JP4608325B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine, and in particular, an image that can reduce costs by detecting a positional deviation of a toner image on an image carrier without using a dedicated detection unit. The present invention relates to a forming apparatus.

As an image forming apparatus such as a copying machine, an apparatus that forms a toner image on a transfer paper set inside in advance is generally used. In this type of apparatus that forms an image by transferring and fixing a toner image on a transfer sheet, it is required to maintain the image quality as set. For this reason, it is necessary to deal with problems related to image quality degradation such as toner image density change and image formation position shift.
For example, in Patent Document 1, two sensors that detect the leading edge of the recording paper are arranged, image formation control on the photosensitive drum is performed by the first detection, and the registration roller is stopped / restarted by the second detection. A technique for controlling driving and performing alignment in the image sub-scanning direction is disclosed.
Patent Documents 2 and 3 do not disclose the detection of the position of the transfer material, but disclose a technique for reading a test pattern transferred onto a conveying unit and correcting a registration error based on reference position information. Further, Patent Document 4 discloses a configuration in which means for detecting the end position of the transfer paper width direction before transfer is arranged, although the position of the image pattern is not detected.
In Japanese Patent Application Laid-Open No. 2005-228867, image position deviation detection / correction is not performed, but the reflectance of the detection target is stored using a density sensor, and a case where the transfer paper does not reach the sensor unit is detected as a jam. I can do it. In Patent Document 6, the leading edge and the side of the transfer paper can be detected, and the transferred detection pattern can also be detected.
JP-A-8-95324 JP-A-8-85236 JP-A-8-85237 Japanese Patent Laid-Open No. 9-219776 JP-A-11-282223 Japanese Patent Laid-Open No. 10-186752

However, since the techniques of Patent Documents 1 to 5 described above do not monitor both the position of the visualized image and the position of the transfer paper, alignment is performed on the assumption that one side is in an ideal state. there were. For this reason, for example, a new detection means or the like must be provided in order to cope with a problem that the positions of the image and the transfer paper are relatively shifted, and thus an increase in cost cannot be avoided.
In the technique of Patent Document 6, the transfer paper and the position of the image transferred onto the transfer paper are viewed, but the image has to be transferred in order to read the adjustment data. In addition, it is necessary to newly install a sensor for viewing the position of the transfer paper, which is disadvantageous in terms of cost.
Therefore, the present invention has been made in consideration of the above-described circumstances, and an image forming apparatus that can reduce the cost by detecting the positional deviation of the image on the image carrier without using a dedicated detection unit. The purpose is to provide.

In order to solve the above-described problems, the invention according to claim 1 forms an electrostatic latent image on a charging portion for uniformly charging the image carrier in the main scanning direction and a charged portion of the image carrier. A writing unit, a developing unit for developing the electrostatic latent image with toner, and a transfer unit for transferring the visualized toner image to a transfer sheet fed from a paper feeding unit, In the image forming apparatus for managing the toner density of the toner image output from the developing unit onto the image carrier by detecting a toner density management pattern formed on the image carrier with a toner density sensor, the image carrier A first storage means for storing the position information of the toner image above, and a second storage means for storing the position information of the transfer paper , wherein the toner density sensor comprises a plurality of light emitting diode arrays. In addition to the configuration, the light receiving unit is aligned. The width of the detectable region of the toner density sensor is equal to or larger than the width of the toner density management pattern, and faces the toner density sensor so as to cover at least the entire toner density management pattern. Across the border between the toner adhering part and the non-toner adhering part of the toner density management pattern visualized at the end of the maximum size transfer paper that can be passed and the end of the effective recording image area. An image forming apparatus in which the toner density sensors are attached to face each other is the main feature.
According to the second aspect of the present invention, there is provided a charging unit that uniformly charges the image carrier in the main scanning direction, a writing unit that forms an electrostatic latent image on the charged part of the image carrier, and an electrostatic latent image. A developing unit for developing an image with toner and a transfer unit for transferring the visualized toner image onto a transfer paper fed from a paper feeding unit, and formed on the image carrier In the image forming apparatus for managing the toner density of the toner image output from the developing unit on the image carrier by detecting the toner density management pattern with a toner density sensor, the position information of the toner image on the image carrier And a second storage means for storing the transfer paper position information. The toner concentration sensor includes a light emitting section composed of a plurality of light emitting diode arrays, and a light receiving section. Aligned array of phototrans The width of the detectable region of the toner density sensor is set so as to detect a part of the toner density management pattern including one of the ends in the main scanning direction, and the toner density sensor The toner density visualized at the end of the maximum size transfer paper and the end of the effective recording image area facing the boundary between the toner adhering portion and the non-toner adhering portion of the toner density management pattern An image forming apparatus in which the toner density sensor is attached to face each other so as to straddle the boundary between the toner adhering portion and the toner non-adhering portion of the management pattern is a main feature.

