JP2019168721A - Fixing device and image forming apparatus - Google Patents

Abstract

To provide a fixing device that surely detects an abnormal increase in temperature of a heating element.SOLUTION: There is provided a fixing device comprising: a belt-like fixing member that rotates in contact with an unfixed image; a pressing member that forms a fixing nip part with the belt-like fixing member; and a heating member that heats the belt-like fixing member. The fixing device fixes the unfixed image carried on a sheet-like recording material at the fixing nip part. The heating member is composed of a long base material extending in the longitudinal direction of the belt-like fixing member and a plurality of heating elements formed on the base material; the plurality of heating elements form at least one heating area that can be ON/OFF-controlled; the heating areas include a plurality of temperature detection means that can detect the temperature of the heating elements.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a printer, a facsimile, and the like, and a heating type fixing device mounted in such an image forming apparatus.

  The image forming apparatus forms a toner image on an image carrier based on image information, transfers the toner image onto a recording material such as paper or an OHP sheet, and passes the recording material carrying the toner image through a fixing device. The toner image is fixed on the recording material by heat and pressure.

  As such a fixing device, as shown in FIG. 9, a configuration in which three regions H81 to H83 are heated by two halogen heaters 801 and 802 is known. The halogen heater 801 heats the region H82, and the halogen heater 802 heats the region H81 and the region H83 simultaneously. The halogen heater 801 is provided with one temperature detecting means 836 for detecting the temperature of the region H82. On the other hand, the halogen heater 802 is provided with one temperature detection means 836 for detecting the temperature of only the region H83. In this way, abnormally high temperatures were detected by the halogen heaters 801 and 802.

  By the way, for the purpose of energy saving in recent years, a plate-like heating body that uses a film as a fixing member and has a plurality of heat generating portions and selectively heats an arbitrary area according to the paper width size as shown in FIG. Configurations with which are provided are known.

  In such a fixing device, the heater member 956 includes a plurality of heat generating portions 956a, and one temperature detecting unit 936 that detects the temperature of one heat generating portion 956a among the plurality of heat generating portions is disposed. Then, the temperature detection means 936 detects the heat generation state of the heater member 956.

  By the way, in such a fixing device, even if one of the plurality of heat generating units is damaged, the other heat generating unit may generate heat. Therefore, when the heat generating part 956a detected by the temperature detecting means 936 is damaged, there is a problem that an abnormal temperature rise by another heat generating part cannot be detected.

  An object of the present invention is to provide a fixing device that appropriately detects an abnormal temperature rise of a heat generating portion.

In order to solve the above-described problem, a fixing device according to a first aspect of the present invention includes:
A belt-like fixing member that rotates in contact with an unfixed image;
A pressing member that forms a fixing nip portion with the belt-shaped fixing member;
A fixing device for fixing a heating member for heating the belt-like fixing member and a sheet-like recording material carrying an unfixed image at the fixing nip portion,
The heating member is composed of a long base extending in the longitudinal direction of the belt-shaped fixing member, and a plurality of heating elements formed on the base.
The plurality of heating elements form at least one heating region capable of ON / OFF control simultaneously,
Each heating region has a plurality of temperature detecting means capable of detecting the temperature of the heating element.

  According to the present invention, it is possible to provide a fixing device that appropriately detects an abnormal temperature rise of a heat generating portion.

1 is a configuration diagram schematically showing an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a configuration diagram schematically illustrating a fixing device of the image forming apparatus illustrated in FIG. 1. FIG. 2 is a configuration diagram schematically illustrating a nip forming member of the image forming apparatus illustrated in FIG. 1. FIG. 2 is a configuration diagram illustrating a heating member of the image forming apparatus illustrated in FIG. 1. It is explanatory drawing explaining the heater member of the image forming apparatus shown in FIG. It is explanatory drawing explaining the heater member which concerns on the 2nd Embodiment of this invention. It is explanatory drawing explaining the heater member which concerns on the 3rd Embodiment of this invention. It is explanatory drawing explaining the modification of the heater member which concerns on this invention. It is explanatory drawing explaining the conventional heater member. It is explanatory drawing explaining the conventional heater member.

  FIG. 1 shows a monochrome printer as an example of an image forming apparatus according to an embodiment of the present invention, which will be described based on this. Naturally, the present invention can be similarly applied to a known color image forming apparatus. It is a thing. As is well known, a monochrome printer has a developing device provided with a charging roller 18 as a charging unit, a mirror 20 constituting an exposure unit, and a developing roller 22a as a developing unit around a photoconductor 8 as an image carrier. 22, a transfer device 10, a cleaning device 24 including a cleaning blade 24a, and the like are disposed. The exposure light Lb is irradiated and scanned between the charging roller 18 and the developing device 22 through the mirror 20 to the exposure unit 26 on the photosensitive member 8. A paper feeding means 4 is disposed at the bottom of the printer. A registration roller pair (positioning roller pair) 6 is provided in the middle of the sheet conveyance path to the image forming unit. At the end of the sheet conveyance path, a fixing device 12 including a fixing belt 28 (belt-shaped fixing member; hereinafter simply referred to as a fixing belt), a heater member 56, and a pressure roller 30 is provided.

  The paper feeding means 4 feeds the paper P as a recording material stored in a stacked state and the paper P stored in the paper feeding tray 14 one by one in order from the top. It has a roller 16 and the like. The paper P sent out by the paper feed roller 16 is temporarily stopped by the registration roller pair 6. Then, after correcting the posture deviation, at the timing synchronized with the rotation of the photoconductor 8, that is, the front end of the toner image formed on the photoconductor 8 coincides with the predetermined position of the front end of the sheet P in the transport direction. It is sent to the transfer site N by the registration roller pair 6 at the timing.

  The image forming operation in this printer is performed in the same manner as before. When the photosensitive member 8 starts to rotate, the surface of the photosensitive member 8 is uniformly charged by the charging roller 18, and the exposure light Lb is irradiated to the exposure unit 26 based on the image information and scanned, and the static image corresponding to the image to be created. An electrostatic latent image is formed. The electrostatic latent image is moved to a position facing the developing device 22 by the rotation of the photosensitive member 8, where toner is supplied to be visualized to form a toner image. The toner image formed on the photoconductor 8 is transferred onto the paper P that has entered the transfer portion N at a predetermined timing by applying a transfer bias of the transfer device 10. The paper P carrying the toner image as an unfixed image is conveyed toward the fixing device 12, fixed by the fixing device 12, and then discharged and stacked on a paper discharge tray outside the apparatus. Residual toner remaining on the photosensitive member 8 without being transferred at the transfer portion N reaches the cleaning device 24 as the photosensitive member 8 rotates, and is scraped off by the cleaning blade 24 a while passing through the cleaning device 24. To be cleaned. Thereafter, the residual potential on the photoconductor 8 is removed by a known charge eliminating means and prepared for the next image forming step.

Next, the configuration of the fixing device according to the embodiment of the present invention will be described with reference to FIG.
The fixing device 12 includes an endless fixing belt 28 that is a flexible heat-resistant film, a pressure roller 30 that is a pressing member that comes into contact with the outer peripheral surface, and a heater member 56 that serves as a heating member. The heater member 56 functions as a nip forming member that forms the fixing nip portion SN together with the heat transfer member 50 for heat equalization in the axial direction (longitudinal direction) of the fixing belt 28. The heat transfer member 50, the heater member 56, and the heater holder 57 that holds the heat transfer member 50 are supported by a stay (support member) 61 connected to the apparatus side plate, and the bending of these members due to the pressure of the pressure roller 30 is prevented. A uniform nip width can be obtained in the longitudinal direction. A low friction sheet may be interposed between the heat transfer member 50 and the inner peripheral surface of the fixing belt 28.

  A first thermistor 34 that detects the surface temperature of the fixing belt 28 is provided downstream of the fixing nip SN and upstream of the heater member 56. A second thermistor 36 is provided as temperature detecting means for detecting the temperature of the heater member 56 itself. On the basis of the detection information of the thermistor, a heating control means 42 for controlling the power source 40 that supplies power to the heater member 56 is provided. The heating control means 42 means a microcomputer including a CPU, ROM, RAM, I / O interface and the like.

  The fixing belt 28 has a nickel base having an outer diameter of 30 mm and a thickness of 10 to 70 μm, an elastic layer coated on the surface of the base, and a release layer formed on the surface. The elastic layer is made of silicone rubber and has a thickness of 50 to 150 μm. The release layer that increases the durability and ensures the release property is formed of a fluorine-based resin such as PFA or PTFE, and is provided with a thickness of 5 to 50 μm. The belt substrate is not limited to nickel, and may be formed of a heat resistant resin material such as SUS or polyimide (PI).

  The pressure roller 30 has an outer diameter of 30 mm, and includes a solid iron core 30a and an elastic layer 30b formed on the surface of the core 30a. The elastic layer 30b is made of silicone rubber and has a thickness of 5 mm. It is desirable to form a fluororesin (PFA or PTFE) layer having a thickness of about 40 μm on the surface of the elastic layer 30b in order to improve the releasability. As is known, the pressure roller 30 is pressed against the heat transfer member 50 and the heater member 56 via the fixing belt 28 by an urging means. The pressure roller 30 is rotated by a driving force transmitted from a driving source such as a motor provided in the image forming apparatus via a gear. The fixing belt 28 is rotated by the pressure roller 30.

  The heater member 56 is a plate-like heating element in which a resistance heating element 56a as a heating element is formed on the surface of a long base material 56b extending in the axial direction (longitudinal direction) of the fixing belt 28, and is a heater module. Is the main component. As shown in FIG. 3, for example, a resistance heating element 56a is printed on a base material 56b having a low thermal conductivity such as glass and fired, and an overcoat (OC) layer 56c is further formed thereon. Although the OC layer 56c located on the fixing belt 28 side is also formed of glass or the like, the heating efficiency of the fixing belt 28 is improved because the OC layer 56c is thinner than the base material 56b and easily transfers heat to the OC layer side rather than the base material side.

  As shown in FIG. 4, the fixing belt 28 slides in contact with the heat transfer member 50 assembled and heated on the surface side of the heater member 56 on the inner peripheral surface thereof, so that the belt temperature rises and the fixing is performed. The unfixed image on the sheet conveyed to the nip portion SN can be heated and fixed. The heat transfer member 50 is formed from a high heat conductive material such as copper or aluminum. The heater member 56 and the heat transfer member 50 may improve adhesion by using heat conductive grease, a heat conductive sheet, or the like. Due to the improved adhesion, the heat transfer from the back surface side (opposite side of the fixing belt) of the heater member 56 to the front surface side is enhanced, ensuring belt heating and improving the heat transfer property in the heater longitudinal direction. Can be secured.

  The heater holder 57 holds the heater member 56 from the back side. In order to minimize heat conduction to the heater holder 57, the heater holder 57 is formed so as not to be in contact with the entire back surface of the heater member 56 but to be in partial contact, and is a heat-resistant resin such as LCP. Low rate materials are used. A nip region is formed when the pressure roller 30 and the heat transfer member 50 come into contact with each other via the fixing belt 28, and the portion where the heater holder 57 protrudes from the contact surface to the belt side is located upstream and downstream in the sheet conveyance direction. By having it on the side, the paper separation property can be improved.

Next, the heater member 56 will be described.
As shown in FIG. 5, the heater member 56 extending in the axial direction of the fixing belt 28 has a plurality of resistance heating elements 56 a in the longitudinal direction, that is, in the direction orthogonal to the paper transport direction. The plurality of resistance heating elements 56a have counter electrodes connected to the upstream side and the downstream side in the paper conveyance direction, and uniformly generate heat in the longitudinal direction. The common electrode Wcom and the individual wires W1 and W2 are connected to the counter electrode to form two heating regions H11 and H12. The heating regions H11 and H12 can be individually and independently heated by turning on / off the individual wirings W1 and W2.

  The first thermistor 34 that detects the surface temperature of the fixing belt 28 and the second thermistor 36 that detects the temperature of the heater member 56 are arranged corresponding to each heating region. In consideration of the detection information and the sheet passing size information, the heating control means 42 controls the temperature of each heating region, thereby changing the heating rate of the heater member 56. By controlling the heating according to the sheet passing size information, a situation where the temperature of the non-sheet passing area becomes too high can be avoided, and damage to the member and image quality deterioration due to excessive temperature rise in the non-sheet passing area can be suppressed. Actually, the power supply may be completely stopped (turned off) at the part corresponding to the non-sheet passing area, but if the temperature is extremely lowered, it will not be in time for the rise to the fixing temperature in the next image area. Sometimes. For this reason, the temperature is controlled so as to keep the fixing belt at a second target temperature that is lower than the first target temperature corresponding to the image area but higher than the room temperature, and to a part corresponding to the non-sheet passing area. Power is also supplied.

  In the heating region H11, two second thermistors 36 that detect the temperature of one resistance heating element 56a are installed. Two second thermistors 36 for detecting the temperature of one resistance heating element 56a are installed in the heating region H12. That is, a plurality of second thermistors 36 are installed in each heating region that can be controlled ON / OFF simultaneously. When the second thermistor 36 detects an abnormal temperature rise of the resistance heating element 156a, the heating control means 42 controls the temperature of the heating region. Therefore, even when the resistance heating element 56a detected by the second thermistor 36 is damaged, an abnormal temperature rise due to the other resistance heating element 56a can be detected. In the present embodiment, two second thermistors 36 are installed in each heating region where ON / OFF control can be performed simultaneously, but three or more may be installed.

  Subsequently, an image forming apparatus according to a second embodiment of the present invention will be described. Note that components common to those in the image forming apparatus according to the first embodiment are denoted by corresponding reference numerals and detailed description thereof is omitted, and different components are described in detail with reference to the drawings.

  The second embodiment differs from the first embodiment in that the configuration of the heater member is different. This will be specifically described below.

  As shown in FIG. 6, the heater member 156 of the present embodiment has a plurality of resistance heating elements 156 a in the longitudinal direction, that is, in the direction orthogonal to the paper transport direction. The plurality of resistance heating elements 156a have counter electrodes connected to the upstream side and the downstream side in the paper conveyance direction, and uniformly generate heat in the longitudinal direction. The common electrode Wcom and the individual wires W1, W2 are connected to the counter electrode to form three heating regions H21, H22, H23. The heating regions H21 and H23 are formed at symmetrical positions from the longitudinal center of the heater member 156, and are configured to be able to be turned ON / OFF simultaneously. That is, the heating regions H21 and H23 that can be turned on / off at the same time are separated from each other and electrically connected in parallel. The heating regions H21 and H23 and the heating region H22 can be individually and independently controlled by turning on / off the individual wirings W1 and W2. As a result, the number of switching elements such as triacs and FETs for turning on / off can be reduced.

  One second thermistor 36 that detects the temperature of one resistance heating element 156a is provided in each of the heating regions H21 and H23. In the heating region H32, two second thermistors 36 that detect the temperature of one resistance heating element 156a are installed. That is, a plurality of second thermistors 36 are installed in each heating region that can be controlled ON / OFF simultaneously. When the second thermistor 36 detects an abnormal temperature rise of the resistance heating element 156a, the heating control means 42 controls the temperature of the heating region. Therefore, even when the resistance heating element 156a detected by the second thermistor 36 is damaged, an abnormal temperature rise due to the other resistance heating element 156a can be detected. By electrically connecting the heating regions H21 and H23 to be heated at the same time in parallel, the voltage applied to each second thermistor 36 is prevented from fluctuating when the second thermistor 36 is damaged, thereby providing a safer configuration. Can do. In the present embodiment, two second thermistors 36 are installed in each heating region where ON / OFF control can be performed simultaneously, but three or more may be installed.

  Subsequently, an image forming apparatus according to a third embodiment of the present invention will be described. Note that components common to those in the image forming apparatus according to the first embodiment are denoted by corresponding reference numerals and detailed description thereof is omitted, and different components are described in detail with reference to the drawings.

  The third embodiment is different from the first embodiment in that the configuration of the heater member is different. This will be specifically described below.

  As shown in FIG. 7, the heater member 256 according to the present embodiment includes a long resistive heating element 256 a in the longitudinal direction, that is, in a direction orthogonal to the paper transport direction. A common wiring Wcom and individual wirings W1, W2 are connected to the resistance heating element 256a. The common wiring Wcom constituting the first current-carrying electrode and the individual wirings W1 and W2 constituting the second current-carrying electrode form a comb-like conductive part with respect to the resistance heating element 256a, and a plurality of heat-generating parts Form. The resistance heating element 256a has three heating regions H31, H32, and H33. The heating regions H31 and H33 are formed at symmetrical positions from the center in the longitudinal direction of the heater member 256, and are configured so that they can be turned ON / OFF simultaneously. That is, the heating regions H31 and H33 that can be turned ON / OFF at the same time are separated from each other and electrically connected in parallel. The heating regions H31, H33 and the heating region H32 can be individually and independently controlled by turning on / off the individual wirings W1, W2. As a result, the number of switching elements such as triacs and FETs for turning on / off can be reduced.

  In the heating regions H31 and H33, one second thermistor 36 that detects the temperature of a part of the heat generating portion of the resistance heating element 256a is provided. In the heating region H32, two second thermistors 36 for detecting the temperature of a part of the heat generating portion of the resistance heating element 256a are installed. That is, a plurality of second thermistors 36 are installed in each heating region that can be controlled ON / OFF simultaneously. When the second thermistor 36 detects an abnormal temperature rise of the resistance heating element 256a, the heating control means 42 controls the temperature of the heating region. Therefore, even when a part of the resistance heating element 256a detected by the second thermistor 36 is damaged, an abnormal temperature rise due to another part of the resistance heating element 56a can be detected. By electrically connecting the heating regions H31 and H33 that are heated at the same time in parallel, the voltage applied to each second thermistor 36 is prevented from fluctuating when the second thermistor 36 is damaged, thereby providing a safer configuration. Can do. In the present embodiment, two second thermistors 36 are installed in each heating region where ON / OFF control can be performed simultaneously, but three or more may be installed.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this.
In the above-described embodiment, two or three heating regions are formed. However, the present invention is not limited to this mode, and more heating regions such as nine can be set. Moreover, as shown in FIG. 8, it is applicable also to the structure where the heating area | region is not divided | segmented.

  In addition, at least one of the plurality of second thermistors arranged in the heating area to be heated at the same time is configured to perform software temperature control based on the detected temperature information and detect a high temperature in hardware. Also good. As a result, when an abnormal temperature rise occurs, the abnormality can be detected even in a lower temperature state, so that safety can be improved.

28 fixing belt (an example of a belt-like fixing member)
30 Pressure roller (an example of a pressing member)
36 Second thermistor (temperature detection means)
56 Heater member (an example of a heating member)
56a Resistance heating element (an example of a heating element)
56b Substrate SN Fixing nip

In order to solve the above-described problem, a fixing device according to a first aspect of the present invention includes:
A fixing member that rotates in contact with an unfixed image;
A pressing member for forming a fixing nip portion between the fixing member,
A heating member for heating the fixing member ;
With
A fixing device for fixing the sheet-like recording material carrying the unfixed image at the fixing nip,
The heating member includes a long base extending in the longitudinal direction of the fixing member , and a plurality of heating elements formed on the base and including at least a first heating element and a second heating element. ,
The plurality of heating elements form a heating region capable of ON / OFF control simultaneously,
In the heating region, the plurality of heating elements are electrically connected in parallel, and
First temperature detection means disposed at a position corresponding to the first heating element;
Second temperature detecting means disposed at a position corresponding to the second heating element;
It is characterized by having.

Claims (6)

A belt-like fixing member that rotates in contact with an unfixed image;
A pressing member that forms a fixing nip portion with the belt-shaped fixing member;
A fixing device for fixing a heating member for heating the belt-like fixing member and a sheet-like recording material carrying an unfixed image at the fixing nip portion,
The heating member is composed of a long base extending in the longitudinal direction of the belt-shaped fixing member, and a plurality of heating elements formed on the base.
The plurality of heating elements form at least one heating region capable of ON / OFF control simultaneously,
Each of the heating regions has a plurality of temperature detecting means capable of detecting the temperature of the heating element.   2. The fixing device according to claim 1, wherein the at least one heating region is separated and arranged in the longitudinal direction of the belt-shaped fixing member and is electrically connected in parallel.   The fixing device according to claim 2, wherein the heating area to be divided is disposed at a position symmetrical to the longitudinal center of the heating member.   4. The fixing device according to claim 2, wherein each of the divided portions of the heating region includes at least one temperature detecting unit capable of detecting the temperature of the heating element. 5.   The at least one of the said temperature detection means performs temperature control in software based on the detected temperature information, and performs high temperature detection in hardware, It is characterized by the above-mentioned. Fixing device.   An image forming apparatus comprising the fixing device according to claim 1.

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