JPH0572963B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a pulse generator (hereinafter referred to as
This relates to a method for detecting abnormalities (for example, deterioration of LEDs, etc. in particular) in the PG (referred to as PG).

[Conventional technology]

Two-phase pulses (phase A, phase B) that are 90° out of phase with each other
A pulse generator that outputs one pulse per rotation is attached to the rotating shaft of a servo motor, etc., and is widely used in NC, robots, etc.

"One pulse per revolution" is a pulse that detects the origin, and the name has not yet been generally determined, and depending on the manufacturer, it is called a C-phase pulse,
Although it is called by various names such as Z pulse and origin pulse, the name C-phase pulse will be used here.

[Problem that the invention seeks to solve]

Now, if an abnormality occurs in such a pulse generator, for example if the light emitting output of a light emitting diode (LED) deteriorates, in order to notify the outside, in addition to the normal signal line and power line, A signal line is required for abnormality notification.

[Means for solving problems]

In order to solve the above problems, a first means of the present invention is to invert the C phase in the event of an abnormality, and detect an abnormality when the inversion time exceeds the normal C phase pulse output time.

The second means of the present invention detects an abnormality by inverting the C-phase at the time of an abnormality, and after detecting the abnormality, the inverted C-phase pulse is further inverted and returned to the original state to be sent to the subsequent stage. It is something that is sent out.

[Effect]

With the first means, it is possible to detect an abnormality without providing a signal line for abnormality detection. However, due to the inversion, the phase of the C phase may shift.

The C phase was originally used for returning to the origin, and 1
This does not matter if it is done only once, but in a system that repeatedly returns to the origin, positional deviation will occur.

Therefore, when applied to such a system, the second means is used to invert the once-inverted C-phase signal again to return it to its original state and send it to the subsequent stage.

〔Example〕

Hereinafter, specific embodiments of the present invention will be illustrated and described.

FIG. 1 is a pulse waveform diagram showing the operation of the present invention.
A phase, B phase, C phase, and an inverted C phase are shown.

FIG. 2 shows a circuit for inverting the C phase, and FIG. 3 shows a circuit for detecting PG abnormality (LED deterioration).

The PG abnormality detection circuit shown in FIG. 3 is a circuit that issues an alarm output when the LED drive current exceeds a predetermined value in a light amount constant control circuit that feeds back the output light of the LED 31 to the photodiode 32.

The illustrated photodiode is for directly receiving light without passing through the PG disc slit and controlling the amount of light to be constant, and is not for obtaining a PG pulse output.

The first means of the present invention is to notify this alarm output to the outside without using a special signal line, and can be realized by the circuit shown in FIG.

Figure 2 shows PG2 when an alarm output is generated.
This is a circuit that inverts the C-phase output of No. 1 (which naturally passes through the waveform shaping section 22), and inputs the exclusive OR 23 of the alarm output and the C-phase output to the transistor 24 to obtain the converted C-phase output. obtain.

As a result, C
Since the phase output "H" becomes abnormally long, an abnormality is detected when it exceeds the originally predetermined pulse width.

For example, as shown in Figure 4, if we assume that the C phase output "H" is the same as the pulse width of the A and B2 phases, we will count three pulses that capture the rising and falling edges of the A and B2 phases. It can be seen that an abnormality occurs if the C-phase output "H" continues for a period of time or longer.

This is sufficient if only an abnormality is detected, but since the C-phase output is inverted, a shift occurs in the output phase.

This can be ignored, but in a system that repeatedly performs positioning, such as when returning to the origin, it will result in a positional deviation error.

This can be solved by providing a circuit that restores the once inverted C-phase output to its original state and transmits it to the subsequent stage.

This is the second means of the present invention, and can be realized by connecting the circuit shown in FIG. 5 to the circuit shown in FIG.

In FIG. 5, 1 is a D flip-flop;
is a multiplexer, 3 is a counter, and 4 is a JK flip-flop.

A circuit that uses D flip-flop 1 and multiplexer 2 to generate a pulse that captures the rise and fall of the A and B phases (called a differential pulse, which emits an UP pulse when rotating in the forward direction and a DOWN pulse when rotating in the reverse direction). And this is publicly known. (For example, Japanese Patent Laid-Open No. 60-94526) In the present invention, a counter 3 is provided to count the differential pulses only during the period when the C-phase output is "H".

Assuming that the C-phase output "H" during normal operation is the same as the pulse width of the A and B2 phases, an abnormality occurs if the C-phase output "H" continues for more than a period of counting three differential pulses.

Therefore, it is sufficient to load "3" into counter 3, but here, we will load "7" to counter 3.
is loading.

In other words, when the C-phase output becomes "H" and counts 8 differential pulses, the counter overflows or underflows, sets JK flip-flop 4, outputs an alarm output, and inverts the C-phase output again. Let it go and put it back together.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to notify the outside of a PG abnormality without using a special signal line, which has the great effect of improving reliability without complicating or increasing the size of the device. It is something to play.

[Brief explanation of the drawing]

FIG. 1 is a waveform diagram showing the concept of the present invention, FIG. 2 is an embodiment of the first invention of the present invention, FIG. 3 is an LED abnormality detection circuit, and FIG. 4 is a diagram showing the principle by which an abnormality can be detected. FIG. 5 shows a second embodiment of the present invention. 1: D flip-flop, 2: multiplexer, 3: counter, 4: JK flip-flop.

Claims (1)

[Claims] 1. A and B two-phase pulses whose phases are shifted by 90 degrees from each other,
In a pulse generator that has a pulse output of one pulse per revolution (hereinafter referred to as a C-phase pulse), in the event of an abnormality, the C-phase pulse is inverted, and the inverted C-phase is used to generate the rise of the A and B two-phase pulses, An abnormality detection method for a pulse generator characterized by detecting an abnormality by counting differential pulses that capture the falling edge and exceeding the normal count value. 2 A and B two-phase pulses that are 90° out of phase with each other,
In a pulse generator that has a pulse output of one pulse per revolution (hereinafter referred to as a C-phase pulse), in the event of an abnormality, the C-phase pulse is inverted, and the inverted C-phase is used to generate the rise of the A and B two-phase pulses, By counting the differential pulse that captures the falling edge and counting beyond the normal count value, an abnormality is detected, and at the same time, the inverted C-phase pulse is further inverted and returned to its original state and sent to the subsequent stage. An abnormality detection method for a pulse generator, which is characterized by: