JPH10142977A - Heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a heating performance by appropriately setting the position of a heater corresponding to a press contact nip part N. SOLUTION: In this heating device 17 and this image forming device provided with the heating device 17, a heating body 1 makes an heating resistance pattern 6 heating by forming the heating resistance pattern 6 in the direction orthogonal to the direction transporting the material to be heated on the press contact nip side surface of a base plate, forming a conductive pattern 7 in approximately parallel with the heating resistance pattern 6, making the heating resistance pattern 6 and the conducting pattern 7 severally connected on one side end part in the same direction and feeding electric power between several end part on the opposite side. The heating body 1 is disposed so that the section located on the upstream side of the width center Nc of the press contact nip part N of the body 1 in the transporting direction of the material to be heated becomes larger than the section located on the downstream side of the width center Nc in the transporting direction of the material to be heated on the press contact nip part N of the heater 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device and an image forming apparatus provided with the heating device as image heating means.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile, an unfixed toner image corresponding to target image information formed and carried on a recording material is heated and fixed by an image forming process means. As a fixing unit to be used, a heat roller type fixing device is generally used, but recently, a film heating type fixing device has been put into practical use as an image heating fixing device. This fixing device
JP-A-63-31382, JP-A-1-26367
9, JP-A-2-157788, JP-A-4-15778
No. 44075-44083 and the like, and a pressure member is pressed against a heater (heating element) via a heat-resistant film, and the heat-resistant film is run to form a gap between the heat-resistant film and the pressure member. The recording material is introduced into the press-contact nip (fixing nip) to be brought into close contact with the heat-resistant film, and the recording material passes through the press-contact nip together with the heat-resistant film, so that the heat of the heater is recorded via the heat-resistant film. The unfixed toner image is applied to the recording material and heat-fixed to the recording material surface.

As a heater, a so-called ceramic heater that has a heat-resistant and insulating ceramic substrate, a heat-generating resistor pattern and a conductive pattern formed on the substrate, and supplies power to the resistor pattern to generate heat is used. ing.

FIG. 8 is a schematic structural view of a film heating and fixing device 17 as such a fixing means, and FIG. 9 is a schematic plan view on the front side of a heater provided in the device.

[0005] Reference numeral 1 denotes a heater that generates heat when supplied with electric power, 2 denotes a heat-resistant film (fixing film), and 3 denotes a pressing roller as a pressing member pressed against the heater 1 via the film 2.

Reference numeral 4 denotes a guide member for the film 2 which is long in a direction perpendicular to the recording material conveyance direction, and also supports the heater 1.

As shown in FIG. 9, a heater 1 has a ceramic substrate 5 such as alumina having an insulating property, high heat resistance, and low heat capacity and having a longitudinal direction perpendicular to the recording material conveying direction, and a surface side of the substrate 5 (a pressure roller). This is a ceramic heater having a linear or strip-shaped heat-generating resistance pattern 6 of silver palladium or the like, on which a pattern is formed through printing and baking along the length on the pressure contact side).

Reference numeral 7 denotes a folded conductive pattern made of silver or the like formed in parallel with the heating resistor pattern by conducting to the heating resistor pattern 6 and turned back to the substrate surface side. And the back side are connected. Reference numerals 8a and 8b denote electrode portions for feeding power to the heating resistor pattern, and reference numeral 8c denotes a feeding electrode portion of a temperature detecting element (temperature measuring device, for example, a thermistor) 9 formed on the back surface of the substrate. Reference numeral 10 also denotes a heating protection means (for example, a thermal fuse) provided on the back surface of the substrate.

In the figure, Nc is the center of the press-contact nip, and the center Nc of the press-contact nip and the heat-generating resistor pattern 6 are arranged so that the heat-generating resistor pattern 6 of the heater 1 fits within the press-nip N.
Are arranged so that the centers of the heaters 1 substantially coincide with each other.
The folded conductive pattern 7 is disposed on the downstream side in the recording material conveyance direction with respect to the nip center N. As a result, the substrate 5 has a smaller area on the upstream side in the transport direction with respect to the nip center N than on the downstream side in the transport direction (L1 <L2). The heat value Q of the heater 1 on the upstream side of the nip center Nc.
1. Q1 <Q2 when the heat generation amount on the downstream side is Q2.

[0010]

However, in the above conventional example, the heater 1 is arranged such that the area on the upstream side is smaller than the area on the downstream side with respect to the nip center Nc. Material P and heat-resistant film 2
Was less heated on the upstream side.

Accordingly, it is an object of the present invention to provide a heating apparatus and an image forming apparatus of this type in which the position of a heating element with respect to a press-contact nip portion is appropriately set, thereby solving the above problems and improving heating performance. .

[0012]

SUMMARY OF THE INVENTION The present invention relates to a heating device and an image forming apparatus having the following features.

(1) A heated body having a heating element and a pressing member which presses directly to the heating element via an intervening member or forms a press-contact nip portion, and is conveyed in the press-contact nip portion. A heating device that applies heat from the heating element to the heating element, the heating element forms a heating resistance pattern in a direction perpendicular to the direction of conveying the material to be heated on the side of the press-contact nip of the substrate, and is substantially parallel to the heating resistance pattern. A conductive pattern is formed on the heating resistor pattern and the conductive pattern are conducted at one end in the same direction, and power is supplied between the opposite ends to cause the heating resistor pattern to generate heat. The portion of the heating element located on the upstream side in the heated material transport direction from the width center of the press-contact nip portion in the heated material transport direction is located at a position closer to the heated material transport direction than the center of the heated contact material nip portion of the heating element in the heated material transport direction. Part located downstream in the direction Heating apparatus characterized by being arranged heat generating member as also increases Ri.

(2) The heating device according to (1), wherein the conductive pattern is located upstream of the heating resistor pattern in the direction of transport of the material to be heated.

(3) The heating device according to (1) or (2), wherein the heating resistance pattern is located at a center of a width of the press-contact nip portion in a conveying direction of the material to be heated.

(4) The heating device according to (1), (2) or (3), wherein the conductive pattern is a resistor that generates heat when energized. (5) The heating device according to (4), wherein the conductive pattern is formed by changing a position in a heating material transport direction for each width corresponding to a width of the heating material.

(6) The material to be heated is a recording material carrying an unfixed image, and heat from a heating body is applied to the recording material carrying the unfixed image in the press nip.
The heating device according to any one of (1) to (5), wherein the unfixed image is heated and fixed on the recording material.

(7) An image forming apparatus comprising: an image forming means for carrying an unfixed image on a recording material; and a fixing means for fixing the unfixed image to the recording material. An image forming apparatus, comprising: the heating apparatus according to claim 1.

(Operation) That is, the heat generating resistor pattern and the conductive pattern are conducted at one end in the same direction, and power is supplied between the opposite ends. While being configured, the portion located on the upstream side in the heated material transport direction from the width center of the pressure contact nip portion of the heating element in the heated material transport direction is the center of the width of the pressure contact nip portion of the heating element in the heated material transport direction. The heating element is disposed so as to be larger than a portion located on the downstream side in the transport direction of the material to be heated,
The material to be heated is cooled, the temperature difference from the heating element is large, and the heat transfer efficiency is high. The amount of heat given to the material to be heated on the upstream side is increased to improve the heating performance.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following first to third embodiments are examples of a fixing device characterized by the above-mentioned configuration.

<Embodiment 1> FIG.
FIG. 1B is a schematic cross-sectional view of a fixing device in which the fixing device 17 of FIG.
FIGS. 3A and 3B are front-side plan views of a heating element provided in the apparatus, and FIG. 3 is a schematic configuration diagram of an image forming apparatus including the fixing device as an image heating and fixing unit.

1. Example of Image Forming Apparatus This image forming apparatus A irradiates a light beam L based on image information from an optical system S onto a surface of a photosensitive drum (image carrier) 16b uniformly charged by a charging unit 16a to form a latent image. Is formed, and toner is applied from the developing sleeve 16c of the developing means to the surface of the photosensitive drum 16b to convert the latent image into a visible image (toner image). And, in synchronization with the formation of the toner image,
The recording material P is transferred from the cassette 21 to the pickup roller 12,
The recording material P is conveyed by conveying means including a conveying roller pair 13, a registration roller pair 14, and the like.
The toner image carried on the photosensitive drum 16 is conveyed to a position where the photosensitive drum 16b of the image forming unit and the transfer roller 15 are formed as a cartridge and is opposed to the transfer roller 15 by the voltage applied to the transfer roller 15. It is sequentially transferred to the top. Next, the recording material P is fixed to a fixing device 1 as a fixing unit.
To 7. After the fixing process by the fixing device 17, the recording material P is conveyed by a pair of discharge rollers 18 and 19, and is discharged to a discharge unit 20 through a reverse conveyance path.

2. 1. Overall Configuration of Fixing Device In the fixing device 17 shown in FIG. 1, the pressing roller 3 is rotationally driven in a clockwise direction as indicated by an arrow by transmitting a rotational driving force through a power transmission system (not shown) by a driving unit M. Due to the rotational driving of the pressure roller 3, a rotational force acts on the fixing film 2 by a frictional force between the roller and the outer surface of the fixing film in the fixing nip portion N, and the film 2 is heated by a heating element (heater) 1
The outer periphery of the stay 4 can be driven to rotate in the clockwise direction as indicated by the arrow while being in close contact with the stay.

The recording material P carrying the unfixed image by the image forming means is introduced between the fixing film 2 and the pressure roller 3 as described above, so that the recording material P The fixing film 2 moves and passes through the fixing nip N together with the fixing film 2 while being in close contact with the heater 1. In the moving passage process, the heat of the heater 1 is applied to the recording material P via the fixing film 2 so that the toner image Ta is transferred to the recording material P.
The surface is heated and fixed. The recording material P that has passed through the fixing nip N is separated from the surface of the fixing film 2 and is conveyed.

3. Heater 1 As shown in FIG. 2, the heater 1 has a plate-shaped substrate 5 and a heat-generating resistor pattern 6 formed on the substrate as basic components.

The substrate 5 is a ceramic substrate made of alumina or the like having an insulating property, high heat resistance and low heat capacity and having a longitudinal direction perpendicular to the recording material conveyance direction. On the (side) side, it is formed in a linear or narrow band shape of patterned silver palladium through printing and baking along the length.

Reference numeral 7 denotes a folded conductive pattern of silver or the like formed in parallel with the heating resistor pattern 6, and one end thereof is electrically connected to the heating resistor layer or one end in the same direction. 8a is an electrode portion provided at the front end of the substrate 5 and electrically connected to the heating resistor pattern 6 through the through hole 11.
Reference numeral 8b denotes an electrode portion provided on the back surface of the substrate and electrically connected to the folded conductive pattern 7. By supplying power between the electrode portions 8a and 8b, the heating resistor pattern 6 generates heat. In this example, the heat generating resistor pattern 6 and the conductive pattern 7 are arranged from the side end of the heat generating pattern 6 to the substrate side end so as to keep the board width as narrow as possible while securing a sufficient creepage distance in the lateral direction of the board. And the distance Lb from the end of the heat generating pattern 6 to the end of the conductive pattern 7 and the distance Lc from the end of the conductive pattern 7 to the end of the substrate are substantially the same. It is located off center.

Reference numeral 9 denotes a temperature detecting element (temperature measuring device, for example, a thermistor) provided on the back side of the substrate 5 for detecting the temperature of the heater 1; 9a, a conductive pattern for energizing the temperature detecting element 9; A through hole 9b provided on the front side
The electrode portion is electrically connected to the conductive pattern 9a through the electrode.

Numeral 10 denotes a heating protection means (for example, a temperature fuse) for cutting off the power supply to the heating pattern 6 when the temperature rises excessively.
And provided on the back surface side of the substrate.

4. Position of the heater 1 with respect to the center of the press-contact nip N In the fixing device 17 according to the present embodiment, the heater 1
Is arranged such that the width on the upstream side in the recording material conveyance direction is larger than the width on the downstream side with respect to the press-contact nip center Nc, and the heating resistor pattern 6 is positioned at the press-contact nip center Nc. The folded conductive pattern 7 is located upstream of the resistance pattern 6 in the recording material conveyance direction.

That is, the embodiment of FIG. 1 and FIG.
Compared with the conventional example of FIG. 9, the width L of the heater 1 is the same, but in the present embodiment, the conductive pattern 7 is arranged on the upstream side of the heating resistor pattern 6 and is upstream of the nip center Nc in the transport direction. The width (area) L1 on the side is larger than the width (area) L2 on the downstream side in the transport direction (L1> L2). That is, the calorific value Q1 on the upstream side of the nip center of the heater 1 is larger than the calorific value Q2 on the downstream side of the nip center.

As a result, even before the recording material P is introduced into the pressure nip N, the recording material P is largely heated by the portion 1 a of the heater 1 exposed to the outside of the pressure nip N. Also, before the heat-resistant film 2 is introduced into the nip N, the heat-resistant film 2 is greatly heated. Therefore, the heat from the heater 1 is efficiently transmitted to the recording material P, and the fixing property can be improved. Even in an environment where the fixing is severe or when an unfixed image is recorded using thick paper or the like, good fixing can be achieved. An image is obtained.

In particular, in this embodiment, since the conductive pattern 7 is provided on the upstream side of the heating resistor pattern 6, the power supply electrodes 8a and 8b for supplying power to the heating resistor pattern 6 are both provided at one end of the substrate 5, An electrode 8c for a temperature sensing element is provided at the opposite end, and a primary circuit (a circuit relating to a heating element) is provided.
The heating resistor pattern 6 formed off the center of the substrate is positioned at the center of the nip portion N while being compact while sufficiently keeping the creepage distance with the secondary circuit (circuit relating to the temperature sensing element). The fixing property (heating performance) is improved by appropriately setting the arrangement of the heater 1 so that the conductive pattern 7 is located on the upstream side of the pattern 6 in the direction of transport of the material to be heated.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS.

In the first embodiment, the folded conductive pattern 7 is arranged on the upstream side in the recording material conveyance direction with respect to the nip center Nc. However, in the present embodiment, the folded conductive pattern 7 generates heat when energized. An example is shown in which a folded heat generating resistance pattern is formed.

In this embodiment, the heater 1 has a first heat generating resistor pattern 6a formed so that the center thereof coincides with the center Nc of the pressure contact nip portion, and the first heat generating pattern 6a is provided on the upstream side in the recording material conveyance direction. The second heating resistor pattern (turned heating resistor pattern) 6b is formed in parallel with the resistor pattern 6a.

In this embodiment, the recording material and the heat-resistant film 2 are greatly heated before passing through the press-contact nip portion, and the fixability of an unfixed image can be improved. . In addition, since the heating resistor pattern 6 is folded back, the number of electrode patterns can be reduced as compared with the case where a plurality of heating resistor patterns 6 are simply provided side by side, and the tolerance of the width / thickness error of the pattern 6 can be reduced. And easy to manufacture.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIGS.

In the second embodiment described above, the folded heat-generating resistor pattern 6b disposed on the upstream side in the recording material conveyance direction is formed in a straight line in a direction perpendicular to the recording material conveyance direction. In the example, the folded heat-generating resistance pattern 6b is arranged by changing its position stepwise in the transport direction according to the size of the recording material.

As shown in FIG. 7, a first heating resistor pattern 6d corresponding to the minimum recording material width ls in the longitudinal direction, and a second heating resistor pattern 6c corresponding to the intermediate recording material width lm in addition to the first heating resistor pattern 6d. The third heating resistance pattern 6b is formed corresponding to the maximum recording material width 11. Heating resistance pattern 6b,
6c and 6d have different distances from the nip center Nc, 6b is formed within the press-contact nip width _LN , 6c is formed at the boundary of the press-contact nip width _LN , and 6d is formed outside the nip width _LN . When the distance from the nip center Nc changes, the heat transfer efficiency to the recording material also changes, and when the distance from the nip center Nc increases, the efficiency also increases.

For this reason, the heating resistance patterns 6b, 6c, 6
d is desirably arranged so as to increase the distance from the nip center Nc. However, if it is located outside the nip portion, the temperature rises without depriving the recording material P of heat in a portion not in contact with the recording material P. It is possible to do. Therefore, the recording material P
The first heat-generating resistor pattern 6d corresponding to the minimum recording material width ls is provided outside the nip portion N in order to enhance the heat transfer efficiency, and the heat-generating resistor pattern 6b corresponding to the maximum width 11 is designed to prevent overheating. At the intermediate recording material width l
The heating resistance pattern 6c corresponding to m is provided in the middle.

In this embodiment, the temperature measuring element 9 for temperature control is used.
Is provided within the minimum recording material width ls, and the temperature of the heater 1 is appropriately controlled based on the temperature information from the temperature detecting element 9 and the recording material size. For example, in accordance with the size of the recording material detected by a sensor provided in the recording material conveyance path or a sensor for detecting the size information of the paper feed cassette, if the size is large, the temperature control temperature T is increased, and the minimum recording material width ls Make up for the loss of transmission efficiency outside.

As a result, the efficiency of transmitting the heat from the heating resistance pattern 6d to the material to be heated is increased, and the power supplied to the resistance pattern 6 can be reduced even when the recording material having the minimum width is continuously fixed. Thus, damage to the heater supporting member 4 in the non-sheet passing portion can be reduced.

In particular, the heating resistance pattern 6d is
Is disposed outside (upstream side), and after one recording material passes, until the next recording material is introduced (between sheets), there is no heat taken by the pressure member 3 and the temperature decreases. Can be reduced.

<Other Embodiments> In each of Embodiments 1 to 3 described above, a laser beam printer is exemplified as an image forming apparatus. However, the present invention is not limited to this, and may be used in an image forming apparatus such as an electrophotographic copying machine or a facsimile machine. Of course, it is also possible.

[0046] In each of Embodiments 1 to 3 described above, a so-called tensionless type fixing device has been described. However, the driving method of the fixing film is not limited to this. For example, an endless belt-like film is suspended between a heater and a stretching member. Stretched, a pressure member is pressed against the heater via the film to form a pressure contact nip portion, and the film is rotated and conveyed by rotating the pressing member or the tension member, and Instead of using an endless belt-shaped film, use a rolled, long end film that is wound around a roll, passing it from the pay-out shaft to the take-up shaft via the heater, and sandwiching the film into the heater. A configuration in which a pressure roller is provided so as to press the pressure roller to form a nip portion, and the film is traveled and conveyed to a winding shaft side may be used.

[0047]

As described above, according to the present invention,
By appropriately setting the position of the heating element with respect to the pressure nip, the heating performance can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view of a fixing device according to a first embodiment of the present invention;

FIG. 2 is a configuration explanatory view of a heater according to Embodiment 1 of the present invention.

FIG. 3 is a diagram illustrating the configuration of an image forming apparatus according to the present invention.

FIG. 4 is a diagram illustrating a configuration of a fixing device according to a second embodiment of the present invention.

FIG. 5 is a configuration explanatory view of a heater according to a second embodiment of the present invention.

FIG. 6 is a configuration explanatory view of a fixing device according to a third embodiment of the present invention.

FIG. 7 is a configuration explanatory view of a heater according to a third embodiment of the present invention.

FIG. 8 is a diagram illustrating the configuration of a conventional fixing device.

FIG. 9 is a diagram illustrating the configuration of a conventional heater.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heater 2 Heat-resistant film 3 Pressing member 6 Heating resistance pattern 7 Folded conductive pattern N Center of nip portion

Claims (7)

[Claims] 1. A heating element having a heating element and a pressing member that presses directly to the heating element via an intervening member or directly forms a pressure-contact nip portion, wherein the heat-receiving body that is conveyed in the pressure-contact nip portion is provided. In a heating device for applying heat from the heating element, the heating element forms a heating resistance pattern in a direction orthogonal to the direction of conveying the material to be heated on the side of the press-contact nip of the substrate, and is substantially parallel to the heating resistance pattern. Forming a conductive pattern, conducting the heat-generating resistor pattern and the conductive pattern at one end in the same direction, and supplying power between the opposite ends to cause the heat-generating resistor pattern to generate heat; The portion located on the upstream side in the heated material transport direction of the press-contact nip portion of the body from the center of the heated material transport direction in the heated material transport direction from the center of the heated material transport direction of the press-contact nip portion of the heating element. From the part located downstream Heating apparatus characterized by being arranged heat generating member to be larger. 2. The heating apparatus according to claim 1, wherein the conductive pattern is located upstream of the heating resistor pattern in a direction in which the material to be heated is transported. 3. The heating apparatus according to claim 1, wherein the heating resistance pattern is located at a center of a width of the press-contact nip portion in a conveying direction of the material to be heated. 4. The heating device according to claim 1, wherein the conductive pattern is a resistor that generates heat when energized. 5. The heating apparatus according to claim 4, wherein the conductive pattern is formed by changing a position in a heating material transport direction for each width corresponding to a width of the heating material. 6. The non-fixed material is a recording material carrying an unfixed image, and heat is applied from a heating body to the recording material carrying the unfixed image in the press-contact nip. The heating device according to claim 1, wherein the image is heated and fixed on the recording material. 7. An image forming apparatus comprising: an image forming unit for carrying an unfixed image on a recording material; and a fixing unit for fixing the unfixed image to the recording material, wherein the fixing unit is as defined in claim 6. An image forming apparatus, which is the heating apparatus according to any one of the preceding claims.