JP2719370B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) In the present invention, an image is formed on an image carrier such as a photoconductor by an optical scanning means such as an analog type or digital type electrophotographic copying machine. Later, the present invention relates to an image forming apparatus for transferring an image to recording paper fed to the image carrier.

(Prior Art) For example, in an analog type electrophotographic copying machine, a charging device and an optical scanning unit correspond to an original image on a photosensitive drum while the photosensitive drum as an image carrier rotates. An electrostatic latent image is formed, and thereafter, the electrostatic latent image is developed with toner to form a toner image. Then, the toner image is transferred to a recording sheet conveyed to a photosensitive drum, and a predetermined copy image is formed on the recording sheet. In such an electrophotographic copying machine, the transport timing of the recording paper transported to the photosensitive drum is controlled so that the toner image is transferred to a predetermined position on the recording paper. Conventionally, the recording paper is once conveyed to a registration roller, and the optical scanner, which is an optical scanning means, drives the registration roller in synchronization with the timing of exposing a rotating photosensitive drum to a predetermined image, thereby driving the recording paper. To the photosensitive drum. As a result, the recording paper is aligned with the image forming position of the photosensitive drum,
The toner image is transferred to a predetermined position on the recording paper.

As described above, when the conveyance of the recording paper is temporarily stopped by the registration roller and then the recording paper is conveyed by the registration roller, the recording paper may be curled or deformed by being hit against the registration roller. In addition, noise may be generated due to the recording paper being rapidly conveyed by the registration rollers. In order to solve such a problem, Japanese Patent Application Laid-Open No. 60-98459 discloses an optical scanning method for exposing a document image on a photoreceptor in synchronization with the conveyance timing of recording paper fed to a photoreceptor drum. A copier configured to operate the means is disclosed.

(Problems to be Solved by the Invention) In the copying machine disclosed in the above publication, the operation start timing of the optical scanning means is controlled based on the timing at which the recording paper conveyed to the photoconductor passes a predetermined position. The operation start timing of the optical scanning means is a predetermined time set by an adjustment volume, a dip switch, or the like from the timing at which the recording paper passes the predetermined position.

After the operation start timing of the optical scanning unit is set in this way, the optical scanning unit is operated at that timing thereafter. In the case where the optical scanning means has a configuration in which, for example, the optical scanner performs exposure scanning along the original, the optical scanner performs exposure scanning of the original at a time when the optical scanner is accelerated from the stopped home position and reaches a predetermined speed. Must be. The optical scanner returns to the home position after exposing and scanning the document, but the optical scanner does not always stop at a predetermined position of the home position, and the stop position of the optical scanner may vary. If the stop position of the optical scanner is not constant, the exposure start timing of the original by the optical scanner varies,
The transfer position of the toner image on the recording paper is shifted. Also, the exposure start timing of the optical scanner, the recording paper conveyance timing, and the like tend to change over time due to the deterioration of the clutch and be delayed.

Recently, there has been a demand for a high-speed copying operation. For this reason, it has been performed to return the optical scanner to a home position at a high speed after exposing the optical scanner to a document. However, in this case, the stop position at the home position of the optical scanner is likely to vary, and the transfer position of the toner image on the recording paper is likely to vary.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of always forming an image at a predetermined position on a recording sheet.

(Means for Solving the Problems) According to the present invention, an image is formed on a moving image carrier by an operation of an optical scanning device, and then the image is transferred to a recording sheet fed to the image carrier. An image forming apparatus configured to operate the optical scanning unit in synchronization with a timing at which a recording sheet fed to the image carrier passes a predetermined position; and an operation start timing of the optical scanning unit. Is corrected based on the position immediately before the operation of the optical scanning means is started, thereby achieving the above object.

Further, the image forming apparatus of the present invention is an image forming apparatus in which an image is formed on a moving image carrier by an operation of an optical scanning unit, and then the image is transferred to recording paper fed to the image carrier. Wherein the optical scanning unit is configured to operate the optical scanning unit in synchronization with a timing at which a recording sheet fed to the image carrier passes a predetermined position, and the optical scanning unit is operated at a preset operation timing. When the optical scanning device is operated, the time from when the optical scanning device starts operating until it passes a predetermined position, or when the fed recording paper passes the predetermined position, the optical scanning device passes the predetermined position. This is characterized by measuring the time required to perform the operation, and correcting the operation start timing of the optical scanning means based on the measured time, thereby achieving the above object.

EXAMPLES Hereinafter, the present invention will be described with reference to examples.

FIG. 1 is a schematic view of a main part of an electrophotographic copying machine which is an image forming apparatus of the present invention. In the electrophotographic copying machine, a photosensitive drum 11 which is an image carrier that rotates in a clockwise direction indicated by an arrow B is disposed at a substantially central portion of the body, and the photosensitive drum 11 is usually used by using the photosensitive drum 11. A copy image is formed by the electrophotographic process described above. That is, a document on a document table 12 arranged on the upper surface of the machine is exposed by an optical system 13 having an optical scanner 13a that moves in a direction indicated by an arrow A, and the photosensitive drum 11 is charged by a charging device 14. An electrostatic latent image is formed on the image. The optical scanner 13a returns from the home position indicated by the solid line in the drawing to the home position after exposing the document on the document table 12 to the home position. Photoconductor drum
The electrostatic latent image on 11 is developed with toner by developing device 15, and the toner image is transferred by transfer device 17 to recording paper fed from paper feed cassette 16 which is a paper feed unit. The recording paper is separated from the photosensitive drum 11 by a separation device 18, and the toner image is fixed on the recording paper by a fixing device (not shown). The cleaning device 25 removes residual toner from the photosensitive drum 11.

The recording paper fed from the paper feed cassette 16 by, for example, the paper feed roller 21 is continuously transported to the photosensitive drum 11 by three sets of transport rollers 22, 23, and 24. Then, the recording paper comes into contact with the photosensitive drum 11, and the toner image is transferred to the recording paper as described above. The recording paper to which the toner image has been transferred is fixed to the toner image by a fixing device (not shown) and discharged outside the apparatus.

Immediately before the central transport roller 23 of the three transport rollers 22 to 24 that transport the recording paper fed from the paper feed cassette 16, it detects that the recording paper has passed, for example, a recording using a limit switch. A paper transport sensor 31 is provided. The recording sheet conveyance sensor 31, the toner image on the photosensitive drum 11 is provided at a position apart by l ₂ from the position to be transferred to the recording paper. The distance l ₂ is from the position where the original image on the surface of the photosensitive drum 11 is exposed to the photosensitive drum 11
It is longer than the distance l ₁ to the position where the upper toner image is transferred.

The optical scanner 13a is located at the home position of the optical scanner 13a in the optical system 13 disposed on the upper part of the body.
A home position sensor 32 using a photoelectric switch, which detects that is located at the home position, is provided. The home position sensor 32 is connected to the optical scanner 13.
It is turned on and off by a shielding plate 13b provided in a. A document leading edge sensor 39 using a photoelectric switch is disposed below the leading edge of the document placing table 12 on the exposure start side of the document. The document leading edge sensor 39 is turned on and off by the closing plate 13b of the optical scanner 13a, and is turned off when the optical scanner 13a passes the document leading edge position.

FIG. 2 is a block diagram of a control system in the electrophotographic copying machine of the present invention. In the figure, reference numeral 40 denotes a control unit using, for example, a microphone computer. The control unit 40 receives the output of a print key 33 and the number of sheets counter 34 provided on an operation panel of the copying machine main body. The print key 33 is operated to start the copying operation of the copying machine. The copy number counter 34 is operated when setting the number of copies. The number counter 34 is normally set to 1 as the number of copies. However, when a plurality of copies are required, the number counter 34 is operated to control the number of copies.
Set to 40.

Further, the control unit 40 includes an output of the recording paper conveyance sensor 31 in the recording paper conveyance path described above, an output of the home position sensor 32 for detecting that the optical scanner 13a is located at the home position, and a document leading edge sensor 39. Are input.

The output of the control system 40 is the photosensitive drum 11,
To 24 and a main motor 35 for rotating the feed roller 21. The photosensitive drum 11 and each of the transport rollers 22 to 24 except for the paper feed roller 21 are connected to a main motor 35 without using a clutch.
At the same time as the rotation of
24 is rotated. The paper feed roller 21 is connected via a paper feed clutch 36, and the paper feed clutch 36 is controlled by the control unit 40.

The output of the control unit 40 is also supplied to an optical motor 37 for exposing and scanning the optical scanner 13a. The output of the optical motor 37 is connected to the optical system 13. The optical motor 37 has
The forward / reverse clutch is disposed on the forward / reverse clutch 38.
By 38, the optical system motor 37 is rotated forward or backward. The forward / reverse clutch 38 is controlled by the control unit 40. When the optical motor 37 is driven forward, the optical scanner 13 of the optical system 13
In a, the original is exposed and scanned, and conversely, when the optical motor 37 is driven in reverse, the optical scanner 13a of the optical system 13 is reversely scanned and returned to the home position. A rotary encoder 37a is mounted on the output shaft of the optical motor 37. The rotary encoder 37a outputs a pulse signal corresponding to the rotation of the output shaft of the optical motor 37, and the output is
Has been entered.

Next, the control contents of the control unit 40 will be described based on the flowchart of FIG. 3 and the time chart of FIG.

First, an original is placed on the original placing table 12 of the electrophotographic copying machine, and the number counter 34 on the operation panel is set to a predetermined number of copies. When the pudding key 33 is operated in such a state (see step (1) in FIG. 3, the same applies hereinafter), the control unit 40 drives the main motor 35 (2). Thus, the photosensitive drum 11 is rotated, and the respective transport rollers 22 to 24 in the recording paper transport path are respectively rotated. At this time, the optical scanner 13a is located at the home position, and the home position sensor 32 is turned on by the shielding plate 13b.

In this state, after the rotation of the photosensitive drum 11 and the conveying rollers 22 to 24 has elapsed a predetermined time t ₁ to stabilize (3), the paper feed clutch 36 is turned on (4). As a result, the paper feed roller 21 is driven to rotate, and the recording paper in the paper feed cassette 16 is transported to the transport roller 22, and then continuously transported to the transport roller 23 by the transport roller 22. At this time, the recording paper conveyance sensor 31 provided in the conveyance path detects the recording paper and is turned on (5). The control unit 40 starts counting time by the timer 2 by turning on the recording paper transport sensor 31 (6). The timer 2 is operated to measure the timing of control by the control unit 40.

When the timer 2 measures that a predetermined time Δt has elapsed since the recording paper conveyance sensor 31 was turned on (7), the forward / reverse clutch 38 of the optical motor 37 is set in the forward rotation state, and the optical motor 37 is driven ( 8). This time Δt is a distance l from the transfer position of the photosensitive drum 11 to the position where the recording paper transport sensor 31 is provided.
_The optical scanner 13a sets the distance (l ₂ −l ₁ ) corresponding to the difference between the distance ₂ and the distance l ₁ between the exposure position and the transfer position on the photosensitive drum 11 from the time required for the recording paper to move. The predetermined reference position (the position of the optical scanner 13a at the time when the closing plate 13b turns on the home position sensor 32, see FIG. 5A) is obtained by subtracting the time required to reach the leading edge position of the original. Is set in advance. The timer 2 continues the timing operation thereafter. As a result, the optical scanner 13a of the optical system 13 performs exposure scanning and moves from the home position.
Are turned off (9). At this time, the control unit
40 starts timekeeping with tie 1 (10). Timer 1
Is also operated to measure the control timing by the control unit 40. During this time, the recording paper continues to be transported in the transport path.

Recording sheet conveyance sensor 31 has elapsed since the on-the predetermined time t ₂ is (11), the top side of the recording sheet in the sheet feeding cassette 16 is fed from the paper feed cassette 16, the paper feed clutch 36 Is turned off, and the rotation of the paper feed roller 21 is temporarily stopped. At the same time, the timer 2 for measuring the control time in the control unit 40 is also reset once (12).

On the other hand, when the optical scanner 13a moves from the home position and reaches a position below the leading edge of the document on the document table 12, the document leading edge sensor 39 is turned on by the shielding plate 13b, and thereafter, the optical scanner 13a When the document passes the position below the leading edge, the document leading edge sensor 39 is turned off by the separation of the closing plate 13b (13). At this time, the control unit 40
Reads the measured time T ₂ of the resets the timer 1 (14). If the optical scanner 13a is initially at the above-described reference position, the recording paper is turned on during the time T (= Δt + T ₂ ) from the time when the recording paper transport sensor 31 is turned on until the predetermined time t and T ₂ elapse. , And the distance (l ₂ −l ₁ ).

As the optical scanner 13a performs exposure scanning, the original image is exposed on the peripheral surface of the photosensitive drum 11 charged by the charging device 14, and an electrostatic latent image is formed on the photosensitive drum 11. You. The electrostatic latent image is developed by the developing device 15 with toner. During this time, the recording paper continues to be conveyed. And
The leading end of the exposure position of the photosensitive drum 11 (corresponding to the leading end on the exposure start side of the document) by the optical scanner 13a, which is driven in accordance with the timing at which the recording paper transport sensor 31 is disposed, faces the transfer device 17. When the transfer position reaches the transfer position, the leading end of the recording paper reaches the transfer position of the photosensitive drum 11.
Then, the transfer position of the photosensitive drum 11 is reached. Then, the leading end of the exposure position of the photosensitive drum 11 and the leading end of the recording paper coincide with each other, and the toner image on the photosensitive drum 11 is transferred to the recording paper by the transfer device 17.

Recording sheet conveyed by the conveying rollers 22 to 24, through the arrangement position of the recording sheet conveyance sensor 31, (15) after the recording sheet conveyance sensor 31 is turned off, the predetermined time t ₃ has elapsed (16) The forward / reverse clutch 38 of the optical motor 37 is switched to reverse the optical motor 31 (17), and the optical scanner 13a of the optical system 13 performs reverse scanning toward the home position. At this time, the optical motor 37 is driven at a higher speed than when the optical scanner 13a performs exposure scanning, and
13a is reversely scanned at high speed. And optical scanner 1
When 3a reaches the home position and the home position sensor 32 is turned on (18), the drive of the optical motor 37 is stopped (19). Since the optical motor 37 moves at a high speed, its output shaft continues to rotate due to inertia, and the optical scanner 13a also continues to move. When the home position sensor 32 is turned on and the driving of the optical motor 37 is stopped, the control unit 40 starts counting time with the timer 1 set. At the same time, the control unit 40 reads the output of the rotary encoder 37a attached to the output shaft of the optical motor 37, and when the rotation of the output shaft is completely stopped and the rotary encoder 37a is turned off (20), the timer The time T1 measured at ₁ is read, and the timer 1 is reset (21).

At this time, the controller 40 corrects the time Δt from when the recording paper conveyance sensor 31 is turned on to when the optical motor 37 is turned on at the time of the next copying operation. As described above, corresponds to the difference from the arrangement position of the recording sheet conveyance sensor 31 and the distance l ₂ to the transfer position of the photosensitive drum 11, a distance l ₁ from the exposure point of the photosensitive drum 11 to the transfer position The time T during which the recording paper moves the distance (l ₂ −l ₁ ) is, as shown in FIG. 5 (a), the time Δt described above and when the optical scanner 13a is located at a predetermined reference position. This is a time (T = Δt + T ₂ ), which is obtained by adding a time T ₂ from when the home position sensor 32 is turned off to when the document leading edge sensor 39 is once turned on and then turned off. However, as shown in FIGS. 5 (b) and (c), the stop position of the optical scanner 13a is shifted from the predetermined reference position by Δl, so that the recording paper is actually at the distance (l ₂ −l ₁ ). time for movement is also necessary time required the deviation distance to the optical scanner 13a moves (corresponding to T ₁₎ to _{(T = Δt + T 1 +} T 2).

Therefore, the control unit 40, the optical scanner 13a is the required amount of time T ₁ minute to move a distance Δl shifted from the reference position, the optical scanner after the recording sheet conveyance sensor 31 is turned on
To reduce the time Δt for moving 13a, the time Δ
As t, T- (T ₂ + T ₁ ) is set (22). Then, at the time of the next copying operation, the optical scanner 13a is driven based on the set time Δt. Such correction of the time Δt is performed every time a copying operation is performed.

When one copy operation is completed in this way, the control unit 40 sets the number of copies n set in the number counter 34 to n.
It is reset to -1 (23). Then, if the reset number of sheets is not 0 (24),
The paper feed clutch 36 is turned on, and the same operation as described above is repeated.

Ends the copying of all the copy sheets, if the number of copies n of number counter 34 becomes 0 (24), after a predetermined time T ₄ has elapsed (25), the main motor 35 is stopped (26).

In the electrophotographic copying machine of the present invention, the initial value of the time Δt from the time when the recording paper conveyance sensor 31 is turned off to the time when the optical motor 37 is driven is set in advance, for example, at the time of factory shipment. For example, if the optical scanner 13a is operated at the start of copying (print key, on) to set the image density of the original, etc., the optical motor 37 is driven from the driving of the optical motor 37 to the home position. The time from when the sensor 32 is turned off to when the optical scanner 13a stops may be measured, and the measured time may be used for correcting the time Δt in the subsequent copying operation. If there is no such function, once before copying operation,
What is necessary is just to make it the structure which operates an optical scanner.

6 and 7 are a flowchart and a time chart, respectively, for explaining the operation of another embodiment of the image forming apparatus of the present invention. In this embodiment, the original leading edge sensor 39 and the rotary encoder 37a attached to the output shaft of the optical motor 37 used in the above embodiment are not used. To explain the operation based on these, first,
An original is placed on the original placing table 12 in the electrophotographic copying machine, and the number counter 34 on the operation panel is set to a predetermined transfer number.

When the print key 33 is operated in such a state,
(Refer to step (31) in FIG. 6, the same applies hereinafter) Control unit 40
Drives the main motor 35 (32). This allows
As the photosensitive drum 11 rotates, each of the transport rollers 22 to 24 in the recording paper transport path rotates. At this time,
The optical system 13 is located at the home position, and the home position sensor 32 is on.

In this state, after the rotation of the photosensitive drum 11 and the conveying rollers 22 to 24 has elapsed a predetermined time t ₁ to stabilize (33), the paper feed clutch 36 is turned on (34). As a result, the paper feed roller 21 is driven to rotate, and the recording paper in the paper feed cassette 16 is transported to the transport roller 22, and then continuously transported to the transport roller 23 by the transport roller 22. At this time, the recording paper conveyance sensor 31 provided in the conveyance path detects the recording paper and is turned on (35). The control section 40 starts counting time by the timers 1 and 2 when the recording paper transport sensor 31 is turned on (36). One timer 1 is for home position sensor 32 measures the time T ₁ of the up off the other timer 2 is operated to measure the timing of the control by the control unit 40. Recording paper transport sensor
When the timer 2 measures that a predetermined time Δt has elapsed since the turning on of the 31 (37), the forward / reverse clutch 38 of the optical motor 37 is brought into the forward rotation state and the optical motor 37 is driven (38).
This time Δt is the same as in the previous embodiment.

Accordingly, when the optical scanner 13a is exposed and scanned and moves from the home position, the home position sensor 32 is turned off (39). In this case, counting by the timer 1 is stopped, the control unit 40 reads the measurement result T ₁ of the timer 1 at that time. That is, the timer 1 starts the home position sensor after the recording paper conveyance sensor 31 is turned on.
After the time T ₁ until the 32 is turned off, in other words, after the optical scanner 13a of the optical system 13 is driven to perform exposure scanning, the home position sensor 32 is provided for the optical scanner 13a of the optical system 13 position measuring the time T ₁ of the up passes. After the measuring time T ₁ is read into the control unit 40, the timer 1 is reset (40). During this time, the recording paper continues to be transported into the transport path.

The original image is exposed on the peripheral surface of the photosensitive drum 11 charged by the charging device 14 by the exposure scanning of the optical scanner 13a, similarly to the above-described embodiment.
An electrostatic latent image is formed thereon. Then, the electrostatic latent image is developed with toner by the developing device 15. During this time, the recording paper continues to be conveyed, and the optical scanner 13a driven at the timing when the recording paper has passed the position where the recording paper conveyance sensor 31 is provided.
When the leading end of the exposure position of the photosensitive drum 11 reaches the transfer position facing the transfer device 17, the leading end of the recording paper reaches the transfer position of the photosensitive drum 11. Then, the photosensitive drum 11
The upper toner image is transferred to the recording paper by the transfer device 17.

At this time, the control unit 40 performs the following calculation to correct the drive timing of the optical motor 37 at the time of the next copy operation. That is, at the time Δt from when the recording paper transport sensor 31 is turned on during the above-described copying operation to when the optical motor 37 is driven to rotate, the home position is set after the recording paper transport sensor 31 is turned on during the copying operation. Sensor 32
There the measured time T ₁ of the up turned off, the difference between the measured time T ₀ copying operation when performed before the time of the copying operation (T ₁ -
T ₀ ). Then, as a result, ｛Δt + (T ₁ −
T ₀ )｝ is a time Δt from the time when the recording paper conveyance sensor 31 is turned on to the time when the optical motor 37 is driven to rotate in the next copying operation. When such operation is completed, in the next copying operation, as the previous measured time T ₀ used for this correction, previously set the current measurement time T ₁ (41).

Recording sheet conveyance sensor 31 has elapsed since the on-the predetermined time t ₂ is (42), the top side of the recording sheet in the sheet feeding cassette 16 is fed from the paper feed cassette 16, the paper feed clutch 36 Is turned off, and the rotation of the paper feed roller 21 is temporarily stopped. At the same time, the timer 2 for measuring the control time in the control unit 40 is once reset (43).

Recording sheet conveyed by the conveying rollers 22 to 24, through the arrangement position of the recording sheet conveyance sensor 31, (44) after the recording sheet conveyance sensor 31 is turned off, the predetermined time T ₃ has elapsed (45) The forward / reverse clutch 38 of the optical motor 37 is switched to reverse the optical motor 31 (46), and the optical scanner
13a is reversely scanned toward the home position. At this time, the optical motor 37 is driven at a higher speed than when the optical scanner 13a performs exposure scanning, and the optical scanner 13a performs reverse scanning at a higher speed. When the optical scanner 13a reaches the home position and the home position sensor 32 is turned on (47), the driving of the optical motor 37 is stopped (4).
8). At this time, since the optical scanner 13a is moving at high speed, the optical system 13 moves by inertia even when the home position sensor 32 is turned on, and the stop position is not constant. However, in the present invention, the time Δt from when the recording paper conveyance sensor 31 is turned on to when the optical motor 37 is driven is, as described above, the optical motor of the optical system 13 that was driven immediately before.
Since the correction is made based on the time from when the 37 is driven to when the home position sensor 32 is turned off, the optical system scanner
The photosensitive drum 11 exposed at 13a is brought into contact with the exposing end position of the photosensitive drum 11 in alignment with the leading end of the recording paper.

When one copy operation is completed in this way, the control unit 40 sets the number of copies n set in the number counter 34 to n-
It is reset to 1 (49). Next, when the reset copy number n is not 1 (50),
The paper feed clutch 36 is turned on, and the same operation as described above is repeated.

Ends the copying of all the number of copies, in the case (50 number of copies n of number counter 34 becomes 0, after a predetermined time t ₄ has passed (51), the driving of the main motor 35 is stopped (52).

Note that, after the recording paper transport sensor 31 is turned off, the optical motor
The initial value of the time Δt until the 37 is driven is set in advance, for example, at the time of shipment from a factory, as in the above embodiment. For example, if the optical scanner is operated to set the image density of the original at the start of copying (printing, on), the home position sensor 32 starts operating the optical motor 37 during the operation. It may be configured to measure the time until is turned off and use the measured time to correct the time Δt in the subsequent copying operation. When such a function is not provided, the optical scanner may be operated once before the copying operation.

Although the optical scanner 13a is described as moving in the above embodiment, the present invention is also applicable to a configuration in which the document table on which the document is placed moves and the optical system stops. Further, the present invention is not limited to the analog type, and can be applied to a digital type image forming apparatus.

(Effect of the Invention) In the image forming apparatus of the present invention, as described above, the recording paper is continuously conveyed to the image carrier such as the photoconductor without being stopped, and the optical scanning is performed in synchronization with the conveyance timing. Since the means is driven, there is no need to provide a clutch or the like in the recording paper conveying means in order to temporarily stop the conveyance of the recording paper.
In addition, the operation start timing of the optical scanning unit is corrected based on the position immediately before the operation of the optical scanning unit starts. Or, when the optical scanning means is operated at a preset operation timing, the time until the optical scanning means starts operating or passes a predetermined position, or the fed recording paper passes the predetermined position and The time from when the optical scanning means passes through the predetermined position is measured, and the operation start timing of the optical scanning means is corrected based on the measured time. For this reason,
The recording paper and the image position of the image carrier are aligned, and an image can always be formed at a predetermined position on the recording paper.

[Brief description of the drawings]

FIG. 1 is a schematic view of a main part of an electrophotographic copying machine showing an example of an image forming apparatus of the present invention, FIG. 2 is a block diagram of a control system thereof,
FIG. 3 is a flow chart for explaining the operation, FIG. 4 is the same time chart, FIGS. 5A to 5C are explanatory diagrams of the operation, and FIG. 6 is another embodiment of the image forming apparatus of the present invention. The flowchart in the example, and FIG. 7 is a time chart thereof. 11 photoconductor drum, 13 optical system, 15 developing device,
21: paper feed roller, 22 to 24: transport roller, 31: recording paper transport sensor, 32: home position sensor, 39 ...
Document leading edge sensor.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toshihiko Araki 1-2-2, Tamazo, Higashi-ku, Osaka-shi, Osaka Inside Mita Kogyo Co., Ltd. (56) References JP-A-58-125070 (JP, A) JP-A Sho 60-98459 (JP, A) JP-A-64-13349 (JP, A) JP-A-1-144065 (JP, A) JP-A-2-48962 (JP, U)

Claims (2)

(57) [Claims] An image forming apparatus for forming an image on a moving image carrier by an operation of an optical scanning means, and then transferring the image to recording paper fed to the image carrier. The optical scanning unit is configured to operate in synchronization with the timing at which the recording paper fed to the image carrier passes a predetermined position, and the operation start timing of the optical scanning unit is determined by the operation of the optical scanning unit. Wherein the correction is performed based on the position immediately before the start of the image forming. 2. An image forming apparatus wherein an image is formed on a moving image carrier by an operation of an optical scanning means, and then the image is transferred to recording paper fed to the image carrier. The optical scanning unit is configured to operate in synchronization with a timing at which a recording sheet fed to the image carrier passes a predetermined position, and when the optical scanning unit is operated at a preset operation timing. The time from the start of the operation of the optical scanning means to the passage of a predetermined position, or the time from when the fed recording paper passes the predetermined position to when the optical scanning means passes the predetermined position. An image forming apparatus that measures the time and corrects the operation start timing of the optical scanning means based on the measured time.