JP2003156948A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the lives of a transfer carrier, image carrier, etc., and to reduce damage to the transfer carrier caused by heat from a heat fixing unit during an image non-formation period (a stand-by period), by further controlling the device of the transfer carrier during the image non-formation period. SOLUTION: The image forming apparatus that performs image formation by transferring toner images formed on image carriers 222a onto recording material S via the transfer carrier 216 is provided with a driving part M1 capable of driving the transfer carrier 216 at a number of driving speeds. The image forming device is also provided with a drive control means Ca which, without stopping the transfer carrier 216 even during the image non-formation period, drives the transfer carrier 216 continuously at a low speed selected from the driving speeds.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention transfers a toner image formed on an image carrier to a recording material via a transfer carrier.
The present invention relates to an image forming apparatus such as a digital color copying machine that forms an image by fixing a toner image on a recording material with a heat fixing device.

[0002]

2. Description of the Related Art Conventionally, as a so-called electrophotographic image forming apparatus, an image carrier for transferring a toner image onto a sheet and a thermal fixing device for thermally fixing the toner image transferred onto the sheet are provided on a transfer belt or the like. There is known a structure in which the transfer carrier is arranged close to the transfer carrier.

In the electrophotographic system, a direct transfer system in which a toner image formed on an image carrier is directly transferred onto a sheet adsorbed on the transfer carrier, or a transfer image is once transferred onto the transfer carrier. There is an intermediate transfer system in which the formed image is re-transferred onto a conveyed recording material, and then the image is fixed on a sheet by a heating type fixing device.

Among the transfer methods, in the former method, in which the toner image formed on the image carrier is directly transferred to the paper adsorbed on the transfer carrier, the transfer carrier is the next step of transferring the paper. The transfer carrier is arranged in close proximity to the thermal fixing device so that it also functions as a transporting device that transports the thermal fixing device.

Further, in recent years, the size of the image forming apparatus itself has been reduced, and in order to effectively utilize the space in the apparatus, the components arranged in the apparatus are often arranged close to each other. As a result, the thermal fixing device and the transfer carrier tend to be close to each other.

Further, when a transfer belt is used as the transfer carrier, in response to the downsizing of the image forming apparatus, the driving and driven rollers for tensioning the transfer belt are reduced in diameter, which leads to The radius of curvature of the transfer belt portion in contact with the driving and driven rollers is becoming smaller.

Therefore, in the conventional driving method in which the driving of the transfer belt is stopped during non-image formation (standby) when no image is formed, the transfer belt in contact with the driving and driven rollers during the non-image formation. It is easy to get a habit on the part.

Moreover, since the thermal fixing device is disposed in the vicinity of the transfer belt, the ambient temperature of the transfer belt is 20%.
It rises by about 40 ° C. As a result, heat is radiated from the heat fixing device, which causes damage to the part of the transfer belt (the part that has stopped facing the heat fixing device) to make it easier to get a habit. There is a problem that an abnormality or an image transfer abnormality from the image carrier is likely to occur.

In particular, when a transfer belt is used as the transfer carrier and is stretched around a roller, it is frequently exposed to high temperature for a long time as the outer diameter of the roller is reduced. Therefore, the above-mentioned problems are easily caused.

As a countermeasure against the curl caused by heat from the heat fixing device, an image forming apparatus is disclosed in Japanese Patent Application Laid-Open No. 4-29277, in which the transfer carrier is controlled to be driven continuously or intermittently during non-image formation. It is described in the official gazette.

[0011]

However, according to the method disclosed in Japanese Patent Laid-Open No. 4-29277, when the transfer carrier is driven during non-image formation, driving the transfer carrier shortens the service life of the transfer carrier. New problems arise.

In particular, the intermittent driving operation is the most severe condition for the mechanism, and by repeating the complete stop state and the driving state, the transfer carrier and the cleaning member in contact with the transfer carrier, Causes a significant decrease in the service life of the bearing portion of the holding member holding the transfer carrier.

Further, in the image forming apparatus described in the above publication, since the transfer carrier and the image carrier are in contact with each other, when the transfer carrier is driven and the image carrier is not driven, the image carrier Is partially worn, which causes uneven image quality. If the transfer carrier and the image carrier are driven in order to avoid partial abrasion of the image carrier, the service life of the image carrier is also shortened.

In addition, in recent years when energy saving is called for,
It is uneconomical to consume a large amount of energy due to an unnecessary operation during non-image formation, and it may be a cause of noise due to operation noise or the like.

Therefore, in the present invention, the drive of the transfer carrier during non-image formation is further controlled to prolong the life of the transfer carrier, the image carrier, etc., and at the time of non-image formation (standby). An object of the present invention is to provide an image forming apparatus capable of reducing thermal damage to a transfer carrier from a thermal fixing device.

[0016]

To achieve the above object, the present invention has the following constitution. That is, the present invention is
In an image forming apparatus for forming an image by transferring a toner image formed on an image carrier to a recording material via the transfer carrier, a drive unit capable of driving the transfer carrier at a plurality of driving speeds, It is characterized by having a drive control means for continuously driving at a lower speed of the plurality of drive speeds during non-image formation.

According to the above arrangement, the transfer carrier can be driven at a lower speed (slower speed) during non-image formation (standby), so that the power consumption required for driving them can be reduced. In addition, the noise level during non-image formation (standby) can be reduced.

Further, since the transfer carrier is continuously driven at a low speed, damage to the transfer carrier due to heat from the heat fixing device is hardly caused while the service life of the transfer carrier or the image carrier is shortened. Can be reduced or prevented.

During non-image formation, it is preferable that the drive control unit drives the transfer carrier at a speed lower than the drive speed during image formation.

It is preferable to provide a separation / contact state changing means for relatively moving the transfer carrier and the image carrier so as to change the separation / contact state between the transfer carrier and the image carrier.

In this case, the transfer carrier is arranged so as to face the plurality of image carriers, and by the contact / separation state changing means,
When the transfer carrier and each image carrier are moved relative to each other so that the number of contact of the image carrier with the transfer carrier is the same as that in the image forming mode having the smallest number, the transfer carrier during non-image formation and It is possible to further reduce power consumption and drive noise that accompany the driving of the image carrier.

In the above description, the separating / contacting state changing means relatively keeps the transfer carrier and each image carrier so that all the image carriers and the transfer carrier do not come into contact with each other during non-image formation. It may be configured to move.

That is, during non-image formation (standby),
Since all the image bearing members and the transfer bearing members are separated from each other, the transfer bearing members can be driven independently and all the image bearing members can be stationary. As a result, the service life of the image carrier is not shortened, and electric power for driving the image carrier is not required,
Therefore, the driving noise can also be reduced.

Further, a plurality of image forming stations having an image carrier may be arranged side by side in a tandem type.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic front view showing the overall configuration of the image forming apparatus according to the first embodiment. In this embodiment, the image stations Pa to P are used.
A tandem type digital color copying machine A having d will be described as an example of an image forming apparatus.

A digital color copying machine (hereinafter, simply referred to as a copying machine) A has an original table 111 and a replacement panel (not shown) arranged on the upper surface of the copying machine main body 1, and the inside thereof. Image reading unit 110, image forming unit 21
0 and the paper feed mechanism 211 are built in.

On the document table 111, a double-sided automatic document feeder (RADF; Reversing Automatic Document Feeder) 1
12 are equipped.

The double-sided automatic document feeder 112 includes a document table 1
11 located on the upper surface of the document table 111.
It is supported so as to be openable and closable while maintaining a predetermined positional relationship with the upper surface.

This double-sided automatic document feeder 112
Double-sided conveyance (not shown) and front / back reversal are drive-controlled in relation to the operation of the entire copying machine A. Specifically, the following operations 1 to 3 are performed. The document is conveyed so that one side surface thereof faces the image reading unit 110 at a predetermined position on the document table 111. After the image reading on one side of the document is completed, the document is inverted so that the other side faces the image reading unit 110 at a predetermined position of the document table 111. The inverted document is conveyed toward the document table 111, and after the image reading on both side surfaces of the document is completed, the document is ejected.

The image reading unit 110 includes the document table 111.
The first and second scanning units 113 and 114, which form a document scanning body that reciprocates in parallel along the lower surface of the optical axis, and the optical lens 1.
15, and CCD line sensor 11 which is a photoelectric conversion element
6 and is arranged below the document table 111 so that the image of the document fed onto the document table 111 by the double-sided automatic document feeder 112 can be read.

The first scanning unit 113 has an exposure lamp (not shown) for exposing the image surface of the original document, and a first mirror 113a for deflecting the reflected light image from the original document in a predetermined direction. That is, it reciprocates in parallel with the lower surface of the document table 111 at a predetermined scanning speed while maintaining a constant distance.

The second scanning unit 114 further includes a second mirror 114a and a third mirror 114a for further deflecting the reflected light image from the document deflected by the first mirror 113a of the first scanning unit 113 in a predetermined direction. 114b, and is configured to reciprocate in parallel with the first scanning unit 113 while maintaining a constant speed relationship.

The optical lens 115 reduces the reflected light image from the document deflected by the third mirror 114b of the second scanning unit 114, and forms the reduced light image at a predetermined position on the CCD line sensor 116. It is what makes me.

The CCD line sensor 116 sequentially photoelectrically converts the formed light image and outputs it as an electric signal. It reads a black-and-white image or a color image, and R (red), G (green), This is a three-line color CCD that can output line data that is separated into B (blue) color components. The document image information converted into an electric signal by the CCD line sensor 116 is further transferred to an image processing unit (not shown) and subjected to predetermined image data processing.

Next, the paper feeding mechanism 211 and the image forming section 21.
The configuration of 0 will be described. The paper feed mechanism 211 is disposed below the image forming unit 210. The paper feed mechanism 211 includes a paper feed cassette 231 that stacks and stores cut sheet-shaped paper S, which is a recording material, and one paper feed cassette 231 from the paper feed cassette 231. The sheet S fed out one by one is provided with registration rollers 212, 212 that feed the sheet S toward the image forming unit 210.

The image forming section 210 has image stations Pa to Pd as a pair above the transfer / transport mechanism 213 for receiving the sheet S fed from the sheet feeding mechanism 211.
A thermal fixing device 217 is arranged close to the end of the transfer / transport mechanism 213.

The transfer / conveyance mechanism 213 has a driving roller 214 arranged on the same horizontal plane with a required space therebetween.
A transfer conveyance belt 216, which is a transfer carrier for electrostatically adsorbing and conveying the sheet S, is stretched between the driven roller 215 and the driven roller 215. Reference numeral 230 denotes a cleaning member for removing the toner adhering to the transfer / transport belt 216, which is a contact type cleaning blade system made of polyurethane or the like.

The transfer / conveying belt 216 is formed by the driving roller 21.
1 is frictionally driven in a direction indicated by an arrow Z in FIG.
Are sequentially conveyed to the image forming stations Pa to Pd whose details will be described later.

As shown in FIG. 2, the upper surface of the upper portion of the transfer / conveying belt 216 has image stations Pa to Pd.
Is in contact with the photoconductor drums 222a to 222d, which are image bearing members, and the transfer lower surface for transferring the developed toner image on the photoconductor drums 222a to 222d onto the sheet S is formed on the lower surface of the upper portion. The electric appliances 225a to 225d are
The photosensitive drums 222a to 222d are arranged so as to face each other.

The transfer / transport belt 216 is made of polycarbonate (PC) or polyvinylidene fluoride (PV).
DF), ethylene tetrafluoroethylene polymer (ET
FE), polytetrafluoroethylene polymer (PTF
E), polyimide, polyamide or the like can be used, and in the present embodiment, a PC having a thickness of 100 μm is used. Note that, generally, a film having a thickness of 80 to 150 μm can be used.

In the present embodiment, the outer diameter of the driving roller 214 is about 14 to 30 mm, so that the main body 1 of the copying machine can be easily miniaturized. I have to.

Next, the image stations Pa to Pd will be described. The image stations Pa to Pd have substantially the same configuration as each other, and they are provided above the photoconductor drums 222a to 222d which are rotationally driven in the direction of arrow F shown in FIG.
d are arranged, and they are juxtaposed with each other with a predetermined space therebetween.

Around the photosensitive drums 222a to 222d, chargers 223a to 223d for uniformly charging the photosensitive drums 222a to 222d, respectively, and electrostatic latent elements formed on the photosensitive drums 222a to 222d. Developing devices 224a to 224d for developing images, the transfer dischargers 225a to 225d, and the photoconductor drum 222, respectively.
Cleaning devices 226a to 226d for removing the toner remaining on the photosensitive drums 222a to 222d,
They are sequentially arranged along the rotation direction of a to 222d.

