JP2003015014A - Device for driving lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens driving device which has high space utilization efficiency and is suitable for miniaturization. SOLUTION: This lens driving device comprises a lens frame 2, guiding shafts 1, drivers 3 and a circuit part. The lens frame 2 carries a lens and is movable along the optical axis of the lens. The guiding shafts 1 guide and support the lens frame 2 along the optical axis in a movable way. The drivers 3 are disposed between the lens frame 2 and the guiding shafts 1 and consist of an electromechanical sensing element part 4 attached to the lens frame 2, an outer shell with an electroviscous fluid injected thereinto and a leg part 5 coming into contact with the guiding shaft 1. The circuit part energizes the electromechanical sensing element part 4 to bring about mechanical displacement, generates fractional force between the outer shell of the leg part 5 and the surface of the guiding shaft 1 by further energizing the leg part 5 in accordance with the mechanical displacement to change the viscosity of the electroviscous fluid and thereby drives the lens frame 2 along the guiding shafts 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens driving device mounted on an optical device such as a camera. More specifically, the present invention relates to a lens driving device that combines an electromechanical conversion element such as a piezoelectric element and an electrorheological fluid element to generate a mechanical driving force of a lens from electric power.

[0002]

As is well known, a lens is incorporated in an optical device such as a still camera or a video camera. Recently, for automatic focusing and zooming, many motors incorporate a motor for driving the lens barrel. Generally, an electromagnetic motor is often used as an actuator for a lens barrel. The rotational force of the electromagnetic motor is converted into linear motion by a cam or gear, and the lens barrel is driven in the optical axis direction.

In order to miniaturize the optical equipment, it is important not only to miniaturize the lens barrel but also to miniaturize the actuator for driving the lens barrel. However, as the size of the electromagnetic motor is reduced, the output torque also decreases, which makes it difficult to drive the lens barrel. Therefore, ultrasonic motors using a piezoelectric element, which is suitable for miniaturization, as a power source have begun to be used. As an example, JP-A-7-274543
FIG. 7 shows a lens driving device disclosed in the publication. This lens driving device utilizes an electromechanical conversion element such as a piezoelectric element. As shown in the figure, the friction plate 112 is pressed by the pressure contact spring 114 in the direction of sandwiching the drive shaft 113 with the lens barrel 111, and an appropriate friction force is generated on the contact surface. One end of the piezoelectric element 118 is fixed to the end of the drive shaft 113, and the other end is fixed to the support plate 124 of the frame 121. When the piezoelectric element 118 is applied with the sawtooth wave drive pulse and is gradually displaced, the shaft 113 moves substantially in the axial direction together with the driven member 111. Piezoelectric element 1
In the rapid contraction displacement of 18, although the shaft 113 rapidly moves in the opposite direction to the tip, the driven member 111 and the friction plate 112 are moved.
Does not move because the inertial force overcomes the frictional force. Although such a lens driving device can be downsized to some extent, it is necessary to optimize the frictional force generated between the driving part and the driven part because the variation of the movement amount becomes large. Further, there is a limit to further miniaturization.

[0004]

In the lens driving device described above, the piezoelectric element is attached to the end of the fixed drive shaft to expand and contract the piezoelectric element. The lens barrel is driven by utilizing the inertial force generated by the speed change at that time. The change in speed is controlled by controlling the pulse waveform applied to the piezoelectric element. In the lens driving device utilizing such inertial force, since the piezoelectric element is attached to the end portion of the driving shaft, the dimension of the lens driving device in the optical axis direction becomes large,
Not suitable for miniaturization. Even though there is space in the side surface of the drive shaft, it is not used and space efficiency is poor. Therefore, it is an object of the present invention to provide a lens driving device which has high space utilization efficiency and is suitable for downsizing.

[0005]

In view of the above-mentioned problems of the prior art and in order to achieve the object of the present invention, the following means were taken. That is, the lens driving device according to the present invention includes a lens frame that mounts a lens and is movable along the optical axis of the lens, and a fixed guide shaft that guides and supports the lens frame so as to be movable along the optical axis. And a leg portion which is disposed between the lens frame and the guide shaft, is composed of an electromechanical conversion element portion attached to the lens frame and an outer shell into which an electrorheological fluid is injected, and is in contact with the guide shaft. And a circuit section for controlling the energization of the driving body to move the lens frame along the guide axis.

Specifically, the circuit section energizes the electromechanical conversion element section to cause mechanical displacement, and further energizes the leg section corresponding to the mechanical displacement to energize the electrorheological fluid. By changing the viscosity, a frictional force is generated between the outer shell of the leg and the surface of the guide shaft, thereby driving the lens frame along the guide shaft. Preferably, the guide shaft has a plurality of stepped portions formed on the surface thereof corresponding to the intervals at which the legs move. In addition, the leg portion of the driving body is made of a tubular outer shell that is flexible and has a large friction coefficient, and is sealed after an electrorheological fluid is injected into the inner shell, and an electrode for generating an electric field on the outer periphery of the outer shell. A flexible substrate is provided, and one end portion of the leg portion movably contacts the surface of the guide shaft, and the other end portion of the leg portion is tilted in the optical axis direction from the contact portion. Is fixed to the electromechanical conversion element section. Further, the electromechanical conversion element portion of the driving body is an electromechanical conversion element including a piezoelectric element or a magnetostrictive element that generates a mechanical displacement by energization, and one surface is fixedly mounted on the leg portion, and an opposite surface. Are connected to the lens frame, and electrodes are arranged so as to generate mechanical displacement between the pair of surfaces by energization.

According to the present invention, the electrorheological fluid is converted to the linear movement of the lens frame along the optical axis direction by converting the expansion / contraction motion caused by applying a voltage to the electromechanical conversion element portion such as a piezoelectric element. It uses the injected legs. By utilizing the frictional force of the legs, the displacement of the piezoelectric element applied from the direction orthogonal to the guide axis can be converted into the linear displacement of the lens frame along the optical axis direction parallel to the guide axis. The drive body, which is composed of the electromechanical conversion element section such as a piezoelectric element and the leg section made of the outer shell into which the electrorheological fluid is injected, is arranged between the guide shaft and the lens frame, so that the space can be effectively used. It can be used and a compact implementation can be realized.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram showing a basic configuration of a lens driving device according to the present invention. (A) is a plan view seen from the optical axis direction, (B) is a partial side view seen parallel to the optical axis, and (C) is a partially enlarged view. In addition, in (B),
The position C of this partially enlarged view is shown.

As shown in the figure, the present lens driving device comprises a pair of guide shafts 1, a lens frame 2, four driving bodies 3, and a circuit portion (not shown). The lens frame 2 has a circular opening for mounting the lens in the center and is movable along the optical axis of the lens. As shown in (B), the lens frame 2 is composed of a pair of upper and lower frame members 2a and 2b and a connecting member 2c for connecting these. The pair of guide shafts 1 are fixed in parallel with the optical axis, and are engaged with both ends of the lens frame 2. With such a configuration, the guide shaft 1 guides and supports the lens frame 2 so as to be movable along the optical axis. 4 drivers 3
Are arranged between the lens frame 2 and the guide shaft 1, and are composed of the electromechanical conversion element section 4 and the leg section 5. Each driving body 3 is in contact with the side surface of the guide shaft 1 while being held between the upper and lower frame members 2a and 2b. As shown in (C), the electromechanical conversion element portion 4 of the driving body 3 is attached to the lens frame 2 formed of a pair of frame members 2a and 2b. The leg 5 is made of an outer shell in which an electrorheological fluid is injected, and is in contact with the surface of the guide shaft 1. In such a configuration, the circuit unit (not shown) controls the energization of the four driving bodies 3 to drive the lens frame 2 along the guide shaft 1 in the optical axis direction.

FIG. 2 is a schematic sectional view for explaining the operation of the lens driving device shown in FIG. As described above, the circuit section energizes the electromechanical conversion element section 4 to cause mechanical displacement. The electromechanical conversion element section 4 is composed of, for example, a piezoelectric element, and causes mechanical expansion / contraction displacement in the thickness direction thereof. Furthermore,
In response to this mechanical expansion / contraction displacement, the circuit portion energizes the leg portion 5 to change the viscosity of the electrorheological fluid, thereby allowing the leg portion 5 to move.
A frictional force is generated between the outer shell and the surface 1a of the guide shaft 1, thereby driving a lens frame (not shown) integrated with the driving body 3 along the guide shaft 1. Leg 5 of driver 3
Consists of a tube-shaped outer shell that is flexible and has a large coefficient of friction, and is sealed after the electrorheological fluid is injected inside.
A flexible substrate provided with electrodes for generating an electric field is arranged on the outer periphery of the outer shell (not shown). In this structure, one end of the leg 5 has the surface 1a of the guide shaft 1.
Is movably contacted with the other end and is fixed to the electromechanical conversion element part 4 in a state where the other end is inclined in the optical axis direction from the contact part. The electromechanical conversion element part 4 of the driving body 3 is an electromechanical conversion element including a piezoelectric element or a magnetostrictive element that generates a mechanical displacement by energization as described above, and one surface thereof is fixed to the leg portion 5, Opposing surfaces are connected to the lens frame, and electrodes are arranged so as to generate a mechanical displacement between the pair of surfaces by energization.

FIG. 3 shows an improved example of the configuration shown in FIG. As shown in the figure, the guide shaft 1 has a plurality of step portions 1s formed on the surface thereof in correspondence with the intervals at which the legs 5 move. As described above, since the present lens driving device utilizes the friction between the leg portion 5 and the surface of the guide shaft 1, by providing the step portion 1s as shown in the figure, the contact area of the leg portion 5 is reduced. A larger driving force can be obtained. In addition, when the electrorheological fluid injected into the outer shell is energized while entering the step portion 1s, the force generated by the leg portion 5 also becomes large in terms of shape. As a result, a more stable drive torque can be obtained.

FIG. 4 is a block diagram showing an embodiment of the present lens driving device including a circuit portion. In this embodiment, in order to perform more efficient driving, a configuration in which two driving bodies 3 are connected is adopted. As shown in the figure, the present lens driving device includes a guide shaft 1, a lens frame 2, a driving body 3, and a power supply unit 8.
And a drive circuit section 9 and a control section 10. Here, the guide shaft 1 is fixed, while the lens frame 2 is movable. The lens frame 2 is arranged so as to maintain a constant distance L from the guide shaft 1. The distance L is always kept constant by a predetermined means (not shown). The driving body 3 is arranged between the guide shaft 1 and the lens frame 2. Driver 3
Is attached to the lens frame 2 and includes an electromechanical conversion element section 4 and a leg section 5. The leg portion 5 is composed of an outer shell 6 in which an electrorheological fluid 7 is injected. Drive circuit section 9
Receives electric power from the power supply unit 8 and energizes the driving body 3.
The control unit 10 gives a control signal to the drive circuit unit 9 to control the moving speed and the moving direction of the lens frame 2.

The leg portion 5 of the driving body 3 is made of a tubular outer shell 6 which is flexible and has a large friction coefficient, and is sealed after the electrorheological fluid 7 is injected therein. The leg portion 5 is provided with a flexible substrate (not shown) provided with electrodes for generating an electric field on the outer periphery of the outer shell 6. Leg 5
Is fixed to the electromechanical conversion element unit 4 with its free end movably contacting the guide shaft 1 and its fixed end tilting in a predetermined direction from the contact site.

The electromechanical conversion element portion 4 of the driving body 3 is an electromechanical conversion element including a piezoelectric element or a magnetostrictive element that generates a mechanical displacement when energized. One surface of the electromechanical conversion element portion 4 is fixed to the leg portion 5, and the opposite surface is the lens frame 2
It is fixed to. The electromechanical conversion element section 4 is provided with electrodes (not shown) so as to generate mechanical displacement between a pair of surfaces when energized.

The illustrated embodiment comprises a plurality of drivers 3. The plurality of legs 5 are configured to be sequentially energized in response to the mechanical displacement obtained by sequentially energizing the electromechanical conversion element units 4 included in the plurality of driving bodies 3. By changing the viscosity of the electrorheological fluid contained in the leg 5, a frictional force is generated between the surface of the guide shaft 1 and the outer shell 6 of the leg 5, whereby the lens frame 2 is moved in a predetermined direction. Move to. The leg portion 5 of each drive body 3 is composed of a pair of two substantially V-shaped members arranged in a predetermined direction. It is configured such that when one of the two substantially C-shaped sets is energized, it moves in a predetermined direction, and when the other one is energized, it moves in a direction opposite to the predetermined direction. . Thereby, the lens frame 2 can be reciprocally driven.

The operation of the lens driving device shown in FIG. 4 will be briefly described with reference to FIG. In order to facilitate understanding, of the two driving bodies, the one on the right side in the drawing is the driving body 3R.
The left side is represented by the driving body 3L. Regarding each leg 5, one of the two substantially C-shaped sets is represented by a leg 51 and the other is represented by a leg 52. First, as shown in (1), a voltage is applied to the electromechanical conversion element portion 4R of the right driving body 3R, and the thickness is extended by the piezoelectric effect as indicated by the arrow. At this time, electricity is applied to the one leg 51 indicated by the diagonal lines. No electricity is applied to the other leg 52. The leg 51 to which electricity is applied has a strong shearing force, while the leg 52 to which no electricity is applied has a weak shearing force. As a result, the shaded leg 51 is pressed against the guide shaft 1 side, so that the lens frame 2 moves as indicated by the arrow.

Next, as shown in (2), the left driver 3L
A voltage is applied to each of the electromechanical conversion element portion 4L and the leg portion 5 that belong to. At the same time, the application of the voltage to the driving body 3R on the right side is released. As a result, the lens frame 2 moves further in the direction indicated by the arrow. After this (3)
As shown in, the voltage application to the left driving body 3L is released and the voltage application to the right driving body 3R is performed. This is similar to the state shown in (1). By repeating the state shown in (1) and the state shown in (2), the lens frame 2 moves along the guide shaft 1.

Returning to FIG. 4, each element of the lens driving device will be described. The electrorheological fluid 7 is also called an ER fluid and is a fluid that exhibits an electrorheological effect. The electrorheological (ER) effect is the reversible change of the rheological properties of a material by an external electric field.
Examples of changes in the rheological properties include increase and decrease in viscosity, increase and decrease in elastic modulus, and increase and decrease in yield stress. A particle-dispersed (water-containing or non-water-containing) ER fluid is a dispersion of dielectric fine particles in an insulating solvent. When an electric field is applied to these fine particles, chain-like coagulation of the fine particles in the electric field direction occurs. An aggregate is formed. At this time, in order to flow the fluid in a direction different from the electric field,
It is necessary to break the connection between the fine particles of the chain-like aggregate, which becomes a resistance when moving the fluid, and thus the viscosity increases. Further, while the electric field is applied, the separated fine particles form a chain-like aggregate with the next aggregate, so that the apparent shear viscosity and dynamic viscoelasticity greatly change depending on the electric field. As a variant of the ER fluid, an EMR fluid can be mentioned. This is a fluid whose rheological properties change with two external fields, an electric field and a magnetic field. The EMR fluid started its research because the rheological properties were found in the magnetic fluid, and it can be used similarly to the ER fluid.
The outer shell 6 for containing the electrorheological fluid 7 is preferably made of an insulating elastic material such as rubber or elastomer, and is preferably resistant to friction.

The drive circuit section 9 applies a drive voltage having a predetermined waveform to the electromechanical conversion element section 4 and the electrorheological fluid 7 included in the drive body 3. The applied voltage is appropriately set depending on the size of the lens driving device, the value of shear stress, the type of electrorheological fluid used, and the like. When a DC power supply is used, a voltage of several tens to several hundreds of V is applied. The drive voltage is usually applied in a pulse form. A pulse voltage such as an appropriate rectangular wave is applied to the electrorheological fluid 7 in accordance with the pulse voltage applied to the electromechanical conversion element unit 4.

Finally, with reference to FIG. 6, the operation of the driving body 3 shown in FIG. 5 will be described. (A) shows a state in which no voltage is applied to the leg portion 5. In addition, one end of the leg portion 5 has a guide shaft 1
Is movably contacted to the side and the other end is fixed to the electromechanical conversion element part 4 in a state of being inclined in a predetermined direction from the contact part.

As shown in (B), the electromechanical conversion element section 4
When it is energized, the legs 5 extend to the guide shaft 1 side, so that the legs 5 are crushed. Electrorheological fluid 7 contained in leg 5
When no voltage is applied to the leg 5, the leg 5 is collapsed as it is.

As shown in (C), when a voltage is applied to the leg portion 5, a shearing force is exerted on the electrorheological fluid, so that the electrorheological fluid does not collapse as it is, but falls down in a beam state. Since a frictional force is generated in the portion in contact with the tip of the beam when it falls down, the lens frame 2 side will move if the shearing force of the electrorheological fluid is optimally adjusted. Usually, when the maximum shear stress is exceeded with metallic materials, etc., it will be sheared,
In the case of electrorheological fluid, the state of maximum shear stress can be maintained.

[0023]

As described above, according to the present invention, a lens actuator is configured by combining an electromechanical conversion element such as a piezoelectric element and an electrorheological fluid element. The actuator is arranged between the lens frame and a guide shaft that guides the lens frame in the optical axis direction. With such a configuration, the space can be efficiently used, and the lens driving device can be downsized.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a basic configuration of a lens driving device according to the present invention.

FIG. 2 is a schematic diagram for explaining the operation of the lens driving device shown in FIG.

FIG. 3 is a schematic diagram showing an improved example of the configuration shown in FIG.

FIG. 4 is a block diagram showing an overall configuration of a lens driving device according to the present invention.

FIG. 5 is a schematic diagram for explaining the operation of the lens driving device shown in FIG.

FIG. 6 is a schematic diagram for explaining the operation of the lens driving device shown in FIG.

FIG. 7 is a perspective view showing an example of a conventional lens driving device.

[Explanation of symbols]

1 ... Guide shaft, 2 ... Lens frame, 3 ... Driving body,
4 ... Electromechanical conversion element part, 5 ... Leg part, 6 ...
Outer shell, 7 ... Electrorheological fluid, 8 ... Power supply unit, 9 ...
..Driving circuit units, 10 ... Control units

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 41/08 U

Claims (5)

[Claims] 1. A lens frame having a lens mounted thereon and movable along the optical axis of the lens, a fixed guide shaft for guiding and supporting the lens frame so as to be movable along the optical axis, and the lens frame. A driving body which is arranged between the guide shaft and is composed of an electromechanical conversion element part attached to the lens frame and a leg part made of an outer shell into which an electrorheological fluid is injected, the leg part being in contact with the guide shaft. A lens driving device comprising: a circuit unit for controlling energization of the driving body to move the lens frame along the guide axis. 2. The circuit section energizes the electromechanical conversion element section to cause mechanical displacement, and further energizes the leg section in response to the mechanical displacement to change the viscosity of the electrorheological fluid. The lens drive according to claim 1, wherein a frictional force is generated between the outer shell of the leg portion and the surface of the guide shaft by driving the lens frame, and the lens frame is driven along the guide shaft. apparatus. 3. The lens driving device according to claim 1, wherein the guide shaft has a plurality of stepped portions formed on the surface thereof in correspondence with the intervals at which the legs move. 4. The leg portion of the driving body is made of a tubular outer shell that is flexible and has a large coefficient of friction, and is sealed after an electrorheological fluid is injected into the outer shell to generate an electric field on the outer periphery of the outer shell. A flexible substrate provided with an electrode for is disposed, and one end of the leg portion movably contacts the surface of the guide shaft, and the other end of the leg portion in the optical axis direction from the contact portion. The lens driving device according to claim 1, wherein the lens driving device is configured to be fixed to the electromechanical conversion element portion in an inclined state. 5. The electromechanical conversion element part of the driving body is an electromechanical conversion element including a piezoelectric element or a magnetostrictive element that generates a mechanical displacement by energization, and one surface is fixed to the leg part, The lens driving device according to claim 1, wherein opposite surfaces are connected to the lens frame, and electrodes are arranged so as to generate a mechanical displacement between the pair of surfaces when energized. .