Clutch unit and steer-by-wire type steering device

Abstract

To provide a clutch unit capable of immediately separating an armature from a field core when the energization to an electromagnetic coil is stopped.SOLUTION: A clutch unit 1 includes: an armature 20 absorbed to a field core 21 by the energization to an electromagnetic coil 22, and separated from the field core 21 by the stop of energization to the electromagnetic coil 22; and an operation conversion mechanism 23 for moving an engagement element holder 19 between an engagement position and an engagement release position in response to the adsorption and separation operation of the armature 20 to / from the field core 21. There is also provided residual magnetic flux cancelling means for cancelling residual magnetic flux by generating magnetic flux in a direction opposed to magnetic flux flowing to the field core 21 and the armature 20 when the energization to the electromagnetic coil 22 is stopped.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a clutch unit and a steer-by-wire steering device using the clutch unit. [Background technology]

[0002] Steer-by-wire steering devices are known as steering devices that change the direction of steered wheels of a vehicle in response to the rotation of the steering wheel by the driver (for example, see Patent Documents 1 and 2). The steer-by-wire steering devices of Patent Documents 1 and 2 have a steering sensor that detects the amount of steering wheel operation, and a steering actuator that is mechanically separated from the steering wheel, and the steering actuator operates in response to the amount of steering wheel operation detected by the steering sensor to change the direction of a pair of steered wheels (left and right).

[0003] This steer-by-wire steering device converts the amount of steering wheel operation by the driver into an electrical signal and controls the operation of the steering actuator based on that electrical signal. Therefore, it is possible to optimize the correspondence between the amount of steering wheel operation and the amount of operation of the steering actuator according to the vehicle's traveling speed, for example, by adjusting the amount of change in direction of the steered wheels when the steering wheel is operated according to the vehicle's traveling speed, and it is expected to enable improvements in the vehicle's traveling stability and maneuverability.

[0004] In a steer-by-wire steering device, the steering wheel, which is rotated by the driver, and the steering actuator, which changes the direction of the pair of steered wheels, are mechanically separated. Therefore, even when the driver rotates the steering wheel and the direction of the steered wheels reaches its movement limit (stroke end), the driver can still rotate the steering wheel in the same direction. This creates a problem in that the driver does not notice that the direction of the steered wheels has reached the stroke end, even though it has already reached the stroke end.

[0005] This problem exists not only in vehicle steering devices that steer the vehicle's steered wheels, but also in steer-by-wire steering devices, such as steering devices for ships that steer the rudder (outboard motor, etc.) installed at the stern of a ship.

[0006] Therefore, in order to enable the driver to reliably sense the situation through the steering wheel when the direction of the steering object reaches the stroke end, the inventor of the present application has proposed in Patent Documents 1 and 2 that a clutch unit using an engaging element be connected to the steering wheel, and that by switching between energizing and de-energizing the clutch unit, it be possible to switch between a locked state that prevents the steering wheel from rotating and an unlocked state that allows the steering wheel to rotate.

[0007] The clutch units of Patent Documents 1 and 2 differ only in whether they are excitation type or non-excitation type, and have the same basic configuration.

[0008] That is, the clutch units of Patent Documents 1 and 2 each include an outer ring, an inner ring disposed radially inward of the outer ring, an engaging element incorporated between the outer ring and the inner ring, an engaging element holder supported so as to be movable between an engaging position where the engaging element is engaged between the outer ring and the inner ring and a disengaging position where the engaging element is disengaged, a field core formed of a magnetic material, an electromagnetic coil wound around the field core, an armature that is attracted to the field core when current is applied to the electromagnetic coil and that moves away from the field core when current is cut off, and a motion conversion mechanism that moves the engaging element holder between the engaged position and the disengaged position in response to the attraction and disengagement of the armature to the field core. The outer ring is fixed so as not to rotate, and the inner ring is mechanically connected to the steering wheel.

[0009] The clutch unit of Patent Document 1 employs a motion conversion mechanism configured such that when the armature is attracted to the field core, the engaging element holder moves from a disengaged position to an engaged position, and conversely, when the armature separates from the field core, the engaging element holder moves from the engaged position to the disengaged position. That is, the clutch unit of Patent Document 1 is an excitation type, and is configured such that when current is applied to the electromagnetic coil, the engaging element engages between the outer and inner wheels, entering a locked state in which rotation of the steering wheel is prevented, and when current is stopped to the electromagnetic coil, the engaging element disengages between the outer and inner wheels, entering an unlocked state in which rotation of the steering wheel is permitted.

[0010] The clutch unit of Patent Document 2 employs a motion conversion mechanism configured such that when the armature is attracted to the field core, the engaging element holder moves from an engaged position to a disengaged position, and conversely, when the armature separates from the field core, the engaging element holder moves from the disengaged position to the engaged position. That is, the clutch unit of Patent Document 2 is of a non-excitation type, and is configured such that when the supply of current to the electromagnetic coil is stopped, the engaging element engages between the outer and inner wheels, entering a locked state in which rotation of the steering wheel is prevented, and when the electromagnetic coil is energized, the engaging element disengages from between the outer and inner wheels, entering an unlocked state in which rotation of the steering wheel is permitted. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 2023-55395 [Patent Document 2] Japanese Patent Application Publication No. 2023-45468 [Patent Document 3] Patent Publication No. 2021-8939 [Patent Document 4] Japanese Patent Application Publication No. 2020-159494 Summary of the Invention [Problem to be solved by the invention]

[0012] Incidentally, when the inventors prototyped and evaluated a steer-by-wire steering device that uses the clutch units of Patent Documents 1 and 2 to switch between a locked state and an unlocked state of the steering wheel, they encountered a problem that there was a risk that the responsiveness of the switching between the locked state and the unlocked state could not be ensured.

[0013] That is, when a driver operates the steering wheel, there are cases where the driver rotates the steering wheel in the opposite direction immediately after rotating the steering wheel to the stroke end, in which case the clutch unit must instantaneously alternate between a locked state and an unlocked state of the steering wheel.

[0014] However, in the clutch units of Patent Documents 1 and 2, when the electromagnetic coil is energized to attract the armature to the field core and then de-energized, the magnetic flux (magnetic circuit) flowing through the field core and armature does not disappear instantly, but gradually decreases and disappears (hereinafter, this gradually decreasing and disappearing magnetic flux is referred to as residual magnetic flux). Therefore, it takes a relatively long time to separate the armature from the field core, which may result in an inability to ensure responsiveness when switching between the locked and unlocked states of the steering wheel.

[0015] The inventors of the present application have also proposed similar clutch units using engaging elements, as described in Patent Documents 3 and 4. However, these clutch units employ a rotor interposed between the armature and field core. When the electromagnetic coil is energized, the armature is attracted to the rotor located between the armature and field core, rather than to the field core, with an air gap between the rotor and field core. Therefore, when the electromagnetic coil is de-energized, the magnetic flux (magnetic circuit) that had been flowing through the field core, rotor, and armature disappears quickly, and the armature quickly separates from the rotor, eliminating the above-mentioned problem. In contrast, the clutch units of Patent Documents 1 and 2 do not have a rotor interposed between the armature and field core. Therefore, when the electromagnetic coil is de-energized, the armature is attracted to the field core. Therefore, when the electromagnetic coil is de-energized, the magnetic flux that had been flowing through the field core and armature does not disappear easily, resulting in the above-mentioned problem.

[0016] An object of the present invention is to provide a clutch unit that can quickly separate the armature from the field core when the supply of current to the electromagnetic coil is stopped. [Means for solving the problem]

[0017] In order to solve the above problems, the present invention provides a clutch unit having the following configuration. [Configuration 1] The outer ring and an inner ring disposed radially inside the outer ring; an engaging element incorporated between the outer ring and the inner ring; an engaging element holder supported movably between an engaging position where the engaging element is engaged between the outer ring and the inner ring and a disengaging position where the engaging element is disengaged; a field core formed of a magnetic material; an electromagnetic coil wound around the field core; an armature that is attracted to the field core when the electromagnetic coil is energized and that moves away from the field core when the electromagnetic coil is de-energized; a motion conversion mechanism that moves the engaging element holder between the engaged position and the disengaged position in response to an attraction and separation action of the armature to and from the field core, A clutch unit characterized by comprising a residual magnetic flux canceling means for generating a magnetic flux in the opposite direction to the magnetic flux that had been flowing through the field core and the armature until then, when the supply of current to the electromagnetic coil is stopped, thereby canceling the residual magnetic flux.

[0018] With this configuration, when the current to the electromagnetic coil is stopped, the residual magnetic flux elimination means cancels the residual magnetic flux by generating magnetic flux in the opposite direction to the magnetic flux that had previously flowed through the field core and armature, so that the magnetic flux (magnetic circuit) flowing through the field core and armature disappears in a short time, making it possible to quickly separate the armature from the field core.

[0019] [Configuration 2] The residual magnetic flux canceling means includes a power supply unit that supplies current to the electromagnetic coil and a control unit that controls the power supply unit, The clutch unit according to configuration 1, wherein when the control unit stops the supply of current to the electromagnetic coil, the control unit applies a current to the electromagnetic coil in a direction opposite to the current that had been applied to the electromagnetic coil up until then.

[0020] With this configuration, when the current to the electromagnetic coil is stopped, a current is applied to the electromagnetic coil in the opposite direction to the current that had been applied to the electromagnetic coil until then, so that the magnetic flux flowing through the field core and armature can be quickly eliminated and the armature can be quickly separated from the field core.

[0021] [Configuration 3] the residual magnetic flux canceling means includes a second electromagnetic coil wound around the field core separately from the electromagnetic coil, a power supply unit that supplies current to the electromagnetic coil and the second electromagnetic coil, and a control unit that controls the power supply unit; The clutch unit according to configuration 1, wherein when the control unit stops the supply of current to the electromagnetic coil, the control unit performs control to apply to the second electromagnetic coil a current in a direction that generates a magnetic flux that cancels out the magnetic flux that had been flowing through the field core and the armature until then.

[0022] With this configuration, when the current to the electromagnetic coil is stopped, a current is applied to the second electromagnetic coil in a direction that generates a magnetic flux that cancels out the magnetic flux that had been flowing through the field core and armature until then.The magnetic flux generated by the second electromagnetic coil quickly eliminates the magnetic flux flowing through the field core and armature, allowing the armature to quickly move away from the field core.

[0023] [Configuration 4] the field core is an annular body having a C-shaped cross section, the annular body including an outer cylindrical portion, an inner cylindrical portion disposed radially inward of the outer cylindrical portion, and an annular plate-shaped connecting portion connecting end portions of the outer cylindrical portion and the inner cylindrical portion opposite to the armature side, 4. The clutch unit according to configuration 3, wherein the electromagnetic coil and the second electromagnetic coil are both disposed in the annular space between the outer cylindrical portion and the inner cylindrical portion.

[0024] With this configuration, the second electromagnetic coil is housed in the same annular space as the annular space that houses the electromagnetic coil of the field core, so the magnetic flux generated by energizing the second electromagnetic coil flows in the opposite direction along the same path as the magnetic flux generated by energizing the electromagnetic coil. Therefore, energizing the second electromagnetic coil can efficiently cancel out the magnetic flux that would have flowed through the field core and armature due to energizing the electromagnetic coil.

[0025] [Configuration 5] The electromagnetic coil and the second electromagnetic coil are arranged side by side in the radial direction, a lead wire for supplying a current to the electromagnetic coil is drawn out in the axial direction from the electromagnetic coil; 5. The clutch unit according to configuration 4, wherein a second lead wire for supplying current to the second electromagnetic coil is drawn out in the axial direction from the second electromagnetic coil.

[0026] With this configuration, the electromagnetic coil and the second electromagnetic coil do not overlap when viewed in the axial direction, so the lead wire that supplies current to the electromagnetic coil and the second lead wire that supplies current to the second electromagnetic coil can be drawn out in the axial direction without interfering with either the electromagnetic coil or the second electromagnetic coil. This makes it possible to ensure the number of turns of the electromagnetic coil and the second electromagnetic coil while keeping the size of the field core small.

[0027] [Configuration 6] 5. The clutch unit according to configuration 4, wherein the electromagnetic coil and the second electromagnetic coil are arranged side by side in the axial direction.

[0028] The present invention also provides a steer-by-wire steering device using the clutch unit of the above configuration, which has the following configuration. [Configuration 7] A steering wheel that is rotated; a steering sensor that detects an operation amount of the steering wheel; a steering actuator that is provided mechanically separated from the steering wheel and changes the direction of a steering target in accordance with the amount of operation of the steering wheel detected by the steering sensor; and the clutch unit according to any one of configurations 1 to 6, wherein one of the outer wheel and the inner wheel is fixed so as not to rotate, and the other is mechanically connected to the steering wheel. [Effects of the Invention]

[0029] In the clutch unit of this invention, when the supply of current to the electromagnetic coil is stopped, the residual magnetic flux elimination means cancels the residual magnetic flux by generating magnetic flux in the opposite direction to the magnetic flux that had previously flowed through the field core and armature.As a result, the magnetic flux (magnetic circuit) flowing through the field core and armature disappears in a short time, and the armature can be quickly separated from the field core. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 is a diagram schematically illustrating a steer-by-wire vehicle steering device using a clutch unit according to a first embodiment of the present invention; [Figure 2] Cross-sectional view of the clutch unit and its surroundings in Figure 1 [Figure 3] An enlarged view of the vicinity of the motion conversion mechanism of FIG. 2. [Figure 4] Cross-sectional view along line IV-IV in Figure 2 [Figure 5] FIG. 2 is a diagram showing a second embodiment of the present invention; [Figure 6] FIG. 10 is a diagram showing a third embodiment of the present invention, corresponding to FIG. 2. [Figure 7] FIG. 7 is an enlarged view of the vicinity of the motion conversion mechanism of FIG. 6. DETAILED DESCRIPTION OF THE INVENTION

[0031] Fig. 1 shows a steer-by-wire steering device using a clutch unit 1 according to a first embodiment of the present invention. This steering device is of the steer-by-wire type, which converts the amount of operation of a steering wheel 2 by a driver into an electric signal and controls a steering actuator 3 based on the electric signal to change the direction of a pair of steered wheels 4.

[0032] This steering device includes a steering wheel 2 that is rotated by the driver, a steering shaft 5 connected to the steering wheel 2, a steering sensor 6 that detects the amount of operation of the steering wheel 2, a reaction motor 7 that applies a steering reaction force to the steering wheel 2, a clutch unit 1 that switches between a locked state that prevents rotation of the steering wheel 2 and an unlocked state that allows rotation of the steering wheel 2 by switching between energized and de-energized states, a steering actuator 3 that is mechanically separated from the steering wheel 2, and a control device 8.

[0033] The steering shaft 5 is connected to the steering wheel 2 so as to rotate integrally with the steering wheel 2 when the steering wheel 2 is rotated. The steering sensor 6 is attached to the steering shaft 5. Examples of the steering sensor 6 include a steering angle sensor that detects the steering angle of the steering wheel 2, and a steering torque sensor that detects the steering torque input to the steering wheel 2 by the driver.

[0034] The reaction motor 7 is an electric motor that generates rotational torque when energized. The reaction motor 7 is connected to the end of the steering shaft 5. The reaction motor 7 inputs rotational torque to the steering shaft 5, thereby applying a steering reaction force to the steering wheel 2 via the steering shaft 5.

[0035] The steering actuator 3 has a steering shaft 9, a steering shaft housing 10, a steering motor 11 that moves the steering shaft 9 in the left-right direction of the vehicle, and a steering sensor 12 that detects the position of the steering shaft 9. The steering shaft 9 is supported by the steering shaft housing 10 so that it can move in the left-right direction of the vehicle. The steering shaft housing 10 accommodates the central portion of the steering shaft 9 so that both the left and right ends of the steering shaft 9 protrude from the steering shaft housing 10.

[0036] The steering motor 11 and the steering sensor 12 are attached to the steering shaft housing 10. A motion conversion mechanism (not shown) that converts the rotation output by the steering motor 11 into linear motion of the steering shaft 9 is installed between the steering motor 11 and the steering shaft 9. The left and right ends of the steering shaft 9 are connected to the pair of left and right steerable wheels 4 via tie rods 13, so that when the steering shaft 9 moves in the axial direction, the orientation of the pair of left and right steerable wheels 4 changes in conjunction with this.

[0037] As shown in Fig. 2, the reaction motor 7 has a motor case 14 and a motor shaft 15 that protrudes from the motor case 14 on the side opposite (downward in the figure) the steering wheel 2 (see Fig. 1). The motor shaft 15 is rotatably supported by a rolling bearing (not shown) that is incorporated inside the motor case 14. The motor shaft 15 is also connected to the steering shaft 5 (see Fig. 1) so as to rotate integrally with the steering wheel 2 and the steering shaft 5 (see Fig. 1). The motor case 14 is fixed to the vehicle body (not shown) so as not to rotate.

[0038] The clutch unit 1 has an outer ring 16, an inner ring 17 arranged radially inside the outer ring 16, a plurality of engaging elements 18 incorporated between the outer ring 16 and the inner ring 17, an engaging element holder 19 that holds the engaging elements 18, an armature 20 supported so as to be movable in the axial direction, a field core 21 arranged axially opposite the armature 20, an electromagnetic coil 22 wound around the field core 21, an operation conversion mechanism 23 that moves the engaging element holder 19 circumferentially in response to the attraction and separation action of the armature 20, a power supply unit 24 (see Figure 1) that supplies current to the electromagnetic coil 22, and a control unit 25 (see Figure 1) that controls the power supply unit 24.

[0039] The axial direction is the direction parallel to the central axis of the outer ring 16 (the central axis of the annular field core 21), the radial direction is the direction perpendicular to the central axis of the outer ring 16, and the circumferential direction is the direction along the circumference that revolves around the central axis of the outer ring 16.

[0040] The outer ring 16 is housed in a clutch case 26. The clutch case 26 is a cylindrical member that houses all of the components of the clutch unit 1 (outer ring 16, inner ring 17, engaging element 18, engaging element holder 19, field core 21, electromagnetic coil 22, armature 20, motion conversion mechanism 23, etc.). The clutch case 26 is formed into a cylindrical shape with a bottom that is open on the side facing the reaction motor 7 (the upper side in the figure) and closed on the side opposite to the reaction motor 7 (the lower side in the figure). The end of the clutch case 26 on the side facing the reaction motor 7 (the upper side in the figure) is fixed to the motor case 14 with bolts (not shown). The clutch case 26 is made of a non-magnetic material (aluminum alloy, copper alloy, etc.). On the other hand, the outer ring 16 is made of steel.

[0041] 4, a rotation prevention locking portion 27 (a key member and a key groove in the figure) that prevents the outer ring 16 from rotating relative to the clutch case 26 is provided between the outer periphery of the outer ring 16 and the inner periphery of the clutch case 26, and the outer ring 16 is fixed in the circumferential direction so as not to rotate by this rotation prevention locking portion 27. In this embodiment, the outer ring 16 is formed separately from the clutch case 26 and is prevented from rotating relative to the clutch case 26, but it is also possible to form the outer ring 16 integrally with the clutch case 26.

[0042] As shown in Figure 2, inner ring 17 is rotatably supported by bearings 28 provided on the inner periphery of outer ring 16. The inner periphery of inner ring 17 is spline-fitted to the outer periphery of motor shaft 15. This spline fitting connects inner ring 17 to motor shaft 15 so as to rotate integrally with motor shaft 15. Here, inner ring 17 is mechanically connected to steering wheel 2 via motor shaft 15 and steering shaft 5 (see Figure 1), and rotation of steering wheel 2 is mechanically transmitted and input to inner ring 17.

[0043] As shown in Figure 4, a plurality of cam surfaces 30 are formed at intervals in the circumferential direction on the outer periphery of the inner ring 17. A cylindrical surface 31 is formed on the inner periphery of the outer ring 16, radially opposing the cam surfaces 30. A wedge space is formed between the cam surfaces 30 and the cylindrical surface 31, the radial width of which gradually narrows from the circumferential center toward both circumferential ends. Each of the engaging elements 18 is incorporated between the cam surface 30 and the cylindrical surface 31. Here, the engaging elements 18 are cylindrical rollers.

[0044] A plurality of radially penetrating pockets 32 (see FIG. 2 ) are formed in the engaging element holder 19 at intervals in the circumferential direction, and an engaging element 18 is housed in each of the pockets 32. The engaging element holder 19 is supported circumferentially movable relative to the inner ring 17 between an engaging position where the engaging element 18 is engaged between the cam surface 30 and the cylindrical surface 31 by moving the engaging element 18 circumferentially from the circumferential center of the cam surface 30, and a disengaging position where the engaging element 18 is disengaged from the cam surface 30 and the cylindrical surface 31 by moving the engaging element 18 to the circumferential center of the cam surface 30.

[0045] 3, the armature 20 is supported on the outer periphery of the inner ring 17 so as to be rotatable and axially movable relative to the inner ring 17. The armature 20 is an annular plate-shaped member made of a magnetic material (iron, silicon steel, etc.). A repulsion spring 33 is installed between the armature 20 and the field core 21 to bias the armature 20 in a direction away from the field core 21.

[0046] As shown in FIG. 2 , the field core 21 is an annular body with a C-shaped cross section. The annular cross section includes an outer cylindrical portion 34, an inner cylindrical portion 35 disposed radially inside the outer cylindrical portion 34, and a circular plate-like connecting portion 36 connecting the ends of the outer cylindrical portion 34 and the inner cylindrical portion 35 opposite the armature 20 (the lower side in the figure). A rotation prevention portion 38 (an axial protrusion and an axial hole in the figure) is provided between the connecting portion 36 of the field core 21 and a bottom 37 of the clutch case 26 to prevent the field core 21 from rotating relative to the clutch case 26. The rotation prevention portion 38 secures the field core 21 in a circumferential direction so that it does not rotate. The axial position of the field core 21 is also fixed by a retaining ring 39 attached to the inner periphery of the clutch case 26. In this way, the field core 21 is secured to the clutch case 26 so as not to move in either the axial or circumferential direction. Like the armature 20, the field core 21 is also formed of a magnetic material (such as iron or silicon steel).

[0047] The electromagnetic coil 22 is disposed in the annular space between the outer cylindrical portion 34 and the inner cylindrical portion 35 of the field core 21. A lead wire 40 for supplying current to the electromagnetic coil 22 is drawn out in the axial direction from the electromagnetic coil 22. The lead wire 40 is inserted in this order through an axial through hole 41 formed in the connecting portion 36 of the field core 21 and an axial through hole 42 formed in the bottom portion 37 of the clutch case 26, drawn out to the outside of the clutch case 26, and connected to the power supply unit 24 (see FIG. 1). A grommet 43 is attached to the through hole 42 of the clutch case 26 to fill the gap between the inner surface of the through hole 42 and the lead wire 40.

[0048] As shown in FIG. 3, the inner cylindrical portion 35 and the outer cylindrical portion 34 of the field core 21 face the armature 20 in the axial direction. When the electromagnetic coil 22 is energized, a magnetic flux is generated around the electromagnetic coil 22. This magnetic flux forms a magnetic circuit that flows sequentially through the outer cylindrical portion 34, the connecting portion 36 (see FIG. 2), the inner cylindrical portion 35, and the armature 20. As a result, the armature 20 is attracted to the field core 21 and moves axially against the biasing force of the recoil spring 33, and is attracted to the axial end faces of the inner cylindrical portion 35 and the outer cylindrical portion 34. When the energization of the electromagnetic coil 22 is stopped, the armature 20 moves away from the axial end faces of the inner cylindrical portion 35 and the outer cylindrical portion 34 due to the biasing force of the recoil spring 33. The electromagnetic coil 22 and the field core 21 constitute an electromagnet that attracts the armature 20 when energized.

[0049] As shown in FIG. 3, the motion converting mechanism 23 has an intermediate plate 44 that is prevented from rotating by the armature 20 and by the engaging element holder 19 while being movable axially relative to the armature 20, and a centering spring 45 that elastically holds the engaging element holder 19 in the disengaged position.

[0050] An engaging protrusion 47 that engages with an engaging recess 46 formed in the engaging element retainer 19 is formed on the outer periphery of the intermediate plate 44. The intermediate plate 44 is prevented from rotating relative to the engaging element retainer 19 by the engagement between the engaging protrusion 47 and the engaging recess 46, so that the intermediate plate 44 can move circumferentially together with the engaging element retainer 19. The intermediate plate 44 is also formed with an axial protrusion 48 that extends in the axial direction toward the armature 20. The armature 20 is formed with an axial hole 49 into which the axial protrusion 48 of the intermediate plate 44 is inserted so as to be slidable in the axial direction. The engagement between the axial protrusion 48 and the axial hole 49 prevents the intermediate plate 44 from rotating relative to the armature 20, so that the intermediate plate 44 can move circumferentially together with the armature 20, while still being movable axially relative to the armature 20.

[0051] 4, the centering spring 45 is composed of a C-shaped annular portion 50 formed by winding a steel wire in a C shape, and a pair of extension portions 51 extending radially outward from both ends of the C-shaped annular portion 50. The C-shaped annular portion 50 is fitted into a circular spring accommodating recess 52 formed in the axial end face of the inner ring 17. The pair of extension portions 51 are inserted into radial grooves 53 formed in the axial end face of the inner ring 17 so as to penetrate radially outward from the spring accommodating recess 52.

[0052] The extension portion 51 of the centering spring 45 protrudes from the radial outer end of the radial groove 53, and the portion of the extension portion 51 protruding from the radial groove 53 is inserted into a retainer groove 54 formed in the engaging member retainer 19. The radial groove 53 and the retainer groove 54 are formed to have the same circumferential width. The extension portion 51 of the centering spring 45 contacts the inner surface of the radial groove 53 and the inner surface of the retainer groove 54, respectively, and the circumferential force acting on the contact portion elastically holds the engaging member retainer 19 in the disengaged position.

[0053] 3 is attracted to the field core 21, the rotation of the armature 20 is limited by the frictional resistance with the field core 21, and since the armature 20 is prevented from rotating by the engaging member cage 19 via the intermediate plate 44, the rotation of the engaging member cage 19 is also limited. When the inner ring 17 rotates in this state, the inner ring 17 rotates relative to the engaging member cage 19, and this relative rotation causes the engaging member cage 19 to move circumferentially from the disengaged position to the engaged position against the elastic force of the centering spring 45, and the engaging member 18 engages between the cam surface 30 on the outer periphery of the inner ring 17 and the cylindrical surface 31 on the inner periphery of the outer ring 16.

[0054] On the other hand, when the armature 20 separates from the field core 21, the frictional resistance between the armature 20 and the field core 21 disappears, so the armature 20 becomes freely rotatable, and the engaging element holder 19, which is prevented from rotating by the armature 20 via the intermediate plate 44, also becomes freely rotatable. Therefore, the engaging element holder 19 moves circumferentially from the engaged position to the disengaged position due to the elastic restoring force of the centering spring 45, and the engaging element 18 is disengaged from between the cam surface 30 on the outer periphery of the inner ring 17 and the cylindrical surface 31 on the inner periphery of the outer ring 16.

[0055] In this way, the operation conversion mechanism 23 is configured to move the engaging element holder 19 from the disengaged position to the engaged position when the armature 20 is attracted to the field core 21, and to move the engaging element holder 19 from the engaged position to the disengaged position when the armature 20 separates from the field core 21.

[0056] 2, the clutch unit 1 is in a locked state where the engaging element 18 engages between the outer wheel 16 and the inner wheel 17, preventing relative rotation of the inner wheel 17 with respect to the outer wheel 16, and whereby rotation of the steering wheel 2 (see FIG. 1) in both forward and reverse directions is prevented, whereas when the electromagnetic coil 22 is de-energized, the engaging element 18 is disengaged from between the outer wheel 16 and the inner wheel 17, allowing relative rotation of the inner wheel 17 with respect to the outer wheel 16, and whereby rotation of the steering wheel 2 in both forward and reverse directions is permitted. In other words, the clutch unit 1 is an excitation-type clutch that is in an idling state when the electromagnetic coil 22 is de-energized, and in an engaged state when the electromagnetic coil 22 is energized.

[0057] Reaction motor 7, clutch unit 1, and steering motor 11 shown in Figure 1 are controlled by control device 8. External sensor 55, steering sensor 6, and steering sensor 12 are electrically connected to the input side of control device 8. External sensor 55 is a vehicle speed sensor or the like that detects the traveling speed of the vehicle. Reaction motor 7, clutch unit 1, and steering actuator 3 are electrically connected to the output side of control device 8. Control device 8 includes power supply unit 24 and control unit 25 of clutch unit 1.

[0058] Control device 8 operates steering motor 11 in accordance with the amount of operation of steering wheel 2 detected by steering sensor 6 and the vehicle running conditions (vehicle speed, etc.) detected by external sensor 55, thereby controlling the direction of pair of left and right steered wheels 4. At this time, control device 8 also controls the operation of reaction force motor 7 so as to generate a steering reaction force of a magnitude in accordance with the amount of operation of steering wheel 2 and the vehicle running conditions.

[0059] Furthermore, control device 8 determines whether the orientation of steered wheels 4 has reached the stroke end based on the position of steering shaft 9 detected by steering sensor 12. If it is determined that the orientation of steered wheels 4 has not reached the stroke end, control device 8 stops energizing the electromagnet (see FIG. 2) of clutch unit 1, thereby establishing an unlocked state that allows rotation of steering wheel 2. On the other hand, if it is determined that the orientation of steered wheels 4 has reached the stroke end, control device 8 energizes the electromagnet (see FIG. 2) of clutch unit 1, thereby establishing a locked state that prevents rotation of steering wheel 2.

[0060] However, with this steer-by-wire steering device, there is a possibility that the responsiveness of the steering wheel 2 when switching between the locked state and the unlocked state may not be ensured.

[0061] That is, when the driver operates the steering wheel 2, there are cases where the driver rotates the steering wheel 2 in the opposite direction immediately after rotating the steering wheel 2 to the stroke end. In this case, the clutch unit 1 needs to instantaneously alternate between the locked state and the unlocked state of the steering wheel 2.

