JPH0437814A - Displacement expanding device - Google Patents

Abstract

PURPOSE:To obtain a displacement expanding device reducing overdisplacement and improving frequency responseness and follow-up property by applying the voltage of a trapezoidal waveform to an electromagnetic actuator to be used as a driving source in a displacement expanding mechanism having new structure. CONSTITUTION:Since the piezo-electric actuator has the laminated structure of piezo-electric elements, the accumulation of charge corresponding to voltage is generated and prescribed operation cannot be obtained until the charge accumulation is removed. Since charge removal is executed at a moment turning the voltage to zero when a sine wave voltage is impressed, the charge is not completely removed. Since operation is executed in a state always having the accumulation of a certain charge, the floating of oscillation displacement is generated during the operation. When the voltage of a rectangular wave is impressed, discharge is completed during the period of a low level voltage, so that the floating of displacement is not generated, but matching with a time constant cannot be obtained and mechanical oscillation may be generated. Thereby, a trapezoidal waveform is used as the voltage to be impressed, and the leading and trailing edge parts of the wave are inclined to suppress the generation of oscillation due to the sudden rise of the waveform, so that the displacement expanding device capable of effectively discharging the actuator and improving frequency responseness and follow-up property can be obtained.

Description

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

[Conventional technology]

Electromagnetic actuators such as piezoelectric elements, electrostrictive elements, and magnetostrictive elements have accurate responses and can open and move 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 order to eliminate the field curvature of the imaging optical system that causes variations in the diameter of the light spot on the surface to be scanned in an optical scanning device, the semiconductor laser that is the light source, the imaging lens, etc. are synchronized with the optical scanning. Recently, it has been proposed to displace a cylindrical lens between the light source and the optical deflection device in the direction of the optical axis to eliminate or reduce body curvature.

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.Furthermore, various conventional displacement magnifying devices have poor frequency response, and poor followability at the driving frequency of several k) Iz when correcting the curvature of field mentioned above. It becomes 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 provide a displacement amplifying device with improved frequency response and followability, taking into account the method of applying voltage to an electromagnetic actuator used as an active source.

[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 and followability of a displacement magnifying device by improving the method of applying voltage to an electromagnetic actuator used as a source.

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 by the electromagnetic actuator to the force application section at both ends, the entire structure 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,
Further, force acting portions CI and 02 are provided at both ends in the longitudinal direction of the array.
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.

Stress concentration parts Di, D4 and 02. The formation position differs from D3 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 to each other in the longitudinal direction of the displacement magnifying mechanism are applied to the force applying parts C1 and C2, a couple of forces in opposite directions to each other will act on the block parts 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 acting portions C1 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, and the distance between the stress concentration part DI and C2 in the block part radial direction 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 Fig. 1 (A)), and the state when the displacement magnification mechanism is deformed in an upward arched manner as shown in Fig. 1 (C) due to the action of the compressive force is represented by the symbol B11, and this deformation is The accompanying displacement on the X and Y axes is u8°U.

At this time, the following relationship clearly holds.

a", +b"=(a-u,)"+(b+u,)"=a"
+b”+uIl”+u, 2-2aux+2bu.

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

2(au, 1-bu,):0 From this, it can be seen that the displacement magnification rate (miuy/uj is (a/b'').

Here, Fig. 2 (C) shows the results of simulating the opening 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 mm and b = 1.5 mm. . Note that a laminated piezoelectric actuator was used as the drive source, that is, the electromagnetic actuator that applies displacement to the force acting 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 approximately 10 μm from frequency 0 to 3000 Hz.

The enlarged displacement amount U at frequency O is 51.3 μm. On the other hand, the theoretically determined expansion ratio (a/b) is.

If 9.0/1.5=6 and the displacement u of the laminated piezoelectric actuator is 9.3, the theoretical expansion displacement is 55.8 μm, which agrees well with the simulation result.

In addition, for a drive frequency of 300 lHz, the theoretical value is 60 μm compared to the simulated expanded displacement amount of 61 μm, which is an extremely good agreement between the two. This makes it easy to design the displacement magnifying device of the present invention. It means that.

By the way, in the displacement magnifying device described above.

It is necessary to consider the voltage application method to the electromagnetic actuator that applies the acting force to the force acting parts C1 and C2 on both sides of the displacement magnification mechanism, and when a piezoelectric actuator is used as the electromagnetic actuator, special consideration must be given to the voltage application method. There is a need to.

That is, the method of applying voltage to the piezoelectric actuator used as the drive source of the displacement magnifying mechanism configured as described above is as follows.
For example, there is a method of applying a rectangular wave voltage of a predetermined frequency, but in this method, the time constant of the drive system (electrical system) is small (
It is known that if the response is fast), the displacement of the displacement amplifying mechanism may exceed the required value, which is a problem.

Therefore, in the present invention, in order to suppress overshoot and/or undershoot of drive displacement that occurs when frequency response is improved by reducing the time constant of the electrical system including the electromagnetic actuator of the displacement magnifying device, Second, the voltage applied to the electromagnetic actuator is made into a trapezoidal wave to reduce the excessive amount of displacement of the displacement magnifying mechanism.

〔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, the parallel light beam from the light source device Wt1 consisting of the semiconductor laser LD and the collimating lens CL is shaped into a beam shape by the aperture 8, and then is powered only in the sub-scanning direction (direction perpendicular to the drawing). The deflection reflection surface 4 of the rotating polygon mirror 3 is
A long line image is formed in the vicinity of the main scanning direction. The light beam reflected by the deflection reflection surface 4 is a rotating polygon #! fθ deflected by the rotation of 3 and configured by lenses 5 and 6
The light enters the lens and is imaged as a light spot on the surface to be scanned 7 by the action of the f.theta. lens, so that the surface to be scanned 7 is scanned with light.

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, if the cylinder lens 2A is displaced along 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 Figure 5 (B) can be expressed as 0.1322 cos (13 + 0.5033) mm, 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 an amplitude of 264 μm at a frequency of 2.8 kHz, 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 numeral 13.15 in the figure indicates an electromagnetic actuator installed between the force acting part of the displacement magnification mechanism IO and the fixing member 17, and this electromagnetic actuator 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 10.

Now, in the displacement magnification device having the configuration shown in FIG. 3, the laminated piezoelectric actuator 13.15 is driven at a frequency of 2.8 kHz in synchronization with optical scanning, and the two cylinder lenses are oscillated in the optical axis direction. It is possible to perform simple vibration at approximately 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, in the above-mentioned displacement magnification device, the piezoelectric actuator 13.15 exerts an acting force on the displacement magnification mechanism 10.
Various types of voltage waveforms can be considered as the voltage waveforms to be applied.

Therefore, as an example, as shown in FIG.
Consider the case where a sine wave corresponding to z is applied to a piezoelectric actuator.

Generally, piezoelectric actuators have electrical response characteristics and mechanical response characteristics, and the higher the active frequency, the more pronounced the delay characteristics.

In addition, piezoelectric actuators have a lateral movement made by laminating several hundred piezoelectric elements, so like a capacitor, charge accumulates in accordance with the applied voltage, and unless this accumulated charge is removed, the desired operation cannot be performed. I can't.

In the voltage application method shown in FIG. 6, if the response delay is O and the piezoelectric actuator 13.
0 and the cylinder lens 2A move in a predetermined manner,
This is the most desirable voltage application method.

However, in the method of applying a sinusoidal voltage as shown in FIG. 6, the problem of accumulated charge described above occurs, and the piezoelectric actuator does not move in a predetermined manner. That is, when a sinusoidal voltage is applied to a piezoelectric actuator, the accumulated charge is removed during the moment when the applied voltage becomes 0, and is not completely removed.
Therefore, during continuous operation, the piezoelectric actuator operates with a certain amount of charge stored at all times, so the piezoelectric actuator operates as shown in FIG. However, the rise X in the vibration displacement shown in FIG. 7 is also due to the characteristic that the piezoelectric actuator itself does not maintain linearity with respect to high-frequency alternating voltage.

Therefore, as a method to improve such a problem, there is a method of obtaining a substantially sinusoidal displacement by using a rectangular wave voltage as the applied voltage and manipulating the time constant of the drive electrical system. According to this method, since the piezoelectric actuator completes discharging while the voltage is at a low level, displacement does not rise due to charge accumulation. However, even with this method, depending on the drive frequency, matching with the 1 time constant may not be achieved, and mechanical vibrations may occur as shown in FIG.

Therefore, in the present invention, a trapezoidal wave is used instead of a rectangular wave as the voltage applied to the electromagnetic actuator, and the rise and fall portions are sloped, thereby making it difficult to generate mechanical vibrations due to sudden rises. It is said that

Therefore, according to the present invention, it is possible to discharge the piezoelectric actuator well and vibrate the displacement magnification mechanism without causing mechanical vibration, and it is possible to provide a displacement magnification device with good frequency response and followability. .

〔Effect of the invention〕

As described above, according to the present invention, a displacement amplifying device with a novel configuration and driving method can be provided.

Further, according to the present invention, it is possible to provide a displacement amplifying device in which the frequency response and followability of the mechanical system are improved by considering the method of applying voltage to the electromagnetic actuator used as a drive source.

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 specific example, and FIGS. 3 to 5 are diagrams for implementing the displacement amplifying device of the present invention. FIGS. 6 to 8, which are diagrams for explaining an example, are explanatory diagrams of a method of applying voltage to an electromagnetic actuator and problems. 10...Displacement magnifying mechanism, 13.15...Electromagnetic actuator, 17...Fixing member, Bl, B2
．． B3...Block part, C1, C2...Force acting part, DI, C2, C3, C4...Stress concentration part. (G)

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. The displacement amplifying mechanism is configured to amplify the displacement of both ends due to the action of force as the amplitude of the bowed deformation, and the voltage applied to the electromagnetic actuator is made into a trapezoidal wave. A displacement magnifying device characterized by reducing an excessive amount of displacement.