JP2000272781A - Image forming device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To increase the printing speed by adjusting the paper feeding timing without increasing the process speed. SOLUTION: A detection switch 40 for detecting a sheet length is provided between a take-out roller 34 for taking out a sheet S from a sheet cassette 30 and a registration roller 37, and the length of the first sheet S fed is determined. To detect. The timing at which the next sheet S is fed while the previous sheet S is being conveyed by the registration rollers 37 is set as the sheet feeding timing of the sheet S to be fed after the third sheet based on the detected sheet length. To decide. The second sheet S is fed at a constant feed timing regardless of the sheet length. From the third sheet onward, the timing for feeding the sheet S is advanced, and the number of sheets to be printed increases.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding timing when a sheet is conveyed for image formation in an image forming apparatus such as a copying machine, a printer, a facsimile or the like.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, a sheet stored in a sheet cassette is picked up by a take-out roller, conveyed to a registration roller by a sheet feed roller, temporarily stopped, and aligned. Then, the paper is conveyed to the photoconductor (electrostatic latent image carrier) in synchronization with the start timing of the printing process. In order to realize high-speed printing by increasing the printing speed, the rotation speed (process speed) of the photoconductor is increased, the conveyance speed of the paper is increased, and the image forming unit such as the photoconductor is formed. The number of sheets passing therethrough is increased.

The printing speed of the image forming apparatus is the time required for a printing process from feeding one sheet of paper to printing and discharging the paper. This is the time required for a series of printing operations such as fixing the toner image transferred to the paper after formation, and the printing speed is 1
It is represented by the number of prints per minute. The number of prints per minute is determined by the distance between the trailing edge of the leading sheet and the leading edge of the next sheet in the continuous paper of the rotation speed of the photoconductor and the sheet length. That is, the following equation determines the number of prints as an invariant matter.

V = A / (P + B) (1) V: Print speed of image forming apparatus (ppm) A: Rotation speed of photoconductor (mm / min) P: Length of reference paper size in transport direction (Mm) B: Distance between sheets (mm) By the way, increasing the rotation speed of the photoconductor is achieved by controlling a processing mechanism such as image processing control and electrical control of the image forming apparatus,
In addition, an excessive load is applied to a driving mechanism such as a motor for driving the sheet conveying roller, which complicates the control, shortens the life of the driving mechanism, and causes a failure.

In order to solve such a problem, the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 10-258953 is provided with a paper feed sensor for detecting the passage of the leading edge of a sheet in a sheet conveying process. The start timing of conveyance of the next sheet is determined based on the detection result, and the next sheet is fed from the sheet cassette at a timing after a lapse of a predetermined time from the point when the leading edge of the sheet is detected to pass. Thus, it is possible to carry the sheet to the image forming position at an accurate timing without providing a registration roller. Therefore, the time required for the printing process can be shortened by increasing the timing at which the paper is conveyed from the paper cassette.

[0006]

In the above-described paper feeding method,
When the paper cassette is a dedicated cassette that stores only a fixed paper size, it is possible to control the paper feed timing.
However, in a dual-purpose cassette called a universal cassette that can store a plurality of types of paper, the length in the transport direction differs depending on the stored paper, and if the paper feed timing is determined by passing the leading edge of the paper, the size of the paper is reduced. In the case of a small sheet, the interval between the previously fed sheet and the next fed sheet becomes large, and a wasteful time is generated in the transport time, and the printing time may not be reduced.

In addition, although the registration roller can be made unnecessary by the above-described paper feeding method, it has a drawback that it cannot be applied to an image forming apparatus having a registration roller. In view of the above, it is an object of the present invention to increase the printing speed without increasing the process speed in an image forming apparatus provided with a registration roller to increase the number of print processing sheets.

[0008]

Means for Solving the Problems According to the present invention, a sheet is fed from a sheet accommodating portion such as a sheet cassette by a sheet feeding means such as a take-out roller, a sheet feeding roller or a transport belt, and the sheet is fed. In an image forming apparatus provided with alignment means such as a registration roller that conveys the sheet to the image forming section after delaying the progress of the sheet on the way, the length of the fed sheet is detected by a sheet detector. The paper feed is controlled so that the paper feed timing is advanced based on the paper length. Further, it is preferable that the start timing of the image forming process is controlled so as to be earlier with the change of the paper feed timing.

That is, by determining the paper feed timing so that the feed of the next sheet is started when the previous sheet is being conveyed by the registration rollers, the interval between the previous sheet and the next sheet is reduced. Paper can be fed in a jammed state, the number of sheets fed within a certain time can be increased, and the printing speed can be increased without increasing the process speed.

However, if there is a registration roller, the progress of the sheet is delayed due to a temporary stop or the like, and the sheet is not fed from the sheet storage section to the image forming section at a constant speed. When the timing is determined, when the feeding of a large-sized sheet is delayed by the registration rollers, the next sheet is fed, and the sheets may overlap with each other. If the paper feed timing is determined based on the paper length, such a situation cannot occur.

Here, detecting the length of the sheet is most efficient in detecting the length of the sheet before the sheet reaches the registration roller in performing the subsequent sheet feeding. And a registration roller. In this case, the length of the paper is calculated from the time required for the paper to pass through, which is obtained from the output from the paper detector, and the stop time during which the paper was temporarily stopped by the registration rollers.

If the length of the first sheet fed is detected, the effect of reducing the time required for the entire printing process when printing a large number of sheets is maximized. Here, when the length of the first sheet fed is detected, applying the determined sheet feeding timing to the second sheet fed complicates the sheet feeding control.
The feeding timing according to the sheet length is applied to the third and subsequent sheets. Therefore, smooth feeding can be performed without performing complicated control such as feeding the second sheet at a fixed feeding timing regardless of the length of the sheet.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The outline of an image forming apparatus according to the present embodiment will be described with reference to the drawings. This image forming apparatus is a digital copying machine having a facsimile function and a printer function. A scanner unit for reading a document D shown in FIG. And an image forming mechanism for forming (printing) an image on the sheet S by a process. The image forming apparatus is not limited to this, and may have an independent function such as an analog copier or a printer.

The scanner unit includes a document table 1 made of transparent glass, a double-sided automatic document feeder 2 for automatically supplying the document D onto the document table 1, and an image of the document D on the document table 1. And an image reading unit (scanner unit) 3 for scanning and reading. In the document feeder 2,
A plurality of originals D are set on an original tray 4, and are fed onto the original table 1 by a pickup roller 5, a separating roller 6, and a conveying roller 7, and the original is discharged by a discharge roller 8 which can be rotated forward and reverse. It is transported to the tray 9. A swingable guide 11 for switching the transport path 10 is provided so that one side or both sides of the document D can be read in accordance with a user's selection.

The scanner unit 3 is arranged below the document table 1 and irradiates the document D moving on the document table 1 with light. The exposure light source 12 and the reflected light from the document D are indicated by solid lines in FIG. Through the imaging lens 13 as shown in FIG.
D) and a plurality of reflecting mirrors 15 for leading to 14.

The document image data read by the CCD 14 is subjected to image processing, temporarily stored in a memory, and then output to an image forming mechanism in response to an output instruction. The image forming mechanism includes a sheet transport unit 20, a laser scanning unit (hereinafter, referred to as LSU) 21, and an image forming unit 22 for executing an electrophotographic process. The laser beam is generated by the LSU 21 according to the image data in the image forming unit 2.
By irradiating the surface of the second photoconductor 23, an electrostatic latent image is formed. The photoreceptor 23 has a drum shape that is driven to rotate in the direction of the arrow. Around the photoreceptor 23, along the rotation direction of the photoreceptor 23 from the laser irradiation point, the surface of the photoreceptor 23 exposed by the laser is A developing device 24 for visualizing the electrostatic latent image with toner, a transfer charger 25 for transferring the toner image on the photoconductor 23 to the sheet S, and a photoconductor 23
A cleaning device 26 for removing the residual toner on the surface and a main charger 27 for charging the photoconductor 23 to a predetermined potential are sequentially provided, and a fixing roller 28 for fixing the toner image on the paper S is disposed downstream of the photoconductor 23. Thus, the image forming unit 22 is configured.

The paper transport section 20 includes a plurality of paper cassettes 30 and a manual feed tray 31.
0, the paper S is stored for each size, and the user selects the paper S of a desired size, and conveys the paper S one by one from any of the cassettes 30 or the manual feed tray 31 to the image forming unit 22 so that the image is In order to further transport the formed paper S to the paper discharge tray 33, a plurality of passages and a plurality of transport rollers are provided.

Paper cassette 30 and manual feed tray 31
A half-moon-shaped take-out roller (pickup roller) 34 for taking out and feeding the paper S is disposed above the leading end of the cassette 30, the manual feed tray 31 and the photosensitive member 23.
A paper feed path 35 is formed between the paper feed path 35 and a paper feed roller 36 and a registration roller 37 that aligns the toner image on the photoconductor 23 and the paper S are disposed in the paper feed path 35. Then, from the photosensitive member 23 via the fixing roller 28,
3 is formed, a forward / reverse rotatable transport roller 39 is disposed downstream of the fixing roller 28, and the transport roller 39 is driven by a forward / reverse rotatable motor. Registration roller 37 and paper feed roller 36 in paper feed path 35
A paper detector for detecting the passage of the sheet S is disposed between the pre-registration detection switch 4 such as a micro switch that is turned on in contact with the sheet S passing therethrough.
Consists of zero. Further, a re-feeding path 41 branching from the middle of the discharge path 38 and communicating with the feeding path 35 is formed for performing double-sided printing, and a re-feeding roller 42 is provided. Further, although not shown, a fixing paper detection switch for detecting that the paper S has passed through the fixing roller 28 and a conveyance roller 3 are provided.
A paper ejection detection switch for detecting that the paper S has passed before the position 9 is provided to detect a paper jam.

A swingable conveyance guide 43 is provided at a branch portion between the discharge path 38 and the re-feed path 41, and is driven by a solenoid, a motor, or the like. That is, the conveyance guide 43 has a discharge posture for closing the re-feed path 41 so that the discharge path can be discharged to the discharge tray 33, and the discharge path 3 for performing double-sided printing.
8 is switched to the carry-in posture.

The paper S supplied from the cassette 30 or the manual feed tray 31 reaches the registration roller 37 through the paper feed path 35, and is temporarily stopped to align the paper S. Is conveyed to the photoreceptor 23 and printing is performed. Printed paper S
Is discharged to the discharge tray 33 through the discharge path 38. When performing double-sided printing, the transport roller 39 is stopped when the paper S passes through the branch portion of the discharge path 38, and the transport guide 4
By switching the posture of No. 3 and rotating the transport roller 39 in the reverse direction, the sheet S is sent to the re-feeding path 41 and double-sided printing is performed.

FIG. 1 is a diagram showing a schematic configuration of the image forming apparatus, and does not show an actual structure. In general, in the case of a copying machine (including analog and digital), there is a type in which an image can be taken in a size larger than the sheet S. For example, the image capture size in the scanner unit is set to a maximum of A3 or B4, and the sheet S is set to a maximum of A4.
Then, the image captured by the scanner unit is reduced and printed. In this case, the scanner unit that requires the largest area among the scanner unit, the image forming unit, and the cassette 30 is the scanner unit. This is because it is necessary to take in a large-sized document D, so that a large area is inevitably required.

The control device mounted on the image forming apparatus controls the paper feed timing in order to increase the printing speed in addition to the control for the printing process.
The paper feed timing is determined based on the length of the paper S in the transport direction detected based on the output signal of the detection switch 40. That is, as shown in Expression (1), the printing speed is determined by the length of the paper in the transport direction and the distance between the papers, but the length of the paper S in the transport direction is shortened. The printing speed can be improved by shortening the interval from S to the next sheet S.
Therefore, by controlling the drive of the take-out roller 34 and the paper feed roller 36 in accordance with the length of the paper S to advance the paper feed timing, the paper S fed first and the paper S fed next The distance between them is so short that they do not overlap.

Further, the start timing of the printing process is advanced in accordance with the determined paper feed timing. The timing control of the printing process includes the rotation timing of the photoconductor 23, the writing timing of the image information, the charging timing of the main charger 27, the rotation timing of the developing roller in the developing device 24, the developing bias application timing, the transfer charger 2
5, transfer timing and transfer voltage control, photoconductor 23
Of the residual potential, the rotation timing of the fixing roller 28, the rotation timing of the transport roller 39, the cleaning device 2
6 is to control the operation timing.

FIG. 2 shows the timing for feeding the sheet S. At this time, as shown in FIG.
When the distance between the paper A and the paper B in the paper supply path 35 is Y1, the distance between the paper A and the paper B in the paper feed path 35 is Y1, and the distance between the paper B and the paper C is X. The interval is defined as Y2. Conventionally, when paper B is fed after paper A,
When the sheet A has passed the detection switch 40, the take-out roller 34 is driven to start feeding the next sheet B. Therefore, the following relationship is established.

Y1 = Y2 ≧ X (2) On the other hand, in the present embodiment, the length of the sheet S is reduced by passing the first sheet A to be printed first through the detection switch 40. Ask. Specifically, since the time required for the paper S to pass through the detection switch 40 corresponds to the paper length because the paper feeding speed of the paper S is constant, the ON time α of the detection switch 40 may be measured. However, since the sheet S is temporarily stopped by the registration rollers 37, the time (α−β) obtained by subtracting the stop time β from the ON time α is obtained.
To calculate the paper length. The paper feed timing is determined based on the paper length. The paper feed timing is set in advance for the paper length, and when the paper length is calculated, the one corresponding to this is selected.

When the sheet A has passed the detection switch 40 and has passed the registration roller 37, the driving of the registration roller 37 is stopped, and the sheet A reaches the image forming section 22 to perform printing. By the way, when the paper B to be fed next is to be fed at the newly determined paper feed timing, the paper feed timing is earlier as the paper length is shorter, so that the paper A finishes passing through the detection switch 40. Since the paper is fed beforehand, complicated waiting processing and strict management of the processing speed are required, which is difficult to realize.
Therefore, the sheet B is fed at a constant sheet feed timing γ1 irrespective of a preset sheet length. The paper C to be fed next has the determined paper feed timing γ2
The paper is fed by the drive of the take-out roller 34.
That is, since the next sheet feeding is started while the sheet B is being conveyed by the registration rollers 37 and is passing through the detection switch 40, the state shown in FIG. 4 is established, and the following relationship is established.

Y1.gtoreq.X.gtoreq.Y2 (3) In the formula (3), the time required for the printing process is not changed from the conventional one because the length of the sheet A is detected.
Is clearly shorter than X as shown in FIG. In all subsequent sheets, the sheet feed timing γ3 (= γ2 <
γ1), the paper S
When the sheet is conveyed toward the photoconductor 23 by the registration roller 37, the interval can be set so that the sheets do not overlap with each other, so that the time required for sheet feeding can be reduced. .

