JPH0734380Y2 - Rotation detection sensor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation detecting sensor including a magnetic sensor for detecting the rotation speed of a magnetic body embedded in a rotating body.

Problems to be Solved by Prior Art and Invention Recently, in order to manage the driving situation of a vehicle, a device for detecting the speed of the vehicle and managing the operating state of the vehicle has been developed. In this device, to detect the speed of the vehicle,
A rotation detection sensor for detecting the rotation speed of an axle is attached to an automobile. This rotation detection sensor has a rotating body that is integral with the axle and in which a magnetic body is embedded, and a Hall IC that is an example of a three-wire magnetic sensor that is mounted close to the rotating body on the vehicle body side of an automobile. is doing. The Hall IC 2 has a power supply terminal to which a DC power supply V for supplying a drive voltage is connected, a ground terminal, and an output terminal for oscillating an output signal when the magnetic body approaches as shown in FIG. , Hall IC
When 2 is turned on, the rotation of the rotating body is detected by detecting the time when the voltage appearing at the output terminal changes from the power supply voltage level to the 0V level.

In this rotation detection sensor 1, the voltage at the output terminal of the Hall IC 2 fluctuates with the rotation of the rotating body and the number of rotations of the rotating body can be detected. However, the Hall IC 2 is short-circuited for some reason, Alternatively, if any of the terminals is broken, even if a magnetic substance passes
The voltage fluctuation at the output terminal of IC2 disappears, and the rotation of the rotating body cannot be detected.

Means for Solving the Problems The present invention is intended to eliminate the above-mentioned drawbacks, and has a three-wire magnetic sensor for detecting passage of a magnetic body embedded in a rotating body. A constant voltage circuit for supplying a drive voltage of the magnetic sensor is connected between both terminals of the power source terminal and the ground terminal of the magnetic sensor, and the power source terminal of the magnetic sensor has at least 3 for dividing the power source voltage. The voltage dividing resistors are connected in series. Among the voltage dividing resistors, a switch that operates in response to the output signal of the magnetic sensor is connected in parallel with the voltage dividing resistor located in the middle, and one end of this switch is configured as an output end.

On the other hand, one end of the switch is provided with a voltage level detecting device having a detection resistor for detecting the voltage value at one end of the switch, which is sufficiently larger than the voltage dividing resistor on the power supply side. The voltage value generated across the detection resistor is compared with the threshold voltage, the voltage between this voltage and the power supply voltage, and the voltage below the threshold voltage to determine which of the rotation detection signal, disconnection detection signal, and short circuit detection signal. It is configured to output.

Function In the above rotation detection sensor, when the power supply voltage is supplied, the voltage determined by the constant voltage circuit is supplied between the power supply terminal and the ground terminal of the magnetic sensor, and the magnetic sensor is kept in a state where it can detect the passage of the magnetic substance. It Even if the rotating body starts rotating, the magnetic sensor remains in the off state and the output signal is not transmitted until the magnetic body embedded in the rotating body approaches the magnetic sensor. Therefore, the switch remains off,
The voltage appearing at one end of the switch is held at a voltage obtained by dividing the power supply voltage by the ratio of the voltage dividing resistors. Therefore, this voltage is maintained at a voltage sufficiently lower than the power supply voltage, sufficiently lower than the voltage of the constant voltage circuit, and sufficiently higher than the voltage of the constant voltage circuit.

When the magnetic body approaches the magnetic sensor, the magnetic sensor is turned on, and an output signal of 0V level is transmitted from the output end thereof. Therefore, the switch is turned on, and the current flowing through the voltage dividing resistor connected in parallel with this switch flows through the switch side. As a result, the voltage at the one end of the switch drops close to the voltage determined by the constant voltage circuit. The rotation of the rotating body can be detected by detecting this voltage drop with the voltage level detecting device.

On the other hand, if the connection portion of the rotation detection sensor is broken, the voltage appearing at one end of the switch rises to almost the power supply voltage. Therefore, the voltage is much higher than the voltage that appears at one end of the switch when the magnetic body is in a position away from the magnetic sensor during normal operation. By detecting this voltage rise by the voltage level detection device,
Disconnection can be detected.

If the output terminal of the rotation detection sensor is short-circuited for some reason, the voltage appearing at one end of the switch drops to 0V level, which is lower than the voltage when the switch is on. A short circuit can be detected by detecting the voltage drop of 0V level by the voltage level detecting device.

Examples Hereinafter, examples will be described with reference to the drawings. In FIG. 1, reference numeral 1 is a rotation detection sensor used when detecting the speed of an automobile (not shown) sent to an automobile operation management device (not shown). The rotation detecting sensor 1 is composed of a rotating body (not shown) which is integral with the axle of the automobile and in which a magnetic body (not shown) is embedded, and a rotation detecting portion which is attached to the vehicle body of the automobile. . The rotation detector has a Hall IC2, which is an example of a three-wire magnetic sensor, at a position approaching the rotating body on the vehicle body side of an automobile, and is configured to detect passage of the magnetic body by the Hall IC2. ing. The Hall IC 2 has a power supply terminal, a ground terminal, and an output terminal, and a constant voltage circuit 3 including a Zener diode ZD and a diode D between the power supply terminal and the ground terminal.
And a smoothing circuit 4 formed of a capacitor is connected. The voltage of the constant voltage circuit 3 may be a voltage sufficient to supply the drive voltage of the Hall IC 2, and is configured to be maintained at the 5V level. Also, the power terminal has 3
A plurality of voltage dividing resistors R1, R2, R3 are connected in series, and among these voltage dividing resistors, a semiconductor switch 5 which is an example of a switch is connected in parallel with the voltage dividing resistor R2 located in the middle. The semiconductor switch 5 is configured to be turned on by an output signal transmitted from its output terminal when the Hall IC 2 is turned on. Moreover, one end of the semiconductor switch 5 is configured to be the output end of the rotation detection sensor 1, and is configured to send an output signal to the voltage level detection device 7 described later.

Further, the DC power source V has a power source voltage of 12V which is sufficiently higher than the voltage of the constant voltage circuit 3, and the voltage dividing ratio by the voltage dividing resistors R1, R2, R3 is changed by turning on / off the semiconductor switch 5, The voltage at one end of the switch 5 is configured to fluctuate between a voltage (8V level) approximately in the middle of the voltage of the constant voltage circuit 3 and the power supply voltage and a voltage (5V level) of the constant voltage circuit 3 ( (See FIG. 2).

On the other hand, a voltage level detecting device 7 for detecting the voltage level of the voltage appearing at one end of the semiconductor switch 5
(See FIG. 3) are connected. This voltage level detection device 7 is constructed by connecting one end of the semiconductor switch 5 and the Hall IC
2 has a detection resistor R4 connected between the ground terminal and
This detection resistor R4 reduces the current flowing through it,
It has an extremely large resistance value as compared with the voltage dividing resistor R3, and is configured so that the output signal of the rotation detection sensor accurately appears at both ends of the detection resistor R4. The voltage applied to the detection resistor R4 of the voltage level detection device 7 is sent to the input side of the first comparator 8, and the voltage (5V level) that appears at one end of the semiconductor switch 5 when it is on and the semiconductor switch 5 is off. The voltage that appears at one end of the (8V level)
Is compared with the threshold voltage (6.5V) which is an intermediate value between
A rotation detection signal is transmitted from the comparator 8 and the rotation of the rotating body is counted by a counter (not shown) (not shown).

The voltage applied to the detection resistor R4 is sent to the input side of the second comparator 9, and is intermediate between the power supply voltage (12V) and the voltage (8V level) appearing at one end when the semiconductor switch 5 is off. Is compared with this voltage (9.5 V), and when the voltage exceeds this value, the disconnection detection signal is transmitted from the second comparator 9 (see FIG. 2).

Further, the voltage applied to the detection resistor R4 is sent to the input side of the third comparator 10 which is an inverter, and is equal to or less than the intermediate value (2.5V) between the voltage appearing at one end of the semiconductor switch 5 when it is on and 0 volt. Then, the short circuit detection signal is transmitted from the third comparator 10.

In the rotation detection sensor, when the power supply voltage is supplied from the DC power supply V, the driving voltage is applied to the Hall IC2, and the Hall IC2
Is held in a state where passage of a magnetic substance can be detected. From this state, even if the rotating body integrated with the axle of the automobile rotates, if the magnetic body is located away from the Hall IC2, the Hall IC2 is held in the OFF state. At this time, the voltage appearing at one end of the semiconductor switch 5 is a voltage obtained by dividing the power supply voltage by a ratio determined by the three voltage dividing resistors R1, R2, R3, which is sufficiently smaller than the power supply voltage (12V). Moreover, the voltage (8V level) is sufficiently higher than the voltage (5V level) appearing at one end when the semiconductor switch 5 is on. This voltage is compared by the first comparator 8, the second comparator 9, and the third comparator 10 of the voltage level detection device 7, respectively, but no output signal is transmitted from any of the comparators, and the rotation of the rotating body is reduced. Neither the detection signal, the disconnection detection signal, nor the short circuit detection signal is transmitted.

When the magnetic body approaches the Hall IC2, the Hall IC2 is turned on, and an output signal of 0V level is transmitted from the output terminal thereof. Therefore, the semiconductor switch 5 is turned on, the current flowing through the voltage dividing resistor R2 flows through the semiconductor switch 5, and the voltage appearing at one end thereof is obtained by dividing the power supply voltage at a ratio determined by the voltage dividing resistors R1 and R3. It becomes a voltage and drops to near the voltage of the constant voltage circuit 3 (5V level). Due to this voltage fluctuation, an output signal is transmitted from the first comparator 8,
A rotation detection signal is transmitted from the first comparator 8, rotation of the rotating body is detected, and the counting unit counts the rotation. At this time, neither the disconnection detection signal nor the short circuit detection signal is transmitted from the second comparator 9 and the second comparator 10.

Further, if the rotation detection sensor 1 is disconnected from the voltage level detection device 7 for some reason, the voltage appearing at one end of the semiconductor switch 5 is divided by the ratio of the voltage dividing resistor R3 and the detecting resistor R4. Although it becomes a compressed power supply voltage, since the resistance value of the detection resistor R4 is larger than that of the voltage dividing resistor R3, it rises to near the power supply voltage. Therefore, this voltage increase is detected by the second comparator 9, the disconnection detection signal is transmitted from the second comparator 9, and the disconnection is detected.

On the other hand, if the output terminal of the rotation detection sensor 1 is short-circuited for some reason and the voltage appearing at one end of the semiconductor switch 5 drops to the 0V level, the inverter forming the third comparator 10 is inverted, A short circuit detection signal is transmitted from the third comparator 10 to detect a short circuit.

Effect of the Invention As described above, the present invention is configured to detect the passage of a magnetic material embedded in a rotating body by a magnetic sensor, and a switch arranged in parallel with one of the voltage dividing resistors is provided in the magnetic sensor. It is configured to turn on and off by turning on and off to change the voltage division ratio of the power supply voltage so that the voltage appearing at one end of the switch is sufficiently lower than the power supply voltage and sufficiently higher than 0V level and with a sufficient fluctuation range. Therefore, there is an advantage that a detection signal of disconnection and a detection signal of short circuit can be extracted from the output signal in addition to the rotation detection signal, and a rotation detection sensor capable of detecting disconnection and short circuit can be provided.

Although the number of voltage dividing resistors for dividing the power supply voltage is limited to three in the embodiment, it may be two, or four or more.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram of a main part of the present invention, FIG. 2 is an explanatory diagram showing an output signal range of the present invention, FIG. 3 is an electric circuit diagram of a voltage level detecting device according to the present invention, and FIG. It is a principal part electric circuit diagram which shows a prior art example. 1 ... Rotation detection sensor, 2 ... Hall IC, 3 ... Constant voltage circuit, 4 ... Smoothing circuit, 5 ... Semiconductor switch, 6, 7
...... Voltage level detection device, 8 …… First comparator, 9 …… Second comparator, 10 …… Third comparator, ZD …… Zener diode, D …… Diode, R1 …… Voltage division resistance, R2 ...... Voltage resistance, R3 ...... Voltage resistance, R4 ...... Detection resistance,

Claims (1)

[Scope of utility model registration request] 1. A constant voltage circuit for supplying a drive voltage of a magnetic sensor is connected between both terminals of a power supply terminal and a ground terminal of a three-wire magnetic sensor for detecting passage of a magnetic material embedded in a rotating body, At least three voltage dividing resistors for dividing the power supply voltage are connected in series to the power supply terminal of the magnetic sensor, and a switch operated by the output signal of the magnetic sensor is connected in parallel to the voltage dividing resistance located in the middle. While one end of this switch is used as an output end, it has a detection resistor that is sufficiently larger than the voltage-dividing resistor on the voltage side and detects the voltage value at one end of the switch. A voltage level detection device that outputs a rotation detection signal, a disconnection detection signal, or a short circuit detection signal in comparison with the voltage between the power supply voltage and the voltage below the threshold voltage A rotation detection sensor characterized by.