JP3342246B2 - Image heating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image heating apparatus for generating an eddy current using electromagnetic induction and heating the image.

[0002] This apparatus is a fixing device in an image forming apparatus such as an electrophotographic copying machine, a printer and a facsimile, that is, a resin which is heat-meltable by an appropriate image forming process means such as electrophotography, electrostatic recording and magnetic recording. The present invention relates to an apparatus for heat-fixing an unfixed toner image formed directly or indirectly on the surface of a recording material by using a toner made of the above as a permanent fixed image on the surface of the recording material.

[0003]

2. Description of the Related Art FIG. 9 is a diagram for explaining a conventional technique.
FIG. 1 is a schematic sectional view of a laser beam printer in which electrophotography is applied to a printer. The operation of this device will be described below.

The intensity of the laser beam from the scanner 13 is modulated by an image information signal sent from a host computer, and an electrostatic latent image is formed on the photosensitive drum 11. The intensity of the laser beam and the irradiation spot diameter are appropriately set according to the resolution of the image forming apparatus and the desired image density. The portion of the electrostatic latent image on the photosensitive drum 11 where the laser beam is irradiated is a bright portion potential _VL. The other parts are the primary charger 12
In form by being held in the charged dark portion potential V _D. The photosensitive drum 11 rotates in the direction of the arrow, and the electrostatic latent images are sequentially developed by the developing device 14. The toner in the developing device 14 is a developing sleeve 140 which is a toner supply rotating body.
2 and the developing blade 1401, the toner height and tribo are controlled, and a uniform toner layer is formed on the developing sleeve 1402. The developing blade 1401 is usually made of metal or resin, and the resin blade is in contact with the developing sleeve 1402 with an appropriate contact pressure. The toner layer formed on the developing sleeve 1402 faces the photosensitive drum 11 with the rotation of the developing sleeve 1402 itself, and V is applied by the voltage _Vdc applied to the developing sleeve 1402 and the electric field formed by the surface potential of the photosensitive drum 11. Only the part of _L is visualized selectively. The toner image on the photosensitive drum 11 is sequentially transferred by the transfer device 15 to the paper sent from the paper feeding device. As a transfer device, in addition to the corona charger shown in the figure, there is a transfer roller system which supplies current from a power supply to a conductive elastic rotating body to transfer the paper while applying transfer charge to paper. The paper on which the toner image has been transferred is sent to the fixing device 10 with the rotation of the photosensitive drum 11, and becomes a permanent fixed image by heating and pressing.

As an image heating device represented by a heat fixing device, a contact heating system such as a film heating system has been widely used in addition to the heat roller system shown in FIG.

Among them, as a fixing device of a device for forming a full-color image which is required to be capable of sufficiently heating and melting a maximum of four toner layers, a core metal of a fixing roller having a high heat capacity and a toner image are wrapped. The toner image is heated via a rubber elastic layer for uniform melting.

On the other hand, Japanese Utility Model Laid-Open Publication No. 51-109737 discloses an induction heating fixing device in which a magnetic flux induces a current in a fixing roller to generate heat by Joule heat. This makes it possible to directly generate heat in the fixing roller by utilizing the generation of an induced current, and achieves a fixing process with higher efficiency than a heat roller using a halogen lamp.

Further, Japanese Utility Model Laid-Open No. 54-17973 discloses a configuration in which excitation coils are provided on both a fixing roller and a pressure roller.

US Pat. No. 5,278,618 discloses an example in which the fixing roller is heated by an exciting member near the nip using a fixing film having a small heat capacity.

[0010]

However, in the above fixing device, there is a problem that not only the heat capacity of the fixing roller is large, the power required for heating becomes large, but also the wait time becomes long.

When a fixing roller having a large heat capacity such as a full-color image recording apparatus is used, a delay occurs between the temperature control and the temperature rise on the surface of the fixing roller. Had occurred.

Further, in the fixing device disclosed in Japanese Utility Model Laid-Open Publication No. 51-109737, the energy of the alternating magnetic flux generated by the exciting coil is used to raise the temperature of the entire fixing roller, so that the heat loss is large, and the fixing to the input energy is performed. There was a drawback that the energy density was low and the efficiency was poor.

In the fixing device disclosed in Japanese Utility Model Laid-Open No. 54-19773, the pressure roller is heated by induction heating. However, the fixing roller that contacts the toner image has the same configuration as the above. However, as described above, there is a problem that the temperature of the fixing roller cannot be rapidly increased due to a large energy loss. Further, since the excitation coils prepared for both rollers are simultaneously driven, there is a disadvantage that power consumption is large.

In US Pat. No. 5,278,618, a fixing film as a member to be heated is used to obtain a rapid temperature rise by local heating. However, since the heated portion is limited to the inside of the nip, magnetic saturation occurs. In addition, there is a problem that sufficient efficiency cannot be obtained, and a preheating effect cannot be obtained. Therefore, an image having a large amount of toner, such as a full-color image, has an image disorder due to rapid heating.

An object of the invention according to the present application is to make it possible to reduce the wait time with low power consumption by effectively utilizing input power in an image heating apparatus, and to reduce the amount of toner such as a full-color image. Another object of the present invention is to provide an image heating apparatus capable of maintaining a high image quality and obtaining a fixing ability.

[0016]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a rotary heating member in which a release layer is coated on the surface of a cylindrical film made of an electric resistance material, an exciting coil included therein, In an image heating apparatus having a heating member and a rotary pressing member forming a nip, the exciting coil is wound around the nip, and the number of coils on the rotation direction upstream side of the rotary heating member relative to the nip is reduced. The power supply line of the exciting coil is drawn out from both ends of the cylindrical film so that the number of coils is larger than the number of coils on the downstream side in the rotation direction.

[0017]

[0018]

In the above configuration, by making the number of turns of the coil on the upstream side of the rotation greater than the number of turns of the coil on the downstream side in the rotation direction, the rotation heating member can be heated in a wide range on the upstream side, so that the recording material is An effect can be provided, and energy consumed for heat generation can be saved on the downstream side, and a desired fixing ability can be secured with energy saving.

The second invention according to the present application is characterized in that, in addition to the features of the first invention, the core of the rotary pressing member is formed of a hollow resistance material, and one of the power supply lines of the exciting coil is rotated. It is characterized by passing through the hollow part of the pressure member.

In the above configuration, the influence of the power supply line can be shielded from the outside by passing the power supply line of the excitation coil through the hollow portion of the rotary pressing member.

According to a third aspect of the present invention, in addition to the features of the second aspect, one of the power supply lines of the exciting coil is formed with the second exciting coil in the hollow portion of the rotary pressing member. It is characterized by.

In the above configuration, the second exciting coil has a function of heating the rotary pressing member.

The fourth invention according to the present application is characterized in that, in addition to the features of the third invention, the second exciting coil is formed in a spiral shape around the axis of the rotary pressurizing body.

In the above configuration, the spiral second exciting coil differs from the other exciting coils in the frequency dependence of the exciting current with respect to the output.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 is a drawing showing the features of the present invention, and FIG. 2 is a perspective view for explaining a main part thereof. In FIG. 1, reference numeral 1 denotes a fixing film which is a rotary heating member; 105, an insulating film guide which does not hinder the passage of magnetic flux;
While the transport stability is ensured by this, it rotates in the direction of the arrow. 201 is an excitation coil for generating an alternating magnetic flux;
Reference numeral 02 denotes a ferrite core that guides the alternating magnetic flux generated by the exciting coil 201 to the fixing film 1, and is supported by the film guide 105.

An excitation circuit is connected to the excitation coil 201, and this excitation circuit can supply an alternating current of 80 KHz to the excitation coil 201. Reference numeral 3 denotes a pressing roller which is a rotary pressing member, which covers the core metal 301 with a silicone rubber layer 302 by 2 mm to have elasticity.
A nip N is formed with the fixing film 1. Further, the pressure roller 3 also serves as a drive roller for driving the fixing film 1 to rotate in the conveying direction of the recording material P.

