JPS6236224B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a contact heating type roller fixing device.
In particular, it relates to improving the accuracy of temperature control.

This type of heating control is performed by bringing a thermistor into contact with the heating roller, but due to poor contact, the heating roller may be heated abnormally, causing damage to the bearing portion or other accidents. The present invention eliminates these drawbacks.

An object of the present invention is to accurately detect the temperature of a heating roller and improve temperature control accuracy.

In order to achieve this object, the present invention provides a contact heating type roller fixing device that fuses a toner image by bringing the toner image into contact with a heating roller and passing it through. A temperature detecting element, a member disposed on the front side of the detecting element with respect to the rotational direction of the heating roller and scraping the surface of the heating roller in contact with the heating roller surface, and disposing the detecting element within the area scraped by the scraping member. This is a contact heating type roller fixing device characterized by improved temperature control accuracy.

First, an example of a contact heating type roller fixing device to be applied will be described with reference to FIG. 1. 1 is a copying drum;
A toner image is formed on the surface by various well-known means such as charging, exposure, and development, which are arranged sequentially in the circumferential direction and are omitted in the drawing, and then rotated to the transfer position T. Copy paper P fed from a paper feeding device (not shown) is moved at a constant speed to the circumferential speed of copying drum 1 by timing rollers 21 and 22, and then passes through guides 31 and 32 to copy drum 1.
The toner image is transferred thereto until it is separated by the action of the separation belt 15 or other means at the position of the separation rollers 4, 4A, 4B while being in close contact with the drum surface.

After the copy paper is subjected to a corona effect from the separation roller 4 by the static eliminating charger 5, it is sent between the heating roller 8 and the pressure roller 9 via a guide 6 and a guide plate 7, each having a comb-shaped cross section, to heat the toner image. The sheet is fixed and guided by claw-like guides 10 and 11, and then discharged onto rollers 12,
13 and sent out of the machine from the discharge port 14.
16 is a transfer corona charger; 17 is a tilting shaft for separating the fixing unit U from the copying drum 1; 18;
19 is a fastener for that purpose.

The heat fixing device consisting of the heating roller 8 and the pressure roller 9 uses a thermistor to detect the temperature of the heating roller 8, and turns on or off the heat source in the heating roller depending on the temperature difference from a specified temperature. Controls the temperature of the heating roller surface.

Next, preferred thermistors for implementing the present invention will be described. Thermistors used in thermal fixing devices must not be damaged when the copy paper is jammed and must be positioned correctly on the surface of the heating roller. Conventionally, the thermistor element is housed in a box, and this box is connected to the thermal insulator. It is pressed against the heating roller with a springy member.

On the other hand, the heating roller 8 is coated with an anti-offset liquid such as silicone oil using a coating material 20 in order to prevent the toner-adhered copy paper from wrapping around. When the temperature exceeds 200 degrees Celsius, this oil evaporates violently and produces smoke, which is undesirable from the viewpoint of consumption and aesthetics. Also, 0.3mm on the metal roller
For example, when the surface temperature is 220℃, the core metal temperature at the interface is calculated to be about 270℃, which has a negative effect on the bearing and other parts.

Therefore, as shown in the second diagram, the thermistor element 10
1A is covered with a spherical glass 110 with a diameter of about 1.6 mm, and a lead wire 106 of Teflon-coated nickel stranded wire is attached.
and protect the connected portion with a heat-resistant insulating adhesive 105. Support plate 104A such as stainless steel plate in Fig. 3
Pass the lead wire 106 through the hole 107 of the element 101A.
is brought into direct contact with the surface of the heating roller 8 through the glass coating 110.

The above configuration reduces the heat capacity, and the temperature difference range is 1°C or less for a set temperature of 180°C, which is extremely superior compared to the conventional example.

The Teflon-coated nickel lead wire 106 and the stainless steel support plate 104A are not affected by heat at all at an ambient temperature of about 210°C. Since the thermistor unit is installed on the relief side in the rotation direction of the heating roller,
Even when the force of the jam paper is applied, it easily escapes, and when the paper is removed, the elasticity of the support plate 104A makes it easy to make a predetermined contact again.

FIG. 3 is a perspective view of such a thermistor set on a heating roller.

Since the thermistor element is in a nearly bare state as described above, there appears to be a risk of damage if a screwdriver or the like is dropped during operation, but the upper part is protected by the top cover 24 shown in the first figure.

Note that the heating roller 8 may If there is a possibility that the response to the surface temperature of the
In order to eliminate the influence of air convection, a box-shaped enclosure member 111 shown in FIGS. 4 and 5 may be provided. When the lower edge 111A of this enclosing member 111 is brought into contact with the heating roller 8 and the excess offset liquid applied with the coating material 20, such as felt, is wiped off, the thermistor comes into contact with the clean surface, thereby controlling the temperature. Improve accuracy. In this sense, it is possible to arrange the thermistor 110 within the area l scraped by the guide claw 10 of FIG. 1 as shown in FIG. 3.

Since the thermistor is protected as described above, there is no risk of damage even if it is used naked. Even if it were to be damaged, the resistance of the thermistor section would be O, and therefore the detected temperature would be ∞°C, and the heat source would remain off in the event of a short circuit. When the thermistor is open, it is detected that the resistance at both ends of the lead wire is ∞, allowing safety design on the electrical circuit side.

In the present invention, since the temperature sensing element 110 is provided on the clean scraped surface of the heating roller, accurate sensing can be performed.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view showing an example of a contact heating type roller fuser unit, FIG. 2 is a partially cutaway side view of a thermistor suitable for implementing the present invention, and FIG. 3 is a diagram showing how the thermistor is set on a heating roller. FIG. 4 is a longitudinal sectional view of the thermistor provided with a surrounding member, and FIG. 5 is a perspective view of the surrounding member. 8 is a heating roller, 9 is a pressure roller, 111 is a surrounding member, l is a scraped area, and 101 is a thermistor element.

Claims (1)

[Claims] 1. In a contact heating type roller fixing device that fuses the toner image by bringing the toner image into contact with a heating roller and passing it through, the roller surface temperature is detected by contacting the heating roller. a sensing element, a member located upstream of the sensing element with respect to the heating roller rotational direction to contact and scrape the heating roller surface, and a member located downstream of the heating roller surface with respect to the heating roller rotational direction to prevent offset on the heating roller surface. 1. A contact heating type roller fixing device, comprising means for applying a liquid, and the detection element is disposed within an area scraped by the scraping member to improve temperature control accuracy.