JP2002033180A - Heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating device capable of preventing the temperature of the end part on the side from which heat is taken more from being lower than the other part in a heater having a heat-taking factor differed between both longitudinal ends thereof. SOLUTION: In this film type heating device, a body to be heated introduced to a fixing nip part with the center orthogonal to a carrying direction as a carrying reference c is moved and passed integrally with a film 1, whereby the heating value of a heating element 7 is imparted to the body to be heated through the film 1. The heating element 7 comprises a resistant heating element 4 whose lengths A1 and A2 to both lateral ends are differed to each other with the carrying reference C as the center.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device for fixing a visible image such as a toner image formed on a heated member such as a recording material to the heated member, and a copying apparatus using the heating device as a fixing device. The present invention relates to an image forming apparatus such as a printer or a printer.

[0002]

2. Description of the Related Art Conventionally, as a heating device (fixing device) used in an electrophotographic image forming apparatus such as a copying machine and a laser beam printer, a heating roller fixing type is well known.

[0003] However, in this method, a high temperature must be maintained at all times, which consumes a large amount of energy and is contrary to energy saving. In addition, even during standby, heat is released into the machine, causing a problem of temperature rise in the machine.

In addition, it takes time to heat the roller to a temperature suitable for heating an object to be heated such as paper.

Japanese Patent Application Laid-Open No. 63-313182 discloses a method in which a pattern of a resistance heating element is provided on an insulating ceramic substrate to form a heater, and the heater is heated to heat the object to be heated via a thin film. It is proposed in the gazette.

According to this method, since the temperature of the heating body rises in a short time, even if the heated body is passed without warming up, the heated body as a paper sheet must reach the fixing nip. The heater can be heated to a required temperature. In addition, no heating is performed during standby, so there is no temperature rise inside the machine and no energy is consumed.

In the heating apparatus (fixing apparatus) of the film heating and fixing method, a bias is applied to the film in order to charge the film surface to a charge of a predetermined polarity. A conductive ring is provided at an end of the pressure roller disposed opposite to the film so as to contact the end of the film, and a bias is applied to the film via the conductive ring.

[0008]

However, in the above-described film heat fixing method, for example, since the heating element is in contact with the conductive ring on the end side, the heating element is connected to the end of the heating element via the conductive ring. Heat is easily taken away, and the amount of heat applied to the object to be heated may not be uniform in the nip.

Further, for example, when the factor for removing heat is different at both ends in the longitudinal direction of the heater, the temperature of the end on the side from which heat is removed is lower than that of other portions.

This phenomenon affects image quality such as poor edge fixing property, uneven fixing property, and uneven gloss when an image is formed.

The thermal conductivity of the substrate of the heating element is 10 to 30 [W
/ m · k], such a problem does not occur much, but the thermal conductivity is higher than this, for example, 50 to 150.
This is particularly likely to occur when a substance of [W / mk] is used as a heater substrate.

An object of the invention according to the present application is to solve the above-mentioned problem by a relatively simple method and to provide a heating apparatus and an image forming apparatus for forming a high-quality image.

[0013]

According to a first aspect of the present invention, there is provided a heating element comprising at least an insulating substrate and a resistance heating element, a film being pressed against and adhered to the heating element, and the film being slid on the surface of the heating element. A rotating pressurized body that is driven while moving, between the film and the pressurized body in the press-contact nip portion of the heated body and the pressurized body via the film, in the transport direction. In the heating device, the heating object is introduced to the heating object through the film by moving and moving the heating object introduced with the center in the direction orthogonal to the film integrally with the film. Is characterized in that the length of the resistance heating element to both ends in the left-right direction with respect to the conveyance reference is different.

According to a second aspect of the present invention, in the first aspect, the heating element has a different length to both ends in the left-right direction of the insulating substrate with respect to the conveyance reference, and the resistance heating element in the longer dimension is used. Is characterized by having a long length.

According to a third aspect of the present invention, in the first aspect, the heating element has different lengths to both ends in the left-right direction of a stay holding the insulating substrate with respect to the conveyance reference. The length of the resistance heating element is also long.

According to a fourth aspect of the present invention, in the first aspect, the pressing body has different lengths to both ends in the left-right direction with respect to the conveyance reference, and the longer resistance heating element has a longer length. It is characterized by.

According to a fifth aspect of the present invention, in the first aspect, the film has different lengths to both ends in the left-right direction with respect to the transport reference, and the longer length of the resistance heating element is longer. And

According to a sixth aspect of the present invention, in any one of the above-mentioned inventions, a fan for inhaling or exhausting air inside the machine in which the heating device is incorporated is mounted on one of the right and left sides with respect to the transport reference. It is characterized by.

According to a seventh aspect of the present invention, in any one of the above aspects, the insulating substrate of the heating element has a thermal conductivity of 50 to 150 [W].
/ m · k].

According to an eighth aspect of the present invention, there is provided an image forming apparatus having any one of the above-mentioned heating devices as a fixing device, wherein the visible image formed by toner transferred to the recording material by the image forming means is fixed by the fixing device. It is in.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) This embodiment relates to a fixing device as a heating device used in a laser beam printer as an image forming apparatus, and a recording paper as a member to be heated is positioned at a center position in FIG. It is transported on the basis of C.

This embodiment is directed to a case where factors for depriving heat are different at both ends in the longitudinal direction of the heater, such as when the length from the transport center C of the object to be heated to the end of the heater substrate 3 is different on the left and right. Is shown.

FIG. 1A shows a state in which a heater 7 is mounted on a stay 2 which also has a function of a heater holder, as viewed from the nip surface side, and FIG. FIG. 3 is a schematic diagram showing a case where a positional relationship between the pressure roller and the pressure roller 5 is viewed from a direction in which a heated body enters.

The heater 7 is formed by coating an electric resistance material such as Ag / Pd (silver palladium) on the surface of the heater substrate 3 made of alumina or the like to a thickness of about 10 μm and a width of 1 to 3 mm by screen printing or the like. Glass or fluororesin is coated thereon as a protective film, and the heater substrate 3 having a thermal conductivity of 50 to 150 [W / mk] is used.

The temperature in the sheet passing area is controlled by a temperature control device (not shown) so that the inside temperature becomes constant.

The stay 2 is formed by molding with a heat resistant resin such as PPS, liquid crystal polymer, phenol resin and the like. The film 1 has a film thickness of 100 μm or less, preferably 40 μm or less, preferably 20 μm or more in PTFE having heat resistance, release property, strength, durability and the like in order to reduce the heat capacity and improve the quick start property. -Single layer of PFA, FEP, etc.
Or polyimide, polyamide imide, PEEK, P
PTFE, PFA, FEP on the outer surface of ES, PPS, etc.
And the like.

FIG. 7 shows a cross section at the center of the fixing device, and shows a state in which the recording paper is heated by the heating device (fixing device) together with the toner on the recording paper in the press-contact nip portion. As shown in FIG. 1, in the present embodiment, the length from the center C (center conveyance reference) of the recording paper as the object to be heated to the end of the heater substrate 3 is represented by a1 on the left side and a2 on the right side. a1 <a2.

In the present embodiment, when the above-described conductive ring is provided on the right side of the roller shaft 6 of the pressure roller 5, the amount of heat flowing out of the resistance heating element 4 is considered to be larger on the right side. Therefore, when the length from the center C of the object to be heated to the end of the resistance heating element 4 is the same on the left and right, heat is not uniformly applied to the object to be heated inside the nip.

FIG. 9 shows an example of the temperature distribution inside the nip in this case. The temperature of the circled portion is lower than the target temperature inside the heated object width. In order to solve this, as shown in FIG. 1, when the length from the heated object center C to the end of the resistance heating element 4 is A1 on the left side and A2 on the right side, the length relationship is A1 <A2. And

The length (A1 + A2) of the resistance heating element 4 is longer than the width of the recording material serving as the heating object having the maximum width to be passed. Outside.

At both ends of the resistance heating element 4, heat can easily escape to the end of the heater substrate 3. On the other hand, the portion having no heat radiation by paper passing cancels out the heat and makes the temperature uniform.

(Second Embodiment) FIG. 2 shows a second embodiment in which the length from the center C of the object to be heated to the end of the stay 2 is different on the left and right. .

FIG. 2 is a schematic diagram similar to that of the first embodiment. In the first embodiment, the case where the length from the center C of the object to be heated to the end of the heater substrate 3 is different on the left and right is shown. In the present embodiment shown in FIG. 2, the length from the heated object center C to the end of the heater substrate 3 is equal to the left and right, but the length to the end of the stay 2 is b1 on the left side. The length on the right is b2
Then, in the case of b1 <b2, the amount of heat flowing out of the resistance heating element 4 is considered to be larger on the right side as the stay 2 is longer.

In the present embodiment, for the same reason as in the first embodiment, the left side length from the heated object center C to the end of the resistance heating element 4 is B1, and the right side length is B2. , B1
<B2.

The length (B1 + B2) of the resistance heating element 4 is longer than the maximum width of the object to be passed, and the ends of the resistance heating element 4 are located outside the ends of the object at both ends. At both ends of the resistance heating element 4, heat can easily escape to the end of the heater substrate 3. On the other hand, a portion having no heat radiation by paper passing cancels out the heat to make the temperature uniform.

(Third Embodiment) FIG. 3 shows a third embodiment. This embodiment shows an embodiment in which the length from the center C of the heated object to the end of the pressure roller 5 is different on the left and right.

FIG. 3 is a schematic diagram similar to that of the first embodiment. The end of the pressure roller 5 contacts the heater substrate 3 without the resistance heating element 4, and the pressure roller 5 rotates. The surface is always in contact with the air at a high speed, so it is easy to cool. Therefore, a large amount of heat easily escapes from the end of the resistance heating element 4 to the end of the pressure roller 5 through the heater substrate 3.

Therefore, in the present embodiment shown in FIG. 3, if the left side length from the heated object center C to the end of the pressure roller 5 is c1, and the right side length is c2, the length relationship is c1. <C
It is 2.

In this embodiment, in order to uniformly apply heat to the object to be heated inside the nip, the length from the center C of the object to be heated to the left end of the resistance heating element 4 is C1, and the length from the right end to C2 is C2.
Then, C1 <C2.

The length (C1 + C2) of the resistance heating element 4 is longer than the maximum width of the object to be fed, and the ends of the resistance heating element 4 are located outside the ends of the object at both ends.

In the present embodiment, heat is easily released to the end of the pressure roller at both ends of the resistance heating element 4 through the end of the heater substrate 3, but on the other hand, there is a portion where no heat is released by paper passing. This is offset and the temperature is made uniform.

As shown in FIG. 8, in order to apply a bias to the film 1 via a roller shaft 6 as a core metal of the pressure roller 5, the end of the pressure roller 5 is made of conductive rubber or the like. When the ring 11 is attached, the ring 11 is approximately the same size as the diameter of the pressure roller 5 and the pressure roller 5
Since it is considered that the amount of heat flows from the film 1 even when it is not brought into contact with the heating roller, if this is also considered as a part of the pressure roller 5, the length of the heating resistor is made different between the left and right similarly to this embodiment. Thus, the object to be heated can be uniformly heated.

(Fourth Embodiment) FIG. 4 shows a fourth embodiment. This embodiment shows a case in which the length from the center C of the object to be heated to the end of the film 1 is different on the left and right.

FIG. 4 is a schematic diagram similar to that of the first embodiment, showing a configuration in which the length from the center C of the object to be heated to the end of the film 1 is different between the left and right sides. Used when different things are used.

The end of the film 1 is in contact with the heater substrate 3 having no resistance heating element 4. Furthermore, the film 1 rotates and its surface is constantly in contact with air at a high speed, so that it is easy to cool. Therefore, a large amount of heat easily escapes from the end of the resistance heating element 4 to the end of the film 1 through the heater substrate 3.

In the present embodiment, as shown in FIG. 4, the length from the center C of the object to be heated to the left end of the film 1 is d1,
Assuming that the length to the right end is d2, d1 <d2.

At this time, in order to uniformly apply heat to the object to be heated inside the nip, the length D1 from the center C of the object to be heated to the left end of the resistance heating element 4 and the length D2 to the right end thereof are D1 <
D2.

The length of the resistance heating element (D1 + D2) is longer than the width of the heated object at the maximum sheet passing, and the ends of the resistance heating element are located outside the ends of the heated object at both ends. Although both ends of the resistance heating element can easily release heat to the ends of the heater substrate, on the other hand, the presence of a portion where heat is not dissipated by paper passing cancels out the heat and makes the temperature uniform.

(Fifth Embodiment) FIGS. 5 and 6 show a fifth embodiment of the present invention.

As shown in FIG. 5, the fan 1 in the printer
0 is the heated object center line C shown in each of the above embodiments.
In the following, a description will be given of a case where the camera is attached to either the left or right.

Taking a laser beam printer as an example, the fan 10 is usually mounted on either the left or right with respect to the center line C of the object to be heated in order to prevent the temperature inside the machine and the humidity inside the machine from rising. is there.

FIG. 5 shows a laser beam printer viewed from a cross section. The fan 10 is mounted slightly upstream of the fixing device. FIG. 6 is a conceptual diagram when this configuration is viewed from above. Regardless of whether the fan 10 is the intake air or the exhaust air, the one near the fan 10 of the fixing device is likely to have a lower ambient temperature, so that it is considered that the amount of heat is easily released. For this reason, even if the way of escaping heat is not different between the right and left of the fixing device itself, there is a possibility that the influence of the fan 10 may be exerted on one side of the center of the heated object. In this case as well, the problem can be solved by increasing the length from the heated object center C to the end of the resistance heating element 4 on the side where heat is easily taken away.

In the present embodiment, the widths of the heating elements are all the same in the longitudinal direction. However, the heating elements may have portions having different widths. If the width is set, a uniform amount of temperature can be obtained by increasing the calorific value per unit length near the end.

In each of the above embodiments, the stay 2 is formed with a concave portion for fitting the heater 7, but the stay 2 becomes smaller with the downsizing of the heating device. If heat stress occurs in -2, there is a possibility that cracks will occur in the concave portions. However, in each of the embodiments of the present invention, occurrence of such cracks can be prevented.

[0056]

As described above, according to the present invention, it is possible to compensate for a partial difference in fixability of the object to be heated due to a difference in the amount of heat flowing out by the length of the heater. In addition, since a substance having a high thermal conductivity of about 50 to 150 [W / m · k] can be used for the insulating substrate of the heating element, thermal stress generated inside the heater as the heating element is reduced to prevent cracking. I can do it.

[Brief description of the drawings]

FIG. 1 is a schematic view of a fixing device according to a first embodiment,
(A) is a figure which looked at the heater from the nip side, (b) is a front view.

FIG. 2 is a schematic diagram of a fixing device according to a second embodiment;
(A) is a figure which looked at the heater from the nip side, (b) is a front view.

FIG. 3 is a schematic diagram of a fixing device according to a third embodiment;
(A) is a figure which looked at the heater from the nip side, (b) is a front view.

FIG. 4 is a schematic diagram of a fixing device according to a fourth embodiment,
(A) is a figure which looked at the heater from the nip side, (b) is a front view.

FIG. 5 is a schematic diagram of a fixing device according to a fifth embodiment.

FIG. 6 is a schematic diagram of a fixing device according to a fifth embodiment.

FIG. 7 is a schematic diagram illustrating a cross section of the fixing device.

8A and 8B are schematic diagrams illustrating an example of use of a film bias ring, where FIG. 8A is a view of a heater viewed from a nip side, and FIG.
Is a front view.

FIG. 9 is a diagram illustrating a temperature distribution state of the fixing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Film 2 Stay (film guide) 3 Heater board 4 Resistance heating element 5 Pressure roller (Pressure body) 6 Core metal 7 Heater 8 T stay 9 Flange (Film guide) 10 Fan 11 Conductive rubber ring

Claims (8)

[Claims] 1. A heating element comprising at least an insulating substrate and a resistance heating element, and a film press-contacted to said heating element,
And a rotary pressurizing body which is driven to move while sliding the film on the surface of the heating body, wherein the film and the film at a press-contact nip portion of the heating body and the pressurizing body which are pressed against each other via the film. The heat of the heating element is heated via the film by moving and moving the object to be heated, which is introduced with the center in the direction perpendicular to the conveyance direction as the conveyance reference, integrally with the film, between the pressure body and the pressure body. A heating device for applying to a body, wherein the heating body has different lengths to both left and right ends of the resistance heating body with respect to the conveyance reference. 2. The heating element has a different length to both ends in the left-right direction of the insulating substrate with respect to the conveyance reference,
The heating device according to claim 1, wherein the length of the resistance heating element in the longer length is also longer. 3. The heating element is characterized in that the length of the stay holding the insulating substrate to both ends in the left-right direction with respect to the conveyance reference is different, and the length of the longer resistance heating element is longer. The heating device according to claim 1, wherein 4. The heating apparatus according to claim 1, wherein the pressing body has different lengths to both ends in the left-right direction with respect to the conveyance reference, and the longer resistance heating element has a longer length. . 5. The film according to claim 1, wherein a length of the film to both ends in the left-right direction with respect to the conveyance reference is different, and a length of the longer resistance heating element is longer.
A heating device as described. 6. A fan according to claim 1, wherein a fan for taking in or exhausting air inside the machine in which the heating device is incorporated is mounted on one of the right and left sides with respect to the conveyance reference. A heating device according to any one of the above. 7. The heating apparatus according to claim 1, wherein the insulating substrate of the heating body has a thermal conductivity of 50 to 150 [W / m · k]. 8. A fixing device comprising the heating device according to claim 1, wherein a visible image of toner transferred to a recording material by an image forming means is fixed by the fixing device. Image forming device.