JPH09309012A - Spindle device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily increase a natural frequency of a draw bar so as to correspond to high speed rotation, by providing a constitution interposing at least one support member between an internal peripheral surface of a shaft hole and an external peripheral surface of the draw bar so as to support the draw bar. SOLUTION: A spindle device is provided with a shaft hole 1A communicating with a tapered hole 2 in a spindle shaft 1, draw bar 7 internally inserted so as to be movable in an axial direction, belleville spring 8 externally inserted to energize the draw bar 7 rearward and a drive means connected to a drive end of the draw bar 7 to move it forward against energizing force of the belleville spring 8. In the draw bar 7 in a tip end side from the belleville spring 8, two sleeves 9a, 9b are separately externally inserted, clearance between a peripheral surface of each sleeve 9a, 9b and an internal peripheral surface of the shaft hole 1A is decreased. In this way, a natural frequency of the draw bar 7 in its turn a total unit natural frequency of the spindle shaft 1 is increased, to be made capable of corresponding to high speed rotation.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a spindle device for a machine tool or the like.

[0002]

2. Description of the Related Art In a spindle device for a machine tool such as a machining center (MC), as shown in FIG. 5, a spindle hole 1 is formed with a taper hole 2 for attaching a tool,
A predetermined tool is mounted by fitting the taper shank portion 4 of the tool holder 3 into the taper hole 2.

A draw bar 7 having a tool holder holding portion 6 for pulling in the pull stud 5 of the tool holder 3 and fixing the tool holder 3 to the spindle shaft 1 is inserted in the shaft center portion of the spindle shaft 1. There is. A disc spring 8 is externally inserted into the draw bar 7 and is housed and mounted in a shaft hole 1A provided in the spindle shaft 1. Further, in order to remove the tool holder 3, a hydraulic cylinder (not shown) or the like is used to apply an axial load to the rear end of the draw bar 7 to compress the disc spring 8.

[0004]

However, recently,
The spindle device tends to be rapidly increased in speed, and as described above, in the method in which the draw bar 7 is pulled in by using the elastic force of the large number of disc springs 8 when the tool is mounted, the device is affected by the disc springs 8 when rotated at a high speed. There is a problem that the vibration of becomes large. In addition, since a certain amount of clearance is required between the inner peripheral surface of the shaft hole of the spindle shaft 1 and the outer peripheral surface of the draw bar in order to impart flexure to the disc spring 8, the balance can be corrected to suppress vibration. There is a limit.

The present invention has been made in order to eliminate such inconvenience, and an object of the present invention is to provide a spindle device capable of coping with high speed rotation at a low cost by easily increasing the natural frequency of the drawbar. And

[0006]

In order to achieve the above object, a spindle device according to a first aspect of the present invention has a spindle hole at a shaft end for attaching a tool holder, and is rotatably supported by a housing via a bearing. And a tool holder holding portion that engages with the pull stud of the tool holder and a draw bar drive end at the rear end, and the spindle shaft is formed in the spindle shaft so as to communicate with the tapered hole. A drawbar axially movably inserted into the hole, a plurality of disc springs externally inserted into the drawbar within the shaft hole to bias the drawbar backward, and the drawbar connected to the drawbar driving end. In a spindle device including a driving means for moving the shaft forward against the biasing force of the disc spring, at least one support is provided between an inner peripheral surface of the shaft hole and an outer peripheral surface of the draw bar. With intervening timber characterized by being adapted to support the drawbar.

According to a second aspect of the present invention, there is provided a spindle device, which has a tapered hole for mounting a tool holder at a shaft end, and is engaged with a spindle shaft rotatably supported by a housing via a bearing and a pull stud of the tool holder. A drawbar having a tool holder holding portion at the front end and a drawbar driving end at the rear end, and being axially movably inserted in a shaft hole formed in the spindle shaft so as to communicate with the taper hole; , A large number of disc springs that are externally inserted into the draw bar in the shaft hole to bias the draw bar backward, and are connected to the draw bar drive end to move the draw bar forward against the biasing force of the disc spring. In a spindle device provided with a drive means for driving the sleeve, a sleeve having a tip portion formed to have a smaller diameter than a rear end portion is externally fitted to a draw bar on the tip side of the disc spring, and a tip surface of the sleeve is attached to the shaft hole. To support the load in the axial direction by the disc springs is brought into contact with the difference unit, characterized by being adapted to support the drawbar by a rear end of the sleeve.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory sectional view for explaining a spindle device as an example of an embodiment of the invention of claim 1. In this embodiment, the same parts as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted.

In this spindle device, two sleeves 9 as support members are provided on the draw bar 7 on the tip side of the disc spring 8.
a and 9b are axially spaced apart from each other and externally inserted, and the radial gap between the outer peripheral surface of each sleeve 9a and 9b and the inner peripheral surface of the shaft hole is reduced. As a result, the natural frequency of the drawbar 7, and thus the natural frequency of the entire spindle shaft, is increased to enable high speed rotation. In the figure, reference numeral 9c is a retaining ring for locking the sleeve 9a on the front end side in the shaft hole 1A.

Next, a spindle device as an example of the embodiment of the invention of claim 2 will be described. FIG. 2 is an explanatory sectional view for explaining the spindle device. This spindle device is suitable for a type with a long spindle shaft, and is used for processing to reduce the gap at the deep position of the shaft hole (for example, grinding of deep holes, coaxiality, dimensional tolerance This eliminates the need for management processing).

First, the structure will be described. A spindle shaft 10 of a spindle device is inserted and arranged in a housing 11, and a front end portion (left end portion) thereof is provided with a plurality of ball bearings 12 (two in the drawing), and a rear bearing. Roller bearing 13 with one end (right end)
Is rotatably supported horizontally. Housing 1
1 includes a cylindrical outer cylinder 14, a front lid 15 fixed to a front end surface of the outer cylinder 14, and a rear lid 16 fixed to a rear end surface of the outer cylinder 14. A mounting flange 17 for mounting the spindle device on a spindle mounting machine base of a machine tool or the like is formed on the outer peripheral portion of the outer cylinder 14 substantially in the axial direction.

An outer spacer 18 is interposed between the outer rings 12a adjacent to each other of the two ball bearings 12 that support the front end of the spindle shaft 10. The outer ring 12a of the front ball bearing 12 at the front end is pressed by the front lid 15, and the outer ring 12a of the rear ball bearing 12 at the front end is received by the step portion 19 formed on the inner peripheral portion of the outer cylinder 14. Has been
As a result, each outer ring 12a is fixedly arranged on the inner peripheral portion of the outer cylinder 14. Inner rings 12 of the ball bearings 12 adjacent to each other
The inner spacer 20 is interposed between b. Further, the inner ring 12b of the ball bearing 12 on the rear side of the front end is received by the step portion 21 of the spindle shaft 10, and the inner ring 12b of the ball bearing 12 on the front end side is fitted on the outer peripheral part of the spindle shaft 10 by an inner ring retainer. The inner ring 12b is fixedly arranged on the outer peripheral portion of the spindle shaft 10 by being held by 22.

On the other hand, the outer ring 13a of the roller bearing 13 that supports the rear end of the spindle shaft 10 has its front side face received by the stepped portion 23 of the rear lid 16, and its rear side face pressed by the outer ring retainer 24. Thereby, the outer ring 13a is fixed to the inner peripheral surface of the rear lid 16. The inner ring 13b of the roller bearing 13 has its front side face received by a ring-shaped member 25 externally fitted and fixed to the spindle shaft 10, and
The rear side surface is pressed by the ring-shaped inner ring holding cover 26, which causes the inner ring 13b to move toward the spindle shaft 10.
Is fixed to the outer peripheral surface of.

A rotor 27 of the built-in motor M is fixed to the outer peripheral surface of the central portion of the spindle shaft 10 by an interference fit. The stator 28, which is disposed coaxially with the rotor 27 so as to face the circumferential surface, has the stator sleeve 2 on the inner circumferential surface of the outer cylinder 14.
9 is fixed.

The spindle shaft 10 has a taper hole 30 for mounting a tool, the diameter of which gradually decreases from the front end face toward the rear end side.
A shaft hole 31 is formed along the axis of the spindle shaft 10 and extends from the inner side of the tapered hole 30 to the rear end of the spindle shaft 10.

A tapered shank portion 33 of a tool holder 32 for holding a tool (not shown) is fitted in the tapered hole 30. A pull stud 34 including a neck portion 34a having a small diameter and a head portion 34b having a large diameter is attached to the tip of the taper shank portion 33, and the pull stud 34 is axially movable in the shaft hole 31. Interpolated sleeve 3
5 is detachably held via a ball 36. Here, the sleeve 35 and the ball 36 constitute the tool holder holding portion of the present invention.

A plurality of balls 36 are arranged in the circumferential direction and are held by the sleeve 35 so as to be retractable radially outward. At the rear end of the sleeve 35, a drive drawbar 37 for driving the sleeve 35 to advance and retract in the axial direction is connected. The draw bar 37 projects from the rear end of the spindle shaft 10 through the shaft hole 31, and the projecting end is a draw bar drive end 37a. Drawbar drive end 3
A piston (not shown) as a driving means is connected to 7a.

When the piston is released from driving, the drawbar 37 is provided in the shaft hole 31 and the disc spring storage hole portion 3 is formed.
8. A large number of disc springs 39 externally attached to the draw bar 37
And the sleeve 35 also retracts. At this time, the ball 36 has the axial hole 31 adjacent to the tapered hole 30.
Is moved from the relatively large diameter space 31a to the small diameter space 31b on the rear end side and is pushed by the inner peripheral surface of the shaft hole 31 to project radially inward from the inner peripheral surface of the sleeve 35, whereby the ball 36 Grips the head portion 34b of the pull stud 34 to attach the tool holder 32, and thus the tool.

When the piston is driven, the draw bar 37 moves forward against the biasing force of the disc spring 39 and the sleeve 35 moves forward. At this time, the ball 36 moves from the small-diameter space 31b provided in the shaft hole 31 to the large-diameter space 31a, retreats radially outward, and retracts from the inner diameter surface of the sleeve 35. The grip of the portion 34b is released, and the tool holder 32 and thus the tool can be removed. In the figure, reference numeral 40 is a pressing ring inserted from the rear end of the spindle shaft 10 into the shaft hole 31 to press the disc spring 39, and 41 is a lock nut for fixing the pressing ring 40 to the spindle shaft 10.

A sleeve 42 is externally fitted to the draw bar 37 on the tip side of the disc spring 39. Sleeve 4
2, the front end portion 43 is formed to have a smaller diameter than the rear end portion 44, and the front end portion 43 is inserted into a small diameter hole portion 45 having a smaller diameter than the disc spring accommodating hole portion 38 so that the front end surface thereof contacts the step portion 46. In contact with each other, the axial load of the disc spring 39 is supported. On the other hand, the rear end portion 44 of the sleeve 42 is located in the disc spring storage hole portion 38, and the radial gap between the outer peripheral surface thereof and the inner peripheral surface of the disc spring storage hole portion 38 is made as small as possible. The drawbar 37 is supported by. The natural frequency of the draw bar 37, and thus the entire spindle shaft 10, is increased by such support and the above-mentioned axial support, thereby making it possible to cope with high-speed rotation of the spindle shaft 10.

To fit and mount the taper shank portion 33 of the tool holder 32 into the taper hole 30 of the spindle shaft 10, the piston is driven and the draw bar 37 is moved forward against the biasing force of the disc spring 39. As a result, the sleeve 35 is advanced to retract the ball 36 radially outward. Then, in this state, the taper shank portion 33 of the tool holder 32 carried by the ATC is inserted into the taper hole 30 of the spindle shaft 10.

Then, the tool holder 32 is further pushed in to fit the tapered shank portion 33 into the tapered hole 30, and the pull stud 34 at the tip of the tapered shank portion 33 is inserted into the sleeve 35. When the driving of the piston is released in this state, the draw bar 37 moves in the shaft hole 31 and the disc spring 3
The sleeve 35 is retracted by the urging force of the shaft 9 and the ball 36 is pushed by the inner peripheral surface of the shaft hole 31 while moving from the large diameter space 31a of the shaft hole 31 to the small diameter space 31b on the rear end side. It projects radially inward from the inner peripheral surface of 35, whereby the ball 36 grips the head 34b of the pull stud 34 and the tool holder 32 and thus the tool are mounted. When mounted, the draw bar 37 is biased toward the rear end side by the disc spring 39, so that the tool holder 32
Is pulled rearward, which causes the tapered shank portion 3
The outer peripheral surface of 3 and the inner peripheral surface of the tapered hole 30 are pressed into contact with each other and closely adhere to each other.

As described above, in this embodiment,
A portion for supporting the draw bar 37 with a small radial gap is provided at a shallow position of the shaft hole 31, and a portion for supporting an axial load by the disc spring 39 is provided at a deep position of the shaft hole 31 for providing a draw bar 37. Since the natural frequency of is increased, it is not necessary to perform difficult machining to reduce the radial clearance at the deep position of the shaft hole, and as a result,
It is possible to easily increase the natural frequency of the drawbar, and it is possible to provide a spindle device that can support high-speed rotation at low cost.

FIG. 3 shows another embodiment of the invention of claim 2. The same parts as those of the embodiment of FIG. 2 are designated by the same reference numerals and the description thereof will be omitted. In this embodiment,
This is an example of the case where the number of the disc springs 39 is larger than that of the embodiment of FIG. 2, and in such a case, one or two or more thin-walled sleeves 50 (two in the figure) are interposed between the many disc springs 39. Thus, the radial gap between the outer peripheral surface of the sleeve 50 and the inner peripheral surface of the Belleville spring housing hole 38 is reduced to reduce the draw bar 3.
7 may be supported at multiple points.

[0025]

FIG. 4 shows a spindle device according to a second aspect of the present invention.
2 is an elongated type of spindle device, and is structurally the same as that of FIG. 2 except that it is elongated. On the other hand, FIG. 5 shows a conventional spindle device that does not include the sleeve 42, and is structurally different from that of the conventional spindle device that does not include the sleeve 42 and the small diameter hole portion 45 into which the tip end portion 43 of the sleeve 42 is inserted. It is exactly the same as FIG.

When the natural frequency of the drawbar of each spindle device of FIGS. 4 and 5 is calculated, the calculated natural frequency of the drawbar of the spindle device according to claim 2 of FIG. 4 is 65.
The calculated natural frequency of the drawbar of the conventional spindle device shown in FIG. 5 was 4.316 Hz, which was 231.150 Hz.

[0027]

As is apparent from the above description, according to the first aspect of the invention, it is possible to easily increase the natural frequency of the drawbar and provide a spindle device capable of high speed rotation at a low cost. The effect of being able to do is obtained.

According to the second aspect of the present invention, when the natural frequency of the drawbar is increased, it is not necessary to perform difficult machining for reducing the radial clearance in the deep position of the shaft hole, so that the spindle shaft has a long length. Even in the length type, it is possible to easily increase the natural frequency of the drawbar, and it is possible to provide a spindle device that can support high-speed rotation at a low cost.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view for explaining a spindle device that is an example of an embodiment of the invention of claim 1;

FIG. 2 is an explanatory cross-sectional view for explaining a spindle device which is an example of an embodiment of the invention of claim 2;

FIG. 3 is an explanatory sectional view for explaining a spindle device which is another embodiment of the invention of claim 2;

FIG. 4 is a cross-sectional view of a spindle device used for comparison with a conventional example.

FIG. 5 is an explanatory sectional view for explaining a conventional spindle device.

[Explanation of symbols]

 1 ... Spindle shaft 1A ... Shaft hole 2 ... Tapered hole 3 ... Tool holder 4 ... Tapered shank portion 5 ... Pull stud 6 ... Tool holder holding portion 7 ... Drawbar 8 ... Disc springs 9a, 9b ... Sleeve (supporting member) 10 ... Spindle Shaft 11 ... Housing 12, 13 ... Bearing 30 ... Tapered hole 31 ... Shaft hole 32 ... Tool holder 34 ... Pull stud 35 ... Sleeve (tool holder holding part) 36 ... Ball (tool holder holding part) 37a ... Drawbar drive end 37 ... Drawbar 39 ... Disc spring 42 ... Sleeve

Claims (2)

[Claims] 1. A spindle shaft rotatably supported by a housing through a bearing, which has a tapered hole for mounting a tool holder on the shaft end, and a tool holder holding portion which engages with a pull stud of the tool holder. And a drawbar drive end at the rear end, and a drawbar movably inserted in an axial hole formed in the spindle shaft so as to communicate with the tapered hole, and a drawbar in the axial hole. A plurality of disc springs externally inserted to urge the drawbar backward, and drive means connected to the drawbar drive end to move the drawbar forward against the urging force of the disc spring. In the spindle device, at least one support member is interposed between the inner peripheral surface of the shaft hole and the outer peripheral surface of the draw bar to support the draw bar. . 2. A spindle shaft, which has a tapered hole for mounting a tool holder on the shaft end, is rotatably supported by a housing via a bearing, and a tool holder holding portion that engages with a pull stud of the tool holder. And a drawbar drive end at the rear end, and a drawbar movably inserted in an axial hole formed in the spindle shaft so as to communicate with the tapered hole, and a drawbar in the axial hole. A plurality of disc springs externally inserted to urge the drawbar backward, and drive means connected to the drawbar drive end to move the drawbar forward against the urging force of the disc spring. In a spindle device, a sleeve whose front end is formed with a diameter smaller than that of a rear end is externally fitted to a draw bar on the front end side of the disc spring, and the front end surface of the sleeve is brought into contact with the stepped portion of the shaft hole. To That to support the axial load, the spindle device being characterized in that so as to support the drawbar by a rear end of the sleeve.