JP2011248246A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of accurately determining at optimum timing that a toner transfer mechanism is in contact with an intermediate transfer belt with normal pressure, securely obtaining expected image quality, and preventing a situation in which image quality nonuniformity occurs in individual image forming apparatuses.SOLUTION: A multifunction machine 1 comprises a developing unit 2M and so on, an intermediate transfer belt 10, a transfer roller 9, a movement mechanism 100 for moving the intermediate transfer belt 10; a density sensor 18; a control section 111 for causing a toner pattern to be formed on the intermediate transfer belt 10; a determination part 112 for determining that a pressing condition between the developing unit 2M, and so on, and the intermediate transfer belt 10 is normal if a toner pattern density reaches a predetermined density value after the toner pattern is transferred to the intermediate transfer belt 10; and a timing designation reception part 113 for receiving a time designation instruction of an execution timing of a pressing condition determination operation. The control part 111 and determination part 112 execute a pressing condition determination operation at a timing shown by the time designation instruction.

Description

  The present invention relates to an image forming apparatus, and more particularly to a technique for determining whether or not a pressing state between an intermediate transfer belt and a mechanism for transferring a toner image between the intermediate transfer belt is normal.

  Conventionally, image formation in which a toner image formed by a developing unit including a photosensitive drum is temporarily transferred to an intermediate transfer belt, and further, a toner image on the peripheral surface of the intermediate transfer belt is transferred to a recording sheet by a secondary transfer roller. The device is known. In such an image forming apparatus, for example, as shown in Patent Document 1 below, the photosensitive drum forming a part of the developing unit is rotated in a direction in which the photosensitive drum is pressed and separated from the peripheral surface of the intermediate transfer belt. A moving mechanism; a pressing / separating motor that applies a rotational driving force to the moving mechanism; a drive control unit that drives and controls the pressing / separating motor; and a state in which the photosensitive drum presses the peripheral surface of the intermediate transfer belt And a pressing state sensor for detecting color, so that only the black developing unit presses the intermediate transfer belt when forming a monochrome image, and all the developing units for each color press the intermediate transfer belt when forming a color image. The drive controller drives the pressing / separating motor to move the intermediate transfer belt toward the photosensitive drum by the moving mechanism, and the peripheral surface of the intermediate transfer belt is pressed by the photosensitive drum. When the pressed state sensor that a state has been detected to be, the drive control unit stops the pressing / separation motor, an image formation is performed on the recording paper in this pressing state.

JP 2009-175581 A

  However, in the case of the conventional image forming apparatus, even when the pressing state sensor detects the pressing state between the photosensitive drum and the peripheral surface of the intermediate transfer belt, the variation in accuracy at the time of assembling each component constituting the image forming mechanism, In some cases, the photosensitive drum and the peripheral surface of the intermediate transfer belt may not actually be in a pressing state suitable for image formation due to variations in detection accuracy of the pressing state sensor itself. For this reason, even if the image formation on the recording paper is performed according to the detection result by the pressing state sensor, the planned image quality cannot be obtained, or the image quality is uneven for each individual image forming apparatus. There was a thing.

  The present invention has been made in order to solve the above-described problem, and it is possible to accurately determine at an optimal timing that the toner transfer mechanism is in contact with the intermediate transfer belt in a normal pressing state, and to achieve a predetermined image quality. It is an object of the present invention to avoid such a situation that image quality unevenness is obtained for each individual image forming apparatus.

The invention according to claim 1 of the present invention comprises a developing unit for forming a toner image;
An intermediate transfer belt having a peripheral surface to which a toner image is transferred by the developing unit;
A transfer portion for transferring the toner image from the developing unit to the intermediate transfer belt;
A moving mechanism for moving the intermediate transfer belt in a direction of contacting and separating from the developing unit and pressing the intermediate transfer belt against the developing unit;
A control unit that causes the developing unit to form the toner pattern and causes the transfer unit to perform transfer to the intermediate transfer belt;
Provided on the downstream side in the toner image conveying direction by the intermediate transfer belt from the nip portion between the developing unit and the intermediate transfer belt that has transferred the toner pattern to the intermediate transfer belt. A toner pattern density detection unit for detecting the density of a toner pattern which is a density detection toner image transferred onto the surface;
The toner pattern density detected by the toner pattern density detection unit reaches a predetermined density value after the toner pattern is transferred to the intermediate transfer belt under the control of the control unit. A determination unit that determines that the pressing state of the developing unit and the intermediate transfer belt moved by the moving mechanism is normal;
A timing designation receiving unit for receiving from the user a timing designation instruction for designating a determination operation execution timing for executing the pressing state determination operation including the toner pattern formation and transfer by the control unit and the determination by the determination unit;
The control unit and the determination unit are image forming apparatuses that execute the pressing state determination operation at a time indicated by the time specification instruction received from a user by the time specification reception unit.

  For example, when the contact between the developing unit and the intermediate transfer belt is insufficient or excessive, and the nip portion in an appropriate pressing state is not formed between the developing unit and the intermediate transfer belt, the toner from the developing unit to the intermediate transfer belt Since the transfer of the image becomes insufficient, the density of the toner pattern transferred to the peripheral surface of the intermediate transfer belt by the developing unit is reduced. For this reason, the present invention provides a case where the density of the toner pattern detected by the toner pattern density detection unit has reached a predetermined density value after the toner pattern is transferred to the intermediate transfer belt. The determination unit can accurately determine that the pressing state of the developing unit and the intermediate transfer belt is normal by determining that the pressing state of the developing unit and the intermediate transfer belt is normal. In the present invention, the determination unit uses the density of the toner pattern actually formed on the peripheral surface of the intermediate transfer belt to determine that the pressing state of the developing unit and the intermediate transfer belt is normal. When the density reaches a predetermined density value, the pressing state of the development unit and the intermediate transfer belt is determined to be normal. Therefore, if image formation is performed with the pressing state determined to be normal, the expected image quality Is guaranteed, and it is also possible to avoid the occurrence of uneven image quality for each individual image forming apparatus.

  In the present invention, since the pressing state determination operation is executed at the time indicated by the time specification instruction received from the user by the time specification receiving unit, the pressing state of the developing unit and the intermediate transfer belt is normal at the time desired by the user. It can be determined whether or not there is.

According to a second aspect of the present invention, there is provided a developing unit for forming a toner image;
An intermediate transfer belt having a peripheral surface to which a toner image is transferred by the developing unit and running endlessly by being stretched by a plurality of rollers;
A transfer portion for transferring the toner image from the developing unit to the intermediate transfer belt;
A secondary transfer roller portion for secondary transfer of the toner image transferred by the developing unit onto the peripheral surface of the intermediate transfer belt onto a recording paper;
A moving mechanism for moving the secondary transfer roller portion in a direction of coming into contact with and separating from the intermediate transfer belt and pressing the secondary transfer roller portion against the intermediate transfer belt;
A toner pattern density detection unit that detects the density of a toner pattern that is a density detection toner image transferred from the developing unit onto the peripheral surface of the intermediate transfer belt;
The developing unit forms the toner pattern, causes the transfer unit to perform transfer to the intermediate transfer belt, and causes the secondary transfer roller unit to transfer the toner pattern on the peripheral surface of the intermediate transfer belt to the secondary transfer roller. A control unit that performs toner pattern transfer control to transfer the toner pattern again from the secondary transfer roller unit to the intermediate transfer belt after being transferred to the part side;
After the toner pattern transfer control by the control unit, when the toner pattern density on the peripheral surface of the intermediate transfer belt detected by the toner pattern density detection unit has reached a predetermined normal value, the movement A determination unit that determines that the pressing state of the intermediate transfer belt and the secondary transfer roller unit moved by a mechanism is normal;
A timing designation receiving unit for receiving from the user a timing designation instruction for designating a determination operation execution timing for executing the pressing state determination operation including the toner pattern formation and transfer by the control unit and the determination by the determination unit;
The control unit and the determination unit are image forming apparatuses that execute the pressing state determination operation at a time indicated by the time specification instruction received from a user by the time specification reception unit.

  For example, when the contact between the secondary transfer roller portion and the intermediate transfer belt is insufficient or excessive, and the nip portion in an appropriate pressing state is not formed between the secondary transfer roller portion and the intermediate transfer belt, the intermediate transfer belt Since the transfer of the toner image from the toner to the secondary transfer roller portion becomes insufficient, the density of the toner pattern that performs the above-described transfer between the intermediate transfer belt and the secondary transfer roller portion becomes thin.

  Based on this, in the present invention, the determination unit determines the density of the toner pattern actually formed on the peripheral surface of the intermediate transfer belt to determine that the pressing state of the secondary transfer roller unit and the intermediate transfer belt is normal. By using this, it is possible to accurately determine that the pressed state of the secondary transfer roller unit and the intermediate transfer belt is normal when the density of the toner pattern reaches a predetermined normal value. . As a result, if image formation is performed in the pressed state determined to be normal, scheduled image quality is assured and a situation in which image quality unevenness occurs for each individual image forming apparatus can be avoided.

  In the present invention, since the pressing state determination operation is executed at the time indicated by the time specification instruction received from the user by the time specification receiving unit, the pressing state of the secondary transfer roller and the intermediate transfer belt is determined at the user-desired time. Whether or not it is normal can be determined.

  According to a third aspect of the present invention, there is provided the image forming apparatus according to the second aspect, wherein the determination unit is configured to perform the toner pattern density detection unit after the toner pattern transfer control by the control unit. The toner pattern density is detected by the endless running of the intermediate transfer belt after the toner pattern is transferred to the intermediate transfer belt by the developing unit and the transfer unit. The toner pattern is satisfied when a condition that a predetermined time required for the toner pattern transfer in the bidirectional direction of the intermediate transfer belt and the secondary transfer roller unit is delayed from a timing at which the density detection position is reached is satisfied. The toner pattern on the peripheral surface of the intermediate transfer belt detected by the density detector Degrees are those for judging whether reaches the normal value set in advance.

  In the present invention, the determination unit determines that the pressing state of the secondary transfer roller unit and the intermediate transfer belt is normal, and after the toner pattern is transferred from the developing unit to the intermediate transfer belt, the toner pattern density The timing at which the density of the toner pattern is detected by the detection unit is higher than the timing at which the toner pattern reaches the density detection position by the toner pattern density detection unit due to endless running of the intermediate transfer belt. Further, a delay of a predetermined time required for the above-described bidirectional toner pattern transfer is used as a further condition. For this reason, since the contact between the secondary transfer roller unit and the intermediate transfer belt is insufficient, the toner pattern transferred to the intermediate transfer belt by the developing unit reaches the density detection position by the toner pattern density detection unit as it is. When the density of the toner pattern reaches a predetermined normal value, it is not determined that the pressing state of the secondary transfer roller unit and the intermediate transfer belt is normal. Accordingly, the present invention can accurately determine that the pressing state of the secondary transfer roller unit and the intermediate transfer belt is normal.

  According to a fourth aspect of the present invention, there is provided the image forming apparatus according to any one of the first to third aspects, wherein the time designation receiving unit immediately executes the pressing state determination operation. An instruction to do so is received from the user as the determination operation execution time.

  According to the present invention, the user can immediately execute the pressing state determination operation at a time desired by the user.