Laser beam scanner unit 227a ...
227d is a semiconductor laser element (not shown) that emits dot light modulated according to image data, a polygon mirror (deflecting device) 240d for deflecting the laser beam from this semiconductor laser element in the main scanning direction, F for forming an image of the laser beam deflected by the polygon mirror 240d on the surfaces of the photoconductor drums 222a to 222d.
It is composed of eight lenses 241d and mirrors 242d and 243d.

The laser beam scanner 227a includes
A pixel signal corresponding to a black component image of a color original image, a pixel signal corresponding to a cyan color component image of a color original image, a laser beam scanner 2
A pixel signal corresponding to the magenta color component image of the color original image is input to 27c, and a pixel signal corresponding to the yellow color component image of the color original image is input to the laser beam scanner 227d.

As a result, an electrostatic latent image corresponding to the color-converted original image information is formed on each of the photosensitive drums 222a to 222d. The developing device 224a contains black toner, the developing device 224b contains cyan toner, the developing device 224c contains magenta toner, and the developing device 224d contains yellow toner. The electrostatic latent images on the body drums 222a to 222d are developed with the toners of the respective colors. As a result, the document image information color-converted by the image forming unit 210 is reproduced as a toner image of each color.

Between the first image forming station Pa and the transfer / transport belt 216 of the transfer / transport mechanism 213, a suction (brush) charger 22 for electrostatically attracting the paper S is provided.
8 are provided.

The adsorbing charger 228 charges the surface of the transfer / conveying belt 216 so that the paper S can be surely adsorbed onto the transfer belt 216.

Therefore, the sheet S fed from the sheet feeding mechanism 211 is passed between the first image forming station Pa and the fourth image forming station Pd while being surely adsorbed on the transfer / conveying belt 216. It can be transported without displacement.

Between the fourth image station Pd and a thermal fixing device 217, which will be described later, and just above the driving roller 214, the sheet S electrostatically adsorbed thereto is transferred from the transfer / conveying belt 216. A static eliminator 229 to which an alternating current for separating is applied is provided.

A thermal fixing device 217 for fixing the toner image transferred and formed on the paper S on the paper S is disposed on the downstream side (left side in the drawing) of the transfer belt transport mechanism 213. The heat fixing device 217 includes a pair of upper and lower heating rollers 24.
1 and a pressure roller 242.

The temperature of the heating roller 241 is based on the temperature detected by a temperature detector such as a thermistor provided in contact with the heating roller 241, on the heater lamp provided inside the heating roller 241, and the pressure roller. It is controlled by energizing under a heater lamp provided in 242.
In this embodiment, the heater lamps are provided on the upper and lower heating / pressurizing rollers, but they may be provided on either one. Generally, it is often provided on a roller that comes into contact with an unfixed image.

During non-image formation (standby), 650 W above the heater lamp and 450 W below the heater lamp are ON / OFF.
The temperature of the heating roller 241 is controlled and kept at 180 ° C.

At the time of image formation, the heater lamp 850 to 850
ON / OFF control is performed at 950 W, and power is not supplied to the bottom of the heater lamp. The temperature during image formation is the same as that during standby 180
It is controlled to ℃.

The temperature of the end portion (a) of the transfer / conveying belt 216 adjacent to the thermal fixing device 217 is approximately 20 to 40 ° C. higher than the temperature outside the image forming apparatus. This temperature may differ from the above value depending on the degree of clogging of each unit inside the image forming apparatus. However, if the space inside the image forming apparatus does not have enough space, the temperature may become higher.

Although the amount of temperature rise is not so high, the shape bent to a large curvature can be maintained at a relatively high temperature for a long time, so that the end portion (a) of the transfer / conveying belt 216 is liable to be bent. I will follow you.

A pair of fixing rollers 24 of the heat fixing device 217.
The sheet S that has passed through the nip portion between the first and second rollers 242 passes through the conveyance direction switching gate 218, and then discharge rollers 219,
The paper is discharged onto a paper discharge tray 220 attached to the outer wall of the copying machine main body 1 by 219.

The switching gate 218 is used for the sheet S after fixing.
Is selectively switched between a path for discharging the sheet S to the copying machine main body 1 and a path for re-feeding the sheet S toward the image forming unit 210.

The sheet S whose conveyance direction has been switched again toward the image forming section 210 by the switching gate 218 is turned upside down through the switchback conveyance path 221, and then supplied again to the image forming section 210. It has become so.

Next, the electric system will be described. The drive roller 214 has a motor М1 and photosensitive drums 222a to 222a.
Motors М2 to 5 are connected to 2d, and the motors M1 to 5 are connected to the control unit C. The motor М1 is a drive unit that can drive the transfer conveyance belt 216, which is a transfer carrier, at a plurality of drive speeds.

The control section C has a function (drive control means Ca) of continuously driving at a lower speed of the plurality of driving speeds without stopping the driving of the transfer / conveying belt 216 even during non-image formation. ing.

Specifically, the transfer / conveying belt 216 is driven at different speeds during image formation and during non-image formation, and more specifically, during non-image formation, it is driven at a speed lower than the drive speed during image formation. ing.

In the present embodiment, for example, when the driving speed of the transfer / conveying belt 216 at the time of image formation differs between the color image formation and the monochrome image formation, and the driving speed at the time of color image formation is set to be slower. By driving the transfer / conveying belt 216 at the driving speed at the time of forming a color image during non-image formation (standby), it is possible to prevent the transfer / conveying belt 216 from getting blunt at both ends.

As described above, if the driving roller 214 is driven continuously and at a slower speed, the power consumption required for driving can be reduced, and the life of the transfer / conveying belt 216, the cleaning member 230, the bearing portion of the driving roller 214, etc. can be reduced. It is possible to reduce the influence on the drive noise while suppressing the drive noise during standby.

Further, the photosensitive drums 222a to 222d contacting the transfer / conveying belt 216 during non-image formation (standby).
Also needs to be rotated at the same speed, so that the lower the rotation speed is set, the less the influence on the life of the photoconductor drums 222a to 222d can be reduced, and the consumption consumed for driving the photoconductor drums 222a to 222d. Electric power and noise generation can also be reduced.

By the way, for example, in a black-and-white copier, even when the drive speed setting of the transfer / conveying belt 216 at the time of image formation is only one, the speed lower than this drive speed (for example, the drive speed at the time of image formation is 1 / 2-1 to 1/1
The transfer / conveying belt 216 may be driven at the time of non-image formation (standby) at a speed of about 0). The speed slower than the driving speed at the time of image formation can be arbitrarily set depending on the load of the entire drive system and the type and characteristics of the motor, and is not limited to the above speed.

