CN101482728B - Image forming apparatus - Google Patents

Abstract

An image forming apparatus has an image forming station and a fixing unit. The fixing unit includes a coil for generating a magnetic field for induction heating the heating member. A first core made of a magnetic material is arranged fixedly around the coil. A second core made of a magnetic material is between the first core and the heating member in a generation direction of the magnetic field to form a magnetic path in cooperation with the first core and capable of changing a posture thereof. A shield made of a nonmagnetic metal is arranged along the outer surface of the second core to shield magnetism in the magnetic field and a magnetic shielding portion for changing the posture of the second core between a first posture where the shield shields the magnetism and a second posture where the shield does not shield the magnetism. Thus, the apparatus can reduce heat capacity and preheating time and save space by reducing the members configured in the heating member.

Description

Image processing system

Technical field

The present invention relates to have image forming apparatus comprising fixing unit, described fixation unit comprises heater and pressing element, be used to make the paper (thin slice body) that has carried toner image by between this heater and the pressing element, the toner heating and melting of not photographic fixing, photographic fixing is on paper.

Background technology

In recent years, preheating time from shorten fixation unit and energy-conservation equal angles consider, adopts the band mode that can reduce thermal capacity receive publicity (for example opening flat 6-318001 number with reference to the open communique spy of Jap.P.) in image processing system.In addition in recent years, can Fast Heating and the electromagnetic induction heating mode (IH) of efficient heating also receive publicity, angle energy-conservation during from the coloured image photographic fixing considers, produced much the product that electromagnetic induction heating mode and band mode are made up.Under the situation that band mode and electromagnetic induction heating mode are made up, because of the layout of coil and cooling easily, direct advantage such as heating tape, mostly electromagnetic induction device is configured in the outside (so-called outsourcing IH) of band.

In described electromagnetic induction heating mode, consider width (paper passes through width) by the paper of fixation unit, excessively heat up by the zone in order to prevent that paper is non-, developed various technology.Particularly, following prior art is arranged as the size switching device shifter among the outsourcing IH.

First prior art (Jap.P. open communique spy open 2003-107941 number) is disclosed to be: magnetic component is divided into a plurality of, come paper by on the Width, according to the size (paper passes through width) of the paper that passes through, make a part and the field coil generation clutch of magnetic component.In this case, non-at paper by in the zone, reduce heating efficiency by making magnetic component leave field coil, to compare by the corresponding zone of the paper of width with minimum paper, thermal value is little.

Second prior art (No. the 3527442nd, Japanese patent gazette) is disclosed to be: in heat generating roller inside, other electroconductive member is configured in the outside of minimum paper by width, and the position of this electroconductive member is switched in magnetic field range or outside the scope.In second prior art, electroconductive member is positioned at outside the magnetic field range, heat generating roller is carried out electromagnetic induction heating.Near the heat generating roller temperature rises to Curie temperature, just electroconductive member is moved on in the magnetic field range.So in the outside of minimum paper by width, magnetic flux leaks from heat generating roller, can prevent that paper is non-by excessively intensification of zone.

The movable range of the magnetic component of first prior art is big, needs unnecessary space for this reason, can cause whole device to maximize accidentally.Second prior art is configured in heat generating roller inside to the member that is used to switch size, can save the space.But heat generating roller inside is hot environment, disposes there under the situation of any member, all need Curie temperature is made as height, and bigger problem is that the big member of thermal capacity prolongs preheating time.

Summary of the invention

The object of the present invention is to provide a kind of image processing system, it can be cut down the member that is configured in heater inside and reduce thermal capacity, shortens preheating time, and can save the space.

The invention provides a kind of image processing system, comprising: image forming part is transferred to toner image on the thin slice body; And fixation unit, have heater and pressing element, and described thin slice body is clipped between this heater and the pressing element carries, in this course of conveying, at least be used to heat from described heater, toner image on the thin slice body; Wherein, described fixation unit comprises: coil produces the magnetic field that is used for described heater is carried out induction heating; First magnetic core is made by magnetic material, and fixed configurations is used for forming magnetic circuit around described coil around described coil; Second magnetic core is made by magnetic material, on the magnetic direction that is produced by described coil, is configured between described first magnetic core and the described heater, and this second magnetic core can change posture, is used for forming magnetic circuit with described first magnetic core; Shield member is made by nonmagnetic metal, along the outside surface setting of described second magnetic core, is used for carrying out magnetic shielding in the magnetic field that described coil produces; And magnetic shielding portion, be used to make described second magnetic core to carry out changing the described shield member of posture between the prime of magnetic shielding and the second that described shield member does not carry out magnetic shielding and have annular shape portion at described shield member, be under the state of described prime at described second magnetic core, the magnetic field that described coil produces connects in the annular shape portion of described shield member, be under the state of described second at described second magnetic core, the magnetic field that described coil produces is by the outside of the annular shape portion of described shield member.

Adopt this structure, owing to adopt the magnetic field that utilizes coil to produce that heater is carried out the mode (outsourcing IH) that induction heating makes the toner image heating and melting, so there is no need special member to be set in the inboard of heater.In addition first magnetic core be configured in coil around, be used to form the magnetic circuit in the magnetic field that the guiding coil produces, second magnetic core also only is configured between first magnetic core and the heater, so take up room can be not excessive for integral body.

Like this, owing to there is no need magnetic shielding mechanism to be set, can correspondingly reduce thermal capacity, so can shorten the preheating time of fixation unit in the inside of heater.In addition, though adopt outsourcing IH, the posture of movable just second magnetic core changes, so can reduce whole movable range, can realize correspondingly that fixation unit and entire image form the miniaturization of device.

Adopt this structure, if make second magnetic core be in second, then the magnetic field of coil generation is produced vortex flow by first magnetic core, second core directs in heater, carries out the magnetic induction heating.On the other hand, if make second magnetic core be in prime, then the magnetic resistance in the magnetic circuit increases, and magnetic field intensity reduces, and can reduce the thermal value of heater.Therefore, when adjusting the thermal value of heater, there is no need to make magnetic core to leave heater, can save the space thus.

In addition, because shield member is annular, if vertical magnetic field (interlinkage flux) connects this annular inboard face, then the circumferencial direction at ring produces induction current, produces thus and the rightabout counter field in perforation magnetic field.Because this counter field is eliminated the magnetic field (interlinkage flux) that connects annular inboard in vertical direction, shield member can carry out magnetic shielding.On the other hand, under the magnetic field twocouese comes and goes by inboard of encircling or situation about passing through in the U-shaped mode of turning back, do not produce induction current, do not bring into play the effect of magnetic shielding.According to this character of shield member, magnetic field is connected in the annular, can produce Magnetic Shielding Effectiveness thus, on the other hand, on retreating position (second), make magnetic field not by in the annular, can allow magnetic field to pass through thus.

In described structure preferably: described second magnetic core changes posture around the axis rotation that the magnetic field direction of passage that produces with described coil intersects; Described magnetic shielding portion comprises rotating mechanism, is used to make described second magnetic core to rotate around described axis, makes this second magnetic core change posture between described prime and described second.Adopt this structure,, shield member is moved to the position that shields or the position of keeping out of the way as long as second magnetic core is rotated.Therefore the mechanism simplifying that shield member is moved more helps to save the space.

In described structure preferably: described shield member is a Q-RING shape with common outer peripheral portion, and on the long side direction of described heater, the inside of this Q-RING is divided into a plurality of parts.Shield member so if shield member is divided into a plurality of annular sections, then make up by a ring of generation Magnetic Shielding Effectiveness, can adapt to the paper of various sizes owing to bring into play the effect of magnetic shielding in the annular inboard scope.

In described structure preferably: described coil is along the configuration of the outside surface of described heater, and described first magnetic core is cut apart the both sides along the center of described outside surface that are configured in described coil; Described second magnetic core is arranged on the position that magnetic circuit converges through the center of divided described first magnetic core and described coil.Adopt this structure,, switch so just can be effectively cross between the state at magnetic shielding state and magnetic flux with a movable magnetic core because movable magnetic core is positioned at the center of magnetic circuit.

In described structure, can be to the concrete shape and the geometry parameter of various member regulations as following (4)～(6).

(4) preferably: at least a portion of described heater has the outside surface of circular arc; Described coil configuration is on the arc surface that the circular arc outside surface imagination along described heater forms, and this imaginary circle cambered surface is formed on the outside of the circular arc outside surface of described heater, and concentric with the circular arc outside surface of this heater; Described second magnetic core is a cylindrical shape or cylindrical; Described shield member is along the outer surface bending of described second magnetic core shape in the arc-shaped; Wherein, when the radius-of-curvature of the imaginary circle cambered surface of the described coil of configuration is made as r1, position at described shield member is switched under the state of screening-off position, when the bee-line from the center of curvature of the circular arc outside surface of described heater to described shield member outside surface was made as r2, the relation of r1＞r2 was set up.

The condition of described by setting (4) on screening-off position, can make shield member be positioned at position than the more close heater of coil, so when making shield member move to screening-off position, can carry out magnetic shielding more reliably.

(5) preferably: the imaginary circle cambered surface that disposes described coil is under the state of described prime at described second magnetic core, is located near the position of described shield member end points on the described second magnetic core circumferencial direction.Like this, on screening-off position, can make shield member be positioned at position, so can bring into play the shield effectiveness of shield member well near coil.

(6) preferably: described first magnetic core is under the state of described second at described second magnetic core, is positioned at than on the position of the more close described heater in position of the described shield member end points on the described second magnetic core circumferencial direction.Like this, when shield member was moved to retreating position, from not conductively-closed of magnetic field (magnetic flux) the member shielding that fixed magnetic core comes out, the condition coupling with described (5) helped to realize good preheating environment.

In described structure preferably: described heater is made of the heating tape that fixing roller or volume hang on warm-up mill and the fixing roller, also comprises temperature control part, controls described coil carries out induction heating to described heater state; Described temperature control part has the aitiogenic thermotonus element of the temperature of described warm-up mill or fixing roller, and controls the action of described coil according to the reaction result of this thermotonus element along the inner peripheral surface configuration of described warm-up mill or fixing roller.Wherein " thermotonus element " for example is the device of the such thermotonus type of thermistor or temperature controller.

In the present invention owing to magnetic shielding mechanism is not set, so can be configured in thermistor or temperature controller on the position relative with the hub of a spool of the easiest heating in the inboard of heater.Particularly since the desired temperature controller when stopping to drive, also can work, so the inboard that is configured in heater is comparatively desirable.By having temperature control part, according to the action of the reaction result control coil of described thermotonus element, can carry out temperature control to heater, be controlled at exactly and be fit to the temperature that photographic fixing is handled.

In described structure preferably: the material of described shield member is a copper.Copper resistance is little, and magnetic susceptibility is low, so it is used for shield member, can bring into play good Magnetic Shielding Effectiveness.

In described structure preferably: described shield member is made by nonmagnetic metal, and thickness is in 0.5mm～3mm scope.That is, the Joule heat of shield member in order to suppress to produce itself carries out magnetic shielding effectively, need be made as the intrinsic resistance of member little as far as possible.If shield member thickness is then enough little by the intrinsic resistance that makes shield member in above-mentioned scope, can guarantee good electrical conductivity, fully obtain Magnetic Shielding Effectiveness, on the other hand, can alleviate shield member weight.

In described structure preferably: described coil configuration is in the outside of described heater, and described second magnetic core is configured in the inboard of described heater.In this case, equally by make shield member in the medial movement of heater to screening-off position or retreating position, can bring into play Magnetic Shielding Effectiveness, and under situation about not shielding, can realize good preheating environment.

Description of drawings

Fig. 1 is the sketch of the image processing system structure of expression embodiment of the present invention.

Fig. 2 is the longitudinal diagram of the fixation unit structure of expression first embodiment of the invention.

Fig. 3 A, Fig. 3 B are the figure of expression shield member ios dhcp sample configuration IOS DHCP.

Fig. 4 A is the side view of the structure of expression rotating mechanism, and Fig. 4 B is the IVB-IVB directional profile figure of Fig. 4 A.

Fig. 5 A, Fig. 5 B are the figure that the action example that the rotation of center magnetic core (second magnetic core) produces is followed in expression.

Fig. 6 is the figure that represents the structural parameter set in the first embodiment.

Fig. 7 is the figure of first variation of expression first embodiment.

Fig. 8 is the figure of second variation of expression first embodiment.

Fig. 9 is the longitudinal diagram of the fixation unit structure of expression second embodiment of the invention.

Figure 10 is the stereographic map of the topology example (1) of expression shield member.

Figure 11 A～Figure 11 C is used to illustrate that shield member causes the schematic diagram of the principle of magnetic field shielding effect.

Figure 12 A, Figure 12 B are the figure of the topology example (2) of expression shield member.

Figure 13 A is the side view of the structure of expression rotating mechanism, and Figure 13 B is XIIIB-XIIIB directional profile figure of Figure 13 A.

Figure 14 A, Figure 14 B are the figure of the action example of expression when utilizing the shield member of topology example (2).

Figure 15 is the stereographic map of the topology example (3) of expression shield member.

Figure 16 A, Figure 16 B are the figure of the action example of expression when utilizing the shield member of topology example (3).

Figure 17 is the figure that is illustrated in the structural parameter of setting in second embodiment.

Figure 18 is the stereographic map of the topology example (4) of expression shield member.

Figure 19 A is the figure that the shield member of expression bar structure example (4) is installed in the state on the center magnetic core (second magnetic core), and Figure 19 B, Figure 19 C, Figure 19 D are respectively XIXB direction, XIXC direction, the XIXD directional profile figure of Figure 19 A.

Figure 20 is the stereographic map of the action example when being illustrated in the shield member that utilizes topology example (4) and shielding comprehensively.

Figure 21, Figure 22, Figure 23, Figure 24 and Figure 25 represent respectively the stereographic map of shield member from the state of Figure 20 action example when clockwise direction is rotated 60 °, 120 °, 180 °, 240 ° and 300 °.

Figure 26 is the figure of first variation of expression second embodiment.

Figure 27 is the figure of second variation of expression second embodiment.

Figure 28 is the figure of the 3rd variation of expression second embodiment.

Embodiment

Utilize accompanying drawing that embodiments of the present invention are elaborated below.

Fig. 1 is the sketch of structure of the image processing system 1 of expression one embodiment of the present invention.Image processing system 1 for example can be printer, duplicating machine, facsimile recorder and the digital complex machine etc. that has these functions concurrently, is used for according to the image information from the outside input, toner image is transferred on the printed medium surface such as printing paper, prints.

Image processing system 1 shown in Figure 1 is the tandem color printer.This image processing system 1 has the apparatus main body 2 of square box shape, in the inside of this apparatus main body 2, coloured image is formed (printing) on paper (thin slice body).Above the apparatus main body 2, be provided with paper delivery portion (paper discharge tray) 3 at this, be used to discharge the paper that is printed with coloured image.

In apparatus main body 2, dispose the paper feeding cassette 5 that is used to take in paper in the bottom, dispose the heap paper disc 6 that is used for the hand paper supply at central part, be provided with image forming part 7 on top.Image forming part 7 forms (transfer printing) toner image according to from installing view data such as the literal that sends the outside or pattern on paper.

In Fig. 1, on the left-hand portion of apparatus main body 2, dispose first transfer passage 9, be used for the paper of extracting out from paper feeding cassette 5 is transported to image forming part 7; Apparatus main body 2 from the position, right side on left-hand portion, dispose second transfer passage 10, be used for the paper of extracting out from heap paper disc 6 is transported to image forming part 7.Position, upper left side in this external apparatus main body 2 disposes: fixation unit 14, carry out photographic fixing to the paper that is formed image in image forming part 7 and handle; And the 3rd transfer passage 11, the paper that carries out after photographic fixing is handled is transported to paper delivery portion 3.

Paper feeding cassette 5 under the state that pull out the outside of apparatus main body 2 (for example last side of the body among Fig. 1), can replenish paper.This paper feeding cassette 5 has incorporating section 16, in this incorporating section 16, and the different paper of size of at least two kinds of paper supply directions of can optionally packing into.The paper of packing in the incorporating section 16 is extracted out to first transfer passage 9 one by one by paper feed roller 17 and distribution rollers 18.

Heap paper disc 6 can open or close in the outside of apparatus main body 2, can put paper one by one with hand on its manual sheet feed section 19, or can stackedly put plurality of sheets of paper.Be placed on paper on the manual sheet feed section 19 by pickup roller 20 and distribution rollers 21, extract out to second transfer passage 10 one by one.

First transfer passage 9 and second transfer passage 10 nearby converge at alignment roller 22.The paper that offers alignment roller 22, is sent to the second transfer printing portion 23 after carrying out the adjustment of tilt adjustments and opportunity in this temporary transient standby.In the second transfer printing portion 23, be transferred to (second transfer printing) on the paper that is sent at the full color toner image on the intermediate transfer belt 40.After this, the toner image in fixation unit 14 on the paper by photographic fixing after, the upset in the 4th transfer passage 12 as required of this paper, with the face of the initial opposite side of face on the also toner image (second transfer printing) by the second transfer printing portion, 23 transfer printing full colors.Then in fixation unit 14 after the toner image of opposite one side, this paper is discharged to paper delivery portion 3 through the 3rd transfer passage 11 by distributing roller 24.

Image forming part 7 has four image formation units 26,27,28 and 29, forms black (B), yellow (Y), blue or green (C) and pinkish red (M) versicolor toner image.In addition, image forming part 7 has intermediate transfer portion 30, is used for versicolor toner image synthetic and that carrying is formed by described image formation unit 26～29.

Each image formation unit 26～29 comprises: photosensitive drums 32; Electro-mechanical part 33 is with relative configuration of periphery of photosensitive drums 32; Laser scan unit 34, the ratio electro-mechanical part 33 on photosensitive drums 32 peripheries more relies on the ad-hoc location illuminating laser beam of downstream one side; Development section 35 is in the position that more relies on downstream one side than the laser beam irradiation position of laser scan unit 34, with relative configuration of periphery of photosensitive drums 32; And cleaning section 36, in the position that more relies on downstream one side than development section 35, with relative configuration of periphery of photosensitive drums 32.

The photosensitive drums 32 of each image formation unit 26～29 utilizes the counter clockwise direction of driving motor in figure that does not have expression among the figure to rotate.In addition, in the development section 35 of each image formation unit 26～29, in each toner Cartridge 51, black toner, Yellow toner, cyan toner and magenta toner are housed respectively.

Intermediate transfer portion 30 comprises: driven roller 38 is configured near the position the image formation unit 26; Driven voller 39 is configured near the position the image formation unit 29; Intermediate transfer belt 40, volume hangs on driven roller 38 and the driven voller 39; And four transfer rolls 41, corresponding to the photosensitive drums 32 of each image formation unit 26～29.Each transfer roll 41 is configured in the position that ratio development section 35 in each image formation unit 26～29 more relies on downstream one side, can contact with each photosensitive drums 32 pressure across intermediate transfer belt 40.

In described intermediate transfer portion 30, in the position of the transfer roll 41 of each image formation unit 26～29, the toner image of each color overlaps respectively and is transferred on the intermediate transfer belt 40.Its result, the last toner image that on intermediate transfer belt 40, forms full color.

First transfer passage 9 is transported to intermediate transfer portion 30 to the paper of extracting out from paper feeding cassette 5.Comprise in first transfer passage 9: a plurality of conveying rollers 43 are configured in the assigned position in the apparatus main body 2; And alignment roller 22, be configured near the intermediate transfer portion 30, be used to adjust the image formation action of image forming part 7 and the opportunity that paper supply moves.

Fixation unit 14 is undertaken the processing of the toner image of not photographic fixing on paper by the paper that has been transferred toner image in image forming part 7 being heated and pressurizeing.It is right that fixation unit 14 has the roller that is made of the backer roll 44 (pressing element) of heated type and fixing roller 45.Backer roll 44 is metal rollers, and fixing roller 45 has metal core, elastomeric top layer (for example silicon sponge) and release layer (for example PFA).With the fixing roller 45 adjacent warm-up mills 46 that are provided with, volume is hung heating tape 48 (heater) on this warm-up mill 46 and fixing roller 45 in addition.The detailed structure of relevant fixation unit 14 will be narrated in the back.

On the throughput direction of paper, the position that relies on upstream one side and downstream one side than fixation unit 14 is respectively arranged with transfer passage 47.Paper through intermediate transfer portion 30 transports by the transfer passage 47 of upstream one side, is directed in the crack between backer roll 44 and the fixing roller 45 (heating tape 48).And through the paper between backer roll 44 and the fixing roller 45, the transfer passage 47 by downstream one side is directed to the 3rd transfer passage 11.

The 3rd transfer passage 11 is transported to paper delivery portion 3 to the paper that is implemented the photographic fixing processing in fixation unit 14.Appropriate position in the 3rd transfer passage 11 is provided with conveying roller 49 for this reason, and at the described distributing roller 24 of its outlet configuration.

First embodiment of fixation unit

Fixation unit 14 to first embodiment that is used for described image processing system 1 is elaborated below.

Fig. 2 is the longitudinal diagram of fixation unit 14 structures of expression first embodiment.In Fig. 2, expression is changeed about 90 ° state to the fixation unit 14 that is installed on the image processing system 1 around counter clockwise direction.Therefore, from bottom to top paper feeding direction becomes from right to left in Fig. 2 in Fig. 1.In addition, be under the situation of more large-scale (digital complex machine etc.) at apparatus main body 2, also be mounted to sometimes shown in Figure 2 towards.

Fixation unit 14 has backer roll 44, fixing roller 45, warm-up mill 46 and heating tape 48 as mentioned above.As mentioned above, because backer roll 44 is metal rollers, and the top layer of fixing roller 45 has the elastic layer of silicon sponge, so form flat crack NP between heating tape 48 (backer roll 44) and fixing roller 45.In addition, be provided with halogen heater 44a in the inboard of backer roll 44.The matrix material of heating tape 48 is strong magnetic material (for example Ni), forms thin flexible film layer (for example silicon rubber) on its top layer, forms release layer (for example PFA) at its outside surface.The axle core of warm-up mill 46 is magnetic metal (for example Fe), forms release layer (for example PFA) in its surface.

Fixation unit 14 is partly being carried this paper to folder across the backer roll 44 of heating tape 48 and the crack NP between the fixing roller 45.In this course of conveying, the 48 pairs of paper heat supplieds in backer roll 44 and heating tape, transfer printing in the toner image on the paper on paper.

In addition, fixation unit 14 is equipped with IH coil unit 50 (not expression among Fig. 1) in the outside of warm-up mill 46 and heating tape 48.IH coil unit 50 comprises: load coil 52 (coil), a pair of arch magnetic core 54 (part of first magnetic core), an offside magnetic core 56 (part of first magnetic core) and center magnetic core 58 (second magnetic core).

Coil

As shown in Figure 2, load coil 52 is configured in along on the imaginary circle cambered surface of this circular arc outside surface in order to carry out induction heating in the circular arc shaped portion of warm-up mill 46 and heating tape 48.In addition, load coil 52 extends (with reference to Fig. 4 A) along the long side direction of warm-up mill 46, covers the long side direction of whole warm-up mill 46 substantially.In fact, for example dispose the resin cap that does not have expression among the figure in the outside of warm-up mill 46 and heating tape 48, load coil 52 is to wind the line state configuration on this resin cap.

First magnetic core

In Fig. 2, center magnetic core 58 is positioned at central authorities, disposes described arch magnetic core 54 and side magnetic core 56 in pairs in its both sides.Wherein the arch magnetic core 54 of both sides be symmetrically, section makees ferrite (ferrite) the system magnetic core that overarches, total length is all long than the coiling zone of load coil 52.The side magnetic core 56 of both sides is ferrite system magnetic cores of making piece shape.The side magnetic core 56 of both sides is connected an end (lower end among Fig. 2) of each arch magnetic core 54, and these side magnetic cores 56 cover the outside in the coiling zone of load coil 52.Arch magnetic core 54 and side magnetic core 56 be devices spaced apart fixed configurations on a plurality of positions of warm-up mill 46 long side directions for example.The configuration of arch magnetic core 54, side magnetic core 56 for example distributes to determine according to the magnetic flux density (magnetic field intensity) of load coil 52.

Temperature control part

In the example of Fig. 2, temperature control part comprises thermistor 62 (thermotonus element) and temperature-control circuit 621.Thermistor 62 is arranged on the inboard of warm-up mill 46 in order to detect the temperature of warm-up mill 46.One or more thermistors 62 can be configured in the inboard at the big position of the thermal value that especially produces because of induction heating of warm-up mill 46.In the first embodiment, preferably thermistor 62 is configured in and the axial middle position of warm-up mill 46 (in minimum paper that narrate later, the shown in Figure 3 zone by width W 1) opposed inside.

According to described thermistor 62 detected temperature, the temperature-control circuit 621 that is configured in the image processing system 1 is controlled the supply unit 521 that alternating current is provided to load coil 52.The alternating current that temperature-control circuit 621 controls provide to load coil 52 from supply unit 521 is so that the temperature T that is detected by thermistor 62 remains on a toner image needed target temperature Ta on paper.This control can be the on-off control of supply unit 521, perhaps also can be voltage or the frequency by the alternating current that changes supply unit 521 generations, and the control of the ac electric increase and decrease that provides to load coil 52 is provided.

In addition, the temperature controller (thermotonus element) that does not have expression among one or more figure also can be set in the inboard of warm-up mill 46.Temperature controller can be configured in the inboard at the big position of the thermal value that especially produces because of induction heating of warm-up mill 46, and the excessive intensification of warm-up mill 46 is produced reaction and moves, and stops the heating of load coil 52.

Second magnetic core

Center magnetic core 58 is that section is made columnar ferrite system magnetic core.Center magnetic core 58 is identical substantially with warm-up mill 46, and length is passed through width (in the paper of being carried by fixation unit 14, the width of full-size paper) correspondence with maximum paper substantially.Though not expression among Fig. 2, center magnetic core 58 is connected in rotating mechanism (with reference to Fig. 4 A), can rotate by the axis of this rotating mechanism around its long side direction.In addition, the section of center magnetic core 58 also can be made cylindrical.

Center magnetic core 58 on the magnetic direction that is produced by load coil 52, is disposed between arch magnetic core 54 and the warm-up mill 46 (heating tape 48), is used for forming magnetic circuit with arch magnetic core 54 and side magnetic core 56.In detail, the end 54a of arch magnetic core 54 (inlet portion of magnetic circuit or export department) is positioned at the position of leaving heating tape 48, and center magnetic core 58 is used to form the middle magnetic circuit between end 54a and the heating tape 48.

Shield member

Its outside surface is equipped with shield member 60 in center magnetic core 58 upper edges.Shield member 60 is made plate-shaped, curves circular arc according to the external surface shape integral body of center magnetic core 58.As shown in the figure, shield member 60 also can be imbedded in the wall thickness part of center magnetic core 58, can also stick on the outside surface of center magnetic core 58.For pasting shield member 60, for example can utilize silicon class bonding agent.

As the constituent material of shield member 60, preferably adopt non magnetic and high conductive material, for example can adopt oxygen-free copper etc.Shield member 60 utilizes the induction current of the vertical magnetic field generation that connects its surface, produces counter field, eliminates interlinkage flux (interlinkage flux: vertical perforation magnetic field) shield.By utilizing high conductive material, can suppress Joule heat, effectively armoured magnetic field in addition because of the induction current generation.In order to improve electric conductivity, effective method for example has: (1) selects the little material of intrinsic resistance as far as possible, and (2) increase the thickness of member etc.Specifically, the thickness of slab of preferable mask member 60 is in the scope of 0.5mm～3mm.Can make the intrinsic resistance of shield member 60 enough little like this, can obtain enough Magnetic Shielding Effectiveness, on the other hand, can alleviate the weight of shield member 60.Utilize the member of thickness of slab 1mm in the present embodiment.

Magnetic shielding portion

As shown in Figure 2, if shield member 60 is positioned at the position (screening-off position near 48 surfaces, heating tape; Prime), then around load coil 52, magnetic resistance increases, and magnetic field intensity reduces.On the other hand, if center magnetic core 58 is rotated 180 ° (there is no particular limitation for direction) from state shown in Figure 2, shield member 60 moves to apart from the heating tape 48 farthest position (retreating positions; Second), then around load coil 52, magnetic resistance reduces, and is the center with center magnetic core 58, and by the arch magnetic core 54 and the side magnetic core 56 formation magnetic circuits of both sides, the action of a magnetic field is on heating tape 48 and warm-up mill 46.

Fig. 3 A, Fig. 3 B are the figure of an example of expression configuration shield member 60.State shown in Fig. 3 A is corresponding to described screening-off position, and the state shown in Fig. 3 B is corresponding to retreating position.Fig. 3 A, Fig. 3 B represent the side view of center magnetic core 58 respectively on the upper strata, represent vertical view in lower floor.The site that among the figure, added (being coated with full) at the outside surface of center magnetic core 58.

As mentioned above, the length of center magnetic core 58 is identical substantially by width W 2 (first area) with maximum paper, or longer than it.At this moment, shield member 60 is divided into two on the long side direction of center magnetic core 58, and their shape is symmetrical.Each shield member 60 is overlooked to trapezoidal shown in Fig. 3 B.On the circumferencial direction of center magnetic core 58, near the length of the shield member 60 position central authorities of center magnetic core 58 is the shortest, increases gradually from the two side ends of this position to center magnetic core 58.

Shield member 60 is arranged on the minimum paper vertical with the paper direction of passage by width W 1 (second area; In the paper of carrying by fixation unit 14, the width of the paper of size minimum) two outsides, at minimum paper by only there being the seldom shield member 60 of part in the scope of width W 1.And at the two ends of center magnetic core 58, shield member 60 arrives the slightly outside of maximum paper by width W 2.Wherein, minimum paper determines according to the minimum dimension that can be printed by image processing system 1 or maximum sized paper by width W 2 by width W 1 and maximum paper.

As mentioned above, in the present embodiment, on the rotation direction of center magnetic core 58, the length of shield member 60 accounts for the ratio of outer circumference of center magnetic core 58 along axial (long side direction) difference of center magnetic core 58.At this moment, the length (Lc) of establishing shield member 60 account for the ratio of the outer circumference (L) of center magnetic core 58 be coverage rate (=Lc/L), coverage rate is inboard little center magnetic core 58, and is more big more to the axial outside (two ends) from this inboard.Specifically, coverage rate is minimum near minimum paper passes through zone (minimum paper is by the scope of width W 1), and in the two ends of center magnetic core 58 maximum.

By switching the position of shield member 60, partly suppress the magnetic flux of generation, can treat each paper size (paper passes through width).At this moment, according to the rotational angle (rotational displacement) of paper size change center magnetic core 58, paper size ambassador's magnetic shielding amount more is more little, and on the contrary, the more for a short time shielding amount that makes of paper size is big more, can prevent that thus the two end portions of warm-up mill 46 and heating tape 48 from excessively heating up.In addition, represent to clockwise direction and anticlockwise rotation with arrow respectively among Fig. 3 A, Fig. 3 B, but center magnetic core 58 also can only be rotated to a direction.And the paper direction of passage also can be opposite with the direction shown in Fig. 3 A.

Rotating mechanism

Below to center magnetic core 58 is described around the mechanism that axis rotates.Fig. 4 A represents the side view of the structure of rotating mechanism 64, and Fig. 4 B is the sectional view of IVB-IVB direction of Fig. 4 A.Shown in Fig. 4 A, rotating mechanism 64 comprises step-by-step motor 66, reducing gear 68, driving shaft 70 and controller 69.Rotating mechanism 64 utilizes reducing gear 68 that the rotation of step-by-step motor 66 is reduced to the rotating speed of regulation, and driving shaft 70 is driven, and center magnetic core 58 is rotated around its axis.The axis of center magnetic core 58 extends along the direction that the magnetic field with load coil 52 generations intersects by the direction of center magnetic core 58.

Reducing gear 68 for example adopts worm screw, also can utilize other mode.In addition, the rotational angle (from the rotational displacement of reference position) for inspection center's magnetic core 58 is provided with nicked dish 72 in the end of driving shaft 70, and itself and optical chopper (photointerrupter) 74 are combined.

Driving shaft 70 is connected with an end of center magnetic core 58, and this driving shaft 70 does not connect the inside of center magnetic core 58, centre of support magnetic core 58.The rotational angle of center magnetic core 58 is controlled by the number of drive pulses that is applied on the step-by-step motor 66.Controller 69 comprises the control circuit that is used for controlling and driving step-by-step motor 66.This control circuit for example can be made of with IC, input/output driver and semiconductor memory etc. control.

Detection signal from optical chopper 74 passes through enter drive, is input to controller 69, and controller 69 detects the rotational angle (position) of current center magnetic core 58 according to this detection signal.On the other hand, the information that forms the relevant current paper size of control part from the image that does not have expression among the figure is notified to controller 69.According to this paper size information, control the information of reading the rotational angle that is fit to paper size from semiconductor memory (ROM), with cycle output and its target rotational angle corresponding driving pulse of arrival of regulation with IC.Driving pulse is applied on the step-by-step motor 66 by output driver, makes step-by-step motor 66 actions.

Fig. 5 A, Fig. 5 B are the figure that the action example that the rotation of center magnetic core 58 produces is followed in expression.Fig. 5 A represents to follow the rotation of center magnetic core 58, the action example the when position of shield member 60 is switched to retreating position (second magnetic core is in second).Under this state, in the magnetic field that load coil 52 produces, shield member 60 does not carry out magnetic shielding.In this case, side magnetic core 56, arch magnetic core 54 and center magnetic core 58 are passed through in the magnetic field that load coil 52 produces, through heating tape 48 and warm-up mill 46.Produce vortex flow this moment in the heating tape 48 of ferromagnetism body and warm-up mill 46, because of the intrinsic resistance that each material had produces Joule heat, heating tape 48 and warm-up mill 46 are heated.

