JP2006111079A - Hydraulic power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic power steering device in which the steering assist characteristic is varied by changing the effective length of a torsion bar, capable of preventing the steering characteristics from being different between the right-hand steering and the left-hand steering. <P>SOLUTION: A control valve 30 controls the oil pressure for generating a steering assist force by changing the relative rotating angle of valve members 31 and 32 owing to a twist of the torsion bar 6. In case the relative rotating angle is below the set value, the effective length of the torsion bar 6 is shortened by pressing of a part to be pressed on the outer periphery of the torsion bar 6 by a pressing member 50 rotating along with one of the input shaft 2 and output shaft 3, and is elongated by releasing the pressing in case the relative rotating angle is equal to or over the set value. A holder 60 for the pressing member 50 is installed in such a way as rotating along with one of the input shaft 2 and output shaft 3, and the installing position of the same is made changeable in the circumferential direction of the torsion bar 6, so as to make adjustable the circumferential direction relative position of the part to be pressed to the pressing member 50. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydraulic power steering apparatus that changes a steering assist characteristic by changing an effective length of a torsion bar that twists according to a steering torque.

  In a conventional hydraulic power steering device, in the vicinity of a straight-ahead steering state where the steering torque is small, the change rate of the steering assist force with respect to the steering torque is reduced to improve traveling stability, and when the steering torque is increased, the change rate is increased. The steering performance is improved by the above (see Patent Document 1).

The conventional hydraulic power steering apparatus includes a torsion bar that coaxially connects an input shaft and an output shaft to elastically rotate relative to each other according to a steering torque, and pressure oil supplied to a hydraulic actuator for generating a steering assist force. A hydraulic control valve that controls hydraulic pressure according to the relative rotation angle of the valve member that rotates together with the input shaft with respect to the valve member that rotates along with the output shaft, and a pressing member that rotates along with the output shaft and can be displaced in the shaft radial direction And a pressed portion provided on the outer periphery of the torsion bar, and an elastic body that provides elasticity for pressing the pressing member against the pressed portion. One end of the torsion bar is connected to the input shaft, the other end is connected to the output shaft, and the pressing member is pressed against the pressed portion by elasticity. When the relative rotation angle of both valve members is less than the set value, the torsion bar is effectively controlled by the torsion between the other end of the torsion bar and the pressed part by pressing the pressed part with the pressing member. The length is shortened. When the relative rotation angle of both valve members is greater than or equal to the set value, the pressing is released and the effective length of the torsion bar is lengthened. As a result, when the relative rotational angle is less than the set value, the rigidity of the torsion bar is substantially greater than when the relative rotational angle is greater than or equal to the set value, and the change in the relative rotational angle of both valve members due to the change in steering torque. The ratio decreases, and the change ratio of the steering assist force decreases.
JP-A-10-329733

  In the hydraulic power steering device described above, the to-be-pressed portion is displaced relative to the pressing member in the circumferential direction due to the torsion of the torsion bar when the relative rotation angle of both valve members reaches the set value. The pressing of the pressing part is released. Further, the twisting directions of the torsion bar are opposite to each other during right steering and left steering. Therefore, in order to make the set value of the relative rotation angle of both valve members when the pressing of the pressed part by the pressing member is released equal between the right steering and the left steering, the pressing is performed at the rudder angle midpoint. It is necessary to position the member at the center position of the pressed portion in the circumferential direction of the torsion bar.

  On the other hand, the hydraulic control valve in the hydraulic power steering device controls the hydraulic pressure for generating the steering assist force according to the relative rotation angle of the valve member that rotates along with the output shaft with respect to the valve member that rotates along with the input shaft. ing. Therefore, it is necessary to position the relative positions in the circumferential direction of the valve member that rotates along with the input shaft and the valve member that rotates along with the output shaft so that the steering assist force is not generated at the steering angle midpoint.

  However, one end side of the torsion bar is connected to the input shaft so as to rotate together, the other end side is connected to the output shaft so as to rotate together, and the pressing member rotates together with the output shaft. Therefore, if the torsion bar is connected to the input shaft and the output shaft in order to complete the positioning of the relative position in the circumferential direction of the valve member that rotates together with the input shaft and the valve member that rotates together with the output shaft, manufacturing tolerances may occur. For this reason, the pressing member cannot be positioned at the center position of the pressed portion in the circumferential direction of the torsion bar. As a result, there arises a problem that steering characteristics are different between right steering and left steering. An object of the present invention is to provide a hydraulic power steering apparatus that can solve such a problem.

The present invention includes an input shaft, an output shaft, a torsion bar that coaxially connects the input shaft and the output shaft so as to elastically rotate relative to each other according to a steering torque, a hydraulic assist actuator for generating a steering assist force, A hydraulic control valve that controls the hydraulic pressure of the pressure oil supplied to the hydraulic actuator according to the relative rotation angle of the valve member that rotates coaxially with the input shaft relative to the valve member that rotates coaxially with the output shaft. A pressing member that rotates together with one of the input / output shafts and is radially displaceable, a pressed portion that is provided on an outer periphery of the torsion bar, and a force that presses the pressed portion by the pressing member. One of the one end side and the other end side of the torsion bar is connected to the input shaft. When the relative rotation angle of both the valve members is less than a set value, the other is connected to the output shaft so as to rotate along with the shaft, and the other is connected to the output shaft along the same axis. When the portion is pressed, torsion between one end side of the torsion bar and the pressed portion is restricted, and the relative rotation angle of both valve members is equal to or larger than a set value, the torsion bar is twisted to press the portion. In the hydraulic power steering apparatus in which the pressed portion is released by the relative displacement of the pressed portion with respect to the member, the hydraulic power steering device is attached so as to rotate along with one of the input / output shafts, and the mounting position thereof A holder that can be changed in the circumferential direction of the torsion bar is provided. Only member is held, by changes in the circumferential direction of the mounting position of the holder, the circumferential relative position of the object pressing portion with respect to the pressing member, characterized in that it is adjusted.
According to the present invention, the relative positions in the circumferential direction of the valve member that rotates along with the input shaft and the valve member that rotates along with the output shaft are positioned so that no steering assist force is generated at the steering angle midpoint. The torsion bar is completed by connecting the input shaft and the output shaft. Thereafter, the pressing position of the pressed portion by the pressing member is changed by changing the mounting position of the holder with respect to one of the input / output shafts in the circumferential direction of the torsion bar. Thereby, the pressing member can be positioned at the center position of the pressed portion in the circumferential direction of the torsion bar at the steering angle midpoint. The positioning is completed by attaching the holder to one of the input / output shafts so as to rotate together.

  The holder has an elastically deformable holding body, the pressing member is disposed between the holding body and the pressed portion, and the pressing force of the pressed portion by the pressing member is caused by the elastic deformation of the holding body. It is preferable to be provided. This eliminates the need for a dedicated member for applying a force for pressing the pressing member against the pressed portion, and does not complicate the structure.

  According to the hydraulic power steering device of the present invention, when the steering assist characteristic is changed by changing the effective length of the torsion bar that is twisted according to the steering torque, the steering characteristic is different between the right steering and the left steering. Differences can be prevented by a simple structure.

  A rack and pinion hydraulic power steering device 1 according to an embodiment of the present invention shown in FIG. 1 includes a cylindrical input shaft 2, an output shaft 3, an input shaft 2, and an output shaft connected to a steering wheel (not shown) of a vehicle. And a torsion bar 6 that is connected to a coaxial core so as to elastically rotate relative to the steering torque. The torsion bar 6 penetrates the input shaft 2, one end side is connected to the input shaft 2 through the pin 4 so as to rotate coaxially and the other end side is inserted into a recess 3 a formed at one end of the output shaft 3. At the same time, it is connected to the output shaft 3 via the serration 5 so as to rotate along the same axis. The torsion bar 6 has a rotating body shape, the end portion 6a has an outer periphery along the cylindrical surface, and the diameter between the one end side and the end portion 6a is between the other end side and the end portion 6a. It is smaller than the diameter.

  One end side of the input shaft 2 is supported by the housing 7 via the bearing 8, and the other end side is supported by the inner periphery of the recess 3 a of the output shaft 3 via the bush 12. The output shaft 3 is rotatably supported by a housing of a steering gear (not shown). A pinion 15 is integrally formed on the outer periphery of the other end side of the output shaft 3. The steering gear has a rack 16 that meshes with the pinion 15, and a wheel is connected to each end of the rack 16 via a tie rod, a knuckle arm, or the like. As a result, the rotation of the input shaft 2 due to steering is transmitted to the output shaft 3 via the torsion bar 6, so that the pinion 15 rotates, and the rack 16 moves in the vehicle width direction, thereby changing the steering angle.

  A hydraulic cylinder 20 is provided as a steering assist force generating hydraulic actuator. The hydraulic cylinder 20 includes a cylinder tube 20a and a piston 21 integrated with the rack 16, and oil chambers 22 and 23 partitioned by the piston 21 are formed in the cylinder tube 20a.

  The relative pressure of the second valve member 32 rotating coaxially with the input shaft 2 relative to the cylindrical first valve member 31 rotating coaxially with the output shaft 3 with respect to the hydraulic pressure of the pressure oil supplied to the hydraulic cylinder 20. A rotary hydraulic control valve 30 is provided to control according to the rotation angle. The first valve member 31 is inserted into the housing 7 so as to be rotatable, and the second valve member 32 is inserted into the first valve member 31 so as to be relatively rotatable about a coaxial center. The first valve member 31 is connected to the output shaft 3 via a pin 33 so as to rotate along the same axis. The second valve member 32 is integrally formed on the outer periphery of the input shaft 2 so as to rotate along the same axis as the input shaft 2. The housing 7 is connected to a port connected to the pressure oil discharge pump 42, a port connected to the tank 43, a port connected to one oil chamber 22 of the hydraulic cylinder 20, and the other oil chamber 23. The ports communicate with each other via a flow path between the first valve member 31 and the second valve member 32. The opening degree of the throttle portion in the flow path between both valve members 31 and 32 changes according to the relative rotation angle of the input / output shafts 2 and 3. For example, as shown in FIG. 2, between the axial edges of the plurality of first grooves 48 on the inner periphery of the first valve member 31 and the axial edges of the plurality of second grooves 49 on the outer periphery of the second valve member 32. Are the aperture portions A, B, C, and D. The first grooves 48 that communicate with one oil chamber 22 and the first grooves 48 that communicate with the other oil chamber 23 are alternately arranged in the circumferential direction. A second groove 49 that communicates with the pump 42 and a second groove 49 that communicates with the tank 43 through a through hole 2a formed in the input shaft 2 and a space between the torsion bar 6 and the input shaft 2 are provided in the circumferential direction. Alternatingly arranged. Thereby, the hydraulic circuit shown in FIG. 3 is configured. When the steering is not performed, the throttle portions A, B, C, and D are opened and the hydraulic pressure does not increase, so that the steering assist force is not generated. During right steering, the apertures of the throttles A and D increase according to the relative rotation angles of the valve members 31 and 32 due to the relative rotation of the input shaft 2 and the output shaft 3, and the apertures of the throttles B and C are increased. Pressure oil is supplied to one of the oil chambers 22, the oil flows back to the tank 43 from the other oil chamber 23, and the hydraulic cylinder 20 generates a steering assist force in the right direction according to the relative rotation angle. . During left steering, the apertures of the throttles A, B, C, and D are opposite to those during right steering, and the hydraulic cylinder 20 generates a steering assist force in the left direction according to the relative rotation angle.