  The invention according to claim 5 of the present invention is the image forming apparatus according to any one of claims 1 to 4, wherein the timing designation receiving unit determines the pressing state determination operation in advance. An instruction to periodically execute at a predetermined time is received from the user as the determination operation execution time.

  According to the present invention, the user can periodically execute the pressing state determination operation without giving an instruction every time the pressing state determination operation is performed.

  The image forming apparatus according to claim 6 of the present invention is the image forming apparatus according to claim 5, wherein the timing designation receiving unit forms an image by the developing unit during a warm-up operation of the image forming apparatus. The determination operation execution timing is received from the user by setting at least one or more before the start of the operation or after execution of the calibration as the predetermined timing.

  According to the present invention, the pressing state determination operation can be accurately executed periodically without giving an instruction every time when the pressing state determination operation is assumed to be necessary.

  According to the present invention, it is possible to accurately determine at an optimal timing that the toner transfer mechanism is in contact with the intermediate transfer belt in a normal pressing state, and a predetermined image quality can be obtained with certainty. A situation in which image quality unevenness occurs for each individual can be avoided.

1 is a front sectional view showing a structure of a multifunction machine. FIG. 4 is a schematic diagram illustrating an intermediate transfer belt on which a toner pattern for detecting a contact state between the developing unit and the intermediate transfer belt is formed, and a density sensor. It is a figure which shows the structure of a density sensor. FIG. 2 is a block diagram illustrating a schematic configuration of a control system of the multifunction machine. 4A and 4B are schematic views showing a moving mechanism provided on the intermediate transfer belt, wherein FIG. 5A shows a posture when forming a color image, and FIG. 5B shows a posture when forming a monochrome image. It is a flowchart which shows the flow of the process at the time of setting the execution timing of a press adjustment process. It is a figure which shows an example of the display screen of a display part. It is a figure which shows an example of the display screen of a display part. It is a flowchart which shows the discrimination | determination process of the timing which performs a press state adjustment process. 6 is a flowchart illustrating an adjustment process in a state in which an intermediate transfer belt is pressed by each photosensitive drum. It is a timing chart of the drive signal of the drive motor of a moving mechanism, and the detection signal from a cam position detection sensor. During the adjustment process of the pressing state of the intermediate transfer belt and each photosensitive drum, the drive signal of the drive motor of the moving mechanism, the detection signal from the cam position detection sensor, the image output signal output to the developing unit, and the density sensor It is a timing chart of the density | concentration detection signal. FIG. 5 is a graph showing the density of each toner pattern transferred onto the peripheral surface of an intermediate transfer belt. 6 is a flowchart showing drive control of a moving mechanism during a normal color image forming operation. It is a timing chart of the drive signal of the drive motor of a moving mechanism, and the detection signal from a cam position detection sensor. It is front sectional drawing which shows the structure of the multifunctional device which concerns on 2nd Embodiment. FIG. 4 is a schematic diagram illustrating a moving mechanism provided on an intermediate transfer belt, and illustrates a posture in which a secondary transfer roller is separated from the intermediate transfer belt. FIG. 4 is a schematic diagram illustrating a moving mechanism provided in the intermediate transfer belt, and illustrates a posture in which a secondary transfer roller is pressed against the intermediate transfer belt. 3 is a flowchart illustrating a first embodiment of an adjustment process in a state where an intermediate transfer belt is pressed by a secondary transfer roller. During the adjustment process of the pressing state of the intermediate transfer belt and the secondary transfer roller, the drive signal of the drive motor of the moving mechanism, the detection signal from the cam position detection sensor, the image output signal output to the developing unit, and the density sensor 6 is a timing chart of the density detection signal, a bias application signal for applying the secondary transfer bias to the second bias application unit of the bias application unit, and a drive signal for causing the belt cleaning device to perform belt cleaning. 12 is a flowchart illustrating a second form of adjustment processing in a state where the intermediate transfer belt is pressed by the secondary transfer roller.

[First Embodiment]
Hereinafter, a first embodiment of a multifunction machine 1 as an example of an image forming apparatus according to an embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a front sectional view showing the structure of the multifunction machine 1. As shown in FIG. 1, the multifunction machine 1 includes an image forming unit 2 in the main body. The image forming unit 2 forms (prints) a color image on the recording paper P.

  An operation unit 310 is provided at the front part of the multifunction machine 1. The operation unit 310 displays a start key 312 for a user to input a print execution instruction, a numeric keypad 313 for inputting the number of copies to be printed, operation guide information such as a copy operation, and the like. For this purpose, a display unit 311 including a liquid crystal display or the like having a touch panel function and a timing setting instruction input button 314 for inputting an instruction for starting timing adjustment of pressing adjustment described later from the user are provided.

  The image forming unit 2 includes developing units 2M, 2C, 2Y, and 2K arranged in the main body for each color of magenta (M), cyan (C), yellow (Y), and black (K), a driving roller 11a, two An intermediate transfer belt 10 stretched between a plurality of rollers such as the next transfer counter roller 13 so as to be capable of endless running in the sub-scanning direction in image formation, and the developing units 2M, 2C, 2Y, and 2K with the intermediate transfer belt 10 interposed therebetween. A transfer roller (transfer section) 9 provided at a position facing each photoconductor drum 3 and an intermediate transfer belt 10 that are stretched around a secondary transfer counter roller 13 abut against the outer peripheral surface of the intermediate transfer belt 10. A secondary transfer roller 14 that contacts and transfers the toner image on the intermediate transfer belt 10 to the recording paper P, a density sensor 18, and a belt cleaning device 19 are provided.

  The developing units 2M, 2C, 2Y, and 2K are, for example, a photosensitive drum 3 made of amorphous silicon or the like, a charging device 4, an exposure device 5, a developing device 6, and a drum cleaning device disposed around the photosensitive drum 3. 7, a toner image corresponding to the image data is formed on the circumferential surface of the photosensitive drum 3 and transferred to the intermediate transfer belt 10.

  The charging device 4 uniformly charges the peripheral surface of the photosensitive drum 3 to a predetermined potential. The exposure device 5 irradiates the peripheral surface of the photosensitive drum 3 with laser light generated based on image data transmitted by the control unit 111 described later, and forms an electrostatic latent image on the peripheral surface of the photosensitive drum 3. To do. The developing device 6 causes the toner supplied from the toner supply unit 61 to adhere to the electrostatic latent image formed on the photosensitive drum 3, thereby exposing the electrostatic latent image as a toner image. The drum cleaning device 7 cleans the toner remaining on the peripheral surface of the photosensitive drum 3 after the primary transfer of the toner image to the intermediate transfer belt 10 described later is completed.

  Below the developing units 2M to 2K, an intermediate transfer belt 10 on which the toner image that has been made visible on the peripheral surface of the photosensitive drum 3 is intermediately transferred (primary transfer) is disposed. The intermediate transfer belt 10 is pressed against the photosensitive drum 3 by a transfer roller 9 disposed opposite to each photosensitive drum 3, and the right driving roller 11a, the right driven roller 11b in FIG. The roller 11a and the secondary transfer counter roller 13 are stretched between the roller 11a and the driven roller 11b so as to be able to run endlessly.

  The intermediate transfer belt 10 is driven by a driving roller 11a and travels endlessly between the rollers. The toner images of the respective colors formed on the photosensitive drum 3 are transferred and superimposed on the intermediate transfer belt 10 that is running endlessly in the order of M, C, Y, and K at the same timing. As a result, a color image composed of four colors M, C, Y, and K is formed on the intermediate transfer belt 10. In this embodiment, it is also possible to form a monochrome toner image in which image formation is performed only by the development units 2K of the development units 2M, 2Y, 2C, and 2K.

  A belt cleaning device 19 is provided at a position facing the driven roller 11 b on the outer peripheral surface of the intermediate transfer belt 10. The belt cleaning device 19 removes (collects) residual toner on the intermediate transfer belt 10. The belt cleaning device 19 includes a cleaning electrode (not shown) and a cleaning brush (rotating brush). The cleaning electrode applies a cleaning bias having a polarity opposite to the charged charge of the toner to the cleaning brush by the cleaning electrode. The toner is removed by moving the upper toner to the cleaning brush. Note that a toner pattern tp, which will be described later, formed on the intermediate transfer belt 10 is removed by the belt cleaning device 19 after density detection by the density sensor 18.

  In the present embodiment, a moving mechanism 100 is provided that moves the intermediate transfer belt 10 in a direction in which the intermediate transfer belt 10 contacts and separates from the developing units 2M, 2C, and 2Y. Details of the moving mechanism 100 will be described later in detail with reference to FIGS. 5 and 6, and only an outline of the moving mechanism 100 is shown in FIG. 1.

  The secondary transfer roller 14 applies a predetermined transfer bias to the recording paper P based on an instruction from the control unit 111 (see FIG. 4), and secondary-transfers the color image on the intermediate transfer belt 10 to the recording paper P. Let

  In addition, the multifunction machine 1 includes a paper feeding unit 15 that feeds paper toward the developing units 2Y to 2K. The paper feed unit 15 includes a paper feed cassette 151 that stores the recording paper P, a paper transport path 152 that is a path through which the recording paper P is transported, a transport roller 153 that transports the recording paper P in the paper transport path 152, and the like. The recording paper P taken out one by one from the paper feed cassette 151 is conveyed toward the position of the secondary transfer roller 14. The paper feeding unit 15 conveys the recording paper P that has been subjected to the secondary transfer process to the fixing device 16, and discharges the recording paper P that has been subjected to the fixing process to a discharge tray 17 at the top of the main body of the multifunction device 1.

  The fixing device 16 is provided on the downstream side of the roller 12 in the paper conveyance path 152 and fixes the toner image transferred to the recording paper P. The fixing device 16 includes a heat roller 161 and a pressure roller 162, melts the toner on the recording paper P by the heat of the heat roller 161, and applies pressure by the pressure roller 162 to fix the toner on the recording paper P.

  On the outer peripheral surface of the intermediate transfer belt 10, a density sensor (toner pattern density detection unit) 18 is provided downstream of the intermediate transfer belt 10 in the running direction with respect to each nip portion between the developing units 2 </ b> M, 2 </ b> C, 2 </ b> Y, and 2 </ b> K. Is provided. The density sensor 18 can detect the density of a toner pattern, which is a density detection toner image transferred from the photosensitive drums 3 of the development units 2M, 2C, 2Y, and 2K onto the peripheral surface of the intermediate transfer belt 10. . The density sensor 18 is used to detect the density of the toner pattern formed on the intermediate transfer belt 10 by the developing units 2M, 2Y, 2C, and 2K and the transfer rollers 9 during calibration. In the present embodiment, when adjusting the pressing state of the intermediate transfer belt 10 and the developing units 2M, 2Y, and 2C, which will be described later, toner formed on the intermediate transfer belt 10 by the developing unit 2M and the transfer roller 9 corresponding thereto. It is also used to detect the pattern density. However, the density sensor for adjusting the pressing state of the intermediate transfer belt 10 and the developing units 2M, 2Y, and 2C may be provided separately from the density sensor 18 for calibration.

  A document reading unit 20 and a document feeding unit 24 are provided on the top of the main body of the multifunction machine 1. The document reading unit 20 includes a scanner unit 21 including a CCD (Charge Coupled Device) sensor having a plurality of pixels and an exposure lamp, a document table 22 and a document reading slit 23 formed of a transparent member such as glass. Is provided. The scanner unit 21 is configured to be movable by a drive unit (not shown). When reading a document placed on the document table 22, the scanner unit 21 is moved along the document surface at a position facing the document table 22 to scan the document image. Image data (each pixel data) acquired while scanning is output to the control unit 111 (see FIG. 4). Further, when reading a document fed by the document feeding unit 24, the document is moved to a position facing the document reading slit 23, and is synchronized with the document feeding operation by the document feeding unit 24 via the document reading slit 23. The image of the original is acquired, and the image data is output to the control unit 111.

  The document feeder 24 includes a document placement unit 25 for placing a document, a document discharge unit 26 for discharging a document whose image has been read, and a document placed on the document placement unit 25. A document transport mechanism 27 including a paper feed roller, a transport roller (not shown), and the like for feeding the paper one by one to a position facing the document reading slit 23 and discharging it to the document discharge section 26 is provided. The document transport mechanism 27 further includes a sheet reversing mechanism (not shown) that reverses the document and reversely transports the document to a position facing the document reading slit 23, and images on both sides of the document are passed through the document reading slit 23. Reading is possible from the scanner unit 21.

  Further, the document feeding unit 24 is provided so as to be rotatable with respect to the main body of the multifunction machine 1 so that the front side thereof can move upward. By moving the front side of the document feeder 24 upward to open the upper surface of the document table 22, the user can place a read document, for example, a book in a spread state, on the upper surface of the document table 22. It has become.

  Next, the density sensor 18 will be described. FIG. 2 is a schematic diagram showing the intermediate transfer belt 10 and the density sensor 18 on which a toner pattern for detecting a contact state between the developing units 2M, 2C, 2Y and 2K and the intermediate transfer belt 10 is formed. FIG. 3 is a diagram showing the configuration of the density sensor 18.

  The density sensors 18 are provided, for example, at two different positions in the length direction (rotational axis direction) of the drive roller 11a of the intermediate transfer belt 10 (the number of density sensors 18 is not intended to be limited to two). . As shown in FIG. 2, each density sensor 18 is spaced apart from the peripheral surface of the intermediate transfer belt 10 by a predetermined distance so as to face both ends of the intermediate transfer belt 10 in the width direction (the length direction of the driving roller 11a). It is arranged. The density sensor 18 is electrically connected to the control unit 111, and outputs the detected toner pattern density to the control unit 111.

  The density sensor 18 has the following configuration, for example. As shown in FIG. 3, in the density sensor 18, a light emitting unit 181 is disposed on one side in the traveling direction of the intermediate transfer belt 10 with respect to an arbitrary point p on the circumferential surface of the intermediate transfer belt 10, and a light receiving unit 182 is disposed on the other side. Is arranged. The light emitting unit 181 includes a light source unit 1811 that outputs light toward the point p on the circumferential surface of the intermediate transfer belt 10, and a beam splitter 1812 that splits the light output from the light source unit 1811 into first and second polarization components. And a light receiving element 1813 that receives one polarization component from the beam splitter 1812. The first and second polarization components are a P wave that provides a large output for the black toner image and an S wave that provides a large output for the color toner images of magenta toner, cyan toner, and yellow toner. The P wave is incident on the peripheral surface of the intermediate transfer belt 10 as it is, and the S wave is extracted from the beam splitter 1812 and then incident on the light receiving element 1813.

  The light emitting unit 181 is configured to include, for example, an LED (Light Emitting Diode), and includes the same amount of P wave and S wave toward the point p in an aspect that forms an angle θ with respect to the circumferential surface of the intermediate transfer belt 10. Output light. The light receiving element 1813 is installed to control the output operation of the light emitting unit 181, and a signal proportional to the amount of irradiation light is output from the light receiving element 1813 to the control unit 111. The control unit 111 controls the output light of the light source unit 1811 so that the output signal of the light receiving element 1813 is always constant.

  The light receiving unit 182 includes a beam splitter 1821 that splits light reflected from the circumferential surface of the intermediate transfer belt 10 into first and second polarization components, and the first and second polarization components that are split by the beam splitter 1821. A first light receiving element 1822 that receives light of the first polarization component and a second light receiving element 1823 that receives light of the second polarization component of the first and second polarization components are provided.

  The light from the light emitting portion 181 reflected on the circumferential surface of the intermediate transfer belt 10 includes regular reflected light in the vicinity of the same angle as the incident angle θ and other diffused light, and is transferred to the circumferential surface of the intermediate transfer belt 10. Depending on the amount of toner, the ratio of the diffused light component increases, and the ratio of the first and second polarization components received by the first and second light receiving elements 1822 and 1823 changes.

  Using this principle, the density sensor 18 outputs an analog voltage corresponding to the ratio of the first and second polarization components received by the first and second light receiving elements 1822 and 1823 to the control unit 111, and the intermediate sensor 18 When there is no toner on the circumferential surface of the transfer belt 10, the first polarization component received by the first light receiving element 1822 is maximized, the output voltage is maximized, and the amount of toner on the circumferential surface of the intermediate transfer belt 10 is As the amount increases, the amount of light of the first polarization component decreases and the output voltage decreases. For example, the concentration sensor 18 inverts the output voltage by an inversion circuit or the like and outputs the inverted output voltage to the control unit 111. The control unit 111 calculates the amount of toner attached to the peripheral surface of the intermediate transfer belt 10 based on the output signal of the density sensor 18.

  Next, the configuration of the control system of the multifunction machine 1 will be described. FIG. 4 is a block diagram showing a schematic configuration of the control system of the multifunction machine 1.

  The control unit 110 includes a CPU, a ROM, a RAM, and the like. The control unit 110 includes a control unit 111 that performs input / output and calculation of various signals, a determination unit 112, and a timing designation receiving unit 113.

  The control unit 111 applies the transfer bias to the image forming unit 2 having the development units 2M, 2Y, 2C, and 2K for each color, the first bias applying unit that applies the transfer bias to the transfer roller 9, and the secondary transfer roller 14. The bias application unit 32 having the second bias application unit, the bias application unit 32, and the operation unit 310 including the display unit 311 are controlled. The concentration sensor 18 described above is connected to the control unit 111 so that a detection signal can be output. The control unit 111 is responsible for overall operation control of the multifunction machine 1 and controls the mechanism of each part of the apparatus. FIG. 4 shows a contact state between the developing units 2M, 2Y, 2C, and 2K and the intermediate transfer belt 10 (see FIG. Only the mechanism relating to the adjustment process of the pressed state is shown.

  The control unit 111 also controls drive motors (collective names of the respective drive sources) 500 that are drive sources of the secondary transfer roller 14, the intermediate transfer belt 10, the image forming unit 2, the fixing device 16, and the moving mechanism 100 described later. Is done.

  When adjusting the pressing state of the developing units 2M, 2Y, 2C, and 2K and the intermediate transfer belt 10, the control unit 111 drives the toner pattern tp the image forming unit 2, the drive motor 500, and the like, for example, the image forming unit 2 Are formed in the vicinity of both ends in the width direction on the intermediate transfer belt 10 (FIG. 2). The toner pattern tp has a predetermined density (for example, ID value 1.4 (sensor value 633)), and has a square shape with one side of about 2 cm, for example. However, the purpose is not to limit the toner pattern tp to the density and the shape. In the present embodiment, when the toner pattern tp is formed, the control unit 111 has a density of the toner pattern tp, for example, a nip portion between the developing units 2M, 2Y, 2C, and 2K and the intermediate transfer belt 10 (that is, The density sensor 18 is detected further downstream than the most downstream developing unit 2K in the traveling direction of the intermediate transfer belt 10 and the intermediate transfer belt 10).

  The determination unit 112 determines whether or not the density of the toner pattern tp detected by the density sensor 18 has reached a predetermined density value (described later), and the density of the toner pattern tp is determined in advance. When the value has reached the value, it is determined that the state in which the intermediate transfer belt 10 is pressed by the developing units 2M, 2Y, 2C, and 2K is normal.

  When the determination unit 112 determines that the state where the intermediate transfer belt 10 is pressed by the developing units 2M, 2Y, 2C, and 2K is not normal, the control unit 111 causes the display unit 311 to issue a warning to the user. .

  That is, in the case of image formation by the secondary transfer method using the intermediate transfer belt 10, when the toner pattern is transferred from the developing unit 2M to the intermediate transfer belt 10, the photosensitive drum 3 and the intermediate transfer belt 10 of the developing unit 2M are transferred. If the contact between the photosensitive drum 3 and the intermediate transfer belt 10 of the developing unit 2M does not form a properly pressed nip portion, the intermediate transfer belt is moved from the photosensitive drum 3 to the intermediate transfer belt. Since the transfer of the toner image to 10 becomes insufficient, the density of the toner pattern tp transferred to the peripheral surface of the intermediate transfer belt 10 by the developing unit 2M becomes light. Based on this, in the present embodiment, after the toner pattern tp is transferred to the intermediate transfer belt 10, the density of the toner pattern detected by the density sensor 18 reaches the predetermined density value. The determination unit 112 determines that the 10 pressing states of the developing units 2M, 2Y, 2C, 2K and the intermediate transfer belt are normal.

  The time designation accepting unit 113 accepts a time designation instruction for designating the time for executing the pressing state adjustment process from the user based on the operation of the operation unit 310 by the user. The pressing state adjustment process includes a pressing state determination (including toner pattern formation and transfer performed by the developing unit 2M and the transfer roller 9 under the control of the control unit 111 and the determination by the determination unit 112). Include as part. For this reason, in this embodiment, when the said time designation | designated instruction | indication is received from the user in the time designation | designated reception part 113, a press state determination is performed as a part of press state adjustment process. Thereby, in this embodiment, the time specification reception part 113 will also receive the time specification instruction | indication which specifies the execution time of a press state determination from a user. Note that the operation unit 310 and the time designation receiving unit 113 in this embodiment are an example of the time designation receiving unit in the claims.

  Next, a moving mechanism for moving the intermediate transfer belt 10 in the contact / separation direction with respect to the developing units 2M, 2Y, 2C, 2K will be described. 5A and 5B are schematic views showing a moving mechanism provided in the intermediate transfer belt 10, wherein FIG. 5A shows a posture when forming a color image, and FIG. 5B shows a posture when forming a monochrome image.

  In the running direction of the intermediate transfer belt 10, a first backup roller 30 is provided between the photosensitive drum 3 of the developing unit 2K and the photosensitive drum 3 of the developing unit 3Y.

  The moving mechanism 100 is a mechanism that moves the intermediate transfer belt 10 in a direction in which the intermediate transfer belt 10 contacts and separates from the photosensitive drums 3 of the developing units 2M, 2C, and 2Y. The moving mechanism 100 includes a support member 101, an eccentric cam 102, a drive motor 103, and an urging member 104. The moving mechanism 100 is provided at a position facing the photosensitive drums 3 of the developing units 2M, 2C, and 2Y with the intermediate transfer belt 10 interposed therebetween.

  As shown in FIGS. 5A and 5B, the support member 101 extends over the transfer rollers 9 corresponding to the developing units 2M, 2C, and 2Y in the traveling direction of the intermediate transfer belt 10, and the transfer rollers 9 9 extends in the direction of the rotation axis up to a length over both ends of the rotation axis. On the support member 101, the transfer rollers 9 corresponding to the developing units 2M, 2C, and 2Y are rotatably supported. The support member 101 has a rotation shaft of the backup roller 30 as a support shaft, a position contacting the intermediate transfer belt 10 shown in FIG. 5A, and a position separating from the intermediate transfer belt 10 shown in FIG. 5B. It is set as the structure which can be rotated between. Further, the support member 101 is urged by the urging member 104 in a direction away from the intermediate transfer belt 10.

  Second backup rollers 33 a and 33 b are provided on the opposite side (driven roller 11 b side) of the first backup roller 30 in the traveling direction of the intermediate transfer belt 10 with the support member 101 interposed therebetween. The second backup roller 33a is disposed between the developing unit 2M and the driven roller 11b in the traveling direction of the intermediate transfer belt 10. The second backup roller 33 a and the second backup roller 33 b are rotatably supported by the support member 101 and rotate together with the support member 101.

The eccentric cam 102 has a cam drive shaft 102a that extends longer than the width of the support member 101 in the rotation axis direction of the transfer roller 9, and the cam drive shaft 102a is pivotally supported on the side wall of the apparatus main body 2a. The cam portion 102b of the eccentric cam 102 is provided at a plurality of locations in the length direction of the cam drive shaft 102a, and its peripheral surface portion 102b ₁ abuts against a part of the support member 101 and rotates. The drive motor 103 is a drive source that applies a rotational drive force to the eccentric cam 102. By eccentric cam 102 by a driving force applied from the driving motor 103 is rotated, the peripheral surface 102b ₁ of the cam portion 102b presses the support member 101 developing unit 2M, 2Y, 2C, the 2K direction. As a result, the support member 101 rotates from the position shown in FIG. 5A to the position shown in FIG. 5B together with the transfer rollers 9 and the second backup roller 33a that support the shaft.

  The transfer rollers 9 and the second backup rollers 33a that are pivotally supported by the support member 101 are pressed toward the photosensitive drums 3 of the developing units 2M, 2C, and 2Y with the intermediate transfer belt 10 interposed therebetween. As described above, the support member 101 is biased by a biasing member such as a spring (not shown). On the other hand, the transfer roller 9 corresponding to the photosensitive drum 3 of the developing unit 2K is biased by a biasing member (not shown) such as a spring so as to come into contact with the photosensitive drum 3 with the intermediate transfer belt 10 interposed therebetween. Yes.

  Further, on the bottom surface of the support member 101 in the vicinity of the position where the cam portion 102b is disposed on the cam drive shaft 102a, a cam position detection sensor (pressing state detection portion) that detects the posture of the cam portion 102b rotated by the cam drive shaft 102a. ) 35 is attached. The cam position detection sensor 35 includes a light emitting unit 35a and a light receiving unit 35b. The light emitting portion 35a is provided on one side of the cam portion 102b with the cam portion 102b interposed therebetween, and the light receiving portion 35b is provided on the other side of the cam portion 102b. The light emitting portion 35a and the light receiving portion 35b are eccentric when the cam portion 102b is rotated by the cam drive shaft 102a and is in a certain range before and after the posture shown in FIG. 5A (of the cam portion 102b). Due to the change in the amount of eccentricity accompanying the rotation, the intermediate transfer belt 10 is pressed against the photosensitive drums 3 of the developing units 2M, 2Y, 2C, and then the amount of eccentricity accompanying the further rotation of the cam portion 102b. Until the pressed state is released), the light emitted from the light emitting portion 35a is blocked by the cam portion 102b and is not received by the light receiving portion 35b, and the cam portion 102b has a posture other than that shown in FIG. When it is in the posture, the light emitted from the light emitting portion 35a is disposed at, for example, a position on the bottom surface of the support member 101, which is received by the light receiving portion 35b without being blocked by the cam portion 102b.

  The cam position detection sensor 35 sends a cam detection signal to the control unit 111 when the light receiving unit 35b does not receive light from the light emitting unit 35a. That is, the cam detection signal is decentered by the cam drive shaft 102a being rotated and decentered, and the support member 101 approaches the developing units 2M, 2Y, and 2C side as shown in FIG. Then, it is sent out when the intermediate transfer belt 10 is pressed against the photosensitive drums 3 of the developing units 2M, 2Y, and 2C by the transfer rollers 9 on the support member 101. For this reason, the cam detection signal indicates that the intermediate transfer belt 10 is pressed by the photosensitive drums 3 (the photosensitive drums 3 of the intermediate transfer belt 10 and the developing units 2M, 2Y, 2C, and 2K). Is a pressing state detection signal indicating that the pressing state is a state during color image forming operation).

  The moving mechanism 100 is moved to the position shown in FIG. 5A when a color image is formed, and moved to the position shown in FIG. 5B when a monochrome image is formed, by driving control of the drive motor 103 by the control unit 111. The operation is controlled.

  At the time of color image formation, the support member 101 moves to the position shown in FIG. 5A, for example, by the rotation of the eccentric cam 102, and the transfer roller of each of the developing units 2M, 2Y, 2C, and 2K. The second backup roller 33a applies tension to the intermediate transfer belt 10 when 9 is in contact. For this reason, the contact portion between the intermediate transfer belt 10 and the photosensitive drum 3 of the developing unit 2K and the contact portion between the intermediate transfer belt 10 and each of the photosensitive drums 3 of the developing units 2M, 2C, and 2Y are separated from the intermediate transfer belt 10. It becomes difficult to be affected by fluctuations of vibration and vibration. Since the support member 101 swings about the first backup roller 30 as a support shaft, the contact of the photosensitive drum 3 of the developing unit 2K with the intermediate transfer belt 10 during the color image forming operation and the monochrome image forming operation. The state does not change.

  On the other hand, during the monochrome image forming operation, as shown in FIG. 5B, the support member 101 rotates in the direction away from the photosensitive drums 3 of the development units 2M, 2C, and 2Y, and moves to the support member 101. The intermediate transfer belt 10 released from the pressing of the developing units 2M, 2C, and 2Y to the photosensitive drums 3 by the shaft-supported transfer rollers 9 is transferred to the photosensitive drums 3 of the developing units 2M, 2C, and 2Y. Separate from. When the intermediate transfer belt 10 is not given any tension along with the rotation of the support member 101, the second backup roller 33a moves in a direction to release the bias, so that the tension of the intermediate transfer belt 10 decreases. To do.

  However, along with the change in the posture of the support member 101 at this time, the second backup roller 33b is driven roller 11b on the opposite side of each of the developing units 2M, 2C, and 2Y with respect to the photosensitive drums 3 with the support member 101 interposed therebetween. And the secondary transfer counter roller 13 are pressed against the inner surface of the intermediate transfer belt 10, and the second backup roller 33 b applies a constant tension to the intermediate transfer belt 10. As a result, a decrease in the tension of the intermediate transfer belt 10 is prevented, and the tension of the intermediate transfer belt 10 is substantially reduced when the developing units 2M, 2C, and 2Y are in contact with the photosensitive drums 3 and when they are separated from each other. Can be constant.

  Accordingly, even when the posture during the color image forming operation is switched to the posture during the monochrome image forming operation, the contact state between the intermediate transfer belt 10 and the photosensitive drum 3 of the developing unit 2K can be made substantially constant, and the black Changes in the transfer state of the image can be suppressed. During the monochrome image forming operation, the intermediate transfer belt 10 is stretched by the drive roller 11a, the driven roller 11b, the second backup roller 33b, the secondary transfer counter roller 13 and the first backup roller 30, and is driven by the drive roller 11a. Then, only the photosensitive drum 3 of the developing unit 2K comes into contact, and travels in the direction of the arrow shown in FIGS. 5 (a) and 5 (b) while receiving the primary transfer by the transfer roller 9.

  In the switching from the position at the time of the color image forming operation to the position at the time of the monochrome image forming operation, the tension applied to the intermediate transfer belt 10 by the second backup roller 33b pressing the inner surface is the same as that during the color image forming operation. Any amount can be used as long as the decrease in tension applied by the second backup roller 33a at the position can be compensated. For example, the relationship between the amount of rotation of the support member 101 in the separating direction and the decrease or increase in the tension of the intermediate transfer belt 10 can be determined and set as appropriate through preliminary experiments or the like.

  Next, the setting of the timing for executing the process (press adjusting process) for adjusting the state in which the intermediate transfer belt 10 moved by the moving mechanism 100 is pressed by the developing units 2M, 2Y, and 2C in the multifunction machine 1 will be described. . FIG. 6 is a flowchart showing the flow of processing when setting the execution timing of the pressing adjustment processing. 7 and 8 are diagrams illustrating an example of a display screen of the display unit 311. FIG.

  In the multifunction device 1, when the power switch is turned on, an initial screen such as a copy operation acceptance screen (not shown) is displayed on the display unit 311 under the control of the control unit 111. In this state, when the user operates the timing setting instruction input button 314 of the operation unit 310 and receives an instruction from the user to start setting the execution timing of the press adjustment process (YES in S1), the control is performed. The unit 111 causes the display unit 311 to display a pressing state adjustment timing setting screen 3101 as shown in FIG. 7 (S2). Note that the screen data of each display screen displayed on the display unit 311 is stored in a data storage unit including a memory provided in the control unit 110.

  The pressing state adjustment timing setting screen 3101 displays a manual button 3101a, an automatic button 3101b, an OFF button 3101c, an OK button 3101d, and a cancel button 3101e.

  The manual button 3101a is a button that is input from the user as the time designation instruction by the touch panel function in response to a pressing operation by the user.

  The automatic button 3101b is a button in which an instruction to periodically execute the pressing state adjustment at a predetermined time is input from the user as the time specification instruction by the touch panel function.

  The OFF button 3101c is a button for inputting an instruction to stop the execution of the regular pressing state adjustment at a predetermined time from the user as the time specifying instruction by the touch panel function.

  The OK button 3101d is a button for inputting an instruction for confirming each instruction input by the manual button 3101a, the automatic button 3101b, and the OFF button 3101c by a touch panel function.

  The cancel button 3101e is a button by which a user inputs an instruction to cancel each instruction input by the manual button 3101a, the automatic button 3101b, and the OFF button 3101c by a touch panel function.

  While the pressing state adjustment timing setting screen 3101 is displayed, when an instruction to stop the execution of the periodic pressing state adjustment at a predetermined time is input by the user's operation of the OFF button 3101c (NO in S3) ), The time designation accepting unit 113 accepts the instruction, and stores the setting for stopping the execution of the periodic pressing state adjustment at a predetermined time (S7).

  On the other hand, when the manual button 3101a or the automatic button 3101b is operated by the user while the pressing state adjustment timing setting screen 3101 is displayed and an instruction for specifying the timing for performing the pressing state adjustment is input (YES in S3), The designation receiving unit 113 determines whether the instruction is based on the operation of the manual button 3101a or the automatic button 3101b (S4), and immediately executes the pressing state adjustment operation by the operation of the manual button 3101a. When the instruction to that effect is input (“manual” in S4), the timing designation receiving unit 113 receives the instruction and stores the timing setting so that the pressing state adjustment is immediately executed (S6).

  When the user presses the OFF button 3101c while the pressing state adjustment timing setting screen 3101 is displayed, the control unit 111 displays the adjustment execution timing display portion 3101f on the pressing state adjustment timing setting screen 3101. And, for example, “when warming up”, “before printing (copying) (before starting image forming operation)”, “after calibration”, etc., are displayed as pull-down display candidates for timing adjustment. . Thus, when the candidate of the timing for executing the pressing state adjustment is displayed on the display unit 311, if any of the display portions of the candidates is pressed by the user operation, the touch panel function is pressed. The timing corresponding to the displayed portion is input as a timing designation instruction, and the timing designation receiving unit 113 receives the timing designation instruction.

  The timing designation receiving unit 113 determines that the instruction input in S3 is an instruction based on the operation of the automatic button 3101b, and an instruction to periodically execute the pressing state adjustment at a predetermined time is input. If it is (“automatic” in S4), the timing designation accepting unit 113 determines the timing indicated by the timing designation instruction input by pressing the display portion of each candidate in advance as described above at which the regular pressing state adjustment is executed. The setting (automatic adjustment setting) is stored as the given timing (S5).

  Next, a timing determination process for executing the pressing state adjustment process will be described. FIG. 9 is a flowchart showing a timing determination process for executing the pressing state adjustment process. The details of the pressing state adjustment process will be described later.

  When the multifunction device 1 is turned on and the multifunction device 1 is in an input standby state for various jobs such as a copy operation, the control unit 111 sets the setting stored in the time designation receiving unit 113 as follows: It is determined whether the automatic adjustment setting is set (S11).

  Here, when the control unit 111 determines that the setting stored in the timing designation receiving unit 113 is not the automatic adjustment setting but the timing is set so that the pressing state adjustment is immediately executed ( NO in S11, YES in S16), the pressing state adjustment process is immediately started at this point (S15). If the control unit 111 determines that the timing is not set so that the pressing state adjustment is immediately executed (NO in S16), the processing from S11 is performed again without starting the pressing state adjustment. repeat.

  On the other hand, when the control unit 111 determines that the setting stored in the time designation receiving unit 113 is the automatic adjustment setting (YES in S11), the control unit 111 determines that the operation state of the multifunction device 1 is warm-up. In operation, it is determined whether it corresponds to before printing (copying) or after calibration, and when the multifunction device 1 reaches any of the states (YES in S12, YES in S13, YES in S14) ) At this time, the pressing state adjustment process is started (S15).

  Also, when the operation state of the multifunction device 1 has not reached any state during the warm-up operation, before printing (copying) or after calibration (NO in S12, NO in S13, NO in S14), the pressing The process is repeated from S11 again without starting the state adjustment.

  Next, an adjustment process (pressing state adjustment process) in which the intermediate transfer belt 10 is pressed by each photosensitive drum 3 by the multifunction machine 1 will be described. FIG. 10 is a flowchart showing an adjustment process in a state where the intermediate transfer belt 10 is pressed by each photosensitive drum 3. FIG. 11 is a timing chart of the drive signal of the drive motor 103 of the moving mechanism 100 and the detection signal from the cam position detection sensor 35. FIG. 12 shows the drive signal of the drive motor 103 of the moving mechanism 100, the detection signal from the cam position detection sensor 35, and the developing unit 2M during the adjustment process of the pressing state of the intermediate transfer belt 10 and each photosensitive drum 3. 6 is a timing chart of the image output signal and the density detection signal from the density sensor 18. FIG. 13 is a graph showing each density of the toner pattern transferred onto the circumferential surface of the intermediate transfer belt 10.

  The said press state adjustment process is performed at the timing mentioned above. When the pressing state adjustment process is executed, under the control of the control unit 111, the moving mechanism 100 uses the transfer rollers 9 corresponding to the developing units 2M, 2C, and 2Y, and the intermediate transfer belt 10 during the monochrome image forming operation uses the respective photosensitive rollers. From the position away from the body drum 3, the corresponding photosensitive drum 3 is moved to a position where the intermediate transfer belt 10 is sandwiched during the color image forming operation.

  When the moving mechanism 100 rotates the support member 101 to move each transfer roller 9 and the intermediate transfer belt 10 from the position at the time of the monochrome image forming operation to the position at the time of the color image forming operation, the initial setting of the multifunction device 1 is performed. Then, as shown in FIG. 11, the controller 111 sends a drive signal to the drive motor 103 to rotate the support member 101 with the rotational drive force of the drive motor 103, and the cam position detection sensor (press separation detection). An example of the unit) When the pressing state detection signal output from 35 is received, sending of the driving signal to the driving motor 103 is stopped. That is, the intermediate transfer belt 10 is pressed by the photosensitive drums 3 of the developing units 2M, 2Y, and 2C at the position when the pressing detection signal is received from the cam position detecting sensor 35. The pressing state adjustment is performed on the basis of this state.

  When adjusting the degree to which the intermediate transfer belt 10 is pressed by each photosensitive drum 3, first, the control unit 111 sends a drive signal to the drive motor 103 to drive the drive motor 103 (S21). The support member 101 is rotated by the rotational driving force 103, and the support member 101 at the position at the time of the monochrome image forming operation is moved to the position at the time of the color image forming operation.

  The control unit 111 determines whether the intermediate transfer belt 10 is pressed by the photosensitive drums 3 of the developing units 2M, 2Y, and 2C based on the pressure detection signal from the cam position detection sensor 35. (S22). When the control unit 111 receives a pressing detection signal from the cam position detection sensor 35 (YES in S22), it is determined that the intermediate transfer belt 10 is pressed by each photosensitive drum 3 with this, A predetermined delay amount (a delay time from the reception of the pressing state detection signal, the delay amount d = 0 (msec) when the drive motor 103 is driven for the first time (delay amount 0 in FIG. 12)) Whether or not a delay amount obtained by adding a predetermined time t (msec) to the delay amount d has elapsed has been measured by a timer or the like built in the control unit 111 (S23). When the control unit 111 measures the passage of the delay amount from the time when the pressing state detection signal is received (YES in S23), the sending of the drive signal to the drive motor 103 is stopped at this time, and the drive motor 103 is driven. Is stopped (S24). In addition, as shown in FIG. 12, the transmission stop timing of the drive signal of the drive motor 103 at the first time is when the pressing state detection signal is received.

  Further, as shown in FIG. 12, the control unit 111 drives the developing unit 2M on the most upstream side in the traveling direction of the intermediate transfer belt 10 to form the toner pattern tp when the driving of the driving motor 103 is stopped. And further transferred to the intermediate transfer belt 10 (S25).

  Thereafter, when the density sensor 18 detects the density of the toner pattern tp (YES in S26), the determination unit 112 detects the detected toner pattern density based on the density detection signal received from the density sensor 18 last time. It is determined whether or not the toner pattern density is smaller (S27). Note that the determination unit 112 uses a density value indicating the lowest density as the previously detected toner pattern density in the first determination.

  Here, when the determination unit 112 determines that the detected toner pattern density is equal to or higher than the previously detected toner pattern density (NO in S27), the determination unit 112 determines the currently detected toner pattern density. Then, it is stored as the previously detected toner pattern density used for the next determination in S7 (S28). When it is determined for the first time, S27 is NO and the process proceeds to S28.

  Then, the control unit 111 sets the delay amount d used for the delay amount measurement in S23 to be performed next time to the delay amount d = d + t (msec) (S29, delay amount A in FIG. 12). Then, the control unit 111 sends a drive signal to the drive motor 103 to drive the drive motor 103 (S30), rotates the support member 101 with the rotational driving force of the drive motor 103, and causes the intermediate transfer belt 10 to move. Then, the developing units 2M, 2Y, and 2C are moved away from the respective photosensitive drums 3 from the positions pressed by the respective photosensitive drums 3. When the control unit 111 does not receive the pressing state detection signal from the cam position detection sensor 35 and the intermediate transfer belt 10 is separated from each photosensitive drum 3 (YES in S31), the process returns to S21.

  Then, when the control unit 111 starts the processing after S21 again and receives a pressing state detection signal from the cam position detection sensor 35 (YES in S22), has a predetermined delay amount elapsed since this reception? No is performed using the delay amount d = d + t (msec) set in S29 (S23, delay amount B in FIG. 12). Thereafter, the processing of S14 to S27 is performed as in the first time. If the determination unit 112 determines in S27 that the detected toner pattern density is equal to or higher than the previously detected toner pattern density (NO in S27), the processes in S28 to S31 are repeated again. In S28, the determination unit 112 sets the toner pattern density detected this time as the previously detected toner pattern density used for the next determination in S27 (S28).

  As described above, the processing from S21 to S31 is repeated (as shown in FIG. 12, the delay amount is 0, A, B, C,... In S23, for example). As shown in sequence C of FIG. 12, when it is determined that the detected toner pattern density is lower than the previously detected toner pattern density (YES in S27), the control unit 111 performs 1 of S23 of this time. The delay amount d (for example, the delay amount B of the sequence B in FIG. 12) used in the processing of S23 performed before the operation is stored in a built-in memory or the like (S32), and the drive motor is used during a normal color image forming operation. 103, when the cam position detection sensor 35 detects that the intermediate transfer belt 10 is pressed by the respective photosensitive drums 3 and when the stored delay amount d has elapsed. In the state where the moving operation by the moving mechanism 100 is stopped, the color image forming operation by the developing units 2M, 2C, 2Y, 2K is set to be performed.

  That is, after the toner pattern is transferred to the intermediate transfer belt 10 under the control of the control unit 111, the determination unit 112 determines the density of the toner pattern detected by the density sensor 18 (that is, a predetermined value (that is, The photosensitive drums 3 of the developing units 2M, 2Y, 2C, and 2K moved by the moving mechanism 100 when the driving motor 103 reaches a value higher than that in the state where the driving motor 103 is stopped at the other delay amount. In addition, it is determined that the pressing state of the intermediate transfer belt 10 at that time is a normal pressing state.

  In the above description, when the drive of the drive motor 103 is stopped, the control unit 111 drives the most upstream developing unit 2M in the traveling direction of the intermediate transfer belt 10 to form a toner pattern tp to transfer the transfer roller. 9 is transferred to the intermediate transfer belt 10 (S25), and the subsequent photosensitive drum processing is performed based on the toner pattern tp transferred onto the peripheral surface of the intermediate transfer belt 10 by the developing unit 2M. The unit 111 uses the delay amounts d of S3 to drive the developing units 2M, 2Y, 2C, and 2K to form the toner patterns tp on the intermediate transfer belt 10 and transfer them to the intermediate transfer belt 10 in S25. Processing is performed based on each toner pattern tp transferred onto the peripheral surface of the intermediate transfer belt 10 by the developing units 2M, 2Y, 2C, and 2K. For the toner pattern tp, when the determination unit 112 determines that the density of all the toner patterns detected this time is lower than the previously detected toner pattern density in the process of S7 (YES in S27), the control unit 111 stores the delay amount d used in the processing of S23 performed once before S23 (S32), and when driving the drive motor 103 during the normal color image forming operation, the cam position detection sensor 35 is stored. The developing unit 2M is in a state where the moving operation by the moving mechanism 100 is stopped when the stored delay amount d has elapsed from the time when the intermediate transfer belt 10 is detected to be pressed by the respective photosensitive drums 3. , 2C, 2Y, 2K may be set so that a color image forming operation is performed.

  Next, drive control of the moving mechanism 100 during a normal color image forming operation will be described. FIG. 14 is a flowchart showing drive control of the moving mechanism 100 during a normal color image forming operation. FIG. 15 is a timing chart of the drive signal of the drive motor 103 of the moving mechanism 100 and the detection signal from the cam position detection sensor 35.

  When the moving mechanism 100 moves the intermediate transfer belt 10 and each transfer roller 9 from the position at the time of the color image forming operation to the position at the time of the color image forming operation during the color image forming operation, the controller 111 first drives. A drive signal is sent to the motor 103 to drive the drive motor 103 (S41), the support member 101 is rotated by the rotational driving force of the drive motor 103, and the support member 101 is moved from the position during the monochrome image forming operation to a color image. Move toward the position during the forming operation.

  When the control unit 111 receives a pressing state detection signal from the cam position detection sensor 35 (YES in S42), whether or not the delay amount d stored by the control unit 111 in the process of S32 shown in FIG. 10 has elapsed. The control unit 111 measures this with a built-in timer or the like, and stops sending the drive signal to the drive motor 103 when the delay amount d is measured (YES in S43) as shown in FIG. Then, the drive of the drive motor 103 is stopped (S44).

  Thereafter, the control unit 111 is in a state in which the intermediate transfer belt 10 at the time of the stop is pressed by each photosensitive drum 3 based on a color image forming job input from the operation unit (not shown) by the user. Then, a color image forming operation is performed by the developing units 2M, 2C, 2Y, and 2K.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, in the above-described embodiment, the multifunction device 1 includes the developing units 2M, 2Y, 2C, and 2K, and the moving mechanism moves from the position during the monochrome image forming operation to the position during the color image forming operation during the color image forming operation. 100, the process of adjusting the pressing state of the intermediate transfer belt 10 and each photosensitive drum 3 when the intermediate transfer belt 10 and each transfer roller 9 are moved is described. However, the present invention is not limited to this, and the present invention is not limited to this. The present invention can be widely applied as a process for adjusting the pressing state between the transfer body and the photosensitive drum (development unit) for transferring to the transfer body. For example, the series of processes shown in FIGS. 6, 9, 10, and 14 can be applied to adjusting the pressing state of the photosensitive drum that transfers the toner image to the transfer belt and the transfer drum. is there.

  The configuration and processing according to the first embodiment shown in FIGS. 1 to 15 are merely examples of the configuration and processing of the image forming apparatus according to the present invention, and the configuration and processing of the image forming apparatus according to the present invention are the same. The contents are not limited to those described above.

[Second Embodiment]
Hereinafter, a second embodiment of a multifunction machine 1 as an example of an image forming apparatus according to an embodiment of the present disclosure will be described with reference to the drawings. Note that the description of the same configuration and processing as those in the first embodiment is omitted. FIG. 16 is a front cross-sectional view showing the structure of the multifunction machine 1 according to the second embodiment.

  In the present embodiment, a moving mechanism 76 is provided for moving the secondary transfer roller 14 in the direction of moving toward and away from the intermediate transfer belt 10. The details of the moving mechanism 76 will be described later in detail in FIGS. 5 and 6, and FIG. 1 shows only the outline of the moving mechanism 76.

  As in the first embodiment, on the outer peripheral surface of the intermediate transfer belt 10, a density sensor is disposed downstream of the intermediate transfer belt 10 in the running direction with respect to each nip portion between the developing units 2M, 2C, 2Y, and 2K and the intermediate transfer belt 10. A (toner pattern density detection unit) 18 is provided. In this embodiment, when adjusting the pressing state of the secondary transfer roller 14 and the intermediate transfer belt 10 described later, at least one of the developing units 2M, 2Y, 2C, and 2K and the transfer roller 9 corresponding thereto are used to perform intermediate adjustment. It is also used to detect the density of the toner pattern formed on the transfer belt 10. However, a density sensor for adjusting the pressing state of the secondary transfer roller 14 and the intermediate transfer belt 10 may be provided separately from the density sensor 18 for calibration.

  The configuration of the control system of the MFP 1 according to the second embodiment is the same as the schematic configuration of the control system of the MFP 1 according to the first embodiment shown in FIG. The second embodiment has the same configuration as that of the first embodiment unless otherwise described. However, each part of the multifunction machine 1 in the second embodiment is in a contact state between the secondary transfer roller 14 and the intermediate transfer belt 10. Processing related to adjustment of (pressed state) is performed. That is, each part in the second embodiment does not perform the process shown in the first embodiment for adjusting the state in which the intermediate transfer belt 10 is pressed by the developing units 2M, 2Y, and 2C.

  In the second embodiment, the drive motor 500 controlled by the control unit 111 is a generic name for each drive source of the secondary transfer roller 14, the intermediate transfer belt 10, the image forming unit 2, the fixing device 16, and a moving mechanism 76 described later. is there.

  In the second embodiment, the control unit 111 drives the toner pattern tp with the image forming unit 2 and the drive motor 500 to develop the toner pattern tp when adjusting the pressing state between the secondary transfer roller 14 and the intermediate transfer belt 10. At least one of the units 2M, 2Y, 2C, and 2K, for example, a magenta developing unit 2M of the image forming unit 2 is formed in the vicinity of both ends in the width direction on the intermediate transfer belt 10 (FIG. 2). After the toner pattern tp on the circumferential surface of the intermediate transfer belt 10 is transferred to the secondary transfer roller 14 to the secondary transfer roller 14 side, the toner pattern tp is transferred from the secondary transfer roller 14 to the intermediate transfer belt 10. The toner pattern transfer control is performed to transfer the toner again. In this embodiment, the developing unit 2M will be described as forming the toner pattern tp. This toner pattern tp is similar to the above-described predetermined density and shape. However, the purpose is not to limit the toner pattern tp to the density and the shape. In the present embodiment, when the control unit 111 forms the toner pattern tp, the density of the toner pattern tp is detected by the density sensor 18.

  In the second embodiment, the determination unit 112 determines whether or not the density of the toner pattern on the peripheral surface of the intermediate transfer belt 10 detected by the density sensor 18 has reached a predetermined normal value. Is determined to be satisfied, the secondary transfer roller 14 determines that the state where the intermediate transfer belt 10 is pressed is normal.

  When the determination unit 112 determines that the state where the intermediate transfer belt 10 is pressed by the secondary transfer roller 14 is not normal, the control unit 111 causes the display unit 311 to warn the user.

  That is, in the case of image formation by the secondary transfer method using the intermediate transfer belt 10, when the toner pattern is appropriately transferred from the developing unit 2M to the intermediate transfer belt 10, the secondary transfer roller 14 and the intermediate transfer belt 10 When the contact between the intermediate transfer belt 10 and the intermediate transfer belt 10 is insufficient or excessive, and a suitable nip portion is not formed between the secondary transfer roller 14 and the intermediate transfer belt 10, a toner image from the intermediate transfer belt 10 to the secondary transfer roller 14 is obtained. Therefore, even if the toner pattern tp transferred onto the secondary transfer roller 14 is transferred again to the intermediate transfer belt 10 and returned, the toner pattern returned to the intermediate transfer belt 10 is returned. The concentration of tp decreases. Based on this, in the present embodiment, the density of the toner pattern detected by the density sensor 18 after the transfer of the toner pattern tp in both directions of the intermediate transfer belt 10 and the secondary transfer roller 14 is determined in advance. When the density value has been reached, the determination unit 112 determines that the 10-press state of the secondary transfer roller 14 and the intermediate transfer belt is normal.

  Next, a moving mechanism for moving the secondary transfer roller 14 in the contact / separation direction with respect to the intermediate transfer belt 10 will be described. FIG. 17 is a schematic view showing a moving mechanism provided on the intermediate transfer belt, and shows a posture in which the secondary transfer roller is separated from the intermediate transfer belt. FIG. 18 is a schematic view showing a moving mechanism provided on the intermediate transfer belt, and shows a posture in which the secondary transfer roller is pressed against the intermediate transfer belt.

  The moving mechanism 76 is a mechanism for moving the secondary transfer roller 14 in the contact / separation direction with respect to the intermediate transfer belt 10. As shown in FIGS. 17 and 18, the moving mechanism 76 is disposed below the intermediate transfer belt 10 portion stretched around the secondary transfer counter roller 13.

  The moving mechanism 76 includes a support frame 762, a rotation shaft 763, a coil spring 764, a first gear 765, a rotation shaft 768, a second gear 766, a cam 767, and a drive motor 769. ing.

  The secondary transfer roller 14 is disposed so as to face the secondary transfer counter roller 13 with the intermediate transfer belt 10 interposed therebetween, and is at a transfer position closest to the intermediate transfer belt 10 side (a position where the intermediate transfer belt 10 is pressed). The sheet is held between the intermediate transfer belt 10. Here, the secondary transfer roller 14 can be positioned at the transfer position (position shown in FIG. 17) and the separation position (position shown in FIG. 18) farthest from the intermediate transfer belt 10.

  The support frame 762 is a member for rotatably supporting the secondary transfer roller 14 and is a plate-like member extending in one direction. The support frame 762 rotatably supports the secondary transfer roller 14 at the upper part of one end, and a coil spring 764 is attached to the upper part of the other end. Further, the support frame 762 has a contact portion 762b for making contact with the cam 767 at a lower portion thereof, and a through hole 762c is provided at an upper portion substantially in the longitudinal direction. A rotation shaft 763 for rotating the support frame 762 is rotatably supported. The rotation shaft 763 is disposed so as to penetrate the through hole 762c. Further, the rotating shaft 763 is rotatably attached to a frame (not shown) of the moving mechanism 76. The support frame 762 pivotally supports the secondary transfer roller 14 at both axial ends of the rotation shaft.

  The coil spring 764 is composed of a tension spring or the like, and applies a biasing force to the support frame 762 in a direction in which the secondary transfer roller 14 is brought close to the intermediate transfer belt 10. Specifically, the coil spring 764 biases the other end portion (the right end portion in FIGS. 17 and 18) of the support frame 762 downward in both drawings. When the other end portion of the support frame 762 is biased downward, the biasing force causes the support frame 762 to pivot about the pivot shaft 763, and the end portion side supporting the secondary transfer roller 14 moves upward. To do. That is, the secondary transfer roller 14 moves to the intermediate transfer belt 10 side.

  The first gear 765 is a member attached to the rotation shaft 768 and meshes with the second gear 766 of the cam 767. The first gear 765 rotates with the rotation of the rotation shaft 768.

  The second gear 766 is arranged side by side with the first gear 765 and rotates with the rotation of the first gear 765.

  The cam 767 is a member for moving the secondary transfer roller 14 away from the intermediate transfer belt 10 by pushing up the support frame 762 upward, and is arranged so as to be able to contact the contact portion 762b of the support frame 762. ing. The cam 767 is a member attached to the rotation shaft 768 of the second gear 766 and rotates with the rotation of the second gear 766. Further, the cam 767 is an elliptical member due to the rotational driving force of the drive motor 769, and the position of the cam 767 is changed each time the first portion 767 a and the second portion 767 b having different distances from the rotation shaft 768 rotate 180 °. It is supposed to be replaced.

  The rotation shaft 768 is a member that rotates the first gear 765 and extends in a direction substantially orthogonal to the support frame 762.

  Further, the cam drive shaft 767 c of the cam 767 extends in the direction of the rotation axis of the secondary transfer roller 14. A cam 767 is disposed at a position of a cam drive shaft 767c that can press the support frame 762 in the rotation axis direction. A cam position detection sensor (pressing state detector) 35 for detecting the posture of the cam 767 rotated by the cam drive shaft 767c is attached to the bottom surface of the support frame 762 near the position where the cam 767 is disposed or the apparatus main body 2a. It has been. The cam position detection sensor 35 includes a light emitting unit 35a and a light receiving unit 35b. The light emitting portion 35 a is provided on one side of the cam 767 with the cam 767 interposed therebetween, and the light receiving portion 35 b is provided on the other side of the cam 767. The light emitting unit 35a and the light receiving unit 35b are eccentric when the cam 767 is rotated by the cam drive shaft 767c and the posture is within a certain range before and after the posture shown in FIG. ) Until the secondary transfer roller 14 presses the intermediate transfer belt 10 until the pressing state is released due to a change in the amount of eccentricity caused by further rotation of the cam 767). When the cam 767 is blocked by the cam 767 and is not received by the light receiving portion 35b, and the cam 767 has a posture other than the posture shown in FIG. 17, the light emitted by the light emitting portion 35a is blocked by the cam 767. For example, the light receiving portion 35b receives light at a bottom surface of the support frame 762 or a position on the apparatus main body 2a.

  The cam position detection sensor 35 sends a cam detection signal to the control unit 111 when the light receiving unit 35b does not receive light from the light emitting unit 35a. That is, the cam detection signal is decentered by rotation of the cam 767 by the cam drive shaft 767c, and is in a state close to the posture shown in FIG. 17, so that the support frame 762 approaches the intermediate transfer belt 10 and is on the support frame 762. Sent when the intermediate transfer belt 10 is pressed by the secondary transfer roller 14. For this reason, the cam detection signal indicates that the intermediate transfer belt 10 is pressed by the secondary transfer roller 14 (the pressing state between the intermediate transfer belt 10 and the secondary transfer roller 14 is a color image forming operation). It is a pressed state detection signal indicating that the state has been reached.

  Next, a first mode of adjustment processing in a state where the intermediate transfer belt 10 is pressed by the secondary transfer roller 14 by the multifunction machine 1 according to the second embodiment will be described. FIG. 19 is a flowchart illustrating a first embodiment of the adjustment process in a state where the intermediate transfer belt 10 is pressed by the secondary transfer roller 14. FIG. 20 shows the drive signal of the drive motor 769 of the moving mechanism 76, the detection signal from the cam position detection sensor 35, and the developing unit 2M output during the adjustment process of the pressing state of the intermediate transfer belt 10 and the secondary transfer roller 14. An image output signal, a density detection signal from the density sensor 18, a bias application signal for applying a secondary transfer bias to the second bias application section of the bias application section 32, and a drive for causing the belt cleaning device 19 to perform belt cleaning. It is a timing chart of a signal.

  The timing chart of the drive signal of the drive motor 769 of the moving mechanism 76 and the detection signal from the cam position detection sensor 35 is shown in FIG. The above-described FIG. 13 is used as a graph showing the density of each toner pattern transferred onto the peripheral surface of the intermediate transfer belt 10.

  The pressing state adjustment process is executed at the timing described with reference to FIG. When the pressing state adjustment process is executed, the secondary transfer roller 14 is moved by the moving mechanism 76 under the control of the control unit 111, and the intermediate transfer belt 14 is moved by the secondary transfer roller 14 from the position where the secondary transfer roller 14 separates the intermediate transfer belt 10. The transfer belt 10 is moved to a position where it is pressed.

  When the moving mechanism 76 rotates the support frame 762 to move the secondary transfer roller 14 to a position where the intermediate transfer belt 10 is pressed, in the initial setting of the multifunction machine 1, as shown in FIG. Sends a drive signal to the drive motor 769 and rotates the support frame 762 by the rotation of the gear 765 and the cam 767 by the rotational driving force of the drive motor 769, and the cam position detection sensor (an example of a press separation detection unit). When the pressing state detection signal output from 35 is received, sending of the drive signal to the drive motor 769 is set to stop. That is, the intermediate transfer belt 10 is pressed by the secondary transfer roller 14 at the position when the pressing detection signal is received from the cam position detection sensor 35. The pressing state adjustment is performed on the basis of this state.

  When adjusting the degree to which the intermediate transfer belt 10 is pressed by the secondary transfer roller 14, first, the control unit 111 sends a drive signal to the drive motor 769 to drive the drive motor 769 (S51). The support frame 762 is rotated by the rotation of the gear 765 and the cam 767 by the rotational driving force 769, and the secondary transfer roller 14 is separated from the intermediate transfer belt 10 (FIG. 18). The transfer roller 14 is moved to a state where the intermediate transfer belt 10 is pressed (FIG. 17).

  Then, the control unit 111 determines whether the intermediate transfer belt 10 is pressed by the secondary transfer roller 14 based on the pressure detection signal from the cam position detection sensor 35 (S52). When the control unit 111 receives a pressure detection signal from the cam position detection sensor 35 (YES in S52), it determines that the intermediate transfer belt 10 is pressed by the secondary transfer roller 14 with this, A predetermined delay amount (a delay time from the reception of the pressing state detection signal, and a delay amount d = 0 (msec) when the drive motor 769 is driven for the first time (delay amount 0 in FIG. 20). Whether or not a delay amount obtained by adding a predetermined time t (msec) to the delay amount d has elapsed has been measured by a timer or the like built in the control unit 111 (S53). When the control unit 111 measures the passage of the delay amount from the time when the pressing state detection signal is received (YES in S53), at this time, the transmission of the drive signal to the drive motor 769 is stopped and the drive motor 769 is driven. Is stopped (S54). In addition, as shown in FIG. 20, the transmission stop timing of the drive signal of the drive motor 769 for the first time is when the pressing state detection signal is received.

  Further, as shown in FIG. 20, when the driving of the drive motor 769 is stopped, the control unit 111 drives the developing unit 2M in the traveling direction of the intermediate transfer belt 10 to form a toner pattern tp, and further intermediate Transfer is performed on the transfer belt 10 (S55).

  Thereafter, the density sensor 18 detects the density of the toner pattern tp, but this detection value is not used in the actual pressing state adjustment process.

  Subsequently, the control unit 111 moves the bias transfer unit at a timing when the toner pattern tp transferred onto the intermediate transfer belt 10 is conveyed to a position facing the secondary transfer roller 14 by the traveling of the intermediate transfer belt 10. A bias application signal for applying the secondary transfer bias is output to the 32 second bias application units (S56). As a result, the toner pattern tp on the intermediate transfer belt 10 is transferred to the secondary transfer roller 14 and moves to the secondary transfer roller 14 side.

  The control unit 111 stops outputting the drive signal for performing belt cleaning to the belt cleaning device 19 substantially simultaneously with the output of the bias application signal (S57).

  Further, the control unit 111 completes the movement of the toner pattern tp on the intermediate transfer belt 10 toward the secondary transfer roller 14 as described above, and then applies the bias application signal to the second bias application unit of the bias application unit 32. Is stopped (S58), the toner pattern tp moved to the secondary transfer roller 14 side is transferred to the intermediate transfer belt 10 side, and the toner pattern tp is moved again to the intermediate transfer belt 10 side.

  The control unit 111 applies the drive signal to the belt cleaning device 19 until the toner pattern tp returned to the intermediate transfer belt 10 passes the cleaning position by the belt cleaning device 19 due to the travel of the intermediate transfer belt 10. The output is stopped, and the output of the drive signal to the belt cleaning device 19 is resumed at the timing after the toner pattern tp has passed the cleaning position (S59).

  The toner pattern tp moves to a density detection position by the density sensor 18 as the intermediate transfer belt 10 travels. When the toner pattern tp moves to the density detection position by the density sensor 18 and density detection is performed by the density sensor 18 (YES in S60), the determination unit 112 is based on the density detection signal received from the density sensor 18. It is determined whether the condition that the detected toner pattern density is smaller than the previously detected toner pattern density is satisfied (S61). Note that the determination unit 112 uses a density value indicating the lowest density as the previously detected toner pattern density at the time of the first determination.

  Here, when the determination unit 112 determines that the detected toner pattern density is equal to or higher than the previously detected toner pattern density (NO in S61), the determination unit 112 determines the currently detected toner pattern density. Then, it is stored as the previously detected toner pattern density used for the next determination in S61 (S62). When it is determined for the first time, NO is determined in S61, and the process proceeds to S62.

  Then, the control unit 111 sets the delay amount d used for the delay amount measurement in the next S3 to be the delay amount d = d + t (msec) (S63, delay amount A in FIG. 20). Then, the control unit 111 sends a drive signal to the drive motor 769 to drive the drive motor 769 (S64), rotates the support frame 762 by the gear 765 and the cam 767, and moves the secondary transfer roller 14 to the intermediate position. The transfer belt 10 is moved away from the intermediate transfer belt 10 from a position where the transfer belt 10 is pressed. When the control unit 111 does not receive the pressing state detection signal from the cam position detection sensor 35 and the secondary transfer roller 14 is separated from the intermediate transfer belt 10 (YES in S65), the process returns to S51.

  Then, the control unit 111 starts the processing after S51 again, and when a pressing state detection signal is received from the cam position detection sensor 35 (YES in S52), has a predetermined delay amount elapsed since this reception? No is performed using the delay amount d = d + t (msec) set in S63 (S53, delay amount B in FIG. 20). Thereafter, the processing from S54 to S61 is performed as in the first time. If the determination unit 112 determines in S61 that the detected toner pattern density is equal to or higher than the previously detected toner pattern density (NO in S61), the processes of S62 to S65 are repeated again. In S62, the determination unit 112 sets the toner pattern density detected this time as the previously detected toner pattern density used for the next determination in S61 (S62).

  As described above, the processing from S51 to S65 is repeated (as shown in FIG. 20, the delay amount is 0, A, B, C,... In S53, for example). As shown in sequence C of FIG. 20, when it is determined that the detected toner pattern density is lower than the previously detected toner pattern density (YES in S61), the control unit 111 performs 1 of S53 of this time. The delay amount d (for example, the delay amount B of the sequence B in FIG. 20) used in the processing of S53 performed before the operation is stored in a built-in memory or the like (S66), and the drive motor is used during a normal color image forming operation. When the 769 is driven, from the time when the cam position detection sensor 35 detects that the intermediate transfer belt 10 is pressed by the secondary transfer roller 14 to the time when the stored delay amount d has elapsed. In the state where the moving operation by the moving mechanism 76 is stopped, the color image forming operation is performed by the developing units 2M, 2C, 2Y, 2K, the transfer roller 9, and the secondary transfer roller 14.

  That is, the determination unit 112 performs the transfer of the toner pattern to the intermediate transfer belt 10 and the transfer of the toner pattern tp in both directions of the intermediate transfer belt 10 and the secondary transfer roller 14 under the control of the control unit 111. When the density of the toner pattern detected by the density sensor 18 reaches a predetermined normal value (that is, a value indicating a higher density than when the driving motor 769 is stopped with the other delay amount). In addition, it is determined that the pressing state of the secondary transfer roller 14 and the intermediate transfer belt 10 moved by the moving mechanism 76 at the time is a normal pressing state.

  In the above description, when the drive of the drive motor 769 is stopped, the control unit 111 drives the developing unit 2M to form the toner pattern tp and transfers it to the intermediate transfer belt 10 by the transfer roller 9 (S55). The subsequent photosensitive drum processing is performed based on the toner pattern tp transferred onto the peripheral surface of the intermediate transfer belt 10 by the developing unit 2M. However, the control unit 111 sets each delay amount d in S53. In step S55, the developing units 2M, 2Y, 2C, and 2K are driven to form toner patterns tp on the respective units and transferred to the intermediate transfer belt 10, and the subsequent processes are performed on the developing units 2M, 2Y, 2C, and so on. 2K is performed based on each toner pattern tp transferred onto the circumferential surface of the intermediate transfer belt 10 by 2K, and all the toner patterns tp are processed in S57. When the determination unit 112 determines that the density of all the toner patterns detected this time is lower than the toner pattern density detected last time (YES in S61), the control unit 111 performs one time in S53. The delay amount d used in the previous processing of S53 is stored (S62), and when the drive motor 769 is driven during the normal color image forming operation, the intermediate transfer belt 10 is moved to the respective photosensitive belts by the cam position detection sensor 35. The color by the developing units 2M, 2C, 2Y, and 2K in a state in which the moving operation by the moving mechanism 76 is stopped when the stored delay amount d has elapsed from the time when it is detected that the body drum 3 is pressed. You may set so that image formation operation may be performed.

  The drive control of the moving mechanism 76 performed during the normal image forming operation in the multifunction machine 1 according to the second embodiment will be described with reference to FIGS. 14 and 15 described above.

  When the secondary transfer roller 14 is moved by the moving mechanism 76, the control unit 111 first sends a drive signal to the drive motor 769 to drive the drive motor 769 (S41), and is supported by the gear 765 and the cam 767. The frame 762 is rotated, and the secondary transfer roller 14 is moved toward the intermediate transfer belt 10 by the support frame 762.

  When the control unit 111 receives a pressing state detection signal from the cam position detection sensor 35 (YES in S42), whether or not the delay amount d stored by the control unit 111 in the process of S66 shown in FIG. 19 has elapsed. The control unit 111 measures this with a built-in timer or the like, and stops sending the drive signal to the drive motor 769 when the delay amount d is measured (YES in S43) as shown in FIG. Then, the drive of the drive motor 769 is stopped (S44).

  Thereafter, the control unit 111 presses the intermediate transfer belt 10 by the secondary transfer roller 14 at the stop point based on a color or monochrome image forming job input from an operation unit (not shown) by the operator. In this state, the image forming operation is performed only by the developing units 2M, 2C, 2Y, 2K, or the developing unit 2K.

  Next, a second form of processing for adjusting the state in which the intermediate transfer belt 10 is pressed by the secondary transfer roller 14 by the multifunction machine 1 according to the second embodiment will be described. FIG. 21 is a flowchart showing a second form of the adjustment process in a state where the intermediate transfer belt 10 is pressed by the secondary transfer roller 14. Note that description of the same processing as in the first embodiment is omitted.

  In the second embodiment, after detecting the density of the toner pattern tp by the density sensor 18 in S60, the determination unit 112 further determines that the timing at which the density of the toner pattern tp is detected by the density sensor 18 is the development unit 2M and the transfer unit. The intermediate transfer performed in S56 and S58 is before the timing at which the toner pattern reaches the density detection position by the density sensor 18 by the endless running of the intermediate transfer belt 10 after the toner pattern is transferred to the intermediate transfer belt 10 by the roller 9. A condition is determined as to whether or not the toner pattern transfer in both directions of the belt 10 and the secondary transfer roller 14 is delayed by a predetermined time (S68).

  The predetermined time is the time required for the transfer of the toner pattern tp in both directions of the intermediate transfer belt 10 and the secondary transfer roller 14 by the manufacturer before the factory shipment of the multifunction machine 1 or the like. Then, it is stored in a memory or the like built in the determination unit 112.

  If the determination unit 112 determines that the condition is not satisfied (NO in S68), the process proceeds to S63. That is, the determination unit 112 does not perform the process of storing the currently detected toner pattern density in S62 as the previously detected toner pattern density used for the next determination in S61, and the control unit 111 performs the process of S63. Done.

  Then, the processes from S63 to S65 are performed to increase the delay amount d, and the processes after S51 are repeated again.

  If the determination unit 112 determines that the above condition is satisfied (YES in S68), the determination unit 112 further performs the determination in S61.

  That is, in the second embodiment, since the contact between the secondary transfer roller 14 and the intermediate transfer belt 10 is insufficient, the toner pattern tp on the intermediate transfer belt 10 is moved to the secondary transfer roller 14 side. When the toner pattern tp reaches the density detection position by the density sensor 18 and does not return to the intermediate transfer belt 10 again, and the density of the toner pattern tp reaches a predetermined normal value. It is not determined that the pressing state of the secondary transfer roller 14 and the intermediate transfer belt is normal. Thereby, it is accurately determined that the pressing state of the secondary transfer roller 14 and the intermediate transfer belt 10 is normal.

  In each of the above-described forms by the multifunction machine 1 according to the second embodiment, the second density sensor that detects the density of the toner pattern tp for the pressing state adjustment process of the secondary transfer roller 14 and the intermediate transfer belt 10 is provided. The calibration density sensor 18 may be provided separately. In this case, if the second density sensor 180 is disposed at the position shown in FIG. 16, the density of the toner pattern tp that has undergone bidirectional transfer between the intermediate transfer belt 10 and the secondary transfer roller 14 is immediately determined. Can be detected. That is, it is necessary to perform the processing in which the density of the toner pattern tp detected by the density sensor 18 after the processing of S55 shown in the description of the pressing state adjustment processing according to the first embodiment is not used in the pressing state adjustment processing. The density of the toner pattern tp detected by the second density sensor 180 can be used for the determination in S61.

  The configuration and processing according to the second embodiment shown in FIGS. 16 to 21 are merely examples of the configuration and processing of the image forming apparatus according to the present invention, and the configuration and processing of the image forming apparatus according to the present invention are the same. The contents are not limited to those described above.

1 MFP
2 Image forming unit 2M, 2Y, 2C, 2K Developing unit 3 Photosensitive drum 9 Transfer roller 10 Intermediate transfer belt 14 Secondary transfer roller 30 Backup roller 35 Cam position detection sensor 76 Moving mechanism 762 Support frame 764 Coil spring 767 Cam 769 Drive Motor 100 Moving mechanism 101 Support member 102b Cam part 102 Eccentric cam 103 Drive motor 110 Control unit 111 Control part 112 Determination part 113 Timing designation receiving part 18 Concentration sensor 180 Second density sensor 310 Operation part 311 Display display part 314 Timing setting instruction input button

Claims (6)

A developing unit for forming a toner image;
An intermediate transfer belt having a peripheral surface to which a toner image is transferred by the developing unit;
A transfer portion for transferring the toner image from the developing unit to the intermediate transfer belt;
A moving mechanism for moving the intermediate transfer belt in a direction of contacting and separating from the developing unit and pressing the intermediate transfer belt against the developing unit;
A control unit that causes the developing unit to form the toner pattern and causes the transfer unit to perform transfer to the intermediate transfer belt;
Provided on the downstream side in the toner image conveying direction by the intermediate transfer belt from the nip portion between the developing unit and the intermediate transfer belt that has transferred the toner pattern to the intermediate transfer belt. A toner pattern density detection unit for detecting the density of a toner pattern which is a density detection toner image transferred onto the surface;
The toner pattern density detected by the toner pattern density detection unit reaches a predetermined density value after the toner pattern is transferred to the intermediate transfer belt under the control of the control unit. A determination unit that determines that the pressing state of the developing unit and the intermediate transfer belt moved by the moving mechanism is normal;
A timing designation receiving unit for receiving from the user a timing designation instruction for designating a determination operation execution timing for executing the pressing state determination operation including the toner pattern formation and transfer by the control unit and the determination by the determination unit;
The control unit and the determination unit are configured to perform the pressing state determination operation at a time indicated by the time specification instruction received from the user by the time specification reception unit. A developing unit for forming a toner image;
An intermediate transfer belt having a peripheral surface to which a toner image is transferred by the developing unit and running endlessly by being stretched by a plurality of rollers;
A transfer portion for transferring the toner image from the developing unit to the intermediate transfer belt;
A secondary transfer roller portion for secondary transfer of the toner image transferred by the developing unit onto the peripheral surface of the intermediate transfer belt onto a recording paper;
A moving mechanism for moving the secondary transfer roller portion in a direction of coming into contact with and separating from the intermediate transfer belt and pressing the secondary transfer roller portion against the intermediate transfer belt;
A toner pattern density detection unit that detects the density of a toner pattern that is a density detection toner image transferred from the developing unit onto the peripheral surface of the intermediate transfer belt;
The developing unit forms the toner pattern, causes the transfer unit to perform transfer to the intermediate transfer belt, and causes the secondary transfer roller unit to transfer the toner pattern on the peripheral surface of the intermediate transfer belt to the secondary transfer roller. A control unit that performs toner pattern transfer control to transfer the toner pattern again from the secondary transfer roller unit to the intermediate transfer belt after being transferred to the part side;
After the toner pattern transfer control by the control unit, when the toner pattern density on the peripheral surface of the intermediate transfer belt detected by the toner pattern density detection unit has reached a predetermined normal value, the movement A determination unit that determines that the pressing state of the intermediate transfer belt and the secondary transfer roller unit moved by a mechanism is normal;
A timing designation receiving unit for receiving from the user a timing designation instruction for designating a determination operation execution timing for executing the pressing state determination operation including the toner pattern formation and transfer by the control unit and the determination by the determination unit;
The control unit and the determination unit are configured to perform the pressing state determination operation at a time indicated by the time specification instruction received from the user by the time specification reception unit.   After the toner pattern transfer control by the control unit, the determination unit detects when the toner pattern density detection unit detects the density of the toner pattern to the intermediate transfer belt by the developing unit and the transfer unit. After the transfer of the toner pattern, the intermediate transfer belt and the secondary transfer roller unit in both directions are ahead of the timing at which the toner pattern reaches the density detection position by the toner pattern density detection unit due to endless running of the intermediate transfer belt. The toner pattern density on the peripheral surface of the intermediate transfer belt detected by the toner pattern density detection unit is set to a predetermined normal value when a condition that the toner pattern transfer is delayed by a predetermined time is satisfied. The image according to claim 2, wherein a determination is made as to whether or not the image has been reached. Forming apparatus.   The image forming apparatus according to claim 1, wherein the time designation receiving unit receives an instruction to immediately execute the pressing state determination operation from the user as the determination operation execution time.   The said time designation | designated reception part receives the instruction | indication to perform regularly the said press state determination operation | movement at the predetermined time from a user as the said determination operation execution time. Image forming apparatus.   The timing designation receiving unit is configured to perform the determination operation using at least one or more of the predetermined timing as a warm-up operation of the image forming apparatus, before the start of the image forming operation by the developing unit, or after execution of calibration. The image forming apparatus according to claim 5, wherein the execution time is received from a user.

Images