JP7472633B2 - Workpiece support device - Google Patents

Description

The present invention relates to a workpiece support device that supports at least the axial end of a workpiece while positioning the workpiece radially when a rolling process or the like is performed on a workpiece provided on the outer peripheral surface of the workpiece to form a male engaging portion such as a male thread portion.

In machine tools and steering wheel position adjustment devices, the rotary motion of a drive source such as an electric motor is converted into linear motion by a feed screw mechanism. There are two types of feed screw mechanism: a sliding screw type and a ball screw type.

A sliding screw type feed screw mechanism is composed of a screw shaft having a male thread portion on its outer circumferential surface, in which a male thread groove with a triangular or trapezoidal cross section is formed in a spiral shape, and a nut having a female thread portion on its inner circumferential surface, in which a female thread groove with a triangular or trapezoidal cross section is formed in a spiral shape, and the male thread groove and the female thread groove are screwed together.

A ball screw type feed screw mechanism comprises a screw shaft having a male threaded portion on its outer circumferential surface, in which a male thread groove with a circular arc cross section is formed in a helical shape, a nut having a female threaded portion on its inner circumferential surface, in which a female thread groove with a circular arc cross section is formed in a helical shape, and a number of balls arranged to roll freely between the male thread groove and the female thread groove.

Whether it is a sliding screw type or a ball screw type, the male thread of the screw shaft that constitutes the feed screw mechanism can be formed, for example, by rolling. Japanese Patent Application Laid-Open No. 8-318340 (Patent Document 1) describes a rolling machine for forming a male thread on the outer circumferential surface of a cylindrical metal workpiece (work material) by rolling. This rolling machine holds the workpiece between a pair of circular dies while supporting both axial ends of the workpiece rotatably with a jig (center) having a conical tip, and rolls a male thread on the outer circumferential surface of the workpiece by pressing the pair of circular dies while rotating them.

Japanese Patent Application Laid-Open No. 8-318340

When rolling a male thread on the outer peripheral surface of a workpiece using the rolling machine described in JP 8-318340 A, it is necessary to form a conical concave hole on both axial end surfaces of the workpiece, and then abut the conical tip of a jig against the inner peripheral surface of the hole to radially position the workpiece (center the workpiece relative to the rolling machine).

When incorporating a feed screw mechanism into a structure in which the axial end face of the screw shaft pushes other components, or when marking information for identifying a product on the axial end face of the screw shaft, it is preferable that the axial end face of the screw shaft is a flat or curved surface without any recesses. Therefore, a method can be considered in which the tip of a jig is abutted against the inner peripheral surface of a recess formed on both axial end faces of a cylindrical workpiece to position the workpiece radially, and then a male thread is rolled on the outer peripheral surface of the workpiece, and the axial end of the workpiece is cut off and removed.

However, when the axial end of the workpiece is cut and removed, if the axial end of the workpiece is cut while the workpiece is supported by gripping the male thread, the male thread may be deformed, and the accuracy of the male thread may be reduced. In other words, when the male thread of the screw shaft is gripped and the thread of the male thread is deformed to be concave (a dent is formed), the inner surface of the screw groove is deformed to be bulged (risen) by that amount. For example, if a screw shaft with such deformation is used to construct a ball screw type feed screw mechanism, the balls may ride up on the bulged part of the screw groove, making it difficult for the balls to move smoothly.

In view of the above circumstances, the present invention aims to realize a structure for a workpiece support device that supports at least the axial end of a workpiece while positioning the workpiece radially when performing processing to form a male engaging portion on a workpiece provided on the outer peripheral surface of the workpiece, which does not require the accurate formation of recesses in the axial end surface of the workpiece for radial positioning of the workpiece, and which can ensure good shape accuracy of the male engaging portion in the completed state.

The support device for a workpiece of the present invention comprises:
At least one support jig is provided, the support jig including a recess having a first tapered surface on an inner circumferential surface thereof;
By pressing the connection portion between the outer peripheral surface and the axial end face of the workpiece against the first tapered surface, the workpiece is positioned radially and at least the axial end portion of the workpiece (either one of the axial end portions of a cylindrical workpiece, or both axial end portions) is supported.

By using the workpiece support device of the present invention, the workpiece is positioned in the radial direction, and at least the axial end of the workpiece is supported, and a rolling die is pressed against the workpiece provided on the outer peripheral surface of the workpiece, or the workpiece is cut, thereby forming a male engaging portion such as a male thread portion or a male spline portion.

In particular, in the workpiece support device of the present invention, the at least one support jig further includes a through hole that opens (communicates) to the bottom of the recess.

It is preferable that the arithmetic mean surface roughness of at least the portion of the first tapered surface that contacts the connection portion is 0.025 μm or less. Specifically, for example, at least the portion of the first tapered surface that contacts the connection portion can be mirror-finished.

At least the portion of the support jig that includes the recess can be made of high speed steel, cemented carbide, or diamond.

The workpiece support device of the present invention may further include an auxiliary jig that is supported so as to be capable of relative axial displacement with respect to the support jig, has a through hole that penetrates in the axial direction and through which the workpiece is inserted, and has a second tapered surface formed on at least a portion of the inner peripheral surface of the through hole, inclined in the same direction as the first tapered surface, and for pressing a chamfered portion formed in the axial middle portion of the workpiece. The arithmetic mean surface roughness of the second tapered surface is preferably 0.025 μm or less.

The auxiliary tool may have an auxiliary through hole whose one end opens to the inner peripheral surface of the through hole and whose other end opens to the outer peripheral surface or axial side surface of the auxiliary tool.

The workpiece support device of the present invention may further include a displacement meter that measures the displacement of the workpiece. In this case, the measuring element of the displacement meter is inserted into the through hole.

By using the workpiece support device of the present invention, when processing to form a male engaging portion on a workpiece portion provided on the outer peripheral surface of the workpiece, at least the axial end portion of the workpiece can be supported while the workpiece is positioned radially. Furthermore, by using the workpiece support device of the present invention, it is not necessary to precisely form a recess in the axial end surface of the workpiece to position the workpiece radially, and the shape precision of the male engaging portion can be well ensured in the completed state.

FIG. 1 is a partial cutaway side view showing a state in which a workpiece is supported by a workpiece supporting device according to a first embodiment of the present invention. FIG. 2 is an enlarged view of the left portion of FIG. 3A is an enlarged view of a portion A in FIG. 1, showing the workpiece taken out, and FIG. 3B is an enlarged view of a portion B in FIG. 1, showing the workpiece taken out. 4(A) to 4(E) are schematic side views showing how a rolling process is performed on a processed portion of a workpiece using a workpiece supporting device according to a first embodiment of the present invention. FIG. 5 is a cross-sectional view taken along line CC of FIG. FIG. 6 is a side view showing the completed male shaft. 7(A) and 7(B) are cross-sectional views showing another example of a method for forming a male thread portion by rolling. 8A to 8C are views corresponding to FIG. 3A , showing three other examples of the workpiece. FIG. 9 is a partial cutaway side view showing a state in which a workpiece is supported by a workpiece supporting device according to a second embodiment of the present invention. FIG. 10 is an enlarged view of a portion D in FIG. FIG. 11 is a partial cutaway side view showing a state in which a workpiece is supported by a workpiece supporting device according to a third embodiment of the present invention. FIG. 12 is a view showing a workpiece supporting device according to a fourth embodiment of the present invention, which corresponds to an enlarged view of the right side portion of FIG. FIG. 13 is a view showing a workpiece supporting device according to a fifth embodiment of the present invention, which corresponds to an enlarged view of the right side portion of FIG. FIG. 14 is a view showing a workpiece supporting device according to a sixth embodiment of the present invention, which corresponds to an enlarged view of the right side portion of FIG.

[First Example of the Embodiment]
A first embodiment of the present invention will be described with reference to Figures 1 to 6. The support device 1 of this embodiment includes a pair of support jigs 3, each having a recess 2 opening on a tip end surface that faces each other in the axial direction. That is, the support jig 3 on one axial side (left side in Figure 1) has a recess 2 opening on an end surface on the other axial side (right side in Figure 1), and the support jig 3 on the other axial side has a recess 2 opening on an end surface on one axial side. The pair of support jigs 3 have shapes symmetrical to each other in the axial direction.

Each of the recesses 2 has a first tapered surface 4 on its inner circumferential surface. The first tapered surface 4 on the inner circumferential surface of each of the recesses 2 of a pair of support jigs 3 is inclined in a direction in which the inner diameter becomes larger as they approach each other (from the bottom to the opening). That is, the recesses 2 of the support jig 3 on one axial side have a first tapered surface 4 inclined in a direction in which the inner diameter becomes larger as they approach the other axial side, and the recesses 2 of the support jig 3 on the other axial side have a first tapered surface 4 inclined in a direction in which the inner diameter becomes larger as they approach one axial side. The angle θ between the generatrix and the central axis of the first tapered surface 4 is preferably 20 degrees or more and 60 degrees or less, and is about 30 degrees in the illustrated example.

Each of the first tapered surfaces 4 has an arithmetic mean surface roughness (Ra) of 0.025 μm or less, preferably 0.013 μm or less. For this reason, in this example, the first tapered surfaces 4 are mirror-finished.

Each of the pair of support jigs 3 further has a through hole 5 that opens to the bottom of the recess 2 and the outer surface of the support jig 3 (parts other than the first tapered surface 4). In this example, the through hole 5 is formed so as to axially penetrate (communicate) the base end surface of the support jig 3 (the end surface that is on the opposite side in the axial direction from the tip surface where the recess 2 opens) and the bottom of the recess 2. That is, the support jig 3 on one axial side further has a through hole 5 that axially penetrates one axial side surface and the bottom of the recess 2, and the support jig 3 on the other axial side further has a through hole 5 that axially penetrates the other axial side surface and the bottom of the recess 2. In this example, the cooling oil supply device 25, the compressor 26, and the lubricating oil supply device 27 are connected to the upstream opening formed on the base end surface of the support jig 3 through a switching valve 28. This makes it possible to supply lubricating oil, cooling oil, etc., or to blow compressed air onto the first tapered surface 4.

In this example, each of the pair of support jigs 3 is formed by connecting and fixing a base metal 6 and a jig body 7.

The base metal 6 is made of an iron-based metal such as chrome molybdenum steel (SCM440, SCM415, etc.) or bearing steel (SUJ2, etc.). The base metal 6 has a fitting recess 8 that opens at the tip end surface and has a cylindrical inner peripheral surface. That is, the base metal 6 constituting the support jig 3 on one axial side has a fitting recess 8 that opens at the other axial side surface, and the base metal 6 constituting the support jig 3 on the other axial side has a fitting recess 8 that opens at the one axial side surface.

The base metal 6 further includes an upstream through hole 9 that opens to the base end surface and the center of the bottom surface of the fitting recess 8. That is, the base metal 6 constituting the support jig 3 on one axial side further includes an upstream through hole 9 that opens to one axial side surface and the center of the bottom surface (surface facing the other axial side) of the fitting recess 8, and the base metal 6 constituting the support jig 3 on the other axial side further includes an upstream through hole 9 that opens to the other axial side surface and the center of the bottom surface (surface facing one axial side) of the fitting recess 8.

In addition, the base metal 6 further includes ventilation holes 10 that open to the outer peripheral surface and the bottom of the fitting recess 8 (the portion of the inner peripheral surface of the fitting recess 8 that is closest to the bottom surface).

The jig body 7 is made of a material with sufficient strength and hardness. Specifically, for example, the jig body 7 is made of a metal material with excellent durability, such as high speed steel or cemented carbide, or a material with excellent heat dissipation properties, such as diamond. The jig body 7 has a cylindrical outer peripheral surface and a recess 2 that opens to the tip surface.

The jig body 7 further includes a downstream through hole 11 that opens to the base end surface and the bottom of the recess 2. That is, the jig body 7 constituting the support jig 3 on one axial side further includes a downstream through hole 11 that opens to one axial side surface and the bottom of the recess 2, and the jig body 7 constituting the support jig 3 on the other axial side further includes a downstream through hole 11 that opens to the other axial side surface and the bottom of the recess 2.

In this example, each of the support jigs 3 is fixed by brazing or the like after the outer circumferential surface of the jig body 7 is fitted into the inner circumferential surface of the fitting recess 8 of the base metal 6 without any rattle in the radial direction. In this example, the base metal 6 has an air vent 10 that opens to the outer circumferential surface and the bottom of the fitting recess 8. When the outer circumferential surface of the jig body 7 is inserted (e.g., pressed) into the inner circumferential surface of the fitting recess 8 of the base metal 6, the internal pressure of the space surrounded by the inner circumferential surface and bottom surface of the fitting recess 8 and the base end surface of the jig body 7 can be prevented from becoming excessively high.

In this example, the fitting portion between the inner peripheral surface of the fitting recess 8 of the base metal 6 and the outer peripheral surface of the jig body 7 is formed by a circular fitting portion formed by fitting cylindrical surfaces together, but the fitting portion between the fitting recess 8 of the base metal 6 and the jig body 7 can also be formed by a non-circular fitting portion formed by fitting non-cylindrical surfaces together. Alternatively, each of the support jigs 3 can be formed only by the jig body 7 (the base metal 6 can be omitted).

The support device 1 of this example as described above is used to support the axial end of the shaft member 12 while positioning the shaft member 12 radially when rolling the processed portion 13 of the shaft member 12, which is the workpiece, and processing the processed portion 13 into a male threaded portion 14 to produce a male shaft 15, as shown in FIG. 6, as shown in FIG. 1 and FIG. 4(A).

The male shaft 15 is a ball screw shaft that constitutes a ball screw type feed screw mechanism, and as shown in FIG. 6, has an outer peripheral surface 16, end faces 17a and 17b on both axial sides, and a male threaded portion 14 that is a male engaging portion.

None of the end faces 17a, 17b on either side in the axial direction have recesses opening into these end faces 17a, 17b. In this example, of the end faces 17a, 17b on either side in the axial direction, the end face 17a on one side in the axial direction (the left side in FIG. 6) is composed of a single partially spherical convex curved surface, and the end face 17b on the other side in the axial direction (the right side in FIG. 6) is composed of a flat surface perpendicular to the central axis of the male shaft 15.

The male thread portion 14 has a male thread groove 18 with an arc-shaped cross section formed in a spiral shape in the axial middle part of the outer circumferential surface 16 of the male shaft 15.

The male shaft 15 is combined with a ball nut having a female threaded portion formed with a spiral female thread groove with a cross section of an arc shape on its inner circumferential surface, and multiple balls to form a ball screw type feed screw mechanism. In other words, the ball nut is placed around the male threaded portion 14 of the male shaft 15, and the balls are placed between the male thread groove 18 and the female thread groove so that they can roll freely, thereby forming a feed screw mechanism.

The male shaft 15 is obtained by performing a rolling process on the processed portion 13 of the shaft member 12. The shaft member 12 has an outer peripheral surface 16 having the processed portion 13 in the axial middle portion, end faces 17a, 17b on both axial sides, and chamfered portions 21a, 21b formed at the connection portions between the end edges 19a, 19b on both axial sides of the outer peripheral surface 16 and the outer peripheral edges 20a, 20b of the end faces 17a, 17b on both axial sides.

The processed portion 13 is located in the axial middle of the outer peripheral surface 16 and has an outer diameter dimension that is larger than the outer diameter dimensions of the adjacent portions on both axial sides.

Each of the chamfered portions 21a, 21b is composed of a composite surface formed by combining three or more surfaces in which the inclination angle or radius of curvature of the generatrix of adjacent surfaces relative to the central axis O of the shaft member 12 is different. Each of the chamfered portions 21a, 21b has a supported surface portion 22a, 22b that is arranged in the axial middle portion of the chamfered portion 21a, 21b and is inclined in a radially outward direction as it approaches the male thread portion 14 in the axial direction. In this example, each of the supported surface portions 22a, 22b is a conical surface having a linear generatrix shape. In addition, in a cross section in the axial direction (a cross section including the central axis O of the shaft member 12), the axial end edges 19a, 19b of the outer peripheral surface 16 and the outer peripheral edges 20a, 20b of the end faces 17a, 17b on both axial sides are located radially inward from the generatrix (including the extension of the generatrix) α, β of the supported surface portions 22a, 22b.

For this reason, in this example, of the chamfered portions 21a and 21b, the chamfered portion 21a on one axial side, which is formed at the connection between the edge 19a on one axial side of the outer peripheral surface 16 and the outer peripheral edge 20a of the end face 17a on one axial side, has a supported surface portion 22a and a pair of connecting inclined surface portions 23a1 and 23a2.

The supported surface portion 22a is disposed in the axial middle portion of the chamfered portion 21a on one axial side, and is a conical surface having a linear generatrix shape inclined in a radially outward direction toward the other axial side. The inclination angle _φa of the generatrix of the supported surface portion 22a with respect to the central axis O of the shaft member 12 is preferably 20 degrees or more and 60 degrees or less, and is about 30 degrees in the illustrated example.

Of the pair of connecting inclined surface portions 23a1, 23a2, the connecting inclined surface portion 23a1 on one axial side, which connects the outer peripheral edge 20a of the end face 17a on one axial side and the edge on one axial side of the supported surface portion 22a, is a convex curved surface having an arc-shaped generatrix shape that is inclined in a direction toward the radially outward direction toward the other axial side. The connecting inclined surface portion 23a2 on the other axial side, which connects the edge on the other axial side of the supported surface portion 22a and the edge 19a on one axial side of the outer peripheral surface 16, is a convex curved surface having an arc-shaped generatrix shape that is inclined in a direction toward the radially outward direction toward the other axial side. Note that the axial dimensions d _23a1 , d 23a2 of the connecting inclined surface portions 23a1, _23a2 are preferably 10% to 35% of the axial dimension L _a of the entire chamfered portion 21a. It is preferable that the radius of curvature of the generatrix shape of the connecting inclined surface portions 23a1, 23a2 is 1% or more and 30% or less of the outer diameter dimension of the portion of the shaft member 12 adjacent to the other axial side of the connecting inclined surface portion 23a2 (the outer diameter dimension of the edge 19a on one axial side of the outer circumferential surface 16).

Of the chamfered portions 21a and 21b, the chamfered portion 21b on the other axial side, which connects the edge 19b on the other axial side of the outer peripheral surface 16 to the outer peripheral edge 20b of the end face 17b on the other axial side, has a supported surface portion 22b and a pair of connecting inclined surface portions 23b1 and 23b2.

The supported surface portion 22b is disposed in the axial middle portion of the chamfered portion 21b on the other axial side, and is a conical surface having a linear generatrix shape inclined in a radially outward direction toward one axial side. The inclination angle φ _b of the generatrix of the supported surface portion 22b with respect to the central axis O of the shaft member 12 is preferably 20 degrees or more and 60 degrees or less, and is about 30 degrees in the illustrated example.

Of the pair of connecting inclined surface portions 23b1, 23b2, the connecting inclined surface portion 23b1 on the other axial side, which connects the outer peripheral edge 20b of the end face 17b on the other axial side and the edge on the other axial side of the supported surface portion 22b, is a convex curved surface having an arc-shaped generatrix shape that is inclined in a direction toward the radially outward direction toward one axial side. The connecting inclined surface portion 23b2 on one axial side, which connects the edge on one axial side of the supported surface portion 22b and the edge 19b on the other axial side of the outer peripheral surface 16, is a convex curved surface having an arc-shaped generatrix shape that is inclined in a direction toward the radially outward direction toward one axial side. Note that the axial dimensions _d23b1 , d23b2 of the connecting inclined surface portions 23b1, _23b2 are preferably 10% to 35% of the axial dimension _Lb of the entire chamfered portion 21b. It is preferable that the radius of curvature of the generatrix shape of the connecting inclined surface portions 23b1, 23b2 is 1% or more and 30% or less of the outer diameter dimension of the portion of the shaft member 12 adjacent to one axial side of the connecting inclined surface portion 23b2 (the outer diameter dimension of the edge 19b on the other axial side of the outer circumferential surface 16).

Next, a method for manufacturing a male shaft 15 from a shaft member 12 using the support device 1 of this example will be described with reference to Figures 4 and 5.

First, a rod made of an iron-based metal such as carbon steel or chrome molybdenum steel and having a circular cross-sectional shape is cut to a predetermined length to obtain a cylindrical material. Next, the material is subjected to cutting processes such as cutting and grinding to obtain a shaft member 12 as shown in FIG. 4(A). When processing the cylindrical material into the shaft member 12, after forming chamfered portions 21a and 21b at the connection between the outer peripheral surface 16 and the end faces 17a and 17b on both axial sides, as shown in the following FIG. 4(B) to FIG. 4(D), the first tapered surface 4 provided on the inner peripheral surface of the recess 2 of the support jig 3 is pressed against the supported surface portions 22a and 22b of the chamfered portions 21a and 21b during the rolling process to form the male thread portion 14, so that the shaft member 12 is positioned radially, and the outer peripheral surface 16 and the end faces 17a and 17b can be finished.

Next, the processed portion 13 of the shaft member 12 is subjected to rolling to form a male thread portion 14, thereby obtaining a male shaft 15. For this purpose, first, as shown in Fig. 4(B), both axial ends of the shaft member 12 are supported by the recesses 2 provided in each of a pair of support jigs 3 constituting the support device 1. Specifically, the pair of support jigs 3 are brought close to the shaft member 12 from both axial sides, and the first tapered surfaces 4 provided on the inner peripheral surfaces of the recesses 2 of each of the pair of support jigs 3 are pressed against the supported surface portions 22a, 22b. In this example, the inclination angles _φa , _φb of the supported surface portions 22a, 22b of the chamfered portions 21a, 21b of the shaft member 12 are set to be the same as the inclination angle θ of the generatrix of the recess 2 with respect to the central axis O. Therefore, when the first tapered surfaces 4 of the recesses 2 are pressed against the supported surface portions 22a, 22b, the shaft member 12 is displaced in the radial direction while being guided by the first tapered surfaces 4, and the central axis of the shaft member 12 coincides with the central axis of the first tapered surfaces 4 (the shaft member 12 is positioned in the radial direction). In this way, the support device 1 supports both axial ends of the shaft member 12 in a state in which the radial positioning is achieved. In this state, the axially opposite end edges 19a, 19b of the outer peripheral surface 16 of the shaft member 12 and the outer peripheral edges 20a, 20b of the end faces 17a, 17b do not come into contact with the first tapered surfaces 4.

As described above, the support device 1 positions the shaft member 12 in the radial direction, and while supporting both axial ends of the shaft member 12, the pair of round dies 24 are rotated and brought close to the shaft member 12 from both radial sides. Each of the round dies 24 has a spirally formed thread cutting tooth 33 (shown only in FIG. 5) on the outer circumferential surface. Therefore, as shown in FIG. 4(C) and FIG. 5, when the shaft member 12 is pressed from both radial sides between the pair of round dies 24, the shaft member 12 rotates while sliding the supported surface portions 22a, 22b against the first tapered surface 4. As a result, as shown in FIG. 4(D), the male screw portion 14, which is formed by forming the male screw groove 18 in a spiral shape, is rolled in the processed portion 13 of the shaft member 12. Then, as shown in FIG. 4(E), the pair of circular dies 24 are retracted in the radial direction, and the pair of support jigs 3 are retracted in the axial direction to remove the male shaft 15 having the male thread portion 14. The male shaft 15 thus obtained is washed, finished, heat-treated, etc. as necessary to give it a finished shape.

After removing the male shaft 15 from the support device 1, first, the cooling oil discharged from the cooling oil supply device 25 is supplied to the first tapered surface 4 through the through hole 5 to cool the first tapered surface 4. Next, compressed air discharged from the compressor 26 is blown onto the first tapered surface 4 through the through hole 5 to remove the wear powder and cooling oil that are generated when the first tapered surface 4 and the supported surface portions 22a and 22b slide against each other and that are attached to the first tapered surface 4. Then, the lubricating oil discharged from the lubricating oil supply device 27 is supplied to the first tapered surface 4 through the through hole 5. This lubricates the supported surface portions 22a and 22b of the shaft member 12 to be machined next and the first tapered surface 4.

However, if the cooling oil is the same as the lubricating oil, the cooling oil supply device 25 and the lubricating oil supply device 27 can be integrated into one unit. Also, during the machining of the male thread portion 14, the lubricating oil discharged from the lubricating oil supply device 27 can be supplied to the sliding contact portion between the first tapered surface 4 and the supported surface portions 22a, 22b through the through hole 5. In this case, the lubricating oil supplied through the through hole 5 balances the force pressing the end face 17a (or 17b) of the shaft member 12 with the force that causes the shaft member 12 to displace in the axial direction due to rolling, thereby preventing the shaft member 12 from displacing in the axial direction unnecessarily during machining. This allows the male thread portion 14 to be formed with high precision.

In this example, when the male thread portion 14 is formed by rolling, the first tapered surface 4 provided on the inner peripheral surface of the recess 2 of a pair of support jigs 3 constituting the support device 1 is pressed against the supported surface portions 22a, 22b of the chamfered portions 21a, 21b, thereby positioning the shaft member 12 in the radial direction. That is, according to the manufacturing method of the shaft member 12 using the support device 1 of this example, it is not necessary to form a recessed hole for abutting the conical tip portion provided on the jig with high precision (a recessed hole with high coaxiality with the outer peripheral surface of the material) on both end surfaces in the axial direction of the material, as in the case of rolling the male thread portion on the outer peripheral surface of the material using a rolling machine described in JP-A-8-318340. Therefore, according to the manufacturing method using the support device 1 of this example, after the male thread portion is formed on the outer peripheral surface of the material, it is not necessary to cut and remove the axial end portion of the material while holding the male thread portion and supporting the material. In short, the manufacturing method using the support device 1 of this example makes it possible to prevent the male thread portion 14 from deforming, and ensures good shape precision of the male thread portion 14 in the completed male shaft 15.

In particular, in this example, each of the support jigs 3 has a through hole 5 that opens to the bottom of the recess 2 and the outer surface of the support jig 3. Therefore, in order to manufacture the male shaft 15, even when the supported surface portions 22a, 22b of the shaft member 12 are pressed against the first tapered surface 4 provided in the recess 2 and the opening of the recess 2 is covered by the end faces 17a, 17b of the shaft member 12, the space inside the recess 2 is connected to the external space by the through hole 5. Therefore, by pressing the supported surface portions 22a, 22b of the shaft member 12 against the first tapered surface 4 provided in the recess 2, the internal pressure of the space covered by the end faces 17a, 17b of the shaft member 12 can be prevented from becoming excessively large, and the shaft member 12 can be stably supported by the support device 1. As a result, the machining accuracy of the male thread portion 14 can be ensured.

In this example, the surface roughness of the first tapered surface 4, which is pressed against the supported surface portions 22a and 22b of the chamfered portions 21a and 21b, is set to 0.025 μm or less, preferably 0.013 μm or less, in terms of arithmetic mean surface roughness (Ra). Specifically, the first tapered surface 4 is mirror-finished. Therefore, when forming the male thread portion 14, the shaft member 12 is pressed from both radial sides between a pair of rotating round dies 24, so that the resistance of the supported surface portions 22a and 22b to sliding against the first tapered surface 4 as the shaft member 12 rotates can be reduced. Therefore, when forming the male thread portion 14, the wear powder generated by the sliding contact between the first tapered surface 4 and the supported surface portions 22a and 22b as the shaft member 12 rotates can be reduced.

In this example, in a cross section of the shaft member 12 in the axial direction, the axial end edges 19a, 19b of the outer peripheral surface 16 and the outer peripheral edges 20a, 20b of the end faces 17a, 17b on both axial sides are located radially inward from the generatrix α, β of the supported surface portions 22a, 22b. Therefore, when the first tapered surface 4 provided on the inner peripheral surface of the recess 2 of the pair of support jigs 3 is pressed against the supported surface portions 22a, 22b of the chamfered portions 21a, 21b, the axial end edges 19a, 19b on both axial sides of the outer peripheral surface 16 of the shaft member 12 and the outer peripheral edges 20a, 20b of the end faces 17a, 17b do not contact the first tapered surface 4. Therefore, even if the shaft member 12 is deformed by strongly pressing the first tapered surface 4 against the supported surface portions 22a, 22b of the chamfered portions 21a, 21b during rolling of the male thread portion 14, this deformation can be contained within the connecting inclined surface portions 23a1, 23a2, 23b1, 23b2 adjacent to the supported surface portions 22a, 22b in the axial direction. In other words, the deformation of the shaft member 12 can be suppressed to the extent that the connecting inclined surface portions 23a1, 23a2, 23b1, 23b2 slightly bulge outward in the radial direction. In short, according to the manufacturing method of this example, it is possible to prevent burr-like or protruding thin excess material from being formed so as to protrude radially from the end edges 19a, 19b on both axial sides of the outer circumferential surface 16 of the shaft member 12, or from being formed so as to protrude axially from the outer circumferential edges 20a, 20b of the end faces 17a, 17b on both axial sides. This makes it possible to prevent large hoop stress from occurring in the shaft member 12 during heat treatment such as quenching, and to prevent damage such as cracks and delayed fracture from occurring in the completed male shaft 15. Note that the shape of the connection between the axial end edges 19a, 19b of the outer circumferential surface 16 and the outer circumferential edges 20a, 20b of the end faces 17a, 17b on both axial sides in the completed male shaft 15 does not necessarily have to match the shape of the chamfered portions 21a, 21b of the shaft member 12.

In this example, each of the chamfered portions 21a, 21b is configured as a composite surface in which the connecting inclined surface portions 23a1, 23a2, 23b1, 23b2, which are convex curved surfaces having an arc-shaped generatrix, are arranged on both sides of the supported surface portions 22a, 22b, which are conical surfaces having a linear generatrix shape. However, the shape of the chamfered portion formed at the connection between the axially opposite end edges of the outer peripheral surface of the shaft member and the axially opposite end edges of the outer peripheral surfaces is not limited to the example shown in the figure.

Specifically, for example, the structures shown in Figures 8(A) to 8(C) can be adopted.

In the example shown in Fig. 8 (A), the chamfered portion 21c includes a supported surface portion 22a, which is a conical surface having a linear generatrix shape, and a pair of steps 30a, 30b. Of the pair of steps 30a, 30b, the step portion 30a on one axial side, which connects the outer peripheral edge 20a of the end face 17a on one axial side to the edge on one axial side of the supported surface portion 22a, includes a flat surface portion 31a in the shape of a ring bent radially inward from the edge on one axial side of the supported surface portion 22a, and a cylindrical surface portion 32a bent from the inner peripheral edge of the flat surface portion 31a to one axial side, and the edge on one axial side is connected to the outer peripheral edge 20a of the end face 17a on one axial side. The step portion 30b on the other axial side, which connects the edge on the other axial side of the supported surface portion 22a to the edge 19a on one axial side of the outer peripheral surface 16, is made up of a circular flat surface portion 31b that is bent radially inward from the edge 19a on one axial side of the outer peripheral surface 16, and a cylindrical surface portion 32b that is bent from the inner peripheral edge of the flat surface portion 31b to one axial side and has an edge on one axial side connected to the edge on the other axial side of the supported surface portion 22a.

In the example shown in Fig. 8(B), the chamfered portion 21d includes a supported surface portion 22c and a pair of step portions 30c, 30d. The supported surface portion 22c is disposed in the axial middle portion of the chamfered portion 21d, and is a convex curved surface having a generatrix shape of an arc that is inclined in a direction toward the radially outward direction toward the other axial side. Of the pair of step portions 30c, 30d, the step portion 30c on one axial side that connects the outer peripheral edge 20a of the end face 17a on one axial side to the edge on one axial side of the supported surface portion 22c includes a cylindrical surface portion 32c that is bent from the outer peripheral edge 20a of the end face 17a on one axial side to the other axial side, and has an edge on the other axial side connected to the edge on one axial side of the supported surface portion 22c . The step portion 30d on the other axial side, which connects the edge on the other axial side of the supported surface portion 22c to the edge 19a on one axial side of the outer peripheral surface 16, is bent radially inward from the edge 19a on one axial side of the outer peripheral surface 16 and has a circular flat surface portion 31c whose inner peripheral edge is connected to the edge on the other axial side of the supported surface portion 22c.

In the example shown in Figure 8 (C), the chamfered portion 21e has a two-stage structure consisting of a pair of supported surfaces 22d, 22e and three steps 30e-30g. The pair of supported surfaces 22d, 22e are located at two axially intermediate positions of the chamfered portion 21e, and are conical surfaces having a linear generatricle shape that is inclined radially outward as it approaches the other axial side. The pair of supported surfaces 22d, 22e exist on the same conical surface. Of the three step portions 30e to 30g, step portion 30e, which connects the outer peripheral edge 20a of end face 17a on one axial side and one axial side edge of supported surface portion 22d on one axial side, comprises a circular flat surface portion 31d bent radially inward from one axial side edge of supported surface portion 22d on one axial side, and a cylindrical surface portion 32d bent from the inner peripheral edge of flat surface portion 31d to one axial side and having one axial side edge connected to the outer peripheral edge 20a of end face 17a on one axial side. The step portion 30f connecting the other axial side edge of the supported surface portion 22d on one axial side and the other axial side edge of the supported surface portion 22e on the other axial side includes a circular flat surface portion 31e bent radially inward from the one axial side edge of the supported surface portion 22e on the other axial side, and a cylindrical surface portion 32e bent from the flat surface portion 31e to one axial side and having one axial side edge connected to the other axial side edge of the supported surface portion 22d on one axial side. The step portion 30g connecting the other axial side edge of the supported surface portion 22e on the other axial side and the edge 19a on one axial side of the outer peripheral surface 16 includes a circular flat surface portion 31f bent radially inward from the edge 19a on one axial side of the outer peripheral surface 16, and a cylindrical surface portion 32f bent from the flat surface portion 31f to one axial side and having one axial side edge connected to the other axial side edge of the supported surface portion 22e on the other axial side.

8(A) to 8(C), in a state where the first tapered surface 4 provided on the inner peripheral surface of the recess 2 of the support jig 3 is pressed against the supported surface portions 22a, 22c to 22e of the chamfered portions 21c to 21e, the edges 19a on both axial sides of the outer peripheral surface 16 of the shaft member 12 and the outer peripheral edge 20a of the end face 17a do not come into contact with the first tapered surface 4. Therefore, even if the shaft member 12 is deformed as a result of the first tapered surface 4 provided on the inner peripheral surface of the recess 2 of the support jig 3 being strongly pressed against the supported surface portions 22a, 22c to 22e of the chamfered portions 21c to 21e during rolling of the male thread portion 14, this deformation can be contained within the step portions 30a to 30g adjacent to the supported surface portions 22a, 22c to 22e in the axial direction.

Furthermore, according to the structure shown in FIG. 8(C), when the male thread portion 14 is formed by rolling, a gap can be created between the middle step 30f of the three steps 30e-30g and the first tapered surface 4 in a state where the first tapered surface 4 provided on the inner peripheral surface of the recess 2 of the support jig 3 is pressed against the pair of supported surfaces 22d, 22e of the chamfered portion 21e. In the example shown in FIG. 8(C), grease can be held in such a gap, and when the male thread portion 14 is formed, the chamfered portion 21e of the shaft member 12 can slide smoothly against the first tapered surface 4. In addition, when the male thread portion 14 is rolled, the deformation caused by strongly pressing the first tapered surface 4 against the pair of supported surfaces 22d, 22e of the chamfered portion 21e can be absorbed to some extent by the middle step 30f, and the amount of deformation of the steps 30e, 30g on both sides in the axial direction can be suppressed.

Alternatively, the chamfered portion formed at the connection between the axially opposite end edges of the outer peripheral surface of the shaft member and the axially opposite end edges of the outer peripheral surface of the shaft member can be configured as a C-chamfered portion consisting only of a conical surface having a linear generatrix shape, or as an R-chamfered portion having an arc-shaped generatrix shape.

In this example, the male thread portion 14 is rolled by pressing the shaft member 12 from both radial sides between a pair of round dies 24 having helical thread cutting teeth 33 (shown only in FIG. 5; omitted in FIGS. 4(B) to 4(E)) on the outer peripheral surface. However, the method of forming the male thread portion 14 is not particularly limited as long as the first tapered surface 4 provided on the inner peripheral surface of the recess 2 of the support jig 3 is pressed against the supported surface portions 22a and 22b of the chamfered portions 21a and 21b to position the shaft member 12 in the radial direction. For example, as shown in FIG. 7(A) and FIG. 7(B), the male thread portion 14 can be rolled by moving a pair of flat dies 29 arranged opposite each other toward and away from each other. Alternatively, the male thread portion 14 can be formed by a process other than rolling, such as cutting. In this case, however, one end of the shaft member 12 needs to be gripped (chucked) by a rotation drive mechanism.

In this example, the method of manufacturing a male shaft 15, which is a ball screw shaft constituting a ball screw type feed screw mechanism, using the support device 1 and which has a male screw portion 14 formed with a male screw groove 18 having a circular arc cross-sectional shape formed in a spiral shape on the outer circumferential surface 16, has been described. However, the support device for a workpiece of the present invention can also be used, for example, when manufacturing a screw shaft constituting a slide screw type feed screw mechanism. In this case, the male side engagement portion provided on the outer circumferential surface is a male screw portion formed with a male screw groove having a substantially trapezoidal or substantially triangular cross-sectional shape formed in a spiral shape. Alternatively, the support device for a workpiece of the present invention can also be used when manufacturing an inner shaft having a male spline portion or male serration portion on the outer circumferential surface, a worm having worm teeth on the outer circumferential surface, etc. In addition, the workpiece supported by the support device for a workpiece of the present invention is not limited to a cylindrical (solid) shaft member, but can also be a cylindrical shaft member having a recess or through hole formed in the center for weight reduction, etc.

[Second Example of the Embodiment]
9 and 10 show a second embodiment of the present invention. A supporting device 1a of this embodiment includes a pair of supporting jigs 3 and an auxiliary jig 34.

The auxiliary jig 34 is supported on the frame of the support device 1a so as to be capable of axial displacement, has a through hole 35 penetrating in the axial direction, and has a second tapered surface 36 on the other axial side of the through hole 35, which is inclined in a direction such that the inner diameter becomes larger toward the other axial side. In this example, the surface roughness of the second tapered surface 36 is set to an arithmetic mean surface roughness (Ra) of 0.025 μm or less, preferably 0.013 μm or less. Specifically, the second tapered surface 36 is mirror-finished.

The auxiliary jig 34 further has an auxiliary through hole 46 (shown only in FIG. 10) whose one end opens on the inner circumferential surface of the through hole 35 and whose other end opens on the outer circumferential surface or axial side surface (one axial side surface or the other axial side surface) of the auxiliary jig 34. Specifically, one opening of the auxiliary through hole 46 opens on a portion of the inner circumferential surface of the through hole 35 that is axially off from the portion that slides against the supported surface portion 22f of the shaft member 12a, as described later. In this example, the auxiliary through hole 46 opens on one axial side portion of the through hole 35 (a portion off from the second tapered surface 36). However, the auxiliary through hole 46 can also open on the second tapered surface 36 as long as it is a portion that is axially off from the portion that slides against the supported surface portion 22f of the shaft member 12a. The other opening of the auxiliary through hole 46 is connected to a lubricating oil supply device or an air pump.

The support device 1a of this example is preferably used when machining a shaft member 12a in which the axial dimension of the shaft portion 42, which is axially displaced from the workpiece 13 (in the illustrated example, displaced to one side in the axial direction) is relatively long, to produce a male shaft 15 (see Figure 6).

The shaft member 12a has chamfered portions 21a and 21b formed at the connection between the axially opposite end edges 19a and 19b of the outer peripheral surface 16a and the axially opposite end edges 20a and 20b of the axially opposite end faces 17a and 17b, respectively, and also has a chamfered portion 21f in the axial middle portion. For this reason, the shaft member 12a has a stepped cylindrical portion 37 in a portion of the outer peripheral surface 16a that is offset from the processed portion 13 to one axial side. The stepped cylindrical portion 37 is formed by connecting a small diameter cylindrical portion 38 on one axial side and a large diameter cylindrical portion 39 on the other axial side by a step surface 40 facing one axial side. The chamfered portion 21f is formed at the connection between the axially opposite end edge 19c of the large diameter cylindrical portion 39 and the outer peripheral edge 20c of the step surface 40, and includes a supported surface portion 22f and a pair of connecting inclined surface portions 23c1 and 23c2. The supported surface portion 22f is a conical surface having a linear generatrix shape. In addition, in a cross section in the axial direction (a cross section including the central axis O of the shaft member 12a), the edge 19c on one axial side of the large diameter cylindrical portion 39 and the outer circumferential edge 20c of the step surface 40 are located radially inward from the generatrix (including the extension of the generatrix) of the supported surface portion 22f.

Of the pair of connecting inclined surface portions 23c1, 23c2, the connecting inclined surface portion 23c1 on one axial side, which connects the outer peripheral edge 20c of the step surface 40 and the edge on one axial side of the supported surface portion 22f, is a convex curved surface having an arc-shaped generatrix shape that is inclined in a direction radially outward as it approaches the other axial side. The connecting inclined surface portion 23c2 on the other axial side, which connects the edge on the other axial side of the supported surface portion 22f and the edge 19c on one axial side of the large diameter cylindrical portion 30, is a convex curved surface having an arc-shaped generatrix shape that is inclined in a direction radially outward as it approaches the other axial side.

Furthermore, the shaft member 12a has a groove 41 that is recessed radially inward around the entire circumference at the other axial end of the small diameter cylindrical portion 38.

When the support device 1a of this embodiment is used to perform rolling on the processed portion 13 of the shaft member 12a to form the male thread portion 14 (see FIG. 6), first, the first tapered surface 4 provided on the inner peripheral surface of each recess 2 of the pair of support jigs 3 is pressed against the supported surface portions 22a, 22b of the chamfered portions 21a, 21b formed on both axial ends of the shaft member 12a. At this time, as shown by the two-dot chain line in FIG. 9, with the end face on one axial side of the auxiliary jig 34 overlapping the tip face (the end face on the other axial side) of the support jig 3 on one axial side of the pair of support jigs 3, the first tapered surface 4 provided on the inner peripheral surface of the recess 2 of the support jig 3 on one axial side is pressed against the supported surface portion 22a of the chamfered portion 21a on one axial side. Next, the auxiliary jig 34 is slid from the position indicated by x = _x0 to the position indicated by x = _x1 in Fig. 9 toward the other axial direction, and the second tapered surface 36 is pressed against the supported surface portion 22f of the axially intermediate chamfered portion 21f. In this state, the processed portion 13 of the shaft member 12a is pressed from both radial sides between a pair of rotating circular dies 24 (see Figs. 4(B) to 4(E)), thereby subjecting the processed portion 13 to a rolling process to form the male thread portion 14 and obtaining the male shaft 15.

According to the support device 1a of this example, the second tapered surface 36 of the auxiliary jig 34 is pressed against the supported surface portion 22f of the chamfered portion 21f formed in the axial middle portion of the shaft member 12a, thereby supporting the axial middle portion of the shaft member 12a. Therefore, even if the axial dimension of the shaft portion 42 of the shaft member 12a that is axially separated from the processed portion 13 is relatively long, it is possible to prevent the shaft member 12a from being deformed (buckling deformation) so as to be bent when forming the male thread portion 14. Furthermore, it is possible to reduce the frictional resistance acting on the sliding contact portion between the first tapered surface 4 of the pair of support jigs 3 arranged on both axial sides and the supported surface portions 22a, 22b provided on both axial ends of the shaft member 12, and to prevent the occurrence of seizure at these sliding contact portions.

The position of the shaft member 12a supported by the auxiliary jig 34, i.e., the axial position of the chamfered portion 21f, is determined from the viewpoint of effectively preventing buckling deformation of the shaft member 12a when the male thread portion 14 is formed. Specifically, for example, when the axial length _d1 of the processed portion 13 is equal to or greater than ½ of the total axial length _d2 of the processed portion 13 and the shaft portion 42 ( _d1 ≧ _d2 /2), the position of the chamfered portion 21f is preferably shifted to one axial side from the end of the processed portion 13 on one axial side by the length L of one lead of the male thread groove 18 that constitutes the male thread portion 14 (including the vicinity thereof). When the axial length _d1 of the workpiece 13 is shorter than _1/2 of the total axial length d2 of the workpiece 13 and the shank 42 ( _d1 < _d2 /2), it is preferable that the contact hole be between a position shifted axially to one side from the end of one axial side of the workpiece 13 by the length L of one lead of the male thread groove 18 that constitutes the male thread portion 14, and a position shifted axially to the other side from the end of one axial side of the shank 42 by 1/3 of the total axial length _d2 of the workpiece 13 and the shank 42 ( _d2 /3).

In particular, in the support device 1a of this embodiment, the surface roughness of the second tapered surface 36 is 0.025 μm or less, preferably 0.013 μm or less, in terms of arithmetic mean surface roughness (Ra). Specifically, the second tapered surface 36 is mirror-finished. As a result, when forming the male thread portion 14, the resistance of the supported surface portion 22f to sliding contact with the second tapered surface 36 as the shaft member 12a rotates can be reduced. Therefore, when forming the male thread portion 14, the amount of wear powder generated by the sliding contact between the second tapered surface 36 and the supported surface portion 22f as the shaft member 12a rotates can be reduced.

In this example, when the second tapered surface 36 of the auxiliary jig 34 is pressed against the supported surface portion 22f of the chamfered portion 21f, the end edge 19c on one axial side of the large diameter cylindrical portion 39 of the shaft member 12a and the outer peripheral edge 20c of the step surface 40 do not come into contact with the second tapered surface 36. Therefore, even if the shaft member 12a is deformed by strongly pressing the second tapered surface 36 of the auxiliary jig 34 against the supported surface portion 22f of the chamfered portion 21f when rolling the male thread portion 14, this deformation can be contained within the connecting inclined surface portions 23c1 and 23c2 that are adjacent to the supported surface portion 22f in the axial direction.

In addition, in this example, grease can be held in the groove 41 provided at the other axial end of the small diameter cylindrical portion 38 of the shaft member 12a, which allows the chamfered portion 21f of the shaft member 12a to slide smoothly against the second tapered surface 36 of the auxiliary jig 34 when forming the male thread portion 14.

In addition, in this example, the auxiliary jig 34 has an auxiliary through hole 46, so that during or after machining of the male thread portion 14, lubricating oil for cooling or cleaning can be supplied to the sliding contact portion between the second tapered surface 36 of the auxiliary jig 34 and the supported surface portion 22f of the chamfered portion 21f, or compressed air for removing wear powder can be supplied through the auxiliary through hole 46. Therefore, the sliding contact state between the second tapered surface 36 of the auxiliary jig 34 and the supported surface portion 22f of the chamfered portion 21f can be improved, and the machining accuracy of the male thread portion 14 can be ensured. The configuration and effects of the other parts are the same as those of the first example of the embodiment.

[Third Example of the Embodiment]
11 shows a third embodiment of the present invention. A supporting device 1b of this embodiment includes a supporting jig 3 having a recess 2 opening on its tip surface, and a jig 44 having a conical tip portion 43.

The support device 1b of this example is preferably used when machining a shaft member 12b having a recessed hole 45 in the center of the other axial end face 17c to produce a male shaft 15 (see Figure 6).

The shaft member 12b has a chamfered portion 21a only at the connection between the edge 19a on one axial side of the outer peripheral surface 16b and the outer peripheral edge 20a of the end face 17a on one axial side, and has a conical concave hole 45 in the center of the end face 17c on the other axial side.

When using the support device 1b of this example to perform rolling on the processed portion 13 of the shaft member 12b to form the male thread portion 14 (see FIG. 6), the first tapered surface 4 provided on the inner peripheral surface of the recess 2 of the support jig 3 is pressed against the supported surface portion 22a of the chamfered portion 21a formed on one axial end of the shaft member 12b, and the outer peripheral surface of the conical tip portion 43 provided on the jig 44 is abutted against the inner peripheral surface of the recessed hole 45 formed on the end face 17c on the other axial side of the shaft member 12b, thereby supporting the shaft member 12b. The configuration and effects of the other parts are the same as those of the first example of the embodiment.

[Fourth Example of the Embodiment]
A fourth embodiment of the present invention will be described with reference to Fig. 12. The support device 1c of this embodiment is equipped with a displacement meter 48 having a probe 47. The probe 47 is inserted into the through hole 5 of the support jig 3 on one side in the axial direction. The displacement meter 48 is composed of, for example, a contact type displacement meter such as a dial gauge, or a non-contact type displacement meter such as an optical type or a laser type.

When manufacturing a male shaft 15 (see FIG. 6) from a shaft member 12 using the support device 1c of this example, the tip of the probe 47 (the right end in FIG. 12) is abutted against or opposed to the end face 17a on one axial side of the shaft member 12 to measure the displacement (axial displacement) of the shaft member 12 during machining of the male thread portion 14 (see FIG. 6). This makes it possible to detect any abnormality that occurs during machining of the male thread portion 14, in which the shaft member 12 is displaced by more than a predetermined amount (a displacement that would not occur if machining was performed normally).

According to the support device 1c of this example, the displacement meter 48 can detect abnormalities during machining based on measuring the displacement of the shaft member 12 during machining of the male thread portion 14, and it can be determined whether machining is being performed properly.

The displacement meter 48 can also function as a tachometer (rotation sensor) that measures the rotation of the shaft member 12. When the displacement meter 48 functions as a tachometer, it is possible to detect whether an abnormality such as excessive slippage has occurred between the shaft member 12 and the round die 24 by comparing the number of rotations (rotational speed) of the shaft member 12 measured by the displacement meter 48 with the number of rotations of the round die 24 (see Figures 4(B) to 5) measured by another sensor. Therefore, it is possible to more accurately determine whether the male thread portion 14 has been properly machined. The configuration and effects of the other parts are the same as those of the first embodiment.

[Fifth Example of the Embodiment]
A fifth embodiment of the present invention will be described with reference to Fig. 13. A supporting device 1d of this embodiment includes a pair of supporting jigs 3, 3a, a displacement meter 48 having a probe 47, and a rotation meter (rotation sensor) 50 having a detection unit 49.

Of the pair of support jigs 3, 3a, the support jig 3a on one axial side has a through hole 5 that opens to the bottom of the recess 2 and the base end face of the support jig 3a (the left side face in FIG. 13), and a radial through hole 51 that opens to the first tapered surface 4 and the outer peripheral surface of the support jig 3a.

The displacement gauge 48 has a probe 47 inserted through the through hole 5 of the support jig 3a on one axial side, so that the tip end (the right end in FIG. 13) of the probe 47 abuts against or faces the end face 17a on one axial side of the shaft member 12. This makes it possible for the displacement gauge 48 to measure the displacement (axial displacement) of the shaft member 12 during machining of the male thread portion 14 (see FIG. 6) .

The tachometer 50 has a detection section 49 inserted into a radial through hole 51 in the support jig 3a on one axial side, so that the detection section 49 faces or abuts against the outer peripheral surface of the end section on one axial side of the shaft member 12. This allows the tachometer 50 to measure the number of rotations of the shaft member 12 during machining of the male threaded portion 14. Note that the tachometer 50 is preferably a non-contact type, but a contact type can also be used. The configuration and effects of the other parts are the same as those of the first and fourth examples of the embodiment.

[Sixth Example of the Embodiment]
A sixth embodiment of the present invention will be described with reference to Fig. 14. In a support device 1e of this embodiment, a support jig 3b on one axial side has an oil supply hole 52 that opens to the outer circumferential surface of the support jig 3b and to the through hole 5.

In this example, the probe 47 of the displacement gauge 48 is inserted into the through hole 5 of the support jig 3b on one axial side. This allows the tip of the probe 47 (the right end in FIG. 14) to be abutted against or opposed to the end face 17a on one axial side of the shaft member 12, making it possible to measure the displacement (axial displacement) of the shaft member 12 by the displacement gauge 48. At the same time, the lubricating oil supplied to the oil supply hole 52 from the lubricating oil supply device 27 (see FIG. 2) can be supplied to the first tapered surface 4 through the through hole 5. The configuration and effects of the other parts are the same as those of the first and fourth examples of the embodiment.

The structures of the first to sixth examples of the above-mentioned embodiment can be combined as appropriate as long as no contradictions arise.

REFERENCE SIGNS LIST 1, 1a, 1b, 1c, 1d, 1e Support device 2 Recess 3, 3a, 3b Support jig 4 First tapered surface 5 Through hole 6 Base metal 7 Jig body 8 Fitting recess 9 Upstream through hole 10 Vent hole 11 Downstream through hole 12, 12a, 12b Shaft member 13 Workpiece 14 Male threaded portion 15 Male shaft 16 Outer circumferential surface 17a, 17b, 17c End face 18 Male thread groove 19a, 19b, 19c End edge 20a, 20b, 20c Outer circumferential edge 21a, 21b, 21c, 21d, 21e, 21f Chamfered portion 22a, 22b, 22c, 22d, 22e, 22f Supported surface portion 23a1, 23a2, 23b1, 23b2, 23c1, 23c2 Connecting inclined surface portion 24 Round die 25 Cooling oil supply device 26 Compressor 27 Lubricating oil supply device 28 Switching valve 29 Flat die 30a, 30b, 30c, 30d, 30e, 30f, 30g Step portion 31a, 31b, 31c, 31d, 31e, 31f Flat surface portion 32a, 32b, 32c, 32d, 32e, 32f Cylindrical surface portion 33 Thread cutting teeth 34 Auxiliary jig 35 Through hole 36 Second tapered surface 37 Stepped cylindrical portion 38 Small diameter cylindrical portion 39 Large diameter cylindrical portion 40 Step surface 41 Concave groove 42 Shaft portion 43 Tip portion 44 Jig 45 Recess 46 Auxiliary through hole 47 Probe 48 Displacement gauge 49 Detector 50 Revolution gauge 51 Radial through hole 52 Oil supply hole

Claims (6)

At least one support jig is provided, the support jig including a recess having a first tapered surface on an inner circumferential surface thereof;
A support device for a workpiece, which supports at least an axial end portion of the workpiece while positioning the workpiece in a radial direction by pressing a connection portion between an outer circumferential surface and an axial end surface of the workpiece against the first tapered surface,
The at least one support jig further includes a through hole that opens to a bottom of the recess,
a support device for a workpiece , wherein the arithmetic mean surface roughness of at least a portion of the first tapered surface that contacts the connection portion is 0.025 μm or less . 2. The workpiece supporting device according to claim 1 , wherein at least a portion of said first tapered surface that comes into contact with said connecting portion is mirror-finished. At least one support jig is provided, the support jig including a recess having a first tapered surface on an inner circumferential surface thereof;
A support device for a workpiece, which supports at least an axial end portion of the workpiece while positioning the workpiece in a radial direction by pressing a connection portion between an outer circumferential surface and an axial end surface of the workpiece against the first tapered surface,
The at least one support jig further includes a through hole that opens to a bottom of the recess,
The support device for a workpiece further includes an auxiliary jig that is supported to allow relative axial displacement with respect to the at least one support jig, the auxiliary jig having a through hole penetrating in the axial direction, and a second tapered surface formed on at least a portion of the inner surface of the through hole and inclined in the same direction as the first tapered surface . The auxiliary jig has an auxiliary through hole, one end of which opens to the inner circumferential surface of the through hole and the other end of which opens to the outer circumferential surface or the axial side surface of the auxiliary jig.
4. The workpiece supporting device according to claim 3 . At least one support jig is provided, the support jig including a recess having a first tapered surface on an inner circumferential surface thereof;
A support device for a workpiece, which supports at least an axial end portion of the workpiece while positioning the workpiece in a radial direction by pressing a connection portion between an outer circumferential surface and an axial end surface of the workpiece against the first tapered surface,
The at least one support jig further includes a through hole that opens to a bottom of the recess,
Further comprising a displacement meter for measuring the displacement of the workpiece,
A support device for a workpiece , wherein a probe of the displacement meter is inserted into the through hole . 6. The workpiece supporting device according to claim 1 , wherein at least a portion of said at least one supporting jig, which includes said recessed portion, is made of high speed steel, cemented carbide or diamond.

Images