JPH04198807A - Displacement enlarging device - Google Patents

Abstract

PURPOSE:To improve the displacement enlarging accuracy of the title device by using a state, where a prescribed voltage is applied in order to make the close adhesion between an electromagnetic actuator and a force applying section perfect, as a displacement starting point. CONSTITUTION:When, for example, reverse forces are applied to force acting sections C1 and C2 as tensile forces, blocks B1 and B3 respectively rotate clockwise and counterclockwise and the entire body of this displacement enlarging device deforms to an arch-like shape. When, on the contrary, a pair of compressive forces are applied to the sections C1 and C2, the entire body of the device deforms to an upward arch shape. Accordingly, the displacement of the sections C1 and C2 is enlarged by utilizing this deformation. In addition, a prescribed voltage V<p> is applied so that electromagnetic actuators 13 and 15 can be closely attached to a fixed frame 17 and sections C1 and C2, respectively, during the standby time from time ta to time tb and the time tb when the state is stabilized is used as a displacement starting point. When the actuators 13 and 15 are driven synchronously to optical scanning and a cylinder lens 2A is made to make single harmonic motion in the direction of the optical axis after the voltage Vp is applied, excellent correction of the curvature of field can be realized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a displacement magnification device that magnifies minute displacement of an electromagnetic actuator, and is suitable for minutely driving optical elements of optical scanning optical systems such as laser printers. The present invention relates to a suitable displacement magnifying device.

[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 displacement, depending on the purpose of use, a displacement magnifying device is required to magnify the displacement of the electromagnetic actuator.

For example, in an optical scanning device, in order to eliminate field curvature of the imaging optical system, which causes fluctuations in the diameter of the light spot on the scanned surface, the light source such as a semiconductor laser or an imaging lens is used for optical scanning. It is known that the cylinder lenses are displaced synchronously, and recently it has been proposed to displace the cylinder lens between the light source and the optical deflection device in the optical axis direction to eliminate or reduce field curvature. The amount of displacement of a cylinder lens, etc. required to correct such field curvature is usually 100 μm, but the amount of displacement of an electromagnetic actuator is usually about several tens of μm, and the displacement must be increased several to several tens of times. .

[Problem to be solved by the invention]

Therefore, a displacement magnifying device that has a simple configuration and can realize a designed magnification factor with good frequency characteristics has already been proposed. The displacement magnifying device will be explained according to the drawings.

FIG. 9 shows an example of the displacement magnifying device.

In this example, the displacement magnifying device includes three block parts B1 to B.
3, force acting parts C1 and C2, and stress concentration parts D1 to D4. The block parts B1 to B3 are linearly arranged in a rectangular shape, and force acting parts C1 and 02 are provided at both longitudinal ends of the arrangement. These block parts B1
~Between B3 and the force acting parts C1 and C2 is a stress concentration part D1
- Connected by 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. Since the displacement is expanded by deforming the stress concentration part as explained below, the material used for the displacement expansion device is such that the deformation of the stress concentration part required for displacement expansion is realized as elastic deformation.

Stress concentration parts Di, D4 and D2. The formation position differs from D3 in the width direction of the block portion, that is, in the vertical direction in FIG. Therefore, when forces acting in opposite directions to each other in the longitudinal direction of the displacement magnifying device are applied to the force acting parts, the block parts B1 and B
3, a couple of forces in opposite directions will act on each other.

For example, if the force in the opposite direction is a tensile force, the block portion B1 rotates clockwise as shown in FIG.

The block portion B3 rotates counterclockwise, and the entire displacement magnifying device 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. Therefore, the displacement of the force-applying part can be expanded in the direction orthogonal to this displacement by utilizing this arched deformation.In the example shown in Figs. 9 to 11, there are three block parts, but this However, the number of block parts may be five, or the displacement amplifying device may be configured to have an odd number of seven or more block parts. Note that if the moving object is placed directly in the center, the number of blocks will be an appropriate number.

Next, the magnification rate of displacement will be explained based on the examples shown in FIGS. 9 to 11.

It is clear that the increased displacement in the example described above is caused by the rotation of the block parts B1 and B3 in opposite directions.

Therefore, as shown in FIG. 12, for the block portion Bl, its length is a, and the stress concentration portion Di in the width direction of the block portion is
, D2 is assumed to be b, and as shown in FIG. 13, the block portion B1 is considered as a rod-shaped body whose both ends are restrained on the X and Y axes, respectively. In addition, the state in which no force is acting on the force acting part is denoted by Bl (corresponding to the state in FIG. 9),
The state when the displacement magnifying device is deformed in an upward arched manner as shown in FIG. 11 due to the action of the compressive force is represented by the symbol B1□,
The displacements on the X and Y axes due to this deformation are defined as u,,u.

shall be.

At this time, the following relationship clearly holds.

a2+b2= (a-u,) 2+ (b+u,)=
a2+b"+u,"+u,"-2au,+2bu.

Considering that u, , ua are minute quantities compared to a and b, and ignoring the square term of u, , u, compared to other terms, we get 5.
The following relationship is obtained.

2 (au, -bu,)=0 From now on, the expansion rate of displacement (: u, / u,) is (a
/b).

Figure 14 shows the results of simulating the driving frequency characteristics of the enlarged displacement of the displacement magnifying device shown in Fig. 9 using the finite element method when a = 9.0 mm and b = 1.5 + am. A laminated piezoelectric actuator was used as the electromagnetic actuator for displacing the force acting parts at both ends of the device. The amount of displacement of this laminated piezoelectric actuator is determined by the frequency 0 as shown by the broken line 52 in the figure.
It is stable at approximately 10 μm from 3000 Hz to 3000 Hz.

The enlarged displacement amount u at the frequency O is 51.3 μm, as shown by the − dotted chain line 52. 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 It is 55.8 μm, which agrees well with the simulation result.

In addition, for a rolling frequency of 3000 Hz, the theoretical value is 61 μm for the expanded displacement amount in the simulation.
At 0 μm, the two coincide extremely well. This means that the design of this displacement magnifying device is easy.

However, in the displacement amplifying device described above, the piezoelectric actuator is usually fixed to the displacement amplifying mechanism with an adhesive or the like, so it cannot be said that the piezoelectric actuator and the displacement amplifying mechanism are in complete contact with each other.

If a voltage is applied to the piezoelectric actuator while the piezoelectric actuator and the displacement magnification mechanism are in incomplete contact with each other, and the voltage Ov is used as the starting point of vibration, accurate vibration cannot be obtained. Also,
If the piezoelectric actuator and the displacement magnification mechanism are driven with incomplete contact, the piezoelectric actuator and the displacement magnification mechanism will collide at the beginning of vibration, causing a shock that will affect later vibrations.

The present invention has been devised with attention to these points, and its purpose is to improve the accuracy of displacement magnification by devising a method of applying voltage to the displacement magnifying device.

[Means to solve the problem]

The displacement magnification device of the present invention has a plurality of rectangular block portions arranged in a straight line, and has force acting portions at both ends in the longitudinal direction of the block portion array for receiving the deforming force of the electromagnetic actuator. Each block part and the block part and the force acting part are connected by the stress concentration part, and the whole is integrally formed, and a pair of deforming forces in opposite directions are applied to the force acting part at both ends in the longitudinal direction. The position of each stress concentration area is determined so that when the force is applied to the stress concentration area, the entire body deforms in a bow due to the deformation of the stress concentration area, and the displacement of both ends due to the action of the deformation force is magnified as the amplitude of the bow deformation. configured to do so. A displacement magnifying device for magnifying minute displacement of an electromagnetic actuator, the displacement starting point being a state in which a predetermined voltage is applied for perfecting the close contact between the electromagnetic actuator and the force acting part. It is configured.

[For production]

In order to improve the above-mentioned problems, the present invention realizes the application of pressure to the electromagnetic actuator using a voltage.

That is, at the start of vibration, a preset voltage is applied to the electromagnetic actuator to displace the electromagnetic actuator by several μm. Thereafter, a voltage may be applied to the electromagnetic actuator so that a predetermined vibration occurs with this position as a reference.

Usually, the gap between the electromagnetic actuator and the displacement magnification mechanism due to adhesion is 1 μm or less, so at the start of vibration, the voltage applied to the electromagnetic actuator is several tens of volts, that is, the expansion of the electromagnetic actuator is sufficient to be about 2 μm. In this way, by applying a certain voltage to the electromagnetic actuator in advance at the initial stage of vibration and using that position as the starting point of vibration, accurate and reliable vibration can be obtained.

Note that applying pressure using a screw may be considered as a method of applying pressure to the electromagnetic actuator from the initial stage of vibration, but if pressure is applied mechanically, pressure is constantly applied to the electromagnetic actuator, so the life of the electromagnetic actuator may be shortened. undesirable.

〔Example〕

The present invention will be explained in detail below.

FIG. 1 shows a configuration diagram of an embodiment of a displacement amplifying device according to the present invention.

The displacement magnification device i10 according to this embodiment includes three block parts B1 to B3, force acting parts CI and C2, and a stress concentration part D.
1 to D4, electromagnetic actuators 13.15 whose one ends are in close contact with the force acting parts C1 and C2, and a fixed frame 17 with the other ends of these electromagnetic actuators 13.15 in close contact.

The block parts B1 to B3 are rectangular and linearly arranged,
Furthermore, force acting portions C1 and 02 are provided at both ends of the array in the longitudinal direction.
are in place. These block portions B1 to B3 and force acting portions C1 and C2 are connected to each other by stress concentration portions D1 to D4.

In addition, this electromagnetic actuator 13.15 is composed of two laminated piezoelectric actuators with a displacement of approximately 1 μm as described above.
By combining them in series, a displacement of 40 μm was achieved.

A cylinder lens 2A for correcting field curvature in an optical scanning device, which will be described later, is fixed to a central block portion B2 of the displacement magnifying device 1o.

The block parts B1 to B3, the force acting parts C1 and C2, and the stress concentration parts D1 to D4 are all integrally formed of a single material.

Since the displacement is expanded by deformation of the stress concentration part, the material used for the displacement expansion device is such that the deformation of the stress concentration part required for displacement expansion is realized as elastic deformation.

Stress concentration parts Di, D4 and D2. The formation position differs from D3 in the width direction of the block portion, that is, in the vertical direction in FIG.

Therefore, when forces in opposite directions are applied to the force acting parts in the longitudinal direction of the displacement magnifying device, the block parts B1 and B3
Couples in opposite directions act on each other.

For example, if the above-mentioned opposite force is a tensile force, the block portion B1 rotates clockwise, the block portion B3 rotates counterclockwise, and the entire displacement magnifying device deforms into a downward arcuate shape. Conversely, when a pair of compressive forces is applied to the single-force application portions C1 and C2, the deformation becomes an upward arcuate shape. Therefore, by utilizing this arched deformation, the displacement of the force applying portion can be expanded in a direction perpendicular to this displacement.

Next, a correction mechanism for field curvature in an optical scanning device using the displacement magnifying device of this embodiment will be explained with reference to FIG.

In Fig. 2, the parallel light beam from the light source device 1, which is composed of a semiconductor laser LD and a collimating lens CL, is shaped into a beam shape by an aperture 8, and then is directed in a direction corresponding to sub-scanning (a direction perpendicular to the drawing). The cylindrical lens 2A having only one power 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 direction corresponding to the main scanning.

The light beam reflected by the deflection reflecting surface 4 is deflected by the rotation of the rotating polygon mirror 3, and is reflected by the fθ formed by the lenses 5 and 6.
It enters the lens, and due to the action of the same fθ lens, the surface to be scanned 7
An image is formed as a light spot on the surface and 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. 3. At this time, the cylinder lens 2A is
By displacing the lens according to the sinusoidal curve shown in the figure, the curvature of field in the sub-scanning direction can be reduced as shown in FIG. Note that in FIG. 4, β is the imaging magnification of the fθ lens in the sub-scanning direction.

The sine curve in Figure 4 can be expressed as 0.1322 cO5 (θ + 0.5033) + am, where the deflection angle of the deflected light beam is θ, and its frequency is 2.8 k from the optical scanning speed.
Hz.

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.

In order to realize this simple harmonic motion, a displacement device as shown in FIG. 1 is used.

Here, the voltage application method of this embodiment will be explained with reference to FIGS. 6 to 8.

FIG. 6 is a diagram showing the voltage application method of this embodiment,
The horizontal axis represents time, and the vertical axis represents the voltage applied to the electromagnetic actuator 13.15. In this embodiment, during the standby time from time ta to time tb, the electromagnetic actuator 13.
A predetermined voltage Vp is applied as an offset voltage so that each of the parts 15 and 15 can be completely brought into close contact with the fixed frame 17 and the force acting parts C1 and C2. Then, the time when the predetermined voltage VP is applied and the state becomes stable (time tb) is set as the starting point of displacement.

7 and 8 are enlarged views of the electromagnetic actuator 13, the fixed frame 17, and the force acting part C1 of the displacement magnifying device shown in FIG. 1, respectively, and FIG. 7 shows the state before the offset voltage Vp is applied. FIG. 8 shows the state after the offset voltage Vp is applied. Before the offset voltage Vp is applied, as shown in FIG. 7, there is a gap Δd of about 0.5 to 1.0 μm between the fixed frame 17 and the electromagnetic actuator 13, and between the electromagnetic actuator 13 and the force acting part C1. . These defects inevitably occur due to deformation such as adhesion.

On the other hand, as shown in FIG. 8, after the offset voltage Vp is applied, the gap Δd becomes zero, and the fixed frame 17 and the electromagnetic actuator 13, and the electromagnetic actuator 13 and the force acting part C1 are completely in close contact with each other. It turns out.

After applying the offset voltage Vp in this way, the piezoelectric actuator 13.15 is activated at 2.8kHz in synchronization with optical scanning.
If the cylinder lens 2A is driven at a frequency of This means that correction can be achieved.

Note that by applying the present invention, depending on the voltage applied initially, it is possible to convert the spot diameter for writing to that obtained by the optical scanning optical device, and it can also be used for contact conversion for writing.

〔Effect of the invention〕

As explained above, according to the present invention, an offset voltage is applied in advance so that the fixing frame (base member) and the electromagnetic actuator and between the electromagnetic actuator and the force acting part are in complete contact with each other, and the state is By setting the starting point of displacement, it is possible to improve the accuracy of displacement expansion.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment of a displacement magnification device according to the present invention, FIG. 2 is an explanatory diagram of a correction mechanism for field curvature in an optical scanning device using the displacement magnification device of this embodiment, figure~
5 is an explanatory diagram of the principle of correction of field curvature, FIG. 6 is a diagram illustrating the voltage application method of this embodiment, and FIGS. 7 and 8 are partially enlarged views of FIG. 1, respectively. 9 to 14 are explanatory diagrams of displacement amplifying devices that have been proposed. B1 to B3...Block part, C1, C2/force acting part,
D1-D4... Stress concentration part, 13.15... Piezoelectric actuator (electromagnetic actuator), 17 - Fixed frame, Vp - Offset voltage. , Fu/7? ri7 Figure μm4 Figure

Claims (1)

[Scope of Claims] A plurality of rectangular block portions are arranged in a straight line, and each block has force acting portions at both ends in the longitudinal direction of the array of block portions to receive the deforming force of the electromagnetic actuator. The parts and the block part and the force acting part are connected by the stress concentration part, and the whole is integrally formed, and a pair of deforming forces in opposite directions are applied to the force acting part at both ends in the longitudinal direction. The position of each stress concentration part is determined so that when the stress concentration part is deformed, the entire part deforms in a bow shape, and the displacement of both ends due to the action of the deformation force is magnified as the amplitude of the bow deformation. A displacement magnifying device configured to magnify minute displacement of an electromagnetic actuator, wherein a state in which a predetermined voltage is applied for perfecting the close contact between the electromagnetic actuator and the force acting part is the start of displacement. A displacement magnification device characterized by a point.