JP4523810B2 - Torque sensor - Google Patents

Description

  The present invention relates to an improvement in 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. However, in this strain gauge type torque sensor, since the torque sensor and the wiring rotate together with the steering shaft, a signal line extending from the torque sensor must be wound around the steering shaft. There was a problem that it was easy to get involved.

  As a measure against this, there is a non-contact type torque sensor disclosed in Patent Document 1 that is provided without contacting a rotating shaft, which can solve the wiring problem.

  As shown in FIG. 5, the non-contact type torque sensor includes a shaft 1 to which torsional torque is applied, first and second rings 2 and 3 whose relative rotational positions change as the shaft 1 is twisted, Between the magnetic flux loop component 10 fixed opposite to each of the end faces 2c, 3c of the first and second rings 2, 3 from the axial direction, and the magnetic poles 11a, 12a provided in the magnetic flux loop component 10 and facing each other A magnetic field changing means (first magnetic flux density detecting means) 5 for detecting magnetic flux and a magnetic field changing means (first magnetic flux changing means) for changing the magnetic field of the magnetic flux loop constituting section 10 as the relative rotational positions of the first and second rings 2 and 3 change. And notches 2b and 3b) opened to the opposing end faces 2a and 3a of the second rings 2 and 3, respectively.

  The magnetic flux loop constituting portion 10 is composed of L-shaped magnets 11 and 12 which are fixed to the respective end faces 2c and 3c of the first and second rings 2 and 3 opposite to each other in the axial direction.

  In this torque sensor, when torsional torque is applied to the shaft 1 and the shaft 1 is twisted, the first and second rings 2 and 3 rotate relative to each other, and the magnetic field of the magnetic flux loop component 10 changes. At this time, the torsional torque applied to the shaft 1 can be detected by measuring the magnetic flux density between the magnetic poles 11a and 12a opposed to each other in the magnetic flux loop constituting section 10 of the Hall element 5.

In this torque sensor, the first and second rings 2 and 3 rotate as the shaft 1 rotates, but the magnetic flux loop component 10 and the Hall element 5 can be fixed so as not to rotate. There is no fear that the signal line extending from the element 5 will be tangled.
JP 2002-310819 A

  However, in such a conventional non-contact type torque sensor, the L-shaped magnets 11 and 12 and the first and second rings 2 and 2 in the magnetic flux loop component 10 are caused by eccentricity of the rotating shaft 1 or the like. 3 is slightly changed, the magnetic flux density of the magnetic flux loop component 10 changes even though the swing angle (torque) is constant, resulting in a torque detection error.

  Further, when the shaft 1 rotates with respect to the first and second rings 2 and 3, the opposed end faces 2 a of the first and second rings 2 and 3 with respect to the magnetic path cross section of the magnetic flux loop in the magnetic flux loop component 10. , 3a, the notches 2b and 3b that open intermittently face each other, so that the magnetic flux density of the magnetic flux loop component 10 periodically changes with the rotation of the shaft 1 despite a constant swing angle (torque). There is a problem that a torque detection error occurs.

  The present invention has been made in view of the above problems, and an object of the present invention is to improve the detection accuracy of a non-contact type torque sensor that detects torque from torsion of a rotating shaft.

  The present invention relates to a shaft to which torsion torque is applied, first and second rings whose relative rotational positions change as the shaft is twisted, and magnetic flux that guides magnetism to pass through each of the first and second rings. A loop constituent part, a magnetic field changing means for changing the magnetic field of the magnetic flux loop constituent part as the first and second rings rotate relative to each other, and a magnetic flux density detecting means for detecting the magnetic flux density of the magnetic flux loop constituent part. Applies to non-contact type torque sensors.

An annular first and second yoke respectively facing the first and second rings, and an annular ring magnet interposed in the middle of the magnetic flux loop constituent part, the magnetic flux loop constituent part being the first and second It is formed in an annular shape by a yoke and a ring magnet so that magnetism is guided annularly to each of the first and second rings, and as the magnetic field changing means, the first and second rings face each other substantially parallel to each other. A plurality of notches are formed on each opposed end face with a predetermined uneven pitch P in the rotational angle direction, and each notch is formed symmetrically with respect to the rotational axis of the shaft. There are magnetized convex portions protruding opposite to each other, and a magnetic flux density detecting means is interposed between the magnetic flux collecting convex portions, and the magnetic flux collecting convex portions are in the rotational angle direction with respect to the first and second yokes. The protruding pitch T is the same as that of the first and second rings. That has been set equal to the uneven pitch P of each notch is formed on the facing end surface was assumed to be characterized.

  According to the present invention, the torque sensor forms an annular magnetic flux loop component by the annular first and second yokes facing the first and second rings, respectively, and is magnetically coupled to each of the first and second rings. As the shaft rotates, the magnetic fields in the first and second rings change even if the first and second rings rotate relative to the first and second yoke as the shaft rotates. Is suppressed. For this reason, it can suppress that the magnetic flux density of a magnetic flux loop structure part changes as a shaft rotates, and can improve the detection accuracy of a torque.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  In FIG. 1, 1 indicates a steering shaft (hereinafter referred to as a shaft) of a vehicle, for example. The shaft 1 has one end connected to a steering wheel and the other end connected to a steering gear (not shown) to transmit a steering force to the wheels.

  A torsion bar portion having a partially reduced diameter is formed in the middle of the shaft 1, and the shaft 1 has an input side 1 a and an output side 1 b across the torsion bar portion. The torsion bar portion expands the torsional distortion of the shaft 1 with respect to the rotational torque applied to the input side 1a.

  The torque sensor includes first and second rings 2 and 3 that rotate relative to each other as the shaft 1 is twisted, and a magnetic flux loop component 20 that guides the magnetism to pass through each of the first and second rings 2 and 3. Magnetic field changing means for changing the magnetic field of the magnetic flux loop component 20 as the first and second rings 2 and 3 rotate relative to each other, and a Hall element (magnetic flux density detection) for detecting the magnetic flux density of the magnetic flux loop component 20 Means) 5. The Hall element 5 outputs a voltage corresponding to the change in the magnetic field as a signal, and a torsional torque applied to the shaft 1 is determined according to the output.

  The annular first and second rings 2 and 3 are fixed coaxially to the shaft 1 on the input side 1a and the output side 1b of the shaft 1 with the torsion bar portion interposed therebetween, and relatively rotate as the shaft 1 is twisted. It is like that.

  The first and second rings 2 and 3 are formed in a right cylindrical shape by a magnetic material such as iron. As magnetic field changing means, the first and second rings 2 and 3 have opposing end faces 2a and 3a that face each other with a slight gap 6 between them. A plurality of notches 2b and 3b are formed on each of the opposing end faces 2a and 3a extending in a ring shape with a predetermined uneven pitch (center angle) P in the rotational angle direction. One opposed end face 2a, 3a and one notch 2b, 3b are provided side by side in the rotation angle range of the uneven pitch P.

  The notches 2b and 3b are formed symmetrically with respect to the rotation axis of the shaft 1. When the relative rotation position of the first and second rings 2 and 3 changes as the shaft 1 twists, the area where the opposed end faces 2a and 3a face each other changes, and the magnetic field of the magnetic flux loop component 20 changes. It is like that.

  The torque sensor includes annular first and second yokes 21 and 22 that face the first and second rings 2 and 3, respectively, and the magnetic flux loop component 20 is annularly formed by the first and second yokes 21 and 22. The magnetism is guided to each of the first and second rings 2 and 3 in a ring shape.

  The first and second yokes 21 and 22 are formed in an annular shape having an L-shaped cross section by a magnetic material such as iron.

  The first and second yokes 21 and 22 are fixedly attached to the vehicle body (not shown) and are provided so as not to contact the shaft 1 and the first and second rings 2 and 3. That is, the inner peripheral surfaces of the first and second yokes 21 and 22 are opposed to each other from the radial direction with gaps 27 and 28 in the outer peripheral surfaces 2d and 3d of the first and second rings 2 and 3, respectively.

  Not limited to this, the gaps 27 and 28 are not provided, and the inner peripheral surfaces of the first and second yokes 21 and 22 are brought into sliding contact with the outer peripheral surfaces 2d and 3d of the first and second rings 2 and 3, respectively. It is good also as a structure.

  Further, the end surfaces of the first and second yokes may be opposed to the respective end surfaces of the first and second rings from the axial direction.

  In the present embodiment, the first and second yokes 21 and 22 are respectively provided with annular ring magnets 25 at portions facing the outer peripheral surfaces 2d and 3d of the first and second rings 2 and 3, respectively. The ring magnet 25 is magnetized so that its inner periphery is an S pole and its outer periphery is an N pole.

  As shown in FIG. 2, the first and second yokes 21 and 22 have two pairs of magnetic flux collecting convex portions 21 a and 22 a that protrude to face each other. Each magnetism collecting convex portion 21a becomes an N pole, and each magnetism collecting convex portion 22a becomes an S pole.

  The two pairs of magnetic flux collecting convex portions 21 a and 22 a are formed symmetrically with respect to the central axes of the first and second yokes 21 and 22. Each Hall element 5 is arranged symmetrically with respect to the central axes of the first and second yokes 21 and 22.

  Not limited to this, three or more pairs of magnetic flux collecting convex portions are formed symmetrically with respect to the central axes of the first and second yokes 21 and 22, and three or more Hall elements 5 are arranged between the magnetic flux collecting convex portions. You may interpose.

  Alternatively, the pair of magnetic flux collecting convex portions may be formed symmetrically with respect to the central axes of the first and second yokes 21 and 22, and a single Hall element 5 may be interposed between the magnetic flux collecting convex portions.

  As shown in FIG. 3, the magnetic flux collecting convex portions 21a and 22a protrude from the end surfaces 21b and 22b of the first and second yokes 21 and 22 with a predetermined pitch (center angle) T in the rotational angle direction.

  The pitch T of the magnetic flux collecting convex portions 21a and 22a is set equal to the concave / convex pitch P of the notches 2b and 3b formed on the opposing end surfaces 2a and 3a of the first and second rings 2 and 3, respectively.

  The Hall element 5 is provided as a magnetic flux density detection means. A voltage corresponding to the magnetic flux density between the N pole and the S pole of the magnetic flux loop component 20 is output as a signal via an electric wire (not shown) interposed between the magnetic flux collecting convex portions 21a and 22a.

  Each of the magnetic flux collecting convex portions 21 a and 22 a is formed in a tapered shape that is narrowed toward the Hall element 5 from the end faces 21 b and 22 b of the first and second yokes 21 and 22, and collects the magnetic field in the Hall element 5. . The end faces of the magnetic flux collecting convex portions 21 a and 22 a are formed in a rectangular shape similar to the outer shape of the Hall element 5.

  The torque sensor includes a nonmagnetic member 30 that couples the first and second yokes 21 and 22, the ring magnet 25, and the Hall element 5 to each other. The nonmagnetic member 30 is made of resin and is formed between the first and second yokes 21 and 22. In the torque sensor, the first and second yokes 21 and 22, the ring magnet 25, and the Hall element 5 are unitized as a subassembly via the nonmagnetic member 30.

  During manufacture of the torque sensor, the first and second yokes 21 and 22 and the hall element 5 are held in place via a jig (formwork) (not shown), between the first and second yokes 21 and 22. The resin material is filled in and solidified.

  The nonmagnetic member 30 is formed in an annular cylindrical shape having a T-shaped cross section, and is formed between the first and second yokes 21 and 22 without a gap so as to avoid the magnetic flux collecting convex portions 21a and 22a. .

  Next, the operation of the embodiment of the present invention configured as described above will be described.

  When torsional torque is applied to the shaft 1 and the torsion bar portion of the shaft 1 is twisted, the first and second rings 2 and 3 rotate relative to each other, and the opposed end faces 2a and 3a of the first and second rings 2 and 3 are mutually connected. The facing area changes, and the magnetic flux density passing through the magnetic flux loop constituting part 20 via the first and second yokes 21 and 22 changes. The magnetic flux passing through the first and second rings 2 and 3 of the magnetic flux loop constituent part 20 increases the magnetic field of the magnetic flux loop constituent part 20 as the area where the opposing end faces 2a and 3a face each other increases. The magnetic field of the magnetic flux loop component 20 becomes weak as the area where the opposing end faces 2a and 3a face each other decreases. The Hall element 5 outputs a voltage corresponding to the change in the magnetic field as a signal, and a torsion torque applied to the shaft 1 is detected according to the output.

  As the shaft 1 is rotated by the operation of the steering wheel, the first and second rings 2 and 3 are rotated, but the first and second yokes 21 and 22 and the hall element 5 fixed to the vehicle body are not rotated. There is no fear that the signal line extending from the Hall element 5 will be tangled.

  Since the first and second yokes 21 and 22 are opposed to each other with the gaps 27 and 28 on the outer peripheral surfaces 2d and 3d of the first and second rings 2 and 3, wear between them is avoided and durability is ensured. it can.

  Since the opposing end faces 2a and 3a of the first and second rings 2 and 3 are opposed to each other with a gap therebetween, wear of both is avoided and durability can be ensured.

  The torque sensor is formed as the shaft 1 rotates by forming the annular magnetic flux loop constituting portion 20 by the annular first and second yokes 21 and 22 that face the first and second rings 2 and 3, respectively. Even if the first and second rings 2 and 3 rotate relative to the first and second yokes 21 and 22, the conditions under which magnetism passes through the first and second rings 2 and 3 are unlikely to change. For this reason, it is suppressed that the magnetic flux density of the magnetic flux loop structure part 20 changes with rotation of the shaft 1, and the detection accuracy of a torque can be improved.

  Due to the structure in which the inner peripheral surfaces of the first and second yokes 21 and 22 are opposed to the outer peripheral surfaces 2d and 3d of the first and second rings 2 and 3 from the radial direction, the shaft 1 is eccentric. When the positional relationship between the magnetic flux loop constituting portion 20 and the first and second rings 21 and 22 changes, the magnetic loop is defined between the first and second yokes 21 and 22 and the first and second rings 2 and 3. If one of the cross-sectional areas of the gaps 27 and 28 decreases, the other increases and the sum of the cross-sectional areas of the gaps 27 and 28 does not change, so that the magnetic flux density of the magnetic flux loop component 20 changes as the shaft 1 rotates. Torque can be suppressed and torque detection accuracy can be improved.

  As magnetic field changing means, the first and second rings 2 and 3 have opposing end faces 2a and 3a facing each other substantially in parallel, and a plurality of notches 2b and 3b are predetermined in the rotational angle direction on each of the opposing end faces 2a and 3a. Since the magnetic field in the annular magnetic flux loop constituting portion 20 changes symmetrically with respect to the central axis of the shaft 1 as the shaft 1 is twisted, as the shaft 1 is twisted, Thus, the change in the magnetic flux density of the magnetic flux loop component 20 can be suppressed, and the torque detection accuracy can be improved.

  By making the magnetic flux collecting convex portions 21a and 22a protrude from the end faces 21b and 22b of the first and second yokes 21 and 22, the magnetic flux of the magnetic flux loop constituting portion 20 is transferred to the Hall element 5 via the magnetic flux collecting convex portions 21a and 22a. Therefore, the output voltage of the Hall element 5 can be increased.

  By arranging two pairs of magnetic flux collecting convex portions 21a, 22a and two Hall elements 5 symmetrically about the central axes of the first and second yokes 21, 22, each of the first and second rings 2, 3 is cut. Periodic output changes that occur in each Hall element 5 due to the strength of the magnetic flux density generated by the notches 2b and 3b occur in opposite directions.

  Furthermore, when the positional relationship between the magnetic flux loop constituting portion 20 and the first and second rings 21 and 22 changes due to the eccentricity of the shaft 1, output changes of the Hall elements 5 occur in opposite directions.

  For this reason, by adding the outputs of the hall elements 5 and calculating the torque applied to the shaft 1, the detection errors of the hall elements 5 cancel each other, and the torque detection accuracy can be improved.

  The pitch T at which each of the magnetic flux collecting convex portions 21a and 22a protrudes is set equal to the concave and convex pitch P of the plurality of notches 2b and 3b formed on the opposing end surfaces 2a and 3a of the first and second rings 2 and 3. Thus, when the shaft 1 rotates with respect to the first and second rings 2 and 3, the first and second magnetic flux cross-sections 20 are arranged with respect to the magnetic path cross section where the magnetic flux collecting convex portions 21 a and 22 a are arranged. The ratio of the notches 2b and 3b that open to the opposing end faces 2a and 3a of the rings 2 and 3 is kept constant. For this reason, when the swing angle (torque) is constant, a change in the magnetic flux density of the magnetic flux loop constituting unit 20 can be suppressed, and detection that depends on the relative positional relationship between the Hall element 5 and the first and second rings 2 and 3 is detected. It is possible to reduce the error.

  In the torque sensor, the first and second yokes 21 and 22, the ring magnet 25, and the hall element 5 are coupled to each other via the nonmagnetic member 30, so that the position of the hall element 5 with respect to the first and second yokes 21 and 22 is increased. Increases accuracy. This facilitates control of the installation positions of the parts constituting the magnetic flux loop constituting unit 20 in the assembly process, suppresses variations in the installation positions of the parts, and improves the quality of the torque sensor.

  In the torque sensor, the first and second yokes 21 and 22, the ring magnet 25 and the hall element 5 are unitized as a subassembly via the nonmagnetic member 30, thereby reducing the number of parts and facilitating assembly to the vehicle body. Yes.

  At the time of manufacturing the torque sensor, the first and second yokes 21 and 22, the ring magnet 25, and the hall element 5 are held at predetermined positions via a jig (formwork) (not shown). , 22 is filled with a resin material and solidified, so that the positional accuracy of the Hall element 5 with respect to the first and second yokes 21 and 22 can be increased.

  Since the nonmagnetic member 30 is formed between the first and second yokes 21 and 22 so as to avoid the Hall element 5, the magnetic flux collecting effect on the Hall element 5 in the magnetic flux loop component 20 can be enhanced. The output voltage of 5 can be increased.

  As another embodiment, the first and second yokes 21 and 22 shown in FIG. 4 are annular ring magnets 25 and 26 at portions facing the outer peripheral surfaces 2d and 3d of the first and second rings 2 and 3, respectively. Are provided respectively. The ring magnets 25 and 26 are arranged so that the south pole and the north pole are aligned along the magnetic flux loop component 20. That is, the ring magnet 25 is magnetized so that its inner periphery has an S pole and its outer periphery has an N pole, while the ring magnet 26 has its inner periphery an N pole and its outer periphery an S pole. Thereby, the magnetic field of the magnetic flux loop component 20 can be strengthened.

  However, the present invention is not limited to this, and an annular ring magnet may be interposed between the first and second yokes 21 and 22. Further, the first and second yokes 21 and 22 may be integrally formed by a ring magnet.

  An annular ring magnet may be provided on the first and second rings 2 and 3 side.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  The present invention can be used for a non-contact type torque sensor that detects torque from torsion of a rotating shaft.

The perspective view of the torque sensor which shows embodiment of this invention. The side view of a torque sensor similarly. Sectional drawing which follows the AA line of FIG. The perspective view of the torque sensor which shows other embodiment of this invention. The perspective view of the torque sensor which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shaft 2 1st ring 2a Opposing end surface 2b Notch 3 2nd ring 3a Opposing end surface 3b Notch 5 Hall element (magnetic flux density detection means)
20 Magnetic flux loop component 21 First yoke 22 Second yoke 25 Ring magnet

Claims (2)

A shaft to which torsional torque is applied, first and second rings whose relative rotational positions change as the shaft is twisted, and a magnetic flux loop component that guides each of the first and second rings to pass magnetism A torque provided with magnetic field changing means for changing the magnetic field of the magnetic flux loop constituent part as the first and second rings rotate relative to each other, and magnetic flux density detecting means for detecting the magnetic flux density of the magnetic flux loop constituent part In the sensor
An annular first and second yoke respectively facing the first and second rings, and an annular ring magnet interposed in the middle of the magnetic flux loop constituent part, the magnetic flux loop constituent part being the first and second It is formed in an annular shape by two yokes and a ring magnet, and each of the first and second rings is configured to guide the magnetism in an annular shape ,
As the magnetic field changing means, the first and second rings have opposing end faces facing each other substantially in parallel, and a plurality of notches are formed on each opposing end face with a predetermined uneven pitch P in the rotational angle direction, Forming each notch symmetrically about the axis of rotation of the shaft,
The first and second yokes have magnetism-convex protrusions that protrude opposite to each other, and the magnetic flux density detection means is interposed between the magnetism-collection protrusions.
A pitch T at which the magnetism-convex convex portion protrudes in the rotation angle direction with respect to the first and second yokes, and a concave / convex pitch P at which the notches are formed on the opposing end surfaces of the first and second rings. Torque sensor characterized by being set equal to 2. The magnetic flux collecting convex portions are provided in a plurality of pairs, and the magnetic flux collecting convex portions and a plurality of magnetic flux density detecting means interposed therebetween are arranged symmetrically with respect to the rotation axis of the shaft. The torque sensor described in 1 .

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