JP2021138526A - Recording medium conveyance device and image formation device - Google Patents

Abstract

To provide a recording medium conveyance device capable of conveying a recording medium without trouble even a recording medium of an irregular size and an irregular-shaped recording medium of neither a rectangle shape nor a square shape.SOLUTION: A recording medium conveyance device includes: first detection means A which is arranged on an upstream side in a recording medium conveying direction and detects a recording medium P; second detection means B1 which is arranged on a downstream side in the recording medium conveying direction of the first detection means A and detects the recording medium; and control means 80 for assigning a timing for detecting the recording medium by the second detection means B1 to the second detection means B1 based on a detection result by the first detection means A.SELECTED DRAWING: Figure 2

Description

The present invention relates to a recording medium transport device and an image forming device.

Generally, in an image forming apparatus, in the case of a standard paper size, the paper size is selected, an image is formed on the paper conveyed from the paper feeding unit, and the paper is ejected. When outputting irregular size paper, the paper width and paper length are set, and the paper is put in the paper feed section for copying or printing.

The paper passing time of a plurality of paper transport sensors installed in the image forming apparatus is calculated based on the square paper length.

Conventionally, even in the case of irregularly shaped paper, the maximum width and maximum length of the paper are input to the device to copy or print. In a device in which the paper transport sensors are placed at different positions in the paper width direction due to the limitation of the system layout of the image forming apparatus, the time required for the irregularly shaped paper to pass through the paper transport sensor is regarded as a square. Unlike the calculated timing, there is a difference between the actual time and the calculated time. Due to this difference in paper detection, it is determined that the paper detection is defective, and there is a problem that a paper transport error occurs.

Patent Document 1 provides sensors (PSA1, PSA2, PS8) for detecting the presence or absence of paper at a position in the width direction intersecting the paper transport direction, and ON / from the front end to the rear end in the paper transport direction detected by this sensor. Specify the paper shape from OFF.

However, this technique has low paper shape detection accuracy.

Therefore, an object of the present invention is to provide a recording medium transporting device capable of transporting a recording medium without any trouble even if the recording medium has an irregular size or a deformed recording medium that is not rectangular or square.

In order to solve this problem, a first detection means arranged on the upstream side in the recording medium transport direction to detect the recording medium and a first detection means arranged on the downstream side in the recording medium transport direction of the first detection means to detect the recording medium. A recording characterized by having two detection means and a control means for assigning a timing for detecting a recording medium by the second detection means to the second detection means based on a detection result by the first detection means. It features a medium transfer device.

The recording medium can be conveyed without any problem even if the recording medium has an irregular size or a deformed recording medium that is not rectangular or square.

It is a schematic block diagram which shows the printer 100 which concerns on embodiment. It is a schematic plan view of the paper transport device which concerns on 1st Embodiment. It is a timing chart which shows the method of detecting the size of paper P. It is a timing chart which shows the method of detecting the size of paper P. It is a schematic plan view of the paper transport device which concerns on 2nd Embodiment. It is a timing chart which shows the method of detecting the size of paper P. It is a schematic plan view of the paper transport device which concerns on 3rd Embodiment. It is a schematic diagram which shows the example which the paper P of a different shape is conveyed by another paper transporting apparatus. It is a schematic plan view of the paper transport device which concerns on 4th Embodiment.

Hereinafter, an embodiment of an electrophotographic printer will be described as an image forming apparatus to which the present invention is applied.
FIG. 1 is a schematic configuration diagram showing a printer 100 according to an embodiment. As shown in FIG. 1, the printer 100 has four image forming units 2 (Y, M,) for forming a toner image of yellow (Y), magenta (M), cyan (C), and black (K). C, K) is provided. The four image-forming units 2 are arranged side by side with respect to the intermediate transfer belt 61 as the image-carrying belt along the endless movement direction, which is a so-called tandem type configuration.

The printer 100 includes a paper feed path 30, a pre-transfer transfer path 31, a manual feed path 32, a manual feed tray 33, a resist roller pair 34, a transfer belt unit 35, a fixing device 40, a transfer switching device 50, a paper discharge path 51, and an ejection path. It is provided with a paper roller pair 52, a paper ejection tray 53, and the like. Further, it includes two optical writing units 1 (YM, CK), a primary transfer unit 60, a secondary transfer unit 78, a first paper feed cassette 101, a second paper feed cassette 102, and the like.

The four image forming units 2 (Y, M, C, K) each have a drum-shaped photoconductor 3 (Y, M, C, K) which is a latent image carrier. Further, the first paper cassette 101 and the second paper cassette 102 each house a bundle of paper P, which is a recording sheet, inside. Then, by rotationally driving the first feeding roller 101a or the second feeding roller 102a, the topmost paper P in the paper bundle is sent out toward the paper feed path 30.

