JPS6391682A - Fixing device - Google Patents

Abstract

PURPOSE:To minimize a capacity viewed from an overall heater and to save electricity by minimize the capacity of a heater for a fixing roller, relatively increasing the capacity of a heater for a pressurizing roller and permitting the heater for the pressurizing roller to share the heating of the outer periphery of the fixing roller. CONSTITUTION:The heater for the pressurizing roller 10 is disposed in the interior of the pressurizing roller 4 pressed against the fixing roller 3. The capacity of the heater for the pressurizing roller 10 is larger than that of the heater for the fixing roller 8. The capacity of the heater for the fixing roller 8 is minimized, but enough to secure the temperature at which the fixing roller can fix satisfactorily. If fixing work is repeated, the heat of the fixing roller 3 is taken away by a transfer sheet, and the temperature of the fixing roller gradually drops accordingly. Hence heat from the heating roller 4 is transmitted to the fixing roller 3, whose surface is instantaneously heated. Consequently the prescribed fixing temperature is maintained without fail.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a fixing device used in external recording devices such as copying machines, facsimile machines, printers, and the like. In particular, the fixing roller has a heater for the fixing roller inside the core part and an elastic body with a thickness of 1.5 or more on the outside of the core part, and the fixing roller that comes into contact with this fixing roller is heated by the heater for the pressure roller. The present invention relates to a fixing device including a pressure roller and a pressure roller in which the temperature of the perforating roller is controlled based on a temperature measuring element provided in a core metal portion.

Prior Art In the fixing device described above, both the fixing roller and the pressure roller are equipped with heaters, and each roller is individually heated by these heaters. Such fixing devices are mainly used in color electrostatic recording devices. In a color electrostatic recording device, heat fixing is performed with toners of different colors superimposed on the transfer paper, so heat is applied from the surface of the transfer paper (the surface on which the toner is placed), that is, by the fixing roller. This is because heating from the pressure roller side (back side of the transfer paper) is also required. When using regular toner to perform color recording by overlapping three or four colors of toner, the range that can be fixed in relation to the fixing roller temperature and pressure roller temperature is the area shown by the diagonal line in Figure 7, which is the zero pressure applied. It is understood that heating from the pressure roller side is a factor in determining the quality of fixing.

In addition, in the above-mentioned fixing device, in the case of local electrostatic recording, in which an elastic body such as Si (silicon) rubber is used as the fixing roller, color reproduction is particularly important for films for overhead projectors in order to improve color reproduction. In order to further improve translucency, a toner made of a polymer material that has a low molecular weight, a low softening temperature, and can be fixed in an atmosphere is used. As shown in FIG. 8B, this toner has a property of melting at a relatively low temperature compared to toner A for Teflon rollers, and has a narrow area called the rubber area where the mold releasability is not impaired. Therefore, a hard material such as Teflon cannot be used as the fixing roller, and an elastic body is used instead.

Furthermore, in the above fixing device, the thickness of the fixing roller is 1.5 mm.
A material using a thick elastic material of 1111 or more is used. As shown in FIG. 9, when a pressure roller 52 is brought into pressure contact with this type of fixing roller 51, the elastic body deforms into an arc shape as shown. When the transfer paper passes through this portion, the transfer paper is conveyed in a direction away from the fixing roller 51 as shown by arrow C and is automatically separated from the fixing roller. For this reason, there is no need to provide a separating means such as a separating claw for separating the transfer paper on the fixing roller. Thus, a thick elastic body is used for the fixing roller. In this case, 1. Normally, it would be useful to detect the temperature on the surface of the elastic body and control the temperature of the fixing roller based on this temperature, but if this method is adopted, the surface of the elastic body will not reach the desired fixation temperature. When the core metal reaches this temperature, it becomes overheated, exceeding the heat resistance temperature of the primer or elastic body in contact with it, and there is a risk that these will be destroyed. Therefore, in this type of fixing device using a thick elastic body, a temperature measuring element is generally provided in the core metal part, and the temperature of the fixing roller is controlled based on the temperature measurement result from the temperature measuring element.

As described above, the fixing roller and pressure roller are heated individually, the fixing roller is made of a thick elastic material, and the temperature of the fixing roller is controlled based on the temperature of the core metal part. The fixing device has a disadvantage in that it consumes a large amount of power because it uses two heaters.

Furthermore, conventionally, the temperature of the fixing roller (in other words, the surface temperature of the elastic body) is controlled only by the fixing roller heater based on the temperature of the core metal portion. Therefore, if the capacity of the heater for the fixing roller is small, even if the humidity of the core metal part is controlled to a predetermined temperature, the surface temperature of the elastic body will be inconveniently lower than the fixable temperature Ta as shown in C in FIG. 10. 0 In order to eliminate this inconvenience and improve the followability of the elastic body surface temperature to the core metal temperature, a large capacity heater for the fixing roller is required. The power consumption becomes even larger, which is uneconomical.

Purpose In view of the above points, it is an object of the present invention to save power while maintaining good fixing performance in a fixing device of the type described above.

Structure To achieve the above object, the present invention includes a fixing roller that has a heater for the fixing roller inside the core metal part and an elastic body with a thickness of 1.5 m or more outside the core metal part, and a fixing roller corresponding to the fixing roller. 1. A fixing device comprising a pressure roller heated by a pressure roller heater in contact with the fixing roller and controlling the temperature of the fixing roller based on a temperature measuring element provided in a core metal part, wherein electric power is applied to the pressure roller heater. The fixing device is characterized in that the electric power applied to the fixing roller heater is greater than the electric power applied to the fixing roller heater.

The present invention will be described below based on implementation sequences.

FIG. 1 is a side sectional view of one embodiment. In the figure, a transfer paper 2 carrying an unfixed toner image 1 is conveyed to a pressure contact portion between a fixing roller 3 rotating counterclockwise and a pressure roller 4 rotating clockwise, and passes through the waist. During this time, the sheet is heated and fixed, and is then discharged to the outside by a sheet discharge roller 5.

The fixing roller 3 has a core metal part 6 and an elastic body 7 made of Si rubber or the like and having a thickness of 2 to 4 cm, provided on the outside of the core metal part. A fixing port heater 8 is disposed inside the core metal portion 6 . The outer peripheral surface of the fixing roller 3 is connected to this heater 8.
However, the temperature is maintained at a predetermined temperature by a temperature control device (not shown), for example, a device that turns on/off power supply to the heater 8 . In this case, the temperature of the fixing roller 3, which serves as a reference for temperature control, is determined by a temperature measuring element 9 such as a thermistor provided on the core metal part 6, as shown in FIG.
It is extracted as the temperature of the core metal part.

In FIG. 1, a pressure roller 4 is pressed against a fixing roller 3.
The elastic body 7 of the fixing roller is made of a relatively hard material, such as Teflon or a rigid roller coated with a thin Si rubber of about 0.5 W, into which the elastic body 7 of the fixing roller can be pushed as shown in FIG. On the other hand, a pressure roller heater 10 is disposed inside the roller. The pressure roller 4 is heated by the heater 10, and further temperature-controlled based on temperature information from a temperature measuring element 11 provided on its outer periphery.

Note that the oil 13 in the oil tank 12 is applied to the felt 1.
4, oil supply roller 15, and oil application roller 1
6 to the surface of the fixing roller 3, and on the surface -
This prevents toner offset. A separation claw 17 provided on the right side of the pressure roller 4 separates the transfer paper from the pressure roller 4 when the transfer paper is in close contact with the pressure roller 4 .

In this embodiment, the capacity of the pressure roller heater 10 is larger than the capacity of the fixing roller heater 8. The capacity of the fixing roller heater 8 is kept as small as possible, although it is the minimum required capacity to ensure a sufficient temperature of the fixing roller to perform a good fixing operation. By configuring both heaters 10.8 in this manner, when the fixing operation is repeated, the heat of the fixing roller 3 is absorbed by the transfer paper, and the temperature of the fixing roller gradually decreases. At this time, since the capacity of the fixing roller heater 8 is kept small as described above, the surface of the fixing roller 3 cannot be quickly reheated by the heater 8. However, instead of this, since the capacity of the pressure roller heater 10 is increased as described above, the heat from the heating roller 4 is transmitted to the fixing roller 3, and the surface of the fixing roller 3 is immediately heated. A predetermined fixing temperature is always maintained.

In this way, by slightly increasing the capacity of the pressure roller heater IO and sharing the heating of the fixing roller 3 without making the heating roller heater 8 needlessly large in capacity, both heaters 8, 10 The total heater capacity can be kept low, and the fuser roller heater 8 can be used efficiently (if this heater has a large capacity, on/off temperature control will be performed frequently, and the As a result, power saving is achieved and it is economical.

Note that this fixing device uses thick Si rubber with poor thermal response as the fixing roller, so when paper is continuously passed through this fixing device, the temperature of the core bar 6 is controlled. Although the set temperature is always maintained, the surface temperature of the Si rubber decreases as the paper passes through the paper. In this case, for example, as shown in FIG. 3, when the surface temperature of the fixing roller decreases from 160C to 135C, the roller temperature decreases as shown in FIG. It has come off and is no longer able to be properly fixed. As a way to prevent this, as shown at point C in Figure 7, the set temperature of the pressure roller 4 is changed from 160C to 180C, and when several sheets of transfer paper are passed through and the roller temperature state drops to a steady state, However, there is a method in which the temperature of the roller remains within the fixable range. However, in this method, the temperature of the fixing roller hardly decreases during the first one or two sheet fixing operations, and there is a risk that hot offset may occur at point C in FIG.

In order to eliminate the above-mentioned inconveniences during continuous paper passing, the core metal part of the fixing roller is controlled to a constant 180C as shown in the flowchart of Fig. 4a, and the core part of the fixing roller is controlled to be constant at 180C as shown in the flowchart of Fig. 4b. The set temperature of the pressure roller at 08 o'clock) is set higher than the set temperature at standby (in the example, 1
(Raised from 60C to 180C). By doing so, it is possible to prevent offset and poor fixing for all transfer papers and obtain good fixed images.

(Example) (1) Fixing roller: A core metal having a diameter of 311111 mm was coated with Si rubber having a thickness of 31 cm to give a diameter of 40 mm.

Pressure roller: At diameter 40cm was coated with 20μ Teflon.

Fixing oil: KF-96300C8 (manufactured by Shin-Etsu Chemical Co., Ltd.) Fixing roller heater: 400W Pressure roller heater: 400W Fixing roller core metal part setting temperature: 180C Pressure roller setting temperature: 160r Under the above conditions, color A4 size paper transfer paper carrying toner was passed through at a rate of 18 sheets/min. The roller temperature distribution at 6 o'clock was as shown in Figure 5.

At this fixing and pressure roller temperature, fixing is impossible as shown at point E in FIG.

(2) When the fixing roller heater was set to 300 W s, the pressure roller heater was set to 500 W, and the other conditions were the same as in Example (1), a temperature distribution as shown in FIG. 6 was obtained. This state was as indicated by the dots in FIG. 7, and there was no problem with fixing.

In this case, the total heater capacity is the same as in the previous example (1) < s
By effectively utilizing the pressure roller heater, which has a relatively large capacity, normal fixing was made possible. As a result, it was possible to achieve one power saving without using a large-capacity heater for the fixing roller.

Effects According to the present invention, the capacity of the heater for the fixing roller is kept to the minimum necessary, the capacity of the heater for the pressure roller is made relatively large, and the outer peripheral surface of the fixing roller is heated by the heater for the pressure roller as well. I shared it. This made it possible to keep the capacity of the heater as a whole low, thereby achieving overall power savings.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of one embodiment, FIG. 2 is a perspective view of main parts of the fixing roller, FIG. 3 is a graph showing changes in roller temperature distribution over time, and FIGS. 4a and 4b are temperature control of the roller. A flowchart showing an example, Figures 5 and 6 are graphs showing the results of an experimental example of roller temperature changes, Figure 7 is a graph showing fixing possibility with respect to roller temperature 1 Figure 8 shows toner melting characteristics FIG. 9 is a graph showing the pressure contact state of the fixing and pressure rollers, and FIG. 10 is a graph showing the temperature drop on the surface of the fixing roller. 6...Core metal part, 8...Fixing roller heater, 7...
・Elastic body, 3... Fixing roller, 10... Heater for pressure roller 14°°° Pressure roller 9... Temperature measuring element Figure 3 Time pressure roller temperature ('C) Figure 5 7. 6th illustration koshi ichihoki ku sunha ku 10 sunko

Claims (2)

[Claims] (1) A fixing roller with a heater for the fixing roller inside the core metal part and an elastic body with a thickness of 1.5 mm or more on the outside of the core metal part, and a heater for the pressure roller that comes into contact with this fixing roller. In the fixing device, the temperature of the fixing roller is controlled based on a temperature measuring element provided in a core metal part, and the fixing roller is heated by applying electric power to the heater for the pressure roller. A fixing device characterized in that the electric power applied to the heater is greater than the electric power applied to the heater. (2) The fixing device according to claim 1, wherein the set temperature of the pressure roller during paper passing is higher than the set temperature of the pressure roller during standby.