Steer-by-wire unit

Abstract

A first unit (151) for turning wheels (7) of a vehicle includes: a first turning motor (31); a first pinion shaft (33) configured to allow a driving force from the first turning motor (31) to be input; and a first rack shaft (41) having a first rack gear (41a) meshing with the first pinion shaft (33), and configured to turn the wheels (7) of the vehicle. When the first unit (151) is viewed along a predetermined direction D, an output shaft of the first turning motor (31) is inclined with respect to the first rack shaft (41), and the first turning motor (31) and the first rack shaft (41) are disposed to overlap each other, the predetermined direction D being a direction in which the first pinion shaft (33) extends when viewed from an axial direction of the first rack shaft (41).

Description

STEER-BY-WIRE UNIT

[0001] The present invention relates to a steer-by-wire unit.

[0002] JP2007-290462A (see, for example, FIGS. 1 to 2) discloses a power steering device in which an output shaft of a motor is disposed horizontally with respect to a rack shaft in a case of being viewed from a vehicle front-rear direction.

[0003] When the motor largely protrudes from the device, there is a concern that interference with vehicle components may occur or a clearance with the vehicle components may be insufficient, and the vehicle mountability is poor.

[0004] The present invention has been made in view of such a problem, and an object thereof is to improve the vehicle mountability.

[0005] According to one aspect of the present invention, a steer-by-wire unit for turning wheels of a vehicle includes: a motor; a pinion shaft configured to allow a driving force from the motor to be input; and a rack shaft having a rack gear meshing with the pinion shaft and configured to turn the wheel of the vehicle. When the steer-by-wire unit is viewed along a predetermined direction, an output shaft of the motor is disposed to be inclined with respect to the rack shaft, and the motor and the rack shaft are disposed to overlap each other, the predetermined direction being a direction in which the pinion shaft extends when viewed from an axial direction of the rack shaft.

[0006] FIG. 1 is a schematic configuration diagram of a steer-by-wire device according to an embodiment of the present invention.FIG. 2 is a view of a steer-by-wire unit according to the embodiment of the present invention when viewed from a vehicle front-rear direction.FIG. 3 is a view of the steer-by-wire unit according to the embodiment of the present invention when viewed from a vehicle up-down direction.FIG. 4 is a view of the steer-by-wire unit according to the embodiment of the present invention when viewed from a vehicle left-right direction.

[0007] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0008] A steer-by-wire device 100 according to an embodiment of the present invention will be described with reference to FIG. 1. The steer-by-wire device 100 can perform a steer-by-wire control of turning wheels 7 according to an operation state of a steering wheel 1 by a driver, and includes the steering wheel 1 by which a steering operation is performed by the driver, a steering shaft 2 that rotates in accordance with the steering operation by the driver, a first rack shaft 41 and a second rack shaft 42 that turn the wheels 7, a first turning motor 31 that applies a turning force to the first rack shaft 41, a second turning motor 36 that applies a turning force to the second rack shaft 42, and a reaction force motor 51 that applies a steering reaction force to the steering shaft 2.

[0009] The steer-by-wire device 100 is mounted on a vehicle such as an EV truck, and includes a first pinion shaft 33 configured to allow a driving force from the first turning motor 31 to be input and a second pinion shaft 38 configured to allow a driving force from the second turning motor 36 to be input.

[0010] The driving force of the first turning motor 31 is transmitted to the first pinion shaft 33 after a rotation speed is reduced by a first reduction mechanism 32. The first reduction mechanism 32 includes a first worm shaft 32a coupled to an output shaft 31a of the first turning motor 31, and a first worm wheel 32b that meshes with the first worm shaft 32a and is coupled to the first pinion shaft 33, and decelerate input rotation from the first turning motor 31 and transmit the decelerated input rotation to the first pinion shaft 33. The first pinion shaft 33 has a first pinion gear 33a that meshes with a first rack gear 41a formed on the first rack shaft 41, and meshes with the first rack shaft 41.

[0011] The driving force of the second turning motor 36 is transmitted to the second pinion shaft 38 after the rotation speed is reduced by a second reduction mechanism 37. The second reduction mechanism 37 includes a second worm shaft 37a coupled to an output shaft 36a of the second turning motor 36, and a second worm wheel 37b that meshes with the second worm shaft 37a and is coupled to the second pinion shaft 38, and decelerate input rotation from the second turning motor 36 and transmit the decelerated input rotation to the second pinion shaft 38. The second pinion shaft 38 has a second pinion gear 38a that meshes with a second rack gear 42a formed on the second rack shaft 42, and meshes with the second rack shaft 42.

[0012] When the first turning motor 31 and the second turning motor 36 are driven in accordance with the steering operation by the driver, a turning force for turning the wheels 7 is applied to the first rack shaft 41 and the second rack shaft 42 through the first pinion shaft 33 and the second pinion shaft 38. In this case, rotation of each of the pinion shafts 33, 38 is converted into a linear motion by each of the pinion gears 33a, 38a and each of the rack gears 41a, 42a, and the wheel 7 is turned by the linear motion of each of the rack shafts 41, 42 via a tie rod 91 for transmitting the steering operation to the wheel 7 and a knuckle arm 6 that rotatably holds the wheel 7.

[0013] A steering reaction force is applied by the reaction force motor 51 in response to the steering operation by the driver. A driving force of the reaction force motor 51 is input to the steering shaft 2 after the rotation speed is reduced by a third reduction mechanism 52. The third reduction mechanism 52 includes a worm shaft 52a coupled to an output shaft 51a of the reaction force motor 51, and a worm wheel 52b that meshes with the worm shaft 52a and is coupled to the steering shaft 2. When the reaction force motor 51 is driven, the steering reaction force is applied to the steering shaft 2, whereby a pseudo weight of a handle is applied.

[0014] The steer-by-wire device 100 further includes a first turning controller 30 that controls driving of the first turning motor 31, a second turning controller 35 that controls driving of the second turning motor 36, and a reaction force controller 50 that controls driving of the reaction force motor 51.

[0015] Each of the controllers 30, 35, and 50 is implemented by a microcomputer including a central processing unit (CPU) that executes arithmetic processing, a read-only memory (ROM) that stores a control program and the like executed by the CPU, and a random access memory (RAM) that stores an arithmetic result and the like of the CPU. Each of the controllers 30, 35, and 50 may be implemented by a single microcomputer or a plurality of microcomputers.

[0016] State information of the vehicle such as a vehicle speed is input to the controllers 30, 35, and 50 in addition to a detection signal of a steering angle sensor 21 that detects a steering angle that is a rotation angle of the steering wheel 1. The steering angle sensor 21 is provided on the steering shaft 2, includes, although not illustrated, a center gear that rotates integrally with the steering shaft 2 and two outer gears that mesh with the center gear, and calculates a rotation angle of the center gear, that is, a rotation angle of the steering shaft 2 based on a change in magnetic flux accompanying rotation of the two outer gears. The state information of the vehicle such as the vehicle speed is input to the first turning controller 30 via a first cable 53 in addition to the detection signal of the steering angle sensor 21. The state information of the vehicle such as the vehicle speed is input to the second turning controller 35 via a second cable 54 in addition to the detection signal of the steering angle sensor 21.

[0017] In the steer-by-wire control, the turning controllers 30, 35 control the turning motors 31, 36 according to the operation state of the steering wheel 1 to turn the wheels 7. The turning controllers 30, 35 set a target turning angle based on a detection result of the steering angle sensor 21 and the vehicle speed, and control the turning motors 31, 36 such that a turning angle of the wheels 7 matches the target turning angle. In addition, in the steer-by-wire control, the reaction force controller 50 controls the reaction force motor 51 according to a turning state of the wheels 7 to apply a steering reaction force to the steering wheel 1. The reaction force controller 50 sets a target steering reaction force corresponding to a reaction force received from a road surface by the steering operation, and controls the reaction force motor 51 such that the steering reaction force applied to the steering shaft 2 matches the target steering reaction force.

[0018] The first turning motor 31, the first reduction mechanism 32, the first pinion shaft 33, and the first rack shaft 41 constitute a first unit 151 serving as a steer-by-wire unit that turns the wheels 7. Similarly, the second turning motor 36, the second reduction mechanism 37, the second pinion shaft 38, and the second rack shaft 42 constitute a second unit 152 serving as a steer-by-wire unit that turns the wheels 7. Both the units 151, 152 constitute a steer-by-wire unit capable of independently turning each wheel 7 (that is, capable of turning a single wheel), and are implemented similarly to each other.

[0019] The first unit 151 and the second unit 152 are required to avoid interference with vehicle components and ensure a clearance. Therefore, the units 151, 152 are further implemented as described below.

[0020] The first rack shaft 41 has a tip portion 41b connected to the wheel 7 (that is, tip portion 41b serving as end portion connected to wheel 7), and a terminal portion 41c located on a side opposite to the tip portion 41b and not connected to the wheel 7 (that is, terminal portion 41c serving as end portion not connected to wheel 7). Similarly, the second rack shaft 42 has a tip portion 42b connected to the wheel 7 and a terminal portion 42c located on a side opposite to the tip portion 42b and not connected to the wheel 7. The tip portions 41b, 42b each face a side on which the rack shafts 41, 42 turn the wheel 7 in the vehicle left-right direction, and are connected to the wheel 7 via the tie rod 91. The tie rod 91 serving as a connection member to the wheel 7 is coupled to the tip portions 41b, 42b, but is not coupled to the terminal portions 41c, 42c.

[0021] One end portion of the tie rod 91 is coupled to the tip portions 41b, 42b via a ball joint (not illustrated). The other end portion of the tie rod 91 is coupled to a knuckle arm 6, and the tip portion 41b, 42b are connected to the wheels 7 via the ball joint, the tie rod 91, and the knuckle arm 6.

[0022] The tip portion 41b of the first rack shaft 41 is connected to a wheel 71 serving as one of left and right wheels of the vehicle. Similarly, the tip portion 42b of the second rack shaft 42 is connected to a wheel 72 serving as one of the left and right wheels. The wheels 71, 72 may be front wheels or rear wheels of the vehicle. The units 151, 152 further include an extension shaft 45 provided at the terminal portions 41c, 42c and extending the rack shafts 41, 42. The extension shaft 45 may be formed integrally with the rack shafts 41, 42, and the extension shaft 45 can be understood as a part of the rack shafts 41, 42. In this case, the terminal portions 41c, 42c are formed by an end portion of the extension shaft 45 on an inner side in the vehicle left-right direction.

[0023] The units 151, 152 further include a first boot 95 covering the tip portions 41b, 42b of the rack shafts 41, 42, and a second boot 96 covering the terminal portions 41c, 42c of the rack shafts 41, 42. The boots 95, 96 can be formed of elastomer (resin or rubber), and are fixed to an outer periphery of an end portion of rack housings 61, 65 to be described later on an outer side in the vehicle left-right direction. The boots 95, 96 prevent water and foreign matter from entering a first rack housing 61.

[0024] The units 151, 152 serving as the steer-by-wire unit do not need to transmit power between the steering wheel 1 and the wheel 7. Therefore, in combination with relaxation of a limitation on layout, a space can be formed near a center of the vehicle in the left-right direction by disposing the terminal portions 41c, 42c of the rack shafts 41, 42 near the center. As a result, interference with vehicle components near the center is less likely to occur and a clearance with the vehicle components can be sufficiently ensured, and the vehicle mountability can be improved.

[0025] The first unit 151 further includes: the first rack housing 61 accommodating the first rack shaft 41; a first gear housing 62 coupled to the first rack housing 61 and accommodating the first reduction mechanism 32; a first motor housing 63 coupled to the first gear housing 62 and accommodating the first turning motor 31; a first control housing 64 coupled to the first motor housing 63 and accommodating the first turning controller 30; and a first connector 81 provided in the first control housing 64 and used for electrically connecting the first cable 53 to be connected and the first turning controller 30.

[0026] The second unit 152 further includes: a second rack housing 65 accommodating the second rack shaft 42; a second gear housing 66 coupled to the second rack housing 65 and accommodating the second reduction mechanism 37; a second motor housing 67 coupled to the second gear housing 66 and accommodating the second turning motor 36; a second control housing 68 coupled to the second motor housing 67 and accommodating the second turning controller 35; and a second connector 82 provided in the second control housing 68 and used for electrically connecting the second cable 54 to be connected and the second turning controller 35.

[0027] The turning motors 31, 36 are accommodated in the motor housings 63, 67 in a state where the output shafts 31a, 36a are coupled to the worm shafts 32a, 37a of the reduction mechanisms 32, 37 in the gear housings 62, 66. In axial directions of the rack shafts 41, 42, the turning motors 31, 36 are disposed on a terminal portion 41c side and a terminal portion 42c side (accordingly, on inner side in vehicle left-right direction) with respect to the reduction mechanisms 32, 37 and the pinion shafts 33, 38. The first pinion shaft 33 is accommodated in the first rack housing 61 and the first gear housing 62, and the second pinion shaft 38 is accommodated in the second rack housing 65 and the second gear housing 66.

[0028] As described above, the units 151, 152 are implemented similarly to each other. Therefore, hereinafter, the units 151, 152 will be described using the first unit 151 as an example.

[0029] FIG. 2 is a view of the first unit 151 when viewed from a vehicle front-rear direction (horizontal front-rear direction), and a portion A illustrated in FIG. 2 is a portion where the first rack housing 61 accommodates the first pinion shaft 33 (see FIG. 1). As illustrated in FIG. 2, in the first rack housing 61, a pressing mechanism 46 used for adjusting a backlash between the first rack gear 41a (see FIG. 1) of the first rack shaft 41 and the first pinion gear 33a (see FIG. 1) of the first pinion shaft 33 is provided on a side opposite to the first pinion shaft 33 with the first rack shaft 41 sandwiched therebetween.

[0030] As can be seen from FIG. 1 and a positional relation between the portion A and the pressing mechanism 46 illustrated in FIG. 2, the first pinion gear 33a of the first pinion shaft 33 meshes with the first rack gear 41a of the first rack shaft 41 from below in the vehicle up-down direction. In other words, the vehicle up-down direction is a height direction and is a vertical direction.

[0031] As illustrated in FIG. 2, the first gear housing 62 has a worm shaft portion 621a accommodating the first worm shaft 32a (see FIG. 1) of the first reduction mechanism 32, and a worm wheel portion 621b accommodating the first worm wheel 32b (see FIG. 1) of the first reduction mechanism 32. As can be seen from FIG. 2, the first worm shaft 32a accommodated in the worm shaft portion 621a is provided above the first rack shaft 41 (see FIG. 1) accommodated in the first rack housing 61 so as to mesh with the first worm wheel 32b accommodated in the worm wheel portion 621b.

[0032] Therefore, a meshing position of the first worm shaft 32a (see FIG. 1) and the first worm wheel 32b (see FIG. 1) of the first reduction mechanism 32 and a meshing position of the first pinion gear 33a (see FIG. 1) of the first pinion shaft 33 and the first rack gear 41a (see FIG. 1) of the first rack shaft 41 have a positional relation in which the former is on an upper side of the first rack shaft 41 and the latter is on a lower side of the first rack shaft 41. In addition, as illustrated in FIG. 1, the first pinion shaft 33 is disposed to be inclined so as to be positioned on a tip portion 41b side (outer side in vehicle left-right direction) in the axial direction of the first rack shaft 41 toward a first reduction mechanism 32 side.

[0033] Next, the first unit 151 will be further described.

[0034] FIG. 4 is a view of the first unit 151 when viewed from the vehicle left-right direction (horizontal left-right direction), and as illustrated in FIG. 4, the first rack shaft 41 (see FIG. 1), which is accommodated in the first rack housing 61 and coupled to the extension shaft 45, has an axis O1. In addition, the first pinion shaft 33 (see FIG. 1) accommodated over the first rack housing 61 and the first gear housing 62 has an axis O2.

[0035] The axis O2 extends along a predetermined direction D when viewed from the direction in which the axis O1 extends (that is, axial direction of first rack shaft 41). In other words, the predetermined direction D is the direction in which the axis O2 of the first pinion shaft 33 extends when the first pinion shaft 33 is viewed from the axial direction of the first rack shaft 41. To be more precise, the predetermined direction D is the direction in which the axis O2 of the first pinion shaft 33 extends in the plane perpendicular to the axial direction of the first rack shaft 41 (the paper plane in FIG. 4). A parallel line L is a line parallel to the predetermined direction D when viewed from the axial direction of the first rack shaft 41, passes through the axis O1 of the first rack shaft 41, and extends along a radial direction of the first rack shaft 41.

[0036] Based on the above, a case of being viewed along the predetermined direction D can be said to be a case of being viewed along the parallel line L (being viewed along radial direction of first rack shaft 41 parallel to predetermined direction D), and FIG. 2 substantially corresponds to the case of being viewed along the predetermined direction D. In FIG. 2, the first motor housing 63 is disposed at a position where the first motor housing 63 slightly rotates upward around the first rack shaft 41 (see FIG. 1) as compared with the case of being viewed along the predetermined direction D. In addition, in FIG. 2, the tie rod 91 extends along the axial direction of the first rack shaft 41 (see FIG. 1) accommodated in the first rack housing 61 and the boots 95, 96.

[0037] As can be seen from FIGS. 1 and 2, the output shaft 31a of the first turning motor 31 accommodated over the first gear housing 62 and the first motor housing 63 is disposed to be inclined with respect to the first rack shaft 41 when the first unit 151 is viewed along the predetermined direction D. In addition, the first turning motor 31 is disposed to overlap the first rack shaft 41 when the first unit 151 is viewed along the predetermined direction D.

[0038] Accordingly, protrusion of the first turning motor 31 and the first motor housing 63 accommodating the first turning motor 31 in the vehicle up-down direction can be suppressed, and the vehicle mountability can be improved. In the case of being viewed along the predetermined direction D, the output shaft 31a of the first turning motor 31 is inclined such that the first turning motor 31 is closer to the first rack shaft 41 as compared with a case where the output shaft 31a is disposed parallel to the first rack shaft 41.

[0039] As can be seen from FIG. 2, the first motor housing 63 is disposed to overlap the second boot 96 in the case of being viewed along the predetermined direction D, whereby the first turning motor 31 (see FIG. 1) accommodated in the first motor housing 63 and the first rack shaft 41 (see FIG. 1) accommodated in the second boot 96 are disposed to overlap each other. The first turning motor 31 and the first rack shaft 41 are disposed to at least partially overlap each other when the first unit 151 is viewed from the front of the vehicle (that is, in plan view of first unit 151 when viewing FIG. 2) in a vehicle-mounted state of the first unit 151.

[0040] FIG. 3 is a view of the first unit 151 when viewed from the vehicle up-down direction, and corresponds to a plan view of the units 151, 152 when viewing FIG. 1.

[0041] As illustrated in FIGS. 2 and 3, the first control housing 64 has a rectangular base 64a and a box-shaped cover 64b provided on the base 64a and covering the base 64a. A longitudinal direction of the first control housing 64 faces the vehicle front-rear direction, and a back surface of the first control housing 64 (surface of base 64a on side opposite to cover 64b) faces the outer side in the vehicle left-right direction. In the first unit 151, the back surface of the first control housing 64 faces a first pinion shaft 33 (see FIG. 1) side in the axial direction of the first rack shaft 41 (see FIG. 1). In other words, the first pinion shaft 33 side can be said to be a first reduction mechanism 32 (see FIG. 1) side or a first gear housing 62 side.

[0042] The first motor housing 63 and the first connector 81 are provided in a portion of the first control housing 64 on the first pinion shaft 33 (see FIG. 1) side in the axial direction of the first rack shaft 41 (see FIG. 1). The first motor housing 63 and the first connector 81 are coupled to the back surface of the first control housing 64. The first motor housing 63 is provided from a center of the back surface of the first control housing 64 to one side (first rack housing 61 side) in the vehicle front-rear direction, and the first connector 81 is provided on the other side (side opposite to first rack housing 61) of the back surface of the first control housing 64 in the vehicle front-rear direction.

[0043] As can be seen from FIGS. 1 and 3, the first connector 81 is disposed side by side with the first turning motor 31, and the first connector 81 faces the first pinion shaft 33 side. Accordingly, the first connector 81 and the first cable 53 connected to the first connector 81 can be suppressed from protruding in the axial direction of the first rack shaft 41, so that the first unit 151 can be made compact in the axial direction of the first rack shaft 41.

[0044] As can be seen from FIGS. 1 and 3, the first connector 81 is disposed around the axis of the first turning motor 31 so as to be disposed side by side with the first turning motor 31 in the radial direction of the first turning motor 31. The first connector 81 is disposed side by side in the vehicle front-rear direction. Therefore, the first connector 81 can be suppressed from protruding in the vehicle up-down direction, and the first unit 151 can be made compact in the vehicle up-down direction.

[0045] As illustrated in FIGS. 2 to 4, the first rack housing 61 is fastened to the first gear housing 62 via a bolt 85. The first rack housing 61 is fastened to the first gear housing 62 by the bolt 85 from a back side of the first gear housing 62. The first rack housing 61 is fastened to the first gear housing 62 by a plurality of (here, four) bolts 85.

[0046] The first gear housing 62 has a main body portion 621 accommodating the first reduction mechanism 32 (see FIG. 1) and a first fastening portion T1 to which the bolt 85 is screwed. The main body portion 621 has, in addition to the worm shaft portion 621a and the worm wheel portion 621b described above, a first coupling portion 621c provided at an end portion of the worm wheel portion 621b and coupled to the first rack housing 61. The worm shaft portion 621a has an elongated tubular shape with a closed tip, and the worm wheel portion 621b has a thick and short tubular shape integrally formed with the worm shaft portion 621a.

[0047] The first fastening portion T1 has a boss shape and is provided in the first coupling portion 621c. As illustrated in FIG. 2, a plurality of (here, four) first fastening portions T1 are provided on an outer edge portion of the first coupling portion 621c. The first fastening portion T1 on the lower right portion in FIG. 2 is hidden behind the first rack housing 61. A fastening portion T11 indicates a first fastening portion T1 disposed at an uppermost position (that is, uppermost position in vehicle up-down direction) in FIG. 2 among the plurality of first fastening portions T1, and a fastening portion T12 indicates a first fastening portion T1 disposed at a lower left position (that is, lower side in vehicle up-down direction and outer side in vehicle left-right direction) in FIG. 2 among the plurality of first fastening portions T1.

[0048] As illustrated in FIGS. 2 to 4, the first rack housing 61 has a tubular accommodation portion 611 in which the first rack shaft 41 (see FIG. 1) is accommodated, and a second coupling portion 612 integrally formed with the accommodation portion 611 and coupled to the first coupling portion 621c via the bolt 85. The first coupling portion 621c and the second coupling portion 612 are coupled to each other with their mating surfaces facing each other.

[0049] The second coupling portion 612 is provided with a second fastening portion T2 through which the bolt 85 is inserted. The second fastening portion T2 has a boss shape, and a seat surface S of the bolt 85 is formed in the second fastening portion T2. As illustrated in FIG. 2, a plurality of (here, four) second fastening portions T2 are provided on an outer edge portion of the second coupling portion 612. The second fastening portion T2 on the lower right portion in FIG. 2 is hidden behind the first rack housing 61. A fastening portion T21 indicates a second fastening portion T2 disposed at an uppermost position (that is, uppermost position in vehicle up-down direction) in FIG. 2 among the plurality of second fastening portions T2, and a fastening portion T22 indicates a second fastening portion T2 disposed at a lower left position (that is, lower side in vehicle up-down direction and outer side in vehicle left-right direction) in FIG. 2 among the plurality of second fastening portions T2.

[0050] As can be seen from FIGS. 2 to 4, the fastening portion T21 is provided so as not to protrude from the worm shaft portion 621a of the main body portion 621 toward an outer side in a radial direction of the first pinion shaft 33 (see FIG. 1). In addition, as can be seen from FIG. 2, the fastening portion T22 is provided so as not to protrude from the worm wheel portion 621b of the main body portion 621 toward the outer side in the radial direction of the first pinion shaft 33 (see FIG. 1).

[0051] That is, the first rack housing 61 has the plurality of second fastening portions T2 through which the bolts 85 are inserted, and the fastening portions T21, T22 serving as at least one of the plurality of second fastening portions T2 are provided so as not to protrude from the main body portion 621 toward the outer side in the radial direction of the first pinion shaft 33 (see FIG. 1). The fastening portions T21, T22 are provided so as not to protrude from the main body portion 621 in a case of being viewed along the direction in which the first pinion shaft 33 extends.

[0052] As described above, by providing the second fastening portion T2 without protruding from the main body portion 621 while fastening the first rack housing 61 to the first gear housing 62 with the bolt 85 from the back side, it is possible to eliminate protrusion of a fastening portion required in a case where the first gear housing 62 is fastened to the first rack housing 61 with the bolt 85.

[0053] That is, in the case where the first gear housing 62 is fastened to the first rack housing 61 with the bolt 85, the bolt 85 needs to be set from an upper left portion in FIG. 3, and the fastening portions T11, T21 and the fastening portions T12, T22 (see FIG. 2) must be provided on an outer side of the main body portion 621 in the radial direction of the first pinion shaft 33 (see FIG. 1), but this is not necessary in the present embodiment. Therefore, the first unit 151 can be made compact.

[0054] As illustrated in FIG. 4 (in other words, in plan view when viewing FIG. 4, that is, when being viewed along axis O1), in the vehicle-mounted state of the first unit 151, a dimension H1 of the first motor housing 63 in the height direction (vehicle up-down direction) and a dimension H2 of the first control housing 64 in the height direction are smaller than a dimension H3 of the first gear housing 62 in the height direction. Accordingly, the first motor housing 63 and the first control housing 64 can be suppressed from protruding beyond the first gear housing 62 in the height direction, and the first unit 151 can be made compact in the height direction in the vehicle-mounted state.

[0055] In the vehicle-mounted state of the first unit 151, the first motor housing 63 and the first control housing 64 are provided within a range of a maximum outer shape of the first gear housing 62 in the height direction (within a range of the dimension H3 in the drawing) in the height direction. Accordingly, the first motor housing 63 and the first control housing 64 do not protrude beyond the first gear housing 62 in the height direction. Therefore, the first unit 151 can be made compact by suppressing a maximum outer shape dimension of the first unit 151 in the height direction to the dimension H3 of the first gear housing 62 in the height direction.

[0056] In the vehicle-mounted state of the first unit 151, the dimension H1 of the first motor housing 63 in the height direction and the dimension H2 of the first control housing 64 in the height direction are smaller than a dimension H31 of the worm wheel portion 621b of the first gear housing 62 in the height direction. Accordingly, the first motor housing 63 and the first control housing 64 can be suppressed from protruding beyond the worm wheel portion 621b in the height direction, and the first unit 151 can be made more compact in the height direction in the vehicle-mounted state.

[0057] In the vehicle-mounted state of the first unit 151, the first control housing 64 is provided within a range of a maximum outer shape of the worm wheel portion 621b in the height direction (within a range of the dimension H31 in the drawing) in the height direction. Accordingly, the first control housing 64 does not protrude beyond the worm wheel portion 621b in the height direction, so that the first unit 151 can be made more compact in the height direction. (Modification) In the units 151, 152, by adopting a steer-by-wire system, positions of the turning motors 31, 36 can be freely set around the rack shafts 41, 42 in combination with relaxation of a limitation on layout in the vehicle. Therefore, the turning motors 31, 36 and the rack shafts 41, 42 may be disposed to at least partially overlap each other in a case of viewing the units 151, 152 from the radial direction of the rack shafts 41, 42 other than the front of the vehicle in the vehicle-mounted state of the units 151, 152. Accordingly, the vehicle mountability of the units 151, 152 can be improved in view of the point that the turning motors 31, 36 can be suppressed from protruding in a direction in which interference with vehicle components or a clearance condition is severe.

[0058] The connectors 81, 82 may be disposed side by side with the turning motors 31, 36 in a direction other than the vehicle front-rear direction. Accordingly, the vehicle mountability of the units 151, 152 can be improved in view of the point that the connectors 81, 82 can be suppressed from protruding in a direction in which interference with vehicle components or a clearance condition is severe.

[0059] At least one of the dimension H1 of the first motor housing 63 in the height direction and the dimension H2 of the first control housing 64 in the height direction may be smaller than the dimension H3 of the first gear housing 62 in the height direction. Also in this case, the first unit 151 can be made compact in the height direction in the vehicle-mounted state.

[0060] When the first unit 151 is viewed along the axis O2 of the first pinion shaft 33, the output shaft 31a of the first turning motor 31 may be inclined with respect to the first rack shaft 41, and the first turning motor 31 and the first rack shaft 41 may be disposed so as to at least partially overlap each other. According to the configuration, since when the first unit 151 is viewed along the axis O2 of the first pinion shaft 33, the first pinion shaft 33, the first rack shaft 41, and the first turning motor 31 overlap, thereby improving the vehicle mountability of the first unit 151.

[0061] Hereinafter, configurations, operations, and effects of the embodiment of the present invention will be collectively described.

[0062] The units 151, 152 are steer-by-wire units that turn the wheels 7 of the vehicle, and includes: the turning motors 31, 36; the pinion shafts 33, 38 configured to allow a driving force from the turning motors 31, 36 to be input; and the rack shafts 41, 42 having the rack gears 41a, 42a meshing with the pinion shafts 33, 38 and configured to turn the wheels 7 of the vehicle. In the units 151, 152, in a case of being viewed along the predetermined direction D, which is a direction in which the pinion shafts 33, 38 extend when viewed from the axial direction of the rack shafts 41, 42, the output shafts 31a, 36a of the turning motors 31, 36 are disposed to be inclined with respect to the rack shafts 41, 42, and the turning motors 31, 36 and the rack shafts 41, 42 are disposed to overlap each other.

[0063] According to the configuration, since the turning motors 31, 36 and the rack shafts 41, 42 are disposed to overlap each other when the units 151, 152 are viewed along the predetermined direction D, protrusion of the turning motors 31, 36 and the motor housings 63, 67 accommodating the turning motors 31, 36 can be suppressed, and the vehicle mountability can be improved. In addition, by adopting the steer-by-wire system, the positions of the turning motors 31, 36 can be freely set around the rack shafts 41, 42 in combination with relaxation of a limitation on layout, so that the vehicle mountability can be improved in view of the point that the turning motors 31, 36 and the motor housings 63, 67 can be suppressed from protruding in a direction in which interference with vehicle components or a clearance condition is severe.

[0064] The rack shafts 41, 42 have the tip portions 41b, 42b connected to the wheels 7 of the vehicle, and the terminal portions 41c, 42c located on the sides opposite to the tip portions 41b, 42b and not connected to the wheels 7 of the vehicle.

[0065] According to the configuration, by adopting the steer-by-wire system, in combination with relaxation of a limitation on layout, a space can be formed near the center of the vehicle in the left-right direction by disposing the terminal portions 41c, 42c near the center. Therefore, interference with the vehicle component near the center is less likely to occur and a sufficient clearance can be ensured, and the vehicle mountability can be further improved.

[0066] The units 151, 152 further includes: the motor housings 63, 67 accommodating the turning motors 31, 36; the control housings 64, 68 coupled to the motor housings 63, 67 and accommodating the turning controllers 30, 35 that control driving of the turning motors 31, 36; and the connectors 81, 82 provided in the control housings 64, 68 and used for electrically connecting the cables 53, 54 to be connected and the turning controllers 30, 35, and the connectors 81, 82 are disposed side by side with the turning motors 31, 36 and each face the pinion shaft 33 side and a pinion shaft 38 side.

[0067] According to the configuration, since the connectors 81, 82 and the cables 53, 54 can be suppressed from protruding in the axial direction of the rack shafts 41, 42, the units 151, 152 can be made compact in the axial direction of the rack shafts 41, 42.

[0068] The first unit 151 further includes: the first reduction mechanism 32 configured to decelerate the input rotation from the first turning motor 31 and transmit the decelerated input rotation to the first pinion shaft 33; the first gear housing 62 accommodating the first reduction mechanism 32; and the first rack housing 61 fastened to the first gear housing 62 via the bolt 85 and accommodating the first rack shaft 41. The first gear housing 62 has the main body portion 621 accommodating the first reduction mechanism 32 and the first fastening portion T1 to which the bolt 85 is screwed, the first rack housing 61 has the plurality of second fastening portions T2 through which the bolt 85 is inserted, and at least one of the plurality of second fastening portions T2 is provided so as not to protrude from the main body portion 621 toward the outer side in the radial direction of the first pinion shaft 33.

[0069] According to the configuration, since the second fastening portion T2 is provided without protruding from the main body portion 621 while the first rack housing 61 is fastened to the first gear housing 62 with the bolt 85 from the back side, it is possible to eliminate the protrusion of the fastening portion required in the case where the first gear housing 62 is fastened to the first rack housing 61 with the bolt 85, and the unit can be made compact. The configuration, operations, and effects are the same for those of the second unit 152.

[0070] The first unit 151 further includes: the first reduction mechanism 32 configured to decelerate the input rotation from the first turning motor 31 and transmit the decelerated input rotation to the first pinion shaft 33; the first gear housing 62 accommodating the first reduction mechanism 32; the first motor housing 63 coupled to the first gear housing 62 and accommodating the first turning motor 31; and the first control housing 64 coupled to the first motor housing 63 and accommodating the first turning controller 30 that controls the driving of the first turning motor 31, and in the vehicle-mounted state, the dimensions H1 and H2 of at least one of the first motor housing 63 and the first control housing 64 in the height direction are smaller than the dimension H3 of the first gear housing 62 in the height direction.

[0071] According to the configuration, the first unit 151 can be made compact in the height direction in the vehicle-mounted state. The configuration, operations, and effects are the same for those of the second unit 152.

[0072] Embodiments of the present invention were described above, but the above embodiments are merely examples of applications of the present invention, and the technical scope of the present invention is not limited to the specific constitutions of the above embodiments.

[0073] With respect to the above description, the contents of application No. 2024-45240, with a filing date of March 21, 2024 in Japan, are incorporated herein by reference.

Claims

1. A steer-by-wire unit for turning wheels of a vehicle, the steer-by-wire unit comprising: a motor; a pinion shaft configured to allow a driving force from the motor to be input; and a rack shaft having a rack gear meshing with the pinion shaft and configured to turn the wheel of the vehicle, wherein when the steer-by-wire unit is viewed along a predetermined direction, an output shaft of the motor is inclined with respect to the rack shaft, and the motor and the rack shaft are disposed to overlap each other, the predetermined direction being a direction in which the pinion shaft extends when viewed from an axial direction of the rack shaft.

2. The steer-by-wire unit according to claim 1, wherein the rack shaft has a tip portion connected to the wheel of the vehicle, and a terminal portion located on a side opposite to the tip portion and not connected to the wheel of the vehicle.

3. The steer-by-wire unit according to claim 1, further comprising: a motor housing accommodating the motor; a control housing coupled to the motor housing and accommodating a controller configured to control driving of the motor; and a connector provided in the control housing and electrically connecting a cable and the controller, wherein the connector is disposed side by side with the motor and faces a pinion shaft side.

4. The steer-by-wire unit according to claim 1, further comprising: a reduction mechanism configured to decelerate input rotation from the motor and transmit the decelerated input rotation to the pinion shaft; a gear housing accommodating the reduction mechanism; and a rack housing fastened to the gear housing via a bolt and accommodating the rack shaft, wherein the gear housing has a main body portion accommodating the reduction mechanism and a first fastening portion to which the bolt is screwed, and the rack housing has a plurality of second fastening portions through which the bolt is inserted, and at least one of the plurality of second fastening portions is provided so as not to protrude from the main body portion toward an outer side in a radial direction of the pinion shaft.

5. The steer-by-wire unit according to claim 1, further comprising: a reduction mechanism configured to decelerate input rotation from the motor and transmit the decelerated input rotation to the pinion shaft; a gear housing accommodating the reduction mechanism; a motor housing coupled to the gear housing and accommodating the motor; and a control housing coupled to the motor housing and accommodating a controller configured to control driving of the motor, wherein in a vehicle-mounted state, a dimension of at least one of the control housing and the motor housing in a height direction is smaller than a dimension of the gear housing in the height direction.

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