JP2013015459A - Torque sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a torque sensor having a distortion detection part whose detection sensitivity and detection accuracy have been improved.SOLUTION: A torque sensor comprises: a torque transmission shaft 2 that transmits torque with torsion generated between a load-side end portion 2d to which a load-side shaft P1 of a load device P is connected and a drive-side end portion 2c to which driving force is input; bearings 5, 5 that rotatably support the torque transmission shaft 2; and a distortion detection part 40 that detects distortion generated on the torque transmission shaft 2 due to torque input. On the load-side end portion 2d of the torque transmission shaft 2, a load-side connection part 2s is formed that fits in the load-side shaft P1 in the inner circumference of the load-side shaft P1 to allow an engaging structure for keeping almost constant a phase relationship between the load-side connection part and the load-side shaft P1 in their rotational directions. On the torque transmission shaft 2, between the bearings 5 closer to the load-side connection part 2s and the load-side connection part 2s, a thin thickness part 2t is circumferentially formed, whose thickness is further thinner than a spline groove 2s1 having the smallest thickness in the radial direction in the load-side connection part 2s. The distortion detection part 40 is disposed on the thin thickness part 2t.

Description

  The present invention relates to a torque sensor with optimized detection accuracy and detection sensitivity.

  2. Description of the Related Art Conventionally, a torque sensor that detects torque acting on a shaft of a driving device such as a motor that is rotationally driven by electromagnetic action is known. For example, Patent Document 1 discloses a coupling that transmits a torque while being twisted between the drive side and the load side, having a hollow shaft shape and both axial ends connected to the shaft of the drive device and the shaft of the load device, respectively. A torque transmission shaft, a strain detector such as a strain gauge that is attached to the inner peripheral surface forming a hollow space inside the torque transmission shaft and detects strain generated on the inner peripheral surface by torque input, and a strain detection housed in the hollow space Disclosed is a strain gauge type torque sensor that includes a transmission unit such as a telemeter that transmits a detection result of a part to the outside of the hollow space, and calculates the magnitude of torque acting on the torque transmission shaft based on the detection result received from the transmission unit Has been. Generally, the strain gauge type torque sensor is attached to the drive device in a cantilever state or is integrally incorporated therein.

Japanese Patent Laid-Open No. 51-131777

  2. Description of the Related Art In recent years, a torque sensor corresponding to high-speed rotation such as 50,000 rotations / minute is desired, for example, as drive devices such as motors are driven at high speed. In order to cope with high-speed rotation, in addition to the improvement in detection sensitivity of the strain detection unit, the diameter of the torque transmission shaft is reduced in order to prevent the torque transmission shaft from being destroyed by centrifugal force. There is a need to. In the strain gauge type torque sensor in which the transmission unit is housed in the torque transmission shaft as in the conventional case, the shaft itself is more easily bent as the shaft is made thinner, and torque transmission is performed to secure a space for housing the transmission unit. Since the axial dimension of the shaft must be secured to some extent, a general cantilever support structure does not hold, and it is necessary to have a structure that rotatably supports the torque transmission shaft via a plurality of bearings arranged along the axial direction. There is.

  In such a bearing support structure, for example, if a strain detection unit is disposed between two bearings, friction (mechanical loss) at the bearing adversely affects the strain detection unit, and detection accuracy at the strain detection unit is impaired. Can be considered.

  In order to reduce this adverse effect, it is conceivable as an effective means to dispose a strain detector between the load-side shaft end of the torque transmission shaft and the load-side bearing. In this configuration, when connecting portions having spline grooves are provided in the shaft end of the load side of the torque transmission shaft and the shaft of the load device, and the shafts are connected to each other so that torque can be transmitted. In addition, the strain detector is disposed in the vicinity of the connecting portion of the torque transmission shaft. In this case, there is a possibility that stress is biased due to the concave portion or the convex portion constituting the connecting portion, and distortion due to torque input cannot be detected in a well-balanced manner by the strain detecting portion, and the detection accuracy may be impaired.

  In addition to the above, factors that impair the detection accuracy of the strain detection unit include conical mode vibration and parallel mode vibration that occur in the torque transmission shaft as it rotates. In order to suppress the occurrence of such vibrations, it is desirable to dispose the bearing as close to the shaft end of the torque transmission shaft as possible by increasing the distance between the bearings.

  The same applies to not only the strain gauge type torque sensor using a strain gauge as a strain detector, but also a magnetostrictive type torque sensor having a magnetostrictive film whose permeability changes depending on strain on the outer peripheral surface of the torque transmission shaft. The same can be said not only when the connecting portion for connecting the torque transmission shaft and the shaft of the load device is constituted by a spline groove, but also when the connecting portion is constituted by a key or a key groove, for example. Of course, the same applies to the case where the strain detection unit is disposed between the driving-side shaft end of the torque transmission shaft and the driving-side bearing.

  The present invention has been made paying attention to such problems, and an object of the present invention is to provide a torque sensor with improved detection sensitivity and detection accuracy of a strain detection unit.

  In order to achieve this object, the present invention takes the following measures.

  In other words, the torque sensor according to the present invention is driven with the load side by the load being input to one end in the axial direction via the load side shaft of the load device and the driving force being input to the other end in the axial direction via the drive side shaft of the drive device. A torque transmission shaft that transmits torque while twisting between the side, a fixed support portion that rotatably supports the torque transmission shaft via a plurality of bearings arranged along the axial direction, and the torque input by torque input A torque sensor that detects a distortion generated in the transmission shaft, and calculates a magnitude of a torque acting on the torque transmission shaft based on a detection result of the strain detection unit, wherein the torque transmission shaft At least one of the load-side end and the drive-side end is fitted to the shaft on either the outer peripheral side or the inner peripheral side of the shaft to be connected to each other, thereby rotating each other in the rotational direction phase. A connecting portion having a meshing structure for maintaining the engagement substantially constant is formed, and the diameter of the connecting portion is between the bearing and the connecting portion closer to the connecting portion of the torque transmission shaft. A thin portion having a thinner thickness than the thinnest portion in the direction is formed around the thin portion, and the strain detecting portion is disposed in the thin portion.

  In order to maintain the phase relationship in the rotational direction to be almost constant, in addition to being mounted on the same axis so as to be able to rotate synchronously, the phase in the rotational direction can be mounted so as to be able to rotate integrally while allowing some backlash or misalignment. Means the case. Examples of this meshing structure include spline grooves and key grooves.

  As described above, although the stress concentration location is biased by the convex and concave portions such as the spline grooves constituting the connection portion, the thickness in the radial direction is the thinnest in the connection portion in order to reduce the influence due to the bias of the stress concentration location. A thin part with a smaller thickness than the part is formed around the part, and the strain detection part is placed in this thin part, reducing the influence on the strain detection part due to uneven stress concentration in the connection part. Is possible. In addition, since the strain detection unit is located outside the load (load side or drive side), the influence of friction (mechanical loss) on the bearing on the strain detection unit is reduced, and the detection accuracy at the strain detection unit is reduced. Can be improved. Further, since the portion where the strain detection unit is disposed is a thin portion having a thin radial thickness compared to the surroundings, stress is more likely to be concentrated than other portions, and the detection sensitivity of the strain detection unit is improved. It becomes possible.

  Also, for example, when the connecting part is a spline shaft or bearing having a spline groove, the axial dimension of the relief part of the gear cutting tool necessary for forming the spline groove is a dimension that can be attached to the strain detection part. Since the relief part can be used as a thin part simply by spreading it out to the shaft part, the shaft dimension from the shaft end to the bearing (overhang dimension) can be reduced compared to the case where a thin part is formed separately from the relief part. It is also possible to suppress the occurrence of vibration in the parallel mode.

  In order to improve detection accuracy by improving the detection balance of the plurality of strain detection units, the connection unit includes a plurality of spline grooves arranged at regular intervals along the circumferential direction, A plurality of pairs are attached so as to make a pair at symmetrical positions around the axis, and the circumferential phase relationship between the strain detector and the spline groove is set to be the same for all strain detectors. It is effective.

  As described above, the present invention further reduces the thickness of the connecting portion from the thinnest portion in the radial direction in order to reduce the influence of the bias of the stress concentration portion caused by the concave portion or the convex portion in the connecting portion. Since the thinned thin part is formed around and the strain detection part is arranged in this thin part, the influence on the strain detection part due to the bias of the stress concentration part of the connection part can be reduced, and the detection accuracy of the strain detection part Can be improved.

  Furthermore, since the part where the strain detection unit is arranged is a thin part that is thinner in the radial direction than the surrounding area, stress is more likely to concentrate than other parts, and the detection sensitivity of the strain detection part is improved. Is possible.

  Therefore, it is possible to provide a torque sensor with improved detection accuracy and detection sensitivity.

Sectional drawing which shows the structure of the torque sensor which concerns on one Embodiment of this invention. The figure which shows typically drive apparatuses, such as a motor, to which the torque sensor is applied. The block diagram of a fitting shaft, and the figure which shows the fitting state of a torque transmission shaft and a fitting shaft. The figure which shows typically the structure of the connection part of a torque transmission shaft and a load apparatus, and its vicinity. The figure which looked at the load side connection part of a torque transmission shaft from the axial direction. The figure which shows typically the positional relationship of a spline groove | channel and a distortion | strain detection part. The figure which shows typically the structure of the torque sensor which concerns on other embodiment of this invention.

  Hereinafter, a torque sensor according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the torque sensor Ts is a device that measures the magnitude of torque acting on the torque transmission shaft 2 interposed between the drive device M and the load device P, and has a substantially hollow shaft shape. Both ends 2c and 2d in the direction are connected to the drive side (drive device M) and the load side (load device P), respectively, and a torque transmission shaft 2 that transmits torque while being twisted between the drive side and the load side, and a torque transmission shaft A strain gauge that is attached to an inner peripheral surface 2a that forms an internal space SP1 in the interior of 2 and outputs a detection signal (differential signal) corresponding to strain generated in the torque transmission shaft 2 by torque input to the torque transmission shaft 2 was used. Acting on the torque transmission shaft 2 based on the strain detection unit 40, the transmission unit 30 that transmits the detection signal of the strain detection unit 40 to the outside of the torque transmission shaft 2, and the detection signal received from the transmission unit 30 via the antenna unit 33. Do A torque calculation unit 31 for calculating the size of the torque and a substantially hollow shaft shape are fitted into the torque transmission shaft 2 on the inner peripheral side of the torque transmission shaft 2, thereby forming a double hollow shaft together with the torque transmission shaft 2. And a fitting shaft 8. As illustrated in FIG. 2, the torque sensor Ts includes a driving device such as a motor provided with the torque sensor Ts by connecting the axial end 1 c of the torque transmission shaft 2 and the driving force output shaft M <b> 3 a (driving side shaft). Used to construct M. In the present specification, the axial direction is X, the drive side is X1, and the load side is X2.

  As shown in FIG. 1, the torque transmission shaft 2 is made of a steel material having a substantially hollow shaft shape in which an internal space SP <b> 1 is formed, and the cross-sectional shape of the inner peripheral surface 2 a is the outer periphery of the fitting shaft 8. The shape corresponds to the cross section of the surface 8b. The fitting shaft 8 is press-fitted into the internal space SP1 from the drive side X1 by an interference fit so that the outer peripheral surface 8b of the fitting shaft 8 and the inner peripheral surface 2a of the torque transmission shaft 2 are brought into contact with each other. ing. As shown in FIGS. 1 and 4, one end 2c in the axial direction of the torque transmission shaft 2 (end portion 2c on the driving side X1) is connected to a driving force output shaft M3a (shaft) of a driving device M such as a motor that rotates and splines. The driving force is input by the driving device M in association with the connection, and the other axial end 2d of the torque transmission shaft 2 (end portion 2d on the load side X2) is associated with the load side shaft P1 of the load device P by spline connection. The load is input by the load device P.

  As shown in FIGS. 1 and 4, the torque transmission shaft 2 is rotatably supported by a fixed support portion 6 via a bearing 5. The bearing 5 uses a rolling bearing such as a ball bearing, and a plurality (two in this embodiment) are provided along the axial direction so as to support the torque transmission shaft 2 at a plurality of places (two in this embodiment). Has been placed.

  As shown in FIG. 4, the load-side end 2d of the torque transmission shaft 2 is fitted with the load-side shaft P1 on the inner peripheral side of the load-side shaft P1 to be connected to each other, so that the phase relationship in the rotational direction is mutually established. There is provided a load side connection portion 2s having a meshing structure that is maintained substantially constant. Similarly, a drive side connection portion 2r for connecting to the output shaft M3a (drive side shaft) is also provided at the drive side end portion 2c of the torque transmission shaft 2. As shown in FIG. 5, the load side connection portion 2s and the drive side connection portion 2r have a plurality of spline grooves 2s1 formed on the outer peripheral surface 2b of the torque transmission shaft 2 at regular intervals along the circumferential direction. The torque transmission shaft 2 forms a male involute spline shaft. The load side shaft P1 shown in FIG. 4 forms a female involute spline bearing corresponding to this. As shown in FIG. 5, the outer peripheral surface 2b of the torque transmission shaft 2 has tooth portions 2s2 divided by spline grooves 2s1, and the spline grooves 2s1 and the tooth portions 2s2 are alternately formed along the circumferential direction. The groove bottom is the thinnest part in the radial direction. The radial dimension of the groove bottom is represented as D1.

  As shown in FIG. 4, the radial thickness of the load side connection portion 2s is the largest between the bearing 5 near the load side connection portion 2s of the torque transmission shaft 2 and the load side connection portion 2s. A thin portion 2t having a thinner thickness than the thin portion (spline groove 2s1) is formed to circulate. That is, it can be said that the thin portion 2t is formed outside the plurality of bearings 5 and inside the load side connection portion 2s. The thin portion 2t can also be called a constricted portion whose radial direction dimension D2 is thinner than the radial direction dimension D1 of the spline groove 2s1 constituting the load side connection portion 2s, and for forming the spline groove 2s1 in the torque transmission shaft 2. It is also a relief of a cutting tool such as a gear cutting tool to be used, and its axial dimension W1 is set to a dimension that allows the strain detector 40 to be attached by making it wider than the minimum required dimension W2 as a relief of the cutting tool. Yes. The boundary portion between the thin-walled portion 2t and the load-side connecting portion 2s has a curved longitudinal sectional shape so that the wall thickness smoothly changes along the axial direction, thereby avoiding stress concentration.

As shown in FIGS. 3 (a) and 3 (c), the fitting shaft 8 is made of a resin such as a glass epoxy resin having a bottomed substantially hollow shaft shape in which a hollow space SP0 is formed. Yes. The hollow space SP0 provided inside the fitting shaft 8 is closed on the axial one end 8c side (drive side X1), while being opened on the other axial end 8d side (load side X2) through the opening 8e. Has been. In the fitted state, as shown in FIG. 1, an internal space SP1 inside the torque transmission shaft 2 in which the strain detecting unit 40 is arranged and a hollow space SP0 inside the fitting shaft 8 are arranged through the opening 8e. Communicate. The hollow space SP0 for accommodating the transmitting unit 30 in the fitting shaft 8 has an elongated shape along the axial direction, and passes through the shaft center Cn and ends of the load side X2 as shown in FIG. from part 8d (one axial end) and the first hole 8h ₁ toward the driving side X1 (axial end), as shown in FIG. 3 (a) and FIG. 3 (d), the axially X in cross-section the orthogonal lines Li conducting a second hole 8h ₂ is a through-hole along the street radially X3 are formed. These first bore 8h ₁ and the second hole 8h ₂ of are emptied by working such as drills and wire cutting. As shown in FIG. 1, in the fitted state with the torque transmission shaft 2, the protruding fitting shaft support portion 20 provided on the inner peripheral surface 2 a of the torque transmission shaft 2 and the shaft of the fitting shaft 8. The fitting shaft 8 is positioned in the axial direction by contacting the other end 8d in the direction (the end 8d on the load side X2).

  As shown in FIG. 1, the strain detector 40 uses a sheet-like strain gauge that detects a minute change in mechanical dimensions as an electrical signal, and forms an internal space SP <b> 1 inside the torque transmission shaft 2. And it is affixed on the inner peripheral surface 2a along the circle centered on the axis Cn via an adhesive. The application position of the strain detector 40 is set on the inner peripheral surface 2a of the thin portion. In the present embodiment, the strain detectors 40 are respectively attached to positions symmetrical about the axis Cn so that the strain detectors 40 are paired or paired, and the plurality of strain detectors are subjected to a Wheatstone bridge by a known 4-gauge method. They are connected to form a circuit. This bridge circuit outputs a change in resistance value caused by the distortion of the distortion detector 40 as a differential voltage that can also be called a detection signal in a state where an excitation voltage that can also be called an excitation signal is applied. This differential voltage is a voltage proportional to the amount of distortion, and is a signal corresponding to the distortion. Further, as shown schematically in FIG. 6 in which the outer peripheral surface 2b and the inner peripheral surface 2a of the torque transmission shaft 2 are developed and schematically shown, all of the phase relationships in the circumferential direction RD between the strain detector 40 and the spline groove 2s1 are The distortion detection unit 40 is set to be the same. In the present embodiment, as shown in FIG. 6, the center of the sensitive area of the strain detector 40 and the center of the spline groove 2s1 are set to overlap in the circumferential direction, but the present invention is not limited to this. is not.

  As shown in FIG. 1 and FIG. 3A, the transmission unit 30 has a plate-like portion 30a such as a printed circuit board, applies an excitation voltage to the strain detection unit 40, and receives a differential voltage from the strain detection unit 40. A telemeter that transmits to the outside of the torque transmission shaft 2 is used. The telemeter is disposed in the hollow space SP0 of the fitting shaft 8 and is held by a mounting portion 80 provided on the inner surface 8a of the hollow space SP0.

  As shown in FIGS. 1 and 3A, the attachment portion 80 is a slit into which an end portion of the plate-like portion 30a of the transmission portion 30 can be inserted, and a plurality of attachment portions 80 are formed on the inner surface 8a forming the hollow space SP0. Yes. Specifically, as shown in FIGS. 3A and 3C, when the hollow space SP0 is regarded as a bottomed cylindrical hollow portion, the first attachment portion is provided on the inner surface 8a corresponding to the bottom portion. 80a is formed, and second mounting portions 80b and 80b that are paired with the inner peripheral surface 8a in the vicinity of the opening 8e are formed. The first and second mounting portions 80a and 80b are long. The transmitter 30 is supported in a both-sided state.

  As shown in FIG. 1, an antenna portion 33 is provided on the outer peripheral side of the torque transmission shaft 2. Two bearings 5, 5 are arranged on both sides of the antenna portion 33 in the axial direction. Further, outside the torque transmission shaft 2, a torque calculation unit 31 that receives the detection signal transmitted from the transmission unit 30 via the antenna unit 33 and calculates the magnitude of the torque by calculation processing, and the transmission unit 30 On the other hand, a power supply unit 32 that supplies power via the antenna unit 33 in a non-contact manner is provided.

  That is, as shown in FIG. 1, power is supplied from the power supply unit 32 to the transmission unit 30 via the antenna unit 33, and an excitation voltage is applied to the distortion detection unit 40. When torque acts on the torque transmission shaft 2, the torque transmission shaft 2 is twisted, and this twist is detected as a strain amount by the strain detector 40 attached to the inner peripheral surface 2 a of the torque transmission shaft 2. A detection signal (differential voltage) corresponding to the amount of strain output from the strain detection unit 40 is transmitted from the transmission unit 30 to the torque calculation unit 31, and the torque calculation unit 31 calculates the magnitude of torque based on the detection signal. .