  As shown in FIGS. 4 and 5, a pressing member 50 that rotates along with the input shaft 2 and that can be displaced in the radial direction is disposed in a through hole 2 b formed in the input shaft 2 along the radial direction. The pressing member 50 of this embodiment is configured by a steel ball. A pressed portion 51 is provided on the outer periphery of the torsion bar 6. The pressed portion 51 of the present embodiment is configured by a groove formed along the axial direction in the portion 6a between both ends of the torsion bar 6, and has a V shape when viewed in the axial direction. Thus, the pressed portion 51 has a pair of pressed surfaces 51 ′ that are in contact with each other at the center position in the circumferential direction of the torsion bar 6. The pressing member 50 is positioned at the center position of the pressed portion 51 in the circumferential direction of the torsion bar 6 by contacting the pressed surfaces 51 ′.

  A holder 60 that holds the pressing member 50 is attached to the input shaft 2 so as to rotate together. The holder 60 according to the present embodiment includes a ring-shaped main body 60a having a split portion, receiving portions 60b and 60c protruding radially outward from respective end portions of the main body 60a, and protruding radially inward from the inner periphery of the main body 60a. A pair of leaf spring-shaped holding bodies 60d, 60e, a bolt 60f with a head passing through both receiving portions 60b, 60c, and a nut 60g screwed to the bolt 60f. By inserting the input shaft 2 into the main body 60a and screwing the nut 60g into the bolt 60f, the outer periphery of the input shaft 2 is tightened by the main body 60a, and the holder 60 is attached to the input shaft 2 so as to rotate along with the input shaft 2. The mounting position of the holder 60 on the input shaft 2 can be changed in the circumferential direction of the torsion bar 6 by loosening the screwing of the nut 60g into the bolt 60f.

  The pair of holding bodies 60d and 60e are disposed in the through hole 2b of the input shaft 2 and have holding surfaces 60d 'and 60e' that are separated from each other in the circumferential direction of the torsion bar 6 as they approach the torsion bar 6. The pressing member 50 is disposed between the holding bodies 60d and 60e and the pressed member 51 by contacting both the holding surfaces 60d 'and 60e' and the pressed surfaces 51 '. The holding bodies 60d and 60e can be elastically deformed along the radial direction of the torsion bar 6. A force for pressing the pressed portion 51 by the pressing member 50 is applied by the elastic deformation of the holding bodies 60d and 60e. As a result, a dedicated member for applying the pressing force becomes unnecessary, and the structure is not complicated. The dimension of the through hole 2 b is set so that the holding bodies 60 d and 60 e and the pressing member 50 can be displaced in the circumferential direction of the torsion bar 6 with respect to the input shaft 2. Thereby, the circumferential relative position of the pressed portion 51 with respect to the pressing member 50 is adjusted by changing the mounting position of the holder 60 to the input shaft 2 in the circumferential direction of the torsion bar 6.

  When the relative rotation angle of both the valve members 31 and 32 is less than the set value, the torsion between the one end side of the torsion bar 6 and the pressed portion 51 is restricted by the pressing of the pressed portion 51 by the pressing member 50. The In this case, the effective length of the torsion bar 6 is the distance between the other end side of the torsion bar 6 and the pressed portion 51 (L1 in FIG. 1). When the relative rotation angle of both the valve members 31 and 32 is equal to or larger than the set value, the pressed portion 51 is relatively displaced in the circumferential direction with respect to the pressing member 50 due to the torsion bar 6 being twisted. Since it touches the portion along the cylindrical surface of the outer periphery of the pressing portion, the pressing of the pressed portion 51 is released. In this case, the effective length of the torsion bar 6 is the distance between the one end side and the other end side of the torsion bar 6 (L2 in FIG. 1). As a result, as shown in FIG. 6, the rigidity of the torsion bar 6 is substantially greater when the relative rotational angle δ of both valve members 31 and 32 is less than the set value δa than when the relative rotation angle δ is greater than or equal to the set value δa. Thus, the rate of change of the relative rotation angle δ of both valve members 31 and 32 due to the change of the steering torque T becomes small, and the rate of change of the steering assist force becomes small.

  According to the embodiment, the relative position in the circumferential direction between the first valve member 31 that rotates along with the output shaft 3 and the second valve member 32 that rotates along with the input shaft 2 is determined by the steering assist force at the steering angle midpoint. The positioning is completed by connecting the torsion bar 6 to the input shaft 2 and the output shaft 3 via the pin 4 and the serration 5. Thereafter, the pressing position of the pressed portion 51 by the pressing member 50 is changed by changing the mounting position of the holder 60 with respect to the input shaft 2 in the circumferential direction of the torsion bar 6. Thereby, the pressing member 50 can be positioned at the center position of the pressed portion 51 in the circumferential direction of the torsion bar 6 at the steering angle midpoint. The positioning is completed by screwing the nut 60g into the bolt 60f and attaching the holder 60 to the input shaft 2 so as to rotate together.

  The present invention is not limited to the above embodiment. For example, the shape of the pressing member and the pressed portion is not particularly limited, and the pressing member has a cylindrical shape with a curved tip, or a flat surface provided on the outer periphery of the torsion bar 6 as shown by a two-dot chain line L1 in FIG. It is good also as a pressing part. A plurality of pressing members and pressed portions may be provided. The holding body is not limited to a leaf spring shape, and may be a coil spring shape, for example. Further, a holder may be provided on the output shaft so that the pressing member rotates along with the output shaft instead of the input shaft, and one end side of the torsion bar may be connected to the output shaft and the other end side may be connected to the input shaft.

1 is a longitudinal sectional view of a hydraulic power steering apparatus according to an embodiment of the present invention. The cross-sectional view of the control valve in the hydraulic power steering device of the embodiment of the present invention Hydraulic circuit in hydraulic power steering apparatus according to an embodiment of the present invention IV-IV sectional view of FIG. V arrow view of FIG. The figure which shows the relationship between the steering torque in the hydraulic power steering device of embodiment of this invention, and the relative rotation angle of a valve member.

Explanation of symbols

2 Input shaft 3 Output shaft 6 Torsion bar 20 Hydraulic cylinder (hydraulic actuator for generating steering assist force)
30 control valve 31 first valve member 32 second valve member 50 pressing member 51 pressed portion 60 holder 60d, 60e holder

Claims (2)

An input shaft;
An output shaft;
A torsion bar that connects the input shaft and the output shaft coaxially so as to elastically rotate relative to each other according to a steering torque;
A hydraulic actuator for generating steering assist force;
Hydraulic control for controlling the hydraulic pressure of the pressure oil supplied to the hydraulic actuator according to the relative rotation angle of the valve member that rotates coaxially with the input shaft relative to the valve member that rotates coaxially with the output shaft. A valve,
A pressing member that rotates together with one of the input / output shafts and is radially displaceable;
A pressed portion provided on the outer periphery of the torsion bar;
Means for applying a force to press the pressed portion by the pressing member,
One of the one end side and the other end side of the torsion bar is connected to the input shaft so as to rotate coaxially and the other is connected to the output shaft so as to rotate coaxially.
When the relative rotation angle of the both valve members is less than a set value, the pressing of the pressed portion by the pressing member restricts torsion between one end side of the torsion bar and the pressed portion,
When the relative rotation angle of both the valve members is equal to or greater than a set value, the pressed portion is released by the relative displacement of the pressed portion with respect to the pressing member due to torsion of the torsion bar, so that the pressing is released. In the device
It is attached to one of the input / output shafts so as to rotate together, and a holder is provided that can change its attachment position in the circumferential direction of the torsion bar,
The pressing member is held by the holder,
The hydraulic power steering device according to claim 1, wherein a circumferential relative position of the pressed portion with respect to the pressing member is adjusted by a change in a circumferential direction of a mounting position of the holder. The holder has an elastically deformable holding body,
The pressing member is disposed between the holding body and the pressed portion,
The hydraulic power steering apparatus according to claim 1, wherein a pressing force of the pressed portion by the pressing member is applied by elastic deformation of the holding body.

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