JPH04322122A - Motor controller or business machine - Google Patents

Abstract

PURPOSE:To protect a device against breakdown by detecting a current to be fed from a power supply through a driver to a motor, comparing the detected current with preset current detection level and overcurrent detection level, and lowering the current detection level and the overcurrent detection level upon detection of overcurrent. CONSTITUTION:Current is fed from a power supply 1 through a driver 2 to the coil 3 of the rotor 4 of a motor. Driving current detected through a current detector 5 is fed to a current limiter 6 and an overcurrent detector 8. The current limiter 6 compares the level of the driving current with a level set by a current detection level setter 7 and when the set level is exceeded, a signal is outputted to limit the current of the driver 2. The overcurrent detector 8 compares the level of the driving current with a level previously set by an overcurrent detection level setter 9 and when the set level is exceeded, a signal is outputted to lower the current detection level and the overcurrent detection level. Consequently, the driver and the coil are protected against breakdown. It is suitable for a business machine.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a control device for an electric motor or office equipment equipped with this control device, and in particular, to
The present invention relates to a highly reliable electric motor control device or office equipment using the same, which prevents destruction of the drive means even in abnormal conditions such as overcurrent and overload, and prevents fire from occurring.

0002

2. Description of the Related Art Conventionally, in motor control devices, it has been common practice to prevent burning of switching elements such as motors and power transistors due to large currents.

[0003] The protection device described in Japanese Patent Application Laid-Open No. 62-281717 also relates to this technique.

This publication describes an electronic current protection device that has means for detecting the current flowing through the load and a comparator, and is capable of preventing the load from becoming overheated even if intermittent overcurrent conditions continue. It is written about.

[0005]

However, the above-mentioned prior art does not take into consideration the protection of the switching element in the case where the rotor of the DC motor is restricted or in a similar overload state. In addition, in order to prevent destruction of the switching element in overload conditions such as when the rotor is locked, it is necessary to set the voltage and current ratings of the switching element considerably higher than the voltage and current applied when the rotor is locked. This is necessary and poses an obstacle to miniaturization of the control device.

An object of the present invention is to provide a highly reliable electric motor control device or the like, which avoids the above-mentioned disadvantages and prevents the drive device from being destroyed even when the rotor is locked or is overloaded. The aim is to provide used office equipment, etc.

[0007]

[Means for Solving the Problems] The above object is to provide a drive device that is connected to a power source and applies a drive current to a motor, a current detection device that detects the current flowing through the drive device, and a detected value of the current detection device. and a current limiting device that limits the current value flowing through the drive device by comparing it with a preset current detection level; an overcurrent detection device that generates a detection signal by comparing the detected overcurrent detection level with the overcurrent detection level; and a current detection level setting device that switches the current detection level of the current limiting device based on the detection signal output from the overcurrent detection device. , comprising an overcurrent detection level setting device that switches and sets the overcurrent detection level of the overcurrent detection device to a low value according to the detection signal of the overcurrent detection device, and detects overtorque of the electric motor in the same manner. It can be achieved in this way.

[0008]

[Operation] When an overcurrent of a certain level or more flows to a DC motor or drive device, for example, the overcurrent detection device receives the output of the current detection device and outputs an overcurrent detection signal, and the current detection device receives the overcurrent detection signal. By lowering the current detection level provided by the level setting device to the current limiting device, the value of the current flowing through the DC motor and the drive device is lowered. This prevents the drive device from being destroyed. Further, the overcurrent detection level setting device that receives the overcurrent detection signal lowers the overcurrent detection level given to the overcurrent detection device. This results in
Even if the current value decreases, the overcurrent detection signal continues to be output, so the current detection level and overcurrent detection level continue to remain at the lowered levels, and the DC motor and drive device continue to be output until the overload condition is released. The state in which the current flows continues to be lowered.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a control block diagram of a brushless motor showing an embodiment of the present invention. In FIG. 1, 1 is a DC power supply, 2 is a drive device including switching elements such as power transistors, and this drive device 2 converts the DC voltage applied from the DC power supply 1 into AC voltage and applies it to the coil 3 of the motor. . The electric motor has a three-phase coil 3,
It is composed of a rotor 4 that rotates according to the magnetic field generated by a coil 3. The current detection device 5 detects the current that returns from the coil 3 of the motor to the DC power supply 1 via the drive device, replaces the magnitude of the current with a voltage value, and controls the current limiting device 6.
and the overcurrent detection device 8. The current limiting device 6 is
When the output of the current detection device 5 reaches the output level of the current detection level setting device 7, a command signal to cut off the drive current is output to the drive device 2. When the output level of the current detection device 5 reaches the set level of the overcurrent detection level setting device 9, the overcurrent detection device 8 transmits the overcurrent detection signal to the current detection level setting device 7 and the overcurrent detection level setting device 9. Output to. Current detection level setting device 7 receives the output signal of overcurrent detection device 8 and outputs a current detection level corresponding thereto to current limiting device 6. The overcurrent detection level setting device 9 is
Upon receiving the output signal of the overcurrent detection device 8, an overcurrent detection level corresponding to the output signal is outputted to the overcurrent detection device 8.

Next, the specific configuration of the current limiting device 6 in the control block diagram will be explained based on FIG. 2. . In FIG. 2, reference numeral 10 denotes an integrator, and this integrator 10 receives the output of the current detection device 5 and outputs it to the comparator 11. Comparator 11 compares the output of integrator 10 and reference voltage 13 and outputs the result to one-shot circuit 12 . The one-shot circuit 12 connects the output of the comparator 11 and the reference voltage 14.
Then, a command signal to cut off the drive current is output to the drive device.

FIG. 3 shows a specific circuit diagram of the current limiting device 6. Further, FIG. 4 shows a waveform diagram of V1 to V7 corresponding to each component of the current limiting device 6 of FIG. 3. The drive current is converted into a voltage V1 by a resistor R1, which is further applied to an integrator composed of a resistor R2 and a capacitor C1, and its output V2 has a smoothed waveform as shown in V2 of FIG. Voltage V2 is connected to control power supply voltage VCC and resistor R3,
When the voltage V3 set by R4 is reached, comparator 1
5's output V4 is inverted, resulting in a voltage V5 after passing through an integrator consisting of resistors R5, R6 and capacitor C2.
becomes like the waveform V5 in FIG. This voltage V5 is further applied to a comparator 16. The comparator 16 compares the voltage V5 with the voltage V6 set by the control power supply voltage VCC and the resistors R7 and R8, and outputs a waveform like the waveform V7 in FIG. 4. In the case of FIG. 4, the high level of V7 is the drive current cutoff command.

FIG. 5 shows a block diagram of the overcurrent detection device 8. In FIG. 5, 17 is an integrator, and this integrator 17
receives the output of the current detection device 5 and outputs it to the comparator 18. Comparator 18 compares the output of integrator 17 and reference voltage 21 and outputs the result to integrator 19 . Comparator 20 receives the output of integrator 19 and reference voltage 22, and outputs an overcurrent detection signal when the output of integrator 19 reaches reference voltage 22.

FIG. 6 shows a specific circuit diagram of the overcurrent detection device 8. FIG. 7 shows a waveform diagram of V8 to V13 corresponding to each component of the overcurrent detection device of FIG. 8. The driving current is
It is converted into a voltage V8 by a resistor R1 and applied to an integrator composed of a resistor R9 and a capacitor C3, and its output V9 has a smoothed waveform as shown in FIG. When voltage V8 increases due to overload, etc., the smoothed voltage V9 also increases accordingly, and voltage V9 becomes equal to voltage V1 set by control power supply voltage VCC and resistors R10 and R11.
When reaching or exceeding 0, the output of comparator 23 V
11 starts to rise as shown in FIG. This voltage V
11 is applied to the comparator 24 together with the voltage V12 set by the control power supply voltage VCC and resistors R7 and R8, and when the voltage V11 reaches the value of the voltage V12, the output of the comparator 24 is inverted as shown in FIG. In the case of Figure 7, V13
The high level of is the overcurrent detection signal.

FIG. 8 is a circuit diagram showing an overall embodiment of the present invention including the current limiting device 6, overcurrent detecting device 8, etc. Comparator 24 that serves as the output of overcurrent detection device 8
The output terminal of the comparator 24 is connected to the control power supply VCC via a resistor R20, and the output terminal of the comparator 24 is connected to a resistor R20.
Transistor 4 whose emitter terminal is grounded via 16
The collector terminal of the transistor 45 is connected to the resistor R4 via R17. Also,
A capacitor C5 is connected in parallel to the resistor R4. In a similar configuration, the output terminal of the comparator 24 is connected to the resistor R1.
8, a transistor 46 whose emitter terminal is grounded
The collector terminal of the transistor 45 is connected to the resistor R11 via R19. Also,
A capacitor C6 is connected in parallel to the resistor R11.

FIG. 9 shows an example of the operation of the present invention with reference to the configuration shown in FIG. When an overload is applied to the motor 4 from time T1, the drive current increases, and the voltage V14, which is the output of the resistor R1 of the current detection device 5, also increases as shown in FIG. Also, voltage V14 is connected to resistor R2 and capacitor C1.
The smoothed voltage V15 outputted in addition to the integrator configured with is also increased. At this time, since the voltage V15 is higher than the voltage V19 divided by the control power supply voltage VCC and the resistors R10 and R11, the output voltage V16 of the comparator 23 increases as shown in FIG. Voltage V16
When reaches the voltage V12, which is divided by the control power supply voltage VCC and resistors R14 and R15, at time T2, the output voltage V17 of the comparator 24 enters an intermittent state in which high level and low level are alternately repeated as shown in FIG. becomes. the result,
The collector and emitter of the transistor 45 are also in an intermittent state, and the level of the voltage V18 is lowered as shown in FIG. At this time, since there is a capacitor C5, the voltage V18 is
Although it has ripples, it is not intermittent. By lowering this current detection level V18, the drive current is limited to a lower level than before time T2. Similarly, the collector and emitter of the transistor 46 are also in an intermittent state, and the level of the voltage V19 is lowered as shown in FIG. At this time, since there is a capacitor C6, the voltage V
No. 19 has ripples but is not intermittent. Even if the drive current is limited to a small value by lowering the voltage V19, which is the overcurrent detection level, the overcurrent detection signal continues to be output, so the state in which the drive current is limited to a small value continues.

FIG. 10 shows an embodiment in which the present invention is applied to a DC brush motor. In the figure, a DC brushed electric motor 25 is connected to a DC power supply 1 and a drive device 27,
Further, the drive device 27 is connected to the current detection device 5. Further, a diode 26 is connected in parallel to the DC brush motor 25. The other configurations are the same as in FIG. 1. Further, the operation of the entire device is also the same as in FIG.

FIG. 11 shows another embodiment in which the present invention is applied to a DC brush motor. In FIG. 11, the drive device 2
9 is connected to the DC power supply 1 and the DC brushed motor 25, and the DC brushed motor 29 is connected to the current detection device 5.
connected to. Further, the cathode of the diode 28 is connected to the DC brush motor 29, and the anode of the diode 28 is grounded. The other configurations are the same as in FIG. Further, the operation of the entire device is also similar to that in FIG.

FIG. 12 shows an embodiment in which a load torque detection device is used to detect overload. The output of the load torque detection device 30 is transmitted to the torque limiting device 31.
The torque limiting device 31 compares the set torque detection level with the output of the load torque detecting device 30, and outputs a command signal to the drive device 2 according to the result. Further, the output of the overcurrent detection device 8 is connected to a torque detection level setting device 32 , and the output of the torque detection level setting device 32 is connected to a torque limiting device 31 . The other configurations are the same as in FIG. 1. Further, the operation of the entire device is also similar to that in FIG.

FIG. 13 shows a configuration diagram in which the electric motor to which the above invention is applied is applied to a paper feeding electric motor for office equipment such as a printer, facsimile, or copying machine. The system controller 33 controls the laser light source 34 and
The polygonal mirror 35 is irradiated with a laser beam to expose the photosensitive drum 41 to light. The print pattern imaged on the photosensitive drum 41 by laser light is transferred to the transfer drum 42, and the developer 36 is attached thereto. paper 37 on tray 38
is sent to the copying or printing section of the office equipment using power from the paper feed motor 39. The fed paper 37 has the developer 36 attached to the transfer drum 42, is sent by the paper feed belt 43, and after the developer 36 is fixed by the fixing device 44, it is sent to a printer, facsimile, or copying machine. sent outside.

[0020] Office equipment such as printers, facsimile machines, and copying machines often experience paper jams during use. If you operate for a long time with a paper jam,
This method has problems such as friction between the paper feed roller and the paper, a locking of the motor, which can cause fires, and damage to many sheets of paper. Therefore, it is desirable to stop operation immediately when a paper jam occurs.

[0021] When a paper jam occurs, the load on the paper feed roller increases significantly or it becomes locked. When the paper feed roller is locked, the motor that drives this roller is also locked, and the current increases. Regarding this matter, the present invention is safe because the current is cut off if the overcurrent continues for a predetermined period of time, and there is no risk of fire. In particular, since the present invention lowers the reference voltage for overcurrent detection, safety is further improved.

[0022]

[Effects of the Invention] As explained above, according to the present invention,
The motor control device includes a drive device that is connected to a power source and applies a drive current to the motor, a current detection device that detects the current flowing through the drive device, and a detected value of this current detection device and a preset current detection. a current limiting device that limits a current value flowing through the driving device in comparison with a level; and a current detecting device that detects the magnitude of the current flowing through the driving device;
an overcurrent detection device that generates a detection signal by comparing this detection value with a preset overcurrent detection level; and a current detection level of the current limiting device is switched based on the detection signal output from the overcurrent detection device. Since the configuration is equipped with a current detection level setting device and an overcurrent detection level setting device that switches and sets the overcurrent detection level of the overcurrent detection device to a low value based on the detection signal of the overcurrent detection device, the motor It is possible to provide a highly reliable control device in which the drive device is not destroyed even in an overload state such as when the rotor is locked. In addition, it has become possible to apply a small and inexpensive drive element, and if this is used in a control device for the paper feed motor of office equipment that has a copying or printing device, it can prevent fires caused by paper jams. can do.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the configuration of the present invention.

FIG. 2 is a functional block diagram of a current limiting device.

FIG. 3 is a circuit diagram of an embodiment of a current limiting device.

FIG. 4 is a time chart showing the operation of the current limiting device.

FIG. 5 is a functional block diagram of an overcurrent detection device.

FIG. 6 is a circuit diagram of an embodiment of an overcurrent detection device.

FIG. 7 is a time chart showing the operation of the overcurrent detection device.

FIG. 8 is a circuit diagram showing an embodiment of the present invention.

FIG. 9 is a time chart showing the operation of the present invention.

FIG. 10 is a block diagram showing another embodiment of the present invention.

FIG. 11 is a block diagram showing another embodiment of the present invention.

FIG. 12 is a block diagram showing another embodiment of the present invention.

FIG. 13 is a configuration diagram of a printer, facsimile, copying machine, etc. equipped with the electric motor of the present invention.

[Explanation of symbols]

1... DC power supply, 2... Drive device, 3... Motor coil, 4
... Motor rotor, 5... Current detection device, 6... Current limiting device, 7... Current detection level setting device, 8... Overcurrent detection device, 9... Overcurrent detection level setting device, 10... Integrator, 11
...Comparator, 12...One-shot circuit, 13...Reference voltage,
14... Reference voltage, 15... Comparator, 16... Comparator, 17... Integrator, 18... Comparator, 19... Integrator, 2
0... Comparator, 21... Reference voltage, 22... Reference voltage, 23...
Comparator, 24... Comparator, 25... DC brush motor, 26... Diode, 27... Drive device, 28
...Diode, 29...Diode, 30...Load torque detection device, 31...Torque limiting device, 32...Torque detection level setting device, 33...System controller, 34...Laser emission source, 35...Polygon mirror, 36...Developer, 37...
paper, 38...tray, 39...paper feeding motor, 40...developing motor, 41...photosensitive drum, 42...transfer drum, 43
...Paper transport belt, 44...Fuser, 45...Transistor, 4
6...Transistor, R1...Resistance, R2...Resistance, R3...Resistance, R4...Resistance, R5...Resistance, R6...Resistance, R7...Resistance, R8...Resistance, R9...Resistance, R10...Resistance, R11...Resistance, R12... Resistor, R13...Resistance, R14...Resistance, R1
5...Resistor, R16...Resistor, R17...Resistor, R18...Resistor, R19...Resistor, C1...Capacitor, C2...Capacitor, C3...Capacitor, C4...Capacitor, C5...Capacitor, C6...Capacitor, VCC...Control power supply, V1...
Voltage waveform, V2...voltage waveform, V3...voltage waveform, V4...voltage waveform, V5...voltage waveform, V6...voltage waveform, V7...voltage waveform, V8...voltage waveform, V9...voltage waveform, V10...voltage waveform, V11... Voltage waveform, V12... Voltage waveform, V13...
Voltage waveform, V14...voltage waveform, V15...voltage waveform, V1
6... Voltage waveform, V17... Voltage waveform, V18... Voltage waveform,
V19...voltage waveform, T1...time, T2...time.

Claims (5)

[Claims] 1. A drive device that is connected to a power source and applies a drive current to an electric motor, a current detection device that detects the current flowing through the drive device, and a detected value of the current detection device and a preset current detection level. a current limiting device that limits a current value flowing through the driving device in comparison with the current value, and a current detecting device that detects the magnitude of the current flowing through the driving device, and compares this detected value with a preset overcurrent detection level. an overcurrent detection device that compares and generates a detection signal; a current detection level setting device that switches the current detection level of the current limiting device based on the detection signal output from the overcurrent detection device; and a detection signal of the overcurrent detection device. A control device for an electric motor, comprising an overcurrent detection level setting device that switches and sets an overcurrent detection level of an overcurrent detection device to a low value in response to a signal. 2. A drive device connected to a power source and applying a drive current to the electric motor; a torque detection device that detects the torque of the electric motor; and a torque detection device that compares the detection value of the torque detection device with a preset torque detection level. a torque limiting device that limits the torque flowing to the drive device; and a torque detecting device that detects the magnitude of the torque generated by the electric motor, and detects by comparing this detected value with a preset overtorque detection level. An overtorque detection device that generates a signal; a torque detection level setting device that switches the torque detection level of the torque limiting device based on the detection signal output from the overtorque detection device; A control device for an electric motor, comprising an overtorque detection level setting device that switches and sets an overtorque detection level of a torque detection device to a low value. 3. The motor control device according to claim 1, wherein an integrator is provided in either or both of the current limiting device and the overcurrent detecting device. 4. Office equipment having a copying or printing section and a paper feeding motor for driving a paper feeding roller in the copying or printing section, wherein the motor is connected to a drive device connected to a power supply, and the motor is connected to a drive device connected to a power source. The control device includes a current detection device that detects the current flowing through the drive device, a current limiting device that limits the current value flowing through the drive device by comparing the detection value of the current detection device with a preset current detection level, an overcurrent detection device that detects the magnitude of the current flowing through the drive device using the current detection device, and generates a detection signal by comparing the detected value with a preset overcurrent detection level; a current detection level setting device that switches the current detection level of the current limiting device based on a detection signal output from the device; and a current detection level setting device that switches the overcurrent detection level of the overcurrent detection device to a low value based on the detection signal of the overcurrent detection device. Office equipment characterized by being equipped with an overcurrent detection level setting device. 5. Office equipment having a copying or printing section and a paper feeding motor for driving a paper feeding roller in the copying or printing section, wherein the motor is connected to a drive device connected to a power supply, and the motor is connected to a drive device connected to a power source. The control device includes a torque detecting device that detects the torque of the electric motor, a torque limiting device that limits the torque flowing to the drive device by comparing the detected value of the torque detecting device with a preset torque detection level, and the torque detecting device that detects the torque of the electric motor. an overtorque detection device that detects the magnitude of torque generated by the electric motor and generates a detection signal by comparing the detected value with a preset overtorque detection level; and an output from the overtorque detection device. a torque detection level setting device that switches the torque detection level of the torque limiting device based on a detection signal generated by the overtorque detection device; Office equipment characterized by being equipped with a detection level setting device.