JPH11300512A - Chucking device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To downsize a motor for opening/closing jaws by preventing a gripping force by the jaw from changing during rotation of a rotary shaft. SOLUTION: A chuck attached to a front end of a spindle 2, having jaws and a jaw opening/closing mechanism is provided. In the spindle 2, a drawbar 5 having a male screw 5a at its rear end is provided coaxially so as to be movable in the axial direction but not to be rotatable with respect to the spindle 2. A front end of the drawbar 5 is connected to the jaw opening/closing mechanism of the chuck, to actuate the jaw opening/closing mechanism upon axial movement of the drawbar 5. In the spindle 2, a nut 12 screwed onto the male screw 5a of the drawbar 5 is provided so as to be rotatable but not to be movable in the axial direction with respect to the spindle 2. The nut 12 is rotated by a motor 20. A clutch 22 for transmitting or cutting off output of the motor 20 to the nut is also provided. The spindle 2 is formed with a hole 16 having a bottom directed outwardly in the radial direction of the spindle 2, inside of which a steel ball 17 and a spring 18 for energizing the steel ball 17 outwardly in the hole 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chuck device, and more particularly, to a chuck device for gripping an article by opening and closing a pawl at a front end of a rotating shaft.

[0002] In this specification, the right side of FIG. 1 is referred to as front, and the opposite side is referred to as rear.

[0003]

2. Description of the Related Art For example, in a machine tool such as a lathe, a chuck device is provided at a leading end of a main shaft for holding a work.

Heretofore, this type of chuck device has a chuck attached to the front end of a hollow main shaft and having a knurling and pawl opening / closing mechanism, and has a structure in which the main shaft does not rotate with respect to the main shaft but can move in the axial direction. The drawbar is arranged coaxially with the front end connected to the pawl opening / closing mechanism of the chuck, and operates the pawl opening / closing mechanism by axial movement. A hydraulic chuck device including a moving hydraulic cylinder has been common. As the hydraulic cylinder, a hydraulic cylinder having a relatively large diameter has been used in order to ensure a sufficient gripping force of the workpiece by the pawl of the chuck.

[0005] However, the above-mentioned hydraulic chuck device has the following problems. That is, since it is necessary to rotate a large hydraulic cylinder together with the main shaft, the motor for rotating the main shaft must be large. Since the hydraulic cylinder comes to a position protruding more than the rear bearing that supports the main shaft on the fixed housing, imbalance is likely to occur. Since the hydraulic cylinder also rotates with the main shaft, the inertia increases, and the acceleration / deceleration characteristics of the main shaft deteriorate. Heat deformation of the headstock and the spindle occurs due to the heat generated by the pressure oil supplied to the hydraulic cylinder, thereby reducing machining accuracy. Furthermore, because the viscosity of pressure oil changes with temperature,
The chuck opening / closing operation time is not stable.

Japanese Patent Application Laid-Open No. Sho 62-157 discloses a chuck device which solves the above problems of the hydraulic chuck device.
An electric chuck device disclosed in Japanese Patent Publication No. 705 is known. The electric chuck device is attached to a front end of a hollow rotary shaft rotatably supported in a fixed housing, and has a chuck and a jaw opening and closing mechanism.
The rotary shaft is arranged so as not to rotate with respect to the rotary shaft but to be movable in the axial direction, and the front end is connected to the pawl opening / closing mechanism of the chuck, and the pawl opening / closing mechanism is operated by the axial movement. A drawbar, a rotor that is rotatable with respect to the rotation axis, is connected to the drawbar via a moving screw, and a motor including a stator provided in a fixed housing around the rotor. The possible tooth of the coupling ring is pressed against the tooth of the rotating shaft by the urging force of the spring, thereby stopping the rotation of the rotor with respect to the rotating shaft during rotation of the rotating shaft and maintaining a constant gripping force of the work by the pawl. When the rotating shaft is stopped, the urging force of the spring is released by the magnetic field generated by the motor, and the rotor is rotated with respect to the rotating shaft. This invention was made to move axially drawbar with.

[0007] However, the electric chuck device described in the above publication has the following problems. That is,
The gripping force of the pawl is kept constant by the biasing force of the spring, and the biasing force of the spring is released by the magnetic field generated by the motor.If the biasing force of the spring is weak, the spring is rotated when the rotating shaft rotates. The rotation of the rotor with respect to the rotation axis against the urging force of the rotation may cause the draw bar to move in the axial direction via the moving screw, and the work gripping force by the pawl may change. On the other hand, in order to prevent such a change in the work gripping force, it is necessary to increase the urging force of the spring.In this case, however, the magnetic field generated by the motor must be increased to release the urging force of the spring. Instead, the motor becomes larger.

An object of the present invention is to provide a chuck device which solves the above-mentioned problems of the hydraulic chuck device, prevents a change in gripping force due to a pawl during rotation of a rotary shaft, and can reduce the size of a motor. It is in.

[0009]

A chuck device according to the present invention is mounted on the front end of a hollow rotary shaft,
A chuck having a pawl and pawl opening / closing mechanism, disposed coaxially within the rotating shaft so as not to rotate with respect to the rotating shaft but to be movable in the axial direction, and having a front end connected to the pawl opening / closing mechanism of the chuck; A drawbar that has a threaded portion at the rear end and that activates the pawl opening and closing mechanism by axial movement, and is arranged on the rotating shaft so that it can rotate but does not move in the axial direction with respect to the rotating shaft. A nut that is screwed into the external thread of the drawbar, a motor that rotates the nut, a clutch that transmits and shuts off the output of the motor to the nut, and a nut that rotates the nut by the centrifugal force generated when the rotation shaft rotates. And a detent means for fixing with respect to

According to the chuck device of the present invention, when the rotation shaft is stopped, when the motor is started and the output of the motor is transmitted to the nut by the clutch, the nut rotates and the male screw portion screwed with the nut is rotated. The draw bar is moved in the axial direction by the action, and the pawl opening / closing mechanism of the chuck is operated to hold and release the article by the pawl.

During rotation of the rotating shaft, when the motor is stopped and transmission of the motor output to the nut is cut off by the clutch, the nut is prevented from rotating with respect to the rotating shaft by the rotation preventing means due to the centrifugal force generated when the rotating shaft rotates. The nut is fixed and relative rotation of the nut is prevented. Therefore, the rotation of the nut with respect to the drawbar rotating with the rotation shaft is prevented, and the drawbar is prevented from moving in the axial direction. Is held.
At this time, power transmission between the motor and the nut is interrupted by the clutch, so that damage to the motor is prevented.

In addition, since the hydraulic cylinder is not used for opening and closing the pawl of the chuck, the above-mentioned problem of the hydraulic chuck device can be solved.

[0013] For example, a detent means is provided in a bottomed hole formed on the rotating shaft and facing radially outward of the rotating shaft, and a steel ball disposed in the bottomed hole to remove the steel ball from the hole. In some cases, a steel ball is pressed against a nut by a centrifugal force generated when the rotating shaft rotates.

In this case, the structure of the detent means is simple and can be implemented at low cost.

For example, the detent means has a pusher pivotally attached to a nut so as to swing about an axis extending in the longitudinal direction of the rotary shaft, and does not contact the pusher with the rotary shaft when the rotary shaft is stopped. The pusher may be configured to be pressed against the rotary shaft by a centrifugal force generated when the rotary shaft rotates, in some cases.

For example, the pusher pivotally attached to the rotation shaft at one end from the center of gravity so that the rotation prevention device swings around an axis extending in the longitudinal direction of the rotation shaft. And a spring that holds the one end portion of the pusher at a position where the pusher does not contact the nut when the rotary shaft stops, and the centrifugal force generated when the rotary shaft rotates rotates the pusher at the other end portion. In some cases, the pusher swings so as to move radially outward, so that the one end portion of the pusher moves radially inward and is pressed against the nut.

In this case, due to the principle of leverage, the pressing force on the nut at the one end side of the pusher is increased, and the force for fixing the nut to the rotating shaft and the drawbar and preventing its relative rotation is strong. Become. Even when the rotating shaft is stopped, even if the nut is rotated in order to grip and release the article by the jaws of the chuck, centrifugal force due to the rotation of the nut does not act on the pusher, so the rotation of the nut can be performed at high speed. It is possible to quickly carry out gripping and releasing of the article by the pawl of the chuck.

Further, the motor may be provided outside the housing that supports the rotating shaft and in parallel with the rotating shaft.

In this case, the overall length of the chuck device can be reduced. Further, it is possible to prevent the heat generated during rotation of the motor from being transmitted to the rotating shaft, thereby suppressing thermal deformation of the rotating shaft.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, the chuck device of the present invention is applied to a lathe.

FIG. 1 shows the entire configuration of a lathe provided with the chuck device of the present invention, and FIGS. 2 to 4 show the configuration of a main part thereof.

In FIG. 1, a fixed housing of a headstock is shown.
In (1), the front and rear ends of a hollow main shaft (2) (rotary shaft) are supported via bearings (3) and (4) so that they do not move in the axial direction but can rotate. In the main shaft (2), a drawbar (5) extending in the front-rear direction is coaxially arranged so as not to rotate with respect to the main shaft (2) but to be movable in the axial direction.
The drawbar (5) has bushings (6) at the front and rear ends.
It is supported on the main shaft (2) via (7). Drawbar (5)
The chuck (8) is attached to the front end of the. Chuck
(8) is a nail (9) that grips the work and a drawbar (5)
A known pawl opening / closing mechanism (not shown) connected to the front end of the pawl and opening and closing the pawl (9) by the axial movement of the draw bar (5)
And Here, the pawl (9) means anything that grips the work regardless of its shape. A thread (5a) is provided at the rear end of the draw bar (5).

A nut sleeve (11) is fixed to the rear end of the main shaft (2) via a flange (10). Nut sleeve
Inside (11), a nut (12) whose axis is oriented in the front-rear direction is supported so as not to move in the axial direction with respect to the nut sleeve (11) but to be rotatable. Nuts (12) are drawbars (5)
It is screwed into the external thread (5a). Nut sleeve
A key (14) is attached to the front end of (11) via a bracket (13), and this key (14) The drawbar (5) does not rotate with respect to the main shaft (2) but can move in the axial direction, because it is fitted in a key groove (5b) formed in the surface. Further, a short cylindrical portion (11a) protruding rearward is integrally formed with the nut sleeve (11), and the short cylindrical portion (11a) is formed.
Have teeth (15) formed on the inner peripheral surface thereof.

The nut sleeve (11) has a plurality of bottomed holes (16) inclined radially inward from the rear end face toward the front.
Are formed so as to be circumferentially spaced and on the same circumference, and the nut (12) has an outward flange (12a) at the rear end.
Has an outer peripheral portion facing the rear end opening of each bottomed hole (16). A steel ball (17) is arranged in each bottomed hole (16), and the steel ball (17) is urged outward by a compression coil spring (18) also inserted in the bottomed hole (16). ing. The steel ball (17) and the compression coil spring (18) arranged in the bottomed hole (16) constitute a rotation preventing means for the nut (12).

A torque motor (20) is arranged outside the cover (19) attached to the rear end of the fixed housing (1) in parallel with the main shaft (2). The power is transmitted to the nut (12) via the clutch (22). The gear train (21) includes a drive-side gear (23) fixed to an output shaft (20a) extending in the front-rear direction of the torque motor (20), and a pin extending in the front-rear direction fixed to a rear end face of the cover (19). (twenty four)
A play gear (26) rotatably mounted via a bearing (25) around the shaft, and a coaxially disposed rearward of the drawbar (5) and a front-rear direction rotatably supported by a cover (19). It comprises a driven gear (28) mounted around an extending shaft (27). A keyway (28a) is formed on the inner peripheral surface of the driven gear (28), and a key (29) fixed to the outer peripheral surface of the shaft (27) is attached to the keyway (28).
a), whereby the shaft (27) is driven by the driven gear (2
It rotates with 8).

The electromagnetic clutch (22) includes a drive-side clutch component (30) fixed around a shaft (27) and a driven-side clutch component (31) rotatably mounted around the shaft (27). )
And a ring (3) fitted into the rear end opening of the cover (19).
And an electromagnet (33) buried in 2).

A disk mounting sleeve (30a) of the drive side clutch component (30) is fitted around the shaft (27).
(30a) is rotatably supported by a ring (32) via a bearing (34). A key groove (30b) is formed on the inner peripheral surface of the sleeve (30a), and a key (35) fixed to the outer peripheral surface of the shaft (27) is fitted in the key groove (30b), thereby the sleeve (30a). ),
That is, the drive-side clutch component (30) rotates with the shaft (27). Therefore, the shaft (27) is also a bearing
It is rotatably supported by the ring via (34). Disk mounting sleeve of driven side clutch component (31)
(31a) is rotatably mounted on a shaft (27) via a bearing (36). Also, the outer surface of the rear end of the sleeve (31a) has teeth.
(37) is formed between the rear end of the sleeve (31a) and the rear end of the short cylindrical portion (11a) of the nut sleeve (11).
A plurality of pinions (38) having teeth (38a) meshing with 7)
It is arranged so as to be out of phase with the bottomed hole (16). Each pinion (38) has an outward flange (12) at the rear end of the nut (12).
a) is rotatably supported by a pin (39) extending in the front-rear direction, which is fixed to (a).

A large diameter portion (27a) is integrally formed at the front end of the shaft (27), and a bearing (36) is provided at a portion behind the large diameter portion (27a).
Inner ring, intermediate ring (40), drive side clutch component (30)
The sleeve (30a) and the driven gear (28) are fitted from the front side, and the male thread (27) formed at the rear end of the shaft (27) is fitted.
b) is fixed to the shaft (27) by a fixing nut (41) screwed into.

A through hole extending in the front-rear direction on the axis of the shaft (27)
(42) is formed, and a sensor rod (43) fixed to the rear end face of the draw bar (5) is passed through the through hole (42). The detector (44) (resolver) attached to the cover (19) detects the position of the rear end of the sensor rod (43) in the front-rear direction, whereby the work by the pawl (9) of the chuck (8) is performed. The gripping force is detected.

In the lathe chuck device having the above configuration,
To grip and release the work when the main shaft (2) is stopped, the electromagnetic clutch (22) is set in the power transmission state, and the torque motor (20) is started. The output of the torque motor (20) is transmitted to a shaft (27) via a gear train (21) to rotate the shaft (27), and the rotating force of the shaft (27) is further reduced by an electromagnetic clutch (22) and a pinion ( 38) transmitted to the nut (12) via the nut (12)
Is rotated. When the nut (12) rotates, the nut (1
2) Drawbar via male thread (5a)
(5) is moved in the axial direction. Therefore, the pawl (9) is opened and closed by the pawl opening / closing mechanism, and the work is gripped and released.

At the time of machining with a lathe, the work is gripped by the pawl (9) of the chuck (8), the power transmission is cut off with the electromagnetic clutch (22), and the torque motor (20) is stopped. When the spindle (2) is rotated in this state, the flange (1
0), nut sleeve (11) and drawbar (5)
(2) and rotate in the same direction at the same speed. And the main shaft
Due to the centrifugal force generated by the rotation of (2) and the urging force of the compression spring (18), the steel ball (17) is moved outside the bottomed hole (16), and the outward flange ( Pressed to 12a). Therefore, the nut (12) is always stopped against the spindle (2) and the drawbar (5), so that the spindle (2)
This prevents a change in the workpiece gripping force due to the pawl (9) of the chuck (8) during the rotation of.

FIGS. 5 and 6 show another embodiment of the means for preventing the rotation of the nut (12).

5 and 6, a plurality of pushers (51) are provided on the rear surface of the outward flange (12a) at the rear end of the nut (12).
It is pivotally connected by a plurality of pins (50) extending in the front-rear direction so as to be equally spaced in the circumferential direction on the same circumference. Pusher (51)
Are located out of phase with the pinion (38). Each presser (5
1) is urged clockwise in FIG. 5 by a torsion coil spring (52) disposed between the pin (50) and the pusher (51).
Each pusher (51) engages with the teeth (15) of the nut sleeve (11) when swinging in the counterclockwise direction in FIG.

In the case of this embodiment, the work is chucked.
(8) When the spindle (2) is rotated while being gripped by the pawl (9), each pusher (51) is attached with a torsion coil spring (52) due to the centrifugal force generated by the rotation of the spindle (2). It is swung counterclockwise in FIG. 5 against the force and the nut sleeve (1
Engage with the teeth (15) of 1). Therefore, the nut (12) is always stopped with respect to the spindle (2) and the drawbar (5),
As a result, the jaws of the chuck (8) during rotation of the spindle (2)
The change of the workpiece gripping force due to (9) is prevented.

FIGS. 7 and 8 show still another embodiment of the means for stopping the rotation of the nut (12).

Referring to FIGS. 7 and 8, the nut sleeve
An annular inward protruding portion (11b) protruding radially inward is formed integrally with a portion of the short cylindrical portion (11a) of (11) in front of the portion where the teeth (15) are formed. Annular inward protrusion (1
1b), a plurality of notches (55) are formed at equal intervals in the circumferential direction from the inner peripheral edge thereof. The notch (55) is at a position out of phase with the pinion (38). A substantially arc-shaped presser (56) is arranged in each notch (55), and a nut (57) extending in the front-rear direction at one end side from the center of gravity, here, the clockwise front end side in FIG. It is pivotally attached to the sleeve (11). Each pusher (56) is located at the bottom of the notch (55) and the pusher (5
7) is urged in the counterclockwise direction in FIG. 7 by a compression coil spring (58) disposed between the compression coil spring (58).

In the case of this embodiment, the work is chucked.
(8) When the main shaft (2) is rotated while being gripped by the pawl (9), each pusher resists the urging force of the compression coil spring (58) due to the centrifugal force generated by the rotation of the main shaft (2). 7, and the clockwise front end portion of FIG. 7 moves inward in the radial direction to move the outward flange of the nut (12).
(12a) It is pressed against the outer peripheral surface. At this time, due to the principle of leverage, the pressing force against the nut (12) increases, and the nut (1
The force for stopping the relative rotation of (2) with respect to the main shaft (2) is increased. Therefore, the nut (12) is always stopped with respect to the spindle (2) and the draw bar, and as a result, a change in the workpiece gripping force due to the pawl (9) of the chuck (8) during rotation of the spindle (2) is prevented. .

When the spindle (2) stops, the chuck (8)
Even if the nut (12) is rotated to grip and release the work with the pawl (9), the nut (12)
The centrifugal force generated by the rotation of
The rotation of (12) can be performed at high speed, and the chuck
(8) The workpiece can be quickly gripped and released by the pawl (9).

[Brief description of the drawings]

FIG. 1 is a partial longitudinal sectional view of a lathe provided with a chuck device of the present invention.

FIG. 2 is a partially enlarged view of FIG.

FIG. 3 is a sectional view taken along line III-III of FIG. 2;

FIG. 4 is an enlarged sectional view taken along the line IV-IV of FIG. 3;

FIG. 5 is a sectional view corresponding to FIG. 3, showing another embodiment of a nut rotation preventing means.

FIG. 6 is an enlarged sectional view taken along line VI-VI of FIG. 5;

FIG. 7 is a sectional view corresponding to FIG. 3, showing still another embodiment of a nut rotation preventing means.

8 is an enlarged sectional view taken along line VIII-VIII in FIG. 7;

[Explanation of symbols]

 (2): Spindle (rotary axis) (5): Drawbar (5a): Male thread (8): Chuck (9): Pawl (12): Nut (16): Hole with bottom (17): Steel ball ( 18): Compression coil spring (20): Torque motor (22): Electromagnetic clutch (51): Presser (52): Torsion coil spring (56): Presser (58): Compression coil spring

Claims (5)

[Claims] 1. A chuck attached to a front end of a hollow rotary shaft and having a clasp and pawl opening / closing mechanism, wherein the chuck is coaxial with the rotary shaft so as not to rotate with respect to the rotary shaft but to move in the axial direction. A drawbar that is arranged and has a front end connected to the pawl opening / closing mechanism of the chuck and having a threaded portion at the rear end, and operating the pawl opening / closing mechanism by moving in the axial direction; A nut that is not rotatable in the axial direction but is rotatable, and is screwed to the external thread of the drawbar, a motor that rotates the nut, and a clutch that transmits and shuts off the output of the motor to the nut. And a rotation preventing means for fixing the nut to the rotating shaft by centrifugal force generated when the rotating shaft rotates. 2. A steel ball disposed in a bottomed hole formed on the rotating shaft and facing outward in the radial direction of the rotating shaft, and a detent means provided in the bottomed hole to move the steel ball outward from the hole. 2. The chuck device according to claim 1, wherein the steel ball is pressed against the nut by a centrifugal force generated when the rotating shaft rotates. 3. A pusher pivotally mounted on a nut so as to swing around an axis extending in a longitudinal direction of the rotating shaft, wherein the rotation preventing means does not contact the pusher with the rotating shaft when the rotating shaft is stopped. 2. The chuck device according to claim 1, further comprising a spring for holding the pusher against the rotary shaft by a centrifugal force generated when the rotary shaft rotates. 4. A pusher pivotally attached to the rotating shaft at a portion on one end side of the center of gravity so that the rotation preventing means swings around an axis extending in the longitudinal direction of the rotating shaft, A spring for holding the one end portion of the pusher at a position where it does not contact the nut when stopped, and the centrifugal force generated when the rotating shaft rotates causes the other end portion of the pusher to move radially outward. 2. The chuck device according to claim 1, wherein the pusher swings such that the one end portion of the pusher moves radially inward and is pressed against the nut. 5. The chuck device according to claim 1, wherein the motor is provided in parallel with the rotation shaft outside the housing that supports the rotation shaft.