JPH11231715A - Temperature detection unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature detector which correctly detects a temperature without insulation failure of a temperature detection element and also resists scratches on a releasing layer on the surface of a fixing roller. SOLUTION: In the temperature detection unit 20 made to abut on the fixing roller 13, a metal strip 23 is disposed between a protective member 22 and the temperature detection element 21, and also an insulating heat-resistant sheet 25 is disposed between the metal strip 23 and the temperature detection element 21. This prevents contact of the metal strip 23 with lead wires 26, and hence erroneous temperature-detection caused by short-circuiting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature detecting unit mounted on a fixing device in an image forming apparatus such as a copying machine, a printer, a facsimile, etc., for detecting a temperature of a fixing roller.

[0002]

2. Description of the Related Art An unfixed image (image formed by a toner made of a heat-fusible resin or the like) mounted on an image forming apparatus such as a copying machine, a printer, a facsimile, and transferred onto a recording material such as transfer paper. As a fixing device for heating the recording material to fix it on a recording material, a fixing roller (heating roller) having a built-in heater is pressed against a pressure roller, and the recording material is passed between the two rollers to generate heat and pressure. Thus, a fixing device of a heat roller type, which fixes an unfixed toner image on a recording material, is widely used.

In a general heat roller type fixing device, in order to control the temperature of the fixing roller, a temperature detector is provided in contact with the surface of the fixing roller, and based on the output of the temperature detector. Thus, the power supply to the heater incorporated in the fixing roller is controlled. Normally, the temperature detector of the fixing roller is pressed against the surface of the fixing roller with a predetermined pressure. In order to protect the sensor (detection element) of the temperature detector, cover the sensor with a heat-resistant film. is there.

However, since the sensor is hard, the sensor part of the temperature detector rises, and the release layer such as Teflon coated on the surface of the fixing roller in contact with the temperature sensor may be worn.

FIG. 6 is a sectional view showing an example of a temperature detector in which measures are taken to prevent the swelling of the sensor portion.
The temperature detector 60 shown in this figure has a detection element 61 placed on an elastic material 64 such as sponge, and an insulating heat-resistant tape 6.
2 covers the sensing element. This detector 60
In order to prevent swelling of the sensor portion, a metal piece 63 is placed on the sensing element 61 to make the upper surface flat, and a sponge under the sensing element 61 is cut into a sponge 65.
Is provided so that the sensor portion does not rise. Reference numerals 66 and 66 are lead wires of the detection element 61.

[0006]

However, in the conventional temperature detector having the structure as shown in FIG. 6, the metal piece 63 placed on the sensing element 61 and the lead wires 66, 66 come into contact with each other, and the insulation is insulated. There was a problem of causing defects. Note that the two lead wires are separately arranged on the left and right so as not to contact each other, so that the contact between the lead wires does not usually pose a problem.

In order to prevent insulation failure due to the above metal pieces,
As shown in FIG. 7, countermeasures were taken such as inserting an insulating tube into the lead wire 66. However, the insulating tube moved, resulting in insufficient insulation and erroneous temperature detection.

The present invention solves the above-mentioned problems in the conventional temperature detector, performs accurate temperature detection without causing insulation failure of the temperature detection element, and detects the temperature at which the release layer on the surface of the fixing roller is not easily damaged. It is an object to provide a vessel.

[0009]

According to the present invention, there is provided a protective member for protecting a temperature detecting element, wherein the temperature detecting element is indirectly contacted with a fixing roller via the protective member. In the temperature detection unit that detects the temperature of the fixing roller, a metal piece is disposed between the protective member and the temperature detection element, and an insulating heat-resistant sheet is disposed between the metal piece and the temperature detection element. Will be resolved.

In order to solve the above-mentioned problems, the present invention proposes that the protective member is a Teflon sheet and the insulating heat-resistant sheet is a polyimide sheet. Furthermore, the present invention provides
It is proposed that the thickness of the Teflon sheet is greater than 40 μm.

Further, in order to solve the above-mentioned problems, the present invention proposes disposing a polyimide insulating heat-resistant sheet between the Teflon sheet protection member and the metal piece.

Further, according to the present invention, in order to solve the above-mentioned problems, the Teflon sheet as the protective member has a thickness of 4 mm.
It is proposed to be less than 0 μm.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view illustrating a schematic configuration of a copying machine as an example of an image forming apparatus to which a fixing device including a temperature detection unit according to an embodiment of the present invention is mounted. The copying machine shown in FIG. 1 includes a main body 1, a paper feed table 2, and an ADF 3.

A scanner 4 is arranged at an upper position in the main body 1, and various devices necessary for an electrophotographic process are arranged below the scanner 4 around a photosensitive drum 5. In the figure, among the devices arranged around the photosensitive drum 5, the developing unit 6, the transfer / conveying unit 7, and the cleaning unit 8 are denoted by reference numerals. A fixing device 10 having a temperature detection unit according to the present invention is provided on the side of the transfer / conveyance unit 7. This copier also has a paper feed tray 9 in the main body.
a, and a three-stage paper feed tray 9b in the paper feed table 2,
9c and 9d, and a total of four paper feed trays. A manual tray 9e is provided on a side surface of the main body 1.

The operation of the copying machine will be briefly described. The surface of the photosensitive drum 5, which is rotationally driven by a driving unit (not shown), is uniformly charged by a charger.
The original image on the contact glass is read by the scanner 4 and is exposed on the photosensitive drum 5 to form an electrostatic latent image. The latent image on the photosensitive drum 5 is visualized by the developing device 6 to form a toner image.

On the other hand, four-stage paper feed trays 9a, 9b, 9
Paper is called from any of c, 9d and the manual feed tray 9e, and is conveyed to the registration roller 11. Then, the toner image on the photosensitive drum 5 is transferred to the transfer position at a transfer timing.

The toner image on the photosensitive drum 5 is transferred onto the sheet sent to the transfer position by the transfer / conveyance unit 7, and the sheet is separated from the photosensitive drum 5 and fixed to the fixing device 1.
Sent to 0. After the unfixed toner image on the sheet is fixed by the fixing device 10, the sheet is
Is discharged to After the transfer of the toner image, the photosensitive drum 5 is cleaned by the cleaning device 8 to prepare for the next copy.

FIG. 2 is a perspective view showing the main structure of the fixing device 10. In FIG. 2, a pressure roller 14 is pressed against a fixing roller 13 at a predetermined pressure. Pressure roller 14
Is pressed by a spring 16 via a pressure lever 15. In the fixing roller 13, a halogen lamp 17 as a fixing heater is provided. Further, a temperature detecting unit 20 attached to a biasing member 18 such as a leaf spring is provided so as to contact the outer peripheral surface of the fixing roller 13. The temperature of the fixing roller 13 is detected by the temperature detecting unit 20, and the heat generated by the heater 17 is controlled based on the detected output, and the temperature of the fixing roller 13 is controlled to a predetermined temperature.

Now, the temperature detecting unit 20 of the present embodiment
Will be described with reference to FIG. In FIG. 3, the temperature detecting unit 20 has a temperature detecting element 21 placed on an elastic member 24 such as a sponge, and the insulating heat-resistant sheet 2
Reference numeral 5 covers the sensing element. Then, the metal piece 23 is placed on the insulating heat-resistant sheet 25, and further covered with the insulating heat-resistant sheet 22. Reference numeral 26 denotes a lead wire of the sensing element 21. The temperature detecting unit 20 thus configured is attached to the urging member 18 and is in contact with the fixing roller 13.

In the detecting unit 20, the temperature detecting element 2 is formed by a metal piece 23 disposed between the outer insulating heat-resistant sheet 22 and the inner insulating heat-resistant sheet 25.
1 is alleviated, and the Teflon coat on the surface of the fixing roller 13 is not damaged. In addition, metal piece 2
Since the insulating heat-resistant sheet 25 is disposed between the sensor element 3 and the sensing element 21 (and the lead wire 26 thereof), the metal piece 23 and the lead wire 26 are insulated from each other, and no erroneous temperature detection due to short circuit occurs. . That is, proper temperature control of the fixing roller is performed by accurate temperature detection.

The metal piece 23 is made of aluminum,
Metals such as phosphorous rust copper and copper can be used. Also,
As the insulating heat-resistant sheets 22 and 25, a polyimide sheet or the like can be used.

According to the invention of claim 2, a Teflon sheet is used as the outer insulating heat-resistant sheet 22, and a polyimide sheet is used as the inner insulating heat-resistant sheet 25. In this case, since the Teflon sheet has good releasability, use of the Teflon sheet on the outside in contact with the fixing roller 13 makes it difficult for toner to adhere. Therefore, there is no problem that the toner adhering to the surface of the temperature detection unit 20 cools and solidifies to form a convex shape, thereby damaging the fixing roller surface. Further, the polyimide sheet is excellent in heat resistance, has strength, and has electrical insulation. Therefore, by using a polyimide sheet for the inner sheet, insulation between the metal piece 23 and the lead wire 26 of the sensing element is ensured.

In this embodiment, as the Teflon sheet and the polyimide sheet, tape-shaped ones provided as a Teflon tape and a polyimide tape are used.

When a Teflon sheet is used as the outer insulating heat-resistant sheet 22, a sheet having a thickness of more than 40 μm is used according to the third aspect of the present invention. The reason is that the Teflon sheet has lower strength than the polyimide sheet, and there is no particular problem when the polyimide sheet is used as the outer heat-resistant sheet. However, when the Teflon sheet is used, the Teflon coat of the fixing roller 13 and the temperature When the thickness of the insulating heat-resistant sheet 22 is small, partial breakage or the like may occur due to abrasion caused by sliding of the Teflon sheets by the Teflon sheet of the detection unit 20.
Then, the metal piece 23 comes out on the surface of the unit, and the fixing roller 13 is easily damaged. Therefore, according to the third aspect of the present invention, when a Teflon sheet is used as the outer insulating heat-resistant sheet 22, its thickness is set to be larger than 40 μm.
When using Teflon tape, the thickness of the substrate is 40 μm
To be larger.

The configuration according to the second aspect of the present invention is as follows.
This is also effective for a temperature detection unit having a configuration as shown in FIG. The temperature detecting unit 30 shown in FIG. 4 has a temperature detecting element 21 mounted on an elastic member 34 such as a sponge. At a portion corresponding to a lower portion of the detection element 21, a cut 35 is provided in the elastic member 34 to prevent the detection element 21 from rising outward. Temperature sensing element 2
1 is doubly covered by an insulating heat-resistant sheet 25 which is a polyimide tape and an insulating heat-resistant sheet 22 which is a Teflon tape. In this temperature detection unit 30,
Although no metal piece is arranged between the double heat-resistant sheets, the cutout 35 provided in the elastic member 34 suppresses the outward swelling and does not damage the fixing roller.

Also in this temperature detecting unit 30, a Teflon tape is used as the outer insulating heat-resistant sheet 22 and a polyimide tape is used as the inner insulating heat-resistant sheet 25. The protection of the detection element 21 can be surely realized.

Next, another embodiment of the present invention will be described. The temperature detecting unit 40 shown in FIG. 5 has a temperature detecting element 21 placed on an elastic member 24 such as a sponge, and covers the detecting element from above with an insulating heat-resistant sheet 25. Then, the metal piece 2 is placed on the insulating heat-resistant sheet 25.
3 and further place the insulating heat-resistant sheets 27 and 2 thereon.
2 covers it twice. Reference numeral 26 denotes a lead wire of the sensing element 21.

In this temperature detecting unit 40, a Teflon tape is used for the outermost insulating heat-resistant sheet 22, and the inner insulating heat-resistant sheet 27 and the detecting element 21 are used.
A polyimide tape is used for the insulating heat-resistant sheet 25 on the top. With this configuration, the heat-resistant sheet 2 on the unit surface
Even if 2 is worn, since the polyimide heat-resistant sheet 27 is on (outside) the metal piece 23, the metal piece 23 does not damage the fixing roller.

By the way, in the temperature detecting unit 40 of the present embodiment, the metal pieces 23 are made of the insulating heat-resistant sheets 27 and 22.
Is covered twice. Therefore, even when the outer insulating heat-resistant sheet 22 is worn out, the metal piece 23 is not exposed to the outside, so that the outermost insulating heat-resistant sheet 22 can be thinned. Further, the thinner the sheet on the temperature detecting element 21 (between the temperature detecting element 21 and the fixing roller) is, the better the thermal response of the detecting element 21 is.
In the present embodiment, the thickness of the outermost Teflon insulating heat-resistant sheet 22 is set to 40 μm or less. In the case of a Teflon tape, the thickness of the substrate is set to 40 μm or less. This allows
It is possible to perform temperature detection with good thermal responsiveness and perform reliable fixing temperature control while preventing the fixing roller from being damaged.

[0030]

As described above, according to the temperature detecting unit of the present invention, a metal piece is disposed between the protective member and the temperature detecting element, and an insulating heat-resistant material is provided between the metal piece and the temperature detecting element. Since the sheet is provided, erroneous temperature detection due to insulation failure of the temperature detecting element does not occur, and the fixing roller surface can be configured not to be easily damaged.

According to the second aspect of the present invention, since the protective member is a Teflon sheet and the insulating heat-resistant sheet is a polyimide sheet, toner adhesion to the unit surface is prevented and the fixing roller surface is not damaged. Further, insulation of the sensing element can be ensured.

According to the third aspect of the present invention, since the thickness of the Teflon sheet is larger than 40 μm, exposure of the metal piece due to wear of the protective member is prevented, and the surface of the fixing roller is not damaged.

According to the fourth aspect of the present invention, since the polyimide insulating heat-resistant sheet is disposed between the Teflon sheet protection member and the metal piece, the metal piece is double-covered and even if the protection member is worn, the metal piece is covered. No pieces are exposed and the fixing roller surface is not damaged.

According to the fifth aspect of the present invention, when the thickness of the Teflon sheet as the protective member is 40 μm or less,
Temperature detection with good thermal responsiveness can be performed while preventing the fixing roller from being damaged.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a copying machine as an example of an image forming apparatus to which a fixing device including a temperature detection unit according to an embodiment of the present invention is mounted.

FIG. 2 is a perspective view showing a main configuration of the fixing device.

FIG. 3 is a cross-sectional view illustrating a configuration of a temperature detection unit according to an embodiment of the present invention.

FIG. 4 is a sectional view showing an example of a temperature detection unit to which the present invention is applied.

FIG. 5 is a cross-sectional view illustrating a configuration of a temperature detection unit according to another embodiment of the present invention.

FIG. 6 is a sectional view showing an example of a conventional temperature detector.

FIG. 7 is a plan view showing measures for preventing insulation failure in the temperature detector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copier main body 10 Fixing device 13 Fixing roller 18 Energizing member 20, 30, 40, 60 Temperature detecting unit 21, 61 Temperature detecting element 22, 62 Protective member 23, 63 Metal piece 24, 34, 64 Elastic member 25, 27 Insulating heat-resistant sheet 26,66 Lead wire 35,65 Cut

Claims (5)

[Claims] 1. A temperature detecting unit having a protective member for protecting a temperature detecting element, wherein the temperature detecting element indirectly abuts on a fixing roller via the protective member to detect a temperature of the fixing roller. A temperature detecting unit, wherein a metal piece is disposed between the protective member and the temperature detecting element, and an insulating heat-resistant sheet is disposed between the metal piece and the temperature detecting element. 2. The protection member is a Teflon sheet,
The temperature detecting unit according to claim 1, wherein the insulating heat-resistant sheet is a polyimide sheet. 3. The temperature detecting unit according to claim 2, wherein the thickness of the Teflon sheet is larger than 40 μm. 4. The temperature detecting unit according to claim 2, wherein a polyimide insulating heat-resistant sheet is disposed between the Teflon sheet protection member and the metal piece. 5. The temperature detection unit according to claim 4, wherein the thickness of the Teflon sheet as the protection member is 40 μm or less.