JPH06250065A - Power transmission device - Google Patents

Abstract

(57) [Summary] [Purpose] The conventional lens drive mechanism has poor operability because the lens drive system is loaded with a lens natural movement prevention force during manual drive. An object of the present invention is to provide a power transmission device capable of driving a lens with a smaller operating force than before when driving manually. In the manual drive state, no friction load is applied to the gear carrying member 8 integrated with the intermediate gear 9, so that the drive gear 3 can be driven lightly even if the operation ring 2 is rotationally operated. When the knob 15 is rotated when not in use, the drive pin 18 eccentrically fixed to the cam 16 moves to the right of the shaft 7 to move the member 8 and the gear 9 to the right, and the member 8 When the friction plate 13 fixed to the above is pressed against the protrusion of the housing 4, the member 8 is fixed to the cylindrical body 4 by a frictional force. The natural movement of the lens is equal to or less than the frictional force of the gear 9, and the frictional force of the gear 9 prevents the natural movement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power transmission device, and more particularly to a power transmission device suitable for optical equipment such as a lens barrel for a camera.

[0002]

2. Description of the Related Art A lens barrel mounted on a single-lens reflex camera or a video camera is equipped with a lens driving mechanism for focusing and zooming a photographing lens, which is generally a manual driving mechanism. Power transmission switching means is provided in the lens barrel so that the lens barrel can be driven by either a motor drive or a motor drive. Also, recent lens barrels are equipped with a natural movement prevention device that applies an appropriate load to the lens drive system so that the photographing lens does not naturally move due to gravity when the lens drive is switched to the manual drive state. Is also known.

[0003]

In the conventional lens barrel having the above-described natural lens movement prevention device, when the lens drive is switched to the manual drive, the natural movement prevention torque generated from the lens natural movement prevention device is generated. Since it is always added to the power transmission mechanism of the lens drive system, a large manual operation force is required, and as a result, operability is deteriorated. In particular, in recent lens barrels, the weight of zoom and focusing lenses has become heavier to improve optical performance, and the natural movement force of the lenses has also increased. The natural movement prevention torque to be applied to the mechanism must be increased, but if the natural movement prevention torque applied from the lens natural movement prevention device to the lens drive mechanism is increased, the operability during manual driving is further deteriorated. In addition, since the natural movement of the lens is less likely to occur during use under low temperature conditions in which the viscosity of grease increases and the clearance between moving members decreases, the load torque from the lens natural movement prevention device is applied, Even if the lens driving load during driving is increased, the lens natural movement preventing device adversely affects the lens driving.

An object of the present invention is to eliminate the above-mentioned drawbacks inherent in the lens driving mechanism of the lens barrel and to provide a power transmission device with improved operability during manual driving.

[0005]

A conventional lens driving power transmission mechanism for a lens barrel has a drawback in that a load torque generated by the lens natural movement preventing device is constantly applied in a manually driven state. In the present invention, the lens natural movement prevention torque is not applied to the drive system during manual driving, and the lens natural movement prevention torque is applied to the lens driving mechanism only when the lens barrel is not used or when the lens is likely to move naturally. It is characterized by having done. Specifically, in the power transmission device of the present invention, the linked state of the power transmission system can be selected at three operation positions, and electric drive by a motor is selected at the first operation position, and the second operation position is selected. Manual drive is selected, and in the second operation position, the load for preventing natural movement of the driven object is not applied to the drive mechanism, and in the third operation position, manual drive is enabled. At the same time, a natural movement prevention load for preventing the natural movement of the driven object is added to the drive mechanism.

[0006]

In the power transmission device of the present invention, when the switching operation member of the power transmission system is operated to the first operation position, a power transmission state in which the driven object can be driven by electric drive by the motor is set, and the operation member is moved to the second operation position. When it is moved to the operation position, the driven object can be driven manually, and the manual driving force transmission system enters a driving force transmission state in which a load for preventing natural movement of the driven object is not applied. When the driven object is operated to the third operation position, the driven object can be manually driven, and a load for preventing natural movement of the driven object is applied to the manual drive force transmission system in a driving force transmission state. Therefore, if the operation member is operated to the second operation position, a driving force transmission state in which a natural movement preventing load of the driven object is not applied is exerted, so that the driven object can be driven by a small manual force. it can.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

<Embodiment 1> FIGS. 1 to 6 show a first embodiment of a power transmission device in a lens barrel to which the present invention is applied. FIG. 1 is a manually driven state, and FIG. 5 is an electrically driven state. Shows the state of.

In FIG. 1, 1 is a fixed barrel which is a component of a lens barrel, 2 is a known operation ring, and 3 is the ring 2.
A gear fixed to the outer periphery of the housing 4, a housing of a drive unit attached to the fixed barrel 1, 5 a motor held in the housing 4, 6 a motor gear fixed to the shaft of the motor 5, 7
Is a shaft attached to the housing 4, 8 is an intermediate gear carrying member rotatably and slidably held by the shaft 7, and 8a and 8b.
Is a flange portion of the member 8, 9 is an intermediate gear rotatably fitted to the member 8, 10 is a wave washer inserted in the member 8, 11 is a washer whose rotation is restricted with respect to the member 8, Reference numeral 12 is a nut attached to the member 8, 13 is a friction plate fixed to the flange portion 8b of the member 8, 14 is a retaining knob, 15 is a switching knob, 16 is a cam, and 17 is a cam 16 fixed to the housing. Cam shaft rotatable with respect to 4, 18
Is a drive pin fixed to the cam 16 at a position eccentric to the cam shaft 17 by engaging the flange portions 8a and 8b of the intermediate gear carrying member 8, and 19 is a leaf spring attached to the housing 4 and pressing the cam 16. Is. Switching knob 15 to drive pin 1
The members up to 8 constitute a switching operation member and an intermediate gear moving means. 16a and 16 in FIGS.
Reference numerals b and 16c represent cam surfaces of the cam 16.

In the above-mentioned structure, when the switching knob 15 is rotated counterclockwise in the state of FIG. 2 and rotated to a position where the cam surface 16a and the leaf spring 19 are in contact with each other as shown in FIG.
The drive pin 18 at a position eccentric with respect to the rotary shaft 17 pushes the flange 8a of the intermediate gear carrying member 8 from the position shown in FIG. 1 to the position shown in FIG. Engage with 6. The intermediate gear 9 meshes with the gear 3 provided on the operation ring 2, and the driving force of the motor 5 is transmitted via the motor gear 6 and the intermediate gear 9 to the operation ring 2.
To the electric drive state. In the state shown in the drawing, since there is a proper clearance between the drive pin 18 and the flange of the member 8, the drive pin 18 does not hinder the rotation of the member 8.

Next, as shown in FIG. 4, when the switching knob 15 is turned to a position where the cam surface 16b and the leaf spring 19 are in contact with each other, the drive pin 18 pushes the flange portion 8b to move the member 8 from the position shown in FIG. 5 to the right. The intermediate gear 9 and the motor gear 6 are disengaged from each other, and the friction plate 13 of the flange portion 8b is applied to the housing 4. At this time, the cam surface 16b and the leaf spring 19 are not yet in full contact with each other, and the friction plate 13 is constantly pressed by the spring 19 via the drive pin 18 and the cam 16, so that the member 8 is applied to the housing 4 by the friction force. It will be almost fixed. The intermediate gear 9 meshes with the gear 3 and is fixed by frictional force on the member 8 by being pressed by the wave washer 10 and the nut 12, and this frictional force is a load for preventing natural movement of the lens. Becomes It should be noted that the friction plate 13 and the housing 4 can be calculated from the frictional force generated by the wave washer 10.
The frictional force with must be greater.

Next, as shown in FIG. 2, the switching knob 15 is brought into a position where the cam surface 16c and the leaf spring 19 are in contact with each other as shown in FIG. When the operating ring 2 is rotationally operated, the frictional load is not applied to the operating ring 2 because the member 8 is rotatable, so that the ring 2 can be operated lightly.

<Second Embodiment> FIGS. 7 to 12 show a second embodiment of a power transmission device for a lens barrel to which the present invention is applied.
FIG. 7 shows an electric drive state, and FIGS. 9 and 11 show a manual drive state.

In FIG. 7, 20 is a rotation regulating pin driven into the shaft 57, 21 is a coil spring, 22 is a stepped washer fixed to the shaft 57, 51 is a lens barrel fixed cylinder.
Reference numeral 52 is an operation ring, 53 is a gear provided on the outer periphery of the operation ring 52, 54 is a housing of a drive unit attached to the fixed cylinder 51, 55 is a motor held by the housing 54, 5
6 is a motor gear fixed to the shaft of the motor 55, 57
Is a shaft attached to the housing 54, 58 is slidably held by the shaft 57, and the intermediate gear carrying members 58a and 58b having a key groove for engaging the rotation restricting pin 20 in the inner diameter are flanges of the member 58. Reference numeral 59 is an intermediate gear rotatably carried by the member 58, 61 is a washer fixed to the member 58 so as not to rotate, and 64 is a stopper.
Reference numeral 5 is a switching knob, 66 is a cam, 67 is a cam shaft fixed to the cam 66 and rotatable with respect to the casing 54, 68 is eccentric with respect to the cam shaft 67 by engaging with flange portions 58a and 58b of the member 58. Drive pin fixed to cam 66 at position 6,
A leaf spring 9 is attached to the housing 54 and presses the cam 66.

In the above structure, when the switching knob 65 is rotated clockwise from the position shown in FIG. 10 to the position where the cam surface 66b and the leaf spring 69 come into contact with each other to change the state to that shown in FIG. Flange portion 58b from position 9
To the right to slide the member 58 to the right,
By engaging the intermediate gear 59 and the motor gear 56 as shown in FIG. At this time, in the state of FIG. 7, the used length of the coil spring 21 becomes a natural length, and no axial force is applied to the intermediate gear 59 from the spring 21. Since the stepped washer 22 is inserted into the inner diameter of the coil spring 21, even if the coil spring 21 has a natural length, it does not deviate from the shaft 57.

Next, the switching knob 65 from the position shown in FIG.
By rotating it counterclockwise as shown in FIG.
When the c and the leaf spring 69 are brought into contact with each other, the drive pin 68 pushes the flange portion 58a to the left from the position of FIG. 7 to slide the member 58 to the left, so that the intermediate gear 59 and the motor gear 56 are engaged with each other. After being separated, it becomes a manual state as shown in FIG. At this time, the used length of the coil spring 21 is reduced by the sliding length of the member 58.
When the washer 61 is pressed against the intermediate gear 59 by the force of, the friction load is applied to the intermediate gear 59. This frictional load gives the operation ring 52 a feeling of operation resistance.

Next, the switch knob 6 from the position shown in FIG.
5 is rotated counterclockwise to change the cam surface 66a and the plate spring 69 into contact with each other as shown in FIG.
1 is further contracted from the state of FIG. 9 and becomes the state of FIG. 11, and the washer 61 is pressed against the intermediate gear 59 with a force larger than that of the state of FIG. Larger frictional loads are applied. The friction load in this state is a natural movement preventing load that prevents natural movement of the lens group.

[0018]

As described above, in the power transmission device according to the present invention, the natural movement preventing device for preventing the natural movement of the driven object does not operate in the manually driven state, so that the manual operation member is conventionally used. It can be operated with a smaller operating force compared to the device, and therefore the operability of optical equipment such as a lens barrel is improved, and the lens operation can be performed lightly even in optical equipment equipped with a heavy lens. You can Further, it is possible to make a selection so as to prevent the natural movement of the lens depending on the use environment.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a power transmission device according to a first embodiment of the present invention, showing a manual drive state.

FIG. 2 is a plan view showing a state of a cam that is a part of a switching operation member / intermediate gear moving means and a spring that locks the member in the structure shown in FIG.

FIG. 3 is a diagram showing a non-use state or a manual drive state of the power transmission device.

FIG. 4 is a plan view showing a state of the cam and the spring in the state of FIG.

FIG. 5 is a diagram showing an electric drive state of the power transmission device.

FIG. 6 is a plan view showing a state of the cam and the spring in the state of FIG.

FIG. 7 is a cross-sectional view of an essential part of a power transmission device according to a second embodiment of the present invention, showing an electrically driven state.

FIG. 8 is a view showing a state of the cam and the spring in the state of FIG.

FIG. 9 is a diagram showing a manual drive state of the device of the second embodiment.

FIG. 10 is a view showing a state of the cam and the spring in the state of FIG.

FIG. 11 is a diagram showing a manual drive state or a non-use state in which a load for preventing natural movement of a driven object is applied to the intermediate gear in the apparatus of the second embodiment.

FIG. 12 is a view showing a state of the cam and a spring in the state of FIG.

[Explanation of symbols]

1; Fixed barrel of lens barrel 2; Operation ring 3; Gear 4; Housing 5; Motor 6; Motor gear 7; Shaft 8; Intermediate gear supporting member 8a, 8b; Flange portion 9; Intermediate gear 10; Wave washer 11 Washer 12; Nut 13; Friction plate 14; Lockout 15; Switching knob 16; Cam 17; Cam shaft 18; Drive pin 19; Leaf spring 20; Rotation restriction pin 21; Coil spring 22; Step washer 51; Fixed cylinder 52 Operation ring 53; gear 54; housing 55; motor 56; motor gear 57; shaft 58; intermediate gear support members 58a, 58
b; flange portion 59; intermediate gear 61; washer 64; retainer 65; switching knob 66; cam 67; cam shaft 68; drive pin 69; leaf spring

Claims (6)

[Claims] 1. A first gear rotatably driven by a drive source, and a second gear directly or indirectly connected to a driven object and rotatably driven by a manual force. A third gear that is moved to a first position that meshes with both the gear and the second gear, and second and third positions that mesh only with the second gear, and the first position and the second of the third gear The first operation position, the second operation position and the third operation position respectively corresponding to the position and the third position, and when the operation is performed in the first operation position, the third gear is operated. The third gear is moved to the first position, the third gear is moved to the second position when operated to the second operation position, and the third gear is moved to the third position when operated to the third operation position. Switching operation member and third gear moving means for moving, and the third gear A load torque generating means for applying a load torque to the third gear only to prevent the driven object from moving naturally when the third gear is in the second position. A power transmission device characterized in that, at a certain time, the second gear can be rotationally driven by a manual force in a state where the load torque is not applied. 2. The load torque generating means applies a friction load to the third gear itself or a member rotatable integrally with the third gear when the third gear is moved to the third position. The power transmission device according to claim 1, which is a frictional force generating means. 3. A first gear rotationally driven by a drive source, a second gear directly or indirectly connected to a driven object and rotationally driven by a manual force, the first gear and the second gear. A third gear that is movable to a first position that meshes with both gears and a second and third position that meshes only with the second gear; and a third gear that carries the third gear and rotates and shafts integrally with the third gear. Corresponding to each of the first position, the second position, and the third position of the third gear, which is movable in the direction, the friction plate fixed to the end surface of the third gear supporting member, and the third gear. Is configured to be operable in a first operation position, a second operation position, and a third operation position, and when operated in the first operation position, the third gear is moved to the first position, When operated to the operation position, the third gear is moved to the second position, A switching operation member / third gear moving means for moving the third gear to the third position when operated to the third operation position, wherein the switching operation member / third gear moving means is the third By driving the gear carrying member in the axial direction, the third gear is moved to the first to third positions, and when the third gear is moved to the third position, the switching operation member / third gear movement A power transmission device characterized in that a load torque is applied to the third gear by pressing the friction plate against another stationary structural member or the like by means. 4. A first gear rotationally driven by a drive source, a second gear directly or indirectly coupled to a driven object and rotationally driven by a manual force, the first gear and the second gear. A third gear that is moved to a first position that meshes with both gears and a second and third position that meshes only with the second gear; and a third gear that rotatably carries the third gear and an axis line with the third gear. The third gear supporting member movable only in the direction, a washer provided on the third gear supporting member in contact with one end surface of the third gear, and the washer facing the end surface of the third gear. A spring which becomes a natural length when the third gear moves to the first position while being pressed, and a first operation corresponding to each of the first position, the second position and the third position of the third gear. Operate to position, second operation position and third operation position When it is operated to the first operation position, it drives the third gear supporting member to move the third gear to the first position, and when operated to the second operation position. The third gear carrying member is driven to move the third gear to the second position, and when operated to the third operation position, the third gear carrying member is driven to move the third gear to the second position. A switching operation member / third gear moving means for moving to the third position, and when the third gear is moved to the third position, the switching operation member / third gear moving means transfers the third gear The power transmission device characterized in that the spring is most compressed by the axial force applied to the member and the washer is in a state of being strongly pressed against the end face of the third gear. 5. The switching operation member / third gear moving means comprises a plate cam that is rotated and a drive pin that is provided at a position eccentric from the center of rotation of the plate cam. The power transmission device according to any one of claims 1 to 4, wherein the drive pin moves along the axial direction of the third gear in response to rotation. 6. The operation member is locked every time the switching operation member / third gear moving means is operated to the operation position, and the third gear is moved to the axial position for each of the first to third positions. The power transmission device according to any one of claims 1 to 4, further comprising a lock spring that prevents the power transmission from changing.