WO2024253085A1 - Rotational load device - Google Patents

Abstract

This rotational load device comprises a slide tube (16) which is fitted around the outer perimeter of a rotary shaft (15) so as to be slidable in the axial direction and an elastic member (17) which biases the slide tube (16) in the axial direction, wherein a cam groove (30), the axial position of which changes along the circumferential direction, is formed in the slide tube (16), and a cam pin (31), which slides inside the cam groove (30) when the rotary shaft (15) rotates, is provided in the outer periphery of the rotary shaft (15).

Description

Rotating Load Device

This invention relates to a rotational load device that generates a rotational reaction force.

A known rotational load device used to apply a steering reaction force to a steering wheel is described in Patent Document 1. The rotational load device in Patent Document 1 has a cylindrical drum that rotates integrally with the steering shaft that is connected to the steering wheel, a band-shaped member that is in frictional contact with the outer periphery of the drum, and a coil spring that adjusts the tension of the band-shaped member, and is configured to generate a rotational reaction force due to frictional resistance between the drum and the band-shaped member when the driver rotates the steering wheel.

Patent No. 4853412

However, if a rotational reaction force is generated by frictional resistance between a drum and a band-shaped member, as in Patent Document 1, a constant rotational reaction force (rotational resistance) is always generated in the opposite direction to the direction of rotation of the steering wheel. Therefore, when the steering wheel is rotated from the neutral position (the position of the steering wheel when the vehicle is moving straight ahead) and when the steering wheel is subsequently returned to the neutral position, a rotational reaction force of the same magnitude is generated in the opposite direction to the direction of rotation of the steering wheel.

However, if the same rotational reaction force occurs when returning the steering wheel to the neutral position as when rotating the steering wheel from the neutral position, the driver will feel a heavy steering feeling when turning the steering wheel.

The inventors of this application believed that if a rotation load device could generate a force to return the steering wheel to the neutral position, it would be possible to improve the steering feel felt by the driver when turning the steering wheel.

The problem that the first and second inventions aim to solve is to provide a rotational load device that is capable of generating a rotational reaction force using only mechanical parts and is suitable for applying a steering reaction force to a steering wheel.

In order to solve the above problems, a first aspect of the present invention provides a rotational load device having the following configuration.
[Configuration 1]
Housing and
a rotating shaft rotatably supported relative to the housing;
a slide cylinder that is fixed to the housing and is fitted to an outer periphery of the rotating shaft so as to be slidable in the axial direction;
an elastic member that biases the slide cylinder in the axial direction,
A cam groove whose axial position changes along the circumferential direction is formed in the slide cylinder,
A cam pin is provided on an outer periphery of the rotating shaft, and slides in the cam groove when the rotating shaft rotates to move the slide cylinder in the axial direction.
The elastic member is arranged so as to elastically deform due to the axial movement of the sliding tube when the rotating shaft rotates, and a rotational reaction force is generated by the elastic force transmitted from the elastic member to the rotating shaft via the sliding tube and the cam pin.

When this configuration is adopted, when rotation is input from the outside to the rotating shaft and the rotating shaft rotates, the cam pin on the outer periphery of the rotating shaft slides in the cam groove of the sliding cylinder and moves rotationally together with the rotating shaft. Here, the sliding cylinder is prevented from rotating relative to the housing, and the cam groove of the sliding cylinder is formed so that the axial position changes along the circumferential direction. Therefore, when the cam pin slides in the cam groove and moves rotationally together with the rotating shaft, the sliding cylinder moves axially in response to the rotational movement of the cam pin. The axial movement of the sliding cylinder elastically deforms the elastic member, and the elastic force transmitted from the elastic member to the rotating shaft via the sliding cylinder and the cam pin generates a rotational reaction force of a magnitude corresponding to the rotation angle of the rotating shaft. In this way, when rotation is input from the outside, it is possible to generate a rotational reaction force using only mechanical parts. In addition, since a rotational reaction force of a magnitude corresponding to the rotation angle of the rotating shaft is generated, it is suitable for applications that impart a steering reaction force to a steering wheel.

[Configuration 2]
an outer ring that is prevented from rotating relative to the housing and has a rolling groove extending in the axial direction on its inner circumference;
The slide cylinder further includes a ball that is held in a ball holding hole formed radially through the slide cylinder and that rolls and contacts the rolling groove.
2. The rotational load device according to claim 1, wherein the sliding cylinder is prevented from rotating relative to the housing by the engagement of the balls with the rolling grooves.

When this configuration is adopted, the outer ring is prevented from rotating by the housing, and the balls held in the ball retaining holes of the sliding cylinder are in rolling contact with the rolling grooves that extend axially around the inner circumference of the outer ring, making it possible to prevent the sliding cylinder from rotating relative to the housing while keeping frictional resistance when the sliding cylinder moves in the axial direction extremely small. This allows the sliding cylinder to move smoothly in the axial direction, and a stable amount of rotational reaction force can be generated.

[Configuration 3]
The rolling grooves are provided at three or more locations circumferentially spaced apart on the inner circumference of the outer ring,
The rotational load device according to configuration 2, wherein the balls and the ball holding holes are also provided at three or more locations on the slide cylinder at intervals in the circumferential direction.

When this configuration is adopted, the sliding cylinder is guided so that it can move axially at three or more positions spaced apart in the circumferential direction, so the center position of the sliding cylinder is stable and the operation of the sliding cylinder can be made particularly stable.

[Configuration 4]
The rotational load device according to configuration 2 or 3, wherein the balls and the ball retaining holes are provided at two or more locations at the same circumferential position of the slide cylinder and spaced apart in the axial direction.

When this configuration is adopted, the sliding cylinder is guided so that it can move axially at two or more positions spaced apart in the axial direction, preventing the sliding cylinder from tilting and making the operation of the sliding cylinder particularly stable.

[Configuration 5]
The cam groove is formed in a V-shape such that the axial position of the cam groove changes to one side in the axial direction from the circumferential center of the cam groove toward either one circumferential direction or the other circumferential direction,
5. The rotational load device according to any one of configurations 1 to 4, wherein the elastic member is provided so as to bias the slide cylinder to the one side in the axial direction.

By adopting this configuration, it is possible to generate a rotational reaction force in the opposite direction to the rotational direction of the rotating shaft, regardless of whether the rotating shaft is rotated in one circumferential direction or the other circumferential direction. This makes it particularly suitable for use in steer-by-wire type steering devices.

[Configuration 6]
a stopper groove extending in a circumferential direction within an angular range of less than 360° is provided on one of the rotating shaft and the housing, and a stopper protrusion positioned within the stopper groove is provided on the other of the rotating shaft and the housing;
A rotating load device described in any one of configurations 1 to 5, in which when the rotating shaft rotates, the stopper protrusion abuts against the circumferential end of the stopper groove before the cam pin abuts against the circumferential end of the cam groove, thereby regulating the rotatable range of the rotating shaft.

By adopting this configuration, it is possible to prevent the cam pin from coming into contact with the circumferential end of the cam groove when the rotating shaft is rotated to the limit of its rotatable range, thereby ensuring the durability of the cam pin and cam groove.

[Configuration 7]
7. The rotary load device according to any one of configurations 1 to 6, further comprising a rotation angle sensor for detecting a rotation angle of the rotary shaft.

This configuration is particularly suitable for use in steer-by-wire steering devices, as the rotation angle of the rotating shaft is detected by the rotation angle sensor.

[Configuration 8]
Further, a reduction gear is provided to reduce the speed of rotation input from the outside and transmit the reduced speed to the rotating shaft.
The cam groove is provided at three or more locations at intervals in the circumferential direction of the slide cylinder,
The rotation load device according to any one of configurations 1 to 7, wherein the cam pins are also provided at three or more locations circumferentially spaced apart on the outer periphery of the rotating shaft.

When this configuration is adopted, a reducer is provided that reduces the speed of the rotation input from the outside and transmits it to the rotating shaft, so the rotation angle of the rotating shaft is smaller than the rotation angle input from the outside, and the circumferential width of the cam groove can be set smaller. As a result, three or more cam grooves can be provided in the circumferential direction, which stabilizes the center position of the sliding cylinder and makes it possible to make the operation of the sliding cylinder particularly stable.

[Configuration 9]
the speed reducer is configured such that a rotation center of a rotation input part to which rotation is input from an outside and a rotation center of a rotation output part which reduces the rotation of the rotation input part and outputs the reduced rotation are positioned on the same line,
the rotation input portion has an input side convex portion which rotates and moves integrally with the rotation input portion about the rotation center of the rotation input portion when a rotation is input to the rotation input portion from the outside, and the rotation output portion has an output side convex portion which rotates and moves integrally with the rotation output portion about the rotation center of the rotation output portion at the same axial position as the input side convex portion when a rotation is input to the rotation input portion from the outside,
A rotational load device as described in configuration 8, in which the input side convex portion and the output side convex portion regulate the rotatable range of the rotational input portion by the input side convex portion catching up with and abutting the output side convex portion when rotation is input to the rotational input portion from the outside.

When this configuration is adopted, the rotational range of the rotational input part is restricted by utilizing the difference in rotational speed between the rotational input part and the rotational output part of the reducer, making it possible to set a large rotational range for the rotational input part (for example, an angle range of 360° or more).

[Configuration 10]
10. The rotary load device according to configuration 9, wherein the rotatable range of the rotary input portion is set to an angular range of 360° or greater.

