JP2005345774A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To heat a heat member in real time so as to have a proper temperature distribution, even when images are formed mixed on recording media of different sizes. <P>SOLUTION: A copying machine 100 as an image forming apparatus includes an image forming means 20 for forming a toner image onto a recording medium, based on image information for image formation to be carried out; a heat roller 41 as a heat member for heating a toner image on the recording medium; a pressure member 45 for applying pressure to the recording medium, with the toner image formed thereon; an induction coil 43, as a heating means, for heating the middle section of the heat roller 41 in the widthwise direction of paper passage; induction coils 42 and 44 for heating both ends of the heat roller 41 in the widthwise direction of the paper passage; and a control means 10 for exerting power supply control by altering a power supply pattern for each of induction coils 42, 43, and 44 according to the size of a recording medium being fed to the image forming means 20, which is detected by a paper size detecting means 61 as a medium size detecting means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus.

  Conventionally, when an image is recorded on a recording sheet in a laser-type image forming apparatus, the surface of the photosensitive drum is charged by a charging unit, and the charging surface is exposed by an exposure unit based on image information. A latent image is formed, toner is attached to the electrostatic latent image to develop the toner image, and the toner image is transferred to a recording sheet. Then, the transferred recording paper is heated and pressed by a fixing device to form an image on the recording paper.

  The fixing device has a heating roller and a pressure member as heating members, and the recording paper is passed through the nip portion for fixing. The heating roller is heated by heat generation by energization of a halogen lamp, IH (Induction Heating) (electromagnetic induction heating), or the like. In the electromagnetic induction heating, a coil is provided in the vicinity of a heating roller such as a metal, and a magnetic field generated by energizing the coil is applied to the heating roller and heated by the Joule loss of the generated eddy current.

  In the fixing device, the temperature of the heating roller is lost when the recording paper is passed, and temperature unevenness occurs in the heating roller. This temperature unevenness may cause over-fixing or under-fixing (insufficiency) such as offset, and may cause image unevenness on the recording paper. For this reason, temperature control of the fixing device for preventing image unevenness has been considered.

  For example, the temperature of the heating roller is detected during an image forming operation, and it is determined that the detected temperature is not an appropriate temperature based on the detected temperature and paper size information input from the scanner's ADF (Automatic Document Feeder) or the operation panel. In such a case, a configuration is considered in which the paper feeding operation and the image forming operation are interrupted and the paper feeding operation is resumed after waiting until the heating roller reaches an appropriate temperature (see, for example, Patent Document 1).

In addition, the heating roller of the fixing device can be heated separately at the central portion and the two end portions, and the heating portion is changed according to the size of the recording paper to be fixed. A configuration for reducing temperature unevenness has been considered (see, for example, Patent Document 2).
JP 2001-272897 A JP 2002-23557 A

  However, the conventional configuration in which the paper feeding operation and the image forming operation are interrupted until the heating roller reaches an appropriate temperature has a problem that the image forming speed is lowered. Further, in the conventional configuration in which the heated portion of the heating roller is changed according to the size of the recording paper to be fixed, when the image is formed by mixing recording papers of different sizes, there is a possibility that the temperature unevenness of the heating roller may occur. was there.

An object of the present invention is to heat a heating member to an appropriate temperature distribution in real time even when an image is formed by mixing recording media of different sizes.

In order to solve the above problem, the invention according to claim 1
Image forming means for forming a toner image on a recording medium based on image data to be imaged;
A heating member for heating the toner image on the recording medium;
A recording medium on which the toner image is formed, and a pressure member;
A plurality of heating means for respectively heating a plurality of portions in the sheet passing width direction of the heating member;
An image forming apparatus comprising: a control unit that performs energization control by changing an energization pattern of the plurality of heating units according to a size of a recording medium being fed to the image forming unit.

The invention described in claim 2
Image forming means for forming a toner image on a recording medium based on image data to be imaged;
A heating member for heating the toner image on the recording medium;
A pressure member that pressurizes the recording medium on which the toner image is formed;
A plurality of heating means for respectively heating a plurality of portions in the sheet passing width direction of the heating member;
In accordance with the size of the first recording medium instructed to form an image, the energization pattern of the plurality of heating units is initially set to perform energization control, and according to the size of the recording medium being fed to the image forming unit, An image forming apparatus comprising: a control unit that performs energization control by changing energization patterns of the plurality of heating units.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect,
A medium size detecting unit that is provided on a conveyance path through which the recording medium passes in common in the front side feeding and the back side feeding to the image forming unit, and detects the size of the recording medium conveyed on the conveyance path; Prepared,
The control means performs energization control by changing energization patterns of the plurality of heating means according to the size of the recording medium detected by the medium size detection means.

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect,
The control unit is configured to control the plurality of heating units according to the size of the recording medium detected by the size detecting unit at a predetermined time period or a predetermined number of passage times of the recording medium detected by the medium size detecting unit. The energization control is performed by changing the energization pattern.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects,
The plurality of heating means can switch energization of each heating means,
The control means performs energization control by changing the energization ratio of each heating means based on the energization switching time ratio of the plurality of heating means.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects,
The plurality of heating units include a first heating unit that heats a central portion of the heating member in the sheet passing width direction, and a second heating unit that heats both end portions of the heating member in the sheet passing width direction. It is characterized by.

  According to the first aspect of the present invention, since the energization control is performed by changing the energization pattern of the plurality of heating units according to the size of the recording medium being fed to the image forming unit, recording media of different sizes are mixed. Even in the case of forming an image, the heating member can be heated to an appropriate temperature distribution in real time. In particular, it is effective for a heating member having a small heat capacity and a rapid temperature change.

  According to the second aspect of the present invention, the energization pattern of the plurality of heating units is initialized and energization control is performed according to the size of the first recording medium instructed to form an image, and the image forming unit is fed. The energization control is performed by changing the energization pattern of the plurality of heating means in accordance with the size of the recording medium in the medium. While being able to heat to suitable temperature distribution, a heating member can be heated to suitable temperature distribution in real time. In particular, it is effective for a heating member having a small heat capacity and a rapid temperature change.

  According to the invention described in claim 3, since the size of the recording medium conveyed on the conveyance path through which the recording medium passes is detected in common for the front surface feeding and the back surface feeding, in the image formation on one side and both sides. However, the heating member can be heated to an appropriate temperature distribution in real time.

  According to the fourth aspect of the present invention, the energization patterns of the plurality of heating means are changed in accordance with the size of the recording medium being fed at a predetermined time period or a predetermined number of times of passage of the detected recording medium. Since the energization control is performed, the change timing of the energization pattern can be made appropriate according to the followability from the recording medium size detection to the heating member temperature change.

  According to the invention described in claim 5, since the energization control is performed by changing the energization ratio of the plurality of heating means and switching the energization of each heating means, the heating means is compared with the configuration in which each heating means is energized simultaneously. Power consumption can be reduced.

  According to the sixth aspect of the invention, the central portion and both end portions of the heating member in the sheet passing width direction can be heated to an appropriate temperature distribution in real time by the first and second heating means.

  Hereinafter, first and second embodiments of the present invention will be described in order with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

(First embodiment)
A first embodiment according to the present invention will be described with reference to FIGS. First, the features of the apparatus according to the present embodiment will be described with reference to FIGS. FIG. 1 shows an internal configuration of the copying machine 100 according to the present embodiment. FIG. 2 shows the configuration of the image forming unit 20. FIG. 3 shows the configuration of the recording paper conveyance path. FIG. 4 shows the configuration of the paper size detection means 61.

  As shown in FIG. 1, a copying machine 100 as an image forming apparatus that forms and records an image on a recording medium by toner fixing includes a control unit 10, an image forming unit 20, a high frequency power supply 30, a fixing device 40, and the like. , Operation means 50, paper transport means 60, paper size detection means 61 provided on the paper transport path, storage means 81, scanner 82, and communication means 83.

  The fixing device 40 includes a heating roller 41 as a heating member, induction coils 42, 43, and 44 as heating means, a pressure member 45, and temperature detection means 46 and 47.

  In the present embodiment, the copying machine 100 is used as an image forming apparatus, but the image forming apparatus is not limited to this, and has at least an image recording function on a recording medium such as a printer or an MFP (Multi Function Printer). An image forming apparatus may be used.

  The control unit 10 includes a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), and the like, and controls each unit in the copying machine 100.

  The image forming unit 20 forms an image on a recording sheet as a recording medium under the control of the control unit 10. The recording medium is not limited to the recording paper, and may be another recording medium such as an OHP sheet.

  Here, with reference to FIG. 2, the configuration in the image forming means 20 will be described. Around the photosensitive drum 21, a static eliminating unit 22, a charging unit 23, an exposure unit 24, a developing unit 25, a transfer unit 26, and a cleaner 27 are sequentially arranged in the arrow direction. The transfer unit 26 includes a transfer electrode 26A and a separation electrode 26B.

  A temperature sensor 28 that detects the surface temperature of the photosensitive drum 21 and a potential sensor 29 that detects the surface potential of the photosensitive drum 21 are provided around the photosensitive drum 21. Based on the temperature information from the temperature sensor 28 and the surface potential information from the photosensitive drum 21, the temperature and potential state of the photosensitive drum 21 are controlled to be appropriate.

  In forming an image, first, the photosensitive drum 21 rotates in the direction of the arrow, and the surface of the photosensitive drum 21 is neutralized by a neutralizing unit 22 such as an LED. Then, the charging surface of the photosensitive drum 21 is negatively charged by the charging unit 23. Then, a laser light signal corresponding to the image data to be imaged is emitted from the exposure means 24, and the charged surface of the photosensitive drum 21 is made positive based on the light signal to form an electrostatic latent image. Then, the negatively charged toner by the developing unit 25 is attached to the positive electrostatic portion of the charging surface of the photosensitive drum 21 to develop the toner image. Then, the recording paper P is supplied by the paper conveying means 60 and conveyed toward the toner image on the photosensitive drum 21.

  The recording electrode P is charged by the transfer electrode 26A so as to be in pressure contact with the developing surface of the photosensitive drum 21, and the toner image on the photosensitive drum 21 is attracted to the recording paper P and transferred. Then, the charged recording paper P is neutralized by the separation electrode 26B, and the recording paper P is separated from the photosensitive drum 21. Thereafter, the recording paper P on which the toner image is recorded is heated and pressurized by the fixing device 40 to fix the toner image, and is conveyed to the paper discharge tray. Then, the toner remaining on the surface of the photosensitive drum 21 is removed by the cleaner 27, and the process returns to the charge removal process by the charge removal unit 22 again.

  In addition, as shown in FIG. 1, the high frequency power supply 30 inputs a high frequency power supply current to the induction coils 42, 43, 44 in accordance with an instruction from the control means 10. The high frequency power supply 30 includes two circuits, a circuit that inputs a power supply current to the induction coils 42 and 44 and a circuit that inputs a power supply current to the induction coil 43.

  The fixing device 40 heats and pressurizes the toner image on the photosensitive drum of the image forming unit 20 and fixes the recording sheet conveyed by the paper conveying unit 60. The heating roller 41 is rotatable about an axis, generates an eddy current in the roller by a magnetic field generated by energizing the induction coils 42, 43, and 44, and generates heat by the Joule loss. The pressure member 45 is configured by a roller, a belt, or the like, and presses the roller surface of the heating roller 41 to form a nip portion. When the recording paper on which the toner image is formed passes through the nip portion, the image is recorded by being heated and pressurized.

  The heating roller 41 is assumed to be thin with a thickness of 0.6 to 0.7 mm, for example. This is to shorten the warm-up time. Such a thin-walled product is likely to have an unstable surface temperature due to a change in temperature caused by paper passing. Further, the heating roller 41 may have a normal thickness or a thick thickness.

  The induction coils 42, 43, 44 are provided in the heating roller 41, and a power source current is input from the high frequency power source 30 to generate a magnetic field. The high-frequency power supply 30 inputs a power supply current that can be alternately switched in time between the induction coil 42 and the induction coils 43 and 44. The induction coils 42 and 44 are provided at positions for heating both end portions of the heating roller 41 in the axial direction. The induction coil 43 is provided at a position for heating the central portion of the heating roller 41 in the axial direction. In addition, the induction coils 42 and 44 shall be comprised on one circuit.

  The induction coils 42, 43, 44 are configured to have windings circumferentially around the axis of the heating roller 41. However, the induction coils 42, 43, 44 have a hairpin shape in which windings are formed in parallel to the axis of the heating roller 41. It is good also as a structure and another structure. In addition, the induction coils 42, 43, 44 are not limited to the configuration provided inside the heating roller 41, and may be a configuration provided near the outside of the heating roller 41.

  The temperature detection means 46 and 47 are temperature sensors such as a thermistor, and output detected temperature information to the control means 10. The temperature detection means 46 is provided in the vicinity of the central portion of the heating roller 41 and detects the temperature of the central portion of the heating roller 41. The temperature detection means 47 is provided in the vicinity of one end of the heating roller 41 and detects the temperature of one end of the heating roller 41 (for example, a portion corresponding to the induction coil 44 in the present embodiment). For example, when an abnormal temperature is detected by the temperature detection means 46 and 47, the image forming operation is stopped.

  The paper transport unit 60 includes a transport roller and the like, and transports a recording paper as an image recording medium under the control of the control unit 10. The paper size detection unit 61 is provided on a conveyance path through which the recording paper passes in common for the front surface conveyance and the back surface conveyance in conveyance to the image forming unit 20 (transfer unit 26), and determines the size of the recording paper being conveyed. Detected and outputs the conveyed paper size information to the control means 10.

  Here, the conveyance path of the recording paper will be described with reference to FIG. The copying machine 100 includes a paper feed tray 70 that stores recording paper before image formation. The paper feed tray 70 is provided with a plurality of trays, and recording paper is accommodated in each tray in addition to the paper size, paper type (plain paper, recycled paper, etc.), and back paper. In this embodiment, trays 70A, 70B, and 70C are provided according to the paper size. The paper transport unit 60 includes transport rollers provided on the transport path in FIG. 3, and transports the recording paper by rotationally driving the transport rollers.

  At the time of image formation, first, recording sheets accommodated in the trays 70A, 70B, and 70C are conveyed through the paper feed path 62. Then, according to the image formation timing of the image forming unit 20, the recording paper is conveyed through the conveyance path 63 by the registration rollers 6 </ b> A and is fed to the transfer unit 26 of the image forming unit 20. This process is referred to as surface feeding of the recording paper. The recording paper on which the toner image is formed by the image forming unit 20 is fixed on the toner image by the fixing device 40 and discharged to a paper discharge tray (not shown).

  In the case of duplex printing, the conveyance path of the recording medium after the image is formed and fixed on one side by the image forming unit 20 and the fixing device 40 is switched to the circulation path 65 by the switching unit 64. Then, the reversing unit 66 reverses the front and back of the recording sheet, and the recording sheet is conveyed again to the registration roller 6A and supplied to the image forming unit 20 via the conveyance path 63. This process is called reverse feeding. The image forming unit 20 forms an image on the back side of the recording paper, is fixed by the fixing device 40, and is discharged onto a paper discharge tray. Also in single-sided printing, recording paper on which an image is formed on one side is conveyed by the circulation path 65 and reversed by the reversing means 66, and is discharged via the conveyance path 67 with the image forming surface facing down. Good.

  A conveyance path 63 from the registration roller 6 </ b> A to the transfer unit 26 of the image forming unit 20 is a path through which a recording sheet passes in common for front-side feeding and back-side feeding. Means 61 are provided. Note that the paper size detection means 61 is provided on the upstream side of the conveyance path 63. In the temperature control of the heating roller 41, the paper size information of the recording paper being conveyed detected by the paper size detection means 61 is This is because a time margin reflected in the temperature change of the heating roller 41 can be made.

  Here, the configuration of the paper size detection means 61 will be described with reference to FIG. The paper size detection unit 61 includes a plurality of photosensors 61A provided orthogonal to the conveyance direction of the recording paper P. The photosensor 61A includes a laser light emitting means (not shown) and a light receiving means for receiving the laser light emitted by the light emitting means. The recording paper is blocked by the recording paper, thereby passing the recording paper. Detect. Based on which photosensor of the plurality of photosensors 61A detects the passage of the recording paper P and the detection time of the passage of the recording paper, the size of the recording paper P is acquired, and the conveyance paper size Information is output to the control means 10.

  The operation unit 50 includes an input key and the like, receives various information input from the user, and outputs the input information to the control unit 10. The operation means 50 may have a display function of various display information, and may be a touch panel, for example.

  The storage unit 81 stores various information in a readable and writable manner, and includes, for example, a flash memory, an HDD (Hard Disk Drive), or the like. Moreover, you may include ROM etc. which memorize | store the information which does not change. The storage unit 81 can store image data for image formation. The storage unit 81 stores at least an energization ratio table 200 described later.

  The scanner 82 reads an image recorded on a document set on the platen and generates image information. The scanner 82 includes an image reading unit such as a CCD (Charge Coupled Device), a scanning unit that moves the image reading unit, an image processing unit that processes an image signal read by the image reading unit, and includes an ADF. May be. The scanner 82 automatically detects the size of the read document and outputs document size information to the control means 10.

  The communication means 83 is communicatively connected to an external device such as a PC (Personal Computer) via a communication network and transmits / receives various communication information. For example, the image data received from the external device is received by the communication unit 83 and printed out by the copying machine 100. Also in this case, when the received image data has the size information of the recording paper to be printed, the paper size information can be output to the control means 10.

  Next, the energization ratio table 200 stored in the storage unit 81 will be described. FIG. 5 shows the configuration of the energization ratio table 200. As shown in FIG. 5, the energization ratio table 200 includes numerical values of the first energization ratio and the second energization ratio corresponding to various sizes of recording paper such as A4, A4R, and B5. The energization ratio is an energization ratio corresponding to the energization switching time ratio between the induction coil 43 and the induction coils 42 and 44.

  The energization ratio is expressed as X: Y = 1: 0 to 0: 1, where (energization time of induction coil 43) :( energization time of induction coils 42 and 44) is expressed as X: Y. In the energization ratio table 200, for example, the A4 size first energization ratio X11: Y11 = 0.6: 0.4, and the B5 size second energization ratio X23: Y23 = 0.7: 0.4. . Although not shown, the fixed energization ratio during idling (other than during the image forming operation) described later is, for example, 0.6: 0.5.

  The first energization ratio is included in the recording sheet size information input from the operation unit 50 during the image forming operation, the document size information acquired from the scanner 82, and the image data received via the communication unit 83. And the energization ratio set corresponding to the initial paper size information as the first recording paper size information during the image forming operation set based on at least one piece of information. The second energization ratio is an energization ratio that is set corresponding to the conveyance paper size information acquired from the paper size detection unit 61.

  In the present embodiment, the first energization ratio and the second energization ratio are expressed as different values, but the present invention is not limited to this, and may be a common energization ratio value.

  Next, the temperature control operation of the fixing device 40 of the copying machine 100 will be described with reference to FIG. FIG. 6 shows the first fixing heating control process. The first fixing heating control process is a process that is periodically executed except when this process is being executed. The first fixing heating control process is executed by the control means 10 when the power is turned on or when a predetermined time elapses from the end of execution of the first fixing heating control process. For example, a first fixing temperature control program stored in the ROM of the control unit 10 is read out and expanded in the RAM of the control unit 10, and the first fixing temperature control program and the control unit 10 cooperate with each other. A first fixing heating control process is executed.

  First, it is determined whether or not an image forming operation has been started (step S11). For example, it is determined based on whether an image formation execution start operation is input from the operation unit 50 or whether image data to be subjected to image formation is received via the communication unit 83. When the image forming operation is not started (step S11; NO), the fixed energization ratio corresponding to the idling state is set in the high frequency power source 30 (step S12), and the first fixing heating control process is ended.

  When the image forming operation is started (step S11; YES), the counter stored in the RAM of the control means 10 is reset (step S13). This counter is used to count and store the number of times the recording paper is passed through the paper size detecting means 61, and is set with an initial count value of 0 when first executing step S13.

  Then, initial paper size information is acquired (step S14). The initial paper size information is information indicating the size of the first sheet of recording paper on which image formation is performed, and is acquired from the size information of the recording paper input from the operation unit 50 and the scanner 82 as described above. It is set on the basis of at least one information of the size information of the document and the size information of the recording paper included in the image data received via the communication unit 83.

  Then, the energization ratio table 200 is referred to, and the first energization ratio corresponding to the initial paper size information is set in the high frequency power supply 30 (step S15). The high-frequency power source 30 energizes the induction coils 42, 43, and 44 based on the set first energization ratio to heat the heating roller.

  Then, in the paper size detection means 61, it is determined whether or not one recording sheet has been passed (step S16). That is, detection of one sheet of recording paper is started by the paper size detection means 61, and the paper feeding ends when the detection ends. When the sheet passing is not completed (step S16; NO), the process proceeds to step S16. When the sheet passing is completed (step S16; YES), the counter in the RAM of the control means 10 is incremented by 1 (step S17).

  Then, it is determined whether or not the counter in the RAM is greater than or equal to a predetermined count value (step S18). The predetermined count value indicates the execution frequency of the fixing temperature control based on the conveyance paper size information. For example, when the heating roller 41 is thin and the temperature is likely to become unstable, it is preferable to stably control the fixing temperature with a small predetermined count value. However, if the predetermined count value is reduced, the durability of the components of the fixing device 40 is lowered. In the present embodiment, since the heating roller 41 is heated by the induction heating method, the temperature follow-up performance is better than that of the halogen lamp method, and therefore the predetermined count value may be increased.

  If the counter is equal to or greater than the predetermined count value (step S18; YES), the transport paper size information of the recording paper that has been passed is acquired from the paper size detection means 61 (step S19). Then, the energization ratio table 200 is referred to, and the second energization ratio corresponding to the conveyance paper size information is set in the high frequency power supply 30 (step S20). The high frequency power supply 30 energizes the induction coils 42, 43, 44 based on the set second energization ratio and heats the heating roller.

  Then, the counter in the RAM is reset (step S21). Then, it is determined whether or not the recording sheet passed immediately before corresponds to the last print for image formation (step S22). In step S22, for example, the operation information input from the operation unit 50 during the image forming operation, the reading surface number information of the document acquired from the scanner 82, and the recording data included in the image data received via the communication unit 83. The determination is made based on at least one piece of information on the number of image recording surfaces of the sheet. If the counter is not equal to or greater than the predetermined count value (step S18; NO), the process proceeds to step S22.

  If the recording paper does not correspond to the last print (step S22; NO), the process proceeds to step S16. If the recording paper corresponds to the last print (step S22; YES), the fixing device 40 determines whether or not the fixing operation of the recording paper for the last print is completed (step S23). If the fixing operation has not been completed (step S23; NO), the process proceeds to step S23. When the fixing operation is finished (step S23; YES), the first fixing control process is finished.

  As described above, according to the present embodiment, the energization ratio of the induction coils 42, 43, and 44 is initially set according to the size of the first recording sheet instructed to form an image, and energization control is performed. Since the energization control is performed by changing the energization ratio between the induction coil 43 and the induction coils 42 and 44 in accordance with the size of the recording paper detected by the above, when an image is formed by mixing recording papers of different sizes. In addition, the heating roller 41 can be heated to an appropriate temperature distribution from the start of image formation, and the heating roller 41 can be heated to an appropriate temperature distribution in real time.

  In particular, the heating roller 41 is effective for a thin wall (having a small heat capacity) and a rapid temperature change.

  In addition, since the size of the recording sheet conveyed on the conveyance path 63 through which the recording sheet passes is commonly detected in the front side feeding and the back side feeding, the paper size detecting unit 61 detects the size of the recording sheet in either one side or both sides. However, the heating roller 41 can be heated to an appropriate temperature distribution in real time.

  In addition, the induction coil 42 according to the size of the recording paper detected by the paper size detecting means 61 in the predetermined number of passage times of the recording paper detected by the paper size detecting means 61 (period corresponding to the predetermined count value). , 43, and 44, the energization control is performed, so that the energization pattern change timing can be appropriately adjusted according to the followability from the recording sheet size detection to the heating roller 41 temperature change.

  For example, when the followability is good, the size of the recording paper is detected by the paper size detecting means 61 at a rate of once every two recording papers, and the fixing heating control is performed. The predetermined count value is set so that the size of the recording paper is detected by the paper size detecting means 61 at a rate of once per 10 sheets of paper and the fixing heating control is performed.

  Further, since the energization control is performed by changing the energization ratio of the induction coil 43 and the induction coils 42 and 44 and switching the energization of each induction coil, the induction is compared with the configuration in which each dielectric coil is energized simultaneously. The power consumption of the entire coil can be suppressed. Further, the combination of the induction coil 43 and the induction coils 42 and 44 can heat the central portion and both end portions of the heating roller 41 in the sheet passing width direction to an appropriate temperature distribution in real time.

(Second Embodiment)
A second embodiment according to the present invention will be described with reference to FIG. Since the apparatus configuration of the present embodiment is the same as the apparatus configuration of the first embodiment, the description thereof is omitted. Further, the energization ratio table 200 stored in the storage unit 81 includes only the second energization ratio corresponding to the conveyance paper size information.

  Next, the temperature control operation of the fixing device 40 of the copying machine 100 will be described with reference to FIG. FIG. 7 shows the second fixing heating control process. In the first fixing heating control process, the fixing temperature is controlled based on the initial paper size information and the transported paper size information during image formation. In the second fixing heating control process, only the transported paper size information is displayed during image formation. The fixing temperature is controlled based on the above.

  The second fixing heating control process is a process that is periodically executed except when this process is being executed. The second fixing heating control process is executed by the control unit 10 when the power is turned on or when a predetermined time elapses from the end of execution of the second fixing heating control process. For example, the second fixing temperature control program stored in the ROM of the control means 10 is read out and expanded in the RAM of the control means 10, and by the cooperation of the second fixing temperature control program and the control means 10, A second fixing heating control process is executed.

  First, steps S31 and S32 are the same as steps S11 and S12 of the first fixing heating control process. When the image forming operation is started (step S31; YES), the paper size detection unit 61 determines whether or not one recording sheet has been passed (step S33). When the sheet passing is not completed (step S33; NO), the process proceeds to step S33. When the sheet passing is completed (step S33; YES), the conveyance sheet size information of the recording sheet for which the sheet has been completed is acquired from the sheet size detecting means 61 (step S34). Then, the energization ratio table 200 is referred to, and the second energization ratio corresponding to the conveyance paper size information is set in the high frequency power supply 30 (step S35).

  Then, it is determined whether or not the recording sheet passed immediately before corresponds to the last print (step S36). If the recording paper does not correspond to the last print (step S36; NO), the process proceeds to step S33. If the recording sheet corresponds to the last print (step S36; YES), the fixing device 40 determines whether or not the fixing operation of the recording sheet for the last print is completed (step S37). If the fixing operation has not been completed (step S37; NO), the process proceeds to step S37. When the fixing operation is finished (step S37; YES), the second fixing control process is finished.

  As described above, according to the present embodiment, the energization control is performed by changing the energization ratio between the induction coil 43 and the induction coils 42 and 44 in accordance with the size of the recording paper detected by the paper size detection means 61. Even in the case of forming an image by mixing recording papers of different sizes, the heating roller 41 can be heated to an appropriate temperature distribution in real time.

  It should be noted that the detailed configuration and detailed operation of each part constituting the image forming apparatus (copier 100) in each of the above embodiments can be changed as appropriate without departing from the spirit of the present invention.

  In the first embodiment, the energization ratio is set based on the initial paper size information for the first recording paper for image formation, and all the second and subsequent recording papers are based on the transport paper size information. The energization ratio may be set.

  In the second embodiment, the energization ratio of the recording paper on which an image is formed may be set based on the conveyance paper size information for each predetermined counter value.

  Further, in the first embodiment, the configuration is such that the paper size is detected by the paper size detection 61 and the energization ratio of the induction coil is changed at a predetermined number of paper passing cycles of the recording paper detected by the paper size detection 61. However, the present invention is not limited to this. For example, a configuration may be adopted in which the paper size is detected by the paper size detection 61 and the energization ratio of the induction coil is changed at a predetermined time period.

  Further, in each of the above-described embodiments, the induction coil 43 and the induction coils 42 and 44 are energized alternately based on the paper size information, and the energization ratio is changed. It is not a thing. A combination pattern in which the induction coils 42, 43, 44 are energized at the same time may be changed according to the paper size information. For example, it may be configured to switch between simultaneous energization of the induction coils 42, 43, 44 and energization only of the induction coil 43 according to the paper size information.

  Further, the number of induction coils provided in the axial direction of the heating roller 41 is not limited to two (central portion and both end portions), and may be two or more. In each of the above embodiments, the heating roller is heated by an induction heating method. However, the present invention is not limited to this, and another heating unit such as a halogen lamp may be used. However, two or more heating means are provided in the axial direction of the heating roller, and each part of the heating roller corresponding to each heating means can be controlled to be heated separately.

1 is a diagram showing an internal configuration of a copying machine 100 according to an embodiment of the present invention. 2 is a diagram illustrating a configuration of an image forming unit 20. FIG. FIG. 4 is a diagram illustrating a configuration of a recording paper conveyance path. FIG. 6 is a diagram illustrating a configuration of a paper size detection unit 61. It is a figure which shows the structure of the electricity supply ratio table. 3 is a flowchart showing a first fixing heating control process. 10 is a flowchart illustrating a second fixing heating control process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 10 Control means 20 Image forming means 21 Photoconductor drum 22 Static elimination means 23 Charging means 24 Exposure means 25 Development means 26 Transfer means 26A Transfer electrode 26B Separation electrode 27 Cleaner 28 Temperature sensor 29 Potential sensor 30 High frequency power supply 40 Fixing device 41 Heating roller 42, 43, 44 Induction coil 45 Pressure member 46, 47 Temperature detection means 60 Paper transport means 61 Paper size detection means 61A Photo sensor 62 Paper feed path 63 Transport path 64 Switching means 65 Circulation path 66 Reversing means 67 Transport Path 70 Paper feed tray 70A, 70B, 70C Tray 81 Storage means 82 Scanner 83 Communication means

Claims (6)

Image forming means for forming a toner image on a recording medium based on image data to be imaged;
A heating member for heating the toner image on the recording medium;
A recording medium on which the toner image is formed, and a pressure member;
A plurality of heating means for respectively heating a plurality of portions in the sheet passing width direction of the heating member;
An image forming apparatus comprising: a control unit that performs energization control by changing an energization pattern of the plurality of heating units according to a size of a recording medium being fed to the image forming unit. Image forming means for forming a toner image on a recording medium based on image data to be imaged;
A heating member for heating the toner image on the recording medium;
A pressure member that pressurizes the recording medium on which the toner image is formed;
A plurality of heating means for respectively heating a plurality of portions in the sheet passing width direction of the heating member;
Depending on the size of the first recording medium instructed to form an image, the energization pattern of the plurality of heating units is initially set to perform energization control, and according to the size of the recording medium being fed to the image forming unit, An image forming apparatus comprising: a control unit that performs energization control by changing energization patterns of the plurality of heating units. A medium size detecting unit that is provided on a conveyance path through which the recording medium passes in common in the front side feeding and the back side feeding to the image forming unit, and detects the size of the recording medium conveyed on the conveyance path; Prepared,
3. The control unit according to claim 1, wherein the control unit performs energization control by changing an energization pattern of the plurality of heating units in accordance with the size of the recording medium detected by the medium size detection unit. Image forming apparatus.   The control unit is configured to control the plurality of heating units according to the size of the recording medium detected by the size detecting unit at a predetermined time period or a predetermined number of passage times of the recording medium detected by the medium size detecting unit. The image forming apparatus according to claim 3, wherein energization control is performed by changing an energization pattern. The plurality of heating means can switch energization of each heating means,
5. The image according to claim 1, wherein the control unit performs energization control by changing an energization ratio of each heating unit based on an energization switching time ratio of the plurality of heating units. 6. Forming equipment.   The plurality of heating units include a first heating unit that heats a central portion of the heating member in the sheet passing width direction, and a second heating unit that heats both end portions of the heating member in the sheet passing width direction. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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