JP2599981B2 - Fixing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fixing device of an image forming apparatus such as an electrophotographic copying machine.

(Prior Art) Conventionally, when an image is formed by an image forming apparatus such as an electrophotographic copying machine, various fixing methods have been adopted, but at present, a heat roller type fixing apparatus is often used. . In this heat roller type fixing device, for example, at least one of a pair of fixing rollers rotating while being pressed against each other is heated, and a transfer material carrying an unfixed developed image (toner image) is sandwiched between the rollers. The developed image is melted and fixed to the transfer material by heat.

Here, as a heating means of the roller, an electric heater is provided inside the roller, and a temperature detecting means is brought into contact with the roller surface, and the heater is heated by the temperature detecting means.
It is generally known to control the surface temperature of the roller by turning it on and off.

By the way, if the temperature detecting means is separated from the roller surface or the control is malfunctioning, the roller temperature may rise abnormally, causing inconvenience such as smoking and ignition.
In order to prevent such an abnormal situation from occurring, a safety device is provided for shutting off the supply of electric current to the heater and stopping the heater.

Here, since the surface of the roller is generally often made of a material having a relatively low thermal conductivity such as silicon rubber, the temperature difference between the roller surface and the metal core inside the roller is large, for example, Even when the roller surface temperature is about 170 ° C., the temperature of the bonded portion between the cored bar and rubber or the like may reach 240 ° C. in some cases. Therefore, the safety device detects the temperature of the metal part having a high thermal conductivity at the roller core, rather than detecting the roller surface temperature, and immediately transmits the temperature to the heater when the temperature of the core shows an abnormality. An early response type that interrupts the supply of a current is often used. Such a safety device has a built-in thermo switch using a bimetal or the like in the wiring to the heater, and contacts the thermo switch with a core bar exposed to the outside of the roller end, and when an abnormally high temperature is detected, the thermo switch is connected to the heater. There is a type that interrupts the supply of current.

(Problems to be Solved by the Invention) However, the cored portion of the roller is generally not finished well and is easily damaged by a chuck or the like during the manufacturing process. Therefore, when the temperature detecting member of the safety device is pressed against the cored bar with a certain force, the contact surface of the temperature detecting member is damaged due to a scratch on the cored bar, and the operation of the safety device is impaired. There was a problem.

In addition, even when there is no particularly noticeable scratch on the cored bar, the contact surface of the temperature detecting member of the safety device is generally more easily damaged than the surface of the cored bar. There has been a problem that the contact surface of the temperature detecting portion is damaged or the contact surface is further worn to change the state of contact with the cored bar, thereby impairing the operation of the safety device.

The present invention has been made in view of the above problems, and an object thereof is to improve the durability of a roller by preventing damage to a contact portion of a temperature detecting member with respect to a core of a roller with a simple configuration. An object of the present invention is to provide a fixing device.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a roller having a rotatable core, a temperature detecting member for detecting a temperature by contacting the roller with the core, Wherein a low friction tape is adhered to a contact portion of the core of the roller with the temperature detecting member.

(Operation) According to the present invention, since the low friction tape is stuck to the rotating core, the sliding between the core and the temperature detecting member becomes smooth, and the wear of the temperature detecting member is suppressed. Even if there is a scratch or damage caused by a poorly finished core, the temperature detection member may be damaged by rotation of the damaged core because the scratch is covered with low friction tape. Therefore, the durability of the temperature detecting member is improved.

In addition, the low friction tape can be easily adhered simply by wrapping it around the core metal, and can be easily peeled off, so that the replacement operation is extremely simplified.

Embodiment An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a perspective view of an end portion of a fixing roller in a fixing device according to the present invention. In FIG. 1, reference numeral 1 denotes a fixing roller. A cylindrical release layer 10 is provided, and the release layer 10 is bonded and fixed to a core metal 11 made of a cylindrical metal material.

Both ends (only one side is shown in FIG. 1) of the core metal 11 constitute an exposed portion 11a protruding from the release layer 10, and the core metal 11
An electric heater 4 for heating the release layer 10 is provided in the inner hole 11b. The electric heater 4 is ON / OFF controlled by a thermistor (not shown) for adjusting the temperature, which is in contact with the release layer 10, so that the surface temperature of the release layer 10 is kept constant.

Further, the fixing roller 1 has an inner hole 11 b of
Are rotatably supported by a fixing device main body (not shown) through both ends of the fixing device. Although not shown, the fixing device includes a release layer of the fixing roller 1.
There is provided another fixing roller which is pressed against the fixing roller 10, and the other fixing roller is rotated by the fixing roller 1. For convenience of explanation, it is assumed that a fixing roller (not shown) is not provided with a heater.

When the transfer material carrying the unfixed developed image (toner image) is conveyed to the fixing device, the transfer material is transferred to the fixing roller 1.
While being held between the fixing rollers (not shown) by the rotation of the fixing roller 1 and the like, the developed image carried thereon is heated and melted by the release layer 10 of the fixing roller 1 and fixed to the transfer material.

By the way, the safety device 2 is provided on one exposed portion 11a of the metal core 11.
The temperature detecting member 2a is pressed with a predetermined force, but the control of the electric heater 4 is inconvenient due to the separation of the thermistor from the release layer 10 or a malfunction of the thermistor circuit. Even if the roller 1 is in an abnormally high temperature state, the supply of current to the electric heater 4 is cut off by the safety device 2, and the safety of the fixing device is ensured.

Here, the safety device 2 is incorporated into the power supply circuit of the electric heater 4 via the terminals 2b and 2b. Since the safety device 2 has a built-in thermoswitch using bimetal or the like, the electric heater 4 If the core metal 11 of the fixing roller 1 shows an abnormally high temperature, the safety device 2 opens the thermoswitch via the temperature detecting member 2a and cuts off the supply of electric current to the electric heater 4.

Since the fixing roller 1 is constantly rotating and the temperature detecting member 2a of the safety device 2 slides on the outer peripheral portion of the metal core 11, the temperature of the safety device 2 on the outer peripheral portion of the metal core 11 is increased. Detection member
A fluororesin tape 5, which is a low-friction member having a predetermined width, is wound and adhered to a portion where 2a contacts and slides. Incidentally, the fluororesin tape 5 is effective when the life of the fixing roller 1 is relatively short and the general life of the safety device 2 is slightly longer than that of the fixing roller 1.

By the way, the fluororesin tape 5 has a short life due to the fact that the part to be adhered to the metal core 11 is generally easily peeled off, but its construction is easy, and even if it comes off, it can be easily adhered many times. It has the advantage of being able to. The winding direction of the fluororesin tape 5 around the core 11 is as shown in FIG.
The end opposite to the rotation direction of the fixing roller 1 is set in a direction in which it is located above.

As described above, in the present embodiment, the rotation-side core metal 11
Since the fluororesin tape 5 is stuck to the outer surface where the temperature detecting member 2 abuts, the sliding between the cored bar 11 and the temperature detecting member 2a becomes smooth, and the wear of the temperature detecting member 2a is suppressed. Even if the cored bar 11 has a flaw or damage caused by a poorly finished state, since the flaw is covered with the fluororesin tape 5, the temperature detecting member 2a is rotated by the damaged cored bar 11 Temperature sensor 2a without damage
Is improved in durability.

 Next, a reference example of the present invention will be described with reference to FIG.

FIG. 2 is a perspective view of an end portion of the fixing roller in the fixing device according to the reference example. In FIG. 2, the same elements as those shown in FIG. 1 are denoted by the same reference numerals. Omitted.

In the present embodiment, a fluororesin coating 3 having a predetermined width is applied to a portion of the outer peripheral portion of the cored bar 11 where the temperature detecting member 2a of the safety device 2 comes into contact with and slides. It is similar.

Thus, the fluororesin coating 3 is soft and damaged with respect to the metal core 11 in order to reduce friction between the metal core 11 and the temperature detecting member 2a of the safety device 2 and to make the sliding between the two smooth. The contact portion of the temperature detecting member 2a of the safety device 2 which is easy to protect can be sufficiently protected from the metal core 11, and the fluororesin coating 3 can hide the processing damage or the like of the metal core 11, so The temperature detecting member 2a of the safety device 2
The contact portion can be prevented from being damaged. Accordingly, the life of the safety device 2 is greatly extended, and the safety device 2 can reliably detect an abnormally high temperature, and can reliably cut off the supply of current to the electric heater 4.

In the above embodiments, the fluororesin tape is used as the low friction tape. However, the present invention is not limited to this, and it goes without saying that any low friction tape having the same function may be used. In particular, if a polyimide tape is adhered to the contact portion of the temperature detector 2a of the safety device 2 with the core 11, the coefficient of friction between the temperature detector 2a and the core 11 is further reduced, and the fixing roller 1 The life of both safety devices 2 can be further extended.

(Effects of the Invention) As is apparent from the above description, according to the present invention, since the low friction tape is stuck to the rotating core, the sliding between the core and the temperature detecting member becomes smooth. Abrasion of the temperature detecting member is suppressed, and even if there is a scratch or damage caused by a poorly finished core, the temperature detecting member is damaged by the low friction tape. The effect that the durability of the temperature detecting member can be improved without being damaged by the rotation of the cored metal having the above-mentioned structure can be obtained.

Further, according to the present invention, the low-friction tape can be easily stuck and wound off simply by wrapping it around the cored bar, so that the replacement operation can be greatly simplified.

[Brief description of the drawings]

FIG. 1 is a perspective view of a fixing roller end of a fixing device according to the present invention, and FIG. 2 is a perspective view of a fixing roller end similar to FIG. 1 showing a reference example. 1 ... fixing roller (roller) 2 ... safety device, 2a ...
Temperature detecting member, 4 ... electric heater, 5 ... fluororesin tape (low friction tape), 11 ... core metal.

Claims (1)

(57) [Claims] 1. A fixing device comprising: a roller having a rotatable core, and a temperature detecting member for detecting a temperature by contacting the roller with the core, wherein the temperature detection of the core of the roller is performed. A fixing device wherein a low friction tape is attached to a member contact portion.