JPH09100048A - Sheet conveyor system and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet conveyor system that is capable of solving a paper jam and jam recovery operations or any possible pollution, etc., by obviating the double feed of sheets and an image former in addition. SOLUTION: Length in the conveying direction of a sheet S serving as a basis is compared with length of another sheet actually conveyed by a pre-feed sensor 15 (a length detecting means), and when such a fact that the length of the sheet being actually conveyed is longer than that in the conveying direction of the sheet serving as the basis is detected, it is so judged as a double feed. Accordingly, when the sheet being actually conveyed is fed as far as reference length from a conveying route H1 (first conveying means) to a conveying route H2 (second conveying means), this route H1 (first conveying means) is stopped, whereby the rearward sheet being double fed is pinched into stoppage and thereby the double-fed sheet is separated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet material conveying device and an image forming apparatus such as a printer, a facsimile machine, and a copying machine, which is provided with the sheet material conveying device and forms an image on a conveyed sheet material. In particular, the present invention relates to detection / separation of sheet materials fed by double feeding on a conveyance path, and post-processing of separated sheet materials.

[0002]

2. Description of the Related Art The main structure and operation of a printer will be described as an example of a conventional image forming apparatus. FIG. 6 is an explanatory diagram of a cross-sectional configuration of the printer device 100.

The image forming unit 100A will be described with reference to FIG. 101 is a photosensitive drum, which is an electrostatic latent image carrier,
Reference numeral 102 is a semiconductor laser as a light source, 104 is a rotary polygon mirror rotated by a scanner motor 103, and 105 is a laser beam emitted from the semiconductor laser 102 and reflected by the rotary polygon mirror 104 to scan the photosensitive drum 101.

Reference numeral 106 is a charging roller for uniformly charging the photosensitive drum 101, and 107 is a developing device for developing the electrostatic latent image formed on the photosensitive drum 101 with toner.

Reference numeral 108 designates a transfer roller for transferring the toner image developed by the developing device 107 onto a predetermined recording sheet.
Reference numeral 09 denotes a fixing roller pair for fusing the toner transferred onto the recording sheet.

Next, a carrying system 100B for carrying a sheet material for forming an image on the image forming section 100A will be described.

The sheet material S on which an image is formed is placed on the cassettes 110a and 110b having a function of identifying the size, and the uppermost sheet material is the pickup roller 1.
11 a and 111 b are driven by one rotation to be picked up and conveyed to the conveyance path H 101 by the conveyance roller pairs 112 a and 112 b, respectively.

Further, reference numeral 120 denotes a manual sheet feeding section which does not have a function of identifying the size of the sheet material, and is for feeding the sheet material to the conveying path H102 by the manual sheet feeding roller 121.

Reference numerals 113 and 114 denote the sheet material S fed from the above-mentioned cassette and the manual feeding portion, respectively, on the photosensitive drum 10.
It is a pair of transport rollers that feed in one direction.

Further, 115 is a cassette 110a, 110
A pre-feed sensor for detecting the leading edge and the trailing edge of the sheet material S fed from b, and 116 for writing (recording / printing) an image on the photosensitive drum 101 with respect to the fed sheet material S. It is a top sensor that synchronizes sheet material conveyance.

Reference numeral 117 denotes a paper discharge sensor for detecting the presence or absence of the sheet material after fixing, and 118 and 119 are discharge roller pairs for discharging the sheet material after fixing to the outside of the apparatus.

FIG. 7 is a block diagram showing a circuit configuration of a control system 200 for controlling the above mechanical section.

In FIG. 7, reference numeral 201 is for expanding the image code data sent from an external device such as a host computer (not shown) into bit data necessary for printing by the printer and reading the internal information of the printer for communication and displaying it. Printer controller.

Reference numeral 202 denotes a printer engine control unit for controlling the operation of each unit constituting the printer engine in accordance with an instruction from the printer controller 201 and notifying the printer controller 201 of printer internal information.

Reference numeral 203 denotes a sheet material conveyance control section which drives / stops a motor, rollers and the like for conveying a sheet material according to an instruction from the printer engine control section 202.

A printer engine control unit 202 controls output of each high voltage in each process such as charging, developing, and transferring.
This is a high-voltage control unit for performing according to the instructions of.

Reference numeral 205 denotes an optical system control unit for driving / stopping the scanner motor 103 and blinking the laser beam in accordance with instructions from the engine control unit 202.

Reference numeral 206 denotes a sensor input unit for inputting a detection signal from each sensor and using it as control information of the engine control unit 202.

Reference numeral 207 is a temperature control unit for adjusting the temperature of the fixing unit to the temperature designated by the printer engine control unit 202.

Reference numeral 208 denotes a control unit of the cassette 110b as a removable optional cassette, which drives / stops the drive system in accordance with an instruction from the printer engine control unit 202, and determines the presence / absence of sheet material and sheet material size information. This is an option cassette control unit that notifies the control unit 202. In addition, the cassette 110 attached to the main body
Information on the sheet material relating to a is performed by the sheet material conveyance control unit 203 described above.

Such a conventional engine control unit 202 recognizes a print request from the print signal from the printer controller 201 and drives each component. That is,
The engine control unit 202, which has recognized the print request by "true" of the print signal, starts sheet feeding from the designated cassette or the manual sheet feeding unit, and also starts up the electrophotographic process such as driving of the scanner motor. To do. When all the conditions necessary for printing are satisfied, a vertical synchronizing signal is output to the printer controller 201 to start printing.

The printer controller 201 sets the print signal to "true", and as a result, the engine control unit 202
Is driven to confirm that the vertical synchronizing signal has been output from the engine control unit 202 without any problem, and then the print signal is set to “false”.

Further, when the engine control unit 202 detects a print signal "false" which is transmitted from the sensor input unit or the like and which conveys an apparatus abnormality before outputting the vertical synchronizing signal, it judges that the print is canceled and the fed sheet is fed. The material is discharged outside the device without printing.

For example, the pre-feed sensor 115 and the top sensor 116 are for monitoring in order to realize the normal conveyance of the sheet material, and the pre-feed sensor 115 is
The leading edge of the sheet material fed from the cassette is detected, and when the predetermined time has elapsed, the driving of the transport roller 113 and the pickup rollers 111a and 111b is stopped, and the leading edge of the sheet material is transported to a predetermined position before the photosensitive drum 101. Yes (pre-feed).

This is because it takes time to start up the electrophotographic process in the first print, and control is restarted when the start-up is completed. This is because, in order to keep the interval constant, the sheet is stopped when the interval is shorter than a predetermined interval.

Further, the top sensor 116 measures the passage time of the conveyed sheet material in the conveying direction, compares it with the passage time set for each sheet material size, and detects a sheet material size mismatch or a jam jam. Was there.

[0027]

However, in the above-mentioned conventional example, even when the fed sheet material is double-fed,
The top sensor 116 has determined that the sheet material sizes do not match or that jams have accumulated.

Therefore, when a problem such as double feeding of the sheet material occurs, it may be judged that the sheet material sizes do not match. In this case, the sheet material in the double fed state is conveyed and the image is transferred. The probability of jamming at the forming section increases. In case of a further jam, the recovery work must be dependent on the operator.

Further, when it is determined that the jammed sheet is jammed, the driving of the image forming unit and the conveying path is stopped, and the sheet material remains in the state of being sandwiched between the image forming units. It will make the inside dirty.

The present invention has been made to solve the above-mentioned problems of the prior art. The purpose of the present invention is to prevent double feeding of sheet material before jamming and jam recovery work.
Another object of the present invention is to provide a sheet material conveying device and an image forming apparatus that can solve problems such as contamination.

[0031]

In order to achieve the above object, according to the present invention, a sheet material feeding means for feeding a sheet material from a sheet material placing means to a conveying path, and an upstream side of the conveying path. And a second conveying unit arranged downstream of the first conveying unit for sandwiching and conveying the sheet material.
In the sheet material conveying device, the size detecting means for detecting the size of the sheet material placed on the sheet material placing means, and the sheet provided and conveyed in the first conveying means. Length detecting means for detecting the length of the material in the conveying direction, the length in the conveying direction of the reference sheet material obtained from the size of the sheet material detected by the size detecting means, and actually by the length detecting means The length of the sheet material that is being conveyed is compared with the length of the sheet material that is being conveyed, and if it is detected that the length of the sheet material that is actually being conveyed is longer than the length of the reference sheet material in the conveying direction, it is judged as a double feed. When the actually conveyed sheet material is conveyed from the first conveying means to the second conveying means by the length of the reference sheet material in the conveying direction, the first conveying means is stopped. Double feed by And a control means for controlling to stop by holding the rear of the sheet material being.

Further, a sheet material feeding means for feeding the sheet material from the sheet material placing means to the conveying path, and a first conveying means arranged upstream of the conveying path for nipping and conveying the sheet material. In an image forming apparatus provided with a second conveying means arranged downstream of the first conveying means and an image forming means for forming an image on a sheet material conveyed by the second conveying means. A size detecting means for detecting the size of the sheet material placed on the sheet material placing means;
A length detecting means for detecting the length of the sheet material in the conveying direction conveyed to the conveying means, and a length in the conveying direction of the reference sheet material obtained from the sheet material size detected by the size detecting means, Comparing the length of the sheet material actually conveyed by the length detecting means, and detecting that the length of the sheet material actually conveyed is longer than the reference sheet length in the conveying direction. When it is determined that the sheet material is being conveyed, the sheet material that is actually conveyed is conveyed from the first conveying means to the second conveying means by the length of the reference sheet material in the conveying direction. , And a control unit that controls to stop the first sheet feeding unit by sandwiching the rear sheet material that is being double fed.

However, in the image forming apparatus, the second conveying means is provided with a sheet material detecting means for detecting the conveyed sheet material and synchronizing the image forming means with the sheet material conveyance, and the control means is The rear sheet is detected based on the detection result of the rear sheet material separated and stopped on the conveyance path by the sheet material detection means after a predetermined time has elapsed since the first conveyance means was stopped for the double feed separation. When the sheet material is detected by the sheet material detection means on the second conveying means, the stopped sheet material is discharged without performing image formation, and the rear sheet material is When the sheet material detecting means on the second conveying means does not detect the sheet material, the rearwardly separated sheet material is conveyed without newly feeding the sheet material from the sheet material feeding means. Image formation It is preferred.

Further, when the next image formation is not carried out, the control means conveys the separated and stopped rear sheet material by the first and second conveying means to perform the paper discharge processing. Is also suitable.

Further, the image forming apparatus is provided with a plurality of sheet material mounting means for separately mounting sheet materials of different sizes, and the control means controls the sheet material used for the next image formation. When the sheet material is fed from a sheet material placement means different from the sheet material stopped on the first conveying means, the separated and stopped rear sheet material is the first and second sheets. It is also preferable to carry out the paper discharge processing by carrying the paper by the carrying means.

Further, the length detecting means may be a pre-feed sensor for detecting the leading end of the sheet material in order to pre-feed the sheet material.

With the above construction, the control means detects the double-fed sheet material and at the same time stops the first feeding means to sandwich and stop the rearward-fed sheet material, thereby stopping the double-fed sheet material. The sheet material is separated.

Further, when the rear sheet material which is separated and stopped is stopped in a state where the leading edge for performing image formation at a predetermined position of the sheet material cannot be performed, the sheet discharging process is performed. Done.

When the next image formation is not performed,
If the sheet material used for the next image formation is to be fed from the sheet material placement means different from the sheet material separated and stopped on the first transport means, stop the sheet material. The sheet material is discharged.

[0040]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 is a cross-sectional explanatory view of a printer device 1 as an image forming apparatus described in the embodiment of the present invention. The printer device 1 has the same configuration as the printer device 100 described in the related art with respect to the mechanical components, but the control method of each component is different, and in particular, the transport system 1B. It is characterized by the control method and action of.

Therefore, the same components are designated by the same reference numerals and treated as the same as the prior art, and a detailed description thereof will be omitted, but the double feed separation control method of the sheet material, which is a feature of the present invention, is related. The part to be performed will be described below.

Reference numerals 110a and 110b are cassettes as sheet material mounting means, and the size of the sheet material mounted on this cassette is detected by a size detecting means (not shown). As the size detecting means, most of the commonly used sheet materials are standard sheet materials such as A4 and B5. Therefore, it is possible to detect the type of sheet material and whether the sheet material is placed vertically or horizontally, and separately. A method of using the stored length data of the sheet material in the conveying direction is generally used, but there is no problem in adopting another known method.

Sheet material S from the upper cassette 110a
As an example, the sheet material S of which the size is determined is picked up by one rotation of the pickup roller 111a serving as a sheet material feeding unit, and is conveyed to the conveyance path H1 by the conveyance roller pair 112a. To be done.

The transport path H1 is a portion on the upstream side of the transport system 1B through which the sheet material is transported. As the first transport means,
In addition to the pair of conveying rollers 112a, a pair of conveying rollers 113, 11 for feeding the sheet material S toward the photosensitive drum 101.
4 is provided. The pair of conveying rollers 113 and 114 are two rollers that are opposed to each other and are in contact with each other, and are composed of a driving roller and a driven roller that rotates along with the driving roller.

The transport path H1 as the first transport means
Is provided with a pre-feed sensor 15 as a length detecting means for detecting the leading end and the trailing end of the fed sheet material S and measuring the length of the fed sheet material in the conveying direction. Has been done.

A downstream side of the transport roller pair 114 of the transport path H1 is a transport path H2 as a second transport means.
An image is formed on the sheet material by the well-known electrophotographic image forming unit 100A in the transport path H2. Specifically, the photosensitive drum 101 and the transfer roller 10
By 8, the toner image is transferred onto the surface of the sheet material, and at the same time, the sheet material is nipped and conveyed.

Further, a top sensor as a sheet material detecting means for detecting the conveyed sheet material S on the conveying path H2 and synchronizing the image writing (recording / printing) on the photosensitive drum 101 and the sheet material conveyance. 16 are provided.

A transport path H3 is provided downstream of the image forming means 100A, and the sheet material on which the image is formed is discharged to a discharge tray or the like (not shown).

Since the circuit configuration of the control system 200 for controlling the above mechanical parts of the printer device 1 is the same as that of the prior art shown in the block diagram of FIG. 7,
Description of the parts described in the section of the prior art will be omitted, but FIG. 7 will be used to describe the sheet material conveying sequence described in detail below.

FIG. 2 shows a chart of a sheet material conveying sequence from the cassette at the time of printing according to the present embodiment.

In FIG. 2, in a sequence (301), when the engine control unit 202 receives a print request from the printer controller 201, it starts driving each roller required for sheet material conveyance. And the sequence (30
In 2), the pickup roller 111a or 111b is rotated once to move the stacked sheet materials S to the transport path H1.
Send to.

It is detected that the fed sheet material S reaches the pre-feed sensor 15 (303), and after the detection, the leading edge of the sheet material passes through the conveying roller pair 114 and the top sensor 16 is detected.
The pair of conveying rollers 113 and 114 are stopped at the timing when the value reaches (304).

Thereafter, it is confirmed that the pre-processing of the electrophotographic process is completed and that the scanner motor 103 has reached the steady rotation (305). At the same time as the confirmation, the driving of the pair of conveying rollers 113 and 114 is started (306).

Thereafter, the presence or absence of the sheet material being conveyed is monitored by the pre-feed sensor 15 (307),
When the pre-feed sensor 15 detects the absence of sheet material,
The sequence is ended by recognizing that the paper is normally conveyed. Also,
The presence / absence state of the sheet material is monitored for a predetermined time set for each size of the sheet material (308). If the pre-feed sensor 15 does not detect the paper out state within the predetermined time, the sheet material being conveyed is used as a reference. Since it is longer than the length, it is determined that double feeding has occurred, and separation control described later is performed.

In the separation control of the double feed, the pair of feed rollers 113 and 114 are stopped at the timing when the trailing edge of the sheet material passes through the feed roller 114 when the paper feed is normal (309), and the double feed of the rear sheet is performed. The material is pinched and stopped to separate the multi-fed paper.

After the multi-feed separation, the printer controller 201
The print request from the printer is detected (310). When a print request is recognized, the rear sheet material that is separated without being fed from the cassette and is sandwiched by the pair of transport rollers 113 or 114 and stopped is started from the sequence (305).

When the print request is completed, the sheet is conveyed until the post-processing of the electrophotographic process is completed (311).
If there is no print request during this post-processing, the separated sheet material is discharged to the outside of the machine after the post-processing of the electrophotographic process is completed (312).

(Embodiment 2) FIG. 3 shows a sequence chart of sheet feeding and conveyance from a cassette at the time of printing according to the second embodiment.

In this embodiment, the sequence (41
Control when the sheet material to be supplied after 1) is instructed to feed the sheet material from a different sheet material placing means by changing the sheet material placing means such as a cassette or a manual paper feeding unit It features a method.

Sequences (401) to (409) are the same as sequences (301) to (309).

In the sequence 410, after the multi-feeding is separated, the print request from the printer controller 201 is detected.

When the print request is detected, the feeding sequence after the sequence (405) is started by using the sheet material which is separated from the cassette without feeding the sheet.

When the print request is completed, the sheet is conveyed until the post-processing of the electrophotographic process is completed (411).
If there is no print request during this post-processing, it is detected whether there is a request for changing the paper feed port after finishing the post-processing of the electrophotographic process (412). When the change of the paper feed port is detected, the separated sheet material is discharged to the outside of the apparatus (413), and this sequence ends. Note that this detection operation is performed until the post-processing of the electrophotographic process is completed, as in the case of the above-described print request detection.

(Embodiment 3) FIG. 4 shows a sequence of sheet feeding / conveyance from a cassette during printing according to the third embodiment.

This embodiment shows a control method in the case where the printer controller 201 determines the processing method of the separated sheet material.

Sequences (501) to (511) are the same as sequences (301) to (311).

After the post-processing of the process is completed (511), the printer controller 201 is notified that the sheet material remains on the conveyance path (512). Based on the information, the printer controller 201 outputs "true" of the print signal if the staying sheet material is necessary, and the engine control unit 202 receives the print signal (51).
3) The feeding sequence is started from 505 without feeding paper.

If the accumulated sheet material is unnecessary, the engine control unit 202 is instructed to discharge the sheet material outside the apparatus (504). The instruction is given by canceling the print.

(Embodiment 4) In the above-described first to third embodiments, the separated rear sheet material is a toner image formed on the photosensitive drum 101 (recording / transferred to the sheet material). The control method has been described on the assumption that the printing is stopped at a position not detected by the top sensor 16 as a sheet material detection unit that synchronizes printing and sheet material conveyance.

FIG. 5A shows a state in which the vehicle is stopped at a position where it is not detected by the top sensor 16. In the state of this drawing, after the image is formed on the front sheet material S1, and the rear sheet material is conveyed to form the next image, the leading edge S2a of the sheet material S2 is detected by the top sensor 16. It is possible to know the leading end position of the sheet material S2, and it is possible to synchronize the conveyance of the sheet material with the photosensitive drum 101.

However, when the overlapped sheet materials have a large overlap, the rear sheet material S2 is stopped in the state as shown in FIG. 5B. In this state, the tip S2b has passed the position detected by the top sensor 16.

In this state, it is impossible to synchronize the leading edge of the sheet material S2 when the next image is formed. In this case, the sheet material S2 is discharged and a new sheet material is fed. Form an image.

[0073]

According to the present invention having the above-mentioned structure and operation, the control means detects that the length of the sheet material actually conveyed is longer than the reference length of the sheet material in the conveying direction. In this case, it is determined that the sheet material is double-fed, and when the actually conveyed sheet material is conveyed by the reference length from the first conveying means to the second conveying means, the first conveying means is stopped. It becomes possible to separate the sheet material in the double feed state by sandwiching and stopping the rearwardly fed sheet material by the first conveying means.

Therefore, in the image forming apparatus, the sheet material in the double feeding state is not conveyed to the image forming portion, the occurrence of jam is reduced, and the jam recovery operation is performed or the sheet material is stopped at the image forming portion. Problems such as contamination due to unfixed toner are solved and operability is improved.

If the leading edge synchronization cannot be performed when the image formation is performed on the rear sheet material that has been separated and stopped, the stopped rear sheet material is discharged, so that the sheet material is always placed at an appropriate position. Image formation can be performed.

Further, when the next image formation is not performed in the state where the sheet materials that have been double fed are separated, or when the sheet material in the different sheet material placement means is used for the next image formation, the sheet is conveyed. Since the sheet material stopped in the path is unnecessary and the unnecessary sheet material is automatically discharged, the operator does not need to remove the unnecessary sheet material.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view of a printer device as an embodiment to which the present invention is applied.

FIG. 2 is a sequence diagram of sheet material conveyance according to the first embodiment of the present invention.

FIG. 3 is a sequence diagram of sheet material conveyance according to the second embodiment of the present invention.

FIG. 4 is a sequence diagram of sheet material conveyance in the third embodiment of the present invention.

FIG. 5 is a state diagram of a sheet material that has been separated and stopped according to a fourth embodiment of the present invention.

FIG. 6 is an explanatory diagram of a configuration of a conventional printer device.

FIG. 7 is a diagram of a circuit configuration of a control system of a conventional printer device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Printer device (image forming device) 15 Pre-feed sensor (length detecting means) 16 Top sensor (sheet material detecting means) 100A Image forming means 110a, 110b Cassette (sheet material placing means) 111a, 111b Pickup roller (sheet material) Feeding means) 112a, 113, 114 Conveying roller pair H1 Conveying path (first conveying means) H2 Conveying path (second conveying means) 200 Control system S Sheet material

Claims (6)

[Claims] 1. A sheet material feeding means for feeding a sheet material from a sheet material placing means to a conveying path, and a first conveying means arranged upstream of the conveying path for nipping and conveying the sheet material. A sheet material conveying device including a second conveying means arranged downstream of the first conveying means, a size for detecting a size of the sheet material placed on the sheet material placing means A detection unit, a length detection unit that is provided in the first conveyance unit and detects the length of the sheet material in the conveyance direction, and a reference obtained from the sheet material size detected by the size detection unit. The length of the sheet material in the transport direction,
The length detecting means compares the length of the sheet material actually conveyed, and detects that the length of the sheet material actually conveyed is longer than the length of the reference sheet material in the conveying direction. In this case, when the sheet material is determined to be double-fed, and the sheet material that is actually transported is transported from the first transporting means to the second transporting means by the length of the reference sheet material in the transport direction, A sheet material conveying device, comprising: a control means that controls the first sheet conveying means by stopping so as to sandwich and stop the rearwardly fed sheet material. 2. A sheet material feeding means for feeding the sheet material from the sheet material placing means to the feeding path, and a first feeding means arranged upstream of the feeding path for nipping and feeding the sheet material. In an image forming apparatus provided with a second conveying means arranged downstream of the first conveying means and an image forming means for forming an image on a sheet material conveyed by the second conveying means. A size detecting means for detecting the size of the sheet material placed on the sheet material placing means, and a length detecting means for detecting the length in the carrying direction of the sheet material carried by the first carrying means. And a length in the conveyance direction of the reference sheet material obtained from the sheet material size detected by the size detection means,
The length detecting means compares the length of the sheet material actually conveyed, and detects that the length of the sheet material actually conveyed is longer than the length of the reference sheet material in the conveying direction. In this case, when the sheet material is determined to be double-fed, and the sheet material that is actually transported is transported from the first transporting means to the second transporting means by the length of the reference sheet material in the transport direction, An image forming apparatus comprising: a control unit that controls to stop the first sheet feeding unit by sandwiching a rear sheet material that is being double-fed. 3. A sheet material detecting means for detecting the conveyed sheet material and synchronizing the image forming means with the sheet material conveyance is provided in the second conveying means, and the control means is provided for the double feed separation. Therefore, based on the detection result of the rear sheet material separated and stopped on the conveyance path by the sheet material detection means after a predetermined time has elapsed since the first conveyance means was stopped, the rear sheet material is When it is detected by the sheet material detecting means on the second conveying means, the sheet discharging processing is performed without forming an image on the stopped rear sheet material, and the rear sheet material is the second conveying material. When the sheet material detecting means on the means does not detect the sheet material, the sheet material feeding means does not newly feed the sheet material, and the separated and stopped rear sheet material is conveyed to form an image. According to claim 2, characterized in that Image forming apparatus. 4. The control means conveys the separated and stopped rear sheet material by the first and second conveying means to perform a paper discharge process when the next image formation is not performed. The image forming apparatus according to claim 2, wherein: 5. The image forming apparatus is provided with a plurality of sheet material mounting means for separately mounting sheet materials of different sizes, and the control means controls the sheet material used for the next image formation. When the sheet material is fed from a sheet material placement means different from the sheet material stopped on the first conveying means, the separated and stopped rear sheet material is the first and second sheets.
The image forming apparatus according to claim 2, wherein the image forming apparatus conveys the sheet by the sheet conveying unit and discharges the sheet. 6. The sheet material conveying device according to claim 1, wherein the length detecting means is a pre-feed sensor for detecting a leading edge of the sheet material for pre-feeding the sheet material.