JPH0799897B2 - Disconnection or short circuit failure detection device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a device for detecting disconnection or short circuit of a circuit load in a copying machine or other electric equipment.

(Prior Art) Conventionally, as a device that detects a cross section or a short circuit of various loads in an electric device such as a copying machine, it is possible to determine whether the load is normal or abnormal by detecting the load current for each of various loads to be detected. There is something I did.

An example of this conventional apparatus is shown in FIG. 4 for a copying machine. In the figure, 1, 2, 3 are motors, fan motors, fixing heaters as various loads, 4 is an output circuit which is supplied with electric power from a power source and drives the various loads, 5, 6,
Reference numeral 7 is a circuit for detecting each load current, and 5a, 6a, 7a are current sensors (current detecting means) in the circuit, which are provided in the power supply line of each load. 8 is the CP that controls the entire control
At U, the outputs of the detection circuits 5, 6, and 7 are input, and it is determined which load in the CPU 8 is not normal. That is, it is sequentially determined whether current is normally flowing in the load of the object or normal current is not flowing, and disconnection detection / short circuit detection is performed.

However, such a detection device has a problem that the current sensors are required for the number of objects to be detected, the circuit becomes complicated, the failure rate increases, and the cost also increases.

Also, for example, as disclosed in Japanese Patent Laid-Open No. 60-17764, there is a device in which a current is sequentially applied to each load during a failure detection operation, and an abnormality is detected by the current value at that time. However, with such a detection method, although the above-mentioned problems are solved, it is not to detect whether there is any failure at all, but it is possible to detect an abnormality only in the failure detection operation mode. Therefore, during normal operation of the device, that is, in the case of a copying machine, for example, when a continuous copy operation is performed, even if any load abnormality occurs, it cannot be detected immediately and prompt action is required. I can't take it
As a result, a large number of defective copies may be produced, which is inconvenient.

(Object of the Invention) The present invention solves the above-mentioned problems, and it is possible to detect an abnormality in all target loads with a single current detection unit.
It is an object of the present invention to provide a disconnection or short-circuit failure detection device that has a simple structure, is low in cost, has a low failure rate, and is capable of successively detecting abnormalities and taking prompt action.

(Structure of the Invention) The present invention is a device for detecting a current flowing through a plurality of loads connected to one power source to detect a circuit disconnection or a short circuit failure, and a power supply input for detecting a total current flowing through a plurality of loads. A current detecting means provided at an end, a storing means for storing data corresponding to a current value corresponding to a load used in a normal state, and a data corresponding to a current value detected by the current detecting means for the storing means. The comparison judgment means for judging the type of the load in the abnormal state according to the difference between the data in the normal state and the detected data and the output of the comparison judgment means causes the load to be in the abnormal state. And a display means for displaying a certain thing.

With this configuration, when a wire break or short circuit abnormality occurs in any of the loads, the current value of the load during normal operation changes by the current value according to the abnormal state of the load or the type of abnormal load. It can be detected and displayed.

(Embodiment) FIG. 1 shows the construction of one embodiment of the disconnection or short-circuit failure detection device of the present invention. This embodiment is a control circuit of a copying machine,
Is a power supply, 12 is an output circuit fed by the power supply 11, 13, 14,
Reference numerals 15 and 16 are a motor as a load, a cooling fan motor, a fixing heater, and an exposure lamp, and these loads are drive-controlled by the output circuit 12. Reference numeral 17 is a circuit for detecting the current at the power input terminal, which includes a current sensor 17a (current detection means) provided on the power input line, a rectifier circuit 17b for rectifying the current detected by the current sensor 17a, and a smoothed DC component. It is composed of a capacitor 17c for obtaining a voltage.

18 is an A / D converter that converts the analog amount, which is the charging voltage of the capacitor 17c, into a digital amount, and 19 is the CPU that receives the digital amount and outputs a remote signal to the output circuit 12 to control the overall operation. Is. Also, this CPU19
Has a table (storage means) that sequentially stores digital data corresponding to the current value corresponding to the load being used during normal operation. When the digital data detected from the A / D converter 18 and the above table are normal, Comparing the digital data of, if there is a difference between the data at the normal time and the detected data,
It has a function (comparison and determination means) for determining the type of load in an abnormal state in accordance with it. Further, 20 is a display means using an LED or the like for displaying an abnormality if the result of the determination is abnormal.

The detection operation by the CPU 19 in the above configuration will be described with reference to the flowchart shown in FIG. First, the motor
If 13 is ON (step S ₁ ), and if it is ON, and the motor current is, for example, 1 amp, the memory value is A = 1 (step S ₂ ), and so on.
15 look whether ON (Step S _3), when if ON the heater current is assumed to be 9.5 amperes for example, to update the memory value A to A + 9.5 (Step S _4). Then lamp 16
Is ON (step S ₅ ), and if it is ON, assuming that the lamp current is 3.5 amps, the memory value A
To update to +3.5 (step S _6). Then fan motor 1
4 is viewed whether ON (step S _7), When a fan motor current, for example 0.6 amps if ON, the update memory values A to A + 0.6 (Step S _8).
The data corresponding to the current values of the above-mentioned various loads under normal conditions are stored in the table.

