JP3386243B2 - Electrophotographic equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus such as a color copying machine or a color printer, and more specifically, after a toner image of each color formed on a photoconductor is superposed on an intermediate transfer belt and intermediately transferred. The present invention relates to an electrophotographic apparatus that transfers images onto a transfer paper.

[0002]

2. Description of the Related Art Conventionally, as an electrophotographic apparatus such as a color copying machine or a color printer, a toner image of each color formed on a photoconductor by an optical writing unit and a developing unit is rotated in contact with the photoconductor. 2. Description of the Related Art There is known an electrophotographic apparatus of a type in which a transfer sheet is superposed on a transfer belt and transferred, and then transferred to a transfer sheet fed toward the intermediate transfer belt. By the way, in the electrophotographic apparatus of this type, when the toner images of the respective colors are formed on the photoconductor and are sequentially superposed on the intermediate transfer belt and the intermediate transfer is performed, the intermediate transfer positions of the toner images of the respective colors are displaced. In this case, color misregistration occurs in the image transferred on the transfer paper.

As a method for preventing such color misregistration of an image, (1) when a transfer position is displaced, the movable optical writing device is moved by expanding and contracting due to the temperature change. The optical writing position of the photoconductor (latent image carrier) is corrected (“color image forming apparatus” described in Japanese Patent Laid-Open No. 1-130172). (2) The rotation of the drum-shaped photosensitive member (image forming member) and the rotation of the deflector which is the optical writing unit (horizontal scanning unit) are synchronously driven to improve the color superposition resist (Japanese Patent Laid-Open No. 2-17).
"Color image processing device" described in Japanese Patent No. 3767). (3) By synchronizing and controlling the movements of the photoconductor belt and the intermediate transfer belt by using different driving means, the color component image is properly registered when a composite image is formed. (JP-A-63-264
"Color electrophotographic printing apparatus" described in Japanese Patent No. 778). Conventional techniques such as are proposed.

[0004]

By the way, in color image formation by electrophotography, Y (yellow) and M are usually used.
(Yellow), M (magenta), C (cyan), and BK because these are performed by superposing toner images of toners of (magenta), C (cyan), and BK (black). If the image positions of the toner images of the respective colors (black) are misaligned, color unevenness or image misalignment occurs in the superposed color images, and the image quality deteriorates. Therefore, in such a color image formation, it is important to accurately superpose the image positions of the toner images of the respective colors in order to eliminate the positional deviation of the color images.

On the other hand, as a method for superimposing the toner images of the respective colors, the toner images of the respective colors are once superposed on the intermediate transfer body, and then the color images on the intermediate transfer body are transferred at once on the transfer paper. There is a method of directly superimposing toner images of respective colors on a transfer paper, and as an optical writing method for forming a latent image of a toner image, there is a method of scanning with a laser beam.

Here, as a latent image optical writing system, a polygon motor system in which a motor that rotates at a constant speed rotates a polygonal mirror body is used to scan a laser beam at regular intervals, while a toner image of each color is formed. As a method of overlapping
The position of the toner image of each color is detected by forming a belt-shaped intermediate transfer member, detecting the reference mark provided on the intermediate transfer belt driven by a roller such as a rubber roller, and starting the optical writing of the latent image of each color. When the alignment is performed, it is necessary to synchronize the scanning of the laser beam with the reference mark.

However, in this case, the rotational position of the drive roller of the intermediate transfer belt is set in the conventional example (Japanese Patent Laid-Open No. 2-173).
767), it is possible to synchronize with the optical scanning, but the moving amount of the intermediate transfer belt driven by the roller changes due to variations in the outer diameter of the driving roller, slip between the belt and the roller, and the like. However, the reference mark on the intermediate transfer belt and the optical scanning timing cannot be synchronized.

Therefore, as described above, in the case of the simple method in which the optical scanning is started by detecting the reference mark on the intermediate transfer belt, the positional deviation of one scanning at maximum occurs between the toner images of the respective colors. Will be done.

