JP2005067388A - Electric power steering device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To dispense with a separate member for reinforcing strength when a steering shaft is press-fitted to a gear box side in assembling of a steering device, to realize cost-reduction and to impart no bad influence to respective members on the gear box side while maintaining the exact positioning state. <P>SOLUTION: A key lock mechanism is provided on the steering shaft 11 and a torque sensor 8 is provided between the key lock mechanism and a worm wheel 3. A fixture attachment part 14 for fixing a mounting fixture is provided on a part of a torque sensor shaft 10. The steering shaft 11 is press-fitted to the torque sensor shaft 10 attached to the gear box at the fixture attachment part 14 in the state where an assembly of the gear box is fixed by the fixture. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an improvement in an electric power steering apparatus in which a steering shaft has a theft prevention function such as a key lock mechanism.

  In general, a steering shaft that constitutes a part of a steering system is fitted to a torque sensor shaft and then passed through a gear box to be assembled integrally with the gear box. Further, the steering shaft is usually provided with a key lock mechanism for theft prevention.

  In that case, when the gear box assembly is mounted on the steering shaft, the outer diameter of the collar of the key lock mechanism provided on the steering shaft becomes large. Therefore, unless the inner diameter of the coil assembly used for the non-contact type sensor is increased, the steering shaft cannot pass through the inside of the coil assembly.

  Therefore, in a conventional electric power steering apparatus, as disclosed in, for example, Patent Document 1, in FIG. 6, a steering shaft 103 is rotatably disposed in a steering column 101 by a bearing 102 in the steering column 101, An antitheft lock member 104 is provided. In the literature 1, when the steering device is assembled, when the outer diameter D1 of the receiving portion 105 of the lock member 104 is larger than the inner diameter of the magnetic flux generating coil of the torque sensor, the sensor housing, coil, input / output shaft, magnetic flux After assembling the steering assisting portion such as the passing member and the driven gear, the steering shaft 103 and the input shaft 106 of the steering assisting portion are connected so as to be able to rotate together by press fitting.

Further, for example, in Patent Document 2, as shown in FIG. 7, a lock member 113 for preventing theft is provided on a steering shaft 112 disposed in a steering column 111, and a column portion 114 having the lock member 113 and a steering assisting portion are provided. 115 are designed as separate units. Then, when assembling the steering device, the column portion 114 and the steering assisting portion 115 are connected to the steering shaft 112 by fitting the concave and convex portions such as splines and serrations or using tightening tools such as screws and nuts. They are connected by press-fitting with the input shaft 116.
JP 2003-72566 A JP 2000-85596 A

  However, in each of the above conventional examples, when the steering device is assembled, when the steering shafts 103 and 112 and the input shafts 106 and 116 of the steering assisting portion are assembled, a large load acts on the fitting portion and the like, and the coil There is a risk that the torque sensor portion may be damaged, and the fitting portion has to be reinforced in strength. Also, during assembly, an excessive force acts on the connection between the steering shafts 103 and 112 and the input shafts 106 and 116 on the gear box side, and an error occurs in the assembly position of the torque sensor, etc., and the generated magnetic flux of the coil is detected The relative position of the detection unit to be shifted may deviate from the design position, or the torsion bar may be deformed, which may reduce the detection accuracy of the torque sensor.

  Accordingly, an object of the present invention is to provide a jig mounting portion on the torque sensor shaft on the gear box side to improve the strength at the time of fitting when the steering shaft is press-fitted to the gear box side when assembling the steering device. In addition, it is not necessary to provide a separate member for reinforcing the strength in the press-fitting fitting portion, so that the cost can be reduced and the gearbox side members are not adversely affected while maintaining an accurate positioning state. There is.

  An object of the present invention is to provide an electric power steering apparatus that assists steering of a steering shaft from a motor through a worm wheel arranged in a gear box based on a signal detected by a torque sensor. A key lock mechanism is provided on the steering shaft, the torque sensor is provided between the key lock mechanism and the worm wheel, and a mounting jig for the gear box is fixed to a part of the torque sensor shaft. The jig mounting portion is provided, and the steering shaft is press-fitted to the torque sensor shaft mounted on the gear box in a state where the assembly of the gear box is fixed by the jig at the jig mounting portion. Is achieved.

  Further, the object is to form the jig mounting portion on the torque sensor shaft by the annular flange portion that protrudes outside the torque sensor shaft between the gear box and the lock mechanism. It is achieved effectively by comprising the recessed groove formed.

  Further, the object is to provide an electric power steering device in which steering assistance of a steering shaft is performed from an electric motor via a worm wheel arranged in a gear box based on a signal detected by a torque sensor. After assembling a speed reduction mechanism such as the worm wheel or a torque sensor such as a coil assembly in the gear box and mounting the torque sensor shaft, the jig is mounted on the jig mounting portion of the torque sensor shaft and the torque sensor shaft is mounted. This is achieved effectively by fixing and fitting the steering shaft to the torque sensor shaft in that state.

  As described above, according to the electric power steering apparatus of the present invention, the torque sensor is provided between the key lock mechanism and the worm wheel, and the gearbox mounting jig is fixed to a part of the torque sensor shaft. In this state, the steering shaft is press-fitted to the torque sensor shaft in a state where the assembly of the gear box is fixed by the mounting jig. As a result, when the steering shaft is press-fitted to the torque sensor shaft on the gear box side, the steering shaft can be press-fitted with the jig firmly fixed with a jig, improving the strength during assembly. Can be made. In addition, when the torque sensor shaft is press-fitted to the steering shaft, the large load acting on the torque sensor shaft or the like eliminates the relative shift in the assembly position of each member on the gear box side, and a coil assembly is designed. Can be placed in the street. Therefore, the strength at the time of assembling the steering shaft and the torque sensor shaft is improved, and the detection accuracy of the torque sensor can be kept good without adversely affecting each member.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In FIG. 1, a hollow output shaft 2 extending in the vertical direction is disposed in a housing 1 of a speed reduction mechanism disposed below. A worm wheel 3 is fixedly attached to the outer periphery of the center portion of the output shaft 2 by press fitting or the like. The worm wheel 3 meshes with a worm 5 connected to a rotating shaft 4 of an electric motor (not shown).

  Further, the output shaft 2 is rotatably supported with respect to the housing 1 by bearings 6 a and 6 b, and a torsion bar 7 is disposed in the output shaft 2. The torsion bar 7 is attached to the output shaft 2 side, and the upper end is attached to the input shaft 8. In addition, a rotary contact type torque sensor 9 is disposed around the torsion bar 7, and the torque sensor 9 includes two coil bobbins around which a coil is wound, and a cylindrical coil yoke that accommodates the coil bobbin inside. And a circuit board for detecting a current generated in the coil.

  A torque sensor shaft 10 is constituted by the output shaft 2 and the input shaft 8 of the torque sensor 9, and a steering shaft 11 connected to a steering wheel (not shown) is mounted on the torque sensor shaft 10. A key lock mechanism 12 for preventing theft is attached to the center of the steering shaft 11.

  Further, as shown in FIG. 2, the torque sensor shaft 10 and the steering shaft 11 are each formed with a serration portion at the connecting portion. On the inner periphery of the steering shaft 11, there are formed a slit 11a, which is four elongated cutouts extending in parallel with the axis from the lower end (lower side in FIG. 1), and a female serration portion 11b. On the other hand, a male serration portion 10a as a convex portion is formed on the outer periphery of the upper end (upper side in FIG. 1) of the torque sensor shaft 10, and both are connected by engagement with the female serration portion 11b. Thereby, the steering shaft 11 and the torque sensor shaft 10 are connected so as not to be relatively rotatable.

  An annular flange portion 13 is formed below the steering shaft 11 (downward in FIG. 1) so as to protrude outward. The annular flange portion 13 forms a jig mounting portion 14 between the outer periphery of the torque sensor shaft 10 and the housing 1 of the gear box. As a result, as shown in FIG. 3, when the steering shaft 11 is press-fitted into the torque sensor shaft 10 on the gear box side, the jig 15 is mounted on the jig mounting portion 14. In other words, the jig 15 moves in the direction of the arrow in FIG. 3 and firmly holds the torque sensor shaft 10 from both sides at a predetermined position of the jig mounting portion 14. In this state, the steering shaft 11 is fixed to the gear box side by press-fitting the steering shaft 11 and the torque sensor shaft 10.

As described above, in the manufacturing process of the electric power steering apparatus, first, before connecting the torque sensor shaft 10 to the steering shaft 11, the housing 1 is inserted alone. Since the maximum outer diameter of the torque sensor shaft 10 is smaller than the inner diameter of the coil of the torque sensor 9, such insertion is easily performed. Thereby, the upper end (upper part of FIG. 1) of the torque sensor shaft 10 protrudes upward (upper part of FIG. 1) from the inside of the housing 1.
In parallel with the above, with the key lock collar 12 attached to the center of the steering shaft 11, the torque sensor shaft 10 and the steering shaft 11 are press-fitted and fitted in the serration portion, and the steering shaft 11 is mounted on the gear box side. It is fixed to the torque sensor shaft 10.
At that time, the torque sensor shaft 10 is clamped and fixed by the jig 15 in the direction shown by the arrow in FIG. 4 before being press-fitted into the steering shaft 11. In this state, the steering shaft 11 is press-fitted into the torque sensor shaft 10.
Incidentally, when the steering shaft 11 and the torque sensor 10 are press-fitted and fitted, a load of 1.0 to 2.0 kN is generally applied to the annular flange portion 13. Therefore, as a result of experimenting with the flange width (thickness) of the annular flange 13 set to 5 mm and the jig 15 also set to 5 mm, the relative arrangement of the coil of the torque sensor 9 and the torque sensor unit 10 was determined. The error disappeared and the torsion bar 7 was not deformed.

  Therefore, when the torque sensor shaft 10 and the steering shaft 11 are fitted, a large load acts on each member on the gear box side, but the strength of the fitting portion of the steering shaft 11 is strongly reinforced by using a jig. Can do. As a result, since the strength of the fitting portion is improved, it is not necessary to separately provide another member for reinforcing the strength on the support portion of the steering shaft 11 and the cost can be reduced.

  Even if an excessive force is applied to the connecting portion between the torque sensor shaft 10 and the steering shaft 11 during fitting, the torque sensor shaft 10 on the gearbox side is firmly fixed by a jig, so that during press fitting The relative positions of the coils of the torque sensor shaft 10 and the torque sensor 9 are not shifted, and the torsion bar 7 is not deformed. Therefore, there is no error in the arrangement of each member on the gear box side, accurate positioning is maintained, deterioration in detection accuracy of the torque sensor 9 is prevented, and the basic performance of the EPS is not impaired.

  Furthermore, since the jig mounting portion 14 is simply formed by projecting the annular flange portion 13 concentric with the torque sensor shaft 10 on the outer side of the torque sensor shaft 10, the jig mounting portion 14 is easy to process and keeps the manufacturing cost low. be able to.

  As a modification of the present invention, as shown in FIG. 5, the torque sensor shaft 10 may be fixed to the gear box side by a pin 20, and the axial direction that acts when press-fitting with the steering shaft 11 is used. The strength with respect to the load can be improved, and the same operations and effects as in the above embodiment can be achieved.

It is a partially cutaway sectional view showing a main part of the electric power steering apparatus according to the present invention. It is sectional drawing in the II-II line of FIG. It is a figure explaining the assembly state of an electric power steering device. It is a figure explaining the state which grips a torque sensor shaft with a jig. It is explanatory drawing of the principal part which shows the modification of this invention. It is a figure explaining the principal part of the conventional electric power steering device. It is a figure explaining the principal part of other conventional electric power steering devices.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 2 Output shaft 7 Torsion bar 8 Input shaft 9 Torque sensor 10 Torque sensor shaft 11 Steering shaft 12 Key lock collar 13 Annular flange part 14 Jig mounting part 15 Jig 20 pin

Claims (3)

In the electric power steering apparatus configured to perform steering assistance of the steering shaft from the electric motor via a worm wheel arranged in the gear box based on the signal detected by the torque sensor,
A key lock mechanism is provided on the steering shaft, the torque sensor is provided between the key lock mechanism and the worm wheel, and a mounting jig for the gear box is fixed to a part of the torque sensor shaft. The jig mounting part of
The electric power steering characterized in that the steering shaft is press-fitted into a torque sensor shaft mounted on the gear box in a state where the assembly of the gear box is fixed by a jig at the jig mounting portion. apparatus. The jig mounting portion is between the gear box and the lock mechanism, and includes an annular flange portion that protrudes outside the torque sensor shaft, and a concave groove formed in the torque sensor shaft by the annular flange portion. The electric power steering apparatus according to claim 1 configured. In the electric power steering apparatus configured to perform steering assistance of the steering shaft from the electric motor via a worm wheel arranged in the gear box based on the signal detected by the torque sensor,
After assembling a reduction mechanism such as the worm wheel or a torque sensor such as a coil assembly in the gear box, and mounting a torque sensor shaft,
An electric power steering apparatus characterized in that a jig is mounted on a jig mounting portion of the torque sensor shaft to fix the torque sensor shaft, and the steering shaft is press-fitted into the torque sensor shaft in that state. Manufacturing method.

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