JP2010026448A - Heating unit, fixing unit and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating unit which suppresses utilization amount of a heat resistor, as well as, has high responsiveness for temperature control. <P>SOLUTION: The heating unit comprises: a heating body provided with a substrate with a longitudinal direction, going straight in the transporting direction of recording material and the heat resistor which is formed along the longitudinal direction of the substrate for generating heat through energization; a temperature detection means for detecting the temperature of the heating body by being abutted against the heating body; a fixing film which is slid in contact with the heating body; and a pressing member which forms a nip section between the heat resistor via the fixing film. The heat resistor which is formed in the vicinity of a temperature detection means for the heating body is formed, in a close contact with the temperature detection means in the heating unit. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a heating apparatus, a fixing apparatus, and an image forming apparatus that are used in an image forming apparatus such as an electrophotographic printer and a copying machine, and that heat and fix an unfixed image on a recording material.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic printer or a copying machine, a heating device typified by a film heating method is used as means for fixing a toner image on a recording material from the viewpoint of quick start and energy saving.

  This heating device of the film heating system uses a ceramic heater (hereinafter also referred to as a heater or a heating body) as a heating body, and sandwiches a heat-resistant film between the heater and a pressure roller as a pressure member, thereby pressing the nip. A recording material carrying an unfixed toner image to be image-fixed between the fixing film and the pressure roller in the pressure nip, and sandwiched and conveyed between the fixing film and the pressure roller. The heat of the heater is applied to the recording material through the fixing film at the pressure nip portion, and the unfixed toner image is fixed on the surface of the recording material by pressure by the pressure at the pressure nip portion (Patent Documents 1 to 5). Reference 4).

  For example, a plurality of heaters used in the heating device are arranged on the substrate with one end of the heating resistor connected between the upstream and downstream in the recording material conveyance direction, and are formed in the heater substrate longitudinal direction with a certain resistance value. Yes. A thermistor as temperature detecting means for detecting the temperature of the heating resistor is disposed on the back surface of the heater substrate. The temperature control of the heating resistor controls the energization of the heater by inputting the detection signal of the thermistor arranged on the back surface of the heater substrate to the CPU and controlling the triac.

  There has been a demand for further downsizing and cost reduction in the heating apparatus used in such electrophotographic printers and copiers. For example, in the heater substrate, the number of heater substrates obtained by cutting a single ceramic sheet into smaller pieces is increased, and now the width of one substrate is also reduced to several millimeters. In addition, the heating resistor is mainly composed of silver and palladium. Particularly, since palladium is an expensive material, a heating resistor pattern in which the amount of the heating resistor used is reduced is used.

FIG. 5 is a plan view showing the arrangement of the heating resistor pattern based on the reduction of the heater substrate width and the reduction of the usage amount of the heating resistor. In order to reduce the usage amount of the heating resistor, the pattern width of the heating resistor is formed narrow. In addition, the upstream and downstream heating resistors have a heater substrate so as to have a desired insulation distance so that current leakage or short circuit does not occur between the upstream and downstream heating resistors even when an overvoltage is supplied to the heating resistor. The pattern is close to the edge.
JP 63-313182 A Japanese Unexamined Patent Publication No. 2-157878 JP-A-4-44075 Japanese Unexamined Patent Publication No. 4-204980

  However, when the heating resistor pattern is used, the heating resistor and the temperature detection element such as a thermistor installed at the center of the heater back surface in the lateral direction of the heater are separated from each other.

  As a result, the responsiveness of temperature control is dull and it becomes difficult to perform desired temperature control. Also, when the heating resistor becomes abnormally hot due to a failure of the heating device, the operation of the high-temperature protection by the software is delayed, so there is a risk that thermal safety protection elements such as thermal fuses and thermo switches installed on the back of the heater will operate. Problems arise.

  Accordingly, an object of the invention according to the present application is to provide a heating device having a high temperature control responsiveness in a heating device having a configuration in which the upstream and downstream heating resistor patterns formed on the heater substrate are separated from each other.

  In order to achieve the above object, an invention according to the present application includes a substrate having a longitudinal direction as a direction orthogonal to a conveyance direction of a recording material, and a heating resistor that is formed along the longitudinal direction of the substrate and generates heat when energized. Between the heating body having a temperature detection means for detecting the temperature of the heating body in contact with the heating body, a fixing film sliding in contact with the heating body, and the heating resistor via the fixing film In the heating device having a pressure member for forming a nip portion, the heating resistor is formed in the vicinity of the temperature detecting means of the heating body, and the heating resistor is formed close to the temperature detecting means. Features.

  Further, the heating resistor is formed so as to reciprocate at least once in the longitudinal direction of the heating body, and the upstream heating resistor and the downstream heating resistor in the recording material conveyance direction in the vicinity of the temperature detection means are close to the temperature detection means. It is characterized by forming.

  Further, the heating resistor is formed by reciprocating at least once in the longitudinal direction of the heating body, and only one of the upstream heating resistor or the downstream heating resistor in the recording material conveyance direction in the vicinity of the temperature detection means is temperature-detected. It is characterized by being formed close to the means.

  As described above, according to the present invention, in the heating element in which the heating resistor is formed at the upstream and downstream positions of the heater substrate, the heating resistor formed in the vicinity of the temperature detection unit is formed close to the temperature detection unit. It becomes possible to provide a highly responsive heating device.

  Next, details of the present invention will be described in accordance with the description of the embodiments.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  The fixing device as a heating device in the present invention is a film heating type heating device using a fixing film as a heating member.

  FIG. 2 is a cross-sectional view of the fixing device along the conveyance direction of the recording material 201, and FIG. 3 is a structural model diagram showing an example of a heating device.

  In FIG. 2, the fixing device includes a ceramic heater 203 (hereinafter referred to as a heater) that heats the toner 202, a fixing film 204 that contains the heater, and a fixing film that is in contact with the fixing film 204 to form a fixing nip N. It is driven by a pressure roller 205 as a fixing rotator, a thermistor 206 that is a temperature detecting element in contact with the back surface of the heater, a CPU that performs desired control based on the temperature detected by the thermistor, and an output signal of the CPU. , And a rotation control means for controlling the conveyance of the recording material, and controls the conveyance of the recording material and the heater.

  FIG. 3 is a schematic configuration diagram of the heating device, (a) is a plan view of the heating device, and (b) is a cross-sectional view taken along line AA ′ in (a). The heater is formed on a heat-resistant substrate 301 such as alumina or aluminum nitride on a heat-resistant resistor pattern 302 formed by, for example, thick film printing and having a thickness of several μm to several tens of μm, and an electric end of the heat generating resistor. Conductive paste 303 that forms an electrical contact and a heating resistor folded contact of several μm to several tens of μm formed by Ag, etc., on the upper layer of the heating paste and some of the conductive paste, a pressure nip portion And a glass protective layer 304 having functions of pressure resistance against N, heat resistance, and low friction. The heater is fixedly supported by a heater holder 305 as a heating body holding member attached to the fixing device. The heater holder is a member formed of heat-resistant resin, and also acts as a guide member that guides the rotation of the fixing film 204. The thermistor 306, which is a temperature detection element, is fixedly supported by the heater holder so as to be in contact with the back surface of the heater at the central portion in the recording paper conveyance direction.

  In the fixing device described above, the recording material is nipped and conveyed at the fixing nip N by the rotation of the pressure roller 205 in the direction of the arrow, and the toner on the recording material is heated by the heater. At this time, the rotation of the pressure roller is controlled by the rotation control means to appropriately control the conveyance of the recording material, and the temperature of the heater is controlled by the thermistor to provide a fixed image.

  FIG. 1 shows a schematic configuration diagram of the heater of the heating device in the present embodiment. A heating resistor 102 is formed on the heater substrate 101 as a pattern that reciprocates once in the longitudinal direction of the heater. The upstream heating resistor and the downstream heating resistor of the heating resistor have the desired insulation so that no current leakage or short circuit occurs between the upstream and downstream heating resistors even when an overvoltage is supplied to the heating resistor. A pattern is taken at a distance from the heater substrate end. The thermistor 103 (temperature detection means) is disposed on the back surface of the heater in an area where the minimum width paper that can be passed can pass, in contact with the central portion in the short side direction of the heater.

  Here, the upstream and downstream heating resistors formed in the vicinity of the thermistor are formed so as to be close to the thermistor in the heater short direction in order to improve the response of the thermistor. At this time, since the potential difference generated between the upstream and downstream heating resistors is lower in the vicinity of the thermistor than in the vicinity of the feeding electrode, the insulation distance between the upstream and downstream required when overvoltage is supplied is near the thermistor. There is little to do. However, the distance between the upstream and downstream heating resistors arranged in the vicinity of the thermistor needs to be an insulation distance corresponding to the potential difference that can occur.

  As described above, in the heating element in which the upstream and downstream heating resistors are formed at the end of the heater substrate, only the upstream and downstream heating resistors in the vicinity of the thermistor are formed so as to be close to the thermistor. Since the conducted heat is conducted to the thermistor more quickly, it is possible to provide a highly responsive heating device.

