JP2015034780A - Revolution speed sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resolution speed sensor capable of detection even for a thin object to be detected such as a blade.SOLUTION: A revolution speed detector detects the passage of a blade 3 in a compressor impeller by using a revolution speed sensor. The revolution speed sensor, comprising a coil 2 for generating a magnetic field by electricity conduction and a core 4 for discharging the magnetic field generated by the coil 2 into a space α which the blade 3 passes through, detects the passage of the blade 3 without touching it. Specifically, the revolution speed sensor supplies a high frequency current to the coil 2, causing an eddy current to be generated in the blade 3 passing though a measurement space, and detects the passage of the blade 3 without touching it on the basis of a change of inductance in the coil 2. The core 4 shows a ring shape (e.g., a shape of the letter U), with one end 4a and the other end 4b separated. Since the eddy current is generated in the blade 3 between the one end 4a and the other end 4b which are disposed apart from each other, an influence range of the magnetic field can be expanded, making it possible to detect a thin object to be detected such as the blade 3.

Description

  The present invention relates to a rotation speed sensor that generates an eddy current in a rotation detection object (detection target) and detects the rotation detection object in a non-contact manner based on a change in inductance of a coil used for excitation, and particularly has a thickness such as a blade (fin). The present invention relates to a technique suitable for use in detecting the passage of a thin detection target.

[Conventional technology]
As a known technique of the rotational speed sensor, a technique disclosed in JP-A-8-240406 is known. The detection target of this rotational speed sensor is a conductive “rotating shaft”. A rod-shaped core arranged in a direction perpendicular to the rotating shaft and an exciting coil wound around the core are arranged. It has.
Then, a high frequency current is supplied to the coil to generate an eddy current in the “rotating shaft”, and a “distance” between the rotational speed sensor and the rotating shaft is detected based on a change in the inductance of the coil.

[Problem 1]
The rotational speed sensor in the prior art generates a magnetic field from the end surface of the rod-shaped core toward the measurement space (the space where the rotation axis to be detected exists). Therefore, as described above, it is suitable for detecting the “distance”.
However, when the detection target is “blade (thin detection target)”, the range of influence of the magnetic field emitted from the end of the core to the measurement space is narrow in the conventional rotational speed sensor. It is difficult to detect.

[Problem 2]
In some cases, the rotational speed sensor is used by being embedded in a conductive base material. In that case, in order not to be affected by the base material, it is necessary to provide an annular magnetic body between the rotation speed sensor and the conductive base material, which increases the cost.

Japanese Patent Laid-Open No. 08-240406

  The present invention has been made in view of the above problems, and an object thereof is to provide a rotation speed sensor that can detect even a thin detection target such as a blade.

The rotational speed sensor of the present invention uses a ring-shaped core that is partially separated, generates a magnetic field in a space between one end and the other end, and detects a rotation detection object in the generation space of the magnetic field.
Thereby, since the influence range of the magnetic field in measurement space can be expanded, even if it is a thin detection target like a blade | wing, it can detect.

Further, since a magnetic field is generated between one end and the other end of the core, the sensor output is hardly affected by the base material even when the rotational speed sensor is embedded in a conductive base material.
As a result, there is no need to “provide an annular magnetic body between the rotational speed sensor and the conductive base material”, and the cost does not increase.

(Example 1) which is a schematic block diagram of a rotation speed sensor. (A) It is explanatory drawing of the moment when a blade | wing exists in the generation space of a magnetic field, (b) It is explanatory drawing of the moment when a blade | wing does not exist in the generation space of a magnetic field (Example 1). (A) Waveform diagram of detection output, (b) Waveform diagram of arithmetic circuit output (Example 1). (Example 2) which is a schematic block diagram of a rotation speed sensor.

  [Description of Embodiments] [Mode for carrying out the invention] will be described below with reference to the drawings.

  The examples are specific examples (application examples) to which the invention is applied, and it goes without saying that the present invention is not limited to the examples.

[Example 1]
Embodiment 1 will be described with reference to FIGS.
In the first embodiment, the “rotational speed sensor” of the present invention is applied to a “rotational speed detector” in a “turbocharger”.

The turbocharger is a well-known supercharger that pressurizes intake air sucked into the engine by the energy of exhaust gas discharged from the engine.
A turbine impeller that is rotationally driven by exhaust gas discharged from the engine;
A spiral-shaped turbine housing that houses this turbine impeller;
A compressor impeller that is driven by the rotational force of the turbine impeller to pressurize the intake air;
A spiral-shaped compressor housing 1 that houses the compressor impeller,
A shaft that transmits the rotation of the turbine impeller to the compressor impeller,
・ A center housing that supports this shaft for high-speed rotation,
Is provided.

The rotation speed detection device is configured using a rotation speed sensor.
The rotational speed sensor includes a coil 2 that generates a magnetic field when energized, and a core 4 that releases the magnetic field generated by the coil 2 to a measurement space (specifically, a space through which the blades 3 of an aluminum compressor impeller pass). 1, and detects the passage of blades 3 (conductive rotation detection object) rotating in the measurement space in a non-contact manner. As shown in FIG. 1, an aluminum compressor housing 1 (conductive substrate) It is attached in a state embedded in an example).

This rotational speed sensor supplies a high frequency current to the coil 2, generates an eddy current in the blade 3 passing through the measurement space, and detects the passage of the blade 3 in a non-contact manner based on a change in the inductance of the coil 2. And
An oscillation circuit 5 for supplying a high frequency current to the coil 2;
A resistor 6 for detecting a change in inductance of the coil 2;
It is configured using.

The rotation speed detector is
An envelope detector circuit 7 that outputs voltage fluctuations in the resistor 6 as an envelope;
An arithmetic circuit 8 that counts the number of fluctuations of the envelope obtained by the envelope detection circuit 7 and generates one pulse output every time the count reaches a predetermined number;
It is configured with.

As shown in FIG. 1, the core 4 of the rotational speed sensor has an annular shape in which one end 4 a and the other end 4 b are separated from each other, and the one end 4 a and the other end 4 b are spaced apart in the rotation direction of the blade 3. Specifically, the core 4 of the first embodiment has a U shape as shown in FIG.
The core 4 is made of a ferromagnetic material such as amorphous, ferrite, or soft iron, and is disposed so as to penetrate the inside of the coil 2 wound in an annular shape. When a high frequency current is supplied to the coil 2, one end 4a A magnetic field is generated in the space between the other end 4b (symbol α).

The magnetic field generation space α is the above-described measurement space (the space through which the blades 3 pass), and the rotation speed sensor detects the passage of the blades 3 in a non-contact manner in the measurement space (the magnetic field generation space α).
Specifically, as shown in FIGS. 2 (a) and 2 (b), whether or not the coil 2 exists in the magnetic field generation space α between the one end 4a and the other end 4b of the core 4 depends on whether or not the blade 3 is present. Inductance changes.

Therefore, in the state where the compressor impeller rotates, the output waveform (voltage waveform) of the envelope detection circuit 7 every time the blade 3 passes through the magnetic field generation space α as shown by the solid line A in FIG. Increases or decreases. Then, as indicated by a solid line B in FIG. 3B, every time the count number of the output waveform reaches a predetermined number, the arithmetic circuit 8 generates one pulse output.
The output of the rotation speed detection device (that is, the output of the arithmetic circuit 8) is given to an ECU (not shown) which is not shown. Engine control is performed based on the generation state (the number of rotations of the compressor).

  In addition, the code | symbol 9 in FIG. 1 is resin which molds the coil 2 and the core 4. FIG. In addition, reference numeral 10 in FIG. 1 is a resin case that covers the sensor portion including the coil 2, the core 4, and the resin 9.

(Effect 1 of Example 1)
As described above, the rotational speed sensor according to the first embodiment uses a U-shaped core 4 (a core 4 having an annular shape with a part apart), and generates a magnetic field in a space between one end 4a and the other end 4b. The passing state of the blade 3 is detected in the magnetic field generation space α.
That is, a configuration is adopted in which an eddy current is generated in the blade 3 between the “one end 4a and the other end 4b of the core 4” spaced apart in the rotation direction of the blade 3. Thus, since the range of influence of the magnetic field can be expanded as compared with the prior art, the passage of the blade 3 can be detected even with a thin detection target such as the blade 3.

(Effect 2 of Example 1)
In the rotational speed sensor of the first embodiment, the blade 3 passes between the one end 4a and the other end 4b of the U-shaped core 4, and the blade 3 exists between the one end 4a and the other end 4b. , The state that does not exist is switched. For this reason, the fluctuation of the magnetic field is increased, and the change of the inductance of the coil 2 is increased. As a result, the voltage fluctuation of the resistor 6 becomes large, and the sensitivity of the rotational speed sensor can be increased. That is, the detection accuracy of the blade 3 by the rotation speed sensor can be increased.

(Effect 3 of Example 1)
The rotational speed sensor of the first embodiment is embedded in the conductive compressor housing 1, but generates a magnetic field between the one end 4a and the other end 4b of the U-shaped core 4, so that the sensor output is Insensitive to the compressor housing 1 made of aluminum. For this reason, there is no “necessary to provide an annular magnetic body between the rotational speed sensor and the compressor housing 1”, and the cost can be reduced.

(Effect 4 of Example 1)
The rotation speed sensor of Example 1 provided the core 4 in a U shape. Thereby, the corner | angular part in the core 4 is lose | eliminated and the loss of the magnetic field in the core 4 (loss of generated magnetic flux) can be reduced. As a result, the amount of magnetic field generated in the measurement space (magnetic field generation space α) can be increased, and the sensitivity of the rotational speed sensor can be increased.

[Example 2]
Embodiment 2 will be described with reference to FIG. In addition, in this Example 2, the same code | symbol as the said Example 1 shows the same function thing.
In the said Example 1, the example which provides the core 4 in a U-shape was shown.
On the other hand, in the second embodiment, the core 4 is provided in a U shape.
The shape of the core 4 is not limited to a U-shape or a U-shape, and may be provided in another shape such as a C-shape (a shape exhibiting an annular shape in which a part is separated).

  In the above embodiment, the sensor surface of the rotation speed sensor (the end surface that generates the magnetic field) is provided on a flat surface. However, a curved surface or a gentle surface is formed according to the locus of the rotation end of the rotation detection object (blade 3 in the above embodiment). It may be provided in a V shape.

  In the above-described embodiment, an example in which the passage of the blade 3 of the compressor impeller is detected has been described. However, the passage of the “radial convex portion” provided on the rotation shaft may be detected by the rotation speed sensor. (For example, it may be used for a rotation angle sensor of an engine or the like), and may be provided so as to detect passage of teeth (tooth) in a gear (for example, it may be used for a rotation speed sensor of a gear).

2 Coil 3 Blade (Rotation detection object)
4 core 4a one end 4b other end α magnetic field generation space

Claims (3)

A coil (2) that generates a magnetic field by energization and a core (4) that releases the magnetic field generated by the coil (2) to the measurement space, and the rotation detection object (3) that rotates in the measurement space is contactless. In the rotation speed sensor detected by
The rotation speed sensor supplies a high frequency current to the coil (2) to generate an eddy current in the rotation detection object (3) in the measurement space, and the rotation based on a change in inductance of the coil (2). Detected object (3) is detected without contact,
The core (4) has an annular shape in which one end (4a) and the other end (4b) are separated, such as a C shape, a U shape, and a U shape, and a space between the one end (4a) and the other end (4b). A rotation speed sensor that generates a magnetic field at (α) and detects the rotation detection object (3) in a generation space (α) of the magnetic field. The rotational speed sensor according to claim 1,
The rotation sensor (3), wherein the rotation detection object (3) is a blade (3) passing through the measurement space. The rotational speed sensor according to claim 2,
The rotation speed sensor according to claim 1, wherein the blade (3) is a blade (3) of a compressor impeller in a turbocharger.

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