JP2019052913A - Torque load member and torque transmission device - Google Patents

Abstract

To realize a torque load member capable of effectively improving sensitivity of torque measurement while suppressing hysteresis of the torque measurement.SOLUTION: As a structure of a rotating shaft 1 as a torque load member, a structure that a detected surface 5 facing a magnetostrictive torque sensor 3 is included and that circumferential-direction residual compressive stress in a range from 7.5 μm to 50 μm of depth from the detected surface 5 is 800 MPa or more is adopted.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a torque load member that is loaded with torque during use and used to measure the torque, and a torque transmission device.

  In the field of automobiles, in recent years, the torque transmitted by the rotating shaft that constitutes the powertrain (power transmission mechanism) is measured, and the measurement results are used to control the output of the engine and electric motor that are power sources, Development of a system for executing transmission shift control is in progress.

  Conventionally, as a technique for measuring torque transmitted by a torque load member such as a rotating shaft, magnetostrictive techniques are known (for example, Japanese Patent Application Laid-Open Nos. 2017-96825 and 2017-96826). reference). In the magnetostrictive torque measurement technique, the torque is measured using a phenomenon (inverse magnetostrictive effect) in which the permeability of the torque load member changes according to the applied torque. Specifically, using a torque sensor opposed to the torque load member, the torque loaded on the torque load member is measured as a change in the magnetic permeability of the surface layer portion of the torque load member.

JP 2017-96825 A JP 2017-96826 A

  In the magnetostrictive torque measurement technique, it is desired to provide specific means capable of effectively improving the sensitivity of torque measurement while suppressing the hysteresis of torque measurement.

  The present invention has been made in view of the circumstances as described above, and an object thereof is to provide specific means capable of effectively improving the sensitivity of torque measurement while suppressing the hysteresis of torque measurement. There is.

The torque load member of the present invention has a detected surface that opposes the magnetostrictive torque sensor, and the circumferential residual compressive stress in the range from 7.5 μm to 50 μm in depth from the detected surface is 800 MPa or more. It has become.
In the torque load member of the present invention, the circumferential residual compressive stress in the range from 7.5 μm to 100 μm in depth from the detected surface can be 800 MPa or more.

The torque transmission device according to the present invention includes a torque load member having a detected surface and a magnetostrictive torque sensor opposed to the detected surface.
In particular, in the torque transmission device of the present invention, the torque load member is the torque load member of the present invention.
The torque sensor includes a coil that generates an alternating magnetic field in the surroundings, and the magnetic flux of the alternating magnetic field passes through the surface layer portion of the detection surface of the torque load member. What outputs a detection signal according to the magnetic permeability of a part can be employ | adopted.

  The torque transmission device according to the present invention employs a configuration in which a rolling bearing that rotatably supports the torque load member with respect to a portion that does not rotate during use is further provided, and the torque sensor is supported by the rolling bearing. can do.

  ADVANTAGE OF THE INVENTION According to this invention, the sensitivity of torque measurement can be improved effectively, suppressing the hysteresis of torque measurement.

FIG. 1 is a cross-sectional view of a torque transmission device showing an example of an embodiment of the present invention. FIG. 2A is a diagram showing only the rotating shaft and the torque sensor taken out from the torque transmission device shown in FIG. 1 and viewed from the outside in the radial direction. FIG. 2B is a diagram showing FIG. It is the figure seen from the axial direction. FIG. 3 is a developed view of the first to fourth coil layers constituting the detection unit of the torque sensor as viewed from the outside in the radial direction. FIG. 4A to FIG. 4D are developed views of the first to fourth coil layers constituting the detection unit of the torque sensor as viewed from the outside in the radial direction in a single state. FIG. 5 is a diagram illustrating a bridge circuit including first to fourth coil layers that constitute a detection unit of the torque sensor. FIG. 6 is a graph showing the relationship between the depth of the rotating shaft from the surface to be detected and the circumferential residual stress σR with respect to Examples 1 to 7 and Comparative Examples 1 to 5. FIG. 7 is a diagram showing the relationship between torque and sensor output. FIG. 8 is a graph showing torque measurement sensitivity and hysteresis with respect to Examples 1 to 7 and Comparative Examples 1 to 5.

[Example of Embodiment]
An example of the embodiment will be described with reference to FIGS.
FIG. 1 shows a torque transmission device. This torque transmission device includes a rotating shaft 1, a rolling bearing 2, and a torque sensor 3. In this example, the rotating shaft 1 corresponds to a torque load member.
In the following description regarding this example, regarding the torque transmission device, one axial side is the right side in FIG. 1 and the other axial side is the left side in FIG.

  The rotating shaft 1 is a torque transmitting shaft such as a rotating shaft of a transmission, a rotating shaft of a differential gear, a propeller shaft, and a drive shaft, which constitutes a power train of an automobile. The rotating shaft 1 is made of steel (iron alloy) such as SCr420 (chromium steel), SCM420 (chromium molybdenum steel), SNCM420 (nickel chromium molybdenum steel), which is a material having magnetostrictive characteristics, and is configured in a columnar shape or a cylindrical shape. Has been.

  The rotating shaft 1 has a cylindrical inner ring raceway 4 on a partial outer peripheral surface in the axial direction. Moreover, the rotating shaft 1 has the to-be-detected surface 5 in the location which adjoins the axial direction one side of the inner ring | wheel track 4 among the outer peripheral surfaces (location which attached the diagonal lattice in FIG. 1 and FIG. 2). The rotating shaft 1 has a circumferential residual compressive stress of 800 MPa or more in the range of the depth from the detected surface 5 to 7.5 μm to 50 μm in the surface layer portion of the detected surface 5.

  In this example, when the rotating shaft 1 is manufactured, the carburizing process is performed on the outer peripheral surface of the intermediate material of the rotating shaft 1, and then the shot peening process is performed on the detected surface 5. The circumferential residual compressive stress in the depth range of 7.5 μm to 50 μm is adjusted to be 800 MPa or more. Of the surface layer portion of the detection surface 5, at least a range from the detection surface 5 to a depth of 50 μm is a compression-processed hardened layer formed by shot peening. However, when carrying out the present invention, the adjustment method of the circumferential residual compressive stress of the surface layer portion of the detection surface 5 is not particularly limited. Such a rotating shaft 1 is rotatably supported by a rolling bearing 2 with respect to a stationary member that does not rotate during use, such as a housing constituting a power train of an automobile.

The rolling bearing 2 is a needle bearing and includes an outer ring 6, a plurality of needles 7, and a cage 8.
The outer ring 6 is made of steel such as bearing steel and has a cylindrical shape. The outer ring 6 has inward flanges 9 at both ends in the axial direction. Further, the outer ring 6 has a cylindrical outer ring raceway 10 on the inner circumferential surface in the axially intermediate portion sandwiched between the pair of inward flanges 9. Such an outer ring 6 is fitted in a stationary member such as a housing constituting a power train of an automobile and does not rotate during use.
Each of the plurality of needles 7 is made of steel such as bearing steel and has a cylindrical shape. These needles 7 are arranged between the outer ring raceway 10 and the inner ring raceway 4 so as to roll freely.
The cage 8 is made of steel or synthetic resin and has a cylindrical shape. The cage 8 has pockets at a plurality of locations in the circumferential direction, and the needles 7 are held in these pockets so that they can roll one by one.

  The torque sensor 3 is supported on the outer ring 6 via the sensor holder 11. The sensor holder 11 has a cylindrical shape made of metal, synthetic resin, or the like, and is attached to the outer ring 6 in a state of being adjacently disposed on one axial side of the outer ring 6. For this purpose, specifically, the fitting cylinder portion 12 provided at the other axial end of the sensor holder 11 is fitted and fixed to the inward flange portion 9 on one axial side of the outer ring 6. However, the sensor holder 11 can also be formed integrally with the outer ring 6.

  The torque sensor 3 includes a cylindrical back yoke 13 made of a magnetic material, and a detection unit 14 held inside the back yoke 13 in the radial direction. Such a torque sensor 3 is arranged around the detection surface 5 of the rotating shaft 1 coaxially with the detection surface 5, that is, with the detection unit 14 facing the detection surface 5, The sensor holder 11 is internally fitted and held.

  The detection unit 14 includes first to fourth coil layers 15 to 18 which are four coil layers each configured in a cylindrical shape. The first to fourth coil layers 15 to 18 are arranged in the radial direction with the first coil layer 15, the second coil layer 16, the third coil layer 17, and the fourth coil layer 18 arranged in this order from the radially inner side. Laminated. The first coil layer 15 and the second coil layer 16 are formed separately on one side and the other side of a strip-like flexible substrate (not shown), and are formed into a cylindrical shape by rolling the flexible substrate into a cylindrical shape. Has been. The third coil layer 17 and the fourth coil layer 18 are separately formed on one side surface and the other side surface of another strip-shaped flexible substrate (not shown), and the flexible substrate is rounded into a cylindrical shape to form a cylindrical shape. It is configured. An insulating layer is provided between the second coil layer 16 and the third coil layer 17.

  FIG. 3 shows a developed view of the detection unit 14 as viewed from the outside in the radial direction. 4 (a) to 4 (d) show development views in which the first to fourth coil layers 15 to 18 constituting the detection unit 14 are individually viewed from the outside in the radial direction.

  The first coil layer 15 (second coil layer 16, third coil layer 17, fourth coil layer 18) is formed as shown in FIG. 4A {FIG. 4B, FIG. 4C, FIG. 4D}. As shown in FIG. 2, a plurality of first detection coils 19 (second detection coil 20, third detection coil 21, and fourth detection coil 22) are provided. These first detection coils 19 (second detection coil 20, third detection coil 21, and fourth detection coil 22) are arranged side by side at equal pitches in the circumferential direction. The first detection coils 19 (second detection coil 20, third detection coil 21, and fourth detection coil 22) are adjacent to each other in the circumferential direction (adjacent to each other across both ends of the flexible substrate). Are connected in series. In addition, each of the first detection coil 19 and the fourth detection coil 22 includes wirings inclined at + 45 ° with respect to the axial direction of the rotary shaft 1 on both sides in the circumferential direction. On the other hand, each of the second detection coil 20 and the third detection coil 21 includes wirings inclined at −45 ° with respect to the axial direction of the rotary shaft 1 on both sides in the circumferential direction. In addition, when implementing this invention, the 1st-4th coil layers 15-18 can also be comprised by winding a coil around support members, such as a bobbin.

  The first to fourth coil layers 15 to 18 constitute a bridge circuit 23 as shown in FIG. In addition to the first to fourth coil layers 15 to 18, the bridge circuit 23 includes an oscillator 24 for applying an AC voltage between the points A and B, and a potential difference (medium) between the points C and D. And a lock-in amplifier 25 for detecting and amplifying a point voltage and a differential voltage).

  When the torque transmission device of this example is used, an alternating voltage is applied between the point A and the point B of the bridge circuit 23 by the oscillator 24 and an alternating current is passed through the first to fourth coil layers 15-18. Then, the first to fourth coil layers 15 to 18 include detection coils adjacent to each other in the circumferential direction, as indicated by arrows i, b, c, and d in FIGS. Currents in opposite directions flow (in other words, each detection coil is wound so that currents in such directions flow). As a result, an alternating magnetic field is generated around the first to fourth coil layers 15 to 18, and a part of the magnetic flux of the alternating magnetic field passes through the surface layer portion of the detection surface 5 of the rotating shaft 1.

  In this state, when the torque T in the direction shown in FIG. 2A is applied to the rotating shaft 1, the rotating shaft 1 has a tensile stress (+ σ) in the direction of + 45 ° relative to the axial direction and the axial direction. Compressive stress (−σ) in the −45 ° direction acts. Then, due to the inverse magnetostrictive effect, the permeability of the rotating shaft 1 increases in the + 45 ° direction where the tensile stress (+ σ) acts, and in the −45 ° direction where the compressive stress (−σ) acts. The magnetic permeability of the rotating shaft 1 is reduced.

  On the other hand, the first coil layer 15 and the fourth coil layer 18 are configured to include a wiring inclined by + 45 ° with respect to the axial direction of the rotary shaft 1, and one of the magnetic fluxes of the alternating magnetic field generated around the wiring. The part passes through the surface layer part of the detected surface 5 of the rotating shaft 1 in the −45 ° direction, which is the direction in which the magnetic permeability decreases. For this reason, the inductances of the first coil layer 15 and the fourth coil layer 18 are reduced. Further, the second coil layer 16 and the third coil layer 17 are configured to include a wiring inclined by −45 ° with respect to the axial direction of the rotating shaft 1, and the magnetic flux of the alternating magnetic field generated around the wiring. A part passes through the surface layer portion of the surface to be detected 5 of the rotating shaft 1 in the + 45 ° direction, which is the direction in which the magnetic permeability is increased. For this reason, the inductance of the 3rd detection coil 17 and the 4th detection coil 18 each increases.

  On the other hand, when the torque T in the direction opposite to the direction shown in FIG. 2A is applied to the rotating shaft 1, the first coil layer 15 and the fourth coil layer 18 have a reverse action to that described above. The inductance increases, and the inductance of the second coil layer 16 and the third coil layer 17 decreases.

  In any case, the bridge circuit 23 detects and amplifies the potential difference between the point C and the point D (midpoint voltage, differential voltage) by the lock-in amplifier 25, and thereby the torque applied to the rotary shaft 1 An output V corresponding to the direction and size of T is obtained. Therefore, if the relationship between the output V and the torque T is examined in advance, the direction and magnitude of the torque T can be obtained from the output V.

  In particular, in this example, in the surface layer portion of the detection surface 5 of the rotating shaft 1, the circumferential residual compressive stress in the range from 7.5 μm to 50 μm in depth from the detection surface 5 is 800 MPa or more. Yes. That is, in the surface layer portion of the detected surface 5 of the rotating shaft 1, the magnetic characteristic of the portion through which the magnetic flux generated from the torque sensor 3 passes is good, so that torque measurement is suppressed while suppressing torque measurement hysteresis. Can be effectively improved.

The torque load member that is the subject of the present invention is not limited to the rotating shaft, and may be, for example, a sleeve that is externally fixed to the rotating shaft and is loaded with torque together with the rotating shaft.
Further, the torque load member is not limited to a member having a detection surface on the peripheral surface, but is detected on the axial side surface as described in, for example, Japanese Patent Application Laid-Open No. 2017-96825 and Japanese Patent Application Laid-Open No. 2017-96826. It can also be a member having a surface.
When the torque load member that is the subject of the present invention is used by being incorporated in a power train of an automobile, the subject device is not particularly limited. For example, manual transmission (MT), automatic transmission (AT), belt type continuously variable transmission, toroidal type continuously variable transmission, automatic manual transmission (AMT), dual clutch transmission (DCT), etc. The transmission to be performed or the transfer can be targeted. Further, the driving method (FF, FR, MR, RR, 4WD, etc.) of the target vehicle is not particularly limited.
The torque load member that is the subject of the present invention is not limited to the rotating shaft that constitutes the power train of an automobile. For example, the rotating shaft of a windmill (main shaft, rotating shaft of a speed increasing device), the roll neck of a rolling mill, Rotating shafts of various mechanical devices such as rotating shafts (axles, rotating shafts of reduction gears), rotating shafts of machine tools (main shafts, rotating shafts of feed systems), construction machinery, agricultural machinery, household appliances, rotating shafts of motors, etc. Etc. can be adopted.

