JPH06318002A - Fixing device - Google Patents

Abstract

PURPOSE:To eliminate the malfunction of a temperature fuse and to enhance safety. CONSTITUTION:This device is provided with a fixing roller 15 including a heater 17, a pressing roller 16 turnably press-contacting with the roller 15, and the temperature fuse 24 provided near the surface of the roller 15 and preventing the temperature of the roller 15 from abnormally rising; and unfixed toner on a sheet is thermally melted to be fixed at a nip formed by the rollers 16 and 15 in this device. It is provided with a supporting base 25 in which the fuse 24 is assembled and the place in the vicinity of the assembling position of the fuse 24 is formed concentric with the roller 15.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a copying machine, a facsimile,
The present invention relates to a fixing device used in an image forming apparatus such as a printer.

[0002]

2. Description of the Related Art Conventionally, a heat roller fixing device has a fixing roller having a built-in heater and a pressure roller rotatably pressed against the fixing roller, and a temperature control circuit controls energization of the heater. Then, the surface temperature of the fixing roller is controlled to a constant temperature, and the unfixed toner on the sheet is fused by heat at the nip portion formed by the pressure roller and the fixing roller to be fixed on the sheet.

Further, the thermal roller fixing device is generally provided with a temperature fuse as a safety device at a position having a certain gap with respect to the surface of the fixing roller. It operates when the surface temperature rises abnormally and cuts off the power supply to the heater. As shown in FIG. 4, the mounting method of the thermal fuse is such that the thermal fuse 1 is covered with an insulating tube 2 and is supported by a bracket 3 made of sheet metal, and the bracket 3 is attached to a stay 4 provided between both side plates of the fixing device. It is generally supported by.

Further, in recent years, the heat roller fixing device is divided into upper and lower parts of the frame so that the components can be easily assembled.
It has been proposed that the serviceability of replacement parts is improved. Further, it has been proposed that the design concept of the fixing device is developed and the upper and lower frames of the fixing device are made of resin to reduce the number of parts and further improve the assembling property and reduce the cost.

[0005]

In the above fixing device, since the frame is divided into two parts, the thermal fuse 1
As compared with the above-described fixing device in which the sheet metal bracket 3 is supported by the sheet metal bracket 3, there is a drawback in that it is difficult to obtain the positional accuracy between the components during assembly. In particular, in the fixing device, since the upper and lower frames are made of resin, the precision is lower than that of the conventional fixing device due to the influence of warpage during molding of the frame.

Therefore, in the above-mentioned fixing device, it is difficult to control the gap between the fixing roller and the thermal fuse, which causes a problem in safety. That is, the gap between the fixing roller and the thermal fuse does not operate when the surface temperature control of the fixing roller by the temperature control circuit is normal, and becomes short when the surface temperature control of the fixing roller by the temperature control circuit becomes abnormal. It is desirable to operate in time. However, if the gap between the fixing roller and the temperature fuse is not normal and is too small, the temperature fuse malfunctions.If the gap between the fixing roller and the temperature fuse is too large, the fixing roller is overheated and the fixing device is overheated. There is a risk of smoke and ignition.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the above-mentioned drawbacks and to provide a fixing device capable of eliminating malfunction of a thermal fuse and having high safety.

[0008]

In order to achieve the above object, the invention according to claim 1 is a fixing roller having a built-in heater, a pressure roller rotatably pressed against the fixing roller, and the fixing roller. A temperature fuse is provided near the surface of the roller to prevent an abnormal temperature rise of the fixing roller, and heats unfixed toner on the sheet at a nip portion formed by the pressure roller and the fixing roller. In a fixing device for melting and fixing to a sheet, the temperature fuse is mounted, and a support base is provided in the vicinity of the mounting position of the temperature fuse in a concentric circle with respect to the mounting position of the fixing roller.

According to a second aspect of the present invention, in the fixing device according to the first aspect, the connection portion of the thermal fuse and the harness is arranged so that the thermal fuse is pressed against the support base when the thermal fuse is assembled. And a step is provided on the support base.

The invention according to claim 3 is the invention according to claim 1 or 2.
In the fixing device described above, the support base is made of an insulating material.

According to a fourth aspect of the present invention, in the fixing device according to the first, second or third aspect, the fixing device frame is made of an insulating resin and the fixing device frame and the support base are integrally molded. Is.

The invention according to claim 5 is the invention as claimed in claims 1, 2, and 3.
Alternatively, in the fixing device described in item 4, a member for preventing rotation of the thermal fuse is provided in the vicinity of a connecting portion between the thermal fuse and the harness.

[0013]

According to the first aspect of the invention, the support base is formed concentrically with respect to the mounting position of the thermal fuse in the vicinity of the mounting position of the thermal fuse, so that even if the thermal fuse is mounted with a slight deviation, the fixing roller and the thermal fuse will not work. The gap between is properly maintained. For this reason, the temperature fuse performs proper operation without malfunctioning, and the safety is enhanced.

According to a second aspect of the invention, in the fixing device according to the first aspect, a step is provided between the connection portion of the thermal fuse and the harness and the support base, and the thermal fuse is attached to the support base when the thermal fuse is assembled. The gap between the fixing roller and the thermal fuse is properly maintained by being pressed.

According to a third aspect of the invention, in the fixing device according to the first or second aspect, the support base is made of an insulating material, and it is not necessary to cover the thermal fuse with an insulating tube, so that the response of the thermal fuse is improved. It becomes faster and can secure safety.

According to a fourth aspect of the invention, in the fixing device according to the first, second or third aspect, the fixing device frame is made of an insulating resin, and the fixing device frame and the support base are integrally molded, and the fixing roller is fixed. The gap between the thermal fuse and the thermal fuse can be maintained more appropriately, and the cost can be reduced.

According to the invention of claim 5, claims 1, 2,
In the fixing device described in 3 or 4, a member for preventing rotation of the thermal fuse is provided in the vicinity of the connection portion between the thermal fuse and the harness, so that the gap between the fixing roller and the thermal fuse can be maintained more appropriately.

[0018]

FIG. 1 shows an embodiment of the present invention. Sheet 1 having unfixed toner in an image forming apparatus such as a copying machine
1 is conveyed from the transfer section to the heat roller fixing device 12 of the present embodiment and guided by the entrance guide plates 13 and 14, and is fixed by the fixing roller 15 and the pressure roller 16 rotatably pressed against the fixing roller 15. It passes through the nip formed. At this time, the sheet 11 is sandwiched between the fixing roller 15 and the pressure roller 16, and the unfixed toner 11 a on the sheet 11 is thermally melted by the fixing roller 15 and fixed on the sheet 11.

Here, the fixing roller 11 is heated by a heater 17 incorporated therein, and a temperature detecting element 18 composed of a thermistor is brought into contact with the surface of the fixing roller 15 at a constant pressure so that the surface temperature of the fixing roller 15 is increased. To detect. A temperature control circuit (not shown) controls the energization of the heater 17 based on the temperature detection signal from the thermistor 18 so that the surface temperature of the fixing roller 15 becomes a constant temperature.
Is rotationally driven by the drive unit. The thermal fuse 24 is
The heater 17 is provided so as to open and close the energization path and is normally closed. When the temperature control circuit runs away and the surface temperature of the fixing roller 15 rises abnormally, the heater 17 is energized to open. To cut.

The separating claw 19 is arranged so as to contact the surface of the fixing roller 15, and the sheet 11 is fixed to the fixing roller 15.
After passing between the pressure roller 16 and the pressure roller 16, the separation claw 19 peels the fixing roller 15 from the fixing roller 15,
The sheet is guided by 1 and is discharged by the discharge rollers 22 and 23. Further, the temperature fuse 24 is provided at a position having a certain gap with respect to the surface of the fixing roller 15, and is attached to the support base 25.

The frames 26 and 27 of the fixing device 12 are vertically divided into two parts, which are molded of an insulating resin. The entrance guide plates 13 and 14 are provided at the entrances of the frames 26 and 27, and the paper ejection guide plates 20 and 21 and the paper ejection roller 2 are provided.
2, 23 are provided at the outlets of the frames 26, 27. Fixing roller 15, pressure roller 16, thermistor 1
8. The thermal fuse 24 is installed inside the frames 26 and 27.

2 and 3 show an enlarged part of the present embodiment. The supporting base 25 is formed so that the vicinity of the position where the thermal fuse 24 is mounted is concentric with the position where the fixing roller 15 is mounted inside the frames 26 and 27, that is, the lower surface of the supporting base 25 is circular. It is formed to be concentric with. Therefore, even if the temperature fuse 24 is assembled to the support base 24 with some deviation as shown by the dotted line in FIG.
5 is kept constant and the thermal fuse 24
Will operate properly without malfunctioning, improving safety.

Further, since the support base 25 is made of an insulating material and the temperature fuse 24 does not need to be covered with an insulating tube, the thermal responsiveness is good and the response of the temperature fuse 24 when the fixing roller 15 has an abnormal temperature rise. Will be faster. Therefore, when the temperature of the fixing roller 15 is abnormally increased, the heater 17 can be cut off more quickly, and safety can be ensured. Further, since the frames 26 and 27 are made of an insulating resin, the support base 25 is attached to the frames 26 and 27.
The cost can be reduced by integrally molding with.

The thermal fuse 24 is connected to harnesses 28 and 29 made of phosphor bronze plate by screws 30 and 31, and a step is provided on the frame 26 so that the connecting portion is one step lower than the supporting base 25. As a result, the temperature fuse 24 is always pressed against the support base 25, the temperature fuse 24 does not float on the support base 25, and the gap between the temperature fuse 24 and the fixing roller 15 is properly maintained. Be drunk In this case, the screws 30 and 31 are connected to the terminals 24a and 24b of the thermal fuse 24 and the harness 2 respectively.
The screw mounts 32 and 33 are screwed through the holes 8 and 29, and the screw mounts 32 and 33 are fixed to the frame 26.

In the vicinity of the terminals 24a and 24b of the thermal fuse 24, members 34 and 3 for preventing rotation of the thermal fuse 24 are provided.
5 are arranged, and these members 34 and 35 are fixed to the frame 26. Terminals 24a and 24b of the thermal fuse 24
Is fitted in a gap provided in the vertical direction of the rotation preventing members 34, 35 to prevent rotation, and the temperature fuse 24
Connect terminals 24a, 24b of harness to harnesses 28, 29 with screws 3
The temperature fuse 24 is prevented from being detached from the support base 25 due to the rotational torque at the time of being stopped and connected at 0 and 31.

As described above, in this embodiment, since the vicinity of the mounting position of the thermal fuse 24 is formed concentrically with the mounting position of the fixing roller 15 in the support base 25, the thermal fuse 24 is mounted with a slight deviation. Also, the gap between the fixing roller 15 and the thermal fuse 24 is properly maintained, the thermal fuse 24 performs proper operation without malfunction, and the safety is enhanced.

Further, the thermal fuse 24 and the harness 2
Since a step is provided between the connection part of 8 and 29 and the support base 25,
At the time of assembling the temperature fuse 24, the temperature fuse 24 is pressed against the support base 25 so that the fixing roller 15 can be operated freely.
The gap between the temperature fuse 24 and the thermal fuse 24 can be properly maintained. Further, since the support base 25 is made of an insulating material, it is not necessary to cover the thermal fuse 24 with an insulating tube, and the thermal fuse 24 responds faster,
It is possible to ensure safety.

Further, since the frames 26 and 27 are made of an insulating resin and the frames 26 and 27 and the support base 25 are integrally molded, the gap between the fixing roller 15 and the thermal fuse 24 is maintained more appropriately. It is possible to reduce the cost. Further, since the members 34 and 35 for preventing rotation of the thermal fuse 24 are provided near the connecting portion between the thermal fuse 24 and the harnesses 28 and 29, the fixing roller 1
The gap between the 5 and the thermal fuse 24 can be maintained more properly.

[0029]

As described above, according to the first aspect of the invention, the fixing roller having the heater built therein, the pressure roller rotatably pressed against the fixing roller, and the vicinity of the surface of the fixing roller are provided. A temperature fuse is provided to prevent the temperature of the fixing roller from rising above, and the unfixed toner on the sheet is thermally melted into a sheet at a nip portion formed by the pressure roller and the fixing roller. In the fixing device for fixing, since the temperature fuse is assembled and the supporting base is formed concentrically with the fixing roller in the vicinity of the assembling position of the temperature fuse, even if the temperature fuse is assembled with a slight deviation, the fixing roller is fixed. The gap between the thermal fuse and the thermal fuse can be maintained properly, the thermal fuse can operate properly without malfunctioning, and high safety can be obtained. It can be.

According to a second aspect of the present invention, in the fixing device according to the first aspect, the temperature fuse and the harness are arranged so that the temperature fuse is pressed against the support base when the temperature fuse is assembled. Since the step is provided between the connection portion and the support base, the temperature fuse can be pressed against the support base when the thermal fuse is assembled, and the gap between the fixing roller and the thermal fuse can be properly maintained. According to the invention described in claim 3, in the fixing device according to claim 1 or 2, since the support base is made of an insulating material, it is not necessary to cover the thermal fuse with an insulating tube, and the response of the thermal fuse is eliminated. Can be faster and secure.

According to the invention described in claim 4,
In the fixing device described in the paragraph 2 or 3, since the fixing device frame is made of an insulating resin and the fixing device frame and the support base are integrally molded, the gap between the fixing roller and the thermal fuse can be made more appropriate. You can keep it and reduce costs.

According to the invention of claim 5, claim 1,
In the fixing device described in 2, 3, or 4, since a member for preventing rotation of the thermal fuse is provided in the vicinity of the connecting portion between the thermal fuse and the harness, the gap between the fixing roller and the thermal fuse can be made more appropriate. Can be kept.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is an enlarged view showing a part of the embodiment.

FIG. 3 is an enlarged perspective view showing a part of the embodiment.

FIG. 4 is a perspective view showing a part of a conventional fixing device.

[Explanation of symbols]

 15 fixing roller 16 pressure roller 17 heater 24 temperature fuse 25 support base 26, 27 frame 28, 29 harness 30, 31 screw 34, 35 non-rotating member

Claims (5)

[Claims] 1. A fixing roller having a built-in heater, a pressure roller rotatably pressed against the fixing roller, and a fixing roller provided near the surface of the fixing roller for preventing an abnormal temperature rise of the fixing roller. In a fixing device having a temperature fuse and fixing the unfixed toner on the sheet by melting the unfixed toner on the sheet in a nip portion formed by the pressure roller and the fixing roller, the temperature fuse is attached to the temperature fuse. A fixing device comprising a support base formed concentrically with the fixing roller in the vicinity of a fuse mounting position. 2. The fixing device according to claim 1, wherein the connection portion of the temperature fuse and the harness and the support base are arranged so that the temperature fuse is pressed against the support base when the thermal fuse is assembled. A fixing device having a step. 3. The fixing device according to claim 1, wherein the support base is made of an insulating material. 4. The fixing device according to claim 1, wherein the fixing device frame is made of an insulating resin and the fixing device frame and the support base are integrally molded. . 5. The fixing device according to claim 1, 2, 3 or 4, wherein a member for preventing rotation of the temperature fuse is provided in the vicinity of a connecting portion between the temperature fuse and the harness. .