LENS BARREL

Provided is a lens barrel capable of improving stop accuracy. A roller support shaft (61) is attached to an outer peripheral portion of a cam cylinder (16). A torque applying roller (102) is rotatably supported by the roller support shaft (61). A biasing ring (104) is fitted to an outer peripheral portion of a second fixed cylinder (12B) and is held to be movable in an axial direction. The biasing ring (104) is biased by a biasing spring (106) and pressed to abut against the torque applying roller (102). In a case where the cam cylinder (16) is rotated, the torque applying roller (102) rolls along the biasing ring (104). A load torque is applied to the rotation of the cam cylinder (16) by frictional force generated between the torque applying roller (102) and the roller support shaft (61) due to the rotation of the torque applying roller (102).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lens barrel, and particularly relates to a lens barrel that is rotationally driven.

2. Description of the Related Art

JP2011-133592A discloses that a thrust ring is made to abut against an end surface of a cam cylinder that is rotationally driven and the cam cylinder is biased in an optical axis direction to reduce backlash of the cam cylinder and to improve stop accuracy of the cam cylinder.

SUMMARY OF THE INVENTION

One embodiment according to the technique of the present disclosure provides a lens barrel capable of improving stop accuracy.

(1) A lens barrel comprising: a first cylinder having a first groove disposed along an axial direction and a second groove disposed along a circumferential direction; a second cylinder having a cam groove and rotatably held by being fitted to an inner peripheral portion of the first cylinder; a third cylinder accommodated in the second cylinder and held to be movable in the axial direction; a cam follower attached to an outer peripheral portion of the third cylinder and fitted to the cam groove and the first groove; a roller support shaft attached to an outer peripheral portion of the second cylinder through the second groove; a first roller supported by the roller support shaft; a first frame fitted to an outer peripheral portion of the first cylinder and held to be movable in the axial direction; and a biasing member that biases the first frame in the axial direction and presses the first frame to make the first frame abut against the first roller.

(2) The lens barrel according to (1), further comprising: a second roller supported by the roller support shaft and fitted to the second groove to position the second cylinder in the axial direction with respect to the first cylinder and/or regulate a movable range of the second cylinder.

(3) The lens barrel according to (2), in which any one of the first roller or the second roller is composed of a bearing.

(4) The lens barrel according to any one of (1) to (3), in which the second cylinder has a pair of the cam grooves disposed in parallel with each other, and a pair of the cam followers individually fitted to the pair of cam grooves is provided.

(5) The lens barrel according to (4), in which the third cylinder has a third cylinder body part, a third cylinder movable part fitted to an outer peripheral portion of the third cylinder body part and held to be movable in the axial direction, and a biasing part biasing the third cylinder movable part in the axial direction with respect to the third cylinder body part, and one of the pair of cam followers is attached to the third cylinder movable part, and the other is attached to the third cylinder body part.

(6) The lens barrel according to any one of (1) to (5), in which in the second cylinder, an opening portion of the cam groove is shielded by the third cylinder in an entire movable area of the third cylinder.

(7) The lens barrel according to (5), in which in the second cylinder, an opening portion of the cam groove is shielded by the third cylinder body part and the third cylinder movable part in an entire movable area of the third cylinder by mounting the third cylinder movable part on the third cylinder body part.

(8) The lens barrel according to any one of (1) to (7), further comprising: a second frame fixedly mounted on the outer peripheral portion of the first cylinder, in which the biasing member is composed of a spring disposed between the first frame and the second frame.

(9) The lens barrel according to any one of (1) to (7), in which the first cylinder has a flange portion, and the biasing member is composed of a spring disposed between the first frame and the flange portion.

(10) The lens barrel according to any one of (1) to (9), in which the cam follower has a shaft portion attached to the outer peripheral portion of the third cylinder, and a bearing mounted on the shaft portion and fitted to the cam groove and the first groove.

(11) The lens barrel according to any one of (1) to (10), further comprising: a driving unit that rotationally drives the second cylinder.

(12) The lens barrel according to (11), in which the driving unit has a motor, and a reduction gear that has a gear train and reduces a speed of rotation of the motor to transmit the speed-reduced rotation to the second cylinder.

(13) The lens barrel according to any one of (1) to (12), in which the third cylinder holds a lens in an inner peripheral portion.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

Here, a case where the present invention is applied to an interchangeable lens of a lens interchangeable camera will be described as an example. In a lens interchangeable camera, the interchangeable lens is attachably and detachably mounted on a camera body.

FIG. 1is a cross-sectional view showing an overall schematic configuration of an interchangeable lens according to a first embodiment. An interchangeable lens1of the present embodiment is a so-called single focus AF lens. The AF lens is a lens capable of auto-focusing (AF). In particular, the interchangeable lens1of the present embodiment has a built-in motor for focusing.

As shown inFIG. 1, the interchangeable lens1of the present embodiment has a first lens group L1and a second lens group L2in order along an optical axis Z. The first lens group L1is a fixed lens group. The second lens group L2is a lens group that moves along the optical axis Z. The second lens group L2is a focus lens group. Focusing is performed by moving the second lens group L2along the optical axis Z.

A lens barrel10of the interchangeable lens1of the present embodiment is mainly composed of a fixed cylinder12, a first lens cylinder14, a cam cylinder16, a second lens cylinder18, an exterior body20, a mount22, and the like.

The fixed cylinder12is an element that is fixed to the camera body in a case where the interchangeable lens1is mounted on the camera body. The fixed cylinder12is constituted by integrating a first fixed cylinder12A, a second fixed cylinder12B, and a rear end cover12C. The first fixed cylinder12A and the second fixed cylinder12B are coaxially connected by fastening flange portions thereof with screws (not shown). The rear end cover12C is screwed to an end part of the second fixed cylinder12B with a screw (not shown), thereby being attached to the end part of the second fixed cylinder12B. The fixed cylinder12is an example of a first cylinder.

The first lens cylinder14is a frame for holding the first lens group L1. The first lens group L1is positioned and held on an inner peripheral portion of the first lens cylinder14. The first lens cylinder14is positioned and held on an inner peripheral portion of the first fixed cylinder12A.

The cam cylinder16is fitted to an inner peripheral portion of the second fixed cylinder12B and is rotatably held by the inner peripheral portion of the second fixed cylinder12B. The cam cylinder16is an example of a second cylinder.

The second lens cylinder18is a frame for holding the second lens group L2. The second lens group L2is positioned and held on an inner peripheral portion of the second lens cylinder18. The second lens cylinder18is accommodated in an inner peripheral portion of the cam cylinder16and is held to be movable in an axial direction. The second lens cylinder18moves in a front-rear direction along the optical axis Z by rotating the cam cylinder16. A drive mechanism and a position detection mechanism of the second lens cylinder18will be described below. The second lens cylinder18is an example of a third cylinder.

The exterior body20constitutes the exterior of the interchangeable lens1. The exterior body20is constituted by combining a plurality of elements. The elements constituting the exterior body20also include an operation member (for example, a focus ring2) of the interchangeable lens1. The exterior body20is fixedly attached to the fixed cylinder12.

The mount22is provided at a rear end part of the lens barrel10. The mount22is composed of, for example, a bayonet mount. The interchangeable lens1is attachably and detachably mounted on the camera body via the mount22.

[Drive Mechanism of Second Lens Cylinder]

FIGS. 2 and 3are perspective views of a rear portion (a portion on the rear side with respect to the second fixed cylinder12B of the fixed cylinder12) of the lens barrel with the exterior body removed.FIG. 2is a perspective view of the rear portion of the lens barrel as viewed from the front side. In addition,FIG. 3is a perspective view of the rear portion of the lens barrel as viewed from the rear side. In addition,FIG. 4is an exploded perspective view of the rear portion of the lens barrel.

The drive mechanism of the second lens cylinder18is composed of a so-called cam mechanism. The cam mechanism comprises a pair of cam followers30A and30B provided in the second lens cylinder18, a pair of cam grooves40A and40B provided in the cam cylinder16, a straight advance groove50provided in the second fixed cylinder12B, a positioning roller60provided in the cam cylinder16, a positioning groove70provided in the second fixed cylinder12B, and a driving unit80for rotating the cam cylinder16. In addition, the drive mechanism of the second lens cylinder18includes a torque applying mechanism100that applies a load torque to the rotation of the cam cylinder16.

The pair of cam followers30A and30B is provided at three locations on an outer peripheral surface of the second lens cylinder18. The pairs of cam followers30A and30B are disposed at equal intervals along a circumferential direction. In each installation portion, the pair of cam followers30A and30B is disposed in the front-rear direction along the optical axis Z. Hereinafter, the cam follower30A located on the front side (subject side) is referred to as a first cam follower30A, and the cam follower30B located on the rear side (image side) is referred to as a second cam follower30B, as necessary, to distinguish between them.

FIG. 5is a cross-sectional view showing the configuration of the cam follower. AlthoughFIG. 5shows the second cam follower30B, the first cam follower30A has the same configuration.

As shown inFIG. 5, the cam follower has a shaft portion31and a pair of bearings32A and32B mounted on the shaft portion31.

The shaft portion31has a cylindrical shape. A screw33is passed through a hollow portion of the shaft portion31, and the shaft portion31is screwed to an outer peripheral portion of the second lens cylinder18. The outer peripheral portion of the second lens cylinder18is provided with a screw hole35at a location where the shaft portion31is attached.

Each of the pair of bearings32A and32B is composed of a rolling bearing such as a ball bearing. The pair of bearings32A and32B is composed of a first bearing32A located on the distal end side of the shaft portion31and a second bearing32B located on the base end side of the shaft portion31. A spacer34is disposed between the first bearing32A and the second bearing32B. An inner ring portion of each of the first bearing32A and the second bearing32B is lightly press-fitted to the shaft portion31and is mounted on the shaft portion31. An outer ring portion of each of the first bearing32A and the second bearing32B mounted on the shaft portion31is rotatably held with respect to the shaft portion31.

As shown inFIGS. 1 and 4, the second lens cylinder18has a body part18A and a movable part18B provided at the distal end of the body part18A.

The movable part18B has a cylindrical shape. The body part18A has a fitting portion18ato which the movable part18B fits at the distal end. The fitting portion18ais composed of a stepped portion, and is constituted by reducing the distal end portion of the body part18A. The movable part18B is fitted to the outer periphery of the fitting portion18aand attached to the body part18A. The body part18A is an example of a third cylinder body part, and the movable part18B is an example of a third cylinder movable part.

As a slip-off prevention mechanism, a protrusion24is provided on the inner periphery of the movable part18B. On the other hand, a groove portion26is provided on the outer periphery of the fitting portion18a. The protrusion24is provided at three locations on an inner peripheral surface of the movable part18B. The groove portion26is composed of a groove to which the protrusion24is fitted. The groove portion26is provided at three locations on an outer peripheral surface of the fitting portion18a. The groove portion26has an introduction portion26A and a regulation portion26B. The introduction portion26A is formed from the distal end of the body part18A along the optical axis Z. The regulation portion26B is formed along the circumferential direction from an end part of the introduction portion26A.

The movable part18B is attached to the body part18A by fitting the protrusion24to the regulation portion26B of the groove portion26. As a result, the movable part18B is attached to the body part18A by being prevented from slipping off.

The protrusion24is fitted to the regulation portion26B with a certain play. That is, the width of the protrusion24in an optical axis direction is narrower than the width of the regulation portion26B in the optical axis direction. As a result, the movable part18B can be movably held along the optical axis Z in a state where the protrusion24is fitted to the regulation portion26B.

In a case where the movable part18B is attached to the body part18A, the movable part18B is attached to the body part18A via a biasing spring18C. The biasing spring18C is composed of a wave washer. The wave washer is formed by bending a flat washer into a wavy shape, and by being crushed, acts as a spring to remove a gap in the axial direction. The biasing spring18C is disposed between the movable part18B and the body part18A at a rear end part of the movable part18B. As a result, the movable part18B is biased toward a distal end direction along the optical axis Z with respect to the body part18A.

The first cam follower30A on the front side, which is one cam follower, is provided on the movable part18B, and the second cam follower30B on the rear side, which is the other cam follower, is provided on the body part18A. As described above, the movable part18B is biased toward a distal end direction along the optical axis Z with respect to the body part18A. Therefore, the first cam follower30A and the second cam follower30B are biased in a direction of separating from each other along the optical axis Z.

As shown inFIG. 4, the pair of cam grooves40A and40B is provided at three locations on a peripheral surface of the cam cylinder16. A disposition interval of the pairs of cam grooves40A and40B is the same as the disposition interval of the pairs of cam followers30A and30B. That is, the pairs of cam grooves40A and40B are disposed at equal intervals along the circumferential direction. The pair of cam grooves40A and40B has the same shape (cam locus) and is disposed in the front-rear direction along the optical axis Z. Therefore, the pair of cam grooves40A and40B is disposed in parallel with each other. Hereinafter, the cam groove40A located on the front side is referred to as a first cam groove40A, and the cam groove40B located on the rear side is referred to as a second cam groove40B, as necessary, to distinguish between them.

The pair of cam followers30A and30B is individually fitted to the pair of cam grooves40A and40B. That is, the first cam follower30A is fitted to the first cam groove40A, and the second cam follower30B is fitted to the second cam groove40B.FIG. 6is an enlarged cross-sectional view of an installation portion of the pair of cam followers. As described above, the first cam follower30A and the second cam follower30B are biased in a direction of separating from each other along the optical axis Z by the biasing spring18C. Therefore, in a case where the first cam follower30A is fitted to the first cam groove40A, the first cam follower30A is pressed to abut against an inner wall surface40aon the front side of the first cam groove40A, thereby being fitted to the first cam groove40A. On the other hand, in a case where the second cam follower30B is fitted to the second cam groove40B, the second cam follower30B is pressed to abut against an inner wall surface40bon the rear side of the second cam groove40B, thereby being fitted to the second cam groove40B. As a result, the backlash generated between the cam cylinder16and the second lens cylinder18can be removed, and the second lens cylinder18can be stably held with respect to the cam cylinder16.

As shown inFIG. 4, the straight advance groove50is composed of a straight-shaped groove disposed along the optical axis Z. The straight advance groove50is provided at three locations on a peripheral surface of the second fixed cylinder12B. A disposition interval of the straight advance grooves50is the same as the disposition interval of the pairs of cam followers30A and30B. That is, the straight advance grooves50are disposed at equal intervals along the circumferential direction. The pair of cam followers30A and30B is fitted to the same straight advance groove50. The straight advance groove50is an example of a first groove.

The positioning roller60is a roller that positions the cam cylinder16in the optical axis direction with respect to the second fixed cylinder12B. The positioning roller60also functions as a roller that regulates a rotation range of the cam cylinder16.

As shown inFIG. 4, the positioning roller60is provided at three locations on an outer peripheral surface of the cam cylinder16. The positioning rollers60are disposed at equal intervals along the circumferential direction.

FIG. 7is a cross-sectional view of the interchangeable lens at a location where the positioning roller is installed.FIG. 8is an enlarged cross-sectional view of an installation portion of the positioning roller.FIG. 9is a cross-sectional view showing the configuration of the positioning roller and the torque applying roller.

The positioning roller60is composed of a bearing (rolling bearing such as a ball bearing). An inner ring portion of the positioning roller60is lightly press-fitted to a roller support shaft61provided on the cam cylinder16and is mounted on the roller support shaft61. An outer ring portion of the positioning roller60mounted on the roller support shaft61is rotatably supported.

The roller support shaft61has a cylindrical shape. A screw62is passed through a hollow portion of the roller support shaft61, and the roller support shaft61is screwed to an outer peripheral portion of the cam cylinder16. The outer peripheral portion of the cam cylinder16is provided with a screw hole64at a location where the roller support shaft61is attached.

As shown inFIG. 4, the positioning groove70is composed of a straight-shaped groove disposed along the circumferential direction. The positioning groove70is provided at three locations on the peripheral surface of the second fixed cylinder12B. A disposition interval of the positioning grooves70is the same as the disposition interval of the positioning rollers60. That is, the straight advance grooves50are disposed at equal intervals along the circumferential direction. The positioning groove70is an example of a second groove.

The positioning roller60is fitted to the positioning groove70. As a result, the cam cylinder16is positioned in the optical axis direction with respect to the second fixed cylinder12B. In addition, the rotation range (movable range) of the cam cylinder16is regulated with respect to the second fixed cylinder12B. The positioning roller60is an example of a second roller.

The driving unit80rotationally drives the cam cylinder16. The cam cylinder16has a gear portion16A for driving on the inner peripheral portion at the rear end thereof. The driving unit80rotationally drives the gear portion16A to rotate the cam cylinder16.

As shown inFIG. 4, the driving unit80is attached to the rear end cover12C of the fixed cylinder12. The driving unit80includes a motor and a reduction gear, and these are assembled into a case82to be unitized.

FIG. 10is a perspective view showing a schematic configuration of the driving unit with the case removed.FIGS. 11 and 12are diagrams showing the state in which the motor and the reduction gear are attached to the lens barrel.FIG. 11corresponds to a rear view of the lens barrel with the exterior body removed. In addition,FIG. 12corresponds to a rear perspective view of the rear portion of the lens barrel with the exterior body removed.FIGS. 11 and 12show a state in which the rear end cover12C of the fixed cylinder12and the case82of the driving unit80are omitted for convenience.

As described above, the driving unit80has a motor84and a reduction gear88that reduces the speed of rotation of the motor84. The driving unit80is an example of a driving unit.

The motor84is composed of, for example, a stepping motor. The motor84comprises an encoder86for detecting the rotation speed.

The reduction gear88has a gear train. The gear train is composed of a combination of a plurality of gears88A to88F. The reduction gear88of the present embodiment includes a worm gear in a part of the gear train. The worm gear is composed of a worm and a worm wheel. In the reduction gear88of the present embodiment, the gear88A connected to an output shaft of the motor84is composed of a worm. The final gear88F constitutes a driving gear. The driving unit80is attached to the rear end cover12C, whereby the driving gear88F is engaged with the gear portion16A of the cam cylinder16. As a result, in a case where the motor84is driven, the rotation of the motor84is transmitted to the gear portion16A of the cam cylinder16via the reduction gear88, and the cam cylinder16is rotated.

The torque applying mechanism100applies a load torque to the rotation of the cam cylinder16. As shown inFIG. 4, the torque applying mechanism100has a torque applying roller102provided in the cam cylinder16, a biasing ring104that is pressed to abut against the torque applying roller102, a biasing spring106for biasing the biasing ring104, and a spring support frame108for supporting the biasing spring106.

The torque applying roller102is composed of a cylindrical body (so-called normal roller). As shown inFIG. 9, the torque applying roller102is supported by the roller support shaft61provided on the cam cylinder16. More specifically, the roller support shaft61is fitted to the inner peripheral portion of the torque applying roller102, whereby the torque applying roller102is mounted on the roller support shaft61and rotatably supported with respect to the roller support shaft61.

As described above, the roller support shaft61is also a shaft that supports the positioning roller60. The torque applying roller102is mounted on the roller support shaft61via a spacer110on the positioning roller60. The torque applying roller102mounted on the roller support shaft61is rotatably supported by being prevented from slipping off by a head portion62A of the screw62for fixing the roller support shaft61.

Unlike the positioning roller60composed of a bearing, the torque applying roller102is only fitted to the roller support shaft61, so that a load is generated during the rotation. Specifically, a load is generated in the rotation due to friction (rotational friction) between an inner peripheral portion of the torque applying roller102and an outer peripheral portion of the roller support shaft61. Since friction is generated between the torque applying roller102and the roller support shaft61in this way, it is preferable to select a material resistant to wear for the torque applying roller102and the roller support shaft61. For example, one of the torque applying roller102and the roller support shaft61may be made of stainless steel, and the other may be made of brass. The torque applying roller102may be made of resin. For example, the torque applying roller102made of polyacetal having excellent sliding characteristics can also be used. The torque applying roller102is an example of a first roller.

As shown inFIG. 4, the biasing ring104has a ring shape, is fitted to an outer peripheral portion of the second fixed cylinder12B, and is mounted on the outer peripheral portion of the second fixed cylinder12B. The biasing ring104mounted on the outer peripheral portion of the second fixed cylinder12B is held to be movable in the front-rear direction along the optical axis Z. The biasing ring104may be made of, for example, anodized aluminum. The biasing ring104is an example of a first frame.

The biasing spring106is composed of a wave washer. The biasing spring106is mounted on the outer peripheral portion of the second fixed cylinder12B to bias the biasing ring104toward the torque applying roller102. The biasing spring106is an example of a biasing member.

As shown inFIG. 4, the spring support frame108is composed of a ring-shaped frame. The spring support frame108is fitted to the outer peripheral portion of the second fixed cylinder12B and is mounted on the outer peripheral portion of the second fixed cylinder12B. The spring support frame108mounted on the second fixed cylinder12B is fixed to the second fixed cylinder12B by screwing a plurality of locations on the peripheral surface with a screw108A. The spring support frame108is an example of a second frame.

The biasing spring106is disposed between the spring support frame108and the biasing ring104, and biases the biasing ring104toward the torque applying roller102. As a result, the biasing ring104is pressed to abut against the torque applying roller102. In addition, in a case where the biasing ring104is pressed to abut against the torque applying roller102, the load torque is applied to the rotation of the cam cylinder16. In a case where the biasing ring104is pressed to abut against the torque applying roller102, the cam cylinder16is biased along the optical axis Z, and the backlash of the cam cylinder16with respect to the fixed cylinder12is removed.

[Position Detection Mechanism of Second Lens Cylinder]

The position detection mechanism of the second lens cylinder18is composed of the encoder86provided in the motor84and a photo interrupter120provided in the fixed cylinder12.

As described above, the encoder86detects the rotation speed of the motor84. The photo interrupter120detects that the second lens cylinder18is located at the origin position. The photo interrupter120is provided on the rear end cover12C of the fixed cylinder12. The photo interrupter120detects a light shielding portion122provided on the second lens cylinder18to detect that the second lens cylinder18is located at the origin position.

The position of the second lens cylinder18is detected by the following procedure. First, the photo interrupter120detects that the second lens cylinder18is located at the origin position. The rotation speed of the motor84after the detection is detected by the encoder86. As a result, the position of the second lens cylinder18with respect to the origin position is detected. That is, since the amount of movement of the second lens cylinder18with respect to the rotation speed of the motor84is known, the position of the second lens cylinder18with respect to the origin position can be detected by detecting the rotation speed of the motor84from the origin position.

In the interchangeable lens1of the present embodiment configured as described above, the motor84is driven, whereby the second lens group L2, which is a focus lens group, moves in the front-rear direction along the optical axis Z to adjust the focus. More specifically, in a case where the motor84is driven, the rotation of the motor84is transmitted to the cam cylinder16, and the cam cylinder16is rotated, thereby causing the second lens cylinder18that holds the second lens group L2to move in the front-rear direction along the optical axis Z by the action of the cam.

The rotation of the motor84is transmitted to the cam cylinder16via the gear train. Therefore, in a case of stopping, the stop position of the second lens cylinder18becomes unstable within a range of the backlash due to the influence of the inertia force and gravity of the movable part. However, since the interchangeable lens1of the present embodiment comprises the torque applying mechanism100, high stop accuracy can be ensured. That is, since the torque applying mechanism100applies the load torque to the rotation of the cam cylinder16, the second lens cylinder18can be stably stopped even in a case where there is the backlash in the engaging portion of the gear.

The load torque is applied as follows. The cam cylinder16comprises the torque applying roller102. The biasing ring104biased by the biasing spring106is pressed to abut against the torque applying roller102. In a case where the cam cylinder16is rotated, the torque applying roller102rolls along the biasing ring104. As a result, the rotational friction is generated between the inner periphery of the torque applying roller102and the outer periphery of the roller support shaft61. This rotational friction acts as the load torque for the cam cylinder16.

As described above, according to the interchangeable lens1of the present embodiment, since the load torque is applied to the rotation of the cam cylinder16, the second lens cylinder18can be stably stopped. In addition, since the load torque is generated by the rotational friction of the torque applying roller102, the load torque can always be applied in a stable state.

The torque applying mechanism100also has a function of removing the backlash of the cam cylinder16. That is, the torque applying roller102provided coaxially with the positioning roller60is biased in the optical axis direction by the biasing ring104, whereby the positioning roller60is pressed to abut against an inner wall surface of the positioning groove70. As a result, the backlash of the cam cylinder16with respect to the fixed cylinder12can be removed. In addition, by sharing the positioning roller60and the shaft (roller support shaft61), the configuration can be simplified.

[Optimization of Load Torque]

The load torque is set to a value that can suppress the rotation due to the inertia force and gravity. As an example, in a case where the torque required to stop the cam cylinder at set deceleration is T1, and the torque required to stop the second lens cylinder at set deceleration is T2in a case where the second lens cylinder is driven in a direction in which the second lens cylinder falls by its own weight with the lens facing downward or upward, a load torque TF is set so as to satisfy the following conditional expression.

The torques T1and T2are calculated from the deceleration of the motor set by the drive control. Since the coefficient of dynamic friction of the bearing is extremely small, it is ignored in the calculation.

FIG. 13is an explanatory diagram of a calculation method of torques T1, T2, and T3.

The torque T1[N·m] is calculated by the following equation.

Here, I is the moment of inertia I of the cam cylinder, and AC is the deceleration [rad/s2] of the cam cylinder.

The deceleration AC [rad/s2] of the cam cylinder is calculated by the following equation.

Here, AM is the deceleration [rad/s2] of the motor. In addition, RR is the reduction ratio. The reduction ratio RR is calculated by the following equation.

RR=rotation speed of motor/rotation speed of cam cylinder

The torque T2[N·m] is calculated by the following equation.

Here, FR is the rotation direction component force [N] of the cam cylinder, as shown inFIG. 13. In addition, R is the distance [m] from the center of rotation to the cam groove. The rotation direction component force FR [N] of the cam cylinder is calculated by the following equation.

Here, θ is the cam angle [rad], as shown inFIG. 13. In addition, FL is the force [N] required to decelerate the second lens cylinder in a case where the second lens cylinder is driven in a direction in which the second lens cylinder falls by its own weight with the lens facing downward or upward. FL [N] is calculated by the following equation.

Here, M [Kg] is the total weight of the second lens cylinder including the second lens group. In addition, AL is the deceleration of the second lens cylinder [rad/s2]. AL [rad/s2] is calculated by the following equation.

Here, AM is the deceleration [rad/s2] of the motor. In addition, L is the cam lead [m/rad]. The cam lead is the amount of movement that proceeds to 1 [rad].

(3) Load Torque TF

The load torque TF [N·m] is calculated by the following equation.

Here, W is the load [N] perpendicular to the friction surface. In addition, μ is the coefficient of dynamic friction of the friction surface. In addition, RM is the distance [m] from the center of rotation of the friction surface.

The load applied to the torque applying roller102, the coefficient of dynamic friction between the torque applying roller102and the roller support shaft61, and the like are set so that the load torque TF satisfies the above-described conditions. The load applied to the torque applying roller102can be adjusted by the spring constant of the biasing spring106(power of the biasing spring). The coefficient of dynamic friction can be adjusted by the material and surface roughness of the torque applying roller102and the roller support shaft61.

In a case where the load torque TF satisfies the above-described conditions, the motor can be stopped faster than the deceleration of the motor set by the drive control of the lens, and the state can be maintained. As a result, stable position accuracy can be ensured. The load torque TF is set as small as possible within the range satisfying the above-described conditions, thereby achieving both the drive speed and the stop accuracy.

Modification Example

(1) Modification Example of Torque Applying Mechanism

(a) First Modification Example

FIG. 14is a diagram showing a first modification example of the torque applying mechanism.

In the torque applying mechanism100of the above embodiment, the torque applying roller (first roller)102and the positioning roller (second roller)60share the roller support shaft61.

In the configuration in which the torque applying roller102and the positioning roller60share the roller support shaft61, as shown inFIG. 14, the same operation and effect can be obtained also in a case where the torque applying roller102is composed of a bearing (roller bearing or the like) and the positioning roller60is composed of a so-called normal roller (cylindrical body). In this case, an inner peripheral surface of the positioning roller60and an outer peripheral surface of the roller support shaft61function as friction surfaces. That is, the frictional force generated between the inner peripheral surface of the positioning roller60and the outer peripheral surface of the roller support shaft61acts as the load torque.

(b) Second Modification Example

FIG. 15is a diagram showing a second modification example of the torque applying mechanism.

In the example shown inFIG. 15, both the torque applying roller102and the positioning roller60are composed of normal rollers. In this case as well, the same operation and effect can be obtained. In this case, the inner peripheral surfaces of the torque applying roller102and the positioning roller60and the outer peripheral surface of the roller support shaft61function as friction surfaces.

(c) Third Modification Example

FIG. 16is a diagram showing a third modification example of the torque applying mechanism.

FIG. 16shows an example of a case where the torque applying roller102is supported by a dedicated shaft (roller support shaft). As shown inFIG. 16, the roller support shaft112that supports the torque applying roller102is provided in the cam cylinder16. The roller support shaft112has a cylindrical shape, and a screw66is passed through a hollow portion of the roller support shaft112, and the roller support shaft112is screwed to the cam cylinder16. The cam cylinder16is provided with a screw hole58at a location where a roller support shaft102A is attached. In addition, the second fixed cylinder12B is provided with a groove72through which the roller support shaft102A is passed. The groove72is disposed along the circumferential direction.

As described above, the torque applying roller102can be provided separately from the positioning roller60. In a case where the torque applying roller102and the positioning roller60share the shaft as in the above embodiment, the configuration can be simplified.

In the above embodiment, the spring support frame108, which is a support portion of the biasing spring106, is attached to the second fixed cylinder12B with the screw108A, but the support portion of the biasing spring106may be provided integrally with the second fixed cylinder12B.

FIG. 17is a diagram showing a modification example of the support portion of the biasing spring.

In the example shown inFIG. 17, the second fixed cylinder12B has a flange portion12bon the outer peripheral portion, and the flange portion12bfunctions as the support portion of the biasing spring106. The biasing spring106is disposed between the biasing ring104and the flange portion12b, and biases the biasing ring104in the direction of the torque applying roller102along the optical axis Z.

In the example shown inFIG. 17, an example of a case where the torque applying roller102is biased from the front side is shown. That is, the biasing ring104is disposed on the front side of the torque applying roller102to bias the torque applying roller102from the front side. In this way, the torque applying roller102can be biased from the front side.

In this way, in a case where the support portion of the biasing spring106is integrated with the second fixed cylinder12B, the configuration can be simplified. On the other hand, in a case where the spring support frame108is configured to be attached to and detached from the second fixed cylinder12B as in the above embodiment, the assemblability and maintainability can be improved.

In the above embodiment, the biasing spring106is composed of a wave washer, but the configuration of the biasing spring is not limited to this. In addition, for example, the biasing spring106may be composed of a coil spring or the like.

(2) Modification Example of Adjustment Method of Load Torque

The load torque applied by the torque applying mechanism100can also be adjusted by the number of torque applying rollers102to be installed. That is, the number of torque applying rollers102to be installed is increased or decreased according to the required load torque.

In a case where the torque applying roller102is attached to the roller support shaft61on which the positioning roller60is supported as in the above embodiment, rollers (normal rollers) used as the torque applying roller102are replaced with bearings, whereby the number of rollers to be installed can be adjusted.FIG. 18is an explanatory view of a method of adjusting the load torque by adjusting the number of torque applying rollers to be installed.FIG. 18shows an example of a case where one of the three torque applying rollers102is replaced with a bearing.

In the configuration in which the torque applying roller102and the positioning roller60share the roller support shaft61, the load torque can be adjusted by replacing the roller constituting the positioning roller60with a normal roller from a bearing.

(3) Modification Example of Lens Barrel

In the above embodiment, the second lens cylinder18is driven by the pair of cam followers30A and30B and the pair of cam grooves40A and40B, but the second lens cylinder18may be driven by one cam follower and one cam groove.

Second Embodiment

FIG. 19is a cross-sectional view showing an overall schematic configuration of an interchangeable lens according to the second embodiment.

In the interchangeable lens1of the present embodiment, the configuration of the second lens cylinder18is different from the configuration of the interchangeable lens of the first embodiment. In the interchangeable lens1of the present embodiment, the second lens cylinder18is configured to shield opening portions of the pair of cam grooves40A and40B provided in the cam cylinder16in the entire movable area. That is, at any position, the second lens cylinder18is configured to shield the opening portions of the pair of cam grooves40A and40B.

First, for comparison, a relationship between the cam cylinder16and the second lens cylinder18in the interchangeable lens1of the first embodiment will be described.

(1) Interchangeable Lens of First Embodiment

FIG. 20is a diagram showing a relationship between the cam cylinder and the second lens cylinder in a case where the second lens cylinder is moved to the foremost side in the interchangeable lens of the first embodiment. In addition,FIG. 21is a diagram showing a relationship between the cam cylinder and the second lens cylinder in a case where the second lens cylinder is moved to the rearmost side in the interchangeable lens of the first embodiment. InFIG. 21, the broken line indicates the cam cylinder16, and the solid line indicates the second lens cylinder18. In addition, inFIG. 21, the cam follower is omitted for convenience.

As shown inFIG. 20, in the interchangeable lens1of the first embodiment, in a case where the second lens cylinder18is moved to the foremost side, a rear end portion (the end part on the rear side in the optical axis direction) of the second cam groove40B is opened without being shielded by the second lens cylinder18.

As shown inFIG. 21, in a case where the second lens cylinder18is moved to the rearmost side, a front end portion (the end part on the front side in the optical axis direction) of the first cam groove40A is opened without being shielded by the second lens cylinder18.

(2) Interchangeable Lens of Second Embodiment

Next, a relationship between the cam cylinder16and the second lens cylinder18in the interchangeable lens1of the present embodiment will be described.

FIG. 22is a diagram showing a relationship between the cam cylinder and the second lens cylinder in a case where the second lens cylinder is moved to the foremost side in the interchangeable lens of the present embodiment.FIG. 23is a diagram showing a relationship between the cam cylinder and the second lens cylinder in a case where the second lens cylinder is moved to the rearmost side in the interchangeable lens of the present embodiment. InFIG. 23, the broken line indicates the cam cylinder16, and the solid line indicates the second lens cylinder18. In addition, inFIG. 23, the cam follower is omitted for convenience.

As shown inFIG. 22, in a case of the interchangeable lens1of the present embodiment, in a case where the second lens cylinder18is moved to the foremost side, the opening portion of each of the pair of cam grooves40A and40B provided in the cam cylinder16is shielded by the second lens cylinder18. As shown inFIG. 23, in a case where the second lens cylinder18is moved to the rearmost side, similarly, the opening portion of each of the pair of cam grooves40A and40B provided in the cam cylinder16is shielded by the second lens cylinder18.

As described above, in the interchangeable lens1of the present embodiment, the opening portions of the pair of cam grooves40A and40B are shielded by the second lens cylinder18in the entire movable area of the second lens cylinder18. As a result, it is possible to prevent dust from entering the inside of the cam cylinder16via the cam grooves40A and40B. In particular, in a case where a friction portion is provided on the outside of the cam cylinder16as in the interchangeable lens1of the present embodiment, the friction powder can be prevented from entering the cam cylinder16, so that the present invention works effectively.

The second lens cylinder18shields the opening portions of the cam grooves40A and40B in the entire movable area by adjusting the length (length in the optical axis direction) of the portion of the second lens cylinder18fitted to the inner peripheral surface of the cam cylinder16. That is, the fitting portion overlaps the cam grooves40A and40B.

In a case where the second lens cylinder18has the movable part18B as in the interchangeable lens1of the present embodiment, the function of shielding the opening portion of the first cam groove40A can be realized by adjusting the length of the movable part18B.

OTHER EMBODIMENTS

In the above embodiment, a case where the present invention is applied to the interchangeable lens of the lens interchangeable camera has been described as an example, but the application of the present invention is not limited to this. For example, the present invention can be applied to a lens barrel of a lens-integrated camera (a camera in which a lens is integrally provided in a camera body). In addition to the camera, the present invention can also be applied to a lens barrel of a microscope, a telescope, or the like. The camera includes various cameras such as a still camera, a video camera, a television camera, and a cine camera, and further includes a device having a camera function (for example, a mobile phone with a camera, a smartphone, and a tablet computer).

In the above embodiment, a case where the driving unit is built in the lens barrel has been described as an example, but the driving unit may be provided outside the lens barrel. For example, in the lens interchangeable camera, the same can be applied to a case where the driving unit (motor) is provided on the camera body side, and the rotational power is obtained from the camera body side to rotationally drive the cam cylinder.

In the above embodiment, the driving unit is composed of a motor with a so-called reduction gear, but the configuration of the driving unit is not limited to this. As described above, in the motor with the reduction gear having the gear train, in a case of stopping, the stop position of the second lens cylinder18becomes unstable within a range of the backlash due to the influence of the inertia force and gravity of the movable part. Therefore, the present invention works particularly effectively.

EXPLANATION OF REFERENCES