JPH10186904A - Image forming machine provided with transfer belt mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming machine provided with a transfer belt mechanism capable of stably separating a transfer paper after a transfer is performed from a photoreceptor drum, even if an environmental condition is changed. SOLUTION: The image forming machine is provided with the photoreceptor drum 2, the transfer belt mechanism 4 for transferring a toner image formed on the periphery of the photoreceptor drum 2 to the transfer paper, to carry it and a pair of resist rollers 6 which are disposed on the upstream side in the carrying direction of the transfer paper of the transfer belt mechanism 4 and carries the transfer paper to a transferring area where the drum 2 faces the transfer belt mechanism 4. In such a case, the transfer belt mechanism 4 is provided with a driving roller 41, a driven roller 42, a transfer belt 43 which is wound on both rollers 41 and 42 and comes into contact with the periphery of the drum 2 with a fixed nip range and a bias voltage applying means 46 for applying a prescribed transfer bias voltage to the transfer belt 43. A transfer paper guiding means 8 for guiding the transfer paper fed by a pair of the resist rollers 6 toward the transfer belt 43 on the upstream side in the carrying direction of the transfer paper, from a nip range is disposed between a pair of the resist rollers 6 and the transfer belt mechanism 4.

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, such as an electrostatic copying machine or a laser printer, which electrostatically transfers a toner image formed on a peripheral surface of a photosensitive drum to transfer paper. More specifically, the present invention relates to an image forming machine provided with a transfer belt mechanism as a transfer unit.

[0002]

2. Description of the Related Art An image forming machine of this type is arranged rotatably and sequentially passes through a charging area, an electrostatic latent image forming area, a developing area, a transfer area and a separation area. A charger that is provided and charges the peripheral surface of the photosensitive drum to a specific polarity;
A developing device disposed in the developing area and developing the electrostatic latent image formed on the peripheral surface of the photosensitive drum in the electrostatic latent image forming area into a toner image; and a developing device disposed in the transfer area and the separation area. A transfer / separation device is provided for transferring the toner image formed on the peripheral surface to transfer paper and separating the transfer paper from the photosensitive drum. The image forming apparatus includes a transfer paper feeding device for feeding the transfer paper to the transfer area.

As the transfer / separation device, a corona discharge system is generally used. This corona discharge type transfer / separation device applies a corona discharge to the back surface of the transfer paper fed to the transfer area by a corona discharger for transfer to transfer the toner image formed on the peripheral surface of the photosensitive drum to the transfer paper. The corona discharge is applied to the back side of the transfer paper on which the toner image has been transferred to the back side of the transfer paper by a separating corona discharger, thereby separating the transfer paper from the photosensitive drum. In order to electrostatically attract the transfer paper to the peripheral surface of the photosensitive drum in the transfer area,
The transfer paper fed to the transfer area is sent so that its front end is in contact with the peripheral surface of the photosensitive drum. Such a corona discharge type transfer / separation apparatus has an environmental health problem because ozone is generated by an alternating current (AC) electric field applied to a corona discharger for separation.

In order to address the above-mentioned problem of the corona discharge type transfer / separation device, a transfer belt type transfer / separation device has been put to practical use. The transfer / separation device of the transfer belt type is provided with a transfer belt mechanism having a transfer belt that comes into contact with the photosensitive drum in the transfer area, and applies a bias voltage to the transfer belt so that the peripheral surface of the photosensitive drum is The toner image formed on the transfer belt is transferred to a transfer paper conveyed between the photosensitive drum and the transfer belt, and the transfer paper is electrostatically attracted to the transfer belt, separated from the photosensitive drum and directed to the fixing device. It is designed to be transported.

The transfer belt mechanism includes a driving roller and a driven roller disposed in parallel with each other with the photosensitive drum interposed therebetween, and a predetermined nip wound around the driving roller and the driven roller on the peripheral surface of the photosensitive drum. The transfer belt includes a transfer belt that contacts the transfer belt, and a bias voltage applying unit that applies a predetermined transfer bias voltage to the transfer belt.
In an image forming apparatus provided with such a transfer belt mechanism, the transfer paper is fed toward a nip area where the peripheral surface of the photosensitive drum and the transfer belt are in contact. The transfer paper fed toward the nip area is transferred and transferred by the corona discharge method described above.
Similarly to an image forming machine provided with a separating device, the sheet is fed so that its front end is in contact with the peripheral surface of the photosensitive drum.

However, in the image forming machine having the above-described transfer belt mechanism, there is no problem when the transfer paper is not distorted, but when the front end of the transfer paper is curled upward, that is, toward the photosensitive drum. In some cases, depending on the environmental conditions, the transfer paper may not be properly separated from the photosensitive drum after the transfer, resulting in poor separation. That is, the transfer belt has a volume electric resistance of 10 ⁶ or more at room temperature (25 ° C.).
It is made of a material of about 10 ¹² Ωcm, but its volume electric resistance decreases in a high-temperature and high-humidity environment such as a temperature of 35 ° C. and a humidity of 85%. Therefore, the charge amount of the transfer belt is reduced, and the electrostatic force is weakened.
Therefore, when the front end of the transfer paper is curled upward as described above, the front end of the transfer paper is wound around the photosensitive drum, which is one of the dielectrics, and the volume of the transfer paper is increased in a high temperature and high humidity environment. When the resistance decreases and the electrostatic force weakens, separation of the transfer paper from the photosensitive drum becomes unstable. Further, the bias voltage applying means includes a bias voltage applying member such as a transfer roller connected to a power supply and disposed in contact with the transfer belt, and the transfer roller is connected to a peripheral surface of the photosensitive drum. It is arranged on the back surface of the transfer belt at the center (transfer point) of the nip area where the transfer belt contacts. By making the transfer point of the transfer belt and the bias voltage application point coincide with each other, the transfer performance is improved, but a discharge phenomenon occurs between the transfer belt and the photosensitive drum in the separation area downstream of the nip area. Occurs, and the separation of the transfer paper from the photosensitive drum becomes unstable. That is, it is known that the charging potential of the transfer belt having a high resistance value of about 10 < ⁶ > to 10 < ¹² > [Omega] cm increases as the distance from the bias voltage application point increases. However, when the transfer point and the bias voltage application point are matched as described above, the distance from the bias voltage application point to the separation region becomes longer, so that the charging potential of the separation region increases and a discharge phenomenon occurs. At this time, if the front end of the transfer paper is curled upward, the transfer paper separates from the transfer belt and wraps around the photosensitive drum, and the separation of the transfer paper from the photosensitive drum is unstable. Become.

[0007]

In order to solve such a problem, a bias voltage applying point is set downstream of the nip region to prevent the occurrence of a discharge phenomenon in the separation region. However, for example, JP-A-6-167
No. 896.

[0008]

However, if the transfer point and the bias voltage application point are separated from each other as in the technique disclosed in the above-mentioned publication, the current flows inside the transfer belt from the bias voltage application point to the transfer point. It is necessary to make the volume electric resistance of the transfer belt uniform. However,
The transfer belt is made of a material having a volume electric resistance of about 10 ⁶ to 10 ¹² Ωcm at room temperature (25 ° C.) as described above. In order to manufacture a uniform transfer belt with such a high resistance value. It is necessary to precisely control resistance unevenness and belt thickness. For this reason, the yield decreases during the production of the transfer belt, which is a factor that increases the cost of the transfer belt. Further, since the bias voltage application point is located downstream of the nip area as described above, the transfer operation may be performed in the separation area where the photosensitive drum and the transfer belt are not in contact, and a stable transfer image may be obtained. There is a problem that it cannot be obtained.

The present invention has been made in view of the above-mentioned facts, and a first technical problem is to stably separate transfer paper from a photosensitive drum after transfer even if environmental conditions change. It is an object of the present invention to provide an image forming machine provided with a transfer belt mechanism capable of performing such a transfer.

A second technical object of the present invention is to provide an image forming machine having a transfer belt mechanism capable of stably separating transfer paper from a photosensitive drum while maintaining transfer performance. It is in.

[0011]

According to the present invention, there is provided a photoconductor drum rotatably disposed on a peripheral surface of which a toner image is formed, and a photoconductor drum according to the present invention. A transfer belt mechanism that is disposed opposite to the drum and transfers and transports the toner image formed on the peripheral surface of the photosensitive drum onto transfer paper; and a transfer belt mechanism that is disposed upstream of the transfer belt mechanism in the transfer paper transport direction. A registration roller pair that conveys the transfer paper toward a transfer area where the photoconductor drum and the transfer belt mechanism are opposed to each other, wherein the transfer belt mechanism includes a driving roller and a driven roller disposed in parallel with each other, A transfer belt wound around the driving roller and the driven roller and in contact with the peripheral surface of the photosensitive drum with a predetermined nip range; and a bias voltage applying means for applying a predetermined transfer bias voltage to the transfer belt. In an image forming machine having a transfer belt mechanism, the transfer paper fed by the pair of registration rollers is disposed between the registration roller pair and the transfer belt mechanism at a position upstream of the nip area in the transfer paper conveyance direction. An image forming apparatus provided with a transfer belt mechanism, wherein transfer paper guide means for guiding the transfer paper toward the transfer belt is provided.

The transfer paper guide means includes an upper guide plate and a lower guide plate, and the upper guide plate is formed to be inclined from the pair of registration rollers toward the photosensitive drum. A second guide portion formed from a downstream end of the first guide portion to a transfer belt upstream of the nip area in the transfer paper transfer direction, and the second guide portion and the second guide portion are provided. The angle α between the transfer belt and the transfer belt on the upstream side in the transfer paper transport direction from the nip range is 0 ° to 30 ° (0 ° <α <3).
0 °).

According to another aspect of the present invention, there is provided a photoconductor drum rotatably disposed on a peripheral surface of which a toner image is formed, and a photoconductor drum facing the photoconductor drum. And a transfer belt mechanism that transfers the toner image formed on the peripheral surface of the photosensitive drum to transfer paper and conveys the transfer image, and the transfer belt mechanism is provided with a drive roller and a drive roller that are arranged in parallel with each other. A driven roller, a transfer belt wound around the drive roller and the driven roller, and in contact with the peripheral surface of the photosensitive drum with a predetermined nip range, and a bias voltage application unit for applying a predetermined transfer bias voltage to the transfer belt. Wherein the bias voltage applying point of the bias voltage applying means is set at the downstream end of the nip range in the transfer paper transport direction. Image-forming machine is provided with a transfer belt mechanism according to claim.

Further, according to the present invention, to solve the first and second technical problems, according to the present invention, a photosensitive drum having a toner image formed on a peripheral surface thereof and a photosensitive drum, A transfer belt mechanism, which is disposed to face and transfers the toner image formed on the peripheral surface of the photosensitive drum to a transfer sheet and conveys the transfer image; and a transfer sheet disposed upstream of the transfer belt mechanism in the transfer sheet conveyance direction. A pair of registration rollers for transporting the photosensitive drum and a transfer belt mechanism toward a transfer area facing the transfer belt mechanism, wherein the transfer belt mechanism includes a driving roller and a driven roller disposed in parallel with each other; A transfer belt wound around the roller and the driven roller and in contact with the peripheral surface of the photosensitive drum with a predetermined nip range; and a bias voltage applying means for applying a predetermined transfer bias voltage to the transfer belt. In an image forming apparatus provided with a transfer belt mechanism, a bias voltage application point of the bias voltage application unit is set at a downstream end of the nip range in a transfer paper transport direction, and the registration roller pair and the transfer belt mechanism are connected to each other. A transfer paper guide means for guiding the transfer paper fed by the pair of registration rollers toward the transfer belt upstream of the nip area in the transfer paper transfer direction. An image forming machine provided with a mechanism is provided.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus having a transfer belt mechanism constructed according to the present invention will be described below in detail with reference to the accompanying drawings. 1 and 2 show an embodiment of an image forming apparatus having a transfer belt mechanism configured according to the present invention. In FIG. 1, a photosensitive drum as an image carrier denoted by reference numeral 2 is rotatably disposed in a body housing, and is driven to rotate in a direction indicated by an arrow A by a drive mechanism (not shown). The peripheral surface of the photosensitive drum 2 rotating in the direction indicated by the arrow A is uniformly charged (for example, +800 V) to a specific polarity by a charger in a charging area. On the peripheral surface of the photosensitive drum 2 charged in this way, an electrostatic latent image of image information is formed by an exposure unit such as a laser unit in an electrostatic latent image forming area. The electrostatic latent image thus formed on the peripheral surface of the photosensitive drum 2 is developed into a toner image by a developing device in a developing area. The toner image formed on the peripheral surface of the photosensitive drum 2 is transferred to the transfer area B
Is transferred to a transfer paper as described later.

A transfer belt mechanism 4 as a transfer / separation means is provided in a transfer area B located below the photosensitive drum 2. The transfer belt mechanism 4 includes a driving roller 41 and a driven roller 42 disposed in parallel with each other,
A transfer belt 43 wound around the drive roller 41 and the driven roller 42 and in contact with the peripheral surface of the photosensitive drum 2 with a predetermined nip range N; and a back surface of the transfer belt 43 disposed on both sides of the nip range N, respectively. Tension rollers 44 and 45 for applying tension to the transfer belt 43 by pressing
And a bias voltage applying means 46 for applying a predetermined transfer bias voltage to the transfer belt 43.

The drive roller 41, the driven roller 42, and the tension rollers 44 and 45 are made of an aluminum alloy in the illustrated embodiment, and the drive roller 41 is driven to rotate in a direction indicated by an arrow by a drive mechanism (not shown). As a result, the transfer belt 43 is operated in the direction shown by the arrow D.

The transfer belt 43 is an endless belt having a thickness of about 0.6 mm in which urethane rubber is coated with a fluorine tetrachloride resin (trade name: Teflon), and has a volume electric resistance of about 10 ⁶ to 10 ¹² Ωcm. Have been.

The bias voltage applying means 46 comprises a transfer roller 47 disposed in contact with the back surface of the transfer belt 43 in the nip range N, and a power supply 48 connected to the transfer roller 47. The transfer roller 47 is made of foamed urethane rubber having an Asker F hardness of 85 ° or less, and has a volume electric resistance of 10 ³ to 10 ⁴ Ω.
cm. The power supply 48 applies a predetermined bias voltage (for example, +3 kV) having a polarity opposite to the charging polarity (minus polarity in the illustrated embodiment) of the toner attached to the peripheral surface of the photosensitive drum 2 to the transfer roller 4.
7 is applied to the transfer belt 43. In the illustrated embodiment, the drive roller 41 and the downstream tension roller 44 are grounded, and the transfer belt 4 passes through the drive roller 41 and the downstream tension roller 44.
3 is configured to remove the electric charge.
The driven roller 42 and the tension roller 45 on the upstream side may also be grounded in order to reliably remove the electric charge charged on the transfer belt 43.

The transfer belt mechanism 4 configured as described above
The nip range N is set to 8 mm, and the interval E between the transfer roller 47 and the upstream tension roller 45 is set to 20 mm. The image forming machine in the illustrated embodiment is disposed on the upstream side of the transfer belt mechanism 4 in the direction of transfer of the transfer paper, and forms a transfer paper feeding device that feeds the transfer paper P toward the nip range N. A roller pair 6 is provided. The registration roller pair 6 temporarily stops the transfer paper fed by the paper feeding means constituting the transfer paper feeding device, and takes a timing with the toner image formed on the peripheral surface of the photosensitive drum 2 so as to take the transfer area. Feed to B.

Transfer paper guide means 8 for guiding the transfer paper conveyed by the pair of registration rollers 6 is provided between the pair of registration rollers 6 and the transfer belt mechanism 4.
The transfer paper guide means 8 comprises an upper guide plate 81 and a lower guide plate 82 in the illustrated embodiment. The upper guide plate 81 has a first guide portion 811 formed to be inclined obliquely upward in the direction of the photoconductor drum 2 from the upstream side in the transfer paper transport direction, and from a downstream end of the first guide portion 811. A second guide portion 812 formed downward on the downstream side in the transfer paper transport direction. The lower guide plate 82 is configured to be substantially parallel to the first guide portion 811 of the upper guide plate 81. Therefore, the transfer paper P guided by the first guide portion 811 of the upper guide plate 81 and the lower guide plate 82 is moved after the front end thereof contacts the second guide portion 812 of the upper guide plate 81. The sheet is conveyed toward the transfer belt 43 on the upstream side in the transfer sheet conveying direction from the area B.

Next, a second part of the upper guide plate 81 will be described.
Will be described with reference to FIG. The angle α between the second guide portion 812 constituting the upper guide plate 81 and the transfer belt 43 on the upstream side of the nip range N in the transfer paper transfer direction, the second guide portion 812 and the nip range N
Of the transfer belt 43 from the upstream end of the transfer paper conveyance direction to the tension roller 45 on the upstream side in the transfer paper conveyance direction is 0 ° to 30 °.
° (0 ° <α <30 °). In the illustrated embodiment, the angle α is set to 3.04 °. The angle α is smaller than 0 ° (0 °> α), that is, the second guide 812 is positioned above the transfer belt 43 from the upstream end of the nip range N in the transfer paper transfer direction to the tension roller 45 on the upstream side above the transfer belt 43. If it is configured obliquely, the transfer paper comes into contact with the peripheral surface of the photosensitive drum 2 first. Also,
When the angle α is larger than 30 °, the angle between the transfer direction of the transfer paper and the transfer belt 43 becomes large, and the front end of the transfer paper comes into contact with the transfer belt 43 at a large angle. The transport stops, and trouble occurs in the transport of the transfer paper.

The image forming apparatus having the transfer belt mechanism in the illustrated embodiment is configured as described above, and the operation thereof will be described below. The transfer paper P fed by paper feeding means constituting a transfer paper feeding device (not shown) comes into contact with the nip portion of the pair of registration rollers 6 and stops at one end. Will be modified. Thereafter, the registration roller pair 6 is driven at a timing with the toner image formed on the peripheral surface of the photosensitive drum 2, and
The transfer paper P is fed toward the transfer area B. The transfer paper P fed by the pair of registration rollers 6 is guided by the first guide portion 811 of the upper guide plate 81 and the lower guide plate 82, and is conveyed obliquely leftward and upward in FIG.
Then, the transfer paper P has its front end abutting on the second guide portion 812 of the upper guide plate 81, and the transfer direction is changed.
The paper is conveyed toward the transfer belt 43 on the upstream side in the transfer paper conveyance direction from the nip range N formed as described above. Transfer belt 4
The transfer paper P conveyed toward 3 is polarized by the electric charge charged on the transfer belt 43, and the polarized electric charge of the transfer paper P and the true electric charge charged on the transfer belt 43 generate an electrostatic force. The transfer paper P is transferred to the transfer belt 4 by the electrostatic force.
3 and is transported to the nip area N. When the transfer paper P passes through the nip range N, the transfer belt 43
A predetermined bias voltage having a polarity opposite to the polarity of the toner attached to the peripheral surface of the photosensitive drum 2 is applied from a power source 48 to the toner image attached to the peripheral surface of the photosensitive drum 2. Is transferred to the transfer paper P.

As described above, the transfer paper P on which the toner image has been transferred when passing through the nip area N is polarized by the electric charge already charged on the transfer belt 43 before passing through the nip area N as described above. Then, this polarization charge and the transfer belt 43
Since the toner is attracted to the transfer belt 43 by the electrostatic force generated by the true charges charged to the photosensitive drum 2, the toner is conveyed in the direction indicated by the arrow D in FIG. Therefore, even when the front end of the transfer paper P fed by the registration roller pair 5 is curled upward, the transfer paper P is reliably separated and attracted to the transfer belt 43 without winding around the photosensitive drum 2.

[0025]

Embodiment 1 In the illustrated image forming machine described above, the second guide portion 812 constituting the upper guide plate 81 and the transfer belt 43 upstream of the nip range N in the transfer paper transport direction.
Was set at 3.04 °, and 50 sheets of A4-size transfer paper made of plain paper were continuously passed at room temperature (temperature: 20 ° C., humidity: 65%). No defective separation from the photosensitive drum 2 was found.

[0026]

COMPARATIVE EXAMPLE The angle α formed between the second guide portion 812 constituting the upper guide plate 81 and the transfer belt 43 on the upstream side of the nip range N in the transfer paper transport direction is set to -5 °. As a result, 50 experiments of A4 size transfer paper were continuously passed in a normal temperature state (temperature: 20 ° C., humidity: 65%), and the experiment was performed twice. As a result, the first time, the transfer paper was poorly separated from the photosensitive drum 2. There were 8 sheets and the second time had 12 sheets of poor separation.

Next, another embodiment of an image forming apparatus having a transfer belt mechanism constructed according to the present invention will be described with reference to FIGS. In FIGS. 3 and 4, the same members as those in the embodiment shown in FIGS. 1 and 2 are denoted by the same reference numerals, and detailed description thereof will be omitted. In the present embodiment, the bias voltage application point is set at the downstream end of the nip range N where the peripheral surface of the photosensitive drum 2 contacts the transfer belt 43 in the transfer paper transport direction. That is, the transfer roller 47 constituting the bias voltage application member of the bias voltage application unit 46 is disposed in contact with the back surface of the transfer belt 43 at the downstream end of the nip range N in the transfer paper transport direction.

As described above, the bias voltage application point is set at the downstream end of the nip range N in the transfer paper transport direction, so that the separation area C from the bias voltage application point is set.
Since the distance to the transfer belt 43 is short, the charging potential in the separation region of the transfer belt 43 does not become so high that a discharge phenomenon occurs.
It is possible to prevent the transfer paper from being poorly separated from the photosensitive drum 2 caused by the occurrence of the discharge phenomenon in the separation area C. Further, since the bias voltage application point is in the nip range N, that is, in the transfer region B where the nip range N exists, the transfer performance is reliably maintained.

[0029]

Second Embodiment In the illustrated image forming machine described above, the second guide portion 812 constituting the upper guide plate 81 and the transfer belt 43 upstream of the nip range N in the transfer paper transport direction, as in the first embodiment. The result of an experiment in which 50 sheets of A4 size transfer paper made of plain paper were continuously passed in a high-temperature and high-humidity state (temperature: 35 ° C., humidity: 85%) with an angle α of 3.04 ° In addition, there were three separation failures of the transfer paper from the photosensitive drum 2.

[0030]

Third Embodiment In the illustrated image forming machine described above, the second guide portion 812 constituting the upper guide plate 81 and the upstream side in the transfer paper transport direction from the nip range N in the same manner as in the first and second embodiments. 2. The angle .alpha.
A4 size transfer paper made of plain paper in a high-temperature and high-humidity state (temperature: 35 ° C., humidity: 85%) with the transfer roller 47 disposed at the downstream end of the nip area in the transfer paper transport direction. As a result of passing 50 sheets of paper continuously, there was no defective separation of the transfer paper from the photosensitive drum 2.

[0031]

The image forming apparatus provided with the transfer belt mechanism according to the present invention is constructed as described above, and has the following effects.

That is, according to the present invention, the transfer paper fed by the pair of registration rollers is moved from the nip area between the peripheral surface of the photosensitive drum and the transfer belt between the pair of registration rollers and the transfer belt mechanism. Since the transfer paper guiding means for guiding the transfer paper toward the transfer belt on the upstream side in the transport direction is provided, the front end of the transfer paper is transported toward the transfer belt on the upstream side in the transfer paper transport direction from the nip range, and is transferred to the transfer belt. Polarized by the charged charge, an electrostatic force is generated by the polarized charge of the transfer paper and the true charge charged on the transfer belt,
The transfer paper is attracted to the transfer belt by this electrostatic force and is conveyed to the nip area. The transfer paper on which the toner image has been transferred when passing through the nip area is polarized by the electric charge already charged on the transfer belt before passing through the nip area, and this polarized electric charge and the true electric charge charged on the transfer belt Therefore, the toner is conveyed without being adsorbed on the photosensitive drum in the separation area that has passed through the nip area because of the electrostatic force generated by the transfer belt. Therefore, even if the front end of the transfer paper fed by the pair of registration rollers is curled upward, the transfer paper is reliably separated and attracted to the transfer bell without winding around the photosensitive drum.

Further, according to the present invention, the bias voltage application point of the bias voltage applying means for applying a predetermined transfer bias voltage to the transfer belt is set such that the transfer paper is transported within the nip area between the peripheral surface of the photosensitive drum and the transfer belt. Since the distance is set at the downstream end in the direction, the distance from the bias voltage application point to the separation area is short, so that the charging potential in the separation area of the transfer belt does not become so high that a discharge phenomenon occurs. Therefore,
It is possible to prevent the transfer paper from being separated poorly from the photosensitive drum, which is caused by the occurrence of the discharge phenomenon in the separation area. In addition, since the bias voltage application point is in the transfer area where the nip range exists, the transfer performance is reliably maintained.

[Brief description of the drawings]

FIG. 1 is a front view schematically showing an embodiment of an image forming apparatus provided with a transfer belt mechanism configured according to the present invention.

FIG. 2 is an explanatory diagram showing a main part of the image forming apparatus including the transfer belt mechanism shown in FIG. 1 in an enlarged manner.

FIG. 3 is a front view schematically showing another embodiment of an image forming apparatus provided with a transfer belt mechanism configured according to the present invention.

FIG. 4 is an explanatory diagram showing an enlarged main part of an image forming apparatus provided with the transfer belt mechanism shown in FIG. 3;

[Explanation of symbols]

 2: photosensitive drum 4: transfer belt mechanism 41: drive roller 42: driven roller 43: transfer belt 44: tension roller 45: tension roller 46: bias voltage applying means 47: transfer roller 48: power supply 6: registration roller pair 8: Transfer paper guide means 81: Upper guide plate 811: First guide portion 812: Second guide portion 82: Lower guide plate

Claims (5)

[Claims] 1. A photoconductor drum rotatably disposed on a peripheral surface of which a toner image is formed, and a toner image formed on a peripheral surface of the photoconductor drum disposed opposite to the photoconductor drum. A transfer belt mechanism for transferring and transferring the transfer paper to a transfer paper; and a transfer belt disposed upstream of the transfer belt mechanism in the transfer paper transfer direction and transporting the transfer paper toward a transfer area where the photosensitive drum and the transfer belt mechanism face each other. A registration roller pair, wherein the transfer belt mechanism is provided with a driving roller and a driven roller disposed in parallel with each other, and a predetermined nip area wound around the driving roller and the driven roller on the peripheral surface of the photosensitive drum. An image forming apparatus including a transfer belt mechanism, the transfer roller including: a transfer belt that contacts with the transfer belt; and a bias voltage application unit that applies a predetermined transfer bias voltage to the transfer belt. Transfer paper guide means for guiding the transfer paper fed by the pair of registration rollers toward the transfer belt upstream of the nip area in the transfer paper transport direction is provided between the transfer belt mechanism and the transfer belt mechanism. An image forming machine provided with a transfer belt mechanism. 2. The transfer paper guide means comprises an upper guide plate and a lower guide plate, wherein the upper guide plate is formed by a first guide formed from the pair of registration rollers toward the photosensitive drum. 2. The transfer according to claim 1, further comprising: a second guide portion formed from the downstream end of the first guide portion to the transfer belt on the upstream side of the nip area in the transfer paper transfer direction. 3. An image forming machine equipped with a belt mechanism. 3. An angle α between the second guide portion of the upper guide plate and the transfer belt upstream of the nip range in the transfer paper transfer direction is 0 ° to 30 ° (0 ° <α <30 °). An image forming apparatus provided with the transfer belt mechanism according to claim 2, wherein 4. A photoreceptor drum rotatably disposed and having a toner image formed on a peripheral surface thereof, and a toner image formed on a peripheral surface of the photoreceptor drum disposed opposite to the photoreceptor drum. A transfer belt mechanism for transferring the image onto a transfer sheet and transporting the same, the transfer belt mechanism comprising: a drive roller and a driven roller disposed in parallel with each other; and the photosensitive drum wound around the drive roller and the driven roller. An image forming apparatus having a transfer belt mechanism, comprising: a transfer belt that contacts a peripheral surface of the transfer belt with a predetermined nip range; and a bias voltage applying unit that applies a predetermined transfer bias voltage to the transfer belt. An image forming apparatus comprising a transfer belt mechanism, wherein a bias voltage application point of a bias voltage application unit is set at a downstream end of the nip range in a transfer paper transport direction. 5. A photoreceptor drum rotatably disposed on a peripheral surface of which a toner image is formed, and a toner image formed on a peripheral surface of the photoreceptor drum disposed opposite to the photoreceptor drum. A transfer belt mechanism for transferring and transferring the transfer paper to a transfer paper; and a transfer belt disposed upstream of the transfer belt mechanism in the transfer paper transfer direction and transporting the transfer paper toward a transfer area where the photosensitive drum and the transfer belt mechanism face each other. A registration roller pair, wherein the transfer belt mechanism is provided with a driving roller and a driven roller disposed in parallel with each other, and a predetermined nip area wound around the driving roller and the driven roller on the peripheral surface of the photosensitive drum. And a bias voltage applying means for applying a predetermined transfer bias voltage to the transfer belt, the image forming apparatus having a transfer belt mechanism. The bias voltage application point of the step is set at the downstream end of the transfer paper in the nip area in the direction of conveyance of the transfer paper, and the transfer paper fed by the registration roller pair is placed between the registration roller pair and the transfer belt mechanism. An image forming apparatus comprising a transfer belt mechanism, further comprising transfer paper guide means for guiding the transfer belt upstream of the nip range in the transfer paper transport direction.