JPH0373415B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a vacuum chuck device that holds a workpiece by vacuum suction.

<Prior art> In an ultra-precision polishing machine, the surface of a thin plate workpiece is rotated against a lap surface plate that is immersed in a polishing liquid to give an ultra-precision mirror finish.
The work to be attached to the lower surface of the work holder that holds the work is attached with adhesive. Therefore, it was very troublesome to attach and detach the workpiece, resulting in poor processing efficiency.

It is very efficient to hold such a thin workpiece with a vacuum chuck, but in the ultra-precision polishing machine mentioned above, it is necessary to bring the surface of the held workpiece into proper contact with the surface of the lap surface plate. For this purpose, the work holder needs to be connected to the rotational drive shaft so that it can float. Therefore, at the fitting part between the work holder and the rotation drive shaft,
A gap is formed to allow the work holder to float, so when the vacuum chuck is used, it is difficult to ensure a vacuum because the gap communicates with the atmosphere, and the vacuum suction holding power of the work is reduced. Vacuum chucks are no longer in use because of the problems that the vacuum chucks have and the external force applied to the vacuum chucks by the rubber hoses that connect the vacuum chucks and the vacuum source affects the machining accuracy of workpieces that require ultra-precision. Ta.

<Object of the invention> The object of the invention is to solve the above problems and enable the use of a vacuum chuck, which allows easy attachment and removal of a work, as a work holder that is floatingly supported on a rotational drive shaft. It is.

<Configuration of the Invention> The characteristic configuration of the present invention is to allow a vacuum chuck body provided with a vacuum suction surface to float relative to a rotational drive shaft, and to connect the vacuum chuck body by engaging in the rotational direction.
A negative pressure passage communicating between the vacuum suction surface and a vacuum source is provided in the rotary drive shaft, a magnetic fluid is sealed in the fitting gap between the vacuum chuck body and the rotary drive shaft, and a portion where the magnetic fluid is sealed is provided. A magnet is disposed on the vacuum chuck body or rotational drive shaft, and a magnetic fluid seal is provided in the fitting gap.

<Examples> Examples of the present invention will be described below based on the drawings.
Figure 1 shows the main configuration of an ultra-precision polishing machine using the device of the present invention, where 1 is a fixed base;
A turntable 2 that rotates about a rotation center 0 is provided on the fixed base 1, and a lap surface plate 3 that rotates integrally with the same rotation center 0 is provided on the turntable 2. Reference numeral 4 denotes a spindle head, which is integrally provided with the slide base 5 which is fed and moved in a direction parallel to the surface of the lap surface plate 3 along the guide surface 8 of the support rail 7 of the support stand 6 installed on the fixed base 1. It is being The spindle head 4 has a ram 9 that moves up and down in the vertical axis direction perpendicular to the surface of the lap surface plate 3, and the main shaft 11 (Fig. 2) runs vertically through the ram 9 and rotates around the vertical axis. A work holder 10 is connected to the lower end of the main shaft 11 so as to be relatively slidable and floating in the vertical direction. 12 is a drive motor for rotating the main shaft, and 13 is a drive motor for vertically feeding the ram. W is a thin plate-shaped work held on the lower surface of the work holder 10. The work W held on the lower surface of the work holder 10 is brought into contact with the surface of the lap surface plate 3, and polished to an ultra-precise mirror surface by the rotation of the work holder 10 and the rotation of the lap surface plate 3 by the turntable 2. be.

Therefore, the present invention uses the work holder 10 as a vacuum chuck. Its specific configuration will be explained with reference to FIG.

14 is a vacuum chuck body. The vacuum chuck main body 14 has a vacuum chamber 16, and a vacuum suction surface 17 for the workpiece W having a large number of annular suction grooves 19 communicating with the vacuum chamber 16 via communication passages 18. 15 is a holder integral with the vacuum chuck body 14.

The upper end of a drive shaft 20 is integrally connected to the lower end of the main shaft 11 on the same axis.
0, the vacuum chuck main body 14 allows movement and floating in the axial direction, and is connected by engaging in the rotational direction. That is, the vacuum chuck main body 14 is provided with an engagement groove 22 having a long width across flats in the axial direction of the drive shaft 20, and a drive pin 2 that engages with the engagement groove 22 is provided at the lower end of the drive shaft 20.
1, and a holder 1 that fits around the outer periphery of the drive shaft 20.
The hole 5 has a diameter that allows the vacuum chuck body 14 to be loosely fitted with a gap 27 to allow floating of the vacuum chuck body 14.

Further, a negative pressure passage 2 is provided within the drive shaft 20 and communicates with a vacuum chamber 16 provided in the vacuum chuck body 14.
3 is provided and connected to a vacuum source (not shown). The connection structure between the negative pressure passage 23 and the vacuum source is such that a distributor 25 is fixed to the lower end of the ram 9, and a connecting pipe 2 is connected to the distributor 25 to the vacuum source.
4 are connected to each other, and the negative pressure passage 23 is communicated through the distributor 25. 26 is a sealing material that seals the relative rotation surfaces between the distributor 25 and the main shaft 11.

