JP2003271006A - Heater temperature detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heater temperature detector in which variations in pressing force is reduced, and assembly and disassembly are improved. <P>SOLUTION: A fixing device has: a heater having as a basic structure a substrate and a heat generating resistor on the substrate, which generates heat by energization; a film guide member which holds the heater; a temperature detection means which measures the temperature of the heater; a holding member which holds the temperature detecting means; an elastic member which presses and fixes the temperature detecting means to the heater; and a fixing means which fixes the elastic member to the film guide member. In the fixing device, the heater temperature detector is structured by integrating the holding member, the elastic member, and the fixing means. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heater detecting device of a fixing device used for an image forming apparatus such as an electrophotographic device and an electrostatic recording device and fixing an image on a recording material.

[0002]

2. Description of the Related Art A fixing device according to the present invention melts toner by heat and fixes it on a recording sheet 1. Therefore, when fixing at a temperature equal to or higher than a predetermined temperature, the toner adheres to the fixing device, and when fixing at a temperature equal to or lower than the predetermined temperature, unfixed toner causes an image quality deterioration such as offset.

When fixing at a temperature below a predetermined temperature,
Toner is not fixed on the recording sheet, causing a fixing failure.
Therefore, at the time of fixing, it is necessary to control the temperature so as to be within a predetermined temperature range. Therefore, a thermistor is usually used as a temperature sensor to control the temperature.

A conventional configuration will be described with reference to FIG.

Thermistor chip (not shown), thermistor chip holding member (not shown), protective sheet member (not shown)
The thermistor unit 17 consisting of is fixed to the heating means by an elastic member 20 such as a spring, and is brought into close contact with the heating means to measure the temperature of the heating means. Among the fixing devices, particularly in the film fixing system, the film guide member 16 that holds the heating means and guides the film 10, the thermistor unit 17, and the elastic member 2 are provided.
0, and the thermistor unit 17 is pressed against the heater 15 by the elastic member 20. By controlling the pressing force at the time of pressure contact, the temperature measurement can be performed more accurately.

The fixed end of the elastic member 20 is in contact with a base member 21 for holding an elastic body, and the base member 21 is fixed to the film guide member 16 by a fastening means such as a retaining ring 22 made of a thin metal plate. It The point of action of the elastic member 20 is in pressure contact with the thermistor unit 17, and the thermistor unit 17 is pressed and fixed to the heater 15 by the elastic force. That is, the thermistor unit 1 for the heater 15
The pressing force of 7 is defined by the elastic force of the elastic member 20.

[0007]

In the above-mentioned conventional example, the pressing force of the thermistor unit 17 against the heater 15 is defined by the positions of the film guide member 16 and the base member 21, and the position of the base member 21 is determined by the snap ring. It changes depending on the fastening position of 22. Therefore, the pressing force changes depending on the dimensional accuracy of each part, that is, when the retaining ring 22 cannot be assembled in the proper position, the position of the base member 21 varies, and as a result, the pressing force decreases. There is concern that the accuracy of temperature measurement will deteriorate.

Further, since the number of parts is large and the structure is complicated, the assembling workability is poor and the large number of parts leads to an increase in cost. Further, although the retaining ring 22 is used to fix the base member 21, when the retaining ring 22 is assembled, the base member 21 and the retaining ring 22 are pressed, and the retaining ring 22 is assembled while partially plastically deforming. Therefore, assembly workability is poor. Further, since the retaining ring 22 once deformed and assembled is plastically deformed, it is difficult to disassemble. In the conventional example, the shaft 16a on the film guide member 16 into which the retaining ring 22 is fitted is fitted.
It couldn't be disassembled unless it was destroyed.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a heater temperature detecting device capable of reducing variations in pressing force and improving assemblability and disassembly. It is in.

[0010]

In order to achieve the above object, the present invention provides a substrate and a heater having a heating resistor which is provided on the substrate and generates heat when energized, and a film which holds the heater. A guide member, a temperature detecting means for measuring the temperature of the heater, a holding member for holding the temperature detecting means, an elastic member for pressing and fixing the temperature detecting means to the heater, and the elastic member for a film guide member. In the fixing device having the fixing means for fixing to, the holding temperature, the elastic member and the fixing means are integrated to constitute a heater temperature detecting device.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment> First, a laser beam printer will be described with reference to FIG.

In FIG. 2, 2 is a paper feed tray for stacking recording sheets 1 as recording media, and 3 is a paper feed tray 2.
A sheet feeding roller that feeds the recording sheets 1 stacked on the sheet one by one, and 4 is a recording sheet 1 fed from the sheet feeding roller 3.
Transport roller for transporting the sheet, 5 a roller shaft facing the transport roller 4, 6 a paper guide for guiding the transfer material to the contact portion between the photoconductor and the transfer roller, 7 a photosensitive drum 7a, toner (not shown), developing A process cartridge having a roller 7b, 8 is a transfer roller for transferring a toner image from the photosensitive drum 7a to the recording sheet 1, 9 is a laser light source (not shown), and a scanner mirror 9 rotates at high speed.
a, a laser scanner having a folding mirror 9b,
10 is a fixing film described later, 15 is a heater which is a heating body described later, 11 is a pressure roller described later, 12 is a pair of discharge rollers for discharging the recording sheet after fixing, 13 is a stack for stacking the recording sheet after discharging. A surface 14 is an electrical board having a power source and electric components for driving each mechanical component.

The process of forming an image on a recording sheet by the image forming apparatus is as follows.

That is, the laser scanner 9 irradiates the photosensitive drum 7a with information light based on image information to form a latent image on the photosensitive drum 7a, and the latent image is developed to form a toner image. Then, in synchronization with the formation of the toner image, the recording sheets 1 stacked on the paper feed tray 2 are transferred to the paper feed tray 2
Sheets are fed one by one by a paper feed roller 3 provided at the tip of the. This is conveyed to the image forming portion by the conveying roller pairs 4 and 5, and the toner image formed on the photosensitive drum 7a is transferred to the recording sheet 1 by applying a voltage to the transfer roller 8 as a transfer unit. Then, the recording sheet 1 after the image transfer is conveyed to a fixing unit including a fixing film 10, a heater 15, a fixing roller 10 and a pressure roller 11, and the transferred toner image is fixed on the recording sheet 1. Then, the recording sheet 1 is discharged onto the stacking surface 13 by the discharge roller pair 12.

A fixing device and process for fixing the toner image on the recording sheet 1 will be described with reference to FIG.

Reference numeral 10 is a heat-resistant fixing film in the form of an endless belt, and heaters 15 and 11 serving as heating bodies fixedly supported by a holding member 16 are rubbers having good releasability such as silicone rubber serving as a pressing member. A pressure roller having an elastic layer. The fixing film 10 conveys the recording sheet 1 as a material to be heated, which has a predetermined peripheral speed as the pressure roller 11 is rotated, that is, an unfixed toner image conveyed from the image forming unit side (not shown) is carried on the upper surface. It is driven to rotate at the same peripheral speed as the speed without wrinkling, meandering or speed delay.

The recording sheet 1 after the image transfer is the entrance guide 1
The unfixed toner image transferred by entering the space between the fixing film 10 and the pressure roller 11 at the pressure contact portion N (fixing nip portion) between the heater 15 and the pressure roller 11 whose temperature is controlled by the guide roller 8. The fixing nip portion N between the heater 15 and the pressure roller 11 is sandwiched in a state where the surface is in close contact with the lower surface of the film 10 in the surface moving state in the same direction at the same speed as the conveyance speed of the recording sheet 1 and the film 10 is overlapped. It passes under pressure. The toner image bearing surface of the recording sheet 1 receives the heat of the heater 15 through the film 10 in the process of passing through the fixing nip portion N in a pressed contact state with the film surface, the toner image is melted at a high temperature, and the recording sheet 1 surface To soften and adhere to.

The separation between the recording sheet 1 and the film 10 is performed when the recording sheet 1 passes through the fixing nip portion N and comes out. While the recording sheet 1 separated from the film 10 is guided by the guide 19 and reaches the discharge roller pair 12, the temperature of the toner higher than the glass transition point is naturally lowered (natural cooling) to a temperature below the glass transition point. Then, the recording sheet 1 on which the image has been fixed is output.

A film guide member 16 is provided with a heater fitting groove along the length of the member at a substantially central portion of the outer lower surface, and the heater 15 is fitted and supported in the groove. The inner tubular fixing film 10 is loosely fitted to the film guide member 16 with the heater 15, and the film 10 is sandwiched between the heater 15 and the pressure roller 11 with respect to the heater 15. It is pressed.
When the pressure roller 11 is rotationally driven, the cylindrical fixing film 10 is brought into close contact with the lower surface of the heater 15 to rotate around the film guide member 16.

The thermistor unit 17, which is a heater temperature detecting means for controlling the temperature of the heater 15 used in the fixing device and the fixing process, will be described.

In FIG. 4, the thermistor chip 17a attached to the thermistor unit 17 is a heater 15
Is in contact with and is detecting the temperature. The resistance value of the thermistor chip 17a changes in proportion to the detected temperature, and the temperature of the heater 15 can be detected by reading the resistance value with a controller (not shown).
The thermistor holding member 26 holding the thermistor chip 17a needs to be robust against the heat generated by the heater 15, and is therefore made of a thermoplastic resin having heat resistance.

In FIG. 1, a sheet member 24 having heat resistance and insulation is wound around the substantially central outer periphery of the thermistor holding member 26, and the thermistor unit 17 is narrowed between the sheet member 24 and the thermistor holding member 26. By being held, the thermistor unit 17 is held. A metal plate 27 having conductivity and elasticity is integrally molded with the thermistor holding member 26.
6 is firmly connected to the metal plate 27. Each of the thermistor electric wires 17b connected to the thermistor chip 17a is electrically connected to the metal plate 27, and is connected to a controller (not shown) on the image forming apparatus main body by a signal electric wire 25 connected to the metal plate 27.

The resistance value of the thermistor chip 17a is sent to the controller through the above path to control the temperature of the heater 15. By configuring the thermistor unit 17 as described above, the metal plate 27 functions as a conductive component and also as an elastic member for pressing the thermistor chip 17a against the heater 15. As a result, it is not necessary to separately provide an elastic member for urging the thermistor unit 17 to the heater 15, and the structure can be simplified. Both metal plates 27
A fastening member 28 made of a thermoplastic resin having heat resistance is integrally molded at one end of the.

The fastening member 28 is formed with a positioning hole 28b and a leaf spring portion 28a utilizing the elasticity of the resin, and is further provided with a hook portion 28c at the end portion of the leaf spring. The film guide member 16 is integrally formed with a fastening shaft 16a, and the fastening shaft 16a is provided with a hooking portion.

As described above, the thermistor chip 17a,
The thermistor unit 17 including the thermistor electric wire 17b, the holding member 26, the metal plate 27, and the fastening member 28,
It is detachably attached to the film guide member 16 by the following procedure.

That is, the positioning hole 28b provided in the fastening member 28 on the thermistor unit 17 is fitted to the fastening shaft 16a formed integrally with the film guide member 16. By applying a force to the fastening member 28 from above, the leaf spring portion 28 a is deformed and engaged with the fastening shaft 26. Further, when the deformed plate spring portion 28a returns to its original state, the hook portion 28c is fitted into the fastening shaft 16a, so that the thermistor unit 17 is fixed to the film guide member 16.

As described above, the thermistor unit 17
The holding member 26, the metal plate 27, and the fastening member 28 are integrally formed, and the position of the thermistor unit 17 when attached to the film guide member 16 is
Only defined by the fastening member 28. Since the fastening member 28 is fixed to the film guide member 16 by the positioning hole 28b and the fastening shaft 16a, the positional accuracy is defined by the component accuracy of the positioning hole 28b and the fastening shaft 16a.

Since there is no intervening part as in the conventional example, it is possible to fix with accurate position accuracy. The fastening member 27 is fixed to the film guide member 16 by the leaf spring portion 28a and the hook portion 28c, which can be disassembled by deforming the leaf spring portion 28a and removing the hook portion 28c from the fastening shaft 16a. Become.

<Second Embodiment> Next, a second embodiment of the present invention will be described.

In the present embodiment, the plate spring portion 16 having elasticity for the film guide member 16 is fastened to the thermistor unit 17 which is the heater temperature detecting means described in the first embodiment.
This is done by providing b.

In FIG. 6, the leaf spring portion 16b having a slit in the shaft has a hook portion at its tip. The fixing member 28 of the thermistor unit 17 has a positioning hole 28b, and the positioning hole 28b is engaged with the leaf spring portion 16b on the film guide member 16. By pressing the fixing member 28, the leaf spring portion 16b of the film guide member 16
Deforms and fits into the positioning hole 28b.

Furthermore, when the fixing member 28 is pushed in, the deformation of the leaf spring portion 16b is restored, so that the leaf spring portion 16b is restored.
The hooking portion provided in b abuts the positioning hole, and the fastening is completed. When the thermistor unit 17 is removed, the leaf spring portion 16b is bent by an external force and the positioning hole 28b is pulled out to allow disassembly, which allows easier disassembly work than in the first embodiment.

<Third Embodiment> Next, a third embodiment of the present invention will be described.

In the present embodiment, the thermistor unit 17, which is the heater temperature detecting means described in the first embodiment, is fastened by using the elasticity of the metal plate 27 of the thermistor unit 17.

As shown in FIG. 7, the fixing member 28 is provided with a spherical positioning shaft 28d. Further, the film guide member 16 includes a positioning hole 16b and a hooking portion 16
c is provided. To assemble the thermistor unit 17 to the film guide member 16, the metal plate 27 of the thermistor unit 17 is bent and the positioning shaft 28b is engaged with the positioning hole 16c provided in the film guide member 16.

The fixing member 28 is hooked on the hooking portion 16c of the film guide member 16, and further the pressing force is applied from the heater 15, so that the fixing member 28 is pressed against the hooking portion 16c of the film guide member 16 to be pressed and fixed. . Since the thermistor unit 17 is fixed as described above, there is no need to provide a leaf spring portion on the resin, and there is no concern about damage to the leaf spring portion during deformation.

[0038]

As is apparent from the above description, according to the present invention, the thermistor unit is formed by integrally molding the holding member, the metal plate having the function of conducting and biasing, and the fastening member with the film guide member. By doing so, a simple thermistor unit can be provided. By simplifying,
It is possible to suppress variations in pressing force, and it is possible to measure temperature with higher accuracy. Further, by utilizing the elasticity of the members to fasten the thermistor unit and the film guide member together, it is possible to provide a thermistor unit which is easy to assemble and is easy to disassemble.

[Brief description of drawings]

FIG. 1 is an external perspective view showing a thermistor unit according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing an image forming apparatus according to Embodiment 1 of the present invention.

FIG. 3 is a side view showing the fixing device according to the first embodiment of the present invention.

FIG. 4 is a side view showing the thermistor unit according to the first embodiment of the present invention.

FIG. 5 is a side view showing the fastening means according to the first embodiment of the present invention.

FIG. 6 is a perspective view showing a fastening means according to a second embodiment of the present invention.

FIG. 7 is a side view showing a fastening means according to a third embodiment of the present invention.

FIG. 8 is a side view showing a conventional example.

[Explanation of symbols]

15 heater 16 Film guide member 17 Thermistor unit 26 Holding member 27 metal plate 28 Fastening members

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Miura Mietsu             Kyano, 3-30-2 Shimomaruko, Ota-ku, Tokyo             Within the corporation F term (reference) 2H033 AA18 AA31 BA25 BA26 BA31                       BA32 BB29 BE03 CA07 CA30                 3K058 AA42 BA18 CA12 CA22 CA61                       GA06

Claims (3)

[Claims] 1. A heater having a substrate and a heat-generating resistor which is provided on the substrate and generates heat when energized, a film guide member for holding the heater, and a temperature detecting means for measuring the temperature of the heater. A fixing device having a holding member for holding the temperature detecting means, an elastic member for pressing and fixing the temperature detecting means to the heater, and a fixing means for fixing the elastic member to a film guide member, A heater temperature detecting device characterized in that a holding member, an elastic member and a fixing means are integrated. 2. The elastic member is made of a metal material and electrically connected to the temperature detecting means.
The heater temperature detection device described. 3. The heater temperature detecting device according to claim 1, wherein the fixing means is removably fastened to the film guide member.