JP2001039547A - Image forming device - Google Patents

Abstract

(57) [Problem] To provide an image forming apparatus capable of reducing manufacturing cost. A sheet (3) conveyed from a conveyance path (18) and stored in a switchback path (17) is conveyed by conveyance rollers (21, 21).
2 and is conveyed toward the image forming unit 2 through the conveyance path 19. The transport roller 21 also has the function of a conventional registration roller. That is, the leading end of the sheet 3 sent out from the switchback path 17 by the transport roller 22 is detected by the registration sensor 24 at a position before the transport roller 21 in the transport path 19, and after a predetermined period, the paper 3 is output by the transport roller 22. The transport is stopped. As a result, the sheet 3 is abutted against the transport roller 21 and a registration operation is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art In a conventional electrophotographic image forming apparatus, stacked and stored sheets are separated and taken out one by one, and are conveyed on a predetermined conveyance path to form an image by electrophotography. Supply to the image forming unit. In this case, a registration operation is performed by a registration roller just before the image forming section to align the image with the sheet.

Japanese Patent Application Laid-Open No. Hei 5-289453 discloses a technique for shortening the interval between sheets on which an image is formed in an image forming section by increasing the speed of a sheet on a conveying path for a certain period. I have.

Further, Japanese Patent Application Laid-Open Nos. Hei 8-259045, Hei 8-20106 and Hei 5-97305 are disclosed.
In the publication, after forming an image of one side of a sheet in an image forming unit, the sheet is guided to a switchback path, and the sheet is switched back in the switchback path and returned to the image forming unit to form an image on the back side of the sheet. There is disclosed a technique that can be performed.

[0005]

However, in the above-described conventional image forming apparatus which performs a registration operation immediately before the image forming section, variations in the leading edge position of the sheet when the sheet is separated from the stacked and stored sheets, Due to factors such as the aging of the transport speed, fluctuations due to the environment, and the stop time for performing the registration operation, image formation performed by continuously supplying paper to the image forming unit is generally performed with a paper interval of several tens mm. Had been

The technique disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 5-289453 discloses a technique for shortening the sheet interval.
This technology aims to improve the efficiency of continuous image formation without increasing the speed of the electrophotographic process.However, since it is intended to shorten the paper interval by increasing the speed, it is necessary to increase the speed up to the position where the speed is increased. If the transport path is long, it is necessary to transport all the papers existing on this path at the same speed, and the shift control of the device becomes large, which complicates the configuration and increases noise. There is a problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of reducing the interval between sheets continuously conveyed to an image forming section and improving the productivity of image formation.

Another object of the present invention is to provide an image forming apparatus capable of reducing manufacturing costs.

Another object of the present invention is to provide an image forming apparatus capable of preventing a decrease in sheet conveyance quality such as a slip of a sheet feeding device due to a stop of sheet conveyance.

Another object of the present invention is to provide an image forming apparatus capable of reducing the abrasion deterioration of the image forming section caused by the increase in the interval between sheets and improving the productivity of image formation. .

[0011]

According to a first aspect of the present invention, there is provided an image forming section for forming an image on a sheet, a stacking and storing section in which sheets are stacked and stored, and a stacking section for storing the stacked sheets. An image forming apparatus comprising: a sheet feeding device that separates one sheet at a time and transports the sheet to the image forming unit. A temporary storage unit to be stored, and the paper conveyed from the stacked storage unit in the temporary storage unit is stored from the front end, and the rear end of the paper stored in the temporary storage unit is set to the front end. A sheet reversing device for switching back the sheet and sending it out toward the image forming section; and adjusting the timing of the conveyance of the sheet by the sheet feeding device and the timing of sending the sheet by the sheet reversing device. It is an image forming apparatus, comprising a timing of supply of the paper to the forming unit and a registration means for performing a registration operation for synchronizing the operation of the image forming.

Therefore, since the sheets can be temporarily stored in the temporary storage section, variations in the leading end position of the sheets when separated from the stacked and stored state can be absorbed, and the sheet conveyance speed can be reduced. Without transiently accelerating, the interval between sheets continuously conveyed to the image forming unit can be reduced, and the productivity of image formation can be improved. Further, since the registration operation is performed using the sheet feeding device and the sheet reversing device, the conventional registration roller is not required, and the manufacturing cost can be reduced.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, a sheet detecting sensor for detecting the sheet in the temporary storage section is provided, and the registration means is provided by the sheet detecting sensor. The registration operation is performed based on the sheet detection signal.

