JP7638784B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus that uses an electrophotographic method.

Conventionally, image forming apparatuses having an intermediate transfer body have been known as electrophotographic image forming apparatuses. In the primary transfer process, a toner image formed on a photosensitive drum, which is an image carrier, is transferred to an intermediate transfer body (hereinafter referred to as intermediate transfer belt). This primary transfer process is then repeatedly performed on the toner images formed at each of the image forming stations for yellow (Y), magenta (M), cyan (C), and black (Bk), forming toner images of multiple colors on the intermediate transfer belt.

Paper loaded in the paper feed section is fed into the machine at any time. When the leading edge of the fed paper is detected by a transport sensor installed downstream of the paper feed section, the transport is controlled in the secondary transfer process so that the toner image formed on the intermediate transfer belt is transferred to the appropriate position on the fed paper. The toner image transferred to the paper is then fixed to the paper by a fixing device, forming a color image.

In such an image forming device, the controller receives print data from an external device such as a host computer, and develops bitmap data based on the received print data. After the controller finishes developing the bitmap data, it outputs the developed bitmap data as video data to the engine section that controls image formation. The controller section has a development circuit corresponding to each image forming station in order to send video data to each image forming station controlled by the engine section. The controller section forms an image by sending video data to each image forming station via the development circuit in accordance with an image write signal (hereinafter referred to as a /TOP signal) output from the engine section.

On the other hand, image forming devices assume that users will use non-standard sized paper and often have a multipurpose tray (hereinafter referred to as MP tray) for non-standard sized paper. When printing on non-standard sized paper transported from the MP tray, the engine unit is required to perform appropriate printing according to the size of the paper without causing transport problems such as paper jams, regardless of the size of the paper (length of the paper in the transport direction).

For example, in Patent Document 1, when the size of the paper placed on the MP tray is unknown, image formation control and transport control are performed based on the maximum size of paper that can be placed on the paper feed section. The paper size is then measured by a transport sensor, and when the paper size is determined, the image formation control and transport control are changed to match the determined paper size. This makes it possible to perform printing operations without causing transport problems, improving throughput and suppressing declines in productivity.

JP 2015-143795 A

In the image forming device proposed in Patent Document 1, when printing on non-standard size paper, the size of the paper is measured while the paper is being transported by a registration sensor (hereinafter referred to as the registration sensor) located upstream of the transport path near the secondary transfer unit. The registration sensor not only corrects misalignment of the paper, but is also used as a sensor to change the paper transport speed or, in some cases, stop the paper transport so that the toner image formed on the intermediate transfer belt and the transfer position of the paper match at the secondary transfer unit.

In the image forming device having the above-mentioned configuration, when printing on non-standard size paper, if the size of the image formed by the controller unit (image length in the transport direction) is larger than the size of the paper loaded in the paper feed unit (paper length in the transport direction), the following situation occurs. That is, until the registration sensor completes measuring the size of the paper, image formation is performed according to the image sent from the controller unit, so the formed image is transferred to the secondary transfer unit beyond the paper. When such a printing operation is performed, the amount of waste toner increases due to increased wasted toner consumption, and as a result, there is a risk of the waste toner overflowing from the waste toner container that contains the waste toner. In addition, the secondary transfer roller becomes dirty when the image that extends beyond the paper is transferred by the secondary transfer roller, and as a result, the dirt on the secondary transfer roller is transferred to the subsequent paper, causing problems such as poor image quality.

The present invention was made under these circumstances, and aims to form an image without the image going beyond the edge of the paper when printing on non-standard size paper.

To solve the above problems, the present invention has the following configuration:

(1) An output means for converting image information into an image signal and outputting the image signal based on a timing signal; a notification means for notifying an image size, which is the length of an output section of the image signal; an image forming means for forming an image on an image carrier based on the image signal output from the output means; a feeding means for feeding a recording material loaded in a paper feed section; a transfer means for transferring the image formed on the image carrier to the recording material fed by the feeding means; and a first detection means for detecting the recording material, which is disposed on a recording material transport path between the paper feed section and the transfer means. and a second detection means that is positioned upstream of the first detection means in the transport direction of the recording material on the transport path and at a position farther from the first detection means than the length in the transport direction of a recording material of an upper limit size determined in control when forming an image on a recording material of an unknown size among the recording materials fed by the feeding means, and that detects the recording material, wherein the image forming means outputs the timing signal to the output means in accordance with the timing at which the second detection means detects the first sheet of recording material of a print job.

According to the present invention, when printing on non-standard size paper, images can be formed without the image extending beyond the edge of the paper.

FIG. 1 is a cross-sectional view showing a configuration of an image forming apparatus according to first and second embodiments. A control block diagram illustrating a system configuration of an image forming apparatus according to first and second embodiments. 1 is a timing chart of a conventional printing operation for comparison with an embodiment of the present invention. FIG. 1 is a diagram showing a configuration of a sheet transport path of an MP tray in an image forming apparatus according to first and second embodiments; Timing chart for printing operation in the first embodiment A flowchart showing a control sequence of an image control unit and a paper transport unit according to the first embodiment. Timing chart for printing operation in the second embodiment A flowchart showing a control sequence of an image control unit and a paper transport unit according to a second embodiment.

Below, an embodiment of the present invention will be described in detail with reference to the drawings.

[Configuration of Image Forming Apparatus]
FIG. 1 is a cross-sectional view showing the overall configuration of a laser printer as an example of an image forming apparatus according to the first embodiment. The image forming apparatus shown in FIG. 1 has four image forming stations, which are image forming stations having yellow (Y), magenta (M), cyan (C), and black (Bk) toners from the left in the figure. The suffixes a, b, c, and d in the figures indicate the components of the image forming stations of yellow (Y), magenta (M), cyan (C), and black (Bk), respectively. The image forming stations have the same configuration, and in the following description, the symbols a to d will not be used unless otherwise necessary.

[Image forming unit]
In each image forming station, a photosensitive drum 1, which is an image carrier, is driven by a drive motor (not shown) and rotated in the direction of the arrow (counterclockwise direction) in the figure. A charging roller 2, which is a charging means, contacts the photosensitive drum 1 and uniformly charges the surface of the photosensitive drum 1 while rotating in accordance with the rotation of the photosensitive drum 1. A voltage in which a DC voltage or an AC voltage is superimposed is applied to the charging roller 2, and the photosensitive drum 1 is charged through a contact nip portion between the charging roller 2 and the surface of the photosensitive drum 1. A scanning unit 11, which is an exposure means, is composed of a scanner unit or an LED array that deflects a laser beam by a rotating polygon mirror and scans the surface of the photosensitive drum 1 with the deflected laser beam. The scanning unit 11 irradiates the photosensitive drum 1 with a laser beam 12 modulated based on a video signal (image signal), forming an electrostatic latent image on the surface of the photosensitive drum 1. A developing unit 8, which is a developing means, is composed of a developing roller 4 that contacts the photosensitive drum 1, a developer (toner) 5, and a developer application blade 7, and develops the electrostatic latent image formed on the photosensitive drum 1 by attaching toner to the electrostatic latent image, thereby forming a toner image. A waste toner container 3 collects toner that has not been transferred to an intermediate transfer belt 80 (described later) and remains on the photosensitive drum 1.