As described above, the timing at which the paper S reaches the photosensitive member 23 is advanced by changing the paper feed timing for the third and subsequent papers S after the start of printing a plurality of papers. Therefore, by adjusting the start timing of the printing process such as the rotation timing of the photoconductor 23 related to the printing process processing on the conveyed paper S in accordance with the changed paper feed timing, each timing is optimized, The time required for the entire printing process is reduced.
Therefore, the number of print processing sheets can be increased without increasing the process speed, and the printing speed can be increased. As the number of print processing sheets increases, the effect of reducing the time becomes remarkable. Moreover, there is no need to perform complicated control,
Since no excessive load is applied to the drive mechanism, no load is imposed on the apparatus, design work in consideration of durability and reliability is not required, and high-speed printing can be realized at low cost.

Further, as the detection switch 40 provided for detecting the paper length, an existing sensor for detecting the passage of the paper S for detecting a paper jam can be used, so that the number of parts does not increase and the cost can be reduced. I can do it. By detecting the sheet length from the conveyed sheet S, the sheet feeding timing can be determined to be the shortest regardless of the size of the sheet S stored in the sheet cassette 30 or the manual feed tray 31. In addition, the printing time can be reduced.

Next, a control procedure for performing the above-described sheet feeding will be described with reference to FIGS. Although details of each timing process are omitted in the figure, for example, when a timer starts counting, it can be easily realized by a general interface that specifies a timer type and a timing value as parameters. . Although the method of terminating printing in the multiple-sheet printing process is not particularly described, an existing termination procedure may be used.

First, in STEP 001, after setting a sheet calculation completion flag to be a trigger for determining whether or not the sheet length has already been calculated in a process to be described later to “OFF”, the apparatus waits for each event and waits for printing. By receiving the request, the process proceeds to STEP 101, in which the take-out roller 34 is driven to take out the sheet S from the sheet cassette 30 in STEP 102, and in STEP 103, the timer for the take-out roller 34 starts counting, and then the feed roller 36 is set in STEP 104. The paper S is conveyed in the paper feed path 35 by also driving.
After confirming that the printing has not been completed yet in STEP002, the process waits in an event waiting state after STEP001. This state is the state of A in FIG.

Next, when the time-out of the timer performed in STEP 103 occurs, the process proceeds to STEP 201. In STEP 202, the take-out roller 34 is stopped. Wait in the subsequent event wait state. This state is the state of B in FIG.

When the paper S reaches the detection switch 40 and the detection switch 40 is turned on, the STE
Proceeding to P301, the timer of the print start timer is started in STEP 302, the timer of the paper feed roller 36 is also started in STEP 303, and the sheet S reaches the registration roller 37 and temporarily stops. After confirming that the printing has not been completed yet in STEP002, the process waits in an event waiting state after STEP001. This state is the state of C in FIG.

When the timeout of the timer performed in STEP 303 occurs, the process proceeds to STEP 401, and
In STEP 402, after stopping the paper feed roller 36,
After confirming that the printing has not been completed yet in 002,
It waits in the event waiting state after TEP001. This state is the state of D in FIG.

When the timeout of the timer performed in STEP 302 occurs, the process proceeds to STEP 501,
In STEP 502, the registration roller 37 is driven to
In TEP 503, the paper feed roller 36 is driven again, and the paper S
Is conveyed toward the photoconductor 23, and in STEP 504, the timer for the paper feed roller 36 starts counting time. Note that STE
The timer started in P504 and the timer started in STEP 303 are both timers for stopping the sheet feeding roller 36, but have different timing values.
In the next STEP 505, the sheet calculation completed flag is set to “OF”.
F ”or not, and if“ OFF ”, STEP50.
6; otherwise, the process proceeds to STEP 507. However, at this time, the sheet calculation completed flag is still set to “OFF” in STEP 001.
Then, after confirming that the printing has not been completed yet in STEP002, the process waits in an event waiting state after STEP001. This state is the state of E in FIG.

When the timeout of the timer performed in STEP 504 occurs, the process proceeds to STEP 401, and
In STEP 402, the paper feed roller 36 is stopped, and
After confirming that the printing has not been completed yet in 002,
It waits in the event waiting state after TEP001. This state is the state of F in FIG.

Thereafter, when the sheet S passes through the detection switch 40, the detection switch 40 is turned off and the STE
Proceed to P601, and in STEP602, the registration roller 3
After the timer for 7 starts counting, in STEP 603
By stopping the sheet length calculation timer started in EP 506, the elapsed time from STEP 506 is acquired, and based on the elapsed time, the sheet length of the sheet S that has passed in STEP 604 is calculated. Find the paper timing. By this, STEP described later
The set timing value in 507 is set as this paper feed timing, and in STEP 606 the paper calculation completed flag is set to “ON”.
When performing STEP 505 in the subsequent processing,
The process proceeds to STEP 507. Then STEP00
After confirming that printing has not yet been completed in step 2,
It waits in the event waiting state after P001. This state is the state G in FIG.

Then, when the time-out of the timer performed in STEP 602 occurs, STEP 701 is executed.
In STEP 702, the registration roller 37 is stopped. In STEP 703, the timer of the next page print request timer is started. In STEP 002, it is confirmed that the printing has not been completed, and then the apparatus waits for an event after STEP 001. I do. This state is the state of H in FIG. 2, and the state in which the feeding of the first sheet S to the photoconductor 23 is completed.

When the timeout of the timer performed in STEP 703 occurs, the process proceeds to STEP 801 and
In STEP 802, a print request event is generated,
After confirming that the printing has not been completed yet in EP002, the process waits in an event waiting state after STEP001.
Proceed to TEP101. This state is the state I in FIG. 2, and the feeding of the second sheet S is started. Although the subsequent processing is the same, the description is omitted. However, as described in STEP 606 above, the processing after STEP 501 which is the timeout processing of the print start timer activated when the second sheet S reaches the detection switch 40 is executed. In processing, STE
Since the process proceeds to STEP 507 in P505, the timing of the shortest print request timer is started in STEP 507. The timing value used here is the above-mentioned ST value.
The paper feed timing based on the paper length calculated in EP 605 is used. Then, it waits again in the event waiting state, and this state is M in FIG.

When the timeout of the timer performed in STEP 507 occurs, the process proceeds to STEP 901 and
In step 902, the paper feed roller 36 is stopped, and
At 903, the timer of the next page print request timer is started. The timing value used here is different from the timing value at the start of the timer performed in STEP 703, and the timing value is related to the paper feed timing calculated in STEP 605. May be generated. Therefore, the process proceeds to STEP 801 without waiting in the event waiting state, and S
By generating a print request event in TEP 802, the third sheet S is fed and printing is started. This state is the state of N in FIG. 2, and the take-out roller 34 shown in FIG.
When the sheet feeding timing, which is the time from the driving of the first sheet S to the start of the next driving, is compared with the time from the first sheet S to the second sheet S, It can be seen that the time to the paper S and the time thereafter are significantly reduced.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that many modifications and changes can be made to the above-described embodiment within the scope of the present invention. For example, in the present embodiment, the paper detector uses a contact switch such as a microswitch, but an optical sensor such as a non-contact photo interrupter may be used, and the detection of the paper is performed by detecting the passage of the paper. Detect length. Further, since it is only necessary to detect the length of the conveyed paper, the installation position of the paper detector is not limited to between the paper feed roller and the registration roller, and is not limited to being taken out of the paper cassette and discharged to the paper output tray. It should be between.

In place of the registration rollers, a shutter may be provided in the paper feed path so as to be freely inserted and removed, and the paper may be conveyed by a plurality of paper feed rollers so as to stop the advance of the paper.

[0043]

As is clear from the above description, according to the present invention, the length of the fed paper is detected, and the control is performed so that the timing of feeding the subsequent paper is advanced based on the detection result. By doing so, paper can be fed one after another at short intervals, the number of print processing sheets can be increased, and high-speed printing can be achieved without increasing the process speed. Such control is useful for an image forming apparatus provided with alignment means such as a registration roller. That is, if the feeding timing is determined so that the feeding of the next sheet is started while the previous sheet is being conveyed by the registration rollers, even if the sheet is temporarily stopped during the feeding by the registration rollers, Since the stop time can be shortened, the waiting time can be reduced, and the printing time can be shortened. Therefore, the effect of shortening the time becomes more remarkable as the number of print processing sheets increases.

If the paper detector for detecting the paper length is disposed between the paper storage section and the registration roller, and if the first fed paper is to be detected,
The paper length can be detected quickly. Therefore, it is possible to quickly control the subsequent sheet feeding timing, and it is possible to further increase the printing speed. In particular, when the length of the first sheet fed is detected, the feeding timing is controlled for the third and subsequent sheets, and the length of the second sheet is related to the length of the sheet. By setting the paper feed timing to be constant, the control of the paper feed timing for the second sheet is simplified.

[Brief description of the drawings]

FIG. 1 shows an image forming apparatus according to an embodiment of the present invention,
(A) is a schematic configuration diagram of a scanner unit, and (b) is a schematic configuration diagram of an image forming unit.

FIG. 2 is a time chart showing a paper feeding timing;

FIG. 3 is a diagram showing a paper feeding state at a conventional paper feeding timing.

FIG. 4 is a diagram illustrating a sheet feeding state at the sheet feeding timing of the present invention.

FIG. 5 is a flowchart of a control procedure at the time of a multi-sheet printing process.

FIG. 6 is a flowchart of a control procedure at the time of multi-sheet printing processing.

[Explanation of symbols]

 30 paper cassette 34 take-out roller 36 paper feed roller 37 registration roller 40 detection switch

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shotaro Okamoto 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Inside (72) Inventor Hiroaki Hori 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Inside (72) Inventor Atsushi Saito 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Takashi Hori 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation F Terms (reference) 2H072 AA22 AB06 CA01 CB05 CB09 HB07 3F048 AA02 AA04 AA05 AB01 BA07 BB02 CA03 CC01 CC17 DA04 DA06 EA15 EB11 3F102 AA02 AB01 BA01 BB02 CB02 DA08 EA01 FA08 3F343 FA02 FB02 MC03 KB03 MC05 KB03 MC03

Claims (6)

[Claims] An image forming unit configured to form an image on a sheet; a sheet feeding unit that takes out the sheet from the sheet storing unit and feeds the sheet to the image forming unit; An alignment unit that delays the advance of the paper sheet fed between the paper forming unit and the image forming unit and conveys the paper sheet to the image forming unit; and the feeding unit and the aligning unit that match the start timing of the image forming process. In an image forming apparatus having control means for controlling driving, a paper detector for detecting a paper length of the fed paper is provided, and the control means controls a paper feed timing based on the detected paper length. An image forming apparatus characterized in that control is performed so as to be faster. 2. The aligning means is a registration roller for temporarily stopping the paper and transporting the paper again, and the control means starts feeding of the next paper when the previous paper is being transported by the registration roller. 2. The image forming apparatus according to claim 1, wherein the sheet feeding timing is determined as described above. The paper detector is provided between the paper storage unit and the registration roller, and is a detection switch that is turned on by the passage of the paper. The ON time of the detection switch and the paper are temporarily stopped by the registration roller. 3. The image forming apparatus according to claim 2, wherein the sheet length is calculated from the stopped time. 4. The control device according to claim 1, wherein when the length of the first sheet fed is detected, the control unit controls the feed timing for the third and subsequent sheets. 2
The image forming apparatus as described in the above. 5. The image forming apparatus according to claim 4, wherein the control unit sets a constant paper feed timing for the second sheet regardless of the length of the sheet. 6. The image forming apparatus according to claim 1, wherein the control unit controls the start timing of the image forming process to be advanced in accordance with the change of the paper feed timing.