JPH10138071A - Super-precision vacuum chuck device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a super-precision vacuum chuck device suitable for super- precision processing in which a sufficient work fixing performance, positioning of it to a work machine in attaching/detaching it, and dividing precision can be secured, and in which the work can be fixed without deformation. SOLUTION: A device is provided with a jig main body part 20 having a suction surface 21 where a work is sucked, a vacuum suction groove part formed in the suction surface 21, a vacuum chamber 25 formed inside, and a passage to communicate the vacuum suction groove part to the vacuum chamber 25, and a valve 31 to communicate the vacuum chamber 25 in the jig main body part 20 with a vacuum generation system to sealably close the vacuum chamber 25, an installation flange 44 is provided on the jig main body part 20 through a flexible part 47, and a step Δe is set to provide an installation reference surface 49 of the jig main body part 20 to a work machine protruded from an installation surface 48 of the flange 44.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum suction type ultra-precision chuck device which can be used for fixing a workpiece in ultra-precision machining.

[0002]

2. Description of the Related Art As a conventional method of fixing a work in general machining, for example, cutting and grinding using a lathe, milling machine, grinding machine, etc., a lathe uses a three-jaw or four-jaw chuck. For a milling machine, there is a method of clamping a work to a table using a presser foot, and for a grinding machine, there is a method of firmly clamping a work with a magnet chuck or a presser foot.

[0003] In such a conventional mechanical chuck method, although a large machining force can be tolerated, the work itself is deformed due to an excessively applied work holding force, and the work is removed from the processing machine. In order to restore the work, there is a problem in terms of the shape accuracy, and when it is repeatedly attached and detached, it cannot be used for ultra-precision machining requiring an accuracy of several μm or less.

[0004] In this ultra-precision machining, a suction method using a vacuum chuck having a small clamping force or a bonding method using wax is adopted by utilizing the feature that the cutting force is minute.

FIG. 10 shows an example of a vacuum chuck provided at the tip of a lathe spindle. In this conventional vacuum chuck, a hole 2 opening at the center of the main shaft 1 and circumferential grooves 3 and 4 concentric with the hole 2 are formed on the end surface of the main shaft 1. The orbiting grooves 3 and 4 are connected to axial passages 5 and 6 that open at the bottom thereof and radial passages 7 and 8. A vacuum passage 10 extending along the axis of the main shaft 2 and leading to the hole 2 is connected to a vacuum pump (not shown).
The vacuum passage 10 communicates with the orbital grooves 3 and 4 via the passages 7 and 8 and the passages 5 and 6, so that the air in the holes 2 and the orifice grooves 3 and 4 can be evacuated by a vacuum pump. Has become. In such a vacuum chuck, the work W
Is attracted to the end face of the main shaft 1.

[0006] On the other hand, the bonding method using wax is usually
A wax having a melting point of several tens of degrees Celsius to one hundred and several tens degrees Celsius is coagulated to bond a pair of objects to be bonded,
Either one needs to be heated and heated. For machine tools,
The temperature of the machine cannot be increased due to thermal deformation.

Conventionally, as shown in FIG. 11, a mounting plate 11 having a shape suitable for adhering a work, mounting to a chuck, and positioning is used. When the mounting plate 11 is heated using an electric heater (not shown) and the work W is placed on a predetermined position when the wax 12 is melted and then cooled, the work W is adhered to the mounting plate 11 by the solidified wax 12. You.

[0008]

The bonding with wax has a drawback that the fixing and holding force of the work is basically small. Further, when the mounting plate 11 is heated,
The lower surface of 1 is warped by thermal expansion due to the higher temperature, and even if the work W is placed via wax in this state and cooled, the work W adheres while being deformed due to uneven heat dissipation. Inevitable. Therefore, even if the workpiece W is mounted on the vacuum chuck via the mounting plate 11 as it is, stabilization of the parallelism of the workpiece W with respect to the chuck mounting surface cannot be expected.

In the case of a vacuum chuck, although the fixed holding force is good, when the work W is mounted on the vacuum chuck as shown in FIG. 10, there is no reproducibility in positioning and indexing when the work is attached and detached. Has become a major problem when applied to ultra-precision machining. Further, it is impossible to make the contact portion of the work completely contact the work mounting portion serving as the suction surface because of the flatness and the surface roughness, so that a slight air leak occurs. For this reason, it is necessary to operate the vacuum pump to continue suction as long as chucking of the workpiece is required during machining and stoppage by the machine.
There was a disadvantage that the structure of the machine became complicated. Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to adopt the present invention to a general machine. An object of the present invention is to provide an ultra-precision vacuum chuck device suitable for ultra-precision machining capable of securing accuracy and fixing a work without deformation.

[0010]

In order to achieve the above object, the present invention provides a suction surface on which a workpiece is sucked, a vacuum suction groove formed on the suction surface, and a vacuum formed inside. Chamber, a jig body having a passage for communicating the vacuum suction groove and the vacuum chamber, a vacuum chamber of the jig body, and a vacuum generating system. The jig main body is provided with a mounting flange via a flexible portion, and the jig main body is mounted on a processing machine with a reference surface for mounting the flange on the processing machine. It is characterized by projecting beyond the surface.

According to the present invention thus configured, since the mounting reference surface and the mounting surface of the flange have a step, the flexible portion bends as the bolt is tightened into the flange. The bending of the flexible portion acts as a force for pressing the jig body against the mounting surface of the processing machine. Since only the flexible portion is deformed so as to obtain the minimum pressing force required for processing the work, the jig main body hardly deforms. Position errors can also be reduced.

In the construction of the present invention, positioning means for fixing the jig body to a predetermined mounting position on the processing machine is further added to the mounting reference surface of the jig main body.
Although the vacuum chuck method is basically used, the accuracy of positioning and indexing reproducibility can be improved.

In this ultra-precision vacuum chuck device, the valve and the piping of the vacuum system are connected by a connection joint having operating means for opening and closing the valve, and the connection joint is detachably attached to the valve. Is preferred.

In addition, a sealing groove is formed on the suction surface so as to surround the outside of the vacuum suction groove, and a sealing member is attached to the sealing groove, so that the sealing surface of the jig main body is formed. It is possible to prevent a decrease in the degree of vacuum due to surface accuracy or the like, and to secure a sufficient suction force.

Further, according to a preferred embodiment of the present invention, the jig body has a cylindrical shape, and the vacuum chamber is formed of a concentric hole or a set of a plurality of small holes communicating with each other. In particular, by forming a vacuum chamber from a group of small holes, the rigidity of the jig main body and the volume of the vacuum chamber can be secured.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an ultra-precision vacuum chuck device according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an embodiment of the ultra-precision vacuum chuck device according to the present embodiment, and reference numeral 20 denotes a cylindrical jig main body. The upper surface of the jig body 20 is a suction surface 21 for the workpiece W. The suction surface 21 has a center hole 22 as a groove for vacuum suction for generating a negative pressure by vacuum suction. Annular groove 2 concentric with center hole 22
3 and 24 are formed. A vacuum chamber 25 is formed inside the jig body 20, and the center hole 22 and the annular grooves 23 and 24 of the suction surface 21 are respectively formed by passages 26, 27 and 28 extending in the axial direction. 25.

The vacuum chamber 25 is hermetically sealed by a lid 29. A passage 30 extends radially from the vacuum chamber 25, and a valve 31 is provided in an opening of the jig body 20 on the outer peripheral surface side of the passage 30. Installed. A hose 33 is connected to the valve 31 via a connection joint 32, and the hose 33 is connected to a vacuum generating system including a vacuum pump (not shown).

