JPH0611531A - Controller of electromagnetic equipment - Google Patents

Abstract

PURPOSE:To obtain a controller of electromagnetic equipment which immediately detects the failure of the electromagnetic equipment which is used widely when transferring the rotation of a motor to a roll or driving an actuator causing a paper to be jammed and can search for the cause of the paper jam easily. CONSTITUTION:When a CPU 5 changes a control signal A from a high level to a low level, a transistor Q is turned off and a surge voltage is generated when a coil 2' of an electromagnetic clutch 2 is not disconnected. The surge voltage is output to the + input of a comparator 4 and is compared with a reference value supplied to the - input and then a detection signal D is output from the comparator 4. Then, the CPU 5 confirms the detection signal, thus judging that the coil 2' of the electromagnetic clutch 2 is not disconnected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic device which is widely used for transmitting a rotational drive of a motor to a roll or for driving an actuator, and more particularly to a control device for the electromagnetic device.

[0002]

2. Description of the Related Art Electromagnetic devices are used for a wide range of applications, such as clutch switching control for transmitting rotational drive of a motor to a roll, power for driving an actuator, and the like. For example, in an image forming apparatus such as a printer, a clutch is used to switch transmission of rotational force to a transport roll used to transport recording paper, and an electromagnetic device is used to drive switching of this clutch.

That is, in the above-mentioned example, the recording paper is carried out from the paper feed cassette and sent to the transfer portion, and the toner adsorbed on the photoconductor is transferred at the transfer portion, and then discharged to the tray. The recording paper is carried by a plurality of carrying rolls provided in the apparatus. Then, switching the transmission of the rotational force of the motor to this transport roll (rotation / non-rotation control)
Is performed by the electromagnetic clutch described above.

FIG. 4 is a diagram showing a conventional electromagnetic clutch and its control circuit. The electromagnetic clutch 10 is driven by a CPU.
It is performed by a control signal output from 11. That is, by outputting a high signal from the CPU 11 to the transistor Q'via the resistor R, a current is passed through the coil 10 'in the electromagnetic clutch 10 and the electromagnetic force generated in the coil 10' drives the clutch. The diode 12 connected in parallel with the electromagnetic clutch 10 is for bypassing a surge current generated when the power to the electromagnetic clutch 10 is turned off.

[0005]

However, in the above-mentioned electromagnetic equipment, there is a case where an abnormality such as disconnection occurs in the coil in the electromagnetic clutch 10, for example. In such a case, the rotation / non-rotation control of the transport roll or the like by the electromagnetic clutch 10 becomes impossible, which causes a paper jam or the like. In this case, the paper jam detection device normally operates to stop the operation of the machine itself. However, since a paper jam is detected by confirming whether or not the recording paper passes a specified position within a predetermined time, for example, it takes time to detect a paper jam, and when the operation of the machine stops. The condition of the paper jam is severe, and in some cases, the actuator or the like arranged on the conveying path may be damaged.

Further, there are many causes of paper jam, and what is the cause of jam when processing the paper jam? Further, even if the electromagnetic clutch 10 is found out, it takes time to find out the cause such as a mechanical system trouble of the electromagnetic clutch 10 or an electrical system trouble.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, an object of the present invention is to provide an electromagnetic device in which a defect of an electromagnetic device that causes a paper jam can be immediately detected, and even if a paper jam occurs, the cause can be easily investigated. An object is to provide a control device.

[0008]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a control device for an electromagnetic device which operates a mechanism section by passing a current through an exciting coil, wherein a control means for applying an operating current to the exciting coil is provided. A detector is provided for detecting a surge current generated when the current supplied to the exciting coil is cut off, and when the surge current is not detected in response to the control circuit cutting off the operating current, the electromagnetic device is defective. It is characterized in that identification means for identification is provided.

[0009]

EXAMPLES An example of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of a control device for an electromagnetic device according to this embodiment. In the figure, the electromagnetic device 1 is composed of an electromagnetic clutch 2 and a control circuit 3. The electromagnetic clutch 2 has a coil 2'built-in, and drives a movable part (not shown) by a current flowing through the coil 2'to switch the transmission of rotational force to, for example, a transport roll. The control circuit 3 is composed of a transistor Q, a comparator 4, a CPU 5, etc., and controls switching of the electromagnetic clutch 2 and also detects disconnection of the coil 2'described above.

CPU 5 as control means and identification means
Is a central processing unit that controls the overall operation of the machine attached to the electromagnetic device 1 of this embodiment. However, in this embodiment, only the configuration related to the control of the electromagnetic clutch 2 is shown.
A control signal A for driving and controlling the electromagnetic clutch 2 is output from the output O1 of the CPU 5. The output of the control signal A is output at the timing of driving the transport roll in consideration of, for example, the toner transfer timing described above. The control signal A is output to the base B of the transistor Q via the resistor R1 and controls the transistor Q to be turned on or off. One end of the coil 2'is connected to the collector C of the transistor Q, and when the transistor Q is on, the transistor Q is turned on.
A predetermined current (current flowing in the direction of the arrow shown by the solid line) from the power supply (VDD) through the coil 2'is made to flow through the coil 2 '.

The voltage of the collector C of the transistor Q is applied to the non-inverting input (hereinafter referred to as the + input) of the comparator 4. Since the resistor R2 connected between the + input of the comparator 4 (collector of the transistor Q) and the ground has a high resistance value, when the transistor Q is off, the above-mentioned power supply voltage (VDD) is almost equal to the + of the comparator 4. Output to input. Since the Zener diode 6 is also connected between the + input of the comparator 4 and the ground, the Zener voltage (VTH) of the Zener diode 6 is output to the + input of the comparator 4 when the transistor Q is on.

On the other hand, the inverting input (hereinafter referred to as "-input") of the comparator 4 as the detecting means is connected to the series circuit of the resistor R3 and the Zener diode 7 connected between the power supply voltage (VCC) and the ground, and the connecting point. Is a connection point between the resistor R3 and the Zener diode 7. Therefore, the resistance R
The voltage generated at the connection point of the zener diode 7 and the zener diode 7 is supplied to the-input of the (VTH ') comparator 4.

The comparator 4 compares the potentials output to the + input and the − input, and when the potential output to the + input is higher than the potential output to the − input (reference value), a high signal (hereinafter referred to as H signal). Is output and the potential output to the + input is −
When it is lower than the potential output to the input (reference value), a low signal (hereinafter referred to as L signal) is output. This signal (hereinafter referred to as detection signal D) output from the comparator 4 is CP
It is supplied to the input I of U5. The voltage (VSS) is applied to the input I of the CPU 5 through the pull-up resistor R4.

The CPU 5 judges the disconnection of the coil 2'of the electromagnetic clutch 2 based on the detection signal D output from the comparator 4, and if it judges that the coil 2'is disconnected, the output O
2 outputs a control signal to a buzzer circuit (not shown).

Next, the coil 2'of the electromagnetic clutch 2 described above.
The disconnection detection operation of is described with reference to the time charts of FIGS. 2 and 3. First, the operation when the coil 2'is not broken will be described. A diagram for explaining this operation is the time chart shown in FIG.

As shown in the drawing, first, in the initial stage, the control signal A is not output from the CPU 5 (the control signal A output from the CPU 5 is at L level), and the transistor Q is off. Therefore, at this time, no current flows through the coil 2'and the electromagnetic clutch 1 is not driven. At this time, the voltage of the collector C of the transistor Q is almost the power supply voltage (VDD, which is 24 V in this embodiment).

In this state, the timing (T
In 1), when the CPU 5 outputs the control signal A to the H level and outputs it to the transistor Q, the transistor Q is turned on and a current flows through the coil 2 '. Therefore, an electromagnetic force is generated in the coil 2 ', and the electromagnetic clutch 1 is driven so as to transmit the rotational force of the motor to the transport roll or the like. At this time, the voltage value of the collector of the transistor Q becomes almost 0V.

After that, the electromagnetic clutch 2 is turned off in order to stop the rotation of the transport roll to which the rotational force is transmitted by the driving of the electromagnetic clutch 2, so the timing (T
The control signal output from the CPU 5 in 2) is changed from H level to L
When switched to the level, the transistor Q immediately turns off. At the same time, a surge current is generated in the direction of the arrow indicated by the dotted line (FIG. 1) in order to suppress the current that decreases due to the characteristics of the coil 2 '. Although the voltage generated by this surge current has an extremely high voltage value, it can be suppressed to a constant voltage (VTH is 36 V in this embodiment) by the Zener diode 6 described above. However, since this voltage value is higher than the above-mentioned reference value (VTH 'is 30 V in this embodiment), the comparator 4 outputs the pulsed detection signal D to the CPU 5. The CPU 5 judges the disconnection of the coil 2'by inputting the detection signal D. That is, when the CPU 5 changes the control signal A output from the output O1 from the H level to the L level (the above timing (T2)), the detection signal D is output to the input I, and thus the coil 2'is normal ( It has not been broken). Therefore, the CPU 5 does not output the control signal for sounding the buzzer from the output O2 at this time.

Next, FIG. 3 shows a time chart when the coil 2'is broken. At this time, similarly to the above, at the timing (T1), the control signal A is output to drive the electromagnetic clutch 1 and the transistor Q is turned on, but since the coil 2'is disconnected, no current flows in the coil 2 ', The voltage of the collector C of the transistor Q is the ground potential (0V) via the resistor R2.
It remains. Therefore, in this state, the timing (T
In 2), even if the CPU 5 changes the output of the control signal A from the H level to the L level, the surge current does not occur in the coil 2 '. Therefore, the voltage value (0V) at this time
Remains below the reference value mentioned above (eg 30V),
The comparator 4 sends a pulse signal (detection signal D) to the CPU 5
Not output to. At this time, the CPU 5 determines whether the coil 2'is disconnected. That is, in this case, the CPU 5 outputs 0
When the control signal A changes from H level to L level from 1 (timing (T2) described above), it is determined that the coil 2'is disconnected because the pulse signal is not supplied to the input I.

Therefore, at this time, a control signal for sounding the buzzer is output from the output O2 to a buzzer circuit (not shown),
The operator is informed of a defect in the electromagnetic clutch 2. This allows the operator to know the disconnection of the coil 2'of the electromagnetic clutch 2. If a paper jam occurs on the recording paper at the same time, the cause of the paper jam is the coil 2 '.
It can be immediately judged that it is a disconnection.

In this embodiment, the Zener diode 6 is used instead of connecting the diode in parallel to the coil 2'of the electromagnetic clutch 2 as in the conventional example shown in FIG. 4, so that the electromagnetic clutch 2 operates normally. Even in the state, the Zener diode 6 absorbs the surge voltage as soon as the control signal A changes to the L signal, and the off driving time of the electromagnetic clutch 2 can be shortened.

In the above embodiment, the method of identifying the disconnection of the coil 2'when the control signal A is output for the actual conveyance of the recording paper has been described. It is also possible to output the control signal A for a short period of time when the apparatus is not conveyed to identify an abnormality in the apparatus.

[0023]

As described above in detail, according to the present invention, the surge voltage generated when the electromagnetic clutch is turned off is used to detect the disconnection of the coil in the electromagnetic clutch. Can be detected.

Further, when the electromagnetic equipment is used to switch the conveyance roll of the recording paper in the image forming apparatus or the like, when the cause of the paper jam is in the electromagnetic equipment, the cause can be immediately investigated, and the paper jam can be dealt with. Can be easy.

Further, the electromagnetic device of the present invention absorbs the surge voltage by the Zener diode, so that the off-drive time of the electromagnetic device can be improved.

[Brief description of drawings]

FIG. 1 is a control circuit diagram of an electromagnetic device according to an embodiment.

FIG. 2 is a flowchart illustrating the operation of the electromagnetic clutch when the coil is not broken.

FIG. 3 is a flowchart illustrating the operation of the electromagnetic clutch when the coil is broken.

FIG. 4 is a diagram illustrating a configuration of a conventional electromagnetic device.

[Explanation of symbols]

 1 Electromagnetic device 2 Electromagnetic clutch 3 Control circuit 4 Comparator 5 CPU 6, 7 Zener diode

Claims (1)

[Claims] 1. A control device for an electromagnetic device, which operates a mechanism section by supplying a current to an exciting coil, wherein a control means applies an operating current to the exciting coil, and a current is supplied when the current supplied to the exciting coil is cut off. Detecting means for detecting a surge current, and an identifying means for identifying a defect of the electromagnetic device when the surge current is not detected in response to the control circuit interrupting the operating current. Control device for electromagnetic equipment.