JPS63196375A - Shaping method for grinding wheel - Google Patents

Abstract

PURPOSE:To reduce a size variation in a grinding wheel after truing as well as to improve accuracy of finishing of a workpiece and roundness in particular, by offsetting a rotary presser to the grinding wheel, and making a direction of rotation of the wheel mutually orthogonal with that of the rotary presser, at a contact part between them. CONSTITUTION:A rotary dresser 10 is set up in the state that an eccentric reference line Oe parallelled with a rotational center axis Og of a grinding wheel 4 and separated from this rotational center axis Og as much as the eccentric value epsilon is situated on an extension of a rotational center axis Od of the rotary dresser 10. Thus, both 4 and 10 are offset, whereby at a contact part between them, a direction of rotation of the wheel 4 and that of the rotary dresser 10 are made orthogonal with each other, and a flat shaping part 11 of the rotary dresser 10 is contacted over a wide range of a semispherical part 11 of the wheel 4, thus shaping takes place. Therefore, a size variation in the semispherical part 11 of the wheel 4 after being shaped becomes lessened, so that accuracy of finishing (for example, roundness) of a workpiece is improved.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a grinding wheel for shaping a grinding wheel used for grinding an arc-shaped groove such as a ball track groove of an outer race in a constant velocity joint. Regarding plastic surgery methods.

(Industrial Application Field) Figure 2 shows the ball track groove 2 of an outer race 1 used in a constant velocity joint being ground by a cylindrical grindstone 4 attached to the tip of a spindle 3. .

The illustrated outer race 1 is a Barfield type constant velocity joint, and six ball track grooves 2 are provided. The tip portion 5 of the cylindrical grindstone 4 for grinding each of these ball track grooves 2 has a hemispherical shape, and the inner surface of the ball track groove 2 is ground by this hemispherical portion 5. The grinding method using this grindstone 4 is performed by pressing the grindstone 4 against the outer race 1, which is a workpiece, and performing creep grinding, which is also called plunge grinding or plunge cutting. In this grinding process, the grinding wheel 4 is rotated by the spindle 3 around the rotation center Og, while the work piece, the outer race 1, is moved along the ball track from the position 01 shown in FIG. 2 to the position shown θ2. The central axis Qw of the outer race 1 swings about the center Qa of the groove 12. In addition, in Figure 2, the symbol @
6 indicates the grinding allowance, that is, the machining allowance.

After grinding in this way for the specified grinding depth,
Usually, the grindstone 4 is shaped using a dresser. This shaping involves refining, sharpening, or dressing, which involves using an appropriate tool to create a sharp cutting edge on the surface of the grinding wheel to remove chips within the pores and improve grinding efficiency. This is called reshaping, grindstone correction, or truing, in which the outer periphery of the grindstone is finished into the correct geometric shape with respect to the center line of the rotation center axis using an appropriate tool. Generally, the above-mentioned dressing and truing are performed at the same time.

In normal shaping work, a single dresser is used, and the tip 5 of the grindstone 4 shown in FIG.
Also, the shape of the grinding wheel is made spherical using a single-line dresser so that the cross-sectional shape of the ball track groove 2 is a circular arc, which is a perfect circle, or a Gothic arc, which is designed so that the ball and ball track groove make positive point contact. It has been formatted.

Further, in order to minimize curling of the grindstone 4, truing is performed using a cylindrical dress over the entire length of the outer circumference.

(Problems to be Solved by the Invention) However, in the conventional shaping method as described above, a soft whetstone 4 of WA abrasive grain system (white alumina abrasive grain)
Because of this, the shape of the whetstone does not change uniformly around the entire circumference as a result of abrasive grains falling off and self-growth during the grinding process. It was necessary to perform shaping after each coarse and fine polishing. For example, in the case of the ball track groove 2 of the outer race 1, it is necessary to perform one shaping every time one groove 2 is roughly ground, and one shaping after every three times fine grinding is carried out. there were.

Therefore, in the past, there was a problem in that the number of shaping operations was large and the productivity of the outer lace was low.

As a result, the number of workpieces processed per grindstone 4 was also small. For example, if the usable length of the grindstone 4 is 1°, the depth of cut of the dresser is 0.05 mm/time, and the number of dressings per workpiece is 8 times, the life of the grindstone 4 is 10 mm/(
0.05 mm x 8 times), and the number of workpieces processed per grindstone 4 was about 25 at most.

Generally speaking, in the grinding action, the cutting edge on the surface of the grindstone becomes dull due to grinding, the force applied to the cutting edge increases, and the abrasive grains are crushed or fallen off, so that the force becomes weak again. As a result, the cutting edge of the grindstone is automatically updated, and this is considered to be a so-called self-growth effect of the grindstone. Furthermore, if the grindstone becomes dull, crushed, or clogged, resulting in poor sharpness, shaping is performed to renew and restore the sharpness.

CBN has superior hardness, bonding, etc. compared to regular whetstones.
By using (borazon) grinding wheels, it has become possible to extremely reduce the self-growth effect during grinding and maintain the life of the grinding wheels for an extremely long time. However, when grinding the ball track groove 2, the cutting length when the abrasive grain grinds the workpiece is approximately equal to the circumference of the cross-sectional arc of the ball track groove 2 of the workpiece, as shown in Figure 2.3. Since the lengths are approximately equal, clogging with chips is likely to occur.

Therefore, with the aim of recovering from this clogging and improving the appearance, plastic surgery is performed.
In other words, it is necessary to perform dressing.

A single-row dresser is often used when shaping a normal grindstone such as a W△ type grindstone, but a rotary dresser is used when dressing a CBN grindstone because the wear of the diamond cutting edge progresses significantly with a single-row dressing.

Conventionally, in order to shape the hemispherical tip 5 of the grinding wheel 4 shown in FIG. 2 using a rotary dress, the method shown in FIGS.
) is the formatting method shown below. As shown in the figure, this is carried out using a rotary dresser 10. This rotary dresser 10 is a rotating body, and has a flat shaping section 1 at the tip.
1. In order to shape the grindstone 4 using such a rotary dresser 10, as shown in FIG. The rotation center axis Og of the grindstone 4 is on the extension line of the rotation center axis Qd of 10.
While rotating the rotary dresser 10 in the direction shown by the arrow with the rotary dresser 10 disposed so as to intersect with the angle .alpha., the rotary dresser 10 is oscillated relative to the grindstone 4 within the range shown by the angle α.

When we conducted a shaping experiment on the grinding wheel 4 shown in FIG. 2 using the conventional shaping method shown in FIG. The trend was shown in the figure. When the shape of the grindstone 4 was measured at that time, as shown in FIG. 5, the dresser caused part B to dig into the normal dressing locus. Moreover, this portion B corresponds to the portion where portions A and Aa in FIG. 3 of the ball track groove 2 of the workpiece are machined.

The present invention has been made in view of the above-mentioned problems of the prior art, and it reduces the dimensional change of the hemispherical part when the hemispherical part of the whetstone is shaped by the rotary dresser, and improves the hemispherical shape of the whetstone by the rotary dresser. The purpose is to improve the accuracy of grinding workpieces using a grindstone.

(Means for Solving the Problems) The present invention to achieve the above object rotates a cylindrical grindstone having a substantially hemispherical tip around the central axis of rotation of the T11 stone, and A rotary dresser having a flat shaped part formed at the tip thereof and in contact with the grinding wheel is positioned on an extension line of the rotation center axis of the rotary dresser on an eccentric reference line parallel to the rotation center axis of the grindstone. rotating, and moving the contact portion along the rotation center axis of the grindstone while making the rotation direction of the grindstone and the rotation direction of the rotary dresser perpendicular to each other at a contact portion between the grindstone and the rotary dresser. This is a method of shaping a grinding wheel.

(Function) The rotary dresser of the present invention grinds the grindstone in an offset state with respect to the grindstone. As a result, the rotating direction of the grinding wheel and the rotating direction of the rotary dresser at the contact area between the grinding wheel and the rotary dresser are orthogonal to each other, so that the shaping part of the rotary dresser comes into contact over a wide range of the hemispherical part. . Therefore, even when shaping is performed, there is little dimensional change in the hemispherical portion of the grindstone, and the machining accuracy of the workpiece, particularly the roundness, is improved, and the life of the rotary dresser is also extended.

Furthermore, conventional CBN can be used as the grindstone.

(Example) The present invention will be described below based on the drawings. Figure 1 (A) ~
(C) is a diagram showing a shaping device embodying the grinding wheel shaping method of the present invention, in which a cylindrical grinding wheel 4 having a substantially hemispherical tip 5 is shaped (dressed) using a rotary dresser 10. Indicates the state in which

As shown in FIG. 2, the grindstone 4 is attached to the spindle 3 and rotates in the direction indicated by the arrow around the rotation center axis 0 ( ), as in the case of grinding.

The rotary dresser 10 is a rotating body, and a flat shaping portion 11 that comes into contact with the grindstone 4 is formed at the tip thereof. This shaping portion 11 is formed into an annular shape, and a diamond 12 is bonded to this portion by a bonding agent (not shown). The rotary dresser 10 is rotated by a spindle (not shown) in the direction indicated by the arrow about the rotation center axis Od.

As shown in the figure, the positional relationship between the grinding wheel 4 and the rotary dresser 10 is such that the rotational center axis Od of the rotary dredge 4-10 is offset by an eccentric amount ε with respect to the rotational center axis Og of the grinding wheel 4. ing. That is, the first
As shown in the diagrams (A>(C)), the rotary dresser 10 is aligned with the eccentricity reference line Qe that is parallel to the rotation center axis OC+ of the grindstone 4 and is separated from the rotation center axis Og by the eccentricity ε. Position it on the extension line of the rotation center axis Od,
A rotary dresser 10 is installed. The eccentricity, that is, the offset range ε, has a dimension corresponding to the distance from the radial center of the annular molded part 11 to the rotation center axis Qd. As a result, as shown in FIG. 1(C), the rotational direction of the grindstone 4 at the contact portion between the grindstone 4 and the rotary dresser 10 (direction of arrow a), and the rotation direction of the rotary dresser 10 (direction of arrow A) are mutually orthogonal.

Further, the rotary dresser 10 is configured to swing in a direction along the rotation center axis Og, as indicated by an arrow in FIG. 1(B). This rocking causes the contact portion to move in the direction along the rotation center axis Og.

Next, a procedure for shaping (dressing) the grindstone 4 using a shaping device embodying the present invention shown in FIGS. 1A to 1C will be described.

With the rotary dresser 10 waiting at the position indicated by the imaginary line in FIG. 1(B), the grindstone 4 is advanced in the direction of its rotation center axis Oa.

At this time, the grindstone 4 and the rotary dresser 10 are rotating in the directions shown by the arrows. Next, the grindstone 4 is advanced by the set dressing depth δ. Under this state, the rotary dresser 10 is swung from the position shown by the imaginary line to the position shown by the solid line in FIG. 1(B). This rocking causes the contact portion between the grinding wheel 4 and the rotary dresser 10 to move, but the movement of this contact portion only needs to be relative, and the grinding wheel 4 can be moved without rocking the rotary dresser 10. It may be made to move.

In addition, the rotary dresser 1o for the dresser is shown in Figure 1 (
In B), a cut of δ/2 may be made at the position shown by the imaginary line, and an additional cut of δ/2 may be made at the position shown by the solid line.

When the dressing is completed as described above, as shown in FIG. 2, the grindstone 4 that has been shaped approaches the workpiece 1, which is waiting with the center of rotation NOV at the position θ1. Next, the work 1 swings from the position θ1 to the position θ2 in FIG. 2, and the work 1 is subjected to creep grinding. When the workpiece 1 reaches the 02 position, it returns to the 01 position at the spark-out speed. This results in 1
After the grinding of the two ball track grooves 2 is completed, the workpiece 1 is rotated 60' by an indexing device (not shown), and then indexed and rotated to the ball track groove 2 to be ground. This groove 2 is ground in the same manner as described above, and the grinding of six grooves is repeated.

By using a CBN grindstone with less grain loss as the grindstone 4, it is possible to continuously grind the ball track grooves 2 at 30 locations before clogging of chips occurs and cutting quality deteriorates. Whether or not to dress the whetstone 4 is determined by the fact that when the sharpness of the whetstone 4 decreases, the current of the motor (not shown) of the spindle 3 for rotating the whetstone 4 decreases by 15 to 25%.
This can be detected by monitoring the current.

