JP2010029968A - Workpiece holding device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To hold even a workpiece having a small bottom area by a stable holding force. <P>SOLUTION: A workpiece holding device 30 includes: a suction surface 6 for vacuum-sucking a bottom surface 5 of a workpiece 1; a vacuum-sucking hole 17 opened to the suction surface 6 and communicating with a vacuum-generation apparatus 13; a fitting groove 7 formed at the outer peripheral side of the suction surface 6 coaxially with a main axis A; a vacuum chuck 3 formed at the bottom of the fitting groove 7 and having a communication hole 20 that communicates with the vacuum-sucking hole 17; a cylinder 8 fit to the fitting groove 7 so as to be sealable; a bottom 22 integrated with the cylinder 8; a holding hole 14 formed at the bottom 22; and a cap member 4 with a dimension of the holding hole 14 larger than the diameter of a working surface 15 and smaller than the diameter of the bottom surface 5. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a workpiece holding device that holds a workpiece by vacuum suction with a negative pressure.

  Molds for molding optical components such as rotationally symmetric lenses and prisms are required not only to have a high-precision shape, but also to match the optical axis of the optical component and the reference axis with high accuracy. Is done. In order to perform such highly accurate parts machining, it is necessary to adjust the eccentricity so that the eccentric error with the work piece is less than the standard value with respect to the rotation axis of the machine tool, and to hold the work piece. is there.

Conventionally, for example, Patent Document 1 proposes a technique related to a vacuum chuck as an apparatus for holding such a workpiece.
In Patent Document 1, as shown in FIG. 7, a vacuum chuck 103 is provided on the tip end side of a spindle spindle 102 that rotates around a spindle A ′, and a hollow hole 101 is provided in the center. Further, the suction surface portion 106 of the vacuum chuck 103 is provided with a concentric groove 104 that communicates with the hollow hole 101. Furthermore, the workpiece 105 is held by attaching the bottom surface of the workpiece 105 to the suction surface portion 106 and performing vacuum suction from the opposite side of the vacuum chuck 103.

Although not shown, the eccentricity adjustment of the workpiece 105 is generally performed with high accuracy by adjusting the shift direction with respect to the spindle O by hitting the cylindrical portion of the workpiece 105 with a hammer. .
JP 59-19647 A

  However, in Patent Document 1, when the area of the bottom surface portion of the workpiece 105 to be attracted is small, a desired holding force cannot be obtained even if the width and number of the concentric grooves 104 are increased. In addition, the workpiece 105 may move due to a machining load, or the workpiece 105 may fall from the vacuum chuck 103. For this reason, it is necessary to make the area of the bottom face part of the workpiece 105 larger than a certain size.

  The present invention has been made to solve such a problem, and provides a workpiece holding device capable of holding a workpiece with a stable holding force even when the area of the workpiece holding portion is small. With the goal.

In order to achieve the object, the invention according to claim 1
In the workpiece holding device that holds the workpiece on the spindle end surface of the machine tool,
The workpiece has a processing surface portion whose outer dimension in a direction perpendicular to the holding portion and the main shaft is smaller than that of the holding portion,
A suction surface portion that vacuum-sucks the holding portion, a vacuum suction hole that opens to the suction surface portion and communicates with a vacuum generator, a fitting groove that is formed coaxially with the main shaft on the outer peripheral side of the suction surface portion, and the fitting groove A vacuum chuck having a communication path formed at the bottom of the groove and communicating with the vacuum suction hole;
It has a cylinder part fitted in the fitting groove in an airtight manner, a bottom part integral with the cylinder part, and an opening formed in the bottom part, and the dimension of the opening part is larger than the outer dimension of the processed surface part. And a cap member smaller than the outer dimension of the holding portion.

The invention according to claim 2 is the workpiece holding device according to claim 1,
An outer circumferential groove provided on at least one of the outer circumferential wall of the fitting groove or the outer circumferential wall of the cylindrical portion;
A first elastic member mounted in the outer circumferential groove;
An inner circumferential groove provided on at least one of the inner circumferential wall of the fitting groove or the inner circumferential wall of the cylindrical portion;
And a second elastic member mounted in the inner circumferential groove.

The invention according to claim 3 is the workpiece holding device according to claim 2,
The positions of the outer peripheral groove and the inner peripheral groove are different in the main axis direction.
The invention according to claim 4 is the workpiece holding device according to any one of claims 1 to 3,
The cap member has an inspection window in the cylindrical portion closer to the bottom than the inner circumferential groove and the outer circumferential groove.

  According to the present invention, even when the area of the holding portion of the workpiece is small, it can be firmly held with a stable holding force.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Overall configuration of machining equipment]
FIG. 1 is a diagram showing an overall configuration of a machining apparatus 12 for machining a workpiece 1 that is symmetrical about a rotational axis.

  The machining apparatus 12 includes a spindle stock 33 and a tool post 34 which are provided upright adjacent to each other on a base 32. The spindle stock 33 is provided with a spindle spindle 2 that rotates with high accuracy with respect to the spindle rotation axis A. The inside of the main spindle 2 is hollow.

  A workpiece holding device 30 that holds the workpiece 1 is attached to the end surface of the main spindle 2 in the axial direction. The workpiece holding device 30 includes a vacuum chuck 3 that vacuum-sucks the workpiece 1 and a cap member 4 that holds the workpiece 1 vacuum-sucked.

A tool 19 for processing the workpiece 1 is attached to the tool post 34.
The vacuum chuck 3 is connected to a vacuum generator 13 such as a vacuum pump or a vacuum generator via a hose 18. The vacuum generator 13 generates a negative pressure on the suction surface portion 6 (see FIG. 2) of the vacuum chuck 3 and vacuums the workpiece 1. The vacuum generator 13 can control the vacuum pressure by the device itself or by another device.
[First Embodiment]
FIG. 2 is a cross-sectional view of a state in which the workpiece 1 is held by the workpiece holding device 30. FIG. 3 is a sectional view showing a state before the workpiece 1 is held by the workpiece holding device 30.

  In the present embodiment, the workpiece 1 has a rotationally symmetrical shape. The workpiece 1 includes a disk-shaped bottom surface portion 5 as a holding portion attracted by the vacuum chuck 3, a column portion 25 extending from the bottom surface portion 5 in the direction of the main shaft rotation axis A, and a main shaft from the column portion 25. It has a spherical or aspherical processed surface portion 15 that is uneven in the direction of the rotation axis A.

  The diameter of the processed surface portion 15 is smaller than the diameter of the cylindrical portion 25 and the diameter of the cylindrical portion 25 is smaller than the diameter of the bottom surface portion 5. That is, the diameter of the processed surface portion 15 is smaller than the diameter of the bottom surface portion 5.

  Further, the suction surface side of the bottom surface portion 5 is formed with high accuracy flatness. Then, this bottom surface portion 5 is used as an impact (reference) of the workpiece 1. In addition, the workpiece 1 should just be a rotational-axisymmetric shape, and the shape is not restricted to this.

  Further, a flat suction surface portion 6 extending in a direction perpendicular to the main shaft rotation axis A is provided at the tip of the vacuum chuck 3 in the main shaft rotation axis A direction. The suction surface portion 6 is provided with a vacuum hole 17 serving as a vacuum suction hole opened on the surface. In addition to the vacuum hole 17, some other vacuum holes may be formed from the suction surface portion 6 to the hollow portion of the main spindle 2.

  The suction surface portion 6 has a diameter larger than the diameter of the bottom surface portion 5 of the workpiece 1. A fitting groove 7 is formed on the outer peripheral side of the suction surface portion 6 as a fitting groove having an annular groove shape that is coaxial with the main shaft rotation axis A. Further, a communication hole 20 is provided at the bottom of the fitting groove 7 as a communication path that communicates with the vacuum generator 13 and prevents gas from leaking outside.

  Next, the cap member 4 for pressing the workpiece 1 from the upper surface (right side in FIG. 2) includes an annular portion 8 as a cylindrical portion that is airtightly fitted into the fitting groove 7 of the vacuum chuck 3, and this annular shape. It has the part 8 and the bottom part 22 integral.

  Then, the clearance between the outer peripheral wall 7a of the fitting groove 7 and the outer peripheral wall 8a of the annular portion 8 and the inner peripheral wall 7b of the fitting groove 7 in a state where the cap member 4 is airtightly fitted to the vacuum chuck 3. And the inner peripheral wall 8b of the annular portion 8 are all set between 0.005 mm and 1 mm (see FIG. 3).

  A holding hole 14 as an opening is provided at the center of the bottom 22 of the cap member 4. The holding hole 14 has a diameter (a hole diameter in a direction perpendicular to the spindle rotation axis A) larger than the diameter of the processed surface portion 15 and the diameter of the cylindrical portion 25 and smaller than the diameter of the bottom surface portion 5. That is, even if the processed surface portion 15 and the cylindrical portion 25 of the workpiece 1 can pass through the holding hole 14, the bottom surface portion 5 of the workpiece 1 cannot pass through.

  Further, as shown in FIG. 3, the height H1 of the annular portion 8 of the cap member 4 in the direction of the main shaft rotation axis A (excluding the height of the bottom portion 22) H1 is the height H2 of the bottom surface portion 5 of the workpiece 1. And the height H3 of the fitting groove 7 is smaller than the sum of the heights H3 and larger than the height H2 of the bottom surface portion 5 of the workpiece 1.

  Thereby, in the state which vacuum-sucked the bottom face part 5 of the to-be-processed object 1 with the adsorption | suction surface part 6, the front-end | tip part of the opening side of the annular part 8 of the cap member 4 and the deepest part of the fitting groove 7 do not contact (FIG. 2). reference). Thereby, the height H2 of the bottom surface part 5 of the workpiece 1 can be set to an arbitrary height.

  Furthermore, an outer peripheral groove 11 is provided in the circumferential direction on the outer peripheral wall 8a of the annular portion 8 of the cap member 4 (or the outer peripheral wall 7a of the fitting groove 7). An elastic member 9 as a first elastic member made of rubber or silicone is fitted into the outer circumferential groove 11 and fitted. At this time, the depth of the outer circumferential groove 11 (depth in the direction orthogonal to the main shaft rotation axis A) is formed smaller than the difference in clearance between the fitting groove 7 and the annular portion 8 due to the thickness of the elastic member 9. ing.

  Similarly, an inner peripheral groove 10 is provided in the circumferential direction on the inner peripheral wall 8b of the annular portion 8 of the cap member 4 (or the inner peripheral wall 7b of the fitting groove 7). An elastic member 9 as a second elastic member made of rubber, silicone or the like is fitted into the inner circumferential groove 10 and fitted. At this time, the depth of the inner circumferential groove 10 (depth in the direction orthogonal to the main shaft rotation axis A) is smaller than the difference in clearance between the fitting groove 7 and the annular portion 8 due to the thickness of the elastic member 9. Has been.

As described above, in the state where the cap member 4 is fitted in the fitting groove 7, the inside of the fitting groove 7 is kept airtight from the outside by the action of the elastic member 9.
In the present embodiment, the positional relationship between the inner circumferential groove 10 and the outer circumferential groove 11 along the main shaft rotation axis A is set to be different. Furthermore, the distance from the surface (B surface) that presses the workpiece 1 at the bottom 22 of the cap member 4 to the inner circumferential groove 10 and the outer circumferential groove 11 along the spindle rotation axis A is determined by the bottom surface portion 5 of the workpiece 1. It is set larger than the height. The positions of the inner peripheral groove 10 and the outer peripheral groove 11 are set so as to enter the fitting groove 7 of the vacuum chuck 3.

  Next, FIG. 4 is a view showing a flowchart from the planar processing of the suction surface portion 6 in the vacuum chuck 3 to the holding of the workpiece 1. Hereinafter, based on FIG. 4, the effect | action of this embodiment is demonstrated, referring FIGS. 1-3.

In addition, the specific effect | action of this Embodiment does not limit this invention at all.
First, the vacuum chuck 3 is fixed to the main spindle 2 of the machining device 12. At this time, the eccentricity adjustment is performed in advance so that the eccentricity error in the shift direction of the vacuum chuck 3 (the direction perpendicular to the main spindle rotation axis A) with respect to the main spindle rotation axis A becomes less than the standard accuracy.

In this state, the suction surface portion 6 of the vacuum chuck 3 is set to high flatness and high-precision perpendicularity to the spindle rotation axis A by cutting or grinding (S201).
Next, the cap member 4 is covered through the holding hole 14 from the upper surface of the workpiece 1 (right side in FIG. 2). In this way, the upper surface (C surface) of the bottom surface portion 5 of the workpiece 1 and the inner surface (B surface) of the bottom portion 22 of the cap member 4 are brought into contact with each other (S202).

  In this state, the annular portion 8 of the cap member 4 is inserted into the fitting groove 7 of the vacuum chuck 3, and the cap member 4 is fitted in the same direction (S203). Accordingly, the upper surface (C surface) of the bottom surface portion 5 of the workpiece 1 is pressed by the inner surface (B surface) of the bottom portion 22 of the cap member 4, and the bottom surface portion 5 comes into close contact with the suction surface portion 6.

  Next, evacuation is started by the vacuum generator 13, and the bottom surface portion 5 of the workpiece 1 is vacuum-sucked and held by the suction surface portion 6 of the vacuum chuck 3 (S204). At this time, the space formed between the groove bottom portion of the fitting groove 7 and the tip opening of the annular portion 8 is sealed by the elastic member 9 fitted in the inner circumferential groove 10 and the outer circumferential groove 11 of the annular portion 8. And vacuumed. As a result, the cap member 4 is pulled toward the vacuum chuck 3 with a negative pressure.

  In this case, as described above, the diameter of the holding hole 14 of the cap member 4 is set larger than the diameter of the processed surface portion 15 of the workpiece 1 and smaller than the diameter of the bottom surface portion 5. For this reason, the holding hole 14 of the cap member 4 is caught on the upper surface (C surface) of the bottom surface portion 5 of the workpiece 1. Then, the cap member 4 is pulled in the direction of the vacuum chuck 3 by the vacuum suction of the cap member 4. Thus, the cap member 4 pushes the workpiece 1 into the suction surface portion 6. Thereby, the holding power of the workpiece 1 is improved.

  Further, the annular portion 8 is supported at two points in the fitting groove 7 by changing the positions of the inner circumferential groove 10 and the outer circumferential groove 11 of the annular portion 8 in the direction along the main shaft rotation axis A. For this reason, the cap member 4 is vertically inserted into the suction surface portion 6 of the vacuum chuck 3. In addition, the cap member 4 is supported more stably by the two-point support than the one-point support, and the rigidity is increased. Thereby, the inner surface (B surface) of the bottom portion 22 of the cap member 4 uniformly contacts the workpiece 1 with the upper surface (C surface) of the bottom surface portion 5 in the circumferential direction and pushes it uniformly.

  Further, the eccentric adjustment in the shift direction with respect to the spindle rotation axis A of the workpiece 1 is performed under a low vacuum pressure condition by lowering the vacuum pressure with an air pressure regulator or the like. Then, for example, adjustment is performed by hitting the side surface of the workpiece 1 in the direction with the largest eccentricity in the shift direction with a hammer (S205).

  In the present embodiment, the adjustment in the tilt (tilt) direction with respect to the spindle rotation axis A of the bottom surface portion 5 of the workpiece 1 is not necessary because the tilt in the tilt direction is small. This is because machining is performed on the machine so that the bottom surface portion 5 of the workpiece 1 has a high-precision squareness with respect to the spindle rotation axis A in advance. In addition, this is because the workpiece 1 is in close contact with the suction surface portion 6 of the vacuum chuck 3.

  Next, after adjusting the shift direction of the workpiece 1, the vacuum pressure of the vacuum generator 13 is increased to a normal pressure to improve the suction force. In this way, the holding of the workpiece 1 is strengthened (S206).

According to the present embodiment, even if the area of the bottom surface portion 5 of the workpiece 1 is small, the upper surface (C surface) of the bottom surface portion 5 of the workpiece 1 can be pressed by the holding hole 14 of the cap member 4. .
For this reason, according to the present embodiment, the workpiece 1 can be held firmly and in a highly accurate state with no eccentricity with respect to the spindle rotation axis A. Even if the height of the bottom surface portion 5 of the workpiece 1 is arbitrary, the size of the space between the tip opening portion of the annular portion 8 of the cap member 4 and the groove bottom portion of the fitting groove 7 of the vacuum chuck 3 is large. Only changes. And since the vacuum pressure in the space mentioned above does not change, the to-be-processed object 1 can be hold | maintained with the stable holding force.

Furthermore, according to the present embodiment, the positions of the inner peripheral groove 10 and the outer peripheral groove 11 of the annular portion 8 of the cap member 4 are made different along the direction of the main shaft rotation axis A, so that the holding hole 14 of the cap member 4 The workpiece 1 can be uniformly contacted with the upper surface (C surface) of the bottom surface portion 5 in the circumferential direction. For this reason, the workpiece 1 can be held with high accuracy.
[Second Embodiment]
FIG. 5 shows a cross-sectional view of the cap member 4 in the second embodiment. FIG. 6 is a sectional view showing a state in which the workpiece 1 is held by the workpiece holding device 30. In addition, the same code | symbol is attached | subjected and demonstrated to the member which is the same as that of 1st Embodiment, or corresponds.

  In the present embodiment, the perpendicularity of the workpiece 1 can be measured after the workpiece 1 is held by the vacuum chuck 3. Thereby, it becomes possible to grasp whether dust or dust is sandwiched between the suction surface portion 6 of the vacuum chuck 3 and the bottom surface portion 5 of the workpiece 1.

FIG. 5 shows a cross-sectional view of the cap member 4 in the present embodiment.
In the cap member 4, an elongated hole 16 as an inspection window is provided symmetrically with respect to the main shaft rotation axis A on the side surface of the annular portion 8. The peep holes 16 are provided at two or more locations (four locations in the present embodiment) in the circumferential direction. The peep hole 16 is provided at a side surface position of the annular portion 8 closer to the bottom portion 22 (holding hole 14) of the cap member 4 than the elastic members 9 and 9.

  In the present embodiment, as shown in FIG. 6, the diameter of the suction surface portion 6 of the vacuum chuck 3 is set to be smaller than the diameter of the bottom surface portion 5 of the workpiece 1. For example, a notch portion may be provided on the suction surface portion 6 of the vacuum chuck 3 from the outer peripheral portion to a position where the diameter is smaller than the diameter of the bottom surface portion 5 of the workpiece 1. Also in this case, two or more notches are provided symmetrically with respect to the spindle rotation axis A in the diameter direction.

  Furthermore, in this embodiment, the surface (D surface) in which the fitting groove 7 of the vacuum chuck 3 is formed is set lower than the height of the suction surface portion 6 along the direction of the spindle rotation axis A. Note that two or more circumferentially symmetrical hole portions with respect to the spindle rotation axis A may be provided in the side surface position of the outer peripheral portion of the fitting groove 7 of the vacuum chuck 3. Further, when providing a notch in the suction surface portion 6, a hole is provided in the same angular direction as the notch with respect to the spindle rotation axis A.

Next, the operation of this embodiment will be described with reference to FIG.
In the present embodiment, the diameter of the suction surface portion 6 of the vacuum chuck 3 is set smaller than the diameter of the bottom surface portion 5 of the workpiece 1. For this reason, when the workpiece 1 is sucked and held by the vacuum chuck 3, a portion where the outer peripheral portion of the bottom surface portion 5 of the workpiece 1 protrudes is generated.

