JP6137731B2 - 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. Note that recovery of residual toner remaining on the image carrier after transfer is disclosed in, for example, Japanese Patent Application Laid-Open No. 07-084484.

  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 area for selecting the necessary heating area, wherein a cleaning failure detection means for detecting defective removal of residual developer by the cleaning means is disposed, and the switching is performed. The heating area switching control mode of the heating means by the means corresponds to the visible image when the cleaning failure detection means does not detect the removal failure of the residual developer. The normal control mode for the heating region is set, and when the residual developer removal failure is detected by the cleaning failure detection means, the clean control mode is set to eliminate the residual developer removal failure. An image forming apparatus characterized by the above.

  According to the present invention, even when the developer adhering to the non-image area due to poor cleaning of the image carrier is transferred to the recording medium, the residual developer due to poor cleaning on the image carrier is removed by the cleaning failure detection means. By detecting and controlling the heating means in the clean control mode, 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.

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 means. It is a figure which shows the example of a cleaning defect detection means. It is a figure which shows the example of a cleaning defect detection means. It is a figure which shows the example of a cleaning defect detection means. 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 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 means provided in the transfer belt. It is a figure which shows the other example of the cleaning defect detection means 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 a flowchart which shows the example of switching of the control mode of a heating means. It is a flowchart which shows the example of switching of the control mode of a heating means. It is a flowchart which shows the example of cleaning defect recovery determination.

  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. On the outer periphery of the photoreceptor 13, cleaning failure detection means 30 to 32 described later are disposed. 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 photosensitive member 13, that is, at the timing at which the leading end of the toner image formed on the photosensitive member 13 coincides with the predetermined position of the leading end portion in the conveyance 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 means 30 to 32, a charging roller 16 as a charging means, a mirror 17 constituting a part of an exposure means (not shown), and development in the order of rotation indicated by arrows. A developing means 18 provided with a roller 18a, a transfer means 14, a cleaning means 19 provided with 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. The heating control unit 24 is connected to a cleaning failure detection unit 30 described later, and is configured to operate the heating unit 20 in the normal control mode or the clean control mode in response to a signal from the cleaning failure detection unit 30. .

  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).

(Means for detecting defective cleaning of residual toner)
3A to 3D show a plurality of examples of cleaning failure detection means 30 to 36 for detecting a removal failure (cleaning failure) of residual toner on the photoreceptor 13. The cleaning failure detection unit 30 in FIGS. 3A and 3B is disposed between the cleaning unit 19 and the charging roller 16. The cleaning failure detection means 30 has a photoreceptor surface measurement means for measuring the surface of the photoreceptor 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 means 30 or may be used as the microcomputer for the heating control means 24 described above.

  FIG. 3B shows an embodiment of the photoconductor surface measurement means of the cleaning failure detection means 30. The photoconductor surface measuring means includes a line illumination light source 30a, an imaging lens 30b, and a line sensor 30c, which are light sources. The line illumination light source 30a has a function of irradiating irradiation light including visible light and non-visible light over the entire axial direction of the photoconductor 13. The line illumination light source 30a 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 line illumination light source 30a, for example, a white LED (Light Emitting Diode) array can be used. As the line illumination light source 30a, a fluorescent lamp such as a cold cathode tube or a lamp light source may be used. However, the line illumination light source is preferably capable of being illuminated uniformly over the entire observation region.

  The light irradiated by the line illumination light source 30a is reflected on the photoreceptor 13, and forms an image on the line sensor 30c through the imaging lens 30b. The line sensor 30 c has a structure in which pixels that receive light are arranged in a line in the axial direction of the photosensitive member 13. As the line sensor 30c, 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 that is an irradiation target is a smooth surface, most of the irradiation light from the line illumination light source 30a is normally regularly reflected and detected by the line sensor 30c. 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 line sensor 30c 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 line sensor 30c is recorded in advance in a ROM or RAM on the microcomputer, the light reception amount of the line sensor 30c is reduced below the reference light amount. In addition, it can be determined that a cleaning failure has been detected. Considering that there is some variation in the reference light amount, a cleaning failure determination threshold value based on the reference light amount is set in advance, and if the received light amount of the line sensor 30c becomes smaller than the threshold value, a cleaning failure is determined. You may judge.

  FIG. 3C shows another embodiment of the photoconductor surface measuring means used for the cleaning failure detecting means 31. This cleaning failure detection means 31 is disposed so as to be capable of reciprocating along a guide rod 31 b disposed in the longitudinal direction of the photosensitive member 13. Such a cleaning failure detection means 31 capable of reciprocating movement uses a configuration known in the prior art (Patent Document 3: Japanese Patent Laid-Open No. 5-281818, Patent Document 4: Japanese Patent Laid-Open No. 2012-63560). Also good.

  This cleaning defect detection means 31 is an optical sensor (residual toner detection sensor) that reciprocates along the surface of the photosensitive member 13 in the longitudinal direction of the exposure region of the photosensitive member 13 instead of the line illumination light source 30a and the line sensor 30c described above. A cleaning failure detection sensor 31a such as is used. This cleaning failure detection sensor 31a detects the amount of residual toner adhering to the surface of the photoreceptor 13.

  The cleaning failure detection sensor 31a includes a light emitting unit and a light receiving unit, and the light receiving unit is disposed at a position where the regular reflected light of the light emitting unit can be detected or a position where the diffuse reflected light of the light emitting unit can be detected. When the light receiving means is arranged at a position where the regular reflection light of the light emitting means can be detected, since the surface of the photosensitive member, which is an irradiation object, is a smooth surface, most of the irradiation light from the light emitting means is regularly reflected and most of the reflected light is It is detected by the light receiving means.

  On the other hand, when toner adheres on the photosensitive member 13, the diffuse reflection light increases and the specular reflection light decreases, so the amount of light detected by the specular reflection light receiving means decreases. From this difference in the amount of received light, the surface state of the photoconductor can be detected satisfactorily, and defects on the surface of the photoconductor 13 such as poor cleaning of the surface of the photoconductor 13 and toner dropping can be detected well. For example, the reference light amount when the reflected light on the surface of the photosensitive member is received by the regular reflection light receiving means is recorded in advance in the ROM or RAM on the microcomputer, and the received light amount of the regular reflection light receiving means is reduced from the reference light amount. In this case, it can be determined that a cleaning failure has been detected.

  Considering that there is some variation in the reference light quantity, a cleaning failure judgment threshold value based on the reference light quantity is set in advance, and the cleaning failure occurs when the amount of light received by the regular reflection light receiving means becomes smaller than the threshold value. May be determined. In the configuration of FIG. 3C, it is difficult to detect the entire axial direction of the photosensitive member 13 at the same time, but the cleaning failure detection means can be configured at a lower cost than the configuration using the line sensor.

  FIG. 3D shows still another embodiment of the cleaning failure detection means 32. This defective cleaning detection means 32 is arranged downstream of the developing means 18.

  In the image forming apparatus, a reflective optical sensor is disposed at the same position as the cleaning failure detection unit 32 in FIG. 3D, and the density of the reference toner image (patch image) formed on the photoreceptor 13 by the developing unit 18 is detected. In some cases, the image is stabilized. In the image forming apparatus having such a configuration, it is possible to construct the cleaning failure detection means 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 means 32.

  The optical sensor used for the cleaning failure detection means 32 may be a line sensor as shown in FIG. 3B or a movable optical sensor as shown in FIG. 3C. Mobile optical sensors are less expensive than line sensors. By sharing the optical sensor for stabilizing the image and the optical sensor for detecting the defective cleaning, the number of sensors can be reduced, and the cleaning defective detecting means can be configured at a lower cost.

  4A and 4B show two examples of specific detection methods when the cleaning failure detection means 32 of FIG. 3D is used. When the defective cleaning detection means 32 is arranged between the developing means 18 and the cleaning means 19 as shown in FIG. 3D, an image for printing also passes through the surface of the photoconductor 13 measured by the defective cleaning detection means 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. 4A distinguishes and detects the toner adhesion by 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. 4A utilizes this non-printing area (non-image area), and performs cleaning failure detection 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.

  However, the method of FIG. 4A is difficult to handle when poorly cleaned toner adheres only to the print area or when toner drops temporarily. In addition, there is a problem in that the output of the paper P accompanied by unfixed toner due to poor cleaning that occurs during printing cannot be completely prevented. Therefore, the detection method of FIG. 4B solves the above problem by detecting the cleaning failure by utilizing the power supply information to the heating means 20 (thermal heaters 20a to 20g) of the heating control means 24.

  The cleaning failure detection means 32 always measures the surface of the photosensitive member 13, and records (mappings) the measurement result (the amount of received light) in the RAM on the microcomputer in association with the measurement position. For example, if the measurement position is configured to use the line sensor 30c of FIG. 3B, the light receiving pixels and the positions on the photosensitive member 13 are associated in advance, and the correspondence is recorded (mapped) in the ROM on the microcomputer. Can be specified. Further, in the case of the optical sensor as shown in FIG. 3C that reciprocates along the surface in the longitudinal direction of the exposure area of the photoconductor 13, the reciprocating time and reciprocating distance are related to the position on the photoconductor 13 and the microcomputer. It can also be specified by recording (mapping) it in the ROM above.

  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 unit 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 unit 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 means 32 can distinguish and detect printing toner adhesion and toner adhesion due to cleaning failure.

  5A and 5B show an embodiment in which cleaning failure detection means 33 to 36 are attached to a 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 stabilizing the image and the optical sensor of the cleaning failure detection unit are used together, the most downstream photoreceptor 13 </ b> Y and the transfer nip as in the cleaning failure detection unit 33 of FIG. 5A are used. N. When the optical sensor for image stabilization and the optical sensor for the cleaning failure detection unit are separately arranged, they are arranged downstream of the belt cleaning unit 39 like the cleaning failure detection unit 34 of FIG. 5A. By doing so, it is not necessary to provide a cleaning failure detection means for each photoconductor 13 of each developing device, and a cleaning failure detection means can be realized with an inexpensive configuration. In addition, by providing an opening / closing mechanism for the transfer nip N, it is possible to dispose the cleaning failure detection means 33 on the downstream side of the nip N. In this case, with the transfer nip N opened, the cleaning failure detection means 33 detects the presence or absence of residual toner in the non-printing area and the non-image area.

  FIG. 5B shows an embodiment in which the cleaning failure detection means 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 image stabilization and the optical sensor for the cleaning failure detection means are used together, the most downstream photosensitive member 13Y and the transfer / fixing as in the cleaning failure detection means 35 of FIG. 5B. It arrange | positions between nip SN. When the optical sensor of the cleaning failure detection unit is arranged separately from the optical sensor for image stabilization, it is arranged downstream of the belt cleaning unit 46 like the cleaning unit 36 of FIG. 5B. In any case, since it is not necessary to provide a cleaning failure detection means for each photoconductor 13 of each developing device, the cleaning failure detection means 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 units 30 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. 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 or a paper gap formed between 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 for explaining a first control method of the heating unit 20 when a toner removal failure is detected by the cleaning failure detection unit 30. In this first control method, when a toner removal failure (cleaning failure) is detected by the cleaning failure detection means 30, all the thermal heaters 20a to 20g of the heating means 20 have electric power that can obtain the first target temperature. 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 means 30, 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 of the heating unit 20 when a toner removal failure is detected by the cleaning failure detection unit 30. In the second control method, when a toner removal failure (cleaning failure) is detected by the cleaning failure detection means 30, the cleaning failure detection means 30 detects the removal failure in relation to 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.

  When the toner removal failure (cleaning failure) is not detected by the cleaning failure detection means 30, 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.

  9A to 9C are flowcharts showing an example of control of the heating means. In order to solve the above problem, the present invention has cleaning failure detection means 30 to 36, and the heating control means 24 has a switching means for switching the heating area for selecting a heating area necessary for the heating means 20.

  This switching means first detects defective cleaning in step S1 of FIG. 9A. If it is determined in step S2 that no cleaning failure is detected on the photosensitive member 13 by the cleaning failure detection means 30 (line illumination light source 30a, imaging lens 30b, line sensor 30c), the image is displayed as usual in step S3. Heating (normal control mode) for fixing only the image area described in FIGS. 8A and 8B is performed.

  On the other hand, if a cleaning failure is detected, the mode is switched to the clean control mode in step S4. The switching means for performing this switching is realized by a program mounted on the microcomputer of the heating control means 24.

(Cleaning failure recovery judgment)
FIG. 9B is a diagram illustrating a cleaning failure recovery determination unit. The cleaning failure usually occurs due to deterioration with time such as chipping or hardening of the cleaning blade 19a. For example, when the ambient temperature changes and the temperature around the printer 10 increases, the cleaning blade 19a softens and the cleaning failure naturally recovers. There is. In the present invention, in response to such a phenomenon, cleaning failure recovery determination means for determining whether or not recovery from a cleaning failure is provided is provided.

  When it is determined that the cleaning failure has been recovered (residual toner removal failure has been resolved), the control mode of the thermal heaters 20a to 20g is automatically returned from the clean control mode to the normal control mode. By providing the cleaning failure recovery determination means in this manner, the control mode of the thermal heaters 20a to 20g can be quickly returned to the normal control mode after the cleaning failure recovery. Therefore, waste of power consumption of the thermal heaters 20a to 20g can be minimized.

  First, in step S1, the cleaning failure recovery determination means determines whether or not the current control mode is the clean control mode. If it is determined in step S1 that the control mode is the clean control mode, the cleaning failure recovery determination in step S2, that is, the cleaning failure recovery determination steps S1 to S5 as shown in FIG. 9C is executed. If it is determined in step S3 that the cleaning failure has been recovered as a result of the cleaning failure recovery determination, the control mode is switched to the normal control mode in step S4.

  If it is determined that the cleaning failure has not been recovered, the clean control mode is maintained in step S5. This cleaning failure recovery determination means is realized by a program mounted on the microcomputer of the heating control means 24, similarly to the switching means for switching the heating region of the heating means 20 (thermal heaters 20a to 20g).

  FIG. 9C is a diagram illustrating a specific example of the cleaning failure recovery determination unit described above. When the cleaning failure recovery determination is started, a cleaning recovery determination timer is first started in step S1. In step S2, it is determined whether a cleaning failure is detected by the cleaning failure detection means.

  If it is determined in step S2 that a cleaning failure has been detected, the timer is reset in step S3 and the determination ends. If it is determined in step S2 that no cleaning failure has been detected, it is determined in step S4 whether a fixed time has elapsed since the timer start.

  Here, for example, the “certain time” can be recorded in the ROM of the heating control means 24 in advance as the time for which the photosensitive member 13 rotates once, and this time can be set as the “constant time”. In consideration of the possibility of erroneous detection of the cleaning failure detection means due to electrical noise or the like, it is better to allow a margin for the “certain time”. That is, for example, the time for two rotations or three rotations of the photosensitive member 13 is set to the “certain time”. If a cleaning failure is not detected more than a predetermined number of times (for example, 2 times or more) within this fixed time, it is determined that the cleaning failure has been recovered.

  If the predetermined time has not elapsed, step S2 and step S4 are alternately repeated until the predetermined time has elapsed. If a cleaning failure is detected during this process, the timer is reset in step S3 and the determination is terminated.

  After a cleaning failure is detected in step S2, if it is determined in step S4 that a fixed time has elapsed from the start of the timer, it is determined in step S5 that the cleaning failure has been recovered, and the determination ends. This process may always be performed during image formation, or a cleaning failure detection mode may be executed after image formation, and if no cleaning failure is detected in the cleaning failure detection mode, it may be determined that the image has been recovered.

  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 30-36: Cleaning failure detecting means 30a: Line illumination light source 30b: Imaging Lens 30c: Line sensor 38: Transfer belt 40: Transfer / fixing belt

JP 2001-343860 A Japanese Patent Application Laid-Open No. 07-084484 JP-A-5-281818 JP 2012-63560 A

Claims (18)

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 unit that detects a removal failure of the residual developer by the cleaning unit is provided, and a heating region switching control mode of the heating unit by the switching unit is set,
When the cleaning failure detection means does not detect the residual developer removal failure, the normal control mode for the heating area corresponding to the visible image is set,
Clean control for eliminating the residual developer removal failure for all heating regions including the heating region corresponding to the visible image when the cleaning failure detection means detects the residual developer removal failure. An image forming apparatus having a mode. 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 unit that detects a removal failure of the residual developer by the cleaning unit is provided, and a heating region switching control mode of the heating unit by the switching unit is set,
When the cleaning failure detection means does not detect the residual developer removal failure, the normal control mode for the heating area corresponding to the visible image is set,
When the residual developer removal failure is detected by the cleaning failure detection means, the cleaning failure detection means relates the removal failure of the residual developer to the position of the removal failure on the surface of the image carrier. And a heating control area corresponding to the removal failure position and necessary for fixing the residual developer, and a clean control mode for eliminating the residual developer removal failure for the heating area corresponding to the visible image. An image forming apparatus characterized by that. 3. The image forming apparatus according to claim 1, wherein a patch image for image density adjustment is detected by the cleaning failure detection means. The cleaning failure detection means, the image forming apparatus according to claim 1 or 2, characterized in that detecting the removal failure of the remaining developer of the non-printing area on said image bearing member. The cleaning failure detection means detects a removal failure of a residual developer in a printing area on the image carrier based on information on a heating area for fixing the visible image possessed by the heating means. the image forming apparatus according to claim 1 or 2, characterized. The image bearing member includes a photosensitive member, the cleaning unit is disposed on an outer periphery of the photosensitive member, and the heating unit transfers the recording medium on which the visible image is transferred on the downstream side of the transfer position. sandwich fixing member and the pressing image forming apparatus according to claim 1 or 2, characterized in that it is arranged in one of material. The image carrier has a first image carrier by a plurality of photosensitive members and a second image carrier by an intermediate transfer member to which a visible image on the first image carrier is transferred, and the cleaning means A fixing member and a pressure member that are disposed on the second image carrier, and in which the heating unit sandwiches the recording medium on which the visible image is transferred from the second image carrier on the downstream side of the transfer position. the image forming apparatus according to claim 1 or 2, characterized in that it is arranged in one of. The image carrier has a first image carrier by a plurality of photoconductors and a second image carrier by a transfer / fixing member to which a visible image on the first image carrier is transferred, and the cleaning means Is disposed on the second image carrier, and the heating means is disposed on the second image carrier upstream of the pressure member that presses the recording medium against the second image carrier. the image forming apparatus according to claim 1 or 2, characterized in. The fixing member is constituted by a fixing roller or fixing belt, the pressure member is any one of the image forming apparatus of claim 6, characterized in that it is constituted by a pressure roller or pressure belt 8. It said heating means, thermal heaters, electromagnetic induction heating or the image forming apparatus according to claim 1 or 2, characterized by the use of light energy. Said heating means, while heating the region of the visible image to a fixing temperature required for fixing, claim 1 region other than the visible image, wherein the heating at a temperature lower than the fixing temperature or 2. Image forming apparatus of 2 . 3. The image forming apparatus according to claim 1, further comprising a notification unit configured to notify that the control is performed when the heating unit is controlled in the clean control mode. 3. The image forming apparatus according to claim 1, wherein the cleaning failure detection unit includes a line sensor or a reflective optical sensor. The image forming apparatus according to claim 13 , wherein the reflective optical sensor is disposed so as to be movable in a longitudinal direction of the image carrier. 3. The image forming apparatus according to claim 1, further comprising a cleaning failure detection mode for detecting a removal failure of the residual developer by the cleaning failure detection means. 3. The image forming apparatus according to claim 1, further comprising a cleaning failure recovery determination unit that determines that the cleaning failure has been recovered, wherein the clean control mode is switched to the normal control mode when it is determined that the cleaning failure has been recovered. apparatus. 17. The image forming apparatus according to claim 16 , wherein the cleaning failure recovery determination unit determines that the cleaning failure has been recovered when the residual developer removal failure by the cleaning failure detection unit is not detected for a predetermined time. The cleaning failure recovery determination unit determines that the cleaning failure has been recovered when a residual developer removal failure by the cleaning failure detection unit is not detected during one rotation of the image carrier. 16 image forming apparatuses.