JP2020066247A - Steering unit - Google Patents

Abstract

To provide a steering unit including a restraining mechanism suitable for a steering part actuator which transmits rotation of a steering part motor via a deceleration mechanism.SOLUTION: A steering part actuator includes: a deceleration mechanism including a worm shaft that is driven to rotate by a steering part motor, and a worm wheel 25 that is engaged with the worm shaft and rotates together with a steering shaft 11; a housing 23 accommodating the deceleration mechanism; and a restraining mechanism 26 that mechanically restrains the steering angle of a steering wheel so that the steering angle may not exceed a threshold angle. The restraining mechanism 26 includes a groove 98 that is formed in the worm wheel 25 and opens on an upper end in an axial direction of the steering shaft 11, and a projection 67 included in a sensor housing 61 and fitted into the groove 98. The groove 98 has locking ends that extend in the circumferential direction of the steering shaft 11 and that can lock the projection 67 on both sides in the circumferential direction.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a steering device.

  BACKGROUND ART Conventionally, as a kind of steering device, a steer-by-wire system in which a power transmission system between a steering unit to which a steering wheel is connected and a steering unit that steers the steered wheels according to steering input to the steering unit is separated. There is a formula. Such a steering device includes a steering section actuator that uses a steering section motor as a drive source, and applies a steering reaction force, which is a force against steering, to the steering wheel by the steering section actuator. Some steering unit actuators are provided with a restricting mechanism that mechanically restricts the steering angle of the steering wheel from exceeding a preset threshold angle (for example, Patent Document 1).

JP2012-91677A

  By the way, in the above-mentioned Patent Document 1, the steering portion actuator is configured such that the steering shaft to which the steering wheel is connected and the steering portion motor are arranged coaxially. Further, the size reduction of the steering device is achieved by providing the regulation mechanism in the rotor of the steering motor.

  As described above, it is desirable that the regulation mechanism is optimized according to the type of the steering actuator. However, the document does not disclose the configuration of the restricting mechanism in the case where the steering section actuator is of another type, for example, the rotation of the steering section motor is transmitted to the steering shaft through the reduction mechanism.

  An object of the present invention is to provide a steering device provided with a restriction mechanism suitable for a steering actuator that transmits rotation of a steering motor via a reduction mechanism.

  In a steering device that solves the above-mentioned problems, in a structure having a structure in which a power transmission system between a steering unit and a steering unit that steers the steered wheels in accordance with steering input to the steering unit is separable, The steering unit includes a steering shaft to which a steering wheel is connected, and a steering unit actuator that can apply a steering reaction force that is a force against steering to the steering wheel. A reduction gear having a drive gear that is rotationally driven and a driven gear that meshes with the drive gear and rotates integrally with the steering shaft, a housing that houses the reduction gear, and a steering angle of the steering wheel exceeds a threshold angle. And a restriction mechanism for mechanically restricting it so that the restriction mechanism is provided in the driven gear, The steering shaft includes a groove portion that opens in at least one of the axial directions, and a protrusion portion that is provided in the housing and that is inserted into the groove portion. The groove portion extends in the circumferential direction of the steering shaft and both sides in the circumferential direction. Has a locking end to which the protrusion can be locked.

  According to the above configuration, the restricting mechanism restricts the rotation of the steering shaft, that is, the steering wheel by locking the protrusion to one of the locking ends of the groove to prevent the steering angle from exceeding the threshold angle. Can be regulated.

  Here, it is assumed that the driver operates the steering wheel when the steering motor is not operated and the rotation of the steering wheel is restricted by the restriction mechanism. At this time, the rotation of the steering shaft due to the driver's steering suddenly stops, and the load due to the sudden stop of the rotation of the steering section motor that rotates with the steering shaft acts on the steering device. As a result of earnest research, the inventor has found that, among such loads, the load based on the inertia of the steering section motor (motor inertial load) when the rotation of the motor suddenly stops increases. Therefore, the member on which the motor inertial load acts is required to have high strength, which may lead to weight increase of the steering device.

  In this respect, in the regulation mechanism having the above configuration, since the motor inertial load is received between the driven gear and the housing, it is difficult for the motor inertial load to be transmitted to the downstream side of the driven gear in the motor torque transmission path. Therefore, the strength required for a member to which the motor inertial load is hard to be transmitted, such as a steering shaft, can be suppressed low, and the weight of the steering device can be suppressed.

  In the above steering device, the driven gear includes a metal base portion fitted to the steering shaft, and a resin gear portion provided on an outer periphery of the base portion, and the groove portion is provided in the gear portion. It is preferably provided.

According to the above configuration, compared to the case where both the gear portion and the protrusion in which the groove is formed are made of metal, the generation of abnormal noise when the protrusion is locked to any one of the locking ends of the groove is reduced. Can be suppressed.
In the steering device described above, it is preferable that the base portion has an extension portion extending outward in the radial direction, and the extension portion is located between both locking end portions of the groove portion.

  According to the above configuration, since the metal extension portion is located between both the locking end portions of the groove portion, the extension portion receives a shock when the protrusion is locked to any one of the locking end portions. be able to. As a result, the strength of the driven gear can be improved.

  In the above steering device, the external teeth of the driven gear are formed by helical teeth, and the steering shaft is provided inside the housing through bearings provided adjacent to both sides in the axial direction of the fitting portion of the driven gear. It is preferably rotatably supported on.

  According to the above configuration, since the driven teeth are formed by the oblique teeth, it is possible to suppress the generation of abnormal noise due to the meshing of the drive gear and the driven gear. On the other hand, the driven gear has a beveled tooth as a beveled tooth, and a component force of meshing along the axial direction acts on the driven gear, and the component force increases when a motor inertial load acts. In this respect, in the above configuration, since the bearings are provided on both sides of the driven gear in the axial direction, the component force of the meshing can be firmly supported by these bearings.

In the above steering device, it is preferable that the axial range in which the external teeth of the driven gear are formed does not overlap with the axial range in which the groove is formed.
According to the above configuration, since it is possible to prevent a hollow portion from being formed inside the driven tooth due to the formation of the groove portion in the driven gear, it is possible to suppress deformation of the driven gear and smooth the drive gear and the driven gear. The mesh can be maintained.

  According to the present invention, the configuration of the regulation mechanism can be optimized for the steering section actuator that transmits the rotation of the steering section motor via the reduction mechanism.

The schematic block diagram of a steering device. Sectional drawing which followed the axial direction of a steering part. FIG. 3 is an enlarged cross-sectional view along the axial direction in the vicinity of a steering unit actuator of the steering unit. FIG. 6 is a cross-sectional view orthogonal to the axial direction at a position passing through a driven gear of the steering unit. The front view which looked at the driven gear from the axial upper end side. The side view which looked at the driven gear from the radial direction.

An embodiment of a steering device will be described below with reference to the drawings.
As shown in FIG. 1, a steering device 1 of a steer-by-wire type includes a steering unit 3 to which a steering wheel 2 is connected, and a steering unit 5 that steers steered wheels 4 in response to steering of the steering unit 3 by a driver. It has and. In the steering device 1, the steering unit 3 and the steered unit 5 are mechanically separated, and the power transmission system between the steering unit 3 and the steered unit 5 is separated. Such a linkless structure is also an aspect of the structure capable of separating the power transmission system in the present embodiment.

  The steering unit 3 includes a steering shaft 11 to which the steering wheel 2 is fixed, a steering column 12 that rotatably accommodates the steering shaft 11, and a steering reaction force that is a force that resists steering via the steering shaft 11. The steering unit actuator 13 capable of applying force is provided.

  The steering portion actuator 13 includes a steering portion motor 21 that is a drive source, a speed reduction mechanism 22 that reduces the rotation of the steering portion motor 21, and a housing 23 that houses the speed reduction mechanism 22. The reduction mechanism 22 includes a worm shaft 24 as a drive gear that is rotationally driven by the steering motor 21, and a worm wheel 25 as a driven gear that meshes with the worm shaft 24. The housing 23 constitutes a part of the steering column 12 as described later. The steering actuator 13 decelerates the rotation of the steering motor 21 and transmits the decelerated rotation to the steering shaft 11 to apply a steering reaction force to the steering wheel 2.

  Further, the steering section actuator 13 is provided with a restriction mechanism 26 that mechanically restricts the steering angle of the steering wheel 2 from exceeding a threshold angle. The threshold angle is preset based on the transmission ratio (gear ratio) between the steering angle and the steered angle of the steered wheels, and can be set to, for example, about ± 160 °.

  The steered unit 5 includes a first pinion shaft 31, a rack shaft 32 as a steered shaft connected to the first pinion shaft 31, a rack housing 33 that accommodates the rack shaft 32 in a reciprocating manner, and a first pinion. A first rack and pinion mechanism 34 that converts the rotation of the shaft 31 into the reciprocating motion of the rack shaft 32 is provided. The first pinion shaft 31 and the rack shaft 32 are arranged at a predetermined intersecting angle, and the first rack and pinion mechanism 34 includes a first pinion tooth 31 a formed on the first pinion shaft 31 and a rack shaft 32. It is configured by meshing with the formed first rack teeth 32a. Tie rods 36 are connected to both ends of the rack shaft 32 via rack ends 35 formed of ball joints, and the tips of the tie rods 36 are connected to a knuckle (not shown) to which the steered wheels 4 are attached.

  Further, the steered portion 5 is provided with a steered portion actuator 41 that applies a steered force that steers the steered wheels 4 to the rack shaft 32. The steered portion actuator 41 includes a steered portion motor 42 serving as a drive source, a transmission mechanism 43, and a conversion mechanism 44. Then, the steered portion actuator 41 transmits the rotation of the steered portion motor 42 to the conversion mechanism 44 via the transmission mechanism 43, and the conversion mechanism 44 converts the rotation into the reciprocating motion of the rack shaft 32, thereby turning the steered portion 5. The steering force is applied to. A belt mechanism is adopted as the transmission mechanism 43 of this embodiment, and a ball screw mechanism is adopted as the conversion mechanism 44.

  In the steering device 1 configured as described above, the steering angle of the steered wheels 4 is changed by applying a steering force to the rack shaft 32 from the steering actuator 41 in accordance with a steering operation by the driver. . At this time, a steering reaction force against the steering of the driver is applied to the steering wheel 2 from the steering actuator 13.

  Next, the configuration of the steering unit 3 will be described in detail. In the following, for convenience of explanation, the side on which the steering wheel 2 is located (right side in FIG. 2) is the upper end side, and the side opposite to the steering wheel 2 (left side in FIG. 2) is the lower end side.

  As shown in FIG. 2, the steering shaft 11 includes a hollow upper shaft 51, an axial lower shaft 52, and a drive shaft 53 connected to a lower end portion of the lower shaft 52 in the axial direction. The steering wheel 2 is connected to an upper end portion (right side in FIG. 2) of the upper shaft 51. The lower shaft 52 is spline-fitted to the upper shaft 51. The drive shaft 53 is connected to the lower end portion (the left end portion in FIG. 2) of the lower shaft 52. The drive shaft 53 also includes a hollow input shaft 54 and an output shaft 55, and a torsion bar 56 that connects the input shaft 54 and the output shaft 55 to each other. The input shaft 54 is connected to the lower shaft 52.

  The steering column 12 includes a cylindrical outer tube 57 that rotatably accommodates the upper shaft 51, a cylindrical inner tube 58 that rotatably accommodates the lower shaft 52, and the housing 23 that constitutes the steering portion actuator 13. Is equipped with. The outer tube 57 rotatably supports the upper shaft 51 via a bearing 59. The outer tube 57 is fitted on the outer circumference of the inner tube 58 so as to be movable in the axial direction.

Next, the configuration of the steering actuator 13 will be described.
As shown in FIGS. 2 and 3, the housing 23 includes a sensor housing 61 connected to the lower end of the inner tube 58 and a worm housing 62 fixed to the lower end of the sensor housing 61. The sensor housing 61 and the worm housing 62 are made of a metal material.

  The sensor housing 61 is formed with an insertion hole 63 penetrating in the axial direction. The drive shaft 53 is inserted through the insertion hole 63. The sensor housing 61 rotatably supports the input shaft 54 via a bearing 64 provided on the axially upper end side of the insertion hole 63, and via a bearing 65 provided on the axially lower end side of the insertion hole 63. The upper end of the output shaft 55 is rotatably supported. A sensor unit 66 that detects the steering torque based on the amount of twist of the torsion bar 56 is provided on the inner periphery of the insertion hole 63. Further, on the side surface on the lower end side in the axial direction of the sensor housing 61, a columnar protrusion 67 protruding in the axial direction is integrally formed at a position facing the groove 98 of the worm wheel 25 described later in the axial direction. There is.

  As shown in FIGS. 3 and 4, the worm housing 62 is formed continuously with the worm shaft housing portion 71 in which the worm shaft 24 is housed, and the worm wheel housing 25 in which the worm wheel 25 is housed. It has a wheel housing portion 72. The worm shaft accommodating portion 71 has a cylindrical space corresponding to the worm shaft 24, and communicates with a mounting opening 73 to which the steering motor 21 is fixed.

  The worm wheel housing portion 72 has a disk-shaped space corresponding to the worm wheel 25. The worm wheel accommodating portion 72 has an opening in the axial upper end side (sensor housing 61 side) and is covered by the sensor housing 61. A through hole 74 through which the output shaft 55 is inserted is formed at the lower end portion of the worm wheel housing portion 72 in the axial direction. The worm wheel accommodating portion 72 rotatably supports the vicinity of the axial center of the output shaft 55 via a bearing 75 provided in the through hole 74.

  As shown in FIG. 4, the steering portion motor 21 is fixed to the worm housing 62 such that a part of the steering portion motor 21 fits into the mounting opening 73. The worm shaft 24 is coupled to the steering portion motor 21 via a joint member 81 and is rotatably accommodated in the worm shaft accommodating portion 71 via bearings 82 and 83. On the outer circumference of the worm shaft 24, worm teeth 84 extending in a spiral shape are formed.

  As shown in FIGS. 3 to 5, the worm wheel 25 includes a base portion 91 fitted to the output shaft 55 (steering shaft 11) and a gear portion 92 provided on the outer periphery of the base portion 91. The base portion 91 is made of a metal material. The base portion 91 is formed in a disc shape, and has a fitting hole 94 penetrating in the axial direction in the center thereof. As shown in FIG. 5, a fan-shaped extending portion 95 extending outward in the radial direction is formed on the outer periphery of the upper end of the base portion 91 in the axial direction.

  As shown in FIGS. 3 and 4, the worm wheel 25 is integrally rotatably coupled to the output shaft 55 by pressing the output shaft 55 into the fitting hole 94. As described above, the output shaft 55 is rotatably supported by the bearings 65 and 75, and the worm wheel 25 is located between the bearings 65 and 75. That is, the output shaft 55 (steering shaft 11) is rotatably supported in the housing 23 through bearings 65 and 75 provided adjacent to both sides in the axial direction of the fitting portion of the worm wheel 25.

  As shown in FIGS. 3 to 6, the gear portion 92 is made of a resin material. The gear portion 92 is formed in an annular shape. The inner diameter of the gear portion 92 is set to be substantially equal to the outer diameter of the base portion 91. A substantially fan-shaped recess 96 into which the extending portion 95 is fitted is formed on the axially upper end side of the inner periphery of the gear portion 92. Further, on the outer peripheral surface of the gear portion 92, a plurality of external teeth 97 as driven teeth that mesh with the worm teeth 84 of the worm shaft 24 are formed. The external teeth 97 of this embodiment are configured as oblique teeth whose tooth lines are inclined with respect to the axial direction. Each external tooth 97 is formed on the outer peripheral surface of the worm wheel 25 toward the lower end side in the axial direction.

  As shown in FIGS. 3, 5 and 6, a groove portion 98 into which the protrusion 67 of the sensor housing 61 is inserted is formed on the side surface of the gear portion 92 on the upper end side in the axial direction. The groove portion 98 extends in the circumferential direction of the gear portion 92 and is formed in a C shape having locking end portions 98a at both ends in the circumferential direction. The circumferential range in which the groove portion 98 exists is determined according to the threshold angle, and is formed over the circumferential range of 320 ° in the gear portion 92 in the present embodiment. The locking end portion 98a is formed at a position where the extending portion 95 is sandwiched from both sides in the circumferential direction. The depth of the groove portion 98 is set so that the groove portion 98 exists in the axial range where the external teeth 97 of the gear portion 92 are not formed. That is, the axial range of the worm wheel 25 where the external teeth 97 are formed does not overlap the axial range where the groove 98 is formed. Then, as shown in FIG. 3, the projection portion 67 provided on the sensor housing 61 is inserted into the groove portion 98.

  The steering section actuator 13 configured as described above transmits the rotation of the steering section motor 21 to the steering shaft 11 via the speed reduction mechanism 22, thereby applying a steering reaction force according to the steering of the driver to the steering wheel 2. To do. Then, when the protrusion 67 is locked to one of the locking ends 98a of the groove 98 with the rotation of the worm wheel 25 that rotates integrally with the steering shaft 11, the rotation of the steering shaft 11, that is, the steering wheel 2 is restricted. It That is, the protrusion 67 and the groove 98 constitute the regulation mechanism 26 that mechanically regulates the steering angle of the steering wheel 2 so as not to exceed the threshold angle.

Next, the operation and effect of this embodiment will be described.
(1) Since the regulation mechanism 26 includes the C-shaped groove portion 98 provided on the worm wheel 25 and the protruding portion 67 provided on the sensor housing 61, the protruding portion 67 locks one of the groove portions 98. By locking to the end portion 98a, the rotation of the steering wheel 2 can be restricted, and the steering angle can be restricted from exceeding the threshold angle.

  Here, the driver operates the steering wheel 2 when the steering motor 21 is not operating (when the drive power is not supplied and the steering reaction force is not generated), and the steering mechanism 2 is rotated by the restriction mechanism 26. Suppose it is regulated. At this time, the rotation of the steering shaft 11 due to the steering of the driver suddenly stops, and the load due to the sudden stop of the rotation of the steering portion motor 21 that rotates together with the steering shaft 11 acts on the steering device 1. As a result of earnest research, the inventor has found that, among such loads, the load based on the inertia of the motor 21 when the rotation of the steering motor 21 suddenly stops (motor inertia load) increases. Therefore, a member on which the motor inertial load acts is required to have high strength, which may lead to weight increase of the steering device 1.

  In this respect, in the present embodiment, since the motor inertial load is received between the worm wheel 25 and the sensor housing 61, it is difficult for the motor inertial load to be transmitted to the downstream side of the worm wheel 25 in the motor torque transmission path. Therefore, the strength required for a member to which the motor inertial load is hard to be transmitted, such as the steering shaft 11, can be suppressed to be low, and the weight of the steering device 1 can be suppressed.

  (2) The worm wheel 25 has the metal base portion 91 and the resin gear portion 92 provided on the outer periphery of the base portion 91, and the groove portion 98 is provided in the gear portion 92. As compared with the case where both the protrusion 67 and the protrusion 67 are made of metal, it is possible to suppress the generation of abnormal noise when the protrusion 67 is locked to any one of the locking ends 98a of the groove 98.

  (3) The base portion 91 is formed with the extending portion 95 extending inward in the radial direction, and the worm wheel 25 is formed so that the extending portion 95 is located between both locking end portions 98a of the groove portion 98. The extension portion 95 can receive an impact when the protrusion 67 is locked to any one of the locking ends 98a. Thereby, the strength of the worm wheel 25 can be improved.

  (4) The external teeth 97 of the worm wheel 25 are formed as beveled teeth, and the steering shaft 11 is housed in the housing 23 via bearings 65 and 75 provided adjacent to both sides in the axial direction of the fitting portion of the worm wheel 25. Supported rotatably. Since the external teeth 97 are configured by the oblique teeth in this manner, it is possible to suppress the generation of abnormal noise due to the meshing between the worm shaft 24 and the worm wheel 25. On the other hand, since the external teeth 97 are inclined teeth, a meshing force component along the axial direction acts on the worm wheel 25, and the component force increases when the motor inertial load acts. In this respect, in the present embodiment, since the bearings 65 and 75 are provided on both sides of the worm wheel 25 in the axial direction, the component force of meshing can be firmly supported by these bearings 65 and 75.

  (5) Since the worm wheel 25 is formed so that the axial range in which the external teeth 97 are formed and the axial range in which the groove 98 is formed do not overlap, it is caused by forming the groove 98 in the worm wheel 25. As a result, it is possible to prevent a hollow portion from being formed inside the outer teeth 97. As a result, the deformation of the worm wheel 25 can be suppressed and the smooth engagement between the worm shaft 24 and the worm wheel 25 can be maintained.

The present embodiment can be modified and implemented as follows. The present embodiment and the following modifications can be implemented in combination with each other within a technically consistent range.
In the above embodiment, the worm wheel 25 may be formed such that the axial range in which the external teeth 97 are formed and the axial range in which the groove 98 is formed overlap.

In the above embodiment, the bearings 65 and 75 may be axially spaced from the worm wheel 25, or either one of the bearings 65 and 75 may be omitted.
-In the said embodiment, the extension part 95 does not need to be formed in the base part 91.

-In the above embodiment, the groove portion 98 may be formed in the base portion 91.
In the above-described embodiment, the protrusion 67 may be configured by a pin or the like that is a member separate from the sensor housing 61.

  In the above embodiment, the groove portion 98 is formed on the side surface of the gear portion 92 on the upper end side in the axial direction and the protrusion 67 is formed on the sensor housing 61. However, the present invention is not limited to this, and the groove portion 98 may be formed in the axial direction of the gear portion 92. The protrusion 67 may be formed on the side surface on the lower end side and formed on the worm housing 62. Further, for example, the groove portions 98 may be formed on both axial side surfaces of the gear portion 92, and the protrusion portions 67 may be formed on both the sensor housing 61 and the worm housing 62.

  In the above-described embodiment, the steering device 1 has a linkless structure in which the power transmission system between the steering unit 3 and the steering unit 5 is separated, but the invention is not limited to this, and the steering unit 3 and the steering unit may be steered by a clutch. The power transmission system with the portion 5 may be a structure that can be separated (disconnectable). In this case, if the clutch is connected, so-called power assist can be performed by the steering actuator 13.

  DESCRIPTION OF SYMBOLS 1 ... Steering device, 2 ... Steering wheel, 3 ... Steering part, 4 ... Steering wheel, 5 ... Steering part, 11 ... Steering shaft, 12 ... Steering column, 13 ... Steering part actuator, 21 ... Steering part motor, 22 ... Reduction mechanism, 23 ... Housing, 24 ... Worm shaft (driving gear), 25 ... Worm wheel (driven gear), 26 ... Regulation mechanism, 61 ... Sensor housing, 62 ... Worm housing, 67 ... Projection portion, 65, 75 ... Bearing , 91 ... Base portion, 92 ... Gear portion, 95 ... Extension portion, 97 ... External teeth, 98 ... Groove portion, 98a ... Locking end portion.

Claims (5)

In a steering device having a structure in which a power transmission system between a steering unit and a steering unit that steers steered wheels according to steering input to the steering unit is separable,
The steering section,
A steering shaft to which the steering wheel is connected,
A steering unit actuator capable of applying a steering reaction force that is a force against steering to the steering wheel,
The steering actuator is
A reduction gear having a drive gear that is rotationally driven by a steering motor, and a driven gear that meshes with the drive gear and that rotates integrally with the steering shaft;
A housing that houses the reduction mechanism,
A steering mechanism that mechanically regulates the steering angle of the steering wheel so as not to exceed a threshold angle,
The regulation mechanism is
A groove portion provided in the driven gear and opening in at least one of the steering shaft in the axial direction,
A protrusion provided on the housing and inserted into the groove,
The steering device includes a groove that extends in the circumferential direction of the steering shaft, and has locking end portions on both sides in the circumferential direction that can lock the protrusions. The steering device according to claim 1,
The driven gear is
A metal base part fitted to the steering shaft,
With a resin gear portion provided on the outer periphery of the base portion,
The groove portion is a steering device provided in the gear portion. The steering device according to claim 2,
The base portion is formed with an extension portion extending outward in the radial direction,
The steering device, wherein the extending portion is located between both locking end portions of the groove portion. The steering device according to any one of claims 1 to 3,
The driven teeth of the driven gear are composed of beveled teeth,
The steering device is rotatably supported in the housing via bearings provided adjacent to both sides of the steering shaft in the axial direction in the fitting portion of the driven gear. The steering device according to any one of claims 1 to 4,
A steering device in which the axial range of the driven gear in which the driven teeth are formed and the axial range in which the groove is formed do not overlap.