JP2019078817A - Heater and image forming apparatus - Google Patents

Abstract

To provide a heater that can prevent the occurrence of unevenness in heat applied to a sheet to improve the quality of an image, and an image forming apparatus.SOLUTION: A heater (5) according to one embodiment comprises: a plurality of heat elements (520 to 528) that are respectively selectively supplied with power from a power supply in a conveyance direction of a recording medium (P) on which an image is formed and heat the recording medium symmetrically with respect to a central axis along the conveyance direction of the recording medium; a first electrode (500) that is connected to the power supply at one portion, connected commonly to the plurality of heat elements at one side in the conveyance direction, and connects the heat elements at symmetrical positions with respect to the central axis to the power supply at the same resistance value; and second electrodes (504 to 512) that are connected respectively to the plurality of heat elements on the other side in the conveyance direction, and connect at least the heat elements at symmetrical positions with respect to the central axis to the power supply at the same resistance value.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a heater and an image forming apparatus.

  A first electrode which is used in the fixing portion of the electrode image forming apparatus and includes a plurality of divided heating elements and which is commonly connected between the plurality of heating elements and the power supply, and a part of each of the electrodes There is known a heater including a second electrode connected to each of a group of resistors including the power source and a power source.

JP, 2016-6501, A

  In the heater shown as the background art, the first electrode simply connects the plurality of resistors and the power supply without considering the resistance value between the plurality of heaters and the power supply. In addition, the second electrode simply connects the plurality of resistor groups with the power supply without considering the resistance value of the conductor between the plurality of resistor groups and the power supply. In such a heater, the difference in resistance between the resistor and the resistor group and the power supply causes a difference in heat generation between the resistor and the resistor group, so the heat applied to the recording medium Unevenness may occur and the quality of the image after fixing may be degraded.

  An object of the present invention is to provide a heater and an image forming apparatus capable of improving the quality of an image without causing unevenness in heat applied to a recording medium.

  In order to solve the problems described above, the heaters according to one embodiment are each selectively supplied with power from the power source in the direction of the conveyance direction of the recording medium to be subjected to image formation to generate heat. A plurality of heating resistors for heating the recording medium symmetrically with respect to a central axis along the transport direction, and one power source are connected to the power source, and the heating resistors are commonly used in one of the transport direction and the plurality of heating resistors. It is connected, and the first electrodes connecting the heating resistors at symmetrical positions with respect to the central axis and the power supply with the same resistance value, and the plurality of heating resistors are connected in the other of the transport direction A plurality of second electrodes are provided, which connect the heating resistors at least at symmetrical positions with respect to the central axis and the power supply with the same resistance value.

FIG. 1 is a diagram showing a configuration of an image forming apparatus according to an embodiment. FIG. 2 is a view showing the configuration of an image forming unit for black shown in FIG. 1; FIG. 2 is a view showing the configuration of a fixing device shown in FIG. 1; It is XY sectional drawing of the heater shown by FIG. FIG. 5 is a Y-Z plan view of the heater shown in FIG. 4; It is a figure which shows the connection of the terminal of the heater shown by FIG. 5, and the switch circuit which connects these with a power supply selectively. It is a figure which shows the structure of the control apparatus shown by FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the embodiment, the same components are denoted by the same reference numerals. Moreover, in each figure, the size of each component may differ from the time of implementation, and between each figure, the size of each component and the ratio are not constant. Further, in the following drawings, some components may be omitted as appropriate in order to avoid complicating the drawings and clarify them.

[MFP10]
FIG. 1 is a diagram showing the configuration of an image forming apparatus according to the embodiment. In FIG. 1, the image forming apparatus is a multi-function peripheral (MFP), a printer, a copying machine, etc., and in the following description, the MFP 10 is a specific example. The main body 11 of the MFP 10 includes an operation panel 14 at an upper portion, and the operation panel 14 includes various keys and a touch panel display unit.

[Printer unit 17]
The main body 11 of the MFP 10 includes a control device 36 in the upper portion and a printer unit 17 in the central portion, and a plurality of sheet feeding cassettes 18 each storing any of sheets P of a plurality of types of sizes in the lower portion. The printer unit 17 is a tandem-type color laser printer, and includes a photosensitive drum and a scanning head 19 including an LED as an exposure device. The printer unit 17 processes image data read by a scanner, image data generated by a personal computer, etc., scans a photosensitive drum with a light beam from the scanning head 19, and obtains an image obtained by processing the image data. On a sheet P.

  The printer unit 17 is an image forming unit 20Y for each color of yellow (Y), magenta (M), cyan (C) and black (K) on the lower side of the intermediate transfer belt 21 and in parallel along the upstream to the downstream side. , 20M, 20C, and 20K. The printer unit 17 also includes a plurality of scanning heads 19 corresponding to the image forming units 20Y, 20M, 20C, and 20K. The image forming units 20Y, 20M, 20C, and 20K have the same configuration.

  FIG. 2 is a diagram showing the configuration of the image forming unit 20K for black shown in FIG. The image forming unit 20K has a photosensitive drum 22K of an image carrier. The image forming unit 20K includes a charger 23K, a developer 24K, a primary transfer roller 25K, a cleaner 26K, and a blade 27K around the photosensitive drum 22K along the rotational direction t. At the exposure position of the photosensitive drum 22K, light is irradiated from the scanning head 19K to form an electrostatic latent image.

  The charger 23K of the image forming unit 20K uniformly charges the surface of the photosensitive drum 22K. The developing device 24K supplies a two-component developer including a black toner and a carrier to the photosensitive drum 22K by the developing roller 24a to which a developing bias is applied, to develop the electrostatic latent image. The cleaner 26K removes residual toner on the surface of the photosensitive drum 22K using a blade 27K.

  Further, as shown in FIG. 1, the intermediate transfer belt 21 is stretched around the driving roller 31 and the driven roller 32 and moves cyclically. Also, the intermediate transfer belt 21 faces and contacts the photosensitive drums 22Y, 22M, 22C, and 22K. A primary transfer voltage is applied by the primary transfer rollers 25Y, 25M, 25C, 25K to the positions facing the photosensitive drums 22Y, 22M, 22C, 22K of the intermediate transfer belt 21, and the photosensitive drums 22Y, 22M, 22C, 22K The upper toner image is primarily transferred to the intermediate transfer belt 21. However, in FIG. 1, for convenience of illustration, the reference numerals 25Y, 25M and 25C are not shown, but the reference numeral 25K is attached only to the temporary transfer roller on the photosensitive drum 22K.

  The secondary transfer roller 33 is disposed to face the driving roller 31 that stretches the intermediate transfer belt 21. While the sheet P passes between the driving roller 31 and the secondary transfer roller 33, the secondary transfer voltage is applied to the sheet P by the secondary transfer roller 33, and the toner image on the intermediate transfer belt 21 is transferred onto the sheet P Next transferred. Further, a fixing device 4 is provided downstream of the secondary transfer roller 33.

[Fixing device 4]
FIG. 3 is a view showing the configuration of the fixing device 4 shown in FIG. As shown in FIG. 3, the fixing device 4 includes a heating device 400 that is driven to rotate in the S direction, and a pressure roller 440 that rotates according to the rotation of the heating device 400. The pressure roller 440 has a protective layer 442 made of PFA (copolymer of tetrafluoroethylene (C ₂ F ₄ ) and perfluoroalkoxyethylene), a silicone sponge layer 444 with a thickness of about 5 mm, and a diameter of 10 mm. And a degree of iron core 446.

  The endless fixing belt 402 of the heating device 400 is provided, and the fixing belt 402 has a front surface 404 and a rear surface 406. In the fixing belt 402, a heat insulating silicone rubber layer having a thickness of about 200 μm is formed on a base layer such as polyimide (PI) having a thickness of 70 μm, Ni having a thickness of about 70 μm, and SUS (stainless steel) having a thickness of 70 μm. It has a multi-layered structure. The heating device 400 further includes a heater 50 that is pressed to the pressure roller 440 side with the fixing belt 402 and forms a fixing nip portion that heats the sheet P. With such a configuration, the heat responsiveness of the fixing nip portion in the fixing device 4 is higher than that of the fixing nip portion heated by the halogen lamp.

[Heater 50]
4 is an X-Y cross-sectional view of the heater 50 shown in FIG. FIG. 5 is a Y-Z plan view of the heater 50 shown in FIG. FIG. 6 shows the connection between the terminals T502, T504, T506, T508-1, 508-2, T510 and T512 of the heater 1 shown in FIG. 5 and the switch circuit 56 for selectively connecting these to the power supply. FIG.

  As shown in FIG. 4 to FIG. 6, the heater 50 is formed of a common side silver electrode 500, 514 and an individual side silver electrode 504, 506, 508, 510, 512 formed on a ceramic substrate 518, and resistive heating. A surface protection layer 516 covering the layer 52, the ceramic substrate 518, the common side silver electrodes 500 and 514, the individual side silver electrodes 504, 506, 508, 510 and 512, and the resistive heating layer 52, and holding these components And a holder 519 made of heat resistant resin. In the actual MFP 10, the heater 50 is formed in an elongated rectangular shape of about 360 mm in the longitudinal direction (Z-axis direction) and about 10 mm in the short direction (Y direction).

  The heater 50 includes six silver electrodes 500, 504, 506, 508, 510, 512 formed on a ceramic substrate 518 using silver as a raw material. A convex portion 502 is provided at a portion corresponding to the central axis of the silver electrode 500. The resistance heating layer 52 is made of silver having a thickness of about 10 μm on the ceramic substrate 518 as a raw material, and the manufacturing method similar to the screen (thick film) printing step (printing, drying and firing are repeated a plurality of times in this order) It forms by laminating | stacking. The resistive heating layer 52 includes resistors 520, 522, 524, 526, and 528 which selectively receive the supply of an alternating current flowing in the conveyance direction of the sheet P (the Y-axis direction) from the AC power supply 54 and generate heat.

  Each of the silver electrodes 504 and 506 is connected to each of the terminals T 504 and T 506 drawn from one short side of the heater 50. The silver electrode 508 is connected to terminals T508-1 and T508-2 drawn from both short sides of the heater 50. The silver electrodes 510 and 512 are connected to terminals T510 and T512 drawn from the other short side of the heater 50, respectively. The convex portion 502 of the silver electrode 500 is connected to a terminal T 502 drawn from one short side of the heater 50.

  The resistors 520, 522, 524, 526, 528 are connected to the AC power supply 54 through the silver electrode 500 and the terminal T502. The resistors 520, 522, 524, 526, 528 are connected through the switch circuit 56, the silver electrodes 504, 506, 508, 510, 512 and the terminals T504, T506, T508-1, T508-2, T510, T512. It is selectively connected to an AC power supply 54.

  Note that the resistor 528 on the central axis A to -A of the sheet P is formed so that the resistance value is uniformly distributed over the entire surface with a uniform thickness in a target shape with respect to the central axis A to -A. Ru. In addition, the resistors 522 and 528 located at symmetrical parts with respect to the central axis A to -A are formed to have the same thickness and a symmetrical shape about the central axis so that the same resistance value is evenly distributed over the entire surface. Ru. Similarly, the resistors 524 and 526 located in a target portion with respect to the central axis A to -A are formed to have the same thickness and a symmetrical shape about the central axis so that the same resistance value is evenly distributed over the entire surface Be done. Therefore, the distribution of heat generation of the resistors 520, 522, 524, 526, 528 of the resistive heating layer 52 is symmetrical with respect to the central axes A to -A.

  The silver electrode 500 is an elongated rectangle symmetrical with respect to the central axis and elongated in the longitudinal direction, and about 0.5 mm in the entire range of the upstream side in the transport direction of the resistors 520, 522, 524, 526, 528, It is formed to overlap. The overlapping length of the other silver electrode and the resistor is also about 0.5 mm. Therefore, in the silver electrode 500, the resistances between the convex portion 502 and the resistors 520 and 528 located at symmetrical portions with respect to the central axis are equal, and the convex portion 502 and a symmetrical portion with respect to the central axis The resistances between the resistors 522 and 526 located at the same position are also equal.

  The silver electrode 504 and the silver electrode 512 located at symmetrical parts with respect to the central axis are formed to be symmetrical with respect to the central axis at the same thickness. Therefore, the resistance between the resistor 520 at the silver electrode 504 and the terminal T 504 and the resistance between the resistor 528 at the silver electrode 512 and the terminal T 508 are equal.

  Similarly, the silver electrode 506 and the silver electrode 510 located at symmetrical parts with respect to the central axis are formed to be symmetrical with respect to the central axis at the same thickness. Therefore, the resistance value between the resistor 522 and the terminal T 506 in the silver electrode 506 and the resistance value between the resistor 526 in the silver electrode 510 and the terminal T 510 are equal.

  The width in the short direction including the convex portion 502 of the silver electrode 500 is about 3.2 mm. Further, the width in the short direction between the silver electrodes 504 and 512 is about 0.6 mm. Further, in the silver electrodes 506 and 510, the width in the short direction of the portions connected to the terminals T506 and T512 is about 1 to 2 mm. In the silver electrode 508, the width in the short direction of the portion connected to the terminals T508-1 and T508-2 is about 2.4 mm. Thus, in each silver electrode, by adjusting the width of the portion connected to each terminal, the resistance value between each resistor and each terminal in each silver electrode can be adjusted to be equal.

  As shown in FIG. 6, the switch circuit 56 connects or disconnects between the terminals T506 and T510 of the silver electrodes 506 and 510 drawn from the heater 50 and the AC power supply 54 in accordance with an external switch control signal SC. A switch 564 is provided. The switch circuit 56 further includes a switch 566 for connecting or disconnecting the terminals T 504 and T 512 of the silver electrodes 504 and 512 drawn from the heater 50 and the AC power supply 54 in accordance with the switch control signal SC from the outside.

  The switch circuit 56 further includes a switch 562 for connecting or disconnecting between the terminals T508-1 and T508-2 of the silver electrode 508 drawn from the heater 50 and the AC power supply 54 in accordance with an external switch control signal SC. . The terminal T 502 of the silver electrode 500 is connected to the AC power supply 54 without passing through the switch circuit 56.

[Control unit 36]
FIG. 7 is a diagram showing a configuration of control device 36 shown in FIG. As shown in FIG. 7, control device 36 includes CPU 360 including a CPU and its peripheral circuits, memory 362 including ROM, RAM, flash memory, etc., and operation panel interface (IF) 364 to which operation panel 14 is connected. And

  Further, the control device 36 controls a component between the sheet feeding cassette 18 and the sheet discharge tray of the main body 11 shown in FIG. 1 to perform sheet feeding and sheet conveyance control circuit. 368 is further provided. The control device 36 further includes an image formation control circuit 370 that controls the printer unit 17 and a fixing control circuit 372 that controls the operation of the fixing device 4. The components of control device 36 are connected to one another via a bus 374.

  Further, the control device 36 generates the switch control signal SC shown in FIG. 6 to connect or release the switches 562, 564, 566 included in the AC power supply 54 so as to fit the width of the sheet to be conveyed. Control is performed so that the entire surface of the conveyed sheet is heated sufficiently. By these components, the operation of each component of MFP 10 is controlled in accordance with the user's operation on the operation panel, etc., and image formation on sheet P by MFP 10 is realized.

  When the convex portion 502 is provided at the center of the silver electrode 500 and the center of the silver electrode 500 is connected to the AC power supply 54 as in the embodiment described above, both sides of the silver electrode 500 and the AC power supply 54 are provided. The current flowing to the heater 50 can reduce the influence of the voltage drop by branching the silver electrode pattern on the common side from the central axis, as compared with the case where the Can. Further, in FIG. 5, one resistor 524 is disposed on the central axis of the heater 50, and two sets of resistors 520 and 528 and resistors 522 and 526 are disposed in a portion symmetrical to the central axis. However, the heater 50 can be configured without a resistor on the central axis.

  While the embodiments of the present invention have been described above, this embodiment is presented as an example and is not intended to limit the scope of the invention. This novel embodiment can be implemented in other various forms, and various omissions, replacements and changes can be made without departing from the scope of the invention. While this embodiment and its modification are included in the range and subject matter of invention, they are included in the invention indicated to the claim, and the equivalent range.

10 MFP (MFP)
11 main body 14 operation panel 17 printer section 18 paper feed cassette 19 scan head 20 image formation section 21 intermediate transfer belt 22 photosensitive drum 23K charger 24K development unit 25K primary transfer roller 26K cleaner 27K blade 31 drive roller 33 secondary transfer roller 4 Fixing device 400 Heating device 402 Fixing belt 404 Surface 406 Back surface 440 Pressure roller 442 Protective layer 444 Silicon sponge layer 446 Iron core 50 Heaters 500 and 504 to 512 Silver electrodes T502 and T504 to T512 Terminal 502 Convex portion 516 Surface protection layer 518 Ceramic substrate 519 holder 52 resistance heating layer 520 to 528 resistor 56 switch circuit 562 to 566 switch

Claims (5)

Power is selectively supplied from the power source in the conveyance direction of the recording medium to be subjected to the image formation to generate heat, and the plurality of recording media are heated symmetrically with respect to the central axis along the conveyance direction of the recording medium The heating resistor of the
It is connected to the power supply at one location, connected commonly to the plurality of heating resistors and one of the transport direction, and the heating resistors at symmetrical positions with respect to the central axis and the power supply have the same resistance value. A first electrode to be connected,
A plurality of second electrodes which are respectively connected to the plurality of heat generating resistors in the other side of the transport direction and which connect the heat generating resistors and the power supply at the same symmetrical value with at least the central axis. And a heater. The heater according to claim 1, wherein the first electrode is connected to the plurality of heating resistors along a straight line orthogonal to the transport direction. The heater according to claim 2, wherein the first electrode is connected to all one side ends of the plurality of heat generating resistors in the transport direction. The heater according to claim 3, wherein the first electrode is connected to the power supply at a portion corresponding to the central axis. Photosensitive drum,
A latent image forming unit for forming a latent image on the photosensitive drum;
A developer for the latent image;
A transfer unit for transferring a toner image visualized by the developing unit to a recording medium;
An image forming apparatus comprising: a fixing device including the heater according to any one of claims 1 to 4.

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