Locking mechanism

Abstract

A locking mechanism (100) mounted on a steer-by-wire device (1) including a rack shaft (10) as a turning shaft for turning a vehicle wheels (7), and a turning mechanism (20) that applies a turning force to the rack shaft (10) by a turning motor (21) includes a locking unit (81) that locks the rack shaft (10) or the turning mechanism (20) so as not to be operable, and a releasing unit (solenoid (87)) that releases the locking of the rack shaft (10) or the turning mechanism (20) by the locking unit (81).

Description

LOCKING MECHANISM

[0001] The present invention relates to a locking mechanism.

[0002] JP 2024-004084 A discloses a steer-by-wire turning control device. The turning control device includes four turning actuators having motors. In the turning control device, four wheels are controlled by separate turning actuators based on a steering operation performed by a driver, and the wheels are turned.

[0003] In the turning control device according to JP 2024-004084 A, the wheels are not connected to a steering side. Therefore, for example, if some of the wheels cannot be turned because the motors of some of the steering actuators fail, those wheels may move freely. Therefore, when the wheels come into contact with an obstacle such as a curb, an impact can cause directions of the wheels to change, and the vehicle may move in an unexpected direction.

[0004] An object of the present invention is to improve safety of a steer-by-wire device.

[0005] According to one aspect of the present invention, a locking mechanism to be mounted on a steer-by-wire device including a turning shaft for turning a wheel of a vehicle and a turning mechanism for applying a turning force to the turning shaft by a motor, the locking mechanism includes: a locking unit configured to lock the turning shaft or the turning mechanism so as not to be operable; and a releasing unit configured to release the locking of the turning shaft or the turning mechanism by the locking unit.

[0006] FIG. 1 is a schematic configuration diagram of a steer-by-wire device according to an embodiment of the present invention.FIG. 2 is a perspective view of a locking mechanism according to the embodiment of the present invention.FIG. 3 is a schematic diagram showing operations of a locking unit and a solenoid.FIG. 4 is a schematic diagram of a locking unit and a solenoid according to a second modification of the embodiment of the present invention.

[0007] Hereinafter, a locking mechanism 100 according to an embodiment of the present invention will be described with reference to the drawings. The locking mechanism 100 is mounted on a steer-by-wire device 1. First, the steer-by-wire device 1 will be described.

[0008] The steer-by-wire device 1 can perform a steer-by-wire control for turning wheels 7 in response to an operation state of a steering wheel 2 performed by a driver. The steer-by-wire device 1 includes the steering wheel 2 on which the driver performs a steering operation, a steering shaft 3 which rotates in accordance with the steering operation by the driver, a rack shaft 10 as a turning shaft for turning the wheel 7, a turning mechanism 20 which applies a turning force to the rack shaft 10 by a turning motor 21, and a reaction force motor 51 which applies a steering reaction force to the steering shaft 3.

[0009] In the steer-by-wire device 1 of the present embodiment, the four wheels 7 are turned independently. Specifically, the steer-by-wire device 1 has four rack shafts 10 and four turning mechanisms 20, and each of the four wheels 7 is connected with the rack shaft 10 and the turning mechanism 20 for individual control. Configurations of the rack shafts 10 and the turning mechanisms 20 which control the wheels 7 are the same. Therefore, in the following, a first rack shaft 10a and a first turning mechanism 20a that turn a wheel 7a, which is a front wheel on a left side of a vehicle, and a second rack shaft 10b and a second turning mechanism 20b that turn a wheel 7b, which is a front wheel on a right side of the vehicle, will be described as representatives, and illustrations and specific descriptions of the rack shafts 10 and the turning mechanisms 20 that turn left and right rear wheels 7 will be omitted.

[0010] The first turning mechanism 20a includes a first turning motor 21a that applies a turning force to the first rack shaft 10a, a first worm shaft 23a connected to an output shaft 22a of the first turning motor 21a, a first worm wheel 24a that meshes with the first worm shaft 23a, and a first pinion shaft 25a that is connected to the first worm wheel 24a and transmits rotational torque to the first rack shaft 10a. The locking mechanism 100 is provided between the output shaft 22a of the first turning motor 21a and the first worm shaft 23a.

[0011] A driving force of the first turning motor 21a is transmitted to the first pinion shaft 25a after a rotation speed is reduced by the first worm shaft 23a and the first worm wheel 24a. The first pinion shaft 25a includes a first pinion gear 26a that meshes with a first rack gear 11a formed on the first rack shaft 10a, and is connected to the first rack shaft 10a.

[0012] The second turning mechanism 20b includes a second turning motor 21b that applies a turning force to the second rack shaft 10b, a second worm shaft 23b that is connected to an output shaft 22b of the second turning motor 21b, a second worm wheel 24b that meshes with the second worm shaft 23b, and a second pinion shaft 25b that is connected to the second worm wheel 24b and transmits rotational torque to the second rack shaft 10b. The locking mechanism 100 is provided between the output shaft 22b of the second turning motor 21b and the second worm shaft 23b.

[0013] A driving force of the second turning motor 21b is transmitted to the second pinion shaft 25b after a rotation speed is reduced by the second worm shaft 23b and the second worm wheel 24b. The second pinion shaft 25b includes a second pinion gear 26b that meshes with a second rack gear 11b formed on the second rack shaft 10b, and is connected to the second rack shaft 10b.

[0014] As described below, the first turning motor 21a and the second turning motor 21b are driven in response to the steering operation of the driver. When the first turning motor 21a is driven, a turning force for turning the wheel 7a is applied to the first rack shaft 10a through the first pinion shaft 25a. In this case, rotation of the first pinion shaft 25a is converted into linear motion by the first pinion gear 26a and the first rack gear 11a, and the linear motion of the first rack shaft 10a turns the wheel 7a via a tie rod 9 and a knuckle arm 6. In addition, when the second turning motor 21b is driven, a turning force for turning the wheel 7b is applied to the second rack shaft 10b through the second pinion shaft 25b. In this case, rotation of the second pinion shaft 25b is converted into linear motion by the second pinion gear 26b and the second rack gear 11b, and the linear motion of the second rack shaft 10b turns the wheel 7b via the tie rod 9 and the knuckle arm 6. Other wheels 7 are similarly turned by the corresponding rack shafts 10 and the corresponding turning mechanisms 20.

[0015] A steering reaction force is applied by a reaction force motor 51 in response to the steering operation of the driver. A driving force of the reaction force motor 51 is input to the steering shaft 3 after a rotation speed is reduced by a third worm shaft 52 connected to an output shaft 51a of the reaction force motor 51 and a third worm wheel 53 that meshes with the third worm shaft 52 and is connected to the steering shaft 3. When the reaction force motor 51 is driven, a steering reaction force is applied to the steering shaft 3, and a pseudo weight is given to the steering wheel 2 accordingly.

[0016] The steer-by-wire device 1 further includes a plurality of turning controllers 40 that respectively control driving of the turning motors 21 of the turning mechanisms 20, and a reaction force controller 50 that controls driving of the reaction force motor 51. The plurality of turning controllers 40 include a first turning controller 40a that controls driving of the first turning motor 21a of the first turning mechanism 20a, a second turning controller 40b that controls driving of the second turning motor 21b of the second turning mechanism 20b, and a turning controller (not shown) that respectively controls driving of the two turning motors 21 of the two turning mechanisms 20 not shown in FIG. 1. The controllers 40 and 50 are communicatably connected to each other. In addition to a detection signal of a steering angle sensor 55 that is provided on the steering shaft 3 and detects a rotation angle (steering angle) of the steering wheel 2, vehicle state information such as a vehicle speed is input to the controllers 40 and 50.

[0017] In the steer-by-wire control, the first turning controller 40a and the second turning controller 40b control the first turning motor 21a and the second turning motor 21b, respectively, in accordance with the operation state of the steering wheel 2 and the vehicle state information to turn the wheels 7a and 7b. Specifically, the first turning controller 40a and the second turning controller 40b set a target turning angle based on the detection result of the steering angle sensor 55 and the vehicle speed, and control the first turning motor 21a and the second turning motor 21b, respectively, such that turning angles of the wheels 7a and 7b match the target turning angles. Other turning controllers 40 similarly control the corresponding turning motors 21. In addition, in the steer-by-wire control, the reaction force controller 50 controls the reaction force motor 51 according to a turning state of the wheel 7, and applies the steering reaction force to the steering wheel 2. The reaction force controller 50 sets a target steering reaction force equivalent to a reaction force received from a road surface due to the steering operation, and controls the reaction force motor 51 such that the steering reaction force applied to the steering shaft 3 matches the target steering reaction force.

[0018] Here, in the steer-by-wire device 1, the wheels 7 are not connected to a steering side (steering wheel 2, steering shaft 3). Therefore, if some of the wheels 7 cannot be turned due to a malfunction, the wheels 7 may move freely. For example, if the turning motor 21 of one of the plurality of the turning mechanisms 20 fails (for example, power to the turning motor 21 is cut off), the wheel 7 corresponding to the failed turning mechanism 20 cannot be turned and may move freely. In particular, in the steer-by-wire device 1 of the present embodiment, the rack shaft 10 and the turning mechanism 20 are independently connected to each of the wheels 7, and thus the wheels 7 move more easily than in a configuration in which one rack shaft 10 and one turning mechanism 20 are connected to two wheels 7. Therefore, in a case where some of the wheels 7 cannot be turned during traveling, if the wheels 7 come into contact with an obstacle such as a curb, an impact may cause the wheels 7 to change directions, and the vehicle may move in an unexpected direction.

[0019] Therefore, the locking mechanism 100 is mounted on the steer-by-wire device 1 of the present embodiment. If the turning motor 21 of the turning mechanism 20 fails, the locking mechanism 100 locks the corresponding wheel 7 to prevent the corresponding wheel 7 from moving freely, thereby improving safety of the steer-by-wire device 1. On the other hand, if there is no abnormality in the turning mechanism 20, the locking mechanism 100 causes a releasing unit to be described later to release the locking of the wheel 7 such that the wheel 7 can be turned.

[0020] Next, the locking mechanism 100 will be described in detail.

[0021] The locking mechanism 100 is provided (as a separate mechanism) separately from each of the turning mechanisms 20. The locking mechanism 100 is provided between the output shaft 22 and the worm shaft 23 of the turning motor 21 in each of the turning mechanisms 20. In FIG. 1, the locking mechanisms 100 are provided between the output shaft 22a of the first turning motor 21a and the first worm shaft 23a, and between the output shaft 22b and the second worm shaft 23b of the second turning motor 21b. Since configurations of the locking mechanisms 100 are the same, the locking mechanism 100 provided between the output shaft 22a of the first turning motor 21a and the first worm shaft 23a will be described below as a representative.

[0022] FIG. 2 is a perspective view of the locking mechanism 100. As shown in FIG. 2, the locking mechanism 100 includes a connection shaft 86 that is provided between and connected to the output shaft 22a of the first turning motor 21a and the first worm shaft 23a, a locking unit 81 that restricts rotation of the connection shaft 86, and a solenoid 87 as the releasing unit that releases locking of the connection shaft 86 by the locking unit 81. The locking mechanism 100 is accommodated in a lock housing (not shown) that is provided between a motor housing (not shown) that accommodates the first turning motor 21a and a gear housing (not shown) that accommodates the first worm shaft 23a and the first worm wheel 24a.

[0023] A spline is formed on an outer circumferential surface of the connection shaft 86. A first connection portion 86a that is connected to the output shaft 22a of the first turning motor 21a and a second connection portion 86b that is connected to the first worm shaft 23a are provided at both ends of the connection shaft 86, respectively. A first claw portion 86c that protrudes in a shaft direction toward the output shaft 22a is formed on the first connection portion 86a, and a second claw portion 86d that protrudes in the shaft direction toward the first worm shaft 23a is formed on the second connection portion 86b. A plurality of first claw portions 86c and second claw portions 86d (four each in the present embodiment) are formed at intervals in a circumferential direction.

[0024] A connection portion (not shown) having the same shape as that of the first connection portion 86a is provided at an end of the output shaft 22a of the first turning motor 21a. The first claw portions 86c of the first connection portion 86a each enter claw portions (not shown) of the connection portion of the output shaft 22a and come into contact with and engage with the claw portions in the circumferential direction. Accordingly, the connection shaft 86 is connected to the output shaft 22a of the first turning motor 21a, and the rotational torque of the first turning motor 21a is transmitted to the connection shaft 86. In addition, a connection portion (not shown) having the same shape as that of the second connection portion 86b is provided at an end of the first worm shaft 23a. The second claw portions 86d of the second connection portion 86b each enter claw portions (not shown) of the connection portion of the first worm shaft 23a, and come into contact with and engage with the claw portions in the circumferential direction. Accordingly, the connection shaft 86 is connected to the first worm shaft 23a, and the rotational torque of the connection shaft 86 is transmitted to the first worm shaft 23a.

[0025] If the rotation of the connection shaft 86 is restricted by the locking unit 81, the connection shaft 86 does not transmit the rotational torque between the output shaft 22a of the first turning motor 21a and the first worm shaft 23a. In other words, if the rotation of the connection shaft 86 is restricted, the rotation of the output shaft 22a of the first turning motor 21a and the rotation of the first worm shaft 23a connected to the connection shaft 86 are restricted, the first turning mechanism 20a is locked so as not to be rotatable, and the wheel 7a is locked. On the other hand, if the rotation of the connection shaft 86 is not restricted by the locking unit 81, the connection shaft 86 transmits the rotational torque between the output shaft 22a of the first turning motor 21a and the first worm shaft 23a. In this way, in the present embodiment, an object to be locked by the locking unit 81 is the connection shaft 86, and the rotation of the connection shaft 86 is restricted by the locking unit 81, so that the first turning mechanism 20a is locked so as not to be rotatable. When the locking of the connection shaft 86 by the locking unit 81 is released by the solenoid 87 and the connection shaft 86 becomes rotatable, the rotational torque is transmitted from the output shaft 22a of the first turning motor 21a to the first worm shaft 23a, and the wheel 7a becomes turnable.

[0026] FIG. 3 is a schematic diagram showing an operation of the locking unit 81 and the solenoid 87. (a) of FIG. 3 shows a state where the locking unit 81 locks the connection shaft 86, and (b) of FIG. 3 shows a state where the locking of the connection shaft 86 is released by the solenoid 87.

[0027] As shown in FIGS. 2 and 3, the locking unit 81 includes an engaging portion 82 that engages with the connection shaft 86 as the object to be locked and restricts the rotation (operation) of the connection shaft 86, a spring 83 (see FIG. 3) as a biasing member that biases the engaging portion 82 toward the connection shaft 86, and a cam 84 that is rotatably provided in contact with the engaging portion 82 and is driven by the solenoid 87.

[0028] The engaging portion 82 includes an opposing portion 82a (see FIG. 3) that is formed opposite to the connection shaft 86 and engages with the connection shaft 86, and a cam accommodating portion 82b that is formed hollow and accommodates the cam 84. The engaging portion 82 does not come into contact with the first connection portion 86a or the second connection portion 86b.

[0029] The engaging portion 82 is formed in a substantially fan shape. A pivot shaft 82d is provided at an end of the engaging portion 82, and the engaging portion 82 can pivot about the pivot shaft 82d. The opposing portion 82a is formed on an outer circumferential surface of the engaging portion 82 and away from the pivot shaft 82d. The opposing portion 82a is formed along a shape of the object to be locked, and in the present embodiment, is formed in an uneven shape along the spline on the outer circumferential surface of the connection shaft 86 (see FIG. 3). The spring 83 is compressed and provided between the outer circumferential surface of the engaging portion 82 opposite to the opposing portion 82a and the lock housing, and biases the engaging portion 82 such that the opposing portion 82a engages with (comes closer to) the connection shaft 86.

[0030] An outer circumferential surface of the cam 84 is a shape in which a part of a circle is cut out. Specifically, the outer circumferential surface of the cam 84 has an arc portion 84a and a flat portion 84b formed by cutting out a part of a circle. As shown in (a) of FIG. 3, in a state where the opposing portion 82a is engaged with the connection shaft 86, the flat portion 84b of the cam 84 is in surface contact with an inner circumferential surface of the cam accommodating portion 82b, and the arc portion 84a is not in contact with the inner circumferential surface of the cam accommodating portion 82b. The cam 84 is driven and rotated by the solenoid 87 as described below.

[0031] The solenoid 87 is controlled by an ECU (not shown) and is supported by and attached to a base 88 (see FIG. 2). A power source (not shown) of the solenoid 87 is provided separately from the power source (not shown) of the first turning motor 21a. Therefore, even if an abnormality occurs in the power source of the first turning motor 21a, the solenoid 87 operates normally. A shaft portion 87a of the solenoid 87 is fixed to the cam 84 eccentrically with respect to a center C (see FIG. 3) of the cam 84. In the state where the opposing portion 82a is engaged with the connection shaft 86, the shaft portion 87a is provided farther from the connection shaft 86 and the opposing portion 82a than the center C (see FIG. 3) of the cam 84. If the solenoid 87 becomes an energized state, the shaft portion 87a rotates due to a solenoid thrust force. When the shaft portion 87a rotates, the cam 84 rotates about the shaft portion 87a.

[0032] An operation of releasing the locking of the connection shaft 86 by the solenoid 87 will be specifically described. The solenoid 87 is not energized if an ignition switch (not shown) of the vehicle is in an off state, and is energized if the ignition switch is turned on.

[0033] When the ignition switch is in the off state and the solenoid 87 is in a non-energized state, the shaft portion 87a does not rotate, and as shown in (a) of FIG. 3, the engaging portion 82 (opposing portion 82a) is engaged with the connection shaft 86 by the biasing force of the spring 83. Therefore, the rotation of the connection shaft 86 is restricted, and the wheel 7a is locked.

[0034] If the ignition switch is turned on, the solenoid 87 is energized and enters the energized state. As shown in (b) of FIG. 3, in the energized state of the solenoid 87, the shaft portion 87a rotates in a direction indicated by an arrow B due to the solenoid thrust force, and the cam 84 rotates integrally with the shaft portion 87a. That is, the cam 84 rotates about the shaft portion 87a. In a state where the engaging portion 82 is engaged with the connection shaft 86, the shaft portion 87a is provided farther from the connection shaft 86 than the center C of the cam 84, and thus, when the cam 84 rotates integrally with the shaft portion 87a, the arc portion 84a pivots away from the connection shaft 86 while sliding against the inner circumferential surface of the cam accommodating portion 82b. Accordingly, the engaging portion 82 pivots about the pivot shaft 82d against the biasing force of the spring 83 so as to come off the connection shaft 86. Therefore, the locking of the connection shaft 86 is released, and the wheel 7a becomes turnable. In this way, the solenoid 87 releases the engagement of the engaging portion 82 with the connection shaft 86 in the energized state.

[0035] Even if the ignition switch is in the on state, if the first turning motor 21a fails (for example, if it is detected that the power to the first turning motor 21a is cut off), the solenoid 87 is controlled by the ECU to cut off the power supply to the solenoid 87, and the solenoid 87 enters the non-energized state. Therefore, as shown in (a) of FIG. 3, the engaging portion 82 is engaged with the connection shaft 86 by the biasing force of the spring 83, and the rotation of the connection shaft 86 is restricted, so that the wheel 7a is locked.

[0036] In this way, in the locking mechanism 100 of the present embodiment, by restricting the rotation of the connection shaft 86 by the locking unit 81, the first turning mechanism 20a is locked so as not to be rotatable, and the wheel 7 is locked. Therefore, as described above, it is possible to prevent the wheel 7 from moving freely when the first turning motor 21a of the first turning mechanism 20a fails or the like. Accordingly, when some of the wheels 7 become unable to turn during traveling, even if the wheels 7 come into contact with an obstacle such as a curb, the impact may change the directions of the wheels 7, and can prevent the vehicle from moving in an unexpected direction. Therefore, the safety of the steer-by-wire device 1 can be improved.

[0037] In addition, when the vehicle is towed after the turning motors 21 of some of the turning mechanisms 20 fail, the ignition switch is in the on state, and the driver operates the steering wheel 2 to tow the vehicle. Therefore, the turning mechanisms 20 without abnormalities are not locked so as not to be rotatable by the locking mechanism 100, and the corresponding wheels 7 can be turned without being locked. On the other hand, the turning mechanism 20 in which the turning motor 21 fails is locked so as not to be rotatable by the locking mechanism 100, and the corresponding wheel 7 is locked. Therefore, even if the vehicle is towed, it can be prevented that the vehicle in which the direction of the wheel 7 that cannot be turned is changed advances in an unexpected direction while the corresponding wheels 7 can be turned by the turning mechanisms 20 without abnormalities.

[0038] In the locking mechanism 100, the locking unit 81 locks the connection shaft 86 provided between the output shaft 22a of the first turning motor 21a and the first worm shaft 23a, and thus the first turning mechanism 20a can be locked with a force smaller than that in a case where the first worm wheel 24a and the first pinion shaft 25a, which rotate at a reduced speed, are locked. The locking mechanism 100 may be accommodated in the lock housing and be provided between the motor housing that accommodates the first turning motor 21a and the gear housing that accommodates the first worm shaft 23a and the first worm wheel 24a, and thus the locking mechanism 100 can be easily mounted in the steer-by-wire device 1 in the related art, and a size of the steer-by-wire device 1 can be prevented from increasing.

[0039] In the locking mechanism 100, the engaging portion 82 is driven by rotating the cam 84 using the solenoid 87, and thus the engaging portion 82 can be driven with a force smaller than that in a case of being driven directly.

[0040] In the locking mechanism 100, the cam 84 includes the flat portion 84b that comes into surface contact with the engaging portion 82 (cam accommodating portion 82b) in the non-energized state of the solenoid 87. Therefore, even if a load acts on the engaging portion 82 from a connection shaft 86 side in a state where the connection shaft 86 and the wheel 7 are locked (in other words, even if the load acts on the engaging portion 82 in a direction away from the connection shaft 86), as shown by an arrow A in (a) of FIG. 3, the load acts on the flat portion 84b of the cam 84, and thus the cam 84 is prevented from rotating. Therefore, even if the load acts on the engaging portion 82, the engaging portion 82 is prevented from coming off the connection shaft 86. Furthermore, since a locked state can be maintained by the flat portion 84b as described above without relying on the biasing force of the spring 83, the load of the spring 83 can be reduced.

[0041] It is also considered that the locking mechanism may be configured to lock the wheels against an external force acting on the wheels by, for example, using a reduction ratio of a worm wheel to a worm shaft to prevent the worm shaft from rotating due to input from the worm wheel. However, in this configuration, the wheels are always locked against the external force even if there is no abnormality in the turning mechanism, and thus so-called self-alignment in which the wheels naturally return to a neutral state after being turned does not work, and thus the driver needs to operate the steering wheel 2 to return the directions of the wheels to the neutral state. Regarding this, in the locking mechanism 100 of the present embodiment, the ignition switch is in the on state and the wheel 7a is not locked during normal traveling when there is no abnormality in the first turning motor 21a, and thus the self-alignment of the wheel 7a is not hindered.

[0042] According to the above embodiment, the following effects are exerted.

[0043] In the locking mechanism 100, the turning mechanism 20 is locked by the locking unit 81 so as not to be rotatable (operable), and the wheels 7 are locked. Therefore, if the turning motor 21 of the turning mechanism 20 fails, the wheels 7 can be prevented from moving freely, and the safety of the steer-by-wire device 1 can be improved.

[0044] Next, modifications of the present embodiment will be described. The following modifications are also within the scope of the present invention, and it is also possible to combine configurations shown in the modifications with the configurations described in the above-described embodiment, or to combine the configurations described in the following different modifications.

[0045] <First Modification> In the above embodiment, the connection shaft 86 of the locking mechanism 100 is provided between the output shaft 22 of the turning motor 21 and the worm shaft 23. The present invention is not limited thereto, and the connection shaft 86 may be provided at an end of the worm shaft 23 or an end of the pinion shaft 25. In this configuration, the locking unit 81 can also restrict the rotation of the connection shaft 86 to lock the wheels 7. The connection shaft 86 is not an essential component of the locking mechanism 100. The locking mechanism 100 may not include the connection shaft 86, and the engaging portion 82 of the locking unit 81 may directly engage with the worm wheel 24, the worm shaft 23, the pinion shaft 25, or the rack shaft 10 to perform locking so as not to be operable (rotatable or moveable). In other words, the locking unit 81 may be configured to lock the rack shaft 10 or the turning mechanism 20 so as not to be operable, and the object to be locked by the locking unit 81 is any of the worm shaft 23, the worm wheel 24, the pinion shaft 25, the rack shaft 10, and the connection shaft 86 connected thereto.

[0046] <Second Modification> In the above embodiment, the cam 84 is provided on the engaging portion 82 (cam accommodating portion 82b) of the locking unit 81 of the locking mechanism 100. The flat portion 84b of the cam 84 prevents the engaging portion 82 from coming off the connection shaft 86 even if a load acts on the engaging portion 82 from the connection shaft 86 side in a state where the connection shaft 86 and the wheel 7 are locked. However, the cam 84 is not an essential component, and the cam 84 may not be provided in cases where there is no risk of the engaging portion 82 coming off the connection shaft 86, for example, by increasing a spring constant of the spring 83. For example, as shown in FIG. 4, the engaging portion 82 may be curved along the connection shaft 86, the opposing portion 82a may engage with the connection shaft 86, and the solenoid 87 may directly drive (rotate) the engaging portion 82. In this configuration, the solenoid 87 drives the engaging portion 82 in a direction indicated by an arrow D in FIG. 4 to release the locking of the connection shaft 86. In this configuration, the locking mechanism 100 can be simplified.

[0047] <Third Modification> In the above embodiment, the locking mechanism 100 locks the corresponding wheel 7 when the turning motor 21 of the turning mechanism 20 fails. The present invention is not limited thereto, and the locking mechanism 100 may lock the wheel 7 when there is a risk that the wheel 7 may move freely. For example, the locking mechanism 100 may lock the corresponding wheel 7 when the turning controller 40 that controls the turning motor 21 fails.

[0048] <Fourth Modification> In the above embodiment, in the locking mechanism 100, the cam 84 is provided in the cam accommodating portion 82b which is the inside of the engaging portion 82. The present invention is not limited thereto, and the cam 84 may be provided rotatably in contact with the outer circumferential surface of the engaging portion 82.

[0049] <Fifth Modification> In the above embodiment, the steer-by-wire device 1 on which the locking mechanism 100 is mounted includes the four wheels 7 turned independently, and each of the four wheels 7 is connected to the rack shaft 10 and the turning mechanism 20 for individual control. The present invention is not limited thereto, in the steer-by-wire device 1, the wheels 7 at the front of the vehicle may be connected to one rack shaft 10 and one turning mechanism 20, and the wheels 7 at the rear of the vehicle may be connected to one rack shaft 10 and one turning mechanism 20. According to this configuration, the same effects as the above embodiment can also be exerted.

[0050] Hereinafter, configurations, functions, and effects of the embodiment of the present invention will be collectively described.

[0051] The locking mechanism 100 mounted on the steer-by-wire device 1 including the rack shaft 10 as a turning shaft for turning the vehicle wheels 7, and the turning mechanism 20 that applies the turning force to the rack shaft 10 by the turning motor 21 as a motor includes the locking unit 81 that locks the rack shaft 10 or the turning mechanism 20 so as not to be operable, and the releasing unit (solenoid 87) that releases the locking of the rack shaft 10 or the turning mechanism 20 by the locking unit 81.

[0052] The turning mechanism 20 includes the worm shaft 23 connected to the output shaft 22 of the turning motor 21, the worm wheel 24 that meshes with the worm shaft 23, and the pinion shaft 25 that is connected to the worm wheel 24 and transmits the rotational torque to the rack shaft 10, and the object to be locked by the locking unit 81 is any of the worm shaft 23, the worm wheel 24, the pinion shaft 25, the rack shaft 10, and the connection shaft 86 connected thereto.

[0053] In this configuration, the locking unit 81 locks the rack shaft 10 or the turning mechanism 20 so as not to be operable, and the wheel 7 is locked. Therefore, the wheel 7 can be prevented from moving freely when the turning motor 21 of the turning mechanism 20 fails or the like. Therefore, the safety of the steer-by-wire device 1 can be improved.

[0054] In the locking mechanism 100, the turning mechanism 20 includes the worm shaft 23 that is connected to the output shaft 22 of the turning motor 21, and the worm wheel 24 that meshes with the worm shaft 23, and the object to be locked by the locking unit 81 is the connection shaft 86 that is provided between and connected to the output shaft 22 of the turning motor 21 and the worm shaft 23.

[0055] In this configuration, the locking unit 81 locks the connection shaft 86 that is provided between the output shaft 22 of the turning motor 21 and the worm shaft 23, and thus the turning mechanism 20 can be locked with a force smaller than that in a case of locking the worm wheel 24 or the pinion shaft 25 which rotates at a reduced speed.

[0056] In the locking mechanism 100, the locking unit 81 includes the engaging portion 82 that engages with the object to be locked to restrict the operation of the object to be locked, and the releasing unit is the solenoid 87 that releases the engagement of the engaging portion 82 with the object to be locked in the energized state.

[0057] In this configuration, the locking mechanism 100 can be simplified.

[0058] In the locking mechanism 100, the solenoid 87 is not energized when the turning motor 21 fails.

[0059] In this configuration, the wheel 7 can be locked when the turning motor 21 fails, and the safety of the steer-by-wire device 1 can be improved.

[0060] In the locking mechanism 100, the locking unit 81 further includes the spring 83 as a biasing member that biases the engaging portion 82 toward the object to be locked, and the cam 84 that is rotatably provided in contact with the engaging portion 82 and driven by the solenoid 87, and in the energized state of the solenoid 87, the cam 84 rotates due to the thrust force of the solenoid 87, causing the engaging portion 82 to come off the object to be locked against the biasing force, and in the non-energized state of the solenoid 87, the engaging portion 82 is engaged with the object to be locked by the biasing force of the spring 83.

[0061] In this configuration, the engaging portion 82 is driven by driving the cam 84 using the solenoid 87, and thus the engaging portion 82 can be driven with a small force.

[0062] In the locking mechanism 100, the cam 84 includes the flat portion 84b that comes into surface contact with the engaging portion 82 in the non-energized state of the solenoid 87.

[0063] In this configuration, the cam 84 and the engaging portion 82 are in surface contact in the non-energized state, and thus even if a load acts on the engaging portion 82 from an object to be locked side, the engaging portion 82 is prevented from coming off the object to be locked.

[0064] Embodiments of the present invention were described above, but the above embodiments are merely examples of applications of the present invention, and the technical scope of the present invention is not limited to the specific constitutions of the above embodiments.

[0065] With respect to the above description, the contents of application No. 2024-166308, with a filing date of September 25, 2024 in Japan, are incorporated herein by reference.

Claims

1. A locking mechanism to be mounted on a steer-by-wire device including a turning shaft for turning a wheel of a vehicle and a turning mechanism for applying a turning force to the turning shaft by a motor, the locking mechanism comprising: a locking unit configured to lock the turning shaft or the turning mechanism so as not to be operable; and a releasing unit configured to release the locking of the turning shaft or the turning mechanism by the locking unit.

2. The locking mechanism according to claim 1, wherein the turning mechanism includes: a worm shaft that is connected to an output shaft of the motor; a worm wheel that meshes with the worm shaft; and a pinion shaft that is connected to the worm wheel and transmits rotational torque to the turning shaft, and an object to be locked by the locking unit is any of the worm shaft, the worm wheel, the pinion shaft, the turning shaft, and a connection shaft connected thereto.

3. The locking mechanism according to claim 1, wherein the turning mechanism includes: a worm shaft that is connected to an output shaft of the motor; and a worm wheel that meshes with the worm shaft, and an object to be locked by the locking unit is a connection shaft provided between and connected to the output shaft of the motor and the worm shaft.

4. The locking mechanism according to any one of claims 1 to 3, wherein the locking unit includes an engaging portion configured to engage with an object to be locked to restrict an operation of the object to be locked, and the releasing unit is a solenoid configured to release engagement of the engaging portion with the object to be locked in an energized state.

5. The locking mechanism according to claim 4, wherein the solenoid is not energized when the motor fails.

6. The locking mechanism according to claim 4, wherein the locking unit further includes: a biasing member configured to bias the engaging portion toward the object to be locked; and a cam rotatably provided in contact with the engaging portion and driven by the solenoid, in the energized state of the solenoid, the engaging portion comes off the object to be locked against a biasing force due to rotation of the cam by a solenoid thrust force, and in a non-energized state of the solenoid, the engaging portion engages with the object to be locked due to the biasing force of the biasing member.

7. The locking mechanism according to claim 6, wherein the cam has a flat portion that comes into surface contact with the engaging portion in the non-energized state of the solenoid.

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