JPH07160065A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent a waste of recording media even when the media are carried in superposed state and form an image without any drop in overall recording speed. CONSTITUTION:This device has the first guide passage for guiding recording media to a discharge section, the second guide passage branched from the first guide passage, a transfer direction selector member for guiding the recording media to either of the first and second guide passages, a superposed transfer detecting means 66, and recording media separation means 67 and 69 to control the member for the separation of the recording media therewith.

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 such as a copying machine or a printer.

[0002]

2. Description of the Related Art Conventionally, image forming apparatuses include copying machines, printers, etc., and FIG. 6 shows an example of a laser printer. In this laser printer, at the time of single-sided recording in which an image is recorded on one side of a recording medium made of recording paper, the recording paper 12 stored in a paper feed cassette 11 is fed by a paper feed roller 13 and one by a friction pad 14. The recording papers are separated one by one, and are conveyed by conveying rollers 15 and 16, and an image is formed on the surface by a known electrophotographic process.

That is, the photosensitive belt 17 is composed of the roller 1
8 to 21 are rotated and driven to be uniformly charged by the charging device 22, and then an image is written by image exposure by the writing device 23 to form an electrostatic latent image. The electrostatic latent image is developed by the developing device 24 into a toner image, and the transfer device 25 transfers the toner image on the photosensitive belt 17 to the recording paper from the conveying roller 16. The toner image is transferred onto the recording paper, and the toner image is fixed by the fixing device 26.
8, the recording paper from the fixing device 26 is guided by the first guide path 28 and is discharged to the paper discharge unit 30 by the paper discharge roller 29. Further, the photosensitive belt 17 is cleaned by the cleaning device 31 after the transfer of the toner image to remove the residual toner.

Further, in double-sided recording in which images are recorded on both sides of the recording paper, after the image is formed on the front surface of the recording paper as in the case of single-sided recording, the recording paper is transferred to the conveying direction switching plate 2.
7 is guided to the second guide path 32 by switching to the second guide path 32, and is re-fed by the double-sided paper feed roller 35 via the double-sided conveyance path 34 in the double-sided unit 33. By doing so, the paper is re-fed with the front and back reversed. The re-fed recording paper is conveyed by the conveyance rollers 15 and 16 and an image is formed on the back surface by an electrophotographic process in the same manner as described above, so that an image is formed on both sides,
The conveyance direction switching plate 27 is switched to the first guide path 28 so that the recording paper for double-sided image formation is guided from the fixing device 26 through the first guide path 28, and is discharged by the paper discharge roller 29 to the paper discharge unit 3.
It is discharged to 0.

Further, in Japanese Patent Application Laid-Open No. 60-90353, in a copying machine, a copy sheet having an image transferred on one side is sent to a conveyance direction control roller via a return belt to be inverted and then on the other side. When an image is transferred and double-sided copying is performed, and the copy sheets are fed in duplicate and detected by the double feed detection means, a double feed rotation operation of the conveyance direction control roller is performed in response to a command signal from the double feed detection means. An apparatus for feeding the sent copy paper to the discharged copy tray is described.

Japanese Unexamined Patent Publication No. 60-220366 discloses an automatic double-sided copying machine having an intermediate tray for stocking transfer paper having been transferred to one side, and the transfer paper is double-fed to a transfer paper passage reaching the intermediate tray. In addition to providing detection means for detecting, a separation means for separating a blank transfer sheet is provided in the transfer paper passage on the downstream side of the detection means, and the separation means is provided when the detection means detects the double feeding of the transfer paper. An automatic two-sided copier is described which is operative to remove a blank transfer sheet from a transfer sheet path.

Japanese Unexamined Patent Publication (Kokai) No. 60-41056 discloses a first method.
In a double-sided copying machine equipped with an intermediate tray for temporarily storing the transfer sheets whose surfaces have been copied, if the transfer sheets are double-fed during the copying of the first side, the number of sheets stored in the intermediate tray is A double-sided copying machine is described in which the copying of the second side is continued until it reaches zero.

[0008]

In the above laser printer, the recording paper is not wasted even when the recording paper is double-fed and an image is recorded on the front surface during the single-sided recording. However, if the recording papers are double-fed during double-sided recording, the image is recorded separately on both of the double-feeding recording papers 12 ₁ and 12 ₂ as shown in FIG. 7, and the recording papers 12 ₁ and 12 ₂ are wasted. As a result, the overall recording speed decreases. Further, the above-mentioned JP-A-6
In the paper described in Japanese Patent Publication No. 0-90353, when the copy sheets are fed in a double feed and detected by the double feed detection means, the double feed is performed by the double feed rotation operation of the conveyance direction control roller in response to a command signal from the double feed detection means. Since the copy paper of is sent to the discharge copy tray,
Since the copying is not performed on each of the double-fed copying papers, the overall recording speed is reduced.

In the one disclosed in Japanese Patent Laid-Open No. 60-220366, when the detecting means detects the double feeding of the transfer paper, the separating means operates to remove the blank transfer paper from the transfer paper passage. Since the copying is not performed on any of the copying papers, the total recording speed is reduced. Furthermore, JP-A-60-41
In the case of the 056 publication, when double feeding of transfer paper occurs during copying of the first side, copying of the second side is continued until the number of sheets stored in the intermediate tray reaches zero. The overall recording speed is reduced because copying is not performed in either case.

The present invention provides an image forming apparatus capable of improving the above-mentioned drawbacks and making it possible to form an image without wasting the recording medium and reducing the overall recording speed even when the recording medium is double-fed. The purpose is to do.

[0011]

In order to achieve the above-mentioned object, the invention according to claim 1 records the image on the feeding means for feeding the recording medium and the recording medium fed from the feeding means. Recording means, a first guide path for guiding the recording medium on which the image is recorded by the recording means to the discharge section, a second guide path branched from the first guide path, and an image by the recording means. The recording medium on which is recorded the first guide path and the second guide path.
In the image forming apparatus, there is provided a conveyance direction switching member for guiding the recording medium fed to one of the guide paths, and a multi-feed detection unit for detecting the double feeding of the recording medium fed from the feeding unit. The recording medium separating device is provided with a recording medium separating unit that controls the members to separate the recording mediums that are multi-fed by the conveying direction switching member.

According to a second aspect of the invention, a feeding means for feeding the recording medium, a recording means for recording an image on the recording medium fed from the feeding means, and an image is recorded by the recording means. A first guide path for guiding the recording medium to the discharge section, a second guide path branching from the first guide path, and a recording medium on which an image is recorded by the recording means for the first guide path. In the image forming apparatus, a conveyance direction switching member that guides to either one of the second guide path and the second guide path, and a double feed detection unit that detects double feed of the recording medium fed from the feeding unit, In the case where the recording medium is double-fed based on the detection signal from the double-feed detecting means, the distance from the leading end of the most preceding recording medium to the second preceding recording medium is detected, The transfer direction switching member is provided on the side of the second guide path. The leading recording medium is guided to the second guide path, and the feeding direction switching member is moved before the leading recording medium passes the feeding direction switching member and is fed by the distance. The recording medium separation means is provided for switching the recording medium to the first guide path side and guiding the second and subsequent recording media to the first guide path.

[0013]

According to the first aspect of the present invention, the recording medium separating means controls the conveying direction switching member to separate the recording medium to be multi-fed by the conveying direction switching member. According to the second aspect of the invention, the recording medium separating means is the second from the leading edge of the most preceding recording medium among the recording media that are double-fed when the recording medium is double-fed based on the detection signal from the double-feed detection means. The distance to the recording medium preceding the first recording medium is detected, the conveyance direction switching member is switched to the second guide path side to guide the first recording medium to the second guide path, and the first recording medium is the conveyance direction switching member. The transport direction switching member is switched to the side of the first guide path before the sheet is transported by the above distance and is transported by the above distance to guide the second and subsequent recording media to the first guide path.

[0014]

FIG. 2 shows the outline of one embodiment of the present invention. This embodiment is an embodiment of the invention described in claims 1 and 2, and is an example of a laser printer. During single-sided recording in which an image is recorded on one side of a recording medium made of recording paper, the recording paper 42 stored in the paper feed cassette 41 is fed by a paper feed roller 43 and separated one by one by a friction pad 44. The paper is conveyed by conveyance rollers 45 and 46, and an image is formed on the surface by a known electrophotographic process.

