Patent Application
20160029435
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 proposed (Japanese Laid-open Patent Application 2012-37613) in these days 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 fixing device in which a heat generating region width of the heat generating element (heater) is controlled in accordance with a width size of the sheet. The heater used in this fixing device is provided with a heat generate resistor layer on which a plurality of resistors are arranged in a longitudinal direction of a substrate, and each of the resistors is provided on the substrate with an electroconductive line layer including a plurality of electroconductive lines for supplying electric power (energy). This electroconductive line layer has a plurality of electroconductive line patterns different in the number of the resistors, and is constituted so as to be capable of selectively supplying the electric power to a specific resistor of the plurality of resistors. Further, this fixing device supplies the electric power to only a resistor, of the plurality of resistors, intended to be heated, so that a width size of a heat generating region of the heater is changed correspondingly to the plurality of resistors.
The heater disclosed in Japanese Laid-Open Patent Application 2012-37613 is susceptible to further improvement with respect to a structure thereof. In the case where, the electric power is supplied to such a heater, a part of the supplied electric power is consumed by an electrical resistance of the electroconductive line. Particularly, a larger amount of a current flows into the electroconductive line connected with a large number of a plurality of heat generation resistors layers, so that an amount of electric power consumption is larger. When the electric power is consumed by the electroconductive line, a heat generation efficiency at the heat generation resistor layer lowers, and therefore such a heater is required that the electric power consumption is suppressed.
Accordingly, it is an object of the present invention to provide a heater capable of suppressing electric power consumption.
It is another object of the present invention to provide an image heating apparatus capable of suppressing electric power consumption in the heater.
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 the heater is contactable to the belt to heat the belt, the heater comprising: a substrate; a first electrical contact provided on the substrate and electrically connectable with the first terminal; a plurality of second electrical contacts provided on the substrate and electrically connectable with the second terminal; a plurality of electrode portions including first electrode portions electrically connected with the first electrical contact and second electrode portions electrically connected with the second electrical contacts, the first electrode portions and the second electrode portions being arranged alternately with predetermined gaps in a longitudinal direction of the substrate; a plurality of heat generating portions provided between adjacent ones of the electrode portions so as to electrically connect between adjacent electrode portions, the heat generating portions being capable of generating heat by electric power supply between adjacent electrode portions; a first electroconductive line portion configured to electrically connect the first electrical contact and the first electrode portions; and a second electroconductive line portion configured to electrically connect one of the plurality of second electrical contacts and a part of the second electrode portions; wherein a cross-sectional area of a portion, of the first electroconductive line portion, into which all of currents flowing through the first electrode portions merge when the currents flow from the first electrode portions toward the first electrical contact is larger than a cross-sectional area of a portion, of the second electroconductive line portion, into which all of currents flowing through the part of the second electrode portions merge when the currents flow from the part of the second electrode portions toward the one of second electrical contacts.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
In
In
In
In
In
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 or placed on a multi-feeding tray 25 is picked up by a feeding mechanism (unshown) and fed to a pair of registration rollers 23. 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 for correcting 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 the 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 up-down 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 of the heater 600 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 to the belt 603. 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 30 mm in the outer diameter, 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 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
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 156.8 N (16 kgf) at one end portion side and 313.6 N (32 kgf) in total.
As shown in
As shown in
The roller 70 of this embodiment includes a core metal 71 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 25 mm in outer diameter, and 330 mm in length.
A themistor 630 is a temperature sensor provided on a back side of the heater 600 (opposite side from the sliding surface side. The themistor 630 is bonded to the heater 600 in the state that it is insulated from the heat generating element 620. The themistor 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 themistor 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 themistor 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 (180 degree C., for example).
As shown in
The motor M is a driving means for driving the roller 70 through the gear G. The control circuit 100 is electrically connected with the motor M to control the electric power supply to the motor M. When the electric energy is supplied by the control of the control circuit 100, the motor M starts to rotate the gear G.
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 (200 [mm/sec], for example).
The structure of the heater 600 used in the fixing device 40 will be described in detail. In
The heater 600 of this embodiment is a heater using the heat generating type shown in (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 (a) of
For example, when the heat generating element material is applied on the substrate along the longitudinal direction by screen printing or like, a thickness non-uniformity of about 5% may result in the widthwise direction. This is because a heat generating element material painting non-uniformity occurs due to a small pressure difference in the widthwise direction by a painting blade. For this reason, it is preferable that the heat generating elements and the electrodes are arranged so that the electric currents flow in the longitudinal direction.
In the case that the electric power is supplied individually 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 between the heat generating elements. 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 a space between the electrodes can be eliminated.
In this embodiment, a common electroconductive line 640 shown in
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 element 620 (620a-620l) is a resistor capable of generating joule heat by electric power supply (energization). 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 other end portion side 610c (
On the heat generating element 620, seven 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 the electrodes 642a-642g along the longitudinal direction. The lengths measured in the longitudinal direction of the substrate 610 of each section are 53.3 mm. On central portions of the respective sections of the heat generating element 620, one of the six 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 (plurality of heat generating portions, plurality of resistance 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 26.7 mm. Resistance values of the sub-section of the heat generating element 620 with respect to the longitudinal direction are 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 resistances 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 local temperature lowering at the longitudinal end portions of the heat generating element 620.
The electrodes 642 (642a-642g) are a part of the above-described electroconductor pattern. The 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, of the electroconductive pattern formed on the heater 600, only a region contacting the heat generating element 620 is called the electrode. In this embodiment, the electrode 642 is laminated on the heat generating element 620. The 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 electrode 642 is connected to one contact 110a of the voltage source 110 through the electroconductive line 640 which will be described hereinafter.
The electrodes 652, 662 are a part of the above-described electroconductor pattern. The electrodes 652, 662 extend in the widthwise direction of the substrate 610 perpendicular to the longitudinal direction of the heat generating element 620. The electrodes 652, 662 are the other electrodes of the electrodes connected with the heat generating element 620 other than the above-described 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 electrode 642 and the electrodes 662, 652 are alternately arranged along the longitudinal direction of the heat generating element. The 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 electrode 642 and the opposite electrode 652, 662 function as electrode portions 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 as a first feeder is a part of the above-described electroconductor pattern. The 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 electroconductive line 640 is connected with the electrodes 642 (642a-642g) which is in turn connected with the heat generating element 620 (620a-620l). In this embodiment, the electroconductive patterns connecting the electrodes with the electrical contacts are called the electroconductive lines. That is, also a region extending in the widthwise direction of the substrate 610 is a part of the electroconductive line. The 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 400 μm is provided between the electroconductive line 640 and each electrode.
The opposite electroconductive line 650 as a second feeder is a part of the above-described electroconductor pattern. The electroconductive line 650 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 electroconductive line 650 is connected with the electrodes 652 (652a-652d) which are in turn connected with heat generating elements 620 (620c-620j). 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 electroconductive line 660a as a third feeder (second feeder) 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 electroconductive line 660a is connected with the electrode 662a which is in turn connected with the heat generating element 620 (620a, 620b). The electroconductive line 660a is connected to the electrical contact 661a which will be described hereinafter. The electroconductive line 660b as a fourth feeder (third feeder) 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 electroconductive line 660b is connected with the opposite electrode 662b which is in turn connected with the heat generating element 620. The electroconductive line 660b is connected to the electrical contact 661b which will be described hereinafter. In this embodiment, in order to assure the insulation of the insulation coating layer 680, a gap of 400 μm is provided between the electroconductive line 660a and the common electrode 642. In addition, between the electroconductive lines 660a and 650 and between the electroconductive lines 660b and 650, gaps of 100 μm are provided.
The common electroconductive line 640 and the opposite electroconductive lines 650, 660 will be described hereinafter in detail.
The electrical contacts 641, 651, 661 (661a, 661b) as portions-to-be-energized are a part of the above-described electroconductor pattern. Each of the electrical contacts 641, 651, 661 preferably has an area of not less than 2.5 mm×2.5 mm in order to assure the reception of the electric power supply from the connector 700 as an energizing portion (electric power supplying portion) which will be described hereinafter. In this embodiment, the electrical contacts 641, 651, 661 has a length 3 mm measured in the longitudinal direction of the substrate 610 and a width of not less than 2.5 mm measured in the widthwise direction of the substrate 610. The electrical contacts 641, 651, 661a, 661b are disposed in the one end portion side 610a of the substrate beyond the heat generating element 620 with gaps of 4 mm in the longitudinal direction of the substrate 610. As shown in
When voltage is applied between the electrical contact 641 and the electrical contact 651 via the electroconductive lines 640 and 650 through the connection between the heater 600 and the connector 700, a potential difference is produced between the electrode 642 (642b-642f) and the 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.
When voltage is applied between the electrical contact 641 and the electrical contact 661a via the electroconductive lines 640 and 660a through the connection between the heater 600 and the connector 700, a potential difference is produced between the electrodes 642a, 642b and the 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 opposite to each other.
When voltage is applied between the electrical contact 641 and the electrical contact 661b through the connection between the heater 600 and the connector 700, a potential difference is produced between the electrodes 642f, 642g and the electrode 662b through the electroconductive line 640 and the 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 opposite to each other.
In this manner, a part of the heat generating elements 620 can be selectively energized.
The connector 700 used with the fixing device 40 will be described in detail. The connector 700 of this embodiment is electrically connected with the heater 600 by mounting to the heater 600. The connector 700 comprises a contact terminal 710 electrically connectable with the electrical contact 641, and a contact terminal 730 electrically connectable with the electrical contact 651. The connector 700 also comprises a contact terminal 720a electrically connectable with the electrical contact 661a, and a contact terminal 720b electrically connectable with the electrical contact 661b. Further, the connector 700 comprises a housing 750 for integrally holding the contact terminals 710, 720a, 720b, 730. The contact terminal 710 is connected with a switch SW643 by a cable (unshown). The contact terminal 720a is connected with a switch SW663 by a cable (unshown). The contact terminal 720b is connected with the switch SW663 by a cable (unshown). The contact terminal 730 is connected with a switch SW653 by a cable (unshown). The connector 700 sandwiches a region of the heater 600 extending out of the belt 603 so as not to contact with the belt 603, by which the contact terminals an electrically connected with the electrical contacts, respectively. Further, as shown in
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 100V in effective value (single phase AC) is used. 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 SW653 connects or disconnects between the voltage source contact 110b and the electrical contact 651 in accordance with the instructions from the control circuit 100. The switch SW663 is a switch provided between the voltage source contact 110b and the electrical contact 661 (661a, 661b). The switch SW663 connects or disconnects between the voltage source contact 110b and the electrical contact 661 (661a, 661b) 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 power (energy) supplying means (electric power supplying portion) the electric power to the heater 600.
When the sheet P is a large size sheet (an introducible 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 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 size by a predetermined 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 210 mm. Therefore, the control circuit 100 provides a heat generation width A (
Widths of the common electroconductive line 640 and the opposite electroconductive lines 650, 660 (hereinafter, the common electroconductive line 640 and the opposite electroconductive lines 650, 660 are collectively referred to as a feeder (electric power feeder) in the case where these electroconductive lines are not required to be distinguished) will be described in detail.
As in this embodiment, in the heater 600 changing the heat generating region depending on the width size of the sheet P, heat generation of the heater 600 in the region where the sheet P does not pass is suppressed. For that reason, the heater 600 has such a feature that an amount of heat generation unnecessary for the fixing process is small and thus the heater 600 is excellent in energy (electric power) efficiency. However, controllable heat generation in such a heater 600 is only heat generation of the heat generating element 620. For that reason, in the case where the heat generation is caused at a portion other than the heat generating element 620, there is a liability that the heat generation constitutes the heat generation unnecessary for the fixing process.
As the unnecessary heat generation, it is possible to cite heat generation caused at the feeder. The feeders such as the electroconductive line 640 and the electroconductive lines 650, 660 have a resistance to no small extent, and therefore when the current flows into the feeder, the feeder generates heat to no small extent. Further, in the case where the feeder generates heat, the heat generation thereof constitutes heat generation which does not readily contribute to the fixing, and therefore the electric power is uselessly consumed correspondingly. The heat generation which does not readily contribute to the fixing is, e.g., heat generation in a non-sheet P-passing region at longitudinal end portions of the heater 600 or heat generation in a region (region apart from the nip N) outside a region of 4 mm including the heat generating element 620 as a center with respect to the widthwise direction of the substrate 610. Accordingly, in order to efficiently use the electric power consumed by the heater 600 for the fixing process, it is desirable that the electric power consumption at the feeder is suppressed.
As a method of suppressing the electric power consumption of the feeder, it is possible to cite a reduction of the feeder resistance. A resistance r of the lead wire can be expressed by the following formula.
Resistance r=ρ×L/(w×t)
ρ: specific resistance, L: line length, w: line width, t: line thickness
Here, when the electric power is supplied to each of two lead wires different in line width w and prepared under the same condition except for the line width w, a relationship as shown in
For that reason, it is desirable that the heater 600 is lowered in resistance by thickening the feeder width and thus the electric power consumption of the feeder is suppressed. However, when the width of all the feeders is simply thicken, a space for disposing the thick feeder is required on the substrate 610, and therefore there is a liability that the size of the substrate 610 is increased. Particularly, the influence of a change in width of the feeder on a widthwise size of the substrate 610 short in original dimension is conspicuous.
Accordingly, the feeder may desirably be provided in a proper thickness. For that reason, the feeder may desirably be different in thickness depending on a magnitude of a current flowing through the feeder. Specifically, with respect to the feeder, the lead wire through which a large current flows may desirably be provided in a large width, and the lead wire through which a small current flows may desirably be provided in a small width.
The feeder of the heater 600 is configured so that a total of currents flowing through the electroconductive lines 650, 660a, 660b concentratedly flows through a part of the lead wire for the electroconductive line 640. For that reason, the part of the lead wire for the electroconductive line 640 is liable to constitutes the electric power compared with another portion of the feeder. For that reason, the part of the lead wire through which the current concentratedly flows may desirably has a small electrical resistance. In this embodiment, the width of the part of the lead wire for the electroconductive line 640 in increased to lower the electroconductive line resistance, so that the electric power consumption at this portion is suppressed. On the other hand, with respect to the electroconductive lines 650, 660, even at the lead wire where the current most concentrates, the amount of the current is smaller than that of the current flowing through the part of the lead wire for the electroconductive line 640 described above. For that reason, in this embodiment, the width of the lead wire, extending along the longitudinal direction of the substrate, for the electroconductive lines 650, 660 is made smaller (thinner) than the width of the part of the lead wire for the electroconductive line 640. Accordingly, in this embodiment, the lead wire for the electroconductive lines 650, 660 arranged substantially in parallel can be disposed in a narrow space with respect to the widthwise direction of the substrate, so that an enlargement in size of the substrate 610 with respect to the widthwise direction can be suppressed. An adjusting method of the electroconductive line resistance is not limited thereto. For example, the line thickness of the electroconductive lines 640, 650, 660 may also be increased to about 20 μm-30 μm. Adjustment of the electroconductive line thickness can be realized performing repetitive coating in screen printing. However, from the viewpoint that the number of steps of the screen printing can be reduced, it is desirable that the constitution in this embodiment is employed. In the following description, a thick line width of the electroconductive line means that a cross-sectional area of the electroconductive line is large, and a narrow (thin) line width of the electrode means that a cross-sectional area of the electrode is small. Description will be made in detail with reference to the drawings.
A structure of the feeder of the heart 600 in this embodiment will be described. In
The resistance of the lead wire, for the electroconductive line 660a, extending from the electrical contact 661a to connect with the electrode 662a is r8. The resistance of the lead wire, for the electroconductive line 650, extending from the electrode 651 to a point branching to the electrode 652a is r9. Further, in the electroconductive line 650, the resistance of the lead wire between the electrode 652a and the electrode 652b is r10, the resistance of the lead wire between the electrode 652b and the electrode 652c is r11, and the resistance of the lead wire between the electrode 652c and the electrode 652d is r12.
The resistance of the lead wire, for the electroconductive line 660b, extending from the electrical contact 661b to connect with the electrode 662b is r13.
A relationship of currents flowing through the feeders will be described with reference to
In such a heater 600, in the case where the current flows from the heat generating element 620 toward the electrical contact 641, the current i1 into which the currents from the heat generating elements 620a-620l merge flows through the lead wire, for the electroconductive line 640, having the resistance r1. In this case, the magnitudes of the currents flowing through the respective lead wires for the electroconductive line 640 satisfy the relationship of: i1>i2>i3>i4>i5>i6>i7. The largest current flows through the lead wire having the resistance r1.
Further, in such a heater 600, in the case where the current flows from the heat generating element 620 toward the electrical contact 651, the current i9 into which the currents from the heat generating elements 620c-620i merge flows through the lead wire, for the electroconductive line 650, having the resistance r9. In this case, the magnitudes of the currents flowing through the respective lead wires for the electroconductive line 650 satisfy the relationship of: i9>i10>i11>i12.
Further, in such a heater 600, in the case where the current flows from the heat generating element 620 toward the electrical contact 661a, the current i8 into which the currents from the heat generating elements 620a, 620b merge flows through the lead wire, for the electroconductive line 660a, having the resistance r8.
Further, in such a heater 600, in the case where the current flows from the heat generating element 620 toward the electrical contact 661b, the current i13 into which the currents from the heat generating elements 620k, 620l merge flows through the lead wire, for the electroconductive line 660b, having the resistance r13.
