JP2002144119A - Chuck device of machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To firmly grip a shaft-like member w by simple operation so that the center hole n of the member and a center member 3 are disposed accurately concentrically and large force for regulating the relative rotational displacement to a main shaft 2 can be obtained. SOLUTION: The center member 3 positioned concentrically with the main shaft 2 and having the conical tip, and a collet driving part 5 supporting a collet 4 positioned to surround the center member 3 to float a little in the radial direction of the main shaft and driving the same forward and backward are mounted on the front of the main shaft 2. An annular support surface part 20 fixed to the front side of the collet driving part 5 to be integrated with the main shaft 2 is provided, and a collet guide 21 having a tapered hole h for deforming the collet 4 to be expanded and contracted in the radial direction thereof is engaged on the front of the annular support surface part 20 to be a little displaced in the arbitrary radial direction of the main shaft.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chuck device for a machine tool having a center located concentrically with a spindle and having a conical tip, and a collet for gripping one end of a work.

[0002]

2. Description of the Related Art FIG. 4 shows the vicinity of a chuck device of a conventional grinding machine. As shown in this figure, the tip of a headstock center 3 provided concentrically with a spindle 2 is inserted into a center hole n of an axial workpiece w. A chuck device that allows the collet 4 to grip the outer peripheral surface m at one end of the shaft-shaped work w at the same time as the fitting is already present (for example, see JP-A-2000-254803). According to this, the axial work w is supported by the headstock center 3 and the collet 4 in the same manner as the spindle 2.

[0003]

In the above-mentioned conventional chuck device, the collet 4 is firmly supported by its surrounding members and does not substantially move in the radial direction of the main shaft. That is, for example, in the collet shown in FIG. 4, the rear end of the collet 4 is fixed to the main body frame 5a of the collet driving unit 5 which is fixed to the main shaft 2 and the front end thereof is only allowed to move forward and backward. It is supported by the tapered hole h of the guide 21 and does not generate play in the main shaft radial direction as a whole.

[0004] When the axial work w is supported by such a chuck device, the following adverse effects may occur. That is, when the center hole n of the axial work w and its outer peripheral surface m are not concentric, the chucking force of the collet 4 strongly affects the determination of the support position of the axial work w, and the chuck device Center hole n of axial workpiece w held in
Does not exactly match the center of the headstock center 3.

If the center of the headstock center 3 and the center of the collet 4 do not exactly match for any reason, even if the center of the center hole n of the axial work w and the center of the outer peripheral surface m are not aligned. However, even if they are exactly the same, the gripping force of the collet 4 strongly affects the determination of the support position of the axial work w, as described above. This causes a state in which the center of the center hole n of w does not exactly match the center of the headstock center 3.

[0006] An object of the present invention is to provide a chuck device for a machine tool capable of preventing such adverse effects from occurring and performing high-precision machining.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, a center member which is located concentrically with the main shaft and has a conical tip at the front of the main shaft;
A collet driving unit which supports the collet positioned so as to surround the center member so as to be able to freely move in the radial direction of the main shaft and drives the collet driving unit forward and backward; A collet guide having a tapered hole for expanding and contracting the collet in the radial direction of the collet guide is provided on the front surface of the annular support surface portion fixed in a shape such that the collet guide can be slightly displaced in any main shaft radial direction. It has a locked configuration.

In the present invention, when the shaft-shaped work is fixed to the main shaft, the collet is expanded in diameter, one end of the shaft-shaped work is inserted inward of the collet, and the center formed on the end surface of the one end. The hole is pressed against the tip of the conical portion of the center member. Under this condition, the collet driving unit is operated to drive and displace the collet to the rear side of the main shaft. Due to this displacement, the collet is deformed into a reduced-diameter state in relation to the collet guide, grips the outer peripheral surface of the shaft-like work, and further strongly presses the center hole of the shaft-like work against the conical portion of the center member. . In this pressing state, the collet is displaced by a relatively small force in the radial direction of the main shaft, while the conical portion of the center member is forcibly displaced by the engaging action with the center hole of the axial work. It is intended to move the work so that its center hole and the center member are concentric, so that the axial work is positioned without being excessively affected by the gripping force of the collet,
The center hole and the center member of the shaft-shaped work are concentrically gripped by the center member and the collet in a state where they are concentric, and the relative rotation with respect to the main shaft is reliably restricted by the collet.

According to the present invention, as described in claim 2, between the annular support surface portion and the collet guide, a compression spring for pressing the collet guide in a direction away from the annular support surface portion, and the collet guide is annular. It is preferable to mount ball guide means for smoothly displacing the support surface portion in an arbitrary main shaft radial direction.

With this arrangement, when the collet grips the axial work, the displacement of the collet guide in the radial direction of the main shaft is smoothly performed. Therefore, the axial work is less affected by the gripping force of the collet. , It is more accurately positioned concentrically with the center member.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 to 3 relate to a grinding machine embodying the present invention. FIG. 1 is a side sectional view of a chuck device and an axial work fixed to the chuck device, and FIG. FIG. 3 is a front view of the apparatus. FIG. 3 shows a collet, A is a plan view, and B is a front view.

In FIG. 1, reference numeral 1 denotes a headstock frame supported by a work table (not shown), and reference numeral 2 denotes a horizontal spindle supported rotatably by the headstock frame 1. At the front of the spindle 2, a center member (headstock center) 3 having a conical tip is fixed concentrically. Reference numeral 4 denotes a collet disposed so as to surround the headstock center 3, and reference numeral 5 denotes a collet driving section for driving and displacing the collet 4 in the front-back direction f1.

The collet 4 has a cylindrical shape as a whole, and the thickness of the portion 4a between both ends is made smaller than that of the other portions as shown in FIG. 3 and the like, and a plurality of slits a are formed in a proper length range on the front side. In addition to forming the portion between the slits as the chuck claw portion 4b, the outer peripheral surface of the front end portion as the male tapered surface b, the outer peripheral portion of the rear end portion as the male screw portion 4c, and the innermost portion of the uppermost slit a for guiding. An elongated hole c is provided.

The collet driving section 5 is formed in a cylindrical shape surrounding the headstock center 3 and the collet 4, and a rear end member 6 fixed to the front end face d of the main spindle 2 via a fitting portion 6a and a bolt 7. A cylinder portion 7 fixed to the front side of the rear end member 6, and a piston portion 8 inserted into the cylinder portion 7 so as to be able to move back and forth.

The components of the drive section 5 will be described. The cylinder section 7 fixes an outer cylinder member 9 and an inner cylinder member 10 having a rear surface to a rear end member 6 with bolts 11 and 12, A front end member 13 is fixed to a front end surface of the member 9 with bolts 14. The piston portion 8 is guided by the outer cylinder member 9 and the inner cylinder member 10 of the cylinder portion 7 so as to be freely movable. In addition to a cylindrical portion 8a, a small-diameter cylindrical portion 8b that is slightly movably guided in an inner hole portion of the front end member 13, a male screw portion 4c of the collet 4 is provided on an inner peripheral surface of the small-diameter cylindrical portion 8b. Is formed to form a female screw portion 8c to be screwed.

At this time, the front end member 13 of the cylinder portion 7
A pin member 15 for restricting displacement of the piston portion 8 around the main shaft 2 is provided between the small-diameter cylindrical portion 8b of the piston portion 8 and a linear hole formed linearly in the front end member 13 and the piston portion 8. Are slidably fitted in the slidable body. e1 is a cylinder chamber formed on the rear side of the piston section 8, e2 is a cylinder chamber formed on the front side of the piston section 8, and g is an oil passage through which pressure oil flows. Reference numeral 16 denotes a positioning bolt screwed into a through hole formed in a radial portion of the front end member 13.
Is inserted into the rotation preventing slot c of the collet 4 to allow the collet 4 to be displaced in the front-rear direction with respect to the cylinder portion 7 to reliably restrict the relative rotation about the main shaft 2. Reference numeral 17 denotes an O-ring mounted on the front end member 13, and reference numerals 18 and 19 denote O-rings mounted on the large-diameter cylindrical portion 8a of the piston portion 8.
It is a ring.

An annular support surface portion 20 is provided on the front side of the driving portion 5.
The supporting surface portion 20 is fixed to the front surface of the front end member 13 by bolts 30 in the same manner as the main shaft 2, and has a flat supporting surface formed on the front surface. A collet guide 21 having a tapered hole h which is fitted to the male tapered surface b of the collet 4 is provided on the front side of the annular support surface portion 20.

The collet guide 21 is formed on the annular support surface portion 20 in an arbitrary main shaft radial direction by, for example, 0.5 mm.
The stud bolt has a large diameter head at a plurality of positions (three positions in the illustrated example) near the outer peripheral edge of the annular support surface portion 20 and has a guide shaft portion 22a. On the other hand, a through hole having a diameter slightly larger than the guide shaft portion 22a of the stud bolt 22 corresponding to the stud bolt 22 and smaller than the large diameter head is provided in the collet guide 21. i are provided, and the guide shaft portion 22a is inserted into these through holes i. At this time, it is preferable that the collet guide 21 can be slightly moved back and forth with respect to the annular support surface portion 20.

An annular groove j is formed on the front surface of the annular support surface portion 20, and an appropriate number of spring mounting holes k are provided at specific radial positions on the bottom surface of the annular groove j.
Are mounted with a compression spring 23, and an annular push plate 24 is arranged at the front end of the compression spring 23, and the forward and backward movement of the push plate 24 is guided to the inner peripheral surface of the annular groove j. .

A ball guide means 25 is provided on the front side of the push plate 24 in the annular groove j. The ball guide means 25 includes a ball holding wheel 27 and a number of balls 28 held by the holding wheel 27. At this time, the balls 28 are moved by the elasticity of the compression spring 23 to the collet guide 2.
1 is pressed against the rear surface. 31 is an annular groove j
Is a seal member fitted inside.

Reference numeral 29 denotes a tailstock center which is supported by a work table (not shown) so as to be movable back and forth. The center 29 has a conical tip.

Next, an example of use and operation of the chuck device of the grinding machine will be described. The axial work w gripped by the chuck device may be arbitrary, but in this use example, after the outer peripheral surface m is roughly processed by centerless processing, the center hole n is corrected on each end face by the center hole correcting machine. It is assumed that the center of the center hole n does not match the center of the outer peripheral surface m due to a processing error, and the distance between these centers is, for example, 0.1 mm.

When causing the chuck device to grasp the shaft-shaped work w, one of the cylinder chambers e is passed through an oil passage (not shown).
1 is supplied with pressure oil, and the other cylinder chamber e2 is opened to the atmosphere. As a result, the piston portion 8 moves together with the collet 4 as shown in the range above the center line CL in FIG.
It is moved toward the front side f11. By this movement, the group of chuck claws 4b is expanded and deformed by its own elasticity. Under this condition, one end of the shaft-shaped work w is inserted into the inner hole of the collet 4, and the tip of the conical portion of the headstock center 3 is fitted into the center hole n on the inserted side. The tailstock center 29 is inserted into the center hole n on the other side of the shaft-shaped work w.
The tip of the conical part is fitted and pressed strongly. As a result, the axial work w is moved to the headstock center 3 and the tailstock center 29.
By the guiding action of the respective conical portions, the positions are adjusted substantially concentrically with the centers 3, 29.

Thereafter, pressure oil is supplied to the other cylinder chamber e2 through an oil passage g, and the pressure is supplied to the one cylinder chamber e1.
Open to the atmosphere. As a result, the piston portion 8 is
Is moved toward the rear side f12 of the main shaft 2 together with the collet 4 as shown in a range below the center line CL of the center line CL, and the chuck claws 4 of the collet 4 move inside the tapered hole h of the collet guide 21 to the rear side f12 of the main shaft.

In the initial stage of the movement of the piston portion 8 to the rear side f12 of the main shaft 2, when the male tapered surface b of the collet 4 is pressed against the tapered hole h, the rear surface of the collet guide 21 is compressed by a compression spring via the ball guide means 25. Since the collet guide 21 is supported by the elasticity 23, the rear surface of the collet guide 21 does not come into strong contact with the front surface of the annular support surface portion 20. In addition, chuck claw 4b
The group is reduced in diameter by the wedge action of the male tapered surface b and the tapered hole h, grips the outer peripheral surface m of the axial work w with an appropriate force, and the center hole n of the axial work w faces backward of the piston portion 8. The driving force strongly presses the tip of the conical portion of the headstock center 3. Accordingly, the axial work w tends to be supported by the headstock center 3 and the tailstock center 29 so as to be concentric with the centers 3 and 29, while the collet guide 21 is controlled by the outer peripheral surface m of the axial work w. The position of the main shaft in the radial direction tends to be defined, and the interaction of these tendencies causes the collet guide 21 to move the ball guide means 2.
5, the collet guide 21 is relatively displaced so that the center of the collet guide 21 is separated from the centers of the headstock center 3 and the tailstock center 29 by approximately 0.1 mm.

At this time, the piston portion 8 is slightly movable with respect to the cylinder portion 7, and the collet guide 21 is guided by the ball guide means 25 so as to be smoothly displaced in an arbitrary main shaft radial direction. As a result, the chuck claws 4b of the collet 4 are moved in the radial direction of the spindle with a relatively small force, and do not exert excessive force on the headstock center 3 and the tailstock center 29.

In the later stage of the movement of the piston portion 8 to the rear side f12 of the main spindle 2, the rearward driving force of the piston portion 8 becomes larger than the elasticity of the compression spring 23, and the center of the collet guide 21 is shifted to the headstock center. 3 and tailstock center 29
The rear surface thereof is pressed against the flat support surface on the front surface of the annular support surface portion 20 in a state of being displaced by about 0.1 mm from the center of the main shaft in the radial direction of the main shaft. At this time, the chuck claws 4b slide on the outer peripheral surface m of the shaft-shaped work w as much as necessary against the frictional force of the gripping state, and the relative positions of the respective parts are adjusted. Then, the piston 8 reaches the moving end by the pressure oil in the cylinder chamber e2, and in this state, the rear surface of the collet guide 21 is pressed against the flat support surface on the front surface of the annular support surface portion 20 with a strong force,
In addition, the group of chuck claws 4b grips the outer peripheral surface m of the axial workpiece w with a large radial force due to the wedge action of the male tapered surface b and the tapered hole h, and the axial workpiece w is collet 4 and the headstock. It is gripped by the center 3 in a fastening state. At this time, the center of the shaft-shaped work w is in a state in which the center of the headstock center 3 and the center of the tailstock center 29 exactly coincide with each other. The distance in the radial direction of the main shaft is about 1 to 3 μm, which is practically negligible.

Up to this point, a case has been described in which the chuck device grips an axial workpiece w in which the center of the center hole n does not match the center of the outer peripheral surface m. Even if the shaft-like workpiece w is accurately concentric, when the headstock center 3 and the collet 4 are in a misalignment state that cannot be ignored for some reason, the same operation as described above is obtained. That is, when the collet 4 and the headstock center 3 grip the shaft-shaped work w in a fastening state, the group of chuck claws 4b of the collet 4 allows the main shaft radial displacement of the outer peripheral surface m of the shaft-shaped work w. Therefore, the center of the center hole n of the axial workpiece w is
You will be in a state of being exactly matched with your heart.

As described above, the axial work w is attached to the chuck device.
After the gripping is performed, the rotational power of a motor (not shown) is transmitted to the main shaft 2 to rotate the shaft-shaped work w, and the grinding wheel t that is rotated by the power is brought into contact with the outer peripheral surface m of the shaft-shaped work w. Is started. During this grinding, a rotational force due to the processing reaction force acts on the axial work w to try to rotate the axial work w with respect to the main shaft 2. This rotational force is applied to the male tapered surface b and the tapered hole h. Of the collet guide 21, the friction between the collet guide 21 and the annular support surface portion 20, and the positioning bolt 16
The shaft-like work w is completely supported by the main shaft 2 by being reliably supported by the locking action between the shaft and the guide slot c. When removing the axial work w gripped by the chuck device, the reverse procedure for gripping the shaft-shaped work w by the chuck device may be performed. In the above-described embodiment, the case where the present invention is applied to the grinding machine is shown. However, the present invention is not limited to this, and may be applied to other machine tools.

[0030]

According to the present invention, when the chuck device grips the shaft-like member, the axial work, which is positioned on the center member, is excessively affected by the spindle radial force related to the collet gripping force. Even if the center hole and the outer peripheral surface are not concentric, or if the center member (headstock center) and the collet are not precisely concentrically arranged, By a simple operation, a large opposing force can be obtained for the shaft-shaped member so that the center hole and the center member (headstock center) are accurately concentrically arranged and the relative rotational displacement with respect to the main shaft is regulated. It can be firmly held as described above.

According to the second aspect of the present invention, when the collet grips the axial work, the displacement of the collet guide in the main shaft radial direction is performed smoothly. It can be positioned concentrically with the center member.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a chuck device of a grinding machine embodying the present invention and a shaft-like work fixed to the same.

FIG. 2 is a view of the chuck device of the grinding machine as viewed from the front side.

FIG. 3 is a plan view showing a collet of the grinding machine, and FIG.
Is a front view.

FIG. 4 is a side view sectional view of the periphery of a chuck device of a conventional grinding machine.

[Explanation of symbols]

 2 Spindle 3 Center member 4 Collet 5 Collet drive section 20 Annular support surface section 21 Collet guide 23 Compression spring 25 Ball guide means

Claims (2)

[Claims] At the front part of the main shaft, a center member concentric with the main shaft and having a conical tip and a collet surrounding the center member are supported so as to be able to freely move in the radial direction of the main shaft. And a collet drive unit that is driven forward and backward, and an annular support surface fixed to the main shaft in the same manner as the main shaft is provided at the front side of the collet drive unit. A chuck device for a machine tool, wherein a collet guide having a tapered hole for radially expanding / contracting deformation is engaged so as to be slightly displaceable in an arbitrary main shaft radial direction. 2. A compression spring, which presses the collet guide in a direction away from the annular support surface portion, between the annular support surface portion and the collet guide, and smoothly moves the collet guide to an arbitrary main shaft radial direction with respect to the annular support surface portion. 2. A chuck device for a machine tool according to claim 1, further comprising a ball guide means for displacing the chuck.