JP6080000B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus including a fixing device that fixes an image on a recording medium.

  Generally, in an image forming apparatus such as an electrophotographic system, a fixing device that fixes a toner image onto a sheet as a recording medium is provided. The fixing device includes a fixing member heated by a heating unit and a facing member that comes into contact with the fixing member, and the sheet passes through a nip portion formed by the contact between the fixing member and the facing member. The toner on the paper is heated and melted and fixed.

  The fixing member is basically configured to be heated over the entire sheet passing width by the heating means, whereby the entire sheet is heated. However, when the image exists only in a partial area of the paper, heat energy is wasted in the non-image area where the image does not exist.

  Therefore, in order to reduce wasteful heat energy consumption in the non-image area, for example, in Patent Documents 1 to 3 and the like, the heating area is changed according to the image on the recording medium, and the portion necessary for fixing is heated. A fixing device has been proposed in which a portion not required for fixing is not heated.

  In the fixing device that changes the heating range in accordance with the image information as described above, when the image areas of the sheet to be fixed first and the sheet to be fixed later are at different positions, The portion to be heated of the fixing member differs between the fixing process and the subsequent fixing process. Therefore, in this case, even if heat remains in the portion heated for the previous fixing process, the heat is dissipated while being hardly used in the subsequent fixing process. Will be wasted.

  In view of such circumstances, an object of the present invention is to provide an image forming apparatus capable of effectively utilizing heat stored in a fixing member.

In order to solve the above-described problems, the present invention includes a fixing member, a facing member that contacts the fixing member to form a nip portion, and a heating unit that heats the fixing member, and the heating unit includes a recording medium. Based on the image information formed thereon, the portion of the fixing member corresponding to the non-image area on the recording medium is heated with a lower calorific value than the portion of the fixing member corresponding to the image area on the recording medium. In the image forming apparatus including the fixing device configured as described above, an image region to be sent to the nip portion first and then to the nip portion with respect to the portion of the fixing member heated with a high calorific value based on image information. The position of at least one of the image area sent to the nip portion first and the image area sent to the nip portion after that is changed so that the image area to be touched is changed .

According to the present invention, the position of the image area on the recording medium is changed, and the part of the fixing member in which the image area sent to the nip part first and the image area sent to the nip part after that are heated with a high calorific value. Therefore, the heat stored in the fixing member can be effectively used for the fixing process of the subsequent image area . As a result, it is possible to reduce the amount of heat newly given for the fixing process of the subsequent image area , thereby reducing energy consumption.

1 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus to which the present invention is applicable. FIG. 2 is a cross-sectional view illustrating a basic configuration of a fixing device. FIG. 3 is a perspective view of a main part of the fixing device. It is a top view which shows an image formation pattern. FIG. 7 is a diagram illustrating a heater output and a temperature change of a fixing belt during paper passing. It is a figure which shows the thermal storage state before the heating part of a fixing belt passes a nip part. FIG. 4 is a diagram illustrating a heat storage state after the heating unit of the fixing belt has passed through the nip portion. It is a figure which shows the structure of 1st Embodiment of this invention. It is a figure which shows the fixing method which concerns on 1st Embodiment of this invention. It is a figure which shows the structure of 2nd Embodiment of this invention. It is a figure which shows the fixing method which concerns on 2nd Embodiment of this invention. It is a figure which shows the fixing method which concerns on 3rd Embodiment of this invention. It is a figure which shows the fixing method which concerns on 4th Embodiment of this invention. FIG. 6 is a cross-sectional view illustrating a configuration of another fixing device to which the present invention is applicable. It is a schematic block diagram of the other image forming apparatus which can apply this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In each of the drawings for explaining the embodiments of the present invention, constituent elements such as members and components having the same function or shape are described once by giving the same reference numerals as much as possible. Then, the explanation is omitted.

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.
The image forming apparatus shown in FIG. 1 is a monochrome image forming apparatus, and a photoconductor 2 as an image carrier is disposed in the center of the apparatus main body 1. Around the photosensitive member 2, a charging roller 3 as a charging unit, a light source 4 and a mirror 5 constituting an exposure unit, a developing unit 7 including a developing roller 6, a transfer unit 8, and a cleaning blade 9 are provided. Means 10 and the like are arranged.

  Further, the apparatus main body 1 includes a paper feed tray 11 that stores paper P as a recording medium, a paper feed roller 12 that carries the paper P out of the paper feed tray 11, a pair of registration rollers 13 as timing rollers, A fixing device 14 that fixes an image on the paper P and a paper discharge roller 15 that discharges the paper P outside the device are provided. In addition to plain paper, the recording medium includes cardboard, postcard, envelope, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet, and the like. Although not shown, a manual paper feed mechanism may be provided.

Next, the basic operation of the image forming apparatus according to the present embodiment will be described with reference to FIG.
When the image forming operation is started, the photosensitive member 2 is rotationally driven clockwise by a driving device (not shown), and the surface of the photosensitive member 2 is uniformly charged to a predetermined polarity by the charging roller 3. Next, based on image information from a reading device or a computer (not shown), the exposure light L emitted from the light source 4 is scanned through the mirror 5 and applied to the charged surface of the photoreceptor 2. As a result, an electrostatic latent image is formed on the surface of the photoreceptor 2. By supplying toner from the developing roller 6 to the electrostatic latent image, the electrostatic latent image is visualized (visualized) as a toner image.

  When the image forming operation is started, the paper feed roller 12 starts to rotate, and the paper P is separated and sent out from the paper feed tray 11 one by one. The transport of the fed paper P is temporarily stopped by the registration roller 13, and the deviation of the posture is corrected. Thereafter, the registration roller 13 is driven to rotate in synchronization with the rotation of the photosensitive member 2, and the paper P is conveyed at a timing when the leading end of the toner image on the photosensitive member 2 coincides with a predetermined position at the leading end of the conveying direction of the paper P. Then, the toner image on the photoreceptor 2 is transferred onto the conveyed paper P by the transfer electric field formed by the transfer unit 8. The paper P on which the toner image has been transferred is conveyed to the fixing device 14, and the toner image on the paper P is fixed by the fixing device 14. Thereafter, the paper P is discharged out of the apparatus by the paper discharge roller 15.

  Residual toner remaining on the photosensitive member 2 without being transferred onto the paper P reaches the cleaning blade 9 as the photosensitive member 2 rotates, and is scraped off and removed by the cleaning blade 9. Then, the surface of the photoreceptor 2 is neutralized by a neutralizing unit (not shown) and is prepared for the next image forming process.

FIG. 2 is a cross-sectional view showing the basic configuration of the fixing device according to the present embodiment.
As shown in FIG. 2, the fixing device 14 includes a fixing belt 21 as a fixing member (or fixing rotator), and a counter member (or counter rotator) that forms a nip portion N in contact with the fixing belt 21. A pressure roller 22 and a heater 23 as a heating means for heating the fixing belt are provided.

  The fixing belt 21 is composed of an endless belt member (including a film) that is thin and flexible. Specifically, the fixing belt 21 includes a base material 21a made of SUS having an outer diameter of 40 mm and a thickness of 40 μm, an elastic layer 21 b made of silicone rubber having a thickness of 100 μm covering the outer peripheral surface of the base material 21 a, and the elastic layer 21 b. And a release layer 21c made of a fluororesin such as PFA or PTFE having a thickness of 5 to 50 μm covering the outer peripheral surface. The base 21a of the fixing belt 21 may be made of a resin material such as polyimide.

  The pressure roller 22 includes an iron cored bar 22a having an outer diameter of 40 mm and a thickness of 2 mm, and an elastic layer 22b covering the outer peripheral surface of the cored bar 22a. The elastic layer 22b of the pressure roller 22 is made of silicone rubber and has a thickness of 5 mm. Moreover, in order to improve mold release property, you may arrange | position the mold release layer which consists of fluorine resin about 40 micrometers thick in the outer peripheral surface of the elastic layer 22b.

  A nip forming member 24 is disposed at a position facing the pressure roller 22 on the inner peripheral side of the fixing belt 21. The nip forming member 24 is supported by a side plate (not shown) of the fixing device 14 at both ends thereof. When the pressure roller 22 is brought into pressure contact with the nip forming member 24 by a pressure means such as a pressure lever, a nip portion N having a predetermined width is formed at the pressure contact portion between the fixing belt 21 and the pressure roller 22. ing. Note that the fixing member and the opposing member may be simply brought into contact with each other without applying pressure.

  The pressure roller 22 is configured to be rotationally driven in the direction of arrow B in the figure by a drive source such as a motor (not shown). When the pressure roller 22 is rotationally driven, the driving force is transmitted to the fixing belt 21 at the nip portion N, and the fixing belt 21 is driven to rotate in the direction of arrow C in the figure. A belt support member 29 that supports the fixing belt 21 is disposed on the inner peripheral side of the fixing belt 21.

  The heater 23 is composed of a planar or plate-like heating element such as a thermal heater or a ceramic heater. A stay 31 as a support member is disposed on the inner peripheral side of the fixing belt 21, and the stay 31 causes the heater 23 to be upstream of the nip portion N in the sheet conveyance direction A, and the fixing belt 21. It is supported so as to face the inner peripheral surface. The heater 23 may be disposed at the position of the nip portion N so as to have a function as the nip forming member 24. Further, a power source 25 is connected to the heater 23 so that power is supplied from the power source 25 to the heater 23. The output of the power source 25 is controlled by the heating control means 26. The heating control means 26 is composed of a microcomputer including a CPU, ROM, RAM, I / O interface and the like.

  The fixing device 14 includes a first thermistor 27 as a heater temperature detecting unit that detects the temperature of the heater 23, and a second thermistor 28 as a belt temperature detecting unit that detects the temperature of the fixing belt 21. The first thermistor 27 is disposed so as to be in direct contact with the heater 23, and the second thermistor 28 is opposed to the outer peripheral surface of the fixing belt 21 on the upstream side in the belt rotation direction C with respect to the heater 23. It is arranged. The temperature information detected by each thermistor 27, 28 is input to the heating control means 26, and the heating control means 26 is configured to control the output of the power source 25 based on this input information. ing.

  A pressing roller 30 as a pressing member that presses the fixing belt 21 from the outer peripheral side is disposed at a position facing the heater 23. The fixing belt 21 is brought into contact with the heater 23 by pressing the fixing belt 21 from the outer peripheral side by the pressing roller 30. The pressing roller 30 has an outer diameter of 15 mm to 30 mm, an iron core metal 30 a having an outer diameter of 8 mm, and an elastic layer 30 b made of silicone rubber having a thickness of 3.5 mm to 11 mm covering the outer peripheral surface of the core metal 30 a. It consists of and. Further, in order to improve the mold release property, a mold release layer made of a fluorine resin having a thickness of about 40 μm may be disposed on the outer peripheral surface of the elastic layer 30b. Here, the pressing roller 30 is pressed against the fixing belt 21 by a pressing unit (not shown). However, the pressing roller 30 may be configured to simply abut without pressing.

The basic operation of the fixing device will be described with reference to FIG.
When the power switch of the image forming apparatus main body is turned on, power is supplied from the power source 25 to the heater 23, and the pressure roller 22 starts to rotate in the direction of arrow B in the figure. As a result, the fixing belt 21 is driven to rotate in the direction of arrow C in the figure by the frictional force with the pressure roller 22.

  Thereafter, when the sheet P carrying the unfixed toner image G through the image forming process is conveyed to the nip portion N between the fixing belt 21 and the pressure roller 22, the sheet P is heated and heated. The toner image G on the paper P is fixed. Then, after the sheet P is carried out from the nip portion N, it is discharged out of the apparatus.

Hereinafter, the configuration of the fixing device according to the present embodiment will be described in more detail.
As shown in FIG. 3, the heater 23 has a plurality of (seven in the figure) heating elements 32 arranged at equal intervals in the width direction of the paper P, and each heating element 32 is independent of each other. It is configured to generate heat. Each heating element 32 is configured such that its heating is controlled by the heating control means 26.

  Specifically, the heating control means 26 controls the change of the heating range in the sheet width direction by selecting the heating element 32 to generate heat from among the plurality of heating elements 32 and the ON / OFF timing of the heating element 32. Thus, the heating range in the rotation direction can be changed, and the heating amount (heating temperature) can be changed by controlling the heat generation amount of the heating element 32. Note that the amount of heat generated (output) of the heat generating element 32 is controlled by increasing or decreasing the power supplied to the heat generating element 32 or changing the lighting duty (the ratio of the ON time during a predetermined time).

  For example, as shown in FIG. 4A, in the case of the paper P on which the image area a, the non-image area b, and the image area c are formed in order from the leading end side in the paper conveyance direction A, the image area In a and c, fixing is necessary, but in the non-image area c, fixing is not necessary. In such a case, the heating control means 26 determines the temperature of the part of the fixing belt 21 corresponding to the non-image area b based on the image information obtained from the image processing means 33 (see FIG. 2). The heater 23 is controlled to be lower than the temperature of the portion of the fixing belt 21 corresponding to. That is, in this case, the power supply to all the heating elements 32 is normally performed at the locations corresponding to the image areas a and c, but the power supply to all the heating elements 32 is reduced at the locations corresponding to the non-image areas b. Or stop. As described above, in the portion corresponding to the non-image area b, wasteful heat energy consumption to the non-image area b can be reduced by reducing or stopping the power supplied to the heating element 32.

  As shown in FIG. 4B, when the image area d and the non-image area e are mixed in the width direction of the paper P, it corresponds to the non-image area e among the plurality of heating elements 32. The power supply to the heating element 32 at the position (right side in the figure) is reduced or stopped. Thereby, useless heat energy consumption to the non-image area e can be reduced.

  In the example shown in FIG. 4C, the image area and the non-image area are mixed in the width direction and the conveyance direction of the paper P. In this case, the power supply to the heating element 32 is reduced or stopped in correspondence with the non-image area formed in the portion where the range of the symbol g and the range of the symbol i in the figure overlap with each other. Similarly, useless heat energy consumption to non-image areas can be reduced.

  FIG. 5 is a diagram illustrating the output of the heater and the temperature change of the fixing belt when the sheet illustrated in FIG. 4A is passed. Hereinafter, the temperature control of the fixing belt will be described with reference to FIG.

  As shown in FIG. 5, at the timings Ta and Tc when the image areas a and c on the paper pass through the nip portion, the temperature of the fixing belt is set to a predetermined first target temperature Q1 necessary for fixing. Controls the power supplied to the heating element. On the other hand, at the timing Tb when the non-image area b passes through the nip portion, power supply to the heating element is reduced to control the second target temperature Q2 that is lower than the first target temperature Q1, which is wasteful. Reduce energy consumption. Here, in the times Tb, T1, and T2 when the image areas a and c do not pass through the nip portion, the power supply to the heating element may be stopped completely. Alternatively, the temperature rise corresponding to the first image area may not be in time. Therefore, as in the example shown in FIG. 5, the output W2 smaller than the output W1 for the first target temperature Q1 is set as the output of the heating element, and the non-passing times Tb, T1, T2 of the image area It is desirable to perform control so as to maintain the second target temperature Q2 that is lower than the first target temperature Q1 but higher than room temperature by heating with a small output W2.

  In general, it takes a certain time for the temperature of the fixing belt to reach the target temperature after the heating of the fixing belt is started. Accordingly, when the rise at the output W1 for the first target temperature Q1 is started when the leading edge of the image area a reaches the nip portion, the temperature rise to the first target temperature Q1 is not in time. Therefore, as in the example shown in FIG. 5, in consideration of the heating time of the fixing belt, the output is performed for a predetermined time Tx from the timing before the leading ends of the image areas a and c reach the nip portion. It is desirable to perform preheating with W1. However, from the viewpoint of energy saving, it is desirable that the preheating time Tx is as short as possible. In addition, the temperature increase time of the fixing belt varies depending on the heat transfer coefficient of the fixing belt itself, the heat generation length in the rotation direction, and the like, and therefore it is preferable to specify the temperature beforehand by experiments.

  In the example shown in FIG. 5, the fixing temperatures of the image areas a and c are set to the same first target temperature Q1, but the target temperatures may be varied depending on the image areas.

  For example, when the image type of each image area is different for characters, photographs, drawings, etc., the target temperature corresponding to each image area may be varied depending on the image type. In particular, when the image is a photograph, it may be necessary to increase the glossiness of the image. Therefore, a desired glossiness can be obtained by setting a high target temperature for the image area of the photograph.

  Also, if the image pattern of each image area is different for solid images, halftone images, line images, character images, etc., or if the image pattern processing method is different for dither method, error diffusion method, etc., the image pattern and processing The target temperature corresponding to each image region may be varied depending on the method. It is known that the degree of isolation or density of toner particles differs depending on various image patterns, and the toner is more easily peeled off when it is isolated than when it is dense. Therefore, for image patterns with isolated toner, the target temperature is raised to make it difficult to peel off. On the other hand, for image patterns with dense toner, reducing the target temperature reduces energy consumption. Is possible.

  In addition, when the toner adhesion amount of each image area is different, the temperature required for fixing is different, so the toner adhesion amount is grasped based on the image information, and the target temperature is different for each image area accordingly. It may be allowed. Usually, in an image with a large amount of toner adhesion, a large amount of heat is required for melting the toner, and thus it is necessary to raise the target temperature. On the contrary, for an image with a small amount of toner, the target temperature can be lowered to reduce energy consumption.

  In a color image forming apparatus using a plurality of color toners, the amount of heat required for fixing may differ depending on the color of the toner. In this case, the target temperature may be varied depending on the color of the toner. For example, black toner often requires less heat than other color toners, such as yellow, cyan, and magenta. Therefore, in an image area where only black toner is used, the target temperature By reducing the value, energy consumption can be reduced.

  By the way, in the image forming apparatus of the present embodiment, as shown in FIG. 6A, when a part D on the fixing belt 21 is heated in correspondence with the image G on the paper, it is shown in FIG. As such, heat is stored in the portion D, and the temperature rises. When the image G passes through the nip portion N and the fixing process is performed as shown in FIG. 7A, the temperature of the portion D decreases as shown in FIG. Since all the heat stored in is not used by the fixing process, it remains on the fixing belt 21 even after the fixing process. Therefore, once heated, the portion D is maintained in a state in which heat is stored more than other portions for a while.

  However, since the heat stored on the fixing belt 21 is only radiated if it is not used for the fixing process thereafter, heat energy is wasted. Therefore, in the present invention, in order to effectively use the stored heat, it is used in the subsequent fixing process. Hereafter, the characteristic part of this invention is demonstrated.

FIG. 8 is a diagram showing the configuration of the first exemplary embodiment of the present invention.
As shown in FIG. 8, in the first embodiment, in the fixing device 14 having the configuration shown in FIG. 2, the storage unit 34 that stores the heat generation history for each of the plurality of heating elements 32, and the heat generation history stored by the storage unit 34. And a control means 35 for controlling the image processing means 33 based on the above.

  As described above, a heat storage pattern (a portion where heat is stored) is formed on the fixing belt 21 due to the presence or absence of heat storage or a difference in the degree of heat storage in accordance with the fixing process. As the fixing process is performed, it changes in a complicated manner. The heat storage pattern on the fixing belt 21 changes based on the heat generation history of each heat generating element 32, that is, the presence or absence of heat generation of each heat generating element 32, the start and stop timing of heat generation, the heat generation time, the heat generation amount (output), and the like. To do. Focusing on this, in the present embodiment, the thermal history for each of the plurality of heating elements 32 is stored by the storage means 34, and the control means 35 grasps the heat storage pattern on the fixing belt 21 based on the stored heat generation history. I am doing so. In this embodiment, the image processing unit 33 is controlled by the control unit 35 so that the image area on the sheet is arranged at a position corresponding to the heat storage pattern on the fixing belt 21. The control means 35 is, for example, a microcomputer mounted on the image forming apparatus or driver software for a personal computer such as a user.

  Specifically, as shown in FIG. 9A, images G1 and G2 that are to be formed on the first sheet P1 and the second sheet P2 to be subjected to the fixing process are formed on the sheets P1 and P2. In the present embodiment, when the positions are different from each other, in this embodiment, an image G2 formed on the second sheet P2 passes through the center of the sheet and is perpendicular to the sheet, as shown in FIG. It is moved to a position that is inverted 180 ° around. In this way, by forming the image G2 on the second sheet P2 at a position inverted by 180 °, the image G2 is adjusted to the location F corresponding to the heat storage pattern on the second sheet P2. To place. The location F corresponding to the heat storage pattern is a location where the heated portion of the fixing belt 21 contacts the second paper P2 for fixing the image G1 of the first paper P1. That is. Thereby, the heat stored by fixing the first sheet P1 can be used for the fixing process of the second sheet P2.

  Also, without changing the position of the image G2 on the second sheet P2, the image G1 on the first sheet P1 is formed at a position inverted by 180 ° around the center axis of the sheet. Similarly, heat storage on the fixing belt 21 can be used for fixing the second sheet P2.

FIG. 10 shows the configuration of the second embodiment of the present invention.
As shown in FIG. 10, in the second embodiment, in addition to the configuration of the first embodiment shown in FIG. 8, the recording medium supply means 36 is also controlled by the control means 35. That is, the control unit 35 controls both the recording medium supply unit 36 and the image processing unit 33 based on the heat generation history of each heating element 32.

  The recording medium supply means 36 is a means capable of supplying paper by changing the vertical and horizontal orientations of the paper. For example, the recording medium supply unit 36 supplies various sheets for supplying paper to a fixing device such as a paper feed cassette, a paper feed roller, a registration roller, other transport rollers, and a transport guide as a recording medium container for storing paper. Means are included. In this embodiment, a first paper feed cassette that stores paper vertically and a second paper feed cassette that stores paper horizontally are provided, and it is easy to change the paper feed cassette that feeds paper. The paper can be fed in a different direction. Note that when there is no sheet in the paper cassette in the middle of continuous printing, there is a control for switching to another paper cassette and feeding paper, but the present invention is different from this. That is, according to the present invention, the change of the direction of the sheet is performed based on the heat generation history of the heat generating element 32, and therefore can be executed at a timing different from the timing at which the sheet in the sheet feeding cassette is exhausted.

  Specifically, in the second embodiment, as shown in FIG. 11A, the images G1 and G2 scheduled to be formed on the first sheet P1 and the second sheet P2 are the sheets P1 and P2. In this embodiment, the image G2 formed on the second sheet P2 is rotated by 90 ° around the sheet central axis, as shown in FIG. Form in position. In accordance with the change in the image forming position, the second sheet P2 is similarly rotated 90 ° around the axis to change the vertical and horizontal orientations. In this manner, by changing the orientation of the second sheet P2 and the position of the image G2, the image G2 can be arranged at the location F corresponding to the heat storage pattern on the second sheet P2. As a result, the heat stored by fixing the first sheet P1 can be used for fixing the second sheet P2.

  Similarly, the orientation of the first sheet P1 and the image G1 are rotated by 90 ° around the central axis of the sheet without changing the orientation of the second sheet P2 and the position of the image G2. In addition, the heat storage on the fixing belt 21 can be used for the fixing process of the second sheet P2.

Hereinafter, a third embodiment of the present invention will be described.
In the third embodiment, similarly to the second embodiment shown in FIG. 10, the storage unit 34 that stores the heat generation history for each of the plurality of heating elements 32, and the image processing unit 33 based on the heat generation history stored in the storage unit 34. Control means 35 for controlling both the recording medium supply means 36 and the recording medium supply means 36. However, the recording medium supply means 36 here is a means such as a registration roller capable of changing the timing of supplying paper to the fixing device.

  In the third embodiment, as shown in FIG. 12A, the images G1 and G2 to be formed on the first sheet P1 and the second sheet P2 are at the same position in the sheet width direction. When the image G2 on the second sheet P2 deviates from the location F corresponding to the heat storage pattern, the sheet supply timing and the image formation timing are changed. Specifically, in this case, as shown in FIG. 12B, the second sheet P2 is supplied so as to widen the space W between the first sheet P1 and the second sheet P2. Accordingly, the image processing means 33 also adjusts the formation timing of the image G2 transferred to the second sheet P2. As a result, the image G2 can be arranged at a location F corresponding to the heat storage pattern on the second sheet P2, and the heat stored by the fixing of the first sheet P1 can be transferred to the second sheet P2. Can be used for the fixing process.

Subsequently, a fourth embodiment of the present invention will be described.
In the fourth embodiment, similarly to the first embodiment shown in FIG. 8, the storage unit 34 that stores the heat generation history for each of the plurality of heating elements 32, and the image processing unit 33 based on the heat generation history stored in the storage unit 34. And control means 35 for controlling. However, in the third embodiment, the method of changing the image forming position by the image processing means 33 is different.

  Specifically, in the fourth embodiment, as shown in FIGS. 13A and 13B, the image P1 on the first sheet P1 is moved in the width direction of the sheet, and the second sheet P2 is moved. The image G2 formed on the second sheet P2 is arranged at a location F corresponding to the heat storage pattern by moving the image P2 in the sheet width direction and the conveyance direction. As a result, similarly to the above, the heat stored by fixing the first sheet P1 can be used for the fixing process of the second sheet P2.

  However, in this case, since the position of the image with respect to the paper is changed, the changed image is displayed on the operation panel of the image forming apparatus or on the screen of a personal computer connected to the image forming apparatus. It is desirable to start printing after obtaining the confirmation. In addition, it is possible to prevent the image from being shifted with respect to the paper by moving the paper feeding position by the same amount in the same direction as the image moving in accordance with the movement of the image.

  In the example shown in FIG. 13, both the image P1 on the first sheet P1 and the image P2 on the second sheet P2 are moved, but only one image may be moved. . Further, depending on how the two images are shifted, one or both of the images may be moved only in the width direction of the paper or only in the transport direction.

  As described above, according to each embodiment of the present invention, the heat stored by fixing the previous sheet can be effectively used for the subsequent fixing process of the sheet. As a result, the amount of heat newly given for the fixing process of the subsequent sheet can be reduced, so that the energy consumption can be reduced. In the above description of the embodiment of the present invention, four methods (embodiments) are listed as methods for arranging the image area on the paper at a position corresponding to the heat storage pattern on the fixing belt. Any one of them may be appropriately selected and used properly.

  In addition, this invention is not limited to the said embodiment, Of course, a various change can be added in the range which does not deviate from the summary of this invention. For example, it is possible to change only the arrangement of a part of the image formed on the subsequent sheet and arrange the image at a location corresponding to the heat storage pattern. Further, when the fixing belt is rotated more than once when one sheet passes through the nip portion, the second rotation is performed in order to use the heat accumulation by the first rotation fixing for the second and subsequent fixings. It is also possible to change the arrangement of the image corresponding to the subsequent portions.

  Moreover, in the said embodiment, although it is trying to grasp | ascertain the thermal storage pattern based on the heat_generation | fever log | history for every heat generating body, since the heat_generation | fever log | history of each heat generating body changes according to the image formed, image information formed It is also possible to grasp the heat storage pattern based on the above. Alternatively, the surface temperature of the fixing belt may be detected to grasp the heat storage pattern on the fixing belt.

  In the above embodiment, the fixing belt 21 is used as the fixing rotator, and the heater 23 that is heated from the inner peripheral side of the fixing belt 21 is used as a heating unit. However, the fixing to which the present invention is applicable is described. The device is not limited to this.

  For example, as shown in FIG. 14, the present invention can be applied to a configuration in which a fixing roller 60 is used as a fixing rotating body, and a heater 23 that is heated from the outer peripheral side of the fixing roller 60 is used as a heating unit. The fixing roller 60 in this embodiment includes an aluminum cored bar 60a having an outer diameter of 40 mm and a thickness of 1 mm, a heat insulating layer 60b that covers the outer peripheral surface of the cored bar 60a, and heat that covers the outer peripheral surface of the heat insulating layer 60b. The conductive layer 60c and the release layer 60d covering the outer peripheral surface of the heat conductive layer 60c are configured.

  The heat insulation layer 60b is made of silicone rubber and has a thickness of 3 mm. Further, in order to further enhance the heat insulating function of the heat insulating layer 60b, the heat insulating layer 60b may be formed of a foamed silicone rubber with little heat escape.

  The heat conductive layer 60c is made of nickel. However, the material of the heat conductive layer 60c is not limited to nickel, and may be any material having higher heat conductivity than that of the heat insulating layer 60b, such as an iron-based alloy such as stainless steel, a metal-based material such as aluminum or copper, or a graphite sheet. . By providing such a heat conductive layer 60c with good heat conductivity, local temperature variations in the surface temperature of the fixing roller 60 due to uneven heat generation of the heater 23 can be reduced. Further, since the temperature can be raised in a region slightly wider than the region where the heater 23 is provided by the heat conductive layer 60c, there is also an advantage that a deviation from the image can be compensated. That is, by providing the heat conductive layer 60c, it is possible to improve the degree of freedom in setting the sizes and intervals of the plurality of heating elements constituting the heater 23.

  The release layer 60c is made of a fluorine resin such as PTF or PTFE, and has a thickness of 5 to 30 μm.

  Further, the fixing device 14 shown in FIG. 14 includes a power source 25 that supplies power to the heater 23, a heating control unit 26 that controls the heater 23 based on information obtained from the image processing unit 33, and a first unit that detects the temperature of the heater 23. The first thermistor 27, the second thermistor 28 for detecting the temperature of the fixing roller 60, and the like are provided. However, since these configurations are basically the same as those in the above-described embodiment, the description thereof is omitted.

  In the configuration shown in FIG. 14, the heater 23 is brought into contact with the surface of the fixing roller 60. However, a non-contact type heating unit using an IH method using a coil and an inverter may be used. In the case of the IH system, a plurality of heating coils are arranged in the axial direction of the fixing roller 60, or a plurality of members for canceling the magnetic flux are arranged in the axial direction of the fixing roller 60. Thus, it is possible to control the heating region and the heating amount.

  The image forming apparatus to which the present invention is applicable is not limited to a monochrome image forming apparatus as shown in FIG.

The present invention is also applicable to a fixing device mounted on a color image forming apparatus as shown in FIG.
The color image forming apparatus shown in FIG. 15 includes four process units 20Y, 20M, 20C, and 20K that are detachable from the apparatus main body 1. Each process unit 20Y, 20M, 20C, and 20K contains developers of different colors of yellow (Y), magenta (M), cyan (C), and black (K) corresponding to the color separation components of the color image. The configuration is the same except that. Specifically, each of the process units 20Y, 20M, 20C, and 20K includes a photosensitive member 2, a charging roller 3 that charges the surface of the photosensitive member 2, a developing unit 7 that includes a developing roller 6, and a surface of the photosensitive member 2. A cleaning means 10 for cleaning is provided.

  Above each process unit 20Y, 20M, 20C, 20K, an intermediate transfer belt 16, a plurality of primary transfer rollers 17, and a secondary transfer roller 18 are provided as transfer means 8. An exposure device 19 is provided below each process unit 20Y, 20M, 20C, 20K.

The basic image forming operation of the color image forming apparatus shown in FIG. 15 will be described below.
When the image forming operation is started, each photoconductor 2 in each process unit 20Y, 20M, 20C, 20K is rotationally driven, and the surface of each photoconductor 2 is uniformly charged to a predetermined polarity by the charging roller 3. . An electrostatic latent image is formed on the surface of each charged photoreceptor 2 by irradiating laser light from the exposure device 19. At this time, the image information to be exposed on each photoconductor 2 is single-color image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. The electrostatic latent images formed on the respective photoreceptors 2 in this way are supplied with toner by the developing means 7 so that the electrostatic latent images are visualized (visualized) as toner images. .

  When the image forming operation is started, the intermediate transfer belt 16 is rotationally driven in the direction indicated by the arrow in the figure, and a predetermined voltage is applied to each primary transfer roller 17, thereby causing each primary transfer roller 17 and each A transfer electric field is formed at the primary transfer nip with the photoreceptor 2. Thereafter, when each color toner image on the photoconductor 2 reaches the primary transfer nip as the photoconductor 2 rotates, the toner image on each photoconductor 2 is generated by the transfer electric field formed in the primary transfer nip. Are sequentially superimposed and transferred onto the intermediate transfer belt 16. Thus, a full-color toner image is carried on the surface of the intermediate transfer belt 16. Further, residual toner on each photoconductor 2 is removed by the cleaning means 10. Then, the surface of each photoconductor 2 is neutralized by a neutralizing device (not shown), and the surface potential is initialized.

  In the lower part of the apparatus main body 1, the paper feed roller 12 starts to rotate, and the paper P is sent from the paper feed tray 11 to the transport path R. The paper P sent to the transport path R is temporarily stopped by the registration rollers 13 and then transported to the secondary transfer nip at a predetermined timing. At this time, a predetermined voltage is applied to the secondary transfer roller 18, thereby forming a transfer electric field in the secondary transfer nip. Then, the toner images on the intermediate transfer belt 16 are collectively transferred onto the paper P by this transfer electric field. Thereafter, the paper P is conveyed to the fixing device 14, and after the toner image on the paper P is fixed to the paper P by the fixing device 14, the paper P is discharged out of the device by the paper discharge roller 15.

  The above description is an image forming operation when a full-color image is formed on a sheet. A single-color image is formed using any one of the four process units 20Y, 20M, 20C, and 20K. Two or three image forming units can be used to form a two-color or three-color image.

  The image forming apparatus to which the present invention can be applied is not limited to the above, and may be other printers, copiers, facsimiles, or complex machines thereof.

14 Fixing device 21 Fixing belt (fixing member)
22 Pressure roller (opposing member)
23 Heater (heating means)
32 Heating element 60 Fixing roller (fixing member)
N nip P Paper (recording medium)

JP-A-6-95540 JP 2001-343860 A JP 2005-181946 A

Claims (9)

A fixing member, an opposing member that contacts the fixing member to form a nip portion, and a heating unit that heats the fixing member.
Based on the image information formed on the recording medium, the heating means moves the fixing member portion corresponding to the non-image area on the recording medium from the fixing member portion corresponding to the image area on the recording medium. In an image forming apparatus including a fixing device configured to be heated with a low calorific value ,
First, the nip portion of the fixing member heated at a high calorific value based on the image information is first contacted with the image region sent to the nip portion first and the image region sent to the nip portion thereafter. An image forming apparatus characterized in that the position of at least one of the image area sent to the image area and the image area sent to the nip portion is changed . The heating means is arranged side by side in the width direction of the recording medium, and has a plurality of heating elements capable of generating heat independently of each other,
The image forming apparatus according to claim 1, wherein the image forming apparatus is configured to grasp a portion of the fixing member heated with the high heat generation amount based on a heat generation history of each of the heat generating elements. The image forming apparatus according to claim 1, wherein the image forming apparatus is configured to grasp a portion of the fixing member heated with the high calorific value based on image information to be formed. The image forming apparatus according to claim 1, wherein the image forming apparatus is configured to detect a surface temperature of the fixing member and grasp a portion of the fixing member that is heated with the high heat generation amount . An image area on the recording medium is moved in at least one of a conveyance direction and a width direction of the recording medium, and the image area is controlled to come into contact with the portion of the fixing member that is heated with the high heat generation amount. Item 5. The image forming apparatus according to any one of Items 1 to 4. The image area on the recording medium is inverted 180 ° around the vertical axis through the center of the recording medium, and the image area is controlled to come into contact with the portion of the fixing member that is heated with the high heat generation amount. The image forming apparatus according to any one of claims 1 to 4. The recording medium is supplied by changing the vertical and horizontal orientations of the recording medium, and the image area is rotated by 90 ° about the vertical axis through the center of the recording medium so that the image area is heated with the high heat generation amount. 5. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled so as to come into contact with a portion of the fixing member . The change in the vertical and horizontal orientation of the recording medium and the 90 ° rotation of the image area around the axis can be executed at a timing different from the timing when the recording medium in the recording medium container is exhausted. Image forming apparatus. The timing of supplying the recording medium to the fixing device is changed to control the image area on the recording medium so as to come into contact with the portion of the fixing member heated by the high heat generation amount . The image forming apparatus according to claim 1.

Images