JP3317419B2 - Hydraulic chuck - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic chuck mounted on a main shaft of a machine tool for gripping various tools and workpieces.

[0002]

2. Description of the Related Art Generally, a chuck is mounted on a main shaft of a machine tool to hold various tools and workpieces.
For example, a chuck is used to hold a rotating tool such as a drill, an end mill, a reel, or the like, or is used to hold an inner peripheral surface of a cylindrical portion of a workpiece processed by a machine tool such as a lathe.

[0003] As an example of such a chuck mechanism, for example, a liquid chuck as disclosed in Japanese Utility Model Publication No. 61-969 is known. In general, this type of liquid chuck constitutes a hydraulic chamber filled with a working fluid such as highly viscous grease or non-compressed oil, and is pressed to the working fluid by pressing a plunger which constitutes a part of the hydraulic chamber. A pressure is applied to the thin cylindrical body to thereby elastically deform the thin cylindrical body, so that a cylindrical portion of a tool or a workpiece can be gripped.

[0004]

However, in a conventional hydraulic chuck, a thin cylindrical body which elastically deforms and grips a cylindrical portion of a tool or a workpiece has insufficient rigidity.
In machine tools that rotate at high speed, such as milling machines and high-speed lathes that perform high-speed precision end mill processing, when the hydraulic chuck is rotated at high speed, the oil sealed in the hydraulic chamber is forced out of the radial direction by the centrifugal force. It acts to swing to the side, so the oil reduces the tightening force of the thin cylindrical body against the cylindrical part of the tool or workpiece, and there is a possibility that the gripped tool or the like may come off from the hydraulic chuck and fly, There is a problem of danger.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to increase the tightening force of a thin cylindrical body particularly for a tool or the like gripped under high-speed rotation. Another object of the present invention is to provide a hydraulic chuck capable of improving safety.

[0006]

According to the first aspect of the present invention,
A chuck body whose base end is attached to the main shaft of the machine tool,
An outer cylinder formed on the tip side of the chuck body, a thin inner cylinder portion disposed inside the outer cylinder and holding a tool on the inner peripheral surface, and between an inner peripheral surface of the outer cylinder and an outer peripheral surface of the thin inner cylinder portion. A hydraulic chamber for applying a tightening force to the outer peripheral surface of the thin inner cylindrical portion with a working fluid sealed therein and a plurality of tightening pieces rotatably housed and disposed in the hydraulic chamber. The fastening piece has an outer abutting portion abutting on the inner peripheral surface of the outer cylinder and an inner abutting portion abutting on the outer peripheral surface of the thin inner cylindrical portion, and the center of gravity of the fastening piece is The fastening piece is located on a side opposite to the inner contact portion with respect to a line connecting the outer contact portion and the axis of the chuck body.

According to a second aspect of the present invention, there is provided a chuck body having a base end mounted on a main shaft of a machine tool, an outer cylinder formed on a distal end side of the chuck body, and a tool disposed inside the outer cylinder and having an inner periphery. A thin inner cylinder portion gripped by a surface, and a clamping force is applied to the outer peripheral surface of the thin inner cylinder portion by a working fluid sealed between the inner peripheral surface of the outer cylinder and the outer peripheral surface of the thin inner cylinder portion. A hydraulic chamber to be provided, and a plurality of tightening pieces rotatably housed and arranged in the hydraulic chamber, wherein the tightening pieces have an outer contact portion that can freely contact the inner peripheral surface of the outer cylinder, An inner contact portion which can freely contact the outer peripheral surface of the thin inner cylindrical portion, and the center of gravity of the fastening piece is located more inward than a line connecting the outer contact portion and the axis of the chuck body in the fastening piece. It is characterized by being located on the opposite side of the contact portion.

According to a third aspect of the present invention, there is provided a thin outer cylinder for gripping a hole of a cylindrical portion of a workpiece with an outer peripheral surface, a shaft portion disposed inside the thin outer cylinder and having an annular groove, and a thin outer cylinder. A hydraulic chamber formed between the inner peripheral surface of the shaft and the annular groove of the shaft portion to apply a tightening force to the inner peripheral surface of the outer cylinder with a working fluid sealed therein; and a rotatable housing disposed in the hydraulic chamber. A plurality of tightening pieces, the tightening piece has an outer abutting portion abutting on the inner peripheral surface of the thin outer cylinder and an inner abutting portion abutting on the annular groove of the shaft portion. The center of gravity of the fastening piece is located on a side of the fastening piece opposite to the inner contacting part with respect to a line connecting the outer contact part and the axis of the chuck body.

According to a fourth aspect of the present invention, there is provided a thin outer cylinder for gripping a hole of a cylindrical portion of a workpiece with an outer peripheral surface, a shaft portion disposed inside the thin outer cylinder and having an annular groove, and a thin outer cylinder. A hydraulic chamber formed between the inner peripheral surface of the shaft and the annular groove of the shaft portion to apply a tightening force to the inner peripheral surface of the outer cylinder with a working fluid sealed therein; and a rotatable housing disposed in the hydraulic chamber. A plurality of tightening pieces, the tightening piece has an outer abutting part that can abut on the inner peripheral surface of the thin outer cylinder and an inner abutting part that can abut on the annular groove of the shaft part. Wherein the center of gravity of the fastening piece is located on a side of the fastening piece opposite to the inner contact portion with respect to a line connecting the outer contact portion and the axis of the chuck body.

[0010]

According to the first aspect of the present invention, the base end of the chuck body of the hydraulic chuck is mounted on the main shaft of the machine tool. The working fluid sealed in the hydraulic chamber of the hydraulic chuck applies a clamping force to the outer peripheral surface of the thin inner cylindrical portion. The tool is gripped via the inner peripheral surface of the thin inner cylindrical portion by the tightening force of the working fluid and the tightening force of a tightening piece described later.

To explain the tightening force of the tightening piece, when the main shaft of the machine tool rotates, the center of gravity of the tightening piece which receives centrifugal force turns radially outward with its outer abutting portion as a fulcrum. I do. At the same time, the inner contact portion of the fastening piece rotates radially inward with the outer contact portion as a fulcrum. Therefore, the inner contact portion of the fastening piece presses the outer peripheral surface of the inner cylinder. The thin inner cylinder portion elastically deformed radially inward by this pressing force increases the tightening force on the tool.

The inner peripheral surface of the outer cylinder in a state where the outer abutting portion of the fastening piece abuts is prevented from being deformed even by centrifugal force unlike the thin inner cylindrical portion which is elastically deformed. According to the second aspect of the invention, the same operation as that of the first aspect of the invention occurs, but the following points are different. That is, in the fastening piece according to the first aspect, the outer contact portion is in contact with the inner peripheral surface of the outer cylinder when the main shaft is not rotating, and at the same time, the inner contact portion is the thin inner cylinder portion. In contrast to being in contact with the outer peripheral surface, the fastening piece according to claim 2 is configured to be rotatable even when the main spindle is not rotating.
Rotate outward by centrifugal force. Therefore, when the main shaft rotates, the outer contact portion comes into contact with the inner peripheral surface of the outer cylinder, and the inner contact portion comes into contact with the outer peripheral surface of the thin inner cylinder portion.

According to the third aspect of the present invention, the hydraulic chuck gripping the cylindrical portion of the workpiece is mounted on a main shaft of a machine tool such as a lathe. At this time, a tightening force is applied to the inner peripheral surface of the thin outer cylinder by the working fluid sealed in the hydraulic chamber of the hydraulic chuck. The cylindrical portion of the workpiece is gripped via the outer peripheral surface of the thin outer cylinder by the tightening force of the working fluid and the tightening force of a tightening piece described later.

To explain the tightening force of the tightening piece, when the main shaft of a machine tool such as a lathe rotates, the center of gravity of the tightening piece that receives the centrifugal force is in contact with the inner groove in the state of being in contact with the annular groove of the shaft portion. It pivots radially outward with the contact portion as a fulcrum. As a result, the outer abutting portion of the fastening piece presses the inner peripheral surface of the thin outer cylinder, and the pressing force causes the thin outer cylinder to elastically deform radially outward. The thin outer cylinder increases gripping power of the tool.

The outer peripheral surface of the shaft portion in a state where the inner abutting portion of the fastening piece is in contact is prevented from being deformed. According to the fourth aspect of the invention, the same operation as that of the third aspect of the invention occurs, but the following points are different. In other words, according to the third aspect of the present invention, the outer contact portion is in contact with the inner peripheral surface of the thin outer cylinder when the main shaft is not rotating, and at the same time, the inner contact portion is formed in an annular shape of the shaft portion. In contrast to being in contact with the groove, the fastening piece according to claim 4 is configured to be rotatable even when the main spindle is not rotating.
Rotate outward by centrifugal force. Therefore, when the main shaft rotates, the outer contact portion comes into contact with the inner peripheral surface of the thin outer cylinder, and the inner contact portion comes into contact with the annular groove of the shaft portion.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show a hydraulic chuck according to an embodiment of the present invention.

1 and 2, reference numeral 1 denotes a chuck main body, and a tapered portion 1A formed on the base end side of the chuck main body 1 has a main spindle 2 of a milling machine (not shown) for processing a high-speed precision end mill or the like. It is attached to.

An outer cylinder 3 is formed on the tip side of the chuck body 1. The outer cylinder 3 has a large thickness and sufficient strength, and has an outer contact portion 11 of a fastening piece 10 described later.
Is not deformed by the pressing force of An annular flange 4 is formed in the outer cylinder 3, a screw hole 4 </ b> A is formed in the annular flange 4, and an oil passage 5 is formed continuously from the tip of the screw hole 4 </ b> A. The oil passage 5 is bent in a crank shape, and its tip 5A is open to a hydraulic chamber 9 described later. Plug 4 is inserted into screw hole 4A.
B is screwed. With this plug 4B, the oil passage 5
The piston 13 slidably housed in the hydraulic chamber 9 is pressed.
Pressure on the oil inside.

The outer peripheral surface of the inner cylinder 6 is fitted to the inner peripheral surface 3A of the outer cylinder 3. At the center of the inner cylinder 6, a thin inner cylinder 7 located inside the outer cylinder 3 is formed, and an inner peripheral surface 7 of the thin inner cylinder 7 is formed.
The tool 8 is tightened and gripped by B.

An annular flange 6A is formed at an end of the inner cylinder 6, and a screw 6B is screwed into the annular flange 6A so that the inner cylinder 6A is closed.
And the outer cylinder 3 are securely fixed. Inner peripheral surface 3A of outer cylinder 3
A hydraulic pressure chamber 9 is formed between the outer peripheral surface 7 </ b> A of the thin inner cylinder portion 7 and the inner wall portion 7. The hydraulic chamber 9 is filled with incompressible oil as a working fluid, and this oil increases the pressure of the oil in the hydraulic chamber 9 and applies a tightening force to the outer peripheral surface 7 </ b> A of the thin inner cylinder 7. Has become.

A tightening piece 10 composed of a plurality of (12 in this embodiment) pieces is rotatably accommodated in the hydraulic pressure chamber 9. As shown in FIG. 3, the fastening piece 10 is
The outer contact portion 11 is in contact with the inner peripheral surface 3A, and the inner contact portion 12 is in contact with the outer peripheral surface 7A of the thin inner cylindrical portion 7.

The fastening piece 10 has a bottom 10A and a bottom 10A.
The relief portion 10B slightly raised from the first edge portion 10C,
It comprises a first inclined portion 10D continuous with the first edge portion 10C, a second inclined portion 10E forming a predetermined angle with the first inclined portion 10D, and a second edge portion 10F. 1st inclined part 10D
The ridge line of the second inclined portion 10E is the outer contact portion 11, and the ridge line of the second edge portion 10F and the bottom portion 10A is the inner contact portion 12.

The position of the center of gravity 14 of the fastening piece 10 is located on the opposite side of the inner contact portion 12 with respect to the line L1 connecting the outer contact portion 11 and the axis 1B of the chuck body 1. In this embodiment, the tapered portion 1A of the chuck body 1 of the hydraulic chuck is mounted on the main shaft 2 of the machine tool. Tightening force is applied to the outer peripheral surface 7A of the thin-walled inner cylindrical portion 7 by the oil sealed in the hydraulic chamber 9 of the hydraulic chuck, and the tightening force by the oil and the tightening force by the tightening piece 10 described later are applied. The tool 8 is gripped via the inner peripheral surface 7B of the thin inner cylindrical portion 7.

To explain the tightening force of the tightening piece 10, as shown in FIG. 4, when the main shaft 2 is not rotating, the tightening piece 10 of the hydraulic chuck is at a position indicated by a solid line X. When the main shaft 2 rotates, the fastening piece 10 is displaced radially outward due to the centrifugal force E, and is in a state shown by a two-dot chain line Y.
The position of the center of gravity 14 of the tightening piece 10 receiving the centrifugal force E rotates radially outward with the outer contact portion 11 as a fulcrum.
At the same time, the inner contact portion 12 of the fastening piece 10 is
Is pivoted radially inward about the fulcrum. Therefore, the inner contact portion 12 of the fastening piece 10 presses the outer peripheral surface 7A of the thin inner cylinder portion 7,
With this pressing force F, the thin inner cylinder portion 7 is elastically deformed radially inward.
The tightening force on the tool 8 is increased by the elastically deformed thin inner cylindrical portion 7.

The inner peripheral surface 3A of the outer cylinder 3 in a state where the outer abutting portion 11 of the fastening piece 10 abuts is also prevented from being deformed by the centrifugal force E. According to the above configuration, when the main shaft 2 of the machine tool rotates, the outer contact portion 11 of the fastening piece 10 presses the outer peripheral surface 7A of the thin inner cylinder portion 7 with the pressing force F generated by the centrifugal force E. Therefore, the thin inner cylindrical portion 7 is elastically deformed inward in the radial direction, so that the tool 8 can be provided with the tightening force of the tightening piece 10 in addition to the tightening force of the liquid.

Therefore, the spindle 2 of the machine tool rotating at high speed
When the hydraulic chuck is attached and used, even if the thin inner cylinder portion 7 reduces the tightening force due to the oil pressure, the mechanical tightening force of the tightening piece 10 is added to this tightening force. In addition, the overall tightening force can be increased.

As a result, especially under high-speed rotation, the tightening force of the gripping tool 8 is increased, the slip of the tool 8 due to the decrease of the tightening force is prevented, and the safety can be improved. .

Further, a minute vibration called so-called "chatter phenomenon" can be prevented due to insufficient rigidity of the thin inner cylinder portion 7. The tool 8 can be reliably held under high-speed rotation. In the present embodiment, a piece having the shape shown in FIG. 3 is taken as an example of the fastening piece, and the number of the fastening pieces is 12, but it is needless to say that the number is not limited to this. It is. At least two are sufficient. The shape will also differ according to the number of fastening pieces.

Further, in this embodiment, the outer contact portion 11 of the fastening piece 10 has the first inclined portion 10D and the second inclined portion 10E.
And the inner contact portion 12 of the fastening piece 10
Is formed by the ridge line of the second edge 10F and the bottom 10A, but the shape of the outer contact portion and the inner contact portion is not limited to such a shape, and the "lever lever""
The centrifugal force E may be transmitted to the inner contact portion according to the principle described above, and the outer contact portion and the inner contact portion may be constituted by, for example, protrusions.

Further, in the present embodiment, the fastening piece 10 is not positioned in the hydraulic chamber 9;
Shafts 16 and 16 are provided on both end surfaces of the tightening piece 10, respectively, and supported by the groove-shaped receiving portions formed in the chuck body 1 to position the tightening piece 10 and to rotate the tightening piece 10. Can be ensured.

In the fastening piece 10 of the present embodiment, the outer contact portion 11 is in contact with the inner peripheral surface 3A of the outer cylinder 3, and at the same time, the inner contact portion 12 is in the thin inner portion. Although it is in contact with the outer peripheral surface 7 </ b> A of the cylindrical portion 7, the fastening piece is configured to be rotatable even when the main shaft 2 is not rotating, and the outer abutting portion is configured to rotate when the main shaft 2 rotates. And the inner contact portion can be brought into contact with the outer peripheral surface 7A of the thin inner cylindrical portion 7.

In the present embodiment, non-compressed oil is used as the working fluid. However, the working fluid is not limited to this, and a viscous fluid such as grease may be used.

Further, as shown in FIG. 3, for example, a weight composed of a lead rod 15 having a high specific gravity along the axial direction can be filled or embedded in the vicinity of the first edge 10C of the fastening piece 10. . As a result, the fastening piece 10 can be easily subjected to the centrifugal force E.

[0034] FIGS. 5-7 show a hydraulic chuck according to an embodiment of the invention of claim 3, wherein. This hydraulic chuck grips a hole in a cylindrical portion of a workpiece, and an example in which the hydraulic chuck is applied to a mandrel will be described.

In the drawing, reference numeral 21 denotes a chuck body,
A shank portion 21A formed on the base end side of the chuck body 21 is mounted on a main shaft 22 of a machine tool (not shown) such as a lathe.

A shaft section 23 having a circular cross section is formed on the distal end side of the chuck body 21, and a thin outer cylinder 24 is disposed outside the shaft section 23. An annular groove 25 is formed at the center of the shaft portion 23, and the cylindrical portion 2 of the workpiece is
The hole 6 is tightened and gripped. The inner peripheral surface 24B of the thin outer cylinder 24 is fitted to the outer peripheral surface 23E of the shaft portion 23. Annular groove 25 and inner peripheral surface 24 of thin outer cylinder 24
The space surrounded by B is formed as a hydraulic chamber 27.
The hydraulic chamber 27 is filled with incompressible oil as a working fluid.

A screw hole 23A is formed in the end face of the shank portion 21A of the shaft portion 23, and an oil passage 28 is formed continuously from the tip of the screw hole 23A. Oil passage 28
Is along the axial direction of the shaft portion 23, is bent in the middle,
The tip 28A is open to the hydraulic chamber 27. A plug 23B is screwed into the screw hole 23A. Further, a hard ball 29A and a piston 29B are accommodated in the oil passage 28 in contact with the tip of the plug 23B. By tightening the plug 23B, pressure is applied to the oil in the oil passage 28 via the piston 29B. Thereby, the pressure of the oil in the hydraulic chamber 27 is increased, and a tightening force is applied to the inner peripheral surface 24 </ b> B of the thin outer cylinder 24.

Similarly, a screw hole 23C is formed in the end face of the tip side 21B of the shaft portion 23, and an oil passage 30 is formed continuously from the tip of the screw hole 23C. The oil passage 30 extends in the axial direction, bends at a right angle from the middle, and has a distal end 30 </ b> C opening to the hydraulic pressure chamber 27. A plug 23D is screwed into the screw hole 23C.

In the oil passage 30, the plug 23
The rigid ball 30A and the piston 30B are housed in contact with the tip of D. By tightening the plug 23D ,
Oil passage 30 is provided via piston 30B and hard ball 30A.
Pressure is applied to the oil inside. Thereby, the hydraulic chamber 2
7 to increase the pressure of the oil in the inner peripheral surface 24 of the thin outer cylinder 24.
B is to be tightened.

A plurality of (twelve in this embodiment) locking pieces 31 are rotatably accommodated in the hydraulic chamber 27. As shown in FIG. 7, the fastening piece 31 includes an outer contact portion 32 that contacts the inner peripheral surface 24 </ b> B of the thin outer cylinder 24.
And a piece having an inner contact portion 33 in contact with the annular groove 25 of the shaft portion 23.

The fastening piece 31 has a bottom 31A and a bottom 31A.
Escape portion 31B slightly raised from the first edge portion 31C,
It is composed of a first inclined portion 31D that is continuous with the first edge portion 31C, a second inclined portion 31E that forms a predetermined angle with the first inclined portion 31D, and a second edge portion 31F. 1st inclined part 31D
The ridge line of the second inclined portion 31E is the outer contact portion 32, and the ridge line of the second edge portion 31F and the bottom portion 31A is the inner contact portion 33.

The position of the center of gravity 35 of the fastening piece 31 is located on the opposite side of the inner contact portion 33 with respect to the line L2 connecting the outer contact portion 32 and the axis 21C of the chuck body 21. In this embodiment, the main shaft 22 of the machine tool such as a lathe is used.
The shank 2 of the chuck body 21 of the hydraulic chuck
1A is attached. Tightening force is applied to the inner peripheral surface 24B of the thin outer cylinder 24 by the oil sealed in the hydraulic chamber 9 of the hydraulic chuck.
1, the cylindrical portion 26 of the workpiece is gripped via the outer peripheral surface 24A of the thin outer cylinder 24.

To explain the tightening force of the tightening piece 31, the annular groove 25 of the shaft portion 23 in a state where the inner abutting portion 33 of the tightening piece 31 is in contact is prevented from being deformed even by the centrifugal force E. I have. Therefore, as shown in FIG. 6, when the main shaft 22 of a machine tool such as a lathe rotates, the center of gravity 35 of the tightening piece 31 receiving the centrifugal force E is directed radially outward with the inner contact portion 33 as a fulcrum. Rotate. At the same time, the outer contact portion 32 of the fastening piece 31 rotates radially outward with the inner contact portion 33 as a fulcrum. As a result, the outer contact portion 32 of the fastening piece 31 presses the inner peripheral surface 24B of the thin outer cylinder 24. With this pressing force F, the thin outer cylinder 24 elastically deforms radially outward, and the thin outer cylinder 24 The cylindrical part 2 of the workpiece
The tightening force on the hole 6 increases.

According to the above configuration, when the main shaft 22 of a machine tool such as a lathe rotates, the outer contact portion 11 of the fastening piece 31 presses the inner peripheral surface 24B of the thin outer cylinder 24 by the centrifugal force E. Therefore, the tightening force against the hole of the cylindrical portion 26 of the workpiece can be increased by the thin outer cylinder 24 elastically deformed radially outward.

Accordingly, when the hydraulic chuck is mounted on the main shaft 22 of a machine tool such as a lathe that rotates at a high speed and used,
Even if the tightening force due to the pressure of the liquid is reduced,
A mechanical tightening force by the tightening piece 31 is added to this tightening force, so that the overall tightening force can be increased.

As a result, in particular, under high-speed rotation, the tightening force on the cylindrical portion 26 of the workpiece being gripped is increased,
Slip of the cylindrical portion 26 of the workpiece due to a decrease in the tightening force can be prevented, and safety can be improved.

Further, a minute vibration called so-called "chatter phenomenon" due to insufficient rigidity of the thin outer cylinder 24 can be prevented. It is possible to reliably hold the cylindrical portion 26 and the like of the workpiece under high-speed rotation.

In this embodiment, a piece having the shape shown in FIG. 7 is taken as an example of the fastening piece, and the number of the fastening pieces is 12, but the number is not limited to this. Of course. At least two are sufficient. The shape will also differ according to the number of fastening pieces.

Further, in this embodiment, the outer contact portion 32 of the fastening piece 31 has the first inclined portion 31D and the second inclined portion 31E.
And the inner contact portion 33 is formed by the ridge line of the second edge portion 31F and the bottom portion 31A, but the shapes of the outer contact portion and the inner contact portion are limited to such shapes. The centrifugal force E is based on the principle of leverage with the inner contact portion as a fulcrum.
May be transmitted to the outer contact portion, and the outer contact portion and the inner contact portion may be constituted by, for example, protrusions.

Further, in the present embodiment, the fastening piece 31 is not positioned in the hydraulic chamber 9;
Shafts 34, 34 are provided on both end surfaces of the tightening piece 31 respectively, and are supported by groove-shaped receiving portions 23F, 23F (only one portion is shown) of the shaft portion 23, thereby positioning the tightening piece 31. In addition, the rotation of the fastening piece 31 can be ensured.

In the fastening piece 31 of this embodiment, the outer contact portion 32 is in contact with the inner peripheral surface 24B of the thin outer cylinder 24, and at the same time, the inner contact portion 33 is Although it is in a state of contact with the annular groove 25 of the portion 23, the fastening piece is configured to be rotatable even when the main shaft 22 is not rotating, and the outer contact portion is formed with a thin outer cylinder 24 when the main shaft 22 rotates. Inner peripheral surface 2
4B, and the inner contact portion may contact the annular groove 25 of the shaft portion 23.

In the present embodiment, non-compressed oil is used as the working fluid. However, the working fluid is not limited to this, and a viscous fluid such as grease may be used.

Further, as shown in FIG. 7, for example, a weight made of a lead rod 36 having a high specific gravity along the axial direction can be filled or embedded near the first edge 31C of the fastening piece 31. . This makes it easier for the fastening piece 31 to receive the centrifugal force E.

[0054]

As described above, according to the first aspect of the present invention, when the main shaft of the machine tool is rotated, the inner contact portion of the tightening piece is thinned by the pressing force generated by the centrifugal force. Since the outer peripheral surface of the portion is pressed, the thin inner cylindrical portion is elastically deformed radially inward, so that the tool can be given a clamping force by the clamping piece in addition to the clamping force by the liquid.

Therefore, the main shaft of a machine tool rotating at high speed has:
When the hydraulic chuck is attached and used, the thin inner cylinder portion is reduced in the tightening force due to the pressure of the liquid even if the tightening force is reduced.
By applying a mechanical tightening force by the tightening piece, the overall tightening force can be increased.

As a result, especially under high-speed rotation, the tightening force of the gripped tool is increased, the slip of the tool due to the decrease of the tightening force is prevented, and the safety can be improved.

Further, it is possible to prevent a minute vibration referred to as a so-called "chatter phenomenon" due to insufficient rigidity of the thin inner cylinder portion.
The gripping of the tool under high-speed rotation can be ensured. According to the second aspect of the invention, the same effect as the first aspect of the invention can be obtained.

According to the third aspect of the present invention, when the main shaft of a machine tool such as a lathe rotates, the outer contact portion of the fastening piece presses the inner peripheral surface of the thin outer cylinder by centrifugal force. The thin outer cylinder elastically deformed radially outward can increase the tightening force on the hole of the cylindrical portion of the workpiece.

Therefore, when the hydraulic chuck is mounted on the main shaft of a machine tool such as a lathe that rotates at high speed, the thin outer cylinder can reduce this tightening force even if the tightening force is reduced by the pressure of the liquid. In addition, a mechanical tightening force by the tightening pieces can be applied to increase the overall tightening force.

As a result, especially under high-speed rotation, the clamping force is increased with respect to the cylindrical portion or the like of the workpiece being gripped, thereby preventing the cylindrical portion of the workpiece from slipping due to a decrease in the clamping force. Safety can be improved.

Further, it is possible to prevent micro vibration called so-called "chatter phenomenon" due to insufficient rigidity of the thin outer cylinder. It is possible to reliably hold a cylindrical portion or the like of a workpiece under high-speed rotation.
According to the fourth aspect of the invention, the same effect as the third aspect of the invention can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a hydraulic chuck according to the first embodiment.

FIG. 2 is a cross-sectional view taken along the line II of FIG. 1;

FIG. 3 is an external view of a fastening piece of FIG. 1;

FIG. 4 is an explanatory view of an operation state of a fastening piece of FIG. 1;

FIG. 5 is a longitudinal sectional view of a hydraulic chuck according to the third aspect of the present invention.

6 is a cross-sectional view taken along the line II-II of FIG.

FIG. 7 is an external view of a fastening piece of FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Chuck main body 1B Shaft center 2 Main shaft 3 Outer cylinder 3A Inner peripheral surface 7 Thin inner cylindrical part 7A Outer peripheral surface 7B Inner peripheral surface 8 Tool 9 Hydraulic chamber 10 Tightening piece 11 Outer contact part 12 Inner contact part 14 Center of gravity 21 Chuck body 21C Shaft center 22 Main shaft 23 Shaft part 24 Thin outer cylinder 24A Outer peripheral surface 24B Inner peripheral surface 25 Annular groove 26 Cylindrical part 27 Hydraulic chamber 31 Tightening piece 32 Outer contact part 33 Inner contact part L1 line L2 line

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B23B 31/117 610 B23B 31/14 B23B 31/40 B23B 31/02

Claims (4)

(57) [Claims] 1. A chuck body having a base end mounted on a main shaft of a machine tool, an outer cylinder formed on a distal end side of the chuck body, and a thin inner wall disposed inside the outer cylinder and holding a tool on an inner peripheral surface. A cylinder portion, a hydraulic chamber formed between the inner peripheral surface of the outer cylinder and the outer peripheral surface of the thin inner cylinder portion and applying a clamping force to the outer peripheral surface of the thin inner cylinder portion with a sealed working fluid; A plurality of tightening pieces rotatably housed and arranged in the hydraulic chamber, wherein the tightening pieces have an outer contact portion abutting on the inner peripheral surface of the outer cylinder,
An inner abutting portion abutting on the outer peripheral surface of the thin inner cylindrical portion, wherein the center of gravity of the fastening piece is inwardly abutting more than a line connecting the outer abutting portion and the axis of the chuck body in the fastening piece. A hydraulic chuck, which is located on the opposite side of the part. 2. A chuck body having a base end mounted on a main shaft of a machine tool, an outer cylinder formed on a distal end side of the chuck body, and a thin inner wall disposed inside the outer cylinder and holding a tool on an inner peripheral surface. A cylinder portion, a hydraulic chamber formed between the inner peripheral surface of the outer cylinder and the outer peripheral surface of the thin inner cylinder portion and applying a clamping force to the outer peripheral surface of the thin inner cylinder portion with a sealed working fluid; A plurality of tightening pieces rotatably housed and arranged in the hydraulic chamber, wherein the tightening pieces are capable of abutting on the inner peripheral surface of the outer cylinder and an outer peripheral portion of the thin inner cylindrical section. The surface has an inner contact portion that can be freely contacted, and the center of gravity of the fastening piece is on the opposite side of the inner contact portion from the line connecting the outer contact portion and the axis of the chuck body in the fastening piece. A hydraulic chuck characterized by being located. 3. A thin outer cylinder for gripping a hole of a cylindrical portion of a workpiece with an outer peripheral surface, a shaft portion disposed inside the thin outer cylinder and having an annular groove, and an inner peripheral surface and a shaft of the thin outer cylinder. A hydraulic chamber formed between the annular grooves of the section to apply a clamping force to the inner peripheral surface of the thin outer cylinder with a working fluid sealed therein; and a plurality of clamps rotatably housed and disposed in the hydraulic chamber. An outer contact portion abutting the inner peripheral surface of the thin outer cylinder;
An inner contact portion in contact with the annular groove of the shaft portion, and the center of gravity of the fastening piece is located on the inner contact portion with respect to a line connecting the outer contact portion and the axis of the chuck body in the fastening piece. A hydraulic chuck, which is located on the opposite side. 4. A thin outer cylinder for gripping a hole of a cylindrical portion of a workpiece with an outer peripheral surface, a shaft portion disposed inside the thin outer cylinder and having an annular groove, and an inner peripheral surface and a shaft of the thin outer cylinder. A hydraulic chamber formed between the annular grooves of the section to apply a clamping force to the inner peripheral surface of the thin outer cylinder with a working fluid sealed therein; and a plurality of clamps rotatably housed and disposed in the hydraulic chamber. The fastening piece has an outer abutting portion that can abut on the inner peripheral surface of the thin outer cylinder and an inner abutting portion that can abut on the annular groove of the shaft portion. The hydraulic chuck according to claim 1, wherein a center of gravity of the piece is located on a side of the fastening piece opposite to an inner contact portion with respect to a line connecting the outer contact portion and the axis of the chuck body.