Even when there are a plurality of drive speed settings during image formation, the transfer / conveying belt 216 is driven during non-image formation (standby) at a drive speed slower than the slowest drive speed among them. be able to.

Even in the above case, the transfer conveyance belt 216 at the time of non-image formation (standby) is driven at a drive speed of about 1/2 to 1/10 of the drive speed at the time of image formation as described above.
The drive speed is preferably set to, and it is most preferable to drive at the slowest speed at which continuous driving is possible and the speed at which the output consumed for driving is the lowest.

Generally, the transfer / transport belt 2 at the time of image formation
Since the driving speed of 16 is several 10 to 200 mm / sec,
When the speed is set to 1/10, the drive speed during standby is several meters
It is set to m / sec to 20 mm / sec.

With this setting, the driving roller 214 is driven at a slower driving speed while maintaining the effect of preventing the end portion (a) of the transfer / conveying belt 216 from being blunted. The power consumption can be further reduced, the influence of the transfer conveyor belt 216, the cleaning member 230, the photoconductor drums 222a to 222d, the bearing portions of the drive roller 214, etc., on the service life can be further reduced, and the drive noise during standby can be further reduced.

The operation of the digital color copying machine A having the above structure will be described. The paper S is the paper feed cassette 2
When the paper S is sent out from the paper 31 and fed into the guide of the paper feed transport path of the paper feed mechanism 211, the leading edge of the paper S is detected by a sensor (not shown), and based on the detection signal output from this sensor. A pair of registration rollers 212,
It is temporarily stopped by 212.

Then, the paper S is fed onto the transfer / conveying belt 216 rotating in the direction of arrow Z in FIG. 1 while keeping timing with the image stations Pa to Pd. At this time, since the transfer / conveying belt 216 is charged by the adsorption charger 228 as described above,
The sheet S fed to the transfer / conveying belt 216 is stably conveyed and supplied without being displaced while passing through the image stations Pa to Pd.

In each of the image stations Pa to Pd, a toner image of each color is formed and superposed on the supporting surface of the sheet S which is electrostatically attracted by the transfer and transport belt 216 and is transported.

When the transfer of the image by the fourth image station Pd is completed, the paper S is sequentially transferred from the leading end thereof.
It is peeled off from the transfer / conveying belt 216 by the static eliminator 229 and guided to the thermal fixing device 217. Then, the paper S on which the toner image is fixed is discharged onto the paper discharge tray 220 from a paper discharge port (not shown).

The sheet S having an image formed on one side thereof is re-supplied and conveyed to the image forming section 210 at the same timing as the image formation of the image forming section 210.

Next, the image forming section according to the first modification will be described with reference to FIGS. FIG. 3 is a schematic side view showing an operation state during image formation, and FIG. 4 is a schematic side view showing an operation state during non-image formation. The same components as those described with reference to FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the image forming section according to the first modification, the structure of the transfer / transport mechanism 213A is mainly different, and therefore the transfer / transport mechanism 213A will be mainly described here. Two
57 is a support frame, which is composed of a horizontally long movable support base 251 and a horizontally long fixed support base 252.

At the upper edge of the movable support base 251, the transfer discharger 225 is provided so as to face the photosensitive drums 222b to 222d.
b to 225d are arranged, a drive roller 214 is pivotally supported at the outer end portion, and a holding roller 255 is pivotally supported at the inner edge upper edge portion side.

A horizontally elongated slot 251a for an eccentric shaft is formed in a substantially middle portion of the movable support 251. The eccentric shaft slot 251a is provided with a motor M6 forming a separation / contact drive unit 253. An eccentric pin 256, which is convexly provided on the drive shaft, is inserted.

At the upper edge of the fixed support 252, a transfer discharger 225a is arranged so as to face the photosensitive drum 222a, and a driven roller 215 is pivotally supported at the outer end.

The movable support base 251 is arranged with respect to the fixed support base 252 with the holding roller 255 as the center, and the photosensitive members 222b to 222b.
An abutting position (B) (shown in FIG. 3) at which the transfer / transport belt 216 contacts the 222d, and a spaced position (C) at which the transfer / transport belt 216 is separated from the photoconductors 222b to 222d (FIG. 4).
(Shown in FIG. 4) is pivotally supported so as to be rockable. It should be noted that the swinging of the movable support base 251 is performed by controlling the drive of the motor М6.

Next, the electric system will be described. The drive roller 251 has a motor М1 and photoconductor drums 222a to 222a.
The motors М2 to М5 are respectively connected to 2d, and the motors M1 to М5 and the motor М described above.
6 is connected to the control unit C. The motor М1 is a drive unit that can drive the transfer conveyance belt 216, which is a transfer carrier, at a plurality of drive speeds.

The control section C has the following functions. It has a function (drive control unit Ca) of continuously driving at a lower speed of the plurality of driving speeds without stopping the driving of the transfer / conveying belt 216 even during non-image formation. The specific example of the driving speed is the same as that described in the first embodiment.

Transfer conveyance belt 21 which is a transfer carrier
6, a function of relatively moving the transfer / conveying belt 216 and the photoconductor drums 222a to 222d so as to change the contact / separation state between the image carrier 6 and the photoconductor drum 222 (separation / contact state changing unit Cb).

In this embodiment, the movable support 251 is oscillated by the motor М6 to change the contact / separation state between the transfer / transport belt 216 and the photosensitive drums 222a to 222d. It is as follows.

<During color image formation> Separation / contact state changing means C
b, the transfer support belt 21 is provided on the movable support base 251 to the photoconductors 222b to 222d around the holding roller 255.
6 is moved to the contact position (B) (shown in FIG. 3) where it contacts.

<Non-image formation (standby)> The separation / contact state changing means Cb mounts the movable supporting base 251 on the photosensitive drum 222.
Only “a” and the transfer discharger 225a are brought into contact with each other, and the transfer conveyer belt 216 is moved away from the photoconductors 222b to 222d to a separated position (C) (shown in FIG. 4).

That is, by appropriately rotating the motor M6 by a control signal from the control unit C which is the contact / separation state changing means Cb, the movable support base 251 is vertically moved about the holding roller 255 by a predetermined angle. The movable support base 251 is reciprocally moved between the contact position (b) and the separation position (c).

