JPH02276745A - Image forming device - Google Patents

Abstract

PURPOSE:To position and form an image on a copying paper with a high precision independently of the optical characteristic of the copying paper by installing an optical characteristic judging means for judging the optical characteristic of the copying paper driven out by a paper feeding means and a restart timing correcting means for correcting the timing for driving a transport roller again according to the result of the judgement for the optical characteristic. CONSTITUTION:The output of the second sensor 9 is read into a microcomputer 20, and the optical characteristic (reflection rate) of a copying paper is judged from the output level. Then, the correction time is calculated on the basis of the optical characteristic, and the correction time is stored into a restart timing correction timer. Then, the output of the first sensor 6 is read, and when the level exceeds a threshold level, it is judged that the top edge of the copying paper is detected, and a copying paper detection flag is set to '1', and a resistor clutch 17 is turned-OFF, and a transport roller 7 is stopped. Then, the time on a timer is subtraction-calculated, and when the value becomes zero, the resistor clutch 17 is turned ON, and the transport roller 7 is driven again, and the flag is set to zero.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a laser printer, and particularly relates to an image alignment technique thereof.

[Conventional technology]

An electrophotographic image forming apparatus generally uses a drum-shaped or belt-shaped photoreceptor that rotates while carrying a toner image, and transfers the toner image onto a transfer paper at a predetermined position around the photoreceptor. A transfer unit (transfer charger, etc.), a paper feed unit (paper feed tray, etc.) that stores the transfer paper, a paper feed unit (paper feed roller, etc.) that feeds the transfer paper from this paper supply unit, and this paper feed unit It has a conveyance roller (registration roller) that conveys the fed-out transfer paper to the transfer section.

Then, the leading edge of the transfer paper is detected by an optical sensor placed between the conveyance roller and the transfer section, and the conveyance of the transfer paper by the conveyance roller is temporarily stopped, and a predetermined period of time has elapsed since the start of image formation on the photoreceptor. Afterwards, the transfer roller is driven again to feed the transfer paper to the transfer section.

In this way, the leading edge of the transfer paper can be detected by the optical sensor due to slight fluctuations in the feeding start timing of the transfer paper being fed and conveyed from the paper feed unit or slipping during conveyance. Even if variations occur, the restart timing remains constant just by changing the temporary stop period of the conveying roller, and the timing when the transfer paper reaches the transfer section can be made to coincide with the timing when the leading edge of the toner image reaches the transfer section.

An example of an image alignment technique used in such an image forming apparatus is the one described in Japanese Patent Laid-Open No. 56-39562.

[Problem to be solved by the invention]

Incidentally, in such an image forming apparatus, various types of transfer paper are used.

The leading edge of the transfer paper fed from the paper feeder is detected when the output signal from the optical sensor (corresponding to optical characteristics such as light transmittance or light reflectance) exceeds a predetermined level or falls below that level. are doing. However, the type of transfer paper, e.g. blank paper.

Since the optical characteristics differ depending on the translucent second base paper, the transparent OHP paper, etc., the detection position will be different.

Therefore, depending on the detection signal of the optical sensor, there will be variations in the waiting position of the transfer paper when the conveyance roller once stops, and there will also be variations in the point at which the leading edge of the transfer paper reaches the transfer section after restarting, resulting in the transfer There was a problem in that the image position on paper could not always be maintained with high precision.

This invention has been made in view of the above points, and in the image forming apparatus described above, it is possible to align the transfer paper and the image transferred thereto with high precision regardless of the type of transfer paper used. The purpose is to do so.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an image forming apparatus as described above, which includes an optical characteristic determining means for determining the optical characteristics of the transfer paper fed out by the paper feeding means, and a conveying roller according to the determination result. A restart timing correction means is provided for correcting the timing of restarting the drive.

[For production]

According to the image forming apparatus configured in this way, the optical characteristic determining means determines the optical characteristics of the transfer paper fed out by the paper feeding means, and the restart timing correcting means re-drives the conveyance roller according to the determination result. Since the timing is corrected, the restart timing is advanced or delayed by the above-mentioned variation in the standby position due to the optical characteristics of the transfer paper, so that the time when the leading edge of the transfer section reaches the transfer section is always a certain amount of time from the start of image formation. You can do it later.

As a result, even if various types of transfer paper with different optical characteristics are used, such as blank paper, second base paper, oHP paper, etc., the image can always be transferred in the optimum position.

〔Example〕

Embodiments of the present invention will be specifically described below with reference to the accompanying drawings.

