JPH09113975A - Gear transmission mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gear transmission mechanism which does not cause a delay in the transmission of rotation resulted from a backlash in the backward rotation. SOLUTION: The respective gear units 10, 30 of a gear transmission mechanism 1 are provided with cylindrical parts 24, 44 which are coaxially supported adjacently to gear parts 22, 42. Both units 10, 30 are fixed in proximity so that these gear parts 22, 42 are meshed with each other and that the cylindrical parts 24, 44 come into contact with each other. The rotation is immediately transmitted by the contact of the cylindrical parts 24, 44 even if there is the backlash in the gear parts 22, 42 right after the start of the backward rotation of the gear transmission device 1. Then, the delay in the transmission of the rotation by the backlash does not arise any more in the backward rotation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear transmission mechanism, and more particularly to a gear transmission mechanism that immediately transmits reverse rotation even if a gear has a backlash.

[0002]

2. Description of the Related Art Generally, in a gear transmission mechanism that transmits rotation by gears, a backlash is provided in the mesh of the gears so that the gears rotate smoothly. But,
When there is a backlash, immediately after the rotation direction changes, when the meshing tooth surface changes to the opposite tooth surface, the rotation for the backlash is not transmitted. If the rotation is not immediately transmitted immediately after the rotation direction is changed in this way, for example, the amount of operation in both the forward and reverse directions is detected and the lens extension / movement is detected.
In a power zoom lens or the like that retracts, the lens drive start is delayed immediately after the rotation direction is changed, which is not preferable because the operator feels uncomfortable.

To reduce the delay in rotation transmission immediately after the rotation direction is changed, backlash may be reduced. However, for that purpose, it is necessary to take special consideration such as improving the machining accuracy of the gears and individually adjusting the distance between the gear shafts, which results in an increase in manufacturing cost.

[0004]

SUMMARY OF THE INVENTION Therefore, the technical problem to be solved by the present invention is to provide a gear transmission mechanism that does not cause a delay in rotation transmission immediately after the rotation direction is changed.

[0005]

In order to solve the above technical problems, the present invention provides a gear transmission mechanism having the following configuration.

That is, the gear transmission mechanism includes a pair of gear units. The pair of gear units coaxially integrally support a gear portion having teeth on the periphery thereof and a rotor portion disposed adjacent to the gear portion and having a flat peripheral surface on the periphery thereof. The pair of gear units are fixed such that the gear portions of the gear units mesh with each other and the peripheral surfaces of the rotor portions of the gear units contact each other. In other words, in each gear unit, the overall shape of the teeth of the gear portion, that is, the envelope shape, and the flat peripheral surface shape of the rotor portion are substantially similar.

In the above structure, the peripheral surfaces of the rotor portion of the gear unit are in contact with each other, and the diameter of the rotor portion causes
The axial distance between both gear units is determined. Since the rotor portion and the gear portion are coaxially and integrally supported, the axial distance of the gear portion is also determined. Even if there is backlash in the gear portion, the rotation is immediately transmitted immediately after the rotation direction is changed, as described below.

That is, generally, a gear has a different combination of tooth flanks that come into contact with the other gear depending on the direction of rotation, and when changing the direction of rotation, it comes into contact with a second tooth flank that is opposite to the first tooth flank that has been in contact until then. Come to do. However, if the gear has backlash, the second flanks are separated from each other by the amount of backlash when the first flanks are in contact with each other. Therefore, immediately after the rotation direction is changed, the rotation corresponding to the backlash cannot be transmitted. Therefore, even in the gear transmission mechanism having the above configuration,
Immediately after the rotation direction is changed, depending on the meshing of the gears,
Rotation is not transmitted.

However, in the gear transmission mechanism having the above structure,
Immediately after the rotation direction is changed, the rotor portions of the gear units are in contact with each other in a state where they do not slide relative to each other, that is, in a static friction state. Therefore, a relatively large static friction force acts on the flat peripheral surface of the rotor portion, that is, the contact surface, so that one rotation of the rotor portion is transmitted to the other.
After that, when rotation progresses and relative slip occurs on the contact surface of the rotor part, the contact surface of the rotor part shifts from a static friction state to a sliding friction state, and a relatively small sliding friction between the rotor parts. Since force is applied, rotation transmission is also reduced. Then, the rotation thereafter is transmitted by the meshing of the gears. That is, even if there is backlash in the gear portion, the rotation is immediately transmitted immediately after the rotation direction is changed due to the contact between the rotor portions. Then, after the rotation progresses to some extent, the rotation is transmitted by the meshing of the gear parts.

Therefore, the gear transmission mechanism having the above structure is
There is no delay in rotation transmission immediately after the rotation direction is changed.

Furthermore, the axial distance and backlash of the gear parts are determined by the dimensions and shapes of the rotor part and the gear part of each gear unit. Therefore, it is possible to optimally adjust the backlash of the gear unit by a simple work of machining the rotor unit and the gear unit of each gear unit to a predetermined size and fixing the gear unit so that the rotor units contact each other. This eliminates the need for troublesome work such as individually adjusting the shaft distance.

The gear transmission mechanism having the above-mentioned structure is not limited to a structure in which the rotating shafts of both gear units are parallel and the gear portion has a shape of a spur gear, a helical gear, etc. Intersect each other, and the gear portion is in the shape of a bevel gear or the like, or the gear portion is composed of an internal gear and an external gear, and the inner peripheral surface of one rotor portion and the outer peripheral surface of the other rotor portion are in contact with each other. It is also possible to Further, the gear unit and the rotor unit of each gear unit may be supported coaxially and integrally, and the gear unit and the rotor unit may be eccentrically supported. Furthermore, the gear part and the rotor part are circular, cylindrical,
The shape is not limited to the shape of a cone or the like, and may be an arbitrary meshing and sliding contact shape. Further, the gear part and the rotor part may be arranged with a gap provided that no inconvenience such as shaft deflection occurs.

In the above structure, if the contact between the rotor parts of the gear unit is weak, the rotation transmission at the time of changing the rotation direction becomes impossible. On the contrary, if the contact between the rotor parts is too strong, smooth rotation is hindered.

Preferably, a biasing means for resiliently biasing one of the gear units to the other of the gear units is further provided.

In the above structure, the urging means causes the rotor portions of the gear unit to contact each other with an appropriate pressing force. As a result, an appropriate frictional force is generated immediately after the rotation direction is changed, and the rotation is smoothly transmitted. Therefore, it is not necessary to adjust the contact of the rotor portion of the gear unit, and the gear unit can be easily fixed.

Preferably, in the drive-side gear unit, the rotor portion has a diameter larger than the gear engagement pitch circle, while in the driven-side gear unit, the rotor portion is larger than the gear engagement pitch circle. It has a small diameter.

In the above structure, the rotation transmission by the rotor portion is larger than the rotation transmission by the gear portion due to the difference in reduction ratio between the rotor portion and the gear portion. Therefore, even immediately after the rotation direction is changed in the state where the first tooth surface of the gear portion is in contact, the reverse rotation is performed in the state where the first tooth surface is still in contact. Because the gear unit and the rotor unit are integrally supported, even if the rotation transmission by the rotor unit is faster than the rotation transmission by the gear unit, the rotor unit does not move the driven gear first.
This is because it cannot rotate beyond the tooth flank. Then, when the rotation progresses to some extent, relative slip occurs in the rotor portion whose rotation is restricted by the first tooth surface of the gear portion,
The rotation transmission force by the rotor unit becomes small. Then, after that, the rotation is transmitted by the contact of the second tooth surface of the gear portion. When the rotation transmission by the rotor portion is switched to the rotation transmission by the gear portion in this way, a rotation transmission delay corresponding to backlash of the gear portion occurs. However, at this time, since the rotation has already progressed considerably, the amount of delay in the rotation transmission amount up to that point becomes relatively small, and the influence of the delay is much smaller than in the case where there is a delay immediately after the rotation direction change. Becomes smaller.

In the above construction, if a suitable difference is provided between the pitch circle of the gear portion and the diameter of the rotor portion, the rotation transmission by the rotor portion can be switched to the rotation transmission by the gear portion at a desired timing. Then, except when the rotation transmission by the rotor portion is switched to the rotation transmission by the gear portion, the rotation is accurately transmitted at the gear reduction ratio.

Therefore, with the above structure, the rotation can be accurately transmitted by the reduction ratio of the gear portion immediately after the rotation direction is changed.

Preferably, the gear portion of the gear unit and the rotor portion are formed as one part, the gear portion of the gear unit is spur gear-shaped, and the rotor portion of the gear unit is cylindrical-shaped. is there.

In the above structure, since the gear part and the rotor part are formed as one part, the accuracy of each part is easy to obtain and the assembly is easy. Further, for example, when the outer diameter of the cylindrical rotor portion is larger than the outer diameter of the gear portion adjacent to the rotor portion, it can be easily machined by integral molding such as plastic injection molding or sintered metal machining instead of machining. it can. Therefore, the manufacturing cost can be reduced.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The gear transmission mechanism according to the embodiment of the present invention shown in FIGS. 1 to 4 will be described in detail below.

First, the basic structure of the gear transmission mechanism 1 will be described with reference to FIGS.

As shown in FIG. 1, the gear transmission mechanism 1 has two
It is composed of two gear units 10 and 30. Each gear unit 10, 30 includes a rotary shaft 14, 34 and a rotary shaft 14,
Gears 22, 42 and a cylindrical portion 2 supported concentrically with 34
4,44 and the base portion 12, which supports the rotating shafts 14,34,
32 and 32, respectively. The gear parts 22 and 42 and the cylindrical parts 24 and 44 are adjacent to each other, and
Is configured as However, the gear portions 22 and 42 and the cylindrical portions 24 and 44 may be separated from each other or may be formed as separate members within a range that does not cause inconvenience such as axial deflection. Each gear unit 10,30
The rotary shafts 14 and 34 are connected to a mechanism (not shown).
For example, the rotary shaft 14 of the drive-side gear unit 10 is connected to a rotary operation member, the rotary shaft 34 of the driven-side gear unit 30 is connected to a rotation detector, and the operation amount is amplified by setting the gear tooth ratio. And configured to be detected.

In the above construction, preferably, the outer diameter of the cylindrical portion 24 of the drive-side gear unit 10 is larger than the meshing pitch circle of the gear portion 22, and the outer diameter of the cylindrical portion 44 of the driven-side gear unit 30 is. , Smaller than the meshing pitch circle of the gear portion 42. For example, as shown in FIG. 1, the outer diameter of the cylindrical portion 24 of the gear unit 10 on the drive side is equal to that of the gear portion 2.
Make it equal to the tip circle diameter of 2. The outer diameter of the cylindrical portion 44 of the gear unit 30 on the driven side is equal to the root diameter of the gear portion 42. Of course, as shown in FIG. 2, for example, the gear portion 62 is provided with a cylindrical portion 64 having an outer diameter larger than the tip circle diameter, and although not shown, a cylindrical portion having an outer diameter smaller than the root circle diameter is provided. A configuration and the like are also possible.

This gear transmission mechanism 1 includes both units 10,
30 are brought closer to each other as indicated by arrows 90, 92, the gear parts 22, 42 mesh with each other, and the cylindrical parts 24, 44
Both units 10 and 30 are fixed to a common base plate (not shown) in a state where they contact each other.

Next, with reference to FIGS. 3 and 4, the operation and the configuration will be described in more detail. FIG. 3 is a sectional view of the gear transmission mechanism 1 during assembly. In FIG. 1, the gear cylinder member 20 is supported by the base portion 12 in a cantilever manner, but in FIG. 3, the gear cylinder member 21 is supported by the shaft support portions 16a and 16b of the upper and lower base portions 12a and 12b. It is designed to be supported. In addition, the gear cylinder members 21, 40
Is a single member integrally formed not only with the gear parts 22, 42 and the cylindrical parts 24, 44, but also with the rotating shafts 14a, 14b, 34. By integral molding, each part 14a, 14b, 22,
It is possible to easily manufacture while maintaining the mutual positional accuracy of 24, 34, 42 and 44.

When the gear transmission mechanism 1 is assembled, FIG.
As shown in the cross-sectional view of FIG. 1, the gear portions 22, 42 of the gear units 10, 30 mesh with each other, and the cylindrical portion 24,
The outer peripheral surfaces 24a and 44a of 44 contact each other. At this time, the distance between the shafts of both gear units 10 and 30 is determined by the cylindrical portion 2
Determined by an outer diameter of 4,44. Gears 22, 42
Has a predetermined backlash so as to smoothly rotate at the determined axial distance.

In the above structure, when the rotary shaft 14 of the drive-side gear unit 10 is rotated, the rotation is mainly transmitted by the gear portions 22 and 42, and the cylindrical portions 24 and 44 cause relative slip. That is, since the reduction gear ratios of the gear portions 22 and 42 and the reduction gear ratios of the cylindrical portions 24 and 44 are different,
The rotation transmission by the cylindrical portions 24 and 44 is such that if no slip occurs in the contact portions of the cylindrical portions 24 and 44, the gear portions 22 and
It becomes faster than the rotation transmission by 42. However, the cylindrical portion 2
Even if the rotation transmission by the gears 4, 44 is faster than the rotation transmission by the gears 22, 42, the tooth surfaces of the gears 22, 42 come into contact with each other, and the rotations by the cylindrical portions 24, 44 are restricted. Therefore, a relative slip occurs at the contact portion between the cylindrical portions 24 and 44. Once slippage occurs, the sliding frictional force is smaller than the static frictional force, so that the rotation transmission force due to the contact between the cylindrical portions 10 and 30 is rapidly reduced, and the rotation transmission is mainly performed by the meshing of the gear portions 22 and 42. In other words, although the rotation transmission varies due to backlash, the gear unit 2
It is governed by the rotation transmission by 2,42.

Next, the case where the rotary shaft 14 of the drive unit 10 is reversely rotated will be described. During reverse rotation, the gear portions 22 and 42 mesh with the second tooth surface on the side opposite to the first tooth surface that was meshing during forward rotation, so there is a delay in rotation transmission corresponding to the backlash. Occurs.

However, since the cylindrical portions 24 and 44 are in contact with each other, the rotation on the driving side is reversely rotated and immediately transmitted to the driven side. Therefore, there is no delay in rotation transmission immediately after reverse rotation. At this time, the rotation transmission by the cylindrical portions 24 and 44 is faster than the rotation transmission by the gear portions 22 and 42, so that the gear portions 22 and 42 are in the state where the tooth surfaces are in contact with each other as in the normal rotation. . That is, immediately after the reverse rotation, the rotation transmission is not delayed due to the backlash of the gear portions 22 and 42, and the rotation is transmitted at the reduction ratio of the gear portions 22 and 42. Therefore, the rotation at the beginning of the reverse rotation is quickly and accurately transmitted to the driven side, which is convenient for a power focus lens barrel or the like that needs to detect an initial operation quickly.

When the reverse rotation progresses, the cylindrical portion 2
Due to the speed difference between the rotation transmission by the gears 22, 44 and the rotation transmission by the gears 22, 42, relative sliding occurs at the contact portions of the cylindrical portions 24, 44. Once a slip occurs,
Since the sliding friction force is smaller than the static friction force, the cylindrical portion 2
The rotation transmission force due to the contact of the gears 4, 44 is rapidly reduced, and the rotation transmission is performed by the meshing of the gear portions 22, 42. At this time, there is a delay in rotation transmission due to backlash during the transition until the first tooth flanks of the gear parts 22 and 42 separate from each other and come into contact with the second tooth flank. Due to the contact of the surfaces, the rotation is transmitted at the reduction ratio of the gear portions 22 and 42.

This gear transmission mechanism 1 has cylindrical portions 24 and 44.
In order to keep the contact state of each of them constant, an urging unit 50 is further provided, and the gear unit 30 on the driven side is urged by the urging unit 50.
Is urged toward the drive-side gear unit 10.

That is, as shown in FIG. 4 which is a sectional view taken along line IV-IV of FIG. 3, both units 10, 3 are provided on both sides of the base portion 32 of the gear unit 30 on the driven side.
A contact plate 36 extending in a direction perpendicular to the direction connecting the 0 rotation shafts 14 and 34 (hereinafter referred to as “inter-axis direction”) is provided, and the contact plate 36 is opposite to the drive-side gear unit 10. A biasing unit 50 is provided on the side facing the contact plate 36.
The driven unit 30 is fixed to a common base plate (not shown) of the gear transmission mechanism 1 so as to be movable in the axis direction. The biasing unit 50 includes a base portion 52, a biasing spring 56, a spring guide shaft 54, and a spring guide shaft 54.
And The base portion 52 is fixed to a common base plate (not shown) of the gear transmission mechanism 1. A spring guide shaft 54 is provided on the base portion 52 so as to extend in the axial direction toward the contact plate 36 of the driven unit 30. A biasing spring 56, which is a coil spring, is fitted on the outer circumference of the spring guide shaft 54. The urging spring 56 urges the driven-side gear unit 30 toward the drive-side gear unit 10 via the contact plate 36 of the driven unit 30. Biasing spring 56 of biasing unit 50
The friction force between the cylindrical portion 24 of the drive-side gear unit 10 and the cylindrical portion 44 of the driven-side gear unit 30 is kept constant by the biasing by. Therefore, it is not necessary to adjust the contact between the rotor portions 24 and 44 of the gear units 10 and 30, and the gear units 10 and 30 can be easily fixed.

The present invention is not limited to the above embodiment, but can be implemented in various other modes.
For example, in the case of a cross shaft gear such as a bevel gear, a conical rotor portion may be formed instead of the cylindrical portion. Further, the outer diameter of the cylindrical portion of the drive-side gear unit may be smaller than the meshing pitch circle diameter of the gear portion of the drive unit, and the rotation transmission by the gear portion may be larger than the rotation transmission by the cylindrical portion. In this case as well, the rotation is transmitted from the beginning of the reverse rotation, but the rotation transmission by the cylindrical portion at the beginning of the reverse rotation becomes slower than the rotation transmission by the gear portion. Further, the biasing means may be configured to bias the gear unit on the drive side, or
It may be configured to urge both gear units.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a basic configuration of a gear transmission mechanism according to an embodiment of the present invention.

FIG. 2 is a perspective view of a gear unit of a modified example.

FIG. 3 is a sectional view of the gear transmission mechanism according to the embodiment of the present invention.

FIG. 4 is a sectional view of FIG.

[Explanation of symbols]

 1 Gear transmission mechanism 10 Gear unit 12, 12a. , 12b Base portion 14, 14a, 14b Rotating shaft 16a, 16b Shaft support portion 20, 21 Gear cylinder member (one part) 22 Gear portion 24 Cylindrical portion (rotor portion) 24a Outer peripheral surface (flat peripheral surface) 30 Gear unit 32 Base portion 34 rotary shaft 36 contact plate 40 gear cylinder member (one part) 42 gear part 44 cylindrical part (rotor part) 44a outer peripheral surface (flat peripheral surface) 50 biasing unit (biasing means) 52 base part 54 guide shaft 56 with Power spring

Claims (4)

[Claims] 1. A gear part (22, 42) having teeth on its periphery.
And a pair of gear units (10, 30) coaxially and integrally supporting the rotor portion (24, 44) arranged next to the gear portion (22, 42) and having a flat peripheral surface around the gear portion (22, 42). ,
In the pair of gear units (10, 30), the gear portions (22, 42) of the gear units (10, 30) mesh with each other and the rotor portion of the gear units (10, 30)
A gear transmission mechanism characterized in that peripheral surfaces (24a, 44a) of (24, 44) are fixed so as to be in contact with each other. 2. A urging means (50) for elastically urging one of the gear units (10, 30) to the other of the gear units (10, 30) is further provided. The gear transmission mechanism according to Item 1. 3. In the gear unit (10) on the driving side, the rotor portion (24) has a diameter larger than the meshing pitch circle of the gear portion (22), while in the gear unit (30) on the driven side. The gear transmission mechanism according to claim 1 or 2, wherein the rotor portion (44) has a diameter smaller than the meshing pitch circle of the gear portion (42). 4. The gear part (22, 42) and the rotor part (24, 44) of the gear unit (10, 30) are one component.
(20, 40), the gear unit (10,
The gear part (22, 42) of (30) has a spur gear shape, and the rotor part (24, 44) of the gear unit (10, 30).
The gear transmission mechanism according to claim 1, 2 or 3, wherein is a cylindrical shape.