JP5352903B2 - Lens barrel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens barrel that effectively and reliably enables tooth jump without an increase in the size of the barrel, an increase in the number of components for the prevention of teeth skip, and without sacrificing the strength of a conventionally existing member. <P>SOLUTION: The lens barrel includes: a rotating drive source shaft; an external cylindrical member free to be rotated around an optical axis in order to move a lens along an optical axis, and having an internal gear on the inside thereof; an external gear connected to the rotating drive source shaft and engaged with the internal gear; a gear case having an external-gear-shaft support portion journaling the shaft of the external gear; and a fixed internal cylindrical member disposed inside the gear case and integrated with a mount member. The fixed internal cylindrical member limits displacement of the gear case in the direction of the optical axis so that the displacement is less than the effective tooth depth of the internal and external gears. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a lens barrel, and more particularly to a lens barrel that prevents tooth skipping of a gear mechanism that rotates a cylindrical member in the barrel.

  For example, in order to move the focusing lens group of the zoom lens along the optical axis direction, internal teeth are provided inside the cam cylinder member that is cam-engaged with the frame member that supports the focusing lens group. On the other hand, an external gear that meshes with the internal teeth is attached to a drive shaft from a motor that operates as a focusing operation drive source provided in the lens barrel or the camera body. The focal lens group is moved along the optical axis direction.

  When the cam cylinder member is rotated by the rotation of the motor to move the focusing lens group along the optical axis, the cam cylinder is caused by frictional resistance of a sliding member related to the focusing lens group. A resistance force of the driving force of the motor is generated on the member. Therefore, when the rotation of the motor is suddenly performed, the inner teeth and the outer teeth are disengaged, and so-called tooth skipping occurs. Further, the internal teeth or the external teeth may be damaged.

  In order to solve such problems, the following inventions are known. In other words, the gear base plate that supports the gear teeth is added with a function to regulate the fluctuation amount of the central axis of the gear, thereby preventing the occurrence of tooth jumps of the internal and external gears. There has been proposed a lens barrel provided with a tooth skip prevention piece for receiving an outer peripheral surface of a cylindrical portion having an internal gear (for example, see Patent Document 1).

  Also, for the purpose of eliminating backlash of the gear pair in a narrow space, one of the pair of gears is pivotally attached at one end to the pair of gears meshing with each other, and the other end is between the rotation centers of the pair of gears. Is fixed to the other end of the rotating shaft that is swingable in a direction perpendicular to the axis connecting the two. There has been proposed a gear transmission means that can be employed in a photographic lens or the like, characterized by comprising an urging means for urging the other end of the rotating shaft to mesh a pair of gears (for example, Patent Document 2). reference).

  Further, the gear used for driving the movable body is provided with a gear skip prevention function so that the gear can be reliably driven, or the movable body can be reliably driven thereby. In a gear mechanism that transmits a driving force via meshing between a drive gear member and a driven gear member, at least one of the gear members is displaced due to an overload generated in the driven gear member, and the meshing is released. In order to prevent this from happening, by providing a sliding guide member that brings the gear member that displaces closer to the counterpart gear member in accordance with the displacement, a gear mechanism that can perform reliable driving, or A device capable of reliably driving the movable body has been proposed (see, for example, Patent Document 3).

JP-A-7-120648 JP-A-11-141623 Japanese Patent Laid-Open No. 10-30702

  In the lens barrel proposed by Cited Document 1, a gear base plate that supports the external gear is added with a function of restricting the fluctuation amount of the central axis of the gear, thereby generating tooth skipping of the internal and external gears. The lens barrel is designed to eliminate as much as possible, and the meshing part of the external gear and the internal gear of the cylindrical part is sandwiched from both the inner and outer sides by the gear base plate and the tooth skip prevention piece provided integrally therewith. Supported by the state. For this reason, the tooth skip prevention piece added to the gear base plate has a structure for receiving the outer peripheral surface of the cylindrical portion, and the mirror is increased in size by adjusting the space of the lens barrel inner member when the tooth skip prevention piece is arranged. There is concern about the problem of reducing the strength of the cylindrical member.

  In the gear transmission mechanism proposed by the cited document 2, one end of a pair of gears meshing with each other is pivoted at one end, and the other end is pivotable in a direction perpendicular to the axis connecting the rotation centers of the pair of gears. Biasing means for biasing the shaft to the other end side by a spring member and meshing the pair of gears is provided. Therefore, there is a problem that the number of parts constituting the gear transmission mechanism increases.

  In the gear mechanism and the device equipped with the gear mechanism proposed by the cited document 3, it is prevented that at least one of the gear members that mesh with each other is displaced due to an overload generated in the gear member and the meshing is attempted to be released. Therefore, a configuration is provided in which a sliding guide member is provided to bring the gear member that is displaced according to the displacement closer to the counterpart gear member. Therefore, there is a problem of enlargement of the lens barrel by adjusting the space of the speed reducer for providing the sliding guide member.

(Object of invention)
The present invention is a lens barrel that has been made in view of the above-described problems of these configurations that have been proposed in the past, does not increase the size of the barrel, does not increase the number of parts to prevent tooth skipping, It is another object of the present invention to provide a lens barrel capable of effectively and reliably performing tooth skipping without sacrificing the strength of existing members.

The present invention
A rotational drive source shaft;
In order to move the lens along the optical axis, an outer cylindrical member that is rotatable around the optical axis and has an internal gear inside,
An external gear coupled to the rotational drive source shaft and meshing with the internal gear;
A gear case having an external gear shaft support portion for supporting the shaft of the external gear;
Provided inside the gear case, and having a fixed inner cylinder member integral with the mount member;
The fixed inner cylinder member restricts the displacement of the gear case toward the optical axis to be smaller than the effective tooth depth of the internal gear and the external gear;
The distance between the fixed inner cylinder member and the gear case in the radial direction about the optical axis is determined by a protrusion provided on at least one of the fixed inner cylinder member and the external gear shaft support member. It is a lens barrel.

According to the lens barrel of the present invention, the size of the lens barrel is not increased, the number of parts is not increased to prevent tooth skipping, and the tooth skipping is not sacrificed without sacrificing the strength of existing members. It has an effect that can be performed effectively and reliably.
In particular, the radial interval between the fixed inner cylinder member and the gear case in the optical axis center is determined by a protrusion provided on at least one of the fixed inner cylinder member and the gear case, so that the fixed inner cylinder member and the gear case It is possible to save the molding resin material of at least one of the gear cases.

(Embodiment of the Invention)
The fixed inner cylinder member is in contact with the gear case.
When the fixed inner cylinder member and the gear case are in contact with each other, the gear case, that is, the external gear is not displaced, and the tooth skipping can be more reliably prevented.

The distance between the fixed inner cylinder member and the gear case in the radial direction about the optical axis is smaller than the effective tooth gap between the internal gear and the external gear.
If the distance between the fixed inner cylinder member and the gear case in the radial direction about the optical axis is smaller than the effective tooth gap between the internal gear and the external gear, tooth skipping does not occur. In addition, the blade edge of the gear becomes thinner as it becomes higher. Accordingly, the radial distance between the fixed inner cylinder member and the gear case in the optical axis center is 2/3 or less, preferably 1/2 or less, more preferably 1/2 or less of the effective tooth gap of the internal gear and the external gear. If 1/3 or less and 1/4 or less, tooth missing, that is, tooth breakage, can be effectively prevented.

There is a fixed outer cylinder member that is provided outside the outer cylinder member and is integral with the mount member, and the fixed outer cylinder member limits displacement in a direction away from the optical axis of the outer cylinder member.
There is a fixed outer cylinder member that is provided outside the outer cylinder member and is integral with the mount member. Even if the fixed outer cylinder member limits the displacement of the outer cylinder member in the direction away from the optical axis, the tooth skipping can be achieved. In combination with the configuration in which the fixed inner cylinder member limits the displacement of the gear case toward the optical axis, tooth jump prevention can be more reliably prevented.

The total of the radial distance between the fixed outer cylinder member and the outer cylindrical member in the radial direction around the optical axis and the radial distance between the fixed inner cylinder member and the gear case in the radial direction around the optical axis is the internal gear. And smaller than the effective tooth depth of the external gear.
The total of the radial distance between the fixed outer cylinder member and the outer cylindrical member in the radial direction around the optical axis and the radial distance between the fixed inner cylinder member and the gear case in the radial direction around the optical axis is the internal gear. If it is smaller than the effective tooth depth of the external gear, tooth skipping can be prevented no matter how the gear case is displaced.
If the total is 2/3 or less, preferably 1/2 or less, more preferably 1/3 or less, 1/4 or less of the effective toothpaste of the internal gear and the external gear, tooth missing, Damage can be effectively prevented.

It is sectional explanatory drawing along the optical axis of the lens-barrel of embodiment of this invention. It is sectional drawing along line II-II of FIG. 1 of the lens-barrel of embodiment of this invention. FIG. 3 is a cross-sectional view of the lens barrel according to the embodiment of the present invention, taken along line III-III in FIG. 2.

  The lens barrel 10 according to an embodiment of the present invention will be described below with reference to the accompanying drawings. As shown in FIG. 1, the lens barrel 10 is an inner focus type zoom lens including a first lens group 11, a second lens group 12, a third lens group 13, and a fourth lens group 14. The second lens group 12 is a focusing lens, and performs a focusing operation by moving the second lens group 12 along the optical axis O.

The second lens group 12 is supported by a second lens group support frame 20. The second lens group support frame 20 has a cam pin 26 that engages with the cam groove 24 of the cam cylinder 22. Therefore, when the cam barrel 22 rotates about the optical axis O, the second lens group 12 moves in focus along the optical axis O due to the engagement of the cam groove 24 and the cam pin 26.
A fixed outer cylinder member 28 that is integral with the mount 30 is disposed outside the cam cylinder 22.

As shown in FIGS. 2 and 3, the lens barrel 10 supports, on the mount 30 side, a motor 32 as a focusing drive source, a reduction gear train 34 for reducing the output of the motor 32, and a reduction gear train 34. And it has the gear case 36 which covers, and the output external gear 40 attached to the output shaft 38 of the reduction gear train 34. The cam barrel 22 has cam barrel inner teeth 50 that mesh with the output external gear 40 at the end portion on the mount 30 side.
Inside the gear case 36, a fixed inner cylinder member 54 that is integral with the mount 30 is disposed.

  The gear case 36 includes an external gear shaft support portion 52 that supports the output external gear 40. The external gear shaft support member 52 of the gear case 36 further has a gear case protrusion 53 extending in the optical axis direction in order to reduce the distance D between the gear case 36 and the fixed inner cylinder member 54.

  The distance D between the fixed inner cylinder member 54 and the gear case projection 53 of the external gear shaft shaft support portion 52 in the radial direction about the optical axis is zero, that is, is in contact with each other, or the cam cylindrical internal gear 50 and the output outside It is smaller than the effective tooth depth of the tooth gear 40. With this configuration, the fixed inner cylinder member 54 restricts the displacement of the external gear shaft shaft support portion 52 toward the optical axis and prevents tooth skipping.

  Instead of providing the gear case protrusion 53, the same tooth skip prevention effect can be obtained by increasing the thickness of the gear case 36 or by increasing the thickness of the fixed inner cylinder member 54.

  The same tooth skip prevention effect can be obtained by providing a protrusion on the fixed inner cylinder member 54 instead of providing the gear case protrusion 53.

  Further, the distance between the cam cylinder 22 and the fixed outer cylinder member 28 in the radial direction about the optical axis is smaller than the effective tooth gap of the cam cylinder internal gear 50 and the output external gear 40. With this configuration, the displacement of the fixed outer cylinder member 28 in the direction away from the optical axis O of the cam cylinder 22 is limited, and tooth skipping is prevented.

Furthermore, the sum of the distance between the fixed inner cylinder member 54 and the external gear shaft shaft support member 52 in the radial direction around the optical axis and the distance between the cam cylinder 22 and the fixed outer cylinder member 28 in the radial direction around the optical axis, By making it smaller than the effective tooth depth of the cam barrel internal gear 50 and the output external gear 40, tooth skipping can be more reliably prevented.
If the total is 2/3 or less, preferably 1/2 or less, more preferably 1/3 or less, and 1/4 or less of the effective tooth depth of the cam barrel internal gear 50 and the output external gear 40, the teeth are missing. That is, tooth damage can be effectively prevented.

DESCRIPTION OF SYMBOLS 10 Lens barrel 11 1st lens group 12 2nd lens group 13 3rd lens group 14 4th lens group 20 2nd lens group support frame 22 Cam cylinder 24 Cam groove 26 Cam pin 28 Fixed outer cylinder member 30 Mount 32 Motor 34 Deceleration Gear train 36 Gear case 38 Output shaft 40 Output external gear 50 Cam cylinder internal gear 52 External gear shaft support 53 Gear case projection 54 Fixed internal cylinder member

Claims (5)

A rotational drive source shaft;
In order to move the lens along the optical axis, an outer cylindrical member that is rotatable around the optical axis and has an internal gear inside,
An external gear coupled to the rotational drive source shaft and meshing with the internal gear;
A gear case having an external gear shaft support portion for supporting the shaft of the external gear;
Provided inside the gear case, and having a fixed inner cylinder member integral with the mount member;
The fixed inner cylinder member restricts the displacement of the gear case toward the optical axis to be smaller than the effective tooth depth of the internal gear and the external gear ;
The distance between the fixed inner cylinder member and the gear case in the radial direction about the optical axis is determined by a protrusion provided on at least one of the fixed inner cylinder member and the external gear shaft support member. A lens barrel.   The lens barrel according to claim 1, wherein the fixed inner cylinder member is in contact with the gear case.   2. The lens barrel according to claim 1, wherein an interval between the fixed inner cylinder member and the gear case in the radial direction about the optical axis is smaller than an effective tooth gap of the internal gear and the external gear. .   The fixed outer cylinder member that is provided outside the outer cylinder member and is integral with the mount member, and the fixed outer cylinder member limits displacement in a direction away from the optical axis of the outer cylinder member. The lens barrel according to 1. The total of the radial distance between the fixed outer cylinder member and the outer cylindrical member in the radial direction around the optical axis and the radial distance between the fixed inner cylinder member and the gear case in the radial direction around the optical axis is the internal gear. The lens barrel according to claim 4 , wherein the lens barrel is smaller than the effective tooth depth of the external gear.

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