Rotation transmission device

Abstract

A rotation transmission device (100) comprises an input member (110), an intermediate member (120), an output member (130), a first biasing member (210), a cam mechanism (300), and a housing (101). The first biasing member (210) connects the intermediate member (120) and the output member (130), and biases the intermediate member (120) toward the input member (110). The intermediate member (120) includes an intermediate body part (121), a rotating friction part (125), and a second biasing member (220). The rotating friction part (125) is disposed at a position facing a fixed friction surface (109). The second biasing member (220) connects the intermediate body part (121) and the rotating friction part (125), and biases the rotating friction part (125) toward the fixed friction surface (109). The first biasing member (210) has a greater elastic coefficient than the second biasing member (220).

Description

Rotation Transmission Device

[0001] The present invention relates to a rotation transmission device.

[0002] Conventionally, there exists a device that transmits a rotational force given from a driving source such as a motor to a predetermined target, and that is configured to block the input (reverse input) of the rotational force (torque) transmitted from the target to the driving source.

[0003] For example, Patent Document 1 discloses a power transmission mechanism used in a drive unit of an automobile. In this power transmission mechanism, when an input member receives input rotational power from a drive source and rotates, a portion of the input rotational power is converted into an axial force by the engagement of a substantially V-shaped concave cam and a convex cam, causing the intermediate member to axially displace toward the output member against a spring. The axial displacement of the intermediate member toward the output member releases a friction clutch, allowing the intermediate member to rotate relative to the stationary member. Meanwhile, when the drive source stops, the intermediate member is axially displaced toward the input member due to the pressing force of the spring, activating the friction clutch and restricting the intermediate member in the rotational direction relative to the stationary member.

[0004] Japanese Patent Application Laid-Open No. 2000-346099

[0005] In the conventional power transmission mechanism described above, the intermediate member has a slide spline hole on its inner periphery, and this slide spline hole is fitted to a slide spline formed on the outer periphery of the output member, thereby making the intermediate member non-rotatable but axially movable relative to the output member. Therefore, when the intermediate member moves axially relative to the output member, friction inevitably occurs between the intermediate member and the output member. This causes a decrease in torque transmission efficiency.

[0006] The present invention was made by the inventors of the present application by focusing on the above-mentioned problem, and has an object to provide a rotation transmission device that can suppress a decrease in torque transmission efficiency.

[0007] A rotation transmission device according to one aspect of the present invention includes an input member that rotates around a central axis extending in a first direction by torque input from a drive source, an intermediate member that is arranged coaxially with the input member on one side of the input member in the first direction, an output member that is arranged coaxially with the input member and the intermediate member on one side of the intermediate member in the first direction, a first biasing member that connects the intermediate member and the output member and biases the intermediate member toward the input member, a cam mechanism that is arranged between the input member and the intermediate member and transmits rotation of the input member to the intermediate member, and a handle that houses the intermediate member and the cam mechanism, rotatably holds the input member and the output member, and has a fixed friction surface. and a housing, wherein the intermediate member has an intermediate main body portion disposed at a position through which the central axis passes and to which the first biasing member is fixed, a rotary friction portion disposed at a position facing the fixed friction surface in the first direction, and a second biasing member connecting the intermediate main body portion and the rotary friction portion and biasing the rotary friction portion toward the fixed friction surface, wherein the elastic coefficient of the first biasing member is greater than the elastic coefficient of the second biasing member, and when the input member rotates, the cam mechanism moves the intermediate main body portion in a direction approaching the output member while maintaining a state in which the rotation of the input member is transmitted to the intermediate main body portion, thereby moving the rotary friction portion in a direction away from the fixed friction surface via the second biasing member.

[0008] According to the rotation transmission device of the present invention, it is possible to suppress a decrease in torque transmission efficiency.

[0009] FIG. 1 is a schematic diagram showing an outline of the configuration of a steering device and its periphery according to an embodiment. FIG. 2 is a cross-sectional view showing an outline of the configuration of a rotation transmission device according to an embodiment. FIG. 3 is an exploded perspective view of a rotation transmission device according to an embodiment. FIG. 4 is an exploded perspective view of an intermediate member according to an embodiment. FIG. 5 is a perspective view showing the appearance of an input member and a first cam portion according to an embodiment. FIG. 6 is a first partial cross-sectional view of a rotation transmission device according to an embodiment. FIG. 7 is a second partial cross-sectional view of a rotation transmission device according to an embodiment.

[0010] Hereinafter, the embodiments will be described in detail with reference to the drawings. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection configurations, and manufacturing process sequences shown in the following embodiments are merely examples and are not intended to limit the present invention. Furthermore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concepts will be described as optional components.

[0011] The drawings are schematic diagrams in which emphasis, omission, or adjustment of proportions is appropriately made to illustrate the present invention, and may differ from the actual shapes, positional relationships, and proportions. Furthermore, in the following embodiments and claims, expressions indicating relative directions or attitudes, such as "parallel" and "orthogonal," may be used, but these expressions also include cases where the directions or attitudes are not strictly those of the same kind. For example, "two directions are parallel" does not only mean that the two directions are completely parallel, but also means that the two directions are substantially parallel, i.e., include a difference of, for example, a few percent.

[0012] (Embodiment) [1. Overview of the configuration of the steering device] The overall configuration of a steering device 10 according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing an overview of the configuration of the steering device 10 and its surroundings according to this embodiment. In Fig. 1, a cross section of the rotation transmission device 100 taken on an XZ plane passing through the central axis Sa of the input member 110 is shown, and the approximate outline of the wheel 202 is indicated by a dotted line. In Fig. 1, to simplify the illustration of the steering device 10, an axle suspension mechanism (shock absorbers, arms, etc.) that supports the wheel 202 is omitted from the illustration.