The prior art disclosed in Japanese Patent Laid-Open No. 1-130172 is a system for correcting the positional deviation of an image by moving the entire optical writing unit, but this system rotates at high speed by moving the unit. Vibration is generated in the polygon motor, which is not preferable.

Further, the prior art described in Japanese Patent Laid-Open No. 63-264778 does not use a laser beam for the optical writing system. Therefore, when the laser beam is used for this optical writing system, There arises a problem of image misregistration as described above.

The present invention has been made in view of the above points, and an object thereof is to accurately align the toner images of the respective colors when the toner images of the respective colors are transferred onto the intermediate transfer belt in an overlapping manner. An object of the present invention is to provide an electrophotographic apparatus that can be frequently used (claims 1, 2, 3, 4, 6). Another object of the present invention is to provide an electrophotographic apparatus capable of correcting the position of each color toner image more easily (Claim 5). It is still another object of the present invention to provide an electrophotographic apparatus which does not disturb an image due to vibration generated when the toner image is aligned and corrected (claim 7).

[0012]

In order to solve the above-mentioned problems, the present invention provides, in claim 1, an image formed on a photoconductor by an optical writing unit and a developing unit, which is brought into contact with the photoconductor. In the electrophotographic apparatus of the type in which the image is once transferred onto the rotating intermediate transfer belt and then transferred onto the transfer paper fed toward the intermediate transfer belt, the light synchronized with the main scanning of the optical writing on the photoconductor is used. A scanning reference detection device for generating a write synchronization signal and a belt reference detection device for detecting a reference position of the intermediate transfer belt to generate a belt reference detection signal are provided, and the optical writing synchronization signal and the belt reference detection signal are provided. detecting a temporal difference between, corresponding to the time difference, only setting the transfer position correcting apparatus for correcting an intermediate transfer position of the image to the intermediate transfer belt from the photosensitive member, the intermediate transfer belt
Move the photoconductor to the middle of the photoconductor
The configuration is such that the intermediate transfer position of the image on the inter-transfer belt is corrected .

According to a second aspect of the present invention, the image formed on the photoconductor by the optical writing unit and the developing unit is once transferred onto the intermediate transfer belt which rotates in contact with the photoconductor, and then the intermediate transfer belt. In an electrophotographic apparatus of the type that transfers onto a transfer sheet fed toward a sheet, a scanning reference detection device that generates an optical writing synchronization signal in synchronization with the main scanning of the optical writing on the photoconductor, and the intermediate transfer belt. And a belt reference detection device for generating a belt reference detection signal by detecting the reference position, detecting the time difference between the optical writing synchronization signal and the belt reference detection signal, and corresponding to this time difference, The intermediate transfer position of the image from the photoreceptor to the intermediate transfer belt is set to the rotational position of the drive motor shaft of the intermediate transfer belt.
Then, the phase of rotation of the drive roller shaft of the intermediate transfer belt
A two-axis relative rotation position variable mechanism that corrects by changing
The structure is provided between the drive motor shaft and the drive roller shaft .

Further, in claim 3, the biaxial relative rotational position is
The variable position mechanism is a planetary gear mechanism .

Further, in claim 4, the intermediate transfer belt
Drive motor to drive the step motor or encoder
The motor with a dam is used to detect the optical writing sync signal and the belt
Rotation of the drive motor according to the time difference from the semi-detection signal
The intermediate transfer position by accelerating or decelerating the number for a certain period of time.
The position is corrected .

Further, in claim 5, an optical writing on the photoconductor is performed.
Imprinting and intermediate transfer of the image onto the intermediate transfer belt
During the time when neither is performed, the intermediate transfer position
The configuration is such that correction is performed .

[0017]

[0018]

[0019]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows a schematic sectional view of an electrophotographic apparatus in which the present invention is implemented. In FIG. 1, the photosensitive belt 1 is
After being rotated in the direction of the arrow by the photoconductor driving roller 2 and the surface thereof is uniformly charged by the charging roller 9, the laser beam is irradiated by the optical writing device 3 so that the latent image for each color is formed on the surface. Images are sequentially formed.

