JP2000162052A - Temperature sensor for fixing roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature sensor having a simple structure and excellent thermal responsiveness. SOLUTION: A temperature sensor for fixing roller is provided with a pair of plate springs 1a, 1b, a retainer 4, a heat sensing element 2 and a cover sheet 3. The plate springs 1a, 1b consist of master parts 5 and island parts 6. A pair of master parts 5, 5 are retained with the retainer 4 of an insulation resin and arranged in parallel each other. The island parts 6 are connected to the master parts 5 with a tie-bar. A pair of the island parts 6, 6 are arranged mutually adjacent and the element 2 is set so as to be laid across both of islands 6, 6. The element 2 is a solid typed square chip thermistor or a thick film typed chip thermistor. Both springs 1a, 1b are covered with a cover sheet except for the island 6 on a surface side on which the element 2 is set. The element 2 is electrically connected to the master parts 5, 5 with the tie-bar but actually isolated from the parts in heat. Therefore, heat dissipation is prevented and heat time constant is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD OF THE INVENTION

The present invention relates to a fixing roller temperature sensor for measuring the surface temperature of a fixing roller used in a fixing device such as a copying machine, a printer, and a facsimile, by contacting the surface of the fixing roller.

[0002]

2. Description of the Related Art A bead-type thermistor has been mainly used as a thermal element of a temperature sensor for a fixing roller used for detecting a temperature of a fixing roller of a copying machine or the like. However, when a bead-type thermistor is used as a heat-sensitive element of a sensor that measures the temperature of the roller surface by contacting the surface of a fixing roller of a copying machine or the like, the problem described in Japanese Patent Laid-Open No.
No. 170 (Prior art 1) points out the following problems.

That is, when a bead thermistor element is used as a heat-sensitive element of the temperature sensor, the element has a spherical shape or an ellipse of about 1 mm, and when the temperature sensor is pressed against the surface of the heat fixing roller. In addition, the heat-sensitive part of the heat-sensitive element comes into point contact with the heat-fixing roller, which may cause damage to the object to be detected. There is a disadvantage that it is difficult to accurately detect the temperature due to being displaced from the roller surface or being mounted away from the detection position.

In order to solve such a problem, the prior art 1 discloses a concept of using a thin thermistor having a flat surface in contact with an object to be detected. Further, in the preceding example 1, for example, FIG.
As a conventional example, a structure in which a thermosensitive element 24 is mounted between the distal ends of narrow metal plates 23 of a pair of metal plates 20 as shown in FIG.
With such a structure, the stability of temperature detection is still insufficient for a temperature sensor used under severe conditions where mechanical vibration occurs, and there is room for improvement from the viewpoint of thermal response. Was raised.

As an attempt to solve this problem, in Prior Example 1, as shown in FIG. 7, a narrow metal plate portion 31 extending continuously from one terminal portion and surrounding the narrow metal plate portion 31 are arranged. And a narrow metal plate portion 31 and a U-shaped metal portion 32 connected to the other terminal portion.
A temperature sensor is proposed in which a heat sensitive element 33 is mounted between the letter-shaped metal portions 32 and a thin film sheet 34 is provided on the surface of the metal plate portion. According to this structure, mechanical vibration of a detection target or the like is reduced. It has the advantage of improving contact failure and disconnection failure, and emphasizes the effect of minimizing the heat dissipated from the thermal element through the lead, thereby increasing thermal resistance and improving thermal responsiveness. Have been.

[0006]

By the way, the temperature sensor according to the invention of the preceding example 1 is different from the conventional temperature sensor as a temperature sensor used under severe conditions where mechanical vibrations occur. Proposed for the purpose of providing a temperature sensor that is resistant to mechanical vibrations from the object to be detected and its surroundings, has durability, is stable in temperature detection, and has excellent thermal responsiveness. It was done.

However, it cannot be considered that the fixing roller used in a fixing device such as a copying machine or a printer is driven under severe conditions such as to cause mechanical vibration which is a problem in the first prior art. It seems that the durability against severe mechanical vibration as emphasized in the prior art example 1 is not necessarily required as long as the temperature is used in contact with the fixing roller to detect its temperature.

[0008] It is not always clear why the structure of the prior art example 1 can improve the durability against severe mechanical vibrations, but it is probably the U-shaped metal plate portion. It seems that this is the effect of surrounding the thin wire metal plate portion with.

Further, according to the structure of the first prior art, the effect of improving the thermal response by increasing the thermal resistance by minimizing the heat dissipated through the lead portion from the thermal element. As mentioned, according to the structure shown in FIG.
The heat-sensitive element 33 is provided between the distal end of the narrow metal plate 31 and the tongue piece 35 of the U-shaped metal plate 32. And a heat-sensitive element is placed on the heat insulating material, and the narrow metal plate 31 is provided.
In addition to the case where the thermal element 33 is thermally isolated from the U-shaped metal plate portion 32, in the structure of FIG. It is thought that there is basically no difference from the structure shown in FIG.

