JPS6046711B2 - heat source device - Google Patents

Description

[Detailed Description of the Invention] A heat source device such as a heat fixing device, a drying device, etc. that uses heat, RFI, Ushin7'', Pilgrimage transfer, decoding, and decoding. It is.

For ease of explanation, an electronic copying machine will be described below as an example, but the present invention is not limited to copying machines.

In an electronic copying machine, a drum having a photosensitive layer is uniformly charged by corona discharge, and then the image is exposed to form an electrostatic latent image. Usually, toner is attached to the electrostatic latent image, the image is developed and visualized, and then transferred onto ordinary paper, and the transferred paper is heated with a heat source to fix the toner on the paper. There are many types of fixing devices, including a method of heating a metal plate made of aluminum, iron, etc. using an infrared lamp, hot air, or nichrome wire.

FIG. 1 shows such a conventional heating device, in which a fixing device 11 includes a plurality of infrared lamps 12, an upper lamp 14 located above the paper 13 in the fixing device, and an upper lamp 14 located above the paper 13. Lower lamp 1 located below/toward
The lower lamp 15 is always on, and the upper lamp 14 is turned on and off based on the temperature output detected by a temperature sensing element 16 located within the fixing device. Therefore, the temperature inside the fixing device 11 is as shown in FIG.
The upper lamp lights up until the set temperature reaches 0, and the upper lamp turns off when the temperature inside the fixing device 11 reaches TO at the time of turning, but after the temperature rises slightly due to preheating, it drops. However, when the temperature drops below the set temperature after time Tb, the upper lamp lights up again, but since the temperature of the lamp cannot rise immediately, the temperature continues to fall for a while, and after a certain period of time, it starts to rise, and then the temperature rises again. When it is too busy, the upper lamp will turn off again. There is a system that keeps the temperature of the fixing device at approximately TO by repeating such an operation, but with this method, when the upper lamp is on, the temperature on the top surface of the paper located in the device is high; There were variations in the temperature distribution, with the temperature being lower when the lights were off. FIG. 3 shows another embodiment of a conventionally used heating device, in which a first nichrome wire 17 to which a current is constantly applied and a second nichrome wire to which ON-OFF control is performed by the output of a temperature sensing element 18. The wires 19 are arranged alternately, the insulating material 20 is arranged so as to surround the nichrome wires 18 and 19, and the metal plate 2 is placed over the insulating material 20.
By covering the metal plate 21 with a heat sink, the metal plate 21 can be used as a heat sink.

In this heating device as well, the second nichrome wire 19 is controlled ON-OFF in the same manner as in FIG.
Looking at the temperature distribution inside the fixing device, when both the first and second nichrome wires are heated, even though the surface of the metal plate has a roughly uniform temperature distribution, only the first nichrome wire is heated. When being driven, the temperature of the part adjacent to the first nichrome wire is high and the temperature is high in the part adjacent to the second nichrome wire. The temperature distribution was uneven. In order to eliminate this drawback, a single heater is used, and the phase angle of the alternating current signal, which is the drive signal for the heater, is continuously controlled by the output of a temperature sensing element. However, such continuous control of the phase angle has the disadvantage that noise is generated because the drive signal is switched at a high level point of the AC signal.

The present invention eliminates the above-mentioned drawbacks of the conventional heat source.The present invention is designed to eliminate the above-mentioned drawbacks of the conventional heat source.The present invention is designed to eliminate the above-mentioned drawbacks of the conventional heat source. By controlling the temperature sensing element to determine whether the wave is used as the driving power to be applied to the heat source, the temperature distribution within the heating device is made uniform, and the generation of noise during temperature control is prevented.

That is, the present invention comprises an AC power source 27 (22 in FIG. 4), a single heat source 39 (23 in FIG. 4) that generates heat when energized, and a first switching element for controlling the flow of current to the heat source. 44, a temperature sensing element 38 (24 in FIG. 4) for detecting the temperature from the heat source, and the temperature sensing element 3
8) a control circuit (25 in FIG. 4) that controls the timing of energization of the first switching element 44 in accordance with the temperature to control the amount of energization to the heat source 39; The circuit includes a second switching element TRl that performs a switching operation near the zero point of the AC in synchronization with the AC waveform of the AC power supply 27, and further includes a control pulse having a period determined by the temperature detection signal from the temperature detection element 38. has a third switching element 33 that generates electricity in response to the switching operation of the second switching element, and controls the timing of energization of the first switching element 44 by a control pulse from the third switching element 33. The heat source device is characterized in that the basic waveform of the AC power source 27 is applied to the heat source 39 at a predetermined period determined by the detected temperature.

Below, the present invention will be described with reference to the drawings, and FIG. By applying the power to the drive control circuit 25 controlled by the output of the heating element 24, the drive power applied from the drive control circuit 25 to the heater 23 can be changed to A, B, C, Dl in FIG. 5 or other power. Or a combination of these cycles.

That is, in the initial driving state of the heater 23, the temperature inside the fixing device 25 is sufficiently lower than the predetermined temperature, so this state is detected by the temperature sensing element 24, and the AC driving power is changed as shown in FIG. 5A. The entire half cycle is applied to the heater 23,
As the temperature inside the fixing device rises, the interval between the driving power as shown in FIG. 5B and the driving power and half-cycle power as shown in FIG. , drive power is applied alternately or selectively at a certain half-period interval or with a certain half-period interval. FIG. 6 shows a more detailed embodiment of the heat source device according to the present invention, in which the AC component from the AC power source 27 is full-wave rectified by a diode bridge B as shown in FIG. , 29 and applied to the base of the transistor TRl (second switching element).

The collector of the transistor TRl is connected to a reference potential source via a diode 30, a resistor 31, and a capacitor 32, and the cathode of a switching diode 33 is connected to the connection point between the resistor 31 and the capacitor 32. The anode of the third switching element) is connected to a reference potential source via a pulse transformer PTl. Further, a resistor 3 is provided between the collector of the transistor TRl (second switching element) and the power supply 34, and between the control electrode of the diode 33 and the power supply 34, respectively.
5 and 36 are connected, and a capacitor 3 is connected between the collector of the transistor TRl and the control electrode of the diode 37.
7 and the thermistor 38 (temperature sensing element) are inserted in series. Furthermore, a heater 39 (heat source) is provided at one end of the AC power source 27.
A capacitor 40 and an inductance 41 are connected to one end of the heater 39, one end of the capacitor 40 is connected to one end of the power source 27, and a capacitor 42 fixed to the other end of the inductance 41 is also connected to a resistor 43.
It is connected to the power supply 27 via.

A triac 44 (first switching element) is further connected between the other end of the inductance 41 and the power source 27, and the gate of the triac is connected via a diode 45 to the pulse transformer PT2.

Since this pulse transformer is inductively coupled to the pulse transformer PTl, after a pulse is applied to the pulse transformer PT2, the heater 39 is turned on while the AC power supply is at zero potential, that is, for approximately half a period. Driving power will be applied.

Now, the fifth output rectified by bridge circuit B.
In Figure E, the transistor TRl is divided by resistors 28 and 29.
(the second switching element). If the threshold voltage of this transistor TRl (second switching element) is I as shown in FIG. 5E, then the collector potential can obtain a pulse output P near the zero potential of the rectified output as shown in FIG. 5F. It is possible.
Such a pulse output is charged to a capacitor 32 via a diode 30 and a resistor 31, and its terminal potential becomes E.
Step up to 1. After the arrival of the pulse P1, the collector potential becomes O potential, and a current initially flows through the resistor 35, the resistor 36, the positive temperature sensing element 38, and the capacitor 37. Therefore, a resistor 36 is connected to the gate of the switching diode 33 (third switching element).
A voltage EG divided by the voltage E1 and the voltage E1 is applied, but if there is a relationship such as E1>EG, the charge in the capacitor 32 is held as it is until the next pulse P2 arrives. Upon arrival of the pulse P2, the capacitor 32 is charged up again, and its potential becomes E2. Thereafter, when the collector potential becomes zero again and EG is applied to the gate, assuming that E2>EG, the electric charge teared to the capacitor 32 is discharged via the switching diode 33 (third switching element) and a pulse is generated. These pulses are passed through the pulse transformers PTl and PT2 to the triax 44 (
A driving power such as PW2 is applied to the heater 39. In the above explanation, it has been explained that the resistance value of the POSISTOR is constant, but since this POSISTOR is installed adjacent to the heater 39 and its resistance value changes depending on the temperature, the EG also changes, and the resistance value of the POSISTOR changes depending on the temperature. When the temperature around J39 is high, EG is also large, and when the temperature around heater 39 is low, EG is also low.

Therefore, if the ambient temperature of the heater 39 is sufficiently low, EG will be low, and each time this pulse P7 arrives, the potential E of the capacitor 32 will satisfy E>EG, so driving power will be generated for each pulse P. However, electric power approximately as shown in FIG. 5A is applied to the heater.

As mentioned above, in the heat source device according to the present invention, the half-cycle application of driving power to the heater is determined by the output of the temperature sensing element, and the switching of the driving power for temperature control is performed at approximately zero potential. Therefore, noise generation due to switching can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a conventional fixing device, in which 11 is a fixing device, 12 is a lamp, 13 is paper, and 16 is a temperature sensing element. FIG. 2 is an explanatory diagram showing the temperature control state of the fixing device shown in FIG. 1. FIG. 3 is an explanatory diagram showing a conventional heating device.
9 is a heater, 21 is a metal plate, and 18 is a temperature sensing element. FIG. 4 is a diagram showing a heat source device according to the present invention, in which 22 is a drive power source, 25 is a drive control circuit, 23 is a heater, and 24 is a temperature sensing element.
FIG. 5 is a waveform diagram for explaining the operation of the heat source device shown in FIG. 4 and FIG. 5, which will be described later. F represents the collector potential waveform of the transistor TRl, and G represents the voltage waveform applied to the heater 39. FIG. 6 is a circuit diagram showing a heat source device according to the present invention, and 2
7 is a drive power source, B is a full-wave rectifier circuit, TRl is a transistor, 30 is a diode, 32 is a capacitor, 33 is a switching transistor, 36 is a resistor, 38 is a positive temperature sensing element, PTl, PT2 are pulse transformers, 44 is a triax, and 39 is a heater.

Claims (1)

[Scope of Claims] 1. An AC power supply, a single heat source that generates heat when energized, a first switching element for controlling the flow of current to the heat source, and a temperature detection element for detecting the temperature caused by the heat source. and a control circuit that controls the timing of energization of the first switching element according to the temperature detected by the temperature detection element to control the amount of energization of the heat source, and the control circuit is configured to control the amount of energization of the heat source. It has a second switching element that operates as a switch near the zero point of the alternating current in synchronization with the waveform, and further corresponds to the switching operation of the second switching element with a control pulse having a period determined by the temperature detection signal from the temperature detection element. and a third switching element that generates electricity, and controls the timing of energization of the first switching element by a control pulse from the third switching element, so that the basic waveform of the AC power source is applied to the heat source at a predetermined period determined by the detected temperature. A heat source device characterized by applying heat.