JPH0775811B2 - Rotational power transmission device in precision processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is intended for driving a spindle in a precision machining apparatus such as an ultra-precision lathe that clamps a workpiece by a vacuum chuck to perform machining with a relatively light load. The present invention relates to a rotary power transmission device used.

[Prior art]

In this type of ultra-precision lathe, the spindle drive motor is driven to rotate so that vibration of the spindle drive motor and thrust in the axial and radial directions are not transmitted to the spindle that supports the workpiece and reduce the machining accuracy of the workpiece. In some cases, the drive shaft is separated from the main shaft and provided coaxially, and the main shaft and the drive shaft are connected by an elastic shaft coupling such as a diaphragm coupling that transmits only rotation or a non-contact type shaft coupling such as a magnetic coupling.

[Problems to be solved by the invention]

Since shaft couplings such as diaphragm couplings and magnetic couplings used in such conventional techniques are not airtight, when a vacuum chuck is provided on the main shaft, the vacuum chuck is biased from the drive shaft side via the shaft coupling. I can't. For this reason, the vacuum chuck must be biased from the drive shaft side by providing a flexible pipe joint in parallel with the shaft joint, or directly on the main shaft via the main bearing. In the former case, both the shaft joint and the pipe joint are required, so the structure becomes complicated, and in the latter case, the structure of the main shaft becomes complicated and imbalance easily occurs, so that the main shaft easily vibrates. There's a problem. Further, in the case of a small transmission torque such as a magnetic coupling, the spindle cannot be rapidly accelerated or decelerated at the time of starting and stopping, so that there is a problem that the machining cycle time increases and productivity decreases. According to the present invention, a main shaft and a drive shaft are connected by a bellows coupling which has a relatively small transmission torque but is airtight, and a friction coupling which can be engaged / disengaged by an external operation is provided in parallel with the bellows coupling. The above problems are solved.

[Means for solving problems]

For this reason, the rotary power transmission device in the precision machining apparatus according to the present invention includes, as illustrated in the accompanying drawings, a main shaft 20 supported by a bearing device 10 and provided with a vacuum chuck 60 at its front end, and a main shaft at the rear side of the main shaft. A drive shaft coaxially supported by the bearing device 10 and rotationally driven by a main shaft drive motor 35.
In a rotary power transmission device in a precision machining apparatus, which includes a shaft coupling 30 for connecting the main shaft 20 and the drive shaft 30, the shaft coupling A includes end portions 25 of the main shaft 20 and the drive shaft 30 facing each other. A pair of end members 41 and 42 which are airtightly fixed to the respective end parts 32 and 32, and a bellows coupling 40 having bellows 43 whose both ends are integrally and airtightly fixed to the end members 41 and 42, respectively, and which face each other. The vacuum chuck 60 comprises a friction coupling 50 which is provided between the end portions 25 and 32 and which is engaged and disengaged by an external operation, and the vacuum chuck 60 has a spindle channel 61 formed in the spindle 20 and the bellows coupling. The vacuum pressure is applied or released from the drive shaft 30 side through 40.

[Action]

A workpiece is clamped / unclamped at the front end of the spindle 20 by a vacuum chuck 60 to which a vacuum pressure is applied or released from the drive shaft 30 side through a spindle conduit 61 formed in the spindle 20 and a bellows coupling 40. When the spindle 20 with the workpiece clamped is accelerated by the spindle drive motor 35 from the stopped state to a predetermined machining rotation speed, the friction coupling 50
To increase the transmission torque between the main shaft 20 and the drive shaft 30. When the main spindle 20 reaches a predetermined processing rotation speed, the friction coupling 50 is released, the main spindle 20 and the drive shaft 30 are connected only via the bellows coupling 40, and the main spindle drive motor 35
Thus, the spindle 20 is rotationally driven to lightly machine the workpiece clamped by the vacuum chuck 60. After the processing is completed, the friction coupling 50 is engaged again, and the drive shaft 30 side is braked to stop the main shaft 20.

〔The invention's effect〕

As described above, according to the present invention, the rotational power in the processed state is transmitted from the drive shaft to the main shaft only by the bellows coupling which is flexible in the axial direction, the radial direction and the bending direction and is airtight. The vibration of the main shaft drive motor is not transmitted to the main shaft to improve the processing accuracy, and the vacuum chuck is biased from the drive shaft side without using a special flexible pipe joint between the main shaft and the drive shaft. Therefore, the structure can be simplified. In addition, since a friction coupling that can be engaged / disengaged by an external operation is provided in parallel with the bellows coupling between the main shaft and drive shaft, this friction coupling is engaged when starting and stopping the main shaft. Then, the torque transmitted to the drive shaft is increased to enable rapid acceleration / deceleration, thereby reducing the machining cycle time and improving the productivity.

〔Example〕

 An embodiment of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, a bearing device 10 is composed of a main bearing 12, a drive bearing 16 and a base 11 that supports both bearings. The main bearing 12 is composed of a headstock 13 and a bearing metal 14 that supports the main shaft 20 with a slight bearing gap, and a pressurized fluid (for example, compressed air) introduced from a fluid inlet 15a passes through the passage 15 and the bearing metal. The main shaft 20 is rotatably supported only by being supplied to the radial surface 14a and the thrust surface 14b of 14. Similarly, the drive bearing 16 comprises a drive headstock 17 and a bearing metal 18, and a fluid inlet 19
The pressurized fluid introduced from a is supplied from the passage 19 to the radial surface 18a and the thrust surface 18b of the bearing metal 18 to rotatably support the drive shaft 30. The drive shaft 30 is coaxially supported on the rear side of the main shaft 20, and the opposite ends 25, 32 of both shafts 20, 30 are
They are connected by a shaft joint A composed of a bellows coupling 40 and a friction coupling 50. At the rear of the drive shaft 30, a built-in type main shaft drive motor 35 is provided.

As shown in FIG. 1, the main shaft 20 includes a main shaft body 21 made of a material having a low coefficient of thermal expansion such as ceramics, a coupling shaft 22 and a coupling member 23 which are coaxially fitted and inserted into the main spindle body 21 from the front end and the rear end, respectively. , A fastening bolt 24 for integrally connecting both members 22 and 23 to the main spindle body 21, and a main spindle body 21 at the rear end of the connecting member 23.
Consisting of a rear end 25 bolted coaxially with
2, the tightening bolt 24 and the rear end portion 25 are formed with a main shaft conduit 61 that coaxially penetrates the main shaft 20. A vacuum chuck 60 is coaxially bolted to the front end of the spindle 20 via a coupling shaft 22, and the vacuum chuck 60 chucks a workpiece (not shown) by the vacuum pressure supplied through the spindle conduit 61. There is.

As shown in FIG. 1, the drive shaft 30 is composed of a drive shaft main body 31, a front end portion 32 and a projecting portion 33, which are coaxial with the drive shaft main body 31 and are bolted to the front end and the rear end thereof, respectively. , 3
A drive shaft conduit 62 that coaxially penetrates the drive shaft 60 is formed in the shafts 2, 33. The rotor 37 of the built-in type spindle drive motor 35 is fitted to the taper surface of the rear portion of the drive shaft main body 31 and is tightened and fixed by the nut.
Is fixed to the rear side of the drive headstock 17 via a housing 36. An end plate 65 is fixed to the rear end of the housing 36, and a protruding portion 33 is airtightly inserted through a seal 64 into a joint member 63 fixed to the center of the end plate 65. The joint member 63 is connected to a vacuum source (not shown) and is adapted to apply or release a vacuum pressure to the vacuum chuck 60 via the drive shaft conduit 62, the bellows coupling 40 and the main shaft conduit 61 to operate it. ing.

The bellows coupling 40 that constitutes a part of the shaft coupling A is
Mainly as shown in FIG. 2, a pair of flange-shaped end members 41 and 42 having the same shape and a bellows 43 formed of a thin metal are formed, and both ends of the bellows 43 are brazed to each end member 41. , 42 are concentrically and integrally airtightly fixed. The tips of the end portions 25, 32 of the main shaft 20 and the drive shaft 30 facing each other are airtightly fitted into the boss portions of the end members 41, 42 via O-rings and fixed by a set screw or the like. As a result, the main shaft 20 and the drive shaft 30 are
A through hole that is elastically bendable in the axial direction and the bending direction and that is capable of transmitting rotational power and that is formed at each end 25, 32 and forms a part of the main shaft conduit 61 and the drive shaft conduit 62. 61a,
62a is airtightly connected.

The friction coupling 50 forming another part of the shaft coupling A is parallel to the bellows coupling 40 and can be engaged / disengaged with the main shaft.
20 and the drive shaft 30 are connected, mainly in FIG.
As shown in FIG. 4, a drive disc 51 is fixed to the front end 32 of the drive shaft 30 via a key and a screw, and the front end 32 is rotatable between the drive disc 51 and the flange 32a. A cylindrical driven member 53 formed integrally with the rear end portion 25 of the main shaft 20 so as to surround the friction plate 52 and the bellows coupling 40 that are fitted and supported.
Is the main component. Two cylindrical protrusions 52a, which are provided on the outer periphery of the friction plate 52 so as to project in the radial direction, are located in two notches 53a formed at the rear end of the driven member 53. The driven members 53 are relatively movable in the axial direction and are engaged with each other so as to rotate together. Further, the tubular portion of the annular member 54 fixed to the drive shaft 30 via the flange portion 32a of the tip portion 32 is airtightly and slidably fitted to the outer periphery of the boss portion of the friction plate 52. As shown in FIG.
A non-contact rotary joint 70 is provided in the middle of the drive shaft 30 between the drive shaft 16 and the drive shaft 16. If a pressurized fluid (for example, compressed air) is introduced from a passage 71 formed in the drive shaft base 17, the pressure of the pressure is increased. Is applied to the space surrounded by the flange portion 32a of the tip portion 32, the boss portion of the friction plate 52 and the annular member 54 through the passage 72 formed in the non-contact rotary joint 70 and the drive shaft 30, and this pressure is applied. As a result, the friction plate 52 is pressed against the drive disc 51 and frictionally engaged,
The rotational power of the drive shaft 30 is transmitted to the main shaft 20.

The workpiece to be lightly machined such as an aluminum disk to be mirror-finished is brought into contact with the suction surface of the vacuum chuck 60, and the drive shaft conduit 62, the bellows coupling 40 and the main shaft conduit 61 are used. It is adsorbed by the vacuum pressure applied from the drive shaft 30 side. In this state, a pressurized fluid is introduced into the passage 71, pressure is applied through the non-contact rotary joint 70 and the passage 72 to couple the friction coupling 50, and then the main spindle drive motor 35 is activated to set the main spindle 20 to a predetermined position. It accelerates rapidly to the processing rotation speed. Since the transmission torque of the shaft coupling A is increased due to the coupling of the friction coupling 50, even if the transmission torque between the main shaft 20 and the drive shaft 30 is increased by rapidly accelerating to the machining rotation speed, it can withstand this. be able to. Then, the introduction of the pressure fluid into the passage 71 is released to release the friction coupling 50.
After releasing the connection, the work piece is mirror-cut. In this state, since the main shaft 20 is connected to the drive shaft 30 only via the bellows coupling 40, the vibration of the drive shaft 30 due to the main shaft drive motor 35 or the like is not transmitted to the main shaft 20, and therefore the machining of the workpiece is performed. The accuracy can be improved. In this state, the transmission torque between the main shaft 20 and the drive shaft 30 is only due to the processing reaction force of the workpiece, so it is relatively small, and the bellows coupling 40 alone can withstand it. After the machining of the workpiece is completed, the pressure fluid is again introduced into the passage 71 to couple the friction coupling 50 to increase the transmission torque of the shaft coupling A and brake the drive shaft 30 side to rapidly decelerate the spindle 20. And stop.

As described above, according to the present embodiment, it is possible to prevent the vibration of the spindle 20 to improve the machining accuracy of the workpiece, and to accelerate and stop the spindle 20 before and after machining the workpiece.
Since the deceleration can be performed rapidly, the processing cycle time can be reduced and the productivity can be improved. Further, since the spindle 20 is provided with the vacuum chuck 60 and the simple spindle conduit 61 for supplying a vacuum pressure to the vacuum chuck 60 and does not require complicated machining, the machinability is taken into consideration in order to prevent the deterioration of the machining accuracy due to the temperature change. It is possible to select an appropriate material without needing to do so, there is no possibility of imbalance, and it is possible to further improve the processing accuracy.

In the above embodiment, an example in which the friction coupling 50 is operated by fluid pressure has been described, but not limited to this, it is also possible to use a friction coupling that is engaged / disengaged by being operated by an electromagnet or the like. is there.

[Brief description of drawings]

The attached drawings show an embodiment of a rotary power transmission device in a precision machining apparatus according to the present invention. FIG. 1 is a longitudinal sectional view of the whole, FIG. 2 is a longitudinal sectional view of an essential part, and FIG. FIG. 4 is a sectional view taken along the line III-III in FIG. 4, and FIG. Explanation of symbols 10 …… Bearing device, 20 …… Spindle, 25 …… End (rear end),
30 …… Drive shaft, 32 …… End (front end), 35 …… Spindle drive motor, 40 …… Bellows coupling, 41,42 …… End member, 43 …… Bellows, 50 …… Friction coupling, 60 ……
Vacuum chuck, 61 …… Main shaft line, A …… Shaft coupling.

Claims (1)

[Claims] 1. A main shaft supported by a bearing device and provided with a vacuum chuck at its front end, and a drive shaft which is supported by the bearing device coaxially with the main shaft on the rear side of the main shaft and is rotationally driven by a main shaft drive motor. In a rotary power transmission device in a precision machining apparatus including a shaft coupling that connects the main shaft and the drive shaft, the shaft coupling has a pair of ends that are airtightly fixed to opposite ends of the main shaft and the drive shaft, respectively. A bellows coupling having a bellows member and both ends integrally and airtightly fixed to the both end members, and a friction cup provided between the end members facing each other and engaged and disengaged by an external operation. A ring, and a vacuum pressure is applied or released to the vacuum chuck from the drive shaft side through a main shaft channel formed in the main shaft and the bellows coupling. Rotating power transmission device in the precision machining apparatus characterized by being configured to.