting valve 4 and the variable throttle valve 3 are linked so that the opening degree of the variable throttle valve 3 decreases as the opening degree of the flow rate adjusting valve 4 increases.

  The flow control valve 9 is configured as described above. When the spool 11 is separated from the seat surface 38 by the discharge pressure of the pump guided to the upstream side chamber 20, the variable throttle valve 3 is first opened. When the variable throttle valve 3 is opened, the working fluid discharged from the pump flows in the order of the pump port 22 → the upstream side chamber 20 → the variable throttle valve 3 → the downstream side chamber 32 → the power steering output unit 8. The power steering output unit 8 assists the steering force of the wheel by this fluid pressure.

  Since the load pressure of the power steering output unit 8 is guided from the downstream chamber 32 to the spring chamber 27, the differential pressure across the variable throttle valve 3 increases as the pump rotation speed increases and the pump discharge flow rate increases. As it increases, the spool 11 gradually moves against the spring 13.

  In a state where the pump is rotating in the low speed region, the flow rate adjusting valve 4 is closed, and a working fluid having a flow rate proportional to the rotational speed of the pump is supplied to the power steering output unit 8.

  When the rotational speed of the pump reaches the middle speed range, the flow rate adjusting valve 4 is opened, and a part of the working fluid flowing into the upstream chamber 20 is returned to the return port 23 as the rotational speed of the pump increases. The flow rate of the working fluid supplied to the power steering output unit 8 via the variable throttle valve 3 is kept substantially constant.

When the number of rotations of the pump further increases, the variable throttle valve 3 moves the taper rod 12 together with the spool 11 so that the opening area of the supply port 34 gradually decreases, and the flow rate of the working fluid supplied to the power steering output unit 8 gradually decreases. To do.
Japanese Patent Laid-Open No. 10-230860

  However, in such a conventional flow control valve 9, when the working fluid flows at high speed between the supply port 34 of the variable throttle valve 3 and the taper rod 12, the taper rod 12 and the spool 11 are caused by the fluid pressure received by the taper rod 12. May move in the axial direction, and the flow rate of the working fluid guided to the power steering output unit 8 through the supply port 34 may fluctuate.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a power steering device capable of improving the control accuracy of the working fluid flow rate.

  According to a first aspect of the present invention, there is provided a supply passage for guiding the working fluid discharged from the pump to the power steering output portion, a supply port interposed in the middle of the supply passage, and a supply passage according to the differential pressure across the supply port This is applied to a power steering apparatus that includes a spool that returns the working fluid to the pump suction side and a taper rod that is inserted into the supply port to form a variable throttle valve, and is connected to the spool.

  The supply passage is provided with a solenoid valve interposed in series with the variable throttle valve.

  According to a second invention, in the first invention, the solenoid valve has a valve hole through which a working fluid flows and a shaft for restricting the valve hole, and the shaft is displaced to be defined between the shaft and the valve hole. The flow path cross-sectional area is adjusted.

  According to a third aspect, in the second aspect, the solenoid valve includes a means for restricting the displacement of the shaft so as not to block the flow path defined between the shaft and the valve hole, and the supply passage is always opened. It was characterized by that.

  According to the first aspect of the present invention, since the working fluid that has passed through the variable throttle valve passes through the solenoid valve and travels toward the power steering output unit, the power steering device can perform power steering from the supply passage according to the opening of the solenoid valve. The flow rate supplied to the output unit is increased or decreased, and the steering assist force can be adjusted.

  Since the flow path of the supply passage is throttled stepwise by the variable throttle valve and the solenoid valve, the opening of the variable throttle valve is increased by the amount that the flow path is throttled by the solenoid valve, and the supply port of the variable throttle valve The flow rate of the working fluid flowing between the taper rods is reduced. For this reason, the taper rod and the spool are prevented from moving in the axial direction by the fluid pressure received by the taper rod, and the flow rate of the working fluid supplied to the power steering output unit can be adjusted accurately.

  According to the second invention, the sonoid valve has a configuration in which the shaft is displaced in the axial direction to adjust the cross-sectional area of the flow path defined by the valve body portion in the valve hole. It is possible to ensure the control accuracy and accurately adjust the flow rate of the working fluid supplied to the power steering output unit.

  According to the third invention, the solenoid valve regulates the displacement of the shaft, and the valve body part is slightly separated from the valve hole so as not to block the supply passage. Application of the steering assist force to the steering output unit is reliably maintained.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  As shown in FIG. 1, the flow control valve 9 provided in the power steering apparatus is interposed in the supply passage 2 for guiding the working fluid discharged from the pump 1 to the power steering output portion 8 and in the middle of the supply passage 2. A variable throttle valve 3, a flow rate adjusting valve 4 that returns the working fluid in the supply passage 2 to the pump suction side in accordance with the differential pressure across the variable throttle valve 3, and a relief valve 7 that communicates downstream from the variable throttle valve 3. With.

  The flow control valve 9 includes a valve body 21 and a cap 31 as its casing, and the flow rate adjusting valve 4 and the variable throttle valve 3 are accommodated therein. The valve body 21 is formed with a spool hole 26 into which the spool 11 is slidably inserted, a pump port 22 communicating with the discharge side of the pump 1, and a return port 23 communicating with the pump suction side.

  The flow rate adjusting valve 4 includes a spool 11 that is biased by a spring 13, and a land portion 10 that is in sliding contact with the inner peripheral surface of the spool hole 26 is formed on the outer periphery of the spool 11. When the spool 11 moves to the left in the drawing against the spring 13, the tip of the land portion 10 faces the return port 23 so that the pump port 22 communicates with the return port 23, and the pump is pumped according to the sliding position of the spool 11. The flow rate of the working fluid returned from the port 22 to the return port 23 is adjusted.

  A spring 13 is compressed and interposed between the spool 11 and the bottom surface of the spool hole 26. The spool 1 is urged in the valve closing direction by the elastic restoring force of the spring 13.

  An upstream chamber 20 that communicates with the upstream side of the variable throttle valve 3 is defined at one end of the spool 11. A spring chamber 27 in which a spring 13 is interposed is defined at the other end of the spool 11, and the spring chamber 27 communicates with the downstream side of the variable throttle valve 3 through a through hole 28. Thus, the flow regulating valve 4 is guided to the opposite ends of the spool 11 by the differential pressure across the variable throttle valve 3, and the spool 11 moves to a position where the differential pressure across the variable throttle valve 3 and the spring force of the spring 13 are balanced.

  The variable throttle valve 3 includes a supply port 34 interposed in the middle of the supply passage 2 and a taper rod 12 that changes the opening area of the supply port 34.

  The taper rod 12 is connected to the spool 11. The taper rod 12 protrudes from one end of the spool 11 and is formed integrally with the spool 11.

  As the taper rod 12 moves together with the spool 11, the opening area of the supply port 34 gradually decreases in a predetermined stroke area. In this way, the flow rate adjusting valve 4 and the variable throttle valve 3 are linked so that the opening degree of the variable throttle valve 3 decreases as the opening degree of the flow rate adjusting valve 4 increases.

  However, when the working fluid flows at high speed between the supply port 34 of the variable throttle valve 3 and the taper rod 12, the taper rod 12 and the spool 11 move in the axial direction by the fluid pressure received by the taper rod 12, and the power passes through the supply passage 2. There is a possibility that the flow rate of the working fluid guided to the steering output unit 8 varies.

  The present invention has been made to cope with this, and includes a solenoid valve 6 interposed in series with the variable throttle valve 3 with respect to the supply passage 2, and the flow path of the supply passage 2 is connected to the variable throttle valve 3 and the solenoid. The valve 6 is configured to be throttled in stages.

  The cap 31 is formed with a supply port 34 constituting the variable throttle valve 3, a downstream chamber 32 constituting the supply passage 2, an outlet chamber 75, and the like. The downstream chamber 32 and the outlet chamber 75 are partitioned by a partition wall 74 formed integrally with the cap 31.

  The valve body 21 is formed with through holes 71 and 72 constituting the supply passage 2. The through hole 71 communicates the downstream chamber 32 and the upstream chamber 64 of the solenoid valve 6. The through hole 72 communicates the downstream chamber 67 and the outlet chamber 75 of the solenoid valve 6.

  The sonoid valve 6 includes a cylindrical housing 61 that is inserted and attached to the valve body 21, and a shaft 62 that is slidably inserted into the housing 61. The cylindrical shaft 62 has a conical valve body 63 formed at the tip thereof. The housing 61 is formed with a valve hole 66 defining a variable throttle portion between the upstream chamber 64 communicating with the discharge side of the pump 1 and the shaft 62 and a downstream chamber 67 communicating with the power steering output portion 8. The working fluid discharged from the pump 1 flows through the upstream chamber 64, the valve hole 66, and the downstream chamber 67 to the power steering output unit 8.

  The sonoid valve 6 has a configuration in which the shaft 62 is displaced in the axial direction to adjust the flow path cross-sectional area defined by the valve body 63 in the valve hole 66. The shaft 62 is driven in the valve opening direction (upward in FIG. 1) against the spring 68 by electromagnetic force generated in the coil 69. As the shaft 62 is displaced upward in FIG. 1, the flow path cross-sectional area defined between the valve body 63 and the valve hole 66 gradually increases.

  As a means for restricting the displacement of the shaft 62, a step portion 78 is formed in the housing 61. The solenoid valve 6 has a structure in which the valve body 63 is slightly separated from the valve hole 66 and does not block the supply passage 2 with the core 77 seated on the stepped portion 78 of the housing 61.

  The flow control valve 9 provided in the power steering apparatus is configured as described above. Next, the operation will be described.

  The pump 1 is also stopped when the engine is stopped, the spool 11 is seated on the seat surface 38 of the cap 31 by the urging force of the spring 13, the flow rate adjusting valve 4 is fully closed, and the variable throttle valve 3 is fully closed. Yes.

  When the pump 1 is driven during engine operation and the spool 11 is separated from the seat surface 38 of the cap 31 by the discharge pressure of the pump 1 guided to the upstream chamber 20, the variable throttle valve 3 is opened and discharged from the pump 1. The working fluid flows in the order of the pump port 22 → the upstream chamber 20 → the variable throttle valve 3 → the downstream chamber 32 → the solenoid valve 6 → the outlet chamber 75 → the power steering output unit 8. The power steering output unit 8 assists the steering force of the wheel by this fluid pressure.

  Since the load pressure of the power steering output unit 8 is guided from the outlet chamber 75 to the spring chamber 27, the front-rear difference of the variable throttle valve 3 increases as the rotational speed of the pump 1 increases and the discharge flow rate of the pump 1 increases. As the pressure increases, the spool 11 gradually moves against the spring 13.

  In a state where the pump 1 is rotating in the low speed region, the flow rate adjusting valve 4 is closed, and a working fluid having a flow rate proportional to the rotational speed of the pump 1 is supplied to the power steering output unit 8.

  When the rotational speed of the pump 1 reaches the middle speed range, the flow rate adjusting valve 4 is opened, and a part of the working fluid flowing into the upstream chamber 20 is returned to the return port 23 as the rotational speed of the pump 1 increases. Therefore, the flow rate of the working fluid supplied to the power steering output unit 8 via the variable throttle valve 3 and the solenoid valve 6 is kept substantially constant.

  When the rotational speed of the pump 1 further increases, the variable throttle valve 3 moves the taper rod 12 together with the spool 11 to gradually reduce the opening area of the supply port 34, and the flow rate of the working fluid supplied to the power steering output unit 8 gradually increases. Decrease.

  When the flow control valve 9 is operated, the flow rate supplied from the supply passage 2 to the power steering output unit 8 is appropriately increased or decreased as necessary according to the opening degree of the solenoid valve 6, and the steering assist force with a higher degree of freedom can be obtained. Adjustment can be realized.

  Thus, since the flow path of the supply passage 2 is throttled stepwise by the variable throttle valve 3 and the solenoid valve 6, by increasing the opening degree of the variable throttle valve 3 by the amount that the flow path is throttled by the solenoid valve 6, The flow rate of the working fluid flowing between the supply port 34 of the variable throttle valve 3 and the taper rod 12 becomes low. For this reason, it is suppressed that the taper rod 12 and the spool 11 move to the axial direction by the fluid pressure which the taper rod 12 receives. Thereby, the control accuracy of the working fluid flow rate adjusted by the flow control valve 9 can be enhanced, and the flow rate of the working fluid supplied to the power steering output unit 8 can be adjusted accurately.

  Since the sonoid valve 6 has a configuration in which the shaft 62 is displaced in the axial direction to adjust the cross-sectional area of the flow path defined by the valve body 63 in the valve hole 66, the working fluid flow rate adjusted by the electromagnetic force generated in the coil 69 is adjusted. And the flow rate of the working fluid supplied to the power steering output unit 8 can be accurately adjusted.

  The solenoid valve 6 has a structure in which the displacement of the shaft 62 is restricted by the core 77 seated on the stepped portion 78 of the housing 61 and the valve body portion 63 is slightly separated from the valve hole 66 so that the supply passage 2 is not blocked. The valve stick 62 can be prevented from sticking to the housing 61. As a result, the application of the steering assist force to the power steering output unit 8 is reliably maintained.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  The power steering device of the present invention can be used for a power steering device that assists the steering force of a wheel by fluid pressure.

Sectional drawing of the flow control valve which shows embodiment of this invention. Sectional drawing of the flow control valve which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pump 2 Supply passage 3 Variable throttle valve 4 Flow control valve 6 Solenoid valve 7 Relief valve 8 Power steering output part 9 Flow control valve 11 Spool 12 Taper rod 34 Supply port 63 Valve body part 66 Valve hole 77 Core 78 Step part

Claims (3)

A supply passage for guiding the working fluid discharged from the pump to the power steering output section, a supply port interposed in the middle of the supply passage, and the suction of the working fluid in the supply passage according to the differential pressure across the supply port In a power steering apparatus comprising a spool returning to the side and a taper rod inserted into a supply port to constitute a variable throttle valve, and connecting the taper rod to the spool,
A power steering device comprising a solenoid valve interposed in series with the variable throttle valve with respect to the supply passage.   The solenoid valve has a valve hole through which a working fluid flows, and a shaft that restricts the valve hole, and is configured to adjust the flow path cross-sectional area defined between the shaft and the valve hole by displacing the shaft. The power steering apparatus according to claim 1.   2. The solenoid valve according to claim 1, wherein the solenoid valve includes means for regulating displacement of the shaft so as not to block a flow path defined between the shaft and the valve hole, and the supply passage is always opened. 2. The power steering device according to 2.

Images