JP4644045B2 - Electrophotographic printing device - Google Patents

Description

  The present invention relates to an electrophotographic printing apparatus, and more particularly to a paper position detection mechanism of the apparatus.

  FIG. 3 is an overall configuration diagram showing an example of an electrophotographic apparatus, and a laser beam printer is given as an example. FIG. 4 is an example showing a configuration diagram of a paper edge position detection mechanism using, for example, a line sensor as a position detection mechanism for detecting the edge of the paper. Hereinafter, the prior art will be described with reference to FIGS. 2, 3, and 4.

  In FIG. 3, reference numeral 408 denotes a sheet feeding device which can be pulled out in the direction perpendicular to the paper surface of the drawing.

  When the sheet feeding device 408 is pushed into a predetermined mounting position and loaded into the printer 401 main body, a sensor (not shown) detects loading of each sheet feeding device 408 and engages with a lifting table driving gear (not shown). Then, the lifting table is raised until the uppermost surface of the paper stacked on the lifting table (upper surface of the lifting table when there is no sheet on the lifting table) comes into contact with the paper feed roller 409.

  Reference numeral 403 denotes a photosensitive drum, which starts rotating based on a signal from a controller (not shown). When the photosensitive drum 403 starts to rotate, the surface of the photosensitive drum 403 is uniformly charged by a corona charger (not shown).

  Next, the charged photosensitive drum 403 is irradiated with laser light based on image data transmitted from a host system (not shown) from the scanning optical unit 402 to form an electrostatic latent image corresponding to the image signal. When the electrostatic latent image reaches a position of a developing device (not shown), the electrostatic latent image is developed with toner and visualized on the photosensitive drum 403 as a toner image.

  Thus, the toner image formed by a known electrophotographic process is transferred to the paper fed from the sheet supply device 408 by the transfer peeling device 405. The toner transferred onto the paper is fixed on the paper by the fixing device 404.

  The gate member 410 switches the sheet conveyance path, and selectively switches whether the sheet conveyed from the fixing device 404 is conveyed as it is to the discharge unit in the left direction in the drawing or in the downstream direction from the gate member 410. . The sheet conveyed to the left in the drawing by the gate member 410 is discharged to a post-processing machine (not shown). The sheet conveyed in the downstream direction from the gate member 410 is once drawn downward from a roller near the reverse gate 411 and then conveyed to the double-sided conveyance path 412.

  The gate member 413 switches whether the sheet conveyed from the conveyance path 407 or the sheet conveyed from the duplex conveyance path 412 is sent to the print conveyance path 406. The sheet conveyed from the duplex conveyance path 412 is conveyed again to the print conveyance path 406 by the gate member 413. Since the surface of the paper that has not been printed by the reversal gate 411 is the upper surface, printing is also performed on the unprinted surface by the above-described process. The sheet printed on both sides in this way is conveyed to the left in the figure by the gate member 410 and is discharged to a post-processing machine not shown.

  Ideally, when the toner image is transferred to the paper by the transfer / separation device 405, the paper conveyed by the sheet feeding device 408 or the double-sided conveyance path 412 always has a constant conveyance position in the width direction. In addition, a deviation occurs in the conveyance position in the width direction of each page due to shakiness of the paper in the sheet feeding device 408, skew at the time of conveyance, paper contraction when passing through the fixing device 404, and the printing in the width direction is started as a result. Printed with the position shifted. In order to prevent such a deviation of the print start position, a line sensor 501 shown in FIG. 4 is conventionally arranged on the conveyance path to detect the paper edge position in the paper width direction and correct the print start position. (For example, refer to Patent Document 1).

  Paper edge position detection and print start position correction using the line sensor 501 will be described below. The line sensor 501 is a reflective line sensor including a plurality of LEDs (not shown), a plurality of light receiving elements, and an internal control circuit unit. The line sensor 501 conveys a sheet fed from the sheet feeding device 408 and a duplex conveyance path 412. The paper guide 504 in FIG. 4 through which the paper to be passed passes is disposed at right angles to the paper transport direction. Further, the end faces of the various sized paper sheets are always arranged at positions that pass over the detection surface of the line sensor 501. Further, in order to increase the detection accuracy by the line sensor 501, the paper guide 503 and the paper guide 504 shown in FIG. 4 are arranged at a distance so as to keep the behavior of the paper within the regulation.

  When printing is started (S21), processing is executed according to the control flow of FIG. First, the printer control unit 505 determines whether or not Xms has passed after the paper arrives at the timing sensor 502 (S22). When Xms elapses after the paper reaches the timing sensor 502, the light source LED of the line sensor 501 is turned on with the specified light amount α obtained during the adjustment process of the line sensor 501, and the paper edge position data is acquired (S23). The reason why the arrival of the sheet at the timing sensor 502 is triggered by the acquisition of the sheet edge position data is to make the sheet edge position data acquisition timing constant for each sheet. The obtained data and the reference sheet edge position data recorded in the memory in the printer control unit 505 are compared, and a calculation process for adding the print start position correction data set at the time of initial adjustment to this difference is performed. A correction value for starting position correction is determined (S24).

  Subsequently, the printer control unit 505 outputs print start position correction data to a print start position correction circuit unit (not shown). The print start position correction circuit unit corrects the print start position in the paper width direction for the image data transmitted from the host system based on the print start position correction data (S25), and ends the print start position correction process (S25). S26).

  After the print start correction process is performed, the scanning optical unit 402 forms a latent image on the photosensitive drum 403 at the timing when the image data transmitted from the host system is corrected by the print start position correction circuit unit. The sheet edge position detection and the printing start position correction are performed for both the sheet conveyed from the sheet feeding device 408 and the sheet conveyed from the double-sided conveyance path 412.

  The acquisition sequence of the sheet edge position data by the line sensor 501 is as follows. First, the printer control unit 505 transmits a signal for causing the LED of the line sensor 501 to emit light, a clock, and a start signal to the line sensor 501. The LED of the line sensor 501 is turned on by the LED light emission signal, and the LED light reflected on the paper enters the light receiving element portion covered with the paper.

  Subsequently, the internal control circuit unit of the line sensor 501 outputs a voltage output photoelectrically converted by the light receiving element in synchronization with the clock for each light receiving element. The output voltage of each light receiving element is a high output voltage in a portion where LED light is incident, that is, a portion where paper is present, and a low output voltage analog voltage signal is generated in a portion where there is little reflected light, ie, a portion where paper is not present. This analog output outputted in synchronization with the clock is binarized by a threshold value set by an AD converter circuit (not shown) provided between the printer control unit 505 and the line sensor 501, and a portion with paper is “H” A portion without a “signal” and a sheet is transmitted to the printer control unit 505 as an “L” signal.

  Since the line sensor 501 and the paper are in the above-described positional relationship, an “H” signal is transmitted from a portion where the paper covers the light receiving element surface of the line sensor 501. The printer control unit 505 is provided with a paper end recognition circuit that counts the number of “H” signals output from the line sensor 501 and recognizes a portion where the “H” signal can be continuously counted 19 times as a paper end. . In the case of a system that counts all the “H” signals from the line sensor 501, sufficient output cannot be obtained when the preprint printing unit is detected by the line sensor 501 during printing of preprinted paper. This is to prevent the sheet edge portion from being erroneously recognized as a result of being output as an “L” signal without exceeding the threshold value.

  After the output corresponding to the number of pixels is output from the line sensor 501, the printer control unit 505 turns off the LED emission signal to the line sensor 501 and ends a series of paper edge position data acquisition sequence.

JP-A-8-230231

  In a printing apparatus that uses a line sensor to detect the edge position of the paper, in order to prevent erroneous detection due to paper dust adhering to the paper guide facing the line sensor, the LED light quantity of the line sensor is It is set higher than the amount of light used during printing, and a stain check is performed to read the line sensor output. If the sensor output at the time of the smudge check is equal to or higher than a specified value, an error message prompting cleaning is displayed on the operator panel, and control is performed so as not to start the printing operation. The output of the line sensor during the dirt check depends on the reflected light from the paper guide portion facing the sensor, and the reflected light to the sensor increases as paper dust adheres to the paper guide. The reflected light increases in accordance with the amount of paper dust adhering to the paper guide, that is, the printing amount. If the amount of paper dust is the same, the reflected light increases in accordance with the light quantity of the LED of the line sensor.

  Although it is possible to prevent erroneous detection of the end position of the paper due to paper dust adhering to the paper guide by the stain check, since the amount of paper dust attached increases according to the printing amount, printing is performed at a certain level. If this is done, a dirt check error will always occur. Occurrence of a smudge check error necessitates cleaning together with the stop of the printing operation, which hinders the printing operation. Therefore, it is desirable to extend the occurrence period of the dirt check error as much as possible. Moreover, using the light source LED of the line sensor with a high light amount may accelerate deterioration over time. For this reason, the light amount of the light source LED of the line sensor is adjusted to a necessary and sufficient value that can detect the edge position of the blank paper used for normal printing.

  On the other hand, when pre-printed paper with dark color printing on the edge of the paper or dark colored paper is used, the position of the edge of the paper is not accurately detected by the line sensor because the reflected light from the paper is reduced. However, there is a problem in that the print start position shifts in the horizontal direction. Conventionally, when the preprinted paper or the color paper is used due to the occurrence of the printing start position deviation, the light quantity of the light source LED of the line sensor is increased. The light intensity setting of the light source LED of the line sensor is an important setting parameter related to the print start position accuracy. Therefore, the maintenance staff changes the light intensity setting of the LED of the line sensor, and the paper edge by the line sensor remains unchanged. The part position was detected. However, even when printing ordinary white paper that does not require an increase in the amount of light, the edge position of the paper is detected with the LED light amount after the setting change, and the stain check is based on the high LED light amount after the setting change. Since it is necessary to carry out with a high LED light quantity, there is a problem that the above-described stain check error is likely to occur frequently and the deterioration of the light source LED is accelerated.

  The above-mentioned problem is that after the paper to be printed reaches the line sensor unit, the paper edge position is detected with a specified light quantity and a light quantity higher than the specified light quantity, and based on the comparison result of the respective paper edge position data, This can be solved by determining the light amount of the line sensor at the end position detection.

  According to the paper edge position detection control of the present invention, when the preprint paper or the dark color paper is used, the light amount setting of the line sensor is automatically changed to be high, and the horizontal direction detection due to the erroneous detection of the line sensor is performed. In addition to preventing misalignment of the print start position, when printing on white paper such as white paper that does not need to increase the light intensity of the line sensor LED more than necessary, printing is performed by automatically changing to the necessary and sufficient light quantity setting. It is possible to provide a printing apparatus with high reliability of the start position accuracy.

  After starting printing, the paper edge position data of the first sheet is acquired twice with the light quantity of the line sensor varied, and the obtained paper edge position data of each sheet is compared by comparing the obtained paper edge position data. The present invention for determining the amount of line sensor light at the time of acquiring paper edge position data is a line sensor for detecting the paper edge position in the width direction, detecting the paper edge position by the line sensor, varying the LED light intensity of the line sensor, and printing the printer. This is realized by the same configuration as the conventional printer control unit that controls the operation.

  Embodiments of the present invention will be described below with reference to FIGS.

  First, a case will be described in which preprinted paper having a width of 5 mm, for example, and strip-shaped preprint printing is printed on the paper edge. When printing is started (S11), control is executed according to the flow shown in FIG. First, when the printer control unit 505 receives a print activation command from a host controller (not shown), it starts a printing operation and picks up a sheet from a designated sheet feeding apparatus. A sheet is picked from the sheet feeding apparatus, and it is determined whether Xms has elapsed after the sheet arrives at the timing sensor 502 shown in FIG. 4 (S12).

  Subsequently, it is determined whether or not this sheet is the first sheet from the sheet feeding apparatus (S13). If it is not the first sheet, the printing operation is performed according to the flow described later. In the case of the first sheet, the light source LED of the line sensor 501 in FIG. 4 is turned on with a prescribed light amount = α sufficient to detect a blank sheet, and sheet edge position data A is acquired (S14). Subsequently, the light of the light source LED of the line sensor 501 is turned on with α = β, and the sheet edge position data B is acquired (S15). The amount of light of α + β is a sufficient amount of light that can accurately detect the edge of the paper even with preprinted paper or dark color paper. The light quantity of the light source LED is varied by varying the on-duty with a PWM drive circuit provided in the printer control unit 505.

  Subsequently, it is determined whether or not the “paper edge position data B−paper edge position data A” acquired above is equal to or greater than a predetermined difference Cmm (S16). Here, since the pre-printed paper is used, the paper edge position data A acquired with the light amount α is acquired under the condition that sufficient reflected light cannot be obtained from the paper, and the actual paper edge position is obtained. The value is smaller than the data.

  On the other hand, the sheet edge position data B acquired with the light amount α + β is obtained from the sheet as sufficient reflected light and becomes accurate sheet edge position data. For example, when C = 1 mm is set, the width of the preprint band of the preprinted paper used is 5 mm, so that (paper edge position data B−paper edge position data A)> C. Accordingly, the light amount of the line sensor when the edge of the second and subsequent sheets is detected is set to α + β (S17). Thereafter, the print start position correction value is calculated from the value of the paper edge position data B acquired as described above (S18), the print start position correction process is further executed (S19), and the process ends (S20).

  When the second sheet is picked from the sheet feeding apparatus, it is determined whether or not Xms has elapsed after the arrival of the sheet at the timing sensor 502 as described above (S12), and then the first sheet. It is determined whether or not (S13). Here, since it is determined to be the second sheet, it is subsequently determined whether or not the set light quantity of the line sensor 501 is α (S21). Here, since the line sensor light amount at the time of detecting the edge position of the second sheet in the flow is set to α + β, the sheet edge position data is continuously acquired with the line sensor light amount α + β (S22). Thereafter, the printing start position correction value is calculated in the same manner as described above (S23), the printing start position correction process is further performed (S19), and the process ends (S20).

  For the third and subsequent sheets, the print start position correction process is executed in the same flow as the second sheet. In this way, in the case of preprinted paper having a strip-shaped preprint on the front edge of the paper, the line sensor 501 is operated with the light amount α + β to obtain the paper edge position data, and the print start position correction processing is executed. To do. As described above, even when preprinted paper or color paper that may be erroneously detected by the line sensor 501 is used, accurate paper edge position detection can be performed.

  Next, a case where white paper is printed will be described. When printing is started as in the case of printing on preprinted paper (S11), the paper is picked from the designated sheet feeding apparatus. A sheet is picked from the sheet feeding device, and it is determined whether Xms has elapsed after the sheet arrives at the timing sensor 502 (S12).

  Subsequently, it is determined whether or not this sheet is the first sheet from the sheet feeding apparatus (S13). If it is not the first sheet, the printing operation is performed according to the flow described later. In the case of the first sheet, the light source LED of the line sensor 501 is turned on with a light amount = α sufficient to detect a blank sheet, and the sheet edge position data A is acquired (S14). Subsequently, the light of the light source LED of the line sensor 501 is turned on with α = β, and the sheet edge position data B is acquired (S15). Thereafter, it is determined whether or not the “paper edge position data B−paper edge position data A” acquired above is equal to or greater than a predetermined difference Cmm (S16).

  When white paper is used, the paper edge position can be accurately recognized even under the condition of the light quantity α, and therefore the difference between “paper edge position data B−paper edge position data A” is within a certain range. Normally, when white paper is used, the difference due to the amount of LED light in the paper edge position data increases as the gap between the line sensor 501 and the paper increases. In the positional relationship among the paper guide 503, the paper guide 504, and the line sensor 501 shown in FIG. 4 in the present invention, the gap between the line sensor 501 and the paper is about 1.5 mm at the maximum. “Paper edge position data B−paper edge position data A” falls within about 0.3 mm. Here, since C = 1 mm is set, it is determined that (paper edge position data B−paper edge position data A) ≧ Cmm is not satisfied, and then the line sensor at the time of detecting the paper edge of the second and subsequent sheets. The light quantity is set to α (S24).

  Thereafter, the print start position correction value is calculated using the value of the paper edge position data A acquired above (S25), the print start position correction process is executed (S19), and the process ends (S20). When the second sheet is picked from the sheet feeding apparatus, it is determined whether Xms has elapsed after the sheet arrives at the timing sensor 502 as described above (S12), and then the first sheet (S13). Here, it is determined that the sheet is the second sheet. Subsequently, it is determined whether or not the set light amount of the line sensor 501 is α (S21). Now, since the line sensor light quantity is set to α according to the result of the flow, the sheet edge position data is continuously acquired with the line sensor light quantity α (S26). Thereafter, the printing start position correction value is calculated in the same manner as described above (S23), the printing start position correction process is further performed (S19), and the process ends (S20). For the third and subsequent sheets, the print start position correction process is executed in the same flow as the second sheet. In this way, when a blank sheet is used, the sheet end position detection by the line sensor 501 is performed with the light amount α.

When the line sensor 501 is used with the light amount α, it becomes difficult to detect the paper dust adhering to the surface of the paper guide 503, and as a result, the generation period of the stain check error performed for preventing the printing start position deviation is extended. It becomes possible.
Further, the LED of the line sensor 501 can be used with a light amount of α + β only for a paper that needs to increase the light amount, and can be used with a light amount of α for a paper that does not need to increase the light amount. It is possible to reduce the rate of occurrence of misdetection of the line sensor 501 due to the deterioration of the LED over time and the resulting horizontal print start position deviation.

3 is a sheet edge position detection flowchart in the electrophotographic printing apparatus according to the present invention. 10 is a conventional sheet edge position detection flowchart. 1 is a configuration diagram of an electrophotographic printing apparatus including a paper edge position detection mechanism. FIG. 6 is a configuration diagram of a paper edge position detection mechanism.

Explanation of symbols

Reference numeral 501 denotes a line sensor, 502 denotes a timing sensor, 503 and 504 denote paper guides, and 505 denotes a printer control unit.

Claims (3)

An optical sensor for detecting the edge position in the paper width direction in the paper transport path , a function for correcting the print start position in the paper width direction, a function for changing the light amount of the light source of the optical sensor, and the optical sensor In an electrophotographic printing apparatus provided with a control unit having a function of recognizing the paper conveyance position based on the edge position detection value, in addition to operating the optical sensor with a predetermined light amount and acquiring the paper edge position data, by operating the optical sensor at atmospheric made quantity than quantity defined acquires paper end position data, it becomes larger than the prescribed amount of light in the said optical sheet edge position data obtained by operating the sensor quantity The paper edge position data obtained by operating the optical sensor with the amount of light is compared, and if the difference between the paper edge position data is greater than or equal to an arbitrary value or greater than an arbitrary value, the mark Starting paper end position data to be used for position correction, the prescribed electrophotographic printing apparatus, characterized in that the acquired paper end position data when operating the optical sensor at atmospheric made quantity than the light amount of. The paper edge position data acquired by operating the optical sensor with the specified light amount is compared with the paper edge position data acquired by operating the optical sensor with a light amount larger than the light amount, When the difference between the paper edge position data is less than an arbitrary value or less than an arbitrary value , the paper edge position data used for the print start position correction is obtained when the optical sensor is operated with the specified light amount. claim 1, wherein the electrophotographic printing apparatus according to the obtained paper end position data and to said Rukoto. Light quantity when obtaining the paper end position data used for the printing start position correction, in any one of claims 1 or 2, characterized that you get the paper end position data of the next subsequent sheet The electrophotographic printing apparatus described.

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