JPS649139B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for grinding a workpiece consisting of a large diameter cylindrical portion and a small diameter shaft portion axially protruding from the axial end thereof using a centerless grinder.

Examples of workpieces consisting of a large-diameter cylindrical portion and a shaft portion protruding from its axial end include a shaft press-fitted into the center of a motor core, a poppet valve for an engine, and the like. Note that "large diameter" and "small diameter" are used here in a relative sense, meaning that the shaft portion has a smaller diameter than the cylindrical portion. An example of such a workpiece is shown in FIG. In the figure, 1 indicates a shaft portion, and 2 indicates a cylindrical portion.

In order to grind the circumferential surface of the cylindrical portion 2 of such a workpiece W using a centerless grinder, conventionally, the workpiece is placed between a grinding wheel G and an adjustment wheel R facing each other, as shown in FIG. A support blade 3 is provided, and the grindstone G and adjustment wheel R are rotated while supporting the workpiece on this blade. In this case, the shaft 1 is attached to the blade 3 from the beginning.
A supporting surface 3b is provided which is supported by the higher supporting surface 3a and which is lowered to accommodate the circumferential surface of the cylindrical part 2 to be ground. The adjustment wheel R has a cylindrical surface R1 that is in contact with the outer peripheral surface of the cylindrical portion 2 and a cylindrical surface R that is in contact with the shaft portion 1 in order to apply a reaction force against the feeding of the grindstone G.
Therefore, the circumferential surface of the adjusting wheel R is annularly recessed at the cylindrical surface R1.

This configuration is for grinding the circumferential surface of the cylindrical portion 2 in order to obtain concentricity with the axis 1, and as the circumferential surface of the cylindrical portion 2 undergoes grinding and its diameter decreases, the axis A large load will be placed on section 1. That is, when the workpiece W starts grinding, it is supported by the blade 3 and the adjusting wheel R only by the shaft 1, so if the shaft 1 is thin, the shaft cannot withstand a large load. As a result, heavy grinding becomes impossible. Furthermore, since the shaft portion 1 is always in contact with the adjustment wheel surface R2, it is likely to be scratched. If any scratches remain on the shaft, post-processing of only the shaft must be performed after grinding of the cylindrical portion 2 is completed. On the other hand, the surface R that is annularly recessed on the circumferential surface of the adjustment wheel R as described above.
1, in order to load the workpiece W so that the cylindrical portion 2 faces the concave surface, the workpiece must be moved considerably upward and then displaced downward, and the workpiece Movement in the axial direction (direction perpendicular to the plane of the paper in FIG. 2) is quite troublesome and has the drawback of requiring time for loading. moreover,
Since the surfaces R1 and R2 of the adjusting wheel R must be made different depending on the size of the workpiece, there is also the problem that the adjusting wheel must be replaced every time a workpiece of a different size is ground.

The present invention provides a grinding method for a centerless grinder that can solve the above-mentioned problems of the prior art.

Hereinafter, embodiments of the present invention will be described with reference to FIG. 3 and subsequent figures.

In Figure 3, G is the grinding wheel of the centerless grinder, R
also indicates the adjustment wheel. These grinding wheels G and adjusting wheels R face each other, and a workpiece supporting blade 3 is provided between them as in the conventional case. The blade 3 has a high support surface 3a and a low support surface 3b as in the conventional case. As shown in FIG. 4, the low support surface 3b is located between a pair of high support surfaces 3a, and the low support surface 3b
corresponds to the large diameter cylindrical portion 2 of the workpiece W, and the high support surface 3a corresponds to the small diameter shaft portion 1 of the workpiece W. These support surfaces 3a, 3b are lowered toward the adjusting wheel R, as in the known case.

In the state before grinding, the workpiece W normally has a cylindrical portion 2 that is not completely concentric with the shaft portion 1 serving as a reference. The cylindrical portion 2 before such grinding is indicated by a solid line eccentric to the shaft portion 1 in FIG. After the cylindrical portion 2 in such an eccentric state undergoes grinding and reaches the finished dimensions, it becomes concentric with the reference shaft portion 1 as shown by the chain line 2a.

According to the present invention, the step, that is, the difference in height between the shaft part support surface 3a and the cylindrical part support surface 3b of the workpiece support blade 3 is the radius of the cylindrical part 2 and the shaft part 1 in the finished dimension of the workpiece. Begin grinding with a difference equal to or slightly greater than the difference. The radius difference between the cylindrical portion 2 and the shaft portion 1 of the workpiece before the start of grinding has various values due to eccentricity, but even the minimum radius difference is larger than the radius difference in the finished dimension. Therefore, when the unground workpiece W is supported on the blade 3 by defining the steps between the support surfaces 3a and 3b as described above, the cylindrical portion 2 is placed on the support surface 3 as shown in FIG.
b, the shaft portion 1 floats from the support surface 3a, and there is a gap C therebetween. In the present invention, grinding of the cylindrical portion 2 is started in this state.

Grinding progresses in this way, but at the initial stage, the shaft part 1 rotates without interfering with the blade 3, and the cylindrical part 2 also rotates accordingly.
It is then ground to create a smooth eccentric circle.

As the diameter of the cylindrical portion 2 is reduced by grinding, the shaft portion 1 gradually approaches the support surface 3a, and finally, as shown in FIG. 5, the shaft portion 1 comes into contact with the support surface 3a. After that, the workpiece W is mainly supported only by the reference shaft 1 and the grinding progresses. In this final stage of grinding, the direction of eccentricity of the cylindrical portion 2 causes vertical movement of the workpiece as shown in FIG. This motion is exactly the same as the circle-forming action in general centerless grinding, and the thicker the uneven thickness, the greater the grinding allowance. When each part of the workpiece is considered to be a rigid body, the amount of change in grinding allowance per revolution of the workpiece is determined only by the center height angle α (Fig. 6), the blade apex angle β (Fig. 5), and the eccentricity e (Fig. 5). It is determined accordingly. To give an example, the center height angle α
is 7° (about this amount in normal centerless grinding), the blade apex angle β is 60°, the eccentricity e is 0.05mmTIR (total indicator reading), and the grinding allowance change (radius) is approximately 5μ. . However, in actual grinding work, the reference shaft 1 is elastically deformed, so the shaft portion 1
Although there is a transient state in which the motion is determined only by the cylindrical part 2 even though the blade 3 interferes with the blade 3, in this case it is expected that there will be little concentricity improvement effect, so cutting It is necessary to appropriately determine the loading speed and the level difference of the blade support surface according to the workpiece.

According to the test results, when a carbon tool steel blade was used and the height difference was made equal to the radius difference between the cylindrical part and the shaft part in the finished dimensions of the workpiece, and grinding was performed at each grinding allowance and compared, it was found that the blade height difference was Better concentricity was obtained when the radius difference was 10 to 20μ greater than the shaft radius difference.

The test employed a direct method of measuring the direction and amount of eccentricity while grinding the workpiece in steps of 0.02-0.05 mm (about diameter). The test results show that even though the outer periphery of the cylindrical part was ground smoothly until just before the difference in radius of the axial part of the workpiece became equal to the step of the blade, the direction and amount of eccentricity hardly changed, and even after further grinding When this was done so that the radius difference was 0.02 to 0.03 mm smaller than the step difference, the grinding sound showed changes in intensity in synchronization with the rotation of the workpiece, and an improvement in concentricity was observed. FIG. 7 shows an example of the change in sound when grinding is performed continuously.

In the figure, the vertical axis represents sound pressure, the horizontal axis represents time or diameter reduction, S represents the burr grinding range, T represents the uniform grinding range, and U represents the concentric improvement range.
In the range U, r indicates one rotation of the workpiece, and it can be seen that the sound pressure increases periodically corresponding to each rotation. It was confirmed that the periodic sound change in the concentricity improvement range U characterizes the grinding method of the present invention, and that increasing the cutting speed in this range results in a uniform grinding sound and the concentricity improvement effect disappears. .
This is presumed to be due to the deflection of the shaft.

The grinding sound in the uniform grinding range T is almost the same as the sound during normal centerless grinding. Furthermore, in the burr grinding range S, it seems that there is a large influence due to the dropout of abrasive grains, and an appropriate air cut area seems to be necessary. Thus, the final grinding cycle can be as follows, for example.

Air cut...2 seconds Uniform grinding range T...1 second (grinding allowance φ0.1mm approx.) Concentricity improvement range U...1 second (grinding allowance φ0.05mm approx.) Spark out...0.5 seconds Rapid retreat...0.5 seconds As is clear from the above description, in the present invention, there is no need to use the adjusting wheel having the concave surface R1 as shown in FIG.
can be a simple cylindrical surface. Therefore, when loading or unloading the workpiece W in the axial direction, it is sufficient to displace the workpiece W upward by at least the difference in radius between the cylindrical portion and the shaft portion.
FIG. 8 shows an example of a means for loading and unloading a workpiece with a slight displacement in the vertical direction.

In the figure, reference numeral 10 denotes a loading/unloading arm, which consists of two parallel plates.These plates 10 are arranged parallel to the axial direction of the workpiece W on both sides of the blade 3, as shown in FIG. It will be established. The proximal ends of these plates 10 are pivotally connected to a rotating disk 13 by pins 12, and the distal ends thereof are supported by means not shown so that the plates 10 can be moved in parallel. Therefore, when the disk 13 is driven to rotate in the direction of the arrow by a suitable means, the plate 10 moves in parallel in the order shown by the chain lines, and performs vertical and longitudinal movements. On the plate 10,
Workpiece supporting recesses 11a and 11b are provided at intervals. The recess 11a is a loading recess, and when a workpiece Wa is placed in the recess 11a and the rotating disk 13 is driven, the workpiece Wa sent in the direction of the arrow L in FIG. It is placed on the blade 3 with the trajectory shown. Also,
The ground workpiece Wb similarly moves along a trajectory ~ and is sent out in the direction indicated by the arrow UL. Note that the diameter D of the trajectory circle of the pivot pin 12 of the rotating disk 13 is preferably 1.5 times the axial length of the workpiece W.

According to the present invention, the embodiments of which have been described above, the large-diameter cylindrical portion of the workpiece is supported by the adjustment wheel, and the contact between the reference shaft portion and the blade is made only at the time of spark-out, which is different from the case of the conventional example. In contrast, the shaft part is less likely to be damaged, so post-processing of the shaft part is not required. Furthermore, even if the workpiece has a thin shaft such as a motor core, heavy grinding is possible because the large diameter cylindrical portion is always supported by the blade and no load is easily applied to the shaft. In addition, the minimum lift amount of the workpiece can be reduced for loading and unloading the workpiece, shortening the loading time, and the grinding wheel and adjusting wheel can be changed when changing the set of workpieces with different dimensions of the grinding part. Benefits can be obtained without the need for

[Brief explanation of drawings]

Fig. 1 is a perspective view showing the overall shape of the workpiece, Fig. 2 is an explanatory drawing showing the conventional grinding method, Fig. 3 is an explanatory drawing showing the initial stage of the grinding method of the present invention, and Fig. 4 is the same. A side view showing the relationship between the blade used in the method and the workpiece, FIG. 5 is an explanatory diagram showing the latter stage of the grinding method of the present invention, and FIG. 6 is an explanation of the concentricity improvement stage after reaching the state shown in FIG. 5. Fig. 7 is a graph showing the state of grinding noise during grinding, Fig. 8 is a principle diagram of a loading/unloading device suitable for use in conjunction with the method of the present invention, and Fig. 9 is a graph showing the movement of the workpiece by the same device. It is a figure showing a state. G... Grindstone, R... Adjustment wheel, W, Wa, Wb...
...Workpiece, 1...Shaft part, 2...Cylindrical part, 3...Workpiece support blade, 3a...Support surface for shaft part, 3b
... Supporting surface for cylindrical part, C ... Gap, S ... Burr grinding range, T ... Uniform grinding range, U ... Concentric improvement range, 10 ... Plate for loading and unloading, 12 ... Pin.

Claims (1)

[Claims] 1 A method of grinding a workpiece consisting of a large-diameter cylindrical part and a small-diameter shaft part that protrudes in the axial direction from the axial end of the large-diameter part using a centerless grinder. The workpiece support blade, which is located between the grinding wheel and the adjusting wheel, has a support surface for the shaft part that can contact the small diameter shaft part from below, and a support surface for the cylindrical part that can contact the large diameter cylinder part from below. The difference in height between the two support surfaces is set to a value that is equal to or slightly larger than the difference in radius between the cylindrical part and the shaft part in the finished dimensions of the workpiece, so that the cylindrical part becomes the support for the cylindrical part at the start of grinding. A grinding method characterized in that the cylindrical part is held between a grindstone and an adjustment wheel and ground while the cylindrical part is supported by a surface and the shaft part is separated upward from the support surface for the shaft part.