JPH11237768A - Recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recorder which can accurately align images on both sides of recording paper, with respect to a recorder that records the image on the front of the recording paper, thereafter inverts the recording paper back to front, and records the image on the back of the recording paper. SOLUTION: Relating to the recorder, which records an image on the front of recording paper 5, thereafter inverts the recording paper 5 back to front, and records an image on the back of the recording paper 5, a detection means 15 is provided for detecting a relation between the position of the rear end of the recording paper 5 in the direction of the carrying of it and an image recording position when the image is recorded on the front of the recording paper 5, and for detecting the position of the front end of the recording paper 5 in the direction of the carrying of it when the image is recorded on the back of the recording paper 5. Also, a means for setting an image recording position for the back of the recording paper 5 based on the detection signal of the detection means 15 is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus having a function of recording images on both sides of a recording sheet.

[0002]

2. Description of the Related Art Hitherto, many recording apparatuses such as laser printers having a function of recording images on both sides of recording paper have been proposed. These recording devices
An image forming means is provided on both sides of a recording paper conveyance path, and these image forming means simultaneously transfer and fix an image on both front and back surfaces of the recording paper by one conveyance of the recording paper. After the image forming means is provided on one side of the path and the image is transferred and fixed on one side of the recording sheet by the image forming means, the image is transferred to the other side of the recording sheet by reversing the front and back of the recording sheet. Some are established.

[0003] Also, Japanese Patent Application Laid-Open No. 61-275774,
JP-A-61-275775, JP-A-61-275
Japanese Patent Application Laid-Open No. 780 discloses an image forming apparatus that detects a positional shift amount of a transfer sheet and corrects image forming positions on the front and back sides. Japanese Patent Publication No. Hei 6-100847 discloses that when images are recorded on both sides of one recording sheet from two different single-sided originals or one double-sided original, the binding margin of the recording paper is corrected and both sides of the recording paper are corrected. Describes a double-sided copying apparatus that matches the position of an image recorded in the printer.

[0004]

In the above recording apparatus,
Since the positional relationship between the images on both sides of the recording paper is determined by the positional relationship between the image forming means, the images on both surfaces of the recording paper can be aligned with high accuracy. However, in the above-described recording apparatus, it is necessary to invert and convey the recording sheet after recording the image on one side of the recording sheet, and to record the image on one side of the recording sheet and the image on the other side of the recording sheet. Since the leading edge and the trailing edge of the recording paper are switched between when recording the image, considering the variation in the length of the recording paper, it is extremely difficult to accurately align the images on both sides of the recording paper even with a registration roller. Have difficulty.

Similarly, when the recording paper is inverted, conveyed, or the like, the recording paper is displaced in the left-right direction, which makes it more difficult to accurately align images on both sides of the recording paper. The present invention is a recording apparatus for recording an image on the back side of a recording sheet by recording an image on the front side of the recording sheet after recording the image on the front side of the recording sheet, and accurately aligning images on both sides of the recording sheet. It is an object of the present invention to provide a recording device that can perform the recording.

[0006]

According to a first aspect of the present invention, an image is recorded on the front side of a recording sheet, and then the image is reversed on the back side of the recording sheet. A recording apparatus that records the image on the front surface of the recording sheet, detects the relationship between the rear end position of the recording sheet in the transport direction and the image recording position, and records the image when recording the image on the back surface of the recording sheet. A detecting means for detecting the leading end position of the sheet in the sheet conveying direction, and means for setting an image recording position on the back surface of the recording sheet based on a detection signal of the detecting means.

According to a second aspect of the present invention, in the recording apparatus according to the first aspect, there is provided a registration roller for sending a recording sheet to an image recording position, and the detecting means is provided between the registration roller and the image recording position. It is provided in.

According to a third aspect of the present invention, there is provided a recording apparatus for recording an image on the back side of a recording sheet by recording an image on the front side of the recording sheet after recording the image on the front side of the recording sheet. Detecting the relationship between the position of the left or right end of the recording sheet and the image recording position when recording the image, and detecting the position of the end of the recording sheet when recording an image on the back surface of the recording sheet Means for setting an image recording position on the back surface of the recording paper based on the detection signal of the detecting means.

According to a fourth aspect of the present invention, in the recording apparatus according to the first aspect, when an image is recorded on both the front and back surfaces of the recording sheet, the image is transferred to the front and back surfaces of the recording sheet sent from the registration roller at a predetermined transfer position. And the detecting means is provided between the registration roller and the transfer position.

According to a fifth aspect of the present invention, in the recording apparatus according to any one of the first to fourth aspects, the front, rear, left, and right positions of the recording paper are detected by the same detecting means.

According to a sixth aspect of the present invention, there is provided the recording apparatus according to the first or second aspect, comprising a color recording apparatus for recording a color image on both sides of a recording sheet.

According to a seventh aspect of the present invention, in the recording apparatus according to the third aspect, a color image is formed by superimposing and transferring a plurality of color images onto the recording paper while holding and transporting the recording paper with a transfer body. The recording means is provided, and at least a light receiving element of the detecting means is provided inside the transfer body.

[0013]

FIG. 1 shows a first embodiment of the present invention. The first embodiment is an embodiment of a monolithic printer that records a single-color image on a recording sheet, and an electrostatic latent image carrier 1 composed of a drum-shaped photosensitive member is driven to rotate by a driving unit during image recording to be charged. After being uniformly charged by a charging device having a roller 2, the surface is scanned and exposed on the basis of image information by an optical writing device 3 including a laser writing device as an exposure device, thereby forming an electrostatic latent image on the surface. Here, the direction of the exposure scanning (the direction perpendicular to the direction of travel of the photoconductor 1) is referred to as the main scanning direction, and the direction of travel of the photoconductor 1 perpendicular thereto is referred to as the sub-scanning direction.

The electrostatic latent image formed on the photosensitive member 1 is reversely developed by the developing device 4 to become a visible image composed of a toner image. The image (visible image) formed on the photoreceptor 1 is electrostatically transferred by a transfer unit having a transfer roller 6 onto a recording sheet 5 sent to a transfer position in synchronization with an image forming signal. Of course, a transfer unit such as a corona transfer device may be used instead of the transfer unit having the transfer roller 6.

The recording paper 5 is fed from a paper feeder having a paper feed cassette 7 to a registration roller 9 by a paper feeding roller 8 and sent to a transfer position by the registration roller 9 in synchronization with an image on the photoconductor 1. Is done. Recording paper 5
After the image on the photoconductor 1 is transferred, the image is separated from the photoconductor 1 and the image is fixed by the fixing device 10, and the image recording on one surface (front surface) is completed. Further, the photoconductor 1 is initialized by the cleaning device 11.

When recording images on both sides of the recording sheet, following the above operation, the recording sheet 5 after the image fixing on one side is sent to the reversing unit 12, and the reversing unit 12 reverses the recording sheet. Then, the sheet is fed to the double-sided sheet feeding device 13, and is again fed to the registration roller 9 by the sheet feeding roller 14. An image is formed on the photoconductor 1 in the same manner as described above, and the registration roller 9 sends the recording paper 5 fed from the double-sided paper feeder 13 to the transfer position in synchronization with the image on the photoconductor 1.

The image on the photosensitive member 1 is transferred to another side (back side) of the recording sheet 5 by a transfer unit having a transfer roller 6.
Is separated from the photoreceptor 1 after being transferred to the fixing device 10
As a result, the image on the other side is fixed and discharged to the outside as a double-sided recorded matter. Here, between the registration roller 9 and the transfer position, there is provided a position detecting means 15 for detecting the leading and trailing end positions of the recording paper 5 which is a feature of the present embodiment. As the position detecting means 15, for example, a transmission type optical sensor is used.

