JPH11268843A - Sheet conveying device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the conveyance accuracy and quality property of a sheet by making the angle between the conveying direction by a first conveying means and the conveying direction by a second conveying means adjustable. SOLUTION: Reflection type sensors (detecting means detecting the deviation of the heights (h) of loops) 110f, 110r are installed at two positions on this side and on the depth side in the width direction of a transfer material in a paper conveyance path between registration rollers 101, 102 and a transfer belt 74 to measure the heights (h) of the loops formed between the registration rollers 101, 102 and the transfer belt 71. The information of the loop height detecting means 110f, 110r is transmitted to a stepping motor 10M via a microprocessor MP as movement revolving speed information, and the bus line positions of the registration rollers 101, 102 are moved by the prescribed quantities in the direction to make the heights of the loops equal. The conveying direction by the registration rollers 101, 102 is made equal to the conveying direction by the transfer belt 71 by an adjustment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying apparatus for conveying a sheet, which is applied to, for example, an image forming apparatus such as a copying machine or a printer. This is effective for a color image forming apparatus in which a plurality of colors are overlapped while being held and conveyed by a shape transfer material holding means.

[0002]

2. Description of the Related Art Conventionally, as this type of image forming apparatus, for example, there are a copying machine and a printer.

Referring to FIG. 7, a schematic configuration of the image forming apparatus will be described. FIG. 7 is a schematic configuration diagram of an image forming apparatus (full color image forming apparatus).

The transfer material (sheet) P supplied by the transfer material supply means 8 from the cassette 14
After the skew is removed, the transfer material transport belt 7 is sent out at a proper timing at the nip position of the nipping roller 11.
1 (hereinafter referred to as a transfer belt), and the first image forming portion Na
A yellow image is formed and transferred.

At the same time, the transfer material P is transferred to the transfer belt 71.
After the image is formed and transferred in the second image forming section Nb (magenta), the third image forming section Nc (cyan), and the fourth image forming section Nd (black) in the same manner, The image is fixed by the fixing device 12 to obtain a full-color image, and is discharged onto the tray 16 by the discharge roller 13.

Next, the detailed configuration of the conventional registration roller pair 10 and the transfer belt device 7 and the positioning means will be described with reference to FIG. FIG. 8 is a schematic perspective view of a main part of an image forming apparatus according to the related art.

The registration drive roller 101 is supported by a bearing 103 fitted and positioned on the front and rear side plates Hf, Hr of the main body, and the registration driven roller 102 is movable in the up-down direction and is positioned only in the left-right direction.
4 and is supported by a tension spring 10S.
The nip between the registration driving roller 101 and the registration driven roller 102 is obtained as a registration roller pair, and the registration driving roller 10
1 is driven, the drive is transmitted to the driven roller 102 by the gears 101G and 102G, and the transfer material is transported in the direction of the arrow.

The transfer belt device 7 has a configuration in which a user or a serviceman can pull out the front side of the image forming apparatus main body with the handle 76 by using the rail 7R to perform a work of replacing the transfer belt 71 with a paper jam (jam). Has become.

The transfer belt 71 is suspended by a belt driving roller 72 supported by a transfer belt frame 7W and other driven rollers 73, 74, 75.

[0010] The belt drive roller 72 is a transfer belt device 7
Is inserted into the main body, the coupling C attached to the shaft of the motor M whose center is positioned on the rear side plate of the main body.
, The drive roller shaft is fitted, the coupling 7C is engaged, the drive is transmitted, and the transfer belt 71 is rotated in the direction of the arrow.

Here, the transfer belt device 7 is positioned on the main body as follows.

A pin Ph provided on the front side plate of the main body is inserted into a fitting hole 78l and an oblong hole 78r provided in the transfer belt frame 7W, and a front depth direction (Y direction) of the transfer device is a transfer frame front side plate. Positioning is performed by contacting the back surface of the front plate 77f with the front surface of the front plate Hf.

Further, as described above, the X and Y directions on the back side of the transfer belt frame 7W are positioned with respect to the image forming apparatus main body by fitting the belt driving roller shaft into the main body side coupling C as described above.

[0014]

However, in the case of the above-described prior art, the following problems have occurred. Hereinafter, problems of the image forming apparatus according to the related art will be described with reference to FIGS.

FIG. 9 shows the registration drive roller 101, the four image carriers 1a, 1b, 1c and 1d, the transfer belt 71, the transfer belt drive roller 72, the driven roller 75, and the sandwiching roller 11 with respect to the front and rear side plates Hf and Hr of the main body. FIG. 3 is a top view showing an installed state.

First, in the above-described conventional positioning method of the registration drive roller 101 and the transfer belt drive roller 72, there are many components interposed between the two and between the support members on the front side and the back side of each. The displacement of the generatrix between the pair and the transfer belt driving roller 72 becomes large,
As a result, the following problems occurred (see FIG. 10).

When the transfer material P is sandwiched between the registration rollers, a force of the component in the Y-axis direction in the figure is applied to the transfer belt 71 through the transfer material P due to the restraining force of the registration roller on the transfer material P. After the transfer material P changes its traveling direction, and then the transfer material P comes off the registration roller, it is conveyed in the traveling direction depending only on the transfer belt driving roller 72.

As a result, while the transfer material P is held between the registration rollers (see FIGS. 10A and 10D), the colors being transferred sequentially have different transfer positions with respect to the paper, and the color shift in the main scanning direction (Y-axis direction). And the case where the transfer material P is sandwiched between the registration rollers and the case where it is not (FIGS. C and d).
), The image is bent in the Y-axis direction.

The holding force of the registration roller and the transfer material holding force of the transfer belt by the holding roller or the electrostatic attraction squeeze through the transfer material P, and the size is one immediately before the rear end of the transfer material passes through the registration roller. The shock that releases the distortion of the transfer material P caused by both forces at the moment of the release is transmitted to the transfer portion through the transfer material P and causes an image defect (see FIGS. 10B and 10D). .

When the binding force of the registration roller is applied to the transfer belt, the transfer belt is pressed in a biased direction, and the transfer belt is biased against a deviation regulating rib 71r (see FIG. 11) on the back side of the belt end that regulates deviation of the belt with respect to the driving roller. Unnecessary stress in the axial direction has been applied, causing a problem that the durability of the ribs and, consequently, the transfer belt is deteriorated.

Even if the parallelism of the generatrix between the registration roller and the transfer belt driving roller is correctly arranged, the following problem occurs. Hereinafter, as shown in the prior art (FIG. 8) particularly described with reference to FIG. 12, the pair of registration rollers obtains the roller conveyance force by springs hooked at two places in front of the bearings of the driving roller and the driven roller. The difference between the spring pressure (variation occurring during manufacturing) and the change over time, for example, the difference in the outer diameter shaving amount between the front side and the back side of the driving roller made of rubber material, etc. Transfer material transfer speed is different.

Normally, this difference in transport speed is caused by forming and absorbing a loop PI in the transfer material between the registration roller and the transfer belt by setting the speed relationship Vr, Vb between the registration roller and the transfer belt so that Vr> Vb. See FIG. 12).

Here, the size of this loop (the amount obtained by subtracting the shortest distance from the registration roller to the holding roller from the length of the transfer material in the transport direction between the registration roller and the holding roller) λ is the registration roller speed Vr. , The transfer belt speed Vb, and the time t from the time when the leading end of the transfer material reaches the nipping roller, and the magnitude thereof is λ = (Vr−Vb
) Xt (1).

The maximum value is further determined by the length L of the transfer material.
And determined by the registration roller-holding rollers distance l ₁ its value _{λ max = {(Vr -Vb)} / Vr} X (L-
l ₁ ) (2).

However, in the case of a transfer material having a strong stiffness, a loop is hardly formed, and in the case of forming a loop, a reaction force acts to return the transfer material to a flat state. Until it gets bigger.

[0026] Thus the loop amount λ increases as the time goes by as shown in Equation (1) described above, also the registration roller front speed Vr _f, it will become larger as time also the back-side velocity Vr _r went Accordingly, the difference between the forces for returning the transfer material to the front side and the back side to be flat also increases.

As a result, the above-mentioned problems have been caused.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and it is an object of the present invention to improve the sheet conveyance accuracy and improve the quality of a sheet conveyance apparatus and an image forming apparatus. Is to provide.

[0029]

In order to achieve the above object, according to the present invention, a first conveying means for conveying a sheet while sandwiching the sheet, and a sheet conveyed by the first conveying means are further provided. A sheet conveying device having a second conveying means for conveying downstream, wherein an angle between a conveying direction by the first conveying means and a conveying direction by the second conveying means can be adjusted. Features.

Therefore, the sheet can be conveyed by adjusting the conveying direction by each conveying means.

The first conveying means comprises a pair of conveying rollers. One end of the conveying roller is provided so as to be movable in a substantially sheet conveying direction, and the conveying roller is rotated about the other end to form a first conveying means. It is preferable to adjust the angle between the transport direction by the first transport unit and the transport direction by the second transport unit.

By setting the sheet conveying speed of the first conveying means higher than the sheet conveying speed of the second conveying means, the sheet is conveyed while forming a loop, and the deviation of the height of the loop in the sheet width direction. Detecting means for detecting the difference between the transport direction of the first transport means and the transport direction of the second transport means so as to correct the deviation of the height of the loop based on the detection result by the detection means. It is advisable to adjust the angle formed.

Therefore, the deviation of the loop height in the sheet width direction indicates the deviation of the conveying direction by each conveying means, and the conveying direction can be adjusted based on the deviation.

Further, there is provided a detecting means for detecting a deviation of the arrival time of the leading end of the sheet in the sheet width direction of the sheet conveyed to the predetermined position by the first conveying means, and based on a detection result by the detecting means, The angle between the transport direction by the first transport unit and the transport direction by the second transport unit can be adjusted so as to correct the time lag.

Therefore, the shift in the transport direction by each transport means can be determined by the shift in the arrival time of the sheet leading end in the sheet width direction, and the transport direction can be adjusted based on this.

Further, a detecting means for detecting a deviation of the sheet conveying speed by the first conveying means in the sheet width direction is provided, and the deviation of the sheet conveying speed is corrected based on the detection result by the detecting means. It is also possible to adjust the angle between the transport direction of the first transport unit and the transport direction of the second transport unit.

Therefore, the shift in the sheet conveying speed by the first conveying means in the sheet width direction indicates the shift in the conveying direction by each conveying means, and the conveying direction can be adjusted based on this.

The second conveying means has a belt-like or drum-like holding member, and preferably conveys the sheet while attracting the sheet to the holding member by electrostatic attraction.

According to another aspect of the present invention, there is provided an image forming apparatus including an image forming means for forming an image on a sheet conveyed by the sheet conveying apparatus. .

It is preferable that the image forming means has a plurality of image forming sections, and a color image is formed by sequentially superimposing a plurality of colors by each image forming section.

[0041]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The material, shape, relative arrangement, and the like are not intended to limit the scope of the present invention only to them unless otherwise specified.

In the following embodiment, the basic configuration such as the overall configuration of the image forming apparatus is the same as the configuration described with reference to FIG. 7 in the above description of the prior art. Therefore, the description is omitted.

(First Embodiment) A sheet conveying apparatus and an image forming apparatus according to a first embodiment of the present invention will be described with reference to FIGS.

Hereinafter, the features of the present embodiment, that is, the loop height detecting means, the registration roller including the registration roller position moving means, and the periphery of the transfer belt will be described in detail.

FIG. 1 is a schematic perspective view of a main part of an image forming apparatus according to the first embodiment of the present invention, and FIG. 2 is a perspective view of the main part of the image forming apparatus according to the first embodiment of the present invention. It is explanatory drawing (explanatory drawing seen from the side surface side) of a part.

The configuration for controlling the position of the registration roller will be described below.

The registration driving roller 101 and the registration driven roller 102 constituting the first conveying means are mutually pressed by a spring (not shown), and the front side in the Y-axis direction in FIG. Have been.

The movable side plate 105 has a notch 10
5a is installed so as to be movable only in the X-axis direction in the figure with respect to the main body front side plate (not shown).

A rack gear 10 is provided below the movable side plate 105.
A stepping motor 10M that enables the movable side plate 105 to move in the X-axis direction in the drawing together with the rack gear 108 is provided, and a pinion gear 109 that engages with the rack gear 108 is provided on the axis of the stepping motor 10M. .

Next, the loop height detecting means in the registration roller position control means will be described.

As described above, normally, the transfer material conveyance speed v _r by the transfer rollers 71 and the transfer material transfer speed v _b by the transfer belt 71 constituting the second transfer means. v
set to be _r> v _b, as a transfer material in the transfer is not pulled between the registration roller and the transfer belt, also, the front of the registration roller, subtle caused by clamping force and outer diameter difference on the back side A speed difference between the front side and the back side is absorbed by forming a loop.

In this embodiment, the reflection type sensors (detection means for detecting a deviation in the height of the loop) 110f and 11 are provided during the paper conveyance path between the registration roller and the transfer belt.
As shown in FIG. 1, Or is set at two positions on the front side and the back side in the width direction of the transfer material, and the height of a loop formed between the registration roller and the transfer belt is measured (see FIG. 2).

Here, the two reflective sensors 110
f and 110r are directly installed on the transfer belt frame 77f that supports a transfer belt driving roller (not shown), so that the accuracy of the sensor position with respect to the transfer belt driving roller is increased. As a result, the registration roller in this embodiment is used. The position control accuracy of the position movement control means can be improved.

Then, the information of the loop height detecting means is transmitted to a stepping motor via a microprocessor, and the rotation speed information is transmitted to the stepping motor to shift the generatrix position of the registration roller by a predetermined amount in the direction in which the loop heights become equal (FIG. 3).

Therefore, the conveyance direction by the registration roller and the conveyance direction by the transfer belt 71 are adjusted to be equal.

Next, a control method from the detection of the loop height to the change of the registration roller generatrix position in this embodiment will be described with reference to FIG. FIG. 4 is a flowchart illustrating a control method of the sheet conveying apparatus according to the first embodiment of the present invention.

First, a transfer material is fed by a copy start (S1) and a registration roller (register driving roller 10) is fed.
1 and the registration driven roller 102), the skew of the transfer material is removed, the registration roller clutch is turned on at a proper timing (S2), and the transfer material is sent out.

When the leading end of the transfer material reaches the nipping roller 11 (S3), monitoring (measurement) of the loop height is started at that timing (S4).

[0059] Then, the loop height h _f, the difference α and the predetermined value .alpha.0 (loop height of the back before the transfer material to a predetermined value .alpha.0 of h _r the front of the transfer material width direction, the sensors of the rear side two places detected Difference is not negligible for color shift or image stretch,
(For example, a value set to about 2 to 5 mm) (S5), and when α becomes equal to or more than α0 (α ≧ α0) (S6), a direction in which the difference in the loop height is canceled. 10M to move the registration roller bus
To a predetermined value θ (the predetermined value θ is, for example, 0.5 to 1
(rotation angle of the motor required to move about mm) (S8).

When α is smaller than α0 (α <α0), it is determined whether or not the rear end of the transfer material has passed through the registration roller pair (S7). And the above-described control is repeated until the rear end of the transfer material passes through the registration roller pair.

By performing the above control, the transfer direction of the transfer material (sheet) by the registration roller and the transfer direction of the transfer material by the transfer belt become equal, and a uniform loop is formed in the width direction of the transfer material. While the paper is being conveyed, the image is bent due to the difference in the reaction force due to the loop on the front side and the back side of the transfer material.
Shock when the trailing edge of the transfer material comes out of the registration roller,
Further, it is possible to prevent the transfer belt from being damaged due to skew of the transfer material with respect to the transfer belt.

The above-described position control of the registration roller bus may be performed for each copy, or may be performed every time the number of copies reaches a predetermined value (for example, about 1000).

The loop height detecting sensor 110f,
When the front end and the back end of the transfer material P are detected at 110r by 110r, the generatrix deviation between the pair of registration rollers 101 and 102 unique to each image forming apparatus main body and the transfer belt driving roller (not shown) is corrected. The generatrix of the registration roller pair may be moved by an amount.

That is, the sensors 110f and 110r detect the shift in the arrival time of the leading end of the transfer material P at the front side and the back side of the transfer material P, and move the registration roller pair so as to eliminate the shift and convey. This is to eliminate the deviation in the direction.

By doing so, it is possible to correct the bus position of the registration roller before the leading end of the transfer material reaches the first photosensitive drum 1a (earlier), and the front-back difference of the leading end position of the image with respect to the transfer material is eliminated. Thus, a higher quality image can be formed.

(Second Embodiment) FIGS. 5 and 6 show a second embodiment of the present invention. In the first embodiment, the configuration in which the sheet conveyance direction is adjusted based on the deviation of the height of the loop in the width direction of the sheet (transfer material) has been described. In the present embodiment, however, the width of the sheet (transfer material) is adjusted. A configuration is shown in which the conveying direction of the sheet is adjusted based on the deviation of the conveying speed in the direction.

Since other structures and operations are the same as those of the first embodiment, the same components are denoted by the same reference numerals and description thereof will be omitted.

In this embodiment, the function of the sensor used between the registration roller and the transfer belt and the method of controlling the position of the registration roller are different from those in the first embodiment. It will be described with reference to FIG.

FIG. 5 is a schematic perspective view of a main part of an image forming apparatus according to a second embodiment of the present invention, and FIG. 6 is a control of a sheet conveying apparatus according to the second embodiment of the present invention. 5 is a flowchart illustrating a method.

In the above-described first embodiment, the deviation of the loop height is detected by the reflection type sensors 110f and 110r during the paper conveyance path between the registration roller and the transfer belt. In the embodiment, the transfer material P
Is measured as the conveying speed at each position, and functions as detecting means for detecting a shift in the conveying speed in the width direction.

That is, in the present embodiment, the speed between two front-rear sides of the transfer material P being conveyed by the registration rollers is measured by a sensor using the principle of laser Doppler between the registration rollers and the transfer belt. The transfer speed deviation in the width direction of the transfer material is transmitted to a stepping motor via a microprocessor (MP) to move the registration roller mother ship position.

Next, a control method according to the present embodiment from the detection of the deviation of the conveying speed in the width direction of the transfer material to the change of the registration roller generatrix position will be described with reference to FIG. FIG. 6 is a flowchart illustrating a control method of the sheet conveying apparatus according to the second embodiment of the present invention.

First, the transfer material is fed by copy start (S11), the skew of the transfer material is removed by hitting the registration roller, and the registration roller clutch is turned on at a proper timing (S12) to transfer the transfer material. .

When the leading end of the transfer material reaches the nipping roller (S
13), measurement of the paper transport speed is started at that timing (S14).

[0075] Then, the front side in the transfer material width direction, the conveying speed Vh _f the sensor on the rear side two places has detected, by comparing with a predetermined value β0 difference V _r β (S15), β is β0 more (beta ≧ β
0) (S16), the motor 10M is rotated by a predetermined value θ in order to move the generatrix of the registration roller in a direction to cancel the speed difference (S18).

If β is smaller than β0 (β <β0), it is determined whether or not the rear end of the transfer material has passed through the registration roller pair (S17).
Returning to S14, the above control is repeated until the rear end of the transfer material passes through the registration roller pair.

As described above, by monitoring the speed instead of the loop height, the speed difference between the front and back of the registration roller and, consequently, the transfer material is moved to the front and back of the transfer belt before the difference in the loop height appears. Since the difference in the applied force can be known, the registration roller bus can be moved more agilely, and a higher quality image can be obtained.

[0078]

As described above, the sheet conveying apparatus of the present invention can adjust the angle between the conveying direction by the first conveying unit and the conveying direction by the second conveying unit. , The sheet can be conveyed by adjusting the conveying direction, thereby improving the sheet conveying accuracy and the quality.

The first conveying means comprises a pair of conveying rollers. One end of the conveying roller is provided so as to be movable in a substantially sheet conveying direction, and the conveying roller is rotated about the other end to rotate the conveying roller. The angle between the transport direction by the first transport unit and the transport direction by the second transport unit can be adjusted.

The angle is adjusted so as to correct the deviation of the height of the loop based on the detection result of the detection means for detecting the deviation of the height of the loop in the sheet width direction. The deviation in the transport direction can be adjusted.

The deviation of the arrival time of the sheet conveyed to the predetermined position by the first conveying means is corrected based on the detection result of the detection means for detecting the deviation of the arrival time of the leading end of the sheet in the sheet width direction. As described above, if the angle is adjusted, it is possible to adjust the shift in the transport direction by each transport unit more quickly.

Further, based on the detection result of the detecting means for detecting the deviation of the sheet conveying speed by the first conveying means in the sheet width direction, the angle may be adjusted so as to correct the deviation of the sheet conveying speed. In addition, it is possible to more quickly adjust the shift in the transport direction by each transport unit.

Further, by applying the above-described sheet conveying device having excellent conveying accuracy to the image forming apparatus of the present invention, it is possible to form a high-quality image without image bending.

Even when the image forming means has a plurality of image forming sections and a plurality of colors are sequentially superimposed by each image forming section to form a color image, a high quality image without color shift can be obtained. Image can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration perspective view of a main part of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a main part of the image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is an operation explanatory diagram of the sheet conveying device according to the first embodiment of the present invention.

FIG. 4 is a flowchart illustrating a control method of the sheet conveying apparatus according to the first embodiment of the present invention.

FIG. 5 is a schematic configuration perspective view of a main part of an image forming apparatus according to a second embodiment of the present invention.

FIG. 6 is a flowchart illustrating a control method of a sheet conveying apparatus according to a second embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of an image forming apparatus (full color image forming apparatus).

FIG. 8 is a schematic configuration perspective view of a main part of an image forming apparatus according to the related art.

FIG. 9 is an explanatory diagram illustrating a problem of the image forming apparatus according to the related art.

FIG. 10 is an explanatory diagram illustrating a problem of the image forming apparatus according to the related art.

FIG. 11 is an explanatory diagram illustrating a problem of the image forming apparatus according to the related art.

FIG. 12 is an explanatory diagram illustrating a problem of the image forming apparatus according to the related art.

[Description of Signs] 10M Motor 11 Nipping Roller 71 Transfer Belt 110f, 110r Sensor 101 Registration Driving Roller 102 Registration Follower Roller 105 Movable Side Plate

Claims (8)

[Claims] 1. A sheet conveying device comprising: first conveying means for conveying a sheet while nipping the sheet; and second conveying means for conveying a sheet conveyed by the first conveying means further downstream. 2. The sheet conveying apparatus according to claim 1, wherein an angle between a conveying direction by the first conveying unit and a conveying direction by the second conveying unit is adjustable. 2. The first conveying means comprises a pair of conveying rollers, one end of which is provided so as to be movable in a substantially sheet conveying direction, and the conveying roller is rotated about the other end. 2. The sheet conveying apparatus according to claim 1, wherein an angle between a conveying direction by the first conveying unit and a conveying direction by the second conveying unit is adjusted. 3. The sheet is conveyed while forming a loop by setting the sheet conveying speed of the first conveying means higher than the sheet conveying speed of the second conveying means, and the height of the loop in the sheet width direction is set. Detecting means for detecting the shift of the loop, based on the detection result of the detecting means, so as to correct the shift in the height of the loop, so that the transfer direction by the first transfer means and the transfer direction by the second transfer means. The sheet conveying device according to claim 1, wherein an angle between the sheet conveying device and the sheet conveying device is adjusted. 4. A detecting means for detecting a shift in the arrival time of a sheet leading end in a sheet width direction of a sheet conveyed to a predetermined position by a first conveying means, and based on a detection result by the detecting means, 3. The sheet conveying apparatus according to claim 1, wherein an angle between a conveying direction by the first conveying unit and a conveying direction by the second conveying unit is adjusted so as to correct a time lag. 5. A detecting means for detecting a deviation of the sheet conveying speed by the first conveying means in a sheet width direction, wherein the deviation of the sheet conveying speed is corrected based on a detection result by the detecting means. 3. The sheet conveying apparatus according to claim 1, wherein an angle between a conveying direction by the first conveying unit and a conveying direction by the second conveying unit is adjusted. 6. The apparatus according to claim 1, wherein said second conveying means has a belt-shaped or drum-shaped holding member, and conveys the sheet while attracting the sheet to said holding member by electrostatic attraction. 6. The sheet conveying apparatus according to claim 3, 3, 4, or 5. 7. An image forming apparatus comprising an image forming means for forming an image on a sheet conveyed by the sheet conveying apparatus according to claim 1. 8. The image forming apparatus according to claim 7, wherein said image forming means has a plurality of image forming units, and forms a color image by sequentially superimposing a plurality of colors by each image forming unit. apparatus.