The present invention relates to an image heating apparatus suitable when it is used as a fixing apparatus (fixing device) to be mounted in an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer.
As the fixing apparatus to be mounted in the image forming apparatus, a fixing apparatus of a belt type in which a cylindrical film which has high energy efficiency to quickly raise a surface temperature and which has a very small thermal capacity (hereinafter referred to as a belt member) is radiation-heated from its inside by a heat source such as a halogen heater has been proposed (Japanese Laid-Open Patent Application (JP-A) 2009-93141).
Such a fixing apparatus of the belt type has the small thermal capacity and a high temperature rise speed, and therefore may only be required to be heated only during printing. Accordingly, the fixing apparatus has advantages such that a time from turning-on of a main switch until the image forming apparatus is in a printable state is short and that also electric power consumption during stand-by for printing is considerably small.
The present invention relates to an image heating apparatus suitable for use as a fixing apparatus (fixing device) to be mounted in an image forming apparatus, such as an electrophotographic copying machine or an electrophotographic printer.
As the fixing apparatus to be mounted in the image forming apparatus, a fixing apparatus of a belt type has been proposed in which a cylindrical film which has high energy efficiency to quickly raise a surface temperature and which has a very small thermal capacity (hereinafter referred to as a belt member) is radiation heated from its inside by a heat source such as a halogen heater (Japanese Laid Open Patent Application (JP A) 2009 93141).
Such a fixing apparatus of the belt type has the small thermal capacity and a high temperature rise speed, and therefore may only be required to be heated only during printing. Accordingly, the fixing apparatus has advantages such that the time from turning on of a main switch until the image forming apparatus is in a printable state is short and that electrical power consumption during a printing stand-by state is considerably small.
Incidentally, the fixing apparatus includes an overheating preventing element, such as a thermo switch or a thermal fuse, for interrupting electrical power supply to the heat source, which is ready for the case where the heat source is abnormally heated due to breakdown (failure) of a controller or the like, and therefore also the fixing apparatus of the belt type requires the overheating preventing element. As an example of a position where the overheating preventing element is provided, it would be considered that the overheating preventing element is disposed in non-contact with the belt member so that a surface of the belt member is not damaged. Further, the overheating preventing element is needed to be disposed, for ensuring its operation reliability, at a position where the overheating preventing element is prevented from being directly subjected to radiation of heat radiation by the halogen heater. Therefore, in order to prevent the damage on the belt member and to ensure the operation reliability of the overheating preventing element, the type in which the overheating preventing element is disposed in non-contact with the belt member in the neighborhood of an outside of the cylinder of the belt member has been used in general.
However, the fixing apparatus of the belt type involves the following problem. When the overheating preventing element is disposed in non-contact with the belt member in the neighborhood of the outside of the cylinder of the belt member, the operation time of the overheating preventing element becomes slow compared with the case where the overheating preventing element is disposed in contact with the belt member. Further, when the cases where the belt member is rotated and is not rotated are compared, a spatial distance is changed and also the operation time of the overheating preventing element varies. Further, during rotation of the belt member, the shape and attitude of the belt member fluctuate (i.e., a rotation locus is fluctuated), but even when this fluctuation is caused, the surface damage of the belt member must be prevented.
Therefore, when the spatial distance between the overheating preventing element and the belt member is made sufficiently large in order to prevent the contact between the overheating preventing element and the belt member, the time until the overheating preventing element is actuated becomes long.
Further, with an increase in electrical power of the fixing apparatus due to speeding up of the fixing apparatus, further reduction in the operation time of the overheating preventing element is required. For that reason, when the overheating preventing element is disposed in non-contact with the belt member in the neighborhood of the outside of the cylinder of the belt member, there arises the case where the demands for reduction and stabilization in the operation time of such an overheating preventing element cannot be met.