Accordingly, the conventional registration sensor can be used instead of the paper detection sensor, so that the manufacturing cost can be reduced.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the paper feeding device sends the sheet from the stacking storage section to the temporary storage section, and It is characterized in that the case where the paper is sent from the temporary storage section to the image forming section can be performed independently.

Therefore, the paper can be transported to the temporary storage section even during the execution of the registration operation, and the paper transported from the stacked storage section to the temporary storage section is accompanied by the preceding paper registration operation. There is no need to stop, and there is a means to stop the transport of paper from the stacked storage section to the temporary storage section. Reduction of manufacturing costs and improvement of paper transport quality such as slippage of the paper feeder due to stoppage of paper transport It is possible to prevent the lowering.

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the registration unit is configured to temporarily stop the conveyance of the sheet by the registration operation. The stop is performed in a state in which the paper for which the temporary stop is performed is partially sent to the image forming unit until the rear end side of the paper in the transport direction does not prevent the subsequent paper from entering the temporary storage unit. It is characterized by.

Therefore, the sheet can be stored in the temporary storage section without being hindered by the registration operation of the preceding sheet. Therefore, means for stopping the conveyance of the subsequent sheet along with the registration operation of the preceding sheet is provided. It is possible to reduce the manufacturing cost to be provided and to prevent a decrease in sheet conveyance quality such as a slip of a sheet feeding device due to a stop of sheet conveyance.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, after the registration operation, the sheet feeding device feeds the sheet after the registration operation. The image forming apparatus further includes a speed change unit that increases a transport speed for a predetermined period of time than the transport speed of the sheet in the image forming unit.

Therefore, the interval between sheets, which is enlarged by the registration operation, is shortened after the registration operation, so that the abrasion deterioration of the image forming section due to the increase in the interval between the sheets and the productivity of image formation are improved. Can be achieved.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first and fifth aspects, the paper feeder is configured to connect the transport unit that connects the loading storage unit and the temporary storage unit. A first roller pair provided in a path for transporting the sheet, and a second roller pair provided in the transport path connecting the temporary storage unit and the image forming unit and transporting the sheet, The sheet reversing device includes a third pair of rollers for nipping the paper and rotating the paper forward and backward to store the paper in the temporary storage unit and feed the paper toward the image forming unit. The registration unit performs the registration operation by adjusting the timing of the conveyance of the sheet by the second roller pair and the timing of sending the sheet by the third roller pair. That.

Therefore, by performing the registration operation in cooperation with the second and third roller pairs, the conventional registration roller is not required, the manufacturing cost can be reduced, and the paper can be transported with high reliability. it can.

According to a seventh aspect of the present invention, in the image forming apparatus according to the second aspect, the paper feeder is provided in the transport path connecting the stacking storage section and the temporary storage section. A first roller pair that transports the sheet, and a second roller pair that is provided in the transport path that connects the temporary storage unit and the image forming unit and transports the sheet. A third pair of rollers for nipping the paper and rotating the paper forward and backward to store the paper in the temporary storage unit and feed the paper toward the image forming unit; The registration operation is executed by performing the sending with the third roller pair until the leading edge of the sheet hits the second roller pair based on the detection signal of the sheet by the sensor. It is characterized in.

Therefore, the conventional registration sensor can be used instead of the paper detection sensor, so that the manufacturing cost can be reduced.

According to an eighth aspect of the present invention, in the image forming apparatus according to the third aspect, the sheet feeding device is provided in the transport path connecting the stacking storage section and the temporary storage section. A first roller pair that transports the sheet, and a second roller pair that is provided in the transport path that connects the temporary storage unit and the image forming unit and transports the sheet. A third pair of rollers for nipping the paper and rotating the paper forward and backward to store the paper in the temporary storage unit and feed the paper toward the image forming unit; Roller pair and the second
By independently performing the operation of the roller pair, the sheet can be conveyed from the stacked storage section to the temporary storage section even during the execution of the registration operation.

Therefore, the paper conveyed from the stacked storage unit to the temporary storage unit does not stop due to the registration operation of the preceding paper, and the conveyance of the paper from the stacked storage unit to the temporary storage unit is prevented. The provision of the stopping means can reduce the manufacturing cost and prevent the paper transport quality from deteriorating due to slippage of the paper feeder due to the stoppage of the paper transport.

According to a ninth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the paper feeder is provided in the transport path connecting the stacking storage section and the temporary storage section. A first roller pair that transports the sheet, and a second roller pair that is provided in the transport path that connects the temporary storage unit and the image forming unit and transports the sheet. A third pair of rollers for nipping the paper and rotating the paper forward and backward to store the paper in the temporary storage unit and to send the paper toward the image forming unit; After driving the second and third roller pairs to convey the paper toward the image forming unit until the rear end of the sending direction is separated from the third roller pair, Images by department By performing the registration operation by temporarily stopping the second roller pair until the forming operation is started, the sheet enters the temporary storage unit by driving the first and third roller pairs. It is characterized in that it is prevented from overlapping with a subsequent sheet at the position of the third roller pair.

Therefore, the sheet can be stored in the temporary storage unit without being hindered by the registration operation of the preceding sheet. Therefore, a means for stopping the conveyance of the subsequent sheet along with the registration operation of the preceding sheet is provided. It is possible to reduce the manufacturing cost due to the provision, and to prevent the paper transport quality from deteriorating due to the slippage of the paper feeder due to the stoppage of the paper transport.

According to a tenth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the paper feeding device is provided in the transport path connecting the stacking storage portion and the temporary storage portion. A first roller pair that transports the sheet, and a second roller pair that is provided in the transport path that connects the temporary storage unit and the image forming unit and transports the sheet. A third pair of rollers for nipping the paper and rotating the paper forward and backward to store the paper in the temporary storage unit and to send the paper toward the image forming unit; Thereafter, the transport speed of the paper after the registration operation by the second and third roller pairs is set to be higher than the transport speed of the paper in the image forming unit for a predetermined period.

Therefore, the interval between the sheets, which is enlarged by the registration operation, is shortened after the registration operation, so that the deterioration of the abrasion of the image forming section due to the increase in the interval between the sheets and the improvement of the productivity of the image formation are achieved. Can be achieved.

The eleventh aspect of the present invention is the first aspect of the present invention.
0, wherein the image forming unit performs the image formation by an electrophotographic method.

Therefore, the interval between sheets continuously conveyed to the image forming section can be reduced, so that abrasion deterioration of the apparatus caused by performing an electrophotographic image forming operation without sheets can be reduced.

According to a twelfth aspect of the present invention, in the image forming apparatus according to the eleventh aspect, the image forming section uses a digital optical writing device for optically writing the electrostatic latent image on the photosensitive member. It is characterized in that it is performed by a digital electrophotographic method used.

Therefore, even in a digital electrophotographic image forming apparatus whose productivity could not be improved due to the upper limit of the number of rotations of the driving motor of the polygon mirror of the digital optical writing apparatus, the digital optical writing apparatus is also required. An image forming apparatus with high productivity can be provided without increasing the manufacturing cost of the image forming apparatus.

[0035]

FIG. 1 is a conceptual diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. As shown in FIG. 1, the image forming apparatus 1 is an image forming unit 2 that forms an image by an electrophotographic method, and a stacking unit that stacks and stores sheets 3 to be supplied to the image forming unit 2. The image forming apparatus includes a sheet cassette 4 and a sheet feeding device 5 that separates the stacked sheets 3 one by one and transports the stacked sheets 3 to the image forming unit 2.

The image forming section 2 includes a photoconductor 6, a charger 7 for charging the photoconductor 6, a digital optical writing device 8 for optically writing an electrostatic latent image on the photoconductor 6, A developing device 9 for developing the electrostatic latent image with toner, a transfer device 10 for transferring the developed toner image onto the paper 3, and a cleaning device 11 for removing residual toner on the photoconductor 6. And forming an image on the paper 3 by a digital electrophotographic process. The fixing device 12 fixes the toner image transferred onto the sheet 3, and the fixed sheet 3
Is discharged out of the image forming section 2 by the

The paper feeding device 5 includes a paper feeding roller 14 for taking out the sheets 3 stacked in the paper cassette 4 one by one, and a separating roller 15 for separating the taken out papers 3 one by one.
And a transport path 16 for transporting the extracted paper 3 to the image forming unit 2. This transport path 16
From the middle position of, the innermost part is a dead end,
A switchback path 17 serving as a temporary storage unit for temporarily storing the paper 3 is branched. The transport path 16 is divided into two transport paths 18 and 19 by a switchback path 17. The transport path 18 is a path connecting the paper cassette 4 and the entrance and exit of the switchback path 17, and includes a motor 26.
A transport roller 20, which is a first pair of rollers that transports the sheet 3 driven by (see FIG. 2), is provided. The transport path 19 is a path connecting the entrance and exit of the switchback path 17 and the image forming unit 2, and is a second roller pair that is driven by a motor 28 (see FIG. 2) and transports the sheet 3.
1 is provided. Conveying roller 2 which is a sheet reversing device
Reference numeral 2 denotes a third pair of rollers driven by a motor 30 (see FIG. 2) and capable of rotating forward and reverse.
It is provided in. The transport roller 22 nips the paper 3 and rotates the paper 3 forward and backward so that the transport path 18 stores the paper 3 transported from the paper cassette 4 into the switchback path 17 from the leading end.
The paper 3 stored in the printer 3 is switched back so that the rear end of the paper 3 is the leading end, and is sent out to the transport path 19 toward the image forming unit 2. The switchback path 17 is provided with a sheet detection sensor 23 that detects the sheet 3 in order to set the timing of the switchback operation of the sheet 3. A registration sensor 24 that detects the sheet 3 and takes the timing of a registration operation performed by the image forming apparatus 1 is provided at a position before the conveyance roller 21 in the conveyance path 19.
Is provided.

FIG. 2 is a block diagram showing the electrical connection of the control system of the sheet feeding device 5. This control system includes the sheet feeding device 5
A microcomputer 25 that drives a motor 26 that rotates the transport roller 20 is provided to a microcomputer 25 that centrally controls the whole
7, a motor driver 29 for driving a motor 28 for rotating the transport roller 21; a motor driver 31 for driving a motor 30 for rotating the transport roller 22;
2, a solenoid driver 33 for driving a solenoid 32 to be opened and opened, and a paper detection sensor 23 are connected. Although not shown in FIG. 2,
The registration sensor 24 is also connected to the microcomputer 25.

In the image forming apparatus 1 having the above configuration, the paper 3 enters the switchback path 17 by rotating the separation roller 15 and the transport roller 20, and the edge of the paper 3 is detected by the paper detection sensor 23. From the detection timing,
The microcomputer 25 (see FIG. 2) calculates the timing of completion of entry into the switchback path 17 to complete the entry operation.

The paper 3 is sent out from the switchback path 17 by rotating the transport rollers 22 and 21.
The registration operation conventionally performed by the registration rollers is performed by the conveyance rollers 21 and 22.

The leading end of the sheet 3 is always guided toward the image forming section 2 by a guide member (not shown) at the branch portion of the transport path 16. For example, the leading end of the sheet 3 is guided upward by a flexible guide member, or the transfer path 18 is forcibly forced by a gate provided with a driving means such as a solenoid.
May be switched to the transport path 19.

In the prior art, the switchback path 17
Since the rear end of the paper 3 waiting by the registration operation is stopped while being held between the transport rollers 20, 21 and the separation roller 15, the separation and separation of the next paper 3 are not performed. It was not possible to perform operations such as pre-adjustment of variations in the leading end position of the sheet 3 after starting the feeding. Further, it is necessary to design the transport rollers 20 and 21 and the separation roller 15 to be able to stop and start feeding in a state where the sheet is nipped. In addition, when the paper 3 is stopped or when feeding is started, the conveyance load of the registration roller may fluctuate. The driving force of the registration roller may be designed to be sufficiently strong so as not to cause a change in the conveyance speed. It was necessary to increase the pinching force. In addition, such a load variation may cause a large problem such as a horizontal line image defect called a shock jitter or an image defect such as a density change before and after the conveyance speed change.

In the image forming apparatus 1 according to the embodiment of the present invention, by using the switchback path 17 as a portion for temporarily storing the paper 3, the start of the image forming operation is awaited by the registration operation or the like. Paper 3
Since the trailing end of the sheet 3 does not stay on the transport roller 20 or the separation roller 15, it is possible to perform operations such as starting feeding of the next sheet 3 and correcting variations. Therefore, the interval between the sheets 3 and 3 that are continuously conveyed to the image forming unit 2 can be shortened and the productivity of image formation can be improved without transiently increasing the conveying speed of the sheet 3 as in the related art. .

Further, since the separation load on the separation roller 15 can be avoided, the conveyance speed of the sheet 3 on which an image is formed can be stabilized, and the deterioration of the image due to the fluctuation of the conveyance speed can be avoided.

As described above, the conventional registration roller is not provided in the vicinity of the image forming section 2 on the transport path 16. Instead, the transport roller 21 also functions as a registration roller. The transport roller 21 has a nip shape capable of correcting the skew of the leading end of the sheet 3 and can execute a registration operation. With such a configuration, a pair of rollers (registration rollers) and components required for driving the rollers can be reduced, so that the apparatus can be downsized and the manufacturing cost can be reduced.

FIGS. 3 and 4 show the registration operation in the image forming apparatus 1. FIG. Transport roller 22
Paper a (hereinafter, paper a and paper b are transported by
Of the sheets 3 that are continuously conveyed to the image forming unit 2 by the sheet feeding device 5, the leading sheet is referred to as a sheet a and the sheet behind the sheet a is referred to as a sheet b) before the conveying roller 21 in the conveying path 19. After the registration sensor 24 detects the leading edge of the sheet a at a predetermined position,
By stopping the conveyance by 2, the sheet is abutted against the conveyance roller 21 to perform a registration operation. This implements a registration unit. In this state, the transport roller 22 is nipping the sheet a.
It is necessary to start feeding the subsequent sheet b at a timing when the leading end of the sheet b does not arrive at the transport roller 22 until this operation is completed. This situation is shown in FIGS. In the example of FIG. 5, at the transport speed Va, the interval between the sheets a and b is widened in order to satisfy the above condition, and the transport is performed. In order to keep the interval between the sheets a and b narrow, it is necessary to increase the conveying speed of the succeeding sheet b to Va2 as shown in FIG. 6 and maintain the interval between the sheets a and b while satisfying the above conditions. is there.

As described above, since the registration operation is performed using the transport rollers 21 and 22, the conventional registration roller is not required, and the manufacturing cost can be reduced.

In the example shown in FIG. 7, the registration sensor 24 shown in FIGS. 1 and 3 is eliminated, and the position of the leading end of the sheet 3 is originally set for the purpose of detecting the timing of the switchback operation of the sheet 3. The registration operation is performed in consideration of the entire length of the sheet 3 based on the timing at which the sheet detection sensor 23 detects the rear end of the sheet 3. FIG. 8 shows the paper detection sensor 23.
2 shows a detection timing of the sheet 3 and an execution diagram of the registration operation. FIG. 9 shows a range in which the paper detection sensor 23 can be arranged as an “arrangement range”.

FIG. 10 shows a flowchart of the registration operation. That is, under the control of the microcomputer 25, the transmission of the sheet a from the switchback path 17 is started (step S1), and the sheet detection sensor 23 detects the sheet a.
Is detected (step S2), the transport time T is set to "T = ((from the paper detection sensor 23 to the registration roller 24.
(Length of paper) − (total length of paper)) / Vb ″ (step S3), the timing when the leading edge of the paper a arrives at the registration roller 24 is grasped, and the registration operation is executed (step S4). With such a configuration, the manufacturing cost can be reduced because the registration sensor is not required.

In the registration operation, the transport rollers 21 and 22 are temporarily stopped. However, if the transport roller 20 is configured to be continuously driven, the transport roller 20 does not stop at least up to the nipping position of the transport roller 22. Since the paper b can enter, it is possible to avoid problems such as adhesion of a roller mark to the paper b at the separation roller 15 due to the above-described stop operation, and manufacture by providing a means for stopping conveyance of the paper 3 Costs can also be reduced.

For this purpose, as shown in FIG. 2, the transport rollers 20, 21, 22 are configured to be independently driven by motors 26, 28, 30, respectively. , 22 can be driven together, and only the transport roller 21 that temporarily stops is driven via a clutch. In FIG. 2, if the motor 26 is commonly used as a drive source for the separation roller 15 and other rollers, it is suitable for cost reduction.

In general, the conveyance of the paper 3 is started in a state where the image forming unit 2 is ready to form an image. However, since the conveyance distance of the paper 3 is long, the feeding of the paper 3 is started without waiting for the completion of the preparation. After the paper 3 is fed, the image forming unit 2 may not be ready for image formation due to a change in the content of the image formation. In such a case, the timing is usually adjusted by extending the stop period in accordance with the registration operation.

After the registration operation as shown in FIG. 11 is performed and before the leading end of the sheet a reaches the image forming section 2, as shown in FIG. For example, even if the above-described timing adjustment period with the image forming unit 2 occurs, the conveyance of the subsequent sheet b to the reversal stop position can be prevented, and the problem such as the stop of the separation roller 15 can be avoided. This is preferable because it is possible to reduce the manufacturing cost by providing a means for stopping the conveyance of the succeeding paper b along with the registration operation of the preceding paper a. That is, when the paper feed rollers 21 and 22 temporarily stop the conveyance of the paper a by the registration operation, the rear end side of the paper a in the conveyance direction does not prevent the subsequent paper b from entering the switchback path 17. The paper feed rollers 21 and 22 are stopped in a state in which a is partially sent out to the image forming unit 2.

The above processing is shown in the transport diagram of FIG. If the paper 3 is long and the trailing end of the paper a reaches the nipping position of the transport roller 22 at the stop position of the paper a, at least the transport roller 20 can be transported by opening the transport roller 22 by driving the solenoid 32. The conveyance of the succeeding sheet b can be continued up to the position, and troubles such as stopping the separation roller 15 can be avoided. In this case, since the conveyance to the sheet reversing position becomes difficult with the opening operation of the conveyance roller 22, it is possible to control the conveyance by the conveyance roller 20 to temporarily stop in a state where the above-described problem can be avoided.

In the registration operation, the skew and the sending timing are adjusted by abutting the leading end of the sheet 3 against the stopped conveying roller 21. Accordingly, the interval between the sheets 3 and 3 is necessarily increased.

As shown in FIG. 14, after the registration operation, after the transport speed is set to Vc higher than Vb for a predetermined specific period, the speed is changed to Vb which is the same as the transport speed of the sheet 3 in the image forming unit 2. If control is performed to perform
The interval b is shortened according to the speed difference and the high-speed transport period. This implements the speed change means. This is shown in the transport diagram of FIG. In this example, the speed is increased to such an extent as to offset the enlargement of the interval between the sheets a and b caused by the registration operation period.

The speed may be further increased so that the interval between the sheets a and b is controlled to be shorter than before the registration operation. In such a case, it is preferable to drive the solenoid 32 so that the sheets a and b can be superimposed on each other at the nipping position of the conveying roller 22 to open the conveying roller 20 so that the start of conveyance of the succeeding sheet 2 is further advanced.

By the way, in a line printer such as an ink jet printer, the image forming operation in an area where there is no sheet between sheets is easily stopped, so that the image forming section is not deteriorated. Apparatus 1
In an electrophotographic image forming apparatus such as, for example, a page printer such as a laser beam printer, an image forming unit represented by a photoconductor cannot be temporarily stopped in an area where there is no paper between sheets, and image forming is not performed. Part of the idle period,
Abrasion degradation proceeds as in image formation.

However, in the image forming apparatus 1, since the interval between the sheets 3 can be greatly reduced as described above,
By greatly shortening the idling period between the two, the life degradation is greatly reduced.

At present, high-speed printer technology is constituted by a digital electrophotographic image forming apparatus. For example, a digital optical writer is provided for optically writing an electrostatic latent image, such as a laser beam printer. Image forming apparatus,
A factor typified by the rotation speed of the polygon motor is the upper limit of the image forming speed, and it is difficult to improve the paper conveying speed.

In the embodiment of the present invention, a digital electrophotographic image forming apparatus 1 having a digital optical writing device 8
In the above, since the interval between the sheets 3 and 3 is configured to be greatly reduced as described above, the idle rotation period between the sheets 3 and 3 is significantly shortened so that the continuous image forming speed can be reduced to the same transport speed. It is possible to improve as it is.

[0062]

According to the first aspect of the present invention, since the sheets can be temporarily stored in the temporary storage section, variations in the leading end position of the sheets when separated from the stacked and stored state are absorbed. Therefore, the interval between sheets continuously conveyed to the image forming unit can be shortened without transiently increasing the sheet conveying speed, and the productivity of image formation can be improved. Further, since the registration operation is performed using the sheet feeding device and the sheet reversing device, the conventional registration roller is not required, and the manufacturing cost can be reduced.

According to the second aspect of the present invention, in the image forming apparatus according to the second aspect, the conventional registration sensor can be used instead of the sheet detection sensor, so that the manufacturing cost can be reduced.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the sheet can be transported to the temporary storage section even during the execution of the registration operation. The paper conveyed toward the temporary storage unit is no longer stopped by the registration operation of the preceding paper, and a means for stopping the conveyance of the paper from the stacked storage unit to the temporary storage unit is reduced. In addition, it is possible to prevent a decrease in sheet conveyance quality such as a slip of a sheet feeding device due to a stop of sheet conveyance.

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the sheets can be stored in the temporary storage section without being hindered by the registration operation of the preceding sheets. It is possible to reduce the manufacturing cost by providing a means for stopping the conveyance of the subsequent paper in accordance with the registration operation of the paper, and to prevent the deterioration of the paper conveyance quality such as the slip of the paper feeding device due to the stop of the paper conveyance. it can.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the interval between sheets which is enlarged by the registration operation is reduced after the registration operation. It is possible to reduce the abrasion deterioration of the image forming unit due to the increase in the interval between sheets and to improve the productivity of image formation.

According to a sixth aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein
By performing the registration operation in cooperation with the third roller pair, the conventional registration roller is not required, the manufacturing cost can be reduced, and highly reliable paper conveyance can be performed.

According to the seventh aspect of the present invention, in the image forming apparatus according to the second aspect, since the conventional registration sensor can be used instead of the sheet detection sensor, the manufacturing cost can be reduced.

According to an eighth aspect of the present invention, in the image forming apparatus according to the third aspect, the sheet conveyed from the stacked storage section to the temporary storage section stops along with the registration operation of the preceding sheet. Means to stop paper transport from the stacked storage section to the temporary storage section, thereby reducing manufacturing costs and deteriorating paper transport quality such as slippage of the paper feeder due to the stoppage of paper transport. Can be prevented.

According to a ninth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the sheets can be stored in the temporary storage section without being hindered by the registration operation of the preceding sheets, so that the preceding steps can be performed. The provision of a means for stopping the conveyance of the subsequent paper in accordance with the registration operation of the paper reduces the manufacturing cost and prevents the deterioration of the paper conveyance quality such as the slip of the paper feeding device due to the stop of the conveyance of the paper. be able to.

According to a tenth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the interval between sheets which is enlarged by the registration operation is shortened after the registration operation, and the interval between the sheets is increased. Therefore, it is possible to reduce the abrasion deterioration of the image forming unit and to improve the productivity of image formation.

The eleventh aspect of the present invention relates to the first to the first aspects.
0, the distance between sheets continuously conveyed to the image forming unit can be reduced, so that the wear of the apparatus caused by performing the electrophotographic image forming operation without the sheets is reduced. Can be reduced.

According to the twelfth aspect of the present invention, in the image forming apparatus of the eleventh aspect, productivity can be improved due to an upper limit of the number of revolutions of a drive motor of a polygon mirror of a digital optical writing device. Even in a digital electrophotographic image forming apparatus, a highly productive image forming apparatus can be provided without increasing the manufacturing cost of the digital optical writing apparatus.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating an electrical connection of a control system of a sheet feeding device of the image forming apparatus.

FIG. 3 is a conceptual diagram illustrating the operation of the paper feeding device.

FIG. 4 is a conceptual diagram illustrating the operation of the sheet feeding device.

FIG. 5 is a diagram illustrating an operation of the sheet feeding device.

FIG. 6 is a diagram illustrating the operation of the paper feeding device.

FIG. 7 is a conceptual diagram illustrating the operation of the paper feeding device.

FIG. 8 is a diagram illustrating the operation of the paper feeding device.

FIG. 9 is a conceptual diagram illustrating an operation of a transport roller provided in a switchback path of the sheet feeding device.

FIG. 10 is a flowchart illustrating a registration operation of the sheet feeding device.

FIG. 11 is a conceptual diagram illustrating the operation of the paper feeding device.

FIG. 12 is a conceptual diagram illustrating the operation of the paper feeding device.

FIG. 13 is a diagram illustrating an operation of the sheet feeding device.

FIG. 14 is a conceptual diagram illustrating the operation of the sheet feeding device.

FIG. 15 is a diagram illustrating the operation of the sheet feeding device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming part 3 Paper 4 Stacking storage part 5 Paper supply device 8 Digital optical writing device 16 Transport path 17 Temporary storage part 18 Transport path 19 Transport path 22 Paper reversing device 23 Paper detection sensor

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 2H027 DC03 ED16 ED17 EE02 EE03 EE05 2H072 AA13 AA24 AA32 AB14 BA03 BA12 BB08 CB05 FA01 3F343 FA02 FB01 FB02 GA01 GB01 GC01 GD04 KB06 KB20 LA12 LC09 LC17 LC22 MA09 MB23

Claims (12)

[Claims] 1. An image forming section for forming an image on a sheet, a stacking and storing section in which sheets are stacked and stored, and the stacked sheets are separated one by one and conveyed to the image forming section. An image forming apparatus including a paper feeding device, a temporary storage unit provided on a transport path for performing the transport and temporarily storing the paper taken out from the stacked storage unit; The sheet conveyed from the stacked storage section is stored from the front end, and the sheet is switched back so that the rear end of the sheet stored in the temporary storage section is set as the front end, and the switch is performed on the image forming section. A sheet reversing device that sends the sheet to the image forming unit by adjusting timing of conveying the sheet by the sheet feeding device and sending the sheet by the sheet reversing device. A registration unit for performing a registration operation for synchronizing the registration with the image forming operation. 2. The image forming apparatus according to claim 1, further comprising: a sheet detection sensor that detects the sheet in the temporary storage unit, wherein the registration unit performs the registration operation based on a detection signal of the sheet by the sheet detection sensor. The image forming apparatus according to claim 1. 3. The paper feeding device independently performs a case where the paper is sent from the loading storage unit to the temporary storage unit and a case where the paper is sent from the temporary storage unit to the image forming unit. The image forming apparatus according to claim 1, wherein the image forming apparatus can perform the operation. 4. The registration unit according to claim 1, wherein, when the sheet feeding device temporarily stops conveyance of the sheet by the registration operation, a rear end side of the sheet in the conveyance direction of the sheet is transferred to the temporary storage unit of the subsequent sheet. 4. The image forming apparatus according to claim 3, wherein the stop is performed in a state in which the paper on which the pause is performed is not partially hindered and is partially sent to the image forming unit. 5. A shift means for increasing, after the registration operation, a transport speed of the paper after the registration operation by the paper feeding device for a predetermined period of time higher than a transport speed of the paper in the image forming unit. The image forming apparatus according to claim 1, wherein: 6. A paper feeding device comprising: a first pair of rollers provided in the transport path connecting the stacking storage section and the temporary storage section to transport the sheet; the temporary storage section and the image forming apparatus. And a second pair of rollers provided in the transport path connecting the first and second sections to transport the sheet, wherein the sheet reversing device nips the sheet and rotates the sheet forward and backward to temporarily store the sheet. A third roller pair for carrying the sheet into the image forming unit and sending the sheet toward the image forming unit, wherein the registration unit transports the sheet by the second roller pair and the sheet by the third roller pair 2. The registration operation is performed by adjusting the transmission timing of the data.
Or the image forming apparatus according to any one of 5. 7. The image forming apparatus according to claim 1, wherein the sheet feeding device includes a first pair of rollers provided in the transport path connecting the stacking storage unit and the temporary storage unit and transporting the sheet, the temporary storage unit and the image forming apparatus. And a second pair of rollers provided in the transport path connecting the first and second rollers to transport the paper, wherein the paper reversing device nips the paper and rotates the paper forward and reverse to temporarily store the paper. And a third pair of rollers for feeding the sheet toward the image forming unit, and the registration unit moves the leading edge of the sheet to the second position based on a detection signal of the sheet by the sheet detection sensor. 3. The image forming apparatus according to claim 2, wherein the registration operation is performed by performing the sending with the third roller pair until the registration operation is performed. 8. A paper feeding device comprising: a first roller pair provided in the transport path connecting the stacking storage unit and the temporary storage unit for transporting the sheet; the temporary storage unit and the image forming apparatus. And a second pair of rollers provided in the transport path connecting the first and second rollers to transport the paper, wherein the paper reversing device nips the paper and rotates the paper forward and reverse to temporarily store the paper. And a third pair of rollers for feeding the sheet to the image forming unit and feeding the sheet to the image forming unit. The sheet feeding device performs the operations of the first pair of rollers and the second pair of rollers independently. 4. The image forming apparatus according to claim 3, wherein the sheet can be conveyed from the stacked storage section to the temporary storage section even during the execution of the registration operation. 9. A paper feeding device comprising: a first pair of rollers provided in the transport path connecting the stacking storage unit and the temporary storage unit to transport the sheet; the temporary storage unit and the image forming apparatus. And a second pair of rollers provided in the transport path connecting the first and second rollers to transport the paper, wherein the paper reversing device nips the paper and rotates the paper forward and reverse to temporarily store the paper. And a third roller pair for feeding the paper toward the image forming unit, wherein the registration unit separates a rear end of the paper in the paper feeding direction from the third roller pair. After driving the second and third roller pairs to the position to convey the paper toward the image forming unit, the second roller pair is temporarily moved until the image forming operation by the image forming unit is started. To stop By performing the registration operation, it is possible to prevent the sheet from overlapping the subsequent sheet entering the temporary storage section at the position of the third roller pair by driving the first and third roller pairs. The image forming apparatus according to claim 4, wherein: 10. The paper supply device, a first roller pair provided in the transport path that connects the stacking storage unit and the temporary storage unit and transporting the sheet, the temporary storage unit and the image forming apparatus. And a second pair of rollers provided in the transport path connecting the first and second sections to transport the sheet, wherein the sheet reversing device nips the sheet and rotates the sheet forward and backward to temporarily store the sheet. And a third pair of rollers for feeding the sheet to the image forming section and the transmission means, after the registration operation, the second and third rollers of the sheet after the registration operation. 6. The image forming apparatus according to claim 5, wherein a conveying speed of the pair of rollers is set to be longer than a conveying speed of the sheet in the image forming unit for a predetermined period. 11. The image forming apparatus according to claim 1, wherein the image forming unit performs the image forming by an electrophotographic method. 12. The image forming apparatus according to claim 11, wherein the image forming unit performs the image forming by a digital electrophotographic method using a digital writing device for optically writing an electrostatic latent image on a photosensitive member. apparatus.