JP2010190685A - Reflected light intensity detecting sensor and image forming apparatus employing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflected light intensity detecting sensor capable of stably sensing a reflected light intensity from a surface of an image carrier, by shifting the center of a light receiving element and the optical axis center of reflection light from each other, and to provide an image forming apparatus employing the same. <P>SOLUTION: In the reflected light intensity detecting sensor 20, at least one light emitting element 1 and one light receiving element 2 are disposed in a light shielding case 5, so as to keep a fixed interval L with respect to an object to be sensed 4, and the reflection light 7 resulting from light 6 with which the object to be sensed 4 is obliquely irradiated by the light emitting element 1, is received by the light receiving element 2. The light receiving element is shifted in parallel to a reflecting surface 4A of the object to be sensed in a direction in which both elements get away mutually from a reference position on which the optical axis 7A of the reflection light 7 coincides with the center 2A of the light receiving element 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a reflected light amount detection sensor that receives reflected light of incident light irradiated to an irradiation object, and an image forming apparatus such as a copying machine, a printer, a facsimile, and a multifunction machine using the reflected light amount detection sensor. Is.

  In the field of image forming apparatuses, in order to obtain a stable image density, a reference pattern called a density detection toner patch is formed on the surface of an image carrier such as a photoconductor, and the density of the reference pattern is detected by an optical sensor. ing. Patent Documents 1 and 2 are examples of detecting the density of a reference pattern using such an optical sensor. In such an image forming apparatus that detects the density of the reference pattern, the developing potential can be adjusted by changing the writing light intensity, the charging bias, the developing bias, etc. for forming the latent image based on the detection result by the optical sensor. Such image density control is performed.

  In general, an optical sensor is called a P (pattern) sensor because a reference pattern is a detection target, and a reflective optical sensor including a light emitting unit and a light receiving unit is generally used. As shown in FIG. 18, there is a reflection type optical sensor that detects regularly reflected light when the light irradiated from the light emitting unit is regularly reflected on the irradiation target by the light receiving unit. Is disclosed in Patent Document 1 and the like.

  The detection principle when a reflective optical sensor that detects specularly reflected light is used as a P sensor will be described by taking as an example the case of detecting the toner concentration (toner adhesion amount) on the surface of the image carrier. When no toner adheres to the surface of the image carrier to be irradiated, incident light irradiated from the light emitting means and reaching the surface of the image carrier is regularly reflected on the surface of the image carrier, and the image carrier The regular reflection light corresponding to the reflectance of the surface (reflection surface) is received by the light receiving element. On the other hand, when toner adheres to the surface of the image carrier, incident light that is irradiated from the light emitting means and travels toward the surface of the image carrier is absorbed by the toner, or is irregularly reflected by the toner. Therefore, the incident light is blocked by the toner before reaching the surface of the image carrier from the light emitting means, or the regular reflection light from the surface of the image carrier is blocked by the toner before reaching the light receiving element. The regular reflection light is hardly received by the light receiving element. Therefore, the amount of light received by the light receiving element is reduced as the amount of toner attached on the surface of the image carrier increases. Therefore, the toner on the surface of the image carrier is determined based on the amount of light received by the light receiving element. The amount of adhesion can be detected.

  In Patent Document 3, in order to provide an inexpensive and small sensor for measuring the distance from the sensor to the measurement surface, a light emitting element and a plurality of light receiving elements are integrally provided, and the optical axes of each of the plurality of light receiving elements are An optical sensor arranged so as not to cross is described.

  In Patent Document 4, the center axis of the light emitting element is shifted from the center axis of the light emitting side lens toward the light receiving element side, and the light component emitted from the light emitting element that is the source of the specularly reflected light is cut off and specularly reflected. An optical sensor is described that prevents light from entering the light receiving element.

  In the cited document 5, the center of the sensor is installed at a position shifted in parallel by a certain distance from the central optical axis of the optical system to the light source side, and the light source is placed in a region where the specularly reflected light from the reading target is not incident on the sensor. A configuration is described in which the light source is installed at a position close to the operator's hand with respect to the central optical axis, and the sensor is installed at a position where the center is shifted in parallel from the central optical axis to the light source by a required distance. ing.

  In the detection methods of the toner adhesion amount on the surface of the image carrier as in Patent Documents 1 and 2, accurate adhesion amount detection cannot always be performed. This is because it is necessary to operate the image carrier itself in order to detect the toner adhesion amount. For example, when the detection target part is an intermediate transfer belt (image carrier), a reference pattern in which toner is attached to the intermediate transfer belt is prepared, and various reference patterns are detected by rotating the intermediate transfer belt. Will be detected. When the intermediate transfer belt as the detection target is operated in this way, the detection distance from the optical sensor to the intermediate transfer belt varies due to vibration caused by the operation, or the optical sensor moves the intermediate transfer belt as shown in FIG. When the angle to be detected fluctuates, the output of the optical sensor also changes. Therefore, there is a need for an optical sensor that exhibits a stable output even when there is a detection distance variation or a detection angle variation.

  Patent Document 3 describes an optical sensor that is integrally provided with a light emitting element and a plurality of light receiving elements, and is arranged so that the optical axes of the plurality of light receiving elements do not cross each other. The distance to the measurement surface is measured.

  Patent Document 4 describes a sensor configuration in which the center axis of the light emitting element is shifted from the center axis of the light emitting side lens toward the light receiving element side. This sensor is used for detecting the presence or absence of a document.

  Cited Document 5 describes a configuration in which the center of the image sensor and the light source are installed at positions shifted in parallel from the central optical axis of the optical system. This configuration is the center of the image sensor and the center of the imaging means. This relates to the deviation from the optical axis.

  The present invention provides a reflected light amount detection sensor capable of stably detecting a reflected light amount from the surface of a detection object by shifting the center of a light receiving element and the center of an optical axis of reflected light, and an image forming apparatus using the same. Its purpose is to provide.

  In order to achieve the above object, in the present invention, at least one light emitting element and one light receiving element are provided in a light-shielding case and held at a fixed interval with respect to the detection target, and are detected by tilting from the light emitting element. In the reflected light amount detection sensor that receives the reflected light of the light irradiated to the object by the light receiving element, from the reference position where the optical axis of the reflected light and the center of the light receiving element overlap, both the light receiving element or the light emitting element and the light receiving element Are arranged so as to be moved parallel to the reflection surface of the object to be detected in a direction in which the elements move away from each other.

  The light shielding case includes a first cylindrical portion having a light emitting element positioning portion, a light emitting aperture for restricting spread of irradiation light from the light emitting element to the detection target, a light receiving element positioning portion, and the light receiving element. And a second cylindrical portion having a light receiving aperture for defining the amount of reflected light.

  The first cylindrical shape portion and the second cylindrical shape portion are formed integrally with the light shielding case, the light emitting aperture is in the optical axis direction of the light emitted from the light emitting element, and the light receiving aperture is the reflected light. Each extends in the axial direction.

  For this reason, the light emitted from the light emitting element positioned by the first cylindrical portion is irradiated to the detection target through the light emitting aperture extending in the optical axis direction, and is reflected by the detection target. Is received by the light receiving element through a light receiving aperture extending in the optical axis direction of the reflected light.

  In the present invention, the optical axis of the incident light to the detection target is on the central axis of the light emitting aperture, and the optical axis of the reflected light from the detection target is positioned in a direction parallel to the central axis of the light receiving aperture. Yes.

  The light shielding case is provided not only with a light receiving element that receives light regularly reflected by the detection object, but also with a diffused light receiving element that receives light emitted from the light emitting element and diffusely reflected by the detection object. ing.

  In the present invention, an image carrier having a surface that regularly reflects light, a toner image forming unit that forms a toner image on the image carrier, and a toner image deposited on the image carrier by the toner image forming unit. In an image forming apparatus including an optical sensor for detecting the amount of toner adhesion and an image density control unit that performs image density control based on the detection result of the optical sensor, the reflected light amount detection sensor described above is used as the optical sensor. It is characterized by having used.

  According to the present invention, from the reference position where the optical axis of the reflected light and the center of the light receiving element overlap, the light receiving element or both of the light emitting element and the light receiving element are parallel to the reflecting surface of the detection object in a direction in which the elements move away from each other. By moving and arranging it, the center of the light receiving element and the optical axis of the reflected light are intentionally prevented from overlapping, so that the amount of light received by the light receiving element can be changed compared to when it is at the reference position, In addition, the relationship between the amount of received light and the variation in the detection distance that occurs when the detection object is operated can be changed. For this reason, the amount of reflected light from the surface of the object to be detected can be reduced by arranging the light receiving element or both the light emitting element and the light receiving element so that the change in the amount of received light is less with respect to the variation in the detection distance than in the reference position. It can be detected stably.

  By using such a stable reflected light amount detection sensor as an optical sensor for detecting the toner adhesion amount when the toner is deposited on the image carrier by the toner image forming means, the detection result of the optical sensor is obtained. The stability of the image density control performed based on this improves, and a good image can be obtained.

1 is a schematic configuration diagram of an image forming apparatus including a reflected light amount detection sensor according to the present invention. FIG. 4 is an enlarged view showing a form in which an optical sensor detects a toner adhesion amount when toner is adhered on an image carrier by a toner image forming unit. It is a block diagram which shows the structure of the principal part of the image density control means which performs image density control based on the detection result of an optical sensor. It is an expanded sectional view which shows the structure of the reflected light amount detection sensor concerning this invention. It is an expanded sectional view which shows the structure of the light-shielding case which comprises a reflected light amount detection sensor. It is the figure which looked at the light-shielding case from the arrow A direction. It is an optical simulation model of the conventional reflected light amount detection sensor in which the center of the light receiving element is located with respect to the optical axis of the reflected light. It is an enlarged view by the side of the light emitting element of FIG. It is an enlarged view which shows a light ray locus when the number of light rays from the light emitting element side is 100,000 in the optical simulation model of FIG. It is an optical simulation model of the reflected light amount detection sensor in which the center of the light receiving element is shifted with respect to the optical axis of the reflected light according to the present invention. It is an enlarged view which shows a light ray locus when the number of light rays from the light emitting element side is 100,000 in the optical simulation model of FIG. It is a figure which shows a model in order to implement the illumination distribution analysis of the light ray which arrived at the light-receiving side by the optical simulation in which the center of the light receiving element was located with respect to the optical axis of reflected light. 13 is an illuminance distribution for regular reflection light on the light receiving side according to the model of FIG. It is a figure which shows the model which has arrange | positioned the light receiver in the aperture entrance by the side of a light receiving element in FIG. It is a figure which shows the illumination intensity distribution result of the light receiver of the aperture entrance of a light receiving element with respect to the detection distance fluctuation | variation in case the center of a light receiving element corresponds with the optical axis of reflected light. It is a figure which shows the illumination intensity distribution result of the light receiver of the aperture entrance of a light receiving element with respect to the detection distance fluctuation | variation when the center of a light receiving element has shifted | deviated with respect to the optical axis of reflected light. It is a characteristic view which shows the relationship between the detection distance in an optical simulation model, and the light reception amount in the light receiver for regular reflection light. It is an enlarged view which shows schematic structure of the structure of the conventional reflected light amount detection sensor in which the optical axis center of reflected light and the center of the light receiving element corresponded. It is a figure for demonstrating the problem by the reflected light amount detection sensor of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, the configuration and characteristics of the reflected light amount detection sensor 20 to which the present invention is applied will be described, and then the configuration and operation of the image forming apparatus to which the reflected light amount detection sensor 20 is applied will be described.

  As shown in FIG. 4, the reflected light amount detection sensor 20 includes at least one light emitting element, at least one light receiving element, and a light shielding case 5. In this embodiment, a description will be given assuming that the light emitting element 1 and the two light receiving elements 2 and 3 are provided. The light emitting element 1 and the light receiving elements 2 and 3 are arranged with a certain distance (hereinafter referred to as “detection distance L”) with respect to the detection target 4. This detection distance L is the distance between the surface 5A facing the detection target 4 of the light shielding case 5 and the reflection surface 4A of the detection target 4. That is, the light shielding case 5 holds each element such that the light emitting element 1 and the light receiving elements 2 and 3 are at a constant interval with respect to the detection target 5.

  The light emitting element 1 is arranged in the light shielding case 5 so that the irradiation light 6 is irradiated with being inclined with respect to the reflection surface 4 </ b> A of the detection object 4. The irradiation light 6 is reflected at the same angle by the reflection surface 4 </ b> A and becomes reflected light 7. The light emitting element 1 and the light receiving element 2 have a reference position where the center 2A of the light receiving element 2 overlaps the optical axis 7A of the reflected light 7 from the reflecting surface 4A. In this embodiment, the light receiving element 2 detects so-called specularly reflected light, and is disposed at a position translated from the basic position in a direction away from the light emitting element 1 with respect to the reflecting surface 4A. The optical axis 7 </ b> A and the center 2 </ b> A of the light receiving element 2 are arranged so as to have a shifted positional relationship. The light receiving element 2 detects the diffusely reflected light reflected by the reflecting surface 4A.

  In this embodiment, the light receiving element 2 is moved relative to the light emitting element 1 to shift the optical axis 7A of the reflected light 7 and the center 2A of the light receiving element 2, but both the light emitting element 1 and the light receiving element 2 are Arranged so that the optical axis 7A of the reflected light 7 and the center 2A of the light receiving element 2 are shifted from each other by moving to a position where the elements are moved parallel to the reflecting surface 4A in a direction away from each other. May be.

  As shown in FIGS. 5 and 6, the light shielding case 5 includes a cylindrical portion 8 for a light emitting element and cylindrical portions 9 and 10 for a light receiving element. The cylindrical portion 8 is formed so as to penetrate the light shielding case 5.

  The cylindrical member 8 is for mounting and fixing the light emitting element 1, and is formed by drilling holes 8 </ b> A to 8 </ b> C having different diameters in the light shielding case 5. The hole 8A constitutes a positioning portion used for restricting the amount of insertion of the light emitting element 1 into the hole 8B. The hole 8B constitutes a mounting portion used when the light emitting element 1 is fixed. The hole 8 </ b> C is a so-called aperture and regulates the spread of the irradiation light 6 emitted from the light emitting element 1. The hole 8C (light emitting aperture) extends in the direction of the optical axis of the irradiation light 6 emitted from the light emitting element 1, and its center 9D is configured to overlap the optical axis 6A of the irradiation light 6.

  The cylindrical portion 9 is for mounting and fixing the light receiving element 2 that receives regular reflection light on the reflection surface 4A, and is formed by drilling holes 9A to 9C having three different diameters in the light shielding case 5. . The hole 9A constitutes a positioning portion used for restricting the amount of insertion of the light receiving element 2 into the hole 9B. The hole 9B constitutes a mounting portion used when the light receiving element 2 is fixed. The hole 9 </ b> C is a so-called aperture and regulates the spread of the reflected light 6 with respect to the light receiving element 2. The hole 9C (light receiving aperture) extends in the optical axis direction of the reflected light 7 and is configured such that its center 10D overlaps the optical axis 7A of the reflected light 7.

  The cylindrical portion 10 is for mounting and fixing the light receiving element 3 that receives diffusely reflected light on the reflecting surface 4A, and is formed by drilling two different holes 10A and 10C in the light shielding case 5. The hole 10A constitutes a positioning portion used for restricting the insertion amount of the light receiving element 3 into the hole 10C. The hole 10C functions as a mounting portion and an aperture used when the light receiving element 3 is fixed. It is assumed that the light receiving element 3 is arranged at a position where regular reflection light from the light emitting element 1 does not enter.

  In this way, if the center 2A of the light receiving element 2 and the optical axis 7A of the reflected light 7 are not intentionally overlapped, the amount of light received by the light receiving element 2 can be changed, and when the detection object 4 operates. It is also possible to change the relationship of the amount of received light with respect to fluctuations in the detection distance that occur.

Since the relationship between the amount of received light of the light receiving element 2 having such an arrangement and the amount of received light with respect to the fluctuation of the detection distance L that occurs when the detection target 4 is operated is confirmed by optical simulation using a computer. This will be described below.
(Explanation of optical simulation model)
The following two models were used in the optical simulation. One is the center 2A of the light receiving element 2 with respect to the optical axis 7A of the reflected light 7 as shown in FIG. 7, and the other is as shown in FIG. The center 2A of the light receiving element 2 is not provided with respect to the optical axis 7A of the reflected light 7 constituting the structure. FIG. 8 is an enlarged view of the light emitting element portion of FIG.
(Configuration of optical simulation model)
As shown in FIGS. 7 and 10, the light-emitting element 1 has a light-emitting element lens 11A and a light-emitting element chip 11B with a light-emitting element electrode. The light-shielding case of the model has a hole 8B for fixing the light-emitting element and a light-emitting aperture. A cylindrical portion 8 having 8C was formed.
As shown in FIGS. 7 and 10, the light receiving element 2 has a light receiving element lens 12 </ b> A and a light receiver 12 </ b> B (for regular reflection light). A cylindrical portion 9 having a working aperture 9C was formed. The model may be provided with a configuration of a light receiving element portion for diffuse reflected light, but here, description will be made using an optical model of the light emitting element 1 and the light receiving element 2 for regular reflected light.

  7, the centers of the light receiver 12B and the cylindrical portion 9 are positioned on the optical axis 7A of the reflected light 7. In FIG. 10, the light receiver 12B, the light receiving element 2, and the cylindrical portion 9 are compared to FIG. Are translated with respect to the reflecting surface 4A in the direction in which the elements move away from each other.

  In the optical simulation, an illuminance analysis and an illuminance distribution analysis can be performed by preparing a light source, emitting light from the light source, and receiving the light by the light receiver 12B. The light source in this model is the light emitting element chip 11B. Each light beam emitted from the light emitting element chip 11B has the same intensity and is set so as to be irradiated randomly in the convex direction of the light emitting element lens 11A. The light beam from the light emitting element chip 11B passes through the light emitting aperture 8C and reaches the reflection surface 4A of the detection target. Since all the light emitting apertures 8C are set as absorbing surfaces, only the light rays that have not contacted the light emitting apertures 8C reach the reflecting surface 4A and are reflected at the same angle as the incident angle. Similarly, in the reflected light 7 as well, only the light beam that has not contacted the light receiving aperture 9C enters the light receiving element lens 12A, and the condensed light beam enters the light receiver 12B. FIG. 9 shows a light ray locus when the number of light rays from the light emitting element chip 11B is 100,000. In the configuration of FIG. 7, it can be seen that the center 2A of the light receiving element 2 is located with respect to the optical axis 7A of the reflected light 7 as shown in FIG.

On the other hand, in FIG. 10, similarly to the case where the center 2A of the light receiving element 2 is present with respect to the optical axis 7A of the reflected light 7 shown in FIG. 7, light is emitted from the light emitting element chip 11B and reflected by the light emitting aperture 8C. The number of rays reaching 4A is regulated. Since all the light receiving apertures 9C are set as absorbing surfaces, only the light rays that have passed through the light emitting apertures 8C reach the reflecting surface 4A and are reflected at the same angle as the incident angle. The reflected light 7 passes through the light receiving aperture 9C, is condensed by the light receiving element lens 12A, and enters the light receiver 12B. FIG. 11 shows a light ray locus when the number of light rays from the light emitting element chip 11B is 100,000. In this configuration, it can be seen that there is no center of the light receiving element 2 with respect to the optical axis 7A of the reflected light 7.
(How to read illuminance distribution)
In the optical simulation, the illuminance distribution analysis of the light beam reaching the light receiver 12B can be performed. The size of the light receiver 12B was a square of about 0.5 mm × 0.5 mm. Here, how to read the illuminance distribution in the light receiver 12B will be described. FIG. 11 is a model in the case where the center 2A of the light receiving element 2 is on the optical axis 7A of the reflected light 7 shown in FIG. 6, and FIG. 13 shows the illuminance distribution in the light receiving device 12B for regular reflected light in FIG. . The X and Y directions in FIG. 12 correspond to the X and Y directions in FIG. In the illuminance distribution of FIG. 13, the difference in color represents the light intensity. The original drawing of FIG. 13 is displayed as a nine-color image, but here it is expressed only as light and dark as a grace case display. In FIG. 13, the portion corresponding to red in the original drawing shows a higher light intensity, and the blue color in the original drawing shows a lower light intensity. The cross line in the figure is the center of the light receiver 12B in the X and Y directions, and is the center of the light receiving element 2.
(Result: Illuminance distribution analysis)
In this optical simulation, the detection distance L with respect to the reflecting surface 4A is set to a constant value (reference value). When the detection distance L due to the operation of the reflection surface 4A of the detection target is varied, it is expected that the detection distance L varies about ± 1.0 mm when the detection target is an intermediate transfer belt. For this reason, the illuminance distribution analysis of the light receiver 12B was performed when the detection distance L varied ± 1.0 mm from the reference value in the optical simulation. As shown in FIG. 14, the light receiver 12B is arranged at the entrance 9C1 of the light receiving side aperture 9C. 15 and 16 show the illuminance distribution results of the light receiver 12B at the entrance 9C1 of the aperture 9C with respect to the variation in the detection distance L. FIG. 15 shows an illuminance distribution when the center 2A of the light receiving element 2 is present with respect to the optical axis 7A of the reflected light 7, and FIG. 16 shows no center 2A of the light receiving element 2 with respect to the optical axis 7A of the reflected light 7. The illumination distribution in the case is shown. The original drawings in FIGS. 15 and 16 are displayed as nine-color images as in FIG. 13, but here they are expressed only in light and dark as a grace case display. In the figure, the darker area corresponding to the red area in the original map has a higher light intensity, and the save area corresponding to the blue area in the original figure in the figure has a lower light intensity. The circles in the illuminance distributions of FIGS. 15 and 16 indicate the aperture diameter of the light receiving element 2 (for regular reflection light). The light in the aperture diameter region is directed to the light receiver 12B (for regular reflection light). Here, it should be noted that the maximum amount of light of the illuminance distribution at each detection distance is different. That is, in the illuminance distributions shown in FIGS. 15 and 16, the portion corresponding to the red region in the original drawing is the maximum light amount region, but the light amount of the region differs for each light receiving device for each detection distance.

  In both the case where the center 2A of the light receiving element 2 is present with respect to the optical axis 7A of the reflected light 7 and the case where the center 2A of the light receiving element 2 is not present relative to the optical axis 7A of the reflected light 7, the detection distance L is shorter. It can be seen that the maximum amount of light is high. This indicates that the light density is high because the detection distance L from the light emitting element 2 to the detection surface (reflection surface 4A) is short.

  When the center 2A of the light receiving element 2 is on the optical axis 7A of the reflected light 7, it is set so that strong light enters the light receiving element 2 when the detection distance L is short, and conversely, it is received when the detection distance L is long. It is set so that weak light enters the element 2.

When the center 2A of the light receiving element 2 is not located with respect to the optical axis 7A of the reflected light 7, it is set so that weak light enters the light receiving element 2 for regular reflection light when the detection distance L is short, and conversely the detection distance. It is set so that strong light enters the light receiving element 2 when L is long.
(Result: Relationship between detection distance and detection amount: Illuminance analysis)
Separately from the analysis of the illuminance distribution shown in FIGS. 15 and 16, the amount of light received by the light receiver 12 </ b> B at the detection distance: reference value ± 4.0 mm was investigated. The result is shown in FIG. In FIG. 17, the horizontal axis represents the detection distance (mm), and the vertical axis represents the amount of received light (W). The amount of light at the light receiver 12B is the number of light beams reaching the light receiver (0.5 mm × 0.5 mm size) because the intensity of each light beam is set to be the same. The light amount is corrected so that the light amount at the detection distance: reference value is 1 W. In the figure, ♦ indicates the characteristics of the amount of received light when the center 2A of the light receiving element 2 is located with respect to the optical axis 7A of the reflected light 7, and ■ indicates the center of the light receiving element 2 with respect to the optical axis 7A of the reflected light 7. The characteristics of the amount of received light when 2A is not present are shown.

In the case where the center 2A of the light receiving element 2 is on the optical axis 7A of the reflected light 7, the light amount is maximum when the detection distance is -1.0 mm. On the other hand, when there is no center 2A of the light receiving element 2 with respect to the optical axis 7A of the reflected 7 light as in the present application, when the detection distance is -1.0 mm, the maximum light amount decreases and the detection distance is the reference value. The maximum amount of light was obtained. If the detection target is an intermediate transfer belt, the detection distance is expected to vary by about ± 1.0 mm with respect to the reference value (dotted line region). When the center of the light receiving element 2 is not centered with respect to the optical axis 7A of the reflected light 7 in this fluctuation region, it can be seen that there is little variation in the amount of light received due to fluctuations in the detection distance, as indicated by. When there is no center 2A of the light receiving element 2 with respect to the optical axis 7A of the reflected light 7 as compared with the case where the center 2A of the light receiving element 2 is present with respect to the optical axis 7A of the reflected light 7, the detection distance fluctuation is more stable. I can say that.
(Consideration of results)
If the center 2A of the light receiving element 2 is not located with respect to the optical axis 7A of the reflected light 7, it will be as follows when it is considered based on FIGS.

  First, when the detection distance L is short, the light intensity increases because the light density increases. When there is no center of the light receiving element with respect to the optical axis 7A of the reflected light 7, as shown in FIG. 16, when the detection distance L is short (−1.0 mm), the light receiving element 2 receives weak light, and conversely When the detection distance L is long (+1.0 mm), the light receiving element 2 receives strong light. For this reason, the amount of light reaching the light receiver 12B becomes uniform. Such characteristics are the same even when the positions of the light-emitting element 1 and the light-receiving element 2 are shifted from the reference position and, as a result, the center 2A of the light-receiving element 2 is not (shifted) with respect to the optical axis 7A of the reflected light 7. is there.

  On the other hand, when the center 2A of the light receiving element 2 is located with respect to the optical axis 7A of the reflected light 7, the light receiving element 2 is strong when the detection distance L is short (−1.0 mm) as shown in FIG. On the contrary, when the detection distance (+1.0 mm) is long, the light receiving element 2 receives weak light. For this reason, the amount of light reaching the light receiver 2 varies.

  From the above, at least one light-emitting element 1 and at least one light-receiving element 2 are integrally provided in the light-shielding case 5 and emit light to the detection object 4 having a constant interval (detection distance L). The light is emitted from the element 1 at an angle, and the light receiving element 2 or both the light emitting element 1 and the light receiving element 2 are moved away from each other from a reference position where the optical axis 7A of the reflected light 7 and the center 2A of the light receiving element 2 overlap. The relationship of the amount of received light with respect to the detection distance L can be changed by translating the reflecting surface 4A in the direction, and a stable output can be obtained depending on the positional relationship between the light-emitting element 1 and the light-receiving element 2 that have been translated. Can do. That is, even when the detection target 4 is operating by predicting the fluctuation range of the detection distance L due to vibration of the detection target object 4 and reducing the change in the amount of light received by the light receiving element 2 within the fluctuation range. In the light receiving element 2, a stable amount of received light can be secured, and the detection accuracy can be improved.

  Next, an image forming apparatus using the reflected light amount detection sensor 20 having such characteristics will be described. An image forming apparatus 100 shown in FIG. 1 is an electrophotographic image forming apparatus that performs exposure, charging, development, transfer, and fixing. In addition to the components shown in FIG. 1, the image forming apparatus 100 includes a print controller 410 for processing image data sent from a PC (personal computer) or the like and converting it into exposure data, as shown in FIG. A high pressure generating device 416 for generating a high pressure used for printing, a main body control unit 406 for controlling an image forming operation, a paper feeding device (not shown) for supplying transfer paper 115 as a transfer material as a recording material, and manual feeding of the transfer paper 115 There are provided a manual feed tray (not shown) and a paper discharge tray (not shown) on which the image-formed transfer paper 115 is discharged.

  As shown in FIG. 1, the image forming apparatus 100 includes an image forming unit 300. The image forming unit 300 is provided with an endless belt-shaped intermediate transfer belt 105 and a charging device (primary transfer device 106), which are image carriers and intermediate transfer members, as a first transfer device. The intermediate transfer belt 105 is rotationally driven counterclockwise in the figure by the support roller 112 having a function as a drive roller while being stretched around the four support rollers 112, 113, 114, and 119. In this embodiment, the image carrier having a surface that regularly reflects light is the intermediate transfer belt 105, which is a detection target.

  There are four image forming units for each color of yellow (Y), cyan (C), magenta (M), and black (K) in the stretched portion of the intermediate transfer belt. The four image forming units for each color have the same configuration and are composed of the same constituent members. In FIG. 1, the same constituent members represent numerical parts with the same numerals, and end with color identification codes Y (yellow), C (cyan), M ( Magenta) and K (black). In each image forming unit, photoreceptor units 103Y, 103C, 103M, and 103K and developing units 102Y, 102C, 102M, and 102K are arranged side by side. The developing units 102Y, 102C, 102M, and 102K are supplied with toner from the toner bottles 104K, 104Y, 104C, and 104M.

  Below these image forming units 300, an exposure device 200 is provided. Based on the image information, writing is performed by driving a semiconductor laser from a laser exposure unit (not shown) provided in the exposure device 200. The light Lb is emitted to form an electrostatic latent image on the photosensitive drums 101Y, 101C, 101M, and 101K as the first image carriers provided in the respective photosensitive units. Here, the emission of the writing light is not limited to the laser, but may be an LED, for example.

  Each image forming unit 300 includes a charging device for charging the photosensitive drum around each photosensitive drum, and a developing device for developing the electrostatic latent image formed on the surface of the photosensitive drum by the writing light Lb with toner. A cleaning device is provided for cleaning the drum surface after the toner image is transferred to the intermediate transfer belt 105. Further, primary transfer devices 106Y, 106C, 106M, and 106K as charging devices are respectively provided at positions facing the respective photosensitive drums via the intermediate transfer belt 105. Each developing device is provided with a toner concentration sensor 104 for detecting the toner concentration of the developer in the device 102. When the toner density becomes low in each developing device, the toner density sensor 104 detects this, and the toner is replenished based on the detection result.

  In the image forming unit 300 having such a configuration, the surface of the photosensitive drum is uniformly charged by the charging device 1 as each photosensitive drum rotates, and the exposure device uses a laser based on image information from the print controller 410. The writing light Lb is irradiated to form an electrostatic latent image on the photosensitive drum. Thereafter, the electrostatic latent image is visualized by each developing device to form a toner image. This toner image is primarily transferred onto the intermediate transfer belt 105 by each primary transfer device. The transfer residual toner remaining on the surface of the photoconductive drum after the primary transfer is removed by the photoconductive cleaning device and used for the next image formation. Such an image forming unit functions as a toner image forming unit that forms a toner image on the intermediate transfer belt 105.

  1 and 3, a secondary transfer roller 108 is provided as a second transfer device at a position facing the support roller 112 with the intermediate transfer belt 105 interposed therebetween. The secondary transfer roller 108 transfers the toner image formed on the intermediate transfer belt 105 onto the transfer paper 115 with electrostatic force. When the toner image on the transfer belt 105 is secondarily transferred onto the transfer paper 115, the secondary transfer roller 108 is pressed against the portion of the intermediate transfer belt 105 wound around the support roller 112 to perform secondary transfer.

  The axial width of the intermediate transfer belt 105 is larger than the longitudinal width (axial width) of the secondary transfer roller 108, and the maximum width of the transfer paper 115 (during lateral feed) is the longitudinal width (axial width) of the secondary transfer roller 108. ) A test pattern forming region is set in a region having a size difference between the axial width of the intermediate transfer belt 105 and the longitudinal width (axial width) of the secondary transfer roller 108. A test pattern is formed in the test pattern formation region. In the example shown in FIG. 3, the axial range 203 corresponding to the longitudinal width of the secondary transfer roller 108 is located at the center of the axial width of the intermediate transfer belt 105, and the test pattern formation region is the intermediate transfer belt 105. It is formed in a strip shape at both ends of the axial width.

  In FIG. 1, a fixing device 111 for fixing the toner image transferred onto the transfer paper 115 is provided on the downstream side of the secondary transfer roller 108 in the conveyance direction of the transfer paper 115. The fixing device 111 has a configuration in which a pressure roller 118 is pressed against a heating roller 117. 1 and 3, photosensors 109F (front side) and 109R (front side) that serve as photosensors for estimating the density and relative position of the test pattern are provided at positions facing the support roller 112 with the intermediate transfer belt 105 therebetween. The back side (hereinafter referred to as P / TM sensor 109) is provided at two locations on the front side and the back side of the support roller 112 in the axial direction. A belt cleaning device 110 is provided at a position facing the support roller 113 with the intermediate transfer belt 105 interposed therebetween. The P / TM sensor 109 is an optical sensor for detecting the toner adhesion amount when the toner image is formed on the intermediate transfer belt 105 by the toner image forming unit. In this embodiment, the P / TM sensor 109 The reflected light amount detection sensor 20 described above is used.

  As shown in FIG. 2, the image forming apparatus 100 includes a main body control unit 406 having a computer configuration. The main body control unit 406 controls driving of each unit and based on the detection result of the P / TM sensor 109. It also functions as image density control means for performing image density control. The main body control unit 406 includes a ROM 405 that stores in advance fixed data such as a computer program and a work area that stores various data in a rewritable manner via the bus line 409 to the CPU 402 that executes various calculations and drive control of each unit. A functioning RAM 403 is connected. The ROM 405 stores the test pattern formation position and density information necessary for generating the test pattern, the bias conditions for forming the test pattern gradation, and the TM / P sensor 109 for estimating the test pattern adhesion amount. An output adhesion amount conversion LUT (Look up table) is stored.

  A print controller 410 is connected to the main body control unit 406, and the print controller 410 transmits image information from a PC (personal computer), a FAX (facsimile), a scanner, or the like as unified image data to the main body control unit 406. . Also connected are an A / D conversion circuit 401 that converts various sensor information into digital data, a drive circuit that drives motors and clutches of each component, a high voltage generator 416 that generates a voltage necessary for image formation, and the like.

  When printing with information from a PC using the image forming apparatus 100 having such a configuration, first, image information is transmitted using a printer driver on the PC. The print controller 410 receives print information from the printer driver and sends an exposure signal to the exposure apparatus 200. Upon receiving the print command, the main body control unit 406 drives a drive motor (not shown) so that the support roller 112 is rotated and the intermediate transfer belt 105 is rotated. At the same time, the photosensitive drums 101Y, 101C, 101M, and 101K of each image forming unit 300 shown in FIG.

  Thereafter, based on information from the print controller 410, the exposure apparatus 200 irradiates the writing light Lb onto the photosensitive drums 101Y, 101C, 101M, and 101K of the image forming units. As a result, electrostatic latent images are formed on the respective photosensitive drums 101Y, 101C, 101M, and 101K, and are visualized by the developing devices 102Y, 102C, 102M, and 102K. Then, yellow, cyan, magenta, and black toner images are formed on the photosensitive drums 101Y, 101C, 101M, and 101K, respectively.

  Each color toner image formed in this way is primarily transferred by the primary transfer devices 106Y, 106C, 106M, and 106K so as to sequentially overlap the intermediate transfer belt 105. As a result, a composite toner image in which the toner images of the respective colors overlap is formed on the intermediate transfer belt 105. The transfer residual toner remaining on the intermediate transfer belt 105 after the secondary transfer is removed by the belt cleaning device 110.

  In response to the image information, a paper feed roller of a paper feed device (not shown) corresponding to the transfer paper 115 selected by the user rotates, and the transfer paper 115 is sent out from one paper feed cassette (not shown). The fed transfer paper 115 is separated into one sheet by a separation roller (not shown), enters a paper feed path (not shown), and is conveyed to a conveyance path in the printer main body by a conveyance roller (not shown). The transfer paper 105 conveyed in this way is stopped when it abuts against the registration roller 107. The registration roller 107 starts to rotate in accordance with the timing at which the composite toner image formed on the intermediate transfer belt 105 as described above is conveyed to the secondary transfer unit facing the secondary transfer roller 108.

  The transfer paper 115 sent out by the registration roller 107 is sent between the intermediate transfer belt 105 and the secondary transfer roller 108, and the secondary transfer roller 108 causes the composite toner image on the intermediate transfer belt 105 to be transferred onto the transfer paper 115. Secondary transfer is performed. Thereafter, the transfer paper 115 is conveyed to the fixing device 111 while being attracted to the secondary transfer roller 108, and heat and pressure are applied by the fixing device 111 to perform a toner image fixing process. The transfer paper 115 that has passed through the fixing device 111 is discharged and stacked on a discharge tray (not shown) by a discharge roller (not shown).

  Next, image density control performed by the CPU 402 of the main body control unit 406 based on a computer program will be described. The image density control determines whether it is necessary when the power switch of the main body is turned on or when printing is started, and is executed if necessary. Immediately after the power is turned on, the image processing control is performed because the heating time of the fixing heater and the preparation time of the print controller are necessary, and it may be left until then and the usage environment may be changing. There are things to do.

  Further, during the printing operation, there is a possibility that toner supply and consumption, and changes in characteristics of the photoreceptors of the respective photoreceptor drums and the intermediate transfer belt 105 may occur, and image process control may be performed. Immediately after the power is turned on, the image process control is performed when the stop time of the photosensitive drum is 6 hours or more in advance, the internal temperature has changed by 10 ° C or more, or the internal humidity has changed by 50% or more. Execute.

  The stop time of the photosensitive drum is obtained as follows. When the photosensitive member stops, time information is acquired from the real-time clock held by the print controller 410 shown in FIG. Similarly, when the power is turned on, time information is acquired from the real-time clock, and the stop time of the photosensitive drum is obtained from the difference. During printing, a test pattern is created when the number of printed sheets reaches a predetermined interval. The interval in this case is determined by the amount of process variation obtained in advance through experiments or the like. In addition to the number of prints, the travel distance of the intermediate transfer belt 105 may be set as a threshold value.

  Next, when it is determined that image process control is necessary, a test pattern is formed. The test pattern indicates a test pattern (P pattern) for detecting the toner adhesion amount indicated by reference numeral 201 shown in FIG. 2 and a test pattern (TM pattern) for detecting the image position indicated by reference numeral 202. Further, the P pattern and the TM pattern are formed on the near side and the far side in the axial direction of the intermediate transfer belt 105, respectively, the near side P pattern is 201F, the far side P pattern is 201R, the near side TM pattern is 202F, and the far side TM pattern. Is indicated by 202R.

  After forming the test pattern, the main body control unit 406 detects the reflected light that is irradiated from the light emitting element of the TM / P sensor 109 and reflected from the surface of the intermediate transfer belt 105 by the light receiving element, and from the output change of the light receiving element. The toner density is detected, and toner replenishment is executed according to the detection result.

  By using the “reflected light amount detection sensor 20” for such a TM / P sensor 109, stability of image density control performed based on the detection result of the TM / P sensor 109 is improved, and a good image can be obtained. .

  The present invention can be applied to the measurement of the amount of powder or liquid adhering to the surface of an object reflected by specularly reflected light.

DESCRIPTION OF SYMBOLS 1 Light emitting element 2 Light receiving element for specular reflection 3 Light receiving element for diffused light 2A Center of light receiving element 4 Object to be detected 4A Reflecting surface 5 Light shielding case 6 Incident light 6A Optical axis of incident light 7 Reflected light 7A Optical axis of reflected light 8 First cylindrical shape portion 8A Light emitting element positioning portion 8C Light emitting aperture 9 Second cylindrical shape portion 9A Light receiving element positioning portion 9C Light receiving aperture L Constant interval 20 Reflected light amount detection sensor 105 Image carrier 109 Optical sensor 300 Toner image forming means 406 Image density control means 100 Image forming apparatus

JP-A-08-82599 JP 09-89769 A JP 2007-93586 A Japanese Patent No. 4057293 JP 11-282949 A

Claims (6)

At least one light emitting element and one light receiving element are provided in the light-shielding case and are held at a constant interval with respect to the detection target, and are inclined from the light emitting element and irradiated to the detection target In the reflected light amount detection sensor that receives the reflected light of the light by the light receiving element,
From the reference position where the optical axis of the reflected light and the center of the light receiving element overlap, the light receiving element or both of the light emitting element and the light receiving element are moved in parallel with respect to the reflecting surface of the detection object in a direction in which the elements move away from each other. A reflected light amount detection sensor characterized by being arranged.   The light shielding case includes a light emitting element positioning part, a first cylindrical part provided with a light emitting aperture for restricting the spread of irradiation light from the light emitting element to the detection target, and the light receiving element positioning part. 2. The reflected light amount detection sensor according to claim 1, further comprising: a second cylindrical portion having a light receiving aperture for defining an amount of reflected light to the light receiving element.   The first cylindrical shape portion and the second cylindrical shape portion are formed integrally with the light shielding case, and the light emitting aperture is configured to receive the light in the optical axis direction of light emitted from the light emitting element. The reflected light amount detection sensor according to claim 2, wherein the aperture is extended in an optical axis direction of the reflected light.   The optical axis of the incident light on the detection target is on the central axis of the light emitting aperture, and the optical axis of the reflected light from the detection target is positioned in a direction parallel to the central axis of the light receiving aperture. The reflected light amount detection sensor according to claim 2 or 3,   5. The diffused light receiving element for receiving the light irradiated from the light emitting element and diffusely reflected by the detection object is provided in the light shielding case. The reflected light amount detection sensor according to claim 1. An image carrier having a surface for regularly reflecting light, a toner image forming unit for forming a toner image on the image carrier, and the toner image when the toner is adhered to the image carrier by the toner image forming unit. In an image forming apparatus comprising: an optical sensor for detecting an amount of toner adhesion; and an image density control unit that performs image density control based on a detection result of the optical sensor.
An image forming apparatus comprising the reflected light amount detection sensor according to claim 1 as the optical sensor.

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