JP2001194927A - Electrophotographic recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic recording device capable of surely obtaining a good image. SOLUTION: The electrophotographic recording device 10 includes a transferred image carrying member 16 to which a visible image on an image carrier 12 is transferred from the image carrier by a primary transfer mechanism 17, a secondary transfer mechanism 19 for transferring the visible image on the transferred image carrying member to a sheet-like recording medium 18, and a fixing mechanism 20 to which the transferred image carrying member and also the recording medium are carried from the secondary transfer mechanism so as to fix the visible image transferred on the recording medium. The secondary transfer mechanism 19 and the fixing mechanism 20 are arranged at intervals of L0 equal to or below the length of the recording medium in the recording medium 18 carrying direction so that either of the mechanisms 19 and 20 may mutually restrain the recording medium 18 and the transferred image carrying member 16 in a fixed state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic recording apparatus suitable for incorporating in a device such as a facsimile machine, a copying machine or a printer.

[0002]

2. Description of the Related Art An electrophotographic recording apparatus is used alone or incorporated in an apparatus such as a facsimile apparatus, a copying machine or a printer. In an electrophotographic recording apparatus of this type, the surface of an image carrier such as a photosensitive drum is charged substantially uniformly, and then selectively irradiated with light by an exposure mechanism, whereby the photosensitive drum serving as the image carrier is charged. An electrostatic latent image is formed on the surface. The electrostatic latent image on the photosensitive drum is visualized by the adhesion of the toner supplied from the developing mechanism. The visible image on the photosensitive drum is
When a transfer voltage is applied to the transfer roller with a recording medium such as a recording paper interposed between the transfer roller and the transfer roller that is rotated synchronously in contact with the transfer roller, the transfer voltage is applied to the toner on the photosensitive drum. The image is transferred onto the recording paper by the transfer voltage. After that, the toner constituting the visible image on the recording paper is fused to the recording paper by heat and pressure given by the fixing mechanism, whereby the transferred visible image is fixed on the recording paper.

In the above-mentioned transfer step, in order to obtain a good transfer of a visible image onto a recording paper, a transfer current flowing from the transfer roller to the photosensitive drum via the recording paper by a transfer voltage applied to the transfer roller is required. Is one of the important factors. Therefore, an appropriate transfer voltage according to the electric resistance of the recording paper is set in advance. However, the electrical resistance of the recording paper used varies greatly depending on the environment in which it is used. If the electric resistance of the recording paper is higher than a resistance value considered in advance, a predetermined transfer current does not flow from the transfer roller to the photosensitive drum via the recording paper, so that when the recording paper is peeled off from the transfer roller, the recording is performed. The voltage remaining on the paper exceeds the discharge threshold of the so-called Paschen curve, causing a discharge between the recording paper and the photosensitive drum. This discharge causes release of the toner transferred on the recording paper from the recording paper. Also, due to the high voltage remaining on the recording paper,
A so-called jam is caused in which the recording paper is wound around the photosensitive drum.

Therefore, in order to obtain a good transfer onto the recording paper without being affected by a change in the electric resistance of the recording paper in the use environment, the visible image on the photosensitive drum is transferred to an infinite circulation belt made of, for example, a synthetic resin material. After transfer to such a transfer image bearing member, transfer to recording paper from the endless circulating belt has been proposed. The endless circulating belt is not so affected by the use environment as recording paper, and exhibits a substantially predetermined electric resistance value regardless of the change in the use environment. A good transfer image can be obtained on the endless circulating belt with current. The transfer image on the endless circulating belt is transferred from the endless circulating belt onto recording paper by a secondary transfer mechanism. In the secondary transfer process by the secondary transfer mechanism, the electrical resistance of the recording paper is affected by the use environment, but the secondary transfer is performed in a state where the recording paper is arranged so as to cover the toner on the infinite circulation belt. Since this operation is performed, it is possible to prevent the toner from being released from the recording paper immediately after the transfer, and to prevent the recording paper from being jammed.

[0005]

However, in the above-described electrophotographic recording apparatus using a transfer image carrier such as an endless circulating belt, the transfer image is caused by vibration or the like during a period from the secondary transfer mechanism to the fixing mechanism. When the recording medium on the carrier moves with respect to the transfer image carrier, a clear image may not be obtained on the recording medium. SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic recording apparatus capable of reliably obtaining a good image.

[0006]

The present invention adopts the following constitution in order to solve the above points. <Constitution> The present invention provides a transfer image carrying member that transfers a visible image visualized on the image carrier by developing a latent image formed on the image carrier from the image carrier by a primary transfer mechanism, A secondary transfer mechanism for transferring the visible image transferred to the transfer image carrying member to a sheet-shaped recording medium; and a visible image transferred on the recording medium by the secondary transfer mechanism. A fixing mechanism that receives the transfer of the recording medium together with the transfer image carrying member from the secondary transfer mechanism to fix the image on the recording medium, wherein the secondary transfer mechanism and the fixing mechanism The length of the recording medium along the transport direction of the recording medium, so that at least one of the recording medium and the transferred image carrying member at least one of which is transferred with the visible image is fixedly constrained to each other. It is arranged at intervals less than the dimensions And wherein the door.

According to the present invention, the recording medium sent from the secondary transfer mechanism to the fixing mechanism integrally with the transfer image bearing member on the transfer image bearing member is provided by the secondary transfer mechanism or the fixing mechanism. Since the recording medium is conveyed to the fixing mechanism while maintaining the integrity with the transfer image carrying member by at least one of the transfer image carrying members, even if the recording medium receives vibration or the like on the transfer image carrying member, Since the image transferred from the transfer image bearing member does not cause any relative displacement on the transfer image bearing member and is sent to the fixing mechanism in a state where the image transferred from the transfer image bearing member is securely held, the above-described recording is performed. A clear image can be obtained on the recording paper medium without causing image blurring due to the displacement of the medium.

[0008] The transfer image bearing member may be constituted by an annular endless circulating belt which goes around a predetermined endless circulating path as in the prior art, and the secondary transfer mechanism and the fixing mechanism are provided with an endless circulating path of the endless circulating belt. They can be spaced from one another along the path.

The secondary transfer mechanism includes a secondary transfer roller disposed on one surface side of the belt and a secondary transfer roller disposed on the other surface side of the belt in cooperation with the secondary transfer roller. And a secondary transfer backup roller that sandwiches the recording medium that receives a visible image transferred from the belt. The fixing mechanism further includes a fixing roller disposed on one surface side of the belt and a fixing roller disposed on the other surface side of the belt in cooperation with the fixing roller. A fixing backup roller for sandwiching the recording medium after the transfer can be provided.

Instead of the above-described example, the secondary transfer mechanism is provided with a secondary transfer roller disposed on one side of the belt and a secondary transfer roller disposed on the other side of the belt. In the meantime, a secondary transfer backup roller that sandwiches the belt and the recording medium that receives the transfer of the visible image from the belt can be provided. Further, in this example, the fixing mechanism is arranged on the other surface side of the belt at an interval from the secondary transfer backup roller and cooperates with the secondary transfer roller. A fixing roller may be provided to sandwich the recording medium to which the visible image has been transferred.

Since the secondary transfer roller functions as a backup roller for the fixing roller, a backup roller dedicated to the secondary transfer roller is not required, thereby simplifying the configuration. it can.

Further, in this example, in order to releasably sandwich the belt between the secondary transfer roller and the secondary transfer backup roller and the fixing roller, the release position and the sandwiching position are determined. In between, it can be movable. Due to the movement of the secondary transfer roller, the belt can be released from contact with the fixing roller during a non-operation such as an idling operation, thereby causing unnecessary heating of the belt from the fixing roller. The deterioration of the belt can be prevented.

The present invention can be applied to a multicolor electrophotographic recording apparatus in which a plurality of image carriers are arranged at intervals from one another in the direction of circulation of the belt. In this multicolor electrophotographic recording apparatus, the belt is sandwiched between the primary transfer mechanism in cooperation with each image carrier so as to sequentially transfer the visible images of the plurality of image carriers to the belt. A plurality of primary transfer rollers arranged corresponding to the respective image carriers and a power supply circuit for applying a transfer voltage to each of the primary transfer rollers so as to supply a transfer current to each of the primary transfer rollers are provided. . In this multicolor electrophotographic recording apparatus,
The electric resistance value of each primary transfer roller is increased in the direction of circulation of the belt in order to gradually increase the transfer current flowing through each primary transfer roller in the direction of circulation of the belt regardless of application of the same voltage from the power supply circuit. It gradually decreases gradually.

In the multicolor electrophotographic recording apparatus of the present invention, the electric resistance value of each primary transfer roller is sequentially changed without generating a plurality of voltage values for the plurality of primary transfer rollers. By applying a predetermined voltage to each primary transfer roller, the transfer voltage of each primary transfer roller can be gradually increased in the direction opposite to the circulating direction of the belt. With this, a different transfer voltage is sequentially applied to each of the plurality of primary transfer rollers in the same manner as in the conventional multi-color electrophotographic recording apparatus without using a special voltage conversion unit with a power supply circuit that outputs a single voltage. Since a voltage can be applied, a multicolor electrophotographic recording apparatus capable of obtaining a good image with a simple configuration as compared with the related art is provided.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments. <Embodiment 1> FIG. 1 shows Embodiment 1 in which the electrophotographic recording apparatus according to the present invention is applied to a monochrome copying machine. The electrophotographic recording apparatus 10 shown in FIG. 1 is arranged in relation to a photosensitive drum 12 having an insulating photoconductive layer 11 formed on the surface thereof, as in a conventional electronic copying machine, A charging mechanism 13 for uniformly applying charges to the photoconductive layer 11 of the photosensitive drum 12 in a dark place, and forming a latent image corresponding to a desired image on the photoconductive layer 11 provided with uniform charges. An exposure mechanism 14 for exposing the photoconductive layer 11;
And a developing mechanism 15 for forming a visible image corresponding to the latent image on the photoconductive layer 11 that has been exposed to the photosensitive drum 12.

Further, the electrophotographic recording apparatus 10 transfers the visible image obtained on the photosensitive drum 12 by development to a transfer image carrying member 16 constituted by an annular endless circulating belt made of, for example, a synthetic resin material. A primary transfer mechanism 17, a secondary transfer mechanism 19 for transferring the visible image transferred by the transfer mechanism onto the endless circulating belt 16 as an image bearing member to a recording medium 18 such as a recording paper, and recording. A fixing mechanism 20 for fixing the visible image transferred on the recording paper 18 as a paper medium to the recording paper. The resin material constituting the endless circulation belt 16 does not show large water absorption like paper, and does not show a large change in electric resistance as much as paper irrespective of changes in environmental temperature or humidity.

The charging mechanism 13 has a charging roller 22 which receives a voltage of, for example, -1350 V from a DC power supply 21 in the illustrated example. The charging roller 22 contacts the surface (11) of the photosensitive drum 12 which is driven and rotated counterclockwise in the drawing, and is rotated in synchronization with the photosensitive drum 12, so that the surface of the photosensitive drum 12 contacting the charging roller 22, The photoconductive layer 11 is uniformly charged to, for example, -800V. Photoconductive layer 1 uniformly charged on photosensitive drum 12
1 receives selective exposure from an exposure mechanism 14 constituted by, for example, an LED head having an LED light source, and receives selective exposure due to disappearance of electric charges in the exposed portion of the photoconductive layer 11. The potential of the portion changes from 0 to -70. The changed portion of the potential is held on the photoconductive layer 11 of the photosensitive drum 12 as an electrostatic latent image.

The developing mechanism 15 for forming a visible image corresponding to the electrostatic latent image includes a developing roller 24 to which a negative potential is applied from a DC power supply 23 in the illustrated example. The developing roller 24 is rotated in synchronization with the photosensitive drum 12, and supplies toner particles 25 charged to, for example, -300V onto the photoconductive layer 11 by being in contact with the photosensitive drum 12. The negatively charged toner particles 25 supplied to the photoconductive layer 11 are selectively held corresponding to the electrostatic latent image by the Coulomb force with the charge of the photoconductive layer 11, By the toner particles 25 held on the photoconductive layer 11,
A visible image corresponding to the electrostatic latent image is formed on the photosensitive drum 12.

The endless circulating belt 16 for receiving the visible image composed of the toner particles 25 on the photosensitive drum 12 has its surface driven by a driving force of a driving roller 26 operated synchronously with the photosensitive drum 12. 12 is circulated clockwise in FIG. The electric resistance of the surface of the endless circulating belt 16 which is in contact with the photosensitive drum 12 is desirably set to a value between 1 × 10 ^{9 and} 1 × 10 ¹² Ω.
The surface treatment is performed so that the toner particles 25 melted in a fixing step described below do not soak. In addition, the infinite circulation belt 16
Is appropriately selected from synthetic resin materials that are unlikely to cause deformation, deterioration, melting, electric resistance change, and the like due to heat.

The primary transfer mechanism 17 includes a primary transfer roller 27 that cooperates with the photosensitive drum 12 to sandwich the endless circulating belt 16 therebetween. The transfer potential necessary for transferring the negatively charged toner particles 25 constituting the visible image on the photosensitive drum 12 to the surface of the endless circulating belt 16 with a positive potential is applied to the primary transfer roller 27.
DC power supply 28 is provided.

In the primary transfer mechanism 17, a transfer potential from a DC power supply 28 is applied from the primary transfer roller 27 to the photosensitive drum 12 via the endless circulating belt 16. Since the endless circulating belt 16 sandwiched between the primary transfer roller 27 and the photosensitive drum 12 does not cause a large change in electric resistance according to an environmental change as in the recording paper 18 and exhibits a substantially constant electric resistance value, Regardless of the environmental change, an appropriate transfer potential is always applied by the appropriately selected DC power supply 28. Therefore, in the primary transfer mechanism 17,
A visible image composed of toner particles 25 is suitably transferred to the endless circulating belt 16 with an appropriate transfer current. After the transfer, that is, when the endless circulating belt 16 separates from the photosensitive drum 12, a discharge occurs between the two. Since the high voltage does not remain on the endless circulating belt 16 as much as possible, the remaining high voltage does not cause disturbance of the toner particles 25, and a good visible image is transferred onto the endless circulating belt 16. Is done.

As shown by the phantom line in FIG.
Therefore, it is desirable that the detection circuit 29 detects a voltage drop due to the electric resistance of each of the primary transfer roller 27 and the photosensitive drum 12, and finely adjusts the transfer potential based on a change in the detected value. With this detection circuit 29, it is possible to maintain an appropriate transfer potential for a long period of time irrespective of a change in electrical resistance due to deterioration of the endless circulating belt 16 or the like.

The recording paper 18 that receives the transfer of the visible image transferred to the endless circulation belt 16 is guided to a secondary transfer mechanism 19 along a guide plate 31 by the operation of a pair of paper feed rollers 30. .

Secondary transfer mechanism 1 receiving supply of recording paper 18
Numeral 9 is arranged along the circulation path of the endless circulation belt 16 at a predetermined interval from the primary transfer mechanism 17 in the circulation direction. The secondary transfer mechanism 19 includes a secondary transfer roller 32 disposed on one surface side of the endless circulation belt 16, that is, the surface side of the endless circulation belt 16, and a second transfer roller 32 disposed on the other surface side of the endless circulation belt 16, A secondary transfer backup roller 33 is provided on the opposite side of the secondary transfer roller 32 with the infinite circulation belt 16 therebetween.

The rollers 32 and 33 are operated synchronously with the endless circulating belt 16 so as to sandwich the endless circulating belt 16 and the recording paper 18 therebetween. The recording paper 18 is guided by the secondary transfer mechanism 19 along the guide plate 31 so as to be inserted between the endless circulation belt 16 on which the visible image is formed and the secondary transfer roller 32. Is done.

The secondary transfer roller 32 applies a transfer potential necessary for transferring the negatively charged toner particles 25 constituting the visible image on the infinite circulation belt 16 onto the recording paper 18 with a positive potential. DC power supply 34 for application to
Is provided. Secondary transfer backup roller 33
Is grounded.

In the secondary transfer mechanism 19, when a transfer potential from a DC power supply 34 is applied to a secondary transfer backup roller 33 via the secondary transfer roller 32, the recording paper 18 and the endless circulating belt 16, The toner particles 25 on the endless circulation belt 16 are transferred onto the recording paper 18 by the positive potential of the next transfer roller 32. In the secondary transfer process by the secondary transfer mechanism 19, even if the recording paper 18 changes in electric resistance due to an environmental change as in the related art, a high voltage from the secondary transfer roller 32 remains on the recording paper 18, for example. However, the recording paper 18 does not generate a discharge between the high potential secondary transfer roller 32 and the endless circulating belt between the recording paper 18 and the grounded secondary transfer backup roller 33. Because of the interposition of 16, no discharge occurs between the two 18 and 33. Further, since the toner particles 25 are transferred to the recording paper 18 while being sandwiched between the recording paper 18 and the endless circulating belt 16, the toner particles 25 are not disturbed by vibration or electric discharge. Is transferred to the recording paper 18 properly.

As shown by the phantom line in FIG.
The detection circuit 35 detects the voltage drop due to the electric resistance of each of the secondary transfer roller 32, the recording paper 18, the endless circulating belt 16 and the secondary transfer backup roller 33, and based on the change of this detected value, It is desirable to adjust the transfer potential in the secondary transfer.

Since the change in the detected value by the detection circuit 35 largely depends on the change in the electrical resistance of the recording paper 18, the secondary transfer potential is adjusted according to the detection result of the detection circuit 35. An appropriate secondary transfer voltage can be applied irrespective of the change in the electric resistance of the recording paper 18, whereby a predetermined appropriate transfer current can be obtained irrespective of the change in the electric resistance of the recording paper 18. Therefore, by controlling the secondary transfer potential according to the detection result of the detection circuit 35, it is possible to obtain a better visible image on the recording paper 18 irrespective of a change in the electric resistance of the recording paper 18. . The adjustment timing of the secondary transfer potential, that is, the timing at which the recording paper 18 reaches between the secondary transfer roller 32 and the secondary transfer backup roller 33 can be calculated based on a signal from a sensor 46 described later.

A fixing mechanism 20 for fixing the visible image to the recording paper 18 is adjacent to and spaced from the secondary transfer mechanism 19 in the direction of circulation along the circulation path of the endless circulation belt 16. It is arranged. The secondary transfer mechanism 19
In the illustrated example, the fixing roller 36 disposed on the surface side of the endless circulating belt 16 and the endless circulating belt 1
6 is a fixing backup roller 3 disposed on the other surface side.
7 is provided. The infinite circulation belt 16 includes the fixing backup roller 37 and the secondary transfer backup roller 3.
3. The endless circulating belt 16 is arranged around the primary transfer roller 27 and the driving roller 26 so that the circulating path of the belt 37, 33, 27 and 26
Stipulated by

The fixing roller 36 and the fixing backup roller 37 cooperate with each other between the endless circulating belt 1 and the fixing roller 36.
6 and recording paper 18 which has undergone a transfer of a visible image from the belt
Is operated synchronously with the endless circulating belt 16 so as to sandwich the belt. The fixing roller 36 heats the toner particles 25 on the recording paper through the recording paper 18 by power supply from a heating power supply 38. Also, the toner particles 25 on the recording paper 18
Is pressed onto the recording paper 18 between the rollers 36 and 37. Due to the heat and pressure between the rollers 36 and 37, the toner particles 25 are melted and penetrate into the recording paper 18, so that the visible image is fixed on the recording paper 18.

The distance between the secondary transfer mechanism 19 and the fixing mechanism 20, in the illustrated example, a pair of rollers 3 of the secondary transfer mechanism 19
A distance L ₀ between a virtual line 39 connecting both rotation axes 2 and 33 and a virtual line 40 connecting both rotation axes of the pair of rollers 36 and 37 of the fixing mechanism 20 is a length dimension in the conveyance direction of the recording paper 18. It is set as follows.

Since the length of the recording paper 18 in the transport direction is larger than the interval L ₀ , the leading end of the recording paper 18 in the transport direction is the two rollers 3 of the secondary transfer mechanism 19.
2 and 33, the leading edge of the recording paper 18 reaches between the rollers 36 and 37 of the fixing mechanism 20 until the leading end thereof reaches
The recording paper 18 is driven by both rollers 32 and 3 of the secondary transfer mechanism 19.
By being sandwiched integrally with the endless circulation belt 16 between the three, the endless circulation belt 16 is fixedly restrained.

Accordingly, the recording paper 18 to which the visible image has been transferred from the endless circulation belt 16 is completely released from the secondary transfer mechanism 19 and the fixing mechanism 20 with respect to the endless circulation belt 16. Since the recording paper 18 to which the visible image has been transferred by the secondary transfer mechanism 19 is not separated, the recording paper 18 is sent to the fixing mechanism 20 without being separated from the endless circulating belt 16. Thereby, the recording paper 18
Does not cause a positional shift with respect to the endless circulating belt 16 until it reaches the fixing mechanism 20, and even if vibration or the like acts on the recording paper 18, the visible image is blurred due to the displacement of the recording paper 18. And the fixing mechanism 20 undergoes the above-described fixing step, so that a clear visible image can be obtained on the recording paper 18.

A residual charge is removed from the recording paper 18 on which the visible image is fixed by the fixing mechanism 20 by the charge elimination brush 42, and the recording paper 18 is prevented from being attracted to the infinite circulation belt 16 by the peeling plate 41. As a result, the toner is properly discharged from the fixing mechanism 20.

Residual toner and paper dust remaining on the surface of the endless circulation belt 16 during the fixing step by the fixing mechanism 20 can be collected by a collection tray 43 provided in the circulation path of the endless circulation belt 16. Further, in order to suppress deterioration of the endless circulating belt 16 due to heat due to heating of the fixing roller 36, it is desirable to provide a cooling means 44 such as a blower.

The timing of exposure by the exposure mechanism 14 and the timing of feeding of the recording paper 18 to the secondary transfer mechanism 19 by the pair of paper feed rollers 30 are, for example, a mark indicating a printing start position on the infinite circulation belt 16 in advance. 45 is provided, and control can be performed based on a signal from a sensor 46 that detects that the mark 45 has reached a predetermined position. That is, when the sensor 46 detects the mark 45, the exposure process is started, and after a predetermined time, the toner particles 25 are supplied to the photosensitive drum 12 by the developing process, and the visible image on the infinite circulation belt 16 is fixed. The recording paper 18 is fed in synchronization with a predetermined time reaching the mechanism 20.
The feeding of the recording paper 18 is controlled by a sensor 47 that detects the passage of the leading end of the recording paper 18.

According to the electrophotographic recording apparatus 10 of Embodiment 1 shown in FIG. 1, as described above, a visible image is formed on the recording paper 18 from the photosensitive drum 12 through the endless circulating belt 16 by the primary transfer. Since the image is transferred, the recording paper 18 does not come into contact with the photosensitive drum 12, and the recording paper 18 does not become entangled with the photosensitive drum 12 or the paper dust does not adhere. In addition, the endless circulating belt 16 receiving the transfer of the visible image from the photosensitive drum 12 does not cause a large change in electric resistance as in the recording paper 18 and has a proper transfer current by applying a proper transfer potential. , Toner particles 2
5, a good visible image can be formed on the endless circulating belt 16 without causing large disturbances. further,
The recording paper 18 to which the visible image on the endless circulation belt 16 has been transferred by the secondary transfer is sent to the fixing mechanism 20 while holding the toner particles 25 integrally with the endless circulation belt 16. Therefore, even if vibration or the like acts on the recording paper 18 during the period from the secondary transfer process to the fixing process, the toner particles 25 are not disturbed, so that a clear visible image is formed on the recording paper 18. Can be obtained.

<Embodiment 2> FIG. 2 shows an embodiment 2 of the electrophotographic recording apparatus according to the present invention, in which functional parts similar to those shown in Embodiment 1 are given the same reference numerals as in Embodiment 1. Shown.

The electrophotographic recording apparatus 1 of the embodiment 2 shown in FIG.
Reference numeral 10 designates an annular endless circulation path of the endless circulation belt 16 by a driving roller 26, a driven roller 26 ', a primary transfer roller 27, a secondary transfer backup roller 33, and a fixing roller 36. In the specific example 2, the endless circulating belt 16 is circulated counterclockwise as viewed in FIG. 2, and these roller groups (26, 2
6 ', 27, 33, and 36) are disposed on the other surface side, which is the back surface side of the endless circulating belt 16, and a secondary transfer having a diameter larger than the diameter of both rollers 33 and 36 is provided on the other side. The roller 32 is disposed on the front side of the endless circulation belt 16.

The secondary transfer roller 32 cooperates with a secondary transfer backup roller 33 and a fixing roller 36 so as to sandwich the infinite circulation belt 16 therebetween.
The belt is rotated synchronously with the belt. The secondary transfer roller 32 and the secondary transfer backup roller 33 receive the recording paper 18 from the paper feed roller 30 during that time. Between the rollers 32 and 33, the secondary transfer roller 32
By applying a transfer potential from the DC power supply 34 to the
The visible image primarily transferred onto the endless circulation belt 16 by the primary transfer roller 27 is secondarily transferred from the endless circulation belt 16 to the recording paper 18. Therefore, the secondary transfer roller 32 and the secondary transfer backup roller 33 of the specific example 2 function as the secondary transfer mechanism 19 similar to each of the rollers 32 and 33 of the specific example 1.

Secondary transfer roller 32 and fixing roller 36
In the meantime, is rotated synchronously with the endless circulating belt 16 so as to sandwich the endless circulating belt 16 from the secondary transfer mechanism 19 and the recording paper 18 to which the visible image has been transferred from the belt. The fixing roller 36 heats the toner particles 25 by power supply from the heating power supply 38 and presses the toner particles 25 against the recording paper 18 between the fixing roller 36 and the secondary transfer roller 32, as in the first embodiment. Therefore, the secondary transfer roller 32 functions as a fixing backup roller for the fixing roller 36 in relation to the fixing roller 36.

An imaginary line 39 'connecting the rotation axes of the secondary transfer roller 32 and the secondary transfer backup roller 33 functioning as the secondary transfer mechanism 19, and a fixing roller 36 and a secondary transfer roller functioning as the fixing mechanism 20. 32
The length L ₀ of the arc of the secondary transfer roller 32 indicated by the acute angle defined by the imaginary line 40 ′ connecting the respective rotation axes is equal to or less than the length of the recording paper 18 in the transport direction. is there.

With this dimension setting, the recording paper 18 from the secondary transfer mechanism 19 to the fixing mechanism 20 is applied to the secondary transfer roller 3
2 and at least one of between the fixing roller 36 or between the fixing roller 36 and the secondary transfer roller 32,
Since the movement of the recording paper 18 with respect to the endless circulating belt 16 is restricted, blurring of the visible image due to the displacement of the recording paper 18 due to vibration or the like is prevented as in the specific example 1 described above. 18, it is possible to obtain a clear visible image.

Further, according to the second embodiment, the secondary transfer roller 32 can be provided with a function of a fixing backup roller for the fixing roller 36, and a dedicated roller for the fixing backup roller is not required. Therefore, the size of the electrophotographic recording apparatus 110 can be reduced. Moreover, as compared with the first embodiment, the distance L ₀ between the secondary transfer mechanism 19 and the fixing mechanism 20 can be set smaller, which is advantageous in obtaining a clear visible image.

Further, from the secondary transfer mechanism 19 to the fixing mechanism 20
During this time, the recording paper 18 is conveyed integrally with the endless circulating belt 16 in a state where a predetermined voltage is applied from the DC power supply 34 by the secondary transfer roller 32, so that a stable conveyance state with respect to the toner particles 25 Can be maintained.

<Embodiment 3> FIG. 3 shows Embodiment 3 in which the present invention is applied to a multicolor electrophotographic recording apparatus. In the specific example 3 of FIG. 3, the same functional parts as those in the specific examples 1 and 2 shown in FIGS. 1 and 2 are denoted by the same reference numerals.

The multicolor electrophotographic recording device 12 according to the present invention
0, as shown in FIG. 3, is applied to the endless circulating belt 16 around the driving roller 26 and the driven roller 26 'similar to that shown in FIG.
The respective photosensitive drums 12 (12a, 12b, 12c) for red (magenta), purple (cyan) and black (black)
And 12d), the exposure mechanism 14 (14a, 14b, 14)
c and 14d) are sequentially arranged in the circulation direction of the endless circulation belt 16.

Each photosensitive drum 12 (12a, 12b, 12
c and 12d) have respective DC power supplies 21 (21
a, 21b, 21c and 21d) are applied with a potential for charging via the respective charging rollers 22 (22a, 22b, 22c and 22d). Also, after charging,
Each exposure mechanism 14 (14a, 14b, 14c and 14
Each of the photosensitive drums 12 (12a, 12b, 12c, and 12d) on which a latent image has been formed by exposure by d) is supplied with a negative potential from each DC power supply 23 (23a, 23b, 23c, and 23d). Developing roller 24 (24
a, 24b, 24c and 24d), and the respective colored toner particles 25 (25a, 25b, 25c and 2).
5d). Thereby, each photosensitive drum 12
A visible image is formed on (12a, 12b, 12c, and 12d) by the respective colored toner particles 25 (25a, 25b, 25c, and 25d).

In the multicolor electrophotographic recording apparatus 120, each photosensitive drum 12 (12a, 12b, 12c and 12d)
Each of the colored toner particles 25 (25
a, 25b, 25c and 25d), the primary transfer mechanisms 17 (17a, 17b,
According to 17c and 17d), in the example shown in FIG. 3, the images are sequentially superimposed and transferred in the order of yellow, red, purple and black.

Each primary transfer mechanism 17 (17a, 17b, 1
7c and 17d) are the respective DC power supplies 28 (28
a, 28b, 28c and 28d) to which the primary transfer potential is applied from the primary transfer roller 27 (27a, 27b, 2c).
7c and 27d). Each primary transfer roller 27
(27a, 27b, 27c and 27d) correspond to the corresponding photosensitive drums 12 (12a, 12b, 12c and 12d).
d), the respective photosensitive drums 12 (12a, 12a
b, 12c and 12d), and is rotated synchronously with the photosensitive drum 12 so as to sandwich the endless circulation belt 16 therebetween.

The primary transfer roller 27 (27a, 27b, 2
7c and 27d), the primary transfer rollers 27 (27a, 27b, 2
7c and 27d), the visible images are sequentially formed so as to overlap each other. Therefore, the colored toner particles 25 (25a, 25b, 25c and 25d) are provided for each primary transfer stage.
Of the toner particles 2
As the degree of overlap of No. 5 increases, the transfer efficiency decreases.

In order to prevent a decrease in transfer efficiency at each primary transfer stage along the direction of circulation of the endless circulating belt 16, DC power supplies 28a, 28b for the respective primary transfer rollers 27a, 27b, 27c and 27d are used. The voltage values of 28c and 28d are transferred to primary transfer rollers 27a, 27b, 2
The transfer efficiency is increased in the order of 7c and 27d, whereby the primary transfer current value in each primary transfer stage is sequentially increased for each primary transfer stage toward the subsequent stage, thereby preventing the above-described decrease in transfer efficiency. However, in this case, a plurality of DC power supplies 2 having different output voltage values are used.
8 (28a, 28b, 28c and 28d), voltage conversion means for obtaining a plurality of output voltages from a single output voltage source is indispensable.
The configuration of the power supply device used as (28a, 28b, 28c and 28d) is complicated.

In order to prevent the power supply from becoming complicated, the respective electric resistance values (Ra, Rb, Rc, Rd) of the respective primary transfer rollers 27a, 27b, 27c and 27d are directed to the subsequent primary transfer stage. It is desirable to reduce them sequentially. That is, the primary transfer rollers 27a, 27b, 2
The resistance values of 7c and 27d are Ra, R
b, Rc and Rd, the following formula Ra
>Rb>Rc> Rd (1) to give the DC power supplies 28a, 28b, 28c and 28d
Of the primary transfer currents (Ia, Ib, Ic and Ic) at each primary transfer stage,
d) can be sequentially increased toward the subsequent stage, thereby preventing a decrease in transfer efficiency toward the subsequent stage at each primary transfer stage.

For example, each DC power supply 28a, 28b, 28
When the same voltage value of 3 KV is adopted for c and 28d, the primary transfer current values Ia, Ib, Ic and Id at the last primary transfer stage from the primary transfer current value at the foremost primary transfer stage are 4 μA and 5 μm, respectively.
A, 6 μA and 7 μA, the electrical resistance of the photosensitive drum 12, the electrical resistance of the endless circulating belt 16, and the combined resistance of the recording paper 18 and the primary transfer roller 27 at each primary transfer stage are primary From the transfer stage to the last primary transfer stage, for example,
Each primary transfer roller 27a, 27b, 50MΩ, 600MΩ, 500MΩ and 429MΩ
27c and 27d (Ra, Rb, Rc,
Rd) is appropriately selected.

Each primary transfer roller 27a as described above,
27b, 27c and 27d (Ra, R
b, Rc, Rd), a single voltage value is adopted for each DC power supply 28 (28a, 28b, 28c and 28d), and the primary transfer current value at each primary transfer stage is set at a subsequent stage for each primary transfer stage. , The transfer efficiency can be prevented from decreasing, and the power supply device can be favorably placed on the endless circulating belt 16 with a relatively simple configuration without complicating the power supply device. A multicolor visible image can be formed.

The visible image formed on the endless circulating belt 16 through each primary transfer stage is, as in the second embodiment, a secondary transfer backup roller 33 and a secondary transfer backup roller 33 as shown in FIG. The recording paper 18 fed by the transfer roller 32 via the paper feed rollers 30 and 30 ′
Is preferably transferred. Also, the recording paper 1 that has undergone the secondary transfer
Reference numeral 8 denotes a secondary transfer roller 32 through a transport distance L ₀ set to be equal to or less than the length of the recording paper 18 in the transport direction.
Is subjected to a fixing process of a visible image by being conveyed to a fixing roller 36 serving as a fixing backup roller.

Accordingly, the electrophotographic recording device 12 of the third embodiment is
0, the secondary transfer roller 32 and the secondary transfer backup roller 33 as in the specific example 2 described above.
From the secondary transfer mechanism 19 including the secondary transfer roller 32 to the fixing mechanism 20 including the fixing roller 36.
Reference numeral 8 denotes a state in which the movement of the recording paper 18 relative to the endless circulating belt 16 is restricted at least one of between the secondary transfer roller 32 and the fixing roller 36 or between the fixing roller 36 and the secondary transfer roller 32. Paper 18
The blur of the visible image due to the displacement due to the vibration of the image is prevented, and a clear visible image on the recording paper 18 can be obtained.

<Embodiment 4> In the multicolor electrophotographic recording apparatus 130 shown in FIG.
The infinite circulation path mainly includes one drive roller 26
And three driven rollers 26a ', 26b', 26c '. Drive roller 26 and driven roller 26
a ′ has their rotation axes fixedly held,
It is pivoted about each fixed axis of rotation. On the other hand, the driven roller 26b 'disposed below the driving roller 26 and the driven roller 26a' corresponding thereto.
And 26c 'are the offset positions shown in FIG.
It can be moved between the operating positions shown by the solid lines in FIG.

The two driven rollers 26b 'and 26c'
Although held at the above-mentioned bias position by its own weight, although not shown, the multicolor electrophotographic recording apparatus 13 is provided by a spring force of a bias means including an elastic member such as a coil spring.
In the idling state of 0, it can be reliably held at the offset position. In this bias position, the driven rollers 26b 'and 26c' are located below the secondary transfer backup roller 33 and the fixing roller 36 of the secondary transfer mechanism 19 and the fixing mechanism 20, respectively.

Further, the secondary transfer backup roller 33 and the fixing roller 36 and the secondary transfer roller 32 constituting the secondary transfer mechanism 19 and the fixing mechanism 20, respectively, are moved by the operation of the elevating mechanism 48 shown in FIG. The endless circulating belt 16 that separates from the backup roller 33 and the fixing roller 36 and circulates between the rollers 33 and 36 and the fixing roller 36 is transferred to the secondary transfer backup roller 3.
5 and the pressing position where the endless circulation belt 16 is pressed against the secondary transfer backup roller 33 and the fixing roller 36.

In the idling state of the electrophotographic recording device 130, the secondary transfer roller 32 is held at the release position shown in FIG. Driven rollers 26
The endless circulation belt 16 around b 'and 26c'
Without being pressed against the secondary transfer backup roller 33 and the fixing roller 36 by the secondary transfer roller 32,
The endless circulating belt 16 is not partially heated by the fixing roller 36 heated by the power supply from the heating power supply 38 shown in FIG.

On the other hand, in the operation state of the electrophotographic recording apparatus 130, the secondary transfer roller 32
Overcomes the biasing force acting on both driven rollers 26b 'and 26c', and is moved to a pressing position where the endless circulating belt 16 is pressed against the secondary transfer backup roller 33 and the fixing roller 36.

Therefore, at the above-mentioned pressing position of the secondary transfer roller 32, a good transfer between the secondary transfer roller 32 and the secondary transfer backup roller 33 is performed in the same manner as described in the specific examples 2 and 3. The next transfer is performed, and the recording paper 18 is conveyed integrally between the fixing roller 36 and the secondary transfer roller 32 together with the endless circulation belt 16, and a good fixing process is performed between the two rollers 36 and 32.

When the electrophotographic recording apparatus 130 enters the idling state, the secondary transfer roller 32 is held at the release position by the operation of the elevating mechanism 48, whereby the endless circulating belt 16 is connected to the fixing roller 36. Is kept released from the contact of Accordingly, it is possible to prevent a local change in electric resistance due to local heating of the fixing roller 36 during the non-circulating operation of the endless circulating belt 16, and to prevent a local deterioration due to unnecessary heating. The durability of the belt 16 can be improved.

Further, in the specific example 4 shown in FIG. 4, the primary transfer rollers 27 (27a, 27b, 27c and 27d)
Has a DC power supply 28 (28a, 28b, 28c and 2
8d) and an AC power supply 28 '(28a', 28a).
b ', 28c' and 28d ') are superimposed and applied. FIG. 6 is a graph showing a change in the primary transfer voltage. The horizontal axis is the time axis, and the vertical axis is the transfer voltage.
To the secondary transfer roller 32, an AC power supply 34 'is added to the DC power supply 34 in order to apply a similar superimposed secondary transfer voltage.

In the case of multi-color printing, for example, when an image represented by a plurality of toners is displayed on a background displayed by one color toner, a white portion may be formed at the boundary between the background and the image. As described above, by superimposing the DC component and the AC component on the transfer voltage, it is possible to prevent the above-mentioned density unevenness due to the so-called white spots or image boundary portion bias, and to prevent color shift due to the density unevenness.

[0068]

According to the present invention, as described above, the recording medium is kept in a state in which the recording medium is kept integral with the transfer image bearing member by at least one of the secondary transfer mechanism and the fixing mechanism. The recording medium conveyed from the secondary transfer mechanism to the fixing mechanism, whereby the image is transferred in a state where the relative displacement of the recording medium on the transfer image bearing member is securely prevented, is fixed to the fixing medium. Since the image is sent to the mechanism, the blurring of the image due to the displacement of the preceding recording medium is reliably prevented, whereby a clear image is reliably obtained on the recording paper medium.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing a specific example 1 of an electrophotographic recording apparatus according to the present invention.

FIG. 2 is a configuration diagram schematically showing a specific example 2 of the electrophotographic recording apparatus according to the present invention.

FIG. 3 is a configuration diagram schematically showing a specific example 3 of the electrophotographic recording apparatus according to the present invention.

FIG. 4 is a configuration diagram schematically showing a specific example 4 of the electrophotographic recording apparatus according to the present invention.

FIGS. 5A and 5B are explanatory diagrams illustrating (a) an idling state and (b) an operating state during operation of the fixing roller in the specific example 3, respectively.

FIG. 6 is a transfer voltage waveform graph showing an example of a transfer voltage in a specific example 3.

[Explanation of symbols]

10, 110, 120, 130 Electrophotographic recording device 12 (12a, 12b, 12c, 12d) Image carrier (photosensitive drum) 16 Transfer image bearing member (infinite circulation belt) 17 (17a, 17b, 17c, 17d) Primary transfer Mechanism 18 Recording medium (recording paper) 19 Secondary transfer mechanism 20 Fixing mechanism

Claims (6)

[Claims] 1. A transfer image bearing member for transferring a visible image visualized on an image carrier by developing a latent image formed on the image carrier from the image carrier by a primary transfer mechanism; A secondary transfer mechanism for transferring the visible image transferred to the image bearing member to a sheet-shaped recording medium, and fixing the visible image transferred onto the recording medium by the secondary transfer mechanism onto the recording medium And a fixing mechanism for receiving the transfer of the recording medium from the secondary transfer mechanism together with the transfer image bearing member, wherein the secondary transfer mechanism and the fixing mechanism are disposed between the two mechanisms. At least one of the recording medium and the transferred image bearing member on which the visible image has been transferred, and the length of the recording medium is less than or equal to the length of the recording medium along the transport direction of the recording medium so as to fixedly restrain each other. Are arranged at intervals of An electrophotographic recording device characterized by the above-mentioned. 2. The transfer image carrying member comprises an annular endless circulating belt that goes around a predetermined endless circulation path, and the secondary transfer mechanism and the fixing mechanism are arranged along the endless circulation path. An electrophotographic recording device as described in the above. 3. The secondary transfer mechanism includes a secondary transfer roller disposed on one surface of the belt and a secondary transfer roller disposed on the other surface of the belt in cooperation with the secondary transfer roller. A secondary transfer backup roller that sandwiches the belt and the recording medium that receives a visible image transferred from the belt, wherein the fixing mechanism includes a fixing roller disposed on one surface side of the belt and the other of the belt. 3. A fixing backup roller which is disposed on a surface side and cooperates with the fixing roller to sandwich the belt and the recording medium on which a visible image has been transferred from the belt.
An electrophotographic recording device as described in the above. 4. The secondary transfer mechanism includes a secondary transfer roller disposed on one surface of the belt and a secondary transfer roller disposed on the other surface of the belt in cooperation with the secondary transfer roller. A secondary transfer backup roller that sandwiches the belt and the recording medium that receives the transfer of a visible image from the belt; and the fixing mechanism has an interval between the secondary transfer backup roller and the other surface of the belt. 3. The electrophotographic recording apparatus according to claim 2, further comprising a fixing roller disposed between the belt and the recording medium on which the visible image has been transferred from the belt in cooperation with the secondary transfer roller. apparatus. 5. The secondary transfer roller, between the release position and the sandwiching position, to releaseably sandwich the belt between the roller, the secondary transfer backup roller, and the fixing roller. Claim 4 which is movable.
An electrophotographic recording device as described in the above. 6. The multicolor electrophotographic recording apparatus in which a plurality of the image carriers arranged at intervals from each other in a circulating direction of the belt are provided, and the primary transfer mechanism is provided. The plurality of image carriers are arranged corresponding to each image carrier so that the visible images of the plurality of image carriers are sequentially transferred onto the belt in cooperation with the respective image carriers and the belt is sandwiched therebetween. A primary transfer roller and a power supply circuit for applying a transfer voltage to each of the primary transfer rollers so as to supply a transfer current to each of the primary transfer rollers. 3. The electrophotographic recording apparatus according to claim 2, wherein the transfer current is gradually reduced in the belt circulating direction so as to gradually increase the transfer current in the circulating direction of the belt irrespective of application of the predetermined voltage.