Next, determine the current detection value B via the current detection circuit 17, A / D converter 18 (Step S _9), and compares the latest memory value A and the current detection value B obtained as described above (Step
S ₁₀ ). As a result, if A = B, it is determined to be normal (step S ₁₁ ), and if A = B, it is checked whether A> B (step S ₁₂ ). If A> B, a short circuit occurs. and has a determined (step S _13), a> B unless A-
B = 1 if the checked (step S _14), it is determined that if A-B = 1 motor is disconnected (step
S ₁₅ ). In the same manner, to determine whether A-B = 9.5 (Step S _16), if A-B = 9.5 is determined that the heater is disconnected (step S _17), in A-B = 9.5 without it checks whether a-B = 3.5 (step S _18), a-B
If = 3.5 is determined that the lamp is disconnected (step S _19), it is determined that A-B = 3.5 unless the fan motor is disconnected (step S _20).

When the above-mentioned determination of short circuit or disconnection is made, the CPU 19 drives the display device 20 to immediately display an abnormality, and particularly at the time of disconnection, it can also display the corresponding load type. In addition, while the above flow is sequentially executed, various loads are individually turned on and off during the copying operation and standby while the main power switch of the copying machine is ON. S ₁ , S
_{In 3} , S ₅ , and S ₇ , when the load is off, the process proceeds to the next step without updating the memory value A corresponding to the current flowing through the load in a normal state. On the other hand, at that time, the current detection value B also has become small as the current in the load that is OFF if the normal state, consequently, is established always step S ₁₀ following flow is smoothly performed Will be.

Next, another embodiment of the present invention will be described with reference to FIG. In this embodiment, a resistor (having a small resistance value) 21 inserted in a power supply line capable of detecting the total current flowing through a plurality of loads is used as the current detecting means. Further, using a DC power source 11 'as a power supply, as an output circuit, a driver 22 driven by a CPU 19, transistors T ₁ which conduction is controlled by the driver 22, T _2, T _3, using ...... Tn, the load L ₁ , L ₂ , L ₃ ,
.. Ln are respectively connected in series with the transistors T ₁ , T ₂ , T ₃ , ... Tn, and are connected between the DC power supply 11 ′ and the GND via the resistor 21. The voltage across the resistor 21 is converted to digital data by the A / D converter 18 and input to the CPU 19.

Also in the above configuration, the CPU 19 can perform the same detection operation as that of the above-described embodiment, and display it on the display means 20 in the abnormal state.

In each of the above embodiments, the load current is detected, converted into a voltage value, A / D converted, and compared and judged as a digital amount.However, the present invention is not limited to this. Even if the analog amount corresponding to the load current value is not changed, it is detected and judged by comparing it with reference data corresponding to a plurality of normal load current values a plurality of times in an electric circuit. Good.

(Effects of the Invention) As described above, according to the present invention, it is possible to detect and display a disconnection or short circuit of a load by using one current detection unit that detects a total current flowing through a plurality of target loads. , The circuit configuration is simple, the failure rate is reduced, the cost is low, and the abnormality is detected immediately, so quick failure countermeasures can be taken and some loads remain in a defective state. There is no waste of use.

[Brief description of drawings]

FIG. 1 is a block diagram of a disconnection or short circuit failure detection device according to an embodiment of the present invention, FIG. 2 is a flow chart of the control operation of the device, FIG. 3 is a block diagram of another embodiment, and FIG. It is a block diagram of the disconnection or short circuit failure detection device of FIG. 11,11 '... Power supply, 13,14,15,16 ... Load, 17a ... Current sensor (current detection means), 17 ... Current detection circuit, 19
...... CPU (storage means, comparison / judgment means), 20 …… display means, 21 …… resistors (current detection means), L ₁ , L ₂ , L ₃ , Ln …… load.

Claims (1)

[Claims] 1. A device for detecting a current flowing through a plurality of loads connected to one power source to detect a disconnection or a short circuit failure of a circuit, the device being provided at a power source input terminal for detecting a total current flowing through a plurality of loads. Current detection means, storage means for storing data corresponding to the current value corresponding to the load that is normally used, and data stored in the storage means for data corresponding to the current value detected by the current detection means Compared to
Comparison determining means for determining the type of load in an abnormal state according to the difference between these normal data and the detected data,
A disconnection or short-circuit failure detection device comprising: a display unit that displays that the load is in an abnormal state by the output of the comparison determination unit.