JPH10282805A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a device by composing a power feeding mechanism of a transferring unit with a simple constitution. SOLUTION: In this image forming device, a transferring roller 150 is connected with a power source for feeding the transfer electric current through a conductive bearing 168, a side plate 142, a conductive spring 176 and a transferring current terminal. Moreover, the driving roller 146, the driven roller 148 and the tension roller 152 is respectively ground-connected through the conductive bearing 168, the side plate 144, the conductive spring 176 and a lower frame 172.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly, to a method in which a toner image formed on a photosensitive drum is transferred to a recording medium by a transfer unit in accordance with image information, and the image is formed on the recording medium. The present invention relates to an electrophotographic image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, in an image recording apparatus for forming a color image by using an electrophotographic process, a multicolor toner image (cyan, magenta, yellow, black) is superposed on a photosensitive drum. And transfer and record the multicolor toner image onto a recording medium, for example, recording paper, disposed between the transfer / conveying belt and the photosensitive drum in a single transfer operation. In such an image recording apparatus, during development, the transfer conveyance belt is maintained at a position away from the photoconductor drum, and the transfer conveyance belt is moved to contact the photoconductor drum when recording on recording paper (for example, JP-A-3-18
No. 5474, JP-A-3-107180). In order to perform such an operation, the transfer conveyance belt is integrally formed as a transfer unit. Further, such a transfer unit further incorporates a cleaning device for the transfer conveyance belt.

For example, as shown in FIG. 7, such an image forming apparatus 300 is provided near a photosensitive drum 308 around which yellow, magenta and cyan developing units 302, 304 and 306 are provided. Transfer transfer belt 31
4 and a transfer device 316 are provided. The transfer conveyance belt 314 is wound around two rotation rollers 310 and 312, and the transfer device 316 is connected to the photosensitive drum 308.
Are arranged to face each other. A spring member 320 is attached to the transfer conveyance belt 314, and the transfer conveyance belt 3
It moves with the rotation of 14. The transfer conveyance belt 314 is urged toward the housing by a spring 318, and when the transfer conveyance belt 314 rotates, the spring member 320 contacts the photosensitive drum 308.
For this reason, in the image forming apparatus 300, when the recording paper is disposed between the photosensitive drum 308 and the transfer conveyance belt 314, the recording paper is moved by the spring member 320 to the photosensitive drum 3.
08, and when the transfer device 316 is driven at this time,
The image on the photosensitive drum 308 is transferred to a recording sheet. In the image forming apparatus 300, the transfer conveyance belt 3 is placed at an arbitrary position on the transfer conveyance belt 314.
A cleaning device for cleaning 14 can be attached.

[0004]

However, in such a transfer unit, a supply mechanism for directly supplying a transfer current from a power source to a transfer means such as a transfer roller or a transfer corotron, and an earth roller for grounding the current are provided. It is necessary to provide a grounding means such as a ground brush or a ground brush. Also,
When a cleaning device is provided, it is necessary to supply a current to the cleaning roller. For this reason, the transfer unit must surely perform the operation of approaching and separating from the photosensitive drum while constituting a power supply mechanism for three types of currents. If these power supply mechanisms are provided for each of the members of the transfer unit that performs the movement operation, the transfer unit becomes complicated and large, and the image forming apparatus becomes large, resulting in a problem that the cost is increased.

The present invention has been made in view of the above facts, and has a simple configuration of a power supply mechanism for a transfer unit.
An image forming apparatus capable of simplifying the apparatus is provided.

[0006]

According to the first aspect of the present invention,
An image forming apparatus that transfers a toner image formed on a photosensitive drum according to image information to a recording medium while moving a transfer unit toward or away from the photosensitive drum to form an image on the recording medium. A transfer unit configured to position the recording medium at a transfer position facing the photosensitive drum; a semiconductive transfer / transport belt; and charging the surface of the transfer / transport belt to approach the photosensitive drum. Transfer means for transferring a toner image from the photosensitive drum onto the recording medium when the transfer is completed, first and second conductive side plates disposed on the sides of the transfer and conveyance belt and insulated from each other; A plurality of conductive rollers supported by a conductive bearing on at least one of the first and second conductive side plates around which a conveyor belt is wound; at least the transfer unit and the photoconductor; When a ram is separated state, the plurality of electrically conductive roller, and characterized in that and a ground connection means for grounding through the conductive plate.

According to the present invention, the plurality of conductive rollers provided in the transfer unit are connected by the ground connection means.
Since the grounding is performed via the conductive side plate supported by the conductive bearing, it is not necessary to provide the grounding directly and individually for the plurality of conductive rollers. Also, since the ground connection means grounds the plurality of conductive rollers via the conductive side plate, the grounding of the plurality of conductive rollers can be performed by one connection means. Therefore, the transfer unit can have a simple configuration, and the apparatus can be simplified.

According to a second aspect of the present invention, a toner image formed on a photosensitive drum according to image information is transferred to a recording medium while a transfer unit is moved toward or away from the photosensitive drum. An image forming apparatus for forming an image on the transfer belt, wherein the transfer unit positions the recording medium at a transfer position facing the photosensitive drum, and a surface of the transfer belt. And a transfer unit that transfers a toner image from the photoconductor drum onto the recording medium when the photoconductor drum approaches the photoconductor drum, and a first transfer unit that is disposed beside the transfer conveyance belt and is insulated from each other. And a second conductive side plate, a plurality of conductive rollers around which the transfer conveyance belt is wound, and supported by a conductive bearing on at least one of the first and second conductive side plates, Power supply connecting means for connecting the transfer means to a power supply for supplying a transfer current to the transfer means via the conductive side plate when the transfer means and the photosensitive drum are in an approaching state. It is characterized by having.

According to the present invention, the transfer means provided in the transfer unit is connected to the power supply via the conductive side plate supported by the conductive bearing by the power supply connection means. No need to connect. For this reason, it is not necessary to provide a power supply for the transfer unit to the transfer unit that moves at the time of transfer, so that a transfer current can be stably supplied to the transfer unit, and the configuration of the transfer unit is simplified. be able to.

According to a third aspect of the present invention, when at least the transfer means and the photosensitive drum are in an approaching state, the transfer means is moved between the first conductive side plate and the second conductive side plate. The image forming apparatus further includes a power supply connection unit that connects to a power supply that supplies a transfer current to the transfer unit via another conductive side plate that is not grounded.

According to the present invention, since both the ground connection means and the power supply connection means are provided, the conductive roller is grounded via one conductive side plate and grounded via the other conductive side plate. The transfer unit can be connected to a power source, and both power supply and grounding can be performed with a simple configuration, so that the configuration of the transfer unit can be further simplified.

Here, a transfer unit such as a corotron transfer unit can be used as a transfer unit used in the image forming apparatus. In this case, a transfer device is provided at a position facing the photosensitive drum.

In the transfer means, the transfer means may be wound around the transfer / transport belt, and a conductive bearing may be attached to at least one of the plurality of conductive side plates. It is also possible to use a conductive transfer roller supported by.

According to the present invention, the transfer roller can be connected to the power supply through at least one of the conductive side plates by the conductive bearing, whereby power is supplied in the same manner as the other conductive rollers. A mechanism can be configured.
At this time, when another conductive roller is connected to a conductive side plate that is not connected by a conductive bearing, the transfer current can be easily supplied only to the transfer roller.
In this manner, the transfer roller can be easily provided in the transfer unit, and the grounding of the conductive roller and the supply of the transfer current to the transfer roller can be easily and independently performed with a simple configuration. Can be. As a result, the transfer unit can be further simplified, and the apparatus can be further downsized.

If the conductive side plates are disposed on the side surface of the transfer unit, they may be disposed on both sides, or may be disposed on one side surface.

When the conductive side plates are arranged on both side surfaces, the bearing of the conductive roller provided in the transfer unit is connected to only one of the conductive side plates selected from the conductive side plates arranged on both side surfaces. It can be attached to one end of the conductive roller so as to be in a state. Thereby, it is possible to divide into one conductive side plate and the other conductive side plate according to the electrical characteristics of the conductive roller and connect them to earth ground or power supply.

In the case where the conductive side plates are arranged on one side surface, these conductive side plates can be arranged along the side surface of the transfer unit. Thus, each conductive roller can be brought into conduction with only one conductive side plate selected from the conductive side plates arranged along the side surface according to the electrical characteristics of the conductive roller.

When a conductive side plate is provided on one side of the transfer unit, the side plate disposed on the other side may be conductive or non-conductive. When the conductive roller is made conductive, the conductive roller can be brought into a conductive state by being supported by a conductive bearing with respect to one conductive side plate selected for each of the three conductive side plates. Thereby, the conductive roller can be divided into three according to the electrical characteristics. As a result, the electrical connection to the three conductive rollers can be made with a simple configuration via the conductive side plate, and various electrical connections or ground connections can be made with the simple configuration. The number of such conductive side plates is not limited to three.

Further, in the present invention, a conductive cleaning roller can be arranged in addition to the conductive roller. For example, when three conductive side plates are provided as described above, one of the conductive side plates is supported by a conductive bearing to make the conductive state, and the cleaning roller is connected via the conductive side plate of the transfer unit. Power supply can be connected. Thus, power can be supplied to the cleaning roller with a simple configuration, and the size of the transfer unit to which the cleaning roller is attached can be reduced. As a result,
Even if a cleaning roller is provided in the transfer unit, the size of the apparatus can be reduced.

[0020]

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

[First Embodiment] FIG. 1 shows an image forming apparatus 100 according to an embodiment of the present invention. The image forming apparatus 100 is covered by a substantially rectangular main body frame 102, and inside the main body frame 102,
A photosensitive drum 104 is provided.

The photoreceptor drum 104 is rotated in the direction of arrow Q by a photoreceptor drive motor (not shown), and the surface of the photoreceptor drum 104 is disposed near the peripheral surface of the photoreceptor drum 104 along the rotation direction. Charging device 1 for uniformly charging
06, and four developing units 108A, 108B, 108C, and 10 for attaching yellow, magenta, cyan, and black toners to the surface of the photosensitive drum 104, respectively.
8D are arranged in order.

An exposure unit 110 is arranged above the photosensitive drum 104 in FIG. 1 between the charging device 106 and the developing unit 108A. The exposure unit 110 includes a polygon mirror 1 that deflects a light beam emitted from a light source (not shown) in a predetermined direction (in FIG. 1, leftward on the page).
12 are provided. An fθ lens 114 is provided on the optical axis L of the light beam deflected by the polygon mirror 112.
And the reflection mirror 116 are arranged in this order. Accordingly, the light beam deflected by the polygon mirror 112 irradiates the reflection mirror 116 via the fθ lens 114, is reflected by the reflection mirror 116, and is reflected by the photosensitive drum 104 between the charging device 106 and the developing device 108A.
Reaches the surface (exposure position).

The photosensitive drum 104 is made of a material having a characteristic that a potential of a light receiving portion by a light beam is reduced. After the surface of the photoconductor drum 104 is charged by the charging device 106 and then sequentially irradiated with a laser beam corresponding to each color component of an image to be formed, the potential of the irradiated portion decreases. Thereby, the photosensitive drum 10
An electrostatic latent image corresponding to each color component of the image is formed on 4, and toner from the developing units 108 A, 108 B, 108 C, and 108 D can be attached.

In the vicinity of the peripheral surface of the photosensitive drum 104 downstream of the developing device 108D in the rotation direction Q, the photosensitive drum 1
A transfer unit 118 that can be arranged at a position (approaching position, the position shown in FIG. 1) close to the recording paper P and a position away from the recording paper P (separation position) is provided. ing. This will be described later.

A precharge corotron 120 and a cleaning device 122 are disposed near the peripheral surface of the photosensitive drum 104 between the charging device 106 and the transfer unit 118. The precharge corotron 120 removes electricity from the photosensitive drum 104 after the transfer. The cleaning device 122 includes a cleaning roller 124 that comes into contact with the peripheral surface of the photoconductor drum 104, and removes the toner on the photoconductor drum 104 that has been neutralized by the precharge corotron 120.

On the other hand, below the transfer unit 118, a paper supply unit 126 on which the recording paper P is disposed is arranged. In the vicinity of the paper feed unit 126, the paper feed unit 1
Paper feed roller 128 for discharging recording paper P from 26
A transport roller 130 for transporting the discharged recording paper P to the transfer unit 118 is provided. The paper feed roller 128 and the transport roller 130 are connected to a drive device and a drive control device (not shown). Accordingly, the paper feed roller 128 and the transport roller 130 rotate in synchronization with the rotation of the photosensitive drum 104, and the recording paper P
And is supplied to the transfer unit 118.

In the transport path W of the recording paper P, a fixing device 132 is disposed downstream of the transfer unit 118. The fixing device 132 includes a heat roll 134 that heats the recording paper P from the toner transfer side and a pressure roll 136 that presses the recording paper P against the heat roll 134. Heat roll 134 and pressure roll 13
Each of the reference numerals 6 has a width dimension capable of contacting the entire surface of the supplied recording paper P.

The image forming apparatus 100 includes a fixing device 132
A discharge port 138 is provided on the transport path W on the downstream side of the recording paper P, and the recording sheet P on which the color toner image is formed by electrostatically transferring and fixing the toner image is discharged from the image forming apparatus 100. .

Next, the transfer unit 118 will be described with reference to FIGS. The transfer unit 118 includes a transfer conveyance belt 140 for conveying the recording paper P supplied from the paper supply unit 126 and supplying the recording paper P to a transfer position. A pair of conductive side plates 142 and 144 that are insulated from each other are arranged on the circumferential side surface of the transfer conveyance belt 140. A drive roller 146, a driven roller 148, a transfer roller 150, and a tension roller 152 are rotatably connected to the pair of side plates 142 and 144.
The transfer conveyance belt 140 is wound around a driving roller 146 and a driven roller 148, and the inner peripheral surface of the transfer conveyance belt 140 is in contact with the peripheral surfaces of the transfer roller 150 and the tension roller 152.

The transfer / transport belt 140 is an endless member composed of a semiconductive member. When the drive roller 146 rotates, the driving of the drive roller 146 is driven by the driven roller 148 via the transfer / transport belt 140. , Transfer roller 15
0 and transmitted to the tension roller 152.

Each of the side plates 142 and 144 is formed of a substantially rectangular plate-like member whose longitudinal direction is the left-right direction in FIG. Notches 142A and 144A are provided on the upper surfaces of the side plates 142 and 144 at positions where the transfer unit 118 and the photosensitive drum 104 arranged at the close position face each other. The side plates 142 and 144 have notches 142A and
Connection portions 142B and 144B projecting downward are provided on the side of the driven roller 148 relative to 44A (only one is shown in FIG. 2).

Driving roller 146 and driven roller 148
Is made of a conductive member such as aluminum together with the rotating shafts 146A and 148A.

The rotation shaft 146A of the drive roller 146 penetrates the pair of side plates 142 and 144, and is rotatably supported by the main body frame 102. As a result, the transfer unit 1 is rotated around the rotation shaft 146A of the drive roller 146.
18 is rotatable. A drive gear 154 is attached to the rotation shaft 146A, and the rotation shaft 146A is connected to the drive unit of the main body (not shown) via the drive gear 154. Thus, the driving roller 146 is driven to rotate in the direction indicated by the arrow M via the driving gear 154.

The rotating shaft 148A of the driven roller 148 has
A cam mechanism (not shown) is connected. The cam mechanism has
In accordance with the rotation of the photosensitive drum 104, the driven roller 148
Has a cam plate capable of moving the rotary shaft 148A in the direction indicated by the arrow T in FIG. That is, the transfer mechanism 118 is driven by the driving roller 146 by the cam mechanism.
Can be rotated along the arrow T about the rotation shaft 146A.

The transfer roller 150 is a photosensitive drum 104
Are arranged to face each other. The transfer roller 150 and a rotation shaft 150A of the transfer roller 150 are both formed of a conductive member such as aluminum, and are connected to a power supply for supplying a transfer current to the transfer roller 150 via the rotation shaft 150A as described later. . The transfer current from the power supply is
The potential of a part of the transfer conveyance belt 140 that is in contact with the transfer roller 150 is changed through the peripheral surface of the transfer roller 150.

The tension roller 152 is disposed on the inner peripheral side of the transfer and conveyance belt 140 and below the transfer roller 150. The tension roller 152 and its rotating shaft 152A are both made of a conductive material such as aluminum. The rotation shaft 152A of the tension roller 152 is connected to a tension mechanism (not shown) for applying a constant tension to the transfer conveyance belt 140 in order to hold the transfer conveyance belt 140 at a position pulled down in FIG.

A structure 156 made of an insulating material such as plastic is disposed between the pair of side plates 142 and 144. The structure 156 includes the transfer unit 118
In order not to prevent the rotation of the driving roller 146, the driven roller 148, the transfer roller 150, and the tension roller 152 provided in the printer, the portions corresponding to the arrangement portions of the rollers are concave.

The transfer unit 118 has a conductive cleaning roller 15 opposed to the drive roller 146.
8 are arranged.

As shown in FIG. 3, the cleaning roller 158 is disposed in contact with the outer peripheral surface of the transfer / conveying belt 140 wound around the driving roller 146. Insulating pressure spring bearings 160 are attached to both ends of the cleaning roller 158 to urge the cleaning roller 158 toward the drive roller 146. The cleaning roller 158 is attached to the receiving portion 162 via a pressure spring receiving bearing 160. A blade 164 that contacts the surface of the cleaning roller 158 is disposed on a side surface of the receiving portion 162.

Rotary shaft 158 of cleaning roller 158
One end of A is in contact with the power supply plate 166. Power supply plate 1
An electric wire 167 is attached to 66, and the electric wire 167 is
A power supply (not shown) capable of supplying a cleaning current to the cleaning roller 158 is connected.

Incidentally, the driving roller 146, the driven roller 148, the transfer roller 150, and the tension roller 152
Of each rotation shaft 148A, 150A and 152A and the side plate 14
4, a conductive bearing 168A or an insulating bearing 170B that rotatably supports each roller is selected and arranged.

As shown in FIG.
6, each connection portion between the driven roller 148, the tension roller 152 and the side plate 144, and the transfer roller 150 and the side plate 1
A conductive bearing 168 </ b> A is attached to a portion connected to the conductive member 42. At other connection portions, an insulating bearing 170B is attached.

That is, the driving roller 146, the driven roller 148, and the tension roller 152 are
The conductive plate 168 is used for the side plate 142.
, An insulating bearing 170 is used. Therefore, the driving roller 146, the driven roller 148, and the tension roller 152 are all in a conductive state only with respect to the side plate 144A.

On the other hand, the transfer roller 150 uses a conductive bearing 168 for the side plate 142 and an insulating bearing 170 for the side plate 142. Therefore, the transfer roller 150 is brought into conduction only with the side plate 142.

As shown in FIG. 2, a lower frame 172 supporting the transfer unit 118 is disposed below the side plates 142 and 144. The lower frame 172 is formed of a conductive plate-shaped member.

As shown in FIG. 3A, a projection 174 is provided on the surface of the lower frame 172 so as to face the connecting portion 144B of the side plate 144. A conductive spring 176 is wound around the projection 174, and the spring 17
One end of 6 is in contact with lower frame 172. The spring 176 is also wound around the connection portion 144B of the side plate 144 facing the projection 174, and the other end of the spring 176 is in contact with the side plate 144. That is, the side plate 14
4 and the lower frame 172 are in a conductive state via a spring 176.

On the other hand, as shown in FIG. 3B, the insulating member 1 is provided on the surface of the lower frame 172 at a position facing the connecting portion 142B provided on the other side plate 142.
78 is fitted. The insulating member 178 is provided with a projection 180 projecting upward at the center. A disc-shaped transfer current terminal 182 is inserted into the protrusion 180.

An electric wire 184 is connected to the transfer current terminal 182, and the image forming apparatus 100 is connected via the electric wire 184.
Are connected to a power supply (not shown) provided in the power supply. A conductive spring 176 is wound around the projection 180 to which the transfer current terminal 182 is attached.
Is in contact with the transfer current terminal 182. The spring 176 is also wound around the connection portion 142B of the side plate 142 facing the projection 180, and the other end of the spring 176 is in contact with the side plate 142. That is, the side plate 14
2B and the transfer current terminal 182 are in a conductive state via the spring 176.

As described above, in the transfer unit 118, the transfer roller 150 to which the transfer current is to be supplied includes the conductive bearing 168, the side plate 142, and the conductive spring 17.
6 and the transfer current terminal 182 are connected to a power supply in this order. In the transfer unit 118, the driving roller 146, the driven roller 148, and the tension roller 1
52 is grounded via a conductive bearing 168, a side plate 144, a conductive spring 176, and a lower frame 172 in this order.

Next, the operation of the present embodiment will be described. First, the operation of the image forming apparatus 100 will be described.

When image formation is started, the transfer unit 118 is moved to the spring 17 by a cam mechanism (not shown).
6 is pressed down against the bias of 6 and fixed at the separated position.

The photosensitive drum 104 starts rotating in the direction indicated by the arrow Q in FIG. 1, and the charging device 106 uniformly charges the surface of the photosensitive drum 104. Exposure unit 110
Irradiates a laser beam according to image information of an image to be formed, which is decomposed into four color components, and exposes the surface of the photosensitive drum 104 disposed at the exposure position. When an electrostatic latent image corresponding to each color component is formed on the surface of the photoconductor drum 104 by exposure, the developing units 108A, 108B, 108C, and 108 provided opposite to the surface of the photoconductor drum 104
D performs development processing on the electrostatic latent image of the corresponding color component. This development process is performed for each color component of the image to be formed.

For example, first, a cyan component laser beam is applied to the photosensitive drum 104 to cause the cyan developing unit 108A
As a result, a cyan image is formed on the surface of the photosensitive drum 104. When the cyan image is formed on the photoconductor drum 104, the photoconductor drum 104 continues to rotate while the cyan image is formed on the photoconductor drum 104. When the surface of the photosensitive drum 104 on which the cyan image has been formed reaches the exposure position again, a magenta component laser beam is irradiated so as to overlap the cyan image, and the magenta image is formed on the photosensitive drum 104 by the magenta developing unit 108B. Formed. Similarly, by irradiating laser light to the yellow and black color components, images of four colors are superimposed and formed on the photosensitive drum 104.

During the development of the final color, black, when the leading end in the rotation direction of the photosensitive drum 104 of the formed image reaches the vicinity of the transfer unit 118, the paper feed unit 126 synchronizes with this. The recording paper P is sent out to the inside of the apparatus.

Further, in synchronization with this, a cam mechanism (not shown) operates to release the fixing of the transfer unit 118. When the fixing is released, the driven unit 148 of the transfer unit 118 moves toward the photosensitive drum 104 due to the urging force of the conductive spring 176 in contact with the lower frame 172. This allows
The transfer unit 118 is arranged at an approach position where the transfer unit 118 contacts the photosensitive drum 104.

When the transfer unit 118 is located at the approach position, the transfer conveyance belt 140 is rotated by the driving of the drive roller 146, and the recording paper P is transferred to the transfer conveyance belt 140.
And the photosensitive drum 104. The transfer conveyance belt 140 presses the recording paper P against the photosensitive drum 104 with a predetermined tension by a tension roller 152, and when a transfer current is supplied to the transfer roller 150, the transfer conveyance belt 140 is formed so as to overlap the surface of the photosensitive drum 104. The four color images are transferred to the recording paper P.

The recording paper P on which the image has been transferred is supplied to the fixing device 132 by the conveyance of the transfer conveyance belt 140, where the image is fixed, and discharged from the discharge port 138.

The photosensitive drum 104 after transferring the image
Is the photoconductor drum 10 in the cleaning device 122.
4 to remove the residual toner adhering to the charging device 10
After being uniformly charged by 6, an image can be formed again.

When the transfer of the image onto the recording paper P is completed, the transfer unit 118 is pulled down again by the operation of the cam mechanism, and is fixed at the separated position. At the same time, a cleaning current is supplied to the cleaning roller 158 to remove toner and the like attached to the transfer conveyance belt 140, and the transfer conveyance belt 140 is cleaned. Thus, the next transfer processing can be performed.

Next, a power supply mechanism of the transfer unit 118 will be described. As described above, the transfer roller 15 is used to transfer the image formed on the surface of the photosensitive drum 104.
A transfer current is supplied to 0.

As shown in FIG. 4, the transfer roller 150
Are electrically connected to the side plate 142 by the conductive bearing 168. Drive roller 146, driven roller 148, tension roller 15 attached to side plate 142
2 is in a non-conductive state with the side plate 142 by the insulating bearing 170.

Therefore, the transfer current from the power source is transferred from the transfer current supply terminal 182 (see FIG. 3B) on the lower frame 172 to the conductive spring 176, the side plate 142, and the conductive bearing 168 in this order. Then, it is supplied to the transfer roller 150. At this time, the side plate 142 and the side plate 14
The transfer current is not supplied to the side plate 144 via the lower frame 172 because they are insulated from each other.

On the other hand, the driving roller 146 and the driven roller 14
8. The tension roller 152 is a conductive bearing 16
8 makes the side plate 144 conductive. Side plate 1
The transfer roller 150 attached to 44 is in a non-conductive state with the side plate 144 by the insulating bearing 170. The lower frame 172 is grounded via the main body frame 102.

Therefore, the transfer roller 150, the driven roller 148, and the tension roller 152 are grounded via the conductive bearing 168, the side plate 144, the spring 176, and the lower frame 172, and the transfer roller 150, the driven roller 148, and the tension roller 152 , The charge of the transfer / conveyance belt 140 is removed.

Since the cleaning roller 158 is not connected to any of the side plates 142 and 144, the transfer roller 150, the driving roller 146, and the driven roller 148 are not connected.
And the tension roller 152 is kept in a non-conductive state.

For this reason, when a cleaning current is supplied from a power supply to the power supply plate 166 that is in contact with the rotating shaft 158 A of the cleaning roller 158, the cleaning current is applied to the other rollers around which the transfer conveyance belt 140 is wound. Is not supplied, cleaning roller 1
58 only.

As a result, the transfer unit 11 that moves
8, the transfer roller 150, the drive roller 146, the driven roller 148, and the tension roller 152 are connected to the power supply or the ground via the immovable lower frame 172, so that there is no need to provide the transfer unit 118 with a power supply.
There is no need to connect directly to ground. Further, it is possible to stably supply a transfer current with a simple configuration and ground the transfer current. Even when a plurality of rollers are arranged in the transfer unit 118, it is not necessary to individually ground the rollers, and the apparatus can be simplified.

As a result, the power supply mechanism of the transfer unit can be configured with a simple configuration, and the image forming apparatus 100 itself can be simplified.

Further, since the transfer roller 150 and each roller are connected to the side plates 142 and 144 which are insulated from each other via the conductive and insulating bearings 168 and 170,
The transfer roller 150 included in the transfer unit 118 and the respective rollers can be easily attached and detached.

[Second Embodiment] FIGS. 5 and 6 show
A transfer unit 200 according to a second embodiment of the present invention is shown. The transfer unit 200 is the transfer unit 1 of the image forming apparatus 100 according to the first embodiment of the present invention.
Since only a part is different from 18, members having the same functions and effects are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 5, the transfer unit 20
No. 0 has a side plate 144 and a side plate 202 on both sides in the circumferential direction of the transfer conveyance belt 140. The side plate 202
Further, the front side plate 204 disposed on the driven roller 148 side is used.
And a rear plate 206 disposed on the drive roller 146 side. Each of the front plate 204 and the rear plate 206 has a connection portion 204B, 206B
(See FIG. 6).

A driven roller 148 and a tension roller 152 are rotatably mounted on the front side plate 204 by means of an insulating bearing 170, and a transfer roller 150 is rotatably mounted by means of a conductive bearing 170. For this reason, the front side plate 204 is in a conductive state only with the transfer roller 150.

A drive roller 146 is rotatably attached to the rear side plate 206 by an insulating bearing 170. In addition, a cleaning roller 208 is rotatably attached to the rear plate 206 by a conductive bearing 168. The cleaning roller 208 includes a first
The cleaning roller 158 according to this embodiment is formed of the same member except that one end of the rotating shaft 158A is extended and penetrates the rear plate 206.

Therefore, the rear plate 206 is in a conductive state only with the cleaning roller 208.

As shown in FIG. 6, the transfer unit 20
Below 0, a lower frame 210 is arranged. The lower frame 210 has a projection (not shown) facing the connecting portion 144B of the side plate 144 (see FIG. 3A). Further, the lower frame 210 is provided with insulating members 212 and 21 at positions facing the front side plate 204 and the rear side plate 206, respectively.
4 are fitted. The insulating members 212 and 214 have protrusions 21 toward the front plate 204 and the rear plate 206, respectively.
6, 218 are projected.

The projection 216 has a transfer current supply terminal 182
Is inserted. A conductive spring 176 is wound around the protrusion 216, and one end of the spring 176 is in contact with the transfer current supply terminal 182. The transfer current supply terminal 182 is connected by a wire 184 to a power supply that supplies a transfer current. This spring 176
Is a connecting portion 204 of the front plate 204 facing the protrusion 216.
The other end of the spring 176 is in contact with the front side plate 204. That is, the front side plate 204 is connected to the power supply of the transfer current via the spring 176.

The protrusion 2 of the insulating member 214 on the rear plate 206 side
The cleaning current supply terminal 220 is inserted through 18. The projection 218 has a conductive spring 1
The one end of the spring 176 is in contact with the cleaning current supply terminal 220. The cleaning current supply terminal 220 is connected by an electric wire 184 to a power supply that supplies a cleaning current. The spring 176 is connected to the rear plate 206 facing the projection 218.
Of the spring 176
Is in contact with the rear side plate 206. That is, the rear plate 206 is connected to a power supply for supplying a cleaning current via the spring 176.

Next, the operation of the present embodiment will be described. The image forming process performed by the transfer unit 200 includes
The description is omitted because it is the same as that of the first embodiment, and the current supply mechanism in the transfer unit 200 will be described.

A transfer current is supplied to the transfer roller 150 from a power supply for transferring an image formed on the surface of the photosensitive drum 104 (see FIG. 2).

As shown in FIG. 5, the transfer roller 150
Are electrically connected to the front side plate 204 by the conductive bearing 168. The driven roller 148 and the tension roller 152 attached to the front plate 204 are in a non-conductive state with the front plate 204 by the insulating bearing 170.

For this reason, when the transfer current is supplied, the transfer current from the power supply is transferred to only the transfer roller 150 from the transfer current supply terminal 182 via the conductive spring 210, the front side plate 204 and the conductive bearing 168. Supplied. At this time, since the front plate 204 and the rear plate 206 are insulated from each other, the transfer current is
0 is not supplied to the rear side plate 206.

On the other hand, when the transfer process is completed, a cleaning process is performed on the transfer conveyance belt 140 of the transfer unit 20. At this time, a cleaning current is supplied from a power supply.

The cleaning roller 208 is electrically connected to the rear plate 206 by the conductive bearing 168. Drive roller 146 attached to rear side plate 206
Are in a non-conductive state with the rear side plate 206 by the insulating bearing 170.

For this reason, when the cleaning current is supplied, the cleaning current from the power source is supplied only from the cleaning current supply terminal 220 to the cleaning roller 208 via the conductive spring 210, the rear side plate 206 and the conductive bearing 168. Supplied.

On the other hand, the driving roller 146 and the driven roller 14
8, the tension roller 152 is a front side plate 204;
The rear plate 206 is in a non-conductive state, and is in a conductive state with the side plate 144. The transfer roller 150 attached to the front plate 204 and the cleaning roller 208 attached to the rear plate 206 are both in a non-conductive state with the side plate 144. The lower frame 210 is grounded via the main body frame 102.

For this reason, the transfer roller 150, the driven roller 148, and the tension roller 152 are grounded via the conductive bearing 168, the side plate 144, the conductive spring 210, and the lower frame 210, and the static electricity of the stop belt 140 is removed. Thus, similarly to the above, there is no need to provide a power supply to the moving transfer unit 200 and it is not necessary to directly ground the transfer unit 200, so that the transfer current can be stably supplied and grounded with a simple configuration. Further, it is not necessary to provide the transfer unit 200 with the respective power supplies for supplying the transfer current and the cleaning current to the transfer roller 150 and the cleaning roller 208.
00 can be further simplified.

Since the transfer roller 150 and the cleaning roller 208 are not directly connected to a power source, the transfer roller 150 and the cleaning roller 208 can be easily attached and detached.

In the embodiment of the present invention, the power supply and the ground are connected to the lower frames 172 and 210 disposed below the transfer units 118 and 200, but the present invention is not limited to this.

For example, an upper plate that contacts only when the transfer units 118 and 200 are arranged at the approach position and a lower plate that contacts only when the transfer units 118 and 200 are arranged at the separation position are provided, and connected to a power source via the upper plate. Alternatively, it may be grounded via the lower plate. In this case, when performing the transfer while approaching the photosensitive drum 104, the transfer current can be supplied to the transfer roller 150 by connecting the power supply by contacting the upper plate at the approach position. At times other than transfer, the photosensitive drum 104 can be separated from the photosensitive drum 104 and contacted with the lower plate at the separated position to be grounded. With this, the same effect as described above can be obtained.

In this embodiment, the tension roller 152
Is provided, but the tension roller 152 may not be provided.
Further, other conductive rollers may be provided in the transfer units 118 and 200.

In this embodiment, the transfer roller 150 is used as the transfer means, but the present invention is not limited to this. For example, a transfer device such as a transfer corotron that transfers a toner image to the recording medium P by discharging may be used. In this case, power supply to the transfer units attached to the transfer units 118 and 200 may be performed via the side plate 142 or the front side plate 204 or may be provided separately.

[0093]

As described above, according to the present invention, a plurality of conductive rollers provided in the transfer unit are grounded by conductive bearings via conductive side plates by ground connection means or power supply connection means. Or the transfer unit is connected to a power source via a conductive side plate by a conductive bearing, so that the transfer unit can have a simple configuration.

Further, when the conductive roller and the transfer means are connected to different conductive side plates via the ground connection means and the power supply connection means, respectively, the grounding and power supply are performed with a simpler configuration. And the apparatus can be further simplified.

Therefore, the supply of electricity to the transfer unit can be simplified, the replacement and maintenance of the transfer unit can be simplified, the number of parts can be reduced, and the apparatus can be easily downsized. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view of the transfer unit according to the first embodiment of the present invention.

FIG. 3A is a side view from one direction of the transfer unit according to the embodiment, and FIG. 3B is a partial side view from another direction of FIG.

FIG. 4 is a plan view of the transfer unit according to the exemplary embodiment.

FIG. 5 is a plan view of a transfer unit according to a second embodiment of the present invention.

FIG. 6 is a side view from one direction of a transfer unit according to another embodiment of the present invention.

FIG. 7 is a schematic diagram of a conventional image forming apparatus.

[Explanation of symbols]

REFERENCE SIGNS LIST 100 image forming apparatus 104 photoreceptor drum 118 transfer unit 140 transfer / transport belt 142 side plate (conductive side plate) 142B connection part (power supply connection means) 144 side plate (conductive side plate) 144B connection part (earth connection means) 146 drive roller (conductive) Roller 148 driven roller (conductive roller) 150 transfer roller (conductive roller, transfer means) 152 tension roller (conductive roller) 158 cleaning roller 166 power supply plate 168 conductive bearing (conductive bearing) 170 insulating bearing 172 Lower frame 174 Projection (ground connection means) 176 Spring (ground connection means, power supply connection means) 180 Projection (power supply connection means) 182 Transfer current terminal 200 Transfer unit 204 Front side plate (conductive side plate) 206 Rear side plate (conductive side plate) )

Claims (4)

[Claims] An image is formed on a recording medium by transferring a toner image formed on a photosensitive drum according to image information while moving a transfer unit toward or away from the photosensitive drum. An image forming apparatus, wherein the transfer unit is: a semi-conductive transfer / conveying belt that positions the recording medium at a transfer position facing the photoconductor drum; and charging a surface of the transfer / conveyance belt; A transfer unit for transferring a toner image from the photosensitive drum onto the recording medium when approaching the photosensitive drum; and first and second conductive members disposed on the sides of the transfer and conveyance belt and insulated from each other. A side plate and the transfer / transport belt are wound around the first and second transfer conveyor belts;
A plurality of conductive rollers supported by conductive bearings on at least one of the conductive side plates, and at least when the transfer unit and the photosensitive drum are separated from each other, the plurality of conductive rollers are An image forming apparatus, comprising: ground connection means for grounding through a conductive side plate. 2. A method according to claim 1, wherein the toner image formed on the photosensitive drum is transferred to a recording medium while a transfer unit is moved toward or away from the photosensitive drum to form an image on the recording medium. An image forming apparatus, wherein the transfer unit is: a semiconductive transfer / conveying belt that positions the recording medium at a transfer position facing the photoconductor drum; and charging a surface of the transfer / conveyance belt, A transfer unit that transfers a toner image from the photosensitive drum onto the recording medium when approaching the photosensitive drum; and first and second conductive members that are arranged on the sides of the transfer conveyance belt and are insulated from each other. A side plate and the transfer / transport belt are wound around the first and second transfer conveyor belts;
A plurality of conductive rollers supported on at least one of the conductive side plates by a conductive bearing; and at least when the transfer unit and the photosensitive drum are in an approaching state, the transfer unit includes the conductive side plate. And a power supply connecting means for connecting the transfer means to a power supply for supplying a transfer current to the transfer means. 3. When at least the transfer unit and the photosensitive drum are in an approaching state, the transfer unit is moved to the first position.
Power supply connecting means for connecting to a power supply for supplying a transfer current to the transfer means via the other conductive side plate which is not grounded among the conductive side plate and the second conductive side plate of the above. The image forming apparatus according to claim 1, wherein: 4. The transfer means is a conductive transfer roller around which the transfer conveyance belt is wound and supported by a conductive bearing on at least one of the plurality of conductive side plates. The image forming apparatus according to claim 1.