JPS5946668A - Fixing roll - Google Patents

Abstract

PURPOSE:To obtain a fixing roll having short warming-up time, good temp. setting accuracy, and good heat efficiency, by installing a heat insulating layer, a heat generating layer, a heat-conductive layer, and an offset preventing layer from the center. CONSTITUTION:A pressing roll 11 is made of a heat insulator having proper elasticity and heat resistance, 12 is a metallic shaft, 13 is a heater, 14 is a heat- conductive layer formed as thin as possible, and 15 is an offset preventing layer. A metallic roll 16 having a highly heat-insulating material layer, such as a metallic roll having a hollow mirror-lined vacuum space or heat-insulating ceramics, is suitable. When the power supply switch of the device is turned on and the heater 13 begins to be energized, the generated heat is first used for warming up the heater itself 13 and the thin layer 14 both having extremely small heat capacities for a short time, and soon used for heating the fixing roll to raise its surface temp. Since the heat time constant of the fixing roll is very small, overshoot and undershoot due to the on-off control of temp. become small, and temperature setting good in accuracy can be made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a fixing roller for visualizing and fixing an electrostatic latent image using developing powder (toner) in electrostatic recording, electrophotography, etc. .

Conventional Structure and Problems Conventionally, in electrostatic recording or electrophotography, a fixing roller that visualizes an electrostatic latent image using developing powder (toner) and fixes it is shown in Fig. 1, for example. It is configured as shown. In Fig. 1, 2 is a hollow metal roll, 3 is a heater, 4 is a silicone rubber layer with relatively good heat resistance,
1 is a pressure roller that is pressed against the silicone rubber layer 4 with an appropriate force, and A is a toner. The heater 3 of such a fixing roller is placed in the center of the roller, so if the device is turned on after it has completely cooled down due to a long-term shutdown, the heat will accumulate in the silicone rubber layer 4 and then raise the surface temperature. The drawback is that it takes a long warm-up time to raise the temperature to a certain value. Also, as a temperature control method for such a fixing roller, the surface temperature of the roller is detected, and when the surface temperature reaches the required and sufficient temperature, the heater power is turned off, and when the surface temperature falls below the required and sufficient temperature. The so-called ON-OFF control, in which the heater power is turned on again at the same time, is widely adopted because it is the simplest method. However, in the conventional example described above, the thermal time constant of the fixing roller tends to be large, resulting in overshoot of the surface temperature. ,
It is inevitable that the undershoot will increase (third
(See solid line a in the figure).

Further, the fixing roller is normally rotated while being supported by a bearing (not shown), and a part of the heat generated from the heater 3 does not pass through the silicone rubber layer 4, so it is not involved in the fixing action and is wasted. There were some drawbacks.

OBJECTS OF THE INVENTION The present invention aims to eliminate the above-mentioned conventional drawbacks, and to provide a fixing roller that takes a short time to raise to a predetermined temperature (so-called warm-up time), has good temperature setting accuracy, and has good thermal efficiency. In order to achieve the above object, the present invention is characterized in that a heat insulating layer, a heating layer, a heat transfer layer, and an onset prevention layer are provided from the center of gravity.

DESCRIPTION OF THE EMBODIMENTS FIG. 2 shows a fixing roller in one embodiment of the present invention. In FIG. 2, 11 is a pressure roller;
The pressure roller 11 is made of a poor heat conductor having appropriate elasticity and heat resistance. 12 is a metal shaft, 13 is a heater, 14 is a heat conductive layer made as thin as possible, and 15 is an offset prevention layer, which can be simply coated with silicone oil, or the heat conduction layer 14 has an offset prevention effect. In some cases, a thin layer of Teflon or the like may be provided. 16 is a highly insulating layer, and a metal roller whose hollow wall is mirror-finished and evacuated, or a heat insulating ceramic is suitable.

When the power switch of the device is turned on and electricity starts flowing to the heater 3, the generated heat is transferred to the heater 13 itself and the thin heat conductive layer 1.
The surface temperature of the fixing roller increases in the short warm-up time required to store heat for an object with an extremely small heat capacity of 4. Furthermore, since the thermal time constant of the fixing roller becomes extremely small, overshoot and undershoot due to temperature ON/OFF control are reduced, making it possible to set the temperature with high accuracy (see broken line b in FIG. 3). Also, the fact that the thermal time constant of the fixing roller is small means that less heat is wasted in the fixing roller when the device power is turned off, and the solid electric heating path from the heater 13 to the metal shaft 12, bearings, frame, etc. is high. Since it is isolated by the heat insulating layer, there is little heat loss during steady operation, so the thermal energy utilization efficiency is high.

Effects of the Invention The present invention has the above configuration, and according to the present invention, it is possible to eliminate the drawbacks of conventional fixing rollers, provide a fixing roller with short warm-up time, good temperature setting viscosity, and high thermal efficiency. It is something.

[Brief explanation of the drawing]

FIG. 1 is a side view of a conventional fixing roller, FIG. 2 is a side view of a fixing roller in an embodiment of the present invention, and FIG. 3 is a diagram showing the surface and temperature changes of the fixing roller of the conventional example and the present invention. It is. DESCRIPTION OF SYMBOLS 11... Pressure roller, 12... Metal shaft, 13... Heater, 14... Heat conductive layer, 15 Offset prevention layer, 16...
metal roller.

Claims (1)

[Claims] A heat insulating layer formed on the shaft, a heat generating layer formed on the outer periphery of this heat insulating layer, a heat conductive layer with good heat conduction formed around the outer periphery of this heat generating layer, and this heat conductive layer. and an anti-offset layer formed on the outer periphery of the fixing roller.