JP2014016567A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of correcting positional deviation between an image and a recording medium.SOLUTION: An image forming apparatus is configured to convey a recording sheet 5 to a transfer position on a transfer belt 31 by conveyance means 50, to form a toner patch in a non-image area positioned between the recording sheets 5 conveyed by the transfer belt 31, to detect by detection means 80 positions of the recording sheet 5 conveyed by the transfer belt 31 and the toner patch, and to control by control means at least one of an image formation position on an image carrier and a conveyance position of the recording sheet 5 conveyed by the conveyance means according to detection results of positions of the recording sheet 5 and the toner patch detected by the detection means 80.

Description

  The present invention relates to an image forming apparatus.

  Conventionally, in the image forming apparatus, for example, a technique disclosed in, for example, Patent Document 1 has already been proposed as a technique for correcting a positional deviation of an image formed on a recording sheet.

  Japanese Patent Application Laid-Open No. 2004-228688 detects an image formed on an image carrier belt and detects the position of an image formed on an upstream side of an image transfer position by a transfer unit. And a control means for controlling the paper conveyance speed by the paper conveyance means based on the detection results of the image detection means and the paper passage detection means.

Japanese Patent No. 3978837

  Incidentally, the problem to be solved by the present invention is to provide an image forming apparatus capable of correcting the positional deviation between an image and a recording medium.

That is, the invention described in claim 1 includes an image carrier,
A transfer belt that conveys a recording medium on which an image formed on the image carrier is transferred directly or via an image carrier belt;
Conveying means for conveying the recording medium to a transfer position of the transfer belt;
Image detecting means for detecting the position of the image transferred on the transfer belt;
Recording medium detecting means for detecting the position of the recording medium conveyed by the transfer belt;
Control means for controlling at least one of the image forming position of the image carrier and the transport position of the recording medium by the transport means based on the detection result of the image detection means and the detection result of the recording medium detection means. An image forming apparatus characterized by that.

  The invention described in claim 2 calculates the amount of deviation between the ideal image and the position of the recording medium based on the detection result of the image detection means and the detection result of the recording medium detection means. The image forming apparatus according to claim 1, further comprising a calculation unit.

  Furthermore, the invention described in claim 3 performs the detection of the image position by the image detection means and the detection of the position of the recording medium by the recording medium detection means a plurality of times. 3. The image forming apparatus according to claim 1, wherein an average value of the positions is used for controlling at least one of an image forming position of the image carrier and a transport position of the recording medium by the transport unit. is there.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the image detection unit also serves as the recording medium detection unit.

  According to the first aspect of the present invention, it is possible to correct the positional deviation between the image and the recording medium.

  According to the second aspect of the present invention, the amount of deviation between the image and the position of the recording medium can be easily calculated.

  According to the third aspect of the present invention, it is possible to improve the detection accuracy of the amount of deviation between the image and the position of the recording medium.

  According to the invention described in claim 4, the apparatus configuration can be simplified.

1 is a configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. 1 is a configuration diagram showing a main part of an image forming apparatus according to Embodiment 1 of the present invention. 1 is a configuration diagram showing a main part of an image forming apparatus according to Embodiment 1 of the present invention. It is a block diagram which shows a control circuit. FIG. 6 is a schematic diagram illustrating a detection state of a toner patch and a recording sheet. FIG. 6 is a schematic diagram illustrating a deviation amount between a toner patch and a recording sheet. It is a block diagram which shows the image forming apparatus which concerns on Embodiment 2 of this invention. FIG. 6 is a schematic diagram illustrating image positions on the front surface and the back surface of a recording sheet. FIG. 6 is a schematic diagram illustrating image positions after correction of the front and back surfaces of a recording sheet.

  Hereinafter, modes for carrying out the present invention (hereinafter referred to as “embodiments”) will be described with reference to the drawings.

[Embodiment 1]
1 and 2 show an image forming apparatus according to the first embodiment. FIG. 1 shows an outline of the entire image forming apparatus, and FIG. 2 shows an enlarged main part (image forming apparatus, etc.) in the image forming apparatus.

<Overall Configuration of Image Forming Apparatus>
The image forming apparatus 1 according to the first embodiment is configured as a color printer, for example. The image forming apparatus 1 holds a plurality of image forming apparatuses 10 as image forming means for forming toner images developed with toner constituting the developer 4 and toner images formed by the respective image forming apparatuses 10. Then, an intermediate transfer device 20 that finally transports to a secondary transfer position for secondary transfer to a recording paper 5 as an example of a recording medium, and a required recording paper 5 to be supplied to the secondary transfer position of the intermediate transfer device 20 A sheet feeding device 50 that accommodates and conveys the toner, and a fixing device 40 that fixes the toner image on the recording paper 5 secondarily transferred by the intermediate transfer device 20.

  For example, the image forming apparatus 1 can be configured as a color copying machine when an image input device 60 for inputting a document image to be formed on the recording paper 5 is additionally provided. In the drawing, 1a represents a housing of the image forming apparatus, and the housing 1a is formed of a support structure member, an exterior cover, and the like. Also, the alternate long and short dash line in the figure indicates the main transport path through which the recording paper 5 is transported in the housing 1a.

<Configuration of Main Part of Image Forming Apparatus>
The image forming apparatus 10 exclusively forms four color toner images of yellow (Y), magenta (M), cyan (C), and black (K) and two types of toner images of special colors S1 and S2. It is composed of six image forming apparatuses 10Y, 10M, 10C, 10K, 10S1, and 10S2. The six image forming apparatuses 10 (S1, S2, Y, M, C, and K) are arranged so as to be arranged in a line in the internal space of the housing 1a. As the developer 4 (S1, S2) of the special color (S1, S2), for example, those composed of color materials that are difficult or impossible to express with the above four colors are used. Is a toner of a color other than the above four colors, a toner having the same color as that of the above four color toners and having a different saturation, a transparent toner for improving gloss, a foaming toner for Braille, a fluorescent color toner, and the like. In addition, the image forming apparatuses 10 (S1, S2, Y, M, C, and K) have substantially the same configuration as described below except that the types of developers to be handled are different.

  Each image forming apparatus 10 (S1, S2, Y, M, C, K) includes a rotating photosensitive drum 11 as shown in FIG. 1 and FIG. Such devices are mainly arranged. The main devices are a charging device 12 that charges a peripheral surface (image holding surface) on which the image can be formed on the photosensitive drum 11 to a required potential, and image information (signal) on the charged peripheral surface of the photosensitive drum 11. Exposure device 13 that forms an electrostatic latent image having a potential difference (for each color) by irradiating light LB based on the above, and corresponding colors (S1, S2, Y, M, C, K) of the electrostatic latent image A developing device 14 (S1, S2, Y, M, C, K) that is developed with the toner of the developer 4 to form a toner image, a primary transfer device 15 that transfers the toner images to the intermediate transfer device 20, and A pre-cleaning charging device 16 for charging a toner or other adhering matter remaining on the image holding surface of the photosensitive drum 11 after the primary transfer, a drum cleaning device 17 for removing the recharged adhering matter and cleaning, and a photosensitive member A static eliminator 18 for neutralizing the image holding surface after cleaning the drum 11. It is.

  The photosensitive drum 11 is formed by forming an image holding surface having a photoconductive layer (photosensitive layer) made of a photosensitive material on the peripheral surface of a cylindrical or columnar substrate to be grounded. The photosensitive drum 11 is supported so as to rotate in a direction indicated by an arrow A when power is transmitted from a rotation driving device (not shown).

  The charging device 12 is configured by a non-contact type charging device such as a corona discharger that is disposed without being in contact with the photosensitive drum 11. The charging device 12 is supplied with a charging voltage to the discharge member. As the charging voltage, when the developing device 14 performs reversal development, a voltage or current having the same polarity as the charging polarity of the toner supplied from the developing device 14 is supplied.

  The exposure device 13 irradiates light (dotted line with arrows) LB configured according to image information input to the image forming apparatus 1 onto the peripheral surface of the photosensitive drum 11 after being charged. It forms a latent image. When the latent image is formed, image information (signal) input to the image forming apparatus 1 by any means is transmitted to the exposure apparatus 13.

  As shown in FIG. 2, each of the developing devices 14 (S1, S2, Y, M, C, and K) includes a developer in a housing 140 in which an opening and a storage chamber for the developer 4 are formed. 2 developing rolls 141 and 142 that respectively convey the developer 4 to two development areas facing the photosensitive drum 11, and two screw augers that convey the developer 4 while passing the developing roll 142 while stirring. The agitating / conveying members 143 and 144 and the layer thickness regulating member 145 for regulating the amount (layer thickness) of the developer held on the developing roll 142 are arranged. A developing voltage is supplied to the developing device 14 between the developing rolls 141 and 142 and the photosensitive drum 11 from a power supply device (not shown). Further, the developing rolls 141 and 142 and the agitating / conveying members 143 and 144 are rotated in a required direction by receiving power from a rotation driving device (not shown). Further, as the four color developers 4 (Y, M, C, K) and the two special color developers 4 (S1, S2), a two-component developer containing a non-magnetic toner and a magnetic carrier is used. Is done.

  The primary transfer device 15 is a contact type transfer device including a primary transfer roll that rotates in contact with the peripheral surface of the photosensitive drum 11 and is supplied with a primary transfer voltage. As the primary transfer voltage, a DC voltage having a polarity opposite to the charging polarity of the toner is supplied from a power supply device (not shown).

  As shown in FIG. 2, the drum cleaning device 17 is disposed so as to be in contact with the peripheral surface of the photosensitive drum 11 after the primary transfer and the peripheral surface of the photosensitive drum 11 after the primary transfer with a required pressure. A cleaning plate 171 that removes deposits such as a cleaning member, a rotating brush roll 172 that is arranged to contact and rotate on the circumferential surface of the photosensitive drum 11 on the upstream side of the cleaning plate 171 in the rotational direction of the photosensitive drum 11; It consists of a sending member 173 such as a screw auger that collects and removes the adhered matter such as toner removed by the cleaning plate 171 and sends it to a collecting system (not shown). As the cleaning plate 171, a plate-like member (for example, a blade) made of a material such as rubber is used.

  As shown in FIG. 1, the intermediate transfer device 20 is disposed so as to exist at a position below each image forming device 10 (S1, S2, Y, M, C, K). The intermediate transfer device 20 includes an intermediate transfer belt 21 as an image carrier belt that rotates in a direction indicated by an arrow B while passing a primary transfer position between the photosensitive drum 11 and the primary transfer device 15 (primary transfer roll). A plurality of belt support rolls 22 to 27 that hold the intermediate transfer belt 21 in a desired state from the inner surface thereof and rotatably support the outer peripheral surface of the intermediate transfer belt 21 supported by the belt support roll 26 (image holding). A secondary transfer device 30 that is arranged on the surface) side for secondary transfer of the toner image on the intermediate transfer belt 21 to the recording paper 5, and remains on the outer peripheral surface of the intermediate transfer belt 21 after passing through the secondary transfer device 30. And a belt cleaning device 28 that removes and removes adhering substances such as toner and paper dust.

  As the intermediate transfer belt 21, for example, an endless belt made of a material in which a resistance adjusting agent such as carbon black is dispersed in a synthetic resin such as polyimide resin or polyamide resin is used. The belt support roll 22 is configured as a drive roll, the belt support rolls 23, 25, and 27 are configured as driven rolls that hold the travel position of the intermediate transfer belt 21, and the belt support roll 24 is configured as a tension applying roll. The belt support roll 26 is configured as a secondary transfer backup roll.

  As shown in FIG. 1, the secondary transfer device 30 passes through a secondary transfer position that is an outer peripheral surface portion of the intermediate transfer belt 31 supported by the belt support roll 26 in the intermediate transfer device 20 by an arrow C. A secondary transfer belt 31 as a transfer belt that rotates in the direction shown, a plurality of support rolls 32-36 that hold the secondary transfer belt 31 in a desired state from its inner surface and rotatably support it, and secondary transfer The toner adhering to the outer peripheral surface of the secondary transfer bell 31 after passing the position, the toner image for detecting the image position transferred to the outer peripheral surface of the secondary transfer bell 31, and the adhering material such as paper dust are removed and cleaned. It comprises a belt cleaning device 37. As the secondary transfer belt 31, for example, an endless belt manufactured with substantially the same configuration as the above-described intermediate transfer belt 21 is used. The belt support roll 32 is disposed so as to press the secondary transfer belt 31 against the outer peripheral surface of the intermediate transfer belt 21 supported by the belt support roll 26 with a required pressure. The belt support roll 32 is configured as a drive roll, and the belt support roll 36 is configured as a tension applying roll. Further, a DC voltage having a polarity opposite to or the same as the charging polarity of the toner is supplied as a secondary transfer voltage to the belt support roll 32 of the secondary transfer device 30 or the support roll 26 of the intermediate transfer device 20.

  The fixing device 40 is heated by a heating unit so as to rotate in a direction indicated by an arrow and to keep a surface temperature at a predetermined temperature inside a casing 41 in which an inlet and an outlet for the recording paper 5 are formed. A heating rotator 42 provided with a fixing belt, and a drum-type pressurizing rotator 43 that rotates in contact with the heating rotator 42 in a state substantially along the axial direction of the heating rotator 42 are arranged. Is. In the fixing device 40, the contact portion where the heating rotator 42 and the pressing rotator 43 come into contact becomes a fixing processing unit that performs a required fixing process (heating and pressing).

  The paper feeding device 50 is disposed so as to exist at a position below the intermediate transfer device 20 and the secondary transfer device 30. The paper feeding device 50 is a single (or plural) paper container 51 that accommodates recording papers 5 of a desired size and type, and sends out the recording paper 5 from the paper container 51 one by one. The apparatus 52 is mainly configured. The paper container 51 is attached, for example, so that it can be pulled out to the front surface (side surface that the user faces during operation) of the housing 1a.

  Between the paper feeding device 50 and the secondary transfer device 30, a plurality of paper conveyance roll pairs 53 to 57 for conveying the recording paper 5 delivered from the paper feeding device 50 to the secondary transfer position and a conveyance guide material (not shown). A sheet feeding / conveying device 58 is provided as a configured conveying means. A pair of paper transport rollers 57 disposed at a position immediately before the secondary transfer position in the paper feed transport device 58 adjusts the transport timing of the recording paper 5, for example, so that the recording paper eventually reaches the secondary transfer position. 5 is configured as a roll (registration roll) for adjusting the position 5. Further, between the secondary transfer device 30 and the fixing device 40, a belt form for conveying the recording paper 5 after the secondary transfer fed from the secondary transfer belt 31 of the secondary transfer device 30 to the fixing device 40. A conveying device 58a is provided. Further, a sheet discharge roll pair 59a for discharging the fixed recording sheet 5 sent out from the fixing device 40 to the outside of the casing 1a is provided in a portion near the sheet discharge port formed in the casing 1a. ing.

  The image input device 60 provided in the case of configuring as the above-described color copying machine is an image reading device that reads an image of a document having image information to be printed. For example, as shown in FIG. Arranged at the top of la. This image input device 60 illuminates while moving a document placing plate (platen glass) 61 made of a transparent glass plate or the like on which a document 6 having image information to be read is placed, and a document 6 placed on the document placing plate 61. A light source 62 that moves along with the light source 62, receives the reflected light from the document 6 and reflects it in a predetermined direction, and moves at a predetermined speed and a predetermined distance with respect to the reflective mirror 63. The first reflection mirror 64 and the second reflection mirror 65, the image reading element 66 composed of a CCD or the like that receives and reads the reflected light from the document 6 and converts it into an electrical signal, and forms an image of the reflected light on the image reading element 66. It is mainly composed of an imaging lens 67 and the like. A reference numeral 68 in FIG. 1 is an open / close cover that closes the document placing plate 61.

  Further, the image information of the document read and input by the image input device 60 is subjected to necessary image processing by the image processing device 70. First, in the image input device 60, the image information of the read original is converted into, for example, red (R), green (G), and blue (B) image data (for example, 8-bit data) to the image processing device 70. Send. On the other hand, the image processing device 70 performs predetermined image processing such as shading correction, misregistration correction, brightness / color space conversion, gamma correction, bordering, color / movement editing, and the like on the image data transmitted from the image input device 60. Apply processing. Further, the image processing apparatus 70 changes the image signal subjected to the image processing to each of the four color (Y, M, C, K) image signals, and then transmits them to the exposure apparatus 13. The image processing device 40 also generates image signals for the two special colors (S1, S2).

<Operation of Entire and Main Parts of Image Forming Apparatus>
Hereinafter, a basic image forming operation by the image forming apparatus 1 will be described.

  Here, first, a full-color image constituted by combining toner images of four colors (Y, M, C, K) using the four image forming devices 10 (Y, M, C, K). The image forming operation at the time of forming will be described as a representative.

  When the image forming apparatus 1 receives command information for requesting an image forming operation (printing), the four image forming apparatuses 10 (Y, M, C, K), the intermediate transfer apparatus 20, the secondary transfer apparatus 30, and the fixing apparatus. 40 etc. starts.

  In each image forming device 10 (Y, M, C, K), each photosensitive drum 11 is first rotated in the direction indicated by arrow A, and each charging device 12 causes the surface of each photosensitive drum 11 to have a required polarity ( In Embodiment Mode 1, they are charged to a negative polarity) and a potential. Subsequently, the exposure device 13 converts the image information input to the image forming device 1 into each color component (Y, M, C, K) on the surface of the photosensitive drum 11 after charging. Light LB emitted based on the signal is irradiated, and an electrostatic latent image of each color component constituted by a required potential difference is formed on the surface thereof.

  Subsequently, each developing device 14 (Y, M, C, K) corresponds to an electrostatic latent image of each color component formed on the photosensitive drum 11 with a corresponding color (negative polarity) charged to a required polarity (minus polarity). Y, M, C, and K) toners are supplied from the developing rolls 141 and 142, respectively, and electrostatically attached to perform development. By this development, the electrostatic latent images of the respective color components formed on the respective photosensitive drums 11 are visualized as toner images of four colors (Y, M, C, K) respectively developed with the corresponding color toners. Is done.

  Subsequently, when each color toner image formed on the photosensitive drum 11 of each image forming device 10 (Y, M, C, K) is conveyed to the primary transfer position, the primary transfer device 15 causes the toner of each color. The image is primarily transferred in such a manner that the image is sequentially superimposed on the intermediate transfer belt 21 rotating in the direction indicated by the arrow B of the intermediate transfer device 20.

  In each image forming apparatus 10 after the primary transfer, the pre-cleaning charging device 16 recharges the adhering matter such as toner remaining on the surface of the photosensitive drum 11 after the primary transfer, and then the drum cleaning device 17 recharges. The surface of the photosensitive drum 11 is cleaned by scraping off the adhered matter, and finally the static eliminator 18 neutralizes the surface of the photosensitive drum 11 after cleaning. Thereby, each image forming apparatus 10 is brought into a state in which the next image forming operation can be performed.

  Subsequently, in the intermediate transfer device 20, the toner image primarily transferred by the rotation of the intermediate transfer belt 21 is held and conveyed to the secondary transfer position. On the other hand, the paper feeding device 50 sends the required recording paper 5 to the paper feeding / conveying device 58 in accordance with the image forming operation. In the paper feeding / conveying device 58, a pair of paper conveying rolls 57 serving as registration rolls feeds the recording paper 5 to the secondary transfer position in accordance with the transfer timing.

  At the secondary transfer position, the secondary transfer device 30 collectively transfers the toner image on the intermediate transfer belt 21 onto the recording paper 5. In addition, in the intermediate transfer device 20 that has finished the secondary transfer, the belt cleaning device 28 removes and removes deposits such as toner remaining on the surface of the intermediate transfer belt 21 after the secondary transfer.

  Subsequently, the recording sheet 5 on which the toner image is secondarily transferred is peeled from the intermediate transfer belt 21 and the secondary transfer belt 31 and then conveyed to the fixing device 40 by the conveying device 58a. In the fixing device 40, necessary recording processing (heating and pressing) is performed by introducing the recording paper 5 after the secondary transfer through the contact portion between the rotating heating rotating body 42 and the pressing rotating body 43. ) To fix the unfixed toner image on the paper 5. Finally, the recording paper 5 after the fixing is completed is set, for example, outside the casing 1a by the paper discharge roll pair 59a in the image forming operation only for forming an image on one side thereof. Not discharged to the discharge container.

  Through the above operation, the recording paper 5 on which a full color image formed by combining four color toner images is output.

  Next, the operation when the image forming apparatus 1 forms a special color toner image composed of the developer of the special colors S1 and S2 when performing the normal image formation described above, for example, will be described.

  In this case, first, in the image forming apparatuses 10S1 and 10S2, the same image forming operation as that of the image forming apparatus 10 (Y, M, C, K) described above is performed. Special color toner images (S1, S2) are formed on the photosensitive drum 11, respectively. Subsequently, the special color toner images formed by the image forming devices 10S1 and 10S2 are primarily transferred to the intermediate transfer belt 21 of the intermediate transfer device 20 in the same manner as the image forming operation related to the four color toner images described above. After that, the secondary transfer device 30 performs secondary transfer from the intermediate transfer belt 21 to the recording paper 5 (along with toner images of other colors). Finally, the recording paper 5 on which the special color toner image and the other color toner image are secondarily transferred is subjected to a fixing process in the fixing device 40 and then discharged to the outside of the housing 1a.

  Through the above operation, the recording paper 5 formed so that the two special color toner images are overlapped on the entire surface or a part of the full color image formed by combining the above-described four color toner images is output. The

  In addition, when the image forming apparatus 1 is a color copying machine equipped with the image input device 60, the basic image forming operation is performed as follows.

  That is, in this case, when the document 6 is set in the image input device 60 and the command information for the request for the image forming operation (copy) is received, the image input device 60 reads the document image of the document 6 and then The information of the read original image is subjected to the image processing as described above in the image processing device 70 and is generated as an image signal. Thereafter, the image signal is transmitted to each image forming device 10 (S1, S2, Y, (M, C, K). As a result, each image forming device 10 performs electrostatic latent image formation and toner image formation based on the image information of the document 6. Thereafter, the same operation as in the case of the image forming operation (printing) described above is performed, and finally an image composed of the toner image is formed on the recording paper 5 and output.

<Recording Medium and Image Forming Position Detection Toner Image Detection Device>
In this image forming apparatus 1, as shown in FIG. 3, on the surface of the secondary transfer belt 31, the position of the recording paper 5 conveyed by the secondary transfer belt 31 and the surface of the secondary transfer belt 31 are transferred. An image forming position detection toner image (hereinafter referred to as “toner patch”) 38 is provided with a detection device 80 including a registration sensor that detects both positions. The detection device 80 is arranged in the moving direction of the secondary transfer belt 31 with respect to the secondary transfer position where the support roll 26 that supports the intermediate transfer belt 21 and the support roll 32 that supports the secondary transfer belt 31 are in contact with each other. The detection position is arranged at a position separated by a predetermined distance L0 on the downstream side.

  The detection device 80 is transferred to the surface of the secondary transfer belt 31, for example, a light emitting element that irradiates light on the surface of the secondary transfer belt 31, the recording paper 5 conveyed by the secondary transfer belt 31, and the surface of the secondary transfer belt 31. The optical sensor is combined with a light receiving element that receives reflected light from the toner patch 38. A detection signal is output from the detection device 80 when the recording sheet 5 conveyed by the secondary transfer belt 31 and the toner patch 38 transferred to the surface of the secondary transfer belt 31 are detected.

  In the illustrated example, the case where both the recording paper 5 and the toner patch 38 are detected by one detection device 80 has been described. However, the detection devices for detecting the recording paper 5 and the toner patch 38 are provided separately. May be.

<Configuration of control device>
FIG. 4 is a block diagram showing a control device of the image forming apparatus according to this embodiment.

  In FIG. 4, reference numeral 100 denotes a CPU as a control unit and a calculation unit that controls the operation of the image forming apparatus 1. The CPU 100 is stored in the RAM 102 based on a program stored in advance in the ROM 101. Various operations of the image forming apparatus are controlled with reference to parameters and the like.

  Reference numeral 103 denotes a user interface for the user to operate the image forming apparatus, 104 denotes an environmental sensor for detecting at least one of temperature and humidity, and 80 denotes a detection device as a registration sensor.

  Further, reference numerals 10S1, 10S2, 10Y, 10M, 10C, and 10K indicate special color S1 and S2, and image forming apparatuses for yellow (Y), magenta (M), cyan (C), and black (K). .

  Reference numeral 59 denotes a registration motor that rotationally drives the registration roll 57.

  In the above configuration, the image forming apparatus according to the present embodiment can correct the positional deviation between the image and the recording medium in the following manner.

  By the way, in recent image forming apparatuses, the process speed in each image forming apparatus 10 (S1, S2, Y, M, C, K, and the like) has been increased with the improvement of productivity, and the needs of users. The types of recording paper 5 have been diversified along with the diversification of the recording medium. At this time, there may be a difference between the image formation position and the recording paper 5 conveyance position, including the case where the environment changes or the type of the recording medium is different. There is a possibility that the position of the image to be shifted will be displaced.

  Therefore, in the image forming apparatus 1 according to this embodiment, when the environment such as temperature and humidity fluctuates beyond a predetermined threshold, the image is formed on the recording paper 5 of a predetermined number of sheets when the apparatus is turned on. When a predetermined condition is satisfied, such as when the number of rotations of the photosensitive drum 11 reaches a predetermined value when formed, or when the pause time of the image forming apparatus 1 exceeds a predetermined value. The adjustment mode is executed automatically or by the user operating the user interface 103.

  When the predetermined condition described above is satisfied, or when a command (signal) for starting the adjustment mode is received, the CPU 100 selects yellow (Y), magenta (M), cyan (C), and black (K). Each color image forming device 10 (Y, M, C, K) and each color image forming device 10 (S1, S2) of special colors S1, S2 form toner patches 38 of each color, and this toner patch 38 is used. As shown in FIG. 5, the image is transferred to a predetermined position of a non-image area (inter-image portion) 39 located between adjacent recording sheets 5 on the secondary transfer belt 31 through the intermediate transfer belt 21. To do.

  Further, the CPU 100, for example, records the recording paper 5 of a predetermined size and type or a size and type specified by the user through the user interface 103 at the same timing as that for normal image formation. In addition to feeding from the sheet feeding device 50, the sheet is conveyed through a sheet conveying device 58 having a pair of sheet conveying rolls 53 to 57, and passes through the secondary transfer position by the secondary transfer belt 31 without transferring an image. The operation of conveying and discharging as it is is performed. At that time, the fixing device 40 is in an unheated state, for example.

  Next, on the secondary transfer belt 31, the CPU 100 detects the center position of the toner patch 38 formed in the non-image area 39 and the leading edge position 5 a and the trailing edge position 5 b of the recording paper 5 by the detection device 80. At that time, in order to improve detection accuracy, the CPU 100 feeds a plurality of (for example, about 20) recording sheets 5 and forms and detects a plurality (for example, about 20) of toner patches 38. Is desirable.

  Image forming devices 10 (Y, M, C, K) of four colors of yellow (Y), magenta (M), cyan (C), and black (K), and image forming devices 10 of special colors S1, S2. When there is no position shift in the image forming position of (S1, S2), as shown in FIGS. 5 and 6, the position of the toner patch 38 is set as a predetermined target reference position 38a. 80. For example, the toner patch 38 is formed of an image formed in a straight line having a predetermined width along a direction intersecting the moving direction of the secondary transfer belt 31, and the position (for example, the center position) is set. It is detected by the detection device 80.

  On the other hand, each image forming device 10 (Y, M, C, K) of four colors of yellow (Y), magenta (M), cyan (C), and black (K), and special colors S1, S2 are formed. When the image forming position of the apparatus 10 (S1, S2) is displaced, the detection position of the toner patch 38 is detected in a state of being deviated from a predetermined reference position 38a.

  As shown in FIG. 6, the CPU 100 shifts the actual toner patch 38 position from the ideal position 38 a of the target toner patch 38, so that the actual toner patch 38 position and the leading edge 5 a of the recording paper 5 Therefore, the position of the image formed on the recording paper 5 is shifted.

  Therefore, the CPU 100 calculates the positional deviation amount ΔG so that the distance G between the actual position of the toner patch 38 and the leading edge 5a of the recording paper 5 is equal to the ideal distance, and cancels the deviation amount ΔG. A correction amount of the image forming position is obtained. At this time, it is desirable that the CPU 100 detects the positions of the plurality of toner patches 38 of the same color and performs an arithmetic process for averaging the deviation amount ΔG from the reference position to calculate the deviation amount. A correction amount that cancels the calculated deviation amount of the toner patch 38 is stored in the RAM 102. The toner patch 38 is formed of any one single color among the six colors of special colors S1 and S2, yellow (Y), magenta (M), cyan (C), and black (K). The color may be a color used as a reference for a relative color misregistration adjustment operation of a plurality of colors, or may be a color used for misregistration adjustment between a sheet and an image. For example, black (K), special color S1 arranged at the head, or yellow (Y).

  Then, at the time of the next image formation, the image forming position of each image forming device 10 (S1, S2, Y, M, C, K) is an appropriate position so that correction processing based on the obtained correction amount is performed. Thus, the image forming position is controlled. Note that an image other than the color on which the toner patch 38 is formed can be adjusted by a known relative color misregistration adjustment operation for a plurality of colors. Here, since the position of the toner patch 38 detected by the detection device 80 is a position along the process direction, that is, the rotation direction of the photosensitive drum 11, the position of the photosensitive drum 11 is controlled in order to control the image forming position. The CPU 100 performs correction processing for changing the writing start time of the image by the exposure device 13 on the peripheral surface.

  As described above, in the image forming apparatus according to the above-described embodiment, the image forming apparatuses 10 (Y, M, C, and Y) of four colors of yellow (Y), magenta (M), cyan (C), and black (K) are used. K) and the position of the toner patch 38 and the recording paper 5 formed by any one of the image forming devices 10 (S1, S2) of the special colors S1, S2 are detected on the secondary transfer belt 31. Thus, the positions of the toner patch 38 and the recording paper 5 can be detected under the same conditions as in actual image formation. For this reason, even when the image is misaligned due to a variation factor such as environmental variation or the type of the recording paper 5, the normal transfer of the toner image onto the recording paper 5 is normally performed on the secondary transfer belt 31. The positions of the toner patch 38 and the recording paper 5 can be detected under the same conditions as in image formation, and correction control in accordance with actual image formation is possible.

  Further, in the image forming apparatus according to the above-described embodiment, the toner patch 38 and the recording paper 5 can be continuously formed, and the amount of deviation between the two can be continuously detected. Thereafter, the image forming operation can be started without causing a long time.

  Since the recording paper 5 used for detection has no image transferred thereon, it can be used for image formation in the same way as the normal recording paper 5, and the recording paper 5 is not wasted.

  Furthermore, in the above-described embodiment, it is only necessary that the position of the image on the secondary transfer belt 31 is a predetermined position. Therefore, it is not always necessary to correct both the image position and the conveyance position of the recording paper 5. One position may be corrected so that the positions of the patch 38 and the recording paper 5 satisfy a predetermined positional relationship.

  That is, in this embodiment, by controlling the rotational drive timing of the registration motor 59, the timing at which the leading edge of the recording paper 5 reaches the secondary transfer portion, that is, the leading edge position of the recording paper 5 is controlled. May be.

  Further, by using the average value of the values measured a plurality of times, it is possible to reduce the variation for each recording sheet 5. This average value is reset when the type of the recording paper 5 is changed or when the environmental conditions are changed.

[Embodiment 2]
FIG. 7 shows an image forming apparatus according to the second embodiment. This image forming apparatus can form images on both sides of a recording sheet.

  As shown in FIG. 7, the image forming apparatus 1 reverses the front and back of the recording paper 5 on which the image is formed on the front surface (first surface), and conveys it again to the secondary transfer position of the intermediate transfer belt 21. A double-sided paper transport device 90 is provided. On the downstream side of the fixing device 40, a conveyance path switching unit 91 that switches the conveyance path of the recording paper 5 between the paper discharge roll pair 59 side and the double-sided paper conveyance device 90 side is disposed. The double-sided paper conveyance device 90 includes a paper reversing unit 92 that reverses the front and back of the recording paper 5 that has been subjected to fixing processing on the front surface (first surface) by the fixing device 40, and the back surface of the recording paper 5 that has been reversed. A pair of conveyance rolls 93 to 98 that convey the (second surface) again so as to reach the secondary transfer position of the intermediate transfer belt 12 of the intermediate transfer device 20 and a conveyance guide (not shown) are provided. It is connected to the transport device 58.

  Incidentally, the double-sided paper transport device 90 reverses the front and back by reversing the transport direction of the recording paper 5 on which the image is formed on the front surface (first surface). The image forming direction for forming an image on the first surface and the image forming direction for forming an image on the back surface (second surface) of the recording paper 5 are opposite to each other.

  In the image forming apparatus 1, as shown in FIG. 8, both the front surface and the back surface of the recording paper 5 are formed with a predetermined length d in the leading edge 5 a of the recording paper 5. On the back surface (second surface) that is set and the transport direction is the reverse direction, the image formation position may deviate from the front surface (first surface).

  Therefore, in the second embodiment, the position of the image formed on the back surface of the recording paper 5 is set as follows so that the position of the image formed on the front surface of the recording paper 5 matches the position of the image formed on the back surface. I have control.

  That is, the CPU 100 actually feeds the recording paper 5 in the adjustment mode, detects the leading edge 5a and the trailing edge 5b of the recording paper 5 on the secondary transfer belt 31 by the detection device 80, and determines the total length of the recording paper 5. L1 is obtained. Then, when the CPU 100 forms an image on the back surface of the recording paper 5, the CPU 100 does not form an image with a predetermined length d at the leading end of the recording paper 5, but obtains the obtained recording paper. A value (L1-L2-d) obtained by subtracting the length L2 of the image area and the length d of the leading edge margin from the total length L1 of 5 is set to the margin length set at the leading edge of the back surface of the recording paper 5. An image is formed during actual image formation.

  In this embodiment, in order to be able to detect a change in the length of the recording paper 5 due to the recording paper 5 passing through the fixing device 40, the fixing device 40 is heated in the same manner as in normal image formation. It is desirable.

  By controlling in this way, it is possible to form an image without causing image displacement on the front and back surfaces of the recording paper 5. Further, even when the total length L1 of the recording paper 5 changes due to the recording paper 5 passing through the fixing device 40, the positions of the images formed on the front surface and the back surface of the recording paper 5 can be made to coincide with each other. it can.

  In the above embodiment, the configuration of the image forming apparatus using the intermediate transfer member and the secondary transfer belt has been described. However, regardless of this configuration, the image is directly transferred from the photosensitive drum to the recording medium conveyed by the transfer belt. The present invention is also applicable to an image forming apparatus using a direct transfer method.

  In such a tandem type direct transfer type image forming apparatus, a registration sensor for color registration adjustment is generally arranged on a transfer belt, but a patch formed between sheets by this registration sensor is detected. And paper edge detection may be performed.

  11: photosensitive drum, 21: intermediate transfer belt, 31: secondary transfer belt, 38: toner patch, 50: paper feeding device, 80: detection device, 100: CPU.

Claims (4)

An image carrier,
A transfer belt that conveys a recording medium on which an image formed on the image carrier is transferred directly or via an image carrier belt;
Conveying means for conveying the recording medium to a transfer position of the transfer belt;
Image detecting means for detecting the position of the image transferred on the transfer belt;
Recording medium detecting means for detecting the position of the recording medium conveyed by the transfer belt;
Control means for controlling at least one of the image forming position of the image carrier and the transport position of the recording medium by the transport means based on the detection result of the image detection means and the detection result of the recording medium detection means. An image forming apparatus.   And a calculation unit configured to calculate a deviation amount between an ideal image and the position of the recording medium based on a detection result of the image detection unit and a detection result of the recording medium detection unit. Item 2. The image forming apparatus according to Item 1.   The detection of the image position by the image detection means and the detection of the position of the recording medium by the recording medium detection means are performed a plurality of times, and the average value of the image position and the position of the recording medium detected a plurality of times is used as the image of the image carrier. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus is used for controlling at least one of a forming position and a conveying position of the recording medium by the conveying unit.   The image forming apparatus according to claim 1, wherein the image detection unit also serves as the recording medium detection unit.

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