JPH0469607A - Lens driving mechanism - Google Patents

Abstract

PURPOSE:To simplify the structure and to move a lens with a small error, a constant load, and high accuracy by coupling a lead screw (male screw) directly with a motor shaft, forming a half nut or rack-shaped female screw part, and energizing the female screw part to the male screw with a magnetic force. CONSTITUTION:The lead screw 2 (male screw) which is coaxial with the motor shaft is rotated by the motor. The female screw moves by the rotation of the lead screw and is united with a holding member. Further, the lens 4 is held by a holding member, so the lens moves by the movement of the female screw. The female screw is a magnetized half nut or rack type and fixed to the holding member with a phosphorus bronze plate. The surface which engages the lead screw is, for example, an N pole. The lead screw is clamped at the position opposite the half nut to set a magnetized member, which is magnetized into, for example, an S pole to the lead side and fixed to the holding member. The magnetized member attracts the half nut at the opposite position with the magnetic force to energize it to the lead screw. The error between the lead screw and female screw part is eliminated and even if the moving direction changes, no backlash error is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lens drive mechanism, and more particularly to the removal of adverse effects due to mechanical errors caused by a lens drive force transmission system.

[Conventional technology]

As described in Japanese Patent Application Laid-Open No. 63-94210, a conventional lens driving device measures errors occurring in a transmission system using a detector and corrects the errors.

In addition, in the method of using gears in the transmission mechanism, errors that occur when the rotation direction is changed are reduced by using two gears to eliminate errors or by adjusting the distance between the centers of the driving gear and the driven gear.

In addition, in a transmission mechanism using a lead screw, the female thread is biased in one direction by a coil spring to reduce errors.

[Problems to be Solved by the Invention] In the above-mentioned prior art, the lens is accurately moved in the optical axis direction by measuring and correcting errors occurring in the transmission mechanism with a detector. Therefore, a detector is required, and calculations for correcting the detected values are required, making the structure complicated.

In addition, in the method using two gears or the method in which the distance between the centers is adjusted, a large force is generated between the gears, and a large drive source is required to drive the gears.

Furthermore, the method of biasing the female screw with a coil spring has a problem in that the load varies depending on the amount of movement of the female screw.

SUMMARY OF THE INVENTION An object of the present invention is to provide a lens drive mechanism that has a simple structure, minimizes unnecessary increases in torque in order to reduce errors, and can keep the load constant.

[Means to solve the problem]

In order to achieve the above purpose, a lead screw (male thread) is directly connected to the motor shaft, the female thread part is a half-nut or rack-shaped female thread part, and the female thread part is biased toward the male thread by magnetic force. That's what I decided to do.

[Effect]

The lead screw (male thread) coaxial with the motor shaft is
Rotated by a motor (eg, step motor).

The female thread that engages with the lead screw is moved by the rotation of the lead screw. The female screw is integrated with the holding member, and since the lens is held by the holding member, the lens moves as the female screw moves. The holding member is guided by two guide rods,
By moving the female screw, the lens is moved along the optical axis with high precision. The female screw is in the form of a half-nut or rack, and is fixed to the holding member with a phosphor bronze plate. The half nut is magnetized, and the surface that engages with the lead screw has, for example, an N pole. Place the magnetized member in a position facing the half-split nut by sandwiching the lead screw. This magnetized member is magnetized to, for example, an S pole on the lead screw side, and is fixed to the holding member. The magnetized member uses magnetic force to pull the half nuts located at opposing positions and biases the lead screw. The biasing force is determined by the extent to which the magnetized member and the female thread are magnetized and the distance between the magnetized member and the female thread. In this way, errors caused by the clearance between the lead screw thread and the female threaded portion can be eliminated, and even if the direction of movement changes, backlash errors do not occur. Further, the biasing force can also be kept constant. A permanent magnet or an electromagnet is used for the magnetized member and the female screw portion. Alternatively, it may be formed using a plastic magnet. Although the magnetized member was used by sandwiching the lead screw opposite the female threaded portion, the lead screw may be magnetized.

Since the magnetized member does not need to be brought into contact with the lead screw, no unnecessary force is generated.

[Example] A first example of the present invention will be described below with reference to FIG.

FIG. 1 is a side view of a first embodiment of the invention. 1 is a motor (for example, a step motor), and 2 is a lead screw made of a magnetic material, which is coaxial with the shaft of the motor 1. A holding member 3 holds the lens 4. 5 is a first guide rod, and 6 is a second guide rod.

The lens 4 held by the holding member 3 moves on the optical axis (in the direction perpendicular to the drawing) by the first guide rod 5 and the second guide rod 6. Reference numeral 7 denotes a half-nut-shaped or rack-shaped female screw portion, which is threadedly engaged with the lead screw 2. The female screw portion 7 is fixed to the holding member 3 via a plate spring (for example, a phosphor bronze plate 9). Further, the female threaded portion 7 is magnetized and is attracted to the lead screw 2 by magnetic action.

When the step motor 1 is driven, the lead screw 2 rotates,
The female threaded portion 7 that engages with the lead screw 2 is fixed to the holding member 3 via the phosphor bronze plate 9, so that the lens 4 is regulated by the first guide rod 5 and the second guide rod 6.
move it onto the optical axis.

According to this embodiment, since the female threaded portion 7 is magnetically attracted to the lead screw 2, no error occurs between the lead screw 2 and the female threaded portion 7 even when the direction of rotation of the lead screw 2 is changed.

Next, a second embodiment of the present invention will be described using FIGS. 2 and 3.

FIG. 2 is a front view of a second embodiment of the invention, and FIG. 3 is a side view. 1 is a step motor, 2 is a lead screw directly connected to the step motor shaft, 3 is a holding member, 4 is a lens, and 5 and 6 are guide rods (1,), (2). Reference numeral 7 denotes a half-nut-shaped female screw portion which is screwed into the lead screw 2. 8 is a magnetized member provided at a position facing the female screw 2, and 9 is a phosphor bronze plate interposed between the holding member 3 and the female screw 7, and plays the role of a suspension.

When the step motor 1 is rotated, the lead screw 2 rotates, and the female threaded portion 7 that is screwed into the lead screw 2 moves. The female screw portion 7 is attached to a phosphor bronze plate 9, and is magnetized to the N pole on the lead screw 2 side, for example.

A magnetized member 8 provided opposite to the female screw portion 7 is magnetized to the S pole on the lead screw 2 side, for example. Due to the magnetic force of the magnetized member 8 and the magnetic force of the female threaded portion 7, the female threaded portion 7 is attached to the lead screw 2.
is energized by

According to this embodiment, even when the lead screw 2 is rotated in the forward and reverse directions, backlash does not occur because the female screw portion 7 is biased with a constant force. Therefore, even if the 1-nons is moved back and forth, no error will occur due to the clearance of the threaded portion.

〔Effect of the invention〕

According to the present invention, since the lead screw and the female screw part are urged by magnetic attraction force, it is possible to eliminate or reduce errors that occur when changing the direction of movement, and the lens can be moved with high precision. be able to.

[Brief explanation of drawings]

FIG. 1 is a side view showing one embodiment of the invention, FIG. 2 is a front view showing another embodiment of the invention, and FIG. 3 is a side view of the same. 1...Step motor 2...Lead screw 3...Holding member 4...Lens 5...First guide rod 6... ... Second guide rod 7 ... Female threaded part 8 ... Magnet 9 ... Phosphor bronze plate

Claims (1)

[Scope of Claims] 1. A lens holding member that holds a lens, a male screw member that is rotationally driven by a motor, and a lens that is engaged with the male screw member and when the male screw member is rotationally driven, A female threaded member that moves in a certain direction along with this, and a female threaded member and the lens holding member are coupled, and the movement of the female threaded member in the certain direction is prevented from moving in the certain direction. a coupling member that moves the lens holding member along a guide member and drives the holding lens by transmitting a magnetic coupling force between the male screw member and the female screw member. A lens drive mechanism characterized by having. 2. The lens drive mechanism according to claim 1, wherein the male screw member is a lead screw made of a magnetic material, and the female screw member is a magnetized half-shaped or rack-shaped nut. Lens drive mechanism. 3. A lens holding member that holds a lens, a male threaded member that is rotationally driven by a motor, and is engaged with the male threaded member, and when the male threaded member is rotationally driven, a certain constant A female screw member that moves in a direction, and a female screw member and the lens holding member are coupled, and the movement of the female screw member in the certain direction is transmitted to the lens holding member. and a coupling member that moves the holding member along a guide member to drive the holding lens, wherein the female screw member is constituted by a magnetized half-shaped or rack-shaped nut, The male threaded member is made of a non-magnetic material, and a magnet having a magnetization polarity opposite to the magnetization polarity of the female threaded member is disposed on the opposite side of the male threaded member from the female threaded member. Installed movably in one piece,
A lens drive mechanism characterized in that a bonding force is provided between the male threaded member and the female threaded member by utilizing an attractive force acting between the magnet and the female threaded member.