JPH01148099A - Malfunction detector for pulse motor - Google Patents

Abstract

PURPOSE:To simply detect the abnormal rotation of a pulse motor due to a load by detecting a slope at the time of rising of a phase current flowing to an exciting phase by slope detecting means. CONSTITUTION:Slope detecting means 2 is composed of a pulse motor phase current rise detector 3 and a 1-chip microprocessor 4, thereby detecting slopes of the terminal voltages of resistors R5, R8 at the time of rising. The periods of time in which the terminal voltages of the resistors R5, R8 arrive from '0' at a reference voltage depend upon the magnitude of a load applied to a pulse motor, becomes short as the load increases, and long as the load decreases. When the motor is shifted from an overload state to a stepout state, its phase current slowly rises. Accordingly. the stepout of the motor can be detected by this slow rise of the phase current.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a pulse motor abnormality detection device.

(Prior Art) Pulse motors can be driven relatively easily by open-loop control, so they are often used in control equipment using microprocessors, such as printers and copying machines.

As a method for detecting abnormal rotation of a pulse motor, for example, a method is known in which an encoder and a photosensor are attached to the rotating shaft of the pulse motor, and the rotation speed of the pulse motor is detected by output pulses from the photosensor. According to this method, abnormal rotation of the pulse motor can be detected, but other mechanical switches, photo sensors, etc. are required, which increases the cost.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to provide a pulse motor abnormality detection device that can inexpensively and easily detect abnormal rotation of a pulse motor caused by a load.

[Means for solving problems]

The pulse motor abnormality detection device according to the present invention is provided with a slope detection means for detecting the slope at the rise of the phase current flowing through the excitation phase during excitation of the excitation phase.

[Effect]

The pulse motor abnormality detection device according to the present invention detects the slope at the rise of the phase current flowing through the excitation phase when the excitation phase is excited, using the slope detection means.

〔Example〕

FIG. 1 is a circuit diagram showing one embodiment of the present invention. This is an example of a pulse motor driven by a two-phase excitation method. In the figure, reference numeral 1 denotes a known constant current drive type pulse motor driver, which is composed of a switching circuit 11, an excitation switching circuit 12, and a back electromotive force canceling circuit 13.

The switching circuit 11 controls the phase current of the pulse motor, and includes transistors Q1, Q2, and resistors R1 to
R12, diodes D7, D8, comparator ICI,
It is composed of IC2.

The excitation switching circuit 12 switches the excitation phase of the pulse motor, and is composed of transistors Q3 to Q6.

The back electromotive force canceling circuit 13 absorbs back electromotive force, and includes diodes D3 to D6 and a Zener diode ZDI.
It is made up of.

Reference numeral 2 denotes a slope detection means, which is composed of a pulse motor phase current rise detection circuit (hereinafter referred to as a phase current rise detection circuit) 3 and a 1-chip microprocessor (hereinafter referred to as CPU) 4, and detects the terminal voltage of the resistors R5 and R8. This is to detect the inclination at the time of rise.

The phase current rise detection circuit 3 includes a comparator IC3,
It is composed of IC4 and resistors R13 to R20, and compares the terminal voltage of the resistors R5 and R8 with a predetermined reference voltage. The reference voltage is determined by resistors R13 to R20.

The cpυ4 is a control ROM and RAM.

It has a built-in timer circuit, an event counter, etc., and has ports P5 and R6 as input ports for the event counter, and ports P1 to P4 as output ports for excitation signals.

Further, the CPU 4 starts counting internal clock pulses using an event counter in synchronization with the rising edge of the pulse from the comparator IC3 input to the port P5, and when the voltage level of the port P5 becomes low level, Counting is stopped, the obtained count value is intermediately stored in a buffer register, and the pulse width, that is, the slope at the rise of the terminal voltage of the resistor R5 is detected from the stored count value.

The slope at the rise of the terminal voltage of the resistor R5 can be detected from the pulse width of the pulse output from the control IC3 when the reference voltage value of the comparator IC3 is set smaller than vR, the output waveform of the comparator IC3 is like the broken line shown in Fig. 4. As shown in Fig. 4, when the load of the pulse motor changes, the slice level of the comparator Ic3 changes, and as a result, the duty of the output of the comparator IC3, that is, the pulse This is because the width changes.

Further, the CPU 4 detects the pulse width of the input from the comparator IC4 which is manually input to the boat P6, that is, the slope at the time of rising of the terminal voltage of the resistor R8. FIG. 5 shows the waveforms of signals input to boats P5 and R6. The boats P5 and R6 correspond to, for example, a CI boat of a microcomputer μC0M-87AD manufactured by NEC Corporation.

Furthermore, the CPU 4 controls the transistors Q3 to Q6 by 0N10 using excitation signals from the boats P1 to P4.
This is for FF control. FIG. 3 shows the waveforms of the excitation signals output from the boats pt to P4.

Next, the operation will be explained based on the flowchart shown in FIG.

When the transistor Q3 is turned on by the excitation signal output from the boat Pi of the CPU 4 (S-1), the coil L1
A phase current begins to flow from the power supply vcc1 (S-2). As shown in Fig. 4, the phase current increases with a time constant determined by the inductance of the coil L1 and the resistance value of the resistor R5.
At the same time, the terminal voltage of resistor R5 also increases with the same time constant (S-3). When this terminal voltage exceeds a predetermined reference voltage (voltage value VR) (S-4), the level of the output signal of the comparator IC3 is inverted and becomes high level (S-S), and at this time, the output signal In synchronization with the rising edge of , the event counter starts counting internal clock pulses (S-6).

Furthermore, when the level of the output pulse of the comparator IC3 is reversed, the transistor Q1 is turned off (S-6).
, the voltage of the power supply vcc1 is no longer applied to the coil L1. When the voltage of the power supply Vcct is no longer applied to the coil L1, at the same time, a back electromotive force is generated in the coil L1 (S-7
), the current flowing through the coil 1 is the transistor Q1
, coil L1, diode D3, Zener diode Z
The current flows through D1 in this order, and the phase current value of coil Ll is quickly reduced by Zener diode ZDI.

When the phase current value decreases, the terminal voltage of the resistor R5 decreases (5-8), and when this terminal voltage becomes smaller than the reference voltage value vR, the level of the output pulse of the comparator IC3 is inverted and becomes a low level (S -9). Then, the transistor Q1 is turned on and the counting of internal clock pulses by the event counter is stopped (S
-10), the obtained count value is intermediately stored in a buffer register (S-11).

The pulse width, that is, the slope at the rise of the terminal voltage of resistor R5 is detected from this stored count value (S-
12).

Further, since the slope of the terminal voltage of the resistor R8 at the time of rising is also detected in the same manner as described above, a redundant explanation will be omitted.

In addition, in Fig. 4, the waveform of the terminal voltage of resistors R5 and R8 changes in a sawtooth shape after the terminal voltage rises from 0 volts and reaches the reference voltage value vR, which is due to the value of the phase current flowing through the coil. This is because it is controlled so that it remains constant.

Next, detection of step-out of the pulse motor will be explained.

The time it takes for the terminal voltages of resistors R5 and R8 to reach the reference voltage from O varies depending on the magnitude of the load applied to the pulse motor; it becomes shorter as the load increases, and becomes longer as the load decreases. This is because the small movements of the magnetic poles (rotor) in the pulse motor vary depending on the load condition, and the magnetic circuit formed between the magnetic poles and the windings varies depending on the load. This state is shown by the broken line in FIG.

When the pulse motor shifts from an overload state to an out-of-step state, the phase current rises slowly, so the terminal voltage of resistor R5 rises slowly as shown in FIG. in this case,
The duty of the output of the comparator IC3 changes rapidly, and the high level section decreases.

Furthermore, when the phase goes out, the phase current may not reach its limit level, as shown in FIG. In this case, no pulse is output from comparator IC3.

Therefore, conversely, if the high level section is detected and the high level section is decreasing or does not exist, the pulse motor is out of synchronization.

Above, we have explained an example in which a 2-phase pulse motor is driven using a 2-phase excitation force method, but driving it using an I-phase excitation method or 1-2 phase excitation force method is the same as when it is driven using a 2-phase excitation force method. load abnormalities can be detected.

FIG. 8 shows an example of voltage waveforms at various parts when driven by a one-phase excitation force type.

As shown in Figure 8, when the load fluctuates, the resistance R5
, the rise time of the terminal voltage of R8 changes, and the terminal voltage of boat P5 changes.
, R6 changes, and therefore, as described above, by measuring the high level time of the voltage input to boat P5 or boat P6, it is possible to know whether there is a load abnormality in the pulse motor.

FIG. 9 shows another embodiment of the invention. This is because the configuration of the tilt detection means is different from the above embodiment. That is, in the above embodiment, the phase current rise detection circuit 3 and the CP
U4 is configured to detect the pulse width of the pulses from the comparators I'C3 and IC4, but in this embodiment, the operational amplifier 5.6 amplifies the detected terminal voltages of the resistors R5 and R8, and the It consists of an A/D converter 7.8 that converts voltage into digital data and a microprocessor 9, and the microprocessor 9 monitors the output of the A/D converter 7.8.

The operation and effect are not essentially different from those of the previous embodiment.

(Effects of the Invention) As described above, according to the present invention, it is possible to obtain a pulse motor abnormality detection device that can inexpensively and easily detect abnormal rotation of a pulse motor caused by a load.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is an operation flowchart, FIG. 3 is a waveform diagram of an excitation signal, FIG. 4 is a terminal voltage waveform diagram of resistors R5 and R8, and FIG. Boat P
5. Waveform diagram of the pulse manually applied to R6, Figures 6 and 7 are explanatory diagrams of the operation during step-out, and Figure 8 is a waveform diagram of each part shown in Figure 1 when driven by the one-phase excitation method. , FIG. 9 is a circuit diagram showing another embodiment of the present invention. 3---------Pulse motor phase current rise detection circuit 4------Microprocessor L1 to L4------Coil R5, R8------Resistance

Claims (3)

[Claims] (1) A pulse motor abnormality detection device characterized by comprising a slope detection means for detecting the slope at the rise of a phase current flowing through an excitation phase when the excitation phase is excited. (2) The slope detection means includes a comparator that compares the value of the terminal voltage obtained by passing the phase current through a predetermined resistance with a predetermined reference value, and a counter that counts the pulse width of the output pulse of the comparator. A pulse motor abnormality detection device according to claim 1, characterized in that: (3) The slope detection means includes an A/D converter that converts a terminal voltage obtained by passing a phase current through a predetermined resistance into digital data, and an increment detection means that detects an increment of the digital data over a predetermined period. A pulse motor abnormality detection device according to claim 1, comprising: