Patent Application
20150338806
The present invention relates to a heater for heating an image on a sheet and an image heating apparatus provided with the same. The image heating apparatus is usable with an image forming apparatus such as a copying machine, a printer, a facsimile machine, a multifunction machine having a plurality of functions thereof or the like.
An image forming apparatus is known in which a toner image is formed on the sheet and is fixed on the sheet by heat and pressure in a fixing device (image heating apparatus). As for such a fixing device, a type of fixing device is recently proposed (Japanese Laid-open Patent Application 2012-37613) in which a heat generating element (heater) is contacted to an inner surface of a thin flexible belt to apply heat to the belt. Such a fixing device is advantageous in that the structure has a low thermal capacity, and therefore, the temperature rise to the fixing operation allowable is quick.
Japanese Laid-open Patent Application 2012-37613 discloses a structure of a fixing device in which a heat generating region width of a heat generating element (heater) is controlled in accordance with a width size of the sheet.
In this fixing device, each electrode is electrically connected with an electroconductive line layers 1029 (1029a, 1029b) formed on the substrate. More in detail, the electroconductive line layer connected with the electrode 1027b and the electrode 1027d extends toward one longitudinal end of the substrate. The electroconductive line layer 1029a connected with the electrode 1027c and the electrode 1027e extends toward another longitudinal end of the substrate. In the one end portion of the substrate with respect to the longitudinal direction, the electrode 1027a and the electroconductive line layer 1029b are connectable with respective electroconductive members. In the other end portion of the substrate with respect to the longitudinal direction, the electrode 1027f and the electroconductive line layer 1029a are connectable with respective electroconductive members. More in detail, the opposite longitudinal end portions of the substrate is not coated with an insulation layer for protecting the electroconductive lines, and the electroconductive line layers 1029a 1029b and the electrodes 1027a, 1027f are exposed. Therefore, the heater 1006 is connected to a voltage supply circuit by the electroconductive member contacted to exposed stations of electroconductive line layers 1029a, 1029b and electrodes 1027a, 1027f. The voltage supply circuit includes an AC voltage source and switches 1033 (1033a, 1033b, 1033c, 1033d), by combinations of the actuations of which heater energization pattern is controlled. In other words, the electroconductive line layers 1029a, 1029b are selectively connected with a voltage source contact 1031a or a voltage source contact 1031b in accordance with the intended connection pattern. With such a structure, the fixing device disclosed in Japanese Laid-open Patent Application 2012-37613 changes the width size of the heat generating region of the heat generating resistance layer 1025 in accordance with the width size of the sheet to be heated thereby.
Here, for simplicity, the exposed portion of the electroconductive line layer 1029a will be called electrical contact A, the exposed portion of the electroconductive line layer 1029b is called electrical contact B, the exposed portion of the electrode 1027a will be called electrical contact C, and the exposed portion of the electrode 1027f will be called electrical contact D. With the structure disclosed in Japanese Laid-open Patent Application 2012-37613 in which the electrical contacts An and D and electrical contacts B and C are arranged in the widthwise direction of the substrate, the length of the substrate can be reduced as compared with the structure in which the electrical contacts are arranged in the longitudinal direction of the substrate.
As shown in part (a) of
However, if sufficiently wide gaps are provided between the electrical contacts arranged in the widthwise direction of the substrate 1021, the substrate 1021 is required to have a sufficiently large width. As a result, the substrate 1021 upsizes in the widthwise direction which leads to increase in cost.
A heater in which a width size of the heat generating region is changeable is desired to have a suppressed increase of the width of the substrate resulting from the arrangement of the electrical contacts in the widthwise direction of the substrate.
It is an object of the present invention to provide a heater having a relatively smaller width.
It is another object of the present invention to provide an image heating apparatus having a relatively smaller width.
According to an aspect of the present invention, there is provided a heater usable with an image heating apparatus including an electric energy supplying portion provided with a first terminal and a second terminal, and an endless belt for heating an image on a sheet, wherein said heater is contactable to the belt to heat the belt, said heater comprising a substrate; a first connecting portion electrically connectable with the first terminal; a second connecting portion electrically connectable with the second terminal and provided adjacent to said first connecting portion with a gap in a longitudinal direction of said substrate; a third connecting portion electrically connectable with the second terminal; a fourth connecting portion electrically connectable with the second terminal and provided adjacent to said third connecting portion with a gap in the widthwise direction of said substrate; a plurality of heat generating portions arranged in the longitudinal direction of said substrate, said heat generating portions including at least one heat generating portion capable of generating heat by electric energy supply from said first connecting portion and said second connecting portion, at least one heat generating portion capable of generating heat by electric energy supply from said first connecting portion and said third connecting portion, and at least one heat generating portion capable of the generating heat by electric energy supply from said first connecting portion and said fourth connecting portion; a gap between said third connecting portion and said fourth connecting portion in the widthwise direction is smaller than a gap between said first connecting portion and said second connecting portion in the longitudinal direction.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Embodiments of the present invention will be described in conjunction with the accompanying drawings. In this embodiment, the image forming apparatus is a laser beam printer using an electrophotographic process as an example. The laser beam printer will be simply called printer
As shown in
The photosensitive drum 11 as an electrophotographic photosensitive member is rotated by a driving source (unshown) in the direction indicated by an arrow (counterclockwise direction in
A surface of the photosensitive drum 11 is electrically charged by the charger 12. Thereafter, the surface of the photosensitive drum 11 exposed to a laser beam in accordance with image information by the exposure device 13, so that an electrostatic latent image is formed. The electrostatic latent image is developed into a Bk toner image by the developing device 14. At this time, similar processes are carried out for the other colors. The toner image is transferred from the photosensitive drum 11 onto an intermediary transfer belt 31 by the primary transfer blade 17 sequentially (primary-transfer). The toner remaining on the photosensitive drum 11 after the primary-image transfer is removed by the cleaner 15. By this, the surface of the photosensitive drum 11 is cleaned so as to be prepared for the next image formation.
On the other hand, the sheet P contained in a feeding cassette 20 are placed on a multi-feeding tray 25 is picked up by a feeding mechanism (unshown) and fed to a pair of registration rollers. The sheet P is a member on which the image is formed. Specific examples of the sheet P is plain paper, thick sheet, resin material sheet, overhead projector film or the like. The pair of registration rollers 23 once stops the sheet P the correct oblique feeding. The registration rollers 23 then feed the sheet P into between the intermediary transfer belt 31 and the secondary transfer roller 35 in timed relation with the toner image on the intermediary transfer belt 31. The roller 35 functions to transfer the color toner images from the belt 31 onto the sheet P. Thereafter, the sheet P is fed into the fixing device (image heating apparatus) 40. The fixing device 40 applies heat and pressure to the toner image T on the sheet P to fix the toner image on the sheet P.
The fixing device 40 which is the image heating apparatus used in the printer 1 will be described
The fixing device 40 is an image heating apparatus for heating the image on the sheet by a heater unit 60 (unit 60). The unit 60 includes a flexible thin fixing belt 603 and a heater 600 contacted to the inner surface of the belt 603 to heat the belt 603 (low thermal capacity structure). Therefore, the belt 603 can be efficiently heated, so that quick temperature rise at the start of the fixing operation is accomplished. As shown in
Unit 60 is a unit for heating and pressing an image on the sheet P. A longitudinal direction of the unit 60 is parallel with the longitudinal direction of the roller 70. The unit 60 comprises a heater 600, a heater holder 601, a support stay 602 and a belt 603.
The heater 600 is a heating member for heating the belt 603, slidably contacting with the inner surface of the belt 603. The heater 600 is pressed to the inside surface of the belt 603 toward the roller 70 so as to provide a desired nip width of the nip N. The dimensions of the heater 600 in this embodiment are 5-20 mm in the width (the dimension as measured in the left-right direction in
The heater 600 is fixed on the lower surface of the heater holder 601 along the longitudinal direction of the heater holder 601. In this embodiment, the heat generating element 620 is provided on the back side of the substrate 610 which is not in slidable contact with the belt 603, but the heat generating element 620 may be provided on the front surface of the substrate 610 which is in slidable contact with the belt 603. However, the heat generating element 620 is preferably provided on the back side of the substrate 610, by which uniform heating effect to the substrate 610 is accomplished, from the standpoint of preventing non-uniform heat application which may be caused by a non-heat generating portion of the heat generating element 620. The details of the heater 600 will be described hereinafter.
The belt 603 is a cylindrical (endless) belt (film) for heating the image on the sheet in the nip N. The belt 603 comprises a base material 603a, an elastic layer 603b thereon, and a parting layer 603c on the elastic layer 603b, for example. The base material 603a may be made of metal material such as stainless steel or nickel, or a heat resistive resin material such as polyimide. The elastic layer 603b may be made of an elastic and heat resistive material such as a silicone rubber or a fluorine-containing rubber. The parting layer 603c may be made of fluorinated resin material or silicone resin material.
The belt 603 of this embodiment has dimensions of approx. 30 mm in the outer diameter, approx. 330 mm in the length (the dimension measured in the front-rear direction in
The belt contacting surface of the substrate 610 may be provided with a polyimide layer having a thickness of approx. 10 μm as a sliding layer 603d. When the polyimide layer is provided, the rubbing resistance between the fixing belt 603 and the heater 600 is low, and therefore, the wearing of the inner surface of the belt 603 can be suppressed. In order to further enhance the slidability, a lubricant such as grease may be applied to the inner surface of the belt.
The heater holder 601 (holder 601) functions to hold the heater 600 in the state of urging the heater 600 toward the inner surface of the belt 603. The holder 601 has a semi-arcuate cross-section (the surface of
The support stay 602 supports the heater 600 by way of the holder 601. The support stay 602 is preferably made of a material which is not easily deformed even when a high pressure is applied thereto, and in this embodiment, it is made of SUS304 (stainless steel).
As shown in
Between the flange 411a and a pressing arm 414a, an urging spring 415a is compressed. Also, between a flange 411b and a pressing arm 414b, an urging spring 415b is compressed. The urging springs 415a and 415b may be simply called urging spring 415. With such a structure, an elastic force of the urging spring 415 is applied to the heater 600 through the flange 411 and the support stay 602. The belt 603 is pressed against the upper surface of the roller 70 at a predetermined urging force to form the nip N having a predetermined nip width. In this embodiment, the pressure is approx. 156.8 N at one end portion side and approx. 313.6 N (32 kgf) in total.
As shown in
As shown in
The roller 70 of this embodiment includes a core metal of steel, an elastic layer 72 of silicone rubber foam on the core metal 71, and a parting layer 73 of fluorine resin tube on the elastic layer 72. Dimensions of the portion of the roller 70 having the elastic layer 72 and the parting layer 73 are approx. 25 mm in outer diameter, and approx. 330 mm in length.
A thermister 630 is a temperature sensor provided on a back side of the heater 600 (opposite side from the sliding surface side. The thermister 630 is bonded to the heater 600 in the state that it is insulated from the heat generating element 620. The thermister 630 has a function of detecting a temperature of the heater 600. As shown in
The control circuit 100 comprises a circuit including a CPU operating for various controls, a non-volatilization medium such as a ROM storing various programs. The programs are stored in the ROM, and the CPU reads and execute them to effect the various controls. The control circuit 100 may be an integrated circuit such as ASIC if it is capable of performing the similar operation.
As shown in
The control circuit 100 uses the temperature information acquired from the thermister 630 for the electric power supply control for the voltage source 110. More particularly, the control circuit 100 controls the electric power to the heater 600 through the voltage source 110 on the basis of the output of the thermister 630. In this embodiment, the control circuit 100 carries out a wave number control of the output of the voltage source 110 to adjust an amount of heat generation of the heater 600. By such a control, the heater 600 is maintained at a predetermined temperature (approx. 180 degree C., for example).
As shown in
The motor M is a driving portion for driving the roller 70 through the gear G. As shown in
The control circuit 100 controls the rotation of the motor M. The control circuit 100 rotates the roller 70 and the belt 603 using the motor M at a predetermined speed. It controls the motor so that the speed of the sheet P nipped and fed by the nip N in the fixing process operation is the same as a predetermined process speed (approx. 200 [mm/sec], for example).
The structure of the heater 600 used in the fixing device 40 will be described in detail.
The heater 600 of this embodiment is a heater using the heat generating type shown in parts (a) and (b) of
The heat generating element generates heat when energized, irrespective of the direction of the electric current, but it is preferable that the heat generating elements and the electrodes are arranged so that the currents flow along the longitudinal direction. Such an arrangement is advantageous over the arrangement in which the directions of the electric currents are in the widthwise direction perpendicular to the longitudinal direction (up-down direction in part (a) of
In the case that the electric power is supplied individuality to the heat generating elements arranged in the longitudinal direction, it is preferable that the electrodes and the heat generating elements are disposed such that the directions of the electric current flow alternates between adjacent ones. As to the arrangements of the heat generating members and the electrodes, it would be considered to arrange the heat generating elements each connected with the electrodes at the opposite ends thereof, in the longitudinal direction, and the electric power is supplied in the longitudinal direction. However, with such an arrangement, two electrodes are provided between adjacent heat generating elements, with the result of the likelihood of short circuit. In addition, the number of required electrodes is large with the result of large non-heat generating portion. Therefore, it is preferable to arrange the heat generating elements and the electrodes such that an electrode is made common between adjacent heat generating elements. With such an arrangement, the likelihood of the short circuit between the electrodes can be avoided, and the non-heat generating portion can be made small.
In this embodiment, a common electroconductive line 640 corresponds to A-electroconductive-line of part (a) of
As shown in
The substrate 610 determines the dimensions and the configuration of the heater 600 and is contactable to the belt 603 along the longitudinal direction of the substrate 610. The material of the substrate 610 is a ceramic material such as alumina, aluminum nitride or the like, which has high heat resistivity, thermo-conductivity, electrical insulative property or the like. In this embodiment, the substrate is a plate member of alumina having a length (measured in the left-right direction in
On the back side of the substrate 610, the heat generating element 620 and the electroconductor pattern (electroconductive line) are provided through thick film printing method (screen printing method) using an electroconductive thick film paste. In this embodiment, a silver paste is used for the electroconductor pattern so that the resistivity is low, and a silver-palladium alloy paste is used for the heat generating element 620 so that the resistivity is high. As shown in
As shown in
The heat generating elements 620 (620a-620l) are resistors for generating joule heat upon electric power supply thereto. The heat generating element 620 is one heat generating element member extending in the longitudinal direction on the substrate 610, and is disposed in the region 610c (
On the heat generating element 620, seven common electrodes 642a-642g which will be described hereinafter are laminated with intervals in the longitudinal direction. In other words, the heat generating element 620 is isolated into six sections by common electrodes 642a-642g along the longitudinal direction. The lengths measured in the longitudinal direction of the substrate 610 of each section are approx. 53.3 mm. On central portions of the respective sections of the heat generating element 620, one of the six opposite electrodes 652, 662 (652a-652d, 662a, 662b) are laminated. In this manner, the heat generating element 620 is divided into 12 sub-sections. The heat generating element 620 divided into 12 sub-sections can be deemed as a plurality of heat generating elements 620a-620l. In other words, the heat generating elements 620a-620l electrically connect adjacent electrodes with each other. Lengths of the sub-section measured in the longitudinal direction of the substrate 610 are approx. 26.7 mm. Resistance values of the sub-section of the heat generating element 620 with respect to the longitudinal direction are approx. 120Ω. With such a structure, the heat generating element 620 is capable of generating heat in a partial area or areas with respect to the longitudinal direction.