[0013] The steering device 10 is a device that steers the vehicle on which the steering device 10 is mounted by turning the wheels 202 in response to the operation of the steering wheel 15 operated by the driver. The steering device 10 is equipped with a rotation transmission device 100 according to this embodiment.

[0014] The steering device 10 includes a motor 190 that generates a driving force for steering the wheels 202, a rotation transmission device 100 that transmits the driving force from the motor 190 to the wheels 202 and operates to block or suppress reverse input from the wheels 202, and a reducer 180.

[0015] The rotation transmission device 100 includes an input member 110, an intermediate member 120, an output member 130, a cam mechanism 300, and a housing 101. The input member 110 rotates about a central axis Sa in response to input from a motor 190, which serves as a drive source. Torque generated by the rotation of the input member 110 is transmitted to the output member 130 via the cam mechanism 300 and the intermediate member 120, causing the output member 130 to rotate. In this embodiment, the input member 110, the intermediate member 120, and the output member 130 are arranged to rotate about the central axis Sa. In other words, the input member 110, the intermediate member 120, and the output member 130 are arranged coaxially. In this embodiment, the central axis Sa is a virtual axis parallel to the Z-axis direction. Although FIGS. 1 to 7 illustrate the Z-axis direction as coinciding with the up-down direction, the Z-axis direction does not necessarily have to coincide with the up-down direction. Details of the rotation transmission device 100 will be described later with reference to FIGS. 2 to 7.

[0016] The torque generated by the rotation of output member 130 of rotation transmission device 100 is input to reducer 180 and is output from reducer 180 at a slower rotation speed and with a larger torque. Reducer 180 is connected to support shaft 181 that supports wheels 202, and support shaft 181 rotates around central axis Sb by the torque output from reducer 180. This causes wheels 202 to turn.

[0017] More specifically, in this embodiment, the wheels 202 are rotationally driven by a travel drive motor (not shown) attached to the hub carrier 80 located in the center, thereby causing the vehicle equipped with the steering device 10 to travel. The hub carrier 80 is fixed to a support shaft 181, and the wheels 202 receive a rotational drive force from the reducer 180 via the hub carrier 80 and the support shaft 181. As a result, the wheels 202 are steered.

[0018] Note that in FIG. 1 , the center axis Sb of the support shaft 181 supporting the wheel 202 is illustrated as being parallel to the vertical direction (Z-axis direction), but the center axis Sb does not need to be parallel to the vertical direction. For example, to improve the contact area between the wheel 202 and the road surface when the vehicle turns a corner, the center axis Sb may be tilted inward (opening outward as it approaches the road surface). In other words, the camber angle of the wheel 202 may be negative. In this case, the center axis Sa of the input member 110 may be parallel to the center axis Sb of the support shaft 181 (including being on the same line) or parallel to the vertical direction. If the center axis Sb and the center axis Sa are not parallel, a universal joint may be disposed between the reducer 180 and the support shaft 181. Furthermore, although not shown in FIG. 1 , for example, the center axis Sb of the support shaft 181 may be tilted rearward as it moves away from the road surface (toward the positive Y-axis direction as it moves toward the positive Z-axis direction). That is, the caster angle of the wheels 202 may be greater than 0°.

[0019] The steering device 10 configured as described above operates under the control of a host ECU (Electronic Control Unit) 30. Specifically, for example, when the steering wheel 15 is turned by the driver's operation, the rotation angle and angular velocity of a shaft connected to the steering wheel 15 are detected by a steering angle sensor 20. The detection result by the steering angle sensor 20 is transmitted to the host ECU 30, which then transmits a control signal based on the detection result to the steering ECU 40. The steering ECU 40 controls the motor 190 in accordance with the received control signal. This causes the wheels 202 to rotate so as to change the steering angle. Such a system is called, for example, an SBW (Steer By Wire) system. Note that various information such as the detection results from a vehicle speed sensor is input to the host ECU 30, but details of the processing by the host ECU 30 will be omitted.

[0020] 1 illustrates the right front wheel 202 and its surrounding configuration among the four wheels 202 equipped on the vehicle, but in this embodiment, a motor 190, a rotation transmission device 100, a travel drive motor, etc. are also provided for at least the left front wheel of the other three wheels 202. In other words, in this embodiment, each of the at least two wheels 202 has a driving force independent of the others and can be steered independently of the others.

[0021] In this way, in the steering device 10, each of the left and right front wheels (wheels 202) is steered by the driving force of the electrically operated motor 190. Therefore, compared to a conventional structure in which the left and right front wheels are steered synchronously using a link mechanism, this has advantages such as effective use of the interior space of the vehicle, increased freedom in the steering angle of the front wheels, and improved maneuverability of the vehicle due to independent steering of the left and right front wheels.

[0022] However, in a steering system that uses a motor to steer the left and right wheels independently, maintaining the steering angle of the front wheels, for example, while the vehicle is stopped, presents a problem. This problem is particularly pronounced when the kingpin inclination angle of the front wheels is not 0° and the scrub radius is not 0 mm, and / or the caster angle is not 0° and the trail is not 0 mm. Even while the vehicle is moving, maintaining the steering angle of the front wheels against torque (lifting torque) generated when the front wheels are lifted from the road surface or vibrations experienced by the steering system presents a problem. To solve these problems, for example, an electrically operated device (such as an electromagnetic brake) could be used to maintain the steering angle of the front wheels. However, in this case, the device continues to consume power even while the vehicle is stopped, which reduces the capacity of the onboard battery.

[0023] Therefore, rotation transmission device 100 according to this embodiment is configured to mechanically suppress changes in the steering angle during periods when there is no torque input (positive input) from motor 190, and is equipped with a configuration that can suppress a decrease in torque transmission efficiency. Hereinafter, rotation transmission device 100 according to this embodiment will be described in more detail.

[0024] [2. Details of the Rotation Transmission Device] Fig. 2 is a cross-sectional view showing the general configuration of a rotation transmission device 100 according to an embodiment. Fig. 3 is an exploded perspective view of the rotation transmission device 100 according to an embodiment. Fig. 4 is an exploded perspective view of an intermediate member 120 according to an embodiment. Figs. 2 to 4 show bolts used to fasten various members together, and although these bolts include bolts of different sizes and shapes, for ease of explanation, all of these bolts will be referred to as "bolt 700."

[0025] FIG. 5 is a perspective view showing the appearance of the input member 110 and the first cam portion 310 according to the embodiment. FIG. 6 is a first partial cross-sectional view of the rotation transmission device 100 according to the embodiment. FIG. 7 is a second partial cross-sectional view of the rotation transmission device 100 according to the embodiment. FIG. 6 schematically illustrates a cross-section of the intermediate member 120 and its peripheral members in a state in which no torque is input from the motor 190 to the rotation transmission device 100 (stopped state). FIG. 7 schematically illustrates a cross-section of the intermediate member 120 and its peripheral members in a state in which torque is input from the motor 190 to the rotation transmission device 100 (operating state). In FIGS. 6 and 7, bolts 700 and the like for fixing the various members are omitted.

[0026] As shown in Figures 1 to 5, the rotation transmission device 100 according to this embodiment includes a housing 101 fixed to a vehicle, an intermediate member 120 and a cam mechanism 300 housed in the housing 101, an input member 110 and an output member 130 rotatably held in the housing 101, and a first biasing member 210 connecting the intermediate member 120 and the output member 130.

[0027] The housing 101 has a housing main body 101a that houses the intermediate member 120 and the like, and a housing lid 101b that is fixed to an opening of the housing main body 101a in the direction in which the output shaft 139 projects. The housing lid 101b is fixed to the housing main body 101a using bolts or the like (not shown).

[0028] The input member 110 is a member rotatably supported by an input bearing 420 disposed in the housing 101. In this embodiment, the input bearing 420 is an angular contact ball bearing capable of supporting a radial load and an axial load simultaneously. The input member 110 has a fixing hole 110a, into which a motor shaft 191, which is the shaft of the motor 190, is inserted and fixed. As a result, the input member 110 receives torque input from the motor 190 and rotates about the central axis Sa.

[0029] As shown in FIGS. 3 and 4 , the intermediate member 120 includes an intermediate main body portion 121 disposed at a position through which the central axis Sa passes, a rotational friction portion 125 that is annular when viewed from the axial direction, and a second biasing member 220 that connects the intermediate main body portion 121 and the rotational friction portion 125. The "axial direction" refers to the direction of the central axis Sa, which in this embodiment is a direction parallel to the Z-axis direction. The Z-axis direction is an example of a first direction. In other words, the central axis Sa is a virtual axis extending in the first direction. The rotational direction about the central axis Sa is hereinafter referred to as the "circumferential direction," and the direction of a straight line that is perpendicular to the central axis Sa and passes through the central axis Sa is hereinafter referred to as the "radial direction." The radial direction is an example of a second direction.

[0030] In the intermediate member 120, the second biasing member 220 biases the rotational friction portion 125 toward the fixed friction surface 109 of the housing 101. In the present embodiment, the housing 101 includes a fixed friction portion 108 that is annular when viewed from the axial direction, at a position facing the rotational friction portion 125 in the Z-axis direction. The surface of the fixed friction portion 108 facing the negative Z-axis direction functions as the fixed friction surface 109.

[0031] More specifically, the intermediate member 120 has an intermediate main body portion 121 disposed at the center of an annular rotational friction portion 125, and a second biasing member 220 disposed to connect the intermediate main body portion 121 and the rotational friction portion 125. In this embodiment, a leaf spring, which is an example of a plate-shaped elastic member, is used as the second biasing member 220. The second biasing member 220 is disposed with its thickness direction oriented in the Z-axis direction.

[0032] More specifically, as shown in FIG. 4 , the second biasing member 220 has a second fixing portion 222 fixed to the intermediate main body portion 121 and a plurality of second connecting portions 221 extending radially outward from the second fixing portion 222. In the present embodiment, the second biasing member 220 is provided with three second connecting portions 221 arranged at equal intervals in the circumferential direction Cd (see FIG. 5 ). A bolt 700 passing through each of three through holes 222 a provided in the second fixing portion 222 is threadedly engaged with a threaded hole 121 b in the intermediate main body portion 121, thereby fixing the second fixing portion 222 to the intermediate main body portion 121. Furthermore, a bolt 700 passing through each of the through holes 221 a provided in the three second connecting portions 221 is threadedly engaged with a threaded hole 125 a in the rotational friction portion 125, thereby fixing each of the three second connecting portions 221 to the rotational friction portion 125. As a result, the intermediate main body portion 121 and the rotational friction portion 125 are connected by the second biasing member 220. When the rotation transmission device 100 is in a stopped state, the second biasing member 220 biases the rotational friction portion 125 toward the fixed friction surface 109. In other words, the rotational friction portion 125 is pressed against the fixed friction surface 109.

[0033] The output member 130 is a member rotatably supported by an output bearing 410 disposed in the housing 101. In this embodiment, the output bearing 410 is an angular contact ball bearing, similar to the input bearing 420. As shown in FIGS. 2 and 3 , the output member 130 includes a disk-shaped output main body 131 and an output shaft 139 that protrudes from the output main body 131 in the negative Z-axis direction. In this embodiment, the output shaft 139 is integrally provided with the output main body 131, but the output shaft 139 may be a member separate from the output main body 131. When the output shaft 139 is a member separate from the output main body 131, examples of means for joining the output shaft 139 and the output main body 131 include welding, press fitting, or fastening with bolts and nuts, or a combination of these. In this embodiment, as shown in Figures 2 and 3, the bearing retaining member 450 is fastened to the housing lid portion 101b by four bolts 700, and the output bearing 410 is fixed between the bearing retaining member 450 and the output main body portion 131.

[0034] The output main body 131 is a portion that receives torque caused by the rotation of the intermediate member 120. Specifically, the intermediate member 120 and the output main body 131 are connected by a first biasing member 210. The output main body 131 receives torque caused by the rotation of the intermediate member 120 via the first biasing member 210, which causes the output main body 131 and the output shaft 139 (i.e., the output member 130) to rotate around the central axis Sa. In this embodiment, a leaf spring, which is an example of a plate-shaped elastic member, is used as the first biasing member 210. The first biasing member 210 is disposed with its thickness direction oriented in the Z-axis direction.

[0035] More specifically, as shown in FIG. 3 , the first biasing member 210 has a first fixing portion 212 fixed to the intermediate main body portion 121 and a plurality of first connecting portions 211 extending radially outward from the first fixing portion 212. In this embodiment, the first biasing member 210 is provided with two first connecting portions 211 extending in opposite directions from the first fixing portion 212. The first fixing portion 212 is fixed to the intermediate main body portion 121 by a bolt 700 passing through the spacer 140 (see FIGS. 2 and 3 ). Specifically, the bolt 700 passing through the through hole 140 a provided in the spacer 140 and the through hole 212 a provided in the first fixing portion 212 is threadedly engaged with the screw hole 121 a (see FIG. 2 ) of the intermediate main body portion 121. This fixes the first fixing portion 212 to the intermediate main body portion 121. In this embodiment, there are four pairs of through holes 140a and through holes 212a. That is, in this embodiment, the spacer 140 and the first fixing portion 212 are fastened together to the intermediate main body portion 121 by four bolts 700. This fixes the spacer 140 and the first fixing portion 212 to the intermediate main body portion 121. Furthermore, a bolt 700 passing through the through hole 131a of the output main body portion 131 is inserted into each of the two through holes 211a provided in each of the two first connecting portions 211, and is screwed into a nut 710 (see FIG. 3 ). This fixes each of the two first connecting portions 211 to the output main body portion 131. As a result, the output member 130 and the intermediate member 120 are connected by the first biasing member 210.

[0036] The first biasing member 210 thus arranged can bias the intermediate member 120 toward the input member 110 regardless of whether the rotation transmission device 100 is in a stationary state or an operating state.

[0037] In the rotation transmission device 100 configured as described above, a cam mechanism 300 is disposed between the input member 110 and the intermediate member 120. The cam mechanism 300 is a mechanism that moves the intermediate main body portion 121 in a direction toward the output member 130 (the positive direction of the Z axis) while maintaining a state in which the rotation of the input member 110 is transmitted to the intermediate main body portion 121. When the cam mechanism 300 moves the intermediate main body portion 121 in the positive direction of the Z axis, the rotation friction portion 125, which is connected to the intermediate main body portion 121 by the second biasing member 220, moves in a direction away from the fixed friction surface 109. In other words, the friction force between the rotation friction portion 125 and the fixed friction surface 109 can be reduced, allowing the intermediate member 120 to rotate efficiently by the torque received from the input member 110.

[0038] Specifically, the cam mechanism 300 according to this embodiment includes a first cam portion 310 and a second cam portion 320. The first cam portion 310 is provided at the end of the input member 110 facing in the negative direction along the Z axis. The second cam portion 320 is provided at the end of the intermediate main body portion 121 facing in the positive direction along the Z axis. In this embodiment, the first cam portion 310 is integrally formed with the input member 110, and therefore, it can also be described as a part of the input member 110 being the first cam portion 310. Similarly, the second cam portion 320 is integrally formed with the intermediate main body portion 121, and therefore, it can also be described as a part of the intermediate main body portion 121 being the second cam portion 320. In other words, the cam mechanism 300 can also be described as being formed by a part of the input member 110 and a part of the intermediate main body portion 121.

[0039] As shown in FIG. 5 , the first cam portion 310 has three concave cams 311, each recessed in the positive direction of the Z axis. As shown in FIG. 4 , the second cam portion 320 has three convex cams 321, each protruding in the positive direction of the Z axis. The three concave cams 311 correspond one-to-one to the three convex cams 321. The concave cam 311 is a concave portion whose cross section along the circumferential direction Cd (see FIG. 5 ) is approximately triangular. The convex cam 321 is a convex portion whose cross section along the circumferential direction Cd is approximately triangular. When the convex cam 321 is inserted into the concave cam 311 having such a shape and moves in the circumferential direction Cd relative to the convex cam 321, the inner surface of the concave cam 311 and the outer surface of the convex cam 321 come into contact and slide against each other. As a result, a component force acts on the convex cam 321 in a direction that moves the convex cam 321 away from the concave cam 311.

[0040] In the cam mechanism 300 configured as described above, when the rotation transmission device 100 is in a stopped state, the convex cam 321 is inserted into the concave cam 311, as shown in FIG. 6 . Specifically, the convex cam 321 receives a biasing force from the first biasing member 210 via the intermediate main body portion 121, biasing it toward the input member 110. In this state, no power for torque output is input to the motor 190, and the input member 110, to which the motor shaft 191 is fixed, is essentially rotatable about the central axis Sa. Therefore, the input member 110 rotates such that the inner surface of the concave cam 311 is aligned with the outer surface of the convex cam 321. For example, the input member 110 rotates from the rotation position shown in FIG. 7 until it reaches the rotation position shown in FIG. 6 . Note that in FIGS. 6 and 7 , the concave cam 311 and the convex cam 321 are simply and schematically illustrated to clarify the structural relationship between the concave cam 311 and the convex cam 321.

[0041] When the cam mechanism 300 is in the state shown in FIG. 6 , the intermediate main body portion 121 receives a biasing force from the first biasing member 210 and presses the input member 110 in the positive direction of the Z axis. In this embodiment, the input bearing 420, which rotatably supports the input member 110, is an angular contact ball bearing, as described above. As shown in FIGS. 6 and 7 , the input bearing 420 is disposed in a position capable of supporting a load in the positive direction of the Z axis. That is, in this embodiment, the biasing force of the first biasing member 210 can apply a preload to the input bearing 420, which is an angular contact ball bearing. This suppresses rattles and other movements of the input member 110. In this state, the rotational friction portion 125, which is connected to the intermediate main body portion 121 via the second biasing member 220, is pressed against the fixed friction surface 109 by the biasing force from the second biasing member 220.

[0042] More specifically, in this embodiment, the elastic coefficient of the first biasing member 210 is greater than the elastic coefficient of the second biasing member 220. Therefore, when the intermediate main body portion 121 moves, for example, from the position shown in FIG. 7 to the position shown in FIG. 6 due to the biasing force of the first biasing member 210, the rotational friction portion 125 contacts the fixed friction surface 109, and then the rotational friction surface 125b, which is the surface of the rotational friction portion 125 facing in the positive direction of the Z axis, is pressed against the fixed friction surface 109. In other words, both a state in which the intermediate main body portion 121 presses the input member 110 in the positive direction of the Z axis and a state in which the rotational friction portion 125 is pressed against the fixed friction surface 109 are achieved. In this case, the frictional force between the rotational friction portion 125 and the fixed friction surface 109 is maintained at a relatively high level, thereby suppressing rotation of the intermediate member 120 around the central axis Sa. Therefore, even if torque (reverse input) is input from the wheel 202 side to the output shaft 139 of the output member 130, rotation of the intermediate member 120 due to the reverse input is suppressed. In other words, a change in the steering angle of the wheel 202 is suppressed.

[0043] When the rotation transmission device 100 changes from a stopped state to an operating state, that is, when torque is input from the motor 190 to the input member 110, the input member 110 rotates, for example, clockwise as viewed from the positive Z-axis direction, as shown in FIG. 7 . In this case, the concave cam 311 also rotates clockwise along with the input member 110. As a result, as shown in FIG. 7 , the inner surface of the concave cam 311 slides against the outer surface of the convex cam 321, causing the convex cam 321 to receive a force from the concave cam 311 in the negative Z-axis direction. As a result, the intermediate main body portion 121 moves away from the input member 110 against the biasing force from the first biasing member 210. Accordingly, the biasing force from the second biasing member 220 to the rotational friction portion 125 connected to the intermediate main body portion 121 via the second biasing member 220 weakens. This reduces the frictional force between the rotational friction portion 125 and the fixed friction surface 109. 7 , the rotational friction portion 125 and the fixed friction surface 109 are separated from each other. As a result, the frictional force becomes zero. Therefore, the intermediate member 120 is not subjected to the frictional resistance of the fixed friction surface 109 and is able to rotate around the central axis Sa.

[0044] Thus, when the friction force between the rotational friction portion 125 and the fixed friction surface 109 is reduced, the concave cam 311 and the convex cam 321 are maintained in an engaged state in the rotational direction of the input member 110 (i.e., the circumferential direction Cd). Specifically, in this embodiment, the spacer 140, arranged in the negative Z-axis direction of the intermediate main body portion 121, contacts the output member 130, thereby restricting movement of the intermediate main body portion 121 in the negative Z-axis direction. This suppresses the maximum deformation of the first biasing member 210 and also restricts the convex cam 321 from coming out of the concave cam 311, i.e., preventing the convex cam 321 from coming off the concave cam 311. As a result, as shown in FIG. 7 , for example, the first cam portion 310 and the second cam portion 320 are maintained in an engaged state in the circumferential direction Cd. Therefore, torque generated by the rotation of the input member 110 is transmitted to the intermediate member 120 via the cam mechanism 300. At this time, the friction force between the rotational friction portion 125 and the fixed friction surface 109 is reduced, so that the intermediate member 120 can start rotating with a relatively low input torque. After that, the rotational friction portion 125 and the fixed friction surface 109 separate from each other, so that the friction force becomes zero. As a result, the intermediate member 120 can efficiently rotate by the torque input from the input member 110.

[0045] The output member 130, which is connected to the intermediate member 120 via the first biasing member 210, is rotated by the torque generated by the rotation of the intermediate member 120. The torque generated by the rotation of the output shaft 139 of the output member 130 is converted into a larger torque by the reducer 180 and transmitted to the support shaft 181. This causes the support shaft 181 to rotate around the central axis Sb, and as a result, the wheels 202 are steered.

[0046] When the rotation transmission device 100 is in an operating state, the input member 110 applies a force in the negative Z-axis direction to the intermediate main body portion 121, and receives a reaction force from the first biasing member 210 via the intermediate main body portion 121. Therefore, even when the rotation transmission device 100 is in an operating state, the first biasing member 210 can apply a preload to the input bearing 420, which is an angular contact ball bearing. This allows the input member 110 to rotate more stably.

[0047] In the rotation transmission device 100 configured as described above, the input member 110, the intermediate body portion 121, the rotational friction portion 125, the spacer 140, the output member 130, and the housing 101 are formed of a metal such as iron or an aluminum alloy. The rotational friction portion 125 and the fixed friction portion 108 forming the fixed friction surface 109 are formed of a material used for, for example, brake linings in order to increase the frictional force when they come into contact with each other. In this embodiment, the first biasing member 210 and the second biasing member 220, each of which is a leaf spring, are formed of, for example, carbon tool steel such as SK85 specified in Japanese Industrial Standards (JIS) G4401.

[0048] The configuration of the cam mechanism 300 according to this embodiment is described, for example, as follows: The cam mechanism 300 has a first cam portion 310 arranged at one end of the input member 110 in the Z-axis direction, and a second cam portion 320 arranged at the other end of the intermediate main body portion 121 in the Z-axis direction. The first cam portion 310 and the second cam portion 320 are shaped to move the intermediate main body portion 121 in a direction approaching the output member 130 when the input member 110 rotates, and are shaped to maintain engagement in the rotational direction of the input member 110 when the intermediate main body portion 121 is closest to the output member 130.

[0049] [3. Summary of the embodiment] The technical features of the rotation transmission device 100 according to the embodiment described above can be explained as follows, for example, in (1) to (5).

[0050] (1) The rotation transmission device 100 according to this embodiment includes an input member 110, an intermediate member 120, an output member 130, a first biasing member 210, a cam mechanism 300, and a housing 101. The input member 110 rotates around a central axis Sa extending in the Z-axis direction by torque input from a drive source (a motor 190 in this embodiment). The intermediate member 120 is disposed coaxially with the input member 110 on one side of the input member 110 in the Z-axis direction. The output member 130 is disposed coaxially with the input member 110 and the intermediate member 120 on one side of the intermediate member 120 in the Z-axis direction. The first biasing member 210 connects the intermediate member 120 and the output member 130 and biases the intermediate member 120 toward the input member 110. The cam mechanism 300 is disposed between the input member 110 and the intermediate member 120 and transmits rotation of the input member 110 to the intermediate member 120. The housing 101 accommodates the intermediate member 120 and the cam mechanism 300, rotatably holds the input member 110 and the output member 130, and has a fixed friction surface 109. The intermediate member 120 has an intermediate main body portion 121, a rotational friction portion 125, and a second biasing member 220. The intermediate main body portion 121 is disposed at a position where the central axis Sa passes, and the first biasing member 210 is fixed thereto. The rotational friction portion 125 is disposed at a position facing the fixed friction surface 109 in the Z-axis direction. The second biasing member 220 connects the intermediate main body portion 121 and the rotational friction portion 125, and biases the rotational friction portion 125 toward the fixed friction surface 109. The elastic modulus of the first biasing member 210 is greater than the elastic modulus of the second biasing member 220. When the input member 110 rotates, the cam mechanism 300 moves the intermediate main body portion 121 in a direction toward the output member 130 while maintaining a state in which the rotation of the input member 110 is transmitted to the intermediate main body portion 121, thereby moving the rotation friction portion 125 in a direction away from the fixed friction surface 109 via the second biasing member 220. In this embodiment, one side in the Z-axis direction is the negative Z-axis direction, and the other side in the Z-axis direction is the positive Z-axis direction. The same applies hereinafter.

[0051] According to the rotation transmission device 100 described in (1) above, the cam mechanism 300 can move the intermediate body portion 121 toward the output member 130 against the biasing force of the first biasing member 210 when the input member 110 rotates. This reduces the frictional force between the fixed friction surface 109 and the rotational friction portion 125 connected to the intermediate body portion 121 via the second biasing member 220. As a result, the rotation of the input member 110 is efficiently transmitted to the output member 130 via the intermediate body portion 121 and the first biasing member 210. In this series of operations, the intermediate body portion 121 moves in the direction of the central axis Sa (the Z-axis direction) while being supported by the first biasing member 210. Therefore, unlike, for example, when the intermediate body portion 121 slides relative to the output member 130, the rotational friction portion 125 can be switched into and out of contact with the fixed friction surface 109 without generating frictional force between the intermediate body portion 121 and the output member 130. This prevents a decrease in torque transmission efficiency.

[0052] Furthermore, the rotational friction portion 125 is connected to the intermediate main body portion 121 via the second biasing member 220. Therefore, the position of the rotational friction portion 125 in the Z-axis direction relative to the intermediate main body portion 121 is variable (see FIGS. 6 and 7 ). More specifically, the elastic coefficient of the first biasing member 210 is greater than the elastic coefficient of the second biasing member 220. Therefore, it is easy to achieve both a state in which the intermediate main body portion 121 presses the input member 110 in the positive direction of the Z-axis due to the biasing force from the first biasing member 210, and a state in which the rotational friction portion 125 is pressed against the fixed friction surface 109. In other words, by receiving the biasing force of the first biasing member 210 on the input member 110 via the intermediate main body portion 121, rattle of the input member 110 is suppressed, and the frictional force between the rotational friction portion 125 and the fixed friction surface 109 can block the input (reverse input) of the rotational force (torque) transmitted from the output member 130 to the input member 110.

[0053] (2) The rotation transmission device 100 described in (1) above further includes an angular ball bearing (input bearing 420) that is disposed between the input member 110 and the housing 101 on the other side of the input member 110 in the Z-axis direction, and supports the input member 110 rotatably relative to the housing 101 but immovably in the Z-axis direction.

[0054] According to the rotation transmission device 100 described in (2) above, the input bearing 420, which is an angular ball bearing, can rotatably support the input member 110 in a state in which a preload is applied by the biasing force from the first biasing member 210. This allows the input member 110 to rotate efficiently while, for example, more reliably suppressing rattles and the like of the input member 110.

[0055] (3) In the rotation transmission device 100 described in (1) or (2) above, the first biasing member 210 is a plate-shaped elastic member that connects the intermediate main body portion 121 and the output member 130 in a second direction (radial direction) perpendicular to the Z-axis direction and has a thickness direction oriented in the Z-axis direction. In this embodiment, the first biasing member 210 is a leaf spring.

[0056] According to the rotation transmission device 100 described in (3) above, the first biasing member 210 can be realized by a flat plate-shaped member, so that, for example, an increase in size in the Z-axis direction due to the first biasing member 210 is suppressed.

[0057] (4) In the rotation transmission device 100 described in any one of (1) to (3) above, the second biasing member 220 is a plate-shaped elastic member that connects the intermediate main body portion 121 and the rotation friction portion 125 in a second direction perpendicular to the Z-axis direction and has a thickness direction aligned with the Z-axis direction. In this embodiment, the second biasing member 220 is a leaf spring.

[0058] According to the rotation transmission device 100 described in (4) above, the second biasing member 220 can be realized by a flat plate-shaped member, so that, for example, an increase in size in the Z-axis direction due to the second biasing member 220 is suppressed.

[0059] (5) The rotation transmission device 100 described in any one of (1) to (4) above further includes a spacer 140 disposed between the intermediate main body portion 121 and the output member 130. The intermediate main body portion 121 is pressed against the output member 130 in the Z-axis direction via the spacer 140, thereby restricting movement of the intermediate main body portion 121 in a direction toward the output member 130.

[0060] According to the rotation transmission device 100 described in (5) above, by limiting the movement of the intermediate main body portion 121 in a direction toward the output member 130, it is possible to suppress, for example, the maximum deformation amount of the first biasing member 210. This suppresses the occurrence of defects such as damage or deterioration of the first biasing member 210. Furthermore, by changing the thickness of the spacer 140, for example, it is possible to adjust the maximum movement amount of the intermediate main body portion 121 and the maximum deformation amount of the first biasing member 210. In other words, it is easy to adjust the maximum deformation amount, etc.

[0061] Other Embodiments The rotation transmission device according to the present invention has been described above based on the embodiments. However, the present invention is not limited to the above-described embodiments and modifications. As long as they do not deviate from the spirit of the present invention, various modifications that would occur to those skilled in the art to the above-described embodiments, or configurations constructed by combining multiple components described above, are also included within the scope of the present invention.

[0062] The shapes of the first biasing member 210 and the second biasing member 220 do not need to be the shapes shown in FIGS. 3 and 4 . For example, the number of first connecting portions 211 included in the first biasing member 210 may be one or three or more. The number of second connecting portions 221 included in the second biasing member 220 may be two or less, or four or more. However, from the viewpoint of, for example, the first biasing member 210 applying a balanced biasing force to the intermediate main body portion 121, it is preferable that the first biasing member 210 include a plurality of first connecting portions 211 arranged at equal intervals in the circumferential direction Cd. For example, from the viewpoint of, for example, the second biasing member 220 applying a balanced biasing force to the rotational friction portion 125, it is preferable that the second biasing member 220 include a plurality of second connecting portions 221 arranged at equal intervals in the circumferential direction Cd.

[0063] The first biasing member 210 and the second biasing member 220 may be realized by one or more elastic members other than leaf springs. For example, the first biasing member 210 may include one or more compression springs that elastically deform in the Z-axis direction, which are disposed between the intermediate main body portion 121 and the output member 130, and which connect the intermediate main body portion 121 and the output member 130 via the one or more compression springs. For example, the second biasing member 220 may be realized by an elastic member other than a leaf spring. For example, each of the intermediate main body portion 121 and the rotational friction portion 125 may have a portion (opposing portion) that faces the other in the Z-axis direction, and one or more compression springs that elastically deform in the Z-axis direction may be disposed between these opposing portions. In either case, the rotational friction portion 125 and the fixed friction surface 109 can be switched between contact and separation without generating frictional force between the intermediate main body portion 121 and the output member 130. Furthermore, it is possible to easily achieve both a state in which the intermediate main body portion 121 presses the input member 110 in the positive direction of the Z axis and a state in which the rotational friction portion 125 is pressed against the fixed friction surface 109 .

[0064] There are no particular limitations on the number of concave cams 311 included in the first cam portion 310 and the number of convex cams 321 included in the second cam portion 320. The first cam portion 310 is required to include at least one concave cam 311, and the second cam portion 320 is required to include at least one convex cam 321. However, from the viewpoint of transmitting torque in a balanced manner in the circumferential direction Cd, it is preferable that the first cam portion 310 be provided with N (an integer of 2 or greater) concave cams 311 arranged at equal intervals in the circumferential direction Cd, and that the second cam portion 320 be provided with N convex cams 321 arranged at equal intervals in the circumferential direction Cd.

[0065] A crown gear may be employed as each of the first cam portion 310 and the second cam portion 320. In this case, the recess between two teeth adjacent to each other in the circumferential direction Cd in the first cam portion 310 can be described as the concave cam 311. Also, each of the teeth arranged at equal intervals in the circumferential direction Cd in the second cam portion 320 can be described as a convex cam.

[0066] It is not essential that the first cam portion 310 includes one or more concave cams 311 and the second cam portion 320 includes one or more convex cams 321. The first cam portion 310 may include one or more convex cams and the second cam portion 320 may include one or more concave cams.

[0067] The shapes of the convex cam 321 and the concave cam 311 are not limited to those shown in Figures 4 and 5. The convex cam 321 and the concave cam 311 may have any shape as long as, when one of them presses the other in the circumferential direction Cd, they generate a component force in the pressing direction and a component force in a direction that moves one of them away from the other in the axial direction.

[0068] It is not essential that the motor shaft 191 directly transmits torque to the input member 110. For example, torque may be transmitted from the motor 190 to the input member 110 by interposing one or more gears, or a belt and pulley, between the motor shaft 191 and the input member 110.

[0069] The rotation transmission device 100 according to the embodiment may be provided in a device of a different type than the steering device 10. For example, in a device that lifts an object by winding up a wire using output from a motor, the rotation transmission device 100 may be used as a device that blocks the force (reverse input) that pulls the wire by the object.

[0070] The steering device 10 including the rotation transmission device 100 according to the embodiment may be used in a vehicle having, for example, three wheels or five or more wheels, instead of a four-wheel vehicle.

[0071] In addition, any combination of two or more claims from among the multiple claims set forth in the claims at the time of filing of this application, within the scope of no technical contradiction, is also included in the present invention.

[0072] The rotation transmission device of the present invention is useful as a rotation transmission device for transmitting input from a motor to a specified object and blocking reverse input from the specified object, and can be employed, for example, as a rotation transmission device for vehicles such as automobiles, agricultural machinery, or construction machinery.

[0073] 10: steering device, 15: steering wheel, 20: steering angle sensor, 30: host ECU, 40: steering ECU, 80: hub carrier, 100: rotation transmission device, 101: housing, 101a: housing main body, 101b: housing lid, 108: fixed friction part, 109: fixed friction surface, 110: input member, 110a: fixing hole, 120: intermediate member, 121: intermediate main body, 121a, 121b, 125a: screw hole, 125: rotation friction part, 125b: rotation friction surface, 130: output member, 131: output main body, 131a, 140a , 211a, 212a, 221a, 222a: through holes, 139: output shaft, 140: spacer, 180: reducer, 181: support shaft, 190: motor, 191: motor shaft, 202: wheel, 210: first biasing member, 211: first connecting portion, 212: first fixing portion, 220: second biasing member, 221: second connecting portion, 222: second fixing portion, 300: cam mechanism, 310: first cam portion, 311: concave cam, 320: second cam portion, 321: convex cam, 410: output bearing, 420: input bearing, 450: bearing holding member, 700: bolt, 710: nut

Claims

a cam mechanism disposed between the input member and the intermediate member and transmitting rotation of the input member to the intermediate member; and a housing that houses the intermediate member and the cam mechanism, rotatably holds the input member and the output member, and has a fixed friction surface. The intermediate member has: an intermediate main body portion disposed at a position through which the central axis passes and to which the first biasing member is fixed; a rotational friction portion disposed at a position facing the fixed friction surface in the first direction; and a second biasing member that connects the intermediate main body portion and the rotational friction portion and biases the rotational friction portion toward the fixed friction surface. a coefficient of elasticity of the first biasing member is greater than a coefficient of elasticity of the second biasing member, and the cam mechanism, when the input member rotates, moves the intermediate main body portion in a direction approaching the output member while maintaining a state in which the rotation of the input member is transmitted to the intermediate main body portion, thereby moving the rotating friction portion in a direction away from the fixed friction surface via the second biasing member.

2. The rotation transmission device according to claim 1, further comprising an angular ball bearing disposed between said input member and said housing on the other side of said input member in said first direction, and supporting said input member rotatably relative to said housing and immovable in said first direction.

3. A rotation transmission device as described in claim 1 or 2, wherein the first biasing member connects the intermediate body portion and the output member in a second direction perpendicular to the first direction, and is a plate-shaped elastic member with a thickness direction oriented in the first direction.

4. A rotation transmission device as claimed in claim 1 or 2, wherein the second biasing member connects the intermediate main body portion and the rotational friction portion in a second direction perpendicular to the first direction, and is a plate-shaped elastic member with a thickness direction oriented in the first direction.

5. A rotation transmission device as claimed in claim 1 or 2, further comprising a spacer disposed between said intermediate body portion and said output member, wherein said intermediate body portion is pressed against said output member in said first direction via said spacer, thereby restricting movement of said intermediate body portion in a direction approaching said output member.

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