JP2023062938A - Image forming apparatus - Google Patents

Abstract

To control a plurality of heaters for fixation based on a temperature detected by one temperature sensor.SOLUTION: An image forming apparatus 1 has: a fixing roller 20 whose surface is heated; a pressure roller 25 that forms a fixing nip with the fixing roller 20; a main heater 21 that heats a first area R1 of the fixing roller 20; a sub heater 22 that heats a second area R2 of the fixing roller 20; a temperature sensor 26 that detects a temperature of the first area R1 of the fixing roller 20; and a fixation control unit 51 that controls the main heater 21 and the sub heater 22 based on a temperature detected by the temperature sensor 26. The fixation control unit 51 controls the sub heater 22 by using a correction value A determined in advance based on a ratio between a value of current flowing in the main heater 21 and a value of current flowing in the sub heater 22 under a predetermined condition.SELECTED DRAWING: Figure 6

Description

The present disclosure relates to an image forming apparatus that forms an image on a medium.

An image forming apparatus using an electrophotographic process includes a fixing device that applies heat and pressure to an image (toner image) transferred onto a medium to fix the image onto the medium. A fixing device has a fixing body such as a fixing roller or a fixing belt, and heats the fixing body with a heater.

In recent years, a fixing device has been proposed in which a plurality of heaters are arranged in the width direction of a medium in order to deal with a plurality of types of media having different widths (see, for example, Japanese Unexamined Patent Application Publication No. 2002-100002).

JP 2014-240945 (see FIGS. 7A and 7B)

However, since the conventional fixing device controls a plurality of heaters while detecting the respective temperatures, it is necessary to provide a plurality of temperature sensors.

The present disclosure has been made to solve the above problems, and aims to control a plurality of heaters for fixing based on the temperature detected by one temperature sensor.

An image forming apparatus according to the present disclosure includes a fixing member whose surface is heated, a pressure member that forms a fixing nip with the fixing member, a first heater that heats a first region of the fixing member, and a fixing member. a second heater that heats a second region of the body; a temperature sensor that detects the temperature of the first region of the fixing body; and controls the first heater and the second heater based on the temperature detected by the temperature sensor. and a control unit for The controller controls the second heater using a correction value determined in advance based on a ratio of a current value flowing through the first heater and a current value flowing through the second heater under predetermined conditions.

According to the present disclosure, since the second heater is controlled using the correction value determined based on the ratio of the current values flowing through the first heater and the second heater, the detected temperature of one temperature sensor Based on this, both the first heater and the second heater can be controlled.

1 illustrates a basic configuration of an image forming apparatus according to a first embodiment; FIG. 2 is a block diagram showing a control system of the image forming apparatus according to the first embodiment; FIG. 3A, 3B, and 3C show the basic configuration of the fixing device according to the first embodiment; FIG. It is a figure which shows the structure of the main heater of 1st Embodiment. It is a figure which shows the structure of the sub-heater of 1st Embodiment. It is a figure which shows the structure for control of the main heater of 1st Embodiment, and a sub-heater. It is the figure which represented the process for control of the main heater of 1st Embodiment with the functional block. FIG. 4 is a diagram showing processing for controlling a sub-heater according to the first embodiment using functional blocks; FIG. 4 is a diagram showing a configuration for determining a correction value used for controlling sub-heaters according to the first embodiment; FIG. 10 is a graph (A) showing temperature changes when the duties of heater ON signals of two heaters are the same, and a graph (B) showing temperature changes when the duties of the heater ON signals of the two heaters are different. 7A and 7B are graphs showing the output distribution of the main heater and the sub-heater and the temperature distribution on the surface of the fixing roller; 8A and 8B are schematic diagrams showing the basic configuration of a fixing device according to a second embodiment; FIG. It is a figure which shows the structure for control of the main heater of 2nd Embodiment, and a sub-heater. FIG. 10 is a diagram showing a configuration for determining a correction value used for controlling sub-heaters according to the second embodiment;

First embodiment.
<Image forming apparatus>
First, the image forming apparatus 1 of the first embodiment will be described. FIG. 1 is a diagram showing an image forming apparatus 1. As shown in FIG. The image forming apparatus 1 forms an image using an electrophotographic process, and is, for example, a color printer.

The image forming apparatus 1 includes a medium supply unit 7 that supplies a medium P, and an image forming unit that forms toner images (developer images) of black (K), yellow (Y), magenta (M), and cyan (C). a transfer unit 8 for transferring an image onto a medium P; a fixing device 2 for fixing an image on the medium P;

These components are housed in the housing 1A. An openable and closable top cover 1B is provided on the top of the housing 1A.

The medium supply unit 7 includes a medium cassette 70 that accommodates media P such as printing paper, hopping rollers 71 and retard rollers 72 that separate the media P in the medium cassette 70 one by one and feed them onto the transport path. It has registration rollers 73 for correcting skew of the sent medium P, and transport rollers 74 for transporting the medium P to the transfer unit 8 . As the medium P, in addition to printing paper, OHP sheets, envelopes, copy paper, special paper, and the like can be used.

The process units 10K, 10Y, 10M, and 10C are arranged in this order from the upstream side to the downstream side (here, from the right side to the left side) along the medium P transport path.

The process units 10K, 10Y, 10M, and 10C respectively include photosensitive drums 11K, 11Y, 11M, and 11C as image bearing members, charging rollers 12K, 12Y, 12M, and 12C as charging members, and developer bearing members. Developing rollers 13K, 13Y, 13M and 13C and supply rollers 14K, 14Y, 14M and 14C as supply members are provided.

Print heads 18K, 18Y, 18M and 18C as exposure devices (print heads) are arranged above the photosensitive drums 11K, 11Y, 11M and 11C so as to face each other. The print heads 18K, 18Y, 18M and 18C are suspended and supported by the top cover 1B.

The photosensitive drums 11K, 11Y, 11M, and 11C are cylindrical members having photosensitive layers on their surfaces, and rotate counterclockwise in FIG. The charging rollers 12K, 12Y, 12M and 12C uniformly charge the surfaces of the photosensitive drums 11K, 11Y, 11M and 11C. The print heads 18K, 18Y, 18M, and 18C have light-emitting element arrays in which light-emitting elements such as LEDs (light-emitting diodes) are arranged, and expose the surfaces of the photosensitive drums 11K, 11Y, 11M, and 11C to form electrostatic latent images. to form

Developing rollers 13K, 13Y, 13M, and 13C adhere toner (developer) to the electrostatic latent images on the surfaces of photoreceptor drums 11K, 11Y, 11M, and 11C to form toner images. Supply rollers 14K, 14Y, 14M and 14C supply toner to developing rollers 13K, 13Y, 13M and 13C.

In addition, toner cartridges 15K, 15Y, 15M, and 15C as developer containers for containing unused toner are detachably attached to the process units 10K, 10Y, 10M, and 10C.

The transfer unit 8 includes a transfer belt 80 that moves while attracting the medium P, a drive roller 81 that drives the transfer belt 80, a tension roller 82 that applies tension to the transfer belt 80, and photosensitive drums 11K, 11Y, and 11M. , 11C as transfer members so as to sandwich the transfer belt 80 therebetween. The transfer rollers 19K, 19Y, 19M, and 19C transfer onto the medium P the toner images of respective colors formed on the photosensitive drums 11K, 11Y, 11M, and 11C.

The fixing device 2 has a fixing roller 20 as a fixing member, heaters 21 and 22 as heat sources, a pressure roller 25 as a pressure member, and a temperature sensor 26 as a temperature detection section. Heaters 21 and 22 heat the fixing roller 20 from the inner peripheral side. The pressure roller 25 is pressed against the fixing roller 20 to form a fixing nip therebetween. The temperature sensor 26 is, for example, a thermopile and detects the surface temperature of the fixing roller 20 . Details of the fixing device 2 will be described later.

The medium ejection section 9 has two pairs of ejection rollers 91 and 92 for conveying the medium P that has passed through the fixing device 2 and ejecting it from an ejection port. A top cover 1B of the image forming apparatus 1 is provided with a stacker section 93 on which the medium P ejected by the ejection rollers 91 and 92 is placed.

A writing sensor S1 and an ejection sensor S2 for detecting passage of the medium P are arranged in the transport path of the medium P. As shown in FIG. The write sensor S<b>1 is arranged downstream of the conveying roller 74 , and the discharge sensor S<b>2 is arranged downstream of the fixing device 2 . The detection signal of the writing sensor S1 is used to determine the exposure start timing of the print heads 18K, 18Y, 18M and 18C and the application timing of the transfer voltage to the transfer rollers 19K, 19Y, 19M and 19C. A detection signal from the ejection sensor S2 is used to determine whether the image forming operation on the medium P is completed.

The process units 10K, 10Y, 10M, and 10C and their constituent elements will be described by omitting K, Y, M, and C unless it is necessary to distinguish them. The print heads 18K, 18Y, 18M, and 18C will also be described by omitting K, Y, M, and C unless it is necessary to distinguish them.

In FIG. 1, the axial direction of the photosensitive drum 11 and each roller of the image forming apparatus 1 is the X direction. The X direction is the width direction of the image forming apparatus 1 and the width direction of the medium P as well. The moving direction of the medium P when passing through the process unit 10 is defined as the Y direction. A direction orthogonal to the XY plane is defined as a Z direction. In addition, in FIG. 1, the Y direction is inclined about 10 degrees with respect to the horizontal plane, but the inclination is not necessarily required.

Regarding the Y direction, the moving direction of the medium P when passing through the process unit 10 is the +Y direction, and the opposite direction is the -Y direction. Regarding the X direction, the right direction is the +X direction and the left direction is the -X direction in the +Y direction. As for the Z direction, in FIG. 1, the substantially upward direction is the +Z direction, and the substantially downward direction is the -Z direction. Note that these directions do not limit the orientation of the image forming apparatus 1 .

<Control System of Image Forming Apparatus>
Next, a control system of the image forming apparatus 1 will be described. FIG. 2 is a block diagram showing the control system of the image forming apparatus 1. As shown in FIG. The image forming apparatus 1 includes a print control unit 100, an I/F (interface) control unit 101, a reception memory 102, an image data editing memory 103, an operation unit 104, a sensor group 105, and a power control unit 106. , a head control unit 111 , a drive control unit 112 , a belt drive control unit 113 , a fixing control unit 51 , a fixing drive control unit 114 , and a paper feed/conveyance control unit 115 .

Note that these control units and memory can be mounted on the same control board, except for the power supply control unit 106 .

The print control unit 100 includes a microprocessor, a ROM (Read Only Memory), a RAM (Random Access Memory), an input/output port, a timer, and the like. The print control unit 100 receives print data and control commands from a host device via the I/F control unit 101 and controls the printing operation of the image forming apparatus 1 .

A reception memory 102 temporarily stores print data input from a host device via the I/F control unit 101 . The image data editing memory 103 receives the print data stored in the reception memory 102 and records image data formed by editing the print data, that is, image data.

The operation unit 104 includes a display unit (for example, LED) for displaying the state of the image forming apparatus 1 and an operation unit (for example, switch) for the operator to input instructions. The sensor group 105 includes various sensors for monitoring the operating state of the image forming apparatus 1, such as the write sensor S1 and the discharge sensor S2, the temperature/humidity sensor, and the density sensor.

A power supply control unit (high voltage control unit) 106 applies a charging voltage power supply 107 that applies a charging voltage to the charging roller 12 , a developing voltage power supply 108 that applies a developing voltage to the developing roller 13 , and a supply voltage to the supply roller 14 . A supply voltage power supply 109 and a transfer voltage power supply 110 for applying a transfer voltage to the transfer roller 19 are controlled.

A head control unit 111 controls light emission of the print head 18 based on the image data recorded in the image data editing memory 103 .

The drive control unit 112 performs control to drive the drive motor 116 that rotates the photosensitive drum 11 of each process unit 10 . The belt drive control unit 113 controls the driving of the belt motor 117 that rotates the drive roller 81 .

The fixing control section 51 has a storage section such as a temperature control circuit and a memory, and controls the heaters 21 and 22 based on the output signal of the temperature sensor 26 of the fixing device 2 . Control of the heaters 21 and 22 by the fixing controller 51 will be described later.

A fixing drive control unit 114 controls driving of a fixing motor 118 that rotates the fixing roller 20 . Note that the discharge rollers 91 and 92 are rotated by rotation transmission from the fixing motor 118 .

The sheet feeding/conveying control unit 115 controls the driving of the sheet feeding motor 119 that rotates the hopping roller 71 and the conveying motor 120 that rotates the registration rollers 73 and the conveying rollers 74 .

<Basic Operation of Image Forming Apparatus>
Next, basic operations of the image forming apparatus 1 will be described with reference to FIGS. 1 and 2. FIG. When the print control unit 100 of the image forming apparatus 1 receives a print command and print data from the host device via the I/F control unit 101, it starts an image forming operation. The print control unit 100 temporarily records the print data in the reception memory 102 , edits the recorded print data to generate image data, and records the image data in the image data edit memory 103 .

In the medium supply unit 7, the hopping roller 71 is rotated by the paper feed motor 119, and the medium P in the medium cassette 70 is fed one by one to the transport path. Further, the registration rollers 73 and the transport rollers 74 are rotated at predetermined timings by the transport motor 120 to correct the skew of the medium P and transport it to the transfer unit 8 .

In the transfer unit 8, the driving roller 81 is rotated by the belt motor 117, whereby the transfer belt 80 runs to attract and hold the medium P and convey it. The medium P passes through the process units 10K, 10Y, 10M and 10C in this order.

In each process unit 10, charging voltage, developing voltage and supply voltage are applied to charging roller 12, developing roller 13 and supply roller 14 from charging voltage power supply 107, developing voltage power supply 108 and supply voltage power supply 109, respectively.

Further, the photosensitive drum 11 is rotated by the drive motor 116 . As the photosensitive drum 11 rotates, the charging roller 12, the developing roller 13, and the supply roller 14 also rotate. The charging roller 12 uniformly charges the surface of the photosensitive drum 11 with its charging voltage.

The print control unit 100 also transmits the image data recorded in the image data editing memory 103 to the head control unit 111, and the head control unit 111 drives the print head 18 to expose the surface of the photosensitive drum 11. , forming an electrostatic latent image.

The electrostatic latent image formed on the surface of photoreceptor drum 11 is developed with toner adhering to developing roller 13 to form a toner image on the surface of photoreceptor drum 11 . When the toner image approaches the surface of the transfer belt 80 due to the rotation of the photosensitive drum 11 , a transfer voltage is applied to the transfer roller 19 from the transfer voltage power source 110 . As a result, the toner image formed on the photosensitive drum 11 is transferred onto the medium P on the transfer belt 80 .

In this manner, the toner images of each color formed by each of the process units 10K, 10Y, 10M, and 10C are sequentially transferred onto the medium P and superimposed. The medium P onto which the toner image of each color has been transferred is further conveyed by the transfer belt 80 and reaches the fixing device 2 .

In the fixing device 2 , the fixing drive control section 114 drives the fixing motor 118 at the start of the image forming operation, thereby rotating the pressure roller 25 . Further, the heaters 21 and 22 are heated to a predetermined fixing temperature by the fixing controller 51 . The medium P conveyed from the transfer unit 8 to the fixing device 2 passes through the fixing nip between the fixing roller 20 and the pressure roller 25, and the toner image is fixed on the medium P by application of heat and pressure.

The medium P on which the toner image is fixed is discharged outside the image forming apparatus 1 by discharge rollers 91 and 92 and stacked on the stacker section 93 . Thus, the image forming operation on the medium P is completed.

<Structure of Fixing Device>
Next, the configuration of the fixing device 2 according to the first embodiment will be described. 3A, 3B, and 3C are diagrams showing the basic configuration of the fixing device 2. FIG. More specifically, FIGS. 3A, 3B, and 3C are a side view, a plan view, and a front view of fixing roller 20 and pressure roller 25, respectively.

Both the fixing roller 20 and the pressure roller 25 have their longitudinal directions in the X direction. A fixing nip is formed between the fixing roller 20 and the pressure roller 25, and the medium P conveyed from the transfer unit 8 is introduced into the fixing nip. The toner image transferred to the medium P by the transfer unit 8 adheres to the medium P with a weak electrostatic force, but is melted by the heat of the fixing roller 20 and fixed to the medium P by the pressure of the pressure roller 25 .

The fixing roller 20 is a roller in which an elastic layer and a surface layer are laminated on the surface of a substantially cylindrical base material. The base material is made of aluminum, stainless steel, or the like. The elastic layer is composed of silicone rubber. The surface layer is composed of a coating layer or a tube made of fluororesin such as PTFE (polytetrafluoroethylene) or PFA (perfluoroalkoxyalkane).

Although not shown, shaft portions are formed at both ends of the base material of the fixing roller 20 in the X direction, and are rotatably supported by bearings provided on the frame of the fixing device 2 .

As shown in FIG. 3B, the +X direction end of the roller portion (cylindrical portion excluding the shaft portion) of the fixing roller 20 is defined as a reference position P1. The medium P is transported so that one end in the X direction coincides with the reference position P1 regardless of the size. Therefore, the reference position P1 is also called a medium transport reference position.

The fixing roller 20 has a hollow structure, inside which a main heater 21 as a first heater and a sub-heater 22 as a second heater are arranged. Here, as shown in FIG. 3A, the main heater 21 is arranged in the -Y direction (that is, upstream in the transport direction of the medium P) relative to the sub-heater 22 . However, the sub-heater 22 is not limited to such arrangement, and the sub-heater 22 may be arranged in the -Y direction (that is, upstream in the transport direction of the medium P) relative to the main heater 21 .

Both the main heater 21 and the sub-heater 22 are halogen heaters, and extend from the +X direction end (reference position P1) of the roller portion of the fixing roller 20 to the −X direction end.

The main heater 21 heats the first region R1 of the fixing roller 20 in the X direction, and the sub-heater 22 heats the second region R2 of the fixing roller 20 in the X direction. The first region R1 includes the reference position P1 described above. Although the first region R1 is larger than the second region R2 in FIG. 3B, both may be the same, or the sizes may be reversed.

The width of the main heater 21 in the X direction (that is, the width of the first region R1) is set according to the narrow medium. The combined width of the main heater 21 and the sub-heater 22 in the X direction (that is, the combined width of the regions R1 and R2) is set according to the wide media.

Narrow media is, for example, media that is 3 inches wide in the X direction. Wide media is, for example, media that is 4 inches or 5 inches wide in the X direction. However, it is not limited to this example, and for example, the narrow medium may be B5 size (longitudinal feed) and the wide medium may be A4 size (horizontal feed).

As shown in FIGS. 3A and 3C, a temperature sensor 26 for detecting the surface temperature of the fixing roller 20 is arranged outside the fixing roller 20 . The temperature sensor 26 here consists of a thermopile. The thermopile is a non-contact temperature sensor that receives infrared rays emitted from the surface of the fixing roller 20 and converts them into electrical signals representing temperature.

The temperature sensor 26 is arranged in the X direction at a position corresponding to the first area R1 of the fixing roller 20 (that is, the area heated by the main heater 21). The temperature sensor 26 faces the -Y side surface of the fixing roller 20, that is, the surface on the upstream side in the direction in which the medium P is conveyed. The temperature sensor 26 is not limited to the thermopile, and other non-contact or contact temperature sensors may be used. Also, the arrangement of the temperature sensor 26 is not limited to the above example, and the temperature sensor 26 may be arranged so as to face the surface on the +Y side of the fixing roller 20, that is, the surface on the downstream side in the transport direction of the medium P.

FIG. 4 is a diagram showing the configuration of the main heater 21. As shown in FIG. The main heater 21 has a bulb 33 formed of a glass tube and elongated in the X direction, and the bulb 33 is filled with halogen gas. A filament 31 and an in-bulb lead wire 32 are provided in the bulb 33 .

The filament 31 extends from the +X direction end of the bulb 33 (the reference position P1 shown in FIG. 3B) by a length corresponding to the first region R1. The in-bulb lead wire 32 extends from the end of the filament 31 to the end of the bulb 33 in the -X direction.

The filament 31 is connected to a lead wire 34 provided outside the bulb 33 . The intra-bulb lead wire 32 is connected to a lead wire 35 provided outside the valve 33 .

A connecting portion between the filament 31 and the lead wire 34 and a connecting portion between the in-bulb lead wire 32 and the lead wire 35 are sealed so as not to leak the halogen gas in the bulb 33 . The lead wires 34, 35 are connected to a commercial power supply 56 and a triac 53 (FIG. 6) to be operated later.

It should be noted that the main heater 21 is not limited to the configuration shown in FIG. In that case, the lead wire 35 is connected to the filament 31 without providing the in-bulb lead wire 32 .

FIG. 5 is a diagram showing the configuration of the sub-heater 22. As shown in FIG. The sub-heater 22 has a bulb 43 formed of a glass tube and elongated in the X direction, and the bulb 43 is filled with halogen gas. A filament 41 and an intra-bulb lead wire 42 are provided in the bulb 43 .

The filament 41 extends from the -X direction end of the bulb 43 by a length corresponding to the second region R2. The in-bulb lead wire 42 extends from the end of the filament 41 to the +X direction end of the bulb 43 .

The filament 41 is connected to a lead wire 44 provided outside the bulb 43 . The intra-bulb lead wire 42 is connected to a lead wire 45 provided outside the valve 43 .

A connecting portion between the filament 41 and the lead wire 45 and a connecting portion between the in-bulb lead wire 42 and the lead wire 44 are sealed so as not to leak the halogen gas in the bulb 43 . The lead wires 44, 45 are connected to a commercial power supply 56 and a triac 54 (FIG. 6) to be operated later.

Incidentally, the sub-heater 22 is not limited to the configuration shown in FIG. In that case, the lead wire 44 is connected to the filament 41 without providing the in-bulb lead wire 42 .

<Heater control>
FIG. 6 is a diagram showing a configuration for controlling the heaters 21 and 22. As shown in FIG. Lead wires 34 and 44 of main heater 21 and sub-heater 22 are connected to commercial power source 56 . A lead wire 35 of the main heater 21 is connected to one terminal of a triac 53 as a first switching element. A lead wire 45 of the sub-heater 22 is connected to one terminal of a triac 54 as a second switching element. The other terminal of each triac 53 , 54 is connected to commercial power supply 56 .

Gate terminals of the triacs 53 and 54 are connected to a triac drive circuit 52 as a switching drive circuit. A signal from the fixing control section 51 is input to the triac driving circuit 52 . The triac drive circuit 52 is configured to insulate the primary and secondary sides of each of the triacs 53 and 54 using phototriacs.

When the heater ON signal H1 to the main heater 21 is input, the triac drive circuit 52 operates the triac 53 to supply power to the main heater 21 . Further, when the heater ON signal H2 to the sub-heater 22 is input, the triac drive circuit 52 operates the triac 54 to supply power to the sub-heater 22 .

The fixing controller 51 outputs heater ON signals H1 and H2 to the triac drive circuit 52 based on the temperature detection signal input from the temperature sensor 26 and the control signal input from the print controller 100 .

FIG. 7 is a functional block diagram showing processing executed when the fixing control unit 51 controls the main heater 21. As shown in FIG. This process is executed every 100 [ms], which is a control cycle, by the fixing control unit 51 starting a predetermined control program.

First, the duty calculator 501 calculates the duty from the difference between the temperature detected by the temperature sensor 26 and the preset target temperature. The calculation of duty is based on, for example, PID (Proportional Integral Differential) control.

Specifically, if the duty of the main heater 21 in the n-th round (n is an integer equal to or greater than 1) of the control cycle is expressed as Duty(n), this Duty(n) is obtained by the following equation.
Duty (n)
=Kp×ε+Ki×Σ(ε)+Kd×d(ε)/dt+Duty Mod(n−1)

In the above formula, ε is the temperature deviation, which is the value obtained by subtracting the detected temperature from the target temperature. Kp is a proportional gain, Ki is an integral gain, and Kd is a differential gain, which are predetermined. DutyMod(n-1) is the remainder of the duty not consumed in the n-1th control cycle. This DutyMod(n-1) does not necessarily have to be used.

The limit processing unit 502 limits the duty output from the duty calculation unit 501 to a range of 0 to 100 and outputs it. Specifically, when the duty value output from the duty calculation unit 501 is 0 or less, it is converted to 0, and when it is 100 or more, it is converted to 100. FIG.

The heater ON signal generator 503 outputs the heater ON signal H1 with a prescribed time constant based on the duty output from the limit processor 502 .

FIG. 8 is a functional block diagram of processing executed when the fixing control unit 51 controls the sub-heater 22. As shown in FIG. This process is executed every 100 [ms], which is a control cycle, by the fixing control unit 51 starting a predetermined control program.

First, the duty calculator 504 calculates the duty from the difference between the temperature detected by the temperature sensor 26 and the preset target temperature. The method of calculating the duty is as described for the duty calculator 501 in FIG.

The correction processing unit 505 corrects the duty using the correction value A pre-stored in the fixing control unit 51 and outputs the corrected value. The correction value A will be described later.

A limit processing unit 506 limits the duty after correction output from the correction processing unit 505 to a range of 0 to 100 and outputs it.

Based on the duty output from the limit processor 506, the heater ON signal generator 507 outputs the heater ON signal H2 with a prescribed time constant.

<Determination of correction value>
Next, a method for determining the correction value A will be described. FIG. 9 shows a system for determining the correction value A; Ideally, the main heater 21 and the sub-heater 22 should have the same amount of heat (output) per unit length if the duty of the heater ON signal is the same. Variation causes a difference in the amount of heat generated per unit length.

Therefore, it is conceivable to control both the main heater 21 and the sub-heater 22 while detecting the temperature thereof, but in that case, the same number of temperature sensors as the heaters 21 and 22 must be provided.

Therefore, in the present embodiment, the ratio of current values flowing through the main heater 21 and the sub-heater 22 when the same power is supplied is measured in advance, and the heater ON signal for the sub-heater 22 is generated based on the ratio. Then, the correction value A (FIG. 8) is determined. It is desirable to determine the correction value A after the image forming apparatus 1 is completed (for example, before product shipment).

For determining correction value A, output measuring section 201, triac driving circuit 202, triacs 203 and 204, current detecting section 206, and commercial power source 207 are used. These elements may be incorporated into the image forming apparatus 1 or may be independent units separate from the image forming apparatus 1 .

Note that if the configuration (201 to 207) for determining the correction value A is an independent unit (output measurement unit), the fixing device 2 is temporarily removed from the image forming apparatus 1 when determining the correction value A. , an output measuring unit may be connected to the fixing device 2 . In that case, after determining the correction value A, the fixing device 2 is removed from the output measuring unit, and the fixing device 2 is incorporated into the image forming apparatus 1 .

The lead wire 34 of the main heater 21 and the lead wire 44 of the sub-heater 22 are connected to the commercial power source 207 . A current detector 206 is connected between the lead wires 34 and 44 and the commercial power source 207 . A current detection unit 206 detects currents flowing through the heaters 21 and 22 and outputs detection results to the output measurement unit 201 .

A lead wire 35 of the main heater 21 is connected to one terminal of the triac 203 . A lead wire 45 of the sub-heater 22 is connected to one terminal of the triac 204 . The other terminal of each triac 203 , 204 is connected to commercial power source 207 . Gate terminals of the triacs 203 and 204 are connected to the triac drive circuit 202 .

The triac drive circuit 202 activates the triac 203 when the heater ON signal B1 to the main heater 21 is input, and activates the triac 204 when the heater ON signal B2 to the sub-heater 22 is input.

The correction value A is obtained by the following method. First, a heater ON signal B1 to the main heater 21 is input from the output measuring unit 201 to the triac driving circuit 52 . The heater ON signal B1 is not a pulse-like signal but a signal whose ON state continues for a certain period of time. Thereby, a predetermined power is supplied from the commercial power source 207 to the main heater 21 . For example, a predetermined voltage (100 V, for example) is applied to the main heater 21 . At this time, the current _IM flowing through the main heater 21 is detected by the current detecting section 206 and output to the output measuring section 201 .

Next, a heater ON signal B2 to the sub-heater 22 is input from the output measurement unit 201 to the triac drive circuit 202 . The heater ON signal B2 to the sub-heater 22 is the same signal as the heater ON signal B1 to the main heater 21 . As a result, the predetermined electric power is supplied from the commercial power source 207 to the sub-heater 22 . For example, the predetermined voltage is applied to the sub-heater 22 . At this time, the current _IS flowing through the sub-heater 22 is detected by the current detection section 206 and output to the output measurement section 201 .

Further, the designed current value (design value) flowing through the main heater 21 when the main heater 21 is supplied with a predetermined power from the commercial power source 56 is assumed to be I _M 0, and the sub-heater 22 is supplied with a predetermined power from the commercial power source 207 . The design current value (design value) that flows through the sub-heater 22 when supplied is assumed to be I _S 0 . Both I _M 0 and I _S 0 are obtained in advance by experiments and stored in the output measuring section 201 .

The current I _M is proportional to the output of the main heater 21 and the current I _S is proportional to the output of the sub-heater 22 . Therefore, the ratio a of the deviation from the design value of the output of the main heater 21 and the output of the sub-heater 22 is expressed by (I _S /I _S 0)/(I _M /I _M 0). Based on this ratio a, the correction value A is derived. The ratio a is also called an output variation ratio.

When the output measurement unit 201 calculates the correction value A, the operator reads the value and stores it in the fixing control unit 51 of the image forming apparatus 1 . If the output measuring section 201 is incorporated in the image forming apparatus 1, the correction value A may be input from the output measuring section 201 to the fixing control section 51 as indicated by the dashed line in FIG.

Here, the relationship between the heater ON signal and the temperature at which the fixing roller 20 is heated by the heaters 21 and 22 will be described. FIGS. 10A and 10B are diagrams showing the relationship between heater ON signals for two heaters α and β having the same output per unit length and the temperature (detected temperature) of the heating portion by the heaters α and β. is.

As shown in FIG. 10A, when heaters α and β have the same output per unit length, the temperatures of both heaters α and β change in the same manner when heater ON signals with the same duty are given. . The cycle of temperature change of both heaters α and β is the same as the cycle of the heater ON signal.

On the other hand, as shown in FIG. 10B, when the duty of the heater ON signal to the heater α is made higher than the duty of the heater ON signal to the heater β, the temperature of the heater α becomes higher than the temperature of the heater β. High temperature.

Based on this point, in the present embodiment, the duty of the heater ON signal to the main heater 21 or the sub-heater 22 whose temperature is desired to be raised is increased.

11A and 11B are graphs showing the output distribution of the heaters 21 and 22 and the temperature distribution on the surface of the fixing roller 20, respectively. At the design stage, the heaters 21 and 22 have the same output per unit length, and the first region R1 (the portion heated by the main heater 21) and the second region R2 (the portion heated by the sub-heater 22) of the fixing roller 20 are the same. are assumed to be heated to the same temperature.

However, in practice, the outputs of the heaters 21 and 22 often differ from the design values due to output variations that occur in the manufacturing stage. Further, in the present embodiment, both heaters 21 and 22 are controlled based on the detected temperature of the first region R1 heated by the main heater 21 (that is, the output of the temperature sensor 26), so the output of the main heater 21 It is controlled according to As the difference between the output of the sub-heater 22 and the output of the main heater 21 increases, the temperature of the portion heated by the sub-heater 22 (second region R2) changes from the temperature of the portion heated by the main heater 21 (first region R1). It becomes distant.

Here, as shown in FIG. 11A, for example, the output W1 per unit length of the main heater 21 is higher than the design output _WSET , and the output W2 per unit length of the sub-heater 22 is higher than the design output _WSET . is also low. It is assumed that the outputs W1 and W2 are equal to or less than the upper limit W _HIGH and equal to or more than the lower limit W _LOW of the allowable output range.

Since the main heater 21 is controlled based on the detected temperature of its heating portion (that is, the output of the temperature sensor 26), the temperature of the main heater 21 is controlled within the target temperature range.

On the other hand, since the sub-heater 22 is controlled based on the detected temperature of the heating portion of the main heater 21, a heating shortage corresponding to the output difference per unit length between the two heaters 21 and 22 occurs due to variations in output. As a result, the temperature of the portion heated by the sub-heater 22 (the second region R2) may fall below the lower limit T _LOW of the target temperature range, as indicated by the dashed line in FIG. 11(B).

On the other hand, when the sub-heater 22 is controlled by the heater ON signal whose duty is increased by the above correction value A, the temperature of the portion heated by the sub-heater 22 is within the target temperature range as indicated by the solid line in FIG. 11(B). (that is, the upper limit T _HIGH or less and the lower limit T _LOW or more).

As an example, in the fixing device 2 in which the target temperature of the fixing roller 20 has an upper limit of 170° C. and a lower limit of 150° C., when the temperature of the portion heated by the main heater 21 is approximately 160° C., the heater ON signal of the main heater 21 is By setting the duty of the heater ON signal of the sub-heater 22 to 1.1 (that is, setting the correction value A to 1.1) with respect to the duty of 1.0 of the sub-heater 22, the temperature of the heating portion of the sub-heater 22 is reduced from approximately 140°C to approximately It can go up to 150°C and stay within the target temperature range.

Regarding the determination of the correction value A described above, the current I _M flowing through the main heater 21 and the designed current value (design value) I _M0 flowing through the main heater 21 are the same, and the current I _S flowing through the sub-heater 22 is the same. and the design current value (design value) I _S 0 flowing through the sub-heater 22 may be the same.

<Effect of Embodiment>
As described above, the image forming apparatus 1 of the present embodiment includes the fixing roller 20 (fixing member), the pressure roller 25 (pressure member), and the main heater that heats the first region R1 of the fixing roller 20. 21 (first heater), a sub-heater 22 (second heater) that heats the second region R2 of the fixing roller 20, a temperature sensor 26 that detects the temperature of the first region R1 of the fixing roller 20, It also has a fixing controller 51 (controller) that controls the heaters 21 and 22 based on the temperature detected by the temperature sensor 26 . The fixing control unit 51 controls the sub-heater 22 using the correction value A determined based on the ratio I _S /I _M of the current values flowing through the main heater 21 and the sub-heater 22 . Therefore, based on the temperature detected by one temperature sensor 26, the main heater 21 and the sub-heater 22 can be controlled with high accuracy.

In particular, since the duty of the heater ON signal to the sub-heater 22 is corrected by the correction value A, the output variation of the main heater 21 and the sub-heater 22 can be reflected, and the output of the sub-heater 22 can be controlled with high accuracy.

Further, since the correction value _A is determined based on the current _IM flowing through the main heater 21 and the current IS flowing through the sub-heater 22 when the same power is supplied to the main heater 21 and the sub-heater 22, the main heater 21 and the sub-heater 22 It is possible to obtain the correction value A that accurately reflects the output variation from .

Second embodiment.
Next, a second embodiment will be described. In the first embodiment, the heaters 21 and 22, which are halogen heaters, heat the two regions R1 and R2. The regions R1, R2, R3 are heated. Further, while the fixing roller 20 is used in the first embodiment, the fixing belt 60 is used in the second embodiment.

12A and 12B are a side view and a front view showing the basic configuration of the fixing device 6 of Embodiment 2. FIG. The fixing device 6 has a fixing belt 60 as a fixing member, a planar heater 6H, a pressure roller 65 as a pressure member, and a temperature sensor 66 . The planar heater 6H heats the fixing belt 60 from the inner peripheral side. The pressure roller 65 is pressed against the fixing belt 60 to form a fixing nip therebetween. A temperature sensor 66 is, for example, a thermopile, and detects the surface temperature of the fixing belt 60 .

The fixing belt 60 is an endless belt, and has a base material made of metal and an elastic layer formed on the outer peripheral surface of the base material. The base material is made of, for example, stainless steel having moderate rigidity and flexibility. The elastic layer is made of silicone rubber, for example.

A planar heater 6</b>H is arranged on the inner peripheral side of the fixing belt 60 . A thermal diffusion member 64 made of, for example, stainless steel may be arranged between the planar heater 6H and the fixing belt 60 .

The planar heater 6H is formed by laminating an electrical insulating layer, a resistance heating element, and a protective layer in this order on a substrate made of, for example, stainless steel, and generates heat by energizing the resistance heating element. The planar heater 6</b>H is arranged such that the protective layer is in contact with the heat diffusion member 64 and transfers heat to the fixing belt 60 via the heat diffusion member 64 .

The planar heater 6H is divided into five in the X direction (longitudinal direction). The planar heater 6H includes a main heater 61 as a first heat generating portion located in the center in the X direction, and sub-heaters 62L and 62R as second heat generating portions located on the -X side and +X side of the main heater 61, respectively. (first sub-heater), and sub-heaters 63L and 63R (second sub-heaters), which are third heat generating portions located on the −X side of the sub-heater 62L and the +X side of the sub-heater 62R, respectively.

The main heater 61, sub-heaters 62L, 62R, and sub-heaters 63L, 63R are arranged symmetrically with respect to the center of the planar heater 6H in the X direction. The left and right sub-heaters 62L and 62R are electrically connected and heated simultaneously by energization. Similarly, the left and right sub-heaters 63L and 63R are also electrically connected and heated simultaneously by energization.

The main heater 61 heats a first region R1 in the center of the fixing belt 60 in the X direction. The sub-heaters 62L and 62R heat the second regions R2 on both sides of the first region R1 in the X direction. The sub-heaters 63L and 63R heat third regions R3 at both ends of the fixing belt 60 in the X direction. In the second embodiment, the center position of the fixing belt 60 in the X direction is the reference position P1 for conveying the medium.

The width of the main heater 61 in the X direction is set according to the narrow medium. The total width of the main heater 61 and the sub-heaters 62L and 62R is set according to the media of medium width. The total width of the main heater 61, the sub-heaters 62L, 62R, and the sub-heaters 63L, 63R is set according to the wide media.

The pressure roller 65 is configured similarly to the pressure roller 25 of the first embodiment, and forms a fixing nip with the fixing belt 60 . The temperature sensor 66 is configured similarly to the temperature sensor 26 of the first embodiment, and detects the temperature of the first region R1 of the fixing belt 60. FIG.

FIG. 13 shows main heater 61 and sub-heater 62L. FIG. 4 is a diagram showing a configuration for controlling 62R, 63L, and 63R; Here, the case where the left and right sub-heaters 62L and 62R are collectively controlled will be described, but these may be controlled separately in consideration of individual differences. The same applies to the left and right sub-heaters 63L and 63R.

One electrode of the main heater 61 is connected to a commercial power source 56 via a lead wire 61a, and the other electrode is connected to one terminal of the triac 53 via a lead wire 61b.

One electrode of each sub-heater 62L, 62R is connected to the commercial power supply 56 via a lead wire 62a, and the other electrode is connected to one terminal of the triac 54 via a lead wire 62b.

One electrode of each sub-heater 63L, 63R is connected to the commercial power source 56 through the lead wire 63a, and the other electrode is connected to one terminal of the triac 55 through the lead wire 63b.

The other terminal of each triac 53 , 54 , 55 is connected to commercial power supply 56 . A gate terminal of each triac 53 , 54 , 55 is connected to a triac drive circuit 52 . The triac drive circuit 52 is configured to insulate the primary and secondary sides of each of the triacs 53, 54 and 55 using phototriacs.

When the heater ON signal H1 to the main heater 61 is input, the triac drive circuit 52 operates the triac 53 and supplies power to the main heater 61 . Also, when a heater ON signal H2 is input to the sub-heaters 62L, 62R, the triac 54 is operated to supply power to the sub-heaters 62L, 62R. Further, when a heater ON signal H3 is input to the sub-heaters 63L and 63R, the triac 55 is operated to supply power to the sub-heaters 63L and 63R.

The fixing control section 51 outputs heater ON signals H1, H2 and H3 to the triac drive circuit 52 based on the temperature detection signal input from the temperature sensor 26 and the control signal input from the print control section 100 .

In the second embodiment, the temperatures of the main heater 61 and the sub-heaters 62L, 62R, 63L, 63R are controlled based on the temperature of the first region R1 (heated region by the main heater 61) of the fixing belt 60 detected by the temperature sensor 66. do. Therefore, the correction value A1 is used to control the sub-heaters 62L and 62R, and the correction value A2 is used to control the sub-heaters 63L and 63R.

FIG. 14 is a diagram showing a configuration for determining correction values A1 and A2. The correction values A1 and A2 are desirably determined after the image forming apparatus 1 is manufactured (for example, before product shipment).

The output measuring section 301, the triac driving circuit 302, the triacs 303, 304, 305, the current detecting section 306, and the commercial power source 307 are used to determine the correction values A1 and A2. These elements may be incorporated into the image forming apparatus 1 or may be independent units separate from the image forming apparatus 1 .

If the configuration (301 to 307) for determining the correction values A1 and A2 is an independent unit (output measurement unit), the fixing device 6 and the image forming apparatus are used when determining the correction values A1 and A2. 1, and the output measuring unit may be connected to the fixing device 6. FIG. In that case, after the correction value A is determined, the fixing device 6 is removed from the output measuring unit, and the fixing device 6 is incorporated into the image forming apparatus 1 .

A lead wire 61 a of the main heater 61 , a lead wire 62 a of the sub-heaters 62 L and 62 R, and a lead wire 63 a of the sub-heaters 63 L and 63 R are connected to the commercial power source 307 . A current detector 306 is connected between the lead wires 61 a , 62 a , 63 a and the commercial power source 307 . The current detection unit 306 measures currents flowing through the heaters 61 , 62 L, 62 R, 63 L, and 63 R and outputs the measurement results to the output measurement unit 301 .

A lead wire 61 b of the main heater 61 is connected to one terminal of the triac 303 . A lead wire 62 b of each sub-heater 62 L, 62 R is connected to one terminal of the triac 304 . A lead wire 63 b of each sub-heater 63 L, 63 R is connected to one terminal of the triac 305 . The other terminal of each triac 303 , 304 , 305 is connected to commercial power source 307 . A gate terminal of each triac 303 , 304 , 305 is connected to the triac drive circuit 302 .

The triac drive circuit 302 operates the triac 303 when a heater ON signal B1 is input to the main heater 61, and operates the triac 304 when a heater ON signal B2 is input to the sub-heaters 62L and 62R. When the heater ON signal B3 is input to 63L and 63R, the triac 305 is activated.

The correction values A1 and A2 are obtained by the following method. First, a heater ON signal B1 to the main heater 61 is input from the output measuring unit 301 to the triac driving circuit 302 . The heater ON signal B1 is not a pulse-like signal but a signal whose ON state continues for a certain period of time. As a result, a predetermined power is supplied from the commercial power source 307 to the main heater 61 . For example, a predetermined voltage (100 V, for example) is applied to the main heater 61 . At this time, the current _IM flowing through the main heater 61 is detected by the current detecting section 306 and output to the output measuring section 301 .

Next, a heater ON signal B2 to the sub-heaters 62L and 62R is input from the output measuring section 301 to the triac driving circuit 302. FIG. The heater ON signal B2 to the sub-heaters 62L and 62R is the same signal as the heater ON signal B1 to the main heater 61. FIG. As a result, the predetermined electric power is supplied from the commercial power supply 307 to the sub-heaters 62L and 62R. For example, the predetermined voltage is applied to the sub-heaters 62L and 62R. At this time, the current _IS1 flowing through the sub-heaters 62L and 62R is detected by the current detecting section 306 and output to the output measuring section 201. FIG.

Further, a heater ON signal B3 to the sub-heaters 63L and 63R is input to the triac driving circuit 302 from the output measuring section 301. FIG. The heater ON signal B3 to the sub-heaters 63L and 63R is the same signal as the heater ON signal B1 to the main heater 61. FIG. As a result, the predetermined electric power is supplied from the commercial power source 307 to the sub-heaters 63L and 63R. For example, the predetermined voltage is applied to the sub-heaters 63L and 63R. At this time, the current _IS2 flowing through the sub-heaters 63L and 63R is detected by the current detecting section 306 and output to the output measuring section 301. FIG.

Further, the designed current value (design value) flowing through the main heater 21 when the main heater 61 is supplied with a predetermined power from the commercial power supply 307 is assumed to be _IM 0 . The design current value (design value) flowing through the sub-heaters 62L and 62R when a predetermined power is supplied from the commercial power supply 307 to the sub-heaters 62L and 62R is assumed to be I _S10 . The designed current value (design value) flowing through the sub-heaters 63L and 63R when a predetermined power is supplied from the commercial power source 307 to the sub-heaters 63L and 63R is assumed to be I _S20 . All of I _M 0, I _S1 0, and I _S2 0 are obtained in advance by experiments and stored in the output measuring section 301 .

Current _IM and current _IS1 are proportional to the outputs of main heater 61 and sub-heaters 62L and 62R, respectively. Therefore, the ratio a1 of deviations from the design values of the outputs of the main heater 61 and the sub-heaters 62L and 62R is expressed by a1=(I _S1 /I _S1 0)/(I _M /I _M 0). A correction value A1 is derived based on this ratio a1.

Similarly, current I _M and current I _S2 are proportional to the outputs of main heater 61 and sub-heaters 63L and 63R, respectively. Therefore, the ratio a2 of the deviation from the design value of the outputs of the main heater 61 and the sub-heaters 63L and 63R is expressed by a2=(I _S2 /I _S2 0)/(I _M /I _M 0). A correction value A2 is derived based on this ratio a2.

Generation of heater ON signals to the sub-heaters 62L and 62R using the correction value A1 is performed as described with reference to FIG. 8 in the first embodiment. That is, the fixing control unit 51 calculates the duty by PID control from the temperature detected by the temperature sensor 66 and the target temperature, corrects the duty with the correction value A1, and limits the value of the duty to the range of 0 to 100. , to generate heater ON signals to the sub-heaters 62L and 62R.

Generation of heater ON signals to the sub-heaters 63L and 63R using the correction value A2 is also performed in the same manner. That is, the fixing control unit 51 calculates the duty by PID control from the temperature detected by the temperature sensor 66 and the target temperature, corrects the duty with the correction value A2, and limits the value of the duty to the range of 0 to 100. , to generate heater ON signals to the sub-heaters 63L and 63R.

As described above, in the second embodiment, the heaters 61, 62L, 62R, 63L, and 63R, which are planar heaters having heating resistors, cover the areas R1, R2, and R3 of the fixing belt 60 (fixing member). Also in a fixing device that heats, the main heater 61 and the sub-heaters 62L, 62R, 63L, 63R can be controlled with high accuracy based on the temperature detected by one temperature sensor 66. FIG.

In the first embodiment, the heater is a halogen heater, and in the second embodiment, the heater is a planar heater (having a heating resistor). good too.

In the first embodiment, the fixing member is divided into two regions R1 and R2 and heated, and in the second embodiment, the fixing member is divided into three regions R1, R2, and R3 and heated. Any number of regions may be used.

Although the image forming apparatus that forms a color image has been described in the above embodiment, the present invention can also be applied to an image forming apparatus that forms a single-color (monochrome) image. The present invention can also be applied to, for example, an image forming apparatus (such as a copier, a facsimile machine, a printer, a multifunction machine, etc.) that forms an image on a medium using an electrophotographic method, and a fixing device thereof.

REFERENCE SIGNS LIST 1 image forming apparatus 2, 6 fixing device 6H planar heater 7 medium supply section 8 transfer unit 9 medium discharge section 10, 10K, 10Y, 10M, 10C process unit (image forming unit) 11, 11K , 11Y, 11M, 11C photoreceptor drum (image carrier) 18, 18K, 18Y, 18M, 18C print head 20 fixing roller (fixing member) 21 main heater (first heater) 22 sub-heater (second heater), 25 pressure roller (pressure body), 26 thermopile (temperature sensor), 31, 41 filament (heat generating part), 32, 42 lead wire, 33, 43 valve, 51 fixing control section (control section), 52 triac drive circuit (switching drive circuit), 53, 54, 55 triac (switching element), 60 fixing belt (fixing body), 61 main heater (first heater), 62L, 62R sub-heater (second heater), 63L, 63R sub-heater (second heater) 65 pressure roller (pressure body) 66 thermopile (temperature sensor) 100 print control section 201, 301 output measurement section 202, 302 triac drive circuit 203, 204 , 303, 304, 305 triacs, 206, 306 current detectors.

Claims (11)

a fuser having a heated surface;
a pressure member forming a fixing nip with the fixing member;
a first heater that heats a first region of the fixing body;
a second heater that heats the second region of the fixing body;
a temperature sensor that detects the temperature of the first region of the fixing body;
a control unit that controls the first heater and the second heater based on the temperature detected by the temperature sensor;
Using a correction value determined in advance based on a ratio of a current value flowing through the first heater and a current value flowing through the second heater under a predetermined condition, the control unit adjusts the second heater. An image forming apparatus characterized by controlling The control unit
controlling the output of the first heater by changing the duty of a heater ON signal that drives the first heater;
2. The image forming apparatus according to claim 1, wherein the output of said second heater is controlled by changing the duty of a heater ON signal for driving said second heater. 3. The image forming apparatus according to claim 2, wherein the controller corrects the duty of the heater ON signal of the second heater according to the correction value. The correction value is a measured value IM of the current flowing through the first heater when the predetermined power is supplied to the first heater, and a measurement value _IM of the current flowing through the first heater when the predetermined power is supplied to the second heater. from the measured value I _S of the current flowing through the second heater, the design value I _M 0 of the current flowing through the first heater, and the design value I _S 0 of the current flowing through the second heater ,
a = ( _Is / _Is0 )/( _Im / _Im0 )
4. The image forming apparatus according to any one of claims 1 to 3, wherein the image forming apparatus is determined based on the value a calculated in . a current detection unit that detects the current flowing through the first heater and the current flowing through the second heater to obtain the measured value _IM and the measured value _IS ;
5. The image forming apparatus according to claim 4, further comprising an output measuring unit that calculates the correction value from the measured value _IM and the measured value _IS . The image forming apparatus according to any one of Claims 1 to 5, wherein the first area includes a conveyance reference position for a medium passing through the fixing nip. The image forming apparatus according to any one of claims 1 to 6, further comprising two or more second heaters for heating two or more of the second regions. The image forming apparatus according to any one of Claims 1 to 7, wherein the first heater and the second heater each comprise a halogen heater. The image forming apparatus according to any one of Claims 1 to 7, wherein the first heater and the second heater each comprise a planar heater having a heating resistor. The image forming apparatus according to any one of Claims 1 to 9, wherein the fixing member is a fixing roller or a fixing belt. a medium supply unit that supplies a medium;
an image forming unit that forms an image;
11. The image forming method according to any one of claims 1 to 10, further comprising a transfer unit that transfers the image formed by the image forming unit onto the medium and conveys the medium to the fixing nip. Device.

Images