JP2019214240A - Steering system - Google Patents

Abstract

To realize a structure capable of effectively suppressing vibrations of a steering wheel, and saving energy.SOLUTION: A steering shaft 5a includes a backward upper shaft 15, a forward lower shaft 16, and a reverse input cutoff clutch 17 interposed between the upper shaft 15 and lower shaft 16. When a rotational torque is inputted to the upper shaft 15, the reverse input cutoff clutch 17 transmits the rotational torque of the upper shaft 15 to the lower shaft 16. When a rotational torque is inputted to the lower shaft 16, the reverse input cutoff clutch does not transmit the rotational torque of the lower shaft 16 to the upper shaft 15 or transmits part of the rotational torque of the lower shaft 16 to the upper shaft 15 and cuts off the remainder.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a steering device for giving a steering angle to a steered wheel of a vehicle such as an automobile.

  FIG. 23 shows an example of a steering device for an automobile. The rotation of the steering wheel 1 is transmitted to the input shaft 3 of the steering gear unit 2, and the rotation of the input shaft 3 pushes and pulls a pair of tie rods 4 on the left and right sides to impart a steering angle to the front wheels. The steering wheel 1 is supported and fixed to the rear end of the steering shaft 5. The steering shaft 5 is inserted through the inside of the steering column 6 in the axial direction, and is rotatably supported by the steering column 6. The front end of the steering shaft 5 is connected to the rear end of the intermediate shaft 8 via a first universal joint 7, and the front end of the intermediate shaft 8 is connected to the input shaft 3 via a second universal joint 9. It is connected.

  When a vehicle equipped with the above-described steering device travels on a rough road or the like, vibration is input to wheels, and when the vibration is transmitted to the steering wheel 1 via the steering device, the steering wheel There is a possibility that the driver operating the wheel 1 may feel uncomfortable.

  Japanese Patent Application Laid-Open No. 61-218474 discloses that vibration of a steering wheel is detected by a vibrometer, and a vibration damping force is applied to the steering wheel by an actuator based on a detection signal from the vibrometer to thereby reduce the vibration of the steering wheel. A steering device is described that reduces

JP-A-61-218474

  The steering apparatus described in Japanese Patent Application Laid-Open No. 61-218474 has room for improvement in terms of more effectively suppressing the vibration of the steering wheel. If the frequency of the vibration applied to the steering wheel from the wheel via the steering device is close to the resonance frequency of the upper portion of the steering device including the steering wheel and the steering shaft, the portion resonates and the vibration of the steering wheel is reduced. growing. When such resonance occurs, there is a possibility that the vibration of the steering wheel cannot be sufficiently suppressed only by applying the damping force to the steering wheel by the actuator.

  Further, the steering apparatus described in Japanese Patent Application Laid-Open No. 61-218474 has room for improvement in terms of energy saving because the electric actuator applies a damping force to the steering wheel.

  The present invention has been made in view of the above circumstances, and has as its object to realize a structure of a steering device capable of effectively suppressing vibration of a steering wheel and achieving energy saving.

The steering device according to the present invention includes a steering shaft, an intermediate shaft, and a steering gear unit.
The steering shaft fixes a steering wheel to a rear end.
The intermediate shaft has a rear end connected to a front end of the steering shaft so as to freely transmit torque.
The steering gear unit includes, at the front end of the intermediate shaft, an input shaft having a rear end connected to transmit torque freely, and a linear motion shaft that is displaced in the axial direction with rotation of the input shaft.
Any one of the steering shaft, the intermediate shaft, and the input shaft is installed on a rear upper shaft, a front lower shaft, and between the upper shaft and the lower shaft. A reverse input cutoff clutch.
When the rotational torque is input to the upper shaft, the reverse input cut-off clutch transmits the rotational torque input to the upper shaft to the lower shaft, and the rotational torque is reversely input to the lower shaft. In this case, the rotational torque reversely input to the lower shaft is not transmitted to the upper shaft, or a part of the rotational torque reversely input to the lower shaft is transmitted to the upper shaft to block the remaining portion. .

The reverse input cutoff clutch may include an input unit, an output unit, a pressed member, and an engaging element.
The input unit rotates integrally with the upper shaft.
The output unit is arranged coaxially with the input unit, and rotates integrally with the lower shaft.
The pressed member has a pressed surface.
When a rotational torque is input to the input unit, the engagement element moves in a direction away from the pressed surface based on engagement with the input unit, and engages with the output unit. The rotational torque input to the input unit is transmitted to the output unit, and, when the rotational torque is reversely input to the output unit, in the direction approaching the pressed surface based on the engagement with the output unit. By moving and being pressed against the pressed surface, the rotational torque reversely input to the output unit is not transmitted to the input unit, or a part of the rotational torque reversely input to the output unit. The signal is transmitted to the input unit, and the rest is cut off.

  The input unit has an input engagement projection at a portion radially deviated from the rotation center of the input unit, the output unit has an output engagement cam unit, and the engagement element is The input engagement projection is provided between the pressed surface and the output engagement cam portion, and the input engagement projection is provided inside the input engagement hole with respect to the pressed surface. Engagement can be performed so that perspective movement is possible.

  The pressed surface may be a cylindrical concave surface, and the engaging element may have a cylindrical convex pressing surface against which the engaging element is pressed against the pressed surface.

  The output section may include an output engagement cam section, and a pair of the engagement elements may be provided so as to sandwich the output engagement cam section from a radially outer side of the reverse input cutoff clutch.

  The steering gear unit may be a rack-and-pinion type steering gear unit including the input shaft having pinion teeth and a rack shaft having the rack teeth meshing with the linear motion shaft and the pinion teeth. it can.

  Alternatively, the steering gear unit may include the input shaft, a ball nut that rotates with the rotation of the input shaft and has an outer-diameter-side ball screw groove on an inner peripheral surface, and the linear motion shaft, Ball screw steering comprising: a ball screw shaft having an inner diameter ball screw groove; and a plurality of balls rotatably arranged between the outer diameter ball screw groove and the inner diameter ball screw groove. It can be a gear unit.

  Alternatively, the steering gear unit includes the input shaft, a nut that rotates with the rotation of the input shaft, and has a female thread groove on an inner peripheral surface, and the linear motion shaft, which has a male thread groove on an outer peripheral surface. The screw shaft, between the inner peripheral surface of the nut and the outer peripheral surface of the screw shaft, revolves around the central axis of the screw shaft and its own central axis parallel to the central axis of the screw shaft. A planetary roller screw-type steering gear unit, comprising a plurality of planetary rollers engaged with the female screw groove and the male screw groove, and a roller screw groove formed on the outer peripheral surface, which is rotatably supported. can do.

  An electric assist mechanism for applying auxiliary power of an electric motor to a shaft disposed on a steering wheel side of a portion of the steering shaft, the intermediate shaft, and the input shaft that is located closer to a steering wheel than a portion where the reverse input cutoff clutch is installed. Further provisions may be made.

  ADVANTAGE OF THE INVENTION According to the steering device of this invention, vibration of a steering wheel can be suppressed effectively and energy saving can be achieved.

FIG. 1 is a schematic diagram of a steering device according to a first example of an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the installation portion of the reverse input cutoff clutch. FIG. 3 is a sectional view showing the reverse input cutoff clutch taken out. FIG. 4 is a perspective view showing the reverse input cutoff clutch. FIG. 5 is a perspective view showing the input portion of the reverse input cutoff clutch. FIG. 6 is a perspective view showing the output portion of the reverse input cutoff clutch. FIG. 7 is a cross-sectional view showing the reverse input cutoff clutch in which the rotation torque is input to the input unit. FIG. 8 is a cross-sectional view showing the reverse input cutoff clutch in which the rotational torque is reversely input to the output unit. FIG. 9 is a partially enlarged view of FIG. 8 showing a relationship of a force acting on the engagement element from the output unit when a rotational torque is reversely input to the output unit. FIG. 10 is a cross-sectional view of the reverse input cut-off clutch for explaining a condition in which the output unit locks or semi-locks when a rotational torque is reversely input to the output unit. FIG. 11 is a schematic diagram of a steering device according to a second example of the embodiment of the present invention. FIG. 12 is a schematic diagram of a steering device according to a third example of the embodiment of the present invention. FIG. 13 is a schematic diagram of a steering device according to a fourth example of an embodiment of the present invention. FIG. 14 is a schematic diagram of a steering device according to a fifth example of the embodiment of the present invention. FIG. 15 is a schematic diagram of a steering device according to a sixth example of an embodiment of the present invention. FIG. 16 is a schematic diagram of a steering device according to a seventh example of an embodiment of the present invention. FIG. 17 is a schematic diagram of a steering device according to an eighth embodiment of the present invention. FIG. 18 is a schematic diagram of a steering device according to a ninth embodiment of the present invention. FIG. 19 is a schematic diagram of a steering device according to a tenth example of an embodiment of the present invention. FIG. 20 is a sectional view of the eleventh example of the embodiment of the present invention, illustrating the reverse input cutoff clutch taken out therefrom. FIG. 21 is a cross-sectional view showing an installation portion of a reverse input cutoff clutch according to an eleventh example of the embodiment of the present invention. FIG. 22 is a cross-sectional view illustrating a twelfth example of the embodiment of the present invention by extracting and showing the reverse input cutoff clutch. FIG. 23 is a partially cut-away side view showing an example of a conventional structure of a steering device.

[First Example of Embodiment]
1 to 10 show a first example of an embodiment of the present invention. The steering device of this example includes a steering shaft 5a, an intermediate shaft 8a, and a steering gear unit 2a.

  The steering shaft 5a supports and fixes the steering wheel 1a at the rear end. The steering shaft 5a is inserted through the inside of a cylindrical steering column 6a, and is rotatably supported by the steering column 6a. By supporting and fixing the steering column 6a to the vehicle body via a support bracket, the steering shaft 5a is rotatably supported by the vehicle body.

  The intermediate shaft 8a has a rear end connected to a front end of the steering shaft 5a via a first universal joint 7a to freely transmit torque.

  The steering gear unit 2a converts the rotational motion of the intermediate shaft 8a into a linear motion in the width direction of the vehicle body. In this example, the steering gear unit 2a is a rack-and-pinion type steering gear unit including an input shaft 3a and a rack shaft 10 that is a direct-acting shaft.

  The input shaft 3a has a rear end connected to a front end of the intermediate shaft 8a via a second universal joint 9a so as to freely transmit torque. The input shaft 3a has pinion teeth 11 on the outer peripheral surface of the front end.

  The rack shaft 10 is supported by the vehicle body so that the axial direction matches the width direction of the vehicle body and the rack shaft 10 can be displaced in the axial direction. The rack shaft 10 has a rack tooth 12 that meshes with a pinion tooth 11 of the input shaft 3a, at least on the front side surface in the axial middle part. The base end of the tie rod 4a is connected to both axial ends of the rack shaft 10, and the base end of the knuckle arm 13 is supported at the front end of the tie rod 4a. A steering wheel 14 is rotatably supported at the tip of the knuckle arm 13 via a hub unit bearing. In addition, the steering wheel 14 is usually a front wheel in an automobile. However, in special vehicles such as forklifts, the steered wheels may be rear wheels.

  In this example, the steering shaft 5a includes a rear upper shaft 15, a front lower shaft 16, and a reverse input cutoff clutch 17 installed between the upper shaft 15 and the lower shaft 16. When the steering shaft has a telescopic structure in which an inner shaft and an outer tube are combined, one of the inner shaft and the outer tube is connected to the rear upper shaft 15 and the front lower shaft. 16 and a reverse input cutoff clutch 17 installed between the upper shaft 15 and the lower shaft 16.

  That is, the upper shaft 15 supports and fixes the steering wheel 1a at the rear end. The lower shaft 16 has a rear end connected to a front end of the upper shaft 15 via a reverse input cutoff clutch 17 and a front end connected to the rear of the intermediate shaft 8a via a first universal joint 7a. Connect the torque transmission freely to the end.

  When the rotational torque is input to the upper shaft 15, the reverse input cutoff clutch 17 transmits the rotational torque input to the upper shaft 15 to the lower shaft 16, and the rotational torque is reversely input to the lower shaft 16. In this case, the rotational torque reversely input to the lower shaft 16 is not transmitted to the upper shaft 15 or a part of the rotational torque reversely input to the lower shaft 16 is transmitted to the upper shaft 15 to block the remaining portion. .

  In this example, the reverse input cutoff clutch 17 includes an input section 18, an output section 19, a pressed member 20, and a pair of engagement elements 21.

  The input unit 18 rotates integrally with the upper shaft 15. The input section 18 has an input shaft section 22 and a pair of input engagement projections 23.

  The input shaft portion 22 has a central axis that is coaxial with the central axis of the upper shaft 15. Each of the pair of input engagement projections 23 has a substantially elliptical columnar shape, and extends in the axial direction from two positions on the front end face of the input shaft 22 opposite to each other in the radial direction. The pair of input engagement projections 23 are separated from each other in the radial direction of the input unit 18. In short, the pair of input engagement projections 23 is formed so as to extend in the axial direction from a portion of the front end face of the input shaft 22 radially outward from the center axis of the input shaft 22. I have. Each of the input engaging projections 23 has a radially outer surface having the same contour as the cylindrical surface constituting the outer peripheral surface of the front end portion of the input shaft portion 22, and a circumferentially central portion extending radially inward. And a radially inner surface having a protruding cylindrical shape.

  For example, the input unit 18 can be fixed to the front end of the upper shaft 15, that is, can be formed integrally with the upper shaft 15. Alternatively, the input section 18 is formed separately from the upper shaft 15, and the rear end of the input shaft section 22 of the input section 18 is connected to the front end of the upper shaft 15, and the center axis of the input shaft section 22 and the upper shaft 15. The input shaft 18 and the upper shaft 15 can be connected and fixed so that they coincide with the central axis and the input unit 18 and the upper shaft 15 rotate integrally.

  The output unit 19 is arranged coaxially with the input unit 18 and rotates integrally with the lower shaft 16. The output section 19 has an output shaft section 24 and an output engagement cam 25. The output shaft portion 24 and the output engagement cam 25 are coaxially arranged in series with each other.

  The output shaft portion 24 has a central axis that is coaxial with the central axis of the lower shaft 16 and has a cylindrical shape. The output engagement cam 25 has a substantially elongated cylindrical shape, and extends in the axial direction from the center of the rear end surface of the output shaft 24. The output engagement cam 25 has an outer peripheral side surface composed of a pair of flat surfaces parallel to each other and a pair of partially convex cylindrical surfaces. Specifically, a pair of flat surfaces are provided on both sides in the short axis direction on the outer peripheral side surface of the output engagement cam 25, and a pair of partially convex cylindrical surfaces are provided on both sides in the long axis direction. For this reason, the distance from the central axis of the output engagement cam 25 to the outer peripheral side surface changes in the circumferential direction. The output engagement cam 25 is disposed between the pair of input engagement projections 23.

  The pressed member 20 has a cylindrical shape, and has a cylindrical concave pressed surface 26 on the inner peripheral surface. The pressed member 20 is disposed radially outward of the input unit 18 and the output unit 19 and is coaxial with the input unit 18 and the output unit 19, and is prevented from rotating. Specifically, a pair of input engagement projections 23 and output engagement cams 25 are arranged radially inside the pressed member 20. Further, the pressed member 20 is fixed to the steering column 6a by press-fitting the outer peripheral surface thereof into the small diameter portion 27 formed on the inner peripheral surface of the intermediate portion of the steering column 6a, and is prevented from rotating. In addition, a serration is formed on the outer peripheral surface of the pressed member 20, or a key engagement between the pressed member 20 and the small-diameter portion 27 of the steering column 6a is performed to secure the rotation preventing force of the pressed member 20. You can also. Alternatively, the pressed member may be a steering column, and the pressed surface may be formed directly on the inner peripheral surface of the steering column.