First, at the time of front side recording for recording an image on the surface of the recording sheet 5, the position detecting means 15 detects the front and rear end positions of the recording sheet 5 and detects the rear end of the recording sheet 5 so as to be determined in advance. The positional relationship of the trailing edge of the recording sheet 5 with respect to the image forming position on the surface of the photoconductor 1 thus detected, that is, the relationship between the trailing edge position of the recording sheet 5 and the image recording position is detected. A control unit (not shown) obtains the positional relationship between the image forming position on the surface of the photoconductor 1 and the rear end of the recording paper 5 based on the output signal of the position detecting unit 15 and stores the positional relationship in the storage unit. Here, photoconductor 1
The image forming position on the front surface refers to the entire range in which an image can be formed by performing scanning exposure based on image information by the laser writing device 3 regardless of the presence or absence of an actual formed image on the photoconductor 1. I have.

Next, at the time of back side recording for recording an image on the back side of the recording sheet 5, the position detecting means 15 detects the front and rear end positions of the recording sheet 5. The control unit detects the leading end position (the trailing end position during front side recording) of the recording paper 5 from the output signal of the position detecting unit 15, and detects the detection signal and the image formation of the surface of the photoconductor 1 stored in the storage unit. Based on the positional relationship between the position and the rear end of the recording sheet 5, an image formation start position on the photoconductor 1 (a position at which scanning exposure on the photoconductor 1 is started based on image information by the laser writing device 3) is set. .

That is, the control unit controls the image forming position on the surface of the photoreceptor 1 stored in the storage means during the surface recording and the recording paper 5
Relative to the rear end, and the position detecting means 15 during backside recording.
By controlling the writing start position (start of scanning exposure) of the scanning exposure by the laser writing device 3 on the photoconductor 1 at the time of back surface recording, from the leading end position of the recording paper 5 (back end position at the time of front surface recording) detected by Positioning of the images on both sides of the recording paper 5 is accurately performed. This embodiment eliminates the need to require high precision in feeding, transporting, and inverting the recording paper, and performs low-cost, high-accuracy image registration on both sides of the recording paper. be able to.

In the present embodiment, the distance from the optical writing position by the laser writing device 3 on the photosensitive member 1 to the transfer position is set to be smaller than the distance from the position detecting means 15 to the transfer position. Detection means 15
It is possible to control the scanning exposure start position on the photoconductor 1 by controlling the timing of starting the scanning exposure of the photoconductor 1 by the laser writing device 3 based on the leading edge detection information of the recording paper 5. Of course, in the present embodiment, a system is used in which the start and end of the recording paper 5 are detected by the position detecting means 15 without the registration roller 9 and the start of image writing on the photoconductor 1 by the laser writing device 3 is realized. Is also possible.

The first embodiment is an embodiment of the invention according to claim 1, wherein after recording an image on the front surface of the recording sheet 5, the recording sheet 5 is turned upside down and the back side of the recording sheet 5 is reversed. When recording an image on the front surface of the recording paper 5, the recording device detects the relationship between the rear end position of the recording paper 5 in the transport direction and the image recording position, and prints the image on the back surface of the recording paper 5. Position detecting means 15 as detecting means for detecting the leading end position of the recording paper 5 in the transport direction when recording.
And a control unit as a means for setting an image recording position on the back surface of the recording paper 5 based on the detection signal of the detection means 15, so that the position of the images on the front and back of the recording paper in the recording paper advancing direction can be adjusted. It can be performed at low cost.

Further, the first embodiment is an embodiment of the invention according to claim 2, and has a registration roller 9 for sending out the recording paper 5 to the image recording position side in the recording apparatus according to claim 1. Since the detection means 15 is provided between the registration roller 9 and the image recording position, it is possible to more accurately position the images on the front and back of the recording sheet before and after in the recording sheet traveling direction.

Further, the first embodiment is an embodiment of the invention according to claim 4, and in the recording apparatus according to claim 1, when recording images on both front and back surfaces of the recording paper 5, the registration roller 9 is used. The image is transferred to both the front and back surfaces of the recording paper 5 sent from the printer at a predetermined transfer position, and the detection means 15 is provided between the registration roller 9 and the transfer position. Positioning before and after the recording paper traveling direction can be performed with higher accuracy.

Next, a second embodiment of the present invention will be described. In the second embodiment, in the first embodiment, as shown in FIG. 2, the position detecting means 15 includes a light source 16 composed of a light emitting diode, a light receiving element 17 composed of a photodiode, and a slit member having a slit 18a. 18, which is provided so as to detect either one of the left and right reference side ends of the transfer sheet 5. The light source 16, the slit member 18, and the light receiving element 17 are arranged on both sides of the transfer path of the transfer sheet 5, and light from the light source 16 disposed above the transfer path of the transfer sheet 5 transfers the transfer sheet 5. The light is irradiated on the light receiving element 17 through the slit and the slit 18a of the slit member 18.

The slit 18a of the slit member 18 is formed obliquely to the traveling direction of the recording paper 5,
The reference side end of the recording sheet 5 is set so as to pass between the light source 16 and the slit member 18, including the variation in the conveyance of the recording sheet 5. When the leading end of the recording paper 5 reaches the position detecting means 15, the output signal of the position detecting means 15 changes as shown in FIG.

Here, a of the output signal of the position detecting means 15
As shown in FIG. 4, the slit is provided obliquely with respect to the traveling direction of the recording sheet 5 after the corner at the tip end of the reference side end of the recording sheet 5 starts to cover the slit 18a of the slit member 18 as shown in FIG. The portion of the recording paper 5 which reaches the foremost portion 18a can be used to determine the positional relationship of the reference side end of the recording sheet 5 with respect to the position detecting means 15 by its length.

The output signal of the position detecting means 15 is
Thereafter, the output signal b is substantially constant until the rear end corner at the reference end of the recording paper 5 reaches the slit 18a of the slit member 18. Further, the output signal of the position detecting means 15 is such that when the rear end corner at the reference end of the recording paper 5 reaches the slit 18 a of the slit member 18,
It returns to the steady state via the output signal c. Therefore, the control unit can accurately detect the positions of the leading and trailing edges and the edge of the recording paper 5 based on the output signal of the position detecting unit 15.

This second embodiment is an embodiment of the third aspect of the present invention, in which an image is recorded on the front side of the recording sheet 5 and then the recording sheet 5 is turned over so that the back side of the recording sheet 5 is reversed. When recording an image on the front surface of the recording sheet 5, the recording apparatus detects the relationship between the position of one of the left and right ends of the recording sheet 5 and the image recording position and records the image on the back surface of the recording sheet 5. Position detecting means 15 as detecting means for detecting the position of the end of the recording paper 5 when recording an image.
And a control unit as a means for setting an image recording position on the back surface of the recording paper 5 based on the detection signal of the detection means 15, so that the left and right alignment of the images on the front and back of the recording paper in the recording paper traveling direction can be performed. It can be performed at low cost.

In each of the other embodiments of the present invention, the front and rear, left and right positions of the recording sheet 5 (or any one of the left and right end portions of the recording sheet 5) are different from the first and second embodiments. Is detected by the same position detecting means, and the control section determines the image recording position on the back surface of the recording paper 5 based on the detection signal from the detecting means in the first and second embodiments. The settings are made in the same manner as in the embodiment.

These embodiments are one embodiment of the invention according to claim 5, and in the recording apparatus according to any one of claims 1 to 4, the front, rear, left and right positions of the recording paper 5 are detected by the same detection. Since the detection is performed by the means 15, the alignment of the images on the front and back of the recording paper can be performed at low cost.

FIG. 5 shows a third embodiment of the present invention. The third embodiment is an embodiment of a tandem-type color printing apparatus provided with four image forming units corresponding to each recording color.
In this color recording apparatus, in the image forming means of each recording color, the electrostatic latent image carriers 1Y, 1M, 1C, and 1K each composed of a drum-shaped photoreceptor are rotated and driven by a driving unit when recording a color image. Rollers 2Y, 2M, 2
After being uniformly charged by a charging device having C and 2K, optical writing devices 3Y, 3M, 3C and 3
By K, scanning exposure is performed based on image information of each color (each recording color), and an electrostatic latent image is formed on the surface.

Here, the optical writing devices 3Y, 3M, 3M
For C and 3K, an optical writing device having a light emitting diode array is used. Further, the direction of the exposure scan (photoconductor 1
Y, 1M, 1C, 1K)
Is referred to as a main scanning direction, and a traveling direction of the photoconductor 1 perpendicular to the main scanning direction is referred to as a sub-scanning direction. In addition, the optical writing devices 3Y, 3M, 3
The image information of each color that C and 3K expose to the photoconductors 1Y, 1M, 1C and 1K is obtained by converting a desired full-color image into yellow (hereinafter referred to as Y), magenta (hereinafter referred to as M), cyan (hereinafter referred to as C) and black (hereinafter referred to as black). (Hereinafter referred to as K), and the optical writing devices 3Y, 3M, 3C, 3
Sent to K at a time.

The electrostatic latent images formed on the photoconductors 1Y, 1M, 1C and 1K are developed by developing devices 4Y, 4M, 4C and 4K, respectively.
By K, the image is reversely developed with predetermined Y toner, M toner, C toner, and K toner, and becomes a visible image of each color of a Y toner image, an M toner image, a C toner image, and a K toner image. The recording sheet is fed from a sheet feeding device having a sheet feeding cassette 19 to a registration roller 21 by a sheet feeding roller 20, and is sent to a transfer body 22 formed of a transfer belt at a timing by the registration roller 21. The transfer belt 22 is made of a transparent polyester film.

The transfer belt 22 holds and conveys the recording paper sent from the registration roller 21 and transfers the recording paper.
A predetermined appropriate transfer bias from a transfer power source is applied to the back surface at each transfer position facing Y, 1M, 1C and 1K by transfer bias applying brushes 23Y, 23M, 23C and 23K as transfer bias applying means. Thus, the full-color image is formed by sequentially superimposing and transferring the images of the respective colors on the photoconductors 1Y, 1M, 1C, and 1K on the recording paper at the respective transfer positions.

Of course, also here, transfer bias applying means such as a corona transfer device or a transfer roller may be used instead of the transfer bias applying brushes 23Y, 23M, 23C and 23K. The recording paper is separated from the transfer belt 22 after the full-color image is formed, and the full-color image is fixed by the fixing device 24, and the recording of the full-color image on one surface (front surface) is completed. Also, the photoconductors 1Y, 1M, 1
C and 1K are cleaning devices 25Y, 25M, 25C,
Initialized by 25K.

When a full-color image is recorded on both sides of the recording sheet, the recording sheet after the full-color image fixing on one side is sent to the reversing unit 26 following the above operation, and the reversing unit 26 reverses the recording sheet. Then, the sheet is fed to the double-sided paper feeding device 27, and is again fed to the registration roller 21 by the double-sided paper feeding device 27. Photoconductor 1
Images of respective colors are formed on Y, 1M, 1C, and 1K in the same manner as described above, and the registration roller 21 sends the recording paper fed from the double-sided paper feeder 27 to the transfer belt 22 at a proper timing.

The transfer belt 22 holds and conveys the recording paper sent from the registration roller 21 and transfers the recording paper.
Transfer bias application brushes 23Y, 23M, 23C, 23 on the back surface at respective transfer positions facing Y, 1M, 1C, 1K.
When a predetermined appropriate transfer bias is applied from a transfer power supply by K, images of the respective colors on the photoconductors 1Y, 1M, 1C, and 1K are sequentially transferred onto the other surface (back surface) of the recording paper at each transfer position. To form a full-color image.

The recording paper is separated from the transfer belt 22 after a full-color image is formed on the other side, and the full-color image is fixed by the fixing device 24, and is discharged as a double-sided color recording. Also, the photoconductors 1Y, 1
M, 1C, 1K are cleaning devices 25Y, 25M, 2
Initialized by 5C and 25K.

In the third embodiment, similarly to the second embodiment, the position between the registration roller 21 and the transfer position is
Position detecting means 29a for detecting the leading and trailing edge positions of the recording paper;
29 b are provided on both sides of the transfer belt 22. The position detecting means 29a and 29b are such that at least a light receiving element is provided inside the transfer belt 22, for example, a light source 29a is provided outside the transfer belt 22 and a light receiving section 29b including a slit member and a light receiving element is provided on the transfer belt 22. Provided inside. Then, similarly to the above-described second embodiment, first, at the time of front surface recording for recording an image on the surface of the recording paper,
The position detecting means 29a and 29b detect the leading and trailing edge positions of the recording sheet and detect the trailing edge of the recording sheet to thereby determine the recording sheet with respect to the predetermined image forming position on the surface of the photoconductor 1Y, 1M, 1C or 1K. The position of the rear end of
The relationship between the rear end position of the recording paper 5 and the image recording position is detected.

A control unit (not shown) includes a position detecting means 29
a, 29B by the output signals of the photoconductors 1Y, 1M, 1C,
The positional relationship between the image forming position on the 1K surface and the rear end of the recording paper is obtained and stored in the storage means. Here, the photoconductors 1Y, 1
The image forming positions on the surfaces of M, 1C, and 1K are the photoconductors 1Y,
Regardless of the presence or absence of actual formed images on 1M, 1C and 1K,
It indicates the entire range in which an image can be formed by performing scanning exposure based on image information of each color by the optical writing devices 3Y, 3M, 3C, and 3K.

Next, at the time of backside recording for recording an image on the backside of the recording paper, the position detecting means 29a and 29b detect the front and rear end positions of the recording paper. The control unit detects the leading end position of the recording paper (the rear end position during front side recording) from the output signals of the position detecting units 29a and 29b, and detects the detection signal and the photosensitive members 1Y, 1M, Based on the positional relationship between the image forming positions on the 1C and 1K surfaces and the rear end of the recording paper,
The image forming start position on the photoconductors 1Y, 1M, 1C, and 1K (the position where the scanning exposure on the photoconductors 1Y, 1M, 1C, and 1K is started based on the image information by the optical writing devices 3Y, 3M, 3C, and 3K) Set.

That is, the control unit controls the positional relationship between the image forming positions of the photoconductors 1Y, 1M, 1C, and 1K stored in the storage unit during the front side recording and the rear end of the recording paper, and the position detecting unit 29a during the back side recording. , 29b from the leading edge position of the recording paper (the trailing edge position during front side recording) to the scanning exposure by the optical writing devices 3Y, 3M, 3C, 3K on the photoconductors 1Y, 1M, 1C, 1K during back side recording. By controlling the writing start position (scanning exposure start position), the positions of the images on both sides of the recording paper are accurately adjusted. This embodiment eliminates the need to require high precision in feeding, transporting, and inverting the recording paper, and performs low-cost, high-accuracy image registration on both sides of the recording paper. be able to.

The distance from the light writing position to the transfer position by the light writing devices 3Y, 3M, 3C and 3K on the photoconductors 1Y, 1M, 1C and 1K is determined by the position detecting means 29.
a, 29b, the distance from the transfer position is set to be smaller than that of the optical writing devices 3Y, 3Y based on the detection information of the leading edge of the recording paper by the position detecting means 29a, 29b.
M, 3C and 3K to control the timing of starting the scanning exposure of the photoconductors 1Y, 1M, 1C and 1K to control the photoconductors 1Y and 1K.
It becomes possible to control the scanning exposure start positions on M, 1C and 1K.

The position where the position detecting means 29a and 29b are installed is most preferably at the transfer belt 22, but is not limited to this, and may be between the registration roller 21 and the transfer belt 22, or without the registration roller 21. The position detectors 29a and 29b detect the leading and trailing edges of the recording paper, and detect the photosensitive members 1Y and 1Y of the optical writing devices 3Y, 3M, 3C and 3K.
In the case of a system that controls the start of image writing for M, 1C, and 1K, the position detection units 29a and 29
b may be provided further forward.

The third embodiment is an embodiment of the invention according to claim 6 and is a recording apparatus according to claim 1 or 2, wherein the color recording apparatus records a color image on both sides of recording paper. Therefore, the alignment of the images on the front and back of the recording paper can be performed at low cost.

This third embodiment is an embodiment of the invention according to claim 7, and in the recording apparatus according to claim 3, the recording paper is held and conveyed by a transfer belt 22 as a transfer member. While a color image is recorded by superimposing and transferring a plurality of color images on the recording paper, at least a light receiving element among the position detecting means 29a and 29b as the detecting means is provided inside the transfer body 22. So
Positioning of the images on the front and back of the recording paper can be performed with higher accuracy.

[0048]

As described above, according to the first aspect of the present invention, with the above-described configuration, it is possible to perform low-cost positioning of the images on the front and back of the recording sheet in the front and rear directions of the recording sheet.

According to the second aspect of the present invention, with the above configuration, the positioning of the images on the front and back of the recording paper in the recording paper advance direction can be performed with higher accuracy.

According to the third aspect of the present invention, with the above configuration, it is possible to perform low-cost alignment of the images on the front and back of the recording paper in the recording paper advancing direction.

According to the fourth aspect of the present invention, with the above-described configuration, it is possible to more accurately align the images on the front and back of the recording paper in the front and rear directions in the recording paper traveling direction.

According to the fifth aspect of the present invention, with the above-described configuration, the alignment of the images on the front and back of the recording paper can be performed at low cost.

According to the sixth aspect of the present invention, with the above configuration, it is possible to perform the alignment of the images on the front and back of the recording sheet at low cost.

According to the seventh aspect of the invention, with the above-described configuration, it is possible to more accurately perform the alignment of the images on the front and back of the recording paper.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view illustrating a position detecting unit according to a second embodiment of the present invention.

FIG. 3 is a waveform chart showing an output signal of the position detecting means.

FIG. 4 is a top view showing a slit member of the position detecting means.

FIG. 5 is a sectional view showing a third embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 5 Recording paper 15, 29a, 29b Position detecting means 9 Registration roller 22 Transfer belt

Claims (7)

[Claims] 1. A recording apparatus for recording an image on the back side of a recording sheet by recording an image on the back side of the recording sheet by recording the image on the back side of the recording sheet after recording the image on the front side of the recording sheet. Detecting means for detecting the relationship between the rear end position of the sheet in the sheet conveying direction and the image recording position, and detecting the leading end position of the recording sheet in the sheet conveying direction when recording an image on the back side of the recording sheet; Means for setting an image recording position on the back surface of the recording paper based on a signal. 2. A recording apparatus according to claim 1, further comprising a registration roller for sending a recording sheet to an image recording position.
A recording apparatus, wherein the detecting means is provided between the registration roller and an image recording position. 3. A recording apparatus for recording an image on the back side of a recording sheet by recording an image on the back side of the recording sheet by recording the image on the front side of the recording sheet after recording the image on the front side of the recording sheet. Detecting means for detecting the relationship between the position of one of the right and left ends of the sheet and the image recording position, and detecting the position of the end of the recording sheet when recording an image on the back of the recording sheet; Means for setting an image recording position on the back surface of the recording paper based on the detection signal of (i). 4. The recording apparatus according to claim 1, wherein when recording the image on both sides of the recording sheet, the image is transferred at a predetermined transfer position to both sides of the recording sheet sent from the registration roller. 2. A recording apparatus according to claim 1, wherein said detecting means is provided between said registration roller and said transfer position. 5. A recording apparatus according to claim 1, wherein the front, rear, left and right positions of the recording paper are detected by the same detecting means. 6. The recording apparatus according to claim 1, wherein:
A recording apparatus comprising a color recording apparatus for recording a color image on both sides of a recording sheet. 7. A recording apparatus according to claim 3, wherein a color image is recorded by superimposing and transferring a plurality of color images onto the recording paper while holding and transporting the recording paper with a transfer body. A recording apparatus, wherein at least a light receiving element of the detecting means is provided inside the transfer body.