JP2006247801A - Working method of worm gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a working method of a worm gear capable of obtaining an involute shape that roughness of a tooth flank is enhanced and enhancing engagement accuracy of a worm gear. <P>SOLUTION: In the working method of the worm gear 2, a tool of wheel shape having a grinding tool 1 having a cross section of trapezoid shape on an outer peripheral part is used. In a blade part 1a of the trapezoidal grinding tool 1, the respective tooth flanks 2a, 2b of the worm gear 2 is grinding-worked to the involute shape by using the grinding tool 1 in which correction working that it is made to an inner recession shape by slightly making its blade tip and a blade base thick is applied to the existing grinding tool of trapezoid shape. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for processing a worm gear used in an electric power steering device or the like.

  As a method for finishing the worm gear, grinding with a trapezoidal grindstone is generally used. As shown in FIG. 4, this processing method uses a trapezoidal grindstone 10 inclined by a lead angle α ° with respect to a grindstone turning axis P that is a straight line perpendicular to the rotation center axis O of the worm gear 2 (hereinafter referred to as worm 2). The worm 2 is processed.

  Further, as shown in FIG. 5, the first tooth surface 2a and part of the tooth bottom 2c are moved by a trapezoidal first single-blade tool 8a which is arranged to be translated by a predetermined distance with respect to a plane including the central axis O of the worm 2. There is also a method in which the second tooth surface 2b and the rest of the tooth bottom 2c are cut with a trapezoidal second single-blade tool 8b which is cut and then translated by a predetermined distance in the opposite direction from the plane.

  As shown in the figure, the intersecting curve of each tooth surface 2a, 2b formed by this method and the surface orthogonal to the central axis O is an involute curve 9a whose radius is the circle 9 having the predetermined distance. Since each tooth surface 2a, 2b is formed in a convex curved surface, this convex curved surface is called an involute shape. The involute tooth surfaces 2a and 2b do not deteriorate the engagement with the worm wheel (not shown) even if there is a slight processing error or assembly error, and generally speaking, the advantage is that the engagement accuracy is improved. There is.

  In the case of the method of processing with the trapezoidal grindstone 10 described above (see FIG. 4), the tooth surfaces 2a and 2b of the formed worm 2 are involute shapes as shown by broken lines in the axial sectional shape as shown in FIG. 3 has a flat shape (or a concave shape with a thick tooth tip or tooth root), which affects the meshing accuracy with the worm wheel.

As a method for obtaining this involute shape, for example, in Patent Document 1, an end mill type tool is used and the processing surface at the tip is applied to the first tooth surface (or the second tooth surface) of the worm. A method is disclosed in which the tool is moved in parallel with the central axis of the worm at a speed proportional to the rotational speed of the worm while rotating the tip portion.
JP 2001-198730 A Japanese Patent Application Laid-Open No. 08-1555749

  However, the conventional worm gear machining method (Patent Document 1) has a problem that it is difficult to improve the roughness of the tooth surface because it is an end mill type tool and is not suitable for finishing. .

  Moreover, in patent document 2, the overall shape of the wheel shape by which the concave surface which can shape | mold a tooth surface, such as a gearwheel, in an involute shape was formed in the outer peripheral part, and the CBN abrasive grain layer was formed in the surface. Although a tool is shown, there has been a need for a simpler method for producing a blade portion having this concavely shaped blade surface.

  Accordingly, the present invention provides a worm gear machining method that improves the conventional inconveniences described above, obtains an involute shape with improved tooth surface roughness, and improves the meshing accuracy of the worm gear. It is an issue.

  In order to achieve the above object, according to the present invention, in the worm gear processing method for grinding each tooth surface of the worm gear using a wheel-shaped tool having a trapezoidal grinding wheel in the outer peripheral portion, the trapezoidal grinding stone Further, the cutting edge portion and the cutting edge portion are slightly thickened so as to have a concave shape, and each tooth surface of the worm gear is ground into an involute shape by using this.

  The present invention uses the above-described method, and a trapezoidal grindstone capable of forming an involute-shaped tooth surface relatively easily can be obtained by subjecting an existing trapezoidal grindstone to correction processing. Thus, the grinding process using the trapezoidal grindstone can improve the roughness of the tooth surface of the worm, and the tooth surface is formed into an involute shape, thereby improving the meshing accuracy between the worm and the worm wheel. be able to. Along with this, it is possible to prevent noise, increase in surface pressure, uneven wear, and the like due to worm engagement errors.

  Embodiments of the present invention will be described below with reference to the drawings.

  1 is a perspective view of a grindstone showing an embodiment according to the present invention, FIG. 2 is a cross-sectional view showing a processed blade surface of the grindstone of FIG. 1, and FIG. 3 is a cross-sectional view showing a tooth surface shape of a worm gear processed. is there.

  As shown in FIG. 1, the trapezoidal grindstone used in the machining method of the present invention has a wheel shape, and the blade portion 1a is applied to the tooth surface of the worm (see FIG. 4) and is rotated by rotating around the shaft 1b. Is to do.

  As shown in FIG. 2, the blade portion 1a of the trapezoidal grindstone 1 is modified to the original shape indicated by the broken line in the axial cross-sectional shape, and the blade tip portion and the blade base portion are formed in a middle concave shape with a slightly thicker shape. Molding. The shape of the grindstone 1 can be obtained by modifying the existing trapezoidal grindstone by modifying the shape of the dresser to be molded.

  When a worm (not shown) is processed using the trapezoidal grindstone 1, the tooth surfaces 2a and 2b of the worm can be formed into an involute shape as shown in FIG. When processing using a conventional trapezoidal grindstone, as shown in FIG. 6 of the background art, the first tooth surface 2a and the second tooth surface 2b of the worm indicated by the broken line are substantially flat compared to the involute shape 3. It has a shape. In contrast, when the grindstone 1 of the present embodiment is used, the first tooth surface 2a and the second tooth surface 2b of the worm are formed into convex curved surfaces as shown in FIG. It can be seen that they are almost overlapping. In the same figure, 2c is a tooth bottom.

  As described above, in the present invention, the trapezoidal grindstone 1 capable of forming the tooth surface of the involute shape 3 relatively easily is obtained by modifying the shape of the dresser and performing the modification process on the existing trapezoidal grindstone. Can do. Thus, since the grinding process is performed using the wheel-shaped trapezoidal grindstone 1, the roughness of the tooth surface of the worm can be improved, and the tooth surface has the involute shape 3, so that the worm and the worm wheel can be improved. The meshing accuracy can be improved. Along with this, it is possible to prevent noise, an increase in surface pressure, uneven wear, and the like due to meshing errors.

It is a perspective view of a grindstone showing an embodiment concerning the present invention. It is sectional drawing which shows the blade surface shape by which the grindstone of FIG. 1 was processed. It is sectional drawing which shows the tooth surface shape by which the worm gear was processed. It is a perspective schematic diagram which shows the grinding process of the conventional worm gear. It is explanatory drawing which shows the grinding method of obtaining the conventional involute shape. It is sectional drawing which shows the tooth surface shape by which the conventional worm gear was processed.

Explanation of symbols

1: Grinding wheel 2: Worm gear 2a: First tooth surface 2b: Second tooth surface 3: Involute shape

Claims (1)

In the processing method of the worm gear that grinds each tooth surface of the worm gear using a wheel-shaped tool having a trapezoidal grinding wheel in the outer periphery,
The trapezoidal grindstone is subjected to a modification process to make the blade edge part and the blade edge part slightly thick to make a concave shape, and using this, each tooth surface of the worm gear is ground into an involute shape, How to process the worm gear.

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