JPH1062112A - Magnetic-type sensor for angle of rotation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve measurement precision of angle of rotation by keeping good linearity between rotation angle and measurement value of magnetic flux density ion wide of angle or rotation range. SOLUTION: A sleeve 2 concentric with a rotation axis 1 is fixed to a fixing side. The rotation axis 1 goes through inside the sleeve 2 and a Hall element 3 which measures magnetic flux density is attached on the outside of the sleeve 2. Around the sleeve 2, a magnetic circuit 7 comprising a magnetic 4 and ferromagnetic material yokes 5 and 6 is formed, and the magnetic circuit is fixed to the rotation axis 1, for rotation together with the rotation axis 1 in a body. The Hall element 2 measures and outputs changes in magnetic flux density at that time. Due to the yokes, magnetic flux density in the space in the magnetic circuit does not decrease rapidly, so linearity between the angle of rotation and the magnetic flux density measured with the Hall element is kept favorably.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic rotation angle sensor using a magnetic detection element.

[0002]

2. Description of the Related Art Conventional magnetic rotation angle sensors include:
For example, there is one disclosed in JP-A-62-168004. FIG. 4 is an explanatory view of this conventional magnetic rotation angle sensor. An arm 12 extending in a radial direction is attached to the rotating shaft 11, and a magnetic detection element 13 is fixed to a tip of the arm 12. The magnetic detecting element 13 detects a magnetic flux density in a radial direction. An annular ring 14 made of a ferromagnetic material is arranged concentrically with the rotating shaft 11. The ring 14 is fixed at a predetermined position, and incorporates a wedge-shaped magnet 15. These rings 14 and magnets 15
Constitute the magnetic circuit 16.

[0003] The magnetic flux created by the magnet 15 passes through a closed loop in the ring 14, but there is some leakage of the magnetic flux from the magnetic circuit 16. The magnetic flux density leaking from the magnetic circuit 16 in the radial direction is the largest near the magnet 15, decreases as the distance from the magnet 15 decreases, and becomes almost zero at the 0 ° position opposite to the magnet 15. When the rotation shaft 11 rotates, the position of the magnetic detection element 13 changes, and the output also changes. FIG. 5 shows the relationship between the rotation angle θ ′ of the rotating shaft and the magnetic flux density B ′ detected by the magnetic detection element. The angle at which the magnetic detection element is arranged at a position opposite to the magnet is θ ′ = 0 °
And Based on this figure, the relative rotation angle θ ′ between the rotation axis and the magnetic circuit can be obtained from the magnetic flux density B ′ measured by the magnetic detection element.

[0004]

However, in such a conventional magnetic rotation angle sensor, since the magnetic flux density in the radial direction decreases sharply as it moves away from the magnet, the linearity of the measured value of the rotation angle and the magnetic flux density is reduced. However, there is a problem that the measurement accuracy of the rotation angle is reduced. Further, when used in a range where linearity is maintained, that is, in the vicinity of 0 degrees in FIG. 5, there is a problem that the sensitivity is extremely low and the rotation angle detection range is narrow. Accordingly, the present invention has been made in view of the above-described conventional problems, and provides a magnetic rotation angle sensor in which the linearity between the rotation angle and the measured value of the magnetic flux density is kept good in a wide rotation angle range and the measurement accuracy is improved. The purpose is to:

[0005]

SUMMARY OF THE INVENTION Therefore, according to the present invention, a magnetic detecting element and a magnetic circuit are arranged around a rotation axis, and the magnetic detecting element and the magnetic circuit are arranged based on a change in magnetic flux density detected by the magnetic detecting element. In a magnetic rotation angle sensor that measures a relative rotation angle in a non-contact manner, a magnetic circuit has a columnar shape and a magnetic pole in a longitudinal direction on a plane perpendicular to the rotation axis, and a middle point in the longitudinal direction is a rotation center of the rotation axis. The magnet is formed from a magnet offset from the center of rotation by a predetermined distance so as to be the shortest distance from the magnet, and a ferromagnetic yoke extending from both ends of the magnet and facing each other with the rotation axis interposed therebetween. It is assumed that it is arranged in the space surrounded by.

The magnet has a prismatic shape, and the yoke is plate-shaped and connected to each end face of the magnet, and can be extended perpendicularly to the longitudinal direction of the magnet. Further, it is preferable that the magnetic circuit is fixed to the rotating shaft and rotates integrally, and the magnetic detecting element is fixed to a fixed position in the magnetic circuit. Furthermore, a cylindrical sleeve concentric with the rotation axis is arranged in a space surrounded by the magnetic circuit, and the magnetic detection element can be fixed to the outer periphery of the sleeve.

[0007]

Since the end of the ferromagnetic yoke constituting the magnetic circuit is open, this magnetic circuit does not form a closed loop, and no magnetic flux is trapped in the yoke. The ferromagnetic yoke increases the surrounding magnetic flux density and maintains a high level of magnetic flux density in the space surrounded by the magnet and the yoke. When the magnetic circuit and the magnetic sensing element rotate relative to each other, the measured value of the magnetic flux density becomes largest when the magnetic sensing element is located closest to the end of the magnet. When the magnet and the magnetic sensing element rotate away from each other, the measured value of the magnetic flux density decreases, but the magnetic flux density decreases sharply because the distance between the ferromagnetic yoke and the magnetic sensing element decreases. Without, it gradually decreases. Further rotation further increases the distance between the yoke and the magnetic sensing element, but the magnetic flux density does not decrease extremely near the open end of the ferromagnetic yoke, so that the measurable sensitivity is obtained. Is kept.

The above magnet is formed into a prismatic shape, and a plate-like yoke is vertically extended from each end face of the magnet to assemble the magnet.
Easy to create. In addition, the magnetic circuit is fixed to the rotating shaft and rotates integrally. By fixing the magnetic detection element at a fixed position in the magnetic circuit, wiring with the magnetic detection element is simplified. Further, by fixing the magnetic detecting element to the outer periphery of a cylindrical sleeve concentric with the rotation axis, the overall configuration is simplified.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to examples. 1 and 2 show the configuration of an embodiment of the present invention. FIG. 1 is a front view, and FIG. 2 is a side view as viewed from a direction A in FIG. A cylindrical sleeve 2 having an outer diameter of 12 mm and an inner diameter of 10.4 mm is arranged concentrically with the rotating shaft 1. The sleeve 2 is made of magnetic stainless steel having high magnetic permeability, and is fixed at a fixed position on the fixed side. The rotation shaft 1 passes through the inside of the sleeve 2. A flat part is formed on a part of the outer periphery of the sleeve 2, and a Hall element 3 as a magnetic detecting element is attached thereto. Hall element 3 is Ga
It is made of an As semiconductor and generates a Hall voltage proportional to the magnetic flux density passing through the Hall element. The Hall element 3 is arranged to detect the magnetic flux density in the radial direction.

[0010] Around the sleeve 2 is provided a magnetic circuit 7 comprising a magnet 4 and yokes 5 and 6. The magnet 4 is made of high-performance samarium-cobalt having excellent temperature characteristics and a thickness of 3 mm, a width of 5 mm, and a length of 17 mm.
mm prismatic shape and has a magnetic pole in the longitudinal direction. The midpoint M in the longitudinal direction of the magnet 4 is 8.5 m from the rotation center O of the rotation shaft 1.
m, the longitudinal direction of the magnet 4 is perpendicular to the radial direction of the rotating shaft 1 in a plane perpendicular to the rotating shaft 1. Distance.

The two yokes 5 and 6 are made of magnetic stainless steel and have a thickness of 0.5 mm, a width of 5 mm, and a length of 23 mm.
, And each longitudinal end is fixed to the longitudinal end face of the magnet 4. The yokes 5 and 6
It extends in a plane perpendicular to the axis of rotation in a direction perpendicular to the longitudinal direction of the magnet. Therefore, the shortest distance between the yokes 5 and 6 and the rotation center O is 8.5 mm, which is the same as the distance between the center point M of the magnet and the rotation center O. The angle to make is about 90 degrees. The magnetic circuit 7 is fixed to the rotating shaft 1 and rotates in a plane perpendicular to the rotating shaft 1 at the same time as the rotating shaft 1 rotates.
The Hall element 3 measures and outputs the change in the magnetic flux density at this time.

FIG. 3 shows the relationship between the rotation angle θ of the rotating shaft 1 and the magnetic flux density B detected by the Hall element 3. Magnet 4
The angle at which the Hall element 3 is arranged at a position opposite to
0 °. The largest measured value of the magnetic flux density B when the magnetic circuit 7 rotates is that the Hall element 3
This is, for example, a position where the Hall element is located at a position of θ = + 135 ° in FIG. When the magnetic circuit 7 rotates in a direction in which the magnet 4 and the Hall element 3 move away from each other, the measured value of the magnetic flux density B decreases, but from θ = + 135 ° to θ = + 90 °.
Since the distance between the yoke portion 6 and the Hall element 3 becomes smaller between 0 ° and 0 °, the magnetic flux density B does not suddenly decrease but gradually decreases.

Further, the rotation is further performed, and θ = + 90 ° to θ
In the range of = 0 °, the distance between the yoke portion 6 and the Hall element 3 is increased this time, but the magnetic flux density does not extremely decrease near the open end of the yoke portion 6 and can be measured. Sensitivity is maintained. With further rotation, the direction of the electromotive force of the Hall voltage is reversed, but similar measurement values are obtained up to θ = −135 °. Therefore, the magnetic flux density B,
The relative rotation angle θ between the rotating shaft 1 and the magnetic circuit 7 is substantially linear when the range of θ is between −135 ° and + 135 °. 3, the relative rotation angle θ between the rotation axis and the magnetic circuit can be obtained from the magnetic flux density B measured by the Hall element 3.

The present embodiment is configured as described above. In a wide rotation angle range, the linearity between the rotation angle θ and the measured value of the magnetic flux density B is kept good, and high measurement accuracy of the rotation angle can be obtained. Note that, for relative rotation between the Hall element and the magnetic circuit, the magnetic circuit may be fixed and the Hall element may be rotated, thereby also enabling highly accurate measurement. However, it is preferable to fix the Hall element as in the present embodiment, since the electric wiring with the Hall element does not become complicated.

[0015]

As described above, the present invention relates to a magnetic rotation angle sensor for measuring a relative rotation angle between a magnetic detection element and a magnetic circuit from a change in magnetic flux density detected by the magnetic detection element. A magnet having a columnar shape and having a magnetic pole in the longitudinal direction in a vertical plane with respect to the rotation axis, the magnet being offset by a predetermined distance from the rotation center of the rotation axis such that the midpoint in the longitudinal direction is the shortest distance from the rotation center of the rotation axis; Formed from a ferromagnetic yoke which extends from both ends of the rotating shaft and faces each other with the rotation axis interposed therebetween, and the magnetic detecting element is arranged in a space surrounded by the magnetic circuit. The magnetic flux density does not suddenly decrease, and thus, the linearity between the rotation angle and the measured value of the magnetic flux density is kept good over a wide rotation angle range, and the measurement accuracy of the rotation angle is high. An effect that is.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of the present invention.

FIG. 2 is a side view of the embodiment.

FIG. 3 is a diagram illustrating a relationship between a rotation angle and a magnetic flux density in the example.

FIG. 4 is a diagram showing a conventional example.

FIG. 5 is a diagram showing a relationship between a rotation angle and a magnetic flux density in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotation axis 2 Sleeve 3 Hall element (magnetic detection element) 4 Magnet 5, 6 Yoke 7 Magnetic circuit O Rotation center M Middle point

Claims (5)

[Claims] 1. A magnetic detection element and a magnetic circuit are arranged around a rotation axis, and a relative rotation angle between the magnetic detection element and the magnetic circuit is measured in a non-contact manner from a change in magnetic flux density detected by the magnetic detection element. In the magnetic rotation angle sensor, the magnetic circuit has a columnar shape and has magnetic poles in a longitudinal direction on a plane perpendicular to the rotation axis, and the rotation is such that a middle point in the longitudinal direction is a shortest distance from a rotation center of the rotation axis. A space formed by a magnet offset from a center by a predetermined distance, and a ferromagnetic yoke extending from both ends of the magnet and facing each other with the rotation axis interposed therebetween, wherein the magnetic detection element is surrounded by the magnetic circuit. A magnetic rotation angle sensor, wherein the rotation angle sensor is disposed inside the magnetic rotation angle sensor. 2. The magnet according to claim 1, wherein the magnet has a prismatic shape, and the yoke is plate-shaped and connected to each end face of the magnet and extends perpendicularly to the longitudinal direction of the magnet. Magnetic rotation angle sensor. 3. The magnetic circuit according to claim 1, wherein the magnetic circuit is fixed to the rotating shaft and rotates integrally with the rotating shaft, and the magnetic detecting element is fixed at a fixed position in the magnetic circuit. Or a magnetic rotation angle sensor according to 2. 4. A method according to claim 1, wherein a cylindrical sleeve concentric with said rotating shaft is disposed in a space surrounded by said magnetic circuit, and said magnetic detecting element is fixed to an outer periphery of said sleeve. 4. The magnetic rotation angle sensor according to 1, 2, or 3. 5. The magnetic rotation angle sensor according to claim 1, wherein the magnetic detection element is installed to detect a magnetic flux density in a radial direction of the rotation shaft. .