Steering device

Abstract

A steering device (10) comprises: a steering shaft that rotates by operation of a driver; a housing (60) that rotatably supports the steering shaft; and a magnet, a magnetic flux sensing unit, and a partition member that are housed in the housing. The housing includes a housing body and a cover. The cover is a magnetic body. The magnet and the magnetic flux sensing unit are configured such that the magnetic flux of the magnet sensed by the magnetic flux sensing unit changes in accordance with rotational operation of the steering shaft by the driver. The partition member is a member partitioning the space in the housing into a first space and a second space, and is a magnetic body. The cover and the partition member are magnetically coupled to each other on the radially outer side of the steering shaft relative to the magnet and the magnetic flux sensing unit.

Description

Steering gear

[0001] The present disclosure relates to a steering device.

[0002] For example, Patent Document 1 listed below describes a steering device equipped with a sensor device that detects steering torque according to the degree of torsion of a torsion bar. This steering device is housed in a housing. The housing includes a housing body and a cover. A partition member is provided inside the housing. The sensor device is housed in a space within the housing that is partitioned by the cover and the partition member.

[0003] Japanese Patent Application Laid-Open No. 2023-132532

[0004] However, during the manufacture of a vehicle, on-board components may become magnetized, and the magnetic field from the on-board components may enter the sensor device, causing an error in the detected value by the sensor device.

[0005] One aspect of the present disclosure provides a steering device. The steering device includes a steering shaft that rotates when operated by a driver, a housing that rotatably supports the steering shaft, a magnet housed in the housing, a magnetic flux sensing unit housed in the housing, and a partition member housed in the housing. The housing includes a housing main body and a cover. The cover is made of a magnetic material. The magnet and the magnetic flux sensing unit are configured so that the magnetic flux of the magnet sensed by the magnetic flux sensing unit changes in response to the rotation of the steering shaft by the driver. The partition member is a magnetic material and separates the space within the housing into a first space including the magnet and the magnetic flux sensing unit and a second space other than the first space. The first space is partitioned by the cover and the partition member. The cover and the partition member are magnetically coupled to each other at a position radially outward of the steering shaft relative to the magnet and the magnetic flux sensing unit.

[0006] Fig. 3 is a schematic configuration diagram of an electric power steering device according to a first embodiment. Fig. 4 is an enlarged cross-sectional view of the vicinity of a sensor device in the electric power steering device shown in Fig. 1. Fig. 5 is an exploded perspective view of the sensor device and its peripheral components shown in Fig. 2. Fig. 6 is an enlarged cross-sectional view of the vicinity of the sensor device in the electric power steering device shown in Fig. 1. Fig. 7 is a diagram for explaining the action of the sensor device shown in Fig. 2. Fig. 8 is an enlarged cross-sectional view of the vicinity of the sensor device in the electric power steering device according to a second embodiment. Fig. 9 is an enlarged cross-sectional view of the vicinity of the sensor device in the electric power steering device according to a third embodiment.

[0007] <First embodiment> A first embodiment will be described below with reference to the drawings. "Overall configuration" As shown in FIG. 1, an electric power steering device 10 as a steering device includes a column shaft 20 constituting a steering axis, and a steering column 30 that rotatably houses the column shaft 20. The column shaft 20 and the steering column 30 are arranged on a common axis L. The steering column 30 is mounted on a vehicle so as to extend generally along the longitudinal direction of the vehicle. In the following description, the left side in FIG. 1 is the front side of the vehicle, and the right side in FIG. 1 is the rear side of the vehicle. Furthermore, directions expressed by terms such as "front," "rear," "up," "down," "left," and "right" are defined relative to the vehicle.

[0008] A steering wheel 16 is connected to the rear end of the column shaft 20. An intermediate shaft and a pinion shaft (neither of which are shown) that form a steering shaft are connected to the front end of the column shaft 20. The pinion shaft is connected to the steered wheels via a rack shaft. This allows the steered wheels to turn in response to the driver's steering operation.

[0009] The electric power steering device 10 also includes an electric actuator 40. The electric actuator 40 includes a motor 42 and a reducer 44. The rotation of the motor 42 is reduced by the reducer 44 and transmitted to the column shaft 20. In this way, the electric actuator 40 applies an assist force to assist the steering operation by the driver. The reducer 44 in this embodiment is a worm reducer having a worm shaft 44a and a worm wheel 44b, but is not limited to this and any other reducer may be used.

[0010] The column shaft 20 includes an upper shaft 22 and a lower shaft 24. The upper shaft 22 has, for example, an elongated cylindrical shape. The steering wheel 16 is connected to the rear end of the upper shaft 22. The upper shaft 22 has, for example, a circular shape when viewed in the axial direction.

[0011] The lower shaft 24 includes an input shaft 24 a, an output shaft 24 b, and a torsion bar 24 c that connects the input shaft 24 a and the output shaft 24 b to each other. The input shaft 24 a has, for example, an elongated cylindrical shape. The input shaft 24 a is connected to the upper shaft 22 so as to be rotatable together with the upper shaft 22 and to be movable in the axial direction relative to the upper shaft 22.

[0012] The output shaft 24b has, for example, an elongated cylindrical shape. As an example, the output shaft 24b has a circular shape when viewed in the axial direction. The front end of the input shaft 24a is inserted into the rear end of the output shaft 24b. A bearing 50 is provided between the outer circumferential surface of the front end of the input shaft 24a and the inner circumferential surface of the rear end of the output shaft 24b. This allows the output shaft 24b to rotatably support the input shaft 24a. A worm wheel 44b is fixed to the outer periphery of the output shaft 24b.

[0013] The torsion bar 24c has, for example, an elongated cylindrical shape. The rear end of the torsion bar 24c is connected to the input shaft 24a so as to be rotatable together with the input shaft 24a. The front end of the torsion bar 24c is fitted onto the inner periphery of the front end of the output shaft 24b, thereby being connected to the output shaft 24b so as to be rotatable together with the output shaft 24b. As a result, the input shaft 24a and the output shaft 24b rotate relative to each other by twisting the torsion bar 24c.

[0014] The steering column 30 includes an outer tube 30a, an inner tube 30b, and a housing 60. The outer tube 30a is cylindrical. The outer tube 30a rotatably supports the upper shaft 22. The inner tube 30b is cylindrical and thinner than the outer tube 30a. The outer tube 30a and the inner tube 30b have, for example, a circular shape when viewed in the axial direction. The rear end of the inner tube 30b is fitted into the inner periphery of the outer tube 30a. The front end of the inner tube 30b is fixed to the housing 60.

[0015] Details of the Interior of the Housing As shown in FIG. 2, the housing 60 includes a housing body 62 and a cover 64 .

[0016] The housing body 62 has a cylindrical shape. As an example, the housing body 62 has a circular shape when viewed in the axial direction. The housing body 62 has an end wall at one axial end thereof. In the example shown, the end wall is provided at the front end of the housing body 62. The end wall of the housing body 62 has a through-hole 62a that penetrates in the axial direction. The housing body 62 is made of a non-magnetic material. The housing body 62 may be made of, for example, resin.

[0017] The cover 64 is disk-shaped. The cover 64 is fixed to the rear end of the housing main body 62 so as to cover the opening of the housing main body 62. The cover 64 has a through-hole 64a that penetrates in the axial direction. The cover 64 is made of a magnetic material. It is desirable that the material of the cover 64 has sufficient strength. As an example, the cover 64 may be made of a steel plate.

[0018] A partition member 70 is disposed within the space defined by the housing 60. The partition member 70 has a disk-shaped main body 72 that is perpendicular to the axial direction of the column shaft 20, for example. The partition member 70 is fixed to the inner circumferential surface of the housing main body 62 by press fitting, for example. The partition member 70 thereby divides the space within the housing main body 62 into two spaces: a first space and a second space. The first space is a reducer accommodating space S1 located on the front side. The second space is a sensor accommodating space S2 located on the rear side. The reducer accommodating space S1 and the sensor accommodating space S2 are arranged side by side in the axial direction of the column shaft 20. In other words, the partition member 70 divides the internal space of the housing 60 in the axial direction so that the reducer accommodating space S1 and the sensor accommodating space S2 are arranged side by side in the axial direction of the column shaft 20. The reducer 44 is accommodated in the reducer accommodating space S1, and the sensor device 90 is accommodated in the sensor accommodating space S2. The sensor device 90 outputs a signal for detecting the steering torque, which is the torque input to the steering shaft via the steering wheel 16. The steering torque corresponds to a state quantity that indicates the steering state. The reducer housing space S1 is filled with grease.

