JP2002055541A - Sheet feeding device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet feeding device and an image forming device by which the image of an excellent quality is formed by preventing image slippage from being caused by eliminating the occurrence of a change in speed in a feeding process. SOLUTION: The sheet feeding device by which a sheet material S is fed by arranging plural feeding members in a feeding path is provided with a first feeding member 6E positioned at the last end side of the feeding path and to hold and feed the sheet material S and a second feeding member 8 which is arranged on the upstream side of the sheet material S in a feeding direction than the first feeding member 6E and by which the feeding timing of the sheet material S to the first feeding member 6E is set and the sheet material S is held and fed, and the holding pressure of the sheet material S is made changeable in the first feeding member 6E.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a sheet conveying apparatus and an image forming apparatus, and more particularly, to a structure for stabilizing a sheet conveying speed.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, or a facsimile machine, a visible image such as a toner image carried on the surface of a photoconductor as a latent image carrier is transferred onto a sheet such as a recording paper. After the sheet is heated and fixed by the fixing device, the sheet is discharged. The sheets are accommodated in a cassette or the like provided in a sheet feeding device provided as a conveying device, and are separated and fed out one by one from the cassette. The image forming apparatus may form a multicolor image such as a full color image in addition to a case where a single color image is formed.

FIG. 1 is a schematic diagram showing one configuration used in a full-color copying machine. In FIG. 1, a full-color copying machine 1 has a single drum-shaped photoconductor (hereinafter referred to as a photoconductor drum) 2. And the photosensitive drum 2 rotates in the direction of the arrow shown in the figure. Around the photosensitive drum 2, a charging device 3, a writing device (a writing optical path is shown in the drawing) 4, a developing device 5, an intermediate transfer device 6, and a cleaning device 10 are arranged along the rotation direction. Have been.

The photosensitive drum 2 is configured such that electrostatic latent images corresponding to a plurality of colors are formed by light writing from a writing device 4, and the electrostatic latent image is mounted on a developing device 5. Developing toner (yellow (indicated by a symbol Y in the figure), magenta (indicated by a symbol M), and cyan (indicated by a symbol C in the drawing) having a complementary color relationship with the separation color written in the writing device 4. ) And black (also denoted by reference numeral B))
A, 5B, 5C, and 5D perform a visible image process, and a toner image of a visible color is superimposed and transferred to the intermediate transfer device 6.

The intermediate transfer device 6 is a portion where the toner images of each color are temporarily transferred, and a portion where the temporarily transferred and superimposed images can be collectively transferred to a recording sheet. And an intermediate transfer belt 6D wound around a plurality of pulleys 6A to 6C, and a transfer roller 6E which abuts on the intermediate transfer belt 6D and applies a transfer bias.

The intermediate transfer belt 6D has a resistance layer of 15 mm.
Materials such as EPDM, BR, and chloroprene rubber having a thickness of about 0 μm are used and have a volume resistance of 10 ⁵ Ω to
Is set to 10 ^{1 2} Ω, preferably, ^{10 7} Ω~10 10 Ω
Is set in the range. Furthermore, the surface is coated with a fluorine-based resin that is adjusted to 10 ¹⁰ Ω to ^{10 15} Ω with a thickness of about 10 μm to maintain the charge on the surface,
Filming, which is a phenomenon in which toner is deposited and thinned, can be prevented.

The transfer roller 6E is a member for collectively transferring a superimposed image carried on the intermediate transfer belt 4 to a recording sheet, and has a thickness of 10 to 3 on a metal core also serving as a drive shaft.
EPDM, SB with smoothness as a resistance layer of about 0 mm
Materials such as R, BR, and chloroprene rubber are used, the volume resistance is set to 10 ⁷ to 10 ¹⁰ Ω, and the Asker hardness is 3
It is composed of rollers set at about 0 ° (Japanese Rubber Association Standard SRIS0101). Transfer roller 6E
Is applied with a transfer bias by a constant current control from a power supply (not shown), and applies a transfer bias to the recording sheet S while nipping and conveying the recording sheet S fed from the sheet feeding device 7 together with the intermediate transfer belt 6D. It has become. The paper feeding device 7 is provided with a storage section for the recording sheets S and a feeding roller 7A which can be moved toward and away from the leading end of the recording sheets in the storage section, so that the recording sheets S are fed out one by one from the storage section. It has become.

A registration roller 8 is disposed in front of a transfer position, which is a position where the intermediate transfer belt 6D and the transfer roller 4E face each other, and determines a transfer start position for a superimposed image carried on the intermediate transfer belt 6D. The recording sheet S is fed toward the transfer position after the alignment adjustment.
Recording sheet S on which batch transfer has been performed by transfer roller 4E
Is heated and fixed by a fixing device 9 located behind the transfer device 4 and discharged onto a tray (not shown).

A cleaning device 10 including a cleaning blade 10A and a static eliminator 10B is disposed at a position where the photosensitive drum 2 after the image transfer to the intermediate transfer belt 4D is moved. The residual toner on the body drum 2 is removed, and the residual charge is removed by the charge removing device 10B.

[0010]

The recording sheet fed toward the transfer position needs to be aligned with the transfer start position of the image carried on the intermediate transfer belt 4D. Conventionally, a registration roller for setting registration timing is provided in front of the transfer position. Usually, the speed at which the recording sheet is fed out from the registration roller is 1 to the moving speed at the transfer position.
In a specific example, the linear velocity at the transfer position is 200 mm / sec, while the linear velocity at the registration roller is 202.4 mm / sec. This is to prevent the recording sheet from being dragged toward the registration roller side at the transfer position to cause a shift in the image. As a method for preventing such image misalignment and conveyance failure, the recording sheet is formed in a loop shape by setting the leading end of the recording sheet at a transfer position so that the loop amount can be optimized. A method for setting the transfer timing (for example, see Japanese Unexamined Patent Application Publication No.
338854), a method in which the conveyance speed for forming the loop is changed by the interlocking relation of the recording sheet at the transfer position to prevent the generation of inadvertent tension on the recording sheet (Japanese Patent Application Laid-Open No. Hei 6 (1994) -6380). Further, a method of setting a feeding timing of a feeding roller to apply a low-brightness tension to a recording sheet to prevent a conveyance failure such as a wrinkle (for example, Japanese Patent Application Laid-Open No. 334063
Publication).

However, all of the methods disclosed in these publications focus on adjusting the tension of the recording sheet by setting the feeding timing of the recording sheet with respect to the transfer position. Can not deal with. Generally, the recording sheet fed from the registration roller has a speed higher than the moving speed at the transfer position as described in the above-mentioned publication, and therefore, as shown by a solid line in FIG. (FIG. 2 shows a state shown by a two-dot chain line). This bending causes the recording sheet S to assume a loop shape. At the transfer position, a pressing force is generated in the traveling direction due to the rigidity of the recording sheet, so that the recording sheet S is pressed and moves at a speed higher than the speed at the transfer position.

When the trailing edge of the recording sheet S comes off the registration roller 8, the recording sheet S moves at a speed in accordance with the nipping / conveying speed at the transfer position from the state where the recording sheet S has been moving at that speed. Become. For this reason, the speed of the recording sheet S during the conveyance process changes between the time when the leading end moves from the registration roller to the transfer position and reaches the transfer position and the time when the rear end moves off the registration roller. Cause

In recent years, full-color image formation and high image quality have been promoted, and the gradation is 1200 dpi (about 20 μm / d).
ot) is often required, and in the case where the dot size is reduced to 20 μm, a desired high-definition image can be obtained if the above-mentioned speed change occurs in the conveyance process. Can not. In addition, in the case of a full-color image, color misregistration may occur due to relative displacement of the superimposed toner in the laminating direction due to a change in speed due to image formation by multicolor superposition.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems in the conventional sheet conveying apparatus and the image forming apparatus using the same.
It is an object of the present invention to provide a sheet conveying apparatus and an image forming apparatus having a configuration capable of forming a high-quality image by preventing occurrence of a speed change in a conveying process and preventing image shift.

[0015]

According to the first aspect of the present invention,
In a sheet conveying apparatus having a configuration in which a plurality of conveying members are arranged in a conveying path to convey a sheet material, a first conveying member which is located at the end of the conveying path and is capable of nipping and conveying the sheet material, A second transport member that is disposed upstream of the first transport member in the transport direction of the sheet material and is capable of setting the transport timing of the sheet material with respect to the first transport member and capable of nipping and transporting the sheet material. The first transport member is characterized in that the nipping pressure of the sheet material can be changed.

According to a second aspect of the present invention, in the sheet transporting device according to the first aspect, the holding pressure of the first transporting member on the sheet material can be changed in a process of transporting the sheet material. Features.

The third aspect of the present invention is the first or second aspect.
In the sheet conveying apparatus described above, the sheet material can be fed from any of a plurality of feeding units, and a clamping pressure in the first conveying member can be changed according to the feeding unit of the sheet material. It is characterized by that.

According to a fourth aspect of the present invention, in the sheet conveying apparatus according to the third aspect, the nipping pressure can be changed according to a deformation state of the sheet material generated in a process of conveying the sheet material from a feeding unit. It is characterized by having.

According to a fifth aspect of the present invention, in the sheet transport apparatus according to the first aspect, the holding pressure of the first transport member on the sheet material is a temperature and humidity in an atmosphere of a transport path of the sheet material. It can be changed according to.

According to a sixth aspect of the present invention, in the sheet transporting apparatus of the fifth aspect, the first transporting member sets the timing for changing the nipping pressure in accordance with the temperature and humidity in the atmosphere of the sheet transporting path. It is characterized by being possible.

According to a seventh aspect of the present invention, in the sheet transport apparatus according to the first aspect, the pressure for holding the sheet material in the first transport member can be changed according to the type of the sheet material to be fed. It is characterized by having.

According to an eighth aspect of the present invention, in the sheet transport apparatus according to the seventh aspect, the first transporting member adjusts the timing of changing the holding pressure in the process of transporting the sheet material according to the type of the sheet material. It is characterized by being able to set.

According to a ninth aspect of the present invention, in the sheet transporting device of the first aspect, the clamping pressure of the sheet material in the first transporting member can be changed according to the size of the sheet material. Features.

The invention according to claim 10 is the invention according to claims 1 to 9
An image forming apparatus using the sheet conveying device according to any one of the above, wherein the first conveying member is an image transfer member to the sheet material, and the second conveying member is configured by a registration roller. It is characterized by having.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an embodiment showing an example of an image forming apparatus provided with a sheet conveying apparatus according to the present invention. The image forming apparatus shown in FIG. 1 is a color copying machine capable of forming a full-color image. In the present invention, it goes without saying that not only the copying machine shown in FIG. 1 but also a printer and a facsimile machine are included as the image forming apparatus.

The configuration of the main part of the full-color image forming apparatus shown in FIG. 1 has been described above, and therefore will be omitted, and only the features in FIG. 1 will be described. In FIG. 1, the starting end of the conveyance path of the recording sheet S is the registration roller 8 side,
The end side is the intermediate transfer belt 6D side. A transfer roller 6E, which is a first transport member capable of nipping and transporting the recording sheet S, is disposed at a terminal side of the transport path. The transport direction of the recording sheet S is higher than the terminal side (indicated by an arrow in the drawing). 2.) A registration roller 8 serving as a second transport member located on the upstream side is disposed.

The transfer roller 6E is provided so as to be in contact with the intermediate transfer belt 6D.
Can be changed. As shown in FIGS. 2 and 6, a configuration for changing the holding pressure includes, for example, a spring that locks one end of the transfer roller 6E in the extending direction and urges the transfer roller 6E toward the intermediate transfer belt 6D. An elastic member 11, a cam follower 12 having the other end in the extension direction of the elastic member 11 locked, and an eccentric cam 13 that can rotate in contact with the cam follower 12. The amount of rotation of the eccentric cam 13 is set by a motor M driven and controlled by the control unit 14, so that the amount of vertical displacement of the cam follower can be changed steplessly.

The control unit 14 can calculate the moving distance of the recording sheet S in the transport direction by inputting the rotation amount of the registration roller 8 (the rotation amount of a motor indicated by reference numeral 8A in FIG. 2). The time when the leading end of the recording sheet S in the conveying direction reaches the transfer position, which is the position where the intermediate transfer belt 6D and the transfer roller 6E face each other, and the time when the rear end of the recording sheet S is disengaged from the registration roller 8 are determined. Rotation position,
In other words, the contact position of the peripheral surface with respect to the cam follower 12 can be changed. The state in which the leading end of the recording sheet S is nipped by the registration roller 8 is detected by a detection sensor (not shown), and is set in advance from the time when a detection signal from the detection sensor is output to the control unit 14. After a lapse of time or registration roller 8
Is determined by the amount of rotation.

In the present embodiment, the configuration as described above allows the transport speed of the recording sheet S moving on the transport path to be controlled by changing the clamping pressure. That is, the nipping pressure affects the sliding of the transfer roller 6E with respect to the recording sheet S, and as the nipping pressure increases, the state in which the slip does not occur is made. As a result, the nipping pressure easily matches the moving speed of the intermediate transfer belt 6D.

In FIG. 2, when the leading end of the recording sheet S reaches the transfer position, the recording sheet S bends because the linear velocity of the registration roller 8 is set faster than that at the transfer position. (The state shown by the two-dot chain line in FIG. 2). When the leading end of the recording sheet S passes through the transfer position, if a deflection occurs at a certain distance from the leading end due to a difference in linear velocity with respect to the registration roller 8, in this embodiment, when the leading end of the recording sheet S advances about 10 mm from the leading end, recording is performed by the rigidity due to the bending. The sheet S is pushed, and the moving speed becomes faster than the linear speed at the transfer position. Therefore, in this embodiment, in this state, the nipping pressure on the recording sheet S is increased to match the speed of the recording sheet S with the speed of the photosensitive drum 2. To enable this, the motor M is driven when the control unit 14 determines that the leading end of the recording sheet S has moved a predetermined distance from the transfer position, and the eccentric cam 1
By rotating 3, the urging force of the elastic body 11 is increased via the cam follower 12.

When the trailing edge of the recording sheet S comes off the registration roller 8, the recording sheet S moves at a speed in accordance with the moving speed at the transfer position. This is the pressure at the time when the leading end reaches the transfer position.

In the present embodiment, the following clamping pressure is set. When the temperature of the use environment is 23 ° C. and the humidity is 50%, the clamping pressure is set to 10 N when the leading edge of the recording sheet S advances 50 mm from the transfer position, and the clamping pressure starts when the recording sheet S starts to bend from the point when 50 mM has passed. Is set to 20N, and the holding pressure is returned to 10N when the trailing edge of the recording sheet S is released from the registration roller 8. Due to such a change in the nipping pressure, the recording sheet S is changed in slippage at the transfer position in the entire conveying process, so that a uniform conveying speed can be obtained, and image shift due to the speed change in the conveying process is prevented. Will be.

Next, another embodiment of the present invention will be described. The embodiment shown in FIG. 3 is characterized in that when a plurality of paper feed units are provided, the clamping pressure is changed corresponding to the paper feed unit from which the recording sheet S is fed. As a paper feeding unit, a paper feeding cassette (shown by reference numeral 7C for convenience) having a storage unit for recording sheets S is provided, and in addition to this paper feeding cassette 7C, a manual paper feeding unit (shown by reference numeral 7H for convenience) is provided. ) May be provided. When such a plurality of sheet feeding units are provided, the recording sheet S may be habitually conveyed during the conveyance process due to a difference in installation location. That is, when the paper is fed from the paper feed cassette 7C, the transport path from the paper feed cassette 7C to the registration roller 8 is in a folded state, and the transport path from the manual paper feed unit 7H to the registration roller is substantially linear. Have been. For this reason, the recording sheet S fed out from the paper feed cassette 7C
Is fed out from the registration roller 8 with the curl generated according to the shape of the transport path. As shown by the solid line in FIG. 3, the recording sheet S having the curl has a large amount of bending and a strong force to progress at the transfer position. Extremely bigger than speed.

In this embodiment, in order to cope with such a situation, paper feed unit sensors S1 and S2 for detecting the paper feed unit from which the recording sheet S is fed are provided at the recording sheet feed position of each paper feed unit. The paper feed unit sensors S1 and S2 are connected to the control unit 14. The control unit 14 changes the holding pressure at the transfer position in accordance with a signal from the paper feed unit sensors S1 and S2. In the present embodiment, when the paper is fed out of the paper feed cassette 7C, the manual feeding is performed. The holding pressure is increased earlier than when the sheet is fed from the paper section 7H.

In the case of this embodiment, when the recording sheet is fed out of the paper feed cassette 7C, the nipping pressure is increased when the leading end of the recording sheet passes through 35 mm from the transfer position, and when the recording sheet is fed out of the manual feed section 7H. The nip pressure is increased when the leading end of the recording sheet S passes by 50 mm from the transfer position. When the recording sheet S is fed out from the paper feed cassette 7C, the trailing edge of the recording sheet S often has a curl. The recording sheet S is returned to 15N when a position 50 mm from the rear end of the recording sheet S approaches the transfer position.

Since the present embodiment has the above configuration,
The holding pressure is changed according to the state of feeding from the sheet feeding unit. In particular, when feeding from a paper feeding unit where the bending amount due to the curl becomes large and the moving speed at the transfer position may be faster than the linear speed at the transfer position, it is longer than when feeding from other paper feeding units. Also increase the clamping pressure quickly. As a result, it is possible to prevent the moving speed of the recording sheet S from changing at the transfer position due to the curl, and to maintain a uniform speed throughout the conveying process. In the present embodiment, the deformation state of the recording sheet fed from the sheet feeding unit is determined by detecting the feeding state of the sheet feeding unit and switching the change timing of the clamping pressure, regardless of the type of the sheet feeding unit. The transport speed can be made uniform regardless of the state.

Next, another embodiment of the present invention will be described. The embodiment shown in FIG. 4 is characterized in that the holding pressure is changed in accordance with the temperature and humidity in the use environment which affects the expansion and contraction of the recording sheet. In FIG.
The controller 14 is connected to a temperature / humidity detection sensor S3 that detects the temperature / humidity of the atmosphere in which the sheet conveying device is installed. The control unit 14 controls the rotation of the eccentric cam 3 to change the clamping pressure in accordance with the signal from the temperature and humidity detection sensor S3.

The rigidity of the recording sheet S changes in accordance with the temperature and humidity, and the amount of deflection also changes. For example, in a high-temperature and high-humidity environment, the rigidity is weakened, so that the bending amount is reduced. In a low-temperature, low-humidity environment, the rigidity is increased and the bending amount is increased. For this reason, in the control unit 14, the moving progress speed is changed according to the progress of the recording sheet S at the transfer position, that is, the change in the progress speed of the recording sheet with respect to the linear speed at the transfer position due to the difference in the amount of bending due to the change in rigidity. The nipping pressure is changed so as to match the linear velocity at the transfer position.

In the present embodiment, 28 corresponding to high temperature and high humidity
°, under an environment of 70%, the clamping pressure is set to 10 N from the transfer position until the leading end of the recording sheet passes through 70 mm, and then to 15 N. Further, when the trailing end of the recording sheet comes off the registration roller 8, 80m from the end
The holding pressure for the range of m is returned to 10N. In addition, 10 degrees corresponding to low temperature and low humidity,
Under an environment of 20%, the recording sheet S
10 N until the tip of
After that, when the rear end of the recording sheet S comes off from the registration roller 8, the distance is set to 22 N,
Is returned to 10N.

Since the present embodiment has the above configuration,
The holding pressure is changed according to the temperature and humidity. Particularly, in the case of high temperature and high humidity where the rigidity of the recording sheet is reduced and the amount of deflection is reduced, the phenomenon that the recording sheet S pushes forward at the transfer position is weakened. In the case of low temperature and low humidity where the holding pressure is reduced and the rigidity of the recording sheet S is increased and the amount of deflection is increased, on the contrary, the force of pushing the recording sheet S at the transfer position is increased. The advancing speed of the recording sheet S matches the linear speed at the transfer position by increasing the holding pressure when the sheet S passes through the transfer position. This makes it possible to equalize the transport speed in the entire transport process of the recording sheet S, and to prevent an image shift caused by a change in the transport speed.

Next, still another example of the embodiment of the present invention will be described. The embodiment shown in FIG. 5 is characterized in that the holding pressure is changed according to the type of the recording sheet. 5, a thickness detection sensor S4 that can detect the thickness of the recording sheet S is connected to the control unit 14. The control unit 14 controls the rotation of the eccentric cam 3 to change the clamping pressure in accordance with the signal from the temperature and humidity detection sensor S3. The rigidity of the recording sheet S varies depending on the thickness. The rigidity is high when the recording sheet S is thick, and the rigidity is low when the recording sheet S is thin. For this reason, when the rigidity is high, the amount of deflection generated on the recording sheet S also increases, and the force for pushing the recording sheet S at the transfer position also increases. Therefore, when the thickness of the recording sheet S is large, the traveling speed of the recording sheet S at the transfer position becomes higher than the linear velocity at the transfer position, and
The difference from the traveling speed when the trailing end is off is large. In the present embodiment, when the thickness of the recording sheet S is large, the control unit 14 increases the nipping pressure so that the traveling speed of the recording sheet matches the linear velocity at the transfer position. The thickness detection sensor S4 used in the present embodiment is not limited to the configuration for detecting the thickness of the recording sheet S actually passing through the transport path. For example, a recording sheet classification switch provided on an operation panel (not shown) It is also possible to use such as.

In this embodiment, when a thick recording sheet such as a postcard is used for a high quality paper (thickness: 90 μm) which is generally used (thickness: 180 μm), the transfer position is shifted from the point at which the leading end of the recording sheet passes. The holding pressure is set to 15N, and when the leading end passes through 30 mm from the transfer position, the holding pressure is set to 25N. The holding pressure of 25N is maintained until the trailing end of the registration roller 8 is released and the trailing end reaches the transfer position. I have. On the other hand, in the case of a thin recording sheet such as high-quality paper of 45K, the rigidity is relatively weak, the amount of deflection is small, and the change in the traveling speed at the transfer position is small. 10N is maintained in the entire conveying process from the time when the sheet passes through to the time when the rear end passes. As a result, in the case of thin paper, it is possible to prevent wrinkles and the like from occurring due to an increase in the holding pressure.

The case where the holding pressure is changed based on properties such as the thickness of the recording sheet S may be based on the size of the recording sheet S. In this case, the traveling speed of the recording sheet S at the transfer position changes depending on the width of the recording sheet S. That is, the rigidity when the bending occurs is different between the case where the A4 size recording sheet S is conveyed in the longitudinal direction and the case where the A4 size recording sheet S is conveyed in the horizontal direction, and the traveling speed at the transfer position based on the rigidity is also different. For this reason, in the control unit 14, for example,
When the thickness detection sensor S4 described above is replaced with a size detection sensor, or when the conveyance mode of the recording sheet S is set by selection on the operation panel, the size of the recording sheet S in the conveyance direction according to the conveyance mode is set. Change the clamping pressure according to. In the present embodiment, focusing on the fact that the rigidity when flexing is higher in the case of the horizontally long conveyance mode than in the case of the vertically long conveyance mode, and in the case of the horizontally long conveyance mode, the leading end of the recording sheet S passes through the transfer position. The clamping pressure is set to 23 N at a position 50 mm from the point of time when the pressure is increased. By the way, in the case of the longitudinal conveyance, the pressure is set to 20 N which is weaker than the above-described clamping pressure. In this configuration, when a horizontally long conveyance mode having high rigidity when flexing is selected,
The recording sheet S at the transfer position is increased by increasing the clamping pressure as compared with the case where the vertically long conveyance with lower rigidity is selected than in this case.
, The change in the transport speed due to the pushing advance can be suppressed. Accordingly, it is possible to eliminate the image shift by eliminating the change in the transport speed in the entire transport process of the recording sheet S.

In the above embodiment, a color copying machine capable of forming a full-color image by multi-color superimposition is intended. However, in the present invention, as shown in FIG. It is also possible to use an apparatus (indicated by reference numeral 1 ′ for convenience). In this case, a transfer roller 4 </ b> E is provided so as to face the photosensitive drum 2, and the intermediate roller shown in FIG. There is no transfer device 6. In FIG. 7, the developing device has a configuration capable of supplying a single color (monochrome) developing toner, and is denoted by reference numeral 5 'for convenience.

In FIG. 7, a transfer roller 6E opposed to the photosensitive drum 2 is provided with an elastic body 1 in order to change the pressure when the recording sheet S is pinched in cooperation with the photosensitive drum 2.
1, a cam follower 12 and an eccentric cam 13 are provided. In this configuration, FIGS.
The nipping pressure is changed based on the same conditions as described in the above.

[0046]

According to the first and second aspects of the present invention,
Since the nipping pressure of the sheet material can be changed by the first conveyance member, the conveyance speed can be changed by adjusting the magnitude of the slip between the sheet material and the first conveyance member. Accordingly, the conveying speed of the sheet material in the conveying process can be made uniform throughout the conveying process, so that it is possible to prevent the image shift and prevent the image quality from deteriorating.

According to the third and fourth aspects of the present invention, the pinching pressure can be changed according to the feeding section in which the sheet material is accommodated, and in particular, the deformation of the sheet material occurs in the conveyance path from the feeding section. In this case, the nipping pressure can be changed in accordance with the deformation state.
It can be optimized by adjusting the sliding state with the transfer member. Thereby, the conveyance speed does not change in the conveyance process of the sheet material, so that it is possible to reliably prevent the image shift.

According to the fifth and sixth aspects of the present invention, the nipping pressure of the first conveying member can be changed in accordance with the temperature and humidity which affect the expansion and contraction of the sheet material. This can be prevented by adjusting the transport speed. This makes it possible to obtain good image quality irrespective of changes in the use environment.

According to the seventh and eighth aspects of the present invention, the holding pressure can be changed according to the type of the sheet material, and therefore, particularly according to the thickness of the sheet material held by the first conveying member. By adjusting the clamping pressure, and particularly by adjusting the change timing, it is possible to prevent a change in the transport speed due to a change in the slip. Accordingly, regardless of the type of the factor that affects the nipping and conveying force of the first conveying member, such as the thickness, smoothness, and surface roughness of the sheet material, it is possible to prevent a speed change in the conveying process of the sheet material and shift the image. And the occurrence of transport failure can be prevented.

According to the ninth aspect of the present invention, the nipping pressure of the first conveying member can be changed in accordance with the size of the sheet material. The transfer speed in the process can be made uniform and the image shift can be reliably prevented.

According to the tenth aspect, it is possible to correct the speed change between the time when the sheet material arrives at the image transfer member and the time when the sheet material comes off the registration roller to maintain a uniform speed. it can. As a result, it is possible to obtain a good image quality without occurrence of image shift by eliminating a change in speed in the process of conveying the sheet material.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of an image forming apparatus for explaining an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a main configuration of a sheet conveying unit used in the image forming apparatus illustrated in FIG. 1;

FIG. 3 is a schematic diagram for explaining another embodiment of a main part of a sheet conveying unit used in the image forming apparatus shown in FIG.

FIG. 4 is a schematic diagram for explaining another embodiment relating to a main part of a sheet conveying unit used in the image forming apparatus shown in FIG. 1;

FIG. 5 is a schematic diagram for explaining still another embodiment of a main part of a sheet conveying unit used in the image forming apparatus shown in FIG.

FIG. 6 is a schematic perspective view showing a configuration of a change portion of a clamping pressure used in the embodiment shown in FIGS. 2 to 5;

FIG. 7 is a schematic diagram illustrating another example of the image forming apparatus illustrated in FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Color copying machine which is one of image forming apparatuses 2 Photoreceptor drum 6 Intermediate transfer device 6D Intermediate transfer belt 6E Transfer roller corresponding to the 1st conveyance member 7 Paper feed device 7C Paper feed which is one of the paper feed units Cassette 7H Manual paper feed unit that is another one of the paper feed units 8 Registration roller 11 corresponding to the second transport member 11 Elastic body provided in the holding pressure changing unit 12 Cam follower provided in the holding pressure changing unit 13 Holding Eccentric cam provided in the pressure changing unit 14 Control unit S1, S2 Feed unit sensor S3 Temperature / humidity detection sensor S4 Thickness detection sensor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H027 DA11 DA14 DA20 DA21 DA38 DC02 DC03 DC04 DE07 EA18 EC06 ED17 ED24 EE02 EE03 EF10 2H032 AA05 BA09 BA12 BA19 BA23 CA12 CA13 CA14 2H072 AB07 CA01 CA02 CB09 3F049 DA12 DA03 LA05 LA07 LB03 3F102 AA01 AB01 BA02 BB02 DA08 EA03 FA08

Claims (10)

[Claims] 1. A sheet conveying apparatus having a structure in which a plurality of conveying members are arranged in a conveying path to convey a sheet material, wherein a first sheet conveying member is located at the end of the conveying path and is capable of nipping and conveying the sheet material. And a second transport member which is disposed upstream of the first transport member in the transport direction of the sheet material and is capable of setting the transport timing of the sheet material with respect to the first transport member and capable of pinching and transporting the sheet material. A sheet conveying device, comprising: a conveying member; and wherein the first conveying member is configured to be capable of changing a holding pressure of the sheet material. 2. The sheet conveying apparatus according to claim 1, wherein the pressure of the first conveying member for pinching the sheet material can be changed in the process of conveying the sheet material. . 3. The sheet conveying device according to claim 1, wherein the sheet material can be fed from any one of a plurality of feeding portions, and the pressure of the sheet held by the first conveying member is reduced. A sheet conveying device characterized in that it can be changed according to a material feeding section. 4. The sheet conveying apparatus according to claim 3, wherein the nipping pressure can be changed according to a deformation state of the sheet material generated in a process of conveying the sheet material from a feeding unit. Sheet transport device. 5. The sheet conveying apparatus according to claim 1, wherein a pressure for holding the sheet material by the first conveying member can be changed according to a temperature and a humidity in an atmosphere of a conveying path of the sheet material. A sheet conveying device, comprising: 6. The sheet conveying apparatus according to claim 5, wherein the first conveying member can set a timing for changing the nipping pressure according to the temperature and humidity in the atmosphere of the sheet conveying path. Sheet conveying device. 7. The sheet conveying apparatus according to claim 1, wherein the holding pressure of the sheet material in the first conveying member can be changed according to the type of the sheet material fed. Sheet transport device. 8. The sheet conveying apparatus according to claim 7, wherein the first conveying member is capable of setting a timing for changing the holding pressure in a process of conveying the sheet material in accordance with a type of the sheet material. A sheet conveying device characterized by the above-mentioned. 9. The sheet conveying apparatus according to claim 1, wherein a clamping pressure of said sheet material in said first conveying member can be changed according to a size of said sheet material. . 10. An image forming apparatus using the sheet conveying device according to claim 1, wherein the first conveying member is an image transfer member to the sheet material, and the first conveying member is an image transferring member. An image forming apparatus, wherein the second conveying member is constituted by a registration roller.