  FIG. 4 is a diagram for explaining the outline of the heating apparatus according to the second embodiment. Since the basic configuration of the fixing device is the same as that of the first embodiment, a description of the overall configuration is omitted here.

  The feature of this embodiment is that in the heating resistor 402 formed on the heater substrate 401, the heating resistor is formed along the longitudinal direction of the heater substrate. The upstream heating resistor and the downstream heating resistor of the heating resistor have the desired insulation so that no current leakage or short circuit occurs between the upstream and downstream heating resistors even when an overvoltage is supplied to the heating resistor. A pattern is taken at a distance from the heater substrate end. The thermistor 403 is arranged on the back surface of the heater in a region where the minimum width paper that can be passed can pass, in contact with the central portion in the heater short direction.

  Here, the heating resistor formed in the vicinity of the thermistor A is formed so as to be close to the thermistor in the short direction of the heater in order to improve the response of the thermistor. However, since the heating element resistance portion close to the thermistor has the thermistor in contact with the back surface of the heater, the heat of the thermistor contact portion is dissipated to the thermistor, and temperature unevenness may occur locally. . Therefore, in order to eliminate this temperature unevenness, in this embodiment, the heating resistor has a configuration in which only the upstream heating resistor is close to the thermistor as shown in FIG. 4 (a), or as shown in FIG. 4 (b). Only such a downstream heating resistor is set close to the thermistor. At this time, since the potential difference generated between the upstream and downstream heating resistors is lower in the vicinity of the thermistor than in the power supply electrode section, the insulation distance between the upstream and downstream required when overvoltage is supplied is near the thermistor. Is less. However, the distance between the upstream and downstream heating resistors arranged in the vicinity of the thermistor needs to be an insulation distance corresponding to the potential difference that can occur.

  As described above, by forming only the heating resistor upstream or downstream of the thermistor vicinity A so as to be close to the thermistor, it was generated in the heating resistor without causing uneven heat generation in the thermistor part. Since heat is transferred to the thermistor more quickly, it is possible to provide a highly responsive heating device.

It is a figure which shows the detailed structure of the heating apparatus in Example 1 which concerns on this invention. 1 is a diagram illustrating an overall configuration of a fixing device according to a first embodiment of the present invention. 1 is a diagram showing a schematic configuration of a heating device in Example 1 according to the present invention. It is a figure which shows the detailed structure of the heating apparatus in Example 2 which concerns on this invention. It is a figure which shows the structure of the heating apparatus in a prior art example.

Explanation of symbols

101 substrate
102 Heating resistor
103 thermistor
104 Feeding conductive part
105 Folded conductive part
A Near the temperature detector
N Nip part
201 Recording material
202 Toner
203 Heater
204 Fixing film
205 Pressure roller
206 Thermistor
207 Heater holder
301 substrate
302 Heating resistor
303 Feeding conductive part
304 insulating glass
305 Heater holder
306 Thermistor
307 Folded conductive part
A Near the temperature detector
401 substrate
402 Heating resistor
403 thermistor
404 Feeding conductive part
405 Folded conductive part
A Near the temperature detector
501 board
502 Feeding conductive part
503 Heating resistor
504 Thermistor
505 Folded conductive part

Claims (5)

A substrate whose longitudinal direction is a direction perpendicular to the conveyance direction of the recording material;
A heating element having a heating resistor formed along the longitudinal direction of the substrate and generating heat when energized;
Temperature detecting means for detecting the temperature of the heating body in contact with the heating body;
A fixing film that slides in contact with the heating body;
In a heating device having a pressure member that forms a nip portion with the heating resistor via the fixing film,
The heating resistor formed in the vicinity of the temperature detection means of the heating body,
A heating apparatus characterized by being formed close to a temperature detecting means. The heating resistor is formed by reciprocating at least once in the longitudinal direction of the heating body,
2. The heating apparatus according to claim 1, wherein an upstream side heating resistor and a downstream side heating resistor in the recording material conveyance direction in the vicinity of the temperature detection unit are formed close to the temperature detection unit. The heating resistor is formed by reciprocating at least once in the longitudinal direction of the heating body,
2. The heating apparatus according to claim 1, wherein only one of the upstream side heating resistor or the downstream side heating resistor in the recording material conveyance direction in the vicinity of the temperature detection unit is formed close to the temperature detection unit. A heating device according to any one of claims 1 to 3,
A fixing device for fixing toner on a recording material conveyed between the fixing film and a pressure member on the recording material. Image forming means for forming a toner image on the recording material;
An image forming apparatus comprising: a conveying unit configured to convey a recording material on which a toner image is formed by the image forming unit to the fixing device according to claim 4.

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