  Further, two or more peep holes 16 are provided on the side surface of the cap member 4. For this reason, the height position of the bottom surface portion 5 protruding from the suction surface portion 6 is measured using a measuring instrument 21 such as a micrometer or a laser displacement meter from one viewing hole 16.

  Next, the vacuum chuck 3 is rotated about the spindle rotation axis A, and the height of the bottom surface portion 5 is measured by the measuring instrument 21 from the observation hole 16 different from the observation hole 16 described above. By repeating this and obtaining the difference between the maximum and the minimum of a plurality of measurement results, the perpendicularity of the bottom surface portion 5 of the workpiece 1 with respect to the spindle rotation axis A can be measured.

  According to this embodiment, since the perpendicularity of the workpiece 1 can be measured after the workpiece 1 is held by the vacuum chuck 3, the suction surface portion 6 of the vacuum chuck 3 and the bottom surface portion 5 of the workpiece 1. It is possible to grasp whether there is any garbage or dust between the two. As a result, the accuracy of the workpiece 1 can be guaranteed immediately before machining.

  Other effects are the same as those described in the first embodiment.

It is a figure which shows the whole structure of the machining apparatus provided with the workpiece holding apparatus. It is sectional drawing of the state which hold | maintained the workpiece by the workpiece holding apparatus of 1st Embodiment. It is sectional drawing which shows the state before hold | maintaining a workpiece by the workpiece holding apparatus same as the above. It is a figure which shows the flowchart of an operation | work same as the above. It is a figure which shows the cross section of the cap member of 2nd Embodiment. It is sectional drawing of the state which hold | maintained the workpiece by the workpiece holding apparatus same as the above. It is principal part sectional drawing of the conventional workpiece holding apparatus (vacuum chuck).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Workpiece 2 Spindle spindle 3 Vacuum chuck 4 Cap member 5 Bottom surface part 6 Adsorption surface part 7 Insertion groove 7a Outer peripheral wall 7b Inner peripheral wall 8 Annular part 8a Outer peripheral wall 8b Inner peripheral wall 9 Elastic member 10 Inner peripheral groove 11 Outer peripheral groove 12 Machine Processing device 13 Vacuum generating device 14 Holding hole 15 Processing surface portion 16 Peep hole 17 Vacuum hole 18 Hose 19 Processing tool 20 Communication hole 21 Measuring device 22 Bottom portion 25 Column portion 30 Workpiece holding device 32 Base 33 Spindle base 34 Tool post 101 Hole 102 Spindle spindle 103 Vacuum chuck 104 Groove 105 Work piece 106 Suction surface A Spindle rotation axis

Claims (4)

In the workpiece holding device that holds the workpiece on the spindle end surface of the machine tool,
The workpiece has a processing surface portion whose outer dimension in a direction perpendicular to the holding portion and the main shaft is smaller than that of the holding portion,
A suction surface portion that vacuum-sucks the holding portion, a vacuum suction hole that opens to the suction surface portion and communicates with a vacuum generator, a fitting groove that is formed coaxially with the main shaft on the outer peripheral side of the suction surface portion, and the fitting groove A vacuum chuck having a communication path formed at the bottom of the groove and communicating with the vacuum suction hole;
It has a cylinder part fitted in the fitting groove in an airtight manner, a bottom part integral with the cylinder part, and an opening formed in the bottom part, and the dimension of the opening part is larger than the outer dimension of the processed surface part. And a cap member that is smaller than the outer dimension of the holding portion. An outer circumferential groove provided on at least one of the outer circumferential wall of the fitting groove or the outer circumferential wall of the cylindrical portion;
A first elastic member mounted in the outer circumferential groove;
An inner circumferential groove provided on at least one of the inner circumferential wall of the fitting groove or the inner circumferential wall of the cylindrical portion;
The workpiece holding device according to claim 1, further comprising: a second elastic member mounted in the inner circumferential groove. The workpiece holding device according to claim 2, wherein positions of the outer circumferential groove and the inner circumferential groove are different in the main axis direction. The workpiece holding according to claim 1, wherein the cap member has an inspection window in the cylindrical portion closer to the bottom than the inner and outer circumferential grooves. apparatus.