JP2001194948A - Thermal fixing unit and image recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that current conduction control itself becomes complicated when it is performed by estimating the temperature of an end part outside a paper passing area by the relation of temperature and paper size because it must be changed according to the paper size in order to prevent the temperature rise of the end part outside the paper passing area from occurring. SOLUTION: This device is provided with plural temperature detection means arranged at different positions, a temperature difference calculation means calculating difference between temperature detected by the temperature detection means and a control means controlling a heat source based on the difference between the detected temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for heating an unfixed toner image formed on a recording material (hereinafter referred to as transfer paper or paper) by electrophotography using a copying machine, a laser beam printer, or the like. The present invention relates to a heat fixing device for fixing and an image recording apparatus (image forming apparatus) to which the heat fixing device is applied.

[0002]

2. Description of the Related Art Conventionally, this type of heat fixing device is provided with a plurality of heating elements such as ceramic heaters and halogen heaters provided with heating elements at different positions and one temperature detecting means such as a thermistor at a predetermined position. The heating element is turned on and off according to the detected temperature to control the temperature.

On the other hand, when small-sized paper is passed, heat is taken away by the paper only in the paper passing portion, and the temperature of the end outside the paper passing area rises. In order to prevent this temperature rise, the temperature of the end portion is predicted based on the paper size, and the heating element is controlled.

[0004]

However, in this case, the control must be changed depending on the paper size in order to prevent a temperature rise at the end outside the paper passing area. Since the control is performed by predicting the temperature of the section, there is a problem that the control itself is complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and there is provided a heat fixing device capable of eliminating abnormal temperature rise in the outer end portion of a sheet passing area by simple control and preventing thermal damage. It is another object of the present invention to provide an image forming apparatus capable of forming a high quality image by applying the heat fixing device.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a heat fixing device and an image recording apparatus having the following constitution.

(1) In a heating and fixing device for heating and fixing unfixed toner formed and carried on a recording material to a recording material by using a plurality of heat sources having different positions of heating elements, a plurality of heat sources are provided at different positions. Temperature detection means, and a temperature difference calculation means for calculating the difference between the temperatures detected by these temperature detection means,
And a control unit for controlling the amount of heat generated by each heat source so as to reduce the difference according to the detected temperature difference.

(2) The heating / fixing device according to (1), wherein the control means changes a paper passing interval according to the detected temperature difference.

(3) An image recording apparatus having image forming means for forming an image with unfixed toner, and heat fixing means for heating and fixing the unfixed toner formed and carried on the recording material by the image forming means to the recording material. , Wherein the heat fixing means is the heat fixing device according to (1) or (2).

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a schematic structural view of an image recording apparatus using an electrophotographic process to which the heat fixing device of the present invention is applied, and shows, for example, a case of a laser beam printer. Laser beam printer main body 101 (hereinafter, main body 1)
01) is a cassette 102 for storing the recording paper S.
A cassette presence / absence sensor 103 for detecting the presence / absence of the recording paper S stored in the cassette 102;
A cassette size sensor 104 (comprised of a plurality of microswitches) for detecting the size of the recording paper S stored in the cassette 2 and a paper feed roller 105 for feeding out the recording paper S from the cassette 102 are provided.

A registration roller pair 106 is provided downstream of the paper feed roller 105 to convey the recording paper S in synchronization with image formation on a photosensitive drum 117 described later. An image forming unit 108 that forms an unfixed toner image on the recording paper S based on a laser beam from the laser scanner unit 107 is provided downstream of the registration roller pair 106. The recording paper S is located downstream of the image forming unit 108.
A heat fixing device (hereinafter, referred to as a fixing device) 10 of the present invention for heating and fixing an unfixed toner image formed on the recording paper.
In the downstream of the fixing device 109, a paper discharge sensor 110 for detecting a conveyance state of a paper discharge unit, a paper discharge roller 111 for discharging the recording paper S, and a recording paper S on which recording is completed are stacked. The loading tray 112 is provided.

The laser scanner 107 includes a laser unit 113 that emits a laser beam modulated based on an image signal (image signal VDO) sent from an external device 128 described later, and a laser beam from the laser unit 113. Are constituted by a polygon motor 114 for scanning a photosensitive drum 117 to be described later, an imaging lens 115, a return mirror 116, and the like.

The image recording apparatus 108 includes a photosensitive drum 117, a primary charging roller 119, a developing unit 120, a transfer charging roller 121, a cleaner 122, and the like, which are necessary for a known electrophotographic process. Further, the heat fixing device 10
9 is a fixing film 109a, a pressure roller 109b, a ceramic heater 109c provided inside the fixing film,
It comprises a thermistor 109d provided at the center of the heater for detecting the surface temperature of the ceramic heater 109c, and a thermistor 109e provided at the end of the heater.

The main motor 123 applies a driving force to the paper feed roller 105 via a paper feed roller clutch 124 and to the registration roller pair 106 via a registration roller 125, respectively. Further, a driving force is applied to each unit of the image forming unit 108 including the photosensitive drum 117, the fixing device 109, and the paper discharge roller 111.

The engine controller 126 includes a laser scanner unit 107, an image forming unit 108, and a heat fixing unit 109.
Controls the electrophotographic process, transports the recording paper in the main body 101, and the like.

The video controller 127 is connected to an external device 131 such as a personal computer by a general-purpose interface (Centronics, RS232C, etc.) 130, and develops image information sent from the general-purpose interface 130 into bit data. Using the bit data as a VDO signal, the engine controller 1
26.

FIG. 2 shows a ceramic heater 1 according to the present invention.
A drive and control circuit 09c is shown, and 201 is a commercial AC power supply. This AC power supply 201 is an AC filter 2
The ceramic heater 109c generates heat by being supplied to the ceramic heater 109c through the line 02.

As shown in FIG. 3, the ceramic heater 109c has a heat resistance and an insulating property, and is formed on a flat substrate using a material having good heat conductivity, such as aluminum nitride (heat conductivity: 100 W / mK). And two heating elements (109c-1 having a heat generating position at the center and 109c-2 having a heat generating position at an end) are formed.
The heating element is switched according to the width of the recording paper to be printed.

The power supply to the ceramic heater 109c is controlled by turning on and off the triacs 204 and 304. The resistors 205, 206, 305, and 306 are bias resistors for the triacs 204 and 205, and the phototriac couplers 207 and 307 are devices for securing a creepage distance between primary and secondary. The energization of the relay 213 is controlled by a signal from the control circuit 212.

The triacs 204 and 304 are turned on when the light emitting diodes of the phototriac couplers 207 and 307 are energized. The resistors 208 and 308 are resistors for limiting the current of the phototriac couplers 207 and 307, and their energization is controlled by turning on / off the transistors 209 and 309.

The transistors 209 and 309 are connected to the resistor 21
0, 310, and is connected to the control circuit 212, and operates according to an ON signal from the control circuit 212. Filter 2
11, 311 are ceramic heaters 109c-1, 10c.
It is provided to suppress noise generated when the 9c-2 is turned on / off.

The AC power supply 201 includes an AC filter 2
The signal is input to the zero-crossing detection unit of the control circuit 212 via the signal line 02. A zero-crossing detector (not shown) of the control circuit 212 notifies the inside of the control circuit 212 by a pulse signal that the voltage of the AC power supply 201 is lower than a certain threshold. Hereinafter, this signal transmitted by the zero-cross detection unit of the control circuit 212 is referred to as a ZEROX signal. The control circuit 212 detects the edge of the pulse of the ZEROX signal and controls the triac 20 by phase control or wave number control.
4, 304 on / off.

The temperature detecting elements 109d and 109e are, for example, thermistor temperature detecting elements and detect the temperature of the ceramic heater 109c. This temperature detecting element 109
The temperature detected by d,.
a, 215b and the divided voltage between the temperature detecting elements 109d, 109e are detected and input to the control circuit 212 as a TH signal to be subjected to analog / digital (A / D) conversion. The control circuit 212 has an ALI 212c for calculating the difference (T = T2−T1) between the TH signals T1 and T2, a ROM 212b for presetting a constant value Ta, a value T for these difference and a preset value. A comparator 212a for comparing Ta is provided, and the difference between the temperature detecting means 109d and 109e is calculated and compared with a preset value Ta.

The preset value Ta is set differently depending on the paper size. The temperature of the ceramic heater 109c is controlled by the control circuit 2 as a TH signal.
12, the power to be supplied to the ceramic heater 109 is calculated by comparing with the set temperature of the ceramic heater 109c set in the control circuit 212, and the phase angle (phase) corresponding to the supplied power is calculated. Control) or a wave number (wave number control), and the control circuit 212 sends an ON signal to the transistors 209 and 309.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG.

First, when the printing operation is started, the triacs 204 and 304 are turned on to drive the heaters 109c-1 and 109c-2 (step S1).
Then, the sheet feeding and conveying operations are performed (S2), and the temperature detection element 109d detects the temperature T1 of the heater 109c-1.
(S3), the heater 1 is detected by the temperature detecting element 109e.
A temperature detection T2 of 09c-2 is performed (S4).

Then, the temperature detecting elements 109d, 109e
Is input to the ALI 212c, and the ALI
T = T2-T1 is calculated from 2c (S5), and T becomes R
A value Ta corresponding to the paper size set and stored in the OM 212b
It is determined whether it is larger than (S6).
If it is larger, it is determined that the temperature at the end outside the historical region is rising, and the triac 304 is turned off to turn off the heater 109c-2 (S7).

Further, T = T2-T by ALI 212c.
1 is calculated (S8), and it is determined whether the value is smaller than a value Ta set in the ROM 212b (S8).
9) If larger, return to S7; if smaller, heater 109
The triac 304 is turned on to turn on c-2 (S10), and the process returns to S3.

