JP2883159B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and in particular, for example, by arranging an exposure light source inside a photoconductor drum and simultaneously or immediately after exposing from inside the photoconductor drum. Further, the present invention relates to an image forming apparatus for developing toner.

[Prior Art] Conventionally, in this type of image forming apparatus, the pressure transfer roller is formed of a conductive material over the entire area.

[Problems to be Solved by the Invention] According to the above-mentioned conventional method, when the width of the pressure transfer roller is larger than the width of the recording paper, the pressure transfer roller directly contacts the photoconductor drum. Could be destroyed. In addition, there are dents on the photoreceptor, a conductive path leading to the electrode is formed on the back of the photoreceptor, and when the transfer roller directly contacts that portion, excessive current flows from the transfer member and is applied to the transfer roller. Voltage drops.

The above-described voltage drop of the transfer roller due to the leak current to the photosensitive member causes a problem that the transfer rate is significantly reduced over the contact area of the transfer roller in the longitudinal direction of the photosensitive member.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to provide an image forming apparatus which prevents a leak current from a pressure transfer roller and improves transfer efficiency.

[Means for Solving the Problems] In the image forming apparatus according to the present invention, the pressure transfer roller is conductive at a position facing an image area having a length equal to or less than the sheet width, and is insulated at positions other than the image area. Sex.

[Operation] In the present invention, since the portion where the pressure transfer roller directly contacts the photoconductor layer of the photoreceptor is the insulating portion of the pressure transfer roller, it is not affected even if a transfer bias is applied.

Embodiment FIG. 1 is a sectional view showing an optical printer as one embodiment of the present invention. FIG. 2 is an exploded perspective view showing a fitted state of the photosensitive drum, the positioning member and the magnet roller in the embodiment of FIG. 1, FIG. 3 is a partially enlarged sectional view showing an example of the photosensitive drum, and FIG. FIG. 4 is a side view of a main part shown partially broken. Hereinafter, the present invention will be described as applied to an optical printer, but the present invention can also be applied to other image forming apparatuses such as a copying machine and a facsimile.

In FIG. 1, an optical printer 10 includes a main body 11,
A photosensitive drum 12 is rotatably supported inside 11. As shown in FIG. 3, the photosensitive drum 12 includes a transparent base 12a made of, for example, glass, and a transparent conductive layer 12b and a photoconductive layer 12c laminated on the transparent base 12a.

A driving roller 13 is provided so as to come into contact with the outer surface of the photosensitive drum 12 (the surface of the photoconductor layer 12c).
Reference numeral 13 rotates the photosensitive drum 12 by a driving force from a driving source such as a motor (not shown). The photosensitive drum 12 has two fixed support rollers 14 and 15 which contact the inner surface thereof, that is, the surface of the transparent substrate 12a, and one movable support roller 16
And are rotatably supported by the
When 13 rotates in the direction of arrow A, the photosensitive drum 12 also rotates in the direction of arrow B accordingly. Although not apparent in the drawing, the drive roller 13 is disposed at the widthwise end (preferably both ends) of the photoconductor drum 12, while the surface of the end of the photoconductor drum 12 that contacts the drive roller 13 is slightly exposed The photosensitive drum 12 is formed to be coarse, whereby the photosensitive drum 12 is accurately rotated by the friction between the two.

As described above, the photoconductor drum 12 is supported at three points by the fixed support rollers 14 and 15 and the movable support roller 16 inside thereof. As can be clearly seen from FIG.
Each of these support rollers 14 to 16 is a photosensitive drum 12
Are arranged at both ends in the width direction. And the movable support roller 16
Is preferably arranged at a center symmetric position on a line connecting the drive roller 13 and the center of the photosensitive drum 12. That is, the movable support roller 16 is provided at a position facing the drive roller 13 with the rotation center of the photosensitive drum 12 interposed therebetween. In addition, the fixed support roller 14 is disposed on an extension of an exposure position of the photosensitive drum 12 described later.

Then, the mounting shaft 17 of the fixed support rollers 14 and 15 and
As shown in FIG. 2, reference numerals 18 are directly fixed to side plates 19 arranged at both ends of the photosensitive drum 12, respectively.

On the other hand, the mounting shaft 20 of the movable support roller 16 is not directly fixed to the side plate 19. That is, the mounting shaft 20 of the movable support roller 16 is attached to the side plates 19 on both sides so that the movable support roller 16 can apply a pressing force to the inside of the photosensitive drum 12 by the coil spring 21. Accordingly, the movable support roller 16 follows the radial fluctuation of the inner circumference of the photosensitive drum 12 and is always kept under a pressing force.
Can adhere to 12. Therefore, the fixed support rollers 14 and
The contact position of the photoconductor drum 12 with the inner periphery of the photoconductor drum 12 is constant even if the inner periphery of the photoconductor drum 12 is eccentric, but the contact position of the movable support roller 16 is eccentric with the inner periphery of the photoconductor drum 12. To follow. Therefore, for example, even if the diameter or roundness of the photosensitive drum 12 varies, the movable support roller 16
By such displacement, such a dimensional variation can be absorbed. As can be clearly understood from FIG. 2, the mounting shaft 18 of the fixed support roller 15 and the mounting shaft 20 of the movable support roller 16 each have a length penetrating both ends in the width direction of the photosensitive drum 12. The mounting shaft 17 of the support roller 14 is short, and each is substantially equal to the length of the fixed support roller 14. The respective mounting shafts 17 are individually mounted on the side plates 19 at both ends. That is, fixed support rollers at both ends
An interval for exposing the photosensitive drum 12 to be described later is formed between them.

Inside the photoconductor drum 12, an LED head 22 is further arranged. On one main surface of the LED head 22, a large number of L
An LED array 22a in which ED elements are arranged on a straight line extending in the width direction of the photosensitive drum 12 is formed, and light from this LED array 22a is a rod lens array fixed to the LED head 22 by an arm 23a, that is, a focusing lens array. The photosensitive drum between the fixed support rollers 14 at both ends by the conductive light transmitting body 23
The photoconductor layer 12c is irradiated through the 12 transparent substrates 12a and the transparent conductive layer 12b.

By arranging the fixed support roller 14 on the optical axis of the exposure light in this way, the focus of the exposure light is reliably brought on the photoconductor layer 12c of the photosensitive drum 12. That is,
At the position where the exposure light is irradiated, the photosensitive drum 12 is always maintained at a fixed position by the fixed support roller 14, and therefore, the position of the photoconductor layer 12c to which the exposure light is irradiated does not change. Therefore, if the focus of the exposure light is adjusted in advance to match the position, the exposure light always forms an image on the surface of the photoconductor layer 12c. Therefore, for example, even when the diameter or roundness of the photosensitive drum 12 varies, it does not affect the focus.

The LED head 22 is integrally fixed to the side plate 19 by screws 24 at both ends. Therefore, the position of light irradiation from the converging light transmitting body 23, that is, the relationship between the exposure position and the position where the fixed support roller 14 contacts the inner surface of the photosensitive drum 12 is always constant even when the photosensitive drum 12 rotates. is there. Therefore, if the focus of the converging light transmitting body 23 is adjusted to match the surface of the photoconductor layer 12c of the photosensitive drum 12, the exposure light from there is always imaged on the surface of the photoconductor layer 12c. Is done. Therefore, for example, even when the photoconductor drum 12 is incorporated or detached, there is no need to make the focus position of the converging light transmission body 23 coincide with the surface of the photoconductor layer 12c.

Returning to FIG. 1, the main body 11 is provided with a developing device 25 on the left side of the photosensitive drum 12. The developing device 25 is attached to the chassis of the main body 11 by a coil spring 26 so as to be constantly engaged with the photosensitive drum 12 side. The developing device 25 is loaded with a toner cartridge 27, and the toner cartridge
The toner supplied from 27 into the developer chamber 28 is transported to the magnet roller 30 by the transport screw 29. The transported toner is formed as a magnetic brush on the circumference of the magnet roller 30. And the height of the magnetic brush,
That is, the height of the spike is adjusted by the spike restricting plate 31, and is transferred to a portion facing the photosensitive drum 12 according to the rotation of the magnet roller 30. That is, the toner is sent between the magnet roller 30 and the photoconductor layer 12c of the photosensitive drum 12.

On the other hand, although not shown, a DC voltage of, for example, 200 V is applied between the magnet roller 30 and the transparent conductive layer 12b of the photosensitive drum 12. The photoconductive layer 12c of the photosensitive drum 12 facing the magnet roller 30 has the LED
Exposure light according to image information is emitted by the head 22 and the converging light transmitter 23. Photoconductor layer 12c which received exposure light
In the portion, the resistance value decreases, and therefore, a current flows between the magnet roller 30 and the transparent conductive layer 12b due to the above-described voltage. Therefore, the toner present in that portion is charged by the current. On the other hand, the resistance of the photoconductor layer 12c remains high in the part that is not exposed,
Since no current flows, the toner is hardly charged. Further, the exposed photosensitive drum 12, i.e., the photoconductor layer 12
A latent image charge having a polarity opposite to the charge polarity of the toner is generated on c by the above-described current, and the charged toner is attracted to the surface of the photoconductor layer 12c of the photosensitive drum 12 by electrostatic force. In this manner, a toner image is formed on the photosensitive drum 12 by the developing device 25 almost simultaneously with the exposure by the LED head 22.

In order to perform good toner development, it is necessary not only to accurately set the gap between the portion where the above-described magnet roller 30 and the photosensitive drum 12 face each other, but also to set the gap with respect to the optical axis of the exposure light. The magnet roller 30 and the photosensitive drum 12 need to be positioned so as to be perpendicular to each other.

Therefore, in this embodiment, the above-described positioning of this portion is set by two positioning members 32 arranged at both ends in the width direction of the photosensitive drum 12 and parallel to each other, as shown in FIG. On the other hand, the above-mentioned interval is defined by providing a gap roller 33 rotatably at both ends of the magnet roller 30 as shown in FIG. 2, and bringing the gap roller 33 into contact with the surface of the photosensitive drum 12. . At the left end of each positioning member 32, a semicircular fitting portion 35 into which the mounting shaft 34 of the magnet roller 30 is fitted is formed.

On the other hand, as described above, the support shafts 36 are provided on the two side plates 19 to which the LED head 22 and the like are integrally fixed in order to set the gap with the magnet roller 30 by the positioning member 32.
And 37 are formed. As can be clearly understood from FIG. 2, the support shaft 36 is fixed substantially at the center of the disc-shaped side plate 19,
The support shaft 37 is fixed near the end of the side plate 19. Each of the positioning members 32 has a substantially L-shaped fitting portion 38 for fitting the support shafts 36 and 37 at the same time.
In addition, one side plate 19, that is, the side plate 19 on the near side in FIG.
In order to facilitate rotation of the photosensitive drum 12 described later, a rotation grip portion 39 is formed integrally with the drum.

And the positioning member already attached to the main body 11
By fitting the support shafts 36 and 37 into the fitting portion 38 of the photosensitive drum 32, the photosensitive drum 12 and its integral body are attached to the main body 11. At this time, since the entrance of the fitting portion 38 is narrow, the support shaft
36 and 37 cannot be fitted into the fitting portion 38 at the same time. Then, first, the support shaft 36 is fitted into the fitting portion 38, and when the support shafts 36 on both sides are fitted into the fitting portion 38, the photosensitive drum 12 is The shaft 37 is also fitted into the fitting portion. In this way, the support shafts 36, 37
Is fitted into the fitting portion 38, the magnet roller 30 and the photoconductor layer 12c of the photosensitive drum 12 are positioned so that the opposing portion is orthogonal to the optical axis of the exposure light. The gap between the magnet roller 30 and the photosensitive drum 12 is set optimally by setting the diameter of the gap roller 33 optimally.

However, simply fitting the support shafts 36 and 37 into the fitting portion 38 as described above does not necessarily mean that the portion facing the magnet roller 30 is exactly perpendicular to the optical axis of the exposure light. In this case, the support shafts 36 and 37
After fitting, the rotating grip portion 39 may be slightly rotated so as to rotate the photosensitive drum 12 about the support shaft 36, as can be clearly understood from FIG. At this time, the support shaft 37 comes into sliding contact with the fitting portion 38 and serves as a guide for its rotation. Then, the projection 40 formed with the rotating grip 39 is the main body.
The rotating grip 39 is rotated so as to coincide with the center of the scale 42 provided on the chassis 41 of the eleventh. If the projection 40 and the center of the scale 42 match, the portion where the magnet roller 30 and the photosensitive drum 12 face the optical axis of the exposure light from the converging light transmitter 23 is in a state of being orthogonal to the optical axis. .

In this way, when finely adjusting the relative positional relationship between the developing position by the magnet roller 30 and the irradiation position of the exposure light, the photosensitive member can be simply rotated by the rotating grip 39 around the support shaft 36. The position of the LED head 22 provided in the drum 12, that is, the position of the converging light transmitter 23 can be easily adjusted.

The side plate 19 is fixed to the chassis 41 in a state where the exposure position is located at a position facing the magnet roller 30 as described above. That is, the rotary grip portion 39 is formed with a long elliptical hole 43 for integrally fixing the one side plate 19 to the chassis 41. Therefore, the side plate 19 may be integrally fixed to the chassis 41 with the screw 44 through the hole 43 by checking the coincidence between the protrusion 40 and the scale 42.

As shown in FIG. 1, a sheet cassette 45 is detachably mounted on the main body 11 above the developing device 25 at an angle. A large number of recording papers 46 are stacked and stored in the paper supply cassette 45, and the recording papers 46 are arranged on a plate 47.
Since the plate 47 is pushed up by the coil spring 48, the uppermost recording paper 46 stacked is pressed against the paper feed roller 49. Therefore, when the paper feed roller 49 is driven, the recording paper 46 is sent to a pair of register rollers including the drive roller 50 and the driven roller 51.

Near the upper part of the photosensitive drum 12, specifically, a fixed support roller
A transfer roller 52 having a width substantially equal to the length of the photosensitive drum 12 is provided at a position facing the transfer roller 52. The transfer roller 52 is supported and configured to be rotatable about a support shaft 53. The axial cross section is as shown in FIG. 5, and comprises a support shaft 52a, a conductive rubber roller 52b, and insulating rubber rollers 52c at both ends thereof. The recording paper 46 is applied to the recording paper 46 via the conductive rubber roller 52b.

Returning to FIG. 1, the transfer roller 52 applies a photosensitive drum to the recording paper 46 whose timing is controlled by a pair of register rollers including a driving roller 50 and a driven roller 51.
The toner image formed as described above is transferred to the surface 12.

As shown in FIG. 5, the transfer roller 52 has insulating rubber rollers 52c at both ends and a conductive rubber roller 52b at the center.
It is a structure in which the support shaft 52a is inserted and fixed at the center with
The length of the transfer roller 52 is the length of the insulating rubber roller 52 at both ends.
The distance between the outside of c and the length is longer than the width of the recording paper, and the length of the conductive rubber roller is equal to or smaller than the width of the recording paper.
The voltage from the external power supply 54 is applied to the support shaft 52a. Here, the conductive rubber roller of the photosensitive drum 12 and the transfer roller 52
When 52b comes in direct contact with the transfer voltage, the photosensitive drum 12
Of the photoconductor layer 12c may be broken down. Also, if a pinhole is formed on the photoconductor layer 12c due to a dent or the like,
A current easily flows into the pinhole from the surroundings, that is, a current path toward the pinhole increases, and a voltage effect tends to occur.

However, as in the above embodiment, the insulating rubber roller 52c of the transfer roller 52 is disposed at a position facing the outside of the image area, that is, the photosensitive drum 12 and the conductive rubber roller 52b of the transfer roller 52 are not directly in contact with each other. By doing
The above problem does not occur. Here, the image area is the same as or smaller than the recording paper 46.

The transfer roller 52 is separated from the photosensitive drum 12 when there is no recording paper 46 as shown in FIG. The recording paper 46 starts running from the paper feed cassette 45, and at the same time as the start end of the recording paper 46 passes through the drive roller 50, and after a certain period of time by a sensor (not shown), that is, the start end of the recording paper 46
And at the same time, upon reaching a line connecting the photoconductor drum 12 and the photoconductor drum 12, the photoconductor drum 12 is pressed against the photoconductor drum 12, and then a transfer bias is applied.

Further, immediately before the end of the transfer, that is, immediately before the rear end of the recording paper 46 passes through the photosensitive drum 12 and the transfer roller 52, the application of the transfer bias voltage is stopped, and then the transfer roller 52 is separated from the photosensitive drum 12. A structure is provided. As a result, there is no direct contact of the transfer roller 52 with the photosensitive drum 12, and damage to the photosensitive drum 12 is prevented.

The recording paper 46 after the transfer is peeled off from the photosensitive drum 12 by the separation claw 55. Then, in order that the unfixed toner image on the recording paper 46 is not disturbed, the recording paper 46 is fixed to the fixing device including the heating roller 57 and the pressure roller 58 while a slightly upward suction force is applied by the suction fan 56. Transported to

Inside the heating roller 57, for example, a halogen lamp of about 850 W is built in, and a part of the surface is pressed against a felt 59 impregnated with silicone oil. Therefore, the recording paper
When the roller 46 passes between the heating roller 57 and the pressure roller 58, the toner image ends the heated and pressed fixing process.
Then, the recording paper 46 is peeled off from the surface of the heating roller 57 by the separation claw 60, conveyed to a pair of paper discharge rollers including paper discharge rollers 61 and 62, and discharged out of the main body 11.

A cleaning blade 63 is attached below the separation claw 55 and near the peripheral side surface of the photosensitive drum 12 so that a part thereof comes into contact with the surface of the photosensitive drum 12. The cleaning blade 63 is made of rubber and scrapes off residual toner by contacting the surface of the photosensitive drum 12. The scraped residual toner is stored in a waste toner container 64 below. This waste toner container 64 is also removably loaded into the main body 11 similarly to the toner cartridge 27 described above. Therefore, when the waste toner is full, the waste toner container 64 is replaced with an empty one.

In this embodiment, a part of the main body 11 is configured as an openable separation unit 65 so that the recording paper 46 having the jam can be easily removed. The separation unit 65 includes a driven roller 51, a pressure roller 58, a paper discharge roller 62, and a transfer roller 52, which constitute one pair of a register roller, a fixing roller, and a paper discharge roller. The separation unit 65 is mounted on the main body 11 so as to be openable upward about the support shaft 53 as a rotation center. Therefore, for example, when a jam occurs, the division unit 65 is supported by the support shaft 53.
, The recording paper transport path is exposed. This makes it possible to easily remove the jammed recording paper 46 from the recording paper transport path.

The photosensitive drum 12 is detached from the main body 12 in the following procedure, for example, when it is necessary to inspect the surface. First, the separation unit 65 is rotated upward about the support shaft 53 to separate the transfer roller 52 from the surface of the photosensitive drum 12. As a result, a work space is created in a portion where the transfer roller 52 is disposed above the photosensitive drum 12. Next, the screw 44 as shown in FIG. 4 is loosened and removed. Then, the rotating grip 39
Is a support shaft fitted to the fitting portion 38 of the positioning member 32.
It becomes a state where it can rotate around 36. Therefore, the rotating grip portion 39 is slightly rotated upward, the support shaft 37 is slightly lifted from the bottom of the fitting portion 38, and the support shaft 37 is guided to the outlet of the fitting portion 38.
Then, after both support shafts 36 can be disengaged from the fitting portion 38, when the rotating grip portion 39 is lifted and the entire photosensitive drum 12 is pulled out along with the side plate 19 in the horizontal direction, the photosensitive drum 12 and the integral with the photosensitive drum 12 are removed. The object comes off the main body 11 completely.

Attachment of the photosensitive drum 12 to the main body 11 is performed in a procedure reverse to that when the photosensitive drum 12 is removed from the main body 11. The gap between the magnet roller 30 and the exposure position of the photosensitive drum 12 at this time is determined by the diameter of the gap roller 33,
The gap between the magnet roller 30 and the exposure position is automatically set simply by mounting the photoconductor drum 12 on 11. Then, at this time, the relative position between the magnet roller 30 and the photosensitive drum 12 is adjusted by the rotating gripping part 39 as needed.

In the above-described embodiment, the photosensitive drum 12 is rotated by the driving roller 13 that contacts the outside. However, the photosensitive drum 12 may be driven directly by a motor, for example, or may be driven via another driving means such as a combination of a timing pulley and a timing belt or a gear train. Further, the photoreceptor does not necessarily have to have a drum shape.

[Effect of the Invention] As described above, in the present invention, the pressure transfer roller is made conductive at a position facing an image region having a length equal to or less than the sheet width, and is made insulative at positions other than the position facing the image region. In addition, there is an advantage that the bias of the pressure transfer roller does not affect the photoconductor layer of the photoreceptor, and a great improvement can be brought about in terms of printing defects and transfer efficiency.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an entire optical printer as one embodiment of the present invention, and FIG. 2 is a fitting state of a photosensitive drum, a positioning member and a magnet roller in the optical printer in the embodiment of FIG. FIG. 3 is an exploded perspective view showing
FIG. 4 is a partially enlarged cross-sectional view showing an example of a photosensitive drum used in the embodiment shown in FIG. 4, FIG. 4 is a side view of a main part of the photoreceptor drum, and FIG. FIG. In the figure, 10 is an optical printer, 11 is a main body, 12 is a photosensitive drum, 13 is a drive roller, 14 and 15 are fixed support rollers, 16 is a movable support roller, 19 is a side plate, 22 is an LED head, and 23 is a focusing property. Optical transmission body, 25 is a developing device, 30 is a magnet roller, 32
Is a positioning member, 33 is a gap roller, 34 is a mounting shaft, 3
Reference numerals 5 and 38 denote fitting portions, 36 denotes a support shaft, 45 denotes a paper feed cassette, 46 denotes a recording sheet, 57 denotes a heating roller, and 58 denotes a pressure roller.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toru Nose 2--18-18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Fumihiko Hamada 2--18-3 Keihanhondori, Moriguchi-shi, Osaka (56) References JP-A-62-217259 (JP, A) JP-A-64-46784 (JP, A) JP-A-2-165173 (JP, A) (58) Fields investigated ( Int.Cl. ⁶ , DB name) G03G 15/16 103 G03G 15/00 115

Claims (1)

(57) [Claims] A photosensitive member including a transparent substrate and a transparent conductive layer and a photoconductor layer formed thereon and moving in a predetermined direction; A plurality of support rollers for supporting movement of the photoconductor, an exposure light source disposed on the transparent substrate side of the photoconductor, and exposing the photoconductor layer through the transparent substrate and the transparent conductive layer; and the photoconductor. A developing means which is disposed at or near the exposure position by the light source for exposure on the side of the photoconductor layer, and selectively adheres toner to the surface of the photoconductor layer at the same time as or immediately after the exposure to form a toner image; A transfer device having a pressure transfer roller for transferring a toner image formed on the outer surface of the photoconductor onto a sheet, wherein the pressure transfer roller faces an image area having a length equal to or less than the sheet width. The conductive An image forming apparatus, wherein: a portion other than the position facing the image area is insulated.