JPH06130845A - Fixing device for copying machine - Google Patents

Abstract

PURPOSE:To eliminate the insufficient elevation of a temperature at both end parts of a fixing roll without impairing the temperature elevation of the fixing roll at the time of warming up. CONSTITUTION:In this fixing device for a copying machine composed of the fixing roll 1 constituted thin in thickness, with a small heat capacity and having the insertion of a bar-like heater inside and a pressure roll 9 in pressurized-and rotated-contact with the fixing roll 1, a constitution is adopted both end parts of the fixing roll 1 are closed with end plates 6 and simultaneously surface like heaters 7 are provided on the inside surfaces of the end plates 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device of a copying machine for heating and fixing a toner image transferred on a copy sheet with a heated fixing roll.

[0002]

2. Description of the Related Art The above-mentioned fixing device comprises a fixing roll having a heater therein, and a pressure roll for pressure-contacting the fixing roll. Both rolls are made of a metal tube so as to have a predetermined strength, and an offset prevention layer for preventing offset of the toner image is attached to the surface thereof. In this type of predetermined device, the time from when the power of the heater is turned on to when the fixing roll can be heated enough to start fixing, that is, the warming-up time is short, and the temperature distribution in the longitudinal direction of the fixing roll is large. Is preferably uniform.

As a conventional example, a fixing device as disclosed in Japanese Utility Model Publication No. 61-4926 is known to meet such technical requirements. The configuration of this conventional example is as shown in FIG. 1, in which the sleeve a of the fixing roll is made thin with a small heat capacity, and both ends thereof are closed by end plates b and c, and the inside thereof is formed. A heater d is provided through the both end plates b and c. The fixing roll a
The inner side of the inner frame f is an inner frame f supported by support bars e on both end plates b and c.
Supported by. Thermal insulators g and h are interposed between the end plates b and c and the inner frame f and the inner surface of the sleeve a. i is an offset prevention layer.

[0004]

In the above-mentioned conventional fixing roll, since the sleeve a is made of a thin material having a small heat capacity, the heat from the heater d is applied to the surface of the sleeve a in a short time. Moreover, since the heat of the sleeve a is hard to be transferred to the end plates b, c and the inner frame f by the heat insulators g, h,
Although the warm-up time in the fixing roll can be shortened, there was a problem in the temperature distribution in the longitudinal direction immediately after the warm-up was completed.

That is, since the sleeve a of the fixing roll is made of a thin material having a small heat capacity, the heating of the heater a by the heater d is fast, but the temperature rise at both ends of the sleeve is delayed from the central part. Since the amount of heat radiated at both ends is larger than that at the center, the temperature rise at both ends may be insufficient immediately after the warm-up is completed. May occur. This was especially large in the case of copy paper of large size such as A3.

The present invention has been made in view of the above, and it is possible to eliminate the insufficient temperature rise at both ends of the fixing roll without deteriorating the temperature rising rate of the fixing roll during warming up, and fixing at the completion of warming up. An object of the present invention is to provide a fixing device for a copying machine in which the temperature of the end portion of the roll becomes equal to or higher than the fixing temperature and the fixing failure does not occur at the end portion of the large-sized copy paper in the morning. is there.

[0007]

In order to achieve the above object, a fixing device for a copying machine according to the present invention has a small heat capacity and a thin wall, and a fixing roll having a rod-shaped heater inside thereof. 1 and a pressure roll 9 that is pressure-rolled to the fixing roll 1 in a fixing device of a copying machine,
Both ends of the fixing roll 1 are closed by end plates 6, and a planar heater 7 is provided on the inner surface of the end plate 6.

[0008]

[Operation] The central portion of the fixing roll 1 is heated by the rod-shaped heater 4, and both ends thereof are heated by the rod-shaped heater 4 and the planar heater 7 provided on the end plate 6. It

[0009]

EXAMPLE An example of the present invention will be described with reference to FIG. In the figure, 1 is a fixing roll having a small heat capacity and made of a thin member, and both ends of the fixing roll 1 are bearing members 2
It is supported by the machine frame 3 via a and 2b, and is rotationally driven by a drive device (not shown). Four
Is a rod-shaped heater that is inserted into the fixing roll 1, and both ends of the heater are supported by the machine frame 3 via brackets 5a and 5b. An offset prevention layer (not shown) is applied to the outer surface of the sleeve 1.

Both ends of the fixing roll 1 are closed by end plates 6, and a planar heater 7 is attached to the inner surface of the end plate 6. Reference numeral 8 indicates the temperature of the outer surface of the fixing roll 1. It is a temperature sensor for detecting. Reference numeral 9 is a pressure roll that is in contact with the fixing roll 1, and 10 is a copy sheet.

In the above structure, the heaters 4 and 7 of the fixing device are turned on and heated, whereby the fixing roll 1 is heated by the rod-shaped heater 4 along its longitudinal direction, and both ends are heated. The portion is heated by a planar heater 7 attached to the inside of the end plate 6.
As a result, both end portions of the fixing roll 1 are heated by both the heaters 4 and 7, and the both end portions are heated without delaying to the central portion, and when the warming-up is completed, it is necessary and sufficient together with the central portion. It has become a temperature.

FIG. 3 shows the temperature distribution of the surface of the fixing roll in the longitudinal direction during warming up of the fixing roll 1. In the figure, A is a conventional technique, B is an embodiment of the present invention, and C is a C. Is the fixing temperature. As is apparent from this figure, in the case of the conventional technique, the temperature at both ends of the fixing roll was not raised to the fixing temperature, whereas in the embodiment of the present invention, a large size such as A3 is used. The temperature of both ends corresponding to the copy sheet width L is raised to the fixing temperature C or higher.

[0013]

According to the present invention, the temperature deficiency at both ends of the fixing roll can be eliminated without impairing the temperature rise of the fixing roll during warming up, and the temperature of the end of the fixing roll at the time of completion of warming up can be improved. When the temperature is higher than the fixing temperature, it is possible to prevent the occurrence of defective fixing at the end of a large-sized copy sheet in the morning copy.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a conventional example.

FIG. 2 is a sectional view showing an embodiment of the present invention.

FIG. 3 is a diagram showing a sleeve surface temperature with respect to a sleeve longitudinal direction of a fixing roll during warming up.

[Explanation of symbols]

1 ... Fusing roll, 2a, 2b ... Bearing member, 3 ... Machine frame,
4, 7 ... Heater, 5a, 5b ... Bracket, 6 ... End plate, 8 ... Temperature sensor, 9 ... Pressure roll, 10 ... Copy paper.

Claims (1)

[Claims] 1. A fixing roll 1 having a small heat capacity and a thin wall, and having a rod-shaped heater 4 inserted therein.
In the fixing device of the copying machine, which is composed of the pressure roller 9 and the pressure roller 9 that is pressure-rolled to the fixing roller 1, both end portions of the fixing roller 1 are closed by the end plates 6 and the inner surface of the end plate 6 has a planar shape A fixing device for a copying machine, characterized in that the heater 7 is provided.