JP4984489B2 - Rack and pinion type steering gear - Google Patents

Description

  The present invention relates to a rack and pinion type steering gear that transmits a steering force to wheels, and more particularly to a rack and pinion type steering gear having a lightweight rack shaft.

  In recent years, various automobile parts have been reduced in weight for the purpose of improving fuel efficiency. As shown in the rack shaft of Patent Document 1, the rack shaft used in the rack and pinion type steering gear has an axis center of the rack shaft. A hollow slot is machined to reduce weight.

  2 to 4 show a conventional rack and pinion type steering gear, FIG. 2 is an overall view of the conventional rack and pinion type steering gear, and FIG. 3 (1) is a reciprocating slide inside the rack and pinion type steering gear of FIG. 3 is a cross-sectional view of the rack shaft that is movably assembled, FIG. 3B is a front view of a tie rod screwed into both ends of the rack shaft of FIG. 3A, and FIG. 4A is the rack of FIG. FIG. 4B is an enlarged cross-sectional view of the end surface on the rack tooth side of the rack shaft of FIG. 3A.

  As shown in FIGS. 2 to 4, in a conventional rack and pinion type steering gear 1, a rack shaft 3 that meshes with a pinion (not shown) is supported in a housing 2 so as to be reciprocally slidable. Tie rods 4 are screwed and fixed to female screws 5 and 6 formed at the left and right ends of the rack shaft 3, and tie rod ends 41 are attached to the left and right ends of the tie rod 4. The tie rod end 41 is connected to a knuckle arm (not shown) that supports the wheel via a ball joint, and transmits the reciprocating motion of the rack shaft 3 to the wheel.

  As shown in FIG. 3 (2), a ball portion (not shown) formed at the left end of the tie rod 4 is rotatably fitted to the ball joint 42, and a male screw 43 is attached to the left end surface of the ball joint 42. The male screw 43 is screwed into female screws 5 and 6 formed on the left and right ends of the rack shaft 3 to connect the tie rod 4 to the rack shaft 3.

  As shown in FIG. 3 (1), rack teeth 31 are formed on the lower left surface of the rack shaft 3, and the above-described female screw 5 is formed on the axis of the rack tooth side end surface (left end surface) of the rack shaft 3. Yes. Further, the female screw 6 described above is formed on the shaft center of the rack shaft 3 on the side opposite to the rack teeth (right end surface). Further, in order to reduce the weight of the rack shaft 3, the rack shaft 3 has a hollow long hole 7 formed in the axial center of the rack shaft 3 from the end surface on the side opposite to the rack tooth of the rack shaft 3. However, it extends to the vicinity of the right end of the rack tooth 31.

  In order to further reduce the weight of such a conventional rack shaft 3, it is only necessary to increase the inner diameter D1 of the hollow slot 7. However, if the inner diameter D1 of the hollow slot 7 is increased, the inner diameter D1 is increased. It is necessary to increase the nominal diameter of the female screw 6 on the end surface on the side opposite to the rack tooth. That is, as shown in FIG. 4 (2), the hollow long hole 7 cannot be processed by the gun drill tool unless the inner diameter D1 of the hollow long hole 7 is smaller than the inner diameter D2 of the female screw 6.

  Further, if the nominal diameter of the female screw 6 on the opposite end surface of the rack tooth side and the nominal diameter of the female screw 5 on the end face of the rack tooth side are set to the same nominal diameter, the male screw 43 of the ball joint 42 connecting the tie rod 4 becomes common. This is preferable because the number of parts can be reduced and the manufacturing cost can be reduced.

  However, as shown in FIG. 4A, the screw hole 51 of the female screw 5 on the rack tooth side end face is closest to the rack tooth bottom 32 on the leftmost side. Therefore, when the nominal diameter of the female screw 5 on the rack tooth side end surface is increased in order to obtain the same nominal diameter as the female screw 6 on the non-rack tooth side end surface having a larger nominal diameter, the expanded screw lower hole 51 and the leftmost end side Since the distance to the rack tooth bottom 32 approaches and the strength of the rack shaft 3 decreases, there is a limit to increasing the nominal diameter of the female screw 5 on the rack tooth side end surface.

Japanese Utility Model Publication No. 5-67575

  The present invention reduces the weight of the rack shaft by increasing the inner diameter of the hollow long hole, and secures the distance between the screw bottom hole of the female screw on the rack tooth side end face and the rack tooth bottom, It is an object of the present invention to provide a rack and pinion type steering gear in which the nominal diameter of the female screw and the nominal diameter of the female screw at the end face of the rack tooth are the same.

The above problem is solved by the following means. That is, the first invention is a rack and pinion type steering gear for transmitting a steering force to a wheel, a rack shaft in which rack teeth meshing with the pinion are formed, and a female screw formed on a rack tooth side end surface of the rack shaft A hollow slot having a diameter larger than the inner diameter of the female screw on the rack tooth side end surface, formed from a non-rack tooth side end surface of the rack shaft toward the rack tooth side by a gun drill tool , a ball screw insert is inserted into the female screw which is tapped from the opposite rack teeth side end face to the hollow elongated hole, which has a female screw of the female screw same nominal diameter as the rack teeth side end face to the inner diameter, the outer diameter said has a greater nominal diameter than the internal thread of the rack teeth side end face, provided with a threaded insert having an external thread to be screwed into the tapped processed internal thread A rack and pinion type steering gear characterized.

  In the rack and pinion type steering gear of the present invention, a hollow long hole having a diameter larger than the inner diameter of the female screw on the rack tooth side end surface of the rack shaft is formed from the end surface on the opposite rack tooth side toward the rack tooth side. A screw insert having a female screw having the same nominal diameter as the female screw on the rack tooth side end face is inserted. Therefore, the inner diameter of the hollow long hole is increased to reduce the weight of the rack shaft, and the distance between the screw lower hole of the female screw on the rack tooth side end surface and the rack tooth bottom is ensured to ensure the strength of the rack shaft. At the same time, the nominal diameter of the female screw on the end surface on the opposite side of the rack tooth and the nominal diameter of the female screw on the end surface on the rack tooth side can be made the same size.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 (1) is a cross-sectional view of the end surface on the side opposite to the rack teeth of the rack shaft according to the embodiment of the present invention, and FIG. 1 (2) is an enlarged cross-sectional view of FIG.

  As shown in FIGS. 1 (1) and (2), the axial center of the rack shaft 33 on the side opposite to the rack teeth (right end surface) of the rack shaft 33 of the present invention is larger than the inner diameter D1 of the conventional hollow slot 7 described above. A hollow long hole 71 having an inner diameter D3 is processed by a gun drill tool. In the hollow long hole 71, a female screw 61 is processed from the end surface (right end surface) on the side opposite to the rack tooth of the rack shaft 33 by a tap tool.

  The nominal diameter of the female screw 61 is larger than the nominal diameter of the female screw 5 on the conventional rack tooth side end face and the female screw 6 on the non-rack tooth side end face shown in FIGS. 4 (1) and (2). Yes. The screw insert 8 is screwed into the female screw 61.

  As shown in FIG. 1 (2), the screw insert 8 of the embodiment of the present invention is manufactured by winding up a wire having a rhombus cross section in a coil shape. A female screw 81 having the same nominal diameter as that of the conventional female screws 5 and 6 is formed on the inner diameter of the screw insert 8, and a male screw 82 having the same nominal diameter as that of the female screw 61 is formed on the outer diameter of the screw insert 8. ing. That is, the inner diameter D3 of the hollow elongated hole 71 can be formed larger than the inner diameter D2 of the female screw 81 of the screw insert 8.

  Therefore, if the screw insert 8 is screwed into the female screw 61 on the end surface on the side opposite to the rack teeth by using a dedicated insertion tool (mandrel), a rack in which a hollow slot 71 having a larger inner diameter D3 than the conventional one is formed. A female screw 81 having the same nominal diameter as the conventional one can be formed on the end surface of the shaft 33 on the side opposite to the rack teeth.

  Therefore, since it is only necessary to form the female screw 5 having the same nominal diameter as shown in FIG. 4 (1) on the end surface of the rack tooth side, the screw lower hole 51 of the female screw 5 and the rack tooth bottom 32 on the leftmost end side. Since the distance between them is ensured, the strength of the rack shaft 33 does not decrease. Therefore, since the nominal diameters of the female screw 81 on the non-rack tooth side end surface and the female screw 5 on the rack tooth side end surface are the same, the number of parts can be reduced and the manufacturing cost can be reduced. Moreover, since the inner diameter D3 of the hollow long hole 71 can be made larger than the inner diameter D1 of the conventional hollow long hole 7 as described above, the rack shaft 33 can be reduced in weight.

  In the above embodiment, the screw insert 8 is formed by winding a wire having a rhombus cross section into a coil shape. However, the present invention is not limited to this embodiment, and a female screw is provided on the inner diameter of the cylindrical bush. Various types of screw inserts can be used, such as those in which a male screw is formed, or a female screw is formed on the inner diameter of a cylindrical bush and the outer diameter is press-fitted into the pilot hole of the rack shaft.

The rack shaft of embodiment of this invention is shown, (1) is sectional drawing of the non-rack tooth side end surface of a rack shaft, (2) is an expanded sectional view of (1). It is a general view of a conventional rack and pinion type steering gear. (1) is a cross-sectional view of a rack shaft that is slidably assembled in the rack and pinion type steering gear of FIG. 2, and (2) is a front view of a tie rod screwed into both ends of the rack shaft of (1). It is. (1) is an enlarged sectional view of the rack tooth side end surface of the rack shaft of FIG. 3 (1), and (2) is an enlarged sectional view of the non-rack tooth side end surface of the rack shaft of FIG. 3 (1).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rack pinion type steering gear 2 Housing 3 Rack shaft 31 Rack tooth 32 Rack tooth bottom 33 Rack shaft 4 Tie rod 41 Tie rod end 42 Ball joint 43 Male screw 5 Female screw 51 Screw pilot hole 6 Female screw 61 Female screw 7 Hollow long hole 71 Hollow long hole 8 Screw insert 81 Female screw 82 Male screw

Claims (1)

In the rack and pinion type steering gear that transmits the steering force to the wheels,
Rack shaft formed with rack teeth meshing with the pinion,
An internal thread formed on the rack tooth side end surface of the rack shaft,
A hollow oblong hole having a diameter larger than the inner diameter of the female screw on the rack tooth side end surface, formed from a non-rack tooth side end surface of the rack shaft toward the rack tooth side by a gun drill tool to the vicinity of the rack tooth side end surface, and
A ball screw insert is inserted into the female screw which is tapped from the opposite rack teeth side end face to the hollow elongated hole, which has a female screw of the female screw same nominal diameter as the rack teeth side end face to the inner diameter, the outer diameter A rack and pinion type steering gear having a nominal diameter larger than the female screw on the rack tooth side end surface and having a male screw screwed into the tapped female screw.

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