Further, from a relationship of: i1=i8+i9+i13, the current i1 is larger than the currents i8, i9 and i13. For that reason, the lead wire having the resistance r1 may desirably be made thicker in width than the lead wire having the resistance r8, the lead wire having the resistance r9 and the lead wire having the resistance r13. In other words, the lead wire having the resistance r8, the lead wire having the resistance r9 and the lead wire having the resistance r13 may desirably be made thinner in width than the lead wire having the resistance r1. That is, when the current flowing from the heat generating elements 620 toward the electrical contact flows through the electroconductive line 650, the widthwise width of the lead wire, for the electroconductive line 650, through which the current, into which the currents from the heat generating elements 620c-620j merge, flows is as follows. That is, this width is narrower than the widthwise width of the lead wire, for the electroconductive line 640, through which the current, into which the currents from the heat generating elements 620 merge, flows when the current flowing from the heat generating elements 620 toward the electrical contact flow through the electroconductive line 640.
Therefore, in this embodiment, the width of the lead wire, for the electroconductive line 640, extending along the longitudinal direction of the substrate was set at 2.0 mm. The width of the lead wire extending from this lead wire and branching to the electrode 642 along the widthwise direction of the substrate was set at 0.4 mm. Further, in this embodiment, the width of the lead wire, for the electroconductive lines 650, 660, extending in the longitudinal direction of the substrate was set at 0.7 mm. The width of the lead wire extending from this lead wire and branching to the electrode 642 along the widthwise direction of the substrate was set at 0.4 mm. These lead wires may desirably have a uniform line width to the possible extent in the entire region in order to suppress a variation in resistance. However, these lead wires can locally cause an error of less than 0.1 m in line width depending on manufacturing accuracy. However, when the line widths in the entire region of the lead wires is averaged, the average approaches a desired line width. For that reason, the lead wires can obtain desired resistances. The feeders were 0.00002Ω·mm in resistivity ρ and 10 μm in height h. When resistance values of the respective lead wires for the feeders are derived, the following result is obtained. That is, r1 is 0.47Ω, r2 to r7 are 0.53Ω, r8 is 0.173Ω, r9 is 0.227Ω, r10 to r12 are 0.153Ω, and r13 is 0.933 Ω.
The resistance R of the respective heat generating elements 620 is 120Ω, and a combined resistance of the heat generating elements 520a-620l is 10Ω. Accordingly, in the case where a voltage of 100 V is applied to the heater 600, the electric power consumption of the heater 600 is ideally 100 W.
A result of the electric power supply of 100 V to the heater 600 including the feeders having the above-described constitutions so that the heat generating region is the heat generation width B is shown in Table 1. Table 1 shows the resistance, the current and the electric power consumption of each of the lead wires for the feeders. According to Table 1, the current i1 flowing through the lead wire having the resistance r1 is 9.67 A which is the largest value of values of the currents flowing through the feeders. However, the electroconductive line 640 in this embodiment is provided thickly so as to have the thick width of 2.0 mm, and therefore the resistance r1 is a low value of 0.047Ω. For that reason, the electric power consumption at the lead wire having the resistance r1 is suppressed to a low value of 4.39 W. This value of the electric power consumption is less than 1% (10 W) of 100 W which is the ideal electric power consumption of the heater 600, and therefore it can be said that the value is a sufficiently low value. In this embodiment, the width of each of the electroconductive lines 650, 660 is determined so that the electric power consumption of each of the lead wires for the electroconductive lines 650, 660 is less than 10 W similarly as in the case of the lead wire having the resistance r1. That is, the largest current of the respective lead wires for the electroconductive lines 650, 660 is i9 of 6.41 A, but the electric power consumption of the lead wire having the resistance r9 is 9.3 W which is less than 10 W.
Therefore, in this embodiment, the width of the lead wire smaller in flowing current than the lead wire having the resistance r1 is made thinner than the width of the lead wire having the resistance r1. Specifically, the electroconductive line 650, the electroconductive line 660a and the electroconductive line 660b are made thinner (narrower) than the lead wire having the resistance r1. Here, description that the electroconductive line 650 is thinner than the lead wire having the resistance r1 is made above, but this means that the width (length with respect to the widthwise direction of the substrate) of the lead wire, for the electroconductive line 650, along the longitudinal direction of the substrate is uniformly thin compared with the width of the lead wire having the resistance r1. That is, the width of the lead wire, for the electroconductive line 650, along the longitudinal direction of the substrate is less than 2.0 mm. Accordingly, the width of the lead wire having the resistance r8 is less than 2.0 mm in the entire region with respect to the longitudinal direction of the lead wire having the resistance r8.
Further, description that the electroconductive line 660a is thinner than the lead wire having the resistance r1 is made above, but this means that the width (length with respect to the widthwise direction of the substrate) of the lead wire, for the electroconductive line 660a, extending along the longitudinal direction of the substrate is uniformly thin compared with the width of the lead wire having the resistance r1. That is, the width of the lead wire, for the electroconductive line 660a, along the longitudinal direction of the substrate is less than 2.0 mm. Accordingly, the width of the lead wire having the resistance r9 is less than 2.0 mm in the entire region with respect to the longitudinal direction of the lead wire having the resistance r9.
Further, description that the electroconductive line 660b is thinner than the lead wire having the resistance r1 is made above, but this means that the width (length with respect to the widthwise direction of the substrate) of the lead wire, for the electroconductive line 660b, extending along the longitudinal direction of the substrate is uniformly thin compared with the width of the lead wire having the resistance r1. That is, the width of the lead wire, for the electroconductive line 660b, along the longitudinal direction of the substrate is less than 2.0 mm. Accordingly, the width of the lead wire having the resistance r13 is less than 2.0 mm in the entire region with respect to the longitudinal direction of the lead wire having the resistance r13.
By such a constitution, in this embodiment, an arrangement space for the feeders arranged in the widthwise direction of the substrate 610 can be saved. For that reason, enlargement of the substrate 610 in the widthwise direction can be suppressed.
As described above, the heater 600 in this embodiment is 0.7 mm in width of the electroconductive lines 650,660 and 2.0 mm in width of the electroconductive line 640 with respect to the widthwise direction of the substrate. Accordingly, the sum of the line widths of the electroconductive line 640 and the electroconductive lines 650, 660a, 660b is 4.1 mm. In the case where the feeders are arranged in the widthwise direction of the substrate 610, in consideration of the width of the heat generating element 620 and the interval between the electroconductive lines, the widthwise length of the substrate 610 is 10 mm. Further, the sum of values of the electric power consumed by the heater 600 at the electroconductive line 640 is 14.2 W, and the sum of values of the electric power consumed by the heater 600 at the electroconductive lines 650, 660 is 17.6 W. That is, the electric power consumed by the heater 600 at the feeders is 31.8 W.
In order to verify an effect of this embodiment, a comparison with Comparison Examples is made. Comparison Example 1 is an example in the case where the width of the feeders in the heater 600 is uniformly 0.7 mm (the same width as that in this embodiment). Comparison Example 2 is an example in the case where the width of the feeders in the heater 600 is uniformly 2.0 mm (the same width as that in this embodiment). Comparison Example 3 is example in the case where the width of the feeders in the heater 600 is uniformly 1.025 mm (the sum of the respective line widths is 4.1 mm similarly as in this embodiment).
In the case where the voltage of 100 V is applied to the heater 600 in Comparison Example 1, the sum of the values of the electric power consumed by the electroconductive line 640 is 41 W, and the sum of the values of the electric power consumed by the electroconductive lines 650, 660 is 17.6 W. Accordingly, in this embodiment, as shown in
Further, in the case where the voltage of 100 V is applied to the heater 600 in Comparison Example 2, the electric power consumption at the electroconductive line 640 can be reduced similarly as in Embodiment 1. However, the sum of the line widths of the electroconductive line 640 and the electroconductive lines 650, 660a, 660b in Comparison Example 2 is 8 mm. For that reason, in Comparison Example 2, the length of the substrate 610 with respect to the widthwise direction is 13.9 mm which is larger than 10 mm in Embodiment 1. That is, in this embodiment, compared with Comparison Example 2, the size of the substrate 610 with respect to the widthwise direction can be made small.
Further, in Comparison Example 3, the sum of the respective line widths of the feeders is 4.1 mm similarly as in Embodiment 1. Further, the widthwise length of the substrate 610 is 10 mm similarly as in Embodiment 1. However, between Comparison Example 3 and Embodiment 1, in the case where the voltage is applied to the heater 600, a difference in electric power consumed at the feeders generates. In the case where the voltage of 100 V is applied to the heater 600 in Comparison Example 3, the sum of the values of the electric power consumed by the heater 600 at the electroconductive line 640 is 27 W, and the sum of the values of the electric power consumed at the electroconductive lines 650, 660 is 12 W. That is, the electric power consumed by the heater 600 at the feeders in Comparison Example 3 is 39 W. Accordingly, in this embodiment, compared with Comparison Example 3, the electric power consumption at the electroconductive line can be reduced. That is, according to this embodiment, it is possible to suppress the electric power consumption at the feeders while suppressing enlargement in size of the substrate 610 with respect to the widthwise direction.
As described above, in this embodiment, in the heater 600, the width of the lead wire having the resistance r1 is made thicker than the widths of the lead wire having the resistance r8, the lead wire having the resistance r9 and the lead wire having the resistance r13. For that reason, it is possible to suppress the electric power consumption (heat generation) at the lead wire having the resistance r1. That is, in this embodiment, by preferentially lowering the resistance of the lead wire through which a large current flows, the electric power consumption at the feeders can be reduced.
The lead wire having the resistance r1 is positioned in the region, of the heater 600, where the sheet P does not pass. For that reason, the heat generated at the lead wire having the resistance r1 is liable to become heat unnecessary for the fixing process. That is, by suppressing the heat generation of the lead wire having the resistance r1, it is possible to reduce a degree of the heat generation unnecessary for the fixing process of the heater 600. Therefore, according to this embodiment, the heat generation of the heater 600 required for the fixing process can be made with high electric power efficiency.
Further, in this embodiment, the width of the electroconductive lines 650, 660 is made thinner than the width of the electroconductive line 640. For that reason, the electroconductive lines 650, 660 can be disposed in a narrow space of the substrate 610 with respect to the widthwise direction. For that reason, it is possible to suppress upsizing of the substrate 610 with respect to the widthwise direction. That is, according to this embodiment, by thinning the width of the lead wire through which a small current flows, it is possible to suppress the upsizing of the substrate 610 with respect to the widthwise direction. Further, an increase in cost of the heater 600 can be suppressed.
In the above description, the electroconductive line 640 of 2.0 mm in width of the lead wire along the longitudinal direction of the substrate is described as an example, but a shape of the electroconductive line 640 is not limited thereto. For example, as shown in (a) of
A heater according to Embodiment 2 of the present invention will be described.
In Embodiment 1, from a difference in magnitude between the current flowing through the electroconductive line 640 and the current flowing through the electroconductive lines 650, 660, the line width of the electroconductive lines 650, 660 was uniformly made thin compared with the line width of the electroconductive line 640. However, the magnitude of the flowing current is also different between the electroconductive lines 650 and 660. As shown in Table 1 in Embodiment 1, the largest current flowing through the electroconductive line 650 is 6.71 A. The current flowing through the electroconductive line 660a is 1.65 A. The current flowing through the electroconductive line 660b is 1.6 A. This difference in magnitude of the current is influenced by the number of the heat generating elements 620 with which the electroconductive lines 650, 660 are connected. The electroconductive line 650 is connected with 8 heat generating elements 620c-620j as shown in
Further, the electroconductive line 660a is connected with 2 heat generating elements 620a, 620b. For that reason, in the case where the current flows from the heat generating elements 620 toward the electrical contact 661a, the current i8 into which the currents from the heat generating elements 620a, 620b merge flows through the lead wire, for the electroconductive line 660a, having the resistance r8. The heat generating elements 620a, 620b are connected with the electroconductive line 660a in a parallel state, and therefore a combined resistance thereof is 60 Ω.
