JPH05265331A - Recorder - Google Patents

Abstract

PURPOSE:To reduce image distortion and a deviation in the position of color superimposing by controlling a tension varying means according to detected fluctuations in rotation. CONSTITUTION:A neutral point not moved by the stretching of a medium to be transferred 32, is set to the contact point of a photosensitive body 31 and the medium 32 to be transferred and simultaneously, the tension varying means 45 varying the tension of the medium to be transferred 32, a detecting means 49 detecting fluctuations in the rotation of the photosensitive body 31, and a control means 44 controlling the tension varying means 45, according to the detected fluctuations in the rotation, are provided. Then, the fluctuations in the rotation of the photosensitive body 31 is detected, and the tension varying means 45 is controlled according to the detected fluctuations in the rotation. For instance, when the photosensitive body 31 is at speed faster than prescribed speed, the tension is control led so as to shrink the medium to be transferred 32 as an intermediate transfer belt. When the tension of the medium to be transferred 32 is changed, the neutral point of the medium to be transferred 32 is in the contact point of the photosensitive body 31 and the medium to be transferred 32. At this time, the tension varying means 45 is composed of a nut 39, and linear motors 40 and 41. Moreover, the fluctuations in the rotation is detected/stored at the time of exposing the photosensitive body, and the position of the medium to be transferred is corrected from the deviation in the position of an image at the time of exposing, by referring to the stored fluctuations in the rotation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus for forming an image on a photoreceptor and transferring the formed image onto a transfer medium. In the exposure process in which a latent image is formed on the photoconductor, a developing device or a transfer belt may come into contact with or separate from the photoconductor. For this reason, the rotation speed of the photosensitive member fluctuates, which causes distortion of the image and displacement of the color overlapping position. It is desired to prevent the deterioration of the image quality due to the fluctuation of the rotation speed of the photoconductor.

[0002]

2. Description of the Related Art As a conventional electrophotographic recording apparatus, for example, there is one shown in FIG. In FIG. 6, reference numeral 1 is a photosensitive drum, and around the photosensitive drum 1,
A charging device 2, an exposure system 3, developing devices 4 to 7 for developing a YMCK color toner image on the photosensitive drum 1, and a cleaner blade 8 are provided.

Reference numeral 9 denotes an intermediate transfer belt, and the toner images on the photosensitive drum 1 are sequentially transferred and superposed on the intermediate transfer belt 9 by the discharge of the transfer corotron 10. Reference numeral 11 is a cleaner blade, and the cleaner blade 11 presses against the roller 12 to clean the intermediate transfer belt 9.
13 is a transfer roller, and the transfer roller 13 is a roller 14.
Then, the toner image is transferred onto the recording paper 15 by pressing. The recording paper 15 is taken out from the paper cassette 16 and is conveyed at a predetermined timing by a registration roller 18 via a roller 17.

A fixing device 19 has a fixing roller 20 and a pressure roller 21, and fixes the toner image on the recording paper 15. The roller 12 is driven by the motor 22 and rotationally drives the intermediate transfer belt 9. Next, the operation will be described. When a recording command is issued from a control unit (not shown), the feeding operation of the recording paper 15 is started. The recording paper 15 taken out from the paper cassette 16 is fed to the roller 17
After that, the registration roller 18 is temporarily stopped at the nip portion of the registration roller 18, and the timing with the recording process is set.
After that, the recording paper 15 is rotated again and the registration roller 1 is restarted.
The color toner image, which is sent to the transfer roller 13 and superposed on the intermediate transfer belt 9, is transferred onto the recording paper 15 by the transfer roller 8. The recording paper 15 is further sent to the fixing device 19, and the toner image is fixed on the recording paper 15 by heat and pressure applied from the fixing roller 20 and the pressure roller 21. The photosensitive drum 1 is cleaned by the cleaner blade 8.

The charging device 2, the exposure system 3, and the developing devices 4 to 7 provided around the photosensitive drum 1 undergo a known electrophotographic process, and the YM is rotated on the photosensitive drum 1 every rotation of the drum.
A toner image is formed in the order of CK. The formed toner image is transferred to the photosensitive drum 1 by the discharge of the transfer corotron 10.
Are sequentially superposed and transferred onto the intermediate transfer belt 9 (primary transfer).

The cleaner blade 11 and the transfer roller 13 are separated from the intermediate transfer belt 9 during the superposition of the four colors. When the transfer of the four colors of YMCK is completed, the transfer roller 13 is pressed against the roller 14, and the color toner images are collectively transferred to the recording paper 15 (secondary transfer). When the transfer onto the recording paper 15 is completed, the transfer roller 13 is the roller 1.
It is separated from 4. The cleaner blade 11 is pressed against the roller 12 to clean the intermediate transfer belt 9 after the transfer, and is separated from the roller 12 after the cleaning is completed.

By repeating such an operation, color recording is performed one after another.

[0008]

In such a conventional recording apparatus, in the exposure process in which a latent image is formed on the photosensitive drum, the developing device or the intermediate transfer belt may come into contact with or separate from the photosensitive drum. However, there is a problem in that the rotational speed of the photosensitive drum fluctuates, the image is distorted in the transfer portion, and the color superposition position shift occurs when the image is superposed on the recording paper.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a recording apparatus capable of preventing the occurrence of image distortion and color registration misalignment. ..

[0010]

In order to achieve the above object, according to the present invention, as shown in FIG. 1, an image formed on a photoconductor 31 is driven by a plurality of rollers 33 to 36 under tension. In a recording apparatus for recording on a recording sheet after being transferred to a transfer medium 32, a neutral point that does not move due to tension of the transfer medium 32 is set at a contact point between the photoconductor 31 and the transfer medium 32, and Transfer medium 32
Tension varying means 45 for varying the tension of the photoconductor 3 and the photoconductor 3
The detection means 49 for detecting the rotational fluctuation of No. 1 and the control means 44 for controlling the tension varying means 45 according to the detected rotational fluctuation.

Another aspect of the present invention is a recording apparatus for transferring or recording an image formed on a photoconductor 51 on a transfer medium 52 as shown in FIG. A detection unit 67 for detecting the rotational fluctuation, a recording unit 63 for accumulating the detected rotational fluctuation, and a correction unit 68 for correcting the position of the transfer target medium 52 at the time of transfer by obtaining the positional deviation at the time of image exposure from the rotational fluctuation. Be prepared.

[0012]

In the present invention, the rotational fluctuation of the photosensitive member is detected, and the tension varying means is controlled according to the detected rotational fluctuation. For example, when the photoconductor is faster than a predetermined speed, tension control is performed so that the transfer medium contracts. When changing the tension of the transfer medium, the neutral point (the point that does not move due to tension) of the transfer medium is set to be the contact point between the photoconductor and the transfer medium. This is because unless the neutral point of the transfer medium is at the contact point between the photoconductor and the transfer medium, the tension change according to the rotation fluctuation cannot be accurately performed.

As a result, it is possible to reduce the distortion of the image and the misregistration of the color overlapping due to the fluctuation of the rotation of the photosensitive member. Further, in another invention, the rotational fluctuation of the photoconductor at the time of exposure is detected, the detected rotational fluctuation is stored, and the positional deviation at the time of exposure of the image is obtained by referring to the stored rotational fluctuation. To correct the position of the medium to be transferred during transfer.

As a result, it is possible to reduce the distortion of the image and the misregistration of the color due to the rotation fluctuation of the photosensitive member.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 are views showing an embodiment of the present invention.
In FIG. 1, reference numeral 31 is a photosensitive drum as a photosensitive member, and a toner image is formed on the photosensitive drum 31 in order of YMCK for each rotation by a charging device, an exposing device, and a developing device of YMCK.

Reference numeral 32 denotes an intermediate transfer belt as a transfer medium provided in contact with the photosensitive drum 31, and the toner images on the photosensitive drum 31 are sequentially superposed on the intermediate transfer belt 32 by the discharge of the transfer corotron. Is transcribed. The intermediate transfer belt 31 is tensioned by four rollers, that is, a tension roller 33, a support roller 34, a drive roller 35, and a backup roller 36.

The drive roller 35 drives the intermediate transfer belt 32, and a gear 37 for deceleration is attached to the end of the drive roller 35, and the gear 37 is driven by a belt drive motor 38. Nuts 39 are attached to both ends of the backup roller 36.
It is possible to move linearly by 0,41. That is, the backup roller 36 has its shaft 42.
And is movable in a direction (x, reference) orthogonal to the feeding direction of the recording paper. The linear motors 40 and 41 are drivers 43
Is controlled by the control circuit 44 as a control means. The nut 39 and the linear motors 40 and 41 together constitute a tension varying means 45 for varying the tension of the intermediate transfer belt 32.

When the intermediate transfer belt 32 is stretched by the rollers 33 to 36, the structure of the intermediate transfer belt 32 is left and right symmetrically so that when the tension of the intermediate transfer belt 32 is changed, the intermediate transfer belt 32 does not move due to the tension. The neutral point is set at the contact point between the photosensitive drum 31 and the intermediate transfer belt 32. When the neutral point and the contact point shift, the photoconductor drum 3
It becomes impossible to accurately perform the tension control according to the rotation fluctuation of No. 1, and more complicated tension correction is required.

On the other hand, in order to measure the peripheral speed of the photosensitive drum 31 at the transfer position with respect to the intermediate transfer belt 32, the width of the photosensitive drum 31 is made wider than the width of the intermediate transfer belt 32, and the laser among them is used. A thin film 46 having a thickness that reflects the laser well and having a uniform thickness is attached to a portion irradiated with. 47
Is an optical head that irradiates the thin film 46 with a laser and receives the reflected light, and the optical head 47 and the amplifier 48 constitute a laser Doppler velocimeter as a detecting means 49 for detecting a fluctuation in the rotational speed of the photosensitive drum 31. ing.

The optical head 47 is connected to the control circuit 44 via an amplifier 48, and controls the linear motors 40 and 41 according to the fluctuation of the rotation speed of the photosensitive drum 31 to make the tension of the intermediate medium belt 32 variable. Before performing the feedback control of the tension of the intermediate medium belt 32, as shown in FIG.
A tensile test is performed on the intermediate medium belt 32 to obtain tensile properties.

In FIG. 2, Lo is the intermediate medium belt 32.
, T1 / 2 is the tension at the time of transfer onto the recording paper, and T1 is the critical tension in the linear region. Next, the operation will be described. FIG. 3 shows the intermediate transfer belt 3
It is a flow chart which shows the sequence which performs feedback control of the tension of No. 2.

In FIG. 3, first, in step S1, the laser Doppler velocimeter 49 detects the speed v of the photosensitive drum 31, and the rotational speed fluctuation is caused by the difference between the speed v detected in step S2 and the previous speed v1. Calculate Δv.
Next, in step S3, the required moving distance Δx of the backup roller 36 is calculated.

Then, in order to achieve Δx in step S4, the control voltage ΔV (ΔV∝Δ) is applied to the linear motors 40 and 41.
x) is provided via the driver 48. Here, the required moving distance Δx of the backup roller 36 in the step S3.
Is calculated as follows. First, the belt shape stretched by three rollers will be schematically represented by a triangle as shown in FIG.

Point P is the position of the backup roller 36 before movement. FIG. 4B schematically shows the belt shape when the backup roller 36 is moved by Δx by the linear motors 40 and 41. Figure 4 below
The relationship between Δx and the belt elongation amount ΔL is obtained using the symbol. By the Pythagorean theorem

[0025]

[Equation 1]

ΔL = 2 (b 1 −b) (2) By substituting the equation (1) into the equation (2), the equation (3) is obtained.

[0027]

[Equation 2]

Here, when the speed fluctuation at the contact point between the photosensitive drum 31 and the intermediate transfer belt 32 is Δv, the displacement ΔX can be written by the equation ΔX = ∫Δvdt. ΔL = ΔX That is, in order to obtain Δx such that ΔL = ∫Δvdt (4), the following formula (4) is added to the formula (3).
By substituting the formula, the formula (5) is obtained.

[0029]

[Equation 3]

From the above, the relationship between Δx and Δv could be obtained. However, when the sampling time for speed detection of the photosensitive drum 31 is Δt, ∫Δvdt = Δvdt. In this way, by controlling the position of the backup roller 36 of the intermediate transfer belt 32, the tension of the intermediate transfer belt 32 is indirectly controlled, and the image distortion and the color overlapping position due to the rotation speed fluctuation of the photosensitive drum 31 are controlled. The shift can be reduced.

Although the linear motors 40 and 41 are used as the tension varying means 45 in this embodiment, the present invention is not limited to this, and ball screws may be used. Next, FIG. 5 is a diagram showing another embodiment of the present invention. In FIG. 5, reference numeral 51 is a photosensitive drum as a photosensitive member, and an encoder 60 for detecting the rotation angle of the photosensitive drum 51 is connected to the rotary shaft of the photosensitive drum 51. At the same time, the reference exposure position generation unit 61 constantly generates a reference rotation angle when the photosensitive drum 51 is exposed. The exposure state recording unit 62 compares these outputs and records the exposure position of the photosensitive drum 51 and the rotation fluctuation at the time of exposure in the storage device 63 at any time.

Encoder 60, reference exposure position generator 61
And the exposure state recording section 62 as a whole includes the photosensitive drum 51.
Detecting means 67 for detecting the rotational fluctuation of the photosensitive drum 51, and the storage device 63 stores the rotational fluctuation of the photosensitive drum 51 at the time of exposure. On the other hand, the reference transfer position generation unit 64 always generates a reference rotation angle prior to the transfer of the toner image from the photosensitive drum 51 to the intermediate transfer belt 52 serving as a transfer medium. The exposure state reading unit 65 receives this reference transfer rotation angle and subtracts the rotation angle of the photosensitive drum 51 between the exposure position A and the transfer position B in FIG. The rotation angle of the photosensitive drum 51 when the toner image is exposed at the position A is calculated. By reading the rotation fluctuation in the portion corresponding to this rotation angle from the storage device 63, the amount of positional deviation of the toner image on the transfer position B at the time of exposure can be obtained.

The rotation fluctuation amount read by the exposure state reading unit 65 is sent to the belt position correction amount calculation unit 66, and conversion from the photosensitive drum coordinate system to the transfer belt coordinate system is performed, thereby predicting on the intermediate transfer belt 52. The calculated position amount is determined and used as the correction amount of the target value of the motor 53 that drives the intermediate transfer belt 52. The reference transfer position generation unit 64, the exposure state reading unit 65, and the belt position correction calculation unit 66 collectively form a correction unit 68 that determines the position deviation at the time of exposure from the rotational fluctuation of the photosensitive drum 51 and corrects the position of the transfer target. ing.

In this way, the rotational fluctuation of the photosensitive drum 51 during the exposure is recorded and used as the position correction amount of the intermediate transfer belt 52 during the transfer, so that the rotational fluctuation of the photosensitive drum 51 during the exposure is canceled. I was able to do it. As a result, it is possible to reduce the image distortion and the color registration position deviation due to the rotation fluctuation of the photosensitive drum 51.

In the present embodiment, the example in which the intermediate transfer belt 52 is used as the transfer medium is shown, but the present invention is also applicable to the case of transferring directly to the transfer medium such as recording paper. Further, the photosensitive drum 5 is used to detect the rotation angle of the photosensitive drum 51.
Although the encoder 60 is connected to the rotating shaft of No. 1, other drum rotation angle detecting means such as setting and reading a position pattern on the drum surface may be used.

[0036]

As described above, according to the present invention, it is possible to reduce the image distortion and the color superposition positional deviation due to the rotation fluctuation of the photoconductor.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between belt length and tension.

FIG. 3 is a flowchart showing a control sequence.

FIG. 4 is an explanatory diagram of how to determine a required movement distance Δx.

FIG. 5 is a diagram showing another embodiment of the present invention.

FIG. 6 is a diagram showing a conventional example.

[Explanation of symbols]

 31: Photosensitive drum (photosensitive member) 32: Intermediate transfer belt (transferred medium) 33: Tension roller 34: Support roller 35: Drive roller 36: Backup roller 37: Gear 38: Belt drive motor 39: Nut 40, 41: Linear motor 42: Shaft 43: Driver 44: Control circuit (control means) 45: Tension variable means 46: Thin film 47: Optical head 48: Amplifier 49: Laser Doppler speed meter (detection means) 51: Photoconductor belt (photoconductor) 52: Intermediate transfer belt (transferred medium) 53: Motor 60: Encoder 61: Reference exposure position generation unit 62: Exposure state recording unit 63: Storage device (storage unit) 64: Reference transfer position generation unit 65: Exposure state reading unit 66: Belt position correction amount calculation section 67: Detection means 68: Correction means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideo Kato 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (2)

[Claims] 1. A recording apparatus for recording an image formed on a photosensitive member (31) on a recording medium after transferring the image onto a transfer medium (32) driven by a plurality of rollers (33 to 36). , A neutral point that does not move due to tension of the transfer medium (32) is set at the contact point between the photoconductor (31) and the transfer medium (32), and the tension of the transfer medium (32) is made variable. Tension varying means (45) and detecting means (4) for detecting the rotational fluctuation of the photoconductor (31).
9) and a control device (44) for controlling the tension varying device (45) according to the detected rotation fluctuation. 2. A recording device for transferring or recording an image formed on a photoconductor (51) onto a transfer medium (52), said detection means (for detecting rotation fluctuation of said photoconductor (51) during exposure. 67), a recording means (63) for accumulating the detected rotation fluctuation, and a correction means (68) for correcting the position of the transfer medium (52) at the time of transfer by obtaining a positional deviation at the time of image exposure from the rotation fluctuation. )
A recording device comprising: