JP2000356920A - Heat fixing-device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve, by a simple structure, accuracy in replacement and attachment of a thermostat which is attached to a support member and to obtain accuracy in attaching the thermostat opposite a heat roller even in repeated replacement. SOLUTION: The device has a heating element in its heat roller 15 and comprises a thermostat 17 connected to the heating element and a support member 140, made of a resin, for holding the thermostat 17 opposite the heat roller 15. In the case, a fixing device 19, made of a metal, formed so as to be freely attached/detached to/from the support member 140 is provided, and the thermostat 17 is attached to the fixing device 19 attached to the support member 140.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device adapted to an image forming apparatus utilizing electrophotography.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic apparatus such as a printer, a copying machine, a facsimile machine, etc., utilizing an electrophotographic method includes a photosensitive drum and a transfer device for transferring a toner image formed on the surface of the photosensitive drum to a sheet. And a heat fixing device for fixing the toner image transferred to the sheet.

[0003] In recent years, such a heat fixing apparatus has a heating roller system comprising a heating roller having a heating element therein and a pair of fixing rollers comprising a pressure roller pressed against the heating roller at a predetermined pressure. The toner is transferred to the image forming apparatus while the toner transferred to the surface of the sheet is heated and fixed by the rotation of the pair of fixing rollers. Have been.

[0004] The heat fixing device having such a configuration is usually provided with a thermostat that cuts off a current path of a heating element in order to prevent overheating of the heating roller when abnormal heating of the heating roller occurs. Such a thermostat mounting structure generally has a predetermined distance from the heating roller as shown in Japanese Utility Model Application Laid-Open No. 6-37855 in order not to damage the surface of the heating roller and to easily receive the radiant heat of the heating roller. Are configured to be held face-to-face in a separated state.

FIG. 6 shows such a heat fixing device. That is,
The heat fixing device 20 includes a heating roller 21, a pressure roller 22 pressed against the heating roller 21, a support member 23 made of a material having high rigidity and heat insulation, and fixed to the support member 23 with a screw 24. And heating roller 2
Thermostat 25 held at a predetermined interval from 1
It is composed of

[0006]

However, in the conventional heating and fixing apparatus 20, when the thermostat 25 is replaced or attached due to initial failure or deterioration due to long-term use, the thermostat 25 is directly attached to the support member 23 by the screw 24. Since the thermostat 25 is fixed to the support member 23, the screw thread is widened to attach the thermostat 25 to the support member 23 again.
As a result, the mountability deteriorates. In particular, the thermostat 25 is attached to the support member 2 by repeatedly attaching.
3 has a problem in that the holding force of the thermostat 25 becomes weak, and the thermostat 25 is loose and the mounting accuracy cannot be obtained.

In order to solve this problem, a support member 23 is required.
In order to attach the thermostat 25 to the device, it is firmly fixed with bolts and nuts to prevent looseness, and thereby, the attachment is repeatedly and accurately performed.
However, when the bolts and nuts are fixed, the bolts may fall during mounting, and the mounting performance cannot be improved.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to improve the exchangeability and the mountability of a thermostat to be attached to and exchanged with a support member with a simple structure. Another object of the present invention is to provide a heating and fixing device that can obtain the mounting accuracy of the thermostat facing the heating roller.

[0009]

In order to solve the above problems, the present invention provides a heating roller having a heating element therein,
A pressure roller that is arranged to be in pressure contact with the heating roller and sandwiches a sheet carrying untransferred toner between the heating roller, a thermostat connected to the heating element, and heating the thermostat by heating the thermostat. In a heat fixing device comprising a resin support member for holding the roller face-to-face, a metal fixing tool detachably formed on the support member, wherein the thermostat is attached to the fixing tool attached to the support member. Configuration.

According to the structure of the present invention, since the thermostat is attached to a metal fixture made of a material different from that of the resin support member, the thermostat can be attached and detached only to the metal fixture in the case of replacement. This makes it possible to improve the exchange / attachability without weakening the force by which the thermostat is held by the support member. In addition, since the mounting accuracy of the thermostat is determined by the accuracy with which the fixture is held by the support member, there is no need to adjust the mounting accuracy every time the thermostat is replaced.

Further, since the fixing member is made detachable without forming the fixing member on the resin-made support member by the insert metal, it is easy to separate the resin and the metal at the time of disposal, and the recycling cost can be reduced.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a view for explaining a printer X used in the image forming apparatus of the present invention, and includes a charger 2, an exposure unit 3, a developing unit 4, a transfer unit 5, and a cleaning unit along the rotation direction of the photosensitive drum 1. 9 are sequentially arranged. Further, there is formed a paper transport path 12 which communicates from a paper feed cassette 10 disposed below the photosensitive drum 1 to the upper discharge tray 11 through the transfer unit 5. The heat fixing device 13 of the invention is arranged.

In image formation, first, the surface of the photosensitive drum 1 is charged by the charger 2, then an electrostatic latent image is formed by the exposure device 3, and further, the developing device 4 forms the electrostatic latent image on the surface of the photosensitive drum 1. After the toner is conveyed, the toner is attached to the electrostatic latent image to form a toner image, and the toner image is transferred to paper by the transfer unit 5. Next, the sheet on which the toner image has been transferred onto the surface is passed through the heat fixing device 13 to fix the sheet, thereby forming an image.

FIG. 2 shows the structure of the heat fixing device 13 of the present invention. The heat fixing device 13 includes a heating roller 15 and a pressure roller 16 pressed against the heating roller 15 in a frame 14, and a safety device 18 that is located above the heating roller 15 and joined to the frame 14. It is composed of The heating roller 15 is provided with a heating element 151 made of a halogen lamp or the like inside an aluminum tube 150 having a thickness of about 2 mm, and is provided on the surface of the aluminum tube 150 with PTFE, PFA or the like (not shown). Releasability, and
A heat-resistant resin layer is formed. The pressure roller 16
A foam layer 161 of silicon rubber is formed on the surface of the cored bar 160, and a tube 162 formed of PFA having a thickness of 100 μm or less is formed thereon.

The safety device 18 comprises the thermostat 17 and a support member 140 for holding the thermostat 17.
Due to 40, the thermostat 17 is held facing the surface of the heating roller 15 at a predetermined interval. Although the thermostat 17 and the heating roller 15 are shown as being spaced apart from each other by a predetermined distance, the present invention is not limited to this, and they may be in contact with each other.

The thermostat 17 is used to cut off the power supplied to the heating element 151 when the temperature of the heating roller 15 becomes higher than the set temperature, and is generally used in the present invention, for example, a single unit using a repulsive disk bimetal. The pole single throw type is used.

As shown in FIGS. 3 and 4, the thermostat 17 is held by fixing members 19, 19 which are detachably provided on a support member 140.
As the fixture 19, a metal member is used. The fixing device 19 is cylindrical and has a female screw 190 penetrating at the center thereof, and two grooves 191 and 191 are formed in a circumferential surface thereof in a direction perpendicular to the screw penetrating direction. ing.

Further, the support member 140 is made of a heat-resistant resin member such as polyethylene terephthalate (PET), polyether ether ketone (PEEK), polyphenylene sulfide (PPS) or the like formed in a strip shape.

As shown in FIG. 4A, the support member 140
2 are formed at both ends in the longitudinal direction of the support member 140 in the thickness direction of the support member 140, and the side walls at both ends in the width direction of the pocket portion 142 are taken along the line AA in FIG.
As shown in FIG. 4B, which is a line sectional view, a guide 143 for inserting and holding the fixture 19 is formed. Further, an insertion opening 144 continuously penetrated from the pocket portion 142 is formed at the center of the support member 140, and the insertion opening 144 is formed larger than the pocket portion 142. By forming the insertion opening 144 larger than the pocket portion 142 in this way, the user can fix the fixture 1.
9 is configured to be easily attached to and detached from the support member 140.

The guide 143 is formed in such a size that it has a certain amount of play in the thickness direction of the groove 191 (the direction in which the female screw 190 penetrates) so that the fixture 19 can be attached and detached. The guide 143 is designed so that the positional accuracy of the thermostat 17 with respect to the heating roller 15 via the fixture 19 is determined.

Further, a fixture 19 is attached to the tip of the guide 143.
Linear projection 143 for temporarily fixing the
a is provided, and the depth of the groove 191 is adjusted so that the fixture 19 is fitted into the support member 140 firmly without providing play between the projections 143a. in this way,
Since the fixture 19 is firmly fixed to the support member 140 and stands up, the thermostat 17 can be easily attached. Moreover, when the fixing tool 19 is pulled out of the support member 140, the fixing tool 19 can be easily pulled out of the support member 140 along the guide 143 due to the play in the thickness direction of the groove 191 of the fixing tool 19. Note that as long as the linear projection 143a has a function of holding the fixture 19, a dot-shaped modification other than the linear projection can be employed.

As a result, the fixture 19 made of metal and the support member 140 made of resin can be easily separated, and the recycling cost can be reduced as compared with a product in which metal fittings are inserted into resin.

The mounting of the thermostat 17 is as follows.
Arm 17 integrally joined to thermostat 17
0, 170 is placed on the fixture 19 fitted to the support member 140, and the mounting screws 171, 171 are engaged from above to assemble the safety device 18. Thereafter, the thermostat 17 is engaged with the frame 14 of the heat fixing device 13 with the mounting screws 172 and 172, so that the heating roller 15
At predetermined intervals.

The thermostat 17 is electrically connected to the thermostat 17 by an electrode 172 connected through a power source Y and a heating element 151 as shown in FIG. The electrode 172 is integrally fixed with a screw 171 in a state where the fixture 19, the arm 170, and the electrode 172 are superposed in this order.

According to the structure of the present invention, the heating element 15 is provided inside.
1, a pressure roller 16 arranged to be in pressure contact with the heating roller 15, and a pressure roller 16 for holding a sheet carrying untransferred toner between the heating roller 15 and a heating element 151. In the heat fixing device 13 comprising the thermostat 17 and the resin support member 140 for holding the thermostat 17 facing the heating roller 15, a metal fixing member 19 detachably formed on the support member 140 is provided. Fixture 19 attached to support member 140
Since the thermostat 17 is directly attached to the fixing member 19, the thermostat 17 can be attached and detached only to the metal fixing member 19, so that the thermostat 17 can be easily exchanged and attached without weakening the holding force of the thermostat 17 on the support member 140 each time it is exchanged. Can be improved. Moreover, since the mounting accuracy of the thermostat is determined by the accuracy with which the fixture 19 is held by the support member 140, there is no need to adjust the mounting accuracy every time the thermostat is replaced.

[0026]

According to the structure of the present invention, since the thermostat is directly attached to the metal fixing member detachably formed on the resin supporting member, only the fixing member made of a different material from the supporting member is used. The thermostat can be attached and detached, so that the exchange / attachability can be improved without weakening the force by which the thermostat is held by the support member.

Also, since the mounting accuracy of the thermostat is determined by the accuracy that can be held by the support member, it is not necessary to adjust the mounting accuracy every time the thermostat is replaced.

Further, since the fixing member is made detachable without forming the fixing member on the resin-made supporting member by the insert metal, it is easy to separate the resin and the metal at the time of disposal, and the recycling cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a printer used in an image forming apparatus of the present invention.

FIG. 2 is a diagram illustrating the structure of a heat fixing device according to the present invention.

FIG. 3A is a perspective view illustrating a thermostat mounting structure of the present invention, and FIG. 3B is a cross-sectional view taken along line AA of FIG.

FIG. 4 is a diagram illustrating attachment of a fixture to the support member of the present invention.

FIG. 5 is a diagram illustrating an electrical structure of the thermostat of the present invention.

FIG. 6 is a diagram illustrating a conventional heat fixing device.

[Explanation of symbols]

 X: Printer 13: Heat fixing device 14: Frame 140: Support member 15: Heat roller 151: Heating element 16: Pressure roller 17: Thermostat 18: Safety device

Claims (1)

[Claims] 1. A heating roller having a heating element therein, and a pressure roller disposed so as to be in pressure contact with the heating roller and holding a sheet carrying untransferred toner between the heating roller and the heating roller. And a thermostat connected to the heating element;
A heat fixing device comprising a resin support member for holding the thermostat facing the heat roller, comprising: a metal fixture detachably formed on the support member; and a fixture attached to the support member. A heating and fixing device, wherein the thermostat is mounted on the fixing device.