JP2003122156A - Induction heat fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that the temperature of an induction coil rises and the temperature of a paper non-passage area rises. SOLUTION: The induction heat fixing device carries a recording material 5 having thereon a toner image 6 to be fixed, by holding the recording material 5 between a heating member 1 and a pressing member 2 and, at the same time, fixes the toner image 6 onto the recording material 5. The heating member 1 has induction coils 7 and 8, which cause an induction current. The induction coils 7 and 8 are disposed outside the pressing member 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating fixing device for fixing a toner image on a recording material to the recording material, and an image forming apparatus such as a copying machine, a printer or a facsimile.

[0002]

2. Description of the Related Art In image forming apparatuses such as copiers, printers, and facsimiles, a fixing device is internally provided in order to fix an unfixed toner image formed on a sheet such as plain paper as a recording material onto the recording material. The main part of the fixing device is provided with a heating member that heats a sheet on which an unfixed toner image is attached, and a pressure member that presses the sheet against the heating member and nips and conveys the sheet with the heating member. Composed of and.

Conventionally, such a fixing device is provided with a halogen lamp or the like as a heating heater inside a heating roller as a heating member, and the inside of the heating roller is heated by this heating heater to raise the heating roller to a predetermined temperature. I am letting you. However, in the fixing device of the type in which the heating member is heated by such a heating heater, it takes a long time to heat the heating roller to a required temperature, and the loss of the heating heater itself is large, so that the global warming and the like are prevented. Now that environmental problems have come to the forefront, there is a demand for a fixing device that is efficient and has a fast rise time.

In such a situation, an induction heating type fixing device (induction heating fixing device) in which a heating roller as a heating member is heated by an eddy current caused by electromagnetic induction by a magnetic flux generating induction coil disposed inside a pressure member. Device), which can heat the heating roller instantly, can dramatically shorten the rise time and is highly efficient, and is one of the methods attracting attention as a method that can contribute to environmental problems. .

Japanese Unexamined Patent Publication No. 10-74004 describes an induction heating fixing device in which an induction heating source for heating by causing an induction current in the fixing belt is arranged to face the fixing belt through a passage of a recording material. Has been done. JP 200
Japanese Laid-Open Patent Publication No. 1-135472 discloses a fixing device in which a heat insulating material is provided on the inner surface of the fixing roller so that heat generated by external heating of the fixing roller is not radiated to the inside of the fixing roller.

Japanese Unexamined Patent Publication (Kokai) No. 9-152807 discloses a heating member which generates heat due to an induced current, a pressure member arranged in pressure contact with the heating member, and a heating member provided inside the pressure member. An induction heating fixing device having an induction coil for generating a magnetic flux supplied to a member is described.

Japanese Unexamined Patent Publication No. 9-197853 discloses a fixing device that heats and fixes an unfixed image on a recording material that holds the unfixed image. The heating member is movable so that it can be conveyed, and an endless belt made of a heat-resistant film for sandwiching and passing the recording material between the heating member is provided. A fixing device is described, which is pressed from the inside of a belt toward the heating member so as to be able to rotate following the movement of the surface of the heating member.

[0008]

In the conventional induction heating fixing device, the heating roller is heated by the eddy current generated by the electromagnetic induction by the induction coil for generating the magnetic flux arranged inside the pressing member. The temperature rise around the induction coil for magnetic flux generation is large due to self-heating of the coil and heat release from the inside of the pressure member.Therefore, it is necessary to use a material and a holding member for the induction coil for magnetic flux generation that have excellent heat resistance at high temperatures. Yes, the cost was high.

Therefore, for example, a cooling mechanism such as a means for blowing air into the pressurizing member has been used in order to prevent the temperature rise of the magnetic flux generating induction coil. In that case, the air is blown into the pressurizing member. At the same time, the pressure member was also cooled to reduce the overall thermal efficiency.

In an image forming apparatus such as a copying machine, a printer, or a facsimile, the heating member of the fixing device is heated to some extent even in a standby state so that it can be used immediately when desired, and the temperature of the heating member is kept at a predetermined time during use. It is general to shorten the return time to return to. However, from the viewpoint of energy saving, it is desirable to reduce the energy consumed in the standby state as much as possible.

