JP2000221747A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an image forming device, which has plural image carriers along the direction of rotation of an intermediate transfer body and is changeable of the speed of the intermediate transfer body and that of a fixing device, small in size, high in operating speed and suppressive in the occurrence of defective image. SOLUTION: In this image forming device, the relation Lt1-t2>Limg, Lt2-fix<Limg is satisfied among distance Lt1-t2 that is from a primary transfer position Pt1d being the most downstream in the moving direction of a belt 1 among plural primary transfer positions Pt1 formed by the intermediate transfer belt 1 and plural photoreceptor drums 11a to 11d to a secondary transfer position Pt2, Lt2-fix that is the distance from the secondary transfer position Pt2 in the carrying direction of a recording member P to a fixing position Pfix, and Limg that is the length of a toner image on the belt in the moving direction of the belt. The belt 1 and the fixing device 17 are switched over to a slow speed and secondary transfer and fixing are carried out after the primary transfer of the toner image is finished and before by the toner image on the belt 1 reaches the secondary transfer position Pt2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer, and a method for obtaining an image by transferring a toner image formed by an appropriate image forming process means such as electrophotography, electrostatic recording, or magnetic recording onto a recording material surface. The present invention relates to a color image forming apparatus such as a facsimile.

[0002]

2. Description of the Related Art FIG. 6 is a schematic view of a conventional electrophotographic image forming apparatus. The present image forming apparatus has photosensitive drums 11a, 11b, 11c, and 11d corresponding to yellow, magenta, cyan, and black as image carriers, respectively. In this embodiment, an intermediate transfer belt 1 as an intermediate transfer member is disposed.

[0003] The resistance of the intermediate transfer belt 1 is preferably about 10 ⁶ to 10 ¹² Ωcm in volume resistivity.
An elastic material such as a urethane-based resin, a fluorine-based resin, a nylon-based resin, a polyimide resin, or a silicone rubber or a hydrin rubber, or a material obtained by dispersing carbon or conductive powder in these materials and adjusting the resistance can be used. In this example, a 20 μm thick surface layer of 10 ¹³ Ωcm fluorine-based resin was provided on a 0.5 mm-thick base layer in which carbon was dispersed in hydrin rubber to adjust the volume resistivity to 10 ⁷ Ωcm. The belt 1 is constituted.

[0004] As shown in the figure, the intermediate transfer belt 1 is suspended around three rollers: a driving roller 1a, a separation roller 1b, and a support roller 1c. Although the tension of the intermediate transfer belt 1 depends on the material, it is preferable that the elongation is set within 1% so that the belt is not broken or permanent distortion is generated. In this example, 150N ( Newton).

[0005] Each primary transfer portion has a medium resistance (volume resistivity of 10%).
Primary transfer rollers 15a, 15b, 15c, and 15d each having a core covered with an elastic material of ⁴ to 10 ¹⁰ Ωcm) are arranged so as to sandwich the intermediate transfer belt 1 together with the photosensitive drums 11a, 11b, 11c, and 11d. .

[0006] A secondary transfer roller 3 is provided at the separation roller 1b of the intermediate transfer belt 1 to form a secondary transfer unit. The secondary transfer roller 3 has a core metal covered with an EPDM foam layer having a medium resistance (volume resistivity of 10 ⁴ to 10 ¹⁰ Ωcm), and is arranged so as to sandwich the intermediate transfer belt 1 together with the separation roller 1b. I have.

Hereinafter, the operation of the image forming process in the present apparatus will be described. The photosensitive drum 11a rotates at a predetermined speed (process speed, 100 mm / sec in this example) in the direction of the arrow. The surface is uniformly charged by 12a, and then a laser beam from a scanner 13a modulated by an image information signal sent from a host computer is irradiated to form an electrostatic latent image on the surface of the photosensitive drum 11a.

The intensity of the laser beam and the diameter of the irradiation spot are properly set according to the resolution of the image forming apparatus and the desired image density. The electrostatic latent image on the photosensitive drum 11a It is formed by keeping the bright portion potential VL (about -100 V) and the other portion at the dark portion potential VD (about -700 V) which is primary charged.

The electrostatic latent image reaches a developing position facing the developing device 14a by the rotation of the photosensitive drum 11a, and the developing device 14a
Is developed using toner charged to the same polarity (minus polarity in this example), and is visualized as a toner image. In full-color image formation, the photosensitive drum 11a
To 11d, a four-color toner image is formed.

The intermediate transfer belt 1 is synchronously rotated in a direction indicated by an arrow by a driving device (not shown).
And a primary transfer portion formed by the photosensitive drums 11a to 11d,
An electric field is formed in each primary transfer nip area by applying a bias having a polarity opposite to that of the toner to primary transfer rollers (conductive rollers) 15a to 15d in contact with the back surface of the intermediate transfer belt 1, and a toner image is formed by the electric field. The primary transfer is performed.

In this manner, the toner images of each color are sequentially superimposed on the intermediate transfer belt 1 at each primary transfer nip.
The next transfer is performed, and a full-color image in which four color toner images are combined is obtained. The intermediate transfer belt 1 is a photosensitive drum 1
At the stage of passing through the primary transfer nip area with No. 1, the full-color image is carried on the intermediate transfer belt 1, and the primary transfer step is completed.

After the primary transfer of the toner image has been completed, the photosensitive drums 11a to 11d have their surfaces cleaned by cleaners 16a to 16d, respectively, and are ready for the next image forming step.

As the primary transfer of the toner image to the intermediate transfer belt 1 progresses, one recording material P is taken out from a paper feeding means (not shown), and the recording material P is inserted into the secondary transfer nip. At this time, a bias having a polarity opposite to that of the toner is applied to the secondary transfer roller 3, and the four color toner images on the intermediate transfer belt 1 are collectively transferred onto the recording material P (secondary transfer).

Next, the recording material P exits the secondary transfer nip area and reaches the fixing device 17, where it is heated and pressed to fix the unfixed toner image on the recording material P to form a permanent image. On the other hand, the secondary transfer residual toner remaining on the surface of the intermediate transfer belt 1 on which the secondary transfer of the toner image has been completed is removed by a cleaning blade 18 a such as urethane rubber of the belt cleaner 18. The removed toner is stored in the waste toner box 18b.

[0015]

However, a full-color image forming apparatus using the above-mentioned intermediate transfer member has the following disadvantages.

In order to secure the fixing property of thick paper and the transparency of OHT, the fixing speed may be reduced to, for example, 1/2 speed, 1/3 speed, 1/4 speed, etc. as compared with the case of ordinary plain paper. Generally done.

The process up to the primary transfer of the toner image to the intermediate transfer member is performed at a normal process speed, and the period from the end of the primary transfer until the leading end of the image reaches the secondary transfer nip area and the secondary transfer is performed. Then, the fixing speed is switched from the normal speed to the low speed.
At this time, if the intermediate transfer member is rotated once while the toner image is carried on the intermediate transfer member, the toner image on the intermediate transfer member comes into contact with the four photosensitive drums. When the toner image on the intermediate transfer member contacts the photosensitive drum, a phenomenon called retransfer occurs.

That is, when the toner image is carried on the intermediate transfer body and the photosensitive drum comes into contact with the toner image, a part of the toner image which must be completely held on the intermediate transfer body is partially exposed to light. It is taken to the drum. The phenomenon in which a part of the toner image primarily transferred onto the intermediate transfer member once is transferred to the photosensitive drum again is called retransfer. This is because, of the toner image on the intermediate transfer member, a portion (reverse toner, here, positive polarity) of a portion charged to the opposite polarity to the original charge polarity is electrostatically reversely transferred to the photosensitive drum, This is due to the mechanical adhesion between the photosensitive drum and the toner.

When the retransferred toner amount is large, the toner amount of the toner image finally transferred on the recording material is reduced, causing a problem such as a low image density. In an image forming apparatus having a plurality of first image bearing members (photoconductors) and a second image bearing member (intermediate transfer member) as shown in FIG. The problem is more serious because the amount of retransfer increases as compared with an image forming apparatus having a single first image carrier and a second image carrier due to contact with the photoconductor.

If it is necessary to spin the intermediate transfer member once when the fixing speed is switched to a low speed, the printing speed is reduced by the time of the idling.

An object of the present invention is to provide an image forming apparatus having a plurality of image carriers along the rotation direction of an intermediate transfer member and capable of switching the speeds of the intermediate transfer member and a fixing device. An object of the present invention is to provide an image forming apparatus capable of increasing the speed and suppressing image defects.

[0022]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
A plurality of rotating image carriers on which toner images of different colors are formed, and the plurality of image carriers on which the toner images on the plurality of image carriers are primarily transferred at a plurality of primary transfer positions Pt1. On the other hand, after the intermediate transfer member that rotates endlessly and the toner image on the intermediate transfer member are secondarily transferred to the recording material at the secondary transfer position Pt2, the recording material is conveyed at the fixing position Pfix on the recording material. And a fixing unit for fixing the toner image. The speed of the intermediate transfer body is switchable between a first speed and a second speed lower than the first speed, and the speed of the fixing unit is set to a third speed. Speed, and can be switched to a fourth speed, which is lower than this, and when the toner image on the intermediate transfer body is transferred to a recording material when the speed of the intermediate transfer body is the first speed, The fixing unit fixes at a third speed, and the speed of the intermediate transfer body is set at a second speed. When the toner image on the intermediate transfer member is transferred to the recording material when the time, the fixing means 4
An image forming apparatus for fixing at a speed of
The distance L in the moving direction of the intermediate transfer member from the primary transfer position Pt1d, which is the most downstream in the moving direction of the intermediate transfer member, of the next transfer position Pt1 to the secondary transfer position Pt2.
t1-t2 and the length Limg of the toner image on the intermediate transfer member in the moving direction of the intermediate transfer member have a relationship of Lt1-t2> Limg, and the secondary transfer position in the recording material conveyance direction. Distance L from Pt2 to the fixing position Pfix
t2-fix and a length Limg of the toner image on the intermediate transfer member in the moving direction of the intermediate transfer member have a relationship of Lt2-fix <Limg, and the intermediate transfer member from the image carrier is After the primary transfer of the toner image to the intermediate transfer member is completed, and before the toner image on the intermediate transfer member reaches the secondary transfer position Pt2, the toner image on the intermediate transfer member is transferred to the primary transfer position Pt1. Wherein the speed of the intermediate transfer body can be switched from the first speed to the second speed without passing the intermediate transfer member.

According to another aspect of the present invention, an image can be formed at an arbitrary position on the intermediate transfer member, and
A distance Lt2-t1 in the moving direction of the intermediate transfer member from the next transfer position Pt2 to the most upstream primary transfer position Pt1a in the moving direction of the intermediate transfer member among the plurality of primary transfer positions Pt1; It has a relationship of t1 <Limg. According to still another aspect, an image can be formed at a plurality of arbitrary positions on the intermediate transfer body, and the intermediate transfer body has a member or a structure for timing image formation. The distance Ltop on the intermediate transfer member and the primary transfer position Pt1 that is the most upstream in the moving direction of the intermediate transfer member among the plurality of primary transfer positions from the secondary transfer position Pt2 in the recording material conveyance direction.
distance Lt2 in the moving direction of the intermediate transfer member up to a
-t1 and the length Limg of the toner image on the intermediate transfer member in the moving direction of the intermediate transfer member have a relationship of Ltop>Limg-Lt2-t1> 0.

[0024]

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

Embodiment 1 FIG. 1 is a schematic view showing a main part of an embodiment of the image forming apparatus of the present invention.

Since the mechanical structure of the image forming apparatus of this embodiment is the same as that of the conventional image forming apparatus shown in FIG. 6, in FIG. 1, the driving roller 1a, the separating roller 1b and the supporting roller 1c The intermediate transfer belt 1 wrapped around a book roller, and the photosensitive drums 11a, 11b, 11c, 11d corresponding to the respective colors of yellow, magenta, cyan, and black, and 2 further arranged along the intermediate transfer belt 1. Only the next transfer roller 3 and the fixing device 17 are illustrated, and other devices are omitted.

In this embodiment, the distance Lt1-t2 between the primary transfer nip Pt1d and the secondary transfer nip Pt2 of the final color on the intermediate transfer belt 1 is determined by the distance Lt1-t2 along the recording material conveyance path. From transfer nip Pt2 to fixing nip P
The distance Lt2-fix to the fix and the maximum size Limg of the image in the moving direction of the intermediate transfer belt 1 have the following relationship: Lt1-t2> Limg (1) Limg> Lt2-fix (2) ing.

The image forming process in this embodiment will be described. FIG. 2 shows an image forming sequence at that time.

First, as shown in FIG. 2, toner images of the first to fourth colors are primary-transferred onto the intermediate transfer belt 1 in the same manner as in the prior art, and four-color toner images are formed on the intermediate transfer belt. Form. In the present embodiment, since the relationship represented by the expression (1) is satisfied, the leading end of the image on the intermediate transfer belt 1 is located before the secondary transfer nip when the primary transfer of the fourth color is completed. Therefore, at this point, if the process speed of the intermediate transfer belt 1 and the fixing device 17 is switched from the normal speed to the low speed, the intermediate transfer belt 1 is not rotated once with the toner image on, and the secondary transfer is performed at the low process speed. Transfer and fixing can be performed.

When the intermediate transfer belt 1 and the fixing device 17 are switched to the low process speed, the recording material P is fed from a paper feeding device (not shown) to the secondary transfer nip in accordance with the low process speed. Transfer is performed, and then fixing is performed.

As a result, a larger amount of heat can be applied to the recording material P than in the case of a normal process speed.
It is possible to obtain insufficient fixability of thick paper and transparency of OHT at a normal speed.

As a comparative example, FIG. 3 shows a case where the distance Lt2-fix between the secondary transfer nip Pt2 and the fixing nip Pfix is longer than the maximum sheet passing size of the apparatus. 3, the same reference numerals as those shown in FIG. 1 indicate the same elements.

In the case of FIG. 3, when fixing is performed at a low process speed, the speed of the recording material existing between the secondary transfer nip Pt2 and the fixing nip Pfix after the secondary transfer may be adjusted to the fixing speed. This leads to an increase in the size of the device.

In the present embodiment, the apparatus has the distance relationship of the above-mentioned formula (2), so that the apparatus can be downsized. Further, since it has the distance relationship of the above-described formula (1), the intermediate transfer belt 1 When the process speed of the fixing device 17 is switched from the normal speed to the low speed, there is no need to make a single idle rotation while the toner image is carried on the intermediate transfer belt, and therefore, it is possible to suppress the occurrence of problems such as low image density due to retransfer.

Embodiment 2 This embodiment is different from Embodiment 1 shown in FIG. 1 in that the leading end position of the image carried on the intermediate transfer belt 1 can be located at any position on the intermediate transfer belt. . This is because, in the present embodiment, there is no flag or the like for setting the image forming timing on the intermediate transfer body.
Therefore, the timing to start image formation for each color is
It is controlled by a clock device (not shown) and an image forming timing control device (not shown).

In this embodiment, the primary transfer nip Pt1 of the final color on the intermediate transfer belt 1 in FIG.
d to the secondary transfer nip Pt2 along the intermediate transfer belt, Lt1-t2, and the distance L from the secondary transfer nip Pt2 to the fixing nip Pfix along the conveyance path of the recording material P.
t2-fix, the distance Lt2-t1 from the secondary transfer nip Pt2 on the intermediate transfer belt to the primary transfer nip Pt1a for the first color, and the maximum image size Limg in the moving direction on the intermediate transfer belt are Lt1-t2> Limg (1) Limg> Lt2-fix (2) Lt2-t1 <Limg (3)

FIG. 4 shows an image forming process in this embodiment.
The sequence will be described. FIG. 4 shows a case where the image of the maximum size is formed for two pages in the present embodiment.

First, as shown in FIG. 4, toner images of the first to fourth colors are primary-transferred onto the intermediate transfer belt 1 in the same manner as in the related art, and four-color toner images are formed on the intermediate transfer belt. Form. In the present embodiment, since the relationship represented by the expression (1) is satisfied, the leading end of the image on the intermediate transfer belt 1 is located before the secondary transfer nip when the primary transfer of the fourth color is completed. At this point, the process speed of the intermediate transfer belt 1 and the fixing device 17 is switched from the normal speed to a low speed, and the secondary transfer and fixing are performed at a low process speed without idling the intermediate transfer belt 1 once with the toner image on. Can be performed.

When the intermediate transfer belt 1 and the fixing device 17 are switched to the low process speed, the recording material P is fed from a paper feeding device (not shown) to the secondary transfer nip in accordance with the low process speed. Transfer and then fix.

As a result, a larger amount of heat can be applied to the recording material than in the case of a normal process speed, so that the fixability of thick paper and the permeability of OHT which are insufficient at the normal speed can be obtained.

The intermediate transfer belt 1 after the completion of the secondary transfer is cleaned by a belt cleaner 18, and preparation for the primary transfer of the next image formation is made. In this embodiment, since an image can be formed at an arbitrary position on the intermediate transfer belt 1, the process speed is returned to the normal speed immediately after the completion of the secondary transfer at a low speed, and the process proceeds to the next image formation.

In this embodiment, since the distance relationship of the above formula (1) is satisfied, the toner image is carried on the intermediate transfer belt when the process speed of the intermediate transfer belt 1 and the fixing device 17 is switched from the normal speed to the low speed. It is not necessary to make a single idle rotation while keeping the state, and it is possible to suppress the occurrence of problems such as low image density due to retransfer.

Further, since the leading edge of the image can be set at an arbitrary position on the intermediate transfer belt 1, the expression (2) and the expression (3) can be set.
By taking the distance relationship of the formula, the process speed of the intermediate transfer member can be switched from the low speed to the normal speed as soon as the secondary transfer is completed, and the next image forming process can be performed, while achieving the miniaturization of the apparatus. In addition, it is possible to prevent a decrease in printing speed.

Embodiment 3 FIG. 5 shows an image forming sequence in this embodiment.

In the present embodiment, in the embodiment 1 shown in FIG. 1, flags for taking the image forming timing are positioned at a plurality of positions on the intermediate transfer belt 1 at equal intervals, and are carried on the intermediate transfer belt 1. The leading end positions of the images to be copied are located at a plurality of specific places on the intermediate transfer belt at equal intervals.

In this embodiment, the timing of detecting the flag is used as a reference of the image forming timing, so that the registration of the images of the respective colors is matched. Assuming that the interval between the flags on the intermediate transfer belt, which is a reference for these image forming timings, is Ltop, the distance Lt1-t2 from the primary transfer nip of the final color on the intermediate transfer belt to the secondary transfer nip, and the conveyance of the recording material 2 in the road
Distance Lt2-fi from next transfer nip to fixing nip
x, distance Lt2-t1 from the secondary transfer nip on the intermediate transfer belt to the primary transfer nip of the first color, maximum size Limg in the moving direction of the image on the intermediate transfer belt
Lt1-t2>Limg> Lt2-fix (4) Ltop>Lmg-Lt2-t1> 0 (5) (Equation (4) is the above equation (4) Same as the combination of 1) and (2)).

FIG. 5 shows an image forming process in this embodiment.
The image forming sequence will be described.

First, as shown in FIG. 5, the toner images of the first to fourth colors are primarily transferred onto the intermediate transfer belt 1 in the same manner as in the prior art, and the four color toner images are formed on the intermediate transfer belt. Form. In the present embodiment, from the distance relationship of Expression (4), 4
At the end of the primary transfer of the color, the leading end of the image on the intermediate transfer belt 1 is in front of the secondary transfer nip. At this point, the process speed of the intermediate transfer drum 1 and the fixing device 17 is reduced to the normal speed. To low speed, thereby making it possible to perform secondary transfer and fixing at a low process speed without idling the intermediate transfer belt 1 once with the toner image on.

When the intermediate transfer belt 1 and the fixing device 17 are switched to a low process speed, the recording material P is fed from a paper feeding device (not shown) to the secondary transfer nip in accordance with the low process speed. Transfer and then fix.

Thus, a larger amount of heat is applied to the recording material than in the case of the normal process speed, so that the fixability of the thick paper and the OHT transparency that are insufficient at the normal speed can be obtained.

The intermediate transfer belt 1 after the completion of the secondary transfer is cleaned by the belt cleaner 18, and preparations for the primary transfer of the next image formation are made. In this embodiment, the leading edge of the image can be set at a plurality of positions on the intermediate transfer belt 1 and has the distance relationship of the above formula (5), so that the flag interval Lt
A lower bound on op is given. Therefore, it is only necessary to dispose a minimum necessary flag on the intermediate transfer belt, thereby achieving cost reduction.

As described above, according to the present embodiment, since the distance relationship of the above formula (4) is obtained, when the process speed of the intermediate transfer belt 1 and the fixing device 17 is switched from the normal speed to the low speed, There is no need to make one idle rotation while the toner image is carried on the transfer belt, and it is possible to suppress the occurrence of problems such as low image density due to retransfer. Further, since the distance relationship represented by the expression (5) is provided, it is only necessary to provide a necessary minimum flag on the intermediate transfer member, and the cost can be reduced.

[0053]

As described above, according to the present invention,
Of the plurality of primary transfer positions Pt1 formed by the intermediate transfer member and the plurality of image carriers arranged along the movement direction, the primary transfer position P that is the most downstream in the movement direction of the intermediate transfer member
The distance Lt1-t2 in the moving direction of the intermediate transfer member from t1d to the secondary transfer position Pt2, the distance Lt2-fix from the secondary transfer position Pt2 in the transport direction of the recording material to the fixing position Pfix, and the distance on the intermediate transfer member With respect to the length Limg of the toner image in the moving direction of the intermediate transfer member, Lt
1-t2> Limg and Lt2-fix <Limg, and after the primary transfer of the toner image from the image carrier to the intermediate transfer member is completed, the toner image on the intermediate transfer member is Before reaching the transfer position Pt2, the speed of the intermediate transfer body and the fixing device is switched to a low speed to perform the secondary transfer and the fixing, so that the apparatus can be reduced in size and speed, and image defects can be suppressed. it can.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of an image forming apparatus of the present invention.

FIG. 2 is a diagram showing an image forming sequence in the image forming apparatus of FIG.

FIG. 3 is a schematic configuration diagram of an image forming apparatus of a comparative example with respect to the image forming apparatus of FIG. 1;

FIG. 4 is a diagram showing an image forming sequence according to another embodiment of the present invention.

FIG. 5 is a diagram showing an image forming sequence according to still another embodiment of the present invention.

FIG. 6 is a schematic diagram illustrating a conventional image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Intermediate transfer belt 1a Drive roller 1b Separation roller 1c Support roller 3 Secondary transfer roller 11a-11d Photosensitive drum 12a-12d Charge roller 15a-15d Primary transfer roller 17 Fixing device P Recording material

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kenichi Iida 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H027 DA38 EB04 EC20 ED16 ED24 ED25 EE02 EE03 EE04 EE07 EF09 2H030 AA06 AB02 AD05 AD17 BB02 BB23 BB42 BB44 BB53 2H032 AA05 BA09 BA19 BA21 BA23 CA13 2H033 AA21 BA08 BB01 BB28 BB37 CA36 CA40

Claims (3)

[Claims] 1. A plurality of rotating image carriers on which toner images of different colors are formed, and the plurality of toner images on the plurality of image carriers are primarily transferred at a plurality of primary transfer positions Pt1. And the toner image on the intermediate transfer member is secondarily transferred to the recording material at a secondary transfer position Pt2, and then the recording material is conveyed at a fixing position Pfix. A fixing unit for fixing the toner image on the recording material while switching the speed of the intermediate transfer body between a first speed and a second speed lower than the first speed. The speed can be switched between a third speed and a fourth speed, which is lower than the third speed.
When the toner image on the intermediate transfer body is transferred to the recording material at the speed of the second speed, the fixing unit fixes the toner image at the third speed, and when the speed of the intermediate transfer body is the second speed, When the toner image on the intermediate transfer member is transferred onto a recording material, the fixing unit fixes the toner image at a fourth speed, and the moving of the intermediate transfer member among the plurality of primary transfer positions Pt1 The distance Lt1-t2 in the moving direction of the intermediate transfer member from the primary transfer position Pt1d at the most downstream direction to the secondary transfer position Pt2, and the distance Lt1-t2 of the toner image on the intermediate transfer member in the moving direction of the intermediate transfer member. Length Limg
Has a relationship of Lt1-t2> Limg, and a distance L from the secondary transfer position Pt2 to the fixing position Pfix in the recording material conveyance direction.
t2-fix and a length Limg of the toner image on the intermediate transfer member in the moving direction of the intermediate transfer member have a relationship of Lt2-fix <Limg, and the intermediate transfer member from the image carrier is After the primary transfer of the toner image to the intermediate transfer member is completed, and before the toner image on the intermediate transfer member reaches the secondary transfer position Pt2, the toner image on the intermediate transfer member is transferred to the primary transfer position Pt1. An image forming apparatus capable of switching the speed of the intermediate transfer member from the first speed to the second speed without passing the intermediate transfer member. 2. An image can be formed at an arbitrary position on the intermediate transfer member, and is the most upstream in the moving direction of the intermediate transfer member from the secondary transfer position Pt2 to the primary transfer positions Pt1. 2. The image forming apparatus according to claim 1, wherein a relationship Lt2-t1 <Limg in a moving direction of the intermediate transfer member to the primary transfer position Pt1a is satisfied. 3. An intermediate transfer member capable of forming an image at a plurality of arbitrary positions on the intermediate transfer member, and having a member or a structure for timing image formation on the intermediate transfer member. The upper interval Ltop and the intermediate transfer from the secondary transfer position Pt2 in the conveying direction of the recording material to the primary transfer position Pt1a which is the most upstream in the moving direction of the intermediate transfer member among the plurality of primary transfer positions. The distance Lt2-t1 in the body movement direction and the length L of the toner image on the intermediate transfer body in the movement direction of the intermediate transfer body
The image forming apparatus according to claim 1, wherein img has a relationship of Ltop>Lmg−Lt2-t1> 0.