JP6019650B2 - Transfer device and image forming apparatus - Google Patents

Description

  The present invention relates to a transfer device and an image forming apparatus, and more particularly to a contact / separation mechanism of a transfer unit used in the transfer device.

  An image forming apparatus using an electrophotographic system includes an image forming unit capable of forming an image of a plurality of colors, and forms a superimposed image by sequentially transferring the color image formed in each image forming unit to a transfer body It has been known.

As a configuration for transferring each image corresponding to each image forming unit, there is a configuration using a belt wound around a plurality of rollers, and an image of a system in which the image forming units are juxtaposed along the belt's stretched surface. As a forming apparatus, there is a tandem image forming apparatus.
In the tandem image forming apparatus, apart from the method of sequentially transferring the transfer paper adsorbed on the belt, a primary transfer process of sequentially transferring each image onto the belt itself, and a superimposed image transferred onto the belt There is a method of executing a secondary transfer process in which a sheet is transferred onto a transfer sheet at once.

In the latter method using the secondary transfer process, a transfer nip is constituted by a belt and a secondary transfer roller which is a transfer means constituting a secondary transfer device arranged opposite to the belt. A configuration in which a superimposed image is transferred in the process of passing a transfer paper inside is often used.
Since the transfer nip is formed by the pressurizing action of the secondary transfer roller against the belt, the secondary transfer roller must always be in pressure contact with the belt.
However, maintaining the secondary transfer roller under constant pressure may cause deformation of the secondary transfer roller or contamination due to toner remaining on the belt side. Therefore, the secondary transfer roller is at least other than during transfer. 2 is made to contact and separate so that it can be separated from the belt.

By the way, when the secondary transfer roller is provided so as to be able to contact and separate from the belt, the operator needs to know that the secondary transfer process is impossible by detecting the state where the secondary transfer roller is separated from the belt. There is.
Therefore, conventionally, a configuration has been proposed in which the contact state of the secondary transfer roller is determined by detecting the light shielding state by an optical sensor using an actuator that is displaced according to the contact operation of the secondary transfer roller (for example, Patent Document 1).

  In Patent Document 1, a bias is applied to the belt side by a pressurizing unit, and a secondary transfer roller bearing that performs contact and separation operations according to the rotation of a cam is interlocked with a contact and separation operation of the secondary transfer roller bearings. And a link mechanism capable of swinging and a link mechanism for detecting passage of recording paper that can be interlocked with one link lever of the link mechanism and one of the swinging ends faces the optical sensor. Has been.

  In this configuration, by swinging the link lever of the recording paper passage detection link mechanism via the link mechanism that swings according to the contact / separation operation of the secondary transfer roller, the link lever is moved to the swing end side. The change in the light shielding state by the arranged optical sensor is used to determine the contact / separation state of the secondary transfer roller.

  In the configuration disclosed in Patent Document 1, the secondary transfer roller that makes contact with and separates from the belt has its own bearings provided at both ends in the axial direction. The structure which pressurizes a bearing is needed. In particular, since a coil spring is used as the pressurizing means, a space in the axial direction is required.

  However, in order to obtain a pressurizing force with a predetermined pressure at the secondary transfer roller, the length of the coil spring becomes longer, so the installation space along the axial direction of the spring becomes larger, which not only increases the size of the apparatus. If the required pressure cannot be obtained, there is a possibility that a deviation occurs in the pressure in the axial direction of the secondary transfer roller.

  On the other hand, since an optical sensor that operates via a plurality of link mechanisms is used to detect contact / separation of the secondary transfer roller, the operation of the link lever in the optical sensor is not effective unless the assembly accuracy of each link mechanism is increased. In addition to being stable, if the number of these link mechanisms increases and the cumulative error related to the amount of operation between the link mechanisms increases, the amount of swing at the link lever corresponding to the optical sensor must be increased. There is also a possibility that the load at the drive source for setting the swing amount also increases.

  An object of the present invention is to suppress an increase in installation space and an increase in driving force and to deviate in the applied pressure at the time of contact / separation in view of the problems in the above-described conventional transfer device, in particular, a structure including a contact / separation mechanism of the transfer means It is an object of the present invention to provide a transfer device and an image forming apparatus having a configuration capable of preventing the occurrence of the above-described problem.

In order to achieve this object, the present invention comprises transfer means used for transferring an image carried on an image carrier provided in a housing to a recording medium, and the transfer means is attached to the image carrier. In the transfer device provided so as to be able to come in contact with and separate from the image carrier, the structure in which the transfer unit is brought into contact with and separated from the image carrier has a pair of urging forces for urging the transfer unit toward the image carrier. And a contact / separation detection mechanism that engages with a part of the urging means and can be displaced according to the contact / separation of the transfer means. The contact / separation detection mechanism includes a longitudinal direction of the transfer means. And a detection lever that is capable of swinging along a portion of the biasing means, and is disposed to face the swing end of the detection lever, depending on the swing state of the swing end. A detection sensor capable of detecting a contact / separation state of the transfer unit, and the biasing unit includes the detection lever. Is disposed is set in the longitudinal direction parallel to the longitudinal direction of said transfer means and said detection sensor is disposed between the pair of biasing means in the longitudinal direction of the transfer unit, the detection lever, The transfer device swings around a support shaft provided in the vicinity of an end portion on the side far from the detection sensor, of both ends of the biasing unit on the detection lever side of the pair of biasing units. It is in.

According to the present invention, as the structure of the contact / separation detection mechanism of the transfer unit, the transfer unit is engaged with a part of the biasing unit that biases the image bearing member toward the image carrier, and swings along the longitudinal direction of the transfer unit. Since the movable detection lever is provided, it is possible to set the length of the biasing means corresponding to the pressure applied to the transfer means without increasing the bulk in the vicinity of the transfer means.
As a result, the space occupied by the contact / separation detection mechanism located in the vicinity of the transfer unit can be reduced, and the above-described increase in the space can be achieved even when the length of the biasing unit that affects the pressing force set in the biasing unit is increased. It can be set without incurring, and the deviation of the applied pressure in the transfer means can be eliminated.

1 is a schematic diagram for explaining an example of an image forming apparatus including a transfer device according to an embodiment of the present invention. FIG. 2 is a diagram for describing characteristics of toner used in the image forming apparatus illustrated in FIG. 1. It is a schematic diagram for demonstrating the contact-and-separation mechanism used for the principal part structure of the transfer apparatus concerning embodiment of this invention. It is a figure for demonstrating the principal part structure used for the transfer apparatus concerning embodiment of this invention. FIG. 2 is a schematic view corresponding to FIG. 1 for explaining another example of the image forming apparatus shown in FIG. 1. FIG. 2 is a schematic view corresponding to FIG. 1 for explaining another example of the image forming apparatus shown in FIG. 1.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
In the image forming apparatus 100 shown in FIG. 1, a belt 10 that is wound around a plurality of rollers 12 and 13 and whose extending surface moves in the direction of the arrow shown in the drawing is used as an image carrier, and the belt 10 extends along the extending surface. The image forming portions of different colors are juxtaposed and used as an intermediate transfer body to which toner images formed in the respective image forming portions are sequentially transferred (hereinafter, the belt is referred to as an intermediate transfer belt 10 for convenience).

  Each image forming unit is provided with photosensitive drums 1Y, 1M, 1C, and 1K (hereinafter, for convenience, omitting alphabets representing colors and using only numbers) as the image forming units. 1, charging devices 4 </ b> Y, 4 </ b> M, 4 </ b> C, 4 </ b> K for performing image forming processing, and writing devices (indicated by arrow lines indicating writing light for convenience) 5 </ b> Y, 5 </ b> M, 5 </ b> C, 5 </ b> K, and optical writing Are provided with developing devices 6Y, 6M, 6C, and 6K for visual processing of the electrostatic latent image formed by the toner, and cleaning devices 2Y, 2M, 2C, and 2K for cleaning the photosensitive drum 1 after transfer. ing.

  Transfer rollers 11Y, 11M, and 11C that perform primary transfer fixing for transferring the toner image carried on the photosensitive drum 1 to the intermediate transfer belt 10 are positioned at positions facing the photosensitive drum 1 with the intermediate transfer belt 10 interposed therebetween. , 11K are arranged. The transfer roller 11 is pressed against the intermediate transfer belt 10 by an urging force of an elastic body.

