JP2009128847A - Optical scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner in which the vibration of an optical member is prevented corresponding to a variety of vibration frequencies and a high quality image is available. <P>SOLUTION: The optical scanner 1 comprises: a support member 31 which supports a reflection mirror 22 being the optical member; a spring 32 being an elastic member which is disposed between the support member 31 and the reflection mirror 22 to support the reflection mirror 22, and of which the spring constant is variable corresponding to the amount of deformation; and a length-varying mechanism 33 which deforms the spring 32. Thus the spring constant supporting the reflection mirror 22 is variable. Accordingly, the natural frequency of the oscillation system composed of the reflection mirror 22 and the spring 32 is variable and further the system can address vibrations generated at a variety of frequencies. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical scanning device that is mounted on an image forming apparatus such as a copying machine, a printer, or a facsimile machine, and exposes and scans the surface of an image carrier with a light beam (for example, laser light).

  In general, an optical scanning device used in a copying machine, a printer, or the like performs exposure while scanning the surface of an image carrier represented by a photosensitive drum, that is, a surface to be scanned, and a predetermined static surface on the surface of the photosensitive drum. It forms an electrostatic latent image. In an optical scanning device, a light beam such as laser light emitted from a light source is deflected in a main scanning direction by a polygon mirror rotated by an optical deflector and directed toward a scanning surface by an optical member such as a lens or a mirror. Are emitted.

  Here, in recent years, image forming apparatuses capable of high-speed printing are remarkably widespread. The optical scanning device also needs to operate correspondingly, and it is necessary to rotate the polygon mirror at high speed. For this reason, in the optical scanning device, vibration is likely to occur around the position of the optical deflector. In addition, vibration generated in other parts of the image forming apparatus due to high-speed printing may propagate to the optical scanning device.

  As described above, the vibration generated and propagated in the optical scanning apparatus is likely to reach the position of an optical member such as a lens or a mirror. Thereby, especially when the mirror vibrates, the predetermined position and angle of the mirror itself cannot be maintained, and the optical axis of the light beam may be shifted. As a result, there arises a problem that the electrostatic latent image formed on the surface of the photosensitive drum is adversely affected and the image quality is deteriorated.

In order to solve such a problem, Patent Documents 1 and 2 can show examples of configurations in which vibrations that can occur in an optical scanning device (optical device) are reduced and suppressed. In the exposure apparatus (optical apparatus) described in Patent Document 1, a spring is provided between a support body that supports a mirror and its mounting portion. The writing unit (optical scanning device) described in Patent Document 2 includes a dynamic vibration absorber.
JP-A-5-224317 (page 3, FIG. 1) JP 2003-75760 A (page 3, FIG. 3)

  The exposure apparatus (optical apparatus) described in Patent Document 1 tries to prevent vibration of the mirror by absorbing the vibration by providing a spring between the support that supports the mirror and its mounting portion. The writing unit (optical scanning device) described in Patent Document 2 aims to reduce vibration of the unit at the resonance frequency by providing a dynamic vibration absorber. However, these methods can only deal with vibrations that oscillate at a certain frequency. The vibration generated in the optical scanning device is affected by various influences such as operating conditions such as scanning speed, environmental conditions such as temperature and humidity, installation conditions, operating conditions of the image forming apparatus in which the optical scanning device is incorporated, and various frequencies. May occur. Thereby, even if it can respond to a fixed vibration frequency, vibration cannot be avoided at other frequencies, and there is a possibility that deterioration in image quality cannot be avoided. Therefore, it is necessary not only to deal with a fixed frequency but also to prevent vibrations corresponding to various frequencies to improve image quality.

  The present invention has been made in view of the above points, and provides an optical scanning device capable of preventing vibration of an optical member corresponding to various vibration frequencies and obtaining a high-quality image. With the goal.

  In order to solve the above-described problems, in an optical scanning device including a housing and an optical member provided inside the housing and guiding a light beam onto a surface to be scanned, a support member that supports the optical member, An elastic member provided between the support member and the optical member to hold the optical member and having a variable spring constant corresponding to the amount of deformation, and a length changing mechanism for deforming the elastic member are provided.

  Further, in the optical scanning device having the above configuration, the elastic member is configured by a non-linear spring.

  In the optical scanning device having the above-described configuration, the nonlinear spring is configured by connecting a plurality of springs having different spring constants.

  According to the configuration of the present invention, in an optical scanning device including a housing and an optical member that is provided inside the housing and guides a light beam onto the surface to be scanned, a support member that supports the optical member, Since it is provided between the support member and the optical member to hold the optical member, an elastic member having a variable spring constant corresponding to the amount of deformation and a length changing mechanism for deforming the elastic member are provided. It is possible to change the spring constant of an elastic member that holds an optical member such as a mirror. As a result, the natural frequency of the vibration system composed of the mirror and the elastic member can be changed, and vibrations generated at various frequencies can be dealt with. Therefore, it is possible to provide an optical scanning device capable of preventing the vibration of the optical member corresponding to various vibration frequencies and obtaining a high-quality image.

  In addition, since the elastic member is composed of a non-linear spring, it is easy to change the natural frequency of the vibration system composed of the mirror and the elastic member, and to cope with various vibration frequencies. It is possible to get to. Therefore, it is possible to provide an optical scanning device that can prevent vibration of the optical member corresponding to various vibration frequencies with a simple configuration and obtain a high-quality image.

  Further, since the non-linear spring is configured by connecting a plurality of springs having different spring constants, it is possible to easily obtain a spring capable of obtaining non-linear elastic characteristics. Thereby, labor is required for molding, and a relatively expensive nonlinear spring can be obtained at low cost. Therefore, it is possible to provide an optical scanning device capable of reducing the cost and capable of preventing the vibration of the optical member corresponding to various vibration frequencies.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  First, the outline of the structure of the optical scanning device according to the first embodiment of the present invention will be described with reference to FIGS. 1 is a top view of the optical scanning device, FIG. 2 is a vertical sectional front view of the optical scanning device, and FIG. 3 is a perspective view of the optical scanning device. In FIG. 1 and FIG. 3, drawing of the lid member disposed on the upper surface of the optical scanning device is omitted. The optical scanning device is designed as an optical scanning device mounted on an image forming apparatus for monochrome printing provided with one photosensitive drum corresponding to one black color.

  As shown in FIGS. 1 to 3, the optical scanning device 1 includes a light source 3, an optical deflector 10, and an optical system 20 inside and around the housing 2.

  The housing 2 has a box shape with an upper surface formed as an open portion. A lid member 4 (see FIG. 2) is mounted on the upper surface of the housing 2 so as to close the opening. The housing 2 and the lid member 4 are made of synthetic resin.

  The light source 3 is provided in the location of the side surface of the housing 2, as shown in FIG.1 and FIG.3. Since the optical scanning device 1 corresponds to one black color, one light source 3 is also provided. The light source 3 is composed of a laser diode having a specification for irradiating a visible region light beam, for example, a laser beam of about 670 nm.

  The optical deflector 10 is provided on one end side of the housing 2, that is, on the right end side in FIGS. The optical deflector 10 includes a polygon mirror 11 and a drive unit 12. The drive unit 12 drives to rotate the polygon mirror 11 having a regular polygonal plane shape in the counterclockwise direction in FIG. 1 about a vertical axis. A reflection surface for reflecting light is provided around the polygon mirror 11 that rotates about the axis.

  The laser beam LB emitted from the light source 3 is incident on the reflection surface around the polygon mirror 11. While rotating, the polygon mirror 11 reflects the laser beam LB on its reflection surface and guides it toward the other end in the housing 2 while deflecting it in the main scanning direction (vertical direction in FIG. 1).

  The optical system 20 is provided in a region in the housing 2 where the laser light LB reflected by the optical deflector 10 travels. The optical system 20 includes an fθ lens 21 and a reflection mirror 22 that are optical members.

  The fθ lens 21 is disposed immediately before the laser beam LB reflected by the optical deflector 10 travels. The fθ lens 21 extends in a plane that is straight in the main scanning direction on the optical deflector 10 side, and the opposite side is curved in an arc shape in the main scanning direction. In the fθ lens 21, the laser beam LB is deflected at a constant speed in the main scanning direction. Further, the fθ lens 21 corrects adverse scanning effects such as the incident angle of the laser beam LB to the polygon mirror 11 and the surface tilt of the polygon mirror 11.

  The reflection mirror 22 is provided on the other end side of the housing 2 with respect to the one end side where the optical deflector 10 is disposed, that is, on the left end side in FIGS. 1 and 2. The reflection mirror 22 extends straight in the main scanning direction and has an elongated shape. The laser beam LB that has passed through the fθ lens 21 is reflected downward by the reflection mirror 22. The laser beam LB reflected by the reflection mirror 22 passes through an opening 5 (see FIGS. 2 and 3) provided at the bottom of the housing 2 and reaches the surface of a photosensitive drum (not shown) which is a scanned surface. Imaged.

  Next, a detailed configuration of the support portion of the reflection mirror 22 that is an optical member will be described with reference to FIGS. 4 and 5 in addition to FIGS. FIG. 4 is a partially enlarged front view of the vertical section showing the periphery of the reflecting mirror, and FIG. 5 is a graph showing the load characteristics of the spring of the reflecting mirror support.

  As shown in FIGS. 1 and 3, the reflection mirror 22 is supported by support portions 30 provided at both ends in the main scanning direction. As shown in FIG. 4, the support unit 30 includes a support member 31, a spring 32 that is an elastic member, and a length changing mechanism 33 of the spring 32.

  The support member 31 is provided on the inner bottom surface of the housing 2 and extends upward. The support member 31 includes a flat surface portion 31a extending in parallel with the reflection surface 22a of the reflection mirror 22 from which the laser beam LB is reflected, and the reflection mirror 22 is supported by the flat surface portion 31a. On the upper part of the flat part 31a, there is provided a protrusion 31b that protrudes toward the reflecting mirror 22 at a right angle to the flat part 31a.

  The spring 32 is disposed above the reflection mirror 22. The spring 32 is provided between the upper plane of the reflection mirror 22 that is substantially perpendicular to the reflection surface 22 a and the protrusion 31 b of the support member 31. The spring 32 urges the reflecting mirror 22 downward to hold it. The spring 32 is an elastic member having a variable spring constant corresponding to the amount of deformation, and is a non-linear spring configured by connecting two springs 32a and 32b having different spring constants. The spring 32 has a load characteristic shown in FIG. That is, the spring 32 has a high spring constant when the amount of deformation increases to some extent, and a large load is required for deformation.

  A length changing mechanism 33 of the spring 32 is disposed below the reflecting mirror 22. The length changing mechanism 33 includes a cam 34 and a rotating device (not shown) for the cam 34. The cam 34 is rotatable around a shaft portion substantially parallel to the main scanning direction, and the outer peripheral surface thereof is in contact with the lower plane of the reflecting mirror 22 that is substantially perpendicular to the reflecting surface 22a from below. . Since the reflection mirror 22 is supported by the flat portion 31a of the support member 31, when the cam 34 is rotated by the rotating device, the reflection mirror 22 moves obliquely along the reflection surface 22a in the vertical direction. When the reflecting mirror 22 is moved upward, the reflecting mirror 22 is moved against the elastic force of the spring 32.

  Next, changes in the frequency characteristics of the vibration system composed of the reflection mirror 22 and the spring 32 by the support portion 30 of the reflection mirror 22 having the above-described configuration will be described with reference to FIG. 6 in addition to FIG. FIG. 6 is a graph showing frequency characteristics of a vibration system including a reflection mirror and a spring.

  The support 30 moves the reflecting mirror 22 upward by the length changing mechanism 33 of the spring 32, thereby deforming the spring 32 against its elastic force, and the spring constant of the spring 32 can be seen from FIG. Can be increased. Therefore, the vibration system including the reflection mirror 22 and the spring 32 has a higher spring constant after the deformation than that before the spring 32 is deformed. As a result, as shown in FIG. 6, it is possible to shift the natural frequency at which the vibration amplitude increases.

  In addition, since the change of the spring constant of the spring 32 as described above is executed by moving the reflection mirror 22 obliquely along the reflection surface 22a, there is almost no adverse effect such as deviation of the optical axis.

  Further, the spring constant of the spring 32 is changed by recognizing that the reflection mirror 22 vibrates by detecting the deviation of the electrostatic latent image formed on the surface of the photosensitive drum that is the surface to be scanned. The

  As described above, in the optical scanning device 1 that includes the housing 2 and the optical member that is provided inside the housing 2 and guides the laser beam LB that is a light beam onto the surface to be scanned, the reflection mirror that is an optical member. A support member 31 that supports 22 and a spring 32 that is provided between the support member 31 and the reflection mirror 22 to hold the reflection mirror 22 and is an elastic member whose spring constant is variable in accordance with the amount of deformation; Since the length changing mechanism 33 that deforms the spring 32 is provided, it is possible to change the spring constant of the spring 32 that holds the reflecting mirror 22. Thus, the natural frequency of the vibration system composed of the reflection mirror 22 and the spring 32 can be changed, and vibrations generated at various frequencies can be dealt with. Accordingly, it is possible to provide the optical scanning device 1 that can prevent the reflection mirror 22 from vibrating in response to various vibration frequencies and obtain a high-quality image.

  Further, since the spring 32 is composed of a non-linear spring, it is possible to easily obtain a configuration that can change the natural frequency of the vibration system composed of the reflection mirror 22 and the spring 32 and can cope with various vibration frequencies. It is possible. Therefore, with a simple configuration, it is possible to provide the optical scanning device 1 that can prevent the reflection mirror 22 from vibrating in response to various vibration frequencies and obtain a high-quality image.

  Furthermore, since the non-linear spring is configured by connecting a plurality of springs 32a and 32b having different spring constants, it is possible to easily obtain the spring 32 having non-linear elastic characteristics. Thereby, labor is required for molding, and a relatively expensive nonlinear spring can be obtained at low cost. Therefore, it is possible to provide the optical scanning device 1 that can prevent the reflection mirror 22 from vibrating in response to various vibration frequencies and can be reduced in cost.

  Next, a detailed configuration of the optical scanning device according to the second embodiment of the present invention will be described with reference to FIG. FIG. 7 is a partially enlarged front view of the vertical section showing the periphery of the reflection mirror of the optical scanning device. Since the basic configuration of this embodiment is the same as that of the first embodiment described with reference to FIGS. 1 to 6, the same reference numerals are used for the same components as those of the first embodiment. The description is omitted.

  As shown in FIG. 7, in the optical scanning device 1 according to the second embodiment, in the support portion 30 of the reflection mirror 22, the length changing mechanism 33 of the spring 32 includes a thermal expansion member 35 and its heating device (not shown). )).

  The thermal expansion member 35 has a block shape and is provided between the lower plane of the reflection mirror 22 that is substantially perpendicular to the reflection surface 22 a and the support member 31, and contacts the lower plane of the reflection mirror 22. It touches. The thermal expansion member 35 is made of a material having a relatively high linear expansion coefficient, such as aluminum or silicon rubber. The temperature of the heating device can be controlled, and the heating device is disposed in the vicinity thereof in order to heat the thermal expansion member 35.

  By controlling the heating device and heating the thermal expansion member 35 or stopping the heating, the thermal expansion member 35 can be expanded and contracted. Thereby, the reflecting mirror 22 moves in the up-down direction obliquely along the reflecting surface 22a. Therefore, the support unit 30 moves the reflecting mirror 22 upward by the length changing mechanism 33 of the spring 32, thereby deforming the spring 32 against its elastic force and increasing the spring constant of the spring 32. it can.

  As described above, since the length changing mechanism 33 that deforms the spring 32 includes the thermal expansion member 35, the spring constant of the spring 32 that holds the reflecting mirror 22 is changed as in the first embodiment. It is possible. Thus, the natural frequency of the vibration system composed of the reflection mirror 22 and the spring 32 can be changed, and vibrations generated at various frequencies can be dealt with. Accordingly, it is possible to provide the optical scanning device 1 that can prevent the reflection mirror 22 from vibrating in response to various vibration frequencies and obtain a high-quality image.

  Next, a detailed configuration of the optical scanning device according to the third embodiment of the present invention will be described with reference to FIG. FIG. 8 is a partially enlarged front view of the vertical section showing the periphery of the reflection mirror of the optical scanning device. Since the basic configuration of this embodiment is the same as that of the first embodiment described with reference to FIGS. 1 to 6, the same reference numerals are used for the same components as those of the first embodiment. The description is omitted.

  In the optical scanning device 1 according to the third embodiment, as shown in FIG. 8, the length changing mechanism 33 of the spring 32 includes an electromagnet 36 in the support portion 30 of the reflection mirror 22. Further, the spring 32 is disposed below the reflection mirror 22.

  The spring 32 is provided between the support member 31 and the lower plane of the reflection mirror 22 that is substantially perpendicular to the reflection surface 22 a. The spring 32 urges the reflecting mirror 22 upward to hold it.

  The electromagnet 36 is further disposed below the reflecting mirror 22 with a portion where the spring 32 is provided. On the other hand, the reflecting mirror 22 contains a metal material that can be attracted by the electromagnet 36.

  By energizing the electromagnet 36 or stopping the energization, the reflection mirror 22 can be pulled toward or away from the electromagnet 36. Thereby, the reflecting mirror 22 moves in the up-down direction obliquely along the reflecting surface 22a. Therefore, the support unit 30 moves the reflecting mirror 22 upward by the length changing mechanism 33 of the spring 32, thereby deforming the spring 32 against its elastic force and increasing the spring constant of the spring 32. it can.

  As described above, since the length changing mechanism 33 that deforms the spring 32 includes the electromagnet 36, the spring constant of the spring 32 that holds the reflecting mirror 22 can be changed as in the first embodiment. Is possible. Thus, the natural frequency of the vibration system composed of the reflection mirror 22 and the spring 32 can be changed, and vibrations generated at various frequencies can be dealt with. Accordingly, it is possible to provide the optical scanning device 1 that can prevent the reflection mirror 22 from vibrating in response to various vibration frequencies and obtain a high-quality image.

  Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention.

  For example, the optical scanning device 1 is an optical scanning device mounted on an image forming apparatus for monochrome printing that uses only black toner in the above-described embodiment, but is not limited to such a model. An optical scanning device mounted on a color printing image forming apparatus of a tandem method or a rotary rack method that includes a belt and can superimpose a plurality of colors to form an image may be used.

  The spring 32, which is an elastic member, is a non-linear spring configured by connecting two springs 32a and 32b having different spring constants. However, the elastic member is not limited to this, and an unequal pitch coil is used. A non-linear spring such as a spring may be used.

  The length changing mechanism 33 for deforming the spring 32 is not limited to the mechanism described in the first to third embodiments. For example, the spring 32 is deformed using a shape memory alloy or a piezoelectric element. It doesn't matter.

  The present invention can be used in all optical scanning devices.

1 is a top view of an optical scanning device according to a first embodiment of the present invention. FIG. 2 is a vertical sectional front view of the optical scanning device shown in FIG. 1. It is a perspective view of the optical scanning device shown in FIG. FIG. 3 is a partially enlarged front view of a vertical section showing the periphery of the reflection mirror of FIG. It is a graph which shows the load characteristic of the spring of the reflective mirror support part shown in FIG. It is a graph which shows the frequency characteristic of the vibration system which consists of a reflective mirror and a spring shown in FIG. It is a vertical cross-section part enlarged front view which shows the reflective mirror periphery of the optical scanning device concerning the 2nd Embodiment of this invention. It is a vertical cross-section part enlarged front view which shows the reflective mirror periphery of the optical scanning device concerning the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical scanning device 2 Housing 3 Light source 10 Optical deflector 20 Optical system 22 Reflection mirror (optical member)
22a Reflecting surface 30 Support part 31 Support member 31a Plane part 31b Projection part 32 Spring (elastic member)
33 Length changing mechanism 34 Cam 35 Thermal expansion member 36 Electromagnet

Claims (3)

In an optical scanning device comprising a housing and an optical member provided inside the housing and guiding a light beam onto the surface to be scanned,
A support member that supports the optical member, an elastic member that is provided between the support member and the optical member, holds the optical member, and has a variable spring constant corresponding to the amount of deformation, and deforms the elastic member. An optical scanning device comprising a length changing mechanism.   The optical scanning device according to claim 1, wherein the elastic member includes a non-linear spring.   The optical scanning device according to claim 2, wherein the nonlinear spring is configured by connecting a plurality of springs having different spring constants.

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