The gap 27 between the drive shaft 20 and the hole in the holder 15 of the vacuum chuck main body 14 loosely fitted to the drive shaft 20 must be sealed to prevent the vacuum chamber 16 from communicating with the atmosphere. Moreover, a special seal is required to permit axial movement and floating of the vacuum chuck body 14 relative to the drive shaft 20. Therefore, in the present invention, a magnetic fluid seal is applied to the gap 27 to satisfy the above requirement. That is, a seal structure in which a magnetic fluid 28, which is a solution in which ferromagnetic particles are stably dispersed in a liquid phase, is sealed in the gap 27, and an annular magnet 29 is arranged on the holder 15 at a portion where the magnetic fluid 28 is sealed. It is. In addition, the vacuum chuck body 14 and the drive shaft 2
0 is the opposite of the above, a protruding shaft is provided on the vacuum chuck main body 14 side, a hole is provided in the drive shaft 20 in which the protruding shaft is loosely fitted with a gap, and the protruding shaft is engaged with a drive pin. The magnetic fluid 28 and the magnet 2 are placed in the loose fitting gap.
A magnetic fluid seal consisting of 9 may also be provided.

Since the present invention has the structure as described above, the ram 9
Due to the rise of the vacuum chuck body 14, which is located above the lap surface plate 3, the drive shaft 20 is moved by its gravity.
The holder 15 moves relative to the drive pin 16 and descends, and the holder 15 hits the drive pin 16 and is in a suspended state. In this state, the workpiece W is held by suction on the vacuum suction surface 17 of the vacuum chuck main body 14, and the ram 9 is moved downward while the main shaft 11 is rotated to move the workpiece W through the drive shaft 20, drive pin 21, and engagement groove 22. The vacuum chuck body 14 constituting the holder 10 is rotated. The downward movement of the ram 9 stops at a position where the workpiece W has further descended by a certain amount after contacting the lap surface plate 3. Therefore, as the ram 9 descends by a certain amount, the workpiece W comes into contact with the lap surface plate 3, and the vacuum chuck body 14 whose downward movement is restricted moves relative to the drive shaft 20, and the drive pin 21 moves through the engagement groove 22. The suspension of the holding body 15 is released by sliding, and the workpiece W is moved onto the lap surface plate 3 under the gravity of the vacuum chuck body 14 itself.
The polishing process is performed by contacting the surface. After machining of the workpiece W is completed, the drive pin 21 engages with the holder 15 when the ram 9 is raised by a certain amount, and then the vacuum chuck main body 14 is lifted together to separate the workpiece W from the lap platen 3 and apply negative pressure. The workpiece W is removed from the vacuum suction surface 17 of the vacuum chuck body 14 by cutting.

Here, when the vacuum chuck main body 14 and the drive shaft 20 move relative to each other in the axial direction due to the vertical movement of the ram 9, the magnetic fluid 28 sealed in the gap between the holder 15 and the drive shaft 20 Since the magnet 29 also moves with the relative movement in the axial direction, the magnet 29 follows and moves, and the gap 27 is always sealed and the vacuum chamber 26
maintains airtightness and ensures the vacuum suction force of the vacuum suction surface 17.

<Other Embodiments> As shown in FIG. 3, the communication structure between the negative pressure passage 23 provided in the drive shaft 20 and the vacuum suction surface 17 of the vacuum chuck 14 is such that a passage is provided in the holder 15 and the vacuum chuck body 14. 30 and communicated with the negative pressure passage 23 via a distributor 31 provided integrally with the holder 15, the holder 1 is formed at upper and lower portions with the distributor 31 in the center.
5 and the drive shaft 20 are filled with magnetic fluids 28a and 28b.
The design can be changed to a structure in which annular magnets 29a and 29b are arranged on the holder 15 side of the enclosing portions a and 28b, and this structure reduces the force of floating the vacuum chuck body 14 due to the difference between vacuum and atmospheric pressure. is reduced, and the machining accuracy of the workpiece W is further improved.

<Effects of the Invention> As described above, according to the present invention, the vacuum chuck body is supported by ensuring vacuum properties and allowing floating with respect to the drive shaft, thereby making it possible to use the vacuum chuck as a work holder. Therefore, by controlling the degree of vacuum, it becomes very easy to attach and detach the workpiece, which improves processing efficiency.In addition, since the rubber hose etc. are not connected to the vacuum chuck body to guide the vacuum, the elasticity of the rubber hose etc. This has the special advantage that no external force is applied to the vacuum chuck body and does not adversely affect the machining accuracy of the workpiece.

[Brief explanation of drawings]

Fig. 1 is a side view of the main part of an ultra-precision polishing machine to which the device of the present invention is applied, Fig. 2 is a cross-sectional view of the main part of the device of the present invention, and Fig. 3 is a cross-section of the main part showing another embodiment of the device of the present invention. It is a diagram. 4... Spindle head, 9... Ram, 10... Work holder, 11... Spindle, 14... Vacuum chuck body, 15
... Holding body, 17 ... Vacuum adsorption surface, 20 ... Drive shaft, 2
DESCRIPTION OF SYMBOLS 1... Drive pin, 22... Engagement groove, 23... Negative pressure passage, 24... Connection pipe, 25... Distributor,
26...Seal, 27...Gap, 28, 28a, 28
b...Magnetic fluid, 29, 29a, 29b...Magnet, 3
0...Aisle, 31...Day streamer.

Claims (1)

[Claims] 1. A vacuum chuck body equipped with a vacuum suction surface is allowed to float relative to the rotational drive shaft, and is connected by engaging in the rotational direction, so that the vacuum suction surface and the vacuum source are communicated within the rotational drive shaft. Provide a negative pressure passage,
A magnetic fluid is sealed in the fitting gap between the vacuum chuck main body and the rotational drive shaft, a magnet is placed on the vacuum chuck body or the rotational drive shaft at the part where the magnetic fluid is sealed, and a magnetic fluid seal is placed in the fitting gap. A vacuum chuck device characterized by: