CN116847947A

CN116847947A - Belt processing device

Info

Publication number: CN116847947A
Application number: CN202280015222.3A
Authority: CN
Inventors: 菅崎尊晓; 神山茜菜
Original assignee: Makino Milling Machine Co Ltd
Current assignee: Makino Milling Machine Co Ltd
Priority date: 2021-03-31
Filing date: 2022-03-31
Publication date: 2023-10-03
Also published as: EP4316733A1; WO2022211085A1; TWI812137B; TW202243799A; KR20230121148A; JP2022157222A; JP7142123B1

Abstract

A belt processing device (10) for processing a workpiece by moving a processing belt (34) relative to the workpiece (W) is provided with: a first roller (40) as a processing roller; a second roller (32) as a driven roller; a processing belt supported by the first roller and the second roller; an air pressure motor (60) for rotating the first roller or the second roller; an elastic ring (44) mounted on the outer periphery of the first roller; and an expansion preventing member (46) attached to the elastic ring and having an elastic modulus larger than that of the elastic ring.

Description

Belt processing device

Technical Field

The present invention relates to a belt processing apparatus for processing a surface of a workpiece by using an endless processing belt which is stretched between a plurality of rollers.

Background

For example, in order to functionally require or improve the appearance of a surface of a mold for plastic injection molding or a precision sealing surface provided in a vacuum chamber, polishing is usually performed after cutting. In order to perform such polishing processing using a conventional machine tool, a belt polishing tool that can be attached to a spindle of the machine tool is sometimes used.

Patent document 1 describes a belt polishing tool equipped with: a main body portion; a holding portion joined to the main body portion; a power generation unit; an endless abrasive belt; a driving roller rotatably supporting the polishing belt and transmitting the rotational power received from the power generation unit to the polishing belt; a first driven roller rotatably supporting the abrasive belt; and a processing roller as a second driven roller which rotatably supports the polishing belt and supports a portion of the polishing belt which is in contact with the workpiece during polishing.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2020-163552

Disclosure of Invention

Problems to be solved by the invention

In the belt polishing tool of patent document 1, the attitude of the polishing belt is made to follow the shape of the work surface (surface to be polished) by rotatably supporting the processing roller about a rotation axis orthogonal to the rotation axis of the processing roller, but in some cases, the entire surface cannot be polished in the width direction of the polishing belt due to poor mounting alignment of the processing roller. In addition, even in the case of a workpiece subjected to planar processing, there is a case where polishing omission of the belt occurs on the processing surface due to the mounting alignment of the workpiece. In any case, a program for moving the processing belt in conformity with the minute undulations of the processing surface in accordance with the processing surface cannot be formed.

The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide a belt processing apparatus capable of efficiently obtaining a good processed surface (polished surface) by simply providing a normal processing belt without adding a complicated structure.

Means for solving the problems

In order to achieve the above object, according to the present invention, there is provided a belt processing apparatus that processes a workpiece by relatively moving a processing belt with respect to the workpiece, wherein the belt processing apparatus is provided with: a first roller as a processing roller; a second roller; a processing belt supported by the first roller and the second roller; a rotational power generation unit that rotates the first roller or the second roller; an annular elastic body mounted on the outer periphery of the first roller; and an annular expansion preventing member attached to the elastic body, the expansion preventing member having an elastic modulus larger than that of the elastic body.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, an elastic body is attached to the surface of a processing roller, and a good processing surface can be obtained by absorbing the elastic body, such as alignment of the processing roller during processing (during belt polishing), mounting alignment of a workpiece, a step of a seam of a processing belt, or a relief shape of a processing surface of the workpiece. Further, the expansion preventing member prevents the elastic body from expanding and deforming in the radial direction due to centrifugal force during rotation of the processing roller.

Drawings

Fig. 1 is a side view of an example of a machine tool to which a belt processing device of the present invention can be attached.

Fig. 2 is a side view of a belt processing apparatus according to one embodiment of the present invention.

Fig. 3 is a perspective view of the belt processing apparatus of fig. 2.

Fig. 4 is a cross-sectional view of the belt processing apparatus of fig. 2.

Fig. 5 is a cross-sectional view of a first roller according to one embodiment.

Fig. 6 is a cross-sectional view of the elastic ring.

