JPH0350142B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a friction drive device for a rotating body that transmits rotational force between two shafts, and particularly to a rotating body suitable for driving electronic equipment such as a cassette tape recorder. The present invention relates to a friction drive device. BACKGROUND TECHNOLOGY AND PROBLEMS In cassette tape recorders and the like that have conventionally adopted a disk drive system, the direction of the rotation axis of the friction wheel on the drive side does not coincide with the center of rotation of the rotating body on the driven side. Subtle positional deviations resulted in subtle speed irregularities, which subtly affected wow and flatta. Furthermore, as this positional relationship becomes even more subtle due to deformation once rotation begins, it is better to shift the position slightly from the normal position during assembly, and it is extremely difficult to adjust this position correctly during assembly. Therefore, in the past, only assembling was carried out according to the specifications without any adjustment, and those with bad wow and flutter were discarded at the final inspection. However, this has a poor yield, and even if it passes, it is not necessarily the best wah
It was difficult to say that it was a flat-out situation.

Purpose of the Invention The present invention has been made in view of the above-mentioned circumstances, and its purpose is to reduce the friction of a rotating body with extremely little speed unevenness by which the position between the friction wheels can be finely adjusted and the best wow, flutter, etc. can always be expected. The purpose is to provide a driving device.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a friction drive device for a rotating body, which includes a rotating body and a motor having a friction wheel that contacts the rotating body and transmits rotational force. A motor support member is provided at the front and rear ends to rotatably support the motor via one fulcrum pin, and each one of the fulcrum pins supports the motor or motor in a direction substantially parallel to the axis of the motor. The fulcrum pins are provided in a protruding manner on the support member and are arranged at opposite positions on the left and right sides with respect to the axis of the motor, and a straight line connecting the support points of the pair of fulcrum pins passes approximately through the center of gravity of the motor. In addition, a movable adjustment plate having a fulcrum pin on the front end side of the motor is provided, and the adjustment plate allows the rotation body to be adjusted around the support point on the rear end side of the motor and in contact with the friction wheel. Rotation provided with a fine adjustment mechanism that moves a fulcrum pin on the front end side of the motor approximately parallel to the contact surface, thereby making the direction of the rotation axis of the friction wheel eccentric with respect to the radial direction of the rotary body. It is a body friction drive device.

With the above configuration, the friction drive device for a rotating body according to the present invention allows fine adjustment of the position between the friction wheels, and provides drive with extremely little speed unevenness, where the best wow, flutter, etc. can always be expected. It is possible.

Embodiment An embodiment in which the present invention is applied to a tape drive device of a cassette tape recorder will be described below with reference to the drawings.

First, the outline of the tape drive device will be explained with reference to FIG. This tape drive device is provided on the back side of the cassette mounting surface of the mechanical board 1. Therefore, in FIG. 1, the supply reel shaft 2, take-up reel shaft 3, and capstan 4 are projected below the mechanical board 1, and these drive shafts are supported by the mechanical board 1 and project upward. .

A motor 5 is supported on the mechanical board 1 by a motor support member 6 provided on the board 1.
A motor pulley 8 fixed to the motor shaft 7 of the motor 5 is connected to a capstan pulley 9 fixed to the upper end of the capstan 4 which also serves as a flywheel.
The capstan 4 is pressed from below to drive the capstan 4 by friction. Further, on the upper part of the mechanical board 1, there is a drive gear support shaft 10 located approximately midway between the supply reel shaft 2, the take-up reel shaft 3, and the capstan 4; A conversion gear support shaft 11 is vertically mounted at an intermediate position between the two.

At the bottom of the capstan pulley 9, a capstan gear 12 made of a wide gear is fixed to the capstan pulley 9. Further, the drive gear support shaft 10 has first and second drive gears 13 and 14.
A clutch mechanism (not shown) is interposed between these parts, and these parts are respectively movable in the direction of the rotational axis and rotatably mounted. The second drive gear 14 is coupled to the first drive gear 13 by the clutch mechanism, and the first drive gear 13 drives the second drive gear 14 to rotate on the same axis. The second drive gear 14 is configured to be able to stop rotating during this rotational drive according to the load applied thereto.

A conversion gear 15 constituted by a wide gear is rotatably attached to the conversion gear support shaft 11 so as to be movable in the direction of the rotation axis. The wide gear 15 is biased upward in FIG. 1 by a compression spring (not shown). Further, a supply reel shaft gear 16 configured as a wide gear is attached to the upper part of the mechanical board 1 of the supply reel shaft 2.
Further, a first
and second take-up reel shaft gears 17, 18 are attached.

The first drive gear 13 is always meshed with the capstan gear 12, and is moved in the direction of the rotation axis to connect the conversion gear 15 and the first take-up reel shaft gear 1.
7 and is configured to be selectively engaged with. Further, the conversion gear 15 is always meshed with the supply reel shaft gear 16 and is configured to be moved in the direction of the rotation axis. Further, the second drive gear 14 is configured to mesh with and disengage from the second supply reel shaft gear 18 by movement in the direction of the rotation axis.

On the other hand, an operation plate support shaft 19 is vertically fixed to the upper part of the mechanical board 1. And this operation plate support shaft 1
A first operation plate 21 is attached to 9 via a sleeve 20 that is slidable in the axial direction, and its tip 21a is engaged with an annular groove provided in the boss of the first drive gear 13. and is configured to move up and down together with the first drive gear 13. Further, a second operation plate 22 is attached between the sleeve 20 of the operation plate support shaft 19 and the first operation plate 21. This second operation plate 22 is made of a leaf spring, and its tip 22a is fitted into the conversion gear support shaft 11 and is in close contact with the upper surface of the conversion gear 15.

The play button (playback button) 23 is configured to press the tip 22a of the second operation plate 22 to move the conversion gear 15 downward, and the fast forward button 24 is configured to press the tip 22a of the second operation plate 22 to move the conversion gear 15 downward. Push to move these to the lowest position, and move the first drive gear 13 to the first
It is configured to mesh with the take-up reel shaft gear 17 of. Further, the rewind button 25 is located on the first operation panel 2.
1 to move it to an intermediate position and engage the first drive gear 13 with the conversion gear 15.
It is configured to release the lock at the forward movement position and return them to their respective states.

In FIG. 1, reference numeral 27 is a reproducing head provided on the back side of the mechanical board 1, and the magnetic tape (not shown) is transferred from the supply reel provided on the supply reel shaft 2 to the front part 27a of the reproducing head 27. The film passes between the pinch roller 28 and the capstan 4, and is wound onto a take-up reel provided on the take-up reel shaft 3.

Next, an outline of the tape drive operation of the tape drive device configured as described above will be explained based on FIG. 1 as well.

In the stopped state, the first and second drive gears 13,1
4 is at the highest position, the second drive gear 14 meshes with the second take-up reel shaft gear 18, and the first drive gear 13 is connected to the conversion gear 1 with a predetermined gap.
It is located above 5.

When the play button 23 is pressed in the above-mentioned stopped state,
The conversion gear 15 is pushed downward and the first drive gear 1
3 and the conversion gear 15 becomes larger, and since the motor 5 rotates in the direction a in the figure, the capstan 4 is rotationally driven in the direction b, and the capstan gear 12, the first drive gear 13, the clutch mechanism, and the second The take-up reel shaft 3 is rotationally driven in the d direction through the drive gear 14 and the second take-up reel shaft gear 18 to obtain a playback state (FWD tape drive state).

Next, when the fast forward button 24 is pressed in the stopped state, the first and second operation plates 21 and 22 are pushed down to the lowest position, and the first and second drive gears 13 and 14 are also pushed down to the lowest position. be pushed down to.
That is, the second drive gear 14 and the second take-up reel shaft gear 18 are disengaged, and the first drive gear 13 and the first take-up reel shaft gear 17 are brought into mesh. Note that the first drive gear 13 and the conversion gear 15 move while maintaining the same gap, so they do not mesh with each other. Therefore, by locking the fast forward button 24 at the forward movement position, the capstan gear 12 and the first drive gear 1
3 and the first take-up reel shaft gear 17, the take-up reel shaft 3 is rotationally driven in the d direction to obtain a fast forward state (FF running drive state of the tape).

Furthermore, when the rewind button 25 is pressed in the stopped state, the first operation plate 21 is pushed down to the intermediate position, and the first and second drive gears 13 and 14 are accordingly moved to the intermediate position. Then, the second drive gear 14 and the second take-up reel shaft gear 18 disengage, the first drive gear 13 and the first take-up reel shaft gear 17 do not mesh, and the first The drive gear 13 meshes with the conversion gear 15. Therefore, by locking the rewind button 25 in its forward movement position, the capstan gear 12 and the first drive gear 1
3. The supply reel shaft 2 is rotationally driven in the f direction via the conversion gear 15 and the supply reel shaft gear 16, and a rewinding state (REW running driving state of the tape) is obtained.

Next, details of the motor support structure will be explained with reference to FIGS. 2 to 7.

As shown in FIG. 3, cylindrical anti-vibration rubber 30 shown in FIG. 5 is press-fitted into both ends of the motor 5 and integrated with the motor 5, and its outer periphery is covered with a shield plate 31. There is. A motor rear side plate 32 is integrally attached to the boss portions of the vibration isolating rubber 30 at both ends of the motor 5 at the rear of the motor, and a front side plate 34 of a motor mounting member 33 is integrally attached to the front of the motor. . That is, the boss portion of the vibration isolating rubber 30 is formed of a toothed portion 30a in which a radial toothed portion is formed on the circumference and a circular portion 30b. The inner diameters of the holes 32a and 34a are slightly smaller than the outer diameter of the circular portion 30b. When the toothed portion 30a is press-fitted, the toothed portion 30a is deformed and the side plates 32, 34 are fixed to the toothed portion 30a, and the circular portion 30b becomes a flange and falls from the circular portion 30b as if it had been fitted into an annular groove. It is prevented from coming off. Also, motor rear side plate 3
A fixing pin 35 is provided at a predetermined position of 2, which is integral with this side plate 32 and is substantially perpendicular thereto. On the other hand, the motor mounting member 33 also has a rear connecting plate 36 on the rear side that is substantially parallel to the front side plate 34, and this rear connecting plate 36 connects the front side plate 34 and the connecting member 37
are connected together in a U-shape. Then, as described above, with the motor rear side plate 32 and the front side plate 34 fixed to the anti-vibration rubber, the rear connecting plate 36
is arranged on the outside of the motor rear side plate 32, and an engagement piece 36a having a semicircular engagement groove 36c is engaged with the fixing pin 35. And the through hole 3 of the connecting plate 36
6b is inserted into the female screw hole 32b of the motor rear side plate 32, the motor rear side plate 32 and the motor mounting member 33 are connected.
Eventually, as shown in FIG. 4, the motor 5 becomes a rigid integral structure with these members, and the fixing pin 35 becomes substantially parallel to the motor shaft 7. An arm 39 is provided on the left side of the front side plate 34 of the motor in a substantially horizontal direction, and a spring receiver 40 is provided at the tip of the arm 39 . Also, a through hole 41 is provided in the corner.

As shown in FIG. 3, the motor support member 6 is composed of a fixing member 43 fixed to the mechanical board 1 and an adjustment plate 44. The fixing member 43 includes a horizontal member 45 bent at right angles on the right side, and a leg portion 46 on the right side that supports this horizontal member 45 on the mechanical board 1.
, a substantially horizontal protruding member 47 protruding from the rear end of the horizontal member 45 at right angles to the motor side, a short horizontal member 48 on the left side, a leg portion 49 on the left side supporting this, and horizontal members 45 on the left and right sides. , 48 and a connecting member 50 that connects them. The fixing member 43 supports the motor 5 integrated with the motor mounting member 33, and is fixed at a predetermined position on the mechanical board 1 by screws inserted through the screw holes 51 of the legs 46, 49. A through hole 52 into which the pin 35 is inserted is formed in the protruding member 47 at a position corresponding to the fixing pin 35 of the motor rear side plate 32, and an L-shaped notch is formed in the front side of the horizontal member 45. A hole 53 is provided. Further, two elongated holes 54 and 55 are formed in the left leg 49 at the top and bottom, and a threaded hole 57 into which an adjustment screw 56 is screwed is provided approximately in the center of the elongated holes 54 and 55. A large opening 58 is formed into which the arm 39 of the motor front side plate 34 can fit.

A through hole 60 through which the motor shaft 7 and motor pulley 8 pass is provided in the center of the adjustment plate 44, and a through hole 41 in the motor front side plate 34 is provided at the corner.
At a position corresponding to , a fixing pin 61 that is fitted into the through hole 41 is provided substantially perpendicularly and integrally with the side plate 34 . On the right side, there is a vertical elongated hole 53a of the L-shaped notch hole 53 of the horizontal member 45.
A guide piece 62 with a rectangular cross section that is fitted into the elongated hole 53a and is slidable in the elongated hole 53a is protruded almost horizontally. A protrusion 63 is provided. Further, on the left side, two guide pieces 64, 65 having a rectangular cross section are fitted into the long holes 54, 55 and slidable at positions corresponding to the long holes 54, 55 of the leg portion 49.
is protruded almost horizontally.

Next, in order to attach the motor 5 to the motor support member 6, the compression coil spring 6 is attached to the guide piece 62 of the adjustment plate 44.
6, and fit the guide pieces 62, 64, 65 into the corresponding elongated holes 53a, 54, 55, respectively. The motor 5 integrated with the motor mounting member 33
Adjustment plate 44 and motor support member 6 fixing member 43
The fixing pins 35 and 61 are inserted into the corresponding through holes 52 and 41 by using the elastic force of the protrusion members 47 to slightly open the protrusion members 47. and adjustment screw 5
6 into the screw hole to adjust the motor pulley 8 to a predetermined position. On the other hand, the arm 39 of the motor front side plate 34
By tensioning a predetermined tension coil spring 67 between the spring receiver 40 and the through hole 51 of the leg portion 49, the assembly is completed as shown in FIG. At this time, fixing pin 6
1 is substantially parallel to the motor shaft 7. That is, the motor 5 is integrated with the motor mounting member 33 and rotatably supported on the motor support member 6 via fixing pins 35 and 61, and is further pivoted about the fixing pins 35 and 61 by a tension coil spring 67. Forced to rotate.

As shown in FIG. 9B, the fixing pins 35 and 61 are located at opposite positions inclined at approximately 45 degrees to the left and right with respect to the motor axis O, and are arranged at equal distances from the axis O, respectively. .

Next, the capstan pulley 9 will be explained based on FIG.

The capstan 4 is rotatably supported by a bearing 69 fixed on the mechanical board 1. The capstan pulley 9, which is disc-shaped and has an annular recess formed in the middle part, is fixed to the upper end of the capstan 4 as described above, and the wide capstan gear 12 is fixed to the lower part of the capstan pulley 9. . The capstan gear 12 is rotatably driven together with the capstan pulley 9 while being pivotally supported on the outer peripheral surface of the bearing 69. On the lower surface side of the outer periphery of the capstan pulley 9,
An annular rubber member 70 whose contact surface is formed into a gentle conical shape is fixed, and the contact surface of the motor pulley 8 that is pressed against this surface is also formed into a conical shape with the same inclination angle. Further, fixed to the annular recess of the capstan pulley 9 is an annular rotor member 72 made of a magnetic material and having a large number of teeth 71 formed at the same pitch in the radial direction on its inner surface.

On the other hand, on the fixed side, also in the annular recess,
Teeth 73 with a pitch corresponding to the teeth 71 on the opposing surface while maintaining a predetermined gap with the teeth 71 of the rotor member 72
A stator member 74 made of a magnetic material and formed with
is provided. And this stator member 74
An annular magnet 75 is provided in the
This magnet is magnetized, for example, with an N pole on the upper surface side and an S pole on the lower surface side, and forms a magnetic path between the rotor member 72 and the stator member 74. Therefore, during rotation, the change in magnetic flux between the uneven portion formed by the teeth 71 on the rotor side and the uneven portion formed by the teeth 73 on the stator side is extracted as an output signal, and is used as a frequency generator. Speed detection is now being performed. The stator member 74 is integrally coupled with a support plate 77 (see FIG. 1 for the shape) via a center member 76, and is fixed to a support 78 vertically provided on the mechanical board 1 with a pin 79.

Reference numeral 80 is a pivot bearing made of Teflon or the like, with a thread on the outer periphery, and a conical recess (80a) formed in the center of the shaft. The rotor member 7 is supported by the top portion 4a and holds the stator side in the correct position relative to the axis of the capstan 4.
The gap between the teeth 71 of No. 2 and the teeth 73 of the stator member 74 is maintained correctly over the circumference. That is, in order to incorporate the stator part, the capstan pulley 9
Using the outer circumferential surface 81 of the circular boss at the center as a reference surface, the inner surface 82 of the circular recess of the stator section is inserted, and the support plate 77 is set with screws 79. Then, when the pivot bearing 80 is screwed in after this, the pivot bearing 80
Since the conical recess 80a is screwed along the conical top 4a of the capstan 4, the axis of the pivot bearing 80 is precisely aligned with the axis of the capstan 4. Therefore, the stator member 74 integrated with the pivot bearing 80 also has the central member 76 and the support plate 7.
7 and is finely adjusted to match the axis of the capstan 4.

Next, the effects of the motor and motor pulley configured and supported as described above will be explained.

In FIGS. 9A and 9B, the motor 5 (including the motor mounting member 33 integrated therewith) is rotatable at the front by the fixing pin 61 and at the rear by the fixing pin 35, respectively. is supported by Therefore, the load shared by the fixing pins 61 and 35 out of their own weight W is W ₁ and W _{2 ,} respectively.
As shown in FIG. 9B, the motor 5 is rotated clockwise at the front with a moment W ₁ m ₁ and rotated counterclockwise at the rear with a moment W ₂ m ₂ . However, since the fixing pins 35 and 61 are at opposite positions inclined to the motor axis O, and are equidistant l from the motor axis O, m ₁ = m ₂ , and the motor 5 is the motor support. Since the straight line connecting the support points R and S of the pins 35 and 61 supported by the member 6 passes approximately through the center of gravity of the motor 5 in FIG. 9A, W ₁ =W ₂ =W/2. Therefore, since W ₁ m ₁ = W ₂ m ₂ , the motor 5
does not rotate due to its own weight. However, since the motor 5 is rotatably supported by the fixed pins 35 and 61, it can be rotated about these pins 35 and 61 by external force.

Next, the friction drive by the motor pulley 8 will be explained. As described above, in FIG. 6, the arm 39 of the motor front side plate 34 is urged downward by the tension coil spring 67. As shown in FIG. Therefore, the motor 5, that is, the motor pulley 8 is urged to rotate in the g direction about the fulcrum 61 in FIG. 10, and is pressed against the rubber member 70 of the capstan pulley 9. With this initial contact pressure, the motor pulley 8 moves in the same direction a as shown in Figure 1.
When is rotated, the motor pulley 8 attempts to rotate the capstan pulley 9 in the direction b by a rotational force P commensurate with this initial contact pressure. reaction force
P' acts in the i direction opposite to b. This reaction force
Since P′ is the force that tries to move the motor shaft 7 in the i direction, the product of its tangential component P″ and the radius l
With a moment of P″・l, the motor pulley 8 is
In Figure 0, it is rotated about a fulcrum 61 in the direction of arrow g. That is, this rotational force causes the motor pulley 8 to be pressed against the capstan pulley 9 with a contact pressure greater than the initial contact pressure, so that the rotational force P becomes even larger. The frictional force that grows as this process progresses is the capstan pulley 9.
When the load reaches , the capstan pulley 9 begins to rotate and enters a steady operating state.

In other words, even if the initial contact pressure is small, if it is the minimum necessary to prevent slipping, the motor pulley 8 will automatically bite into the contact surface of the capstan pulley 9, so the contact pressure will gradually increase and the pressure will be adjusted to match the load. As the contact pressure increases, the capstan pulley 9 is driven to rotate. For example, the cassette tape recorder of this embodiment, which conventionally required a contact pressure of 90 to 100 g, now requires an initial contact pressure of 20 to 30 g. Note that the angle α in Figure 10 is 120 to 150.
degree is the most effective.

Furthermore, in this embodiment, as described above, since the motor is supported so as not to rotate under its own weight, the initial contact pressure is not affected by the motor's own weight. Therefore, since a highly accurate initial contact pressure can be applied, this initial contact pressure can be reduced to the necessary minimum.

Next, the fine adjustment function of the fine adjustment mechanism will be explained.

Adjustment plate 4 of motor support member 6 as shown in FIG.
4 has its arms 62, 64, 65 slidably supported in the elongated holes 53a, 64, 65 of the fixed member 43 of the motor support member 6, respectively, as described above, and is supported by a compression coil spring 66 on the left side. It is configured so that it can be finely adjusted horizontally to the left and right (in the y direction) using an adjustment screw 56. On the other hand, this adjustment plate 4
4, the motor 5 is connected to the motor mounting member 3 by the pin 61 fixed to the adjustment plate 44 as described above.
It is rotatably supported together with 3. Therefore, the adjusting screw 56 moves the adjusting plate 4 from the position shown by the solid line in FIG. 7 to the rightward position shown by the dashed line.
4 is slightly moved, the fixing pin 61 moves horizontally to the right by this fine adjustment amount. However, as described above, the motor 5 is supported by the fixed pins 35 and 61, and the rear fixed pin 35 does not move. Therefore, when the support point S of the front fixed pin 61 moves, the motor 5 is supported by the rear fixed pin 35. It will rotate to the right around the support point R. Therefore, the center shaft of the motor also rotates in accordance with this amount of fine adjustment. For example, the motor shaft center is offset by x with respect to the center Q of the capstan pulley 9, and the motor pulley 8 is set at this eccentric position. Ru. That is, after assembly, the magnetic tape can be run, and the motor pulley 8 can be set at a position that provides the best wow and flutter value by adjusting the motor pulley 8 left and right with the adjustment screw 56 while looking at the pointer of the measuring instrument.

Effects of the Invention As explained above, the friction drive device for a rotating body according to the present invention is provided with a fine adjustment mechanism that can vary the position of the friction wheel with respect to the rotating body.
After assembly, for example, run a magnetic tape and finely adjust the position of the friction wheel while looking at the pointer of the measuring device. For example, place the friction wheel at the position that shows the best wow and flutter value, that is, the best position with the least speed unevenness. can always be set. Further, although this adjustment requires more adjustment man-hours than the conventional non-adjustment method, it is advantageous in that it improves yield and ultimately reduces costs.

[Brief explanation of drawings]

The figures show an embodiment in which the present invention is applied to a tape drive device of a cassette tape recorder. 3 is an exploded perspective view of the same figure as above, FIG. 4 is a perspective view of the motor support member in FIG. 2 with the fixing member removed, and FIG. 5A is a perspective view of the motor. A vertical cross-sectional view of the anti-vibration rubber, Figure 5B is B in Figure 5A.
-B line arrow sectional view, Figure 5C is C-C in Figure 5A
6 is a sectional view taken along the - line in FIG. 2, FIG. 7 is a sectional view taken along the - line in FIG. 2, and FIG.
The figure is a vertical sectional view of the capstan pulley, and Figures 9A and 9B are principle explanatory diagrams of the motor support structure.
Figure A is a side view of the motor support structure, Figure 9B is a front view of the same as above, Figure 10 is a diagram explaining the principle of the friction drive unit and is a front view of the drive unit seen from the motor pulley side, Figure 11
The figure is an explanatory diagram of the fine adjustment mechanism and is a schematic top view of the motor support structure. In addition, in the symbols used in the drawings, 5...Motor, 6...Motor support member, 8...Motor pulley (friction wheel), 9...Capstan pulley (rotating body), 33...Motor mounting member, 35 ...Fixing pin, 43...Fixing member, 44...Adjustment plate (fine adjustment mechanism), 56...Adjustment screw (fine adjustment mechanism), 61...
...fixing pin, 66...compression coil spring (fine adjustment mechanism).

Claims (1)

[Claims] 1. In a friction drive device for a rotating body, which includes a rotating body and a motor having a friction wheel that contacts the rotating body and transmits rotational force, a friction drive device for a rotating body includes one fulcrum pin at each of the front and rear ends of the motor. A motor support member for rotatably supporting the motor is provided, and each of the fulcrum pins is provided protruding from the motor or the motor support member approximately parallel to the axis of the motor, and is connected to the axis of the motor. The straight line connecting the support points of the pair of fulcrum pins is configured to pass approximately through the center of gravity of the motor, and the fulcrum pin is located on the front end side of the motor. A movable adjustment plate is provided, and the adjustment plate allows the adjustment plate to adjust the support point on the front end side of the motor approximately parallel to the contact surface of the rotating body that contacts the friction wheel, with the support point on the rear end side of the motor as the center. A friction drive device for a rotating body, comprising a fine adjustment mechanism that moves a pin, thereby making the direction of the rotating shaft of the friction wheel eccentric with respect to the radial direction of the rotating body.