The fixing film 1 will be described in detail with reference to FIG. The fixing film 1 has a thickness of 5 made of nickel.
The surface of the heat generating layer 101 having a thickness of 0 μm is covered with an elastic layer 102 made of silicone rubber.
3 coated. As the heat generating layer 101, a metal other than nickel, which is an electric good conductor of 10 ⁻⁵ to 10 ⁻¹⁰ Ω · m,
Any metal compound or organic conductor may be used, and more preferably, a pure metal such as iron or cobalt having high magnetic permeability and exhibiting ferromagnetism or a compound thereof can be used. Heat generation layer 10
If the thickness of 1 is reduced, sufficient magnetic path cannot be secured,
Magnetic flux may leak to the outside and the heat-generating energy of the heat-generating element itself may decrease, and if the heat-generating element is thick, the heat capacity tends to increase and the time required for temperature rise tends to increase. Accordingly, the thickness has an appropriate value depending on the specific heat, density, magnetic permeability, and resistivity of the material used for the heating element.
A heating rate of 3 ° C./sec or more could be obtained in the thickness range of μm. On the other hand, if the hardness of the elastic layer 102 is too high, the elastic layer 102 cannot follow the unevenness of the recording material or the toner layer, resulting in uneven image gloss. Therefore, the elastic layer 10
The hardness of No. 2 is preferably 60 ° (JIS-A) or less, more preferably 45 ° (JIS-A) or less. Elastic layer 102
About 6 × 10 ⁻⁴ to 2 × 10 ⁻³ [cal
/ Cm · sec · deg. ] Is good. Thermal conductivity λ is 6 ×
10 ^-4 [cal / cm · sec · deg. ], The thermal resistance is large, and the temperature rise in the surface layer of the fixing film 1 becomes slow.

As the release layer 103, PFA, PTFE,
In addition to a fluororesin such as FEP, a material having good releasability and heat resistance such as a silicone resin, a silicone rubber, a fluororubber, and a silicone rubber can be selected. Release layer 10
3 preferably has a thickness of 20 to 100 μm.
If the thickness is less than 20 μm, there arises a problem that a portion having poor releasability is formed due to coating unevenness of the coating film and durability is insufficient. In addition, when the release layer exceeds 100 μm, there is a problem that heat conduction is deteriorated. In particular, in the case of a resin-based release layer, the hardness becomes too high, and the effect of the elastic layer 102 is lost.

As shown in FIG. 5, a heat insulating layer 104 may be provided in the layer structure of the fixing film 1. Heat insulation layer 1
04 is preferably a heat-resistant resin such as a fluorine resin, a polyimide resin, a polyamide resin, a polyamide-imide resin, a PEEK resin, a PES resin, a PPS resin, a PFA resin, a PTFE resin, and a FEP resin. Further, the thickness of the heat insulating layer 104 is preferably 10 to 1000 μm. When the thickness of the heat insulating layer 104 is smaller than 10 μm, the heat insulating effect cannot be obtained, and the durability is insufficient. On the other hand, if the thickness exceeds 1000 μm, the distance between the high magnetic permeability core 202 and the heat generating layer 101 increases, and the magnetic flux does not reach the heat generating layer 101 sufficiently. When the heat insulating layer 104 is provided, the temperature of the exciting coil 201 and the ferrite core 202 due to the heat generated in the heat generating layer 101 can be prevented, so that stable heating can be performed.

The exciting coil 201 must generate an alternating magnetic flux sufficient for heating. For this purpose, it is necessary to reduce the resistance component and increase the inductance component. In the present embodiment, a high-frequency φ3 bundle of thin wires is used as the core wire of the excitation coil 201, and is wound 3.5 times around the nip N in the fixing film.

The exciting coil 201 generates an alternating magnetic flux by an alternating current supplied from the exciting circuit, and the alternating magnetic flux is guided to the ferrite core 202 to generate the heat generating layer 1 of the fixing film 1.
01 generates an eddy current. This eddy current is generated by the heating layer 101.
Joule heat is generated by the specific resistance of the elastic layer 1
02: The recording material P conveyed to the nip N via the release layer 103 and the toner T on the recording material P can be heated.

According to the present invention, as shown in FIG. 3, the power supply line of the excitation coil 201 is made double-sided and three excitation lines are circulated on the downstream side of the nip and four excitation lines are circulated on the upstream side. It is characterized in that the heat generation amount is increased so that a preheating effect is easily obtained. Due to the preheating effect, the recording material P and the toner T are gradually heated to release moisture and the like, so that the recording material is less likely to be deformed such as wrinkles and waving, and that the toner image is not easily scattered. Conventionally, in an image heating apparatus using high-speed heating by local heating, such a preheating effect tends to be difficult to obtain, but the present invention compensates for such a disadvantage.

On the other hand, since the heat generated by the excitation wire on the downstream side of the nip does not contribute to the fixing process, the number of rounds is reduced to weaken the magnetic coupling with the fixing film 1 and reduce the loss.

The operation and effect when the image heating apparatus of the present embodiment is used as a fixing device of a four-color image forming apparatus will be described together with the operation of the image forming apparatus.

FIG. 6 is a sectional view of an electrophotographic color printer using the present invention. 11 is a photosensitive drum made of an organic photosensitive member, 12 is a charging device for uniformly charging the photosensitive drum 11, and 13 is a signal from an image signal generator (not shown) for turning on / off a laser beam. And a laser optical box that forms an electrostatic latent image on the photosensitive drum 11. 1
101 is a laser beam, 1102 is a mirror. The electrostatic latent image on the photosensitive drum 11 is visualized by selectively attaching toner by the developing device 14. The developing device 14 includes a color developing device for yellow Y, magenta M, and cyan C, and a developing device B for black. The developing device 14 develops a latent image on the photosensitive drum 11 one by one, and transfers the toner image to the intermediate transfer drum 16. A color image is obtained by superimposing sequentially on the top. Intermediate transfer drum 16
Has a medium-resistance elastic layer and a high-resistance surface layer on a metal drum, and applies a bias potential to the metal drum to transfer a toner image by a potential difference from the photosensitive drum 11. On the other hand, the recording material P sent out from the sheet feeding cassette by the sheet feeding roller is sent between the transfer roller 15 and the intermediate transfer drum 16 so as to synchronize with the electrostatic latent image on the photosensitive drum 11. The transfer roller 15 transfers the toner image on the intermediate transfer drum 16 onto the recording material P by supplying a charge having a polarity opposite to that of the toner from the back surface of the recording material P. In this manner, the recording material P on which the unfixed toner image is placed is applied heat and pressure by the heat fixing device 10, is permanently fixed on the recording material P, and is discharged to a paper discharge tray (not shown). . The toner and paper dust remaining on the photosensitive drum 11 are removed by the cleaner 17, and the toner and paper dust remaining on the intermediate transfer drum 16 are removed by the cleaner 18. repeat.

The above-described image heating device is used as the fixing device 10, and the recording material P is heated at the nip to fix the toner image, and is separated at the nip exit.

As described above, the image heating apparatus according to the present embodiment can obtain a preheating effect. Therefore, even when a full-color image having a large amount of toner is fixed in the above configuration, scattering of the toner image can be reduced. As a result, a high quality image forming apparatus can be obtained.

In this embodiment, a four-color image forming apparatus has been described. However, the present invention may be applied to a monochrome or one-pass multi-color image forming apparatus. In this case, the elastic layer 102 can be omitted from the fixing film 1.

(Second Embodiment) FIG. 7 is a perspective view showing a main part of another embodiment of the present invention. In FIG.

In the present embodiment, similarly to the first embodiment, the power supply line of the exciting coil 201 is set as a double wire, and three exciting lines are circulated downstream of the nip and four exciting lines are circulated upstream. After making it easy to obtain the preheating effect,
The pressure roller core metal 301 has a hollow structure made of iron, and one of the lead wires of the excitation coil 201 passes therethrough.

Since a high-frequency exciting current flows through the exciting coil 201, it is preferable that the lead-out from the exciting circuit be as simple and short as possible. However, when the lead wires are double-ended as in the present invention, they tend to be long. Therefore, attention must be paid to metals and elements near the lead wires. In this embodiment, one of the lead wires in the above configuration is connected to the pressure roller 3.
, The lead wire is shielded from the outside, and the influence of the high-frequency exciting current on the outside can be eliminated.

(Third Embodiment) FIG. 8 is a perspective view showing a main part of still another embodiment of the present invention, in which the same reference numerals as those described above denote the same members.

In the present embodiment, similarly to the second embodiment, the power supply line of the excitation coil 201 is provided in both ends, and three excitation lines are circulated on the downstream side of the nip and four excitation lines are circulated on the upstream side. After making it easy to obtain the preheating effect,
The pressure roller core metal 301 has a hollow structure made of iron, and an auxiliary excitation coil 203 is formed and penetrated inside the pressure roller 3 by one of the leads of the excitation coil 201.

The auxiliary excitation coil 203 is spirally wound 60 times around a cylindrical coil bobbin 204 arranged coaxially with the pressure roller 3.

In this embodiment, the exciting coil 20
The pressurizing roller 3 is heated by positively utilizing the action of the exciting current flowing through the lead wire 1.

The excitation coil 201 of the thin fixing film 1 is formed so as to go around the nip, and the auxiliary excitation coil 203 of the pressure roller 3 having the thick metal core 301 is formed spirally concentrically with the pressure roller 3. The inductance with respect to the frequency of the exciting current is greatly changed, so that the former can be driven on the high frequency side and the latter can be driven on the low frequency side.

Accordingly, at the time of printing, the fixing film 1 is mainly heated by driving at a high frequency to rapidly start up and secure high image quality by the preheating effect. The heating of the pressure roller 3 can be carried out.

The heating of the pressure roller 3 is important for obtaining the adhesion between the recording material and the toner particularly when the amount of toner is large, such as in a full-color image. It can be used as an image heating device suitable for a color image forming apparatus.

[0050]

As described above, according to the first aspect of the present invention, by making the number of coils on the upstream side of rotation greater than the number of coils on the downstream side in the rotation direction, the rotation heating member is provided on the upstream side. Heating can be performed in a wide range, and a preheating effect can be given to the recording material. In addition, energy consumed for heat generation can be saved on the downstream side, and a desired fixing ability can be secured with energy saving.

[0051]

According to the second invention of the present application,
By passing the power supply line of the excitation coil through the hollow portion of the rotary pressing member, the influence of the power supply line can be shielded from the outside.

According to the third invention of the present application,
The second exciting coil has a function of heating the rotary pressing member.

According to the fourth invention of the present application,
The spiral second excitation coil differs from the other excitation coils in the frequency dependence of the excitation current with respect to the output.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a first embodiment of the present invention.

FIG. 2 is a perspective view illustrating a main part of the first embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating an effect of the first exemplary embodiment of the present invention.

FIG. 4 is a partial cross-sectional view of the fixing film according to the first embodiment of the present invention.

FIG. 5 is a partial cross-sectional view of the fixing film according to the first embodiment of the present invention.

FIG. 6 is a schematic sectional view illustrating a color image forming apparatus using the image heating device of the present invention.

FIG. 7 is a perspective view illustrating a main part of a second embodiment of the present invention.

FIG. 8 is a perspective view illustrating a main part of a third embodiment of the present invention.

FIG. 9 is a diagram showing a conventional example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing film 201 Excitation coil 202 Core 3 Pressure roller

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Keisuke Kaneda 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-7-1114276 (JP, A) JP-A-6 JP-A-75489 (JP, A) JP-A-54-39645 (JP, A) JP-A-61-261763 (JP, A) JP-A-8-69190 (JP, A) JP-A-9-26715 (JP, A) JP-A-6-314041 (JP, A) JP-A-60-38494 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/20 101

Claims (4)

(57) [Claims] 1. A rotary heating member in which a release layer is coated on a surface of a cylindrical film made of an electric resistance material, an exciting coil included therein, and a rotary pressing member forming a nip with the rotary heating member. In the image heating device having the above, the exciting coil is wound around the nip,
The power supply line of this exciting coil is drawn out from both ends of the cylindrical film so that the number of coils on the upstream side in the rotation direction of the rotary heating member from the nip is greater than the number of coils on the downstream side in the rotation direction. Characteristic image heating device. 2. The image according to claim 1, wherein the core of the rotary pressing member is formed of a hollow resistance material, and one of the power supply lines of the exciting coil passes through the hollow portion of the rotary pressing member. Heating equipment. 3. The image heating apparatus according to claim 2, wherein one of the power supply lines of the excitation coil is formed as another excitation coil in a hollow portion of the rotary pressing member. 4. An image heating apparatus according to claim 3, wherein said another exciting coil is formed in a spiral shape around an axis of the rotary pressing body.