JPH0437813A - Displacement expanding device - Google Patents

Abstract

PURPOSE:To obtain a displacement expanding device improving frequency response by linearly arraying plural block parts having rectangular shapes, and forming force applying parts for receiving deformation on both the end parts of the array in the longitudinal direction. CONSTITUTION:A fixing member 21 is fixed to the force application part C2 on one side of a displacement expanding mechanism and a lamination type piezo-electric actuator 20 is arranged between the other side force application part and the fixing member 21 to constitute the displacement expanding device. In order to improve errors in adhesion, size, etc., and the size of an oscillation system, the actuator 20 is arranged only on one side. Since frequency response is deteriorated due to the shifted arrangement of the actuator 20, a capacitor 23 is connected in series between the actuator 20 and a driving power supply 22 in order to improve the response. Consequently, an effect similar to the serial connection of two piezo-electric actuators can be obtained, the influence of disturbance can be suppressed and the single oscillation of a cylinder lens 2A with high frequency response can be attained at the prescribed frequency.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a displacement magnifying device that uses an electromagnetic actuator as a drive source and magnifies minute displacement of the electromagnetic actuator, and is particularly applicable to optical scanning devices such as laser printers. The present invention relates to a displacement magnifying device that is most suitable for application to field curvature correction mechanisms, etc.

[Conventional technology]

Electromagnetic actuators such as piezoelectric elements, electrostrictive elements, and magnetostrictive elements have accurate responses and can be driven at high speed, and are used as displacement means in various fields.

However, since these electromagnetic actuators have a small amount of displacement, depending on the purpose of use, a displacement magnifying device that magnifies the amount of displacement of the electromagnetic actuator is required.

For example, in an optical scanning device, in order to eliminate field curvature of the imaging optical system, which causes variations in the diameter of the light spot on the scanned surface, the light source such as a semicircular laser or an imaging lens is It is known that the cylinder lens is displaced in synchronization with scanning, and recently it has been proposed to remove or reduce field curvature by displacing the cylinder lens between the light source and the optical deflection device in the optical axis direction. There is.

The amount of displacement of a cylinder lens, etc. required to correct such field curvature is usually several hundred μm, but the amount of displacement of an electromagnetic actuator is usually about several tens of μm, so it is necessary to expand the displacement by several to several tens of times. Become.

[Problem to be solved by the invention]

Various displacement magnifying devices are known and proposed to magnify the amount of displacement of an electromagnetic actuator.
All of them have complicated configurations and are not practical. Further, various conventional displacement magnifying devices have poor frequency response, and poor followability at a drive frequency of several kHz when correcting the curvature of field, which is mentioned above, poses a problem.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a novel displacement amplifying device capable of enlarging displacement with a relatively simple configuration. Another object of the present invention is to improve the frequency response of an electromagnetic actuator used as a drive source, and to provide a displacement amplifying device with improved frequency response.

[Means and operations for solving the problems] The configuration and operation of the displacement amplifying device according to the present invention will be explained below.

The displacement magnifying device according to the present invention is "a device that uses an electromagnetic actuator as a drive source and magnifies minute displacement of this electromagnetic actuator", and the main parts of the invention are to provide a displacement magnifying mechanism with a novel structure and to drive The purpose of this invention is to improve the frequency response of an electromagnetic actuator used as a source, and to improve the frequency response of a displacement magnifying device.

The displacement magnifying mechanism of this displacement magnifying device includes a plurality of rectangular block portions arranged in a straight line, and a “force acting portion” for receiving deformation force at both ends of the block array in the longitudinal direction. have

The block parts and the block part and the force acting part are connected by a "stress concentration part", and the whole is integrally formed.

The arrangement of each stress concentration section is such that when a pair of deformation forces in opposite directions are applied in the longitudinal direction to the force application section at both ends by the electromagnetic actuator, the entire body deforms into an arched shape due to the deformation of the stress concentration section. ``to'' be determined.

Then, the displacement of both ends due to the action of the deforming force is converted into a translational motion as the amplitude of the arched deformation, and the displacement is expanded.

Here, FIG. 1(A) shows an example of the displacement magnification mechanism of the displacement magnification device of the present invention.

In this example, the displacement magnification mechanism includes three block parts 81 to B.
3, force acting parts C1 and C2, and stress concentration parts D1 to D4.

The block parts 81 to B3 are rectangular and linearly arranged,
Furthermore, force acting portions C1 and C2 are provided at both ends of the array in the longitudinal direction.
are in place.

These block portions 81 to B3 and force acting portions CI and C2 are connected to each other by stress concentration portions D1 to D4.

These block portions 81 to B3, force acting portions C1 and C2, and stress concentration portions D1 to D4 are all integrally constructed of a single material. Displacement expansion is achieved by deforming the stress concentration area as explained below, so the material for the displacement expansion mechanism should be such that the deformation of the stress concentration area necessary for displacement expansion is realized as elastic deformation. It will be done.

The stress concentration portions DI, D4 and C2, C3 are formed at different positions in the width direction of the block portion, that is, in the vertical direction in FIG. 1(A). Therefore, when forces acting in opposite directions are applied to the force applying portions CI and C2 in the longitudinal direction of the displacement magnification mechanism, a couple of forces acting in opposite directions will act on the block portions B1 and 83.

For example, if the force in the opposite direction is a tensile force, as shown in Figure 1 (
As shown in B), the block portion B1 rotates clockwise and the block portion B3 rotates counterclockwise, and the entire displacement magnification mechanism deforms into a downward arcuate shape as shown in the figure.

Conversely, when a pair of compressive forces is applied to the force applying portions CI and C2, the deformation becomes an upward arcuate shape as shown in FIG. 1(C).

Therefore, by utilizing this arched deformation, the displacement of the force applying portion can be converted into a displacement in a direction perpendicular to this displacement and can be expanded, and the central block portion B2 can be translated.

In the example shown in FIG. 1, there are three block parts, but the number of block parts is not limited to this, and the number of block parts may be five, or the displacement magnification mechanism may be configured to have an odd number of block parts of seven or more. You can also do that.

Furthermore, if the moving object is placed directly at the central block position, the number of blocks can be configured to be an even number.

Now, an electromagnetic actuator is connected to at least one side of the force application section as a means for applying a deforming force to the force application section of the displacement amplification mechanism, thereby forming a displacement amplification device.

Next, the displacement magnification rate will be explained based on the example of the displacement magnification mechanism shown in FIG.

It is clear that the increased displacement in the example described above is caused by the rotation of the block parts B1 and 83 in opposite directions.

Therefore, as shown in Fig. 2(A), the block part B1 is set, its length is a, the stress concentration part Di in the width direction of the block part, and the distance between 02 is b, as shown in Fig. 2(B). The block portion B1 is considered as a rod-shaped body whose both ends are restrained on the X and Y axes, respectively.

Here, the state where no force is acting on the force acting part is denoted by the symbol B1.
゜ (corresponding to the state in Figure 1 (A)), and the state when the displacement magnification mechanism is deformed in an upward arched manner as shown in Figure 1 (C) due to the action of compressive force is represented by the symbol B1□, and this deformation is The displacement on the X and Y axes due to u.

Let's say Ua.

At this time, the following relationship clearly holds.

a" + b"=(a ux')2+ (b + u
y) 2:a"+b2+u,"+u,"-2au,!+2
bu.

Considering that ux, u, are minute amounts compared to a, b, and ignoring the square of u, , ua compared to other terms, we get
The following relationship is obtained.

2(au, -bu,)=0 From this, it can be seen that the displacement expansion rate (Eua/u8) is (a/b).

Here, the results of simulating the driving frequency characteristics of the enlarged displacement amount of the displacement amplifying mechanism shown in Fig. 1 using the finite element method when a = 9.0 ma + and b: 1.5 mm are shown in Fig. 2.
Shown in Figure (C). Note that a laminated piezoelectric actuator was used as the instant motion source, that is, the electromagnetic actuator that provides displacement to the force application portions at both ends of the displacement magnification mechanism. As shown in the figure, the displacement amount of this laminated piezoelectric actuator is stable at about 10 μm from frequency O to 3000 Hz.

The enlarged displacement amount U when the frequency is 0 is 51.3 μm. On the other hand, the theoretically determined expansion ratio (a/b) is 9.0/
1.5 = 6, and using the displacement u of the laminated piezoelectric actuator = 9.3, the theoretical expansion displacement is 55
．． The thickness is 8 μm, which agrees well with the simulation results.

Further, for an immediate frequency of 3000 Hz, the theoretical value is 60 μm, compared to the expanded displacement amount of 61 μm in the simulation, and the two agree extremely well. This means that the displacement magnification device of the present invention is easy to design.

By the way, the displacement magnifying device described above also has drawbacks. That is, there are problems such as frequency response when an electromagnetic actuator is attached as a drive source to the displacement magnification mechanism configured as shown in FIG. 1. In particular, when electromagnetic actuators are attached to each of the force application parts CI and C2 on both sides of the displacement magnification mechanism, uneven forces are applied to the displacement magnification mechanism on the left and right sides due to individual differences between the actuators on both sides, making it impossible to obtain the desired vibration. The problem arises that it disappears.

Therefore, in the present invention, in order to solve this problem, an electromagnetic actuator is attached to the force acting part on one side of the displacement magnification mechanism, and the force acting part on the other side is fixed to the fixed member, so that the acting force by the electromagnetic actuator and the fixed member are fixed. A pair of parallel forces are applied to the double-edged acting portion of the displacement magnifying device by the reaction force from the side, and the displacement is magnified. Also, at this time, a capacitor is connected in series to the electromagnetic actuator to improve the frequency response of the electromagnetic actuator.

〔Example〕

Hereinafter, specific examples will be described in detail.

An embodiment in which the displacement magnifying device of the present invention is used to correct field curvature in a known optical scanning device as shown in FIG. 4 will be described.

In FIG. 4, a parallel light beam from a light source device 1 consisting of a semiconductor laser LD and a collimating lens CL is shaped into a beam shape by an aperture 8, and then is powered only in the sub-scanning direction (direction perpendicular to the drawing). The cylinder lens 2A forms an image in the vicinity of the deflection reflection surface 4 of the rotating polygon mirror 3 as a long line image in the main scanning direction. The light beam reflected by the deflection reflecting surface 4 is deflected by the rotation of the rotating polygon mirror 3, enters an fθ lens constituted by lenses 5 and 6, and is imaged as a light spot on the scanned surface 7 by the action of the fθ lens. The surface to be scanned 7 is then optically scanned.

The fθ lens has field curvature in the main scanning direction that is very well corrected, but has field curvature in the sub-scanning direction as shown in FIG. 5(A).

At this time, by displacing the two cylinder lenses according to a sine curve as shown in FIG. 5(B), the curvature of field in the sub-scanning direction can be reduced as shown in FIG. 5(C).

In FIG. 5(B), β is the imaging magnification of the fθ lens in the sub-scanning direction.

The sine curve in Fig. 5(B) can be expressed as 0.132:'cos (θ + 0.5033) o + m, where the deflection angle of the deflected light beam is θ, and its frequency is 2.8 kHz from the optical scanning speed.
It becomes z.

Therefore, by making the cylinder lens 2A perform a simple harmonic motion with a frequency of 2.8 kHz and an amplitude of 264 μm, the curvature of field in the sub-scanning direction can be improved as shown in FIG. 5(C).

In order to realize this simple harmonic motion, a displacement magnification device having the configuration shown in FIG. 3 was used.

In FIG. 3, reference numeral 10 indicates the displacement magnification mechanism described in conjunction with FIGS. 1 and 2. Note that the magnification is 6 times.

Reference numerals 13.15 in the figure indicate electromagnetic actuators installed between the force acting part of the displacement magnifying mechanism 10 and the fixing member 17, and the electromagnetic actuators 13.15
In both cases, two laminated piezoelectric actuators with a displacement of approximately 10 μm, which were explained earlier, are combined in series to achieve a displacement of 4.
This achieved 0 μm.

Incidentally, the cylinder lens 2A for field curvature correction was fixed to the central block portion of the displacement magnifying device 1110.

Now, in the displacement magnifying device having the configuration shown in FIG. 3, the laminated piezoelectric actuator 13.15 is activated at a frequency of 2.8 kHz in synchronization with optical scanning to vibrate the cylinder lens 2A in the optical axis direction. It is possible to perform simple vibration at 240 μm, and it is possible to realize field curvature correction in the sub-scanning direction similar to that shown in FIG. 5(C).

By the way, the disadvantages of the displacement magnifying device having the configuration shown in FIG. 3 are as follows.
Since the piezoelectric actuator is fixed to the double-edged action part of the displacement magnification mechanism by adhesive, the positional accuracy at the time of adhesive has a large effect on vibration.

In addition, due to the dimensional accuracy of the piezoelectric actuator and the displacement magnification mechanism, and because force is applied by the piezoelectric actuator from both sides of the displacement magnification mechanism, uneven forces may be applied to the displacement magnification mechanism on the left and right sides due to individual differences between the actuators on both sides. In addition, there is the problem that a predetermined vibration is often not obtained.

In addition, piezoelectric actuators are installed on both sides, so
The vibration system becomes larger, and there is room for improvement in terms of stability in terms of frequency response.

The present invention focuses on these points and provides a displacement amplifying device that can obtain relatively stable vibrations even when subjected to various disturbances.

Here, an embodiment of the displacement magnifying device according to the present invention is shown in FIG.

In FIG. 6, reference numeral 10 denotes a displacement magnification mechanism similar to that shown in FIG. A laminated piezoelectric actuator 20 is installed between C1 and the fixing member 21 to configure a displacement amplifying device.

In the displacement magnifying device of the present invention having the configuration shown in FIG.
The piezoelectric actuator 20 is disposed only on one side of the displacement amplifying mechanism 10 in order to improve the above-mentioned errors in adhesion, dimensions, etc., and the size of the vibration system.

The problem with this method is the piezoelectric actuator 20.
Since only one is used, the problem is that the frequency response of the piezoelectric actuator 20 is poor.

In the method shown in FIG. 3, although not shown, two piezoelectric actuators constituting each electromagnetic actuator 13, 15 are connected in series.

In this case, due to the capacitive load of the piezoelectric actuator,
Individual piezoelectric actuators have improved frequency characteristics.

On the other hand, in the method shown in FIG. 6, as mentioned above,
Since a piezoelectric actuator is used alone to reduce the influence of disturbances, to improve frequency response,
A capacitor 23 is connected in series between the piezoelectric actuator 20 and the drive power source 22.

By doing this, the same effect as when two piezoelectric actuators having the configuration shown in Fig. 3 are connected in series can be obtained, and the influence of disturbance can be minimized.
The cylinder lens 2A for correcting field curvature in the sub-scanning direction can be vibrated at a predetermined frequency in the direction of the optical axis r.

As described above, by using the displacement magnification device according to the present invention having the configuration shown in FIG. 6, it is possible to cause the cylinder lens to undergo simple harmonic vibration at a predetermined frequency with good frequency response, and the optical scanning device as shown in FIG. Field curvature correction in the sub-scanning direction can be effectively performed.

〔Effect of the invention〕

According to the present invention, it is possible to provide a displacement magnification device with a novel configuration and drive method.

Further, according to the present invention, it is possible to improve the frequency response of an electromagnetic actuator used as a perturbation source, and to provide a displacement amplifying device with improved frequency response.

As mentioned above, this device has an extremely simple configuration, so it can be manufactured at low cost, and it can achieve the designed magnification with good frequency characteristics, so it is used as an actuator for correcting field curvature in the sub-scanning direction in optical scanning devices. It's practical though.

[Brief explanation of the drawing]

1 and 2 are diagrams for explaining the displacement amplifying mechanism section of the displacement amplifying device of the present invention based on a concrete example, and FIGS. 3 to 6 are diagrams for implementing the displacement amplifying device of the present invention. FIG. 3 is a diagram for explaining an example. 10... Displacement magnification mechanism, 13.15.20...
Electromagnetic actuator, 17.21...Fixing member, 22...Drive power source, 23...Capacitor,
Bl,,B2. B3...Block part, C1, C2
...Force acting part, DI, C2, C3, C4... Stress concentration part. (C)

Claims (1)

[Claims] A device that uses an electromagnetic actuator as a drive source and magnifies minute displacement of the electromagnetic actuator, comprising: a plurality of rectangular block portions arranged in a straight line; It has a force acting part for receiving deformation force at both ends in the longitudinal direction, and each block part and the block part and the force acting part are connected by a stress concentration part, and the whole is integrally formed. When an electromagnetic actuator applies a pair of deforming forces in opposite directions to the force application part in the longitudinal direction, the position of each stress concentration part is determined so that the whole deforms in a bow due to the deformation of the stress concentration part, and the deformation occurs. A displacement magnification device comprising a displacement magnification mechanism configured to magnify the displacement of both ends due to the action of force as the amplitude of the bowed deformation, and a capacitor connected in series to the electromagnetic actuator.