JPH0234394B2 - NETSUROORAGATATEICHAKUSOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a heat roller type fixing device for an electrostatic recording device, which uses a simple mechanism to accurately control the temperature of a heating roller during fixing.

Various methods are known for heating and fixing toner images formed on a recording medium in electrostatic recording devices such as electrophotographic copying machines and facsimile machines. The currently widely used fixing methods can be roughly divided into non-contact fixing methods, which heat and fix toner using radiant energy such as infrared rays, and non-contact fixing methods, which heat and fix toner using radiant energy, such as infrared rays. There is a contact fixing method that heats the toner and fixes it. The latter has good thermal efficiency and consumes less power,
Since it has advantages such as being capable of high-speed fixing, there is a tendency for it to be increasingly adopted as copying machines become faster.

By the way, as the latter fixing device, as shown in FIG. 1, there is a heat roller type which is composed of a rotatable heating roller 1 having a built-in heater 1a, and a pressure roller 2 that rotates in pressure contact with the heating roller 1. Fixing devices are generally known and are widely put into practical use. In this heat roller type fixing device, a non-contact type temperature sensor 3 such as a thermistor disposed close to the surface of the heat roller 1
The control circuit 4 controls the supply of electricity to the heater 1a of the heating roller 1 based on the surface temperature signal. On the other hand, the heating roller 1 and the pressure roller 2 are rotatably supported by a bearing section 5 at the end of the roller, and the bearing section 5 contains oil to reduce frictional force. Therefore, if the surface temperature of the heating roller continues to be maintained at around 180°C, which is the normal fixing temperature, the bearing part 5 will reach a high temperature of nearly 150°C, so if the fixing device is operated for a long time, thermal deterioration of the oil will become a problem. become. So in order to solve this problem,
It is conceivable to lower the set temperature of the heating roller itself, but considering the fixability of the toner, it cannot be lowered so much. Another solution is to control the temperature of the heater 1a of the heating roller 1 by raising the temperature (for example, 180°C) during recording and returning it to a lower temperature (for example, about 100°C) when not recording. However, a control circuit for this is required. In FIG. 1, reference numerals 11 and 12 are drive gears that drive the heating roller 1 and the fixing roller 2, and are driven by the motor 7 via another gear 6.

In view of the above points, the present invention is designed to extend the life of the bearing part by accurately controlling the temperature of the heater using a mechanism that is simpler than the conventional one.
The level of the output signal of the temperature detector that detects the surface temperature of the heating roller is lowered prior to the fixing operation,
After the fixing operation is completed, the level is returned to the original level.

The present invention will be explained below based on the drawings.

FIG. 2 shows an embodiment of the fixing device according to the invention, in which the same reference numerals as in FIG. 1 indicate the same components. A small fan 8 is provided near the non-contact temperature sensor 3, and the fan 8 is rotated together with the heating roller 1 via a gear 9 that meshes with a drive gear 11.

When the heating roller 1 and the pressure roller 2 rotate periodically during the recording operation, the drive gear 1 of the heating roller 1 rotates.
Since the gear 9 meshing with the fan 8 rotates, the fan 8
rotates. As a result, the heat of the temperature sensor and the atmosphere between the surface of the heating roller 1 and the temperature sensor 3 is taken away, so the temperature sensor 3 detects that the surface temperature of the heating roller 1 is low, and the control circuit 4 sends the heater 1a Increase the current supplied to the In this way, the amount of heat generated by the heater 1a increases, and thereafter the surface temperature of the heating roller rises until the temperature sensor 3 reaches a temperature at which the temperature is balanced.

In this way, when the fixing device rotates,
That is, only when the fixing operation is performed, the surface temperature of the heating roller 1 is set to a temperature that satisfies the fixing performance (for example, 180
℃), and during the rest of the period (this period occupies most of the time), the surface temperature of the heating roller 1 is maintained low (for example, 140℃), so the thermal effect on the bearing part 5 of the roller is reduced. Its durability can be maintained. At this time, the bearing portion 5 is maintained at 100°C.

The above embodiment is an example in which the temperature sensor of the heating roller is provided in the center of the heating roller, but FIG. 3 shows an example in which the temperature sensor is provided near the end bearing portion of the heating roller. A fan 10 is attached to the shaft end of the heating roller 1, and a sleeve 13 made of a material with good thermal conductivity is fixed.
A temperature sensor 3 is disposed close to the outer periphery of the temperature sensor 3 .

Now, when the heating roller 1 is rotated by a drive mechanism (not shown in FIG. 3) in synchronization with the recording operation,
The fan 10 also rotates and blows air in the direction indicated by the arrow. As a result, the temperature sensor 3 detects that the surface temperature of the sleeve 13 is low and lowers the output level.
As in the case of the embodiment shown in FIG. 2, the current flowing through the heater 1a is increased via the control circuit 4, the amount of heat generated by the heater 1a is increased, and the surface temperature of the heating roller 1 is raised.

Both of the above two embodiments utilize the cooling effect of a fan, but the present invention is not limited to such a cooling effect, and the present invention is not limited to such a cooling effect. Alternatively, it may be of a type that blocks heat transmitted from the heating roller to the temperature sensor by radiation action. In short, the present invention is basically characterized in that the level of the output signal of the temperature sensor is lowered prior to the fixing operation.

As explained above, in the present invention, the output signal level of the temperature sensor that detects the surface temperature of the heating roller is lowered prior to the fixing operation, so that the surface temperature of the heating roller increases during the fixing operation. After the fixing operation is completed, the output level is returned to the original level, so the surface temperature drops again, so the simple structure can reduce the effect of heat on the roller bearing and extend its life. be able to.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a conventional fixing device, FIG. 2 is a schematic diagram of an embodiment of the fixing device according to the present invention, and FIG. 3 is a schematic diagram of main parts of another embodiment of the fixing device according to the present invention. FIG. 1... heating roller, 2... pressure roller, 3...
Temperature sensor, 4... Control circuit, 5... Bearing section, 6, 9... Gear, 7... Motor, 8, 10...
...Fan, 11, 12... Drive gear, 13... Sleeve.

Claims (1)

[Claims] 1. A rotatable heating roller with a built-in heating source,
A recording medium having an unfixed toner image is passed between the heating roller and a pressure roller that rotates while being in pressure contact with the heating roller, and the toner image is fixed in a heating roller type fixing device that fixes the toner image on the recording medium. a non-contact type temperature detection means set to maintain the surface temperature of the heating roller within a temperature range insufficient to cause the temperature to rise, and energization to the heating source is controlled based on an output signal of the temperature detection means. The control means operates prior to the fixing operation by at least the two rollers, and cools the surrounding area including the temperature detection means, thereby apparently lowering the detected value of the temperature detection means, so that the heating source is kept energized for a long time. A heat roller type fixing device, characterized in that it has a cooling fan which is turned off after the fixing operation is completed, and the surface temperature of the heat roller is set to a temperature capable of fixing.