Magnetostrictive torque sensor

Abstract

To provide a magnetostrictive torque sensor with improved measurement accuracy.SOLUTION: A main body 11 of a holder 5 is placed around a detection target surface 4 of a rotary shaft 2 in such a way that concave surfaces 14 of positioning protrusions 12 are slidably in contact with or closely facing the detection target surface 4 of the rotary shaft 2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a magnetostrictive torque sensor that utilizes the inverse magnetostrictive effect generated in a rotating body to measure torque transmitted by the rotating body. [Background technology]

[0002] For example, in the technical field of automobiles, it has been conventional to measure the torque transmitted by a rotating shaft that constitutes an automatic transmission and use the measurement results to control the gear shifting of the transmission and the output of the engine.

[0003] Furthermore, as a technique for measuring the torque transmitted by a rotating shaft, for example, JP 2017-96826 A (Patent Document 1) describes a technique for measuring the torque using a magnetostrictive torque sensor arranged around the rotating shaft. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-96826 A Summary of the Invention [Problem to be solved by the invention]

[0005] The magnetostrictive torque sensor described in JP 2017-96826 A has room for further improvement in terms of improving the torque measurement accuracy. That is, in order to improve the torque measurement accuracy of the magnetostrictive torque sensor, it is effective to precisely regulate the distance between the detection unit of the magnetostrictive torque sensor and the detection surface of the rotating shaft. In contrast, in the structure described in JP 2017-96826 A, the drive plate that connects the crankshaft of the engine and the case of the torque converter so as to be able to transmit torque is used as the detection member, and the detection unit of the magnetostrictive torque sensor supported and fixed to the cylinder block of the engine is opposed to the drive plate. Therefore, in order to regulate the distance between the detection unit of the magnetostrictive torque sensor and the detection surface of the rotating shaft, it is necessary to sufficiently ensure the shape accuracy and assembly accuracy of each part constituting the engine and the torque converter, which may increase the manufacturing cost of the automobile.

[0006] In view of the above-mentioned circumstances, an object of the present invention is to realize a magnetostrictive torque sensor structure capable of improving the torque measurement accuracy. [Means for solving the problem]

[0007] The magnetostrictive torque sensor of the present invention is attached to a part that does not rotate even when in use, and is positioned opposite the detection surface of a rotating body having magnetostrictive properties, and measures the torque transmitted by the rotating body by utilizing the inverse magnetostriction effect generated in the rotating body. The magnetostrictive torque sensor of the present invention is It comprises a holder made of synthetic resin and a detection portion embedded in the holder. The detection portion is disposed around the entire circumference of the detection surface. The holder includes a main body portion that holds the detection portion, and At least one positioning protrusion, the tip of which is in sliding contact with or closely opposed to the detection surface of the rotating body. and has. The at least one positioning protrusion is arranged so as to protrude radially inward from three or more circumferential locations on the inner surface of the main body, or is arranged so as to protrude radially inward from the inner surface of the main body around the entire circumference. Effect of the Invention

[0008] According to the magnetostrictive torque sensor of the present invention, the torque measurement accuracy can be improved. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is an end view of a magnetostrictive torque sensor according to an embodiment as viewed from the axial direction. [Diagram 2] FIG. 2 is a cross-sectional view taken along line XX in FIG. [Diagram 3] FIG. 3 is a schematic diagram showing a detection unit of a magnetostrictive torque sensor according to one example of an embodiment in an expanded state, where (A) is a diagram showing the first detection coil and the fourth detection coil, and (B) is a diagram showing the second detection coil and the third detection coil. [Figure 4] FIG. 4 is a circuit diagram showing a measurement section of a magnetostrictive torque sensor according to an embodiment. [Diagram 5] FIG. 5 is a view corresponding to FIG. 2, showing a modified example of the magnetostrictive torque sensor according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An example of an embodiment of the present invention will be described with reference to Figs. 1 to 5. The magnetostrictive torque sensor 1 of this example is attached to a non-rotating member such as a casing that does not rotate even when in use, and is arranged around a rotating shaft 2 having magnetostrictive properties to measure the torque transmitted by the rotating shaft 2. That is, the magnetostrictive torque sensor 1 has a detection unit 3 facing a detection surface 4 provided on the outer circumferential surface of the rotating shaft 2. The magnetostrictive torque sensor 1 detects a change in the magnetic permeability of the rotating shaft 2 that occurs when the rotating shaft 2 transmits torque using the detection unit 3 based on the inverse magnetostriction effect, and measures the torque transmitted by the rotating shaft 2.