The photosensitive drums 222b to 222d separated from the transfer / transport belt 216 are the photosensitive drums 22a to 222d.
The motors M3 to 5 connected to 2b to 222d are stopped, and the motor M2 is controlled by the control unit C so that the driving speed at the time of color image formation is slower than the driving speed at the time of monochrome image formation. In this case, the driving speed may be slower than the driving speed for forming the color image.

By the way, the state where only the photoconductor drum 222a and the transfer discharger 225a are in contact with each other is usually a state in which a black-and-white image is formed, but during non-image formation (standby).
Moreover, by setting the operating state, it is possible to minimize the number of the photoconductor drum and the transfer discharger that are in contact with each other.

According to the image forming section 213A according to the first modified example described in detail above, it is possible to avoid the shortening of the life of the transfer / transport belt 216, which is a transfer carrier, and at the same time, it is required to drive the photosensitive drum and the like. Power consumption can be minimized.

Further, the photosensitive drums 222b to 222d,
Since the image stations Pb to Pd including the transfer dischargers 225b to 225d are stopped, the lifespans of the photosensitive drums 222b to 222d are hardly reduced, and the image including the photosensitive drum 222a and the transfer discharger 225a is not reduced. It is possible to avoid shortening the life of the station Pa.

Next, an image forming section according to the second modification will be described with reference to FIGS. FIG. 5 is a schematic side view showing an operation state during image formation, and FIG. 6 is a schematic side view showing an operation state during non-image formation. The same components as those described in the image forming unit 210 shown in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the image forming section according to the second modification, the structure of the transfer / transport mechanism 213B is mainly different, and therefore the transfer / transport mechanism 213B will be mainly described here. 261
Is a horizontal rectangular support base, and transfer dischargers 225a to 225d are installed on the upper edge of the support base 261 so as to face the photoconductor drums 222a to 222d, and are arranged at both ends. A transfer / transport belt 216, which is a transfer carrier that electrostatically attracts and transports the sheet S, is stretched between the driven roller 214 and the driven roller 215.

A separation / contact drive mechanism section D is disposed below the support base 261. The separation / contact drive mechanism unit D has a fulcrum 266.
a and 267a are swingably supported, and
Support arm 26 having rollers 268, 269 disposed at the upper end
6 and 267, a connecting rod 265 is laid horizontally, and an eccentric cam 264 is attached to the motor M6 at one end of the connecting rod 265.
Is provided with a drive unit 262 to which is attached,
The lower edge of the support 261 is brought into contact with and supported by the rollers 268 and 269.

Next, the electric system will be described. The drive roller 214 has a motor М1 and photosensitive drums 222a to 222a.
The motors М2 to М5 are connected to 2d, and the motors M1 to М5 and the motor М6 are connected to the control unit C. The motor М1 is a drive unit that can drive the transfer conveyance belt 216, which is a transfer carrier, at a plurality of drive speeds.

The control section C has the following functions. It has a function (drive control means Ca) of continuously driving at a lower speed of a plurality of driving speeds without stopping the driving of the transfer / conveying belt 216 even during non-image formation.
Note that a specific example of the driving speed is the same as that described in the first embodiment.

Transfer conveyance belt 21 which is a transfer carrier
6, a function of relatively moving the transfer / conveying belt 216 and the photoconductor drums 222a to 222d so as to change the contact / separation state between the image carrier 6 and the photoconductor drum 222 (separation / contact state changing unit Cb).

In this embodiment, the separation / contact drive mechanism section D is used.
By moving the support base 261 up and down, the contact / separation state between the transfer / conveying belt 216 and the photoconductor drums 222a to 222d is changed, which is specifically as follows.

When the motor M6 of the drive unit 262 is rotationally driven, the drive causes the eccentric cam 264 to rotate, and the connecting rod 365 moves left and right according to the rotation.

When the connecting rod 365 is moved to the left and right, the support arms 266 and 267 swing around the fulcrums 266a and 267a, and the support 261 moves up / down according to this swing.

That is, when the support base 261 moves up, the photoconductor drums 222a to 222d come into contact with the transfer / transport belt 216, and conversely, when the support base 261 moves down, the photoconductor drums 222a to 222d and the transfer / transport belt 216 are contacted.
And are separated.

<At the time of image formation> As shown in FIG. 5, by controlling the motor M6 by the control unit C, the eccentric cam 264 is appropriately rotated to move the support base 261 upward, whereby the transfer / conveyance belt is moved. 216 and the photoconductor drums 222a to 222d are brought into contact with each other.

<Non-image formation (standby)> As shown in FIG. 6, the control unit C controls the motor M6 to rotate the eccentric cam 264 as appropriate to move the support base 261 downward. Causes each photosensitive drum 222a
˜222d and the transfer / transport belt 216 are separated from each other.

At the time of non-image formation (standby), the photosensitive drum 2 is in the lowered state as shown in FIG.
The motors M2 to 5 connected to the drive rollers 214a to 222d are stopped by the control of the controller C.
Is controlled so that the driving speed for forming a color image is slower than the driving speed for forming a monochrome image. Of course, control may be performed to make the driving speed slower.

As described above, the life of the transfer / conveyance belt 216 is not shortened, and the power consumption for driving is small. Further, the photosensitive drums 222a to 222d,
Since the image forming stations Pa to Pd including the transfer dischargers 225a to 225d are stopped, it is possible to prevent the image forming stations Pa to Pd from being short-lived and to minimize the driving noise during standby. .

Next, an image forming section according to the third modification will be described with reference to FIG. FIG. 7 is a schematic side view showing an operation state of an image forming unit having a single image forming station.

In the above description, the tandem type having a plurality of image forming stations Pa to Pd has been described, but in the present modification, an image forming section having a single image forming station will be described as an example.

Reference numeral 270 denotes a laterally rectangular movable support base, and a transfer discharger 225e is arranged at the upper edge of the movable support base 270, slightly toward the one end from the center and facing the photosensitive drum 222e. Between the driving roller 214 and the driven roller 215, which are provided at both ends,
A transfer / transport belt 216, which is a transfer carrier that electrostatically attracts and transports the paper S, is stretched. Incidentally, 271 is a tension roller.

The movable supporting base 270 mounts the transfer discharger 225 on the photosensitive drum 22 by a vertically moving mechanism (not shown).
2 and the image forming position (d) where the drive roller 214 contacts the sheet S, and the non-image forming position where the transfer discharger 225 is separated from the photosensitive drum 222 and the drive roller 214 is separated from the sheet S. (E) And the driven roller 2
It is supported so that it can be vertically swung about 15.

Next, the electric system will be described. The drive roller 214 includes a motor М1 which is a drive unit and a movable support base 27.
0 is connected to the motor М2, and the photosensitive drum 222e is connected to the motor М3.
1 to М3 are connected to the control unit C.

The control section C has the following functions. It has a function (drive control means Ca) of continuously driving at a lower speed of a plurality of driving speeds without stopping the driving of the transfer / conveying belt 216 even during non-image formation.
Note that a specific example of the driving speed is the same as that described in the first embodiment.

Transfer conveyance belt 21 which is a transfer carrier.
6, a function of relatively moving the transfer / conveying belt 216 and the photosensitive drum 222e so as to change the separated state of the photosensitive drum 222e as the image carrier (separation state changing means Cb) In the above, as described above, the movable support base 270 is oscillated and displaced in the vertical direction, and specifically, the following is performed.

<At the time of image formation> At the time of image formation, the movable support base 270 is pivotally displaced to the image formation position (d) so that the photosensitive drum 222e and the transfer / conveying belt 216 are brought into contact with each other as shown by the solid line. .

<Non-image forming> Non-image forming (standby)
Moves the movable supporting base 270 to the non-image forming position (e) by swinging to move the photosensitive drum 222 and the transfer / conveying belt 216 away from each other.

By controlling the motor М2 from the control section C, the photosensitive drum 222e is stopped and the drive roller 214 is controlled so that the drive speed becomes slower than the drive speed of the transfer / transport belt 216 at the time of image formation.

As described above, the power consumption consumed for driving is reduced without shortening the life of the transfer / transport belt 216. Further, since the photosensitive drum 222e is stopped, the life of the image forming station including the photosensitive drum 222e is not shortened, and the drive noise during standby can be minimized.

Next, an image forming section according to the fourth modification will be described with reference to FIG. FIG. 8 is a schematic side view showing an operation state of an image forming unit having a single image forming station.

The photosensitive drum 2 is located at the upper edge portion of a horizontal rectangular fixed support base (not shown), and slightly toward the one end from the center.
A transfer discharger 225e is arranged so as to be movable up and down so as to face 22e. Further, a drive roller 214 and a driven roller 215 are arranged at both ends of the fixed support base, and a transfer carrier for electrostatically adsorbing and conveying the paper S between the drive roller 214 and the driven roller 215. The transfer and transport belt 216 is stretched. Incidentally, 271 is a tension roller.

The transfer discharger 225e is supported by a vertical movement mechanism portion (not shown), and the transfer discharger 2 is provided.
The image forming position (d) 'where 25e contacts the photoconductor drum 222e, and the transfer discharger 225 is set to the photoconductor drum 222.
It is possible to move to a non-image forming position (e) 'which is separated from e.

Next, the electric system will be described. The drive roller 214 is connected to a motor М1 which is a drive section, the vertical movement mechanism section is connected to a motor М2 which drives the motor М2, and the photosensitive drum 222e is connected to a motor М3. It is connected to the control unit C.

The control section C has the following functions. It has a function (drive control means Ca) of continuously driving at a lower speed of a plurality of driving speeds without stopping the driving of the transfer / conveying belt 216 even during non-image formation.
Note that a specific example of the driving speed is the same as that described in the first embodiment.

Transfer conveyance belt 21 which is a transfer carrier
6, a function of relatively moving the transfer / conveying belt 216 and the photosensitive drum 222e so as to change the separated state of the photosensitive drum 222e as the image carrier (separation state changing means Cb) In the transfer discharger 225e
Since only one is moved up and down, a relatively simple structure can be achieved.

The operation of the image forming section is as follows. <At the time of image formation> At the time of image formation, the transfer discharger 225e
Is positioned at the image forming position (d) ', the photosensitive drum 222e and the transfer / conveying belt 216 are brought into contact with each other as shown by the solid line. At this time, the transfer discharger 22 is more than the tangent line that is in contact with the driving roller 214 and the driven roller 215.
5 and the contact point between the photosensitive drum 222 and the photosensitive drum 222 project upward.

<Non-image forming> Non-image forming (standby)
Moves the transfer discharger 225e downward with respect to the photoconductor drum 222e by positioning the transfer discharger 225e at the non-image forming position (e) '. This allows
The upper end of the transfer discharger 225e is below the tangent line that is in contact with the driving roller 214 and the driven roller 215, and the photosensitive drum 222 and the transfer / conveying belt 216 are separated from each other.

By controlling the motor М3 from the control section C, the photosensitive drum 222e is stopped and the drive roller 214 is controlled so that the drive speed becomes slower than the drive speed of the transfer / conveying belt 216 at the time of image formation. To do.

As described above, the life of the transfer / conveyance belt 216 is not shortened and the power consumption for driving is small. Further, since the photosensitive drum 222e is stopped, the life of the image forming station including the photosensitive drum 222e is not shortened, and the drive noise during standby can be minimized.

Next, the image forming apparatus of the present invention according to the second embodiment will be described. FIG. 9 is a schematic front view showing the overall configuration of the image forming apparatus according to the second embodiment, and FIG.
FIG. 4 is a schematic block diagram centering on a transfer conveyance mechanism and a secondary transfer conveyance mechanism for explaining an electric system.

In this embodiment, the double-sided automatic document feeder 112 and the image reading section 110 are the same as those described in FIGS.
The same reference numerals are given to them and the description thereof will be omitted.
The transfer / transport mechanism 313 and the paper feed mechanism 311 will be described.

In the first embodiment or the first to fourth modified examples, the image formed on the photosensitive drum while adhering the sheet S to the transfer / conveying belt 216 is transferred to the sheet S.
However, the image forming apparatus according to the present embodiment is a method in which an image is temporarily transferred onto an intermediate transfer belt and then retransferred to a sheet that is conveyed (hereinafter, the intermediate transfer method. That is).

The sheet feeding mechanism 311 is disposed below the transfer / conveyance mechanism 313, and it includes a sheet feeding cassette 312 for stacking and storing cut sheet-like sheets S, and one sheet from each sheet feeding cassette 312. Registration rollers 311a for feeding the delivered paper S toward the image forming unit 310,
311a and is comprised.

The transport transfer mechanism 313 comprises an intermediate transfer transport mechanism 321 and a secondary transfer transport mechanism 320, and is arranged above the paper feed mechanism 311. Intermediate transfer transport mechanism 3
Reference numeral 21 denotes a driving roller 314, a driven roller 315, and the driving rollers 31 arranged at both ends of a support base (not shown).
4. The intermediate transfer belt 316 is stretched around a backup roller 317 arranged below the intermediate portion of the driven roller 315.

