JP3050027B2 - Encoder pulse count circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for counting the number of A-phase and B-phase rotation pulses which are incremental signals of an encoder.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional counting method. FIG.
1, 1 is a B-phase pulse number counter, 2 is an encoder, 3 is an A-phase, 4 is a B-phase, 5 is a Z-phase, 6 is an A-phase pulse number counter, and 7 is a gate generation circuit.

FIG. 3 shows a timing chart of the A-phase, B-phase, and Z-phase pulses of the encoder. In FIG. 3, 8 is Z
Phase, 9 is A phase, 10 is B phase when the rotation direction is CCW, 11
Is the B phase when the rotation direction is CW. Where T is A phase,
B phase period, t ₁ is the time from the rising edge of A phase to the rising edge of B phase, t ₂ is the time from the rising edge of B phase to the falling edge of A phase, t ₃ is the falling edge of A phase The time from the edge to the falling edge of the B phase, t ₄ is the time from the falling edge of the B phase to the rising edge of the A phase. Tz is the pulse width of the Z phase, and Tzh is the time from the center position of the H level width of the A phase to the rising edge and the falling edge of the Z phase. (Table 1) shows the detailed timing.

[0004]

[Table 1]

[0005] The principle of the conventional system will be described below. Generally, only one pulse is output in one rotation of the Z phase, so the gate generation circuit 7 turns on the gate signal from the rising edge of the Z phase to the rising edge of the next Z phase.
Then, it outputs to the A-phase pulse number counter 6 and the B-phase pulse number counter 1. Counters 1 and 6 turn on this gate signal.
Only during this time, the number of one rotation pulse is counted by counting the A phase and the B phase.

[0006]

However, Z phase and A
Since the timings of the phase and the B phase are in the relationship shown in (Table 1), Z
In some cases, the rising edges of the phases cross the rising edges of the A and B phases. Therefore, in the conventional method,
When the rising edge of the gate signal crosses the A-phase and B-phase edges, the first or last pulse of the A-phase or the B-phase may be miscounted. It became N ± 1 and was very unstable.

[0007] The present invention solves the above-mentioned problems.
An object of the present invention is to generate a stable gate signal regardless of the timing of the phase, the A phase, and the B phase.

[0008]

In order to achieve this object, a count circuit according to the present invention inputs a Z-phase and a B-phase to a gate circuit, and sets the gate timing of the counter to the B-phase when the Z-phase is at Hi level. This is a counter circuit characterized by being performed at a rising edge.

[0009]

When the encoder rotates in the CCW direction (FIG. 3), a rising edge of the B-phase comes near the center of the Z-phase pulse width. If the gate is turned on / off at this edge, regardless of the phase of the Z-phase. A gate signal can always be generated at a stable position. The direction of rotation is opposite (CW direction)
At this time, the phase of the B phase is inverted by 180 degrees compared to the CCW rotation, so that the gate signal can be generated in the same manner by logically inverting the B phase signal.

[0010]

An embodiment of the present invention will be described below.

FIG. 1 is a block diagram of the present invention. In FIG. 1, 12 is an encoder, 13 is an A-phase signal, 14 is a B-phase signal, 15 is a Z-phase signal, 16 is a rotation direction discriminating circuit,
18 is a logic inversion element, 19 is a selector, 20 is a rotation direction signal, 21 is an A-phase pulse number counter, 22 is a B-phase pulse number counter, 23 is a gate generation circuit, and 24 is a gate signal.

In this configuration, the rotation direction determining circuit 16
The rotation direction is determined from the phase difference between the phases B and B, and a rotation direction signal 20 is output to the selector circuit 19. Selector circuit 19
Indicates that when the encoder is in CCW rotation, the B-phase signal is
During rotation, the B-phase signal is inverted and output to the gate generation circuit. As a result, the Z phase and B input to the gate circuit are
The phase timing is as shown in FIG. 4 regardless of the rotation direction. In FIG. 4, 25 is the Z phase, 26 is the A phase, 27 is B
Phase 28 is the gate signal. The gate circuit 23 is shown in FIG.
When the gate signal 28 is turned on / off at the rising edge of the B phase 27 when the Z phase 25 is at the Hi level,
The rising and falling edges of the gate signal 28;
The rising edge of the phase and the falling edge of the B phase do not cross. Therefore, if the A-phase pulse number counter 21 counts the rising edge of the A-phase and the B-phase pulse number counter 22 counts the falling edge of the B-phase while the gate signal 28 is at the Hi level, the rotation direction Z-phase and A-phase,
Regardless of the B-phase difference, the number of pulses for one rotation can be accurately counted. However, the gate signal 28 is on
During this operation, the direction of rotation shall not change.

[0013]

As described above, according to the present invention, the measurement of the number of rotations per rotation, which was conventionally unstable due to the phase difference between the Z phase and the A and B phases, is performed by using the timing of the Z phase and the B phase. By controlling the gate, the measurement can always be performed accurately without any miscount.

[Brief description of the drawings]

FIG. 1 is a diagram showing a pulse count circuit of an encoder according to the present invention.

FIG. 2 is a diagram showing a pulse count circuit of a conventional encoder.

FIG. 3 is an output signal timing chart of an encoder.

FIG. 4 is a timing chart for generating a gate signal according to the present invention;

[Explanation of symbols]

 1,22 B phase pulse number counter 2,12 Encoder 3,9,13,26 A phase 4,14,27 B phase 5,8,15,25 Z phase 6,21 A phase pulse number counter 7 Gate generation circuit 10 B phase (during CCW rotation) 11 B phase (during CW rotation) 16 rotation direction discriminating circuit 17, 18 logic inversion element 19 selector 20 rotation direction signal 23 gate generation circuit 24, 28 gate signal

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-54-37777 (JP, A) JP-A-4-372820 (JP, A) JP-A-5-280999 (JP, A) JP-A-51- 130246 (JP, A) JP-A-1-248020 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01D 5/00-5/252 G01D 5/39-5/62

Claims (2)

(57) [Claims] 1. The number of A-phase and B-phase pulses output from an encoder having an A-phase and a B-phase that outputs a plurality of pulses constant for one rotation and a Z-phase that generates one pulse for each rotation. In a pulse count circuit of an encoder provided with a counter for counting and a gate circuit for generating a gate signal from the Z phase and the B phase, a gate signal using a rising edge of the B phase when the Z phase is at a Hi level is supplied to the counter. A pulse counting circuit for an encoder, wherein the pulse counting circuit counts one rotation pulse of the encoder when input. 2. The method according to claim 1, wherein the rotation direction of the encoder is detected from the A and B phases output from the encoder.
2. The pulse counting circuit according to claim 1, wherein the phase pulse is logically inverted and input to the pulse counting circuit.