JP2009006916A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure for mounting an angle sensor of an electric power steering device suppressing accuracy error of a sensor driving gear connected to a sensor gear and a steering wheel and gearing noises caused by dispersion in assembling. <P>SOLUTION: In the electric power steering device, an eccentric part of an elastic body ring 25 is mounted to a bearing part 20a of the angle sensor 20 to be placed on the opposite side (farther side) against the worm wheel 19 side and the whole angle sensor 20 is drawn to the outside direction from a center line of an output shaft (column shaft). After adjusting the sensor driving gear 19d and the sensor gear 22 of the worm wheel 19 to deeply gear each other, a bolt 24 is inserted to a mounting bracket 23 and the angle sensor 20 is fixed to a housing 11a. Deep gearing of the sensor gear 22 and the sensor driving gear 19d can suppress the gearing noises caused by backlash. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric power steering apparatus equipped with an angle sensor for detecting a rotation angle of a steering shaft, and more particularly to an attachment structure for attaching an angle sensor to an electric power steering apparatus.

  An electric power steering device for a vehicle that is currently widely used detects a steering torque generated in a steering shaft when a steering wheel is operated by a driver, controls an electric motor based on the detection signal, and reduces a speed reduction mechanism. Some are configured to assist the steering force by rotating the steering shaft.

  The above-described control of the electric motor is executed by an electronic control circuit constituted by a CPU. Based on a steering torque signal, a vehicle speed signal, and other signals, a current command value that determines the output of the electric motor is calculated. Various correction values are added to the calculated current command value and output as a current control value. Then, the motor current is controlled to ON / OFF by the duty ratio D determined based on the current control value to control the electric motor, the motor current flowing through the electric motor is detected, and the difference from the current control becomes zero. Thus, feedback control is performed.

  In the electronic control circuit described above, it is necessary to know the steering angle of the steering shaft so that optimum steering characteristics can be obtained corresponding to various driving conditions of the vehicle. Various means have been proposed as means for knowing the steering angle, but a slit disk provided with a number of slits at a fixed angle is attached to the steering shaft, and the slits on the slit disk are optically detected and counted. An angle sensor is known (see Patent Document 1).

  FIG. 7 is a perspective view illustrating an example of the configuration of the angle sensor 100 described above. In FIG. 7, reference numeral 101 denotes a steering shaft, which is not shown, but a steering wheel is attached to one end thereof, and a pinion of a steering mechanism is attached to the other end. Reference numeral 102 denotes a slit disk attached to the steering shaft 101, which is provided with a plurality of slits 103 at a predetermined angle (for example, 0.2 degree or 1.0 degree), and a slit indicating a steering neutral position. 112 is provided.

  In order to count the rotation direction and the number of rotations of the slit disk 102, two photocouplers 104 and 105 are arranged with the slit 103 of the slit disk 102 interposed therebetween, and the photocoupler 105 is connected to the photocoupler 104. Are arranged at a position shifted by 1/4 pitch. Each of the photocouplers 104 and 105 includes a phototransistor and a light-emitting diode, and light projected from the light-emitting diode passes through the slit 103 of the slit disk 102 and enters a phototransistor disposed on the opposite side to generate a pulse signal. Is output.

  The rotation direction of the slit disk 102 is detected from the phase shift between the pulse signal output from the photocoupler 104 and the pulse signal output from the photocoupler 105, and the pulse signal output from the photocoupler 104 (or 105). It is possible to detect the angle position of the steering angle.

  Further, in order to detect the slit 112 of the slit disk 102 indicating the steering neutral position, a photocoupler 113 is disposed across the slit 112 of the slit disk 102, and the slit 112 formed at a position where the steering angle is zero. Can be detected by the photocoupler 113, and the steering neutral position can be detected.

  In the angle sensor 100 described above, a slit disk is directly attached to the steering shaft. However, this configuration is not desirable because the configuration of the steering shaft is complicated. Therefore, the above-described angle sensor has an independent configuration in which a sensor gear is provided on the rotation axis of the slit disk and the rotation of the slit disk is detected by a photocoupler.

  On the other hand, a sensor drive gear for driving the sensor gear is provided on a worm wheel of a steering mechanism coupled to a steering shaft of an electric power steering device, and the sensor drive gear and the sensor gear are engaged with each other to rotate the worm wheel, that is, steering. A configuration has been proposed in which the rotation of the shaft is detected (see Patent Document 2).

  FIG. 8 is a view for explaining the cross-sectional shape of the worm wheel constituting the speed reduction mechanism of the electric power steering apparatus and the configuration in the vicinity of the sensor gear of the angle sensor having the independent configuration described above. FIG. And FIG. 8B is a partial cross-sectional view of the vicinity of the sensor drive gear mounting portion of the worm wheel.

  The worm wheel 121 is subjected to cross roulette processing or the like on the outer peripheral surface of a metal core 122, and a cylindrical resin portion 123 integrally formed with synthetic resin is provided on the processed surface, and a worm gear speed reduction (not shown) is provided on the outer peripheral surface. Worm wheel teeth 124 are formed that mesh with the worm of the mechanism. Further, a sensor drive gear (internal gear) 126 formed of a synthetic resin meshing with the sensor gear is attached to the inner peripheral surface of the cored bar 122 on the worm wheel 121.

  The angle sensor 131 has a sensor gear 133 attached to one end of a rotary shaft 132 to which a slit disk (not shown) is attached, and is engaged with the sensor drive gear (internal gear) 126.

With the above configuration, rotation of the worm wheel 121 connected to the steering shaft rotates the sensor gear 133 via the sensor drive gear (internal gear) 126, and the rotation angle of the steering shaft is detected by the angle sensor 131. .
Japanese Patent Publication No. 3-61886. Japanese Patent Application Laid-Open No. 2004-161150.

  However, in the above-described configuration, when the sensor drive gear 126 and the sensor gear 133 mesh with each other, the backlash between the meshing gears increases due to the accuracy error of each gear and the variation in assembly. When the steering wheel is operated, a rattling noise is generated at the meshing portion between the sensor drive gear 126 and the sensor gear 133, which may cause discomfort to the driver. The present invention aims to solve the above-mentioned problems.

  The present invention solves the above-mentioned problems, and the invention according to claim 1 is a first gear coupled to at least an electric motor, and a second gear meshed with the first gear and coupled to a steering shaft. An electric power steering apparatus that transmits auxiliary power from an electric motor to a steering shaft, and includes an angle sensor that includes a sensor gear that detects a rotation angle of the steering shaft. An electric power steering device characterized by being elastically pressurized and meshed with a sensor drive gear provided in the second gear in a meshing direction.

  The angle sensor has an outer peripheral surface of the bearing portion of the sensor gear as a mounting portion, and an elastic member disposed in the mounting portion is interposed between the angle sensor and the angle sensor mounting portion formed in the housing of the gear reduction mechanism. It shall be installed.

  In this case, the elastic member is an annular member or an arc-shaped member that is eccentric in a direction in which the sensor gear and the sensor driving gear are deeply engaged.

  The angle sensor includes a bracket member having a bolt hole in which an elastic member is disposed on an inner surface for fixing the angle sensor to the housing of the gear reduction mechanism, and the bracket member is attached to the housing by a bolt with the elastic member interposed therebetween. It may be elastically mounted.

  In this case, the elastic member is an annular member or an arc-shaped member that is eccentric in a direction in which the sensor gear and the sensor driving gear are deeply engaged.

  The second gear is a worm wheel in which resin teeth are formed on a synthetic resin member fixed to an outer peripheral surface of a metal core, and the synthetic resin member is coaxial with the worm wheel. It is assumed that a sensor drive gear that meshes with the sensor gear is formed.

  In the electric power steering apparatus according to the present invention, an angle sensor having a sensor gear for detecting the rotation angle of the steering shaft is provided, and the sensor gear is provided on a second gear coupled to the steering shaft of the gear reduction mechanism. Since the drive gear is elastically pressurized and meshed in the meshing direction, the accuracy error of the sensor gear and the sensor drive gear and the variation during assembly are elastically pressurized as described above. It is absorbed by the meshing of the gears, backlash between the gears can be reduced, and the rattling noise generated at the meshing portion can be suppressed, and the driver is not uncomfortable.

  Embodiments of the present invention will be described below.

  FIG. 1 is a perspective view for explaining an outline of the configuration of an electric power steering apparatus 10 according to an embodiment of the present invention. In this electric power steering apparatus, an operation of a steering wheel 1 is performed via a steering column 2 and an intermediate shaft 4. The transmission force is transmitted to the pinion of the steering gear 5 arranged inside the gear box 11, and the rotation of the pinion is converted into the reciprocating motion of the rack. In order to reduce this, a worm wheel is provided coaxially with the pinion of the steering gear 5, and the rotation of the worm wheel is assisted by the electric motor 7 to assist the steering force of the steering wheel 1.

  FIG. 2 is a front view for explaining the external appearance of the gear box 11 that houses the steering gear 5. The steering gear 5 is housed inside, and the worm wheel that is mounted coaxially with the pinion of the steering gear 5 is driven to rotate. An electric motor 7, a control device (ECU) 8 for controlling the electric motor, and an angle sensor 20 are assembled.

  Although the angle sensor 20 will be described in detail later, the angle sensor 20 is separated from the input shaft 14 (that is, the worm wheel) in the vicinity of the worm wheel mounting portion of the gear box 11 that houses the input shaft 14 to which the worm wheel is mounted. It is mounted via an elastic member so as to be movable in the direction. That is, the sensor gear 22 (see FIG. 3) of the angle sensor 20 is elastically pressurized and mounted in a direction in which the engagement with the sensor drive gear 19d (see FIG. 3) formed coaxially with the worm wheel is deepened. Is done.

  The above-described mounting state will be described with reference to FIG. 2. Between the housing 11a of the worm wheel mounting part of the gear box 11 and the outer box of the angle sensor 20, the outer box of the angle sensor 20 is the housing 11a of the worm wheel mounting part. It is mounted so that a gap B is formed so as to be movable away from the head.

  3 is a cross-sectional view illustrating the configuration of the gear box 11 shown in FIG. 2, FIG. 3 (a) is a cross-sectional view taken along line AA in FIG. 2, and FIG. 3 (b) is FIG. 3 (a). It is an expanded sectional view of the bolt 24 and bolt hole 11e vicinity shown in FIG.

  The gear box 11 is configured in a divided structure including two members, a housing 11a and a housing 11b, and the steering gear 5 housed in the gear box 11 is connected to the input shaft 14, the output shaft 15, and the output shaft 15. The worm wheel 19 is fixed, the worm 18 meshes with the worm wheel 19, and the like.

  The tip of the input shaft 14 is connected to the steering wheel via an intermediate shaft 4 (not shown), the output shaft 15 is supported by ball bearings 12 and 13, and the tip of the output shaft 15 is connected to a pinion (not shown). The rotation of the pinion is converted into the reciprocating motion of the rack, and the wheels are steered via the left and right tie rods 6 (see FIG. 1).

  The input shaft 14 and the output shaft 15 are coupled by a torsion bar 16, and the input shaft 14 and the output shaft 15 are relatively twisted according to the steering torque applied to the input shaft 14, and the amount of twist is detected by the torque sensor 17. It is comprised so that.

  A worm wheel 19 is fixedly coupled to the output shaft 15 by means such as a key, and a worm 18 coupled to a rotating shaft of an electric motor (not shown) meshes with the worm wheel 19.

  Furthermore, the housing 11 a of the gear box 11 is provided with a guide hole 11 d for attaching the angle sensor 20 and a bolt hole 11 e for fixing the angle sensor 20.

  FIG. 4 is a plan view for explaining the configuration of the worm wheel 19. As shown in FIG. 4, the worm wheel 19 performs cross roulette processing or the like on the outer peripheral surface of a metal core 19a, and a cylindrical resin portion 19b integrally formed of synthetic resin is provided on the processed surface. Wheel teeth 19c meshing with the worm teeth of the worm 18 are formed on the outer peripheral surface of the worm 18b, and sensor driving gears (internal gears) meshing with the sensor gear 22 of the angle sensor 20 are formed on the inner peripheral surface of the resin portion 19b. ) 19d is formed.

  Next, the angle sensor 20 will be described. The basic configuration of the angle sensor 20 is the same as the configuration described in the background art, and a sensor gear 22 is mounted on one end of a rotating shaft 21 on which a slit disk (not shown) is mounted. The sensor gear 22 is connected to the worm wheel 19. The sensor drive gear (internal gear) 19d is configured to mesh (see FIGS. 3 and 4).

  There are a plurality of embodiments of the mounting structure for attaching the angle sensor 20 to the housing 11a. Hereinafter, description will be made sequentially.

  FIG. 5 is a front view for explaining the mounting structure of the first embodiment of the angle sensor 20. The outer casing of the angle sensor 20 is provided with a bearing portion 20a of the sensor gear 22 formed in a cylindrical shape on the outer side, and the guide provided on the above-described housing 11a using the bearing portion 20a as a mounting portion on the housing 11a. It is comprised so that it may fit in the hole 11d (refer FIG. 3).

  A mounting bracket 23 is provided on the outer box of the angle sensor 20, and the mounting bracket 23 has a bolt insertion hole 23a into which a bolt 24 screwed into the bolt hole 11e provided in the housing 11a is inserted. Is formed.

  The bearing portion 20a is provided with an elastic member ring 25 made of an elastic body that is thick and eccentric on the opposite side when viewed from the worm wheel 19 side with which the sensor gear 22 is engaged. Alternatively, instead of the ring 25 formed of a thick eccentric elastic body, an arcuate member 26 that is mounted only on the opposite side when viewed from the worm wheel 19 side may be mounted.

  FIG. 6 is a front view for explaining the mounting structure of the second embodiment of the angle sensor 20. The outer casing of the angle sensor 20 is provided with a bearing portion 20a of the sensor gear 22 formed in a cylindrical shape on the outer side, and the guide provided on the above-described housing 11a using the bearing portion 20a as a mounting portion on the housing 11a. It is comprised so that it may fit in the hole 11d (refer FIG. 3).

  A mounting bracket 23 is provided on the outer box of the angle sensor 20, and a bolt insertion hole 27 into which a bolt 24 to be screwed into the bolt hole 11e provided in the housing 11a is inserted into the mounting bracket 23. Is formed.

  The bolt insertion hole 27 is fitted with a collar 28 made of an elastic body that is thick and eccentric on the opposite side when viewed from the worm wheel 19 side with which the sensor gear 22 meshes. Alternatively, instead of the collar 28 formed of a thick eccentric elastic body, a collar 29 formed of an arcuate member that is mounted only on the opposite side when viewed from the worm wheel 19 side may be mounted.

  Next, attachment of the angle sensor 20 to the housing 11a of the gear box 11 will be described.

  In the angle sensor 20 of the first embodiment, first, an elastic member ring 25 or an arc-shaped member 26 is mounted on the bearing portion 20a. At this time, the elastic body part or the arc-shaped member 26 that is thick and eccentric from the ring 25 is mounted so as to be positioned on the opposite side (the far side) when viewed from the worm wheel 19 side, and the bearing to which the ring 25 or the arc-shaped member 26 is mounted. The part 20a is inserted into the guide hole 11d of the housing 11a.

  After the sensor gear 22 of the angle sensor 20 is meshed with the sensor drive gear 19d of the worm wheel 19 and the meshing state is adjusted, a bolt 24 is inserted into the mounting bracket 23 and fixed to the housing 11a.

  According to this configuration, the angle sensor 20 as a whole is moved outward from the center line of the output shaft (column shaft) by the arc-shaped member 26 made of the elastic body portion or elastic material that is thick and eccentric of the ring 25, Backlash can be suppressed by deeply engaging the sensor drive gear 19d.

  Further, since the ring 25 or the arc-shaped member 26 is elastically deformed, the accuracy error between the sensor gear 22 and the sensor drive gear 19d and the variation at the time of assembly are adjusted by the elastic deformation of the ring 25 or the arc-shaped member 26. No rattling noise is generated.

  In the angle sensor 20 of the second embodiment, first, a collar 28 made of an elastic body that is thick and eccentric in the bolt insertion hole 27 of the mounting bracket 23 or an arc-shaped member collar 29 made of an elastic body is used as a worm wheel. The bearing portion 20a is inserted into the guide hole 11d of the housing 11a so as to be positioned on the opposite side (far side) as viewed from the 19th side.

  After the sensor gear 22 of the angle sensor 20 is meshed with the sensor drive gear 19d of the worm wheel 19 and the meshing state is adjusted, a bolt 24 is inserted into the mounting bracket 23 and fixed to the housing 11a.

  According to this configuration, the angle sensor 20 as a whole is formed by the collar 28 made of a thick eccentric elastic body attached to the bolt insertion hole 27 of the mounting bracket 23 or the arc-shaped member collar 29 made of an elastic body. Backlash can be suppressed by moving the sensor gear 22 and the sensor drive gear 19d deeply toward the outer side from the center line of the output shaft (column shaft).

  Further, since the collar 28 or the collar 29 described above is elastically deformed, the accuracy error of the sensor gear 22 and the sensor drive gear 19d and the variation during assembly are adjusted by the elastic deformation of the collar 28 or the collar 29, and the toothed portion is driven from the meshing portion. No sound is generated.

  An angle sensor mounting structure for an electric power steering device for detecting a steering angle of a steering wheel, which is necessary for controlling so as to obtain an optimum steering characteristic corresponding to various driving conditions of a vehicle. The meshing state due to the accuracy error of the sensor drive gear connected to the sensor gear of the sensor and the steering wheel or the variation at the time of assembly is adjusted by the elastic member, and the rattling noise generated from the meshing portion can be suppressed.

The perspective view explaining the outline of the composition of the pinion assist type electric power steering device of an embodiment of this invention. The front view explaining the external appearance of the gear box which accommodates a steering gear. Sectional drawing along the AA line of the gearbox shown in FIG. The top view explaining the structure of a worm wheel. The front view explaining the attachment structure of 1st Example of an angle sensor. The front view explaining the attachment structure of 2nd Example of an angle sensor. The perspective view explaining an example of the composition of an angle sensor. Sectional drawing explaining the cross-sectional shape of the worm wheel which comprises the deceleration mechanism of an electric power steering device, and the structure of the sensor gear vicinity of an angle sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering column 4 Intermediate shaft 5 Steering gear 6 Tie rod 7 Electric motor 8 Control apparatus (ECU)
DESCRIPTION OF SYMBOLS 10 Electric power steering apparatus 11 Gear box 11a Housing 11b Housing 11d Guide hole (Guide hole for attaching an angle sensor)
11e Bolt hole (Bolt hole for fixing the angle sensor)
12 ball bearings 13 ball bearings 14 input shaft 15 output shaft 16 torsion bar 17 torque sensor 18 worm 19 worm wheel 19a core metal (core metal of worm wheel)
19b Resin section 19c Wheel teeth (Wheel teeth of worm wheel)
19d Sensor drive gear 20 Angle sensor 20a Bearing (sensor gear bearing)
21 Rotating shaft (Rotating shaft with slit disk)
22 sensor gear 23 mounting bracket 23a bolt insertion hole 24 bolt 25 elastic member (ring)
26 Arc-shaped member 27 Bolt insertion hole 28 Color (color composed of elastic body)
29 colors (colors made of elastic material)

Claims (6)

A gear reduction mechanism comprising at least a first gear coupled to an electric motor and a second gear meshed with the first gear and coupled to a steering shaft is provided, and auxiliary power from the electric motor is steered. In the electric power steering device that transmits to the shaft,
An angle sensor having a sensor gear for detecting a rotation angle of the steering shaft is provided, and the sensor gear is elastically pressurized and meshed with a sensor driving gear provided in the second gear in a meshing direction. An electric power steering device. The angle sensor has an outer peripheral surface of a bearing portion of the sensor gear as a mounting portion, and elastically moves to an angle sensor mounting portion formed in a housing of the gear reduction mechanism via an elastic member disposed in the mounting portion. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is mounted. The electric power steering apparatus according to claim 2, wherein the elastic member is an annular member or an arc-shaped member that is eccentric in a direction in which the sensor gear and the sensor drive gear are deeply engaged with each other. The angle sensor includes a bracket member having a bolt hole in which an elastic member is disposed on an inner surface that fixes the angle sensor to the housing of the gear reduction mechanism, and the bracket member is elastically attached to the housing by a bolt with the elastic member interposed therebetween. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is attached to the electric power steering apparatus. 5. The electric power steering apparatus according to claim 4, wherein the elastic member is an annular member or an arc-shaped member that is eccentric in a direction in which the sensor gear and the sensor drive gear are deeply engaged with each other. The second gear is a worm wheel in which resin teeth are formed on a synthetic resin member fixed to an outer peripheral surface of a metal core, and the sensor gear is coaxial with the worm wheel. The electric power steering apparatus according to claim 1, wherein a sensor drive gear meshing with the motor is formed.

Images