[Configuration 11]
The reducer is a planetary gear reducer having a sun gear arranged so that its center of rotation is on the same line as the center of rotation of the rotating shaft, a ring gear with internal teeth fixed to the inner circumference of the housing, a plurality of planetary gears arranged at intervals in the circumferential direction between the ring gear and the sun gear and meshing simultaneously with the ring gear and the sun gear, and a planetary carrier that supports the plurality of planetary gears so that they can rotate around the center of each planetary gear and revolve around the sun gear, wherein the sun gear constitutes a rotational input section to which rotation is input from the outside, and the planetary carrier constitutes a rotational output section that reduces the rotation of the rotational input section and outputs it.A rotational load device as described in configuration 9 or 10.

By adopting this configuration, the reducer can be compactly arranged in line with the center of rotation of the rotating shaft, and the configuration of the reducer is simple and low cost.

In order to solve the above-mentioned problems, a second aspect of the present invention provides a rotational load device having the following configuration.
[Configuration 12]
a rotating shaft having a cam groove on its outer periphery, the axial position of which changes along a circumferential direction, and being rotatably supported;
an outer ring formed in a cylindrical shape surrounding an outer periphery of the rotating shaft and having an axial groove extending in the axial direction on an inner periphery;
a steel ball inserted between the rotating shaft and the outer ring so as to be in rolling contact with both the cam groove and the axial groove;
a cylindrical cage that holds the steel balls in retaining holes formed radially through the cage and is disposed between the outer periphery of the rotating shaft and the inner periphery of the outer ring so as to be movable in the axial direction;
an elastic member that biases the retainer in the axial direction,
A rotational load device that applies a rotational reaction force to the rotating shaft by an elastic force transmitted from the elastic member through the cage and the steel balls to the inner surface of the cam groove.

When this configuration is adopted, when a rotation is input from the outside to the rotating shaft and the rotating shaft rotates, the cam groove on the outer circumference of the rotating shaft moves circumferentially together with the rotating shaft. Here, the steel balls that roll into the cam groove are restricted from moving circumferentially relative to the outer ring by engaging with the axial groove on the inner circumference of the outer ring, so when the cam groove moves circumferentially, the steel balls that roll into the cam groove are pressed against the inner surface of the cam groove and move axially. When the steel balls move axially, the retainer that holds the steel balls also moves axially, so the elastic member elastically deforms in the axial direction, and a rotational reaction force of a magnitude corresponding to the rotation angle of the rotating shaft is generated by the elastic force transmitted from the elastic member to the inner surface of the cam groove via the retainer and the steel balls. In this way, when rotation is input from the outside, it is possible to generate a rotational reaction force using only mechanical parts. In addition, since the rotation of the rotating shaft is converted into axial movement of the retainer by the rolling of the steel balls, frictional resistance can be kept small, and a rotational reaction force of a stable magnitude can be generated. In addition, because it generates a rotational reaction force whose magnitude corresponds to the rotation angle of the rotating shaft, it is ideal for applying a steering reaction force to a steering wheel.

[Configuration 13]
The cam groove is formed in a V-shape such that the axial position of the cam groove changes to one side in the axial direction from the circumferential center of the cam groove toward either one circumferential direction or the other circumferential direction,
13. The rotary load device according to claim 12, wherein the elastic member is provided so as to bias the retainer to the other side in the axial direction.

By adopting this configuration, it is possible to generate a rotational reaction force in the opposite direction to the rotational direction of the rotating shaft, regardless of whether the rotating shaft is rotated in one circumferential direction or the other circumferential direction. This makes it particularly suitable for use in steer-by-wire type steering devices.

In other words, whether the rotating shaft is rotated circumferentially to one side or the other side from the neutral position (the position where the steel ball is in the circumferential center of the cam groove), the circumferential component of the force with which the steel ball presses axially against the inner surface of the cam groove generates a rotational reaction force in a direction that returns the rotating shaft to the neutral position. Therefore, when this rotational load device is used on a steering wheel, the steering feeling when returning the steering wheel to the neutral position becomes lighter, making it possible to improve the steering feel of the steering wheel. In this way, the rotational load device configured as described above is suitable for applications in which a steering reaction force is applied to a steering wheel.

[Configuration 14]
The steel balls are provided at a plurality of different circumferential positions,
The cam groove is provided in a plurality of grooves corresponding to the plurality of steel balls,
The rotational load device according to configuration 12 or 13, wherein the axial grooves are also provided in a plurality in correspondence with the plurality of steel balls.

When this configuration is adopted, the retainer is guided by multiple steel balls arranged at different circumferential positions, so the center position of the retainer is stable, and the operation of the retainer can be made stable.

[Configuration 15]
The bearing further includes a housing that accommodates the outer ring while preventing it from rotating.
a stopper groove extending in a circumferential direction within an angular range of less than 360° is provided in the housing, and a stopper protrusion positioned within the stopper groove is provided on the rotating shaft;
A rotating load device described in any one of configurations 12 to 14, in which, when the rotating shaft rotates, the stopper protrusion abuts against the circumferential end of the stopper groove before the steel ball abuts against the circumferential end of the cam groove, thereby regulating the rotatable range of the rotating shaft.

By adopting this configuration, it is possible to prevent the steel balls from coming into contact with the circumferential ends of the cam groove when the rotating shaft is rotated to the limit of its rotatable range, thereby ensuring the durability of the steel balls and the cam groove.

[Configuration 16]
16. The rotary load device according to any one of configurations 12 to 15, further comprising a rotation angle sensor for detecting a rotation angle of the rotary shaft.

This configuration is particularly suitable for use in steer-by-wire steering devices, as the rotation angle of the rotating shaft is detected by the rotation angle sensor.

[Configuration 17]
A rotational load device described in any of configurations 12 to 16, wherein the portion extending at an inclination in the axial direction with respect to the circumferential direction of the cam groove has a cross-sectional shape in which, when viewed in a cross section perpendicular to the extension direction of the cam groove, the wedge angle between the tangent direction at the point of contact between the inner surface of the cam groove and the steel ball when the steel ball is pressed against the inner surface of the cam groove and the inner surface of the axial groove by the biasing force of the elastic member and the extension direction of the axial groove is 50° or more and 90° or less.

　When this configuration is adopted, when the steel ball is pressed against the inner surface of the cam groove and the inner surface of the axial groove by the biasing force of the elastic member, the wedge angle between the tangent direction at the point of contact between the inner surface of the cam groove and the steel ball and the extension direction of the axial groove is 50° or more and 90° or less when viewed in a cross section perpendicular to the extension direction of the cam groove, so the steel ball is less likely to get caught in the wedge angle. Therefore, after the rotating shaft is rotated from the neutral position, when the rotating shaft is put into a free state in which it can rotate freely and the rotating shaft is attempted to be returned to the neutral position by the rotational reaction force generated by the rotation load device, the steel ball is less likely to get caught, and the operation of returning the rotating shaft to the neutral position is highly reliable.

[Configuration 18]
18. A rotational load device according to any one of configurations 12 to 17, wherein the inclination angle of the portion of the cam groove that extends inclined in the axial direction with respect to the circumferential direction is set to less than 25° with respect to the circumferential direction.

By adopting this configuration, the inclination angle of the cam groove relative to the circumferential direction is set to less than 25°, so the axial length of the portion of the outer periphery of the rotating shaft where the cam groove is formed can be reduced, making it possible to make the axial length of the rotating load device compact.

In addition, if the inclination angle of the cam groove relative to the circumferential direction is set to less than 25°, there is a large difference in orientation between the direction in which the steel ball is pushed by the biasing force of the elastic member (axial direction) and the extension direction of the cam groove. Therefore, when the steel ball is pushed axially by the biasing force of the elastic member, the problem of the steel ball getting caught in the wedge angle formed by the cam groove and the axial groove when viewed in a cross section perpendicular to the extension direction of the cam groove is easily apparent. However, by setting the wedge angle to a value between 50° and 90°, it is possible to effectively prevent the steel ball from getting caught in the wedge angle.

[Configuration 19]
A rotational load device described in any of configurations 12 to 18, wherein the portion extending at an incline in the axial direction with respect to the circumferential direction of the cam groove has an inner surface that is linear in cross section and rises from the bottom of the cam groove to the other side in the axial direction at an angle of 50° or more and 90° or less when viewed in a cross section perpendicular to the extension direction of the cam groove.

When this configuration is adopted, the cam groove has an inner surface that rises from the bottom of the cam groove to the other side in the axial direction when viewed in a cross section perpendicular to the extension direction of the cam groove, and because this inner surface is linear in cross section, the rising angle of the inner surface is the wedge angle itself. Therefore, the size of the wedge angle is less susceptible to the effects of misalignment of the relative positions of the rotating shaft and outer ring, or dimensional errors in the axial groove and cam groove, and the size of the wedge angle is stable.

[Configuration 20]
20. The rotary load device according to configuration 19, wherein the cross-sectional shape of the cam groove is any one of a triangular shape, a trapezoidal shape, and a rectangular shape.

When this configuration is adopted, the cam groove has an inner surface that is linear in cross section and rises from the bottom of the cam groove to the other side in the axial direction when viewed in a cross section perpendicular to the extension direction of the cam groove.

