JP2012040979A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device, which does not give a driver unpleasant feeling, by preventing generation of abnormal sound of a bearing by accurately pressing the bearing, for pivotally supporting an output shaft, into a bearing hole.SOLUTION: Machining is circularly performed for a tool contact face 222 of a cover 22, and a squareness to the bearing hole 221 is processed with the accuracy of 0.05 or less. Accordingly, if a press-in load support tool 71 is brought into contact with the tool contact face 222, and the bearing is pressed into the bearing hole 221 by the bearing press-in tool 72, the bearing is accurately pressed into the bearing hole 221. Consequently, a load in a X-axis direction by rotation of an output axis is not loaded to the output axis. Thereby, the output axis does not cause stick slip to an inner wheel of the bearing, to prevent generation of abnormal sound, and thereby unpleasant feeling is not given to the driver.

Description

  The present invention relates to a steering apparatus, and more particularly to an electric power steering apparatus that drives an electric motor to apply a required steering assist force to a steering gear.

  As shown in Patent Document 1, an electric power steering device drives an electric motor to rotate a worm wheel that meshes with a worm with a required steering assist force, and rotates an output shaft having the worm wheel so that a steering gear is used. The direction of the steering wheel is changed by moving the connected tie rods.

  5 and 6 show such a conventional electric power steering apparatus. FIG. 5 is a longitudinal sectional view of a main part of a conventional electric power steering apparatus, and FIG. 6 is a view taken in the direction of arrow P in FIG. As shown in FIGS. 5 and 6, an inner shaft (input shaft) 12 </ b> B and an output shaft 23 are arranged on the same central axis in the gear housing 21 of the assist device 20 of the electric power steering apparatus, and the output shaft 23 is A bearing (deep groove radial ball bearing) 41 is rotatably supported by the cover 22.

  The cover 22 is attached to the left end surface of the gear housing 21 with a bolt 223 and covers the left open end of the gear housing 21. The inner shaft 12B and the output shaft 23 are connected by a torsion bar 24. The rotation of the output shaft 23 is transmitted to a steering gear (not shown) via the universal joint 15 and the intermediate shaft 16, and the direction of the steered wheels is changed via a tie rod connected to the steering gear.

  A disc-shaped cored bar 52 is press-fitted into an intermediate portion of the output shaft 23, and a worm wheel 51 that meshes with the worm 53 is press-fitted into the outer periphery of the cored bar 52. The worm 53 is driven by the electric motor 25 (see FIG. 6). The right end surface 521 of the cored bar 52 is in contact with the stepped portion 231 of the output shaft 23 to restrict the cored bar 52 from moving to the right side (rear side of the vehicle body) with respect to the output shaft 23. The output shaft 23 is rotatably supported on the cover 22 of the gear housing 21 by a bearing 41 that abuts on the left end surface 522 of the core metal 52.

  The nut 26 screwed into the output shaft 23 sandwiches the inner ring of the bearing 41 with the left end surface 522 of the core metal 52. Further, the outer ring of the bearing 41 is press-fitted into the bearing hole 221 formed in the cover 22 with an interference fit, and is fixed to the cover 22 by a retaining ring 27 inserted into the ring groove of the bearing hole 221.

  The output shaft 23 is rotatably supported on the gear housing 21 by a bearing (deep groove radial ball bearing) 42 on the outer periphery on the right side of the step portion 231. The outer ring of the bearing 42 is press-fitted into a bearing hole 211 formed in the gear housing 21, and the left end surface of the inner ring of the bearing 42 is in contact with the right end surface 521 of the cored bar 52.

  The torsion bar 24 whose right end (end on the rear side of the vehicle body) is press-fitted into the inner shaft 12B is connected to the left end of the output shaft 23 by a pin (not shown) at the left end (end on the front side of the vehicle body). An intermediate portion of the torsion bar 24 is pivotally supported by a bush 29 at the right end of the output shaft 23.

  A torque sensor 61 that detects torque acting on the torsion bar 24 includes a sensor shaft portion 62, detection coils 63 and 64, and a cylindrical member 65. The sensor shaft portion 62 is formed integrally with the right end (the vehicle body rear side end portion) of the output shaft 23, and detection coils 63 and 64 are disposed on a yoke 66 press-fitted inside the gear housing 21. The cylindrical member 65 is disposed in a gap between the outer periphery of the sensor shaft portion 62 and the inner periphery of the detection coils 63 and 64.

  The cylindrical member 65 is fixed to the left end (the vehicle body front side end) of the inner shaft 12B, and the sensor shaft portion 62 is formed with a plurality of ridges extending in the axial direction at equal intervals in the circumferential direction. The cylindrical member 65 is formed with a plurality of rectangular windows at equal intervals in the circumferential direction at positions facing the detection coils 63 and 64.

  When the inner shaft 12 </ b> B rotates by operating a steering wheel (not shown), the rotational force is transmitted to the output shaft 23 via the torsion bar 24. At this time, the torsion bar 24 that connects the inner shaft 12B and the output shaft 23 is twisted due to the resistance on the steering wheel side, and relative rotation occurs between the protrusion on the surface of the sensor shaft portion 62 and the window of the cylindrical member 65. .

  With this relative rotation, the magnetic flux generated in the sensor shaft portion 62 increases and decreases, and the increase and decrease of the magnetic flux is detected by the detection coils 63 and 64 as a change in inductance. From this detection result, torque acting on the torsion bar 24 is detected, and the electric motor 25 is driven to rotate the worm 53 with a required steering assist force. The rotation of the worm 53 is transmitted to the steering gear via the worm wheel 51, the output shaft 23, the universal joint 15, and the intermediate shaft 16, and changes the direction of the steered wheel via a tie rod connected to the steering gear.

  When the conventional electric power steering apparatus configured as described above is driven, the following load is applied to the output shaft 23. That is, the moment load M acting on the universal joint 15, the slide load F2 acting when the intermediate shaft 16 expands and contracts, and the meshing reaction force F1 acting when the rotation of the worm 53 is transmitted to the worm wheel 51. Since these three loads all include the load in the X-axis direction in FIG. 5, the load in the X-axis direction is applied to the output shaft 23.

  When the bearing 41 is press-fitted into the bearing hole 221 of the cover 22, a press-fit load support jig (not shown) that supports the load during press-fitting is applied to the jig contact surface (left end face in FIG. 5) 222 of the cover 22. Make contact. In the conventional electric power steering apparatus, since the jig contact surface 222 is in a cast state, it is difficult to form the squareness of the jig contact surface 222 with respect to the bearing hole 221 with high accuracy. Therefore, when the press-fit load supporting jig is brought into contact with the jig contact surface 222 in the cast state and the bearing 41 is press-fitted into the bearing hole 221, the bearing 41 is inclined and press-fitted with respect to the bearing hole 221. .

  As a result, the vibration during rotation of the output shaft 23 increases, so that the load in the X-axis direction is applied to the output shaft 23 by the rotation of the output shaft 23 and is added to the above-described load in the X-axis direction. Since the output shaft 23 is a clearance fit with respect to the inner ring of the bearing 41, and a slight gap is formed, the output shaft 23 causes stick-slip with respect to the inner ring of the bearing 41, and an abnormal noise is generated. There was a risk of discomfort.

JP 2000-193541 A

  The present invention provides an electric power steering apparatus in which a bearing that supports an output shaft is accurately press-fitted into a bearing hole to prevent generation of abnormal noise in the bearing and to prevent driver discomfort. This is the issue.

  According to a first aspect of the present invention, there is provided a gear housing, an input shaft that is inserted through the gear housing and transmits the rotation of the steering wheel, an output shaft that is connected to the input shaft and transmits the rotation of the input shaft to the wheel side, and the input shaft. An electric motor that applies a predetermined steering assist force to the output shaft according to a detection value of a torque sensor that detects the acting torque, and the output shaft can be rotated by being press-fitted into a bearing hole formed in the gear housing. In the electric power steering apparatus provided with a shaft-supporting bearing, when the bearing is press-fitted into the bearing hole of the gear housing, a jig contact surface on which a press-fit load supporting jig that supports a load at the time of press-fitting comes into contact with the gear housing. This is an electric power steering device characterized by being machined.

  According to a second aspect of the present invention, in the electric power steering apparatus according to the first aspect, the jig contact surface is machined with an accuracy of 0.05 or less with respect to the bearing hole. This is an electric power steering device.

  According to a third aspect, in the electric power steering apparatus according to the second aspect, the jig contact surface is machined into a cover detachably attached to the gear housing. This is an electric power steering device.

  In the electric power steering apparatus of the present invention, when the bearing is press-fitted into the bearing hole of the gear housing, the jig contact surface with which the press-fit load support jig that supports the load during press-fitting is machined into the gear housing. Yes. Therefore, since the bearing that supports the output shaft is accurately press-fitted into the bearing hole, the vibration during rotation of the output shaft is suppressed to be small, and the load in the X-axis direction due to the rotation of the output shaft is suppressed. Therefore, since the output shaft does not cause stick-slip with respect to the inner ring of the bearing, the generation of abnormal noise is prevented and the driver does not feel uncomfortable.

It is the whole electric power steering device of the example of the present invention, and is the whole front view which cut away a part. It is a longitudinal cross-sectional view of the principal part of FIG. It is Q arrow line view of FIG. The cover simple substance of the Example of this invention is shown, (a) is a front view of a cover, (b) is a longitudinal cross-sectional view of (a). It is a longitudinal cross-sectional view of the principal part of the conventional electric power steering device. It is a P arrow view of FIG.

  FIG. 1 shows an entire electric power steering apparatus according to an embodiment of the present invention, and is an overall front view with a part cut away. 2 is a longitudinal sectional view of the main part of FIG. 1, and FIG. 3 is a view taken in the direction of the arrow Q in FIG.

  As shown in FIGS. 1 to 3, the electric power steering apparatus of the present invention includes a steering shaft 12 on which a steering wheel 11 can be mounted on the rear side of the vehicle body (the right side in FIGS. 1 and 2), and the steering shaft 12. A steering column 13 inserted through, an assist device 20 for applying auxiliary torque to the steering shaft 12, and a rack / pinion mechanism (not shown) are provided on the front side of the vehicle body of the steering shaft 12 (left side in FIGS. 1 and 2). And a steering gear 30 connected to each other.

  In the steering shaft 12, an outer shaft 12A and an inner shaft (input shaft) 12B are combined by spline engagement so that rotational force can be transmitted and relative displacement in the axial direction can be achieved. Therefore, when the outer shaft 12A and the inner shaft 12B collide, the spline engaging portion slides relative to each other so that the entire length can be shortened.

  Further, the cylindrical steering column 13 inserted through the steering shaft 12 combines the outer column 13A and the inner column 13B so that they can be telescopically moved. It has a so-called collapsible structure in which the entire length is shortened while absorbing water.

  The vehicle body front side end portion of the inner column 13B is press-fitted and fixed to the vehicle body rear side end portion of the gear housing 21 of the assist device 20. Further, the vehicle body front side end portion of the inner shaft (input shaft) 12B is passed through the inside of the gear housing 21, and is coupled to the vehicle body rear side end portion of the output shaft (female shaft) 23 of the assist device 20.

  The steering column 13 is supported by a support bracket 14 at a middle portion thereof on a part of the vehicle body 18 such as a lower surface of the dashboard. Further, a locking portion (not shown) is provided between the support bracket 14 and the vehicle body 18, and when an impact in a direction toward the front side of the vehicle body is applied to the support bracket 14, the support bracket 14 is locked to the locking bracket 14. It moves away from the vehicle and moves to the front side of the vehicle.

  The upper end portion of the gear housing 21 is also pivotally supported on a part of the vehicle body 18. In this embodiment, the height position of the steering wheel 11 and the longitudinal position of the vehicle body can be freely adjusted by providing a tilt mechanism and a telescopic mechanism. Such a tilt mechanism and a telescopic mechanism are well known in the art and are not characteristic features of the present invention, and thus detailed description thereof is omitted.

  The output shaft 23 protruding from the end face on the front side of the vehicle body of the gear housing 21 is connected to the rear end portion of the intermediate shaft 16 via the universal joint 15. Further, the input shaft 31 of the steering gear 30 is connected to the front end portion of the intermediate shaft 16 via another universal joint 17. A pinion (not shown) is formed at the vehicle body front side end portion of the input shaft 31. A rack (not shown) meshes with the pinion, and the rotation of the steering wheel 11 moves the tie rod 32 to steer a wheel (not shown).

  2 and 3, an inner shaft (input shaft) 12B and an output shaft 23 are arranged on the same central axis in the gear housing 21 of the assist device 20, and the output shaft 23 is a bearing (groove-shaped radial). A ball bearing 41 is rotatably supported on the cover 22. The cover 22 is attached to the left end surface of the gear housing 21 with a bolt 223 and covers the left open end of the gear housing 21. The inner shaft 12B and the output shaft 23 are connected by a torsion bar 24.

  A disc-shaped cored bar 52 is press-fitted into an intermediate portion of the output shaft 23, and a worm wheel 51 that meshes with the worm 53 is press-fitted into the outer periphery of the cored bar 52. As shown in FIG. 1, a case 251 of the electric motor 25 is fixed to the gear housing 21, and a worm 53 is connected to an output shaft of the electric motor 25.

  The right end surface 521 of the cored bar 52 is in contact with the stepped portion 231 of the output shaft 23 to restrict the cored bar 52 from moving to the right side (rear side of the vehicle body) with respect to the output shaft 23. The output shaft 23 is rotatably supported on the cover 22 of the gear housing 21 by a bearing (deep groove radial ball bearing) 41 that contacts the left end surface 522 of the core metal 52.

  The nut 26 screwed into the output shaft 23 sandwiches the inner ring of the bearing 41 with the left end surface 522 of the core metal 52. Further, the outer ring of the bearing 41 is press-fitted into the bearing hole 221 formed in the cover 22 with an interference fit, and is fixed to the cover 22 by a retaining ring 27 inserted into the ring groove of the bearing hole 221.

  As shown in FIGS. 2 and 4, the jig contact surface 222 of the cover 22 is machined in an annular shape, and is machined with an accuracy of a squareness of 0.05 or less with respect to the bearing hole 221. Therefore, if the press-fit load support jig 71 is brought into contact with the jig contact surface 222 and the bearing 42 is press-fitted into the bearing hole 221 with the bearing press-fit jig 72, the bearing 42 can be press-fitted into the bearing hole 221 with high accuracy. .

  The output shaft 23 is rotatably supported on the gear housing 21 by a bearing (deep groove radial ball bearing) 42 on the outer periphery on the right side of the step portion 231. The outer ring of the bearing 42 is press-fitted into a bearing hole 211 formed in the gear housing 21, and the left end surface of the inner ring of the bearing 42 is in contact with the right end surface 521 of the cored bar 52.

  The torsion bar 24 whose right end (end on the rear side of the vehicle body) is press-fitted into the inner shaft 12B is connected to the left end of the output shaft 23 by a pin (not shown) at the left end (end on the front side of the vehicle body). An intermediate portion of the torsion bar 24 is pivotally supported by a bush 29 at the right end of the output shaft 23.

  A torque sensor 61 that detects torque acting on the torsion bar 24 includes a sensor shaft portion 62, detection coils 63 and 64, and a cylindrical member 65. The sensor shaft portion 62 is formed integrally with the right end (the vehicle body rear side end portion) of the output shaft 23, and detection coils 63 and 64 are disposed on a yoke 66 press-fitted inside the gear housing 21. The cylindrical member 65 is disposed in a gap between the outer periphery of the sensor shaft portion 62 and the inner periphery of the detection coils 63 and 64.

  The cylindrical member 65 is fixed to the left end (the vehicle body front side end) of the inner shaft 12B, and the sensor shaft portion 62 is formed with a plurality of ridges extending in the axial direction at equal intervals in the circumferential direction. The cylindrical member 65 is formed with a plurality of rectangular windows at equal intervals in the circumferential direction at positions facing the detection coils 63 and 64.

  When the inner shaft 12 </ b> B rotates by operating the steering wheel 11, the rotational force is transmitted to the output shaft 23 via the torsion bar 24. At this time, the torsion bar 24 that connects the inner shaft 12B and the output shaft 23 is twisted due to the resistance on the steering wheel side, and relative rotation occurs between the protrusion on the surface of the sensor shaft portion 62 and the window of the cylindrical member 65. .

  With this relative rotation, the magnetic flux generated in the sensor shaft portion 62 increases and decreases, and the increase and decrease of the magnetic flux is detected by the detection coils 63 and 64 as a change in inductance. From this detection result, torque acting on the torsion bar 24 is detected, and the electric motor 25 is driven to rotate the worm 53 with a required steering assist force. The rotation of the worm 53 is transmitted to the steering gear 30 via the worm wheel 51, the output shaft 23, the universal joint 15, and the intermediate shaft 16, and changes the direction of the steered wheel via the tie rod 32 connected to the steering gear 30.

  In the embodiment of the present invention, the moment load M acting on the universal joint 15, the slide load F <b> 2 acting when the intermediate shaft 16 expands and contracts, and the meshing reaction force F <b> 1 acting when the rotation of the worm 53 is transmitted to the worm wheel 51. Due to these three loads, the load in the X-axis direction in FIG. 2 is applied to the output shaft 23. However, since the bearing 41 is press-fitted with high precision into the bearing hole 221, vibration during rotation of the output shaft 23 can be suppressed small. Therefore, the load in the X-axis direction due to the rotation of the output shaft 23 is suppressed. Therefore, since the output shaft 23 does not cause stick-slip with respect to the inner ring of the bearing 41, the generation of abnormal noise is prevented and the driver is not uncomfortable.

DESCRIPTION OF SYMBOLS 11 Steering wheel 12 Steering shaft 12A Outer shaft 12B Inner shaft 13 Steering column 13A Outer column 13B Inner column 14 Support bracket 15 Universal joint 16 Intermediate shaft 17 Universal joint 18 Car body 20 Assist device 21 Gear housing 211 Bearing hole 22 Cover 221 Bearing hole 222 Jig contact surface 223 Bolt 23 Output shaft 231 Step portion 24 Torsion bar 25 Electric motor 251 Case 26 Nut 27 Retaining ring 29 Bush 30 Steering gear 31 Input shaft 32 Tie rod 41 Bearing (Deep groove radial ball bearing)
42 Bearing (Deep groove radial ball bearing)
51 Worm wheel 52 Core metal 521 Right end surface 522 Left end surface 53 Worm 61 Torque sensor 62 Sensor shaft portion 63, 64 Detection coil 65 Cylindrical member 66 Yoke 71 Press-fit load support jig 72 Bearing press-fit jig

Claims (3)

Gear housing,
An input shaft that is inserted into the gear housing and transmits the rotation of the steering wheel;
An output shaft connected to the input shaft for transmitting the rotation of the input shaft to the wheel side;
An electric motor that applies a predetermined steering assist force to the output shaft in accordance with a detection value of a torque sensor that detects torque acting on the input shaft;
In the electric power steering apparatus including a bearing press-fitted into a bearing hole formed in the gear housing and rotatably supporting the output shaft,
An electric power steering device machined on a jig contact surface of a gear housing that a press-fit load support jig for supporting a load at the time of press-fit contacts when the bearing is press-fitted into the bearing hole of the gear housing. . In the electric power steering apparatus according to claim 1,
The jig contact surface is
An electric power steering apparatus, wherein the perpendicularity to the bearing hole is processed with an accuracy of 0.05 or less. In the electric power steering apparatus according to claim 2,
The jig contact surface is
An electric power steering apparatus, wherein a jig contact surface of a cover detachably attached to the gear housing is machined.

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