JP4454081B2 - Rack manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steering gear rack used in a rack and pinion type steering device.
[0002]
[Prior art]
The rack and pinion mechanism of the steering device is engaged with a pinion gear to which a steering force is transmitted to rack teeth of a rack that is slidably supported in the left-right direction, and a rack guide holds a predetermined backlash at the back of the meshing portion. With such a pressing force, the rack is allowed to slide.
[0003]
Such a rack for a steering gear is usually formed by cutting with a hob or plastic working with a forging press. However, cutting requires time and costs are high, and forging press has a short working time but high accuracy can be expected. After all, finishing processing is required in the subsequent process.
[0004]
In view of this, there has been proposed a method (Japanese Patent Laid-Open No. 57-137763) that corrects deformation and distortion of rack teeth in a short working time by applying pressure while meshing a pinion-type support base with a rack formed by forging press.
[0005]
[Problems to be solved by the invention]
Thus, although the device which improves the accuracy of the tooth surface of the rack has been devised, the waviness of the rack tooth surface (the wavy curve of the reference pitch line) is not considered, and the rack tooth surface and the substantially straight back surface The width between the two is not necessarily constant.
[0006]
A schematic diagram of a rack and pinion mechanism using such a rack is shown in FIG.
The pinion gear 02 meshes with the teeth of the rack 01, and the rack guide 03 presses the back of the meshing portion of the rack 01 while allowing the rack 01 to relatively slide.
[0007]
The rack guide 03 is urged by a spring 06 interposed between the rack guide screw 04 and a rack guide screw 04 which is screwed into the gear box and fixed by a lock nut 05 to press the rack 01.
There is a slight clearance d between the rack guide 03 and the rack guide screw 04.
[0008]
As shown in FIG. 5, when the tooth surface of the rack 01 undulates and the reference pitch line p is curved in a wave shape (FIG. 5 schematically shows the degree of curvature larger than actual), the rotation of the pinion gear 02 When the rack 01 moves in the left-right axis direction, the rack 01 is displaced in a direction perpendicular to the left-right axis direction, and the width length between the wavy tooth surface (reference pitch line p) and the substantially straight back surface is not constant. Therefore, the rack guide 03 is displaced, and the clearance d absorbs this displacement.
[0009]
Therefore, it is necessary to set the clearance d large in consideration of the case where the undulation width of the tooth surface of the rack 01 is large and the displacement width of the rack guide 03 is large.
Then, the urging force by the spring 06 changes greatly, and it becomes difficult to maintain an appropriate backlash of the engagement between the rack 01 and the pinion gear 02.
[0010]
When the rack 01 is displaced in a direction approaching the rack guide screw 04, the spring force of the spring 06 is strengthened and friction is generated between the rack guide 03 and the steering feeling becomes heavy. When moving in a direction away from 04, the clearance d increases and the spring force weakens, so that it strikes between the rack 01 and the pinion gear 02, between the rack 01 and the rack guide 03, and between the rack guide 03 and the rack guide screw 04. Sound may be generated.
Thus, when the friction between the rack 01 and the rack guide 03 changes, the rack and pinion mechanism does not operate smoothly and a stable steering feeling cannot be obtained.
[0011]
SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and the object of the present invention is to manufacture a rack for a steering gear rack that can suppress a change in friction and a hitting sound and obtain a stable steering feeling by a smooth operation. The point is to provide a method.
[0014]
[Means for solving the problems and effects]
To achieve the above object, according to the present invention, a rack tooth of a rack having a rack tooth surface is meshed with a pinion gear or a molding gear similar to a pinion gear, and the rear surface of the rack has the same cross-sectional shape as the rack guide support surface. This is a rack manufacturing method in which, while rotating a rotating grindstone or a milling cutter, a constant distance is maintained from the pinion gear or the forming gear and cutting is performed in the longitudinal direction.
[0015]
If the rack is sandwiched between a pinion gear or the like maintained at a fixed distance and a rotating grindstone, etc., and the pinion gear engaged with the rack teeth is rotated while the rotating grindstone or the like is rotated to move the rack in the axial direction, the rack The back surface is cut and the width between the rack tooth surface and the back surface can be easily formed in a long direction in a short working time.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment according to the present invention will be described with reference to FIGS.
A schematic diagram of a rack processing apparatus 5 for cutting the steering rack 1 according to the present embodiment is shown in FIGS.
[0017]
In the rack processing apparatus 5, a forming gear 7 and a rotating shaft 9 of the rotating grindstone 8 protrude from the base 6 at a predetermined distance, and the forming gear 7 and the rotating shaft 9 are driven to rotate by different motors. The
[0018]
The molding gear 7 is similar to a pinion gear having teeth formed on the peripheral surface of a cylinder, and the same gear as the pinion gear of the rack and pinion mechanism may be used.
The rotating grindstone 8 that is integrally fitted to the rotating shaft 9 has a shape in which the outer peripheral grindstone surface to be cut forms an arc-shaped groove, and has substantially the same cross-sectional shape as the rack guide support surface that holds the rack 1 from behind. That is, it has a semicircular arc shape that matches the cylindrical surface of the back surface of the rack 1.
The forming gear 7 and the rotating grindstone 8 are separated by a certain distance, and the rack 1 is sandwiched between them.
[0019]
The rack 1 processed by such a rack processing apparatus 5 has a rack tooth surface 1a formed by subjecting a cylindrical rod-shaped rack member to forging press processing, and a back surface 1b forming a cylindrical surface.
In the rack 1 in this state, the rack tooth surface 1a undulates with respect to the substantially straight back surface 1b, and the reference pitch line p is curved in a wave shape.
[0020]
The rack 1 is inserted between the forming gear 7 and the rotating grindstone 8 of the rack processing apparatus 5, the rack tooth surface 1a is engaged with the forming gear 7, and the rotating grindstone 8 cuts the back surface 1b.
[0021]
That is, the rotating grindstone 8 rotates at a high speed clockwise in FIG. 1, and the molding gear 7 located at a certain distance from the rotating grindstone 8 meshes with the rack tooth surface 1a and rotates at a low speed clockwise in FIG. A rotating grindstone 8 that rotates at a high speed while gradually moving 1 cuts the back surface 1b.
[0022]
The forming gear 7 is rotatably supported, the rack tooth surface 1a of the rack 1 is meshed with the rotating grindstone 8, and the rotating grindstone is moved while gradually moving by pulling or pushing the rack 1. The rear surface 1b of the rack 1 may be cut by the high-speed rotation of 8.
[0023]
Since the molding gear 7 and the rotating grindstone 8 are both fixed in position and the distance between them is constant, the rotating grindstone 8 is rear so that the distance from the rack tooth surface 1a (reference pitch line p) is constant. 1b is cut, and thus the hatched portion in FIG. 1 is cut to form a back surface that is curved in parallel with the reference pitch line p.
In other words, in the cut rack 1, the distance between the reference pitch line p of the rack tooth surface 1a and the back surface 1b is constant over the long direction.
[0024]
An example of a power steering apparatus using the cut rack 1 is shown in FIG.
A steering gear box 10 is provided at the end of a rack housing that houses the rack 1 and supports it slidably in the left-right axial direction.
[0025]
In the steering gear box 10, an input shaft 11 connected via a joint to a steering shaft to which a steering wheel is integrally attached is pivotally supported via a bearing. The input shaft 11 is a steering gear. The box 10 is connected to the pinion gear 12 via a torsion bar so as to be relatively twistable.
[0026]
The pinion gear 12 meshes with the rack teeth of the rack 1.
Therefore, the steering force transmitted to the input shaft 11 by the turning operation of the steering wheel rotates the pinion gear 12 via the torsion bar and slides the rack 1 in the left-right axial direction by meshing the pinion gear 12 with the rack teeth. Rudder is made.
[0027]
In the steering gear box 10, a rack guide cylindrical portion 10a is formed so as to protrude in a direction orthogonal to the rack 1 and the pinion gear 12 behind the rack 1 where the pinion gear 12 and the rack teeth mesh.
[0028]
A rack guide 15 is slidably inserted into the rack guide cylindrical portion 10a, is screwed into an opening of the rack guide cylindrical portion 10a, and is interposed between a rack guide screw 16 fixed by a lock nut 17 and a spring 18 interposed therebetween. Thus, the rack guide 15 is urged to press the back of the rack 1 meshing with the pinion gear 12.
[0029]
As shown in the schematic diagram of FIG. 4, the rack 1 has a long width between the rack tooth surface 1 a (reference pitch line p) and the back surface 1 b even if the rack tooth surface 1 a is curved in a wave shape. Therefore, when the rack 1 moves in the left-right axial direction by the rotation of the pinion gear 12, the distance from the pinion gear 12 is kept constant and the rack guide 15 is not displaced.
[0030]
Therefore, the clearance between the rack guide 15 and the rack guide screw 16 can be set small, and the rack guide 15 is urged by a spring force that is always constant and appropriate for the spring 18, so that the occurrence of friction changes and noise is suppressed. A stable steering feeling due to smooth operation can be obtained.
[0031]
In addition to the rotating grindstone, it is possible to use a milling cutter that rotates by forming a plurality of arc-shaped cutting edges on the circumference of the cylinder.
[Brief description of the drawings]
FIG. 1 is a schematic schematic view of a main part of a rack processing apparatus for processing a rack according to an embodiment of the present invention.
2 is a cross-sectional view taken along line II-II in FIG.
FIG. 3 is a view showing a structure inside a steering gear box of a steering device using the rack.
FIG. 4 is a schematic schematic view of an essential part of a rack and pinion mechanism of the steering device.
FIG. 5 is a schematic diagram of a main part of a rack and pinion mechanism using a conventional rack.
[Explanation of symbols]
1 ... rack,
DESCRIPTION OF SYMBOLS 5 ... Rack processing apparatus, 6 ... Base, 7 ... Molding gear, 8 ... Rotary grindstone, 9 ... Rotary shaft,
10 ... steering gear box, 11 ... input shaft, 12 ... pinion gear, 15 ... rack guide, 16 ... rack guide screw, 17 ... lock nut, 18 ... spring.

Claims (1)

The rack tooth of the rack formed with the rack tooth surface is meshed with a pinion gear or a molding gear similar to the pinion gear,
A rotating grindstone or milling cutter having the same cross-sectional shape as the rack guide support surface is rotated on the back surface of the rack while maintaining a certain distance from the pinion gear or the forming gear and performing cutting in the longitudinal direction. A method for manufacturing a rack.

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