JP2007108296A - Heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating device designed such that elongation of a heating body by heat expansion can be made symmetrical with respect to a conveyance reference for a material to be heated and the temperatures of the heating body can be symmetrically detected by a temperature detecting means. <P>SOLUTION: The heating body 4 and a heating-body holding member 3 are fixed together in a lengthwise middle position 17-C corresponding to the conveyance reference (paper passage reference) for a material S to be heated, and in the lengthwise middle positions 17-R and 17-L symmetrical with respect to the conveyance reference for the material to be heated. The heat generation distribution of the heat generating resistor 4a of the heating body is symmetrical with respect to the conveyance reference for the material to be heated. Temperature detection means 14-1 and 14-2 for detecting the temperatures of the heating body are disposed in the lengthwise ends of the substrate 4b of the heating body so as to be symmetrical with respect to the conveyance reference for the material to be heated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heating device suitable for mounting as an image heating and fixing device in an image forming apparatus such as an electrophotographic copying machine or a laser beam printer.

  In an image forming apparatus such as an electrophotographic copying machine or a laser beam printer, an electrostatic latent image is formed on a photosensitive drum, and the electrostatic latent image is developed as a toner image by a developing device. The image is transferred onto a recording material (heated material) by a transfer device. The recording material is passed through an image heating and fixing device to apply heat and pressure to the toner image, thereby fixing the toner image to the recording material.

  As an image heating fixing device (hereinafter referred to as a fixing device), a film heating type fixing device that heats a toner image using a heat-resistant and thin flexible film (fixing film) has been put into practical use. Such a film heating type fixing device is disclosed in JP-A-63-313182, JP-A-1-263679, JP-A-2-157878, JP-A-4-44075 to 4-44083, and the like. Has been.

  An example of a conventional film heating type fixing device will be described with reference to FIG. (A) is an explanatory view of the relationship between the dimension in the longitudinal direction (width direction orthogonal to the conveyance direction of the recording material) of each member constituting the fixing device and the dimension in the width direction of the recording material. (B) is a top view of a heater.

  The fixing device includes an elongated heater 4 having a heating resistor 4a that generates heat when energized on a substrate 4b, and a pressure roller 2 is disposed opposite to the heater with a heat-resistant flexible film 1 interposed therebetween. Thus, the nip portion N is formed. While the recording material (hereinafter referred to as a sheet) S is nipped and conveyed at the nip portion N, the heat and nip pressure of the heater 4 are applied to the unfixed toner image T on the sheet to heat the unfixed toner image on the sheet. It is to fix. The conveyance reference for conveying the sheet S is a central reference that matches the center in the longitudinal direction of the nip portion N with the center between the end portions of the sheet along the longitudinal direction of the nip portion. Hereinafter, the conveyance standard is referred to as a paper standard.

  The fixing device uses a low heat capacity heater or a thin film material that is rapidly heated. For this reason, it is effective with advantages such as power saving and shortening of the wait time (quick start property), and lowering the temperature rise in the apparatus such as an image forming apparatus. .

  The low-heat-capacity heater 4 is basically composed of a heat-resistant / insulating ceramic substrate 4a and a heating resistor 4b formed on the substrate by means of printing or baking, and supplies power to the heating resistor. A so-called ceramic heater that generates heat is used.

  The ceramic heater 4 is controlled to a predetermined operating temperature by controlling the power supplied to the heating resistor 4a by a temperature control system including temperature detection elements (hereinafter referred to as thermistors) 13 and 14. Also, a safety device such as a thermal fuse or a thermo switch (not shown) is provided, and when the heater temperature rises above the upper limit temperature of use, the power supply to the heating resistor is cut off by the operation of the safety device. I am doing so.

  Regarding the longitudinal relationship of the members of the fixing device, the length of the heating resistor 4a of the heater 4 held by the heater holder 3 (the length of the heating element) is sufficiently longer than the width of the toner image area of the sheet S. Thereby, the heat of the heater 4 can be uniformly applied to the toner image T on the sheet surface. At this time, the longer the length of the heating resistor 4a, the easier it is to ensure uniform fixing properties. However, if the length is too long, it becomes impossible to achieve downsizing and space saving of the apparatus. The heater holder 3 is pressed by the stay 6 toward the pressure roller 2 side.

  The length in the longitudinal direction of the rubber part (pressure roller length) in the pressure roller 2, that is, the length of the nip part formed with the flexible film 1 reliably presses the toner image T, In order to convey the sheet without any problem, it is preferable that the sheet is longer than the sheet width (paper passing area).

  On the other hand, the non-sheet passing area resulting from the difference between the length of the heating resistor 4a and the sheet passing area is widened, so that the end of the heating resistor or the pressure roller surface corresponding to the non-sheet passing area is excessively heated. There is a problem of non-sheet passing portion temperature rise. That is, the difference in the heat balance between the sheet passing area and the non-sheet passing area, that is, the temperature increase in the non-sheet passing portion becomes remarkable due to an increase in the printing speed (process speed).

Therefore, in the conventional fixing device, the relationship between the maximum printable area (maximum toner image area), the resistance heating element area, and the longitudinal dimension of the pressure roller 2 is as follows.
Maximum printable area <resistance heating element area <pressure roller length.

  In addition, a configuration in which the heater and the heater holder are not bonded and fixed by considering the backlash between the heater 4 and the heater holder 3 is also proposed. However, the temperature rise of the non-sheet passing portion is disadvantageous because the heater and the heater holder have a large amount of play.

  Conventionally, in the configuration shown in FIG. 4, a first thermistor (main thermistor) 13 is arranged on the back surface of the heater 4 (the surface on the heater holder 3 side) within the minimum sheet passing region (position 30 mm away from the sheet passing reference). This thermistor 13 detects the temperature of the minimum sheet passing area, and a second thermistor for detecting the temperature rise of the non-sheet passing area at one end of the sheet passing area (position 100 mm away from the sheet passing reference). The thermistor 14 is designed to have a margin with respect to the heat resistant temperature of the members constituting the fixing device to some extent.

  On the other hand, if the heater is firmly bonded to the heater holder 3 at a large number of locations in order to accurately define the positional relationship between the sheet S and the heating resistor 4a of the heater 4, a great stress is generated due to the difference in linear expansion coefficient.

In order to solve this problem, Patent Documents 1 and 2 disclose a technique in which a ceramic heater is bonded to a holder at one end or center.
Japanese Patent Laid-Open No. 04-070688 JP 05-061372 A

  In the fixing device, when the printing speed is further increased, the difference in the heat balance between the paper passing area and the non-paper passing area increases. For this reason, the temperature of the non-sheet passing portion of the heater and the pressure roller tends to increase. In this case, the relationship between the heater position and the thermistor position described above greatly affects the detection of the non-sheet passing portion temperature. That is, when the backlash of the heater with respect to the heater holder is large in the longitudinal direction of the heater, the accuracy of detecting the non-sheet passing portion temperature is greatly reduced.

  Furthermore, the thermal expansion of the heater changes the position of the end portion of the heating resistor and increases the non-sheet passing area, thereby promoting the tendency for the non-sheet passing portion temperature to increase.

  Accordingly, an object of the present invention is to provide a heating device that can make the elongation due to thermal expansion of the heating body symmetrical with respect to the conveyance reference of the material to be heated, and can make the temperature detection of the heating body symmetrical by the temperature detection means. It is in.

  A representative configuration of the heating device according to the present invention includes a heating body having an elongated substrate and a heating resistor provided on the substrate, a heating body holding member that holds the heating body, and a contact with the heating body. A flexible member that slides and a pressure member that forms a nip portion sandwiching the heating body and the flexible member, and heats the material to be heated while nipping and conveying the heated material at the nip portion. In the heating device, the transport reference for transporting the heated material is a central reference that matches the center in the longitudinal direction of the nip portion with the center between the end portions of the heated material along the longitudinal direction of the nip portion. In the heating device, the heating body and the heating body holding member are fixed at a longitudinal center position corresponding to a conveyance reference of the heated material and a longitudinal intermediate position symmetrical to the conveyance reference of the heated material. And the heating resistance with respect to the conveyance reference of the heated material The heat generation distribution is symmetrical, and temperature detecting means for detecting the temperature of the heating body is disposed at the longitudinal end position of the substrate that is symmetrical with respect to the conveyance reference of the material to be heated. A heating device.

  ADVANTAGE OF THE INVENTION According to this invention, provision of the heating apparatus which can make elongation by thermal expansion of a heating body symmetrical with respect to the conveyance reference | standard of a to-be-heated material, and can make temperature detection of a heating body symmetrical by a temperature detection means is realizable.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

(1) Example of Image Forming Apparatus FIG. 3 is a schematic model diagram showing an example of an image forming apparatus in which the heating apparatus according to the present invention can be mounted as an image heating and fixing apparatus. The image forming apparatus shown in FIG. 3 is a copying machine or printer using a transfer type electrophotographic process.

  A rotating drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 31 as an image carrier is rotationally driven in a direction of an arrow (clockwise) at a predetermined peripheral speed (process speed) by a rotational driving system (not shown). Is done. During rotation, the photosensitive drum 31 is uniformly charged with a predetermined polarity and potential by a charging roller 32 as a charging unit (primary charging unit). Image exposure 33 corresponding to target image information is performed on the charging surface by image exposure means (not shown) such as slit exposure means for a document image or laser beam scanning exposure means. As a result, an electrostatic latent image corresponding to the exposure image is formed on the surface of the photosensitive drum. The electrostatic latent image on the surface of the photosensitive drum is developed as a toner image by a developing device 34 as a developing unit.

  On the other hand, a recording material (hereinafter referred to as a sheet) S as a heated material is fed from a paper feeding unit (not shown) to a transfer portion between the surface of the photosensitive drum and a transfer roller 35 as a transfer unit. The transfer roller 35 transfers the toner image onto the sheet S from the surface of the photosensitive drum.

  The sheet S to which the toner image has been transferred is introduced into a nip portion N of an image heating and fixing device (hereinafter abbreviated as a fixing device) R. In the fixing device R, the sheet S is nipped and conveyed at the nip portion N to heat and fix an unfixed toner image on the sheet. The sheet S that has exited the nip portion N is discharged onto a discharge tray (not shown).

  Reference numeral 36 denotes a cleaning device as a cleaning means. The cleaning device 36 removes residual toner remaining on the surface of the photosensitive drum after the toner image is transferred. As a result, the photosensitive drum 31 is used for the next image formation.

(2) Fixing device R
FIG. 2 is a cross-sectional side view of the fixing device R.

  The fixing device R shown in this embodiment is a film heating type fixing device. In the fixing device R, the conveyance standard (sheet feeding standard) of the sheet S is the same as that of the conventional fixing device. Also, members and parts common to the conventional fixing device are denoted by the same reference numerals.

  Reference numeral 1 denotes a cylindrical fixing film (heat resistant film) as a flexible member. Reference numeral 3 denotes a heater holder (hereinafter abbreviated as a holder) as a heating body holding member. The holder 3 holds a heater 4 as a heating body in a groove provided on the lower surface. A fixing film (hereinafter abbreviated as film) 1 is loosely fitted on the holder 3. Reference numeral 2 denotes a pressure roller as a pressure member. The pressure roller 2 is in pressure contact with the lower surface of the heater 4 with the film 1 interposed therebetween. Thus, the nip portion (fixing nip portion) N is formed between the pressure roller 2 and the film 1. Reference numeral 6 denotes a pressure stay, and both ends 6a are pressed against the holder 3 by springs (not shown).

  The above members will be described in more detail.

  The film 1 is, for example, a polyimide (PI) film whose surface is coated with a fluororesin such as PTFE having good toner releasability. Both ends of the film 1 are held by a film guide (not shown) in a form according to the outer shape of the film. This film guide is supported by the apparatus side plate pair and holds both ends of the holder 3.

  The pressure roller 2 has an elastic layer 2b such as silicone rubber or silicone sponge on a metal core 2a such as iron or aluminum, and the surface layer is composed of a release layer 2c such as PFA or PTFE having excellent release properties. Is done. The pressure roller 2 has both ends of the metal core 2a supported by a pair of apparatus side plates so as to be rotatable.

  The holder 3 is formed in an elongated saddle shape having a substantially semicircular cross section. In addition to holding the heater 4, the holder 3 also serves as a rotation guide for the film 1 fitted on the heater 3. The holder 3 is made of, for example, a thermosetting resin and has heat resistance.

  The heater 4 includes a thin and long ceramic substrate 4b, a heating resistor 4a formed on the substrate surface along the length of the substrate, and a protective layer 4c covered with the heating resistor as basic components. Become. Then, heat is quickly generated and the temperature is raised by supplying power to the heating resistor 4a from a temperature control system (not shown), and the temperature is controlled to a predetermined fixing temperature by the temperature control system. The heater 4 is inserted into a groove formed along the length of the lower surface of the holder 3 with respect to the holder 3 and bonded and held with a heat resistant adhesive. The application position and the application amount of the adhesive will be described later.

  The stay 6 is made of iron / SUS or aluminum with high rigidity. Since the stay 6 is pressurized by the spring as described above, two arms 6a protrude from both ends (FIG. 1). The stay 6 has a U-shaped cross section at the longitudinal center, and transmits the applied pressure received from both ends to the holder 3 through the bottom surface 6b. Then, the elastic layer 2 b of the pressure roller 2 is dented with the applied pressure, and a nip portion N is formed between the heater 4 and the pressure roller 2.

  In the fixing device R, the pressure roller 2 is rotationally driven counterclockwise at a predetermined peripheral speed by a drive unit (not shown) via a gear 9 provided on the metal core 2a. A rotational force acts on the film 1 by the frictional force between the roller and the outer surface of the film 1 by the rotational driving of the pressure roller 2, and the film 3 is in contact with and slides on the lower surface of the heater 4, and moves outwardly around the holder 3. It is rotationally driven in the direction. In order to reduce sliding resistance between the inner surface of the film 1 and the protective layer 4c on the lower surface of the heater with which the film 1 contacts and slides, a lubricant such as heat-resistant grease may be interposed therebetween.

  Thus, the sheet S carrying the unfixed toner image T in the nip portion N in a state in which the film 1 is rotated by the rotational driving of the pressure roller 2 and the heater 4 rises to a predetermined fixing temperature and is temperature-controlled. Is introduced with the toner image carrying surface side of the film 1 side. The sheet S is nipped and conveyed together with the film 1 through the nip portion N, whereby the heat of the heater 4 is applied through the film, and the toner image T is heated and fixed on the sheet surface. After passing through the nip portion N, the sheet S is separated from the film 1 and conveyed to a discharge roller (not shown).

(2) Positional relationship in the longitudinal direction of the fixing device and adhesion between the heater and the heater holder In FIG. 1, (a) shows the relationship between the longitudinal dimension of each member of the fixing device R and the widthwise dimension of the recording material. It is explanatory drawing. (B) is a top view of a heater.

  Hereinafter, regarding the fixing device R, a configuration in which a sheet of LETTER (215.9 mm × 279.4 mm) size as a sheet S can be passed through the nip portion N in a posture in which the long side is parallel to the sheet reference will be described. To do.

  In the fixing device R of this embodiment, an adhesion reference (hereinafter referred to as an adhesion reference position) 17-C is provided at the same position as the longitudinal center position corresponding to the sheet passing reference, that is, the sheet passing reference. A thermoswitch 15 as a safety device is arranged on the right side of 15 mm. In addition, a first thermistor 13 as a temperature detection element is disposed 15 mm to the left of the adhesion reference position 17-C. In the fixing device R, the minimum size paper that can be passed through the nip portion N is 3 (inch) × 5 (inch) (76.2 mm × 127 mm). For this reason, the first thermistor 13 and the thermo switch 15 are set within the paper passing area of all papers that can be passed, that is, within the minimum paper passing area (76.2 mm), and the output signal of the first thermistor Based on the above, temperature control is performed to a predetermined fixing temperature by a temperature control system.

  On the other hand, adhesion points are provided at adhesion reference positions 17-C and symmetrical positions (hereinafter referred to as longitudinal intermediate positions) 17-R and 17-L 30 mm to the left and right with respect to the adhesion reference positions. The heater 4 is fixed to the holder 3 by three points at two longitudinal intermediate positions.

  In this embodiment, the number of points is three, but from the viewpoint of adhesive strength, it may be one point at the reference bonding position and four or more points at the longitudinal intermediate position. However, the end of the heater 4 is not bonded, and can be freely expanded with respect to thermal expansion during heating of the heater. Here, the clearance between the end of the heater 4 and the end of the holder 3 was 0.5 mm on the left and right. This value is determined by the relationship between the linear expansion coefficients of the heater 4 and the holder 3, the parts, and the assembly accuracy. In the present embodiment, since the temperature of the heater 4 is rapidly increased, the value is set in consideration of a temperature difference in which the heater is about 200 ° C. and the holder 3 is about room temperature.

  By fixing the heater 4 and the holder 3 as described above, the stress applied to the heater or the holder 3 due to the thermal expansion of the heater 4 can be reduced, and the elongation due to the thermal expansion of the heater becomes equal to the left and right.

  In the heater 4, the temperature distribution (heat generation distribution) of the heating resistor 4a provided on the surface of the substrate 4b is symmetric with respect to the adhesion reference position 17-C. As a result, it is possible to promote left-right symmetrization of the non-sheet-passing portion temperature in the non-sheet-passing region resulting from the difference between the length of the heating resistor 4a (the length of the heating element) and the sheet passing region. Here, the symmetrical temperature distribution is effective when both the longitudinal dimension of the heating resistor 4a and the heat generation distribution are symmetric with respect to the adhesion reference position 17-C.

  Then, the second thermistor 14-1 and the third thermistor 14-2 are arranged at symmetrical positions (hereinafter referred to as longitudinal end positions) 50 mm to the left and right with respect to the adhesion reference position 17-C. As a result, it is possible to accurately detect the temperature distribution of the non-sheet passing portion that is equal to the left and right at the left and right even positions.

  Thus, by disposing the second and third thermistors 14-1 and 14-2 equally on the left and right with respect to the adhesion reference position 17 -C, the non-sheet passing portion region is caused by the thermal expansion of the heater 4. When it increases, it is possible to accurately detect the temperature of the non-sheet passing portion without breaking the left and right balance. Alternatively, even when the paper size changes, the non-sheet passing portion temperature can be accurately detected without losing the left and right balance. For this reason, the maximum printing speed can always be realized below the heat resistant temperature of the members constituting the fixing device R, such as the heater 4, the holder 3, and the pressure roller 2.

  In the present example, the second and third thermistors 14-1 and 14-2 were set at positions 50 mm on the left and right from the adhesion reference position 17-C. Based on the same concept, it is appropriate to set the FULLBLEED (304.8mm x 457.2mm) size paper at a position of 145mm to the left and right from the reference bonding position in the fixing device that can pass the paper vertically through the nip N. . This setting is because a non-sheet passing area of about 10 mm with respect to the maximum sheet passing size is appropriate for detection of the non-sheet passing portion temperature. However, of course, the optimum dimensions differ depending on the printing speed and fixing conditions.

[Others]
1) The heater has a plurality of heating resistors having different heat generation distributions in parallel in the short direction of the substrate (sheet conveyance direction), and the heat generation distribution when each of the plurality of heating resistors is used alone is an adhesion reference position. May be symmetric. Even in this case, the stress applied to the heater or the holder due to the thermal expansion of the heater can be reduced, and the elongation due to the thermal expansion of the heater can be made equal to the left and right.

  2) The heating device of the present invention is not limited to use as the image heating and fixing device of the embodiment, but is a hypothetical fixing device that temporarily fixes an unfixed image on a recording material, and the recording material carrying the fixed image is reheated and glossed. It is also effective as an image heating apparatus such as a surface modification apparatus for modifying the image surface properties such as. In addition, for example, it is effective to be used as a heating device for heat-treating a material to be heated, such as a heat press device for removing wrinkles such as banknotes, a heat laminating device, and a heat drying device for evaporating moisture content such as paper. Of course.

(A) is explanatory drawing of the relationship between the dimension of the longitudinal direction of each member of the fixing device based on Example 1, and the dimension of the width direction of a recording material, (b) is a top view of a heater. Cross-sectional side view of the fixing device Schematic model diagram of an example of an image forming apparatus (A) is explanatory drawing of the relationship between the dimension of the longitudinal direction of each member of the conventional fixing device, and the dimension of the width direction of a recording material, (b) is a top view of a heater.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fixing film, 2 ... Pressure roller, 3 ... Heater holder, 4 ... Heater 4a ... Heating resistor, 4b ... Substrate, 14-1 ... 2nd thermistor,
14-2 Third Thermistor

Claims (3)

A heating body having an elongated substrate and a heating resistor provided on the substrate, a heating body holding member that holds the heating body, a flexible member that slides in contact with the heating body, and the heating body And a pressure member that forms a nip portion with the flexible member interposed therebetween, and a heating device that heats the heated material while pinching and transporting the heated material at the nip portion, and transports the heated material In the heating apparatus in which the conveyance reference is a central reference that matches the center in the longitudinal direction of the nip portion and the center between the ends of the heated material along the longitudinal direction of the nip portion,
The heating body and the heating body holding member are fixed at a longitudinal center position corresponding to the transport reference of the heated material and a longitudinal intermediate position symmetric with respect to the transport reference of the heated material. Temperature detection for detecting the temperature of the heating body at a longitudinal end position of the substrate that is symmetrical with respect to the heating material conveyance reference and is symmetrical with respect to the heating material conveyance reference. A heating device characterized in that means is provided.   The heating apparatus according to claim 1, wherein the longitudinal dimension of the heating resistor is symmetrical with respect to a conveyance reference of the material to be heated.   The heating body has a plurality of heating resistors having different heat generation distributions in parallel in the short direction of the substrate, and the heat generation distribution when the plurality of heating resistors are used individually is the conveyance of the material to be heated. The heating apparatus according to claim 1, wherein the heating apparatus is symmetrical with respect to a reference.