JPS58176559A - Detecting device for disconnection of sensor - Google Patents

Abstract

PURPOSE:To prevent a waste of detection time for the disconnection of a sensor by extending or shortening judgement time for the disconnection according to the level of a wire-breaking detection signal. CONSTITUTION:A comparing resistance R is connected in series to the sensor 1 which has a resistance value varying with temperature and the disconnection of the sensor 1 is detected on the basis of the voltage level at the connection point. In this case, when the resistance of the sensor 1 increases owing to low temperature, it takes a long time to stabilize the voltage V at the connection point, so there is a waste of detection time. For this purpose, the voltage V is inputted to a microcomputer 20 a specific time T later, A/D-converted, and then stored. When the converted value is greater than a specific level, the disconnection is judged and when less, a check on the disconnection is made a time nT later. Thus, the judgement time for the disconnection is extended or shortened, so the waste of detection time is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature sensor disconnection detection device, and more particularly, to a temperature sensor disconnection detection device of a copying machine fuser unit, which eliminates wasted time for detecting a disconnection of the temperature sensor ``V''O and properly detects the disconnection. The present invention relates to a sensor disconnection detection device.

As a temperature sensor disconnection detection device (having a heater heating temperature control function), for example, the one shown in FIG. Decreasing negative 4! A control resistor R1 that can be inserted in series with the sensor sensor 1 having resistance characteristics, a comparison resistor R1 that can be inserted in series with the sensor sensor 1, a capacitor C that collects noise mixed in from the lead wire of the sensor 1, etc., and a control circuit in the base. Transistors 2 and 4 are turned on, off, and turned on by inputting pulses for switching, variable resistor 3 is used to set the temperature of the transistor, and variable resistor 3Ki[ν
It has nine reference resistors 3 located at U', and has a signal output point D.
B + Ds are commonly connected and a comparison resistor Rs
is set to several kiloohms, and the reference resistance ns is set to several hundred ohms to satisfy ms>1m. Reference resistance R
, and the ground, and the output of the common signal output point D1#D is connected to the microcomputer 20 (A/l) converter, input/output interface, program lROM,
Ps I
A control pulse is applied from I's ep= to the pace of transistors 4, 2.5 via the base resistor 6.7.8.

9, resistance 9. An analog reference voltage set by the divided voltage based on lO is input to the input port of the microcomputer 20, and a heater control signal generated based on calculations within the microcomputer 20 is output from the output port P4 to the heater control relay 30. Ru. - Evening control relay 30 is connected to heater 32
Controls the power supply based on the AC power source 31. Pottery, Mu,
B, C, D, and Koto are nine charging sections, an exposure section, a developing section, a transfer section, and a cleaning section arranged on the photosensitive drum aaoms.

In the above configuration, the heater temperature control operation will be explained as follows.

(1) Heater temperature (heater 32) determined by sensor l
[Detection mode by 07' log 2m processing in microcomputer 20) Pss
An on signal is output from Ps and an off signal is output from boat 1, turning on transistor 2.5 and turning off transistor 4. In this state, the common connection point DI? The divided voltage v1 of DI becomes the next transmission.

In other words, the combined resistance of the resistance Bls is R-l1. Therefore, the divided voltage v1 is set by (2) the variable resistor 3, and is determined by the blurring processing in the mode microcomputer 20 that detects the set temperature f.
*An on signal is output from Ps, an off signal is output from boat 1, transistor 4.5 is turned on, and transistor 2 is turned off. In this state, common - comma D 1# D @
The divided voltage V, becomes the following OA.

That is, according to (1) above, the set resistance value of the variable resistance 3 is such that p combined resistance R=R.

The above modes (1) and (2) are set as shown in the chart 70 in FIG. 2, and the divided voltage V1eV1 is input to the analog input port 1 and converted into a digital value V
DI + VDI k. Isa Digital l [VDl
, Vow is based on a predetermined program.
w (D comparison operation is performed.

(a) When Vos > VDI is ye-, the control relay 30 is turned off and the heater 732 is turned off.

(b) VDI) When Voi is no, the control relay 30 is turned on and the heater 32 is turned on.

Based on the above operations, the VDI tans K is brought close to the heater 32 to control the heater temperature to the set temperature. Become).

Further, a disconnection in the sensor l can be detected by turning off the transistor 4°5\r, turning on only the transistor 2, and detecting the divided voltage between the comparison resistor R1 and the resistor RD of the sensor l. In this detection operation, even if the resistance R of the sensor 1 is megohm 5 units O high resistance Kik-z at low temperature, the comparison resistor R1f is set to a relatively high resistance value of several kilohms, so there is a possibility of false detection. There's no fear.

However, in the nine-sensor disconnection detection device described above, when disconnection detection is performed, the sensor? If 1 becomes a high resistance for low-temperature rounding, it may take a long time t for rounding to reach the divided voltage V (temperature detection operation may be delayed due to the time constant O).

The present invention has been made in view of the above-mentioned K11i+, and in order to eliminate the waste of time for detecting a sensor disconnection and prevent the continuation of temperature detection operations for controlling the heater temperature, a disconnection is determined according to the level of a disconnection detection signal. The present invention provides a pull sensor disconnection detection device that increases or decreases the time.

The senna disconnection detection device t*aiit according to the present invention will be explained below.

FIG. 3 shows an embodiment of the present invention, and H8. number of times m−0
The first check (1st check) was carried out at
Transistor 4.5 in the figure turns off '&J),) Kunister 2 turns on. When the predetermined time T has elapsed, the common connection point DB is reached.

is inputted to the analog input port 1 of the microcomputer 20, converted to D/D and stored in a RAM (not shown).

＼ When the M/D conversion value is greater than a predetermined level, sen i1''
1 is determined to be non-broken, and the wire breakage check is completed. on the other hand,
When the A/D conversion value becomes smaller than a predetermined level, the time T
Multiply by Kn (!l>l) and input the required time to check for disconnection. The number of such disconnections is rmt-1 times (j
>1) Implemented (from m-1 to ugly-11), when the wire is detected 4 times in a row, it is determined that the wire is disconnected and the wire is disconnected, ν
complete the process.

In the above embodiments, the number of steps for determining disconnection is 9, but is not limited to this.

As explained above, according to the sensor disconnection detection device according to the present invention, it is possible to prevent a delay in temperature detection operation for wide temperature control of the level of the disconnection detection signal.

[Brief explanation of the drawing]

#11 is an explanatory diagram showing a heating temperature control function [equipped with a nine-sensor disconnection detection device], FIG. 2 is a flowchart for controlling the heating temperature, and FIG. 3 is a flowchart showing an embodiment of the present invention. Explanation of symbols 1...Heater, 3...Variable resistance for setting temperature, 2
0...Microcomputer, 30-...Heater l11111
Jt/-132...Heater, 33...Photoconductor,
34--Fuser heating roll, R1... Comparative resistance,
R1...Reference resistance. Patent applicant: Fuji Xerox Co., Ltd. Figure 2 Figure 3

Claims (1)

[Scope of Claims] A sensor section having a resistance value that changes depending on the temperature of the heating section, a nine ratio resistor provided in series with the wrinkle sensor section, and a connection between the armpit sensor and the comparison resistor. What is claimed is: 1. A sensor disconnection detection device for detecting disconnection in a sensor section based on a voltage level at a point, the sensor disconnection detection device comprising a control means for increasing or decreasing a determination time for disconnection according to the voltage level.