In the rotation load device of the first invention, when a rotation is input from the outside to the rotating shaft and the rotating shaft rotates, the cam pin on the outer periphery of the rotating shaft slides in the cam groove of the sliding cylinder and moves in rotation together with the rotating shaft. Here, the sliding cylinder is prevented from rotating relative to the housing, and the cam groove of the sliding cylinder is formed so that the axial position changes along the circumferential direction. Therefore, when the cam pin slides in the cam groove and moves in rotation together with the rotating shaft, the sliding cylinder moves in the axial direction in response to the rotational movement of the cam pin. The axial movement of the sliding cylinder elastically deforms the elastic member, and the elastic force transmitted from the elastic member to the rotating shaft via the sliding cylinder and the cam pin generates a rotational reaction force of a magnitude corresponding to the rotation angle of the rotating shaft. In this way, when a rotation is input from the outside, it is possible to generate a rotational reaction force using only mechanical parts. In addition, since a rotational reaction force of a magnitude corresponding to the rotation angle of the rotating shaft is generated, it is suitable for applications that impart a steering reaction force to a steering wheel.

In the second invention, when a rotation is input from the outside to the rotating shaft and the rotating shaft rotates, the cam groove on the outer circumference of the rotating shaft moves circumferentially together with the rotating shaft. Here, the steel balls that roll into the cam groove are restricted from moving circumferentially relative to the outer ring by engaging with the axial groove on the inner circumference of the outer ring, so when the cam groove moves circumferentially, the steel balls that roll into the cam groove are pressed against the inner surface of the cam groove and move axially. When the steel balls move axially, the retainer that holds the steel balls also moves axially, so the elastic member elastically deforms in the axial direction, and a rotational reaction force of a magnitude corresponding to the rotation angle of the rotating shaft is generated by the elastic force transmitted from the elastic member to the inner surface of the cam groove via the retainer and the steel balls. In this way, when a rotation is input from the outside, it is possible to generate a rotational reaction force using only mechanical parts. In addition, since the rotation of the rotating shaft is converted into axial movement of the retainer by the rolling of the steel balls, frictional resistance can be kept small, and a rotational reaction force of a stable magnitude can be generated. In addition, because it generates a rotational reaction force whose magnitude corresponds to the rotation angle of the rotating shaft, it is ideal for applying a steering reaction force to a steering wheel.

FIG. 1 is a schematic diagram showing a steer-by-wire steering device using a rotation load device according to a first embodiment of the first invention; 2 is a cross-sectional view of the rotary load device of FIG. 1 ; 3 is a cross-sectional view taken along line III-III in FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. Cross-sectional view taken along line V-V in FIG. FIG. 3 is a top view of the rotary load device of FIG. 2 with the housing body removed. FIG. 7 is a diagram showing a state in which the rotation shaft shown in FIG. 6 is rotated and the slide cylinder is moved in the axial direction. FIG. 3 is a diagram showing a rotation load device according to a second embodiment of the first invention, corresponding to FIG. 2. IX-IX line in FIG. 8. 8. Cross-sectional view taken along line XX in FIG. 10 is a cross-sectional view taken along line XI-XI of FIG. FIG. 9 is a top view of the rotation load device of FIG. 8 with the housing body removed. FIG. 13 is a diagram showing a state in which the input shaft shown in FIG. 12 is rotated and the slide cylinder moves in the axial direction; FIG. 3 is a diagram showing a rotation load device according to an embodiment of the second invention, corresponding to FIG. 2. 15 is a cross-sectional view taken along line XV-XV of FIG. 16 is a cross-sectional view taken along line XVI-XVI of FIG. FIG. 15 is an exploded perspective view showing the outer ring, the rotating shaft, and the cage of FIG. FIG. 15 is a top view of the rotary load device of FIG. 14 with the housing and the outer ring removed. FIG. 19 is a diagram showing a state in which the rotating shaft shown in FIG. 18 is rotated and the cage is moved in the axial direction; 20 is a cross-sectional view taken along line XX-XX of FIG. FIG. 19 is a diagram showing a state in which the rotating shaft shown in FIG. 18 is rotated to a position between a neutral position and a limit position of a rotatable range. 22 is a cross-sectional view taken along line XXII-XXII of FIG. FIG. 23 is a diagram showing an example of a cam groove having a triangular cross section, corresponding to FIG. 22. FIG. 23 is a diagram showing an example of a cam groove having a trapezoidal cross section corresponding to FIG. 22 . FIG. 23 is a diagram showing an example of a cam groove having a rectangular cross section, corresponding to FIG. 22.

Figure 1 shows a steering device using a rotational load device 1 according to a first embodiment of the first invention. This steering device is a steer-by-wire type vehicle steering device that converts the amount of operation of a steering wheel 2 by a driver into an electrical signal and controls a steering actuator 3 based on the electrical signal to change the direction of a pair of steered wheels 4 on the left and right.

This steering device has a steering wheel 2 that is rotated by the driver, a steering shaft 5 connected to the steering wheel 2, a rotation load device 1 that is mechanically connected to the steering wheel 2 via the steering shaft 5, a steering actuator 3 that is mechanically separated from the steering wheel 2, and a control unit 6.

The steering shaft 5 connects the steering shaft 5 to the rotation load device 1 so that when the driver rotates the steering wheel 2, the rotation of the steering wheel 2 is input to the rotation load device 1 via the steering shaft 5. When a rotation is input, the rotation load device 1 generates a rotational reaction force corresponding to the rotation, thereby applying a steering reaction force to the steering wheel 2.

The steering actuator 3 has a steering shaft 7, a steering shaft housing 8, a steering motor 9 that moves the steering shaft 7 in the left-right direction of the vehicle, and a steering sensor 10 that detects the position of the steering shaft 7. The steering shaft 7 is supported by the steering shaft housing 8 so that it can move in the left-right direction of the vehicle. The steering shaft housing 8 contains the center of the steering shaft 7 so that both the left and right ends of the steering shaft 7 protrude from the steering shaft housing 8.

The steering motor 9 and steering sensor 10 are attached to the steering shaft housing 8. Between the steering motor 9 and the steering shaft 7, a motion conversion mechanism (not shown) is installed that converts the rotation output by the steering motor 9 into linear motion of the steering shaft 7. The left and right ends of the steering shaft 7 are connected to a pair of left and right steered wheels 4 via tie rods 11, so that when the steering shaft 7 moves in the axial direction, the orientation of the pair of left and right steered wheels 4 changes in conjunction with this.

The control unit 6 operates the steering motor 9 in response to the amount of operation of the steering wheel 2 detected by a rotation angle sensor 12 built into the rotation load device 1 and the vehicle's driving conditions (vehicle speed, etc.) detected by an external sensor 13, and controls the change in the direction of the pair of steered wheels 4 on the left and right.

As shown in FIG. 2, the rotation load device 1 has a housing 14, a rotating shaft 15 to which the rotation of the steering wheel 2 (see FIG. 1) is input, a sliding tube 16 that fits axially on the outer periphery of the rotating shaft 15 so as to be able to slide axially, and an elastic member 17 that biases the sliding tube 16 in the axial direction.

The housing 14 has a housing body 14A and a housing lid 14B. The housing body 14A is a bottomed cylindrical member having a tubular portion 18 arranged to surround the radial outside of the rotating shaft 15, and an end plate portion 19 formed at one end (the left end in the figure) of the tubular portion 18 so as to face the axial end of the rotating shaft 15. The housing lid 14B is removably attached to the other end (the right end in the figure) of the tubular portion 18 with a bolt 20.

The housing cover 14B is formed in the shape of an annular plate through which the rotating shaft 15 passes, and a rolling bearing 21 that rotatably supports the rotating shaft 15 is mounted on its inner periphery. A rolling bearing 22 that rotatably supports the rotating shaft 15 is also mounted in the housing main body 14A. The rotating shaft 15 is rotatably supported relative to the housing 14 with its axial movement relative to the housing 14 restricted by the rolling bearings 21 and 22. The end of the rotating shaft 15 protruding from the housing 14 is connected to the steering shaft 5 (Figure 1).

An outer ring 23 is fitted and attached to the inner circumference of the tubular portion 18 of the housing body 14A. The outer ring 23 is a tubular member with both ends open, and is made of steel. The housing body 14A is made of a light metal (such as an aluminum alloy). The outer ring 23 is sandwiched in the axial direction between a step 24 formed on the inner circumference of the housing body 14A and the housing lid 14B, thereby restricting its axial movement relative to the housing 14. In addition, a notch 25 (see FIG. 4) is formed on the axial end face of the outer ring 23 on the side of the housing lid 14B, and an axial protrusion 26 formed on the housing lid 14B engages with the notch 25, thereby preventing the outer ring 23 from rotating relative to the housing 14.

Here, the outer ring 23 is prevented from rotating relative to the housing 14 by engaging the notch 25 of the outer ring 23 with the axial protrusion 26 of the housing lid 14B. However, instead of this, a common key member may be fitted into a key groove on the outer periphery of the outer ring 23 and a key groove on the inner periphery of the housing body 14A, or the outer periphery of the outer ring 23 may be spline-fitted with the inner periphery of the housing body 14A. Alternatively, a flat portion may be provided on the outer periphery of the outer ring 23, and a protrusion that engages with the flat portion may be provided on the inner periphery of the housing body 14A.

As shown in FIG. 4, the inner circumference of the outer ring 23 is provided with three rolling grooves 28 at equal intervals in the circumferential direction, in which the balls 27 roll. Each rolling groove 28 is formed to extend linearly in the axial direction around the inner circumference of the outer ring 23. The slide tube 16 is also provided with three ball retaining holes 29 at equal intervals in the circumferential direction for retaining the balls 27. The ball retaining holes 29 are formed to penetrate the slide tube 16 in the radial direction, and the balls 27 retained in the ball retaining holes 29 are in rolling contact with the inner surface of the rolling groove 28 on the inner circumference of the outer ring 23 and the cylindrical surface on the outer circumference of the rotating shaft 15. Due to the engagement between the balls 27 and the rolling grooves 28, the slide tube 16 is prevented from rotating relative to the housing 14 while being movable axially relative to the housing 14.

The balls 27 have a diameter larger than the radial thickness of the sliding tube 16 so that a portion of the balls 27 protrudes radially outward from the ball retaining hole 29 when the balls 27 are in contact with the cylindrical surface of the outer periphery of the rotating shaft 15. Steel balls are used for the balls 27. The ball retaining hole 29 is a circular hole that runs along the outer periphery of the balls 27. The sliding tube 16 may be made of steel, or may be made of an oil-impregnated sintered alloy or synthetic resin. By making the sliding tube 16 out of an oil-impregnated sintered alloy or synthetic resin, it is possible to effectively reduce the axial sliding resistance of the sliding tube 16.

As shown in FIG. 2, the balls 27 and ball retaining holes 29 are provided at two locations at the same circumferential position of the slide cylinder 16, spaced apart in the axial direction. The two balls 27 engage with a common rolling groove 28.

As shown in FIG. 6, the slide cylinder 16 is formed with a cam groove 30 whose axial position changes along the circumferential direction. The cam groove 30 can be formed to extend along the inner circumference of the slide cylinder 16 without penetrating the slide cylinder 16 in the radial direction, but here it is formed as a slit that penetrates the slide cylinder 16 in the radial direction.

As shown in FIG. 3, a cam pin 31 is provided on the outer periphery of the rotating shaft 15. The cam pin 31 is assembled in such a way that one end is press-fitted into a pin hole 32 formed on the outer periphery of the rotating shaft 15 and the other end protrudes from the pin hole 32. The part of the cam pin 31 protruding from the pin hole 32 is inserted into the cam groove 30 of the slide cylinder 16.

As shown in Figures 6 and 7, the cam pin 31 has a cylindrical portion protruding from the pin hole 32 (see Figure 3), and when the rotating shaft 15 rotates, it slides together with the rotating shaft 15 within the cam groove 30 and presses the inner surface of the cam groove 30 in the axial direction, thereby moving the sliding cylinder 16 in the axial direction. The cam groove 30 and cam pin 31 form a motion conversion mechanism that converts the rotation of the rotating shaft 15 into the axial movement of the sliding cylinder 16.

The cam groove 30 is formed in a V-shape such that the axial position of the cam groove 30 changes to one axial side (the right side in the figure) whether moving in one axial direction or the other axial direction from the circumferential center of the cam groove 30 (the position corresponding to the bottom of the V). The elastic member 17 is incorporated so as to bias the slide cylinder 16 to one axial side (the right side in the figure) by pressing against the end face on the other axial side (the left side in the figure) of the slide cylinder 16. In other words, the elastic member 17 is arranged so as to be pressed against the slide cylinder 16 and compressed when the rotating shaft 15 rotates.

In the figure, the V-shaped cam groove 30 is shown as having a shape in which a straight line with a constant angle of inclination with respect to the circumferential direction connects the position corresponding to the bottom of the V with the positions corresponding to both ends of the V, but it is also possible to use a shape in which a plurality of straight lines with a stepwise changing angle of inclination with respect to the circumferential direction connect the position corresponding to the bottom of the V with the positions corresponding to both ends of the V, or a shape in which a curve with a smoothly changing angle of inclination with respect to the circumferential direction connects the position corresponding to the bottom of the V with the positions corresponding to both ends of the V.

As shown in FIG. 2, the elastic member 17 is incorporated into a cylindrical space formed between the inner circumference of the outer ring 23 and the outer circumference of the rotating shaft 15. The elastic member 17 may be a compression spring such as a compression coil spring, a wave spring, or a disc spring.

2 and 5, the outer periphery of the rotating shaft 15 is provided with a stopper groove 33 extending circumferentially over an angular range of less than 360° (180° in the figure), and the housing cover 14B is provided with a stopper protrusion 34 located in the stopper groove 33. The stopper protrusion 34 and the stopper groove 33 form a rotation stopper that restricts the rotatable range of the rotating shaft 15 by the stopper protrusion 34 abutting against the circumferential end of the stopper groove 33 (the circumferential end of the stopper groove 33 receiving the stopper protrusion 34). Here, the circumferential length of the stopper groove 33 is set so that when the rotating shaft 15 shown in FIG. 3 rotates, the stopper protrusion 34 shown in FIG. 5 abuts against the circumferential end of the stopper groove 33 before the cam pin 31 abuts against the circumferential end of the cam groove 30.

2, the end plate 19 of the housing body 14A is provided with a rotation angle sensor 12 that detects the rotation angle of the rotating shaft 15. The rotation angle sensor 12 can be made up of a permanent magnet 35 that is attached to the rotating shaft 15 and is fixed so as to rotate together with the rotating shaft 15, and a magnetic detection unit 36 that is provided facing the permanent magnet 35. The magnetic detection unit 36 is fixed to the end plate 19 with a bolt 37. Here, a rotation type sensor located on the center of rotation of the rotating shaft 15 is used as an example of the rotation angle sensor 12 that detects the rotation angle of the rotating shaft 15, but it is also possible to use a sensor that detects the axial position of the sliding cylinder 16 and detects the rotation angle of the rotating shaft 15 based on the axial position, or a sensor that detects the elastic force of the elastic member 17 and detects the rotation angle of the rotating shaft 15 based on the magnitude of the elastic force.

In this rotation load device 1, when rotation is input from the steering wheel 2 shown in FIG. 1 to the rotating shaft 15 shown in FIG. 2 and the rotating shaft 15 rotates, the cam pin 31 on the outer periphery of the rotating shaft 15 slides in the cam groove 30 of the sliding tube 16 and rotates together with the rotating shaft 15 as shown in FIG. 6 and FIG. 7. Here, the sliding tube 16 is prevented from rotating with respect to the housing 14 shown in FIG. 2, and the cam groove 30 of the sliding tube 16 is formed so that the axial position changes along the circumferential direction as shown in FIG. 6. Therefore, when the cam pin 31 slides in the cam groove 30 and rotates together with the rotating shaft 15, the sliding tube 16 moves in the axial direction in response to the rotational movement of the cam pin 31 as shown in FIG. 7. Then, the axial movement of the sliding tube 16 presses and compresses the elastic member 17 in the axial direction, and the elastic force transmitted from the elastic member 17 to the rotating shaft 15 via the sliding tube 16 and the cam pin 31 generates a rotational reaction force of a magnitude according to the rotation angle of the rotating shaft 15. In this way, when rotation is input from the outside, it is possible to generate a rotational reaction force using only mechanical parts. In addition, since a rotational reaction force of a magnitude corresponding to the rotation angle of the rotating shaft 15 is generated, it is suitable for use in applying a steering reaction force to the steering wheel 2 (see Figure 1).

Furthermore, this rotary load device 1 is less susceptible to wear compared to rotary load devices configured to generate a rotational reaction force by frictional resistance between a drum and a strip-shaped member, such as those in Patent Publication No. 4853412 (Patent Document 1), and can ensure stable operation over a long period of time.

In addition, in this rotational load device 1, the outer ring 23 shown in FIG. 2 is prevented from rotating by the housing 14, and the balls 27 held in the ball holding holes 29 of the sliding tube 16 are in rolling contact with the rolling grooves 28 that extend axially around the inner circumference of the outer ring 23. This makes it possible to prevent the sliding tube 16 from rotating relative to the housing 14 while keeping the frictional resistance when the sliding tube 16 moves in the axial direction extremely small. This allows the sliding tube 16 to move smoothly in the axial direction, and a stable amount of rotational reaction force can be generated.

In addition, as shown in FIG. 4, in this rotational load device 1, the sliding cylinder 16 is guided so as to be movable in the axial direction at three positions spaced apart in the circumferential direction, so that the center position of the sliding cylinder 16 is stable and the operation of the sliding cylinder 16 is particularly stable.

In addition, as shown in FIG. 2, in this rotation load device 1, the sliding tube 16 is guided so as to be movable in the axial direction at two or more positions spaced apart in the axial direction, preventing the sliding tube 16 from tilting, and the operation of the sliding tube 16 is particularly stable.

As shown in FIG. 6, the rotation load device 1 has a V-shaped cam groove 30 whose axial position changes to one side in the axial direction (the right side in the figure) from the circumferential center of the cam groove 30 in either the one circumferential direction or the other circumferential direction, and the elastic member 17 is provided to bias the slide tube 16 to one side in the axial direction (the right side in the figure). Therefore, when the rotation shaft 15 is rotated in either the one circumferential direction or the other circumferential direction, a rotation reaction force in the opposite direction to the rotation direction can be generated. Therefore, when the steering wheel 2 shown in FIG. 1 is rotated from the neutral position (the position of the steering wheel 2 when the vehicle moves straight), the rotation load device 1 generates a rotation reaction force in the opposite direction to the rotation direction of the steering wheel 2, and when the steering wheel 2 is returned to the neutral position, the rotation load device 1 generates a force (a force assisting the rotation operation of the steering wheel 2) that returns the steering wheel 2 to the neutral position, which makes it possible to improve the steering feeling of the steering wheel 2 by the driver.

In addition, in this rotation load device 1, when the rotating shaft 15 shown in FIG. 3 rotates, the stopper protrusion 34 shown in FIG. 5 abuts against the circumferential end of the stopper groove 33 before the cam pin 31 abuts against the circumferential end of the cam groove 30, thereby restricting the rotatable range of the rotating shaft 15. In other words, when the rotating shaft 15 is rotated to the limit of its rotatable range, the cam pin 31 shown in FIG. 3 can be prevented from abutting against the circumferential end of the cam groove 30. This makes it possible to ensure the durability of the cam pin 31 and the cam groove 30.

In addition, as shown in FIG. 2, this rotation load device 1 is provided with a rotation angle sensor 12 that detects the rotation angle of the rotating shaft 15, making it particularly suitable for use in a steer-by-wire type steering device as shown in FIG. 1.

FIGS. 8 to 13 show a second embodiment of the first invention. Parts corresponding to those in the first embodiment are given the same reference numerals and will not be described.

As shown in FIG. 8, the rotation load device 1 has a housing 14, an input shaft 50 to which the rotation of the steering wheel 2 (see FIG. 1) is input, a reducer 51 that reduces the rotation input to the input shaft 50 and transmits it to the rotating shaft 15, a sliding tube 16 that fits axially on the outer periphery of the rotating shaft 15 so as to be slidable in the axial direction, and an elastic member 17 that biases the sliding tube 16 in the axial direction. The input shaft 50 and the rotating shaft 15 are arranged side by side so that the rotation center of the input shaft 50 and the rotation center of the rotating shaft 15 are aligned on the same straight line.

The housing cover 14B is formed in the shape of an annular plate through which the input shaft 50 passes, and a rolling bearing 21 that rotatably supports the input shaft 50 is mounted on its inner periphery. A rolling bearing 22 that rotatably supports the rotating shaft 15 is mounted in the housing main body 14A. The rotating shaft 15 is rotatably supported relative to the housing 14 by the rolling bearings 21, 22, with its axial movement relative to the housing 14 restricted. The end of the input shaft 50 protruding from the housing 14 is connected to the steering shaft 5 (Figure 1).

As shown in FIG. 9, the cam grooves 30 are provided at three locations on the slide cylinder 16 at equal intervals in the circumferential direction. The cam pins 31 are also provided at three locations on the outer periphery of the rotating shaft 15 at equal intervals in the circumferential direction.

As shown in Figures 8 and 11, the reducer 51 is a planetary gear reducer having a sun gear 52, an internally toothed ring gear 53 fixed to the inner circumference of the housing 14, a number of planetary gears 54 spaced apart in the circumferential direction between the ring gear 53 and the sun gear 52, and a planetary carrier 55 that supports the planetary gears 54 so that they can rotate around the center of each planetary gear 54 and revolve around the sun gear 52.

As shown in FIG. 8, the sun gear 52 is provided integrally on the axial end of the input shaft 50. The sun gear 52 is an external gear arranged so that its center of rotation is on the same straight line as the center of rotation of the rotating shaft 15. The planetary gear 54 is simultaneously meshed with the ring gear 53 and the sun gear 52. The planetary carrier 55 has a plurality of carrier pins 56 that support each planetary gear 54 rotatably, and a carrier body 57 that maintains the circumferential spacing of the plurality of carrier pins 56. The carrier body 57 is formed integrally on the axial end of the rotating shaft 15.

The ring gear 53 and outer ring 23 are axially sandwiched between a step 24 formed on the inner circumference of the housing body 14A and the housing lid 14B, restricting axial movement relative to the housing 14. The ring gear 53 has a notch 58 (see FIG. 11) on its axial end face on the housing lid 14B side, and an axial protrusion 26 formed on the housing lid 14B engages with the notch 58, preventing it from rotating relative to the housing 14. A notch 25 (see FIG. 10) is formed on the axial end face of the outer ring 23 on the ring gear 53 side, and an axial protrusion 59 formed on the ring gear 53 engages with the notch 25, preventing the outer ring 23 from rotating relative to the housing 14.

Here, the ring gear 53 is prevented from rotating relative to the housing 14 by engaging the notch 58 of the ring gear 53 with the axial protrusion 26 of the housing cover 14B. However, instead of this, a common key member may be fitted into a key groove on the outer periphery of the ring gear 53 and a key groove on the inner periphery of the housing body 14A, or the outer periphery of the ring gear 53 may be spline-fitted with the inner periphery of the housing body 14A, or a flat portion may be provided on the outer periphery of the ring gear 53, and a protrusion that engages with the flat portion may be provided on the inner periphery of the housing body 14A.

The sun gear 52 constitutes the rotation input section to which rotation is input from the outside (steering wheel 2 shown in Figure 1), and the planetary carrier 55 constitutes the rotation output section that decelerates and outputs the rotation of the rotation input section. The center of rotation of the rotation input section (sun gear 52) to which rotation is input from the outside and the center of rotation of the rotation output section (planetary carrier 55) that decelerates and outputs the rotation of the rotation input section are located on the same straight line.

The rotation input part (sun gear 52) of the reducer 51 has an input side convex part 60 that rotates and moves integrally with the rotation input part (sun gear 52) around the rotation center of the rotation input part (sun gear 52) when rotation is input to the rotation input part (sun gear 52). In addition, the rotation output part (planet carrier 55) of the reducer 51 has an output side convex part 61 that rotates and moves integrally with the rotation output part (planet carrier 55) around the rotation center of the rotation output part (planet carrier 55) when rotation is input to the rotation input part (sun gear 52) from the outside. The output side convex part 61 is provided at the same axial position as the input side convex part 60 (a position having a portion that overlaps with the input side convex part 60 when viewed from the radial direction).

As shown in FIG. 10, the output side protrusion 61 is configured by fixing a key member separate from the rotating shaft 15 to the inner diameter of the shaft end of the rotating shaft 15. It is also possible to use an output side protrusion 61 that is seamlessly formed integrally with the inner diameter of the shaft end of the rotating shaft 15.

The input side convex portion 60 and the output side convex portion 61 shown in FIG. 10 constitute a rotation stopper that restricts the rotatable range of the rotation input portion (sun gear 52) by the input side convex portion 60 catching up with and abutting the output side convex portion 61 when rotation is input from the outside to the rotation input portion (sun gear 52). Here, the rotatable range of the rotation input portion (sun gear 52) is set to an angle range of 360° or more. Also, the input side convex portion 60 and the output side convex portion 61 are configured so that when the rotating shaft 15 shown in FIG. 9 rotates, the input side convex portion 60 and the output side convex portion 61 shown in FIG. 10 abut against each other before the cam pin 31 abuts against the circumferential end of the cam groove 30.

As shown in FIG. 8, the rotation load device 1 of this embodiment has a reducer 51 that reduces the speed of the rotation input to the input shaft 50 and transmits it to the rotating shaft 15. Therefore, the rotation angle of the rotating shaft 15 is smaller than the rotation angle input to the input shaft 50, and the circumferential width of the cam groove 30 can be set small, as shown in FIG. 12. Therefore, as shown in FIG. 9, three or more cam grooves 30 can be provided in the circumferential direction, which stabilizes the center position of the sliding cylinder 16 and makes it possible to particularly stabilize the operation of the sliding cylinder 16.

In addition, since this rotation load device 1 has a reducer 51 that reduces the speed of the rotation input to the input shaft 50 and transmits it to the rotating shaft 15, the rotation angle of the rotating shaft 15 is smaller than the rotation angle input to the input shaft 50. Therefore, as shown in FIG. 12, the inclination angle of the cam groove 30 can be made large, making it possible to make the cam pin 31 slide smoothly within the cam groove 30. In addition, it is possible to reduce the axial length of the cam groove 30 and make the device more compact.

In addition, this rotary load device 1 uses the difference in rotational speed between the rotary input part (sun gear 52) and the rotary output part (planet carrier 55) of the speed reducer 51 to regulate the rotatable range of the rotary input part (sun gear 52), making it possible to set a large rotatable range of the rotary input part (sun gear 52) (to an angle range of 360° or more).

In addition, this rotary load device 1 has a rotary stopper formed by the input side protrusion 60 and the output side protrusion 61 provided on the reducer 51, making it possible to miniaturize the device.

In addition, because this rotating load device 1 employs a planetary gear reducer as the reducer 51, the reducer 51 can be compactly arranged on the same straight line as the center of rotation of the rotating shaft 15, and the configuration of the reducer 51 is simple and low cost. Other effects are the same as those of the first embodiment.

In the above embodiment, a planetary gear reducer is used as the reducer 51 configured so that the center of rotation of the rotation input part, which receives rotation from the outside, and the center of rotation of the rotation output part, which reduces the rotation of the rotation input part and outputs it, are positioned on the same straight line. However, instead of a planetary gear reducer, it is also possible to use an eccentric reducer (such as a roller reducer, ball reducer, or cycloid reducer).

In each of the above embodiments, an elastic member 17 is described as being pressed and compressed in the axial direction by the axial movement of the sliding tube 16 when the rotating shaft 15 rotates. However, it is also possible to adopt an elastic member 17 that is pulled and stretched in the axial direction by the axial movement of the sliding tube 16 when the rotating shaft 15 rotates, and to configure the elastic member 17 to generate a rotational reaction force by the elastic force transmitted from the elastic member 17 to the rotating shaft 15 via the sliding tube 16 and the cam pin 31.

FIG. 14 shows a rotational load device 1 according to an embodiment of the second invention. Hereinafter, parts corresponding to those in the embodiment of the first invention are given the same reference numerals and their explanations are omitted. In each embodiment of the first invention and the second invention, parts given the same reference numerals basically have the same configuration.

As shown in FIG. 14, the rotation load device 1 has a housing 14, a rotating shaft 15 to which the rotation of the steering wheel 2 (see FIG. 1) is input, a cylindrical outer ring 23 that surrounds the outer periphery of the rotating shaft 15, steel balls 40 incorporated between the rotating shaft 15 and the outer ring 23, a retainer 41 that holds the steel balls 40, and an elastic member 42 that biases the retainer 41 in the axial direction. The outer ring 23 is accommodated in the housing 14.

As shown in FIG. 16, two steel balls 40 are provided at different circumferential positions. Here, the circumferential positions of each steel ball 40 are at equally spaced circumferential positions (at circumferential positions equally spaced at 180° intervals in FIG. 16). Two axial grooves 43 are formed on the inner circumference of the outer ring 23 corresponding to the two steel balls 40, and two cam grooves 44 are also formed on the outer circumference of the rotating shaft 15 corresponding to the two steel balls 40. As shown in FIG. 14, the cam grooves 44 are grooves whose axial positions change along the circumferential direction.

As shown in FIG. 14, the retainer 41 is a cylindrical member that is axially movable between the outer periphery of the rotating shaft 15 and the inner periphery of the outer ring 23. The retainer 41 is provided with retaining holes 45 that accommodate and hold each steel ball 40. The retaining holes 45 are circular holes that run along the outer periphery of the steel ball 40. The retaining holes 45 are formed to penetrate the retainer 41 in the radial direction. The steel ball 40 has a diameter larger than the radial thickness of the retainer 41 (the radial length of the retaining hole 45) so that it rolls and comes into contact with both the axial groove 43 on the inner periphery of the outer ring 23 and the cam groove 44 on the outer periphery of the rotating shaft 15. The steel ball 40, the axial groove 43, and the cam groove 44 constitute a motion conversion mechanism that converts the rotation of the rotating shaft 15 into the axial movement of the retainer 41.

As shown in FIG. 16, the axial groove 43 on the inner circumference of the outer ring 23 is formed in a cross-sectional arc shape that follows the outer circumference of the steel ball 40. The two axial grooves 43 are provided at circumferential positions that correspond to the respective circumferential positions of the two steel balls 40 (in FIG. 16, they are circumferential positions equally spaced 180° apart around the inner circumference of the outer ring 23). The retainer 41 is prevented from rotating relative to the outer ring 23 by the engagement between the steel balls 40 and the axial groove 43, while being movable axially relative to the outer ring 23. As shown in FIG. 17, the axial groove 43 extends straight in the axial direction around the inner circumference of the outer ring 23.

As shown in FIG. 16, the two cam grooves 44 are provided at circumferential positions that correspond to the circumferential positions of the two steel balls 40. That is, as shown in FIG. 18, the two cam grooves 44 have the same shape, and are provided so that they are circumferentially offset by 180° to correspond to the circumferential positions of the two steel balls 40.

Also, as shown in FIG. 18, the two steel balls 40 are positioned at positions offset in the axial direction, and the two cam grooves 44 are also provided at positions offset in the axial direction so as to correspond to the axial positions of the two steel balls 40. In this way, by arranging the two cam grooves 44 with an axial offset and correspondingly arranging the two steel balls 40 with an axial offset, it is possible to arrange the multiple cam grooves 44 so that they do not interfere with each other. The cam groove 44 is formed in a cross-sectional arc shape that follows the outer periphery of the steel ball 40.

Each cam groove 44 is formed in a V-shape such that the axial position of the cam groove 44 changes to one axial side (left side in the figure) whether moving in one axial direction or the other axial direction from the circumferential center of the cam groove 44 (the position corresponding to the bottom of the V). The elastic member 42 is incorporated so as to urge the retainer 41 to the other axial side (right side in the figure) by pressing against the end face of the retainer 41 on one axial side (left side in the figure). In other words, the elastic member 42 is arranged so as to be pressed against the retainer 41 and compressed when the rotating shaft 15 rotates, as shown in FIG. 19.

In the figure, the V-shaped cam groove 44 is shown as having a shape in which the position corresponding to the bottom of the V and the positions corresponding to both ends of the V are connected by a straight line with a constant inclination angle with respect to the circumferential direction (i.e., a shape in which the ends of two partial spiral grooves with opposite leads are connected to each other), but a shape in which the position corresponding to the bottom of the V and the positions corresponding to both ends of the V are connected by multiple straight lines with a stepwise changing inclination angle with respect to the circumferential direction may also be used, or a shape in which the position corresponding to the bottom of the V and the positions corresponding to both ends of the V are connected by a curve with a smoothly changing inclination angle with respect to the circumferential direction may also be used. The inclination angle with respect to the circumferential direction of the portion of the cam groove 44 that extends at an incline in the axial direction with respect to the circumferential direction (i.e., the portion other than the portion corresponding to the bottom of the V of the cam groove 44) is set to a value less than 25°.

As shown in Figure 21, the portion of cam groove 44 that extends at an incline in the axial direction with respect to the circumferential direction (portion other than the portion corresponding to the bottom of the V-shape of cam groove 44) has a cross-sectional shape in which, when viewed in a cross section perpendicular to the extension direction of cam groove 44 as shown in Figure 22, the wedge angle θ between the tangent direction at the contact point between the inner surface of cam groove 44 and steel ball 40 and the extension direction of axial groove 43 when steel ball 40 is pressed against the inner surface of cam groove 44 and the inner surface of axial groove 43 by the biasing force of elastic member 42 is 50° or more and 90° or less. Here, the cross-sectional shape of cam groove 44 is arc-shaped, and the wedge angle θ is set to 50° or more by setting the arc radius to a value 110% or more of the radius of steel ball 40.

As shown in FIG. 14, the elastic member 42 is incorporated into a cylindrical space formed between the inner circumference of the outer ring 23 and the outer circumference of the rotating shaft 15. The elastic member 42 may be a compression spring such as a compression coil spring, a wave spring, or a disc spring.

As shown in Figures 14 and 15, the housing cover 14B is provided with a stopper groove 33 extending circumferentially over an angular range of less than 360°, and the outer periphery of the rotating shaft 15 is provided with a stopper protrusion 34 located within the stopper groove 33. The stopper protrusion 34 and the stopper groove 33 form a rotation stopper that restricts the rotatable range of the rotating shaft 15 by the stopper protrusion 34 abutting against the circumferential end of the stopper groove 33 (the circumferential end of the stopper groove 33 receiving the stopper protrusion 34). Here, the circumferential length of the stopper groove 33 is set so that when the rotating shaft 15 shown in Figure 14 rotates, the stopper protrusion 34 shown in Figure 15 abuts against the circumferential end of the stopper groove 33 before the steel ball 40 abuts against the circumferential end of the cam groove 44.

In this rotational load device 1, rotation is input from the steering wheel 2 shown in Figure 1 to the rotating shaft 15 shown in Figure 14, and when the rotating shaft 15 rotates, the cam groove 44 on the outer periphery of the rotating shaft 15 moves circumferentially together with the rotating shaft 15, as shown in Figures 18 and 19. Here, as shown in Figure 16, the steel ball 40 rolling in contact with the cam groove 44 is restricted from moving circumferentially relative to the outer ring 23 by engagement with the axial groove 43 on the inner periphery of the outer ring 23, so that when the cam groove 44 moves circumferentially, as shown in Figures 18 and 19, the steel ball 40 rolling in contact with the cam groove 44 is pressed against the inner surface of the cam groove 44 and rolls axially in the axial groove 43. When the steel ball 40 rolls in the axial groove 43 in the axial direction, the retainer 41 that holds the steel ball 40 also moves in the axial direction, so that the elastic member 42 is pressed in the axial direction and compressed, and a rotational reaction force of a magnitude corresponding to the rotation angle of the rotating shaft 15 is applied to the rotating shaft 15 by the elastic force transmitted from the elastic member 42 to the inner surface of the cam groove 44 via the retainer 41 and the steel ball 40. In this way, when rotation is input from the outside, the rotational load device 1 is capable of generating a rotational reaction force using only mechanical parts. In addition, since the rotation of the rotating shaft 15 is converted into the axial movement of the retainer 41 by the rolling of the steel ball 40, the rotational load device 1 can suppress frictional resistance to a small value and generate a rotational reaction force of a stable magnitude. In addition, since a rotational reaction force of a magnitude corresponding to the rotation angle of the rotating shaft 15 is generated, it is suitable for applications in which a steering reaction force is applied to the steering wheel 2.

In other words, with this rotational load device 1, whether the rotating shaft 15 shown in FIG. 18 is rotated circumferentially from the neutral position (the position where the steel ball 40 is in the circumferential center of the cam groove 44) to one side or the other side, a rotational reaction force in a direction returning the rotating shaft 15 to the neutral position is generated by the circumferential component of the force with which the steel ball 40 presses axially against the inner surface of the cam groove 44. Therefore, when this rotational load device 1 is used with a steering wheel 2 (see FIG. 1), the steering feeling when returning the steering wheel 2 to the neutral position becomes lighter, making it possible to improve the steering feeling of the steering wheel 2. In this way, the rotational load device 1 configured as described above is suitable for applications in which a steering reaction force is applied to the steering wheel 2.

Furthermore, this rotary load device 1 is less prone to wear compared to the rotary load device 1 in Patent Publication No. 4853412 (Patent Document 1) that is configured to generate a rotational reaction force by frictional resistance between a drum and a strip-shaped member, and can ensure stable operation over a long period of time.

In addition, as shown in FIG. 18, the cam groove 44 of the rotation load device 1 is formed in a V-shape such that the axial position of the cam groove 44 changes to one side in the axial direction (left side in the figure) whether moving from the circumferential center of the cam groove 44 to one side in the axial direction or the other side in the circumferential direction, and the elastic member 42 is provided to bias the retainer 41 to the other side in the axial direction (right side in the figure). Therefore, whether the rotating shaft 15 is rotated in one circumferential direction or the other circumferential direction, a rotation reaction force in the opposite direction to the rotation direction can be generated. Therefore, when the steering wheel 2 shown in FIG. 1 is rotated from the neutral position (the position of the steering wheel 2 when the vehicle moves straight), the rotation load device 1 generates a rotation reaction force in the opposite direction to the rotation direction of the steering wheel 2, and when the steering wheel 2 is returned to the neutral position, the rotation load device 1 generates a force (force assisting the rotation operation of the steering wheel 2) that returns the steering wheel 2 to the neutral position, which makes it possible to improve the steering feeling of the steering wheel 2 by the driver.

In addition, as shown in FIG. 14, in this rotational load device 1, the retainer 41 is guided by a number of steel balls 40 arranged at different circumferential positions, so the center position of the retainer 41 is stable, and the operation of the retainer 41 is stable.

In addition, in this rotation load device 1, when the rotating shaft 15 shown in FIG. 14 rotates, the stopper protrusion 34 shown in FIG. 15 abuts against the circumferential end of the stopper groove 33 before the steel ball 40 abuts against the circumferential end of the cam groove 44, thereby restricting the rotatable range of the rotating shaft 15. In other words, as shown in FIG. 19 and FIG. 20, when the rotating shaft 15 is rotated to the limit of its rotatable range, it is possible to prevent the steel ball 40 from abutting against the circumferential end of the cam groove 44 and applying an excessive load. This makes it possible to ensure the durability of the steel ball 40 and the cam groove 44.

In addition, as shown in FIG. 14, this rotation load device 1 is provided with a rotation angle sensor 12 that detects the rotation angle of the rotating shaft 15, making it particularly suitable for use in a steer-by-wire type steering device such as that shown in FIG. 1.

In this rotational load device 1, as shown in Figure 21, when the rotating shaft 15 is rotated from a neutral position and then placed in a free state in which it can rotate freely (the hands are released from the steering wheel 2 shown in Figure 1), the elastic member 42 urges the steel ball 40 in the axial direction via the retainer 41, and the steel ball 40 presses the inner surface of the cam groove 44 in the axial direction, and the circumferential component of the force that the inner surface of the cam groove 44 receives from the steel ball 40 generates a rotational reaction force in a direction that returns the rotating shaft 15 to the neutral position (the position shown in Figure 18). When the rotating shaft 15 starts to rotate due to this rotational reaction force, the steel ball 40 starts to roll along the cam groove 44. In this operation, the steel ball 40 is first pushed in the axial direction by the biasing force of the elastic member 42, but since the direction in which the steel ball 40 is pushed (axial direction) differs from the extension direction of the cam groove 44, as shown in FIG. 22, when viewed in a cross section perpendicular to the extension direction of the cam groove 44, the steel ball 40 may get caught in the wedge angle θ formed by the cam groove 44 and the axial groove 43, which may hinder the rotation of the rotating shaft 15. This problem becomes more noticeable when the wedge angle θ shown in FIG. 22 is small (for example, when the arc radius of the cam groove 44 shown in FIG. 22 is set to about 103% of the arc radius of the steel ball 40. In this case, the wedge angle θ shown in FIG. 22 is less than 30°).

In response to this problem, in the rotational load device 1 of the above embodiment, as shown in FIG. 22, when the steel ball 40 is pressed against the inner surface of the cam groove 44 and the inner surface of the axial groove 43 by the biasing force of the elastic member 42, the wedge angle θ between the tangent direction at the contact point between the inner surface of the cam groove 44 and the steel ball 40 and the extension direction of the axial groove 43 is 50° or more and 90° or less when viewed in a cross section perpendicular to the extension direction of the cam groove 44, so that the steel ball 40 is unlikely to get caught in the wedge angle θ. Therefore, after the rotating shaft 15 is rotated from the neutral position shown in FIG. 18, when the rotating shaft 15 is put into a free state in which it can rotate freely and the rotating shaft 15 is attempted to be returned to the neutral position by the rotational reaction force generated by the rotational load device 1, the steel ball 40 is unlikely to get caught, and the operation of returning the rotating shaft 15 to the neutral position is highly reliable.

In addition, as shown in FIG. 21, the inclination angle of the cam groove 44 in the circumferential direction of this rotational load device 1 is set to less than 25°, so that the axial length of the portion of the outer periphery of the rotating shaft 15 where the cam groove 44 is formed can be reduced, making it possible to make the axial length of the rotational load device 1 compact.

Also, as shown in Figure 21, when the inclination angle of the cam groove 44 with respect to the circumferential direction is set to less than 25°, there is a large difference between the direction (axial direction) in which the steel ball 40 is pushed by the biasing force of the elastic member 42 and the extension direction of the cam groove 44. Therefore, when the steel ball 40 is pushed axially by the biasing force of the elastic member 42, as shown in Figure 22, when viewed in a cross section perpendicular to the extension direction of the cam groove 44, the problem of the steel ball 40 getting caught in the wedge angle θ formed by the cam groove 44 and the axial groove 43 tends to become apparent. However, in this embodiment, by setting the wedge angle θ to a value between 50° and 90°, it is possible to effectively prevent the steel ball 40 from getting caught in the wedge angle θ.

In the above embodiment, the cam groove 44 has an arc-shaped cross-sectional shape as shown in FIG. 22 when viewed in a cross section perpendicular to the extension direction of the cam groove 44. However, it is also possible to adopt a cam groove 44 having a triangular cross-sectional shape as shown in FIG. 23, a cam groove 44 having a trapezoidal cross-sectional shape as shown in FIG. 24, or a cam groove 44 having a rectangular cross-sectional shape as shown in FIG. 25.

All of the cam grooves 44 in Figures 22 to 25 have an inner surface 46 that is linear in cross section and rises from the bottom of the cam groove 44 to one side in the axial direction (the left side in the figures), and an inner surface 47 that is linear in cross section and rises from the bottom of the cam groove 44 to the other side in the axial direction (the right side in the figures). In Figures 23 and 24, the inner surface 47 on the other side in the axial direction of the cam groove 44 (the right side in the figures) is formed in a linear cross section that rises at an angle of 50° or more and less than 90°, and in Figure 25, the inner surface 47 on the other side in the axial direction of the cam groove 44 (the right side in the figures) is formed in a linear cross section that rises at an angle of 90°.

As shown in Figures 23 to 25, when viewed in a cross section perpendicular to the extension direction of the cam groove 44, the cam groove 44 has an inner side surface 47 that rises from the bottom of the cam groove 44 to the other side in the axial direction (the right side in the figure), and when the inner side surface 47 is configured to have a straight cross section, the rise angle of the inner side surface 47 becomes the wedge angle θ shown in Figure 22 (the angle between the tangent direction at the point of contact between the inner surface of the cam groove 44 and the steel ball 40 and the extension direction of the axial groove 43). Therefore, the magnitude of the wedge angle θ is less susceptible to the effects of misalignment of the relative positions of the rotating shaft 15 and the outer ring 23, or dimensional errors of the axial groove 43 and the cam groove 44, and the magnitude of the wedge angle θ is stable.

In the above embodiment, an elastic member 42 is described as being pressed and compressed in the axial direction by the axial movement of the retainer 41 when the rotating shaft 15 rotates. However, it is also possible to adopt an elastic member 42 that is pulled and stretched in the axial direction by the axial movement of the retainer 41 when the rotating shaft 15 rotates, and to configure the elastic member 42 so that a rotational reaction force is generated by the elastic force transmitted from the elastic member 42 to the inner surface of the cam groove 44 via the retainer 41 and the steel ball 40.

In each of the above embodiments of the first and second inventions, as shown in FIG. 1, an example was described in which the rotational load device 1 is used in a steer-by-wire vehicle steering device in which a pair of steered wheels 4 on the left and right sides of a vehicle are the steering objects, but this rotational load device 1 can also be used in, for example, a steer-by-wire ship steering device in which a rudder (such as an outboard motor) mounted at the stern of a ship is the steering object, and can also be applied to steer-by-wire steering devices for construction machinery, agricultural machinery, all-terrain vehicles, utility vehicles, and the like. Furthermore, it can also be used in other devices that require a rotational load, not just steering devices.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope of the claims.

REFERENCE SIGNS LIST 1 Rotation load device 2 Steering wheel 3 Steering actuator 12 Rotation angle sensor 14 Housing 14A Housing main body 14B Housing cover 15 Rotation shaft 16 Slide cylinder 17 Elastic member 18 Cylinder portion 19 End plate portion 23 Outer ring 27 Ball 28 Rolling groove 29 Ball retaining hole 30 Cam groove 31 Cam pin 33 Stopper groove 34 Stopper projection 40 Steel ball 41 Cage 42 Elastic member 43 Axial groove 44 Cam groove 45 Retaining hole 47 Inner surface 51 Reducer 52 Sun gear (rotation input portion)
53 Ring gear 54 Planet gear 55 Planet carrier (rotation output part)
60 Input side convex portion 61 Output side convex portion θ Wedge angle

Claims (20)

A housing (14);
a rotating shaft (15) rotatably supported relative to the housing (14);
a slide cylinder (16) that is fixed to the housing (14) and fitted to the outer periphery of the rotating shaft (15) so as to be slidable in the axial direction;
an elastic member (17) that biases the slide cylinder (16) in the axial direction,
A cam groove (30) whose axial position changes along the circumferential direction is formed in the slide cylinder (16),
A cam pin (31) is provided on the outer periphery of the rotating shaft (15), and the cam pin (31) slides in the cam groove (30) when the rotating shaft (15) rotates, thereby moving the slide cylinder (16) in the axial direction.
The elastic member (17) is arranged so as to elastically deform due to the axial movement of the sliding tube (16) when the rotating shaft (15) rotates, and a rotational reaction force is generated by the elastic force transmitted from the elastic member (17) to the rotating shaft (15) via the sliding tube (16) and the cam pin (31). an outer ring (23) that is prevented from rotating relative to the housing (14) and has an axially extending rolling groove (28) on its inner circumference;
The slide cylinder (16) further includes a ball (27) that is held in a ball holding hole (29) formed radially penetrating the slide cylinder (16) and that rolls and contacts the rolling groove (28),
2. The rotary load device according to claim 1, wherein the slide cylinder (16) is prevented from rotating relative to the housing (14) by the engagement between the balls (27) and the rolling grooves (28). The rolling groove (28) is provided at three or more locations on the inner circumference of the outer ring (23) at intervals in the circumferential direction,
3. The rotary load device according to claim 2, wherein the balls (27) and the ball holding holes (29) are also provided at three or more locations on the slide tube (16) at intervals in the circumferential direction. The rotational load device according to claim 2 or 3, in which the balls (27) and the ball retaining holes (29) are provided at two or more locations axially spaced apart at the same circumferential position on the slide tube (16). The cam groove (30) is formed in a V-shape such that the axial position of the cam groove (30) changes to one side in the axial direction from the circumferential center of the cam groove (30) in either one circumferential direction or the other circumferential direction,
5. The rotary load device according to claim 1, wherein the elastic member (17) is provided so as to bias the slide cylinder (16) toward the one side in the axial direction. A stopper groove (33) extending in a circumferential direction within an angular range of less than 360° is provided on one of the rotating shaft (15) and the housing (14), and a stopper protrusion (34) positioned within the stopper groove (33) is provided on the other member,
A rotating load device as described in any one of claims 1 to 5, wherein when the rotating shaft (15) rotates, the stopper protrusion (34) abuts against the circumferential end of the stopper groove (33) before the cam pin (31) abuts against the circumferential end of the cam groove (30), thereby regulating the rotatable range of the rotating shaft (15). A rotating load device according to any one of claims 1 to 6, which is provided with a rotation angle sensor (12) that detects the rotation angle of the rotating shaft (15). The device further includes a reducer (51) for reducing the speed of rotation input from the outside and transmitting the reduced speed to the rotating shaft (15),
The cam groove (30) is provided at three or more locations at intervals in the circumferential direction of the slide cylinder (16),
8. The rotary load device according to claim 1, wherein the cam pins (31) are also provided at three or more locations on the outer periphery of the rotary shaft (15) at intervals in the circumferential direction. The reducer (51) is configured such that a rotation center of a rotation input section (52) to which rotation is input from the outside and a rotation center of a rotation output section (55) that reduces the rotation of the rotation input section (52) and outputs it are positioned on the same straight line,
The rotation input portion (52) has an input side convex portion (60) which rotates and moves integrally with the rotation input portion (52) around the rotation center of the rotation input portion (52) when rotation is input to the rotation input portion (52) from the outside, and the rotation output portion (55) has an output side convex portion (61) which rotates and moves integrally with the rotation output portion (55) around the rotation center of the rotation output portion (55) at the same axial position as the input side convex portion (60) when rotation is input to the rotation input portion (52) from the outside,
The rotary load device of claim 8, wherein the input side convex portion (60) and the output side convex portion (61) regulate the rotatable range of the rotary input portion (52) by the input side convex portion (60) catching up with and abutting the output side convex portion (61) when rotation is input to the rotary input portion (52) from the outside. The rotary load device according to claim 9, wherein the rotational range of the rotary input portion (52) is set to an angle range of 360° or more. The reducer (51) comprises a sun gear (52) arranged so that its center of rotation is aligned with the center of rotation of the rotating shaft (15), an internally toothed ring gear (53) fixed to the inner circumference of the housing (14), a number of planetary gears (54) spaced apart in the circumferential direction between the ring gear (53) and the sun gear (52) and simultaneously meshing with the ring gear (53) and the sun gear (52), and a number of planetary gears (55) arranged so that the number of planetary gears (55) is aligned with the number of planetary gears (55). A planetary gear reducer having a planetary carrier (55) that supports the gears (54) so that they can rotate around the center of each planetary gear (54) and revolve around the sun gear (52), the sun gear (52) constitutes a rotation input section (52) to which rotation is input from the outside, and the planetary carrier (55) constitutes a rotation output section (55) that reduces the rotation of the rotation input section (52) and outputs it. The rotary load device according to claim 9 or 10. a rotating shaft (15) having a cam groove (44) on its outer periphery, the axial position of which changes along the circumferential direction, and being rotatably supported;
an outer ring (23) formed in a cylindrical shape surrounding the outer periphery of the rotating shaft (15) and having an axial groove (43) extending in the axial direction on its inner periphery;
a steel ball (40) inserted between the rotating shaft (15) and the outer ring (23) so as to be in rolling contact with both the cam groove (44) and the axial groove (43);
a cylindrical retainer (41) that holds the steel balls (40) in retaining holes (45) formed radially penetrating the retainer and is provided between the outer periphery of the rotating shaft (15) and the inner periphery of the outer ring (23) so as to be movable in the axial direction;
and an elastic member (42) that biases the retainer (41) in the axial direction,
A rotational load device which applies a rotational reaction force to the rotating shaft (15) by an elastic force transmitted from the elastic member (42) through the retainer (41) and the steel balls (40) to the inner surface of the cam groove (44). The cam groove (44) is formed in a V-shape such that the axial position of the cam groove (44) changes to one side in the axial direction from the circumferential center of the cam groove (44) in either one circumferential direction or the other circumferential direction,
13. The rotary load device according to claim 12, wherein the elastic member (42) is provided so as to bias the retainer (41) toward the other side in the axial direction. The steel balls (40) are provided at a plurality of different circumferential positions,
The cam groove (44) is provided in a plurality of grooves corresponding to the plurality of steel balls (40),
The rotary load device according to claim 12 or 13, wherein the axial grooves (43) are also provided in a plurality in correspondence with the plurality of steel balls (40). The bearing further includes a housing (14) for accommodating the outer ring (23) in a rotation-preventing manner,
The housing (14) is provided with a stopper groove (33) extending in a circumferential direction within an angular range of less than 360°, and the rotating shaft (15) is provided with a stopper protrusion (34) positioned within the stopper groove (33),
A rotating load device as described in any one of claims 12 to 14, wherein when the rotating shaft (15) rotates, the stopper protrusion (34) abuts against the circumferential end of the stopper groove (33) before the steel ball (40) abuts against the circumferential end of the cam groove (44), thereby regulating the rotatable range of the rotating shaft (15). A rotating load device according to any one of claims 12 to 15, further comprising a rotation angle sensor (12) for detecting the rotation angle of the rotating shaft (15). The rotating load device according to any one of claims 12 to 16, wherein the portion of the cam groove (44) that extends at an incline in the axial direction with respect to the circumferential direction has a cross-sectional shape in which, when viewed in a cross section perpendicular to the extension direction of the cam groove (44), the wedge angle (θ) between the tangent direction at the contact point between the inner surface of the cam groove (44) and the steel ball (40) and the extension direction of the axial groove (43) when the steel ball (40) is pressed against the inner surface of the cam groove (44) and the inner surface of the axial groove (43) by the biasing force of the elastic member (42) is 50° or more and 90° or less. A rotary load device according to any one of claims 12 to 17, in which the inclination angle of the portion of the cam groove (44) that extends at an inclination in the axial direction with respect to the circumferential direction is set to less than 25°. The rotating load device according to any one of claims 12 to 18, wherein the portion of the cam groove (44) that extends at an incline in the axial direction with respect to the circumferential direction has an inner surface (47) that is linear in cross section and rises from the bottom of the cam groove (44) to the other side in the axial direction at an angle of 50° to 90° when viewed in a cross section perpendicular to the extension direction of the cam groove (44). The rotary load device according to claim 19, wherein the cross-sectional shape of the cam groove (44) is either triangular, trapezoidal, or rectangular.

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