  When a rotational torque is input to the input unit 18, the pair of engagement members 21 move away from the pressed surface 26 based on the engagement with the input unit 18 and engage with the output unit 19. By this, when the rotational torque input to the input unit 18 is transmitted to the output unit 19, when the rotational torque is reversely input to the output unit 19, the pressed surface 26 is engaged based on the engagement with the output unit 19. Move in a direction approaching to and pressed against the pressed surface 26, so that the rotational torque input reversely to the output unit 19 is not transmitted to the input unit 18 or the rotational torque input reversely to the output unit 19 Is transmitted to the input unit 18 and the rest is cut off.

  In this example, each of the pair of engagement elements 21 has a substantially semicircular plate shape, in other words, an arcuate plate shape, and is arranged radially inside the pressed member 20. Specifically, the pair of engagement elements 21 are arranged such that the output engagement cam 25 is disposed between the pressed surface 26 and the output engagement cam 25 in both radial directions corresponding to the short axis direction of the output engagement cam 25. (Upper and lower sides in FIGS. 2 and 3). The pair of engaging members 21 are the same parts having the same shape and the same size.

  Each of the pair of engaging members 21 has a cylindrical convex pressing surface 28 on a radially outer surface facing the pressed surface 26, and a radially inner surface facing the output engaging cam 25, It has a bottom surface 29 that can be engaged with the output engagement cam 25. For this reason, the pair of engaging members 21 are arranged radially inside the pressed member 20 with the pressing surfaces 28 facing each other and the bottom surfaces 29 facing each other. In a state in which the pair of engaging elements 21 are arranged radially inside the pressed member 20, a portion between the pressed surface 26 and the pressing surface 28 and a portion between the output engagement cam 25 and the bottom surface 29 are formed. The inner diameter dimension of the pressed member 20 and the radial dimension of the pair of engagement members 21 are regulated so that a gap exists in at least one of the portions.

  Each of the pair of engagement elements 21 has an input engagement hole 30 that penetrates the engagement element 21 in the axial direction at a radially intermediate portion. The input engagement hole 30 is a through hole having a substantially rectangular opening shape extending in the width direction of the engagement element 21, and has a size that allows the input engagement protrusion 23 to be loosely inserted.

  The width direction of the engagement element 21 refers to the direction in which the bottom surface 29 corresponding to the chord of the engagement element 21 extends, and is substantially parallel to the long axis direction of the output engagement cam 25. The width direction of the engagement element 21 is the left-right direction in FIG. 3, but the direction changes as the engagement element 21 rotates. The direction in which the pair of engaging members 21 are arranged, that is, the direction orthogonal to the respective bottom surfaces 29 of the engaging members 21 is referred to as the perspective direction of the pair of engaging members 21. The perspective direction of the pair of engaging members 21 is one of the radial directions, and is the vertical direction in FIG. 3, but the direction changes as the engaging members 21 rotate. In this example, the direction orthogonal to the perspective direction is the width direction.

  In a state where the input engagement projection 23 is inserted inside the input engagement hole 30, the width direction of the engagement element 21 and the direction orthogonal to the width direction are provided between the input engagement projection 23 and the input engagement hole 30. Gaps exist in the direction in which the engaging elements 21 are arranged, that is, in the direction in which the engaging elements 21 are arranged. For this reason, the input engagement projection 23 can move relative to the input engagement hole 30 in the rotation direction of the input unit 18, and the input engagement hole 30 engages with the input engagement projection 23. The relative movement in the direction orthogonal to the width direction of the joint 21 is possible.

  The pressing surface 28 has a surface property having a larger coefficient of friction than the other parts of the engagement element 21 and has the same radius of curvature as the radius of curvature of the surface 26 to be pressed, or the radius of curvature of the surface 26 to be pressed. It has a slightly smaller radius of curvature. The pressing surface 28 may be constituted directly by the surface of the engaging element 21 or may be constituted by a radially outer surface of a friction material fixed to the engaging element 21 by sticking or bonding. The friction coefficient of the pressing surface 28 can be determined according to how much the rotational torque reversely input to the output unit 19 is cut off.

  The bottom surface 29 of the pair of engagement elements 21 is a flat surface, and has an output engagement recess 31 which is a substantially rectangular recess engaged with the output engagement cam 25 at the center in the width direction. The output engagement concave portion 31 has a size and a shape that allows the front half of the output engagement cam 25 in the short axis direction to be arranged without play inside. Specifically, the output engagement concave portion 31 has an opening width substantially the same as the dimension of the output engagement cam 25 in the long axis direction, and is smaller than １ ／ of the dimension of the output engagement cam 25 in the short axis direction. Also have a slightly smaller radial depth. The bottom of the output engagement recess 31 is a flat surface parallel to the bottom surface 29.

  The reverse input cutoff clutch 17 axially inserts a pair of input engagement projections 23 of the input portion 18 disposed on the rear side into respective input engagement holes 30 of the pair of engagement members 21, and The output engagement cam 25 of the output portion 19 disposed on the front side is inserted between the pair of output engagement recesses 31 in the axial direction.

  In the steering device of this example, when the driver operates the steering wheel 1a, the rotational torque is input to the upper shaft 15 of the steering shaft 5a, and the rotational torque is input to the input section 18 of the reverse input cutoff clutch 17.

  In the reverse input cutoff clutch 17 of the present example, when a rotational torque is input to the input unit 18, the pair of engagement members 21 move in a direction away from the pressed surface 26 regardless of the rotation direction of the input unit 18. I do. Then, the rotational torque input to the input unit 18 is transmitted to the output unit 19 via the pair of engagement elements 21.

  Specifically, when a rotational torque is input to the input unit 18, as shown in FIG. 7, regardless of the rotation direction of the input unit 18, the pair of engagement members 21 move away from the pressed surface 26. Move each. That is, the pair of engagement elements 21 move radially inward so as to approach each other in the perspective direction based on the engagement between the input engagement hole 30 and the input engagement projection 23 (the upper position in FIG. 7). The engaging element 21 moves downward, and the engaging element 21 located on the lower side of FIG. 7 moves upward). As a result, the bottom surfaces 29 of the pair of engagement elements 21 move in the direction approaching each other, and the pair of output engagement recesses 31 sandwich the output engagement cam 25 from both sides in the radial direction. That is, while rotating the output portion 19 such that the long axis direction of the output engagement cam 25 is parallel to the bottom of the output engagement recess 31, the output engagement cam 25 and the pair of output engagement recesses 31 are separated. Engage without rattling. Therefore, the rotational torque input to the input unit 18 is transmitted to the output unit 19 via the pair of engagement elements 21 and further transmitted from the output unit 19 to the lower shaft 16 of the steering shaft 5a.

  The rotational torque transmitted to the lower shaft 16 is transmitted to the intermediate shaft 8a via the first universal joint 7a, and the rotational torque of the intermediate shaft 8a is transmitted to the steering gear unit 2a via the second universal joint 9a. To the input shaft 3a. When the input shaft 3a rotates, the rack shaft 10 is moved in the width direction of the vehicle body by an amount corresponding to the rotation amount of the input shaft 3a based on the engagement between the pinion teeth 11 of the input shaft 3a and the rack teeth 12 of the rack shaft 10. Displace. Thereby, the pair of tie rods 4a is pushed and pulled, and a steering angle is given to the pair of left and right steered wheels 14.

  On the other hand, when the automobile equipped with the steering device of the present example travels on a rough road, vibration is input to the steered wheels 14, and the rack shaft 10 of the steering gear unit 2a is moved along with the vibration. There is a possibility of displacement in the width direction. When the rack shaft 10 is displaced in the width direction of the vehicle body, a rotational torque is reversely input to the input shaft 3a based on the engagement between the rack teeth 12 of the rack shaft 10 and the pinion teeth 11 of the input shaft 3a. The rotational torque reversely input to the input shaft 3a is transmitted to the intermediate shaft 8a via the second universal joint 9a, and the rotational torque of the intermediate shaft 8a is transmitted to the steering shaft 5a via the first universal joint 7a. To the lower shaft 16.

