JPH0712927Y2 - Failure detection circuit for electromagnetic pickup - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a failure detection circuit for an electromagnetic pickup, and particularly in a circuit configured to detect rotation using the electromagnetic pickup, the lead wire on the electromagnetic pickup side is The present invention relates to a failure detection circuit that surely detects a failure when the wire is broken.

[Outline of device]

According to the present invention, the output side of the electromagnetic pickup connected to the comparison input terminal on the input side of the comparator is connected to the power supply terminal via a resistor, and the output side of the electromagnetic pickup and the input side of the comparator are connected. If a disconnection occurs between the two, the power supply voltage is applied to the comparison input terminal of the comparator, which inverts the output of the comparator to the output when the rotation is not detected and detects a failure. It is something that is done.

[Conventional technology]

For example, when detecting the number of revolutions of the engine, the electromagnetic pickup 1 is conventionally used.
Is connected to the comparison input terminal of the comparator 2 as shown in FIG. 4, and this comparator 2 is used for comparison with the reference voltage, whereby the square wave is extracted from the comparator 2 (third embodiment). See figure). The square wave is supplied to the CPU 4 through the interface 3, and the CPU 4 detects the rotation speed of the engine from the pulse number of the square wave.

In such a circuit, the resistors R _{1 to} R ₄ contained therein are
Are set as shown in FIG. 4, the comparison input voltage of the comparator 2 is V_, and the output voltage is V ₀ . If the voltage that changes to the high level when the comparator 2 is at the low level is V ₁ and the voltage that changes to the low level when the comparator 2 is at the high level is V ₂ (see FIGS. ₂ and 3), V ₁ ,
V ₂ is given by

V ₁ = Vc ・ R ₄ R ₂ / (R ₄ R ₂ ＋ R ₃ R ₄ ＋ R ₃ R ₂ ) V ₂ ＝ Vc ・ R ₄ (R ₁ ＋ R ₂ ＋ R ₃ ) / [R ₃ (R ₁ ＋ R ₂ ) ＋ R ₄ (R ₁ +
R ₂ + R ₃ )] And in this circuit, the input voltage V_ becomes indefinite when the disconnection occurs at the part marked with X.

[Problems to be solved by the invention]

In such a rotation detection circuit, the electromagnetic pickup 1
When the connection between the and the comparator 2 is disconnected at the position of 5 shown by the mark X, the output of the electromagnetic pickup 1 is not applied to the comparator 2. That is, the output of the comparator 2 is maintained at the high level. In such a state, the engine does not rotate and the electromagnetic pickup 1
Is the same as the state in which no power generation output is generated. Therefore, according to such a conventional circuit, when the output of the comparator 2 is in a high level state, it is not possible to determine whether the lead wire of the pickup 1 is broken or the engine is not rotating, which causes a failure. However, there is a drawback that the detection of is not performed reliably.

The present invention has been made in view of the above problems, and provides a failure detection circuit capable of reliably detecting a disconnection of a lead wire portion of an electromagnetic pickup regardless of whether the engine is rotating. The purpose is.

[Means for solving problems]

The present invention relates to an electromagnetic pickup that generates an AC output in accordance with rotation detection, an output side of the electromagnetic pickup connected to a comparison input terminal, and an AC output voltage of the electromagnetic pickup and a reference voltage applied to a reference input terminal. A comparator for comparing and outputting one square wave pulse per one cycle of the AC output; a detecting means for detecting the rotation speed from the output pulse of the comparator and detecting a failure from the output level of the comparator; The output of the comparator is connected to the comparison input terminal of the comparator at a low level when the electromagnetic pickup does not detect rotation, which is connected between the connection point between the output side of the electromagnetic pickup and the comparison input terminal of the comparator and the power supply terminal. a voltage lower than the voltage V ₁ of the when rises is applied to the high level from the solenoid A resistor output of said comparator to compare the input terminal of the comparator applies a voltage higher than the voltage V ₂ that drops from the high level to the low level when the Kkuappu side is disconnected, to the failure detection circuit of the electromagnetic pickup having a respective It is a thing.

[Action]

The electromagnetic pickup generates an AC output upon detection of rotation. The AC output of the electromagnetic pickup is supplied to the comparison input terminal of the comparator and compared with the reference voltage applied to the reference input terminal of the comparator to generate one square wave pulse per cycle of the AC output of the electromagnetic pickup. Occur. The rotation speed is detected by counting the number of square wave pulses by the detecting means.

When the rotating object stops rotating and the electromagnetic pickup does not generate an AC output, the output of this comparator rises from the low level to the high level via the resistor to the comparator's comparison input terminal. A voltage lower than the rising voltage V ₁ is applied, which maintains the output of the comparator at a high level. On the other hand, when the electromagnetic pickup side is disconnected, the internal resistance on the electromagnetic pickup side increases, and a voltage higher than the voltage V ₂ at which the output of this comparator drops from high level to low level increases at the comparator's comparison input terminal. Applied and the comparator remains low. Therefore, the detection means detects a failure depending on whether the output of the comparator is at a low level.

〔Example〕

The present invention will be described below with reference to an embodiment shown in the drawings. FIG. 1 shows a failure detection circuit for an electromagnetic pickup according to an embodiment of the present invention. For example, an electromagnetic pickup 10 for detecting an engine speed is a comparator via a resistor 11.
Connected to 12 comparison input terminals. This comparator
The reference input terminal 12 is connected to a connection end of a pair of voltage dividing resistors 13 and 14, and the resistor 13 is connected to a constant voltage power supply terminal. Further, the comparison input terminal of the comparator 12 is connected to the power supply terminal of the constant voltage source via the resistor 15. The output side of the comparator 12 is connected to the interface 16, and the interface 16 is further connected to the CPU 17.

In the above structure, when the engine rotates, the magnet provided on the rotating side causes the electromagnetic pickup 10 to generate a sinusoidal output as shown in FIG. 1
It is designed to be compared with the reference voltage generated at the connection points of 3 and 14. This causes the comparator 12 to generate a square wave at its output as shown in FIG. This square wave is supplied to the CPU 17 via the interface 16, and the engine speed is detected from the pulse number thereof.

Here, the comparator 12 that generates a square wave pulse has a threshold value of V ₁ when the output is at a low level and a threshold value of V ₂ when the output is at a high level. Therefore, as shown in FIG. 2, when the input voltage is increased from 0,
Until V ₂ becomes a low level exceeds V ₂ at the high level.
Also is lowered from the state where the input voltage exceeds V _2, until V ₁ is output is at a low level and becomes a high level when it is V ₁ or less. Here, the difference between V ₂ and V ₁ becomes the hysteresis voltage.

In such a failure detection circuit, when the position indicated by reference numeral 20 in FIG. 1 is broken, the connection between the electromagnetic pickup 10 and the comparator 12 is broken. So in this case,
Since the front end side of the resistor 11 is opened and the internal resistance of the electromagnetic pickup 10 becomes infinite, a constant voltage is applied to the comparison input terminal of the comparator 12. That is, in this circuit, a minute current is made to flow from the constant voltage source to the electromagnetic pickup 10 through the resistors 15 and 11, and when not broken, this current flows to the ground side through the electromagnetic pickup 10. .

On the other hand, if the wire breaks at the position of 20, the current no longer flows from the constant voltage source to the electromagnetic pickup 10, so that the power supply voltage is applied to the comparison input terminal of the comparator 12. Therefore, the output of the comparator 12 is held in the low level state, which can be detected by the CPU 17 via the interface 16. That is, by detecting the level of the output voltage of the comparator 12,
It is possible to determine the disconnection of the lead wire of the electromagnetic pickup 10.

To explain this in more detail, R _{1 to} R ₇ are set as shown in FIG. The voltages on the input side and the output side of the comparator 12 are V_ and V ₀ , respectively. Then the voltage V ₂ Hatsugi when the output V ₀ which voltage V ₁ and the comparator 12 when the output V ₀ which the comparator 12 as shown in Figure 2 rises from the low level to the high level is lowered from the high level to the low level become that way.

V ₁ = Vc ・ R ₄ R ₂ / (R ₄ R ₂ ＋ R ₃ R ₄ ＋ R ₃ R ₂ ) V ₂ ＝ Vc ・ R ₄ (R ₁ ＋ R ₂ ＋ R ₃ ) / [R ₃ (R ₁ ＋ R ₂ ) ＋ R ₄ (R ₁ +
R ₂ + R ₃ )] Also, the lead wire is not broken, and the pickup 10
Input voltage V_ of comparator 12 when voltage is not generated is V_ = Vc · (R ₇ + R ₆ ) / (R ₇ + R ₆ + R ₅ ). in case of,
The input voltage V_ of the comparator 12 is V_ = Vc, as is clear from the above equation, V ₁ > V_ (normal) Therefore, it is normal and not rotating, and the pickup 10 generates voltage. When not, the comparator
12 output V ₀ is always high level.

On the other hand, if the internal resistance of the pickup 10 increases due to poor contact or disconnection of the electromagnetic pickup 10, V ₂ <V_ (when disconnected), and the output V _{0 of the} comparator 12 always becomes low level when disconnected.

That is, V_ (normal) <V ₁ <V ₂ V_ (break), and if the lead 20 breaks at the cross mark 20, the input voltage V_ of the comparator 12 is
The voltage V ₂ at which the output V ₀ changes from high level to low level
Will be higher than. Therefore, the output of the comparator 12 is maintained at low level. On the other hand, when the wire is not broken and the rotation is simply stopped, the output of the comparator 12 is maintained at a high level, and therefore the wire can be accurately detected from the output of the comparator 12.

[Effect of device]

As described above, according to the present invention, the electromagnetic pickup that generates an AC output in accordance with rotation detection, the output side of the electromagnetic pickup is connected to the comparison input terminal, and the AC output voltage of the electromagnetic pickup is applied to the reference input terminal. A comparator that outputs one square wave pulse per one cycle of AC output in comparison with the voltage, a detection means that detects the rotation speed from the output pulse of the comparator, and a failure detection from the output level of the comparator, and an electromagnetic pickup It is connected between the connection point between the output side of the and the comparison input terminal of the comparator and the power supply terminal.When the electromagnetic pickup does not detect rotation, the output of the comparator rises from the low level to the high level at the comparison input terminal of the comparator. a voltage lower than the voltages V ₁ is applied when climbing, when the electromagnetic pickup side is broken The output of the comparator to compare the input terminal of the comparator is related failure detection device for electromagnetic pickup comprising respectively a applying a voltage higher than the voltage V ₂ that drops from the high level to the low level resistance.

Therefore, when the rotating body does not rotate and the electromagnetic pickup does not generate an AC output, the comparator input voltage is lower than the voltage V ₁ when the output of this comparator rises from low level to high level. Is applied, which maintains the output of the comparator at a high level. On the other hand, if the electromagnetic pickup side is disconnected,
The voltage from the power supply terminal is applied to the comparison input terminal of the comparator through the resistor. Since this voltage is higher than the voltage V ₂ at which the output of the comparator is processed from high level to low level, the output of the comparator becomes low level. Therefore, by detecting the output level of the comparator by the detecting means, it becomes possible to reliably detect the failure.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a failure detection circuit for an electromagnetic pickup according to an embodiment of the present invention, FIG. 2 is a graph showing an output waveform of a comparator, and FIG. 3 is an output waveform of an electromagnetic pickup and an output waveform of a comparator. Fourth graph showing the relationship
The figure is a circuit diagram of a conventional detection circuit. The names of the main parts in the drawings are as follows. 10 …… Electromagnetic pickup 11 …… Resistance 12 …… Comparator 13, 14… Voltage dividing resistance 15 …… Resistance 16 …… Interface 17 …… CPU 20 …… Disconnection location

Claims (1)

[Scope of utility model registration request] 1. An electromagnetic pickup that generates an AC output upon detection of rotation, and a reference voltage having an output side of the electromagnetic pickup connected to a comparison input terminal and an AC output voltage of the electromagnetic pickup applied to a reference input terminal. And a comparator that outputs one square wave pulse per one cycle of the AC output, and a detection unit that detects the rotation speed from the output pulse of the comparator and detects a failure from the output level of the comparator, It is connected between a connection point between the output side of the electromagnetic pickup and the comparison input terminal of the comparator and a power supply terminal, and when the electromagnetic pickup does not detect rotation, the output of the comparator is low at the comparison input terminal of the comparator. a voltage lower than the voltage V ₁ of the when standing rise from the level to the high level is applied, the electrostatic Failure detection circuit for an electromagnetic pickup comprising a resistor output of said comparator to compare the input terminal of the comparator applies a voltage higher than the voltage V ₂ that drops from the high level to the low level when the pick-up side is broken, respectively.