JPS5934576A - Temperature controller - Google Patents

Abstract

PURPOSE:To reduce noises due to power-on control over a heat source, by controlling the heat source independently of the output of a detecting means for detecting the ambient temperature of a fixation device for a specific time after the powering-on operation of the heat source is controlled. CONSTITUTION:The powering-on state of a halogen heater H1 is switched from full-wave powering-on operation to one-cycle powering on operation according to the temperature detected when the electric power is turned on, making switching temperature different. Further, when a thermistor TH1 detect the temperature in the fixation device 10 rising up to >=185 deg.C, a timer is put in operation; the powering-on operation of the heater H1 is stopped regardless of the detected temperature of the thermistor TH1 up to the time-up state of the timer. Once the thermistor TH1 detects the temperature in the fixation device 10 falling below 180 deg.C, the timer is put in operation; one-cycle electricity feeding to the heater H1 is carried out regardless of the detected temperature of the thermistor TH1 until the time-up state of the timer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control device for a fixing device in a recording apparatus such as a copying machine or a laser beam printer.

Conventionally, in the fixing device of this type of recording apparatus, the temperature of the fixing device is detected using a temperature sensing element such as a thermistor, and the supply of electricity to a heat source such as a heater is controlled when the temperature reaches a certain level. For example, if the temperature level is 180°C, 180°C
If the detected temperature is low, turn on the heater and set it to 180℃.
The heater was turned off when the detected temperature was high, regardless of whether the temperature was high or not.

However, when such control is performed, noise is likely to occur because the heater is frequently turned on and off, and when this noise is superimposed on, for example, the reference signal indicating the temperature level, this noise This caused the inconvenience of the heater being turned on and off unnecessarily.

Furthermore, when the heater is switched from an off state to an on state, a rush current flows through the heater, which also affects the AC load, such as cutting down the input power supply.

SUMMARY OF THE INVENTION An object of the present invention is to provide a temperature control device that eliminates the above-mentioned drawbacks and reduces noise generation due to power supply control of a heat source.

A further object of the present invention is to provide a temperature control device that controls the heat source for a predetermined period of time after controlling the power supply to the heat source, regardless of the detected temperature.

Another object of the present invention is to provide a temperature control device that converts a temperature detection signal into a digital signal, and uses this digital signal to control energization of a heat source at two different temperatures.
Our goal is to provide the following.

The present invention will be described in detail below with reference to embodiments.

FIG. 1 is a sectional view of a copying machine to which the present invention is applicable. In the figure, reference numeral 1 denotes a document mounting table made of a transparent member, which moves back and forth in the direction of the arrow. 2 is a short focus small diameter imaging element array;
The original image reflected by the light source 2a of the M original placed on the original placing table 1 is slit-exposed onto the photosensitive drum 3 by the array 2. A charger 4 uniformly charges the photosensitive drum 3. The uniformly charged drum 3 is subjected to image exposure by the element array 2, and an electrostatic image corresponding to the original S image is formed. Next, this electrostatic image is visualized by the fA imaging system@5. - The transfer paper P that is manually fed from above the male manual feed table 6a is placed between the feed roller 6, which rotates in response to a detection signal from the detection means 6b that detects that the transfer paper P has been manually fed, and the photosensitive drum 3. The image is fed onto the drum 3 by a registration roller 7 that rotates at the appropriate timing so that the image is placed at an appropriate position on the line transfer paper. Then, the toner image on the photosensitive drum 3 is transferred onto the transfer paper P by the transfer charger 8. Then, the transfer paper P separated from the drum 3 by the separating means 8a is guided to the fixing device 10 by the guide 9, and the toner image on the transfer paper P is fixed by the fixing roller 0a having a built-in halogen heater H. Thereafter, the sheet is discharged onto a sheet tray 12 by a sheet discharge roller 1. Note that THI is a thermistor for detecting the surface temperature of the fixing roller 01L, 8b is a cleaning means, 8
C is a cooling fan.

Now, this copying machine has a built-in manual feeding device that can feed only one sheet of transfer paper, but when copying a large number of sheets of transfer paper continuously due to an increase in the amount of copies used, etc. By connecting the attachment 13 to the lower part of the copying machine main body C, continuous feeding using the cassette 14 becomes possible.

The fixing device IO is composed of a fixing roller (ML) having a halogen heater (4) therein and a pressure roller that is in pressure contact with the fixing roller 0a. The pressure roller 10b has a structure in which a sponge layer is adhered to a core metal serving as a central axis, and an elastic coating layer is further provided on the sponge layer. A thermistor TH is provided to detect the surface temperature of the fixing roller.