Therefore, when the overheating preventing element is disposed inside the cylinder of the belt member so that the operation time of the overheating preventing element is not adversely affected even when the belt shape fluctuates, there is a problem of ensuring of the operation reliability of the overheating preventing element. When the overheating preventing element is disposed inside the cylinder of the belt member, the overheating preventing element is directly subjected to the radiation of the heat rays from the halogen heater so that the ambient temperature exceeds the operation environment temperature range of the overheating preventing element. Further, not only a heat sensitive surface of the overheating preventing element but also the overheating preventing element as a whole are increased in temperature, so that there is a possibility that a malfunction and breaking of the overheating preventing element are caused to occur.
A principal object of the present invention, there is provided an image heating apparatus capable of realizing stabilization of an operation time of an overheating preventing element and capable of ensuring operation reliability.
According to an aspect of the present invention, there is provided an image heating apparatus comprising: a rotatable cylindrical belt; a heater, provided inside the belt, for heating the belt; and an overheating preventing element, including a circuit which is opened when an abnormal temperature rise occurs, for interrupting electrical power supply to the heater, wherein the overheating preventing element is provided at a position, inside the belt, where the overheating preventing element is free from direct heat radiation emitted from said heater.
According to another aspect of the present invention, there is provided an image heating apparatus comprising: a rotatable cylindrical belt; a heater, provided inside the belt, for heating the belt; an overheating preventing element, including a circuit which is opened when an abnormal temperature rise occurs, for interrupting electrical power supply to the heater; and a metal member provided at a position, inside the belt, where the metal member is subjected to direct heat radiation emitted from the heater, wherein the metal member includes a protruded portion protruded from an end of the belt with respect to a direction of generatrix of the belt, wherein the overheating preventing element detects a temperature of the metal member at the protruded portion of the metal member.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.
a) is a perspective view of an outer appearance showing a schematic structure of a whole fixing apparatus according to a Second Embodiment.
a) is a perspective view of an outer appearance showing a schematic structure of a whole fixing apparatus according to a Third Embodiment.
In the following, embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments do not limit the present inventions according to claims, and all of combinations of features described in the embodiments are not necessarily essential to solution means of the present invention.
The image forming apparatus in this embodiment includes an image forming portion 17, a fixing portion (fixing apparatus) 6, a controller 18 for controlling the image forming portion 17 and the fixing portion 6, and the like. The controller 18 comprises a CPU and a memory such as RAM or ROM, and in the memory, an image forming sequence, various programs necessary for image formation, and the like are stored.
At the image forming portion 17, as an image bearing member, a rotation-drum-type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 1 is provided. This photosensitive drum 1 is constituted by forming a photosensitive material layer of OPC, amorphous Se, amorphous Si, or the like on an outer peripheral surface of a cylinder (drum) like electroconductive substrate of nickel or aluminum. The controller 18 rotationally drives a motor (not shown) depending on a print command (instruction) outputted from an external device (not shown) such as a host computer, so that the photosensitive drum 1 is rotated in a direction indicated by an arrow a at a predetermined peripheral speed (process speed).
This photosensitive drum 1 is, in a rotation process thereof, electrically charged uniformly to a predetermined polarity and a predetermined potential by a charging roller 2 as a charging means.
Then, the charged surface of the photosensitive drum 1 is subjected to scanning exposure to a laser beam L which is outputted from a laser beam scanner 3 and which is modulation-controlled (ON/OFF-controlled) depending on image information from the external device. As a result, an electrostatic latent image of intended image information is formed on the surface of the photosensitive drum 1.
Then, the electrostatic latent image formed on the surface of the photosensitive drum 1 is developed with a toner T by a developing device 4 as a developing means, thus being visualized as a toner image. As a developing method, a jumping developing method, a two-component developer type developing method and the like are used and are, in many cases, used in combination with image exposure and a reverse developing method.
On the other hand, sheets of a recording material P accommodated in a (sheet) feeding cassette 9 are fed one by one by rotation of a (sheet) feeding roller 8 at predetermined feeding timing. This recording material P passes through a sheet path including a guide 10, a registration roller 11, and the like, and is fed to a transfer nip Tn formed between the surface of the photosensitive drum 1 and an outer peripheral surface of a transfer roller 5 as a transfer means, and then is nipped and conveyed between the surface of the photosensitive drum 1 and the surface of the transfer roller 5. In this conveying process, by applying a predetermined transfer bias to the transfer roller 5, the toner image on the surface of the photosensitive drum 1 is transferred and carried on the recording material P.
The recording material P which is separated from the surface of the photosensitive drum 1 and then comes out of the transfer nip Tn is guided into the fixing apparatus (fixing device) 6 by a conveying guide 12, and then an unfixed toner image on the recording material P is heat-fixed on the recording material P by heat and pressure applied from the fixing apparatus 6. A constitution of the fixing apparatus 6 will be specifically described in (2) below.
The recording material P coming out of the fixing apparatus 6 passes through a sheet path including a conveying roller 13, a guide 14, a discharging roller 15, and the like, thus being printed out on a discharge tray 16.
The surface of the photosensitive drum 1 after the separation of the recording material P is subjected to removal (process) of a deposited contaminant such as a transfer residual toner by a cleaning device 7, thereby to be cleaned, and then is repetitively subjected to the image formation.
In the following description, with respect to the fixing apparatus 6 and members constituting the fixing apparatus 6, a longitudinal direction refers to a direction perpendicular to a recording material conveyance direction C (
In
The fixing apparatus 6 in this embodiment is roughly divided into the heating unit 100 for heating the unfixed toner image (not shown) formed on the recording material P and a pressing roller (pressing member) 102 for forming a fixing nip N in contact with the heating belt 101 of the heating unit 100. The heating unit 100 is prepared by integrally assembling members such as the rotatable cylindrical heating belt (belt member) 101, a slidable member 103 contacted to an inner surface of the heating belt 101 at a position where it opposes the pressing roller 102, a halogen heater 104, a holding member 105 for holding the slidable member 103, a stay (metal member) 106 for imparting rigidity (stiffness) to the fixing apparatus 6 (particularly to the heating unit 100), and the heater fixing member 110.
Each of the heating belt 101, the pressing roller 102, the halogen heater 104, the slidable member 103, the holding member 105 and the stay 106 is an elongated member extending in the longitudinal direction.
The holding member 105 holds the slidable member 103 at a recessed portion 105a (
The stay 106 has a leg portion 106a (
An outer peripheral portion of an assembly of the holding member 105, the slidable member 103, and the stay 106 are externally engaged loosely with the heating belt 101 formed with a cylindrical heat resistant film. In order to limit lateral movement of the heating belt 101 in the longitudinal direction in a rotation state and in order to fix the stay 106 on an apparatus frame (not shown) of the fixing apparatus 6, the flange member 109 is engaged at each of the longitudinal end portions of the stay 106.
The flange member 109, which is disposed at the longitudinal end portion of the stay 106 and which has a substantially D character shape at its side surface, is engaged with the leg portion 106a and connecting portion 106b of the stay 106 (
As shown in
The sealing portion 111 is constituted so that it has an electrical electric energy supplying structure supplying electrical energy to a filament 112 (
In the heating unit 100, the stay 106 is disposed inside the heating belt 101, and inside the stay 106, the halogen heater 104 is provided. Further, radiant light emitted from the halogen heater 104 passes through a cut away portion provided between a pair of the connecting portions 106b of the stay 106, so that the inner peripheral surface of the heating belt 101 is irradiated with the radiant light (
The pressing roller 102 is a member including a metal core 102a, an elastic layer 102b which is provided on the outer peripheral surface of the metal core 102a and which is formed of a silicone rubber or the like, and a parting layer 102c which is provided on the outer peripheral surface of the elastic layer 102b and which is formed of a fluorine containing resin. The pressing roller 102 is disposed opposed to the slidable member 103 of the heating unit 100 via the heating belt 101, and at its position, the metal core 102a is rotatably supported at its longitudinal end portions by the apparatus frame via bearings (not shown).
At each of the longitudinal end portions of the stay 106 of the heating unit 100, the pressing mechanism (not shown) including a pressing spring or the like is provided and presses the stay 106 at the longitudinal end portion of the stay 106 in a direction perpendicular to a direction of generatrix of the heating belt 101. By the pressing of the pressing mechanism, the stay 106 presses the slidable member 103 in the same direction via the holding member 105, so that the slidable member 103 presses the outer peripheral surface of the heating belt 101 to the outer peripheral surface of the pressing roller 102, so that the heating belt 101 is contacted (circumscribed) to the pressing roller 102. As a result, the elastic layer 102b of the pressing roller 102 is deformed, so that the fixing nip N having a predetermined width is formed by the surface of the pressing roller 102 and the surface of the heating belt 101.
In the fixing apparatus 6 in this embodiment, the pressing roller 102 is rotated, in accordance with a print command, by a motor (not shown) in a direction indicated by an arrow A at a predetermined peripheral speed (process speed). Rotation of the pressing roller 102 is transmitted at the fixing nip N to the heating belt surface by a frictional force between the surfaces of the pressing roller 102 and the heating belt 101. As a result, the heating belt 101 follows the rotation of the pressing roller 102 to be rotated in a direction indicated by an arrow B while contacting the surface of the slidable member 103 in the fixing nip N side at its inner peripheral surface.
Further, an electrical energy supply control circuit (not shown) is turned on in accordance with the print command, so that an AC voltage (electrical power) is supplied from a power source (not shown) and thus electrical energy is supplied to the halogen heater 104. The halogen heater 104 is turned on by the electrical energy supply to radiate the heat rays. Then, by the heat rays, the inner peripheral surface of the heating belt 101 and a back surface of the slidable member 103 at the side opposite from the fixing nip N side are heated. As a result, the heating belt 101 and the slidable member 103 are quickly increased in temperature.
The electrical energy supply control circuit obtains temperature information of the inner surface of the heating belt 101 detected by a temperature detecting element (not shown), such as a thermistor. Then, on the basis of the detected temperature, the control circuit controls the electrical power supplied to the halogen heater 104 so that the temperature of the halogen heater 104 is kept at a predetermined fixing temperature (target temperature). Here, the fixing temperature refers to a temperature necessary to heat and melt the unfixed toner image formed on the recording material P.
In a state in which the motor is rotated and the heating belt 101 is kept at the fixing temperature, the recording material P on which the unfixed toner image is carried is introduced into the fixing nip N with an image carrying surface toward the heating belt 101. The recording material P is nipped at the fixing nip N by the surfaces of the heating belt 101 and the pressing roller 102 and is conveyed in a nipped state. In this conveying process, the unfixed toner image on the recording material P is heat-fixed on the recording material P by heat of the heating belt 101 and nip pressure at the fixing nip N, and then the recording material P is separated from the surface of the heating belt 101 and is thereafter discharged from the fixing nip N.
In
In
Here, the element fixing member 113 is a member for fixing the overheating preventing element 107 and for fixing and guiding the electrical wire Ca2 connected to the overheating preventing element 107 while protecting the electrical wire Ca2 from the heat rays. The element fixing member 113 is prepared by a material, having low thermal conductivity, such as a heat resistant resin material.
As described above, the overheating preventing element 107 and the element fixing member 113 are disposed at the position of the stay 106 where they do not receive directly the heat rays radiating from the halogen heater 104, so that it becomes possible to use the overheating preventing element 107 in a temperature range of an operable ambient temperature.
In this embodiment, a constitution is employed in which the overheating preventing element 107 is disposed in the region where the heat rays radiating from the halogen heater 104 are shielded by the stay 106, but the arrangement of the overheating preventing element 107 is not limited to such arrangement that the overheating preventing element 107 is disposed in the region where the heat rays are shielded by the stay 106. For example, the overheating preventing element 107 may also be surrounded by a reflection plate of metal, a resin member having an insulation effect, such as a heat resistant resin material having low thermal conductivity, or an insulation member, and may only be required that the member can shield direct radiation of the heat rays onto the overheating preventing element 107.
In
Further, a spatial distance between the halogen heater 104 and the stay 106 is irrespective of rotation of the heating belt 101 and is not changed. Therefore, the temperature of the stay 106 has a stable linear temperature characteristic that the temperature is increased depending on a turning on time of the halogen heater 104 (heating time by the heat ray rays) and is lowered depending on a turning off time. By employing a constitution in which the temperature of the stay 106 having such a stable linear temperature characteristic is detected by the overheating preventing element 107, improvement in thermal responsiveness of the overheating preventing element 107 can be realized.
In this embodiment, an object for which the overheating preventing element 107 detects its temperature, the stay 106 is used but is not limited to the stay 106. For example, the object may also be a metal member different from the stay 106 or a heat resistant resin member and may only be required to be a member having the stable linear temperature characteristic by the heat rays radiating from the halogen heater 104.
The fixing apparatus 6 in this embodiment performs the following operation at an abnormal time when the turning on of the halogen heater 104 is unintentionally continued. The stay 106 is heated by the heat rays from the halogen heater 104, so that the temperature of the stay 106 is increased. Then, with the increase in temperature of the stay 106 at the longitudinal end portion, the temperature of the heat sensitive portion 114 is increased. When the temperature of the heat sensitive portion 114 reaches the operation temperature of the overheating preventing element 107, the overheating preventing element 107 is operated (i.e., the internal circuit is opened), so that interruption of the electrical energy supply to the halogen heater 104 is performed.
According to the fixing apparatus 6 in this embodiment, the following effects are achieved by the constitution and operation as described above. First, irrespective of the rotation state of the heating belt 101, it is possible to perform a stable operation of the overheating preventing element 107.
Further, the overheating preventing element 107 is disposed in contact with the stay 106 provided inside a cylinder of the heating belt 101. For this reason, compared with the case where the overheating preventing element 107 is disposed in non-contact with the cylinder of the heating belt 101 in the neighborhood of an outside of the cylinder, a time until the overheating preventing element 107 is operated can be shortened. This is because when the overheating preventing element 107 is disposed in contact with the stay 106 provided inside the cylinder of the heating belt 101, the distance between the halogen heater 104 and the stay 106 is short and the stay 106 is formed of metal, and therefore has a higher thermal conductivity than that of an air layer.
Further, the overheating preventing element 107 is prevented by the stay 106 from being directly subjected to radiation of the heat rays from the halogen heater 104, and therefore the temperature of the overheating preventing element 107 itself does not exceed an operable range, so that it is possible to ensure operation reliability of the overheating preventing element 107.
In the First Embodiment, the fixing apparatus 6 was described, in which the overheating preventing element 107 is disposed inside the heating belt 101 at the position where the overheating preventing element 107 is not directly subjected to radiation of the heat rays from the halogen heater 104. In this embodiment, a fixing apparatus 6 constituted so that the overheating preventing element 107 is provided at the inner surface of the leg portion 106a of the stay 106 will be described. In the following description, members identical to those constituting the fixing apparatus 6 in the First Embodiment are represented by the same reference numerals or symbols and will be omitted from description.
a) is a perspective view of an outer appearance showing a schematic structure of a whole fixing apparatus 6.
In the following, a disposition position of the overheating preventing element 107 will be described. As described in the First Embodiment, the heater fixing member 110 is provided with the through hole 110a so that the leg portion 106a of the stay 106 is protruded from the sealing portion 111 of the halogen heater 104 to the outside thereof with respect to the longitudinal direction of
As shown in
Here, the element fixing member 202 protects the overheating preventing element 107 from slight heat rays leaking from the through hole 110a of the heater fixing member 110. Further, the element fixing member 202 has a constitution in which the whole overheating preventing element 107 is covered in order to reduce the influence of the overheating preventing element 107 by a flow of ambient air and a change in the ambient environment such as temperature and humidity.
In
Further, the spatial distance between the halogen heater 104 and the stay 106 is irrespective of the rotation state of the heating belt 101 and is not changed. Therefore, the temperature of the stay 106 has a stable temperature characteristic that the temperature is increased depending on a turning-on time of the halogen heater 104 (heating time by the heat rays) and is lowered depending on a turning-off time. Therefore, also in the fixing apparatus 6 in this embodiment, similarly as in the fixing apparatus 6 in the First Embodiment, improvement in the thermal responsiveness of the overheating preventing element 107 can be realized.
Further, also the electrical wires Ca1 and Ca2 are protected by the heater fixing member 110 from being directly subjected to the radiation of the heat rays from the halogen heater 104.
Further, the overheating preventing element 107 may desirably be fixed at a place close to the heater fixing member 110 so that the overheating preventing element 107 can monitor a temperature change depending on the turning-on time and the turning-off time of the halogen heater 104 with high sensitivity.
The fixing apparatus 6 in this embodiment performs the following operation at an abnormal time when the turning on of the halogen heater 104 is unintentionally continued. The stay 106 is heated by the heat rays from the halogen heater 104, so that the temperature of the stay 106 is increased. The temperature of the stay 106 subjected directly to the radiation of the heat rays from the halogen heater 104 is transmitted to the end portion of the stay 106 where the stay 106 is not subjected directly to the radiation of the heat rays from the halogen heater 104, so that the temperature of the stay 106 at the end portion of the stay 106 is increased. Then, with the increase in temperature of the stay 106 at the longitudinal end portion, the temperature of the heat sensitive portion 114 is increased. When the temperature of the heat sensitive portion 114 reaches an operation temperature of the overheating preventing element 107, the overheating preventing element 107 is operated, so that interruption of the electrical energy supply to the halogen heater 104 is made.
As described above, by providing the metal member which is provided inside the belt and includes a protruded portion protruding from the cylinder of the belt and which is directly subjected to radiation of radiant light emitted from the heater, the overheating preventing element may have a constitution in which the temperature of the metal member is detected at the protruded portion of the metal member.
According to the fixing apparatus 6 in this embodiment, in addition to the effects in the First Embodiment, the following effects can be obtained. By the heater fixing member 110 and the element fixing member 202, the overheating preventing element 107 is not subjected directly to the radiation of the heat rays from the halogen heater 104, and therefore it is possible to ensure the operation reliability of the overheating preventing element 107. Further, the leg portion 106a of the stay 106 is extended in the longitudinal direction, and at the inner surface of the extended leg portion 106a, the overheating preventing element 107 is disposed. For that reason, the electrical wires Ca1, Ca2 and Ca3 for supplying the electrical energy to the halogen heater 104 can be made shorter than those of the fixing apparatus 6 in the First Embodiment, and an electrical wire holding member provided inside the cylinder of the heating belt 101 can be made unnecessary, so that it is possible to realize an overheating preventing function with an inexpensive constitution.
In the First and Second Embodiments, the fixing apparatus 6, in which the overheating preventing element 107 is disposed on the stay 106, was described. In this embodiment, a fixing apparatus 6 constituted so that the overheating preventing element 107 is provided on a metal member different from the stay 106 will be described. In the following description, members identical to those constituting the fixing apparatus 6 in the First Embodiment are represented by the same reference numerals or symbols and will be omitted from description.
Also in this embodiment, by providing the metal member, which is provided inside the belt and includes a protruded portion protruding from the cylinder of the belt and which is directly subjected to radiation of radiant light emitted from the heater, the overheating preventing element has a constitution in which the temperature of the metal member is detected at the protruded portion of the metal member.
a) and 3(b) are illustrations showing a constitution of the fixing apparatus 6 of the belt type and the arrangement of the overheating preventing element 107.
In
In the fixing apparatus 6 in the First and Second Embodiments, the stay 106 is the metal and in order to provide rigidity capable of withstanding the pressure for effecting pressure supporting, the thickness of the stay 106 is required to be several mm which is relatively large, so that the thermal capacity is large. For that reason, there is a possibility of the generation of delay in the time from the start of the turning on of the halogen heater 104 until the temperature of the stay 106 starts its rise. Therefore, the overheating preventing element was provided on the metal member 301 different from the stay 106.
As shown in
Here, the spacer member 302 effects insulation separation between the metal member 301 and the stay 106, thus improving the thermal responsiveness of the metal member 301. The spacer member 302 may be any member if the member has an insulation effect and, e.g., uses heat resistant resin or metal having low thermal conductivity. Further, as the metal member 301, in order to improve the thermal responsiveness, a member having a sufficiently small thermal capacity compared with that of the stay 106 is selected. Further, the metal member 301 may also be made black at its surface in order to improve the thermal responsiveness, thus enhancing a heat collection property.
In this embodiment, the metal member 301 is provided along the entire longitudinal direction of the stay 106, but if there is sufficiently no problem with respect to the thermal responsiveness of the metal member 301, in order to reduce the cost, the longitudinal length of the metal member 301 may also be shortened. In this case, a constitution in which the metal member 301 is disposed only at a position where the metal member 301 opposes the halogen heater 104 at a longitudinal end portion of the halogen heater 104 is employed.
As shown in of
Further, the spatial distance between the halogen heater 104 and the metal member 301 is irrespective of the rotation state of the heating belt 101 and is not changed. Therefore, the temperature of the metal member 301 has a stable temperature characteristic that the temperature is increased depending on a turning-on time of the halogen heater 104 (heating time by the heat rays) and is lowered depending on a turning-off time. Thus, by using the metal member 301 having the stable temperature characteristic, improvement in thermal responsiveness of the overheating preventing element 107 can be realized.
The fixing apparatus 6 in this embodiment performs the following operation at an abnormal time when the turning on of the halogen heater 104 is unintentionally continued. The metal member 301 is heated by the heat rays from the halogen heater 104, so that the temperature of the metal member 301 is increased. Then, with the increase in temperature of the metal member 301 at the longitudinal end portion, the temperature of the heat sensitive portion 114 is increased. When the temperature of the heat sensitive portion 114 reaches an operation temperature of the overheating preventing element 107, the overheating preventing element 107 is operated, so that interruption of the electrical energy supply to the halogen heater 104 is made.
According to the fixing apparatus 6 in this embodiment, by the above-described constitution and operation, in addition to the effects of the fixing apparatus 6 in the Second Embodiment, the following effects can be obtained. The overheating preventing element 107 is disposed on the metal member 301, having the small thermal capacity, different from the stay 106 having the small thermal capacity, and therefore the operation time of the overheating preventing element 107 can be further shortened.
In this embodiment, an example in which the overheating preventing element 107 is provided via the metal member 301 at the inner surface of the leg portion 106a of the stay 106 of the fixing apparatus 6 in the Second Embodiment was described, but the constitution of the fixing apparatus 6 in this embodiment is also applicable to the constitution of the fixing apparatus 6 in the First Embodiment. In this case, the element fixing member 113 provided with the overheating preventing element 107 is mounted via the metal member 301 on the outer surface of the leg portion 106a of the stay 106 of the fixing apparatus 6 in the First Embodiment.
In the Second Embodiment, the fixing apparatus 6 in which the heat sensitive portion 114 of the overheating preventing element 107 directly contacts to the inner surface of the leg portion 106a of the stay 106 was described. In this embodiment, a fixing apparatus 6 constituted so that the heat sensitive portion 114 is provided in non-contact state via a spacer member 401 for maintaining the distance between the stay 106 and the heat sensitive portion 114 will be described. In the following description, members identical to those constituting the fixing apparatus 6 in the Second Embodiment are represented by the same reference numerals or symbols and will be omitted from description.
As shown in
Here, as the spacer member 401, a resin member which is softened at a predetermined temperature is used. The material and thickness of the spacer member 401 can be appropriately selected in accordance with setting of the operation temperature of the overheating preventing element 107. Therefore, the heat sensitive portion 114 is lower in temperature than the stay 106 by the spacer member 401.
The fixing apparatus 6 in this embodiment performs the following operation at an abnormal time when the turning on of the halogen heater 104 is unintentionally continued. The stay 106 is heated by the heat rays from the halogen heater 104, so that the temperature of the stay 106 is increased. Then, with the increase in temperature of the stay 106 at the longitudinal end portion, the temperatures of the spacer member 401 and the heat sensitive portion 114 are increased. The spacer member 401 is softened when its temperature reaches a predetermined temperature, so that the heat sensitive portion 114 approaches the stay 106. When the temperature of the heat sensitive portion 114 reaches an operation temperature of the overheating preventing element 107, the overheating preventing element 107 is operated, so that interruption of the electrical energy supply to the halogen heater 104 is made.
According to the fixing apparatus 6 in this embodiment, by the above-described constitution and operation, in addition to the effects of the fixing apparatus 6 in the Second Embodiment, the following effects can be obtained. The heat sensitive portion 114 of the overheating preventing element 107 is disposed over the stay 106 via the spacer member 401, and therefore compared with the case where the overheating preventing element 107 is directly disposed on the stay 106, the temperature of the heat sensitive portion 114 becomes low. Therefore, it is possible to select an inexpensive overheating preventing element 107 having a low operation temperature.
In this embodiment, a description was provided by using the constitution of the fixing apparatus 6 in the Second Embodiment, but the constitution of the fixing apparatus 6 in this embodiment is also applicable to the constitutions of the fixing apparatuses 6 in the First and Third Embodiments. In the case where the constitution of the fixing apparatus 6 in this embodiment is applied to the fixing apparatus 6 in the First Embodiment, the heat sensitive portion 114 is disposed in a non-contact state via the spacer member 401 for ensuring the distance between the leg portion 106a of the stay 106 and the heat sensitive portion 114. In the case where the constitution of the fixing apparatus 6 in this embodiment is applied to the fixing apparatus 6 in the Third Embodiment, the heat sensitive portion 114 is disposed in a non-contact state via the spacer member 401 for ensuring the distance between the metal member 301 and the heat sensitive portion 114.
The use of the fixing apparatuses 6 in the First to Fourth Embodiments is not limited to the use as the apparatus for heat fixing, on the recording material P, the unfixed toner image carried on the recording material P. For example, the fixing apparatuses 6 can be used also as an image heating apparatus for heating the unfixed toner image to temporarily fix the unfixed toner image on the recording material or as an image heating apparatus for heating the toner image heat fixed on the recording material to impart glossiness to the toner image surface.
While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purpose of the improvements or the scope of the following claims.
This application claims priority from Japanese Patent Application No. 108474/2012 filed May 10, 2012, which is hereby incorporated by reference.
Number | Date | Country | Kind |
---|---|---|---|
2012-108474 | May 2012 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
6075228 | Goto et al. | Jun 2000 | A |
7009153 | Tomatsu | Mar 2006 | B2 |
7650105 | Ogawa et al. | Jan 2010 | B2 |
7881650 | Shin et al. | Feb 2011 | B2 |
8032069 | Shin et al. | Oct 2011 | B2 |
8364067 | Miki et al. | Jan 2013 | B2 |
8412084 | Ishida et al. | Apr 2013 | B2 |
20040222214 | Tomatsu | Nov 2004 | A1 |
20070077077 | Jeong et al. | Apr 2007 | A1 |
20090092423 | Shin et al. | Apr 2009 | A1 |
20110091254 | Shin et al. | Apr 2011 | A1 |
20110150544 | Ishida et al. | Jun 2011 | A1 |
20110236084 | Nishida et al. | Sep 2011 | A1 |
20110305474 | Tanaka et al. | Dec 2011 | A1 |
20120099882 | Tanaka | Apr 2012 | A1 |
20120155938 | Tanaka et al. | Jun 2012 | A1 |
20120308279 | Tanaka et al. | Dec 2012 | A1 |
20130129364 | Kitagawa et al. | May 2013 | A1 |
20130206745 | Tanaka et al. | Aug 2013 | A1 |
20130272762 | Uekawa et al. | Oct 2013 | A1 |
Number | Date | Country |
---|---|---|
1160876 | Oct 1997 | CN |
1521578 | Aug 2004 | CN |
1940771 | Apr 2007 | CN |
101403884 | Apr 2009 | CN |
2009-93141 | Apr 2009 | JP |
Entry |
---|
Chinese Office Action issued in counterpart Chinese Patent Application No. 201310170636.6, dated Mar. 27, 2015 and English translation thereof. |
Number | Date | Country | |
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20130302046 A1 | Nov 2013 | US |