On the intermediate transfer belt 10, a secondary transfer roller 21 as a secondary transfer device is intermediately transferred to a position where a secondary transfer is performed in which images that are sequentially superimposed and transferred at each image forming unit are recorded and collectively transferred. It is arranged to face one of the rollers 12 around which the belt 10 is wound.
One of the rollers 12 in this case functions as a secondary transfer counter roller that faces the secondary transfer roller 21 and is used as a drive roller that interlocks with a drive motor (not shown). Therefore, in the description of this embodiment, the other roller 13 around which the intermediate transfer belt 10 is wound is referred to as a driven roller.

The intermediate transfer belt 10 is provided with a belt cleaning device 19 at a position after the batch transfer of superimposed images using the secondary transfer roller 21.
The belt cleaning device 19 is provided with a cleaning blade 20 made of urethane rubber so that residual toner on the intermediate transfer belt 10 can be dammed and scraped off.

  In the image forming apparatus 100 shown in FIG. 1, a lubricant 155 for reducing the surface friction resistance of the intermediate transfer belt 10 and improving the toner releasability at the position after passing the cleaning blade 19 of the belt cleaning device 19 is intermediate transferred. A lubricant application device is provided in combination with an application brush 152 that is applied to the belt 10. The lubricant will be described later.

The recording paper P fed from the paper feed cassette 25 arranged in the paper feeding device 31 by the feed roller 26 is conveyed to the secondary transfer position where the secondary transfer roller 21 is arranged. The recording paper P is conveyed toward the registration roller 28 by the conveyance roller 27 provided in the conveyance path to the secondary transfer position, and the registration timing is set by the registration roller 28 and then the recording paper P is fed toward the secondary transfer position. Is done.
The recording paper P that has passed the secondary transfer position is discharged to the outside by the paper discharge roller 32 after the toner image is fixed by the fixing device 30.
In FIG. 1, symbols PS1 and PS2 indicate bias power supplies for applying a bias necessary for transfer.

The characteristics of each member used in the image forming apparatus 100 having the above configuration are as follows.
The intermediate transfer belt 10 is composed of PVDF (vinylidene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate) or the like in a single layer or a plurality of layers, such as carbon black. The conductive material is dispersed, and the volume resistivity is adjusted to be in the range of 10 ^ 8 to 10 ^ 12 Ωcm, and the surface resistivity is adjusted to be in the range of 10 ^ 9 to 10 ^ 13 Ωcm.
If necessary, a release layer may be coated on the surface of the intermediate transfer belt 10. Materials used for the coating include ETFE (ethylene-tetrafluoroethylene copolymer), PTFE (polytetrafluoroethylene), PVDF (vinylidene fluoride), PEA (perfluoroalkoxy fluororesin), FEP (four-fluorocarbon). Fluorine resin such as ethylene fluoride-propylene hexafluoride copolymer) or PVF (vinyl fluoride) can be used, but is not limited thereto.
The method of manufacturing the intermediate transfer belt 10 includes a casting method, a centrifugal molding method, and the like, and the surface thereof may be polished if necessary.

  The intermediate transfer belt 10 configured as described above is moved by being driven by the driving roller 12 so that the process speed is adjusted to 150 mm / sec. In the movement process, the primary transfer process and the secondary transfer process are performed. Will be implemented.

The reason why the deposition resistivity of the intermediate transfer belt 10 is set in the above-described range is as follows.
If the volume resistivity of the intermediate transfer belt 10 exceeds the above-described range, the bias required for transfer increases, which increases the power supply cost. Further, since the charging potential of the intermediate transfer belt 10 becomes high and the self-discharge becomes difficult in the transfer process, the transfer paper peeling process, etc., it is necessary to provide a static eliminating means. Also, if the volume resistivity and surface resistivity are below the above ranges, the charge potential decays quickly, which is advantageous for static elimination by self-discharge, but toner scatter occurs because the current during transfer flows in the surface direction. End up.

