JPH09258585A - Heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating device equipped with constitution capable of stably imparting uniform amount of thermal energy on a material to be heated, even in the case of necessitating to partially change the heating distribution of a heating member of a heating device of a film heating system. SOLUTION: In this device, provided with a heat resistant film 5, a pressure roller 6 (pressing means) opposite to and abutting on the film 5, a sheet material S (heat receiving material in a sheet shape) held-transported thereby, the heating means 1 for imparting heat energy through the heat resistant film 5 is composed so as to make a sectional plane shape of a heating resistor 3 (heat generating member) on the part where a temp. detecting element 4 (temp. detecting means) is disposed, as a sectional plane thin thickness part 3a whose thickness is reduced in the vertical direction to the surface opposing the heat resistant film 5 of the heating resistor 3.

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 applying heat energy to a sheet-shaped material to be heated through a heat-resistant film, and particularly to a sheet-shaped material to be coated in an image forming apparatus utilizing an electrophotographic system. It can be used as a heat fixing device for heat fixing a toner image formed on a heating material.

[0002]

2. Description of the Related Art Conventionally, in image forming apparatuses such as copying machines, printers, and fax machines, various types of image forming units have been adopted.
A method such as magnetic recording is generally known. Some of these image forming methods require a post-treatment of applying thermal energy in order to fix an image formed on a sheet-shaped recording material (hereinafter referred to as a sheet material).

This is because, for example, in each of the above-mentioned image forming methods, a toner using a heat-soluble resin or the like is used,
When an image is formed on the surface of a sheet material by a direct method or an indirect (transfer) method, an unfixed toner image corresponding to the target image information carried on the sheet material is heat-fixed as a permanently fixed image, etc. Is typical.

In addition, thermal energy may be applied to the sheet material in a device for heating the sheet material on which an image is formed to modify the surface property, a device for performing a hypothetical dressing treatment, or the like. Conventionally, a heat roller method has been generally used as a method for heating a sheet material as a material to be heated of this type. However, this method takes time to heat the heat roller to a temperature suitable for heating the material to be heated,
Since it is not possible to form an image rapidly and the high temperature must be maintained at all times, the energy consumption is large and it is also disadvantageous in terms of energy saving. Further, even during standby, heat is released into the image forming apparatus, which causes a problem of temperature rise.

Therefore, there is a heating system (film heating system) in which a pattern of a resistance heating element as a heating member is provided on a substrate such as ceramics to form a heating means, and the sheet is heated through a thin film to heat the sheet. JP 63-3
Proposed by 13182.

FIG. 4 is a diagram schematically showing the structure of a film heating type heat fixing device. In FIG. 4, reference numeral 101 denotes a heater as a heating means, which includes a substrate 102 and a substrate 10.
2 has a resistance heating element 103 and a temperature detecting element 104 which are patterned on the surface thereof. Reference numeral 105 denotes a heat-resistant film, and the sheet material S ′ is nipped and conveyed by the pressure roller 106 at the nip portion N ′. Then, while the unfixed toner image T ′ carried on the surface of the sheet material S ′ is being conveyed, heat energy is applied through the heat resistant film 105 to heat-fix the unfixed toner image T ′ as a permanently fixed image. To do.

In this method, since the temperature of the heating means 101 rises in a short time, even if the sheet material S'is passed immediately after the operation of the apparatus is started, it is necessary for the sheet material S'to reach the fixing portion. Heat-resistant film 1 by heating means 101 up to temperature
05 can be heated, and heat fixing is performed at an appropriate temperature. Moreover, since the heating means 101 is not heated during standby, there is no temperature rise in the machine and no energy is consumed.

[0008]

However, the heating device adopting such a film heating system is the heating means 1
When a low-heat-capacity heating means having a configuration in which the resistance heating element 103 is provided on the ceramic substrate 102 as 01 is used, power consumption and wait time can be shortened.
Since the heating means has a small heat capacity, when a temperature detecting element such as a thermistor for controlling the temperature of the heating means, a thermoswitch for safety measures, or a temperature detecting element 104 such as a thermofuse is placed in contact with the heating means as a temperature detecting means, The heat of the portion of the heating means that is in contact with the element is taken by the element, and the temperature of that portion locally drops.

Therefore, the heating of the portion of the sheet material S'corresponding to the portion of the heating means becomes insufficient, and if this heating device is a heating and fixing device for the toner image T'formed on the sheet material, the image is fixed. There is a problem that the sex deteriorates only in that part.

To solve this problem, FIG. 5 is a view of the heating means 101 as seen from the side in contact with the heat resistant film 105.
Conventionally, as shown in FIG. 5, the resistance heating element 103a at a position corresponding to the portion where the temperature detecting element 104 is in contact is formed.
The pattern area was reduced and the amount of heat generated in this portion was made larger than in other portions.

However, the sheet material S'is the arrow A10 in FIG.
In the case of being conveyed in the direction of 1, the heat transfer area of the portion of the resistance heating element 103a is different, so it is very difficult to set the same amount of heat energy that the sheet material receives from the heating means in other portions. Moreover, since the heat transfer area is small, the temperature adjustment margin is also small. Therefore, if the heating device is an image heating and fixing device, it is likely to be deteriorated or excessive in image fixing property only in that part if the heating device is an image heating and fixing device. It was a problem.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and its object is to partially change the heat generation distribution of the heat generating member of the film heating type heating device. Also in the above, it is to provide a heating device having a configuration in which a uniform amount of thermal energy is stably applied to a material to be heated.

[0013]

In order to achieve the above object, in the present invention, a heating means provided with a heat generating member on a substrate and a temperature detecting means for detecting the temperature of the heat generating member is a heat-resistant film and this. In a heating device for applying thermal energy through a heat resistant film to a sheet-shaped material to be heated that is sandwiched and conveyed by a pressurizing means that faces and abuts against the heat resistant film, a portion of the portion where the temperature detecting means is disposed. The heating member is characterized in that the thickness of the heating member in the direction perpendicular to the surface of the heating member facing the heat resistant film is reduced.

In the thus constructed heating means, the amount of heat radiated by the temperature detecting means is compensated for in the portion where the cross-sectional shape is reduced, and the heat transfer area for transferring heat to the heat resistant film of the heat generating member does not change. The partial change in the amount of heat transfer in the conveyance width direction is suppressed, and stable heat energy is applied.

Further, in the image forming apparatus, an image forming section for forming an image on a sheet-shaped heated material, and a heating fixing apparatus for heating and fixing the image formed on the sheet-shaped heated material by the heating device described above. It is provided as.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION A heating device to which the present invention is applied will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a heating device similar to the heating device of FIG. 4 described in the prior art, and is a sheet-shaped heated material carrying an unfixed toner image formed by an image forming apparatus. The sheet is used as a heat fixing device for heat fixing the sheet material.

In FIG. 1, 1 is a heater as a heating means, which is a substrate 2 and a substrate 2 made of a ceramic material.
A resistance heating element 3 as a heating member and a temperature detecting element 4 as a temperature detecting means are formed on the surface of the device. Reference numeral 5 denotes a heat-resistant film, which nips and conveys the sheet material S at the nip portion N by a pressure roller 6 as a pressure means. Then, while the unfixed toner image T carried on the surface of the sheet material S is conveyed, thermal energy is applied through the heat resistant film 5, and the unfixed toner image T is heated and fixed as a permanently fixed image. It is a thing.

The characteristic part of the present invention appears in FIG. 2 shown below. FIG. 2A is a sectional view S1 of FIG.
It shows. As shown in this figure, a thin section 3a having a thin cross section in the direction perpendicular to the surface facing the heat-resistant film 5 is formed in a portion of the resistance heating element 3 corresponding to the position where the temperature detecting element is arranged. Is forming.

FIG. 2 (b) is a view of the heating means 1 of FIG. 2 (a) seen from the side in contact with the heat resistant film 5,
As shown in FIG. 2B, the pattern area of the resistance heating element 3a at the position corresponding to the portion in contact with the temperature detecting element 4 is the same as that of the other portions.

When a current is passed through the resistance heating element 3 having such a structure, the thin section 3a in cross section has a large electric resistance, so that the cross section thin section 3a of the resistance heating element 3 generates more heat than other heating sections. growing.

That is, in order to compensate the heat removal and temperature drop of the heating means 1 to which the temperature detecting element 4 is brought into contact with the temperature detecting element 4, the amount of heat generated by the heating means 1 at the portion where the element is brought into contact is changed to another value. The thickness of the resistance heating element 3 of the heating means 1 is reduced in order to make it larger than that of the heating means. However, the heat transfer area for transferring heat to the heat resistant film 5 of the resistance heating element 3 does not change over the entire area of the surface (nip portion N) where the heating means 1 and the sheet material S which is the material to be heated face each other. A partial change in the amount of heat transfer by the heating means 1 in the conveyance width direction of the sheet material S is suppressed, and stable heat energy is applied.

However, although it is observed in FIG. 2 that the thin-walled portion 3a in cross section does not directly contact the surface of the sheet material S, an insulating heat transfer member is embedded in the recessed portion to prevent heat resistance of the resistance heating element 3. By appropriately smoothing the surface on the side that contacts the film 5, the contact form with the heat resistant film 5 does not change, and stable heat transfer can be obtained.

(Embodiment 2) In the second embodiment, as shown in FIG. 4, the thickness of the portion of the heating means 11 corresponding to the arrangement position of the temperature detecting element 4 in contact with the substrate 2 is set to the glass. The resistance heating element 3 formed on the surface of the resistance heating element 3 is thinned by applying an insulating material such as the above, or the shape of the substrate is changed in advance, and the cross-section thin portion 3a ′ is formed to increase the electric resistance. The amount of heat generated is increased.

In the case of this embodiment, the resistance heating element 3
Since the surface facing the heat resistant film 5 is a smooth flat surface having no unevenness over the entire area, the problem of the contact form of the thin section 3a in the first embodiment does not occur.

Other structures and operations are the same as those of the first embodiment described above, and therefore, the same components are designated by the same reference numerals and their description is omitted.

[0027]

As described above, according to the present invention,
The amount of heat dissipated by the temperature detection means is compensated for in the area where the cross-sectional shape is reduced, and the heat transfer area for transferring heat to the heat-resistant film of the heat-generating member does not change. The change is suppressed and stable heat energy is applied.

Further, in the image forming apparatus, by providing the heating means as the heating and fixing device, uniform heat energy is applied to the sheet to be conveyed, and good image quality can be formed.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram of a heating device according to a first embodiment to which the present invention is applied.

FIG. 2 is a sectional view of the heating means of the first embodiment.

FIG. 3 is a cross-sectional view of the heating means of the second embodiment.

FIG. 4 is a cross-sectional configuration diagram of a conventional heating device.

FIG. 5 is a cross-sectional view of a conventional heating means.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating means 2 Substrate 3 Resistance heating element (heating member) 3a Thin section 4 Temperature detecting element (temperature detecting means) 5 Heat resistant film 6 Pressure roller (pressurizing means) S Sheet material (sheet-shaped heated material)

Claims (2)

[Claims] 1. A sheet shape in which a substrate is provided with a heat generating member and a temperature detecting means for detecting the temperature of the heat generating member, and the sheet is sandwiched and conveyed by a heat resistant film and a pressure means that abuts against the heat resistant film. In the heating device for applying heat energy to the material to be heated through the heat resistant film, the cross-sectional shape of the heat generating member in the portion where the temperature detecting means is disposed is compared with the surface of the heat generating member facing the heat resistant film. The heating device is characterized in that the thickness in the vertical direction is reduced. 2. An image forming unit for forming an image on a sheet-shaped material to be heated, and the heating device according to claim 1 as a heat fixing device for heating and fixing the image formed on the sheet-shaped material to be heated. An image forming apparatus characterized by being provided.