JPH09269333A - Rotational speed sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotational speed sensor which can be used even under a bad environment. SOLUTION: A cylindrical sensor head part 11 is installed so as to protrude from the bottom face of a case 10 in which a circuit part is housed, and a coil which is driven at a high frequency is housed inside the sensor head part 11. A through hole 31b is formed in a hub 31 into and through which an axle 30 is inserted and passed. The sensor head part 11 is inserted into the through hole 31b, and the case 10 is fixed to the outer circumferential face of the hub 31. A ring-shaped rotor 33 is arranged and installed at the axle 30, and the tip part of the sensor head part 11 which is faced with the inside of the hub 31 is faced with the rotor 33. In this manner, only the sensor head part 11 is arranged under a bad environment such as a high-temperature environment, and the case 10 in which the circuit part is housed is arranged at the outside of the hub 31 whose environment is good. As a result, it is possible to prevent a change in the characteristic of the circuit part, and a rotational speed can be detected with good accuracy even under a bad environment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation speed sensor for detecting the speed of a rotating body such as a wheel of a bicycle or an automobile.

[0002]

2. Description of the Related Art FIG. 5 shows an example of a conventional rotation speed sensor, which is made of an annular metal and has an outer peripheral surface in which concave and convex portions 40a are arranged at substantially equal intervals and which are attached to a rotary shaft (not shown) of a rotating body. The permanent magnet 41 is arranged close to the rotor 40, and the pair of Hall elements 42, 42 detect changes in the magnetic flux due to the rotor 40 rotating integrally with the rotating shaft.
It is possible to detect a rotational speed of 0, that is, the rotational speed of the wheels.

[0003]

However, in the above-mentioned conventional example, the circuit portion 43 such as an amplifier for amplifying the output signals of the hall elements 42, 42 and the hall elements 42, 42 are integrated by IC integration or the like. When the rotation speed sensor is used in a bad environment such as a high temperature, the circuit portion 43 is also put in the same bad environment, so that the characteristics are not stable and, for example, the detection accuracy of the rotation speed is deteriorated. was there.

The present invention is intended to solve the above problems, and an object of the present invention is to provide a rotation speed sensor that can be used even in a bad environment.

[0005]

In order to achieve the above object, the invention of claim 1 is a circuit having a sensor unit for detecting a change in a magnetic field due to rotation of a rotating body and a circuit for driving at least the sensor unit. Section, a case in which this circuit section is installed, and a sensor head section projecting from the case and accommodating a sensor unit inside, and a sensor supporting the rotation shaft of the rotating body from the outside to the inside of the sensor. The case is attached to the outer peripheral surface of the support body by penetrating only the head part, and the sensor head part is placed inside the support body which is in a bad environment such as high temperature due to frictional heat between the support body and the rotating shaft. It is possible to provide a rotation speed sensor that can be sufficiently used even in a bad environment, in which only a single unit is arranged and other circuits and the like are not placed in such a bad environment.

According to a second aspect of the present invention, in the first aspect of the present invention, the sensor unit is formed by winding a coil around an iron core formed in a substantially rod shape. It is possible to form the elongated shape and arrange it in a narrow place. The invention of claim 3 is the invention of claim 2
In the invention, the sensor unit is configured to oscillate the coil at a high frequency to generate a high frequency magnetic field and to detect a change in the oscillating state of the coil due to an eddy current loss in the object due to the high frequency magnetic field. Since it can be arranged close to the detection body, that is, the rotating body, high-sensitivity detection is possible.

According to a fourth aspect of the invention, in the invention of the second or third aspect, the sensor unit has a coil bobbin in which an iron core is housed inside and a coil is wound around an outer periphery, and the sensor unit is extended from one end of the coil bobbin. And a holding portion for holding the terminal of the coil, the terminal of the coil is reinforced by the holding portion, and the sensor unit can be assembled to the sensor head portion reliably and easily.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
This will be described in detail with reference to FIG. A substantially cylindrical sensor head portion 11 having a closed tip projects from the bottom surface of the box-shaped synthetic resin case 10, and mounting screws are attached to both side surfaces of the case 10 adjacent to the bottom surface. A mounting portion 12 having an insertion hole 12a for inserting (not shown) is provided. Further, the sensor head portion 11 is the case 1
The bottom end side of 0 communicates with the inside of the case 10, and the sensor unit 1 is inserted into the sensor head 11 from the case 10.

The sensor unit 1 has a coil bobbin 2 made of synthetic resin and formed in a substantially cylindrical shape having an outer collar 2a at the tip.
A rod-shaped iron core 3 housed inside the coil bobbin 2 with its tip exposed to the outside, a coil 4 wound around the outer periphery of the coil bobbin 2, and integrally extended from the rear end of the coil bobbin 2. , A cylindrical holding portion 6 made of synthetic resin for holding a pair of pin-shaped terminals 5 connected to both ends of the coil 4.
And That is, by providing the holding portion 6, the sensor unit 1 is mounted on the sensor head portion 11 of the case 10.
The workability when inserting the sensor unit 1 into the inside can be improved, and the strength of the sensor unit 1 can be increased. The iron core 3 exposed from the tip of the coil bobbin 2 contacts the bottom surface of the inner wall of the sensor head portion 11, and the unevenness of the rotor 33 described later can be detected through the bottom portion of the sensor head portion 11.

Further, the holding portion 6 is formed with a rectangular hole 6a having a rectangular cross section which is open at the bottom surface, and a jig is inserted into the rectangular hole 6a to stably rotate the coil bobbin 2. Thus, the work of winding the coil around the outer peripheral portion of the coil bobbin 2 and winding the coil 4 can be easily performed. The coil 4 is wound with several tens to several hundreds of turns. For example, the coil 4 has a diameter of φ4.0 mm and a length of 5.0 mm, and is capable of high frequency oscillation.

Further, the end portions of the pair of terminals 5 and 5 project from the rear end of the holding portion 6 and are connected to a circuit board 13 made of a ceramic printed board by an appropriate method such as soldering. On this circuit board 13, a circuit unit 14 such as a high frequency power source for generating a high frequency magnetic field by flowing a high frequency current through the terminals 5 and 5 and a detection circuit for detecting a current flowing through the coil 4 is mounted. It should be noted that by simply changing the lengths of these terminals 5 and 5, it is possible to easily deal with the size change of the sensor head portion 11 depending on the usage situation.

On the other hand, in the case 10, the circuit portion 14 is provided.
A support base 16 for holding a pair of signal lines 15 for outputting the detection signal obtained in 1 above is provided upright from the bottom surface. A pair of holding grooves 17 are formed in the support base 16, and the signal lines 15 are fitted and held in the holding grooves 17. A strip-shaped conductor piece 18 is attached to the tip of the signal line 15, and the tip of the conductor piece 18 is connected to the wiring pattern of the circuit board 13. The pair of signal lines 15 are integrally led out to the outside of the case 10 as a harness cable 19, and the connector portion 20 from which the signal line 15 protrudes is provided with a notch portion 21 formed on the side surface of the case 10, a support 16 and the case. The groove 22 is formed between the inner wall 10 and the inner wall 10 and is fixed to the case 10. The circuit board 13 is housed in the case 10, and the vacant space is filled with a heat insulating material (potting material) such as silicone rubber.
The rotation speed sensor is completed by closing the opening of the case 10.

Next, an arrangement state when the present embodiment is actually used will be described with reference to FIG. The rotation speed sensor A of the present embodiment is attached to the outer peripheral surface of a hub 31, which is a support through which the axle 30 of a wheel is inserted. That is, the sensor head portion 11 is inserted into the through hole 31b formed in the body portion 31a of the hub 31, the tip portion of the sensor head portion is exposed to the inside of the hub 31, and the mounting portion 12 of the case 10 is inserted.
It is fixed by a mounting screw (not shown) inserted through the insertion hole 12a provided in the. However, in some cases, the mounting screws may be fixed by adhesion without using them, and may be selected according to the usage conditions.

A large number of rolling elements 32 are arranged in two rows along the circumferential direction between the inner peripheral surface of the hub 31 and the outer peripheral surface of the axle 30 to form a so-called hub bearing. here,
An annular rotor 3 is provided at a position between rows of rolling elements 32 of the axle 30.
3 is fixed along the circumferential direction of the axle 30, and the hub 3
The sensor head portion 11 exposed to the inside from the first through hole 31b
And the rotor 33 face each other.

The rotor 33 includes a main body 33a formed of a metal material in an annular shape, and a large number of rectangular holes 3 formed by press working at substantially equal intervals along the circumferential direction of the main body 33a.
3b. That is, the rotor 33 has the rectangular hole 3
3b and the main body 33a are formed with a large number of irregularities corresponding to the thickness of the main body 33a at substantially equal intervals along the circumferential direction. Here, in the present embodiment, since the rod-shaped iron core 3 is housed inside the coil bobbin 2, it is possible to detect irregularities having a small pitch according to the diameter of the iron core 3. Note that the shape and material of the rotor 33 are not limited to those of the present embodiment, and for example, unevenness may be formed by embedding synthetic resin in the circumferential direction of a band-shaped metal member, which will be described later. In addition, any structure may be used as long as the eddy current is generated by the high frequency magnetic field from the sensor head portion 11 and the distance between the tip end portion of the sensor head portion 11 changes as the axle 30 rotates.

As described above, the sensor unit 1 having the coil 4 is housed in the sensor head portion 11 projecting from the case 10 in which the circuit portion 14 is accommodated, and the through hole 31b provided in the hub 31 is provided. Since the sensor head portion 11 is inserted in and the case 10 is fixed to the outer peripheral surface of the hub 31, a high temperature environment is created due to frictional heat generated as the wheels rotate between the axle 30, the rolling elements 32, and the hub 31. Hub 31
Only the sensor head portion 11 is arranged inside the, and the circuit portion 14 in the case 10 can be arranged outside the hub 31 which is in better condition than under such a bad environment, and the characteristic change in the circuit portion 14 is prevented. It is possible to detect the rotation speed with high accuracy in a bad environment. The heat insulating material filled in the case 10 suppresses the influence of heat on the circuit unit 14.

By the way, the rotation speed sensor A of the present embodiment
Then, a high frequency magnetic field is generated by forming a resonance circuit with the coil 4 of the sensor unit 1 and causing high frequency oscillation,
Further, by accommodating the iron core 3 in the sensor unit 1, the inductance and the Q value of the coil 4 are improved. Then, the magnetic flux of the high frequency magnetic field generated from the coil 4 is transmitted to the axle 30.
Although an eddy current is generated in the metal portion of the rotor 33 that rotates integrally with the axle shaft 30 through the rotor 33 fixed to, the eddy current does not naturally occur in the rectangular hole 33b portion of the rotor 33. On the other hand, the high-frequency magnetic field changes due to the influence of the eddy current generated in the rotor 33, and the impedance of the coil 4 changes accordingly. Therefore, by detecting the change in the impedance of the coil 4, it is possible to extract a signal corresponding to the unevenness arranged at substantially equal intervals in the circumferential direction of the rotor 33, and from this signal, the rotor 33 and, by extension, the wheel that is the rotating body. The rotation speed of can be detected.

Here, in addition to the method using the eddy current effect as in the present embodiment, the circuit method for detecting the rotational speed of the rotor 33 uses a method using a hall element as described in the conventional example, Alternatively, a magnetic field rotor 3 such as a permanent magnet
There is a method of extracting the change caused by the rotation of 3 as the induced voltage of the coil. In the former method, since the detection sensitivity of the rotation speed is affected by the distance between the pair of Hall elements, it is difficult to downsize the sensor unit when configured, and
There is a drawback that iron powder or the like generated by the rotation of the wheels adheres to the Hall element and causes a decrease in sensitivity. Further, in the latter method, the magnitude of the induced voltage generated in the coil depends on the rotor 3
3 has a drawback that the sensitivity at a low speed is remarkably lowered because it depends on the rotation speed, and the size of the coil must be increased to increase the detection sensitivity. However, there is a drawback in that the distance between the rolling elements 32 must be increased in order to arrange the coil.

For example, the diameter of the coil that is generally used at present is about 10 mm, and the number of teeth (number of irregularities) of a detectable rotor is 48 and the diameter of the rotor is φ6.
Since the minimum size is about 0 mm, it is difficult to incorporate it into a normal general hub bearing, and conversely it is necessary to design a bearing of a size that matches the size of the coil. It leads to cost increase. Further, in the conventional example shown in FIG. 5, the IC in which the Hall elements 42, 42 are integrated has an element pitch of 2.5 mm and a chip size of about 4 mm (both are typical values), and further, a capacitor and a surge absorber are absorbed. Since it is necessary to mount an external component such as an element, the diameter of the sensor portion is about φ9 mm, which is the smallest, and it is also difficult to incorporate the sensor into a normal general hub bearing.

However, in the present embodiment, since the unevenness of the metal rotor 33 and its position (distance from the coil 4 to the rotor 33) are detected based on the impedance change of the coil 4 due to the change of the eddy current, The independent coil 4 can be used for both the generation of the high-frequency magnetic field and the detection of the unevenness of the rotor 33 by the eddy current, and the detection sensitivity does not depend on the distance between the Hall elements as in the conventional example. The coil 4 for the vehicle can be downsized. Further, in the present embodiment, the detection output according to the rotation speed of the rotor 33 is obtained based on the change in the oscillation amplitude due to the change in the impedance of the coil 4, so a comparison is made when the induced voltage of the coil is used as the detection output. Even if the coil 4 is downsized, the influence on the detection output is small, and since the coil 4 can be downsized, the pitch of the irregularities of the rotor 33 can be reduced to about 2 mm. Even when the free space is small and the installation location is restricted as described above, the detection can be performed with sufficient accuracy.

[0021]

According to the invention of claim 1, a sensor unit for detecting a change in a magnetic field due to rotation of a rotating body, a circuit section having at least a circuit for driving the sensor unit, and a case in which the circuit section is installed. And a sensor head portion projecting from the case and storing the sensor unit inside,
Since only the sensor head portion is penetrated from the outside to the inside of the support that supports the rotating shaft of the rotating body, and the case is attached to the outer peripheral surface of the supporting body, frictional heat between the supporting body and the rotating shaft causes a high temperature. Provided is a rotational speed sensor that can be used even in a bad environment because only the sensor head is placed inside the support that is in a bad environment, and other circuit parts are not placed in such a bad environment. The effect is that you can do it.

According to the invention of claim 2, since the sensor unit is formed by winding a coil around an iron core formed in a substantially rod shape, the sensor unit and the sensor head portion are formed in an elongated shape so as to be installed in a narrow space. The effect is that they can also be placed. According to the invention of claim 3, the sensor unit oscillates the coil at a high frequency to generate a high-frequency magnetic field and detects a change in the oscillating state of the coil due to an eddy current loss in the object due to the high-frequency magnetic field. The object to be detected, that is, the rotating body, can be arranged close to the object, and there is an effect that highly sensitive detection can be performed.

According to a fourth aspect of the present invention, the sensor unit includes a coil bobbin in which an iron core is housed inside and a coil is wound around the outer circumference, and a holding portion extending from one end of the coil bobbin to hold a terminal of the coil. Since the holding section reinforces the coil terminal, the assembly of the sensor unit to the sensor head section can be reliably and easily performed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a usage state of an embodiment of the present invention.

FIG. 2 is an exploded perspective view of the same.

FIG. 3 is a side sectional view of the same.

FIG. 4 is a perspective view of the sensor unit of the above.

FIG. 5 is a schematic configuration diagram showing a conventional example.

[Explanation of symbols]

 A rotation speed sensor 10 case 11 sensor head part 30 axle 31 hub 31b through hole 33 rotor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naohiro Taniguchi 1048, Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Works Co., Ltd. (72) Noriaki Kaji, 1048, Kadoma, Kadoma, Osaka Prefecture (72) Inventor Masami Hori 1048, Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Works Co., Ltd.

Claims (4)

[Claims] 1. A sensor unit for detecting a change in a magnetic field due to rotation of a rotating body, a circuit section having at least a circuit for driving the sensor unit, a case in which the circuit section is mounted, and a case protruding from the case. A sensor head part in which a sensor unit is housed, and a case is attached to the outer peripheral surface of the support body by penetrating only the sensor head part from the outside into the inside of the support body that supports the rotating shaft of the rotating body. A rotation speed sensor characterized by. 2. The rotation speed sensor according to claim 1, wherein the sensor unit is formed by winding a coil around an iron core formed in a substantially rod shape. 3. The sensor unit is configured to oscillate the coil at a high frequency to generate a high frequency magnetic field and to detect a change in the oscillating state of the coil due to an eddy current loss in the object due to the high frequency magnetic field. The rotation speed sensor described in 2. 4. The sensor unit comprises a coil bobbin in which an iron core is housed inside and a coil is wound around the outer circumference, and a holding portion extending from one end of the coil bobbin and holding a terminal of the coil. The rotation speed sensor according to claim 2 or 3, characterized in that: