JPH1190751A - Main spindle device for machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a main spindle device for machine tool which can prevent movement of an assembly type drive key due to centrifugal force and prevent generation of vibration even in the case of the main spindle whose drive key is formed to have a diameter minimized up to a limit within a fittable range. SOLUTION: This main spindle device for machine tool, which is formed so that the rotational shift of a tool holder against the rotation of a main spindle may be prevented by recessing a key fitting groove 15 involving a pair of side surfaces 15a, 15b extending in the radial direction of the main spindle and a bottom surface 15c, at the front end part of a spindle 3, fitting a drive key in the key fitting groove, bolt-tightening and fixing the drive key at the bottom surface, and fitting it in the key groove recessed at the tool holder, is formed with a regulating part for preventing the drive key from moving outward in its radial direction with dimension D1 on its outer sides in a spindle radial direction of both side surfaces formed smaller than D2 on its inner side, at the key fitting groove, and a base part fitted to the regulating part of the key fitting groove is formed at the drive key.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle device for a machine tool, and more particularly to a drive key mounting structure for preventing a rotational displacement between a spindle and a tool holder.

[0002]

2. Description of the Related Art Generally, in a spindle device of a machine tool, a tapered hole is formed at a tip end of a spindle rotatably supported by a spindle head, and a tapered portion of a tool holder is detachably fitted to the tapered hole. Thus, a structure for transmitting the rotational force of the main shaft to the tool holder is adopted. The drive key fixed to the main shaft is engaged with the key groove formed in the tool holder, thereby preventing rotation of the tool holder with respect to rotation of the main shaft.

[0003] Here, as a structure for providing a drive key at the tip of the spindle, an integrated type in which the drive key is integrally formed at the tip of the spindle, and a separate drive key at the tip of the spindle. Is assembled by bolting. The integrated drive key method is advantageous in terms of the rigidity, accuracy, and assembly cost of the main shaft. However, when using a so-called two-sided restraint tool in which a tool holder is brought into contact with the tip surface of a spindle, this integrated drive key method cannot be adopted. In other words, in the case of a two-sided restraint tool, it is necessary to grind the tip surface of the main shaft, but the above-mentioned integrated drive key hinders the grinding. Therefore, when using this two-sided restraint tool, an assembly type drive key is adopted.

[0004] Incidentally, the above-mentioned two-plane restraint tool is generally used for a spindle for high-speed rotation. On the other hand, the larger the outer diameter of the main shaft, the larger the size of the bearing, making it unsuitable for high-speed rotation,
In addition, the torque required for accelerating and decelerating the spindle increases due to an increase in the rotational moment, and many problems occur, such as an increase in the acceleration time or a need for large electric power. Therefore, it is desirable that the spindle for high-speed rotation be as small as possible.

Here, when the above-mentioned assembling drive key is used for the small-diameter main shaft corresponding to the high-speed rotation, it is conceivable to adopt, for example, the structure shown in FIGS. A pair of key mounting grooves 51,
The key mounting groove 51 is recessed in a slit shape so as to be opposed to the main shaft axis, and a drive key 52 is fitted into the key mounting groove 51 and a bolt 53 is screwed into a screw hole 51b. 51 is fixed to the bottom surface 51a. In this structure, when the tapered portion 54b of the tool holder 54 is fitted into the tapered hole 50b of the main shaft 50, the drive key 52 is engaged with the key groove 54a of the tool holder 54.

When the structure shown in FIGS. 8 and 9 is adopted,
The outer diameter of the tool holder mounting portion of the main shaft 50 can be reduced to a diameter where the outer peripheral surface of the main shaft coincides with the outer peripheral surface of the drive key 52, and can cope with the above-described high-speed rotation.

[0007]

However, FIG.
In the spindle device of FIG. 9, when the centrifugal force caused by the high-speed rotation of the spindle exceeds the fastening force of the bolt 53, the drive key 52 may move radially outward. When the drive key 52 shifts outward as described above, the drive key becomes an unbalanced weight of the rotation of the main shaft, and there is a concern that vibration may occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and can prevent movement of a drive key due to centrifugal force even in the case of a spindle whose diameter is as small as possible within a range in which an assemblable drive key can be mounted. It is an object of the present invention to provide a spindle device of a machine tool that can prevent occurrence of the occurrence.

[0009]

According to a first aspect of the present invention, a tapered hole is formed at a tip end of a spindle rotatably supported by a spindle head, and a tapered portion of a tool holder is detachably attached to the tapered hole. A key mounting groove having a pair of side surfaces and a bottom surface extending in the radial direction of the main shaft is recessed at the tip of the main shaft, a drive key is fitted into the key mounting groove, and the drive key is bolted to the bottom surface. In the spindle device of a machine tool, wherein the drive key is fixed and the drive key is engaged with a key groove recessed in the tool holder, rotation of the tool holder with respect to rotation of the spindle is prevented. A restricting portion for preventing the drive key from moving outward in the radial direction by narrowing a space between the both side surfaces on the outer side in the main shaft radial direction from the inner side, and forming the key mounting groove in the drive key. It is characterized by forming the base portion fitted to the regulating unit.

According to a second aspect of the present invention, in the first aspect, the restricting portion of the key mounting groove is formed by making at least one of the both side surfaces an inclined surface. It is characterized in that it has an inclined surface that comes into contact with the inclined surface of the regulating portion.

According to a third aspect of the present invention, in the first aspect, the restricting portion of the key mounting groove is formed by making at least one of the both side surfaces a stepped surface, and the base portion of the drive key is formed. And a stepped surface that comes into contact with the stepped surface of the restricting portion.

[0012]

According to the spindle device for a machine tool according to the present invention, the key mounting groove into which the drive key is fitted and fixed is provided.
A regulating portion that makes the outer space between both side surfaces narrower than the inside is formed, and a base portion that fits into the regulating portion is formed on the drive key, so that the centrifugal force due to the high-speed rotation of the main shaft exceeds the bolt fastening force of the drive key. In this case, the movement of the drive key to the outside in the radial direction can be prevented by the restricting portion, and there is an effect that the weight imbalance caused by the displacement of the drive key to the outside can be avoided and the occurrence of vibration can be prevented.

Further, since the restricting portion prevents the drive key from moving outward in the radial direction, even if the bolt is broken, the drive key can be prevented from being scattered outward, and the rotation of the drive key can be prevented. Displacement in the direction can also be prevented. Furthermore, when the drive key is attached to the main shaft by bolting, the drive key can be prevented from rotating, and the assembly workability can be improved.

According to the second aspect of the present invention, at least one of the two side surfaces of the key mounting groove is formed as an inclined surface, and the inclined surface which comes into contact with the inclined surface is provided on the drive key side. Since at least one of the surfaces is a stepped surface, and the stepped surface that abuts the stepped surface is provided on the drive key side, the above-described restricting portion can be realized with a simple structure, and the movement of the drive key is prevented to prevent vibration. The above-described effects such as prevention of occurrence can be realized.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 7 are views for explaining a spindle device of a machine tool according to an embodiment of the present invention. FIG. 1 is a sectional view of the spindle device in a state where a tool holder is mounted, and FIG. 2 is a side view of the tool holder. FIGS. 3 and 4 are front views showing the tip of the spindle, FIG. 4 is a cross-sectional view of the key mounting groove, and FIGS.
Is a front view, a bottom view, and a sectional view of the drive key, respectively.

In FIG. 1, reference numeral 1 denotes a spindle device of a machine tool such as a machining center. The spindle device 1 inserts a spindle 3 into a cylindrical spindle head 2 and rotates the spindle 3 via a plurality of bearings 4. It is configured to be freely supported and to be rotationally driven by a drive motor (not shown).

The main shaft 3 has a cylindrical shape in which a through hole 3a is formed in the shaft core. A male tapered portion 5b of a tool holder 5 is detachably fitted to a tip of the through hole 3a. A mating female tapered hole 3b is formed. A collet clamp mechanism 6 is provided in the vicinity of the tapered hole 3b of the through hole 3a. The collet clamp mechanism 6 engages a plurality of collets 8 with a tip of a drawbar 7 inserted into the through hole 3a so as to be able to advance and retreat.
By moving the draw bar 7 forward and backward, the distal end of the collet 8 is configured to expand and contract and retract.

The tool holder 5 has a structure in which a tool 9 is fixed to the tip side of a holder body 5a, and the tapered portion 5b is integrally formed on the opposite side of the tool 9; An annular groove 5e gripped by the exchange arm of the tool exchange device is formed in a recess.

The tapered portion 5b is provided with a mushroom-shaped engaging portion 10 which is engaged with and disengaged from the collet clamp mechanism 6. With the retreat of the drawbar 7 in the direction of the arrow a, the tip of the collet 8 rides on the cam portion 11 to reduce the diameter and engage with the engaging portion 10, whereby the tool holder 5 is retracted and the tapered portion 5b Are firmly fitted in the tapered hole 3b of the main shaft, and the tool holder 5 is clamped to the main shaft 3. When the drawbar 7 is advanced in the direction of arrow b, the distal end of the collet 8 is disengaged from the cam portion 11 to expand the diameter and the engagement is released, and the tool holder 5 becomes removable.

Here, when the tool holder 5 is clamped to the main shaft 3 by the collet clamp mechanism 6, the end surface 5f of the holder main body 5a on the tapered portion 5b side comes into contact with the end surface of the front end portion 3c of the main shaft 3. Therefore, both end faces are polished. As a result, the tool holder 5 is restrained by the main shaft 3 by the tapered portion 5b and the end face 5f.

A pair of key mounting grooves 15, 15 are formed in the distal end portion 3c of the main shaft 3 with the main shaft axis interposed therebetween. A drive key 16 is disposed in each key mounting groove 15, and a bolt is provided. It is fixed at 17.

The key mounting groove 15 is a slit having two side surfaces 15a and 15b extending in the main shaft radial direction and a bottom surface 15c. And the one side surface 15a
Is a straight surface parallel to a straight line A passing through the axis of the main shaft 3, while the other side surface 15b is an inclined surface having a narrow outer space with respect to the straight line A. Thus, a restricting portion is formed in which the groove width D1 on the outer side in the radial direction is smaller than the groove width D2 on the inner diameter. Reference numeral 15d denotes a screw hole into which the bolt 17 is screwed.

The drive key 16 comprises a base portion 16d fitted into the key mounting groove 15 and a key portion 16a protruding from the base portion 16d, and the center of the key portion 16a and the base portion 16d. Are formed in the main shaft axis direction, and a bolt seating surface 16b is formed. Side 1 of base 16d
6e and 16f are side surfaces 15a and 15f of the key mounting groove 15, respectively.
It is formed on a straight surface and an inclined surface corresponding to b.
When the drive key 16 is mounted in the key mounting groove 15, the side faces 16e, 16f,
6g closely contacts the side surfaces 15a, 15b and the bottom surface 15c of the key mounting groove 15 without any gap.

The left and right sides 16h, 16h of the key portion 16a of the drive key 16 are formed parallel to the straight line A. When the tool holder 5 is mounted on the main shaft 3 and clamped, the left and right sides are formed. 16h, 16h are left and right sides 5d, 5d of the key groove 5c recessed in the holder main body 5a.
With an extremely small gap (for example, about 0.1 mm). Due to this engagement, even if the tool holder 5 causes a rotational deviation with respect to the rotation of the main shaft 3, the deviation is prevented to the above-mentioned very small value. The key section 16
A structure in which no gap is provided between the left and right sides 16h, 16h of the key groove a and the left and right sides 5d, 5d of the key groove 5c is also possible. Further, side surfaces 16h, 16h of the drive key 16 are provided.
In addition, induction hardening is performed on the side surfaces 5d and 5d of the key groove 5c.

Next, the operation and effect of this embodiment will be described. In the present embodiment, the side surfaces 15a and 15b of the key mounting groove 15 formed at the tip 3c of the main shaft 3 are straight surfaces,
By forming the inclined surface, a restricting portion in which the radial outer groove width D1 is smaller than the inner groove width D2 is formed, and the side surfaces 16e and 16f of the base portion 16d of the drive key 15 are formed as straight surfaces and inclined surfaces. When the centrifugal force caused by the high-speed rotation of the main shaft 3 exceeds the fastening force of the bolt 17, the drive key 16 is prevented from moving outward in the radial direction by the restricting portion. And the occurrence of weight imbalance can be avoided, and as a result, the occurrence of vibration can be prevented. Incidentally, the rotation speed of the main shaft in recent years has reached 20,000 to 70,000 min ^-1 , and even in such a high-speed operation, even a very slight weight imbalance may cause vibration. Such slight weight imbalance can be avoided, which is effective in preventing vibration.

In this embodiment, the key mounting groove 15
The side surface 15b of the drive key 16 and the side surface 16f of the drive key 16 are inclined. Therefore, the main shaft 3 can be made as small as possible in diameter, and can cope with the above-described high-speed rotation.

Furthermore, in this embodiment, the key mounting groove 1
The movement of the drive key can be prevented simply by forming the one side surface 15b of the drive key 5 and the one side surface 16f of the base portion 16d of the drive key 16 as an inclined surface, and the cost is hardly increased. Further, since the key portion 16a engaging with the key groove 5c of the tool holder 5 has a conventional structure, the conventional tool holder 5 can be used, and a problem that the usable tool holder is limited occurs. Absent.

Further, the drive key 16 is formed by the inclined surface.
Can be prevented from moving outward in the radial direction, so that even if the bolt 17 is broken, the drive key 16 can be prevented from flying outward. In addition, it is possible to prevent the drive key 16 from shifting in the rotation direction, and furthermore, the drive key 16
When the drive key 16 is attached to the main shaft 3 by bolting, the drive key 16 can be prevented from rotating, and the assembly workability can be improved.

In the above embodiment, the key mounting groove 15
Only one side surface 15b is an inclined surface.
Of course, a and 15b may be inclined surfaces, or one or both of the side surfaces 15a and 15b may be partially inclined surfaces. In such a case, both the side surfaces 16e and 16f of the drive key 16 are inclined surfaces, or only a part of one or both of the side surfaces 16e and 16f is inclined surfaces.

Further, in the above-described embodiment, the case where the restricting portion is formed by making the side surface into an inclined surface has been described. However, the restricting portion of the present invention may have at least one side as shown by a two-dot chain line in FIG. The side surface may be a stepped surface 21. In this case, it is natural that the side surface of the drive key 16 is also a stepped surface.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a spindle device of a machine tool according to an embodiment of the present invention.

FIG. 2 is a side view of a tool holder of the spindle device.

FIG. 3 is a front view of the spindle.

FIG. 4 is a cross-sectional view of the key attachment groove of the spindle (IV in FIG. 3).
-IV line sectional view).

FIG. 5 is a front view of a drive key of the spindle device.

FIG. 6 is a bottom view of the drive key.

FIG. 7 is a sectional view of the drive key (VII-V in FIG. 5);
FIG. 2 is a sectional view taken along line II).

FIG. 8 is a front view of a conventional spindle.

FIG. 9 is a cross-sectional view showing a state in which a drive key is attached to a conventional spindle.

[Explanation of symbols]

 Reference Signs List 1 spindle device 2 spindle head 3 spindle 3b taper hole 3c tip 5 tool holder 5b taper portion 5c key groove 15 key mounting groove 15a, 15b side surface (restriction portion) 15c bottom surface 16 drive key 16d base portion 16e, 16f side of drive key 17 Bolt 21 Stepped surface D1 Outer groove width (radial outer space) D2 Inner groove width (radial inner space)

Claims (3)

[Claims] 1. A tapered hole is formed at a tip of a spindle rotatably supported by a spindle head, and a tapered portion of a tool holder is detachably attached to the tapered hole. A key mounting groove having a pair of side surfaces and a bottom surface extending in a recess is provided, a drive key is fitted into the key mounting groove, and the drive key is fixed to the bottom surface with bolts, and the drive key is fixed to the tool holder. In a spindle device of a machine tool, wherein a tool holder is prevented from rotating with respect to the rotation of the spindle by engaging with a recessed key groove, the key mounting groove includes a radially outer portion of the spindle shaft on both side surfaces. Forming a restricting portion for narrowing the interval from the inner side to prevent the drive key from moving outward in the radial direction, forming a base portion on the drive key to be fitted to the restricting portion of the key mounting groove; A spindle device for a machine tool. 2. The restricting portion of the key mounting groove according to claim 1, wherein at least one of the side surfaces has an inclined surface, and the base portion of the drive key has an inclination of the restricting portion. A spindle device for a machine tool having an inclined surface that comes into contact with a surface. 3. The restricting portion of the key mounting groove according to claim 1, wherein at least one of the both side surfaces is formed as a stepped surface, and the base portion of the drive key is formed of the restricting portion. A spindle device for a machine tool having a stepped surface that abuts a stepped surface.