JPS623730Y2 - - Google Patents

Description

[Detailed explanation of the invention] [Industrial application field] This invention uses a Hall IC to measure the rotational speed of the rotating shaft of a vehicle.
This invention relates to a rotation sensor that detects rotation. In particular, it relates to a rotation sensor with a protection circuit that protects this Hall IC.

[Conventional technology]

Conventionally, this type of rotation sensor uses a Hall IC, which is a Hall element that is a magneto-electric conversion element, placed between two disc-shaped permanent magnets that rotate while connected to a rotating shaft.
is fixedly installed. These permanent magnets are provided with S poles and N poles alternately in the direction of rotation, and the two permanent magnets have different poles facing each other, so that when the rotating shaft rotates, the two permanent magnets Pulse signals are extracted from the Hall IC in response to changes in the direction of magnetic force.

FIG. 1 is an electrical circuit diagram of a conventional rotation sensor. In this circuit, a resistive voltage divider circuit consisting of a series circuit of three resistors R ₁ , R ₂ , and R ₃ is provided between the positive and negative DC power supply terminals 2 and G, and a Hall IC 1 is connected to both ends of the intermediate resistor R ₂ . Two power input terminals 1a, 1b
It connects. As an example, if the voltage at terminal 2 is 24V, and the voltage across resistor _R3 is 5V, the resistor
Set so that the voltage across _R2 is 5V. The Hall IC 1 is configured as an integrated circuit in which a transistor amplifier circuit is connected to a detection output of a Hall effect element, and a terminal 3 is an output terminal of the amplifier circuit.

In this circuit, the DC potential of output terminal 3 is Hall
5V to 10V when IC3 is working normally
It's between. However, if the power supply terminal 2 is disconnected, the DC potential of the output terminal 3 becomes 0V. Furthermore, when terminal G is disconnected, the DC potential of output terminal 3 becomes 24V. That is, when a harness wire or the like is disconnected in the electrical circuit of an automobile and the power is cut off, and the sensor is not operating normally, the DC voltage at the output terminal 3 will be outside the range of 5 to 10V. This is devised so that the next-stage circuit connected to the output terminal 3 detects this, thereby preventing the abnormal sensor output from being taken in by mistake.

[Problem that the invention attempts to solve]

In this conventional circuit, if there is a voltage fluctuation in the power supply,
This affects the operation of the Hall IC. In particular, when this sensor is installed in a car, the power supply voltage of the car may increase depending on the rotational speed of the engine, exceeding the rated value of the Hall IC.
Excessive current may flow through the IC and damage the circuit.

The present invention improves this, and provides a rotation sensor with a protection circuit that has little effect even if the power supply voltage of the Hall IC changes and does not damage the Hall IC when the power supply voltage increases. With the goal.

[Means for solving problems]

The present invention consists of a Hall IC that is placed in the magnetic field generated by the magnetic poles attached to the rotating shaft and detects changes in this magnetic field as electrical signals, and three series resistors connected between the positive and negative DC power terminals. In the rotation sensor, the power supply circuit of the Hall IC is connected to both ends of the middle resistor among the three resistors of the resistance voltage divider circuit, and the power supply circuit of the Hall IC is connected in series to the power supply circuit of the Hall IC. A short-circuit current limiting resistor is connected to the rotation sensor, and this resistor is installed inside the rotation sensor.

[Effect]

If the power supply voltage changes and the voltage at the Hall IC's power input terminal becomes abnormally high, the Hall
IC power supply current increases rapidly. At this time, a large voltage drop occurs across the resistor connected to the power supply circuit, limiting the current flowing through the Hall IC power supply circuit and preventing damage to the Hall IC.

〔Example〕

An explanation will be given below based on the drawings of the embodiment.

FIG. 2 is a cutaway perspective view of essential parts of a rotation sensor according to an embodiment of the present invention. In FIG. 2, the shaft 5 of the rotation sensor 4 is connected to a rotation shaft (not shown) for detecting rotation speed. Two disc-shaped permanent magnets 6 and 7 are attached to this shaft 5. This permanent magnet 6,7
are provided with N poles and S poles alternately in their respective rotational directions, and the permanent magnets 6 and 7 are arranged so that different poles face each other. Between the permanent magnets 6 and 7, the Hall IC 1 is fixedly attached to the cylindrical body 8 of the rotation sensor 4.

The characteristic configuration of the present invention is that a substrate 10 is installed inside the cylindrical body 8 of the rotation sensor 4, and a new short-circuit current limiting resistor _R4 is provided on the substrate 10 in addition to the resistors _R2 and _R3 . The reason lies in the fact that an electric circuit as shown in Figure 3 is constructed. That is, a new short-circuit current limiting resistor _R4 is inserted in the ground wire 1a of the Hall IC 1 shown in FIG.

The part surrounded by a dashed line in FIG. 3 is an electric circuit of the rotation sensor 4, and the part surrounded by a broken line is an electric circuit on the substrate 10.

With this configuration, even if the power supply voltage fluctuates and a voltage exceeding the rated voltage is applied between the power supply circuits 1a and 1b of the Hall IC, and a large current flows through the power supply circuit, the short-circuit current limiting resistor R ₄ This limits the current and prevents damage to the Hall IC 1.

[Effect of idea]

As mentioned above, according to the present invention, the hole
By connecting a short-circuit current limiting resistor in series with the ground terminal of the IC and configuring this resistor to be built into the rotation sensor, when the operating voltage of the Hall IC increases, the short-circuit current limiting resistor The power supply current of the Hall IC is limited, which has an excellent effect of preventing electrical damage to the Hall IC.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the main parts of the electrical circuit of a conventional rotation sensor. FIG. 2 is a cutaway perspective view of essential parts of a rotation sensor according to an embodiment of the present invention. FIG. 3 is a diagram showing the main part of the electric circuit of the rotation sensor according to the embodiment of the present invention. 1...Hall IC, 2...Power input terminal, 3...
...Output terminal, 4...Rotation sensor, 5...Axis, 6,
7...Permanent magnet, 8...Cylinder, 10...Substrate,
R ₄ , R ₅ ... Short circuit current limiting resistance.

Claims (1)

[Claims for Utility Model Registration] Three Hall ICs connected between the Hall IC1, which is placed in the magnetic field generated from the magnetic poles attached to the rotating shaft and detects changes in this magnetic field as electrical signals, and the positive and negative DC power terminals. and a resistor voltage divider circuit including series resistors R ₁ , R ₂ , R ₃ , and the power supply circuit of this Hall IC is connected to both ends of the intermediate resistor among the three resistors of the resistor voltage divider circuit. A rotation sensor with a protection circuit, characterized in that a short-circuit current limiting resistor is connected in series to the power supply circuit of the Hall IC, and this resistor is installed inside the rotation sensor.