JPH0445761Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a machine tool that holds and processes a workpiece at both centers.

<Prior art> Figure 6a is a front view of a straight cylindrical grinder;
Figure b is a plan view thereof. As shown in FIG. 6, the cylindrical grinding machine consists of a head stock 11, a tail stock 12, a table 13, a grindstone head 14, etc., and a workpiece 17 held between sword centers 15 and 16 attached to the head stock 11 and tail stock 12. , a whetstone 18 attached to a whetstone stand 14
Grinding is done by Moreover, FIG. 7 is a plan view of the Anguilla type cylindrical grinder. As shown in Figure 7, the Anguilla type cylindrical grinder has a grinding wheel head 14.
The guide surface of the grinding wheel 19 is inclined at a predetermined angle with respect to the guide surface of the table 13.
By this, the cylindrical surface and end surface of the workpiece 17 can be effectively ground simultaneously.

FIG. 8 is a partially cutaway front view of the main parts showing how a workpiece is attached to such a grinding machine.
As shown in FIG. 8, tapered center holes 20 and 21 are pre-drilled on both end faces of the workpiece 17, and holes 20 and 21 on the side of the headstock 11 each having a conical tip are inserted into these center holes 20 and 21, respectively. Sword center 15 and sword center 16 on the tail stock 12 side
are fitted and hold the workpiece 17. In addition, a turner 2 is attached to the end of the workpiece 17 on the headstock 11 side.
2 is fixed, and a drive pin 23 that is rotationally driven by the head stock 11 is connected to the drive pin 22.
It fits loosely into the workpiece 17 and transmits rotational force to the workpiece 17.

FIGS. 9 and 10 are explanatory diagrams of the machining state in a straight type and an angular type cylindrical grinder, respectively; FIG. 9A is a perspective view of a workpiece and a grindstone, and FIG. 1B is a plan view thereof. In a straight type cylindrical grinder, as shown in Fig. 9, the workpiece 17
The cylindrical surface 17a is the outer periphery 18a of the whetstone 18, and the side end surface 17b is the corner edge 1 of the whetstone 18.
It is ground at 8b. On the other hand, in the Angular type cylindrical grinder, as shown in Fig. 10, the workpiece 1
The cylindrical surface 17a of No. 7 is ground by the outer circumference 19a of the angular type grindstone 19, and the side end surface 17b is ground by the side surface 19b of the angular type grindstone 19. In addition, in FIGS. 9 and 10, the thick lines indicate the workpiece 17 and the grindstone 1.
8 and 19 are shown.

<Problems to be solved by the invention> The above-mentioned conical sword centers 15 and 16 are fitted into the center holes 20 and 21 of the workpiece 17.
Conventional center work that maintains

(1) Poor roundness shape accuracy of the center holes 20 and 21 of the workpiece 17 directly leads to a decrease in the roundness shape of the cylindrical surface 17a of the grinding section and the perpendicularity precision of the side end surface 17b.

(2) Furthermore, if the blade centers 15 and 16 of the grinding machine are worn out and the apex angle (60°) of the cone and roundness accuracy are degraded, this also directly leads to a decrease in machining accuracy.

(3) In the case of (1) and (2) above, it is possible to restore accuracy by corrective grinding of the center holes 20, 21 and sword centers 15, 16, but corrective machining is difficult for large diameter workpieces. It is.

(4) Furthermore, due to aging of the grinding machine and heat treatment distortion (bending) of workpiece 17, workpiece 1
If there is a misalignment in the center alignment while holding the workpiece 17, the rotation of the workpiece 17 will cause twisting, resulting in a decrease in machining accuracy. Incidentally, in a straight type cylindrical grinder, the corner edge portion 18b of the grinding wheel 18 cuts the side end surface 17 of the workpiece 17.
When processing b, if the center heights match, regular cut marks called iris will appear on the ground surface, but due to the above-mentioned center alignment error, the cut marks become irregular. There is. This state is a state in which the perpendicularity (face runout) accuracy is degraded, and is often visually observed during rotation.

This invention solves these problems in centering work using conventional sword centers, and allows high-precision centering work to be performed even when the center hole of the workpiece or the precision of the machine tool deteriorates. The purpose is to provide machine tools.

<Means for Solving the Problems> A machine tool according to the present invention for solving the above-mentioned problems is a machine tool that performs center work by holding a workpiece between centers provided in a head stock and a tail stock, respectively. The present invention is characterized in that it includes a sphere that can fit into a center hole of a workpiece, and a female center that has a tapered hole into which the sphere fits and holds the workpiece through the sphere.

<Function> Since the sphere is interposed between the center hole of the workpiece and the female center, the center of the sphere can be located on the center line of the workpiece even if the accuracy of the roundness shape of the center hole of the workpiece is poor. Machining accuracy is not directly affected by the deterioration of center hole accuracy. On the other hand, misalignment of the center is absorbed at the contact portion between the sphere, the center hole, and the female center, thereby preventing the occurrence of twisting.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

Fig. 1 is a partially cutaway front view of the main part showing the attachment state of a workpiece in a grinding machine according to an embodiment of the present invention, Fig. 2 is an enlarged view of the main part, and Fig. 3 is a spherical contact part of the grinding machine. It is an explanatory diagram. In FIGS. 1 to 3, parts that are the same as those in the prior art are denoted by the same reference numerals, and redundant explanation will be omitted.

In FIGS. 1 and 2, 31 and 32 are rigid bodies, for example, spheres made of steel, and each of the workpieces 1
Tapered center hole 2 formed on the end surface of 7
0, 21, and its spherical surface fits into the center hole 20, 2.
The workpiece 17 is sized so that it protrudes from the end surface of the workpiece 17 by approximately a hemisphere while in contact with the tapered surface of the workpiece 17. On the other hand, 33 and 34 are female centers that are attached to the head stock 11 and tail stock 12, respectively, and have tapered holes 35 and 36 into which the spheres 31 and 32 are fitted, respectively. Thus, in this device, the workpiece 17 is held by the two female centers 33 and 34 via the spheres 31 and 32.

In this embodiment, the female center 33 on the head stock 11 side and the female center 34 on the tail stock 12 side are dead centers that do not rotate. A sliding contact is made between 33 and 34. Therefore, headstock 1
As shown in FIG. 3, which is an explanatory view of the contact portion of the sphere 31 on the first side, the apex angle β of the cone of the tapered hole 35 of the female center 33 is made larger than the apex angle a of the cone of the center hole 20 of the workpiece 17. There is. In the illustrated example, β
is set to 90° compared to the standard center hole apex angle α = 60°. By doing this, the diameter D of the contact portion between the sphere 31 and the center hole 20 of the workpiece 17 is
1 and the tapered hole 35 of the female center 33, and as a result, the frictional resistance at the contact portion between the workpiece 17 and the sphere 31, which has a long contact length, is greater than that on the female center 33 side. Thus, the sphere 31 rotates together with the workpiece 17. in this case,
Even when the center hole 20 has poor roundness and shape accuracy,
The precision of the sphere 31 that rotates integrally with the workpiece 17 enables highly accurate machining. The same applies to the female center 34 on the tail stock 12 side.

In this configuration, in this device, the spheres 31 and 32 are interposed between the female centers 33 and 34 on the head stock 11 side and the tail stock 12 side and the center holes 20 and 21 of the workpiece 17, so that the accuracy of the center holes 20 and 21 can be improved. This prevents the processing accuracy from being directly affected by deterioration. On the other hand, work 1
Even if the center alignment becomes incorrect due to distortion (bending) of the sphere 7 or aging of the grinding machine, the spheres 31, 3
2 and the center holes 20, 21 of the workpiece 17 and the tapered holes 35, 36 of the female centers 33, 34. This is absorbed by the deviation of the contact portion between the center holes 20, 21 of the workpiece 17, and the tapered holes 35, 36 of the female centers 33, 34, preventing the occurrence of twisting and enabling high precision machining. Incidentally, Fig. 4 is a graph showing the results of measuring the roundness of a workpiece when a conventional grinder performs grinding with a defective center hole of the workpiece, and Fig. 5 is a graph showing the results of measuring the roundness of the workpiece when the center hole of the workpiece is defective and the workpiece is ground using a conventional grinder. This is a graph showing the results of measuring the roundness of a workpiece when grinding is performed using this device, and it can be confirmed that the machining accuracy is improved by this device.

In the above embodiment, the spheres 31 and 32 are interposed in the center holes 20 and 21 on both sides of the workpiece 17, but the spheres and the female center are also effective even when used only on one side of the workpiece 17. Furthermore, the female center may be a rotating center that rotates itself. Furthermore, although the above-mentioned embodiment describes a cylindrical grinder, the present invention is not limited to this, and is applicable to a worm grinder, for example, which performs center work that requires strict roundness and surface run-out accuracy. It is suitable for application to machine tools such as gear grinders and shaving machines.

<Effects of the invention> As described above in detail with reference to one embodiment, according to the invention, the workpiece is held at the female center with a sphere interposed, so that the roundness of the center hole of the workpiece is improved. Even if the shape accuracy is incorrect, high-precision machining is possible without corrective grinding of the center hole, and the center alignment deviation is absorbed by the sphere, preventing distortion and creating a perfect circle. Machining with good degree shape and true angle (surface runout) accuracy can be performed.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway front view of the main part showing the attachment state of a workpiece in a grinding machine according to an embodiment of the present invention, Fig. 2 is an enlarged view of the main part, and Fig. 3 is a spherical contact part of the grinding machine. Explanatory diagrams, Figures 4 and 5 are graphs of the roundness measurement results of workpieces machined by a conventional grinder and a grinder according to the present invention, respectively, and Figure 6a is a front view of a straight cylindrical grinder. , FIG. 7 is a plan view of an anguilla-type cylindrical grinder, and FIG. 8 is a partially cutaway front view of main parts showing how a workpiece is attached to a conventional grinder.
FIGS. 9 and 10 are explanatory diagrams of the machining state in a straight type and an angular type cylindrical grinder, respectively; FIG. 9A is a perspective view of a workpiece and a grindstone, and FIG. 10B is a plan view thereof. In the drawing, 11...Head stock, 12...Tail stock, 17...Work, 20, 21...
Center hole, 31, 32... sphere, 33, 34...
Female center, 35, 36... Tapered hole.

Claims (1)

[Scope of utility model registration request] A machine tool that performs centering work by holding a workpiece between centers provided in a head stock and a tail stock, respectively, has a spherical body that can fit into a center hole of the workpiece, and a tapered hole into which the spherical body fits, and the spherical body A machine tool comprising: a female center that holds a workpiece through the female center;