JPH07219386A - Device and method for heat fixing - Google Patents

Abstract

PURPOSE:To provide a heat fixing device capable of saving the consumption of electric power and preventing the fixing defect from causing. CONSTITUTION:A heat roller 2 is provided with a heating layer 6 on the outer circumference of the thermal insulation layer 8 disposed therein on the inner circumferential surface and the passive electrode 9 is disposed at the both end part in the direction of the shaft of the heat roller 2 of the heating layer 6. The passive electrode 9 is provided with the electrode 9a divided in the circumferential direction of the heat roller 2 and the conductive plates 9b to 9e abutted on the respective electrode 9a. Then, the power supplying leaf spring 10 is respectively brought into contact with the respective conductive plate 9b. Moreover, by providing a thermistor on the surface of the heat roller 2 for detecting the surface temp. of the heat roller 2, the power is selectively supplied to the respective power supplying leaf spring 10, based on the output signal of the thermistor, corresponding to the heater drive circuit.

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 used in an electrophotographic recording device and the like, and a heat fixing method in this device.

[0002]

2. Description of the Related Art Conventionally, as a heat fixing device used in an electrophotographic recording device or the like, for example, there is one disclosed in JP-A-4-51071.

According to the heat fixing device of the above publication, when one of the plurality of heating elements arranged in parallel in the circumferential direction of the heat roller at a predetermined gap faces the pressure roller at the nip portion,
A voltage is applied only to the opposing heating element to generate heat. If the recording sheet is conveyed to the nip portion at this time, the heating element that is generating heat is in contact with the surface of the recording sheet, so the heat energy of the heating element is transferred to the toner on the recording sheet, and the toner is removed. It is melted and heat-fixed on the recording sheet.

[0004]

However, in the heat fixing device as disclosed in the above-mentioned document, every time each heating element is located in the nip portion, the heating element which has become lower than the fixing temperature rapidly rises to the fixing temperature. It was necessary to raise the temperature, and therefore the temperature displacement was large and the temperature control of the nip portion was difficult. Therefore, the toner may not be fixed on the recording sheet due to insufficient toner dissolution or insufficient toner viscosity due to excessive toner dissolution.

[0005]

In order to solve the above problems, the present invention provides a passive electrode which is divided in the circumferential direction of a heat roller and is disposed in a heat generating layer, and power is supplied to each passive electrode. A power supply electrode, a temperature sensor that detects the surface temperature of the heat roller, and a heat generation control circuit that selectively supplies power to each power supply electrode according to a detection signal of the temperature sensor are provided.

[0006]

According to the above-mentioned solution means, when the temperature sensor detects that the surface temperature of the heat roller has dropped below the set temperature, the heat generation control circuit selectively supplies power to each power feeding electrode, The electric power supplied to is supplied to the passive electrode corresponding to the supplied electric power. The electric power supplied to the passive electrode is supplied to the heating element, so that the heating element generates heat and raises the surface temperature of the heat roller to the set temperature. Further, when the temperature sensor detects that the surface temperature of the heat roller has risen and has reached the set temperature, the heat generation control circuit stops the power supply to each power supply electrode. As described above, the surface of the heat roller is always kept at a temperature at which the toner can be fixed.

[0007]

Embodiments of the present invention will be described in detail below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element common to each drawing.

First Embodiment FIG. 1 is a schematic configuration diagram showing a heat roller of a first embodiment according to the present invention, and FIG. 2 is a schematic configuration diagram showing a heat fixing device of the first embodiment. 3 is a sectional view of the heat roller of the first embodiment, and FIG. 4 is a schematic configuration diagram showing the conductive plate of the first embodiment. The electrophotographic printer has a heat fixing device 1 as shown in FIG. 2, and the heat fixing device 1 includes a heat roller 2, a thermistor 4, which is a temperature sensor, a pressure roller 3, a separation claw 5, and a cleaning pad 11. have. The heat roller 2 includes a heat generating layer 6, a release layer 7 covering the outer peripheral surface of the heat generating layer 6, a heat insulating layer 8 provided on the inner peripheral surface of the heat generating layer 6, and a diagram provided at both ends of the heat generating layer 6. The passive electrode 9 shown in FIG.

The heat generating layer 6 includes four heat generating elements 6 on the heat insulating layer 8.
a to 6d, and a gap h is provided between the heating elements 6a to 6d. Each heating element 6a-6d has a specific strength,
A unidirectional fiber sheet made of a composite material in which carbon fibers having an excellent specific elastic modulus are impregnated with a heat-resistant resin such as a polyimide resin, a bismaleimide resin, a phenol resin, and a heat-resistant epoxy resin at a constant ratio. The fiber direction is parallel to the axial direction of the heat roller 2, and the thickness of each of the heating elements 6a to 6d is smaller than usual. The heat generating layer 6 can also be formed of an integral sheet containing an insulating layer made of glass fiber or the like in the carbon fiber instead of the gap h. Further, when the heat generating layer 6 is a sheet having a low carbon fiber content, the intercarbon fiber resistance is very high in the carbon fiber axial direction, and thus an insulating layer is not necessary.

The release layer 7 is made of a fluororesin such as PFA, PTFE or FEP and has a thickness of 5 to 30 μm.
The heat insulating layer 8 is made of a composite material in which glass fibers are impregnated with a heat-resistant resin such as a polyimide resin, a bismaleimide resin, a phenol resin, and a heat-resistant epoxy resin at a certain ratio, and the thickness thereof is 6 a to 6 d. Is about the same.
As the heat insulating layer 8, a sheet in which fibers are arranged in a direction perpendicular to the axial direction of the heat roller 2 and a sheet in which fibers are arranged in parallel or a sheet in which fibers are woven into a woven state are used. Therefore, the rigidity can be increased. Also,
It is possible to use not only glass fibers but also other heat resistant fibers, or to combine different fibers.

The passive electrode 9 has electrodes 9a provided at both axial ends of each of the heating elements 6a to 6d, and a conductive plate 9b that contacts the electrodes 9a. Each conductive plate 9b is attached to an insulating boss 12 press-fitted into both ends of the heat roller 2,
It is arranged so as not to come into contact with anything other than the corresponding electrode 9a.
The boss 12 has a concentric mounting portion. Further, the tips 10a of the feeding leaf springs 10 which are feeding electrodes are in contact with the conductive plates 9b. A rear end (not shown) of the power supply leaf spring 10 is connected to a heater drive circuit described later.

The heat roller 2 is rotatably supported by bearings 14 at both ends, and the bearings 14 are fixed to the frame 13.

The pressure roller 3 is rotatable about a shaft 3a as a center of rotation and is in pressure contact with the heat roller 2 to form a nip portion I which is a contact portion.

The thermistor 4 contacts the surface of the heat roller 2 and detects the surface temperature of the heat roller 2. In addition, the cleaning pad 1 is attached to the heat roller 2.
1, the cleaning pad 11 cleans the outer peripheral surface of the heat roller 2. Separation claw 5
The tip of the spring is lightly contacted with the heat roller 2 by the spring 12 attached to the frame 13, and the recording sheet 17 which is the recording medium stuck to the heat roller 2 is separated from the heat roller 2.

Next, the control system of the first embodiment will be described with reference to FIG. FIG. 5 is a block diagram showing the control system of the first embodiment. A ROM 19 and a temperature detection circuit 20 are connected to a central control unit (hereinafter referred to as CPU) 18.
The ROM 19 stores the control sequence of the heat fixing device 1. Further, the CPU 18 has ports 21 to 24
Are provided, and each port 21 to 24 has a port 2
Heater drive circuits 21a to 24a, which are heat generation control circuits corresponding to 1 to 24, are respectively connected. The thermistor 4 is connected to the temperature detection circuit 20, and
Each of the heater drive circuits 21a to 24a is connected to the heating elements 6a to 6d via the above-mentioned conductive plate 9b and electrode 9a. The heater drive circuits 21a to 24a are connected to the power supply 25 on the device 1 side. Further, a thermostat 26 is connected to each of the heating elements 6a to 6d, and the thermostat 26 is connected to a power supply 25. The thermostat 26 cuts off the power supply to the heater drive circuits 21a to 24a when the heat roller 2 is abnormally heated.

The detection result of the surface temperature of the heat roller 2 by the thermistor 4 is sent to the temperature detection circuit 20, and the temperature detection circuit 20 compares the set value preset in this circuit 20 with the detection result of the thermistor 4. , The comparison result is C
It is designed to be sent to the PU 18. Based on the comparison result, the CPU 18 selects the required ports 21 to 24 and selectively sends a drive signal to the heater drive circuits 21a to 24a.

Next, the fixing operation of the heat fixing device 1 having the above structure will be described with reference to FIG. FIG. 6 is a time chart showing the fixing operation of the first embodiment, in which a temperature displacement diagram of the surface temperature e of the heat roller 2 is shown.

First, the power supply 25 is turned on and the heat fixing device 1 is turned on.
When a print command is sent to the thermistor 4, the thermistor 4 detects the surface temperature of the heat roller 2, and the detected result is detected by the temperature detection circuit 2.
Send to 0. The temperature detection circuit 20 compares the set value with the detection result of the thermistor 4, and sends the comparison result to the CPU 18. When the detection result is lower than the set temperature F at the time t1, the heater drive circuit 21a is supplied from all the ports 21 to 24.
A drive signal is sent to each of .about.24a. This allows the power supply leaf spring 10 to be connected to the conductive plate 12 through the wiring.
The electrode 9a is energized via. From the above, all heating elements 6
The a to 6d generate heat and the surface temperature of the heat roller 2 rises. When the surface temperature of the heat roller 2 reaches the set temperature E at time t2, the CPU 18 stops sending the drive signal to the ports 21 to 24 and rotates the heat roller 2 in the direction of arrow A as shown in FIG. . The rotation of the heat roller 2 causes the pressure roller 3 to rotate in the direction of arrow B to start the heat fixing operation.

That is, when the recording sheet 17 to which the toner 17a is attached is guided to the sheet guide 16 by the conveying roller (not shown) and is conveyed to the fixing device 1, the recording sheet 17 is pressed and nipped at the nip portion I, and the toner 17a. Is melted by the heat of the heat roller 2 and fixed on the recording sheet 17. The recording sheet 17 is conveyed in the direction of arrow C by the heat roller 2 and the pressure roller 3. At this time, when the recording sheet 17 adheres to the heat roller 2 due to the adhesive property of the toner 17 a, the separation claw 5 separates the recording sheet 17 from the heat roller 2.

During the fixing operation, when the surface temperature of the heat roller 2 decreases to the set temperature E or lower due to the fixing operation, the CPU 18 selects the port 21 and the port 23 at time t3 and sends a drive signal to the heater drive circuits 21a and 23a. The heating element 6a and the heating element 6c are caused to generate heat for a certain period of time from t3 to t4. Next, at time t4, the CPU 18 selects the port 22 and the port 24 to select the heater drive circuit 2
A drive signal is sent to 2a and 24a to heat the heating elements 6b and 6d for the same time as the heating times of the heating elements 6a and 6c. As described above, the CPU 18 controls the heating elements 6 facing each other.
a, 6c and the heating elements 6b, 6d are alternately heated for a certain period of time to raise the surface temperature of the heat roller 2. Then, when the surface temperature reaches the set temperature E again, at time t5, the CPU
Reference numeral 18 stops sending the drive signal to the heater drive circuit 21a until the surface temperature becomes equal to or lower than the set temperature E at time t6. After that, until the fixing operation is completed, the CPU
18 repeats the operation from time t3 to t6. When the fixing operation is completed, the CPU 18 stops sending the drive signal.

In the first embodiment, since the heat roller 2 has a small thickness, all the heating elements 6a to 6a are warmed up during warming up.
By heating 6d, the surface temperature of the heat roller 2 can be raised to the set temperature E in a short time. Further, when the surface temperature decreases and becomes equal to or lower than the set temperature E during the fixing operation, the CPU 18 causes the opposing heating elements 6a and 6c and the heating elements 6b and 6d to alternately generate heat. It becomes half of the electric energy during heat generation of ~ 6d.

In the above embodiment, when the CPU 18 selectively outputs the drive signal from the ports 21 to 24, the port 21 and the port 23 are first selected, but if the surface temperature of the heat roller 2 reaches the set temperature E. Therefore, the ports 22 and 24 may be selected first.

Second Embodiment A second embodiment will be described with reference to FIGS. FIG. 7 is a time chart showing the fixing operation of the second embodiment, in which a temperature displacement diagram of the surface temperature e of the heat roller 2 is shown. FIG. 8 is a schematic configuration diagram showing the heat roller of the second embodiment, and FIG. 9 is a schematic configuration diagram showing the Hall sensor of the second embodiment. In the second embodiment, a range H wider than the nip portion I of the first embodiment is set, and the heating elements 6a to 6d located in this range H are given priority to generate heat.

A shaft 15 is fixed to the center of a boss 12 provided at one end of the heat roller 2 so that the shaft 1
A disk 28 provided with a permanent magnet 27 for a Hall sensor is attached to the tip of 5. The permanent magnet 27 is provided on the disk 28 at a position corresponding to the gap h between the heating element 6a and the heating element 6d, and when the permanent magnet 27 comes to the position of the hall sensor 29,
An output is generated from the hall sensor 29. The Hall sensor 29 is provided in the heat fixing device at a position where the end of the range H on the heating element 6b side is detected. When the permanent magnet 27 passes through the hall sensor 29 due to the rotation of the heat roller 2, the CPU 18 inputs the output of the hall sensor 29,
The position of the gap h between the heating element 6a and the heating element 6d is detected. The other structure is similar to that of the first embodiment.

Next, the fixing operation of the second embodiment will be described. The operation from time t1 to time t3 shown in FIG.
The description is omitted because it is the same as the first embodiment. The thermistor 4 detects the surface temperature of the heat roller 2 and sends the detection result to the temperature detection circuit 20. Temperature detection circuit 20
Compares the set value with the detection result of the thermistor 4, and sends the comparison result to the CPU 18. Also, every time the heat roller 2 makes one rotation, the CPU 18 detects that the gap h between the heating element 6a and the heating element 6d is located at the end of the range H on the heating element 6b side. During the fixing operation, when the CPU 18 detects that the surface temperature of the heat roller 2 has dropped below the set temperature E at time t3 due to the fixing operation, the CPU 18 causes
Finally, after the permanent magnet 27 crosses the Hall sensor 29, the number of pulses supplied to the pulse motor is measured to detect the heating element at the nip position I and heat the heating element.

Therefore, for example, as shown in FIG.
When the CPU 18 detects that a is within the range H, the heating element 6a is prioritized, and at time t3, the CPU 18 selects the port 21 and the port 24 and sends a drive signal to the heater drive circuits 21a and 24a. The heating element 6a and the heating element 6c are caused to generate heat. After this, the hall sensor 29
Based on the number of pulses similarly measured by the CPU 18 based on the output from the CPU 18, the gap h between the heating element 6a and the heating element 6b is obtained at time t7.
When it is detected by the CPU 18 that the temperature is within the range H, the CPU 18 performs the on / off control from the time t7 to the time t8, and the heating elements 6a, 6c,
And the heating elements 6b and 6d are caused to generate heat alternately. After this, the gap h between the heating element 6a and the heating element 6b goes out of the range H, and C
When it is detected that only the heating element 6b is located within the range H at the time t8 by the number of pulses similarly measured by the PU 18, the CPU 18 selects the port 22 and the port 24 and outputs a drive signal to the heater drive circuits 22a and 24a. Send
The heating elements 6b and 6d are caused to generate heat. Then, when the CPU 18 detects that the gap h between the heating element 6b and the heating element 6c is within the range H based on the number of pulses similarly measured by the CPU 18, the CPU 18 performs the control from time t7 to time t8 again.

When the surface temperature rises and reaches the set temperature E at time t9, thereafter, the surface temperature rises at the set temperature E at time t10.
Until the temperature goes below the CPU 18, the CPU 18 keeps the heater drive circuit 2
The output of the drive signal to 1a to 24a is stopped. After that, the CPU 18 repeats the control from the time t3 to the time t10 until the fixing operation is completed. When the fixing operation is completed, the CPU 18 stops sending the drive signal.

In the second embodiment, the CPU 18 sets the range H
By preferentially generating heat inside the heating element,
The temperature of the nip portion I can be controlled more efficiently even at a low temperature or on a recording sheet having poor fixability.

Third Embodiment A third embodiment will be described with reference to FIGS. 5, 8, 10 and 11. FIG. 10 is a time chart showing the fixing operation of the third embodiment, and FIG. 11 is a schematic configuration diagram showing the heat fixing device of the third embodiment. In the third embodiment, the heat roller 2 is not entirely heated but only a part thereof is heated.

One end of a support member 33 is inserted inside the heat roller 2 provided in the heat fixing device 30, and a thermistor 31 is provided at this one end via a spring 32. The thermistor 31 is in pressure contact with the heat insulating layer 8 of the heat roller 2 facing the nip portion I by the biasing force of the spring 32. The other end of the support member 33 is fixed to the frame 13 on the device 30 side. The other structure is similar to that of the second embodiment.

Next, the fixing operation of the third embodiment will be described. First, when the power supply 25 is turned on and a print command is sent to the heating and fixing device 30, the CPU 18 positions the nip portion I by the number of pulses similarly measured from the time when the permanent magnet 27 finally crossed the Hall sensor 29. The heating element is detected, and the heating element and the heating element located upstream of the heating element are caused to generate heat. When the temperature of the nip reaches the set temperature E, the heat roller 2 is rotated in the arrow A direction. The rotation of the heat roller 2 causes the pressure roller 3 to rotate in the direction of arrow B. That is, in FIG. 11, the heating element 6a is attached to the nip portion I at time t1.
When the CPU 18 detects that the
18 selects ports 21 and 22 and sends a drive signal to the heater drive circuits 21a and 22a to generate heat from the heating elements 6a and 6a.
Heat b. At time t11, when it is detected that the heating element 6b is located in the nip portion I by the similarly measured number of pulses, the CPU 18 causes the heater drive circuit 21a to operate.
Sending the drive signal to the heater drive circuit 23a is stopped, the port 23 is selected, and the drive signal is sent to the heater drive circuit 23a. As described above, as the heat roller 2 rotates, the CPU 18
Selectively sends a drive signal to the heater drive circuit. The above operation is repeated when the temperature is equal to or lower than the set temperature E, and the fixing temperature of the nip portion I is kept constant.

In the third embodiment described above, it is sufficient to maintain the fixing temperature not on the entire surface of the heat roller 2 but on the surface of the heat roller 2 in the nip portion I, so that the set temperature can be reached in a shorter time than in the first and second embodiments. Can be raised. Further, in the third embodiment, the heating element of the nip portion I and one heating element adjacent to the upstream of the heating element generate heat, but when the number of heating elements is larger than that of the third embodiment, the nip portion I is heated. Not only the heating element adjacent to the heating element, but also a plurality of heating elements located upstream of the nip portion I may generate heat.

By the way, in the first, second and third embodiments, the case where the heat generating layer is divided into four is explained.
It does not have to be limited to one. Further, by changing the number of divisions of the heat generating layer, it is possible to set the amount of electric power to be a percentage of the heating amount of all the heating elements. Further, when attaching the conductive plate, instead of changing the height of each conductive plate as shown in FIGS. 1 and 8 and attaching it, an insulating member is provided between each adjacent conductive plate, May be mounted flat.

[0034]

As described above in detail, according to the present invention, the heat generating layer provided on the outer peripheral surface of the heat roller is provided with the passive electrodes which are divided in the circumferential direction, and these passive electrodes are respectively provided. The surface of the heat roller is equipped with a power supply electrode that supplies power, a temperature sensor that detects the surface temperature of the heat roller, and a heat generation control circuit that selectively supplies power to each power supply electrode according to the detection signal of the temperature sensor. The temperature is always kept at a temperature at which the toner can be fixed. Therefore, during the fixing operation, it is not necessary to rapidly raise the heat generating layer of the contact portion to the fixing temperature, and it becomes possible to perform control with good responsiveness, and fixing failure due to insufficient toner dissolution or insufficient toner viscosity due to excessive toner dissolution does not occur.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a heat roller of a first embodiment according to the present invention.

FIG. 2 is a schematic configuration diagram illustrating a heat fixing device according to an embodiment.

FIG. 3 is a cross-sectional view of a heat roller of an example.

FIG. 4 is a schematic configuration diagram showing a conductive plate of an example.

FIG. 5 is a block diagram showing a control system of the embodiment.

FIG. 6 is a time chart showing the fixing operation of the first embodiment.

FIG. 7 is a time chart showing a fixing operation of the second embodiment.

FIG. 8 is a schematic configuration diagram showing a heat roller of a second embodiment.

FIG. 9 is a schematic configuration diagram showing a Hall sensor of a second embodiment.

FIG. 10 is a time chart showing the fixing operation of the third embodiment.

FIG. 11 is a schematic configuration diagram showing a heat fixing device of a third embodiment.

[Explanation of symbols]

 1, 30 Heat Fixing Device 2 Heat Roller 4 Thermistor 6 Heating Layer 9 Passive Electrode 10 Power Supply Leaf Spring 17 Recording Sheet 18 CPU 21a to 24a Heater Drive Circuit

Claims (5)

[Claims] 1. A heating layer provided on an outer peripheral surface of a rotatable cylindrical heat roller is supplied with electric power to heat a contact portion in contact with the recording medium, and the recording medium is pressed together with the pressure roller in pressure contact with the contact portion. In a heat fixing device that heat-fixes a toner image on a recording medium to a recording medium by sandwiching and conveying, a passive electrode disposed in a heat generating layer divided in the circumferential direction of the heat roller, and power is supplied to each passive electrode. The heat fixing device is provided with a power supply electrode for supplying heat, a temperature sensor for detecting the surface temperature of the heat roller, and a heat generation control circuit for selectively supplying power to each power supply electrode according to a detection signal of the temperature sensor. apparatus. 2. A heating layer provided on the outer peripheral surface of a rotatable cylindrical heat roller is supplied with electric power to heat a contact portion in contact with the recording medium, and the recording medium is pressed together with the pressure roller in pressure contact with the contact portion. In the heat fixing method of thermally fixing the toner image on the recording medium to the recording medium by nip-conveying, the passive electrodes arranged in the heat generating layer are divided in the circumferential direction of the heat roller, and power is supplied to each passive electrode. Is provided with a power supply electrode for supplying heat, a temperature sensor for detecting the surface temperature of the heat roller, and a heat generation control circuit for selectively supplying power to each power supply electrode according to a detection signal of the temperature sensor. Until the temperature reaches the set temperature, the heat generation control circuit supplies power to all passive electrodes arranged on the heating element, and after reaching the set temperature, power supply to all passive electrodes is stopped. A fixing method in which the heat generation control circuit selectively supplies power to a predetermined combination of passive electrodes to raise the temperature to a set temperature when the temperature falls below the set temperature. 3. The selective power supply of the heat generation control circuit includes:
The heat fixing method according to claim 2, wherein power is sequentially supplied to a predetermined combination of all the passive electrodes for a certain period of time until the surface temperature of the heat roller reaches a set temperature. 4. The selective power supply of the heat generation control circuit includes:
Power is supplied to a predetermined combination of all passive electrodes in sequence for a certain period of time while the divided parts of the passive electrode are located at the contact part, and while the passive electrode is located at the contact part, this passive electrode and this passive electrode are The fixing method according to claim 3, wherein electric power is supplied to a passive electrode paired with the electrode. 5. An electric power is supplied to a heat generating layer provided on the outer peripheral surface of a rotatable cylindrical heat roller to heat a contact portion in contact with the recording medium, and the recording medium is pressed together with the pressure roller in pressure contact with the contact portion. In the heat fixing method of thermally fixing the toner image on the recording medium to the recording medium by nip-conveying, the passive electrodes arranged in the heat generating layer are divided in the circumferential direction of the heat roller, and power is supplied to each passive electrode. The power supply electrode for supplying heat, the temperature sensor for detecting the surface temperature of the heat roller, and the heat generation control circuit for selectively supplying power to each power supply electrode according to the detection signal of the temperature sensor are provided. Fixing method in which electric power is supplied to the passive electrode located in the position and the passive electrode located upstream of the passive electrode for a certain period of time.