JP2022037725A - Image sensor fitting inclination detection device and image forming apparatus including the same - Google Patents

Abstract

To accurately detect the fitting inclination of a pair of registration sensors included in an image forming apparatus.SOLUTION: A registration sensor fitting inclination detection device forms a uniform density image having a predetermined length in its rotation direction on an image carrier; in a transfer operation for transferring the uniform density image to an intermediate transfer belt, stops a transfer bias application operation from a transfer power supply for a predetermined time; and forms a non-transfer image part in the uniform density image transferred to the intermediate transfer belt. Based on edge information on the non-transfer image part obtained by a pair of registration sensors, the registration sensor fitting inclination detection device detects the fitting inclination of the pair of image sensors with respect to a direction orthogonal to a conveyance direction of the intermediate transfer belt.SELECTED DRAWING: Figure 11

Description

The present invention relates to an image sensor mounting tilt detection device provided for adjusting an image writing angle in an image forming device such as a copy machine.

Conventionally, in an image forming apparatus such as a copier, a configuration for adjusting an image writing angle (SKEW) has been adopted. In this configuration, for example, two batch images drawn in the axial direction of the photoconductor drum using an image writing unit are transferred to an image forming region of an intermediate transfer belt, and at positions corresponding to the two patch images, respectively. A resist sensor (image sensor) is provided, and the straight lines connecting the two resist sensors are arranged so as to be orthogonal to the transport direction of the intermediate transfer belt. Then, the two resist sensors detect two batch images on the intermediate transfer belt, and the image writing angle is adjusted so as to eliminate the detection time difference.

By the way, in the two resist sensors, a straight line connecting the two resist sensors is in the middle due to the position tolerance of a plurality of internal elements, the assembly variation, the mounting position tolerance, and the position tolerance of the member to which the resist sensor is mounted. The current situation is that the sensor mounting tilt is not accurately perpendicular to the transfer direction of the transfer belt, and is actually slightly tilted.

When the sensor mounting tilt exists in this way, even if the image writing angle is adjusted based on the detection time difference between the two resist sensors, the adjusted image writing angle is the sensor mounting tilt. It is difficult to accurately adjust the image writing angle because of the deviation. As a result, for example, when producing a printed matter that is folded in half, there is a drawback that the folded lines and the cuts of the print are not parallel to each other, and when printing on both sides of the recording paper, the horizontal lines drawn at the same place are on the front side and the back side. There is a drawback that problems such as crossing are generated because they are not parallel to each other.

Under these circumstances, conventionally, for example, grid patterns are drawn on both sides of a recording paper, the positional deviation between the grid patterns is measured using a measuring instrument, and an image is written based on the measurement results. The operator manually adjusts the angle. However, such manual adjustment requires a lot of time and effort, and has a drawback that the adjustment requires manpower and a long time.

Conventionally, there is a technique described in Patent Document 1 as a technique related to the sensor mounting inclination. This technology draws a horizontal line pattern (a pattern extending in a direction orthogonal to the belt transport direction) on the intermediate transfer belt, detects this horizontal line pattern with two resist sensors, calculates the detection time difference, and calculates this detection time difference. As the sensor mounting tilt, the patch image drawn by the image writing unit is tilted and drawn by the tilt, thereby canceling the sensor mounting tilt, correcting the color shift between each color in this state, and then, Prior to normal image formation, the image writing angle is restored by the amount of the sensor mounting tilt.

Japanese Unexamined Patent Publication No. 2013-195691

However, the technique described in Patent Document 1 has a drawback that the image writing angle cannot be adjusted accurately, although the sensor mounting inclination is taken into consideration. That is, since the horizontal line pattern drawn by the image writing unit usually has a slight inclination in the image writing angle, when this horizontal line pattern is detected by two resist sensors, the detection time difference is increased. Both the tilt of the image writing angle and the tilt of the sensor mounting are included. Therefore, even if the image writing angle is restored by the detection time difference after the correction of the color deviation between the colors, the original minute inclination of the image writing angle still remains in the horizontal line pattern.

In this way, in the past, the image writing angle could not be adjusted accurately, but the cause is that the sensor mounting tilt and the tilt of the image writing angle are added to the detection time difference between the two resist sensors. The present inventor knew that the cause was that the two could not be calculated individually or separated. Further, since the sensor mounting tilt is caused by the mounting position tolerance as described above, the degree of the tilt differs depending on the image forming apparatus in which the resist sensor is placed, and the value of the sensor mounting tilt is used. It also turned out to be difficult to calculate theoretically.

The present invention has been made in view of the above points, and an object thereof is a sensor mounting tilt detecting device capable of detecting the sensor mounting tilt of a resist sensor (image sensor) clearly separated from the tilt of the image writing angle. It is an object of the present invention to provide an image forming apparatus capable of more accurately adjusting an image writing angle by providing a sensor-mounted tilt detecting device thereof.

The image sensor mounting tilt detection device of the present invention has an image carrier that is rotatably supported, and can be rotated by a plurality of image forming portions that form a toner image on the image carrier and a plurality of suspension rollers. It is equipped with a suspended intermediate transfer belt and a transfer power supply that is provided in the same number as the plurality of image forming portions and generates a transfer bias, and the toner image of the image carrier is transferred to the intermediate transfer belt by the application operation of the transfer bias. A pair of transfer portions to be transferred in the image forming region and a pair of both ends of the intermediate transfer belt, which are arranged at positions corresponding to the inside of the image forming region and detect a toner image transferred to the intermediate transfer belt. The image sensor is provided with a plurality of image forming units and a control unit for controlling the plurality of transfer power supplies, and the control unit may be used with respect to at least one image forming unit among the plurality of image forming units. , Corresponds to the one image forming unit during the transfer operation of forming a uniform density image having a predetermined length in the rotation direction of the image carrier and transferring the uniform density image to the intermediate transfer belt. The transfer bias application operation of the transfer power supply is stopped for a predetermined time to form a non-transfer image unit in the uniform density image transferred to the intermediate transfer belt, and the non-transfer image unit obtained by each image sensor is formed. Based on the edge information, it is characterized in that the mounting inclination of the pair of image sensors with respect to the direction orthogonal to the transport direction of the intermediate transfer belt is detected.

Further, the image forming apparatus of the present invention is an image forming apparatus having the attachment tilt detecting device of the image sensor, and has a plurality of image writing units each forming a latent image for the plurality of the image carriers. Each of the plurality of image writing units is provided with a plurality of writing angle adjusting mechanisms for adjusting the image writing angle with respect to the direction orthogonal to the rotation direction of the image carrier, and the control unit is the pair. It is characterized in that each of the plurality of writing angle adjusting mechanisms is controlled based on the edge information of the non-transferred image portion detected by the image sensor of the above.

According to the mounting tilt detection device of the image sensor of the present invention, the uniform density image transferred by stopping the application operation of the transfer bias for a predetermined time during the transfer operation of transferring the uniform density image to the intermediate transfer belt. Since it is possible to form a non-transfer image portion that extends accurately in a direction orthogonal to the transport direction of the intermediate transfer belt, it is possible to accurately detect only the sensor mounting inclination.

Further, according to the image forming apparatus of the present invention, since the sensor mounting inclination can be detected with high accuracy, the image writing angle with respect to the photoconductor drum can be adjusted with high accuracy by controlling the writing angle adjusting mechanism.

It is a vertical sectional front view which shows the internal structure of the image forming apparatus which has the attachment inclination detection apparatus of the resist sensor of embodiment. It is a front view which shows the schematic internal structure of the optical scanning apparatus provided in the image forming apparatus. It is a block diagram which shows the control system of an image forming apparatus. It is a perspective view which looked around the intermediate transfer belt of an image forming apparatus from the lower right. It is a perspective view which shows the mounting structure of a resist sensor. It is a schematic explanatory drawing which shows the state of the light irradiation of the resist sensor on the surface of an intermediate transfer belt. It is a schematic block diagram which shows the internal structure of a resist sensor and the state of light emission and light reception with respect to the surface of an intermediate transfer belt. It is a figure which shows the output signal waveform of the resist sensor at the time of detecting a toner image. It is a flowchart which shows the operation procedure of the attachment inclination detection apparatus of a resist sensor. It is a schematic diagram which shows the appearance that the uniform density image which has a white streak on an intermediate transfer belt goes to a pair of resist sensors. It is a figure which shows the appearance that the white streak passes through a pair of resist sensors, and the output signal waveform of a pair of resist sensors at the time of passing. It is a figure which shows the modification 1 of the detection structure of a sensor mounting inclination. It is a figure which shows the modification 2 of the detection structure of the sensor mounting inclination. It is a perspective view which shows the specific structure of the writing angle adjustment mechanism provided in the optical scanning apparatus. It is a flowchart which shows the operation procedure of registration adjustment. It is a top view which shows an example of the registration adjustment pattern formed on the intermediate transfer belt. It is a top view which shows the modification of the registration adjustment pattern. It is a figure which shows the output signal waveform of a pair of resist sensors which detected the registration adjustment pattern. It is explanatory drawing which shows the concrete state of the adjustment operation of an image writing angle.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view showing an embodiment of the image forming apparatus of the present invention. The image forming apparatus 1 is a multifunction device having a scanner function, a copying function, a printer function, a facsimile function, and the like, and transmits an image of a document read by the image reading device 41 to the outside (corresponding to a scanner function). ), The image of the scanned original or the image received from the outside is recorded and formed on a recording paper in color or a single color.

The image forming apparatus 1 includes an optical scanning device 11, a developing device 12, a photoconductor drum 13, a drum cleaning device 14, a charging device 15, an intermediate transfer belt device 16, an intermediate transfer belt device 16, a fixing device 17, and a paper transfer device 1 for printing an image on recording paper. It includes a path S, a paper feed tray 18, a paper discharge tray 19, and the like.

The image data handled in the image forming apparatus 1 is one corresponding to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y), or a single color (for example, black) is used. It corresponds to the monochrome image that was there. Therefore, the developing device 12, the photoconductor drum 13, the drum cleaning device 14, and the charger 15 are provided with four each so as to form four types of toner images corresponding to each color, and each of them is black, cyan, and magenta. , And yellow, and four image stations Pa, Pb, Pc, and Pd are configured.

Each photoconductor drum (image carrier) 13 is rotatably supported and has a photosensitizing layer on its surface. Each charger 15 is a charging means for uniformly charging the surface of each photoconductor drum 13 to a predetermined potential.

The optical scanning device 11 is a laser scanning unit (LSU) provided with a laser diode and a reflection mirror, and exposes the surface of each charged photoconductor drum 13 according to the image data, and corresponds to the image data on the surface thereof. It is an image writing unit that writes and forms an electrostatic latent image. The details of the configuration will be described later.

Each developing device 12 develops an electrostatic latent image formed on the surface of each photoconductor drum 13 with toner of each color, and forms a toner image on the surface of these photoconductor drums 13. Each drum cleaning device 14 removes and recovers the toner remaining on the surface of each photoconductor drum 13 after development and image transfer.

The intermediate transfer belt device 16 is arranged above each photoconductor drum 13 and includes an intermediate transfer belt 21, an intermediate transfer belt drive roller 22, a driven roller 23, four intermediate transfer rollers 24, and a belt cleaning device 25. ing.

The intermediate transfer belt 21 is formed by forming a film into an endless belt shape. The intermediate transfer belt drive roller 22, the driven roller 23, and each intermediate transfer roller 24 rotatably suspend and support the intermediate transfer belt 21 as a suspension roller, and orbit the intermediate transfer belt 21 in the belt transport direction C indicated by the arrow. Let me.

Each intermediate transfer roller 24 is rotatably supported in the vicinity of the intermediate transfer belt 21 and is pressed against each photoconductor drum 13 via the intermediate transfer belt 21. Each intermediate transfer roller 24 is a roller based on a metal (for example, stainless steel) shaft whose surface is covered with a conductive elastic material (for example, EPDM, urethane foam, etc.) and is pressed against the back surface of the intermediate transfer belt 21. ing. A transfer power supply 30 is connected to each of these intermediate transfer rollers 24. Each transfer power source 30 generates a high voltage transfer bias (a high voltage having a polarity (+) opposite to the charging polarity (−) of the toner), and applies this transfer bias to the corresponding intermediate transfer roller 24. Each intermediate transfer roller 24 transfers the toner image on the surface of the corresponding photoconductor drum 13 into the image forming region AI (see FIGS. 10 and 16) of the intermediate transfer belt 21 by the operation of applying the transfer bias of the transfer power source 30. .. The intermediate transfer belt device 16 including the plurality of intermediate transfer rollers 24 and the plurality of transfer power supplies 30 constitute a plurality of transfer units 35 for transferring the toner image on the surface of each photoconductor drum 13 to the intermediate transfer belt 21. There is.

By these transfer units 35, the toner images on the surface of each photoconductor drum 13 are sequentially superimposed and transferred in the image forming region AI of the intermediate transfer belt 21, and the color toner indicated by the image data is transferred onto the intermediate transfer belt 21. An image (toner image of each color) is formed. The toner image of this color is conveyed together with the intermediate transfer belt 21 and transferred onto the recording paper in the nip area between the intermediate transfer belt 21 and the transfer roller 26a of the secondary transfer device 26.

The transfer roller 26a of the secondary transfer device 26 has a voltage for transferring the toner image of each color on the intermediate transfer belt 21 onto the recording paper (a high voltage having a polarity (+) opposite to the charge polarity (-) of the toner). Has been applied. By applying this high voltage, the secondary transfer device 26 transfers the toner images of each color on the intermediate transfer belt 21 onto the recording paper.

The belt cleaning device 25 removes and recovers the toner remaining on the surface of the intermediate transfer belt 21 after the toner image is transferred to the recording paper.

The recording paper is transferred to the fixing device 17 after the color toner image is transferred in the nip area between the intermediate transfer belt 21 and the transfer roller 26a of the secondary transfer device 26. The fixing device 17 includes a heating roller 31, a pressure roller 32, and the like, and sandwiches and conveys recording paper between the heating roller 31 and the pressure roller 32. The heating roller 31 is controlled to have a predetermined fixing temperature, and by thermocompression bonding the recording paper together with the pressure roller 32, the color toner image transferred to the recording paper is melted, mixed, and pressure-bonded. Heat-fixed to the recording paper.

A paper feed tray 18 for supplying recording paper is provided at the bottom of the image forming apparatus 1. The image forming apparatus 1 is provided with a paper transport path S for feeding the recording paper supplied from the paper feed tray 18 to the paper discharge tray 19 via the secondary transfer device 26 and the fixing device 17.

A paper pickup roller 33 is provided at the end of the paper feed tray 18, and the paper pickup roller 33 pulls out the recording paper from the paper feed tray 18 one by one and transports the recording paper to the paper transport path S. .. In the paper transport path S, the recording paper is fixed with a color toner image by the fixing device 17, passes through the fixing device 17, and then is discharged face-down on the paper ejection tray 19 by the paper ejection roller 36.

On the other hand, an image reading device 41 and a document transporting device 42 are provided on the upper part of the image forming device 1. The document transfer device 42 is mounted on the upper part of the main body of the image forming apparatus 1, and when the front portion thereof is opened upward, the platen glass 44 of the image reading device 41 is opened and the original is placed on the platen glass 44. Placed. Further, the document transport device 42 also has a function of passing the document on the document tray 57 through the document transport path 58 between the document reading glass 55 and the reading guide plate 59, and further transporting the document from the paper ejection roller 61 to the paper ejection tray 62. Be prepared.

The image reading device 41 includes a platen glass 44, a first scanning unit 45, a second scanning unit 46, an imaging lens 47, a CCD (Charge Coupled Device) 48, and the like. The first scanning unit 45 includes a lighting device 51 and a first reflection mirror 52, and illuminates the document on the platen glass 44 while moving at a constant speed V by a distance corresponding to the document size in the sub-scanning direction. The reflected light is reflected by the first reflection mirror 52 and guided to the second scanning unit 46, whereby the image on the surface of the document is scanned in the sub-scanning direction. The second scanning unit 46 includes second and third reflection mirrors 53 and 54, and while following the first scanning unit 45 and moving at a speed of V / 2, the reflected light from the document is transmitted to the second and second scan units. It is reflected by the three reflection mirrors 53 and 54 and guided to the imaging lens 47. The imaging lens 47 collects the reflected light from the document on the CCD 48 to form an image on the surface of the document on the CCD 48. The CCD 48 repeatedly scans the image of the original document in the main scanning direction, and outputs an analog image signal of one main scanning line each time.

The image of the original document read by the CCD 48 in this way is output from the CCD 48 as an analog image signal, and this analog image signal is A / D converted into a digital image signal (image data). Then, this image data is sent to the optical scanning device 11 of the image forming apparatus 1 after being subjected to various image processing.

Next, a schematic configuration of the optical scanning device (image writing unit) 11 will be described. The optical scanning device 11 shown in FIG. 2 has a schematic configuration in which the inside of the housing is viewed from the front, and the photoconductor drum 13 is also shown.

The optical scanning device 11 in the figure is emitted from four semiconductor lasers (not shown) that operate according to the image data (digital image signal) read by the image reading device 41, and these semiconductor lasers. It includes a polygon mirror 202 in which the light beam is incident through a collimating lens and a reflection mirror, a first fθ lens 207, an exit folded mirror 208, and a second fθ lens 209, respectively. The first fθ lens 207 converts each light beam BM of diffused light from the polygon mirror 202 into parallel light in the sub-scanning direction, and converts each light beam BM of parallel light from the polygon mirror 202 into a photoconductor in the main scanning direction. The light is focused and emitted so as to have a predetermined beam diameter on the surface of the drum 13. Further, the first fθ lens 207 moves the light beam BM deflected at the equiangular velocity in the main scanning direction by the equiangular velocity motion of the polygon mirror 202 at the equilinear velocity on the main scanning line on the surface of the photoconductor drum 13. Convert.

Further, each emission folded mirror 208 reflects each light beam BM that has passed through the first fθ lens 207 and causes the light beam BM to be incident on the second fθ lens 209. The second fθ lens 209 focuses each light beam BM of parallel light so as to have a predetermined beam diameter on the surface of the photoconductor drum 13 in the sub-scanning direction, and with the focused light in the first fθ lens 207 in the main scanning direction. Each light beam BM that has become is emitted to the surface of the photoconductor drum 13 as it is.

In such an optical scanning device 11, each light beam BM is reflected and deflected by the reflecting surface of the polygon mirror 202, and is incident on each photoconductor drum 13 through each optical path, and the surface of each photoconductor drum 13 is surfaced. Is repeatedly main scanned. On the other hand, since each photoconductor drum 13 is rotationally driven, the two-dimensional surface (peripheral surface) of each photoconductor drum 13 is scanned by each light beam BM, and an electrostatic latent image is formed on the surface of each photoconductor drum 13. Will be formed.

FIG. 3 is a block diagram showing a control system of the image forming apparatus 1. In the figure, the control unit 71 integrally controls the image forming apparatus 1 and includes a CPU, RAM, ROM, various interfaces, and the like. The image forming unit 72 includes an optical scanning device 11, a developing device 12, a photoconductor drum 13, and a charger 15, and after forming an electrostatic latent image on the surface of each photoconductor drum 13, the electrostatic latent image is displayed in each color. A color toner image is formed on the surface of each photoconductor drum 13 by developing with the toner of. Further, the printing unit 73 includes an intermediate transfer belt device 16, a transfer power supply 30, a secondary transfer device 26, a fixing device 17, and the like, and after laminating and transferring a toner image on the surface of each photoconductor drum 13 onto the intermediate transfer belt 21. , Transfer to recording paper, further fixing processing, and print the image on recording paper.

For example, the control unit 71 causes the image reading device 41 to read the image of the original while the document conveying device 42 conveys the original, stores the image data indicating the image of the original in the memory 75, and the image data in the memory 75. The image of the original document shown by the above is printed on the recording paper by the image forming unit 72 and the printing unit 73, and the recording paper is discharged to the paper ejection tray 19.

In such an image forming apparatus 1, the electrostatic latent image formed on the surface of each photoconductor drum 13 is written by the optical scanning device 11, and the image writing angle thereof is the axis of the photoconductor drum 13 (main scanning direction). It is desirable that the zero degree is in a state parallel to) with high accuracy. Specifically, in the optical scanning device 11 of each color, the light beam BM from the second fθ lens 209 is irradiated to the photoconductor drums 13 of each color of black, cyan, magenta, and yellow in the main scanning direction. Drawing is repeated on the surface of each photoconductor drum 13 in the main scanning direction, but the second fθ lens 209 is not parallel to the axis (main scanning direction) of the photoconductor drum 13 and is slightly deviated and tilted. The image writing angle is also tilted, and the line image extending in the main scanning direction of the photoconductor drum 13 is tilted and drawn. Hereinafter, the skew (SKEW) adjustment structure of this line image will be described.

In the image forming apparatus 1 of FIG. 1, a pair of resists are located below the intermediate transfer belt drive roller 22 at positions on the right side of the drum cleaning device 14 and the charger 15 of the photoconductor drum 13 at the right end of the same figure for black. A sensor (image sensor) 50 is arranged.

<Resist sensor>
FIG. 4 shows a specific configuration around the pair of resist sensors 50, and is a perspective view of the periphery of the intermediate transfer belt 21 as viewed from diagonally lower right. In FIG. 4, the pair of resist sensors 50 is composed of two resist sensors 50F on the front side arranged on the left side of the figure and a resist sensor 50R on the rear side arranged on the right side of the figure. A sensor mounting frame 81 is arranged below the intermediate transfer belt drive roller 22. The sensor mounting frame 81 is located at a position to the left of the intermediate transfer belt drive roller 22 and to the right of the photoconductor drum 13 for black, and is parallel to the axis l of the intermediate transfer belt drive roller 22 in the front-rear direction. It is arranged so as to extend in the direction. As shown in detail in FIG. 5, the front sensor board 82F and the rear sensor board 82R are fixed to the sensor mounting frame 81 by screws 83, respectively, and the front side is fixed to these sensor boards 82F and 82R. And the resist sensors 50F and 50R on the rear side are arranged respectively. As shown in FIG. 6, these resist sensors 50F and 50R are composed of a reflective type that irradiates the surface of the intermediate transfer belt 21 with light from below and receives the reflected light.

Each of the resist sensors 50F and 50R has the same structure, and specifically, as shown in FIG. 7, the main body 50a is provided with a light emitting unit 50b and a light receiving unit 50c. The light emitting unit 50b irradiates the surface of the intermediate transfer belt 21 upward with light shown by a solid line in the figure from a slightly oblique direction, and the spot diameter on the surface of the intermediate transfer belt 21 is a predetermined diameter Φ (FIG. 5). (See) is adjusted to be. The light receiving unit 50c receives the reflected light indicated by the alternate long and short dash line in the figure from the surface of the intermediate transfer belt 21 at a position on the side of the light emitting unit 50b, and detects the toner image transferred to the surface of the intermediate transfer belt 21. Each of the resist sensors 50F and 50R outputs a signal corresponding to the received reflected light, and this output signal is transmitted to the control unit 71 via the connector unit 84 provided on each of the sensor boards 82F and 82R (FIG. 3). reference).

FIG. 8 shows an example of the output signals of the resist sensors 50F and 50R. The figure illustrates an output signal in which the toner image It is detected when the toner image It indicated by a square diagonal line is drawn on the surface of the intermediate transfer belt 21. When the toner image It moves in the transport direction C with the transport motion of the intermediate transfer belt 21, the reflected light is large in the region without the toner image It (that is, the glossy surface), and the output voltage is a predetermined H (High) voltage. Maintaining. When light starts to be applied to the tip end side edge f of the intermediate transfer belt 21 of the toner image It in the transport direction C, the light is scattered and it becomes difficult for the light receiving unit 50c to detect the reflected light, so that the output voltage drops from the H voltage. Then, it becomes a predetermined L (Low) voltage. The output voltage maintains the L voltage while the toner image It is irradiated with light, and when the rear end side edge r of the toner image It is irradiated with the light, a large amount of reflected light starts to be received again, and the output voltage is the L voltage. It rises from and becomes H voltage. In this example, the time a1 at which the output voltage becomes half value ((HL) / 2) when the voltage drops is defined as the detection time of the front edge side f, and the time a2 at which the output voltage becomes half value when the voltage rises is defined as the rear end. The detection time of the side edge r is defined as the intermediate value tm (= (a2-a1) / 2) between the two, that is, the detection time of the center position o of the toner image It is defined as the edge detection time of the toner image It.

The two resist sensors 50F and 50R are arranged on the respective sensor boards 82F and 82R as described above, and these sensor boards 82F and 82R are further fixed to the sensor mounting frame 81 with screws 83, so that these sensor boards The 50F and 50R are the position tolerance of the sensor mounting frame 81 with respect to the image forming apparatus 1, the position tolerance of the sensor substrates 82F and 82R with respect to the sensor mounting frame 81, and the light emitting portion 50b and the light emitting portion 50b with respect to the main body portion 50a in the resist sensors 50F and 50R. The current situation is that the light receiving portion 50c is not accurately positioned at the desired position due to the position tolerance and the existence of assembly variations. Therefore, the straight line connecting the two resist sensors 50F and 50R is not accurately orthogonal to the transport direction C of the intermediate transfer belt 21, and is in a slightly tilted state. Such an inclination is hereinafter referred to as a mounting inclination of the resist sensors 50F and 50R, or simply a sensor mounting inclination. The image forming apparatus 1 is provided with a sensor mounting tilt detecting device 100 (see FIG. 3) for detecting such a sensor mounting tilt.

<Resist sensor mounting tilt detection device>
The sensor mounting tilt detection device 100 includes the pair of resist sensors 50 (50F, 50R), a control unit 71, an image forming unit 72 of each color of the image forming apparatus 1, an intermediate transfer belt 21, and a transfer of each color. It has a part 35.

The control unit 71 controls the image forming unit 72 of four colors (four) and a plurality of transfer power supplies 30 corresponding thereto based on the flowchart shown in FIG. 9, and determines the mounting inclination of the resist sensors 50F and 50R. To detect.

Specifically, in the flowchart of FIG. 9, starting, in step S1, one of the four color image forming units 72, for example, the black image forming unit 72 is controlled to be applied to the surface of the corresponding photoconductor drum 13. A uniform density image of black having a predetermined length in the rotation direction, for example, a rectangular shape (specifically, an electrostatic latent image written on the surface of the photoconductor drum 13 by an optical scanning device 11 is developed. Toner image) is formed. The uniform density image is not limited to black, and may be any color of cyan, magenta, or yellow.

Next, in step S2, the transfer bias of the black transfer power source 30 is applied to the corresponding intermediate transfer roller 24, and the rectangular black uniform density image on the surface of the photoconductor drum 13 is transferred to the intermediate transfer belt 21. As a result, as shown in FIG. 10, a rectangular black uniform density image IK having a predetermined length in the transport direction C is formed in the image forming region AI of the intermediate transfer belt 21. Become.

Further, in step S2, during the transfer operation of the black uniform density image IK, the transfer bias application operation of the black transfer power supply 30 is stopped for a predetermined time to stop the flow of the transfer current. Due to the stop of the transfer bias application operation, the toner image on the surface of the photoconductor drum 13 is not transferred to the intermediate transfer belt 21 during the stop period, and transfer omission occurs. As a result, as shown in FIG. 10, on the surface of the intermediate transfer belt 21, transfer omission extending in the direction V orthogonal to the transport direction C of the intermediate transfer belt 21 in the rectangular black uniform density image IK. White streaks of streaks WL occur. The front end side edge f and the rear end side edge r of the white streaks (non-transfer image portion) WL are straight lines completely perpendicular to the transport direction C of the intermediate transfer belt 21. That is, it is generally guaranteed that the photoconductor drum 13 is attached to the image forming apparatus 1 with the desired positioning accuracy with respect to the intermediate transfer belt 21, and the photoconductor drum 13 and the intermediate transfer belt 21 are attached to each other. The forming direction of the transfer nip region is accurately orthogonal to the transport direction C of the intermediate transfer belt 21. Therefore, the front end side edge f and the rear end side edge r of the white streaks WL generated by stopping the transfer bias application operation coincide with the formation direction of the transfer nip region, and are in the transport direction C of the intermediate transfer belt 21. On the other hand, it is a straight line parallel to the direction V that is completely perpendicular to the direction V.

After that, in step S3, as shown in FIG. 11, the white streaks WL (non-transferred image portion) WL in the black uniform density image IK are detected by two resist sensors 50F and 50R. The figure illustrates a case where the resist sensor 50R on the rear side is displaced by a predetermined distance d on the transport direction C side of the intermediate transfer belt 21 and the sensor mounting inclination at an angle α is generated. The sensor mounting inclination α is the inclination taken by the line connecting the two resist sensors 50F and 50R with respect to the direction V orthogonal to the transport direction C of the intermediate transfer belt 21 (hereinafter, this direction is referred to as the belt orthogonal direction V). Is. In the output signal waveform shown in the figure, the resist sensors 50F and 50R become the L voltage during the detection of the black uniform density image IK, and detect the white streaks WL in the middle of the detection, and suddenly rise to the H voltage. As described above, the voltage rise times t (F) and t (R) of the front and rear resist sensors 50F and 50R are both the front end side edge f and the rear end side edge r of the white streaks WL. It is an intermediate value tm of the detection time, and indicates the edge detection time (edge information) of the white streaks WL.

Subsequently, in step S4, the sensor mounting inclination α is calculated based on the voltage rise time (edge detection time) t (F) and t (R) of the resist sensors 50F and 50R. As described above, the white streaks WL are completely perpendicular to the transport direction C of the intermediate transfer belt 21, so that the sensor mounting inclination α determines the separation of the belt orthogonal direction V between the resist sensors 50F and 50R. L, where the misalignment distance in the transport direction C of the intermediate transfer belt 21 is d,
It can be calculated as α = tan ^-1 (d / L).

Here, the misalignment distance d on the belt transport direction C side between the resist sensors 50F and 50R is an edge detection time difference Δt (difference between the edge detection times t (F) and t (R) of the resist sensors 50F and 50R). = T (R) -t (F)) and the transfer speed PS per unit time of the intermediate transfer belt 21 can be calculated by the following formula d = PS * (t (R) -t (F)). Is.

The edge detection time difference Δt (= t (R) −t (F)) is stored in the memory (storage unit) 75. The memory 75 may further store the calculated misalignment distance d and the calculated sensor mounting inclination α.

<Modification 1>
FIG. 12 shows a modification 1 of the detection structure of the sensor mounting inclination α. In FIG. 10, only one white streak WL was formed in the black uniform density image IK, but in the present modification 1, a plurality of white streaks were formed.

In FIG. 12, specifically, the control unit 71 controls the black image forming unit 72, and a rectangular black uniform density image (toner image) long in the rotation direction on the surface of the corresponding photoconductor drum 13. And the black uniform density image is transferred to the intermediate transfer belt 21 by the transfer bias application operation of the corresponding transfer power source 30, while forming the black uniform density image IK, during the transfer operation. Multiple times (three times in the figure) The transfer bias application operation of the transfer power supply 30 is stopped, and a plurality of white streaks (three are illustrated in the figure) at predetermined intervals during the black uniform density image IK (non-existent). Transfer image part) WL is formed.

In this configuration, every time the edges of the three white streaks WL are detected by the resist sensors 50F and 50R, the edge detection time difference Δt (= t (R)) between the two edge detection times t (F) and t (R) is detected. -T (F)), the positional deviation distances d1, d2, and d3 on the belt transport direction C side between the resist sensors 50F and 50R are calculated, and the average value da (= (d1 + d2 + d3) / 3) is used. Calculate the sensor mounting tilt α. According to this configuration, the detection error of the sensor mounting inclination α can be further reduced, and the sensor mounting inclination α can be detected with higher accuracy.

<Modification 2>
FIG. 13 shows a modification 2 of the detection structure of the sensor mounting inclination α. In the first modification, a plurality of white streaks WL were formed in the black uniform density image IK, but in the second modification, a plurality of color uniform density images were formed, and each of them was formed in the uniform density image. One white streak WL is formed.

In FIG. 13, specifically, the control unit 71 controls the image forming unit 72 of four colors of black, cyan, magenta, and yellow, and each of them is one of the square-shaped colors on the surface of the corresponding photoconductor drum 13. A similar density image (toner image) is formed, and the uniform density image of each color is transferred to the intermediate transfer belt 21 by the transfer bias application operation of the corresponding transfer power supply 30, and the uniform density image of each color is uniformly applied to the image forming region AI. The density images IK, IC, IM, and IY are formed, and the transfer bias application operation of each transfer power source 30 is stopped during the transfer operation, and white is formed in the uniform density images IK, IC, IM, and IY of each color. A missing streak (non-transfer image portion) WL is formed. In addition, the configuration for detecting the edge of each white streak WL and calculating the sensor mounting inclination α based on the average value da of the positional deviation distances d1, d2, d3, etc. between the sensors is the same as that of the first modification.

In this configuration, even if there is some variation in the mounting error between the photoconductor drums 13 of the four-color image forming unit 72, the detection error of the sensor mounting tilt α can be made smaller, and the sensor mounting tilt α can be made more accurate. It has a well-detectable effect.

After the mounting tilt α of the resist sensors 50F and 50R is detected by the sensor mounting tilt detecting device 100 as described above, registration adjustment (superimposition of images of each color) is subsequently performed. Hereinafter, the registration adjustment will be described separately for the adjustment of the image writing angle for the photoconductor drum 13 of each color and the correction of the image writing timing between the colors (color deviation correction).

<Adjustment of image writing angle for each color>
The adjustment of the image writing angle of each color is performed by the optical scanning device 11 of each color. The optical scanning device 11 of each color is provided with a writing angle adjusting mechanism 90 as an automatic skew mechanism for adjusting an image writing angle with respect to a direction orthogonal to the rotation direction of the photoconductor drum 13 (that is, a main scanning direction).

FIG. 14 is a perspective view showing a specific configuration of the writing angle adjusting mechanism 90. The writing angle adjusting mechanism 90 shown in the figure is provided in each of the optical scanning devices 11 of each color. The writing angle adjusting mechanism 90 is an image writing angle with respect to the photoconductor drum 13, that is, a final stage component for irradiating the light beam BM from the optical scanning device 11 toward the photoconductor drum 13, that is, a second fθ lens (lens). The inclination of 209 (see FIG. 2) in the main scanning direction (direction orthogonal to the rotation direction of the photoconductor drum 13) is adjusted.

Specifically, in FIG. 14, the writing angle adjusting mechanism 90 has a lens holder 92 that incorporates and supports a second fθ lens 209 arranged in the main scanning direction (the same direction as the belt orthogonal direction V). The second fθ lens 209 (not shown in the figure) built in the lens holder 92 emits a light beam from the first fθ lens 207 (not shown in the figure) through the scanning optical path SC1 and emits a folded mirror 208. The light is received through the light beam, and the light beam is applied to the photoconductor drum 13 via the scanning optical path SC2.

The lens holder (frame body) 92 extends in a direction orthogonal to the rotation direction D of the photoconductor drum 13 (that is, the main scanning direction V), and one end thereof (rear end in the figure) is a housing of the optical scanning device 11. It is rotatably supported by a fixing portion 92a on the rear portion 210a of the 210. The other end of the lens holder 92 (front end in the figure) is rotatably supported by the front portion 210b of the housing 210 of the optical scanning device 11 in the left-right direction in the drawing, and a spring member 93 is arranged at the other end. The other end is urged to the left in the figure by the spring member 93. Further, at the other end of the lens holder 92, a push pin 95 for pushing the left side surface 92b of the lens holder 92 is arranged. A gear 97 is connected to the rear end of the push pin 95, and the gear 97 meshes with the rotating shaft 98a of the motor 98 arranged below the gear 97. By rotating the rotation shaft 98a of the motor 98 as shown by the arrow in the figure, the gear 97 is rotated in the direction indicated by the arrow in the figure, and the push pin 95 is moved in the left-right direction in the figure, thereby pushing the push pin 95. Adjust the amount. By adjusting the pushing motion amount, the lens holder 92 uses the fixed portion 92a as a rotation fulcrum, and the other end of the lens holder 92 (front end in the figure) is parallel to the rotation direction D of the photoconductor drum 13 (left and right direction in the figure). The image writing angle in the main scanning direction with respect to the photoconductor drum 13 of the second fθ lens 209 is adjusted. The motor 98 is controlled by the control unit 71 (see FIG. 3).

Next, the adjustment of the image writing angle of each color in consideration of the detected sensor mounting inclination α will be described.

FIG. 15 is a flowchart showing the procedure of the sensor mounting inclination α detection operation by the control unit 71 and the subsequent procedure of the image writing angle adjustment operation of each color. In the figure, in step S1, the image forming unit 72 and the transfer power source 30 of each color are controlled to transfer and form the registration adjustment pattern (toner image) formed on the surface of the photoconductor drum 13 on the intermediate transfer belt 21.

An example of the registration adjustment pattern is shown in FIG. In the figure, the registration adjustment pattern 99 is formed in the image forming region AI on the surface of the intermediate transfer belt 21. The two resist sensors 50F and 50R are arranged in the image forming region AI at positions corresponding to positions separated inward from the front end portion AIf and the rear end portion AIR, respectively, by a predetermined distance. The registration adjustment pattern 99 consists of a rectangular black uniform density image IK having white streaks WL and four colors extending in the belt orthogonal direction V in order from the transport direction C side (right side in the drawing) of the intermediate transfer belt 21. It has line images LC, LK, LM, and LY, and each of these images is formed in a rectangular shape extending between the front end AIf and the rear end AIr of the image forming region AI.

<Modification example of registration adjustment pattern>
FIG. 17 shows a modified example of the registration adjustment pattern 99. In FIG. 16, a black uniform density image IK and four-color line images LC, LK, LM, and LY are formed in a long rectangular shape between the front end AIf and the rear end AIr of the image formation region AI, respectively. However, in this modification, it is formed only at the position corresponding to each of the arrangement positions of the two resist sensors 50F and 50R, and is not formed in the intermediate region 99m corresponding between the resist sensors 50F and 50R. In this modification, it is possible to suppress the toner consumption of each color because the black uniform density image IK and the four-color line images LC, LK, LM, and LY are not formed in the intermediate region 99 m.

FIG. 18 shows an output signal waveform when the registration adjustment pattern 99 shown in FIG. 16 or FIG. 17 passes through the resist sensors 50F and 50R. In the figure, the voltage rise time (edge detection time) at which the resist sensors 50F and 50R each detect the white streak WL is described as t (WF) and t (WR), and each color (cyan, black, magenta and yellow) is described as t (WF) and t (WR). The detection times (voltage fall time) (detection information) of the line images LC, LK, LM, and LY are set to [t (CF), t (CR)], [t (KF), t (KR)], respectively. It is described as [t (MF), t (MR)], [t (YF), t (YR)]. Hereinafter, the control of the control unit 71 will be described with reference to FIGS. 15 and 18.

In step S2 of FIG. 15, the control unit 71 receives the output signals of the resist sensors 50F and 50R and calculates the sensor mounting inclination α. As described above, this calculation is based on the edge detection time difference ΔtW (= t (WR) −t (WF)) between the two edge detection times t (WF) and t (WR) detected for the white streaks WL. This is performed based on the distance L between the resist sensors 50F and 50R, and the transport speed PS per unit time of the intermediate transfer belt 21.

Then, in step S3, the detection time difference ΔtK (= t (KR) −t (KF)) between the two detection times t (KF) and t (KR) detected for the black line image LK is calculated, and step S4. In, the edge detection time difference ΔtW (= t (WR) −t (WF)) for the white streak WL is subtracted from this detection time difference ΔtK (= t (KR) −t (KF)), and the difference (= t (WR) −t (WF)) is subtracted. Based on ΔtK−ΔtW), the inclination (that is, the inclination of the image writing angle) K-SKEW of the second fθ lens 209 of the black optical scanning device 11 in the main scanning direction is calculated. Then, in step S5, the writing angle adjusting mechanism 90 is controlled in the direction of canceling the tilt K-SKEW of the second fθ lens 209. The state of adjusting the tilt K-SKEW of the second fθ lens 209 will be specifically described with reference to FIG.

In FIG. 19, when the line image LK transferred to the intermediate transfer belt 21 is initially tilted by the inclination K-SKEW with respect to the belt orthogonal direction V, the detection time difference ΔtK (= t (= t (= t)) for this line image LK. KR) −t (KF)) includes an edge detection time difference ΔtW (= t (WR) −t (WF)) for the white streaks WL. Therefore, the control unit 71 calculates the difference (ΔtK−ΔtW), and the distance in the belt transport direction C according to the difference (d (K) −d (W)) (= PS * ΔtK—PS * ΔtW). ), The writing angle adjusting mechanism 90 is controlled. As a result, the black second fθ lens 209 is positioned accurately parallel to the main scanning direction, and the black line electrostatic latent image formed on the surface of the photoconductor drum 13 is adjusted by the inclination K-SKEW. It is drawn in parallel with high accuracy in the main scanning direction. As a result, the line image LK transferred to the surface of the intermediate transfer belt 21 is also drawn accurately and parallel to the main scanning direction. In FIG. 19, the writing angle adjusting mechanism 90 is controlled so as to eliminate the tilt K-SKEW of the line image LK, but the tilt K-SKEW may be controlled so as to be within a predetermined minute range.

After that, in step S6, the control unit 71 subsequently performs two detection times [t (CF), t (CR)], [t) for the line images LC, LM, and LY of cyan, magenta, and yellow other than black. (MF), t (MR)], [t (YF), t (YR)] detection time difference (t (CR) -t (CF)), (t (MR) -t (MF)), ( Based on t (YR) −t (YF)), the tilts C-SKEW, M-SKEW, and Y-SKEW of the second fθ lens 209 of the three-color optical scanning device 11 are calculated. Each of the slopes C-SKEW, M-SKEW, and Y-SKEW is calculated as a relative slope with the slope K-SKEW in black as a reference value. Then, in step S7, the writing angle adjusting mechanism 90 of the three colors is controlled in the direction of canceling the relative skew C-SKEW, M-SKEW, and Y-SKEW in each of the colors. By adjusting the inclination of each of these colors, the second fθ lens 209 of the optical scanning device 11 for all colors (four colors) is adjusted to be accurately parallel to the main scanning direction.

<Color shift correction>
After controlling the writing angle adjusting mechanism 90 for each color in this way, in step S8, the positional deviation (color deviation) between the color images laminated on the intermediate transfer belt 21 is corrected, and the process ends. This color shift correction controls the image writing timing of the optical scanning device 11 of each color, and specifically, the detection time t (KF) of the front resist sensor 50F that detects the black line image LK. The detection time difference between the detection time t (CF), t (MF), and t (YF) of the front resist sensor 50F that detected the cyan, magenta, and yellow line images LC, LM, and LY (t (CF)- Cyan, based on t (KF)), (t (MF) -t (KF)), (t (YF) -t (KF)) and the transfer rate PS per unit time of the intermediate transfer belt 21. The image writing timing of the optical scanning device 11 of the three colors other than black is calculated so that the three colors of magenta and yellow all overlap with the drawing point of black. The control unit 71 stores these image writing timings in the memory 75.

As described above, in the present embodiment, in the sensor mounting tilt detection device 100, the transfer bias application operation of the transfer power supply 30 is temporarily stopped during the transfer operation of transferring the black uniform density image IK to the intermediate transfer belt 21. Therefore, the white streaks WL that are accurately orthogonal to the belt transport direction C of the intermediate transfer belt 21 can be formed without depending on the optical scanning device 11, so that the edge detection time difference ΔtW for the white streaks WL ( = T (WR) −t (WF)), it is possible to accurately detect only the sensor mounting inclination α.

Further, when detecting the sensor mounting inclination α, regarding the edge detection of the white streaks WL, as illustrated for the toner image It in FIG. 8, the detection time a1 of the front end side edge f and the detection time of the rear end side edge r. The intermediate value tm (= (a2-a1) / 2) with a2 is used as the edge detection time of the white streak WL. Therefore, when the detection time of the front end side or the rear end side edge of the white streak muscle WL is set as the edge detection time of the white streak streak WL, the detection variation due to the position variation of the front end side or the rear end side edge occurs. However, in this configuration, even if the position of the front end side or the rear end side edge varies, it is possible to suppress the detection variation of the edge detection time of the white streaks WL and accurately detect the sensor mounting inclination α. ..

Further, regarding the detection of the white streaks WL, as shown in FIG. 12, a plurality of white streaks WL are formed in the uniform density image IK of one color (black), and the white streaks WL are described. Since the average value of the edge detection time difference Δt is used as the edge detection time difference of the white streaks WL, it is possible to further suppress the edge detection variation of the white streaks WL and detect the sensor mounting inclination α more accurately.

In addition, as shown in FIG. 13, a plurality of white streaks WL were formed in each of the uniform density images IK, IC, IM, and IY of each color, so that between the photoconductor drums 13 of each color. Even if there are variations in mounting accuracy, it is possible to detect the sensor mounting tilt α by averaging those mounting variations, and when correcting the color shift between each color, the position variation in the drawing of each color is minimized. , Can be optimized.

Further, as shown in FIG. 17, the uniform density image IK and the white streak WL are formed only at the positions corresponding to the pair of resist sensors 50F and 50R in the image forming region AI of the intermediate transfer belt 21. Therefore, it is possible to suppress the consumption of toner.

Further, since the calculated edge detection time difference Δt (= t (R) −t (F)) is stored in the memory 75 when detecting the edge of the white streak WL, after that, optical scanning for each photoconductor drum 13 is performed. Even if the image writing angle of the device 11 is deviated, it is not necessary to perform the edge detection operation of the white streaks WL again when the deviation is readjusted.

In addition, in the image forming apparatus 1 provided with the sensor mounting tilt detecting device 100, the edge detection time difference ΔtW (= t (WR) −t (WF)) for the white streaks WL has already been calculated, so that each photosensitive is photosensitive. It is possible to accurately adjust the image writing angle with respect to the body drum 13. That is, for example, the detection time difference ΔtK (= t (KR) − (KF)) for the black line image LK transferred to the intermediate transfer belt 21 is the edge detection time difference ΔtW (= t (WR)) for the white streaks WL. )-T (WF)) is included, but the edge detection time difference ΔtW of this white streak WL is excluded (subtracted), and the second fθ lens 209 tilt of the optical scanning device 11 (tilt of the image writing angle) K- Since the SKEW can be adjusted, the image writing angle can be adjusted accurately in parallel with the main scanning direction. As a result, for example, even if a line image is formed at the same position on the front surface and the back surface of the recording paper, the parallelism of both line images is uniform and the effect of looking beautiful is obtained.

Further, the optical scanning device 11 of each color is provided with the writing angle adjusting mechanism 90 shown in FIG. 14, and since the control unit 71 controls the writing angle adjusting mechanism 90, the image writing angle of each color is automatically set. Can be easily adjusted with.

Further, after adjusting the inclinations of the image writing angle of each color, K-SKEW, C-SKEW, M-SKEW, and Y-SKEW within a predetermined minute range so as to be undesired, color deviation correction between each color is performed. Therefore, the image writing timing of each color can be adjusted easily and accurately, and the accuracy of the registration adjustment can be improved.

The present invention can be practiced in various other forms without departing from its spirit or key features. Therefore, the above embodiments are merely examples and should not be construed in a limited manner. All modifications and modifications belonging to the equivalent scope of the claims of the present invention are within the scope of the present invention.

For example, a white streak (non-transferred image portion) WL was formed in the black uniform density image IK, but instead of the white streak WL, a thin streak having a lower density than the uniform density image IK was formed. You may. In this case, the transfer bias (predetermined high voltage) application operation of the transfer power supply 30 is stopped for a predetermined time during the transfer operation of the uniform density image IK, and the transfer bias application operation of a voltage lower than the high voltage is stopped. To reduce the transfer current value and change the resist sensors 50F and 50R to the density type instead of the reflection type.

Further, in the image forming apparatus 1 of the present embodiment, since the optical scanning apparatus 11 is provided with the writing angle adjusting mechanism 90, the control unit 71 controls the motor 98 of the writing angle adjusting mechanism 90 after detecting the sensor mounting inclination α. Then, the image writing angle of the optical scanning device 11 is automatically adjusted, but when the writing angle adjusting mechanism 90 is not provided, the detected sensor mounting inclination α is displayed on a display unit or the like, and a serviceman or the like is used. The operator may manually adjust the image writing angle.

Since the present invention can accurately detect only the mounting inclination of the resist sensor provided in the image forming apparatus for adjusting the image writing angle, the image writing angle with respect to the photoconductor drum can be accurately adjusted and is applied to the image forming apparatus. And useful.

1 Image forming device 11 Optical scanning device (image writing unit)
13 Photoreceptor drum (image carrier)
21 Intermediate transfer belt AI image formation area 22 Intermediate transfer belt drive roller (suspension roller)
23 Driven roller (suspension roller)
24 Intermediate transfer roller (suspension roller)
30 Transfer power supply 35 Transfer unit 50 Pair of resist sensors (image sensor)
50F Front resist sensor (image sensor)
Resist sensor (image sensor) on the rear side of 50R
71 Control unit 72 Image formation unit 73 Printing unit 75 Memory (storage unit)
90 Writing angle adjustment mechanism 92 Lens holder (frame)
92a Fixed part (rotating fulcrum)
98 Motor 100 Sensor mounting tilt detector 209 2nd fθ lens (lens)
Uniform density image of IK black WL White streaks (non-transfer image part)

Claims (11)

A plurality of image forming portions having an image carrier rotatably supported and forming a toner image on the image carrier,
An intermediate transfer belt rotatably suspended by multiple suspension rollers,
A plurality of image-forming units are provided in the same number as the plurality of image-forming units, and are provided with a transfer power source that generates a transfer bias, and the toner image of the image carrier is transferred into the image-forming region of the intermediate transfer belt by the application operation of the transfer bias. Transfer part and
A pair of image sensors arranged at both ends of the intermediate transfer belt at positions corresponding to the image forming region and detecting a toner image transferred to the intermediate transfer belt.
It has a plurality of the image forming units and a plurality of control units for controlling the transfer power supply.
The control unit
At least one of the plurality of image forming portions is formed with a uniform density image having a predetermined length in the rotation direction of the image carrier, and the uniform density image is transferred to the intermediate transfer belt. In the middle of the transfer operation of transferring to, the transfer bias application operation of the transfer power supply corresponding to the one image forming unit is stopped for a predetermined time, and the non-transfer image unit is placed in the uniform density image transferred to the intermediate transfer belt. It is characterized in that it detects the mounting inclination of the pair of image sensors in a direction orthogonal to the transport direction of the intermediate transfer belt based on the edge information of the non-transfer image portion obtained by each image sensor. Image sensor mounting tilt detection device. The edge information of the non-transfer image unit is two edge detection times in which the edge of the non-transfer image unit in the transport direction of the intermediate transfer belt is detected by the pair of image sensors.
The control unit
The mounting tilt detecting device for an image sensor according to claim 1, wherein the difference between the two edge detection times is calculated, and the mounting tilt of the pair of image sensors is detected based on the calculated edge detection time difference. .. The control unit
The claim is characterized in that an intermediate value of both detection times of the front end side edge and the rear end side edge of the intermediate transfer belt in the transport direction in the non-transfer image unit is calculated, and the intermediate value is set as the edge detection time. 2. The image sensor mounting tilt detection device according to 2. The control unit
2. The image sensor mounting tilt detector described. The control unit
The fourth aspect of claim 4, wherein a plurality of the non-transferred image portions are formed by controlling the plurality of the image-forming portions and the plurality of transfer power supplies to form the non-transferred image portions, respectively. Image sensor mounting tilt detector. The control unit
2. The mounting tilt detection device for the image sensor according to any one of the items. The control unit
The mounting tilt detection device for an image sensor according to any one of claims 2 to 6, further comprising a storage unit for storing the edge detection time difference. An image forming apparatus having the mounting inclination detection device for the image sensor according to any one of claims 1 to 7.
A plurality of image writing units that form latent images for each of the plurality of image carriers, and
Each of the plurality of image writing units is provided with a plurality of writing angle adjusting mechanisms for adjusting the image writing angle with respect to the direction orthogonal to the rotation direction of the image carrier.
The control unit
An image forming apparatus characterized in that each of the plurality of writing angle adjusting mechanisms is controlled based on the edge information of the non-transferred image unit detected by the pair of image sensors. The control unit
A line image orthogonal to the rotation direction of the image carrier is formed for each of the plurality of image forming portions, and each line image is transferred to the intermediate transfer belt to form a plurality of lines on the intermediate transfer belt. An image is formed, the plurality of line images are each detected by the pair of image sensors, and the plurality of writing angles are adjusted based on the detection information of the line images and the edge information of the non-transferred image portion. The image forming apparatus according to claim 8, wherein each of the mechanisms is controlled. Each of the plurality of writing angle adjusting mechanisms is
It has a lens that irradiates the image carrier with light.
The lens is supported by a frame extending in a direction orthogonal to the rotation direction of the image carrier, and the frame has a rotation fulcrum at one end and the other end is rotatable with respect to the image writing portion. Supported by
The control unit
The image forming apparatus according to claim 8 or 9, wherein the other end of the frame is moved in parallel with the rotation direction of the image carrier to adjust the image writing angle with respect to the image carrier. .. The control unit
The image according to any one of claims 8 to 10, wherein after controlling the plurality of writing angle adjusting mechanisms, the image writing timings of the plurality of image writing units are controlled respectively. Forming device.

Images