JP3149545B2 - Color recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color recording apparatus for producing a color image by superimposing and transferring an image developed for each of a plurality of component colors by laser electrophotography.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram for explaining an example of the operation of a known color recording apparatus of a laser electrophotographic system using a single photosensitive drum. An image for each component color of the image (in the example shown in the figure, four color toners of Y: yellow, M: magenta, C: cyan, and K: black is used by the developing units 11 to 14) is used for the photosensitive drum 10. Then, the image is transferred to a transfer belt 20 as an intermediate transfer medium for each color, a color image is generated on the surface of the transfer belt 20, and then transferred to the recording paper 5. The intermediate transfer medium is not belt-shaped,
It may be a drum.

That is, the recording paper 5 is fed out of the paper cassette 1 by a recording start signal of a control mechanism (not shown), but is temporarily stopped by being stopped by the registration rollers 3 which are stopped, and the timing of the recording process is set.

Thereafter, at the timing when a color image is generated on the transfer belt 20, the recording paper 5 is advanced to the transfer roller 30 by the registration roller 3 whose rotation has been resumed, and the color image on the surface of the transfer belt 20 is recorded. It is transferred to paper 5.

Next, the recording paper 5 is advanced to a fixing device 40 to fix the color toner image transferred on the surface, and the fixing process is performed by heat and pressure by a fixing roller 41 and a pressure roller 42 of the fixing device 40. Is done.

[0006] The generation of toner images of each component color on the photosensitive drum 10 is performed by a known electrophotographic process. The photosensitive drum 10 is rotated at a constant speed in the direction of an arrow, and the surface on which the image is generated has a First, after being cleaned by the cleaner blade 15, it is uniformly charged by the charger 16.

This surface is exposed with a laser beam 51 emitted from a laser exposure system 50 to form a latent image of an image of a certain component color, and then the latent image is developed by one of developing units 11 to 14. By developing, a toner image of a required component color is formed on the photosensitive drum 10.
Formed on the surface of

As shown in the figure, the endless transfer belt 20 is driven by a pulley 23 driven by a motor so as to rotate at the same speed as the surface of the photosensitive drum 10.
There is a transfer unit which is conveyed in contact with the surface of the transfer unit.

The toner image of each color formed as described above undergoes so-called primary transfer by the discharge of the transfer corotron 21 when passing through the transfer portion, and is transferred from the photosensitive drum 10 to the transfer belt 20.

The above-mentioned development / primary transfer processing is performed, for example, using YM
The color image is formed on the transfer belt 20 by repeating the transfer of the toner images on the transfer belt 20 sequentially in the order of CK.

During this time, the cleaner blade 25 and the transfer roller 30 are separated from the transfer belt 20, and when a color image is generated, the transfer roller 30 is pressed against the roller 22 so that the color image is transferred from the transfer belt 20. Secondary transfer is performed in which the transfer is collectively performed on the recording paper 5.

When the secondary transfer is completed, the transfer roller 30 is separated from the roller 22, and the cleaner blade 25 is pressed against the pulley 23 to clean the surface of the transfer belt 20 for the next image formation. Then, when the cleaning is completed, it is separated from the pulley 23.

As apparent from the above processing, in order to obtain a clear color image, it is necessary that the transfer positions of the images of the respective colors primarily transferred on the surface of the transfer belt 20 are sufficiently coincident.

In order to synchronize the movement of the surface of the transfer belt 20 with the position of the image to be developed on the photosensitive drum 10, a sensor 27 is provided on the surface of the transfer belt 20 as shown in FIG. The passage of the marker 26 is detected, and the detection signal is given to the laser exposure system 50.

The laser exposure system 50 is configured to irradiate a laser beam at regular time intervals to perform line scanning on the surface of the photosensitive drum 10, and to detect that the laser beam passes a predetermined position on the scanning line. The exposure of the photosensitive drum 10 is started (the page of the toner image of a certain color is started) by receiving the writing control such as the modulation of the laser beam according to the image data by the beam detection signal detected and output by the image sensor. I have.

Therefore, when the above-mentioned marker detection signal is received, writing is started from, for example, the scan which is started first thereafter. FIG. 6A is a diagram for explaining the timings of the above-described recording processing, and shows, in order from the top, marker detection signals, beam detection signals by a beam detector, exposure with laser light, and primary transfer timings. The interval between the detection signals corresponds to one rotation time of the transfer belt 20,
Processing of each color is performed in this cycle.

The processing of the i-th color is started by the beam detection signal detected after the i-th marker detection signal and after the time t _i as described above, as shown in FIG. Exposure is performed for a predetermined time, and primary transfer is performed for a predetermined time from when the page top position of the developed toner image reaches the transfer unit with a delay of Td time from the start of beam exposure. Between the processing of each color, a portion without an image is placed as shown as a sheet interval.

By repeating this process for four colors as shown in the figure, a color image is formed on the transfer belt 20, and thereafter, the secondary transfer to the recording paper 5 starts.

[0019]

As is apparent from the above timing, in the four-color processing, when the top position of the page of the toner image reaches the transfer portion with a delay of Td from the start of beam exposure, the transfer belt is simultaneously driven. If the page top position is not exactly at the same position, a shift occurs between the images of each color, and the recording quality deteriorates.

However, since the irradiation position of the laser beam during scanning at the time when the laser exposure system 50 receives the marker detection signal is hard to be constant, it is indicated by t ₁ to t _{4 in} FIG. The time to a signal (and thus the time to the start of exposure) can vary for each color.

On the other hand, in the movement of the transfer belt, the page head position reaches the transfer position approximately a fixed time after the marker detection, independent of the above-mentioned variation. As a result, the above variation results in a shift of the transfer start position for a maximum of one line scanning time.

If there is a slip in the drive of the transfer belt 20, such an error in the drive of the intermediate transfer medium will cause the transfer belt 20 to slip as shown in FIG.
At the time point indicated by Td time after the beam detection signal, the top position of the page on the surface of the transfer belt 20 is shifted from the transfer start position, which also causes the image to be shifted.

An object of the present invention is to provide a color recording apparatus capable of reducing the synchronization deviation between the photosensitive drum and the intermediate transfer medium.

[0024]

FIG. 1 is a block diagram showing the configuration of the present invention. FIG. 1A shows a configuration of a first aspect of a color recording apparatus, in which an image of each color is exposed on a surface of a rotating photosensitive drum by a laser beam, and the image is developed. Endless intermediate transfer medium 20 that moves the resulting image from the photosensitive drum at the same speed as the surface of the photosensitive drum.
In order to form a color image on the surface of the intermediate transfer medium 20 by sequentially repeating the process of transferring the image on the surface of the intermediate transfer medium 20 for a plurality of predetermined colors, Is a color recording apparatus which detects a point in time at which a marker 26 provided at a predetermined position passes a predetermined position, and starts the exposure from a predetermined exposure start point determined by the detection point.

The control section 60 measures the time from the detection time to the exposure start time, and determines the value of the surface of the intermediate transfer medium by a value determined based on a difference between a predetermined reference value 63 and the measured value. The transfer position of the image on the surface is adjusted by changing the movement amount.

FIG. 1 (b) shows a configuration of a second embodiment of a color printing apparatus, which is the same as the first embodiment, and includes a second sensor 76 and a control unit 70. Provide. Second
The sensor 76 detects the passage of the marker at a predetermined position where the marker 26 of the intermediate transfer medium 20 passes after the start of the exposure.

The control unit 70 measures the time from the start of exposure to the time when the second sensor 76 detects the passage of the marker 26, and determines a value determined based on a difference between a predetermined reference value 63 and the measured value. Only, the movement amount of the surface of the intermediate transfer medium 20 is changed.

According to a third aspect of the present invention, in the configuration shown in FIGS. 1A and 1B, the control unit 60 or 70 includes a driving unit 61 and an arithmetic unit 62 or
And a 72, the drive unit 61, the driving of the intermediate transfer medium 20, normally the surface of the intermediate transfer medium 20 moves at a speed V _0, when the arithmetic unit 62 or 72 is designated, the designated during the time t, is moved at a specified speed V ₁ or V _2, a predetermined value of each said speed has a relationship of _{V 1> V 0> V 2} .

The computing unit 62 or 72 measures the time for each of the processes to obtain the measured values, and stores the measured values for the processes of the first color in the processing order as the reference values 63;
For each process of each of the second and subsequent colors, the reference value is calculated from the measured value.
The difference obtained by subtracting the 63 as _{ΔT, t = | ΔTV 0 /} (vV 0) | between defined time t by specifying the drive unit 61 to drive at the speed v, the velocity v of the V ₁ and V ₂ One of them is determined according to the sign of ΔT.

[0030]

According to the first aspect of the present invention, the interval from the marker detection time of the intermediate transfer medium to the laser exposure start time is measured by the color recording apparatus of the first invention, and the difference between the measured value and the reference value is canceled. By changing the moving amount, a change in the relative position between the photosensitive drum and the intermediate transfer medium due to a change in the exposure start time is compensated, so that the image shift between different colors in the primary transfer can be reduced. Here, the reference value includes the measured value t in the processing of the first color according to the third invention.
₁ (see FIG. 6) can be used.

That is, assuming that the measured value in the processing of the i-th color is t _i and ΔT _Ei = t _i −t ₁ , that ΔT _Ei is positive means that the i-th color is based on the beam detection time. In the processing (1), the marker arrives at the detection point too early, ie, the intermediate transfer medium has advanced too far from the processing of the first color.

The amount is V ₀ ΔT _Ei where the normal moving speed of the intermediate transfer medium is V _0, and when the page top position of the photosensitive drum reaches the transfer section, the page top position of the intermediate transfer medium is It passes the transfer portion by V ₀ ΔT _Ei .

Therefore, in this case, it is necessary to suppress the progress of the intermediate transfer medium by the amount by which it passes before the top position of the page reaches the transfer portion. If ΔT _Ei is negative, the movement must be advanced conversely.

In the case where this adjustment is performed by a method of changing the speed by the required time according to the third invention, first, V ₁ > V ₀ > V ₂
The speed V ₁ of the forward-adjustment of the relationship, if appropriate determining the speed V ₂ for delay adjustment, the time t to apply an adjustment rate, if [Delta] T _Ei is _{positive, V 0 ΔT Ei = V 0} t -V ₂ t, if [Delta] t _Ei is negative, V ₀ ΔT _Ei = V ₀ so as to satisfy t-V ₁ t that may be set to t is apparent, therefore if [Delta] t _Ei is positive Is set to v = V ₂ , v = V _{1 in} the case of a negative value, and time t = ΔT _Ei V ₀ / (V ₀ -v).

Further, according to the color recording apparatus of the second invention,
A second marker detection point of the intermediate transfer medium is separately provided, the time from the start of laser exposure to the subsequent marker detection time is measured, and the intermediate transfer medium is moved so as to cancel the difference between the value and the reference value. By changing the amount, the change in the relative position between the photosensitive drum and the intermediate transfer medium is canceled, and the image shift between different colors in the primary transfer is reduced. In this case, similarly to the first aspect, it is possible to compensate for the fluctuation at the exposure start time and to compensate for the drive error of the intermediate transfer medium.

That is, as shown in FIG. 2, a marker detection signal similar to the above (the first marker detection signal in the figure)
, A beam detection signal serving as an exposure start point is generated, and thereafter, a marker detection signal (referred to as a second marker detection signal in the figure) by the second sensor 76 is generated.

Here, the time t _i from the first marker detection signal to the beam detection signal is the measured value used in the first invention, and the relationship with the exposure system can be corrected as described above. it can.

The time from the first marker detection signal to the second marker detection signal (t _{Bi in the} figure) is equal to the marker on the intermediate transfer medium.
Since 26 is the time it takes to move between the two sensors 27 and 76, that variation is the drive error of the intermediate transfer medium itself.

Again, assuming that the measured value t _B1 in the processing of the first color is used as the reference value, ΔT _Bi = t _Bi −t _B1
Then, the positive ΔT _Bi means that the movement of the intermediate transfer medium has been delayed due to slippage or the like. In this case, the intermediate position of the intermediate transfer medium before the page top position reaches the transfer section is determined. It is necessary to advance the rotation of the processing medium. The required advance amount is V ₀ ΔT _Bi considering the same as above. ΔT
_{If Bi} is negative, the movement must be delayed.

Therefore, in order to correct the relationship between the exposure system of the intermediate transfer medium and its own drive error together, ΔT = Δ
Considering T _Bi −ΔT _Ei , control may be performed such that forward is performed when ΔT is positive and delayed when ΔT is negative.

Here, ΔT is as follows: ΔT = ΔT _Bi −ΔT _Ei = (t _Bi −t _B1 ) − (t _i −t ₁ ) = (t _Bi −t _i ) − (t _B1 −t ₁ ) = T _i the -T _1. However T _i, as shown in FIG. 2, the time from the beam detection signal to the second marker detection signal, T ₁ is the first that
The measured value for color.

Therefore, when the third invention is applied to the second invention, if ΔT is positive, v =
V _1, and v = V ₂ to delay when negative,
The time t may be set to t = ΔTV ₀ / (vV ₀ ).

[0043]

FIG. 3 is a block diagram showing an embodiment of a control unit 70 in the case where the third invention is applied to the second invention. In the following description, the main body of the color recording apparatus is
Except for having the sensor 76 of FIG.

The calculating section 72 of the control section 70 is provided with a marker detection signal from the sensor 27 (hereinafter referred to as a first marker detection signal),
And a beam detection signal from the laser exposure system as inputs to the arithmetic and control circuit 80.

The arithmetic control circuit 80 resets the counter 81 and other components of the arithmetic section 72 to the initial state by the recording start signal of the color recording apparatus, starts monitoring the first marker detection signal, and starts the first first marker detection. Upon receiving the detection signal, the counter 81 is started by the first beam detection signal thereafter.

When the counter 81 is started, it starts counting by the control clock of the arithmetic unit 72 and continues counting until a stop signal is received from the arithmetic control circuit 80. In the arithmetic control circuit 80,
When the second marker detection signal is received after the counter 81 is started, a stop signal is sent to the counter 81 to stop counting. As described above, the counter 81 holds the count value corresponding to the time from the generation of the beam detection signal (ie, the start of the beam exposure) to the detection of the marker by the second sensor 76.

The arithmetic control circuit 80 stores the count value of the counter 81 in the reference value register 87 for use as the reference value 63 in FIG. 1, resets the counter 81, and performs the first color printing operation. The control corresponding to the color processing ends, and the generation of the next first marker signal is waited.

When the transfer belt 20 (FIG. 4) makes one revolution, the marker 26 is detected again, and the first marker detection signal is generated, the main body of the color recording apparatus starts processing for the second color. When receiving the first marker detection signal, the arithmetic and control circuit 80 receives the first beam detection signal and returns to the counter 81 in the same manner as described above.
Is started to start counting, and when the second marker detection signal is received, the counting is stopped.

After the second color, the arithmetic circuit 82 is activated to pass the count value, and then the counter 81 is reset. Arithmetic circuit 82, it receives the count value of the counter 81 T _i
And read the value held in the reference value register 87,
As T _1, it calculates the ΔT = T _i -T _1.

Next, the polarity of ΔT is identified, and if positive, the time t is calculated by t = ΔTK ₁ , and if negative, t = ΔTK ₂ , and the driving unit 61 determines t and the positive or negative of ΔT. Notify. Here, constants K ₁ = V ₀ / (V ₁ -V ₀ ) and K ₂ = V ₀ held in the arithmetic circuit 82
/ (V ₂ -V ₀ ).

If ΔT = 0, nothing is performed that time. The pulley 23 for driving the transfer belt is driven by a belt drive motor. The belt drive motor is a pulse motor, and the speed can be adjusted by the frequency of the drive pulse.

According to the present invention, the drive pulse of the belt drive motor is supplied from the drive unit 61. For this purpose, the drive unit 61 has drive pulse sources 83, 84 and 85 of three different frequencies. These three types of frequencies are f ₀ , f ₁ , and f _2, and are frequencies at which the transfer belt 20 is driven at speeds of V ₀ , V ₁ , and V ₂ , respectively.

[0053] In the drive unit 61, the switching control circuit 86 supplies a drive pulse to the belt drive motor from the drive pulse source 83 of frequency f ₀ at all times. Upon receiving notification of the time t and the sign of ΔT from the arithmetic unit 72, the switching control circuit 86 immediately outputs the supply pulse to the belt drive motor, and if ΔT is positive, the frequency f ₁ , ΔT
There switched to the drive pulse of the drive pulse source 84 or 85 of the negative if the frequency f _2, the drive pulse source 83 of the frequency f ₀ after a specified time t
Return to

When the control corresponding to the processing of the second color described above is similarly executed for the third and fourth colors, the arithmetic control circuit
The control 80 ends the control and waits for the next recording start signal. FIG. 5B shows the timing of the recording process of the present invention by the above control, and corresponds to the conventional timing shown in FIG. 5A.

As is apparent from the drawing, the adjustment of the movement amount of the transfer belt is performed during the period in which the paper interval passes through the transfer portion after the start of the laser exposure, and must be completed by the start of the primary transfer. is there. Therefore, the speeds V ₁ and V ₂ can be generated Δ
A value is determined with respect to the maximum value of T so that the adjustment can be completed during the period.

In the above description, the belt is used as the intermediate transfer medium. However, it is apparent that the same configuration can be used for a drum.

[0057]

As is apparent from the above description, according to the present invention, in a laser electrophotographic color recording apparatus, the synchronization deviation between the photosensitive drum and the intermediate transfer medium is reduced to obtain good recording quality. There is a remarkable industrial effect.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of the present invention.

FIG. 2 is a diagram for explaining the timing of the present invention.

FIG. 3 is a block diagram showing an embodiment of the present invention.

FIG. 4 is a diagram illustrating a configuration of a color recording apparatus.

FIG. 5 is a view for explaining a marker of an intermediate transfer medium.

FIG. 6 is a diagram showing the timing of a recording process;

[Explanation of symbols]

 1 Paper Cassette 5 Recording Paper 10 Photosensitive Drum 11-14 Developing Unit 15, 25 Cleaner Blade 16 Charger 20 Transfer Belt 21 Transfer Corotron 22 Roller 23 Pulley 26 Marker 27, 76 Sensor 30 Transfer Roller 40 Fixing Device 50 Laser Exposure System 51 Laser Light 60, 70 Control unit 61 Drive unit 62, 72 Operation unit 63 Reference value 80 Operation control circuit 81 Counter 82 Operation circuit 83 to 85 Drive pulse source 86 Switching control circuit 87 Reference value register

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI H04N 1/23 103 B41J 3/00 B (56) References JP-A-4-127171 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B41J 2/44 B41J 2/525 G03G 15/01 112 G03G 15/01 114 G03G 15/16 H04N 1/23 103

Claims (3)

(57) [Claims] 1. An image for each color is exposed on a surface of a rotating photosensitive drum by a laser beam, the image is developed, and the developed image of each color is transferred from the photosensitive drum to the surface of the photosensitive drum. The process of transferring the image on the surface of the endless intermediate transfer medium (20) moving at high speed is sequentially repeated for a plurality of predetermined colors, so that a color image is formed on the surface of the intermediate transfer medium. A color recording apparatus that detects a point in time at which a marker (26) provided on the surface of the intermediate transfer medium passes a predetermined position for each of the processes, and starts the exposure from a predetermined exposure start time determined by the detection time. A control unit (60), wherein the control unit (60) measures a time from the detection time to the exposure start time, and calculates a difference between a predetermined reference value (63) and the measured value. The amount of movement of the surface of the intermediate transfer medium (20) is changed by a value determined based on the It allows color recording apparatus characterized by being configured to adjust the transfer position of the image on said surface. 2. An image for each color is exposed on a surface of a rotating photosensitive drum by a laser beam, the image is developed, and the developed image of each color is transferred from the photosensitive drum to the surface of the photosensitive drum. The process of transferring on the surface of the endless intermediate transfer medium (20) moving at high speed is sequentially repeated for a plurality of predetermined colors to form a color image on the surface of the intermediate transfer medium. A color recording apparatus that detects a point in time at which a marker (26) provided on the surface of the intermediate transfer medium passes a predetermined position for each of the processes, and starts the exposure from a predetermined exposure start time determined by the detection time; A second sensor (76) and a control unit (70), wherein the second sensor (76) is provided with a predetermined sensor through which the marker (26) of the intermediate transfer medium passes after the exposure start time. At the position, the passage of the marker is detected, and the control unit (70) From the time of the second sensor (7
The time until the passage of the marker (26) is detected by 6) is measured, and the amount of movement of the surface of the intermediate transfer medium is changed by a value determined based on a difference between a predetermined reference value and the measured value. A color recording device configured to adjust a transfer position of the image on the surface. 3. The control section (60, 70) includes a drive section (61),
And a calculation unit (62, 72), the drive unit (61), said drives the intermediate transfer medium (20) always moves at a speed V ₀ to the surface of the intermediate transfer medium, the operation Department
When the (62, 72) specifies, for a specified time t, is moved at a specified speed V ₁ or V _2, a predetermined value having a relationship to each the speed _{V 1> V 0> V 2} , The calculation units (62, 72) measure the time for each of the processes to obtain the measured values, and store the measured values for the processes of the first color in the processing order as the reference values (63). Then, for each process of each of the second and subsequent colors, drive is performed at a speed v for a time t determined by t = | ΔTV ₀ / (vV ₀ ) |, where ΔT is a difference obtained by subtracting the reference value from the measured value. specified in the drive unit so that, among the velocity v of the V ₁ and V _2, and one for determining in accordance with positive and negative [Delta] T, a color recording apparatus according to claim 1 or claim 2, wherein.