In the first embodiment, by performing such control,
It is possible to eliminate abnormal temperature rise at the end outside the paper passing area by simple control.

(Embodiment 2) FIG. 5 is a flow chart for explaining the operation of a heat fixing device according to Embodiment 2 of the present invention. The configuration of an image recording apparatus to which the heat fixing device of Embodiment 2 is applied is Embodiment 1. This is the same as the image recording apparatus shown in FIG. Next, the operation of this embodiment will be described with reference to the flowchart of FIG.

First, when the printing operation is started, the triacs 204 and 304 are turned on to drive the heaters 109c-1 and 109c-2 (step S1).
1). Then, the paper feeding and conveying operations are performed at a speed corresponding to the designated paper size (S12), and the temperature detecting element 1
09d, the temperature detection T1 of the heater 109c-1 is performed (S13), and the heater 109c is detected by the temperature detection element 109e.
The temperature detection T2 of c-2 is performed (S14).

Then, the temperature detecting elements 109d, 109e
Is input to the ALI 212c, and the ALI
T = T2-T1 is calculated by 2c (S15),
Is a value Ta corresponding to the paper size set in the ROM 212b.
It is determined whether or not it is larger than (S16).
3, if it is larger, it is determined that the temperature at the end outside the paper passing area is raised, and the operation timing of the paper feed motor is set to be such that the paper interval is increased based on the output signal from the control circuit 212 in FIG. The operation is performed at the timing (S17).

Further, T = T2−T is obtained by the ALI 212c.
1 (S18), and determines whether the value is smaller than a value Ta set in the ROM 212b (S1).
9) If it is larger, the process returns to S17; if it is smaller, the operation timing of the paper feed motor is operated at such a timing as to restore the paper interval (S20), and the process returns to S13.

In the second embodiment, by performing such control,
With simple control, it is possible to eliminate abnormal temperature rise at the end of the heating area outside the paper passing area.

[0036]

As described above, according to the present invention, the difference between the temperatures detected by the plurality of temperature detecting means provided at different positions is calculated by the temperature difference calculating means, and the difference between the calculated detected temperatures is calculated. Since the heat source is controlled by the control, it is possible to eliminate abnormal temperature rise at the end outside the paper passing area with simple control without predicting and controlling the correlation between the paper size and the temperature. There is an effect that a heat fixing device in which thermal damage is prevented can be obtained.

Further, since the paper passage interval is changed according to the detected temperature difference, abnormal temperature rise at the end outside the paper passage area can be eliminated by simple control, thereby preventing thermal damage. There is an effect that a heat fixing device can be obtained.

Further, by applying the heat fixing device of the present invention as the heat fixing means, there is an effect that an image recording apparatus capable of forming a high quality image by stable heat fixing can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an image recording apparatus to which a heat fixing device according to a first embodiment of the present invention is applied.

FIG. 2 is a control and drive circuit diagram of a heat fixing device applied to the image recording apparatus according to the first embodiment of the present invention.

FIG. 3 is a plan view showing a configuration of a ceramic heater.

FIG. 4 is a flowchart illustrating an operation of the heat fixing device according to the first exemplary embodiment of the present invention.

FIG. 5 is a flowchart illustrating an operation of the heat fixing device according to the second embodiment of the present invention.

[Explanation of symbols]

101 is an image forming apparatus, 109 is a heat fixing device, 109c
Is a ceramic heater, 109d and 109e are thermistor temperature detecting elements, 126 is an engine controller, and 12 is a control circuit.

Continued on the front page F term (reference) 2H027 DA12 DE10 EA12 ED17 2H033 AA23 AA24 AA42 BA25 BA32 CA04 CA07 CA30 CA37 CA48 5H323 AA36 BB17 CA08 CB02 DA01 DA09 EE11 FF01 FF10 HH02 KK05 MM11 MM14 5H05 EB03 EB03 DD03 DD03 EB38 FF03 FF14 FF21 FF22 KK08

Claims (3)

[Claims] 1. A heating and fixing device for heating and fixing an unfixed toner formed and carried on a recording material to a recording material by using a plurality of heat sources having different positions of heating elements, wherein a plurality of heat sources are provided at different positions. Temperature detecting means, temperature difference calculating means for calculating the difference between the temperatures detected by these temperature detecting means, and control means for controlling the amount of heat generated by each heat source so as to reduce the difference based on the detected detected temperature difference A heating fixing device comprising: 2. The heat fixing device according to claim 1, wherein the control means changes a paper passing interval according to the detected temperature difference. 3. An image recording apparatus comprising: image forming means for forming an image with unfixed toner; and heat fixing means for heating and fixing the unfixed toner formed and carried on the recording material by the image forming means to the recording material. 3. An image recording apparatus, wherein the heat fixing means is the heat fixing device according to claim 1.