Further, the electroconductive line 660b is connected with 2 heat generating elements 620k, 620l. For that reason, in the case where the current flows from the heat generating elements 620 toward the electrical contact 661b, the current i13 into which the currents from the heat generating elements 620k, 620l merge flows through the lead wire, for the electroconductive line 660b, having the resistance r13. The heat generating elements 620, 620l are connected with the electroconductive line 660b in a parallel state, and therefore a combined resistance thereof is 60 Ω.
For that reason, at the electroconductive lines 650, 660a, 660b connected in parallel, the magnitude of the current flowing through the electroconductive line 650 is largest. That is, the electroconductive line 650 most readily generate heat. For that reason, in order to lower the resistance of the electroconductive line 650, it is desirable that the line width of the electroconductive line is made thick.
Therefore, in this embodiment, the width of the lead wire, for the electroconductive line 640, extending in the longitudinal direction of the substrate was set at 2.0 mm as shown in
When resistance values of the respective sections for the feeders are derived, the following result is obtained. That is, r1 is 0.47Ω, r2 to r7 are 0.53Ω, r8 is 0.173Ω, r9 is 0.106Ω, r10 to r12 are 0.0712Ω, and r13 is 0.933 Ω.
A result of the electric power supply of 100 V to the heater 600 including the feeders having the above-described constitutions so that the heat generating region is the heat generation width B is shown in Table 2. Table 2 shows the resistance, the current and the electric power consumption of each of the lead wires for the feeders. According to Table 2, the current i9 flowing through the lead wire having the resistance r9 is 6.41 A which is the largest value of values of the currents flowing through the electroconductive lines 650, 660. However, the electroconductive line 650 in this embodiment is provided thickly so as to have the thick width of 1.5 mm, and therefore the resistance r9 is a low value of 0.106Ω. For that reason, the electric power consumption at the lead wire having the resistance r9 is suppressed to a low value of 4.3 W. This value of the electric power consumption is less than 1% (10 W) of 100 W which is the ideal electric power consumption of the heater 600, and therefore it can be said that the value is a sufficiently low value. In this embodiment, the width of each of the electroconductive line 660 is determined so that the electric power consumption of each of the lead wires for the electroconductive lines 660a, 660b is less than 10 W similarly as in the case of the lead wire having the resistance r9. That is, the largest current of the respective lead wires for the electroconductive lines 650, 660 is i8 of 1.65 A, but the electric power consumption of the lead wire having the resistance r8 is 0.5 W which is less than 10 W.
Therefore, in this embodiment, the width of the feeder smaller in flowing current than the lead wire having the resistance r9 is made thinner than the width of the lead wire having the resistance r9. Specifically, the electroconductive line 660a and the electroconductive line 660b are made thinner (narrower), in widthwise width of the substrate of the lead wire extending along the longitudinal direction of the substrate, than the lead wire having the resistance r1. Further, description that the electroconductive line 660a is thinner than the lead wire having the resistance r9 is made above, but this means that the width (length with respect to the widthwise direction of the substrate) of the lead wire, for the electroconductive line 660a, extending along the longitudinal direction of the substrate is uniformly thin compared with the width of the lead wire having the resistance r9. That is, the width of the lead wire, for the electroconductive line 660a, along the longitudinal direction of the substrate is less than 1.5 mm. Accordingly, also the width of the lead wire having the resistance r9 is less than 1.5 mm in the entire region with respect to the longitudinal direction of the lead wire having the resistance r9.
Further, description that the electroconductive line 660b is thinner than the lead wire having the resistance r9 is made above, but this means that the width (length with respect to the widthwise direction of the substrate) of the lead wire, for the electroconductive line 660b, extending along the longitudinal direction of the substrate is uniformly thin compared with the width of the lead wire having the resistance r9. That is, the width of the lead wire, for the electroconductive line 660b, along the longitudinal direction of the substrate is less than 1.5 mm. Accordingly, also the width of the lead wire having the resistance r13 is less than 1.5 mm in the entire region with respect to the longitudinal direction of the lead wire having the resistance r13.
By such a constitution, in this embodiment, a space in which the feeders are arranged in parallel in the widthwise direction of the substrate 610 can be saved. For that reason, enlargement in size of the substrate 610 in the widthwise direction can be suppressed.
As described above, the heater 600 in this embodiment is 1.5 mm in width of the electroconductive line 650, 0.7 mm in width of the electroconductive line 660 and 2.0 mm in width of the electroconductive line 640. For that reason, the sum of the line widths with respect to the widthwise direction of the substrate is 4.9 mm. In the case where the feeders are arranged in the widthwise direction of the substrate 610, in consideration of the width of the heat generating element 620 and the interval between the electroconductive lines, the widthwise length of the substrate 610 is 10.8 mm. Further, the sum of values of the electric power consumed by the heater 600 at the electroconductive line 640 is 14.1 W, and the sum of values of the electric power consumed by the heater 600 at the electroconductive lines 650, 660 is 7.1 W. That is, the electric power consumed by the heater 600 at the feeders is 21.2 W.
In order to verify an effect of this embodiment, a comparison with Comparison Examples is made. Comparison Example 4 is an example in the case where the width of the feeders in the heater 600 is uniformly 1.225 mm (the sum of the respective line widths is 4.9 mm similarly as in this embodiment).
In Comparison Example 4, the sum of the respective line widths of the feeders is 4.9 mm similarly as in Embodiment 2. Further, the widthwise length of the substrate 610 is 10.8 mm similarly as in Embodiment 2. However, between Comparison Example 4 and Embodiment 2, in the case where the voltage is applied to the heater 600, a difference in electric power consumed at the feeders generates. In the case where the voltage of 100 V is applied to the heater 600 in Comparison Example 4, the sum of the values of the electric power consumed by the heater 600 at the electroconductive line 640 is 27 W, and the sum of the values of the electric power consumed at the electroconductive lines 650, 660 is 12 W. That is, the electric power consumed by the heater 600 at the feeders in Comparison Example 4 is 39 W. Accordingly, in this embodiment, compared with Comparison Example 4, the electric power consumption at the electroconductive line can be reduced. That is, according to this embodiment, it is possible to suppress the electric power consumption at the feeders while suppressing enlargement in size of the substrate 610 with respect to the widthwise direction.
Further, in Embodiment 2, similarly as in Embodiment 1, the electric power consumption of the heater 600 is smaller than that in Comparison Example 2 and the widthwise length of the substrate is shorter than that in Comparison Example 1. Incidentally, the electric power consumed at the electroconductive lines 650, 660 in Embodiment 2 is sufficiently smaller than that in Comparison Example 1. As shown in
As described above, in this embodiment, in the heater 600, the width of the lead wire having the resistance r1 is made thicker than the widths of the lead wire having the resistance r8, the lead wire having the resistance r9 and the lead wire having the resistance r13. For that reason, it is possible to suppress the electric power consumption (heat generation) at the lead wire having the resistance r1. That is, in this embodiment, by preferentially lowering the resistance of the lead wire through which a large current flows, the electric power consumption at the feeders can be reduced.
The lead wire having the resistance r1 is positioned in the region, of the heater 600, where the sheet P does not pass. For that reason, the heat generated at the lead wire having the resistance r1 is liable to become heat unnecessary for the fixing process. That is, by suppressing the heat generation of the lead wire having the resistance r1, it is possible to reduce a degree of the heat generation unnecessary for the fixing process of the heater 600. Therefore, according to this embodiment, the heat generation required for the fixing process can be made with high electric power efficiency.
Further, in this embodiment, the width of the electroconductive lines 650, 660 is made thinner than the width of the electroconductive line 640. For that reason, the electroconductive lines 650, 660 can be disposed in a narrow space of the substrate 610 with respect to the widthwise direction. Further, in this embodiment, the width of the electroconductive line 660 is made thinner than the width of the electroconductive line 650. For that reason, the electroconductive line 660 can be disposed in a narrow space of the substrate 610 with respect to the widthwise direction. For that reason, it is possible to suppress upsizing of the substrate 610 with respect to the widthwise direction. That is, according to this embodiment, by thinning the width of the lead wire through which a small current flows, it is possible to suppress the upsizing of the substrate 610 with respect to the widthwise direction. Further, an increase in cost of the heater 600 can be suppressed.
In the above description, the electroconductive line 650 of 1.5 mm in width of the lead wire along the longitudinal direction of the substrate is described as an example, but a shape of the electroconductive line 650 is not limited thereto. For example, only the width of the lead wire portion, having the resistance r9, where the current concentrates may be set at 1.5 mm and the width of the lead wires having the resistances r10-r12 may be set at 0.7 mm. That is, at this time, a relationship of: (lead wire width with resistance r9)>(lead wire width with resistances r10-r12) is satisfied. In addition, the electroconductive line 650 may also be constituted so as to satisfy a relationship of: (lead wire width with resistance r9)>(lead wire width with resistance r10)>(lead wire width with resistance r11)>(lead wire width with resistance r12). That is, the electroconductive line 650 may also have the width narrowing with an increasing distance from the electrical contact 651. This is because there is a tendency that the value of the current flowing through the electroconductive line 650 is smaller at the position more distant from the electrical contact 651. Further, the width of the electroconductive line 650 in the entire region may also be set at 1.5 mm. That is, the width of the lead wire portion, for the electroconductive line 650, branding toward the electrode and extending in the widthwise direction of the substrate may also be set at 1.5 mm. Even such a constitution is applicable to this embodiment.
A heater according to Embodiment 3 of the present invention will be described.
In Embodiment 1, the line width of the electroconductive line 640 is made thick compared with the line width of the electroconductive lines 650, 660. In Embodiment 3, in addition to the constitution of Embodiment 2, the line width of the electroconductive line 660b is made thick compared with the line width of the electroconductive line 660a.
Specifically, a length of a path of the electroconductive line 660b connecting the electrical contact 661b and the heat generating elements 620k, 620l is longer than a length of a path of electroconductive line 660a connecting the electrical contact 661a and the heat generating elements 620a, 620b. For that reason, the line width of the electroconductive line 660b is made thick compared with the line width of the electroconductive line 660a. For that reason, the fixing device 40 in this embodiment has the constitution further excellent in energy (electric power) efficiency compared with Embodiment 2.
Further, in this embodiment, the line widths of the respective electroconductive lines are adjusted so that the resistances of the electroconductive lines 650, 660a, 660b are the same. For that reason, the value of the electric power consumed between the associated electrical contact and the associated electrode are close to each other, so that it is possible to supply substantially the same electric power to each of the heat generating elements. Accordingly, the heater 600 can generate heat uniformly with respect to the longitudinal direction. That is, it is possible to suppress the heat generation non-uniformity of the heater 600 due to voltage drop by the electroconductive lines. Embodiment 3 is constituted similarly as in Embodiment 2 except for the above-described differences. For that reason, the same reference numerals or symbols as in Embodiment 2 are assigned to the elements having the corresponding functions in this embodiment, and the detailed description thereof is omitted for simplicity.
In Embodiment 2, from a difference in magnitude between the currents flowing through the feeders, the line width of the electroconductive lines 660a, 660b was made thin compared with the line width of the electroconductive line 650. Further, the amounts of the currents flowing through the electroconductive line 660a and the electroconductive line 660b are substantially the same, and therefore the electroconductive lines 660a-660b are made the same in width. However, values of the electric power consumed by the electroconductive lines 660a, 660b are different from each other. According to Table 2, the electric power consumption of the electroconductive line 660a is 0.5 W, whereas the electric power consumption of the electroconductive line 660b is 2.4 W. This difference in electric power consumption results from the difference in path length between the electroconductive line 660a and the electroconductive line 660b. That is the electroconductive line 660b is larger in path length than the electroconductive line 660a, and therefore the resistance becomes large. For that reason, the line width of the electroconductive line 660b may desirably be thicker than the line width of the electroconductive line 660a. In other words, the line width of the electroconductive line 660a may desirably be thinner than the line width of the electroconductive line 660b. The resistance r can be represented by the following formula.
Resistance r=ρ×L/(w×t)
ρ: specific resistance, L: line width, w: line width, t: line thickness
In this embodiment, as shown in
Accordingly, in this embodiment, the width of the electroconductive line 660a shorter in path length than the electroconductive line 660b is made thinner than the electroconductive line 660b. Specifically, the width, with respect to the widthwise direction of the substrate, of the lead wire for the electroconductive line 660a extending along the longitudinal direction of the substrate (i.e., the length with respect to the widthwise direction of the substrate) is made uniformly thin (narrow) compared with the width of the lead wire for the electroconductive line 660b extending along the longitudinal direction of the substrate (i.e., the length with respect to the widthwise direction of the substrate). That is, the width of the lead wire for the electroconductive line 660a extending along the longitudinal direction of the substrate is less than 0.4 mm.
By such a constitution, in this embodiment, a space in which the feeders are arranged in parallel in the widthwise direction of the substrate 610 can be saved. For that reason, enlargement in size of the substrate 610 in the widthwise direction can be suppressed.
Further, in this embodiment, each of the line widths is adjusted so that the respective resistances of the electroconductive lines 650, 660a, 660b are equal to each other. In this embodiment, by such a constitution, the values of the electric power consumed by the respective electroconductive lines are made close to each other, so that the values of the electric power supplied to the respective heat generating elements can be made close to each other.
In order to verify an effect of this embodiment, a comparison with Comparison Examples is made.
As shown in
As described above, in this embodiment, in the heater 600, the width of the lead wire having the resistance r1 is made thicker than the widths of the lead wire having the resistance r8, the lead wire having the resistance r9 and the lead wire having the resistance r13. For that reason, it is possible to suppress the electric power consumption (heat generation) at the lead wire having the resistance r1. That is, in this embodiment, by preferentially lowering the resistance of the lead wire through which a large current flows, the electric power consumption at the feeders can be reduced.
The lead wire having the resistance r1 is positioned in the region, of the heater 600, where the sheet P does not pass. For that reason, the heat generated at the lead wire having the resistance r1 is liable to become heat unnecessary for the fixing process. That is, by suppressing the heat generation of the lead wire having the resistance r1, it is possible to reduce a degree of the heat generation unnecessary for the fixing process of the heater 600. Therefore, according to this embodiment, the heat generation required for the fixing process can be made with high electric power efficiency.
Further, in this embodiment, the width of the electroconductive lines 650, 660 is made thinner than the width of the electroconductive line 640. For that reason, the electroconductive lines 650, 660 can be disposed in a narrow space of the substrate 610 with respect to the widthwise direction. Further, in this embodiment, the width of the electroconductive line 660 is made thinner than the width of the electroconductive line 650. For that reason, the electroconductive line 660 can be disposed in a narrow space of the substrate 610 with respect to the widthwise direction. Thus, it is possible to suppress upsizing of the substrate 610 with respect to the widthwise direction. That is, according to this embodiment, by thinning the width of the lead wire through which a small current flows, it is possible to suppress the upsizing of the substrate 610 with respect to the widthwise direction. Further, an increase in cost of the heater 600 can be suppressed.
Further, in this embodiment, the width of the electroconductive line 660a is made thinner than the width of the electroconductive line 660b. For that reason, the values of the electric power consumption by the electroconductive lines 650, 660a, 660b can be adjusted to substantially close values. Accordingly, according to this embodiment, it is possible to suppress generation of the temperature non-uniformity of the heat generating elements with respect to the longitudinal direction of the heat generating elements.
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 heat generating region of the heater 600 is not limited to the above-described examples which are based on the sheets P are fed with the center thereof aligned with the center of the fixing device 40, but the sheets P may also be supplied on another sheet feeding basis of the fixing device 40. For that reason, e.g., in the case where the sheet feeding basis is an end(-line) feeding basis, 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, but expands at one of the opposite end portions.
The number of patterns of the heat generating region of the heater 600 is not limited to two. For example, three or more patterns may be provided.
The forming method of the heat generating element 620 is not limited to those disclosed in Embodiment 1. In Embodiment 1, the electrode 642 and in the 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. For example, five or more electrical contacts may also be provided depending on the number of heat generating patterns required for the fixing device.
Further, in the fixing device 40 in Embodiment 1, by the constitution in which all of the electrical contacts are disposed in one longitudinal end portion side of the substrate 610, the electric power is supplied from one end portion side to the heater 600, but the present invention is not limited to such a constitution. For example, a fixing device 40 having a constitution in which electrical contacts are disposed in a region extended from the other end of the substrate 610 and then the electric power is supplied to the heater 600 from both of the end portions may also be used.
The arrangement constitution of the switches connecting the heater 600 with the power source 110 is not limited to that in Embodiment 1. For example, a switch constitution as in a conventional example shown in each of (a) and (b) of
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, which are prepared by adding necessary device, equipment and casing structure.
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 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. 2014-150778 filed on Jul. 24, 2014, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-150778 | Jul 2014 | JP | national |
