JP2002199575A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect and cutoff leakage current in an image forming device at a low cost without using a leakage breaker. SOLUTION: The input and output currents are measured on the current detector transformers T1, T2 in the input circuit of a power supply, and the difference between these currents is obtained in the CPU 9 through a current- voltage converter 7 and an analog-digital converter 6. When this difference is larger than the predetermined threshold, the main switch is turned off regarding that there is a leakage, displaying the presence of the leakage on a function/ display 10. If the difference is smaller than the threshold but not zero, the power supply is not cutoff but only the leakage is displayed. By checking the above difference, the leakage can also be detected based on the period and frequency it exceeds the threshold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus, and more particularly to a circuit configuration for preventing leakage of the image.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, a printer, a plotter, etc., in order to prevent a device from leaking, it is necessary to rely on an earth leakage breaker located at a power distribution board of a power supply to the device or individually. Each device had to be equipped with an earth leakage breaker.

[0003]

When relying on the earth leakage breaker of the switchboard, the earth leakage breaker must be installed in the switchboard without fail. Further, when relying on such an earth leakage breaker, the electric power of other devices connected to the same power supply system is cut off when an earth leakage occurs, which may have a serious effect.

In the case where an earth leakage breaker is provided individually for each device, there is a problem that not only an appropriate earth leakage prevention process cannot be performed because the earth leakage detection and cutoff is performed uniformly, but also with an increase in the equipment cost. .

In view of the above, the present invention provides an image forming apparatus which is relatively inexpensive and capable of detecting a leakage of an apparatus and appropriately shutting off a leakage circuit without relying on a leakage breaker of a switchboard. With the goal.

[0006]

According to an aspect of the present invention, there is provided an image forming apparatus for printing and outputting an image, comprising: means for individually detecting forward and return currents of a primary system of a power supply; A means for calculating a difference between the individually detected current values, a means for determining whether the calculated difference value exceeds a predetermined threshold, and a power cutoff means for cutting off power in the primary system. And a control means for driving the power cutoff means to control cutoff of the primary system power supply when the determination means determines that the difference value exceeds the threshold value.

As described above, the current flowing in the primary system of the power supply and the current returning to the primary system are individually detected in the apparatus, and the magnitude of the difference between the two current values is determined. It is possible to detect the leakage of the device and cut off the leakage circuit without relying on the breaker.

The current detecting means may be arranged downstream of the power cut-off means, or may be arranged upstream.

As the current detecting means, for example, a current detecting transformer can be used.

Further, since the magnitude of the difference between the forward and return current values is determined as described above, the following flexible processing can be performed instead of the uniform leakage processing. Becomes

For example, a display unit for displaying a message is provided, and the predetermined threshold value (first threshold value) is provided.
A smaller second threshold value is provided, and the control means determines that the leakage is zero when the difference value is smaller than the second threshold value, and determines that the difference value is between the first and second threshold values. In some cases, it is possible to display on the display unit that leakage is occurring without interrupting the primary power supply by the power supply shutoff means.

Alternatively, there is provided a display unit for displaying a message, and means for backing up the operating power of the display unit, wherein the display unit is connected to the power supply unit even if the primary system power supply is cut off by the power supply cutoff unit. It is also possible to continue to indicate that the power has been shut off.

Further, the control means determines that a normal leakage has occurred based on the determination result of the determination means when the difference value exceeds a predetermined threshold for a certain period of time. Alternatively, when the difference value occurs intermittently within a predetermined time, it is possible to determine that a normal leakage occurs only when the number of occurrences exceeds a predetermined value.

In the case where a plurality of loads driven by the primary system power supply are provided, the control means compares the determination result of the determination means with the control state of the plurality of loads to estimate the location of the leakage. It is possible to

In this case, it is possible to provide a display unit for displaying a message, and a means for backing up the operating power of the display unit, and to display the estimated location of the electric leakage on the display unit.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a power supply circuit of the image forming apparatus according to the present embodiment. In this power supply circuit, a leakage detection unit according to the present invention is incorporated. In the drawing, 1 is a line side of a primary system input of a power supply (commercial AC power supply), 2 is a neutral side of a primary system input, 3 is a main switch (SW) for cutting off a primary system input, 4, 5 are the line sides, Current detection transformers T1, T2, and 6 for detecting the forward and return currents flowing on the neutral side are switches that switch between the two when detecting the forward and return currents, and 7 converts the detected current to a voltage. 8 is an analog-to-digital conversion circuit that converts the voltage converted by the current-voltage conversion circuit 7 into a digital value, 9 is a CPU that controls the entire image forming apparatus, and 10 is an operation / operation of the image forming apparatus. A display unit, 11 is a low-voltage power supply unit for supplying secondary-side power to the image forming apparatus, 12 is a backup battery for backing up the operation / display unit 10, and 13 is a power supply unit on which the above components are mounted. , 14 is a ground terminal of the image forming apparatus.
Each of the current detection transformers T1 and T2 preferably has a reinforced insulation type on the primary side and the secondary side.

Next, regarding the operation when a leakage occurs,
This will be described with reference to the flowchart of FIG. As a concept of the electric leakage, when the going current and the returning current in the primary system input become unbalanced, it is determined that the electric leakage has occurred. In FIG. 1, the case where the current Ia ≠ the current Ib corresponds thereto. The process in FIG. 2 is periodically executed continuously while the power of the apparatus is turned on.

In FIG. 2, first, the switching circuit 6 is switched to the T1 side (S11), and the outgoing current Ia is detected by the current detecting transformer 4. The current value Ia is converted into a voltage by the current-voltage conversion circuit 7. The value is converted into a digital value by the next analog-digital conversion circuit 8 and sent to the CPU 9 which controls the entire apparatus. The CPU 9 stores the converted digital value in a register a (not shown) for temporarily storing (S12). Specific areas of memory may be used instead of registers.

Next, the return current Ib is measured. That is, the switching circuit 6 is switched to the T2 side (S13), and the value of the current Ib is taken into the register b (not shown) of the CPU 9 in the same procedure (S14). It is stored in a register b in the CPU 9. Then, the difference between the registers a and b is calculated in the CPU, and the result is stored in the register c (not shown) (S15). If the value of the register c (that is, the difference value) is zero (S16, Yes), it is determined that there is no leakage (normal) (S17). However, since there is actually an error in the measured value, when the absolute value of the difference is smaller than the allowable error value (second threshold value), it is determined that the difference value is zero.

If the difference value is not zero but is smaller than a predetermined set value (first threshold value) (S18, No), the apparatus is to continue normal operation even when a short circuit is occurring. . At this time, a display indicating that an electric leakage is occurring is displayed on the operation / display unit of the apparatus, and a warning is issued to the user (S19). If the difference value is larger than the set value (S
18, Yes), the condition is determined for a predetermined determination condition (S20). For example, it is determined that a normal leakage occurs for the first time when the generated leakage continues for a predetermined period of time, and when the number of occurrences exceeds a predetermined value, the normal leakage occurs when the leakage occurs intermittently within the predetermined time. Is determined. The “predetermined time” and the “number of occurrences” may be variably set by a maintenance person or a user.

If it is determined that the leakage is legal, the CPU 9 outputs a shut-off signal 15 to the main switch 3 to shut off the main switch 3 (S21), thereby protecting the apparatus from the earth leakage. A message indicating that the power has been cut off due to the electric leakage is displayed on the operation / display unit 10 (S22). In order to operate the operation / display unit 10 even after the power is turned off, the backup battery 12 supplies operating power.

In the circuit of FIG. 1, the current detecting transformers 4, 5
Is arranged on the load side (downstream side) of the main switch 3, but may be arranged on the power supply side (upstream side) of the main switch 3. FIG. 3 shows a circuit configuration of such another embodiment. As a result, leakage detection between the main switch 3 and the current detection transformer 4 becomes possible.

FIG. 4 shows a circuit configuration of still another embodiment of the present invention. In the above embodiment, the occurrence of the earth leakage in the device can be detected, but it is not known which part of the device is caused by the leakage. Actually, a load 16 is connected to the secondary side of the power supply, and the load 16 is often plural. When a leakage occurs in connection with such a load 16, there is a possibility that a portion that causes the leakage may be estimated according to the load control situation. In the present embodiment, an ON / OFF switch 15 is individually provided for a load 16 (for example, a fixing heater, various drive motors, a document exposure lamp, etc.) that receives power supply from the power supply secondary side.
In the present embodiment, the position of the leakage detecting means (upstream of the main switch 3) as shown in FIG. 3 is adopted, but it may be the position as shown in FIG. The CPU 9 makes a judgment according to the control status of each load. Therefore, CPU 9
Is assumed to control each load 16 directly or indirectly and to grasp the control status.

Therefore, in the present embodiment, each load 1
The processing taking into account the control state of No. 6 is performed. An example of such processing is shown in the flowchart of FIG.

In FIG. 5, steps S31 to S40
Are the same as Steps S11 to S20 in FIG. 2, and redundant description will be omitted. When it is determined in S40 that a normal leakage has occurred, the state of the switch of each load 16 is sequentially examined. First, it is checked whether SW1 is ON (S41). If it is ON, an instruction is given to indicate that there is a possibility that a leakage has occurred in connection with SW1 (S4
2). At this time, it is preferable to turn off the SW1. Similarly, it is checked whether or not SW2 to SWN are ON (S43, S45), and when they are ON, an instruction to display the possibility of occurrence of electric leakage is issued (S44, S46). Then, the main SW3 is turned off to cut off the power supply (S
47). In addition, the operation / display unit 10 displays that the earth leakage cutoff circuit has been activated (S48). At this time, according to the display instructions in steps S42, S44, and S46, the display of the estimated leakage location is also performed at the same time. The order of the processing steps does not necessarily have to be as shown. For example, step S47 may be located immediately after step S40.

FIG. 6 is a timing chart showing the control status of each unit in the embodiment of FIG. In the example in this figure,
The CPU detects the occurrence of leakage at time t1 when the loads 1 and 2 are ON, and turns off the main switch 3 at time t2 immediately thereafter.
F to cut off the leakage. Also, from time t1 to t2
During this period, the operation state of each load is grasped, and the result is reflected in the display contents. In this example, it can be inferred that there is a suspicion of leakage in one of the loads 1 and 2 and that there is no suspicion of leakage in the load 3.

As described above, according to the present embodiment, it can be inferred that, when the estimated location is one, the electrical leakage occurs in the load related to the switch with a considerable probability. Also, when a plurality of locations are displayed, it is useful because candidates for locations where electrical leakage occurs can be narrowed down as compared with the above embodiment.

While the preferred embodiment of the present invention has been described above, various modifications and changes other than those described above can be made.

For example, in the above-described embodiment, an example in which all processes are performed digitally has been described as an example. However, in detecting a leakage, an analog differential transformer is used as in the related art to perform forward and return currents. May be detected and it is determined that there is a leak from the magnitude of the value. Further, in the above-described embodiment, a mechanical relay is assumed as a switch for shutting off power supply. However, another mechanism may be used as long as the switch can shut off power supply.

[0031]

According to the present invention, the occurrence of electric leakage can be detected inside the apparatus, and there is no need to use an external earth leakage breaker as in the prior art, so that the apparatus can be provided relatively inexpensively. be able to. Further, even in a case where power is supplied from a switchboard where no earth leakage breaker is installed, safety for the human body can be ensured without the user preparing an external breaker. Further, by performing the leakage detection in consideration of the control state of the load, it becomes possible to shorten the time required for specifying the faulty part and repairing it.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a power supply circuit of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating the operation of the circuit of FIG. 1;

FIG. 3 is a block diagram showing another circuit configuration of a power supply circuit according to another embodiment of the present invention, in which a position of a main switch is changed.

FIG. 4 is a block diagram showing a circuit configuration of still another embodiment of the present invention.

FIG. 5 is a flowchart illustrating a processing example of the power supply circuit of FIG. 4;

6 is a timing chart showing a control situation of each unit in the power supply circuit of FIG. 4;

[Explanation of symbols]

 1, AC primary system input 3 Main switch 4, 5 Current detection transformer 6 Changeover switch 7 Current-voltage conversion circuit 8 Analog-digital conversion circuit 9 CPU 10 Display operation unit 11 Low-voltage power supply unit 12 Backup battery 13 Power supply board 14 Body ground terminal 15 Cutoff signal 16 Threshold

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G03G 21/00 500 G03G 21/00 500 (72) Inventor Koji Minobu 6-3-3 Shimorenjaku, Mitaka-shi, Tokyo Copy (72) Inventor Tomokazu Miyakawa 6-3-3 Shimorenjaku, Mitaka-shi, Tokyo F-term (reference) 2C061 AP04 CQ41 HV01 HV23 HV32 HV45 2H027 DA01 DE04 DE07 EE07 EJ17 EK06 GA47 GB07 JA18 JC16 ZA01 ZA03 5G004 AA01 AB02 BA01 CA02 DA01 DB01 DB04 DC01 DC14 EA03

Claims (9)

[Claims] 1. An image forming apparatus for printing out an image, comprising: means for individually detecting forward and return currents of a primary system of a power supply; means for calculating a difference between the individually detected current values; Means for determining whether the obtained difference value has exceeded a predetermined threshold value; power supply cutoff means for cutting off power in the primary system; and the determination means determines that the difference value has exceeded the threshold value. And a control unit that controls the primary system power supply by driving the power supply cutoff unit when the power supply is turned off. 2. An image forming apparatus according to claim 1, wherein said current detecting means is arranged upstream of said power cutoff means. 3. An image forming apparatus according to claim 1, wherein a current detecting transformer is used as said current detecting means. 4. A display unit for displaying a message, wherein a second threshold value smaller than the predetermined threshold value (first threshold value) is provided, and the control means sets the difference value to be smaller than a second threshold value. If it is smaller, it is determined that the leakage is zero,
When the difference value is between the first and second thresholds, the fact that a leakage is occurring is displayed on the display unit without shutting down the primary power supply by the power cutoff unit. The image forming apparatus according to claim 1. 5. A display unit for displaying a message, and means for backing up the operating power of the display unit, wherein the display unit is connected to the power supply unit even if the primary system power supply is cut off by the power supply cutoff unit. The image forming apparatus according to claim 1, wherein the display that the power is shut down is continuously displayed. 6. The controller according to claim 1, wherein the controller determines that a normal leakage is detected only when the difference value exceeds a predetermined threshold for a predetermined time based on a determination result of the determination unit. The image forming apparatus according to claim 1, wherein: 7. The control means, when the difference value occurs intermittently within a predetermined time based on a result of the determination by the determination means, when the number of occurrences exceeds a predetermined value. 2. The image forming apparatus according to claim 1, wherein a normal leakage is determined for the first time. 8. A control system comprising: a plurality of loads driven by the primary system power supply; wherein the control means compares a determination result of the determination means with a control state of the plurality of loads to estimate a location where a leakage occurs. The image forming apparatus according to claim 1, wherein: 9. A display unit for displaying a message, and means for backing up operating power of the display unit, wherein the estimated location of the leakage is displayed on the display unit. Image forming apparatus.