A manual feed tray 33 is arranged so as to be openable and closable with respect to the housing on the right side surface of the housing of the printer 100 in FIG. NS. The top paper P in the manually fed paper bundle is fed by the delivery roller of the manual feed tray 33 toward the paper feed path 30 via the manual paper feed path 32.

The two optical writing units 1 (YM, CK) each have a laser diode, a polygon mirror, various lenses, and the like. Then, based on the image information read by the scanner, which is an external device of the printer 100, and the image information sent from the personal computer, the laser diode is driven to drive the image forming unit 2 (Y, M, C, K). Photoreceptor 3 (Y, M, C, K) of Specifically, the photoconductors 3 (Y, M, C, K) of the image forming unit 2 (Y, M, C, K) are rotationally driven in the counterclockwise direction in FIG. 1 by the driving means. ..

The first optical writing unit 1YM performs an optical scanning process by irradiating the driving yellow photoconductor 3Y and magenta photoconductor 3M with laser light while being deflected in the direction of the rotation axis. As a result, an electrostatic latent image based on the yellow image information and the magenta image information is formed on the yellow photoconductor 3Y and the magenta photoconductor 3M, respectively.
The second optical writing unit 1CK performs an optical scanning process by irradiating the driving cyan photoconductor 3C and the black photoconductor 3K with laser light while being deflected in the direction of the rotation axis. As a result, an electrostatic latent image based on the cyan image information and the black image information is formed on the cyan photoconductor 3C and the black photoconductor 3K, respectively.

The image forming unit 2 (Y, M, C, K) is a common support in which the photoconductor 3 (Y, M, C, K) and various devices arranged around the photoconductor 3 (Y, M, C, K) are used as one unit. They are integrally attached to and detached from the housing of the printer 100 while being supported by the printer 100. The image forming unit 2 (Y, M, C, K) has the same configuration except that the colors of the toners used are different from each other. Therefore, in the following description, "Y, M, C, K" indicating the color of the toner to be used will be omitted as appropriate.

In addition to the photoconductor 3, the image forming unit 2 has a developing device 4 for developing an electrostatic latent image formed on the surface of the photoconductor 3 into a toner image. It also has a charging device 5 that uniformly charges the surface of the photoconductor 3 that is driven to rotate. Further, it also has a drum cleaning device 6 for cleaning the transfer residual toner adhering to the surface of the photoconductor 3 after passing through the primary transfer nip corresponding to each color described later.

The photoconductor 3 is a drum-shaped body in which a photosensitive layer is formed by applying a photosensitive organic photosensitive material to a raw tube such as aluminum. Instead of the drum-shaped one, an endless belt-shaped one may be used.

The developing device 4 includes a rotatable developing sleeve made of a non-magnetic pipe, and a magnet roller arranged in the hollow of the developing sleeve so as not to rotate with respect to the sleeve. Then, an electrostatic latent image on the photoconductor 3 is formed by a two-component developer (hereinafter, simply referred to as a developer) containing a magnetic carrier supported on the surface of the developing sleeve by the magnetic force generated by the magnet roller and non-magnetic toners of each color. To develop.

To the developing device 4 (Y, M, C, K) of each color, the toner of each color in the toner bottle 103 (Y, M, C, K) of each color is appropriately replenished by the toner replenishing device of each color. A toner concentration sensor as a toner concentration detecting means is provided in the developing device 4. The toner concentration sensor detects the magnetic permeability of the developer due to the carrier, which is a magnetic material. The control unit 400, which will be described later, controls the drive of the toner replenishing device for each color based on the comparison between the output value from the toner density sensor of each color and the output target value from the sensor which is the toner concentration target value. As a result, the toner concentration of the developer is kept within a certain range (for example, 4 [wt%] to 9 [wt%]).

The drum cleaning device 6 is of a type in which the transfer residual toner is scraped from the surface of the photoconductor 3 by a cleaning blade made of polyurethane rubber which is brought into contact with the photoconductor 3. Instead of such a method, another method may be used. In the drum cleaning device 6, in addition to the cleaning blade, a rotatable fur brush is also brought into contact with the photoconductor 3 for the purpose of improving the cleanability. This fur brush also has a role of applying the lubricant to the surface of the photoconductor 3 while scraping the lubricant from the solid lubricant to make a fine powder.

A static elimination lamp is arranged above the photoconductor 3, and this static elimination lamp is also a part of the image forming unit 2. The static elimination lamp eliminates static electricity by irradiating the surface of the photoconductor 3 after passing through the portion facing the drum cleaning device 6. The surface of the statically eliminated photoconductor 3 is uniformly charged by the charging device 5, and then subjected to optical scanning by the above-mentioned optical writing unit 1. The charging device 5 is rotationally driven while receiving a charging bias from a power source. Instead of such a method, a scorotron charger type that performs a non-contact charging treatment on the photoconductor 3 may be adopted.