Fig. 7 is a cross-sectional view showing a modification of the first roller.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

Fig. 1 is a side view showing a machine tool 100 as a general vertical machining center and a belt machining apparatus 10 according to an embodiment of the present invention mounted thereon. The work machine 100 of fig. 1 includes: a base 102, wherein the base 102 is a base fixed on the ground of a factory; a table 104 provided on the upper surface of the base 102 so as to be movable in the Y-axis direction or the front-rear direction (left-right direction in fig. 1), the table 104 fixing a workpiece W on the upper surface of the table 104; a column 108, the column 108 being disposed upright from an upper surface at a rear portion of the housing 102; an X-axis slider 110, the X-axis slider 110 being provided on the front surface of the column 108 so as to be movable in the X-axis direction or the left-right direction (direction perpendicular to the paper surface in fig. 1); a spindle head 112, wherein the spindle head 112 is provided on the front surface of the X-axis slider 110 so as to be movable in the Z-axis direction or the up-down direction with respect to the X-axis slider 110, and supports the spindle 114 so as to be rotatable about a vertical rotation axis O.

Further, the machine tool 100 has an X-axis feeding device (not shown) that reciprocates the X-axis slider 110 in the X-axis direction, a Y-axis feeding device (not shown) that reciprocates the table 104 in the Y-axis direction, and a Z-axis feeding device (not shown) that reciprocates the spindle head 112 in the Z-axis direction. Work machine 100 also has a spindle motor (not shown) that rotationally drives spindle 114. The spindle motor may be disposed outside or inside a housing (not shown) of the spindle head 112. Preferably, the spindle motor can use its torque to hold the spindle 114 in a prescribed angular position about the axis of rotation O. The machine tool 100 further includes NC devices (not shown) for orthogonally intersecting the spindle motor and the feed devices of the three orthogonal axes, i.e., the X axis, the Y axis, and the Z axis.

Preferably, the work machine 100 further has an automatic tool changing device (not shown) for changing a tool (not shown) mounted to the distal end portion of the spindle 114. In this way, the machine tool 100 forms a vertical machining center, and the spindle 114 can be moved and positioned relative to the workpiece W in three orthogonal axial directions, that is, the X axis, the Y axis, and the Z axis, and can be positioned at an angular position about the rotation axis O.

A taper hole (not shown) for attaching a tool (not shown) is formed in a distal end portion of the main shaft 114 of the machine tool 100. A center hole (not shown) is formed in spindle 114 so as to extend along rotation axis O. In the center hole of the main shaft 114, a tool clamping device of a draw rod type (not shown in the drawing) is provided, which secures a tool mounted in the taper hole. In the present embodiment, the tool clamping device is configured to fix an HSK type jig, which is a double-sided constraint type, into a taper hole of the spindle 114.

The belt processing apparatus 10 is mounted to a tapered bore of a main shaft 114 of the machine tool 100. As shown in fig. 2 to 4, the tape processing apparatus 10 includes a main body 20 and a holding portion 12, and the holding portion 12 is fitted into a tapered hole of a main shaft 114 of the machine tool 100. The taper may be a taper for mounting a tool holder (not shown) based on the HSK specification (DIN 69893). The taper hole may be fitted to another shank-shaped taper portion, for example, a 7/24-tapered shank-shaped taper portion.

The holding portion 12 includes: a tapered portion 14, wherein the tapered portion 14 can be in close contact with an inner peripheral surface of a tapered hole of a main shaft 114 of the work machine 100; a cylindrical extension 16, the extension 16 being joined to the main body 20; and a flange portion 18, the flange portion 18 being located between the extension portion 16 and the holding portion 12. The flange 18 has a V-shaped groove 18a extending in the circumferential direction, and the V-shaped groove 18a is formed to engage with a replacement arm (not shown) of an automatic tool replacement device attached to the machine tool 100. In the present embodiment, the holding portion 12, particularly the tapered arm 14 and the flange portion 18 are formed based on the HSK standard (DIN 69893). As shown in fig. 4, a commercially available tool holder based on the HSK standard (DIN 69893) may be used for the holding portion 12. In this case, the inside of the holding portion 12 may be along the central axis O ₁ A center hole 12a and a tool mounting hole 16a are formed.

In the case where the holding portion 12 has a shape based on the HSK standard (DIN 69893), in order to clamp the holding portion 12 into the tapered hole of the spindle 114 on the spindle 114, the hollow spindle 114 is provided with a clamping device provided with: a tie rod (not shown) extending along the rotation axis O in the hollow interior of the spindle; a plurality of chucks (not shown) disposed in the tapered hole at equal angular intervals in the circumferential direction around the tie rod; and a plurality of disc springs (not shown) disposed in the inner space of the spindle centering on the tie rod.

The tie rod of the clamp device is a hollow member, and a fluid passage through which a gas such as pressurized air or a liquid such as a cooling medium flows is formed inside the tie rod. The fluid passageway is connected to a fluid source (not shown). In the case where the fluid to be supplied is pressurized air, the fluid source may include a compressor (not shown) that compresses air, a container (not shown) that stores pressurized air, a pressure adjustment valve (not shown) that is disposed at an outlet of the container and adjusts the pressure of the supplied pressurized air to a prescribed pressure, and the like. In the case where the fluid to be supplied is a liquid such as a cooling medium, the fluid source may include a pump (not shown in the figure) for pressurizing the liquid, a pressure adjustment valve (not shown in the figure) which is disposed at an outlet of the pump and adjusts the pressure of the liquid to be supplied to a predetermined pressure, and the like. As the fluid source, a service air system of a factory where the work machine 100 is provided, a cooling medium supply device (not shown in the figure) attached to the work machine 100 may be used.

The main body 20 includes a belt driving unit 30, a rotational power generating unit 60, and a power transmitting unit 70 as main components. The belt driving unit 30, the rotary power generating unit 60, and the power transmitting unit 70 are attached to the frame 22. The frame 22 has at least a base portion 24 and a side wall portion 26 extending perpendicularly from the base portion 24. The side wall portion 26 extends in a direction approaching the table 104 and the workpiece W fixed to the table 104 when the tape processing apparatus 10 is attached to the distal end portion of the main shaft 114 of the machine tool 100 as shown in fig. 1. In the present embodiment, the base portion 24 and the side wall portion 26 are independent members and are fastened to each other by the bolts 24a, but the base portion 24 and the side wall portion 26 may be integrally formed.

In the case of using a commercially available tool holder as the holding portion 12, the main body portion 20 of the tape processing apparatus 10 is provided with the engagement portion 28 that is engaged with the frame 22. The engaging portion 28 protrudes from the upper surface of the base portion 24 to the opposite side from the side wall portion 26. In the present embodiment, the joint 28 is fastened to the base 24 by a plurality of bolts 24 b. In the case where a commercially available tool holder is not used as the holding portion 12, fastening means such as bolts may be employed to join the extension portion 16 of the holding portion 12 to the base portion 24.

The joint portion 28 has a fitting portion 28a fitted into the tool mounting hole 16a of the holding portion 12, and a flange portion 28b integrally joined to the lower end portion of the fitting portion 28a, and is formed with a flange portion along the central axis O ₂ An extended central bore 28c. When the fitting portion 28a is fitted into the tool mounting hole 16a of the holding portion 12, the center axis O of the holding portion 12 ₁ Central axis O of joint 28 ₂ And are consistent. In the embodiment of fig. 4, the holding portion 12 and the engaging portion 28 are formed of members independent of each other, and the center hole 12a of the holding portion 12 is formed to be open to the tool mounting hole 16a. In the present embodiment, when the fitting portion 28a is fitted into the tool mounting hole 16a of the holding portion 12, the center hole 12a of the holding portion 12 communicates with the center hole 28c of the engaging portion 28, forming one fluid supply passage.

In the case where the holding portion 12 and the engaging portion 28 are integrally formed, the center hole 12a of the holding portion 12 is formed along the center axis O ₁ Through the holding portion 12. In this case, the center hole 12a of the holding portion 12 forms a fluid supply passage. The fluid supply passage communicates with a fluid passage formed in a drawbar of the clamping device when the holding portion 12 is clamped in the tapered hole of the spindle 114.

The belt driving portion 30 is mounted to the side wall portion 26 of the frame 22. The belt driving section 30 includes a first roller 40 and a second roller 32, and the processing belt 34 is stretched between the first roller 40 and the second roller 32. The processing belt 34 is formed in a loop shape by joining both ends of a base material such as cloth to which an abrasive is bonded. The particle size of the bonded abrasive is appropriately determined according to the surface roughness required for the polishing process or the grinding process to be performed.

The first roller 40 is rotatably supported by the side wall 26 and the bracket 36 attached to the side wall 26. More specifically, the first roller 40 is attached to the rotation shaft 38 via bearings 36a and 36b, and the rotation shaft 38 is rotatably supported by the side wall 26 and the bracket 36. At the first roller 40 anda key 38a is disposed between the rotation shafts 38, and the key 38a is engaged with an inner peripheral surface of the first roller 40 and an outer peripheral surface of the rotation shaft 38, so that the first roller 40 is not rotatable relative to the rotation shaft 38. When the first roller 40 is attached to the side wall 26 and the bracket 36, the outer peripheral surface of the first roller 40 is located at the central axis O ₁ Protruding in the direction than the side wall portion 26.

The first roller 40 includes a cylindrical roller body 42, at least one elastic ring 44 as an elastic body fitted to the outer peripheral surface of the roller body 42, and an end plate 48. The roller body 42 has a center hole 42a passing through the rotation shaft 38. On the inner peripheral surface of the roller body 42, a groove 42b extending in the axial direction for passing the key 38a may be formed. A flange portion 42c protruding in the radial direction for preventing the elastic ring 44 from coming off is provided at one end portion of the roller body 42. At the other end of the roller body 42, a recess 42d for accommodating the end plate 48 is formed.

The elastic ring 44 is an annular member formed of an elastic material such as foam rubber, for example, a fluororubber sponge, attached to the outer peripheral surface of the roller main body 42. The elastic ring 44 has a slit 44a extending in the circumferential direction, and an inner peripheral surface 44b in close contact with the outer peripheral surface of the roller main body 42. The slit 44a is formed at a predetermined depth in the radial direction and a predetermined width (axial dimension) in the axial direction from the outer peripheral surface of the elastic ring 44. The slit 44a may be a simple slit cut from the outer peripheral surface to a predetermined depth in the radial direction.

An expansion preventing member 46 is fitted into the slit 44a, and the expansion preventing member 46 prevents the elastic ring 44 from expanding and deforming in the radial direction due to the centrifugal force when the first roller 40 rotates. The expansion preventing member 46 may be a ring-shaped member made of a material having an elastic modulus larger than that of the elastic ring 44 as an elastic body, for example, a resin sheet. Alternatively, the expansion preventing member 46 may be two arcuate members that divide the annular member into two along the diameter, or three arcuate members that divide the annular member into three so that the center angle becomes 120 °. Further, since the expansion preventing member 46 has an adverse effect on the tension of the processing belt 34 when it comes into contact with the processing belt 34, it is preferable that the outer diameter of the expansion preventing member 46 is smaller than the outer diameter of the elastic ring 44 both at the time of processing and at the time of non-processing.

The end plate 48 has a cylindrical main body portion 48a, and a flange portion 48b protruding in the radial direction at one end of the main body portion 48 a. The end plate 48 is formed with a center hole 48c passing through the rotation shaft 38. When the end plate 48 is fitted into the recess 42d of the roller body 42, the elastic ring 44 fitted to the outer peripheral surface of the roller body 42 is sandwiched between the flange portion 42c of the roller body 42 and the flange portion 48b of the end plate 48. Thereby, the elastic ring 44 is prevented from moving and disengaging in the axial direction with respect to the roller main body 42.

The second roller 32 is attached to a rotation shaft 52, and the rotation shaft 52 is rotatably supported by a コ -shaped bracket 50. The carriage 50 is movably provided along the guide 59 in the direction indicated by the arrow a. The stud 54 is fixed to the bracket 36, penetrates through a hole (not shown) of the bracket 50 with a gap therebetween, and a coil spring 56 is disposed around the stud 54. The bracket 50 is biased in a direction away from the bracket 36 by a coil spring 56. The bracket 50 may be fixed by a pin 58 as a fixing mechanism in a state of being separated from the bracket 36 by an arbitrary distance. Specifically, the pin 58 is formed to penetrate through the bracket 50 and to be in contact with the outer periphery of the stud 54 penetrating into the bracket 50, so that the position of the bracket 50 can be fixed when the pin 58 is rotated. In the process of replacing the processing belt, when the processing belt is removed, first, the pins 58 are released from the fixation, the holder 50 is brought close to the bracket 36 along the guides 59, the pins 58 are fixed, and the processing belt 34 is released from the stretched state of the processing belt 34, and then the processing belt 34 can be removed from the first roller 40 and the second roller 32. In the case of attaching the processing belt 34, when the processing belt 34 is attached to the first roller 40 and the second roller 32 with the processing belt 34 removed, the mounting of the processing belt 34 is completed by separating the holder 50 from the bracket 36 by the elastic force of the coil spring 56 when the fixing of the pin 58 is released, and thus, the processing belt 34 is in the stretched state, and further, the position of the holder 50 is fixed by the pin 58. With these configurations and working steps, the replacement work of the belt can be performed regardless of the proficiency of the operator, and the tension of the working belt 34 can be set.

The rotation power generation unit 60 has a rotation motor. The rotary motor may be an electric motor, but is preferably a fluid motor, in particular an air-pressure motor provided with a turbine (not shown in the figures). The air pressure motor as the rotational power generating portion 60 has a turbine housing 62, and the turbine housing 62 forms a housing 64 that rotatably houses a turbine, and a fluid inlet 66 that communicates with the housing 64. The fluid inlet 66 communicates with the fluid supply passage. In the present embodiment, the fluid inlet 66 communicates with the central holes 12a, 28c of the holding portion 12 and the joint portion 28.

The power transmission unit 70 includes a first pulley 72, a second pulley 74, a drive belt 76 stretched between the first pulley 72 and the second pulley 74, and a tensioner 78. The first pulley 72 is mounted to the output shaft 68 so as to rotate together with the output shaft 68 as an air pressure motor of the rotational power generation portion 60, and the first pulley 72 forms an input pulley. The second pulley 74 is mounted to the rotary shaft 38 so as to rotate together with the rotary shaft 38 for the first roller 40. The drive belt 76 may be a toothed belt or a toothed belt. In the case where the drive belt 76 is a toothed belt or a toothed belt, the first pulley 72 and the second pulley 74 are formed of toothed pulleys having a plurality of teeth that mesh with the teeth of the drive belt 76. The drive belt 76 is tensioned between the first pulley 72 and the second pulley 74 by a tensioner 78, and the tensioner 78 has a dancer 78a engaged with the back surface of the drive belt 76.

When clamping the tape processing apparatus 10 into the tapered bore of the spindle 114 of the work machine 100, the fluid supply passages 12a, 28c communicate with the fluid passage of the drawbar of the clamping apparatus. Fluid from a fluid supply source, such as pressurized air or a cooling medium, is supplied to the housing 64 through the fluid passage of the tie rod of the tool clamping device of the spindle, the fluid supply passages 12a, 28c of the belt processing device 10, and the fluid inlet 66 of the fluid motor as the rotational power generating portion 60, so that the turbine disposed in the housing 64 is rotated.

The rotation is transmitted to the rotary shaft 38 via the first pulley 72, the driving belt 76, and the second pulley 74 attached to the output shaft 68 of the fluid motor, and the first roller 40 serving as the pressure roller is rotated, whereby the processing belt 34 stretched between the first roller 40 and the second roller 32 is driven. During this time, the first roller 40 functions as a driving roller, and the second roller 32 functions as a driven roller. In this way, while the processing belt 34 is driven to circulate between the first roller 40 and the second roller 32, the first roller 40 is pressed against the surface of the workpiece W with the processing belt 34 interposed therebetween, and the spindle 114 and the table 104 are moved relatively, whereby the surface of the workpiece W is processed (polished or ground).

By disposing the elastic ring 44 as an elastic body on the outer peripheral portion of the first roller 40 as a processing roller, it is possible to obtain a good processing surface by absorbing, with the elastic body, mounting misalignment of the processing roller, relief shape of the workpiece surface to be processed, or the like, which is a problem in processing, without generating a special program, and by moving the belt processing device along the surface to be processed of the workpiece W in accordance with a processing program (NC program) conforming to the design shape. Further, an expansion preventing member 46 is embedded in the elastic ring 44, and prevents the elastic ring 44 from expanding and deforming in the radial direction due to centrifugal force during rotation of the first roller 40. That is, the problem that the work W is adversely affected by the application of an undesired tensile force to the processing belt 34 and the problem that the elastic ring 44 expands at a portion that does not engage with the processing belt 34 and interferes with each portion of the main body 20 can be solved by the expansion preventing member 46.

In the above embodiment, the expansion preventing member 46 is an annular member, two arcuate members, or three arcuate members, for example, made of a resin sheet, which are disposed in the slit 44a, and the slit 44a is formed at a predetermined depth in the radial direction from each outer peripheral surface of the elastic ring 44, is formed at a predetermined width (axial dimension) in the axial direction, and extends in the circumferential direction, but the present invention is not limited thereto. In the present invention, the expansion preventing member may prevent the elastic body disposed on the outer peripheral portion of the processing roller from expanding and deforming in the radial direction due to centrifugal force during rotation of the processing roller.

Fig. 7 shows a first roller 120 as a modification of the processing roller. The first roller 120 of the present embodiment is substantially the same as the first roller 40 of the above embodiment except that the elastic ring and the expansion preventing member as an elastic body are different from the expansion preventing member 46 of the above embodiment.

In fig. 7, the elastic ring 124 has slits 124a extending in the circumferential direction. The slit 124a is formed at a predetermined depth from both side surfaces on opposite sides in the axial direction of the elastic ring 124 and at a predetermined width (radial dimension) in the radial direction. The slits 124a are fitted with expansion preventing members 126a, 126b, and the expansion preventing members 126a, 126b prevent the elastic ring 124 from expanding and deforming in the radial direction due to the centrifugal force caused by the rotation of the first roller 120.

The expansion preventing members 126a and 126b may be, for example, annular members made of resin sheets. Alternatively, the expansion preventing members 126a and 126b may be two arcuate members that divide the annular member into two along the diameter, or three arcuate members that divide the annular member into three so that the center angle is 120 °. The expansion preventing member 126a is disposed in the slit 128d of the flange portion 128b of the end plate 128 and the slit 124a formed on the side surface of the elastic ring 124 facing the slit 128d, the expansion preventing member 126b is disposed in the slit 124a of the facing side surfaces of the two elastic rings 124, and the expansion preventing member 126c is disposed in the slit 122e of the flange portion 122c of the roller main body 122 and the slit 124a of the side surface of the elastic ring 124 facing the slit 122 e.

The first roller 120 of fig. 7 also functions in the same manner as the first roller 40 of the above embodiment.

Since the spindle 114 can be moved and positioned relative to the workpiece W in three orthogonal directions of the X axis, the Y axis, and the Z axis, and can be positioned at an angular position about the rotation axis O, the workpiece W can be belt-processed by the work machine 100 and the belt processing device 10, and a polishing finish surface or a polishing finish surface having polishing marks or polishing marks parallel to an appropriate tool feed direction can be formed on a precise sealing surface provided in a vacuum chamber or the like. Further, by providing the work machine 100 with a tool changing device, it is possible to integrate a machining process other than grinding or lapping by the belt machining device 10 into a machining process by the work machine 100. Further, by using a fluid motor or an air motor as the rotary motor, the belt processing device 10 can be driven by a fluid supply source that is provided in the machine tool 100 to supply a cooling medium, pressurized air, or the like, for lubrication or cooling, and therefore, a new drive source for the belt processing device 10 is not required.

In the above, the embodiment in which one or two expansion preventing members are mounted on one elastic ring has been described, but in the case where it is desired to strongly prevent expansion of the elastic ring due to centrifugal force or the like, a structure in which more expansion preventing members are mounted may be made as needed.

Description of the reference numerals

10-band processing device

12 holding part

20 main body part

30 belt driving part

32 second roller

34 processing belt

40 first roller

44 elastic ring

46 expansion preventing member

58 pin

60 rotation power generating part

70 power transmission part

100 work machine

Claims

1. A tape processing apparatus for relatively moving a processing tape with respect to a workpiece to process the workpiece, comprising:

a first roller as a processing roller;

a second roller;

a processing belt supported by the first roller and the second roller;

a rotational power generation unit that rotates the first roller or the second roller;

an annular elastic body mounted on the outer periphery of the first roller; and

and an annular expansion preventing member attached to the elastic body, wherein the elastic modulus of the expansion preventing member is larger than that of the elastic body.

2. The belt processing apparatus according to claim 1, wherein a portion of the processing belt engaged with the first roller contacts a surface of a workpiece, and processes the surface of the workpiece.

3. The belt processing apparatus according to claim 1 or 2, wherein the rotation power generation portion has a fluid motor.

4. A belt processing apparatus as claimed in claim 3, wherein the fluid motor is an air pressure motor.

5. The belt processing apparatus according to claim 1, further comprising a holding portion attachable to a spindle end portion of a machine tool, the machine tool comprising: the main shaft; a work table disposed facing the spindle for fixing a workpiece; and a feeding device which moves the spindle and the table relatively.