JP2009128704A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of detecting a position with high accuracy by making the amount of reflected light at a portion of a recording medium constant regardless of the type of the recording medium.
The amount of light of an optical sensor is adjusted for each recording medium.
[Selection] Figure 1

Description

  The present invention relates to an image forming apparatus such as a printer, a copier, or a facsimile machine that forms an image on a recording medium, and relates to processing for positional deviation of the recording medium.

  Conventionally, as a method for registering a toner image on a photosensitive member and a recording medium, a method of temporarily stopping the recording medium by a registration roller is generally used. In this method, the registration roller aligns the sub-scanning direction (conveyance direction) of the recording medium with respect to the toner image on the photosensitive member, and corrects skew (skew) of the recording medium.

  However, in the above-described conventional method, the image position accuracy in the recording medium conveyance direction is dominantly determined by the driving time of the registration rollers. In particular, when performing high-speed printing, there is a problem that the image position accuracy deteriorates in proportion to the printing speed due to the driving time of the registration rollers.

  In addition, when performing high-speed printing, there is a problem that the image position accuracy deteriorates due to a detection deviation of a recording medium conveyance timing by a sensor, a mechanical attachment error of parts, durability, and the like.

  On the other hand, in a configuration in which no registration roller is used, image alignment in the main scanning direction is performed using an optical sensor. Position detection in the main scanning direction using an optical sensor with a predetermined light amount as typified by Japanese Patent Laid-Open No. 09-219776 is to set a threshold between the reflected light amount in a part of the recording medium and the reflected light amount in a part without the recording medium. The position is detected.

However, as shown in FIG. 2, the amount of reflected light varies depending on the type of recording medium. Therefore, there is a problem that the position detection accuracy is lowered.
JP 09-219776

  The present invention has been made in view of the above-described conventional problems, and by adjusting the light amount of the optical sensor for each recording medium, regardless of the type of the recording medium, the reflected light amount of a portion having the recording medium is made constant, An object of the present invention is to provide an image forming apparatus capable of detecting a position with high accuracy.

According to invention of Claim 1,
In an image forming apparatus comprising: a position detection unit for optically detecting a position of a recording medium in a main scanning direction on a conveyance path;
The light quantity adjustment and the position detection are performed within the same recording medium conveyed by the position detection means.

According to invention of Claim 2,
In the invention of claim 1,
The position of the recording medium in the main scanning direction is detected after adjusting the amount of light in the same recording medium.

According to invention of Claim 3,
In the invention of claim 1,
The position of the recording medium in the main scanning direction is detected using the result of the light amount adjustment value.

According to invention of Claim 4,
Position detecting means for optically detecting the position of the recording medium in the main scanning direction on the transport path;
Skew correction means for correcting skew of the recording medium;
In an image forming apparatus having
The light amount adjustment and position detection are performed within the same recording medium conveyed by the position detection means, and the skew correction amount by the skew correction means is determined.

According to invention of Claim 5,
In the invention of claim 4,
The position of the recording medium in the main scanning direction is detected after adjusting the amount of light in the same recording medium.

According to the invention described in claim 6,
In the invention of claim 4,
In the latter half of the recording medium, the position detecting unit detects the position of the recording medium in the main scanning direction.

According to invention of Claim 7,
In the invention of claim 4,
The position detecting means is arranged upstream of the skew feeding correcting means.

According to invention of Claim 8,
Skew correction means for correcting skew of the recording medium;
Position detecting means for optically detecting the position of the recording medium in the main scanning direction on the transport path;
In an image forming apparatus having a writing position correcting means for correcting a writing position of an image,
In the recording medium that has been skew-corrected by the skew-correcting means, light amount adjustment and position detection are performed within the same recording medium conveyed by the position detecting means, and the main scanning direction detected by the position detecting means is detected. Based on the position, the image writing position correction amount in the writing position correcting means is determined.

According to the invention of claim 9,
In the invention of claim 8,
The position of the recording medium in the main scanning direction is detected after adjusting the amount of light in the same recording medium.

According to the invention of claim 10,
In the invention of claim 8,
In the latter half of the recording medium, the position detecting unit detects the position of the recording medium in the main scanning direction.

According to the invention of claim 11,
In the invention of claim 8,
The position detecting means is arranged on the downstream side of the skew feeding correcting means.

  As described above, according to the present invention, by adjusting the light amount of the optical sensor for each recording medium, the reflected light amount of a portion of the recording medium is made constant regardless of the type of the recording medium, and the position is accurately determined. An object of the present invention is to provide an image forming apparatus capable of detection.

  Next, details of the present invention will be described in accordance with the description of the embodiments.

  Hereinafter, an image forming apparatus according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a copying machine according to the present embodiment. The copying machine includes a scanner unit 12 for reading a document, an image processing unit 13 that electrically processes a digital signal output from the scanner unit 12, and an image based on the digital signal output from the image processing unit. Is formed on the transfer paper.

  In the scanner unit 13, an image of a document placed on the document table is read by an image reading device (not shown) via an irradiation lamp, a mirror, and a lens (not shown), and the data is read by the image processing unit. Sent to 13. The image processing unit 13 performs necessary processing on the data, converts it into an image signal, and sends it to the printer unit 14.

  In the printer unit 14, the surface of the photosensitive drum 1 as a latent image carrier that is rotationally driven in the direction of arrow B in the drawing is uniformly charged by the charger 2. A latent image corresponding to the image of the document is formed on the surface of the photosensitive drum 1 by the exposure device 3 including a semiconductor laser, a polygon mirror, a reflection mirror, and the like based on the image signal from the image processing unit 13. . The latent image on the photosensitive drum 1 is developed with a developer supplied from a developing sleeve 42 as a developer carrying member of the developing device 4 at a portion facing the developing device 4 to become a visible image. The visible image is recorded on a recording medium (not shown) placed on a belt-like transport device 7 and transported to a portion facing the photosensitive drum 1 at a timing from the paper feed stage 5 by a registration roller 6. 2) is transferred by the transfer device 8. The transfer paper on which the visible image has been transferred is transported by the transport device 7, and when passing through the fixing device 9, the visible image is fixed and discharged to the paper discharge tray 10. Here, the untransferred toner remaining on the photosensitive drum 1 after the visible image transfer is cleaned from the photosensitive drum 1 by the cleaning device 11 and collected by the cleaning device 11. Then, residual charges are removed from the surface of the photosensitive drum 1 after cleaning by a charge removal lamp (not shown).

  FIG. 3 is a conceptual diagram of position detecting means arranged on the transport path. In FIG. 3, a recording medium front end detection sensor 31, a position detection sensor 30, a conveyance roller 32, and a controller 34 arranged on the conveyance path are shown. The position detection sensor 30 optically detects the position of the recording medium 33 in the main scanning direction, and a CIS (contact image sensor) is used in the present embodiment. In the present embodiment, description will be made using CIS, but the position detection sensor may be a CCD or another optical sensor.

  In the image forming apparatus, various recording media are conveyed. The special point of the present invention is that the light amount adjustment of the optical sensor is performed in the same recording medium, and the recording medium position is detected using the adjustment result. Although not shown, the light amount adjustment timing and the main scanning position measurement timing are determined from the operation panel of the image forming apparatus based on the recording medium size selected by the user and a sensor for detecting the arrival of paper, which will be described later. It is. As for the recording medium size, a detection result by a recording medium size detection sensor (not shown) may be used. The sensor for determining the adjustment timing may be either a method using a recording medium front end detection sensor 31 described later or a main scanning position detection sensor according to the present invention. In this embodiment, a configuration and means for detecting the recording medium size input to the operation panel of the image forming apparatus (not shown) and the position in the main scanning direction using the recording medium leading end detection sensor 30 will be described. .

  This will be described with reference to the timing chart shown in FIG.

  When the leading edge of the recording medium is detected by the recording medium leading edge detection sensor 31, a counter in the controller that measures the light amount adjustment and the main scanning position detection timing is started. When the counter value is “6”, that is, when the recording medium reaches the CIS, the CIS LED emits light with the light amount “A”. After the LED light quantity is stabilized, that is, with the counter value “9”, the reflected light data Va for optimizing the light quantity is captured. Next, with the counter value “16”, the light quantity is changed to “B” different from the previous one. After the counter value “9”, that is, the light quantity of the LED is stabilized, the reflected light data Vb for optimizing the light quantity is fetched. From the reflected light data Va and Vb emitted with different light amounts, an optimal light amount “C” is calculated so that predetermined reflected light can be obtained in this recording medium. Light is emitted when the counter value is “20” and the light intensity is “C”. The reflected light data Vc for main scanning position detection is captured at the counter value “23” after the time when the light quantity of the LED is stabilized. After all the data is collected, that is, when the counter value is “27”, the LED is turned off.

  In this description, the amount of emitted light is changed while the LED is on. However, after capturing the reflected light data, you can turn off the LED. Here, it is necessary to sample when the light quantity of the LED is stable. This leads to an extended life of the LED.

  Further, the light amount adjustment and the main scanning position detection are continuously performed. However, in order to remove the influence of the behavior of the recording medium and detect it with higher accuracy, the main scanning position may be detected at a timing regulated by a conveyance roller or the like before and after the recording medium.

  Hereinafter, description will be made with reference to the flowchart of the present embodiment shown in FIG.

  The recording medium fed from the paper feeding means is supplied via a transport roller. The leading edge of the recording medium is detected by the recording medium leading edge detection sensor 31 (S100), and CIS light quantity adjustment is performed. First, the CIS is caused to emit light with the light emission power P1 (S101), and the reflected light signal V1 at that time is stored in the memory 35. Subsequently, the CIS is caused to emit light with a light emission power P2 different from P1 (S102), and the reflected light signal V2 at that time is stored in the memory 35. The controller 34 calculates a light emission power Pf that becomes a predetermined reflected light signal Vf from V1 and V2 in the memory 35 (S103). Subsequently, in order to detect the position of the recording medium in the main scanning direction, the CIS is caused to emit light with the calculated light emission power Pf (S104). The position E in the main scanning direction of the recording medium is detected from the reflected light signal V at this time.

  Here, a method for calculating the position of the recording medium in the main scanning direction from the reflected light signal will be described. Since the CIS light amount adjustment is performed for each recording medium, the reflected light signal Vp of a portion of the recording medium is constant at Vf regardless of the recording medium. However, actually detected Vp is used to increase accuracy. The median value Vm (= (Vp + Vo) / 2) of the reflected light signal Vp of the part with the recording medium and the reflected light signal Vo of the part without the recording medium is defined as a position E in the main scanning direction of the recording medium.

  In this way, by adjusting the CIS light amount for each recording medium, the reflected light amount of the part where the recording medium is present is made constant, and the reflected light signal from the part where the recording medium is present to the part where the recording medium is absent is constant regardless of the type of recording medium Thus, position detection can be performed with high accuracy.

  FIG. 6 is a conceptual diagram of position detection means arranged on the transport path. In FIG. 6, a recording medium front end detection sensor 61, a position detection sensor 60, a skew feeding correction roller 62, and a controller 64 arranged on the conveyance path are shown. FIG. 7 is a conceptual diagram of the conveyance path as viewed from the side. The position detection sensor 60 optically detects the position of the recording medium 63 in the main scanning direction, and a CIS (contact image sensor) is used in the present embodiment. In this embodiment, the CIS is used, but a CCD or another optical sensor may be used.

  Hereinafter, the description will focus on differences from the first embodiment.

  This will be described with reference to the timing chart shown in FIG.

  When the leading edge of the recording medium is detected by the recording medium leading edge detection sensor 61, a counter in the controller that measures the light amount adjustment and the main scanning position detection timing is started. When the counter value is “6”, that is, when the recording medium reaches the CIS, the CIS LED emits light with the light amount “A”. After the LED light quantity is stabilized, that is, with the counter value “9”, the reflected light data Va for optimizing the light quantity is captured. Next, with the counter value “16”, the light quantity is changed to “B” different from the previous one. After the counter value “9”, that is, the light quantity of the LED is stabilized, the reflected light data Vb for optimizing the light quantity is fetched. From the reflected light data Va and Vb emitted with different light amounts, an optimal light amount “C” is calculated so that predetermined reflected light can be obtained in this recording medium. Light is emitted when the counter value is “20” and the light intensity is “C”. Reflected light data Vc1 and Vc2 for calculating the skew amount are fetched with counter values “23” and “30” after the time when the light quantity of the LED is stabilized. After all the data is collected, that is, when the counter value is “34”, the LED is turned off.

  Here, the capturing timing of the reflected light data Vc1 and Vc2 for calculating the skew amount may be changed depending on the size of the recording medium.

  Hereinafter, description will be made with reference to the flowchart of this embodiment shown in FIG.

  The recording medium fed from the paper feeding means is supplied via a transport roller. The leading edge of the recording medium is detected by the recording medium leading edge detection sensor 61 (S200), and CIS light quantity adjustment is performed. First, the CIS is caused to emit light with the light emission power P1 (S201), and the reflected light signal V1 at that time is stored in the memory. Subsequently, the CIS is caused to emit light with a light emission power P2 different from P1 (S202), and the reflected light signal V2 at that time is stored in the memory. The controller 64 calculates a light emission power Pf that becomes a predetermined reflected light signal Vf from V1 and V2 in the memory 65 (S203). Subsequently, in order to detect the position of the recording medium in the main scanning direction, the CIS is caused to emit light with the calculated light emission power Pf (S204). The position in the main scanning direction of the recording medium is detected at two points E1 (S205) and E2 (S206).

  Here, a method for calculating the position of the recording medium in the main scanning direction from the reflected light signal will be described. Since the CIS light amount adjustment is performed for each recording medium, the reflected light signal Vp of a portion of the recording medium is constant at Vf regardless of the recording medium. However, actually detected Vp is used to increase accuracy. The median value Vm (= (Vp + Vo) / 2) of the reflected light signal Vp of the part with the recording medium and the reflected light signal Vo of the part without the recording medium is defined as the end E in the main scanning direction of the recording medium.

  The skew correction amount is calculated from the distance difference d between the positions E1 and E2 in the main scanning direction of the recording medium and the recording medium conveyance speed (S207). Finally, based on the calculated skew correction amount, the skew correction roller 62 is controlled to remove skew (S208).

  In this way, by adjusting the CIS light amount for each recording medium, the reflected light amount of the part where the recording medium is present is made constant, and the reflected light signal from the part where the recording medium is present to the part where the recording medium is absent is constant regardless of the type of recording medium Thus, the amount of skew can be detected with high accuracy, and the skew can be removed.

  FIG. 10 is a conceptual diagram of position detecting means arranged on the transport path. In FIG. 10, a recording medium front end detection sensor 101, a position detection sensor 100, a conveyance roller 102, and a controller 104 arranged on the conveyance path are shown. FIG. 11 is a conceptual view of the conveyance path as viewed from the side. The position detection sensor 100 optically detects the position of the recording medium 103 in the main scanning direction, and a CIS (contact image sensor) is used in the present embodiment. In this embodiment, the CIS is used, but a CCD or another optical sensor may be used.

  Hereinafter, the description will focus on differences from the first embodiment.

  This will be described with reference to the timing chart shown in FIG.

  When the leading edge of the recording medium is detected by the recording medium leading edge detection sensor 100, a counter in the controller that measures the light amount adjustment and the main scanning position detection timing is started. When the counter value is “6”, that is, when the recording medium reaches the CIS, the CIS LED emits light with the light amount “A”. After the LED light quantity is stabilized, that is, with the counter value “9”, the reflected light data Va for optimizing the light quantity is captured. Next, with the counter value “16”, the light quantity is changed to “B” different from the previous one. After the counter value “9”, that is, the light quantity of the LED is stabilized, the reflected light data Vb for optimizing the light quantity is fetched. From the reflected light data Va and Vb emitted with different light amounts, an optimal light amount “C” is calculated so that predetermined reflected light can be obtained in this recording medium. Light is emitted when the counter value is “20” and the light intensity is “C”. The reflected light data Vc for main scanning position detection is captured at the counter value “23” after the time when the light quantity of the LED is stabilized. After all the data is collected, that is, when the counter value is “27”, the LED is turned off.

  Hereinafter, description will be made with reference to the flowchart of the present embodiment shown in FIG.

  The recording medium fed from the paper feeding means is supplied via a transport roller. The leading edge of the recording medium is detected by the recording medium leading edge detection sensor 100 (S300), and skew correction is performed (S301). Next, CIS light quantity adjustment is performed. First, the CIS is emitted with the light emission power P1 with respect to the recording medium from which the skew has been removed (S302), and the reflected light signal V1 at that time is stored in the memory. Subsequently, the CIS is caused to emit light with a light emission power P2 different from P1 (S303), and the reflected light signal V2 at that time is stored in the memory. The controller 104 calculates a light emission power Pf that becomes a predetermined reflected light signal Vf from V1 and V2 in the memory 105 (S304). Subsequently, in order to detect the position of the recording medium in the main scanning direction, the CIS is caused to emit light with the calculated light emission power Pf (S305). A position E in the main scanning direction of the recording medium is detected (S306).

Here, a method for calculating the position of the recording medium in the main scanning direction from the reflected light signal will be described. Since the CIS light amount adjustment is performed for each recording medium, the reflected light signal Vp of a portion of the recording medium is constant at Vf regardless of the recording medium. However, actually detected Vp is used to increase accuracy. The median value Vm (= (Vp + Vo) / 2) of the reflected light signal Vp of the part with the recording medium and the reflected light signal Vo of the part without the recording medium is defined as the end E in the main scanning direction of the recording medium.
From the detected end E in the main scanning direction of the recording medium, a deviation amount from the planned image writing position is calculated (S307). The laser control unit 113 performs correction control of the writing position of the image in the main scanning direction based on the shift amount in the main scanning direction (S306).

  In this way, by adjusting the CIS light amount for each recording medium, the reflected light amount of the part where the recording medium is present is made constant, and the reflected light signal from the part where the recording medium is present to the part where the recording medium is absent is constant regardless of the type of recording medium Thus, the position of the recording medium in the main scanning direction can be detected with high accuracy, and the image printing position accuracy can be improved.

1 is a schematic configuration diagram of a copier according to an embodiment. It is a conceptual diagram of the position detection means which concerns on a prior art, and its output value. It is a conceptual diagram of the position detection means which concerns on this Embodiment 1. 3 is a timing chart according to the first embodiment. 3 is a flowchart according to the first embodiment. FIG. 5 is a conceptual diagram of position detecting means according to the second embodiment. FIG. 5 is a conceptual diagram in a cross-sectional direction of a position detection unit according to the second embodiment. 6 is a timing chart according to the second embodiment. 3 is a flowchart according to the present embodiment. FIG. 5 is a conceptual diagram of position detecting means according to the third embodiment. FIG. 5 is a conceptual diagram in a cross-sectional direction of a position detection unit according to the third embodiment. 10 is a timing chart according to the third embodiment. 3 is a flowchart according to the present embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 72, 112 Photosensitive drum 2 Charger 4 Developing device 5 Paper feed stage 6 Registration roller 7 Conveyance device 8, 71, 111 Transfer device 9 Fixing device 10 Paper discharge tray 30, 60, 100 Position detection means 21, 33, 63, 103 Recording medium 31, 61, 101 Recording medium leading edge detection sensor 62, 102 Inclination feed correction means 34, 64, 104 Controller 35, 65, 105 Memory 70 Laser element

Claims (11)

In an image forming apparatus comprising: a position detection unit for optically detecting a position of a recording medium in a main scanning direction on a conveyance path;
An image forming apparatus, wherein light quantity adjustment and position detection are performed within the same recording medium conveyed by the position detection means. 2. The image forming apparatus according to claim 1, wherein the position of the recording medium in the main scanning direction is detected after adjusting the amount of light in the same recording medium. 2. The image forming apparatus according to claim 1, wherein a position of the recording medium in a main scanning direction is detected using a result of the light amount adjustment value. Position detecting means for optically detecting the position of the recording medium in the main scanning direction on the transport path;
Skew correction means for correcting skew of the recording medium;
In an image forming apparatus having
An image forming apparatus, wherein light amount adjustment and position detection are performed within the same recording medium conveyed by the position detection means, and a skew correction amount by the skew correction means is determined. 5. The image forming apparatus according to claim 4, wherein the position of the recording medium in the main scanning direction is detected after adjusting the amount of light in the same recording medium. 5. The image forming apparatus according to claim 4, wherein a position in the main scanning direction of the recording medium is detected using a result of the light amount adjustment value. 5. The image forming apparatus according to claim 4, wherein the position detection unit is disposed upstream of the skew feeding correction unit. Skew correction means for correcting skew of the recording medium;
Position detecting means for optically detecting the position of the recording medium in the main scanning direction on the transport path;
Writing position correction means for correcting the writing position of the image;
In an image forming apparatus having
In the recording medium that has been skew-corrected by the skew-correcting means, light amount adjustment and position detection are performed within the same recording medium that has been conveyed by the position detecting means, and the main scanning direction detected by the position detecting means is detected. An image forming apparatus that determines an image writing position correction amount by a writing position correction unit based on a position. 9. The image forming apparatus according to claim 8, wherein the position of the recording medium in the main scanning direction is detected after adjusting the amount of light in the same recording medium. 9. The image forming apparatus according to claim 8, wherein a position in the main scanning direction of the recording medium is detected using a result of the light amount adjustment value. 9. The image forming apparatus according to claim 8, wherein the position detection unit is disposed downstream of the skew feeding correction unit.

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