JP4704018B2 - Torque sensor - Google Patents

Description

  The present invention relates to a non-contact type torque sensor that detects torque from torsion of a rotating shaft.

As a torque sensor provided in a steering system of a vehicle, a strain gauge type torque sensor is generally used. In the this strain gauge type torque sensor, the torque sensor and wiring are rotated together with the steering shaft, must wound wire extending from the torque sensor to a steering shaft, is a problem that the wiring tends to tangle Conceivable.

  As a countermeasure, a non-contact type torque sensor as shown in FIG. 6 is disclosed (Patent Document 1). This is because a pair of magnetic rings 2a and 2b whose relative rotational positions change in accordance with torsion of the shaft 1, a means constituting the magnetic circuit unit 3 together with the pair of magnetic rings 2a and 2b, It comprises means 4 (magnetic sensor) for detecting the magnetic flux density, and means for changing the magnetic field of the magnetic circuit section 3 as the relative rotational position of the pair of magnetic rings 2a, 2b changes.

  As means for constituting the magnetic circuit section 3, L-shaped magnets 5a and 5b are provided which are fixed to the end faces 3a and 3b of the pair of magnetic rings 2a and 2b so as to face each other in the axial direction. As means for changing the magnetic field of the magnetic circuit section 3, the concave and convex portions 7a, 6a, 7b, 6b are formed on the rings 2a, 2b on the end faces 8a, 8b facing each other of the pair of magnetic rings 2a, 2b, respectively. They are alternately formed at equal intervals in the circumferential direction.

  In this torque sensor, when the rotating shaft 1 is twisted, relative rotation occurs between the pair of magnetic rings 2a and 2b, so that the magnetic force increases with changes in the facing area between the convex portions 6a and 6b. The magnetic field of the circuit unit 3 changes. This change is detected by the magnetic sensor 4 (Hall element) from the magnetic flux density between the magnetic poles 9a and 9b facing each other of the L-shaped magnets 5a and 5b, and the torsion torque applied to the shaft 1 is obtained.

When the shaft 1 rotates, the pair of magnetic rings 2a and 2b rotate accordingly. However, the magnetic circuit unit 3 and the magnetic sensor 4 can be fixed at a fixed position, and the wiring of the magnetic sensor 4 is connected to the shaft. There is no entanglement by rotation.
JP2002-310819

  However, in such a non-contact type torque sensor, when the shaft 1 rotates, the unevenness of the end faces 8a and 8b facing each other of the pair of magnetic rings 2a and 2b with respect to the magnetic path cross section of the magnetic circuit 10 is increased. Since the portions 7a, 6a, 7b, and 6b face intermittently, the magnetic flux density of the magnetic circuit portion 3 changes periodically even though the twist angle (torsion torque) of the shaft 1 is constant. For this reason, the problem that it is easy to generate | occur | produce an error in the detection of the torsion torque added to the shaft 1 can be considered.

  For this reason, the present applicant has proposed that an annular magnetic circuit portion centered on a shaft is provided together with a pair of magnetic rings (see Japanese Patent Application No. 2004-230792, Japanese Patent Application No. 2004-233227). The annular magnetic circuit section includes a pair of ring-shaped yokes facing the outer periphery of a pair of magnetic rings, and a magnetic sensor is interposed between the end faces of the ring-shaped yokes facing each other. According to this, since the magnetic flux density generated in the entire circumference between the opposing end faces of the pair of magnetic rings is detected, it is possible to prevent the magnetic flux density of the magnetic circuit portion from periodically changing as the shaft rotates. I will be able to do it.

  In a pair of magnetic rings, due to the uneven portions on the end surfaces facing each other, there is a possibility that the leakage magnetic flux from these surfaces may be shaded in the circumferential direction of the ring. Even in the above-mentioned prior application examples, when this leakage magnetic flux affects the magnetic sensor, the detection of the magnetic sensor periodically changes due to the density of the leakage magnetic flux passing near the magnetic sensor as the shaft rotates. . In other words, the magnetic flux density generated around the entire circumference of the pair of magnetic rings is detected by the annular magnetic circuit section, and the magnetic flux density of the magnetic circuit section can be prevented from periodically changing as the shaft rotates. An error may occur in the detection of the torsional torque applied to the shaft due to the density of the leakage magnetic flux due to the uneven portion.

  The present invention has been made paying attention to such problems, and an object of the present invention is to provide a torque sensor in which the influence of leakage magnetic flux is suppressed and the torsion torque applied to the shaft can be detected with high accuracy.

According to the present invention, in the torque sensor according to claim 1 or 2 , each of the pair of ring-shaped yokes has an axial portion of one ring-shaped yoke longer than an axial portion of the other ring-shaped yoke. by forming, offsetting the detected position of the magnetic flux density is set between the end faces facing each other of said pair of ring-shaped yoke from the center between the mutually facing end surfaces of the magnetic ring of said pair to the axial direction of said shaft It is characterized by that.

A torque sensor according to a first aspect includes a pair of magnetic rings whose relative rotational positions change as the shaft twists, a pair of ring-shaped yokes facing the outer periphery of the pair of magnetic rings, and these rings. and an annular magnet body disposed so on constituting a part of the magnetic circuit on one of Jo yoke, means constituting a magnetic circuit of annular shape centered on the shaft with magnetic rings of the pair When, is interposed between the end surfaces facing each other of said pair of ring-shaped yoke, and means for detecting the magnetic flux density of the magnetic circuit, with for relative rotational position of the magnetic rings of the pair is changed as it means for changing the magnetic field of the magnetic circuit portion Te, and a concave-convex portion formed at equal intervals and alternately in the circumferential direction on the respective end surfaces facing each other of the magnetic rings of the pair.

Torque sensor according to claim 2, sandwiching a magnet body to be configured from a plurality of rod-shaped magnets in an annular body surrounding it about the shaft attached to one end of the shaft, it from the axial direction of the magnet body the magnetic ring of a pair mounted to the other end of the shaft arranged to as having a pair of ring-shaped yoke facing the outer circumference of the magnetic ring of said pair, said with magnetic ring of said pair means for constituting a magnetic circuit of the annular around the shaft, is interposed between the end surfaces facing each other of said pair of ring-shaped yoke, and means for detecting the magnetic flux density of the magnetic circuit, the 1 as means for changing the magnetic field of the magnetic circuit in association with the relative rotational position of the magnetic rings and the annular magnet of the pair is changed, the circumference at each end face, which face each other, of the magnetic ring of said pair Direction And a concave-convex portion formed at equal intervals and alternately to.

  In the present invention, the concave and convex portions are alternately formed in the circumferential direction at equal intervals on each of the opposing end faces of the pair of magnetic rings. Since the offset between the centers of the end faces facing each other is offset in the axial direction of the shaft, it is possible to suppress the leakage magnetic flux from the uneven portion of the magnetic ring from affecting the detection position of the magnetic flux density. Therefore, the diameter of the torque sensor can be reduced (the magnetic circuit can be shortened) by ensuring that the detection position of the magnetic flux density is close to the shaft while ensuring the detection accuracy of the torsional torque applied to the shaft.

  A torque sensor according to an embodiment of the present invention will be described based on the drawings.

  FIG. 3 is a reference diagram for explaining a torque sensor according to a prior application example (Japanese Patent Application No. 2004-230792). The torque sensor is a pair of magnetic rings 12 a and 12 b whose relative rotational positions change as the shaft 11 is twisted. A pair of magnetic rings 12a and 12b together with a means for forming an annular magnetic circuit section 13 centered on the shaft 11, a means 14 (magnetic sensor) for detecting the magnetic flux density of the magnetic circuit section 13, and a pair of Means for changing the magnetic field of the magnetic circuit section 13 as the relative rotational positions of the magnetic rings 12a and 12b change.

As a means for constituting the annular magnetic circuit portion 13, a pair of ring-shaped yokes 20a and 20b facing the outer periphery of the pair of magnetic rings 12a and 12b is provided, and one of these ring-shaped yokes 20a and 20b is provided. The annular magnet body 21 is arranged so as to constitute a part of the magnetic circuit unit 13. The annular magnet body 21 is magnetized so that the outer periphery and the inner periphery have different magnetic poles (in the illustrated case, the outer periphery has an N pole and the inner periphery has an S pole). A pair of ring-shaped yoke 20a, together opposed end faces 19a of 20b, a pair each of 19b magnetism collecting part 22a, 22b is projected, the magnetic sensor 14 for detecting the magnetic flux density between the tips of these opposing (Hall IC) is installed.

  As means for changing the magnetic field of the magnetic circuit section 13, the concave and convex portions 17a, 16a, 17b, 16b are alternately arranged at equal intervals in the circumferential direction on the mutually opposing end faces 18a, 18b of the pair of magnetic rings 12a, 12b. Formed. Reference numeral 23 denotes a non-magnetic member that couples the pair of ring-shaped yokes 20a and 20b, the annular magnet body 21, and the magnetic sensor 14 to each other.

  In this torque sensor, when the rotating shaft 11 is twisted, relative rotation occurs between the pair of magnetic rings 12a and 12b, and accordingly, the opposing area between the convex portions 16a and 16b changes. The magnetic field of the magnetic circuit unit 13 changes. The magnetic field of the magnetic circuit unit 13 becomes stronger as the opposing area between the convex parts 16a and 16b increases, and the magnetic field of the magnetic circuit part 13 becomes weaker as the opposing area between the convex parts 16a and 16b decreases. Become. This change is detected by the magnetic sensor 14 from the magnetic flux density between the magnetized portions 22a and 22b facing each other in the pair of ring-shaped yokes 20a and 20b, and the torsional torque applied to the shaft 1 is obtained.

In the pair of magnetic rings 12a and 12b, the magnetic flux densities of the end faces 18a and 18b facing each other periodically change (dense / dense) in the circumferential direction of the rings 12a and 12b due to the uneven portions 17a, 16a, 17b, and 16b. However, since the magnetic sensor 14 detects the magnetic flux density generated around the entire circumference between the pair of magnetic rings 12a and 12b by the annular magnetic circuit portion 13 (including the annular magnet body 21), the rotation of the shaft 11 is performed. Accordingly, it is possible to prevent the magnetic flux density of the magnetic circuit unit 13 from periodically changing. On the other hand , the detection of the magnetic sensor 14 may periodically increase / decrease (change) as the shaft 11 rotates due to the density of the magnetic flux leakage caused by the uneven portions 17a, 16a, 17b, 16b .

  The present invention is provided with means for preventing the occurrence of an error in the detection of torsional torque applied to the shaft 11 under the influence of the leakage magnetic flux caused by the uneven portions 17a, 16a, 17b, 16b in the torque sensor of FIG. . Specifically, as shown in FIG. 1, the detection position of the magnetic flux density is offset in the axial direction of the shaft 11 from the center P between the end faces 18a, 18b (uneven portions) of the pair of magnetic rings 12a, 12b facing each other. . Each of the pair of ring-shaped yokes 20a and 20b has a substantially L-shaped cross section from an axial portion and a radial portion, and the axial portion of one ring-shaped yoke 20a having an annular magnet body 21 is elongated. By detecting the axial portion of the other ring-shaped yoke 20b to be short, the detection position of the magnetic flux density set between the opposing end surfaces (the magnetic flux collecting portions 22a, 22b) of the pair of ring-shaped yokes 20a, 20b. Can be offset in the axial direction of the shaft 11 from the center P between the opposite end faces 18a, 18b (uneven portions) of the pair of magnetic rings.

  Thereby, it is possible to suppress the leakage magnetic flux from the concave and convex portions 17a, 16a, 17b, and 16b of the pair of magnetic rings 12a and 12b from affecting the detection position of the magnetic flux density (magnetic sensor 14). Thus, the periodic change (detection error) of the detection of the magnetic sensor 14 due to the density of the leakage magnetic flux passing near the magnetic sensor 14 can be mitigated. For this reason, by making the detection position of the magnetic flux density close to the shaft 11, it is possible to reduce the diameter of the torque sensor (shortening the magnetic circuit) while ensuring the detection accuracy of the torsional torque applied to the shaft 11.

FIG. 4 is a reference diagram for explaining the torque sensor according to the prior application example (Japanese Patent Application No. 2004-233227). The torque sensor is composed of a plurality of rod-shaped magnets 35a (see FIG. 5) around the shaft 31. A magnet body 35 that is composed of a surrounding annular body and attached to one end side of the shaft 31, and a pair of magnetic rings 32 a that are disposed so as to sandwich the magnet body 35 from the axial direction and are attached to the other end side of the shaft 31. , 32b , a pair of magnetic rings 32a, 32b and means for forming an annular magnetic circuit section 33 centered on the shaft 31, means 34 (magnetic sensor) for detecting the magnetic flux density of the magnetic circuit section 33, and 1 Means for changing the magnetic field of the magnetic circuit section 33 as the relative rotational position of the pair of magnetic rings 32a and 32b and the annular magnet body 35 changes.

As a means for constituting the annular magnetic circuit portion 33, a pair of ring-shaped yokes 33a and 33b facing the outer periphery of the pair of magnetic rings 32a and 32b are provided. A pair of ring-shaped yoke 33a, an end surface 39a which faces each other 33b, a pair each of 39b magnetism collecting part 42a, 42b is projected, the magnetic sensor 34 for detecting the magnetic flux density between the tips of these opposing (Hall IC) is installed.

