JP2000284644A - Image forming device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve productivity in image-recording in the case of performing recording on single side of recording material and in the case of performing recording on both sides thereof in an electrophotographic system image forming device. SOLUTION: This device is equipped with two image forming units 3a and 3b having a photoreceptor drum and a developing device, and fixing devices 4a and 4b. Recording paper is fed to the units 3a and 3b from cassettes 1a and 1b by paper feeding rollers 2a and 2b. At the time of performing recording on both sides of the recording paper, recording is performed on the different sides of the recording paper by the units 3a and 3b, and at the time of performing recording on either side of plural sheets of recording paper, recording is performed on either side of the recording paper in parallel by the units 3a and 3b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for forming an image by an electrophotographic process, and more particularly to an image forming apparatus and an image forming method for performing high-speed recording on one or both sides of a recording material.

[0002]

2. Description of the Related Art Image forming apparatuses using an electrophotographic process are widely used in offices and the like, but recently, in addition to conventional functions, apparatuses capable of recording on both sides of a recording material from the viewpoint of resource saving and the like. Has also been proposed. 14 and 15
FIG. 1 shows a main part of an electrophotographic image forming apparatus capable of recording on both sides of such a recording material.

In FIG. 14 and FIG. 15, reference numeral 101 denotes a cassette for accommodating recording paper; 102, a paper feed roller; 103, an image forming unit having a photosensitive drum and a developing device;
4 is a fixing device, 105 is a paper discharge tray, 106 is a paper discharge roller, 107 is a path for reversing the recording paper, 108 is a flapper for reversing the recording paper, 109 is an intermediate tray for storing the reversed recording paper, and 110 is It is a paper feed roller.

FIG. 14 shows an intermediate tray system.
It has a flapper 108 and a path 107 for reversing the recording paper, and stacks recording paper on which recording on one side has been completed on the intermediate tray 109, and then performs recording on the opposite side. Since this method has low productivity in double-sided printing, a through-pass double-sided method shown in FIG. 15 is often used. The super duplex method also includes a pass 107 for reversing the recording paper and a flapper 108, and alternately performs recording on the front surface and the back surface of the recording paper.

Further, an image forming apparatus as shown in FIG. 16 has been proposed in order to improve productivity in double-sided recording. This apparatus has two image forming units 103a, 1
03b and fixing devices 104a and 104b, and perform recording on the front and back surfaces of the recording paper in a shared manner.

[0006]

However, in the above-described image forming apparatus, there is a problem that productivity in single-sided recording and double-sided recording cannot be improved.

That is, even in the above-described through-pass double-side system, the transport path length of the recording paper is significantly longer than in single-sided recording, and recording on the front and back sides is performed alternately. Is about twice as long, so that the productivity in double-sided printing is about half as compared with that in single-sided printing.

Further, in an apparatus having two image forming units, the productivity during double-sided printing can be maintained substantially the same as the productivity during single-sided printing.
Despite the increase in the number of image forming units, it does not improve. Therefore, it is effective when only double-sided printing is always performed, and in the case where single-sided printing and double-sided printing are mixed as in actual use, there is no merit justified by increasing the number of image forming units. Is the actual situation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an image forming apparatus and an image forming method which improve productivity in single-sided recording and improve productivity in double-sided recording. It is intended to provide.

[0010]

An image forming apparatus and an image forming method according to the present invention are configured as follows.

(1) An electrophotographic image forming apparatus including two image forming units for recording an image on a recording material,
When recording on both sides of the recording material, recording is performed on different sides of the recording material in each image forming unit. When recording on one side of a plurality of recording materials, recording is performed in parallel by two image forming units. Was recorded on one side.

(2) An electrophotographic image forming apparatus, comprising two image forming units for performing image recording on a recording material,
At least one of the two image forming units can be selectively switched between a position where recording is performed on one surface of the recording material and a position where recording is performed on the opposite surface of the recording material.

(3) In the above configuration (1) or (2), at least one of the two image forming units is located at a position where recording is performed on one surface of the recording material and at a position opposite to the recording material. It moves to a position where recording is performed on the surface in accordance with the image forming mode.

(4) In any one of the above-mentioned constitutions (1) to (3), a path for conveying a recording material to a discharge port without passing through an image forming unit disposed downstream of the two image forming units. It was made to have.

(5) In the configuration of (4) above, the path is switched between a path passing through the downstream image forming section and a path not passing through in accordance with the image forming mode.

(6) In any one of the above constitutions (1) to (5), each image forming section has a photoreceptor and a developing device, and a fixing device is arranged downstream of the photosensitive member and a developing device. The recording medium has a feeding unit for feeding the recording material.

(7) In an electrophotographic image forming method, when recording is performed on both surfaces of a recording material, recording is performed on different surfaces of the recording material by two image forming units, and one side of a plurality of recording materials is recorded. When recording is performed on one side of the recording material, recording is performed in parallel by two image forming units.

(8) In an electrophotographic image forming method, an image forming section for performing image recording on a recording material has a recording position on one surface of the recording material and a recording position on an opposite surface of the recording material. Selective switching to the position to perform.

(9) In the above configuration (7) or (8), the image forming section is formed at a position where recording is performed on one surface of the recording material and a position where recording is performed on the opposite surface of the recording material. The recording is performed by moving according to the mode.

(10) In any one of the above constitutions (7) to (9), the path is switched between a path passing through the downstream image forming section and a path not passing through, depending on the image forming mode.

[0021]

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

(Embodiment 1) FIGS. 1 and 2 are cross-sectional views showing the main part of an electrophotographic image forming apparatus according to Embodiment 1 of the present invention. FIG. The state at the time of single-sided recording is shown.

In the apparatus of this embodiment, a first cassette 1a for accommodating recording paper, which is a recording material, and a first image forming unit 3a are disposed downstream of the paper feed roller 2a. A first fixing unit 4 is provided downstream of the forming unit 3a.
a is arranged. A second image forming unit 3b is disposed downstream of the first fixing unit 4a, and a second fixing unit 4b is disposed downstream of the first fixing unit 4a. The paper is discharged by the paper discharge roller 6.

The second image forming unit 3b and the second fixing unit 4 are located downstream of the first fixing unit 4a.
A path 7 for conveying the recording sheet to the discharge tray 5 without passing through the path b is provided, and the path 7 is selected by the flapper 8. Further, a second cassette 1b for feeding recording paper downstream of the first fixing unit 4a and upstream of the second image forming unit 3b, and a paper feed roller 2b thereof
Is arranged.

In this embodiment, the first image forming unit 3a is either on the same surface as the second image forming unit 3b on the recording paper or the second image forming unit 3a depending on the orientation of the first image forming unit 3a when housed in the main body. 3b, it is possible to record an image on a surface on a recording paper different from that of 3b.

FIG. 3 is a sectional view showing the structure of the first image forming unit 3a. The first image forming unit 3a is housed in a frame 9 that is detachable from the main body.
A cleaning device 11, a primary charging roller 12, and an LED array 13 are arranged around the photosensitive drum 10, and an electrostatic latent image corresponding to an image signal is formed on the photosensitive drum 10 by a well-known image forming process. The image is visualized as a toner image by 14.

Reference numeral 15 denotes a conveyance belt which adsorbs the recording paper together with the registration rollers 16 and conveys the recording paper in synchronization with an image signal. Reference numeral 17 denotes a transfer blade, which
The upper toner image is transferred to recording paper. Then, the recording paper after the transfer is conveyed while being adsorbed on the conveyance belt 15, and
To the fixing device 4a.

FIG. 4 is a sectional view showing the structure of the second image forming unit 3b. This second image forming unit 3b
Similarly to the first image forming unit 3a, a cleaning device 11, a primary charging roller 12, and an LED array 13 are arranged around a photosensitive drum 10, and an electrostatic latent image corresponding to an image signal is formed by a known process. Is formed on the photosensitive drum 10 and is visualized as a toner image by the developing device 14.

A transport belt 15 absorbs the recording paper together with the registration rollers 16 and transports the recording paper in synchronization with the image signal. A transfer blade 17 transfers the toner image on the photosensitive drum 10 to recording paper. Then, the recording paper after the transfer is conveyed while being attracted to the conveyance belt 15, and is conveyed to the second fixing device 4b.

Hereinafter, the recording operation of this embodiment will be described in detail.

FIG. 1 shows a state in which an image is recorded on both sides of a recording paper by the present apparatus. When an image is recorded on both sides of the recording paper, the recording paper is fed from a cassette 1a to a paper feed roller 2a.
a, and is conveyed to the first image forming unit 3a. The recording sheet on which the toner image has been transferred by the image forming unit 3a as described above is sent to the fixing device 4a. The fixing device 4a is composed of two roller pairs that are in pressure contact with each other, and each roller fuses the toner on the recording paper by a heater (not shown) provided at the center of the roller and thermally fixes the toner.

Next, the recording paper reaches a position where the paper path branches, and is conveyed by the flapper 8 to the second image forming unit 3b. At this time, the flapper 8 is in a state shown in FIG. 1 in a mode in which a conveyance path is selectively switched by a plunger (not shown) and a double-sided image is recorded on recording paper.

The recording paper that has passed through the flapper 8 is
Of the first image forming unit 3b.
An image is recorded on a surface different from the surface recorded in a. Thereafter, the toner is sent to a fixing device 4b. The fixing device 4b has the same configuration as the fixing device 4a, and melts the toner on the recording paper and thermally fixes the toner. Then, the recording paper on which the toner image is fixed on the second side by the second fixing device 4 b
Is discharged to the paper discharge tray 5.

As described above, in the present embodiment, two sets of image forming units 3a and 3b are provided, and it is possible to form images on both sides of the recording paper without reversing the recording paper. The productivity is higher than in the case where recording is performed on both sides of a recording sheet by one set of image forming units using the reverse path.

Next, the operation of the present apparatus for recording an image on only one side of the recording paper will be described. When performing recording on one side of the recording paper, the first image forming unit 4a
Is extracted from the frame body 9 and inserted into the frame body 9 in a manner reversed to the above-described double-sided recording. At this time, the flapper 8 is driven by a solenoid (not shown) in accordance with the insertion direction of the first image forming unit 3a to be in a state shown in FIG.

In this state, the first image forming unit 3a
The recording paper having the toner image fixed on one side thereof by the fixing device 4a does not pass through the second image forming unit 3b.
The sheet is directly discharged to the sheet discharge tray 5 via the path 7.

Here, a case where single-sided recording is continuously performed on a plurality of recording papers by the apparatus of this embodiment will be described. Here, a case where an A4-size recording sheet is image-transformed in a horizontal direction will be described, and actual dimensions are shown in parentheses.

The length of the recording paper is L (= 210 mm), and the recording paper is discharged from the leading end of the cassette 1a onto the paper discharge tray 5 through the upper portions of the first image forming unit 3a and the second image forming unit 3b. The transport path length of the first path to the leading edge of the recording paper to be fed is L1 (= 976 mm), and the paper transport interval on the same path is L.
p (= 100 mm), and the image forming speed in the same path is V (= 1
00 mm), from the cassette 1b to the second image forming unit 3
b, the transport path length of the second path to the leading end of the recording paper discharged onto the paper output tray 5 via the second fixing device 4b is L2 (= 532 mm), and the paper transport interval in the same path is L2 (= 532 mm). Lp (=
100 mm), and the image forming speed on the same path is V (= 100 m).
m), the time from the start of image formation to the discharge of the first recording sheet via the first path is L1 / L1.
V (= 9.76 sec).

Thereafter, the recording paper passing through the first path is
One sheet is discharged every (Lp + L) / V (= 3.1 sec).

Similarly, the time from the start of image formation to the discharge of the first recording sheet via the second path is as follows.
L2 / V (= 5.32 sec).

Thereafter, the recording paper passing through the first path is
One sheet is discharged every (Lp + L) / V (= 3.1 sec).

FIG. 5 is a graph of the above description.
The relationship between the elapsed time from the start of image formation in the first path and the number of output recording sheets is shown. Similarly, FIG.
Indicates the relationship between the elapsed time from the start of image formation in the second path and the number of output recording sheets.

As shown in FIGS. 5 and 6, in this embodiment,
From the relationship between the length of the first path and the length of the second path, it can be understood that when the number of single-sided recordings is two or less, the processing time is shorter when the images are sequentially recorded on the second path.

Next, a case where three or more single-sided recordings are continuously performed will be described. In this embodiment, when three or more continuous single-sided recordings are to be performed, the operation of simultaneously starting the image formation by the first path and the image formation by the second path is performed at a predetermined sheet feeding interval (Lp + L) / Vsec. Repeat.

FIG. 7 shows the relationship between the elapsed time after the start of recording in this case and the number of recording sheets discharged to the discharge tray 5.
As shown in the figure, for the first two sheets, the recording paper recorded in the second path is discharged, and thereafter, the recording paper recorded in the first path and the recording paper recorded in the second path Are alternately discharged. Therefore, unlike the order in which the image formation is started, the recording papers are stacked on the discharge tray 5 in a predetermined page order.

A specific operation will be described. First, when the number of recorded images is an even number, the recording of the first image is started on the second path and the recording of the third image is started on the first path.

Next, a predetermined paper feed interval (Lp + L)
After the elapse of / Vsec, the recording of the second sheet is started in the second path, and the recording of the fifth sheet is started in the first path.

When the above operation is repeated, both the recording material recorded on the first path and the recording material recorded on the second path are discharged to the discharge tray 5 as a whole apparatus.

For example, when the number of sheets to be printed is six, the printing of the fourth sheet is started in the second path after the lapse of the next paper feed interval (Lp + L) / Vsec. At this time, recording on the first path is not performed. Then, after the next paper feeding interval, the recording of the sixth sheet is started in the second path.

FIG. 8 shows that the number of recorded images is 2N (N is a positive number).
FIG. 9 is a diagram showing a recording order when an even number is used.
2, (b) shows the case where N = 3, and (c) shows the case where N> = 2.

As shown in FIG. 8, at the start of the second recording, the recording paper started to be recorded on the first path is the recording paper whose recording was started on the second path at the start of the third recording (fourth paper). )
After that, the recording paper (sixth sheet) conveyed along the second path at the start of the fourth recording reaches the paper discharge tray 5 after that.

That is, when the number of recorded images is 2N (N> = 2), the 2N-th and 2 (N-1) -th images are recorded only by the second path, and the 2N-1-th is the 2nd-th image. In the first path, recording is started at the same time as the second (N-2) th sheet passing through the second path.

FIGS. 9A and 9B are diagrams showing a recording order when the number of recordings is 2N-1 and an odd number. FIG. 9A shows N = 2, and FIG.
= 3, (c) shows the case where N> = 2.

As shown in FIG. 9, the recording number is 2N-1.
If (N> = 2), the 2N−1th sheet is recorded on the first path, and at the same time, 2 (N−
2) The second sheet is recorded, and the 2N-2th sheet is recorded last in the second path.

As described above, when a large number of single-sided recordings are continuously performed in this embodiment, the number of output sheets per unit time is almost twice that of the double-sided recording, and the productivity is extremely high.

(Embodiment 2) FIGS. 10 and 11 are cross-sectional views showing the main parts of Embodiment 2 of the present invention. FIG. 10 shows a state during double-sided recording, and FIG. 11 shows a state during single-sided recording. ing.

The arrangement of the image forming units 3a and 3b and the paper transport path 7 of the present embodiment is the same as that of the previous embodiment, and a description thereof will be omitted. 10 and 11, reference numeral 21 denotes a turntable, and reference numeral 22 denotes a drive motor thereof.

FIG. 12 is a perspective view showing the structure of the image forming unit 3a. An image forming unit 23 having a photosensitive drum and a developing device and a drive motor 24 thereof are accommodated in frames 9a and 9b, and are rotatable by a turntable 21. FIG. 13 shows the support state.

In this embodiment, as shown in FIG.
Of the image forming unit 3a is rotatable around a rotation axis parallel to the paper transport direction. That is, as shown in FIG. 12, the first image forming unit 3a includes an image forming unit 23 for controlling the image formation of charging, exposure, and development, and a frame 9b for supporting the image forming unit 23, the transport belt 15, the transfer relationship, and the like. Drive motor 2 for driving the conveyor belt 15 and the image forming unit 23
4, the frame 9 a is supported on the turntable 21. The turntable 21 is configured to be rotatable around a paper conveyance path by a drive motor 22.

In the present embodiment, the two-sided printing shown in FIG.
The first image forming unit 3a switches between a state in which recording is performed on a surface of recording paper different from that of the image forming unit 3b and a state in which recording is performed on the same surface of recording paper as the second image forming unit 3b shown in FIG. Turn around.

The flapper 8 shown in FIGS.
Is switched to the illustrated direction by a driving unit (not shown) according to the direction of the first image forming unit 3a.

As described above, in this embodiment, the recording surface of the first image forming unit 3a is automatically switched in accordance with the image forming mode, and the first and second image forming units 3a and 3b are used for double-sided recording. Recording is performed on both sides of the recording paper with 3a and 3b, and both image forming units 3a and 3b are used for single-side recording.
Since the recording is performed on the same side of the recording paper, the productivity becomes very high, especially when a large number of sheets are continuously recorded.

[0063]

As described above, according to the present invention,
When recording is performed on both sides of a recording material, the recording material is transported via two image forming units, and recording is performed on different surfaces of the recording material in each image forming unit. As compared with the case where the recording material is reversed and recording is performed on both sides of the recording material, the productivity during double-sided recording is increased.

When one-side recording is performed on a logarithmic number of recording materials, the recording material is fed from each feeding means to each image forming unit, and the two image forming units are operated in parallel on one side of the recording material. Therefore, the productivity during single-sided recording is significantly improved as compared with the double-sided recording.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of a first embodiment of the present invention.

FIG. 2 is a sectional view showing a main part of the first embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a configuration of an image forming unit according to the first exemplary embodiment.

FIG. 4 is a cross-sectional view illustrating a configuration of an image forming unit according to the first exemplary embodiment.

FIG. 5 is a diagram illustrating a relationship between the number of output images and time according to the first embodiment.

FIG. 6 is a diagram illustrating a relationship between the number of output images and time according to the first embodiment.

FIG. 7 is a diagram illustrating the relationship between the number of image outputs and time according to the first embodiment.

FIG. 8 is a diagram illustrating a recording order in each path according to the first embodiment.

FIG. 9 is a diagram illustrating a recording order in each path according to the first embodiment.

FIG. 10 is a sectional view showing a main part of a second embodiment of the present invention.

FIG. 11 is a sectional view showing a main part of a second embodiment of the present invention.

FIG. 12 is a perspective view illustrating a configuration of an image forming unit according to a second embodiment.

FIG. 13 is a perspective view illustrating a support state of the image forming unit according to the second exemplary embodiment.

FIG. 14 is a cross-sectional view showing a configuration of a conventional example.

FIG. 15 is a sectional view showing the configuration of another conventional example.

FIG. 16 is a sectional view showing the configuration of another conventional example.

[Explanation of symbols]

 1a Cassette 1b Cassette 2a Feeding Roller 2b Feeding Roller 3a Image Forming Unit 3b Image Forming Unit 4a Fixing Device 4b Fixing Device 5 Discharge Tray 6 Path 8 Flapper 9 Frame 10 Photosensitive Drum 11 Cleaning Device 12 Primary Charging Roller 13 LED Array 14 Developing device 15 Conveyor belt 16 Registration roller 17 Transfer blade 21 Turntable 22 Drive motor 23 Image forming unit 24 Drive motor

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H04N 1/04 G03G 21/00 372 5C072 / 29 H04N 1/04 Z 9A001 F-term (Reference) 2H027 ED16 FA13 ZA10 2H028 BA06 BA16 BC00 2H072 AA32 AB07 5C062 AA05 AB22 AB32 AB46 AB53 AC09 AD01 AD06 BA00 5C072 AA03 BA03 BA05 HA02 RA05 WA02 WA06 XA01 5C074 AA12 BB02 CC26 GG09 HH02 9A001 BB03 JJ35 KK31 KK37 KK42

Claims (10)

[Claims] 1. An electrophotographic image forming apparatus, comprising:
It has two image forming units that perform image recording on the recording material. When recording on both sides of the recording material, each image forming unit performs recording on a different surface of the recording material, and records on one surface of a plurality of recording materials. An image forming apparatus wherein two image forming units perform recording on one side of a recording material in parallel. 2. An electrophotographic image forming apparatus, comprising:
Two image forming units for performing image recording on a recording material;
At least one of the two image forming units is selectively switchable between a position where recording is performed on one surface of the recording material and a position where recording is performed on the opposite surface of the recording material. Image forming apparatus. 3. An image forming unit according to claim 1, wherein at least one of the two image forming units has a position for recording on one surface of the recording material and a position for recording on the opposite surface of the recording material according to the image forming mode. The image forming apparatus according to claim 1, wherein the image forming apparatus moves. 4. The printing apparatus according to claim 1, further comprising a path for transporting the recording material to a discharge port without passing through an image forming unit disposed downstream of the two image forming units. The image forming apparatus according to any one of the above. 5. The image forming apparatus according to claim 4, wherein a path that passes through a downstream image forming unit and a path that does not pass through are switched according to an image forming mode. 6. An image forming section having a photoreceptor and a developing device, a fixing device disposed downstream thereof, and a feeding means for feeding a recording material to each image forming section. The image forming apparatus according to claim 1, wherein: 7. An electrophotographic image forming method, comprising:
When recording is performed on both sides of the recording material, recording is performed on different surfaces of the recording material by two image forming units, and when recording is performed on one surface of a plurality of recording materials, the recording materials are concurrently performed by the two image forming units. Recording on one side of the image forming method. 8. An electrophotographic image forming method, comprising:
An image forming unit for performing image recording on a recording material, wherein the image forming unit selectively switches between a position for performing recording on one surface of the recording material and a position for performing recording on the opposite surface of the recording material. Forming method. 9. The recording device according to claim 1, wherein the image forming section is moved to a position where recording is performed on one surface of the recording material and a position where recording is performed on the opposite surface of the recording material in accordance with the image forming mode. 9. The image forming method according to claim 7, wherein: 10. The image forming method according to claim 7, wherein a path that passes through a downstream image forming unit and a path that does not pass through are switched according to an image forming mode.