JPH06274967A - Driving force transmitting mechanism - Google Patents

Abstract

PURPOSE:To prevent a toothed belt from coming off due to vertical movement of the belt by substituting a thrust washer for a flange on the lower side of a gear with flanges. CONSTITUTION:A pivot 22 fixedly planted on a chassis (or a bracket 10), the gear 21 having a flange 21a, freely rotatably fitted to this pivot 22 and the thrust washer 23, through which the pivot 22 is inserted, to be in contact with and separated from an edge of the toothed belt 2 are assembled into the constitution of the gear 21 to be meshed with the toothed belt 2 as the rotary driving force transmitting mechanism of a magnetic recording and reproducing device for the purpose of transmitting torque via the toothed belt 2. Then, slip torque between the thrust washer 23 and the edge of the belt is set larger than slip torque between the thrust washer 23 and the chassis (or bracket 10).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotational driving force transmission 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 transmission mechanism in a mechanism of a magnetic recording / reproducing apparatus such as a VTR or DAT controls the rotation of a capstan motor 1 to a toothed belt 2.
The configuration in which it is transmitted to the reel stands 3 and 4 via The toothed belt 2 has a rack formed on its inner circumference, and the driving force is transmitted without meshing with the gears 5, 6, 7 and slipping.

However, like the flat belt and the square belt, the toothed belt 2 also moves up and down to some extent during rotation, so that flanges 5a and 5b are provided above and below the gear 5 as shown in FIG. 6 (a). The belt is prevented from coming off. The same applies to the gears 6 and 7.

[0004]

When cutting a gear with upper and lower flanges, a method of attaching the separately processed flange to the gear is adopted. Or, in the case of forming by die molding, as shown in FIG.
A flanged gear 8 in which the flange portion 8b and the boss portion 8c are integrally formed, and a flange 9 are provided at two points, and the flange 9 is fixed to the boss portion 8c by means of ultrasonic welding or the like.

However, the process of fixing the flange 9 is poor in workability, and when the component is downsized, the boss portion 8 is used.
Since the height and diameter of c cannot be designed to have sufficient dimensions, a problem occurs in welding work.

[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 (gear) that meshes with the toothed belt is used as a chassis (or bracket). A support shaft fixedly mounted on the support shaft, a gear with a flange rotatably attached to the support shaft, and an end of a toothed belt inserted through the support shaft.
Assembling with thrust washers separated from each other, the slip torque between the thrust washer and the edge is set to be larger than the slip torque between the thrust washer and the chassis (or bracket).

[0007]

With the above construction, the toothed belt does not come off from the gear during driving of the driving source, and the rotational driving force is stably transmitted.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments 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 a different embodiment.

First, prior to the description of a concrete embodiment of the present invention, a schematic description of the entire mechanism will be given based on FIG. In the figure, a gear 1a is formed on the outer circumference of the rotor of the capster motor 1, and the gear 6 with a driving side flange is provided.
It meshes with a gear 6g that is coaxial with the. The toothed belt 2 meshes with the flanged gear 6 and transmits rotational power to the driven side flanged gear 7. Further, a gear 10 with an idler flange rotatably mounted on the bracket 10 is provided for adjusting the tension of the toothed belt 2, and is fixed to the chassis 12 with a screw 11 at an appropriate position.

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

Among the configurations of the flanged gears 5, 6, 7 of the present invention in the configuration of the mechanism described above, the flanged gear 5 will be described with reference to FIG. The flanged gear 21 is formed integrally with the upper flange 21a, but the boss 8c shown in FIG. 6 (conventional example) is unnecessary. The gear 21 is rotatable with respect to a shaft 22 integrally formed with a seat 22a fixed to the bracket 10 and meshes with the toothed belt 2. As a substitute for the lower flange of the gear 21, a thrust washer 23 as described below is provided in the seat 22.
It is rotatably fitted in part a. 24 is a lock washer.

The inner diameter of the washer 23 is slightly larger (about 0.05 to 0.1 mm) than the outer diameter of the seat 22a,
The outer diameter is about the same as the upper flange 21a, and the thickness is
It is preferable that it is slightly thinner (about 0.05 mm) than the thickness of a. Further, the surface lubricity of the washer 23 depends on the bracket 1
It is assumed that the sliding resistance with the lower end surface of the toothed belt 2 is larger 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, sliding resistance between the lower end surface of the belt 2 and the washer 23 causes the toothed belt 2 (and the flanged one). The gear 21) and the thrust washer 23 rotate at substantially the same number of rotations and act as a lower flange. On the contrary, when the toothed belt 2 rises upward, the washer 23 does not receive sliding resistance from anywhere and is stationary.

The sliding resistance will be described in more detail.
The value of the sliding resistance in this case is generally represented by slip torque. Let slip torque be T: T = P * μ * (R + r) / 2 where P is the force of the toothed belt going down, μ is the friction coefficient of the sliding part, R is the outer radius of the sliding part, r represents the inner radius of the sliding portion. As an example, considering that 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 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, obviously thrust washer 23 and bracket 1
The slip torque with 0 (or chassis 12) is smaller. Therefore, with the structure of the present invention, the friction loss due to sliding is only a slight slip torque between the thrust washer 23 and the bracket 10 (or the chassis 12),
The thrust washer 23 acts as the lower flange of the flanged gear 21.

As shown in FIG. 2, the bracket 10 has a recess 10a.
Is provided, the slip torque between the washer 23 and the bracket 10 is further reduced. Further, modifying the surface of the washer 23 by a method such as coating so as to have a difference in the friction coefficient between the upper surface and the lower surface is also an effective friction reducing means.

In the above-mentioned embodiment, the case where each component is made as small as possible has been described. However, when there is a margin in the height direction, or when the diameter of the shaft 22 can be increased (for example,
A shaft outer diameter of 1.5 mm or more) may have a structure as shown in FIG. 3 or FIG. In the case of FIG. 3, the washer 23 and the shaft 2
Although the slip torque with the second seat 22a is related,
Is usually made of stainless steel, so that the same effect as in FIG. 1 can be obtained.

[0017]

According to the structure of the present invention, even if the gear with flange does not have a lower flange, the thrust washer can substitute for the lower flange, so that it is possible to prevent the toothed belt from coming off. Without this, it becomes possible to improve the assembling workability and reduce the size of the mechanism.

[Brief description of drawings]

FIG. 1 is a 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.

6A and 6B are an external perspective view and an exploded perspective view of a flanged gear of a conventional example.

[Explanation of symbols]

 2 Belt with tooth 10 Bracket 12 Chassis 21 Gear with flange 22 Shaft 23 Thrust washer

Claims (2)

[Claims] 1. A magnetic recording / reproducing apparatus in which torque is transmitted via a toothed belt meshing with a gear, wherein the gear has a structure in which a spindle fixed to a chassis (or a bracket) and the spindle. A drive force transmission mechanism comprising: a rotatable gear with a flange; and a thrust washer that is inserted through the support shaft and comes into contact with and separates from the end edge of the toothed belt. 2. The drive force transmission mechanism according to claim 1, wherein the slip torque between the thrust washer and the end edge is set to be larger than the slip torque between the thrust washer and the chassis (or bracket).