The present application claims priority from Japanese patent application number 2009-285243, filed on Dec. 16, 2009, the entire contents of which are hereby incorporated by reference herein.
1. Field of the Invention
The present invention relates to a fixing device to fix an unfixed image formed on a recording medium as a fixed image onto the recording medium, and an image forming apparatus including such a fixing device.
2. Description of the Related Art
As a fixing device provided to image forming apparatuses such as copiers, printers, facsimile machines, and multifunctional machines including the above functions, there are those provided with a fixing belt stretched over three rollers as disclosed in JP-2007-108635-A and a fixing belt stretched over two rollers as disclosed in JP-2009-25464-A. Specifically, the former fixing belt is stretched over a fixing roller, a heat roller, and a tension roller. The latter fixing belt is stretched over the fixing roller and the heat roller without using the tension roller. Accordingly, the latter realizes greater compactness in the fixing belt. In the 2-roller arrangement, the heat roller also serves as a tension roller to give tension to the fixing belt.
The fixing device as illustrated in
When an image is fixed by this fixing device, first, the pressure roller 400 is driven to rotate by a driving motor, not shown, and the fixing belt 300, the fixing roller 100, and the heat roller 200 are driven by the driving of the pressure roller 400. Then, a sheet of a recording medium P on which an unfixed toner image T is carried is conveyed to the nip between the fixing belt 300 and the pressure roller 400 in the direction shown by the broken line arrow, and toner images T are fixed on the surface of the recording medium P with heat and pressure.
In addition, as illustrated in
However, in the fixing device of the type in which the fixing belt is stretched over two rollers as illustrated in
In order to solve the above-described problem, JP-2000-81804-A discloses a technology in which the temperature detector is integrated into the heat roller via a support member. Accordingly, even though the heat roller moves, since the temperature detector moves integrally with the heat roller, the distance between the heat roller and the temperature detector remains constant. However, a support member to connect the temperature detector with the heat roller is needed. Thus, the number of parts and assembly steps increase, hindering efforts at more compactness or lower manufacturing cost cannot be realized.
Accordingly, the present invent ion provides a novel fixing device, with a simple structure, capable of detecting the temperature of the fixing belt with higher precision, and a novel image forming apparatus provided with such a fixing device.
A fixing device according to the present invention includes a fixing member, a heating member configured to approach and withdraw from the fixing member, an endless fixing belt, wound around the fixing member and the heating member so as to be rotatable, a nip forming member to form a nip while contacting the fixing belt at a position opposite the fixing member, a pressing member to press the heating member so as to separate it from the fixing member, and a temperature detector to detect a temperature of the fixing belt at a position opposite the heating member. The temperature detector is positioned such that either a distance or a contact pressure between the temperature detector and the fixing belt remains substantially constant when the heating member moves from a first position to a second position in a movable range thereof in the approaching and withdrawing direction with respect to the fixing member. Further, the temperature detector is provided at a position on an outermost periphery of a displacement area of a surface of the fixing belt which displaces in accordance with the moving of the heating member that approaches and withdraws from the fixing member and parallel to the moving direction of the heating member, and is so provided as to be opposite or in contact with the fixing belt.
Thus, even though the surface of the fixing belt displaces according to the movement of the heating member, the distance or the contact pressure of the temperature detector with respect to the fixing belt is kept substantially constant.
Accordingly, variations in the detected temperature by the temperature detector can be restricted within an allowable range, thereby enabling detection of the temperature of the fixing belt with higher precision and preventing malfunction of the apparatus due to erroneous temperature detection by the temperature detector. In addition, damage to the fixing belt due to the excessively strong contact with the temperature detector may be prevented. Therefore, by preventing malfunction of the apparatus and damage to the fixing belt, a highly reliable fixing device and image forming apparatus can be provided.
These and other objects, features, and advantages of the present invention will become apparent upon consideration of the following description of the preferred embodiments of the present invention when taken in conjunction with the accompanying drawings.
An embodiment of the present invention will now be described with reference to drawings. In each of the drawings, the same reference numeral is applied to the same or corresponding parts and duplicate explanation thereof is simplified or omitted.
Referring to
This printer includes an image forming apparatus body 1 as a base, a sheet feed section or a sheet feed cassette 2 provided below the image forming apparatus body 1 and containing recording sheets P as recording media, and an image forming section 3 provided above the image forming apparatus body 1. The image forming section 3 includes an imaging section 8, an intermediate transfer unit 7, an optical writing unit 15, and a fixing device 30. The imaging section 8 includes four image forming units, 8Y, 8C, 8M, and 8Bk, as a plurality of image forming means each including an image carrier. The intermediate transfer unit 7 includes an intermediate transfer belt 7a as a flexible endless belt wound around a plurality of rollers 4, 5, and 6. The optical writing unit 15 serves as an optical writing section to optically write images on each image carrier. The fixing device 30 serves to fix a toner image onto a recording sheet P. The image forming units 8Y, 8C, 8M, and 8Bk and the intermediate transfer unit 7 are detachably provided with respect to the apparatus body 1. A conveyance path R in which the recording sheet P is conveyed is formed from a sheet feed section 2 to the fixing device 30. The roller 6 is provided in contact with the conveyance path R. In the present configuration, the intermediate transfer unit 7, the imaging section 8, the optical writing unit 15, and the fixing device 30 are components inside the image forming apparatus and provided substantially in the center of the apparatus body 1.
The portion of the intermediate transfer belt 7a between the roller 4 and the roller 5 corresponds to a lower belt running side. A secondary transfer roller 20 as a secondary transfer device is provided at a position opposite the roller 6 with the conveyance path R sandwiched therebetween. A belt cleaning device 21 serving to clean the belt surface is provided opposite the roller 4.
The imaging section 8 is provided below the intermediate transfer belt 7a. Each image forming unit includes a photoreceptor drum 10 and an image carrier contacting the intermediate transfer belt 7a, and further includes a charger 11, a developing device 12, and a cleaner 13, which are provided around each photoreceptor drum 10. A primary transfer roller 14 serving as a primary transfer means is provided at an inner side of the intermediate transfer belt 7a at a position corresponding to each photoreceptor drum.
In the present embodiment, each image forming unit 8Y, 8C, 8M, and 8Bk has the same basic structure, differing only in the color of toner contained therein as a developer, in each developing unit 12. Accordingly, as illustrated in
The optical writing unit 15 serves to irradiate the surface of each photoreceptor drum with light-modulated laser beams to form a latent image of each color thereon. In the present embodiment, the optical writing unit 15 is provided below the imaging section 8.
The toner supply bottles T1, T2, T3, and T4, the intermediate transfer unit 7, the imaging section 8, and the optical writing unit 15 are all slanted at the same angle to the horizontal inside the apparatus body 1, thereby reducing the installed area compared to a case in which these components are horizontally provided in the apparatus body 1.
When the image forming operation is started, the photoreceptor drum 10 of each image forming unit 8 is driven to rotate in the clockwise direction via a driving device, not shown, and the surface of each photoreceptor drum is uniformly charged with a predetermined polarity by the charger 11. The optical writing unit 15 radiates later beams to irradiate the surface of each charged photoreceptor drum, thereby forming electrostatic latent images on each surface thereof. In this case, the image information exposed on each photoreceptor drum is monochrome image information separated from a desired full-color image into color information of each of yellow, cyan, magenta, and black. The thus-formed electrostatic latent image is rendered visible as a toner image by the toner in each developing device 12 when passing between each photoreceptor drum and developing device 12.
Among the plurality of rollers 4, 5, and 6, over which the intermediate transfer belt 7a is stretched, one of the rollers is driven to rotate in the counterclockwise direction by a driving device, not shown, whereby the intermediate transfer belt 7a is driven in a counterclockwise direction as shown by arrows in
The residual toner deposited on the surface of each photoreceptor drum after primary transfer of the toner image is then removed from the surface thereof by the cleaner 13. Subsequently, the surface of the photoreceptor drum is subjected to a discharging operation by a discharger, not shown, and the surface potential is initialized and the photoreceptor drum is prepared for a next image formation.
A recording sheet P supplied from the sheet feed section 2 is conveyed to the conveyance path R, and further conveyed to a position between the roller 6 and the secondary transfer roller 20 at a timing adjusted by a registration roller pair 24 provided at a position nearer to the sheet feed side than to the secondary transfer roller 20. In this case, the secondary transfer roller 20 is supplied with a transfer voltage having a polarity opposite the charged polarity of the toner of the toner image on the surface of the intermediate transfer belt 7a. Accordingly, the toner image on the surface of the intermediate transfer belt 7a is transferred onto the recording sheet P en bloc. The recording sheet P on which the toner image has been transferred is then transferred to the fixing device 30. When passing through the fixing device 30, the recording sheet P is heated and pressed, fusing the toner image and fixing it on the recording sheet P. The recording sheet P on which the toner image is fixed is conveyed to a discharge section 23 provided at the end of the conveyance path R and is discharged onto a stack section 25 provided at an upper side of the apparatus body 1. The surface of the intermediate transfer belt 7a, of which the toner image thereon has been transferred to the recording sheet P, is cleaned by the cleaning device 21, which removes the residual toner on the intermediate transfer belt 7a.
The thus-configured printer includes four image forming units 8Y, 8M, 8C, and 8Bk provided opposite the intermediate transfer belt 7a, in which each color toner image is transferred sequentially on the intermediate transfer belt 7a. Therefore, compared to the type of printer including one image forming unit and four developing devices, in which toner images superimposed one atop the other on the intermediate transfer belt and the superimposed toner images are transferred onto the recording sheet, the image forming time can be drastically shortened. Moreover, since the stack section 25 is formed at the upper side of the apparatus body 1, the stack section 25 does not protrude from the apparatus body 1, thereby reducing the mount area occupied by the image forming apparatus.
The above description relates to a full-color image forming operation. However, using any one of the image forming units in the imaging section 8, a monochrome image may be formed. Otherwise, a two-color image or three-color image may also be formed. Monochrome printing using the printer according to the present embodiment is performed such that the electrostatic latent image is formed only on the photoreceptor drum in the image forming unit 8Bk, is developed by the same unit and transferred to the recording sheet P, and is fixed by the fixing unit 30.
Next, the fixing device 30 of the belt fixing method according to the present embodiment will now be described in detail.
As illustrated in
The fixing roller 31 includes a metal core 31a formed of SUS304 and the like, and an elastic layer 31b formed of a foam member such as a foamed silicon rubber and the like around the core. The elastic layer 31b is formed by a foamed member so that a nip width or amount in the nip portion may have a comparatively large area and the heat in the fixing belt 33 does not transfer to the fixing roller 31 easily. In the present embodiment, the fixing roller 31 has an outer diameter of 29 mm and the elastic layer 31b has a thickness of 8.5 mm. The heat roller 32 is a hollow cylinder made of a metal material such as aluminum or stainless steel, with a wall thickness of 1 mm or less. In the present embodiment, the heat roller 32 is formed of aluminum having a thickness of 0.6 mm, and the heat roller 32 has an outer diameter of 20 mm. A halogen heater 35 as a heat source is arranged inside the heat roller 32. The halogen heater can also be provided inside the pressure roller 32 similarly to the case of the fixing roller 31. The wall thickness of the heat roller 32 is set to be 1 mm or less in order to reduce its thermal capacity, thereby improving the temperature-raising capability of the apparatus by reducing the rise time required.
The fixing belt 33 includes a base member formed of a resin such as polyimide and having a thickness of 50 to 150 μm, an elastic layer provided on the base member and formed of silicon rubber with a thickness of 100 to 200 μm, and a release layer provided on the silicon rubber layer and formed of fluoropolymers such as tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA), fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE), or the like, with a thickness of 20 to 50 μm. Alternatively, the fixing belt 33 may be formed only of the resin or metallic base member in order to reduce the thermal capacity.
The fixing belt 33 is formed to have a minimum peripheral length to reduce the thermal capacity. The outer diameter of the fixing roller 31 is preferably larger than that of the heat roller 32 to secure a nip width necessary for satisfactory fixing performance, and the heat roller 32 is made as small as possible so as not to interfere with the halogen heater 35 provided inside thereof.
The pressure roller 34 is pressed by a spring, not shown, with a load of 40 to 80 kgf against the fixing roller 31, thereby forming a nip. In addition, the pressure roller 34 includes a metal core 34a formed of aluminum or iron and an elastic layer 34b formed of an aquiform or foamed silicon with a thickness of 2 to 6 mm surrounding the metal core 34a. In the present embodiment, the outer diameter of the pressure roller 34 is 30 mm and the thickness of the silicon layer is 3.5 mm. The surface layer of the pressure roller 34 is a release layer 34c formed of PFA, PTFE, and the like. The surface hardness of the pressure roller is 10 to 70 Hs on the Asker C hardness scale.
A separation plate 38 serving to separate the recording sheet from the fixing belt 33 is provided at a position facing the peripheral surface of the fixing belt 33 and in the vicinity of an outlet of the nip. The separation plate 38 is so provided as to be separated from the fixing belt 33 by a predetermined gap in the widthwise imaging area. In the present embodiment, the gap between the separation plate 38 and the fixing belt 33 is set at 0.3 mm or so. In addition, both ends of the separation plate 38 in the widthwise direction are configured to contact non-imaging areas of the fixing belt 33. Thus, by providing a separation plate 38 which does not contact the imaging area of the fixing belt 33, without adversely affecting the formed image, a phenomenon in which the recording sheet after passing through the fixing process winds around the fixing belt 33 may be prevented.
The thermistor 36 and the thermostat 37, respectively, are provided at a position opposite the heat roller 32 and separated from the peripheral surface of the fixing belt 33 by a predetermined distance. They are fixed to a frame, not shown, provided on the fixing device. Further, in the present embodiment, the thermistor 36 and the thermostat 37 are provided above the heat roller 32 so that the temperature of the heat rising from the fixing belt 33 can be detected easily.
The thermistor 36 serves to detect changes in the temperature of the fixing belt 33 so as to maintain the temperature of the fixing belt 33 at a constant predetermined level. Specifically, the temperature of the fixing belt 33 detected by the thermistor 36 is transmitted to a controller such as a CPU provided in the image forming apparatus that controls activation of the halogen heater 35 inside the heat roller 32 based on the temperature, whereby the fixing temperature of the fixing belt 33 is maintained at a desired, target temperature. It is to be noted that the, instead of the thermistor, a thermopile may be used. However, the thermistor is preferable because of its compactness and low cost.
The thermostat 37, upon detecting that the fixing belt 33 is overheating, serves as a means to prevent excessive temperature rise by shutting off the power supply to the halogen hater 35. In the present embodiment, upon the ambient temperature of the fixing belt 33 reaching approximately 185° C., the thermostat 37 shuts off the power supply to the halogen heater 35.
As illustrated in
In addition, the heat roller 32 is pressed in the X-direction away from the fixing roller 31. In the present embodiment, as a pressing means, a tension spring 42 is provided to pull the heat roller 32 with a load of 2 to 20 kgf. However, the pressing means is not limited to the tension spring, and, for example, a compression spring may be used to press the heat roller 32. When the heat roller is pulled by the tension spring 42, the fixing belt 33 is given a predetermined tension.
The direction in which the heat roller 32 is biased by the tension spring is preferably set to be substantially parallel to the moving direction of the heat roller 32, that is, the X- or Y-direction. As the pressing angle with respect to the moving direction of the heat roller 32 increases, the loss in the pressing force also increases, thereby increasing the size and the manufacturing cost of the apparatus. By contrast, if the pressing direction of the heat roller 32 is set to be parallel to the moving direction of the heat roller 32, the pressing angle with respect to the moving direction of the heat roller 32 becomes minimal, thereby decreasing the loss of the pressing force and reducing the size and the manufacturing cost of the apparatus.
It is preferable to set the pressing direction of the heat roller 32 to be substantially parallel to but slightly deviated from the moving direction of the heat roller 32, rather than setting it to be completely parallel. In
Meanwhile, the halogen heater 35 in the heat roller 32 is fixed to the frame of the fixing device. Accordingly, if the heat roller 32 moves along the guide opening 39a, there is a possibility that the halogen heater 35 and the heat roller 32 may interfere with each other. The position of the heat roller 32 with respect to the halogen heater 35 changes due to deviations of the outer diameter of the heat roller 32 and the fixing roller 31, variations in the peripheral length of the fixing belt 33, variations in the dimensional and assembly precision of the side plate 39 supporting each roller, thermal expansion of the above parts, and the like. However, the moving amount of the heat roller 32 due to the above various factors is predictable considering the precision of respective parts and components, expansion ratios of materials for those parts and components, and the like. By dimensioning appropriately the outer diameter of the heat roller 32 based on the predicted moving amount due to the above various factors, the halogen heater 35 and the heat roller 32 are prevented from interfering with each other.
The pressure roller 34 is rotatably supported by a roller bearing, not shown. This roller bearing is movably supported at the side plate 39 so that the pressure roller 34 approaches to and departs from the fixing roller 31. The pressure roller 34 approaches to and departs from the fixing roller 31, whereby the pressure roller 34 is pressed against or is released from indirect contact with the fixing belt 33. With the apparatus as configured as described above, when sheet clogging occurs, for example, the pressure roller 34 is separated from the fixing belt 33 to be released from indirect contact with the pressure roller 34, thereby facilitating removal of the clogged recording sheet.
In addition, the pressure roller 34 is configured to be a driving roller which is rotatably driven by a driving motor, not shown. When the pressure roller 34 is driven to rotate in the clockwise direction as illustrated in
Referring to
First, an alternating current is supplied to the halogen heater 35 from a power source, not shown, provided in the image forming apparatus body, to thus generate heat in the halogen heater 35. The heat roller 32 is heated by heat radiated from the halogen hater 35 thus activated. Next, the heat of the heat roller 32 is transmitted to the fixing belt 33 to heat the fixing belt 33. The output of the halogen heater 35 is controlled based on the detection result of the belt surface temperature by the thermistor 36 so that the fixing temperature of the fixing belt 33 becomes a desired, target temperature.
Thereafter, the pressure roller 34 is driven to rotate in the clockwise direction in
Even in the event that heater control is not performed correctly due to failure of the thermistor 36, for example, the thermostat 37 shuts off the power supply to the halogen heater 35 upon the ambient temperature of the fixing belt 33 reaching approximately 185° C. Thus, the temperature of the fixing belt 33 is prevented from rising an abnormal temperature (for example, 250° C.) that damages the fixing belt 33 and others.
As illustrated in
As illustrated in
Then, the central portion of the widthwise direction of the fixing belt 33 in which the small-sized sheets pass and the two end portions in which the small-sized sheets do not pass are configured to be heated separately. Then, when the small-sized sheets are continuously passed, only the central portion of the widthwise direction of the fixing belt 33 is heated, thereby preventing the excessive temperature rise in the two end portions from occurring.
In addition, if the central portion and the two end portions of the fixing belt 33 are configured to be heated separately, the thermistor 36 and the thermostat 37 need to be provided one piece each at the central portion in the widthwise direction and the end portion in the widthwise direction of the fixing belt 33. Thus, the temperatures at the central portion in the widthwise direction and the end portion in the widthwise direction of the fixing belt 33 are detected separately, thereby performing temperature adjustment and overheat prevention of the fixing belt 33 effectively and securely.
In addition, the image forming apparatus according to the present invention is not limited to the center-referenced conveyance method as illustrated in
When the fixing belt 33 expands or shrinks due to heating and cooling, the heat roller 32 moves in a direction approaching to or departing from the fixing roller 31 (X- or Y-direction in the figure) in order to maintain the tension on the fixing belt 33. In this case, in accordance with the movement of the heat roller 32, the position of the surface of the fixing belt 33 also displaces. A solid line A in
Since the thermistor 36 and the thermostat 37 (hereinafter simply “thermistor 36”) are provided as described above, even when the heat roller 32 moves in a direction approaching to or departing from the fixing roller 31, the distance between the thermistor 36 and the fixing belt 33 may be kept constant.
Specifically, if the heat roller 32 moves from a state as illustrated in
As illustrated in
The embodiment as illustrated in
Then, in the present embodiment, the thermistor 36 is provided at a portion opposite the portion H parallel to the moving direction of the heat roller 32 and below the heat roller 32, and opposite the fixing belt 33. Accordingly, when the heat roller 32 displaces in a direction approaches and withdraws from the fixing roller 31, the portion of the fixing belt 33 opposite the thermistor 36 expands or shortens in parallel with the moving X- or Y-direction of the heat roller 32, thereby retaining the distance between the thermistor 36 and the fixing belt 33 constant.
As illustrated in
In this case, since the thermistor 36 is provided opposite the curved portion of the fixing belt 33 wound around the heat roller 32, the distance D5 between the fixing belt 33 and the thermistor 36 slightly changes to the distance D6 when the heat roller 32 moves from a state as illustrated in
For example, the present embodiment employs a thermostat 37 to cut off supply of electric current to the halogen heater 35 upon the ambient temperature of the fixing belt 33 reaching approximately 185° C. The thermostat 37 has an allowable range of ±5° C. in detecting temperature. The distance D between the thermostat 37 and the fixing belt 33 is set to be 1.1 mm. If the variations in the distance D are within ±0.3 mm, the detected temperature by the thermostat 37 can be restricted within the allowable range of ±5° C. In this case, by applying the structure of the present invention, the variations in the distance D between the thermostat 37 and the fixing belt 33 can be within ±0.3 mm, and therefore, the variations in the detected temperature by the thermostat 37 can be restricted within an allowable range for temperature detection.
To detect temperature with higher precision, as illustrated in
It is to be noted that although the structure of the present invention is applied to the fixing device including a non-contact-type temperature detecting means (thermistor and thermostat), the structure of the present invention is also applicable to the fixing device including a contact-type temperature detecting means. Hereinafter, an embodiment will now be described in which the present invention is applied to the fixing device including a contact-type temperature detecting means.
The fixing device 30 as illustrated in
As illustrated in
When manufacturing the fixing device, the contact surface 41a of the thermistor 41 is coated with lubricant, thereby making it unnecessary to lubricate the surface of the fixing belt 33, and further, making it unnecessary to lubricate after assembly, thus streamlining manufacturing. In addition, lubricating the thermistor 41 before assembly enables forming a similar lubricant layer 50 for each fixing device between the contact surface 41a of the thermistor 41 and the surface of the fixing belt 33, and realizes a uniform performance of the device.
In the present embodiment, the moving direction of the heat roller 32 is formed parallel to the upper, flat surface of the fixing belt 33. Accordingly, a portion H on the outermost periphery A of the displacement area of the fixing belt 33 which displaces in accordance with the displacement of the heat roller 32 and parallel to the moving X- or Y-direction of the heat roller 32 exists at an upper side of the fixing belt 33. Then, the thermistor 41 is provided at the portion H to be parallel to the moving direction of the heat roller 32 and opposite the heat roller 32, and contacting the fixing belt 33 via the lubricant layer.
Accordingly, when the heat roller 32 displaces from a state as illustrated in
As illustrated in
If the moving direction of the heat roller 32 is configured to be parallel to the lower flat surface of the fixing belt 33 as illustrated in
The structure as illustrated in
In this case, since the thermistor 41 contacts the curved surface of the fixing belt 33 wound around the heat roller 32, when the heat roller 32 displaces from a state as illustrated in
However, in order to detect temperature more precisely, as illustrated in
Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and additional modifications and variations of the present invention are possible in light of the above teachings.
For example, as illustrated in
The pressure roller 34 and the heat roller 32 may be formed of a non-rotatable pressure member and heating member, respectively. In this case, what is required is to rotate the fixing belt 33 by the rotation of at least one of the fixing member, the heating member, and the pressure member. A structure in which a pressure belt is used as a nip forming member, and the fixing belt is pressed by the pressure belt via the pressure roller or the pressure pad and the like, is also possible. The nip forming member is not limited to a structure that presses against the fixing belt, and may be configured to simply contact the fixing belt without pressing against it.
The fixing device of the present invention is not limited to that which is mounted in the color image forming apparatus as illustrated in
As described above, the fixing device in the embodiments of the present invention may retain the distance or the contact pressure of the temperature detecting means with respect to the fixing belt at a constant level, even when the heat roller displaces due to the expansion or shrinkage of the fixing belt. That is, in the structure of the present invention, even when the heat roller displaces from a first position to a second position in the movable area of the heat roller, the temperature detecting means is arranged so that the distance or the contact pressure of the temperature detecting means with respect to the fixing belt is retained substantially constant. Herein, “substantially constant” includes a case in which the distance is strictly coincident as well as a case in which the distance changes within an allowable range for the temperature detection.
Therefore, variations in the detected temperature of the temperature detecting means may be restricted within the allowable range. Thus, the temperature of the fixing belt can be detected with higher precision, and malfunction of the apparatus due to erroneous detection of the temperature detecting means may be prevented. In addition, scratches on the fixing belt caused due to too-tight contact with the temperature detecting means may be prevented. According to the present invention, malfunction of the apparatus and scratches on the fixing belt can be prevented, thereby enabling provision of a highly reliable fixing device and image forming apparatus.
Further, according to the present invention, by providing the temperature detecting means at a predetermined position relative to the fixing device, the temperature of the fixing belt can be detected with higher precision, thus simplifying the structure of the apparatus to achieve a compact, low-cost apparatus.
Additional modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.
Number | Date | Country | Kind |
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2009-285243 | Dec 2009 | JP | national |