Action example when Fig. 5 B represents that the position of shield member 60 switched to screening-off position (second magnetic core is in prime).Under this state, in the magnetic field that load coil 52 produces, shield member 60 carries out magnetic shielding.In this case, because in the outside of minimum paper by the zone, shield member 60 is positioned on the flux path that is generated by load coil 52, so can partly suppress the generation in magnetic field.Therefore can suppress the thermal value of minimum paper, prevent that heating tape 48 and warm-up mill 46 from excessively heating up by the outside, zone.

Bit by bit change by the rotational angle that makes center magnetic core 58 in addition, can adjust the shielding amount in magnetic field.For example, if increase the rotational angle of center magnetic core 58 to counter clockwise direction from the position of Fig. 5 B, then left side does not in the drawings shield and produces magnetic field, but magnetic shielding is proceeded on right side in the drawings.In this case, compare with the position of Fig. 5 A, all in all, because the magnetic field intensity that produces reduction, so can correspondingly reduce thermal value.

Structural parameter

Adjust effect in order to obtain aforesaid magnetic field well, the structure of IH coil unit 50 is set following optimal parameter.Fig. 6 is the figure of the structural parameter set in the present embodiment of expression.Below the relation between the parameter is described.

According to the structure of IH coil unit 50, heating tape 48 with warm-up mill 46 position contacting on form the outside surface of circular arc.And, load coil 52 is configured in along on the arc surface (Reference numeral S1 among the figure) of the outside surface imagination formation of described circular arc, this imaginary circle arc surfaced is formed in the outside of the circular arc outside surface of described heating tape 48, and concentric with the circular arc outside surface of this heating tape 48.In addition, center magnetic core 58 is to be the cylindrical shape at center with the axis, and (or burying underground) shield member 60 of pasting along its outside surface bends to circular arc.At this moment, below relation is set up.

The relation of r1 〉=r2

Parameter r1 is equivalent to dispose the radius-of-curvature of the imaginary circle cambered surface S1 of load coil 52.Parameter r2 is equivalent to be switched under the state of screening-off position in the position of shield member 60, and the center of curvature O1 of 48 circular arc outside surface is to the bee-line of shield member 60 outside surfaces from the heating tape.At this moment, because of the relation of r1 〉=r2 is set up, so can carry out magnetic shielding reliably in screening-off position.

The relation of θ 2 〉=θ 1

Parameter θ 1, θ 2 are that the axis with center magnetic core 58 is the angle at center.Parameter θ 1 is equivalent to the angle between following two straight lines, and one of them straight line is meant, the imaginary line (Reference numeral L1 among the figure) that the center O 2 of the center of curvature O1 of the circular arc outside surface of heating tape 48 and center magnetic core 58 is connected; Another straight line is meant, center O 2 and intersection point (the straight line that in figure Reference numeral a) be connected of center magnetic core 58 outside surfaces with the imaginary circle cambered surface S1 of configuration load coil 52.Parameter θ 2 is switched under the state of screening-off position in the position of shield member 60, is equivalent to the angle between following two straight lines, and one of them straight line is meant described imaginary line L1; Another straight line is meant, connects the straight line of the end points (Reference numeral b among the figure) of center O 2 and shield member 60.At this moment, if the relation of θ 2 〉=θ 1 is set up, then can cut off flux path reliably, so can give full play to the effect that shield member 60 carries out magnetic shielding in the center of load coil 52 side.

The position relation of planar S 2 and end points c

Imaginary plane shown in Fig. 6 (Reference numeral S2) is the center O 2 in center magnetic core 58, with the plane of described imaginary line L1 square crossing.In Fig. 6, the horizontal component of arch magnetic core 54 is formed centrally in this imaginary plane (S2) being.Be switched to the state of retreating position (position that in figure dot) under in the position of shield member 60 this moment, 48 the circular arc outside surface from the heating tape, the position of the end points of shield member 60 (Reference numeral c among the figure) is set at than on the farther position of imaginary plane (S2).That is, be under the situation of circular shape at shield member 60, if it is oversize at circumferencial direction, even then move to retreating position, end-on position also might shielding circuit.So in the present embodiment, the structure of employing is: move at shield member 60 under the state of retreating position, the position that makes its end points (c) than the center of the horizontal component of arch magnetic core 54 further from the heating tape 48, thereby at retreating position armoured magnetic field not.Like this, can not hinder the induction heating efficient of heating tape 48 at retreating position.

Variation 1

Fig. 7 is that first variation of the fixation unit 14 of expression first embodiment is the figure of fixation unit 14A.In this fixation unit 14A, do not utilize described heating tape 48 and carry out photographic fixing with fixing roller 45A and 44 pairs of toner images of backer roll.The relative configuration of periphery of IH coil unit 50 and this fixing roller 45A.

On the excircle of fixing roller 45A, for example be wound with the magnetic identical with described heating tape, carry out induction heating with 52 pairs of magnetics of load coil.In this case, thermistor 62 is arranged on the position of magnetic layer relatively, the fixing roller 45A outside.Other are identical with above-mentioned record, and center magnetic core 58 is rotated, and can adjust the shielding amount to magnetic field thus.

Variation 2

Fig. 8 is that second variation of the fixation unit 14 of expression first embodiment is the figure of fixation unit 14B.Utilize the example of the IH coil unit 50A of different modes in this expression.In this topology example, IH coil unit 50A is not the position of 48 the circular arc in the heating tape, but induction heating is carried out in the plane position between warm-up mill 46 and fixing roller 45.Be that center magnetic core 58 is rotated in this case too, can adjust shielding amount thus magnetic field.

Second embodiment of fixation unit

Fig. 9 is the longitudinal diagram of fixation unit 214 structures of expression second embodiment.As mentioned above, fixation unit 214 comprises backer roll 44, fixing roller 45, warm-up mill 46 and heating tape 48.These members are identical with first embodiment, in this description will be omitted.

In addition, fixation unit 214 has IH coil unit 250 at the warm- up mill 46 and 48 outsides, heating tape.IH coil unit 250 comprises load coil 52 (coil), a pair of arch magnetic core 54 (part of first magnetic core), an offside magnetic core 56 (part of first magnetic core) and center magnetic core 258 (second magnetic core).On this center magnetic core 258, shield member 260 is installed along its outside surface.The point different with the fixation unit 14 of first embodiment be the shield member 260 that has of this center magnetic core 258 in fact just, so followingly describe as the center, omits or simplifies explanation about other parts.

The shield member 260 of second embodiment is an annular.When the shield member on the center magnetic core 258 260 was positioned at screening-off position (prime), the magnetic field that load coil 52 produces connected in the ring of shield member 260.On the other hand, when the shield member on the center magnetic core 258 260 was positioned at retreating position (second), the magnetic field that load coil 52 produces was by outside the ring of shield member 260.

Center magnetic core 258 is that section is columnar ferrite system magnetic core, though not expression in Fig. 9, this center magnetic core 258 is connected (with reference to Figure 13 A) with rotating mechanism, utilize this rotating mechanism, can rotate around the axis of its long side direction.

Shield member 260 is installed along the outside surface of center magnetic core 258.Shield member 260 is an inboard Q-RING shape that also only stays the surrounding edge portion of thin plate of die-cut thin plate, and integrally bending is in the arc-shaped.In addition as shown in the figure, shield member 260 can be imbedded the wall thickness part of center magnetic core 258, also can stick on center magnetic core 258 outside surfaces.For pasting shield member 260, for example can utilize silicon class bonding agent.

As the constituent material of shield member 260, preferably adopt non magnetic and high conductive material, for example can adopt oxygen-free copper etc.Shield member 260 utilizes vertical magnetic field to connect the induction current that produces in its ring, produces counter field, eliminates interlinkage flux (vertical perforation magnetic field) and shields.In addition, by utilizing high conductive material, can suppress Joule heat, effectively armoured magnetic field because of the induction current generation.In order to improve electric conductivity, effective method for example has: (1) selects the thickness of the little material of intrinsic resistance, (2) increase member etc. as far as possible.Specifically, the thickness of slab of preferable mask member 60 is in the scope of 0.5mm～3mm.Adopt the thickness of slab of 1mm in the present embodiment.

As shown in Figure 9, if shield member 260 is positioned at the position (screening-off position near 48 surfaces, heating tape; Prime), then magnetic resistance increases around load coil 52, and magnetic field intensity reduces.On the other hand, center magnetic core 258 is rotated 180 ° (there is no particular limitation for direction) from state shown in Figure 9, and shield member 260 moves to apart from the heating tape 48 farthest position (retreating positions; Second), then magnetic resistance reduces around load coil 52, is arch magnetic core 54 and the side magnetic core 56 formation magnetic circuits of center by both sides with center magnetic core 258, and the action of a magnetic field is on heating tape 48 and warm-up mill 46.

The topology example of shield member (1)

Figure 10 is the stereographic map of the shield member 260 of expression topology example (1).Shield member 260 integral body are the straight-flanked ring shape, and its four limit is made of with relative in the longitudinal direction a pair of arc sections 60b a pair of line part 60a relative on Width.In this example, at an end (minimum paper is by the outside in zone) of center magnetic core 258 configuration shield member 260.Another end of this external center magnetic core 258 also disposes identical shield member 260.

Figure 11 A～Figure 11 C is used to illustrate the schematic diagram that utilizes shield member 260 to obtain the principle of Magnetic Shielding Effectiveness.Among Figure 11 A～Figure 11 C, shield member 260 is simplified as the tinsel pattern.

Shown in Figure 11 A,,, then produce induction current at the circumferencial direction of shield member 260 thus if produce the magnetic field (interlinkage flux) that vertically (direction) connects its anchor ring (imaginary plane) for the shield member 260 of annular.So,, eliminated magnetic field so they are cancelled out each other because of electromagnetic induction produces and perforation rightabout magnetic field, magnetic field (counter field).In second embodiment, utilize the effect in this elimination magnetic field, carry out magnetic shielding.

Shown in Figure 11 B upper strata, on the anchor ring of the shield member 260 of annular, produce the perforation magnetic field of twocouese, this moment interlinkage flux summation approximately to offset be 0 (± 0).In this case, in shield member 260, produce induction current hardly.Therefore shield member 260 is brought into play the effect of eliminating magnetic field hardly, directly passes through shield member 260 to the magnetic field of twocouese.This is with shown in the lower floor of Figure 11 B, and magnetic field is identical by the situation of shield member 260 inboards along the U-shaped direction of turning back.In this external second embodiment, make shield member 260 keep out of the way the position that magnetic field does not connect in any direction, magnetic field is passed through.

Figure 11 C represents to produce the situation in the magnetic field (interlinkage flux) parallel with the anchor ring cardinal principle of annular shield member 260.In this case, in shield member 260, also produce induction current equally hardly, therefore also can not produce the effect of eliminating magnetic field.Though do not adopt this method in the present embodiment, this is the main in the prior art back-off method that adopts.But, around load coil 52, to obtain such magnetic field environment, need make shield member 260 produce bigger displacement, correspondingly motion space will become big.

In topology example (1), be conceived to utilize the principle shown in Figure 11 A can obtain this point of Magnetic Shielding Effectiveness, follow the rotation of center magnetic core 258, make shield member 260 move on to screening-off position or retreating position, carry out best magnetic shielding thus.

The topology example of shield member (2)

Figure 12 A, Figure 12 B are the figure of the shield member 260A of expression topology example (2).Figure 12 A is corresponding to described screening-off position, and Figure 12 B is corresponding to retreating position.The side view of center magnetic core 258 is represented on the upper strata of these Figure 12 A, Figure 12 B, and lower floor represents vertical view.In addition in the drawings, on the part that the outside surface of center magnetic core 258 exposes, added the site.

The total length of center magnetic core 258 is identical or longer than it by width W 2 with maximum paper substantially.At this moment, shield member 260A is divided into two on the long side direction of center magnetic core 258, and they are symmetrical shape.Shown in Figure 12 B, each shield member 260 monnolithic case overlook be seen as trapezoidal.On the circumferencial direction of center magnetic core 258, the length of shield member 260A (ring width) is the shortest at the middle position near center magnetic core 258, and the two side ends to center magnetic core 258 increases gradually from here.

Particularly shield member 260A integral body is side's annular, and its inside is divided into a plurality of rings by a plurality of arc sections 60b.Under this structure, wave the effect of shielding because of utilizing the environment-development of cutting apart one by one, so can adapt to the paper of multiple size.

In addition, shield member 260A is arranged on two outsides of the minimum paper vertical with the paper direction of passage by width W 1, has the seldom shield member 260A of part at minimum paper by in the scope of width W 1.And shield member 260A arrives the slightly outside of maximum paper by width W 2 at the two ends of center magnetic core 258.Wherein, minimum paper determines according to the minimum dimension that can be printed by image processing system 1 or maximum sized paper by width W 2 by width W 1 and maximum paper.

In topology example (2), the length of shield member 260A (ring width) accounts for the ratio of the outer circumference on center magnetic core 258 rotation directions, along axial (long side direction) difference of center magnetic core 258.At this moment, the ring width (being made as Lc) of establishing shield member 260A account for the ratio of the outer circumference (being made as L) of center magnetic core 258 be coverage rate (=Lc/L), this coverage rate is inboard little center magnetic core 258, and is more big more to the axial outside (two ends) by the inboard.Specifically, it is minimum that coverage rate is passed through near the zone (minimum paper is by the scope of width W 1) at minimum paper, and opposite is maximum at the two ends of center magnetic core 258.

By making shield member 260A follow the rotation of center magnetic core 258 to move, part suppresses the magnetic flux of generation, can treat each paper size (paper passes through width).This moment, paper size was big more according to the rotational angle (rotational displacement) of the size change center magnetic core 258 of paper, and the magnetic shielding amount is more little, and on the contrary, paper size is more little, and the shielding amount is big more, can prevent that like this two end portions of warm-up mill 46 and heating tape 48 from excessively heating up.In Figure 12 A, Figure 12 B, represent to rotation counterclockwise, but center magnetic core 258 also can be rotated to clockwise direction with arrow.In addition, the paper direction of passage also can be opposite with the direction shown in Figure 12 A.

About making center magnetic core 258, identical with first embodiment around the mechanism that axis rotates.Figure 13 A is the side view that expression makes the rotating mechanism 64A structure of center magnetic core 258 rotations, and Figure 13 B is XIIIB-XIIIB directional profile figure of Figure 13 A.Rotating mechanism 64A comprises step-by-step motor 66, reducing gear 68, driving shaft 70 and controller 69.Each constitutes identical with first embodiment, so omitted explanation.

The action of topology example (1), topology example (2)

Figure 14 A, Figure 14 B are the figure that the action example of the shield member 260 (260A) that the rotation of center magnetic core 258 produces is followed in expression.Describe respectively below.

Figure 14 A represents to follow the rotation of center magnetic core 258, the action example the when position of shield member 260 is switched to retreating position (second magnetic core is in second).Under this state, in the magnetic field that load coil 52 produces, shield member 260 is armoured magnetic field not.That is, in this case, the magnetic field that load coil 52 produces does not connect in the ring of shield member 260, but by outside the ring.Therefore, magnetic field is through side magnetic core 56, arch magnetic core 54 and center magnetic core 258, by heating tape 48 and warm-up mill 46.Produce vortex flow this moment in the heating tape 48 of ferromagnetism body and warm-up mill 46, the intrinsic resistance that has because of each material produces Joule heat, and heating tape 48 and warm-up mill 46 are heated.

Action example when Figure 14 B represents to make the position of shield member 260 to switch to screening-off position (second magnetic core is in prime).In this state, in the magnetic field that load coil 52 produces, shield member 260 carries out magnetic field shielding.That is, in this case, in the outside of minimum paper by the zone, shield member 260 is positioned on the flux path, and magnetic field connects in the ring of shield member 260.Therefore according to the principle shown in Figure 11 A, can partly suppress the generation in magnetic field.Can prevent that heating tape 48 and warm-up mill 46 from excessively heating up in the outer lateral inhibition thermal value of minimum paper like this by the zone.

Under the situation of topology example (2), bit by bit change by the rotational angle that makes center magnetic core 258, can adjust the shielding amount in magnetic field.For example increase the rotational angle of center magnetic core 258 to counter clockwise direction from the position of Figure 14 B, because of near the part (minimum paper is by the zone) that departs from screening-off position at the ring of shield member 260 does not shield, so generation magnetic field, but proceed magnetic shielding in other parts (minimum paper is by the outside in zone).

The topology example of shield member (3)

Figure 15 is the stereographic map of the shield member 260B of expression topology example (3).Do not represent center magnetic core 258 in the drawings.Shield member 260B integral body is cylindrical shape.That is, the end positions of shield member 260B on long side direction has a pair of ring portion 60c, connects with three line part 60a between them.Line part 60a is along the circumferencial direction arranged spaced of ring portion 60c.In topology example (3), shield member 260B is configured in center magnetic core 258 1 ends (minimum paper is by the outside in zone) and the other end respectively.

In this shield member 260B, along the circumferential direction form the part of annular at three positions.That is, form an annular section with two adjacent line part 60a with the ring portion 60c that is connected them in a circumferential direction, so shield member 260B integral body has three annular sections.

The action of topology example (3)

Figure 16 A, Figure 16 B are the figure of the action example of expression when adopting the shield member 260B of topology example (3).

Figure 16 A represents to follow the rotation of center magnetic core 258, the action example the when position of shield member 260B is switched to retreating position.Under this state, in the magnetic field that load coil 52 produces, shield member 260B does not shield magnetic field.Topology example (3) under the state that shield member 260B is kept out of the way, utilizes the principle shown in Figure 11 B lower floor.

That is, be positioned on the center line of coil 52, make to be arranged in and keep out of the way the outside, magnetic field with an annular section R1 of warm-up mill 46 opposite sides (top of figure) by making among three line part 60a one.Other two annular section R2, R3 make magnetic field along the U-shaped inboard of direction by them of turning back.By such configuration annular section R1, R2, R3, can reach the state that does not produce Magnetic Shielding Effectiveness.Therefore, magnetic field is through side magnetic core 56, arch magnetic core 54 and center magnetic core 258, by heating tape 48 and warm-up mill 46.Produce vortex flow this moment in the heating tape 48 of ferromagnetism body and warm-up mill 46, the intrinsic resistance that has because of each material produces Joule heat and heats.

Action example when Figure 16 B represents that the position of shield member 260B switched to screening-off position.Under this state, in the magnetic field that load coil 52 produces, shield member 260B carries out magnetic shielding.In this case, in the outside of minimum paper by the zone, annular section R1, the R2 of shield member 260B, R3 lay respectively on the flux path, and magnetic field connects in the ring.That is,, and become the path that connects another annular section R2 by the flux path perforation annular section R1 of the arch magnetic core 54 in left side among the figure.In addition, the flux path of the arch magnetic core 54 by right side among the figure connects annular section R3, and becomes the path that connects another annular section R2.Therefore according to the principle shown in Figure 11 A, can partly suppress to produce magnetic field.Can prevent the excessive intensification of heating tape 48 and warm-up mill 46 at minimum paper by lateral inhibition thermal value outside regional thus.

Structural parameter

In topology example (1)～(3),, set following optimal parameter for the structure of IH coil unit 250 for the Magnetic Shielding Effectiveness that obtains.Figure 17 is the figure of the structural parameter set in second embodiment of expression.Wherein exemplified the shield member 260B of topology example (3).Below the relation between the parameter is described.

According to the structure of IH coil unit 250, heating tape 48 with warm-up mill 46 position contacting on form the outside surface of circular arc.Load coil 52 is configured in along on the arc surface (Reference numeral S1 among the figure) of this circular arc outside surface imagination formation, and this imaginary circle cambered surface is formed on the outside of the circular arc outside surface of described heating tape 48, and concentric with the circular arc outside surface of this heating tape 48.In addition, center magnetic core 258 is to be the cylindrical shape at center with the axis, and the shield member 260B that pastes (or burying underground) along its outside surface bends to circular shape.The axis of center magnetic core 258 (center O 2) is positioned at the position by the center line of coil 52.This moment, following relation was set up.

R1〉relation of r2

Parameter r1 is equivalent to dispose the radius-of-curvature of the imaginary circle cambered surface (S1) of load coil 52.Parameter r2 is equivalent to be switched under the state of screening-off position in the position of shield member 260B, and the center of curvature O1 of 48 circular arc outside surface is to the bee-line of shield member 260B outside surface from the heating tape.At this moment, because of r1〉relation of r2 sets up, so can carry out magnetic shielding in screening-off position reliably.

The position relation of coil bottom surface and end points b

In that shield member 260B is moved under the state of screening-off position, on the circumferencial direction of center magnetic core 258, stipulate the position (Reference numeral b among the figure) of shield member 260B end points imaginaryly.Be positioned at end points b near by making the imaginary circle cambered surface S1 that coil 52 is set this moment, can bring into play the Magnetic Shielding Effectiveness of utilizing shield member 260B well.

The position relation of arch magnetic core and end points c

Shown in the dotted line among Figure 17,,, stipulate the position (Reference numeral c among the figure) of shield member 60 end points at the circumferencial direction of center magnetic core 58 in that shield member 260B is moved under the state of retreating position imaginaryly.Be positioned at position than end points c more close heating tape 48 or warm-up mill 46 by making arch magnetic core 54 this moment, and shield member 60 does not hinder magnetic field when carrying out induction heating, can help to realize good preheating environment.

The topology example of shield member (4)

Figure 18 is the stereographic map of the shield member 260C of expression topology example (4), does not represent center magnetic core 258 among the figure.Shield member 260C is the mode that topology example (3) is further developed.Shield member 260C, the end on its long side direction has the disk 60A of hole shape, and this outer long side direction and this disk 60A partition distance ground have identical shaped disk 60B.And shield member 260C has the disk 60C of the hole shape of about 2/3rds circles along long side direction and described disk 60B partition distance ground, and in addition, the other end of shield member 260C has the disk 60D of the hole shape of about 1/3rd circles.

Three disk 60A, 60B, 60C among these four disk 60A～60D interconnect by three line part 60a.The disk 60D of the remaining other end is connected by two line part 60a with adjacent disk 60C.

Figure 19 A is that the shield member 260C of expression bar structure example (4) is installed in the figure of the state on the center magnetic core 258, and Figure 19 B, Figure 19 C, Figure 19 D are respectively XIXB direction, the XIXC direction of Figure 19 A, the sectional view of XIXD direction.Shield member 260C is whole to embed in the center magnetic core 258, but disk 60A～60D exposes periphery slightly from the outside surface of center magnetic core 258.

Shown in Figure 19 A, the shield member 260C of topology example (4) also is arranged on the end on center magnetic core 258 long side directions.At this moment, be positioned at corresponding position from minimum paper by zone disk 60A farthest with full-size P1 (for example A3, A4R size), next disk 60B is positioned at the corresponding position with medium size P2 (for example B4R size), and next again disk 60C is positioned at the corresponding position with medium small size P3 (for example B4 size).And minimum paper is positioned at the corresponding position with minimum dimension P4 (for example A5R size) by near the disk 60D the zone.

Shown in Figure 19 B, disk 60A, 60B make complete annular shape.Shown in Figure 19 C, disk 60C is the incomplete annular shape of about 2/3rds circles.In lacking in the part of disk 60C, fill the Ferrite Material of center magnetic core 258.Shown in Figure 19 D, disk 60D is the fan shape of about 1/3rd circles.The Ferrite Material of also filling center magnetic core 258 in the part that lacks at disk 60D.

The action example of topology example (4)

Being the action example when utilizing the shield member 260C of topology example (4) from Figure 20 to Figure 25, is the stereographic map that order is represented six action examples.Thick-line arrow is represented induction current that produces or the magnetic field of passing through among each figure.Describe respectively below.

Shielding (0 °) comprehensively

At first Figure 20 is the stereographic map of the action example of expression when comprehensively shielding with shield member 260C.In each action example, suppose on the direction that connects from the top down with respect to shield member 260C, to produce magnetic field.In the following description, establishing comprehensive masked state shown in Figure 20 is 0 °, and the rotational angle that begins with state is thus represented the displacement of shield member 260C.

When the rotation of following center magnetic core 258, make shield member 260C move to disk 60D when being positioned at the rotational angle (0 °) of below, effect that then can performance magnetic shielding on whole of the long side direction of shield member 260C.That is, the disk 60A on the end position forms the annular section of maximum shape with the locational disk 60D of the other end by the line part 60a that is connected them, so can carry out magnetic shielding by its integral body.In this case, according to minimum dimension P4, can prevent the overheated of heating tape 48 and warm-up mill 46.

Unshielded (60 °)

Figure 21 is the stereographic map of expression shield member 260C from the action example of state when clockwise direction is rotated 60 ° of Figure 20.In this case, because line part 60a is positioned on the center line of coil 52 (identical with the state of Figure 16 A),, do not produce Magnetic Shielding Effectiveness so shield member 260C is positioned at retreating position.

Medium small size shielding (120 °)

Figure 22 is the stereographic map of expression shield member 260C from the action example of state when clockwise direction is rotated 120 ° of Figure 20.In this case, by an annular section that between disk 60A and disk 60C, forms, can bring into play Magnetic Shielding Effectiveness.In this action example,, can prevent the overheated of heating tape 48 and warm-up mill 46 for example according to medium small size P3.

Unshielded (180 °)

Figure 23 is the stereographic map of expression shield member 260C from the action example of state when clockwise direction is rotated 180 ° of Figure 20.In this case, identical with Figure 21, because line part 60a is positioned on the center line of coil 52 (state of Figure 16 A),, do not produce Magnetic Shielding Effectiveness so shield member 260C is positioned at retreating position.

Medium size shielding (240 °)

Figure 24 is the stereographic map of expression shield member 260C from the action example of state when clockwise direction is rotated 240 ° of Figure 20.In this case, by an annular section that between disk 60A and disk 60B, forms, can bring into play Magnetic Shielding Effectiveness.In this action example,, can prevent the overheated of heating tape 48 and warm-up mill 46 for example according to medium size P2.

Unshielded (300 °)

Figure 25 is the stereographic map of expression shield member 260C from the action example of state when clockwise direction is rotated 300 ° of Figure 20.In this case, identical with Figure 21, Figure 23, because line part 60a is positioned on the center line of coil 52,, do not produce Magnetic Shielding Effectiveness so shield member 260C is positioned at retreating position.Under the situation of unshielded (60 °), (180 °), (300 °),, can carry out induction heating to heating tape 48 and warm-up mill 46 according to full-size P1.

Variation 1

Figure 26 is that fixation unit 214 first variation of expression second embodiment are the figure of fixation unit 214A.In this fixation unit 214A, do not utilize described heating tape 48 but carry out photographic fixing by fixing roller 45A and 44 pairs of toner images of backer roll.The relative configuration of periphery of IH coil unit 250 and this fixing roller 45A.

On the outer circumference surface of fixing roller 45A, for example be wound with the magnetic identical with described heating tape, carry out induction heating with 52 pairs of magnetics of load coil.In this case, thermistor 62 is arranged on the position relative with the magnetic layer, the outside of fixing roller 45A.Other rotate center magnetic core 258 as hereinbefore, can make shield member 260B move to screening-off position and retreating position respectively thus.

Variation 2

Figure 27 is that second variation of the fixation unit 214 of expression second embodiment is the figure of fixation unit 214B.(SUS for example: stainless steel) make, and different with aforementioned embodiments is the inside that center magnetic core 258 is configured in warm-up mill 46A by material with nonmagnetic metal for the warm-up mill 46A of this fixation unit 214B.In addition, in IH coil unit 250A, two arch magnetic cores 54 connect magnetic core 55 in the middle of being provided with in the bottom of intermediate 541 by the intermediate of being made by magnetic metal 541.

Making with nonmagnetic metal under the situation of warm-up mill 46A, pass through side magnetic core 56, arch magnetic core 54, intermediate 541 and middle magnetic core 55 by the magnetic field that load coil 52 produces, connect warm-up mill 46A and arrive inner center magnetic core 258, induction heating is carried out in heating tape 48 with this perforation magnetic field.

In this topology example, as shown in figure 27,, then carry out magnetic shielding if the position of the annular section of shield member 260B is switched to the position (screening-off position) relative with middle magnetic core 55, can excessively heat up in the outer lateral inhibition of paper by the zone.On the other hand, the state that magnetic field does not connect in the shield member 260B ring is a retreating position, in this case, does not produce Magnetic Shielding Effectiveness, by the zone induction heating is carried out in heating tape 48 at maximum paper.

Variation 3

Figure 28 is that the 3rd variation of the fixation unit 214 of expression second embodiment is the figure of fixation unit 214C.Utilized the example of the IH coil unit 250B of different modes in this expression.In this topology example, not in the position of the circular arc of heating tape 48 but on the plane position between warm-up mill 46 and the fixing roller 45, IH coil unit 250B carries out induction heating.Center magnetic core 258 is rotated, carry out magnetic shielding.

More than various embodiments of the present invention are illustrated, but the present invention is not limited to described embodiment, can carry out various distortion.For example the section configuration of center magnetic core 58 (258) is not limited to cylinder or cylinder, also can be polygon.In addition, in the vertical view of shield member 260, the shape of annular also is not limited to trapezoidal or rectangle, can also be triangle.

The concrete mode of each several part such as arch magnetic core 54, side magnetic core 56 also is not limited to the mode represented among the figure in addition, can suitably be out of shape.

In described structure, can be to the concrete shape and the geometry parameter of various member regulations as following (4)～(6).

Claims (11)

1. image processing system is characterized in that comprising:

Image forming part is transferred to toner image on the thin slice body; And

Fixation unit has heater and pressing element, and described thin slice body is clipped between this heater and the pressing element carries, and in this course of conveying, is used to the heat from described heater at least, toner image on the thin slice body; Wherein,

Described fixation unit comprises:

Coil produces the magnetic field that is used for described heater is carried out induction heating;

First magnetic core is made by magnetic material, and fixed configurations is used for forming magnetic circuit around described coil around described coil;

Second magnetic core is made by magnetic material, on the magnetic direction that is produced by described coil, is configured between described first magnetic core and the described heater, and this second magnetic core can change posture, is used for forming magnetic circuit with described first magnetic core;

Shield member is made by nonmagnetic metal, along the outside surface setting of described second magnetic core, is used for carrying out magnetic shielding in the magnetic field that described coil produces; And

Magnetic shielding portion is used to make described second magnetic core to carry out changing posture between the prime of magnetic shielding and the second that described shield member does not carry out magnetic shielding at described shield member,

Described shield member has annular shape portion,

Be under the state of described prime at described second magnetic core, the magnetic field that described coil produces connects in the annular shape portion of described shield member,

Be under the state of described second at described second magnetic core, the magnetic field that described coil produces is by the outside of the annular shape portion of described shield member.

2. image processing system according to claim 1 is characterized in that,

Described second magnetic core rotates around the axis that the magnetic field direction of passage with described coil generation intersects, and changes posture,

Described magnetic shielding portion comprises rotating mechanism, is used to make described second magnetic core to rotate around described axis, makes this second magnetic core change posture between described prime and described second.

3. image processing system according to claim 1 is characterized in that, described shield member is a Q-RING shape with common outer peripheral portion, and on the long side direction of described heater, the inside of this Q-RING is divided into a plurality of parts.

4. image processing system according to claim 1 is characterized in that,

Described coil is along the configuration of the outside surface of described heater, and described first magnetic core cut apart the both sides along the center of described outside surface that are configured in described coil,

Described second magnetic core is arranged on the position that magnetic circuit converges through the center of divided described first magnetic core and described coil.

5. image processing system according to claim 4 is characterized in that,

At least a portion of described heater has the outside surface of circular arc,

Described coil configuration is on the arc surface that the circular arc outside surface imagination along described heater forms, and this imaginary circle cambered surface is formed on the outside of the circular arc outside surface of described heater, and concentric with the circular arc outside surface of this heater,

Described second magnetic core is a cylindrical shape or cylindrical,

Described shield member is along the outer surface bending of described second magnetic core shape in the arc-shaped, wherein,

When the radius-of-curvature of the imaginary circle cambered surface of the described coil of configuration is made as r1, position at described shield member is switched under the state of screening-off position, when the bee-line from the center of curvature of the circular arc outside surface of described heater to described shield member outside surface was made as r2, the relation of r1＞r2 was set up.

6. image processing system according to claim 5, it is characterized in that, the imaginary circle cambered surface that disposes described coil is under the state of described prime at described second magnetic core, is located near the position of described shield member end points on the described second magnetic core circumferencial direction.

7. image processing system according to claim 5, it is characterized in that, described first magnetic core is under the state of described second at described second magnetic core, is positioned at than on the position of the more close described heater in position of the described shield member end points on the described second magnetic core circumferencial direction.

8. image processing system according to claim 1 is characterized in that,

Described heater is made of the heating tape that fixing roller or volume hang on warm-up mill and the fixing roller,

Also comprise temperature control part, control described coil described heater is carried out the state of induction heating,

Described temperature control part has the aitiogenic thermotonus element of the temperature of described warm-up mill or fixing roller, and controls the action of described coil according to the reaction result of this thermotonus element along the inner peripheral surface configuration of described warm-up mill or fixing roller.

9. image processing system according to claim 1 is characterized in that the material of described shield member is a copper.

10. image processing system according to claim 1 is characterized in that described shield member is made by nonmagnetic metal, and thickness is in 0.5mm～3mm scope.

11. image processing system according to claim 1 is characterized in that,

Described coil configuration is in the outside of described heater,

Described second magnetic core is configured in the inboard of described heater.

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