FIG. 1' is a schematic diagram of an electrophotographic copying machine showing a first embodiment of the present invention.

In the figure, reference numeral 1 denotes a belt-shaped photoreceptor, which is stretched between rollers 1a and 1b and rotated in the direction of arrow A.

Around the photoreceptor 1, chargers 2. A transfer charger 4 is arranged in the developing device 3 and the transfer section P, respectively.

When light from an optical system (not shown) forms an image on the surface of the photoreceptor 1 between the charging charger 2 and the developing device 3 and is exposed, the surface of the photoreceptor 1, which has been uniformly charged in advance by the charging charger 2, is exposed. An electrostatic latent image is formed.

The electrostatic latent image is visualized by electrostatic development while passing through the developing device 3, and is formed on the photoreceptor 1 as a toner image. This 1-ner image is designated by the symbol T.

This toner image T is carried by the photoreceptor 1 and moves in the direction of arrow A, and is transferred to the transfer paper by the action of the transfer charger 4 at the transfer portion P. Note that here, it is necessary to feed the transfer paper to the transfer section P in a timely manner with respect to the toner image T to align the image at a predetermined position on the paper surface, but this will be explained later.

After the transfer, the transfer paper is separated from the photoreceptor 1, heated and fixed by a fixing unit (not shown), and then discharged to a paper discharge tray.

The transfer charger 4 is placed near the roller 1a, and uses its curvature to transfer the transfer paper to the photoreceptor 1.
This is to make it easier to separate from the

By the way, if you follow the path of the transfer paper from the downstream side to the upstream side to reach the transfer charger 4, you will see that the guide 5. First sensor 6, conveyance roller (registration roller) 7. Guide 8.
Second sensor9. Guide 10° Paper feed roller 11 and separation roller 12. The paper feed rollers 13 and the paper feed tray 14 are arranged in this order.

The paper feed tray 14 constitutes a paper feed section, and contains many sheets of transfer paper 15.
are stored in layers.

When copying, follow the prescribed sequence program.
The transfer paper 15 in the paper feed tray 14 is fed out by a paper feed roller 13 serving as a paper feed means, separated into sheets one by one by a paper feed roller 11 and a separation roller 12, passes through guides 10 and 8, and reaches a conveyance roller rough. When the transfer paper 15 is nipped therein and further slightly fed, the leading edge of the transfer paper 15 is detected by the first sensor 6, and the conveyance roller 7 is thereby temporarily stopped.

Here, the first sensor 6 is an optical sensor, and for example, as shown in FIG. 2, a reflective optical sensor consisting of a light emitting element (LED) 6a and a light receiving element (phototransistor) 6b is used.

Light is emitted from the light emitting element 6a at a constant light intensity in the direction of the transport path, and as the transfer paper 15 approaches, the amount of light received by the light receiving element 6b increases.

Therefore, the transfer paper 15 can be stopped at a predetermined position by stopping the rotation of the transport roller when the detection signal output from the light receiving element 6b, that is, the photoelectric conversion output exceeds a predetermined threshold level.

In this way, the transfer paper is kept waiting at a predetermined position, and after the start of exposure (image formation) on the photoreceptor 1, at a predetermined timing calculated backward from the time when the toner image T arrives at the transfer portion P by the transfer charger 4. When the drive of the conveyance roller 7 is restarted, the toner image T is transferred to the correct position on the transfer paper by the action of the transfer charger 4.

Note that, as the first sensor, a light transmission type optical sensor that detects the amount of transmitted light may be used instead of the reflective type optical sensor configured as shown in FIG. 2 that detects the amount of reflected light.

Regardless of the type of optical sensor, if the transfer paper has constant optical characteristics such as light reflectance or light transmittance, then the first sensor 6
The distance +2 from the leading edge of the transfer paper 15 to just below the center of the first sensor 6 (hereinafter referred to as "leading edge detection distance") shown in FIG. 3 when the detection signal output from the sensor exceeds a predetermined threshold level is constant. Become.

Therefore, as long as only transfer paper having the same optical characteristics is used, the distance from the leading edge of the transfer paper to the transfer portion P when the above threshold level is exceeded will naturally be constant, so the detection signal will cause the conveyance roller 7 to be Since the waiting position of the transfer paper once stopped is always constant, if the transfer paper is restarted at a predetermined timing thereafter, the image can be transferred to an appropriate position on the transfer paper.

However, in reality, transfer papers with various optical characteristics are used, so if the threshold level shown by the dashed line in Fig. 4 is used as the reference voltage level for detecting the leading edge of the transfer paper, the As shown, blank paper, second base paper (
(semi-transparent), so-called oHP for overherad projectors
Since each paper (transparent) has different optical characteristics, the detection distance of the leading edge of the transfer paper differs as Ql>Qz>03, and the first
There may be variations in the waiting position of the transfer paper when the conveyance roller 7 is stopped based on the detection signal output from the sensor 6, and even if it is restarted at a predetermined timing, depending on the transfer paper, the image may not be formed on the transfer paper. The resulting image may deviate from the proper image position by about 1 to 21111 degrees.

Therefore, in this embodiment, as shown in FIG. 1, a second sensor 9 is provided to detect the optical characteristics of the transfer paper fed upstream of the first sensor 6, that is, the reflectance and transmittance of light. The optical characteristics of the transfer paper are determined based on the detection signal from the second sensor 9, and the transport roller 7 is adjusted according to the determination result.
We are trying to correct the re-drive timing.

This second sensor 9 is not arranged above the paper feed tray 13 but is arranged downstream of the one-separation roller 9.

The reason for this arrangement is that the optical characteristics of each sheet of transferred paper to be fed can be determined, and even a multi-stage paper feed tray can be detected by one optical sensor.

When correcting the re-driving timing of the transport roller rough, the relationship between the leading edge detection distance based on the detection signal of the first sensor 6 and the light reflectance of the transfer paper is as shown in FIG. This is based on the fact that as A3<A2<At, the tip detection distance also increases (Q3<Rz<Qt), which is a substantially proportional relationship.

Therefore, if the optical characteristics of the transfer paper are known, the deviation of the standby position when the standby position of the blank transfer paper is set to the #A quasi-position (in this example, Since it is known that the more transparent the transfer paper is, the shorter the leading edge detection distance Q is, the standby position will be shifted closer to the transfer section P. Therefore, the re-driving timing of the conveyance roller can be delayed by that amount.

As the second sensor 9, basically the same sensor as the first sensor 6 can be used. However, the purpose is not to detect the leading edge of the transfer paper, but to detect the optical characteristics of the transfer paper. , are arranged on the same feed line as the first sensor 6.

As shown in FIG. 6, the output of the first sensor 8 and the output of the second sensor 9 are both input to a microcomputer 20 that sequentially controls this copying machine.

Data as shown in FIG. 5 is stored in advance in the microcomputer 20, and the optical characteristics of the transfer paper are determined based on the detection signal from the second sensor 9.

Furthermore, the detection signal from the first sensor 6 is input and compared with the threshold level shown in FIG.

When it is determined that the leading edge of the transfer paper has reached a predetermined position, the registration clutch 17 is turned off and the conveyance of the transfer paper by the conveyance roller 7 is temporarily stopped.

Although not shown in the figure, the microcomputer 20 inputs and counts timing pulses generated in synchronization with the rotation of the photoreceptor 1, and when the count value reaches the pre-programmed exposure start timing, the timing pulse shown in FIG. Exposure (image formation) of the photoreceptor 1 to light is started.

In addition, when standard white paper is used as transfer paper, the restart timing for re-driving the conveyance roller 7 is also determined by the count value, but the actual restart timing is determined by the determination result of the optical characteristics of the used transfer paper. Modify (delay) accordingly.

This will be explained with reference to FIG. 7, which shows the relationship between the leading edge position of the transfer paper and time.

First, if the transfer paper 15 is a standard white paper and is fed out without slipping by the paper feed roller 13, its leading edge moves from ■ to ■ at a constant speed as shown by the solid line a, and is nipped by the conveyance roller 7 at position p3. , and is detected by the first sensor 6 at a position P4 that is a tip detection distance HQ1 before the center of the first sensor 6, so the conveyance roller 7 stops at that point tc, and at that position p4, the conveyance roller 7 is moved from ■ to ■. stand by.

Then, at a time t when a certain period of time has elapsed from the exposure start time ta
By re-driving the conveyance roller 7 at step d, the leading edge of the transfer paper advances from ■ to ■, reaches the transfer portion P (position ps) at time te, and aligns with the leading edge of the toner image on the photoreceptor 1. It has become.

If paper feeding is delayed due to slipping when the transfer paper 15 is fed out by the paper feed roller 13, the leading edge of the transfer paper 15 moves as shown by the dashed dotted line, is detected by the first sensor 6, and is temporarily stopped. However, the time td at which the transport roller 7 is driven again remains the same, so the time te at which the paper reaches the transfer section P is also the same as in the case where the paper is normally fed as described above.

In this way, even if there is a slight deviation in the paper feeding timing or the transfer paper slips during transportation.

If the delay is within the standard waiting time (td-tc), the waiting time is only shortened, and the transfer paper can always be fed to the transfer section P at the predetermined restart timing.

In addition, when a transfer paper with low reflectance such as OHP paper is used, as shown by the broken line C in FIG. The position of the tip advances as shown by ■'.

Therefore, if the conveyance roller 7 is driven again at the predetermined time td, which is the same as in the case of blank paper, the time at which the paper reaches the transfer portion P will be earlier than the predetermined time te, as shown by ■'.

Therefore, by delaying the time when the conveyance roller 7 is re-driven by the time necessary to convey the advance amount and correcting it as shown in td', the transfer roller 7 advances as shown in ■'→■ and reaches the transfer portion P. This is done in such a way that the time of writing is the same as if it were a blank sheet of paper.

Next, the processing related to the invention as described above by the microcomputer 20 of FIG. 6 will be explained according to the flowchart of FIG. 8.

The flowchart in FIG. 8 shows only the part related to the present invention from the sequence control flow by the microcomputer 20 that controls the entire copying machine, and the entire routine is periodically repeated at a high processing speed. executed.

As described above, when the exposure start timing arrives according to the count value of the timing pulse, the document is scanned by a scanner (not shown) and exposure of the photoreceptor 1 is started.

Thereafter, when the timing for reading the second sensor comes, the output of the second sensor 9 is read and the optical characteristics of the transfer paper (in this embodiment, the reflectance A is determined based on the level of the photoelectric conversion output)
n), and its reflectance An is converted into a tip detection distance Qn using a table as shown in FIG.

Then, the correction time Δ1=(Ω1-12n)/υ is calculated, and the correction time Δt is transferred to the restart timing correction timer R1. Here, Ql is the leading edge detection distance in the case of blank paper (see FIG. 4), and υ is the transfer paper conveyance speed.

Next, the output on the first sensor day is read, and when the level exceeds the threshold level shown in FIG. is turned off to stop the conveyance roller 7.

When the transport roller restart timing arrives with the transfer paper detection flag FO set to 1, the above-mentioned restart timing correction timer R1 (in which the correction time Δt is stored) starts subtraction.

Then, when the value of this timer R1 becomes "0".

The registration clutch 17 is turned on, the conveying roller 7 is driven again, the transfer paper detection flag FO is set to O, and the process proceeds to other processes.

In this way, the re-drive timing of the conveying roller rough is corrected by delaying the timer R1 by the amount of advance of the standby position of the transfer paper when the reflectance of the transfer paper is lower than that of the white paper.

By the way, it is also possible to perform each of the above-mentioned functions of the two sensors, the first sensor 6 and the second sensor 9, by one optical sensor.

Therefore, a second embodiment of the present invention will be described in which the number of primary optical sensors is reduced to one.

9 and 10 are respectively a schematic configuration diagram of a copying machine according to a second embodiment of the present invention and a block diagram showing the main parts of its control section, and correspond to FIGS. 1 and 6, respectively. The parts are given the same reference numerals.

The optical sensor 1 is placed at the same position as the first sensor 8 shown in FIG. When the phototransistor 18b receives the light, it outputs a detection signal Vs (light reflectance data) corresponding to the light reflectance of the transfer paper.

Note that this optical sensor 1B is a reflective optical sensor similar to the first sensor 6 and second sensor 9 shown in FIG. 1, but a transmissive optical sensor may also be used.

Figure 10 (7) CPU3Q is a microcomputer similar to CPU2Q in Figure 6, and has an analog input port (
AN), input the detection signal Vs, and determine the arrival of the leading edge of the transfer paper and the optical characteristics (reflectance) based on its level.
The resist clutch 17, which is the controlled object, is controlled.

Next, the operation of this embodiment configured as described above will be explained with reference to FIG. 11 and subsequent figures.

First, each time t in the timing chart of FIG.
Q-t4 will be explained.

The time to is from the time a when image formation on the photoreceptor 1, that is, the start of exposure, to the time when the optical sensor 16 detects the leading edge of the transfer paper (the time when the rise of the optical sensor 1 exceeds the threshold level in FIG. 4). It shows the time.

Therefore, this time tQ changes depending on the slippage of the transfer paper during feeding and the difference in optical characteristics (reflectance) depending on the type of transfer paper.

The time tl indicates the time from when the optical sensor 16 detects the leading edge of the transfer paper until the registration clutch is turned off and the driving of the conveyance roller 7 is temporarily stopped.

This time t1 starts from the time when the optical sensor 16 detects the leading edge of the transfer paper to the edge detection transient fluctuation area (
This is the time it takes for the photosensor output to pass through the range (corresponding to the area where it changes as shown in FIG. 4) and enter the stable area, and is set to a certain time that matches the transfer paper (OHP paper) with the lowest reflectance.

This is because correct reflectance data for each transfer paper can be obtained by inputting the detection signal from the optical sensor 1B immediately after the set time has elapsed.

The time t2 indicates the time from the time when the driving of the transport roller rough is temporarily stopped to the time td when the driving of the transport roller rough starts again. This time t2 changes depending on the change in time tQ and the correction of the transport roller restart timing according to the determination result of the reflectance of the transfer paper.

The time t3 indicates the time from the time ta when exposure starts for the photoreceptor 1 until the time td when the transport roller is re-driven. Thus, the time t4 until the transfer start time te when the leading edge of the transfer paper reaches the photoreceptor 1 is made constant.

However, if the transfer paper actually used has a lower reflectance than standard white paper, the time t3 is extended accordingly, and the re-driving time td of the transport roller 7 is modified to be delayed. Control is performed so that the time t4 until the transfer start time te is always constant.

Therefore, the microcomputer (CPU) shown in Figure 10
12 to 1.
This will be explained according to the flowchart shown in FIG.

These flowcharts also show only the parts related to the present invention from the flow of sequence control by the microcomputer 30 that controls the entire copying machine, and all routines are executed periodically and repeatedly at a high processing speed. Ru.

Note that when the power is turned on, initial settings and status checks are performed first, and the following settings are made as initial settings related to the processing that will be described below.

Transfer paper detection flag Fo: 0 Conveyance roller feed stop flag F1:0 Conveyance roller restart flag F2:0 Conveyance roller stop timer Ro
:FFH restart timing correction timer R1:
FF) ( Then, the processing of the main routine is started, and in the flowchart of FIG. 12, when the exposure start timing arrives according to the count value of the timing pulse as in the case of Moe's first embodiment, the document is scanned by a scanner (not shown). is scanned to start exposure of the photoreceptor 1.

After that, check the transfer paper detection flag FO, and if it is 1, proceed to the flow shown in Fig. 13, but since it is initially 0, proceed to the next step according to the flow shown in Fig. 12, and check the output of the optical sensor for one day. Load.

Then, when the level exceeds the threshold level shown in Figure 4 for the first time, it is determined that the leading edge of the transfer paper has been detected.
After setting the transfer paper detection flag FO to 1 and further setting the transport roller feed stop flag F1 to 1, the transport roller stop timer RO, which is a subtractive timer that sets the time until the transport roller 7 is stopped, is subtracted. Start and proceed to other processing.

When executing the flow shown in FIG. 12 again after exposure has started, the check to see if it is the exposure start timing will return No, so next check to see if the transfer paper detection flag FO is 1, and if it is 0. If so, the above-mentioned processing is performed, but if it is 1, the process proceeds to the flow shown in FIG. 13.

Therefore, if the value of the conveyance roller stop timer RO is not "0", the process proceeds to the flow shown in FIG. 14.

When it becomes "0", the flow advances to the next step in FIG. 13, where the registration clutch 17 is turned off and the conveyance roller 7
, the conveyance roller feed stop flag F1 is set to 0, and the conveyance roller stop timer Ro is set to FFH.

Then, the output of the optical sensor 16 is read, and the optical characteristic (reflectance An in this embodiment) of the transfer paper is determined based on the level of the photoelectric conversion output, and the reflectance An is determined from the table shown in FIG. First, convert it to end detection distance Qn, calculate correction time Δt=(j2x-Qn)/u, and use the correction time ΔL as restart timing correction timer R.
Do 1 Hesdoor. Here, Ql is the leading edge detection distance in the case of blank paper (see FIG. 4), and υ is the transfer paper conveyance speed.

Thereafter, when the transport roller re-drive timing comes, the restart timing correction timer R1 in which the correction time Δt is stored in the above process starts subtraction, and the transport roller restart flag F2 is set to 1, and the flow shown in FIG. 14 is started. Proceed to.

At this point, the conveyance roller restart flag F2 is first checked, and if it is set to 1 as described above, the first step is to check whether the value of the restart timing correction timer R1 is "0" or not. ”, resist clutch 17
is turned on to drive the conveyance roller 7 again and feed the waiting transfer paper to the transfer section.

Furthermore, the conveyance roller restart flag F2 is set to 0, and the restart timing correction timer R1 is set to FFH.

After that, it is checked whether or not the optical sensor 16 can detect the transfer paper, and if it is possible, the transfer paper detection flag FO is set.
is set to 0, and if it is not possible, proceed directly to other processing.

As described above, in any of the embodiments, the waiting transfer paper can be fed to the transfer section by the transfer charger at the most suitable timing, regardless of the type of transfer paper used. The image can always be aligned with high precision even with respect to the transfer paper.

Furthermore, according to the second embodiment, since one optical sensor is used both for detecting the optical characteristics of the transfer paper and for detecting the leading edge, the present invention can be implemented at a lower cost.

In addition, because the same photoelectric conversion signal is used for detecting the leading edge of the transfer paper and detecting the optical characteristics due to changes in the ambient temperature or dirt on the sensor surface, the level of the photoelectric conversion signal decreases and the detection of the leading edge is delayed, causing the transfer paper to wait. When the position has advanced too far, the reflectance of the transfer paper is also determined to be low, which causes the restart timing to be delayed extra, so the change acts to cancel out the change, so it has almost no effect.

Furthermore, the present invention is applicable not only to copying machines but also to various electrophotographic image forming apparatuses such as laser printers and facsimile machines. In that case, for example, in a laser printer, the start of exposure is the start of writing with a laser beam.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to form an image on a transfer paper with high precision alignment regardless of the optical characteristics of the transfer paper.

An image alignment device can be provided.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a copying machine according to a first embodiment of the present invention, and FIG. 2 is a perspective view showing an example of the arrangement of reflective optical sensors. Fig. 3 is an explanatory diagram for explaining the detection distance of the leading edge of the transfer paper, Fig. 4 is a diagram showing the relationship between the optical sensor output and the detection distance of the leading edge of the transfer paper, and Fig. 5 is a diagram showing the optical characteristics (reflection) of the transfer paper. Figure 6 is a block diagram showing the main parts of the control section of this first embodiment, and Figure 7 is a diagram showing the position of the leading edge of the transfer paper to explain its operation. An explanatory diagram showing the relationship between and time, Figure 8 is the CP of Figure 6.
FIG. 7 is a flowchart showing processing performed by U20 according to the present invention. FIG. 9 is a schematic diagram of a copying machine according to a second embodiment of the invention. FIG. 10 is a block diagram showing the main parts of the control section of this second embodiment, FIG. 11 is a timing diagram for explaining its operation, and FIGS. 12 to 14 are based on the CPU 30 of FIG. FIG. 3 is a flow diagram showing processing related to the present invention. 1... Photoreceptor 3... Developing device 6... First sensor 9... Second sensor 12... Separation roller 14... Paper feed roller 16... Optical sensor 20.30...・Microphone 2...Charger 4...Transfer charger 7...Conveyance roller 11...Paper feed roller 13...Paper feed roller 15...Transfer paper 17...Registration clutch computer (cpU) ) g1 figure 312 figure jI5 figure 4 figure 3 figure tA6 figure 319 figure g10 figure 1112 figure 11 prisoner beginning 1i14. Procedural amendments to figures and other processing (voluntary)

Claims (1)

[Claims] 1. A photoreceptor that rotates while carrying a toner image, a transfer section that transfers the toner image onto a transfer paper at a predetermined position around the photoreceptor, a paper feed section that stores the transfer paper, and a paper feed section that stores the transfer paper. The paper feeding means feeds the transfer paper from the paper section, and the conveyance roller conveys the transfer paper fed out by the paper feeding means to the transfer section, and is disposed between the conveyance roller and the transfer section. The leading edge of the transfer paper is detected by an optical sensor, the transport of the transfer paper by the transport roller is temporarily stopped, and the transport roller is driven again after a predetermined period of time has elapsed from the start of image formation on the photoreceptor. In an image forming apparatus configured to feed a transfer paper to the transfer unit in alignment with the toner image on the photoreceptor, optical characteristics of the transfer paper fed out by the paper feeding means are determined. An image alignment device comprising: a light characteristic determining means; and a restart timing correcting means for correcting the timing for re-driving the conveyance roller according to the result of the determination.