JP2007139644A - Magnetic rotation displacement sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic rotation displacement sensor capable of detecting the rotational displacement of a rotary shaft with high accuracy, even if eccentricity decentering and blurring occur in the rotary shaft. <P>SOLUTION: The magnetic rotation displacement sensor comprises a magnet 11, that is a ring shape around the shaft center of the rotary shaft and is arranged in a fixation side to the rotary shaft, then a half portion in a circumferential direction, and the other half are magnetized in opposed circumferential directions to each other; a yoke 12 arranged in the circumferential surface of the magnet 11; a rotor 31 that is mounted to the rotary shaft located in the ring formed by the magnet 11, while keeping a gap of the inner surface of the magnet 11; a magnetic sensor 13. The rotor 31 comprises two cores 32, 33 that respectively has semicylindrical external circumference surface along the internal circumference surface of the magnet 11 and are arranged in the rotation displacement direction via a gap. In at least one of the cores, a projection 34 is provided, and the projection 34 is made to face the rotary shaft of the other core in parallel and the vertical surface via a gap 35. The magnet sensor 13 is arranged so that the gap 35 detects the changes in the magnetic flux in the rotary shaft direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetic rotational displacement sensor that detects a rotational displacement of a rotating shaft in a non-contact manner.

FIG. 8 shows a configuration described in Patent Document 1 as a conventional example of this type of magnetic rotational displacement sensor. In this example, the magnetic rotational displacement sensor includes a magnet 11, a back yoke 12, and a magnetic sensor 13. And the rotor 14. In FIG. 8, 21 indicates a rotation axis.
The magnet 11 has a ring shape centered on the axis of the rotary shaft 21 and is arranged on the fixed side with respect to the rotary shaft 21. The circumferential half portion 11a and the other half portion 11b are radially opposite to each other. Is magnetized. The magnet 11 is a bonded magnet, for example.
The back yoke 12 made of a soft magnetic material has a ring shape concentric with the magnet 11 and is fixedly disposed in contact with the outer peripheral surface of the magnet 11.

The rotor 14 is composed of two cores 15 and 16 made of a soft magnetic material, and one core 15 has a semi-cylindrical shape, and further includes a protrusion 15 a located on the axis of the rotating shaft 21. It has become. The other core 16 has a semi-cylindrical shape, and the outer peripheral surfaces of the cores 15 and 16 are located on one cylindrical surface centering on the axis of the rotating shaft 21. The peripheral surface of the protrusion 15a constituting the inner surface of the core 15 and the plane connecting the peripheral surface and the semi-cylindrical outer peripheral surface are opposed to the inner peripheral surface and both circumferential end surfaces of the core 16 with a predetermined gap. .
The rotor 14 composed of the two cores 15 and 16 is not shown in the drawing, but is attached to a circular mounting plate attached to the end of the rotating shaft 21, and the magnet 11 has an inner ring within the ring formed by the magnet 11. It is positioned with a predetermined gap from the peripheral surface, and rotates with the rotation of the rotating shaft 21.

The magnetic sensor 13 is fixedly disposed so as to be positioned in the gap 17 along the inner peripheral surface of the core 16 between the cores 15 and 16, and detects a change in the radial magnetic flux between the cores 15 and 16. It is supposed to be. The magnetic sensor 13 is, for example, a Hall IC.
FIG. 9 shows how the magnetic flux lines (shown by dotted lines) formed by the magnet 11 change depending on the rotational displacement position of the rotor 14 in the magnetic rotational displacement sensor configured as described above. As shown in FIG. 9A, when the cores 15 and 16 of the rotor 14 are positioned so as to be evenly opposed to the one half 11a and the other half 11b of the magnet 11, the magnetic flux passes through the cores 15 and 16, respectively. The magnetic flux passing through the magnetic sensor 13 becomes zero.

On the other hand, when the cores 15 and 16 are rotationally displaced with the rotation of the rotating shaft 21, for example, the magnetic flux passes through the magnetic sensor 13 as shown in FIG. Thus, the rotational displacement (rotation angle) of the rotary shaft 21 can be detected.
JP-A-2005-17058

By the way, in the conventional magnetic rotational displacement sensor described above, as shown in FIG. 9B, the magnetic flux concentrates on the protrusion 15a located at the rotational axis of the core 15, that is, one of the rotors 14 has a structure. The core 15 has a structure in which the magnetic flux density increases as the rotational axis is reached.
Therefore, for example, when eccentricity occurs in the rotating shaft 21 due to factors such as assembly accuracy or thermal deformation of parts, or when rotational shaking occurs in the rotating shaft 21, the magnetic sensor 13 of the protrusion 15a where the magnetic flux concentrates. As a result, the magnetic flux passing through the magnetic sensor 13 fluctuates, that is, the output fluctuates and the detection accuracy is greatly impaired.

  In view of such problems, an object of the present invention is to provide a magnetic rotational displacement sensor capable of detecting rotational displacement with high accuracy without impairing detection accuracy due to eccentricity or shaking of the rotating shaft. is there.

  According to the first aspect of the present invention, the magnetic rotational displacement sensor for detecting the rotational displacement of the rotating shaft is formed in a ring shape centered on the axis of the rotating shaft and is disposed on the fixed side with respect to the rotating shaft. A magnet with one half and the other half magnetized in the radial direction opposite to each other, a ring-shaped back yoke made of a soft magnetic material fixedly arranged on the outer peripheral surface of the magnet, and a rotating shaft It consists of a rotor made of a soft magnetic material that is located in a ring formed by the magnet while keeping a gap with the inner peripheral surface of the magnet, and a magnetic sensor fixed to the fixed side, and the rotor is a half along the inner peripheral surface of the magnet. Each of the two cores has a cylindrical outer peripheral surface and is arranged with a gap in the rotational displacement direction. A protrusion is provided on at least one of the cores, and the protrusion is a rotation shaft of the other core. Parallel to the plane perpendicular to the axial direction of the It is directed, the magnetic sensor in the air gap, are assumed to be arranged to detect a change in magnetic flux in the axial direction.

In the invention of claim 2, in the invention of claim 1, the two cores are formed into a semi-cylindrical shape except for the protruding portion.
According to a third aspect of the present invention, in the second aspect of the invention, the projecting portion is provided on one of the two cores, and a pair of leg portions projecting in the axial direction from the circumferential ends of the semi-cylindrical shape of the one core. And both ends are supported by the leg portions, and the plate surface is perpendicular to the axial direction, and is formed of a semicircular arc flat plate portion that forms the gap between the axial end surface of the other core. The
According to a fourth aspect of the present invention, in the second aspect of the present invention, the projecting portion is provided on both of the two cores, and one projecting portion is a leg portion projecting on the axial end surface of the semi-cylindrical shape, The plate surface is extended from the tip of the leg portion so that the plate surface is perpendicular to the axial direction, and the other protrusion has the half surface so that the plate surface forms the gap with the plate portion. It is assumed that it protrudes from the cylindrical end portion in the axial direction.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, a plurality of magnetic sensors are provided.

  According to the present invention, the protrusion is provided on at least one of the two cores constituting the rotor so that the protrusion is parallel to the surface perpendicular to the axial direction of the rotation axis of the other core via the gap. Since the magnetic sensor is arranged in the gap, and the magnetic sensor is configured in the gap having a uniform magnetic field distribution formed by the parallel opposing surfaces, even if the rotation axis is decentered or shaken, As a result, the output does not fluctuate, so that the rotational displacement can be detected with extremely high accuracy.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an embodiment of a magnetic rotational displacement sensor according to the present invention. Parts corresponding to those in FIG. 8 are denoted by the same reference numerals, and detailed description thereof is omitted.
In this example, the magnetic rotational displacement sensor is composed of a magnet 11, a back yoke 12, a magnetic sensor 13, and a rotor 31. The magnetic rotational displacement sensor is attached to a rotating shaft (not shown) and is placed in a ring formed by the magnet 11. The rotor 31 positioned with a predetermined gap from the inner peripheral surface is composed of two cores 32 and 33.

Each of the cores 32 and 33 has a semi-cylindrical shape centered on the axis of the rotation shaft, and has a semi-cylindrical outer peripheral surface along the inner peripheral surface of the magnet 11. The core 32 is further provided with a protrusion 34 that is integrally formed. The semi-cylindrical portions of the cores 32 and 33 are arranged in the rotational displacement direction through a predetermined gap.
The projecting portions 34 provided on the core 32 are a pair of leg portions 34a projecting in the axial direction (Z direction) of the rotation shaft from both circumferential ends of the semi-cylindrical portion of the core 32, and both ends of the leg portions 34a. Are supported, and the plate surface is formed of a semicircular arc-shaped flat plate portion 34b perpendicular to the Z direction. The flat plate portion 34b is formed along the end surface of the core 33 perpendicular to the Z direction. Are opposed to each other in parallel through a predetermined gap 35.

In this example, the magnetic sensor 13 is disposed in the gap 35 so as to detect a change in magnetic flux in the Z direction in the gap 35. The magnetic sensor 13 is fixed to a fixed side (not shown) with respect to the rotating shaft, like the magnet 11 and the back yoke 12.
In the configuration as described above, the cores 32 and 33 and the back yoke 12 are each made of a soft magnetic material, and silicon steel or the like is used as the material. For example, a bonded magnet is used as the magnet 11, and a powder of samarium cobalt or ferrite is used as the permanent magnet powder mixed with the resin. The magnetic sensor 13 is, for example, a Hall IC. In FIG. 1, reference numeral 13a denotes a terminal of the magnetic sensor 13.

  According to the magnetic rotational displacement sensor shown in FIG. 1, the magnetic flux lines formed by the magnet 11 change according to the rotational displacement position of the rotor 31 as the rotor 31 rotates with the rotation of the rotation shaft. It has become a thing. At this time, the magnetic flux that flows from the core 32 to the core 33 or from the core 33 to the core 32 according to the rotational displacement position of the rotor 31 flows in this example via the gap 35 and the protrusion 34. Therefore, the rotational displacement (rotation angle) of the rotating shaft can be detected by the change in the output voltage of the magnetic sensor 13 disposed in the gap 35.

FIG. 2 shows a state where the rotor 31 is rotated, and FIG. 3 shows a relationship between the rotational displacement position of the rotor 31 and the magnetic field (detected magnetic field) generated in the gap 35. The rotational displacement position of 0 degree is a state in which the line connecting the boundary (magnetic pole boundary) between the first half 11a and the other half 11b of the magnet 11 coincides with the line connecting the circumferential centers of the cores 32 and 33. In this state, no magnetic field is generated in the gap 35.
As described above, in this example, one core 32 constituting the rotor 31 is provided with the protruding portion 34, and the protruding portion 34 is disposed on the surface perpendicular to the axial direction of the rotation axis of the other core 33 via the gap 35. The magnetic sensor 13 is arranged in the gap 35 so as to face each other in parallel, and the change in the magnetic flux in the axial direction of the rotating shaft is detected.

Therefore, for example, even if the rotation axis is decentered or shaken, the magnetic sensor 13 is located in the gap 35 that is formed by parallel opposing surfaces and forms a uniform magnetic field distribution. Can be suppressed, so that the rotational displacement of the rotating shaft can be detected with high accuracy.
FIG. 4 shows an example in which the above-described magnetic rotational displacement sensor is used to detect the engine throttle opening of an automobile. The rotary shaft 21 connected to the throttle valve has a bearing at its end. It is supported by case 23 via 22. In this example, the rotor 31 is fixed to the rotary shaft 21 by integrating cores 32 and 33 by a rotor mold 24 made of resin. The rotating shaft 21 is made of a nonmagnetic material.

A back yoke 12 having a magnet 11 on the inner periphery is attached to the case 23, and a resin connector case 25 is further attached. A terminal 13a of the magnetic sensor 13 is soldered to one end of a lead frame 26, and the magnetic sensor 13 and the lead frame 26 are insert-molded in a connector case 25 in a state of being soldered. The other end of the lead frame 26 is led out to a connector portion 25 a for external connection provided in the connector case 25.
By attaching the connector case 25 to the case 23, the magnetic sensor 13 is positioned in the gap 35 as shown in FIG. Note that a groove 24 a is formed in the rotor mold 24 to form the gap 35.

  By using the magnetic rotational displacement sensor according to the present invention for detecting the engine throttle opening, for example, the case 23 is deformed due to a temperature rise, and the axis of the rotating shaft 21 is deviated from the center of the ring formed by the magnet 11 (is eccentric. ), The throttle opening can be accurately detected. Since the magnet 11 and the magnetic sensor 13 can be arranged close to each other as shown in FIG. 4, the temperature difference between them can be reduced. For example, the magnetic sensor 13 has a temperature correction calculation function. When a Hall IC is used, the correction accuracy can be improved.

  The shape of the two cores 32 and 33 constituting the rotor 31 is not limited to the above-described example, and other shapes may be used. 5 and 6 show other shape examples. In FIG. 5, the core 32 has a semicircular flat plate portion 34c in place of the semicircular arc flat plate portion 34b, and this flat plate portion 34c and the other flat plate portion 34c. A gap 35 is formed between the core 33 and the core 33. As in FIG. 1, the flat plate portion 34c is supported by a pair of leg portions 34a. In this example, the semicircular plate portion 32a is formed on the end surface of the core 32 forming the semicylindrical portion on the projecting portion 34 forming side. Is provided and the end is covered.

FIG. 6 shows an example in which protrusions are provided on both the cores 32 and 33, and the protrusions 36 provided on the core 32 are in the axial direction (Z direction) of the semi-cylindrical part of the core 32. The leg part 36a protruded on the end surface, and the flat plate part 36b whose plate surface is perpendicular to the Z direction and extends in the center direction from the tip (upper end) of the leg part 36a.
On the other hand, the projecting portion 37 having a flat plate shape forms a semi-cylindrical portion of the core 33 in the center direction so that a gap 35 is formed between the core 33 and the flat plate portion 36 b of the core 32. The magnetic sensor 13 is positioned in a gap 35 formed between the flat plate portion 36 b of the core 32 and the protruding portion 37 of the core 33.

The configurations shown in FIGS. 5 and 6 are different from the configuration shown in FIG. 1 in that the rotating shaft does not penetrate the rotor 31 and the rotor 31 is attached to the end of the rotating shaft.
In the above-described example, the cores 32 and 33 are each formed in a semi-cylindrical shape except for the protruding portion. However, the cores 32 and 33 are not limited to the semi-cylindrical shape. You can also However, a semi-cylindrical shape is preferable in that the magnetic flux is effectively guided to the gap 35.
FIG. 7 shows an example in which two magnetic sensors 13 are arranged in the gap 35 in the configuration shown in FIG. 1. If such a configuration is adopted, the number of detected outputs can be doubled. it can.

A is a perspective view showing an example of mounting of a magnetic rotational displacement sensor according to the present invention, and B is a sectional view thereof. The perspective view which shows the state which the rotor rotated in the magnetic type rotational displacement sensor shown in FIG. The graph which shows the relationship between the rotational displacement position of the magnetic type rotational displacement sensor shown in FIG. 1, and a detection magnetic field. Sectional drawing which shows one mounting example (usage example) of the magnetic type rotational displacement sensor shown in FIG. The perspective view which shows the other Example of the magnetic type rotational displacement sensor by this invention. The perspective view which shows the other Example of the magnetic type rotational displacement sensor by this invention. The perspective view which shows the other Example of the magnetic type rotational displacement sensor by this invention. The top view which shows the conventional magnetic type rotational displacement sensor. FIG. 9 is a diagram showing how magnetic flux lines change due to rotation of the rotor in the magnetic rotational displacement sensor shown in FIG. 8.

Claims (5)

A magnetic rotational displacement sensor for detecting rotational displacement of a rotational shaft,
A magnet having a ring shape centered on the axis of the rotating shaft and disposed on a fixed side with respect to the rotating shaft, wherein one half of the circumferential direction and the other half are magnetized in the radial direction opposite to each other; ,
A ring-shaped back yoke made of a soft magnetic material fixedly disposed on the outer peripheral surface of the magnet;
A rotor made of a soft magnetic material attached to the rotating shaft and positioned in a ring formed by the magnet while keeping a gap with the inner peripheral surface of the magnet;
It consists of a magnetic sensor fixed to the fixed side,
Each of the rotors has a semi-cylindrical outer peripheral surface along the inner peripheral surface of the magnet, and includes two cores arranged with a gap in the rotational displacement direction.
A protrusion is provided on at least one of the cores, and the protrusion is parallelly opposed to a surface perpendicular to the axial direction of the rotation axis of the other core via a gap,
The magnetic rotational displacement sensor, wherein the magnetic sensor is disposed in the gap so as to detect a change in the magnetic flux in the axial direction. The magnetic rotational displacement sensor according to claim 1,
A magnetic rotational displacement sensor characterized in that the two cores are formed into a semi-cylindrical shape except for the protruding portion. The magnetic rotational displacement sensor according to claim 2,
The projecting portion is provided on one of the two cores, a pair of leg portions projecting in the axial direction from the circumferential ends of the semi-cylindrical shape of the one core, and both ends supported by the leg portions, A magnetic rotational displacement sensor comprising: a semicircular arc-shaped flat plate portion, the surface of which is perpendicular to the axial direction and forms the gap between the axial end surface of the other core. The magnetic rotational displacement sensor according to claim 2,
The protrusion is provided on both of the two cores, and one protrusion is a leg protruding on the axial end surface of the semi-cylindrical shape, and a plate surface from the tip of the leg is the axial direction. The other projecting portion is projected from the axial end of the semi-cylindrical shape so that the plate surface forms the gap with the flat plate portion. A magnetic rotational displacement sensor characterized by comprising: The magnetic rotational displacement sensor according to any one of claims 1 to 4,
A magnetic rotational displacement sensor comprising a plurality of the magnetic sensors.

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