FIG. 2-1 is a block diagram showing the control section of the temperature control device according to the present invention. 100 is ROM.

It is a well-known one-chip microcomputer with built-in RAM, etc., and an 8-bit A/D converter, such as Texas Instruments' TMS 23.
It is configured by 00.

101 is a transformer 110. A full-wave rectifier circuit composed of diodes 111 and 112, 102 is a full-wave rectifier circuit 1
This is an inverting amplifier circuit that inverts and amplifies the output signal from 01. 103 A thermistor for detecting the temperature of the fixing roller, which corresponds to TH in FIG. 104 is a drive circuit for a halogen heater H1 for heating the fixing roller;
Reference numeral 105 denotes a driver for driving the halogen heater drive circuit 104.

A temperature detection signal from the thermistor 103 is input to an analog input terminal A of the microcomputer 100, and is converted into a digital signal.Based on this value, temperature control as described below is performed.

When a pulse signal having a logic level of 1H is input near India and the microcomputer 100 is in an interrupt enabled state, an interrupt program is executed at the rising edge of this pulse signal. Incidentally, the waveforms of the output signals B and C of the full-wave rectifier circuit 1022 and the inverter/amplifier circuit 103 are shown in FIG. Further, a halogen heater drive circuit 104 is connected to the output capacitor R1 via a driver 105. The specific configuration of the halogen heater drive circuit 104 is as shown in FIG. , to AClo
oV is supplied.

Although not shown in FIG. 2-1, other input ports of the microcomputer 10o receive signals from various sensors, keys, etc., such as manual jam detection. The output boat also outputs control signals for various parts of the copying machine, such as the exposure lamp, paper feed roller, and optical system 2 display.

Further, the resistors R, , R2, and R8 are used to set a reference voltage for A/D converting the temperature detection signal from the thermistor 103.

Note that the temperature detection signal input to the input port A is A/D converted as follows. Baud 1 - Let the voltage value input to AI be X (V), and the port of the microcomputer 100. The reference voltage set to +II is Vhas,
Assuming VRycF, (VAS8-VREIIP >
1255 = a(X - VRIF) / a =
b, and the value obtained by converting b into a hex code becomes the digital value in analog human power X (V) 1 Implementation 1
In 1F11, the small value when the thermistor is disconnected is FF.
In addition, the circuit is configured so that the A/D value in the short-circuit state is 00. By A/D converting the temperature detection signal in this way, it becomes possible to read a wide range of temperature levels.

4-1 to 4-3 are flowcharts showing one embodiment of the present invention. In this example, the switching temperature at which the energization state of the halogen heater H is switched from full-wave energization to every other cycle energization is varied depending on the temperature detected when the power is turned on. Furthermore, after the energization starts every other cycle, the temperature inside the fuser increases by the thermistor.
When it detects that the temperature has exceeded 85℃, a timer is activated, and until the timer expires, power to the heater is stopped regardless of the temperature detected by the thermistor, and the thermistor also ensures that the temperature inside the fuser is below 180℃. When it is detected that the temperature is too long, a timer is activated, and the heater is energized every other cycle until the timer times out, regardless of the temperature detected by the thermistor.

A more detailed explanation will be given below according to the flowchart. After turning on the power, initial settings of the memory, etc. are performed in step 1. Next, in step 2, the temperature detection signal from the thermistor 103 is input to the AI and A/D converted as described above.

Then, in steps 3 to 8, the fixing roller surface temperature is determined to be 50°C or less, 80°C or less, or 100°C based on the digital value.
Hereinafter, it is determined whether the temperature is 130°C or lower, 150°C or lower, or 170°C or lower. And below 50℃.

80℃ or less, 100℃ or less, 130℃ or less.

If it is below 150℃ or below 170℃, step 9-1
4 with 7 lag F150, F/80, F/100
.

F/130, F/150, and F/170 are set.

Also, if it is not below 170℃, 7 lag F/
180 is set. When the flag F/180 is set, the copy becomes possible. In this flowchart, all flags set for temperatures lower than the detected temperature are set. Next, in step 16, zero-cross interrupts are enabled, and in step 17, the main program is executed. During this time, when a zero-cross pulse signal is input to the interrupt terminal INT, the interrupt program shown in FIG. 4-2 is executed.

Next, the interrupt program will be explained according to the flowchart shown in FIG. 4-2. 7 lag F/1 in steps 21-26
80, F/170, F/150.

It is determined whether F/130, F/100, or F/80 is set. If the flag F/'180 is set, it is assumed that the wait-up state has already been reached, and in step 27, the energization to the halogen heater is controlled as shown in Figure 4-3.

The details will be described later.

If flag F/180 is not set, step 2
The flag F/170 is checked in step 2, and if it is set, it is determined in step 28 whether or not the fixing roller surface temperature is 170° C. or lower. If the temperature is below 170° C., the heater drive signal is turned on in step 29 to energize the entire cycle.

Also, if the temperature is not below 170℃, in step 30, 7 lag F/
180't- is set to put the wait up state and proceed to step 27.

Similarly, if flag F/150 is set, the fixing roller surface temperature is compared with 165°C in step 31, and 1
Full-wave energization is carried out up to 65° C., and thereafter energization control is performed every other cycle: 1 cycle on, 1 cycle off.

If the flag F/130 is set, the surface temperature of the two fixing rows is compared with 155°C in step 32, and 155°C is set.
Full-wave energization is carried out up to 5°C, and thereafter energization control is performed every other cycle.

Also, if the flag F/100 is set, the fixing roller surface temperature is compared with 145°C in step 33, and 145°C is set.
Full-wave energization is carried out up to 5°C, and thereafter energization control is performed every other cycle.

Further, if the flag F/80 is set, the fixing roller surface temperature is compared with 140°C in step 34, and the temperature is set to 140°C.
Full-wave energization is carried out up to ℃, and thereafter energization control is performed every other cycle.

Further, if flag F/80 is not set, and if flag F150 is set, step 35 is executed.
The surface temperature of the fixing roller is compared with 130° C., and full-wave energization is performed up to 130° C. Thereafter, energization control is performed every other cycle.

After turning off the heater drive signal in step 36,
In step 37, the surface temperature of the fixing row 2 is read again.

Next, the heater control program in step 27 will be explained. According to this program, the temperature at which the heater starts energizing and the temperature at which the heater stops energizing are different, and when these two temperatures are detected, the heater starts or stops energizing at the temperature detected by the thermistor. The control is such that it is performed for a predetermined time regardless of the time.

That is, in step 27-1, it is checked whether the flag F/heater OFF is set. This flag F/Heime OFF is a flag for stopping the halogen heater H6, and is not set when the heater should be turned on. If the flag F/heater OFF is not set, it is checked in step 27-2 whether or not the 7-lag F/timeup is set. This flag F/
timc up c) This is a flag indicating that the timer time required to keep the halogen heater H1 in the on state has expired. Flag 1 in step 27-2;' / tiy
If n@up is not set, step 27-3
Each time a pulse is input to the interrupt terminal INT, 1 is subtracted from the timer set to a value corresponding to the heater on time (4). The heater H4 is energized every other cycle in step 27-5 until the timer expires and overflows in step 27-4. Incidentally, the energization control to the heater in step 27-5 is shown in FIG. 4-4.

This will be explained later. When the pulses input to the interrupt terminal INT are counted and an overflow occurs in step 27-4, the process proceeds to step 27-6, where the timer value (B)
and further sets the flag F/timeup. Here, the timer value (6) is set at a value corresponding to the off time of the heater.

Next, in step 27-2, the flag F/time u
When p is set, the process proceeds to step 27-7, where it is checked whether the temperature υ detected by the thermistor is 185° C. or higher. Step 2 until the temperature reaches 185℃ or higher.
At 7-5, the heater H is energized every other cycle. If the temperature exceeds 185℃, step 27
-8 to set 7 lag F/heater OFF, flag F
/ Reset time up. This stops power supply to the heater.

7 When lug F/heater OFF is set, step 2
From step 7-1, proceed to step 27-9 and set the flag F/ti.
Check whether meup is set.

Until the flag F/time up is set, each time a pulse is input to the interrupt terminal INT, 1 is subtracted from the timer set with the timer value ■ indicating the heater off time in step 27-10. During this time, the halogen heater H1 remains off. If the timer exceeds and overflows in step 27-11, a timer value (4) indicating the on-time of the heater is set in step 27-12, and a flag F/lime up is set in step 27-13.

When the flag li'/time up is set, the process proceeds from step 27-9 to step 27-14, where it is determined whether the temperature detected by the thermistor T'f is 180°C or higher. In this case, the power to the heater remains off.If the temperature becomes 180°C or higher, the process proceeds from step 27-14 to step 27-15, where the flag F/heater OFF is reset, and step 27
-16 to reset 7 lag F/time up. Then, the heater is energized as described above.

Next, the control of energization to the halogen heater every other cycle in step 27-5 will be explained with reference to FIG. 4-4. First, in steps 27-5-1 and 27-5-2, it is determined whether the flags F/1st°F/2nd are set.

Here, 7 lag F/1st. F/2nd are flags for energizing the first half cycle and the next half cycle of one cycle of traffic.

Flag F/1st. If both F/2 are not set, the process proceeds to step 27-5-3, where the heater drive signal is turned on and energization for the first half cycle of one AC cycle is started. At the same time, 7 lag F/2nd is set. Then, during the next interrupt control, the process proceeds from step 27-5-1 to step 27-5-2, and since F/2 is set, the process proceeds to step 27-5-4, where the heater drive signal is turned on. Energization for the next half cycle of one AC cycle is started. At the same time, flag F/1 is set. Then, during the next interrupt control, 7 lag F/1st. F/2nd
Since both are set, steps 27-5-1 to 27-5-5. Proceed to step 27-5-6 and F
/Reset the second. Then, during the next interrupt control, the process proceeds from step 27-5-5 to step 27-5-7, and the flag F/1 is reset. In other words, flag F/2nd. F/
The halogen heater is not energized during one AC cycle in which the first heater is reset.

In this way, the halogen heater is energized every other AC cycle.

Figure M5 shows the temperature characteristics when the heater is fiilJ controlled according to the flowcharts shown in Figures 4-1 to 4-4, where a is the halogen heater off time set by the timer, and b is the timer set by the timer. Shows the on time of the halogen heater set by

In the above embodiment, the on/off control is performed by differentiating the temperature at which the heater is turned on and the temperature at which the heater is turned off. Furthermore, when these two temperatures are detected, a timer is activated, and the temperature detected by the thermistor is set for a predetermined period of time by the timer. Although the heater is controlled to be turned on or off regardless of the situation, it is also possible to control only one of them.

FIG. 6 is a flowchart in the case of controlling the energization of the heater by changing the temperature at which the heater is turned on (180° C.) and the temperature at which the heater is turned off (185° C.). This control may be configured to be performed in step 27 of FIG. 4-1.

Alternatively, the control temperature may be set to one (180° C.), and the heater may be controlled to remain on or off for a predetermined period of time after the heater is turned on or off. In this case, step 27 in the diagram of cylinder 4-3
The configuration may be such that the check at -7 is performed at 180°C. FIG. 7 shows the temperature characteristics when this control is performed.

Figure 7 (a) shows an example in which the heater remains in the on or off state even after the timer time t has elapsed. Further, (6) is an example in which the heater is turned on or off and after the timer time t1 has elapsed, the heater is turned off or on.

In the above embodiment, the flag and timer are set in a predetermined area of the RAM within the microcomputer.

As described above, according to the present invention, generation of noise due to turning on and off of the heater can be suppressed, and malfunctions due to noise can be prevented. In addition, the influence of rush current on AC load can also be reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a copying machine to which the present invention can be applied, and FIG.
Figure 1 is a block diagram showing the control section of the present invention, Figure 2-2 is a diagram showing the drive circuit of the halogen heater, and Figure 3 is Figure 2-1.
4-1 to 4-4 are flowcharts showing one embodiment of the present invention, and FIG.
Figures 1 to 4-4 are diagrams showing temperature characteristics when controlled according to the flowcharts shown, Figure 6 is a flowchart depicting another embodiment of the present invention, and Figure 7 is temperature % according to yet another embodiment of the present invention. A diagram showing gender. In the figure, 10 is a fixing device, loa is a fixing roller, l
Ob is a pressure roller, 100 is a microcomputer, l
ot is a full-wave rectifier circuit, 102 is an inverting amplifier circuit, 1oaV
i thermistor, 104 is a halogen heater drive circuit, TH
is a thermistor. H+ ij ``It's a logon heater.

Claims (1)

[Scope of Claims] (1) A heat source that heats a fixing device, and a detection device that detects a temperature near the fixing device, and a temperature that controls energization of the heat source according to the output of the detection device. A temperature control device, characterized in that the heat source is controlled for a predetermined period of time after controlling the energization to the heat source, regardless of the output of the detection means. (2. A temperature control device according to claim 1, characterized in that the state of the heat source is controlled by switching between an energized state and a non-energized state in accordance with the output of the detection means. (3) Patent The temperature control device according to claim 2, characterized in that the state of the heat source is maintained for a predetermined period of time after the state of the heat source is changed. a temperature control device that has a detection means for detecting a temperature near the device, and controls energization to the heat source according to an output of the detection means, converting an output signal of the detection means into a digital signal,
A temperature control device that controls the heat source to be energized at a first temperature and to be de-energized at a second temperature in accordance with the digital signal.