JP2002023586A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which can form an excellent image free of deviation. SOLUTION: An oblique travel correcting means 106 provided in a conveyance passage R carrying the sheet S from a sheet storage means to an image formation part corrects an oblique run of a sheet S by curving the sheet S and a side end detecting means 105 provided above the oblique run correcting means 106 detects a side end of the sheet S perpendicular to its conveyance direction. Then a control means controls the side end detecting operation of the side end detecting means 105, controls the position of an image formed on the sheet S according to the detection signal from the side end detecting means 105, and performs control so that the side end detecting means 105 performs the side end detecting operation when the sheet S is curved by the oblique travel correcting means 106.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus, and more particularly, to a side edge detection in a direction perpendicular to a sheet conveying direction performed when an image is formed on a sheet.

[0002]

2. Description of the Related Art In a conventional image forming apparatus such as a copying machine, an image forming apparatus for correcting an image forming position in a direction perpendicular to a sheet conveying direction so that an image can be formed at a desired position on a sheet. Some include a position correction device.

Here, such an image forming position correcting apparatus writes a recording sheet to an image writing position of a scanner when a sheet feeding cassette or a sheet feeding tray for storing sheets is mounted on the main body of the image forming apparatus. There is a configuration in which a user or a service person can adjust the position by moving a sheet cassette or a sheet tray in accordance with an environment in which the user or service person uses the apparatus.

Next, such a conventional image forming position correcting operation will be described.

[0005] For example, as shown in FIG.
0, the sheet cassettes 100a, 100b are drawn out, and sheets (not shown) are set in the sheet cassettes 100a, 100b.
Is returned to the image forming apparatus 100, and is fixed by a horizontal registration adjusting unit 60 which is an image forming position correcting apparatus shown in FIG.

Here, the lateral registration adjustment unit 60 is
As shown in the drawing, a paper feed cassette 100a, 1 is provided by a cassette determining plate 63 slidably provided in a direction indicated by an arrow on a stay 62 fixed to an inner plate 61 of the image forming apparatus main body.
00b is fixed. The cassette determining plate 63 includes a click lever 64 that can rotate around a rotation center 63a, and a U-shaped portion 63b.

The paper feed cassettes 100a and 100b
Is returned to the image forming apparatus 100.
a, 100b is provided with a spring 68
The click lever 64 urged in the Q direction is rotated in the direction opposite to the Q direction, enters the groove 63d of the U-shaped portion 63b, and is returned by the spring 68. The paper cassettes 100a and 100b are locked.

Next, the paper feed cassette 100a,
If it is necessary to perform adjustment (correction) in a direction perpendicular to the sheet conveyance direction after fixing the sheet 100b, the adjustment screw 67 is loosened, and the cassette determining plate 63 is moved in the direction of the arrow. Make adjustments. This adjustment is performed for each sheet cassette.

However, in such a conventional image forming apparatus, since the image writing position of the scanner is constant, if the paper feeding cassettes 100a and 100b are moved to adjust the writing position of the recording paper, the image forming Paper feed cassettes 100a and 100
The appearance deteriorates due to the shift of the position of b.

Further, since there is a tolerance in the size of the sheet itself, the user can place the sheet in the sheet feeding cassettes 100a and 100a.
b, there is a gap between the side regulating plate (not shown) and the sheet.
Even if 00a and 100b are fixed, the recording paper may be shifted from the image writing position. Further, the image forming apparatus 1
The position of the seat may be shifted even when the setting location of the sheet No. 00 is inclined.

When the sheet is displaced from the image writing position, an image is not formed at a desired position on the sheet. In other words, the image is displaced and the image forming performance is reduced. . Also, when performing double-sided copying, the transport distance becomes longer,
Image forming performance tends to deteriorate compared to single-sided copying.

Therefore, conventionally, a side edge detecting device for detecting the side edge of the conveyed sheet before arriving at the image forming section is provided, and the image forming position of the sheet is detected based on a detection signal from the side edge detecting device. There are things that you try to control.

