JP2002202651A - Device and method for adjusting color image forming position and recording medium recording its program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color image forming position adjusting device by which correction is performed so that a deviated position is made close to a reference position as much as possible even in the case that there is a variable range for a deviation value. SOLUTION: The regist variable amount (d) (for instance two dots) of a printer is firstly obtained from a storage device. Next, a regist deviation value R is detected by a resist patch printed on a feeding belt. It is checked whether or not the regist deviation value R detected is within the range of the resist variable amount, that is |R|<=d/2 or not when the center of the regist variable amount (d) is located at a printing reference position S, and when it is out of the range (|R|>d/2), it is also checked whether it is on the left side from the printing reference position S (R<0) or on the right side (R>0), and when it is R<0, correction is performed by setting a correction value H=+(|R|-d/2), and when it is R>0, the correction is performed by setting H=-(|R|-d/2). Also, the correction is not performed when it is within the range (|R|<=d/2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a color image forming position adjusting apparatus for precisely adjusting a color image forming position without increasing the apparatus price.

[0002]

2. Description of the Related Art In recent years, color printers (color image forming apparatuses) have been widely used in conjunction with an increase in the number of personal computers sold. In particular, a so-called tandem type color image forming apparatus in which image forming units are arranged in a multi-stage manner has attracted particular attention today because of its excellent printing speed.

FIG. 16 is a diagram schematically showing a configuration of a main part of such a conventional tandem color printer.
As shown in FIG. 1, a tandem-type color printer 1 includes a paper feed cassette 2 in which paper P is stacked and stored, a paper feed roller (not shown) that takes out the paper P one by one from the paper feed cassette 2,
A paper transport guide (not shown) for guiding the paper P fed by the paper feed roller as shown by an arrow A in the drawing, a pair of standby rollers (not shown) arranged at the end of the paper transport guide,
The conveyor belt 3 transports the paper fed by the pair of standby rollers in synchronization with the printing timing in the counterclockwise direction in the drawing, and drive rollers 4 a and 4 b for driving the conveyor belt 3.

Further, four image forming units 5 (5-1, 5-2, 5-3, 5-4) are provided in the vicinity of the paper transport surface of the transport belt 3 from the upstream side to the downstream side in the paper transport direction. Are arranged in a multi-stage manner, and a fixing device 6 is disposed on the downstream side of the transport belt 3 in the sheet transport direction indicated by the arrow B in the drawing.

Each of the four image forming units 5 has the same configuration, and has a cleaner 8, a charger 9, a recording head 10, a developing unit 11, The transfer devices 11 are sequentially arranged with the transport belt 3 interposed therebetween. The developing unit 11 has three subtractive primary colors, yellow (Y), magenta (M), and cyan (C).
, And black (K) toner mainly dedicated to a character portion, respectively, and a developing roller 13 is disposed in an opening on the lower side surface.

The photosensitive drum 7 rotates clockwise as indicated by an arrow C, and its peripheral surface is cleaned by a cleaner 8, and a uniform negative high charge is applied to the cleaned peripheral surface by a charger 9. The electrostatic latent image is given and initialized, and the initialized peripheral surface is exposed by the recording head 10, and is composed of a minus high potential portion by the initialization and a minus low potential portion whose potential is attenuated by the exposure. Is formed.

The toner contained in the developing device 11 is transferred to the negative low potential portion by the developing roller 13, and the electrostatic latent image is visualized (developed). The developed toner image is transferred onto the sheet P conveyed by the conveying belt 3 by the transfer unit 11 in a superimposed manner. The paper P on which the toner images of four colors are sequentially superimposed and transferred as described above is carried into a fixing device, where the toner image is fixed on the paper surface by heat and pressure, and is discharged out of the apparatus by a discharge roller (not shown). Is done. As a result, a color image is formed on the paper P by the combined color of the four toners.

As described above, the tandem type color printer is
Since the four color toner images are sequentially transferred and superimposed, accurate alignment is required for each color in order to form a correct image on the paper P moving in the sub-scanning direction of printing. For this reason, in a tandem color printer,
Various methods have been proposed for performing image position matching. One is a method in which a test chart is actually printed, the correction amount is visually determined, and adjustment is performed based on the judgment. As another method, there is a method in which a sensor is arranged, a test-printed image is detected by the sensor, a correction amount is automatically calculated, and the position is adjusted accordingly.

[0009] In either case of visual inspection or automatically performed by a sensor, a test print mark indicating a current print position called a resist patch is printed (printed) on a test chart and enlarged. It is visually recognized with a mirror or detected with a sensor. The amount of displacement of the position detected from the resist patch is determined as the amount of displacement of the position with a polarity value opposite to that value.

[0010]

In the above-mentioned conventional correction method, for example, the detected value of the registration shift is "-1".
If a dot is indicated, a "+1" dot is fed back to the registration control unit as a correction value.

FIG. 17 is a diagram showing a specific example of correcting such a shift amount of a resist (print position). As shown in the figure, if a registration patch 16a or 16b printed at a position 15 shifted by "-1" dot indicated by a broken line with respect to the reference position 14 is detected, the position shift amount "- The correction value is set to the reverse polarity value “1” of “1”.
Correction is made so that the image is printed at the upper print position 18.

However, at this time, if the printing position of the printer main body is not constant and its variation range is, for example, ± 1 dot, the total variation range is 2 dots. Even if the shift amount of the dot is detected, the print dot that is actually ejected at the position of -1 dot is -3 to -1 dot or -1 dot from the reference position 14.
It has a fluctuation range that is printed at positions of 〜 + 1 dot.

When feedback of a correction amount of +1 is performed on a print dot having such a position variation range, -2 to 0 dots or 0 with respect to the reference position 14 is obtained.
To +2 dots, that is, a position variation range of -2 to +2 dots.
The control is two dots. In this case, no matter how accurately the print position of the resist patch is detected, the correction value still includes the possibility of a large positional change.
There was a problem that a practical correction result could not be obtained as expected.

[0014] The object of the present invention is to solve the above-mentioned conventional problems.
By providing a color image forming position adjusting device that controls a correction position so that an actual shift position is as close as possible to a reference position having a shift amount of “0” when there is a change in the shift amount of a print position. is there.

[0015]

First, a color image forming position adjusting apparatus according to the first aspect of the present invention comprises a storage means for storing a resist fluctuation range d, and a current resist deviation position R from a reference position. | R |> d / 2, where H is the correction value of the resist, based on the detecting means for detecting, and the current displacement position R of the resist detected by the detecting means and the fluctuation range d stored in the storage means. When R>
If 0, H = − (| R | −d / 2), and if R <0,
H = + (| R | −d / 2), and when | R | <d / 2, a correction means for correcting the resist by setting H = 0 regardless of the value of R. It is composed.

Next, the color image forming position adjusting method according to the second aspect of the present invention detects the current shift position of the resist from the reference position, and detects the detected shift position of the resist.
If the center of the resist fluctuation amount is out of the resist fluctuation range when it is assumed to be at the reference position, the next resist position is corrected to the position closest to the shift position of the resist fluctuation range, and the detected resist is detected. Position is
If the center of the resist fluctuation amount is within the resist fluctuation range assuming that it is at the reference position, the procedure includes not performing the next correction of the resist position.

Further, the recording medium of the invention according to claim 3 is:
A recording medium on which a color image forming position adjustment program is recorded so as to be mountable on a color image forming apparatus, wherein a step of detecting a current resist deviation position from a reference position; A step of determining whether or not the center of the amount is within a resist fluctuation range when it is assumed that the center is at the reference position, and when the deviation position is out of the resist fluctuation range from the reference position in this determination, Correct so that the next registration position comes to the position closest to the shift position of the resist fluctuation range,
On the other hand, when the shift position is within the resist fluctuation range from the reference position, a program for not performing the next registration position correction is recorded so as to be mountable on the color image forming apparatus. .

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view illustrating an appearance of a color image forming apparatus (hereinafter, simply referred to as a printer) according to the first embodiment. The printer of this example is an example of a tandem type color printer. Also,
The printer of this example is an example of a color printer for duplex printing.

In FIG. 1, a printer 20 is connected to a host device such as a personal computer (not shown) by a cable. This printer 20 is located at the upper
1 and an apparatus main body lower part 22, an operation panel 23 is disposed on the apparatus main body upper part 21,
A paper discharge section 24 for printing paper is also formed on the upper surface.
The operation panel 23 includes a key operation unit 23a in which a plurality of keys are arranged, and a liquid crystal display 23b that performs display based on display information output from a CPU (not shown). The paper on which a color image is formed by an image forming unit, which will be described later, is discharged to the paper discharge unit 24 by rotation of a paper discharge roller 25, and is sequentially stacked on the paper discharge unit 24.

A transport unit for double-sided printing and a paper feed cassette to be described later are set in the lower portion 22 of the apparatus main body. For example, by opening a lid (not shown) provided on a side surface of the printer 20, a transport unit for double-sided printing described The unit can be attached and detached. Further, a front cover 26 which can be opened and closed on the front surface of the device main body lower portion 22 and the device main body lower portion 2 are provided.
2, a detachable paper feed cassette 27 is provided. For example, the front cover 26 is opened for jam clearance or maintenance.

On the right side of the lower part 22 of the apparatus, M
A mounting section 28 for a PF (multi-paper feeder) and a cover 29 are provided. However, the MPF tray is not mounted on the mounting section 28 in FIG. Also,
The cover 29 is a cover for confirming a sheet conveyance path to be described later. The cover 29 is opened to perform maintenance such as paper jam.

At the bottom of the printer 20 of this embodiment, the paper cassette 27 is housed as described above,
When replenishing the sheets 7, for example, by pulling the handle 27 a toward the user, the sheet cassette 27 can be pulled out in the direction of the arrow. FIG. 2 is a sectional view illustrating the internal configuration of the printer 20 having the above-described external configuration. As shown in FIG. 1, the printer 20 includes an image forming unit 30, a double-sided printing transport unit 31, and a paper feeding unit 32.
The image forming unit 30 includes four image forming units 33
(33-1, 33-2, 33-3, 33-4) are arranged in multiple stages.

Of the four image forming units 33, three image forming units 33-1 on the upstream side in the sheet transport direction,
33-2 and 33-3 form monocolor images using magenta (M), cyan (C) and yellow (Y) color toners, which are three subtractive primary colors, respectively. The image forming unit 33-4 mainly A monochrome image using black (K) toner such as characters is formed.

Each of the image forming units 33 includes a drum set C1 and a toner set C2, and has the same configuration except for the developer (color) stored in the developing container. Therefore, the configuration of the image forming unit 33-3 for yellow (Y) will be described below as an example.

The drum set C1 includes a photosensitive drum 34
The photosensitive drum 34 has a peripheral surface made of, for example, an organic photoconductive material, and surrounds the peripheral surface of the photosensitive drum 34 to form a drum set C1 together with the photosensitive drum 34. The cleaner 35 and the electric device 36 are arranged, the print head 37 supported by the frame of the main body is arranged, and the toner set C2 is further arranged.
Are arranged, and a transport belt 40 and a transfer unit 41 are disposed below the transport belt 40 with the transport belt 40 interposed therebetween. Development container 38 described above
Has a toner therein, and a developing roller 39 is supported at an opening on the lower side surface.

The photosensitive drum 34 is rotated clockwise in the drawing, the peripheral surface is cleaned by a cleaner 35, and the peripheral surface of the photosensitive drum 34 is uniformly charged by applying a charge from a charger 36. I do. Next, an electrostatic latent image is formed on the peripheral surface of the photosensitive drum 34 by optical writing based on print information from the print head 37. And this electrostatic latent image is
By the developing process by the developing roller 39, the developing container 38
The toner image is formed by the yellow (Y) toner stored in the image forming apparatus.

The toner image formed on the peripheral surface of the photosensitive drum 34 in this way reaches a transfer section where the photosensitive drum 34 and the transfer device 41 face each other as the photosensitive drum 34 rotates. . The toner image that has reached the transfer section is transferred onto the sheet that moves from immediately upstream to downstream in the sheet conveyance direction immediately below the photosensitive drum 34.

The above-mentioned paper is carried out of the paper feed cassette 27 by one rotation of the paper feed roller 42, and is fed to a standby roller pair 46 via a guide roller pair 43, a guide path 44, and a feed roller pair 45. You. Alternatively, the opened mounting part 2
From the MPF tray 28a attached to the sheet feeding roller 28
b. The standby roller pair 46 is provided in the image forming unit 3 where the printing start position of the sheet is the most upstream in the sheet conveying direction.
The toner is fed onto the conveyor belt 40 at a timing corresponding to the tip of the toner image on the photosensitive drum 34 in 3-1.

The transport belt 40 is stretched between a driving roller 47 and a driven roller 48, driven by the driving roller 47, and circulates in a counterclockwise direction in the drawing. The paper is electrostatically attracted to the upper surface of the circulating transport belt 40 and transported, and the transfer unit of the image forming unit 33-1 transfers the magenta (M) toner image to the image forming unit 33-2. , A cyan (C) toner image is transferred, a yellow (Y) toner image is transferred at a transfer portion of the image forming unit 33-3, and a black (C) is transferred at a transfer portion of the image forming unit 33-4. K) is transferred.

The sheet on which the toner images of the four colors are transferred in an overlapping manner is carried into the fixing unit 50. The fixing unit 50 includes a heat roller 51, a pressing roller 52, a cleaner 53, and the like. The fixing unit 50 melts the toner image and presses the sheet on the paper surface while nipping and transporting the sheet between the above-described heating roller 51 and the pressing roller 52. Establish. The cleaner 53 removes the toner remaining on the heat roller 51.

As described above, the sheet on which the toner image is fixed by the fixing unit 50 is discharged by the pair of discharge rollers 55 when the switching plate 54 is rotated upward as shown by the solid line in FIG. When the switching plate 54 is rotated downward as shown by the broken line in the figure, the paper is guided upward by the conveying roller pair 57 and is discharged by the paper discharge roller 25 when the switching plate 54 is rotated downward as indicated by the broken line in FIG. Paper output unit 2 with forming surface down
It is discharged to 4.

On the other hand, the transport unit 31 for double-sided printing is configured to be detachable from the main body of the apparatus.
0 is a unit that is attached when performing double-sided printing.
A plurality of transport rollers 58a to 58e are disposed inside. In the case of double-sided printing, the sheet is once fed upward by the switching plate 54, and, for example, the rear end of the sheet is
When the number has reached 7, the conveyance of the sheet is stopped, and the sheet is further conveyed in the reverse direction. By this control, the sheet is conveyed downward on the left side of the switching plate 54 set at the position indicated by the dotted line, is carried into the sheet conveyance path of the conveyance unit 31 for double-sided printing, and is fed by the conveyance rollers 58a to 58e, Guideway 4
4 and the standby roller pair 46 via the feed roller pair 45, and is sent to the transfer unit at the same timing as the toner image as described above, and the toner image is transferred to the back surface of the sheet.

In this embodiment, a near-infrared specular reflection sensor 59 is provided near the driving roller 47. The near-infrared specular reflection sensor 59 measures the toner density and printing position of a toner image (register patch described later) formed directly on the peripheral surface of the transport belt 40 instead of the sheet.

FIG. 3 is a view showing a state in which the upper part 21 of the apparatus main body is opened. As shown in FIG.
Is opened while being kept substantially horizontal with respect to the lower portion 22 of the apparatus main body. Therefore, at the time of opening, the drum set C1 and the toner set C2 can be inserted and removed in a substantially horizontal direction.
That is, as shown in the figure, it is possible to easily pull out the drum set C1 and insert a new drum set C1.

FIG. 4 is a diagram showing a state in which the toner set C2 is replaced. As shown in the drawing, the toner set C2 is pulled out to the near side, and a new toner set C
2 can be easily inserted. As described above, in the printer 20 of the present embodiment, it is easy to individually replace the drum set C1 and the toner set C2 of the image forming unit 33.

FIG. 5 is a diagram for explaining the near-infrared regular reflection sensor (hereinafter referred to as CTD sensor) 59 described above. The CTD sensor 59 shown in the figure has one light emitting unit 61 and three light receiving units 62 (62-1, 62-2, 62-
3) and two deflection beam splitters 63 (63-1, 6)
3-2).

The light emitting section 61 is provided with an infrared light emitting diode (hereinafter, referred to as an LED).
2 is provided with a lamp type or chip type photodiode (hereinafter referred to as PD). Also, a deflection beam splitter (hereinafter referred to as PBS) 63
Is formed of thin-film vapor-deposited glass, and L
Light emitted from an ED (hereinafter, referred to as an LED 61) 64 and reflected light 66 from a detection surface 65 are separated.

The output current of each PD of the light receiving section 62 is converted into a voltage by an IV conversion amplifier (not shown). The output converted to the voltage of the CTD sensor 59 is output to the light receiving unit 6
In addition to an output obtained by subtracting the output of the PD (hereinafter, referred to as PD62-3) of the light receiving unit 62-3 from the output of the PD of 2-2 (hereinafter, referred to as PD62-2) (hereinafter, referred to as a sensor output), An output (hereinafter, referred to as a monitor output) for monitoring the light emission output of the PD 62-1 (hereinafter, referred to as PD62-1) is an external output. This CTD sensor 59
By applying feedback to the light emitting element drive current using the above monitor output, the output stability at power-on is improved, and the temperature characteristics are corrected.

Thus, the CTD sensor 59 can be used immediately after the power is turned on (stabilization time is within 1 second), and is not affected by a change in ambient temperature (the fluctuation rate is 0 to 60).
(± 5% at ° C.), which is advantageous in that the LED 61 is well compensated for a long-term decrease in output performance.

The principle of operation of the CTD sensor 59 is based on the difference in reflection characteristics between the detection surface 65 and the toner surface that the specular surface 65 is specular reflection and the toner surface (not shown) is irregular reflection. This is to detect how much the reflected light 66 from 65 is blocked by the toner.

At this time, the light projection 64 radiated from the LED 61 is in a random polarization state.
As a result, a light component oscillating in a direction perpendicular to the incident surface (hereinafter, referred to as S-wave light) and a light component oscillating in a direction parallel to the incident surface (hereinafter, P-wave light) are separated.

The S-wave light 67 is reflected by the PBS 63-1 and reflected by P
The P-wave light 68 is incident on D62-1, passes through the PBS 63-1 and is projected on the detection surface 65. When there is no toner on the detection surface 65, the P-wave light 68 is specularly reflected on the detection surface 65, so that the polarization state does not change, passes through the PBS 63-2 as it is, and enters the PD 62-2.

On the other hand, when the toner adheres to the detection surface 65, the light projection 68 applied to the toner has a random polarization state due to irregular reflection.
Wave light and S wave light are separated at a separation ratio of 1: 1. Then, the P-wave light 69 passes through the PBS 63-2 and the PD 62-
2, the S-wave light 71 is reflected by the PBS 63-2 and
D62-3.

Accordingly, half of the reflected light from the detection surface 65 and half of the reflected light from the toner enter the PD 62-3,
Only half of the reflected light from the toner enters 2-2. Here, the output of PD62-2 is
By subtracting the output of No. 3, the reflected light from the toner is canceled, and only the increase or decrease of the reflected light from the detection surface 65 is taken out as a sensor output, thereby detecting the toner amount, that is, the toner density.

That is, if the amount of toner on the detection surface increases, the reflected light from the detection surface decreases, and the sensor output decreases.
If the toner amount decreases, the reflected light from the detection surface increases, and the sensor output increases. Since the reflected light from the toner is canceled as described above, the sensor output is not affected by the reflectance of the toner. Therefore, each of the yellow, magenta, cyan, and black colors has the same sensor output curve for the same amount of toner.

The CTD sensor 59 is different from a conventionally used regular reflection detection type or irregular reflection detection type toner density sensor. Therefore, there is an advantage that detection can be performed up to a high concentration region. In addition, there is an advantage that even if the detection angle or the detection range changes, the sensor output does not change much, and high mounting accuracy is not required unlike the diffuse reflection type. Although a slight correction procedure of multiplying the correction coefficient for each color toner is necessary, all the toners including black and color can be processed in the same manner, and the conventional regular reflection detection type or irregular reflection detection type can be used. Compared with the toner density sensor of the above, the correction coefficient cannot be used because the direction and the degree of the output fluctuation are greatly different.
The CTD sensor 59 of this example can obtain a correction value only by performing the same processing and multiplying by the correction coefficient for each color toner, so that the detection method is not only extremely easy to handle but also highly reliable. It can be said that there is.

FIG. 6 is a block diagram showing a circuit configuration of a control device of the printer 20. As shown in the figure, the printer 20 includes an MPU 72 serving as a central control device, a driving unit 73 connected to the MPU 72, a head driver unit 74, a CTD sensor 59, and an EEPROM 75.
The print head 37 is connected to the head driver 74. The MPU 72, the drive unit 73, the head driver unit 74, and the EEPROM 75 are mounted on a circuit board disposed in an electrical unit (not shown) provided inside the main unit.

Under the control of the MPU 72, the drive unit 73 includes a motor for driving a gear train of each drive system (not shown in FIG. 1) and the transport belt 4 (not shown).
0, a clutch for switching the rotation of the drive system between transmission and non-transmission, and the like. Further, the print head 37 is constituted by an LED array having a fine pitch. The head driver unit 74 selectively drives the LED elements of the print head 37 to emit light according to image data under the control of the MPU 72. The CTD sensor 59 detects the toner density and the printing position as described above. EEPR
The OM 75 is a predetermined resist fluctuation amount d which will be described later.
And various reference values, detection data detected by the CTD sensor 75, and the like.

The circuit configuration of the control device and the CTD sensor 59 connected thereto constitute a color image forming position adjusting device of the present invention. Note that the registration correction is performed only by the detected value of the registration position shift amount obtained at the timing of the correction process. As described above, if the value is large, the deviation may exceed the allowable deviation amount.

Therefore, in order to avoid such inconvenience, a method of detecting a resist a plurality of times and calculating a correction value based on an average value thereof is generally considered.
However, this causes a problem that it takes too long to find an appropriate correction value. In addition, since the number of detections is determined and the average is calculated, the accuracy cannot exceed a certain value.

Further, the amount of change of the resist is naturally determined by the specifications of the printer main body.
The control of the detection and correction of the resist cannot control the amount of fluctuation of the resist itself. Even at that point, the correction value cannot exceed a certain value. If the accuracy cannot reach a certain value or more, the time required for the correction control process should be as short as possible. According to the present invention, the resist correction is performed as quickly and accurately as possible based on this viewpoint.

FIGS. 7A, 7B, and 7C illustrate a method of detecting a printing position and performing a correction process based thereon based on the printer 20 having the above-described configuration, for performing the above-described automatic adjustment of registration deviation. FIG. Here, “regist” is redefined as “the position of a target print dot detected by a resist patch that has been test-printed for adjustment of a print position).

First, as shown in FIG. 7A, the amount of registration fluctuation (variation width, variation range) of the printer is d. In the present invention, in the current printing mode, the current printing position is approximated to the reference position as much as possible without checking at which position in the fluctuation amount d the printing is performed. The correction is made as follows.

FIG. 6 (b) shows the variation d of the resist as "2" dots (actually, the unit is arbitrary) for easy understanding of the description. 3 shows an ideal state when the center of the image coincides with the printing reference position S. FIG. 8 is a flowchart for explaining the operation of detecting the print position of the registration patch and performing a correction process based on the detection. The processing operation shown in FIG. 8 will be described with reference to FIGS. 7 (a), (b) and (c) described above. Note that the timing of registration detection for correction in this example is determined when the power is turned on, for maintenance work, or the like.
And when the front cover 26 is opened and closed, and further when an instruction from the operator is given.

In the flowchart shown in FIG. 8, first, the registration fluctuation amount d of the printer 20 is stored in the EEPROM 75.
(Step S1). In this process, FIG.
Is read out. Next, a registration shift value R is detected (step S2). In this process, the current offset position of the resist is detected by reading the resist patch by the near-infrared regular reflection sensor 59.

Subsequently, the detected shift value of the resist falls within the range of the resist shift amount when the center of the resist shift amount d is at the printing reference position S where the resist shift position is ± 0. It is determined whether or not there is (step S
3). This process is based on the assumption that the detected current displacement position of the resist is R, and the position indicating the value R is that the center of the resist fluctuation amount d is at the printing reference position S as shown in FIG. , That is, within ± 1 dot from the printing reference position S in the example of the drawing, that is, whether or not | R | ≦ d / 2.

In the above determination, when the detected shift position R of the resist is not within the range of the resist fluctuation, that is, when | R |> d / 2 (No in S3), if R <0, The correction is performed with the correction value H = + (| R | −d / 2). If R> 0, the correction is performed with the correction value H = − (| R | −d / 2) (step S4).

Thus, in the example shown in FIG. 7C, when the shift position R1 is a position of "-3" dots from the reference position S (when R <0) as in Case 1, ,
By the equation for obtaining the correction value, H = + (| R | −d / 2),
H1 = + 2 is calculated, and the correction value H1 is used to calculate “−1” from the position of the registration R1 ′, that is, the printing reference position S.
It is set at the position of the dot. When the detected resist R1 is at the left end of the resist fluctuation range as in the case 1 above, the correction results in that the center of the resist fluctuation range comes to the reference position S, and the ideal correction result is obtained. It becomes.

In the case 2 shown in FIG.
Since the detected shift position R2 is the position of "-3" dots from the reference position S in the same manner as described above, the correction is performed in the same manner as described above, and the next registration R2 'becomes the print reference position S in the same manner as described above.
Is set to the position of "-1" dot from. However, when the detected resist R2 is at the right end of the resist variation range as in Case 2, the center of the resist variation range set by the correction is the position of the "-2" dot. It can be said that the probability that the next detected resist will be at the position of R2 'is low.

However, the steps S1 to S3 are performed again at the timing of the next correction processing, and the center position of the detected resist deviation position R3 is corrected to the reference position S by the above correction.
When it is detected at the position slightly distant from the right end in the resist fluctuation range d2 that is slightly close, the above-described shift position R3 becomes “−1” by the same correction in step S4.
It is corrected to the dot position R3 '. As a result, the center of the corrected resist fluctuation range d3 comes closer to the reference position S.

Then, steps S1 to S3 are performed again at the timing of the next correction processing, and the detected shift position R4 of the resist is within the resist fluctuation range d3 whose center position is closer to the reference position S by the above correction. However, if the center of the resist fluctuation amount d3 is within the resist fluctuation range when it is assumed that the resist fluctuation amount d3 is at the reference position S (S3 is Yes), the processing is performed without performing the resist correction (step S5). finish. As a result, the possibility that the next registration R4 'will be printed within the registration fluctuation range centered on the reference position S increases.

Thereafter, the above processing is repeated at predetermined processing timings, and when the detected resist R5 deviates again from the resist fluctuation range centered on the reference position S,
By performing the above-described correction, the center of the corrected resist variation range d5 comes closer to the reference position S.

As described above, according to the present invention, when there is a variation in the amount of deviation of the printing position, it is necessary to be conscious of where the actual resist was printed in the deviation variation width (register variation range). Instead, the correction position can be controlled at each correction processing timing such that the center of the deviation variation width is as close as possible to the reference position of the deviation amount “0”.
Further, since the correction is performed by one registration detection at each correction processing timing, it is possible to realize a highly accurate correction without requiring a long time for the registration detection.

The first registration correction may be performed by correcting the deviation amount from the reference position S as a correction value as it is like a normal registration correction, and performing the next registration correction by the above-described method. By doing so,
When the deviation is large at first, the deviation amount of the resist can be reduced.

As a printing method of a printer, there is a method of forming a high-definition and high-gradation image by printing one pixel divided into a plurality of sections.
The minimum unit of the detected value of the resist is one pixel (FIGS. 7B and 7C).
The correction value is smaller than the correction value in units of 1 dot) shown in FIG. In other words, the unit to be corrected is larger than the minimum unit of the amount of deviation of the detected resist.

For example, there is a correction method in which a density sensor detects a reference position and a plurality of resist patches printed with the positions shifted sequentially from the reference position, and detects the resist based on the density. When the appropriate position is between the patch density and the next patch density,
It is necessary to determine whether the position to be corrected should be the print position of a certain patch or the print position of the next patch. In such a case, it can be said that it is not appropriate to perform the registration correction using the end position of the deviation fluctuation width when the center of the deviation fluctuation width is used as the reference position as a threshold value in the same manner as described above.

FIG. 9 is a diagram for explaining a correction method in the case where the unit to be corrected is larger than the minimum unit of the amount of deviation of the detected resist. In the figure, the variation range of the resist is Δ, the minimum correction unit of the resist is T,
The detected resist value is R (see FIG. 7C), and the value to be corrected is A or B. The interval between A and B is T, and | A |
> | B |. In FIG. 9, since the detected resist is on the minus side of the reference position, the reference position of ± 0 is B and the position of -1 is A. However, if the detected resist is on the plus side of the reference position, , ± 0 as B, and +1 as A.

Now, it is assumed that the registration detection value in the fluctuation range に お い て between the correction value A and the correction value B is R. At this time, in this example, | R |> | A |-(T / 2−ξ
/ 2), the correction value is A, and | R | ≦ | A | − (T /
At the time of 2-ξ / 2), the correction value is corrected as B.

As described above, even in the case of an apparatus having a correction unit larger than the registration detection unit, the correction value is obtained by adding the fluctuation range of the registration detection value to the registration detection value. High correction is possible. By the way, in the tandem-type printer described above, in order to detect the above-described resist, a chart of a resist patch is printed on the transport belt 40, and the chart is read by the near-infrared regular reflection sensor 59, and the read. Registration correction and density adjustment are performed based on the values.

At this time, conventionally, the chart read by the near-infrared specular reflection sensor 59 is sufficiently larger than the margin of the reading range in consideration of the variation in the mounting position of the sensor, the variation in the mounting position of the conveyor belt 40, and the like. The size chart is printed. However, in that case, a large amount of toner is used in a portion unnecessary for reading, which is uneconomical. Therefore, in this example, an accurate position where the chart should be correctly printed in the measurement range of the sensor is detected in advance. Then, the registration chart is printed out at the detected position. This will be described below.

FIGS. 10 and 11 (a) to 11 (e) are diagrams schematically showing a resist detection method in the chat position adjustment mode for detecting an accurate measurement range of the near-infrared regular reflection sensor 59. is there. The registration detection process in the chart position adjustment mode is performed when the production belt is changed in a factory or when the transport belt 40 or the near-infrared specular reflection sensor 59 is replaced in maintenance work.

FIG. 10 shows the near-infrared specular reflection sensor 59, the conveyance belt 40, and the approximate known measurement range of the near-infrared specular reflection sensor 59 on the paper conveyance surface 40 a of the conveyance belt 40. Printed positioning patch 7
6a, 76b and 76c are shown. In the figure, the transport belt 40 circulates upward from below indicated by an arrow E. The positioning patch 76a is a reference waveform patch, and the positioning patches 76b and 76c are position detection waveform patches.

FIG. 11A shows the positioning patch 76.
FIGS. 7A and 7B show a case where the center 77 of the printing position of the positions a, 76b and 76c is shifted to the right from the measurement range 78 of the near-infrared regular reflection sensor 59, and FIG.
The case where the center 77 of the printing position of a, 76b, and 76c is shifted to the left from the measurement range 78 of the near-infrared regular reflection sensor 59 is shown. Conveyor belt 4 shown in FIG.
As 0 circulates upward as indicated by arrow E, FIG.
In 1 (a) and (b), the measurement range 78 of the near-infrared regular reflection sensor 59 relatively moves downward as indicated by the arrow F.

In each of the pulse waveforms shown in FIGS. 7C to 7E, the waveforms 81 ', 81, and 81 "are the detected waveforms of the patch 76a, and the waveforms 82', 82, and 82" are the patch waveforms. The detected waveform of 76b and the waveforms 83 ', 83 and 83 "are the detected waveforms of the patch 76c.

When the position of the near-infrared specular reflection sensor 59 and the printing position are originally coincident, the waveform shown in FIG. 11D is obtained, and this waveform is stored in the EEPROM 75. The waveform of FIG. 11D stored in the EEPROM 75 and the waveform of FIG. 11C or FIG. 11E detected when printed as shown in FIG. By comparing the waveform with the waveform, the MPU 72 can easily know the direction and the width of the positional deviation by calculation. Based on the direction and the width of the displacement detected by this calculation, FIG.
In the case of (1), the next printing position is moved to the left, and in the case of (b) in the same figure, the position is moved again to the right, and the chart is printed again. When the detection waveform is obtained as shown in FIG. 4D, the coordinate value of the printing position at that time is expressed as E.
It is stored in the EPROM 75. In this manner, the resist patch can be used for the near-infrared specular reflection sensor 5 during the resist correction processing.
9 can be printed almost accurately in the measurement range 78.

FIGS. 12 (a), 12 (b) and 12 (c) show that the print position was correctly set in the measurement range 78 of the near-infrared regular reflection sensor 59 in the registration detection process in the chart position adjustment mode. FIG. 9 is a diagram illustrating an example in which a resist patch is printed with a minimum necessary spread. FIG. 8A shows a conventional resist patch 84 having a large margin for comparison, and the length of one side of the square is approximately twice as large as the diameter of the measurement range 78, that is, approximately 5 in area. It is twice as large.

On the other hand, the resist patch 85 having a small margin in this example shown in FIG. 9B has a square whose side length is the same as the diameter of the measurement range 78 and an area ratio of about 1. As a result, the toner is tripled, the merge is very small, and almost no wasteful toner is used. Further, a resist patch 86 having no margin, which is shown as another example in this example in FIG. 9C, is printed in the same shape and area as the measurement range 78. This eliminates waste of the toner.

In the examples shown in FIGS. 10 and 11A and 11B, two types of positioning patches 7 are used as position detecting patches.
Although 6b and 76c are printed, the shape and arrangement of the positioning patches are not limited to this, and may be any shape and arrangement that can detect a waveform corresponding to the displacement.

FIG. 13 (a) is a diagram showing another example of the positioning patch, and FIGS. 13 (b) and 13 (d) are diagrams showing the detected waveforms at the shift positions of the positioning patch, and FIGS. () Is a diagram showing a detection waveform of the positioning patch when it is at the correct position. As shown in FIG. 7A, the position detection patch in this positioning patch is only one positioning patch 88 forming an isosceles triangle. In addition, FIG.
For convenience of illustration, the printing position of the positioning patch is fixed, and the near-infrared specular reflection sensor 59 (measurement ranges 78 and 7) is used.
8 ', 78 ") are shown to move relatively.

In the detection waveform shown in FIG. 9B, the centers of the positioning patches 87 and 88 shown in FIG. 9A are shifted rightward with respect to the measurement range 78 'of the near-infrared regular reflection type sensor 59. The detected waveform in the case shown in FIG.
(a) A detection waveform when the centers of the positioning patches 87 and 88 match the measurement range 78 of the near-infrared regular reflection sensor 59, that is, a waveform at a correct position,
In the detection waveform shown in FIG. 5D, the center of the positioning patches 87 and 88 shown in FIG.
9 is a detection waveform when the measurement range 78 ″ of FIG. 9 is shifted to the left.

Also in this case, the correct waveform is
M75, and the stored waveform and FIG.
(b) or (d) is compared with the waveform shown in (b) or (d) of FIG.
Can easily know the direction and the width of the displacement by calculation, and repeat the re-output of the position-corrected chart and the calculation of the detected waveform to obtain the accurate measurement range 78 of the near-infrared regular reflection sensor 59. , And subsequent resist patches can be printed.

FIG. 14 is a diagram showing a further modification of the positioning patch. In the positioning patch shown in FIG. 13A, the positioning patch 88 serving as a position detecting patch is used.
Has an isosceles triangle, but the positioning patch 88 'for position detection shown in FIG. 14 is a right triangle.
Also in this case, the shift position is detected in the same manner as in the case of FIGS.
The print position can be set in the measurement range 78 of No. 9.

The near-infrared specular reflection sensor 59
Is used not only to detect the density of the patch and correct the printing position, but also to correct the density itself of the print (print) image. Generally, in an image forming apparatus having a function of performing automatic density correction using a density sensor, in order to measure a density patch for performing correction, reflected light corresponding to the density of the density patch is within a predetermined range on the light receiving side of the sensor. LED that outputs voltage inside
You have to set the light value. Conventionally, at the time of shipment, a worker adjusts the LED light amount to some extent using a jig at a factory by using a jig.

However, if this is mounted on the printer main body, the LED light amount value adjusted as described above cannot be said to be appropriate due to factors such as the mounting error, the state of the transport belt, and the like, in addition to the variation of each density sensor. In some cases, the printer may be in a state, and therefore, it needs to be adjusted again after being attached to the printer body. Further, if the glossiness of the conveyor belt changes with time or the LED deteriorates with time after shipment of the product, the amount of light received for the density patch changes, and the density correction of the angle may malfunction. Therefore, in the present embodiment, the automatic light amount correction by the near-infrared regular reflection sensor 59 is performed.

FIGS. 15A and 15B are diagrams for explaining a method of performing automatic light amount correction by the near-infrared regular reflection sensor 59. FIG. First, at the time of factory shipment, the density of the surface of the transport belt 40 is measured by a near-infrared regular reflection sensor (hereinafter simply referred to as a density sensor) 59. An output from the light receiving section 62 of the density sensor 59 is output to an MP via an A / D converter (not shown).
It is input to U72. The MPU 72 determines an appropriate LED light amount of the print head 37 based on the measured value, and corrects a voltage value for driving the density sensor 59 to emit light via a D / A converter (not shown).

This correction is performed by the light emitting unit 61 of the density sensor 59.
Is performed in such a manner that the LED light quantity changes linearly in proportion to the input voltage. Based on the result of the density measurement on the conveyor belt surface, the light receiving unit 6 corresponding to the LED light amount set value of the light emitting unit 61 of the density sensor 59 shown at a point P0 in FIG.
Ratio of light receiving amount of belt density of 2 (light receiving amount / LED set value)
From this, the LED set value is determined so that the expected belt density received light amount shown at the point P1 is obtained. The obtained LED set value is stored in the EEPROM 75 as an LED light amount correction value. Then, at the time of the next LED light amount adjustment, the LED of the light emitting unit 61 is turned on using the previous set value.

By the way, in general, when a problem occurs that causes an image obstacle, a printer is conventionally provided with:
Unless printing is actually performed on paper, it cannot be determined that an abnormality has occurred. In this embodiment, when the LED of the light emitting unit 61 is turned on using the previous set value, it is checked again whether the expected amount of received belt density is obtained, and if it is not obtained, the correction is made again. If the correction is not properly performed, it is determined that the density sensor 59 is abnormal.

When it is determined that the density sensor 59 is normal, the conveyor belt 40 is idled without printing to make one revolution. During this rotation, the density sensor 59 detects the density of the conveying surface of the conveyor belt 40. Is measured continuously,
When a certain continuous abnormal value is detected, it is determined that the surface of the transport belt has scratches or dirt.

As a result, it is possible to simplify or reduce the process in which the volume of the light amount of the density sensor is conventionally manually adjusted at the time of shipment. In addition, it is possible to correct not only the individual variations of the density sensors but also the density measurement error caused by the variation of the surface of the conveyor belt and the variation due to the mounting error of the density sensor. In addition, by automatically correcting the LED light amount of the density sensor as described above, it is possible to prevent a malfunction of the density measurement due to a temporal change after the product is shipped.

In the correction of the toner density and the registration in the normal state, the toner density and the resist are detected and corrected by the density sensor from the toner image formed on the conveyor belt at each correction processing timing. . This correction value is fed back to each image forming unit, and high-quality image formation is maintained.

In the present embodiment, if a measured value different from the expected toner density or the resist waveform is output in the correction processing at the above-described correction processing timing, it is determined that an abnormal value has been detected, and the abnormal value is determined. Enter the detection mode to detect the cause of the error. First, abnormalities in the density measurement include a poor toner following property, a poor transfer, a poor detection, a poor cleaning of the transport belt, a toner fog on the photosensitive drum, and the like. Therefore, a test chart in which a plurality of abnormality detection patches, for example, halftone density patches are arranged, is printed out on the conveyor belt and measured. In this case, if a uniform value is not detected as the measured value, it is determined that the possibility of poor toner tracking is high. In this case, the user is notified of a message such as replacement of the toner set. Further, even when the density is not measured, the toner fogging state can be determined by detecting the toner density on the transport belt.

[0092]

As described above in detail, according to the present invention, when there is a variation in the deviation amount of the printing position, the actual resist is printed without being aware of the position in the deviation variation width. In addition, the correction position can be controlled so that the center of the deviation variation width is as close as possible to the reference position of the deviation amount “0” at each correction processing timing.

Further, since the correction is performed by one registration detection at each correction processing timing, a long time is not required for the registration detection, and the deviation variation width centered on the detected deviation position and the reference position is not required. Since the correction is performed by the difference value from the extreme end, the peculiarity of the variation peculiar to the resist can be absorbed, and the correction with high accuracy can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an appearance of a color image forming apparatus (printer) according to a first embodiment.

FIG. 2 is a cross-sectional view illustrating an internal configuration of the printer.

FIG. 3 is a diagram illustrating a state in which an upper portion of the apparatus main body of the printer is opened and a state in which an internal drum set C1 is replaced.

FIG. 4 is a diagram illustrating a state where an internal toner set C2 is replaced.

FIG. 5 is a diagram illustrating a near-infrared specular reflection sensor (CTD sensor).

FIG. 6 is a block diagram illustrating a circuit configuration of a control device of the printer.

FIGS. 7A, 7B, and 7C are diagrams for explaining a print position of a registration patch for automatically adjusting a print position shift in a printer and a method of a correction process based on the print position.

FIG. 8 is a flowchart illustrating an operation of detecting a print position of a registration patch and performing a correction process based on the detection.

FIG. 9 is a diagram for explaining a correction method in a case where a unit to be corrected is larger than a minimum unit of a detected shift amount of a resist.

FIG. 10 is a diagram illustrating a patch printed on a sheet conveyance surface of a conveyance belt to detect an accurate detection area of a near-infrared regular reflection sensor.

FIGS. 11A to 11E are diagrams schematically showing a resist detection method in a chart position adjustment mode for detecting an accurate detection area of a near-infrared regular reflection sensor.

FIGS. 12A, 12B, and 12C are diagrams illustrating an example in which a resist patch is printed with a minimum necessary spread in a measurement range of a near-infrared specular reflection sensor that is set correctly.

FIG. 13A is a diagram showing another example of the positioning patch;
(b), (d) is a diagram showing a detected waveform at a position where the positioning patch is shifted, and (c) is a diagram showing a detected waveform of the positioning patch at a correct position.

FIG. 14 is a diagram showing a further modification of the positioning patch.

FIGS. 15A and 15B are diagrams illustrating a method of performing automatic light amount correction by a near-infrared regular reflection sensor.

FIG. 16 is a diagram schematically illustrating a configuration of a main part of a conventional tandem color printer.

FIG. 17 is a diagram illustrating a specific example of correcting a conventional positional shift amount.

[Explanation of symbols]

Reference Signs List 1 tandem type color printer 2 paper feed cassette P paper 3 transport belt 4a, 4b drive roller 5 (5-1, 5-2, 5-3, 5-4) image forming section 6 fixing device 7 photosensitive drum 8 cleaner 9 Charger 10 Recording head 11 Developing device 12 Transfer device 13 Developing roller 14 Reference position 15 Position shifted by "-1" dot 16a, 16b Resist patch 18 Printing position on reference position 20 Color printer 21 Upper device body 22 Lower device body 23 Operation panel 23a Key operation unit 23b Liquid crystal display 24 Discharge unit 25 Discharge roller 26 Front cover 27 Paper cassette 27a Handle 28 Mounting unit 28a MPF tray 28b Paper feed roller 29 Cover 30 Image forming unit 31 Double-sided printing transport unit 32 Paper part 33 (33-1, 33-2, 33- , 33-4) Image forming unit C1 Drum set C2 Toner set 34 Photoreceptor drum 35 Cleaner 36 Charger 37 Print head 38 Developing container 39 Developing roller 40 Transport belt 40a Paper transport surface 41 Transfer device 42 Feed roller 43 Guide roller pair 44 guide path 45 feed roller pair 46 standby roller pair 47 drive roller 48 driven roller 50 fixing unit 51 heat roller 52 pressing roller 53 cleaner 54 switching plate 55 discharge roller pair 56 side discharge opening 57 transport roller pair 58a to 58e transport roller 59 Near-infrared specular reflection sensor 61 Light emitting unit (LED) 62 (62-1, 62-2, 62-3) Light receiving unit (P
D) 63 (63-1, 63-2) Deflection beam splitter (PBS) 64 Light projection 65 Detection surface 66 Reflected light 67, 69 Incident surface vertical oscillating light component (S-wave light) 68, 71 Incident surface parallel oscillating light Component (P-wave light) 72 MPU 73 Drive unit 74 Head driver unit 75 EEPROM 76a, 76b, 76c Positioning patch 77 Center of printing position 78 Measurement range of near-infrared regular reflection sensor 81, 81 ', 81 "Detection of positioning patch 76a Waveforms 82, 82 ', 82 "Detected waveform of positioning patch 76b 83, 83', 83" Detected waveform of positioning patch 76c 84 Conventionally large resist patch 85 Small resist patch 86 of the present embodiment 86 Resist patch without margin 87, 87 Positioning patch

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Junji Hobo 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Inside Casio Computer Co., Ltd. Tokyo Office (72) Inventor Kenichiro Asako 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Casio Computer Inside the Tokyo office (72) Inventor Hideki Ando 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Casio Computer Co., Ltd. Tokyo office F-term (reference) 2H027 DA09 DE02 DE07 EB04 EC03 EC06 ED04 ED06 ZA07 2H030 AA01 AB02 AD11 AD16 BB02 BB16 BB21 BB43 BB56

Claims (3)

[Claims] 1. A storage means for storing a resist variation range d; a detection means for detecting a current resist deviation position R from a reference position; and a current resist deviation position R detected by the detection means. Based on the variation range d stored in the storage means, assuming that the correction value of the resist is H, if | R |> d / 2, then if R> 0, then H = − (| R | −d / 2 )), If R <0, then H = + (| R | −d / 2). If | R | <d / 2, regardless of the value of R, H = 0 and correction of the resist is performed. A color image forming position adjusting device, comprising: 2. A procedure for detecting a current shift position of a resist from a reference position, wherein the detected shift position of the resist is out of a resist change range when the center of the resist change amount is at the reference position. The procedure of correcting the next registration position to the position closest to the shift position of the resist change range; and the case where the detected shift position of the resist is that the center of the resist change amount is at the reference position. A step of not performing the next registration position correction when the registration position is within the registration variation range. 3. A recording medium on which a color image forming position adjustment program is recorded so as to be mountable on a color image forming apparatus, wherein a step of detecting a current position of the resist from a reference position is provided. A step of determining whether or not the position is within a resist variation range when the center of the resist variation is at the reference position; and in this determination, the deviation position deviates from the resist variation range from the reference position. Is corrected, the next registration position is corrected so as to come to the position closest to the shift position of the resist change range, while if the shift position is within the resist change range from the reference position, A step of not correcting the registration position at the next time, and a program comprising: recording the program such that the program can be mounted on the color image forming apparatus. Media.