Steer-by-Wire Steering Device

Abstract

To provide a steer-by-wire type steering device that is configured so that a turning actuator changes a direction of a turning part in accordance with an operation amount of a steering wheel that is sensed by a steering sensor, and when the direction of the turning part reaches a stroke end, a driver can surely sense the situation where the direction reaches the end through the steering wheel, and can perform steering lock even in a state where there is no power source supply.SOLUTION: The steer-by-wire type steering device comprises: a shaft connected to a steering wheel so as to rotate integrally with the steering wheel; an outer ring having an inner periphery arranged around the shaft; an engagement element arranged between the shaft and the inner periphery of the outer ring; a retainer arranged to be movable in a circumferential direction between an engagement position where the retainer engages the engagement element with the shaft and the inner periphery of the outer ring while retaining the engagement element and a releasing position where the retainer releases the engagement; a centering spring that elastically retains the retainer at the releasing position and is fixed to the shaft and the retainer not to turn so as to rotate integrally with the shaft; and a non-excitation actuating type electromagnetic brake that brakes the retainer.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a steer-by-wire steering device that performs steering in a state mechanically separated from a steering wheel.

Background Art

[0002] As a steering device that changes the direction of a steering part such as a steered wheel (generally a front wheel) of a vehicle or a rudder of a ship in response to a rotational operation of a steering wheel by a driver, a steer-by-wire type is known.

[0003] A steer-by-wire steering device includes a steering sensor that detects an operation amount of a steering wheel and a steering actuator provided so as to be mechanically separated from the steering wheel. The steering actuator operates in response to the operation amount of the steering wheel detected by the steering sensor and changes the direction of the steering part.

[0004] This type of steer-by-wire steering device can convert the operation amount of the steering wheel by the driver into an electric signal once and control the operation of the steering actuator based on the electric signal. Therefore, for example, the correspondence between the operation amount of the steering wheel and the operation amount of the steering actuator can be optimized according to the driving state of the vehicle, ship, etc., such as adjusting the amount of change in the direction of the steering part when the steering wheel is operated according to the moving speed of the vehicle, ship, etc.

[0005] On the other hand, in a steer-by-wire steering device, since the steering wheel rotated by the driver and the steering actuator that changes the direction of the steering part are mechanically separated, even when the direction of the steering part reaches its movement limit (stroke end), the driver can further rotate the steering wheel. Therefore, a vehicle steer-by-wire steering device has been proposed that enables the driver to sense the situation when the direction of the steering part reaches the stroke end through the steering wheel (Patent Document 1).

[0006] The steer-by-wire type steering device for a vehicle disclosed in Patent Document 1 includes a reaction force motor that applies a steering reaction force calculated based on the vehicle speed, the operation amount of the steering wheel, etc. to the steering wheel, and a reaction force controller that controls the reaction force motor. Then, when the direction of the steered wheels reaches the stroke end, the reaction force controller performs control to correct and increase the magnitude of the steering reaction force generated by the reaction force motor. Thereby, the driver can sense through the steering wheel that the direction of the steered wheels has reached the stroke end.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] When control is performed to correct and increase the magnitude of the steering reaction force generated by the reaction force motor when the direction of the steered wheels reaches the stroke end as in Patent Document 1, the control of the reaction force motor becomes complicated. Also, since the rotation of the steering wheel is not blocked but only the steering reaction force of the steering wheel becomes large, there is a possibility that some drivers may not notice that the direction of the steered wheels has reached the stroke end and may continue the rotation operation of the steering wheel as it is.

[0009] Also, when the driver leaves the seat for a long time, it is preferable to perform a steering lock to prevent theft of the vehicle or the like. In such a case, usually, since power supply to the reaction force motor cannot be expected, the steering lock cannot be performed with the steering reaction force. Also, even when power supply to the reaction force motor is continued, it is difficult to apply a steering reaction force large enough to perform the steering lock to the steering wheel.

[0010] Therefore, the problem to be solved by this invention is to provide a steer-by-wire type steering device that can surely let the driver perceive the situation through the steering wheel when the direction of the steering section reaches the stroke end, and can perform steering lock even in a state without power supply.

Means for Solving the Problem

[0011] To solve the above problems, this invention provides a steer-by-wire type steering device including a steering wheel, a steering sensor that detects the operation amount of the steering wheel, and a steering actuator that changes the direction of the steering section according to the operation amount of the steering wheel detected by the steering sensor. In this device, a shaft connected to the steering wheel so as to rotate integrally with the steering wheel, an outer ring having an inner circumference disposed around the shaft, an engaging element disposed between the shaft and the inner circumference of the outer ring, a retainer that holds the engaging element and is disposed so as to be movable in the circumferential direction between an engaging position where the engaging element is engaged with the shaft and the inner circumference of the outer ring and a release position where the engagement is released, a centering spring that elastically holds the retainer at the release position and is rotationally restrained to the shaft and the retainer so as to rotate integrally with the shaft, and a non-excitation operation type electromagnetic brake that brakes the retainer are further provided.

[0012] According to the above configuration, when the non-excitation operation type electromagnetic brake is in the excited state, the retainer is in a state where it is not braked. At this time, when the shaft rotates, the centering spring that is prevented from rotating around the shaft so as to rotate integrally with the shaft transmits the rotational force of the shaft to the retainer and holds the retainer at the release position with respect to the shaft. Therefore, the engaging element cannot engage with the shaft and the inner circumference of the outer ring. That is, when the electromagnetic brake is in the excited state, the rotation of the steering wheel is permitted. On the other hand, when the non-excitation operation type electromagnetic brake is in the non-excited state, the retainer is in a state where it is braked. At this time, when the steering wheel is rotated, since the retainer that is transmitted the rotational force of the shaft from the centering spring is braked by the electromagnetic brake, the shaft rotates relative to the retainer. Due to this relative rotation, when the retainer that moves in the circumferential direction with respect to the shaft reaches the engagement position against the centering spring, the engaging element engages with the shaft and the inner circumference of the outer ring, so that further rotation of the shaft is reliably blocked. When the electromagnetic brake is switched from the non-excited state to the excited state, the retainer is returned to the release position by the elastic restoring force of the centering spring. Therefore, by switching the electromagnetic brake from the excited state to the non-excited state, it is possible to reliably prevent the steering wheel from rotating more than the circumferential movement amount between the release position and the engagement position of the retainer, and through the steering wheel, the driver can be reliably made aware that the direction of the steering section has reached the stroke end. Further, when the electromagnetic brake is in the non-excited state, since the rotation of the shaft is reliably blocked by the engaging element engaging with the shaft and the inner circumference of the outer ring due to the rotation of the steering wheel, it is possible to perform steering lock even in a state where there is no power supply.

[0013] For example, the non-excitation actuated electromagnetic brake may include a friction member that is prevented from rotating by the cage and is axially movable relative to the cage, a friction surface portion that axially faces the friction member and is stationary relative to the shaft, an electromagnet, an armature that axially faces the electromagnet, and an actuating spring that biases the friction member to press against the friction surface portion when the electromagnet is de-energized and whose pressing force weakens in response to the axial movement of the armature that is attracted by the electromagnet when the electromagnet is energized. In this way, when the electromagnet is in a non-energized state where no current is passed through it, the actuating spring biases the friction member to axially press against the friction surface portion, applying an actuating pressure between the friction member and the friction surface portion, thereby braking the cage and causing it to move circumferentially relative to the shaft. On the other hand, when the electromagnet is switched from the non-energized state to the energized state, the axial movement of the attracted armature weakens the aforementioned pressing force, releasing the braking of the cage by the friction surface portion and the friction member.

[0014] The actuating spring may be arranged to support the armature at a position axially away from the electromagnet when the electromagnet is de-energized and to bias the friction member toward the friction surface portion via the armature. In this way, when the electromagnet is de-energized, the actuating spring biases the friction member to press against the friction surface portion via the armature, and the support of the actuating spring can set a predetermined magnetic gap between the armature and the electromagnet. Also, when the electromagnet is switched from the energized state to the non-energized state, the armature can be returned to the position of the predetermined magnetic gap by the elastic restoring force of the actuating spring.

[0015] The friction surface portion may be formed on the end face of the outer ring. In this way, it is not necessary to use a dedicated braking component for the friction surface portion, and the cost of the non-excitation actuated electromagnetic brake can be reduced.

[0016] Further provided is a cylindrical brake case that houses the outer ring and the non-energized operation type electromagnetic brake. The brake case is formed of a non-magnetic material separate from the outer ring, and it is preferable that the outer ring is prevented from rotating relative to the brake case. In this way, when the non-energized operation type electromagnetic brake is in an excited state, it is possible to prevent magnetic flux generated from the non-energized operation type electromagnetic brake from leaking into the brake case.

[0017] Also, further provided is a cylindrical brake case that houses the non-energized operation type electromagnetic brake, and it is preferable that the outer ring is integrally formed with the brake case. In this way, it is possible to eliminate the axial positioning and anti-rotation processes of the outer ring with respect to the brake case.

[0018] Further provided is a reaction force motor that applies a steering reaction force to the steering wheel. The steering section is a pair of left and right steering wheels, and it is preferable that the outer ring, the engagement member, the retainer, and the non-energized operation type electromagnetic brake are provided between the steering wheel and the reaction force motor or on the side axially opposite to the steering wheel with respect to the reaction force motor. In this way, as a steer-by-wire type steering device for a vehicle, when the steering wheel reaches the stroke end, the driver can surely sense through the steering wheel that the direction of the steering wheel has reached the stroke end, and when leaving the vehicle during parking, the steering lock can be performed to prevent vehicle theft.

Advantages of the Invention

[0019] As described above, due to the adoption of the above configuration, the steer-by-wire type steering device according to this invention can surely let the driver sense the situation through the steering wheel when the direction of the steering section reaches the stroke end, and can perform the steering lock even when there is no power supply.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0021] FIGS. 1 and 2 show a steer-by-wire type steering device (hereinafter simply referred to as "steering device") according to the first embodiment as an example of the present invention.

[0022] This steering device can change the directions of a pair of left and right steering wheels 3 as a steering unit by converting the operation amount of the steering wheel 1 by the driver into an electric signal and controlling the steering actuator 2 based on the electric signal.

[0023] This steering device includes a steering wheel 1 steered by a driver, a shaft 4 connected to the steering wheel 1, a steering sensor 5 that detects the operation amount of the steering wheel 1, a reaction force motor 6 that applies a steering reaction force to the steering wheel 1, a brake unit 7 that blocks the rotation of the steering wheel 1 in a non-excited state and allows the rotation of the steering wheel 1 in an excited state, a steering actuator 2 provided so as to be mechanically separated from the steering wheel 1, and a control unit 8.

[0024] The shaft 4 is connected to the steering wheel 1 so as to rotate integrally with the steering wheel 1 when the steering wheel 1 is steered. The steering sensor 5 is attached to the shaft 4. Examples of the steering sensor 5 include a steering angle sensor that detects the steering angle of the steering wheel 1 and a steering torque sensor that detects the steering torque input to the steering wheel 1 by the driver.

[0025] The reaction force motor 6 is an electric motor that generates a rotational torque when energized. The reaction force motor 6 is connected to the end of the shaft 4. The reaction force motor 6 applies a steering reaction force to the steering wheel 1 via the shaft 4 by inputting a rotational torque to the shaft 4.

[0026] The steering actuator 2 includes a steering shaft 10, a steering shaft housing 11, a steering motor 12 that moves the steering shaft 10 in the left-right direction of the vehicle, and a steering sensor 13 that detects the position of the steering shaft 10. The steering shaft 10 is supported by the steering shaft housing 11 so as to be movable in the left-right direction of the vehicle. The steering shaft housing 11 houses the central portion of the steering shaft 10 such that both the left and right ends of the steering shaft 10 protrude from the steering shaft housing 11.

[0027] The steering motor 12 and the steering sensor 13 are attached to the steering shaft housing 11. A motion conversion mechanism (not shown) that converts the rotation output by the steering motor 12 into the linear motion of the steering shaft 10 is incorporated between the steering motor 12 and the steering shaft 10. Both the left and right ends of the steering shaft 10 are connected to a pair of left and right steering wheels 3 via tie rods 14, and when the steering shaft 10 moves in the axial direction, the directions of the pair of left and right steering wheels 3 change in conjunction with this movement.

[0028] The reaction force motor 6 includes a motor case 15 and a motor shaft 16 that protrudes from the motor case 15 to the side opposite to the steering wheel 1 (the lower side in the figure). The motor shaft 16 is rotatably supported by a rolling bearing (not shown) incorporated inside the motor case 15. Further, the motor shaft 16 is a component of the shaft 4 and is connected to the shaft portion on the steering column side of the shaft 4 so as to rotate integrally with the steering wheel 1. The motor case 15 is fixed to the vehicle body (not shown) so as not to rotate.

[0029] The brake unit 7 includes an inner ring 20 connected to the motor shaft 16, an outer ring 21 having an inner circumference disposed around the inner ring 20, a plurality of cam surfaces 22 (see FIG. 3) formed on the outer circumference of the inner ring 20, a cylindrical surface 23 formed on the inner circumference of the outer ring 21, an engaging element 24 disposed between each cam surface 22 and the cylindrical surface 23, a retainer 25 that holds these engaging elements 24, a centering spring 26 that is prevented from rotating with respect to the inner ring 20 and the retainer 25, an electromagnetic brake 27 that operates without excitation to brake the retainer 25, and a brake case 28 connected to the motor case 15.

[0030] The inner ring 20 shown in FIGS. 1 and 3 is a component of the shaft 4 and is spline-fitted to the outer circumference of the motor shaft 16. By this spline fitting, the motor shaft 16 is connected to the inner ring 20 without play so as not to rotate relative to the inner ring 20 at all.

[0031] Note that the entire inner ring 20 is integrally formed by forging. The inner ring 20 and the motor shaft 16 are made separate because it becomes easier to form the plurality of cam surfaces 22 with high precision by forging. The shaft 4 may be configured by connecting a plurality of members such as an inner ring 20, a motor shaft 16, and a steering shaft directly connected to the steering wheel 1 as shown in FIGS. 1 and 2, or may be configured appropriately with a single or a plurality of members, such as integrally forming the motor shaft and the steering shaft or integrally forming the motor shaft and the inner ring.

[0032] The outer ring 21 and the brake case 28 shown in Fig. 1 are formed separately from each other. The brake case 28 is a cylindrical member that collectively houses the components of the brake unit 7 (the inner ring 20, the engaging element 24, the cage 25, the non-excited operating electromagnetic brake 27, etc.). The brake case 28 is formed of a non-magnetic material (such as aluminum alloy, copper, etc.). At one axial end of the brake case 28, a flange portion extending radially outward is formed, and the flange portion is fixed to the axial end face of the motor case 15 with bolts (not shown).

[0033] On the other hand, the outer ring 21 is formed of steel. The outer ring 21 is fitted into the cylindrical brake case 28 and is prevented from coming off the brake case 28 by a retaining ring 29 attached to the inner circumference of the brake case 28. A bearing 30 that rotatably supports the inner ring 20 is disposed between the inner circumference of the outer ring 21 and the outer circumference of the inner ring 20.

[0034] As shown in Figs. 1 and 3, a common key member 33 is fitted into a key groove 31 formed on the inner circumference of the brake case 28 and a key groove 32 formed on the outer circumference of the outer ring 21, and the outer ring 21 is prevented from rotating relative to the brake case 28 by this key member 33.

[0035] The cam surface 22 on the outer circumference of the inner ring 20 shown in Fig. 3 faces the cylindrical surface 23 on the inner circumference of the outer ring 21 in the radial direction. A wedge-shaped space that gradually narrows from the center in the circumferential direction toward both ends in the circumferential direction is formed between the cam surface 22 and the cylindrical surface 23.

[0036] As shown in Figs. 3 and 4, the cage 25 is an annular member in which a plurality of pockets 34 penetrating in the radial direction are formed at intervals in the circumferential direction. The engaging element 24 is housed in each of the pockets 34.

[0037] As shown in Fig. 1, the cage 25 has an inward flange portion 35. The flange portion 35 is located between a retaining ring 36 attached to the outer circumference of the inner ring 20 and a shoulder portion 37 formed on the outer circumference of the inner ring 20. The axial movement of the cage 25 is restricted by the flange portion 35, the retaining ring 36, and the shoulder portion 37.

[0038] The engaging element 24 is composed of a roller having a circular rolling surface that rotates once around the engaging element central axis.

[0039] The retainer 25 is supported so as to be circumferentially movable relative to the inner ring 20 between an engaging position where the engaging element 24 is engaged with the cam surface 22 and the cylindrical surface 23 by moving the engaging element 24 circumferentially from the circumferential center of the cam surface 22 shown in FIG. 3, and a release position where the engagement of the engaging element 24 with the cam surface 22 and the cylindrical surface 23 is released by moving the engaging element 24 to the circumferential center of the cam surface 22.

[0040] The centering spring 26 is an elastic member that elastically holds the retainer 25 in the release position and transmits the rotational force of the shaft 4 to the retainer 25. As shown in FIG. 3, the centering spring 26 includes a C-shaped annular portion 38 formed by winding a steel wire in a C shape, and a pair of extending portions 39 extending radially outward from both ends of the C-shaped annular portion 38.

[0041] A recess 40 and a radial groove 41 for holding the centering spring 26 are formed on the axial end face of the inner ring 20. The recess 40 is in the shape of an arc groove extending along the circumferential direction. The radial groove 41 penetrates radially outward from the recess 40 to the outer periphery of the inner ring 20.

[0042] The C-shaped annular portion 38 of the centering spring 26 is fitted into the recess 40. The pair of extending portions 39 are inserted into the radial groove 41. Further, the extending portions 39 protrude from the radially outer ends of the radial groove 41, and the protruding portions of the extending portions 39 from the radial groove 41 are inserted into the retainer groove 42 formed in the retainer 25. The radial groove 41 and the retainer groove 42 are formed to have the same circumferential width. The extending portions 39 are in contact with the groove inner surfaces at both circumferential ends of the radial groove 41 and the groove inner surfaces at both circumferential ends of the retainer groove 42, respectively. Thereby, the centering spring 26 is prevented from rotating relative to the inner ring 20 so as to rotate integrally with the inner ring 20, and is also prevented from rotating relative to the retainer 25, and the retainer 25 can be elastically held in the release position by the circumferential force acting on the contact portion between the extending portions 39 and the retainer groove 42.

[0043] As shown in FIGS. 5 and 6, the centering spring 26 is axially restricted by an annular cover member 43 fitted on the outer periphery of the inner ring 20 so as not to come out of the recess 40 and the radial groove 41. The axial movement of the cover member 43 is restricted by a retaining ring 44 attached to the outer periphery of the inner ring 20 and the axial end face of the inner ring 20. Note that the cover member may be omitted, and a flange portion for preventing the centering spring from coming out may be formed on the cage.

[0044] As shown in FIGS. 1 and 6, the non-excitation operation type electromagnetic brake 27 includes a friction member 50 axially movably disposed between the outer periphery of the cage 25 and the inner periphery of the brake case 28, a friction surface portion 51 formed on the end face of the outer ring 21, an electromagnet 52 fixed to the brake case 28, an armature 53 axially opposed to the electromagnet 52, and an operating spring 54 for applying an operating pressure between the friction member 50 and the friction surface portion 51.

[0045] As shown in FIGS. 4 to 6, the friction member 50 is provided in a disk shape, is axially slidable along the inner periphery of the brake case 28 at its outer periphery, and is axially slidable along the outer periphery of the cage 25 at its inner periphery. An engaging recess 55 is formed in the cage 25, and an engaging convex portion 56 that engages with the engaging recess 55 of the cage 25 in the circumferential direction is formed on the inner periphery of the friction member 50. Thereby, the friction member 50 is prevented from rotating relative to the cage 25 and is axially movable relative to the cage 25 so as to move circumferentially integrally with the cage 25.

[0046] As shown in FIG. 6, the friction surface portion 51 is formed on the end face of the outer ring 21 on the side facing the friction member 50 in the axial direction. Since the outer ring 21 is fixed to the stationary brake case 28, the friction surface portion 51 also serves as a fixed portion that is stationary with respect to the inner ring 20. The friction surface portion 51 axially receives the friction member 50 against the biasing force generated by the operating spring 54, and can brake the rotation of the friction member 50 when an operating pressure corresponding to the biasing force of the operating spring 54 acts between the friction surface portion 51 and the friction member 50.

[0047] As shown in FIGS. 1 and 6, the electromagnet 52 has an annular field core 57 with a C-shaped cross-section that opens axially toward the armature 53, and a solenoid coil 58 wound around the field core 57. The electromagnet 52 is attached inside the brake case 28 so as not to move in either the axial or circumferential direction. A retaining ring 59 for restricting the axial movement of the electromagnet 52 is attached to the inner circumference of the brake case 28.

[0048] The brake case 28 is formed with a through-hole through which a lead wire for supplying power to the solenoid coil 58 passes, and a rubber grommet for filling the gap between the lead wire and the inner circumference of the through-hole is attached.

[0049] The armature 53 is arranged so as to be axially movable between the inner ring 20 and the inner circumference of the brake case 28 and between the friction member 50 and the electromagnet 52. The armature 53 is a disc-shaped member formed of a magnetic material (such as iron or silicon steel). The armature 53 is axially movably supported on the outer circumference of an inner ring shaft portion 60 provided integrally with the inner ring 20. A bearing 61 for rotatably supporting the inner ring 20 is arranged between the inner ring shaft portion 60 and the inner circumference of the brake case 28.

[0050] The actuating spring 54 is composed of an annular spring such as a wave washer. As shown in Fig. 6, the actuating spring 54 is disposed between the end face of the armature 53 on the side of the anti-friction member 50, the retaining ring 59, and the inner circumference of the brake case 28. When the electromagnet 52 is de-energized, the actuating spring 54 supports the armature 53 at a position axially away from the electromagnet 52 and biases the friction member 50 toward the friction surface portion 51 via the armature 53. Due to this biasing, the friction member 50 can be pressed against the friction surface portion 51 to apply an actuating pressure to the friction contact portion between the two members 50 and 51, thereby braking the rotation of the retainer 25. When the electromagnet 52 is switched from the de-energized state to the energized state, the electromagnet 52 enters an energized state in which it generates a magnetic circuit passing through the field core 57 and the armature 53, and axially attracts the armature 53 to the field core 57 against the actuating spring 54. At this time, since the armature 53 moves in a direction axially away from the friction surface portion 51 while compressing the actuating spring 54 in the axial direction, in response to the axial movement of the armature 53, the pressing force of the friction member 50 against the friction surface portion 51 weakens, and eventually, the rotation of the retainer 25 cannot be braked.

[0051] Note that the actuating spring 54 can also be disposed between the end face of the field core 57 and the armature 53. Further, the actuating spring can be changed to another non-annular spring such as a compression coil spring and dispersed and arranged at a plurality of locations in the circumferential direction.

[0052] When the brake unit 7 shown in Fig. 1 is in an excited state where current is applied to the electromagnet 52 of the non-energized operation type electromagnetic brake 27, the inner ring 20 is in a free rotation state where it can freely rotate in both forward and reverse rotation directions with respect to the outer ring 21. That is, the armature 53 is in a state of being attracted to the electromagnet 52 against the operating spring 54, and the retainer 25 cannot be braked by the friction member 50 and the friction surface portion 51. At this time, no matter whether the inner ring 20 rotates forward or backward, the retainer 25 is carried along by the centering spring 26 that rotates integrally with the inner ring 20, and is held at the release position by the elastic restoring force of the centering spring 26. Therefore, the engaging element 24 held by the retainer 25 does not engage with the cam surface 22 on the outer periphery of the inner ring 20 and the cylindrical surface 23 on the inner periphery of the outer ring 21, and the inner ring 20 and the motor shaft 16 can freely rotate in both forward and reverse directions.

[0053] On the other hand, when the electromagnet 52 of the non-excitation operation type electromagnetic brake 27 is in a non-excitation state where no current is applied, it enters a locked state where it can prevent the inner ring 20 from rotating in either the forward or reverse direction with respect to the outer ring 21. That is, when the power supply to the electromagnet 52 is cut off and switched to the non-excitation state, the armature 53 is separated from the electromagnet 52 by the elastic restoring force of the operating spring 54, and the friction member 50 axially pressed against the armature 53 is pressed against the friction surface portion 51 of the outer ring 21 to be in a friction contact state, and a predetermined magnetic gap is formed between the armature 53 and the electromagnet 52. At this time, when the inner ring 20 rotates in either the forward or reverse direction, the rotational force of the shaft 4 is transmitted from the centering spring 26 that rotates integrally with this to the cage 25. However, since the braking force due to the friction contact between the friction member 50 that is prevented from rotating by the cage 25 and the friction surface portion 51 belonging to the stationary system acts on the cage 25 via the friction member 50, the inner ring 20 rotates relative to the cage 25. As a result, the cage 25 that moves in the circumferential direction with respect to the inner ring 20 elastically deflects by axially pressing one of the pair of extending portions 39 of the centering spring 26 against the inner surface of the cage groove 42, and thus moves in the circumferential direction from the release position toward the engagement position against the centering spring 26. When this circumferential movement reaches a predetermined angular amount, the cage 25 reaches the engagement position, and the engaging element 24 held by the cage 25 engages with the cam surface 22 on the outer periphery of the inner ring 20 and the cylindrical surface 23 on the inner periphery of the outer ring 21, so the rotation of the inner ring 20 is blocked, and the rotation of the motor shaft 16 connected to the inner ring 20 is blocked.

[0054] The control unit 8 shown in FIG. 2 controls the reaction force motor 6, the brake unit 7, and the steering motor 12. An external sensor 62, a steering sensor 5, and a steering sensor 13 are electrically connected to the input side of the control unit 8. The external sensor 62 is a vehicle speed sensor or the like that detects the traveling speed of the vehicle. The reaction force motor 6, the brake unit 7, and the steering actuator 2 are electrically connected to the output side of the control unit 8.

[0055] The control unit 8 operates the steering motor 12 according to the operation amount of the steering wheel 1 detected by the steering sensor 5 and the running state of the vehicle (such as vehicle speed) detected by the external sensor 62, and controls to change the directions of the pair of left and right steering wheels 3. Also, at this time, the control unit 8 controls to operate the reaction force motor 6 so that a steering reaction force of a magnitude corresponding to the operation amount of the steering wheel 1 and the running state of the vehicle is generated.

[0056] Furthermore, the control unit 8 determines whether or not the direction of the steering wheel 3 has reached the stroke end based on the position of the steering shaft 10 detected by the steering sensor 13. Here, when it is determined that the direction of the steering wheel 3 has not reached the stroke end, the non-excitation operation type electromagnetic brake 27 is brought into an excited state by energizing the electromagnet 52 shown in FIG. 1, and the brake unit 7 is maintained in the aforementioned free rotation state. On the other hand, when it is determined that the direction of the steering wheel 3 shown in FIG. 2 has reached the stroke end, the non-excitation operation type electromagnetic brake 27 is brought into a non-excited state by de-energizing the electromagnet 52 shown in FIG. 1, and the brake unit 7 is maintained in the aforementioned locked state.

[0057] In the example of FIG. 2, the brake unit 7 including the outer ring 21, the engagement element 24, the retainer 25, and the non-excitation operation type electromagnetic brake 27 is provided on the side opposite to the steering wheel 1 in the axial direction with respect to the reaction force motor 6. However, as shown in FIG. 7, it is also possible to provide the brake unit 7 between the steering wheel 1 and the reaction force motor 6. When the brake unit 7 is arranged as in the example of FIG. 7, the motor shaft 16 shown in FIG. 1 is extended above the reaction force motor 6, a through hole facing the inner ring shaft portion 60 in the axial direction is added to the brake case 28, the brake unit 7 is attached to the side of the reaction force motor 6 facing the steering wheel 1 with the up and down reversed from FIG. 1, and it is only necessary to connect the inner ring shaft portion 60 to the shaft portion on the steering column side of the shaft 4.

[0058] This steering device is as described above (hereinafter, refer to FIGS. 1 to 7 as appropriate), and includes a steering wheel 1, a steering sensor 5 that detects the operation amount of the steering wheel 1, a steering actuator 2 that changes the direction of the steering wheel 3 as a steering part according to the operation amount of the steering wheel 1 detected by the steering sensor 5, a shaft 4 connected to the steering wheel 1 so as to rotate integrally with the steering wheel 1, an outer ring 21 having an inner circumference disposed around the shaft 4, an engaging element 24 disposed between the shaft 4 and the inner circumference of the outer ring 21, a holder 25 that holds the engaging element 24 and is disposed so as to be movable in the circumferential direction with respect to the shaft 4 between an engaging position where the engaging element 24 is engaged with the inner circumferences of the shaft 4 and the outer ring 21 and a releasing position where the engagement is released, a centering spring 26 that elastically holds the holder 25 in the releasing position and is rotationally locked to the shaft 4 and the holder 25 so as to rotate integrally with the shaft 4, and a non-excitation operation type electromagnetic brake 27 that brakes the holder 25. Thus, when the non-excitation operation type electromagnetic brake 27 is in an excited state and the holder 25 is not braked, the centering spring 26 rotationally locked to the shaft 4 so as to rotate integrally with the shaft 4 transmits the rotational force of the shaft 4 to the holder 25 and holds the holder 25 in the releasing position with respect to the shaft 4. Therefore, the engaging element 24 cannot engage with the inner circumferences of the shaft 4 and the outer ring 21, and the rotation of the steering wheel 1 is allowed. On the other hand, when the non-excitation operation type electromagnetic brake 27 is in a non-excited state and the holder 25 is in a braked state, even if the steering wheel 1 is rotationally operated, the holder 25 that receives the rotational force of the shaft 4 from the centering spring 26 is braked by the non-excitation operation type electromagnetic brake 27. Therefore, the shaft 4 relatively rotates with respect to the holder 25, and when the holder 25 that moves in the circumferential direction with respect to the shaft 4 reaches the engaging position against the centering spring 26, the engaging element 24 engages with the inner circumferences of the shaft 4 and the outer ring 21, and further rotation of the shaft 4 is reliably blocked. When the non-excitation operation type electromagnetic brake 27 switches from the non-excited state to the excited state, the holder 25 is returned to the releasing position by the elastic restoring force of the centering spring 26.

[0059] Therefore, by switching the non-excitation operation type electromagnetic brake 27 from the excited state to the non-excited state, this steering device can surely prevent the steering wheel 1 from rotating by more than the circumferential movement amount between the release position and the engagement position of the retainer 25, and through the steering wheel 1, the driver can surely be made to sense that the direction of the steering wheel 3 has reached the stroke end.

[0060] Note that the circumferential movement amount between the release position and the engagement position of the retainer 25 can be appropriately set based on the dimensions of the engaging element 24, the wedge space formed by the cam surface 22 and the cylindrical surface 23, and the engaging element 25. Therefore, when the circumferential movement amount between the release position and the engagement position of the retainer 25 is small and the brake unit 7 quickly shifts to the locked state, it is possible to slightly reduce the amount of rotation allowed for the steering wheel 1 after the control unit 8 switches the non-excitation operation type electromagnetic brake 27 from the excited state to the non-excited state. In such a case, when the control unit 8 determines that the direction of the steering wheel 3 has reached the stroke end, there is no practical problem even if the non-excitation operation type electromagnetic brake 27 is switched from the excited state to the non-excited state. For example, the circumferential movement amount between the release position and the engagement position of the retainer 25 can be set to 10° or less in terms of the rotation angle between the release position and the engagement position of the retainer 25.

[0061] Also, when the control unit 8 can allow the steering wheel 1 to rotate by a predetermined amount after switching the non-excitation operation type electromagnetic brake 27 from the excited state to the non-excited state, when the control unit 8 determines that the direction of the steering wheel 3 has reached a predetermined stroke position, the non-excitation operation type electromagnetic brake 27 may be switched from the excited state to the non-excited state. The predetermined stroke position allows a predetermined amount of rotation of the steering wheel 1 corresponding to the circumferential movement amount between the release position and the engagement position of the retainer 25 after switching the non-excitation operation type electromagnetic brake 27 from the excited state to the non-excited state, and when the direction of the steering wheel 3 reaches the stroke end due to the change in the direction of the steering wheel 3 corresponding to the rotation operation of the steering wheel 1 for the allowed amount, the retainer 25 may be set to reach the engagement position.

[0062] When determining the timing to switch the non-excitation operation type electromagnetic brake 27 from the excited state to the non-excited state as described above, whether it is set when it is determined that the direction of the steering wheel 3 has reached the stroke end or when it is determined that a predetermined stroke position has been reached, a resistance is applied to the shaft 4 when the centering spring 26 is elastically deformed while the retainer 25 moves from the release position to the engagement position. This resistance increases as the retainer 25 approaches the engagement position, making the rotation operation of the steering wheel 1 heavier for the driver due to the aforementioned increase in resistance. As a result, the driver can be made to sense that the direction of the steering wheel 3 is near the stroke end.

[0063] Also, in this steering device, when the non-excitation operation type electromagnetic brake 27 is in the non-excited state, the engagement element 24 engages with the shaft 4 and the inner circumference of the outer ring 21 by the rotation of the steering wheel 1, reliably preventing the rotation of the shaft 4. Therefore, steering lock can be performed even when there is no power supply to the non-excitation operation type electromagnetic brake 27 and the control unit 8. Consequently, when getting in or out of the vehicle, it does not happen that the driver or the like touches the steering wheel 1 and the steering wheel 1 rotates, causing the positional relationship with the steering wheel 3 to shift.

[0064] In addition, this steering device includes a non-energized operation type electromagnetic brake 27 having a friction member 50 that is prevented from rotating by a retainer 25 and is arranged to be axially movable relative to the retainer 25, a friction surface portion 51 that axially faces the friction member 50 and is stationary relative to the shaft 4, an electromagnet 52, an armature 53 that axially faces the electromagnet 52, and an operating spring 54 that biases the friction member 50 to press against the friction surface portion 51 when the electromagnet 52 is de-energized and is arranged such that the pressing of the friction member 50 weakens in response to the axial movement of the armature 53 that is attracted by the electromagnet 52 when the electromagnet 52 is energized. Therefore, when the electromagnet 52 is in a de-energized state where no current is passed through it, the operating spring 54 biases the friction member 50 to axially press against the friction surface portion 51, thereby applying an operating pressure between the friction member 50 and the friction surface portion 51, and the retainer 25 can be braked and moved circumferentially relative to the shaft 4. On the other hand, when the electromagnet 52 is switched from the de-energized state to the energized state, the axial movement of the attracted armature 53 weakens the aforementioned pressing, and the braking of the retainer 25 by the friction surface portion 51 and the friction member 50 can be released. As a result, when the electromagnet 52 is energized, the armature 53 can be prevented from sliding circumferentially relative to the electromagnet 52, and the increase in the magnetic gap due to the wear of both 52 and 53 can be eliminated.

[0065] Further, in this steering device, the operating spring 54 is arranged to support the armature 53 at a position axially away from the electromagnet 52 when the electromagnet 52 is de-energized and to bias the friction member 50 toward the friction surface portion 51 via the armature 53. Therefore, when the electromagnet 52 is de-energized, the operating spring 54 biases the friction member 50 to press against the friction surface portion 51 via the armature 53, and the operating spring 54 supports the armature 53 to set a predetermined magnetic gap between the armature 53 and the electromagnet 52. Also, when the electromagnet 52 is switched from the energized state to the de-energized state, the armature 53 can be returned to the position of the predetermined magnetic gap by the elastic restoring force of the operating spring 54. As a result, a return spring for separating the electromagnet 52 and the armature 53 from each other separately from the operating spring 54 is not required, and the number of parts of the non-energized operation type electromagnetic brake 27 can be reduced.

[0066] In addition, since the friction surface portion 51 is formed on the end surface of the outer ring 21 in this steering device, it is not necessary to use a braking dedicated component for the friction surface portion 51, and the cost of the non-excitation operation type electromagnetic brake 27 can be suppressed.

[0067] In addition, this steering device includes a cylindrical brake case 28 that houses the non-excitation operation type electromagnetic brake 27 and the outer ring 21. The brake case 28 is formed of a non-magnetic material separate from the outer ring 21, and the outer ring 21 is prevented from rotating relative to the brake case 28. Therefore, when the non-excitation operation type electromagnetic brake 27 is in an excited state, it is possible to prevent the magnetic flux generated from the non-excitation operation type electromagnetic brake 27 from leaking into the brake case 28. For this reason, the size of the non-excitation operation type electromagnetic brake 27 can be suppressed.

[0068] In addition, this steering device further includes a reaction force motor 6 that applies a steering reaction force to the steering wheel 1. The steering section is a pair of left and right steering wheels 3. Since the outer ring 21, the engagement member 24, the retainer 25, and the non-excitation operation type electromagnetic brake 27 are provided between the steering wheel 1 and the reaction force motor 6 or on the side axially opposite to the steering wheel 1 with respect to the reaction force motor 6, as a steer-by-wire type steering device for a vehicle, when the steering wheel 3 reaches the stroke end, the driver can surely sense it through the steering wheel 1, and when leaving the vehicle during parking or stopping, the steering lock can be performed to prevent vehicle theft.

[0069] FIG. 8 shows a second embodiment of the present invention. Hereinafter, differences from the first embodiment will be described, and the same element names will be used for corresponding components in the first embodiment.

[0070] In the steering device according to the second embodiment, the outer ring 71 is integrally formed with the brake case 72. Among the inner circumference of the brake case 72, the part that functions as the outer ring 71 is the rib that forms the cylindrical surface for engaging the engaging element 73. The bearing 74 is disposed between the inner ring 75 and the inner circumference of the brake case 72. The inner circumferential portion of the brake case 72 including the cylindrical surface from the open end of the brake case 72 to the electromagnet 76 has an enlarged inner diameter compared to the first embodiment, and the dimensions of each part such as the outer diameter of the electromagnet 76, the armature 77, the actuating spring 78, the friction member 79, the retainer 80, and the pitch circle diameter of the engaging element 73 are enlarged corresponding to the enlargement of the inner diameter. Thereby, the non-excitation actuating type electromagnetic brake such as the electromagnet 76 and the armature 77 can be inserted from the opening of the brake case 72 into the inside of the brake case 72. On the other hand, since the end face of the outer ring cannot be used as the friction surface portion as in the first embodiment, the friction surface portion 81 is fixed to the inner circumference of the brake case 72 as a ring member 82 separate from the outer ring 71 and the brake case 72.

[0071] The steering device according to the second embodiment includes a cylindrical brake case 72 that houses the non-excitation actuating type electromagnetic brake 27. Since the outer ring 71 is integrally formed with the brake case 72, the steps of axially positioning the outer ring 71 with respect to the brake case 72 by a retaining ring or the like and preventing rotation by a key or the like can be eliminated.

[0072] In each of the above-described embodiments, a roller is exemplified as the engaging element, but it is also possible to use a ball or a sprag as the engaging element.

[0073] Also, in each of the above-described embodiments, the motor case and the brake case of the reaction force motor are formed separately, but they may be integrally formed.

[0074] Also, in each of the above-described embodiments, the friction surface portion that presses the friction member is configured by a separate member such as an outer ring or a ring member that is fixed to the brake case, but the brake case may have a split structure and the friction surface portion may be formed as a part of the brake case.

[0075] In addition, in each of the above-described embodiments, the steer-by-wire type steering device for a vehicle is excited. However, the present invention can also be applied to a steer-by-wire type steering device for a ship including a rudder as a steering unit.

[0076] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0077] 1 Steering wheel 2 Steering actuator 3 Steering wheel (steering unit) 4 Shaft 5 Steering sensor 6 Reaction force motor 16 Motor shaft 20, 75 Inner ring 21, 71 Outer ring 22 Cam surface 23 Cylindrical surface 24, 73 Engager 25, 80 Retainer 26 Centering spring 27 Non-excitation operation type electromagnetic brake 28, 72 Brake case 33 Key member 39 Extension part 41 Radial groove 42 Retainer groove 50, 79 Friction member 51, 81 Friction surface part 52, 76 Electromagnet 53, 77 Armature 54, 78 Actuating spring

Claims

1. A steering wheel, a steering sensor for detecting an operation amount of the steering wheel, In a steer-by-wire type steering apparatus including a steering actuator that changes the direction of a steering section according to the operation amount of the steering wheel detected by the steering sensor, A shaft connected to the steering wheel so as to rotate integrally with the steering wheel, An outer ring having an inner circumference disposed around the shaft, An engaging member disposed between the shaft and the inner circumference of the outer ring, A retainer that holds the engaging member and is disposed so as to be movable in the circumferential direction between an engaging position where the engaging member is engaged with the shaft and the inner circumference of the outer ring and a release position where the engagement is released, A centering spring that elastically holds the retainer in the release position and is rotationally stopped on the shaft and the retainer so as to rotate integrally with the shaft, Further comprising a non-excitation operation type electromagnetic brake that brakes the retainer, The non-excitation operation type electromagnetic brake includes a friction member that is rotationally stopped on the retainer and is disposed so as to be axially movable with respect to the retainer, a friction surface portion that axially faces the friction member and is stationary with respect to the shaft, an electromagnet, an armature that axially faces the electromagnet, and an operation spring that biases the friction member to press against the friction surface portion when the electromagnet is non-excited and is arranged such that the pressing of the friction member becomes weaker in accordance with the axial movement of the armature that is attracted to the electromagnet when the electromagnet is excited. A steer-by-wire type steering apparatus characterized by having the above.

2. The steer-by-wire type steering apparatus according to claim 1, wherein the operation spring is arranged to support the armature at a position axially away from the electromagnet when the electromagnet is non-excited and to bias the friction member toward the friction surface portion via the armature.

3. The steer-by-wire type steering apparatus according to claim 1 or 2, wherein the friction surface portion is formed on an end surface of the outer ring.

4. Further comprising a cylindrical brake case that houses the outer ring and the non-energized operation type electromagnetic brake, The brake case is formed of a non-magnetic material separate from the outer ring, The outer ring is prevented from rotating relative to the brake case. The steer-by-wire type steering device according to any one of claims 1 to 3.

5. Further comprising a cylindrical brake case that houses the non-energized operation type electromagnetic brake, The outer ring is integrally formed with the brake case. The steer-by-wire type steering device according to any one of claims 1 to 3.

6. Further comprising a reaction force motor that applies a steering reaction force to the steering wheel, The steering part is a pair of left and right steering wheels, The outer ring, the engaging element, the retainer, and the non-energized operation type electromagnetic brake are provided between the steering wheel and the reaction force motor or on the side axially opposite to the steering wheel with respect to the reaction force motor. The steer-by-wire type steering device according to any one of claims 1 to 5.

Images