SUMMARY OF THE INVENTION An object of the present invention is to provide a temperature sensor for a fixing roller which is excellent in thermal response by thermally isolating a heat-sensitive element from a leaf spring as a lead wire while having a simple structure.

[0011]

In order to achieve the above object, a fixing roller temperature sensor according to the present invention comprises:
A fixing roller temperature sensor having a leaf spring, a holding body, a heat-sensitive element, and a cover sheet, wherein the leaf spring is a lead wire of the heat-sensitive element, forms a pair, and forms a pair of leaf springs.
The main trunk portion and the main trunk portion having an island portion and forming a pair are connected to the external output line, are arranged in parallel, the island portion is electrically connected to the main trunk portion, and thermally Substantially separated from the main part, it is formed in a part of the main part, and the holding body embeds a part of both main parts and holds the main parts of both leaf springs in parallel adjacent to each other. The pair of islands are electrodes of the thermosensitive element and are arranged adjacent to each other, and the thermosensitive element is a solid type square chip thermistor or a thick film type thermistor. The cover sheet covers both leaf springs except for the surface of the island where the thermal element is mounted.

[0012] The pair of leaf springs is symmetrical,
The island portion is formed to be open at one edge of the main trunk portion, and the two main trunk portions are arranged so as to be oriented so that the island portions are adjacent to each other.

The island portion is a portion formed by cutting out a part of the main trunk portion by etching or press working. The island portion and the main trunk portion are connected by a thin tie bar. And the main part are electrically connected.

The island portion and the trunk portion are connected by a vertical tie bar and a horizontal tie bar, and the vertical tie bar and the horizontal tie bar reduce torsional stress generated between both leaf springs. What is absorbed.

[0015] The cover sheet straddles the back surface of both island portions and the back surface of both main trunk portions, and is folded back and adhered to the front surface side of both main trunk portions except for the surface of the island portion to which the heat-sensitive element is attached. Things.

Further, a moisture-proof coating is provided on the surface of the heat-sensitive element, and the moisture-proof coat prevents contamination due to adhesion of toner powder or the like, or an effect of humidity on the heat-sensitive element.

Further, the island portion and the main portion are connected by a vertical tie bar and a horizontal tie bar, and the vertical tie bar and the horizontal tie bar reduce torsional stress generated between both leaf springs. What is absorbed.

Further, the island portion has a through hole on its plate surface,
The through hole is a hole for receiving an adhesive for bonding the thermosensitive element to the island portion and increasing the bonding strength.

The cover sheet secures the holding strength of the island portion connected to the main trunk portion only by the tie bar.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, the fixing temperature sensor according to the present invention includes a pair of leaf springs 1a and 1b, a heat-sensitive element 2, a cover sheet 3, and a holder 4. The pair of leaf springs 1a and 1b are lead wires of the thermal element 2, and the pair of leaf springs 1a and 1b each have a main trunk portion 5 and an island portion 6, as shown in FIG.

The main trunk portion 5 is a portion of a lead wire connected to an external output line, and a part thereof is supported by the holder 4 and arranged in parallel. The holding body 4 is an insulating resin molded body that embeds a part of both the main trunk portions 5 and 5 and holds the main trunk portions 5.5 of both leaf springs adjacent to and parallel to each other.

A screw hole 7 is opened in the holder 4, and external lead wires 8, 8 are connected to terminals of the two main trunk portions 5, 5 pulled out from the holder 4, respectively. Leaf spring 1
The pair of a and 1b is symmetrical, and the island portion 6 is formed to be open at one edge of the main trunk portion 5, and the two main trunk portions 5, 5 are formed.
Are arranged so that the island portions 6 and 6 are adjacent to each other.

The pair of island portions 6.6 are electrode portions of the thermal element 2, are arranged adjacent to each other, and are electrically connected to the respective main trunk portions 5. The main trunk portion 5 and the island portion 6 are cut out of the spring plate by etching or pressing, and the island portion 6 is formed by cutting out a part of the main trunk portion 5 by etching or pressing. Part. The pair of island portions 6 and 6 are surrounded by a pair of main trunk portions arranged in parallel, and the island portion and the main trunk portion are formed by thin tie bars 9 extending in the vertical and horizontal directions.
a, 9b.

The island portion 6 and the main trunk portion 5 are substantially thermally isolated from each other except for the tie bars 9a and 9b.
Further, they are electrically connected to each other by tie bars 9a and 9b. Of course, since the tie bars 9a and 9b connect the island portion 6 and the main trunk portion 5, it is unavoidable that heat is transmitted from the island portion 6 to the main trunk portion 5 through the tie bars 9a and 9b.

Therefore, it is preferable that the tie bars 9a and 9b are as thin as possible, and a part of the main trunk portion 5 near the tie bars 9a and 9b is etched or processed during processing of the leaf spring in order to suppress heat dissipation as much as possible. It is preferable to provide a window hole 10 opened by pressing. It is desirable that the distance between the island portion 5 and the main trunk portion 5 is large, but if the distance is too wide, the tie bars 9a,
Since the supporting strength of the island portion 6 due to 9b is reduced, it is necessary to appropriately select the interval so that a certain supporting strength can be obtained.

The heat-sensitive element 2 is a solid-type square chip thermistor or a thick-film chip thermistor, and is bonded between the island portions 6 and 6 of both leaf springs 1a and 1b. Both island parts 6, 6 to which thermal element 2 is bonded
Functions as a soaking plate for dispersing the heat generated by the thermosensitive element 2.

The island portion 6 is provided with a through hole 11 in its plate surface. This through hole 11 is also opened in the island portion 6 by etching or pressing during the processing of the leaf spring. In this embodiment, a short through hole 11 is formed at the center of the island portion 6 in the lateral direction. One vertically long through hole 11 is opened in the inner part of the book. The through hole 11 is a hole for receiving the adhesive B used as shown in FIG. 3 into the opening when the thermosensitive element 2 is bonded to the island portion 6. Adhesive B
It penetrates into each through-hole 11 and is hardened to increase the adhesive strength of the thermal element 2.

The cover sheet 3 covers the surfaces of both leaf springs 1a and 1b. For example, a polyimide tape is cut to a certain length, and a rectangular notch 12 is formed in a part of both edges as shown in FIG. Is formed. Cover sheet 3
Is attached across the back surfaces of both island portions 6 and 6 where the thermal element 2 is not attached and the back surfaces of both main trunk portions 5 and 5. The heat-sensitive element 2 is attached to the surface of the main part 5.
The entire surface of the island portion 6 on which the
In the notch 12.

As shown in FIG. 2, a pair of rectangular islands 6
The three sides are surrounded by the main part 5, and the cover sheet 3 is attached over the back side of the island part 6 and the back side of both main parts 5, 5, whereby the island parts 6, 6 are attached.
Is supported by the main trunk portions 5 and 5 via the cover sheet 3. As a result, the holding strength of the island portion 6 is increased, and the heat-sensitive element 2 faces the inside of the notch 12 Exposure to

When the temperature sensor S of the present invention is used for detecting the surface temperature of the fixing roller 13 of a copying machine or the like as shown in FIG.
The island portion 6 to which the thermal element 2 is attached is brought into contact with the surface of the fixing roller 13, and the temperature of the fixing roller 13 is detected by the thermal element 2 through the island portion 6 as shown in FIG. On the other hand, the current supplied from the external lead wire 8 passes through the tie bars 9 a and 9 b from the main trunk portion 5, passes through the island portion 6 to the thermosensitive element 2, generates heat, and detects the temperature of the fixing roller 13. The resulting change in current is taken out as an external output line 8 as an external output line through tie bars 9a and 9b as a temperature detection signal.

In the present invention, although the island portion 6 to which the thermal element 2 is attached and the main trunk portion 5 connected to the external lead wire 8 are electrically connected by tie bars 9a and 9b, the tie bar 9a , 9b are thin and most of the island portions 6 are isolated from the main trunk portion 5, so that the heat-sensitive elements 2
Most of the heat generated is not dissipated, and the thermal time constant of the thermosensitive element 2 is not impaired.

When the temperature sensor S according to the present invention is brought into contact with the fixing roller 13, no problem occurs if a force is applied to the pair of leaf springs 1 a and 1 b on average. Even when the magnitude of the force acting on each of the springs 1a and 1b is different and a twist or the like occurs between the leaf springs 1a and 1b, the island portion 6 and the main trunk portion 5 maintain the vertical and horizontal tie bars 9a. , 9b, the stress caused by twisting even if the tie bar 9 is thin,
The leaf springs 1 are absorbed by the respective tie bars 9a and 9b.
It is not affected by the twist between a and 1b.

Further, in the present invention, it is conceivable that the exposure of the thermal element 2 to the outside may be affected by dirt due to the adhesion of toner powder or humidity, but such dirt and humidity pose a problem. Occasionally, as shown in FIG.
4 can be adequately dealt with.

Further, by exposing the heat-sensitive element 2 to the outer surface, a process of attaching the cover sheet 3 to the pair of leaf springs 1a and 1b is performed first in the manufacturing process of the temperature sensor. , 6 can be selected. If the surface of the thermal element 2 is not covered with the cover sheet 3, the flat leaf spring 1
The cover sheet can be easily attached to the leaf spring by folding back both edges of the cover sheet applied to the back surfaces of the a and 1b to the front side.

[0035]

As described above, according to the present invention, a pair of leaf springs, which are lead wires of a thermal element, are divided into a main part and an island part, and the island part and the main part are electrically connected. However, since it is practically isolated from the heat, a solid-type square chip thermistor or a thick-film chip thermistor is directly attached to the island as a heat-sensitive element without using a heat insulating material such as a sponge. Heat dissipation can be prevented, and the thermal time constant of the thermal element can be improved.

Further, by connecting the island portion to the main trunk portion with a thin tie bar extending in the vertical and horizontal directions, even if a torsional stress acts on the island portion by receiving a force from the rotating fixing roller, the stress can be sufficiently reduced. It can be absorbed and furthermore, it can be supported by the back cover sheet to maintain its strength. ADVANTAGE OF THE INVENTION According to this invention, it is assembled using a small number of parts, the measurement accuracy is high while the structure is simple,
This has the effect of providing a fixing roller temperature sensor that is excellent in durability and inexpensive in manufacturing cost.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a temperature sensor for a fixing roller according to the present invention.

FIG. 2 is an enlarged plan view of a main part of a leaf spring.

FIG. 3 is a cross-sectional view of a temperature sensor corresponding to a line AA in FIG. 2;

FIG. 4 is a development view of a cover sheet.

FIG. 5 is a diagram illustrating a use state of a temperature sensor.

FIG. 6 is a diagram showing a conventional example of a surface temperature sensor.

FIG. 7 illustrates an improved conventional surface temperature sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1a, 1b Leaf spring 2 Thermal element 3 Cover sheet 4 Holder 5 Main trunk part 6 Island part 7 Screw hole 8 External lead wire 9a, 9b Tie bar 10 Window hole 11 Through hole 12 Notch 13 Fixing roller 14 Moistureproof coating S Temperature sensor B adhesive

Claims (8)

[Claims] 1. A fixing roller temperature sensor having a leaf spring, a holder, a thermal element, and a cover sheet, wherein the leaf spring is a lead wire of the thermal element and forms a pair. The leaf spring has a main part and an island part, the pair of main parts is a part connected to an external output line, and is arranged in parallel, the island part is electrically connected to the main part, and Thermally, it is formed in a part of the main part substantially separated from the main part, and the holder embeds a part of both main parts, and the main parts of both leaf springs are adjacent to each other. The pair of islands are electrodes of the thermosensitive element and are arranged adjacent to each other, and the thermosensitive element is a solid type square chip thermistor or a thick film type thermistor, Glued across the islands of both leaf springs The cover sheet covers both leaf springs except for the surface of the island portion on which the thermal element is mounted, wherein the temperature sensor for the fixing roller is provided. 2. A pair of leaf springs is bilaterally symmetric, an island portion is formed open to one edge of a main trunk portion, and both main trunk portions are arranged in an orientation such that the island portions are adjacent to each other. The fixing roller temperature sensor according to claim 1, wherein 3. The island portion is a portion formed by cutting out a part of a main trunk portion by etching or press working, and the island portion and the main trunk portion are connected by a thin tie bar. The fixing roller temperature sensor according to claim 1, wherein the temperature sensor is configured to electrically connect the main part and the main part. 4. The island portion and the main portion are connected by a vertical tie bar and a horizontal tie bar, and the vertical tie bar and the horizontal tie bar reduce torsional stress generated between both leaf springs. 4. The fixing roller temperature sensor according to claim 3, wherein the temperature sensor absorbs the light. 5. The cover sheet covers the back surface of both island portions and the back surface of both main trunk portions, and is folded back and attached to the front surface side of both main trunk portions except for the surface of the island portion to which the heat-sensitive element is attached. The fixing roller temperature sensor according to claim 1, wherein 6. The heat-sensitive element has a moisture-proof coat on the surface thereof, wherein the moisture-proof coat prevents contamination due to adhesion of toner powder or the like, or an effect of humidity on the heat-sensitive element. 6. The fixing roller temperature sensor according to 1 or 5. 7. The island portion has a through hole on its plate surface, and the through hole is a hole for receiving an adhesive for bonding the thermosensitive element to the island portion and increasing the bonding strength. The fixing roller temperature sensor according to claim 1. 8. The fixing roller temperature sensor according to claim 1, wherein the cover sheet secures the holding strength of the island portion connected to the main trunk portion only by the tie bar.