JP3642167B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus, and more particularly to an electrophotographic image forming apparatus such as a copying machine or a laser printer configured to transfer an image onto a recording medium via an intermediate transfer member.
[0002]
[Prior art]
In an electrophotographic image forming apparatus such as a copying machine or a laser printer, after transferring a plurality of color toner images formed on a drum-like or belt-like primary photoreceptor on an intermediate transfer member, There is known an image forming apparatus that obtains a full-color print image by further transferring a superimposed color toner image onto a recording medium such as recording paper. For example, an image forming apparatus using a belt-like photoconductor as a primary photoconductor is described in JP-A-6-130775, and an image forming apparatus using a drum-type photoconductor is disclosed in JP-A-9-204108. It is described in.
[0003]
FIG. 6 is a diagram showing a main configuration of an image forming apparatus using a drum-shaped photoconductor (hereinafter referred to as “photoconductor”). The plurality of color toner images formed on the photosensitive member 1 are transferred to the intermediate transfer member (belt) 3 by the primary transfer device 2 and superimposed, and further transferred to the recording paper P by the secondary transfer device 4. . Here, a reflection portion 5 for detecting the position of the intermediate transfer belt 3 is formed on the intermediate transfer belt 3, and the reflection portion 5 is detected by a reflection type optical sensor 6. The detection signal of the reflection unit 5 is used as a reference signal for controlling the exposure timing of the photosensitive member 1 and the timing of transferring the unfixed toner image on the intermediate transfer belt 3 onto the recording paper P. As described above, the detection signal of the reflection unit 5 is used as a reference signal for the control timing of the image forming apparatus, and plays an important role in obtaining good image quality without image shift.
[0004]
[Problems to be solved by the invention]
However, the method for detecting the position of the intermediate transfer member using the reflecting portion has the following problems. After the toner image is transferred onto the intermediate transfer belt 3 or the recording paper P on the photosensitive member 1 or the intermediate transfer belt 3, there is a toner image that has not been transferred, that is, residual toner. Is scraped off and collected by a collecting device. However, the residual toner scraped off during cleaning of the photosensitive member 1 and the intermediate transfer belt 3 may become dust and float in the image forming apparatus, and the reflecting portion 5 may be soiled by the floating toner. .
[0005]
If the surface of the reflecting portion 5 is soiled, the amount of reflected light received by the reflective optical sensor 6 decreases, and as a result, the detection accuracy of the intermediate transfer belt 3 deteriorates, resulting in image quality deterioration such as color misregistration. is there.
[0006]
Instead of detecting the position of the intermediate transfer member, the image forming apparatus may use a stepping motor as a driving means for the intermediate transfer member and indirectly detect the position of the intermediate transfer member by performing pulse control. . However, in this case, since there is a problem that it is not possible to cope with the deviation and length variation of the intermediate transfer belt and accurate control cannot be performed, the above-described reflection portion detection method that can detect the position more accurately is adopted. Is preferred.
[0007]
An object of the present invention is to eliminate the above-mentioned problems, maintain the reflection portion on the intermediate transfer member cleanly and accurately detect the position, and consequently form a high-quality image without color misregistration. An object of the present invention is to provide an image forming apparatus capable of performing the above.
[0008]
[Means for Solving the Problems]
In order to solve the above problems and achieve the object, the present invention includes an image carrier on which an electrostatic latent image is formed, a developing unit that visualizes the electrostatic latent image with a toner image, and the toner image. A secondary transfer means for secondary transfer of the toner image transferred to the circular intermediate transfer member to a recording medium, and a reflection portion provided on the circular intermediate transfer member. A reflection type optical sensor for receiving the reflected light of the reflection portion to detect the rotation position of the rotating intermediate transfer member, a wiping member that slides on the reflection portion and cleans the reflection portion, and the wipe It is characterized in that it comprises wiping member urging means for bringing the member into contact with the circular intermediate transfer member for at least one rotation of the circular intermediate transfer member at a predetermined cycle.
[0009]
In the present invention having the above characteristics, the wiping member is brought into contact with the rotating intermediate transfer member by the wiping member urging means and makes at least one turn so that the reflecting portion provided on the rotating intermediate transfer member The wiping member comes into sliding contact, and the surface of the reflecting portion is cleaned.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 2 is a main part configuration diagram of a full-color printer which is an example of an image forming apparatus according to an embodiment of the present invention. In FIG. 1, a photosensitive member 1 as an image carrier is provided so as to be rotated in the direction of an arrow 7 by a motor (not shown). Around the photoreceptor 1, a charging device, that is, a charging roll (BCR) 8, an exposure device (ROS) 9, a developing assembly 10, a primary transfer device, that is, a primary BTR 2, and a cleaner device 11 are arranged. The developing assembly 10 includes four developing devices 10Y, 10M, 10C, and 10K for full color development. The developing devices 10Y, 10M, 10C, and 10K develop the latent images on the photoreceptor 1 with yellow (Y), magenta (M), cyan (C), and black (K) toners, respectively. When developing toner of each color, the developing assembly 10 is rotated in the direction of arrow R by a motor (not shown), and the developing device for that color is aligned so as to contact the photoreceptor 1.
[0011]
The toner images of each color developed on the photoreceptor 1 are sequentially transferred to an intermediate transfer belt (hereinafter simply referred to as “belt”) 3 by the primary BTR 2 and the four color toner images are superimposed. The belt 3 is stretched around rolls 12, 13, 14 and 15. Among these, the roll 12 is coupled to a drive source (not shown) and functions as a drive roll that drives the belt 3, the roll 13 functions as a tension roll that adjusts the tension of the belt 3, and the roll 14 is a secondary transfer device. That is, it functions as a backup roll for the secondary BTR 4. A belt cleaner 16 is provided at a position facing the roll 15 with the belt 3 interposed therebetween, and residual toner on the belt 3 is scraped off by a cleaner blade.
[0012]
The recording paper drawn from the recording paper cassettes 17 and 18 to the conveying path by the drawing rolls 19 and 20 is fed to the nip portion, that is, the contact portion between the secondary BTR 4 and the belt 3 by the roll pairs 21, 22 and 23. The The toner image formed on the belt 3 is transferred onto the recording paper at this nip portion, thermally fixed by the fixing device 24, and discharged to the tray 25 or the tray 26 (upper surface of the main body).
[0013]
A reflection type optical sensor 6 is disposed opposite to the belt 3 to detect reflected light from the reflection portion 5 on the belt 3. The detection signal of the reflected light is used as a reference signal for controlling the image forming timing by the ROS 9 and the toner image transfer timing. The reflecting portion 5 is preferably formed by bonding a glossy sheet material such as an aluminum foil on the belt 3.
[0014]
The developing devices 10Y, 10M, 10C, and 10K each have a replaceable toner cartridge, a developing roll that applies a developing bias, a toner supply device that supplies toner to the developing roll, and a conveying device. A corona discharger can be used in place of the BCR 8 or BTR 2 or 4.
[0015]
In the image forming apparatus having the above configuration, an image is formed as follows. First, a voltage is applied to the BCR 8 so that the surface of the photoreceptor 1 is uniformly negatively charged with a predetermined charged portion potential. Subsequently, exposure is performed by the ROS 9 so that the image portion on the charged photoreceptor 1 has a predetermined exposure portion potential, and a latent image is formed. That is, a latent image corresponding to an image is formed by turning on / off the ROS 9 based on an image signal supplied from a control device (not shown).
[0016]
A developing bias set in advance for each color is applied to a developing roll such as the developing device 10Y, and the latent image is developed with toner when passing through the position of the developing roll, and visualized as a toner image. The toner image is transferred to the belt 3 by the primary BTR 2, further transferred to the recording paper by the secondary BTR 4, and then fed to the fixing device 24. In full-color printing, toners of four colors are superimposed on the belt and then transferred onto the recording paper. The toner remaining on the photosensitive member 1 is removed and collected by the cleaner device 11, and finally the photosensitive member 1 is uniformly discharged to near 0 volts by a discharging device (not shown) to prepare for the next image forming cycle.
[0017]
The belt cleaner 16 is detachable from the belt 3. When forming a color image, the belt cleaner 16 is black toner when forming a black and white image until the final color toner image is primarily transferred to the belt 3. The image is separated from the surface of the belt 3 until the image is primarily transferred to the belt 3, and a toner image of the fourth color is scheduled to be transferred from the photosensitive member 1 to the belt 3 and further transferred to the recording paper. Is brought into contact with the belt 3. The residual toner on the belt 3 is removed by the belt cleaner 16 coming into contact with the belt 3. The secondary BTR 4 is also separated from the belt 3 except when the toner image on the belt 3 is transferred to the recording paper. At the time of transfer, the secondary BTR 4 is pressed against the belt 3 immediately before the transfer to perform a transfer function. The belt cleaner 16 and the secondary BTR 4 can be urged by a driving device including, for example, an actuator driven in one direction by a solenoid and spring means for returning the actuator.
[0018]
The detailed configuration of the belt cleaner 16 and the positional relationship with the belt 3 will be described. FIG. 1 is a perspective view of the belt 3 and the belt cleaner 16. The belt 3 is stretched by the rolls 12, 13, 14, and 15 as described above. The toner image is formed on the central portion 3 a excluding the both end portions of the belt 3. The reflecting portion 5 is formed at both end portions, that is, one of the non-image forming regions 3b.
[0019]
The belt cleaner 16 includes a cleaner blade 27 as a toner removing cleaner member having a length L corresponding to at least the width of the image forming area of the belt 3, and a film seal 28 for receiving the toner removed by the cleaner blade 27. Yes. Further, seal members 29 and 30 for preventing the toner removed from the belt 3 from leaking from both ends of the cleaner blade 27 are provided at both ends of the cleaner blade 27. The cleaner blade 27 and the film seal 28 have one ends 27a and 28a fixed to the housing 31 of the belt cleaner 16, and the other ends 27b and 28b are free ends.
[0020]
The seal members 29, 30 are composed of plates 29a, 30a and flocked portions 29b, 30b thereon, and are attached to the surface of the housing 31 via the plates 29a, 30a. For example, polypropylene can be used as the resin fiber constituting the flocked portions 29b and 30b. The housing 31 is biased with respect to the belt 3 in the direction of an arrow 32 by a driving device including a solenoid or the like. The flocked portions 29b and 30b of the seal members 29 and 30 are flocked so that the hairs are aligned in the direction 32. In particular, the seal member 30 is set such that the width of the cleaner blade 27 in the length direction is larger than that of the seal member 29 and is expanded to a position where it meets the extension line of the reflecting portion 5 in the driving direction of the belt 3. .
[0021]
With this configuration, when the belt 3 is circling and the belt cleaner 16 is in contact with the belt 3, the flocked portion 30 b acts to wipe off the reflecting portion 5 for each round of the belt 3. Since the belt cleaner 16 abuts against the belt 3 while the belt 3 rotates once after the toner image is secondarily transferred to the recording paper, the reflecting portion 5 is implanted every time one image is output. It is cleaned by the part 30b.
[0022]
When the belt cleaner 16 contacts the belt 3, residual toner on the belt 3 is removed, but the removed residual toner is removed from the belt 3 and the belt cleaner 16 when the belt cleaner 16 is separated from the belt 3. The toner easily scatters from the gap. However, in the present embodiment, the reflection unit 5 is cleaned every time one image is output, so that the contamination of the reflection unit 5 due to the toner scattered by the belt cleaner 16 or the like is not accumulated.
[0023]
In particular, since the sealing members 29 and 30 are not always in contact with the belt 3, they do not slide more than necessary with the aluminum foil or the like constituting the reflecting portion 5. The risk of attaching or peeling off can be extremely reduced. The seal member 30 has both a function of preventing the toner from leaking from the end of the cleaner blade 27 and a function of wiping the reflective portion 5. However, these functions are not necessarily formed integrally with the seal member 30. That is, the member that performs the sealing function and the member that has the wiping function may be separately attached to the housing 31.
[0024]
Next, a second embodiment of the present invention will be described. In the above-described example, the belt cleaner 16 is provided with a means for wiping the reflecting portion 5. However, if the means for wiping off the reflective portion 5 is provided on a component (component) that makes contact with and separates from the belt 3 at a constant cycle so as to face the reflective portion 5, the object is achieved. Is done.
[0025]
Therefore, in the second embodiment, the secondary BTR 4 is provided with a means for wiping the reflecting portion 5. FIG. 3 is a perspective view of a main part of the secondary BTR 4 provided with a wiping means for the reflecting portion 5. In the figure, the secondary BTR 4 is pivotally supported at both ends by the housing 33 and is rotatably provided to constitute a part of the secondary transfer unit. A wiping member 34 is provided at the end of the housing 33, that is, on the side facing the reflecting portion 5. The wiping member 33 is composed of a plate 34a fixed to the housing 32 and a flocked portion 34b, and the flocking direction of the flocked portion 33b is preferably matched with the contact / separation direction of the secondary BTR 4 with respect to the belt 3. It is the same as the form.
[0026]
The wiping means for the reflecting portion 5 is most preferably a brush-like member planted as described above, but may be a polyurethane sheet material. When a polyurethane sheet is used, the thickness of the polyurethane sheet is preferably about 0.5 mm, and 1 mm is too thick. That is, the pressing force to the reflecting portion 5 becomes too strong, and the aluminum foil constituting the reflecting portion 5 may be peeled off after a short period of use.
[0027]
Further, when the polyurethane sheet is fixed to the housing 33, it is preferable that one end is fixed and the other end is a free end to easily follow the circumferential direction of the belt 3, in other words, to escape easily. FIG. 4 shows an example in which a polyurethane sheet is fixed to the housing 33, and only one end 35 a of the polyurethane sheet 35 is bonded to the housing 33.
[0028]
FIG. 5 is a diagram showing the relationship between the degree of damage of the reflecting portion 5 and the number of circulations of the belt 3. In the figure, the horizontal axis indicates the number of belt turns, and the vertical axis indicates the degree of damage to the reflecting portion 5. Examples of wiping means are those using flocking and those using a polyurethane sheet. The degree of damage of the reflecting portion 5 is represented by grades G1 to G4 corresponding to the intensity of the reflected light amount of the reflective optical sensor 6. In grades G1 and G2, a reflected light amount sufficient for the reflective optical sensor 6 not to make a false detection can be obtained. As shown in the figure, according to the wiping means for flocking, the reflection portion 5 is hardly damaged even by the belt rotation 30K times, and a sufficient amount of reflected light is obtained. On the other hand, in the case of a polyurethane sheet, the amount of reflected light of the reflecting portion 5 is reduced due to a relatively short period of use. In particular, when the thickness is large (1 mm), the reflecting portion 5 is constituted by a short period of use. The aluminum foil is peeled off.
[0029]
From this result, it can be said that flocking is preferable as the wiping means, but a relatively thin polyurethane sheet of less than 1 mm should be used under the condition that the aluminum foil of the reflecting portion 5 can be regularly maintained and replaced. Can do.
[0030]
【The invention's effect】
As is clear from the above description, according to the present invention, since the wiping member is in sliding contact with the reflecting portion, even if scattered toner adheres to the reflecting portion, the amount of reflected light at the reflecting portion is reduced. There is no accumulation. Accordingly, an accurate detection signal is always output from the sensor that detects the reflected position of the belt and detects the belt rotation position. As a result, various timing controls can be accurately performed based on the detection signal, and a high-quality color image without color misregistration can be obtained.
[Brief description of the drawings]
FIG. 1 is a perspective view of a main part of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention.
FIG. 3 is a perspective view of a main part of a secondary transfer BTR according to a second embodiment.
FIG. 4 is a perspective view of a main part of a secondary transfer BTR according to a modification of the second embodiment.
FIG. 5 is a diagram showing the relationship between the degree of damage of the reflecting portion 5 and the number of belt revolutions.
FIG. 6 is a diagram showing an outline of an image forming apparatus using an intermediate transfer member.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Photoconductor, 2 ... Primary BTR, 3 ... Intermediate transfer belt, 4 ... Secondary BTR, 5 ... Reflection part, 6 ... Reflection type optical sensor, 8 ... Charging roll, 9 ... Exposure apparatus, 10 ... Developing assembly, DESCRIPTION OF SYMBOLS 11 ... Photoconductor cleaner apparatus, 16 ... Belt cleaner, 27 ... Cleaner blade, 29, 30 ... Seal member, 29b, 30b ... Flocking part

Claims (3)

An image carrier on which an electrostatic latent image is formed;
Developing means for visualizing the electrostatic latent image with toner;
A circulating intermediate transfer member the visualized toner image is primarily transferred,
Secondary transfer means for secondary transfer of the toner image transferred to the circumferential intermediate transfer member to a recording medium;
A reflective portion provided on the circumferential intermediate transfer member;
A reflection type optical sensor for receiving the reflected light of the reflection part and detecting the position of the circular intermediate transfer member;
A wiping member that cleans the reflective portion in sliding contact with the reflective portion;
Wherein and wiping member, holds the second transfer means is provided in the secondary transfer unit for periodically contact the secondary transfer unit to the circulation intermediate transfer member, at least in the circulating intermediate transfer member An image forming apparatus, wherein the image forming apparatus is in contact with the rotating intermediate transfer member for one turn . An image carrier on which an electrostatic latent image is formed;
Developing means for visualizing the electrostatic latent image with toner;
A circulating intermediate transfer member the visualized toner image is primarily transferred,
Secondary transfer means for secondary transfer of the toner image transferred to the circumferential intermediate transfer member to a recording medium;
A reflective portion provided on the circumferential intermediate transfer member;
A reflection type optical sensor for receiving the reflected light of the reflection part and detecting the position of the circular intermediate transfer member;
A wiping member that slidably contacts the reflective portion to clean the reflective portion;
Comprising a belt cleaner for a cleaner member for removing residual toner on the circumferential intermediate transfer member is periodically abuts the circulating intermediate transfer member,
The wiping member is integrated with a seal member for preventing scattering of toner disposed on both side ends of the cleaner member, and the wiping member is applied to the rotating intermediate transfer member for at least one turn of the rotating intermediate transfer member. An image forming apparatus that is contacted .   The image forming apparatus according to claim 1, wherein the wiping member is a flocking member.

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