For this reason, in this embodiment, the volume resistivity and the surface resistivity of the intermediate transfer belt 10 are set within the above-described ranges. The volume resistivity and the surface resistivity were measured by connecting an HRS probe (inner electrode diameter 5.9 mm, ring electrode inner diameter 11 mm) to a high resistivity meter (manufactured by Mitsubishi Chemical Corporation: Hiresta IP). A measured value 10 seconds after applying a voltage of 100 V (surface resistivity is 500 V) to the front and back of the film was used.
The transfer roller 11 used in the primary transfer process is set to +1800 V as a transfer bias for electrostatically transferring the toner image carried on the photosensitive drum 1 to the intermediate transfer belt 10.

On the other hand, the secondary transfer roller 21 that performs the secondary transfer process is provided with an elastic body such as urethane adjusted to a resistance value of 10 ^ 6 to 10 ^ 10Ω by a conductive material on a metal core such as SUS. It is comprised by covering. The reason why this resistance value range is set is as follows.
If the resistance value of the secondary transfer roller 21 exceeds the above range, it becomes difficult for current to flow. Therefore, a higher voltage must be applied in order to obtain a required transfer property, resulting in an increase in power supply cost. In addition, since a high voltage is applied, discharge occurs in the gaps before and after the transfer portion nip, so that white spots are lost due to the discharge on the halftone image.
On the contrary, if the resistance value of the secondary transfer roller 21 is below the above range, the transferability between the multi-color image portion (for example, three-color superimposed image) and the single-color image portion existing on the same image cannot be achieved.

This is because the resistance value of the secondary transfer roller 21 is low, so that a sufficient current flows to transfer the monochromatic image portion at a relatively low voltage. However, it is optimal for the monochromatic image portion to transfer the multicolor image portion. Since a voltage value higher than the voltage is required, setting a voltage that can transfer a plurality of color image portions causes an excessive transfer current in a single-color image, resulting in a reduction in transfer efficiency.
The resistance value of the secondary transfer roller 21 is measured by installing the secondary transfer roller 21 on a conductive metal plate and applying a load of 4.9 N on one side (total of 9.8 N on both sides) to both ends of the core metal. In this state, it was calculated from the value of the current flowing when a voltage of 1000 V was applied between the metal core and the metal plate. In the present embodiment, the secondary transfer is controlled with a constant current, and the set value is set to −30 μA.

The lubricant 155 used in the belt cleaning device 19 is a fatty acid metal salt having a linear hydrocarbon structure.
The fatty acid metal salt contains at least one fatty acid selected from stearic acid, palmitic acid, myristic acid and oleic acid, and at least one metal selected from zinc, aluminum, calcium, magnesium and lithium The fatty acid metal salt containing is mentioned. Among them, zinc stearate is the most preferable material in terms of cost, quality stability, and reliability because it is produced on an industrial scale and has been used in many fields.
However, the higher fatty acid metal salts that are generally used industrially are not the simple substance composition of the name, but include other fatty acid metal salts, metal oxides, and free fatty acids that are more or less similar. Fatty acid metal salts in form are no exception.

Next, the toner used in the image forming apparatus 100 according to the present embodiment will be described.
The toner used in this embodiment is a polymerized toner produced by a polymerization method.
Regarding the toner shape factors SF-1 and SF-2, SF-1 is set to 100 to 180, and SF-2 is set to 100 to 180.

2A and 2B are diagrams for explaining the shape factor of the toner. FIG. 2A is a schematic diagram of toner for explaining SF-1, and FIG. 2B is a schematic diagram of toner for explaining SF-2.
The shape factor SF-1 indicates the ratio of the roundness of the toner shape and is represented by the following formula (1). This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting the toner on a two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-1 = {(MXLNG) ² / AREA} × (100π / 4) (1)
When the value of SF-1 is 100, the shape of the toner becomes a true sphere, and becomes larger as the value of SF-1 increases.

The shape factor SF-2 indicates the ratio of the unevenness of the toner shape, and is represented by the following formula (2). A value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner on the two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-2 = {(PERI) ² / AREA} × (100 / 4π) (2)
When the value of SF-2 is 100, there is no unevenness on the toner surface, and as the value of SF-2 increases, the unevenness of the toner surface becomes more prominent.
Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.) and introducing it into an image analyzer (LUSEX3: manufactured by Nireco) for analysis. And calculated.

  When the shape of the toner is close to a spherical shape, the contact state between the toner and the toner or the toner and the photoconductor becomes a point contact, so that the adsorbing force between the toners becomes weak and the fluidity increases, and the toner and the photoconductor The attraction force becomes weaker and the transfer rate becomes higher. If either of the shape factors SF-1 and SF-2 exceeds 180, the transfer rate is lowered and the cleaning property when attached to the transfer means is also lowered, which is not preferable.

The toner particle size is preferably in the range of 4 to 10 μm in terms of volume average particle size. When the particle size is smaller than this, it becomes a cause of background stains at the time of development, fluidity is deteriorated, and further, aggregation tends to occur, so that voids are likely to occur.
On the other hand, when the particle size is larger than this, it is impossible to obtain a high-definition image due to toner scattering or resolution deterioration. In this embodiment, a toner having a volume average particle diameter of 6.5 μm is used.

The characteristics of the present embodiment will be described as follows with the above configuration as an object.
The feature of this embodiment is the installation structure of the contact / separation detection mechanism for detecting the contact / separation operation state of the secondary transfer roller 21, particularly the state where the secondary transfer roller 21 is separated.
FIG. 3 is a view for explaining the contact / separation detection mechanism of the secondary transfer roller 21 used as the secondary transfer device shown in FIG.
In FIG. 4, before explaining the contact / separation detection mechanism, the contact / separation drive mechanism of the secondary transfer roller 21 will be described in FIG.
The contact / separation drive mechanism is an eccentric member serving as an eccentric member on the rotation shaft 12A of the secondary transfer counter roller 12 on the drive side among the rollers positioned on the housing side of the image forming apparatus and on which the intermediate transfer belt 10 is wound. The cam 12B is integrated and can rotate.

  A roller-shaped cam follower 21A1 corresponding to a driven member integrated with the rotating shaft 21A of the secondary transfer roller 21 is provided on the peripheral surface of the eccentric cam 12B. Secondary transfer is performed according to the cam profile of the eccentric cam 12B. The roller 21 is brought into contact with and separated from the secondary transfer counter roller 12 side.

The eccentric cam 12B makes one rotation in response to one rotation of the secondary transfer opposing roller 12, and makes the maximum outer diameter portion of the cam profile face the cam follower 21A1 in accordance with the rotation.
Although the contact / separation operation of the secondary transfer roller 21 does not affect the toner image transfer from each image forming unit to the intermediate transfer belt 10, the secondary transfer roller 21 must be brought into contact with the secondary transfer roller 21 during the secondary transfer. For this reason, a cam profile that allows the above-described rollers to come into contact with each other when the secondary transfer is performed is set.
The time when the secondary transfer roller 21 is separated from the secondary transfer position, that is, the secondary transfer counter roller 12, is when the secondary transfer is not performed or when the conveyance path is exposed to the outside for jamming.

On the other hand, FIG. 3 is a diagram showing the configuration of the contact / separation detection mechanism according to the embodiment of the present invention, which shows a state viewed from the direction indicated by the arrow (3) in FIG. (A) is a state in which the secondary transfer roller 21 is in contact with the intermediate transfer belt 10 side.
In FIG. 3, the contact / separation detection mechanism is provided on an opening / closing door (not shown) that is opened when the conveyance path is exposed, and biasing means that biases the secondary transfer roller 21 toward the intermediate transfer belt 10. As a pair of elastic bodies 101 and 101 ′, a pair of detection levers 102 and 103 provided so as to be swingable along the longitudinal direction of the secondary transfer roller 21, that is, the axial direction, and one detection lever 101. And a detection sensor 104 disposed to face one of the swinging ends (the end portion indicated by reference numeral 102A1).

  In this embodiment, the elastic bodies 101 and 101 ′ used as the urging means are coil springs having an axial direction parallel to the axial direction of the secondary transfer roller 21, and one end in the axial direction is an opening / closing door. The other end in the axial direction is locked to the locking portion and to the rocking ends (indicated by reference numerals 102A and 103A for convenience) of the detection levers 102 and 103.

  The pair of detection levers 102 and 103 are provided so as to be able to perform seesaw movement along the axial direction of the secondary transfer roller 21 by the support shafts 101B and 102B, and one of the detection levers 102 is connected to the other detection lever 103. On the other hand, the swing radius from the support shaft 102B to the swing end 102A1 on the detection sensor 104 side is increased so that a large swing amount can be obtained even with a small swing angle.

The elastic bodies 100, 100 ′ and the detection levers 102, 103 are all arranged with the longitudinal direction parallel to the axial direction of the secondary transfer roller 21. In other words, the elastic bodies 100, 100 ′ and the detection levers 102, 103 are The axial direction is related to the direction perpendicular to the moving direction. As a result, when the urging force by the elastic bodies 100, 100 ′ is increased, the length in the axial direction may become long. In this case, however, it is necessary to expand the space in the contact / separation direction of the secondary transfer roller 21. do not do.
This also applies to the detection levers 102 and 103, and even if the swing radius of the detection lever is increased, it is not necessary to expand the space in the contact / separation direction of the secondary transfer roller 21.

As a result, the bulk along the contact / separation direction of the secondary transfer roller 21 is not increased.
Accordingly, the space occupied by the elastic bodies 100 and 100 ′ used to make the secondary transfer roller 21 contact and separate and the detection levers 102 and 103 interlocked with the contact and separation operation in the contact and separation direction of the secondary transfer roller 21. And the elastic force can be changed.
Thus, even when the elastic force of each elastic body 100.100 ′ is set to a value that can be equalized in the axial direction in the axial direction of the secondary transfer roller 21, it can be performed without causing an increase in space. A situation in which a deviation occurs in the pressure applied to the transfer roller 21 can be prevented.

The detection levers 102 and 103 are not both of the same shape and size. For the purpose of obtaining a swing amount in which one of the detection levers 102 can clearly distinguish between the light transmission and light shielding states of the detection sensor 104. Even when the swing radius is set large, it is not necessary to increase the occupied space in the contact / separation direction of the secondary transfer roller 21 so much.
The state of the detection levers 102 and 103 indicated by the two-dot chain line in FIG. 3B indicates that the secondary transfer roller 21 contacts the intermediate transfer belt 10 at the secondary transfer position as shown in FIG. The contact state is shown, and the state shown by the solid line shows the state where the secondary transfer roller 21 is separated from the intermediate transfer belt 10 side.

  In the above embodiment, since one detection lever 101 of the detection levers 102 and 103 interlocked with the elastic bodies 100 and 100 ′ used for the contact / separation detection mechanism is used as an actuator of the detection sensor 108, the number of parts is reduced. The number of occurrences of assembly errors can be reduced.

  In addition, since the installation directions of the elastic bodies 101 and 101 ′ and the detection levers 102 and 103 are along the axial direction of the secondary transfer roller 21, the bulk in the contact / separation direction of the secondary transfer roller 21 can be reduced. In addition to preventing an increase in the size of the structure, it is possible to set a necessary pressure force on the elastic body without causing an increase in space. As a result, it is possible to adjust the applied pressure in each of the elastic bodies 100 and 100 ′ without causing an increase in space, and to prevent a deviation from occurring in the applied pressure in the axial direction of the secondary transfer roller 21.

Next, a modification of the main part according to the embodiment of the present invention will be described.
In the image forming apparatus 100 according to the above-described embodiment, the intermediate transfer belt is used as an image carrier. However, the image forming apparatus illustrated in FIG. 6 is intended for a photoreceptor as a belt-like image carrier.
In FIG. 6, a photoreceptor using a belt (hereinafter referred to as a photoreceptor belt 10 ′ for convenience) has a stretched surface that is wound around rollers 12 and 13 and faces each image forming unit.
Each image forming unit is different from the configuration shown in FIG. 1 in that the photosensitive drum is not present, and other devices are installed as they are. Note that the position of the developing device 6 disposed in each image forming unit is shown in FIG. 1 so that the moving direction of the photosensitive belt 10 ′ is the same as that of the intermediate transfer belt 10 in the case shown in FIG. Unlike the case, the position is replaced by the corresponding position after optical writing.

In the image forming apparatus configured as described above, when an electrostatic latent image is formed by light writing on the photosensitive belt after charging in each image forming unit, the visible image processing is performed by the developing device 6, and the next image forming process is performed. The photosensitive belt 10 'moves toward the image portion, and an image of a new color is superimposed and formed.
When the photosensitive belt 10 ′ on which the toner images formed in the respective image forming portions are superimposed is moved to the secondary transfer position where the secondary transfer roller 21 is disposed, the photosensitive belt 10 ′ is supplied in the same manner as shown in FIG. The recording paper P fed from the paper device 31 is collectively transferred.

Next, further modifications of the main part according to the embodiment of the present invention will be described.
In the image forming apparatus shown in FIG. 7, the belt-like member is not used as an intermediate transfer member or a photosensitive member, but is used as a conveying member for the recording paper P.
That is, the belt-like member (referred to as a conveyor belt 1000 for the sake of convenience) is stretched over the rollers 12 and 13 and has a stretched surface facing each image forming unit, similarly to the configuration shown in FIGS. Yes.

The configuration of each image forming unit is the same as the configuration shown in FIG.
The transport belt 1000 has a function of transporting between the image forming units in a state where the recording paper P fed out from the paper feeding device 31 is electrostatically attracted.
Accordingly, the recording paper P conveyed by the conveying belt 1000 is conveyed toward the fixing device 30 in a state where the toner image transferred in each image forming unit is superimposed.

  In the image forming apparatus described above, since the images of the respective colors are superimposed and transferred in the conveyance process of the recording paper P, the fixing device 30 is arranged in the extending direction of the stretched surface of the conveyance belt 1000. In this configuration, unlike the case illustrated in FIG. 1, the bulk in the vertical direction can be reduced by providing the fixing device and the paper discharge unit on the extended surface of the conveyor belt 1000.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 10 Intermediate transfer belt 10 'Photosensitive belt 12 Secondary transfer opposing roller 100 Image forming apparatus 101, 101' Elastic body 102, 103 Detection lever 104 Detection sensor

JP 2004-264455 A

Claims (6)

A transfer means used for transferring an image carried on an image carrier provided inside the housing to a recording medium, and the transfer means provided so as to be able to contact and separate from the image carrier In the device
In the configuration in which the transfer unit is brought into contact with and separated from the image carrier, a pair of urging units that urge the transfer unit toward the image carrier and a part of the urging unit are engaged. A contact / separation detection mechanism that is displaceable according to the contact / separation of the transfer means,
The contact / separation detection mechanism includes a detection lever that is swingable along a longitudinal direction of the transfer unit and is in contact with a part of the biasing unit, and a swinging end of the detection lever. A detection sensor disposed and capable of detecting a contact / separation state of the transfer means according to a swinging state of the swinging end;
The biasing means is disposed with its longitudinal direction set in parallel with the detection lever along the longitudinal direction of the transfer means,
The detection sensor is disposed between the pair of biasing means in the longitudinal direction of the transfer means,
The detection lever swings around a support shaft provided in the vicinity of an end portion far from the detection sensor of both ends of the biasing means on the detection lever side of the pair of biasing means. Characteristic transfer device. The transfer apparatus according to claim 1, wherein
2. A transfer apparatus according to claim 1, wherein a coil spring is used as the biasing means, and an axial direction corresponding to the longitudinal direction thereof is parallel to the longitudinal direction of the image carrier. The transfer apparatus according to claim 1 or 2,
As the member for moving the transfer unit to and away from the image carrier, an eccentric member that can be linked to the drive unit of the image carrier and a driven member that is integrated with the transfer unit and contacts the eccentric member are used. A transfer device. An image forming apparatus using the transfer device according to claim 1,
An image forming apparatus, wherein a transfer body to which a toner image is transferred is used as the image carrier. An image forming apparatus using the transfer device according to claim 1,
An image forming apparatus, wherein a latent image carrier is used as the image carrier. The image forming apparatus according to claim 4 or 5,
An image forming apparatus, wherein the image carrier is a belt.

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