JP6086232B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a printer, a facsimile, and a composite machine of these.

  In an image forming apparatus such as a copying machine, a printer, or a facsimile, a toner image is formed on an image carrier based on image information. Then, the toner image is transferred onto a recording medium such as paper or an OHP sheet, the recording medium carrying the toner image is passed through a fixing device, and the toner image is fixed onto the recording medium by heat and pressure. Yes. As the fixing device, a heat roller method and a film method are mainly known. As the heat roller system, an internal heating system having a heat source (such as a halogen heater) inside the fixing roller and an external heating system having a heat source outside the fixing roller are known. Recently, there is a tendency to use an external heating method that can satisfy demands such as high-quality image output corresponding to shortening of the rise time, reduction of power consumption, and high speed.

  In such an external heating type fixing device, in order to further shorten the rise time and reduce power consumption, for example, as disclosed in Japanese Patent Application Laid-Open No. 2001-343860, it is divided into a plurality in the width direction of the fixing device. There is known a fixing device in which only the heating region corresponding to the image region is heated (hereinafter referred to as a divided heating method).

  However, in this divided heating method, when toner is transferred to a non-image area of the recording medium due to poor cleaning of the image carrier, the toner is output without being heated and fixed. For this reason, other printed matter is contaminated by the unfixed toner, the user's hand and clothes are contaminated, and the unfixed toner is scattered to contaminate the surroundings.

  By the way, conventionally, a sensor for detecting the surface state of the photoconductor (image density of the reference toner image, etc.) is provided, and the detected information is fed back to the output of the charger, etc., so that the image quality deteriorates as the photoconductor deteriorates with time. And the like are known (for example, Patent Document 2: Japanese Patent Laid-Open No. 5-281818). In the technique of Patent Document 2, a toner density sensor is disposed so as to be movable in the longitudinal direction (axial direction) in order to detect the surface state of the photoreceptor in a wide range. As a result, the toner density is accurately detected without being affected by local residual toner adhesion, and appropriate image quality correction is performed.

  However, the technique disclosed in Patent Document 2 only corrects a decrease in image quality associated with the deterioration of the photoreceptor with the lapse of time using a toner density sensor, and does not take into account the problem of unfixed toner. Also, the toner density on the surface of the photosensitive member is detected. When a toner image is temporarily transferred from the photosensitive member to, for example, an intermediate transfer belt, and then transferred and fixed from the intermediate transfer belt to a recording medium, The toner status cannot be detected. For this reason, the problem of unfixed toner due to poor cleaning occurs in the intermediate transfer belt as well as the photosensitive member, or the same problem occurs due to toner dropping on the intermediate transfer belt.

  An object of the present invention is to prevent toner that has adhered to a non-image area of an image carrier due to defective cleaning or the like from being output unfixed on a recording medium in an image forming apparatus having a fixing device of a division heating method. There is to do.

In order to solve the above problems, the present invention provides an image carrier that carries a latent image in a state of being visualized by a developer, and a transfer unit that transfers the visible image on the image carrier onto a recording medium. Heating means capable of selecting and heating a heating area necessary for fixing the visible image transferred onto the recording medium, and cleaning for removing the developer remaining on the surface of the image carrier after transfer. And an image forming apparatus having a switching means for switching a heating region for selecting the necessary heating region, wherein a cleaning failure detection sensor for detecting defective removal of residual developer by the cleaning device is provided as the image carrier or wherein while disposed on the transfer means, and reciprocally configured in a direction transverse to the cleaning failure detecting sensor with respect to the moving direction of the visible image, the cleaning failure detection When the front end of the visible image reaches the detection position of the sensor, the reciprocation of the cleaning failure detection sensor is stopped, and when the rear end of the visible image passes the detection position of the cleaning failure detection sensor. The reciprocation of the cleaning failure detection sensor is resumed, and the presence or absence of residual developer in the non-printing areas formed on the front end side and the rear end side in the moving direction of the visible image is detected by the reciprocation. An image forming apparatus characterized by the above (claim 1 ).

According to the present invention, it is possible to detect a residual developer adhering to a non-printing area or a non-image area due to poor cleaning of an image carrier or the like with a wide range and high reliability with a single low-cost cleaning sensor. can Ru. In addition, a single cleaning failure detection sensor can be used to remove residual developer adhering to the non-printing areas formed on the front and rear edges of the visible image due to poor cleaning of the image carrier. (Claim 1 ).

1 is a schematic view of an image forming apparatus according to an embodiment of the present invention. 2 is a schematic cross-sectional view of a fixing unit of the image forming apparatus. FIG. 2 is a schematic perspective view of a fixing unit of the image forming apparatus. FIG. It is a schematic sectional drawing which shows the other example of a fixing means. It is a figure which shows the example of a cleaning defect detection sensor. It is a figure which shows the example of a cleaning defect detection sensor. It is a figure which shows the example of a cleaning defect detection sensor. It is a figure which shows the example of a cleaning defect detection sensor. It is a figure which shows the method of detecting the removal state of the residual developer of a non-image area. It is a figure which shows the example of the cleaning defect detection sensor provided in the transfer belt. It is a figure which shows the other example of the cleaning defect detection sensor provided in the transfer belt. It is a figure which shows the example of the image formation area of a recording medium. It is a figure which shows the example of the image formation area of a recording medium. It is a figure which shows the example of the image formation area of a recording medium. It is a figure which shows the example of the image formation area of a recording medium. It is a figure which shows the example of the heating pattern of a heating means. FIG. 3 is a diagram illustrating an example of heat fixing of a recording medium by a fixing unit of the present invention. FIG. 3 is a diagram illustrating an example of heat fixing of a recording medium by a fixing unit of the present invention. It is a figure which shows the example of heat fixing of the recording medium by the conventional fixing means. It is the schematic which shows the operation example 1 of a cleaning defect detection sensor. It is a flowchart which shows the control example of the operation example 1 of a cleaning defect detection sensor. It is the schematic which shows the operation example 2 of a cleaning defect detection sensor. It is a flowchart which shows the control example of the operation example 2 of a cleaning defect detection sensor. It is the schematic which shows the operation example 3 of a cleaning defect detection sensor. It is a flowchart which shows the control example of the operation example 3 of a cleaning defect detection sensor. It is the schematic which shows the modification of the operation example 3 of a cleaning defect detection sensor. It is the schematic which shows the subject of the operation example 1 of a cleaning defect detection sensor. It is the schematic which shows the operation example 4 of a cleaning defect detection sensor. It is a flowchart which shows the control example of the operation example 4 of a cleaning defect detection sensor. It is the schematic which shows the operation example 5 of a cleaning defect detection sensor. It is the schematic which shows the operation example 6 of a cleaning defect detection sensor. It is a flowchart which shows the control example of the operation example 6 of a cleaning defect detection sensor. It is the schematic which shows the operation example 7 of a cleaning defect detection sensor. It is a flowchart which shows the control example of the operation example 7 of a cleaning defect detection sensor.

  Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described with reference to the accompanying drawings. In each drawing for explaining this embodiment, components such as members and components having the same function or shape are given the same reference numerals as much as possible, and once described, Description is omitted.

(Image forming device)
FIG. 1 illustrates a printer 10 as an example of an image forming apparatus according to an embodiment of the present invention. The printer 10 includes a paper feeding unit 11, a timing roller pair 12, a photoconductor 13 as an image carrier, a transfer unit 14, a fixing unit 15 and the like. A cleaning failure detection sensor 31 (32), which will be described later, is disposed on the outer periphery of the photoconductor 13. The transfer unit 14 and the fixing unit 15 are not limited to the configuration shown in FIG.

  The paper feed means 11 has a paper feed tray 11a in which paper P as a recording medium is stored in a stacked state. The paper P stored in the paper feed tray 11a is separated and sent one by one from the top one by the paper feed roller 11b. The paper P sent out by the paper feed roller 11b is temporarily stopped by the timing roller pair 12 and the posture deviation is corrected. Thereafter, at the timing synchronized with the rotation of the photoconductor 13, that is, at the timing when the front end of the toner image formed on the photoconductor 13 coincides with the predetermined position of the front end portion in the transport direction of the paper P, the timing roller pair 12 It is sent to the transfer nip N.

  Around the photosensitive member 13, in addition to the cleaning failure detection sensor 31 (32), a charging roller 16 as a charging unit, a mirror 17 constituting a part of an exposure unit (not shown), in the rotation direction indicated by an arrow, A developing means 18 having a developing roller 18a is provided. Subsequently, a transfer unit 14, a cleaning unit 19 including a cleaning blade 19a, and the like are disposed. Between the charging roller 16 and the developing means 18, exposure light Lb is irradiated to the exposure unit 13 a on the photosensitive member 13 via the mirror 17 and scanned.

  The image forming operation in the printer 10 is performed in the same manner as before. That is, when the photosensitive member 13 starts rotating, the surface of the photosensitive member 13 is uniformly charged by the charging roller 16, and the exposure light Lb is irradiated and scanned on the exposure unit 13a based on the image information to correspond to an image to be created. An electrostatic latent image (latent image) is formed.

  The electrostatic latent image (latent image) is moved to the developing means 18 by the rotation of the photosensitive member 13, where toner as a developer is supplied to be visualized (visualized) to form a toner image. Is done. The toner image formed on the photosensitive member 13 is transferred onto the paper P that has entered the transfer nip N at a predetermined timing by applying a transfer bias by the transfer unit 14.

  The sheet P carrying the toner image is conveyed toward the fixing unit 15, fixed by the fixing unit 15, and then discharged and stacked on a discharge tray (not shown). Residual toner that is not transferred at the transfer nip N and remains on the photoconductor 13 after transfer reaches the cleaning means 19 as the photoconductor 13 rotates, and is scraped by the cleaning blade 19 a while passing through the cleaning means 19. Dropped and cleaned. Thereafter, the residual potential on the photosensitive member 13 is removed by a neutralizing unit (not shown) and prepared for the next image forming step.

(Fixing means)
2A and 2B, the fixing unit 15 includes a fixing roller 15a as a fixing member and a pressure roller 15b as a pressure member that forms a fixing nip SN between the fixing roller 15a. On the outer periphery of the fixing roller 15a, a heating unit 20 to which electric power is supplied from the power source 23 is disposed, and the fixing roller 15a is heated by an external heating method.

  The fixing unit 15 is not limited to the fixing roller 15a and the pressure roller 15b described above. For example, as shown in FIG. 2C, a fixing belt method using a heating roller 15c and a fixing belt 15d in addition to the fixing roller 15a and the pressure roller 15b may be used.

  In this fixing belt system, the heating roller 15c is urged by the tension spring 26 in a direction away from the fixing roller 15a, thereby applying a predetermined tension to the fixing belt 15d. A heating means 20 is disposed on the outer periphery of the heating roller 15c as in FIG. 2A. The paper P is fed into the fixing nip SN along the entrance guide plate 27. A so-called twin belt system may be employed in which a second pressure roller is provided and a pressure belt is stretched between the two pressure rollers in the same manner as the fixing belt 15d.

  The heating unit 20 is configured by a divided heating method and includes a plurality of thermal heaters 20a to 20g arranged at equal intervals in the longitudinal direction of the fixing roller 15a. Each of the thermal heaters 20a to 20g can independently heat the peripheral surface of the fixing roller 15a. In the illustrated example, only seven thermal heaters 20a to 20g are shown for convenience, but a necessary number of thermal heaters are actually arranged corresponding to the width of the paper P to be printed.

  The arrangement of the thermal heaters 20a to 20g along the longitudinal direction of the fixing roller 15a may be a straight line as shown in FIG. 2B, or staggered so that there is no gap in the longitudinal direction between the thermal heaters 20a to 20g. Also good. Further, the configuration is not limited to the configuration in which the fixing roller 15a is heated by the thermal heaters 20a to 20g or other heating means, but the configuration in which the pressure roller 15b side is heated or both the fixing roller 15a and the pressure roller 15b are heated. Is also possible.

  A thermistor 21 serving as a temperature detecting means for detecting the surface temperature of the fixing roller 15 a is disposed downstream of the fixing nip SN of the fixing roller 15 a and upstream of the heating means 20. Corresponding to the thermal heaters 20a to 20g, the thermistors 21 are provided in the same number as the thermal heaters 20a to 20g and at equal intervals in the longitudinal direction of the fixing roller 15a. Further, as the temperature detecting means for detecting the temperature of each of the thermal heaters 20a to 20g, the same number of thermistors 22 as the thermal heaters 20a to 20g are arranged at equal intervals in the longitudinal direction of the fixing roller 15a.

  For example, power of 400 w to 2000 w is supplied from the power source 23 to the thermal heaters 20 a to 20 g of the heating unit 20. This supply amount is controlled by the heating control means 24 based on the detection information of the thermistors 21 and 22. As a result, the surface temperature of the fixing roller 15a is maintained at a temperature (fixing temperature) necessary for heating and melting the toner.

  Specifically, the heating control means 24 is a microcomputer including a CPU, a ROM, a RAM, an I / O interface, and the like. The heating control means 24 also functions as a switching means for switching the heating area by the thermal heaters 20a to 20g to a different heating area. As will be described later, the heating means 20 can be of a non-contact heating method. If such a non-contact heating method is also included in the heating means 20, the above-described “switching of heating area” can be said to be “selection of heating area”. The heating control unit 24 is connected to a cleaning failure detection sensor 31 described later, and is configured to operate the heating unit 20 in a normal control mode or a clean control mode in response to a signal from the cleaning failure detection sensor 31. . The normal control mode and the clean control mode will be described later.

  The fixing roller 15a includes, for example, an aluminum core 15a1 having an outer diameter of 40 mm and a thickness of 1 mm, and a heat insulating layer 15a2 covered on the surface of the core 15a1. The heat insulating layer 15a2 is made of, for example, silicon rubber and has a thickness of 3 mm. The heat insulating layer 15a2 may be formed of foamed silicon rubber with less heat escape in order to further enhance its heat insulating function. A good heat conductive layer 15a3 made of nickel is formed on the heat insulating layer 15a2 of the fixing roller 15a. The good heat conductive layer 15a3 is not limited to nickel, but may be any iron-based alloy such as stainless steel, metal-based aluminum or copper, graphite sheet, or the like as long as the thermal conductivity is at least higher than that of the heat insulating layer 28b.

  By forming the good heat conductive layer 15a3 on the fixing roller 15a, local temperature unevenness of the surface temperature of the fixing roller 15a due to heat generation unevenness of the thermal heaters 20a to 20g is reduced. In addition, the temperature of the region slightly larger than the region heated by the thermal heaters 20a to 20g is raised by the function of the good heat conductive layer 15a3, so that there is an advantage that a slight deviation from the image can be compensated.

  In other words, there is an advantage that the degree of freedom in design is large in setting the size and interval of each heater constituting the thermal heaters 20a to 20g. Further, in order to enhance the durability of the fixing roller 15a and ensure the releasability, a release layer 15a4 having a thickness of 5 to 30 μm made of fluorine resin such as PFA or PTFE may be formed on the surface of the heat insulating layer 15a2. .

  The pressure roller 15b has, for example, an iron core metal 15b1 having an outer diameter of 40 mm and a thickness of 2 mm, and an elastic layer 15b2 covered on the surface of the core metal 15b1. The elastic layer 15b2 is made of, for example, silicon rubber and has a thickness of 5 mm. On the surface of the elastic layer 15b2, it is desirable to form a fluororesin layer having a thickness of, for example, about 40 μm in order to improve the releasability. The pressure roller 15b is pressed against the fixing roller 15a by a pressure spring 25 as an urging means. The thermal heaters 20a to 20g of the heating unit 20 are pressed against the surface of the fixing roller 15a by an urging unit (not shown).

(Residual toner cleaning failure detection sensor)
3A to 3D show examples of cleaning failure detection sensors 31 and 32 that detect the presence or absence of residual toner on the photosensitive member 13, that is, a removal failure (cleaning failure). The cleaning failure detection sensor 31 in FIGS. 3A to 3C is disposed between the cleaning unit 19 and the charging roller 16. The cleaning failure detection sensor 31 has a photoconductor surface measuring means for measuring the surface of the photoconductor 13 and a microcomputer for recording and processing the measurement result. The microcomputer includes a CPU, a ROM, a RAM, an I / O interface, and the like. This microcomputer may be a dedicated computer for the cleaning failure detection sensor 31 or may be used as the microcomputer for the heating control means 24 described above.

  FIG. 3B shows an embodiment of the photoconductor surface measuring means of the cleaning failure detection sensor 31. The photoconductor surface measuring means includes an illumination light source 31a, an imaging lens 31b, and a sensor 31c. The illumination light source 31a has a function of irradiating the surface of the photoreceptor 13 with irradiation light including light in the visible range and light outside the visible range. The illumination light source 31a is disposed at a position where the irradiated light is incident on the photosensitive member 13 at an angle of approximately 45 degrees.

  As the illumination light source 31a, for example, a white LED (Light Emitting Diode) can be used. As the illumination light source 31a, a fluorescent lamp such as a cold cathode tube or a lamp light source may be used.

  The light irradiated by the illumination light source 31a is reflected on the photosensitive member 13 and forms an image on the sensor 31c through the imaging lens 31b. The sensor 31c has a pixel that receives light. As the sensor 31c, for example, a metal oxide semiconductor device (MOS), a complementary metal oxide semiconductor device (CMOS), a charge coupled device (CCD), a contact image sensor (CIS), or the like can be used.

  Since the surface of the photosensitive member 13 as an irradiation target is a smooth surface, most of the irradiation light from the illumination light source 31a is normally regularly reflected and detected by the sensor 31c. On the other hand, when toner adheres on the photosensitive member 13, the amount of reflected light decreases and the amount of light received by the sensor 31c decreases. By utilizing this light amount difference, the surface state of the photoconductor 13 can be detected well in the entire axial direction, and the defect state of the surface of the photoconductor 13 such as defective cleaning of the surface of the photoconductor 13 or toner dropping can be improved. Can be detected.

  For example, when the reference light amount when the reflected light from the surface of the photosensitive member 13 is received by the sensor 31c is recorded in advance in a ROM or RAM on a microcomputer, and the received light amount of the sensor 31c is smaller than the reference light amount, It can be determined that a cleaning failure has been detected. Considering that the reference light amount varies to some extent, a cleaning failure determination threshold value based on the reference light amount is set in advance, and it is determined that the cleaning is defective when the light reception amount of the sensor 31c becomes smaller than the threshold value. May be.

  The cleaning failure detection sensor 31 is disposed so as to be capable of reciprocating along a guide rod 31d disposed in the longitudinal direction of the photosensitive member 13 as shown in FIG. 3C. That is, it is arranged so as to be able to reciprocate in a direction transverse to the moving direction of the visible image on the photoreceptor 13. Such a cleaning failure detection sensor 31 capable of reciprocating motion uses a configuration known in the prior art (Patent Document 2: Japanese Patent Laid-Open No. 5-281818, Patent Document 3: Japanese Patent Laid-Open No. 2012-63560). May be. Although it is difficult for the movable optical sensor of FIG. 3C to simultaneously detect the entire axial direction of the photosensitive member 13, a cleaning failure detection sensor can be configured at a lower cost than a configuration using a line sensor.

  FIG. 3D shows another embodiment of the cleaning failure detection sensor 32. The defective cleaning detection sensor 32 is disposed on the downstream side of the developing unit 18.

  Some image forming apparatuses have a reflective optical sensor disposed at the same position as the cleaning failure detection sensor 32 of FIG. 3D. Then, the sensor 32 detects the density of the reference toner image (patch image) that is the density reference for image quality adjustment formed on the photosensitive member 13 by the developing means 18 so as to stabilize the image. Yes. In the image forming apparatus having such a configuration, it is possible to construct the cleaning failure detection sensor of the present invention by using an existing optical sensor for image stabilization as it is. That is, the patch image for adjusting the image density is detected by the cleaning failure detection sensor 32.

  As described above with respect to the cleaning failure detection sensor 31 of FIG. 3C, the mobile optical sensor can be less expensive than the line sensor. By sharing the optical sensor for image stabilization and the optical sensor for detecting defective cleaning, the number of sensors can be reduced, and the defective cleaning detecting sensor can be configured at a lower cost.

  FIG. 4 shows an example of a specific detection method when the cleaning failure detection sensor 32 of FIG. 3D is used. When the cleaning failure detection sensor 32 is disposed between the developing unit 18 and the cleaning unit 19 as shown in FIG. 3D, an image for printing also passes through the surface of the photoreceptor 13 measured by the cleaning failure detection sensor 32. For this reason, it is necessary to distinguish between toner adhesion for printing and toner adhesion due to poor cleaning.

  The detection method of FIG. 4 distinguishes and detects the toner adhesion using the fact that a print area and a non-print area (non-image area) are generated on the photosensitive member 13 during printing by the image forming apparatus. The image to be printed needs to be created according to the size of the print object (for example, paper, OHP sheet, etc.), and the conveyance of the print object is performed at regular intervals.

  For this reason, a print area and a non-print area (non-image area) are necessarily generated on the photosensitive member 13. The detection method of FIG. 4 utilizes this non-printing area (non-image area) and detects a cleaning failure in the non-printing area (non-image area). Since no image for printing is formed in the non-printing area (non-image area), it is possible to reliably detect only the cleaning failure.

  Further, it may be configured such that the defective cleaning is not detected during the image formation, the photosensitive member 13 is rotated without printing after the image formation, and the defective cleaning is detected when the image is rotated. In this configuration, if a cleaning failure occurs during printing, the output of the paper P with unfixed toner in the printing cannot be completely prevented, but the toner adhesion for printing and the toner adhesion due to the cleaning failure are reliably distinguished. Can be detected. Of course, these detection methods may be combined.

  The cleaning failure detection sensor 32 constantly measures the surface of the photosensitive member 13 and records (mappings) the measurement result (the amount of received light) in association with the measurement position in the RAM on the microcomputer. For example, if the measurement position is configured to use the cleaning failure detection sensor 31 of FIG. 3C, the reciprocating time and the reciprocating distance are recorded in the ROM on the microcomputer in association with the position on the photosensitive member 13 (mapping). This can be specified.

  The heating control unit 24 receives image information input from an image processing apparatus (not shown), and determines the amount of power supplied to each of the thermal heaters 20a to 20g. Therefore, it can be seen that printing toner adheres to locations corresponding to the thermal heaters 20a to 20g that supply power necessary for fixing.

  The cleaning failure detection sensor 32 associates the power supply state to the thermal heaters 20 a to 20 g by the heating control unit 24 and the measurement position information recorded by the cleaning failure detection sensor 32. This association is performed by previously recording (mapping) correspondence information between the thermal heaters 20a to 20g and positions on the photosensitive member 13 in the ROM.

  Then, when toner adhesion (decrease in the amount of received light) is detected at a location where the thermal heaters 20a to 20g are not receiving power supply reaching the fixing temperature, it is determined that a cleaning failure has been detected. By adopting such a configuration, the cleaning failure detection sensor 32 can distinguish and detect the adhesion of printing toner and the toner due to cleaning failure.

  FIGS. 5A and 5B show an embodiment in which cleaning failure detection sensors 33 to 36 are attached to the printer 10 using a transfer belt. Some image forming apparatuses that enable full color printing using a plurality of colors of toner use a transfer belt as shown in FIGS. 5A and 5B.

  The printer 10 of FIG. 5A has four developing devices (photosensitive members 13K, 13C, 13M, and 13Y) along a transfer belt 38 as an intermediate transfer member, and each has different color toners (for example, black, cyan, and magenta). , Yellow). By superimposing the toners of the respective colors on the transfer belt 38, full color printing can be performed.

  In FIG. 5A, assuming that the photosensitive member 13 is a first image carrier, the transfer belt 38 is a second image carrier. The heating means 20 described above is normally disposed on the outer periphery of the fixing roller 15a of the fixing means 15 as shown in FIGS. 2A and 2B. However, it is also possible to arrange the heating means 20 on the outer periphery of the pressure roller 15b.

  In such a printer 10, for example, if the optical sensor for image stabilization and the optical sensor for the cleaning failure detection sensor are used together, the most downstream photosensitive member 13Y and the transfer nip, like the cleaning failure detection sensor 34 in FIG. 5A, are used. N. When the optical sensor for image stabilization and the optical sensor for the defective cleaning detection sensor are separately arranged, they are arranged downstream of the belt cleaning means 39 like the defective cleaning detection sensor 34 in FIG. 5A. By doing so, it is not necessary to provide a cleaning failure detection sensor for each photoconductor 13 of each developing device, and a cleaning failure detection sensor can be realized with an inexpensive configuration. Further, the residual toner can be detected without any leakage by reciprocating the cleaning failure detection sensor 34 including the fallen toner that has fallen into the non-image area, such as the surface of the transfer belt 38 shown in an enlarged manner.

  FIG. 5B shows an embodiment in which a cleaning failure detection sensor 35 or 36 is attached to the printer 10 using the transfer / fixing belt 40 as a transfer / fixing member. Assuming that the photoreceptor 13 is a first image carrier, the transfer / fixing belt 40 is a second image carrier. The printer 10 in FIG. 5A performs transfer and fixing on the paper P separately, whereas the printer 10 in FIG. 5B performs transfer and fixing on the paper P at the same time.

  In the figure, 41 is a driving roller, 42 is a driven roller, 43 is a pressure roller, 44 is a pressing member, 45 is a pressure means, 46 is a cleaning means, and 46a is a cleaning blade. A transfer / fixing nip SN is formed between the driven roller 42 and the pressure roller 43, and the heating means 20 is disposed upstream of the transfer / fixing nip SN.

  In such an image forming apparatus, for example, when the optical sensor for stabilizing the image and the optical sensor of the cleaning failure detection sensor are used together, the most downstream photosensitive member 13Y and the transfer / fixing as in the cleaning failure detection sensor 35 of FIG. 5B are used. It arrange | positions between nip SN. When the optical sensor of the defective cleaning detection sensor is arranged separately from the optical sensor for image stabilization, it is arranged downstream of the belt cleaning means 46 like the cleaning means 36 in FIG. 5B. In any case, since it is not necessary to provide a cleaning failure detection sensor for each photoconductor 13 of each developing device, a cleaning failure detection sensor can be realized with an inexpensive configuration. In addition, by providing an opening / closing mechanism for the transfer / fixing nip SN, it is possible to dispose the cleaning failure detection means 35 on the downstream side of the nip SN. In this case, with the nip SN opened, the cleaning failure detection means 35 detects the presence or absence of residual toner in the non-printing area and the non-image area.

  The printer 10, the fixing unit 15, and the cleaning failure detection sensors 31 to 36 as the image forming apparatus are configured as described above. When information on an image to be formed with toner T on the paper P is input to the heating control unit 24 as shown in FIG. 2A from an image processing apparatus (not shown), the power source 23 is controlled by the heating control unit 24. . As a result, electric power necessary for fixing the toner T is supplied to the predetermined thermal heaters 20a to 20g.

  The “predetermined thermal heater” is a thermal heater corresponding to a heating area necessary for fixing a visible image of the toner T at a predetermined position on the paper P. The heated portion of the fixing roller that has been heated to the fixing temperature in contact with the “predetermined thermal heater” contacts the toner T on the paper P to fix the visible image. As described below, the thermal heaters 20a to 20g realize energy saving by heating only the necessary thermal heaters 20a to 20g according to image information.

  The heating patterns of the thermal heaters 20a to 20g are changed based on information on an image formed on the paper P as shown in FIGS. 6A to 6D, for example. FIG. 7 shows an example of the control, and shows an example of the control of the heating means 20 when the images of FIGS. 6A and 6B are fixed on the paper P. A section indicated by “P” in FIG. 7 is an energization section for fixing toner on the paper P. A section indicated by “P ′” corresponds to a non-image area of the paper P and a paper gap formed between the paper P and the paper P.

  The thermal heaters 20a to 20g are controlled so as to reach the first target temperature in a section between the image area a and the image area a ′. The first target temperature is a temperature at which the toner transferred onto the paper P can be melted and fixed. In the section P, the start side of the image area a and the image area a ′ is extended in consideration of the rising time of the thermal heaters 20a to 20g (the rising slope portion in FIG. 7). The extended portion is a preheating region and corresponds to a region indicated by hatching in FIGS. 6A and 6B.

  Although the hatched area is a non-image area, when the image areas a and a ′ reach the fixing nip SN, power is supplied early so that the thermal heaters 20a to 20g reach the first target temperature. Is done. In the non-image area b, originally, the thermal heaters 20a to 20g are not energized for energy saving. However, in order to shorten the rise time and increase the speed, the non-image area b has a minimum second target temperature in the non-image area b. The thermal heaters 20a to 20g are energized so as to be maintained. The second target temperature is a temperature lower than the first target temperature and does not melt the toner.

  6C and 6D show a case where a part of the paper P in the width direction is an image area and the rest is a non-image area. As described above, when the image areas c, efg, and eh and the non-image areas d and fh are mixed in the width direction of the paper P, the power supply amounts to the thermal heaters 20a to 20g are varied. That is, it is assumed that the thermal heaters corresponding to the image area c are 20a to 20d and the thermal heaters corresponding to the non-image area d are 20e to 20g. In this case, power for achieving the first target temperature is supplied to the thermal heaters 20a to 20d corresponding to the image area, and power for achieving the second target temperature is supplied to the thermal heaters 20e to 20g corresponding to the non-image area. To do. The preliminary heating in the hatching area on the start side of the image areas c, efg, and eh is the same as described above with reference to FIGS. 6A and 6B.

  Although the heating means 20 described above is a contact type that heats by contacting the surface of the fixing roller 15a, the heating means 20 may also be a non-contact heating method by electromagnetic induction heating (IH method) using an electromagnetic induction coil and an inverter. Good. In the IH method, the heating region and the heating amount can be controlled by arranging a large number of heating coils or arranging a large number of members that cancel the magnetic flux. The heating means 20 generally heats the surface of the fixing roller 15a. As described above with respect to the positions where the thermal heaters 20a to 20g are disposed, the pressure roller 15b side is heated, or the fixing roller 15a and the pressure are pressed. A configuration in which both of the rollers 15b are heated is also possible.

  The heating means may utilize light energy from a semiconductor light emitting element such as a semiconductor laser array or a light emitting diode array. Also in this case, the heating region and the heating amount can be controlled by arranging a large number of semiconductor light emitting elements or by arranging a large number of members that shield light from the semiconductor light emitting elements. The light energy can be applied to the fixing roller 15a, the pressure roller 15b, the toner image on the paper P directly, or a combination thereof.

(Fixing control method 1)
FIG. 8A is a diagram illustrating a first control method as a clean control mode of the heating unit 20 when a toner removal failure is detected by the cleaning failure detection sensor 31. In this first control method, when a toner removal failure (cleaning failure) is detected by the cleaning failure detection sensor 31, electric power for obtaining the first target temperature is supplied to all the thermal heaters 20 a to 20 g of the heating unit 20. Supplied. By this heating control, it is possible to fix the toner at the poorly cleaned portion at the same time as the toner image in the image region regardless of whether it is in the image region or the non-image region.

  When the toner removal failure (cleaning failure) is not detected by the cleaning failure detection sensor 31, only the thermal heaters 20a to 20g corresponding to the image area are supplied with electric power for obtaining the first target temperature in the normal control mode. The remaining thermal heater is supplied with electric power for obtaining the second target temperature. As a result, energy-saving normal control can be realized when there is no cleaning failure, and recovery control can be performed in which when the cleaning failure occurs, the failure is recovered and unfixed toner is not output.

(Fixing control method 2)
FIG. 8B is a diagram for explaining a second control method as a clean control mode of the heating unit 20 when a toner removal failure is detected by the cleaning failure detection sensor 31. In the second control method, when a toner removal failure (cleaning failure) is detected by the cleaning failure detection sensor 31, the cleaning failure detection sensor 31 detects the removal failure in association with the removal failure position. Then, the position information is recorded on the RAM mounted on the heating control means 24 of the heating means 20.

  The “position information” here is information that can specify the position of the residual toner on the photosensitive member 13 by the position in the longitudinal direction (axial direction) and the circumferential direction. That is, based on the information, when the sheet P on which the defective removal toner is transferred reaches the fixing nip SN, one or more thermal heaters 20a to 20g corresponding to (contact with) the defective removal toner are specified. The

  The heating control unit 24 associates one or more thermal heaters 20a to 20g corresponding to the position information with the installed program. Then, electric power for obtaining a fixing temperature (first target temperature) is supplied to the associated one or more thermal heaters 20a to 20g. By this fixing control, it becomes possible to fix the toner at the poorly cleaned portion at the same time as the toner image in the image area, and thus it is possible to prevent the paper P from being output while holding the unfixed toner.

  If a toner removal failure is detected by the cleaning failure detection sensor 31, the toner image in the image area may be forwarded to the next printing without being fixed in the current printing. Further, it is possible to control only the toner at the defective cleaning portion to be fixed on the paper P (waste paper) by the current printing. In the case of this control, electric power that provides a fixing temperature (first target temperature) is supplied only to the associated one or more thermal heaters 20a to 20g. No power is supplied to the remaining thermal heaters, or power is supplied so that the above-described second target temperature is maintained.

  When the toner removal failure (cleaning failure) is not detected by the cleaning failure detection sensor 31, only the thermal heaters 20a to 20g corresponding to the image area are supplied with electric power for obtaining the first target temperature in the normal control mode. This is the same as the first control method. The remaining thermal heater is supplied with electric power for obtaining the second target temperature. As a result, energy-saving normal control is realized when there is no cleaning failure, and when cleaning failure occurs, recovery control is performed to recover the failure and output unfixed toner with the minimum necessary thermal heaters 20a to 20g. Can do.

  In this fixing control method, the processing load on the CPU of the heating control means 24 and the amount of RAM used increase, but not all of the thermal heaters 20a to 20g are heated even during the cleaning control of the defective cleaning. Can be maintained. In addition, when such a clean control mode is executed, notification means for displaying that the clean control mode has been executed may be provided on an operation panel or the like of the image forming apparatus.

  By doing so, the user can know that a cleaning failure has occurred and the clean control mode has been executed. Accordingly, it is possible to call a service person after the display of the clean control mode, or to perform maintenance of the cleaning means 19 during the regular maintenance of the service person, and to quickly repair the cause of the cleaning failure. Further, when the communication function of the image forming apparatus can be used, it is possible to automatically notify the service person that the clean control mode has been executed.

  FIG. 8c is a diagram showing a conventional problem in which the thermal heaters 20a to 20g are not heated to the fixing temperature (first target temperature) when the control mode of the heating unit 20 according to the present invention is not performed, that is, in the non-image region. . The cleaning blade 19a of the cleaning means 19 may be chipped due to deterioration, or may cause a so-called poor cleaning, in which the toner cannot be completely cleaned due to aging of the blade. When the control mode of the heating means 20 according to the present invention is not performed, the non-image area to which the toner has adhered due to poor cleaning passes through the fixing nip SN without being fixed.

  As described above, the divided heating type fixing device can save energy by fixing only necessary portions. On the other hand, when such a cleaning failure occurs in a non-image area, the fixing of the defective cleaning portion is not performed and the toner is not determined. It will be output while wearing. As a result, there are problems that other printed matter is contaminated by unfixed toner, the user's hand and clothes are contaminated, and the unfixed toner is scattered and the surroundings are contaminated. By performing the heating control shown in FIGS. 8A and 8B, the above-described problem caused by unfixed toner can be solved while saving energy.

(Operation example of defective cleaning detection sensor)
The image forming apparatus, the fixing unit, and the cleaning failure detection sensors 31 to 36 according to the embodiment of the present invention have been described above. Next, seven examples of operation of the cleaning failure detection sensors 31 to 36 will be described with reference to FIGS. The description will be given with reference.

(Operation example 1)
FIG. 9A is a schematic diagram of Operation Example 1 serving as a basis of the cleaning failure detection sensor 31 (or the sensors 32 to 36) on the image carrier. FIG. 9B is a flowchart showing a control example of the operation example 1. The image carrier is the above-described photoreceptor 13, transfer belt 38 or transfer / fixing belt 40. In the following description, for the sake of simplicity, it is assumed that the image carrier is the photosensitive member 13 and the residual toner is detected by the cleaning failure detection sensor 31.

  In the first operation example, when the front end of the print area (or the front end of the image area) arrives at the detection position directly below the cleaning failure detection sensor 31, the movement of the cleaning failure detection sensor 31 is stopped. When the rear end of the print area (or the rear end of the image area) arrives at the detection position directly below the cleaning failure detection sensor 31, the movement of the cleaning failure detection sensor 31 is resumed. Thereby, the non-printing area extending over the entire length of the photosensitive member 13 can be detected by the cleaning failure detection sensor 31.

  The arrival time of the front edge of the print area (or the front edge of the image area) is obtained by dividing the moving distance of the photosensitive member 13 from the writing position (the exposure unit 13a in FIGS. 1 and 3A) to the cleaning failure detection sensor 31 by the process linear velocity. Can be obtained. As another method, the front end position of the print area may be stored each time the front end of the print area arrives at the writing position (exposure unit 13a). In the case of continuous printing, the front edge of the print area is stored only once at the print start time, and thereafter, the length of the print area (the length of the paper P) and the specified length between the print area and the print area ( It is also possible to calculate the front end position of each print area from the (inter-paper gap).

  FIG. 9B is a flowchart illustrating the first operation example. In this flowchart, when the program is called, image information is acquired in step S1. This image information includes information on the positions of the front end pixel and rear end pixel of the print region and the rotation position of the photosensitive member 13 (or the transfer belts 38 and 40). From the image information and the conveyance speed of the photosensitive member 13, the timing at which the front end and the rear end of the print area arrive at the position of the sensor 31 in step S2 is calculated, and stored in the memory in step S3.

  After the timing is stored in the memory, it is determined in step S4 whether or not the current timing is the timing at which the front end of the print area stored in the memory arrives at the position of the sensor 31. When it is determined that it is not the timing when the front end of the print area arrives at the sensor 31 position, in step S6, the current timing is the timing when the front end of the print area stored in the memory arrives at the sensor 31 position, and It is determined whether or not the trailing edge of the stored print area is between the timing when the sensor 31 position is reached.

  If it is not within the above range, that is, if the non-image area between the print area and the print area is located at the detection position of the cleaning failure detection sensor 31, whether or not the cleaning failure detection sensor 31 is reciprocating in step S7. Is judged. If it is not reciprocating, the reciprocation of the cleaning failure detection sensor 31 is started in step S8. When reciprocation of the cleaning failure detection sensor 31 is started or when it has already reciprocated, residual toner is detected by the cleaning failure detection sensor 31 in step S9, and residual toner is detected in step S10. If it is determined that the cleaning failure is detected, a cleaning failure recovery process is executed in step S11. If it is determined in step S10 that no residual toner has been detected, the program ends.

  When the front end of the print area stored in the memory is at the timing when the cleaning failure detection sensor 31 arrives, the reciprocation of the cleaning failure detection sensor 31 is stopped in step S5. By the above flow, it becomes possible to detect a cleaning failure, a toner drop, a toner dropout, etc. in the non-image area in the entire longitudinal direction of the photoconductor 13 without any leakage.

(Operation example 2)
FIG. 10A is a schematic diagram of an operation example 1 of the cleaning failure detection sensor 31. FIG. 10B is a flowchart showing a control example of the operation example 1. In this operation 2, the density of the patch image 48 for image density adjustment is also measured by the cleaning failure detection sensor 31.

  The patch image for image density adjustment is a toner image that has been visualized after being written as a latent image between print regions or outside the print region. The toner density of the toner image is measured, and based on the measurement result, the developing potential is adjusted by changing the writing light intensity for forming the latent image, the charging bias, the developing bias, and the like. In the case of the two-component development method, image density control is also performed by adjusting a target value of toner density in the developing device based on the measurement result.

  FIG. 10B is a flowchart of the second operation example. In this operation example 2, it is determined whether or not the density adjustment patch image has been written in step S1. If the patch image has been written, the cleaning failure detection sensor is moved to the patch image measurement position in step S2, and stopped for measurement in step S3. Next, when it is time to read the patch image in step S4, the image density is measured, and in step S5, the measurement result is stored in the memory. Thereafter, in step S6, the sensor is returned to the original position before the measurement, and the process returns to step S1 of the operation example 1 in FIG. 9B. By executing the above steps, the cleaning defect detection sensor 31 can also be used as an image density adjustment patch image reading sensor.

(Operation example 3)
FIG. 11A is a schematic diagram of an operation example 3 of the cleaning failure detection sensor 31. FIG. 11B is a flowchart showing a control example of the operation example 3. In the operation example 1 in FIG. 9A described above, as shown in FIG. 11D, when the position of the cleaning failure detection sensor 31 enters the image area near the end of the photosensitive member 13, the movement of the sensor 31 is temporarily stopped. When the cleaning failure detection sensor 31 enters the next non-image area after the image area, it moves to the end of the reciprocating range of the sensor 31 and then folds back toward the opposite end.

  At this time, an overlapping range in the longitudinal direction of the photosensitive member 13 is detected at the folded portion. Since the photosensitive member 13 is rotating during this time, the movement trajectory of the sensor 31 on the photosensitive member 13 does not overlap, but the detection density becomes non-uniform in the longitudinal direction of the photosensitive member 13.

  Therefore, in the operation example 3, when the cleaning failure detection sensor 31 is turned back in the next non-image area as shown in FIG. 11A, while the cleaning failure detection sensor 31 passes the image area before the non-image area, The cleaning failure detection sensor 31 is moved to the end of the photoreceptor 13. Then, until the next non-image area arrives at the position of the sensor 31, the sensor 31 waits (pauses) at the end, and the sensor 31 is moved to the opposite side simultaneously with the arrival of the non-image area. By including such processing, the detection density in the longitudinal direction of the sensor 31 at the end of the photoconductor 13 can be made uniform.

  Further, FIG. 11C shows that the cleaning defect detection sensor 31 enters the image area at a position near the center in the longitudinal direction of the photoconductor 13 and the next non-image area is the sensor 31 before it can move to the end in the image area. It is a case where it arrives at the position of. Also in this case, the sensor 31 may be continuously moved without stopping at the front end of the image area. Then, when the sensor 31 moves to the end of the photosensitive member 13 in the next non-image area, it turns immediately. Thereby, the overlap detection range can be narrower than in the case of FIG. 11D.

  The flowchart of the operation example 3 is as shown in FIG. 11B. In order to eliminate the above-described overlap detection range, steps S12 to S15 are added after step S4 of operation example 1. Others are the same as the operation example 1 of FIG. 9B. In this operation example 3, at the timing when the front end of the print area stored in the memory arrives at the position of the cleaning failure detection sensor 31 in step S12, the current position of the cleaning failure sensor 31 is the end of the photoconductor 13. It is determined whether or not.

  If it is determined in step S12 that the position of the cleaning failure detection sensor 31 is not the end of the photoreceptor 13, the distance from the current position of the sensor 31 to the end is calculated in step S13. Next, in step S14, it is determined whether or not the calculated distance to the end is a distance that allows the sensor 31 to move in the next non-image area.

  If it is the distance that the cleaning failure detection sensor 31 can move, the sensor 31 is moved to the end of the photosensitive member 13 in step S15, stopped in step S5, and the program ends.

  If it is determined in step S12 that the current position of the cleaning failure detection sensor 31 is the end of the photosensitive member 13, the movement of the sensor 31 is stopped (step S5). If it is determined in step S14 that the cleaning failure detection sensor 31 cannot move to the end of the photosensitive member 13 in the next non-image area, the movement of the cleaning failure detection sensor 31 is stopped (step S5). ). With the above flow, the longitudinal detection density of the cleaning failure detection sensor 31 can be made more uniform than in the first operation example.

(Operation example 4)
FIG. 12A is a schematic diagram of an operation example 4 of the cleaning failure detection sensor 31. FIG. 12B is a flowchart showing a control example of the operation example 4. In the fourth operation example, even when an image area and a non-image area are mixed in the longitudinal direction of the photosensitive member 13, only the non-image area can be detected by the cleaning failure detection sensor 31. In this operation example 4, the position of the toner image formed on the photoconductor 13 is stored in the memory in order to distinguish between the image area and the non-image area. Then, at the timing when the position of the cleaning failure detection sensor coincides with the position of the toner image, the cleaning failure is not detected and the cleaning failure is detected only in the non-image area. As a result, the non-image area is detected for a cleaning defect one by one, and a cleaning defect or toner drop is detected. Therefore, the detection range can be expanded as compared with the first operation example.

  In the flowchart of FIG. 12B, when the program is called, the cleaning failure detection sensor 31 is continuously reciprocated in the longitudinal direction of the photosensitive member 13 in step S1. Next, in step S2, it is determined whether or not a latent image has been written by the exposure unit 13a by the writing unit. If the latent image has been written, the writing position on the photosensitive member 13 corresponding to the exposure unit 13a is acquired in step S3. Subsequently, in step S4, the timing at which the toner image as a visible image arrives at the position of the cleaning failure detection sensor 31 from the conveyance speed of the photosensitive member 13 is calculated, and in step S5, the timing is stored in the memory.

  If the latent image is not written in the exposure unit 13a and the toner image is not formed, it is determined in step S6 whether the current timing is the timing when the image stored in the memory arrives. If it is not the timing at which the toner image arrives, in step S7, the state of residual toner is detected by the cleaning failure detection sensor 31 that is continuously reciprocating.

  In step S8, it is determined whether or not residual toner is detected by this detection. If residual toner is detected, cleaning failure recovery processing is executed in step S9, and then the program ends. If no residual toner is detected, the program ends immediately. If it is determined in step S6 that the image stored in the memory has arrived, the program immediately ends.

  According to the above flow, even when the image area and the non-image area are mixed in the longitudinal direction of the photosensitive member 13, the cleaning defect of the non-image area is detected one by one, and the cleaning defect and the toner drop are detected.

(Operation example 5)
FIG. 13 is a schematic diagram of an operation example 5 of the cleaning failure detection sensor 31. For convenience, the multiple heaters 20 a to 20 g are arranged so as to overlap in the moving direction of the cleaning failure detection sensor 31. In this operation example 5, in the process of step S5 in the flowchart of the operation example 4 in FIG. 12B (the timing at which the image arrives is stored in a memory), the resolution is divided heating method in the circumferential direction of the fixing roller 15a in FIG. The length of each of the thermal heaters 20a to 20g.

That is, whether or not the print area or the image area has arrived at the detection position of the cleaning failure detection sensor 31 and whether there is a pixel in the print area or the image area in the heating area of each of the thermal heaters 20a to 20g corresponding to the detection position. Judge by no. In this case, the determination accuracy (detection time interval) of the timing at which the image arrives is such that the pixels in the print area or the image area move by the length of the conveyance direction heating area of each of the thermal heaters 20a to 20g. This is the time it takes to complete. As a result, the storage area on the memory of “timing when the image arrives” can be roughened (the number of timings to be stored is reduced), and the load on the arithmetic device can be reduced.

  FIG. 13 conceptually shows how the image regions passing through the thermal heaters 20a, 20b, 20e, and 20f are fixed. The central vertical line indicates unfixed residual toner due to poor cleaning. Since this residual toner is in a non-image area, it is detected by the cleaning failure detection sensor 31 and fixed by supplying power to the corresponding thermal heater 20d.

(Operation example 6)
FIG. 14A is a schematic diagram of an operation example 6 of the cleaning failure detection sensor 31. In this operation example 6, as shown in FIG. 14A, in the above-described operation examples 1 to 5, the size of the print area (width direction dimension of the recording medium) is stored in advance, and the end of the movement range of the cleaning failure detection sensor is stored. The copy is changed in accordance with the size of the print area. Thereby, only a necessary range according to the size of the print area is detected without waste.

  The flowchart in FIG. 14B is a subroutine that is entered immediately after the start processing in the first to fifth operation examples. In step S1, the size of the print area is acquired, and in step S2, a range in which the cleaning failure detection sensor is moved is determined.

(Operation example 7)
FIG. 15A is a schematic diagram of an operation example 7 of the cleaning failure detection sensor 31. While the cleaning failure detection sensor 31 repeats reciprocation, the position of the sensor 31 stored in the program on the photosensitive member 13 and the actual position of the sensor 31 may shift. Therefore, in this operation example 7, the program is set to the calibration mode after printing a predetermined number of sheets.

  In the calibration mode, as shown in FIG. 15A, the writing unit and the developing unit 18 are connected to both ends of the photosensitive member 13 as the image carrier so as to correspond to both ends of the reciprocating range of the cleaning failure detection sensor 31. Toner images T1 and T2 are formed. The toner images T1 and T2 are read by the cleaning failure detection sensor 31 to calibrate the positions of both ends of the sensor 31.

  FIG. 15B is a flowchart of this operation example 7 (calibration mode). In the calibration mode, first, toner images T1 and T2 are formed at positions corresponding to both ends of the reciprocating range of the cleaning failure detection sensor 31 in step S1. Thereafter, the photosensitive member 13 is driven until the toner images T1 and T2 arrive at the position of the cleaning failure detection sensor 31 in step S2. In step S3, the photosensitive member 13 is stopped at the timing when the toner images T1 and T2 arrive.

  When the photosensitive member 13 is stopped, the cleaning failure detection sensor 31 is moved until one of the left and right toner images T2 in FIG. 15A is detected in step S4. The position of the cleaning failure detection sensor 31 when the toner image T2 is detected is stored as the position of one end of the reciprocation of the sensor 31 in step S5.

  Thereafter, the cleaning failure detection sensor 31 is moved until the toner image T1 at the other end is similarly detected at step S6, and the position at which the toner image is detected at the other end of the reciprocation of the sensor 31 at step S7. Stored as position. This completes the calibration mode. As described above, the absolute position on the photoconductor 13 (or 38, 40) can be matched with the position of the sensor 31 stored in the program.

  As described above, according to the present invention, residual developer adhering to a non-printing area or a non-image area due to an image carrier cleaning defect or the like is detected in a wide range by a low-cost single cleaning defect detection sensor. be able to. Further, by changing the heating area of the heating unit based on the detection information, it is possible to prevent the residual developer from being output unfixed on the recording medium. Therefore, it is possible to prevent the unfixed developer from contaminating other printed materials, the user's hands and clothes, and the like from being contaminated.

  The embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention. The image forming apparatus according to the present invention is not limited to the printer 10 shown in FIG. 1, but may be provided in other copiers, facsimiles, or complex machines thereof.

10: printer 11: paper feeding means 11a: paper feeding tray 11b: paper feeding roller 12: timing roller pair 13: photoconductor 14: transfer means 15: fixing means 15a: fixing roller 15b: pressure roller 16: charging roller 17: Mirror 18: Developing means 19: Cleaning means 20: Heating means 20a-20g: Thermal heater 21: Thermistor 22: Thermistor 23: Power supply 24: Heating control means 31-36: Cleaning failure detection sensor 31a: Illumination light source 31b: Imaging lens 31c: sensor 38: transfer belt 40: transfer / fixing belt 48: patch image for image density adjustment

JP 2001-343860 A JP-A-5-281818 JP 2012-63560 A

Claims (7)

An image carrier that carries the latent image in a state of being visualized by a developer, a transfer unit that transfers the developed image on the image carrier onto a recording medium, and the developer that has been transferred onto the recording medium. Heating means capable of selecting and heating a heating area necessary for fixing an image, cleaning means for removing developer remaining on the surface of the image carrier after transfer, and selection of the necessary heating area An image forming apparatus having switching means for switching a heating region for
A cleaning failure detection sensor for detecting defective removal of the residual developer by the cleaning means is disposed on the image carrier or the transfer means, and the cleaning failure detection sensor is crossed with respect to the moving direction of the visible image. The cleaning failure detection sensor stops reciprocating at the timing when the front end of the visible image arrives at the detection position of the cleaning failure detection sensor, and is detected by the cleaning failure detection sensor. The cleaning failure detection sensor reciprocates at a timing when the rear end of the visible image passes through the non-printing area formed on the front end side and the rear end side in the moving direction of the visible image by the reciprocating motion. Detect the presence or absence of residual developer at
When the defective cleaning of the residual developer is not detected by the cleaning failure detection sensor, the heating unit is operated in a normal control mode for a heating region corresponding to the visible image,
When the residual developer removal failure is detected by the cleaning failure detection sensor, the heating means is operated in a clean control mode to eliminate the residual developer removal failure,
The image forming apparatus according to claim 1, wherein the clean control mode targets all heating regions including a heating region corresponding to the visible image . An image carrier that carries the latent image in a state of being visualized by a developer, a transfer unit that transfers the developed image on the image carrier onto a recording medium, and the developer that has been transferred onto the recording medium. Heating means capable of selecting and heating a heating area necessary for fixing an image, cleaning means for removing developer remaining on the surface of the image carrier after transfer, and selection of the necessary heating area An image forming apparatus having switching means for switching a heating region for
A cleaning failure detection sensor for detecting defective removal of the residual developer by the cleaning means is disposed on the image carrier or the transfer means, and the cleaning failure detection sensor is crossed with respect to the moving direction of the visible image. The cleaning failure detection sensor stops reciprocating at the timing when the front end of the visible image arrives at the detection position of the cleaning failure detection sensor, and is detected by the cleaning failure detection sensor. The cleaning failure detection sensor reciprocates at a timing when the rear end of the visible image passes through the non-printing area formed on the front end side and the rear end side in the moving direction of the visible image by the reciprocating motion. Detect the presence or absence of residual developer at
When the defective cleaning of the residual developer is not detected by the cleaning failure detection sensor, the heating unit is operated in a normal control mode for a heating region corresponding to the visible image,
When the residual developer removal failure is detected by the cleaning failure detection sensor, the heating means is operated in a clean control mode to eliminate the residual developer removal failure,
The cleaning failure detection sensor detects the removal failure of the residual developer in relation to the position of the removal failure on the surface of the image carrier, and the clean control mode corresponds to the removal failure position and the residual development. An image forming apparatus characterized in that a heating area necessary for fixing an agent and a heating area corresponding to the visible image are targeted. The degree of time resolution by the print area or the image area to determine whether arriving at the detection position of the defective cleaning sensor, the printed region or image region heating region of the heating means corresponding to the detection position 3. The image forming apparatus according to claim 1 , wherein the time required for the pixels to pass is set .   The image forming apparatus according to claim 1, wherein a range of reciprocation of the cleaning failure detection sensor is made to correspond to a width direction dimension of a recording medium to which a visible image is transferred.   A toner image serving as a reference for the reciprocating range is formed on both ends in the width direction on the image carrier corresponding to both ends of the reciprocating movement of the cleaning failure detection sensor. The toner images on both ends are formed by the cleaning failure detecting sensor. 2. The image forming apparatus according to claim 1, wherein the detected position of the toner image is stored as both ends of the reciprocating motion of the cleaning failure detection sensor. It said heating means, thermal heaters, electromagnetic induction heating or any one of the image forming apparatus of claims 1 to 5, characterized in that use light energy. The image forming apparatus according to claim 1 , further comprising a notification unit that notifies that the control is being performed when the heating unit is controlled in the clean control mode.

Images