Therefore, as a heating member, a fixing device having a thin heating roller which has a short rise time and which can be turned off during standby is used. However, this fixing device has a drawback that the temperature of the non-sheet passing portion rises when a small size sheet is passed. For example, assume that A4 width paper is continuously passed and then A4 width paper is passed. When an A4 vertical width paper is passed, the non-paper passing portion at the end portion of the heating roller does not take heat from the paper, so the temperature rises, and then when the A4 horizontal width paper is passed, the heating roller Since the temperature is different between the central portion and the end portion of the sheet, this appears as a difference in gloss of the toner image on the paper, or the temperature of the end portion of the heating roller is too high, causing fixing failure.

It is an object of the present invention to provide an induction heating fixing device capable of preventing the temperature rise of the induction coil and efficiently heating the nip portion.

[0013]

In order to achieve the above-mentioned object, the invention according to a first aspect of the present invention is configured so that a recording material having a toner image to be fixed is nipped and conveyed by a heating member and a pressure member to form the toner image. An induction heating fixing device for fixing to the recording material, comprising an induction coil for generating an induction current in the heating member, wherein the induction coil is provided outside the pressing member.

According to a second aspect of the present invention, in the induction heating fixing device according to the first aspect, the pressing member is an endless belt.

The invention according to claim 3 is the invention according to claim 1 or 2.
In the induction heating fixing device described, the induction coil,
The region to be heated of the heating member is composed of a plurality of induction coils which are different in the width direction of the heating member.

According to a fourth aspect of the present invention, in the induction heating fixing device according to the third aspect, the plurality of induction coils heat the heating member via the pressing member.

According to a fifth aspect of the present invention, in the induction heating fixing device according to any one of the first to fourth aspects, the induction coil has a line connecting the center of the induction coil and the center of the heating member. It is located on the recording material inlet side from the center of the nip portion of the heating member and the pressure member.

The invention according to claim 6 has the induction heating fixing device according to any one of claims 1 to 5.

[0019]

1 shows an embodiment of the present invention.
The heating roller 1 as a heating member has an outer diameter (diameter) of 50.
The core metal is Fe or stainless steel, and the wall thickness is 1 mm. The surface layer of the heating roller 1 has a fluororesin layer as a release layer. This fluororesin layer is
PFA or FEP is used as a material, and a material for improving abrasion resistance and a material for adjusting resistance may be mixed as needed.

The endless pressure belt 2 as a non-magnetic pressure member has a base material made of a seamless polyimide film, and a fluororesin layer as a release layer is provided outside the base material. The pressure belt 2 may be provided with a silicone layer on the film layer and a fluororesin layer on the silicone layer, if necessary. Inside the pressure belt 2, a plurality of belt supporting rollers are rotatably provided.

In this embodiment, the plurality of rollers are composed of a belt inlet roller 3 and a belt outlet roller 4, and the pressure belt 2 is a belt inlet roller 3 and a belt outlet roller 4.
Have been hung over. The pressure belt 2 is tensioned by applying a pressing force to the heating roller 1 side by a tension mechanism (not shown) on the belt outlet roller 4, and an appropriate pressure is applied at the fixing nip portion between the pressure belt 2 and the heating roller 1. It depends.

Next, the behavior of the transfer paper 5 as a recording material will be described. The transfer paper 5 is transferred to the main body of the image forming apparatus (not shown).
A toner image 6 is formed on the transfer paper 5, and the transfer paper 5 enters the fixing device of this embodiment on a central basis. The transfer paper 5 is transferred to the pressure belt 2, and the heating roller 1 and the pressure belt 2 are transferred.
The surface on which the toner image 6 is carried is conveyed to the fixing nip portion formed by and with the heating roller 1 side. The heating roller 1 is rotationally driven by a drive unit (not shown), and the pressure belt 2 rotates along with the heating roller 1 and rotates. The transfer paper 5 is nipped and conveyed by the heating roller 1 and the pressure belt 2, and the toner image 6 is fixed by heating and pressing.

The surface pressure of the fixing nip portion formed by the heating roller 1 and the pressure belt 2 is 4.9 N / cm ² or less so as not to crush the toner image 6 on the transfer paper 5 in the fixing nip portion. , A normal pressure roller system (a system in which a pressure roller as a pressure member is brought into pressure contact with a heating roller), a surface pressure (9.8 N
/ Cm ² or more), the heat is transferred to the toner image 6 on the transfer paper 5 with a pressure significantly lower than that.

On the other hand, the passage time of the transfer paper 5 through the fixing nip portion is set to be long in order to guarantee the fixing property against the small pressure applied to the toner image 6 on the transfer paper 5 at the fixing nip portion. Therefore, the toner image 6 on the transfer paper 5 is heated at a low pressure for a long time even when the surface temperature of the heating roller 1 is 120 ° C., is sufficiently melted in the fixing nip portion, and is fixed on the transfer paper 5.

Next, a method of heating the heating roller 1 will be described. The induction coils 7 and 8 for generating magnetic flux are the pressure belt 2
The heating roller 1 is disposed on the outer side of the heating roller 1 via the pressure belt 2.
It is provided to face. The induction coil 7 that heats the entire surface of the heating roller 1 is provided closer to the heating roller 1 than the induction coil 8 that heats the central portion of the heating roller 1.
As shown in FIG. 2, as a core around which the induction coils 7 and 8 are wound, a central ferrite 9 and both end ferrites 10 and 11 are arranged in a line in the axial direction of the heating roller 1.

The heating roller 1 has a width (length in a direction parallel to the axial direction of the heating roller 1) of an A4 size transfer sheet (A4 size sideways transfer sheet) which is generally used for office work. The length of the ferrite 9 to 11 is set to be slightly longer, and the size of the entire ferrite 9 to 11 satisfies the A4 lateral size (heating roller 1
Is a size whose length in the direction parallel to the axial direction of is the same as the width of the A4 horizontal size transfer paper). The ferrite 9 is a size that satisfies the A4 vertical size (the size in which the length in the direction parallel to the axial direction of the heating roller 1 matches the width of the A4 vertical size transfer paper).

The induction coil 7 is wound on the outside of the ferrites 9 to 11 for a plurality of turns and provided in parallel (or substantially parallel) with the heating roller 1 and is connected to a control circuit (not shown).
The induction coil 8 is provided on the outer side of the induction coil 7 (the side farther from the heating roller 1) in parallel (or substantially parallel) to the heating roller 1 via an insulating sheet 12 as an insulating material, and a plurality of turns are provided on the outer side of the ferrite 9. It is wound and connected to the control circuit.

In the induction coils 7 and 8, the line connecting the centers of the induction coils 7 and 8 and the center of the heating roller 1 is located closer to the transfer paper 5 inlet side than the center of the fixing nip portion of the heating roller 1 and the pressure belt 2. There is. That is, the induction coils 7 and 8 form an angle θ1 between the line connecting the centers of the induction coils 7 and 8 and the center of the heating roller 1 and the center of the induction coils 7 and 8 and the transfer paper 5 inlet side end of the fixing nip portion. Is a line connecting the centers of the induction coils 7 and 8 and the center of the heating roller 1, and the induction coil 7,
It is installed so as to be smaller than an angle θ2 formed by the center of 8 and the end of the fixing nip portion on the outlet side of the transfer paper 5.

The induction coils 7 and 8 are the main heating induction coil 7 for heating the central portion of the heating roller 1 in the width direction,
The heating roller 1 includes a widthwise central portion and a widthwise end portion for heating the auxiliary heating induction coil 8. The main heating induction coil heats the widthwise central portion of the heating roller 1, and the main heating induction coil. The coils may be a plurality of induction coils in which the size (width) of the heating region of the heating roller 1 is different and the sizes (width) of the heating regions of the heating roller 1 are different from each other. The plurality of induction coils are selectively driven by the control circuit according to the size of the transfer paper 5 to heat each heating area (paper passing portion) of the heating roller 1.

Next, the temperature control will be described. The surface temperature of the heating roller 1 is the thermistor 1 as a temperature detecting element.
3, the temperature detection signal of the thermistor 13 is output to the control circuit. The control circuit controls the induction coils 7 and 8 in accordance with the sheet passing conditions and the temperature of the heating roller 1, so that temperature unevenness does not occur in the entire heating roller 1.

That is, the control circuit drives the induction coil 8 by the inverter to heat the paper passing portion at the center of the heating roller 1 when the A4 vertical size transfer paper is passed, and the A4 horizontal size transfer paper is passed. When the paper is printed, the inverter drives the induction coil 7 to heat the paper passing portion (entire) of the heating roller 1. In this case, the heating roller 1 induces an induction current (eddy current due to electromagnetic induction) by the magnetic flux from the induction coil 7 or 8.
Occurs and is heated. The control circuit is the thermistor 1.
Based on the temperature detection signal from 3, the current of the induction coil 7 or 8 is controlled so that the surface temperature of the heating roller 1 reaches a predetermined temperature.

For example, consider a case where an A4 vertical size transfer sheet is continuously passed and then an A4 horizontal size transfer sheet is passed. When an A4 vertical size transfer sheet is passed, a current flows only through the induction coil 8 to heat the sheet passing portion in the center of the heating roller 1. Therefore, since the non-sheet passing portion of the heating roller 1 is not heated, the temperature rise at the end portion of the heating roller, which has been a problem in the past, does not occur. When an A4 size transfer sheet is passed, a current flows only through the induction coil 9 and the entire heating roller 1 is heated. This allows
It is possible to prevent unevenness in the surface temperature of the heating roller 1 due to the heat being transferred from the heating roller 1 to the transfer paper 5. Moreover, a single inverter supplies a current to either the induction coil 7 or 8 to heat the heating roller 1. The central part or the whole of one can be heated.

According to this embodiment, the heating roller 1 as a heating member is provided with induction coils 7 and 8 for generating an induced current, and the induction coils 7 and 8 are provided outside the pressure belt 2 as a pressure member. Since the fixing nip portion is provided, the fixing nip portion can be directly heated, the temperature of the induction coil does not rise, and the heat can be efficiently transmitted to the transfer paper and the toner image. Further, by directly heating the vicinity of the fixing nip portion by the induction coils 7 and 8, the heat is transferred from the heating roller to the transfer paper and the toner image immediately, so that it is not necessary to provide a heat insulating material inside the heating roller.

Further, according to this embodiment, since the induction coil has a plurality of induction coils 7 and 8 in which the region to be heated of the heating roller 1 as the heating member is different in the width direction of the heating roller 1, The temperature unevenness of the heating roller due to the temperature rise of the paper passing portion can be eliminated.

Further, according to this embodiment, since the plurality of induction coils 7 and 8 heat the heating roller 1 as a heating member via the pressing belt 2 as a pressing member, the temperature depending on the size of the transfer paper is used. There is no unevenness, the temperature rise of the induction coil can be prevented, and stable fixing can be performed.

Further, according to this embodiment, in the induction coils 7 and 8, the line connecting the centers of the induction coils 7 and 8 and the center of the heating roller 1 as a heating member is a nip between the heating roller 1 and the pressure belt 2. Since it is on the recording material entrance side from the center of the part,
The heating roller can be heated on the inlet side of the nip portion, the transfer paper can be ejected from the nip portion after sufficiently supplying heat to the transfer paper, and the fixing property can be improved.

FIG. 3 shows another embodiment of the present invention. Around the drum-shaped photosensitive member 101 as an image bearing member which is rotated in the arrow direction by a driving unit (not shown), a charging unit 102,
A cleaning unit 103, a developing unit 107 including a developing sleeve 105 as a developing unit that visualizes an electrostatic latent image on the photoconductor 101, and a transfer unit 106 are arranged.

The photoconductor 101 is uniformly charged by the charging means 102 and then exposed by the laser light L modulated by the image data from the laser optical system 140 as a writing means (exposure means) to form an electrostatic latent image. Is formed, the developing unit 1
At 07, the electrostatic latent image is developed into a toner image. The toner image on the photoconductor 101 is transferred to the sheet P as described later, and the photoconductor 101 is cleaned by the cleaning unit 103 after the toner image is transferred. Therefore, the charging unit 102, the laser optical system 140, the developing unit 10
An image forming unit 7 forms a toner image on the photoconductor 101.

At the lower part of the apparatus, there is provided a paper feeding device having a paper feeding cassette 110 which can be attached and detached in the direction of arrow a. Paper P stored in paper feed cassette 110 (paper 5 described above)
Is supported by the middle plate 111 and is pressed against the paper feed roller 113 via the arm 112 by the force of a spring (not shown). When the paper feed roller 113 rotates, the top paper in the paper feed cassette 110 is fed by a command issued from a control unit (not shown) and the paper feed roller 113 rotates, and the separation pad 114 prevents double feeding. While being conveyed, it is conveyed to the registration roller pair 115 on the downstream side.

An operation surface is arranged on the right side of the apparatus, and the operation panel 130 projects from the upper front surface of the exterior part 131 (on the right side of the apparatus in FIG. 3). Further, the paper feed tray 132 is rotatably attached by a pin 133, and the paper feed tray 1
The uppermost sheet in 32 is fed by the sheet feeding roller and conveyed to the registration roller pair 115 on the downstream side while preventing the double feeding by the separation pad. Paper cassettes 110 and 13
Either one of the sheets in 2 is selectively fed.

The pair of registration rollers 115 sends the conveyed paper P toward the transfer means 106 at a timing so as to be synchronized with the image (toner image) on the photoconductor 101. The transfer unit 106 transfers the toner image on the photoconductor 101 to the sheet P sent from the registration roller pair 115, and the sheet P to which the toner image is transferred is conveyed to the fixing device 116. As the fixing device 116, the fixing device of the above embodiment shown in FIG. 1 is used, and the toner image on the paper P is fixed on the paper P by heating and pressing.

The fixed paper P from the fixing device 116
Are discharged onto the discharge tray 122 from the discharge port 121 with the image surface facing downward by the discharge roller pair 120 and stacked. The paper discharge stopper 125 is slidable in the direction of arrow b in order to correspond to the size of the paper to be discharged. In the case 134 arranged on the left side in the figure, the power circuit 135 and the printed board (engine driver board) 1
Electrical components and control devices such as 36 are stored, and a controller board 137 is also stored. The cover 138 forming the paper discharge tray 122 can be opened around a rotation fulcrum 139.

According to the fixing device 116 of this embodiment, the temperature of the induction coil does not rise in the fixing device, heat can be efficiently transferred to the transfer paper and the toner image, and a good image can be obtained.

[0044]

As described above, according to the first and second aspects of the present invention, the temperature of the induction coil does not rise and heat can be efficiently transferred to the recording material and the toner image. According to the third aspect of the invention, it is possible to eliminate the temperature unevenness due to the temperature rise of the non-sheet passing portion. According to the invention of claim 4, there is no temperature unevenness due to the size of the recording material, the temperature rise of the induction coil can be prevented, and stable fixing can be performed.

According to the fifth aspect of the invention, the heating member can be heated on the inlet side of the nip portion, and the recording material can be ejected from the nip portion after sufficiently supplying heat to the recording material. Can be improved. According to the sixth aspect of the invention, the temperature of the induction coil does not rise in the fixing device, heat can be efficiently transferred to the recording material and the toner image, and a good image can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a side view showing an induction coil, a ferrite, and a heating roller in the example.

FIG. 3 is a sectional view showing another embodiment of the present invention.

[Explanation of symbols]

1 heating roller 2 pressure belt 5 recording materials 7, 8 induction coil 9-11 Ferrite 12 Insulation sheet 116 fixing device

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H033 AA02 BA11 BA12 BB12 BB18                       BB33 BE06                 3K059 AA08 AB19 AB28 AD03 AD05                       AD14 AD18 AD39 AD40 BD23                       CD19 CD39 CD53 CD64 CD73                       CD77 CD78

Claims (6)

[Claims] 1. An induction heating fixing device for fixing a toner image onto a recording material while sandwiching and transporting a recording material having a toner image to be fixed between a heating member and a pressing member, wherein the induction heating fixing device guides the toner image to the heating member. With an induction coil that produces an electric current,
An induction heating fixing device characterized in that the induction coil is provided outside the pressing member. 2. The induction heating fixing device according to claim 1, wherein the pressing member is an endless belt. 3. The induction heating fixing device according to claim 1, wherein the induction coil comprises a plurality of induction coils whose regions to be heated by the heating member are different in the width direction of the heating member. Induction heating fixing device. 4. The induction heating fixing device according to claim 3, wherein the plurality of induction coils heat the heating member via the pressing member. 5. The induction heating fixing device according to claim 1, wherein the induction coil has a line connecting the center of the induction coil and the center of the heating member. An induction heating fixing device, which is located closer to the recording material inlet than the center of the nip portion of the pressure member. 6. An image forming apparatus comprising the induction heating fixing device according to claim 1. Description: