JPH0121709B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a motor runaway detection method, and more particularly to a runaway detection method that focuses on the periodicity of rotation to reduce erroneous detection of runaway.

(b) Prior art and its problems Conventional methods for detecting runaway motors include reading the detection signal with a slit optical sensor in a disc attached to the motor shaft at a timing when the motor is not instructed to rotate. There is a way to determine that it is out of control when it is reversed. However, with this method, if the motor is stopped while the optical sensor is exposed to light, the sensor output will turn on and off due to vibration etc., resulting in a false determination that the motor is running out of control.
When stopping, it is necessary to take measures such as applying a brake to the motor or to use two optical sensors. In addition, electrical noise also made it easy to falsely detect runaway.

(c) Object of the Invention It is an object of the present invention to solve such problems in the conventional motor runaway detection method, to use a simple sensor, and to be able to accurately detect runaway.

(d) Structure of the Invention The technical means according to the present invention taken to achieve this object include a detection means for detecting rotational displacement of a motor and outputting a pulse signal, and a period of the pulse signal from the detection means. A cycle counter for counting, a holding register for holding the output of the cycle counter at least one cycle before, and a cycle comparison circuit that compares the cycles of pulse signals by comparing the cycle counter and the contents of the cycle register. , and a determination circuit that determines whether the output of the period counter is within a specified range, and at a timing when rotation of the motor is not instructed.
In accordance with the output of the discrimination circuit, a state in which the period of the pulse signal is within a specified range occurs continuously for a specific period, and in accordance with the output of the period comparison circuit, the period of the pulse signal is within a specified range. A method is adopted in which it is determined that the motor is running out of control when it is detected that a state in which the difference from the cycle period is equal to or less than a specific value has occurred continuously for a specific period.

(e) Embodiments of the Invention Next, how the motor runaway detection method according to the present invention is actually implemented will be explained using embodiments. FIG. 1 is a block diagram showing an embodiment of a motor runaway detection method according to the present invention. A hole 2 in a disk 1 attached to the shaft of a motor M is detected by a photocoupler 3, and after passing through an amplifier circuit 4, the pulse is inputted to a pulse tip cutting circuit 5 to cut out the tip of the pulse.
Then, it is input to a period counter 6, a period register 7, and a period count condition creation circuit 8.

The period counter 6 is connected to the photocoupler 3 for period detection.
It is initialized by the pulse tip cutting signal from , and continues counting at the period of the timer signal until the next pulse tip cutting signal arrives. However, if the counter carries, the counting operation stops at that point.

The period register 7 registers the period counter 6 every time the pulse tip cutting signal is output from the photocoupler 3.
The set value and the period counter output are compared in the period comparator circuit 9.

The cycle upper/lower limit discrimination circuit 10 discriminates whether the cycle T of each cycle in the time chart of FIG. 2 satisfies the condition Tmin (specified value)≦T≦Tmax (specified value).

The signals of these parts are collected in the number count condition generation circuit 8, and are judged every time the pulse tip cutting signal from the period detection photocoupler 3 is output, so that Tmin (specified value)≦T≦Tmax (specified value)... |T _o+1 −Tn|≦T (specified value) ... A count-up signal is sent to the number counter 11 every time the following condition is satisfied.

The number counter 11 is initialized every time there is a motor rotation instruction (or a stop instruction), and when a pulse tip cutting signal is output from the period detection photocoupler 3, at least one of the above conditions is met.
It is also initialized if the conditions are not satisfied.

In this way, when the signal from the period detection photocoupler 3 is generated consecutively a specific number of times under conditions that satisfy both of the above conditions, a runaway detection signal is generated.

The above conditions are used to compensate for the decrease in detection accuracy due to the need to loosen the conditions if there are large variations between devices, and detect when the rotation has reached steady state. Since the detection accuracy can be increased, the noise resistance can also be improved. By doing so, it is possible to accurately detect a motor runaway by identifying periodic pulses having attributes unique to the device or the motor.

(f) Effects of the Invention As described above, according to the present invention, at a timing when the motor is not instructed to rotate, the output cycle of the rotation cycle detection sensor is less than or equal to the value defined as the maximum cycle, which is defined as the minimum cycle. Value or more If the difference from the cycle of the previous cycle is less than the specified value for a specific period or more,
A method is used to identify when the motor is running out of control. Therefore, a simple photocoupler or the like is sufficient as the rotation period detection sensor of the motor, and runaway can be detected with high accuracy.

[Brief explanation of drawings]

The drawings show an embodiment of the motor runaway detection method according to the present invention, and FIG. 1 is a block diagram and FIG. 2 is a time chart. In the figure, 1 is a disk, 3 is a photocoupler, and 5
is a pulse tip extraction circuit, 6 is a period counter,
7 is a cycle register, 8 is a cycle count condition creation circuit, 9 is a cycle comparison circuit, 10 is a cycle upper/lower limit discrimination circuit, and 11 is a number counter.

Claims (1)

[Scope of Claims] 1. A detection means for detecting rotational displacement of a motor and outputting a pulse signal, a period counter for counting the period of the pulse signal from the detection means, and an output of the period counter at least one period before. A period comparison circuit that compares the periods of pulse signals by comparing a holding register to be held, the period counter, and the contents of the period register, and a period comparison circuit that determines whether the output of the period counter is within a specified range. Equipped with a discrimination circuit, when the motor is not instructed to rotate,
In accordance with the output of the discrimination circuit, a state in which the period of the pulse signal is within a specified range occurs continuously for a specific period, and in accordance with the output of the period comparison circuit, the state in which the period of the pulse signal is within a specified range occurs in each period. A motor runaway detection method is characterized in that the motor is determined to be running out of control when it is detected that a state in which the difference from the cycle period is equal to or less than a specific value has occurred continuously for a specific period.