In this case, the dressing (dressing) is done at the level of dressing the grinding wheel 4 for crushing or clogging.
Since the wear of the grinding wheel 4 is extremely reduced, the shaped dimensions of the grindstone 4 are stabilized.

In addition, the life of the grinding wheel when oscillation processing is performed using the nail rotary dresser 10 to shape the grinding wheel 4 is as follows, assuming that the dressing cutting depth is 0.01 mm/time and that shaping is performed once after shaping 5 workpieces 1. Even if the usable length of one grindstone is 5 mm, (5 mm/ (0,01
mm/times)) x 5 pieces/D.

The life of the grinding wheel was determined using the following formula, and a total of 2500 workpieces were processed using one grinding wheel.

This improvement in the life of the whetstone is due to the use of CB as the whetstone 4.
N can be used, and since shaping is performed while being offset by a distance ε from the rotary dresser 10 @ grinding wheel 4, the shaping part 11 of the rotary dresser 10 is aligned with the hemispherical part 5 of the grinding wheel. This is because the contact is dispersed and the amount of shaping done in one shaping is small, resulting in less dimensional changes in the hemispherical portion.

In other words, the shaping of the whetstone 4 by the rotary dresser 10 only needs to be done to sharpen the whetstone 4, and the shaping work is not considered as truing until the tip 5 of the whetstone 4 is finished into the correct geometric shape. This is because there is no need to reshape the image to the extent that it is visible. Further, since the wear of the rotary dresser 10 is also reduced, the chances of dressing for drainer positioning and sample machining of the workpiece, which occur when replacing the rotary dresser 10, can be extremely reduced.

(Effects of the Invention) As described above, according to the present invention, the grinding wheel is ground while the rotary dresser is offset from the grinding wheel, and the rotating direction of the grinding wheel and the rotary dresser are Since the rotating directions of the rotary dresser and the rotating direction are orthogonal to each other, the shaping part of the rotary dresser comes into contact with a wide range of the hemispherical part, so even if the grinding wheel is shaped, there is little change in the dimensions of the grinding wheel. As a result, the machining accuracy of the workpiece, especially the roundness, is improved. Moreover, according to such a shaping method, it becomes possible to use CBN or the like as the grinding wheel, which not only improves the life of the grinding wheel itself, but also reduces the wear of the rotary dresser, thereby extending the life of the rotary dresser. can also be improved.

[Brief explanation of the drawing]

FIG. 1(A) is a perspective view showing a grinding wheel shaping device embodying the grinding wheel shaping method of the present invention, and FIG. 1(B) (C
) are respectively a front view and a side view of Fig. 1 (A>), Fig. 2 is a sectional view showing a state in which a workpiece is being ground with a grindstone, Fig. 3 is an enlarged sectional view of the main part of Fig. 2, Figure 4 shows a front view and a side view showing the conventional method of shaping a grinding wheel.
FIG. 5 is a front view of a grindstone showing the biting phenomenon when the grindstone is ground using a conventional shaping method, and FIG. 6 is a graph showing the roundness of the grindstone when the grindstone is shaped using a conventional shaping method. DESCRIPTION OF SYMBOLS 1... Work (outer race), 2... Ball track groove, 4... Grindstone, 5... Hemisphere shaped part (tip part), 10... Rotary dresser, 11... Shaping part,
12... Diamond, OQ... Center axis of rotation of grindstone, Qd... Center axis of rotation of rotary dresser. Figure 3 Figure 4 (A) (B) Figure 5 Figure 6

Claims (1)

[Claims] A cylindrical grindstone having a substantially hemispherical tip part is rotated about the central axis of rotation of the grindstone, and a rotary dresser having a flat shaped part formed at the tip of the rotating body and in contact with the grindstone is attached to the grindstone. The rotation direction of the grindstone and the rotary dresser are rotated by being positioned on an extension line of the rotation center axis of the rotary dresser on an eccentric reference line that is parallel to the rotation center axis of the rotary dresser. A method for shaping a grinding wheel, comprising moving the contact portion along the rotation center axis of the grindstone while making the rotation directions of the dresser orthogonal to each other.