FIG. 2 is a sectional view showing the structure of the valve 31 and the connection joint 32 in detail. In this embodiment, the valve element 34 of the valve 31 can be opened and closed by operating the knob 35 of the connection joint 32.

The valve body 34 of the valve 31 is urged by a resilient force of a compression spring 37 in a direction in which the valve body 34 is pressed against and seated on a tapered valve seat 36 formed at the entrance of the passage 30, and is connected. It is connected to a knob 35 via a rod 38. The connecting rod 38 is slidably inserted into a disk-shaped guide 39 to guide its movement. This guide 3
9 is a hole 4 for receiving the reaction force of the compression spring 37 and communicating the valve hole 40 with the chamber 41 inside the connection joint 32.
2 are formed.

The connection joint 32 can be easily attached to and detached from the valve 31. In this embodiment,
At the other end of the knob rod 35 whose tip protrudes outward from the joint body 32A so as to be pinched by hand, a female screw part 43 to be screwed into a male screw cut at the tip of the connecting rod 38 is formed. I have. Accordingly, after the female screw portion 43 is screwed into the male screw at the tip end of the connecting rod 38 while rotating the knob rod 35, the vacuum pump (not shown) is operated to pull up the knob rod 35 while evacuating the valve body 34. Is separated from the valve seat 36, the passage 30 is opened, and the air in the vacuum chamber 25 is sucked and discharged. After the degree of vacuum in the vacuum chamber 25 is increased to a predetermined value, when the knob 35 is released, the valve body 34 is seated on the valve seat 36 by the elastic force of the compression spring 37 and the passage 30 is closed. Thereafter, the connection joint 32 can be easily removed by reversing the knob 35 and returning the female screw 43 to separate it from the connecting rod 38. At this time, even when the connection joint 32 is removed, the valve body 34 is kept closed by the atmospheric pressure because the vacuum chamber 25 is in a vacuum state. The work W can be carried while being held. For this reason, the work W and the vacuum chuck device can be handled as a single unit in the processing of the work W or measurement after the processing.

Next, FIG. 3 shows a mounting flange 44 provided integrally with the jig body 20 for fixing and connecting the vacuum chuck device to the processing machine while the work W is being sucked. The mounting flange 44 has a thick portion 46 having a hole through which a bolt 45 for fastening is formed, and a thick portion 4 inside the thick portion 46.
6 is connected to the jig main body 20 side, and comprises a flexible portion 47 which is thinly processed so as to bend when being fastened by the bolt 45. The lower surface of the thick portion 46 is a flange mounting surface 48, and the step is formed such that the mounting reference surface 49 of the lower surface of the jig main body 20 projects by a small step Δe with respect to the flange mounting surface 48. Is set.

The step Δe is set according to the magnitude of the pressing force required to fix the jig body 20 using the bolt 45. Due to the step Δe, the flexible portion 47 bends as the bolt 45 is tightened. At this time, the bending of the flexible portion 47 causes a force that presses the jig body 20 against the mounting surface 50 of the processing machine. It works. Furthermore, since only the flexible portion 47 is deformed by tightening the bolt 45 to obtain the minimum pressing force required for processing the work W, the jig main body 20 side is hardly deformed, and is attracted. Therefore, the position error of the work W can be reduced without deforming the existing work W.

Next, referring to FIG. 1, when the vacuum chuck device is attached to the processing machine as described above, a jig is used as positioning means for ensuring re-positioning and reproducibility of indexing even when the vacuum chuck device is removed. The knock pin 52 projects from the attachment reference surface 49 of the main body 20.

The positioning means includes a knock pin 5
4, as shown in FIG. 4, a mortar-shaped concave portion 55 is formed at the center of the lid 29 that seals the vacuum chamber 25, and a similar concave portion 56 is formed on the mounting surface 50 side of the processing machine. Alternatively, a spherical ball 57 may be inserted between the concave portions 55 and 56 and used together with the knock pin 52.

Next, another embodiment of the present invention will be described with reference to FIGS. In the vacuum chuck device according to the first embodiment, the workpiece W falls off when the degree of vacuum in the vacuum chamber 25 falls below a certain limit.
This decrease in the degree of vacuum causes very little leakage of valves and the like of the vacuum piping, so that there is an error in the degree of parallelism between the suction surface 21 of the jig body 20 and the surface to be suctioned of the work W and the surface roughness of the suction surface. Due to.

In the embodiment shown in FIG. 5, sealing grooves 60, 61 and 62 are formed outside each of the center hole 22 and the annular grooves 23 and 24 so as to surround the center hole 22 almost concentrically. A seal member capable of holding a vacuum with a small force is mounted in the grooves 60, 61, 62. As shown in FIG. 6A, if the sealing member 64 is a lip-shaped sealing member, the deformation resistance is small and the work W
6B, a porous sealing member 65 having a void therein may be used as a sealing material having a small deformation resistance. In addition, such a sealing member 6 having a small deformation resistance is used.
As the materials 4 and 65, a sponge-like porous material, a gel or a tube-like rubber is preferable.

FIG. 7 shows an error in the degree of parallelism between the suction surface 21 of the jig main body 20 and the surface to be suctioned of the work W and the error of the suction surface 2.
FIG. 7 is a diagram showing a change in a decrease in the degree of vacuum in a vacuum chamber 25 caused by leakage due to surface roughness 1;

In FIG. 7, if the amount of leakage is constant, the degree of vacuum changes linearly. However, in actuality, since the leakage occurs in accordance with the pressure difference between the atmospheric pressure and the vacuum chamber 25, the degree of vacuum due to the leakage decreases as the degree of vacuum in the vacuum chamber 25 decreases with time, and the degree of vacuum is Curve P ₀ B
It changes like Here, assuming that the minimum degree of vacuum required to suck the work W is Ps, the time during which the work W can be held by suction is the intersection ts between the curves P ₀ B and Ps. It is practically difficult to calculate the work suction holding time ts by calculation because the resistance of air leakage from the minute gap has a large effect, but as a reference value example,
When the time t _{0 at} which the degree of vacuum decreases from the almost perfect vacuum to a minimum required degree of vacuum Ps (in the case of a straight line P ₀ A) when the degree of vacuum decreases at a constant rate is calculated,

(Equation 1) Holds.

Here, V: vacuum chamber volume (mm ³ ) P: allowable vacuum degree (Ps / 760 (atmospheric pressure)) v: leaked air amount (mm ³ / sec) In the embodiment of FIG. The diameter is 40 mm and the height is 20 mm (in this case, the volumes of the passages and grooves are ignored), the allowable vacuum degree Ps is 152 mmHg, and the leak air amount v
= As 1 mm ³ / sec (in terms of atmospheric pressure), when obtaining the t ₀ are substituted into equation (1), the t ₀ = 83.8 (min).

The change curve P ₀ B of the degree of vacuum decrease in FIG.
As can be seen from FIG.
It is longer than t ₀ calculated above. In addition, the actual work suction holding time ts is determined by the seal member 64,
By mounting 65, it is possible to further reduce the leaked air amount v from the above-mentioned 1 mm ³ / sec, and it is estimated that the air leakage amount will be longer, which is practically sufficient.

Next, FIG. 8 shows a modification in which the vacuum chamber 70 is configured as a set of a plurality of small holes. FIG. 9 shows C-
The C section is shown. In this case, a small hole 71 at the center and a small hole 72 arranged symmetrically with respect to the small hole 71 are formed. They are in communication.

By forming the vacuum chamber 70 from the group of small holes, the rigidity of the jig body 20 can be further increased, while the distance from the suction surface 21 of the work W to the bottom of the small hole is increased. Since n and the thickness of the side surface of the jig body 20 can be made smaller, a sufficient volume for the vacuum chamber 70 can be secured.

[0033]

As is apparent from the above description, according to the first aspect of the present invention, the jig body is provided with the mounting flange via the flexible portion, and the jig body is processed. By configuring the mounting reference surface to the machine to protrude from the mounting surface of the flange to the processing machine, only the flexible portion is deformed so as to obtain the minimum pressing force required for processing the work. As a result, sufficient suction holding performance of the work can be obtained by the suction method, and the jig body side is hardly deformed, so the sucked work is not deformed and the position error of the work is reduced. Can be.

In the construction of the present invention, a positioning means for fixing the jig main body to a predetermined mounting position of the processing machine is added to the mounting reference surface of the jig main body. Accordingly, the accuracy of reproducibility of positioning and indexing can be improved even though the vacuum chuck system is basically used, and it can sufficiently cope with ultra-precision processing.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an ultra-precision vacuum chuck device according to the present invention.

FIG. 2 is a sectional view showing a structure of a connection joint connected to a valve for closing a vacuum chamber of the ultra-precision vacuum chuck device according to the embodiment.

FIG. 3 is a sectional view showing a structure of a mounting flange provided on a jig main body of the ultra-precision vacuum chuck device according to the embodiment.

FIG. 4 is an explanatory view showing an example of a positioning means provided in the ultra-precision vacuum chuck device according to the embodiment.

FIG. 5 is a sectional view showing a configuration of an ultra-precision vacuum chuck device according to another embodiment.

FIG. 6 is a cross-sectional view of a sealing material mounted on the contact surface of the jig main body.

FIG. 7 is a diagram showing a temporal change in the degree of vacuum in a vacuum chamber.

FIG. 8 is a sectional view showing another embodiment of the vacuum chamber.

FIG. 9 is a sectional view taken along line CC of FIG. 8;

FIG. 10 is an explanatory view of a conventional vacuum chuck.

FIG. 11 is an explanatory view showing a conventional work bonding method using wax.

[Explanation of symbols]

 Reference Signs List 20 jig body 21 suction surface 22 center hole 23, 24 annular groove 25 vacuum chamber 26, 27, 28 passage 29 lid 31 valve 32 connection joint 34 valve body 35 knob rod (operation means) 36 valve seat 38 connecting rod 43 female screw Part 44 mounting flange 47 flexible part 48 flange mounting surface 49 mounting reference plane 52 knock pin (positioning means) 64, 65 sealing member

Claims (5)

[Claims] 1. A suction surface on which a work is sucked, a vacuum suction groove formed in the suction surface, a vacuum chamber formed therein, and a passage communicating the vacuum suction groove with the vacuum chamber. A jig body having a jig body, a vacuum chamber of the jig body, and a vacuum generating system.
A valve capable of hermetically closing the vacuum chamber, a mounting flange is provided on the jig body via a flexible portion, and the mounting reference surface of the jig main body to a processing machine is the flange. An ultra-precision vacuum chuck device characterized in that it protrudes from a mounting surface on a processing machine. 2. The ultra-precision vacuum chuck device according to claim 1, wherein the mounting reference surface of the jig main body is provided with positioning means for fixing the mounting reference surface to a predetermined mounting position of a processing machine. 3. The valve according to claim 1, wherein the valve and the piping of the vacuum system are connected by a connection joint having operating means for opening and closing the valve, and the connection joint is detachably attached to the valve. Item 3. The ultra-precision vacuum chuck device according to item 1 or 2. 4. A sealing groove is formed on the suction surface so as to surround the outside of the vacuum suction groove, and a sealing member is attached to the sealing groove.
4. The ultra-precision vacuum chuck device according to 2 or 3. 5. The apparatus according to claim 1, wherein said jig body has a columnar shape, and said vacuum chamber is formed of a concentric hole or a set of a plurality of small holes communicating with each other.
5. The ultra-precision vacuum chuck device according to 2, 3, or 4.