The resistivities of the heat generating elements 620 with respect to the longitudinal direction are uniform, and the heat generating elements 620a-620l have substantially the same dimensions. Therefore, the resistance values of the heat generating elements 620a-620l are substantially equal. When they are supplied with electric power in parallel, the heat generation distribution of the heat generating element 620 is uniform. However, it is not inevitable that the heat generating elements 620a-620l have substantially the same dimensions and/or substantially the same resistivities. For example, the resistance values of the heat generating elements 620a and 620l may be adjusted so as to prevent temperature lowering at the longitudinal end portions of the heat generating element 620. At the positions of the heat generating element 620 where the common electrode 642 and the opposite electrode 652, 662 are provided, the heat generation of the heat generating element 620 is substantially zero. However, the heat uniforming function of the substrate 610 makes the influence on the fixing process negligible if the width of the electrode is not more than 1 mm, for example. In this embodiment, the width of each electrode is not more than 1 mm. The common electrodes 642 (642a-642g) are a part of the above-described electroconductor pattern. The common electrode 642 extends in the widthwise direction of the substrate 610 perpendicular to the longitudinal direction of the heat generating element 620. In this embodiment, the common electrode 642 is laminated on the heat generating element 620. The common electrodes 642 are odd-numbered electrodes of the electrodes connected to the heat generating element 620, as counted from a one longitudinal end of the heat generating element 620. The common electrode 642 is connected to one contact 110a of the voltage source 110 through the common electroconductive line 640 which will be described hereinafter.
The opposite electrodes 652, 662 are a part of the above-described electroconductor pattern. The opposite electrodes 652, 662 extend in the widthwise direction of the substrate 610 perpendicular to the longitudinal direction of the heat generating element 620. The opposite electrodes 652, 662 are laminated on the heat generating element 620. The opposite electrodes 652, 662 are the other electrodes of the electrodes connected with the heat generating element 620 other than the above-described common electrode 642. That is, in this embodiment, they are even-numbered electrodes as counted from the one longitudinal end of the heat generating element 620.
That is, the common electrode 642 and the opposite electrodes 662, 652 are alternately arranged along the longitudinal direction of the heat generating element. The opposite electrodes 652, 662 are connected to the other contact 110b of the voltage source 110 through the opposite electroconductive lines 650, 660 which will be described hereinafter.
The common electrode 642 and the opposite electrode 652, 662 function for supplying the electric power to the heat generating element 620.
In this embodiment, the odd-numbered electrodes are common electrodes 642, and the even-numbered electrodes are opposite electrodes 652, 662, but the structure of the heater 600 is not limited to this example. For example, the even-numbered electrodes may be the common electrodes 642, and the odd-numbered electrodes may be the opposite electrodes 652, 662.
In addition, in this embodiment, four of the all opposite electrodes connected with the heat generating element 620 are the opposite electrode 652. In this embodiment, two of the all opposite electrodes connected with the heat generating element 620 are the opposite electrode 662. However, the allotment of the opposite electrodes is not limited to this example, but may be changed depending on the heat generation widths of the heater 600. For example, two may be the opposite electrode 652, and four maybe the opposite electrode 662.
The common electroconductive line 640 is a part of the above-described electroconductor pattern. The common electroconductive line 640 extends along the longitudinal direction of the substrate 610 toward the one end portion side 610a of the substrate in the one end portion side 610d of the substrate. The common electroconductive line 640 is connected with the common electrodes 642 which is in turn connected with the heat generating element 620. The common electroconductive line 640 is connected to the electrical contact 641 which will be described hereinafter. In this embodiment, in order to assure the insulation of the insulation coating layer 680, a gap of approx. 400 μm is provided between the common electroconductive line 640 and each opposite electrode.
The opposite electroconductive line 650 is a part of the above-described electroconductor pattern. The opposite electroconductive line 650 extends along the longitudinal direction of substrate 610 toward the other end portion 610b of the substrate in the other end portion side 610e of the substrate. The opposite electroconductive line 650 is connected with the opposite electrode 652 which is in turn connected with the heat generating element 620. The opposite electroconductive line 650 is connected to the electrical contact 651 which will be described hereinafter.
The opposite electroconductive line 660 (660a, 660b) is a part of the above-described electroconductor pattern. The opposite electroconductive line 660a extends along the longitudinal direction of substrate 610 toward the one end portion side 610a of the substrate in the other end portion side 610e of the substrate. The opposite electroconductive line 660a is connected with the opposite electrode 662a which is in turn connected with the heat generating element 620 (620a, 620b). The opposite electroconductive line 660a is connected to the electrical contact 661a which will be described hereinafter. The opposite electroconductive line 60b extends along the longitudinal direction of substrate 610 toward the other end portion 610b of the substrate in the other end portion side 610e of the substrate. The opposite electroconductive line 660b is connected to an opposite electrode 662b which is in turn connected with the heat generating element 620 (620k, 620l). The opposite electroconductive line 660b is connected to the electrical contact 661b which will be described hereinafter. In this embodiment, approx. 400 μm gap is provided between the opposite electroconductive line 660a and the common electrode 642 and between the opposite electroconductive line 660b with common electrode 642 so that the electrical insulation is assured by the insulation coating layer 680. In addition, between the opposite electroconductive lines 600b and 650, approx. 100 μm gap is provided.
The electrical contacts 641, 651, 661a, 661b are a part of the above-described electroconductor pattern. In one end portion side 610a of the substrate, the electrical contacts 641, 661a are provided. In other end portion side 610b of the substrate, the electrical contacts 651, 661b are provided. As shown in
When voltage is applied between the electrical contact 641 and the electrical contact 651 through the connection between the heater 600 and the connector 700, a potential difference is produced between the common electrode 642 (642b-642f) and the opposite electrode 652 (652a-652d). Therefore, through the heat generating elements 620c, 620d, 620e, 620f, 620g, 620h, 620i, 620j, the currents flow along the longitudinal direction of the substrate 610, the directions of the currents through the adjacent heat generating elements being substantially opposite to each other. The heat generating elements 620c, 620d, 620e, 620f, 620g, 620h, 620i as a first heat generating region generate heat, respectively.
When voltage is applied between the electrical contact 641 and the electrical contact 661a through the connection between the heater 600 and the connector 700, a potential difference is produced between the common electrode 642a-642b) and the opposite electrode 662a. Therefore, through the heat generating elements 620a, 620b, the currents flow along the longitudinal direction of the substrate 610, the directions of the currents through the adjacent heat generating elements being substantially opposite to each other. The heat generating elements 620a, 620b as a second heat generating region adjacent the first heat generating region generate heat.
When voltage is applied between the electrical contact 641 and the electrical contact 661a through the connection between the heater 600 and the connector 700, a potential difference is produced between the common electrode 642f, 642g and the opposite electrode 662b through the common electroconductive line 640 and the opposite electroconductive line 660b. Therefore, through the heat generating elements 620k, 620l, the currents flow along the longitudinal direction of the substrate 610, the directions of the currents through the adjacent heat generating elements being substantially opposite to each other. By this, the heat generating elements 620k, 620l as a third heat generating region adjacent to the first heat generating region generate heat.
In this manner, by selecting the electrical contacts supplied with the voltage, the desired one or ones of the heat generating elements 620a-620l can be selectively energized. In this embodiment, the first heat generating region, the second heat generating region and the third heat generating region include a plurality of heat generating elements, respectively, but they may include one heat generating element, respectively.
The connector 700 used with the fixing device 40 will be described in detail.
As shown in
The terminals 710, 720a, 720b, 730 will be described taking the terminal 710a as an example. The terminal 710a electrically connects the electrical contact 641 with a switch SW643 which will be described hereinafter. As shown in
Similarly, the contact terminal 720a functions to contact the electrical contact 661a with the switch SW663 which will be described hereinafter. The contact terminal 720a is provided with the electrical contact 721a for contacting to the electrical contact 661a and a cable 722a for the electrical connection with the switch SW643.
Similarly, the contact terminal 720b functions to contact the electrical contact 661b with the switch SW663 which will be described hereinafter. The contact terminal 720b is provided with a cable 722b for the electrical connection between the switch SW643 and the electrical contact 721b for contacting to the electrical contact 661b.
Similarly, the contact terminal 730 functions to contact the electrical contact 651 with the switch SW663 which will be described hereinafter. The contact terminal 730 is provided with a cable 722a for the electrical connection between the switch SW643 and the electrical contact 731 for contacting to the electrical contact 651.
The terminals 710, 720a of metal are supported by the housing 750a of the resin material. The terminals 710, 720a are disposed in the housing 750a with a gap therebetween so as to connect with the electrical contacts 641, 661a when the connector 700a is mounted to the heater 600. Between the terminals, a partition is provided to assure the electrical insulation between the terminals.
The terminals 720b, 730 of metal are supported by the housing 750b of the resin material. The terminal 720b, 730 are disposed with a gap therebetween in the housing 750b so as to contact with the electrical contacts 661b, 651, respectively, when the connector 700b is mounted to the heater. Between the terminals, a partition is provided to assure the electrical insulation is relation between the terminals.
In the above-described example, the connector 700a is mounted to the end portion with respect to the widthwise direction of the substrate 610, and the connector 700b is mounted to the substrate 610 in the longitudinal end portion of the substrate, but this is not limiting to the present invention, and another combination of the mounting directions of the connector 700 to the substrate 610. For example, the connector 700b may also be mounted to the heater from the end portion with respect to the widthwise direction of the substrate, similarly to the connector 700a.
An electric energy supply method to the heater 600 will be described. The fixing device 40 of this embodiment is capable of changing a width of the heat generating region of the heater 600 by controlling the electric energy supply to the heater 600 in accordance with the width size of the sheet P. With such a structure, the heat can be efficiently supplied to the sheet P. In the fixing device 40 of this embodiment, the sheet P is fed with the center of the sheet P aligned with the center of the fixing device 40, and therefore, the heat generating region extend from the center portion. The electric energy supply to the heater 600 will be described in conjunction with the accompanying drawings.
The voltage source 110 is a circuit for supplying the electric power to the heater 600. In this embodiment, the commercial voltage source (AC voltage source) of approx. 100V in effective value (single phase AC). The voltage source 110 of this embodiment is provided with a voltage source contact 110a and a voltage source contact 110b having different electric potential. The voltage source 110 may be DC voltage source if it has a function of supplying the electric power to the heater 600.
As shown in
Switch SW643 is a switch (relay) provided between the voltage source contact 110a and the electrical contact 641. The switch SW643 connects or disconnects between the voltage source contact 110a and the electrical contact 641 in accordance with the instructions from the control circuit 100. The switch SW653 is a switch provided between the voltage source contact 110b and the electrical contact 651. The switch SW643 connects or disconnects between the voltage source contact 110a and the electrical contact 641 in accordance with the instructions from the control circuit 100. The switch SW653 is a switch provided between the voltage source contact 110b and the electrical contact 651. The switch SW643 connects or disconnects between the voltage source contact 110a and the electrical contact 641 in accordance with the instructions from the control circuit 100.
When the control circuit 100 receives the execution instructions of a job, the control circuit 100 acquires the width size information of the sheet P to be subjected to the fixing process. In accordance with the width size information of the sheet P, a combination of ON/OFF of the switch SW643, switch SW653, switch SW663 is controlled so that the heat generation width of the heat generating element 620 fits the sheet P. At this time, the control circuit 100, the voltage source 110, switch SW643, switch SW653, switch SW663 and the connector 700 functions as an electric energy supplying portion for supplying the electric power to the heater 600.
When the sheet P is a large size sheet (an usable maximum width size), that is, when A3 size sheet is fed in the longitudinal direction or when the A4 size is fed in the landscape fashion, the width of the sheet P is approx. 297 mm. Therefore, the control circuit 100 controls the electric power supply to provide the heat generation width B (
When the size of the sheet P is a small size (narrower than the maximum width), that is, when an A4 size sheet is fed longitudinally, or when an A5 size sheet is fed in the landscape fashion, the width of the sheet P is approx. 210 mm. Therefore, the control circuit 100 provides a heat generation width A (
The disposition or arrangement of the electrical contacts will be described.
In this embodiment, in the one end portion side 610a of the substrate, the electrical contact 641 connecting to the voltage source contact 110a and the electrical contact 661a connecting to the voltage source contact 110b are arranged in the longitudinal direction. In addition, in the other end portion side 610b of the substrate, the electrical contacts 651, 661b connecting to the voltage source contact 110b are arranged in the widthwise direction of the substrate 610. The description will be made in detail in conjunction with the accompanying drawings.
As described hereinbefore, in this embodiment, the electrical contact 641661a are disposed in the one end portion side 610a of the substrate, and the electrical contacts 651, 661b are disposed in other end portion side 610b of the substrate. Each electrical contact has a size of not less than 2.5 mm×2.5 mm (widthwise direction and longitudinal direction of the substrate) so as to receive the electric energy from the terminal assuredly, and the area thereof is preferably lives. In this embodiment, the dimensions of the electrical contact 641 is approx. 7 mm×approx. 3 mm, that of the electrical contact 661a is approx. 5 mm×approx. 3 mm, and that of the electrical contact 661b and 651 are approx. 5 mm×approx. 3 mm.
As described hereinbefore, the portion of the substrate 610 provided with the electrical contacts 641, 651, 661a, 661b is not coated with the insulation coating layer. That is, the electrical contacts are exposed, and therefore, the provision of the gaps between adjacent electrical contacts is desirable to prevent the electrical leakage and/or short circuit. With the increase of the insulation distance, the risk of the leakage and/or short circuit decreases, but on the other hand, the substrate 610 is upsized. Therefore, proper sizes of the gaps between the adjacent electrical contacts are desirable.
In this embodiment, the electrical contact 641 is connected to the voltage source contact 110a, and the electrical contact 661a is connected to the voltage source contact 110b. In other words, the electrical contacts 641 and 661a which are connected to the different (opposite polarities) voltage source contacts are adjacent to each other, with the result of large potential difference therebetween. In order to prevent the short circuit due to creepage discharge, it is preferable to provide a sufficiently large insulation distance between the electrical contact 641 and the electrical contact 661a. Japanese Electrical Appliance and Material Safety Law (annex Table of attached Table) stipulates that in a charging portion or other position of different polarities where a voltage between the lines 50V-150V, the required space distance (creeping distance) is approx. 2.5 mm. In this embodiment, taking mounting tolerances of the connector 700 and/or the thermal expansion of the substrate 610 into account, a gap E is approx. 4.0 mm. When the gap between the electrical contacts 641 and 661a is not constant because of non-parallelism between the electrical contacts 641 and 661a, a minimum value of the gap is deemed as the gap E.
In this embodiment, the electrical contacts 651, 661b are connected to the voltage source contact 110b. That is, the electrical contacts 651 and 661b which are adjacent to each other are connected to the same voltage source contact (same polarity), and therefore no large potential difference is produced therebetween. Therefore, the short circuit due to the creepage discharge hardly occurs between the electrical contacts 651 and 661b (gap F). Therefore, as long as a function insulation for normal operation of the heater 600 is provided, the gap F can be made minimum. However, in consideration of the mounting tolerances of the connector 700 and the thermal expansion of the substrate 610, the gap F in this embodiment is approx. 1.5 mm. When the gap between the electrical contacts 641 and 661a is not constant because of non-parallelism between the electrical contacts 641 and 661a, a minimum value of the gap is deemed as the gap F. Gap E>gap F. The gap between the electrical contact 661a and the electrical contact 651 is less than gap E in the entirety, by which the width required by the electrical contacts can be reduced. Therefore, the width of the electrical contacts in total in the other end portion side 610b of the substrate is approx. 7.5 mm, and therefore, the electrical contacts can be accommodating in the substrate 610 having the width of approx. 8 mm. If the electrical contacts 651 and 661b are connected with different voltage source contacts, the width of the electrical contacts in total is approx. 10 mm. Therefore, the electrical contacts are not provided in the substrate 610 of the width of approx. 8 mm, which necessitates enlargement of the width of the substrate 610.
That is, by arranging the electrical contacts connected to the different voltage source contacts are arranged in the longitudinal direction of the substrate 610, the gap between the electrical contacts can be made sufficient. In addition, by arranging the electrical contacts connected to the same voltage source contact are arranged in the widthwise direction of the substrate, the number of the electrical contacts arranged in the longitudinal direction of the substrate can be reduced. Even though the electrical contacts connected to the same voltage source contacts are arranged in the widthwise direction of the substrate, the increase of the width of the substrate 610 can be suppressed by reducing the gap therebetween.
A heater according to Embodiment 2 of the present invention will be described.
As shown in
In the heater 600 of this embodiment, the opposite electroconductive lines 660a and 660b extend so as to surround the electrical contact 651. With such a structure, the opposite electroconductive lines 660a and 660b are connected to the electrical contact 661. The 661 electrical contact functions as the electrical contacts 661a and 661b of Embodiment 1.
In this embodiment, the dimension of the electrical contact 641 is approx. 7 mm×approx. 3 mm, and the dimension of the electrical contacts 661a and 651 are approx. 3 mm×approx. 3 mm.
In the opposite electroconductive line 650 extends along the longitudinal direction of the substrate 610 toward the one end portion side 610a of the substrate in another end portion side with respect to the widthwise direction substrate 610 beyond the heat generating element 620. The opposite electroconductive line 650 is connected to the electrical contact 651.
In this embodiment, the electrical contact 641 is connected to the voltage source contact 110a, and the electrical contact 661 is connected to the voltage source contact 110b. In other words, the electrical contacts 641 and 661 which are connected to the different voltage source contacts are adjacent to each other, with the result of large potential difference therebetween. In order to prevent the short circuit due to creepage discharge, it is preferable to provide a sufficiently large insulation distance between the electrical contact 641 and the electrical contact 661. The desired space distance (creeping distance) is approx. 2.5 mm. In consideration of the mounting tolerances of the connector 700 and the thermal expansion of the substrate 610, the gap E in this embodiment is approx. 4 mm.
Since the electrical contact 651 is connected to the voltage source contact 110b, a sufficient insulation distance is desirably provided between the electrical contact 641 and the electrical contact 661. Therefore, the gap E between the electrical contacts 641 and 651 is approx. 4.0 mm in this embodiment.
Since the electrical contacts 651 and 661 are contacted to the voltage source contact 110b, no large potential difference is produced therebetween. Therefore, the short circuit due to the creepage discharge hardly occurs between the electrical contacts 651 and 661a (gap F). Therefore, as long as a function insulation for normal operation of the heater 600 is provided, the gap F can be made minimum. However, in consideration of the mounting tolerances of the connector 700 and the thermal expansion of the substrate 610, the gap F in this embodiment is approx. 1.5 mm. Thus, gap E>gap F.
