JP2002357456A - Encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To acquire an abnormality occurrence signal of an encoder with a simple structure for outputting the abnormality occurrence signal in an easily detectable state through a Z-phase. SOLUTION: By means of this encoder, an A-phase pulse train signal and a B-phase pulse train signal shifted in a phase from each other by a predetermined angle are generated according to rotation of a pulsar, while a Z-phase pulse signal is generated in the predetermined position according to the rotation of the pulsar. This encoder is provided with an output circuit defining an output voltage of the Z-phase by impressing a bias voltage to the output side of the Z-phase via a resistor, an OR circuit taking a logical sum of the respective A-phase and the B-phase signals, and a transistor turned on/off according to an output signal from the OR circuit and turned on for reversing the output signal of the Z-phase into a low-level state of a failure detection output. The occurrence of an abnormality is detected through deviation of the Z-phase output voltage from a defined normal range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encoder for detecting a rotational speed, a rotational position, and a rotational direction having a function of detecting occurrence of an electrical abnormality.

[0002]

2. Description of the Related Art Conventionally, an encoder used for a steering angle sensor or the like of an automatic steering device for a vehicle is provided with an abnormality detecting circuit for detecting an abnormality occurrence state such as disconnection or ground fault inside the encoder. A signal is given to an ECU that controls the entire apparatus by a signal system different from that of the encoder output to determine whether or not an abnormality has occurred. However, in that case, a dedicated detection signal line is separately required.

For this reason, conventionally, A-phase and B-phase pulse train signals whose phases are shifted from each other by a predetermined angle according to the rotation of the pulsar are generated, and a Z-phase pulse signal is generated at a predetermined position according to the rotation of the pulsar. In the resulting encoder, an abnormality detection circuit for detecting an abnormality occurrence state inside the encoder is provided, and a detection signal of the occurrence of the abnormality is added to the Z phase of the encoder through an exclusive OR circuit. There has been developed a device that detects an occurrence of an abnormality by inverting a signal in a normal state (see Japanese Patent No. 2779498).

[0004]

The problem to be solved is that an abnormality detection circuit for detecting an abnormality occurrence state inside the encoder is provided, and the abnormality occurrence detection signal is passed through an exclusive-OR circuit to the encoder Z. If the phase is output, the overall configuration is complicated.

[0005]

According to the present invention, A-phase and B-phase pulse train signals whose phases are shifted from each other by a predetermined angle according to the rotation of the pulsar are generated, and Z is generated at a predetermined position according to the rotation of the pulsar. An encoder which generates a phase pulse signal, obtains an abnormality occurrence signal of the encoder by a simple configuration, and outputs the abnormality occurrence signal through the Z phase in a state that can be easily determined via a resistor to the output side of the Z phase. An output circuit for defining a Z-phase output voltage by applying a bias voltage, an OR circuit for performing an OR operation of signals of the A-phase and the B-phase, and turning on and off according to the output signal of the OR circuit.
A transistor that operates off and inverts the Z-phase output signal to a low level state of the failure detection output when on,
The occurrence of abnormality is detected when the output voltage of the Z phase deviates from a specified range in a normal state.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the generation of A-phase and B-phase pulse train signals whose phases are shifted from each other by a predetermined angle in accordance with the rotation of an optical pulsar (not shown) using photodiodes PD1 to PD3. 1 shows a circuit configuration of an encoder that generates a Z-phase pulse signal at a predetermined position.

FIG. 2 shows A-phase and B-phase pulse train signals during clockwise rotation.

Here, the case of right rotation is shown, and A
The phase difference a between the phase and the B phase is set to 2.0 ° ± 1.5 °. The circuit constants are set so that the high-level voltage is 4.3 V or higher and the low-level voltage is 1.3 V or lower.

FIG. 3 shows the Z-phase pulse signal.

[0010] Here, a pulse signal that is inverted in the positive and negative directions is output, and the pulse interval b is set so as to be 20 ° ± 2 °.

In such a circuit configuration of the encoder, in the present invention, an output circuit 1 for defining a Z-phase output voltage by applying a bias voltage Vb to a Z-phase output side via a resistor Rz, An OR circuit 2 for calculating the logical sum of the signals of the A-phase and the B-phase; ON / OFF operation according to the output signal of the OR circuit 2; Inverting transistor Q
5 is provided to detect the occurrence of an abnormality when the output voltage of the Z phase deviates from a specified range in a normal state.

Specifically, assuming that Vb = 5.0 ± 0.25V, the high-level voltage of the Z-phase pulse signal is 4.0 ± 0.4V and the low-level voltage is 0.8
It is set to be ± 0.2V.

When an abnormality occurs in which the A-phase or the B-phase or any one of them is broken, the output of the OR circuit 2 goes high and the transistor Q5 is turned on.
As a result, the Z-phase output signal is set to the inversion state of the low level of the failure detection output, and the Z-phase output voltage is set to 0.4 V or less.

Similarly, the transistor Q5 is also turned on when an abnormality occurs in which the A-phase and / or the B-phase is grounded, whereby the output signal of the Z-phase becomes the inverted state of the low level of the failure detection output. And the output voltage of the Z phase becomes 0.
It becomes 4V or less. In addition, the Z phase is grounded (transistor Q5
Is turned on and the Z-phase output signal is in the inverted state of the low level of the failure detection output), the Z-phase output voltage at that time becomes 0.4 V or less.

The power supply Vcc or GN of the encoder
When an abnormality occurs when D is disconnected or when the Z phase is disconnected or short-to-supply, the output voltage of the Z phase at that time is set to be 4.6 V or more.

Table 1 shows the standard values of the Z-phase output voltage under normal and abnormal conditions.

[0017]

According to the present invention, an encoder having such a circuit configuration is used, for example, in an automatic steering device for a vehicle using the encoder as a steering angle sensor, and an ECU for controlling the entire device. By monitoring the output voltage state of the Z-phase, the occurrence of abnormality can be detected based on the fact that the output voltage of the Z-phase is out of the specified range N in a normal state.

In this case, the ECU determines that the encoder is operating normally when the Z-phase output voltage is in the range of 0.6V to 4.4V. When the output voltage of the Z phase is 0.4 V or less, it is determined that an abnormality has occurred in which the A phase and the B phase are disconnected or grounded, or that an abnormality has occurred in which the Z phase is grounded. I do. If the output voltage of the Z phase is equal to or higher than 4.6 V, it is determined that an abnormality has occurred in which the power supply Vcc or GND of the encoder is disconnected, or that an abnormality has occurred in which the Z phase is disconnected or short-to-power. I do.

[0020]

As described above, according to the encoder of the present invention, in the circuit configuration, the Z-phase output voltage is specified by applying a bias voltage to the Z-phase output side via a resistor. And an OR circuit for taking the logical sum of the signals of the B and B phases, and turning on and off according to the OR output thereof,
By applying a simple means of adding a transistor for inverting the Z-phase output signal to the low level state of the failure detection output when turned on, various abnormality occurrence signals of the encoder are obtained, and the various abnormality occurrence signals are obtained. This has the advantage that it can be output in a state that is easy to determine through the Z phase.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing pulse train signals of A phase and B phase of the encoder according to the present invention.

FIG. 3 is a diagram showing a Z-phase output state when the encoder according to the present invention is normal and abnormal.

[Explanation of symbols]

 1 Output circuit 2 OR circuit Q5 Transistor for inverting Z-phase output signal N Specified output voltage range during normal operation AL Output range when low-side error occurs AH Output range when high-side error occurs

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenji Ikuta 1053 Otagaya, Tsurugashima-shi, Saitama F-term (reference) 2F063 AA35 AA36 BA08 CA03 DA05 EA03 LA03 LA14 2F077 AA01 CC02 NN27 PP19 QQ03 QQ11 TT00 TT02 TT35 TT62

Claims (3)

[Claims] 1. An encoder which generates A-phase and B-phase pulse train signals whose phases are shifted from each other by a predetermined angle in accordance with the rotation of a pulsar, and generates a Z-phase pulse signal at a predetermined position in accordance with the rotation of the pulsar. Circuit for defining the Z-phase output voltage by applying a bias voltage to the output side of the Z-phase via a resistor, an OR circuit for calculating the logical sum of the signals of the A-phase and the B-phase, and the OR circuit thereof And a transistor for turning on and off in response to the output signal of the above, and for inverting the output signal of the Z phase when turned on. An encoder characterized by detecting occurrence of abnormality. 2. A specified range when the output voltage of the Z-phase is normal when the transistor is turned on when the A-phase and the B-phase are disconnected or when the ground is short-circuited. 2. The encoder according to claim 1, wherein the abnormality is detected to be lower than that of the abnormality. 3. When the power supply Vcc or GND is disconnected, the Z-phase is disconnected, or the power supply is short-circuited, the output voltage of the Z-phase becomes higher than a normal range, and the occurrence of an abnormality is detected. An encoder according to claim 1, characterized in that: