JPH0339314B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heating temperature control device for a copying machine, and more particularly to a heating temperature control device for a copying machine that allows the heating temperature of a fixing device, etc. of a copying machine to be visually checked. As a heating temperature control device for a copying machine, for example, there is one shown in FIG.
A heat roll including a heater 32 built into a heat fixing roll (heat roll) 34 disposed in contact with the heat roll 5 and a sensor (not shown) such as a thermistor whose resistance value decreases depending on the temperature of the heat roll 34. A temperature signal generation circuit 50, a set level generation circuit 40 that outputs a signal according to the set level of the variable resistor 36, and a comparator 60 that compares the output of the set level generation circuit 40 with the output of the heat roll temperature signal generation circuit 50. and a control relay 30 that turns on and off the AC power supply 8 according to the output of the comparator.
Consists of a. In addition, A in the figure is a charging part, B
1, C is an exposure section, C is a development section, D is a transfer section, and F is a photosensitive drum. To explain the operation in the above configuration,
Heat roll 34 heated by heater 32
A signal V ₁ based on the resistance value of the sensor corresponding to the temperature is output from the heat roll temperature signal generation circuit 50. On the other hand, a signal V ₂ based on the set resistance value R ₃ of the variable resistor 36 corresponding to the set temperature of the heat roll 34 is output from the set level generation circuit 6 . This value V ₂
V ₁ is compared with the signal V ₂ based on the resistance value of the sensor.
= _V2 , connect heater power supply 31 to relay 3
By performing on/off control using 0a, the temperature of the heat roll 34 can be made equal to the set temperature. However, in the above-mentioned heating temperature control device for a copying machine, the temperature of the heat roll 34, etc. is measured by temperature calculation based on a sensor (e.g., thermocouple) signal.
In addition, since the set temperature is based on the volume scale of the variable resistor 36, it is not possible to accurately know the actual temperature of the heated parts such as the heat roll, which may affect workability during the copying machine manufacturing process or maintenance. There are limits to how much improvement can be made. The present invention has been made in view of the above,
For example, in order to improve workability during the manufacturing process or maintenance of a copying machine, the heater temperature setting signal and heater temperature detection signal are processed and the heater temperature and set temperature are displayed on the copying machine display section for visual confirmation. The present invention provides a heating temperature control device for a machine. Hereinafter, the heating temperature control device for a copying machine according to the present invention will be explained in detail. FIG. 2 shows an embodiment of the present invention (in FIG. 2, the same parts as in FIG. a sensor 1 such as a thermistor whose resistance value decreases depending on the temperature of 34;
It is controlled on and off by a comparison resistor R ₁ (several kilohms) inserted in series with sensor 1, a capacitor C that absorbs noise coming in from the sensor 1 lead wire, etc., and a control pulse input to the base. Transistors 2, 4, and 5, a variable resistor 3 that certifies the heater temperature, a reference resistor _R2 of several hundred ohms connected in series with the variable resistor 3, and the outputs of common output points _D1 and _D2 are input. an analog input port A ₁ that outputs control pulses to the bases of the transistors 4, 2, and 5 via base resistors 6, 7, and ₈ ;
P ₂ , P ₃ , and an input port A ₃ that inputs an analog reference voltage set by the divided voltage based on resistors 9 and 10 (input ports A ₁ and A ₃ are connected to A/D as shown in the figure).
A microcomputer ₂₀ (input/output interface, RoM (read only memory), (RAM (random access memory), data bus as shown), a display 21 that displays the A/D converted value of each voltage input (usually a copying machine display that displays the number of copies, etc.),
a switch 22 for switching each display mode described below;
Heater control relay 3 connected to output port P ₄
0, and a heater 3 that receives power supply from an AC power source 31 by turning on and off the heater control relay 30.
2. In the above configuration, the operation will be explained as follows. By switching the display mode changeover switch 22, the detection modes of modes 1, 2, and 3 in the table below can be changed to microcomputer 2.
It is operated by a program written in RoM 0.

[Table] (1) Temperature sensor temperature detection mode Turn on the SWO of the switch 22 to set the sensor temperature detection mode in which the sensor 1 detects the temperature of the heater 32 (or heat roll 34). The boat is operated by microcomputer program processing.
An on signal is output from P ₂ and P ₃ , an off signal is output from boat P ₁ , and transistors 2 and 5 are turned on.
Transistor 4 is turned off. The divided voltage V ₁ of the common contacts D ₁ and D ₂ in this state is determined as follows. Combined resistance R of resistors R ₁ and R ₂ =
R ₁ R ₂ /R ₁ +R ₂ =R ₂ /R+R ₂ /R ₁ , but since R ₁ >>R ₂ , R≈R ₂ . Therefore, the divided voltage V ₁ =R ₂ /R ₂ +R _D Vcc (R _D is the resistance of the sensor 1). This divided voltage V ₂ is input to the analog input port A ₁ and A/D converted.
It is stored in the RAM as a digital value Ds and displayed on the display 21. (2) Set temperature detection mode Turn on SW ₁ of switch 22 to set the set temperature detection mode set by variable resistor 3. Through program processing stored in the RoM of the microcomputer 20, on signals are output from ports P ₁ and P ₃ , and an off signal is output from port P ₂ .
Transistors 4 and 5 turn on, and transistor 2
is turned off. Common connection point D ₁ in this state,
The divided voltage V ₂ of D ₂ is V ₂ =R ₂ /R ₂ +RsVcc (Rs is the set resistance value of the variable resistor 3). This divided voltage _V2 is input to the analog input port _A1 , A/D converted, stored in the RAM as a digital value Dc, and displayed on the number display 21. (3) Temperature sensor disconnection detection mode Turn on SW ₂ of switch 22 to set sensor disconnection detection mode. Since the comparison resistor _R1 has a high resistance of several kilohms, disconnection of the sensor 1 can be accurately detected by turning off the transistors 4 and 5 and turning on the transistor 2. The divided voltage V ₃ in this state is V ₃ = R ₁ /R ₁ +R _TH Vcc = R ₁ /R _TH /1+R ₁ /R _TH Vcc Therefore, even if R _TH at low temperature is on the order of MΩ
Since V ₃ =0, disconnection can be detected accurately. This divided voltage _V3 is input to the analog input port _A1 , A/D converted, and the digital value is
Stored in RAM as D _D , and number display 2
1 is displayed. The above modes (1), (2), and (3) are built into the microcomputer 30 as a program shown in the flowchart of FIG. FIG. 3 shows a flowchart of temperature control. When SW ₃ of the switch 22 is turned on, the digital value Ds in the temperature sensor temperature detection mode described above and the digital value Dc in the set temperature detection mode are set based on a predetermined program. A comparison operation of Ds>Dc is performed as follows. (a) When Ds>Dc is YES, the control relay 30 is turned off and the heater 32 is turned off. (b) When Ds>Dc is No, the control relay 30 is turned on and the heater 32 is turned on. Based on the above operations, the heater is brought close to Ds and the heater temperature (or heat roll temperature) is controlled to reach the set temperature. As explained above, according to the heating temperature control device for a copying machine according to the present invention, the heater temperature setting signal and the heater temperature detection signal are processed to display the heater temperature and the set temperature on the copying machine display section for visual confirmation. This makes it possible to improve workability during the manufacturing process or maintenance of the copying machine.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a conventional heating temperature control device for a copying machine. FIG. 2 is an explanatory diagram showing one embodiment of the present invention. 3 and 4 are flowcharts of FIG. 2. Explanation of symbols, 1...Sensor, 3...Variable resistor for temperature setting, 20...Microcomputer, 30, 30a...
Control relay, 32... Heater, 34... Heat roll, 40... Setting level generation circuit, 50... Heat roll temperature signal generation circuit, 60... Comparator.

Claims (1)

[Scope of Claims] 1. A temperature setting section that outputs a set temperature signal according to the set temperature of the heating section; a heating temperature detection section that outputs a heating temperature signal according to the heating temperature of the heating section; and the set temperature signal. A heating temperature control device for a copying machine, comprising: a control unit that inputs and processes the heating temperature signal to display a set temperature and a heating temperature on a display unit for the copying machine.