JP2009169294A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect a contact state of a secondary transfer part with an intermediate transfer body and to perform appropriate operation guidance in accordance with a state of imperfect contact when the imperfect contact occurs. <P>SOLUTION: The image forming apparatus includes a control part which permits image forming operation based on a print job if the density of a toner pattern on a more downstream side than a nip part between a secondary transfer roller 113 and an intermediate transfer belt 124 detected by a toner pattern density detection sensor 23 after it allows an image forming part 12 to transfer the toner pattern onto the intermediate transfer belt 124 and to transfer the toner pattern to the secondary transfer roller 113 is equal to or lower than a prescribed threshold, and which does not permit the image forming operation based on the print job if the density of the toner pattern is higher than the threshold. The control part allows a display part to give a warning having content made to differ in accordance with frequency of determining that the image forming operation is not permitted on the basis of the counted value by a determination frequency counter and a non-permission frequency counter. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus of a type in which a toner image is once transferred from an image forming unit to an intermediate transfer member, and further, the toner image is transferred to a recording sheet at a nip portion between the intermediate transfer member and a secondary transfer unit. In particular, the present invention relates to a technique for controlling an image forming operation in accordance with a contact state between a peripheral surface of an intermediate transfer member and a secondary transfer portion.

  Conventionally, as an image forming apparatus such as a color printer, a toner image formed on a photosensitive drum for each color is transferred (primary transfer) to an intermediate transfer belt and superimposed, and then superimposed on the intermediate transfer belt. A system is known in which a color image is formed on a recording sheet by transferring the toner image of each color onto the recording sheet (secondary transfer) at a nip portion between an intermediate transfer belt and a secondary transfer roller ( Patent Document 1).

  In such an image forming apparatus, the secondary transfer roller is accommodated in the apparatus main body in a state of being supported by a support member that can be rotated outwardly of the apparatus. , The contact state between the secondary transfer roller and the intermediate transfer belt can be released.

For example, when a jam occurs such that the paper is wound around the intermediate transfer belt after the secondary transfer, the user opens the main body cover 17 provided on the side surface of the apparatus main body 11 as shown in order in FIGS. 22 (a) to 22 (c). The support member 18 is exposed, and further, the support member 18 is rotated so as to be pulled out of the apparatus to expose the intermediate transfer belt 124 and the sheet conveyance path 111, whereby the secondary transfer roller and the intermediate transfer belt. Jam processing in the vicinity of the nip is possible. After the jam processing is completed, the user rotates the support member 18 toward the inside of the apparatus and accommodates it in the apparatus, and after the main body cover 17 is closed, the image forming operation is resumed.
Japanese Patent Application Laid-Open No. 11-59962

  In the conventional image forming apparatus, whether the secondary transfer roller is in proper contact with the intermediate transfer belt, that is, whether the toner image can be appropriately transferred from the intermediate transfer belt to the secondary transfer roller. This is indirectly detected by the open / closed state of the cover with respect to the apparatus main body. Specifically, if the cover is closed, the control unit of the image forming apparatus determines that the secondary transfer roller is in the appropriate contact state. If the cover is open, the secondary transfer roller is Judged that the contact was inappropriate. Then, the open / closed state of the cover with respect to the apparatus main body has been detected by mechanical means such as a switch. However, in this case, the secondary transfer roller is not in contact with the peripheral surface of the intermediate transfer belt only in part in the rotational axis direction of the drive roller for rotating the intermediate transfer belt, or in contact with the rotational axis direction at all. Even if an unsatisfactory contact failure has occurred, if the cover is closed, the control unit determines that the contact state of the secondary transfer roller is normal. Therefore, the intermediate transfer belt, the secondary transfer roller, There is a problem that it is impossible to accurately detect whether or not the contact state is appropriate.

  The present invention has been made to solve the above-described problems, and accurately detects the contact state between the secondary transfer unit and the intermediate transfer member, and responds to the contact failure state when the contact failure occurs. The purpose is to enable proper operation guidance.

The invention according to claim 1 is an image forming unit that forms a toner image;
An intermediate transfer member having a peripheral surface to which a toner image is transferred from the image forming unit;
A secondary transfer portion that contacts the peripheral surface of the intermediate transfer member to form a nip portion, and transfers a toner image on the peripheral surface of the intermediate transfer member to a recording sheet conveyed through the nip portion;
A toner pattern density detector provided on the downstream side of the nip portion in the toner image transport direction by the intermediate transfer body and detecting the density of the toner pattern remaining on the peripheral surface of the intermediate transfer body;
After transferring the toner pattern on the peripheral surface of the intermediate transfer member to the image forming unit with a predetermined content, and transferring the toner pattern on the peripheral surface of the intermediate transfer member to the secondary transfer unit, If the density of the toner pattern detected by the toner pattern density detection unit is equal to or less than a predetermined threshold value, an image forming operation based on a print job is performed on the image forming unit, the intermediate transfer body, and the secondary transfer unit. And when the detected toner density is higher than the threshold, the control unit does not allow the image forming operation based on a print job;
A determination number counter for counting the number of times the image forming operation is permitted or not permitted by the control unit;
A non-permission counter that counts the number of times that the control unit determines that the image forming operation is not permitted in the determination of permission or non-permission of the image forming operation;
A warning section for warning the user,
In the determination of whether the image forming operation is permitted or not permitted, when the control unit determines that the image forming operation is not permitted, the control unit performs the image forming operation based on count values of the determination number counter and the non-permission number counter. The image forming apparatus causes the warning unit to issue a warning with different warning contents according to the frequency at which it is determined not to permit.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, different display data is stored for each frequency corresponding to each frequency determined not to permit the image forming operation. A display data storage unit
The warning unit is a display unit that displays operation guidance for a user,
The control unit reads display data corresponding to the frequency at which it is determined that the image forming operation is not permitted from the display data storage unit, and causes the display unit to display the read display data.

  When image formation by the secondary transfer method using an intermediate transfer body is performed, after the toner pattern is appropriately transferred from the intermediate transfer body to the secondary transfer portion, the surface on the peripheral surface of the intermediate transfer body on the downstream side of the nip portion is used. In the present invention, based on the fact that the density of the toner pattern is lower than the density of the toner pattern on the peripheral surface of the intermediate transfer body on the upstream side of the nip portion, in the present invention, the control unit detects the toner pattern density detection unit described above. Whether the peripheral surface of the intermediate transfer member and the transfer portion are in contact with each other so that appropriate transfer is possible in order to determine whether the image forming operation is permitted or not based on the toner pattern density on the downstream side of the nip portion. This can be directly detected, and based on this, the image forming operation can be controlled. For this reason, each of the inventions according to the present application provides a contact between the transfer unit and the intermediate transfer member rather than indirectly detecting the contact state between the transfer unit and the intermediate transfer member from the open / closed state of the apparatus body cover as in the prior art. The state can be detected with high accuracy.

  In addition, when the control unit determines that the toner pattern density detected by the toner pattern density detection unit is higher than the threshold value and does not permit the image forming operation even when a print job is input, the control unit performs the image forming operation. Since the warning content by the warning unit is made different according to the frequency at which it is determined not to be permitted, appropriate operation guidance according to the state of poor contact is possible at the time of poor contact.

  For example, a secondary transfer portion including a secondary transfer roller is accommodated in the apparatus main body in a state of being supported by a support member that can be rotated outwardly of the apparatus, and the support member is moved outwardly during the jam processing. In the case of an image forming apparatus that can release the contact state between the secondary transfer roller and the midpoint transfer member composed of the intermediate transfer belt by rotating, (1) Frequency at which the control unit determines that the image forming operation is not permitted If it is low, it is assumed that the user has mistakenly performed an operation to return the support member to the state where the secondary transfer roller and the intermediate transfer belt are in contact with each other. And (2) if the frequency at which the control unit determines that the image forming operation is not performed is medium, the user moves the support member to the secondary transfer roller. In contact with the intermediate transfer belt In this case, it is assumed that the user does not understand what operation should be performed in order to return to the state, and at this time, a warning is given to specifically explain the operation, and (3) the control unit performs image formation. If the frequency of determining that the operation is not to be performed is high, it is assumed that a mechanical failure has occurred rather than a user's erroneous operation. At this time, a warning for prompting the repair of the image forming apparatus is issued. As described above, each of the above-described inventions according to the present application makes it possible to change the warning contents step by step according to the state of poor contact, and to make it easier for the user to grasp appropriate operations that differ depending on the situation. is there.

The invention according to claim 3 is the image forming apparatus according to claim 1 or 2, wherein the intermediate transfer member rotates the intermediate transfer belt endlessly and the intermediate transfer belt endlessly. A drive roller,
The control unit causes the image forming unit to form the toner pattern at each position of the intermediate transfer belt that is different in the rotation axis direction of the drive roller, and detects the intermediate transfer body circumference detected by the toner pattern density detection unit. Control based on comparison with the threshold value is performed using the density of each toner pattern remaining on the surface.

  According to the present invention, the control unit is based on the input of the print job when the density of each toner pattern formed at each different position in the rotation axis direction of the driving roller of the intermediate transfer belt is equal to or less than the threshold value. Since the image forming operation is performed, the image forming operation based on the input of the print job is performed when the secondary transfer unit is in contact with the intermediate transfer belt in the state where the appropriate transfer is possible over the rotation axis direction of the driving roller. Can be allowed.

  According to the present invention, the contact state between the transfer unit and the intermediate transfer member is more accurate than when the contact state between the transfer unit and the intermediate transfer member is indirectly detected from the open / closed state of the apparatus body cover as in the prior art. It can be detected well, and based on this, the image forming operation can be controlled. For this reason, according to the present invention, it is possible to detect the contact state between the transfer portion and the intermediate transfer member with higher accuracy than in the past.

  Further, according to the present invention, when the contact between the secondary transfer portion and the intermediate transfer member is poor, appropriate operation guidance according to the state of poor contact is possible.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing the overall configuration of a printer according to an embodiment of the present invention. FIGS. 2A and 2B are diagrams illustrating detection signals output from the paper jam detection sensor 19. FIG. 3 is a schematic view showing an intermediate transfer belt on which a toner pattern for detecting a contact state between the secondary transfer roller 113 and the intermediate transfer belt 124 is formed, and a paper jam detection sensor 19. FIG. 4 is a diagram illustrating the configuration of the toner pattern density sensor.

  An overview of the internal structure of a printer (an example of an image forming apparatus) 1 according to an embodiment of the present invention will be described. As shown in FIG. 1, the printer 1 of the present embodiment includes a device body 11 having a box shape. Inside the apparatus main body 11, an image forming unit 12 that forms an image based on image data transmitted from an external device such as a computer connected to a network, and the like is formed by the image forming unit 12. Are provided with a fixing unit 13 that performs a fixing process on the image transferred to the sheet, and a sheet storage unit 14 that stores recording paper for transfer. Formed on the upper portion of the apparatus main body 11 is a paper discharge portion 15 for discharging the recording paper P after the fixing process.

  On the front side of the upper part of the apparatus main body 11, an operation panel (not shown) for inputting the output conditions of the recording paper P and the like is provided. The operation panel is provided with a power key, a start button, and various keys for inputting output conditions. In addition, the operation panel is provided with a display unit 16 (FIG. 5), and the display unit 16 displays the operation status and state of the printer 1.

  The image forming unit 12 forms a toner image on the recording paper P fed from the paper storage unit 14. In the present embodiment, the image forming unit 12 includes a magenta unit 12M using a magenta developer, which is sequentially arranged from the upstream side (rear side in FIG. 1) to the downstream side, and cyan development. A cyan unit 12C using a developer, a yellow unit 12Y using a yellow developer, and a black unit 12K using a black developer.

  Each unit 12M, 12C, 12Y, 12K is provided with a photosensitive drum 120 and a developing device 121, respectively. The photosensitive drum 120 forms an electrostatic latent image and a toner image (visible image) along the electrostatic latent image on the peripheral surface, and an amorphous silicon layer is laminated on the peripheral surface. The photosensitive drum 120 of each unit receives supply of developer from the developing device 121 while rotating counterclockwise in FIG.

  A charging device 122 is provided immediately below each photosensitive drum 120, and an exposure device 123 is provided further below each charging device 122. Each photosensitive drum 120 is charged uniformly by the charging device 122 and corresponds to each color based on image data input from the computer or the like on the charged peripheral surface of the photosensitive drum 120. Laser light is emitted from each exposure device 123. As a result, an electrostatic latent image is formed on the peripheral surface of each photosensitive drum 120. Developer is supplied from the developing device 121 to the electrostatic latent image, and a toner image is formed on the peripheral surface of the photosensitive drum 120.

  An intermediate transfer belt (intermediate transfer member) 124 that is stretched between the driving roller 124 a and the driven roller 124 b is provided above the photosensitive drum 120. The intermediate transfer belt 124 is provided in contact with each photosensitive drum 120. The intermediate transfer belt 124 is pressed against the peripheral surface of the photoconductive drum 120 by a primary transfer roller 125 provided corresponding to each photoconductive drum 120, and is driven by a drive roller 124 a while synchronizing with the photoconductive drum 120. And the driven roller 124b (circulate endlessly).

  When the intermediate transfer belt 124 rotates, the magenta toner image is transferred onto the peripheral surface of the intermediate transfer belt 124 by the photosensitive drum 120 of the magenta unit 12M by the respective primary transfer rollers 125, and then the intermediate transfer is performed. The toner image of cyan toner is transferred to the same position of the belt 124 by the photosensitive drum 120 of the cyan unit 12C, and then the yellow toner of the photosensitive drum 120 of the yellow unit 12Y is transferred to the same position of the intermediate transfer belt 124. The toner image is transferred in a superimposed manner, and finally, the black toner image is transferred by the photosensitive drum 120 of the black unit 12K. As a result, a color toner image is formed on the peripheral surface of the intermediate transfer belt 124. The color toner image formed on the peripheral surface of the intermediate transfer belt 124 is transferred to the recording paper P conveyed from the paper storage unit 14. Each unit of the image forming unit 12 forms a toner pattern 25 (FIG. 3), which will be described later, on the intermediate transfer belt 124 under the control of the control unit 21 (FIG. 5), which will be described later.

  Each photoconductor drum 120 is provided with a cleaning device 126 that removes and cleans residual toner on the peripheral surface of the photoconductor drum 120. The peripheral surface of the photosensitive drum 120 cleaned by the cleaning device 126 is directed to the charging device 122 for a new charging process.

  A secondary transfer roller (secondary transfer unit) 113 is provided at a position facing the driving roller 124 a of the intermediate transfer belt 124 in a state of being in contact with the peripheral surface of the intermediate transfer belt 124. A sheet conveyance path 111 extending in the vertical direction in FIG. 1 is formed at a nip portion between the driving roller 124a and the secondary transfer roller 113 with the intermediate transfer belt 124 interposed therebetween. The sheet conveying path 111 is provided with a pair of conveying rollers 112 at an appropriate position, and the recording sheet from the sheet storage unit 14 is driven by the conveying roller pair 112 to nip the intermediate transfer belt 124 and the secondary transfer roller 113. It is conveyed toward. At the nip portion between the intermediate transfer belt 124 and the secondary transfer roller 113 in the paper conveyance path 111, the recording paper P conveyed through the paper conveyance path 111 is pressed and clamped by the intermediate transfer belt 124 and the secondary transfer roller 113; The toner image on the intermediate transfer belt 124 is transferred to the recording paper P by the transfer bias of the secondary transfer roller 113. The secondary transfer roller 113 is accommodated in the apparatus main body 11 while being supported by the support member 18 (details will be described later).

  The fixing unit 13 performs a fixing process on the recording paper P with the toner image transferred to the recording paper P at the nip portion between the intermediate transfer belt 124 and the secondary transfer roller 113. The fixing unit 13 includes a heating roller 131 provided with an energization heating element serving as a heating source therein, a fixing roller 132 disposed opposite to the heating roller 131, and the tension roller 132 and the heating roller 131. A fixing belt 133 and a pressure roller 134 disposed to face the fixing roller 40 through the fixing belt 133 are provided. The recording paper P supplied to the fixing unit 13 in a state where the toner image is transferred is subjected to a fixing process by obtaining heat from the heating roller 131 while passing between the pressure roller 134 and the high-temperature fixing belt 133. Is done.

  The recording paper P for which the fixing process has been completed passes through a paper discharge conveyance path 114 extending from the upper part of the fixing unit 13 and is discharged toward a paper discharge tray 151 of a paper discharge unit 15 provided at the top of the apparatus main body 11. Is done.

  The sheet storage unit 14 includes a manual feed tray 141 that can be freely opened and closed on the right side wall of the apparatus main body 11 in FIG. 1, and a paper tray 141 that is removably mounted in the apparatus main body 11 below the exposure device 123. It has. A sheet bundle is stored in the sheet tray 141.

  The sheet tray 141 is configured to include a box body whose upper surface is open on the entire surface, and can store a sheet bundle P1 formed by stacking a plurality of recording sheets P. The uppermost recording sheet P of the sheet bundle P1 stored in the sheet tray 141 is fed out from the sheet bundle P1 toward the sheet conveyance path 111 by driving the pickup roller 143 from the upper end of the downstream end (left end in FIG. 1). The recording paper P is fed out one by one, and is fed toward the nip portion between the secondary transfer roller 113 and the intermediate transfer belt 124 in the image forming unit 12 through the paper conveyance path 111 by driving the conveyance roller pair 112. .

  On the left side of the apparatus main body 11 in FIG. 1, an openable / closable main body cover 17 provided in an outer case for opening the inside of the apparatus, and a secondary transfer roller 113 provided inside the apparatus from the main body cover 17. And a supporting member 18 that supports the pressure roller 134 of the fixing unit 13 and the like. As shown in FIGS. 22B and 22C, the main body cover 17 and the support member 18 are configured such that their postures can be changed by rotating between an upright posture and a forward leaning posture with their lower portions as fulcrums. Yes.

  When the support member 18 is in the upright posture, the secondary transfer roller 113 is in contact with the intermediate transfer belt 124 in a state of being stretched around the drive roller 124 a, and the pressure roller 134 is in contact with the fixing roller 132. Has been. The main body cover 17 is pulled out and rotated in the direction of the arrow shown in FIG. 22 (a), the main body cover 17 is opened as shown in FIG. 22 (b), and the support member 18 is further moved outward (FIG. 22 (b)). ), The secondary transfer roller 113 and the pressure roller 134 are separated from the intermediate transfer belt 124 and the fixing roller 132, respectively, and the sheet conveyance path 111 is exposed (FIG. 22 (c)). For this reason, the user can handle the jam occurring near the nip portion of the secondary transfer roller 113 and the intermediate transfer belt 1247 by rotating the main body cover 17 and the support member 18 to open the inside of the apparatus.

  In addition, the printer 1 detects a paper jam detection sensor (paper jam detection unit) 19 that detects whether or not the recording paper P is jammed at the nip portion between the secondary transfer roller 113 and the intermediate transfer belt 124. It has. The paper jam detection sensor 19 includes, for example, an optical sensor including a light emitting unit and a light receiving unit and a control unit 21.

  The paper jam detection sensor 19 is provided, for example, in the paper conveyance path 111 downstream of the nip portion between the secondary transfer roller 113 and the intermediate transfer belt 124. The light emitting unit of the paper jam detection sensor 19 is disposed on a side wall that forms part of the paper transport path 111, and the light receiving unit is a side wall part of the paper transport path 111 that faces the light emitting unit, and the light emitting unit emits light. It is provided at a position where it can receive light. The paper jam detection sensor 19 may be installed at a plurality of positions on the paper transport path 111. The light emitting unit of the paper jam detection sensor 19 is configured by, for example, a light emitting diode, and the light receiving unit is configured by, for example, a phototransistor. When light output from the light emitting unit is received by the light receiving unit, an H (high) signal is output from the light receiving unit, and when light from the light emitting unit to the light receiving unit is blocked, L ( (Low) signal is output. The paper jam detection sensor 19 may be provided, for example, in the paper transport path 111 upstream of the nip portion between the secondary transfer roller 113 and the intermediate transfer belt 124.

  When the jam does not occur, the recording paper P is intermittently conveyed from the paper feed cassette 142, so that the recording paper P passes between the light emitting portion and the light receiving portion as shown in FIG. An L (low) period T1 (time t1) and an H (high) period T2 (time t2) until the next recording sheet is conveyed between the light emitting unit and the light receiving unit are periodically generated. . The time t1 is a value determined according to the length of the paper P in the transport direction and the transport speed of the paper P. On the other hand, when a jam occurs, the recording paper P stays between the light emitting element and the light receiving element for the time t1 or more, so that a signal for a period L (low) of the time t1 or more is output from the light receiving element.

  Based on this, the control unit 21 determines that a jam has not occurred when a signal (FIG. 2A) that rises from L to H after time t1 from the fall timing from H to L is received, and H When a signal shown in FIG. 2 (b) that does not rise from L to H even after time t1 has elapsed from the falling timing from L to L, it is determined that a jam has occurred.

  Further, at a position downstream of the nip portion between the secondary transfer roller 113 and the intermediate transfer belt 124 in the running direction of the intermediate transfer belt 1240 and at a position facing the peripheral surface of the intermediate transfer belt 1240, A toner pattern density detection sensor (toner pattern density detection unit) 23 is provided. The toner pattern density detection sensor 23 is a sensor that detects the toner density on the circumferential surface of the intermediate transfer belt 124. The toner density detection sensors 23 are provided at two different locations in the length direction (rotation axis direction) of the drive roller 124a of the intermediate transfer belt 1240 (in order to limit the number of toner density detection sensors 23 to two). Absent). As shown in FIG. 3, each toner concentration detection sensor is spaced apart from the peripheral surface of the intermediate transfer belt 124 by a predetermined distance so as to face both ends of the intermediate transfer belt 124 in the width direction (the length direction of the driving roller 124a). 23 is arranged. The toner density detection sensor 23 is electrically connected to the control unit 20 as shown in FIG. 5 described later, and outputs the detected density of the toner pattern to the control unit 21.

  The toner pattern density detection sensor 23 has the following configuration, for example. As shown in FIG. 4, in the toner pattern density detection sensor 23, a light emitting portion 231 is disposed on one side in the running direction of the intermediate transfer belt 124 with respect to an arbitrary point p on the circumferential surface of the intermediate transfer belt 124, and on the other side. A light receiving unit 232 is disposed. The light emitting unit 231 outputs a light source 2311 that outputs light toward the point p on the circumferential surface of the intermediate transfer belt 124, and a beam splitter 2312 that splits the light output from the light source unit 2311 into first and second polarization components. And a light receiving element 2313 that receives one polarization component from the beam splitter 2312. 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 124 as it is, and the S wave is extracted from the beam splitter 2312 and then incident on the light receiving element 2313.

  The light emitting unit 231 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 124. Output light. The light receiving element 2313 is installed to control the output operation of the light emitting unit 231, and a signal proportional to the amount of irradiation light is output from the light receiving element 2313 to the control unit 21. The control unit 21 controls the output light of the light source unit 2311 so that the output signal of the light receiving element 2313 is always constant.

  The light receiving unit 232 splits the light reflected from the circumferential surface of the intermediate transfer belt 124 into first and second polarization components, and of the first and second polarization components dispersed by the beam splitter 2321. A first light receiving element 2322 that receives light of the first polarization component, and a second light receiving element 2323 that receives light of the second polarization component among the first and second polarization components are configured.

  The light from the light emitting portion 231 reflected on the circumferential surface of the intermediate transfer belt 124 includes regular reflection light near the same angle as the incident angle θ and other diffused light, and is transferred to the circumferential surface of the intermediate transfer belt 124. In accordance with 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 2322 and 2323 changes.

  Using this principle, the toner pattern density detection sensor 23 outputs an analog voltage corresponding to the ratio of the first and second polarization components received by the first and second light receiving elements 2322 and 2323 to the control unit 21. Yes, when there is no toner on the circumferential surface of the intermediate transfer belt 124, the first polarization component received by the first light receiving element 2322 is maximized, and the output voltage becomes the maximum value, so that the toner on the circumferential surface of the intermediate transfer belt 124 is maximized. As the amount increases, the amount of light of the first polarization component decreases and the output voltage decreases. The control unit 21 calculates the amount of toner adhering to the peripheral surface of the intermediate transfer belt 124 based on the output signal of the toner pattern density detection sensor 23.

  Further, an open / close detection switch (cover open / close detection unit) 30 for detecting the open / close state of the main body cover 17 is provided on the left side of the apparatus main body 1 in FIG. For example, the opening / closing detection switch 30 is pressed by the body cover 17 when the body cover 17 is closed and turned on, and when the body cover 17 is opened, the opening / closing detection switch 30 is released from the pressed state and turned off. It consists of a switch mechanism, and outputs the detection signal which shows the said ON or OFF with respect to the said control unit 20 (control part 21).

  A cleaning roller (cleaning unit) 35 for removing toner on the intermediate transfer belt 124 is provided at a position facing the driven roller 124b with the intermediate transfer belt 124 interposed therebetween.

  Further, below the front side of the intermediate transfer belt 124, a second toner concentration detection sensor (second toner concentration detection) used for toner concentration detection for color correction of the units 12M, 12C, 12Y, and 12K of the image forming unit 12 is provided. Part) 24 is provided. The second toner concentration detection sensor 24 is also electrically connected to the control unit 21 of the control unit 20, and the control unit 21 performs intermediate transfer based on the toner concentration obtained from the second toner concentration detection sensor 24. The density of the toner image transferred from the belt 124 to the recording paper P is corrected. That is, the control unit 21 makes the toner bias obtained from the second toner density detection sensor 24 close to a predetermined appropriate density, the charging bias, the exposure output of each unit 12M, 12C, 12Y, 12K, or Processing such as development bias change processing or dot number conversion of image data to be printed is performed. The second toner density detection sensor 24 has the same configuration as the toner pattern density detection sensor 23 described above.

  Next, the configuration of the control system of the printer 1 will be described. FIG. 5 is a block diagram showing a control system of the printer 1.

  The control unit 20 includes a CPU, a ROM, and a RAM. The control unit 20 includes a control unit 21 that performs input / output and calculation of various signals, a storage unit 22 that stores data, and a threshold value changing unit 28.

  The control unit 21 includes an image forming unit 12 having color units 12M, 12Y, 12C, and 12K, a bias applying unit 26 that applies a transfer bias to the secondary transfer roller 113, and a display unit that includes an LCD (Liquid Crystal Display) or the like. 16 is controlled. The toner concentration detection sensor 23 and the second toner concentration detection sensor 24 described above are also connected to the control unit 21 so that detection signals can be output. The control unit 21 is responsible for overall operation control of the printer 1 and controls the mechanism of each part of the apparatus. In FIG. 5, only the mechanism related to the detection process of the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124 is shown. Is shown.

  The counter 27 is provided for a predetermined mechanism related to toner pattern formation, for example, the developing unit of the yellow unit 12Y of the image forming unit 12. The counter 27 measures the number of recording sheets on which an image is formed by the yellow unit 12Y and the elapsed time from the start of image formation when a print job is input and an image forming operation is performed. The counter 27 resets the count value when the yellow unit 12Y is removed from the printer 1 and replaced with a new separate yellow unit 12Y. The counter 27 may also serve as unit-specific counters 32M, 32C, 32Y, and 32K, which will be described later.

  The detection process execution number counter 31 measures the number of times that the control unit 21 has performed the detection process of the contact state between the secondary transfer roller 113 and the peripheral surface of the intermediate transfer belt 124.

  The unit-specific counters 32M, 32C, 32Y, and 32K are counters provided in the units 12M, 12C, 12Y, and 12K for each color provided in the image forming unit 12, respectively. The unit-specific counters 32M, 32C, 32Y, and 32K count up in response to an increase in image formation amount (for example, the number of image formation operations (number of recording sheets on which image formation has been performed) or image formation time). .

  The non-permission count counter 33 is controlled in the detection process of the contact state between the secondary transfer roller 113 and the peripheral surface of the intermediate transfer belt 124 by the control unit 21 based on the toner pattern density detected by the toner pattern density detection sensor 23. This is a counter that counts the number of times that the unit 21 determines that the image forming operation is not permitted.

  The driving of the cleaning roller 35 that removes the toner on the intermediate transfer belt 124 is also controlled by the control unit 21. Further, the control unit 21 also controls drive motors (collective names of the respective drive sources) 500 that are drive sources of the secondary transfer roller 113, the intermediate transfer belt 12, the image forming unit 12, and the fixing device 13.

  When the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124 is detected, the control unit 21 drives the toner pattern 25 with the image forming unit 12 and the intermediate transfer belt 124, for example, a yellow unit of the image forming unit 12. 12Y is formed near both ends in the width direction on the intermediate transfer belt 124 (FIG. 2). The toner pattern 25 has a predetermined density (for example, ID value 1.4 (sensor value 633)), and has, for example, a square shape with one side of about 2 cm. Note that the toner pattern 25 may be formed in a belt shape that extends over substantially the entire width of the intermediate transfer belt 124. When the toner pattern 25 is formed, the control unit 21 transfers the toner pattern 25 from the peripheral surface of the intermediate transfer belt 124 onto the surface of the secondary transfer roller 113 so that the secondary transfer roller 113 and the intermediate transfer belt are transferred. The density of the toner pattern 25 remaining on the peripheral surface of the intermediate transfer belt 124 is detected by the toner density detection sensor 23 disposed on the downstream side of the nip portion with respect to 124.

  Then, if the density for each toner pattern obtained from the two toner density detection sensors 23 is equal to or less than a predetermined threshold value (for example), the control unit 21 performs the image forming unit 12 and the intermediate transfer belt 124. , The primary transfer roller 125, the secondary transfer roller 113, the fixing unit 13 and the like are permitted to perform an image forming operation based on the print job, and if the density for each of the toner patterns is larger than the threshold, the image based on the print job The forming operation is not allowed. In this case, when it is determined that the image forming operation based on the print job is not permitted, the control unit 21 causes the display unit 16 to warn the user.

