JP2009098353A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing apparatus and an image forming apparatus reducing the increase of power consumption, the occurrence of noise and wearing-out of a fixing roller and a heating belt at the stand-by. <P>SOLUTION: In a paper passing time, electromagnetic induction heating is performed by an external heater 204 while rotating the fixing roller 201. At the stand-by, electromagnetic induction heating is performed by an internal heater 205 in the rotation stopped state of the fixing roller 201. The internal heater generates magnetic flux with a coil coaxial with the fixing roller 201. A core part 206 guides the magnetic flux to a nickel electrocast sleeve of the fixing roller 201 to efficiently generate heat. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fixing device and an image forming apparatus, and more particularly to a technique for eliminating uneven fixing.

In recent years, the demand for energy-saving image forming apparatuses has increased with the increase in environmental awareness. In the image forming apparatus, most of the electric power is consumed in the fixing process, and energy saving of the fixing device is most effective. For example, a fixing device to which electromagnetic induction heating (IH: Induction Heating) is applied has been proposed.
In view of user convenience, it is essential that the fixing device be rapidly heated at the time of startup. In the IH fixing device, in order to realize rapid heating, an external IH method has been proposed in which the fixing roller and the heating belt are thinned to have a low heat capacity and electromagnetic induction heating is performed from the outside of the fixing roller. According to the external IH method, the magnetic flux can be concentrated on a part of the fixing roller and the heating belt, and these can be rapidly heated.
JP 2002-82549 A

However, if the fixing roller and the heating belt have a low heat capacity, it becomes difficult for heat to be transmitted in the circumferential direction, resulting in uneven temperature. Since the gloss of the finished toner varies depending on the melting temperature of the toner, for example, when the temperature unevenness occurs, a striped pattern due to a change in gloss appears in a photographic image.
Since it is necessary to eliminate such temperature unevenness, conventionally, heating is performed while rotating the fixing roller and the heating belt during standby. For this reason, various problems such as increased power consumption during standby, noise generation, and premature exhaustion of the fixing roller and the heating belt occur.

  The present invention has been made in view of the above-described problems, and provides a fixing device and an image forming apparatus that reduce an increase in power consumption and noise generation during standby and consumption of a fixing roller and a heating belt. The purpose is to do.

  In order to achieve the above object, a fixing device according to the present invention is a fixing device that fuses toner to a recording sheet by a roller and is arranged outside the roller and heats the roller by electromagnetic induction heating. An external coil, an internal coil that is arranged inside the roller and heats the roller evenly in the circumferential direction by electromagnetic induction heating, and when the paper is passed, the heating by the internal coil is stopped, and the roller is rotated by the external coil. And a coil control means for heating the roller with the internal coil in a state where the heating by the external coil is stopped during standby, and the heating temperature by the internal coil is lower than the heating temperature by the external coil It is characterized by.

In this way, the roller is preheated in the circumferential direction evenly by the internal coil during standby, so the occurrence of temperature unevenness when the roller is heated by the external coil during paper feeding is suppressed and fixing unevenness is eliminated. can do.
In the present invention, the roller refers to (a) a fixing roller that presses the pressure roller to fuse the toner to the recording sheet, and (b) a heating belt that is stretched over the fixing roller and presses the pressure roller. In the case of fusing toner on the recording sheet, a heating roller is used which heats the heating belt over a heating belt.

In this case, it is preferable that the internal coil be heated by electromagnetic induction using a coil having the same axis as the roller. The internal coil may generate a magnetic flux that forms a closed loop in a plane orthogonal to the roller axis.
The fixing device according to the present invention is characterized by comprising roller control means for rotating the roller when the paper is passed and stopping the rotation of the roller when waiting. In this way, power consumption during standby can be reduced and generation of noise can be suppressed. In addition, wear of movable parts such as rollers can be suppressed.

  An image forming apparatus according to the present invention is an image forming apparatus provided with a fixing device that melts toner with a roller and fixes the toner on a recording sheet. The fixing device is disposed outside the roller for electromagnetic induction heating. An external coil that heats the roller, an internal coil that is arranged inside the roller and that heats the roller evenly in the circumferential direction by electromagnetic induction heating, and when the paper is passed, while heating by the internal coil is stopped, A coil control means for heating the roller with the internal coil in a state in which the roller is heated with the external coil and the heating with the external coil is stopped during standby, and the heating temperature by the internal coil is heated by the external coil. It is characterized by being lower than the temperature. In this way, the same effect as above can be obtained.

In this case, it is preferable that the internal coil be heated by electromagnetic induction using a coil having the same axis as the roller. The internal coil may generate a magnetic flux that forms a closed loop in a plane orthogonal to the roller axis.
The image forming apparatus according to the present invention includes a roller control unit that rotates the roller when the paper is passed and stops the rotation of the roller when the paper is waiting. In this way, power consumption during standby can be reduced and generation of noise can be suppressed. In addition, wear of movable parts such as rollers can be suppressed.

Note that image quality deterioration due to temperature unevenness is more noticeable in a color image than in a monochrome image. However, according to the present invention, image quality deterioration can be prevented even in a color image.
Further, in order to shorten the image forming time, it is necessary to shorten the start-up time of the fixing device. However, since the temperature rise rate of the internal coil is slower than that of the external coil, the fixing device using only the internal coil is in a standby state. The start-up time cannot be shortened unless the roller temperature is increased.

  On the other hand, according to the present invention, since the external coil is used, the roller temperature during standby can be kept low. Also in this sense, according to the present invention, power consumption during standby can be reduced.

Hereinafter, an embodiment of a fixing device according to the present invention will be described with an image forming apparatus as an example with reference to the drawings.
[1] Configuration of Image Forming Apparatus First, the configuration of the image forming apparatus according to the present embodiment will be described.
FIG. 1 is a diagram illustrating a main configuration of the image forming apparatus according to the present embodiment. As shown in FIG. 1, the image forming apparatus 1 includes a fixing device 100, a control unit 101, image forming units 102 </ b> Y to 102 </ b> K, and an intermediate transfer belt 103.

The control unit 102 controls the fixing device 100, the image forming units 102Y to 102K, the intermediate transfer belt 103, and the like. In addition, the control unit 102 performs image processing on image data obtained by reading a document or image data received from another device.
The image forming units 101 </ b> Y to 101 </ b> K generate toner images of yellow (Y), cyan (C), magenta (M), and black (K) according to the image data, and transfer them onto the intermediate transfer belt 102. The toner image on the intermediate transfer belt 103 is transferred to a recording sheet, thermally fixed by the fixing device 100, and then discharged.

[2] Configuration of Fixing Device 100 First, the main configuration of the fixing device 100 will be described.
FIG. 2 is an external perspective view showing the main configuration of the fixing device according to the present embodiment. As shown in FIG. 2, the fixing device 100 includes a fixing roller 201, a pressure roller 202, a gear 203, electromagnetic induction heaters 204 and 205, a core portion 206, and a fixing roller holding member 207.

The fixing roller 201 includes a tubular cored bar, a silicone sponge rubber layer covering the cored bar, and a belt attached to the outside of the silicone sponge rubber layer. The belt is formed by coating an endless nickel electroformed sleeve surface with silicone rubber and a PFA (Tetrafluoroethylene-perfluoroalkylvinylether copolymer) tube.
The pressure roller 202 includes a tubular cored bar, a silicone sponge rubber layer that covers the cored bar, and a PFA tube that covers the silicone sponge rubber layer. The pressure roller 202 includes a gear 203 at one end in the tube axis direction, and the pressure roller 202 is rotationally driven by the gear 203.

The fixing roller 201 is in pressure contact with the pressure roller 202 and rotates following the rotation of the pressure roller 202. When the paper is passed, the toner on the recording sheet is melted and pressed by the high-temperature fixing roller 201.
An electromagnetic induction heater 204 (hereinafter referred to as “external heater”) is a long magnetic flux generator having the tube axis direction of the fixing roller 201 as a longitudinal direction, and is disposed close to the fixing roller 201 from the outside. Yes. The external heater 204 heats the nickel electroformed sleeve of the fixing roller 201 by electromagnetic induction heating (IH: Induction Heating).

An electromagnetic induction heater 205 (hereinafter, referred to as “internal heater”) is a magnetic flux generator disposed inside the fixing roller 201 and heats the nickel electroformed sleeve of the fixing roller 201 by electromagnetic induction heating.
The core portions 206 are disposed at both ends of the fixing roller 201 in the tube axis direction, and guide the magnetic flux generated by the internal heater 205 to the surface of the fixing roller 201. The fixing roller holding member 207 holds the fixing roller 201.

[3] Heating method when passing paper Next, a heating method when passing paper will be described. The fixing device 100 heats the fixing roller 201 by the external heater 204 when the paper is passed.
FIG. 3 is a cross-sectional view of a plane orthogonal to the tube axis of the fixing device 100. As shown in FIG. 3, the external heater 204 includes a coil 204a, a core 204b, and a coil bobbin 204c. The coil 204 a is wound around the coil bobbin 204 c so as to follow the outer peripheral surface of the fixing roller 201. The core 204b guides the magnetic flux generated by the coil 204a to the surface of the fixing roller 201, particularly to the nickel electroformed sleeve. The internal heater 205 includes a coil 205a. The coil 205 a is formed so as to wind the tube shaft of the fixing roller 201.

FIG. 4 is a diagram showing the magnetic flux generated by the coil 204a. As shown in FIG. 4, the magnetic flux 401 generated by the coil 204a passes through the surface of the nickel electroformed sleeve. Thereby, an eddy current is generated in the nickel electroformed sleeve, and Joule heating is performed.
[4] Standby heating method Next, a standby heating method will be described. The fixing device 100 heats the fixing roller 201 with an internal heater 205.

FIG. 5 is a cross-sectional view of the surface of the fixing device 100 including the tube axis. In FIG. 5, the illustration of the fixing roller holding member 207 is omitted.
As shown in FIG. 5, the internal heater 205 includes a coil 205a, an insulating member 205b, and a coil bobbin 205c. The coil 205a is wound around a coil bobbin 205c and has the same axis as the fixing roller 201. The insulating member 205b electrically insulates the coil 205a and the fixing roller 201 from each other.

The core 206a guides the magnetic flux generated by the coil 205a so as to pass through the surface of the fixing roller 201, particularly the nickel electroformed sleeve. The core holding member 206b is fixed to the fixing roller 201 and holds the core 206a. As a result, the core 206a rotates together with the fixing roller 201.
FIG. 6 is a diagram showing the magnetic flux generated by the coil 206a. As shown in FIG. 6, the magnetic flux 601 generated by the coil 206a is uniformly distributed in the circumferential direction of the fixing roller 201 in the nickel electroformed sleeve, so that temperature unevenness can be eliminated.

FIG. 7 is an external perspective view showing the shape of the core 206a. By taking such a shape, the core 206a guides the magnetic flux generated by the coil 205a into the nickel electroformed sleeve.
Note that the fixing roller 201 stops without rotating during standby. Therefore, power consumption during standby can be reduced, and noise generation can be suppressed. Further, the consumption of the fixing roller 201 is reduced.

[5] Configuration of Control Unit 101 Next, the configuration of the control unit 101 will be described.
FIG. 8 is a circuit diagram illustrating a configuration of the control unit 101. As shown in FIG. 8, the control unit 101 includes a CPU (Central Processing Unit) 801, a motor drive unit 802, an IH inverter 803, a RAM (Random Access Memory) 804, and a ROM (Read Only Memory) 805 via an internal bus 806. Become connected.

  The CPU 801 reads the control program stored in the ROM 805, which is a nonvolatile memory, into the RAM 804 and executes it. The motor drive circuit 802 drives the motor 810 under the control of the CPU 801 to rotate or stop the fixing roller 201 or the like. The IH inverter 803 receives power from the AC power source 820 under the control of the CPU 801 and supplies power to the external heater 204 and the internal heater 205.

The CPU 801 rotationally drives the fixing roller 201 and the like by the motor drive circuit 802 when the paper is passed. The CPU 801 stops power supply to the internal heater 205 by the IH inverter 803 and supplies power to the external heater 204. As a result, the fixing roller 201 is heated to 170 ° C., for example.
On the other hand, during standby, the CPU 801 stops rotational driving of the fixing roller 201 and the like by the motor driving circuit 802. In addition, the CPU 801 stops power supply to the external heater 204 by the IH inverter 803 and supplies power to the internal heater 205. As a result, the fixing roller 201 is heated to 160 ° C., for example.

[6] Modifications Although the present invention has been described based on the embodiments, it is needless to say that the present invention is not limited to the above-described embodiments, and the following modifications can be implemented. .
(1) Although the case where the fixing roller is heated by an external heater has been described in the above embodiment, the present invention is not limited to this, and the following may be used instead.

FIG. 9 is a diagram illustrating a configuration of a fixing device according to this modification. As shown in FIG. 9, the fixing device 9 includes a fixing roller 901, a pressure roller 902, a heating roller 903, coils 904a and 905a, a core 904b, a coil bobbin 904c, and a heating belt 906.
The heating belt 906 is stretched between the fixing roller 901 and the heating roller 903, and rotates according to the rotation of the fixing roller 901 and the like. The heating belt 906 is in pressure contact with the pressure roller 902.

The heating roller 903 is provided with a nickel electroformed sleeve, and generates heat by electromagnetic induction heating by the coil 904a when the paper is passed. The heating belt 906 heated by the heating roller 903 fuses the toner on the recording sheet. Further, at the time of standby, the heating roller 903 is heated by electromagnetic induction by the coil 905a and generates heat uniformly in the circumferential direction.
Therefore, uneven fixing is eliminated. Further, the heating roller 903 does not rotate during standby and stops. Therefore, power consumption during standby can be reduced, and noise generation can be suppressed. Further, wear of the heating roller 903 and the heating belt 906 is reduced.

(2) In the above embodiment, the case where the fixing roller is heated at the time of standby by the coil having the same axis as the fixing roller has been described. However, it goes without saying that the present invention is not limited to this. You may do as follows.
FIG. 10 is a diagram showing a configuration of an internal heater according to this modification. As shown in FIG. 10, the internal heater 10 has a large number of small coils 1001 disposed on a coil holding member 1002. The internal heater 10 is disposed so as to have the same axis as a fixing roller (not shown).

On the other hand, a large number of small coils 1001 are arranged at equal intervals and densely on the coil holding member 1002, and generate a magnetic flux 1001a substantially orthogonal to the peripheral surface of the fixing roller. Even if such an internal coil 10 is used, the temperature unevenness of the fixing roller can be eliminated.
(3) In the above embodiment, the case where the coil 205a rotates together with the fixing roller 201 has been described. However, the present invention is not limited to this, and the coil 205a is used together with the fixing roller 201 instead. May not rotate. Even if it does in this way, the effect of the present invention can be acquired.

(4) In the above embodiment, the case where the nickel electroformed sleeve included in the fixing roller 201 generates heat due to electromagnetic induction heating has been described, but it is needless to say that the present invention is not limited to this, and other embodiments can be used instead. A heat generating material may be used.
(5) In the above embodiment, the case where the image forming apparatus is a tandem type color image forming apparatus has been described, but it is needless to say that the present invention is not limited to this. The present invention can be applied to obtain the effect regardless of whether the image is monochrome. Further, the image forming apparatus may be any of an MFP (Multifunctional Peripheral), a copier, a printer, a facsimile machine, and the like.

  (6) In the above-described embodiment, the case where the fixing roller is set to 170 ° C. when passing the paper and 160 ° C. when waiting is described, but it goes without saying that the present invention is not limited to this. It is also good. The effects of the present invention can be obtained regardless of the heating temperature of the fixing roller.

  The fixing device and the image forming apparatus according to the present invention are useful as a fixing device and an image forming apparatus that eliminate fixing unevenness.

1 is a diagram illustrating a main configuration of an image forming apparatus according to an exemplary embodiment. FIG. 2 is an external perspective view illustrating a main configuration of the fixing device 100. 3 is a cross-sectional view of a surface of the fixing device 100 perpendicular to the tube axis. It is a figure which shows the magnetic flux which the coil 204a generates. 2 is a cross-sectional view of a surface including a tube axis of the fixing device 100. FIG. It is a figure which shows the magnetic flux which the coil 206a generates. It is an external appearance perspective view which shows the shape of the core 206a. 3 is a circuit diagram showing a configuration of a control unit 101. FIG. It is a figure which shows the structure of the fixing device which concerns on the modification (1) of this invention. It is a figure which shows the structure of the internal heater which concerns on the modification (2) of this invention.

Explanation of symbols

1 …………………………………………………… Image forming apparatus 9, 100 ………………………………………… Fixing device 10 ……………… ……………………………… Internal heater 101 …………………………………………… Control units 102Y-102K …………………………… Image formation Unit 103 ………………………………………… Intermediate transfer belt 201,901 ………………………………… Fixing roller 202,902 ………………… ……………… Pressure roller 203 ………………………………………… Gears 204, 205 …………………………………… Electromagnetic induction heater 206… ………………………………………… Core section 207 ……………………………………………… Fixing roller holding members 204a, 205a, 904a, 905a ... coil 204b , 206 , 904b ............. Cores 204c, 205c, 904c ............. Coil bobbins 401, 601, 1001a ............... Magnetic flux 205b ....................... ... Insulating member 206b ………………………………………… Core holding member 801 ………………………………………… CPU
802... ………………………………………… Motor drive unit 803 ……………………………………………… IH inverter 804 …………………… ……………………… RAM
805 …………………………………………… ROM
806 ……………………………………………… Internal bus 810 ……………………………………………… Motor 820 ………………………… ………………… AC power supply 903 …………………………………………… Heating roller 906 …………………………………………… Heating belt 1001 ………………………………………… Small Coil 1002 ………………………………………… Coil Holding Member

Claims (8)

A fixing device for fusing toner with a roller and fixing the toner on a recording sheet,
An external coil arranged outside the roller and heating the roller by electromagnetic induction heating;
An internal coil that is arranged inside the roller and heats the roller evenly in the circumferential direction by electromagnetic induction heating;
When passing the paper, with the heating by the internal coil stopped, the roller is heated by the external coil,
A coil control means for heating the roller with the internal coil in a state where heating by the external coil is stopped at the time of standby,
A fixing device in which a heating temperature by an internal coil is lower than a heating temperature by an external coil. The fixing device according to claim 1, wherein the internal coil is electromagnetically heated by a coil having the same axis as the roller. The fixing device according to claim 1, wherein the internal coil generates a magnetic flux that forms a closed loop in a plane orthogonal to the axis of the roller. The fixing device according to claim 1, further comprising a roller control unit that rotates the roller when the paper is passed and stops the rotation of the roller when the paper is waiting. An image forming apparatus including a fixing device that fuses toner to a recording sheet by a roller,
The fixing device includes:
An external coil arranged outside the roller and heating the roller by electromagnetic induction heating;
An internal coil that is arranged inside the roller and heats the roller evenly in the circumferential direction by electromagnetic induction heating;
When passing the paper, with the heating by the internal coil stopped, the roller is heated by the external coil,
A coil control means for heating the roller with the internal coil in a state where heating by the external coil is stopped at the time of standby,
An image forming apparatus, wherein a heating temperature by an internal coil is lower than a heating temperature by an external coil. 6. The image forming apparatus according to claim 5, wherein the internal coil is heated by electromagnetic induction using a coil having the same axis as the roller. 6. The image forming apparatus according to claim 5, wherein the internal coil generates a magnetic flux that forms a closed loop in a plane perpendicular to the axis of the roller. 6. The image forming apparatus according to claim 5, further comprising a roller control unit that rotates the roller when the paper is passed and stops the rotation of the roller when the paper is waiting.

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