[0011] The magnetostrictive torque sensor 1 includes a detection unit 3, a holder 5, and a measurement circuit 6.

[0012] The detection unit 3 includes a bobbin 7, a plurality of detection coils 8a to 8d each made of an insulated wire wound around the bobbin 7, and a back yoke 9.

[0013] The bobbin 7 has a cylindrical shape and is made of a resin material, which is a non-magnetic material. The bobbin 7 has, on its outer circumferential surface, a plurality of first inclined grooves 10a inclined at a predetermined angle (+45 degrees in the illustrated example) with respect to the axial direction of the bobbin 7, and a plurality of second inclined grooves 10b inclined at a predetermined angle (-45 degrees in the illustrated example) in the opposite direction to the first inclined grooves 10a with respect to the axial direction of the bobbin 7. The inclination angles of the first inclined grooves 10a and the second inclined grooves 10b can be set arbitrarily.

[0014] Of the multiple detection coils 8a to 8d, the first detection coil 8a and the fourth detection coil 8d are each formed by winding an insulated wire along the first inclined groove 10a of the bobbin 7. In contrast, of the multiple detection coils 8a to 8d, the second detection coil 8b and the third detection coil 8c are each formed by winding an insulated wire along the second inclined groove 10b of the bobbin 7.

[0015] That is, the multiple detection coils 8a to 8d are stacked in the radial direction. The first detection coils 8a are arranged at equal intervals in the circumferential direction, and adjacent first detection coils 8a in the circumferential direction are connected in series. The second detection coils 8b are arranged at equal intervals in the circumferential direction, and adjacent second detection coils 8b in the circumferential direction are connected in series. The third detection coils 8c are arranged at equal intervals in the circumferential direction, and adjacent third detection coils 8c in the circumferential direction are connected in series. The fourth detection coils 8d are arranged at equal intervals in the circumferential direction, and adjacent fourth detection coils 8d in the circumferential direction are connected in series.

[0016] The first detection coil 8a and the fourth detection coil 8d detect a change in magnetic permeability of the rotating shaft 2 in a first direction inclined at a predetermined angle (+45 degrees in the illustrated example) with respect to the axial direction of the rotating shaft 2. The second detection coil 8b and the third detection coil 8c detect a change in magnetic permeability of the rotating shaft 2 in a second direction inclined at a predetermined angle (-45 degrees in the illustrated example) opposite to the first direction with respect to the axial direction of the rotating shaft 2. The insulated wires constituting the detection coils 8a to 8d are electrically connected to a measurement circuit 6.

[0017] The back yoke 9 has a cylindrical shape, is made of a magnetic material (ferromagnetic material) such as iron, and is fixed to the outside of the bobbin 7. The back yoke 9 has a function of suppressing leakage of magnetic flux generated by the detection coils 8a to 8d arranged around the bobbin 7 to the outside.

[0018] The holder 5 includes a main body portion 11, a plurality of positioning protrusions 12 (three in the illustrated example), and a connector portion 13.

[0019] The main body 11 has a cylindrical shape. The main body 11 is disposed around the rotating shaft 2, and holds the detection unit 3 therein. In other words, the detection unit 3 is embedded (molded) inside the main body 11.

[0020] Each of the positioning protrusions 12 protrudes radially inward from each of a plurality of circumferential locations (three locations equally spaced circumferentially in the illustrated example) on the inner peripheral surface of the main body 11. Each of the positioning protrusions 12 has a tip (a radially inner end) in sliding contact with or closely facing, preferably in sliding contact with, the detection surface 4 of the rotating shaft 2. In this example, each of the positioning protrusions 12 has, at its tip, a concave curved surface portion 14 in the shape of a partial cylindrical surface centered on the central axis of the main body 11.

[0021] In this example, as shown in Fig. 2, each of the positioning protrusions 12 protrudes radially inward from an end portion on one axial side (the left side in Fig. 2) of the inner circumferential surface of the main body portion 11. However, as shown in Fig. 5, for example, each of the positioning protrusions 12 may protrude over the entire axial length from the inner circumferential surface of the main body portion 11. Alternatively, each of the positioning protrusions may protrude radially inward from an axial middle portion or an end portion on the other axial side of the inner circumferential surface of the main body portion.

[0022] The connector portion 13 protrudes radially outward from one circumferential location on the outer circumferential surface of the main body portion 11. A harness 15 is connected to the connector portion 13. The harness 15 electrically connects the insulated wires constituting the detection coils 8a to 8d to the measurement circuit 6. Alternatively, a substrate portion on which the measurement circuit 6 is mounted may be embedded inside the holder 5, and a torque signal output by a torque calculation portion 16 of the measurement circuit 6 may be extracted by the harness 15.

[0023] The holder 5 of this example can be made by injection molding a thermoplastic resin such as epoxy resin, polyphenylene sulfide (PPS), PA (polyamide), or PPA (polyphthalamide). That is, a mold is placed around the detection unit 3, molten resin is injected into a cavity defined between the detection unit 3 and the mold, and the molten resin is cooled and solidified. In this way, the holder 5 is molded, and the detection unit 3 is embedded inside the main body 11 of the holder 5.

[0024] The measurement circuit 6 detects a change in inductance of each of the detection coils 8a to 8d, thereby measuring the torque transmitted by the rotating shaft 2. The measurement circuit 6 includes a bridge circuit 17, an oscillator 18, a voltage measurement device (lock-in amplifier) ​​19, and a torque calculation unit 16.

[0025] The bridge circuit 17 is formed by connecting the first detection coil 8a, the second detection coil 8b, the third detection coil 8c, and the fourth detection coil 8d in a ring shape. The oscillator 18 applies an AC voltage between a contact A between the first detection coil 8a and the second detection coil 8b and a contact B between the third detection coil 8c and the fourth detection coil 8d. The voltage measuring device 19 detects a voltage between a contact C between the first detection coil 8a and the third detection coil 8c, and a contact D between the second detection coil 8b and the fourth detection coil 8d. The torque calculating unit 16 calculates the torque transmitted by the rotating shaft 2 based on the output signal of the voltage measuring device 19.

[0026] To measure the torque transmitted by the rotating shaft 2 using the magnetostrictive torque sensor 1 of this embodiment, an AC voltage is applied between points A and B by the oscillator 18, and an AC current is passed through each of the detection coils 8a to 8d. Then, in each of the detection coils 8a to 8d, currents in the opposite directions flow between pairs of detection coils adjacent in the circumferential direction. As a result, an AC magnetic field is generated around the detection coils 8a to 8d, and part of the magnetic flux of the AC magnetic field passes through the surface layer of the rotating shaft 2. In this state, when torque is applied to the rotating shaft 2, the magnetic permeability of the rotating shaft 2 increases (or decreases) in the +45 degree direction with respect to the axial direction due to the inverse magnetostriction effect, and the magnetic permeability of the rotating shaft 2 decreases (or increases) in the -45 degree direction with respect to the axial direction. Therefore, the inductance decreases (or increases) in the first detection coil 8a and the fourth detection coil 8d, and the inductance increases (or decreases) in the second detection coil 8b and the third detection coil 8c. As a result, the value of the voltage detected by voltage measuring device 19 changes, and torque calculation unit 16 calculates the torque transmitted by rotating shaft 2 based on this voltage value.

[0027] On the other hand, when the rotating shaft 2 is not transmitting torque, the inductances of the detection coils 8a to 8d are equal to each other, so the voltage detected by the voltage measuring device 19 becomes zero.

[0028] In the magnetostrictive torque sensor 1 of this embodiment, the main body 11 of the holder 5 is disposed around the detection surface 4 of the rotating shaft 2, and the concave curved surface 14 of the positioning protrusion 12 is in sliding contact with or closely facing the detection surface 4 of the rotating shaft 2. As a result, in the magnetostrictive torque sensor 1, the detection unit 3 is disposed around the detection surface 4 and faces the detection surface 4. At least the part of the rotating shaft 2 including the detection surface 4 is made of a material having magnetostrictive properties, such as steel (iron alloy) such as SCr420 (chrome steel), SCM420 (chrome molybdenum steel), and SNCM420 (nickel chrome molybdenum steel). Specifically, the entire rotating shaft 2 can be made of a material having magnetostrictive properties. Alternatively, the part including the detection surface 4 can be made of a material having magnetostrictive properties and can be fixed to a part constituting the remaining part.

[0029] It is also possible to form a modified layer with improved magnetostrictive characteristics by performing a shot peening process on the detection surface 4. By forming such a modified layer, it is possible to improve the sensitivity and hysteresis of the torque measurement by the magnetostrictive torque sensor 1.

[0030] In the magnetostrictive torque sensor 1 of this embodiment, the concave curved surface portions 14 provided at the respective tips of the positioning protrusions 12 of the holder 5 are in sliding contact with or closely facing the detection surface 4 of the rotating shaft 2, preferably in sliding contact with the detection surface 4 of the rotating shaft 2. Therefore, the distance between the detection unit 3 embedded inside the main body 11 of the holder 5 and the detection surface 4 of the rotating shaft 2 can be precisely regulated without excessively increasing the shape precision and assembly precision of the parts of the mechanical device including the magnetostrictive torque sensor 1 and the rotating shaft 2. In other words, the radial positioning of the detection unit 3 with respect to the detection surface 4 of the rotating shaft 2 can be precisely performed. Therefore, the torque measurement precision of the magnetostrictive torque sensor 1 can be improved without excessively increasing the manufacturing cost of the mechanical device.

[0031] Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be modified as appropriate without departing from the technical concept of the invention.

[0032] Books In this example, a positioning protrusion 12 is formed on the holder 5 in which the detection unit 3 is embedded. It is outside the scope of the present invention. However, a positioning protrusion may be formed on the bobbin around which the detection coil is wound, and the tip of the positioning protrusion may be brought into sliding contact with or close to the detection surface of the rotating body. In this case, the radial outside of the bobbin may be covered with a holder made of synthetic resin.

[0033] In this example, the positioning protrusions 12 are disposed at multiple locations in the circumferential direction, but the positioning protrusions may also be formed in an annular shape over the entire circumference. However, when the tip of the positioning protrusion comes into sliding contact with the detection surface of the rotating body, it is preferable to intermittently dispose the positioning protrusions at multiple locations in the circumferential direction, preferably at three or more locations, in order to reduce the sliding contact resistance by reducing the sliding contact area between the tip of the positioning protrusion and the detection surface of the rotating body.

[0034] In this example, four pairs of detection coils 8a to 8d form a bridge circuit 17, but two of the four pairs of detection coils forming the bridge circuit can be replaced with resistors. Alternatively, instead of a coil member consisting of multiple detection coils and a bobbin, a magnetic sensor equipped with a magnetic detection element such as a Hall element, a Hall IC, an MR element, a GMR element, an AMR element, a TMR element, or an MI element can be used.

[0035] In this example, the detection unit 3 of the magnetostrictive torque sensor 1 is disposed around the detection target surface 4 provided on the outer circumferential surface of the rotating shaft 2. Although it is outside the technical scope of The detection portion is disposed so as to face in the axial direction a detection target surface provided on the axial side surface of the rotor. Let In this case, the positioning protrusion is formed so as to protrude in the axial direction toward the detection surface.

[0036] The magnetostrictive torque sensor of the present invention can be incorporated into, for example, an automobile power train for use. In this case, the device into which it is incorporated is not particularly limited, and can be a transmission that changes gears under vehicle control, such as an automatic transmission (AT), a belt-type continuously variable transmission, a toroidal-type continuously variable transmission, an automatic manual transmission (AMT), or a double clutch transmission (DCT), or a transfer case. In addition, the drive system (FF, FR) of the target vehicle is not particularly limited.

[0037] Furthermore, the magnetostrictive torque sensor of the present invention can be incorporated and used not only in automobile powertrains, but also in various types of machinery and devices such as bicycles including electrically assisted bicycles, windmills, railway vehicles, rolling machines, machine tools, construction machinery, agricultural machinery, and household electrical appliances. [Explanation of symbols]

[0038] 1. Magnetostrictive torque sensor 2 Rotation Axis 3. Detection section 4. Surface to be detected 5 Holder 6 Measurement circuit 7 Bobbin 8a First detection coil 8b Second detection coil 8c Third detection coil 8d 4th detection coil 9 Back Yoke 10a 1st inclined groove 10b 2nd inclined groove 11 Main body 12 Positioning protrusion 13 Connector part 14 Concave curved part 15 Harness 16 Torque calculation section 17 Bridge Circuit 18 Oscillators 19 Voltage measuring device

Claims

[Claim 1] A magnetostrictive torque sensor that is attached to a part that does not rotate even when in use, is disposed opposite to a detection surface of a rotating body having magnetostrictive properties, and measures a torque transmitted by the rotating body by utilizing an inverse magnetostrictive effect generated in the rotating body, A synthetic resin holder; A detection unit embedded in the holder; Equipped with The detection portion is disposed around the entire circumference of the detection surface, the holder has a main body portion that holds the detection portion, and at least one positioning protrusion having a tip portion that is in sliding contact with or closely opposed to the detection surface of the rotating body, The at least one positioning protrusion is provided so as to protrude radially inward from three or more circumferential positions on the inner circumferential surface of the main body, or is provided so as to protrude radially inward from the inner circumferential surface of the main body over the entire circumference. Magnetostrictive torque sensor.

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