According to a third aspect of the present invention, there is provided a ROM area for storing a program for continuously detecting the position of the boundary portion of the toner density management pattern and the position of the edge of the transfer paper; 3. The image forming apparatus according to claim 1, further comprising: a third storage unit that stores optimum image position information with respect to the transfer sheet based on information in the first storage unit and the second storage unit. Main features.
According to the fourth aspect of the present invention, when the transfer sheet fed in the transfer sheet end detection operation is being conveyed, the image forming operation of the toner density management pattern is performed on the transfer sheet for correction. 4. An image forming apparatus according to claim 3, wherein an adjustment confirmation operation for confirming the result is added to the ROM area .

According to the present invention, the toner density sensor can detect not only the toner density but also the positional deviation of the image on the image carrier, so that the cost can be reduced.
In addition, the toner density sensor includes a plurality of light emitting units and a plurality of light receiving units, and the width of the detectable region of the toner density sensor is set to be equal to or larger than the width of the toner density management pattern so as to cover at least the entire toner density management pattern. By attaching the toner density sensor to face each other, the boundary position between the toner adhering portion and the toner non-adhering portion is recognized, so that a deviation from the normal position can be detected with high accuracy.
Further, by setting the width of the detectable region of the toner density sensor and the position of the sensor so as to detect a part of the toner adhesion portion including one of the ends in the main scanning direction, the sensor structure is simplified. Cost can be reduced.
By detecting the toner density management pattern and detecting the edge position of the transfer paper in the main scanning direction by the same sensor, it is possible to correct the positional deviation when the image is actually transferred onto the transfer paper.
In addition to creating a toner density management pattern for managing the toner density, an image position adjustment mode is incorporated into the apparatus as a program so that image position adjustment with respect to transfer paper can be performed. The correction value of the image position with respect to the transfer sheet can be calculated by the procedure.
In addition to creating a toner density management pattern for managing toner density, an image position adjustment mode is built into the device as a program so that image position adjustment with respect to transfer paper can be performed for further confirmation. By adding the operation, it becomes possible to check the correction value (transfer the image to the transfer paper) during the paper passing for detecting the main scanning end position of the transfer paper.

The best mode for carrying out the present invention will be described below in detail with reference to the drawings.
Example 1
FIG. 1 is a cross-sectional view of an image forming apparatus for explaining first to sixth embodiments of the present invention. An image forming process in this image forming apparatus will be described. First, image information of a document is read by a reading unit 1, and the image information is exposed on a photoconductor 3 as an image carrier by a writing unit 2 having a writing unit. To become a latent image. The photosensitive member 3 is charged in advance by a charging unit (not shown) before writing. Then, the latent image is visualized as a toner image by the developing unit 4, the toner image is transferred to the transfer paper supplied from the paper feeding unit 6 or the like by the transfer unit 5, and the toner image on the transfer paper is transferred by the fixing unit 7. Let it settle. The transfer paper on which image formation is completed in this manner is discharged out of the apparatus. The image information of the document can be obtained from the outside without using the reading unit 1.
In an image forming apparatus that forms an image by such a process, whether or not a desired toner image is appropriately formed is one of the important factors that determine image quality. Therefore, as shown in FIG. 1, a toner density sensor 8 for detecting the toner density of the toner image on the photoconductor 3 is attached so as to face the photoconductor 3. Then, a toner density management pattern is appropriately formed on the photoconductor 3, and this pattern is detected by the toner density sensor 8, whereby the toner density of the toner image formed on the photoconductor by the toner output from the developing unit 4 is detected. Management is performed.
When creating a toner density management pattern, the roller voltage is controlled so that the toner image does not adhere to the transfer roller (transfer section 5), so the position of the toner density sensor 8 may be upstream or downstream of the transfer roller. In order not to be affected by the transfer, the upstream side is better. In addition, the timing for managing the toner density is set in advance when the power is turned on at a predetermined temperature or lower (for example, 15 ° C. or lower), when the door is opened or closed (in the product software or installed) This may be the case when the creation time of the toner density management pattern arrives at the end of the number of jobs based on the toner density management pattern creation interval (number of copies, etc.).
In general, a sensor for detecting toner density outputs light by changing the amount of reflected light into voltage depending on the presence or absence of a toner density management pattern. , Light emitting side: GaAlAs infrared light emitting diode, light receiving side: Si phototransistor), and the toner density management pattern has a size (for example, a width of 10 mm) that can be detected by the sensor even if misalignment occurs. create. As described above, the conventional sensor only needs to recognize the difference between the reflected light on the surface of the photoconductor on which the toner is not attached and the reflected light with toner, and therefore, the width of the toner density management pattern is set in the detectable region of the sensor. It is set larger than the width.

In contrast, in the image forming apparatus according to the first exemplary embodiment, the width of the toner detectable region of the toner density sensor 8 and the width of the toner density management pattern are set to be substantially the same. Here, as shown in FIG. 2, the width of the toner detectable region of the toner density sensor 8 is increased to be the same as the width of the toner density management pattern 9. Further, as can be seen from the figure, the toner density sensor 8 is attached by selecting a position where the toner detectable region of the toner density sensor 8 faces the toner density management pattern 9.
As described above, when the toner density management pattern 9 and the detectable area of the toner density sensor 8 are matched, as shown in FIG. 3, the output voltage value for a portion where the toner image is present on the photosensitive member 3 drops to a certain value. However, when the detection range of the toner density management pattern 9 and the toner density sensor 8 is deviated, a voltage output indicating the toner adhesion area ratio corresponding to the deviation amount is obtained. Can do. Further, the positional deviation information is stored in a first memory unit (not shown) as first storage means provided in the apparatus and used as data for image position correction.
Therefore, the toner density sensor 8 can be used not only as a toner density detection means but also as an image position deviation amount detection means on the photosensitive member 3, thereby reducing costs and simplifying the configuration while achieving both functions. Can be realized.

(Example 2)
With the use of the image forming apparatus, the toner density after development changes, and even when the range of the toner density management pattern 9 and the detection range of the toner density sensor coincide with each other, the sensor when the toner portion is detected The output will change. Therefore, in the second embodiment, in addition to the function of the first embodiment, information on the image direction shift direction can be obtained.
In the toner density sensor 8 in the image forming apparatus according to the second embodiment, as illustrated in FIG. 4, an array-shaped light receiving unit 8 b in which sensor units having a small detection range (for example, about 0.2 mm) are connected is provided. If necessary, an array of phototransistors on which a lens array is mounted is used, or arranged in a staggered manner to increase the resolution. Further, since the light emitting section needs to give light as uniformly as possible on the photosensitive member 3, a plurality of light emitting elements 8a are used so as to be arranged according to the irradiation characteristics. Also, it is necessary to divide the circuit so that the output of the arrayed phototransistor can be recognized separately.
FIG. 5 is a perspective view of the toner density sensor 8 and the photoreceptor in the second embodiment. In the example of this figure, the width of the detectable region of the toner density sensor 8 in the main scanning direction is set larger than the width of the toner density management pattern 9 and at a position where the entire toner density management pattern 9 can be covered. Although the case where the toner density sensor 8 is attached is shown, the width of the detectable area of the toner density sensor 8 is equal to or larger than the width of the toner density management pattern 9 and at least covers the entire toner density management pattern 9. Similar effects can be obtained even when the density sensors 8 are mounted facing each other.
With such a configuration, it is possible to recognize the boundary position between the toner adhering portion and the toner non-adhering portion, and to grasp the sensor output of the toner portion. Each output of the arrayed phototransistor is taken out, digitally processed to detect the boundary and stored in the first memory unit (in Example 1, the sensor output was stored according to the area ratio. 2 stores the boundary at which sensor number or the deviation of mm calculated from the resolution.) Further, the sensor output of the toner portion obtained by digital processing can be stored in a memory area used for toner management that has been conventionally performed.
The information about the toner part boundary thus obtained is stored as visualized image position information, and the deviation from the ideal position on the writing side or the normal position obtained by experiment can be calculated with high accuracy. The main scanning position deviation is corrected by changing the writing position of 2 in the main scanning direction based on the information. Therefore, in the image forming apparatus according to the second embodiment, it is possible to improve the detection accuracy of the image position deviation.

(Example 3)
In the third embodiment, as shown in FIG. 6, the toner density sensor 8 is installed to face the boundary between the toner adhesion portion and the toner non-adhesion portion of the toner density management pattern 9. That is, as shown in the figure, the width of the detectable region of the toner density sensor 8 and the position of the sensor are set so as to detect a part of the toner adhesion portion including one of the ends in the main scanning direction. In the density sensor of the second embodiment, even if the toner density management pattern 9 is set to be small to some extent, if the resolution is important, a large number of phototransistors are required and the cost is increased. According to the toner density sensor 8, the sensor structure can be simplified as compared with the case of the second embodiment.
In determining the toner detectable region width of the toner density sensor 8, it is necessary to consider the accuracy error of each component. That is, the setting is made so as not to erroneously determine tolerance stacking in the main scanning direction of the mechanism unit and output of the toner portion.
Thereby, in the image forming apparatus of Embodiment 3, the output voltage can be detected according to the area of the toner portion as shown in FIG. Therefore, the configuration is simple, and the cost of the toner density sensor 8 can be reduced.

Example 4
Up to Example 3, the toner density management pattern was read by the density sensor, and the function of properly grasping the toner density and the function of grasping the position of the visualized image as the deviation amount were realized. However, even if the boundary detection of the toner density management pattern is performed, the image position deviation from the target position can be corrected. However, when the transfer paper is actually transferred to the transfer paper because the position of the transfer paper cannot be guaranteed. It is not possible to correct up to the misalignment. Therefore, in the fourth embodiment, the arrangement position of the toner density sensor 8 is defined, and the detection of the toner density management pattern and the end position detection of the transfer paper in the main scanning direction are performed by the same sensor.
The toner density sensor 8 is disposed so as to straddle two positions. As shown in FIG. 7, the two positions are the edge of the maximum transfer paper size through which the apparatus can pass and the boundary of the toner density management pattern 9 visualized at the edge of the effective recording image area. It is. As a result, it is possible to detect the boundary of the toner density management pattern 9 and the voltage detection of the toner density shown in the third embodiment, and further detect the position of the end of the transfer paper when the paper is passed.
Image position information obtained when the toner density management pattern 9 is imaged is stored in the first memory unit. Further, the transfer paper edge position information when the paper is passed is stored in a second memory unit (not shown) as second storage means provided inside the apparatus. From the two pieces of position information of the first memory unit and the second memory unit, the amount of image displacement with respect to the aim is quantified and can be used as correction data. As shown in FIG. 7, this is obtained from the interval between the detection timing of the transfer paper edge and the detection timing of the pattern boundary.
Therefore, the image forming apparatus according to the fourth embodiment can detect the position of the end of the transfer paper in the main scanning direction, and thus can obtain and correct misalignment information when actually transferring to the transfer paper. In the example of FIG. 7, the width of the toner detectable region of the toner density sensor 8 is set so as to detect a part of the toner density management pattern 9 including one of the ends in the main scanning direction. The width may be a width that covers the entire toner density management pattern 9. Even in this case, the same effect can be obtained.

(Example 5)
In the fourth embodiment, the relative deviation between the transfer paper and the image position can be corrected. However, the toner density management pattern is created and detected under the conditions described in the first embodiment. Detection of the transfer paper edge position at the time is another mode. Therefore, in the fifth embodiment, in addition to the creation of a toner density management pattern for managing the toner density, an image position adjustment mode can be incorporated as a program in the ROM inside the apparatus to adjust the image position with respect to the transfer paper. Like that.
FIG. 8 is a flowchart showing the image position adjustment operation of the fifth embodiment. As shown in FIG. 8, when the adjustment mode is selected and a key for starting is pressed, an operation for forming a toner density management pattern on the photosensitive member (image carrier) is first performed. A pattern is formed on the photosensitive member by controlling charging, exposure (pattern writing by the writing unit), and development (visualization) while rotating the photosensitive member (step S1). Here, the bias of the transfer roller is set so that the transfer portion is not soiled.
Next, the toner density management pattern 9 is detected by the toner density sensor 8, and the density of the toner density management pattern 9 portion and the pattern boundary (boundary position information) are detected (step S2). Since there is a single detection mode for toner density, whether or not to replenish toner using this information may be set arbitrarily. Then, the boundary position information of the toner density management pattern 9 is stored in the first memory unit (first storage means) (step S3).
Subsequently, the transfer paper feeding operation is started (step S4). In this case, a normal paper feeding operation is desirable because the end position of the transfer paper during actual paper feeding is detected. When the fed transfer paper reaches the vicinity of the toner density sensor 8, the end position of the transfer paper is detected by the toner density sensor 8 (step S5), and the detected position information is stored in the second memory section (step S5). Step S6).
Further, the actual image position from the edge of the transfer sheet is calculated from the position information of the first memory section and the position information of the second memory section (second storage means) (step S7). Further, the calculated image position information is compared with the target image position in which a predetermined margin is provided at the end of the transfer paper, and a correction value is calculated (step S8). By changing the starting position in the main scanning direction of writing by the calculated value data, the image position in the main scanning direction can be brought to the target value at the edge of the transfer paper. Therefore, the calculated correction value is stored in a third memory unit (adjustment memory) (not shown) as third storage means provided in the apparatus so that it can be used as main scanning writing position adjustment data of the apparatus. The process ends (step S9). As described above, the image forming apparatus according to the fifth exemplary embodiment can calculate the correction value of the image position with respect to the transfer sheet in one procedure.

(Example 6)
In the image forming apparatus of the sixth embodiment, the following confirmation operation is added to the operation of the fifth embodiment (when a program for an investigation confirmation operation is added to the ROM area). FIG. 9 is a flowchart showing the operation of the sixth embodiment. As shown in FIG. 9, following the operation of the fifth embodiment, data in the third memory unit is set as writing position correction data in the main scanning direction. Normally, the writing position of one page is not changed within the page, but the toner density management pattern 9 at the time of position information acquisition and the position of the image to be exposed are shifted by the information in the third memory unit. The image forming operation of the toner density management pattern 9 is executed when the fed transfer paper is being conveyed in the transfer paper edge detection operation (step S12).
Here, the bias of the transfer unit is controlled in the same way as when performing normal image transfer (step S13), and the subsequent fixing and paper discharge operations are also performed as usual (step S14). Incidentally, cleaning and static elimination around the photosensitive member are also performed as usual. With this operation, the adjusted toner density management pattern 9 is transferred and fixed onto the transfer paper, so that the position of the actual image after adjustment using the supplied transfer paper for detecting the end of the transfer paper is used. Can be confirmed on the transfer paper.
As described above, in the image forming apparatus according to the sixth embodiment, the correction result can be confirmed (the image is transferred to the transfer sheet) during the sheet passing operation for detecting the end position of the transfer sheet in the main scanning direction.

1 is a cross-sectional view of an image forming apparatus shown as the best mode for carrying out the present invention in Examples 1 to 6. FIG. FIG. 3 is a perspective view illustrating a toner density sensor and a photoreceptor in Example 1. It is a figure which shows the sensor output in Example 1. FIG. 6 is a perspective view of a toner concentration sensor of Embodiment 2. FIG. It is a figure which shows the image of the sensor output of Example 2. FIG. FIG. 10 is a perspective view illustrating a toner density sensor and a photoreceptor in Example 3. FIG. 6 is a perspective view illustrating a toner density sensor and a photoreceptor in Example 4. 10 is a flowchart illustrating an image position adjustment operation according to the fifth exemplary embodiment. It is a flowchart which shows the operation | movement (a confirmation operation is added to the operation | movement flow of Example 5) of Example 6. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reading part 2 Writing part 3 Photoconductor 4 Developing part 5 Transfer part 6 Paper feeding part 7 Fixing part 8 Toner density sensor 9 Toner density management pattern

Claims (4)

A charging unit that uniformly charges the image carrier in the main scanning direction;
A writing unit that forms an electrostatic latent image on a charged portion of the image carrier, a developing unit that visualizes the electrostatic latent image with toner, and a toner image that has been visualized is fed from a paper feeding unit. A toner image output from the developing unit onto the image carrier by detecting a toner density management pattern formed on the image carrier with a toner density sensor. In an image forming apparatus that performs toner density management of
A first storage means for storing the position information of the toner image on said image bearing member,
Second storage means for storing transfer paper position information ;
The toner density sensor includes a light emitting unit configured by a plurality of light emitting diode arrays and an arrayed phototransistor in which the light receiving units are aligned.
The width of the detectable region of the toner density sensor is equal to or greater than the width of the toner density management pattern, and the toner density sensor is opposed so as to cover at least the entire toner density management pattern ,
The toner density so as to straddle the edge of the transfer paper of the maximum size that can be passed through and the boundary between the toner adhering part and the toner non-adhering part of the toner density management pattern visualized at the end of the effective recording image area. An image forming apparatus, wherein sensors are attached to face each other. A charging unit that uniformly charges the image carrier in the main scanning direction;
A writing unit that forms an electrostatic latent image on a charged portion of the image carrier, a developing unit that visualizes the electrostatic latent image with toner, and a toner image that has been visualized is fed from a paper feeding unit. A toner image output from the developing unit onto the image carrier by detecting a toner density management pattern formed on the image carrier with a toner density sensor. In an image forming apparatus that performs toner density management of
A first storage means for storing the position information of the toner image on said image bearing member,
Second storage means for storing transfer paper position information ;
The toner density sensor includes a light emitting unit configured by a plurality of light emitting diode arrays and an arrayed phototransistor in which the light receiving units are aligned.
The width of the detectable region of the toner density sensor is set so as to detect a part of the toner density management pattern including one of the ends in the main scanning direction, and the toner density sensor is used for the toner density management. Opposite the boundary between the toner adhering part and non-toner adhering part of the pattern ,
The toner density so as to straddle the edge of the transfer paper of the maximum size that can be passed through and the boundary between the toner adhering part and the toner non-adhering part of the toner density management pattern visualized at the end of the effective recording image area An image forming apparatus, wherein sensors are attached to face each other. A ROM area for holding a program for continuously detecting the position of the boundary portion of the toner density management pattern and the position of the edge of the transfer paper;
3. A third storage unit for storing optimum image position information with respect to a transfer sheet based on information in the first storage unit and the second storage unit. Image forming apparatus. Adjustment confirmation operation that enables the confirmation of the correction result by executing the image forming operation of the toner density management pattern on the transfer paper when the fed transfer paper is being conveyed in the transfer paper edge detection operation The image forming apparatus according to claim 3 , wherein: is added to the ROM area .

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