JP2000278995A - Overheating-protecting device of stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect overheating by stopping power feed when the period interval of a drive pulse reaches fixed time or longer when a stepping motor is driven. SOLUTION: A drive pulse circuit 4 does not generate output when a stepping motor drive circuit 3 receives a pulse from a control circuit 1, starts supplying a drive pulse to a stepping motor 6, at the same time a drive pulse is received, and a period interval is a pulse within time determined by a time constant that a drive pulse-monitoring circuit 4 has. Then, when the period interval of the drive pulse reaches a time constant or longer, or when the drive pulse stops while a power feed circuit 5 is closed, output is automatically generated as soon as the period interval of the drive pulse exceeds the time constant for controlling the power feed circuit 5, a circuit is opened to stop the supply of power from the stepping motor drive circuit 3 to the stepping motor 6, thus preventing the stepping motor from overheating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overheat protection device for a stepping motor in an apparatus using a stepping motor driven and controlled by software.

[0002]

2. Description of the Related Art Conventionally, a device using a stepping motor controlled by software, for example, an overheat protection device for a stepping motor used in a device such as an automatic assembling machine, protects a stepping motor from overheating due to a software abnormality. In order to prevent this, a hardware watchdog timer is provided, and software (hereinafter, referred to as a subroutine) for driving the above-mentioned watchdog timer at a fixed cycle is incorporated in software for driving the stepping motor (hereinafter, referred to as a main routine). From the main routine, the watchdog timer is driven by activating the above subroutine at a fixed cycle, and the watchdog timer does not generate an output while the watchdog timer is driven at a fixed cycle by the above subroutine, May The runaway routine, not to activate a subroutine at a period determined from the main routine, or by bugs such subroutine may fail processing for the watchdog timer activation. When such an abnormality occurs and the interval at which the subroutine drives the watchdog timer exceeds a predetermined time, the watchdog timer times out, and the output of the watchdog timer forcibly interrupts the drive control unit, and the main routine is executed. Runaway was stopped, and driving of the stepping motor was stopped.

[0003]

However, it is difficult to anticipate software abnormalities in advance, and it is often impossible to anticipate what state will appear in the main routine or subroutine. In such a case, even if the watchdog timer operates normally, the output from the watchdog timer cannot forcibly interrupt the main routine, and the pulse for driving the stepping motor is suitable for driving the stepping motor. There may be cases where the stepping motor is out of the range or a case where the drive current applied to the stepping motor continuously flows.In these cases, however, according to the above-described conventional technology, the stepping motor cannot be protected from overheating even if the stepping motor overheats. There is a problem.

In order to solve the above-mentioned problem, the present invention provides a method for driving a stepping motor in a case where the pulse interval is out of a range suitable for driving the stepping motor when an abnormality occurs in a main routine or a subroutine. When the stepping motor is continuously pulsed for a long time, or when the driving current applied to the stepping motor continuously flows, the overheating protection of the stepping motor is performed so that the stepping motor does not overheat. .

[0005]

In order to achieve the above object, according to the present invention, a driving control section of a stepping motor, which is driven and controlled by software, includes a stepping motor which controls a period of a driving pulse of the stepping motor when driving the stepping motor. Overheat protection of a stepping motor provided with a drive pulse monitoring circuit unit having a function of detecting that the interval has become longer than a predetermined time and controlling a power supply unit of the stepping motor to stop supplying power to the stepping motor. The device is characterized in that:

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram of an apparatus using a stepping motor controlled by software showing an embodiment of the present invention, for example, a drive control section of a stepping motor of an automatic assembling machine, and 1 includes a main routine. A control circuit having software. The control circuit 1 generates a pulse for driving a stepping motor. Reference numeral 2 denotes a watch dog timer driven by a subroutine of the control circuit 1, 3 denotes a stepping motor drive circuit that receives a pulse from the control circuit 1 and drives the stepping motor 6, and 4 denotes a drive pulse output from the stepping motor drive circuit 3. This is a drive pulse monitoring circuit for monitoring, and in this embodiment, a drive pulse monitor circuit will be described below. Reference numeral 5 denotes a power supply unit for supplying power to the stepping motor 6, and in the present embodiment, a power supply circuit will be described below. 6 is a stepping motor.

FIG. 2 is a circuit diagram showing a specific example of the drive pulse monitoring circuit 4 shown in FIG. 1. T1, T2 and T3 are terminals, and IC1 is an EXOR (exclusive OR) I.
C and IC2 are retrigger flip-flops IC, and IC3 and IC5 are inverters I having Schmitt trigger characteristics.
C and IC4 are OR (OR) ICs, R1, R2 and R3 are resistors, C1 is a capacitor, C2 is an electrolytic capacitor, +5
V is a power supply, and GND is a ground.

Next, the operation will be described. The control circuit 1 includes a CPU, a memory, and the like (not shown), is controlled by a main routine stored in the memory, and drives the stepping motor 6 under the control of the main routine. When the stepping motor 6 is driven, a pulse is generated by a main routine according to an input condition (not shown) and supplied to the stepping motor drive circuit 3.

The stepping motor drive circuit 3 receives the pulse and converts it into a drive pulse for driving the stepping motor 6 and supplies the same to the stepping motor 6.
Electric power is supplied to the stepping motor 6 via the power supply circuit 5. At this time, the circuit of the power supply circuit 5 is closed, and the stepping motor 6 is driven by the power from the power supply circuit 5 and the driving pulse.

The watchdog timer 2 is driven at a constant time interval by a subroutine for driving the watchdog timer 2 included in a main routine (not shown) of the CPU of the control circuit 1. When the driving of the watchdog timer 2 is stopped or when the pulse period becomes longer than a predetermined time interval, the watchdog timer 2 generates an output, and the output of the control circuit 1
To the control circuit 1
Receives the information on occurrence of the abnormality, resets the main routine, and normalizes the main routine.

If an abnormality occurs in the main routine or the subroutine, it may happen that the reset function does not operate and the main routine cannot be normalized. In this case, the driving pulse of the stepping motor 6 may be out of the range suitable for driving the stepping motor 6, or the driving current applied to the stepping motor 6 may continuously flow. The problem of overheating occurs.

The drive pulse monitoring circuit 4 receives the drive pulse from the stepping motor drive circuit 3 in response to the pulse from the control circuit 1 and starts to supply the drive pulse to the stepping motor 6, and receives the drive pulse. Is not generated when the cycle interval of the pulse is within the time determined by the time constant of the drive pulse monitoring circuit 4,
When the driving of the stepping motor is completed, the drive pulse monitoring circuit 3 is restored to a normal state, and the cycle interval of the drive pulse becomes equal to or greater than the time constant of the drive pulse monitor circuit 4, or When the drive pulse is stopped while the power supply circuit 5 is closed, the drive pulse monitoring circuit 4 automatically generates an output at the same time that the cycle interval of the drive pulse exceeds the time constant of the drive pulse. The power supply circuit 5 is controlled, the circuit of the power supply circuit 5 is opened, and the stepping motor
The supply of power to the power supply is stopped.

The operation of the drive pulse monitoring circuit 4 will be described in detail with reference to a circuit diagram shown in FIG.
The stepping motor drive circuit 3 receives a pulse from the control circuit 1 and starts supplying a drive pulse to the stepping motor 6, and the same pulse as the drive pulse supplied to the stepping motor 6 is supplied to the terminal T1. Is sent to one terminal of IC1 as it is, and further sent to IC3 via an integrating circuit composed of resistors R1 and R2 and a capacitor C1, where the waveform is shaped by the Schmitt trigger characteristic of IC3, the polarity is inverted, and IC1 is inverted. Is output to the other terminal, and the number of pulses twice as many as the number of pulses supplied to the terminal T1 is output by the EXOR function of IC1 and sent to the lead B of IC2.

The reason why the pulse supplied to the terminal T1 is supplied to the IC2 as a doubled pulse number is that an IC described later is used.
This is to reduce the time constant determined by the resistor R3 and the capacitor C2 connected to the second lead Cx and the lead R / C.

At the same time that the same pulse as the drive pulse supplied to the stepping motor 6 is supplied to the terminal T1, a selection signal is sent from the stepping motor driving circuit 3 to the terminal T3, and the selection signal is sent to the IC5 via the IC4. After the waveform is shaped by the Schmitt trigger characteristic, the polarity is inverted and sent to the lead CLR of the IC 2.

IC2 is activated by a selection signal to the read CLR, and operates as a retrigger flip-flop. The operation of the IC2 as a retrigger flip-flop is such that the period of the pulse sent to the lead B is equal to the resistance R connected to the lead Cx and the lead R / C.
No pulse is output from the lead Q of IC2 if it is less than the time constant determined by 3 and capacitor C2.

When the period of the pulse sent to the lead B exceeds the time constant determined by the resistor R3 and the capacitor C2, a pulse is output to the lead Q, and the pulse is sent to one terminal of the IC 6. Since the control signal from the terminal T3 is transmitted to the other terminal of the IC 6 via the IC 4, the pulse from the IC 2 is directly transmitted to the terminal T2, and the pulse is transmitted to the power supply circuit 5 in FIG. The power supply circuit 5 is controlled to open the circuit, and the supply of power to the stepping motor 6 is stopped.

If the pulse sent to the lead B exceeds the time constant determined by the resistor R3 and the capacitor C2 in the on or off state, a pulse is output to the lead Q, and the period of the pulse is changed. The above resistor R3
The same operation as that when the time constant determined by the capacitor C2 is exceeded is performed.

As described above, the drive pulse monitoring circuit 4 monitors the cycle interval of the drive pulse of the stepping motor 6, and
If the cycle interval of the drive pulse is equal to or longer than a predetermined time, or if the drive pulse is kept on or off for a certain time or longer, this is detected and the power supply to the stepping motor 6 is stopped. The operation of the control pulse monitoring circuit 4 repeats the same operation every time the stepping motor 6 is driven, monitors the drive pulse of the stepping motor 6 for abnormalities, and prevents the stepping motor 6 from overheating. It is.

[0021]

As described above, according to the present invention, the period of the drive pulse of the stepping motor 6 is determined by the drive pulse monitoring circuit 4.
When the watchdog timer 2 loses its function due to the abnormality of the main routine or the subroutine due to the abnormality of the main routine or the abnormality of the subroutine, the drive of the stepping motor 6 is stopped without being affected by the abnormality. This has the effect that overheat protection can be performed.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram illustrating an example of a drive pulse monitoring circuit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 control circuit 2 watchdog timer 3 stepping motor drive circuit 4 drive pulse monitoring circuit 5 power supply circuit 6 stepping motor

Claims (1)

[Claims] 1. A drive control unit of a device using a stepping motor driven and controlled by software detects that a cycle interval of a drive pulse of the stepping motor has become equal to or longer than a predetermined time when the stepping motor is driven. An overheat protection device for a stepping motor, further comprising a drive pulse monitoring circuit unit having a function of controlling a power supply unit of the stepping motor to stop supplying power to the stepping motor.