When implementing the torque transmission device of the present invention, the torque sensor is not limited to the rolling bearing, and may be supported by another member such as a housing.
When implementing the torque transmission device of the present invention and adopting a configuration in which the torque sensor is supported by a rolling bearing, the rolling bearing is not limited to a needle bearing, but is a ball bearing, a roller bearing, or a tapered roller bearing. Other types of rolling bearings may be used.
When implementing the torque transmission device of the present invention, the magnetostrictive torque sensor is not limited to the above-described embodiment, and is described in, for example, Japanese Patent Application Laid-Open Nos. 2017-96825 and 2017-96826. Various conventionally known ones can be used.

An experiment conducted to confirm the effect of the present invention will be described.
In this experiment, a plurality of rotating shafts (Examples 1 to 7, Comparative Examples 1 to 5) were prepared as samples. These rotating shafts have a surface to be detected in a part of the outer peripheral surface in the axial direction, and the residual compressive stresses in the circumferential direction of the surface layer portion of the surface to be detected are different from each other. For each of these rotating shafts, the applied torque was measured by a magnetostrictive torque sensor 3 (see FIGS. 1 and 2) opposed to the surface to be detected.

[Sample]
Specifications of the respective rotation shafts (Examples 1 to 7, Comparative Examples 1 to 5) are as follows.

Example 1
Shaft diameter D (see FIG. 1): 18 mm
Material: SCr420H
Treatment: After subjecting the outer peripheral surface to heat treatment, the surface to be detected was subjected to shot peening treatment.
Heat treatment conditions: carburization (950 ° C., 5 hours, carbon potential 1.25%)
→ Tempering (175 ° C, 1 hour)
→ Quenching (820 ℃, 1 hour)
→ Tempering (240 ° C, 2 hours)
Conditions for shot peening treatment: Projection material: Steel (spherical)
Projection material diameter 0.6mm
Projection material hardness: Hv700
Tank (air) pressure: 0.2 MPa
Coverage ... 300%

(Example 2)
Example 1 is the same as Example 1 except that the tank pressure in the shot peening process is 0.3 MPa.

(Example 3)
Example 1 is the same as Example 1 except that the tank pressure in the shot peening process is 0.5 MPa.

Example 4
The same as Example 1, except that the carbon potential in the carburizing process is 0.70%, the tempering temperature is 175 ° C., and the tank pressure in the shot peening process is 0.5 MPa.

(Example 5)
The same as Example 1 except that the tempering temperature was 175 ° C.

(Example 6)
The same as Example 1, except that the tempering temperature was 175 ° C. and the tank pressure in the shot peening process was 0.3 MPa.

(Example 7)
The same as Example 1 except that the tempering temperature was 175 ° C. and the tank pressure in the shot peening process was 0.5 MPa.

(Comparative Example 1)
Except that the shot peening process is omitted, the process is the same as in the first embodiment.

(Comparative Example 2)
Example 3 is the same as Example 3 except that the diameter of the projection material in the shot peening process is set to 0.05 mm.

(Comparative Example 3)
Example 4 is the same as Example 4 except that the shot peening process is omitted.

(Comparative Example 4)
Example 5 is the same as Example 5 except that the shot peening process is omitted.

(Comparative Example 5)
Example 7 is the same as Example 7 except that the diameter of the projection material in the shot peening process is set to 0.05 mm.

Table 1 and FIG. 6 show the circumferential residual stress σR of the surface layer portion of the surface to be detected of each rotating shaft (Examples 1 to 7, Comparative Examples 1 to 5).
In the graph of FIG. 6 (and the graph of FIG. 8 described later), Example 1 is abbreviated as “Real 1”, and Comparative Example 1 is abbreviated as “Ratio 1”. The same applies to other examples and comparative examples.
Further, the negative sign of the circumferential residual stress σR means that the circumferential residual stress σR is a circumferential residual compressive stress.

[Evaluation of torque measurement sensitivity and hysteresis]
About each rotating shaft (Examples 1-7, Comparative Examples 1-5), the loaded torque was measured with the magnetostrictive torque sensor 3 made to oppose a to-be-detected surface.
Specifically, an AC magnetic field is generated around the first to fourth coil layers 15 to 18 by applying an AC voltage between the points A and B of the bridge circuit 23 by the oscillator 24 shown in FIG. The magnetic flux generated by this alternating magnetic field passes through the surface layer of the surface to be detected (the range from the surface to be detected to the depth D). D was about 300 μm to 500 μm). In this state, torque measurement is performed while reciprocally changing the torque applied to the rotating shaft between positive and negative rated torques (T ₁ , T ₂ ), and characteristic data relating to torque measurement as shown in FIG. 7 is obtained. Obtained. And the sensitivity and hysteresis of torque measurement were obtained from this characteristic data. Sensitivity and hysteresis were defined as follows.
Sensitivity (mV) = α / γ = | A ₁ −A ₂ | / | T ₁ −T ₂ |
Hysteresis (% FS) = β / γ = | a ₁ −a ₂ | / | T ₁ −T ₂ |
Table 2 and FIG. 8 show the torque measurement sensitivity and hysteresis for each of the rotating shafts (Examples 1 to 7, Comparative Examples 1 to 5).

As shown in Table 2 and FIG. 8, rather than the examples (Comparative Example 1, Comparative Example 3, and Comparative Example 4) in which the shot peening process is omitted, the “Example 1” compared to the example in which the shot peening process is performed (Comparative Example 1). ~ Example 3, Comparative Example 2 "," Example 4 "for Comparative Example 3, and" Example 5 to Example 7, Comparative Example 5 "for Comparative Example 4) have improved torque measurement sensitivity. Is recognized.
In particular, in the example (Example 1 to Example 7) in which the circumferential residual compressive stress in the range from 7.5 μm to 50 μm in depth from the detected surface is 800 MPa or more, the hysteresis of torque measurement is suppressed. It is recognized that the sensitivity of torque measurement can be effectively improved (while keeping it at about 2.0% FS or less).
Further, in the examples (Examples 2, 3, 4, and 7) in which the circumferential residual compressive stress in the depth range from the detected surface to 7.5 μm to 100 μm is 800 MPa or more, the hysteresis of the torque measurement is It is recognized that the sensitivity of torque measurement can be more effectively improved while further suppressing.

DESCRIPTION OF SYMBOLS 1 Rotating shaft 2 Rolling bearing 3 Sensor 4 Inner ring raceway 5 Compression process hardening layer 6 Outer ring 7 Needle 8 Cage 9 Inward flange part 10 Outer ring raceway 11 Sensor holder 12 Fitting cylinder part 13 Back yoke 14 Detection part 15 First detection coil 16 Second detection coil 17 Third detection coil 18 Fourth detection coil 19 Bridge circuit 20 Oscillator 21 Lock-in amplifier

Claims (4)

  A torque load member having a detected surface that opposes a magnetostrictive torque sensor, and having a circumferential residual compressive stress of 800 MPa or more in a depth range from 7.5 μm to 50 μm from the detected surface.   2. The torque load member according to claim 1, wherein a circumferential residual compressive stress in a range from a depth of 7.5 μm to 100 μm from the detected surface is 800 MPa or more. A torque load member having a detected surface;
A magnetostrictive torque sensor opposed to the detected surface,
The torque load member is the torque load member according to any one of claims 1 and 2.
Torque transmission device. A rolling bearing that rotatably supports the torque load member with respect to a portion that does not rotate during use, and the torque sensor is supported by the rolling bearing;
The torque transmission device according to claim 3.

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