Image forming apparatus

Abstract

To provide an image forming apparatus that can ensure safety while ensuring fixability of coloring materials.SOLUTION: An image forming apparatus comprises: a heat source; a fixing belt that is heated by the heat source to thermally fix coloring materials sequentially to a plurality of sheets; an operating unit that allows a user to designate the degree of fixation for fixability of the coloring materials to the plurality of sheets; and a control unit that sequentially passes the plurality of sheets through the fixing belt at a controlled paper passing amount that is a paper passing amount according to the degree of fixation per unit time.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to an image forming apparatus.

Background Art

[0002] Patent Document 1 discloses an image forming apparatus in which a standard mode and an environment mode can be switched by a user, and when the environment mode is selected, drive control of a plurality of heaters that heat a heating roller is changed to lower the temperature of an end region of the heating roller.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the image forming apparatus disclosed in Patent Document 1, for a paper that is difficult to fix due to reasons such as the surface property of the paper, the fixing property is ensured by raising the fixing temperature. However, when the fixing temperature rises and a paper that is relatively smaller in size than the fixing belt continuously passes through the fixing belt, overheating may occur in the non-paper-passing region of the fixing belt, and the fixing belt may be damaged. Therefore, an aspect of the present disclosure aims to provide an image forming apparatus that can ensure safety while ensuring the fixing property of the coloring material.

Means for Solving the Problems

[0005] An image forming apparatus according to an aspect of the present disclosure includes a heat source, a fixing belt that is heated by the heat source and thermally fixes a coloring material to each of a plurality of papers in order, an operation unit that allows a user to set a degree of fixing for the fixing property of the coloring material with respect to the plurality of papers, and a control unit that passes each of the plurality of papers through the fixing belt in order at a control paper passing amount that is a paper passing amount corresponding to the degree of fixing per unit time.

Brief Description of the Drawings

[0006]

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Mode for Carrying Out the Invention

[0007] (First Embodiment) With reference to FIGS. 1 to 15, the first embodiment will be described. Regarding the drawings, the same or similar elements are denoted by the same reference numerals, and duplicate descriptions are omitted.

[0008] FIG. 1 is a diagram showing an example of the structure of the image forming apparatus 100.

[0009] The image forming apparatus 100 forms multi-color and single-color images on a sheet according to the manuscript data transmitted from the outside, and is composed of an apparatus main body 110 and an automatic manuscript processing apparatus 120. The apparatus main body 110 includes an exposure unit 1, a developing device 2, a photosensitive drum 3, a cleaner unit 4, a charger 5, an intermediate transfer belt unit 6, a fixing unit 7, a paper feed cassette 81, a paper discharge tray 91, and the like.

[0010] On the upper part of the apparatus main body 110, there is provided a manuscript placing table 92 made of a transparent glass on which a manuscript is placed, and an automatic manuscript processing apparatus 120 is attached above the manuscript placing table 92. The automatic manuscript processing apparatus 120 automatically conveys the manuscript on the manuscript placing table 92. Further, the automatic manuscript processing apparatus 120 is configured to be rotatable, and the manuscript can be placed manually by opening the upper part of the manuscript placing table 92.

[0011] For example, the image data processed in the image forming apparatus 100 corresponds to a color image using each of the colors black (K), cyan (C), magenta (M), and yellow (Y). In that case, the developing units 2, the photosensitive drums 3, the chargers 5, and the cleaner units 4 are each provided in four units so as to form four types of latent images corresponding to each color, and are respectively set to black, cyan, magenta, and yellow, and these constitute four image stations.

[0012] The charger 5 is a charging means for uniformly charging the surface of the photosensitive drum 3 to a predetermined potential. In addition to the charger type shown in FIG. 1, a contact type roller type or brush type charger may also be used.

[0013] The exposure unit 1 is configured as a laser scanning unit (LSU) including a laser emitting unit and a reflection mirror. The exposure unit 1 is provided with a polygon mirror that scans a laser beam, and optical elements such as lenses and mirrors for guiding the laser light reflected by the polygon mirror to the photosensitive drum 3. Further, the exposure unit 1 may be composed of, for example, an EL or LED writing head in which light emitting elements are arranged in an array.

[0014] The exposure unit 1 has a function of forming an electrostatic latent image corresponding to the image data on the surface by exposing the charged photosensitive drum 3 according to the image data indicated by each of the plurality of print pages included in the print job. The developing unit 2 visualizes the electrostatic latent image formed on each photosensitive drum 3 with toner of black, cyan, magenta, and yellow. The cleaner unit 4 removes and recovers the toner remaining on the surface of the photosensitive drum 3 after development and image transfer.

[0015] The intermediate transfer belt unit 6 disposed above the photoreceptor drum 3 includes an intermediate transfer belt 61, an intermediate transfer belt driving roller 62, an intermediate transfer belt driven roller 63, an intermediate transfer roller 64, and an intermediate transfer belt cleaning unit 65. Four of the above intermediate transfer rollers 64 are provided corresponding to each color of black, cyan, magenta, and yellow.

[0016] The intermediate transfer belt driving roller 62, the intermediate transfer belt driven roller 63, and the intermediate transfer roller 64 stretch and rotationally drive the intermediate transfer belt 61. Also, each intermediate transfer roller 64 applies a transfer bias for transferring the toner image on the photoreceptor drum 3 onto the intermediate transfer belt 61.

[0017] The intermediate transfer belt 61 is provided so as to contact each photoreceptor drum 3. And it has a function of forming a color multi-color toner image on the intermediate transfer belt 61 by sequentially overlapping and transferring the toner images of each color formed on the photoreceptor drum 3 onto the intermediate transfer belt 61.

[0018] The transfer of the toner image from the photoreceptor drum 3 to the intermediate transfer belt 61 is performed by the intermediate transfer roller 64 that is in contact with the back side of the intermediate transfer belt 61. The intermediate transfer roller 64 is a roller whose surface is covered with an elastic material having conductivity. For example, the conductive elastic material is EPDM, foamed urethane, etc. With the conductive elastic material, a uniform high voltage can be applied to the intermediate transfer belt 61. In the present disclosure, a roller shape is used as the transfer electrode, but a brush or the like can also be used.

[0019] The electrostatic latent images visualized according to each color phase on each photoreceptor drum 3 are laminated on the intermediate transfer belt 61. Thus, the toner image is transferred onto the paper 201 by the transfer roller 10 disposed at the contact position between the paper and the intermediate transfer belt 61 due to the rotation of the intermediate transfer belt 61.

[0020] At this time, the intermediate transfer belt 61 and the transfer roller 10 are pressed against each other with a predetermined nip, and a voltage for transferring toner onto the paper 201 is applied to the transfer roller 10. Further, in order to constantly obtain the above nip, either the transfer roller 10 or the intermediate transfer belt driving roller 62 is made of a hard material, and the other is made of a soft material such as an elastic roller. For example, the hard material is metal or the like. Also, for example, the soft material is an elastic rubber roller, a foaming roller, or the like.

[0021] In addition, the toner adhering to the intermediate transfer belt 61 by contacting the photoreceptor drum 3, or the toner remaining on the intermediate transfer belt 61 without being transferred onto the paper 201 by the transfer roller 10, may cause toner color mixing in the next process. Therefore, it is set to be removed and recovered by the intermediate transfer belt cleaning unit 65. The intermediate transfer belt cleaning unit 65 contacts the intermediate transfer belt 61. For example, it is provided with a cleaning blade as a cleaning member, and the intermediate transfer belt 61 contacted by the cleaning blade is supported by the intermediate transfer belt driven roller 63 from the back side.

[0022] The paper feed cassette 81 is a tray for accumulating the paper used for image formation, and is provided below the exposure unit 1 of the apparatus main body 110. Also, the paper 201 used for image formation can be placed in the manual paper feed cassette 82. Further, the paper discharge tray 91 provided above the apparatus main body 110 is a tray for stacking the printed paper 201 face down.

[0023] Also, the apparatus main body 110 is provided with a substantially vertical paper conveyance path S for sending the paper 201 in the paper feed cassette 81 and the manual paper feed cassette 82 to the paper discharge tray 91 via the transfer roller 10 and the fixing unit 7. Near the paper conveyance path S from the paper feed cassette 81 or the manual paper feed cassette 82 to the paper discharge tray 91, pickup rollers 11a, 11b, a plurality of conveyance rollers 12a to 12d, a registration roller 13, a transfer roller 10, a fixing unit 7, etc. are arranged.

[0024] The conveying rollers 12a to 12d are small rollers for promoting and assisting the conveyance of the paper, and a plurality of them are provided along the paper conveyance path S. Further, the pickup roller 11a is provided near the end of the paper feed cassette 81, and picks up the paper one by one from the paper feed cassette 81 and supplies it to the paper conveyance path S. Similarly, the pickup roller 11b is provided near the end of the manual paper feed cassette 82, and picks up the paper one by one from the manual paper feed cassette 82 and supplies it to the paper conveyance path S.

[0025] Also, the registration roller 13 temporarily holds the paper being conveyed along the paper conveyance path S. Then, the paper is conveyed to the transfer roller 10 at the timing when the leading edge of the toner image on the photosensitive drum 3 and the leading edge of the paper are aligned.

[0026] Next, the paper conveyance path S will be described in detail. As described above, the image forming apparatus 100 is provided with a paper feed cassette 81 for storing the paper 201 in advance and a manual paper feed cassette 82. In order to feed the paper from these paper feed cassettes 81 and 82, pickup rollers 11a and 11b are respectively arranged to guide the paper one by one to the paper conveyance path S.

[0027] The paper conveyed from each of the paper feed cassettes 81 and 82 is conveyed to the registration roller 13 by the conveying roller 12a of the paper conveyance path S, and is conveyed to the transfer roller 10 at the timing when the leading edge of the paper and the leading edge of the image information on the intermediate transfer belt 61 are aligned, and the image information is written on the paper. Thereafter, the paper passes through the fixing unit 7 so that the unfixed toner on the paper is melted and fixed by heat, and then is discharged onto the paper discharge tray 91 through the arranged conveying roller 12b.

[0028] The paper conveyance path S is for single-sided printing requests for the paper. In contrast, for double-sided printing requests, when the trailing edge of the paper that has passed through the fixing unit 7 after single-sided printing is completed as described above is gripped by the final conveyance roller 12b, the conveyance roller 12b rotates reversely to guide the paper to the conveyance rollers 12c and 12d. Thereafter, after printing is performed on the back surface of the paper via the registration roller 13, the paper is discharged onto the discharge tray 91.

[0029] Next, with reference to FIGS. 2 to 4, the fixing unit 7 will be described in detail. FIG. 2 is a front view showing an example of the configuration of the fixing unit 7. FIG. 3 is a side view taken along the arrow D in FIG. 2. FIG. 4 is a diagram schematically showing, in the fixing belt 71, a paper passage area 401 through which the paper 201 passes, an end area 403 outside the allowable maximum size 402, and an area 404 inside the allowable maximum size 402 and outside the paper passage area 401. The end area 403 and the area 404 are non-paper passage areas through which the paper 201 does not pass.

[0030] The fixing unit 7 includes a fixing belt 71, a pressure roller 72, a heat source 73, a core material 74, a first temperature detection unit 75, and a second temperature detection unit 76.

[0031] The heat source 73 generates heat at a specified target temperature. The fixing belt 71 is heated by the heat source 73 to thermally fix the coloring material to each of the plurality of papers 201 in sequence. Specifically, the fixing belt 71, together with the pressure roller 72, thermally bonds the toner, which is the coloring material, to each of the plurality of papers 201, thereby melting, mixing, and pressing the multicolor toner images transferred to each of the plurality of papers 201, and thermally fixing them to each of the plurality of papers 201 in sequence.

[0032] The pressure roller 72 is configured to have a heat-resistant elastic material on the outer peripheral surface of the core material 74 such as iron, stainless steel, or aluminum. The pressure roller 72 is pressed against the fixing belt 71 by an elastic member such as a spring (not shown). Thereby, a nip portion having a predetermined width is formed between the fixing belt 71 and the pressure roller 72.

[0033] The fixing belt 71 and the pressure roller 72 are configured to rotate with the sheet 201 sandwiched therebetween.

[0034] The heat source 73 heats the fixing belt 71. The heat source 73 is provided inside the fixing belt 71 and is arranged along the axial direction of the fixing belt 71. For example, the heat source 73 is a halogen heater.

[0035] The first temperature detection unit 75 detects the first temperature C1 in the paper passage area 401. Specifically, the first temperature detection unit 75 detects the first temperature C1 in the area within the paper passage area where the sheet of the allowable minimum size passes through the fixing belt 71. The first temperature detection unit 75 is arranged along the paper passage area 401.

[0036] The second temperature detection unit 76 detects the second temperature C2 in the end area 403. The second temperature detection unit 76 is arranged along the end area 403.

[0037] When the sheet 201 passes through the fixing belt 71, in the paper passage area 401, heat is taken away by the sheet 201, so the first temperature detection unit 75 does not detect an abnormal temperature rise. On the other hand, in the non-paper passage area of the fixing belt 71 when the sheet 201 passes through the fixing belt 71, heat is not taken away by the sheet 201. That is, when the sheet 201 passes through the fixing belt 71, in the non-paper passage area, heat is not taken away by the sheet 201. Therefore, when the sheet 201 passes through the fixing belt 71, as the number of printed sheets increases, the temperature in the non-paper passage area becomes higher than the temperature in the paper passage area 401. Therefore, the more the number of sheets 201 passing through the fixing belt 71 increases, an over-temperature rise occurs in the non-paper passage area, and the second temperature detection unit 76 detects an abnormal temperature rise.

[0038] FIG. 5 is a block diagram showing an example of the functional configuration of the image forming apparatus 100. The image forming apparatus 100 includes an image processing unit 501, a display unit 502, an operation unit 503, a storage unit 504, and a control unit 505.

[0039] The image processing unit 501 is composed of one or more image processing circuits and executes an image forming function. The image processing unit 501 includes an image input unit 511, an image forming unit 512, a fixing unit 7, and an image output unit 513.

[0040] The image input unit 511 acquires a print job including a plurality of print pages. For example, the image input unit 511 acquires the print job by receiving a print job transmitted from a terminal device (not shown) connected to the image forming apparatus 100 via a network. For example, the terminal device is a PC (Personal Computer), a smartphone, a tablet terminal, or the like. Alternatively, it is a job for printing image data generated from a document read by the automatic document processing apparatus 120.

[0041] The image forming unit 512 forms an electrostatic latent image from the image data indicated by each of the plurality of print pages included in the print job. The image forming unit 512 is realized by a developing device 2, a photoreceptor drum 3, a charger 5, a cleaner unit 4, an exposure unit 1, an intermediate transfer belt 61, etc. illustrated in FIG. 1.

[0042] The image output unit 513 outputs the sheet on which the electrostatic latent image is formed.

[0043] The display unit 502 displays information presented to the user. For example, the display unit 502 is composed of a liquid crystal panel, an organic EL (Electro-Luminescence) panel, or the like.

[0044] The operation unit 503 receives a user operation. For example, the operation unit 503 is composed of a touch panel or the like.

[0045] The operation unit 503 enables the user to set the degree of fixing indicating the strength of the fixing property of the coloring material on a plurality of sheets. For example, the operation unit 503 enables the user to select the degree of fixing that can be set by the user from a plurality of candidates indicated by at least one of a numerical value and a character string indicating the fixing property of the coloring material.

[0046] The storage unit 504 is a recording medium capable of recording various data, programs, etc. The storage unit 504 stores control management information 514 (see FIG. 6), print jobs, etc. The control management information 514 shows the registration control values associated with the degree of fixing, the type of the paper 201, and the temperature and humidity environment. The registration control value indicates the ratio to the reference paper feed amount determined by the target temperature and the second temperature C2. The storage unit 504 is composed of a storage circuit including one or more HDDs (Hard Disk Drives), SSDs (Solid State Drives), semiconductor memories, etc.

[0047] The control unit 505 executes various processes according to the programs and data stored in the storage unit 504. For example, the control unit 505 is composed of a control circuit including a processor such as one or more CPUs (Central Processing Units).

[0048] The control unit 505 determines the control paper feed amount, which is the paper feed amount corresponding to the degree of fixing per unit time. Specifically, the control unit 505 determines the control paper feed amount according to the set degree of fixing and the type of the paper. Or, the control unit 505 determines the control paper feed amount according to the set degree of fixing, the type of the paper, and the temperature and humidity environment. Then, the control unit 505 feeds each of the plurality of papers 201 in order through the fixing belt 71 at the control paper feed amount. The control paper feed amount is determined such that the first temperature C1 is a temperature at which the coloring material can be fixed to each of the plurality of papers 201, and the second temperature C2 does not exceed the control threshold temperature. Further, when the set degree of fixing indicates that the fixing property of the coloring material is raised above the reference fixing property, the control paper feed amount is determined to be less than the reference paper feed amount, and when the degree of fixing indicates that the fixing property of the coloring material is lowered below the reference fixing property, the control paper feed amount is determined to be more than the reference paper feed amount. The reference fixing property is the degree of fixing of the coloring material used as a reference according to the target temperature.

[0049] FIG. 6 is a diagram showing an example of the control management information 514.

[0050] The control management information 514 illustrated in FIG. 6 associates registration control values with the difference from the target temperature corresponding to the degree of fixing, the type of paper which is plain paper, thick paper, special paper, envelope, thin paper, recycled paper, glossy paper, embossed paper, and OHP, and the temperature and humidity environment which is the NN environment, the HH environment, and the LL environment. The degree of fixing is indicated by, for example, the amount of temperature change from the target temperature. Also, the registration control value may be a numerical value indicating, for example, a ratio to the reference paper passing amount. Here, the NN environment indicates an environment of normal temperature and normal humidity. The HH environment indicates an environment of high temperature or high humidity. The LL environment indicates an environment of low temperature or low humidity.

[0051] The degree of fixing shown in the control management information 514 illustrated in FIG. 6 is indicated by the amount of temperature change from the target temperature. The larger the amount of temperature change indicated by the degree of fixing, the higher the fixing belt is heated. That is, it indicates that the fixability of the coloring material to the paper being passed is strong. That is, in the control management information 514 illustrated in FIG. 6, the higher the degree of fixing in the right section, the stronger the fixability.

[0052] In the control management information 514 illustrated in FIG. 6, it is shown that the degree of fixing can be changed according to the sections of 0 to 5°C, 6 to 10°C, 11 to 15°C, 16 to 20°C, and 21°C or higher. However, the degree of fixing shown in the control management information 514 illustrated in FIG. 6 is an example and is not intended to limit the degree of fixing.

[0053] For example, the control management information 514 illustrated in FIG. 6 is an environment of normal temperature and normal humidity, and for the paper 201 of the type of plain paper, it shows the registration control value of 95% of the paper passing amount associated with the degree of fixing indicated by the temperature change amount of 5°C.

[0054] Furthermore, for example, the control management information 514 illustrated in FIG. 6 is an environment of low temperature or low humidity, and for the paper 201 of the type of envelope, it shows the registration control value of 60% of the paper passing amount associated with the degree of fixing indicated by the temperature change amount of 20°C.

[0055] The control management information 514 illustrated in FIG. 6 indicates that the smaller the registered control value is, the smaller the paper feed amount per unit time is and the wider the paper feed interval is. That is, the control management information 514 illustrated in FIG. 6 indicates that the larger the temperature change amount indicated by the fixing degree is, the smaller the paper feed amount per unit time is and the wider the paper feed interval is. Therefore, the control management information 514 illustrated in FIG. 6 indicates that the larger the temperature change amount indicated by the fixing degree is, the lower the frequency at which the paper 201 is fed, and heat dissipation in the paper feed area 401 is suppressed, improving the fixability of the coloring material.

[0056] FIGS. 7 to 8 are flowcharts showing an example of the operation of the image forming apparatus 100.

[0057] When the user performs an operation of designating the fixing degree and the type of the paper 201 on the operation unit 503, in step S701, the operation unit 503 receives a fixing property change operation of designating the fixing degree, the type of the paper 201, and the temperature and humidity environment.

[0058] In step S702, the control unit 505 determines a paper feed interval control value according to the fixing degree, the type of the paper 201, and the temperature and humidity environment specified by the fixing degree setting operation received in step S701. The paper feed interval control value is the ratio of the paper feed interval to the reference paper feed interval for feeding paper at the reference paper feed amount. Specifically, in the control management information 514, the control unit 505 acquires the registered control value associated with the fixing degree, the type of the paper 201, and the temperature and humidity environment specified by the received fixing degree setting operation, and determines the paper feed interval control value from the acquired registered control value.

[0059] In step S703, the control unit 505 determines whether or not the operation unit 503 has received an operation to start printing. If the operation to start printing has not been received in step S703, the control unit 505 returns the process to step S703. On the other hand, if the operation to start printing has been received in step S703, in step S704, the control unit 505 determines the target temperature. Then, the image input unit 511 acquires a print job.

[0060] In step S705, the control unit 505 determines a reference paper feed interval for feeding paper at a reference paper feed amount according to the target temperature. The reference paper feed amount is determined by the target temperature and the second temperature C2.

[0061] In step S706, the control unit 505 determines a controlled paper feed interval based on the reference paper feed interval determined in step S705 and the paper feed interval control value determined in step S702, and determines a controlled paper feed amount which is the paper feed amount per unit time. That is, the control unit 505 determines the controlled paper feed amount by determining the paper feed interval according to the set fixing degree.

[0062] With reference to FIG. 8, the operation of the image forming apparatus 100 will be continuously described.

[0063] In step S801, the control unit 505 starts to cause the heat source 73 to generate heat so that the fixing belt 71 reaches the target temperature determined in step S704 illustrated in FIG. 7. For example, when the heat source 73 is constituted by a halogen heater, the control unit 505 causes the heat source 73 to generate heat by lighting the halogen heater so that the fixing belt 71 reaches the target temperature. Specifically, the first temperature detection unit 75 detects the temperature in the paper feed area 401, and causes the heat source 73 to generate heat by lighting the halogen heater so that the temperature detected by the first temperature detection unit 75 reaches the target temperature.

[0064] In step S802, the control unit 505 executes a process of printing a plurality of print pages included in the acquired print job on a plurality of sheets 201 respectively. Specifically, the control unit 505 sequentially conveys each of the plurality of sheets 201 so that the sheet 201 passes through the fixing belt 71 at the control paper conveyance interval determined in step S706 illustrated in FIG. 7. Then, the control unit 505 passes each of the plurality of sheets 201 through the fixing belt 71 in order at the control paper conveyance amount determined in step S706 illustrated in FIG. 7 so that the images indicated by the plurality of print pages included in the print job are sequentially formed on each of the plurality of sheets 201. Then, the control unit 505 sandwiches the sheet between the fixing belt 71 and the pressure roller 72, and thermally bonds the toner to the sheet 201, so that the fixing belt 71 mixes and presses the multicolor toner images transferred to the sheet 201, and thermally fixes them to each of the plurality of sheets 201 in order. Then, the image output unit 513 outputs each of the plurality of sheets 201 on which the multicolor toner image is thermally fixed in order.

[0065] In step S803, the control unit 505 determines whether or not the temperature of the end region 403 detected by the second temperature detection unit 76 has reached the control threshold temperature. If the temperature of the end region 403 has not reached the control threshold temperature in step S803, the control unit 505 returns the process to step S803, conveys the sheet 201 so that the sheet 201 passes through the fixing belt 71 at the control paper conveyance interval, and continues the process of printing each of the plurality of print pages included in the print job in order.

[0066] On the other hand, if the temperature of the end region 403 has reached the control threshold temperature in step S803, in step S804, the control unit 505 determines a new reference paper conveyance interval lower than the reference paper conveyance interval determined in step S705 illustrated in FIG. 7, and determines a new reference paper conveyance amount smaller than the reference paper conveyance amount determined in step S705. The new reference paper conveyance amount is determined by the target temperature set in step S807 described later and the second temperature C2.

[0067] In step S805, the control unit 505 determines a new control paper conveyance interval and a new control paper conveyance amount based on the new reference paper conveyance interval determined in step S804 and the paper conveyance interval control value determined in step S702 illustrated in FIG. 7. That is, the control unit 505 determines a new control paper conveyance amount by determining a new paper conveyance interval according to the degree of fixing.

[0068] Since the new control paper conveyance amount is less than the control paper conveyance amount determined in step S706 illustrated in FIG. 7, the new control paper conveyance interval is wider than the control paper conveyance interval determined in step S706 illustrated in FIG. 7. As a result, the control unit 505 widens the paper conveyance interval before the temperature of the end region 403 reaches the control threshold temperature. As a result, in the paper conveyance region 401, the heat necessary for the next sheet 201 to be radiated from the fixing belt 71 is suppressed, and heat is likely to be stored in the fixing belt 71. As a result, the image forming apparatus 100 can suppress the number of times the heat source 73 generates heat in order to supply heat to the paper conveyance region 401. Thereby, the image forming apparatus 100 can prevent the temperature of the non-paper conveyance region from rising excessively and can ensure safety.

[0069] In step S806, the control unit 505 determines whether or not the paper 201 has been printed on more than a predetermined number of sheets since starting to generate heat from the heat source 73 at the target temperature in step S801. In step S806, when the control unit 505 determines that the paper 201 has not been printed on more than a predetermined number of sheets since the heat source 73 started generating heat, the process returns to step S806. Then, the control unit 505 conveys the paper 201 so that the paper 201 passes through the fixing belt 71 at the new control paper conveyance interval determined in step S805, and continues the process of sequentially printing each of the plurality of print pages included in the print job.

[0070] On the other hand, when the paper 201 has been printed on more than a predetermined number of sheets in step S806, in step S807, the control unit 505 reduces the target temperature and causes the heat source 73 to generate heat.

[0071] In step S808, the control unit 505 determines whether to end the printing. If not all the print pages included in the print job have been printed, the control unit 505 determines not to end the printing. On the other hand, if all the print pages included in the print job have been printed, the control unit 505 determines to end the printing.

[0072] If it is determined in step S808 not to end the printing, the control unit 505 returns the process to step S808, conveys the sheet 201 so that the sheet 201 passes through the fixing belt 71 at the new control paper passing interval determined in step S805, and continues the process of sequentially printing each of the plurality of print pages included in the print job. On the other hand, if it is determined in step S808 to end the printing, the control unit 505 ends heating the heat source 73 and ends the printing process.

[0073] FIG. 9 is a graph showing an example of temperature transition when the sheet 201 passes through the fixing belt 71 at the reference paper passing amount for all the prints included in the print job. In FIG. 9, time is taken on the horizontal axis and temperature is taken on the vertical axis. Specifically, FIG. 9 shows the target temperature 901, the temperature 902 of the paper passing area 401 detected by the first temperature detection unit 75, the temperature 903 of the end area 403 detected by the second temperature detection unit 76, and the temperature 904 of the area 404. The temperature 904 of the area 404 indicates an estimated value calculated from the temperature 903 of the end area 403.

[0074] At time point T911, the control unit 505 starts heating the heat source 73 so that the fixing belt 71 reaches the target temperature 901. Then, the control unit 505 sequentially conveys each of the plurality of sheets 201 so that each of the plurality of sheets 201 passes through the fixing belt 71 at a paper passing amount of 40 CPM (Count Per Minute).

[0075] In the end region 403, heat is dissipated in the axial direction of the fixing belt 71 and in the direction in which the sheet 201 passes, which is perpendicular to the axial direction of the fixing belt 71. On the other hand, in the region 404, heat is dissipated in the direction in which the sheet 201 is fixed, which is perpendicular to the axial direction of the fixing belt 71, and no heat is dissipated in the axial direction of the fixing belt 71. Therefore, as illustrated in FIG. 9, the temperature 904 of the region 404 becomes higher than the temperature 903 of the end region 403. Thus, in order to prevent the fixing belt 71 from being damaged due to the increase in the temperature 904 of the region 404, as illustrated in FIG. 9, it is necessary to secure a margin M1 up to the belt damage temperature, which is the temperature at which the fixing belt 71 is damaged, for the temperature 904 of the region 404.

[0076] When the temperature 903 reaches the control threshold temperature at time point T912, the control unit 505 conveys the sheet 201 so that the sheet 201 passes through the fixing belt 71 at a new sheet passing amount of 30 CPM. Since the sheet passing amount per unit time decreases and the sheet passing interval widens, in the sheet passing region 401, heat required for the next sheet 201 is suppressed from being dissipated from the fixing belt 71, and heat is likely to be stored in the fixing belt 71. As a result, the image forming apparatus 100 can suppress the number of times the heat source 73 generates heat in order to supply heat to the sheet passing region 401. Thereby, the image forming apparatus 100 can prevent the temperature 903 of the end region 403 and the temperature 904 of the region 404 from rising excessively.

[0077] After the time point T912, as the sheet passing interval widens, the temperature 903 of the end region 403 and the temperature 904 of the region 404 temporarily decrease. However, since the heat source 73 generates heat to supply heat required for the sheet passing region 401, the temperature 903 of the end region 403 and the temperature 904 of the region 404 rise again.

[0078] Therefore, when the heat source 73 starts to generate heat at the target temperature 901 at time T913, if the number of sheets printed on the paper 201 reaches a predetermined number or more, the control unit 505 reduces the target temperature 901. As a result, the image forming apparatus 100 can suppress the increase in the temperature 903 of the end region 403 and the temperature 904 of the region 404, which are the temperatures of the non-paper-passing regions.

[0079] FIG. 10 is a diagram showing an example of temperature transition when the target temperature 1001 is increased by 15° C. from the target temperature 901 illustrated in FIG. 9 and the paper 201 passes through the fixing belt 71 at the reference paper passing amount for all the print pages included in the print job. In FIG. 10, time is taken on the horizontal axis and temperature is taken on the vertical axis. Specifically, FIG. 10 shows the target temperature 1001, the temperature 1002 of the paper-passing region 401 detected by the first temperature detection unit 75, the temperature 1003 of the end region 403 detected by the second temperature detection unit 76, and the temperature 1004 of the region 404. The temperature 1004 of the region 404 indicates an estimated value calculated from the temperature 1003 of the end region 403.

[0080] At time T1011, the control unit 505 starts to cause the heat source 73 to generate heat so that the fixing belt 71 reaches the target temperature 1001. Then, the control unit 505 sequentially conveys each of the plurality of sheets of paper 201 so that each of the plurality of sheets of paper 201 passes through the fixing belt 71 at a paper passing amount of 40 CPM.

[0081] As illustrated in FIG. 10, when the target temperature 1001 is 15° C. higher than the target temperature 901, if the temperature 1003 of the end region 403 exceeds the control threshold temperature at time T1012. In that case, there is a risk that the temperature 1004 of the region 404 exceeds the belt damage temperature. That is, in order to ensure the fixability of the coloring material, when the target temperature 1001 increases and the temperature 1002 of the paper-passing region 401 increases, there is a risk that the temperature 904 of the region 404 exceeds the belt damage temperature.

[0082] Therefore, after time point T1012, the control unit 505 conveys the sheet 201 so that the sheet 201 passes through the fixing belt 71 at a new sheet passing rate of 30 CPM. However, since the target temperature 1001 is 15°C higher than the target temperature 901, the temperature 1003 in the end region 403 decreases more gently than the temperature 903 illustrated in FIG. 9. Similarly, since the target temperature 1001 is 15°C higher than the target temperature 901, the temperature 1004 in the region 404 decreases more gently than the temperature 904 illustrated in FIG. 9. Therefore, since the target temperature 1001 is 15°C higher than the target temperature 901, the margin M2 to the belt damage temperature is smaller than the margin M1 illustrated in FIG. 9, and there is a possibility that the margin M2 to the belt damage temperature cannot be sufficiently ensured.

[0083] FIG. 11 is a graph showing an example of temperature transition when the sheet 201 passes through the fixing belt 71 at the controlled sheet passing rate for all the printed pages included in the print job. In FIG. 11, time is taken on the horizontal axis and temperature is taken on the vertical axis. Specifically, FIG. 11 shows the target temperature 1101, the temperature 1102 in the sheet passing region 401 detected by the first temperature detection unit 75, the temperature 1103 in the end region 403 detected by the second temperature detection unit 76, and the temperature 1104 in the region 404. The temperature 1104 in the region 404 shows an estimated value calculated from the transition of the temperature 1103 in the end region 403.

[0084] In this example, it is assumed that the control unit 505 acquires a registration control value of 50% in step S702 illustrated in FIG. 7. Further, in this example, it is assumed that the control unit 505 determines a reference sheet passing rate of 40 CPM in step S705 illustrated in FIG. 7. In that case, the control unit 505 determines a controlled sheet passing rate of 20 CPM (= 40 CPM × 0.5) in step S706 illustrated in FIG. 7. The reference sheet passing rate is determined by the target temperature. For example, when the registration control value acquired in step S702 indicates the ratio to the reference sheet passing rate, the controlled sheet passing rate is determined by the ratio indicated by the registration control value with respect to the reference sheet passing rate.

[0085] At time T1111, the control unit 505 starts to heat the heat source 73 so that the fixing belt 71 reaches the target temperature 1101. Then, the control unit 505 conveys the sheet 201 so that the sheet 201 passes through the fixing belt 71 at a control paper conveyance amount of 20 CPM.

[0086] By causing the control unit 505 to pass the sheet 201 at a control paper conveyance amount of 20 CPM, in the paper conveyance area 401, heat required for the next sheet 201 is suppressed from radiating from the fixing belt 71, and heat is likely to be stored in the fixing belt 71. As a result, as illustrated in FIG. 11, without the control unit 505 increasing the target temperature 1101, the temperature 1102 in the paper conveyance area 401 becomes higher than the temperature 902 illustrated in FIG. 9.

[0087] When the temperature 1103 reaches the control threshold temperature at time T1112, in step S804 illustrated in FIG. 8, the control unit 505 determines a new reference paper conveyance amount of 30 CPM. Then, in step S805 illustrated in FIG. 8, the control unit 505 determines a new control paper conveyance amount of 15 CPM (= 30 CPM × 0.5). For example, when the registered control value acquired in step S702 indicates a ratio to the reference paper conveyance amount, the new control paper conveyance amount is determined by the ratio indicated by the registered control value with respect to the new reference paper conveyance amount.

[0088] The control unit 505 sequentially conveys each of the plurality of sheets 201 so that each of the plurality of sheets 201 passes through the fixing belt 71 at a new control paper passing amount of 15 CPM. As the paper passing interval widens, the control unit 505 suppresses the heat necessary for the next sheet 201 to dissipate from the fixing belt 71 in the paper passing area 401 without increasing the target temperature, and makes it easier for heat to be stored in the fixing belt 71. As a result, the image forming apparatus 100 can improve the fixability in the paper passing area 401 of the fixing belt 71 without excessively heating the fixing belt 71. Further, since the control unit 505 does not increase the target temperature, it is possible to prevent the non-paper passing area of the fixing belt 71 from being excessively heated. As a result, the image forming apparatus 100 can ensure the fixability of the coloring material without excessively heating the fixing belt 71, and can secure a margin M3 up to the belt damage temperature for the temperature 1104 in the area 404. Therefore, the image forming apparatus 100 can ensure safety while ensuring the fixability of the coloring material.

[0089] At time point T1113, when printing is performed on the sheet 201 for a predetermined number of sheets or more after starting the heat generation of the heat source 73 at the target temperature 901 in step S801 illustrated in FIG. 8, the control unit 505 reduces the target temperature 1101 and causes the heat source 73 to generate heat in step S807 illustrated in FIG. 8. Thereby, the image forming apparatus 100 can suppress an increase in the temperature 1103 of the end area 403 and the temperature 1104 of the area 404, which are the temperatures of the non-paper passing area.

[0090] FIGS. 12 to 15 are diagrams showing an example of the display unit 502 and the operation unit 503 configured by a touch panel display.

[0091] FIG. 12 is a diagram showing an example of a key indicating the degree of fixing for the type of paper 201 that is cardboard, thin paper, and recycled paper. The regions 1201, 1202, and 1204 illustrated in FIG. 12 are each in a normal temperature and normal humidity environment, and show the degree of fixing indicated by the amount of temperature change from the target temperature for the type of paper 201 that is cardboard, thin paper, and recycled paper. The region 1203 illustrated in FIG. 12 is in a low temperature and low humidity environment, and shows the degree of fixing indicated by the amount of temperature change from the target temperature for the type of paper 201 that is thin paper.

[0092] FIG. 13 is a diagram showing an example of a key indicating the degree of fixing for the type of paper 201 that is recycled paper, glossy paper, envelopes, and embossed paper. The region 1301 illustrated in FIG. 13 is in a low temperature and low humidity environment, and shows the degree of fixing indicated by the amount of temperature change from the target temperature for the type of paper 201 that is recycled paper. The regions 1302 to 1304 illustrated in FIG. 13 are each in a normal temperature and normal humidity environment, and show the degree of fixing indicated by the amount of temperature change from the target temperature for the type of paper 201 that is glossy paper, envelopes, and embossed paper.

[0093] FIG. 14 is a diagram showing an example of a key indicating the degree of fixing for the type of paper 201 that is plain paper and OHP. The regions 1401 and 1403 illustrated in FIG. 14 are each in a normal temperature and normal humidity environment, and show the degree of fixing indicated by the amount of temperature change from the target temperature for the type of paper 201 that is plain paper and OHP. The region 1402 illustrated in FIG. 14 is in a low temperature and low humidity environment, and shows the degree of fixing indicated by the amount of temperature change from the target temperature for the type of paper 201 that is plain paper.

[0094] Regions 1201 to 1204 illustrated in FIG. 12, regions 1301 to 1304 illustrated in FIG. 13, and regions 1401 to 1403 illustrated in FIG. 14 include keys indicating temperature change amounts from the target temperature of -20°C, -15°C, -10°C, 0°C, +5°C, +10°C, +15°C, and +20°C. The greater the temperature change amount from the target temperature, the higher the fixing property of the coloring material is shown. On the other hand, the greater the temperature change amount from the target temperature, the lower the fixing property of the coloring material is shown.

[0095] For example, when a user performs an operation of printing on a sheet 201 of a type that is plain paper in a low-temperature and low-humidity environment, it is assumed that the user performs a fixing property change operation to specify the degree of fixing indicated by the temperature change amount from the target temperature. In that case, the user performs a fixing property change operation on the operation unit 503 to specify the degree of fixing indicated by the temperature change amount from region 1402 to the target temperature. As a result, in step S701 illustrated in FIG. 7, the operation unit 503 receives a fixing property change operation that specifies the degree of fixing indicated by the temperature change amount selected from region 1402, the type of the sheet 201 that is plain paper, and the temperature and humidity environment that is a low-temperature and low-humidity environment. Then, in step S702 illustrated in FIG. 7, the control unit 505 acquires, in the control management information 514, the registered control value associated with the degree of fixing selected from region 1402, the type of the sheet 201 that is plain paper, and the temperature and humidity environment that is a low-temperature and low-humidity environment.

[0096] FIG. 15 is a diagram showing an example of a key indicating the degree of fixing for a type of paper 201 which is cardboard and special paper. The regions 1501 to 1502 illustrated in FIG. 15 are each in a low-temperature and low-humidity environment, and show the degree of fixing indicated by a temperature change amount smaller than the temperature change amounts illustrated in FIGS. 12 to 14 for the type of paper 201 which is cardboard and special paper. The regions 1503 to 1504 illustrated in FIG. 15 are each in a high-temperature and high-humidity environment, and show the degree of fixing indicated by a temperature change amount smaller than the temperature change amounts illustrated in FIGS. 12 to 14 for the type of paper 201 which is cardboard and special paper. The regions 1501 to 1504 illustrated in FIG. 15 include keys indicating -10°C, -7°C, -5°C, -3°C, 0°C, +3°C, +5°C, +7°C, +10°C which are the temperature change amounts from the target temperature.

[0097] As illustrated in FIGS. 12 to 15, the image forming apparatus 100 can cause the user to specify the type of paper 201, the temperature and humidity environment, and the degree of fixing. Then, the image forming apparatus 100 determines the control paper feed amount according to the specified degree of fixing, the specified type of paper 201, and the temperature and humidity environment.

[0098] When the operation unit 503 receives a fixing property change operation for specifying the degree of fixing indicated by a temperature change amount indicating 0°C, the control unit 505 determines the reference paper feed amount as the control paper feed amount.

[0099] From the above, when the image forming apparatus 100 receives a fixing property change operation for specifying the temperature change amount from the target temperature by the user, without changing the target temperature, by changing the paper feed amount per unit time, the fixing property of the color material is ensured. Thereby, when the image forming apparatus 100 continuously passes small-sized paper through the fixing belt 71 without changing the fixing temperature, while ensuring the fixing property of the color material, the temperature rise in the non-paper feed region can be suppressed and a margin up to the belt damage temperature can be ensured, and safety can be ensured.

[0100] (Modification example) As a modification example of the image forming apparatus 100, the fixing degree may be indicated by at least one of a numerical value and a character string indicating the fixability of the toner. For example, the character string indicating the fixability of the toner is "weak", "medium", or "strong", or "-1", "0", "+1", etc.

[0101] FIG. 16 is a diagram showing an example of the control management information 514 according to this modification example. The control management information 514 illustrated in FIG. 16 shows the registration control value associated with the fixing degree.

[0102] The fixing degree shown in the control management information 514 illustrated in FIG. 16 indicates a numerical value from 1 to 5 indicating the strength of the fixability of the toner. The larger the numerical value indicated by the fixing degree, the stronger the fixability of the toner. Also, the registration control value shown in the control management information 514 illustrated in FIG. 16 indicates the ratio to the reference paper feed amount. The larger the registration control value shown in the control management information 514 illustrated in FIG. 16, the smaller the paper feed amount per unit time and the wider the paper feed interval. Therefore, in the control management information 514 illustrated in FIG. 17, the larger the numerical value indicated by the fixing degree, the lower the frequency of the sheet 201 passing through the fixing belt 71 in the paper feed area 401, and heat dissipation in the paper feed area 401 is suppressed.

[0103] FIG. 17 is a diagram showing an example of a key indicating the fixing degree indicating the strength of the fixability of the toner. The area 1701 illustrated in FIG. 17 includes keys indicating the fixing degrees from 0 to 5. A fixing degree of 0 indicates that the sheet 201 passes through the fixing belt 71 at the reference paper feed interval. When the user performs an operation of selecting any one of the keys indicating 0 to 5 from the area 1701 on the operation unit 503, in step S701 illustrated in FIG. 7, the operation unit 503 receives a fixing property change operation for specifying the fixing degree indicated by the key selected from the area 1701. Then, the control unit 505 executes the processes of steps S704 to S706 to determine the controlled paper feed amount corresponding to the fixing degree indicated by the key selected from the area 1701 in the control management information 514 illustrated in FIG. 16.

[0104] As described above, the image forming apparatus 100 according to this modification example can easily cause the user to select the degree of fixing even when the user does not recognize the relationship between the fixing temperature and the fixability, by indicating the degree of fixing with a numerical value or a character string different from the temperature change amount.

[0105] Each process executed in the above embodiment is not limited to the processing modes exemplified in each embodiment. The functional blocks described above may be realized by either a logic circuit (hardware) formed in an integrated circuit or the like, or software using a CPU. Each process executed in the above embodiment may be executed by a plurality of computers. For example, some of the processes executed by the image forming apparatus 100 may be executed by another computer, or all of the processes may be executed in cooperation by a plurality of computers.

[0106] The present disclosure is not limited to the above embodiments, and may be replaced with a configuration that is substantially the same as the configuration shown in the above embodiments, a configuration that exhibits the same operational effects, or a configuration that can achieve the same object. The present disclosure also includes embodiments obtained by appropriately combining the technical means disclosed in different embodiments. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

Description of Reference Numerals

[0107] 1 Exposure unit, 2 Developing unit, 3 Photoconductor drum, 4 Cleaner unit, 5 Charger, 6 Intermediate transfer belt unit, 7 Fixing unit, 10 Transfer roller, 11a - 11b Pickup rollers, 12a - 12d Conveyor rollers, 13 Resist roller, 61 Intermediate transfer belt, 62 Intermediate transfer belt drive roller, 63 Intermediate transfer belt driven roller, 64 Intermediate transfer roller, 65 Intermediate transfer belt cleaning unit, 71 Fixing belt, 72 Pressing roller, 73 Heat source, 74 Core material, 75 First temperature detection unit, 76 Second temperature detection unit, 81 - 82 Paper feed cassette, 91 Paper discharge tray, 92 Original document placement table, 100 Image forming apparatus, 110 Apparatus main body, 120 Automatic original document processing apparatus, 201 Paper, 401 Paper passing area, 402 Allowable maximum size, 403 End area, 404 Area, 501 Image processing unit, 502 Display unit, 503 Operation unit, 504 Memory unit, 505 Control unit, 511 Image input unit, 512 Image forming unit, 513 Image output unit, 514 Control management information, 901 Target temperature, 902 - 904 Temperatures, 1001 Target temperature, 1002 - 1004 Temperatures, 1101 Target temperature, 1102 - 1104 Temperatures, 1201 - 1204 Areas, 1301 - 1304 Areas, 1401 - 1403 Areas, 1501 - 1504 Areas, 1701 Area

Claims

1. A heat source, A fixing belt heated by the heat source to sequentially heat-fix a coloring material to each of a plurality of sheets, An operation unit that enables a user to specify a fixing degree with respect to the fixability of the coloring material on the plurality of sheets, A control unit that sequentially feeds each of the plurality of sheets through the fixing belt at a control paper feed amount that is a paper feed amount corresponding to the fixing degree per unit time, comprising An image forming apparatus.

2. A first temperature detection unit that detects a first temperature within a region where a sheet of the minimum allowable size passes through the fixing belt, A second temperature detection unit that detects a second temperature in an end region outside the maximum allowable size in the fixing belt, comprising The control paper feed amount is determined such that the first temperature is a temperature at which the coloring material can be fixed to each of the plurality of sheets and the second temperature does not exceed a control threshold temperature. The image forming apparatus according to claim 1.

3. The heat source generates heat at a specified target temperature, The control paper feed amount is determined by a ratio corresponding to the fixing degree with respect to a reference paper feed amount determined by the target temperature and the second temperature. The image forming apparatus according to claim 2.

4. When the fixing degree indicates that the fixability of the coloring material is increased from the reference fixability, the control paper feed amount is less than the reference paper feed amount, and when the fixing degree indicates that the fixability of the coloring material is decreased from the reference fixability, the control paper feed amount is more than the reference paper feed amount. The image forming apparatus according to claim 3.

5. The control unit determines the control paper feed amount by determining a paper feed interval according to the fixing degree. The image forming apparatus according to claim 1 or 2.

6. An image input unit that acquires a print job further comprising The control unit passes each of the plurality of sheets through the fixing belt in the control paper feed amount so that images indicated by each of the plurality of print pages included in the print job are sequentially formed on each of the plurality of sheets. The image forming apparatus according to claim 1 or 2.

7. The control unit determines the control paper feed amount according to the degree of fixing and the type of paper. The image forming apparatus according to claim 1 or 2.

8. The control unit determines the control paper feed amount according to the degree of fixing, the type of paper, and the temperature and humidity environment. The image forming apparatus according to claim 1 or 2.

9. The degree of fixing is indicated by the amount of temperature change from the target temperature. The image forming apparatus according to claim 3.

10. The operation unit enables the user to select a candidate indicating the degree of fixing from a plurality of candidates indicated by at least one of a numerical value and a character string indicating the fixability of the color material. The image forming apparatus according to claim 1 or 2.

Images