JP2893805B2 - Lens drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens driving device used for a photographic lens of a video camera.

2. Description of the Related Art In recent years, the development of small video cameras that are convenient to take out and use outdoors has been actively pursued. It is necessary to reduce the size of the driving device.

Hereinafter, a conventional lens driving device will be described with reference to the drawings.

FIG. 4 is a cross-sectional view of a lens barrel including a conventional lens driving device, and is a cross-sectional view taken along the line SS 'in FIG. In FIG. 4, the outer frame of the lens barrel is composed of the main body 1, the third group frame 8, and the master flange 21.
In FIG. 4, reference numeral 1 denotes a main body, and lenses 2, 3, and 4 constituting the objective lens group 5 are fixed at predetermined positions. 6 is a lens
The spacer between 3 and 4 and 7 is a lens holding nut. 8
The lens 9 is fixed by a three-group frame coupled to the main body 1. Reference numeral 10 denotes a guide pole provided so that both ends thereof are fitted to the master flange 21 and the third group frame 8, respectively. The zoom lens moving frame 11 holding the lenses 12, 13, and 14 constituting the variable power lens group 15 is provided. It can slide on this guide pole.

FIG. 3 shows the focus lens moving frame 23 in FIG.
FIG. 2 is an enlarged cross-sectional view taken along the line AA of FIG. Moving frame for zoom lens
As shown in FIG. 3, a U-groove is provided at the center of the upper end of the zoom rod 11. The guide pole 10 is passed through the U-groove to prevent the zoom lens moving frame 11 from rotating. 16 is the body 1
The cam frame 16 is provided with a spiral groove, and a guide pin 33 provided at the lower end of the zoom lens moving frame 11 is fitted into the spiral frame. In this case, when the cam frame 16 rotates, the zoom lens moving frame 11 is restricted by the spiral groove of the cam frame 16 and can move in the direction of the optical axis 17. Reference numeral 18 denotes a tooth provided at an end of the cam frame 16. Reference numeral 19 denotes a motor unit attached to the upper end of the main body 1. The gear unit attached to the end of the shaft of the motor unit 19 meshes with the teeth 18, and the rotation of the shaft of the motor unit 19 is transmitted to the teeth 18. When the cam frame 16 is rotated, the zoom lens moving frame 11 moves in the direction of the optical axis 17. Reference numeral 20 denotes an iris portion that performs a diaphragm operation, reference numeral 21 denotes a master flange fixed to the third group frame 8, and reference numeral 22 denotes a master flange 21 and both ends fitted to the third group frame 8 so as to be parallel to the optical axis 17. A plurality of guide poles 23 provided on the guide pole 22 are upper and lower ends of the focus pole moving frame supported by the guide pole 22, and fix the lenses 24, 25, 26 constituting the focus lens group 27. I have.

Reference numeral 28 denotes a focus motor, which is fixed to one of the outsides of a focus motor mounting frame 28a for mounting the focus motor 28, and the upper surface of the focus motor mounting frame 28a is fixed to the outside of the master flange 21. The drive shaft 28b of the focus motor 28 meshes with a nut 29, and the upper end of the nut 29 is
Is engaged with the lower end. The center of the upper surface of the focus motor mounting frame 28a and the center of the surface of the master flange 21 on which the upper surface of the focus motor mounting frame 28a is fixed are partially cut away in the Is provided. Both ends cut out on the upper surface of the focus motor mounting frame 28a are nuts 29.
And serves to suppress the rotation of the focus lens moving frame 23 engaged with. Therefore, when the drive shaft 28b of the focus motor 28 rotates, the focus lens moving frame 23 can move in the direction of the optical axis 17 integrally by engaging with the nut 29 meshed with the drive shaft 28b. ing. Reference numeral 30 denotes a variable power sensor, which is integrally connected to the lower end of the guide pin 33. The guide pin 33 is integrated with the zoom lens moving frame 11 along a slit groove 45 provided in the center of the lower end of the main body 1. And can be moved in the direction of the optical axis 17. Reference numeral 31 denotes a CCD portion fixed to the end face of the master flange 21. Reference numeral 32 denotes a focus sensor provided outside the upper end of the master flange 21. Although not shown in detail, an initial position of the focus lens moving frame 23 when the power is turned on. (Origin) is specified. Reference numeral 46 denotes a groove formed in the lower central portion of the master flange 21. In addition,
The lens barrel controls a control unit (not shown) that processes a detection signal from the magnification sensor 30 and sends a control signal at the time of focusing.
It has.

The operation of the lens driving device configured as described above will be described below.

When the power of the apparatus is turned on, first, the focus lens moving frame 23 checks an initial position (origin) predetermined by the focus sensor 32. Next, the position of the zoom lens moving frame 11 is checked by the magnification sensor 30 and a detection signal of the position is sent from the magnification sensor 30 to the control unit.
Sent to Drive shaft 28b of focus motor 28
Rotates by the rotation amount determined by the control signal, the focus lens moving frame 23 engaged with the nut 29 meshed with the driving shaft 28b moves in the direction of the optical axis 17, and the CCD unit 31 is brought into focus. This completes the initial setting.

Next, when performing zooming, first, a signal for performing zooming is sent to the motor unit 19, the shaft of the motor unit 19 rotates, and the rotation meshes with the gear unit attached to the tip of the shaft of the motor unit 19. Transmitted to the tooth section 18 and the cam frame 16
Rotates. Then, the zoom lens moving frame 11 coupled to the upper end of the guide pin 33 engaged with the spiral groove of the cam frame 16
Moves on the guide ball 10. When the zoom lens moving frame 11 moves, the amount of movement is detected by the magnification sensor 30 and a detection signal is sent from the magnification sensor 30 to the control unit. When the control unit processes the detection signal and sends the control signal to the focus motor 28, the focus motor 28 rotates by a rotation amount determined by the control signal, and the focus lens engaged with the nut 29 meshed with the drive shaft 28b. Moving frame 23 is optical axis
The camera moves in the direction of 17 to correct the focus so that the CCD unit 31 is in focus, and the focusing is completed.

However, in the conventional method in which the drive shaft 28b meshes with the nut 29 to drive the focus lens moving frame 23 meshed with the nut 29, the focus lens moving frame 23
A clearance is required between the drive shaft 28b and the nut 29 in order to perform a stable drive of the focus lens. However, there is a problem in that it is often impossible to perform a proper driving.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a structure capable of stably and smoothly driving a lens.

Means for Solving the Problems In order to solve the above problems, a lens driving device of the present invention is a lens driving device that drives a lens group, and includes a lens barrel main body and a part of an outer frame of the main body. A master flange to be configured, a plurality of guide poles supported by the master flange so as to face each other across the optical axis of the lens, and the lens group fixed movably provided by being fitted to the guide pole. A moving frame, a motor fixed to the outside of the master flange, a driving shaft rotated by the motor, and a lens optical axis disposed close to one of the plurality of guide poles; A bearing shaft provided in parallel between the drive shaft and the drive shaft; and a drive shaft engaged with the moving frame and fitted to the bearing shaft. And a nut that is movable with the moving frame in the optical axis direction when the driving shaft is rotationally driven by the driving shaft, and the driving shaft includes an optical axis of the lens group and an axis of the bearing shaft. It is arranged on the extension of the straight line connecting the center.

Action With such a configuration, in particular, the motor on the motor mounting frame,
By integrally arranging the nut, the drive shaft meshed with the nut, and the bearing shaft fitted with the nut, it is possible to simultaneously process each mounting part of the motor mounting frame. It is possible to improve the mutual mounting accuracy of the motor unit with respect to the moving frame to which the group is fixed and the master flange which forms a part of the outer frame of the main body, and to make the engagement between the motor and the nut good and smooth. Vibration during driving of the moving frame with the lens group fixed,
It can suppress the noise, the stick slip, and the like, and can provide the operation of the smooth moving frame, and can be easily mounted on the mounting frame because the motor unit is unitized.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of a lens barrel including the lens driving device of the present embodiment, and is a cross-sectional view taken along the line SS 'in FIG. In FIG. 1, components having the same configuration as the conventional configuration shown in FIG. 4 are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 1, a gear portion 35 is provided at the end of the shaft of the motor portion 19 so as to fit on the shaft. The screw shaft 34 fitted on the main body 41 and the third group frame 8 has a screw shaft on one side.
The gear portion 36 meshes with a gear portion 36 provided by fitting to the gear portion 34.

FIG. 2 is an enlarged cross-sectional view taken along arrow BB in FIG. 1, and a cross-sectional view taken along SS ′ corresponds to FIG. Hereinafter, description will be made with reference to FIG.

A straight line connecting the centers of the plurality of guide poles 22 respectively fitted to a part of the upper and lower ends of the focus lens moving frame 23 has an inclination of about 45 degrees with respect to the vertical direction. 23 has a shape protruding in the centrifugal direction only in a peripheral portion fitted with the guide pole 22, and the other portion has a smaller diameter, and an engaging portion 38 extending downward from a vertically lower central portion is formed. . Further, lenses 24, 25, and 26 constituting a focus lens group 27 are fixed to the center of the focus lens moving frame 23.
A groove 46 is formed in the center of the master flange 21 vertically downward in the direction of the optical axis 17, and a rib 47 integrally formed with the master flange 21 and extending downward is formed along the periphery of the groove 46. . Reference numeral 48 denotes a focus motor unit, which includes a focus motor 28, a bearing shaft 43, and a drive shaft 28.
b, a focus motor mounting frame 42, and a nut 29a. Reference numeral 42 denotes a focus motor mounting frame, on which a focus motor 28 is fixed outside one side surface of the focus motor mounting frame 42, and a bottom end of the focus motor mounting frame 42 is a screw 44 and a lower end of the master flange 21. , And the bottom surface contacts the end surface of the rib 47 so as to cover the groove 46 with the focus motor mounting frame 42. With this structure, the outside air and the inside of the lens barrel are shut off. Further, the bearing shaft 43 is supported inside both side surfaces of the focus motor mounting frame 42, and the drive shaft 28b of the focus motor 28 is supported inside one side surface. Although not shown, a side surface of the focus motor mounting frame 42 to which the focus motor 28 is fixed is provided with a hole sufficient to allow the drive shaft 28b to pass therethrough. Reference numeral 29a denotes a nut. The nut 29a is engaged with the engaging portion 38 of the focus lens moving frame 23 at the upper end, extends downward and fits with the bearing shaft 43, and further extends downward and has the drive shaft at the lower end. It is in mesh with 28b. Although not shown, the nut 29a and the bearing shaft 43 are fitted together so that the nut 29a can move in the direction of the optical axis 17 integrally with the focus lens moving frame 23. Optimum clearance of about 5μm is provided, and the part where the nut 29a and the drive shaft 28b mesh with each other is optimally 30-50μm for smooth lens drive.
A certain degree of clearance is provided. In addition, nut 29
In (a), the length of the portion fitted to the bearing shaft 43 is about twice the length of the portion of the nut 29a meshed with the drive shaft 28b.

The operation of the lens driving device configured as described above will be described below. Note that the focusing operation in the present embodiment is the same as that of the conventional apparatus shown in FIG. 4 except that the rotation of the drive shaft 28b of the focus motor 28 is transmitted to the focus lens moving frame 23. Only the process in which the rotation of the drive shaft 28b of the focus motor 28 is transmitted to the focus lens moving frame 23 will be described below.

1 and 2, when the drive shaft 28b of the focus motor 28 rotates, the focus lens moving frame 23 meshes with the drive shaft 28b and engages with the nut 29a fitted to the bearing shaft 43. It moves in the direction of the optical axis 17. At this time, the nut 29a is attached to the bearing shaft 43.
Are fitted, so that when the nut 29a engaged with the focus lens moving frame 23 slides on the bearing shaft 43, the nut 29a does not tilt with respect to the optical axis 17 direction. The moving frame 23 can be driven stably and smoothly. Further, as described above, the portion where the driving shaft 28b and the nut 29a mesh with each other is provided with a clearance of about 30 to 50 μm which is optimal for smooth lens driving, while the bearing shaft 43 and the nut 29a 5μm is optimal for securing the stability of the nut 29a
Since the clearance is provided to the extent, the effect of smoothly driving the lens and the effect of ensuring the stability of the nut 29a can be simultaneously maximized.

As described above, according to the present embodiment, in addition to the drive shaft 28b meshing with the nut 29a, the bearing shaft 43 fitted with the nut 29a is provided, so that the focus lens moving frame 23 is stable, and Smooth drive is possible.

In the present embodiment, the description has been made using a focus lens. However, the present invention is not limited to the focus lens, but may be applied to, for example, a zoom lens.

Effect of the Invention As described above, the lens driving device of the present invention is a lens driving device that drives a lens group, a main body of a lens barrel, a master flange forming a part of an outer frame of the main body, A plurality of guide poles supported by the master flange so as to face each other across the optical axis of the lens, a movable frame fixed to the lens group and provided movably by fitting the guide poles, A motor fixed to the outside, a drive shaft rotated by the motor, and a drive shaft disposed close to one of the plurality of guide poles and the lens optical axis and the drive shaft. A bearing shaft provided in parallel between the driving frame and the driving frame, the driving shaft being engaged with the moving frame, meshing with the driving shaft, and meshing with the driving shaft; A nut that is movable with the moving frame in the optical axis direction when the shaft is rotationally driven, and the driving shaft is on an extension of a straight line connecting the optical axis of the lens group and the axis center of the bearing shaft. With such a configuration, the lens groups can be driven smoothly.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a lens barrel including a lens driving device according to an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view taken along the arrow BB in FIG. 1, and FIG. The fourth
FIG. 4 is an enlarged cross-sectional view of a moving frame for a zoom lens as viewed in the direction of arrows AA in FIG. 4, and FIG. 4 is a cross-sectional view of a lens barrel including a conventional lens driving device. 21 …… Master flange, 22 …… Guide pole, 23 ……
Moving frame for focus lens, 28 ... Focus motor,
28b: Drive shaft, 29a: Nut, 41: Body,
42: Focus motor mounting frame, 43: Bearing shaft, 48: Focus motor section.

Claims (1)

(57) [Claims] 1. A lens driving device for driving a lens group, comprising a main body of a lens barrel, a master flange constituting a part of an outer frame of the main body, and an optical axis of the lens interposed between the master flange. A plurality of guide poles supported so as to face each other, a moving frame fixedly provided with the lens group provided movably by fitting to the guide pole, a motor fixed outside the master flange, A drive shaft rotated by a motor, and a bearing shaft disposed in proximity to one of the plurality of guide poles and provided in parallel between the lens optical axis and the drive shaft And engaging the moving frame, engaging with the bearing shaft, meshing with the drive shaft, and rotating the drive shaft to rotate the optical axis. And a nut movable with the moving frame, wherein the driving shaft is disposed on an extension of a straight line connecting an optical axis of the lens group and an axial center of the bearing shaft. apparatus.