JP3644178B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus in which a plurality of image output units are arranged along an image carrier belt to form a multicolor image.
[0002]
[Prior art]
FIG. 4 is a schematic diagram showing an example of this type of image forming apparatus.
In FIG. 4, an intermediate transfer belt 1 serving as an image carrier belt is stretched in a loop by a drive roll 2, driven rolls 3 and 3, and a pair of transfer rolls 4. The intermediate transfer belt 1 travels in the direction of the arrow in the figure by the rotational drive of the drive roll 2. A plurality (four) of image output units 5 to 8 are disposed along the intermediate transfer belt 1 between the drive roll 2 and the driven roll 3. These image output units 5 to 8 are arranged in parallel in the order of black (K), yellow (Y), magenta (M), and cyan (C) from the upstream side to the downstream side in the belt traveling direction. ing. Each of the image output units 5 to 8 includes laser writing units 5a to 8a, photosensitive drums 5b to 8b, and peripheral devices (charging device, developing device, transfer device, cleaner, etc.).
[0003]
In the image forming apparatus having the above configuration, the electrostatic latent images written on the surfaces of the photosensitive drums 5b to 8b are developed as toner images by the laser writing units 5a to 8a, and the toner images are transferred onto the intermediate transfer belt 1. Is done. At that time, images of different colors (black → yellow → magenta → cyan) are sequentially transferred and transferred onto the intermediate transfer belt 1 by the image output units 5 to 8, thereby one multicolor image (color image). Is formed. Further, the multi-color image formed on the intermediate transfer belt 1 is collectively transferred onto the paper 10 fed from the paper tray 9 to the transfer roll 4, and then the paper 10 is image-fixed by the fixing device 11 and is externally attached to the apparatus. To be discharged. Further, residual toner remaining on the intermediate transfer belt 1 after image transfer onto the paper 10 is removed by a cleaner 12 disposed in the vicinity of the drive roll 2.
[0004]
By the way, in this type of image forming apparatus, images of different colors are sequentially superimposed on the intermediate transfer belt 1 to form one multi-color image. When the transfer position of the toner image is relatively shifted, a color registration shift (registration shift) occurs, resulting in a reduction in the quality of the output image.
[0005]
Therefore, in general, the above-described registration deviation is corrected based on the following registration control technique.
That is, a registration error detection pattern is formed on the intermediate transfer belt 1 and the registration error detection pattern is read by the registration sensor 13. At this time, it is detected how much the position of the pattern read by the registration sensor 13 is deviated from the normal position, and registration correction such as adjusting the writing timing of the laser writing units 5a to 8a according to the amount of deviation is performed. Do.
[0006]
Here, types of registration misalignment include misalignment of the image writing position in the main scanning direction corresponding to the width direction of the intermediate transfer belt 1 (hereinafter referred to as side registration), and sub-scanning direction corresponding to the running direction of the intermediate transfer belt 1. There are image writing position shifts (hereinafter referred to as lead registration), oblique image tilt shifts (hereinafter referred to as skew), and full magnification shifts in the main scanning direction. In addition to this, a BOW in which the image is curved as if curved in the sub-scanning direction as shown in FIG. 5A, or a left-right magnification difference in the main scanning direction as shown in FIG. 5B. There is a left / right magnification difference.
As a result of such various misregistrations, for example, as shown in FIGS. 5A and 5B, when the image position of magenta (M) is relatively deviated from the image position of black (K), the amount of deviation α , Β occurs, and a high-quality image cannot be obtained.
Therefore, among the above-described various registration deviations, a registration registration detection pattern is formed at one end of the side registration and the lead registration in the width direction (main scanning direction) of the intermediate transfer belt 1 and is read by the registration sensor 13. Can be detected.
[0007]
[Problems to be solved by the invention]
However, in order to detect skew and total magnification deviation, it is necessary to form a registration deviation detection pattern at least at both ends (IN / OUT) of the intermediate transfer belt 1, and in order to detect BOW and lateral magnification difference deviation, It is necessary to form a registration error detection pattern at least at both ends of the intermediate transfer belt 1 and the center thereof (CENTER).
Therefore, conventionally, with respect to skew and total magnification deviation, the registration deviation detection patterns formed at both ends of the intermediate transfer belt 1 are read by the two registration sensors 13, and BOW and lateral magnification difference deviation are shown in FIG. As shown, the registration shift detection pattern P formed at both ends and the center of the intermediate transfer belt 1 is read by the three registration sensors 13a to 13c, but the registration sensor 13 itself is very expensive. Increasing the number of sensors led to a significant cost increase of the entire device.
[0008]
SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of detecting various registration deviations without increasing the number of registration sensors. .
[0009]
[Means for Solving the Problems]
The present invention has been made to achieve the above object, and a plurality of image output units are arranged along the image carrier belt, and images of different colors are sequentially arranged on the image carrier belt by the plurality of image output units. In the image forming apparatus capable of forming a multicolor image by superimposing the registration error detection pattern forming means for forming the registration error detection pattern at a plurality of different positions in the main scanning direction of the image carrier belt; A registration sensor that can move in the main scanning direction to a position where the registration error detection pattern formed at the position can be read, and a registration error detection pattern formed at a plurality of different positions read by the movement of the registration sensor A registration error calculation unit for calculating a registration error amount based on the read data of the registration error, a registration error detection pattern forming means, a registration sensor, and a registration error calculation Parts are be capable of detecting different types of misregistration, it is to increase or decrease the position detected by the registration sensor according to the type of misregistration detecting.
[0010]
In the image forming apparatus having the above-described configuration, when the registration error detection pattern formed on the image carrier belt by the plurality of image output units is read by the registration sensor, the registration sensor is set according to the formation position of the registration error detection pattern. By moving in the main scanning direction, even when a registration error detection pattern is formed at a plurality of locations in the main scanning direction on the image carrier belt, the registration error detection pattern at each location can be read by one registration sensor. It becomes possible.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In the present embodiment, the same components as those in the image forming apparatus (see FIG. 4) exemplified in the above prior art are denoted by the same reference numerals, and redundant description is omitted.
FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus according to the present invention.
In FIG. 1, each of the image output units 5 to 8 disposed along the intermediate transfer belt (image carrier belt) 1 forms an image according to a control signal from the controller 14, and a pattern generator (not shown). The registration error detection pattern P created in the above is formed on the photosensitive drum 5b (6b, 7b, 8b), and the registration error detection pattern P is transferred onto the intermediate transfer belt 1.
[0012]
A registration sensor 13 is disposed downstream of the intermediate transfer belt 1 in the running direction so as to face the belt. The registration sensor 13 reads the registration deviation detection pattern P formed on the intermediate transfer belt 1 as described above. For example, the registration sensor 13 is a CCD sensor formed by arranging a plurality of read pixels in a straight line, or a registration deviation detection pattern. It consists of photocells corresponding to the shape.
As for the registration deviation detection pattern P, as shown in the figure, a pattern (chevron) composed of line segments having a predetermined inclination with respect to the sub-scanning direction (belt running direction), or a line along the main scanning direction. Any shape such as a vertical / horizontal pattern composed of a combination of a minute and a line segment along the sub-scanning direction may be adopted.
[0013]
Further, in the present embodiment, the following sensor moving mechanism 15 is provided as a sensor moving means for moving the above-described registration sensor 13 in the width direction of the intermediate transfer belt 1, that is, in the main scanning direction X.
The sensor moving mechanism 15 mainly includes a sensor support shaft 16 that is stretched along the width direction (main scanning direction X) of the intermediate transfer belt 1, and a pulse motor 17 that is connected to one end of the sensor support shaft 16. It is composed of Among these, the sensor support shaft 16 is composed of, for example, a ball screw shaft having a spiral groove on its outer peripheral surface, and this ball screw shaft is associated with a nut member (not shown) incorporated in the housing of the registration sensor 13. Match. When the pulse motor 17 is rotated, the sensor support shaft 16 is also rotated in conjunction therewith, and the registration sensor 13 is moved in the main scanning direction X in accordance with the rotation amount and the rotation direction.
[0014]
The controller 14 takes in the read data of the registration error detection pattern P read by the registration sensor 13, calculates the registration error amount of each color based on the read data, and corrects the registration error based on the calculation result. . Further, when detecting the registration error, the controller 14 gives a pulse signal as a sensor movement command to the pulse motor 17 and moves the registration sensor 13 in the main scanning direction X by rotational driving of the pulse motor 17 according to the pulse signal.
[0015]
The sensor moving means is not limited to the sensor moving mechanism 15 as long as it can move the registration sensor 13 in the main scanning direction X in accordance with a sensor movement command from the controller 14. Is converted into a linear motion of the registration sensor 13 by a power transmission mechanism such as a gear or a belt, or the registration sensor 13 is moved in the main scanning direction X by using a linear pulse motor that advances in a linear direction by a predetermined pitch by an input pulse signal. It may be a thing.
Further, as a simple means not using a driving source such as a motor, the registration sensor 13 is supported so as to be movable in the main scanning direction X by an arbitrary guide mechanism, for example. It may be moved in the main scanning direction X by manual operation.
[0016]
FIG. 2 is a flowchart showing an operation procedure of registration error detection and correction in the image forming apparatus according to the present invention.
First, when detecting registration misalignment, the controller 14 controls driving of the sensor moving mechanism 15 in accordance with a preset pattern forming position, thereby causing the registration sensor 13 to move one end of the intermediate transfer belt 1 shown in FIG. 3A, for example. Move to A (hereinafter, position A) (step S1).
Next, the controller 14 operates each of the image output units 5 to 8 to detect registration deviation on the intermediate transfer belt 1 in a manner corresponding to the position A as shown in FIG. A pattern Pa is formed (step S2).
Then, the registration displacement detection pattern Pa is read by the registration sensor 13 at the position A (step S3). At this time, the reading length (sampling period) of the registration error detection pattern Pa in the registration sensor 13 is set to a length that satisfies at least the number of data necessary for the registration error calculation in the controller 14, and specifically, the intermediate transfer belt. One round may be sufficient, and the photoreceptor drum 5b may be rounded.
[0017]
Thereafter, as in the case of the position A, the controller 14 moves the registration sensor 13 to the center B (hereinafter referred to as position B) of the intermediate transfer belt 1 shown in FIG. 3B and further to the intermediate transfer belt shown in FIG. 1 are sequentially moved to the other end C (hereinafter referred to as position C) of 1 and registration displacement detection patterns Pb and Pc are respectively corresponding to the positions B and C as shown in FIGS. The registration deviation detection patterns Pb and Pc are read by the registration sensor 13 at positions B and C (steps S4 to S9).
[0018]
When the pattern reading at each position A, B, C is thus completed, the controller 14 makes various registration deviations (read registration, side registration, total magnification deviation, skew, BOW based on the reading data at each position A, B, C. , Left-right magnification difference deviation) is detected (step S10), and registration correction is performed based on the respective registration deviation amounts (step S11).
[0019]
In the above embodiment, the registration deviation detection patterns Pa, Pb, and Pc are formed and read each time the registration sensor 13 is moved to the respective positions A, B, and C. In addition to this, for example, registration misregistration detection patterns Pa, Pb, and Pc are simultaneously formed on both ends (IN, OUT) and the center (CENTER) of the intermediate transfer belt 1, and each of the patterns corresponding to each pattern formation position is formed thereafter. The registration sensor 13 may be sequentially moved to the positions A, B, and C to read the registration deviation detection patterns Pa, Pb, and Pc.
[0020]
Incidentally, among the various registration deviations, the skew, total magnification deviation, BOW, and left / right magnification difference deviation hardly change during the period in which the intermediate transfer belt 1 rotates several times, and thus the registration sensor 13 is moved as in the present embodiment. In the case of detection by a plurality of registration sensors 13 as in the prior art, there is almost no error in the detection data of both, and even if it occurs, the error is very slight (within several μm).
[0021]
Furthermore, in the above embodiment, the movement step of the registration sensor 13 is three steps corresponding to the positions A, B, and C. However, the sensor movement step at the time of registration deviation detection is not necessarily limited to three steps. When there is no need to detect the left / right magnification difference deviation, the sensor movement step is set to two steps corresponding to only the positions A and C, and when it is desired to detect various registration deviations with higher accuracy, the sensor movement step is performed. What is necessary is just four steps or more.
[0022]
Further, as described above, the registration deviation detection accompanying the movement of the registration sensor 13 may be performed every time prior to the registration deviation correction. However, when the registration sensor 13 is moved, the registration deviation detection time is longer than when the registration sensor 13 is not moved. Therefore, it is preferable to perform the process only when any one of the conditions (1) to (6) listed below is satisfied.
(1) When the device power is turned on (2) When parts such as the belt module / photosensitive drum are replaced (3) When the belt module is moved up and down during the maintenance of the device (4) The temperature inside the device fluctuates (5) When the number of processed images reaches the specified number (6) When the lead registration or side registration exceeds an allowable value
In addition, in the above-described embodiment, an image forming apparatus that forms a registration error detection pattern on the intermediate transfer belt 1 has been described. However, the present invention is not limited to this, and for example, registration on a photosensitive belt. The present invention can be similarly applied to an image forming apparatus that forms a deviation detection pattern, or a paper conveyance belt or an image forming apparatus that forms a registration deviation detection pattern on a sheet on the belt.
[0024]
【The invention's effect】
As described above, according to the image forming apparatus of the present invention, the registration sensor can be moved in the main scanning direction in accordance with the formation position of the registration deviation detection pattern. Even when the registration error detection pattern is formed over the entire area, the registration error detection pattern at each position can be read by one registration sensor. As a result, even when various registration deviations (lead registration, side registration, total magnification deviation, skew, BOW, left-right magnification difference deviation) are detected , the type of deviation detected by moving one registration sensor in the main scanning direction. Therefore, it is possible to cope with the problem by increasing the number of detection positions, and the cost of the entire apparatus can be reduced by reducing the number of sensors. Further, by setting the movement step of the registration sensor finely, it is possible to detect the registration deviation with higher accuracy.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.
FIG. 2 is a flowchart illustrating an operation procedure for registration error detection / correction.
FIG. 3 is a diagram for explaining a sensor movement position when a registration error is detected.
FIG. 4 is a schematic configuration diagram illustrating an example of an image forming apparatus.
FIG. 5 is a diagram for explaining types of registration misalignment.
FIG. 6 is a diagram for explaining a conventional example.
[Explanation of symbols]
1 Intermediate transfer belt 5 to 8 Image output unit 13 Registration sensor 14 Controller 15 Sensor moving mechanism

Claims (4)

Image formation in which a plurality of image output units are arranged along the image carrier belt, and images of different colors are sequentially superimposed on the image carrier belt by the plurality of image output units. In the device
A registration error detection pattern forming means for forming registration error detection patterns at a plurality of different positions in the main scanning direction of the image carrier belt;
A registration sensor capable of moving in the main scanning direction to a position where the registration error detection patterns formed at the plurality of different positions can be read;
A registration error calculation unit that calculates a registration error amount based on read data of a registration error detection pattern formed at the plurality of different positions read by the registration sensor moving;
The registration deviation detection pattern forming means, the registration sensor, and the registration deviation calculation unit can detect different types of registration deviation, and increase or decrease the detection position by the registration sensor according to the type of registration deviation to be detected. An image forming apparatus.   The image forming apparatus according to claim 1, further comprising a registration correction unit that performs registration correction based on a registration deviation amount calculated by the registration deviation calculation unit.   The image forming apparatus according to claim 1, wherein the registration deviation calculation unit calculates at least one of a lead registration, a side registration, a total magnification deviation, and a skew as the registration deviation amount. The registration deviation calculation unit calculates at least one of BOW and right / left magnification difference deviation as the registration deviation amount,
4. The detection position is increased when it is necessary to detect the BOW or the left / right magnification difference deviation, compared to when it is not necessary to detect the BOW and the left / right magnification difference deviation. Image forming apparatus.

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