JP4108584B2 - Power steering device - Google Patents

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 are fluid pressure sources of this type of power steering apparatus as shown in FIGS. 4 and 5 (see Patent Document 1).

  In FIG. 4, a power steering output unit 8 is operated by a power steering control valve (not shown) for controlling the fluid pressure and the fluid flow direction in accordance with various signals from the vehicle, and is operated by this controlled fluid pressure and steered. The power cylinder (not shown) etc. which assist force are comprised.

  The fluid pressure source of the power steering device includes a pump 1 driven by an engine (not shown), a supply passage 2 that supplies the working fluid discharged from the pump 1 to the power steering output unit 8, and an intermediate portion of the supply passage 2. A variable throttle valve 3 to be mounted, a flow rate adjusting valve 4 for returning a part of the working fluid to the pump suction side in accordance with a differential pressure across the variable throttle valve 3, and a bypass for the variable throttle valve 3 to guide the working fluid. A bypass passage 5, a solenoid valve 6 that opens and closes the bypass passage 5, and a relief valve 7 that communicates downstream from the variable throttle valve 3 are provided.

  As shown in FIG. 5, 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. In the valve body 21, 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, a return port 23 communicating with the pump suction side, and a bypass port constituting a bypass passage 24, 25, etc. are formed. The cap 31 includes a supply port 34 constituting a variable throttle valve, a downstream chamber 32 constituting a supply passage 2, a bypass port 33 constituting a bypass passage, and the like.

  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 rate adjusting 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 pump 1 is also stopped when the engine is stopped, the flow control valve 9 is seated on the end surface 38 of the cap 31 by the biasing force of the spring 13, the flow rate adjustment valve 4 is fully closed, The variable throttle valve 3 is fully closed.

  When the pump 1 is driven during engine operation and the spool 11 is separated from the end face 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 first opened. When the variable throttle valve 3 is opened, the working fluid discharged from the pump 1 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 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 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 solenoid valve 6 is opened, a part of the working fluid discharged from the pump 1 flows in the order of the upstream chamber 20 → the bypass port 24 → the solenoid valve 6 → the bypass port 25 → the downstream chamber 32 → the power steering output unit 8. By opening and closing the solenoid valve 6 in this way, the flow rate supplied to the power steering output unit 8 is increased or decreased, and the steering assist force can be adjusted.
PCT WO 03/023227 A1 Japanese Patent Laid-Open No. 10-230860

  However, such a conventional flow control valve 9 has a structure in which the variable throttle valve 3 is defined to have an annular cross section between the taper rod 12 formed integrally with the spool 11 and the supply port 34. Therefore, when the supply port 34 is eccentric with respect to the taper rod 12 due to a processing error of each member, the flow rate of the working fluid flowing through the variable throttle valve 3 is significantly changed, and the flow rate characteristics of the flow rate adjustment valve 4 are likely to vary. There was a point. For this reason, high machining accuracy is required in relation to the taper rod 12 and the supply port 34, and the cost of the product is increased.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a power steering device that can suppress variations in flow rate characteristics of a flow control valve.

  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 unit, a variable throttle valve interposed in the supply passage, and a differential pressure across the variable throttle valve. The present invention is applied to a power steering device that includes a flow rate adjusting valve that returns the working fluid in the supply passage to the pump suction side, and assists the steering force of the wheels by the power steering output unit.

The variable throttle valve includes a supply port interposed in the middle of the supply passage, a sleeve that changes the opening area of the supply port, and a spring that urges the sleeve in the opening direction of the supply port. A bypass passage connected to the supply passage in parallel with the variable throttle valve is configured to move to a position where the differential pressure across the port and the spring force of the spring balance to adjust the opening of the variable throttle valve, and this bypass A solenoid valve that opens and closes the passage, and the solenoid valve has a valve hole through which a working fluid flows and a shaft that restricts the valve hole, and the variable throttle valve is connected to the supply passage between the valve hole and the shaft. defining a throttle passage connecting the upstream side and the downstream side, the solenoid valve and characterized in that a structure in which the shaft is not fully closed the bypass passage away from the normally valve hole It was a shall.

  According to the first aspect of the present invention, the flow control valve is configured such that the spool is displaced in accordance with the differential pressure across the variable throttle valve to adjust the opening degree of the flow regulating valve, and the sleeve is also in accordance with the differential pressure across the variable throttle valve. Is displaced to adjust the opening of the variable throttle valve to control the flow rate supplied to the power steering output unit.

  The flow control valve has a structure in which the sleeve for adjusting the opening of the variable throttle valve is provided separately from the spool of the flow control valve, so even if the sleeve and the spool are eccentric due to processing errors of each member, The flow rate of the working fluid flowing through the variable throttle valve does not change, and variations in the flow rate characteristics of the flow rate adjustment valve can be suppressed. As a result, the machining accuracy required in connection with the conventional taper rod and the supply port is reduced, and the cost of the product can be reduced.

And by electrically controlling the opening degree of the solenoid valve, the flow rate supplied to the power steering output unit is increased or decreased, and the steering assist force can be adjusted.

For example, even when the sleeve is fixed and the working fluid cannot pass through the supply port, the working fluid discharged from the pump passes through the throttle passage defined between the valve hole and the shaft to the power steering output unit. Supplied. As a result, a steering assist force can be obtained at the power steering output section, and an excessive load on the pump can be avoided to achieve a fail-safe function.

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

  As shown in FIGS. 1A and 1B, the flow control valve 9 provided in the power steering apparatus includes a supply passage 2 that guides the working fluid discharged from the pump 1 to the power steering output unit 8, and this supply. A variable throttle valve 3 interposed in the middle of the passage 2, a flow rate adjusting valve 4 for returning the working fluid in the supply passage 2 to the pump suction side according to the differential pressure across the variable throttle valve 3, and the variable throttle valve 3 A bypass passage 5 that bypasses and guides the working fluid, a solenoid valve 6 that opens and closes the bypass passage 5, and a relief valve 7 that communicates downstream from the variable throttle valve 3 are provided.

  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 includes 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, a return port 23 communicating with the pump suction side, and a bypass that constitutes the bypass passage 5. Ports 24, 25, etc. are formed. 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, a bypass port 33 constituting the bypass passage 5, and the like.

  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 a through hole 28. Thus, the flow rate adjusting 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 supply passage 2, a sleeve 41 that changes the opening area of the supply port 34, and a spring 42 that biases the sleeve 41 in the opening direction of the supply port 34. The sleeve 41 is configured to move to a position where the differential pressure across the supply port 34 and the spring force of the spring 42 are balanced. That is, the sleeve 41 that makes the throttle of the variable throttle valve 3 variable is provided separately from the spool 11 of the flow rate adjusting valve 4.

  As shown in FIG. 2, the sleeve 41 is formed in a bottomed cylindrical shape, and the cap 31 is formed with a sleeve hole 35 into which the sleeve 41 is slidably inserted. The supply port 34 opens into the sleeve hole 35, and the opening area thereof is adjusted according to the sliding position of the sleeve 41.

  A disc-shaped retainer 36 is fitted in the cap 31, and a spring 42 is compressed and interposed between the retainer 36 and the bottom of the sleeve 41. A plurality of through holes 37 are formed in the retainer 36 so that the working fluid passing through the supply passage 2 flows through the through holes 37.

  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 housing 61 is formed with an upstream chamber 64 communicating with the discharge side of the pump 1, a valve hole 66 defining a variable throttle portion between the shaft 62, and a downstream chamber 67 communicating with the power steering output unit 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 shaft 62 is driven in the valve opening direction (upward in FIG. 1A) against the spring 68 by the electromagnetic force generated in the coil 69.

  The cylindrical shaft 62 has a conical valve body 63 formed at the tip thereof, and the valve body 63 is inserted into the valve hole 66. As the shaft 2 is displaced upward in FIG. 2, the opening area of the variable throttle portion defined between the valve body portion 63 and the valve hole 66 gradually increases.

  The solenoid valve 6 has a structure in which the core 77 is seated on the stepped portion 78 of the housing 61 and the valve body 63 is slightly separated from the valve hole 66 so that the bypass passage 5 is not fully closed. In other words, the flow control valve 9 is provided with a throttle passage 52 between the valve hole 66 and the valve body portion 63, and the throttle passage 52 always runs upstream and downstream of the variable throttle valve 3 with respect to the supply passage 2. Communicate.

  When the pump 1 is driven during the operation of the engine and the variable throttle valve 3 is opened by the discharge pressure of the pump 1 guided to the upstream chamber 20, the working fluid discharged from the pump 1 is supplied to the pump port. It flows in the order of 22 → upstream chamber 20 → variable throttle valve 3 → downstream chamber 32 → power steering output section 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 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 is kept substantially constant.

  When the rotational speed of the pump 1 further increases, the differential pressure across the variable throttle valve 3 increases, the pressure difference acting on both ends of the spool 11 increases, and the pressure difference acting on both ends of the sleeve 41 also increases. When the pressure difference increases in this way, the spool 11 moves in the left direction in the drawing against the spring force of the spring 13, and the sleeve 41 moves in the right direction in the drawing by the spring force of the spring 42 as shown in FIG. Then, 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.

  A part of the working fluid discharged from the pump 1 flows in the order of the upstream chamber 20 → the bypass port 24 → the solenoid valve 6 → the bypass port 25 → the downstream chamber 32 → the power steering output unit 8. And by electrically controlling the opening degree of the variable throttle part of the solenoid valve 6, the flow rate supplied to the power steering output part 8 is increased or decreased, and the steering assist force can be adjusted.

  Since the flow control valve 9 has a structure in which a sleeve 41 for making the throttle of the variable throttle valve 3 variable is provided separately from the spool 11 of the flow rate adjusting valve 4, the sleeve 41 and the spool 11 are separated by a processing error of each member. Even if it is eccentric, the flow rate of the working fluid flowing through the variable throttle valve 3 does not change, and the flow rate characteristics of the flow rate adjustment valve 4 do not vary. Therefore, the processing accuracy required in connection with the conventional taper rod 12 and the supply port 34 is reduced, and the cost of the product can be reduced.

  Furthermore, since the sleeve 41 and the spool 11 are provided separately, the degree of freedom in setting the flow characteristics of the variable throttle valve 3 and the flow characteristics of the flow control valve 4 can be increased.

  In the above-described embodiment, the solenoid bubble 6 having a structure in which the valve hole 66 is not fully closed by the throttle passage 52 is used, so that the upstream side and the downstream side of the variable throttle valve 3 always communicate with each other. Even when the working fluid passing through the supply port 34 becomes unable to move due to the valve body 21 and the sleeve 41 being fixed to the cap 31, the working fluid passing through the bubble hole 66 bypasses the supply port 34 to power. It is supplied to the steering output unit 8. As a result, the steering assist force to the power steering output unit 8 can be ensured, the load on the pump 1 can be prevented from becoming excessive, and the fail-safe function can be achieved.

  However, the solenoid valve 6 is not limited to the fully closed solenoid valve 6 as long as it has a structure in which the above-described fixing phenomenon cannot occur.

  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.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiment of this invention is shown, (a) is sectional drawing of a flow control valve, (b) is a front view of a flow control valve. Sectional drawing of a flow control valve. Sectional drawing which similarly shows operation | movement of a flow control valve. The block diagram of the power steering apparatus which shows a prior art example. Similarly, the cross section of the flow control valve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pump 2 Supply passage 3 Variable orifice 4 Flow control valve 5 Bypass passage 6 Solenoid valve 7 Relief valve 8 Power steering output part 9 Flow control valve 20 Upstream chamber 32 Downstream chamber 34 Supply port 41 Sleeve 42 Spring 52 Restriction passage 62 Shaft 66 Valve hole

Claims (1)

A supply passage for leading the working fluid discharged from the pump to the power steering output section, a variable throttle valve interposed in the middle of the supply passage, and a working fluid in the supply passage according to the differential pressure across the variable throttle valve A power steering device that includes a flow rate adjusting valve that returns to the pump suction side, and assists the steering force of the wheel by a power steering output unit, wherein the variable throttle valve is provided in the middle of the supply passage, and the supply port a sleeve for changing the opening area of, and a spring for biasing the sleeve in the opening direction of the supply port, the variable throttle sleeve is moved to the spring force is balanced position of the differential pressure and the spring of the supply ports a structure for adjusting the degree of opening of the valve, a bypass passage connected in parallel with the variable throttle valve with respect to the supply passage, the bypass passage A solenoid valve that opens and closes, the solenoid valve having a valve hole through which a working fluid flows, and a shaft that throttles the valve hole, and the variable throttle valve between the valve hole and the shaft with respect to the supply passage. The power steering apparatus is characterized in that a throttle passage connecting the upstream side and the downstream side is defined, and the solenoid valve has a structure in which the shaft is always away from the valve hole and the bypass passage is not fully closed .

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