JP2007193038A - Image forming apparatus, and position control method for optical sensor in the apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that it is necessary to improve component precision and add a positioning member in order to prevent the deterioration of detecting precision and enhance the detecting precision. <P>SOLUTION: A color sensor 42 is displaced between an image detection position and a retracting position retracting from the detection position by a motor 68 and cams 66 and 67, the displacement range of the sensor that the output of the color sensor is a predetermined value or above is stored on the basis of the relationship between the position of the displaced color sensor 42 and the output of the color sensor 42. When the image is detected by the color sensor, the motor 68 and the cams 66 and 67 are controlled (S2 to S4) based on the stored displacement range. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer or a copying machine, and an optical sensor position control method in the apparatus.

  In recent years, color stability of printed images has been demanded in color printers and color copiers, and a color sensor for reading and correcting the chromaticity of an image on a recording medium that is a printed matter is mounted (Patent Literature). 1). Such a color sensor uses, for example, three or more kinds of LEDs having different emission spectra such as red (R), green (G), and blue (B) as light emitting elements, and a photodiode having sensitivity in the visible region as a light receiving element. Is used. Alternatively, an LED that emits white (W) light is used as the light emitting element, and three or more filters having different spectral transmittances such as red (R), green (G), and blue (B) are provided on the photodiode as the light receiving element. Is formed. Thereby, three or more different color signals such as RGB corresponding to the color of the detection target are obtained.

  As a configuration of this color sensor, when detecting the color of the image on the recording medium, the recording sheet projects so as to sandwich the recording sheet in order to reduce the flutter of the recording sheet as the recording medium. In order to avoid the influence on the image due to the protrusion of the sensor during normal printing, a configuration for retreating from the recording sheet conveyance path has been studied.

  FIG. 11 is a diagram for explaining a protruding and retracting mechanism of a color sensor that has been studied in recent years.

In the figure, reference numerals 61 and 62 denote rollers for holding the recording sheet and suppressing the fluttering of the sheet. The spring member 63 urges the conveyance roller 62 toward the roller 61 and presses the recording sheet conveyed in the thick arrow direction against the roller 61 side. The sensor facing member 64 functions to hold the recording sheet in order to suppress the fluttering of the recording sheet. The sensor facing member 64 is disposed at a position facing the color sensor 42 and presses and releases the recording sheet in conjunction with the operation of the cam 66. The sensor facing member 64 has a predetermined reflectance. Reference numeral 65 denotes a holding member for the color sensor 42. The color sensor 42 protrudes and retracts in the recording sheet direction in conjunction with the operation of the cam 67. The cams 66 and 67 operate in conjunction with the rotation of the motor 68, and the position of the flag 69 is detected by the sensor 70 and controlled to stop at a predetermined position.
JP 2003-107835 A

  However, the above configuration has the following problems. Since the position of the color sensor 42 changes due to the protrusion and retraction of the color sensor 42, the distance between the sensor and the recording sheet varies when the color sensor 42 is in the protruding state. Thereby, the detection accuracy by the color sensor 42 may be deteriorated. Further, in order to avoid the deterioration of the detection accuracy and increase the detection accuracy, it is necessary to improve the component accuracy or add a positioning member. This may result in an expensive configuration. Furthermore, it is necessary to add another sensor to control the protruding and retracting states of the color sensor 42, resulting in a more expensive configuration.

  An object of the present invention is to solve the above-mentioned problems of the prior art.

  In addition, the present invention provides an image forming apparatus capable of reducing deterioration in detection accuracy by a sensor accompanying the protrusion and retraction operation of the optical sensor of the image forming apparatus and improving detection accuracy with an inexpensive configuration, and a position control method of the optical sensor in the apparatus. The purpose is to provide.

In order to achieve the above object, an image forming apparatus according to an aspect of the present invention has the following configuration. That is,
An image forming apparatus including an optical sensor that detects an image formed on a recording medium,
A displacement means for displacing the optical sensor between a detection position of the image and a retraction position retracted from the detection position;
Storage means for storing information related to the displacement range of the optical sensor based on the relationship between the position of the optical sensor displaced by the displacement means and the output of the optical sensor based on the output of the optical sensor being a predetermined value or more. When,
Control means for controlling the displacement means based on information relating to the displacement range stored in the storage means at the time of detection of an image by the optical sensor;
It is characterized by having.

In order to achieve the above object, a position control method for an optical sensor in an image forming apparatus according to an aspect of the present invention includes the following steps. That is,
A method for controlling the position of an optical sensor in an image forming apparatus including an optical sensor for detecting an image formed on a recording medium,
A displacement step of displacing the optical sensor between a detection position of the image and a retraction position retracted from the detection position;
A control step of controlling the displacement step based on information relating to a displacement range of the optical sensor when an image is detected by the optical sensor;
It is characterized by having.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to perform control which positions an optical sensor in the optimal position with respect to a detection target object, and can improve a detection precision with an inexpensive structure.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments do not limit the present invention according to the claims, and all combinations of features described in the present embodiments are essential to the solution means of the present invention. Not exclusively.

[Embodiment 1]
FIG. 1 is a block diagram showing the overall configuration of an electrophotographic color image forming apparatus according to an embodiment of the present invention. This color image forming apparatus includes an image processing unit 100 and an image forming unit 110.

  First, processing in the image processing unit 100 will be described.

  The color matching table 111 converts an RGB signal representing the color of an image sent from a host such as a personal computer into a device RGB signal (hereinafter referred to as DevRGB) that matches the color gamut of the color image forming apparatus. The color separation table 112 converts the converted DevRGB signal into a CMYK signal that is a color material color such as toner in the image forming unit 110. The calibration table 113 is a table for correcting density-gradation characteristics specific to the image forming unit 110, and converts the CMYK signal into a C′M′Y′K ′ signal with density-gradation characteristics corrected. . Further, a PWM (Pulse Width Modulation) table 114 converts the C′M′Y′K ′ signal into exposure times Tc, Tm, Ty, Tk by the exposure unit 123 in the image forming unit 110.

  Next, the image forming unit 110 will be described. The main parts involved in image formation here include a charging unit 122, an exposure unit 123, a developing unit 124, a transfer unit 125, and a fixing unit 126. These are controlled by the CPU 121. The memory 121a stores a program executed by the CPU 121.

  FIG. 2 is a diagram illustrating a configuration of the image forming unit 110 of the color image forming apparatus according to the present embodiment. As shown in the figure, this color image forming apparatus is a tandem type color image forming apparatus that employs an intermediate transfer member 28 which is an example of an electrophotographic color image forming apparatus.

  In the image forming unit 110, electrostatic latent images are formed on the photosensitive drums 22 </ b> Y to 22 </ b> K corresponding to the respective colors by the exposure light that is turned on based on the exposure time converted by the image processing unit 100. The electrostatic latent image is developed with each corresponding color toner to form a single color toner image, and this single color toner image is superimposed on an intermediate transfer member (belt) 28 to form a multicolor toner image. The multicolor toner image thus formed is transferred to a recording medium (recording sheet) 11, and the multicolor toner image on the recording medium 11 is fixed by a fixing device 31.

  The charging unit 122 includes four injection charging units for charging the photosensitive drums 22Y, 22M, 22C, and 22K for each of the yellow (Y), magenta (M), cyan (C), and black (K) stations. The devices 23Y, 23M, 23C, and 23K are provided. Here, each injection charger is provided with sleeves 23YS, 23MS, 23CS, and 23KS. The photosensitive drums 22Y, 22M, 22C, and 22K are configured by applying an organic optical transmission layer to the outer periphery of an aluminum cylinder, and rotate by receiving a driving force of a driving motor (not shown). This drive motor rotates the photoconductors 22Y, 22M, 22C, and 22K in the counterclockwise direction according to the image forming operation.

  The exposure unit 123 irradiates the photosensitive drums 22Y, 22M, 22C, and 22K with exposure light from the scanner units 24Y, 24M, 24C, and 24K, and selectively exposes the surfaces of the photosensitive members 22Y, 22M, 22C, and 22K. An electrostatic latent image is formed.

  The developing unit 124 develops yellow (Y), magenta (M), cyan (C), and black (K) for each station in order to visualize the electrostatic latent image on the sightseeing drum corresponding to each color. Four developing units 26Y, 26M, 26C, and 26K are provided. Each developing device is provided with sleeves 26YS, 26MS, 26CS, and 26KS. Each developing device 26 is detachable.

  The transfer unit 125 rotates the intermediate transfer member 28 in the clockwise direction in order to transfer the single color toner image from the photosensitive drum 22 to the intermediate transfer member 28. A monochrome toner image is transferred in accordance with the rotation of the photosensitive drums 22Y, 22M, 22C, and 22K and the primary transfer rollers 27Y, 27M, 27C, and 27K that are positioned opposite to the photosensitive drums. At this time, an appropriate bias voltage is applied to each primary transfer roller 27 and a difference is made between the rotation speed of each photosensitive drum 22 and the rotation speed of the intermediate transfer body 28, thereby efficiently transferring a single color toner image to the intermediate transfer body 28. It is transcribed above. This is called primary transfer.

  Further, the transfer unit 125 superimposes a single color toner image on the intermediate transfer member 28 for each station, and conveys the superposed multicolor toner image to the secondary transfer roller 29 as the intermediate transfer member 28 rotates. Further, the recording medium 11 is nipped and conveyed from the paper feed tray 21 to the position of the secondary transfer roller 29, and the multicolor toner image on the intermediate transfer member 28 is transferred to the recording medium 11. At this time, an appropriate bias voltage is applied to the secondary transfer roller 29 to electrostatically transfer the toner image. This is called secondary transfer. The secondary transfer roller 29 contacts the recording medium 11 at a position 29a while the multicolor toner image is being transferred onto the recording medium 11, and is separated to a position 29b after the transfer process.

  The fixing unit 126 (fixing device 31) fixes the multi-color toner image transferred to the recording medium 11 to the recording medium 11 by melting and fixing the fixing roller 32 that heats the recording medium 11 and the recording medium 11 to the fixing roller 32. A pressure roller 33 is provided for pressure contact. The fixing roller 32 and the pressure roller 33 are formed in a hollow shape, and heaters 34 and 35 are incorporated therein, respectively. The fixing device 31 conveys the recording medium 11 holding the multicolor toner image by the fixing roller 32 and the pressure roller 33 and applies heat and pressure to fix the toner on the recording medium 11.

  After the toner is fixed in this manner, the recording medium 11 is then discharged to a discharge tray (not shown) by rotation of a discharge roller (not shown), and the image forming operation is completed.

  The cleaning unit 30 cleans the toner remaining on the intermediate transfer member 28. The waste toner after transferring the four-color multicolor toner image formed on the intermediate transfer member 28 to the recording medium 11 is: Stored in a cleaner container.

  The color sensor 42 is disposed toward the image forming surface of the recording medium 11 downstream of the fixing device 31 in the conveyance path of the recording medium. The color sensor 42 detects the color of the fixed image formed on the recording medium and outputs the detected result as an RGB value. By arranging the color sensor 42 in the color image forming apparatus in this way, the color of the fixed color image is automatically detected before the fixed image is discharged to the paper discharge unit. Can do.

  FIG. 3 is a diagram for explaining the configuration of the color sensor 42 and its surroundings according to the present embodiment.

  The color sensor 42 and its peripheral devices include a light emitting element 101, a light receiving element 102, an A / D converter 104, and a CPU 121. The light emitting element 101 is a light source of the color sensor 42 and makes light incident on the detection target object 103 (here, a recording medium). This light is reflected by the detection object, and the reflected light enters the light receiving element 102 that converts the light into an analog electric signal. Further, the analog electric signal is converted into a digital electric signal by the A / D converter 104. This digital electrical signal is captured by the CPU 121, and computations for color detection and correction are performed.

  FIG. 4 is a diagram for explaining color detection by the color sensor 42 according to the present embodiment.

  The color sensor 42 has a white LED as the light emitting element 101 and uses a charge storage sensor with an on-chip filter of three or more colors such as RGB as the light receiving element 102. Light from the white LED is incident on the recording medium 11 on which the patch after fixing is formed at an angle of 45 degrees, and the intensity of diffuse reflection in the 0 degree direction is detected by a charge storage type sensor with an RGB on-chip filter. In the light receiving portion of the charge storage type sensor with RGB on-chip filter, as shown by 54b, RGB are independent pixels. The light receiving element 102 may be a photodiode. Further, a plurality of sets of three pixels of RGB may be arranged. Further, a configuration in which the incident angle is 0 degree and the reflection angle is 45 degrees may be employed. Furthermore, you may comprise by LED which light-emits three or more colors, such as RGB, and a sensor without a filter.

  Hereinafter, a position control method of the color sensor mechanism that realizes improvement in detection accuracy of the color sensor mounted on the color image forming apparatus according to the present embodiment will be described.

  FIG. 5 is a diagram for explaining a mechanism for projecting and retracting the color sensor 42 according to the present embodiment. In this configuration, the flag 69 and the sensor 70 are removed from the configuration of the conventional example described above.

  In the figure, reference numerals 61 and 62 denote rollers for holding a recording medium (not shown) and suppressing fluttering of the recording medium. The spring member 63 urges the conveyance roller 62 toward the roller 61 and presses the recording medium conveyed in the thick arrow direction against the roller 61 side. The sensor facing member 64 functions to hold down the recording medium in order to suppress the fluttering of the recording medium. The sensor facing member 64 is disposed at a position facing the color sensor 42 and presses and releases the recording medium in conjunction with the operation of the cam 66. The sensor facing member 64 has a predetermined reflectance. Reference numeral 65 denotes a holding member for the color sensor 42. The color sensor 42 protrudes and retracts in the recording sheet direction in conjunction with the operation of the cam 67. The cams 66 and 67 operate in conjunction with the rotation of the motor 68.

  FIG. 6 is a diagram illustrating the relationship between the distance between the sensor facing member 64 and the color sensor 42 and the output of the color sensor 42.

  In the figure, the horizontal axis indicates the distance between the sensor facing member 64 and the color sensor 42. The vertical axis represents the sensor output (normalized value). Now, when the distance between the recording medium 11 and the color sensor 42 is 3 mm, the output of the sensor 42 is maximum. In the figure, the arrows indicate the controllable range of the distance between the sensor facing member 64 and the color sensor 42 as the cams 66 and 67 operate. In the present embodiment, the distance varies from 2 mm to 6 mm with one rotation of the cams 66 and 67.

  FIG. 7 is a diagram showing the relationship between the rotation angle of the cams 66 and 67 and the output of the color sensor 42 according to the present embodiment.

  FIG. 7 shows the result of rotating the cams 66 and 67 by driving the motor 68 while monitoring the output of the color sensor 42. Here, it can be seen that the output of the color sensor 42 becomes maximum when the angles of the cams 66 and 67 are 150 ° and 265 °. Based on the detection result, the color image forming apparatus stops the rotation of the motor 68 when the cam angle is within a predetermined range (for example, ± 20 °) from 150 ° or 265 °.

  Information relating to the rotation amount of the motor 68 corresponding to the angles of the cams 66 and 67 corresponding to the optimum sensor position obtained in this way is stored in, for example, the memory 121a described above.

  FIG. 8 is a flowchart for explaining the positioning process of the color sensor 42 in the color image forming apparatus according to the first embodiment, and a program for executing this process is stored in the memory 121a.

  This process is executed to position the color sensor 42 at the reading position in order to read the image on the recording medium 11 by the color sensor 42. First, in step S1, rotation of the motor 68 is started, and in step S2, the angles of the cams 66 and 67 are within a predetermined range of 150 ° or 265 ° as described with reference to FIG. 20 °). This can be estimated based on the rotation amount of the motor 68. If it is that angle, the process proceeds to step S4. If not, the process proceeds to step S3, and the rotation of the motor 68 is continued. In step S2, when the angles of the cams 66 and 67 become a predetermined angle, that is, when the motor 68 rotates by an amount corresponding to the rotation amount stored in the memory 121a, the process proceeds to step S4 to stop the rotation of the motor 68. . Thereby, the color sensor 42 can be positioned at a position with the highest detection accuracy.

  When the rotation of the motor 68 is controlled, since the angles of the cams 66 and 67 with respect to the rotation amount of the motor 68 are known in advance, the cam position can be controlled by the rotation amount of the motor 68. The rotation control of the motor 68 in this case is an open loop control. Further, a table for storing the angles of the cams 66 and 67 with respect to the rotation amount of the motor 68 may be provided.

  As described above, according to the first embodiment, the distance between the optical sensor and the passage of the recording medium can be controlled within a predetermined range including the position where the output of the sensor is maximum. Thereby, it is possible to eliminate the influence of variations in the focal length of the optical sensor and various variations in the mechanical dimensions without using special parts such as a photosensor for position detection. Thus, the detection accuracy by the optical sensor can be improved with a simple configuration.

[Embodiment 2]
A color image forming apparatus according to Embodiment 2 of the present invention will be described. The configuration of the image forming apparatus according to the second embodiment and the mechanism for projecting and retracting the color sensor 42 are the same as those in the first embodiment, and thus the description thereof is omitted.

  In the second embodiment, the determination condition regarding the stop range of the cams 66 and 67 during the position control of the color sensor 42 is different from that of the first embodiment.

  FIG. 9 is a diagram showing the relationship between the rotation angle of the cams 66 and 67 and the output of the color sensor 42 according to the second embodiment.

  According to the figure, when the angles of the cams 66 and 67 are about 130 ° to 180 ° and about 240 ° to 280 °, the output of the color sensor 42 is a predetermined value (for example, 0.95) or more.

  Therefore, in the second embodiment, the rotation of the motor 68 is stopped when the angles of the cams 66 and 67 are in the range of about 130 ° to 180 ° and about 240 ° to 280 °.

  The processing of the CPU 121 in this case proceeds to step S4 when the angles of the cams 66 and 67 are in the range of about 130 ° to 180 ° and about 240 ° to 280 ° in step S2 of FIG. Stop. Also in this case, the relationship between the rotation amount control of the motor 68 and the cam position can be estimated in the same manner as in the first embodiment. That is, the rotation amount information of the motor is stored in the memory 121a so that the angles of the cams 66 and 67 are within the range of about 130 ° to 180 ° and about 240 ° to 280 °, and the amount according to the rotation amount. The rotation of the motor 68 is controlled.

  As described above, according to the second embodiment, the distance between the optical sensor and the passage portion of the recording medium can be controlled within a range in which the output value of the sensor becomes a predetermined value or more. As a result, it is possible to eliminate the influence of variations in the focal length of the optical sensor and various variations in mechanical dimensions without requiring special parts such as a photosensor for position detection. Thereby, the detection accuracy by the optical sensor can be improved with a simple configuration.

[Embodiment 3]
Next, a color image forming apparatus according to Embodiment 3 of the present invention will be described. Since the configuration of the color image forming apparatus according to the third embodiment is the same as that of the first and second embodiments, the description thereof is omitted.

  In the third embodiment, the position of the recording medium 11 at the time of position control of the color sensor 42 is different from those of the first and second embodiments.

  FIG. 10 is a diagram for explaining a mechanism for projecting and retracting the color sensor according to the third embodiment. The basic configuration is the same as in the first and second embodiments.

  In the third embodiment, the recording medium 11 is conveyed to a position facing the color sensor 42 before the color sensor 42 protrudes or retracts. Then, the position of the color sensor as described in the first and second embodiments is controlled while the recording medium 11 is disposed at the position facing the color sensor 42. In that case, since the position where the output of the color sensor 42 is maximum is shifted by the thickness of the recording medium 11, position control including the shift is performed.

  For example, the thickness information of the recording medium is stored in advance in the memory 121a according to the type of paper designated by the user, and the rotation amount correction information of the motor 68 is also stored in the memory 121a together with the thickness information.

  The memory 121a stores the rotation amount information of the motor 68 as described in the first and second embodiments, and the rotation amount obtained by correcting the rotation amount using the rotation amount correction information in accordance with the paper thickness information. The motor 68 may be rotated.

  Regarding the thickness information, a sensor (not shown) for detecting the thickness of the recording medium may be provided at a position before feeding the recording medium to form an image.

  In this case, the processing of the CPU 121 sets the angle including the thickness of the recording medium 11 with respect to the angle of the cams 66 and 67 set in step S2 in FIG. The rotation of 68 may be stopped.

  As described above, according to the third embodiment, the influence of the thickness of the recording medium can be removed by adjusting the position of the optical sensor in a state where the recording medium is disposed at the position facing the optical sensor. Thereby, the detection accuracy by the optical sensor can be further improved with a simple configuration.

  In the first to third embodiments, the color sensor 42 has been described as an example, but the present invention is not limited to this. An optical sensor whose output varies depending on the distance between the object to be detected and the optical sensor (a density sensor that detects the density of the image, a registration sensor that detects the position of the image, and the surface properties of the transfer material) This is also effective for media sensors that detect transfer materials.

  In the first to third embodiments described above, the case where the position control of the color sensor 42 and the sensor facing member 64 is performed by the cam mechanism has been described as an example. Any mechanism may be used as long as the mechanism is capable of fine-tuning.

1 is a block diagram showing an overall configuration of an electrophotographic color image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration of an image forming unit of a color image forming apparatus according to the present embodiment. It is a figure explaining the structure of the color sensor which concerns on this Embodiment, and its periphery. It is a figure explaining the detection of the color by the color sensor which concerns on this Embodiment. It is a figure explaining the mechanism which performs the protrusion and evacuation of the color sensor which concerns on this Embodiment. It is a figure which shows the relationship between the distance between a sensor opposing member and a color sensor, and the output of a color sensor. It is a figure which shows the relationship between the rotation angle of the cam which concerns on this Embodiment, and the output of a color sensor. 4 is a flowchart for explaining color sensor positioning processing in the color image forming apparatus according to Embodiment 1; It is a figure which shows the relationship between the rotation angle of the cam which concerns on this Embodiment 2, and the output of a color sensor. It is a figure explaining the mechanism which performs the protrusion and evacuation of the color sensor which concerns on this Embodiment 3. FIG. It is a figure explaining the protrusion and evacuation mechanism of the color sensor in a prior art example.

Claims (8)

An image forming apparatus including an optical sensor that detects an image formed on a recording medium,
A displacement means for displacing the optical sensor between a detection position of the image and a retraction position retracted from the detection position;
Storage means for storing information related to the displacement range of the optical sensor based on the relationship between the position of the optical sensor displaced by the displacement means and the output of the optical sensor, the output of the optical sensor being equal to or greater than a predetermined value. When,
Control means for controlling the displacement means based on information relating to the displacement range stored in the storage means when detecting an image by the optical sensor;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the optical sensor includes a light emitting unit that emits light and a light receiving unit that receives and detects reflected light from a recording medium.   The said displacement means has a cam and a cam which changes an angle according to the rotation amount of the said motor, The said control means controls the rotation amount of the said motor. Image forming apparatus.   4. The control device according to claim 1, wherein the control unit further controls the displacement unit by using information on a thickness of the recording medium when a recording medium is arranged at the detection position. 2. The image forming apparatus according to item 1. A method for controlling the position of an optical sensor in an image forming apparatus including an optical sensor for detecting an image formed on a recording medium,
A displacement step of displacing the optical sensor between a detection position of the image and a retraction position retracted from the detection position;
A control step of controlling the displacement step based on information relating to a displacement range of the optical sensor when an image is detected by the optical sensor;
A method for controlling the position of an optical sensor in an image forming apparatus.   6. The position control of the optical sensor in the image forming apparatus according to claim 5, wherein the optical sensor includes a light emitting unit that emits light and a light receiving unit that receives and detects reflected light from the recording medium. Method.   7. The displacement step includes displacing the optical sensor by a motor and a cam that changes an angle according to the rotation amount of the motor, and the control step controls the rotation amount of the motor. The position control method of the optical sensor in the image forming apparatus described in 1.   8. The control process according to claim 5, further comprising controlling the displacement process using information relating to a thickness of the recording medium when a recording medium is arranged at the detection position. A position control method for an optical sensor in the image forming apparatus according to claim 1.

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