JP2007186012A - Hydraulic power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic power steering device, capable of coping with change of auxiliary force characteristics in simple constitution. <P>SOLUTION: The hydraulic power steering device is provided with an output shaft 2a and an input shaft 2b coaxially connected through a torsion bar 22, and a hydraulic control valve 6 to control feed hydraulic pressure to a power cylinder for assisting steering in accordance with relative angular displacement between the output shaft 2a and the input shaft 2b caused by twisting of the torsion bar 22. A connection end part 23 at a lower part of the torsion bar 22 is fixed to the output shaft 2a, and a connection end part 24 at an upper part is relatively rotatably engaged with the input shaft 2b. A motor bracket 73 is fitted and fixed around an upper end part of the input shaft 2b, and rotation torque generated by an assisting motor 7 fixed and supported by the motor bracket 73 is added through a pinion and a gear wheel 71 to the connection end part 24 at an upper part of the torsion bar 22. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydraulic power steering apparatus using a double-acting hydraulic cylinder (power cylinder) as a generation source of steering assist force.

  A hydraulic power steering device that assists the steering of a vehicle with hydraulic pressure is in accordance with the operation of a steering member between a power cylinder provided in a part of the steering mechanism, a hydraulic pump as a hydraulic source, and an oil tank as a drain destination. A hydraulic control valve for supplying and discharging hydraulic pressure is provided, and hydraulic pressure (steering assisting force) generated by the power cylinder is applied to the steering mechanism by the hydraulic pressure supplied through the hydraulic control valve.

  As the hydraulic control valve, a rotary hydraulic control valve constructed in the middle of a steering shaft that connects a steering member and a steering mechanism is generally used. This hydraulic control valve divides the middle part of the steering shaft into an input shaft on the steering member side and an output shaft on the steering mechanism side, and is connected coaxially via a torsion bar having a known torsional characteristic, A valve spool that is integrally formed with one of the two shafts is fitted into a cylindrical valve body that is connected to the other, and a plurality of throttles are juxtaposed on the circumference of these fittings. When torque is applied, the throttle area of the throttle on the fitting circumference of the valve spool and valve body changes with torsion of the torsion bar, and the hydraulic pressure supplied to the power cylinder is controlled according to this change. It is the composition which becomes.

  In the hydraulic power steering apparatus configured as described above, the torsion provided in the hydraulic control valve has a correspondence relationship (auxiliary force characteristic) between the steering torque applied to the steering member and the steering assist force generated by the power cylinder. Since it is uniquely determined by the torsional characteristic of the bar, there is a problem that it cannot cope with the change control of the auxiliary force characteristic according to the change in the running state such as the vehicle speed and the steering angle.

  In order to cope with such a problem, conventionally, a hydraulic reaction force part is provided in parallel with one side of the hydraulic control valve configured as described above, and the action of the reaction force generated by the hydraulic reaction force part causes the torsion bar to There has been proposed a hydraulic power steering device configured to limit the relative angular displacement between the valve spool and the valve body due to torsion, and to respond to the change of the assisting force characteristic according to the traveling state (for example, Patent Document) 1).

  The hydraulic reaction force part extends the fitting part between the valve spool and the valve body to one side, and provides a plurality of radial through holes in the extension part of the valve body so that each of these through holes can slide freely. The tip of the held reaction force plunger is engaged with the extension portion of the valve spool facing inward, and the outside of each through hole is communicated with a common pressure guiding chamber.

In the hydraulic reaction force portion configured in this way, for example, when a hydraulic pressure that rises or falls according to the level of the vehicle speed is introduced into the pressure guiding chamber, the hydraulic pressure acts on the reaction force plungers in the respective through holes, and The tip is pressed against the extension of the valve spool, and the relative angular displacement between the valve spool and the valve body, that is, the operation of the hydraulic control valve is limited. As a result, during high-speed driving, steering assistance is not performed unless a steering torque with a magnitude exceeding the pressing force in the hydraulic reaction force is applied, and the steering member is provided with appropriate rigidity to ensure straight-running stability while stopping. During driving at low speeds and low speeds, a steering assist force is generated under the action of a small steering torque, and the force required to operate the steering member is reduced, so that a desirable assist force characteristic can be obtained.
JP-A-6-303752

  However, in the hydraulic reaction force portion configured as described above, a plurality of reaction force plungers and through holes that hold these are required to be processed with high precision, and in order to generate an introduction hydraulic pressure into the pressure guiding chamber, For example, a pressure control valve that responds to the height of the vehicle speed is required, and there is a problem that the device configuration is complicated and the cost is high.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a hydraulic power steering apparatus that can cope with a change in auxiliary force characteristics with a simple configuration.

  The hydraulic power steering apparatus according to the first aspect of the present invention is configured such that an input shaft on the steering member side and an output shaft on the steering mechanism side are connected coaxially via a torsion bar, and the steering is performed for vehicle steering. Hydraulic pressure for controlling the hydraulic pressure supplied to the power cylinder for assisting steering in accordance with the relative angular displacement between the input shaft and the output shaft caused by the torsion bar being twisted by the action of the steering torque applied to the member In the hydraulic power steering apparatus including a control valve, the torsion bar is connected to the output shaft so that the steering torque is applied to the other end portion of the output shaft fixed to the input shaft so as to be relatively rotatable. And an assisting means that is fixedly supported so as to be integrally rotatable with a part of the input shaft, and that applies rotational torque to assist the relative angular displacement at the other end of the torsion bar. And butterflies.

  According to a second aspect of the present invention, there is provided a hydraulic power steering apparatus for controlling the assisting means for increasing or decreasing the rotational torque based on a traveling state sensor for detecting a traveling state of the vehicle and a detection result of the traveling state sensor. And a control means.

  In the hydraulic power steering apparatus according to the first aspect of the present invention, the torsion bar that connects the input shaft and the output shaft can be configured using a steering torque applied to the steering member for steering, a motor, and the like. The steering assist force generated by the power cylinder by the hydraulic pressure supplied according to the relative angular displacement between the input shaft and the output shaft due to the twist, because the twist is caused by the action of the combined torque with the rotational torque applied by the means, The correspondence relationship with the steering torque applied to the steering member can be changed by increasing or decreasing the rotational torque applied by the assisting means, and a desired assisting force characteristic can be realized with a simple configuration.

  In the hydraulic power steering apparatus according to the second invention, the assisting means is controlled based on the detection result of the running state of the vehicle, and the rotational torque applied to the torsion bar is increased or decreased. The present invention has an excellent effect that this control can be easily implemented by direct control of the assisting means using a motor or the like.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof. FIG. 1 is a schematic diagram showing the overall configuration of a hydraulic power steering apparatus according to the present invention. The power steering apparatus shown in this figure has an axial length inside a rack housing 10 that extends in the left-right direction of a vehicle body (not shown). Rack-and-pinion-type steering mechanism having a rack shaft 1 supported so as to be movable in the direction and a pinion shaft 2 supported rotatably inside a pinion housing 20 that intersects the vicinity of one end of the rack housing 10 It has.

Both ends of the rack shaft 1 projecting outward from both sides of the rack housing 10 are connected to left and right front wheels 12, 12 as steering wheels via separate tie rods 11, 11, respectively. Further, the upper end of the pinion shaft 2 protruding above the pinion housing 20 is connected to one end of the steering shaft 3 via an intermediate shaft 4 having universal joints at both ends as described later, and the steering shaft 3 extended upward. A steering wheel 30 as a steering member is fixed to the other end. A pinion 21 (see FIG. 2) is formed in the lower part of the pinion shaft 2 extending into the pinion housing 20, and the pinion 21 has an appropriate length on the outer surface of the rack shaft 1 at the intersection with the rack housing 10. It is meshed with rack teeth 13 (see FIG. 2) formed over the entire length.

  With the above configuration, when the steering wheel 30 is rotated for steering, this rotation is transmitted to the pinion shaft 2 via the steering shaft 3 and the intermediate shaft 4, and further, the pinion 21 and the rack teeth 13 The movement of the rack shaft 1 is converted into the movement of the rack shaft 1 in the meshing portion, and the movement of the rack shaft 1 pushes and pulls the left and right front wheels 12 and 12 through the separate tie rods 11 and 11, respectively. Made.

  The hydraulic power steering apparatus according to the present invention assists the steering performed in this way by hydraulic pressure, and is provided in the other half of the rack housing 10 that supports the rack shaft 1 over a predetermined length range. The power cylinder 5 and a hydraulic control valve 6 (see FIG. 2) provided inside the pinion housing 20 that supports the pinion shaft 2 are provided. Further, in order to assist the operation of the hydraulic control valve 6, the pinion housing An assisting motor 7 is provided as assisting means attached to the projecting portion of the pinion shaft 2 to the upper portion of 20 as described later.

  FIG. 2 is a longitudinal sectional view taken along line II-II in FIG. 1 showing an example of the configuration of the hydraulic control valve 6 and the assisting means 7. As shown in the figure, the pinion shaft 2 includes an output shaft 2a and a hollow input shaft 2b that are coaxially supported inside a cylindrical pinion housing 20. A pinion 21 is integrally formed in the lower half of the output shaft 2a at the lower position, and this pinion 21 is meshed with rack teeth 13 formed on the outer surface of the rack shaft 1 at the intersection with the rack housing 10. It is.

  A torsion bar 22 is inserted in the hollow portion of the input shaft 2b at the upper position. The torsion bar 22 includes large-diameter connecting ends 23 and 24 connected to both sides of an intermediate portion having a known torsional characteristic, and the lower connecting end 23 is connected to the upper end of the output shaft 2a. It is fitted in a fitting hole drilled at the axial center position, and is concentrically fixed by restraining movement in the circumferential direction and axial direction by spline and pin coupling.

  On the other hand, the upper connection end 24 of the torsion bar 22 is fitted to the upper end of the input shaft 2b so as to be relatively rotatable, and protrudes upward by an appropriate length. A cylindrical connecting cylinder 70 is coaxially fitted to the projecting portion, and the connecting cylinder 70 is connected to the upper end of the torsion bar 22 along with the intermediate shaft 4 indicated by a two-dot chain line in FIG. The lower end portion is pin-coupled by a connecting pin 25. A gear cylinder 71 having teeth on the outer periphery is integrally connected to the lower part of the connecting cylinder 70, and this gear cylinder 71 is connected to the upper end of the input shaft 2b protruding from the upper part of the pinion housing 20 with a sliding bush. It is externally fitted through 72 so as to be relatively rotatable.

  Further, a motor bracket 73 is externally fitted and fixed at a position below the gear cylinder 71 to the protruding portion of the input shaft 2b above the pinion housing 20, and an assisting motor 7 as assisting means is attached to the motor bracket 73. Is fixedly supported. The assist motor 7 includes a small gear 74 at the tip of a motor shaft that protrudes upward. The small gear 74 is engaged with a gear cylinder 71.

  With the above configuration, when the steering wheel 30 is rotated for steering, the rotation of the steering shaft 3 is transmitted to the upper end of the torsion bar 22 via the intermediate shaft 4 and the connecting cylinder 70. It is transmitted to the output shaft 2a connected to the lower end of the bar 22 and converted into the movement of the rack shaft 1 having the rack teeth 13 meshing with the pinion 21 in the lower half of the output shaft 2a, and steering is performed as described above. .

  Here, the rotation state of the input shaft 2b constituting the upper half of the pinion shaft 2 changes depending on whether the assist motor 7 is rotated. When the assisting motor 7 is in a non-rotating state, the assisting motor 7 acts as a lever rod projecting from the motor bracket 73, and includes a gear cylinder 71 and a small gear 74 in which the rotation of the connecting cylinder 70 meshes with each other. Is transmitted to the assist motor 7 through the motor bracket 73 and further transmitted to the input shaft 2b through the motor bracket 73. The input shaft 2b rotates integrally with the connecting cylinder 70 and the upper end portions of the torsion bar 22. At this time, the torsion bar 22 is twisted only in accordance with the steering torque applied to the steering wheel 30, and the torsion bar 22 is twisted between the input shaft 2b and the output shaft 2a, that is, the steering wheel 30 is twisted. A relative angular displacement corresponding to the applied steering torque occurs.

  On the other hand, when the assist motor 7 is driven to rotate, the rotational torque generated by the assist motor 7 is applied to the upper end portions of the connecting cylinder 70 and the torsion bar 22 via the small gear 74 and the gear cylinder 71. Therefore, a twist corresponding to the combined torque of the steering torque applied to the steering wheel 30 and the rotational torque of the assisting motor 7 occurs. At this time, the relative angular displacement between the input shaft 2b and the output shaft 2a is larger than the relative angular displacement corresponding to the steering torque applied to the steering wheel 30.

  When the assist motor 7 is rotationally driven in the direction opposite to the steering torque direction, the rotational torque of the assist motor 7 can be applied so as to reduce the torsion of the torsion bar 22, but in the following description, the assist motor 7 The case where the motor 7 is rotated in the direction in which the twist of the torsion bar 22 is increased will be described. In this case, the relative angular displacement between the input shaft 2b and the output shaft 2a is minimized when the assisting motor 7 is in a non-driven state, and increases as the rotational torque generated by the assisting motor 7 increases.

  The hydraulic control valve 6 is a known rotary valve that controls the hydraulic pressure supplied to the power cylinder 5 using the relative angular displacement generated between the input shaft 2b and the output shaft 2a as described above. It comprises a cylindrical valve body 60 that is coaxially fitted inside and a valve spool 61 that is fitted inside thereof. The valve body 60 is connected to the upper end of the output shaft 2a via a dowel pin 62 provided on the outer periphery of the output shaft 2a so as to rotate integrally with the output shaft 2a. The valve spool 61 is integrally formed on the outer periphery of the midway part of the input shaft 2b that fits inside the valve body 60. As a result, the same relative angular displacement occurs between the valve body 60 and the valve spool 61 of the hydraulic control valve 6 as between the input shaft 2b and the output shaft 2a.

  In such a hydraulic control valve 6, hydraulic oil whose pressure has been increased by a hydraulic pump (not shown) is introduced through a pump port 26 provided at a corresponding position of the pinion housing 20. The pinion housing 20 is provided with a pair of cylinder ports 27 and 28, and these cylinder ports 27 and 28 are provided with power for steering assistance via respective oil supply pipes 14 and 15 (see FIG. 1). The cylinder chambers 5L and 5R are connected to the left and right cylinder chambers. Further, inside the pinion housing 20, a reflux chamber 63 is provided above the hydraulic control valve 6. This reflux chamber 63 communicates with an oil tank (not shown) via a tank port 29 provided in the pinion housing 20. Has been.

A plurality of throttle portions that change the throttle area in accordance with the relative angular displacement are arranged in parallel on the fitting periphery of the valve body 60 and the valve spool 61. The hydraulic control valve 6 passes through the pump port 26. The introduced hydraulic oil is distributed according to the change in the throttle area of the throttle portion described above, and is sent to one of the left and right cylinder chambers S _L and S _R of the power cylinder 5 through the cylinder ports 27 and 28. With this feed, the hydraulic oil recirculated from the other cylinder chambers S _L and S _R is supplied and discharged to the oil tank through the recirculation chamber 63 and the tank port 29. In addition, the hydraulic fluid which recirculates from the cylinder chamber S _L or S _R to the hydraulic control valve 6 is introduced into the recirculation chamber 63 through the hollow portion of the input shaft 2b.

By this operation, the power cylinder 5 generates an oil pressure from the one cylinder chamber S _L , S _R to which the hydraulic oil is fed toward the other, and this oil pressure is applied to the rack shaft 1 to assist the above-described steering. Is done. The direction and magnitude of the hydraulic pressure (steering assisting force) generated by the power cylinder 5 at this time corresponds to the direction and magnitude of the relative angular displacement between the valve body 60 and the valve spool 61, and the hydraulic pressure according to the present invention. In the power steering apparatus, the relative angular displacement between the valve body 60 and the valve spool 61 corresponds to the combined torque of the steering torque applied to the steering wheel 30 and the rotational torque generated by the assist motor 7 as described above. The correspondence relationship (auxiliary force characteristic) between the steering torque applied to the steering wheel 30 by the driver and the steering assist force generated by the power cylinder 5 can be freely changed by driving control of the assist motor 7.

  As shown in the figure, the assist motor 7 is configured to be driven in accordance with a control command given from the assist control unit 8 to a drive circuit (not shown). The assist control unit 8 is provided with detection results of various traveling states that affect the steering, such as a traveling speed and a steering angle, from a traveling state sensor 9 disposed in each part of the vehicle.

  For example, based on the detected value of the vehicle speed, the assist controller 8 performs a control operation of driving the assist motor 7 during low-speed traveling and not driving the assist motor 7 during high-speed traveling. As a result, at low speed, the operation of the hydraulic control valve 6 is assisted by the rotational torque generated by the assisting motor 7, and a light steering feeling can be realized. On the other hand, at the time of high speed traveling, the assist motor 7 is not assisted, and the torsion bar 22 is twisted only by the steering torque applied to the steering wheel 30, and the above-described supply / discharge operation of the hydraulic control valve 6 is performed according to this twist. Thus, an assist force characteristic with a small increase rate of the steering assist force is realized, and stable steering can be performed under moderate neutral rigidity.

  The drive control of the assist motor 7 by the assist control unit 8 is not limited to the drive / non-drive switching control as described above, and the drive current of the assist motor 7 is reduced stepwise or steplessly as the vehicle speed increases. It can also be done. Thereby, a steering assist force that increases or decreases according to the slow speed of the vehicle speed is obtained, and a better steering feeling can be achieved.

  Further, other traveling states detected by the traveling state sensor 9 can be similarly used for driving control of the assisting motor 7, and appropriate assisting force characteristics such as a characteristic in which the steering assisting force decreases as the steering angle increases are obtained. Can be realized.

  In the hydraulic power steering apparatus according to the present invention, it is possible to respond to the change in the assisting force characteristic as described above by driving control of the assisting motor 7 arranged to apply rotational torque to the input end of the torsion bar 22, Such drive control can be realized, for example, by applying the detection result of the traveling state by the traveling state sensor 9 to a map stored in advance in the assist control unit 8 and increasing / decreasing the driving current of the assist motor 7. Thus, the assist force characteristic can be changed with a simple configuration including the actuator and the control unit.

  The assisting means is not limited to the assisting motor 7 shown in the embodiment, and an appropriate rotating or non-rotating actuator can be adopted. However, in order to simplify the transmission system to the torsion bar 22, a rotating actuator is used. It is desirable to employ the motor, and when the ease of control is taken into consideration, it is desirable to employ the motor described in the embodiment.

  In the present embodiment, an example of application to a vehicle having a rack and pinion type steering mechanism has been described. However, the scope of application of the present invention is not limited to this, and also in other types of steering mechanisms such as a ball screw type. Needless to say, it is applicable.

1 is a schematic diagram of a hydraulic power steering apparatus according to the present invention. It is a longitudinal cross-sectional view by the II-II line of FIG. 1 which shows the structural example of a hydraulic control valve and an assistance means.

Explanation of symbols

2a Output shaft
2b Input shaft 5 Power cylinder 6 Hydraulic control valve 7 Support motor (support means)
8 Assist control unit (control means)
9 Running state sensor
22 Torsion bar
30 Steering wheel (steering member)

Claims (2)

An input shaft on the steering member side and an output shaft on the steering mechanism side are coaxially connected via a torsion bar, and the torsion bar is twisted by the action of steering torque applied to the steering member for steering the vehicle. In a hydraulic power steering apparatus including a hydraulic control valve that controls a hydraulic pressure supplied to a power cylinder for assisting steering in accordance with a relative angular displacement between the input shaft and the output shaft generated along with
The torsion bar is configured so that one end is fixed to the output shaft and the steering torque is applied to the other end fitted to the input shaft so as to be relatively rotatable,
A hydraulic power steering apparatus, comprising: an assisting means fixed to and supported by a part of the input shaft so as to be integrally rotatable, and applying a rotational torque for assisting the relative angular displacement at the other end of the torsion bar.   The hydraulic power steering apparatus according to claim 1, further comprising: a traveling state sensor that detects a traveling state of the vehicle; and a control unit that controls the assisting unit to increase or decrease the rotational torque based on a detection result of the traveling state sensor. .

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