JP2001213548A - Image forming apparatus and image forming method - Google Patents

Abstract

(57) [Summary] (with correction) [PROBLEMS] To provide an image forming apparatus capable of efficiently improving productivity while ensuring a high printing accuracy by shortening a sheet interval with a simple configuration. An image forming method is provided. SOLUTION: After detecting the arrival of a conveyed preceding sheet S1 to a determination sensor 109, a next sheet S2 is detected.
, The arrival time t of the sheet S2 up to the arrival at the determination sensor 109 is detected. If the arrival time t is shorter than a predetermined early arrival limit time (t ≦ T1−Ta), the sheet S2 is detected.
2 before the sheet S2 is conveyed to the registration roller pair 107.
Is stopped for the time t5, and if the arrival time t is between the early arrival limit time and the delay limit time, (T1-Ta
<T <T1 + Tb), the sheet S2 is directly conveyed to the registration roller pair 107, and if the arrival time t is equal to or longer than a predetermined delay limit time (T1 + Tb ≦ t), the exposure timing of the sheet S2, the registration ON timing, and The sheet feeding timing of the sheet S3 is delayed by the time t6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus and an image forming method, and more particularly to an image forming apparatus and an image forming method capable of forming an image continuously and reliably on a plurality of sheets at high speed.

[0002]

2. Description of the Related Art Conventional image forming apparatuses such as copying machines and printers are provided with registration means for correcting the position of a sheet (recording paper) and synchronizing an image with the sheet immediately before an image forming section. There are things that are. Various methods are used for the registration means.However, as a low-cost, reliable, and simple registration means, the leading edge of the sheet is brought into contact with the nip portion of the stopped registration roller pair, and the sheet is applied to the sheet. By making a flexure, the front end of the sheet is adjusted along the nip of the pair of registration rollers by the elasticity of the sheet to correct a posture such as skew, and further, by starting rotation of the pair of registration rollers at a predetermined timing, an image and Synchronized loop registration methods are generally and widely employed.

In a conventional analog image forming apparatus, for example, a copying machine, when a plurality of originals are continuously copied, an optical device for exposing the originals has to reciprocate for the number of copies. The distance between sheets (paper interval) was inevitably determined. Conventionally, the operation by the registration means has been performed using the time between papers. In recent years, as copiers have been digitized, the number of sheets has been reduced in a short period of time by shortening the sheet interval. For example, in the case of image forming, substantial image forming without increasing the process speed of image forming. Speed, that is, productivity, has been improved. In this case, the reading of the document and the image formation thereof are digitized, so that once the document is read, the image information is electrically encoded and can be stored in the memory. Sometimes, when the image information in the memory is read out and a plurality of originals are continuously copied in order to form an image corresponding to the image information of the original on a photoreceptor by an exposure device such as a laser beam or an LED array. However, the optical device does not reciprocate, and no mechanical movement is required. Therefore, the time between sheets can be set shorter, and the productivity can be improved efficiently.

[0004]

However, if the time between sheets is shortened, in the case of the loop registration method, the above-described operation of temporarily stopping the sheet by the pair of registration rollers is performed. (The sheet is conveyed), the sheet interval becomes further shorter than the sheet interval (process sheet interval) on the downstream side, and it is in a standby state for skew correction and synchronization with the image. The next sheet may collide with the preceding sheet and cause a jam.

Further, the control means for controlling the driving of the pair of registration rollers transmits a stop signal for the pair of registration rollers so as to stop the rotation operation after the preceding sheet completely passes through the pair of registration rollers. If the paper interval is set short, the next sheet enters the nip of the pair of registration rollers before the rotation of the pair of registration rollers does not stop sufficiently, so that the leading end of the sheet cannot follow the nip, and Since correction and synchronization with the image cannot be performed, printing accuracy cannot be ensured.

The distance L from the exposure position to the transfer position is
In a copying machine in which the distance L2 from the position of the registration roller pair to the transfer position is longer than that of FIG. 1 (FIG. 1), the start of driving of the registration roller pair is controlled so that the position of the sheet is synchronized with the image on the photosensitive drum. Need to do. Therefore, if the sheet is not conveyed by the start timing of driving the registration roller pair due to some problem, that is, if the sheet conveyance is delayed, the sheet cannot be synchronized with the image on the photosensitive drum, Printing accuracy cannot be ensured, and proper image formation on a sheet cannot be performed.

Even if the preceding sheet is barely synchronized with the image on the photosensitive drum, the next sheet arrives at the pair of registration rollers without delay. In order to avoid such a situation, the interval between the papers becomes relatively shorter between the pair of registration rollers, and as a result, the next sheet may collide with the rear end of the preceding sheet and cause a jam. There was naturally a limit to shortening the paper interval.

An object of the present invention is to provide an image forming apparatus and an image forming method capable of shortening a sheet interval with a simple structure and efficiently improving productivity while ensuring high printing accuracy. With the goal.

[0009]

According to a first aspect of the present invention, there is provided an image forming apparatus, comprising:
Sheet feeding means for feeding a sheet at a predetermined feeding timing, registration means for performing a registration operation on the sheet at a predetermined registration operation timing, and sheet conveyance means for conveying the fed sheet to the registration means; An image forming apparatus including a control unit that controls each of the sheet feeding unit, the registration unit, and the sheet conveying unit, wherein the sheet conveying unit includes one sheet of the sheet and a next sheet of the sheet. And a sheet detection unit for detecting the conveyance time interval, wherein the control unit controls each of the sheet feeding unit, the registration unit, and the sheet conveyance unit based on the conveyance time interval.

[0010] The image forming apparatus according to the second aspect is the first aspect.
In the image forming apparatus described above, the control unit, when the conveyance time interval is equal to or less than a predetermined time, before the sheet conveyance unit conveys the next sheet of the sheet to the registration unit, The sheet conveying means is stopped for a predetermined time.

According to the third aspect of the present invention, there is provided an image forming apparatus.
Or in the image forming apparatus according to 2, wherein the control unit includes:
When the transport time interval is equal to or longer than the predetermined time, the predetermined registration operation timing of the next sheet of the sheet is delayed by a predetermined time.

According to a fourth aspect of the present invention, there is provided the image forming apparatus according to the third aspect.
In the image forming apparatus described above, when the predetermined register operation timing of the next sheet of the sheet is delayed by a predetermined time, the control unit delays the predetermined sheet feeding timing of the next sheet of the sheet by the predetermined time. It is characterized by the following.

[0013] The image forming apparatus according to the fifth aspect is the first aspect.
The image forming apparatus according to any one of claims 1 to 4,
An image carrier for forming an image on a sheet on which a registration operation has been performed by the registration unit, and an image forming unit for forming an image on the image carrier at a predetermined image forming start timing, the control unit includes: Controlling the registration means so that an image formed on the image carrier and the sheet on which the registration operation has been performed are synchronized, and controlling the imaging means based on the transport time interval. I do.

[0014] The image forming apparatus according to the sixth aspect of the present invention provides the image forming apparatus according to the fifth aspect.
In the image forming apparatus described above, when the predetermined sheet feeding timing of the next sheet of the sheet is delayed by the predetermined time, the control unit sets the predetermined image forming start timing of the next sheet of the sheet. It is characterized in that it is delayed for another predetermined time.

According to another aspect of the present invention, there is provided an image forming method, wherein a plurality of sheets are fed one by one at a predetermined feeding timing, and the sheets are registered at a predetermined registration operation timing. A registration step of performing a registration operation, a sheet conveyance step of conveying the fed sheet to the registration step, and a control step of controlling each of the sheet feeding step, the registration step, and the sheet conveyance step. In the image forming method of the image forming apparatus provided with, the sheet conveying step includes a sheet detecting step of detecting a conveying time interval between one sheet of the sheet and a next sheet of the sheet, and the controlling step includes: The control of each of the sheet feeding step, the registration step, and the sheet conveying step is performed based on a time interval.

[0016] The image forming method according to the eighth aspect is the seventh aspect.
In the image forming method according to the aspect, the control step may include, if the transport time interval is equal to or less than a predetermined time, before the sheet transport step transports the next sheet of the sheet to the resist step. The sheet conveying process is stopped for a predetermined time.

According to a ninth aspect of the present invention, there is provided the image forming method according to the seventh aspect.
Or the image forming method according to 8, wherein the controlling step includes:
When the transport time interval is equal to or longer than the predetermined time, the predetermined registration operation timing of the next sheet of the sheet is delayed by a predetermined time.

According to a tenth aspect of the present invention, in the image forming method according to the ninth aspect, the control step includes a step of, when a predetermined registration operation timing of the next sheet of the sheet is delayed by a predetermined time, The next predetermined sheet feeding timing is delayed by the predetermined time.

According to an eleventh aspect of the present invention, there is provided the image forming method according to any one of the seventh to tenth aspects, wherein an image is formed on a sheet on which a resist operation has been performed in the resist step. Body, and an image forming step of forming an image on the image carrier at a predetermined image forming start timing, wherein the control step includes the step of performing the registration step in which an image formed on the image carrier and the registration operation are performed. The image forming process is controlled so as to be synchronized with the performed sheet, and the image forming process is controlled based on the transport time interval.

According to a twelfth aspect of the present invention, in the image forming method according to the eleventh aspect, the control step includes a step of: delaying the predetermined sheet feeding timing of the next sheet of the sheet by the predetermined time. It is characterized in that the predetermined image forming start timing of the next one of the sheets is delayed by another predetermined time.

[0021]

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

(First Embodiment) FIG. 1 is a sectional view schematically showing an image forming apparatus according to a first embodiment of the present invention. In FIG. 1, reference numeral 1000 denotes a printer unit for forming an image, and 100 in the printer unit 1000 denotes an upper sheet cassette for storing sheets (recording paper).
Reference numeral 02 denotes a lower sheet cassette, which together constitutes a sheet feeding unit. In the sheet cassettes 100 and 102, a sheet size detection sensor 100 connected to the controller 120 is provided.
a and 100b (FIG. 2) are provided. These sensors detect sheet size information (sheet length information) of the sheet and transmit a signal to the controller 120.

Sheet cassettes 100 and 10 serving as a sheet feeding unit
2, a separation claw (not shown) and paper feed rollers 101 and 10 are provided.
The sheets in the sheet feeding section are separated and fed one by one by the separation claw and the sheet feeding rollers 101 and 103. A sheet guide plate (not shown), a pair of conveyance rollers 104 and 105, a pair of pre-registration rollers 10 are provided in a sheet conveyance path from the sheet feeding section to the registration roller pair 107.
6, and each roller of the registration roller pair 107 are arranged,
By driving these rollers, the sheet is conveyed to the image forming unit.

Two sensors, a registration sensor 108 and a determination sensor 109, connected to the controller 120 are arranged in the sheet paper conveyance path. The registration sensor 108 is a sensor located on the upstream side in the conveyance direction near the registration roller pair 107 and used to control the formation of a loop of a predetermined amount of the sheet performed by the registration roller pair 107. The sensor is used to detect a sheet conveyed by each roller in the sheet paper conveyance path, and to control the exposure start timing of the sheet and the conveyance of the sheet from the sheet feeding unit to the registration roller pair 107. Registration sensor 108,
Each of the determination sensors 109 includes a photo interrupter and a sensor flag. The sheet abuts on the sensor flag, and detects that the sheet has reached the sensor unit by rotating the sensor unit. The detected signal is transmitted to the controller 120.

The paper feed rollers 101 and 103 are provided with paper feed clutches (hereinafter, "clutch" is referred to as "CL") 101b,
103b, connected to the main motor M,
The transport roller pairs 104 and 105 are transport CLs 104b and 10
5b, the pre-registration roller pair 106 is connected to the main motor M via the pre-registration CL 106b, and the registration roller pair 107 is connected to the main motor M via the registration CL 107b, and is driven by receiving a driving force from the main motor M. (FIG. 2). The main motor M is connected to the controller 120 via a main motor M drive circuit, and is controlled by the controller 120 (FIG. 2).

The paper feed CLs 101b and 103b are
Each of the transport CLs 104b, 1 is connected to the controller 120 via the drive circuits 101a, 103a.
05b is through the transport CL drive circuits 104a and 105a, the CL before resist 106b is through the CL drive circuit 106a before resist, and the resist CL 107b is through the resist C
Each of the controllers 12 via the L drive circuit 107a
0, and connects / stops each CL based on a control signal transmitted from the controller 120 (FIG. 2).

Reference numeral 111 denotes a laser modulator (laser scanner) serving as an image forming means, and a laser modulation circuit driving circuit 1
11a is connected to the controller 120 (FIG. 2). Reference numeral 112 denotes a photosensitive drum which rotates clockwise in the drawing. The laser light emitted from the laser modulator 111 is reflected by a mirror 113, is irradiated on an exposure position 112a on the photosensitive drum 112, forms a latent image on the photosensitive drum 112, and is visualized as a toner image by a developing unit 114. Be transformed into Reference numeral 115 denotes a transfer charger for transferring a toner image on the photosensitive drum 112 to a sheet, and reference numeral 116 denotes a separation charger for electrostatically separating the photosensitive drum 112 and a sheet, and together constitute an image forming unit. Reference numeral 112b denotes a transfer unit at which the toner image on the photosensitive drum 112 is transferred onto a sheet.

Reference numeral 117 denotes a conveying belt for conveying the sheet on which an image has been formed, and reference numeral 118 denotes a fixing device for fixing the image on the sheet on which the image has been formed. Reference numeral 119 denotes a discharge roller pair for discharging the sheet. The sheet on which the image is formed is discharged to the sorter 2 by the discharge roller pair 119. The controller 120 is a controller serving as control means, and is connected to the above-described sensors, drive circuits, and an arithmetic circuit that performs arithmetic processing (FIG. 2), and controls these components.

The scanner unit 2000 includes the printer unit 100
The scanning optical system light source 201, a platen glass 202, a document pressure plate 203 that opens and closes, a lens 204, a light receiving element (photoelectric conversion) 205, and an image processing unit 206 And the image processing unit 206
And a memory unit 208 for storing the image processing signal processed in. The document set between the platen glass 202 and the document pressing plate 203 is illuminated by the scanning optical light source 201 and the image information is read. The read image information is subjected to image processing in the image processing unit 206, converted into an electrically encoded electric signal 207, and transmitted to the laser modulation unit 111. The image processing unit 2
The image information processed and coded at 06 is temporarily stored in the memory unit 208, and can be transmitted to the laser modulation unit 111 as required by a signal from the controller 120. Note that, instead of the original pressure plate 203 in FIG.
If 0 is attached, the original can be read automatically.

In the present image forming apparatus, the laser modulator 111
On the other hand, if the processing signal of the image forming unit is input, it functions as a copier, if it receives a facsimile transmission signal, it functions as facsimile reception, if it receives the output signal of a personal computer, it functions as a printer, and conversely , Image processing unit 20
6 to another external facsimile,
This is a multifunctional copying machine that functions as facsimile transmission. In the present image forming apparatus, the printer unit 1000 and the scanner unit 2000 are separate but may be integrated. FIG. 2 is a block diagram showing a configuration of the image forming apparatus of FIG.

FIG. 3 is a timing chart showing sheet conveyance control of the image forming apparatus of FIG. 1, and FIG. 4 is an enlarged view of the timing chart of FIG. In FIG. 3, the vertical axis represents the distance X and the horizontal axis represents time t, and the sheet having the sheet length Ls is transferred from the upper sheet cassette 100 serving as the sheet feeding unit to the transfer unit 1.
The sheet is conveyed one by one on the sheet 12a, and the conveying speed V of the sheet is represented by its inclination. Note that the sheet length L
s is detected by the sheet size detection sensors 100a and 100b and is stored in the controller 120 in advance.

In FIG. 3, sheet feeding is started at a predetermined feeding timing, and the first sheet S1 is conveyed at a predetermined conveying speed V. First conveyed sheet S1
Exposure starts after time t1 since the leading edge of is detected by the determination sensor 109 in the sheet paper transport path. Note that, as described above, the determination sensor 109 is disposed upstream of the exposure start position in the transport direction so as to start the exposure t1 after detecting the leading end of the sheet S1.

T3 is a loop forming time for forming a predetermined amount of loop when the leading end of the sheet S1 reaches the nip of the registration roller pair 107, and t4 is a loop holding time for holding the predetermined amount of loop. Time. At the exposure start time t1, the sheet S1 abuts against the nip of the registration roller pair 107 to reliably correct the skew of the sheet S1, and the sheet S1 and the toner image (image) exposed on the photosensitive drum 112 are combined. The timing is set at a timing at which a preset register standby time (t3 + t4) can be secured as a time at which synchronization can be performed.

The loop formation time t3 is represented by the following equation (1), where Lr is a predetermined loop amount to be formed.

T3 = Lr / V (1) Generally, the loop amount Lr is set to a value of about 5 to 10 mm. The loop holding time t4 is generally set to about 50 to 100 ms.

In FIG. 4, after the sheet S1 reaches the nip of the registration roller pair 107 which has been stopped in advance and forms a predetermined loop amount, the registration roller pair 107 rotates by connecting the registration CL 107b. The rotation start timing (registration ON timing) of the pair of registration rollers 107 is t2 from the exposure start timing in order to synchronize with the image previously exposed on the photosensitive drum 112.
After hours. At t2, when the distance from the exposure position 112a on the photosensitive drum 112 to the transfer unit 112b is L1 and the distance from the registration roller pair 107 to the transfer unit 112b is L2 (FIG. 1), the following expression (2) is used. expressed.

T2 = (L1−L2) / V (2) In this way, by starting the rotation operation of the registration roller pair 107 with a delay of t2 time from the exposure start timing, the registration roller pair 107 is started. The sheet S1 restarted to be conveyed can be synchronized with the image on the photosensitive drum 112 by the transfer unit.

Next, the registration of the registration roller pair 107 is turned on.
At the registration roller stop timing after Tr (registration roller rotation time) time from the timing, the registration roller pair 1
07 is stopped to prepare for the correction of the skew of the next sheet S2 and the synchronization with the image. Tr is represented by the following equation (3).

Tr = (Ls + △ L) / V (3) Ls is the sheet size detection sensor 10 as described above.
0a, 100b is the length of the sheet S1 detected in advance, and ΔL is for stopping the driving of the registration roller pair 107 after the rear end of the sheet S1 has surely passed through the nip of the registration roller pair 107. This is a margin, and is usually about 15 to 20 mm in consideration of the variation of the sheet length Ls, the variation of the conveyance speed of the registration roller pair 107, the accuracy of the connection / stop time of the registration clutch 107b, and other various variations. Value.

In FIG. 3, the feeding of the second sheet S2 is started after a lapse of T1 from the start of feeding of the first sheet S1. T1 is expressed by the following equation (4), where X (sheets / minute) is the productivity (productivity) in the image forming apparatus according to the present embodiment.

T1 = 60 / X (second) (4) Specifically, when the productivity of the image forming apparatus according to the present embodiment is 60 (sheets / min), 60/60 =
1 (second). This time is the same as the exposure start interval or the registration ON interval required to achieve X (sheets / minute).

The arrival of the leading end of the sheet S2 which has been started to be fed at such a timing at the transport speed V is detected by the determination sensor 109. Here, the second sheet S
If the conveyance speed and the sheet feeding start position of the second sheet S2 are exactly the same as S1, the arrival (conveyance) time of the sheet S2 to the determination sensor 109 is T1 time after the first sheet S1 reaches the determination sensor 109. Later. However, in practice, variations in the transport speed due to slight slippage between the sheet and the sheet feeding roller 101, each of the transport rollers 105 and 106, variations in the sheet feeding start position (sheet position in the sheet cassette), and other factors. For example, T1 varies.

In FIG. 4, the variation before and after T1 is defined as Ta and Tb, respectively, and after the sheet S1 reaches the determination sensor 109, the sheet S2 is
Assuming that a time interval until the light beam reaches the point 9 is t, t is (T
1-Ta) or less (hereinafter, "T1-Ta" is referred to as "early arrival limit time"), the sheet S2 is conveyed to the registration roller pair 107 as it is, and the sheet S2 is transferred to the registration roller pair as indicated by a dotted line a in the figure. Before the pair 107 stops, the pair enters the registration roller pair 107, and the sheet S2
Cannot be made to follow the nip of the pair of registration rollers 107, and the skew of the sheet S2 cannot be corrected. Therefore, the sheet S2 cannot be synchronized with an image, and a normal image output cannot be obtained.

On the other hand, when t is equal to or longer than (T1 + Tb) time (hereinafter, "T1 + Tb" is referred to as "delay limit time"), the sheet S2 is directly transferred to the registration roller pair 107.
Even if the sheet S2 is conveyed, the skew correction cannot be performed because the sheet S2 cannot secure a predetermined amount of loop forming time t3 with the pair of registration rollers 107 as indicated by the dotted line b in the drawing, and the sheet S2 cannot be in time for the next registration ON timing. Synchronization is not possible and normal image output cannot be obtained.

Therefore, normal image output can be performed only when the next sheet S2 is conveyed during the time between the early arrival limit time and the delay limit time. Note that the above T
a and Tb are represented by the following equations (5) and (6).

Ta = T1−Tr− (t3 + t4) (5) Tb = T1 + (t3 + t4) (6) In the present embodiment, the difference between the preceding sheet S1 detected by the determination sensor 109 and the next sheet S2 is determined. The sheet detection time interval (conveyance time interval) t is compared with a predetermined early arrival limit time and a delay limit time, and the following sheet conveyance control timing is switched according to the comparison result as follows. And a normal image output can be obtained.

When the transport time interval t is equal to or shorter than the early arrival limit time (t ≦ T1−Ta). In FIG. 5, when the transport time interval t of the sheet S2 to the determination sensor 109 is earlier than the early arrival limit time. When the conveyance of the sheet S2 proceeds as it is, the registration roller pair 107 stops before the registration roller pair 107 stops.
, And the loop forming time t4 cannot be secured, so that the sheet S2 is
Stop at time t5 before reaching nip 07.
Specifically, the pre-registration CL 106b is cut for a time t5, and the driving of the pre-registration roller pair 106 is stopped.
t5 is set by the following equation (7).

T5 = T1−t (7) As a result, the sheet S2 reaches the registration roller pair 107 of the preceding sheet S1.
T1 hours after the arrival at the registration roller pair 10
Since the rotation of No. 7 is stopped reliably, the loop forming time t3 and the loop holding time t4 of the sheet S2 can be secured. Therefore, if the controller 120 transmits the exposure start signal and the registration ON signal of the sheet S2 after T1 time of the exposure start timing and the registration ON timing of the sheet S1, the skew of the sheet S2 can be corrected and the image is synchronized with the image. Therefore, image formation can be performed without deteriorating printing accuracy. Further, sheet S
The register O of the sheet S1 preceding the register ON timing of the register 2
Since it is T1 time after the N timing, there is no variation in the sheet interval (hereinafter referred to as "process sheet interval") in the image forming unit, and a stable output image can be obtained.

When the above processing is completed, the next sheet S3
Is started after T1 time from the start of the sheet S2 sheet feeding operation.

When the transport time interval t is between the early arrival limit time and the delay limit time (T1-Ta <t <T
1 + Tb) In FIG. 6, when the conveyance time interval t of the sheet S2 to the determination sensor 109 is between the early arrival limit time and the delay limit time, even if the conveyance of the sheet S2 proceeds as it is, the registration roller The loop forming time t3 can be secured before the pair 107 has already stopped and the operation at the registration ON timing starts. Therefore, the controller 120 sets the exposure start signal of the sheet S2 and the register O
Exposure start timing and registration ON of sheet S1
If the transmission is made after the time T1 of the timing, the skew of the sheet S2 can be corrected and the sheet S2 can be synchronized with the image, so that the image can be formed without deteriorating the printing accuracy. Further, since the registration ON timing of the sheet S2 is T1 time after the registration ON timing of the preceding sheet S1, there is no variation between process sheets in the image forming unit.
A stable output image can be obtained.

When the above processing is completed, the next sheet S3
Is started T1 time after the start of the sheet feeding operation of the sheet S2.

When the transport time interval t is longer than the delay limit time (T1 + Tb ≦ t) In FIG. 7, if the transport time interval t of the sheet S2 to the determination sensor 109 is later than the delay limit time, the sheet S2 is left as it is. Even if the conveyance of the recording medium progresses, the registration roller pair 107 cannot secure the loop formation time t3, and the registration roller pair 107 cannot keep up with the operation of the next registration ON timing.
The exposure start timing and the registration ON timing of the sheet S2 are both delayed by a delay time t6 from the delay limit time. Thereby, the registration roller pair 10 of the sheet S2 is
Since the loop formation time t3 at 7 can be secured and synchronized with the image, image formation can be performed without impairing the printing accuracy.

Further, the sheet feeding start time (sheet feeding timing) of the next sheet S3 is delayed by time t6. this is,
As described above, since the registration ON timing of the sheet S2 is delayed by the time t6, when the next sheet S3 is normally conveyed, the interval between the sheets S2 and S3 becomes relatively shorter by the time t6. This is to prevent the gap between the sheets from being unable to be secured and the occurrence of a jam.

Next, when the feeding of the sheet S3 is started and the leading end thereof reaches the determination sensor 109, the same processing as in the case of the second sheet S2 is performed, and the subsequent sheet conveyance timing is switched. These operations may be repeated for a desired number of sheets.

In the above case, the registration ON timing (registration ON interval) and the exposure start timing (exposure start interval) are lengthened by the time t6, and the productivity is slightly lowered. Maintaining high productivity in consideration of stopping the printer, causing a significant decrease in productivity, or outputting an unsightly image with extremely poor printing accuracy and causing the user to perform the copying operation again. Can be.

According to the first embodiment, in the image forming process for a plurality of sheets, after the arrival of the preceding sheet S1 conveyed from the sheet feeding unit to the determination sensor 109 is detected, the following process is performed. The arrival time t of the sheet S2 until the sheet S2 reaches the determination sensor 109 is detected, and the arrival time t
Is less than or equal to the predetermined early arrival limit time (t ≦
T1-Ta), before the sheet S2 is conveyed to the registration roller pair 107, the conveyance of the sheet S2 is stopped for a time t5,
If the arrival time t is between the early arrival limit time and the delay limit time (T1-Ta <t <T1 + Tb), the sheet S
2 is conveyed to the registration roller pair 107 as it is, and if the arrival time t is equal to or longer than a predetermined delay limit time (T1 + Tb ≦ t), the exposure timing of the sheet S2, the registration ON timing, and the sheet feeding timing of the sheet S3 are changed. By delaying by the time t6, skew correction, which is a sheet registration operation, can be performed, and the sheet and the image can be synchronized, so that image formation can be performed without impairing printing accuracy. High productivity can be maintained.

(Second Embodiment) Next, a second embodiment of the present invention will be described.
8 to 13 regarding the image forming apparatus according to the first embodiment.
This will be described with reference to FIG. The configuration of the second embodiment is the same as that of the first embodiment. In the drawing, the same reference numerals are given to the elements corresponding to those of the first embodiment, and the same reference numerals are used. Description is omitted.

FIG. 8 is a sectional view schematically showing an image forming apparatus according to the second embodiment of the present invention. 8, the image forming apparatus according to the present embodiment has an exposure position 11
The distance L4 from the registration roller pair 107 to the transfer position 112b is longer than the distance L3 from 2a to the transfer position 112b.
Is longer. Note that a block diagram illustrating the overall configuration of the image forming apparatus according to the second embodiment is the same as that of the first embodiment, and thus a description thereof will be omitted.

FIG. 9 is a timing chart showing sheet conveyance control timing in the image forming apparatus of FIG. 8, and FIG. 10 is an enlarged view of the timing chart of FIG. FIG. 9 illustrates a state in which the distance X is on the vertical axis and the time t is on the horizontal axis, and sheets of the sheet length Ls are conveyed one by one from the upper sheet cassette 100, which is a sheet feeding unit, to the transfer unit 112a. The sheet conveying speed V is represented by the inclination. Note that the sheet length Ls is the sheet size detection sensor 1
00a, 100b, and the controller 1
20.

In FIG. 9, sheet feeding is started at a predetermined sheet feeding timing, and the first sheet S1 is conveyed at a predetermined conveying speed V. First conveyed sheet S1
Reaches the nip of the registration roller pair 107 that has been stopped in advance after the arrival thereof is detected by the determination sensor 109 disposed on the upstream side in the transport direction with respect to the registration roller pair 107. Subsequently, after the passage of the loop forming time t3 for forming a predetermined amount of loop at the nip of the registration roller pair 107 and the loop holding time t4 for holding the predetermined amount of loop, the sheet S1 The sheet is conveyed onto the photosensitive drum 112 by the start of driving. In order to synchronize the image position with the sheet S1 after a time t7 from the driving start timing of the registration roller pair 107,
The laser modulation 111 as an image forming means starts exposure. The time t7 is given by the following equation (8).

T7 = (L4-L3) / V (8) In this way, the photosensitive drum 1 is synchronized with the sheet S1.
12, an output image with high printing accuracy is formed.

In FIG. 10, the feeding of the second sheet S2 is started after a lapse of T1 from the start of feeding of the first sheet S1. In the present embodiment, as in the first embodiment, the sheet detection time (arrival time) t of the sheet determination sensor 109 is compared with the arrival time T1 of the preceding sheet to the determination sensor 109. In accordance with the result, the following sheet conveyance control timing is switched as shown in the following.

In the case where the transport time interval t is shorter than the early arrival limit time (t ≦ T1−Ta). In FIG. 11, when the transport time interval t of the sheet S2 to the determination sensor 109 is earlier than the early arrival limit time. When the conveyance of the sheet S2 proceeds as it is, the registration roller pair 107 stops before the registration roller pair 107 stops.
, And the loop forming time t4 cannot be secured, so that the sheet S2 is
Stop at time t5 before reaching nip 07.
Specifically, the pre-registration CL 106b is cut for a time t5, and the driving of the pre-registration roller pair 106 is stopped.
t5 is set by the following equation (9).

T5 = T1-t (9) As a result, the sheet S2 reaches the registration roller pair 107 of the preceding sheet S1.
T1 hours after the arrival at At this time, since the rotation of the pair of registration rollers 107 has been reliably stopped, the sheet S
2 can secure the loop formation time t3 and the loop holding time t4, and can correct the skew of the sheet S2. Therefore, if the registration ON signal of the sheet S2 is transmitted T1 hours after the registration ON timing of the preceding sheet S1, Good. Furthermore,
If the exposure is started t7 hours after the registration ON timing of the sheet S2, the sheet S2 and the photosensitive drum 11
2 can be synchronized, and image formation can be performed without impairing printing accuracy.

When the above processing is completed, the next sheet S3
Is started after T1 time from the start of the sheet S2 sheet feeding operation.

When the transport time interval t is between the early arrival limit time and the delay limit time (T1-Ta <t <T
1 + Tb) In FIG. 12, when the conveyance time interval t of the sheet S2 to the determination sensor 109 is between the early arrival limit time and the delay limit time, even if the conveyance of the sheet S2 proceeds as it is, the registration roller Since the pair 107 has already stopped and the loop formation time t3 can be secured before the operation of the registration ON timing is started, the controller 120 sends the registration ON signal of the sheet S2 to the sheet S1.
, The skew of the sheet S2 can be corrected if it is transmitted after T1 of the registration ON timing, and the exposure on the sheet S2 and the image on the photosensitive drum 112 can be performed by starting the exposure t7 after the registration ON timing of the sheet S2. Can be synchronized.

As described above, since the skew of the sheet S2 can be corrected and synchronized with the image, the image can be formed without deteriorating the printing accuracy.
Sheet S1 preceding registration ON timing of sheet S2
T1 time after the registration ON timing, there is no variation between process papers in the image forming unit, and a stable output image can be obtained.

When the above processing is completed, the next sheet S3
Is started after T1 time from the start of the sheet S2 sheet feeding operation.

When the transport time interval t is longer than the delay limit time (T1 + Tb ≦ t) In FIG. 13, if the transport time interval t of the sheet S2 to the determination sensor 109 is later than the delay limit time, the sheet S2 is left as it is. Even if the conveyance of the recording medium progresses, the registration roller pair 107 cannot secure the loop formation time t3, and the registration roller pair 107 cannot keep up with the operation of the next registration ON timing.
The registration ON timing of the sheet S2 is delayed by a delay time t6 from the delay limit time. Thereby, the sheet S
The loop forming time t3 in the two registration roller pairs 107 can be secured.

Further, if the exposure (image formation) is started by the laser modulation unit 111 at a predetermined image formation start timing delayed by t7 time from the registration ON timing of the sheet S2, the sheet S2 and the photosensitive drum 112 An image can be formed by synchronizing with an image.

As described above, since the skew of the sheet S2 can be corrected and synchronized with the image, the image can be formed without deteriorating the printing accuracy. Further, since the registration ON timing of the sheet S2 is delayed by the time t6, when the next sheet S3 is normally conveyed, the sheet interval is relatively shortened by the time t6, and the sheet S2 and the sheet S2 are delayed. In order to prevent the paper interval from S3 from being ensured and a jam from occurring, the feeding start time (feeding timing) of the next sheet S3 is set to t6.
Delay by time.

Subsequently, when the feeding of the sheet S3 is started and reaches the determination sensor 109, the sheet detection time interval (conveyance time interval) t by the determination sensor 109 of the sheet S3 is the same as in the case of the preceding sheet S2. May be compared with predetermined early arrival limit time and delay limit time in the same manner as described above, and the operation of switching the sheet conveyance control timing according to the comparison result may be repeated. In the present embodiment, the exposure start timing is described to start the exposure t7 hours after the ON timing of the registration roller pair 107.
The determination sensor 109 is disposed downstream of the transfer direction 07 and the distance from the transfer unit to L3.
The exposure start timing may be determined based on the sheet detection signal of No. 9.

According to the second embodiment, in the image forming processing of a plurality of sheets, after the arrival of the preceding sheet S1 conveyed from the paper feed unit to the determination sensor 109 is detected, the following process is performed. The arrival time t of the sheet S2 until the sheet S2 reaches the determination sensor 109 is detected, and the arrival time t
Is less than or equal to the predetermined early arrival limit time (t ≦
T1-Ta), before the sheet S2 is conveyed to the registration roller pair 107, the conveyance of the sheet S2 is stopped for a time t5,
If the arrival time t is between the early arrival limit time and the delay limit time (T1-Ta <t <T1 + Tb), the sheet S
2 is conveyed to the registration roller pair 107 as it is, and if the arrival time t is equal to or longer than a predetermined delay limit time (T1 + Tb ≦ t), the exposure timing of the sheet S2, the registration ON timing, the paper feed timing, and the image formation start By delaying the timing by the time t6, skew correction as a sheet registration operation can be performed, and the sheet and the image can be synchronized, so that image formation can be performed without impairing printing accuracy. Generation can be prevented and high productivity can be maintained.

[0074]

As described above in detail, according to the apparatus of the first aspect and the method of the seventh aspect, the transport time interval between one sheet to be transported and the next sheet is detected. By controlling the sheet feeding, the registration operation, and the conveyance based on the conveyance time interval, a time for correcting the skew of the sheet can be secured, and the sheet and the image can be synchronized. Can shorten the sheet paper,
Productivity can be efficiently improved while ensuring high printing accuracy.

According to the apparatus of the second aspect and the method of the eighth aspect, when the transport time interval is equal to or less than a predetermined time, sheet transport is performed before transporting the next sheet. By stopping the time, a time for correcting skew of the sheet and a time for synchronizing the sheet and the image can be secured, so that image formation can be performed without impairing printing accuracy.

According to the apparatus of the third aspect and the method of the ninth aspect, when the conveyance time interval is equal to or longer than a predetermined time, the predetermined registration operation timing of the next sheet is set to the predetermined time. By delaying, the effects of the device according to claim 2 and the method according to claim 8 can be reliably achieved.

According to the apparatus of the fourth aspect and the method of the tenth aspect, when the predetermined registration operation timing of the next sheet of the sheet is delayed by a predetermined time, the predetermined sheet feeding of the next sheet of the sheet is performed. By delaying the timing by a predetermined time, the effects of the device described in claim 3 and the method described in claim 9 can be more reliably achieved.

According to the apparatus of the fifth aspect and the method of the eleventh aspect, the image formed on the image carrier and the sheet on which the registration operation has been performed are controlled so as to be synchronized with each other. Based on this control, it is possible to secure time for correcting the skew of the sheet and synchronize the image with the sheet. Therefore, the sheet interval can be shortened with a simple configuration, and high printing accuracy is secured. In addition, productivity can be efficiently improved.

According to the apparatus of the sixth aspect and the method of the twelfth aspect, when the predetermined sheet feeding timing of the next sheet is delayed by a predetermined time, the predetermined image formation of the next sheet of the sheet is performed. By delaying the start timing by another predetermined time, the effects of the device according to claim 5 and the method according to claim 11 can be reliably achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of the image forming apparatus of FIG. 1;

FIG. 3 is a timing chart illustrating sheet conveyance control of the image forming apparatus of FIG. 1;

FIG. 4 is an enlarged view of the timing chart of FIG. 3;

FIG. 5 is a timing chart illustrating a case in sheet conveyance control of the image forming apparatus of FIG. 1;

FIG. 6 is a timing chart illustrating a case in sheet conveyance control of the image forming apparatus of FIG. 1;

FIG. 7 is a timing chart illustrating a case in sheet conveyance control of the image forming apparatus of FIG. 1;

FIG. 8 is a sectional view schematically showing an image forming apparatus according to a second embodiment of the present invention.

9 is a timing chart illustrating sheet conveyance control of the image forming apparatus of FIG. 8;

FIG. 10 is an enlarged view of the timing chart of FIG. 9;

FIG. 11 is a timing chart illustrating a case in sheet conveyance control of the image forming apparatus of FIG. 8;

FIG. 12 is a timing chart illustrating a case in sheet conveyance control of the image forming apparatus of FIG. 8;

FIG. 13 is a timing chart illustrating a case in sheet conveyance control of the image forming apparatus of FIG. 8;

[Explanation of symbols]

 100, 102 Sheet cassettes 101, 103 Feed rollers 104, 105 Conveying roller pair 106 Pre-registration roller pair 106b Pre-registration clutch 107 Registration roller pair 108 Registration sensor 109 Judgment sensor 111 Laser modulation unit 112 Photosensitive drum 120 Controller 1000 Printer unit 2000 Scanner Department

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H027 DA38 ED17 EE02 2H072 AA29 AB06 CA01 HB07 JA02 3F049 DA12 EA23 EA24 LA01 LB03 3F102 AA01 AB01 BA02 BB02 DA08 EA02 FA08 FA09

Claims (12)

[Claims] 1. A sheet feeding means for feeding a plurality of sheets one by one at a predetermined feeding timing, a registration means for performing a registration operation on the sheets at a predetermined registration operation timing, and In an image forming apparatus including a sheet conveying unit that conveys the sheet to the registration unit, and a control unit that controls each of the sheet feeding unit, the registration unit, and the sheet conveyance unit, the sheet conveyance unit includes one of the sheets. Sheet detecting means for detecting a transport time interval between a sheet and the next one of the sheets, wherein the control means controls the sheet feeding means based on the transport time interval;
An image forming apparatus, wherein each of the registration unit and the sheet conveyance unit is controlled. 2. The method according to claim 1, wherein when the transporting time interval is equal to or shorter than a predetermined time, the sheet transporting means transports the sheet before transporting the next sheet of the sheet to the registering means. 2. An image forming apparatus according to claim 1, wherein said means is stopped for a predetermined time. 3. The method according to claim 1, wherein the control unit delays the predetermined registration operation timing of the next sheet of the sheet by a predetermined time when the conveyance time interval is equal to or longer than the predetermined time. The image forming apparatus according to claim 1. 4. The control means according to claim 1, wherein when a predetermined registration operation timing of the next sheet of the sheet is delayed by a predetermined time, a predetermined sheet feeding timing of the next sheet of the sheet is delayed by the predetermined time. The image forming apparatus according to claim 3, wherein: 5. An image carrier for forming an image on a sheet on which a registration operation has been performed by the registration unit, and an image forming unit for forming an image on the image carrier at a predetermined image formation start timing, The control unit controls the registration unit so that an image formed on the image carrier and the sheet on which the registration operation has been performed are synchronized, and controls the image formation unit based on the transport time interval. The image forming apparatus according to claim 1, wherein: 6. The control means, when delaying the predetermined sheet feeding timing of the next sheet of the sheet by the predetermined time, sets the predetermined image forming start timing of the next sheet of the sheet to another timing. The image forming apparatus according to claim 5, wherein the image forming apparatus is delayed by a predetermined time. 7. A sheet feeding step of feeding a plurality of sheets one by one at a predetermined sheet feeding timing, a registration step of registering the sheets at a predetermined registration operation timing, and In the image forming method of an image forming apparatus including a sheet conveying step of conveying to the resist step, a sheet feeding step, the resist step, and a control step of controlling each of the sheet conveying steps,
The sheet conveying step includes a sheet detecting step of detecting a conveying time interval between one sheet of the sheet and a next sheet of the sheet, and the control step includes the sheet feeding step based on the conveying time interval, An image forming method, comprising controlling each of the resist step and the sheet conveying step. 8. The method according to claim 1, wherein, if the transport time interval is equal to or shorter than a predetermined time, the sheet transporting step includes transporting the sheet before transporting the next sheet of the sheet to the registration step. The image forming method according to claim 7, wherein the step is stopped for a predetermined time. 9. The method according to claim 1, wherein, if the transport time interval is equal to or longer than the predetermined time, the predetermined registration operation timing of the next sheet of the sheet is delayed by a predetermined time. The image forming method according to claim 7. 10. The method according to claim 10, wherein the controlling step includes:
10. The method according to claim 9, wherein when a predetermined registration operation timing of the sheet is delayed by a predetermined time, a predetermined sheet feeding timing of the next sheet of the sheet is delayed by the predetermined time.
The image forming method as described in the above. 11. An image carrier for forming an image on a sheet on which a registration operation has been performed in the registration step, and an image forming step of forming an image on the image carrier at a predetermined image formation start timing, The control step controls the registration step so that an image formed on the image carrier and the sheet on which the registration operation has been performed are synchronized, and controls the image formation step based on the transport time interval. The image forming method according to any one of claims 7 to 10, wherein: 12. The method according to claim 12, wherein the controlling step includes the step of:
12. The image forming method according to claim 11, wherein when the predetermined sheet feeding timing of the sheet is delayed by the predetermined time, the predetermined image forming start timing of the next sheet of the sheet is delayed by another predetermined time. .