  When the rotational torque is reversely input to the lower shaft 16 and the rotational torque is reversely input to the output unit 19 of the reverse input cutoff clutch 17, as shown in FIG. The engaging element 21 moves in a direction approaching the pressed surface 26 and presses each pressing surface 28 against the pressed surface 26. That is, as the output engagement cam 25 rotates inside the pair of output engagement recesses 31, the bottom of the output engagement recess 31 is radially outward due to the corners of the output engagement cam 25. Then, the pair of engagement members 21 move in a direction approaching the pressed surface 26. In other words, the pair of engaging members 21 move radially outward so as to separate from each other based on the engagement between the output engaging concave portion 31 and the output engaging cam 25 (the upper engaging member 21 in FIG. 8). Moves upward, and the lower engaging element 21 in FIG. 8 moves downward). Thereby, the pressing surfaces 28 of the pair of engaging elements 21 are pressed against the pressed surfaces 26. In short, the pressing surface 28 and the pressed surface 26 come into contact with each other in the entire range or a part of the pressing surface 28 in the circumferential direction, for example, in the center.

  The reverse input cutoff clutch 17 prevents the rotation torque reversely input to the output unit 19 from being transmitted to the input unit 18 based on the contact between the pressing surface 28 and the pressed surface 26, or It functions so that only part of the reversely input rotational torque is transmitted and the rest is cut off.

  When the rotation torque reversely input to the output unit 19 is not transmitted to the input unit 18, the pressing surface 28 does not slide with respect to the pressed surface 26, that is, the pair of engagement members 21 are The pair of engagement members 21 are stretched between the output engagement cam 25 and the pressed member 20 so as not to rotate relative to the pressing member 20, and the output unit 19 is locked. On the other hand, when only a part of the rotational torque reversely input to the output unit 19 is transmitted to the input unit 18 and the remaining portion is cut off, the pressing surface 28 is The pair of engagement members 21 are stretched between the output engagement cam 25 and the pressed member 20 so as to slide, and the output unit 19 is half-locked.

  The principle and conditions under which the output unit 19 locks or semi-locks when the rotation torque is reversely input to the output unit 19 as described above will be described with reference to FIGS. 9 and 10.

When the corner of the output engagement cam 25 comes into contact with the bottom of the output engagement recess 31 by the reverse input of the rotational torque to the output portion 19, as shown in FIG. A normal force Fc acts on a contact portion X between the output engagement recess 31 and the bottom of the output engagement recess 31 in a direction perpendicular to the bottom of the output engagement recess 31. Therefore, assuming that the friction coefficient between the output engagement cam 25 and the bottom of the output engagement recess 31 is μ, the frictional force μFc acts on the contact portion X in a direction parallel to the bottom of the output engagement recess 31. I do. Here, assuming that the wedge angle between the direction of the line of action of the tangential force Ft acting on the contact portion X and the bottom of the output engagement recess 31 is θ, the tangential force Ft is expressed by the following equation (1). Is done.
Ft = Fc · sin θ + μFc · cos θ (1)
For this reason, the normal force Fc is expressed by the following equation (2) using the tangential force Ft.
Fc = Ft / (sin θ + μ · cos θ) (2)

When the corner of the output engagement cam 25 comes into contact with the bottom of the output engagement recess 31, the magnitude of the torque T transmitted from the output section 19 to the engagement element 21 depends on the center axis O of the output section 19. Assuming that the distance to the contact portion X is r, it is expressed by the following equation (3).
T = r · Ft (3)

As described above, since the normal force Fc acts on the contact portion X, the pressing surface 28 of the engaging element 21 is normal to the pressed surface 26 of the pressed member 20 as shown in FIG. It is pressed by the force of the force Fc. Therefore, the friction coefficient between the pressing surface 28 and the pressed surface 26 is represented by μ ′, and the distance from the central axis O of the output portion 19 to the contact portion Y between the pressing surface 28 and the pressed surface 26 is represented by R. Then, the magnitude of the brake torque T ′ acting on the engagement element 21 is expressed by the following equation (4).
T ′ = μ′RFc (4)
Therefore, it can be seen that a larger braking force can be obtained by increasing the friction coefficient μ ′, the distance R, and the normal force Fc.

In order to lock the output unit 19 and prevent the rotation torque reversely input to the output unit 19 from being transmitted to the input unit 18, the transmission torque T and the brake torque T ′ are calculated by the following equation (5). You need to satisfy the relationship.
T <T '(5)

By substituting the equations (1) to (4) into the equation (5), the following equation (6) is obtained.
μ′R / (sin θ + μ · cos θ)> r (6)
From the above equation (6), it can be seen that if the friction coefficient μ ′ between the pressing surface 28 and the pressed surface 26 is increased, the output unit 19 can be locked even if the distance R is reduced.

Assuming that the friction coefficient μ and the friction coefficient μ ′ are respectively 0.1, the following equation (7) is obtained from the above equation (6).
R> 10r (sin θ + 0.1 cos θ) (7)
From the above equation (7), the distance r from the central axis O of the output portion 19 to the contact portion X, the distance R from the central axis O of the output portion 19 to the contact portion Y, and the action line of the tangential force Ft It can be understood that the output unit 19 can be locked by appropriately setting the wedge angle θ between the direction of the arrow and the bottom surface of the output engagement recess 31.

On the other hand, in order for the output unit 19 to be half-locked so that only a part of the rotational torque reversely input to the output unit 19 is transmitted to the input unit 18 and the remaining is cut off, the transmission torque T It is necessary that the brake torque T 'satisfies the following equation (8).
T> T '(8)

  As is clear from the above equation (6), the friction coefficient μ between the output engagement cam 25 and the bottom of the output engagement recess 31, the friction coefficient μ ′ between the pressing surface 28 and the pressed surface 26, the center The distance r from the axis O to the contact portion X, the distance R from the central axis O to the contact portion Y, the wedge angle θ between the direction of the line of action of the tangential force Ft and the bottom of the output engagement recess 31 are respectively By properly setting, the output unit 19 can be half-locked.

  In the steering apparatus of the present embodiment as described above, the reverse input cutoff clutch 17 is provided between the upper shaft 15 and the lower shaft 16 of the steering shaft 5a. For this reason, even when the rotational torque is reversely input to the input shaft 3a based on the vibration being input to the steered wheels 14 as the vehicle travels on a rough road, the rotational torque is applied to the steering wheel 1a. It can be prevented from being transmitted, or the rotational torque transmitted to the steering wheel 1a can be reduced.

  Here, when the rotational torque is reversely input to the lower shaft 16, the output portion 19 of the reverse input cutoff clutch 17 is locked so that the rotational torque of the lower shaft 16 is not transmitted to the upper shaft 15 so that If the rotational torque reversely input to the shaft 3a is not transmitted to the steering wheel 1a, the vibration of the steering wheel 1a based on the input of the vibration to the steered wheels 14 can be prevented. As a result, the driver who operates the steering wheel 1a can feel uncomfortable.

  On the other hand, when the rotational torque is reversely input to the lower shaft 16, a part of the rotational torque of the lower shaft 16 is transmitted to the upper shaft 15 by partially locking the output portion 19 of the reverse input cutoff clutch 17. If the rotation torque transmitted to the steering wheel 1a among the rotation torques reversely input to the input shaft 3a is reduced so as to cut off the remainder, the steering wheel 1a can be reduced. As a result, the driver operating the steering wheel 1a can feel less uncomfortable, and the driver can know the state of the road surface through the steering wheel 1a.

  When the rotation torque is reversely input to the lower shaft 16 and the output portion 19 of the reverse input cutoff clutch 17 is partially locked, a part of the rotation torque of the lower shaft 16 is transmitted to the upper shaft 15 and the remaining portion is cut off. Therefore, the operation of the steering wheel 1a when returning the vehicle from the curve running to the straight running can be easily performed. In other words, when the steering wheel 1a is operated to impart a steering angle to the steered wheels 14 in order to cause the vehicle to travel on a curve, a reaction force in the direction of returning the steered angles to zero from the road surface, that is, a restoring force is applied to the steered wheels 14. Works. Therefore, if a part of the rotation torque of the lower shaft 16 is transmitted to the upper shaft 15 when the rotation torque is input to the lower shaft 16, the steering wheel when returning the vehicle from the curve running to the straight running can be obtained. The operation of 1a can be assisted by the restoring force.

When the output portion 19 of the reverse input cutoff clutch 17 is set to be half-locked when the rotation torque is reversely input to the lower shaft 16, the cutoff amount of the rotation torque reversely input to the output portion 19 is set as follows. 20% or more and 80% or less. If the cutoff amount is less than 20%, the steering torque may be input to the input shaft 3a in a reverse manner based on the fact that vibration is input to the steered wheels 14 as the vehicle travels on a rough road. There is a possibility that the rotational torque transmitted to the wheel 1a cannot be sufficiently reduced. On the other hand, if the cutoff amount is larger than 80%, there is a possibility that a sufficient force for assisting the operation of the steering wheel 1a based on the restoring force may not be obtained when returning the vehicle from the curve running to the straight running. is there. The cutoff amount can be obtained by the following equation (9).
(Interruption amount of the rotational torque reversely input to the output unit 19) = {(rotational torque reversely input to the output unit 19)-(rotational torque transmitted to the input unit 18)} / (reverse input to the output unit 19) Rotation torque) (9)

  Note that the cutoff amount is theoretically constant irrespective of the magnitude of the rotational torque reversely input to the output unit 19. However, in practice, when the magnitude of the rotational torque reversely input to the output unit 19 is equal to or less than a predetermined value, the output unit 19 is affected by the friction loss of the contact portion between the pressing surface 28 and the pressed surface 26. Is not transmitted to the input unit 18. This is advantageous in that minute vibrations of the steered wheels 14 are not transmitted to the steering wheel 1.

  In this example, the function of transmitting the rotational torque input to the input unit 18 to the output unit 19 to the engagement element 21 of the reverse input cutoff clutch 17 and the function of transmitting the rotational torque reversely input to the output unit 19 to the input unit 18. In other words, a function of transmitting a part of the rotational torque reversely input to the output unit 19 to the input unit 18 and blocking the remaining portion is provided. For this reason, the number of components of the reverse input cutoff clutch 17 can be reduced, and the operation can be stabilized, as compared with a case where both functions are provided in separate members. For example, in a case where separate members are provided with a function of transmitting the rotational torque and a function of interrupting the rotational torque, the timing of releasing the interruption of the rotational torque reversely input to the output unit and the rotational torque from the input unit to the output unit There is a possibility that the timing for starting the transmission of the information is shifted. In this case, if the rotation torque is reversely input to the output unit between the time when the interruption of the rotation torque is released and the time when the transmission of the rotation torque to the output unit is started, the output unit is locked or semi-locked again. . In this example, a function of transmitting the rotational torque input to the input unit 18 to the output unit 19 and preventing the rotational torque reversely input to the output unit 19 from being transmitted to the input unit 18, or Since both functions of transmitting a part of the rotational torque reversely input to the output unit 19 to the input unit 18 and shutting off the remaining part are provided, such an inconvenience can be prevented.

  In addition, since the direction of the force acting on the engagement element 21 from the input section 18 and the direction of the force acting on the engagement element 21 from the output section 19 are reversed, it is possible to regulate the magnitude relationship between the two forces. , The moving direction of the engagement element 21 can be controlled. Therefore, the switching operation between the locked state and the unlocked state of the output unit 19 or the switching operation between the semi-locked state and the semi-locked released state can be stably and reliably performed.

  The material constituting each of the input portion 18, the output portion 19, the pressed member 20, and the engagement element 21 of the reverse input cutoff clutch 17 is not particularly limited, and the rotational torque input from the upper shaft 15 to the input portion 18; , Is appropriately selected according to the magnitude of the rotational torque reversely input from the lower shaft 16 to the output unit 19. Specifically, for example, it can be made of a hard metal such as carbon steel or sintered metal, a metal material such as a light alloy such as an aluminum alloy or a magnesium alloy, or a synthetic resin.

  In addition, each of the input unit 18, the output unit 19, the pressed member 20, and the engagement element 21 can be subjected to a heat treatment or a surface treatment for adjusting hardness and a coefficient of friction. Specifically, for example, the pressed member 20 and the engagement element 21 are preferably subjected to a heat treatment or a surface treatment for easily increasing the surface hardness. Thereby, the pressing surface 28 of the engagement element 21 can be hardly worn, and the durability of the engagement element 21 can be ensured, and the durability of the reverse input cutoff clutch 17 can be ensured.

[Second Example of Embodiment]
FIG. 11 shows a second example of the embodiment of the present invention. The steering device of the present example is different from the steering device of the first example of the embodiment in the installation position of the reverse input cutoff clutch 17. Specifically, in the first example of the embodiment, the reverse input cutoff clutch 17 is provided on the steering shaft 5a, whereas in the present example, the reverse input cutoff clutch 17 is provided on the intermediate shaft 8b. .

  The steering device of this example includes a steering shaft 5b, an intermediate shaft 8b, and a steering gear unit 2a. The steering shaft 5b supports and fixes the steering wheel 1a at the rear end. The intermediate shaft 8b has a rear end connected to the front end of the steering shaft 5b via a first universal joint 7a so as to freely transmit torque, and has a front end connected to the input shaft of the steering gear unit 2a. The transmission of torque is freely connected to the rear end of 3a via a second universal joint 9a.

  The intermediate shaft 8b includes a rear upper shaft 15a, a front lower shaft 16a, and a reverse input cutoff clutch 17 installed between the upper shaft 15a and the lower shaft 16a. In the case where the intermediate shaft has a telescopic structure formed by combining an inner shaft and an outer tube, one of the inner shaft and the outer tube is connected to the rear upper shaft 15a and the front lower shaft 15a. 16a and a reverse input cutoff clutch 17 installed between the upper shaft 15a and the lower shaft 16a.

  The upper shaft 15a has a rear end connected to the front end of the steering shaft 5b via a first universal joint 7a so as to freely transmit torque. The lower shaft 16a has a rear end connected to a front end of the upper shaft 15a via a reverse input cutoff clutch 17, and a front end connected to the rear of the input shaft 3a via a second universal joint 9a. Connect the torque transmission freely to the end.

  In this example, the input portion 18 of the reverse input cutoff clutch 17 rotates integrally with the upper shaft 15a, and the output portion 19 rotates integrally with the lower shaft 16a. The reverse input cut-off clutch 17 transmits the rotation torque of the upper shaft 15a to the lower shaft 16a when the rotation torque is input to the upper shaft 15a, and transmits the rotation torque to the lower shaft 16a when the rotation torque is input to the lower shaft 16a. In this case, the rotational torque of the lower shaft 16a is not transmitted to the upper shaft 15a, or a part of the rotational torque of the lower shaft 16a is transmitted to the upper shaft 15a and the remaining portion is cut off.

  In this example, since the reverse input cutoff clutch 17 is installed on the intermediate shaft 8b, all or a part of the rotational torque reversely input to the steering device in response to vibration being input to the steered wheels 14 from the road surface. Can be blocked at a portion closer to the road surface than the steering device of the first example of the embodiment. Therefore, vibration of the steering wheel 1a can be more effectively prevented or reduced as compared with the steering device of the first example of the embodiment. The configuration and operation and effect of the other parts are the same as those of the first example of the embodiment.

[Third Example of Embodiment]
FIG. 12 shows a third example of the embodiment of the present invention. In the steering device of this example, a reverse input cutoff clutch 17 is provided on the input shaft 3b of the steering gear unit 2b.

  The steering device of this example includes a steering shaft 5b, an intermediate shaft 8a, and a steering gear unit 2b. The steering shaft 5b supports and fixes the steering wheel 1a at the rear end. The intermediate shaft 8a has its rear end connected to the front end of the steering shaft 5b via a first universal joint 7a so as to freely transmit torque, and has its front end connected to the input shaft of the steering gear unit 2b. The transmission of torque is freely connected to the rear end of 3b via a second universal joint 9a.

  The input shaft 3b includes a rear upper shaft 15b, a front lower shaft 16b, and a reverse input cutoff clutch 17 installed between the upper shaft 15b and the lower shaft 16b. The upper shaft 15b has a rear end connected to a front end of the intermediate shaft 8a via a second universal joint 9a so as to freely transmit torque. The lower shaft 16b has a rear end connected to a front end of the upper shaft 15b via a reverse input cutoff clutch 17, and a pinion tooth 11 meshed with a rack tooth 12 of the rack shaft 10 on an outer peripheral surface of the front end. Having.

  The input portion 18 of the reverse input cutoff clutch 17 rotates integrally with the upper shaft 15b, and the output portion 19 rotates integrally with the lower shaft 16b.

  In this example, since the reverse input cutoff clutch 17 is installed on the input shaft 3b of the steering gear unit 2b, the rotational torque that is reversely input to the steering device with the input of vibration to the steered wheels 14 from the road surface. Can be completely or partially blocked at a portion closer to the road surface than the steering devices of the first and second examples of the embodiment. Therefore, vibration of the steering wheel 1a can be more effectively prevented or reduced as compared with the steering devices of the first and second examples of the embodiment. The configuration and operation and effect of the other parts are the same as those of the first and second examples of the embodiment.

[Fourth Example of Embodiment]
FIG. 13 shows a fourth example of the embodiment of the present invention. The steering device of the present example is different from the steering device of the third example of the embodiment in the structure of the steering gear unit 2c. Specifically, in the third example of the embodiment, the steering gear unit 2b is a rack and pinion type steering gear unit, whereas in this example, the steering gear unit 2c is a ball screw type steering gear unit. I have.

  The steering gear unit 2c includes an input shaft 3c, a ball nut 32, a ball screw shaft 33 that is a direct-acting shaft, and a plurality of balls 34.

  The input shaft 3c includes a rear upper shaft 15c, a front lower shaft 16c, and a reverse input cutoff clutch 17 installed between the upper shaft 15c and the lower shaft 16c. The upper shaft 15c has a rear end connected to a front end of the intermediate shaft 8a via a second universal joint 9a so as to freely transmit torque.

  The lower shaft 16c has a rear end connected to the front end of the upper shaft 15c via a reverse input cutoff clutch 17, and has a threaded worm tooth 35 on the outer peripheral surface of the front end.

  The ball nut 32 has, on its outer peripheral surface, wheel teeth 36 that mesh with the worm teeth 35, and has, on its inner peripheral surface, a helical outer-diameter-side ball screw groove 37. For example, the wheel teeth 36 can be formed on the outer peripheral surface of a flange portion fixed so as to protrude radially outward. Alternatively, a gear having wheel teeth 36 on an outer peripheral surface is formed separately from a nut body having an outer diameter side ball screw groove 37 on an inner peripheral surface, and the gear is integrally rotated with the nut body. The ball nut 32 can also be configured by externally fitting and fixing.

  The ball screw shaft 33 is supported by the vehicle body so that the axial direction matches the width direction of the vehicle body and the axial direction of the ball screw shaft 33 can be displaced. The ball screw shaft 33 has an inner-diameter-side ball screw groove 38 at least on the outer peripheral surface at the axially intermediate portion.

  Each of the balls 34 is spirally arranged between an outer diameter ball screw groove 37 of the ball nut 32 and an inner diameter ball screw groove 38 of the ball screw shaft 33. The ball nut 32 has a circulation mechanism (not shown) for circulating the ball 34 that moves between the outer diameter side ball screw groove 37 and the inner diameter side ball screw groove 38.

  When the lower shaft 16c of the input shaft 3c rotates as the driver operates the steering wheel 1a, the ball nut 32 moves around the ball screw shaft 33 based on the engagement between the worm teeth 35 and the wheel teeth 36. Rotate. When each of the balls 34 moves between the outer diameter ball screw groove 37 and the inner diameter ball screw groove 38 with the rotation of the ball nut 32, the ball screw shaft 33 is displaced in the width direction of the vehicle body. Thereby, the pair of tie rods 4a is pushed and pulled, and a steering angle is given to the pair of left and right steered wheels 14.

  In the steering device of this example, since the steering gear unit 2c is a ball screw type steering gear unit, as in the first to third examples of the embodiment, the steering gear units 2, 2a, and 2b are rack-and-pinion. It is easier to improve quietness than a structure with a steering gear unit. That is, in the rack and pinion type steering gear unit, there is a possibility that abnormal noise due to backlash is generated at the meshing portion between the pinion teeth and the rack teeth. In this example, since the steering gear unit 2c is a ball screw type steering gear unit, the backlash is easily reduced and the quietness is easily improved as compared with the rack and pinion type steering gear unit.

  Further, since the steering gear unit 2c is a ball screw type steering gear unit, the displacement amount of the ball screw shaft 33 with respect to the rotation amount of the input shaft 3c depends on the rotation amount of the rack shaft with respect to the rotation amount of the input shaft of the rack and pinion type steering gear unit. Small compared to displacement. In other words, the force for pushing and pulling the pair of tie rods 4 by the ball screw shaft 33 can be made larger than the force for pushing and pulling the pair of tie rods 4 by the rack shaft. The required force can be reduced.

  In this embodiment, the worm teeth 35 of the lower shaft 16c and the wheel teeth 36 of the ball nut 32 are engaged with each other in order to transmit torque between the lower shaft 16c and the ball nut 32. However, the invention is not limited to this, and the torque may be transmitted between the lower shaft 16c and the ball nut 32 by meshing the bevel gears with each other.

  Further, the steering gear unit may be a sliding screw type steering gear unit including a nut having an internal thread groove on the inner peripheral surface and a screw shaft having an external thread groove screwed with the internal thread groove on the outer peripheral surface. Further, the reverse input cutoff clutch 17 can be provided on the steering shaft or the intermediate shaft. The structure and operation and effect of the other parts are the same as in the third example of the embodiment.

[Fifth Example of Embodiment]
FIG. 14 shows a fifth example of the embodiment of the present invention. In the steering device of the present example, the steering gear unit 2d is a planetary roller screw type steering gear unit.

  The steering gear unit 2d includes an input shaft 3c, a nut 39, a screw shaft 40, and a plurality of planetary rollers 41.

  The nut 39 has, on its outer peripheral surface, wheel teeth 36 that mesh with the worm teeth 35 of the lower shaft 16c of the input shaft 3c, and has a helical female thread groove 42 on its inner peripheral surface.

  The screw shaft 40 is supported by the vehicle body such that the axial direction matches the width direction of the vehicle body, and the screw shaft 40 can be displaced in the axial direction. The screw shaft 40 has a male screw groove 43 at least on the outer peripheral surface at the axially intermediate portion.

  Each of the planetary rollers 41 has a roller screw groove 44 on the outer peripheral surface. Each of the planetary rollers 41 engages the roller screw groove 44 with the female screw groove 42 and the male screw groove 43 to form a plurality of cylindrical spaces between the inner peripheral surface of the nut 39 and the outer peripheral surface of the screw shaft 40. Further, it is supported so as to be able to revolve around the central axis of the screw shaft 40 and rotate around its own central axis parallel to the central axis of the screw shaft 40.

  When the lower shaft 16c of the input shaft 3c rotates as the driver operates the steering wheel 1a, the nut 39 rotates around the screw shaft 40 based on the engagement between the worm teeth 35 and the wheel teeth 36. . When the nut 39 rotates around the screw shaft 40, each of the planetary rollers 41 revolves around the screw shaft 40, based on the engagement between the female screw groove 42 and the roller screw groove 44. When each of the planetary rollers 41 rotates while revolving around the screw shaft 40, the screw shaft 40 is displaced in the width direction of the vehicle body based on the engagement between the roller screw groove 44 and the male screw groove 43. Thereby, the pair of tie rods 4a is pushed and pulled, and a steering angle is given to the pair of left and right steered wheels 14.

  In this example, a planetary roller-type steering gear unit is used as the steering gear unit 2d, and the rotational torque of the nut 39, which rotates with the rotation of the lower shaft 16c of the input shaft 3c, is increased by a plurality of planetary rollers 41. The light is transmitted to the shaft 40. In short, since the transmission path of the rotational torque from the nut 39 to the screw shaft 40 can be dispersed into a plurality, the durability of the steering gear unit 2d can be easily ensured. The configuration and operation and effect of the other parts are the same as in the third and fourth examples of the embodiment.

