JPH0253180B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cylindrical workpiece precision centering device for precisely centering a workpiece in a machine tool for machining the outer or inner peripheral surface of a cylindrical workpiece.

For example, when cutting the outer or inner circumferential surface of a cylindrical workpiece using a gear cutting machine, if multiple cylindrical workpieces are overlapped in the axial direction, the outer or inner circumferential surface of each workpiece will be Gear cutting can be performed at the same time, improving efficiency. however,
In order to perform gear cutting on the outer or inner peripheral surface of a workpiece with high precision, it is necessary to center the workpiece with high precision with respect to the rotating shaft of the gear cutting machine. Conventionally, when a plurality of cylindrical workpieces were stacked on top of each other in the axial direction, it was not possible to center each workpiece with high precision due to variations in the diameter tolerance of each workpiece.

Therefore, this invention utilizes balls to stack a plurality of cylindrical workpieces in the axial direction, and to machine all of the workpieces in a machine tool that machine the outer or inner circumferential surface of each workpiece. This was done to enable accurate centering. In particular, this invention provides a plurality of balls and a tapered member at each workpiece position, and arranges the balls at each workpiece position at angular intervals along the inner circumferential surface or outer circumferential surface of each workpiece. The tapered members at each workpiece location are arranged so as to contact the balls at each workpiece location. The ball is held so as to be substantially displaceable in the radial direction of the workpiece, but not axially displaced, and the tapered member is precisely held so as to be substantially displaceable in the axial direction of the workpiece, but not radially displaced. However, the tapered members at each workpiece position are individually and simultaneously elastically biased substantially in the axial direction of the workpiece by elastic biasing means such as springs. The balls at each workpiece are pressed against the inner circumferential surface or outer circumferential surface of each workpiece by the elastic biasing force of the elastic biasing means and the wedge action of the tapered member. This allows for precise centering of cylindrical workpieces with varying diameter tolerances. Furthermore, by adopting a ball-like spherical body, there is also the advantage that workpieces can be inserted smoothly.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a gear cutting machine to which the present invention is applied for cutting gears on the outer peripheral surface of a cylindrical workpiece. In this example, five cylindrical workpieces W ₁ to _{W 5} are superimposed in the axial direction. A plurality of balls B ₁ to B ₅ and a tapered member T ₁ to _{T 5} are placed at each workpiece position.
is provided. The advantage of using balls is particularly advantageous when the thickness of each workpiece is small. In this example, each workpiece location is provided with 20 balls, for a total of 100 balls. When balls are used, a large number of balls can be arranged on the circumference, and the tendency to lose positional accuracy can be absorbed by the number of balls, making it easy to maintain precision. The balls at each workpiece position are arranged at equal angular intervals along the inner peripheral surface of each workpiece on a plane perpendicular to the rotation axis 1 of the gear cutting machine, that is, on a horizontal plane, and are formed in the holding sleeve 2. absorbed into the pores. The ball is a leaf spring 3 fitted into the outer and inner peripheral surfaces of the holding sleeve 2.
It is held in place so that it does not fall off. The inner diameter of the hole in the retaining sleeve 2 is only slightly larger than the outer diameter of the ball, and the ball can hardly be displaced in the vertical direction in the figure. However, it can be slightly displaced in the left and right directions in the figure. Therefore, the ball is held by the holding sleeve 2 and the leaf spring 3 so that it can be substantially displaced in the radial direction of the workpiece, but not in the axial direction.

Tapered members T ₁ to _{T 5} at positions of each workpiece W ₁ to _{W 5}
are the balls B ₁ ~ at the positions of each workpiece W ₁ ~ W ₅ , respectively.
It is placed in contact with B ₅ . Tapered member T ₁
~ _T5 is an annular member having a tapered surface 4 that contacts the ball, and is fitted to the outer circumferential surface of the center ring socket 5 so that it can slide vertically, and is movable in the axial direction of the workpiece, and also in the radial direction. It is precisely held so that it does not displace. Tapered surface 4 is the workpiece
The axial direction of W ₁ to W ₅ is radially inclined. The centering socket 5 is arranged concentrically with the rotating shaft 1 of the gear cutting machine and is fixed to the base 6.

Tapered members T ₁ to _{T 5} at positions of each workpiece W ₁ to _{W 5}
are individually elastically biased in the same axial direction of the workpiece by coil springs S ₁ to _{S 5} . The coil springs S ₁ to _{S 5} are housed inside the tapered members T ₁ to _{T 5} ,
One end is engaged with the bottom wall of the tapered member, and the other end is engaged with the collar 8 of the rod 7. The rod 7 extends through the tapered members T ₁ -T ₅ and extends through the tapered members T ₁ -T 5 .
It can slide in the axial direction, that is, in the vertical direction, with respect to _T5 , and is fixed to the rod holder 9.

In this embodiment, a plurality of coil springs S ₁ -S ₅ are accommodated in the tapered members T ₁ -T ₅ at the positions of each workpiece W ₁ -W ₅ , respectively, and therefore a plurality of rods 7 are housed.
is provided and fixed to the rod holder 9. The effect of arranging multiple springs is
The advantage is that each spring force can be lowered. Second
The figure shows the position of the coil springs housed within the tapered members T ₁ -T ₅ of each workpiece W ₁ -W ₅ .
There are three coil springs S ₁ in the tapered member T _1.
are housed in the tapered member _T2 , six coil springs _S2 are housed in the taper member T2, and the coil springs _S1 ,
S ₂ are arranged at equal angular intervals.
Nine coil springs S ₃ are inside the tapered member T ₃
are housed, and three coil springs _S3 are uniformly arranged at angular intervals of 30° and 60°. Twelve coil springs S ₄ and S ₅ are housed in each of the tapered members T ₄ and T ₅ , and the coil springs S ₄ and S ₅ are arranged at equal angular intervals. Therefore, in this embodiment, 12 rods 7 are arranged at equal angular intervals, and each rod 7
One ends of coil springs S ₁ to _{S 5} are respectively engaged with the collars 8 . In this case, the number of springs may be set to 12 for each of S ₁ to S ₅ .

Rod holder 9 is in center ring socket 5
It is fitted to the inner circumferential surface of the
It is elastically biased upward by a coil spring 10.

As will be described later, after the workpieces W ₁ to _{W 5} are centered, they are held and fixed between the support ring 5a of the center ring socket 5 and the clamping sleeve 12 of the support center 11. Support center 11 is clamping sleeve 1
In addition to 2, it has a presser washer 13 that engages with the rod holder 9, and an insertion rod 15 that can be inserted into the draw rod 14. Drorod 14
is the axial direction on the inner circumferential surface of the center ring socket 5,
That is, they are fitted so as to be slidable in the vertical direction, and the lower end is connected to a clamping cylinder (not shown). The upper end has a stopper 16 which limits the displacement of the rod holder 9. The draw rod 14 also has a clamping piece 17 for connection to the insertion rod 15 of the support center 11. Clamping piece 17 is draw rod 14
It is slidably fitted in the hole in the radial direction, that is, in the left-right direction, and can project into the interior of the draw rod 14 and engage the insertion rod 15 as shown. The centering socket 5 has an inner circumferential groove 18 for retracting the clamping piece 17.

In the gear cutting machine cylindrical workpiece centering device configured as described above, when the support center 11 and the draw rod 14 are raised, the clamping piece 17 is inserted into the inner periphery of the center ring socket 5 by the insertion rod 15. It is pushed into the groove 18 and withdrawn. As a result, the clamping piece 17 is separated from the insertion rod 15, and the connection between the two is released. Thereafter, the draw rod 14 is not displaced, only the support center 11 is further raised, and the insertion rod 15 is pulled out from within the draw rod 14. The support center 11 rises together with the clamping sleeve 12 and the presser washer 13. The axially superimposed workpieces W ₁ to _{W 5} can thus be lowered from above and placed around the holding sleeve 2 as shown.

To center the workpieces W ₁ to _{W 5} , the support center 11 is lowered and the insertion rod 15 is inserted into the draw rod 14 . When the support center 11 is lowered, the presser washer 13 first
contacts the rod holder 9, and the rod holder 9
descends while pressing the spring 10. The rod 7 connects tapered members T _{1 to} T ₁ to W ₅ of the workpieces W 1 to W 5 .
It slides against T ₅ and lowers together with the rod holder 9. Therefore, the coil springs S ₁ to _{S 5} at the positions of the workpieces W ₁ to W ₅ are compressed by the collar 8 of the rod 7, and the tapered members T ₁ to _{T 5} are compressed by the coil springs S ₁ to S ₅ . Therefore, it is elastically biased downward, that is, in the same axial direction of the workpiece. Each workpiece
Balls B ₁ to _{B 5} at positions W ₁ to _{W 5} are held so that they can substantially be displaced in the radial direction of the workpiece, but not in the axial direction (this is essential to maintain high precision). requirements), are pressed against the inner circumferential surfaces of the workpieces W1 _{to W5} , respectively, by the elastic urging force of the coil springs _S1 to _S5 and the wedge action of the tapered members _T1 to _T5 . As a result, the workpieces W ₁ to _{W 5} are centered.

Tapered members T ₁ to _{T 5} at positions of each workpiece W ₁ to _{W 5}
Each workpiece is elastically biased individually by
The balls B ₁ to B ₅ at positions W ₁ to _{W 5} are reliably pressed against the inner peripheral surfaces of the respective workpieces W ₁ to _{W 5} . Therefore, even if the diameter tolerance of each workpiece varies, all workpieces can be centered precisely. Since the balls B ₁ to _{B 5} at each workpiece position are arranged at equal angular intervals on a plane perpendicular to the rotation axis 1 of the gear cutting machine, the workpieces W ₁ to _{W 5} can be cut with high precision. Centered. Further, since the ball is spherical and the tapered member has a conical surface, even if there is a position error in the circumferential direction of the ball, there is little effect on centering accuracy. Accuracy can be easily ensured.

Because the balls B ₁ to _{B 5} are only pressed against the inner circumferential surfaces of the workpieces W ₁ to W ₅ by the elastic urging force of the coil springs S ₁ to _{S 5} and the wedge action of the tapered members T ₁ to T ₅ . , not be pushed too hard. The coil springs S ₁ -S ₅ absorb the load transmitted from the support center 11 and the rod 7, and prevent the balls B ₁ -B ₅ from being excessively pressed.
Therefore, the workpiece W ₁ ~ by the balls B ₁ ~ _{B 5}
There is no risk of damage to the inner peripheral surface of _W5 . Furthermore, since 20 balls are provided at each of the positions of the workpieces W ₁ to _{W 5} , the elastic urging force of the coil springs S ₁ to _{S 5} is distributed to each of the 20 balls. Therefore, the pressing force per ball is small and the inner peripheral surface of the workpiece is not damaged. Therefore, when using high-hardness balls, the workpiece hardness increases.
It is especially effective for HRC25 or lower and frees you from worrying about damage.

When the workpieces W ₁ to _{W 5} are stacked on top of each other, the weight of each workpiece acts on the workpiece below it. In this example, there are three coil springs S ₁ in the tapered member T ₁ , six coil springs S ₂ in the tapered member T ₂ , and nine coil springs S ₃ in the tapered member T ₃ . Since 12 coil springs S ₄ and S ₅ are housed in members T ₁ and T ₅ , respectively, the balls at the lower workpiece position are stronger than the balls at the upper workpiece position. Pressed against the inner peripheral surface. Therefore, each of the workpieces W ₁ to _{W 5} is smoothly centered without being hindered by the weight of the workpiece above it. Furthermore, this spring S ₁
~ _S5 may be arranged in the same number.

When the support center 11 is further lowered, the clamping sleeve 12 comes into contact with the end surface of the workpiece.
Thereafter, when the draw rod 14 is lowered by the cylinder, the clamping piece 17 is pulled out from inside the inner circumferential groove 18 of the centering socket 5 by the draw rod 14, and the support center 11
is engaged with the insertion rod 15 of. Therefore, the draw rod 14 and the insertion rod 15 are connected, and the support center 11 is pulled down by the draw rod 14. As a result, the workpieces W ₁ to _{W 5} are attached to the clamping sleeve 1 of the support center 11.
2 and the support ring 5a of the center ring socket 5, and is fixed in a predetermined position.

Thereafter, the outer peripheral surfaces of the workpieces W ₁ to _{W 5} are subjected to gear cutting. After the gear cutting process is completed, when the support center 11 and the draw rod 14 are raised, the clamping piece 17 is retracted into the inner circumferential groove 18 of the center ring socket 5. The support center 11 is further raised, and the insertion rod 15 is moved to the draw rod 14.
be extracted from. Therefore, the workpieces W ₁ to _{W 5} can be lifted upward and removed.

In addition, in the case of a workpiece of low hardness, when the presser washer 13 is brought into contact with the rod holder 9 and the clamping sleeve 12 is brought into contact with the workpiece, if the support center 11 is rapidly lowered, the workpiece will be moved by the balls B ₁ to B ₅ . An impact load is applied to the inner peripheral surface of the workpiece, and an impact load is applied to the end face of the workpiece by the clamping sleeve 12. Therefore, there is a risk that the inner peripheral surface and end surface of the workpiece may be damaged. To avoid this, the support center 11 should be lowered at a slow speed. FIG. 6 shows a hydraulic circuit for lowering and raising the support center 11. When the support center 11 is lowered, hydraulic pressure is supplied to the rod end of the cylinder 19, and initially the hydraulic pressure is discharged from the head end of the cylinder 19 through the switching valve 20. Therefore, the support center 11 descends at high speed. When the support center 11 is lowered to a predetermined height, the limit switch operates and the switching valve 2
Switch 0. Thereafter, hydraulic pressure is discharged from the head end of the cylinder 19 through the throttle 21. Therefore, the support center 11 descends at a slow speed, and the presser washer 13 smoothly contacts the rod holder 19. Therefore, the balls B ₁ to _{B 5} smoothly move to the workpiece W ₁
It is pressed against the inner circumferential surface of ~ _W5 , and the workpieces _W1 ~ _W5 are smoothly centered. The clamping sleeve 12 smoothly contacts the end surface of the workpiece and
W ₁ to _{W 5} are smoothly held between the clamping sleeve 12 and the support ring 5a. This avoids damage to the inner peripheral surfaces and end surfaces of the workpieces _W1 to _W5 .

It should be noted that various modifications of the present invention are possible in addition to the above-mentioned embodiments. Figure 7 shows the ball B ₁ in Figure 1.
In addition to B ₅ , 20 balls B ₁ ′ to _{B 5} ′ are provided at the positions of each workpiece W ₁ to W ₅ . Each workpiece
Balls B ₁ ′ to B ₅ ′ at positions W ₁ to _{W 5} are balls B ₁ to _{B 5}
The angular positions between the balls B ₁ to B ₅ are spaced at equal angular intervals along the inner peripheral surfaces of the workpieces W ₁ to _{W 5} on different horizontal planes, and as shown in FIGS. 8 and 9. are arranged in The tapered members T ₁ ′ to T ₅ ′ have a tapered surface 22 that contacts the balls B _{1 ′} to _{B 5} ′, which is different from the tapered surface 4 that contacts the balls B ₁ to _{B 5} . As shown on the left side of FIG. 7, the workpiece W ₁ ~
If W ₅ is turned in the opposite direction, the position of its inner circumferential surface will shift. Therefore, the balls B ₁ to _{B 5} are connected to the workpiece W ₁ to _{W 5}
cannot be pressed against the inner peripheral surface of the However, since the balls B ₁ ′ to _{B 5} ′ are arranged along the inner peripheral surface of the workpiece on a horizontal plane different from the balls B ₁ to B ₅ , the balls B ₁ to _{B 5} are arranged along the inner peripheral surface of the workpiece. ₁ ' to _B5 ' can be pressed against the inner peripheral surfaces of the workpieces _W1 to _W5 . Balls B ₁ ′ to B ₅ ′ are balls B ₁ to _{B 5}
As in the case of , the workpieces are pressed against the inner circumferential surfaces of the workpieces W _{1 to W 5 by the elastic urging force of the coil springs S 1 to S 5} and the wedge action of the tapered members T _{1 ′} to _{T 5 ′} . Therefore, even if the workpieces W ₁ to _{W 5} are turned in the opposite direction, they can be centered without any problem. In this case, as shown in FIG. 10, the tapered member T ₁ '~
It is also possible to accommodate 16 springs in T ₅ ' and form holes for passing 16 rods 7 therethrough.

In order to use the centering device of the present invention more effectively, the precision of the processing machine must also be high. Therefore, the structure of a gear cutting machine that cuts gears on the outer peripheral surface of a workpiece, particularly a hobbing machine that cuts gears using a hob cutter, will be described. FIG. 12 shows a transmission system in which the drive motor 23 rotates the hob cutter 24 and at the same time rotates the table 25 of the workpiece. The torque of the drive motor 23 is transferred to the small gear 29 by the belt 26 and gears 27, 28.
The hob cutter 24 rotates integrally with the large gear 30. The flywheel 31 is a small gear 2
9 rotates smoothly. Drive motor 2
3 is transmitted from the differential gear 32 to the worm 34 by the index changing gear 33, and the table 25 rotates integrally with the worm wheel 35. This causes the workpiece to rotate, and the hob cutter 24 cuts the outer peripheral surface of the workpiece. It is well known that when gear cutting is performed by the hob cutter 24, the problem of centering accuracy solved by the present invention and the curvature of the tooth line to be processed become a problem. In particular, when using a multi-thread hob cutter, not only does the cutting force increase, but in addition, the more the workpiece rotates relative to the hob, the more the tooth traces tend to bend. This is gear 2 of the transmission system
This is due to the backlash between the worm gears 7, 28, 33, 29, 30 and the worm gears 34, 35. To avoid this, torque or a brake may be applied to the worm 34 that rotates the table 25 by the pump or motor 36. Applying torque or braking via the transmission 37, which can change the transmission ratio, can have a significant positive effect. By adjusting the transmission ratio of the transmission 37 according to various machining conditions, it is possible to effectively eliminate bumps in the gear group of the transmission system, so that the hob cutter and the table rotation drive worm rotate synchronously, allowing gear cutting to be performed. It can prevent the tooth lines of objects from bending. This method can also be applied to NC machines, and can also be applied when the table drive mechanism is other than a worm gear.

When centering a workpiece, if the outer peripheral surface of the holding sleeve 2 is covered with a flexible thin film 38 as shown in FIG. 13, chips from the workpiece will be prevented from entering the hole in the sleeve during gear cutting. It can prevent the ball from entering between the balls. Since the balls are pressed against the inner peripheral surface of the workpiece through the thin film 38, damage to the inner peripheral surface of the workpiece is also avoided. As shown in FIG. 14, rubber 3 is attached to the outer and inner peripheral surfaces of the holding sleeve 2.
9 or the like may be fitted to hold the ball. As shown in FIG.
Caulk the inner and outer surfaces of the
This may help hold the ball. In some cases, as shown in FIG. 16, a roller 40 may be used instead of the ball, and the roller 40 may be pressed against the inner peripheral surface of the workpiece by the wedge action of the tapered member. 1st
As shown in FIG. 7, the outer peripheral surface of the holding sleeve 2 is covered with a flexible sleeve 41, and a flow path 42 formed in the peripheral wall of the holding sleeve 2 is connected to the inner peripheral surface of the flexible sleeve 41. Fluid pressure may also be provided. When the wall thickness of the flexible sleeve 41 is intermittently thinned at the positions of the workpieces _W1 to _W3 , the flexible sleeve 41 is effectively expanded at the positions of the workpieces _W1 to _W3 . , are pressed against the inner circumferential surfaces of the workpieces W ₁ to _{W 3} . This also makes it possible to center the workpieces W ₁ to _{W 3} individually. 18th
The figure shows a general flexible sleeve 41 with a reduced overall wall thickness. As shown in FIG. 19, an annular collet 44 may be arranged between annular tapered members 43 arranged at intervals in the axial direction. When the collet 44 and the taper member 43 are elastically biased in the axial direction, the collet 44 expands due to the wedge action of the taper member 43, and the workpiece W ₁
~ Pressed against the inner peripheral surface of _W5 . Workpieces W ₁ to _{W 5} are thus centered. Figure 20,
As shown in FIG. 21, the taper member 45 at each workpiece position may be individually elastically biased by a spring 46, thereby pressing the collet 47 against the inner peripheral surface of the workpiece. As shown in FIG. 22, a coil spring 49 may be interposed between the tapered members 47 and 48, and a spacer 51 may be arranged between the collets 50. The collet 50 has tapered members 47, 48
is pressed against the inner peripheral surface of the workpiece by the wedge action. Figures 23, 24 (conventional) and 25 (flexible collet) show collets that can be used in the centering devices of Figures 19, 20, 21 and 22. . FIG. 26 shows an enlarged view of the collet shown in FIG. 25 in a deformed state. This has the effect that the collet can be expanded easily by providing the groove on the side opposite to the gripping surface.

In each of the above embodiments, the axial direction of the workpiece is arranged vertically, but it goes without saying that it can be applied to various phases.

In addition, various applications are possible, such as the centering device may be placed on the center side (moving side).

From an economic point of view, the balls used in the present invention are highly hard and highly accurate and can be purchased easily and cheaply from bearing manufacturers.
The price can also be kept low.

As described above, the precision centering device of the present invention has the characteristics of being precise, compact, inexpensive, and easy to manufacture, and can be particularly suitably used for machining cylindrical workpieces.

As explained above, according to the present invention, a plurality of cylindrical workpieces W ₁ to _{W 5} are stacked in the axial direction,
In a machine tool that machine the outer peripheral surface or inner peripheral surface of each workpiece W ₁ to _{W 5} , a plurality of balls B ₁ to B ₅ and a tapered member are installed at the positions of each workpiece W ₁ to _{W 5} .
T ₁ to _{T 5} are provided, and the tapered members T ₁ to T ₅ at the positions of each workpiece W ₁ to _{W 5} contact the balls B ₁ to B ₅ at the positions of each workpiece W ₁ to W ₅ , and the balls B ₁ -B ₅ are held substantially displaceable in the radial direction of the workpieces W ₁ -W ₅ but not displaceable in the axial direction. Taper member
T ₁ to _{T 5} are substantially held so as to be displaceable in the axial direction of the workpieces W ₁ to _{W 5} but not displaceable in the radial direction. Furthermore, the tapered members T ₁ to T ₅ at the positions of the workpieces W ₁ to _{W 5} are elastically biased by the elastic biasing means S ₁ to S ₅ . The elastic bias direction is substantially the workpiece W ₁
~ W ₅ in the same axial direction. Therefore, the tapered members T ₁ to T ₅ at the positions of the workpieces W ₁ to _{W 5} are substantially displaced in the axial direction of the workpieces W ₁ to _{W 5} , _and
~ Ball B ₁ ~ B ₅ at position W ₅ is tapered member T ₁ ~
Under the wedge action of _T5 , it is substantially displaced in the radial direction of the workpieces _W1 to _W5 , and is pressed against the inner circumferential surface of each of the workpieces _W1 to _W5 . Therefore, multiple cylindrical workpieces
W ₁ to W ₅ can be centered accurately. Further, regarding the tapered members T ₁ to T ₅ and the elastic biasing means S ₁ to _{S 5} , the tapered members T ₁ to _{T 5} are substantially connected to the workpiece W 1 at the positions of the respective workpieces W ₁ to _{W 5 .}
~ W ₅ may be elastically biased in the same axial direction and displaced in that direction, and the tapered members T ₁ ~ _{T 5} and the elastic biasing means S ₁ ~ S ₅ can be directly engaged, and the There is no need to use any special member. Moreover,
A common operating member, such as a rod 7, allows the elastic biasing means S ₁ to S ₅ and the tapered members T ₁ to _{T 5} to be operated. Regarding the balls B ₁ to _{B 5} , it is only necessary to hold the balls B ₁ to _{B 5} at the positions of the respective workpieces W ₁ to _{W 5} so as to be substantially displaceable in the radial direction of the workpieces W ₁ to W ₅ , A plurality of cylindrical workpieces W ₁ to W ₅ can be centered with a simple configuration.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention;
2 is an explanatory diagram showing the arrangement of the coil springs in FIG. 1, FIG. 3 is an enlarged sectional view of the taper member and ball in FIG. 1, FIG. 4 is an end view of the taper member in FIG. 1, and FIG. The figure is a longitudinal sectional view of Fig. 4, Fig. 6 is a hydraulic circuit diagram showing a hydraulic circuit for raising and lowering the support center of Fig. 1, Fig. 7 is a longitudinal sectional view showing a modification of Fig. 1, 8 is an end view of the holding sleeve shown in FIG. 7, FIG. 9 is a longitudinal sectional view of FIG. 8, FIG. 10 is an end view of the tapered member shown in FIG. 7, and FIG.
Figure 12 is an explanatory diagram showing the transmission system for rotating the hob cutter of the hobbing machine and the table of the workpiece, and Figures 13 to 22 show various cylindrical workpiece centering devices. Longitudinal sectional view, 2nd
3 is a perspective view of the collet, FIGS. 24 and 25 are longitudinal sectional views of the collet, and FIG. 26 is a longitudinal sectional view showing the collet in a deformed state. W ₁ ~ W ₅ ... workpiece, T ₁ ~ _{T 5} , T ₁ ′ ~ _{T 5} ′...
Tapered member, B ₁ to B ₅ ... ball, S ₁ to _{S 5} ... coil spring.

Claims (1)

[Claims] 1 Overlap multiple cylindrical workpieces in the axial direction,
In a machine tool for machining the outer circumferential surface or inner circumferential surface of each workpiece, a plurality of balls and a tapered member are provided at each of the positions of the workpieces, and the balls at the positions of each of the workpieces are connected to the inside of each workpiece. The tapered members are arranged at angular intervals along the circumferential surface or the outer circumferential surface, and the tapered members at each of the workpiece positions are respectively arranged so as to be able to contact the balls at the respective workpiece positions, and the balls are substantially connected to the workpiece. The tapered member is held so as to be displaceable in the radial direction but not in the axial direction, and the tapered member is held so as to be displaceable in the axial direction of the workpiece but not in the radial direction, and the position of each of the workpieces is The tapered members are individually elastically biased substantially in the same axial direction of the workpiece by an elastic biasing means such as a coil spring, and the balls at the positions of the workpieces are biased by the elastic biasing force of the elastic biasing means. A precision centering device characterized in that the tapered member is pressed against an inner peripheral surface or an outer peripheral surface of each workpiece by a wedge action, thereby centering a plurality of cylindrical workpieces.