JPS63194211A - Lens driving device for camera - Google Patents

Abstract

PURPOSE:To miniaturize a motor and to lower its torque by meshing a small intermediate idle gear placed between a lens barrel and a focus ring with an external tooth gear of a rotor of the motor of the lens barrel side and an internal tooth gear of a focus lens side, and decelerating on the same axis as the lens barrel. CONSTITUTION:To the outside peripheral part of a lens barrel 15, a hollow motor is attached in the shape of a concentric circle, and on a rotor 23 of the motor, an external tooth gear 25 is provided, and on the inside peripheral surface of a focus ring 18, an internal tooth gear 26 is provided. In this state, the external tooth gear 25 and the internal tooth gear 26 are brought to transmission through an intermediate idle gear 29, and by the external tooth gear 25, the internal tooth gear 26 and the intermediate idle gear 29, a gear type speed reducer is constituted, and the rotation of the motor is decelerated and transferred to the focus ring 18. In such a way, a margin is generated in the torque of the motor, and also, its rotation can be accelerated, and the number of vibrations can be reduced.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a lens driving device for a camera, and more particularly to a driving device that uses a hollow motor attached to a lens barrel to rotate and move a lens provided in a focus ring in an axial direction.

Summary of the Invention 1 The present invention provides an autofocus or power zoom camera lens using a hollow motor, in which a small intermediate idler is disposed between the lens barrel and the focus ring.
By meshing this intermediate idler with the external gear of the rotor of the motor on the lens barrel side and the internal gear on the focus lens side, deceleration is achieved coaxially with the lens barrel, thereby making the motor more compact and lower. This is intended to increase torque. [Prior Art] For example, in order to provide an autofocus function or a power zoom function using an optical lens provided in a video camera, it is necessary to move the focus ring equipped with the optical lens in the axial direction while rotating it. . Therefore, a motor is provided on the outer peripheral side of the lens barrel that supports the optical lens, and the focus ring is rotated and moved in the axial direction by this motor via gears. However, with such a structure, the motor becomes a protrusion on the outer periphery of the lens barrel, detracting from the appearance of the camera. Problems to be Solved by the Invention] Therefore, a hollow motor is used to drive the focus ring. That is, the focus ring is supported by the lens barrel via the helicoid, and a hollow motor is provided between the two, so that the focus ring is directly driven by this motor. According to this structure, the focus ring must be directly rotated by the force of the motor, which requires a large output torque. Furthermore, the hollow motor magnet has a disadvantage in that it must have a large area to cover the axial movement stroke of the focus ring. The present invention has been made in view of these problems, and the present invention decelerates the output rotation of a hollow motor arranged concentrically around the outer periphery of the lens barrel to move the focus ring in the axial direction while rotating it. It is an object of the present invention to provide a lens driving device for a camera that allows the camera to drive the lens. Means for Solving Problem K] In the present invention, a focus ring for holding a lens is disposed concentrically on the outer peripheral side of a lens barrel, and the focus ring is moved in the axial direction while rotating with respect to the lens barrel. In the driving device for the purpose of the present invention, a hollow motor is attached to the outer circumference of the lens barrel concentrically with the lens barrel, an external gear is provided on the rotor of the motor, and an internal gear is provided on the inner circumferential surface of the focus ring. wherein the external gear and the internal gear are transmitted via an intermediate lead, and the external gear, the internal gear, and the intermediate lead constitute a gear type reduction gear;
The rotation of the motor is reduced in speed by the gear type reducer and transmitted to the focus ring. 1. Therefore, according to the present invention, a mechanical reduction gear made up of an external gear, an internal gear, and an intermediate gear is arranged concentrically with the lens barrel, and this reduction gear reduces the rotation of the motor. becomes possible to slow down. Therefore, there is a surplus in the torque of the motor, and it is possible to speed up the rotation and reduce vibrations and the like. Furthermore, since there is no need to move the rotor of the motor in the thrust direction, the area of the magnet can be reduced.

【Example】

FIG. 3 shows a video camera equipped with a lens driving device according to this embodiment. , an optical lens 12 is attached to the front of the cabinet 10. The optical system consisting of the optical lens 12 includes a lens barrel 15 shown in FIG. 1, and the CCD 17 is supported by the lens barrel 15 via a holder 16. Also, lens barrel 1
A focus ring 18 is arranged on the outer circumferential side of 5.
The lens 12 is supported. The focus ring 18 is configured such that rotational motion is converted into axial motion by a single helicoid. Drive 1 of the focus ring 18 that supports the lens 12
To explain the lJn structure, this drive mechanism
This is performed by a hollow motor provided on the outer periphery of the lens barrel 15, and includes a stator coil 22 attached to the outer periphery of the lens barrel 15. The stator coil 22 faces a magnet 24 attached to the inner peripheral surface of the rotor yoke 23 with a slight air gap therebetween. An external gear 25 is formed in the small diameter portion of the rotor yoke 23. An internal gear 26 is formed on the inner peripheral surface of the focus ring 18 so as to face the external gear 25 . Note that the internal gear 26 is formed to have a length corresponding to the stroke of the focus ring 18 in the axial direction. The two gears 25 and 26 are connected to the flange 2 of the lens barrel 15.
The power is transmitted through an intermediate idler wheel 29 supported by a support shaft 28 at 7. As shown in FIG. 2, dummy rollers 30 are provided at positions 120 degrees apart in the circumferential direction from the intermediate idler wheel 29, and these rollers 30 together with the intermediate idler wheel 29 stabilize the focus ring 18. It is now supported by In the above configuration, when the coil 22 of the hollow motor is energized, the rotor 23 receives a rotational force due to the interaction between the coil 22 and the magnet 24, which rotates the outer circumference of the lens barrel 15. It becomes like this. Then, the gear 25 formed on the rotor 23 drives the intermediate idler 29 as shown in FIG. Since the intermediate idler 29 meshes with the internal gear 26 of the outer focus ring 18, the rotation of the motor is transmitted to the focus ring 18 provided with this gear 26, causing the ring 18 to rotate. Moreover, since this ring 18 is supported by the lens barrel 15 by a helicoid 19 shown in FIG. The distance between them will be adjusted. In this way, the autofocus operation is performed, and the lens 12 is connected to the CCD 17.
This will cause a light image to form above. According to such a drive mechanism for the optical lens 12 for autofocus, the motor is decelerated by a gear type reduction gear made up of an external gear 25, an internal gear 26, and an intermediate idler 29. Now external gear 25, intermediate idler 29,
When the numbers of teeth of the internal gear 26 are A, B, and C, respectively, the reduction ratio of this reduction gear is as follows. A/B Moreover, since the speed reducer is arranged concentrically around the outer periphery of the lens barrel 15, no protrusions are formed on the outer periphery of the lens barrel 15, which is advantageous in terms of design. Further, since the rotor 23 of the hollow motor does not move in the axial direction, there is no need to increase the area of the magnet 24, and this magnet 24 can be used effectively. In this embodiment, the internal gear 25 is not formed around the entire circumference of the rotor yoke 23, but has a diameter of about 18 mm on the outer circumference.
It is formed over 0°, and constitutes a segment type gear. Further, the rotor 23 of the hollow motor is supported in the thrust direction by the attraction force between the coil 22 and the magnet 24. [Application Example] Although the present invention has been described above with reference to the illustrated embodiment, the present invention is not limited to the above embodiment, and various modifications can be made based on the technical idea of the present invention. For example, although the above embodiment relates to a lens drive mechanism for autofocus, the present invention is also applicable to a lens drive device for power zoom. Further, the present invention is applicable not only to video cameras but also to still cameras using silver halide film. [Effects of the Invention] As described above, in the present invention, a hollow motor is attached to the outer circumference of the lens barrel concentrically with the lens barrel, an external gear is provided on the rotor of this motor, and the inner circumferential surface of the focus ring is The external gear and the internal gear are provided with an internal gear, and the external gear and the internal gear are transmitted through an intermediate idler, and the external gear, internal gear, and intermediate idler constitute a gear type reducer, and the rotation of the motor is controlled. The speed is reduced by a gear reducer and transmitted to the focus ring. Therefore, according to such a structure, it becomes possible to reduce the rotation of the motor using the speed reducer and transmit it to the focus ring, thereby making it possible to reduce the torque of the motor and increase its rotation speed. Furthermore, since the motor and the speed reducer are arranged concentrically on the outer peripheral surface of the cylinder A, the appearance of the camera is not impaired.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a camera lens drive device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line ■ to ■ in FIG. 1, and FIG. 3 is a video camera equipped with this drive device. FIG. 3 is an external perspective view of the camera. In addition, in the symbols used in the drawings, 12... Optical lens 15... Lens barrel 18... Focus ring 19... Helicoid 22... Stator coil 23... Rotor yoke 24... Magnet 25...・External gear 26...Two internal gears...Intermediate transparent type.

Claims (1)

[Claims] A drive device for moving a focus ring in an axial direction while rotating the focus ring with respect to the lens barrel, in which a focus ring for holding a lens is disposed concentrically on the outer periphery of the lens barrel. A hollow motor is installed concentrically with the lens barrel, an external gear is provided on the rotor of the motor, an internal gear is provided on the inner peripheral surface of the focus ring, and the external gear and the internal gear are connected. The external gear, the internal gear, and the intermediate idler constitute a gear type reduction gear, and the rotation of the motor is reduced by the gear type reduction gear to reduce the rotation of the motor to the focus ring. A lens driving device for a camera, characterized in that it transmits information to the camera.