  Each magnet 35a constituting the annular magnet body 35 is arranged so that the magnetic poles (N pole, S pole) at both ends are different from the magnetic poles (S pole, N pole) at both ends of the adjacent magnet (see FIG. 5). ). As means for changing the magnetic field of the magnetic circuit section 33, the concave and convex portions 37a, 36a, 37b, 36b are alternately arranged at equal intervals in the circumferential direction on the mutually opposing end faces 38a, 38b of the pair of magnetic rings 32a, 32b. Formed. The number of the convex portions 36 a and 36 b is set to ½ of the number of magnets constituting the magnet body 35.

  In the neutral position where the twist of the shaft 31 is zero, the centers of the convex portions 36a, 36b of the pair of magnetic rings 32a, 32b facing each other between the adjacent magnets 35a of the magnet body 35 are as shown in FIG. It coincides with the center (the boundary between the N pole and the S pole). In this case, since the same number of lines of magnetic force enter and exit from the N and S poles of the magnet body 35 through the convex portions 36a and 36b of the magnetic rings 32a and 32b, a magnetic flux is generated between the magnet body 35 and the magnetic rings 32a and 32b. It is closed and the magnetic flux density of the magnetic circuit part 33 becomes zero.

When the shaft 31 is twisted, relative rotation occurs between the magnet body 35 and the pair of magnetic rings 32a and 32b sandwiching the magnet body 35. For this reason, as shown in FIG. 5B, the centers of the convex portions 36a and 36b are shifted from the boundary between the N pole and the S pole of the magnet body 35. Therefore, the polarities of the pair of magnetic rings 32a and 32b are different from each other. The lines of magnetic force increase, and a magnetic flux density is generated between the end faces (magnetic collecting portions 42a, 42b) of the pair of ring-shaped yokes 33a, 33b facing each other. By detecting this magnetic flux density by the magnetic sensor 34 , the torsional torque applied to the shaft 31 is obtained.

  In the pair of magnetic rings 32a and 32b, the magnetic flux density of the end faces 38a and 38b facing each other is periodically changed (dense / dense) in the circumferential direction of the rings 32a and 32b by the concave and convex portions 37a, 36a, 37b, and 36b. However, since the magnetic sensor 34 detects the magnetic flux density generated on the entire circumference between the pair of magnetic rings 32a and 32b by the annular magnetic circuit portion 33 (including the annular magnet body 35), the rotation of the shaft 31 is performed. Accordingly, it is possible to prevent the magnetic flux density of the magnetic circuit unit 33 from periodically changing. On the other hand, the detection of the magnetic sensor 34 may periodically increase / decrease (change) as the shaft 31 rotates due to the density of the magnetic flux leakage caused by the uneven portions 37a, 36a, 37b, 36b.

  The present invention is provided with means for preventing the occurrence of an error in the detection of torsional torque applied to the shaft 31 due to the influence of leakage magnetic flux caused by the uneven portions 37a, 36a, 37b, 36b in the torque sensor of FIG. . Specifically, as shown in FIG. 2, the detection position of the magnetic flux density is offset in the axial direction of the shaft 31 from the center P between the end faces 38a, 38b (uneven portions) of the pair of magnetic rings 32a, 32b. . Each of the pair of ring-shaped yokes 33a and 33b is formed to have a substantially L-shaped cross section from an axial portion and a radial portion, the axial portion of one ring-shaped yoke 33a is long, and the other ring-shaped yoke 33b. The pair of magnetic rings 32a has a detection position of the magnetic flux density set between the opposing end surfaces (magnetic collecting portions 42a, 42b) of the pair of ring-shaped yokes 33a, 33b. , 32b can be offset in the axial direction of the shaft 31 from the center P between the end faces 38a, 38b (uneven portions) facing each other.

  Thereby, it is possible to suppress the leakage magnetic flux from the concave and convex portions 37a, 36a, 37b, 36b of the pair of magnetic rings 32a, 32b from affecting the detection position (magnetic sensor 34) of the magnetic flux density. Thus, the periodic change (detection error) of the detection of the magnetic sensor 34 due to the density of the leakage magnetic flux passing near the magnetic sensor 34 can be reduced. Therefore, by bringing the detection position of the magnetic flux density closer to the shaft 31, it is possible to reduce the diameter of the torque sensor (shortening the magnetic circuit) while ensuring the detection accuracy of the torsional torque applied to the shaft 31.

  Since the annular magnet body 35 sandwiched between the pair of magnetic rings 32a and 32b from the axial direction of the shaft 31 also rotates with the rotation of the shaft 32, the density of leakage magnetic flux affecting the magnetic sensor 34 is generated. It is thought that this is because of the offset between the detection position of the magnetic flux density and the center P between the opposing end faces 38a, 38b (uneven portions) of the pair of magnetic rings 32a, 32b. Since the magnet body 35 sandwiched between the opposing end faces 38a and 38b of the magnetic rings 32a and 32b is greatly separated in the axial direction of the shaft 31, the magnetic flux leakage of the magnet body 35 can be prevented from affecting the magnetic sensor 34. is there.

  As described above, in the torque sensor of FIG. 3 or FIG. 4, the annular magnetic circuit portion 13 or 33 is formed on the outer periphery of the pair of magnetic rings 12a, 12b or 32a, 32b, and the detection position of the magnetic flux density is a pair. The magnetic ring 12a, 12b or 32a, 32b is offset from the center P between the opposing end faces, so that the detection accuracy of the magnetic flux density (shaft torsion torque) of the magnetic circuit portion 13 or 33 can be dramatically increased. .

  With respect to the configuration according to the present invention (the magnetic flux density detection position is offset in the axial direction of the shaft from the center between the opposing end surfaces of the pair of magnetic rings), The present invention can be widely applied to a torque sensor provided with uneven portions formed alternately at equal intervals in the circumferential direction of each magnetic ring.

1 is a plan view of a torque sensor according to an embodiment of the present invention. It is a top view of the torque sensor which similarly concerns on another embodiment. It is a partial cross section perspective view (reference drawing) of a torque sensor explaining an embodiment of this invention. It is an axial direction sectional view (reference drawing) of a torque sensor explaining an embodiment of this invention. FIG. 5 is an operation explanatory diagram (reference diagram) relating to the torque sensor of FIG. 4. It is a perspective block diagram of the torque sensor explaining a prior art.

Explanation of symbols

11, 31 Shafts 12a, 12b, 32a, 32b A pair of magnetic rings 13, 33 Magnetic circuit parts 14, 34 Magnetic sensors 17a, 16a, 17b, 16b, 37a, 36a, 37b, 36b Uneven parts 20a, 20b, 33a, 33b One set of ring-shaped yokes 21, 35 Annular magnet bodies 22a, 22b, 42a, 42b

Claims (3)

A pair of magnetic rings whose relative rotational positions change as the shaft twists;
A pair of ring-shaped yokes opposed to the outer periphery of the pair of magnetic rings, and an annular magnet body disposed in one of the ring-shaped yokes so as to constitute a part of the magnetic circuit portion; It means for constituting a magnetic circuit of annular shape centered on the shaft with magnetic ring of the pair,
Means for detecting a magnetic flux density of the magnetic circuit unit , interposed between the opposing end faces of the pair of ring-shaped yokes ;
As means for changing the magnetic field of the magnetic circuit in association with the relative rotational position of the magnetic rings of the pair is changed, equidistantly and circumferentially in each of the mutually facing end surfaces of the magnetic ring of said pair And uneven portions formed alternately ,
Each of the pair of ring-shaped yokes has an end surface facing each other of the pair of ring-shaped yokes by forming an axial portion of one ring-shaped yoke longer than an axial portion of the other ring-shaped yoke. a torque sensor, characterized in that the offset in the axial direction of the shaft to detect the position of the magnetic flux density is set from the center between the end faces facing each other of the magnetic rings of the pair between. A magnet attached to one end of the shaft constitutes the annular body surrounding it about the shaft from a plurality of rod-shaped magnets,
The magnetic ring of a pair mounted arranged so as to sandwich it from the axial direction of the magnet body to the other end of the shaft,
And means for configuring said comprises a set of ring-shaped yoke facing the outer periphery of the pair of magnetic rings, the magnetic circuit of the annular around said shaft with magnetic ring of the pair,
Means for detecting a magnetic flux density of the magnetic circuit unit , interposed between the opposing end faces of the pair of ring-shaped yokes ;
As means for changing the magnetic field of the magnetic circuit in association with the relative rotational position between the magnet body of the annular magnetic ring of the pair is changed, the respective end faces facing each other of the magnetic ring of said pair And uneven portions formed alternately at equal intervals in the circumferential direction ,
Each of the pair of ring-shaped yokes has an end surface facing each other of the pair of ring-shaped yokes by forming an axial portion of one ring-shaped yoke longer than an axial portion of the other ring-shaped yoke. a torque sensor, characterized in that the offset in the axial direction of the shaft to detect the position of the magnetic flux density is set from the center between the end faces facing each other of the magnetic rings of the pair between. 3. The torque sensor according to claim 1, wherein each of the pair of ring-shaped yokes has a substantially L-shaped cross section from an axial portion and a radial portion .

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