Therefore, the width of the electrical contacts in total in the other end portion side 610b of the substrate is approx. 7.5 mm, and therefore, the electrical contacts can be accommodating in the substrate 610 having the width of approx. 8 mm. If the electrical contacts 651 and 661b are connected with different voltage source contacts, the width of the electrical contacts in total is approx. 10 mm, and therefore, the electrical contacts are not provided in the substrate 610 of the width of approx. 8 mm.
This, according to this embodiment, by arranging the electrical contacts connected to the different voltage source contacts are arranged in the longitudinal direction of the substrate 610, the gap between the electrical contacts can be made sufficient. In addition, by arranging the electrical contacts connected to the same voltage source contact are arranged in the widthwise direction of the substrate, the number of the electrical contacts arranged in the longitudinal direction of the substrate can be reduced. Even though the electrical contacts connected to the same voltage source contacts are arranged in the widthwise direction of the substrate, the increase of the width of the substrate 610 can be suppressed by reducing the gap therebetween. The heaters per se of the foregoing embodiments can be summarized as follows:
A heater comprising:
a gap between said third connecting portion and said fourth connecting portion in the widthwise direction is smaller than a gap between said first connecting portion and said second connecting portion in the longitudinal direction.
The present invention is not restricted to the specific dimensions in the foregoing embodiments. The dimensions may be changed properly by one skilled in the art depending on the situations. The embodiments may be modified in the concept of the present invention.
The electric energy supply to the heat generating element 610 is not limited to that in the longitudinal direction of the substrate. For example, by sandwiching the heat generating element in the widthwise direction by electrodes, the electric current may flow in the widthwise direction of the substrate. With such a structure, the present invention is applicable if there are provided an electrical contact connected to one of the terminals of the voltage source and a plurality of electrical contacts connected to the other terminal of the voltage source. In such a case, the electrical contacts connected to the same polarity are arranged in the widthwise direction of the substrate, and the electrical contacts connected to the opposite polarities are arranged in the longitudinal direction of the substrate, so that the gap between the electrical contacts connected to the same polarity is reduced, by which the increase of the width of the substrate can be suppressed.
The heat generating region of the heater 600 is not limited to the above-described examples which are based on the sheets are supplied with the center thereof aligned with the center of the fixing device. Alternatively, the heat generating regions of the heater 600 may be modified so as to meet the case in which the sheets are supplied with one end thereof aligned with an end of the fixing device. More particularly, the heat generating elements corresponding to the heat generating region A are not heat generating elements 620c-620j but are heat generating elements 620a-620e. With such an arrangement, when the heat generating region is switched from that for a small size sheet to that for a large size sheet, the heat generating region does not expand at both of the opposite end portions, cone. The heat generating region in the one end portion side may be enlarged.
The number of patents of the heat generating region of the heater 600 is not limited to two. For example, three or more patents may be provided.
The forming method of the heat generating element 620 is not limited to those disclosed in Embodiments 1, 2. In Embodiment 1, the common electrode 642 and the opposite electrodes 652, 662 are laminated on the heat generating element 620 extending in the longitudinal direction of the substrate 610. However, the electrodes are formed in the form of an array extending in the longitudinal direction of the substrate 610, and the heat generating elements 620a-620l may be formed between the adjacent electrodes.
The number of the electrical contacts limited to three or four. Five or more electrical contacts may be provided if the electrical contacts connected to the same voltage source contact are arranged in the widthwise direction of the substrate. For example, in Embodiment 1, in one end portion side 610a of the substrate, an electrical contact different from the electrical contacts 641, 661a may be provided, and the other end portion side 610b of the substrate, an electrical contact different from the electrical contacts 661b, and 651 may be provided.
The electrical contact connected to the voltage source contact 110a is not limited to the electrical contact 641. For example, in the one end portion side 610a of the substrate, an electrical contact which is different from the electrical contact 641 and which is connected to the voltage source contact 110a may be provided. Furthermore, this electrical contact may be provided adjacent to the electrical contact 641 with a gap therebetween in the widthwise direction of the substrate 610.
The belt 603 is not limited to that supported by the heater 600 at the inner surface thereof and driven by the roller 70. For example, so-called belt unit type in which the belt is extended around a plurality of rollers and is driven by one of the rollers. However, the structures of Embodiments 1-4 are preferable from the standpoint of low thermal capacity.
The member cooperative with the belt 603 to form of the nip N is not limited to the roller member such as a roller 70. For example, it may be a so-called pressing belt unit including a belt extended around a plurality of rollers.
The image forming apparatus which has been a printer 1 is not limited to that capable of forming a full-color, but it may be a monochromatic image forming apparatus. The image forming apparatus may be a copying machine, a facsimile machine, a multifunction machine having the function of them, or the like, for example.
The image heating apparatus is not limited to the apparatus for fixing a toner image on a sheet P. It may be a device for fixing a semi-fixed toner image into a completely fixed image, or a device for heating an already fixed image. Therefore, the fixing device 40 as the image heating apparatus may be a surface heating apparatus for adjusting a glossiness and/or surface property of the image, for example.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2014-108593 filed on May 26, 2014, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-108593 | May 2014 | JP | national |
