JPH04335691A - Fixing device for image forming device - Google Patents

Abstract

PURPOSE:To reuse a heating pipe and to produce an inexpensive fixing roller by attachably/detachably fitting the heating pipe to the core metal of the fixing roller. CONSTITUTION:A constitution that a tolerance is set so that some gap is formed between plural holes 1b in an axial direction which are provided on the core metal of the fixing roller 1 at almost equal intervals, and the heating pipe 8 inserted/fitted in these holes, at an ordinary temp., is adopted and the heating pipe 8 can be removed. Further, the materials of the heating pipe 8 and the core metal are selected so that the coefficient of the linear expansion of the heating pipe 8 is higher than that of the core metal of the fixing roller 1. Both end parts of the heating pipe 8 are lightly pressed and set by a stopper such as a seal 9 and a sealing screw 10, at the ordinary temp. Therefore, the heating pipe 8 is closely touched to the core metal of the fixing roller 1, at the time of heating, thermal conduction is excellently carried out, and the expansion of the heating pipe 8 is recovered at the ordinary temp. Then, the gap is formed again, and the heating pipe 8 is easily attached/detached.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for an image forming apparatus having at least one heat pipe built into a fixing roller.

0002

2. Description of the Related Art It is well known that in addition to a heat source such as a halogen lamp, a heat pipe is built into a fixing roller in order to evenly distribute heat throughout the fixing roller. As a method for incorporating this heat pipe, the fitting tolerance between the heat pipe and the hole provided in the core metal of the fixing roller for inserting the heat pipe is made small, and after inserting the heat pipe into this hole, It has been conventional practice to heat the heat pipe to 400 DEG C. to plastically deform the material of the heat pipe, thereby bringing the heat pipe into close contact with the fixing roller.

0003

[Problems to be Solved by the Invention] With the above-mentioned fixing roller with a built-in heat pipe, if the fluororesin or silicone rubber that is the release layer of the fixing roller deteriorates, even though the heat pipe can still be used, Generally, the fixing roller is discarded with the heat pipe built-in, which is inevitably disadvantageous in terms of cost.

An object of the present invention is to eliminate the above-mentioned drawbacks in a fixing roller with a built-in heat pipe.

[0005]

[Means for Solving the Problems] According to the present invention, the above-mentioned problems are solved by making the heat pipe detachable.

Further, in order to solve the above-mentioned problems, the present invention proposes that the coefficient of linear expansion of the heat pipe built into the fixing roller is larger than that of the fixing roller.

Further, in order to solve the above-mentioned problem, the present invention provides a method in which both ends of the heat pipe built into the fixing roller are in contact with stoppers for the heat pipe provided at the positions of both ends at room temperature. propose.

Furthermore, in order to solve the above problem, the present invention reduces the difference between the inner diameter of the hole provided in the fixing roller for inserting the heat pipe and the outer diameter of the heat pipe to 0.0.
It is proposed to form a gap of 5 mm or more and fill this gap with a heat medium.

[0009]

[Operation] The heat pipe built into the fixing roller can be attached and detached as follows. In other words, the coefficient of linear expansion of the heat pipe is made larger than that of the core metal of the fixing roller, so that the heat pipe can be attached and detached at room temperature, but when heated, the heat pipe is attached to the fixing roller. Closely adheres to the core metal. Alternatively, both ends of the heat pipe can be brought into contact with heat pipe stoppers provided at these positions at room temperature to prevent the axial expansion of the heat pipe during heating and convert it to radial expansion. Make sure that the pipe and the core of the fixing roller come into close contact. Alternatively, the difference between the inner diameter of the hole provided in the core of the fixing roller and the outer diameter of the heat pipe is 0.05 mm or more to form a gap, and by filling this gap with a heat medium, the heat pipe can be attached and detached. and maintain thermal conductivity.

0010

Embodiment One embodiment of the present invention will be explained with reference to FIGS. 1 and 2. FIG.

In the fixing device shown in FIGS. 1 and 2,
A fixing roller 1 and a pressure roller 2 are rotatably arranged in pressure contact with each other. 3 is an inlet guide plate, 4 is an outlet guide plate, 5 is a separation claw, and 6 is a heating temperature control thermistor.

The core metal of the fixing roller 1 has an inner diameter of 10 to 20 mm.
There is a center hole 1a with a diameter of 2 mm, and a halogen lamp 7 as a heat source is provided in this hole to heat the fixing roller from the inside. Furthermore, a plurality of axial holes 1b are provided in the core metal of the fixing roller at approximately equal intervals, and heat pipes 8 are embedded in each of these holes. These heat pipes 8 function to absorb variations in the heating temperature distribution by the halogen lamp 7, and therefore the temperature difference between the paper passing area and the non-paper passing area.

According to the present invention, a tolerance is set so that a slight gap is formed between the hole 1b and the heat pipe 8 inserted therein at room temperature, and the heat pipe 8 is inserted into the hole 1b. is removable. Furthermore, the materials of the heat pipe and the core metal are selected so that the linear expansion coefficient of the heat pipe 8 is larger than that of the core metal of the fixing roller. For example, it is preferable to use stainless steel or Fe as the core metal of the fixing roller and to use Cu or Al as the heat pipe. In addition, both ends of the heat pipe 8 are lightly pressed and fixed using stoppers such as a seal 9 and a sealing screw 10 at room temperature. 11 is a side plate, 12 is a bearing, and 13 is a drive gear.

With the above-mentioned configuration, the gap between the fixing roller hole 1b and the heat pipe 8 at room temperature is such that the heat pipe 8 expands more in the radial and axial directions than the hole 1b during heating. Therefore, the heat pipe 8
The heat pipe is in close contact with the core metal of the heat pipe, and heat transfer between the core metal and the heat pipe is performed well. When both ends of the heat pipe are stopped by stoppers, the heat pipe is prevented from expanding in the axial direction during heating, and is converted into radial expansion, thereby bringing the heat pipe into close contact with the core metal. At room temperature, the expansion returns to its original state and a gap is created again, making it easy to attach and detach the heat pipe 8. In this case, the tolerance of the gap formed between the hole 1b and the heat pipe 8 needs to be selected within a range in which the material of the heat pipe 8 does not undergo plastic deformation during thermal expansion.

Furthermore, as another embodiment, the hole 1b
A gap formed between the heat pipe 8 and the heat pipe 8 does not disappear during thermal expansion during heating, and a liquid can be sealed as a heat medium in this gap. In this case, heat transfer is performed through the liquid, so the gap is preferably narrower. Therefore, in the embodiment of the present invention, the difference between the inner diameter of the hole 1b and the outer diameter of the heat pipe 8 is set to 0.05 to 0.2 m.
m, and this gap is filled with liquid. As this liquid, oils such as silicone oil are preferable in consideration of lubrication during attachment and detachment. Both ends of the hole 1b into which the heat pipe 8 is inserted are sealed as follows. A seal member is press-fitted into one end and welded. At the other end,
After inserting the heat pipe, inject liquid and screw in the sealing pin to seal. In this case, when a sealing material is used as a member that assists in sealing the sealing pin, a heat-resistant elastic material such as fluororubber is used.

[0016]

Effects of the Invention According to the present invention, the heat pipe can be
Since the heat pipe is removably attached to the core metal of the roller, the heat pipe can be reused, making it possible to manufacture a fixing roller at low cost.

According to the present invention, when the coefficient of linear expansion of the heat pipe is made larger than the coefficient of linear expansion of the core metal of the fixing roller, the heat pipe detachably attached with a gap is attached to the core of the fixing roller during heating. It adheres closely to the gold and ensures heat conduction between the heat pipe and the fixing roller.

According to the present invention, when both ends of the heat pipe built into the fixing roller are in contact with the heat pipe stoppers provided at these positions at room temperature, By blocking the axial expansion and converting it to radial expansion, the heat pipe is brought into close contact with the core metal of the fixing roller, and heat conduction between the heat pipe and the fixing roller is facilitated. It becomes like this.

According to the present invention, when a diameter difference is provided between the heat pipe and the hole in the core metal of the fixing roller into which it is inserted, and the gap is filled with oil as a heat medium, the heat pipe can be attached and detached. This makes it possible to maintain thermal conductivity.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a fixing device according to the present invention.

FIG. 2 is a cross-sectional view of the fixing device shown in FIG. 1;

[Explanation of symbols]

1 Fixing roller 1a Center hole 1b for inserting a halogen lamp
Axial hole 7 for heat pipe insertion
Halogen lamp 8 heat pipe

Claims (4)

[Claims] 1. A fixing device for an image forming apparatus having at least one heat pipe built into a fixing roller, wherein the heat pipe is removable. 2. The fixing device according to claim 1, wherein a linear expansion coefficient of the heat pipe built into the fixing roller is larger than a linear expansion coefficient of a core metal of the fixing roller. 3. The fixing roller according to claim 1 or 2, wherein both ends of the heat pipe built in the fixing roller are in contact with heat pipe stoppers provided at both ends at room temperature. Fixing device as described. 4. A gap is formed by setting the difference between the inner diameter of the hole provided in the core metal of the fixing roller into which the heat pipe is inserted and the outer diameter of the heat pipe to be 0.05 mm or more, and in this gap. The fixing device according to claim 1, characterized in that the fixing device is filled with a heat medium.