[0062] Here, by energizing electromagnetic coil 22 (see FIG. 2), the steering wheel 2 is locked to prevent rotation, and then switched to an unlocked state to allow rotation of the steering wheel 2. Therefore, when the energization of electromagnetic coil 22 is stopped, the magnetic flux (magnetic circuit) flowing through field core 21 and armature 20 shown in FIG. 2 does not disappear instantly, but gradually decreases and disappears. Therefore, it takes a relatively long time for armature 20 to separate from field core 21, which may result in a failure to ensure responsiveness in switching between the locked state and the unlocked state of the steering wheel 2.

[0063] Therefore, the clutch unit 1 of this embodiment is provided with residual magnetic flux canceling means that, when the supply of current to the electromagnetic coil 22 shown in Fig. 2 is stopped, cancels the residual magnetic flux by instantaneously generating magnetic flux in the opposite direction to the magnetic flux that had been flowing through the field core 21 and the armature 20 until then. Specifically, when the supply of current to the electromagnetic coil 22 is stopped, control is performed by the control unit 25 shown in Fig. 1 to instantaneously apply to the electromagnetic coil 22 a current in the opposite direction to the current that had been applied to the electromagnetic coil 22 until then.

[0064] When this clutch unit 1 stops the supply of current to the electromagnetic coil 22, it instantaneously applies a current to the electromagnetic coil 22 in the opposite direction to the current that had been applied to the electromagnetic coil 22 until then, thereby quickly eliminating the magnetic flux (magnetic circuit) flowing through the field core 21 and the armature 20 and making it possible to quickly separate the armature 20 from the field core 21.

[0065] 5 shows a second embodiment of the present invention. The second embodiment differs from the first embodiment only in the configuration of the residual magnetic flux canceling means (a configuration for canceling the residual magnetic flux by instantaneously generating a magnetic flux in the opposite direction to the magnetic flux that had been flowing through the field core 21 and the armature 20 when the supply of current to the electromagnetic coil 22 is stopped), but the other configurations are the same. Therefore, parts corresponding to those in the first embodiment are given the same reference numerals and their description will be omitted.

[0066] As shown in FIG. 5 , the field core 21 is wound with an electromagnetic coil 22 and a second electromagnetic coil 56 separate from the electromagnetic coil 22. The electromagnetic coil 22 and the second electromagnetic coil 56 are arranged radially side by side in the annular space between the outer cylindrical portion 34 and the inner cylindrical portion 35 of the field core 21. The second electromagnetic coil 56 has an inner diameter larger than the outer diameter of the electromagnetic coil 22 and is arranged radially outside the electromagnetic coil 22 so as to surround the outer periphery of the electromagnetic coil 22. The cross-sectional area of ​​the second electromagnetic coil 56 is smaller than that of the electromagnetic coil 22 and is less than half the cross-sectional area of ​​the electromagnetic coil 22 in the figure. The winding direction of the second electromagnetic coil 56 is opposite to that of the electromagnetic coil 22. A second lead wire 57 that supplies current to the second electromagnetic coil 56 is drawn out in the axial direction from the second electromagnetic coil 56. The second lead wire 57 is inserted through the through-hole 41 and the through-hole 42 in this order, drawn out to the outside of the clutch case 26, and connected to the power supply unit 24 (see FIG. 1).

[0067] In this clutch unit 1, as in the first embodiment, when the electromagnetic coil 22 is energized, the engaging element 18 engages between the outer ring 16 and the inner ring 17, thereby preventing relative rotation of the inner ring 17 with respect to the outer ring 16, and a locked state is established in which rotation of the steering wheel 2 (see FIG. 1) in both the forward and reverse directions is prevented. At this time, the second electromagnetic coil 56 is not energized.

[0068] On the other hand, when the power supply to the electromagnetic coil 22 is stopped, the engagement of the engaging element 18 between the outer wheel 16 and the inner wheel 17 is released, allowing the inner wheel 17 to rotate relative to the outer wheel 16, and the steering wheel 2 enters an unlocked state that allows rotation in both the forward and reverse directions.

[0069] Here, when the control unit 25 (Figure 1) stops the supply of current to the electromagnetic coil 22, it performs control to instantaneously apply to the second electromagnetic coil 56 a current in a direction that generates a magnetic flux that cancels out the magnetic flux that had been flowing through the field core 21 and the armature 20 until then.

[0070] When this clutch unit 1 stops the supply of current to the electromagnetic coil 22, it instantaneously applies to the second electromagnetic coil 56 a current in a direction that generates a magnetic flux that cancels out the magnetic flux that had been flowing through the field core 21 and the armature 20 until then.Therefore, the magnetic flux generated by the second electromagnetic coil 56 quickly eliminates the magnetic flux flowing through the field core 21 and the armature 20, allowing the armature 20 to quickly move away from the field core 21.

[0071] Furthermore, because the second electromagnetic coil 56 is housed in the same annular space as the annular space that houses the electromagnetic coil 22 of the field core 21, the magnetic flux generated by energizing the second electromagnetic coil 56 flows in the opposite direction through the same path as the magnetic flux generated by energizing the electromagnetic coil 22. Therefore, by energizing the second electromagnetic coil 56, it is possible to efficiently cancel out the magnetic flux that has flowed through the field core 21 and the armature 20 due to energizing the electromagnetic coil 22.

[0072] Furthermore, because the electromagnetic coil 22 and the second electromagnetic coil 56 do not overlap when viewed in the axial direction, the lead wire 40 that supplies current to the electromagnetic coil 22 and the second lead wire 57 that supplies current to the second electromagnetic coil 56 can be drawn out in the axial direction without interfering with either the electromagnetic coil 22 or the second electromagnetic coil 56. Therefore, it is possible to ensure the number of turns of the electromagnetic coil 22 and the second electromagnetic coil 56 while keeping the size of the field core 21 small.

[0073] 6 and 7 show a third embodiment of the present invention. The third embodiment is different from the second embodiment in the configuration of the motion conversion mechanism 23 and the configuration of the second electromagnetic coil 56, but the other configurations are basically the same.

[0074] That is, the second embodiment employs an operation conversion mechanism 23 configured to move the engaging element holder 19 from the disengaged position to the engaged position when the armature 20 is attracted to the field core 21, and to move the engaging element holder 19 from the engaged position to the disengaged position when the armature 20 separates from the field core 21 (i.e., an excitation type clutch unit 1 is employed that enters a free-wheeling state when the supply of current to the electromagnetic coil 22 is stopped and enters an engaged state when the electromagnetic coil 22 is energized). However, the third embodiment differs in that the operation conversion mechanism 23 is configured to move the engaging element holder 19 from the engaged position to the disengaged position when the armature 20 is attracted to the field core 21, and to move the engaging element holder 19 from the disengaged position to the engaged position when the armature 20 separates from the field core 21 (i.e., a non-excitation type clutch unit 1 is employed that enters an engaged state when the supply of current to the electromagnetic coil 22 is stopped and enters an free-wheeling state when the electromagnetic coil 22 is energized).

[0075] Also, in the second embodiment, the electromagnetic coil 22 and the second electromagnetic coil 56 are arranged side by side in the radial direction, whereas in the third embodiment, the electromagnetic coil 22 and the second electromagnetic coil 56 are arranged side by side in the axial direction. Hereinafter, parts corresponding to those in the second embodiment will be given the same reference numerals and descriptions thereof will be omitted.

[0076] As shown in Figure 6, the clutch unit 1 has an outer ring 16, an inner ring 17 arranged radially inside the outer ring 16, a plurality of engaging elements 18 incorporated between the outer ring 16 and the inner ring 17, an engaging element holder 19 that holds the engaging elements 18, an armature 20 supported so as to be movable in the axial direction, a field core 21 arranged axially opposite the armature 20, an electromagnetic coil 22 and a second electromagnetic coil 56 wound around the field core 21, an operation conversion mechanism 23 that moves the engaging element holder 19 circumferentially in response to the attraction and separation action of the armature 20, a power supply unit 24 (see Figure 1) that supplies current to the electromagnetic coil 22, and a control unit 25 (see Figure 1) that controls the power supply unit 24.

[0077] The outer ring 16 is rotatably supported by a bearing 58 provided on the inner periphery of the clutch case 26. The inner periphery of the end of the outer ring 16 is spline-fitted to the outer periphery of the motor shaft 15. This spline fitting connects the outer ring 16 to the motor shaft 15 so that the outer ring 16 rotates integrally with the motor shaft 15. Here, the outer ring 16 is mechanically connected to the steering wheel 2 via the motor shaft 15 and the steering shaft 5 (see FIG. 1), and the rotation of the steering wheel 2 is mechanically transmitted and input to the outer ring 16.

[0078] The outer periphery of the end of the inner ring 17 is spline-fitted to the inner periphery of the field core 21 fixed to the clutch case 26. This spline-fitting fixes the inner ring 17 in the circumferential direction so that it does not rotate.

[0079] The armature 20 is supported on the outer periphery of the inner ring 17 so as to be rotatable and axially movable relative to the inner ring 17. A repulsion spring 33 is incorporated between the armature 20 and the field core 21 to bias the armature 20 in a direction away from the field core 21.

[0080] As shown in FIG. 7, the motion converting mechanism 23 includes a friction plate 59 incorporated between the armature 20 and the outer ring 16, an intermediate plate 44 that prevents the friction plate 59 from rotating relative to the engaging element holder 19 while allowing the friction plate 59 to move axially relative to the engaging element holder 19, and a centering spring 45 that elastically holds the engaging element holder 19 in the disengaged position.

[0081] The friction plate 59 is provided so as to be movable in the axial direction between a position in contact with the axial end face of the outer ring 16 and a position away from the axial end face of the outer ring 16. The friction plate 59 is pressed against the axial end face of the outer ring 16 by the biasing force of a separation spring 33 incorporated between the armature 20 and the field core 21.

[0082] In this motion converting mechanism 23, when the armature 20 shown in FIG. 7 is separated from the field core 21, the friction plate 59 is pressed against the axial end surface of the outer ring 16 by the biasing force of the separation spring 33, so that the relative rotation of the friction plate 59 with respect to the outer ring 16 is restricted. In addition, because the friction plate 59 is prevented from rotating by the engaging element retainer 19 via the intermediate plate 44, the relative rotation of the engaging element retainer 19 with respect to the outer ring 16 is also restricted. When the outer ring 16 rotates in this state, the engaging element retainer 19 rotates together with the outer ring 16, so that the engaging element retainer 19 moves circumferentially from the disengaged position to the engaged position against the elastic force of the centering spring 45, and the engaging element 18 engages between the cam surface 30 on the outer circumference of the inner ring 17 and the cylindrical surface 31 on the inner circumference of the outer ring 16.

[0083] On the other hand, when the armature 20 is attracted to the field core 21, there is no frictional resistance between the friction plate 59 and the axial end face of the outer ring 16, so the friction plate 59 becomes freely rotatable relative to the friction plate 59, and the engaging element holder 19, which is prevented from rotating by the friction plate 59 via the intermediate plate 44, also becomes freely rotatable relative to the friction plate 59. Therefore, the elastic restoring force of the centering spring 45 causes the engaging element holder 19 to move circumferentially from the engaged position to the disengaged position, and the engaging element 18 is disengaged from between the cam surface 30 on the outer circumference of the inner ring 17 and the cylindrical surface 31 on the inner circumference of the outer ring 16.

[0084] In this way, the operation conversion mechanism 23 is configured to move the engaging element holder 19 from the engaged position to the disengaged position when the armature 20 is attracted to the field core 21, and to move the engaging element holder 19 from the disengaged position to the engaged position when the armature 20 separates from the field core 21.

[0085] 6, the clutch unit 1 is placed in an unlocked state in which the engagement of the engaging element 18 between the outer wheel 16 and the inner wheel 17 is released, allowing the outer wheel 16 to rotate relative to the inner wheel 17 and allowing rotation of the steering wheel 2 in both the forward and reverse directions. At this time, the second electromagnetic coil 56 is not energized.

[0086] On the other hand, when the power supply to the electromagnetic coil 22 is stopped, the engaging element 18 engages between the outer wheel 16 and the inner wheel 17, preventing the outer wheel 16 from rotating relative to the inner wheel 17, resulting in a locked state that prevents the steering wheel 2 (see Figure 1) from rotating in both the forward and reverse directions.

[0087] Here, as in the second embodiment, when the control unit 25 (FIG. 1) stops the supply of current to the electromagnetic coil 22, it performs control to instantaneously apply to the second electromagnetic coil 56 a current in a direction that generates a magnetic flux that cancels out the magnetic flux that had been flowing through the field core 21 and the armature 20 until then.

[0088] When this clutch unit 1 stops the supply of current to the electromagnetic coil 22, it instantaneously applies to the second electromagnetic coil 56 a current in a direction that generates a magnetic flux that cancels out the magnetic flux that had been flowing through the field core 21 and the armature 20 until then.Therefore, the magnetic flux generated by the second electromagnetic coil 56 quickly eliminates the magnetic flux flowing through the field core 21 and the armature 20, allowing the armature 20 to quickly move away from the field core 21.

[0089] Furthermore, because the second electromagnetic coil 56 is housed in the same annular space as the annular space that houses the electromagnetic coil 22 of the field core 21, the magnetic flux generated by energizing the second electromagnetic coil 56 flows in the opposite direction through the same path as the magnetic flux generated by energizing the electromagnetic coil 22. Therefore, by energizing the second electromagnetic coil 56, it is possible to efficiently cancel out the magnetic flux that has flowed through the field core 21 and the armature 20 due to energizing the electromagnetic coil 22.

[0090] In each of the above embodiments, a vehicle steering device in which a pair of steered wheels 4 on the left and right sides of a vehicle are to be steered has been described as an example of a steering device according to the present invention. However, the present invention is not limited to vehicle steering devices, and can be similarly applied to steering devices for ships, all-terrain vehicles, utility vehicles, construction machinery, etc.

[0091] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0092] 1 clutch unit 2 steering wheels 3 Steering actuator 6 Steering sensor 16 outer ring 17 Inner Circle 18 Engagement element 19 Engagement retainer 20 Armature 21 Field Core 22 Electromagnetic coil 23 Motion conversion mechanism 24 Power supply section 25 Control Unit 34 Outer cylinder 35 Inner cylinder 36 Connecting part 40 lead wire 56 Second electromagnetic coil 57 Second lead wire

Claims

1. an outer ring (16); an inner ring (17) disposed radially inside the outer ring (16); an engaging element (18) incorporated between the outer ring (16) and the inner ring (17); an engaging element holder (19) supported movably between an engaging position where the engaging element (18) is engaged between the outer ring (16) and the inner ring (17) and a disengaging position where the engaging element (18) is disengaged; a field core (21) formed of a magnetic material; an electromagnetic coil (22) wound around the field core (21); an armature (20) that is attracted to the field core (21) when the electromagnetic coil (22) is energized and that moves away from the field core (21) when the electromagnetic coil (22) is de-energized; and a motion conversion mechanism (23) that moves the engaging element holder (19) between the engaged position and the disengaged position in response to the attraction and separation of the armature (20) to the field core (21), A clutch unit characterized in that a residual magnetic flux canceling means is provided for generating a magnetic flux in the opposite direction to the magnetic flux that had been flowing through the field core (21) and the armature (20) until then, when the supply of current to the electromagnetic coil (22) is stopped, thereby canceling the residual magnetic flux.

2. The residual magnetic flux canceling means includes a power supply unit (24) that supplies current to the electromagnetic coil (22) and a control unit (25) that controls the power supply unit (24), 2. The clutch unit according to claim 1, wherein when the control unit (25) stops the supply of current to the electromagnetic coil (22), the control unit (25) performs control to apply to the electromagnetic coil (22) a current in a direction opposite to the current that had been applied to the electromagnetic coil (22) up until that point.

3. The residual magnetic flux canceling means includes a second electromagnetic coil (56) wound around the field core (21) separately from the electromagnetic coil (22), a power supply unit (24) that supplies current to the electromagnetic coil (22) and the second electromagnetic coil (56), and a control unit (25) that controls the power supply unit (24), 2. The clutch unit according to claim 1, wherein when the control unit (25) stops the supply of current to the electromagnetic coil (22), the control unit (25) performs control to apply to the second electromagnetic coil (56) a current in a direction that generates a magnetic flux that cancels out the magnetic flux that had been flowing through the field core (21) and the armature (20) until then.

4. The field core (21) is an annular body with a C-shaped cross section, which includes an outer cylindrical portion (34), an inner cylindrical portion (35) disposed radially inside the outer cylindrical portion (34), and an annular plate-shaped connecting portion (36) connecting end portions of the outer cylindrical portion (34) and the inner cylindrical portion (35) on the opposite side from the armature (20), 4. The clutch unit according to claim 3, wherein the electromagnetic coil (22) and the second electromagnetic coil (56) are both disposed in the annular space between the outer cylindrical portion (34) and the inner cylindrical portion (35).

5. The electromagnetic coil (22) and the second electromagnetic coil (56) are arranged side by side in the radial direction, A lead wire (40) for supplying current to the electromagnetic coil (22) is drawn out in the axial direction from the electromagnetic coil (22), 5. A clutch unit according to claim 4, wherein a second lead wire (57) for supplying current to said second electromagnetic coil (56) is drawn out in the axial direction from said second electromagnetic coil (56).

6. 5. The clutch unit according to claim 4, wherein the electromagnetic coil (22) and the second electromagnetic coil (56) are arranged side by side in the axial direction.

7. a steering wheel (2) that is rotated; a steering sensor (6) for detecting an amount of operation of the steering wheel (2); a steering actuator (3) that is provided mechanically separate from the steering wheel (2) and changes the direction of a steering target in accordance with the amount of operation of the steering wheel (2) detected by the steering sensor (6); and a clutch unit (1) according to any one of claims 1 to 6, wherein one of the outer wheel (16) and the inner wheel (17) is fixed so as not to rotate, and the other is mechanically connected to the steering wheel (2).

Images