JP2007301653A - Workpiece supporting center used for machine tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the deterioration of machining accuracy by supporting a workpiece w in the state that its radial play is completely restricted even if the cross sectional shape of the center hole c1 of the workpiece w has been permanently deformed into a slightly noncircular shape. <P>SOLUTION: The workpiece abutting portion 9 of a tip end portion 3 has three slender outer peripheral portions 9a forming the regions in the vicinity of the respective generating lines at three equally divided positions about its axis 7 on the outer peripheral surface of a right circular cone shape. Further, other outer peripheral portions of the right circular cone shape except the slender outer peripheral portions are recessed as side surfaces 9b so as to approach to the axis. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a work support center which is mounted on a machine tool and is fitted into a center hole of a work to support the work rotatably.

  There are a spindle center and a tailstock center as workpiece support centers used for rotatably supporting a workpiece between a spindle and a tailstock of a machine tool. These centers are disclosed in Patent Document 1. As shown in the figure, it has a base end portion whose outer peripheral surface is held by the support portion of the main shaft and the support portion of the tailstock, and a tip portion which is a side in contact with the workpiece. The workpiece abutting portion generally has a right cone shape with a gradually decreasing diameter toward the workpiece existing side.

In use, the workpiece support center is fitted and pressed into a right cone-shaped center hole formed at the center of rotation of the workpiece end surface.
In addition, there exists a thing as shown in patent document 2 as a prior art relevant to this invention.

JP2004-130439 Japanese Patent Laid-Open No. 7-80783

  When both end surfaces of the workpiece are supported by the conventional spindle center and tailstock center described above, if the center holes formed in each end surface of the workpiece have an exact right cone shape, When the corresponding tip of each center is pressed into a fitting shape with an appropriate force, the tip of each center supports the workpiece in a state in which the radial movement of the workpiece is completely restricted. Although the hole is very slight due to quenching of the workpiece or external force when machining the workpiece supported by two centers, its cross-sectional shape is permanently deformed into a non-circular shape (such as an ellipse). In this way, when deformed in this way, the tip of each center cannot be in a state in which the radial movement of the workpiece is completely restricted, and the machining accuracy of the workpiece is the performance of the machine tool. It ’s irrelevant, To become. In order to cope with such a situation and maintain the machining accuracy of the machine tool, conventionally, the center hole is corrected with a lot of labor.

  Under such circumstances, the present invention supports the workpiece in a state where the radial movement is completely restricted even if the sectional shape of the center hole of the workpiece is permanently deformed into a slightly non-circular shape. It is an object of the present invention to provide a workpiece support center used in a machine tool that can prevent a reduction in machining accuracy.

  In order to achieve the above object, according to the present invention, as described in claim 1, the workpiece contact portion of the tip portion is formed at each of the mother positions at the three-divided positions around the center line on the outer peripheral surface of the right cone shape. It is provided with three elongated outer peripheral surface portions forming a range near the straight line, and is recessed so that the outer peripheral surface portion in the other range excluding the elongated outer peripheral surface portion from the outer peripheral surface of the right cone shape is close to the center line. It is characterized by being made into a shape.

The present invention is preferably embodied as follows.
That is, as described in claim 2, the workpiece contact portion is formed into a substantially regular triangular pyramid shape, and as described in claim 3, the center passes through the apex of the substantially regular triangular pyramid shape. The line is configured to match the shape center of the base end.

According to the present invention described above, the following effects can be obtained.
That is, according to the first aspect of the present invention, even if the cross-sectional shape of the center hole of the workpiece is permanently deformed to an arbitrary non-circular shape with a very small ratio to the diameter, In the state where the workpiece contact portion is fitted and pressed into the center hole, the three elongated outer peripheral surface portions are always in pressure contact with the inner peripheral surface of the center hole at the same time. The radial movement of the workpiece to the tip of the product of the present invention can be reliably regulated without requiring special processing such as center hole correction processing, and the workpiece can be controlled within the range of machine tool performance. This makes it possible to process with high accuracy.

  In particular, the center hole is permanently deformed during machining under the condition that the tip of the product of the present invention is repressed with an appropriate pressing force at the center hole at each end in the direction of the rotation center line of the workpiece machined by the machine tool. However, the three elongated outer peripheral surface portions are always in pressure contact with the inner peripheral surface of the center hole without any human processing, and the radial movement of the workpiece with respect to the tip portion of the product of the present invention is ensured. Therefore, highly accurate machining can be performed without stopping the rotation of the workpiece during workpiece machining.

  According to the second aspect of the present invention, since the work contact portion has a substantially regular triangular pyramid shape, the tip portion can be easily manufactured.

  Further, according to the third aspect of the present invention, when the product of the present invention is mounted on the center support portion of the main shaft or the center support portion of the tailstock, they can be mounted at an arbitrary angular position around the rotation center line of the base end portion. Even if it is supported by the center support portion, the planned effect of the product of the present invention can be obtained.

Next, an embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 1 shows a center tool provided with a work support center according to the present invention, wherein A is a side view, B is a front view, and FIG. 2 is a modification of the work contact portion of the work support center. FIG. 3 is a plan view of a machine tool (grinding machine) equipped with the workpiece support center, and FIG. 4 is a relationship between the two when the workpiece is supported on the machine tool via the center tool. FIG. 5 is a front view explanatory view showing the relationship between the work contact portion of the work support center and the center hole of the work, and FIG. 6 is a view of the work contact portion of the conventional work support center. FIG. 7 is a side view showing a modification of the work support center, FIGS. 8 to 10 show a first test example, and FIG. FIG. 9 is a view showing the center hole of the workpiece supporting center according to the present invention. FIG. 10 is a diagram showing the cross-sectional shape of the outer peripheral surface of the workpiece processed by using FIG. 10, FIG. 10 is a diagram showing the cross-sectional shape of the outer peripheral surface of the workpiece processed using the conventional work support center, and FIGS. 11 shows a second test example, FIG. 11 is a diagram showing a center hole of a workpiece, and FIG. 12 is a cross-sectional shape of an outer peripheral surface of a workpiece machined using the workpiece support center according to the present invention. FIGS. 13A and 13B are views showing the cross-sectional shape of the outer peripheral surface of a work machined using a conventional work support center.

  In FIG. 1, reference numeral 100 denotes a center tool comprising a workpiece supporting center 101 according to the present invention and a holding means 102 for holding the center in a rotatable manner.

The workpiece support center 101 is an integral product and includes a base end portion 2 and a tip portion 3.
Here, the base end portion 2 has a front supported shaft portion 4 whose outer peripheral surface is a straight cylindrical surface having a relatively large diameter, a tapered portion 5 whose diameter is gradually reduced toward the rear side, and a tapered portion 5 whose outer peripheral surface is a tapered portion 5. The rear supported shaft portion 6 having a right cylindrical surface smaller in diameter than the rear end is formed in this order from the front side to the rear side, and the shape center line of each portion is a straight line (the rotation center line of the main shaft 103 of the machine tool described later) It is assumed that it is located on 7).

  The tip portion 3 includes a projecting portion 8 whose outer peripheral surface is a straight cylindrical surface having a diameter larger than that of the front supported shaft portion 4, and a workpiece that is gradually tapered forward from the front end of the projecting portion 8. The contact portion 9 is formed in this order with the front portion facing forward.

  The work contact portion 9 includes three elongated outer peripheral surface portions 9a that form the vicinity of the generatrix of the bisector around the straight line 7 that is the center line of the right cone-shaped outer peripheral surface, In addition, since the outer peripheral surface portion of the other range excluding the elongated outer peripheral surface portion 9a from the right cone-shaped outer peripheral surface is recessed so as to be close to the center line 7, this is formed into a side surface 9b. In the example shown in the figure, it has a substantially regular triangular pyramid shape for the convenience of production. The center line 7 passing through the apex 9 c of the substantially regular triangular pyramid shape is matched with the shape center line of the base end portion 2.

  The workpiece contact portion 9 may be deformed as follows. For example, as shown in FIG. 2A, the cross-sectional shape of the workpiece contact portion 9 is convex outward from the substantially regular triangular pyramid-shaped side surface 9b. It may be provided with 9b1 to increase the strength, or as shown in FIG. 2B, provided with a side surface 9b1 that protrudes inward from the side surface 9b of the substantially regular triangular pyramid shape. In this case, a large gap with the inner peripheral surface of the center hole of the workpiece described later may be secured.

On the other hand, the holding means 102 includes a cylindrical holding body 10, three front rolling bearings 11 and one rear rolling bearing 12 that are positioned inside the inner hole of the cylindrical holding body 10.
The cylindrical holder 10 includes a large-diameter portion 10a, a tapered portion 10b inserted into a center support portion such as a spindle 103 of a machine tool described later, and a lid portion 10c for closing the rear end opening of the tapered portion 10b. In the inside of the large diameter portion 10a and the taper portion 10b, a circular straight inner hole 10d having a relatively large diameter inserted into the front rolling bearing 11 and a rear end of the inner hole 10d are continuous. A tapered hole 10e whose diameter is gradually reduced toward the rear is formed, a circular straight inner hole 10f which is continuous with the rear end of the tapered hole 10e and into which the rear rolling bearing 12 is inserted, and a female screw into which the lid portion 10c is screwed. The circular straight inner holes 10g are formed in this order from the front side to the rear side, and the shape center lines of these parts are made to coincide with the straight line 7.

  The cylindrical holder 10 is configured such that the front rolling bearing 11 and the rear rolling bearing 12 are inserted from the front side of the inner hole. The lid 10c is fixed by being screwed into a female screw of a circular straight inner hole 10g of the cylindrical holder 10.

  The workpiece supporting center 101 is inserted inward of the holding means 102 described above, and the front supported shaft portion 4 is inserted into the front rolling bearing 11 and the rear supported shaft portion 6 is inserted. It is inserted into the rear rolling bearing 12. Next, a waterproof and dustproof annular seal member 13 is fitted between the circular straight inner hole 10d of the cylindrical holder 10 and the overhanging portion 8 of the workpiece supporting center 101, and the circular straight inner hole 10d. An open annular elastic ring member 14 for restricting the forward displacement of the workpiece supporting center 101, the front rolling bearing 11 and the rear rolling bearing 12 is elastically mounted in an annular groove formed on the inner peripheral surface of the workpiece. The workpiece support center 101 is held by the cylindrical holder 10 so as to be rotatable about a straight line 7 via a front rolling bearing 11 and a rear rolling bearing 12.

  The outline of a grinding machine as a kind of machine tool to which the center tool 100 configured as described above is mounted will be described as follows.

  As shown in FIG. 3, a work table 105 that is movable in the z-axis direction and a grindstone table 106 that is movable in the x-axis direction are provided on a base 104 placed on the floor surface. A spindle stock 107 and a tailstock 108 are provided on the work table 105, and the spindle stock 107 is provided with a spindle 103 that is rotatable about the z-axis, and on the tailstock 108. A support shaft member 110 is provided that can be slidably displaced in a non-rotating state by operating the handle 109. A grindstone 112 that is rotatable about a grindstone rotation axis 111 parallel to the z axis is provided on the grindstone base 106. A center support portion a1 having a tapered hole is formed at seven locations of the rotation center line at the tip of the main shaft 103, and the center support portion a1 of the main shaft 103 is aligned with the center support portion a1 at the tip of the support shaft member 110 on the z axis. A center support portion a2 is formed as a tapered hole in the opposite state. The main shaft 103 and the workpiece w are coupled by the thread b1.

Next, an example of use of the workpiece support center 101 according to the present invention will be described.
Two center tools 100 are prepared, one of which is pushed into the center support portion a1 of the main shaft 103 to be in a fixed state, and the other is placed in the center support portion a2 of the support shaft member 110 of the tailstock 108. Push in to fix. As a result, the workpiece support center 101 of the center tool 100 in the center support portion a1 becomes the main axis center, and the center of rotation thereof coincides with the z axis, and the workpiece support center 101 of the center tool 100 in the center support portion a2 Becomes a centering center, and the center of rotation coincides with the z-axis.

  Next, the workpiece w is positioned between the spindle center 101 and the tailstock center 101, and the handle 109 is rotated to displace the support shaft member 110 toward the spindle 103 on the z-axis. The contact portion 9 is fitted into the center hole on one end surface of the workpiece w, and the workpiece contact portion 9 of the tailstock center 101 is fitted into the center hole on the other end surface of the workpiece w. As shown in FIG. 4, the workpiece contact portions 9 of the spindle center 101 and the tailstock center 101 are pressed against the corresponding center holes c1 with an appropriate pressure through the elastic force of a spring (not shown) provided. . The shape of the center hole c1 is a right cone shape, and the center line thereof matches the z axis.

  In this state, the three elongated outer peripheral surface portions 9a of each workpiece contact portion 9 are simultaneously pressed into contact with the inner peripheral surface of the corresponding center hole c1, so that the workpiece w is the spindle center 101 and the tailstock center 101. As a result, it is supported in a state of being freely rotatable around the z axis in a state where no play in the radial direction and the z axis direction occurs. Thereafter, both the main spindle 103 and the grindstone 112 are rotated and the grindstone base 106 is moved in the x-axis direction so that the grindstone 112 is brought into contact with the workpiece w to execute a necessary grinding process.

  During the grinding process, the center hole c1 is changed from a perfect circle shape c10 to a non-circular shape as shown in FIG. It may occur that the c11 is slightly deformed (for example, an elliptical shape). At this time, even if the relative position between the center hole c1 deformed into the non-circular shape c11 and the workpiece contact portion 9 pressed against the center hole c1 changes, the workpiece contact portions 9 of the spindle center 101 and the tailstock center 101 are changed. Is pressed against the corresponding center hole c1 by the elasticity of the spring, so that the three elongated outer peripheral surface portions 9a of each workpiece contact portion 9 are always within the center hole c1 without requiring any artificial processing. The state of being simultaneously pressed against the peripheral surface is maintained, and at this time, the three elongated outer peripheral surface portions 9a of each workpiece contact portion 9 are in contact with the workpiece against any deformation of the center hole c1. It is possible for the portion 9 to respond without any trouble to stably contact the inner peripheral surface of the center hole c1 in a state where no play occurs, and in connection with the deformation of the center hole c1, Initial rotation center position (round shape) 10 center position O1) and the rotation center line 7 of the workpiece contact portion 9 pressed against the center position O1) may change. In this case, the workpiece w is rotated and ground at a new rotation center. However, since the amount of this change is often smaller than the grinding allowance (for example, approximately 0.4 mm), the final shape of the surface to be ground of the workpiece w is as planned. It can be dimensioned.

  FIG. 5 shows the relationship between the center hole c1 and the workpiece contact portion 9 when the center hole c1 is deformed into a non-circular shape c11. As shown in FIG. Even if the center hole c1 is located at any position such as the first position d1, the second position d2, and the third position d3, the position e corresponding to the three elongated outer peripheral surface portions 9a is the center after deformation. In other words, the inner surface of the hole c1 is in contact with the inner peripheral surface at the same time in a state where no play occurs. At this time, the center of the workpiece contact portion 9 with respect to the center hole c1 at each position d1, d2, and d3 slightly changes.

  For comparison with the case of the present invention, FIG. 6 shows a state in which the conventional right-cone-shaped workpiece contact portion 9 is pressed against the center hole c1 deformed into an elliptical shape c11. As is apparent from the above, the conventional workpiece contact portion 9 can move by a length L corresponding to the flatness in the long axis direction of the center hole c1 in the center hole c1 after deformation. This reduces the grinding accuracy of the workpiece w.

  In the above use example, the case where the center hole c1 is deformed during the grinding of the workpiece w has been described. However, there are cases where the center hole c1 is different from the above, that is, the workpiece by another machine tool in the previous process. The center hole c1 of the workpiece w may be deformed during the machining of w. After the workpiece machining, the workpiece w is removed from the machine tool, and the deformed center hole c1 is used in the next process. In this case, the workpiece support center 101 according to the present invention functions in the same manner as in the previous case. That is, the three elongated outer peripheral surface portions 9a of the workpiece contact portions 9 of the spindle center 101 and the tailstock center 101 are subjected to the spring elastic force on the inner peripheral surface of the center hole c1 into which the workpieces are fitted. Ri is contact simultaneously, and restricts free movement in the radial direction and the z-axis direction of the work w.

  The workpiece supporting center 101 shown in FIG. 1 may be deformed as follows. That is, as shown in FIG. 7, the base end 2 formed as a tapered portion having a simple shape is the same as the above. It is provided with a tip portion 3 having a simple shape. In the case of such a workpiece support center 101, the center support portion a1 of the spindle 103 and the center support portion a2 of the tailstock 108 are directly inserted into the base end portion 2 shown in FIG. The center support portion a1 of the main shaft 103 is in a freely rotatable state on the main shaft 103, and the center support portion a2 of the tailstock 108 is in a freely rotatable state around the z axis on the tailstock 108.

  Next, a test example when the workpiece support center 101 according to the present invention is mounted on the grinding machine and ground will be described.

First, the first test example will be described.
FIG. 8 shows a center hole c1 of a non-circular shape c12 that is permanently deformed into which the workpiece support center 101 is fitted. The center hole c1 has a diameter of about 20 mm, and O1 is the initial position of the workpiece w. The amount of deformation (length) in the radial direction around the initial rotation center O1 of the center hole c1 is shown enlarged by about 2000 times. The roundness (the length obtained by subtracting the minimum diameter from the maximum diameter) of the center hole c1 is 24.76 μm.

  FIG. 9 shows a cross-sectional shape of the workpiece w when the center hole c1 shown in FIG. 8 is supported by the workpiece supporting center 101 and the outer peripheral surface of the workpiece w having the center hole c1 is ground. h3 indicates the outline of the cross-sectional shape of the workpiece w after grinding at three different points on the z-axis (the diameter at each point is approximately 42 mm), and the amount of radial deformation around the shape center O11 of the workpiece w can be recognized. It ’s something. At this time, the amount of deformation in the radial direction of the outlines h1, h2, and h3 is shown enlarged to about 2000 times. When the roundness of each of the outlines h1, h2, and h3 is calculated from the data recognized from FIG. 9, the roundness of the outline h1 is 0.76 μm, and the roundness of the outline h2 is 0. .97 μm, and the roundness of the outline h3 is 1.65 μm.

  FIG. 10 shows a cross-sectional shape of the workpiece w when the center hole c1 shown in FIG. 8 is supported by a conventional workpiece support center 9 and the outer peripheral surface of the workpiece w having the center hole c1 is ground. h20 and h30 indicate the outline of the cross-sectional shape of the ground workpiece w at the three different points on the z-axis (the diameter of each point is approximately 42 mm), and the amount of radial deformation around the shape center O11 of the workpiece w is shown. It can be recognized. At this time, the amount of deformation in the radial direction is enlarged by about 5000 times. When each roundness is calculated from the data recognized from FIG. 10, the roundness of the outline h10 is 1.15 μm, the roundness of the outline h20 is 2.10 μm, and the outline The roundness of h30 is 3.01 μm.

Next, a second test example will be described.
FIG. 11 shows a deformed center hole c1 into which the workpiece supporting center 101 is fitted. The center hole c1 has a diameter of about 20 mm, and O1 is an initial rotation center of the workpiece w. The amount of deformation (length) in the radial direction around the initial rotation center O1 of the center hole c1 is shown enlarged to about 2000 times. The roundness of the center hole is 19.62 μm.

  FIG. 12 shows a cross-sectional shape of the workpiece w when the center hole c1 shown in FIG. 11 is supported by the workpiece support center 101 and the outer peripheral surface of the workpiece w having the center hole c1 is ground. h3 indicates the outline of the cross-sectional shape of the workpiece w after grinding at three different points on the z-axis (the diameter of each point is approximately 42 mm), and the amount of radial deformation around the shape center O11 of the workpiece w can be recognized. It is done. At this time, the amount of deformation in the radial direction of the outlines h1, h2, and h3 is shown enlarged to about 2000 times. When the roundness of each of the outlines h1, h2, and h3 is calculated from the data that can be recognized from FIG. 12, the roundness of the outline h1 is 1.28 μm, and the roundness of the outline h2 is 1. The roundness of the outline h3 is 2.43 μm.

  FIG. 13 shows a cross-sectional shape of the workpiece w when the center hole c1 shown in FIG. 12 is supported by a conventional workpiece support center and the outer peripheral surface of the workpiece w having the center hole c1 is ground, h10 and h20. And h30 indicate the outline of the cross-sectional shape of the ground workpiece w at the three different points on the z-axis (the diameter of each point is approximately 42 mm), and the amount of radial deformation around the shape center O11 of the workpiece w is recognized. It can be done. At this time, the deformation amounts in the radial direction of the outlines h10, h20, and h30 are shown enlarged to about 5000 times. When the roundness of the outlines h10, h20, and h30 is calculated from the data that can be recognized from FIG. 13, the roundness of the outline h20 is 1.92 μm, and the roundness of the outline h20 is 2.29 μm. Further, the roundness of the outline h30 is 3.53 μm.

The center tool provided with the center for workpiece | work support which concerns on this invention is shown, A is a side view and B is a front view. It is a front view which shows the modification of the workpiece | work contact part of the said work support center. It is a top view of the machine tool (grinding machine) with which the said work support center was mounted | worn. It is a side view which shows the relationship between the said center tool and a workpiece | work when a workpiece | work is supported via the said workpiece support tool on the said machine tool. It is explanatory drawing which shows the relationship between the workpiece | work contact part of the said workpiece | work support center, and the center hole of a workpiece | work. It is explanatory drawing which shows the relationship between the workpiece | work contact part of the conventional workpiece | work support center, and the center hole of a workpiece | work. It is a side view which shows the modification of the said work support center. It is a figure which shows the 1st test example and shows the center hole of a workpiece | work. It is a figure which shows the 1st test example and shows the cross-sectional shape of the outer peripheral surface of the workpiece | work processed using the workpiece | work support center which concerns on this invention. It is a figure which shows the 1st test example and shows the cross-sectional shape of the outer peripheral surface of the workpiece | work processed using the conventional workpiece support center. It is a figure which shows the 2nd test example and shows the center hole of a workpiece | work. It is a figure which shows the 2nd test example, and shows the cross-sectional shape of the outer peripheral surface of the workpiece | work processed using the workpiece | work support center which concerns on this invention. It is a figure which shows the 2nd test example, and shows the cross-sectional shape of the outer peripheral surface of the workpiece | work processed using the conventional workpiece support center.

Explanation of symbols

2 Base end portion 3 Tip portion 7 Center line of work support center 9 Work contact portion 9a Elongated outer peripheral surface portion 9b Side surface 9c Vertex

Claims (3)

The workpiece abutting portion at the tip has three elongated outer peripheral surface portions that form the vicinity of each generating line at a bisector around the center line on the outer peripheral surface of the right cone shape, A workpiece support used in a machine tool, characterized in that the outer peripheral surface portion of the other range excluding the elongated outer peripheral surface portion from the conical outer peripheral surface is recessed so as to be close to the center line. For center. A workpiece support center used in a machine tool, wherein the workpiece contact portion has a substantially regular triangular pyramid shape. 2. The work support center used in a machine tool according to claim 1, wherein a center line passing through the apex of the substantially regular triangular pyramid shape is matched with the shape center of the base end portion.

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