The intermediate transfer belt 316 is driven by the drive roller 31.
4, the frictional drive is performed in the arrow Z direction shown in FIGS. A cleaning member 330 removes the toner remaining on the intermediate transfer belt 316, and is a cleaning blade type contact type such as polyurethane.

The secondary transfer / conveyance mechanism 320 includes a drive roller 319, which is arranged below the backup roller 317 and closely adjacent thereto, and a driven roller 321 which is arranged outside the driven roller 315, and a secondary transfer / conveyance belt 318. The secondary transfer / conveyance mechanism 320 has a structure in which
A fixing device 217 having the same structure as that described above for fixing the toner image re-transferred and formed on the sheet S to the sheet S is disposed on the side (downstream side) of the sheet.

The driven roller 315 and the driven roller 3 which support the intermediate transfer belt 316 and the secondary transfer conveyance belt 318.
The outer diameter of 21 is about 14 mm to 30 mm in this embodiment.

The intermediate transfer belt 316 and the secondary transfer / transport belt 318 are made of polycarbonate (PC), polyvinylidene fluoride (PVDF), ethylene tetrafluoroethylene polymer (ETFE), polytetra as in the transfer / transport belt 216. Fluoroethylene polymer (P
TFE), polyimide, polyamide, thickness 80 ~ 15
Those of 0 μm are generally used. In this embodiment,
A PC with a thickness of 100 μm is used.

Above the transport transfer mechanism 313, in the vicinity of the intermediate transfer belt 316, the first image forming station Pa, the second image forming station Pb, and the third image forming station Pa having the same structure as those described above are provided. Similar to the above, the image forming station Pc and the fourth image forming station Pd are arranged in parallel in order from the upstream side of the paper transport path.

In each of the image stations Pa to Pd, a toner image of each color is formed and superposed on a predetermined position of the intermediate transfer belt 316. When the transfer of the image by the fourth image station Pd is completed, the toner image transferred onto the intermediate transfer belt 316 is transferred onto the paper S by the high voltage applied to the secondary transfer charging device 319 on the secondary transfer conveyance belt 318. Re-transferred to. The sheet S on which the image has been retransferred is guided to the fixing device 217 by the secondary transfer conveyance mechanism 320.

A pair of fixing rollers 24 of the fixing device 217.
The sheet S that has passed through the nip portion between the first and second sheets 242 is discharged onto the sheet discharge tray 220 attached to the outer wall of the copying machine body 301 by the discharge rollers 219 and 219. The switchback transport path 221 described above is not shown in FIG.

Next, the electric system will be described. The drive roller 314 has a motor М1 and photosensitive drums 222a to 22a.
Motors М2 to М5 are respectively connected to 2d, and each of the motors M1 to М5 is connected to the control unit C. The motor М1 is a drive unit capable of driving the intermediate transfer belt 316 and the secondary transfer conveyance belt 318, which are transfer carriers, at a plurality of drive speeds.

The controller C does not stop driving the intermediate transfer belt 316 and the secondary transfer conveyance belt 318 even during non-image formation, and continuously drives at a lower speed of the plurality of driving speeds (driving). It has a control means Ca).

Specifically, the intermediate transfer belts 316 and 2
The next transfer conveyance belt 318 is driven at different speeds during image formation and during non-image formation, more specifically, during non-image formation, at a speed lower than the drive speed during image formation.

In this embodiment, the driving speeds of the intermediate transfer belt 316 and the secondary transfer conveyance belt 318 during image formation are different during color image formation and self-image formation, and the driving speed during color image formation is slower. . Therefore, the drive speed of the intermediate transfer belt 316 and the secondary transfer conveyance belt 318 during non-image formation (standby) is set to the drive speed during color image formation. This prevents the both ends of the intermediate transfer belt 316 and the secondary transfer conveyance belt 318 from being entangled.

As described above, if the driving roller 214 is driven continuously and at a slower speed, the power consumption required for driving can be reduced, and the intermediate transfer belt 316 and the secondary transfer conveyance belt 318, the cleaning member 330 and the driving roller. It is possible to reduce the influence on the service life of the bearing portion or the like of 314 and to suppress the drive noise during standby.

Further, the photosensitive drums 222a to 222d contacting the intermediate transfer belt 316 during non-image formation (standby).
Also needs to be rotated at the same speed, so that the lower the rotation speed is set, the less the influence on the life of the photoconductor drums 222a to 222d can be reduced, and the consumption consumed for driving the photoconductor drums 222a to 222d. Electric power and noise generation can also be reduced.

By the way, for example, in a black-and-white copier, even when the drive speed setting of the transfer / conveying belt 216 is only one at the time of image formation, the speed lower than this drive speed (for example, 1 / the drive speed at the time of image formation). 2-1 / 1
The intermediate transfer belt 316 and the secondary transfer conveyance belt 318 at the time of non-image formation (standby) may be driven at a speed of about 0). The speed lower than the driving speed at the time of image formation can be arbitrarily set according to the load of the entire drive system and the type and characteristics of the drive motor, and is not limited to the above speed.

Even when there are a plurality of drive speed settings for image formation, the drive speed is slower than the slowest drive speed among them, and the intermediate transfer belt 316 is in standby.
Also, the secondary transfer conveyance belt 318 can be driven.

Even in the above case, the intermediate transfer belt 316 at the time of non-image formation (standby) is driven at a drive speed of about 1/2 to 1/10 of the drive speed at the time of image formation as described above.
It is preferable to set the drive speed of the secondary transfer conveyance belt 318, and it is most preferable to drive the secondary transfer conveyance belt 318 at the slowest speed that can be continuously driven and at the lowest drive power.

Generally, the intermediate transfer belt 31 during image formation
6 and the secondary transfer / conveyance belt 318 are driven at a speed of several tens.
Since the speed is 200 mm / sec, when the speed is set to 1/10, the drive speed during standby is set to several mm / sec to 20 mm / sec.

When set in this way, the intermediate transfer belt 316 and the secondary transfer conveyer belt 318 are driven at a slower driving speed while maintaining the effect of preventing the end portions (a) and (a) 'from being blunted. Since the roller 314 is driven,
The power consumption required for the driving is further reduced, and the influence of the intermediate transfer belt 316 and the secondary transfer conveyance belt 318, the cleaning member 330, the photoconductor drums 222a to 222d, and the bearing portion of the drive roller 314 on the service life is further reduced. In addition, drive noise during standby can be further reduced.

In the digital color copying machine A having the above-described structure, the paper S is fed and conveyed to the intermediate transfer belt 316 on which an image is formed at the same timing, and is conveyed from the intermediate transfer belt 316 by the secondary transfer roller 317. Images will be transferred.

The present invention is not limited to the above-described embodiment, but the following modifications can be made. The present invention is not limited to the above-described embodiments, and for example, each of the above-described embodiments may be applied to an image forming apparatus adopting an intermediate transfer system.

In the above description, an example is described in which the laser beam scanner units 227a to 227d scan and expose a laser beam to perform optical writing on the photosensitive member. However, instead of these laser beam scanner units, A writing optical system (LED head) including a light emitting diode array and an imaging lens array may be used.

That is, the LED head is smaller in size than the laser beam scanner unit and has no moving parts and is silent. Therefore, it is suitable for an image forming apparatus such as a tandem type digital color copying machine which requires a plurality of optical writing units.

[0155]

According to the inventions described in claims 1 to 6, a driving unit capable of driving the transfer carrier at a plurality of driving speeds and a driving unit which does not stop driving the transfer carrier even during non-image formation are provided. Since there is a drive control unit that continuously drives at a lower speed of a plurality of drive speeds, the transfer carrier is moved at a lower speed (slower speed) during non-image formation (standby). Since they can be driven, the power consumption required for driving them can be reduced, and the noise level during non-image formation (standby) can be reduced.

Further, since the transfer carrier is continuously driven at a low speed, damage to the transfer carrier due to heat from the heat fixing device is hardly caused and the service life of the transfer carrier and the image carrier is hardly reduced. Can be reduced or prevented. From the above, it is possible to prolong the life of the transfer carrier, the image carrier, and the like, and reduce the thermal damage that the transfer carrier receives from the fixing device during non-image formation (standby).

In addition to the common effects obtained by the inventions described in claims 1 to 6, according to the invention described in each claim, the following effects can be obtained. According to the third aspect of the invention, there is provided the contact / disconnection state changing means for relatively moving the transfer carrier and the image carrier so as to change the contact / contact state of the transfer carrier and the image carrier. Therefore, during image formation and during non-image formation,
The number of the transfer carrier and the image carrier that are in contact can be increased or decreased as necessary.

According to the invention described in claim 4, the transfer carrier is arranged so as to face the plurality of image carriers, and the contact / disconnection state changing means determines the number of contact of the image carrier with respect to the transfer carrier. Since the transfer carrier and each image carrier are moved relative to each other so that the number is the same as the smallest number of image forming modes,
The number of image carriers that come into contact with the transfer carrier can be minimized.

Further, since it is not necessary to drive the other image carrier which does not come into contact with the transfer carrier, the service life of the other image carrier which does not come into contact can be prevented from being shortened and the image carrier can be driven. It is possible to reduce the driving elastic noise by reducing the elastic consumption.

According to the fifth aspect of the present invention, the contact / separation state changing means prevents the contact between all the image bearing members and the transfer bearing members during non-image formation. Since the carrier is relatively moved, at the time of non-image formation, the transfer carrier can be driven independently and all the image carriers can be stationary. Therefore, the service life of the image carrier can be prevented from being shortened, and the driving noise can be reduced without requiring the output required for driving the image carrier.

[0161]

[Brief description of drawings]

FIG. 1 is a schematic front view showing the overall configuration of an image forming apparatus of the present invention according to a first embodiment.

FIG. 2 is a schematic block diagram centering on a transfer conveyance mechanism for explaining an electric system.

FIG. 3 is a schematic side view showing an operation state during image formation.

FIG. 4 is a schematic side view showing an operation state during non-image formation.

FIG. 5 is a schematic side view showing an operation state during image formation.

FIG. 6 is a schematic side view showing an operation state of an image forming unit having a single image forming station.

FIG. 7 is a schematic side view showing an operation state during image formation.

FIG. 8 is a schematic side view showing an operation state during non-image formation.

FIG. 9 is a schematic front view showing the overall configuration of an image forming apparatus of the present invention according to a second embodiment.

FIG. 10 is a schematic block diagram centering on a transfer conveyance mechanism and a secondary transfer conveyance mechanism for explaining an electric system.

[Explanation of symbols]

216 Transfer carrier belts 217 and 317 which are transfer carriers, thermal fixing devices 225a to 225d Image carrier A Digital color copying machine Ca as an example of an image forming apparatus Drive control means Cb Contact / contact state changing means М1 Motor Pa which is a drive unit ~ Pd Image forming station S Paper as recording material

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H027 DA32 DA34 ED24 EE03 EE04                 2H030 AA05 AB02 AD05 AD17 BB42                       BB44 BB53 BB63                 2H200 FA02 FA09 GA12 GA34 GA47                       GB22 GB25 HA02 HA12 HB12                       HB22 JA02 JB06 JB25 JB32                       JB42 JB45 JB49 JC03 JC07                       JC12 JC15 JC19 LB02 LB09                       LB13 MA04 MA20 PA10 PA11                       PA12 PA23

Claims (6)

[Claims] 1. An image forming apparatus for forming an image by transferring a toner image formed on an image carrier to a recording material via the transfer carrier, wherein the transfer carrier can be driven at a plurality of driving speeds. And a drive control means for continuously driving the transfer carrier at a lower speed of the plurality of drive speeds without stopping the transfer carrier even during non-image formation. Image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the drive control means drives the transfer carrier at a speed lower than a drive speed at the time of image formation during non-image formation. 3. A separation / contact state changing means for relatively moving the transfer carrier and the image carrier so as to change the separation / contact state of the transfer carrier and the image carrier. The image forming apparatus according to claim 1. 4. The transfer carrier is arranged so as to face the plurality of image carriers, and the separation / contact state changing means has the same number as the image forming mode in which the number of contact of the image carrier with the transfer carrier is the smallest. 4. The image forming apparatus according to claim 3, wherein the transfer carrier and each image carrier are moved relative to each other. 5. The separation / contact state changing means relatively moves the transfer carrier and each image carrier so that all the image carriers and the transfer carrier do not come into contact with each other during non-image formation. The image forming apparatus according to claim 3, wherein the image forming apparatus comprises: 6. The image forming apparatus according to claim 5, wherein a plurality of image forming stations each having an image bearing member are arranged side by side in a tandem type.