JP2002072760A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing apparatus equipped with a temperature detection unit with good assembly efficiency by fitting thermistor elements through single- time assembly even when the apparatus has the plural thermistor elements. SOLUTION: This film fixation type fixing apparatus has two thermistors 102 and 103 arranged at different positions along the length of a heating body 44 constituting a heater and the two thermistors, i.e., a center thermistor element 102 and an end part thermistor element 103 are provided at the lower ends of longitudinal leg parts 101B and 101C fixed to a horizontal substrate 101A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in an image forming apparatus such as a printer, and more particularly, to a fixing device which performs temperature control using a plurality of heat detecting elements and an image forming apparatus. .

[0002]

2. Description of the Related Art FIG. 8 shows an example of an image forming apparatus provided with a fixing device for fixing a toner image by heating and pressing. FIG. 8 is a schematic diagram of a laser beam printer using two thermistors as heat detecting elements.

[0003] The laser beam printer 1 is connected to an external device 31 such as a computer, and prints on a recording paper 28 under the control of the external device 31. The external device 31 supplies various control signals and image information to the video controller 27. The video controller 27 generates and outputs various control signals and video signals based on the image information sent from the external device 31. The print control unit 26 is a control circuit for controlling each unit in the apparatus.

FIG. 9 shows the operation timing of the laser beam printer shown in FIG. The video controller 27 in FIG.
As shown in (a), the RDY signal from the external device 31
When the RUE is reached (when a start signal is input from an external device), the PRINT signal is transmitted to the TRU as shown in FIG.
E (start up). The print control unit 26
When the NT signal becomes TRUE, (f) and (g) in FIG.
As described above, the driving of the main motor 23 and the polygon motor 14 is started. When the main motor 23 is driven, the photosensitive drum 17, the pressure roller 10 of the fixing unit (device) 9,
The paper discharge roller 12 starts rotating. Thereafter, the print control unit 26 controls the light amount of the semiconductor laser 13 and the primary charger 1
9. The high voltage of the developing device 20 and the transfer charger 21 and the temperature control of the heater unit 11 of the fixing unit 9 are started.

[0005] As shown in FIG. 9 (g), when the time T1 has elapsed from the start of driving from the polygon motor 14 and the rotation of the polygon motor 14 is in a steady state, as shown in FIG.
As shown in FIG. 9 (h), the paper feed clutch 24 is turned on to drive the paper feed roller 5, and the recording paper 28 in the paper feed cassette 2 is fed toward the registration roller 6. Then, the print controller 26 outputs a VSREQ signal to the video controller 27 as shown in FIG. 9C at the timing when the recording paper 28 reaches the registration roller 6, and supplies the VSREQ signal as shown in FIG. The paper clutch 24 is turned off and the driving of the paper feed roller 5 is stopped.

On the other hand, the video controller 27
After developing image information from 31 into a dot image,
When the preparation for the output of the DO signal is completed, it is confirmed that the VSREQ signal in (c) of FIG. 9 is TRUE, and then the VSYNC signal is set to TRUE as shown in (d) of FIG.

In synchronization with this, as shown in (e) of FIG.
Output of the O signal is started.

At this time, the print control unit 26 determines the time T from the rising of the VSYNC signal as shown in (i) of FIG.
After three, the registration roller clutch 25 is turned on, and the registration roller 6 is driven.

The registration roller 6 is driven by (i) in FIG.
The process is performed during T4 until the rear end of the recording paper 28 passes through the registration roller 6 as shown in FIG. During this time, the print control unit 26 drives the semiconductor laser 13 according to the VDO signal from the video controller 27.

The laser light emitted from the semiconductor laser 13 is converted into a linear scan by the rotation of the polygon mirror 15 of the scanner unit 7. After that, the laser light is reflected by the mirror 16 and irradiated on the photosensitive drum 17. The laser beam modulated in accordance with the VDO signal is simultaneously scanned on the photosensitive drum 17 to form a latent image on the photosensitive drum 17, and the same operation is repeated to repeat the same operation.
A one-page latent image is formed on the top.

The latent image formed on the photosensitive drum 17 is
Then, the toner image is transferred to the recording paper 28 by the transfer charger 21. When the transfer is completed, the recording paper 28 is conveyed to the fixing unit 9.

FIG. 10 is a sectional view of the fixing unit during the fixing operation.

In FIG. 10, reference numeral 32 denotes a ceramic heater.
A planar (linear) heating element is formed on a ceramic substrate. 34 is a thermistor unit for detecting the temperature of the ceramic heater 32. 36 is the recording paper 28 on the ceramic heater 32
A film for preventing the upper toner images 42 and 43 from adhering, and is formed in a cylindrical shape. The ceramic heater 32 indirectly heats the toner image 42 before fixing via the film 36. Reference numeral 37 denotes a film guide which supports the ceramic heater 32 and supports the film in a cylindrical shape. Reference numeral 38 denotes a stay for supporting the film in a cylindrical shape. Also,
The pressure roller 11 includes a shaft 39, a rubber 40, and a tube 41.

In the fixing unit 9 immediately before the recording paper 28 on which the transfer toner image 42 is placed is conveyed, the temperature of the ceramic heater 32 is adjusted. At this time, the pressure roller 11 and the film 36 are each rotating in the direction of the arrow.

The transfer toner image 42 conveyed together with the recording paper 28 is heated and pressed by a fixing nip between the film 36 and the pressure roller 10 to form a fixed toner image 43.

The recording paper 28 on which the toner image has been fixed is discharged out of the apparatus by the discharge roller 12. To print the next page continuously, the print control unit 26
After time T5 as shown in (b), the PRINT signal is set to TRUE again, and the same control as that for printing the first page is performed.

Next, FIG. 11 shows the ceramic heater 32, the thermoswitch 33, and the thermistor units 34 and 35. The ceramic heater 32 is a ceramic heater having a heating element 44 on the side opposite to the fixing surface.

The thermo switch 33 includes a ceramic heater 32
Are connected in series to the heating element 44. The thermo-switch 33 is turned off when the temperature of the heater is detected to be higher than that normally used. That is, the thermoswitch 33 is a safety circuit.

The first thermistor unit 34 detects the temperature near the center of the ceramic heater 32. 45 is a thermistor element whose resistance value changes according to temperature. An electric wire 46 is connected to the thermistor element 45, and the other end of the electric wire 46 is connected to the print control unit 26 via a connector or the like. The print control section 26 compares the temperature at the center of the ceramic heater 32 with the temperature required for fixing, which is programmed in advance, and turns ON / OFF the energization of the ceramic heater 32. 47 and 48 are mounting holes for fixing the thermistor unit 34 to the film guide 37.

The second thermistor unit 35 detects the temperature of the ceramic heater 32 at the end of the paper passing area. 49 is a thermistor element whose resistance value changes according to the temperature. An electric wire 50 is connected to the thermistor element 49, and the other end of the electric wire 50 is connected to the print control unit 26 via a connector or the like. When the temperature of the end portion of the heating element becomes higher than a certain temperature, the print control unit 26 increases the interval between printings or stops the energization of the ceramic heater 32. Heating element
When a paper narrower than 44 is passed, the temperature of the area of the heating element through which the paper does not pass will be higher than the fixing temperature, which may adversely affect the image or exceed the heat resistance temperature of the constituent members. Therefore, the temperature at the end is detected. Also, 51,52
Is a mounting hole for fixing the thermistor unit 35 to the film guide 37.

FIG. 12 shows an electric circuit diagram of the fixing unit 9. The first thermistor unit 34 is connected via a connector 53 to a relay cable 54 of the multi-harness. Similarly the second
The thermistor unit 35 is also connected to the relay cable 54 via the connector 55. The relay cable 54 is connected to the fixing unit connector 56. The fixing unit connector 56 is connected to the print control unit 26. In addition, the ceramic heater 32 and the thermoswitch 33 are also connected via the fixing unit connector 56,
It is connected to the print control unit 26.

[0022]

In the fixing unit having such a configuration, since there are two thermistor units, the work of attaching the thermistor unit to the heater unit is required twice. Further, when the two types of thermistors are different from each other, there is a problem in that the two types of thermistors need to be managed erroneously.

The present invention has been made in view of the above problems, and a first object is to make a plurality of thermistor units into one thermistor unit, that is, to make a single unit having a plurality of thermistors, It is an object of the present invention to provide a fixing device and an image forming apparatus having a temperature detecting unit which can be attached at a time and has high assembling efficiency.

A second object of the present invention is to provide a compact and inexpensive temperature detecting unit by reducing the number of wirings by sharing a common wiring for connecting a plurality of temperature detecting elements in one structure. A fixing device and an image forming apparatus provided with the fixing device.

By the way, when a failure occurs in a common wire, there is a problem that a plurality of temperature detecting elements cannot be used at the same time.

Therefore, a third object of the present invention is to provide a connector unit and a wire unit which have a high probability of occurrence of a fault by returning a common wire to a plurality of wires so as to be resistant to a fault and to be compact and slightly inexpensive. An object of the present invention is to provide a fixing device and an image forming apparatus provided with a temperature detecting unit.

[0027]

According to a first aspect of the present invention, there is provided a heater for heating an unfixed toner image on a recording sheet passing through a fixing nip, wherein the heater has an electric resistance according to a temperature change. In a fixing device having a heat detecting unit in which a plurality of heat detecting elements having different values are provided at different positions in the width direction of the recording sheet, the plurality of heat detecting elements are provided in one structure.

According to a second aspect of the present invention, in the first aspect, the structure is a separate structure detachable from a fixing device main body.

According to a third aspect of the present invention, in any one of the above-mentioned inventions, a common signal line for extracting a reference potential of each of the plurality of heat detecting elements is wired.

According to a fourth aspect of the present invention, in the above-mentioned third aspect, the common signal line portion is branched into a plurality of signal lines and wired again.

According to a fifth aspect based on the first aspect,
The heater is held at a lower portion of a heater holder, and a film provided between the heater and the pressing body, and a recording sheet carrying an unfixed toner image in a fixing nip formed between the heater and the pressing body. It is characterized by passing through.

According to a sixth aspect of the present invention, there is provided an image forming apparatus including any one of the above fixing devices.

According to each of the above structures, a heat detecting unit in which a plurality of heat detecting elements are integrated can be provided.

[0034]

FIG. 1 shows a first embodiment of a thermistor unit 101 and a ceramic heater 100 in a fixing device for realizing the present invention. Hereinafter, the thermistor unit 101 shown in FIG. 1 will be described.

The thermistor unit 101 is provided with two thermistors, a central thermistor element 102 and an end thermistor element 103, at the lower ends of vertical feet 101B and 101C fixed to a horizontal substrate 101A as one structure. ing. The central thermistor element 102 detects the temperature near the center of the ceramic heater 100, and the end thermistor element 103 detects the temperature at the end of the ceramic heater 100 in the paper passing area. This structure is detachable from the heater substrate.

As described above, a feature of the first embodiment of the present invention is that the two thermistor elements (the central thermistor element 102 and the end thermistor element 103) are integrated into one structure.

The central thermistor element 102 is used for controlling the temperature of the heater. The end thermistor element 103 detects a temperature rise at the end of the heating element that occurs when a sheet narrower than the heating element 44 is passed. When the temperature rise at the end of the heating element 44 is detected, the power supply to the heater is stopped or the sheet feeding interval is increased.

The thermistor unit 101 will be further described. 104 and 105 are mounting holes for fixing the thermistor unit 101 to a film guide (not shown). By combining the thermistor units into one,
The number of mounting holes can be halved, and mounting can be performed only once. In addition, since the number of connectors can be reduced to one, connection of the connectors can be performed only once.

FIG. 2 is a view of the thermistor unit 101 as viewed from a surface not in contact with the ceramic heater 100.

Reference numerals 106 and 107 denote insert frames for extracting the potential of the central thermistor element 102. The first insert frame 106 is connected to the central thermistor element 10 by welding 108.
It is connected to the electric wire drawn from 2. Also, the first insert frame 106 is connected to the electric wire 110 at a weld 109. The electric wire 110100 is connected to the connector 111.

The second insert frame 107 has a
2 connects to the electric wire drawn from the central thermistor 102. In addition, the second insert frame 107
113 is connected to the electric wire 114. Wire 114 is connector 111
Is connected to.

Reference numerals 115 and 116 denote insert frames for extracting the potential of the end thermistor element 103. The third insert frame 115 is welded 117 and the end thermistor element 103
It is connected to the electric wire pulled out from. The third insert frame 115 is connected to the electric wire 119 at a welded portion 118. The electric wire 119 is connected to the connector 111.

[0043] The fourth insert frame 116 is
At 0, it is connected to the electric wire drawn from the end thermistor 103. In addition, the fourth insert frame 116
121 is connected to the electric wire 122. Wire 122 is connector 111
Is connected to.

FIG. 3 shows an electric circuit diagram of the present embodiment.

In FIG. 3, reference numeral 102 denotes a central thermistor element; 103, an end thermistor element; and 111, a connector of the thermistor unit. 123 is a thermoswitch.
Reference numeral 124 denotes a connector for connecting the fixing device and the image forming apparatus main body.

As described above, conventionally, the thermistor unit is divided into a center portion and an end portion. However, in the present embodiment, the thermistor unit is formed by combining two thermistor elements into one thermistor unit. The unit can be installed once.

In this embodiment, the case where one thermistor unit has two thermistor elements has been described. However, the same applies to a case having three or more thermistor elements.

(Second Embodiment) FIGS. 4 and 5 show a second embodiment of the present invention.

FIG. 4 is a view of the thermistor unit as viewed from a surface not in contact with the heater. Hereinafter, the thermistor unit 200 shown in FIG. 4 will be described.

The thermistor unit 200 has insert frames 201, 202 and 203. The first insert frame 201 is connected to the electric wire of the central thermistor element at the weld 204. Also, the first insert frame 20
1 is connected to the electric wire of the end thermistor at the welded portion 205. And, at the welded portion 206, it is connected to the electric wiring 207 of the GND potential. As described above, a feature of the second embodiment of the present invention is that the central thermistor and the end thermistor are connected to a common wiring of the GND potential for a plurality of thermistors of the end thermistor.

[0051] The second insert frame 202 is
At 8 is connected to the central thermistor. The second insert frame 202 is connected to the electric wiring 210 for transmitting the potential of the central thermistor at the welding portion 209.

[0052] The third insert frame 203 is
At 1 the end is connected to the thermistor. The insert frame 203 is connected to the electric wiring 213 that transmits the potential of the end thermistor at the welded portion 212. Electrical wiring 207,
210 and 213 are connected to the connector 214 and are connected to the print control unit 221.

FIG. 5 is an electric circuit diagram of the fixing unit according to the present embodiment.

In FIG. 5, reference numeral 218 denotes a central thermistor element, and 219 denotes an end thermistor element. Since the number of electric wirings is three, it is possible to connect with one less wire than in the related art. Returning to FIG. 4, reference numerals 215 and 216 denote holes for fixing the thermistor unit 200 to the film guide.

The width 21 of the thermistor unit of the present embodiment
7 has a smaller number of insert frames than the width 123 of the thermistor unit in the first embodiment,
Can be narrow.

As described above, in the present embodiment, the width of the thermistor unit can be reduced and the number of wires can be reduced by sharing the GND line of the two thermistors. As a result, a small space and cost reduction are realized.

(Third Embodiment) FIGS. 6 and 7 show a third embodiment of the present invention.

FIG. 6 is a view of the third embodiment of the thermistor unit as viewed from the side not in contact with the heater. Hereinafter, the thermistor unit 300 shown in FIG. 6 will be described.

The thermistor unit 300 has three insert frames 301, 302, 303. The first insert frame 301 is connected to the electric wire of the central thermistor at the welded portion 304. Also, the first insert frame
301 is connected to the electric wire of the end thermistor at the weld 305. Then, at the weld 306, the first GND
It is connected to the electric wiring 307 of the potential. Also, the welded part 308
Is connected to the wiring 309 of the second GND potential. As described above, the third embodiment of the present invention is characterized in that the central thermistor and the end thermistor are connected to a common GND wiring for a plurality of thermistors, and then are branched again.

The second insert frame 302
At 0, it is connected to the central thermistor. The second insert frame 302 is connected to an electric wiring 312 for transmitting a potential of the central thermistor at a welded portion 311.

The third insert frame 303 has a
At 3 is connected to the end thermistor. The third insert frame 303 is connected at a welded portion 314 to an electric wire 315 for transmitting the potential of the end thermistor. Electrical wiring
307, 309, 312, and 315 are connected to the connector 316, and are connected to the print control unit 326.

FIG. 7 shows an electric circuit diagram of the present embodiment.

In FIG. 7, reference numeral 320 denotes a central thermistor;
1 is an end thermistor. 323 is a thermoswitch. Since the number of electrical wires is four, the number of wires is the same as the conventional one.

However, even if one of the GND lines becomes disconnected, no thermistor failure occurs. The second
In this embodiment, when a failure occurs in the shared GND line, both thermistors 118 and 119 become unusable.

In the conventional example, if one of the GND lines fails, the thermistor cannot be used. That is, the wiring is more resistant to failure than in the past.

Returning to FIG. 6, reference numerals 317 and 318 denote holes for fixing the thermistor unit 300 to the film guide.

The width 319 of the thermistor unit can be made smaller than the width of the thermistor unit of the first embodiment and the arrow 123.

As described above, in the third embodiment, by sharing the GND line of the two thermistors, it is possible to reduce the width of the thermistor unit and increase the resistance of the GND line to failure. This allows for smaller spaces,
High reliability is achieved.

[0069]

As described above, according to the present invention,
When a plurality of heat detection elements are used, assembly efficiency can be improved. Further, the number of wirings can be reduced. As a result, the wiring space is reduced, and the material cost can be reduced. At this time,
Space saving and low cost can be realized without lowering reliability.

[Brief description of the drawings]

FIG. 1 is a perspective view of a thermistor unit according to a first embodiment of the present invention as viewed from a side not in contact with a heater.

FIG. 2 is a plan view of the thermistor unit of FIG. 1 as viewed from a side not in contact with a heater.

FIG. 3 is a diagram showing an electric circuit of the unit shown in FIG. 2;

FIG. 4 is a plan view of a thermistor unit according to a second embodiment of the present invention as viewed from a side not in contact with a heater.

FIG. 5 is a diagram showing an electric circuit of the unit shown in FIG. 4;

FIG. 6 is a plan view of a thermistor unit according to a third embodiment of the present invention as viewed from a side not in contact with a heater.

FIG. 7 is a diagram showing an electric circuit of the unit shown in FIG. 6;

FIG. 8 is a sectional view of a conventional laser beam printer.

FIG. 9 is a diagram showing operation timings of the laser beam printer of FIG.

FIG. 10 is a sectional view of a conventional fixing device.

FIG. 11 is a diagram illustrating a thermistor unit and the like of the fixing device in FIG. 10;

FIG. 12 is a diagram showing an electric circuit of the fixing device of FIG.

[Explanation of symbols]

44 Heating element 100 Ceramic heater 101, 200, 300 Thermistor unit 102 Central thermistor element 103 End thermistor element 104, 105, 215, 216, 317, 318 Mounting hole 106, 107, 115, 116, 201, 202, 203, 301, 302, 303 Insert frame 108, 109, 112, 113, 117, 118, 121, 204, 20
5, 208, 209, 211, 212, 308, 311, 313, 314
Welds 110, 122, 114, 119, 122, 207, 210, 213, 30
7, 309, 312, 315 Wire 111, 124, 214, 316 Connector 102, 218, 320 Central thermistor element 103, 219, 321 End thermistor element 123 Thermoswitch 221, 326 Print control unit

Claims (6)

[Claims] 1. A heater for heating an unfixed toner image on a recording sheet passing through a fixing nip, wherein a plurality of heat detecting elements whose electric resistance changes according to a temperature change are recorded on the heater. A fixing device having heat detection units provided at different positions in a sheet width direction, wherein the plurality of heat detection elements are provided in one structure. 2. The fixing device according to claim 1, wherein the structure is a separate structure detachable from a fixing device main body. 3. The fixing device according to claim 1, wherein a signal line for extracting a reference potential of each of the plurality of heat detecting elements is wired in common. 4. The fixing device according to claim 3, wherein the common signal line portion is branched into a plurality of signal lines and wired again. 5. The heater is held at a lower portion of a heater holder, and an unfixed toner image is formed on a film provided between the heater and the pressure body and a fixing nip formed between the heater and the pressure body. The fixing device according to claim 1, wherein the fixing device is configured to pass the carried recording sheet. 6. An image forming apparatus comprising the fixing device according to claim 1.