The process cartridge 9 is an integrated cartridge that contains the photosensitive drum 1, charging roller 2, waste toner container 3, and developing unit 8 and is detachable from the image forming apparatus. The charging roller 2 and developing roller 4 are connected to a charging voltage power source 20, which is a means for supplying voltage to the charging roller 2, and a developing voltage power source 21, which is a means for supplying voltage to the developing roller 4, respectively. By bringing the charging roller 2 into contact with the photosensitive drum 1 and applying a charging voltage from the charging voltage power source 20 to the charging roller 2, the surface of the photosensitive drum 1 is charged to a uniform potential.

The intermediate transfer belt 80 is supported by three rollers, namely, the secondary transfer facing roller 86, the drive roller 14, and the tension roller 15, which are tension members, and is configured to maintain an appropriate tension. The intermediate transfer belt 80 is driven by the drive roller 14 and moves at approximately the same speed in the direction of the arrow in the figure. The primary transfer roller 81 is disposed at a position facing the photosensitive drum 1 through the intermediate transfer belt 80, and is connected to a primary transfer voltage power source 84, which is a voltage supply means to the primary transfer roller 81. By applying a primary transfer voltage to the primary transfer roller 81, the toner image formed on the photosensitive drum 1 is sequentially transferred to the intermediate transfer belt 80 in contact with the photosensitive drum 1, and a multi-color image is formed on the intermediate transfer belt 80. Furthermore, a charge removing member 23 is disposed downstream of each primary transfer roller 81 in the movement direction of the intermediate transfer belt 80. The drive roller 14, the tension roller 15, the charge removing member 23a, and the secondary transfer facing roller 86 are electrically grounded.

[Cassette feeding section]
A sheet P1, which is a recording material, is placed on the paper feed cassette 16. When feeding the sheet P1 (hereinafter simply referred to as paper), a stepping motor (hereinafter referred to as a paper feed motor) (not shown) drives the cassette pickup roller 17 and raises the paper feed cassette bottom plate 29, pushing it up toward the cassette pickup roller 17. Then, the topmost sheet P1 placed on the raised paper feed cassette bottom plate 29 comes into contact with the cassette pickup roller 17, and the cassette pickup roller 17 rotates, so that the sheets P1 are separated and fed one by one. The fed sheet P1 is conveyed to the registration roller 18, and when a registration sensor (hereinafter referred to as a registration sensor) 35, which is a first detection means for detecting the recording material, detects the leading edge of the sheet P1, the driving of the paper feed motor is stopped, and the conveyance of the sheet P1 is temporarily stopped.

The position where the secondary transfer roller 82 and intermediate transfer belt 80 come into contact is called the secondary transfer section. Sheet P1, which is temporarily stopped by registration rollers (hereinafter referred to as registration rollers) 18, resumes transport (also referred to as re-feeding) when the toner image formed on intermediate transfer belt 80 is transferred to the appropriate position on sheet P1 at the secondary transfer section. In addition, the size of sheet P1 (length in the transport direction; hereinafter referred to as paper size) is determined based on the elapsed time from the time (point) when sheet P1 is re-fed to the time (point) when registration sensor 35 detects the rear end of sheet P1.

Here, the distance from the secondary transfer unit to the registration sensor 35 is defined as distance A. Image formation is started based on the timing when a /TOP signal, which will be described later, is output from the secondary transfer unit, and laser light 12a is irradiated from the scanning unit 11a to form an electrostatic latent image. The distance from the secondary transfer unit to an exposure unit (exposure position) where the laser light 12a is irradiated from the scanning unit 11a on the photosensitive drum 1a of the most upstream image forming station (yellow (Y)) is defined as distance B. Then, the registration sensor used to measure the paper size of sheet P1 is disposed at a position that satisfies the following (Equation 1).
Distance A < distance B (Equation 1)

[MP tray feeding section]
A sheet P2, which is a recording material, is placed on the MP tray 50. When feeding the sheet P2 (hereinafter also simply referred to as paper), the MP tray pickup roller 51 is driven by the above-mentioned paper feed motor (not shown). The uppermost sheet P2 placed on the MP tray 50 abuts against the MP tray pickup roller 51, and is fed into the image forming apparatus by the driven MP tray pickup roller 51. The fed sheet P2 is transported to the registration roller 18 via a transport path for the sheet P2 fed from the MP tray 50, which is provided in the image forming apparatus. The sheet P2 transported to the registration roller 18 is printed in the same manner as the sheet P1 fed from the paper feed cassette 16.

[Secondary transfer unit]
The intermediate transfer belt 80, onto which the toner images formed on the photosensitive drums 1 of the image stations have been transferred, is moved by the drive roller 14, and the toner images on the intermediate transfer belt 80 are transported to a secondary transfer section where a secondary transfer roller 82 and the intermediate transfer belt 80 come into contact with each other. Then, in the secondary transfer section, which is a transfer means, the sheet P (sheet P1 or sheet P2) and the intermediate transfer belt 80 are sandwiched and transported by the secondary transfer roller 82 and a secondary transfer opposing roller 86 installed opposite the secondary transfer roller 82. Then, a voltage is applied from a secondary transfer voltage power source 85 to the secondary transfer roller 82, so that the toner image on the intermediate transfer belt 80 is transferred to the sheet P.

[Fuser unit]
The sheet P onto which the toner image has been transferred in the secondary transfer section is conveyed to a fixing section 19, which is a fixing means, and is heated and pressurized in the fixing section 19, so that the toner image is fixed to the sheet P. The fixing section 19 has a fixing belt 19a and a pressure roller 19b, and the pressure roller 19b contacts the fixing belt 19a with a belt guide member (not shown) and a predetermined pressure contact force to form a fixing nip section. In a state in which the temperature of the fixing nip section is adjusted to a predetermined temperature, the sheet P onto which the unfixed toner image has been transferred is introduced between the fixing belt 19a and the pressure roller 19b in the fixing nip section with the image surface facing upward, i.e., facing the fixing belt 19a. Then, in the fixing nip section, the sheet P is conveyed through the fixing nip section while the image surface of the sheet P is in close contact with the outer surface of the fixing belt 19a. In the process in which the sheet P is conveyed through the fixing nip section by the fixing belt 19a, the toner image on the sheet P is heated by the fixing belt 19a and is thermally fixed onto the sheet P. The sheet P on which the toner image has been fixed is then discharged onto the discharge tray 36, and a series of printing operations is completed.

[System Configuration of Image Forming Apparatus]
2 is a control block diagram for explaining the system configuration of the image forming apparatus. In FIG. 2, the image forming apparatus includes a controller unit 201 and an engine unit 202. The controller unit 201 can communicate with the host computer 200, which is an external device, and the engine unit 202. When the controller unit 201 receives a print command including image information (print data) and printing conditions from the host computer 200, it develops bitmap data (image data) based on the received print data. When the controller unit 201 finishes developing the bitmap data, it transmits image size information and a print reservation command to the CPU 204 of the engine unit 202 via the video interface unit 203 in accordance with the print command from the host computer 200. Then, the controller unit 201 transmits a print start command to the CPU 204 when the engine unit 202 becomes ready to print (ready to form an image).

The engine unit 202 is composed of a video interface unit 203, a CPU 204, an image processing GA (gate array) 205, an image control unit 206, a fixing control unit 207, and a paper transport unit 208. The CPU 204, the image processing GA 205, the image control unit 206, the fixing control unit 207, and the paper transport unit 208 are connected via a bidirectional bus, and transmit and receive data to and from each other via the bidirectional bus. The video interface unit 203 relays signals between the engine unit 202 and the controller unit 201. The image control unit 206 controls the image forming unit described above, the fixing control unit 207 controls the fixing unit 19 described above, and the paper transport unit 208 controls the cassette feed unit and the MP tray feed unit described above. When the CPU 204 receives a print reservation command from the controller unit 201, it prepares to execute a print job and waits for a print start command to be sent from the controller unit 201. When the CPU 204 receives a print start command from the controller unit 201, it instructs each control unit (image control unit 206, fixing control unit 207, paper transport unit 208) to start a print operation (also called a print operation) according to the information in the print reservation command that has already been received.

The CPU 204 has a ROM (not shown) and a RAM (not shown), and the ROM stores the control programs and data executed by the CPU 204, and the RAM is used by the control programs executed by the CPU 204 to temporarily store information. The CPU 204 also has a timer. The image control unit 206 and the paper transport unit 208 also have a CPU (not shown), a ROM (not shown), a RAM (not shown), and a timer for measuring time. And, like the CPU 204, the ROM stores the control programs and data, and the RAM is used by the control programs to temporarily store information.

When the image control unit 206, which is a control means, receives an instruction to start a print operation from the CPU 204, it starts preparing for image formation. When the CPU 204 receives a notification from the image control unit 206 that preparation for image formation is complete, it outputs a /TOP signal, which is a timing signal that serves as a reference for outputting a video signal, to the controller unit 201 via the video interface unit 203. When the controller unit 201, which is an output means, receives the /TOP signal from the CPU 204, it outputs a video signal generated from bitmap data based on the timing of receiving the /TOP signal to the image processing GA 205 via the video interface unit 203. When the image processing GA 205 receives a video signal from the controller unit 201, it converts the received video signal into data for image formation and transmits it to the image control unit 206. The image control unit 206 performs image formation based on the data for image formation received from the image processing GA 205. When performing continuous printing, as described below, the image control unit 206 determines the image formation interval, which is the time interval (period) at which the /TOP signal is output, based on the paper size of the sheet P or the image size, described below, received from the controller unit 201. Then, the image control unit 206 instructs the CPU 204 to send the /TOP signal according to the determined image formation interval.

The paper transport unit 208, which is a feeding means, starts the feeding operation when it receives an instruction to start the printing operation from the CPU 204. The paper transport unit 208 drives a paper feed motor (not shown) to transport the sheet P placed on the MP tray 50 or the paper feed cassette 16 (hereinafter also referred to as the paper feed unit) to the secondary transfer unit, and detects the paper size of the sheet P using the registration sensor 35 (Figure 1). Note that the paper size of the sheet P placed on the paper feed unit is undefined from the start of the printing operation until the registration sensor 35 detects the paper size.

When the fixing control unit 207 receives an instruction to start a printing operation from the CPU 204, it starts preparing for the fixing process. The fixing control unit 207 starts adjusting the temperature according to the paper type information (e.g., the thickness of the sheet P) set in the print reservation command, in accordance with the timing when the sheet P on which the secondary transfer has been performed is transported to the fixing unit 19. Then, after fixing the image (toner image) on the sheet P, the fixing control unit 207 transports the sheet P to the discharge tray 36 outside the machine and discharges it.

Printing Operation Overview
Next, a printing operation of the image forming apparatus for a sheet P of unknown paper size (also called non-standard size) at the time when the host computer 200 instructs printing on the sheet P placed on the MP tray 50 (at the start of a print job) will be described. In this embodiment, the minimum required interval between the preceding sheet P and the succeeding sheet P (hereinafter referred to as the paper interval) for performing the printing operation is 40 mm. In addition, in the non-standard size printing control in the image forming apparatus of this embodiment, the upper limit size of the non-standard size sheet P is A4 size. In the following description, the image size formed by the controller unit 201 is A4 size (length in the transport direction: 297 mm), and the size of the sheet P actually placed on the MP tray 50 is A5 landscape size (paper length in the transport direction: 148 mm).

[Outline of conventional printing operation]
First, the printing operation of a conventional image forming apparatus that performs printing according to the paper size of the sheet P detected by the registration sensor 35 will be described with reference to Fig. 3. Fig. 3 is a timing chart showing the signal states related to the printing operation when the paper size of the sheet P placed on the MP tray 50 is unknown at the time when the printing operation is instructed and continuous printing is performed. In Fig. 3, the vertical axis indicates, from the top, (a) the /TOP signal, (b) the video signal, (c) the paper feed start signal, and (d) the state of the registration sensor 35, and the horizontal axis indicates time.

In (a), /TOP signals 301, 302, and 303 are signals transmitted from the engine unit 202 to the controller unit 201. Also, Time 304, Time 305, and Tpaper 306 indicate the image formation interval, which is the interval at which the CPU 204 outputs the /TOP signal. In (b), hatched outputs 311, 313, and 315 indicate sections (output sections) in which image formation is performed based on the video signal from the controller unit 201, and non-outputs 312, 314, and 316 indicate sections in which image formation is not performed based on the video signal. In (c), feed start signals 321, 322, and 323 are signals indicating the feed start timing of the sheet P placed on the MP tray 50. In (d), ON and OFF indicate a state in which the register sensor 35 detects the sheet P and a state in which the sheet P is not detected, respectively. The timings 331 and 333 at which the registration sensor 35 changes from an OFF state to an ON state indicate the timings at which the registration sensor 35 detects the leading edge of the sheet P being transported. Meanwhile, the timings 332 and 334 at which the registration sensor 35 changes from an ON state to an OFF state indicate the timings at which the registration sensor 35 detects the trailing edge of the sheet P being transported. The hatched feed motor stop section 335 indicates a section (period) during which the drive of the feed motor is stopped until the transport of the sheet P is resumed (timings 337 and 338) in accordance with the position at which the toner image formed on the intermediate transfer belt 80 is transferred to the sheet P.

When the engine unit 202 receives a print start command from the controller unit 201, it performs a preparation operation for the print operation. Then, when the engine unit 202 completes the print preparation operation, it outputs a /TOP signal 301 for the first sheet P to the controller unit 201, and thereafter outputs /TOP signals 302, 303 for the subsequent sheets P so that the distance between the sheets P is the desired interval. When the engine unit 202 receives a print start command from the controller unit 201, it starts the operation of feeding the sheet P from the MP tray 50 at a predetermined timing (feed start signals 321, 322, 323). The engine unit 202 temporarily stops the conveyance of the sheet P when the sheet P reaches the registration sensor 35 (timings 331, 333) (feed motor stop section 335). Then, the engine unit 202 resumes conveying the sheet P at the timing when the toner image formed on the intermediate transfer belt 80 is transferred to an appropriate position on the sheet P at the secondary transfer unit (timings 337 and 338), and the toner image is transferred to the sheet P.

In this embodiment, before transmitting a print start command to the CPU 204 of the engine unit 202, the controller unit 201 notifies the CPU 204 of the engine unit 202 of the image size of the image that the controller unit 201 will output to the engine unit 202. The CPU 204 notifies the image control unit 206 of the notified image size. Thereafter, the controller unit 201 transmits a print start command to the CPU 204 of the engine unit 202.

The timing chart shown in FIG. 3 will be described in detail. When the CPU 204 of the engine unit 202 receives a notification from the image control unit 206 that image formation preparation is complete, it outputs a /TOP signal 301 for the first sheet P to the controller unit 201. At this point, the paper size of the sheet P placed on the MP tray 50 is unknown. Therefore, the image control unit 206 sets the paper size of the sheet P to A4 size, which is the upper limit size of non-standard size control, and sets the output interval T, which is the time interval for outputting the /TOP signal for the subsequent sheet P, to Time 304. In addition, since the image formation size notified from the host computer 200 is A4 size as described above, the controller unit 201 outputs a video signal 311 equivalent to A4 size to the engine unit 202. The image control unit 206 performs image formation based on the video signal 311 output from the controller unit 201.

The output interval Timage 304 shown in (a) is specifically the time required for an A4 size sheet P (paper length in the transport direction is 297 mm) to be transported along the transport path at a predetermined transport speed while maintaining the paper interval (40 mm) with the succeeding sheet P. For convenience of explanation, the output interval T will be expressed as a length rather than a time. For example, the output interval Timage is expressed as a length of 337 mm, which is the sum of the A4 size (length in the paper transport direction: 297 mm) and the paper interval (40 mm). The image control unit 206 determines the output interval T of the /TOP signal, and instructs the CPU 204 to send a /TOP signal every time the output interval T has elapsed, and the CPU 204 outputs the /TOP signal to the controller unit 201.

The paper transport unit 208 feeds the first sheet P from the MP tray 50 in response to the paper feed start signal 321. When the fed sheet P reaches the register sensor 35 (timing 331), the paper transport unit 208 stops the paper feed motor (paper feed motor stop section 335) and temporarily stops the transport of the sheet P. Thereafter, the paper transport unit 208 resumes the transport of the sheet P at the timing (timing 337) when the toner image formed on the intermediate transfer belt 80 is transferred to an appropriate position on the sheet P by the secondary transfer unit, and transfers the toner image on the intermediate transfer belt 80 to the sheet P at the secondary transfer unit. Then, the paper transport unit 208 determines the paper size of the first sheet P at the timing (timing 332) when the register sensor 35 detects the rear end of the sheet P (paper size detection timing 336) and notifies the image control unit 206 of the paper size of the sheet P.

The paper transport unit 208 can determine (detect) the paper size, which is the length of the sheet P in the transport direction, by multiplying the time from when the transport of the sheet P is resumed until the registration sensor 35 detects the rear end of the sheet P by the transport speed of the sheet P. The time from when the transport of the sheet P is resumed until the registration sensor 35 detects the rear end of the sheet P is also the time from timing 331 to timing 332 shown in FIG. 3 minus the time of the feed motor stop section 335. In addition, while the paper size of the sheets P stacked on the MP tray 50 is unknown, the feeding of the sheets P is controlled based on the A4 size so that the sheets P can be transported normally even if A4 size sheets P, the maximum size in the non-standard size print control described above, are stacked.

Based on the paper size of the first sheet P (A5 landscape in this embodiment) notified by the paper transport unit 208, the image control unit 206 sets the output interval T of the /TOP signal for the subsequent sheet P to Tpaper 306. Specifically, the output interval Tpaper 306 is the time required for a sheet P with a paper size of A5 landscape (paper length in the transport direction 148 mm) to be transported on the transport path at a predetermined transport speed while maintaining the paper distance (40 mm) from the subsequent sheet P. Note that, hereinafter, the output interval Tpaper is expressed not as time but as the length of A5 landscape (paper length 148 mm) + paper distance (40 mm).

In an image forming apparatus configured to satisfy the above-mentioned condition (Formula 1), when the size of the image to be formed is the same as the size of the sheet P loaded in the paper feed section, image formation on the first sheet P is necessarily completed at the timing 336 when the size of the sheet P is determined. In an image forming apparatus having such a configuration, an image is first formed based on a video signal, and then the sheet P is fed from the paper feed section. Therefore, as can be seen from FIG. 3, during non-standard size printing control, at the timing 336 when the paper size of the first sheet P loaded on the MP tray 50 is determined by the registration sensor 35, image formation on the third sheet P is already being performed. Therefore, the output interval T when the /TOP signals 302 and 303 are output is the above-mentioned time interval Time 304 and Time 305 because the paper size of the first sheet P is unknown. In addition, the video signal outputs 311 and 313 are also performed in the A4 size specified by the controller unit 201.

If, at the time of paper size detection timing 336, the output interval Tpaper 306 has already elapsed since the /TOP signal 303 was output, the image control unit 206 instructs the CPU 204 at that time to output a /TOP signal (not shown) for the next sheet P. On the other hand, if, at the time of paper size detection timing 336, the output interval Tpaper 306 has not elapsed since the /TOP signal 303 was output, the image control unit 206 performs the following process. That is, when the output interval Tpaper 306 has elapsed, the image control unit 206 instructs the CPU 204 to output the /TOP signal. Thereafter, when performing continuous printing, the image control unit 206 sets the output interval T of the /TOP signal to Tpaper 306 and performs the printing operation.

The size of the image to be formed is determined at the timing 336 when the paper size is detected. The image control unit 206 determines whether a time equivalent to the paper size of the sheet P (the time required for the sheet P of the determined paper size to be conveyed) has elapsed since the /TOP signal (303) as follows. That is, the image control unit 206 makes a determination based on the paper size of the sheet P calculated at the paper size detection timing 336 and the time from the timing when the /TOP signal 303 is output to the paper size detection timing 336. If the image control unit 206 determines that a time equivalent to the paper size of the sheet P has not elapsed since the /TOP signal 303 was output, the video signal output 315 is performed for the detected paper size of the sheet P. On the other hand, if the image control unit 206 determines that a time equivalent to the paper size of the sheet P has elapsed since the /TOP signal 303 was output, the video signal output 315 is performed for the paper size of the detected sheet P. On the other hand, if the image control unit 206 determines that a time equivalent to the paper size of the sheet P has elapsed since the /TOP signal 303 was output, the video signal output is stopped at the paper size detection timing 336 and the non-output 316 is set. In this case, the video signal output of the controller unit 201 that is attempting to form an A4 size image is not output in accordance with the paper size of the sheet P, which is referred to as "masking the image." In addition, the image size that is finally output after masking the image is referred to as the "masked image size."

As described above, in the example of non-standard size printing control shown in FIG. 3, the timing when the non-standard size paper size is determined (paper size detection timing 336 in the figure) is during image formation of the third sheet P. In other words, for the first and second sheets P, images of a size larger than the paper size (A5 landscape) of the sheets P actually stacked on the MP tray 50 are formed. If continuous printing is performed in this situation, after the toner images of the first and second sheets P are transferred at the secondary transfer section, toner that could not be transferred to the sheet P remains on the intermediate transfer belt 80 and is collected in the waste toner container 3 of the process cartridge 9. In addition, the toner image that was not transferred to the sheet P on the intermediate transfer belt 80 adheres to the secondary transfer roller 82, and the toner image that adheres is transferred to the next sheet P, soiling the next sheet P and causing image defects.

[Configuration of the transport path from the MP tray to the registration sensor in this embodiment]
Next, in order to prevent the situation as shown in Figure 3 described above from occurring, the printing operation of this embodiment will be described in which image formation is performed from the first sheet onwards according to the paper size of the sheet P loaded on the MP tray 50, thereby preventing the generation of waste toner and toner stains on the secondary transfer roller 82.

4 is a diagram showing the configuration of the transport path of the sheet P loaded on the MP tray 50 from the MP tray 50 to the registration sensor 35 in this embodiment. As shown in FIG. 4, an MP tray transport sensor 52 (second detection means) for detecting the sheet P transported from the MP tray 50 is disposed in the middle of the transport path from the MP tray 50 to the registration sensor 35. The MP tray transport sensor 52 is installed at a position away from the registration sensor 35 in the direction toward the MP tray 50 (upstream side in the transport direction of the sheet P) by more than the upper limit size (length in the transport direction is D) of the non-standard size control. That is, if the distance from the registration sensor 35 to the MP tray transport sensor 52 is distance C, the length (distance) D in the transport direction and distance C satisfy the following (Equation 2).
Distance C>Distance D... (Formula 2)

The upper limit size for non-standard size control in this embodiment is A4 size (paper length in the transport direction: 297 mm), and the MP tray transport sensor 52 is installed at a position 297 mm or more away from the registration sensor 35 in the direction of the MP tray 50 (upstream in the transport direction).

[Outline of the printing operation of this embodiment]
Next, an outline of the printing operation of this embodiment will be described. Fig. 5 is a timing chart showing the signal states related to the printing operation when continuous printing of non-standard size sheets P is performed using the detection result of the MP tray transport sensor 52 described above. In Fig. 5, the vertical axis indicates, from the top, (a) the /TOP signal, (b) the video signal, (c) the paper feed start signal, (d) the state of the register sensor 35, and (e) the state of the MP tray transport sensor 52, and the horizontal axis indicates time.

In (e), ON and OFF indicate the states in which the MP tray transport sensor 52 detects the sheet P and the states in which the MP tray transport sensor 52 does not detect the sheet P, respectively. The timings 551, 553, and 555 at which the MP tray transport sensor 52 changes from the OFF state to the ON state indicate the timings at which the MP tray transport sensor 52 detects the leading edge of the sheet P being transported. Meanwhile, the timings 552, 554, and 556 at which the MP tray transport sensor 52 changes from the ON state to the OFF state indicate the timings at which the MP tray transport sensor 52 detects the trailing edge of the sheet P being transported. The meanings of the other signals and how to view the diagram are the same as those in FIG. 3 described above, and so a description thereof will be omitted.

When the engine unit 202 receives a print start command from the controller unit 201, it performs a preparation operation for the printing operation. The paper transport unit 208 feeds the first sheet P from the MP tray 50 in response to a paper feed start signal 521. The MP tray transport sensor 52 installed on the transport path detects the leading edge of the first sheet P that has been fed (timing 551). The paper transport unit 208 starts measuring the size of the sheet P from the timing when the MP tray transport sensor 52 detects the leading edge of the sheet P (paper leading edge detection timing 557). The paper transport unit 208 can determine (detect) the paper size, which is the length of the sheet P in the transport direction, by multiplying the transport speed of the sheet P by the time from when the MP tray transport sensor 52 detects the leading edge of the sheet P to when it detects the rear end of the sheet P.

When the image control unit 206 confirms that the MP tray transport sensor 52 has detected the leading edge of the first sheet P and that all other image formation conditions have been prepared, it notifies the CPU 204. When the CPU 204 of the engine unit 202 receives a notification from the image control unit 206 that the leading edge of the first sheet P has been detected by the MP tray transport sensor 52 and that all other image formation conditions have been prepared, it outputs a /TOP signal 501 for the first sheet P. At this point, the paper size of the first sheet P is unknown, so the controller unit 201 forms an A4 size image.

When the MP tray transport sensor 52 detects the rear end of the first sheet P (timing 552), the paper transport unit 208 ends the size measurement of the sheet P and notifies the image control unit 206 of the detected paper size of the sheet P (paper size detection timing 558). After the paper size of the sheet P is determined, the paper transport unit 208 also determines the output timing of the feed start signals 522 and 523 for the subsequent sheet P at a timing according to the determined paper size.

The image control unit 206 masks the image so that the video signal is not output (512) when a time corresponding to the paper size of the sheet P notified by the paper transport unit 208 has elapsed from the output timing of the /TOP signal 501 for the first sheet. The image control unit 206 also sets the output interval T of the /TOP signals 502, 503 for the second and subsequent sheets P as the paper size of the sheet P notified by the paper transport unit 208 + the paper interval, that is, the time interval Tpaper 504, 505.

As for the subsequent operations, similar to those in FIG. 3 described above, when the fed sheet P reaches the registration sensor 35 (timing 531), the paper transport unit 208 stops driving the paper feed motor (paper feed motor stop section 537) and temporarily stops transporting the sheet P. Thereafter, the paper transport unit 208 resumes transporting the sheet P (timing 538) at the timing when the toner image formed on the intermediate transfer belt 80 is transferred to the appropriate position on the sheet P at the secondary transfer unit, and the toner image is transferred to the sheet P.

[Image Formation Control Sequence]
6A and 6B are flowcharts showing the control sequence of non-standard size print control in this embodiment. Fig. 6A is a flowchart showing the control sequence of transport control for transporting the sheet P stacked on the MP tray 50 to the registration sensor 35. Fig. 6B is a flowchart showing the control sequence of image formation control for the non-standard size sheet P.

First, FIG. 6(a) will be described in detail. The process shown in FIG. 6(a) is started when the CPU 204 receives an image size designation command, a print reservation command, or a print start command from the controller unit 201, and is executed by the paper transport unit 208.

In step (hereinafter, S) 600, the paper transport unit 208 feeds the first sheet P stacked on the MP tray 50. In S601, since the paper size of the fed sheet P is unknown, the paper transport unit 208 sets the post-mask image size to A4 size, which is the maximum size in non-standard size print control, and initializes the image mask size.

In S602, the paper transport unit 208 determines whether the MP tray transport sensor 52 has detected the leading edge of the sheet P fed from the MP tray 50 (MP tray transport sensor ON?). If the paper transport unit 208 determines that the MP tray transport sensor 52 has detected the leading edge of the sheet P fed from the MP tray 50 and has turned ON, the process proceeds to S603. On the other hand, if the paper transport unit 208 determines that the MP tray transport sensor 52 has not detected the sheet P fed from the MP tray 50 (is OFF), the process returns to S602.

In S603, the paper transport unit 208 starts measuring the size of the sheet P whose leading edge has been detected (measuring the paper length in the transport direction) (start paper size measurement). Specifically, the paper transport unit 208 resets and starts a timer to measure the paper size of the sheet P.

In S604, the paper transport unit 208 determines whether the MP tray transport sensor 52 has detected the rear end of the sheet P fed from the MP tray 50 (MP tray transport sensor OFF?). If the paper transport unit 208 determines that the MP tray transport sensor 52 has detected the rear end of the sheet P fed from the MP tray 50 and has turned OFF, the process proceeds to S606. On the other hand, if the paper transport unit 208 determines that the MP tray transport sensor 52 has not detected the rear end of the sheet P fed from the MP tray 50 (is ON), the process proceeds to S605.

In S605, the paper transport unit 208 determines whether the registration sensor 35 has detected the leading edge of the sheet P fed from the MP tray 50 (is the registration sensor ON?). If the paper transport unit 208 determines that the registration sensor 35 has detected the leading edge of the sheet P fed from the MP tray 50 and has turned ON, the process proceeds to S608. On the other hand, if the paper transport unit 208 determines that the registration sensor 35 has not detected the leading edge of the sheet P fed from the MP tray 50 (is OFF), the process returns to S604.

In S606, the paper transport unit 208 stops the timer started in S603 to measure the paper size, ends the measurement of the paper size of the sheet P fed from the MP tray 50, and calculates the paper size of the sheet P fed from the MP tray 50. Specifically, the paper transport unit 208 stops the timer for measuring the paper size, and calculates the paper size of the sheet P (paper length in the transport direction) by multiplying the acquired timer value by the transport speed of the sheet P. In S607, the paper transport unit 208 sets the paper size of the sheet P calculated in S606 as the post-mask image size, and ends the process.

In S608, the paper transport unit 208 stops the timer for measuring the paper size that was started in S603, and ends the measurement of the paper size of the sheet P fed from the MP tray 50. In S609, the paper transport unit 208 sets the image size specified by the controller unit 201 to the post-mask image size. Note that in this embodiment, the image size specified by the controller unit 201 is A4 size.

As explained in the above (Formula 2), if the register sensor 35 detects the leading edge of the sheet P before the MP tray transport sensor 52 detects the trailing edge of the sheet P, this indicates that the sheet P being transported is longer than the upper limit size (A4 size) of non-standard size control. In this case, even if the masked image size described below is set to the upper limit size (A4 size) of non-standard size control, the formed image will not protrude from the sheet P. Therefore, in this embodiment, if the register sensor 35 detects the leading edge of the sheet P before the MP tray transport sensor 52 detects the trailing edge of the sheet P, the A4 size specified by the controller unit 201 is set as the masked image size.

Next, FIG. 6(b) will be described in detail. The process shown in FIG. 6(b) is started when the CPU 204 receives an image size designation command, a print reservation command, or a print start command from the controller unit 201, and is executed by the image control unit 206.

In S620, the image control unit 206 determines whether the sheet P stacked on the MP tray 50 has been fed and the leading edge of the sheet P has been detected by the MP tray transport sensor 52 (MP tray transport sensor ON?) as described in FIG. 6A. If the image control unit 206 determines that the MP tray transport sensor 52 has detected the leading edge of the sheet P fed from the MP tray 50 and has turned ON, the process proceeds to S621. On the other hand, if the image control unit 206 determines that the MP tray transport sensor 52 has not detected the sheet P fed from the MP tray 50 (is OFF), the process returns to S620.

In S621, the image control unit 206 determines whether the preparations required for other image formation have been completed (image formation preparation completed?). The preparations shown here refer to whether the units required for image formation, such as each image forming station and the scanning unit 11, are ready. If the image control unit 206 determines that the preparations required for other image formation have been completed, it advances the process to S622, and if it determines that the preparations required for other image formation have not been completed, it returns the process to S621.

In S622, the image control unit 206 notifies the CPU 204 that the preparations required for image formation have been completed, and upon receiving the notification of completion of image formation preparations from the image control unit 206, the CPU 204 transmits a /TOP signal to the controller unit 201 (outputs a /TOP signal). In S623, the image control unit 206 starts a mask start timer to start image masking.

In S624, the image control unit 206 refers to the mask start timer to determine whether a time equivalent to the paper size set in the masked image size has elapsed (has a time equivalent to the masked image size elapsed?). As described in FIG. 6A, the masked image size is set to the initial value A4 size set in S601 until the measurement of the paper size of the sheet P is completed. After that, when the MP tray transport sensor 52 detects the rear end of the sheet P and the size detection of the sheet P is completed, in the above-mentioned processing of S607, the measurement result of the detected paper size of the sheet P is set as the masked image size. Therefore, during the processing of S624 in which the mask start timer determines whether a time equivalent to the A4 size has elapsed, the masked image size is updated from the A4 size to the paper size based on the measurement result by the MP tray transport sensor 52 (in this embodiment, the A5 landscape size). If the image control unit 206 determines that the time equivalent to the paper size set in the masked image size has elapsed, the process proceeds to S625, and if the image control unit 206 determines that the time equivalent to the paper size set in the masked image size has not elapsed, the process returns to S624. In S625, the image control unit 206 sets an image mask, switches the video signal output to non-output, and ends the process.

As described above, in non-standard size printing control, even if the image to be formed is larger than the paper size of the fed sheet P, image formation is performed from the printing of the first sheet P so that the image does not extend beyond the paper. This reduces the generation of waste toner and prevents image defects.

In this embodiment, the size of the sheet P is measured by the MP tray transport sensor 52, and the measured paper size is set as the masked image size. This can be controlled in the same way by notifying the image control unit 206 from the paper transport unit 208 of the time it takes for the MP tray transport sensor 52 to change from the ON state to the OFF state, and the timing when the MP tray transport sensor 52 changes to the ON state and OFF state.

In addition, in this embodiment, the maximum size of non-standard sizes in non-standard size print control is A4 size, but this is not necessarily synonymous with the maximum size supported by the image forming device. For example, an image forming device whose maximum supported paper size is LGL (Legal) (paper size: 355.6 mm) has non-standard size print mode 1 with the maximum size being LGL size, and non-standard size print mode 2 with the maximum size being A4 size. In this way, there are no particular restrictions on the maximum supported size and the size maximum of non-standard print control.

As described above, this embodiment allows you to print on non-standard size paper without the image going beyond the edge of the paper.

In the first embodiment, in the non-standard size printing control when the paper size of the sheet placed on the MP tray is unknown, one of the conditions for starting image formation is the detection of the leading edge of the sheet by the MP tray transport sensor that detects the size of the sheet. In the second embodiment, unlike the first embodiment, one of the conditions for starting image formation in the non-standard size printing control is the determination of the paper size of the sheet. Note that the configuration of the image forming device and the system configuration are the same as those in the first embodiment, and the same reference numerals are used for the same members and control units, and detailed explanations are omitted.

[Outline of the printing operation of this embodiment]
Next, as in the first embodiment, the printing operation of the image forming apparatus for a sheet P whose paper size is unknown (irregular size) at the time when the host computer 200 instructs the printing operation of the sheet P placed on the MP tray 50 (at the start of the print job) will be described. The minimum paper space between the sheets P required for the printing operation is 40 mm, as in the first embodiment. In addition, in the irregular size print control in the image forming apparatus of this embodiment, the upper limit size of the irregular size sheet P is A4 size, as in the first embodiment. In the following, the image size formed by the controller unit is A4 size (paper length in the transport direction: 297 mm), and the size of the sheet P actually placed on the MP tray 50 is A5 landscape size (paper length in the transport direction: 148 mm).

Figure 7 is a timing chart showing the signal states related to a printing operation in which non-standard size sheets P are continuously printed using the detection results of the MP tray transport sensor 52. As with Figure 5 of the first embodiment, the vertical axis of Figure 7 shows, from top to bottom, (a) the /TOP signal, (b) the video signal, (c) the feed start signal, (d) the state of the registration sensor 35, and (e) the state of the MP tray transport sensor 52, while the horizontal axis shows time. The meaning of each signal and how to read the figure are the same as in Figures 3 and 5 of the first embodiment, and so a description thereof will be omitted here.

When the engine unit 202 receives a print start command from the controller unit 201, it performs a preparation operation for the print operation. The paper transport unit 208 feeds the first sheet P from the MP tray 50 in response to a paper feed start signal 721. The MP tray transport sensor 52 installed on the transport path detects the leading edge of the fed first sheet P (timing 751). The paper transport unit 208 starts measuring the size of the sheet P from the timing (timing 751) when the MP tray transport sensor 52 detects the leading edge of the sheet P.

After that, when the MP tray transport sensor 52 detects the rear end of the first sheet P (timing 752), the paper transport unit 208 ends the size measurement of the sheet P and notifies the image control unit 206 of the detected paper size of the sheet P (paper size detection timing 757). The paper transport unit 208 can determine (detect) the paper size, which is the length of the sheet P in the transport direction, by multiplying the time from when the MP tray transport sensor 52 detects the leading edge of the sheet P to when it detects the trailing edge of the sheet P by the transport speed of the sheet P.

When the image control unit 206 confirms that the paper size of the first sheet P has been determined and that all other image formation conditions have been prepared, it notifies the CPU 204. When the CPU 204 of the engine unit 202 receives a notification from the image control unit 206 that the paper size of the first sheet P has been determined and that all other image formation conditions have been prepared, it outputs a /TOP signal 701 for the first sheet P. At this point, since the paper size of the first sheet P has already been determined, the engine unit 202 controls the controller unit 201 to mask the A4 size image formed by the controller unit 201 to A5 landscape size. In other words, it controls the output 711 of the video signal for image formation to be A5 landscape size according to the paper size of the sheet P.

The paper transport unit 208 uses the paper size of the first sheet P to determine the output timing of the feed start signals 722, 723 for the subsequent sheets P. The image control unit 206 sets the output interval T of the /TOP signals 702, 703 for the subsequent sheets P after the first sheet P as the paper size notified by the paper transport unit 208 + paper interval, that is, the time interval Tpaper 704, 705.

As for the subsequent operations, similar to FIG. 3 of the first embodiment, when the fed sheet P reaches the registration sensor 35 (timing 731), the paper transport unit 208 stops driving the paper feed motor (paper feed motor stop section 737) and temporarily stops transporting the sheet P. Thereafter, the paper transport unit 208 resumes transporting the sheet P (timing 738) at the timing when the toner image formed on the intermediate transfer belt 80 is transferred to an appropriate position on the sheet P at the secondary transfer unit, and the toner image is transferred to the sheet P.

[Image Formation Control Sequence]
8A and 8B are flowcharts showing the control sequence of non-standard size print control in this embodiment. Fig. 8A is a flowchart showing the control sequence of transport control for transporting the sheet P stacked on the MP tray 50 to the registration sensor 35. Fig. 8B is a flowchart showing the control sequence of image formation control for the non-standard size sheet P.

The process shown in FIG. 8(a) is started when the CPU 204 receives an image size designation command, a print reservation command, or a print start command from the controller unit 201, and is executed by the paper transport unit 208. The transport control flowchart shown in FIG. 8(a) is the same as the control described in FIG. 6(a) of the first embodiment, and a description thereof will be omitted here.

Next, the process shown in FIG. 8(b) will be described in detail. The process shown in FIG. 8(b) is started when the CPU 204 receives an image size designation command, a print reservation command, or a print start command from the controller unit 201, and is executed by the image control unit 206.

In S820, the image control unit 206 determines whether the measurement of the paper size of sheet P has been completed (paper size measurement completed?) by the process shown in FIG. 8A. Here, the process shown in FIG. 8A refers to the process of S806 in which the MP tray transport sensor 52 detects the rear end of sheet P and ends the measurement of the paper size, or the process of S808 in which the registration sensor 35 detects the leading end of sheet P and ends the measurement of the paper size. If the image control unit 206 determines that the measurement of the paper size of sheet P has been completed, the process proceeds to S821, and if it determines that the measurement of the paper size of sheet P has not been completed, the process returns to S820.

The processes in steps S821 to S823 are similar to those in steps S621 to S623 in FIG. 6(b) of the first embodiment, and therefore will not be described.

In S824, the image control unit 206 refers to the mask start timer to determine whether a time equivalent to the paper size set in the masked image size has elapsed (has a time equivalent to the masked image size elapsed?). The masked image size is set to the initial value of A4 size set in S801 of FIG. 8A until the measurement of the paper size of the sheet P is completed. In this embodiment, after the measurement of the paper size of the sheet P shown in FIG. 8A is completed and the masked image size is set in the processing of S807 or S809, the /TOP signal is output in the processing of S822, and then S824 is started. Therefore, the masked image size is not set to the initial value, but is set to an image size corresponding to the detected paper size of the sheet P. If the image control unit 206 determines that a time equivalent to the paper size set in the masked image size has elapsed, the process proceeds to S825, and if the image control unit 206 determines that a time equivalent to the paper size set in the masked image size has not elapsed, the process returns to S824. In S825, the image control unit 206 sets the image mask, switches the video signal output to non-output, and ends the process.

As described above, in non-standard size printing control, even if the image to be formed is larger than the paper size of the fed sheet P, image formation is performed so that the image does not extend beyond the paper from the printing of the first sheet P. This reduces the generation of waste toner and prevents image defects.

In this embodiment, unlike the first embodiment, image formation is performed after the paper size of the sheet P (masked image size) is determined. Therefore, the control of this embodiment forms the image so that the image does not extend beyond the paper, even if sheets P of different paper sizes are mixed in the MP tray 50. As a result, the generation of waste toner is suppressed, and image defects can be prevented.

In addition, in this embodiment, the size of the sheet P is measured by the MP tray transport sensor 52, and the measured paper size is set as the masked image size. This can be achieved by notifying the image control unit 206 from the paper transport unit 208 of the time it takes for the MP tray transport sensor 52 to change from the ON state to the OFF state, and the timing when the MP tray transport sensor 52 is turned ON and OFF.

Furthermore, in this embodiment, the maximum size of the non-standard size print control is A4 size, but this is not necessarily synonymous with the maximum size supported by the image forming device. For example, an image forming device whose maximum supported paper size is LGL (Legal) (paper size: 355.6 mm) has non-standard size print mode 1 with the maximum size being LGL size, and non-standard size print mode 2 with the maximum size being A4 size. In this way, there are no particular restrictions on the maximum supported size and the size maximum of the non-standard print control.

As described above, this embodiment allows you to print on non-standard size paper without the image going beyond the edge of the paper.

35 Registration sensor
50 MP tray 52 MP tray transport sensor 201 Controller unit 206 Image control unit 208 Paper transport unit

Claims (12)

an output means for converting image information into an image signal and outputting the image signal based on a timing signal;
a notification means for notifying an image size, which is the length of an output section of the image signal;
an image forming means for forming an image on an image carrier based on the image signal output from the output means;
A feeding means for feeding the recording material loaded in the paper feeding section;
a transfer means for transferring the image formed on the image carrier onto a recording material fed by the feeding means;
a first detection unit that is disposed on a recording material conveyance path between the paper feed unit and the transfer unit and detects the recording material;
a second detection means that is disposed upstream of the first detection means in the recording material conveying direction on the conveying path and at a position farther away from the first detection means than a length in the conveying direction of a recording material of an upper limit size determined in control when an image is formed on a recording material of an unknown size among the recording materials fed by the feeding means, and that detects the recording material;
Equipped with
The image forming apparatus according to claim 1, wherein the image forming means outputs the timing signal to the output means in response to a timing at which the second detection means detects a first sheet of recording material in a print job. The image forming apparatus according to claim 1, characterized in that the image forming means outputs the timing signal to the output means at the timing when the second detection means detects the leading edge of the recording material. The image forming device according to claim 2, characterized in that, when the second detection means detects the trailing end of the recording material, the image forming means forms an image of an image size according to the detected length of the recording material in the transport direction. The image forming apparatus according to claim 3, characterized in that the length of the recording material in the conveying direction is calculated by multiplying the time from when the second detection means detects the leading edge of the recording material to when it detects the trailing edge of the recording material by the conveying speed at which the recording material is conveyed. The image forming device according to claim 2, characterized in that, when the first detection means detects the leading edge of the recording material before the second detection means detects the trailing edge of the recording material, the image forming means forms an image of the image size notified by the notification means. The image forming apparatus according to claim 1, characterized in that the image forming means outputs the timing signal to the output means at the earlier of the timing when the second detection means detects the trailing edge of the recording material or the timing when the first detection means detects the leading edge of the recording material. The image forming apparatus according to claim 6, characterized in that, if the timing at which the second detection means detects the trailing end of the recording material is earlier, the image forming means forms an image with an image size according to the detected length of the recording material in the conveying direction. The image forming apparatus according to claim 7, characterized in that the length of the recording material in the conveying direction is calculated based on the time from when the second detection means detects the leading edge of the recording material to when it detects the trailing edge of the recording material, and the conveying speed at which the recording material is conveyed. The image forming device according to claim 6, characterized in that, if the first detection means detects the leading edge of the recording material earlier, the image forming means forms an image of the image size notified by the notification means. The image forming apparatus according to any one of claims 3, 4, 7, and 8, characterized in that the image forming means outputs the timing signal for the second and subsequent sheets of recording material of the print job to the output means at time intervals according to the detected length of the first sheet of recording material in the transport direction. The image forming apparatus according to claim 10, characterized in that the time interval is calculated by summing the length of the recording material in the transport direction and the distance to the following recording material, and dividing the sum by the transport speed of the recording material. The image forming apparatus according to any one of claims 1 to 11, characterized in that the length in the transport direction of the recording material fed by the feeding means is indefinite at the start of the print job.