JP3133543B2 - Driving force transmission mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary driving force transmitting mechanism in a magnetic recording / reproducing apparatus such as a video tape recorder (VTR) and a digital audio tape recorder (DAT).

[0002]

2. Description of the Related Art As shown in FIG. 5, a rotary driving force transmitting mechanism in a mechanism of a magnetic recording / reproducing apparatus such as a VTR or a DAT is used to control the rotation of a capstan motor 1 by a toothed belt 2.
Is transmitted to the reel bases 3 and 4 via the. The toothed belt 2 has a rack formed on the inner periphery thereof, so that the driving force is transmitted without slipping due to meshing with the gears 5, 6, 7.

However, since the toothed belt 2 moves up and down a little during rotation as well as the flat belt and the square belt, flanges 5a and 5b are provided above and below the gear 5 as shown in FIG. , To prevent the belt from coming off. The same applies to the gears 6 and 7.

[0004]

When a gear with upper and lower flanges is cut, a method of attaching a separately processed flange to the gear is used. Alternatively, when formed by molding, as shown in FIG.
And a flange 9 in which the flange 8b and the boss 8c are integrally formed, and a flange 9, and the flange 9 is fixed to the boss 8c by means of ultrasonic welding or the like.

[0005] However, the process of fixing the flange 9 is inferior in workability.
The height and diameter of c cannot be designed to a sufficient size, causing a problem in the welding operation.

[0006]

Therefore, in the present invention, as a rotational driving force transmission mechanism of a magnetic recording / reproducing apparatus in which torque is transmitted via a toothed belt, a gear meshing with the toothed belt is constituted by a chassis (or bracket). A shaft fixed to the shaft, a flanged gear rotatably mounted on the shaft, and contacting the end of a toothed belt inserted through the shaft.
The thrust washer is separated from the thrust washer, and a slip torque between the thrust washer and the edge is set to be larger than a slip torque between the thrust washer and a chassis (or a bracket).

[0007]

According to the above construction, the toothed belt does not come off the gears during driving of the driving source, and the rotational driving force is transmitted stably.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of the present invention will be described below with reference to the drawings. 1 to 4 are an assembled sectional view of a flanged gear of the present invention and an assembled sectional view of another different embodiment.

First, prior to the description of a specific embodiment of the present invention, the overall mechanism will be schematically described with reference to FIG. In the figure, a gear 1a is formed on the outer periphery of the rotor of the capster motor 1, and a gear
And a gear 6g coaxially integrated with the gear. The toothed belt 2 meshes with the flanged gear 6, and transmits rotational power to the driven-side flanged gear 7. Further, a gear 5 with an idler flange, which is rotatably mounted on the bracket 10, is provided for adjusting the tension of the toothed belt 2, and is fixed to a chassis 12 with a screw 11 at an appropriate position.

The driven side flanged gear 7 includes a relay gear 7
The rotation of the driven side flanged gear 7 is coaxially formed with the gear g, and transmitted to the gears 3g, 4g of the reel bases 3, 4 via the swinging gear 13. 14 is a capstan, 15 is a pinch roller, 16 is a cylinder, 17a, 17b, 18
Reference numerals a and 18b denote tape guide posts on the supply side and the winding side, respectively, and 19 denotes a tape.

In the configuration of the above-described mechanism, the flanged gear 5 among the configurations of the flanged gears 5, 6, 7 of the present invention will be described with reference to FIG. The flanged gear 21 has an upper flange 21a integrally formed, but does not require the boss 8c shown in FIG. 6 (conventional example). The gear 21 is rotatably meshed with the toothed belt 2 on a shaft 22 integrally formed with a seat 22 a fixed to the bracket 10. In place of the lower flange of the gear 21, a thrust washer 23 as described below is provided on the seat 22.
It is rotatably fitted to the part a. Numeral 24 is a washer for retaining.

The washer 23 has an inner diameter slightly larger (about 0.05 to 0.1 mm) than the outer diameter of the seat 22a.
The outer diameter is approximately the same as that of the upper flange 21a, and the thickness thereof is
It is preferable that the thickness is slightly (about 0.05 mm) smaller than the thickness of a. The surface lubricity of the washer 23 is determined by the bracket 1
It is assumed that the sliding resistance with the lower end surface of the toothed belt 2 is greater than the sliding resistance with 0 (or the chassis 12).

By using such a washer 23, when the toothed belt 2 is lowered downward in the drawing, the sliding resistance between the lower end surface of the belt 2 and the washer 23 causes the toothed belt 2 (and the flanged belt 2). The gear 21) and the thrust washer 23 rotate at substantially the same number of rotations, and act as a lower flange. Conversely, when the toothed belt 2 is lifted upward, the washer 23 is stationary without receiving any sliding resistance.

The sliding resistance will be described in more detail.
The value of the sliding resistance in this case is generally represented by a slip torque. Assuming that the slip torque is T, T = P * μ * (R + r) / 2, where P is the downward force of the toothed belt, μ is the friction coefficient of the sliding portion, R is the outer radius of the sliding portion, r represents the inner radius of the sliding part. As an example, considering the case where the dimensions of each part are as shown in FIG. 1, the toothed belt 2 is urethane rubber, the thrust washer 23 is graphite nylon, and the bracket 10 (or the chassis 12) is a stainless steel plate, The slip torque between the attached belt 2 and the thrust washer 23 is: T1 = P × 0.8 × (3 + 2.5) /2=2.2P The slip torque between the thrust washer 23 and the bracket 10 is T2 = P × 0. 2 × (3 + 2) /2=0.5P, which clearly shows the thrust washer 23 and the bracket 1
0 (or the chassis 12) has a smaller slip torque. Therefore, with the structure of the present invention, the friction loss due to sliding is only a small slip torque between the thrust washer 23 and the bracket 10 (or the chassis 12).
The thrust washer 23 functions as a lower flange of the flanged gear 21.

[0015] As shown in FIG.
Is provided, the slip torque between the washer 23 and the bracket 10 is further reduced. It is also an effective friction reducing means to modify the surface of the washer 23 by a method such as coating to give a difference in the friction coefficient between the upper surface and the lower surface.

In the above-described embodiment, the case where each component is miniaturized as much as possible has been described. However, when there is room in the height direction, or when the diameter of the shaft 22 can be increased (for example,
3 or 4 may be used as the structure shown in FIG. 3 or FIG. In the case of FIG. 3, the washer 23 and the shaft 2
The slip torque with the second seat 22a is related,
Since is usually made of stainless steel, the same effect as in FIG. 1 can be obtained.

[0017]

According to the structure of the present invention, the thrust washer can be used as a substitute for the lower flange even if the gear with flange does not have a lower flange, so that the toothed belt can be prevented from coming off. Therefore, it is possible to improve the assembling workability and to cope with downsizing of the mechanism.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a flanged gear of the present invention.

FIG. 2 is a sectional view of a flanged gear according to another embodiment of the present invention.

FIG. 3 is a sectional view of a flanged gear according to another embodiment of the present invention.

FIG. 4 is a sectional view of a flanged gear according to another embodiment of the present invention.

FIG. 5 is a plan view of the mechanism.

FIG. 6 is an external perspective view and an exploded perspective view of a gear with a flange of a conventional example.

[Explanation of symbols]

 2 toothed belt 10 bracket 12 chassis 21 gear with flange 22 shaft 23 thrust washer

Claims (2)

(57) [Claims] 1. A magnetic recording / reproducing apparatus in which torque is transmitted via a toothed belt meshing with a gear, wherein the gear comprises a support shaft fixedly mounted on a chassis (or a bracket), and the support shaft. And a thrust washer that is rotatable with a flange and a thrust washer that is inserted through the support shaft and contacts and separates from an edge of the toothed belt. 2. The driving force transmission mechanism according to claim 1, wherein a slip torque between the thrust washer and the edge is set to be larger than a slip torque between the thrust washer and the chassis (or bracket).