  As shown in FIG. 1, the fixed support portion 6 has a substantially bottomed cylindrical shape, and a cylindrical support in which a base end portion 60a of the drive side X1 is attached to the housing M1 of the drive device M via a fastening device such as a bolt. Part 60 and a lid-like support part 61 that closes the opening 60k on the load side X2 of the cylindrical support part 60. The bearing 5 is arranged in the internal space SP2 formed by the cylindrical support part 60 and the lid-like support part 61, and the fixed support part 6 has the bottom part 60bt of the cylindrical support part 60 and the lid-like support part 61 in the axial direction. The torque transmission shaft 2 disposed at a position penetrating along X is supported rotatably via a bearing 5 so that the torque transmission shaft 2 and the fitting shaft 8 can rotate together. The bearing 5 includes a projecting rotation-side bearing support portion 64 a formed on the outer peripheral surface 2 b of the torque transmission shaft 2, and a fixed-side bearing support portion using the lid-like support portion 61 and the bottom portion 60 bt of the cylindrical support portion 60 as a scaffold. 64b and is fixed in the axial direction.

  As shown in FIG. 1, a refrigerant supply path 7 is provided for supplying the refrigerant introduced from the axial one end 2c side (drive side X1) of the torque transmission shaft 2 to the bearing 5 so as not to communicate with the internal space SP1. . Specifically, as shown in FIGS. 3A, 3B, and 3C, the outer peripheral surface 8b of the fitting shaft 8 is axially moved from the axial one end 8c side (drive side X1). A groove 81 extending toward the other end 8d side (load side X2) is provided, and as shown in FIGS. 1 and 3 (d), the groove portion is in the fitted state of the torque transmission shaft 2 and the fitting shaft 8. A thrust path 71 for supplying the refrigerant introduced from one side in the axial direction X to the bearing 5 is formed between 81 and the opposing surface of the groove 81 (the inner peripheral surface 2a of the torque transmission shaft 2). I have to.

  As shown in FIG. 1 and FIGS. 3A to 3C, an introduction path 70 and a connection path 72 are provided as components constituting the refrigerant supply path 7 other than the thrust path 71. The introduction path 70 is a path through which the refrigerant is introduced from the axial end 8c (drive side X1) through the axial center Cn of the fitting shaft 8 that is inside in the fitted state, and the connection path 72 is an outer periphery from the introduction path 70. This is a path that extends toward, and connects the introduction path 70 and the thrust path 71. The thrust path 71 is provided with a plurality of injection paths 73 for ejecting refrigerant to each bearing 5, and the thrust path 71 serves as a main path and the injection path 73 serves as a branch path to supply refrigerant to each bearing 5. A flow path is formed by branching from one thrust path 71. Corresponding to the injection path 73, the fixed-side bearing support portion 64b is in a position overlapping with the injection path 73 in the radial direction, and a curved guide surface 64x for guiding the refrigerant supplied from the injection path 73 to the bearing 5 is formed. Has been.

  As shown in FIG. 3D, a plurality (two in this embodiment) of the groove portions 81 are provided to form a pair, and the pair of groove portions 81 and 81 are arranged at positions that are symmetric about the axial center Cn. As shown in FIG. 1, each connection path 72 is connected to a branch portion 70 a at the tip of the introduction path 70. Thereby, the load balance in the whole axis | shaft is taken.

  As schematically shown in FIG. 2 using a conceptual diagram, the driving device M uses a well-known motor or the like, and is fixed to the housing M1 and generates a magnetic field. And a rotor M3 that is supported by the housing M1 in a rotatable state and rotates by receiving a magnetic field. The magnetic field is changed by energization control to the stator M2, and a repulsive force is generated between the stator M2 and the rotor M3. The rotor M3 is rotated by applying a suction force or the like, and the rotational driving force is output from the electric energy. The torque transmission shaft 2 is connected to the driving force output shaft M3a (shaft) of the rotor M3 so that the driving force is input to the torque transmission shaft 2, and the fixed support portion 6 is attached to the housing M1. . Further, the driving force output shaft M3a constituting the driving device M is rotatably supported by an output shaft bearing M4, and a mechanism including an output shaft bearing M4 and a heat generating unit (not shown) through the refrigerant therein. A part of the flow path M5 for supplying the refrigerant to the component is configured, and the introduction path 70 formed inside the torque transmission shaft 2 is configured such that the refrigerant is introduced from the output shaft M3a. Of course, the torque transmission shaft 2 and the driving force output shaft M3a (shaft) may be integrally formed as the same member, and the fixed support portion 6 and the housing M1 may be integrally formed as the same member. In this case, it is possible to reduce the axial dimension of the entire device including the torque sensor and the drive device. The driving device M shown in FIG. 2 is only a conceptual diagram, and is not limited to the illustrated driving device. A drive device other than a motor may be used.

  As described above, in the torque sensor Ts of the present embodiment, the load is input to the one axial end (2d) and the driving force is input to the other axial end (2c) via the load side shaft P1 of the load device P. The torque transmission shaft 2 can be rotated via a torque transmission shaft 2 that transmits torque while twisting between the load side X2 and the drive side X1, and a plurality of bearings 5 and 5 arranged along the axial direction X. A fixed support portion 6 for supporting and a strain detection portion 40 for detecting strain generated in the torque transmission shaft 2 by torque input, and the magnitude of torque acting on the torque transmission shaft 2 based on the detection result of the strain detection portion 40. The torque sensor Ts calculates the rotation direction of the torque transmission shaft 2 by engaging with the load side shaft P1 on the inner side of the load side shaft P1 to be connected to the load side end 2d of the torque transmission shaft 2. The phase relationship of A load-side connecting portion 2s having a meshing structure that is maintained constant is formed. Between the bearing 5 on the load side X2 of the torque transmission shaft 2 and the load-side connecting portion 2s, the load-side connecting portion 2s. A thin portion 2t having a thinner thickness than the thinnest portion in the radial direction (spline groove 2s1) is formed around the thin portion 2t, and the strain detector 40 is disposed in the thin portion 2t.

  As described above, the stress concentration portion is biased by the spline groove 2s1 and the tooth portion 2s2 constituting the load side connection portion 2s. In order to reduce the influence of the bias of the stress concentration portion, the load side connection portion 2s Since the thin portion 2t (radial dimension D2) having a smaller thickness than the radial dimension D1 of the spline groove 2s1, which is the thinnest part in the radial direction, is formed around the load side connection. It is possible to reduce the influence on the strain detection unit 40 due to the uneven stress concentration of the portion 2s. In addition, since the strain detection unit 40 is disposed outside the load 5 (load side X2), the influence of friction (mechanical loss) on the bearing on the strain detection unit 40 is reduced. Detection accuracy can be improved. Furthermore, since the part where the strain detection unit 40 is disposed is the thin part 2t having a small radial thickness compared to the surroundings, stress is more likely to concentrate than other parts, and the detection sensitivity of the strain detection unit 40 Can be improved.

  For example, when the load side connecting portion 2s is a spline shaft or bearing having the spline groove 2s1 as in the present embodiment, the axial dimension W2 of the clearance portion of the gear cutting tool necessary for forming the spline groove 2s1 is set as follows: Since the relief part can be used as the thin part 2t simply by expanding the axial dimension W1 to the extent that the strain detection part 40 can be attached, it is possible to use the relief part from the shaft end to the bearing as compared with the case where the thin part is formed separately from the relief part. The axial dimension (overhang dimension) can be reduced, and it is also possible to suppress the occurrence of vibrations in the conical mode and the parallel mode.

  Further, in the present embodiment, the load side connection portion 2s has a plurality of spline grooves 2s1 arranged at regular intervals along the circumferential direction RD, and the strain detection portion 40 is symmetric about the axis Cn. A plurality of pairs are attached so as to be paired with each other, and the phase relationship in the circumferential direction RD between the strain detection unit 40 and the spline groove 2s1 is set so as to be the same in all the strain detection units 40. It is possible to improve the detection balance at the unit 40 and improve the detection accuracy.

  As mentioned above, although embodiment of this invention was described based on drawing, it should be thought that a specific structure is not limited to these embodiment. The scope of the present invention is shown not only by the above description of the embodiments but also by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the present embodiment, the torque sensor Ts is configured to be incorporated in the drive device M, but may be configured alone. In the present embodiment, the load side end 2d of the torque transmission shaft 2 is provided with a load side connection 2s, and the bearing 5 and the load side connection 2s closer to the load side connection 2s of the torque transmission shaft 2 are provided. A thin-walled portion 2t is provided between them, but a drive-side connection portion is provided at the drive-side end 2c of the torque transmission shaft 2, and the bearing closer to the drive-side connection portion of the torque transmission shaft and the drive-side connection portion A thin portion may be provided between the two, and the strain detector may be disposed on the thin portion. Of course, a connecting portion and a thin portion may be provided at both ends of the torque transmission shaft.

  In the present embodiment, the phase relationship in the rotational direction is maintained substantially constant by a meshing structure in which either the torque transmission shaft 2 or the load side shaft P1 is a spline bearing and the other is a spline shaft. However, it is not limited to spline connection. For example, a key groove may be provided on either the torque transmission shaft or the load side shaft, and a key may be provided on the other side so that torque can be transmitted by a key structure.

  Furthermore, in this embodiment, the torque transmission shaft 2 is a male spline bearing that is fitted to the load-side shaft P1 on the inner peripheral side of the load-side shaft P1, but as shown in FIG. The transmission shaft 102 may be a female type that is fitted to the load side shaft P1 on the outer peripheral side of the load side shaft P1. In this case, the radial dimension of the spline groove, which is the thinnest portion of the load-side connecting portion 102s, is D3, and the radial dimension D4 of the thin portion 102t is formed to be thinner than D3.

  Furthermore, in the present embodiment, the strain detector 40 is provided on the inner peripheral surface 2a of the thin portion 2t, but may be provided on the outer peripheral surface of the thin portion 2t.

  In the present embodiment, a strain gauge is described as an example of the strain detection unit 40, but other strain gauges may be used as long as the strain generated in the torque transmission shaft can be detected. For example, as shown in FIG. 7B, the torque transmission shaft 202 is formed with a connecting portion 202s having a spline groove and a thin portion 202t as a constricted portion, and an outer peripheral surface 202b of the thin portion 202t. It is also possible to provide a magnetostrictive torque sensor that is provided with a magnetostrictive film 241 whose permeability changes depending on strain, and detects a torque by reading a change in the magnetic permeability of the magnetostrictive film 241 with the excitation coil 242 and the detection coil 243.

  The specific configuration of each part is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

2 ... torque transmission shaft 2c ... drive side end 2d ... load side end 2s ... load side connection (connection)
2r ... Drive side connection part (connection part)
2s1 ... Spline groove 2t ... Thin portion 40 ... Strain detection portion 5 ... Bearing 6 ... Fixed support portion P ... Load device P1 ... Load side shaft X ... Axial direction X1 ... Drive side X2 ... Load side

Claims (2)

While a load is input to one end in the axial direction through the load side shaft of the load device and a driving force is input to the other end in the axial direction through the drive side shaft of the drive device, the twist is caused between the load side and the drive side. Torque transmission shaft that transmits torque, a fixed support portion that rotatably supports the torque transmission shaft via a plurality of bearings arranged along the axial direction, and distortion that detects distortion generated in the torque transmission shaft by torque input A torque sensor that calculates a magnitude of torque acting on the torque transmission shaft based on a detection result of the strain detection unit,
At least one of the load side end portion and the drive side end portion of the torque transmission shaft is fitted to the shaft on the outer peripheral side or the inner peripheral side of the shaft to be connected to each other in the rotational direction. A connecting portion that forms a meshing structure that maintains the phase relationship substantially constant is formed, and between the bearing and the connecting portion closer to the connecting portion of the torque transmission shaft, A torque sensor characterized in that a thin portion having a thinner thickness is formed around the portion having the smallest radial thickness, and the strain detecting portion is disposed in the thin portion.   The connecting portion has a plurality of spline grooves arranged at regular intervals along the circumferential direction, and a plurality of strain detecting portions are attached so as to be paired at positions symmetrical about the axis. The torque sensor according to claim 1, wherein a phase relationship in a circumferential direction between the detection unit and the spline groove is set to be the same in all the strain detection units.

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