[0019] The partition member 70 is made of a magnetic material. It is desirable that the material of the partition member 70 has sufficient strength. As an example, the partition member 70 may be made of a steel plate. The main body portion 72 of the partition member 70 has a through hole 74 that penetrates in the axial direction of the column shaft 20. The through hole 74 is provided in the center of the main body portion 72. As a result, the through holes 62a, 64a, and 74 are all provided on the axis L. The housing 60 of this embodiment rotatably supports the output shaft 24b via bearings 80 and 82 provided in the through holes 62a and 74. The bearing 82 is supported by the partition member 70. In other words, a radially inward force is applied to the bearing 82 by the partition member 70.

[0020] As shown in Figure 3, the main body 72 of the partition member 70 has mounting holes 76 that penetrate in the axial direction of the column shaft 20. The mounting holes 76 are, for example, circular holes. The partition member 70 of this embodiment has, for example, three mounting holes 76, but the number may be one and can be changed as appropriate. Furthermore, the mounting holes 76 are provided on the outer periphery side of the through-hole 74, for example, at equal angular intervals in the circumferential direction, but their arrangement can be changed as appropriate.

[0021] Details of the Sensor Device 90 As shown in FIGS. 2 and 3, the sensor device 90 includes a sensor magnet 92, a magnetic yoke assembly 100, and a fixing unit 110.

[0022] The sensor magnet 92 is a ring magnet that has a circular cylindrical shape when viewed in the axial direction. The sensor magnet 92 is magnetized in the radial direction so that magnetic poles of different polarities are alternately arranged in the circumferential direction. The sensor device 90 of this embodiment includes a magnet holder 94, and the sensor magnet 92 is fixed to the outer circumferential surface of the input shaft 24a via the magnet holder 94. In another embodiment, the sensor magnet 92 may be fixed directly to the outer circumferential surface of the input shaft 24a. In another embodiment, the sensor magnet 92 may be a plurality of plate-shaped magnets.

[0023] As shown in FIG. 3, the magnetic yoke assembly 100 includes a pair of yoke cores 102 and 104, a collar 106, and a holder 108 that holds the pair of yoke cores 102 and 104 and the collar 106.

[0024] The yoke cores 102, 104 are made of magnetic material. Each of the yoke cores 102, 104 is annular. The yoke cores 102, 104 are arranged at intervals in the axial direction. Each of the yoke cores 102, 104 has a plurality of claw portions. The claw portions protrude in a direction approaching each other. The claw portions are provided at equal intervals in the circumferential direction, and the claw portions of the yoke core 102 and the claw portions of the yoke core 104 are arranged alternately in the circumferential direction. Each of the yoke cores 102, 104 has, for example, a circular shape when viewed in the axial direction.

[0025] The collar 106 is made of a magnetic material. The collar 106 is made of, for example, a metal material and has an annular shape. As an example, the collar 106 has a circular shape when viewed in the axial direction. The collar 106 is disposed axially forward of the pair of yoke cores 102, 104. The collar 106 is fitted onto the outer periphery of the rear end of the output shaft 24b.

[0026] The holder 108 is made of, for example, a resin material and has a cylindrical shape. When viewed in the axial direction, the holder 108 has, for example, a circular shape. The axial direction of the holder 108 coincides with the direction along the axis L. For example, the holder 108 is integrated with the pair of yoke cores 102, 104 and the collar 106 by insert molding. In another embodiment, the holder 108 may be molded as a single unit, and then the yoke cores 102, 104 and the collar 106 may be assembled to the holder 108. The holder 108 holds the pair of yoke cores 102, 104 and the collar 106 on the axis L. Specifically, the holder 108 holds the yoke cores 102, 104 so that the inner surfaces of the claws are exposed on the inner periphery of the holder 108, and holds the collar 106 so that the inner periphery of the collar 106 is exposed on the inner periphery of the holder 108.

[0027] The magnetic yoke assembly 100 is fixed to the output shaft 24b so as to be rotatable together with the output shaft 24b by press-fitting the collar 106 onto the rear end of the output shaft 24b. With the magnetic yoke assembly 100 fixed to the output shaft 24b, the magnetic yoke assembly 100 is disposed on the outer circumferential side of the sensor magnet 92 with a gap therebetween.

[0028] 3, the fixed unit 110 includes a pair of magnetic flux collecting members 112, 114, a circuit board 116, and a frame 120. A magnetic sensor 130 is mounted on the circuit board 116 as a magnetic sensing unit that generates a signal corresponding to the magnetic flux flowing through the pair of magnetic flux collecting members 112, 114. The signal output from the magnetic sensor 130 corresponds to the steering torque.

[0029] The frame 120 includes a first support frame 122 and a second support frame 124. The first support frame 122 includes an annular first frame portion 122a and a cover portion 122b. The first frame portion 122a holds the magnetic flux collector 112 so that the inner peripheral surface of the magnetic flux collector 112 is exposed to the inner peripheral side of the first support frame 122. The cover portion 122b is provided radially outward from the first frame portion 122a. The cover portion 122b has a shape corresponding to the support portion 124b and connector portion 124c of the second support frame 124, which will be described later. The first support frame 122 is fixed to the second support frame 124 so that the cover portion 122b covers the support portion 124b and connector portion 124c.

[0030] The second support frame 124 has an annular second frame portion 124a, a support portion 124b, a connector portion 124c, and a seat portion 124d. The second frame portion 124a holds the magnetic flux collector 114 so that the inner peripheral surface of the magnetic flux collector 114 is exposed to the inner peripheral side of the second support frame 124. The support portion 124b is provided radially outward from the second frame portion 124a. The support portion 124b supports the circuit board 116. The connector portion 124c is provided radially outward from the second frame portion 124a so as to be aligned circumferentially with the support portion 124b. The connector portion 124c is configured to be connectable to a connector of a wire harness.

[0031] As shown in FIG. 3 , the second support frame 124 has, for example, three seats 124d. In another embodiment, the number of seats 124d may be one, and this number can be changed as appropriate. The seats 124d are provided at a position that protrudes forward from the radially outer portion of the second frame portion 124a relative to other portions of the second support frame 124. The seats 124d are provided, for example, at equal angular intervals in the circumferential direction, but their arrangement can be changed as appropriate. The seats 124d have a flat plate shape that is perpendicular to the axial direction and abuts against the main body portion 72 of the partition member 70 from the rear side. The seats 124d have seat holes 124e that penetrate in the axial direction.

[0032] The second support frame 124 is disposed such that the seat hole 124e faces the mounting hole 76 of the partition member 70. The magnetic flux collectors 112, 114 are made of magnetic material. Each of the magnetic flux collectors 112, 114 is C-shaped. The magnetic flux collector 112 has two protrusions 112a protruding in the radial direction, and the magnetic flux collector 114 has two protrusions 114a protruding in the radial direction. The magnetic flux collector 112 is held by the first frame portion 122a of the first support frame 122, and is disposed at a distance from the outer periphery of the yoke core 102. The magnetic flux collector 114 is held by the second frame portion 124a of the second support frame 124, and is disposed at a distance from the outer periphery of the yoke core 104. In other words, the magnetic flux collectors 112, 114 are disposed at a distance from each other in the axial direction. The magnetic flux flowing through the yoke core 102 is induced in the magnetic flux collecting member 112, and the magnetic flux flowing through the yoke core 104 is induced in the magnetic flux collecting member 114. The protrusions 112a and 114a face each other in the axial direction.

[0033] The circuit board 116 is flat and has an outline corresponding to the shapes of the support portion 124b and connector portion 124c of the second support frame 124 when viewed in the axial direction. Various circuit elements including the magnetic sensor 130 are mounted on the circuit board 116. The circuit board 116 is supported by the support portion 124b of the second support frame 124. The circuit board 116 is covered from the rear by the cover portion 122b of the first support frame 122.

[0034] The magnetic sensor 130 is, for example, a Hall sensor or a magnetoresistive sensor, and is mounted on the circuit board 116 in an area sandwiched between the protrusions 112a and 114a, as shown in FIG.

[0035] Here, the sensor magnet 92 rotates integrally with the input shaft 24a, and the magnetic yoke assembly 100 rotates integrally with the output shaft 24b. When the driver operates the steering wheel 16 to rotate the steering shaft, the torsion bar 24c twists, causing the input shaft 24a and the output shaft 24b to rotate relative to each other. This changes the relative circumferential position of the sensor magnet 92 and the magnetic yoke assembly 100. This causes the magnetic flux flowing through the yoke cores 102 and 104 to change in accordance with the amount of twist of the torsion bar 24c, i.e., the magnitude of the steering torque input by the driver. As a result, the magnetic flux flowing through the magnetic flux collectors 112 and 114 also changes in accordance with the change in the magnetic flux flowing through the yoke cores 102 and 104. The magnetic sensor 130 detects the magnetic flux flowing through the magnetic flux collectors 112 and 114 and generates a signal corresponding to this magnetic flux, i.e., a signal indicating the steering torque.

[0036] The fixed unit 110 is fixed to the partition member 70 by inserting a bolt 77 into the seat hole 124e of the fixed unit 110 and the mounting hole 76 of the partition member 70. The bolt 77 is made of a magnetic material.

[0037] "Countermeasures against magnetic noise in the sensor device 90" As shown in Fig. 4, the partition member 70 and the cover 64 are magnetically coupled by a magnetic shield 140 made of a magnetic material. In other words, a continuous path connecting the partition member 70 and the cover 60 is formed of the magnetic material. The magnetic shield 140 is, for example, a closed-loop member. In other words, the magnetic shield 140 is a ring-shaped member. As shown in Fig. 3, the magnetic shield 140 is an annular member with the axis L as the center of rotation.

[0038] More specifically, the partition member 70 and the cover 64 are magnetically coupled to each other at a position radially outward of the sensor magnet 92 and the magnetic sensor 130 in the steering shaft direction. Specifically, the partition member 70 is magnetically coupled to the cover 64 via a bolt 77 and a magnetic shield 140. The magnetic shield 140 may be fastened together with the partition member 70 by, for example, a collar 106.

[0039] [Operations and Effects of the Present Embodiment] When an on-board component is magnetized during the manufacture of the vehicle, magnetic flux from the on-board component enters the sensor device 90 via the steering shaft.

[0040] 5 schematically shows the path of magnetic flux when the magnetic shield 140 is not provided. As shown in FIG. 5, the magnetic flux not only flows from the output shaft 24b through the magnetic yoke assembly 100 to the magnetic flux collector members 112, 114, as indicated by the hatched arrows, but also flows from the output shaft 24b through the magnetic yoke assembly 100 to the magnetic flux collector members 112, 114, as indicated by the hollow arrows. These magnetic fluxes cause a difference in magnetic flux density between the pair of magnetic flux collector members 112, 114. This difference may cause the steering torque corresponding to the detection value of the magnetic sensor 130 to deviate from the actual steering torque.

[0041] In contrast, in this embodiment, the partition member 70 and the cover 64 are magnetically coupled by the magnetic shield 140. Therefore, it is possible to increase the magnetic flux that has entered the steering shaft and flows out to the partition member 70, the bolt 77, the magnetic shield 140, and the cover 64 without flowing to the pair of magnetic flux collecting members 112, 114. Therefore, it is possible to reduce the amount of magnetic flux that has entered the steering shaft and flows to the pair of magnetic flux collecting members 112, 114.

[0042] Here, the partition member 70 not only serves to separate the reducer accommodating space S1 and the sensor accommodating space S2, but also serves to fix the bearing 82 by being press-fitted into the housing 60. A magnetic material is used to ensure the strength required for this function. A magnetic material is also used for the cover 64 from the perspective of ensuring strength. In this embodiment, the cover 64 and the partition member 70, which are made of magnetic materials for a different reason, are used to form a magnetic flux flow path, thereby making it possible to suppress an increase in the number of parts.

[0043] Furthermore, by providing the magnetic shield 140, it is possible to magnetically couple the cover 64 and the partition member 70 while minimizing changes to the design of existing parts. Second Embodiment Hereinafter, a second embodiment will be described with reference to the drawings, focusing on differences from the first embodiment.

[0044] FIG. 6 shows an enlarged cross-sectional view of the vicinity of the sensor device 90 according to this embodiment. In FIG. 6, the same reference numerals are used for the components shown in FIG. 2 for convenience. As shown in FIG. 6, this embodiment does not include a magnetic shield 140. Instead, in this embodiment, a partition member 70 is configured to come into contact with the cover 64. More specifically, the partition member 70 extends in the axial direction of the steering shaft so as to come into contact with the cover 64 over the entire circumference on the radially outer side of the steering shaft. As an example, the inner and outer peripheries of the contact surface of the partition member 70 with the cover 64 are both circles with the axis L as the center of rotation.

[0045] "Operations and Effects of Second Embodiment" As described above, in this embodiment, the partition member 70 is configured to contact the cover 64. This makes it possible to magnetically couple the partition member 70 and the cover 64 while suppressing an increase in the number of parts.

[0046] Third Embodiment A second embodiment will be described below with reference to the drawings, focusing on differences from the first embodiment.

[0047] Fig. 7 shows an enlarged cross-sectional view of the vicinity of the sensor device 90 according to this embodiment. In Fig. 7, the same reference numerals are used for the components shown in Fig. 2 for convenience. As shown in Fig. 7, this embodiment is configured so that the bolt 77 comes into contact with the cover 64. In this case, the collar 106 may also come into contact with the cover 64.

[0048] <Other Embodiments> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0049] Regarding magnetic noise countermeasures, the magnetic shield 140 is not limited to a closed-loop member. For example, it may be a member whose cross section perpendicular to the axis L is C-shaped.

[0050] In the second embodiment, it is not essential that the partition member 70 contacts the cover 64 over the entire periphery. For example, the partition member 70 may be configured to contact the cover 64 intermittently in the circumferential direction of the cover 64.

[0051] Regarding the magnet and magnetic flux sensing unit: The magnet and magnetic flux sensing unit are not limited to the sensor magnet 92 and magnetic sensor 130 for detecting steering torque. For example, they may be components constituting a sensor for detecting the rotation angle of the steering shaft. In other words, the state quantity indicating the steering state according to the rotation operation of the steering shaft by the driver may be the rotation angle of the steering shaft.

[0052] Regarding the sensor device 90: It is not essential that the sensor device 90 detect the steering torque. The sensor device 90 may be a device that detects the rotation angle of the steering shaft, as described in the section "Regarding the magnet and magnetic flux sensing unit." Furthermore, the sensor device 90 may be a device that detects both the rotation angle of the steering shaft and the steering torque, for example.

[0053] Regarding the steering device: The steering device is not limited to a device in which the steering wheel 16 and the steered wheels are mechanically connected. For example, it may be a steer-by-wire device in which the power transmission between the steering shaft and the steered wheels is cut off. In that case, if a device is provided that detects at least one of the torque applied to the steering shaft and the rotation angle of the steering shaft, the device may be disposed between the partition member 70 and the cover 64 in the same manner as in the above embodiment.

Claims

1. A steering device comprising: a steering shaft that rotates when operated by a driver; a housing that rotatably supports the steering shaft; a magnet housed in the housing; a magnetic flux sensing unit housed in the housing; and a partition member housed in the housing, wherein the housing comprises a housing main body and a cover, the cover being a magnetic body, the magnet and the magnetic flux sensing unit being configured so that the magnetic flux of the magnet sensed by the magnetic flux sensing unit changes in response to the rotation of the steering shaft by the driver, the partition member being a magnetic body and a member that separates the space within the housing into a first space including the magnet and the magnetic flux sensing unit and a second space that is the other space, the first space being partitioned by the cover and the partition member, and the cover and the partition member being magnetically coupled radially outward of the steering shaft than the magnet and the magnetic flux sensing unit.

2. A steering device according to claim 1, wherein said housing body is made of a non-magnetic material.

3. A steering device according to claim 1, further comprising a magnetic shield made of a magnetic material, said magnetic shield being configured to magnetically couple said cover and said partition member.

4. A steering device according to claim 3, wherein a bolt is inserted into the partition member, and the magnetic shield is disposed so as to contact the bolt and the cover.

5. A steering device according to claim 1, wherein the partition member is configured to come into contact with the cover.

6. A steering device according to claim 1, wherein a bolt is inserted into the partition member, and the bolt is arranged so as to come into contact with the cover.

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