JPH0415614A - Displacement enlargement device - Google Patents

Abstract

PURPOSE:To realize the displacement enlargement device which can adjust frequency characteristics and is high in flexibility by providing a couple of force type displacement enlarging mechanism which utilizes the rotary motion of a rigid body and enlarges displacement when the displacing force of an actuator operates, and providing a notch part to the rigid body which constitutes a couple of force type displacement part. CONSTITUTION:This device is provided with an operation part 3C fitted with a body to be displaced, couple of force type displacement enlargement parts 3a and 3b which are arranged on both sides of the operation part 3C respectively and utilize the rotary motion of the rigid body by a couple of forces and force operation parts C1 and C2 which receive the displacing force of the actuator 1. The couple of force type displacement enlargement parts 3a and 3b is equipped with a mechanism which rotates when the displacing force of the actuator 1 operates to put the operation part 3c in translational motion and enlarge the displacement of the operation part 3, and the cut parts 3f, 3g, and 3h are provided to the rigid body which constitutes the couple of force type displacement enlargement parts 3a and 3b. Consequently, the displacement quantity of the actuator which displaces a piezoelectric element, an electrostrictive element, etc., finely can be enlarged several - tens of times with good frequency stability.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a displacement magnifying device for magnifying the minute displacement of an actuator such as a piezoelectric element or an electrostrictive element, and particularly to a device for correcting field curvature in an optical scanning device. This invention relates to a displacement magnifying device that is most suitable for use in actuator parts, etc.

[Conventional technology]

BACKGROUND ART Actuators that make small displacements in response to applied voltages from active circuits such as piezoelectric elements and electrostrictive elements have accurate responses and can be driven at high speed, and are used as displacement means in various fields.

However, since the amount of displacement of these actuators is very small, a displacement amplifying device that increases the amount of displacement of the actuator is required depending on the purpose of use.

For example, in optical scanning devices installed in laser printers, digital copying machines, laser plotters, laser facsimile machines, laser engraving machines, etc., field curvature of the imaging optical system causes fluctuations in the diameter of the light spot on the scanned surface. It is known to displace the light source, such as a semiconductor laser or an imaging lens, in synchronization with optical scanning in order to eliminate the It has been proposed to remove or reduce field curvature by displacing the lens in the optical axis direction, but the amount of displacement of a cylindrical lens etc. required to correct such field curvature is usually several hundred μm. The amount of displacement of the actuator such as the piezoelectric element, electrostrictive element, magnetostrictive element, etc. described above is usually about 10 μm, and the displacement must be increased several times to several tens of times.

[Problem to be solved by the invention]

By the way, various displacement magnification mechanisms are known.
Although many of the proposed devices have complex configurations and tend to be large-scale devices, there are no specific displacement magnifying devices suitable for use in correcting the field curvature of the optical scanning device mentioned above. Not published.

The present invention has been made in view of the above circumstances, and is capable of enlarging the displacement amount of a small displacement actuator such as a piezoelectric element or an electrostrictive element by several times to several tens of times with good frequency stability. It is an object of the present invention to provide a displacement magnification device that is most suitable for use as an actuator section of a device for correcting field curvature of an apparatus.

[Means and operations for solving the problem] In order to achieve the above object, a displacement magnifying device according to the present invention is a device that magnifies the displacement of an actuator that makes a minute displacement in response to an applied voltage from a drive circuit, and comprises: an operating section to which an object to be attached is attached; a couple-type displacement amplifying section that utilizes the rotational movement of a rigid body by a couple and arranged on both sides of the operating section; and a force acting section that receives the displacement force of the actuator. the couple-type displacement amplifying part rotates and translates the operating part when the displacement force of the actuator acts on the couple-type displacement amplifying part, and magnifies the displacement as a displacement of the operating part; The invention is characterized in that the rigid body constituting the couple-type displacement amplification section of the couple-type displacement amplification mechanism is provided with a notch.

Hereinafter, the displacement magnifying device of the present invention will be explained in more detail.

FIG. 4 is an explanatory diagram of the principle of the couple-type displacement amplifying mechanism, and this couple-type displacement amplifying mechanism, as shown in FIG. 4(a),
When a pair of parallel forces (couples) F of equal magnitude and opposite direction are applied to diagonal positions of a rigid body such as a rectangular body, the rigid body has a point of application of the force as shown in Fig. 4(b). As shown in Fig. 5, two of these mechanisms are used to construct a couple displacement magnification mechanism 3, which is combined with the actuator 1. For example, the displacement of the actuator 1 can be converted into a rotational movement by a couple of a displacement amplifying section made of a rigid body, and further converted into a translational movement, which can be applied to amplifying displacement.

More specifically, as shown in FIG. 6(a), the couple-type displacement magnifying mechanism 3 of the present invention includes an operating section 3c to which an object to be displaced is attached, and an operating section 3c disposed on both sides of the operating section 3c. Couple-type displacement amplifying parts 3a, 3 that utilize rotational movement caused by a couple
b. In the illustrated example, the operating portion 3c and the displacement magnifying portions 3a, 3b are constituted by rigid bodies made of rectangular blocks, and each of the rigid bodies includes stress concentration portions di, d2, . d3. They are connected at d4 as shown. Incidentally, in the figure, cl and c2 are force acting parts, and a pair of parallel forces having the same magnitude and opposite directions are applied to these parts.

Now, in the couple type displacement magnification mechanism configured as shown in Fig. 6(a), when a pair of parallel forces of equal magnitude and opposite direction act on the force acting portions cl and c2, each displacement Couples in opposite directions act on the enlarged parts 3a and 3b, causing each displacement enlarged part 3a and 3b to rotate according to the direction of the force, as shown in FIGS. 6(b) and 6(c). The whole can be deformed into a bow shape and the operating portion 3c can be translated. That is, when a tensile force is applied to the force acting parts cl and c2 as shown in FIG. 6(b), one of the displacement magnifying parts 3a rotates clockwise, and the other displacement magnifying part 3b rotates counterclockwise. , the entire body deforms into a downward arcuate shape, and the operating portion 3c is displaced downward. Conversely, when a compressive force is applied to the force acting parts cl, c2 as shown in FIG. 6(c), the whole deforms into an upward arched shape, and the operating part 3c is displaced upward. Therefore, force acting part c
l.

If a pair of parallel forces of equal magnitude and opposite direction are applied alternately to c2 as a tensile force and a compressive force, the operating portion 3c is created.
can be translated and the displacement can be expanded.

In the example shown in FIG. 6, one rectangular block is arranged on both sides of the operating section 30 as a displacement amplifying section, but the number of such blocks may be plural.

Next, the displacement magnification rate of the couple type displacement magnification mechanism shown in FIG. 6 will be explained.

In the above-mentioned couple-type displacement amplification mechanism, the displacement amount is increased by rotating the displacement amplification parts 3a and 3b in mutually opposite directions.

Here, as shown in FIG. 7(a), the length of the displacement expanding portion 3a made of a rectangular block is 89, and the distance between the stress concentration portions di and d2 in the width direction is b, and as shown in FIG. As shown in b), the displacement magnifying portion 3a is considered as a rod-shaped body whose both ends are restrained on the X and Y axes, respectively.

The state where no force is acting on the force acting part is indicated by 3a-O (6th
(corresponding to the state in Fig. 6(a)), and the state when the couple type displacement amplifying mechanism is deformed into an upward arch as shown in Fig. 6(C) due to the action of compressive force is denoted by reference numeral 3a-1. Letting the displacements on the X and Y axes due to deformation be u, , ua, the following relationship holds true.

a2+b2=(a-u,)"+(b+u
y) 2=a"+b2+ux"+u,"-2aug+2b
u.

Here, considering that U, , Ua are minute amounts compared to a and b, and ignoring the square of ux+uy with respect to other terms, the following relationship is obtained.

2(au 1l-bu y)=0 From now on, the expansion rate of displacement (= u, / u,) is (a
/b). That is, by appropriately determining (a/b), the displacement magnification rate can be set.

FIG. 5 shows an example of a displacement amplifying device using only a couple displacement amplifying mechanism. In this device, a couple displacement amplifying mechanism 3 is arranged in a rectangular frame-shaped support member 2A. death,
Actuators 1 are disposed between the force acting portions on both sides and the support member 2, and the two actuators 1 directly operate the couple type displacement magnifying mechanism 3 to magnify the displacement.

By the way, the displacement magnifying device using this couple-type displacement magnifying mechanism 3 has the characteristics that it is small and that the magnification ratio can be set arbitrarily, and also has the advantage of good frequency response due to its small size. However, when the drive frequency is increased, the mass of the rigid body that makes up the couple-type displacement expansion section is large.
This poses a problem as resonance may occur due to the amplitude and inertia.

Therefore, in the displacement amplifying device according to the present invention, a notch is provided in the rigid body constituting the couple displacement amplifying section of the couple displacement amplifying mechanism to reduce the mass while maintaining the rigidity of the rigid body,
The resonance frequency is set to be sufficiently higher than the drive frequency to improve frequency stability and expand displacement with good frequency stability.

〔Example〕

Hereinafter, specific examples of the present invention will be described in detail.

Here, an embodiment will be described in which the displacement magnifying device of the present invention is applied to the correction of field curvature in an optical scanning device as shown in FIG.

First, the optical scanning device will be briefly explained.

In FIG. 8, a parallel light beam from a light source W1 composed of a semiconductor laser LD and a collimating lens CL is shaped into a beam shape by an aperture 18, and then is powered only in the sub-scanning direction (direction perpendicular to the drawing). The cylindrical lens 12A forms an image in the vicinity of the deflection reflection surface 14 of the rotating polygon mirror 13 as a long line image in the main scanning direction.

The light beam reflected by the deflection reflecting surface 14 is transmitted to the rotating polygon mirror 13
is deflected by the rotation of the lens 15 and enters the fθ lens constituted by lenses 15 and 16, and due to the action of this fθ lens, an image is formed on the scanned surface 17 as a light spot, and the scanned surface 1
7 is optically scanned.

Here, although the fθ lens has extremely well corrected field curvature in the main scanning direction, it has field curvature in the sub-scanning direction as shown in FIG. 9(,).

Therefore, as a method of correcting this field curvature in the sub-scanning direction, the cylindrical lens 12A is
By causing harmonic vibration according to a sine curve as shown by the dotted chain line, the curvature of field in the sub-scanning direction can be reduced as shown in FIG. 9(b).

Here, the equation expressing the amount of field curvature in the sub-scanning direction of the optical scanning device and the harmonic vibration of the cylindrical lens 12A vibrated at that time is x = Acos (C1J t÷φ ) Amount of movement (mm) of the Xnijilintric lens A: Amplitude of harmonic vibration (lI+,) ω: Angular frequency (rad/s) φ: Initial phase (rad). Also, the frequency f (=ω/2π) of harmonic vibration is
It is determined by the writing speed of the optical system.

Therefore, the cylindrical lens 12A has a frequency f,
By harmonic vibration with an amplitude of 2 A (mm), the curvature of field in the sub-scanning direction can be corrected as shown in FIG. 9(b).

The present invention provides a displacement magnifying device for realizing the harmonic vibration of the cylindrical lens described above, and a specific example thereof is shown in FIG.

FIG. 1 is a plan view of a displacement magnifying device according to the present invention,
This displacement magnifying device uses a laminated piezoelectric actuator 1 that makes a minute displacement in response to a signal from a drive circuit, and magnifies the displacement to displace a cylindrical lens or the like. An attached operating section 3c, couple-type displacement amplifying sections 3a and 3b that utilize the rotational movement of a rigid body due to a couple and arranged on both sides of the operating section 3c, and a force acting section that receives the displacement force of the actuator 1. cl, c2, and when the displacement force of the actuator 1 acts on the couple displacement amplifying parts 3a, 3b, the couple displacement amplifying parts 3a, 3b rotate and cause the operating part 3c to translate. The structure includes a couple-type displacement amplifying mechanism 3 that magnifies the displacement as the displacement of the operating part 3c, and the couple-type displacement amplifying part 3a of the above-mentioned couple-type displacement amplifying mechanism 3
, 3b and a notch 3f in the rigid body constituting the operating portion 3c.

It is characterized by providing 3g and 3h.

The configuration and operation of the couple displacement amplifying mechanism are as described above with reference to FIGS. 4 to 7.

Incidentally, reference numeral 2 in the figure is a support member, and the laminated piezoelectric actuator 1 is installed between this support member 2 and the force acting portions C1 and C2 of the couple type displacement amplification mechanism 3.

By the way, the displacement magnifying device using this couple-type displacement magnifying mechanism 3 has the characteristics that it is small and that the magnification ratio can be set arbitrarily, and also has the advantage of good frequency response due to its small size. It can be applied as an actuator section for driving the cylindrical lens for sub-scanning direction field curvature correction of the optical scanning device mentioned above, but when the writing speed of the optical scanning device increases, the driving required for the cylindrical lens becomes faster. Since the frequency also increases, if the mass of the rigid body constituting the couple-type displacement amplifying section is large, resonance may occur due to inertia, which poses a problem.

In addition, in order to obtain stable vibration and magnification rate with respect to the driving frequency, it is desirable that the frequency at which the primary resonance of the expanding mechanism occurs is sufficiently higher than the driving frequency, and the resonance frequency of the rigid body that constitutes the displacement expanding section One way to increase this is to increase the rigidity of the objects that make up the rigid body, and the other is to reduce the mass of the object.

Therefore, in the displacement magnifying device according to the present invention, notches 3f, 3g, and 3h are provided in the rigid body constituting the couple displacement magnifying parts 3a and 3b of the couple displacement magnifying mechanism 3, and the rigidity of the rigid body is maintained. The purpose is to reduce the mass, set the resonance frequency to be sufficiently higher than the drive frequency, improve frequency stability, and expand displacement with good frequency stability.

Here, as for the shapes of the above-mentioned notches 3f, 3g, and 3h, the hatched portions shown in FIG. (b), (c
) It is better to use a notch shape as shown in each of the figures below to reduce the mass while maintaining or improving the rigidity of the rigid body.
By setting the resonance frequency sufficiently high relative to the drive frequency, stable vibration and displacement can be obtained. ■ By setting the resonance frequency to the drive frequency, it is possible to obtain large expanded displacement. .

As described above, in the displacement magnifying device shown in FIG. 1, the resonant frequency of the couple type displacement magnifying mechanism 3 can be arbitrarily set within a certain range, and the application range having the effects listed in (2) above can be achieved. It becomes possible to design a wide actuator.

Note that the lower limit of the frequency range that can be set is the resonant frequency of the couple-type displacement amplifying mechanism 3 before the notch, and the upper limit is determined by an appropriate value based on the relationship between the mass and rigidity of the couple-type displacement amplifying section after the notch. .

Incidentally, although the couple type displacement amplification mechanism 3 can amplify displacement up to about 3 kHz with good frequency stability, its displacement amplification rate is about 5 times. For this reason, when a laminated piezoelectric actuator is used as an actuator, the amount of displacement is about 10 μm, so when only the couple displacement magnifying mechanism 3 is used as in the displacement magnifying device shown in FIG. The amount of displacement of 3c is about 50 μm, and depending on the target specifications, the amount of displacement may not reach this amount.

Therefore, as an applied embodiment of the present invention, as shown in FIG. 3, a lever displacement amplifying mechanism 4 is connected to the couple type displacement amplifying mechanism 3, and the amount of displacement is expanded by the lever displacement amplifying mechanism 4. An even larger amount of displacement may be obtained.

The displacement magnifying device shown in FIG. 3 has two arm portions 4a of a symmetrical structure supported by a support member 2 in a lever manner. The swinging end 4b on the other end side is supported between the lever displacement and amplifying mechanism 4 which swings and expands the amount of displacement, and the swinging end 4b of both arm portions 4a of the lever displacement and amplifying mechanism 4. It is an enlarging mechanism and has an operating part 3c to which an object to be displaced is attached, and couple-type displacement enlarging parts 3a and 3b that utilize rotational movement by a couple of rigid bodies disposed on both sides of the operating part 3C, respectively. When a displacement force (parallel force) is applied to the couple-type displacement amplifying parts 3a, 3b by the swinging of both arms 4a of the two-type displacement amplifying mechanism 4, the couple-type displacement amplifying part 3
a, 3b have a structure including a couple-type displacement magnifying device end 3 that causes a rotational movement by a couple and causes a translational movement of the operating part 3C, and the minute displacement of the actuator 1 is The displacement is magnified by both arm portions 4a of the position magnifying mechanism 4 and acts on the couple type displacement magnifying mechanism 3, and the amount of displacement is magnified as a translational movement of the operating portion 3c, causing the cylindrical lens etc. to harmonically vibrate.

That is, in the displacement magnifying device shown in FIG.
A is arbitrarily enlarged with the lever ratio of a and applied to the couple-type displacement amplifying mechanism 3, and the displacement is further amplified by the couple-type displacement amplifying mechanism 3 to control the operating portion 3C at a predetermined frequency and displacement amount (amplitude amount).
This means that it is displaced.

In the device shown in FIG. 3 as well, the rigid bodies constituting the couple displacement amplifying parts 3a and 3b of the couple displacement amplifying mechanism 3 are as shown in FIGS. 2(a), (b), and (c). Notch 3 with a shape
f, 3g, and 3h are provided, the mass can be reduced while maintaining the rigidity of the rigid body, and the resonance frequency can be set to be sufficiently higher than the drive frequency to improve frequency stability. Displacement can be expanded with good frequency stability.

Now, as explained above, the displacement magnifying device having the structure shown in FIGS. When used in an actuator section for correcting field curvature of an apparatus, it becomes possible to effectively correct field curvature in the sub-scanning direction.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a highly versatile displacement magnification device whose frequency characteristics can be adjusted.

Therefore, according to the present invention, the amount of displacement of the actuator, which undergoes minute displacement in response to the applied voltage from the drive circuit of the piezoelectric element, electrostrictive element, etc., can be expanded several times to several tens of times with good frequency characteristics. It is possible to provide a displacement magnification device that is optimal for use as an actuator section of a field curvature correction device of an optical scanning device.

Furthermore, since this device has a relatively simple configuration, it can be manufactured at low cost.

[Brief explanation of drawings]

FIG. 1 is a plan view of a displacement amplifying device showing an embodiment of the present invention, and FIGS. 2(a), (b), and (c) show a rigid body constituting the couple-type displacement amplifying section of the displacement amplifying device. 3 is a plan view of a displacement magnifying device showing an applied example of the present invention, FIGS. 4 to 7 are explanatory diagrams of a couple-type displacement magnifying mechanism, and FIG. The figure is an explanatory diagram of an optical scanning device to which the displacement magnifying device of the present invention is applied, and FIG. 9 is an explanatory diagram of field curvature and its correction method in the optical scanning device shown in FIG. 8. 1... actuator, 2... support member, 3...
... Couple type displacement magnifying mechanism, 3a, 3b... Couple type displacement magnifying section, 3c... Operating section, 3f, 3g, 3h...
...Notch part, CI, C2...Force acting part, CL...
...Cylindrical lens.

Claims (1)

[Claims] This is a device that magnifies the displacement of an actuator that makes minute displacements in response to applied voltage from a drive circuit, and includes an operating part to which an object to be displaced is attached, and a rotation of a rigid body by a couple placed on each side of the operating part. It has a couple-type displacement amplification part that utilizes motion and a force acting part that receives the displacement force of the actuator, and when the displacement force of the actuator acts on the couple-type displacement amplification part, the couple-type displacement amplification part is provided. A rigid body constituting the couple-type displacement amplifying part of the couple-type displacement amplifying mechanism is provided. A displacement magnifying device characterized by having a notch.