JP7519012B2 - Heating body, heating device, fixing device and image forming apparatus - Google Patents

Description

The present invention relates to a heater, a heating device, a fixing device, and an image forming device.

Known devices that include a heating device that uses a heating element to heat a heated member include a fixing device that uses heat to fix toner on paper and a drying device that dries ink on paper.

For example, the following Patent Document 1 discloses a fixing device that includes a heating element (heater) on a longitudinal substrate, the heating element, electrical contacts, and a conductor pattern that electrically connects these.

In a heating element having such a conductor pattern provided on a substrate, when the heating element is heated, the conductor pattern also generates a small amount of heat due to the passage of electricity through the conductor pattern. Therefore, strictly speaking, the heat distribution of the entire heating element is affected by the heat generated by the conductor pattern.

Therefore, depending on the heat distribution of the conductor pattern, there is a risk that this may cause variations in the temperature distribution of the heating element.

The heating element had an issue where there was a discrepancy in the amount of heat generated between one side and the other side of the arrangement direction of multiple resistive heating elements.

In order to solve the above problems, the present invention provides a heating element including a first conductive portion, a second conductive portion, a third conductive portion, a first electrode portion, a second electrode portion, a third electrode portion, and a first heating portion and a second heating portion each composed of at least one resistive heating element, the resistive heating elements being arranged in a line, the first electrode portion, the second electrode portion, and the third electrode portion being provided on one side of the center of the resistive heating elements in the arrangement direction of the resistive heating elements, and the first electrode portion being provided on the first electrode portion and the second electrode portion being provided on the other side of the center of the resistive heating elements in the arrangement direction of the resistive heating elements. the second electrode portion is connected to the first heating portion via the conductive portion, the second electrode portion is connected to the first heating portion and the second heating portion via the second conductive portion, the third electrode portion is connected to the second heating portion via the third conductive portion, and the second conductive portion is characterized in that a portion extending from one resistive heating element on the one side of the center of the multiple resistive heating elements merges with a portion extending from another resistive heating element and extends to the other side opposite the one side, and then folds back and is connected to the second electrode portion.

The present invention can suppress the deviation in heat generation between one side and the other side of the arrangement direction of multiple resistive heating elements in a heating element.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic diagram of a fixing device. FIG. FIG. FIG. FIG. FIG. FIG. FIG. 4 is a perspective view showing a state in which a connector is connected to the heater. FIG. 4 is a diagram showing power supply to a heater. 4A to 4C are diagrams illustrating the configuration of each conductive portion. FIG. 11 is a diagram showing a normal current path in the heater of FIG. 10 . 11 is a diagram showing a current path when unintended current shunting occurs in the heater of FIG. 10. FIG. 10A and 10B are diagrams illustrating a heater configuration and power supply to the heater that are different from those in the present embodiment 15 is a diagram showing the amount of heat generated in the power supply lines for each block when unintended current shunting occurs due to partial energization in the heater of FIG. 14 . FIG. 15 is a diagram showing the amount of heat generated by the power supply lines for each block when all power is applied in the heater of FIG. 14 . 11 is a diagram showing the amount of heat generated in the power supply lines for each block when unintended current shunting occurs due to partial energization in the heater of FIG. 10 . FIG. 11 is a diagram showing the amount of heat generated by the power supply lines for each block when all power is applied in the heater of FIG. 10 . 13A and 13B are diagrams showing modified examples of the arrangement of the third portion. FIG. 20 is a diagram showing the amount of heat generated by the power supply lines for each block when all power is applied in the heater of FIG. 19 . 13A and 13B are diagrams showing modified examples in which the width of the third portion is changed. FIG. 13 is a diagram showing a modified example in which the width of the fourth portion is changed. FIG. 1 is a diagram illustrating an image forming apparatus according to an embodiment provided with a blower. FIG. 24 is a diagram showing an image forming apparatus according to an embodiment, different from that shown in FIG. 23, in which a blower is provided. 10 is a plan view showing dimensions in a direction intersecting the arrangement direction of heaters and dimensions in a direction intersecting the arrangement direction of resistance heating elements. FIG. 1A and 1B are plan views showing modified examples of the heater. FIG. 13 is a diagram showing the configuration of another fixing device. FIG. 13 is a diagram showing the configuration of another fixing device. FIG. 13 is a diagram showing the configuration of still another fixing device. 13A and 13B are diagrams illustrating a heater having a configuration in which the difference between the amount of heat generated by the power supply line and the left and right sides becomes large.

The following describes embodiments of the present invention with reference to the drawings. In each drawing, the same or corresponding parts are given the same reference numerals, and their repeated explanations will be appropriately simplified or omitted. In the following description of each embodiment, a fixing device that fixes toner by heat will be described as a device equipped with a heating device having a heating body.

The monochrome image forming device 1 shown in FIG. 1 is provided with a photoconductor drum 10. The photoconductor drum 10 is a drum-shaped rotating body capable of carrying toner as a developer on its surface, and rotates in the direction of the arrow in the figure. Around the photoconductor drum 10 are a charging roller 11 that uniformly charges the surface of the photoconductor drum 10, a developing device 12 equipped with a developing roller 7 that supplies toner to the surface of the photoconductor drum 10, and a cleaning blade 13 for cleaning the surface of the photoconductor drum 10.

An exposure unit is disposed above the photoconductor drum 10. Laser light Lb emitted by the exposure unit based on image data is irradiated onto the surface of the photoconductor drum 10 via the mirror 14.

In addition, a transfer means 15 equipped with a transfer charger is disposed opposite the photoreceptor drum 10. The transfer means 15 transfers the image on the surface of the photoreceptor drum 10 onto the paper P.

The paper feed section 4 is located at the bottom of the image forming device 1 and is made up of a paper feed cassette 16 that contains paper P as a recording medium, a paper feed roller 17 that conveys the paper P from the paper feed cassette 16 to the conveying path 5, and the like. A registration roller 18 is disposed downstream of the paper feed roller 17 in the conveying direction.

The fixing device 9 includes a fixing belt 20 that is heated by a heating element, which will be described later, and a pressure roller 21 that can apply pressure to the fixing belt 20.

The basic operation of the image forming device 1 will be described below with reference to FIG. 1.

When the printing operation (image forming operation) starts, the surface of the photoconductor drum 10 is first charged by the charging roller 11. Then, a laser beam Lb is irradiated from the exposure section based on image data, and the potential of the irradiated area is reduced to form an electrostatic latent image. Toner is supplied from the developing device 12 to the surface of the photoconductor drum 10 on which the electrostatic latent image has been formed, and the image is visualized as a toner image (developer image). Any toner remaining on the photoconductor drum 10 after transfer is removed by the cleaning blade 13.

When the printing operation is started, the paper feed roller 17 of the paper feed section 4 rotates at the bottom of the image forming device 1, sending the paper P stored in the paper feed cassette 16 to the transport path 5.

The paper P sent to the transport path 5 is timed by the registration roller 18 and transported to the transfer section, which is the opposing part between the transfer means 15 and the photosensitive drum 10, at a timing that faces the toner image on the surface of the photosensitive drum 10, and the toner image is transferred by applying a transfer bias by the transfer means 15.

The paper P with the transferred toner image is transported to the fixing device 9, where it is heated and pressurized by the heated fixing belt 20 and pressure roller 21, fixing the toner image to the paper P. The paper P with the fixed toner image is then separated from the fixing belt 20, transported by a pair of transport rollers provided downstream of the fixing device 9, and discharged to a paper output tray provided outside the device.

Next, we will explain the configuration of the fixing device 9 in more detail.

2, the fixing device 9 according to the present embodiment includes a fixing belt 20 as a belt member or fixing member, a pressure roller 21 as an opposing member or pressure member that contacts the outer peripheral surface of the fixing belt 20 to form a nip portion N, and a heating device 19 that heats the fixing belt 20. The heating device 19 also includes a planar heater 22 as a heating body, a heater holder 23 as a holding member that holds the heater 22, a stay 24 as a support member that supports the heater holder 23, and a thermistor 35 as a temperature detection means. The fixing belt 20, the pressure roller 21, the heater 22, the heater holder 23, and the stay 24 extend in a direction perpendicular to the plane of the paper in FIG. 2 (see the direction of the double-headed arrow B in FIG. 3), and hereinafter, this direction is referred to as the longitudinal direction of each member (however, it is also the axial direction of the pressure roller 21), or the longitudinal direction of the heating device 19 and the fixing device 9. This longitudinal direction is also the width direction of the paper passed through the fixing device 9. However, the longitudinal direction of the heater 22 does not necessarily have to coincide with the longitudinal direction of other components or devices.

The fixing belt 20 is composed of an endless belt member, and has a cylindrical substrate made of polyimide (PI) with an outer diameter of 25 mm and a thickness of 40 to 120 μm. A release layer made of fluorine-based resin such as PFA or PTFE with a thickness of 5 to 50 μm is formed on the outermost layer of the fixing belt 20 to enhance durability and ensure releasability. An elastic layer made of rubber or the like with a thickness of 50 to 500 μm may be provided between the substrate and the release layer. The substrate of the fixing belt 20 is not limited to polyimide, and may be a heat-resistant resin such as PEEK or a metal substrate such as nickel (Ni) or SUS. The inner peripheral surface of the fixing belt 20 may be coated with polyimide, PTFE, or the like as a sliding layer.

The pressure roller 21 has an outer diameter of, for example, 25 mm and is composed of a solid iron core 21a, an elastic layer 21b formed on the surface of the core 21a, and a release layer 21c formed on the outside of the elastic layer 21b. The elastic layer 21b is made of silicone rubber and has a thickness of, for example, 3.5 mm. In order to improve the release properties of the surface of the elastic layer 21b, it is desirable to form a release layer 21c made of a fluororesin layer having a thickness of, for example, about 40 μm.

The fixing belt 20 is pressed against the pressure roller 21 by the pressure mechanism, and is pressed against the pressure roller 21. This forms a nip N between the fixing belt 20 and the pressure roller 21. The pressure roller 21 also functions as a drive roller that is rotated by a driving force transmitted from a drive means provided in the image forming apparatus body. Meanwhile, the fixing belt 20 is configured to rotate in response to the rotation of the pressure roller 21. When the fixing belt 20 rotates, the fixing belt 20 slides against the heater 22, so a lubricant such as oil or grease may be interposed between the heater 22 and the fixing belt 20 to improve the sliding property of the fixing belt 20.

The heater 22 is provided longitudinally along the length of the fixing belt 20 and is in contact with the inner circumferential surface of the fixing belt 20 at a position corresponding to the pressure roller 21. The heater 22 is a member for heating the fixing belt 20 as a heated member, and for heating the fixing belt 20 to a predetermined fixing temperature.

Unlike this embodiment, the heat generating section 60 may be provided on the opposite side of the substrate 50 from the fixing belt 20 side (the heater holder 23 side). In that case, since the heat from the heat generating section 60 is transferred to the fixing belt 20 via the substrate 50, it is desirable that the substrate 50 be made of a material with high thermal conductivity such as aluminum nitride. Furthermore, in the configuration of the heater 22 according to this embodiment, an insulating layer may be further provided on the surface of the substrate 50 opposite the fixing belt 20 (the heater holder 23 side).

The heater 22 may be in non-contact with the fixing belt 20 or indirectly contact with the fixing belt 20 via a low-friction sheet or the like, but in order to increase the efficiency of heat transfer to the fixing belt 20, it is preferable to have the heater 22 in direct contact with the fixing belt 20 as in this embodiment. The heater 22 can also be in contact with the outer peripheral surface of the fixing belt 20, but since there is a risk that the fixing quality will decrease if the outer peripheral surface of the fixing belt 20 is damaged by contact with the heater 22, it is preferable that the surface with which the heater 22 contacts is the inner peripheral surface of the fixing belt 20.

The heater holder 23 and the stay 24 are disposed inside the fixing belt 20. The stay 24 is made of a metal channel material, and both ends are supported by both side walls of the fixing device 9. The stay 24 supports the surface of the heater holder 23 opposite the heater 22 side, so that the heater 22 and the heater holder 23 are maintained without being significantly deflected by the pressure force of the pressure roller 21, and a fixing nip N is formed as a nip portion between the fixing belt 20 and the pressure roller 21.

The heater holder 23 is desirably made of a heat-resistant material because it is prone to becoming hot due to the heat of the heater 22. For example, if the heater holder 23 is made of a heat-resistant resin with low thermal conductivity such as LCP, the transfer of heat from the heater 22 to the heater holder 23 is suppressed, and the fixing belt 20 can be heated efficiently.

The thermistor 35 is provided on the rear surface of the substrate 50 at a position facing the heat generating section 60. Based on the temperature detected by the thermistor 35, the temperature of the fixing belt 20 is controlled to the desired temperature by controlling the power supplied to the heater 22 by the heating control means. The heating control means refers to a microcomputer including a CPU, ROM, RAM, an I/O interface, etc. However, when paper is being passed through, etc., the temperature of the fixing belt 20 is controlled to the desired temperature by appropriately supplying additional power in addition to the detected temperature, taking into account the amount of heat dissipated by the paper passing through.

When the printing operation starts, power is supplied to the heater 22, which causes the heat generating section 60 to generate heat and heat the fixing belt 20. The pressure roller 21 is also rotated and the fixing belt 20 starts to rotate. Then, when the temperature of the fixing belt 20 reaches a predetermined target temperature (fixing temperature), as shown in FIG. 2, the paper P carrying the unfixed toner image is transported between the fixing belt 20 and the pressure roller 21 (fixing nip N) (see the direction of arrow A in FIG. 2), and the unfixed toner image is heated and pressurized to be fixed to the paper P.

Figure 3 is a perspective view of the fixing device, and Figure 4 is an exploded perspective view of the fixing device.

3 and 4, the device frame 40 of the fixing device 9 includes a first device frame 25 consisting of a pair of side walls 28 and a front wall 27, and a second device frame 26 consisting of a rear wall 29. The pair of side walls 28 are disposed at one end and the other end in the longitudinal direction, and both end sides of the fixing belt 20, the pressure roller 21, and the heating device 19 are supported by the side walls 28. Each side wall 28 is provided with a plurality of engagement protrusions 28a, and the first device frame 25 and the second device frame 26 are assembled by engaging each engagement protrusion 28a with an engagement hole 29a provided in the rear wall 29.

Each side wall portion 28 is provided with an insertion groove 28b for inserting the rotating shaft of the pressure roller 21. The insertion groove 28b opens on the rear wall portion 29 side and is a butt portion that does not open on the opposite side. A bearing 30 that supports the rotating shaft of the pressure roller 21 is provided at the end on the butt portion side. The pressure roller 21 is rotatably supported by the side wall portions 28 by mounting both ends of the rotating shaft to the bearings 30.

A drive transmission gear 31 is provided as a drive transmission member on one end of the rotation shaft of the pressure roller 21. The drive transmission gear 31 is arranged in a state where it is exposed outside the side wall portions 28 when the pressure roller 21 is supported by the side wall portions 28. As a result, when the fixing device 9 is mounted on the image forming apparatus main body, the drive transmission gear 31 is connected to a gear provided on the image forming apparatus main body, and is in a state where it can transmit drive force from the drive source. Note that the drive transmission member that transmits drive force to the pressure roller 21 may be a pulley that stretches a drive transmission belt or a coupling mechanism, in addition to the drive transmission gear 31.

A pair of flanges 32 are provided at both longitudinal ends of the heating device 19 to support the fixing belt 20, heater holder 23, stay 24, etc. Each flange 32 is provided with a guide groove 32a. The flanges 32 are assembled to the side wall portion 28 by inserting the guide grooves 32a along the edge of the insertion groove 28b of the side wall portion 28.

A pair of springs 33 acting as urging members contact each flange 32. Each spring 33 urges the stay 24 and the flange 32 toward the pressure roller 21, so that the fixing belt 20 is pressed against the pressure roller 21, forming a fixing nip between the fixing belt 20 and the pressure roller 21.

As shown in FIG. 4, one end of the rear wall 29 constituting the second device frame 26 in the longitudinal direction is provided with a hole 29b as a positioning portion for positioning the fixing device body relative to the image forming device body. On the other hand, the image forming device body is provided with a protrusion 101 as a positioning portion. When the protrusion 101 is inserted into the hole 29b of the fixing device 9, the protrusion 101 and the hole 29b fit together, and the fixing device body is positioned in the longitudinal direction relative to the image forming device body. Note that no positioning portion is provided on the end side opposite the end side where the hole 29b of the rear wall 29 is provided. This prevents the longitudinal expansion and contraction of the fixing device body due to temperature changes from being restricted.

Figure 5 is a perspective view of the heating device 19, and Figure 6 is an exploded perspective view of the heating device 19.

As shown in Figs. 5 and 6, the heater holder 23 has a rectangular storage recess 23a on the fixing belt side (the surface on the near side in Figs. 5 and 6) for storing the heater 22. The storage recess 23a is formed to have approximately the same shape and size as the heater 22, but the longitudinal dimension L2 of the storage recess 23a is set to be slightly longer than the longitudinal dimension L1 of the heater 22. In this way, the storage recess 23a is formed to be slightly longer than the heater 22, so that the heater 22 and the storage recess 23a do not interfere with each other even if the heater 22 expands in the longitudinal direction due to thermal expansion. In addition, the heater 22 is held in the storage recess 23a by being sandwiched together with the heater holder 23 by a connector, which will be described later, as a power supply member.

The pair of flanges 32 have a C-shaped belt support portion 32b that is inserted inside the fixing belt 20 to support the fixing belt 20, a flange-shaped belt regulation portion 32c that contacts the end face of the fixing belt 20 to regulate longitudinal movement (deviation), and support recesses 32d into which both end sides of the heater holder 23 and the stay 24 are inserted to support them. With the belt support portions 32b inserted into both end sides, the fixing belt 20 is supported in a so-called free belt manner in which basically no tension is generated in the circumferential direction (belt rotation direction) when the belt is not rotating.

As shown in Figures 5 and 6, a positioning recess 23e is provided as a positioning portion at one end of the heater holder 23 in the longitudinal direction. The fitting portion 32e of the flange 32 shown on the left side of Figures 5 and 6 fits into this positioning recess 23e, thereby positioning the heater holder 23 and the flange 32 in the longitudinal direction. On the other hand, the flange 32 shown on the right side of Figures 5 and 6 does not have a fitting portion 32e, and is not positioned in the longitudinal direction relative to the heater holder 23. In this way, by positioning the heater holder 23 relative to the flange 32 only on one side in the longitudinal direction, even if the heater holder 23 expands and contracts in the longitudinal direction due to temperature changes, the expansion and contraction is not restricted.

As shown in FIG. 6, steps 24a are provided on both longitudinal ends of the stay 24 to restrict movement of the stay 24 relative to each flange 32. Each step 24a abuts against the flange 32 to restrict longitudinal movement of the stay 24 relative to the flange 32. However, at least one of these step portions 24a is disposed with a gap (backlash) between it and the flange 32. In this way, by disposing at least one step portion 24a with a gap between it and the flange 32, even if the stay 24 expands and contracts in the longitudinal direction due to temperature changes, the expansion and contraction is not restricted.

Figure 7 is a plan view of the heater 22, and Figure 8 is an exploded perspective view of the heater 22.

As shown in FIG. 8, the heater 22 has a substrate 50, a first insulating layer 51 provided on the substrate 50, a conductor layer 52 having a heat generating portion 60 and the like provided on the first insulating layer 51, and a second insulating layer 53 covering the conductor layer 52. In this embodiment, the substrate 50, the first insulating layer 51, the conductor layer 52 (heat generating portion 60), and the second insulating layer 53 are laminated in this order toward the fixing belt 20 side (fixing nip N side), and the heat generated from the heat generating portion 60 is transferred to the fixing belt 20 via the second insulating layer 53 (see FIG. 2).

The substrate 50 is a longitudinal plate made of a metal material such as stainless steel (SUS), iron, or aluminum. In addition to metal materials, ceramics, glass, etc. can also be used as the material for the substrate 50. When an insulating material such as ceramics is used for the substrate 50, the first insulating layer 51 between the substrate 50 and the conductor layer 52 can be omitted. On the other hand, metal materials are excellent in durability against rapid heating and are easy to process, making them suitable for reducing costs. Among metal materials, aluminum and copper are particularly preferred because they have high thermal conductivity and are less likely to cause temperature unevenness. Stainless steel also has the advantage of being cheaper to manufacture than these.

Each insulating layer 51, 53 is made of an insulating material such as heat-resistant glass. Alternatively, ceramic or polyimide (PI) may be used as the material.

The conductor layer 52 is composed of a heating section 60 having a plurality of resistive heating elements 59, a plurality of electrode sections 61, and a plurality of power supply lines 62 as conductors that electrically connect these. Each resistive heating element 59 is electrically connected in parallel to any two of the three electrode sections 61 via a plurality of power supply lines 62 provided on the substrate 50.

The resistance heating element 59 is formed, for example, by applying a paste made of silver palladium (AgPd) and glass powder to the substrate 50 by screen printing or the like, and then firing the substrate 50. In addition to these, the material of the resistance heating element 59 may be a resistance material such as a silver alloy (AgPt) or ruthenium oxide (RuO ₂ ).

The power supply line 62 is made of a conductor with a resistance value smaller than that of the resistive heating element 59. The power supply line 62 and the electrode portion 61 can be made of a material such as silver (Ag) or silver palladium (AgPd), and the power supply line 62 and the electrode portion 61 are formed by screen printing or the like of such a material.

Figure 9 is an oblique view showing the connector 70 connected to the heater 22.

As shown in FIG. 9, the connector 70 has a resin housing 71 and a number of contact terminals 72 provided on the housing 71. Each contact terminal 72 is made of a leaf spring and is connected to a power supply harness 73.

As shown in FIG. 9, the connector 70 is attached so as to sandwich the heater 22 and heater holder 23 together from the front and back sides. In this state, the contact portions 72a provided at the tip of each contact terminal 72 elastically contact (pressure weld) with the corresponding electrode portions 61, electrically connecting the heat generating portion 60 to the power source provided in the image forming device via the connector 70. This makes it possible to supply power from the power source to the heat generating portion 60. Note that in order to ensure connection with the connector 70, at least a portion of each electrode portion 61 is not covered by the second insulating layer 53 and is exposed (see FIG. 7).

10, in this embodiment, among the multiple resistive heating elements 59 arranged in the longitudinal direction of the substrate 50, a first heating section 60A consisting of the resistive heating elements 59 other than those at both ends and a second heating section 60B consisting of the resistive heating elements 59 at both ends are configured to be able to control heat generation independently. Specifically, each resistive heating element 59 other than those at both ends constituting the first heating section 60A is connected to the first electrode section 61A via a first power supply line 62A (first conductive section 67A). In addition, each resistive heating element 59 constituting the first heating section 60A is connected to the second electrode section 61B via a second power supply line 62B (second conductive section 67B). On the other hand, each of the resistance heating elements 59 at both ends constituting the second heating portion 60B is connected to a third electrode portion 61C (separate from the first electrode portion 61A) via a third power supply line 62C and a fourth power supply line 62D (third conductive portion 67C). Also, each of the resistance heating elements 59 at both ends is connected to the second electrode portion 61B via a second power supply line 62B, similar to each of the resistance heating elements 59 of the first heating portion 60A. In other words, the second electrode portion 61B is connected by merging the power supply lines (second power supply line 62B) extending from all the resistance heating elements 59. Also, the first to third electrode portions 61A to 61C are provided at the center position F in the longitudinal direction of the heater 22 (substrate 50) or on one side of the center of the plurality of resistance heating elements 59 in the longitudinal direction. In this embodiment, the left-right direction in FIG. 10, which is the direction in which the multiple resistance heating elements 59 are arranged, coincides with the longitudinal direction of the heater 22 (substrate 50). In the following explanation, the left-right direction (longitudinal direction) in FIG. 10 will be referred to as the arrangement direction of the multiple resistance heating elements 59, or simply as the arrangement direction. Also, a direction that intersects with the arrangement direction and is different from the thickness direction of the heater 22 (particularly in this embodiment, a direction perpendicular to the arrangement direction, which is also the up-down direction in FIG. 10 or the short-side direction of the heater 22) will be referred to as a direction that intersects with the arrangement direction.

Each of the electrode units 61A to 61C is connected to a power source 64 via the connector 70 described above, and receives power from the power source 64. The electrode unit 61A is provided with a switch 65A as a switching unit between the power source 64, and the ON/OFF state of the switch 65A can be switched between applying and not applying a voltage. Similarly, the electrode unit 61C is provided with a switch 65C as a switching unit between the power source 64, and the ON/OFF state of the switch 65C can be switched between applying and not applying a voltage. Furthermore, the ON/OFF state of the switches 65A and 65C and the timing of the power supply to the heater 22 are controlled by a control circuit 66 as a control unit. The control circuit 66 also performs these controls based on the detection results of various sensors in the image forming apparatus. For example, the timing of passing a paper sheet can be determined based on the detection results of sensors provided at the entrance and exit of the fixing nip N, and the supply of power to the heater 22 and the switching of the switches 65A and 65C can be performed. The control circuit 66 may be provided in the heating device or fixing device, or may be provided in the main body of the image forming device.

When a voltage is applied to the first electrode portion 61A and the second electrode portion 61B, the resistive heating elements 59 other than those at both ends are energized, and only the first heating portion 60A is heated. On the other hand, when a voltage is applied to the second electrode portion 61B and the third electrode portion 61C, the resistive heating elements 59 at both ends are energized, and only the second heating portion 60B is heated. In addition, if a voltage is applied to all the electrodes 61A to 61C, both (all) of the resistive heating elements 59 of the first heating portion 60A and the second heating portion 60B can be heated. For example, when a relatively small width paper of A4 size or less (paper passing width: 210 mm) is passed through, only the first heating portion 60A is heated, and when a relatively large width paper of more than A4 size (paper passing width: 210 mm) is passed through, the second heating portion 60B is also heated in addition to the first heating portion 60A, so that a heating area according to the paper width can be obtained.

11, the second power supply line 62B (second conductive portion 67B) has a first portion 62B1, a second portion 62B2, a third portion 62B3, and a fourth portion 62B4. The first portion 62B1 is connected to each resistance heating element 59 of the first heating portion 60A and the second heating portion 60B, extends from each resistance heating element 59, and extends in a direction intersecting the arrangement direction of the heater 22 (arrow Y direction in FIG. 11: a direction intersecting the arrangement direction B along the surface on which the heating portions 60A and 60B of the heater 22 are provided, in the short direction of the heater). The second portion 62B2 extends in the arrangement direction and is a portion where the first portions 62B1 are connected and merge. The third portion 62B3 extends in a direction intersecting the arrangement direction and is a portion that connects the second portion 62B2 and the fourth portion 62B4 at the other end side in the arrangement direction (a position that overlaps with the resistive heating element 59 arranged on the other side in the arrangement direction, or a portion that connects the second portion 62B2 and the fourth portion 62B4 on the other side of that). The fourth portion 62B4 extends in the arrangement direction and is a portion that is connected to the second electrode portion 61B. In other words, the second power supply line 62B (second conductive portion 67B) is a portion in which the portions extending from each resistive heating element 59 join together and turn back at the other end side of the arrangement direction of the heater 22 (the other end side of the center position of the heater 22) and are connected to the second electrode portion 61B on one side of the arrangement direction. Note that FIG. 11 (as well as FIG. 12 described later) is a schematic diagram, and the dimensions in the direction intersecting the arrangement direction of the heater 22 are exaggerated.

In this embodiment, the connection positions K1 of the first power feed line 62A, the third power feed line 62C, and the fourth power feed line 62D to the resistive heating element 59 are arranged on one side of the arrangement direction (particularly the end on one side of the arrangement direction in this embodiment) relative to the center position H of the resistive heating element 59 in the arrangement direction, and the connection position K2 of the second power feed line 62B to the resistive heating element 59 is arranged on the other side of the arrangement direction (particularly the end on the other side of the arrangement direction in this embodiment). Figure 11 shows, as an example, the center position H and connection positions K1 and K2 of the resistive heating element 59 arranged on the furthest other side.

In this embodiment, the width of all power supply lines 62A to 62D is set to the same.

If the region in the arrangement direction where the resistive heating element 59 is arranged is the heating region D of the heater 22, the fourth portion 62B4 is provided over the entire heating region D. This allows the fourth portion 62B4 to be provided in a region that is primarily heated by the heater 22, such as the paper passage region, and the heat generated by the fourth portion 62B4 can be effectively utilized.

Incidentally, in order to further reduce the size of image forming devices and fixing devices, it is important to reduce the size of the heater, which is one of the components arranged inside the fixing belt. In other words, by reducing the size of the heater in the direction intersecting the arrangement direction, the diameter of the fixing belt can be reduced, which in turn makes it possible to reduce the size of the fixing device and image forming device. Specifically, the following methods can be given as examples of methods for reducing the size of the heater in the direction intersecting the arrangement direction.

The method is to reduce the size of the power supply line in the direction intersecting the arrangement direction. However, when the size of the power supply line is reduced in the direction intersecting the arrangement direction, the resistance value of the power supply line increases, so the ratio of the heat generated by the power supply line to the heat generated by the entire heater increases, and the effect of the heat generated by the power supply line cannot be ignored. In addition, when the resistance value of the power supply line increases, there is a risk of unintended shunting occurring on the conductive path of the heater. In particular, when the resistance value of the heating unit is reduced in order to increase the heat generated by the heating unit to meet the high speed of the image forming device, the resistance value of the power supply line and the resistance value of the heating unit become relatively close to each other, making it easier for unintended shunting to occur. Therefore, in order to achieve miniaturization of the heater in the direction intersecting the arrangement direction, it is necessary to reduce the size of the power supply line in the direction intersecting the arrangement direction in anticipation of an increase in resistance value, and to take separate measures against unintended shunting that may occur as a result.

Below, we will explain unintended current diversion using a heater with the same layout as heater 22 described above as an example.

In the heater 22 shown in FIG. 12, when a voltage is applied to the first electrode portion 61A and the second electrode portion 61B to heat only the resistive heating elements 59 of the first heating portion 60A, a current normally flows through the first power supply line 62A, passes through each resistive heating element 59 other than the two ends, and flows into the second power supply line 62B.

However, when the difference between the resistance of the power supply line and the heating part becomes small due to the increase in resistance of the power supply line associated with the above-mentioned miniaturization, or the decrease in resistance of the heating part associated with the increase in the amount of heat generated, an unintended branching of the current occurs, as shown in FIG. 13. That is, part of the current that passed through the second resistive heating element 59 from the left in FIG. 13 flows in the opposite direction to the second electrode part 61B at the branch part X of the second power supply line 62A. The branched current then passes through the resistive heating element 59 at the left end in FIG. 13, and further passes through the third power supply line 62C, the third electrode part 61C, the fourth power supply line 62D, and the resistive heating element 59 at the right end in this order, before joining the second power supply line 62B.

In this way, in the heater 22 shown in FIG. 13, the portion of the second power supply line 62B extending from the branch portion X to the left side of the figure, the resistive heating elements 59 at both ends that constitute the second heating portion 60B, the third electrode portion 61C, and the portion including the third power supply line 62C and the fourth power supply line 62D constitute a branched conductive path E3 that allows current to flow through an unintended path.

In addition, such unintended branching can occur when electricity is applied to the first heat generating portion 60A if the conductive path of the heater 22 has at least a first conductive path E1 connecting the first heat generating portion 60A and the third electrode portion 61C, a second conductive path E2 extending from the first heat generating portion 60A in a first direction S1 (right side in FIG. 13) of the arrangement direction of the heater 22 and connected to the second electrode portion 61B, and a branch conductive path E3 branching from the second conductive path E2 in a second direction S2 (left side in FIG. 13) opposite to the first direction S1 and connected to the second conductive path E2 or the second electrode portion 61B without passing through the first conductive path E1. In other words, the above-mentioned shunting can occur when electricity is applied to the first heat generating part 60A under three conditions: "the first electrode part (first electrode part 61A) is connected to the resistive heating element 59 at the center of the arrangement direction," "the second electrode part (third electrode part 61C) is connected to the resistive heating element 59 at the end of the arrangement direction," and "the power supply lines extending from each resistive heating element 59 join and are connected to the third electrode part (second electrode part 61B)." In this embodiment, the second heat generating part 60B and the first electrode part 61A are provided on the branched conductive path E3, but even in a conductive path that does not have the second heat generating part 60B and the first electrode part 61A or a conductive path that has a conductive member other than these, unintended shunting can occur.

Next, it will be explained that a deviation occurs between the heat generation amount of the power supply line on one side and the other side in the arrangement direction in each case where an unintended shunt occurs when electricity is supplied to all heat generating parts (hereinafter also referred to as the case of full electricity supply) and when electricity is supplied only to the first heat generating part 60A as described above (hereinafter also referred to as the case of partial electricity supply). In the following explanation, first, the configuration of the heater shown in FIG. 14 will be explained as a heater with a configuration different from that of the present invention. Then, it will be explained that a deviation occurs between the heat generation amount of the power supply line on one side and the other side in the arrangement direction in the case of full electricity supply and partial electricity supply in the heater with the configuration of FIG. 14. After that, the heat generation amount of each block in the arrangement direction of the power supply line in the case of full electricity supply and partial electricity supply is shown for the configuration of FIG. 10 of this embodiment in which measures have been taken.

The heater 22 shown in FIG. 14 differs from the heater of the present embodiment in that the second electrode portion 61B is disposed on the other side of the arrangement direction, that is, on the opposite side to the first electrode portion 61A and the third electrode portion 61C. Therefore, the second power supply line 62B connecting each resistance heating element 59 and the second electrode portion 61B is connected to the second electrode portion 61B on the other side of the arrangement direction, and does not have a portion that folds back and extends to the other side of the arrangement direction (the portion corresponding to the third portion 62B3 and the fourth portion 62B4 in FIG. 11). Even in this case, when partial current is applied, unintended current division may occur due to a similar branched conductive path E3 (see FIG. 13).

First, the amount of heat generated by the power supply line when the heater 22 in FIG. 14 is partially energized will be described with reference to FIG. 15. FIG. 15 shows the amount of heat generated by the power supply line in each block divided by the resistive heating element 59 in the heater 22 shown in FIG. 14 when 20% of the current flows evenly from the first electrode portion 61A to each resistive heating element 59 of the first heating portion 60A, and the current passing through the second resistive heating element 59 from the left in the figure is diverted by 5% at the branch portion X beyond that. Note that the boundary position of each block is the midpoint between the resistive heating elements 59.

Here, the portion of each power feed line that extends in a direction intersecting the arrangement direction of the heaters 22 is short, and the amount of heat generated in this portion is small, so this amount of heat is ignored and only the amount of heat generated in the portion of each power feed line that extends in the arrangement direction of the heaters 22 is calculated. Specifically, the amount of heat generated in the portion of the first power feed line 62A, the second power feed line 62B, and the fourth power feed line 62D that extends in the arrangement direction of the heaters 22 is calculated. In addition, since the amount of heat generated (W) is expressed by the following formula (1), the amount of heat generated shown in the table of FIG. 13 is calculated as the square of the current (I) flowing through each power feed line for convenience. Therefore, the numerical values of the amount of heat generated shown in the table of FIG. 13 are merely simply calculated values and differ from the actual amount of heat generated.

The method of calculating the amount of heat generated will be specifically described with reference to FIG. 15. In the first block, the current flowing through the first power supply line 62A is 100%, and the current flowing through the fourth power supply line 62D is 5%, so the sum of the squares of these, 10025 (10000+25), is the total amount of heat generated by the power supply lines in the first block. In the second block, the current flowing through the first power supply line 62A is 80%, the current flowing through the second power supply line 62B is 5%, and the current flowing through the fourth power supply line 62D is 5%, so the sum of the squares of these, 6450 (6400+25+25), is the total amount of heat generated by the power supply lines in the second block. In the other blocks, the amount of heat generated is calculated in a similar manner.

As shown in the table and graph at the bottom of Figure 15, the total heat generation amount of each block is asymmetrical with respect to the fourth block in the center of the heat generation area due to the unintended current diversion described above, with the heat generation amount on one side in the arrangement direction being greater than the other side. However, the first block and the seventh block are non-paper passing areas through which paper does not pass.

Even when electricity is applied to all heat generating parts, the difference in the magnitude of the current flowing through the conductive parts causes the amount of heat generated in the arrangement direction of the heater 22 to be asymmetrical on the left and right. In other words, when trying to miniaturize the heater 22 as described above, the arrangement of the electrode parts and conductive parts is also restricted, making it difficult to make the amount of heat generated in the arrangement direction of the heater 22 symmetrical on the left and right. Also, when trying to increase the speed of the device as described above, the value of the current flowing through the conductive parts increases, and the difference between the left and right becomes large, so that the difference cannot be ignored. Below, we will explain the case where electricity is applied to all heat generating parts.

As shown in Figure 16, when electricity is applied to all the heating parts, 20% of the current also flows through the resistive heating elements 59 at both the left and right ends, and through the power supply lines 62C and 62D connected to them, which is different from the previous case. In contrast, the value of the current flowing through power supply line 62A is the same as before. In this case, in the first block, the current flowing through the first power supply line 62A is 100%, and the current flowing through the fourth power supply line 62D is 20%, so the sum of the squares of these, 10,400 (10,000 + 400), is the total heat generation of the power supply lines in the first block. In the second block, the current flowing through the first power supply line 62A is 80%, the current flowing through the second power supply line 62B is 20%, and the current flowing through the fourth power supply line 62D is 20%, so the sum of these squares, 7200 (6400 + 400 + 400), is the total heat generation amount of the power supply lines in the second block. The heat generation amount is also calculated in the same way in the other blocks.

As shown in the table and graph at the bottom of Figure 16, the total heat generation amount of each block is asymmetrical with respect to the fourth block in the center of the heat generation area. In particular, the second power supply line 62B connected to all the resistive heating elements 59 has a high current value of 120% downstream, i.e., in the seventh block, and the heat generation amount on the other side in the arrangement direction is greater than on the one side. Note that in this embodiment, each block is set to the same length so that small and large size paper can be heated evenly.

Next, in the heater 22 of this embodiment shown in FIG. 10, the heat generation amount of the power supply lines of each block when partial current is applied and unintended current division occurs is shown in FIG.
As shown in Fig. 17, the difference from Fig. 15 of this embodiment is that the portion extending in the arrangement direction of the second power supply line 62B, that is, the main heat generating portion of the second power supply line 62B, is divided into a second portion 62B2 and a fourth portion 62B4. Of these, the heat generation amount of each block of the second portion 62B2 is the same as the heat generation amount of each block of the second power supply line 62B shown in Fig. 15. In addition, the heat generation amount of the first power supply line 62A and the fourth power supply line 62D is the same as that in Fig. 15. Therefore, the total heat generation amount of each block in Fig. 17 is larger by the heat generation amount of the fourth portion 62B4 compared to Fig. 15. This is also the same in the case of full current supply described later.

The fourth portion 62B4 has no branches along the way, so the current value flowing through each block is the same at 100%. Therefore, the heat generation amount of each block in FIG. 17 is increased by 10,000 (the square of 100) from that in FIG. 15. For example, the heat generation amount of the first block is 20,025, which is the heat generation amount of the first block in FIG. 15, 10,000 added to 10,025.

For the above reasons, in FIG. 17, there is no change in the magnitude relationship of the total heat generation amount of each block compared to the case of FIG. 15. Therefore, even in FIG. 17, there is a deviation in the heat generation amount between one side and the other side in the arrangement direction. Specifically, the heat generation amount of the first block is the largest at 20,025, and the heat generation amount on one side in the arrangement direction is greater than that on the other side.

Also, as shown in Figure 18, even when the heater 22 in Figure 10 is fully energized, the total heat generation amount of each block is greater by the amount of heat generation of the fourth portion 62B4. Specifically, since 140% of the current flows through each block of the fourth portion 62B4, the heat generation amount of each block in Figure 18 is increased by 19,600 (the square of 140) from that in Figure 16, and for example, the heat generation amount of the first block is 30,000, which is the sum of 19,600 and the heat generation amount of the first block in Figure 15, 10,040.

For the above reasons, in FIG. 18, there is no change in the magnitude relationship of the total heat generation amount of each block compared to the case of FIG. 16. Therefore, even in FIG. 18, there is a deviation in the heat generation amount between one side and the other side in the arrangement direction. Specifically, the heat generation amount of the seventh block is the largest at 34,000, and the heat generation amount on the other side in the arrangement direction is greater than that on one side.

In this way, even in the heater 22 of FIG. 10, a deviation in the heat generation amount of the heater 22 occurs in the arrangement direction when the heater 22 is partially energized and when the heater 22 is fully energized. Specifically, when the heater 22 is partially energized, one side of the arrangement direction of the heater 22 (left side in FIG. 17) is the side that generates a large amount of heat, and the other side of the arrangement direction (right side in FIG. 17) is the side that generates a small amount of heat. Also, when the heater 22 is fully energized, the other side of the arrangement direction of the heater 22 (right side in FIG. 18) is the side that generates a large amount of heat, and one side of the arrangement direction (left side in FIG. 18) is the side that generates a small amount of heat.

When the above partial or full current is applied, the amount of current in the second portion 62B2 of the second power supply line 62B increases from one side in the arrangement direction to the other side. Also, when current is applied from the second electrode portion 61B to the first electrode portion 61A or the third electrode portion 61C, the resistive heating element 59 on the other side in the arrangement direction is positioned upstream in the current direction, and the resistive heating element 59 on one side is positioned downstream.

The above results are summarized in Tables 1 and 2. In each table, the "comparison configuration" refers to the heater in FIG. 14, and the "embodiment configuration" refers to the heater of this embodiment in FIG. 10. Table 1 shows the results of the comparison in the case of partial current conduction, and Table 2 shows the results of the comparison in the case of full current conduction. That is, the second line of Table 1 shows the results of FIG. 15, the third line shows the results of FIG. 17, and the second line of Table 2 shows the results of FIG. 16, and the third line shows the results of FIG. 18. In addition, each table compares the heat generation amount of the outermost block of the heat generation range by the heat generating part. Specifically, Table 1 compares the heat generation amount of the second block and the sixth block, and Table 2 compares the heat generation amount of the first block and the seventh block. In each table, the "heat generation amount difference" indicates the value obtained by subtracting the small block from the large block, and the "heat generation amount ratio" indicates the ratio of the small block to the large block.

As shown in Tables 1 and 2, there is no difference in the "difference in heat generation" between the "configuration of the embodiment" and the "configuration of the comparison" in both the case of partial current application and the case of full current application. Specifically, the "difference in heat generation" is 800 in the case of partial current application and 4000 in the case of full current application. The blocks with a large heat generation are also the same. However, in each case, the "ratio of heat generation" is larger in the "configuration of the embodiment" than in the "configuration of the comparison", and is closer to 1. Specifically, the "ratio of heat generation" is 0.88 and 0.72 for the "configuration of the comparison", while it is 0.95 and 0.88 for the "configuration of the embodiment". This is because in the "configuration of the embodiment", the heat generation of the fourth portion 62B4 is added equally to all blocks, so that the difference in the total heat generation of each block remains unchanged and only the absolute value of the total heat generation increases, so that the difference in the heat generation of each block becomes relatively smaller.

As described above, in this embodiment, by providing the second electrode portion 61B on one side in the arrangement direction and providing the folded-back portion (the third portion 62B3 and the fourth portion 62B4) on the second power supply line 62B, the difference in the amount of heat generated between one side and the other side in the arrangement direction of the heater 22 can be relatively reduced. Therefore, problems caused by temperature deviation of the heater 22, specifically, uneven images and uneven gloss on the paper, can be suppressed.

Next, we will explain an embodiment that further suppresses the difference between the left and right heat generation amounts of the heater 22. The embodiment shown in Figure 19 or Figure 21 below is a measure that can suppress the temperature difference when the heater 22 is fully energized as described above.

As shown in FIG. 19, in this embodiment, the third portion 62B3 connecting the second portion 62B2 and the fourth portion 62B4 is positioned closer to the center of the arrangement direction of the seventh block than in the embodiment shown in FIG. 10. In other words, in the arrangement direction, the third portion 62B3 is positioned on one side of the arrangement direction relative to the first portion 62B1 connected to the resistive heating element 59 of the seventh block.

By arranging the third portion 62B3 as described above, the amount of heat generated by the power supply line of the seventh block can be reduced for the reasons explained below, compared to when the third portion 62B3 is arranged at the other end of the arrangement direction of the seventh block, that is, at a position corresponding to the other end of the arrangement direction of the resistive heating element 59 arranged at the very end (rightmost end) on the other side of the arrangement direction (as in FIG. 10).

First, as shown in FIG. 19, by arranging the third portion 62B3 closer to the center of the seventh block (on one side from the other end), the length of the fourth portion 62B4 within the seventh block is shortened. This makes it possible to reduce the amount of heat generated by the seventh block. Therefore, the further the third portion 62B3 is arranged on one side, the smaller the amount of heat generated by the seventh block becomes.

Secondly, the amount of heat generated by the second portion 62B2 of the seventh block can be reduced. In other words, the portion of the second portion 62B2 to the right of the third portion 62B3 (the other side in the arrangement direction) only receives the current that flows through the rightmost resistive heating element 59, so the current value is 20%. Also, the portion of the second portion 62B2 to the left of the third portion 62B3 (the other side in the arrangement direction) receives a current value of 120%. Therefore, the amount of heat generated is smaller than when the entire second portion 62B2 of the seventh block is 120%, as shown in FIG. 18. Therefore, the amount of heat generated by the seventh block is smaller the further the third portion 62B3 is positioned to one side.

As described above, by arranging the third portion 62B3 on one side of the seventh block rather than the other end, the amount of heat generated by the power supply line of the seventh block can be reduced. Since the seventh block is the block that generates the greatest amount of heat when fully energized (see FIG. 18), by reducing the amount of heat generated by the seventh block and bringing it closer to the amount of heat generated by the sixth block, the temperature deviation between the amount of heat generated on one side and the other side in the arrangement direction of the heaters 22 can be reduced. Therefore, problems caused by temperature deviations in the heaters 22, specifically uneven images and uneven gloss on the paper, can be suppressed.

As shown in FIG. 19, in the seventh block, the length of the second part 62B2 on one side of the arrangement direction (left side in FIG. 19) from the third part is L1, and the length of the second part 62B2 on the other side of the arrangement direction (right side in FIG. 19) is L2. In this embodiment, as an example, L1:L2 is 0.88:0.12. In other words, the ratio of the part of the second part 62B2 with a current value of 120% to the part with a current value of 20% is also 0.88:0.12. In addition, the length of the fourth part 62B4 is 0.88 times that in FIG. 18 (when L2 is 0). Therefore, the heat generation amount of the power supply line of the seventh block is (14400×0.88)+(20×20×0.12)+(19600×0.88)=29968. Therefore, as shown in FIG. 20, since the heat generation amount of the first block is 30,000, there is almost no difference between the heat generation amounts of the first block and the seventh block, and the ratio of the heat generation amounts described above is approximately 1. This makes it possible to further reduce the temperature deviation in the heat generation amount between one side and the other side of the arrangement direction of the heater 22, and suppresses problems caused by the temperature deviation of the heater 22, specifically, unevenness in the image and uneven gloss of the paper.

As described above, the amount of heat generated by the seventh block decreases as the length L1 is reduced, so the optimal ratio of length L1 to length L2 can be determined by taking into account the amount of heat generated on one side and the other side of the arrangement direction of the heater 22 and the temperature distribution in the arrangement direction of the fixing belt 20.

In addition, in this embodiment, the passing position in the arrangement direction of the other end P1a of the widest paper P1 passed through the fixing device coincides with the third portion 62B3. This allows the amount of heat generated by the fourth portion 62B4 to be efficiently used to heat the fixing belt 20 in the paper passing range, so that the heater 22 can efficiently heat the paper passing range of the fixing belt 20. However, in the embodiment of FIG. 10, the passing position of the third portion 62B3 and the other end P1a may also coincide.

In addition to moving the position of the third portion 62B3 toward the center of the seventh block, the same effect can be obtained by increasing the width of the third portion 62B3 in the arrangement direction as shown in FIG. 21. That is, in this embodiment, by increasing the width of the third portion 62B3 in the arrangement direction, the resistance value of the third portion 62B3 and the portion of the second portion 62B2 and the fourth portion 62B4 connected to the third portion 62B3 (see range C in FIG. 21) is reduced. This reduces the heat generation amount of this portion (see the above-mentioned formula 1), and the heat generation amount of the seventh block can be reduced. Therefore, the temperature difference between the heat generation amount on one side and the other side of the arrangement direction of the heater 22 can be reduced, and defects caused by the temperature difference of the heater 22, specifically, uneven image and uneven gloss of the paper, can be suppressed. As in the above-mentioned embodiment, the size of range C can be set taking into account the difference between the heat generation amount of the first block and the heat generation amount of the seventh block.

21 is an example of a configuration in which the heat generation amount of the second part 62B2 and the fourth part 62B4 in the seventh block (or the position overlapping the resistive heating element 59 on the other side in the arrangement direction) is partially reduced. That is, in FIG. 21, the third part 62B3 is made thicker to partially increase the short-side length of the second part 62B2 and the fourth part 62B4 connected to the third part 62B3. This reduces the resistance value of that part, and reduces the heat generation amount of the second part 62B2 and the fourth part 62B4 in the seventh block. However, without being limited to this, for example, the resistance value per unit length in the arrangement direction of at least one of the second part 62B2 and the fourth part 62B4 in the seventh block, part or all, can be made smaller than the resistance value per unit length of the other power supply line (for example, the resistance value per unit length in the direction intersecting the arrangement direction of the third part 62B3 of the second power supply line 62B). This reduces the amount of heat generated from this portion, thereby reducing the amount of heat generated by the seventh block, and further reducing the temperature deviation between the amount of heat generated on one side and the other side of the arrangement direction of the heater 22. In addition, methods for reducing the resistance value per unit length include increasing the thickness or width (not limited to the portion connected to the third portion 62B3, but also the width of other portions) or changing the material. However, for processing reasons, the power supply lines are often made of the same material and are provided with the same thickness. Therefore, in this case, the resistance values of these portions can be reduced by increasing the width of the second portion 62B2 and the fourth portion 62B4 in the seventh block in the direction intersecting the arrangement direction.

22, the width G1 of the fourth portion 62B4 in the direction intersecting the arrangement direction is smaller than the width of the other power supply lines, and in particular, is smaller than the width G2 of the second portion 62B2 in the direction intersecting the arrangement direction. By reducing the width G1 of the fourth portion 62B4 in the direction intersecting the arrangement direction, the resistance value of this portion can be increased, and the heat generation amount of the fourth portion 62B4 can be increased. Therefore, the ratio of the heat generation amount of the fourth portion 62B4 to the total heat generation amount of the power supply lines of each block can be increased, and the "heat generation amount ratio" in Tables 1 and 2 described above can be made closer to 1. In other words, the difference in the heat generation amount between one side and the other side of the arrangement direction of the heater 22 can be relatively reduced. Therefore, defects caused by the temperature deviation of the heater 22, specifically, image unevenness and gloss unevenness of the paper can be suppressed. The configuration of this embodiment can obtain the above effects in both cases of full current and partial current.

The embodiment of FIG. 22 is an example of a configuration in which the resistance value per unit length in the arrangement direction of the fourth portion 62B4 is increased, and is not limited to the configuration in which the width in the direction intersecting the arrangement direction of the fourth portion 62B4 is reduced as in FIG. 22. Specifically, the resistance value per unit length in the arrangement direction of the fourth portion 62B4 may be increased by reducing the thickness of the fourth portion 62B4 or changing the material. However, since the power supply lines are often made of the same material and are provided with the same thickness for processing reasons, a configuration in which the width in the direction intersecting the arrangement direction of the fourth portion 62B4 is reduced as in FIG. 22 is particularly useful. As a result, as in the above embodiment, the ratio of the heat generation amount of the fourth portion 62B4 to the total heat generation amount of the power supply lines of each block can be increased, and the difference in heat generation amount between one side and the other side of the arrangement direction of the heater 22 can be relatively reduced.

As shown in FIG. 23, in this embodiment, the image forming apparatus 1 is provided with a blower 110 as a blowing means. The blower 110 is provided on the other side of the arrangement direction of the fixing device 9 relative to the center position J in the arrangement direction (opposite the side where the electrode parts 61A to 61C in FIG. 10 are arranged). The blower 110 takes in air from an air intake 102a provided in the housing 102 of the image forming apparatus, and blows air in a direction intersecting the arrangement direction toward the other end of the heater 22 (fixing device 9) in the arrangement direction (see the direction of the arrow in FIG. 23). In this embodiment, the blower 110 particularly blows air in a direction perpendicular to the arrangement direction toward the other end of the heater 22 in the arrangement direction.

The air blown by the blower 110 can remove heat from the components in the fixing device 9, such as the heater 22 and the fixing belt 20, on the side that generates the most heat when fully energized. This makes it possible to suppress defects caused by the difference in the amount of heat generated between one side and the other side of the arrangement direction of the heater 22 when fully energized, specifically uneven image and uneven gloss on the paper. By providing the blower 110 on one side of the arrangement direction, it is also possible to suppress defects caused by the difference in the amount of heat generated between one side and the other side of the arrangement direction of the heater 22 when partially energized, specifically uneven image and uneven gloss on the paper.

As shown in FIG. 24, in this embodiment, a first blower 110A serving as a first blowing means is provided on the other side of the arrangement direction from the fixing device 9, and a second blower 110B serving as a second blowing means is provided on one side of the arrangement direction from the fixing device 9.

The first blower 110A and the second blower 110B can generate an air flow from the other side of the arrangement direction to one side of the heater 22 (fixing device 9) (see the arrow direction in FIG. 24). This allows the heat on the other side of the arrangement direction to be moved to one side. Therefore, when the heater 22 is fully energized, defects caused by the difference in the amount of heat generated between one side and the other side of the arrangement direction of the heater 22, specifically, uneven image and uneven gloss on the paper, can be suppressed. Note that by providing each blower 110A, 110B so that the blowing direction is opposite to that in FIG. 24, defects caused by the difference in the amount of heat generated between one side and the other side of the arrangement direction of the heater 22, when the heater 22 is partially energized, specifically, uneven image and uneven gloss on the paper, can be suppressed. Also, only one of the blowers 110A, 110B may be provided.

The present invention is particularly suitable for heaters that are miniaturized in the direction intersecting the arrangement direction. In other words, as described above, if the size of the heater 22 in the direction intersecting the arrangement direction is to be reduced, the size of the power supply line in the direction intersecting the arrangement direction must be reduced, and the amount of heat generated from the power supply line becomes relatively large, which increases the influence. Specifically, it is preferable to apply the present invention to a heater 22 in which the ratio (R/Q) of the dimension R in the direction intersecting the arrangement direction of the resistance heating element 59 to the dimension Q in the direction intersecting the arrangement direction of the heater 22 (substrate 50) shown in FIG. 25 is 25% or more. Furthermore, it is more preferable to apply the present invention to a heater 22 in which the dimension ratio (R/Q) in the direction intersecting the arrangement direction is 40% or more. By applying the present invention to such a small heater 22, a greater effect can be expected.

Next, the experimental results of the temperature deviation occurring between the center side and the end side of the heater 22 in the arrangement direction when the ratio of dimensions (R/Q) in the direction intersecting the arrangement direction is changed will be described. In the experiment, heaters 22 having the above-mentioned configuration were prepared with the ratio of dimensions (R/Q) in the direction intersecting the arrangement direction of 20% or more and less than 25%, 25% or more and less than 40%, 40% or more and less than 70%, and 70% or more and less than 80%, respectively. Under the condition of the heater alone, a predetermined voltage was applied to all the resistance heating elements of the heater, and the surface temperatures of the center and end sides of the heater arrangement direction were measured using an infrared thermography FLIR T620 manufactured by FLIR Systems. The above experimental results are shown in Table 1. In the results of Table 1, the temperature difference between the center side and the end side was less than 2°C as ○, the temperature difference between 2°C or more and less than 5°C as △, and the temperature difference of 5°C or more as ×. In addition, if the ratio of dimensions in the direction intersecting the arrangement direction (R/Q) is set to 80% or more, there will be no space to place the power supply wires unless the dimensions in the direction intersecting the heater arrangement direction are made extremely large, so this was not included in the experiment.

As shown in Table 3, the temperature difference between the center and end of the heater increased as the ratio of dimensions in the direction intersecting the arrangement direction (R/Q) increased. Specifically, a ratio of 20% or more and less than 25% was rated as ◯, whereas a ratio of 25% or more and less than 40% changed to △, and a ratio of 40% or more and less than 70%, and a ratio of 70% or more and less than 80% changed to ×. As can be seen from these results, the temperature unevenness in the heater arrangement direction becomes noticeable when the ratio of dimensions in the direction intersecting the arrangement direction (R/Q) is 25% or more, and is particularly noticeable when it is 40% or more. Therefore, it is preferable to apply the above configuration of this embodiment to heaters with such dimensional ratios to suppress the temperature deviation.

In addition, to suppress the temperature variation of the heater 22 described above, a resistive heating element having PTC characteristics may be used. PTC characteristics are characteristics in which the resistance value increases as the temperature increases (when a constant voltage is applied, the heater output decreases). By using a heating element with PTC characteristics, it is possible to achieve high output at low temperatures and high speed rise in temperature, and low output at high temperatures to suppress overheating. For example, if the TCR coefficient of the PTC characteristics is set to about 300 to 4000 ppm/degree, it is possible to reduce costs while ensuring the resistance value required for the heater. It is more preferable to set the TCR coefficient to 500 to 2000 ppm/degree.

The temperature coefficient of resistance (TCR) can be calculated using the following formula (2). In formula (2), T0 is the reference temperature, T1 is the arbitrary temperature, R0 is the resistance value at reference temperature T0, and R1 is the resistance value at arbitrary temperature T1. For example, in the heater 22 described above and shown in FIG. 7, if the resistance value between the first electrode portion 61A and the second electrode portion 61B is 10Ω (resistance value R0) at 25°C (reference temperature T0) and 12Ω (resistance value R1) at 125°C (arbitrary temperature T1), the temperature coefficient of resistance is 2000 ppm/°C according to formula (2).

The heater to which the present invention is applied is not limited to the heater 22 having a block-shaped (square-shaped) resistance heating element 59 as shown in FIG. 7, etc., but can also be applied to heaters 22 having a resistance heating element 59 shaped like a folded straight line as shown in FIG. 26(a) or FIG. 26(b), or heaters having resistance heating elements of other shapes. In the figure, the colored parts indicate the resistance heating element 59. FIG. 26(a) shows an example in which the power supply lines 62A, 62D formed along the arrangement direction of the heater 22 extend in a direction intersecting the arrangement direction. On the other hand, FIG. 26(b) shows an example in which the resistance heating element 59 is formed including the area bent from the power supply lines 62A, 62D formed along the arrangement direction of the heater 22 in a direction intersecting the arrangement direction.

In addition to the fixing device described above, the present invention can also be applied to fixing devices such as those shown in Figures 27 to 29. The configuration of each fixing device shown in Figures 27 to 29 will be briefly described below.

First, the fixing device 9 shown in FIG. 27 has a pressure roller 90 disposed on the opposite side of the fixing belt 20 from the pressure roller 21 side, and is configured so that the fixing belt 20 is sandwiched and heated by this pressure roller 90 and heater 22. On the other hand, on the pressure roller 21 side, a nip forming member 91 is disposed on the inner circumference of the fixing belt 20. The nip forming member 91 is supported by a stay 24, and the fixing belt 20 is sandwiched between the nip forming member 91 and the pressure roller 21 to form a fixing nip N.

Next, in the fixing device 9 shown in FIG. 28, the pressure roller 90 described above is omitted, and the heater 22 is formed in an arc shape to match the curvature of the fixing belt 20 in order to ensure the circumferential contact length between the fixing belt 20 and the heater 22. The rest of the configuration is the same as that of the fixing device 9 shown in FIG. 27.

Finally, the fixing device 9 shown in FIG. 29 will be described. The fixing device 9 is composed of a heating assembly 92, a fixing roller 93 as a fixing member, and a pressure assembly 94 as an opposing member. The heating assembly 92 has the heater 22 and heating device 19 described in the previous embodiment, and a heating belt 120 as a belt member. The fixing roller 93 is composed of a solid iron core 93a, an elastic layer 93b formed on the surface of the core 93a, and a release layer 93c formed on the outside of the elastic layer 93b. A pressure assembly 94 is provided on the opposite side of the fixing roller 93 from the heating assembly 92 side. The pressure assembly 94 has a nip forming member 95 and a stay 96 arranged therein, and a pressure belt 97 arranged rotatably so as to enclose the nip forming member 95 and the stay 96. Then, a paper P is passed through the fixing nip N2 between the pressure belt 97 and the fixing roller 93, and the image is fixed by heating and pressing it.

In the fixing device 9 shown in FIG. 29, the heating assembly 92 heats the fixing roller 93. As described above, if there is a difference in the amount of heat generated between one side and the other side of the heater 22 in the arrangement direction (depth direction in the figure), a temperature difference will also occur between one side and the other side of the arrangement direction of the fixing roller 93.

In the fixing devices of Figures 27 to 29 above, by adopting the heater configuration shown in Figure 10, the difference in heat generation amount in the arrangement direction of the heaters 22 can be relatively small. Therefore, problems caused by temperature deviation of the heaters 22, specifically, uneven images and uneven gloss on the paper, can be suppressed.

In addition, devices equipped with a heating device having the heating body of the present invention are not limited to fixing devices as described in the above embodiment, but may also be drying devices that dry ink applied to paper, or thermocompression devices such as laminators that thermocompress a film as a covering member onto the surface of a sheet such as paper, or heat sealers that thermocompress the seal portion of a packaging material. By applying the heating body of the present invention to such devices, the difference in the amount of heat generated in the arrangement direction of the heating body can be relatively small. Therefore, problems caused by temperature deviations in the heating body can be suppressed.

Recording media include paper P (plain paper), as well as cardboard, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, overhead projector sheets, plastic film, prepreg, copper foil, etc.

The configuration of the heating body in each embodiment described above, that is, the configuration in which the second conductive portion is provided with a folded portion, is particularly suitable for application to a heating body in which the portion extending in the arrangement direction of the power feed line generates a large amount of heat. For example, in the heater 22 shown in FIG. 30, the width in the direction intersecting the arrangement direction of the portions 62A1, 62C1, and 62D1 extending in the arrangement direction of the first power feed line 62A, the third power feed line 62C, and the fourth power feed line 62D, and the second portion 62B2 of the second power feed line 62B are smaller than the width in the arrangement direction of the other power feed lines, particularly in this embodiment, the width in the arrangement direction of the portions 62A2, 62C2, and 62D2 extending in the direction intersecting the arrangement direction of the first power feed line 62A, the third power feed line 62C, and the fourth power feed line 62D, and the width in the arrangement direction of the first portion 62B1 of the second power feed line 62B. In such a heater 22, the portions of the first power feed line 62A, the third power feed line 62C, and the fourth power feed line 62D extending in the arrangement direction and the second portion 62B2 of the second power feed line 62B generate large amounts of heat. In particular, the deviation of the amount of heat generated by the heater 22 in the arrangement direction increases as the amount of heat generated by the first power feed line 62A or the second portion 62B2 increases. Therefore, by providing a folded portion in the second power feed line 62B for such a heater 22, the deviation of the heater 22 in the arrangement direction can be effectively reduced relatively. Furthermore, by reducing the width of the portions of the power feed lines extending in the arrangement direction as in this embodiment, the dimension of the heater 22 in the direction intersecting the arrangement direction can be reduced, and the heater 22 can be made more compact. In the present embodiment, the widths of the portions 62A1, 62C1, and 62D1 of the first power feed line 62A, the third power feed line 62C, and the fourth power feed line 62D extending in the arrangement direction and the second portion 62B2 of the second power feed line 62B in the direction intersecting the arrangement direction are all smaller than the widths of the portions 62A2, 62C2, and 62D2 of the first power feed line 62B extending in the direction intersecting the arrangement direction and the first portion 62B1, but any one of these or a part of these may have a smaller width in the direction intersecting the arrangement direction. In addition, as an example in which the resistance value per unit length in the arrangement direction of the portions (62A1, 62C1, and 62D1 and the second portion 62B2 of the second power feed line 62B) extending in the arrangement direction of the power feed lines is large, the case in which the width in the direction intersecting the arrangement direction is small is illustrated. However, the resistance per unit length in the arrangement direction of the power supply lines may be large if the thickness of the parts extending in the arrangement direction of the power supply lines is small or if a material with a high resistance value is used. Even in such a configuration, it is preferable to apply the characteristic parts of the heater of the above embodiment of the present invention.

1 Image forming apparatus 9 Fixing device 19 Heating device 20 Fixing belt (heated member or belt member or fixing member)
21 Pressure roller (opposing member or pressure member)
22 Heater (heating body)
59 Resistance heating element (heating element)
60 Heat generating portion 61 Electrode portion 62 Power supply line (conductor)
67A: First conductive part; 67B: Second conductive part; 67C: Third conductive part; 110: Blower (blowing means)
A: Paper feed direction B: Array direction or heater longitudinal direction F: Center position in the array direction of the resistance heating elements H: Center position in the array direction of the resistance heating elements K1, K2: Connection position N: Fixing nip (nip portion)
P Paper (recording medium or heated object)
Q: Dimension in the direction intersecting the heater arrangement direction R: Dimension in the direction intersecting the resistance heating element arrangement direction Y: Direction intersecting the heater arrangement direction (short side direction of the heater)

JP 2016-62024 A

Claims (18)

a first conductive portion, a second conductive portion, and a third conductive portion;
A first electrode portion, a second electrode portion, and a third electrode portion,
A heating element including a first heating portion and a second heating portion each of which is constituted by at least one resistive heating element,
The resistance heating elements are arranged in a plurality of rows,
In an arrangement direction of the plurality of resistive heating elements, the first electrode portion, the second electrode portion, and the third electrode portion are provided on one side of a center of the plurality of resistive heating elements,
the first electrode portion is connected to the first heat generating portion via the first conductive portion,
the second electrode portion is connected to the first heat generating portion and the second heat generating portion via the second conductive portion;
the third electrode portion is connected to the second heat generating portion via the third conductive portion,
The second conductive portion is characterized in that a portion extending from one resistive heating element on the one side of the center of the multiple resistive heating elements merges with a portion extending from another resistive heating element to extend to the other side opposite the one side, and then folds back to be connected to the second electrode portion. the second conductive portion has a second portion, a third portion, and a fourth portion;
The second portion extends in an arrangement direction of the plurality of resistive heating elements,
the third portion is a portion that connects the second portion and the fourth portion to each other at a position overlapping the resistive heating element that is disposed at the end of the other side in an arrangement direction of the plurality of resistive heating elements or on the other side of the position overlapping the resistive heating element that is disposed at the end of the other side,
2. The heating element according to claim 1, wherein the fourth portion extends from a connection position with the third portion toward one side in an arrangement direction of the plurality of resistive heating elements and is connected to the second electrode portion. The second conductive portion further includes a first portion,
If a direction intersecting the arrangement direction of the plurality of resistance heating elements and different from the thickness direction of the heating elements is defined as a direction intersecting the arrangement direction,
the first portion extends from each of the resistive heating elements in a direction intersecting the arrangement direction and is connected to the second portion,
a connection position between the resistive heating element disposed furthest on the other side and the first portion is provided on the other side of a central position of the resistive heating element in an arrangement direction of the plurality of resistive heating elements,
The heating element according to claim 2 , wherein the third portion is disposed on the one side of the connection position in an arrangement direction of the plurality of resistance heating elements. The heating element according to claim 2, wherein the fourth portion is provided over the entire area of the first heating portion and the second heating portion in the arrangement direction of the plurality of resistive heating elements. If a direction intersecting the arrangement direction of the plurality of resistance heating elements and different from the thickness direction of the heating elements is defined as a direction intersecting the arrangement direction,
5. The heating element according to claim 2, wherein a resistance value per unit length of a part or all of a portion of at least one of the second portion or the fourth portion that overlaps with the resistive heating element arranged furthest on the other side in an arrangement direction of the multiple resistive heating elements is made relatively smaller than a resistance value per unit length of the third portion in a direction intersecting the arrangement direction. The heating element according to claim 5, wherein the width of the third portion in the direction of arrangement of the plurality of resistive heating elements is greater than the width of the fourth portion in a direction intersecting the direction of arrangement. The heating element according to any one of claims 2 to 6, wherein the resistance value per unit length in the arrangement direction of the plurality of resistive heating elements in the fourth portion is greater than the resistance value per unit length in the arrangement direction of the plurality of resistive heating elements in the second portion. If a direction intersecting the arrangement direction of the plurality of resistance heating elements and different from the thickness direction of the heating elements is defined as a direction intersecting the arrangement direction,
The heating element according to claim 7 , wherein a width of the fourth portion in a direction intersecting the arrangement direction is smaller than a width of the second portion in a direction intersecting the arrangement direction. the second conductive portion has a first portion;
If a direction intersecting the arrangement direction of the plurality of resistance heating elements and different from the thickness direction of the heating elements is defined as a direction intersecting the arrangement direction,
the first portion extends from each of the resistive heating elements in a direction intersecting the arrangement direction and is connected to the second portion,
9. The heating element according to claim 2, wherein the width in the arrangement direction of at least one of the first portion, the portion of the first conductive portion extending in a direction intersecting the arrangement direction of the multiple resistive heating elements, and the portion of the third conductive portion extending in a direction intersecting the arrangement direction is wider than the width in the direction intersecting the arrangement direction of at least one of the second portion, the portion of the first conductive portion extending in the arrangement direction of the multiple resistive heating elements, and the portion of the third conductive portion extending in the arrangement direction of the multiple resistive heating elements. the second conductive portion has a first portion;
If a direction intersecting the arrangement direction of the plurality of resistance heating elements and different from the thickness direction of the heating elements is defined as a direction intersecting the arrangement direction,
the first portion extends from each of the resistive heating elements in a direction intersecting the arrangement direction and is connected to the second portion,
9. The heating element according to claim 2, wherein all of the widths in the arrangement direction of the multiple resistive heating elements of the first portion, the portion of the first conductive portion extending in a direction intersecting the arrangement direction, and the portion of the third conductive portion extending in a direction intersecting the arrangement direction are wider than the width in the direction intersecting the arrangement direction of at least one of the second portion, the portion of the first conductive portion extending in the arrangement direction of the multiple resistive heating elements, and the portion of the third conductive portion extending in the arrangement direction of the multiple resistive heating elements. If a direction intersecting the arrangement direction of the plurality of resistance heating elements and different from the thickness direction is defined as a direction intersecting the arrangement direction,
11. The heating element according to claim 1, wherein a ratio of a dimension of the resistance heating element in a direction intersecting the arrangement direction to a dimension of the heating element in a direction intersecting the arrangement direction is 25% or more. If a direction intersecting the arrangement direction of the plurality of resistance heating elements and different from the thickness direction is defined as a direction intersecting the arrangement direction,
11. The heating element according to claim 1, wherein a ratio of a dimension of the resistance heating element in a direction intersecting the arrangement direction to a dimension of the heating element in a direction intersecting the arrangement direction is 40% or more. A heating device equipped with a heating element according to any one of claims 1 to 12. A heating device equipped with a heating element described in claim 2 or any one of claims 3 to 12 relating to claim 2, wherein in the arrangement direction of the multiple resistance heating elements, the other end of the third portion is at the same position as the other end of the heated object passing through the heating device. A fixing device that includes the heating device according to claim 13 or 14 and fixes an image on a recording medium. An image forming apparatus equipped with a heating device or a fixing device according to any one of claims 13 to 15. 17. The image forming apparatus according to claim 16, further comprising a blower,
If a direction intersecting the arrangement direction of the plurality of resistance heating elements and different from the thickness direction of the heating elements is defined as a direction intersecting the arrangement direction,
The image forming apparatus, wherein the air blowing unit generates an air current in a direction intersecting the arrangement direction of the plurality of resistance heating elements of the heating body toward the other side of the center position of the arrangement direction of the plurality of resistance heating elements of the heating body. 17. The image forming apparatus according to claim 16, further comprising a blower,
The air blowing unit generates an air flow from the other side to the one side in a direction in which the plurality of resistance heating elements are arranged with respect to the heating element.

Images