JP2004257894A - Rotation angle detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the fluctuation of outside low frequency magnetic field from affecting the inside of a casing. <P>SOLUTION: In the recessed space A of a casing 1, a rotatable magnet 7 and yokes 8, 9 surrounding the magnet 7 are arranged. The yokes 8, 9 constitute a closed magnetic path together with the magnet 7, also a hole element 10 is held in between the yokes 8, 9. The hole element 10 detects the magnetic flux density in the magnetic path corresponding to the rotational angle of the magnet 7. The casing 1 is covered with a covering member 15 of a magnetic material. Consequently, the fluctuation of outside low frequency magnetic field is prevented from propagating into the casing 1. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation angle detection device suitable for detecting, for example, an opening degree of a throttle valve provided in an automobile engine as a rotation angle of a shaft, and in particular, detects a rotation angle of a shaft magnetically. The present invention relates to a rotation angle detecting device comprising:
[0002]
[Prior art]
Generally, a rotation angle detection device that detects a rotation angle of a shaft or the like includes a casing, a magnet rotatably provided in the casing, and a magnetic detection unit that detects rotation of the magnet as a change in a magnetic field. And is used as a throttle sensor for detecting, for example, the opening degree of a throttle valve (see, for example, Patent Document 1).
[0003]
[Patent Document 1]
JP-A-2-122205
In a conventional throttle sensor of this type, a magnet is connected to a shaft that rotates in conjunction with opening and closing operations of a throttle valve, and the magnet is rotatably accommodated in a casing made of, for example, a resin material. In the casing, a magnetism detecting means such as a Hall element for detecting the rotation of the magnet as a change in the magnetic field is provided.
[0005]
When the magnet rotates with the shaft in conjunction with the opening and closing operation of the throttle valve, a change in magnetic flux density according to the rotation angle is detected by the Hall element, and the throttle sensor detects the change corresponding to the opening of the throttle valve. The signal is output to a control unit for controlling the engine.
[0006]
In the conventional throttle sensor, the casing is covered with a nonmagnetic conductive material such as aluminum. As a result, the external electromagnetic wave is converted into an eddy current and is supplied to the ground or the like, thereby preventing the external electromagnetic wave or the like from being mixed into the output signal of the Hall element.
[0007]
[Problems to be solved by the invention]
By the way, the throttle sensor according to the related art described above is often disposed in an engine room of an automobile or the like. In this engine room, a coil of an injector or an electric motor is driven along with operation of the engine, and a low-frequency Magnetic field fluctuations tend to occur.
[0008]
On the other hand, in the conventional technology, the casing is covered with a non-magnetic conductive material, so that high-frequency electromagnetic waves can be shielded by converting them into eddy currents. Could not be prevented.
[0009]
For this reason, in the related art, low-frequency magnetic field fluctuation in the engine room may enter the casing of the throttle sensor, and the detected value of the magnetic flux density by the Hall element may fluctuate with respect to the opening of the throttle valve. There has been a problem that the detection accuracy of the throttle sensor becomes unstable and reliability is reduced.
[0010]
The present invention has been made in view of the above-described problems of the prior art, and the present invention can reliably prevent a magnetic field in a casing from being adversely affected by a low-frequency magnetic field fluctuation, and stabilize a rotation angle of a shaft or the like. It is an object of the present invention to provide a rotation angle detection device that can detect the rotation angle, improve the detection accuracy, and improve the reliability.
[0011]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a casing having a concave space surrounded by a peripheral wall, a magnet provided in the concave space of the casing, and a magnet provided in the concave space of the casing and facing the magnet. A rotating means for relatively rotating the yoke and the magnet, and a magnetic detecting means for detecting a relative rotation between the magnet and the yoke by the rotating means as a change in a magnetic field. Applied to moving angle detectors.
[0012]
The first aspect of the invention is characterized in that the casing is provided with a low-frequency magnetic shield means formed of a magnetic material so as to shield the inside of the casing from external low-frequency magnetic field fluctuations. It is in.
[0013]
With this configuration, the low-frequency magnetic shield means made of a magnetic material prevents the external low-frequency magnetic field fluctuation from propagating in the casing, and the magnetic field formed in the casing by the magnet is reduced by the external magnetic field. It can be prevented from being adversely affected. For this reason, the magnetic field in the casing formed by a magnet or the like can be maintained in a stable state with respect to the fluctuation of the external magnetic field. be able to.
[0014]
According to the second aspect of the present invention, the low-frequency magnetic shield means is constituted by a cover member that covers the entire casing.
[0015]
As a result, since the cover member made of a magnetic material forms a magnetic path covering the casing, most of the magnetic flux passing through the outside of the casing uses the cover member itself as a magnetic flux passage and almost enters the inside of the casing. Flows without. As a result, external low-frequency magnetic field fluctuation can be prevented from affecting the inside of the casing, and a magnetic field formed between the magnet and the yoke can be prevented from being affected by external magnetic field fluctuation. .
[0016]
According to the third aspect of the present invention, the low-frequency magnetic shield means includes a magnetic lid for closing the concave space of the casing, and a magnetic ring provided on the peripheral wall surrounding the concave space of the casing.
[0017]
As a result, a magnetic path covering the concave space is formed by the magnetic lid and the magnetic ring. Therefore, most of the magnetic flux passing outside the casing passes through the inside of the magnetic lid and the magnetic ring. As a result, it is possible to prevent the magnetic field formed between the magnet and the yoke in the concave space from being affected by external magnetic field fluctuation.
[0018]
Further, the output of the detection signal can be adjusted while the magnetic ring is attached to the peripheral wall of the casing. For this reason, the adjustment of the detection signal and the like can be performed at the same time as the assembly of the components, so that it is possible to achieve both the improvement of the disturbance magnetic field resistance and the improvement of the productivity.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS.
[0020]
Here, FIGS. 1 to 4 show a first embodiment. In this embodiment, a throttle sensor for detecting the opening of a throttle valve will be described as an example of a rotation angle detection device.
[0021]
Reference numeral 1 denotes a casing of the throttle sensor. The casing 1 has a peripheral wall 1A formed of a resin material or the like in a substantially cylindrical shape, a bottom 1B serving as a bottom surface of the peripheral wall 1A, and an inner side of the peripheral wall 1A. A yoke holding portion 1C which projects from the bottom portion 1B and holds yokes 8 and 9 to be described later, and a tube extending from the outer edge of the bottom portion 1B in a direction opposite to the peripheral wall portion 1A (downward). It is roughly constituted by a hem-shaped tubular portion 1D and a bearing holding portion 1E projecting downward from the center of the bottom portion 1B and holding a bearing 5 described later. A concave space A for accommodating a magnet 7, yokes 8, 9 and the like to be described later is recessed inside the peripheral wall portion 1A, and a spring chamber for accommodating a return spring 13 to be described inside the hem tube portion 1D. B is formed.
[0022]
A connector 2 projecting in the radial direction is integrally provided on the rear side of the peripheral wall portion 1A, and a plurality of pin terminals 2A (only one is shown) extending toward the concave space A are provided inside the connector 2. ) Is provided. Further, mounting flanges 3 projecting in the radial direction are provided on both the left and right sides of the peripheral wall portion 1A.
[0023]
Reference numeral 4 denotes a rotating shaft serving as rotating means rotatably provided in the casing 1. The rotating shaft 4 is mounted in a bearing holding portion 1E using a bearing 5, and penetrates the bottom portion 1B. I have. The base end of the rotating shaft 4 projects into the spring chamber B, and a lever 12 described later is attached thereto. The distal end of the rotating shaft 4 projects toward the concave space A, and has a substantially disk shape. The rotating plate 6 is formed integrally.
[0024]
Reference numeral 7 denotes a magnet positioned in the concave space A and fixed on the rotating plate 6. The magnet 7 has a rectangular shape or an oval shape, and has magnetic poles (N pole, N pole, at both ends orthogonal to the axis of the rotating shaft 4). S pole).
[0025]
Reference numerals 8 and 9 denote yokes each having a substantially circular arc-shaped cross section made of a magnetic material. The yokes 8 and 9 are disposed in the concave space A of the casing 1 and face the magnet 7 with a gap therebetween in a radial direction. The pole pieces 8A, 9A extend in the circumferential direction with a predetermined length, and the overhang portions 8B, 9B extend from the pole pieces 8A, 9A to positions covering the upper side of the magnet 7. . The overhang portions 8B and 9B overlap in a state where they are separated from each other in the upward and downward directions, and sandwich a Hall element 10 described later therebetween.
[0026]
As shown in FIG. 4, when the magnet 7 rotates, the facing areas of the magnetic pole piece portions 8A and 9A of the yokes 8 and 9 change according to the rotation angle θ. Further, the magnet 7 forms a closed magnetic path extending from the N pole to the S pole via the yoke 8, a Hall element 10 described later, and the yoke 9.
[0027]
Reference numeral 10 denotes a Hall element as a magnetic detection means for detecting a magnetic flux density in a closed magnetic circuit including the yokes 8, 9 and the like. The Hall element 10 is provided in a concave space A of the casing 1 as shown in FIG. Is mounted on the substrate 11. Then, the Hall element 10 detects a magnetic flux density in the closed magnetic circuit that changes according to the opposing area of the magnet 7 and the yokes 8 and 9, and transmits the detection signal through a pin terminal 2 </ b> A to an external engine control control unit ( (Not shown).
[0028]
Reference numeral 12 denotes a lever integrally fixed to the lower end side of the rotating shaft 4. The lever 12 has a central portion caulked and fixed to the rotating shaft 4 and extends radially outward, and has a distal end provided with a throttle. It is engaged with a lever (not shown) on the valve side. The lever 12 is provided with a return spring 13 disposed in the spring chamber B. The lever 12 rotates the rotating shaft 4 in accordance with the opening and closing operation of the throttle valve, and is constantly urged toward the initial position (the position S in FIG. 4) by the return spring 13. .
[0029]
A cover 14 covers the peripheral wall portion 1A of the casing 1. The cover 14 has a substantially plate shape and closes the concave space A of the casing 1 as shown in FIG. On the other hand, the inside of the concave space A is protected.
[0030]
Reference numeral 15 denotes a cover member as low-frequency magnetic shielding means for shielding the inside of the casing 1 against external low-frequency magnetic field fluctuation. The cover member 15 includes a top plate 15A that covers the lid 14 and a top plate 15A. The casing 1 (concave space A) is constituted by a side wall portion 15B extending from the outer peripheral edge of the side wall portion 15A toward the spring chamber B and mounting portions 15C provided on both left and right sides of the side wall portion 15B to cover the mounting flange 3. Is covered.
[0031]
The cover member 15 is formed using a magnetic material such as a cold-rolled steel plate (SPCC), for example, and has a substantially box shape with an open bottom surface. The cover member 15 is attached to the casing 1 while covering the lid 14 and the peripheral wall portion 1A of the casing 1. When the mounting flange 3 of the casing 1 is fixed to the throttle body using bolts, for example, The mounting portion 15C is fastened and fixed together.
[0032]
Then, when a change in the low-frequency magnetic field occurs outside the casing 1, the cover member 15 guides the magnetic flux due to the fluctuating magnetic field into the inside of the cover member 15 and bypasses and passes the casing 1. Thus, the cover member 15 prevents an external magnetic field change from propagating into the casing 1.
[0033]
The throttle sensor according to the present embodiment has the above-described configuration, and its operation will be described next.
[0034]
First, when the throttle valve is opened and closed, the magnet 7 rotates together with the rotating shaft 4 in conjunction with the opening and closing operation. For example, when the magnet 7 rotates counterclockwise by the rotation angle θ shown in FIG. 4, the facing areas of the magnet 7 and the yokes 8 and 9 increase, and accordingly, the yoke 8 , 9 etc., the magnetic flux density in the closed magnetic path increases. Therefore, each Hall element 10 detects the magnetic flux density in each closed magnetic path, and outputs a detection signal corresponding to the difference to the control unit or the like as the opening degree of the throttle valve (the rotation angle of the rotation shaft 4).
[0035]
However, in the present embodiment, the entire casing 1 is covered with the cover member 15 made of a magnetic material. Thus, even when the low-frequency magnetic field fluctuates outside the casing 1, the magnetic flux due to the fluctuating magnetic field can be guided to the inside of the cover member 15 to bypass the casing 1. As a result, for example, when the cover member 15 is not provided, the detection signal from the Hall element 10 fluctuates by about 80 mV due to external magnetic field fluctuation, whereas when the cover member 15 is provided as in the present embodiment, , The fluctuation width of the detection signal can be attenuated to about 15 mV.
[0036]
Accordingly, the propagation of the fluctuating magnetic field into the casing 1 (concave space A) can be reliably prevented by the cover member 15, and the magnetic flux density in the closed magnetic path formed by the magnet 7 and the like is stabilized with respect to the fluctuation of the external magnetic field. Can be kept in a state. Therefore, according to the present embodiment, it is possible to reliably prevent the magnetic field in the casing 1 from being adversely affected by external magnetic noise and the like, to detect the opening of the throttle valve with high accuracy, and to greatly improve the reliability. Can be improved.
[0037]
In addition, since the cover member 15 for shielding from low-frequency magnetic field fluctuations is provided separately from the yokes 8 and 9 constituting the closed magnetic circuit, the yokes 8 and 9 are expensive and have a low coercive force. While a magnetic permeability material is used, an inexpensive cold-rolled steel plate (SPCC) or the like can be used for the cover member 15. For this reason, even if the cover member 15 is provided as the low-frequency magnetic shield means, the increase in the manufacturing cost can be extremely reduced.
[0038]
Furthermore, since the cover member 15 is formed using a magnetic material such as a cold-rolled steel plate (SPCC), the cover member 15 has conductivity. For this reason, external radio interference can also be shielded using the cover member 15.
[0039]
Further, since the cover member 15 has a box shape and covers the entire casing 1, the entire closed magnetic path including the magnet 7 and the yokes 8 and 9 can be arranged inside the cover member 15. For this reason, the disturbance magnetic field not only in the radial direction of the rotating shaft 4 but also in the axial direction can be guided into the cover member 15, and it is possible to reliably prevent these disturbance magnetic fields from entering the concave space A of the casing 1. Can be.
[0040]
Next, FIGS. 5 and 6 show a second embodiment according to the present invention. The feature of this embodiment is that a low-frequency magnetic shield means is provided by a magnetic lid for closing a concave space of a casing, and a casing of a casing. And a magnetic ring provided on the peripheral wall surrounding the concave space. Note that, in the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.
[0041]
Reference numeral 21 denotes a magnetic lid that constitutes a low-frequency magnetic shielding means together with a magnetic ring 22 described later. The magnetic lid 21 is formed in a plate shape using a magnetic material such as a cold-rolled steel plate (SPCC). . The magnetic lid 21 is provided so as to cover the opening end side of the peripheral wall 1A of the casing 1 in substantially the same manner as the lid 14 according to the first embodiment, and closes the concave space A of the casing 1. ing. Thus, the magnetic lid 21 covers the outer side (upper side) of the magnet 7 in the axial direction with the overhang portions 8B and 9B of the yokes 8 and 9 interposed therebetween.
[0042]
Reference numeral 22 denotes a magnetic ring provided on the inner side (inner wall surface) of the peripheral wall portion 1A surrounding the concave space A of the casing 1. The magnetic ring 22 is made of, for example, a cold rolled steel plate (SPCC) or the like, like the magnetic lid 21. It is formed in a substantially ring shape (annular or C-shaped without a break) using a magnetic material, and extends from the bottom surface portion 1B of the casing 1 toward the magnetic lid 21. The magnetic ring 22 covers the magnet 7 radially outside with the pole pieces 8A and 9A of the yokes 8 and 9 interposed therebetween.
[0043]
Thus, in the present embodiment configured as described above, substantially the same operation and effect as those in the first embodiment can be obtained. In particular, in the present embodiment, the low-frequency magnetic shield means is replaced with the magnetic cover 21. And the magnetic ring 22 are divided into two parts, so that the output of the detection signal is adjusted in a state where the magnet 7, the yokes 8, 9 and the Hall element 10 are attached to the casing 1 to which the magnetic ring 22 is attached. It can be performed.
[0044]
Here, as in the first embodiment, when all parts are assembled to the casing 1 and a low-frequency magnetic shield means such as a cover member is attached after performing detection signal adjustment, the cover member is provided. Since magnetic interference between the internal magnetic circuit and the cover member occurs, the magnetic interference causes a change in the characteristics of the detection signal, and it is necessary to readjust the detection signal characteristics. On the other hand, in the present embodiment, since the output characteristics of the detection signal can be adjusted with the magnetic ring 22 attached, there is no change in the magnetic characteristics, and there is no need to readjust the detection signal. As a result, disturbance magnetic field resistance can be improved without impairing productivity.
[0045]
Next, FIG. 7 shows a third embodiment according to the present invention. The feature of this embodiment is that the low-frequency magnetic shield means is constituted by a magnetic lid and a magnetic ring, and the magnetic ring is combined with the casing. That it is integrated and fixed. Note that, in the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.
[0046]
Numeral 31 denotes a magnetic lid which constitutes a low-frequency magnetic shielding means together with a magnetic ring 32 described later. The magnetic lid 31 is formed in a plate shape using a magnetic material such as a cold-rolled steel plate (SPCC). The first peripheral wall 1A is provided so as to cover the opening end side. The magnetic lid 31 covers the outside of the magnet 7 in the axial direction with the overhang portions 8B and 9B of the yokes 8 and 9 interposed therebetween.
[0047]
Reference numeral 32 denotes a magnetic ring provided on the peripheral wall portion 1A of the casing 1. The magnetic ring 32 is formed in a ring shape using a magnetic material such as a cold-rolled steel plate (SPCC), like the magnetic lid 31, The magnetic pole pieces 8A and 9A of the yokes 8 and 9 sandwich the magnet 7 radially outward with the pole pieces 8A and 9A interposed therebetween. The magnetic ring 32 is provided with, for example, a fixing hole 32A for positioning. When the resin of the casing 1 is filled into the fixing holes 32A when the casing 1 is molded with the resin, the magnetic ring 32 is integrally fixed to the casing 1.
[0048]
Thus, in the present embodiment configured as described above, substantially the same operation and effect as those of the first embodiment can be obtained. However, in the present embodiment, in particular, the magnetic ring 32 is combined with the casing 1 by the resin. Since it is configured to be molded and integrally formed, the step of assembling the magnetic ring 32 can be omitted, and the number of parts can be reduced and the assembling step can be simplified.
[0049]
In each of the above embodiments, the fitting direction (the lever 12 side) with the counterpart member such as the throttle lever cannot be covered with the cover member 15 or the like because the rotating shaft 4 is taken out or fitted. However, since there is usually a lever 12 for fitting with the counterpart member in this portion, by forming the lever 12 with a magnetic material, a magnetic material covering the outer periphery is also arranged on the fitting surface with the counterpart member. Can be achieved, and the disturbance magnetic field resistance can be further improved.
[0050]
Further, in each of the above embodiments, the case where the opening degree of the throttle valve is detected by the rotation angle detection device has been described as an example. However, the present invention is not limited to this, and the rotation angle of the movable portion is determined by the shaft or the like. The present invention can be applied to the case where the detection is performed via the accelerator pedal. For example, the present invention may be applied to an accelerator sensor or the like which detects an operation amount of an accelerator pedal of an automobile or the like as a rotation angle.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a throttle sensor according to a first embodiment.
FIG. 2 is a longitudinal sectional view showing the throttle sensor in FIG. 1 in a state where a cover member is disassembled.
FIG. 3 is a plan view showing the throttle sensor in FIG. 1 in a state where a cover member is disassembled.
FIG. 4 is a schematic configuration diagram showing an arrangement relationship among a magnet, a yoke, and a Hall element in FIG. 1;
FIG. 5 is a longitudinal sectional view showing a throttle sensor according to a second embodiment.
FIG. 6 is a plan view showing a throttle sensor in FIG. 5;
FIG. 7 is a longitudinal sectional view showing a throttle sensor according to a third embodiment.
[Explanation of symbols]
1 casing 1A peripheral wall (peripheral wall)
4 Rotating shaft (rotating means)
7 Magnet 8, 9 Yoke 10 Hall element (magnetic detection means)
15 Cover members 21, 31 Magnetic lids 22, 32 Magnetic ring A Concave space

Claims (3)

A casing having a concave space surrounded by a peripheral wall, a magnet provided in the concave space of the casing, a yoke provided in the concave space of the casing and arranged to face the magnet; In a rotation angle detection device including a rotation unit that relatively rotates a magnet and a magnetic detection unit that detects a relative rotation between the magnet and the yoke by the rotation unit as a change in a magnetic field,
A rotation angle detecting device, wherein the casing is provided with a low frequency magnetic shield means formed of a magnetic material to shield the inside of the casing from external low frequency magnetic field fluctuation. The rotation angle detection device according to claim 1, wherein the low-frequency magnetic shield means is configured by a cover member that covers the entire casing. 2. The circuit according to claim 1, wherein the low-frequency magnetic shield means includes a magnetic lid closing the concave space of the casing, and a magnetic ring provided on the peripheral wall surrounding the concave space of the casing. 3. Motion angle detector.

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