That is, the image carrier 47, which is a photoconductor belt, is wound around rollers 48 to 51 to be rotationally driven, uniformly charged by the charging device 52, and then an image is written by image exposure by the writing device 53. And an electrostatic latent image is formed. This electrostatic latent image is developed by the developing device 54 to become a toner image, and the toner image on the photosensitive belt 47 is transferred to the recording paper from the conveying roller 46 by the transfer device 55. The toner image is fixed on the recording paper on which the toner image is transferred by the fixing device 56, and the conveyance direction switching plate 5
7 is switched to the first guide path 58 and the fixing device 5
The recording paper from 6 is guided by the first guide path 58 and discharged to the paper discharge unit 60 by the paper discharge roller 59. Further, the photoconductor belt 47 has a cleaning device 61 after the toner image is transferred.
To remove the residual toner.

In double-sided recording, in which images are recorded on both sides of the recording paper, after the image is formed on the front surface of the recording paper as in the case of single-sided recording, the recording paper is transferred to the conveyance direction switching plate 5.
7 is switched to the second guide path 62, and is guided by the second guide path 62, and is re-fed by the double-sided paper feed roller 65 via the double-sided conveyance path 64 in the double-sided unit 63. By doing so, the paper is re-fed with the front and back reversed. The re-fed recording paper is conveyed by the conveyance rollers 45 and 46, and an image is formed on both sides by forming an image on the back side by the electrophotographic process in the same manner as described above.
The conveyance direction switching plate 57 is switched to the first guide path 58 so that the recording paper for double-sided image formation is guided from the fixing device 56 through the first guide path 58, and is discharged by the paper discharge roller 59 to the paper discharge unit 6.
It is discharged to 0.

Further, a paper feed cassette 41 and a paper feed roller 43
In the sheet feeding device having the friction pad 44, when the recording paper 42 is not sufficiently separated by the friction pad 44 and the recording paper 42 is double-fed, the recording paper 42
Is detected by the double-feed detection means 66. The multi-feed detecting means 66 is disposed at a predetermined position between the paper feeding device and the fixing device 56, for example, between the double-sided paper feeding roller 65 and the conveying roller 45, and is composed of a photodiode or the like to detect the recording paper. Double feeding of recording paper is detected from changes in transmittance and the like.

The recording sheets to be fed in a double-feeding manner are conveyed direction switching plate 5
7, but in this case, as shown in FIG. 3, the leading edge of the preceding first recording paper 42 ₁ and the second recording paper 42 ₂ of the recording papers 42 ₁ and 42 ₂ that are fed in a double feed manner are used. The conveyance direction switching plate 57 is switched from the side of the second guide path 32 to the side of the first guide path 28 between the leading edge and the leading edge of the first recording paper 42.
_{The first} and second recording papers 42 ₂ are separated by the transport direction switching plate 57 and are guided by the second guide path 32 and the first guide path 28, respectively.

As shown in FIG. 4, the output signal of the double-feed detecting means 66 is one recording paper 4 at the detection position of the double-feed detecting means 66 as compared with the case where there is no recording paper at the detection position of the double-feed detecting means 66.
When there is 2 ₁ , the level becomes high, and the double feed detection means 66
When there are two recording papers 42 ₁ and 42 _{2 at} the detection position of ₁ , the level becomes higher. The time T1 during which the double-feed detection unit 66 detects the leading edge side of only the _first recording sheet 42 ₁ is 1
This is the time from when the leading edge of the second recording paper 42 ₁ reaches the detection position of the double feed detecting means 66 to when the leading edge of the _second recording paper 42 ₂ reaches the detection position of the double feeding detection means 66. 1
It is determined by the distance between the leading edge of the second recording sheet 42 _{1 and} the leading edge of the second recording sheet 42 ₂ and the conveying speed of the recording sheets 42 ₁ , 42 ₂ .

FIG. 1 shows a part of this embodiment. The conveyance direction switching plate control unit 67 controls the recording paper from the fixing device 56 to be the first recording paper.
So as to be selectively guided by the guide path 58 and the second guide path 62 of the first guide path 58 and the second guide path 62, and As shown in FIG. 3, the conveyance direction switching plate 59 is switched so that the multi-fed recording papers 42 ₁ and 42 ₂ are separated and guided by the first guide path 58 and the second guide path 62, respectively. The print control unit 68 controls each unit of this embodiment so that the above-described recording operation is performed.

The microcomputer (CPU) 69 is
While transmitting and receiving signals to and from the print control unit 68, a command is sent to the transport direction switching plate control unit 67 to move the transport direction switching plate 59 to the first guide path 58 side and the second guide path 62 side as described above. When the recording sheets 42 are selectively switched and the recording sheet 42 is double-fed, a command is sent to the conveyance direction switching plate controller 67 at the time of the double feeding of the recording sheets based on the detection signal from the double feeding detection unit 66. _The conveyance direction switching plate 59 is switched so that ₁ , 42 ₂ are separated and guided by the first guide path 58 and the second guide path 62, respectively.

FIG. 6 shows the operation flow of this embodiment. The transport direction switching plate controller 67 normally switches the transport direction switching plate 59 to the first guide path 58 side, and during single-sided recording, the recording paper from the fixing device 56 is guided by the first guide path 58 and discharged. The paper is discharged to the paper discharge unit 60 by the paper roller 59. During double-sided recording, in which images are recorded on both sides of the recording paper, the conveyance direction switching plate control unit 67 causes the conveyance direction switching plate 59 to first move the recording paper from the fixing device 56 to the second guide path 62 according to a command from the CPU 69. Second to be guided
To the side of the guideway 62. If the double feeding of the recording paper is not detected by the double feeding detecting means 66, the normal double-sided printing operation (double-sided printing operation) is performed as described above, and the conveyance direction switching plate control unit 67 controls the back side of the recording paper. The transport direction switching plate 59 is switched to the first guide path 58 side.

The CPU 69 judges from the detection signal from the double feed detecting means 66 whether or not the double feed of the recording paper is detected by the double feed detecting means 66, and the double feed of the recording paper is detected by the double feed detecting means 66.
In from the detection signal level from the double-feed detection means 66 when it is detected, double-fed by the recording paper 42 _1, 42 recording sheet preceding the leading edge of the recording sheet 42 ₁ in the second to most previous of the _two The distance to 42 ₂ is detected, that is, the above T1 is calculated, and a command is issued to the conveyance direction switching plate control unit 67 so that the most preceding recording paper 42 ₁ passes within the conveyance direction switching plate 59 within T1. Transport direction switching plate 5
9 is switched to the first guide path 58 side.

Therefore, the most preceding recording paper 42 ₁ is
The paper is fed by the second guide path 62 and is re-fed by the double-sided paper feed roller 65 via the double-sided conveyance path 64 in the double-sided unit 63 as described above. The image is formed on both sides by printing on a paper and forming an image on the back side by an electrophotographic process. By this time, the conveyance direction switching plate 57 is switched to the first guide path 58, and thus the first guide path 58. The paper is ejected to the paper ejection unit 60 by the paper ejection roller 59. The recording sheet 42 _1, 42 recording paper 42 ₂ preceding the second of the _two paper ejection is guided by the first guide path 58 roller 5 to be double fed
The sheet 9 is discharged to the sheet discharge unit 60.

Therefore, even if the recording papers are double-fed, the recording papers are not wasted, and the double-feeding recording papers 4 are used.
By continuing the double-sided recording operation on the recording paper 42 ₁ which is the most preceding of the 2 ₁ and 42 ₂ , it is possible to perform image recording without reducing the overall recording speed. Although the above embodiment is an example of a laser printer, the present invention can be similarly applied to an image forming apparatus such as a copying machine or a facsimile.

[0026]

As described above, according to the first aspect of the invention, the feeding means for feeding the recording medium, and the recording means for recording the image on the recording medium fed from the feeding means, A first guide path for guiding the recording medium on which an image has been recorded by the recording means to the discharge section, and a second guide path branched from the first guide path.
Of the guide path, a conveyance direction switching member for guiding the recording medium on which the image is recorded by the recording means to one of the first guide path and the second guide path, and the feeding means for feeding from the feeding means. An image forming apparatus having a double-feed detection means for detecting double-feed of fed recording media, in which a recording medium separation control unit controls the transport-direction switching member to separate the multi-feed recording medium into the transport-direction switching member. Since the means is provided, it is possible to perform image formation without wasting the recording medium and reducing the overall recording speed even when the recording medium is double-fed.

According to the second aspect of the present invention, the feeding means for feeding the recording medium, the recording means for recording the image on the recording medium fed from the feeding means, and the image by the recording means The first guide path that guides the recorded recording medium to the discharge unit, the second guide path that branches from the first guide path, and the recording medium on which the image is recorded by the recording unit are the first guide path. An image forming apparatus having a conveyance direction switching member that guides the guide path to either the guide path or the second guide path, and a double feed detection unit that detects double feed of the recording medium fed from the feeding unit. In the case where the recording medium is double-fed by the detection signal from the double-feed detection means, the distance from the leading end of the most preceding recording medium to the second preceding recording medium is detected. , The conveyance direction switching member to the second guide To the second guide path so that the most preceding recording medium is guided to the second guide path and the most preceding recording medium passes through the conveying direction switching member and is conveyed by the distance by the conveying direction switching member. Since the recording medium separating means for switching the recording medium to the first guide path side and guiding the second and subsequent recording media to the first guide path is provided, the recording media are not wasted even if the recording media are double fed. It is possible to form an image without reducing the effective recording speed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a part of an embodiment of the present invention.

FIG. 2 is a sectional view showing the outline of the embodiment.

FIG. 3 is a cross-sectional view showing the vicinity of a transport direction switching plate in the embodiment.

FIG. 4 is a waveform diagram showing an output signal of the double feed detecting means in the embodiment.

FIG. 5 is a flowchart showing an operation flow of the embodiment.

FIG. 6 is a sectional view showing an outline of a conventional laser printer.

FIG. 7 is a diagram showing an example of double-feed recording paper image recording of the same laser printer.

[Explanation of symbols]

 41 Paper Feed Cassette 43 Paper Feed Roller 44 Friction Pad 47 Photosensitive Belt 52 Charging Device 53 Writing Device 54 Developing Device 55 Transfer Device 56 Fixing Device 57 Transfer Direction Switching Plate 58 First Guideway 62 Second Guideway 63 Double-sided Unit 66 double feed detecting means 67 transport direction switching plate control section 69 CPU

Claims (2)

[Claims] 1. A feeding unit for feeding a recording medium, a recording unit for recording an image on the recording medium fed from the feeding unit, and an ejecting unit for ejecting the recording medium on which the image is recorded by the recording unit. To the first guide path, the second guide path branching from the first guide path, and the recording medium on which the image is recorded by the recording means, to the first guide path and the second guide path. In an image forming apparatus having a conveyance direction switching member that guides the recording medium fed from the feeding unit and a conveyance direction switching member that guides the recording medium fed from the feeding unit, An image forming apparatus comprising: a recording medium separating unit that separates a recording medium that is controlled and double-fed by the conveyance direction switching member. 2. A feeding unit for feeding a recording medium, a recording unit for recording an image on the recording medium fed from the feeding unit, and a discharging unit for ejecting the recording medium on which the image is recorded by the recording unit. To the first guide path, the second guide path branching from the first guide path, and the recording medium on which the image is recorded by the recording means, to the first guide path and the second guide path. An image forming apparatus having a conveyance direction switching member for guiding to one of a path and a double feed detecting unit for detecting double feed of a recording medium fed from the feeding unit, In the case where the recording mediums are double-fed, the distance from the leading edge of the most preceding recording medium to the second preceding recording medium is detected based on the detection signal of Switch to the second guideway side and come first The recording medium is guided to the second guide path, and the transport direction switching member is moved to the first guide path side before the most preceding recording medium passes through the transport direction switching member and is transported by the distance. An image forming apparatus comprising recording medium separating means for switching and guiding the second and subsequent recording media to the first guide path.