  The storage unit 22 stores a threshold value used by the control unit 21 to determine whether to perform an image forming operation based on the print job based on the toner concentration obtained from the toner concentration detection sensor 23. The control unit 21 permits the image forming operation based on the print job when the toner concentration obtained from the toner concentration detection sensor 23 is equal to or less than the threshold stored in the storage unit 22, and is obtained from the toner concentration detection sensor 23. When the toner density is higher than the threshold value stored in the storage unit 22, the image forming operation based on the print job is not permitted.

  That is, in the case of image formation by the secondary transfer method using the intermediate transfer belt 124, after the toner pattern is properly transferred from the intermediate transfer belt 124 to the secondary transfer roller 113, the intermediate transfer belt 124 and the secondary transfer roller The density of the toner pattern on the downstream side of the nip portion with the 113 is lower than the density of the toner pattern on the intermediate transfer belt 124 on the upstream side of the nip portion by the amount of toner moved to the secondary transfer roller 113 side by the transfer. Therefore, the fact that the density of the toner pattern detected by the toner pattern density detection sensor 23 does not show the decrease indicates that the intermediate transfer belt 124 and the secondary transfer roller 113 are in contact with each other in a state where appropriate transfer is possible. Indicates not. Based on this, the control unit 21 does not permit the image forming operation based on the print job unless the density of the toner pattern detected by the toner pattern density detection sensor 23 is equal to or less than a predetermined threshold. . From the viewpoint of the user, the control unit 21 can appropriately transfer the secondary transfer roller 113 and the intermediate transfer belt 124 based on the density of the toner pattern detected by the toner pattern density detection sensor 23. It is detected whether it is in a contact state.

  In addition, the storage unit 22 includes the threshold values (the control unit 21 controls the toner concentration detection sensor 23 corresponding to each toner concentration of the toner pattern on the circumferential surface of the intermediate transfer belt 124 detected by the second toner concentration detection sensor 24. (Threshold used for determining whether or not an image forming operation based on the print job is to be performed) is stored based on the toner density obtained from (1). Further, the storage unit 22 stores the respective threshold values corresponding to the count values counted by the counter 27.

  The storage unit 22 stores various display data to be displayed on the display unit 16. The storage unit 22 stores display data corresponding to each case whether or not the control unit 21 permits an image forming operation in the contact state detection process. Further, the storage unit 22 stores display data associated with each frequency at which the control unit 21 determines that the image forming operation is not permitted in the contact state detection process. The control unit 21 reads display data associated with the frequency at which it is determined that the image forming operation is not permitted from the storage unit 22 and displays the read display data on the display unit 16 stages.

  The threshold changing unit 28 is used by the control unit 21 to determine whether the image forming operation is permitted or not based on the toner pattern density detected by the second toner density detection sensor 24 or the count value of the counter 27. When it is determined whether or not to change the threshold value and the threshold value is changed, the threshold value corresponding to the toner density of the toner pattern detected by the second toner density detection sensor 24 or the count value of the counter 27 is determined. Is read from the storage unit 22 and the threshold value used by the control unit 21 is changed.

  Next, a first embodiment of a process for detecting a contact state between the secondary transfer roller 113 and the intermediate transfer belt 124 by the printer 1 will be described. FIG. 6 is a flowchart illustrating a first embodiment of a process for detecting a contact state between the secondary transfer roller 113 and the intermediate transfer belt 124.

  During the operation of the printer 1, based on the signal sent from the paper jam detection sensor 19, the control unit 21 based on the detection signal sent from the paper jam detection sensor 19, the secondary transfer roller 113. When the occurrence of a paper jam in the vicinity of the nip with the intermediate transfer belt 124 is detected (YES in S1), the control unit 21 sends from the open / close detection switch 30 whether the main body cover 17 is closed. Based on a detection signal indicating ON or OFF (S2), a paper jam detection sensor further determines whether the paper jam in the vicinity of the nip portion between the secondary transfer roller 113 and the intermediate transfer belt 124 has been eliminated. The determination is made based on the detection signal sent from 19 (S3).

  When the control unit 21 determines that the main body cover 17 is closed (YES in S2) and the paper jam in the vicinity of the nip portion between the secondary transfer roller 113 and the intermediate transfer belt 124 is resolved (YES in S3). The toner pattern for detecting the contact state with the secondary transfer roller 113 and the intermediate transfer belt 124 by driving the image forming unit 12, the intermediate transfer belt 124 and the secondary transfer roller 113 is displayed in the yellow of the image forming unit 12. The unit 12Y is formed near both ends in the width direction on the intermediate transfer belt 124 (S4). The yellow unit 12Y is used for the toner pattern formation because the toner constituting the toner pattern remains on the intermediate transfer belt 124, and the recording paper on which image formation has been performed based on the print job is applied. This is because even if the residual toner adheres, it is difficult for the user to visually recognize it compared to other color toners.

  At this time, the control unit 21 causes the bias applying unit 26 to apply a positive bias to the secondary transfer roller 113 (S5), thereby transferring the toner pattern 25 from the intermediate transfer belt 124 to the secondary transfer roller 113.

  Subsequently, on the downstream side of the nip portion between the intermediate transfer belt 124 and the secondary transfer roller 114 where the toner pattern is transferred from the intermediate transfer belt 124 to the secondary transfer roller 114, two toner pattern density detection sensors 23 are provided. However, the density of the toner pattern on the intermediate transfer belt 124 is detected (S6). That is, the toner pattern density detection sensor 23 detects the density of toner remaining on the intermediate transfer belt 124 without being transferred from the intermediate transfer belt 124 to the secondary transfer roller 114.

  Then, the control unit 21 determines whether both of the residual toner densities detected by the two toner density detection sensors 23 are equal to or less than the threshold value stored in the storage unit 22 (S7). When the control unit 21 determines that both of the toner densities detected by the two toner density detection sensors 23 are equal to or less than the threshold value (YES in S7), the controller 21 permits image formation by a newly input job. (S8). That is, when a new print job is input next, the control unit 21 drives the image forming unit 12, the intermediate transfer belt 124 and the secondary transfer roller 113, the fixing unit 13, the recording paper transport mechanism, and the like. To start printing. As described above, when both of the toner densities detected by the two toner pattern density detection sensors 23 are equal to or less than the threshold value, appropriate transfer is performed over substantially the entire region of the driving roller 124a of the intermediate transfer belt 124 in the rotation axis direction. This is because it is possible to determine that the secondary transfer roller 113 is in contact with the peripheral surface of the intermediate transfer belt 124 in a state where this is possible.

  Thereafter, the control unit 21 causes the bias applying unit 26 to apply a reverse bias to the secondary transfer roller 113 (S9), and the toner pattern 25 transferred onto the secondary transfer roller 113 is transferred onto the intermediate transfer belt 124. Make a transfer to return. Further, the control unit 21 reads display data to be displayed when image formation is permitted from the storage unit 22 and displays it on the display unit 16 of the operation panel (S10). For example, the control unit 21 causes the display unit 16 to display “Ready” indicating that the print preparation is completed for the user (S10).

  On the other hand, when the control unit 21 determines in S7 that any one of the residual toner densities detected by the two toner pattern density detection sensors 23 is higher than the threshold value (NO in S7), Next, image formation by a newly input job is not permitted (S11). That is, the control unit 21 does not drive the image forming unit 12, the intermediate transfer belt 124 and the secondary transfer roller 113, the fixing unit 13, the recording paper transport mechanism, etc., even if a new print job is input next. Prevent printing operation. If any of the toner densities detected by the two toner pattern density detection sensors 23 is larger than the threshold, appropriate transfer can be performed in substantially the entire region of the drive roller 124a of the intermediate transfer belt 124 in the rotation axis direction. This is because it can be determined that the secondary transfer roller 113 is not in contact with the peripheral surface of the intermediate transfer belt 124.

  At this time, the control unit 21 reads display data to be displayed when image formation is not permitted from the storage unit 22 and displays the display data on the display unit 16 of the operation panel (S12). For example, the display unit 16 of the operation panel displays “Error” indicating that the user cannot print (S12). Further, the control unit 21 causes the bias applying unit 26 to apply a reverse bias to the secondary transfer roller 113 (S13), and the toner pattern 25 transferred onto the secondary transfer roller 113 is transferred onto the intermediate transfer belt 124. Make a transfer to return. In addition, as an alarm part of an abnormal state, not only the display by the said display part 16, but the alarm sound from a speaker, the blink of a lamp | ramp, etc. may be sufficient.

  In S1, the control unit 21 does not detect the occurrence of a paper jam in the vicinity of the nip portion between the secondary transfer roller 113 and the intermediate transfer belt 124 (NO in S1), and the intermediate transfer shown in S4 to S7. A normal printing operation is performed without performing the process of detecting the contact state between the belt 124 and the secondary transfer roller 114 (S20).

  In the first embodiment, the control unit 21 closes the main body cover 17 (YES in S2) and eliminates the paper jam in the vicinity of the nip portion between the secondary transfer roller 113 and the intermediate transfer belt 124. (YES in S3), the above-described contact state detection process shown in S4 to S7 is performed, but instead of this, whether or not the main body cover 17 is closed is 2 If it is determined that the paper jam in the vicinity of the nip portion between the next transfer roller 113 and the intermediate transfer belt 124 has been eliminated, the contact state detection process shown in S4 to S7 may be performed.

  Next, a second embodiment of the process for detecting the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124 will be described. FIG. 7 is a flowchart illustrating a second embodiment of a process for detecting a contact state between the secondary transfer roller 113 and the intermediate transfer belt 124. Note that the same processes as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the first embodiment, a paper jam occurs in the vicinity of the nip portion 124 of the secondary transfer roller 113 and the intermediate transfer roller, and then the main body cover is closed, and when the paper jam is detected (see FIG. 6, YES in S 1, YES in S 2, YES in S 3), and the control unit 21 performs detection processing (S 4 to S 7 in FIG. 5) of the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124. However, in the second embodiment, when the main power supply of the printer 1 is turned on (YES in S21 in FIG. 6), the control unit 21 determines whether the control unit 21 is connected between the secondary transfer roller 113 and the intermediate transfer belt 124. The contact state detection process (S4 to S7 in FIG. 6) is performed.

  In this way, the printer 1 has shifted from the main power off state where the user may have opened and closed the main body cover 17 and the support member 18 (paper jam clearing operation) to the state where the main power is turned on. In this case, since the control unit 21 performs the contact state detection process, the contact state detection process is truly necessary to detect whether the peripheral surface of the intermediate transfer body and the transfer unit are in proper contact with each other. Can be made to focus on. In addition, when the main power is turned on, stabilization processing (warming-up processing, aging processing, etc.) of the developing device provided in the fixing unit 13 and the image forming unit 12 is performed. Since the contact state detection process can be performed in parallel, time is not required only for the contact state detection process.

  Next, a description will be given of a third embodiment of a process for detecting a contact state between the secondary transfer roller 113 and the intermediate transfer belt 124. FIG. 8 is a flowchart illustrating a third embodiment of a process for detecting a contact state between the secondary transfer roller 113 and the intermediate transfer belt 124. Note that description of the same processing as in the first and second embodiments is omitted. In the third embodiment, a specific timing is not shown as the start timing of the contact state detection process between the secondary transfer roller 113 and the intermediate transfer belt 124. However, the third embodiment is different from the first embodiment or the second embodiment described above. It may be started at the same timing.

  When detecting the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124, the control unit 21 drives the image forming unit 12, the intermediate transfer belt 124, and the secondary transfer roller 113 with the toner pattern used for the detection. Then, the yellow unit 12Y is formed near both ends in the width direction on the intermediate transfer belt 124 (S41).

  At this time, the control unit 21 causes the second toner concentration detection sensor 24 disposed on the upstream side of the nip portion between the intermediate transfer belt 124 and the secondary transfer roller 113 to be formed on the intermediate transfer belt 124. The density of each toner pattern is detected (S42).

  Then, the threshold value changing unit 28 prints the threshold value corresponding to the toner pattern density detected by the second toner density detection sensor 24 (the control unit 21 prints based on the toner density obtained from the toner pattern density detection sensor 23. The threshold used for determining whether or not to perform the image forming operation based on the job is read from the storage unit 22 (S43).

  Here, the threshold changing unit 28 (1) assumes that the density of each toner pattern formed on the intermediate transfer belt 124 is the same, and based on the toner density of only one of the toner patterns. The threshold value corresponding to the one toner density may be read from the storage unit 22, or (2) the average value of the density of both toner patterns formed on the intermediate transfer belt 124 is calculated, and the toner A threshold value corresponding to the average density value may be read from the storage unit 22. Thereafter, the threshold value changing unit 28 sets the read threshold value as a threshold value used for determining whether or not the control unit 21 performs the image forming operation based on the print job (S44). The subsequent processing of S45 to S53 shown in FIG. 8 is the same as S5 to S13 of the first embodiment shown in FIG.

  According to the third embodiment, the threshold changing unit 28 is transferred to the toner pattern density detected by the second toner density detection sensor 24 upstream of the nip part (that is, transferred to the secondary transfer roller 113). If the density of the previous toner pattern changes, the threshold value used by the control unit 21 is changed in accordance with the amount of toner density change, so that the image forming unit 12 or the intermediate transfer belt 124 changes with time and the surrounding environment. Even if the density of the toner pattern transferred onto the intermediate transfer belt 124 changes due to the change, the control unit 21 transfers the toner pattern from the peripheral surface of the intermediate transfer belt 124 to the secondary transfer roller 113. A change in density of the toner pattern on the peripheral surface of the intermediate transfer body before and after can be accurately detected. 3 and the state of contact between the intermediate transfer belt 124 becomes accurately detectable.

  Further, since the second toner density detection sensor 24 is a sensor used for density detection at the time of image formation by the image forming unit 12, the mechanism of the third embodiment is used by using a mechanism that has been used conventionally. Processing can be performed.

  Next, a description will be given of a fourth embodiment of processing for detecting a contact state between the secondary transfer roller 113 and the intermediate transfer belt 124. FIG. 9 is a flowchart showing a fourth embodiment of the process for detecting the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124, and FIGS. 10 and 11 are flowcharts showing the count process of the counter 27. 12 and 13 are diagrams showing the image forming amount and the threshold value corresponding to the image forming amount. Note that the description of the same processing as that described in the first to third embodiments is omitted. In the fourth embodiment, the specific timing is not shown as the start timing of the detection process of the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124. However, the fourth embodiment is different from the first embodiment or the second embodiment described above. It may be started at the same timing.

  First, the counting process of the counter 27 will be described with reference to FIG. When a print job indicating a print instruction is transmitted from a network-connected personal computer or the like, the control unit 21 receives the image forming unit 12, the intermediate transfer belt 124, the secondary transfer roller 113, the fixing unit 13, and the conveyance roller pair. 112 and the like are driven to start an image forming operation based on the print job (S81). At this time, whenever the toner image transfer onto the recording paper is completed at the nip portion between the intermediate transfer belt 124 and the secondary transfer roller 113 (YES in S82), the control unit 21 performs the yellow unit 12Y of the image forming unit 12. Is determined (S83), and if the development process is performed by the yellow unit 12Y (YES in S83), the counter 27 provided for the yellow unit 12Y is counted up. (S84).

  The control unit 21 continues the counting process of the counter 27 until the toner image transfer for all the recording sheets is completed in the image formation based on the print job (S85). The counter 27 is provided for the yellow unit 12Y because the toner pattern for detecting the contact state between the intermediate transfer belt 124 and the secondary transfer roller 113 by the control unit 21 is for yellow. This is because it is formed by the unit 12Y.

  Next, the detection process of the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124 will be described with reference to FIG. The threshold value changing unit 28 counts the counter 27 that has been counted up in the counting process shown in FIG. 10 above when the detection timing of the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124 is reached. A value is acquired from the counter 27 (S61).

  Then, the threshold value changing unit 28 causes the image forming operation based on the print job to be performed based on the threshold value corresponding to the count value of the counter 27 (the control unit 21 is based on the toner density obtained from the first toner density detecting sensor 23. Is read from the storage unit 22 (S62). For example, as shown in FIG. 12, the storage unit 22 stores a default threshold value (for example, an ID value of 0.4 (sensor value 154)) as a threshold value of the counter 27 having a count value of 0 to 10,000. Is stored as a threshold value when the value is 10,001 to 50,000, and a threshold value obtained by reducing the value by 20 from the default threshold value is stored as a threshold value when the value is 50,001 to 100,000. , A threshold value obtained by reducing the value by 50 from the default threshold value is stored as a threshold value in the case of 100,001 or more. That is, it is predicted that the toner density of the toner pattern formed on the peripheral surface of the intermediate transfer belt 124 by the yellow unit 12Y will decrease as the performance of the developing unit of the yellow unit 12Y decreases as the usage period elapses. The toner image density of the toner pattern remaining on the peripheral surface of the intermediate transfer belt 124 after the transfer from the intermediate transfer belt 124 to the secondary transfer roller 113 is also assumed to decrease in accordance with the toner density reduction. The unit 28 reduces the threshold value used by the control unit 21 in accordance with the toner density decrease of the toner pattern formed on the peripheral surface of the intermediate transfer belt 124 by the yellow unit 12Y.

  The threshold value changing unit 28 sets the threshold value read from the storage unit 22 as the threshold value used for determining whether or not the control unit 21 performs an image forming operation based on the print job (S63). The processing of S64 to S73 in FIG. 9 performed after this is the same as S4 to S13 of the first embodiment shown in FIG.

  In the fourth embodiment, the threshold value changing unit 28 affects the toner density of the toner pattern transferred onto the peripheral surface of the intermediate transfer belt 124, and changes in performance with the use period of the developing unit of the yellow unit 12Y. Since the threshold value used by the control unit 21 is reduced according to (performance reduction), the control unit 21 causes the intermediate transfer belt 124 before and after transferring the toner pattern from the peripheral surface of the intermediate transfer belt 124 to the secondary transfer roller 113. The change in the density of the toner pattern on the peripheral surface can be accurately detected regardless of the deterioration in the performance of the developing unit of the yellow unit 12Y.

  In the fourth embodiment, the counter 27 counts the number of times of image formation as described above (the number of images formed on the recording paper). Instead, as shown in FIG. It may function as a timer and measure the total drive time of the developing unit of the yellow unit 12Y. The counting process of the counter 27 in this case will be described with reference to FIG. When the image forming operation based on the print job is started (S91), the control unit 21 determines whether the development processing by the yellow unit 12Y of the image forming unit 12 has been performed (S92), and the development processing by the yellow unit 12Y. Is performed (YES in S92), the counter 27 provided for the yellow unit 12Y is caused to measure the elapsed time from the start of the image forming operation by the yellow unit 12Y (S93).

  The control unit 21 continues the processes of S92 and S93 until the image forming operation based on the print job is completed (NO in S94). When the image forming operation is completed (YES in S94), the control unit 21 stores the counter 27 in the counter 27. The measured elapsed time is added to the accumulated value of the previous elapsed time (S95), and the total drive time of the yellow unit 12Y currently applied to the printer 1 is calculated.

  The threshold value changing unit 28 performs the same threshold value changing process as shown in FIG. 9. In this case, for example, the storage unit 22 stores the total drive time calculated by the counter 27 as shown in FIG. 13. A default threshold value (for example, ID value 0.4 (sensor value 154)) is stored as a threshold value in the case of 0 to 10,000 (seconds), and a default threshold value is used as a threshold value in the case of the same total driving time of 10,001 to 50,000 (seconds). Is stored as a threshold when the total driving time is 50,001 to 100,000 (seconds), and a threshold is stored as a threshold when the value is reduced by 20 from the default threshold. A threshold value obtained by reducing the value by 50 from the default threshold value is stored as a threshold value in the case of 100,001 (seconds) or more. However, the numerical values shown here are merely examples. The threshold value changing unit 28 reads a threshold value corresponding to the total drive time calculated by the counter 27 from the storage unit 22 (S62), and the control unit 21 performs an image forming operation based on the read threshold value. It is set as the threshold value used for determining whether or not to perform (S63).

  In the above description, the counter 27 is provided for the developing unit of the yellow unit 12Y. However, the counter 27 may be another mechanism as long as it is a mechanism related to the formation of the toner pattern by the image forming unit 12. For example, the developing unit of another color unit, and further, the photosensitive drum 120, the developing device 121, the charging device 122, the exposure device 123, the exposure device 123 in each color unit 12K, 12Y, 12C, and 12M of the image forming unit 12, The primary transfer roller 125 may be any mechanism such as the intermediate transfer belt 124 and the secondary transfer roller 113.

  Next, a description will be given of a fifth embodiment of a process for detecting a contact state between the secondary transfer roller 113 and the intermediate transfer belt 124. FIG. 14 is a flowchart showing a fifth embodiment of a process for detecting a contact state between the secondary transfer roller 113 and the intermediate transfer belt 124. Note that the description of the same processes as those described in the first to fourth embodiments is omitted. In the fifth embodiment, a specific timing is not particularly shown as the start timing of the contact state detection process between the secondary transfer roller 113 and the intermediate transfer belt 124, but the first embodiment or the second embodiment described above. It may be started at the same timing.

  In the fourth embodiment, the counter 27 is provided for the developing unit of the yellow unit 12Y. In the fifth embodiment, the counter 27 is related to the formation of the toner pattern by the image forming unit 12. Are provided for a plurality of predetermined mechanisms. As the plurality of mechanisms provided with the counter 27, a mechanism whose performance affects the toner density of the toner pattern formed by the image forming unit 12 is selected. For example, the photosensitive drum 120, the developing device 121, the charging device 122, the exposure device 123, the exposure device 123, and the primary transfer roller 125 in each of the color units 12K, 12Y, 12C, and 12M of the image forming unit 12, and the intermediate The entire mechanism such as the transfer belt 124 and the secondary transfer roller 113, or any two or more mechanisms selected from these.

  The storage unit 22 stores the threshold value (control unit) corresponding to the total value of the count values (the number of images to be formed or the total driving time) detected by all the counters 27 provided for the plurality of predetermined mechanisms. 21 stores a threshold value used to determine whether or not to perform an image forming operation based on a print job based on the toner concentration obtained from the first toner concentration detection sensor 23.

  The threshold value changing unit 28 counts up in the count process shown in FIG. 10 or 11 when the detection timing of the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124 is reached. All count values of each counter 27 for a plurality of mechanisms are acquired (S121). Then, the threshold value changing unit 28 calculates a sum value of the count values of all the counters 27 (S122). The threshold value changing unit 28 reads the threshold value corresponding to the calculated total value from the storage unit 22 (S123), and determines whether or not the control unit 21 performs the image forming operation based on the print job based on the read threshold value. It is set as the threshold value used for (S124). The processing of S125 to S134 in FIG. 14 performed after this is the same as S4 to S13 of the first embodiment shown in FIG.

  In the fifth embodiment, when the performance of the predetermined mechanism may be reduced as the image formation amount increases, the performance of each mechanism may synergistically reduce the density of the toner pattern. However, in response to this situation, the threshold value changing unit 28 decreases the threshold value used by the control unit 21 to determine whether the image forming operation is permitted or not based on the print job. The toner pattern density change on the peripheral surface of the intermediate transfer body before and after transferring the toner pattern from the intermediate transfer belt 124 to the secondary transfer roller 113 can be detected more accurately regardless of the increase in the image formation amount. .

  In the fourth and fifth embodiments described above, when the mechanism provided with the counter 27 is removed from the printer 1 and replaced with a new separate one, the mechanism is provided in the replaced mechanism. It is preferable to reset the count value of the counter 27. In this way, when the mechanism in which the counter 27 is provided is replaced and the accumulation of the performance change with the passage of the use period is lost, the counter value of the counter 27 is also reset. Based on the performance change that occurs as the usage period elapses, the control unit 21 more accurately detects the density change of the toner pattern on the intermediate transfer belt 124 before and after the toner pattern transfer from the intermediate transfer belt 124 to the secondary transfer roller 113. can do.

  Next, a sixth embodiment of the process for detecting the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124 will be described. FIG. 15 is a flowchart showing a sixth embodiment of a process for detecting a contact state between the secondary transfer roller 113 and the intermediate transfer belt 124. Note that the description of the same processes as those described in the first to sixth embodiments is omitted. Further, in the sixth embodiment, a predetermined timing is not particularly shown as the start timing of the contact state detection process between the secondary transfer roller 113 and the intermediate transfer belt 124, but the first embodiment or the second embodiment described above. It may be started at the same timing.

  When the control unit 21 reaches the start timing of the detection process of the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124, the control unit 21 increments the detection process execution number counter 31 (S141). That is, the control unit 21 sets the count value N = N + 1 of the detection process execution number counter 31. The control unit 21 acquires the count value of the detection process execution number counter 31 after the count-up, and determines which of the count values is 1 to 4 (S142). Note that the count-up of the detection process execution number counter 31 may be performed at any timing as long as it is after the start of the contact state detection process and before the process of S161. As will be described later, the count by the detection process execution number counter 31 is reset when 4 is counted.

  Then, when the count value of the detection processing execution number counter 31 is 1, the control unit 21 drives the image forming unit 12, the intermediate transfer belt 124, and the secondary transfer roller 113 to drive the secondary transfer roller 113 and the intermediate transfer roller 113. A toner pattern for detecting the contact state with the transfer belt 124 is formed in the yellow unit 12Y of the image forming unit 12 near both ends in the width direction on the intermediate transfer belt 124 (S143). When the count value of the detection process execution number counter 31 is 2, the control unit 21 causes the magenta unit 12M to form each toner pattern (S144), and the count value of the detection process execution number counter 31 is 3. If it is, the toner patterns are formed on the cyan unit 12C (S145), and if the count value of the detection processing execution counter 31 is 4, the toner patterns are formed on the black unit 12K (see FIG. S146).

  The subsequent processing in S147 through S152 and S155 through S157 in FIG. 15 is the same as S5 through S13 in the first embodiment shown in FIG.

  After the process of S152 or S157, when the count value of the detection process execution number counter 31 reaches 4 (YES in S153), the control unit 21 resets the count value of the detection process execution number counter 31 (S154). ) And finish the process. That is, the control unit 21 causes the detection process execution number counter 31 to count only one of the values 1 to 4.

  According to the sixth embodiment, the controller 21 sequentially changes the units for each color used for forming the toner pattern for each contact state detection process, so that only one of the units is used for the toner pattern formation. It is never used continuously. As a result, it is possible to avoid a situation in which only the amount of toner consumed by any one of the color units is increased for forming a toner pattern, and there is a sufficient amount of other color toners during normal image formation based on a print job. Nevertheless, it is possible to prevent a problem that image formation cannot be performed when only a specific color toner is insufficient.

  Next, a seventh embodiment of the process for detecting the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124 will be described. FIG. 16 is a flowchart illustrating a seventh embodiment of a process for detecting a contact state between the secondary transfer roller 113 and the intermediate transfer belt 124. Note that the description of the same processes as those described in the first to sixth embodiments is omitted. In the seventh embodiment, a specific timing is not particularly shown as a start timing of the contact state detection process between the secondary transfer roller 113 and the intermediate transfer belt 124. However, the first embodiment or the second embodiment described above. It may be started at the same timing.

  In the seventh embodiment, after the control unit 21 forms the toner pattern in any one of the color units 12M, 12C, 12Y, and 12K (S162 to S165), the threshold value changing unit 28 includes the unit-specific counters 32M, Among the 32C, 32Y, and 32K, the count value of the unit-specific counter provided for the unit used for forming the toner pattern is acquired (S166), and the threshold value corresponding to the count value (the control unit 21 Based on the toner density obtained from the first toner density detection sensor 23, a threshold value used for determining whether or not to perform an image forming operation based on the print job is read from the storage unit 22 (S167). The threshold value corresponding to the count value stored in the storage unit 22 is the same as the content shown in FIG. The threshold value changing unit 28 sets the threshold value read from the storage unit 22 as a threshold value used for determining whether or not the control unit 21 performs an image forming operation based on the print job (S168). The subsequent processing of S169 through S174 and S177 through S179 shown in FIG. 16 is the same as S5 through S13 of the first embodiment shown in FIG.

  According to the seventh embodiment, the control unit 21 further responds to the performance change (performance decrease) accompanying the increase in the operation amount for each color unit selected as the toner pattern forming unit by the control unit 21. The toner pattern density change on the peripheral surface of the intermediate transfer belt 124 before and after the toner pattern transfer from the peripheral surface of the intermediate transfer belt 124 to the secondary transfer roller 113 can be accurately detected.

  Next, an eighth embodiment of the process for detecting the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124 will be described. FIG. 17 is a flowchart illustrating an eighth embodiment of a process for detecting a contact state between the secondary transfer roller 113 and the intermediate transfer belt 124. Note that the description of the same processes as those described in the first to seventh embodiments is omitted.

  In the eighth embodiment, a specific timing is not particularly shown as the start timing of the contact state detection process between the secondary transfer roller 113 and the intermediate transfer belt 124. However, the eighth embodiment is different from the first embodiment or the second embodiment described above. It may be started at the same timing. Furthermore, in the eighth embodiment, each color unit of the image forming unit 12 used for forming the toner pattern may be a predetermined unit for a specific color as shown in the first embodiment. As shown in the sixth and seventh embodiments, for each detection process of the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124, units for different colors are sequentially changed to form a toner pattern. It may be selected as a unit.

  In the eighth embodiment, the control unit 21 assigns a toner pattern for detecting the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124 to any unit of the image forming unit 12 (for example, the yellow unit 12Y). ) In the vicinity of both ends in the width direction on the intermediate transfer belt 124 (S180), and then the second toner disposed upstream of the nip portion between the intermediate transfer belt 124 and the secondary transfer roller 113. The density detection sensor 24 detects the density of each toner pattern formed on the intermediate transfer belt 124, and the toner density detected by the second toner density detection sensor 24 is a predetermined value (intermediate transfer belt). The toner pattern density used for detecting the contact state between 124 and the secondary transfer roller 113 has reached a predetermined value). It determines whether or not (S181).

  If the control unit 21 determines that the toner concentration detected by the second toner concentration detection sensor 24 has not reached the predetermined value (YES in S181), the control unit 21 sets the bias for toner image transfer to the secondary transfer roller 113. In contrast, the bias applying unit 26 is not applied (S189), and the toner pattern on the circumferential surface of the intermediate transfer belt 124 is not transferred to the secondary transfer roller 113 side.

  When the intermediate transfer belt 124 rotates endlessly and the toner pattern on the intermediate transfer belt 124 formed in S180 returns to the position facing the unit on which the toner pattern is formed in S180, the control unit 21 , The same toner pattern is formed again on the same unit on which the toner pattern is formed in S180, overlaid on the toner pattern (S190).

  The control unit 21 repeats the processes of S189 and S190 until the toner density detected by the second toner density detection sensor 24 reaches the predetermined value (YES in S181). The control unit 21 repeats the processes of S189 and S190, and when the toner density detected by the second toner density detection sensor 24 reaches the predetermined value (NO in S181), the secondary transfer roller 113, a positive bias (bias for toner image transfer) is applied to the bias applying unit 26 (S182), and thereafter, S183 to S187 are the same as S5 to S13 of the first embodiment shown in FIG. Then, the processing of S191 to S193 is performed.

  According to the eighth embodiment, the density of the toner pattern formed by any one of the color units of the image forming unit 12 is changed from the intermediate transfer belt 124 to the secondary transfer roller 113 without adding a special configuration. It is possible to maintain the density suitable for detecting the change in the toner pattern density before and after the toner image transfer. In addition, it is possible to maintain the above-mentioned density with the same color as the initially formed toner pattern without changing the color of the toner pattern formed on the intermediate transfer belt 124.

  In the eighth embodiment, when the control unit 21 determines that the density of the toner pattern detected by the second toner concentration detection sensor 24 has not reached the predetermined value (YES in S181), the control unit 21 In step S180, the same unit on which the toner pattern is formed in step S180 is overlapped on the toner pattern formed in step S180 to form the same toner pattern again (step S190). In this case, the control unit 21 performs step S180. The toner pattern may be formed on a different unit different in color from the unit on which the toner pattern is formed so as to overlap the toner pattern. According to this, even when the performance of the unit that initially formed the toner pattern has deteriorated to such an extent that the toner pattern having the above density cannot be formed even if the toner patterns are formed in multiple layers, A toner pattern can be formed.

  Next, a description will be given of a ninth embodiment of a process for detecting a contact state between the secondary transfer roller 113 and the intermediate transfer belt 124. FIG. 18 is a flowchart showing a ninth embodiment of a process for detecting a contact state between the secondary transfer roller 113 and the intermediate transfer belt 124. Note that the description of the same processes as those described in the first to eighth embodiments is omitted. In the ninth embodiment, no particular timing is shown as the start timing of the contact state detection process between the secondary transfer roller 113 and the intermediate transfer belt 124. However, the first embodiment or the second embodiment described above. It may be started at the same timing.

  The control unit 21 applies a toner pattern for detecting the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124 to any unit (for example, the yellow unit 12Y) of the image forming unit 12 and transfers the toner pattern to the intermediate transfer belt. After being formed near both ends in the width direction on 124 (S201), the toner pattern density detection sensor 23 downstream of the nip portion between the intermediate transfer belt 124 and the secondary transfer roller 113 is transferred to the secondary transfer roller 113. The density of each of the toner patterns remaining on the intermediate transfer belt 124 after the transfer is detected (S203).

  Then, the control unit 21 determines that the toner density detected by the toner pattern density detection sensor 23 is based on the threshold value (the control unit 21 is based on the toner density obtained from the first toner density detection sensor 23 based on the print job. It is determined whether or not the value is within a certain range from a threshold value used for determining whether or not to perform an image forming operation (S204). This fixed range is, for example, a range of ID value ± 0.05 (sensor value ± 10) when the threshold value is, for example, ID value 0.4 (sensor value 154), and the detected toner pattern density is in the vicinity of the threshold value. The accuracy of the toner pattern density detection is a range that greatly affects the determination of whether or not to permit the image forming operation.

  When the toner density detected by the toner pattern density detection sensor 23 is a value within a certain range from the threshold (YES in S204), the control unit 21 determines the toner pattern formation position by the unit of the image forming unit 12. Is changed to a different position in the running direction of the intermediate transfer belt 124 (S206), and the toner pattern is formed again on the unit of the image forming unit 12 (S207), and the toner pattern is transferred to the secondary transfer roller 113. Later (S208), the density of the residual toner pattern on the intermediate transfer belt 124 is detected by the toner pattern density detection sensor 23 (S209).

  After performing the toner pattern formation and the toner pattern density detection again after changing the formation position, the control unit 21 performs the same as S7 to S13 of the first embodiment shown in FIG. Processing for determining whether or not to perform an image forming operation based on a comparison between the detected toner pattern density and a threshold value is performed (S210 to S216).

  According to the ninth embodiment, the control unit 21 determines that the toner pattern density detected by the toner pattern density detection sensor 23 performed for the first time is a value within a certain range from the upper threshold value, and the detected toner pattern density is When the toner pattern density detection accuracy is in the vicinity of the threshold value and greatly affects the determination of whether the image forming operation is permitted or not, the position of the peripheral surface of the intermediate transfer belt 124 in the traveling direction is changed. And determining whether the image forming operation is permitted or not permitted based on the toner pattern density detection and the upper threshold value based on the toner pattern. Therefore, the toner pattern is not formed at the desired density at the first toner pattern formation location. The toner pattern formed at a position, it is possible to control the image forming operation permission or non-permission based on density detection process and the threshold based on the toner pattern consisting of the desired concentration. As a result, it is possible to avoid a density detection process based on a toner pattern due to partial deterioration or partial contamination on the circumferential surface of the intermediate transfer belt 124 and an error in determining whether to permit or disallow an image forming operation based on a threshold value. become.

  On the other hand, when the control unit 21 determines in S204 that the toner pattern density detected by the toner pattern density detection sensor 23 is outside the predetermined range from the threshold value (NO in S204), the detection is performed. Using the toner pattern density, a process for determining whether or not to perform an image forming operation based on a comparison between the detected toner pattern density and a threshold value is performed (S210 to S216). As described above, when the detected toner pattern density deviates greatly from the threshold value, the accuracy of the toner pattern density detection does not greatly affect the determination of whether or not the image forming operation is permitted. Time required for the control for permitting or not permitting the image forming operation while maintaining the detection accuracy of the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124 by omitting the pattern formation and toner pattern density detection processing. To shorten.

  Next, a description will be given of a tenth embodiment of a process for detecting a contact state between the secondary transfer roller 113 and the intermediate transfer belt 124. FIG. 19 is a flowchart illustrating a tenth embodiment of a process for detecting a contact state between the secondary transfer roller 113 and the intermediate transfer belt 124. Note that the description of the same processes as those described in the first to ninth embodiments is omitted. In the tenth embodiment, a specific timing is not particularly shown as the start timing of the detection process of the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124, but the first embodiment or the second embodiment described above. It may be started at the same timing.

  In the ninth embodiment, when the toner pattern density detected by the toner pattern density detection sensor 23 is a value within a certain range from the threshold value (YES in S204 in FIG. 18), the unit of the image forming unit. After changing the toner pattern forming position to a different position in the traveling direction of the intermediate transfer belt 124 (S206 in FIG. 18), the toner pattern is formed, and based on the toner pattern, the toner pattern density detection and the upper threshold value are set. In the tenth embodiment, as shown in FIG. 19, the control unit 21 controls the toner pattern density detection sensor to determine whether the image forming operation is permitted or not based on this (S206 to S216 in FIG. 18). When the toner pattern density detected in step 23 is a value within a certain range from the threshold value (YES in S224), Leaning roller 35 (FIG. 1, FIG. 3), the peripheral surface of the intermediate transferring belt 124 above (S225) were allowed to clean the to form a toner pattern on the unit of the image forming unit 12 again (S226). Then, after transferring the toner pattern to the secondary transfer roller 113 side (S227), the control unit 21 causes the toner pattern density detection sensor 23 to detect the density of the residual toner pattern on the intermediate transfer belt 124 (S228). . The control unit 21 performs the toner pattern formation and the toner pattern density detection again after cleaning the circumferential surface of the intermediate transfer belt 124 by the cleaning roller 35, and thereafter, the control unit 21 performs steps S7 to S13 of the first embodiment shown in FIG. Similarly, processing for determining whether or not to perform an image forming operation based on a comparison between the detected toner pattern density and a threshold value is performed (S229 to S235).

  According to the tenth embodiment, even if the toner pattern is not formed at a desired density in the initial toner pattern formation due to dirt on the circumferential surface of the intermediate transfer belt 124, the desired toner pattern is formed again by forming the toner pattern. Thus, it is possible to perform density detection processing based on a toner pattern having a certain density and control whether to permit or disallow an image forming operation based on a threshold value. For this reason, erroneous detection of the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124 due to dirt or the like on the peripheral surface of the intermediate transfer belt 124, and determination of permission or non-permission of image forming operation based on the threshold value. It becomes possible to avoid mistakes.

  In the ninth and tenth embodiments, the toner pattern is formed again in the same unit. However, the toner pattern may be formed again in different color units.

  Next, an eleventh embodiment of the detection process of the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124 will be described. FIG. 20 is a flowchart illustrating an eleventh embodiment of a process for detecting a contact state between the secondary transfer roller 113 and the intermediate transfer belt 124. FIG. 21 is a diagram illustrating a frequency at which the image forming operation is not permitted by the control unit 21 and display data associated with the frequency. Note that the description of the same processes as those described in the first to tenth embodiments is omitted.

  The eleventh embodiment relates to a warning that is issued when the control unit 21 disallows an image forming operation based on a print job during detection processing of the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124. . As the detection process of the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124 performed as a premise of entering S241 of the eleventh embodiment, any of the contact state detection processes shown in the first to tenth embodiments can be used. Is also applicable.

  The control unit 21 counts up the detection process execution number counter 31 during the process of detecting the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124 (S241). The detection process execution number counter 31 is counted up after the start of the contact state detection process performed on the premise of entering S241 and before the comparison process of the toner pattern density and the threshold value in S243. It may be performed at the timing.

  Subsequently, when the control unit 21 determines that any one of the residual toner densities detected by the two toner pattern density detection sensors 23 is higher than the threshold value (NO in S243), next, Image formation based on a newly input job is not permitted (S244), and the non-permission count counter 33 is incremented (S245).

  Here, the control unit 21 obtains the count values of the detection process execution number counter 31 and the non-permission count counter 33 at this time, and calculates the frequency M for prohibiting the image forming operation based on the print job (S246). . In the present embodiment, the control unit 21 calculates, as the frequency M, how many times the non-permission count counter 33 has been counted up while the detection process execution count counter 31 has been counted up 10 times.

  If the frequency 1 ≧ M (“1 ≧ M” in S247), the control unit 21 reads display data corresponding to the frequency M from the storage unit 22 and causes the display unit 16 to display the display data. (S248). In the present embodiment, as display data associated with the frequency M ≦ 1, as shown in FIG. 21, a message stating “Please reconfirm that the main body cover and the support member are closed” is stored in the storage unit 22. Is stored.

  When the frequency 2 ≦ M <5 (“2 ≦ M <5” in S247), the control unit 21 displays the display data corresponding to the frequency M (frequency 2 ≦ M in this embodiment). As the display data associated with <5>, as shown in FIG. 21, in the storage unit 22, “please open the main body cover and the support member and close it until it clicks. Then, the main body cover and the support member. Is read from the storage unit 22 and displayed on the display unit 16 (S249).

  When the frequency M ≧ 5 (“5 ≧ M” in S247), the control unit 21 associates the display data corresponding to the value of the frequency M (in this embodiment, the frequency 5 ≧ M). As the display data, as shown in FIG. 21, display data indicating a message “Please contact a service person” is stored in the storage unit 22 from the storage unit 22. 16 is displayed (S250).

  According to the eleventh embodiment, when the toner pattern density detected by the toner pattern density detection sensor 23 is higher than the threshold value and the image forming operation is not performed even when a print job is input, The message to be displayed on the display unit 16 according to the frequency at which it is determined that the image forming operation is not permitted (that is, the frequency at which the contact state between the secondary transfer roller 113 and the intermediate transfer belt 124 is inappropriate) is displayed. Thus, when the contact failure between the secondary transfer roller 113 and the intermediate transfer belt 124 occurs, the user can recognize an appropriate operation according to the situation at that time.

  In S248 to S250, the operation guidance for the user by the control unit 21 is a message display by the display unit 16, but instead of the display unit 16, a speaker or LED (Liquid Crystal Display) or the like is used as a warning unit. The control unit 21 may vary the alarm sound from the speaker according to the frequency M, or may vary the LED blinking method and lighting color according to the frequency M.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, in the above embodiment, the printer 1 has been described as an embodiment of the image forming apparatus according to the present invention. However, the present invention is not limited to this, and the present invention is not limited to this. Applicable. The image forming apparatus according to the present invention is not limited to a color printer, and can be applied to a monochrome printer.

  In the above embodiment, an example in which the intermediate transfer belt 124 is applied as an intermediate transfer member is shown, but the intermediate transfer member may be of another type such as an intermediate transfer drum.

  In each of the above embodiments, the control unit 21 causes the unit of the image forming unit 12 to form two toner patterns at different positions in the length direction (rotational axis direction) of the driving roller 124a of the intermediate transfer belt 124. Then, a determination is made as to whether or not to permit the image forming operation by comparing the density of each of the two toner patterns detected by the toner pattern density detection sensor 23 with the threshold value (the intermediate transfer belt 124 and the secondary transfer roller 113) However, the present invention is not limited to this, and the control unit 21 supplies toner to the unit of the image forming unit 12 in the length direction (rotation axis direction) of the driving roller 124a of the intermediate transfer belt 124. Only one pattern is formed, and the one toner pattern detected by the toner pattern density detection sensor 23 May be performed determines whether or not to allow the image forming operation by comparison with the concentration and the threshold value.

1 is a cross-sectional view illustrating an overall configuration of a printer according to an embodiment of the present invention. (A) (b) is a figure which shows the detection signal output from a paper jam detection sensor. FIG. 4 is a schematic diagram illustrating an intermediate transfer belt on which a toner pattern for detecting a contact state between a secondary transfer roller and an intermediate transfer belt is formed, and a paper jam detection sensor. FIG. 3 is a diagram illustrating a configuration of a toner pattern density sensor. 1 is a block diagram showing a control system of a printer according to an embodiment of the present invention. 3 is a flowchart illustrating a first embodiment of a process for detecting a contact state between a secondary transfer roller and an intermediate transfer belt. 10 is a flowchart illustrating a second embodiment of a process for detecting a contact state between a secondary transfer roller and an intermediate transfer belt. 10 is a flowchart illustrating a third embodiment of detection processing of a contact state between a secondary transfer roller and an intermediate transfer belt. 10 is a flowchart illustrating a fourth embodiment of a process for detecting a contact state between a secondary transfer roller and an intermediate transfer belt. It is a flowchart which shows the count process of a counter. It is a flowchart which shows the count process of a counter. It is a figure which shows the threshold value corresponding to an image formation amount and an image formation amount. It is a figure which shows the threshold value corresponding to an image formation amount and an image formation amount. 10 is a flowchart illustrating a fifth embodiment of a process for detecting a contact state between a secondary transfer roller and an intermediate transfer belt. 15 is a flowchart illustrating a sixth embodiment of a process for detecting a contact state between a secondary transfer roller and an intermediate transfer belt. 15 is a flowchart illustrating a seventh embodiment of a process for detecting a contact state between a secondary transfer roller and an intermediate transfer belt. It is a flowchart which shows 8th Embodiment of the detection process of the contact state of a secondary transfer roller and an intermediate transfer belt. It is a flowchart which shows 9th Embodiment of the detection process of the contact state of a secondary transfer roller and an intermediate transfer belt. It is a flowchart which shows 10th Embodiment of the detection process of the contact state of a secondary transfer roller and an intermediate transfer belt. It is a flowchart which shows 11th Embodiment of the detection process of the contact state of a secondary transfer roller and an intermediate transfer belt. It is a figure which shows the frequency by which the image formation operation was disallowed by the control part, and the display data matched with this. FIG. 4 is a perspective view for explaining a jam handling procedure of the printer, (a) is a perspective view showing a state in which a main body cover is closed, and (b) is a perspective view showing a state in which the main body cover is opened. FIG. 8C is a perspective view showing a state in which the support member is rotated outward from the apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 11 Device main body 12Y Yellow unit 12C Cyan unit 12K Black unit 12M Magenta unit 12 Image forming unit 16 Display unit 17 Main body cover 18 Support member 19 Paper jam detection sensor 20 Control unit 21 Control unit 22 Storage unit 23 Toner Pattern density detection sensor 231 Light emitting part 2311 Light source part 2312 Beam splitter 2313 Light receiving element 232 Light receiving part 2321 Beam splitters 2322 and 2323 Light receiving element 24 Second toner density detection sensor 25 Toner pattern 26 Bias applying part 27 Counter 28 Threshold changing part 30 Opening / closing detection Switch 31 Detection processing execution counter 32M, 32C, 32Y, 32K Unit-specific counter 33 Non-permission counter 35 Cleaning roller 113 Secondary transfer roller 120 Photosensitive Body drum 124 intermediate transfer belt 124a driving roller

Claims (3)

An image forming unit for forming a toner image;
An intermediate transfer member having a peripheral surface to which a toner image is transferred from the image forming unit;
A secondary transfer portion that contacts the peripheral surface of the intermediate transfer member to form a nip portion, and transfers a toner image on the peripheral surface of the intermediate transfer member to a recording sheet conveyed through the nip portion;
A toner pattern density detector provided on the downstream side of the nip portion in the toner image transport direction by the intermediate transfer body and detecting the density of the toner pattern remaining on the peripheral surface of the intermediate transfer body;
After transferring the toner pattern on the peripheral surface of the intermediate transfer member to the image forming unit with a predetermined content, and transferring the toner pattern on the peripheral surface of the intermediate transfer member to the secondary transfer unit, If the density of the toner pattern detected by the toner pattern density detection unit is equal to or less than a predetermined threshold value, an image forming operation based on a print job is performed on the image forming unit, the intermediate transfer body, and the secondary transfer unit. And when the detected toner density is higher than the threshold, the control unit does not allow the image forming operation based on a print job;
A determination number counter for counting the number of times the image forming operation is permitted or not permitted by the control unit;
A non-permission counter that counts the number of times that the control unit determines that the image forming operation is not permitted in the determination of permission or non-permission of the image forming operation;
A warning section for warning the user,
In the determination of whether the image forming operation is permitted or not permitted, when the control unit determines that the image forming operation is not permitted, the control unit performs the image forming operation based on count values of the determination number counter and the non-permission number counter. An image forming apparatus that causes the warning unit to issue a warning with different warning contents according to the frequency at which it is determined not to permit. In correspondence with each frequency determined not to permit the image forming operation, further comprising a display data storage unit for storing different display data for each frequency,
The warning unit is a display unit that displays operation guidance for a user,
2. The image formation according to claim 1, wherein the control unit reads display data corresponding to a frequency at which it is determined not to permit the image forming operation from the display data storage unit, and causes the display unit to display the read display data. apparatus. The intermediate transfer body includes an intermediate transfer belt that rotates endlessly, and a drive roller that rotates the intermediate transfer belt endlessly,
The control unit causes the image forming unit to form the toner pattern at each position of the intermediate transfer belt that is different in the rotation axis direction of the drive roller, and detects the intermediate transfer body circumference detected by the toner pattern density detection unit. The image forming apparatus according to claim 1, wherein control is performed based on a comparison with the threshold value using a density of each toner pattern remaining on the surface.

Images