A primary transfer unit 60 is arranged below the four image forming units 2 (Y, M, C, K). The primary transfer unit 60 includes an intermediate transfer belt 61 which is an image carrier stretched by a plurality of rollers (63, 67, 68, 69 and 70). Then, while the intermediate transfer belt 61 is brought into contact with the photoconductor 3 (Y, M, C, K), it is endless in the clockwise direction (arrow “D” direction) in FIG. 1 by the rotational drive of any one roller. Move. As a result, a primary transfer nip for each color (Y, M, C, K) in which the photoconductor 3 (Y, M, C, K) and the intermediate transfer belt 61 abut is formed.

In the vicinity of the primary transfer nip for each color, the intermediate transfer belt 61 is attached to the photoconductor 3 (Y, M, C, K) by the primary transfer roller 62 (Y, M, C, K) arranged inside the belt loop. It is pressing toward. A primary transfer bias is applied to each of the four primary transfer rollers 62 (Y, M, C, K) by a primary transfer power supply. As a result, a primary transfer electric field is formed in the primary transfer nip for each color to electrostatically move the toner image on the photoconductor 3 (Y, M, C, K) toward the intermediate transfer belt 61.

On the front surface of the intermediate transfer belt 61, which sequentially passes through the primary transfer nips for each color as the intermediate transfer belt 61 moves endlessly in the clockwise direction in FIG. 1, a Y toner image and an M toner image, The C toner image and the K toner image are sequentially superimposed and primary transferred. By this superposition primary transfer, a four-color superposition toner image is formed on the front surface of the intermediate transfer belt 61.

A secondary transfer unit 78 is arranged below the intermediate transfer belt 61 in FIG. 1. The secondary transfer unit 78 includes an endless secondary transfer belt 77, a ground driven roller 72, a secondary transfer drive roller 71, a secondary belt cleaning device 76, a toner adhesion amount detection sensor 64, and the like. The secondary transfer belt 77 is tensioned by the ground-driven driven roller 72 arranged inside the loop and the secondary transfer drive roller 71, and is shown in FIG. 1 as the secondary transfer drive roller 71 is rotationally driven. Is moved endlessly in the counterclockwise direction (arrow "B" direction).

The secondary transfer belt 77 of the secondary transfer unit 78 has its own grounding driven roller 72 hung with the secondary transfer bias roller 68 in the intermediate transfer belt 61 of the primary transfer unit 60. It forms a secondary transfer nip. The secondary transfer bias output from the secondary transfer power supply is applied to the secondary transfer bias roller 68 inside the loop of the intermediate transfer belt 61, whereas the ground driven roller 72 inside the loop of the secondary transfer belt 77 It is grounded. As a result, a secondary transfer electric field is formed in the secondary transfer nip.

A resist roller pair 34 is arranged on the right side of FIG. 1 of the secondary transfer nip, and the timing at which the paper P sandwiched between the rollers can be synchronized with the four-color superimposed toner image on the intermediate transfer belt 61. Send it to the secondary transfer nip. In the secondary transfer nip, the four-color toner image on the intermediate transfer belt 61 is collectively secondary-transferred to the paper P due to the influence of the secondary transfer electric field and the nip pressure, and is combined with the white color of the paper P to form a full-color image. Here, the image forming apparatus has an image forming portion for forming an image on the paper P, and the image forming portion includes a secondary transfer unit 78.

The secondary transfer residual toner adheres to the front surface of the intermediate transfer belt 61 after passing through the secondary transfer nip. The secondary transfer residual toner is removed from the surface of the intermediate transfer belt 61 by the intermediate transfer belt cleaning device 75 of the primary transfer unit 60.

The paper P that has passed through the secondary transfer nip is separated from the intermediate transfer belt 61 and the secondary transfer belt 77 and delivered to the transfer belt unit 35. The transport belt unit 35 stretches the endless transport belt 36 by the transport drive roller 37 and the transport driven roller 38, and is driven by the rotation of the transport drive roller 37 in the counterclockwise direction in FIG. 1 (arrow “C”). It is moved endlessly in the "direction). Then, while holding the paper P delivered from the secondary transfer nip on the upper tensioning surface of the transport belt 36, the paper P is transported along with the endless movement of the transport belt 36, and the paper P is delivered to the fixing device 40.

The paper P sent into the fixing device 40 is sandwiched between the fixing nips formed by the contact between the endless fixing belt 41 and the pressure roller 44. Then, the toner image is fixed on the surface by the action of pressurization or heating.

The paper P in which the toner image is transferred to the first surface by the secondary transfer nip and the toner image is fixed on the first surface by the fixing device 40 is sent out to the transfer switching device 50. In the printer 100, the retransmission means is configured by the transfer switching device 50, the retransmission path 54, the switchback path 55, the transfer path 56 after switchback, and the like. The transport switching device 50 switches the subsequent transport destination of the paper P received from the fixing device 40 between the paper discharge path 51 and the retransmission path 54.

Specifically, when executing a print job in the single-sided mode in which an image is formed only on the first surface of the paper P, the transport destination is set to the output path 51. As a result, the paper P on which the image is formed only on the first surface is sent to the output roller pair 52 via the output path 51 and discharged onto the output tray 53 outside the machine. Further, when executing a print job in the double-sided mode in which images are formed on both sides of the paper P, when the paper P having the images fixed on both sides is received from the fixing device 40, the transfer destination is discharged. Set to road 51. As a result, the paper P on which the images are formed on both sides is discharged onto the output tray 53 outside the machine.

On the other hand, when the paper P in which the image is fixed only on the first side is received from the fixing device 40 at the time of executing the print job in the double-sided mode, the transport destination is set to the retransmission path 54. A switchback path 55 is connected to the retransmission path 54, and the paper P sent to the retransmission path 54 enters the switchback path 55. Then, when the entire region of the paper P in the transport direction enters the switchback path 55, the transport direction of the paper P is reversed and the paper P switches back.

In addition to the retransmission path 54, the switchback path 55 is connected to the transfer path 56 after the switchback, and the switched-back paper P enters the transfer path 56 after the switchback. At this time, the paper P is turned upside down. Then, the upside-down paper P is retransmitted to the secondary transfer nip via the transfer path 56 after switchback and the above-mentioned paper feed path 30. The paper P on which the toner image is also transferred to the second surface by the secondary transfer nip has the toner image fixed on the second surface via the fixing device 40, and then the transfer switching device 50 and the paper ejection path 51. Paper is ejected onto the output tray 53 via the output roller pair 52.

<First Embodiment>
FIG. 2 is a schematic plan view of the paper transport device according to the first embodiment.
As shown in FIG. 2, the paper transport device according to the present embodiment is arranged on the upstream side of the paper P in the transport direction, and has a sensor A as a first detection means for detecting the paper P as a recording medium and a sensor A of the sensor A. A sensor B1 as a second detection means for detecting the paper P, which is arranged on the downstream side in the paper transport direction, and a control means for assigning the timing of detecting the paper P by the sensor B1 to the sensor B1 based on the detection result of the sensor A. Has 80 and. When viewed in the paper transport direction, the sensor A, the resist roller pair 34, the paper transport roller 11, the ground driven roller 72, the transport belt 36, the fixing device 40, and the transport switching device 50 are sequentially arranged. The sensor A and the sensor B1 are paper transport sensors that detect whether or not the paper is correctly fed.

The sensor A is a line sensor having a detection width in a direction intersecting the paper transport direction (hereinafter referred to as “paper width direction”). The sensor A is arranged on the upstream side in the paper transport direction with respect to the resist roller pair 34, and can detect the paper P at each position in the paper width direction. Further, when the conveyed paper P passes through the sensor A, the sensor A can also detect the paper length in the paper conveying direction. Therefore, according to the present embodiment, the sensor A can detect the paper shape (for example, A4 width, A4 length, etc.) from the paper length in the paper width direction and the paper length in the paper transport direction.

The sensor B1 is a sensor that turns on when the front end of the paper P comes to the opposite position and turns off when the rear end of the paper P passes. Further, the sensor B1 is arranged on the upstream side of the paper transport roller 11 in the paper transport direction and inside the paper width direction of the sensor A.

Here, when the paper P does not slip or slips, the following pattern is assumed depending on the position of the paper P.
(1) When the paper P does not slip while passing through the sensor A (2) When the paper P slips when the tip of the paper P is between the sensor A and the sensor B1 (3) When the tip of the paper P slips on the sensor B1 When the paper P slips between passing and the rear end of the paper P passing through the sensor A (4) When the paper P slips when the rear end of the paper P is between the sensor A and the sensor B1.

3 and 4 are timing charts showing a method of detecting the size of the paper P. FIG. 3 shows the case where there is no slip of the paper P, which corresponds to the case of the above pattern (1). FIG. 4 shows the case where the paper P is slipped and corresponds to the cases of the above patterns (2) and (3).
In FIG. 3, when the conveyed paper P reaches the sensor A, the portion of the sensor A facing the paper P is turned on (FIG. 3A). The sensor A detects the paper P at each position in the paper width direction, and FIG. 3 shows the detection state at the position of the detection position A1 shown in FIG. The detection position A1 is a detection position at a position where a virtual line extending in the paper transport direction through the sensor B1 intersects the sensor A. FIG. 3A shows the measured value at the detection position A1.

The waveform of the sensor B1'is obtained from the paper head timing (from OFF to ON) at which the paper P arrives and the set length of the paper, which are obtained from the distance between the detection positions A1 and B1 in the sensor A and the rotation speed of the resist roller pair 34. Indicates the end time (ON to OFF). In other words, the waveform of the sensor B1'is an ideal time (calculated value) from the distance between the sensor A and the sensor B1 and the paper transport speed until the paper position detected by the detection position A1 reaches the sensor B1.

Conventionally, when a difference between the ideal time (calculated value) and the actual time as shown in the sensor B1'occurs, it is determined that the paper detection is defective, and a paper transport error occurs.

On the other hand, according to the present embodiment, the control means 80 calculates the timing for detecting the paper P by the sensor B1 based on the detection result of the detection position A1 corresponding to the sensor B1 in the paper transport direction, and the sensor B1. Set the detection timing in. In other words, when the sensor A as the first detection means detects the paper P as the recording medium, the control means assigns the timing for detecting the paper P by the sensor B1 as the second detection means to the sensor B1 and assigns the sensor A to the sensor A. When the paper P is no longer detected, the timing at which the sensor B1 does not detect the paper P is assigned to the sensor B1. The detection timing by the sensor B1 is shown as a waveform of the sensor B1 in FIG. 3C. After that, the control means 80 continues to set the detection timing by the sensor B1 by receiving the detection result by the sensor A and transmitting it to the sensor B1.

In the example shown in FIG. 3, since there is no slip of the paper P, A1 = B1'= B1 holds with respect to the paper length in the paper transport direction and the detection timing (that is, the ON time of the sensor).

On the other hand, in FIG. 4, which is a case where the paper P slips, the actually measured value at the detection position A1 becomes longer by a corresponding to the slip (FIG. 4 (a)). Further, the measured value by the sensor B1 also becomes longer by a corresponding to the slip amount corresponding to the detection position A1 (FIG. 4 (c)). On the other hand, the waveform of the sensor B1'is obtained from the paper head timing (from OFF to ON) at which the paper P arrives and the set length of the paper, which are obtained from the distance between the detection positions A1 and B1 and the rotation speed of the resist roller pair 34. The calculated value of the obtained end time (ON to OFF) is shown (FIG. 4 (b)). In the example of FIG. 4, A1 = B1 and B1 ≠ B1'.

As shown in FIG. 4C, when the paper P slips, the detection timing of the sensor B1 becomes longer. Therefore, according to the prior art, it is determined that the paper length in the paper transport direction is longer by a than in the case of the sensor B1', and due to this difference, it is determined that the paper detection is defective, and a paper transport error occurs. .. However, according to the present embodiment, even if the detection timing (ON time) of the sensor B1 is different from the waveform (ON time) of the sensor B1', it is not determined that the paper detection is defective and the paper transfer is continued. That is, according to the present embodiment, even if the detection position A1 detects that the paper length in the paper transport direction is longer than the actual paper length by a due to the slip of the paper P, the detection time by the sensor B1 is calculated correspondingly. Longer than. As a result, even if the paper P slips, a paper transport error does not occur, and the paper shape detection accuracy can be improved.

<Second embodiment>
FIG. 5 is a schematic plan view of the paper transport device according to the second embodiment.
The second embodiment is an example in which the shape detection method of the first embodiment is applied to the shape detection method of irregularly shaped paper.
As shown in FIG. 5, the paper transport device according to the present embodiment is arranged on the upstream side of the paper P in the transport direction, and has a sensor A as a first detection means for detecting the paper P as a recording medium and a sensor A of the sensor A. Sensors B1, B2, B3, B4 as a second detection means for detecting the paper P, which are arranged on the downstream side in the paper transport direction, and the sensors B1, B2, B3, B4 based on the detection result of the sensor A. It has a control means 80 that assigns the timing of detecting P to the sensors B1, B2, B3, and B4.

The sensor A is a line sensor having a detection width in the paper width direction. The sensor A is arranged on the upstream side in the paper transport direction with respect to the resist roller pair 34, and can detect the paper P at each position in the paper width direction. Further, when the conveyed paper P passes through the sensor A, the sensor A can also detect the paper length in the paper conveying direction. Therefore, according to the present embodiment, the sensor A can detect the paper shape (for example, A4 width, A4 length, etc.) from the paper length in the paper width direction and the paper length in the paper transport direction.

The sensors B1 to B4 are sensors that are turned on when the front end of the paper P comes to the opposite position and turned off when the rear end of the paper P passes.
Further, the sensor B1 is arranged on the upstream side in the paper transport direction with respect to the paper transport roller 11 and inside in the paper width direction of the sensor A. The sensor B2 is arranged on the downstream side of the paper transport roller 11 in the paper transport direction and inside the paper width direction of the sensor A.

According to the present embodiment, the sensor A as the first detection means is a line sensor extending in a direction intersecting the paper transport direction, and a plurality of sensors B1 to B4 as the second detection means are provided within the width of the line sensor. Has been done. As a result, it is possible to allocate the paper detection time according to the paper shape to each of the plurality of sensors arranged downstream of the resist roller vs. 34, and it is possible to transfer the paper even if the shape of the paper is irregularly shaped.

Further, the transport belt 36 is divided and arranged in the paper width direction. Therefore, the sensor B2 is arranged between the transport belt 36 and the transport belt 36 in the paper width direction. The sensor B3 is arranged on the downstream side in the transport direction of the fixing device 40 and in the central portion in the width direction. The sensor B4 is located on the downstream side of the transport switching device 50 in the transport direction and at the center in the width direction.

The detection position A1 is a detection position at a position where a virtual line extending in the paper transport direction through the sensor B1 intersects the sensor A. The detection position A2 is a detection position at a position where a virtual line extending in the paper transport direction through the sensor B2 intersects the sensor A. The detection position A3 is a detection position at a position where a virtual line extending in the paper transport direction through the sensors B3 and B4 intersects the sensor A.

In the present embodiment, the paper P is an envelope and has an accommodating portion Pa for accommodating the inclusions and a sealing portion Pb for accommodating the inclusions in the accommodating portion Pa and then folding back toward the accommodating portion.
The rear end of the sealing portion Pb is tapered toward the paper transport direction, and it can be said that the position of the rear end differs in the paper transport direction in the paper transport direction. Conventionally, an envelope having such a shape is also regarded as a square and the time until the paper passes through the paper transport sensor is calculated. Therefore, when the time until the envelope actually passes through the paper transport sensor is different from the calculation time. Was determined to be paper detection failure, and a paper transport error occurred.

FIG. 6 is a timing chart showing a method of detecting the size of the paper P. FIG. 6 shows the case where the paper P is slipped and corresponds to the cases of the above patterns (2) and (3).
The waveforms of the sensors B1'and B3' are the paper head timing (from OFF to ON) at which the paper P arrives and the paper, which are obtained from the distance between the detection positions A1 and A3 and the sensors B1 and B3 and the number of rotations of the resist roller pair 34. Indicates the end time (ON to OFF) obtained from the set length of. In other words, the waveforms of the sensors B1'and B3' are measured from the distance between the detection positions A1 and A3 and the sensors B1 and B3 and the paper transport speed until the paper position detected by the detection positions A1 and A3 reaches the sensors B1 and B3. Is the ideal time (calculated value) of. Here, the paper transport speed is a speed calculated from the rotation speed of the resist roller pair 34, and at this time, the friction between the paper P and the resist roller pair 34 may be taken into consideration. The method for determining the timing of the sensor A2 and the sensor B2 can be set in the same manner as described above, but the description thereof will be omitted.

As shown in FIGS. 6A and 6D, when the timings from OFF to ON of the detection position A1 and the sensor A3 match, this means that the paper P is not skewed, but the detection position. The ON times of A1 and the detection position A3 are different. This is because, as described above, in the case of irregularly shaped paper such as an envelope, the paper length in the paper transport direction differs between the detection position A1 and the detection position A3.

In FIG. 6, which is a case where the paper P slips, the actually measured values at the detection positions A1 and A3 are longer by a corresponding to the slip (FIGS. 6 (a) and 6 (d)). On the other hand, the waveforms of the sensors B1'and B3'are the paper head timing (from OFF to ON) at which the paper P arrives, which is obtained from the distance between the detection positions A1 and A3 and B1 and B3 and the rotation speed of the resist roller pair 34. , The calculated value of the end time (ON to OFF) obtained from the set length of the paper is shown (FIGS. 6 (b) and 6 (e)). Further, the measured values of the sensors B1 and B3 are also lengthened by a corresponding to the slip amount corresponding to the detection positions A1 and A3 (FIGS. 6 (c) and 6 (f)). In the example of FIG. 6, A1 = B1 and B1 ≠ B1'. Further, A3 = B3, and B3 ≠ B3'.

As shown in FIGS. 6 (c) and 6 (f), when the paper P slips, the detection timings of the sensors B1 and B3 become longer. Therefore, according to the prior art, it is determined that the paper length in the paper transport direction is longer by a than in the case of the sensors B1'and B3', and this difference determines that the paper detection is defective and a paper transport error occurs. Was. However, according to the present embodiment, even if the detection timing (ON time) of the sensors B1 and B3 is different from the waveform (ON time) of the sensors B1'and B3', it is not determined that the paper detection is defective and the paper transfer is continued. do. That is, according to the present embodiment, even if the detection positions A1 and A3 detect that the paper length in the paper transport direction is a longer than the actual length due to the slip of the paper P, the sensors B1 and B3 detect it correspondingly. Make the time longer than the calculated value. As a result, it is possible to improve the detection accuracy of the paper shape while not causing a paper transport error even if the paper has an irregular size or a deformed paper that is not rectangular or square, or even if the paper P slips.

The example of FIG. 6 is a case where the paper slips, but when the slip does not occur, A1 ≠ B1', A1 = with respect to the paper length in the paper transport direction and the detection timing (that is, the ON time of the sensor). B1, A3 = B3'= B3 holds.
B1'is the paper length for which the size of the paper is input, and in the case of the envelope of the present embodiment, it is the length from the tip of the envelope to the apex of the sealing portion Pb. Therefore, the relationship is A1 = B1 <B1', and A1 ≠ B1'.

<Third embodiment>
FIG. 7 is a schematic plan view of the paper transport device according to the third embodiment.
In the third embodiment, in the shape detection method of the second embodiment, a plurality of sensors A1 to A3 are installed in place of the line sensor. That is, the sensors A1 to A3 are aligned in the paper width direction orthogonal to the paper transport direction. The sensors A1 to A3 can detect the paper P at the sensor position in the paper width direction. Further, when the conveyed paper P passes through the sensors A1 to A3, the sensors A1 to A3 can also detect the paper length in the paper conveying direction. Therefore, according to the present embodiment, the sensors A1 to A3 can detect the paper shape (for example, A4 width, A4 length, etc.) from the paper length in the paper width direction and the paper length in the paper transport direction. Further, the sensors A1 and B1, the sensors A2 and B2, and the sensors A3 and B3 and B4 are arranged so as to be located on virtual lines extending in the paper transport direction, respectively. The control means 80 receives the detection results of the sensors A1, A2 and A3 and transmits them to the sensors B1, B2, B3 and B4, respectively, to set the detection timings of the sensors B1, B2, B3 and B4. Continue to do.

As described above, according to the present embodiment, the sensors A1, A2, A3 as the first detection means and the sensors B1, B2, B3, B4 as the second detection means are a plurality of in the direction intersecting the paper transport direction. It is provided.

As described in relation to the second embodiment, the transport belt 36 is divided and arranged in the paper width direction, so that the sensor B2 is located between the transport belt 36 and the transport belt 36 in the paper width direction. It is arranged. Therefore, the position where the sensor B2 can be installed is specified, and the sensor A2 is arranged on the upstream side in the paper transport direction corresponding to the position.

However, the arrangement is not limited to the arrangement shown in FIG. 7, and the sensors A1 to A3 may be arranged at a position corresponding to the position where the sensor B on the downstream side is arranged.

In the present embodiment as well, as in the second embodiment, even if the sensors A1, A2, and A3 detect that the paper length in the paper transport direction is longer than the actual size by a due to the slip of the paper P, the correspondingly The detection time of the sensors B1, B2, B3 and B4 is made longer than the calculated value. As a result, it is possible to improve the detection accuracy of the paper shape while not causing a paper transport error even if the paper has an irregular size or a deformed paper that is not rectangular or square, or even if the paper P slips.

FIG. 8 is a schematic view showing an example in which paper P having a different shape is conveyed by another paper conveying device.
In the present embodiment, the sensors B1 and B2, which are arranged so as to be displaced in the paper width direction in the shape detection method of the second embodiment, are arranged in a straight line in the paper width direction. The sensor A is a line sensor having a detection width in the paper width direction, and is arranged on the upstream side of the sensors B1 and B2 in the transport direction. The control means 80 continues to set the detection timings at the sensors B1 and B2 by receiving the detection results at the detection positions A1 and A2 and transmitting the detection results to the sensors B1 and B2, respectively. In the example shown in FIG. 8, the tip of the paper P entering the sensor A has an uneven shape in the paper width direction, and the above-described embodiment can be applied to the paper P having such a shape.

In this case, the timing from OFF to ON set in the sensor B1 is determined based on the result of the detection position A1 detecting the first tip Px of the paper P. Further, based on the result of the sensor A2 detecting the second tip Py of the paper P, the timing from OFF to ON set in the sensor B2 is determined.

<Fourth Embodiment>
FIG. 9 is a schematic plan view of the paper transport device according to the fourth embodiment. FIG. 9 is a schematic view in which the embodiment of FIG. 8 is applied to an inkjet image forming apparatus.
As shown in FIG. 9, the paper transport device according to the present embodiment has a sensor A as a first detection means for detecting the paper P as a recording medium on the upstream side of the paper P in the transport direction, and a paper transport direction of the sensor A. Sensors B1 and B2 as the second detection means for detecting the paper P on the downstream side, and control means 80 for assigning the timing of detecting the paper P by the sensors B1 and B2 to the sensors B1 and B2 from the detection result of the sensor A. Has.

The sensor A, which is a line sensor having a detection width in the paper width direction, is arranged on the upstream side in the paper transport direction with respect to the resist roller pair 34, and can detect the paper P at each position in the paper width direction.

The sensors B1 to B2 are sensors that are turned on when the front end of the paper P comes to the opposite position and turned off when the rear end of the paper P passes.
Further, the sensor B1 is arranged on the downstream side of the resist roller pair 34 in the paper transport direction and on the upstream side of the recording unit 200 in the paper transport direction, and is arranged inside the sensor A in the paper width direction. The sensor B2 is arranged on the downstream side of the resist roller pair 34 in the paper transport direction and on the upstream side of the recording unit 200 in the paper transport direction, and is arranged inside the sensor A in the paper width direction.

The above-described embodiment can be applied not only to an electrophotographic image forming apparatus but also to an inkjet type image forming apparatus for applying a liquid to paper. In addition, this device can also be said to be a device for applying droplets.

In FIG. 9, recording heads 200a, 200b, and 200c are arranged in a staggered pattern in the recording unit 200 in the paper width direction. When the paper P is conveyed below the recording unit 200, droplets are ejected from each ejection port of the recording head, and an image is formed on the paper.

Here, according to the above-described embodiment, since the paper transport device recognizes that the shape of the paper P is the shape shown in FIG. 9, droplets are discharged from the recording heads 200a, 200b, and 200c only within the range of the recognized shape. It can be controlled to discharge. Therefore, the droplets are not ejected to the portion in front of the second tip portion Py in the transport direction, and the ejection of unnecessary droplets can be suppressed.

Further, even in an image forming apparatus for inputting the length (vertical, horizontal) of the paper used by the user, the above-described embodiment is applied, and the paper shape recognized without using the input length is used. The result may be used to form an image.

To summarize the above, a plurality of paper transport sensors are installed in the image forming apparatus. Conventionally, in the case of standard size or irregular size, the paper width and paper length are input to the device, and the ON / OFF time for normal detection by the paper transport sensor is determined according to the input paper size. Was there. Therefore, the detection by the paper transport sensor, which is different from the normal detection time, is determined to be a paper transport defect, and the output is stopped. Therefore, in the present invention, the shape of the paper is read and stored by using the paper transport sensor or the line sensor arranged at different positions in the paper width direction, and the paper transport sensor arranged further downstream according to the shape of the paper. The paper detection ON / OFF time of is assigned to each paper transport sensor. Therefore, for example, even if the paper transport sensor or the line sensor detects that the paper length in the paper transport direction is longer than the actual length due to the slip of the paper, the detection time of each paper transport sensor arranged downstream corresponding to the detection time is set. Make it longer than the calculated value. In addition, even if irregularly shaped paper or paper slip occurs, the paper can be transported without any trouble in paper transport.

80 Control means A sensor (first detection means)
B1, B2, B3, B4 sensor (second detection means)
P paper (recording medium)

Japanese Unexamined Patent Publication No. 2003-154725

Claims (5)

A first detecting means, which is arranged on the upstream side in the recording medium transport direction and detects the recording medium,
A second detecting means, which is arranged on the downstream side of the first detecting means in the recording medium transport direction and detects the recording medium,
A control means that assigns a timing for detecting a recording medium by the second detection means to the second detection means based on the detection result of the first detection means.
A recording medium transfer device, characterized in that it has. When the first detecting means detects the recording medium, the control means assigns the timing for detecting the recording medium by the second detecting means to the second detecting means, and the first detecting means detects the recording medium. The recording medium transporting apparatus according to claim 1, wherein when the second detection means is used up, a timing at which the recording medium is no longer detected by the second detection means is assigned to the second detection means. The recording medium transporting apparatus according to claim 1 or 2, wherein a plurality of the first detecting means and the second detecting means are provided in a direction intersecting the recording medium transporting direction. The first detection means is a line sensor extending in a direction intersecting the recording medium transport direction.
The recording medium transport device according to any one of claims 1 to 3, wherein a plurality of the second detection means are provided within the width of the line sensor. An image forming unit that forms an image on a recording medium,
An image forming apparatus comprising the recording medium conveying apparatus according to any one of claims 1 to 4, wherein the recording medium is conveyed to the image forming unit.

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