JP2007245804A - Vehicular steering device having electric power steering mechanism, and its assembly method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the cost of a steering device having an electric power steering mechanism by omitting a positioning unit provided on an output shaft for positioning a transmission gear in the steering device with the transmission gear press-fitted in the output shaft. <P>SOLUTION: A vehicular steering device comprises a pinion shaft 11 for outputting the steering force of a driver to a steering wheel, and a worm 23 and a worm wheel 24 for transmitting the torque of an electric motor to the pinion shaft 11. The worm wheel 24 is axially press-fitted in and fixed to the pinion shaft 11. The worm wheel 24 to be press-fitted in the pinion shaft 11 is positioned in the axial direction with respect to the pinion shaft 11 by using a tool used in a press-fitting process. Thus, any positioning unit for positioning the worm wheel 24 is not provided on the pinion shaft 11. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a vehicle steering apparatus including an electric power steering mechanism that transmits torque of an electric motor that generates an auxiliary steering force to an output shaft, and an assembly method thereof.

In a vehicle steering apparatus having an electric power steering mechanism, a transmission gear (for example, a worm wheel) that transmits torque of an electric motor that generates auxiliary steering force is fixed to the output shaft that outputs steering force to a steering wheel by press-fitting. Is known (see, for example, Patent Document 1).
JP 2001-315650 A

  Conventionally, the transmission gear press-fitted into the output shaft is positioned in the axial direction of the output shaft by means of a flange that is integrally formed with the output shaft. Therefore, it is necessary to increase the diameter of the material of the output shaft. For this reason, the amount of processing increases, yield is not good, and labor is required for processing, leading to high costs for the steering device. In addition, when a bag separate from the output shaft is integrated with the output shaft, the number of assembling steps is increased by the integration process, so that the cost also increases.

  The present invention has been made in view of such circumstances, and the invention according to claim 1 is provided in the output shaft for positioning the transmission gear in a steering device in which the transmission gear is press-fitted into the output shaft. An object of the present invention is to reduce the cost of a steering apparatus including an electric power steering mechanism by eliminating the positioning portion. A second object of the present invention is to provide a method for assembling the same.

  The invention according to claim 1 is provided with an output shaft that outputs the steering force of the driver to the steered wheels, and a transmission gear that transmits the torque of the electric motor that generates the auxiliary steering force to the output shaft. In the vehicle steering apparatus comprising: an electric power steering mechanism that is press-fitted and fixed to the force shaft in the axial direction; and the output shaft is in contact with the transmission gear in the axial direction with respect to the output shaft. The vehicle steering apparatus is provided with no positioning portion for positioning the transmission gear.

The invention according to claim 2 is provided with an output shaft that outputs the steering force of the driver to the steered wheels, and a transmission gear that transmits the torque of the electric motor that generates the auxiliary steering force to the output shaft. In a vehicle steering apparatus including an electric power steering mechanism that is press-fitted and fixed to the output shaft, the transmission gear is pressed by a pressing jig with respect to the output shaft that is positioned with respect to a position regulating jig. A vehicle steering device that presses and press-fits a position restricting jig until it abuts against the output shaft in an axial direction, and positions the press-fitted transmission gear relative to the output shaft in the axial direction by the position restricting jig. It is an assembly method.
In the specification or claims, the axial direction is the direction of the rotation center line of the output shaft.

According to the first aspect of the present invention, since the output shaft is not provided with a positioning portion such as a hook for positioning the transmission gear in the axial direction, the diameter of the output shaft can be reduced, and the yield of the output shaft can be reduced. And the processing cost is reduced. As a result, by eliminating the positioning portion provided on the output shaft for positioning the transmission gear, the cost of the steering device including the electric power steering mechanism is reduced.
According to the second aspect of the present invention, since the position restricting jig positions the transmission gear in the axial direction with respect to the output shaft, it is not necessary to provide a positioning portion on the output shaft for positioning the transmission gear. For this reason, the diameter of the output shaft can be reduced, the yield of the output shaft can be improved, the processing cost can be reduced, and the cost of the steering device including the electric power steering mechanism can be reduced.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
Referring to FIG. 1, a vehicle steering apparatus S to which the present invention is applied includes a steering wheel 1, an input-side transmission mechanism 2, and a steering force applied to the steering wheel 1 by a driver via the transmission mechanism 2. A gear box 3 that outputs a steering force that steers the left and right steering wheels, and an output-side transmission mechanism 4 that transmits the steering force from the gear box 3 to the steering wheels are provided.

The gear box 3 includes a housing 6 attached to the vehicle body, a rack and pinion mechanism that is housed in the housing 6 and outputs a steering force to the steered wheels via the transmission mechanism 4, and an electric power that generates an auxiliary steering force. A steering mechanism.
The housing 6 includes a rack housing 7 as a cylindrical first housing that extends horizontally in the left-right direction of the vehicle, and a pinion housing 8 as a second housing extending obliquely upward near one end of the rack housing 7. It consists of. The pinion housing 8 includes a lower housing 8a formed integrally with the rack housing 7 and an upper housing 8b coupled to the upper end of the lower housing 8a.

  Referring also to FIG. 2, the rack and pinion mechanism includes a bearing 17 and an input shaft 10 rotatably supported by the pinion housing 8 via a torque sensor 25 that holds the bearing 17, and the pinion housing 8. A pinion shaft 11 as an output shaft that is housed and rotatably supported, a rack shaft 12 that is housed in the rack housing 7 and supported so as to be able to reciprocate in parallel in the left-right direction, and the rack shaft 12 are provided. And a rack guide 16 that presses the rack 14 against the pinion 13 provided on the pinion shaft 11. The pinion shaft 11 is connected to an input shaft 10 through which a steering force from the handle 1 is input from the transmission mechanism 2 via a torsion bar 15. In the lower housing 8a, the pinion 13 and the rack 14 mesh with each other and are driven by the pinion 13 of the pinion shaft 11 that rotates based on the steering force, so that the rack shaft 12 moves in the left-right direction. The pinion shaft 11 arranged coaxially with the input shaft 10 is rotatably supported by the lower housing 8a via bearings 18a and 18b in a pair of journal portions 11d and 11e, respectively. Therefore, the rotation center line L of the pinion shaft 11 coincides with the rotation center line of the input shaft 10.

The transmission mechanism 4 connects a pair of ball joints 4a coupled to both ends of the rack shaft 12, a pair of tie rods 4b coupled to the ball joint 4a, and the tie rods 4b and the steered wheels. And a link mechanism (not shown).
The electric power steering mechanism 20 that adds an auxiliary steering force to the rack shaft 12 at the time of turning includes an electric motor 21 that is controlled by an electronic control unit (not shown) to which a steering torque detected by a torque sensor 25 is input. And a worm gear 22 as a transmission mechanism that is a reduction mechanism that transmits the torque of the electric motor 21 that generates the auxiliary steering force to the pinion shaft 11.

  The torque sensor 25 attached to the upper housing 8b detects the position of the core 25b held by the holder 25a inserted in the input shaft 10 so as to be movable in the axial direction in proportion to the torsion amount of the torsion bar 15, and the position of the core 25b. And a pair of coils 25c. A pin (not shown) that fits into a spiral groove (not shown) provided on the peripheral wall of the holder 25a is fixed to the input shaft 10, and a pin 1 provided on the peripheral wall of the holder 25a is fixed to the pinion shaft 11. A pair of pins 25d is fixed so as to fit in the pair of guide grooves and guide the holder 25a so as to be movable in parallel in the axial direction. When the input shaft 10 and the pinion shaft 11 rotate relative to each other while twisting the torsion bar 15, the core 25b is displaced in the axial direction from the neutral position with respect to the input shaft 10 and each coil 25c. The inductance of each coil 25c changes according to the amount of displacement and the direction of displacement, and the steering torque is detected based on the change in inductance.

  The worm gear 22 accommodated in the pinion housing 8 is fixed by being press-fitted into the worm 23 as a drive gear that rotates integrally with the rotating shaft of the electric motor 21 attached to the lower housing 8a and the pinion shaft 11. The worm wheel 24 is a driven gear as a transmission gear that rotates integrally with the pinion shaft 11.

  Therefore, when the steering force applied to the steering wheel 1 by the driver is transmitted to the input shaft 10 in the steering device S, the pinion shaft 11 causes the input shaft 10 to twist the torsion bar 15 due to road surface resistance. And the rack shaft 12 driven by the pinion 13 moves in the left-right direction. At the same time, the electric motor 21 that generates an auxiliary steering force proportional to the steering torque detected by the torque sensor 25 moves the rack shaft 12 in the left-right direction via the worm gear 22, the pinion shaft 11, and the pinion 13. Therefore, the auxiliary steering force from the electric motor 2125 is transmitted to the rack shaft 12 via the worm wheel 24 and the pinion shaft 11, and the driver's steering force is reduced. Thus, the pinion shaft 11 outputs the driver's steering force and the auxiliary steering force of the electric motor 21 to the steered wheels via the rack shaft 12 and the transmission mechanism 4.

A structure for fixing the worm wheel 24 to the pinion shaft 11 will be described with reference to FIG.
The worm wheel 24 has a disc-shaped main body 24a made of a synthetic resin having teeth on the outer periphery and a boss portion 24b1 as a coupling portion 30 to be press-fitted into the pinion shaft 11, and a core embedded in the main body 24a. It is composed of gold 24b.

The pinion shaft 11 is provided with a coupling portion 30 with the worm wheel 24 between the pinion 13 and the input shaft side end portion 11a near the input shaft 10 in the axial direction. When the worm wheel 24 is press-fitted into the pinion shaft 11, the coupling portion 30 includes a press-in portion 31 near the pinion side end portion 11b, which is an end portion on the side where the worm wheel 24 is inserted with respect to the pinion shaft 11, and a press-in portion It is comprised from the serration part 32 as an encroaching part near the edge part 11a located in the axial direction with respect to the edge part 11b on the opposite side. An annular groove 33 is provided between the press-fit portion 31 and the serration portion 32 over the entire circumference.
The press-fit portion 31 having an outer peripheral surface made of a cylindrical surface has an outer diameter larger than the inner diameter of the boss portion 24b1 having an inner peripheral surface made of a cylindrical surface. Further, the serration portion 32 formed with serrated cross-sectional serrations over the entire circumference has an outer diameter larger than the outer diameter of the press-fit portion 31. For this reason, in the serration portion 32, the distal end of the serration in the radial direction bites into the boss portion, which contributes to preventing relative rotation between the pinion shaft 11 and the worm wheel 24.

Next, the assembly process of the worm wheel 24 to the pinion shaft 11 when the steering device S is assembled will be described with reference to FIGS.
3A and 3B, in the positioning process of the pinion shaft 11, the pinion shaft 11 to which the torsion bar 15 and the pin 25d are coupled is set in the position regulating jig 40 in a state where the pinion shaft 11 is positioned in the axial direction. Is done. When the torsion bar 15 is inserted into the position restricting jig 40 and the pin 25d and the end portion 11a are received by the receiving hole 41, the end portion 11a abuts in the press-fitting direction parallel to the axial direction. There is provided a restricting portion formed in a step shape that restricts the movement of the pinion shaft 11 in the axial direction.

  Referring to FIG. 4, in the insertion process of the worm wheel 24 and the pressing jig 50 with respect to the pinion shaft 11, the worm wheel 24 has an end portion with respect to the pinion shaft 11 that is positioned in the axial direction with respect to the position regulating jig 40. It is inserted from 11b to the press-fitting start position which is the position immediately before the press-fitting part 31. Next, with respect to the worm wheel 24 set at the press-fitting start position, a cylindrical pressing jig 50 having a receiving hole 51 including a through hole in which the pinion shaft 11 is inserted and the pinion 13 is received is inserted from the end 11b. It is inserted into the pinion shaft 11 and inserted until the boss portion 24b1 of the worm wheel 24 comes into contact with the contact portion 52 (the state shown in FIG. 4A).

In the press-fitting process of the worm wheel 24 to the pinion shaft 11, a pressing force is applied to the pressing jig 50 in contact with the worm wheel 24, and the worm wheel 24 pressed by the pressing jig 50 is positioned from the press-fitting start position. It moves in the press-fitting direction until it abuts against the abutting portion 43 of the regulating jig 40 in the axial direction, and is pushed into the press-fit portion 31, and the serration portion 32 bites into the inner peripheral surface of the boss portion 24b1. Then, when the worm wheel 24 comes into contact with the contact portion 43 and the press-fitting process is completed, the press-fitted worm wheel 24 is positioned with respect to the pinion shaft 11 in the axial direction (shown in FIG. 4B). State.)
Thereafter, the jigs 40 and 50 are removed from the integrated pinion shaft 11 and the worm wheel 24, and the assembly process of the worm wheel 24 to the pinion shaft 11 is completed.

  Thus, the positioning of the worm wheel 24 press-fitted into the pinion shaft 11 in the axial direction with respect to the pinion shaft 11 is performed by the position restricting jig 40, so that the pinion shaft 11 contacts the worm wheel 24. Thus, there is no positioning portion for restricting the movement of the worm wheel 24 in the axial direction and positioning the worm wheel 24 in the axial direction with respect to the pinion shaft 11.

Next, operations and effects of the embodiment configured as described above will be described.
In the method of assembling the vehicle steering apparatus S, when the worm wheel 24 that is press-fitted and fixed to the pinion shaft 11 is assembled to the pinion shaft 11, the pinion shaft 11 positioned with respect to the position regulating jig 40 is used. The worm wheel 24 is pressed by the pressing jig 50 until it abuts against the position restricting jig 40 in the axial direction and press-fitted into the pinion shaft 11, and the press-fitted worm wheel 24 is pinned in the axial direction by the position restricting jig 40. By positioning with respect to the shaft 11, the position regulating jig 40 performs positioning in the axial direction of the worm wheel 24 with respect to the pinion shaft 11 in the press-fitting process of the worm wheel 24 to the pinion shaft 11. There is no need to provide a positioning portion for positioning the worm wheel 24. Thus, by eliminating the positioning portion provided on the pinion shaft 11 for positioning the worm wheel 24, it is possible to reduce the diameter of the pinion shaft 11, improving the yield of the pinion shaft 11, and reducing the machining cost. As a result, the cost of the steering device S including the electric power steering mechanism 20 is reduced.

Hereinafter, an embodiment in which a part of the configuration of the above-described embodiment is changed will be described with respect to the changed configuration.
The output shaft may be configured by a shaft other than the pinion shaft, and the transmission gear may be configured by a gear other than the worm wheel.

1 is a schematic overall view showing a part of a steering device to which the present invention is applied in cross section. FIG. 2 is a schematic sectional view taken along line II-II in FIG. 1. FIG. 2 is a diagram for explaining a worm wheel assembling process with respect to a pinion shaft in the steering device of FIG. 1, wherein (A) shows a state in which the pinion shaft is positioned by a position regulating jig; It is line sectional drawing, (B) is a BB arrow line view of (A). In the steering apparatus of FIG. 1, it is a figure explaining the assembly | attachment process of the worm wheel with respect to a pinion axis | shaft, (A) shows the state which the press jig | tool has contact | abutted with respect to the worm wheel in a press injection start position, (B) shows the state where the press-fitting process of the worm wheel with respect to the pinion shaft is completed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Handle, 2, 4 ... Transmission mechanism, 3 ... Gear box, 6 ... Housing, 7 ... Rack housing, 8 ... Pinion housing, 10 ... Input shaft, 11 ... Pinion shaft, 12 ... Rack shaft, 13 ... Pinion, 14 ... rack, 15 ... torsion bar, 16 ... rack guide, 20 ... power steering mechanism, 21 ... electric motor, 22 ... worm gear, 23 ... worm, 24 ... worm wheel, 25 ... torque sensor, 30 ... coupling part, 31 ... press fit Part, 32 ... serration part, 33 ... annular groove, 40 ... position restricting jig, 41 ... receiving hole, 42 ... restricting part, 43 ... contact part, 50 ... pressing jig, 51 ... receiving hole,
S: Steering device.

Claims (2)

An output shaft that outputs the steering force of the driver to the steered wheels;
A vehicle comprising: a transmission gear that transmits torque of an electric motor that generates an auxiliary steering force to the output shaft; and the transmission gear is fixed by being pushed out into the force shaft in the axial direction. Steering apparatus for
The vehicle steering apparatus according to claim 1, wherein the output shaft is not provided with a positioning portion that positions the transmission gear in an axial direction with respect to the output shaft by contacting the transmission gear. An output shaft that outputs the steering force of the driver to the steered wheels;
In a vehicle steering apparatus, comprising: a transmission gear that transmits torque of an electric motor that generates auxiliary steering force to the output shaft, and the transmission gear is press-fitted and fixed to the output shaft. ,
The transmission shaft is pressed into the output shaft by pressing the transmission gear until it abuts against the position regulating jig in the axial direction with respect to the output shaft positioned with respect to the position regulating jig. An assembly method for a vehicle steering apparatus, wherein the transmission gear is positioned relative to the output shaft in the axial direction by the position restricting jig.

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