JP2006133349A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of suppressing misalignment and irregularities in an image in the midst of a primary transfer process at a primary transfer part, even when cardboard is used as the recording material. <P>SOLUTION: The apparatus is provided with a pair of transport rollers 10g, arranged immediately near the prestage of a secondary transfer part T2 in the transport direction of the recording material S so as to transport the recording material S toward the secondary transfer part T2, and a cleaning blade 81 constituted so as to be detachable from the surface of an intermediate transfer body 51, and for scraping residual toner remaining on the intermediate transfer body 51 after the secondary transfer, while coming to abut against the intermediate transfer body 51; the recording material transport speed by the pair of transport rollers 10g is set higher than the recording material transport speed at the secondary transfer part T2; and when the cardboard is used as the recording material, the cleaning blade 81 is brought into contact with the intermediate transfer body 51, after the trailing end of the cardboard passes through the nip part formed by the pair of transport rollers 10g. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a printer, a facsimile, and a copying machine that forms a toner image using electrophotographic technology.

In general, an image carrier on which a toner image is formed on the surface;
A primary transfer portion is formed at the contact portion with the image carrier, and the toner image on the image carrier is primarily transferred at the primary transfer portion, and a secondary transfer portion is formed at the contact portion with the recording material. An intermediate transfer member that transfers a toner image onto a recording material in the secondary transfer portion;
A secondary transfer roller that is pressed against the intermediate transfer member via a recording material in the secondary transfer unit;
A transport roller pair disposed in the immediate vicinity of the secondary transfer unit with respect to the transport direction of the recording material and transporting the recording material toward the secondary transfer unit;
A cleaning blade configured to come into contact with and separate from the surface of the intermediate transfer member, and scrape residual toner remaining on the intermediate transfer member after the secondary transfer by contacting the intermediate transfer member;
There is known an image forming apparatus including the above (for example, Patent Document 1).

In such an image forming apparatus, if the cleaning blade is brought into contact with the intermediate transfer member during the period during which the primary transfer is performed, vibration in the device that occurs when the cleaning blade comes into contact, rotation of the intermediate transfer member, or the like. There is a problem that the output image is likely to be shifted or distorted due to the fluctuation of the load.
Therefore, in order to solve such a problem, the conventional image forming apparatus is configured to bring the cleaning blade into contact with the intermediate transfer member during a period in which the primary transfer is not performed (Patent Document 1).
JP 2003-195712 A

In general, in the image forming apparatus as described above, a recording material conveyance speed by a pair of conveyance rollers that are arranged immediately before the secondary transfer unit and convey the recording material toward the secondary transfer unit is set to the secondary transfer unit. It is desirable to set the speed faster than the recording material conveyance speed of the recording medium. When the conveyance speed of the recording material by the conveyance roller pair immediately before the secondary transfer section is the same or lower than the conveyance speed of the recording material in the secondary transfer section, recording is performed between the conveyance roller pair and the secondary transfer section. When there is a material, tension acts on the recording material, and this tension may act as a load in the secondary transfer unit, and the transfer operation in the secondary transfer unit becomes unstable (the transfer image is misaligned or disturbed). This is because there is a risk that
On the other hand, if the conveying speed of the recording material by the conveying roller pair is set faster than the conveying speed of the recording material in the secondary transfer section, the tensile force does not act, so the recording material has a thickness less than that of plain paper. In the case of (weakness of waist), the problem due to the pulling force as described above does not occur.

However, when the conveyance speed of the recording material by the conveyance roller pair is set higher than the conveyance speed of the recording material in the secondary transfer unit, the recording material conveyed by the conveyance roller pair and the secondary transfer unit is thick paper. In this case, a compressive force acts on the thick paper between the pair of conveying rollers and the secondary transfer unit. Since this compression force acts to increase the moving speed of the intermediate transfer member in the secondary transfer portion, the moving speed of the intermediate transfer member tends to become unstable.
For this reason, in this situation, if the cleaning blade is brought into contact with the intermediate transfer member, the moving speed of the intermediate transfer member becomes more unstable and the speed fluctuation becomes large, and the primary transfer part is in the middle of the primary transfer. Misalignment and disturbance are likely to occur in the image.
Such a problem cannot be solved by the conventional technique described in Patent Document 1 described above.

In addition to the case where the recording material is a thick paper, such a problem causes the movement speed of the intermediate transfer body to become unstable by acting to increase the movement speed of the intermediate transfer body in the secondary transfer portion. A recording material having a certain level of stiffness is similarly produced. Therefore, in the present application, “thick paper” means “the strength of the waist that destabilizes the moving speed of the intermediate transfer member by acting to increase the moving speed of the intermediate transfer member in the secondary transfer portion”. It means “recording material”.
SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that solves the above-described problems and is unlikely to cause deviation or disturbance in an image during primary transfer in a primary transfer portion even when the recording material is cardboard. .

In order to achieve the above object, the image forming apparatus of the present invention comprises:
An image carrier on which a toner image is formed on the surface;
A primary transfer portion is formed at the contact portion with the image carrier, and the toner image on the image carrier is primarily transferred at the primary transfer portion, and a secondary transfer portion is formed at the contact portion with the recording material. An intermediate transfer member that transfers a toner image onto a recording material in the secondary transfer portion;
A secondary transfer roller that is pressed against the intermediate transfer member via a recording material in the secondary transfer unit;
A transport roller pair disposed in the immediate vicinity of the secondary transfer unit with respect to the transport direction of the recording material and transporting the recording material toward the secondary transfer unit;
A cleaning blade configured to come into contact with and separate from the surface of the intermediate transfer member, and scrape residual toner remaining on the intermediate transfer member after the secondary transfer by contacting the intermediate transfer member;
An image forming apparatus comprising:
The conveyance speed of the recording material by the conveyance roller pair is set faster than the conveyance speed of the recording material in the secondary transfer unit,
When the recording material is cardboard, the cleaning blade is brought into contact with the intermediate transfer member after the trailing end of the recording material passes through the nip portion of the conveying roller pair.
According to such a configuration, since the conveyance speed of the recording material by the conveyance roller pair is set higher than the conveyance speed of the recording material in the secondary transfer portion, the conveyance roller pair and the secondary transfer portion When the recording material no longer acts on the recording material in the meantime, and the recording material has a thickness less than plain paper (waistness), the transfer operation in the secondary transfer portion is stably secondary transferred. Displacement and disturbance will not occur. Further, since the moving speed of the intermediate transfer member is stabilized, the image in the primary transfer portion is not displaced or disturbed.
When the recording material is cardboard, the cleaning blade contacts the intermediate transfer member after the trailing edge of the recording material passes through the nip portion of the pair of conveying rollers, so the cleaning blade contacts the intermediate transfer member. In this case, the intermediate transfer member is already in a state where the acceleration force due to the compression force does not act. For this reason, when the cleaning blade comes into contact with the intermediate transfer member, the moving speed of the intermediate transfer member is stable.
Therefore, even if the cleaning blade is brought into contact with the intermediate transfer member, the moving speed of the intermediate transfer member does not fluctuate greatly. As a result, the image during the primary transfer is less likely to be displaced or disturbed in the primary transfer unit. Become.

Embodiments of an image forming apparatus according to the present invention will be described below with reference to the drawings.
FIG. 1 is a front view showing an internal structure of an embodiment of an image forming apparatus according to the present invention.
This image forming apparatus is a color image forming apparatus capable of longitudinally feeding A4 size paper (including letter size) as a recording material to form full color images on both sides thereof. The accommodated image carrier unit 20, exposure unit 30 as exposure means, developing device (developing device) 40 as developing means, intermediate transfer body unit 50, and fixing unit (fixing device) as fixing means. 60.
The case 10 is provided with a frame (not shown) of the apparatus main body, and each unit is attached to the frame.

  The image carrier unit 20 includes a photoconductor 21 having a photosensitive layer on an outer peripheral surface as an image carrier, and a corona charger (scorotron charger) as a charging unit that uniformly charges the outer peripheral surface of the photoconductor 21. 22 and selectively exposing the outer peripheral surface of the photoreceptor 21 uniformly charged by the corona charger 22 with the laser light L from the exposure unit 30 to form an electrostatic latent image. Then, a toner as a developer is applied to the electrostatic latent image by a developing device 40 to form a visible image (toner image), and this toner image is primarily applied to an intermediate transfer belt 51 which is an intermediate transfer body of the intermediate transfer body unit 50. The primary transfer is performed at the transfer portion T1, and the secondary transfer is further performed at the secondary transfer portion T2 on the paper (recording material) to be transferred.

In the case 10, a conveyance path 16 that conveys a sheet on which an image is formed on one side by the secondary transfer portion T <b> 2 toward a sheet discharge portion (discharge tray portion) 15 on the top surface of the case 10, and the conveyance path 16 A return path 17 is provided for switching back the sheet conveyed toward the sheet discharge unit 15 and returning it to the secondary transfer unit T2 so as to form an image on the other side.
Reference numeral 70 denotes a duplex unit configured to be detachable from the apparatus main body, and the return path 17 is formed by mounting the duplex unit 70.
A paper feed cassette 18 for stacking and holding a plurality of sheets is provided at the bottom of the case 10, and the sheet S (see FIG. 2) is fed one by one toward the secondary transfer unit T2. A paper roller 19 is provided. The paper fed by the paper feed roller 19 is transported toward the secondary transfer portion T2 by the gate roller pair 10g, with the transport timing to the secondary transfer portion T2 controlled by the gate roller pair 10g.

  The developing device 40 is a rotary developing device (rotary developing device), and a plurality of developer cartridges (K (black), C (cyan), M (magenta), A Y (yellow) cartridge (not shown) is detachably mounted. As the rotating body 41 rotates at 90 ° pitch in the direction of arrow R, the developing roller (not shown) provided in each developing device cartridge is selectively brought into contact with the photosensitive member 21, and the surface of the photosensitive member 21. Can be selectively developed.

The exposure unit 30 irradiates the laser 21 with the laser light L.
The intermediate transfer body unit 50 includes a unit frame (not shown), a driving roller 54 rotatably supported by the frame, and the intermediate transfer belt 51 stretched around a plurality of driven rollers 53 and the like. The intermediate transfer belt 51 is circulated and driven in the direction of the arrow in the figure. The primary transfer portion T1 is formed at the contact portion between the photosensitive member 21 and the intermediate transfer belt 51, and the secondary transfer portion T2 at the pressure contact portion between the driving roller and the secondary transfer roller 10b provided on the main body side. Is formed.
The secondary transfer roller 10b can be brought into contact with and separated from the drive roller 54 (and therefore with respect to the intermediate transfer belt 51), and when it comes into contact, a secondary transfer portion T2 is formed.

Accordingly, when forming a color image, a plurality of color toner images are superimposed on the intermediate transfer belt 51 while the secondary transfer roller 10b is separated from the intermediate transfer belt 51, and then a color image is formed. The secondary transfer roller 10b contacts the intermediate transfer belt 51, and the sheet is supplied to the contact portion (secondary transfer portion T2), whereby a color image (toner image) is formed on the sheet from the intermediate transfer belt 51. Transfer (secondary transfer) is performed.
The sheet on which the toner image has been transferred passes through the fixing unit 60 to melt and fix the toner image, and is discharged toward the paper discharge tray unit 15.
The intermediate transfer unit 50 is provided with cleaning means 80 for removing residual toner remaining on the intermediate transfer belt 51 after the secondary transfer.

FIG. 2 is a schematic view showing only the main part of the image forming apparatus, and FIG. 3 is a schematic view showing a gate roller pair 10g and a secondary transfer portion T2.
1 and 2, reference numeral 81 denotes a cleaning blade. The cleaning blade 81 is configured to be able to come into contact with and separate from the surface of the intermediate transfer belt 51 by a contact / separation mechanism, and remains on the intermediate transfer belt 51 after the secondary transfer by contacting the intermediate transfer belt 51. Scrape off the toner.

As shown in FIGS. 1 and 2, the gate roller pair 10g is disposed in the immediate vicinity of the secondary transfer portion T2 in the conveyance direction of the recording material S, and the recording material S is directed toward the secondary transfer portion T2. A pair of conveyance rollers for conveyance is configured.
As shown in FIG. 3, the conveyance speed V1 of the recording material S by the gate roller pair 10g is set faster than the conveyance speed V2 of the recording material S in the secondary transfer portion T2.

In FIG. 2, 52 is a backup roller for backing up the intermediate transfer belt 51 in the primary transfer portion T1, but such a roller may or may not be provided.
As shown in FIG. 1, when the backup roller is not provided, the photosensitive member 21 and the intermediate transfer belt 51 come into contact with each other due to the tension of the intermediate transfer belt 51 in the primary transfer portion T1.

The timing of bringing the cleaning blade 81 into contact with the intermediate transfer belt 51 is controlled by a control unit (not shown) that controls the operation of the entire image forming apparatus.
This image forming apparatus is usually used connected to a personal computer.
Types such as the size and thickness of the paper (recording material) S used for image formation in the image forming apparatus can be set by an operation panel provided in the image forming apparatus, but can usually be set on a personal computer. Information is input to the control unit of the image forming apparatus.

When the recording material S is thick paper (or a recording material with strong stiffness, such as an envelope or an OHP sheet), the control unit sets the rear end S2 of the recording material (see FIG. 3) to the nip of the gate roller pair 10g. After passing the portion N, the cleaning blade contact / separation mechanism is operated so that the cleaning blade 81 contacts the intermediate transfer belt 51.
If the size of the recording material S is known, the time when the trailing edge S2 of the recording material S passes through the nip portion N after the leading edge S1 of the recording material S enters the nip portion N of the gate roller pair 10g, Since it can be obtained by the number of rotations (or, for example, the number of driving steps of the stepping motor that drives the gate roller pair 10g), the control unit determines the trailing edge of the recording material based on the number of driving steps of the stepping motor. After S2 passes through the nip N of the gate roller pair 10g, the cleaning blade contact / separation mechanism is operated so that the cleaning blade 81 contacts the intermediate transfer belt 51.

4A and 4B are timing charts showing the operation of the main part controlled by the control unit. FIG. 4A shows the case of plain paper (or a recording material with low stiffness below plain paper), and FIG. The case of thick paper is shown.
In FIG. 4, “Vsync” is the ON / OFF state of the reference signal, “Video” is the ON / OFF state of the image writing (exposure) signal to the photosensitive member 21, and “Gate roller” is the gate roller pair 10g. ON / OFF state of the driving of “2”, “2nd bias” indicates the ON / OFF state of the secondary transfer bias in the secondary transfer portion T2 and the contact / separation state of the secondary transfer roller 10b to the intermediate transfer belt 51, “Belted cleaner” indicates the contact / separation state of the cleaning blade 81 with respect to the intermediate transfer belt 51.
For the reference signal of “Vsync”, the ON is on the upper side, while the other is on the lower side.
For “Vsync” (reference signal), for example, a protruding piece is provided on the side edge of the intermediate transfer belt 51, and a transmission type photosensor is provided on the path of the protruding piece. It can be obtained as an ON / OFF signal by blocking once per rotation of the transfer belt 51.
Hereinafter, the operation timing of each part will be described with reference to FIG.

<When the recording material S is plain paper (FIG. 4A)>
A black (K) image is written after a predetermined time on the basis of the OFF time t1 of the reference signal immediately before the latent image is written on the photosensitive member 21, and similarly, a cyan (C) image is obtained on the basis of the time t2. A magenta (M) image is written on the basis of time t3, and a yellow (Y) image is written on the basis of time t4.

  Further, with reference to the time point t4, the gate roller pair 10g is driven at the time point t5, and the recording material S is conveyed toward the secondary transfer portion T2 by the gate roller pair 10g. The timing t5 for driving the gate roller pair 10g is the timing at which the superimposed image I of K, C, M, and Y is secondarily transferred to a predetermined position of the recording material S conveyed by the gate roller pair 10g.

At a timing t6 immediately before the leading edge of the recording material S reaches the secondary transfer portion T2, the secondary transfer roller 10b is brought into contact with the intermediate transfer belt 51 and the secondary transfer bias is turned on. As a result, the superimposed image I on the intermediate transfer belt 51 is transferred onto the recording material S (secondary transfer).
On the other hand, the cleaning blade 81 is brought into contact with the intermediate transfer belt 51 at time t6. This timing t6 is the time when the writing of the yellow (Y) image, which is the fourth color image, to the photoconductor 21 is completed, and is also the time immediately before the secondary transfer is started. Therefore, when the cleaning blade 81 contacts the intermediate transfer belt 51, the writing of the yellow (Y) image, which is the fourth color image, to the photosensitive member 21 has been completed, and the secondary transfer has been started. Absent.

Thereafter, at approximately time t7, the transfer remaining portion of the superimposed image reaches the cleaning position by the cleaning blade 81, and the residual toner on the intermediate transfer belt 51 is removed.
The time t7 is also a timing at which the driving of the gate roller pair 10g is stopped.
Thereafter, writing of a black (K) image for the next image is started at time t8 with reference to time t7, and the secondary transfer roller 10b is separated from the intermediate transfer belt 51 and the secondary transfer bias is applied. Turn off.

Thereafter, on the basis of time t9, writing of a cyan (C) image for the next image is started at time t10, and the cleaning blade 81 is separated from the intermediate transfer belt 51.
In addition, a magenta (M) image is written on the basis of time t11, and the above-described operation is repeated.

<When the recording material S is cardboard (FIG. 4B)>
Similarly to the case where the recording material S is normal, black (K) image writing is performed after a predetermined time with reference to the OFF time t1 of the reference signal immediately before writing the latent image on the photosensitive member 21, and similarly at time t2. Are used to write a cyan (C) image, a magenta (M) image based on time t3, and a yellow (Y) image based on time t4.

Here, in this embodiment, the low-speed mode is entered from the reference signal t4 ′ after the completion of the writing of the yellow (Y) image.
If the recording material S is a thick paper, its heat capacity is large. Therefore, in order to reliably melt and fix the toner image on the thick paper, the heat generation amount of the fixing device 60 is increased or the fixing device 60 is passed through. This is because it is necessary to increase the amount of heat received by the recording material S by reducing the speed of the recording material S to be recorded.
In this embodiment, the rotation speed of the fixing roller pair 61 (see FIG. 1) in the fixing device 60 is set to a lower speed (specifically 1/2) than that in the case where the recording paper is plain paper. Accordingly, the conveyance speed of the recording material by the secondary transfer portion T2 and the gate roller pair 10g is also low.
That is, in this embodiment, the reference signal t4 ′ after the completion of the writing of the yellow (Y) image is changed to the low speed mode, and the thick paper is conveyed at a low speed, so that the toner image is reliably melted and fixed on the thick paper. Will be.
For this reason, as shown in FIG. 4B, the pitch of the reference signal after t4 ′ is doubled compared to the case of FIG. 4A.

  Thereafter, the gate roller pair 10g is driven at the time point t5 with respect to the time point t4 '', and the recording material S is conveyed toward the secondary transfer portion T2 by the gate roller pair 10g. The timing t5 for driving the gate roller pair 10g is the timing at which the superimposed image I of K, C, M, and Y is secondarily transferred to a predetermined position of the recording material S conveyed by the gate roller pair 10g.

At a timing t6 immediately before the leading edge of the recording material S reaches the secondary transfer portion T2, the secondary transfer roller 10b is brought into contact with the intermediate transfer belt 51 and the secondary transfer bias is turned on. As a result, the superimposed image I on the intermediate transfer belt 51 is transferred onto the recording material S (secondary transfer).
Thereafter, after the trailing edge of the superimposed image I passes through the primary transfer position at time t7, the driving of the gate roller pair 10g is stopped at time t8, and the secondary transfer roller 10b is separated from the intermediate transfer belt 51 at time t9. Turn off the secondary transfer bias.

  Thereafter, the low speed mode is canceled with the reference signal t10 as a reference to enter the normal mode, the intermediate transfer belt 51 and the like are driven at a normal speed (speed when the recording paper is plain paper), and the reference signal t10 is used as a reference. At time t11, the cleaning blade 81 is brought into contact with the intermediate transfer belt 51. This timing t11 is a time point later than the time point when the trailing edge of the recording material S (thick paper) passes through the nip portion of the gate roller pair 10g (see t8) and the time point when the secondary transfer is finished (t9). It is a late point.

Due to the contact of the cleaning blade 81 with the intermediate transfer belt 51, the transfer remaining portion of the superimposed image reaches the cleaning position, and the residual toner on the intermediate transfer belt 51 is removed.
Thereafter, writing of the black (K) image for the next image is started with the time point t12 as a reference, and writing of the cyan (C) image for the next image is started at the time point t14 with respect to the time point t13. Thereafter, the above-described operation (operation when the recording paper is plain paper or thick paper) is repeated.

The image forming apparatus as described above
An image carrier 21 on the surface of which a toner image is formed;
The primary transfer portion T1 is formed at the contact portion with the image carrier 21, and the toner image on the image carrier 21 is primarily transferred at the primary transfer portion T1, and the secondary transfer is performed at the contact portion with the recording material S. An intermediate transfer member 51 that forms a portion T2 and transfers a toner image onto a recording material at the secondary transfer portion T2.
A secondary transfer roller 10b that is pressed against the intermediate transfer member 51 via the recording material S in the secondary transfer portion T2.
A conveying roller pair 10g that is arranged in the immediate vicinity of the secondary transfer portion T2 and conveys the recording material S toward the secondary transfer portion T2 with respect to the conveyance direction of the recording material S;
A cleaning blade 81 configured to be able to come into contact with and separate from the surface of the intermediate transfer member 51 and scrape residual toner remaining on the intermediate transfer member 51 after the secondary transfer by contacting the intermediate transfer member 51; , With
The conveyance speed V1 of the recording material S by the conveyance roller pair 10g is set faster than the conveyance speed V2 of the recording material in the secondary transfer portion T2,
When the recording material S is thick paper, the cleaning blade 81 is brought into contact with the intermediate transfer member 51 after the trailing end S2 of the recording material S has passed through the nip portion N of the conveying roller pair 10g. Therefore, according to such a configuration, the following operational effects can be obtained.
That is, since the conveyance speed V1 of the recording material S by the conveyance roller pair 10g is set faster than the conveyance speed V2 of the recording material S in the secondary transfer portion T2, the conveyance roller pair 10g and the secondary transfer portion T2 are set. When the recording material S has a thickness equal to or less than that of plain paper (weakness of waist), the transfer operation at the secondary transfer portion T2 is stably performed. Misalignment and disturbance do not occur in the next transferred image. Further, since the moving speed of the intermediate transfer member 51 is stabilized, the image at the primary transfer portion T1 is not displaced or disturbed.
When the recording material S is thick paper, the cleaning blade 81 contacts the intermediate transfer member 51 after the trailing end S2 of the recording material S has passed through the nip portion N of the conveying roller pair 10g. When 81 is in contact with the intermediate transfer member 51, the intermediate transfer member 51 is already in a state where the acceleration force due to the compression force does not act. For this reason, when the cleaning blade 81 contacts the intermediate transfer member 51, the moving speed of the intermediate transfer member 51 is in a stable state.
Therefore, even if the cleaning blade 81 is brought into contact with the intermediate transfer member 51, the moving speed of the intermediate transfer member 51 does not fluctuate greatly. As a result, the image during the primary transfer is shifted or disturbed in the primary transfer portion T1. Is less likely to occur.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be appropriately modified within the scope of the gist of the present invention.
For example, in the above-described embodiment, a configuration in which the cleaning blade 81 is brought into contact with the intermediate transfer member 51 after the rear end of the thick paper passes through the nip portion of the conveying roller pair 10g using the low speed mode in the case of thick paper. However, by increasing the calorific value of the fixing device 60, the conveyance speed is set to the normal speed even for thick paper, and the writing timing for the next image is delayed, so that the trailing edge of the thick paper is 10 g of the conveyance roller pair. The cleaning blade 81 may be brought into contact with the intermediate transfer member 51 after passing through the nip portion.

1 is a front view showing an internal structure of an embodiment of an image forming apparatus according to the present invention. Schematic which shows only the principal part of the said image forming apparatus. Schematic which shows the gate roller pair 10g and secondary transfer part T2. FIG. 4 is a timing chart showing the operation of the main part, where (a) shows the case of plain paper and (b) shows the case of thick paper.

Explanation of symbols

  10b: secondary transfer roller, 10g: gate roller pair (conveying roller pair), 21: photosensitive member (image carrier), T1: primary transfer portion, T2: secondary transfer portion, 51: intermediate transfer member, 81: cleaning blade.

Claims (1)

An image carrier on which a toner image is formed on the surface;
A primary transfer portion is formed at the contact portion with the image carrier, and the toner image on the image carrier is primarily transferred at the primary transfer portion, and a secondary transfer portion is formed at the contact portion with the recording material. An intermediate transfer member that transfers a toner image onto a recording material in the secondary transfer portion;
A secondary transfer roller that is pressed against the intermediate transfer member via a recording material in the secondary transfer unit;
A transport roller pair disposed in the immediate vicinity of the secondary transfer unit with respect to the transport direction of the recording material and transporting the recording material toward the secondary transfer unit;
A cleaning blade configured to come into contact with and separate from the surface of the intermediate transfer member, and scrape residual toner remaining on the intermediate transfer member after the secondary transfer by contacting the intermediate transfer member;
An image forming apparatus comprising:
The conveyance speed of the recording material by the conveyance roller pair is set faster than the conveyance speed of the recording material in the secondary transfer unit,
When the recording material is cardboard, the cleaning blade is brought into contact with the intermediate transfer member after the trailing end of the recording material has passed through the nip portion of the conveying roller pair.

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