JP2003084007A - Rotation direction detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotation direction detecting device which can reliably detect the rotation direction of a rotating object to be detected at every rotation over a comparatively wide range of rotation angle with its simple configuration. SOLUTION: A magnet 8 is attached to the rotating object 3 to rotate integrally and a magnetic detection element 2 is disposed adjacently to the rotation trajectory of the magnet 8 to detect magnetic flux of the magnetic field generated by the magnet 8. The magnet 8 has a curved band shape in accordance with the rotation trajectory of the rotating object 3 and is polarized so that its polarity is reversed at the center of a longitudinal direction. The magnet 8 also has such a shape that the magnet flux density detected by the magnetic detection element 2 continuously increases toward both sides from a butting part 8c.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to rotation direction detection for detecting rotation directions of various rotating bodies with a simple structure in which a magnet and a magnetic detection element are combined.

[0002]

BACKGROUND OF THE INVENTION Conventionally, a structure in which a magnet and a magnetic detection element such as a Hall element for converting the magnetic flux density of a magnetic field generated by the magnet into an electric signal are combined has been used in a non-contact manner such as a mechanical displacement amount or a deformation amount. It is widely used as a simple detection means capable of detecting, for example, a rotation angle detection device for a rotating body to be detected (see JP 2001-59702 A) or a position sensor for a moving body to be detected (JP 2001-74409 A). (See) is known. However, the detection means cannot detect the rotation direction of the detected rotating body.

Therefore, a magnet 1 shown in FIG. 6A can be considered as a magnet capable of detecting the rotation direction. In this figure, the magnet 1 has its magnetic poles reversed with a longitudinal reversal portion as a boundary, and one of them is magnetized so that it is an N-pole magnetic portion 1a and the other is an S-pole magnetic portion 1b. There is. The magnetic detection element 2 is arranged at a position close to and facing the rotation locus of the magnet 1, and when the magnet 1 moves in the direction of the arrow in FIG. The element 2 converts the magnetic flux density of the magnetic field generated by the magnet 1 into an electric signal, and outputs a Hall voltage as shown in FIG.

The Hall voltage of the magnetic detection element 2 becomes zero at the boundary between the magnetic portions 1a and 1b, and the polarity is rapidly inverted. In other words, the portion where the magnetic flux density in the magnet 1 changes, that is, the portion where the Hall voltage of the magnetic detection element 2 changes is only a small section A on both sides of the boundary. Therefore, the rotation direction of the detected rotating body is the same as in the section A
Therefore, it is difficult to use the configuration in which the magnet 1 and the magnetic detection element 2 are combined as a means for detecting the rotational direction of the detected rotating body. It is extremely difficult to magnetize the magnet 1 in a distribution in which the magnetic flux density changes continuously along the longitudinal direction, which cannot be put to practical use.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a rotation direction detecting device capable of surely detecting the rotation direction of a rotating body to be detected each time it rotates over a relatively wide range of rotation angles.

[0006]

In order to achieve the above object, the rotation direction detecting device of the present invention is a rotation direction detecting device for detecting the rotation direction of a rotating body to be detected which rotates around a predetermined axis. And a magnet that is fixed to the detected rotating body and rotates integrally with the detected rotating body, and a magnetic detector that is arranged in a position close to the rotation locus of the magnet and detects the magnetic flux density of the magnetic field generated by the magnet. The magnet is magnetized so as to have a reversing portion in which a magnetic pole is reversed at an intermediate portion in a circumferential direction, the magnet being a strip shape curved corresponding to a rotation locus of the detected rotating body. In addition, the magnetic flux density detected by the magnetic detection element is set to continuously increase from the reversal portion toward both ends in the circumferential direction.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a rotation direction detecting device according to a first embodiment of the present invention.
An example of the detected rotating body 3 to be detected in the rotating direction is one including a rotating shaft 4 and a rotating disk 7 that is attached to the rotating shaft 4 and integrally rotates around an axis C. There is. The rotation direction detecting device includes a magnet 8 fixed to the rotating disk 7 by an adhesive means or the like and rotating integrally with the rotating disk 7, and a rotation locus of the magnet 8 with respect to the magnet 8 in the direction of the axis C of the detected rotating body 3. And a magnetic detection element 2 attached to a frame (not shown) so as to closely face and face each other.
The magnet 8 may be attached to, for example, a plate axially attached to the rotary shaft 4 instead of the rotary disc 7. That is, the magnet 8 may be attached so as to integrally rotate around the predetermined axis C of the rotating body to be detected 3.

The magnetic detection element 2 detects the magnetic flux density of the magnetic field generated by the magnet by converting the amount of change in the magnetic field into the amount of electrical change. As the magnetic detection element 2,
For example, a Hall element that outputs a Hall voltage corresponding to the magnetic flux density of the magnetic field or an MR element whose resistance value changes according to the change of the magnetic field can be used. In this embodiment, a Hall IC in which a Hall element and an amplifier circuit are integrated
The case of using will be described. Therefore, the magnetic detection element 2 detects the magnetic flux density of the magnetic field generated by the magnet 8 and outputs the Hall voltage.

The magnet 8 is composed of first and second rectangular rod-shaped magnetic portions 8a and 8b along the direction of rotation. The both magnetic portions 8a and 8b are magnetized along the axis C direction orthogonal to the circumferential direction (longitudinal direction), and one side surface is magnetized as an S pole and the other side surface is magnetized as an N pole. There is. The magnet 8 is formed by abutting and joining a pair of the magnetic portions 8a and 8b at a butting portion 8c. Here, the polarities of the first magnetic portion 8a and the second magnetic portion 8b are set in mutually opposite directions. Therefore, the polarity is reversed in the abutting portion 8c. In FIG. 2, the magnet 8 has a strip shape (a rectangular bar shape along the rotation direction) curved in a shape along the peripheral edge portion of the rotating disk 7 in the angle range of 90 degrees, and has an intermediate protrusion in the longitudinal direction. The magnetic poles are magnetized so that the magnetic poles are inverted at the matching portion (reversing portion) 8c, and first and second magnetic portions 8a and 8b are formed on both sides with the reversing portion 8c as a boundary. In this embodiment, a case is illustrated in which the directions of the parallel magnetic lines of force generated in both the magnetic portions 8a and 8b are magnetized so as to be inverted at the central inversion portion 8c. However, the first and second
The magnetic portions 8a and 8b of the above may be magnetized to have polarities opposite to each other.
The same applies to the embodiment. Both magnetic parts 8
The magnet 8 may be formed by one magnet in which a and 8b are integrated (not joined).

The magnet 8 has a shape in which the thickness in the direction of the axis C is the smallest at the reversing portion 8c and increases continuously from the reversing portion 8c toward both ends of the magnet 8. Therefore, in this magnet 8, both magnetic parts 8a, 8
b is magnetized to a uniform density throughout, but the strength of the magnetic field generated by both ends having the largest thickness becomes the highest and the magnetic flux density becomes the highest. Is continuously low. Since the magnetism detecting element 2 is arranged on the side of the magnet 8 in the direction of the axis C, the magnetism detecting element 2 moves from the end of the second magnetic portion 8b of the magnet 8 (this point is defined as a rotation angle of 0 °) to the first magnetism. As shown in FIG. 2B, the Hall voltage output from the magnetic detection element 2 is negative over the entire range up to the end of the portion 8a (this point is the rotation angle 90 °), that is, over a wide angle range. Voltage increases from positive voltage.

In this embodiment, the magnet 8 has a shape in which the thickness in the direction of the axis C is the smallest at the reversing portion 8c and continuously increases from the reversing portion 8c toward both ends of both the magnetic portions 8a and 8b. In addition to having FIG.
As clearly shown in (b), both ends of the magnet 8 closely oppose the magnetic detecting element 2 with the smallest gap, and the magnetic detecting element 2 gradually increases with a gap from both ends toward the reversing portion 8c.
The Hall voltage output from the magnetic detection element 2 linearly increases from the negative voltage to the positive voltage at a relatively large rate of change. The magnet 8 is
The magnetism detecting element 2 is opposed to the magnetic detecting element 2 with the same gap over the entire longitudinal direction, and the thickness is the smallest at the reversing portion 8c, and continuously increases from the reversing portion 8c to both ends of both the magnetic portions 8a and 8b. The Hall voltage that linearly increases from the negative voltage to the positive voltage can be taken out from the magnetic detection element 2 only by having the shape.

As shown in FIG. 2A, the magnetic detection element 2
The Hall voltage output from is sampled in the sampling circuit 10 of the calculation unit 9 at a constant cycle by a sampling pulse. The increase / decrease detector 11 determines whether the sampling value from the sampling circuit 10 is increasing or decreasing, and outputs a rotation direction detection signal. Therefore, in the rotation direction detection device of this embodiment, the magnetic flux density is continuous and linear from one end to the other end of the strip-shaped magnet 8 even though the magnet 8 and the magnetic detection element 2 are combined in a simple configuration. Since it is possible to generate a magnetic field that changes with time, it is possible to reliably detect the rotation direction of the detected rotating body 3 each time it rotates in a range of a relatively large rotation angle corresponding to the length of the magnet 8. . here,
As shown in FIG. 6 (c), it is also possible to use only one magnet 1A, that is, not reverse the polarity. However, in this case, the maximum thickness T becomes about twice as large as that in this embodiment.
On the other hand, since the polarity of the magnet 8 of the present embodiment shown in FIG. 2A is reversed, the maximum thickness Tm of the magnet 8 becomes thin, so that the device can be made compact. In addition,
In this embodiment, since the thickness of the magnet 8 is continuously reduced from both ends toward the reversal portion 8c, the total thickness can be made smaller than that of the embodiment of FIG. 4, and the device is compact. There is an advantage that can be realized.

FIG. 3 shows a second embodiment of the present invention. This embodiment is a modification of the first embodiment, in which the magnetic detection element 2 is arranged at a position facing the magnet 8 on the outer side in the radial direction of the rotating disk 7 of the rotating body to be detected 3 and facing each other. ing.
The magnet 8 is composed of first and second rectangular rod-shaped magnetic portions 8a and 8b along the rotation direction of the rotating disk 7. The magnetic portions 8a and 8b are magnetized along the radial direction of the rotary disc 7. For example, the first magnetic portion 8a is magnetized so that the outer peripheral edge side is the S pole and the center C side is the N pole, and the second magnetic portion 8b is the outer peripheral edge side is the N pole and the center C side is the S pole. There is. The magnet 8 includes a pair of the magnetic parts 8
a and 8b are formed by butt-joining each other, and therefore, the first magnetic portion 8a and the second magnetic portion 8b have opposite polarities set in opposite directions at the middle inversion portion 8c in the longitudinal direction. Has been done. As shown in FIG. 3 (b), the magnet 8 has the smallest radial thickness in the reversing portion 8 c as the arrangement position of the magnetic detection element 2 is changed,
In addition, it has a shape that continuously increases from the reversal portion 8c toward both ends of both magnetic portions 8a and 8b. The inversion part 8c of the magnet 8 is closer to the center C side than both ends of the magnet 8, and the distance from the magnetism detecting element 2 is set to gradually increase from both ends of the magnet 8 to the inversion part 8c. Has been done. Other configurations are similar to those of the first embodiment, and the same portions or corresponding portions will be denoted by the same reference numerals and detailed description and illustration thereof will be omitted.

Therefore, as in the case of the first embodiment described above, when the magnet 8 sequentially approaches the magnetic detection element 2 from one end to the other end as the detected rotating body 3 rotates, a negative voltage is applied. Since the Hall voltage linearly increasing from 0 to positive voltage is output from the magnetic detection element 2, the same effect as described in the first embodiment can be obtained.

FIG. 4 shows a third embodiment of the present invention. This embodiment is similar to the first embodiment in that the magnetic detection element 2 is arranged at a position close to and opposed to the magnet 8 in the direction of the axis C of the rotating body 3 to be detected. A shape in which the magnet 8 has substantially the same thickness over the entire length in the longitudinal direction, and both sides are bent toward the arrangement position of the magnetic detection element 2 in the direction of the axis C with the longitudinal reversal portion 8c where the polarity is reversed as the bending point. have. That is, the first and second magnetic portions 8a and 8b forming the magnet 8 are formed.
Are formed in a rectangular rod shape along the rotation direction of the rotating disk 7, and the magnetic portions 8a and 8b are magnetized along the axis C direction. On the other hand, the magnet 8 is fixed to the rotating disc 7 with two spacer members 12 interposed therebetween.

As the magnet 8 rotates, the magnetic detection element 2
On the other hand, the gap between the magnet 8 and the magnetic detection element 2 when approaching from one end to the other end is the largest in the longitudinal reversing portion 8c where the polarity is reversed, and is continuous as going from the reversing portion 8c to both sides. Becomes smaller. The strength of the magnetic field acting on the magnetic detection element 2 from the magnet 8 is larger as the gap is smaller. Therefore, similarly to the first embodiment, the rotating body to be detected 3 is detected.
When the magnet 8 sequentially approaches the magnetic detection element 2 from its one end to the other end as the magnet rotates, the Hall voltage linearly increasing from the negative voltage to the positive voltage is applied to the magnetic detection element 2.
And the same effect as described in the first embodiment can be obtained. In addition to this, in this embodiment, since the magnet 8 can be made to have the same thickness throughout, there is an advantage that the magnet 8 can be easily molded.

FIG. 5 shows a fourth embodiment of the present invention. This embodiment is a modification of the third embodiment, in which the magnetic detection element 2 is arranged at a position facing the magnet 8 on the outer side in the radial direction of the rotating disk 7 of the detected rotating body 3 and facing each other. It is different from the third embodiment in the point. This magnetic detection element 2
The magnet 8 is similar to the third embodiment in that the thickness is substantially the same in the entire longitudinal direction with the change of the arrangement position of the magnet, but the polarity is reversed.
Is the farthest from the outer peripheral edge of the rotating disk 7, and its reversal portion 8c
To gradually approach the outer peripheral edge of the rotating disk 7 toward both end portions, and both end portions are in contact with the outer peripheral edge. Magnet 8
Is disposed at a position close to the outer peripheral edge of the rotating disk 7, and therefore, the gap between the magnet 8 and the magnetic detection element 2 when the magnetic detection element 2 approaches from the one end to the other end with rotation. Is the largest at the inversion portion 8c in the longitudinal direction in which the polarity is inverted, and continuously decreases from the inversion portion 8c to both sides.

In this embodiment, when the magnet 8 sequentially approaches the magnetic detection element 2 from one end to the other end as the detected rotating body 3 rotates, the Hall voltage output from the magnetic detection element 2 is By linearly increasing from the negative voltage to the positive voltage, the same effect as described in the first embodiment can be obtained.
In addition to this, in the fourth embodiment, since the magnet 8 can be made to have the same thickness throughout as in the third embodiment, there is an advantage that the magnet 8 can be easily molded. 8 can be directly fixed to the rotating disk 7 without using the spacer member 12 as in the third embodiment.

In the second and fourth embodiments,
The case where the magnetic detection element 2 is arranged on the outer side in the radial direction of the rotating disk 7 has been described as an example, but the same effect as described above can be obtained even if the magnetic detection element 2 is arranged on the inner side in the radial direction. . Further, the reversal portion (butting portion) 8c may be set at an intermediate portion in the longitudinal direction of the magnet 8, and may be set at a position deviated to either one end of the magnet 8, for example. Furthermore, the magnet 8 may be provided with a minute gap between the two magnetic portions 8a and 8b. Further, in the present invention, in addition to the detection of the rotation direction, the rotation angle may be detected based on the fluctuation of the Hall voltage.

[0020]

As described above, according to the rotation direction detecting device of the present invention, although it has a simple structure in which the magnet and the magnetic detecting element are combined, it corresponds to the length of the strip magnet in the rotating body to be detected. It is possible to reliably detect the rotation direction of the detected rotating body each time it rotates within a relatively wide range of rotation angle. Moreover, because the magnetism is reversed in the middle portion in the longitudinal direction,
The magnet becomes thinner.

Further, according to the invention of claim 2, the thickness of the magnet is set to a shape which continuously increases in the axial direction from the reversing portion toward both ends, whereby the thickness of the magnet is further reduced. Can be made compact. Further, according to the invention of claim 6, by setting the gap between the magnet and the magnetic detection element so as to be continuously reduced from the reversal portion toward both ends in the circumferential direction, the change of the output with respect to the rotation angle is changed. Becomes larger and the detection accuracy is further improved. Further, if the magnets formed to have the same thickness are provided so that the gap between the magnet and the magnetic detection element is continuously reduced from the reversal portion toward both ends in the circumferential direction, the magnet can be easily molded. .

[Brief description of drawings]

FIG. 1 is a perspective view of essential parts showing a rotation direction detection device according to a first embodiment of the present invention.

FIG. 2A is a schematic configuration diagram of the same embodiment, and FIG. 2B is a characteristic diagram showing a relationship between a rotation angle of a detected rotating body and an output of a magnetic detection element.

FIG. 3A is a perspective view of a main part of a rotation direction detection device according to a second embodiment, and FIG. 3B is a front view.

FIG. 4A is a perspective view of a main part of a rotation direction detecting device according to a third embodiment, and FIG. 4B is a front view.

FIG. 5A is a perspective view of an essential part showing a rotation direction detecting device according to a fourth embodiment, and FIG. 5B is a front view.

6 (a) and 6 (b) are schematic plan views of a rotation direction detection device not included in the present invention and a relationship diagram between a rotation angle and an output Hall voltage of a magnetic detection element, and FIG. 6 (c) is a side view thereof. is there.

[Explanation of symbols]

2: Magnetic detection element 3: Detected rotating body 8: Magnet 9: Calculation unit C: axis 8c: Inversion part (butt part)

Claims (6)

[Claims] 1. A rotation direction detecting device for detecting a rotation direction of a detected rotary body that rotates around a predetermined axis, wherein the rotational direction detection device is fixed to the detected rotary body and rotates integrally with the detected rotary body. A magnet and a magnetic detection element that is disposed in a position close to the rotation locus of the magnet to detect the magnetic flux density of the magnetic field generated by the magnet, and the magnet corresponds to the rotation locus of the detected rotating body. It has a curved strip shape, and is magnetized so as to have an inversion portion in which a magnetic pole is inverted at an intermediate portion in the circumferential direction, and the magnetic detection elements are respectively provided from the inversion portion toward both ends in the circumferential direction. 2. A rotation direction detecting device, characterized in that the magnetic flux density detected by is set so as to continuously increase. 2. The rotation direction detecting device according to claim 1, wherein the magnet has a shape in which the thickness in the axial direction continuously increases from the reversal portion toward the both ends. 3. The rotation direction detecting device according to claim 2, wherein the magnetic detection element is arranged at a position facing the magnet in the axial direction of the rotating body to be detected so as to face each other and face each other. 4. The rotation direction detecting device according to claim 1, wherein the magnet has a shape in which the thickness in the radial direction continuously increases from the reversal portion toward the both ends. 5. The rotation direction detection device according to claim 4, wherein the magnetic detection element is arranged at a position that is close to and opposes the magnet in the radial direction of the rotating body to be detected. 6. The magnet according to any one of claims 1 to 5, wherein a gap when the magnet approaches the magnetic detection element due to rotation is continuous from the reversal portion toward both ends in the circumferential direction. Direction detection device that is set to be smaller in size.