[0013]

However, in a conventional image forming apparatus provided with such a side edge detecting device,
Since the side edge of the sheet is detected while the sheet is moving, the accuracy of the side edge detection is reduced due to the movement of the sheet itself, deformation of the sheet when a sensor provided in the side edge detection device touches the sheet, and the like. Sometimes.

Furthermore, when the sensor of the side edge detecting device touches the sheet for side edge detection, the sensor is worn by contact with the sheet, and the abrasion of the sensor may lower the side edge detection accuracy. Then, the image is shifted due to the decrease in the side edge detection accuracy.

Accordingly, the present invention has been made in view of such a situation, and has as its object to provide an image forming apparatus capable of forming a good image without deviation.

[0016]

According to the present invention, there is provided an image forming apparatus comprising a sheet storing means for storing a sheet, and an image forming section for forming an image on the sheet, wherein the sheet is stored in the sheet storing means. A skew correction means provided in a conveyance path for conveying to the forming unit, and configured to correct the skew of the sheet by curving the sheet; and provided upstream of the skew correction means, A side edge detecting means for detecting a side edge in a direction perpendicular to the conveying direction, and an image formed on the sheet based on a detection signal from the side edge detecting means while controlling a side edge detecting operation of the side edge detecting means. And control means for controlling the position of the side edge detecting means so as to perform the side edge detecting operation when the sheet is curved by the skew feeding correcting means. Also It is.

Further, the invention is characterized in that the side end detecting means detects the side end when the sheet stops in a curved state.

Further, the present invention is characterized in that a plurality of the sheet storage means are provided, and the side end detecting means is arranged at a confluence of the conveying paths of the plurality of sheet storage means.

The present invention further comprises a re-feeding path for re-feeding the sheet having the image formed on one side thereof to the image forming section so as to form an image on the back side of the sheet having the image formed on one side thereof, The refeeding path is joined to the junction.

In the present invention, the skew of the sheet is corrected by curving the sheet by skew correcting means provided in a conveying path for conveying the sheet from the sheet storing means to the image forming section. A side edge in a direction orthogonal to the sheet conveying direction is detected by a side edge detection unit provided upstream of the unit. The control means controls the side edge detection operation of the side edge detection means and controls the position of the image formed on the sheet based on the detection signal from the side edge detection means,
When the sheet is curved by the skew feeding correcting unit, the side end detecting unit is controlled to perform the side end detecting operation.

[0021]

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

FIG. 1 is a diagram showing a configuration of a copying machine which is an example of an image forming apparatus according to an embodiment of the present invention.

In FIG. 1, reference numeral 50 denotes a copying machine, and 51 denotes a copying machine main body. A denotes an image forming unit that forms an image by an electrophotographic process. The image forming unit A is a photoconductor drum 112 and a laser that exposes the surface of the photoconductor drum 112 to form an electrostatic latent image on the photoconductor drum. Scanner 11
1, a developing device 114 for developing the latent image formed on the photosensitive drum is provided.

Reference numeral 1 denotes a paper feed cassette which is a sheet storage means for storing recording paper (not shown) which is a sheet. When the paper feed cassette 1 is set in the main body of the copying machine, it is not shown. The paper inside the cassette is raised by the lifter motor, so that the sheet can be fed.

Reference numeral 3 denotes a pickup roller for picking up the recording paper stored in the paper feed cassette 1; 4, 5 a separation roller pair for separating the recording paper picked up by the pickup roller 3 one by one;
Reference numeral denotes a pair of registration rollers which is skew correction means for correcting skew of the recording paper.

Reference numeral 118 denotes a fixing device; 120, a paper discharge tray; 121, a double-sided path which is a re-conveying path for re-conveying the recording paper having an image formed on one side to the image forming section A during double-sided copying. Reference numeral 207 denotes a flapper, which can guide the recording paper to the duplex path 121 by rotating the flapper 207 at the time of duplex copying. Reference numeral 131 denotes an image writing sensor for detecting a shift of the recording paper in the conveying direction.

Next, an image forming (copying) operation of the copying machine 50 having such a configuration will be described.

An original (not shown) is set on the original glass 202, and when a copy button is pressed, the exposure device 201 moves in the direction of arrow a while irradiating the original, and scans the entire original. Then, the light irradiated on the original from the exposure device 201 is turned back by the mirror 204 moving in the same direction,
An image is formed on the CCD 206 through the lens 205. After this,
The read document information is converted into an electric signal by the CCD 206 and transmitted to the laser scanner 111.

Then, the laser scanner 111 scans the photosensitive drum 112 with a laser beam corresponding to the document information by an optical system 113 shown in FIG. 7 described later, and forms an electrostatic latent image on the photosensitive drum 112. Thereafter, the electrostatic latent image is developed by the developing device 114, whereby a toner image is formed on the photosensitive drum 112.

On the other hand, the recording paper stored in the paper feed cassette 1 in parallel with the toner image forming operation is first picked up by the pickup roller 3 and then separated by the separation roller pairs 4 and 5 into one sheet. Rear transport roller 12
5, 126 are conveyed to the registration roller pair 106.

At this time, the registration roller pair 106
Are in a stopped state, and thus the transport rollers 125, 12
When the recording paper is conveyed by 6, the recording paper strikes the pair of registration rollers 106 to form a loop, whereby skew is corrected. After the skew is corrected in this manner, the registration roller pair 106 starts rotating at a timing when an image is formed at a predetermined position on the recording paper, whereby the recording paper is guided to the image forming unit A. Has become.

After the toner image is transferred from the transfer unit 115 to the recording paper guided to the image forming unit A, the recording paper is guided to the fixing unit 118 via the transport unit 117.
The toner image is fixed by heating and pressing in the fixing device 118, and the image formation is completed. In addition,
After the image is formed in this manner, the recording paper is stacked on the paper discharge tray 120 by the paper discharge roller 119.

On the other hand, in the case of double-sided copying, after the image is formed on one side in this way, the recording paper is discharged by the discharge rollers 11.
9, the leading end of the recording paper is temporarily discharged to the paper discharge tray 120, and the paper discharge roller 119 is eventually moved 10 to 20 m from the rear end of the recording paper.
By being reversed at a position sandwiching the position of about m, the sheet is conveyed in the opposite direction.

Here, by the time the recording paper is conveyed in the reverse direction, the flapper 207 has been rotated in the direction b with the rotation shaft 207a as a fulcrum. The recording paper is guided by the flapper 207 and conveyed in the direction E, and is conveyed again to the registration roller pair 106 through the double-sided path 121.

Then, the skew is corrected by the pair of registration rollers 106, and a double-sided copy is enabled. The flow of the recording paper thereafter is the same as in the case of single-sided copying. Note that the flow of recording paper for single-sided and double-sided copying described above is the same for the multi-tray 2 and the same for any of the paper feed trays 1.

Next, the operation of setting recording paper in the paper feed cassette 1 will be described.

The paper feed cassette 1 is fitted on a rail (not shown) provided on the copying machine main body 51. When the recording paper is set, as shown in FIG. After being pulled out from the copier main body 51, the user sets recording paper of an arbitrary size in the paper feed cassette 1.

Here, when setting the recording paper in this manner, first, the side regulating plates 401a and 401b shown in FIG.
Then, the rear end regulating plate 402 is moved in accordance with the size of the recording paper, and the positioning of the recording paper in the front and rear direction and the determination of the transport direction are performed. The side regulating plates 401a and 401b are formed by a rack and pinion (not shown).
When only a is moved, the rear side regulating plate 401b is moved in accordance with the amount of movement on the near side.

On the other hand, in the same figure, reference numeral 403 denotes a size detection cam which is rotated according to the size of the recording paper when the recording paper is set in the paper feed cassette 1; By doing so, when the paper feed cassette 1 is mounted on the copying machine main body 51, a detection unit (not shown) provided on the copying machine main body side can recognize the recording paper size based on the state of the size detection cam 403. It has become.

As described above, the user makes an adjustment so that the side regulating plates 401a and 401b and the rear end regulating plate 402 are aligned with the recording paper. At this time, the side regulating plates 401a and 401b are adjusted in consideration of the tolerance of the recording paper. The interval of 401b is set to be larger than the recording paper by about 1 to 2 mm. Here, in the case of such setting, a gap is generated between the side regulating plates 401a and 401b and the recording paper, and when the recording paper is conveyed to the image forming unit A in a state where the gap is generated, As described above, there is a possibility that the position of the recording paper at the transfer position is shifted in the front-rear direction of the recording paper.

The lateral registration deviation, which is the deviation of the recording paper in the front-rear direction, increases as the paper path increases, so that the recording paper from the lowermost paper feed cassette 1 or the recording paper to be double-sided copied is shifted. In this case, the shift amount of the lateral registration increases, and when the shift amount of the lateral registration increases, the image forming position shifts.

Therefore, in the present embodiment, a side edge detecting device which is a side edge detecting means for detecting an end portion in a direction orthogonal to the recording paper conveyance direction is provided, and the recording detected by the side edge detecting device is provided. The image forming position is controlled based on the side edge information of the paper.

Next, this side end detecting device will be described with reference to FIGS.

3 and 4, reference numerals 102 and 151 denote an upper guide and a lower guide which form a transport path R for transporting the recording paper from the paper feed cassette 1 to the image forming section A. A slide rail 101 having a U-shape is attached.
Is provided with a stepping motor 103.

A slide block 1 having a rack 104a formed inside the slide rail 101.
The slide block 104 is configured to be capable of reciprocating in the forward and rearward directions in FIG. 3 and the arrow f and h directions in FIG. 4 by the stepping motor 103 via the rack 104 a and the pinion 108. .

A side end detecting device 105 is attached to an end of the slide block 104. Here, the side end detection device 105 normally protrudes below the lower guide 151, and rotates with the rotation shaft 105a as a fulcrum. When the light is shielded by the rotation of the arm 105b, recording is performed. A photosensor 109 for outputting a detection signal indicating that a side edge of the paper has been detected.

Here, the detection signal of the side edge detecting device 105 is inputted to the control section 52 as control means as shown in FIG.
When the detection signal is input from the control unit 52, the control unit 52 calculates the amount of movement of the side edge detection device 105 from the value of the counter 53 that counts the number of steps of the stepping motor 103 at this time. The position of the direction is determined.

In this embodiment, the side end detecting device 105 is disposed downstream of the paper path merging portion 301 located upstream of the registration roller pair 106.
By arranging the side edge detecting device 105 at such a position, one side edge can be detected for any of the recording paper conveyed to the registration roller pair 106 through any of the sheet cassette 1, the multi-tray 2, and the double-sided path 121. The device 105 can detect the side edge.

That is, even if the recording paper is fed from any paper feeding port, one paper path is formed at the paper path merging section 301 in front of the registration roller.
, The side edge of the sheet can be detected.

Here, the side edge detecting device 105 is provided upstream of the pair of registration rollers 106. As described above, the pair of registration rollers 106 is for correcting the skew of the recording paper. In order to correct the skew of the recording sheet, the recording sheet itself is bent as shown in FIG. 3, that is, a loop is formed on the recording sheet S.

In the present embodiment, the side edge detecting device 105 detects the side edge position of the recording sheet S when the recording sheet S forms a loop as described above. In FIG. 5, reference numeral 153 denotes a registration sensor that detects that the recording paper has been conveyed to the registration roller pair 106.

Next, a description will be given of the timing of the creation of the loop and the detection of the recording paper side edge with reference to FIG.

To correct the skew of the recording sheet, the recording sheet is moved by the conveying roller 125 to the registration roller pair 1 as described above.
When the sheet is conveyed toward 06, the registration sensor 153 is first turned on, and based on a signal from the registration sensor 153, the control unit 52 thereafter further performs the first predetermined time t1 and the conveyance roller 1
The transport roller clutch CL for rotating the clutch 25 is turned on.

As a result, the recording paper is pressed against the registration roller pair 106 in the stopped state, and a loop is formed on the recording paper as shown in FIG. Further, a first predetermined time t
After 1 has elapsed, the transport roller clutch CL is turned off for the second predetermined time t2 to stop the transport roller 105.

On the other hand, when the registration sensor 153 is turned on,
The control unit 52 starts the rotation of the stepping motor 103. As a result, the slide block 104 moves, and eventually the arm 105b of the side edge detecting device 105 contacts and rotates with the end of the recording paper. When the photo interrupter 109 detects this, the detection signal is sent from the photo interrupter 109 to the control unit. 52 is input.

If necessary, the arm 105b can contact the end of the recording paper in a stopped state while a loop is formed.
03 (see FIG. 2), the side edge detection device 105 may be moved in advance by a predetermined amount.

Then, based on the detection signal from the side edge detecting device 105 (photo interrupter 109), the control unit 5
Reference numeral 2 controls the image forming unit A to form an image on a recording sheet. That is, the control unit 52 thus operates the side edge detection device 105
When the side edge position of the recording paper is detected, the image shift is prevented by adjusting the laser writing position of the scanner 111 (see FIG. 1) according to the side edge position.
Note that the image shift in the transport direction is determined by the image writing sensor 131.
(See FIG. 1) detects the recording paper and controls so as to start writing the image, so that the image is hardly shifted from the recording paper.

FIG. 7 is a view of the scanner 111 as viewed from above, and the optical path is shown in a plane for convenience. In the same figure, reference numeral 701 denotes a scanner frame, on which a scanner unit 702 having a light source 703 is fixed.

The direction of the beam emitted from the light source 703 can be changed by the deflector 704 and at the same time, f-θ
After being corrected by the lens 705, the folding mirror 70
6 through the optical path opening 707 of the scanner unit 702 and the scanner frame 701 through the photosensitive drum 112
Image on top. At this time, the image forming position in the front and rear direction of the photosensitive drum 112 is controlled by the time from when the beam detector 708 detects the beam.

For this reason, the control section 52 controls the side end detecting device 10
5 based on the detection signal from the beam detector 70.
The imaging position on the photosensitive drum can be changed by shifting the time from when the beam is detected by 8. In addition,
In the figure, the beam indicated by the solid line indicates the ideal state, and the beam indicated by the dashed line indicates the state after the adjustment. Also, in the same figure, the beam adjustment amount is plus or minus 5 mm, which indicates that the beam can be adjusted to the positions indicated by arrows 0 to 2. This makes it possible to always obtain a good image with no lateral registration deviation even if the recording paper is displaced in the front-rear direction.

When the edge of the recording paper is detected, the stepping motor 103 rotates in the reverse direction as shown in FIG. Thereafter, the recording paper is conveyed to the image forming section A by simultaneously turning on the conveyance roller clutch CL and the registration roller motor M1. This operation is repeated at the time of continuous paper feeding and at the time of double-sided copying.

As described above, the edge of the recording paper is detected by the side edge detecting device 105, and the laser scanner 11 is detected based on the information.
By adjusting the writing position of No. 1, it is possible to make the writing of the image constant from the end of the recording paper, so that a copy image with high printing accuracy can be obtained.

Thus, even if the horizontal registration adjustment unit 60 shown in FIG. 10 is eliminated, an image with higher printing accuracy can be obtained. In addition, since the lateral registration adjustment is eliminated, the trouble of the adjustment can be saved, and at the time of performing the lateral registration adjustment, it is possible to prevent the appearance of the paper cassette from being deteriorated due to a step difference.

In the normal case, when the recording paper is aligned by the registration roller pair 106, a loop is formed on the recording paper itself, and the conveyance of the recording paper is temporarily stopped slightly to stabilize the loop. I have. And
At this time, since the rigidity of the recording paper itself is increased, the recording paper is not deformed even if the arm 105b contacts the end of the recording paper, and the position of the recording paper is detected with very high accuracy. It becomes possible.

FIG. 8 shows the arm 105 of the side end detecting device 105.
FIG. 7B is a diagram showing the deformation of the recording paper S when b contacts the recording paper S. Since the rigidity of the recording paper itself is improved in a state where a loop is formed as described above, the arm 105b is brought into contact with the recording paper S. In this case, as shown in (a), the one having a loop has improved rigidity in the direction of the arrow, so that the recording paper itself does not bend and the accuracy of position detection is improved. In addition,
(B) is a perspective view showing a case where there is no loop of the recording sheet S. When the arm 105b touches the recording sheet S, the recording sheet S is deformed due to low rigidity of the recording sheet S, and the position detection accuracy is reduced. I do.

As described above, when the side edge detection is performed while the conveyance of the recording sheet is stopped, since the recording sheet is stopped, the recording sheet is stopped by the arm 105b of the side edge detection device 105.
No longer damages you. Therefore, there is no need to worry about the shaving of the arm 105b,
5b can be formed of an inexpensive and lightweight resin material or the like. Note that, in the present embodiment, the arm 105b is formed of a polyacecool resin.

[0067]

As described above, according to the present invention, it is possible to detect the side edge of a sheet with high accuracy by detecting the side edge of the sheet when correcting the skew by curving the sheet. As a result, a good image having no displacement can be formed on the sheet.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a copying machine as an example of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view of a sheet cassette of the copying machine.

FIG. 3 is an enlarged side view of a main part of the copying machine.

FIG. 4 is a view in the direction of arrow G in FIG. 3;

FIG. 5 is a control block diagram of the copying machine.

FIG. 6 is a timing chart for explaining the timing of creating a loop of the copying machine and detecting a recording paper side edge.

FIG. 7 is a top view of the scanner of the copying machine.

FIG. 8 is a view for explaining deformation of the recording paper when the side edge detection device 105 comes into contact with the recording paper.

FIG. 9 is a perspective view illustrating a state in which a sheet cassette is pulled out from a conventional image forming apparatus.

FIG. 10 is a top view of a horizontal registration adjustment unit of a conventional image forming apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 paper feed cassette 50 copier 52 control unit 103 stepping motor 105 side edge detection device 106 registration roller pair 111 scanner 112 photosensitive drum 131 image writing sensor A image forming unit R transport path S recording paper

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/04 F term (Reference) 2H027 DC04 DE07 DE10 ED04 ED06 EF09 FA11 ZA07 2H028 BB06 2H076 AB05 AB12 AB67 3F100 AA02 BA17 CA13 CA15 EA03 EA05 3F102 AA02 AB01 BA02 BB02 CA04 DA08 EA03 EC03 FA08

Claims (4)

[Claims] 1. An image forming apparatus comprising: a sheet storage unit for storing a sheet; and an image forming unit for forming an image on the sheet, wherein the sheet is conveyed from the sheet storage unit to an image forming unit. Skew correction means provided to correct the skew of the sheet by curving the sheet; and a skew correction means provided upstream of the skew correction means and in a direction orthogonal to the sheet conveyance direction. A side edge detection unit for detecting an edge, a control unit for controlling a side edge detection operation of the side edge detection unit, and controlling a position of an image formed on the sheet based on a detection signal from the side edge detection unit. The image forming apparatus according to claim 1, wherein the control unit controls the side edge detection unit to perform the side edge detection operation when the sheet is curved by the skew feeding correction unit. 2. The image forming apparatus according to claim 1, wherein the side edge detection unit detects a side edge when the sheet stops in a curved state. 3. An image forming apparatus according to claim 1, wherein a plurality of said sheet storage means are provided, and said side end detecting means is arranged at a confluence of a conveyance path of said plurality of sheet storage means. 4. A re-feeding path for re-feeding a sheet having an image formed on one side thereof to the image forming section so as to form an image on the back side of the sheet having an image formed on one side thereof, 4. The image forming apparatus according to claim 3, wherein a paper path is merged with the merging section.