JP2011048203A - Heating member, fixing device, and image forming apparatus including the fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating member having a heat generating layer composed of heat generating resistors, configured to secure safety, and also, prevent local peeling of members constituting the heating member and prevent a local reduction in heat transfer efficiency, the heating member having no fluctuation in surface temperature distribution with respect to the setting temperature. <P>SOLUTION: The heating member 20 includes: a heat radiation member 201; a heat conducting member 202; an insulating layer 2031; the heat generating member 203 composed of the heat generating resistors 2036; and a pressure member 204. The heat generating resistor 2036 has two negative and positive resistance temperature characteristics. The Curie point showing the positive resistance temperature characteristic of the resistor is equal to or higher than 300°C, and the maximum electric resistance value Rf at a temperature equal to or lower than an inflection temperature where the negative resistance temperature characteristic of the resistor is changed to the positive resistance temperature characteristic satisfies a characteristic expression. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heating member having a heat generating layer made of a heating resistor that generates heat when energized, a fixing device that fixes a toner image on a recording medium using the heating member, and an image forming apparatus including the fixing device.

  As a fixing device used in an electrophotographic image forming apparatus such as a copying machine or a printer, a heat roller fixing type fixing device is frequently used. A heat roller fixing type fixing device includes a roller pair (fixing roller and pressure roller) that are in pressure contact with each other, and the roller is heated by a heating unit including a halogen heater or the like disposed inside or both of the roller pair. After the pair is heated to a predetermined temperature (fixing temperature), a recording medium such as a recording sheet on which an unfixed toner image is formed is fed to the pressure contact portion (fixing nip portion) of the roller pair and passed through the pressure contact portion. Thus, the toner image is fixed on the recording paper by heat and pressure.

  By the way, in a fixing device provided in a color image forming apparatus, it is common to use an elastic roller provided with an elastic layer made of silicon rubber or the like on the surface of the fixing roller. By using an elastic roller as the fixing roller, the surface of the fixing roller is elastically deformed corresponding to the unevenness of the unfixed toner image, and comes into contact so as to cover the toner image surface. It is possible to perform heat fixing on an unfixed toner image satisfactorily. In addition, a color image forming apparatus using an elastic roller as a fixing roller can improve releasability for color toners that are more likely to be offset than monochrome because of the strain relief effect of the elastic layer at the fixing nip. Further, the color image forming apparatus can improve the peeling performance of the recording paper because the nip shape of the fixing nip portion is convex upward (on the fixing roller side) (so-called reverse nip shape). The recording paper can be peeled without using a peeling means such as (self-stripping), and image defects caused by the peeling means can be eliminated.

  In addition, in order to obtain a color image forming apparatus corresponding to high speed, a fixing device provided in the color image forming apparatus needs to be configured to form a fixing nip portion having a wide nip width. Examples of a method for widening the nip width of the fixing nip portion include a method of increasing the thickness of the elastic layer of the fixing roller and a method of increasing the diameter of the fixing roller. However, since the elastic layer of the fixing roller has a very low thermal conductivity, there is a problem that the surface temperature of the fixing roller does not follow the increase in the process speed when there is a heating means inside the fixing roller. On the other hand, when the diameter of the fixing roller is increased, problems such as an increase in warm-up time until the surface temperature of the fixing roller reaches the fixing temperature and an increase in power consumption occur.

  As a fixing device provided in a color image forming apparatus that solves such a problem, Patent Document 1 discloses a fixing device of a belt fixing type. A belt-fixing type fixing device includes a fixing belt suspended between a fixing roller and a heating roller, and a pressure roller disposed so as to face the fixing roller via the fixing belt. The fixing belt is heated by a heat source disposed inside the roller. In the belt-fixing type fixing device, a fixing nip portion is formed at a pressure contact portion where the fixing roller is pressed against the pressure roller via the fixing belt. Such a belt-fixing type fixing device is configured to heat a fixing belt having a small heat capacity, so that the warm-up time until the surface temperature of the fixing belt reaches the fixing temperature can be shortened. In addition, since the belt fixing type fixing device does not require a heating means such as a halogen lamp inside the fixing roller, use a fixing roller provided with a thick low-elastic layer made of sponge rubber or the like. And a fixing nip portion having a wide nip width can be formed.

  Further, Patent Document 2 is a configuration in which a heating element configured so that a heating resistor that generates heat when energized forms a surface having a certain shape as a whole is used as a heating member that heats the fixing belt. A sheet heating belt fixing type fixing device is disclosed. A sheet heating belt fixing type fixing device includes a fixing belt suspended between a fixing roller and a heating member made of a sheet heating element, and a pressure disposed so as to face the fixing roller via the fixing belt. The fixing belt is heated by a heating member that contacts the fixing belt. Such a sheet heating belt fixing type fixing device can be designed to have a small heat capacity of a heating member for heating the fixing belt, and the sheet heating element that generates heat directly contacts the fixing belt to fix the fixing belt. Since it is configured to heat, compared to a system configured to indirectly heat the fixing belt by a heat source arranged inside the heating roller, the thermal response speed is improved and the warm-up time is further increased. Shortening and energy saving can be achieved. In this way, the sheet heating belt fixing type fixing device has high heating efficiency and fast start-up speed, which makes it possible to eliminate the need for preheating during standby and shorten the waiting time. In addition, it is provided in an image forming apparatus of a large machine or a high speed machine.

  Here, in a fixing device that obtains a predetermined fixing temperature via a fixing belt, such as the fixing device disclosed in Patent Document 2, the maximum sheet passing area of the heating member corresponding to the effective heat generation area in the longitudinal direction of the heating member. When the recording paper as the material to be heated is narrower than the width dimension of the heating member and the heat fixing is continued, the effective heat generation area in the longitudinal direction of the heating member is the area where the recording paper does not pass (non- There arises a problem that the temperature of the (sheet passing portion) is remarkably increased (non-sheet passing portion temperature increase).

  This temperature rise at the non-sheet passing portion also occurs in the fixing device of the heat roller fixing method, but in the fixing device of the heat roller fixing method, the thickness of the core metal included in the fixing roller is increased and the heat conduction in the longitudinal direction of the fixing roller is increased. It can be solved by improving. As a method of eliminating the temperature rise at the non-sheet passing portion in the sheet heating belt fixing method, a sheet heating element is provided with a plurality of electrodes and a heating pattern in accordance with the size of the recording paper, and switching the energization to the electrodes A method of reducing the amount of heat generated at the non-sheet passing portion of the heating element is conceivable. However, the above-described method complicates the structure of the planar heating element and cannot be applied to recording paper having an indefinite shape.

  Further, in the fixing device, there is a possibility that the temperature of the heating member may run away due to malfunction of the temperature control means for controlling the temperature of the heating member and abnormal rotation of the fixing belt. Therefore, the fixing device is provided with a safety circuit using a detection element such as a thermostat or a thermo protector. However, if an abnormality occurs in the temperature control means and the safety circuit, there is a risk of temperature runaway of the heating member.

  In order to solve such a problem, Patent Document 3 discloses a heater provided along a direction crossing the recording paper conveyance direction, a heating element having a positive resistance temperature characteristic, and the length of the heating element. A heating device is disclosed that includes a heater including power supply electrodes provided along a direction and a temperature detection member that detects the temperature of the heater. According to the heating device disclosed in Patent Document 3, by controlling the energization to the heating element based on the temperature detected by the temperature detection member, even when the recording paper has an indefinite shape with a simple and low-cost configuration. The temperature difference between the non-sheet passing portion and the sheet passing portion can be reduced.

  Patent Document 4 discloses an image fixing device using a planar heater including an insulating substrate, a heating element formed from a polyimide resin in which a conductive substance is mixed and dispersed, an electrode, and a heat-resistant insulating layer. Has been. According to the image fixing device disclosed in Patent Document 4, since the planar heater has a positive resistance temperature characteristic, it is possible to prevent an excessive temperature rise in a portion corresponding to the non-sheet passing portion in the heating element.

JP-A-10-30796 JP 2002-333788 A JP-A-6-27840 JP 2006-294604 A

  Here, the heating element used in the heating device of the film heating method disclosed in Patent Document 3 has a self-temperature control function due to a sudden increase in electrical resistance when the temperature of the heating element exceeds the Curie point of 180 ° C. Since the PTC (Positive Temperature Coefficient) characteristic is exhibited, it is possible to prevent an excessive temperature rise in a portion corresponding to the non-sheet passing portion in the heating element. However, for example, a heating element made of a semiconductor ceramic based on barium titanate has an electrical resistance that decreases as the temperature of the heating element increases during the temperature increase from room temperature to the vicinity of the Curie point. Due to the PTC characteristics, the electrical resistance increases rapidly. Therefore, the electric power supplied to the heating element varies depending on the temperature of the heating element itself. When the fixing device is warmed up, the current amount of the heating element is increased, but for use within the range up to the maximum current value allocated to the fixing device, the maximum power at the time of warming up is the minimum electric resistance of the heating element. It is defined by the current value at the time, and sufficient power cannot be supplied during warm-up. Further, since the heat generated from the heating element not only heats the recording paper but also heats the pressure roller, the heating element needs to generate heat up to a higher temperature. However, since the electric resistance of the heating element having the PTC characteristic rapidly increases in the vicinity of the Curie point, the power supplied to the heating element is reduced, and sufficient heat cannot be supplied to the recording paper and the pressure roller.

  Further, in the film heating type fixing device of Patent Document 3, since heat from the heating element is applied to the recording paper through a film having a small heat capacity, the warm-up time is very fast. Since heat is taken away sequentially, the heat supply to the recording paper cannot catch up. Furthermore, since the heating element having the PTC characteristic exhibits a self-temperature control function by rapidly increasing the electric resistance when the Curie point is exceeded, a problem arises in temperature followability. Thus, in a heating member having a heating element having PTC characteristics, sufficient power cannot be supplied at the time of warm-up, and the power supplied to the heating element near the Curie point decreases, which is sufficient for recording paper and a pressure roller. Heat cannot be supplied, causing problems in temperature followability.

  Further, the planar heater used in the image fixing apparatus of Patent Document 4 forms a heating element by dispersing and filling a conductive material in an organic resin such as a polyimide resin. Even if the temperature rise is close to the temperature used for fixing (for example, 200 ° C.) and excessive temperature rise can be suppressed, it is not possible to secure electric power during use.

  In addition, the heat radiating member, the heating element, the insulating layer, and the fixing member constituting the heating member have different thermal expansion coefficients. That is, in the heating member, when a voltage is applied to the heat generating element and the heat generating element generates heat, the heat radiating member, the heat generating element, the insulating layer, and the fixing member are thermally expanded to different degrees. However, if the heating element is firmly fixed so as to be in close contact with the heat radiating member, the difference in thermal expansion cannot be absorbed and relaxed, and it bends in the direction of the member with small thermal expansion, and locally between the heating element and the heat radiating member. Peeling or gaps are created, and the heat transfer efficiency with respect to the inner surface of the heat dissipation member is locally reduced. As described above, when the heat transfer efficiency with respect to the inner surface of the heat radiating member is locally reduced, the temperature distribution on the fixing belt surface becomes uneven with respect to the set temperature, the fixing temperature varies, and the fixing performance deteriorates, resulting in high print quality. Cannot be maintained. When the local heat transfer efficiency is lowered, it is necessary to lengthen the warm-up time until a desired fixing temperature is obtained.

  Accordingly, an object of the present invention is a heating member having a heating member in which a heating layer composed of an insulating layer and a resistance heating element is laminated, and local peeling between members constituting the heating member is prevented. Thus, it is possible to provide a heating member in which a local decrease in heat transfer efficiency is prevented and the surface temperature distribution is uniform with respect to the set temperature. Another object of the present invention is a belt-fixing type fixing device, which prevents the fixing temperature from fluctuating with respect to a set temperature, ensures safety, shortens the warm-up time, and increases power consumption. It is an object of the present invention to provide a fixing device that can be prevented. Another object of the present invention is to provide an image forming apparatus capable of forming a uniform and high-quality image by including a fixing device having a uniform fixing characteristic in which the fixing temperature is prevented from varying with respect to a set temperature. It is to be.

The present invention is a heat dissipation member formed by curving one surface in the thickness direction,
A heat conductive member made of a material having low hardness and high thermal conductivity, and provided in contact with the other surface in the thickness direction of the heat radiating member;
An insulating layer that is provided in contact with the other surface in the thickness direction of the heat conducting member and is made of an insulator;
A heating member comprising a heating resistor that generates heat when energized, and an electrode member laminated so as to sandwich the heating layer, and a heating member provided in contact with the other surface in the thickness direction of the insulating layer;
A pressing member that presses the heat generating member in a direction close to the heat radiating member and fixes the heat generating member to the heat radiating member; and
The heating resistor has two resistance temperature characteristics, a negative resistance temperature characteristic and a positive resistance temperature characteristic, a Curie point indicating the positive resistance temperature characteristic is 300 ° C. or more, and a negative resistance temperature characteristic. The heating member is characterized in that the maximum electric resistance value Rf below the inflection temperature at which the temperature changes from positive to positive resistance temperature characteristics satisfies the following formula (1).
R _f <(V _f ² / W _f ) (1)
(In the formula, R _f represents the maximum electric resistance (Ω), V _f represents the applied voltage (V), and W _f represents the desired power (W).)

Further, in the present invention, the heat generating layer is formed by aligning a plurality of heat generating resistors in the longitudinal direction of the heat radiating member,
The electrical resistance of the heating resistor provided corresponding to both longitudinal ends of the heat radiating member is lower than the electrical resistance of the heating resistor provided corresponding to the longitudinal central portion.

  According to the present invention, the heating resistor is a semiconductive ceramic containing barium titanate.

In the present invention, the heat dissipation member is formed using an alloy selected from an aluminum alloy, a magnesium alloy, and a copper alloy,
An elastic member is provided between the heat generating member and the pressing member,
The pressing member is formed using a material selected from metal, heat-resistant resin, and ceramics, and is provided in point contact with the elastic member.

  Further, the present invention is characterized in that a fixing adapter configured to be able to fix the pressing member connected to the outside is provided at both longitudinal ends of the pressing member.

  The present invention is characterized in that an inner surface coating layer made of a material having heat resistance and high heat radiation is formed on the other surface in the thickness direction of the heat radiating member.

  Further, the present invention is characterized in that an outer surface coating layer made of a material having heat resistance and a low friction coefficient is formed on one surface in the thickness direction of the heat radiating member.

  In the invention, it is preferable that the outer surface coating layer is made of at least one material of PTFE resin and PFA resin containing fluorine.

The present invention also provides a first fixing member, a heating unit, a rotatable endless belt stretched between the first fixing member and the heating member, and the first fixing member via the endless belt. A toner image carried on the recording paper at a fixing nip formed by contact between the endless belt and the second fixing member. A fixing device for fixing on a recording sheet,
The heating unit is the heating member, and is a fixing device that heats the endless belt in contact with the endless belt on one surface in the thickness direction of the heat radiating member.

According to another aspect of the present invention, there is provided an image forming apparatus comprising the fixing device.
Further, the present invention is characterized by comprising power control means for controlling the input power to the heating resistor of the heating member to be constant.

  According to the present invention, the heating member includes a heat radiating member formed by bending one surface in the thickness direction, a heat conducting member disposed in contact with the other surface in the thickness direction of the heat radiating member, and a thickness direction of the heat conducting member. An insulating layer made of an insulator disposed in contact with the other surface, a heat generating member disposed in contact with the other surface in the thickness direction of the insulating layer, and pressing the heat generating member in a direction close to the heat radiating member, And a pressing member to be fixed to. Here, in the heating member, one surface in the thickness direction is referred to as an “outer surface”, and the other surface in the thickness direction is referred to as an “inner surface”.

  In the heating member of the present invention, the heat generating member is pressed by the pressing member in the direction approaching the heat radiating member, and is fixed to the heat radiating member. Thereby, the heat generating member is fixed in a state in which the adhesion to the inner surface of the heat radiating member is improved.

  In addition, since a heat conductive member made of a material having low hardness and high thermal conductivity is disposed between the heat radiating member and the heat generating member, the heat transfer efficiency from the heat generating member to the heat radiating member is not reduced. The difference in thermal expansion of each member constituting the heating member can be absorbed and relaxed, and local peeling between the members can be prevented from occurring. As described above, the heating member of the present invention is maintained in a state where the adhesion of the heat generating member to the inner surface of the heat radiating member is high, and it is prevented that local peeling occurs between the respective members. The occurrence of a general decrease in heat transfer efficiency can be prevented, and the surface temperature distribution can be prevented from varying with respect to the set temperature.

  The heat generating member includes a heat generating layer made of a heat generating resistor that generates heat when energized, and an electrode member laminated so as to sandwich the heat generating layer. The heating resistor has two resistance temperature characteristics, a negative resistance temperature characteristic and a positive resistance temperature characteristic, a Curie point indicating the positive resistance temperature characteristic is 300 ° C. or more, and a negative resistance temperature characteristic. Since the maximum electric resistance value Rf below the inflection temperature changing from the temperature characteristic to the positive resistance temperature characteristic satisfies the formula (1), even if the electric resistance of the heating resistor decreases with increasing temperature, it is about 200 ° C. Desired electric power can be supplied to the heating resistor until the desired temperature is reached. Therefore, the heating member can exhibit sufficient heat supply capability.

  Further, according to the present invention, the heat generating layer includes a plurality of heat generating resistors aligned in the longitudinal direction of the heat radiating member, and the electric resistance of the heat generating resistor provided corresponding to both ends of the heat radiating member in the longitudinal direction is The electric resistance of the heating resistor provided corresponding to the central portion in the longitudinal direction is lower.

  As a result, the heating resistor at the end in the longitudinal direction of the heat radiating member has a short heating time and can set a large electric power, so that it is possible to compensate for the heat dissipation loss at the end in the longitudinal direction of the heat radiating member. The temperature distribution in the longitudinal direction can be made uniform.

  Further, according to the present invention, since the heating resistor is made of a semiconductive ceramic containing barium titanate, it is possible to constitute a highly reliable heating member with a general-purpose material while having high heat resistance. is there.

  According to the invention, the heat dissipation member is formed using an alloy selected from an aluminum alloy, a magnesium alloy, and a copper alloy. Since the heat radiating member comprised with the said material turns into a member which has high heat conductivity, it can heat a heating target object efficiently. The pressing member is formed using a material selected from metals, heat-resistant resins, and ceramics, and an elastic member is provided between the heat generating member and the pressing member. The pressing member made of the material is a member having high strength and high toughness, and further, since an elastic member is provided between the heat generating member and the pressing member, the heat generating member is placed in a direction close to the heat radiating member. It can be pressed elastically. Therefore, the heat generating member is fixed in a state where the adhesion to the inner surface of the heat radiating member is improved. Furthermore, since the pressing member is provided in point contact with the elastic member, heat conduction to the pressing member is suppressed when the heating resistor is heated, and the heat capacity of the pressing member can be reduced. Can be fast.

  Further, according to the present invention, since the fixing adapter configured to be able to fix the pressing member by connecting to the outside is provided at both longitudinal ends of the pressing member, the fixing adapter can be fixed to the outside of the apparatus and pressed. The arrangement position of the member with respect to the heat generating member can be regulated. In this way, by restricting the arrangement position of the pressing member, the external force due to the restriction can be applied as a pressing force that elastically presses the heat generating member in the direction approaching the heat radiating member.

  According to the present invention, the inner surface coating layer made of a material having heat resistance and high heat radiation is formed on the inner surface of the heat dissipation member. Accordingly, it is possible to prevent the occurrence of corrosion at the interface between the heat radiating member and the heat conducting member, and it is possible to prevent a decrease in heat transfer efficiency from the heat generating member to the heat radiating member over a long period of time.

  According to the invention, the outer surface coating layer made of a material having heat resistance and a low friction coefficient is formed on the outer surface of the heat radiating member. For example, when the endless belt is brought into contact with the outer surface of the heat radiating member and the heating member is used as a member for heating the endless belt, the frictional force between the heat radiating member and the endless belt can be reduced, It is possible to prevent the endless belt from being worn and to ensure high durability of the endless belt. Further, when the frictional force between the heat radiating member and the endless belt can be reduced, the rotation of the endless belt can be made smooth, and the heat transfer efficiency of the heating member to the endless belt can be prevented from being lowered. Can do. Furthermore, friction noise between the heat radiating member and the endless belt can be suppressed, and the power consumption of the rotation drive motor for rotating the endless belt can be suppressed.

  According to the invention, the outer surface coating layer formed on the outer surface of the heat dissipation member is made of at least one material of PTFE resin and PFA resin containing fluorine. Thereby, the frictional force between the heat radiating member and the heating object can be reduced.

  According to the invention, the fixing device includes the first fixing member, the heating unit, the endless belt stretched between the first fixing member and the heating unit, and the first fixing via the endless belt. And a second fixing member disposed so as to face the member, and the toner image is heated and melted and fixed on the recording paper in a fixing nip portion formed by contact between the endless belt and the second fixing member. . The fixing device according to the present invention includes the heating member according to the present invention as a heating unit in which the temperature distribution on the surface does not vary with respect to the set temperature, so that the temperature distribution on the surface of the endless belt becomes the set temperature. On the other hand, it is uniform and the fixing temperature is prevented from varying, and uniform fixing characteristics can be realized. Further, the heating member of the present invention provided in the fixing device is one in which a local decrease in heat transfer efficiency is prevented. Therefore, the fixing device has a short warm-up time until a desired fixing temperature is obtained, and can prevent an increase in power consumption.

  In addition, according to the present invention, the image forming apparatus has a uniform fixing characteristic in which the fixing temperature is prevented from being varied with respect to the set temperature. The temperature of the non-sheet passing portion of the paper recording paper can be efficiently reduced. Further, it is possible to provide an image forming apparatus capable of achieving both convenience and energy saving by effectively using electric power.

  According to the invention, the image forming apparatus further includes power control means for controlling the input power to the heating resistor of the heating member to be constant. When a heating resistor having a positive resistance temperature characteristic is used, there is power fluctuation according to the temperature of the heating resistor. Since the power control means controls the input power to the heating resistor with a predetermined constant value, it becomes possible to effectively supply the power at the time of warm-up and sleep return, and the warm-up time and sleep return time can be shortened. Can do. Therefore, the workability is improved and the power of the fixing device can be turned off immediately when printing is not being performed, thereby reducing power consumption.

It is a figure which shows the cross section perpendicular | vertical to the longitudinal direction of the heating member 20 which is 1st Embodiment of this invention. It is an expanded sectional view of the heat generating member 203 shown in FIG. 5 is a graph showing the relationship between the electrical resistance of a heating resistor 2036 and temperature. It is a graph which shows the relationship between the electric power of the heat generating resistor 2036, and temperature when the heat generating resistor 2036 which has a PTC characteristic as shown in FIG. 3 is used. It is a side view of the heating member 20 shown in FIG. 1 is a diagram illustrating a configuration of a fixing device 15 according to an embodiment of the present invention. FIG. 3 is a diagram illustrating a configuration of a fixing device 15 in the vicinity of a region where a fixing belt is suspended from a heating member. FIG. 8A is a side view showing the structure of the fixed adapter 205 at the end in the longitudinal direction of the heating member 20, and FIG. 8B shows the heating member 20 shown in FIG. It is sectional drawing seen from. 3 is a block diagram showing an electrical configuration of the fixing device 15. FIG. FIG. 6 is a diagram illustrating a configuration of a fixing device 150 according to another embodiment of the present invention. 1 is a diagram illustrating a configuration of an image forming apparatus 100 according to an embodiment of the present invention. It is a graph which shows the relationship between the electrical resistance and temperature of the conventional heating resistor whose Curie point is 200 degreeC. It is a graph which shows the relationship between the temperature of a heating resistor, and electric power when the conventional heating resistor which has the PTC characteristic shown in FIG. 12 is used. It is a graph which shows the relationship between the electric power of a heating resistor, and the temperature of a heating member at the time of comprising a heating member using the conventional heating resistor which has the PTC characteristic shown in FIG.

1. Heating member FIG. 1 is a view showing a cross section perpendicular to the longitudinal direction of a heating member 20 according to a first embodiment of the present invention. The heating member 20 includes a heat radiating member 201 formed by curving one surface in the thickness direction, a heat conducting member 202 disposed in contact with the other surface in the thickness direction of the heat radiating member 201, a thickness direction of the heat conducting member 202, and the like. A first insulating layer 2031 disposed in contact with the surface, a heat generating member 203 disposed in contact with the other surface in the thickness direction of the first insulating layer 2031, and disposed in contact with the other surface in the thickness direction of the heat generating member 203. The second insulating layer 2032, the elastic member 2037 disposed in contact with the other surface in the thickness direction of the second insulating layer 2032, and the pressing member 204 that presses the heat generating member 203 in the direction close to the heat radiating member 201. Consists of including. Here, in the heating member, one surface in the thickness direction is referred to as an “outer surface”, and the other surface in the thickness direction is referred to as an “inner surface”. In the heating member 20, the heat generated in the heat generating member 203 is conducted to the heat radiating member 201 through the first insulating layer 2031 and the heat conducting member 202, and heats the object that contacts the outer surface of the heat radiating member 201. The heating member 20 of the present embodiment can be suitably mounted on a fixing device described later. The heating object 20 heated by the heating member 20 will be described below by taking a fixing belt provided in the fixing device as an example.

(Heat dissipation member)
The heat radiating member 201 is a member having a curved outer surface, and is formed in a cylindrical shape that forms a part of a cylindrical body in the present embodiment. The heat radiating member 201 is disposed on the outer surface so as to contact the fixing belt, and conducts heat generated by the heat generating member 203 to the fixing belt. The material constituting the heat radiating member 201 is not particularly limited, but is preferably a metal material or an alloy material having high thermal conductivity, and examples of the material include an aluminum alloy, a magnesium alloy, and a copper alloy. . By configuring the heat dissipation member 201 with these materials, the object to be heated can be efficiently heated. The heat radiating member 201 can be produced by cutting out a part of the cylindrical body in the circumferential direction, and can also be produced by curving a plate-like member.

(Heat conduction member)
The heat conducting member 202 is provided in contact with the inner surface of the heat radiating member 201. That is, the heat conducting member 202 is interposed between the heat radiating member 201 and a first insulating layer 2031 described later. The heat conductive member 202 is a member made of a material having low hardness and high heat conductivity. Here, the “hardness” in the present invention is a hardness calculated by a length of a needle having a specified weight, which is standardized in JIS K2207, which is vertically entered into the sample.

  The heat conductive member 202 is preferably formed of a material having a hardness at 25 ° C. of 30 to 300 and a heat conductivity of 0.5 W / m · K to 30 W / m · K. By interposing the heat conducting member 202 having such physical property values between the heat radiating member 201 and the heat generating member 203, the heating member 20 can be provided without reducing the heat transfer efficiency from the heat generating member 203 to the heat radiating member 201. It is possible to absorb and relax the difference in thermal expansion between the constituent members, and to prevent local peeling between the members.

  If local peeling occurs between the members and a gap is opened between the heat radiating member 201 and the heat generating member 203, an air layer is interposed, resulting in poor thermal conductivity. On the other hand, by disposing the heat conductive member 202 between the heat radiating member 201 and the heat generating member 203, the air layer that increases the thermal resistance can be removed and the thermal conductivity can be improved.

  The material constituting the heat conductive member 202 is preferably a material that is excellent in heat conductivity even in a high temperature environment and hardly changes over time, and examples thereof include heat-resistant silicone grease and heat-resistant silicone gel sheet. Further, in order to further improve the thermal conductivity, a material obtained by adding a powder of gold, silver, copper, platinum, carbon, graphite or the like to the material may be used.

(First insulation layer)
The first insulating layer 2031 is provided in contact with the inner surface of the heat conducting member 202. That is, the first insulating layer 2031 is interposed between the heat conducting member 202 and a heat generating member 203 described later. The first insulating layer 2031 is a layer formed of a material having both heat resistance and electrical insulation. The material having both heat resistance and electrical insulation is not particularly limited, and examples thereof include a heat resistant polymer material such as polyimide resin, a ceramic material such as alumina, and an inorganic material such as mica. In the present embodiment, the first insulating layer 2031 is a layer made of mica.

  The first insulating layer 2031 is interposed between the heat generating member 203 and the heat conducting member 202 to ensure insulation between them. As described above, the first insulating layer 2031 electrically insulates the heat generating member 203 having the heat generating layer 2033 (described later) that generates heat when energized, so that the heating member 20 having the safe heat generating member 203 can be obtained. In addition, when the heat generating layer 2033 can be electrically insulated, for example, even if a low heat capacity metal material such as aluminum or stainless steel is used as a constituent material of the heat radiating member 201, electrical insulation from the heat generating layer 2033 is ensured. The selection range of the material which the heat radiating member 201 comprises can be expanded.

(Heat generation member)
FIG. 2 is an enlarged cross-sectional view of the heat generating member 203 shown in FIG. The heat generating member 203 is provided such that a second insulating layer 2032 described later is in contact with the inner surface and the outer surface is in contact with the inner surface of the heat conducting member 202. The heat generating member 203 has a stacked structure in which a heat generating layer 2033 composed of a heat generating resistor 2036 that generates Joule heat by energization and a first power supplying electrode 2034 are stacked in this order on the surface of the second power supply electrode 2035. The surface on the side where the first power supply electrode 2034 is formed becomes the surface on the side in contact with the inner surface of the first insulating layer 2031, and the surface on the side on which the second power supply electrode 2035 is formed contacts with the outer surface of the second insulating layer 2032. It becomes the side surface.

  The heat generating layer 2033 is formed with a plurality of heat generating resistors 2036 aligned in the longitudinal direction of the heat radiating member 201. In the present embodiment, each heating resistor 2036 is a semiconductor ceramic heating element fired by adding a Curie point adjusting agent and a dopant based on barium titanate, and has a thickness of 1 mm and a width of 10 mm. The length is 20 mm. The first feeding electrode 2034 and the second feeding electrode 2035 are arranged in a sandwich on the outer and inner surfaces of the heating layer 2033 in the longitudinal direction so as to sandwich the heating resistor 2036. By forming the heating resistor 2036 from a semiconductive ceramic containing barium titanate, it is possible to configure the highly reliable heating member 20 with a general-purpose material while having high heat resistance. If the heating resistor is made of an organic resin such as polyimide resin, it is easy to adjust the electrical resistance of the heating resistor in the initial stage of manufacture, but the electrical resistance of the heating resistor changes depending on the thermal characteristics of the polyimide resin. Therefore, when the heating and cooling cycles are repeated, the reproducibility of the electric resistance of the heating resistor is deteriorated. Therefore, the quality of the heating member 20 cannot be ensured, and the reliability decreases. In the present embodiment, the first feeding electrode 2034 and the second feeding electrode 2035 are stainless steel (SUS) feeding electrodes having a thickness of 0.2 mm and made of nickel and silver.

  The heating resistor 2036 has a resistance temperature characteristic as shown in FIG. FIG. 3 is a graph showing the relationship between the electrical resistance of the heating resistor 2036 and the temperature. The heating resistor 2036 has two characteristics of a negative resistance temperature (Negative Temperature Coefficient; NTC) characteristic and a positive resistance temperature (Positive Temperature Coefficient; PTC) characteristic, and a Curie point (temperature d) indicating the PTC characteristic. ) Is 300 ° C. or higher.

  That is, the heating resistor 2036 is energized to generate heat, and in the temperature range from room temperature a (25 ° C.) to the temperature c (280 ° C.) in the vicinity of the Curie point d, the NTC characteristic in which the electrical resistance decreases as the temperature increases. In the temperature region higher than the temperature c, the PTC characteristic in which the electric resistance rapidly increases as the temperature rises is shown.

  The heating resistor 2036 is used in a temperature range below the temperature c, which is an inflection temperature changing from the NTC characteristic to the PTC characteristic, that is, in a temperature range from room temperature a to temperature c showing the NTC characteristic. The fixing belt, which is a product, is heated to a predetermined set temperature b (200 ° C.). The heating resistor 2036 exhibits a maximum electric resistance value Rf at room temperature a when used in a temperature range showing NTC characteristics.

  Here, the problems of the heating member including the conventional heating resistor having a Curie point of 200 ° C. are as follows.

  FIG. 12 is a graph showing the relationship between the electrical resistance and temperature of a conventional heating resistor having a Curie point of 200 ° C. FIG. 13 is a graph showing the relationship between the temperature of the heating resistor and the power when the conventional heating resistor having the PTC characteristic shown in FIG. 12 is used. In the conventional heating resistor, the power increases as the temperature rises from room temperature, and when the temperature of the heating resistor rises to the temperature e, the power decreases rapidly. Since the power at the time of warm-up is defined by the maximum current value of the fixing device, the maximum power f at which the power is maximum is set as the rated power of the heating resistor. Therefore, in the conventional heating resistor, the power fluctuates from the room temperature power g to the maximum power f as the temperature rises, and a power loss as shown by hatching in FIG. 13 occurs. ineffective.

  FIG. 14 is a graph showing the relationship between the power of the heating resistor and the temperature of the heating member when the heating member is configured using the conventional heating resistor having the PTC characteristic shown in FIG. As shown in FIG. 14, the temperature h of the heating member at the maximum power f of the heating resistor is 100 ° C. or less during warm-up, and it takes a long time to raise the temperature of the heating member to the desired fixing temperature. become. This is because the temperature of the heating resistor itself rises above the Curie point, and the heat supply capability is reduced by the self-temperature suppression function of the heating resistor itself. Therefore, in the conventional heating resistor, a power loss as shown by hatching in FIG. 14 occurs, and there is a problem in coexistence of the self-temperature control function and the heat supply capability of the heating resistor.

On the other hand, the heating resistor 2036 provided in the heating member 20 of the present embodiment has two characteristics of NTC characteristics and PTC characteristics as described above, and the Curie point indicating the PTC characteristics is 300 ° C. The maximum electrical resistance value Rf in the operating temperature range showing the NTC characteristics as described above satisfies the following formula (1).
R _f <(V _f ² / W _f ) (1)
(In the formula, R _f represents the maximum electric resistance (Ω), V _f represents the applied voltage (V), and W _f represents the desired power (W).)

  The Curie point of the heating resistor 2036 can be adjusted by the composition of the material of the heating resistor 2036 and the manufacturing conditions, and can be adjusted, for example, by the amount of Curie point adjusting agent added to barium titanate. Examples of the Curie point adjusting agent include strontium and lead.

In addition, the maximum electrical resistance value R _f of the heating resistor 2036 can be adjusted by the composition of the material of the heating resistor 2036 and the manufacturing conditions. For example, the maximum resistance value R _f is adjusted by the kind and amount of the dopant added to the barium titanate. can do. Examples of the dopant include rare earth metals, antimony, niobium, bismuth and tungsten. By appropriately combining these dopants having different electric resistance values, the maximum electric resistance value _{Rf of the} heating resistor 2036 is adjusted so as to satisfy the above formula (1).

  The heating resistor 2036 can be manufactured by a conventional method of wet mixing, molding and firing.

  FIG. 4 is a graph showing the relationship between the power and temperature of the heating resistor 2036 when the heating resistor 2036 having the PTC characteristic as shown in FIG. 3 is used.

The desired power W _f in the equation (1) satisfied by the heating resistor 2036 is set in advance according to the object to be heated, and the fixing belt is heated at the set temperature b (200 ° C.) to melt the toner on the recording paper. For example, 1200 W is set when warming up, and 970 W is set when passing paper.

When a constant voltage is applied to the heating resistor 2036, as indicated by C1 in FIG. 4, the heating resistor 2036 has a room temperature a indicating the maximum electrical resistance value Rf within the operating temperature range showing the NTC characteristics. desired power W to the rated power W _m at inflection temperature c to _f in, the power increases according to the temperature rise. And in the temperature range higher than the inflection temperature c which shows a PTC characteristic, electric power falls according to a temperature rise.

  As described above, the heating resistor 2036 provided in the heating member 20 of the present embodiment has two characteristics of the NTC characteristic and the PTC characteristic, the Curie point indicating the PTC characteristic is 300 ° C. or higher, and the NTC. Since the maximum electrical resistance value Rf in the operating temperature range showing the characteristics satisfies the above formula (1), even if the electrical resistance of the heating resistor 2036 decreases with increasing temperature, it is about 200 ° C. A desired power can be supplied to the heating resistor 2036 until the temperature reaches a desired temperature. Therefore, the heating member 20 can exhibit a sufficient heat supply capability.

Further, the heating resistor 2036, as indicated by C2 in FIG. 4, the power supplied at the use temperature region showing the NTC characteristics, preferably controlled to be constant at a desired power W _f. Power control means for controlling the power supplied to the heating resistor 2036 to be constant is provided in an image forming apparatus described later.

The power control means varies the applied voltage V _f applied to the heating resistor 2036 so as to be constant at the desired power W _f based on the electric resistance or current value of the heating resistor 2036 that varies according to the temperature change. Configured to control.

  As a result, it is possible to effectively supply power during warm-up and sleep recovery, and the warm-up time and sleep recovery time can be shortened. Therefore, the workability is improved and the power of the fixing device can be turned off immediately when printing is not being performed, thereby reducing power consumption.

  Returning to FIG. 2, the electrical resistance of the heating resistor 2036 at the longitudinal end portion 2036b of the heat radiating member 201 is lower at the same temperature than the electrical resistance of the heating resistor 2036 at the longitudinal center portion 2036a. preferable. As a result, the heating time of the heating resistor 2036 at the longitudinal end 2036b of the heat radiating member 201 is short and the power can be set large, so that the heat dissipation loss from the heating resistor 2036 at the longitudinal end 2036b of the radiating member 201 is achieved. Therefore, the temperature distribution of the heat generating member 203 in the longitudinal direction of the heat radiating member 201 can be made uniform.

(Second insulation layer)
The second insulating layer 2032 is provided in contact with the inner surface of the heat generating member 203. That is, the second insulating layer 2032 is interposed between the heat generating member 203 and an elastic member 2037 described later, and is interposed between the heat generating member 203 and the elastic member 2037 to ensure insulation between the two. The second insulating layer 2032 has the same configuration as the first insulating layer 2031 described above, but each insulating layer may be formed of the same material or may be formed of different materials.

(Elastic member)
The elastic member 2037 is provided in contact with the inner surface of the second insulating layer 2032. That is, the elastic member 2037 is interposed between the second insulating layer 2032 and a pressing member 204 described later. Although the material which comprises the elastic member 2037 is not restrict | limited in particular, For example, a 2 mm-thick fluororubber is mentioned.

(Pressing member)
The pressing member 204 contacts the inner surface of the elastic member 2037 on the outer surface, presses the heat generating member 203 in the direction approaching the heat radiating member 201 via the elastic member 2037, and fixes the heat generating member 203 to the heat radiating member 201.

  The material constituting the pressing member 204 is not particularly limited, and examples thereof include metals such as stainless steel, heat resistant resins such as polyimide and polyphenylene sulfide (PPS), and ceramics. The pressing member 204 made of the material is a member having high strength and high toughness. Since the elastic member 2037 is provided between the heat generating member 203 and the pressing member 204, the heat generating member 203 is replaced with the heat radiating member. It can be elastically pressed in the direction close to 201. Therefore, the heat generating member 203 is fixed in a state where the adhesion to the inner surface of the heat radiating member 201 is improved.

  FIG. 5 is a side view of the heating member 20 shown in FIG. As shown in FIG. 5, a convex portion 204 a is formed on the surface of the pressing member 204 that contacts the elastic member 2037, and the convex portion 204 a is in point contact with the elastic member 2037. Accordingly, heat conduction to the pressing member 204 is suppressed when the heating resistor 2036 is heated, and the heat capacity of the pressing member 204 can be reduced, so that the heating rate of the heat radiating member 201 is increased.

  As described above, the heating member 20 of the present embodiment is disposed in contact with the heat radiating member 201, the heat conducting member 202 disposed in contact with the inner surface of the heat radiating member 201, and the inner surface of the heat conducting member 202. A first insulating layer 2031 made of an insulator, a heat generating member 203 arranged in contact with the inner surface of the first insulating layer 2031, and a second insulating layer made of an insulating material arranged in contact with the inner surface of the heat generating member 203 2032, an elastic member 2037 disposed in contact with the inner surface of the second insulating layer 2032, and a pressing member 204 that presses the heat generating member 203 in a direction approaching the heat radiating member 201. Since the heat generating member 203 is pressed by the pressing member 204 in the direction approaching the heat radiating member 201 and is fixed to the heat radiating member 201, the heat generating member 203 is fixed in a state where the adhesion to the heat radiating member 201 is improved. Is done. Furthermore, since the heat conducting member 202 made of a material having low hardness and high thermal conductivity is disposed between the heat radiating member 201 and the heat generating member 203, the heat transfer efficiency from the heat generating member 203 to the heat radiating member 201 is improved. Without lowering, the thermal expansion difference of each member constituting the heating member 20 can be absorbed and relaxed, and local separation between the members can be prevented.

  As described above, since the heating member 20 of the present embodiment is maintained in a state where the adhesion of the heat generating member 203 to the heat radiating member 201 is high, it is possible to prevent local peeling between the members. The local heat transfer efficiency is prevented from being lowered, and the surface temperature distribution is the heating member 20 with no variation with respect to the set temperature. Therefore, the heating member 20 can ensure a short warm-up time until reaching the set temperature and a uniform temperature distribution on the surface in a short time, and a sufficient amount of heat can be obtained from the heat radiating member 201 even in high-speed printing. It can be supplied to a fixing belt, which is an object to be heated.

(Inner coat layer and outer coat layer)
Moreover, in the heat radiating member 201, the inner surface coating layer may be formed on the inner surface, and the outer surface coating layer may be formed on the outer surface.

  The inner surface coating layer is made of a material having heat resistance and high heat radiation (for example, a material having an emissivity of 0.9 to 1.0 in a wide wavelength region and having heat resistance). By forming an inner surface coating layer made of a material having heat resistance and high heat radiation on the inner surface of the heat radiating member 201, the heat generated in the heat generating member 203 is absorbed and radiated with high efficiency, and is an object to be heated. Heat can be transferred to the fixing belt with high efficiency.

  Examples of the material having heat resistance and high heat radiation property include silicone resins. The inner surface coating layer can be formed, for example, by spraying a liquid material in which the material is dissolved or dispersed in a solvent on the inner surface of the heat dissipation member 201. Specifically, the inner surface coat layer can be formed by spray-coating B-600 manufactured by Okitsumo Co., Ltd., which is a material made of silicone resin, on the inner surface of the heat dissipation member 201. As described above, it is possible to prevent the occurrence of corrosion at the interface between the heat dissipation member 201 and the heat conduction member 202 by forming the inner surface coating layer on the inner surface of the heat dissipation member 201 that is in contact with the heat conduction member 202. Further, it is possible to prevent a decrease in heat transfer efficiency from the heat generating member 203 to the heat radiating member 301 over a long period of time.

  The outer surface coat layer is made of a material having heat resistance and a low friction coefficient. Examples of the material having heat resistance and a low friction coefficient include fluororesins such as PFA (a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) and PTFE (polytetrafluoroethylene). These fluororesins May be used alone or in combination of two or more.

  As described above, by forming the outer surface coating layer on the outer surface of the heat radiating member 201 that is in contact with the fixing belt that is the heating target, the frictional force between the heat radiating member 201 and the fixing belt can be reduced, and the fixing is performed. The belt can be prevented from being worn to ensure high durability of the fixing belt, and the load on the fixing roller and the pressure roller for driving the fixing belt to be reduced can also be reduced to increase the durability of each roller. It can be secured and driven to rotate with low power. Further, when the frictional force between the heat radiating member 201 and the fixing belt can be reduced, the rotation of the fixing belt can be made smooth, and the heat transfer efficiency of the heating member 20 to the fixing belt can be prevented from being lowered. it can.

2. Fixing Device FIG. 6 is a diagram showing a configuration of a fixing device 15 according to an embodiment of the present invention. FIG. 7 is a diagram illustrating the configuration of the fixing device 15 in the vicinity of the region where the fixing belt is suspended from the heating member. The fixing device 15 is a device provided in the image forming apparatus 100 to be described later, and is a device that heats and presses a toner image 31 carried on a recording paper 32 that is a recording paper and fixes the toner image 31 on the recording paper 32. . The fixing device 15 includes the heating member 20 of the present embodiment described above.

  The fixing device 15 includes a fixing roller 15 a that is a first fixing member, a pressure roller 15 b that is a second fixing member, a fixing belt 25 that is an endless belt, and a heating member 20. In the fixing device 15, the fixing belt 25 is stretched between the fixing roller 15 a and the heating member 20, and the pressure roller 15 b is disposed so as to face the fixing roller 15 a through the fixing belt 25. The fixing roller 15a and the heating member 20 are arranged so as to be substantially parallel in the axial direction of the fixing roller 15a. That is, the axis of the fixing roller 15a and the axis of the heating member 20 are substantially parallel. As a result, when the fixing belt 25 stretched between the fixing roller 15a and the heating member 20 slides, the fixing belt 25 can be prevented from meandering and the durability of the fixing belt 25 can be maintained high.

  In the fixing device 15, the heating member 20 contacts the fixing belt 25 to heat the fixing belt 25, and the fixing nip portion 15c formed by the fixing belt 25 and the pressure roller 15b is recorded at a predetermined fixing speed and copying speed. This is a device for fixing an unfixed toner image 31 carried on the recording paper 32 by applying heat and pressure on the recording paper 32 when the recording paper 32 which is paper passes.

  The unfixed toner image 31 is a developer (such as a non-magnetic one-component developer (non-magnetic toner), a non-magnetic two-component developer (non-magnetic toner and carrier), or a magnetic developer (magnetic toner). Toner). The fixing speed is a so-called process speed, and the copying speed is the number of copies per minute. When the recording paper 32 passes through the fixing nip portion 15c, the fixing belt 25 comes into contact with the surface of the recording paper 32 opposite to the toner image carrying surface.

(Fixing roller)
The fixing roller 15a is pressed against the pressure roller 15b via the fixing belt 25 to form a fixing nip portion 15c, and is driven to rotate in the rotation direction A around the rotation axis by a drive motor (driving means) 113. Thus, the fixing belt 25 is conveyed. The fixing roller 15a has a diameter of 30 mm and has a two-layer structure in which a core metal and an elastic layer are formed in order from the inside. The core metal includes, for example, a metal such as iron, stainless steel, aluminum, copper, or the like. An alloy or the like is used. For the elastic layer, a heat-resistant rubber material such as silicon rubber or fluorine rubber is suitable. In the present embodiment, the force when the fixing roller 15a is pressed against the pressure roller 15b via the fixing belt 25 is about 216N.

(Pressure roller)
The pressure roller 15b is opposed to and pressed against the fixing roller 15a via the fixing belt 25, and is provided to be rotatable about the rotation axis. The pressure roller 15b rotates in the rotation direction B following the rotation of the fixing roller 15a. The pressure roller 15b has a three-layer structure in which a metal core, an elastic layer, and a release layer are formed in this order from the inside. For the core metal, for example, a metal such as iron, stainless steel, aluminum, copper, or an alloy thereof is used. In addition, a rubber material having heat resistance such as silicon rubber and fluorine rubber is suitable for the elastic layer, and a fluorine resin such as PFA and PTFE is suitable for the release layer. The pressure roller 15b has, for example, a roller diameter of 30 mm, a core (STKM) pipe with a diameter of 24 mm (wall thickness 2 mm), a silicon solid rubber with a thickness of 3 mm as an elastic layer, and a thickness of 30 μm as a release layer. A roller made of a PFA tube can be used.

  A heater lamp 26 (for example, rated power 400 W) for heating the pressure roller 15b is disposed inside the pressure roller 15b. The apparatus control means 111 described later supplies power to the heater lamp 26 from the power supply circuit 1111 (energization), whereby the heater lamp 26 emits light, and infrared light is emitted from the heater lamp 26. As a result, the inner peripheral surface of the pressure roller 15b is heated by absorbing infrared rays, and the entire pressure roller 15b is heated. The above-described heater lamp 26 is heated from the inner surface of the pressure roller 15b. Alternatively, a method of heating from the surface of the pressure roller 15b with an outer peripheral surface heating roller can be configured. is there.

(Fixing belt)
The fixing belt 25 is heated to a predetermined temperature by the heating member 20 and heats the recording paper 32 on which the unfixed toner image 31 that passes through the fixing nip portion 15c is formed. The fixing belt 25 is an endless belt, is suspended by the heating member 20 and the fixing roller 15a, and is wound around the fixing roller 15a at a predetermined angle. When the fixing roller 15a rotates, the fixing belt 25 follows the fixing roller 15a and rotates in the rotation direction A. The fixing belt 25 is formed of an elastomer material (for example, silicon rubber) having excellent heat resistance and elasticity as an elastic layer on the surface of a hollow cylindrical base material made of a heat resistant resin such as polyimide or a metal material such as stainless steel or nickel. Furthermore, the surface has a three-layer structure in which a synthetic resin material (for example, a fluororesin such as PFA or PTFE) having excellent heat resistance and releasability is formed on the surface as a release layer. Moreover, you may add a fluororesin internally to the polyimide of a base material. Thereby, the sliding load with the heating member 20 can be reduced.

(Heating member)
The heating member 20 provided in the fixing device 15 contacts the fixing belt 25 on the outer surface of the heat radiating member 201 to heat the fixing belt 25 to a predetermined temperature.

  Two fixing adapters 205 are provided in the frame fixing portions provided at both ends in the axial direction of the heating member 20 so as to correspond to the respective ends, and the heating member 20 is connected to the fixing device 15 via the fixing adapter 205. It is fixed to the side frame 110. FIG. 8A is a side view showing the structure of the fixed adapter 205 at the end in the longitudinal direction of the heating member 20. FIG.8 (b) is sectional drawing which looked at the heating member 20 shown to Fig.8 (a) from cut surface line S21-S21. As described above, since the heating member 20 is fixed to the side frame 110 by the power supply connector 205a and the screw 205b through the fixed adapter 205, the heating member 20 itself is rotated by the frictional force with the fixing belt 25. Is prevented. Therefore, even if a high current is supplied to the heat generating member 203 included in the heating member 20, safety can be sufficiently ensured. Furthermore, since the pressing member 204 is fixed to the side frame 110 via the fixed adapter 205, the arrangement position of the pressing member 204 with respect to the heat generating member 203 is restricted. In this way, by restricting the arrangement position of the pressing member 204, external force (belt tension acting between the fixing belt 25 and the pressing member 204) due to the restriction is used to bring the heat generating member 203 close to the heat radiating member 201. It can be applied as a pressing force that elastically presses in the direction. The fixed adapter 205 is made of a metal such as aluminum, for example.

  Further, the fixing device 15 may be configured such that meandering preventing collars that prevent meandering when the fixing belt 25 rotates and slides are disposed at both ends of the pressing member 204. As the meander-preventing collar, a color made of polyphenylene sulfide (PPS) can be used. However, the collar is not limited to this, and any collar that can rotate independently of the pressing member 204 may be used. Thus, since the meandering prevention collar is independently rotatable, even if the fixing belt 25 abuts on the meandering prevention collar, no load is applied and the fixing belt 25 is prevented from being broken. Thus, the durability of the fixing belt 25 can be maintained high. Depending on the rotation state of the fixing belt 25, the meandering prevention collar may be provided only on the fixing roller 15a without providing the pressing member 204 with the meandering prevention collar.

(Temperature detection means)
Further, in the fixing device 15, as temperature detection means, a heating element side thermistor 24 a is provided in the vicinity of the peripheral surface of the fixing belt 25 that contacts the heating member 20, and a pressure roller side thermistor 24 b is provided in the vicinity of the peripheral surface of the pressure roller 15 b. Each surface temperature is detected. The heating element side thermistor 24a in the present embodiment is a non-contact type temperature detection means, and is an infrared detection type temperature sensor. In the configuration in which the contact-type temperature detection unit is arranged in contact with the fixing belt 25, the contact-type temperature detection unit may wear the surface release layer of the fixing belt 25 at the interface in contact with the fixing belt 25. When the surface release layer of the fixing belt 25 is damaged or deteriorated in this manner, the fixing property with respect to the toner image 31 is affected, and an inferior fixed image is formed on the recording paper 32. In the vicinity of the peripheral surface of the fixing belt 25, a thermostat or a thermal protector 24c that detects an abnormal temperature rise of the fixing belt 25 and cuts off the power supply circuit 1111 when the temperature exceeds a predetermined temperature is provided.

  Next, electrical control in the fixing device 15 will be described. FIG. 9 is a block diagram showing an electrical configuration of the fixing device 15. In the fixing device 15, a control circuit 1112 as temperature control means is based on temperature data detected by the heating element side thermistor 24 a and pressure roller side thermistor 24 b and abnormal temperature rise data of the fixing belt 25 detected by the thermal protector 24 c. However, the power supply to the heat generating member 203 and the heater lamp 26 included in the heating member 20 is controlled via the power supply circuit 1111 so that the surface temperatures of the fixing belt 25 and the pressure roller 15b are set to predetermined temperatures. In addition, the control circuit 1112 controls the drive motor 113 to rotate the fixing roller 15a around the rotation axis and rotate the fixing belt 25. The control circuit 1112 and the power supply circuit 1111 are comprehensively controlled by a device control unit 111 that controls all operations of the fixing device 15.

  Specifically, when receiving an image formation instruction, the apparatus control unit 111 outputs a control signal instructing the power supply circuit 1111 to supply power. Here, the image forming instruction is an instruction input from an operation panel provided on the upper surface in the vertical direction of the image forming apparatus 100, which will be described later, or an external device such as a computer connected to the image forming apparatus 100. By receiving the input, the fixing device 15 starts the fixing processing operation.

  The power supply circuit 1111 to which the control signal is input from the apparatus control unit 111 supplies power to the heat generating member 203 of the heating member 20 through the power control unit 206 to heat the fixing belt 25, and supplies power to the heater lamp 26. Supply and heat the pressure roller 15b. Here, the power control means 206 also serves as power control means for controlling the input power to the heating resistor 2036 of the heating member 203 of the heating member 20 to a predetermined constant value. A signal related to the surface temperature data of the fixing belt 25 detected by the heating element side thermistor 24a, a signal related to the surface temperature data of the pressure roller 15b detected by the pressure roller side thermistor 24b, and an abnormal temperature rise of the fixing belt 25 detected by the thermal protector 24c. A signal related to data is input to the control circuit 1112.

  The control circuit 1112 controlled by the device control means 111 is supplied from the power supply circuit 1111 so that the surface temperature of the fixing belt 25 and the pressure roller 15b becomes a predetermined temperature (fixing temperature) based on the input signal. The power supplied to the heating member 20 and the heater lamp 26 is controlled. Specifically, the power control means 206 controlled by the power supply circuit 1111 is based on the temperature data detected by the heating element side thermistor 24a, or based on the temperature data and the power calculation value calculated by the power calculation unit. The power supplied to the heating member 20 is controlled. The power supply circuit 1111 controls the power supplied to the heater lamp 26 based on the temperature data detected by the pressure roller side thermistor 24b.

  When the control circuit 1112 determines that the surface temperature of the fixing belt 25 and the pressure roller 15b has reached a predetermined fixing temperature based on the input signal, the control circuit 1112 controls the drive motor 113 to move the fixing roller 15a around the rotation axis. And the fixing belt 25 is rotated. When the fixing belt 25 rotates in this way, the recording paper 32 on which the unfixed toner image 31 is formed is conveyed to the fixing nip portion 15c formed between the fixing belt 25 and the pressure roller 15b. At this time, the recording paper 32 is conveyed with the surface carrying the unfixed toner image 31 facing the fixing belt 25 side. The unfixed toner image 31 on the recording paper 32 is nipped and conveyed while being in close contact with the outer peripheral surface of the fixing belt 25, whereby heat is applied from the fixing belt 25 and the recording paper 32 is subjected to pressure. To be fixed on the surface.

  The fixing device 15 configured as described above includes the heating member 20 of the present embodiment in which the temperature distribution on the surface does not vary with respect to the set temperature, so that the temperature distribution on the surface of the fixing belt 25 becomes the set temperature. On the other hand, the fixing device is uniform and the fixing temperature is prevented from varying, and the fixing device has uniform fixing characteristics. Further, since the heating member 20 of the present embodiment provided in the fixing device 15 is one in which a local decrease in heat transfer efficiency is prevented, the fixing device 15 has a warm-up time until a desired fixing temperature is obtained. And a fixing device in which an increase in power consumption is prevented.

  In the present embodiment, the fixing device 15 is configured such that the fixing nip portion 15c is formed at the pressure contact portion where the pressure roller 15b is in pressure contact with the fixing roller 15a via the fixing belt 25. The fixing nip portion may be formed at a pressure contact portion 15b in pressure contact with the heating member 20 via the fixing belt 25.

  FIG. 10 is a diagram illustrating a configuration of a fixing device 150 according to another embodiment of the present invention. The fixing device 150 of FIG. 10 is obtained by replacing the fixing roller 15a of the fixing device 15 shown in FIG. 6 with a fixing pad 150a, and the other configuration is the same as that of the fixing device 15. The fixing pad 150a is composed of an elastic layer 150c made of an elastic material such as silicon rubber, a surface layer 150d that reduces sliding frictional force between the fixing belt 25, and a cored bar 150b, and the pressure roller 15b via the fixing belt 25. Are arranged opposite to each other.

  FIG. 11 is a diagram illustrating a configuration of an image forming apparatus 100 according to an embodiment of the present invention. The image forming apparatus 100 is an apparatus that forms multi-color and single-color images on the recording paper 32 based on image data of a read original or image data transmitted via a network or the like. The image forming apparatus 100 includes any one of the fixing devices 15 and 150 of the present embodiment described above. A case where the image forming apparatus 100 includes the fixing device 15 will be described below.

  The image forming apparatus 100 includes an exposure unit 10, a photosensitive drum 101 (101a to 101d), a developing device 102 (102a to 102d), a charging roller 103 (103a to 103d), a cleaning unit 104 (104a to 104d), and an intermediate transfer belt. 11, a primary transfer roller 13 (13 a to 13 d), a secondary transfer roller 14, a fixing device 15, paper transport paths P 1, P 2 and P 3, a paper cassette 16, a manual paper feed tray 17 and a paper discharge tray 18.

  The image forming apparatus 100 corresponds to the hues of four colors of cyan (C), magenta (M), and yellow (Y), which are three subtractive primary colors obtained by color separation of black (K) and a color image. Using the image data, image formation is performed in the image forming units Pa to Pd corresponding to each hue. Each of the image forming units Pa to Pd has the same configuration. For example, the black (K) image forming unit Pa includes the photosensitive drum 101a, the developing device 102a, the charging roller 103a, the primary transfer roller 13a, the cleaning unit 104a, and the like. Consists of The image forming portions Pa to Pd are arranged in a line in the moving direction (sub-scanning direction) of the intermediate transfer belt 11.

  The charging roller 103 is a contact-type charger that uniformly charges the surface of the photosensitive drum 101 to a predetermined potential. Instead of the charging roller 103, a contact type charger using a charging brush or a non-contact type charger using a charging wire may be used.

  The exposure unit 10 includes a semiconductor laser (not shown), a polygon mirror 4, a first reflection mirror, a second reflection mirror 8, and the like, and includes black (K), cyan (C), magenta (M), and yellow (Y). Each of the photosensitive drums 101a to 101d is irradiated with a light beam such as a laser beam modulated by the image data of each hue. Each of the photosensitive drums 101a to 101d forms an electrostatic latent image based on image data of each hue of black (K), cyan (C), magenta (M), and yellow (Y).

  The developing device 102 supplies toner as a developer to the surface of the photosensitive drum 101 on which the electrostatic latent image is formed, and develops the electrostatic latent image into a toner image. Each of the developing devices 102a to 102d contains toner of each hue of black (K), cyan (C), magenta (M), and yellow (Y), and is formed on each of the photosensitive drums 101a to 101d. The electrostatic latent image of each hue is visualized into a toner image of each hue. The cleaning unit 104 removes and collects toner remaining on the surface of the photosensitive drum 101 after development and image transfer.

  The intermediate transfer belt 11 is disposed above the photosensitive drum 101, and is stretched between the driving roller 11a and the driven roller 11b to form a loop-shaped moving path. The outer peripheral surface of the intermediate transfer belt 11 faces the photosensitive drum 101d, the photosensitive drum 101c, the photosensitive drum 101b, and the photosensitive drum 101a in this order. Primary transfer rollers 13a to 13d are arranged at positions facing the respective photosensitive drums 101a to 101d with the intermediate transfer belt 11 interposed therebetween. Each of the positions where the intermediate transfer belt 11 faces the photosensitive drums 101a to 101d is a primary transfer position. The intermediate transfer belt 11 is formed of a film having a thickness of about 100 to 150 μm.

  The primary transfer rollers 13a to 13d have constant voltage control of a primary transfer bias opposite to the charging polarity of the toner in order to transfer the toner images carried on the surfaces of the photosensitive drums 101a to 101d onto the intermediate transfer belt 11. Applied. As a result, the toner images of the respective colors formed on the photosensitive drums 101a to 101d are sequentially transferred onto the outer peripheral surface of the intermediate transfer belt 11, and a full-color toner image is formed on the outer peripheral surface of the intermediate transfer belt 11. .

  However, when image data of only a part of the hues of yellow (Y), magenta (M), cyan (C), and black (K) is input, input is performed among the four photosensitive drums 101a to 101d. The electrostatic latent image and the toner image are formed only on a part of the photosensitive drums 101 corresponding to the hue of the image data. For example, when forming a monochrome image, an electrostatic latent image and a toner image are formed only on the photosensitive drum 101a corresponding to the black hue, and only the black toner image is transferred to the outer peripheral surface of the intermediate transfer belt 11. Is done.

  Each of the primary transfer rollers 13a to 13d is configured by covering the surface of a shaft whose base is a metal such as stainless steel having a diameter of 8 to 10 mm with a conductive elastic material (for example, EPDM, urethane foam, etc.). A high voltage is uniformly applied to the intermediate transfer belt 11 by the elastic material.

  The toner image transferred to the outer peripheral surface of the intermediate transfer belt 11 at each primary transfer position is conveyed to a secondary transfer position that is a position facing the secondary transfer roller 14 by the rotation of the intermediate transfer belt 11. The secondary transfer roller 14 is pressed against the outer peripheral surface of the intermediate transfer belt 11 whose inner peripheral surface is in contact with the peripheral surface of the driving roller 11a at a predetermined nip pressure during image formation. When the recording paper 32 fed from the paper cassette 16 or the manual paper feed tray 17 passes between the secondary transfer roller 14 and the intermediate transfer belt 11, what is the charging polarity of the toner on the secondary transfer roller 14? A high voltage of reverse polarity is applied. As a result, the toner image is transferred from the outer peripheral surface of the intermediate transfer belt 11 to the surface of the recording paper 32.

  Of the toner adhering to the intermediate transfer belt 11 from the photosensitive drum 101, the toner remaining on the intermediate transfer belt 11 without being transferred onto the recording paper 32 is transferred in order to prevent color mixing in the next process. Collected by the cleaning unit 12.

  The recording paper 32 onto which the toner image has been transferred is guided to the fixing device 15 of the present invention described above, and passes through the fixing nip portion and is heated and pressurized. As a result, the toner image is firmly fixed on the surface of the recording paper 32. The recording paper 32 on which the toner image is fixed is discharged onto the paper discharge tray 18 by the paper discharge roller 18a.

  In the image forming apparatus 100, the recording paper 32 stored in the paper cassette 16 is sent to the paper discharge tray 18 between the secondary transfer roller 14 and the intermediate transfer belt 11 and via the fixing device 15. For this purpose, a sheet conveyance path P1 extending in a substantially vertical direction is provided. A pickup roller 16a that feeds the recording paper 32 in the paper cassette 16 one by one into the paper transport path P1 and a transport roller 16b that transports the fed recording paper 32 upward are transported to the paper transport path P1. A registration roller 19 that guides the recording sheet 32 between the secondary transfer roller 14 and the intermediate transfer belt 11 at a predetermined timing, and a discharge roller 18 a that discharges the recording sheet 32 to the discharge tray 18 are disposed.

  Further, inside the image forming apparatus 100, a paper conveyance path P2 in which a pickup roller 17a and a conveyance roller 16b are arranged is formed between the manual paper feed tray 17 and the registration rollers 19. Further, a paper transport path P3 is formed between the paper discharge roller 18a and the upstream side of the registration roller 19 in the paper transport path P1.

  The paper discharge roller 18a is rotatable in both forward and reverse directions, and is used for the second time in forming a single-sided image for forming an image on one side of the recording paper 32 and in forming a double-sided image for forming images on both sides of the recording paper 32. When the surface image is formed, the recording paper 32 is driven in the forward rotation direction and discharged to the paper discharge tray 18. On the other hand, when the first side image is formed in the double-sided image formation, the paper discharge roller 18a is driven in the normal direction until the rear end of the paper passes through the fixing device 15, and then sandwiches the rear end of the recording paper 32. In this state, the recording paper 32 is driven in the reverse direction to guide the recording paper 32 into the paper transport path P3. As a result, the recording paper 32 on which an image is formed only on one side at the time of double-sided image formation is guided to the paper transport path P1 with the front and back sides and front and rear ends reversed.

  The registration roller 19 receives the recording paper 32 fed from the paper cassette 16 or the manual paper feed tray 17 or transported via the paper transport path P <b> 3 at the timing synchronized with the rotation of the intermediate transfer belt 11. Guided between the transfer roller 14 and the intermediate transfer belt 11. For this reason, the registration roller 19 stops rotating when the operation of the photosensitive drum 101 and the intermediate transfer belt 11 is started, and the recording paper 32 fed or conveyed prior to the rotation of the intermediate transfer belt 11 has a leading edge. The movement in the paper conveyance path P1 is stopped in a state where it is in contact with the registration roller 19. Thereafter, the registration roller 19 is located at a position where the secondary transfer roller 14 and the intermediate transfer belt 11 are pressed against each other, and the front end portion of the recording paper 32 and the front end portion of the toner image formed on the intermediate transfer belt 11 face each other. Start rotation at the timing.

  At the time of full color image formation in which image formation is performed in all of the image forming portions Pa to Pd, the primary transfer rollers 13a to 13d press the intermediate transfer belt 11 against all of the photosensitive drums 101a to 101d. On the other hand, at the time of monochrome image formation in which image formation is performed only in the image forming portion Pa, only the primary transfer roller 13a is brought into pressure contact with the photosensitive drum 101a.

  The image forming apparatus 100 configured as described above includes the fixing device 15 having a uniform fixing characteristic in which the fixing temperature is prevented from being varied with respect to the set temperature, so that a uniform and high-quality image is recorded. It can be formed on paper 32.

(Example)
EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited to these Examples.

Example 1
The fixing device used in Example 1 is the fixing device 15 described above. The fixing device 15 was mounted on a copying machine (trade name: MX-4500N, manufactured by Sharp Corporation). Detailed conditions in Example 1 were as follows.

<Fixing roller>
A stainless steel having a diameter of 30 mm, a core metal of 15 mm in diameter, and an elastic layer made of silicon sponge rubber having a thickness of 5 mm was used.

<Pressure roller>
A diameter of 30 mm made of silicon solid rubber, a core metal diameter of 24 mm (thickness 2 mm), a release layer having a 30 μm thick PFA tube, and a heater lamp with a rated power of 400 W inside was used.

<Fixing belt>
A belt in which a polyimide having a thickness of 70 μm was formed on a belt substrate, a silicon rubber having a thickness of 150 μm was formed on an elastic layer, and a PTFE coat having a thickness of 30 μm was formed on a release layer was used.

<Color to prevent meandering>
A polyphenylene sulfide (PPS) collar having an inner diameter of 20 mm, a diameter of 32 mm, and a width of 7 mm was disposed at the end of the fixing roller so as to contact the end of the fixing belt.

<Heating member>
The heating member used in Example 1 is the heating member 20 described above.

[Heat dissipation member]
A groove having a depth of 3 mm and a width of 12 mm was formed on the inner surface of a substantially cylindrical body made of aluminum having a longitudinal length of 335 mm and a thickness of 2.5 mm. A mixed material of PTFE and PFA was applied to the outer surface of the substantially cylindrical body so as to have a thickness of 15 μm to form an outer surface coating layer. Next, a material made of a silicone resin (trade name: B-600, manufactured by Okitsumo Co., Ltd.) is spray-applied to the inner surface of the substantially cylindrical body, and then baked at 180 ° C. for 20 minutes, and the inner surface coating layer having a thickness of 35 μm Formed. Thus, the heat radiating member A in which the outer surface coating layer and the inner surface coating layer were formed was produced.

[Pressing member]
A notch is formed in a concave and convex portion having a pitch of 10 mm and a height of 3 mm at the end of the plate-like object made of stainless steel having a length of 370 mm and a thickness of 1.0 mm perpendicular to the heating member axial direction. It was bent into a U shape. Further, the longitudinal end portion of the plate-like material was bent so that it could be attached to a fixing adapter for fixing to the fixing device frame, and the heat radiating member A was produced.

[Heat conduction member]
As a material constituting the insulating heat conducting member A, a heat dissipating silicone SCH-30 manufactured by Sanhayato Co., Ltd., which is an insulating silicone grease heat dissipating agent A (heat resistance 300 ° C., heat conductivity 0.84 W / m). -Viscosity grease at 25 ° C.

As a conductive material constituting the heat conducting member B, percopolyether based conductive grease B, Molycoat HP-800 (volume resistivity 4 × 10 ² Ω / cm, manufactured by Toray Dow Corning Co., Ltd., heat conduction) 1.0 W / m · K, viscous grease at 25 ° C.).

[Heat-generating resistor and heating member A]
The heating resistor used in Example 1 was obtained by a conventional method of mixing 100 parts by weight of barium titanate with a Curie point adjusting agent and a dopant, wet mixing, molding and firing. This is a semiconductor ceramic heating element having a thickness of 1 mm, a width of 10 mm, a length of 20 mm, a Curie point of 300 ° C., and an electric resistance of 7.25Ω at room temperature. As shown in FIG. PTC characteristics that increase electrical resistance. In this semiconductor ceramic heating element, a feeding electrode made of nickel and silver is formed on the surface having a width of 10 mm and a length of 20 mm.

  Here, since the toner used in the present embodiment has a warm-up power required for fixing of 1200 W, the electric resistance value shown in the above formula (1) is set so that power exceeding this power can be supplied.

  Ten heating resistors are arranged in the longitudinal direction, and conductive and good thermal conductivity perfluoropolyether type conductive grease B is applied to both surfaces, and a 0.2 mm thick stainless steel is formed on the upper and lower sides of the semiconductor ceramic. Insulating silicone grease heat-dissipating agent A was applied between the power supply electrode consisting of mica sheet, a 30-um thick mica sheet (insulating layer), and the heat dissipating member. Insert a heat-dissipating member A into the fixed adapter so that the heat-dissipating member is pressed against the heat-dissipating member using the pressing member A by inserting fluoro rubber (elastic member) having a thickness of 2 mm between the pressing member and the mica sheet. Was fixed to the fixed adapter with screws to produce a heating member A. The heating member A of Example 1 had an insulation resistance of 100 MΩ or more, and had a withstand voltage of AC 1500 V / 1 minute.

<Thermistor>
One non-contact infrared sensor as the heating resistor side thermistor is installed at the center and one end of the fixing belt in the width direction, and the contact thermistor as the pressure roller side thermistor contacts the surface of the pressure roller. Was installed.

<Device control means>
Based on the temperature detected by the heating element side thermistor, the device control means controls the power supply to the heating resistors corresponding to the three regions of the heat dissipation member in the longitudinal center and both ends, and the input power to all the heating resistors Was made constant at 1200W. If the input power to the heating resistor is not controlled, the power is theoretically 1380 to 4200 W and the maximum current value of the fixing device is 15 A, so that the fixing device is not established. Further, the apparatus control means controls the power supply to the heater lamp of the pressure roller based on the temperature detected by the pressure roller side thermistor when the paper is passed.

<Safety device>
A thermal protector is arranged in the vicinity of the outer peripheral surface of the fixing belt, and the power supply circuit is disconnected when the surface temperature of the fixing belt becomes abnormally high.

<Fixing conditions>
Fixing nip length: 8.5 mm (length of the fixing nip in the recording paper conveyance direction)
Fixing speed: 220mm / sec
Heating nip length: 44 mm (contact length in the recording paper conveyance direction between the fixing belt and the heating member)
Heating nip width: 330 mm (length corresponding to the axial direction of the fixing roller)

<Evaluation by operation of copying machine>
First, a 100 V power source and device control means were connected to the heating member A of the heating member A produced as described above, and the electrical resistance value of the heating member A at 25 ° C., that is, the electrical resistance value of all the heating resistors was measured. However, it was 7.25Ω. Next, the warm-up time in the copying machine, the temperature variation when 50 sheets were continuously passed, and the temperature rise at the end of the heating member when small-size sheets were passed were measured.

  When a voltage of 100 V is applied to the entire heating resistor of the heating member A, it can be confirmed that the power control function works and maintains 1200 W, and the time until the entire fixing belt surface temperature on the fixing roller reaches 180 ° C. The (warm-up time) was 19.0 seconds, which is the target of 20.0 seconds or less, at both the widthwise center and both ends of the fixing belt. There was no problem with the fixability of the fixed image on the recording paper immediately after the warm-up was completed.

  Also, as the power supplied to the heating member A, the heating resistor corresponding to the central portion in the longitudinal direction is set to 730 W, both ends are set to 470 W (the power density is increased by 5% compared to the central portion), and the central portion and both end portions are set. By distinguishing and controlling the energization, a high-quality image was obtained with almost no image density unevenness in A4 size continuous paper feeding. Furthermore, when the temperature at both ends in the longitudinal direction of the heating member A when the B5 small size paper was passed was measured with a heating element side thermistor, no excessive temperature rise was observed, and an increase in power consumption could be efficiently suppressed. .

  In addition, since the outer coating layer is formed on the outer surface of the heat radiating member A that contacts the fixing belt, the heating member A is suppressed from increasing the frictional force between the heat radiating member A and the fixing belt. The sliding was smooth with no frictional resistance, and there was no meandering of the fixing belt. Furthermore, since a non-contact thermistor was used for temperature detection on the surface of the fixing belt, the surface of the fixing belt was not damaged, and a belt life of 200K sheets could be secured.

  Further, the temperature distribution on the surface of the heating member A did not vary with respect to the set temperature even during continuous paper feeding, and the heat transfer efficiency with respect to the fixing belt did not decrease. Furthermore, even after printing 200K sheets, there is no local separation between the members constituting the heating member A, there is no safety problem, and the warm-up time and the electrical resistance value of the heating resistor are also initial. Was the same.

  The temperature of the surface of the fixing belt when the rotation of the fixing belt was stopped while the fixing device was energized was saturated at 280 ° C., and no smoke was generated from the heating member and the fixing belt.

  Therefore, not only the reliability and safety are ensured over a long period of time and the life of the heating member A is maintained, but also a copying machine provided with an energy-saving fixing device.

(Comparative Example 1)
Example 1 was the same as Example 1 except that the heat generating member was configured as follows.

<Heat-generating resistor and heating member B>
The heating resistor used in Comparative Example 1 was obtained by a conventional method of mixing 100 parts by weight of barium titanate with a Curie point adjusting agent and a dopant, wet mixing, molding and firing. A semiconductor ceramic heating element having a thickness of 1 mm, a width of 10 mm, a length of 20 mm, a Curie point of 260 ° C., and a room temperature resistance of 150Ω, and has a PTC characteristic in which the electrical resistance increases rapidly when the temperature rises above about 240 ° C. . In this semiconductor ceramic heating element, as in Example 1, a current-carrying electrode made of nickel and silver is formed on the surface having a width of 10 mm and a length of 20 mm.

  In this comparative example, the power required for fixing is 1200 W as in the first embodiment. Ten heating resistors were arranged in the longitudinal direction, and power supply electrodes made of stainless steel having a thickness of 0.2 mm were provided above and below the semiconductor ceramic, and mica sheets having a thickness of 30 μm were provided on both outer sides thereof. Insert a fluoro rubber with a thickness of 2 mm between the pressing member and the mica sheet, insert the heat dissipating member A into the fixed adapter so that the heat dissipating member is pressed using the pressing member A, and screw both ends of the pressing member into the adapter. It stopped and the heating member B was produced. The heating member B of Comparative Example 1 had an insulation resistance of 100 MΩ or higher, and had a withstand voltage of AC 1500 V / 1 minute.

<Evaluation by operation of copying machine>
First, a 100V power source and device control means were connected to the heating member B of the heating member B produced as described above, and the electrical resistance at 25 ° C. of the heating member B was measured. The overall electrical resistance was 15.0Ω. there were. Next, the warm-up time in the copying machine, the temperature variation when 50 sheets were continuously fed, and the edge temperature rise when small-size sheets were passed were measured.

  When a voltage of 100 V is applied to the entire heating member B, the time required for the entire fixing belt surface temperature on the fixing roller to reach 180 ° C. (warm-up time) is 32.5 sec, which is the target 20. A warm-up time of 0 sec or less could not be stably achieved. Immediately after the completion of warm-up, the fixing property of the fixed image on the recording paper was partially fixed.

  Further, even when continuous paper is passed, image density unevenness occurs, and a high-quality image cannot be obtained.

  When the temperature at both ends in the axial direction of the heating member B when the small size paper was passed was measured with a thermistor-side thermistor, overheating was not observed, but the fixing property was not good due to insufficient power. .

DESCRIPTION OF SYMBOLS 15,150 Fixing device 15a Fixing roller 15b Pressure roller 20 Heating member 25 Fixing belt 100 Image forming apparatus 201 Heat radiating member 202 Heat conducting member 203 Heat generating member 204 Pressing member 205 Fixed adapter 2033 Heat generating layer

Claims (11)

A heat dissipation member formed by curving one surface in the thickness direction;
A heat conductive member made of a material having low hardness and high thermal conductivity, and provided in contact with the other surface in the thickness direction of the heat radiating member;
An insulating layer that is provided in contact with the other surface in the thickness direction of the heat conducting member and is made of an insulator;
A heating member comprising a heating resistor that generates heat when energized, and an electrode member laminated so as to sandwich the heating layer, and a heating member provided in contact with the other surface in the thickness direction of the insulating layer;
A pressing member that presses the heat generating member in a direction close to the heat radiating member and fixes the heat generating member to the heat radiating member; and
The heating resistor has two resistance temperature characteristics, a negative resistance temperature characteristic and a positive resistance temperature characteristic, a Curie point indicating the positive resistance temperature characteristic is 300 ° C. or more, and a negative resistance temperature characteristic. A heating member characterized in that a maximum electrical resistance value Rf at an inflection temperature or less that changes from a positive resistance temperature characteristic to a positive resistance temperature characteristic satisfies the following formula (1).
R _f <(V _f ² / W _f ) (1)
(In the formula, R _f represents the maximum electric resistance (Ω), V _f represents the applied voltage (V), and W _f represents the desired power (W).) The heat generating layer is formed by aligning a plurality of heat generating resistors in the longitudinal direction of the heat radiating member,
The electrical resistance of the heating resistor provided corresponding to both longitudinal ends of the heat radiating member is lower than the electrical resistance of the heating resistor provided corresponding to the central portion in the longitudinal direction. The heating member as described.   The heating member according to claim 1 or 2, wherein the heating resistor is a semiconductive ceramic containing barium titanate. The heat dissipation member is formed using an alloy selected from an aluminum alloy, a magnesium alloy, and a copper alloy,
An elastic member is provided between the heat generating member and the pressing member,
The said pressing member is formed using the material chosen from a metal, a heat resistant resin, and ceramics, and is provided in point contact with the said elastic member, The any one of Claims 1-3 characterized by the above-mentioned. Heating member.   The heating according to any one of claims 1 to 4, wherein a fixing adapter connected to the outside and configured to be able to fix the pressing member is provided at both longitudinal ends of the pressing member. Element.   The heating according to any one of claims 1 to 5, wherein an inner surface coating layer made of a material having heat resistance and high heat radiation is formed on the other surface in the thickness direction of the heat radiating member. Element.   The heating member according to any one of claims 1 to 6, wherein an outer surface coating layer made of a material having heat resistance and a low friction coefficient is formed on one surface in the thickness direction of the heat radiating member. .   The heating member according to claim 7, wherein the outer surface coating layer is made of at least one material of PTFE resin and PFA resin containing fluorine. A first fixing member, a heating unit, a rotatable endless belt stretched between the first fixing member and the heating member, and the first fixing member so as to face the first fixing member via the endless belt A toner image carried on the recording paper and fixed on the recording paper at a fixing nip portion formed by contact between the endless belt and the second fixing member. A fixing device that
The heating means is the heating member according to any one of claims 1 to 8, wherein the endless belt is heated by contacting the endless belt on one surface in the thickness direction of the heat radiating member. A fixing device characterized.   An image forming apparatus comprising the fixing device according to claim 9.   The image forming apparatus according to claim 10, further comprising a power control unit configured to control power supplied to the heating resistor of the heating member to be constant.