JPS63169680A - Fixing device - Google Patents

Abstract

PURPOSE:To supply heat of a sufficient quantity of heat from a curved surface of a heat transfer member to a thermal fuse to quickly raise the temp. of the fuse by pressing the heat transfer member which has the curved surface conforming to the outside peripheral face of a fixing roller, contains a temp. switch and has large heat conductivity to the fixing roller. CONSTITUTION:The curved face 16a of the heat transfer member 16 conforming to the outside circumference of the fixing roller 1 is pressed to the outside circumference of the fixing roller 1 by a leaf spring 20 fixed to a chassis 19. The heat transfer member 16 contg. the thermal fuse 5 consists of an aluminum block having the large heat conductivity and the curved surface 16 is subjected to 'Teflon(R)' coating or is attached with a polyimide sheet. The formation of the member 16 of a 'Teflon(R)' resin is equally satisfactory. The curved surface 16a is preferably colored black. The sufficient quantity of the heat is thereby supplied from the curved surface 16a to the thermal fuse 5, by which the temp. thereof is quickly increased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a fixing device that fuses a powder image formed on a recording paper to the recording paper by heating it.

2. Description of the Related Art Conventionally, electrophotographic apparatuses have generally used a fixing device that fixes a powder image onto recording paper by heating. Such a fixing device requires precise temperature control and also requires a safety device to prevent the fixing device from reaching an abnormal temperature.

FIG. 7 is a circuit diagram of a general fixing device, in which 1 is a pipe-shaped fixing roller, 2 is a halogen heater disposed inside the fixing roller 1, 3 is an AC power supply that supplies current to the halogen heater 2, 4 is a switch, 5 is a temperature fuse that is placed near the fixing roller 1 and blows when the temperature around the fixing roller 1 reaches a high temperature, 6 is a thermistor that is placed in contact with the fixing roller 1, and 7 is a thermistor from the thermistor 6. A temperature adjustment circuit for controlling the halogen heater 2 and keeping the temperature constant according to the sent temperature data; 8 is a control circuit; 9, 10, 11, and 12 are lines connecting the AC power source 3 and the halogen heater 2.

FIG. 8 is a sectional view of a main part of a conventional fixing device, and 13 is a bearing that supports the outer periphery of the fixing roller 1. As shown in FIG. The temperature fuse 5 is arranged at a certain distance from the surface of the fixing roller 1.

Regarding the conventional fixing device configured as described above, temperature control thereof will be described below.

The control circuit 8 outputs a signal in accordance with the temperature data sent from the thermistor 6, and the temperature adjustment circuit 7 repeatedly turns on and off the switch 4 in accordance with this signal, thereby controlling the temperature of the halogen heater 2 to be kept constant.

Further, if the halogen heater 2 reaches a temperature higher than the fixing temperature due to some abnormality, the temperature fuse 5 is blown by this high temperature and the supply of current to the halogen heater 2 is cut off.

Problems to be Solved by the Invention However, in the above-mentioned conventional configuration, the temperature fuse 5 is arranged at a certain distance from the surface of the fixing roller 1, and the temperature fuse 5 is separated from the surface of the fixing roller 1 by radiated heat and air. When the temperature fuse 5 melts at a certain temperature, the surface of the fixing roller 1 may reach a higher temperature, and the surface of the fixing roller 1 may reach a higher temperature.
There was a problem in that it could be damaged.

Means for Solving the Problems The present invention has a heat transfer member having a curved surface along the outer peripheral surface of the fixing roller and having a high thermal conductivity and supporting a temperature switch inside, which is brought into contact with the fixing roller. It is.

Effect: With the above configuration, a sufficient amount of heat is supplied from the curved surface, and the temperature of the temperature fuse increases rapidly.

Embodiment A fixing device in an embodiment of the present invention will be described below.

The circuit diagram of the fixing device of this embodiment has the same configuration as that shown in FIG. 7, and therefore its explanation will be omitted.

FIG. 2 is a perspective view of the main parts of the fixing device in this embodiment, in which 14 is a gear that rotates together with the fixing roller 1, 15 is a drive gear driven by a motor (not shown), and 16 has an internal temperature fuse 5 as shown in Figure 1.
17 is a recording medium, and 18 is an elastic member 18 around a metal shaft 18a.
b is a pressure roller which is arranged to sandwich the recording medium 17 together with the fixing roller 1.

FIG. 3 is a perspective view of the main parts of the fixing device of this embodiment, and is 19
2 is a chassis, and 20 is a plate fixed to the chassis 19 and urging the heat transfer member 16 toward the fixing roller l.

The heat transfer member 16 has a curved surface 16 along the outer circumference of the fixing roller 1.
a, and the curved surface 16a is in contact with the outer periphery of the fixing roller 1.

In this embodiment, by providing the heat transfer member 16 with a curved surface along the outer circumference of the fixing roller 1 and bringing it into contact with the outer circumference of the fixing roller 1, a sufficiently larger amount of heat is transferred than the outer circumference of the fixing roller 1, and the temperature By holding the fuse 5 inside the heat transfer member 16 made of a material with high thermal conductivity, the amount of heat conduction is also large (as a result, the reaction speed of the temperature fuse 5 can be increased, and the fixing roller Damage caused by abnormal heat rise in step 1 can be prevented.

Note that although an aluminum block was used as the heat transfer member in this example, it may also be made of Teflon resin.
In this case, damage to the surface of the fixing roller can be prevented. Further, even when an aluminum block is used as in this embodiment, damage to the surface of the fixing roller can be prevented by coating the curved surface in contact with the fixing roller with Teflon coating or applying a polyimide sheet. At this time, as shown in Figure 4, a higher heat transfer coefficient can be obtained by forming a black Teflon coating 21 or by applying a black colored polyimide sheet. The reaction speed can be further accelerated.

Hereinafter, in the fixing device of this embodiment, the relationship between the temperature rise of the outer periphery of the fixing roller and the temperature rise of the temperature fuse will be explained using graphs of experimental results shown in FIGS. 5 and 6.

Figure 5 shows the temperature change when a halogen heater with an output of 600 W is placed inside an aluminum fixing roller with a wall thickness of 2 mm, and heating is performed at an outside temperature of 25°C. The vertical axis is the temperature, and the horizontal axis is the temperature. The axis is time, A1 is the temperature change around the outer circumference of the fixing roller, and B1 is 4 m from the fixing roller as explained in the conventional example.
C1 is the change in temperature of the temperature fuse when the temperature fuses are placed at positions m apart from each other, C1 is the change in temperature of the temperature fuse when aluminum heat transfer members are used as explained in this example, and Dl is the change in temperature of the fixing roller. This figure shows the temperature change of the temperature fuse when using a heat transfer member whose surface that comes in contact with is black. All temperature fuses are rated at 196℃±1
．． A temperature of 67°C was used.

First, the temperature fuse arranged as shown in the conventional example was blown out 108 seconds after heating started, but at this time the surface of the fixing roller had risen to 500 degrees Celsius, and the resin around the fixing roller was melted. did.

Next, when an aluminum heat transfer member was used, the temperature fuse was blown out after 60 seconds, and the temperature around the fixing roller reached 285° C., but no melting of the resin around the fixing roller was observed.

Next, when a heat transfer member whose part was black was used, the temperature fuse was blown out after 58 seconds, and the temperature at the outer periphery of the fixing roller reached 270°C.

Figure 6 shows the above experiment conducted at an outside temperature of 0°C, where the vertical axis is temperature, the horizontal axis is time, A2 is the temperature change around the outer circumference of the fixing roller, and B2 is the temperature change from the fixing roller as explained in the conventional example. The temperature change of the temperature fuse when the temperature fuses are placed 4 mm apart, C2 is the temperature change of the temperature fuse when an aluminum heat transfer member is used as explained in this example, and B2 is the temperature change of the fixing roller. This figure shows the temperature change of the temperature fuse when using a heat transfer member whose surface that comes in contact with is black.

First, the temperature fuse arranged as shown in the conventional example was blown out 132 seconds after the start of heating, but at this time the temperature of the surface of the fixing roller rose to 580°C.

Next, when an aluminum heat transfer member was used, the temperature fuse was blown out after 65 seconds, and the temperature at the outer periphery of the fixing roller reached 305°C.

Next, when a heat transfer member whose part was black was used, the temperature fuse was blown out after 62 seconds, and the temperature at the outer periphery of the fixing roller reached 285°C.

As is clear from this experiment, in the conventional configuration, after the surface of the fixing roller reaches 200°C, it takes 68 seconds for temperature change B1 and 89 seconds for temperature change B2 until the temperature fuse blows.
In contrast, in the configuration of this embodiment, it takes 20 seconds for temperature change C1 and 22 seconds for temperature change C2, which is 40 seconds each.
2 seconds and 67 seconds, allowing for faster reaction speed.
This prevents damage to the fixing roller.

In addition, when using a heat transfer member with a part black, it takes 18 seconds for temperature change D1 and 19 seconds for temperature change D2 from the time when the surface of the fixing roller reaches 200°C until the temperature fuse blows out. Even faster reaction rates can be obtained.

Effects of the Invention The present invention has a curved surface along the outer peripheral surface of the fixing roller, and a thermally conductive member with high thermal conductivity that supports a temperature switch inside is brought into contact with the fixing roller. Since a sufficient amount of heat is supplied and the humidity of the temperature fuse increases rapidly, □ a fast reaction speed can be obtained and damage to the fixing roller can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of a fixing device in one embodiment of the present invention, FIG. 2 is a perspective view of the same, FIG. 3 is a perspective view of the main part, and FIG. 4 is a main part of a fixing device in another embodiment. Part 1? -1,! figure,
5 and 6 are graphs showing experimental results, FIG. 7 is a circuit diagram of a general fixing device, and FIG. 8 is a sectional view of the main part of a conventional fixing device. 1... Fixing roller, 3... AC power supply, 5
... Temperature fuse, 16 ... Heat transfer member, 16
a...Surface Agent's name Patent attorney Toshio Nakao and one other person IC・-卆-It-1jtepshiX I6a,・-Sze9Δ Figure 4 @ 5 Figure 6

Claims (5)

[Claims] (1) A fixing roller having a heating element inside, a power source for supplying current to the heating element, and a fixing roller provided in the middle of a line leading from the power source to the heating element and close to the outer peripheral surface of the fixing roller. a temperature switch disposed at a position to cut off the line in accordance with the temperature of the fixing roller;
A fixing device characterized in that a heat transfer member having a high thermal conductivity and having a curved surface along an outer peripheral surface of the fixing roller and supporting the temperature switch inside is brought into contact with the fixing roller. (2) The fixing device according to claim 1, wherein the heat transfer member is formed of an aluminum block, and the curved surface in contact with the fixing roller is coated with Teflon. (3) The fixing device according to claim 1, wherein the heat transfer member is formed of an aluminum block, and a polyimide sheet is attached to the curved surface in contact with the fixing roller. (4) The fixing device according to claim 1, wherein the heat transfer member is made of Teflon resin. (5) The fixing device according to claim 1, wherein the curved surface of the heat transfer member that contacts the fixing roller is colored black.