[Sixth Example of Embodiment]
FIG. 15 shows a sixth example of the embodiment of the present invention. The steering device of the present embodiment is different from the steering device of the first embodiment in that the output torque of the electric motor 45, which is an auxiliary power source, is applied to the steering shaft 5a in order to reduce the force for the driver to operate the steering wheel 1a. Further provided is a column assist type electric assist mechanism 46 to be provided. More specifically, the auxiliary power of the electric motor 45 is applied to the upper shaft 15 of the steering shaft 5a, which is disposed closer to the steering wheel 1a than the portion where the reverse input cutoff clutch 17 is provided, via the reduction mechanism 47. Like that. In other words, the reverse input cutoff clutch 17 is provided in a portion of the steering device that is located closer to the steered wheels 14 than a portion to which the assist power of the electric motor 45 is applied.

  The electric assist mechanism 46 measures the rotational torque input to the upper shaft 15 of the steering shaft 5a by the driver operating the steering wheel 1a by the torque measuring device 48, and transmits the measured value to the controller ( ECU) 49. The controller 49 calculates the assisting force applied to the upper shaft 15 based on the measured value, and drives the electric motor 45 via the drive circuit 50 to rotate based on the calculated value. The electric motor 45 applies the output torque to the upper shaft 15 via the reduction mechanism 47. Thereby, the driver's force for operating the steering wheel 1a can be reduced.

  In this example, the reduction mechanism 47 is a parallel shaft gear reducer that meshes a spur gear supported and fixed to the output shaft of the electric motor 45 and a spur gear supported and fixed to an axially intermediate portion of the upper shaft 15. And However, the reduction mechanism 47 is not limited to the parallel shaft gear reducer. Specifically, for example, as the reduction mechanism 47, a planetary gear reducer, a bevel gear reducer, a worm reducer, a wave gear reducer, a cycloid reducer or a wedge roller traction reducer, or a belt between pulleys , Or a speed reducer formed by extending a chain between gears.

  In this example, the reverse input cutoff clutch 17 is provided in a portion of the steering device that is located closer to the steered wheels 14 than a portion to which the assist power of the electric motor 45 is applied. Therefore, when vibration is input to the steered wheels 14 from the road surface, the rotational torque input reversely to the steering device is not transmitted to the electric motor 45, or the rotational torque input reversely to the steering device is reduced. It is possible to reduce the rotational torque reversely input to the electric motor 45 by shutting off the section. The configuration and operation and effect of the other parts are the same as those of the first example of the embodiment.

[Seventh Example of Embodiment]
FIG. 16 shows a seventh example of the embodiment of the present invention. The steering device of the present example is different from the steering device of the second example of the embodiment in that a column assist type electric assist mechanism 46 is further provided. That is, in the steering device of the present embodiment, the reverse input cutoff clutch 17 is provided on the intermediate shaft 8b, and the output torque of the electric motor 45 of the electric assist mechanism 46 is applied to the steering shaft 5b. The configuration and operation and effect of the other parts are the same as those of the second and sixth examples of the embodiment.

[Eighth Example of Embodiment]
FIG. 17 shows an eighth embodiment of the present invention. The steering device of the present example is different from the steering device of the third example of the embodiment in that a column assist type electric assist mechanism 46 is further provided. That is, in the steering device of the present embodiment, the reverse input cutoff clutch 17 is installed on the input shaft 3b of the steering gear unit 2b, and the output torque of the electric motor 45 of the electric assist mechanism 46 is applied to the steering shaft 5b. Make up. The configuration and operation and effect of the other parts are the same as those of the third and sixth examples of the embodiment.

[Ninth Example of Embodiment]
FIG. 18 shows a ninth embodiment of the present invention. In the steering device of this example, the reverse input cutoff clutch 17 is installed on the input shaft 3b of the steering gear unit 2b, and the output torque of the electric motor 45a of the electric assist mechanism 46a is applied to the upper shaft 15b of the input shaft 3b. It is configured as follows. That is, the electric assist mechanism 46a is of a pinion assist type.

  Specifically, the electric assist mechanism 46a measures the rotational torque input to the steering shaft 5b by the torque measuring device 48, and outputs the output torque of the electric motor 45a to the reduction mechanism 47a which is a parallel gear type reduction gear. Through the upper shaft 15b of the input shaft 3b. The configuration and operation and effect of the other parts are the same as those of the third and sixth examples of the embodiment.

[Tenth Example of Embodiment]
FIG. 19 shows a tenth example of the embodiment of the present invention. The steering device of the present example has a structure in which the structure of the fourth example of the embodiment and the structure of the ninth example of the embodiment are combined. That is, in the steering device of this embodiment, the reverse input cutoff clutch 17 is installed on the input shaft 3c of the ball screw type steering gear unit 2c, and the output torque of the electric motor 45a of the electric assist mechanism 46a is changed to the input shaft 3c. Is provided to the upper shaft 15c. The configuration and operation and effect of the other parts are the same as those of the fourth and ninth examples of the embodiment.

[Eleventh Example of Embodiment]
20 and 21 show an eleventh embodiment of the present invention. In the steering device of this example, the structure of the reverse input cutoff clutch 17a is changed from the structure of the reverse input cutoff clutch 17 of the first example of the embodiment.

  In the present example, the pair of engagement elements 21a has a pressing surface 28a pressed against the pressed surface 26 at each of two circumferentially separated positions on the outer surface in the perspective direction, and A flat surface that is not pressed against the pressed surface 26 is provided at a circumferentially intermediate portion between the pair of pressing surfaces 28a among the outer surfaces in the perspective direction. Each of the pressing surfaces 28a is a partially convex cylindrical surface having a radius of curvature smaller than the radius of curvature of the pressed surface 26.

  In the reverse input cut-off clutch 17a of this example, when the rotational torque is reversely input to the output portion 19a and the engaging member 21a is pressed against the pressed surface 26 by the output engagement cam 25a, a wedge effect is generated and the pressed portion is pressed. The frictional engagement force between the surface 26 and the pressing surface 28a can be increased. For this reason, the brake torque T 'acting on the engagement element 21a can be increased. Therefore, the diameter of the reverse input cutoff clutch 17a for obtaining the required brake torque T 'can be made smaller than that of the reverse input cutoff clutch 17 of the first example of the embodiment.

  In the present example, the pair of engagement elements 21a are provided at the center in the width direction of the respective bottom surfaces 29a, and the output engagement recesses 31 () are recessed outward in the perspective direction to sandwich the output engagement cam 25a from both sides in the perspective direction. 3 (see FIG. 3). The pair of engagement elements 21a has an output engagement surface 51 which is a flat surface existing in the same virtual plane as a portion adjacent on both sides in the width direction at the center in the width direction of the bottom surface 29a.

  Each of the pair of engagement elements 21a has a guide hole 52 formed in the perspective direction, which opens at the widthwise central portion of the bottom surface 29a and the inner surface of the input engagement hole 30. The output engagement cam 25a of the output portion 19a has an insertion hole 53 that passes through the center of the output engagement cam 25a and penetrates the output engagement cam 25a in the short axis direction. The guide shaft 54, which is a guide member, has both ends in the axial direction inserted into the respective guide holes 52 of the pair of engagement members 21a so as to be able to move in the axial direction without rattling in the radial direction. The intermediate portion is loosely inserted into the insertion hole 53 of the output engagement cam 25a.

  In this example, a pair of engaging members 21a are relatively moved in the width direction by a guide mechanism including the guide holes 52 and the guide shafts 54 of the pair of engaging members 21a. The pair of engaging members 21a is prevented from inclining with each other so that the mating surfaces 51 are not parallel, and only the pair of engaging members 21a is allowed to relatively move in the perspective direction.

  Each of the pair of engaging members 21a has a bottomed cylindrical guide recess 55 which is recessed in the vertical direction with respect to the bottom surface 29a on both sides in the width direction of the bottom surface 29a. In a state in which the bottom surfaces 29a of the pair of engaging members 21a are opposed to each other, a coil spring 56 as an elastic member is arranged so as to bridge over a pair of guide concave portions 55 existing on the same straight line. I have. The elastic force of the pair of coil springs 56 urges the pair of engagement elements 21a toward the pressed surface 26. Therefore, the postures of the pair of engagement members 21a can be stabilized while synchronizing with each other, and the pair of engagement members 21a can be accurately moved in the perspective direction.

  In the reverse input cutoff clutch 17a of this example, the pressed member 20 is fixed to the small diameter portion 27 of the steering column 6a by electron beam welding, and is prevented from rotating. However, the pressed member can be fixed by being pressed into the steering column, or the pressed member can be a steering column, and the pressed surface can be formed directly on the inner peripheral surface of the steering column. The configuration and operation and effect of the other parts are the same as those of the first example of the embodiment.

[Twelfth Example of Embodiment]
FIG. 22 shows a twelfth example of the embodiment of the present invention. The reverse input cutoff clutch 17b of this embodiment is different from the eleventh embodiment of the embodiment in that the reverse input cutoff clutch 17a has a coil spring 56, an inner circumferential surface of the insertion hole 53 of the output engagement cam 25a, and a guide shaft 54. There is further provided a coil spring 56a for urging the pair of engagement members 21b toward the pressed surface 26 between the outer peripheral surface of the intermediate portion in the axial direction. Each of the pair of engaging members 21b has a pressing surface 28 which is a partially convex cylindrical surface on the outer surface in the perspective direction, similarly to the engaging member 21 in the first example of the embodiment. Has an output engagement recess 31. The configuration and operation and effect of the other parts are the same as those of the first and eleventh embodiments.

  The structures of the first to twelfth examples of the above-described embodiment can be appropriately combined and implemented as long as no contradiction occurs. For example, in a structure including a planetary roller screw type steering gear unit 2c as in the fifth example of the embodiment, a column assist type electric assist mechanism 46 as in the eighth example of the embodiment may be provided, It is also possible to provide a pinion assist type electric assist mechanism 46a as in the ninth example of the embodiment. Further, the reverse input cutoff clutch 17 in the steering apparatus of the second to tenth examples of the embodiment is replaced with the reverse input cutoff clutch 17a of the eleventh example of the embodiment or the reverse input cutoff clutch of the twelfth example of the embodiment. 17b.

  In addition, of the front wheel and the rear wheel of the vehicle equipped with the steering device of the present invention, the operation of the steering wheel 1a is transmitted by an electric signal for the wheel that is not the steered wheel 14, and the steering according to the operation amount of the steering wheel 1a is transmitted. A steer-by-wire method that gives a corner can also be adopted.

1, 1a Steering wheel 2, 2a, 2b, 2c, 2d Steering gear unit 3, 3a, 3b, 3c Input shaft 4, 4a Tie rod 5, 5a, 5b Steering shaft 6, 6a Steering column 7, 7a First universal joint 8, 8a, 8b Intermediate shaft 9, 9a Second universal joint 10 Rack shaft 11 Pinion tooth 12 Rack tooth 13 Knuckle arm 14 Steering wheel 15, 15a, 15b, 15c Upper shaft 16, 16a, 16b, 16c Lower shaft 17, 17a, 17b Reverse input cut-off clutch 18 Input part 19, 19a Output part 20 Pressed member 21, 21a, 21b Engagement element 22 Input shaft part 23 Input engagement convex part 24 Output shaft part 25, 25a Output engagement cam 26 Pressed Surface 27 Small diameter portion 28, 28a Pressing surface 29, 29a Surface 30 Input engaging hole 31 Output engaging concave portion 32 Ball nut 33 Ball screw shaft 34 Ball 35 Worm tooth 36 Wheel tooth 37 Outer diameter ball screw groove 38 Inner diameter ball screw groove 39 Nut 40 Screw shaft 41 Planetary roller 42 Female screw groove 43 Male thread groove 44 Roller thread groove 45 Electric motor 46 Electric assist mechanism 47 Reduction mechanism 48 Torque measuring device 49 Controller 50 Drive circuit 51 Output engagement surface 52 Guide hole 53 Insertion hole 54 Guide shaft 55 Guide recess 56, 56a Coil spring

Claims (9)

A steering shaft that fixes the steering wheel to the rear end,
An intermediate shaft having a rear end connected to a front end of the steering shaft so as to freely transmit torque;
A steering gear unit having an input shaft, a rear end of which is connected to a front end of the intermediate shaft so as to freely transmit torque, and a linear motion shaft that is displaced in an axial direction with rotation of the input shaft;
With
Any one of the steering shaft, the intermediate shaft, and the input shaft is installed on a rear upper shaft, a front lower shaft, and between the upper shaft and the lower shaft. Equipped with a reverse input cutoff clutch,
When the rotational torque is input to the upper shaft, the reverse input cut-off clutch transmits the rotational torque input to the upper shaft to the lower shaft, and the rotational torque is reversely input to the lower shaft. In this case, the rotational torque reversely input to the lower shaft is not transmitted to the upper shaft, or a part of the rotational torque reversely input to the lower shaft is transmitted to the upper shaft to block the remaining portion. , Steering device. The reverse input cutoff clutch,
An input unit that rotates integrally with the upper shaft,
An output unit disposed coaxially with the input unit and rotating integrally with the lower shaft;
A pressed member having a pressed surface,
When a rotational torque is input to the input unit, the input unit is moved to a direction away from the pressed surface based on engagement with the input unit, and is input to the input unit by engaging with the output unit. When the rotational torque is transmitted to the output unit and the rotational torque is reversely input to the output unit, the rotational unit moves in a direction approaching the pressed surface based on engagement with the output unit, and By being pressed against the pressing surface, the rotational torque reversely input to the output unit is not transmitted to the input unit, or a part of the rotational torque reversely input to the output unit is transmitted to the input unit. And an engaging element for cutting off the remaining part,
The steering device according to claim 1, comprising: The input unit has an input engagement protrusion at a portion radially deviated from a rotation center of the input unit,
The output section has an output engagement cam section,
The engagement element has an input engagement hole, and is disposed between the pressed surface and the output engagement cam portion,
3. The steering device according to claim 2, wherein the input engagement convex portion is engaged with the inside of the input engagement hole such that the input engagement convex portion can move toward and away from the pressed surface. The pressed surface is a cylindrical concave surface,
The steering device according to claim 2, wherein the engagement element has a cylindrical convex pressing surface that is pressed against the pressed surface. The output section has an output engagement cam section,
The steering device according to any one of claims 2 to 4, wherein a pair of the engagement elements is provided so as to sandwich the output engagement cam portion from a radially outer side of the reverse input cutoff clutch. .   The said steering gear unit is provided with the said input shaft which has a pinion tooth, and the said linear motion shaft, and the rack shaft which has the rack tooth which meshes with the said pinion tooth, The any one of Claims 1-5. The steering device according to the paragraph.   The steering gear unit, the input shaft, a ball nut that rotates with the rotation of the input shaft, and has a ball screw groove having an outer diameter side on an inner peripheral surface; 6. A ball screw shaft having a side ball screw groove, and a plurality of balls rotatably arranged between the outer diameter ball screw groove and the inner ball screw groove. The steering device according to any one of the preceding claims.   The steering gear unit, wherein the input shaft, a nut that rotates with the rotation of the input shaft and has a female thread groove on an inner peripheral surface, and a screw shaft that is the linear motion shaft and has a male thread groove on an outer peripheral surface Between the inner peripheral surface of the nut and the outer peripheral surface of the screw shaft, the revolution about the central axis of the screw shaft and the rotation about its own central axis parallel to the central axis of the screw shaft. And a plurality of planetary rollers engaged with the female screw groove and the male screw groove, the roller screw grooves being formed so as to be able to be supported and formed on the outer peripheral surface. 2. The steering device according to claim 1.   An electric assist mechanism for applying auxiliary power of an electric motor to a shaft disposed on a steering wheel side of a portion of the steering shaft, the intermediate shaft, and the input shaft that is located closer to a steering wheel than a portion where the reverse input cutoff clutch is installed. The steering device according to any one of claims 1 to 8, further comprising:

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