JP2007292502A - Rotation angle detecting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotation angle detecting apparatus with reduced influence of external noise. <P>SOLUTION: The rotation angle detecting apparatus comprises a tubular magnetic circuit 6 which comprises a first yoke section 22, a second yoke section 23 which are made of a magnetic material and a pair of permanent magnets 20, 21 which are provided facing each other with their magnetic poles aligned in the same direction and allows magnetic fluxes to flow through its internal space in the same direction, a noncontact sensor 30 placed within the internal space, and a shielding member 31 which is provided on the magnetic circuit 6 and prevents electromagnetic noise from intruding from the outside into the inside of the magnetic circuit 6. The noncontact sensor 30 detects the rotation angle of a rotating body by detecting a change in the direction of the magnetic fluxes with the rotation of the magnetic circuit 6 mounted to the rotating body. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rotation angle detection apparatus including a non-contact sensor that detects a rotation angle of a rotating body by detecting a change in the direction of magnetic flux.

  Conventionally, as a rotation angle detection device for detecting the rotation angle of a throttle valve, a permanent magnet fixed to a rotating body, a first yoke having an end face fixed to the S pole side of the permanent magnet, and N of the permanent magnet A second yoke having an end face fixed to the pole side and a tip portion facing the tip portion of the first yoke; the tip portion of the first yoke; and the tip portion of the second yoke; A non-contact sensor that is disposed in a gap formed between and fixed to a non-rotating body, and the non-contact sensor detects a change in the direction of magnetic flux generated in the permanent magnet in the gap. Thus, a rotation angle detection device for detecting the rotation angle of the rotating body is known.

JP 2005-233768 A

  However, in the above rotation angle detection device, since the non-contact sensor is only partially surrounded by the first yoke and the second yoke, the electromagnetic wave propagating through the space adversely affects the magnetic flux in the gap. There are problems such as the output signal from the non-contact sensor becoming unstable.

  An object of the present invention is to solve the above-described problems, and an object of the present invention is to obtain a rotation angle detection device that can reduce the influence of external noise.

  A rotation angle detecting device according to the present invention is composed of a yoke made of a magnetic material and a pair of permanent magnets arranged opposite to each other and having magnetic poles aligned in the same direction, and a magnetic flux flows in the same direction in the internal space. A magnetic circuit having a shape; a non-contact sensor disposed in the internal space; and a shield member provided in the magnetic circuit for preventing noise from entering the internal space of the magnetic circuit from the outside. The sensor detects the rotation angle of the rotating body by detecting a change in the direction of the magnetic flux accompanying the rotation of the magnetic circuit attached to the rotating body.

  According to the rotation angle detection device of the present invention, there are effects such as the influence of noise from the outside being reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding members and parts will be described with the same reference numerals.

Embodiment 1 FIG.
1 is a front view of an intake control device 1 for an engine (hereinafter referred to as an intake control device) in which the rotation angle detection device of Embodiment 1 is incorporated, and FIG. 2 is a front sectional view of FIG.
In this intake control device 1, a spur gear 11 is fixed to the shaft of a drive motor 12 driven by a direct current. The spur gear 11 is meshed with a reduction gear 10 made of resin. The reduction gear 10 has a fan-shaped shape and is meshed with a resin-made throttle gear 9. A cup-shaped bottomed member 13 made of a nonmagnetic material is embedded in the throttle gear 9.
Inside the bottomed member 13, a substantially cylindrical magnetic circuit 6 and a shield member 31 covering the outer peripheral wall surface of the magnetic circuit 6 are provided.
The magnetic circuit 6, the shield member 31, and the bottomed member 13 are integrated with the throttle gear 9 by insert molding. The bottomed member 13 is fixed to the end of the shaft 4 that is a rotating body. The shaft 4 is rotatably supported via a first bearing 14a and a second bearing 14b with respect to the body 2 in which an intake passage is formed. A throttle valve 3 is fixed to the shaft 4. The throttle valve 3 is always urged in the direction to close the intake passage by the elastic force of the spring 5 transmitted through the throttle gear 9.

  A cover 7 covering the spur gear 11, the reduction gear 10 and the throttle gear 9 is provided on one side of the body 2. A non-contact sensor 30 that constitutes a rotation angle detection device together with the magnetic circuit 6 is integrated with the cover 7 by insert molding.

As shown in FIG. 3, the magnetic circuit 6 includes a pair of first and second yoke portions 22 and 23 made of a magnetic material and facing each other. For example, both end surfaces of the first yoke portion 22 have N poles. The second yoke portion 23 is composed of a first permanent magnet 20 and a second permanent magnet 21 arranged so that both end surface sides thereof become S poles.
The first yoke portion 22 and the second yoke portion 23 have the same semicircular shape. Moreover, the 1st permanent magnet 20 and the 2nd permanent magnet 21 are also the same shape.
The shield member 31 is made of a magnetic conductive material such as carbon steel, and prevents electromagnetic waves from entering the internal space of the magnetic circuit 6 from the outside.
At the end of the shield member 31 on the bottomed member 13 side, caulking portions 31a bent toward the first yoke portion 22 and the second yoke portion 23 are formed at equal intervals in the circumferential direction.
The shield member 31 and the magnetic circuit 6 are integrated by bending and caulking the caulking portion 31a of the shield member 31 toward the first yoke portion 22 and the second yoke portion 23. This is integrated with the bottomed member 13 by being inserted into the bottomed member 13 and insert-molded.

The non-contact sensor 30 is provided on the axis of the shaft 4 and on the center line of the internal space of the magnetic circuit 6. The entire non-contact sensor 30 is surrounded by a shield member 31.
The non-contact sensor 30 includes a magnetic detection unit that includes a magnetoresistive element that detects the rotation angle of the shaft 4 by detecting the direction of magnetic flux from the first permanent magnet 20 and the second permanent magnet 21, Output calculation unit for calculating the output signal from the magnetic detection unit.

  In the intake control device having the above-described configuration, when the driver depresses the accelerator pedal, an accelerator opening signal from an accelerator opening sensor (not shown) is input to an engine control device (hereinafter referred to as ECU). In the ECU, the drive motor 12 is energized so that the throttle valve 3 has a predetermined opening, and the shaft of the drive motor 12 rotates. And the spur gear 11, the reduction gear 10, and the throttle gear 9 rotate with the shaft. As a result, the shaft 4 integrated with the throttle gear 9 rotates by a predetermined rotation angle, and the throttle valve 3 is held at the predetermined rotation angle in the intake passage formed in the body 2.

  On the other hand, in the non-contact sensor 30 of the magnetic flux direction detection type, the magnetic detection unit detects the direction of the magnetic lines of force from the first permanent magnet 20 and the second permanent magnet 21 that rotate together with the shaft 4. The output signal from the magnetism detection unit is processed by the output calculation unit and then sent to the ECU as an opening signal of the throttle valve 3. Based on the opening signal, the ECU determines how much fuel is injected into the cylinder.

In the rotation angle detection device of the intake control device 1 configured as described above, the magnetic flux generated from the first permanent magnet 20 is in the direction of the arrow A in FIG. 3, that is, the N pole of the first permanent magnet 20, the first yoke. It flows along the magnetic path formed by the S pole of the portion 22, the internal space, the non-contact sensor 30, the second yoke portion 23, and the first permanent magnet 20.
Further, the magnetic flux generated from the second permanent magnet 21 is in the direction of arrow B in FIG. 3, that is, the N pole of the second permanent magnet 21, the first yoke portion 22, the internal space, the non-contact sensor 30, It flows along the magnetic path formed by the S poles of the two yoke portions 23 and the second permanent magnet 21.

Thus, in the internal space of the magnetic circuit 30, the magnetic lines of force generated by the first permanent magnet 20 and the second permanent magnet 21 flow in parallel with each other, and the non-contact sensor 30 has these parallel magnetic lines of force. Has passed.
The rotation range of the magnetic lines of force ranges from 0 ° when the throttle valve 3 is fully closed to 90 ° when it is fully open. In this range, the non-contact sensor 30 responds to linearity with respect to the rotation angle of the throttle valve 3. To do.

As described above, according to the rotation angle detection device according to this embodiment, the outer periphery of the magnetic circuit 6 is covered with the shield member 31 made of a magnetic conductive material, so that the permeability is permanent like air. It is possible to prevent electromagnetic wave noise from entering the internal space of the magnetic circuit 6 through the magnets 20 and 21, prevent malfunction of the non-contact sensor 30, and stabilize the output signal.
In addition, since the entire non-contact sensor 30 is surrounded by the shield member 31, electromagnetic wave noise is further prevented from entering the internal space of the magnetic circuit 6, and the output signal can be further stabilized.

The shield member 31 may be made of a nonmagnetic conductive material such as aluminum.
In this case, although the shield member 31 cannot prevent an external magnetic field from entering the internal space of the magnetic circuit 30, it acts as a magnetic air gap, and the first yoke portion 22, the second yoke Leakage of the magnetic field from the permanent magnets 20 and 21 flowing along the portion 23 to the outside can be reduced.
Therefore, by appropriately increasing the thickness of the shield member 31, magnetic leakage from the magnetic circuit 6 to the bottomed member 13 can be reduced, and there is no need to dare to configure the bottomed member 13 with an expensive nonmagnetic material. There is an effect that it is possible to use low carbon steel and the like that are inexpensive and have good workability.

Further, the shield member 31 and the magnetic circuit 6 are integrated by using the caulking portion 31a of the shield member 31. The shield member 31 and the magnetic circuit 6 are integrated into the bottomed member 13, positioned in the mold, and insert-molded. Thus, it is integrated with the bottomed member 13.
Therefore, the shield member 31 and the magnetic circuit 6 together with the bottomed member 13 are simply formed integrally with a resin material, and the throttle gear 9 is also formed at the same time.

Embodiment 2. FIG.
FIG. 5 is a plan view showing the magnetic circuit 6A in which the outer peripheral wall surface is covered with the shield member 31 in the rotation angle detection device according to the second embodiment.
In this embodiment, the permanent magnets 20A and 21A have a trapezoidal shape in which the cross section when the magnetic circuit 6A is cut along the circumferential direction is shorter in the radial direction than in the outer side.
Further, the respective end surfaces of the first yoke portion 22A and the second yoke portion 23A are inclined so as to come into contact with both end surfaces of the permanent magnets 20A and 21A.
Other configurations are the same as those in the first embodiment.

In this embodiment, when the permanent magnets 20A and 21A having the same volume are used in order to ensure the magnetic force characteristics equivalent to those of the permanent magnets 20 and 21 of the first embodiment, the inner diameter side of the permanent magnets 20A and 21A is The dimensions are short compared to the outer diameter side.
Therefore, the passage through which the magnetic field noise enters the internal space of the magnetic circuit 6A through the permanent magnets 20A and 21A whose permeability is close to air is narrowed, and the magnetic field noise can be further prevented from entering the magnetic circuit 6A.
Further, in this case, the permanent magnets 20A and 21A are prevented from moving toward the inner diameter side during the insert molding by the inclined end surfaces of the first yoke portion 22A and the second yoke portion 23A. Misalignment of the magnets 20A and 21A is prevented.
Other effects are the same as those of the first embodiment.

Embodiment 3 FIG.
FIG. 6 is a cross-sectional view of a main part of the rotation angle detection device according to the third embodiment.
In this embodiment, the shield member 31A is arranged on the inner diameter side of the magnetic circuit 6B. The shield member 31A made of a nonmagnetic conductive material is integrally formed with the first yoke part 22 and the second yoke part 23 by caulking the caulking parts 31Aa formed at both ends in the circumferential direction. It has become.
The caulking portion 31Aa on the shaft 4 side is caulked after passing through a plurality of holes 40a formed in the throttle lever 40, and the magnetic circuit 6B integrated with the shield member 31A is integrated with the throttle lever 40. It has become.
The throttle lever 40 is made of metal, and a fan-shaped throttle gear 50 is formed at the end.
Although this shield member 31A is made of a nonmagnetic conductive material and shields the electric field, the magnetic field passes through it, so that the flow of magnetic lines of force in the internal space of the magnetic circuit 6B generated by the permanent magnets 20 and 21 is The shield member 31A is not obstructed.
Other configurations are the same as those in the first embodiment.

  In this embodiment, as in the first and second embodiments, the insert molding step of integrating the shield member 31 and the magnetic circuits 6 and 6A together with the resin together with the bottomed member 13 becomes unnecessary.

Of course, the rotation angle detection device according to the present invention can also be applied to devices for detecting the rotation angles of various rotating bodies other than the engine intake control device for detecting the opening of the throttle valve. .
Further, the magnetic circuit may be composed of a yoke having a pair of notch portions formed to face each other and a permanent magnet fitted into the notch portion.
Moreover, about the shield member 31, you may cover only the whole surface of permanent magnet 20A, 21A whose magnetic permeability is close to air, without covering the perimeter of the surrounding wall surface of the magnetic circuits 6, 6A, 6B.

1 is a front view of an intake control device for an engine in which a rotation angle detection device according to Embodiment 1 of the present invention is incorporated. FIG. 2 is a front sectional view of FIG. 1. FIG. 3 is a plan view of the magnetic circuit shown in FIG. 2 whose periphery is covered with a shield member. FIG. 3 is an enlarged view of a main part of FIG. 2. It is a top view of the magnetic circuit with which the circumference | surroundings were covered with the shielding member in the rotation angle detection apparatus of Embodiment 2 of this invention. It is principal part sectional drawing of the rotation angle detection apparatus of Embodiment 3 of this invention.

Explanation of symbols

  2 body, 3 throttle valve, 4 shaft, 6, 6A, 6B magnetic circuit, 13 bottomed member, 20, 20A first permanent magnet, 21, 21A second permanent magnet, 22, 22A first yoke portion, 23, 23A Second yoke portion, 30 Non-contact sensor, 31, 31A Shield member, 31a, 31Aa Caulking portion, 40 Throttle lever, 40a hole.

Claims (6)

A cylindrical magnetic circuit composed of a yoke made of a magnetic material and a pair of permanent magnets arranged opposite to each other and having magnetic poles aligned in the same direction, and the magnetic flux flows in the same direction in the internal space;
A non-contact sensor disposed in the internal space;
A shield member that is provided in the magnetic circuit and prevents noise from entering the internal space of the magnetic circuit from the outside;
The non-contact sensor detects a rotation angle of the rotating body by detecting a change in the direction of the magnetic flux with the rotation of the magnetic circuit attached to the rotating body.   The rotation angle detection device according to claim 1, wherein the shield member covering the inner peripheral surface of the magnetic circuit is made of a nonmagnetic conductive material.   The rotation angle detection device according to claim 1, wherein the entire non-contact sensor is surrounded by the shield member.   The said shield member is integrated with the said magnetic circuit by crimping an edge part via the lever integral with the said rotary body, The any one of Claims 1-3 characterized by the above-mentioned. Rotation angle detector.   The rotation angle detection device according to any one of claims 1 to 4, wherein the shield member covers at least the permanent magnet.   6. The permanent magnet according to claim 1, wherein a cross-sectional shape of the permanent magnet when the magnetic circuit is cut along a circumferential direction is a trapezoidal shape whose inner side in the radial direction is shorter than the outer side. The rotation angle detection device described in 1.

Images