The latent image for each color is provided with C, M, and C provided on the outer periphery of the developing device 4 as the developing device 4 rotates by 90 °.
By making the developing rollers of the respective colors individually supplying the four color toners of Y and BK sequentially correspond to the photoconductor belt 1,
A toner image is sequentially formed with toner of a predetermined color.

The toner images of the respective colors formed on the photosensitive belt 1 for each of the predetermined colors are transferred onto the intermediate transfer belt 5 while being sequentially superposed on each other, whereby the toner images of the respective colors are transferred onto the intermediate transfer belt 5. Form a full-color toner image.

The full-color toner image is transferred by the transfer roller 8 onto the transfer paper P which is fed in synchronization with the intermediate transfer belt 5 which is rotated by the intermediate transfer belt drive roller 6 in the direction of the arrow. It is fixed by the fixing device 12. The transfer paper P on which the full-color image has been formed in this manner is discharged onto the discharge tray by the discharge rollers.

On the other hand, the toner remaining on the photoreceptor belt 1 is cleaned and removed by the photoreceptor cleaning device 10 and the toner remaining on the intermediate transfer belt 5 is cleaned and removed by the intermediate transfer belt cleaning device 11, respectively. It

As shown in FIG. 2, the optical writing device 3 comprises a polygon mirror (polyhedral reflecting mirror) 22, a lens 23, a reflecting mirror 24 rotated by a polygon motor 20, and a laser emitted from a light emitting section 25. The beam is configured to scan by the rotation of the polygon mirror 22, and the reference position for the scanning is the scanning reference detector 26.
Is set by detecting the passage of the laser beam and generating a scanning reference detection signal.

On the other hand, when the toner image is transferred from the photosensitive belt 1 to the intermediate transfer belt 5, it is necessary to align and superimpose the toner images of four colors, respectively. The belt reference mark 21 provided on the intermediate transfer belt 5 is detected by the belt reference detector 7, and the toner image to be transferred and the rotation of the intermediate transfer belt 5 are synchronized with each other.

By the way, in such an electrophotographic apparatus,
As described above, since it is difficult to match the movement (rotation) of the intermediate transfer belt 5 and the timing of beam scanning, as shown in FIG. 3, a symbol A is provided between the belt reference detection signal and the scanning reference detection signal. There is a time lag indicated by.

Therefore, in this electrophotographic apparatus, if the four color toner images are superimposed as they are without correcting the above-mentioned time lag, an image position shift in the belt scanning direction corresponding to one scan at maximum occurs. Therefore, in the electrophotographic apparatus according to the present invention, a time difference (deviation amount A) between the scanning reference detection signal (optical writing synchronization signal) and the belt reference detection signal is detected and the time difference is dealt with. Then, a transfer position correcting device for correcting the intermediate transfer position of the toner image from the photosensitive belt 1 to the intermediate transfer belt 5 is provided.

FIG. 4 shows an embodiment of this transfer position correcting device. In FIG. 4, tension is applied to the photosensitive belt 1 and the intermediate transfer belt 5 by springs 31a and 31b, respectively.

Further, the intermediate transfer belt drive roller 6 has
A belt position correction arm 32 for correcting the position of the intermediate transfer belt 5 is provided, and the belt position correction arm 32 is pivotally supported about a support shaft 33 so as to be swingable. At the free end of the belt position correction arm 32,
A female screw 34 is fixed, and a male screw 35 provided on a motor shaft of a belt position correction motor 36 for swinging the belt position correction arm 32 is screwed into the female screw 34.

In FIG. 4, the belt position correction motor 36
When the male screw 35 is rotated by driving the belt, the belt position correcting arm 32 is passed through the female screw 34 screwed to the male screw 35.
The free end of is moved up and down in the direction of arrow a.

As a result, the belt position correction arm 32 is swung about the support shaft 33, and the intermediate transfer belt 5 is finely adjusted and moved in the direction of arrow b in FIG. 4 via the intermediate transfer belt drive roller 6. . The correction amount of the intermediate transfer position by the fine adjustment movement of the intermediate transfer belt 5 is the time difference (deviation amount A) between the scanning reference detection signal (optical writing synchronization signal) and the belt reference detection signal shown in FIG. It is decided according to.

Here, the support shaft 33, as shown in FIG.
It is supported by the receiving holes 42 of the pair of side plates 41 (the rear side plate is not shown) of the apparatus body. The driven roller shaft 40 that stretches the intermediate transfer belt 5 is supported by the elongated hole 43 of the side plate 41 via the slider 44.

As the belt position correcting motor 36, DC is used.
A motor or stepping motor is used, and a home position for correction of the intermediate transfer belt 5 is determined by a sensor (not shown) that detects the reference position of the belt position correction arm 32.
Controlled to return to the home position.

FIG. 6 shows another embodiment of the transfer position correcting device. In this embodiment, by moving the photosensitive belt 1 with respect to the intermediate transfer belt 5, the intermediate transfer position of the toner image from the photosensitive belt 1 to the intermediate transfer belt 5 is corrected,
It is configured to eliminate the color shift of the transferred image.

That is, in this embodiment, the support shaft 52 is provided by the swing mechanism using the motor similar to that of the embodiment shown in FIG.
A belt position correction arm 51 that swings about the photoconductor belt 1 is provided by the belt position correction arm 51.
By swinging the driven roller shaft 53 around the driving roller shaft 54 in the direction of arrow c, the intermediate transfer position of the toner image of each color is corrected.

FIG. 7 shows still another embodiment of the transfer position correcting device. In the present embodiment, the drive roller 6 of the intermediate transfer belt 5 is decelerated and rotated by the drive motor 61 via the planetary gear device 62, and the correction motor 64 drives the internal rotation of the planetary gear device 62 via the worm gear 63. By rotating a tooth gear (gear with a large diameter) by a small amount, the intermediate transfer position of the toner image on the intermediate transfer belt 5 is corrected to eliminate the color shift of the transferred image. Here, as the drive motor 61, a DC brushless motor or the like that rotates at a constant speed is used.

In the planetary gear unit 62 of this embodiment, as shown in detail in FIG. 8, the rotation of the drive motor 61 is transmitted to the central sun gear 65, and the three planetary gears 66 meshing with the sun gear 65. Is transmitted to the intermediate transfer belt drive roller 6.

A worm wheel 68 that meshes with the worm gear 63 rotated by the correction motor 64 is formed on the outer periphery of the internal gear 67 that meshes with the three planetary gears 66.

The correction of the intermediate transfer position of the toner image on the intermediate transfer belt 5 according to this embodiment is performed by rotating the internal gear 67 via the worm gear 63 by the correction motor 64, and determining the rotation amount of the internal gear 67. This is performed by advancing or delaying the position of the intermediate transfer belt 5 in the feeding direction by a corresponding distance.

Thus, the drive motor 61 that rotates at a constant speed
By interposing the planetary gear device 62 in the drive system of 1, the intermediate transfer position of the toner image on the intermediate transfer belt 5 can be corrected.

As the correction motor 64 of this embodiment, a stepping motor, a DC motor or the like can be used. Also,
In this embodiment, the motor is used as the drive source for correcting the intermediate transfer position, but it is also possible to use a solenoid or the like as the drive source. Further, in this embodiment, the planetary gear device 62 is used as a means for changing the phase between the input shaft and the output shaft of the intermediate transfer roller driving roller 6, but as the phase displacement means, for example, other means such as a clutch is used. It is also possible to use a mechanism.

FIG. 9 shows an embodiment in which a servomotor 70 with an encoder is used as a drive motor for the intermediate transfer belt 5 shown in FIG. In this embodiment, compared to the case where a DC brushless motor used for normal constant speed rotation is used as a drive motor, its control becomes complicated and the drive motor becomes expensive, but this makes the intermediate transfer belt 5 The intermediate transfer position of the toner image on the can be electrically corrected easily.

In this embodiment, the support shaft of the intermediate transfer belt driving roller 6 is connected to the motor 72 via the coupling 71. The motor 72 is provided with an encoder 73 and a sensor 74.

In the present embodiment, the deviation amount A between the belt reference detection signal and the scanning reference detection signal shown in FIG. 3 is detected, and a voltage corresponding to the deviation amount A is applied to the motor 72 to make the intermediate transfer belt. Then, the intermediate transfer position of the toner image on the image forming apparatus 5 is corrected.

As described above, although the servomotor 70 with an encoder is used in this embodiment, the same correction can be performed by adjusting the drive pulse interval of the stepping motor according to the shift amount A.

By the way, in the above-described embodiment, the intermediate transfer position of the toner image on the intermediate transfer belt 5 is corrected by changing the rotation speed of the intermediate transfer belt 5 for a certain period of time. Therefore, there is a risk that the photosensitive belt 1 that comes into contact with the intermediate transfer belt 5 to perform the intermediate transfer of the toner image may temporarily have uneven rotation. Such rotation unevenness of the photosensitive belt 1 causes unevenness in the pitch of optical writing on the photosensitive belt 1 and causes image deterioration.

Therefore, in this embodiment, during the time period when neither the optical writing to the photosensitive belt 1 nor the intermediate transfer of the toner image to the intermediate transfer belt 5 is performed,
It is preferable that the intermediate transfer position of the toner image on the intermediate transfer belt 5 is corrected.

[0048]

As described above, according to the present invention, in claim 1, the rotation error due to the slip of the intermediate transfer belt can be corrected, so that the intermediate transfer position of the toner image of each color is
It is possible to perform accurate matching without causing color misregistration. Further, in claim 1, the position of the drive shaft of the intermediate transfer belt is
Intermediate transfer of toner image to intermediate transfer belt without changing the position
The position can be easily corrected.

In the second aspect, the transmission of the motor shaft that rotates at a constant speed.
Increase or decrease the feeding amount of the intermediate transfer belt depending on the delivery system
And the progress of the intermediate transfer belt can be corrected.
Intermediate transfer without changing the positions of the body belt and intermediate transfer belt.
Easily correct the intermediate transfer position of the toner image on the transfer belt
be able to.

In the third aspect, the transmission of the motor shaft that rotates at a constant speed.
Intermediate transfer by using a planetary gear system as a delivery system
Increase or decrease the belt feed amount to
Since the progress of the image can be corrected, the photoconductor belt and the intermediate transfer
Toner image on the intermediate transfer belt without changing the belt position
The intermediate transfer position of can be corrected more easily.

In the fourth aspect, the transmission of the motor shaft that rotates at a constant speed.
With stepping motor or encoder
By using a motor, the feed amount of the intermediate transfer belt
To increase or decrease to correct the progress of the intermediate transfer belt
Position of the photoconductor belt and the intermediate transfer belt.
The intermediate transfer position of the toner image on the intermediate transfer belt without changing
Can be easily corrected electrically.

According to a fifth aspect of the present invention, the photosensitive material that causes image deterioration is exposed.
Optical writing to the body belt and to the intermediate transfer belt
Intermediate transfer during the time when the intermediate transfer of the toner image is performed
Correction of the intermediate transfer position of the toner image on the belt is avoided
Therefore, a high quality image can be obtained.

The intermediate transfer position of the toner image on the intermediate transfer belt can be easily corrected without changing the positions of the optical writing unit and the developing unit.

[0054]

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an electrophotographic apparatus in which the present invention is implemented.

FIG. 2 is a schematic perspective view of an image forming unit in the electrophotographic apparatus.

FIG. 3 is a diagram showing a relationship between a belt reference detection signal of an intermediate transfer belt and a scanning reference detection signal of a laser beam in the electrophotographic apparatus.

FIG. 4 is a schematic side view of an embodiment of the present invention.

FIG. 5 is a schematic exploded perspective view showing the configuration of the above embodiment.

FIG. 6 is a schematic side view of another embodiment of the present invention.

FIG. 7 is a schematic side view of still another embodiment of the present invention.

8 is a detailed view of a planetary gear mechanism in the embodiment shown in FIG.

FIG. 9 is a schematic perspective view of an embodiment in which a servomotor with an encoder is used as a drive motor for the intermediate transfer belt in the present invention.

[Explanation of symbols]

1 photoconductor belt 2 inter-koa drive roller 3 Optical writing device 4 developing device 5 Intermediate transfer belt 6 Intermediate transfer belt drive roller 7 Belt reference detector 20 polygon motor 21 Belt reference mark 22 polygon mirror 23 lenses 24 reflective mirror 25 Light emitting part 26 Scan reference detector 31a, 31b springs 32 Belt position correction arm 33 spindle 34 female screw 35 male screw 36 Belt position correction motor 41 Side plate 42 receiving hole 43 slot 44 slider 51 Belt position correction 8 arms 52 spindle 53 Driven roller shaft 54 Drive roller shaft 61 Drive motor 62 Planetary gear unit 63 worm gear 64 correction motor 65 sun gear 66 planetary gears 67 Internal gear 68 Worm Wheel 70 Servo motor with encoder 71 Coupling 72 motor 73 encoder 74 sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takahiro Tamiya 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (56) Reference JP-A-6-8511 (JP, A) JP Hei 5-265331 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/16 G03G 15/01 111 G03G 15/01 114 G03G 21/14

Claims (5)

(57) [Claims] 1. An image formed on a photoconductor by an optical writing unit and a developing unit is once transferred onto an intermediate transfer belt rotating in contact with the photoconductor, and then fed toward the intermediate transfer belt. And a scanning reference detecting device for generating an optical writing synchronization signal in synchronism with the main scanning of the optical writing on the photoconductor,
A belt reference detection device that detects a reference position of the intermediate transfer belt and generates a belt reference detection signal is provided, and a time difference between the optical writing synchronization signal and the belt reference detection signal is detected. correspondingly, only setting the transfer position correcting apparatus for correcting an intermediate transfer position of the image to the intermediate transfer belt from the photosensitive member, the photosensitive member relative to the intermediate transfer belt
Image from the photoconductor to the intermediate transfer belt.
Electrophotographic device characterized by correcting the intermediate transfer position
Place 2. An image formed on a photoconductor by an optical writing unit and a developing unit is once transferred onto an intermediate transfer belt rotating in contact with the photoconductor, and then fed toward the intermediate transfer belt. And a scanning reference detecting device for generating an optical writing synchronization signal in synchronism with the main scanning of the optical writing on the photoconductor,
A belt reference detection device that detects a reference position of the intermediate transfer belt and generates a belt reference detection signal is provided, and a time difference between the optical writing synchronization signal and the belt reference detection signal is detected. Correspondingly, the intermediate transfer position of the image from the photoreceptor to the intermediate transfer belt is set to the intermediate transfer belt.
For the rotation position of the drive motor shaft of
Correction by changing the rotation phase of the drive roller shaft
The two-axis relative rotational position varying mechanism includes the above-mentioned drive motor shaft and the above-mentioned
Electrophotography characterized by being provided between the drive roller shaft
apparatus. 3. The biaxial relative rotational position changing mechanism comprises a planetary tooth.
The electronic photograph according to claim 2, which is a car mechanism.
apparatus. 4. A drive motor for driving the intermediate transfer belt.
Is a step motor or a motor with an encoder ,
Time difference between the optical writing sync signal and the belt reference detection signal
Depending on the
Or slow down to correct the intermediate transfer position.
The electrophotographic apparatus according to claim 2, which is used as a characteristic. 5. Optical writing to the photosensitive member, and the above
Neither intermediate transfer of the image to the intermediate transfer belt is performed.
The intermediate transfer position is corrected during a certain period of time.
The electron according to any one of claims 1 to 4.
Photographic equipment.