JP6729769B2 - Fixing device and image forming apparatus - Google Patents

Description

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

In an image forming apparatus, a toner image is formed on an image carrier based on image information, the toner image is transferred onto a recording material such as paper or an OHP sheet, and the recording material carrying the toner image is passed 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 is known in which two halogen heaters 801 and 802 heat three regions H81 to H83. The halogen heater 801 heats the area H82, and the halogen heater 802 simultaneously heats the area H81 and the area H83. Further, 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 detecting means 836 for detecting the temperature of only the region H83. In this way, the halogen heaters 801 and 802 detect the abnormally high temperature.

By the way, in recent years, for the purpose of energy saving, a plate-shaped heating body which uses a film as a fixing member and has a plurality of heat generating portions as shown in FIG. 10 and which selectively heats an arbitrary region according to the paper width size is provided. Known configurations are provided.

In such a fixing device, the heater member 956 is provided with a plurality of heat generating parts 956a, and one temperature detecting means 936 for detecting the temperature of one heat generating part 956a among the plurality of heat generating parts is arranged. Then, the temperature detecting 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 parts is damaged, other heat generating parts may generate heat. Therefore, when the heat generating unit 956a detected by the temperature detecting unit 936 is damaged, there is a problem that the abnormal temperature rise due to other heat generating units cannot be detected.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device that appropriately detects abnormal temperature rise of a heat generating portion.

In order to solve the above problems, the fixing device according to claim 1 of the present invention is
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 ,
Equipped with
A fixing device for fixing the sheet-shaped recording material carrying the unfixed image in the fixing nip portion,
The heating member includes an elongated base member extending in the longitudinal direction of the fixing member , and a plurality of heating elements formed on the base member 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 at the same time,
In the heating region, the plurality of heating elements are electrically connected in parallel, and
A first temperature detecting means arranged at a position corresponding to the first heating element;
Second temperature detecting means arranged at a position corresponding to the second heating element,
It is characterized by having.

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

It is a block diagram which shows schematically the image forming apparatus which concerns on the 1st Embodiment of this invention. FIG. 2 is a configuration diagram schematically showing a fixing device of the image forming apparatus shown in FIG. 1. FIG. 2 is a configuration diagram schematically showing a nip forming member of the image forming apparatus shown in FIG. 1. FIG. 3 is a configuration diagram showing a heating member of the image forming apparatus shown in FIG. 1. FIG. 3 is an explanatory diagram illustrating a heater member of the image forming apparatus illustrated in FIG. 1. 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, and a description will be given based on this, of course, the present invention can be similarly applied to a known color image forming apparatus. It is something. In a monochrome printer, as is known, a developing device including a charging roller 18 as a charging unit, a mirror 20 constituting an exposing unit, and a developing roller 22a as a developing unit around a photosensitive member 8 as an image carrier. 22, a transfer device 10, a cleaning device 24 including a cleaning blade 24a, and the like are arranged. Then, between the charging roller 18 and the developing device 22, the exposure portion 26 on the photoconductor 8 is irradiated with the exposure light Lb via the mirror 20 and is scanned. Further, a paper feeding means 4 is arranged below the printer. A registration roller pair (positioning roller pair) 6 is provided in the middle of the sheet conveying path to the image forming unit. At the end of the sheet conveyance path, a fixing belt 28 (belt-shaped fixing member; hereinafter simply referred to as a fixing belt), a fixing device 12 having a heater member 56 and a pressure roller 30 as main constituent members are provided.

The paper feeding means 4 is a paper feeding tray 14 in which paper P as a recording material is accommodated in a stacked state, and a paper feeding in which the paper P accommodated in the paper feeding tray 14 is separated one by one in order from the top. It has rollers 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 the posture deviation is corrected, 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 and the predetermined position of the front end of the paper P in the transport direction match. It is sent to the transfer portion N by the registration roller pair 6 at a timing.

The image forming operation in this printer is performed in the same manner as the conventional one. When the photoconductor 8 starts rotating, the surface of the photoconductor 8 is uniformly charged by the charging roller 18, and the exposure light Lb is applied to the exposure unit 26 based on the image information and is scanned so that a static image corresponding to the image to be created is obtained. A latent image is formed. This electrostatic latent image is moved to a position facing the developing device 22 by the rotation of the photoconductor 8, where toner is supplied and visualized to form a toner image. The toner image formed on the photoconductor 8 is transferred onto the sheet P entering the transfer portion N at a predetermined timing by applying a transfer bias of the transfer device 10. The sheet P carrying the toner image, which is an unfixed image, is conveyed toward the fixing device 12, fixed by the fixing device 12, and then discharged and stacked on a discharge tray outside the machine. The residual toner remaining on the photoconductor 8 without being transferred at the transfer portion N reaches the cleaning device 24 as the photoconductor 8 rotates and is scraped off by the cleaning blade 24a while passing through the cleaning device 24. To be cleaned. After that, the residual potential on the photoconductor 8 is removed by a known static eliminator to prepare for the next image forming step.

Next, the configuration of the fixing device according to the exemplary 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 contacts the outer peripheral surface of the fixing belt 28, and a heater member 56 that is 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 equalizing the heat 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 is 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 portion SN and upstream of the heater member 56. Further, a second thermistor 36 is provided as a temperature detecting means for detecting the temperature of the heater member 56 itself. Heating control means 42 is provided for controlling the power supply 40 for supplying electric power to the heater member 56 based on the detection information of these thermistors. The heating control means 42 means a microcomputer including a CPU, a ROM, a RAM, an 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 enhances the durability and secures the releasability is formed of a fluorine-based resin such as PFA or PTFE and has a thickness of 5 to 50 μm. The belt substrate is not limited to nickel and may be made of a heat resistant resin material such as SUS or polyimide (PI).

The pressure roller 30 has an outer diameter of 30 mm and has a solid iron cored bar 30a and an elastic layer 30b formed on the surface of the cored bar 30a. The elastic layer 30b is made of silicone rubber and has a thickness of 5 mm. On the surface of the elastic layer 30b, it is desirable to form a fluororesin (PFA or PTFE) layer having a thickness of about 40 μm in order to enhance 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 the biasing means. The pressure roller 30 rotates by receiving a driving force from a driving source such as a motor provided in the image forming apparatus via a gear. The pressure roller 30 rotates the fixing belt 28 together.

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

As shown in FIG. 4, the fixing belt 28 contacts and slides on the inner peripheral surface of the heat transfer member 50 assembled and heated on the front surface side of the heater member 56, 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 of a high heat conductive material such as copper or aluminum. The heater member 56 and the heat transfer member 50 may be improved in adhesion by using heat conductive grease or a heat conductive sheet. Due to the improved adhesion, the heat transfer property to the front surface side of the heater member 56 is improved rather than the back surface side (the side opposite to the fixing belt) to ensure the belt heating and to improve the heat transfer property in the heater longitudinal direction to improve the thermal uniformity. Can be secured.

Further, the heater holder 57 holds the heater member 56 from the back surface side thereof. In order to minimize heat conduction to the heater holder 57, the heater holder 57 is shaped so as not to come into contact with the entire back surface of the heater member 56 but to remain in partial contact, and is made of a heat-resistant resin such as LCP and the like. Materials with low rates are used. The pressure roller 30 and the heat transfer member 50 come into contact with each other via the fixing belt 28 to form a nip region, but the portion where the heater holder 57 projects toward the belt side from this contact surface is located upstream and downstream in the paper transport direction. By having it on the side, the separability of the paper 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 56a in the longitudinal direction thereof, that is, in the direction orthogonal to the sheet conveying direction. The plurality of resistance heating elements 56a are connected to the counter electrodes on the upstream side and the downstream side in the paper transport direction, and generate heat uniformly in the longitudinal direction. The common wiring Wcom and the individual wirings W1 and W2 are connected to the counter electrode to form two heating regions H11 and H12. Each heating region H11, H12 can be individually and independently heated controlled by turning on/off the individual wirings W1, 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. The heating control means 42 controls the temperature of each heating region in consideration of the detection information and the sheet size information, and changes the heating rate of the heater member 56. By controlling the heating according to the paper passing size information as well, it is possible to avoid the situation where the temperature of the non-paper passing area becomes too high, and it is possible to prevent the damage of the member and the deterioration of the image quality due to the excessive temperature rise of the non-paper passing area. Actually, the power supply may be completely stopped (turned off) at a portion corresponding to the non-sheet passing area, but if the temperature is excessively decreased, it may not be possible to reach the fixing temperature in the next image area in time. Sometimes. For this reason, the temperature is controlled so that the fixing belt is kept at the second target temperature which is lower than the first target temperature corresponding to the image area but is a predetermined value or more higher than room temperature, and to the portion corresponding to the non-sheet passing area. Is also supplied with electricity.

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

Next, an image forming apparatus according to the second exemplary embodiment of the present invention will be described. The same components as those of the image forming apparatus according to the first embodiment are designated by the corresponding reference numerals and detailed description thereof will be omitted, and different components will be described in detail with reference to the drawings.

The second embodiment is different from the first embodiment in that the heater member has a different configuration. The details will be described below.

As shown in FIG. 6, the heater member 156 of the present embodiment has a plurality of resistance heating elements 156a in the longitudinal direction thereof, that is, in the direction orthogonal to the sheet conveying direction. The plurality of resistance heating elements 156a are connected to the counter electrodes on the upstream side and the downstream side in the paper transport direction, and generate heat uniformly in the longitudinal direction. The common wiring Wcom and the individual wirings W1 and W2 are connected to the counter electrode to form three heating regions H21, H22, and H23. The heating regions H21 and H23 are formed at symmetrical positions from the center of the heater member 156 in the longitudinal direction, and are configured so that they can be turned on/off at the same time. That is, the heating regions H21 and H23, which can be turned on/off at the same time, are separately arranged separately 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 switch 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 installed in each of the heating regions H21 and H23. Two second thermistors 36 that detect the temperature of one resistance heating element 156a are installed in the heating region H32. That is, a plurality of second thermistors 36 are installed in each heating region where ON/OFF control can be performed simultaneously. Then, when the second thermistor 36 detects the abnormal temperature rise of the resistance heating element 156a, the heating control means 42 controls the temperature of the heating region. Therefore, even if the resistance heating element 156a detected by the second thermistor 36 is damaged, an abnormal temperature rise due to another resistance heating element 156a can be detected. By electrically connecting the heating regions H21 and H23 that are heated at the same time in parallel, it is possible to prevent the voltage applied to each second thermistor 36 from changing when the second thermistor 36 is damaged, thereby providing a safer configuration. You can In addition, in the present embodiment, two second thermistors 36 are installed in each heating area that can be controlled to be turned on and off at the same time, but three or more second thermistors 36 may be installed.

Next, an image forming apparatus according to the third exemplary embodiment of the present invention will be described. The same components as those of the image forming apparatus according to the first embodiment are designated by the corresponding reference numerals and detailed description thereof will be omitted, and different components will be described in detail with reference to the drawings.

The third embodiment is different from the first embodiment in that the heater member has a different configuration. The details will be described below.

As shown in FIG. 7, the heater member 256 of the present embodiment has a long resistance heating element 256a in the longitudinal direction thereof, that is, in the direction orthogonal to the sheet conveying direction. The common wire Wcom and the individual wires W1 and W2 are connected to the resistance heating element 256a. The common wiring Wcom forming the first current-carrying electrode and the individual wirings W1 and W2 forming the second current-carrying electrode form a comb-tooth-shaped conductive portion with respect to the resistance heating element 256a. To form. The resistance heating element 256a has three heating regions H31, H32, H33. The heating regions H31 and H33 are formed at symmetrical positions from the center of the heater member 256 in the longitudinal direction, and are configured so that they can be turned on/off at the same time. That is, the heating regions H31 and H33, which can be turned on/off at the same time, are separately arranged separately and electrically connected in parallel. The heating regions H31, H33 and the heating region H32 can be individually and independently heated controlled by turning on/off the individual wirings W1, W2. As a result, the number of switch 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 heating portion of the resistance heating element 256a is installed. In the heating area 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 where ON/OFF control can be performed simultaneously. Then, when the second thermistor 36 detects the abnormal temperature rise of the resistance heating element 256a, the heating control means 42 controls the temperature of the heating region. Therefore, even if a part of the resistance heating element 256a detected by the second thermistor 36 is damaged, it is possible to detect an abnormal temperature rise due to another part of the resistance heating element 56a. By electrically connecting the heating areas H31 and H33 that are heated at the same time in parallel, it is possible to prevent the voltage applied to each second thermistor 36 from changing when the second thermistor 36 is damaged, thereby providing a safer configuration. You can In addition, in the present embodiment, two second thermistors 36 are installed in each heating area that can be controlled to be turned on and off at the same time, but three or more second thermistors 36 may be installed.

Although the embodiment of the present invention has been described above, the present invention is not limited to this.
In the above-described embodiment, two or three heating regions are formed, but the present invention is not limited to this aspect, and more heating regions such as nine can be set. Moreover, as shown in FIG. 8, it is also applicable to a configuration in which the heating region is not divided.

In addition, at least one of the plurality of second thermistors arranged in the heating area for heating at the same time is configured to detect the high temperature by hardware while controlling the temperature by software based on the detected temperature information. Is also good. With this, when an abnormal temperature rise occurs, the abnormality can be detected even in a lower temperature state, so that the safety can be improved.

28 fixing belt (an example of belt-like fixing member)
30 pressure roller (an example of a pressing member)
36 Second Thermistor (Temperature Detector)
56 Heater member (an example of a heating member)
56a Resistance heating element (example of heating element)
56b Substrate SN Fixing nip part

Claims (9)

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 ,
Equipped with
A fixing device for fixing the sheet-shaped recording material carrying the unfixed image in the fixing nip portion,
The heating member includes an elongated base member extending in the longitudinal direction of the fixing member , and a plurality of heating elements formed on the base member 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 at the same time,
In the heating region, the plurality of heating elements are electrically connected in parallel, and
A first temperature detecting means arranged at a position corresponding to the first heating element;
Second temperature detecting means arranged at a position corresponding to the second heating element,
A fixing device comprising: The fixing device according to claim 1, further comprising a fixing member temperature detecting unit that detects a temperature of the fixing member. The fixing device according to claim 2, wherein the fixing member temperature detecting means is in contact with an outer surface of the fixing member. The first temperature detecting means detects the temperature of the first heating element,
The fixing device according to claim 1, wherein the second temperature detecting unit detects a temperature of the second heating element. The heating region, in the longitudinal direction of the fixing member is divided spaced, and characterized in that it is electrically connected in parallel, according to any one of claims 1-4 Fixing device. The fixing device according to claim 5, wherein the divided heating areas are arranged symmetrically with respect to the longitudinal center of the heating member. 7. The fixing device according to claim 5 , wherein each of the divided portions of the heating area has at least one temperature detecting unit capable of detecting the temperature of the heating element. 8. At least one of the temperature detection means performs temperature control by software based on the detected temperature information and performs high temperature detection by hardware, and the temperature detection means according to claim 1. Fixing device. An image forming apparatus comprising the fixing device according to claim 1 .

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