JP6216879B2 - Torque detection device - Google Patents

Description

  The present invention relates to an apparatus for detecting torque applied to a rotating shaft using a strain sensor such as a semiconductor strain sensor.

  In recent years, various devices for detecting torque generated in a rotating shaft used in an automobile have been developed. As an example, there is a torque detection device described in JP2013-174562A (Patent Document 1). The torque detection device of this document has a structure in which an attachment component having a strain detection portion is attached to a shaft for the purpose of reducing the size and weight of the device. Specifically, the torque detection device includes an attachment having a flat portion that is fixed to the outer peripheral surface of the rotary drive shaft and converts the torque of the rotary drive shaft into a strain on a plane, and a surface elasticity that is attached to the flat portion of the attachment. It is equipped with a wave sensor and a film antenna that is mounted around the rotary drive shaft and transmits / receives a transceiver antenna (see summary).

  Moreover, there is a semiconductor strain sensor as a sensor for detecting strain generated in the shaft when torque is applied. A semiconductor strain sensor is a device that uses a semiconductor piezoresistor in which a strain detector is formed by doping impurities such as silicon (Si) instead of a metal thin film. A semiconductor strain sensor has a resistance change rate with respect to strain as large as several tens of times that of a strain gauge using a metal thin film, and can measure a minute strain. In addition, since the resistance change is small in the metal thin film strain gauge, an external amplifier for amplifying the obtained electric signal is required. Since the semiconductor strain sensor has a large resistance change, the obtained electrical signal can be used without using an external amplifier. Even when an amplifier is required, an amplifier circuit can be built in the semiconductor chip of the semiconductor strain sensor, so that miniaturization and high accuracy can be realized. By using this sensor, it is considered that the application and convenience in use can be greatly improved. An example of a torque detection device using this sensor is, for example, a rotating body mechanical quantity measurement device described in Japanese Patent Application Laid-Open No. 2006-220574 (Patent Document 2). Specifically, the rotating body mechanical quantity measuring device has a chip shape formed of a semiconductor single crystal including a Wheatstone bridge circuit composed of an impurity diffusion layer having a specific crystal orientation as a longitudinal direction, and is attached to a rotating shaft. (See summary and paragraph 0010).

JP 2013-174562 A JP 2006-220574 A

  However, when the strain is measured by directly attaching the semiconductor strain sensor to the outer peripheral surface of the shaft (rotating shaft) as the object to be measured, if the strain amount of the shaft increases, the semiconductor strain sensor itself, which is silicon, will be destroyed. There are challenges. Silicon is susceptible to brittle fracture when a large strain is applied, and the strain range of elastic deformation is not wide compared to other materials. The strain range in which strain measurement is possible depends on the mounting conditions of the sensor, but one criterion is, for example, within ± 1000 με (hereinafter, ε is used as a symbol representing the amount of strain).

  Therefore, when applying a semiconductor strain sensor to a torque detector, it is necessary to design the shaft dimensions so that the amount of strain generated in this sensor when maximum torque is applied is within a certain allowable strain value (eg ± 1000 με). is there. If the generated strain is equal to or greater than the allowable strain value, generally, in order to reduce the generated strain, the shaft outer diameter is increased to increase the shaft rigidity. However, shaft dimensions are often determined from other factors and are often not easily changed.

  In Patent Document 1, a surface acoustic wave sensor that detects torque is attached to an attachment fixed to the outer peripheral surface of a shaft. However, the piezoelectric material substrate constituting the surface acoustic wave sensor is attached to the central portion in the axial direction of the shaft of the flat portion that converts the torque of the shaft into the strain on the plane. And in patent document 1, the attachment position of the sensor on a flat part is not considered in particular.

  The object of the present invention is to provide torque detection that can realize measurement of a large torque while ensuring reliability so that the sensor does not break even when a sensor that easily causes brittle fracture such as a semiconductor strain sensor is used. To provide an apparatus.

  In order to achieve the above object, a torque detection device of the present invention includes a protrusion 2 provided on the outer peripheral surface of a shaft member 1 to be subjected to torque measurement, and a strain sensor that measures strain mounted on the protrusion 2. 5, and the projecting portion 2 connects and fixes the mounting portion 4 on which the strain sensor 5 is mounted and the both end portions of the mounting portion 4 to the outer peripheral surface of the shaft member 1 at two locations separated in the axial direction of the shaft member 1. In the torque detection device that is configured with two connection portions 3 and the mounting portion 4 is provided apart from the outer peripheral surface of the shaft member 1, the strain sensor 5 includes one connection portion from the center in the axial direction of the mounting portion 4. 3 is biased to the side.

  According to the present invention, even when a sensor that easily causes brittle fracture, such as a semiconductor strain sensor, is used as a strain sensor, the reliability of the sensor is ensured so that the sensor is not broken, and the large torque applied to the shaft is measured. A torque detection device capable of achieving the above can be realized.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is a perspective view of the torque detection apparatus which is an Example of this invention. It is a side view of the torque detection apparatus which is an Example of this invention. It is a perspective view of the torque detection apparatus from which a shaft shape differs. It is a side view of the torque detection apparatus from which a shaft shape differs. It is a top view which shows typically the structure of the surface side of a semiconductor strain sensor. It is a top view which shows typically the structure of the surface side of a semiconductor strain sensor. It is a side view which shows typically the structure seen from the side surface of the semiconductor strain sensor. It is an enlarged view of a semiconductor strain sensor periphery of the torque detection apparatus which is the Example of this invention. It is a deformation | transformation schematic diagram of the shaft to which the torque was applied. It is a deformation | transformation figure of the shaft member at the time of torque application. It is a distortion distribution map which generate | occur | produces in the shaft member at the time of torque application. It is a strain distribution figure on the flat plate part at the time of torque application. It is a side view of the torque detection apparatus which is Example 2 of this invention. It is a side view of the torque detection apparatus which is Example 3 of this invention. It is a side view of the torque detection apparatus which is Example 4 of this invention. It is a side view of the shaft used for the torque detection apparatus which is Example 4 of this invention. It is a top view of the metal plate used for the torque detection apparatus which is Example 4 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted.

  1 and 2 are a perspective view and a side view of the torque detector of the present invention. The torque detector includes a shaft 1 to be measured, a semiconductor strain sensor 5, a wiring portion 10 (such as a flexible wiring board or a glass epoxy substrate) electrically connected to the semiconductor strain sensor 5, a battery component 11, and a wireless The communication part 12 is comprised. The purpose of this embodiment is to detect the torque 6 applied to the shaft 1. In FIG. 1, the wiring portion 10, the battery component 11, and the wireless communication component 12 are not shown.

  Details of the shaft 1 will be described with reference to FIGS. 1 and 2. Although the illustrated shaft is a hollow shaft, the present embodiment is not limited to the hollow shaft, and a solid shaft is also an object. The shaft 1 has a protrusion 2 on the outer peripheral surface. The protrusion 2 is formed integrally with the rotating shaft of the shaft 1 by cutting or the like. Therefore, the protrusion 2 is made of the same material as the shaft 1. The protrusion 2 is composed of two connection portions 3 and a flat plate portion 4. The two connection portions 3 are arranged at intervals in the direction of the rotation axis (axial center) 8 of the shaft 1 and are connected to the outer peripheral surface of the shaft 1. The flat plate portion 4 is formed between the two connection portions 3, and both ends of the flat plate portion 4 are connected to the connection portion 3. The flat plate portion 4 has a flat plate shape, the longitudinal direction of the flat plate is disposed substantially parallel to the rotation axis 8 of the shaft 1, and the surface 7 on which the sensor is mounted is formed substantially perpendicular to the circumferential direction of the shaft 1. That is, the flat plate portion 4 is arranged on a straight line extending in a radial direction (radial direction) from the rotation axis 8 of the shaft 1 on a cross section perpendicular to the rotation axis 8 of the shaft 1, and the sensor mounting surface 7 is in the straight line. Parallel.

  3 and 4 are a perspective view and a side view of another shape plan of the shaft 1. The connecting portion 3 of the shaft 1 shown in FIGS. 1 and 2 is formed on a part of the outer peripheral surface of the shaft. However, the shape of the connecting portion 3 may be formed on the entire outer periphery of the shaft 1 as shown in FIGS. 3 and 4. The material of the shaft 1 is not particularly specified, but a metal material such as steel for machine structure is often used.

  The protrusion 2 is reduced in size and weight in consideration of the rotation balance of the shaft 1 that is a rotating body. Nevertheless, in the configuration of FIGS. 1 and 2, there is a considerable unbalance of rotation. According to the configuration of FIGS. 3 and 4, the connecting portion 3 is formed on the entire circumference of the outer peripheral surface of the shaft, which is advantageous in eliminating the imbalance.

  5A and 5B are plan views schematically showing the configuration of the surface side of the semiconductor strain sensor 5. FIG. 5C is a side view schematically showing a configuration viewed from the side of the semiconductor strain sensor 5. The side view of FIG. 5C is common to the semiconductor strain sensor 5 shown in FIGS. 5A and 5B.

  As shown in FIGS. 5A, 5B, and 5C, the semiconductor strain sensor 5 includes a front surface (main surface) 5a and a back surface 5b located on the opposite side of the front surface 5a. A metal film is formed on the back surface 5 b of the semiconductor strain sensor 5. This metal film is composed of a laminated film (metal laminated film) in which, for example, titanium (Ti), nickel (Ni), and gold (Au) are sequentially laminated from the semiconductor substrate side, and can be formed, for example, by sputtering. Thus, by forming the metal film on the back surface 5b of the semiconductor strain sensor 5, the bonding strength with a metal bonding material such as solder can be improved. Further, the front surface 5a and the back surface 5b each form a quadrilateral (quadrangle), and in the example shown in FIGS. 5A and 5B, for example, each side has a length of about 2 mm to 5 mm. The semiconductor strain sensor 5 includes a plurality of resistance elements 15 (piezoresistive elements) formed in the sensor region 14 located in the central portion on the surface 5a side.

  The semiconductor strain sensor 5 includes a plurality of electrodes (pads, electrode pads 9) that are electrically connected to a plurality of resistance elements 15 (piezoresistive elements). The electrode pad 9 is formed in the input / output circuit region located on the peripheral side of the sensor region 14 on the surface 5a side. The plurality of resistance elements 15 are constituted by impurity diffusion regions in which, for example, an element formation surface of a silicon substrate having a (100) plane is doped and diffused. The semiconductor strain sensor 5 includes a Wheatstone bridge circuit 25 in which, for example, four resistance elements 15 are electrically connected. The Wheatstone bridge circuit 25 constitutes a detection circuit (strain detection circuit) that detects a strain by measuring a resistance change of the resistance element 15 due to the piezoresistance effect.

  The detection circuit 25 is connected to the plurality of electrode pads 9 via a plurality of wirings. The plurality of electrode pads 9 are input / output terminals of the semiconductor strain sensor 5. For example, a terminal Vcc that supplies a power supply potential (first power supply potential) to the sensor chip 1 and a reference potential (second power supply potential) are supplied. And a terminal SIG that outputs a detection signal. Further, the layout of the plurality of resistance elements 15 constituting the detection circuit 25 is not limited to the mode shown in FIG. 5, but the following configuration is adopted in the present embodiment. That is, when the semiconductor substrate (for example, a silicon substrate made of silicon (Si)) provided in the semiconductor strain sensor 5 is a single crystal (silicon single crystal), the extending direction (longitudinal direction) of the plurality of resistance elements 15 constituting the detection circuit 25 is described. Direction) coincides with the <110> direction or <100> direction of the semiconductor substrate having the (100) plane. For example, in the example shown in FIG. 5A, the semiconductor substrate (silicon substrate) provided in the semiconductor strain sensor 5 has a crystal orientation in the <110> direction of the silicon single crystal (the X direction and the Y direction orthogonal to the X direction in FIG. 5A). Four p-type diffusion regions (regions doped with impurities whose conductivity type is p-type) are formed so that a current flows along. In other words, in the semiconductor strain sensor 5, four resistance elements 15 are formed by doping p-type impurities at four locations so as to extend along the crystal orientation in the <110> direction of the silicon single crystal of the silicon substrate. The

  In the example shown in FIG. 5B, the semiconductor substrate (silicon substrate) included in the semiconductor strain sensor 5 has a crystal orientation in the <100> direction of the silicon single crystal (the X direction and the Y direction orthogonal to the X direction in FIG. 5B). Four n-type diffusion regions (regions doped with impurities whose conductivity type is n-type) are formed so that a current flows along. In other words, in the semiconductor strain sensor 5, four resistance elements 15 are formed by doping n-type impurities at four locations so as to extend along the crystal orientation in the <100> direction of the silicon single crystal of the silicon substrate. The

  As shown in FIGS. A and 5B, the semiconductor strain in which the extending directions of the plurality of resistance elements 15 constituting the detection circuit respectively coincide with the <110> direction or the <100> direction of the semiconductor substrate having the (100) plane. The sensor 5 can output the difference between the strain in the X direction shown in FIGS. 5A and 5B and the strain in the Y direction, for example. Specifically, the difference between the strain in the X direction and the strain in the Y direction can be output as a potential difference from the terminal SIG shown in FIGS. 5A and 5B. Thus, the measurement method that outputs the difference between the strain in the X direction and the strain in the Y direction is advantageous from the viewpoint of reducing the influence of the thermal strain applied to the semiconductor strain sensor 5.

  That is, as shown in FIG. 1, the semiconductor strain sensor 5 is mounted on the object to be measured which is the shaft 1, and therefore, when the measurement environment temperature changes, it is caused by the difference in the linear expansion coefficient between the shaft 1 and the semiconductor strain sensor 5. Thermal distortion occurs. Since this thermal strain is a noise component different from the strain to be measured, it is preferable to reduce the influence of thermal strain.

  Here, as shown in FIGS. 5A and 5B, when the planar shape of the semiconductor strain sensor 5 is a square, the influence of thermal strain is approximately the same in the X direction and the Y direction. For this reason, for example, when detecting the strain generated in the X direction, if the difference between the strain in the X direction and the strain in the Y direction is output, the strain amount due to the thermal strain is canceled, and the strain to be measured. Can be selectively detected.

  That is, if the semiconductor strain sensor 5 is used, the influence of thermal strain can be reduced, so that variation in strain values due to changes in environmental temperature can be reduced. In addition, since each member such as the resistance element 15 and the electrode pad 9 constituting the semiconductor strain sensor 5 can be formed by applying a known semiconductor device manufacturing technique, the elements and wirings can be easily miniaturized. . Moreover, manufacturing efficiency can be improved and manufacturing cost can be reduced.

  Next, a bonding material (not shown) for attaching the semiconductor strain sensor 5 to the shaft 1 will be described. The bonding material is provided so as to cover the entire back surface 5 b of the semiconductor strain sensor 5 and a part of the side surface of the semiconductor strain sensor 5. In other words, the peripheral edge portion of the bonding material may extend to the outside of the side surface of the semiconductor strain sensor 5 to form a fillet. From the viewpoint of fixing the semiconductor strain sensor 5 and the shaft 1, the bonding material is not limited to a metal material, and for example, a resin adhesive such as a thermosetting resin can be used.

  FIG. 6 shows an enlarged view of the vicinity of the semiconductor strain sensor 5. The semiconductor strain sensor 5 and the wiring part 10 are mounted on the flat plate part 4 of the shaft 1. The wiring unit 10 includes a plurality of wirings that are electrically connected to the plurality of electrode pads 9 of the semiconductor strain sensor 5. In addition, the wiring part 10 has a structure in which a wiring part that is a plurality of metal patterns is sealed in a resin film, and a part of the plurality of wirings is exposed in an opening provided in a part of the resin film. Thus, the exposed portion constitutes a plurality of terminals 10a. In the example shown in FIG. 6, the plurality of electrode pads 9 of the semiconductor strain sensor 5 and the plurality of terminals 10a of the wiring portion are electrically connected via a plurality of Au wires 13 (conductive members). . The wire 13 is, for example, a gold wire (Au wire) having a wire diameter of about 10 μm to 200 μm. Further, the semiconductor strain sensor 5 and the Au wire 13 are sealed with a sealing resin 16. By covering the wire 13 with the sealing resin 16, a short circuit between adjacent wires can be prevented. One end of the wiring part 10 is fixed to the flat plate part 4 as shown in FIG. For example, a connector (not shown) is formed at the other end of the wiring part 10 and is electrically connected to, for example, a board component or the like on which a circuit (not shown) for measuring strain is mounted. The other end of the wiring part 10 may be directly connected to a board component on which a strain measurement circuit is mounted. In FIG. 6, the wiring portion 10 and the wire 13 are described separately, but a plurality of wires 13 can also be regarded as a wiring portion. Moreover, the wiring part 10 should just be able to transmit input-output current between the semiconductor strain sensor 5 and the external apparatus which is not shown in figure, and is not limited to the aspect shown in FIG.

  As shown in FIG. 2, a battery 11 and a wireless communication component 12 are mounted on the shaft 1. The semiconductor strain sensor 5 is fixed to a shaft 1 that is a rotating body. Therefore, the battery 10 for operating the semiconductor strain sensor 5 is also fixed to the shaft 1. Further, the measured strain value is transmitted to an external measurement system unit (not shown) via the wireless communication component 12. Although an embodiment using a battery is shown in FIG. 2, in the present invention, it is also possible to use wireless power feeding by an electromagnetic induction method or a magnetic resonance method without mounting a battery.

  Next, the principle of torque detection will be described with reference to FIGS.

  When torque 6 is applied to the shaft 1, torsional deformation occurs on the outer peripheral surface of the shaft 1. FIG. 7 schematically shows the deformation amount of the outer peripheral surface of the shaft due to torsional deformation. FIG. 7 shows the amount of torsional deformation with an arrow when the right end 17 of the shaft in the figure is completely fixed and torque is applied to the left end 18. As shown in the figure, the amount of torsional deformation changes along the direction of the rotation axis 8 of the shaft 1. That is, there is a difference in the amount of torsional deformation at the two locations P1 and P2 that are separated from each other along the direction of the rotation axis 8 on the outer peripheral surface of the shaft. Here, in the case of the shaft of the present embodiment, as shown in FIG. 2, two connecting portions 3 are formed on the outer peripheral surface of the shaft at positions separated along the direction of the rotation axis 8. A difference occurs in the torsional deformation amount of the portion 3. Next, the flat plate portion 4 has a structure in which only both ends in the longitudinal direction are connected to the connection portion 3. A gap is formed between the side 4a (see FIG. 2) along the direction of the rotation axis 8 of the flat plate portion 4 and the shaft outer peripheral surface, and the side 4a and the shaft outer peripheral surface are not connected. Therefore, when a difference in the amount of torsional deformation occurs in the two connecting portions 3, bending deformation occurs in the flat plate portion 4.

  In summary, when a torque is applied to the shaft 1, bending strain occurs in the flat plate portion 4. This bending strain can be measured by the semiconductor strain sensor 5 mounted on the flat plate portion 4, and the torque applied to the shaft 1 can be measured.

  8 to 10 show the stress analysis results for verifying the measurement principle. A stress analysis was performed when torque was applied to the shaft material of the present example, and the deformation diagram of the flat plate portion 4 and the strain distribution generated on the flat plate portion 4 were verified. The analysis model was the shaft 1 shown in FIGS. 3 and 4 (a model in which the connecting portion 3 is formed on the entire outer periphery of the shaft). The right end portion of the shaft 1 was completely fixed, and torque was applied to the left end portion of the shaft 1. FIG. 8 shows a shaft deformation view when torque is applied. It can be seen that bending deformation occurs in the flat plate portion 4 due to the difference in torsional deformation amount of the two connection portions 3. Further, the fixed side 19 (right half side of the flat plate portion) of the flat plate portion 4 is deformed downward in the drawing, and the torque load side 20 (left half side of the flat plate portion) of the flat plate portion 4 is protruded upward in the drawing. It turns out that it becomes a deformation | transformation.

  Next, FIG. 9 shows a distribution diagram of bending strain generated in the flat plate portion 4. FIG. 10 shows a strain distribution diagram in the longitudinal direction of the flat plate portion 4 (on the line AA ′ in FIG. 9). In FIG. 9, the magnitude of the distortion is represented by shades of black and white. The closer to white, the greater the compressive strain, and the closer to black, the greater the tensile strain.

  As shown in FIGS. 9 and 10, compressive strain is generated on the upper surface 19 a of the fixed side 19 of the flat plate portion 4. This is because the flat plate portion 4 is deformed downward. On the other hand, tensile strain is generated on the upper surface 20 a of the flat plate portion 4 on the torque load side 20. This is due to the upward convex deformation. In addition, a tensile strain is generated on the lower surface 19b of the fixed side 19 of the flat plate portion 4, and a compressive strain is generated on the lower surface 20b of the torque load side 20.

  Further, as shown in FIG. 10, the strain generated in the center line 21 in the longitudinal direction of the flat plate portion 4 is 0, and the strain generated in the upper surfaces 19a and 20a of the flat plate portion 4 is substantially along the longitudinal direction on the flat plate portion. It can be seen that there is a linear change from compression to tensile strain. From the above, it was confirmed that bending strain was generated on the flat plate portion 4 as expected.

  The effect of the torque detection device according to the embodiment of the present invention will be described.

  The semiconductor strain sensor 5 of the present embodiment is not mounted on the center line 21 of the flat plate portion 4 but is mounted at a position off the center line 21. As can be seen from the stress analysis results shown in FIGS. 8 to 10, the generated strain on the center line 21 of the flat plate portion 4 is zero. Therefore, the semiconductor strain sensor 5 is not mounted on the center line 21 but mounted at a position away from the center line 21.

  In the present embodiment, in particular, the entire semiconductor strain sensor 5 is disposed at a position deviated from the center line (center line) 21 toward the one connection portion 3 side. Thereby, distortion can be detected reliably. The center line 21 represents a central position that is equidistant from the position at which the flat plate portion 4 is connected to the two connecting portions 3 in the longitudinal direction of the flat plate portion 4. According to the present embodiment, the semiconductor strain sensor 5 is arranged so as to be biased toward the one connecting portion 3 side from the central portion in the direction of the rotation axis (axial center) 8 of the flat plate portion (mounting portion) 4.

  Further, from the stress analysis result, the strain generated in the flat plate portion 4 changes from compression to tensile strain almost linearly along the longitudinal direction on the flat plate portion. Here, there is a strain value generated in the semiconductor strain sensor 5 when maximum torque is applied in order to enable measurement of a large torque while ensuring reliability so that the sensor is not destroyed. It is necessary to design so as to be within an allowable strain value (eg, ± 1000 με). In the case of the present embodiment, the bending strain on the flat plate portion 4 changes almost linearly from compression to tensile strain. Therefore, there is always a position on the flat plate portion 4 at which the strain value generated when the maximum torque is applied is equal to or less than the allowable strain value. If the semiconductor strain sensor 5 is mounted at such a position, it is possible to prevent the semiconductor strain sensor 5 from being broken and to ensure reliability. In the case of directly measuring the strain on the outer peripheral surface of the shaft, it has been stated that the shaft shape needs to be changed so that the generated strain value is below a certain allowable value. In the case of this embodiment, the shaft shape is changed. Without changing, only the attachment position to the flat plate portion 4 can be changed so that the generated strain can be designed to be a certain allowable value or less.

  In FIG. 11, the side view of the torque detection apparatus of a present Example is shown. The basic configuration is the same as that of the first embodiment. The difference from the first embodiment is that two semiconductor strain sensors 5 are mounted. As shown in FIG. 11, the semiconductor strain sensor 5 is mounted at a symmetrical position with respect to the center line 21 of the flat plate portion 4.

  As shown in FIG. 9 and FIG. 10, the strain generated on the flat plate portion 4 generates a compressive strain and a tensile strain with the center line 21 being symmetrical. That is, one of the strains generated in the two semiconductor strain sensors 5 is tensile strain and the other is compressive strain. Therefore, when estimating the load torque, it is possible to increase the magnitude of the sensor output value with respect to the load torque (that is, the sensor sensitivity) by acquiring the difference between the strain values measured by both sensors, and to improve the torque detection accuracy. Can be improved.

  In FIG. 12, the side view of the torque detection apparatus of a present Example is shown. The basic configuration is the same as that of the first embodiment. In this embodiment, two semiconductor strain sensors 5 mounted on the protrusions 2 </ b> A and 2 </ b> B are formed at point-symmetrical positions with respect to the shaft rotation axis 8. The protrusion 2A and the protrusion 2B have the same configuration as the protrusion 2 described in the first embodiment. However, the protrusions 2A and 2B are distinguished from each other by giving different reference numerals like the protrusion 2A and the protrusion 2B.

  The effect of the torque detector of the present embodiment will be described. It is conceivable that the bending deformation 22 shown in FIG. 12 is applied to the shaft 1 due to the influence of external force in addition to the torsional deformation caused by the torque. In this case, bending strain due to the bending deformation 22 is generated in the semiconductor strain sensor 5. For example, when the bending deformation 22 shown in FIG. 12 is applied, tensile strain is generated in the semiconductor strain sensor 5A and compressive strain is generated in the semiconductor strain sensor 5B. Here, when there is one protrusion 2 and one semiconductor strain sensor 5, the sensor output value is output by adding the strain generated by the torque and the strain generated by the bending deformation 22. Accuracy will be reduced.

  On the other hand, when a plurality of protrusions 2 and semiconductor strain sensors 5 are arranged symmetrically with respect to the shaft rotation axis 8 and bending deformation as shown in FIG. As for the strain, a compressive strain having the same magnitude as the tensile strain is generated in the semiconductor strain sensor 5B. For this reason, by adding the output values of both sensors 5A and 5B, it is possible to cancel the distortion caused by the bending deformation.

  As described above, in the case of the present embodiment, it is possible to cancel the influence of the strain variation caused by the bending deformation of the shaft 1, so that it is possible to improve the detection accuracy of the torque value that is the measurement target.

  The protruding portion 2A and the protruding portion 2B of the present embodiment may be configured like the protruding portion 2 of the second embodiment. That is, two semiconductor strain sensors 5 may be provided on each of the protrusions 2A and 2B.

  13 and 14 are a perspective view and a side view of the torque detection device of the present embodiment. Although the basic configuration is the same as that of the first embodiment, the flat plate portion 4 on which the semiconductor strain sensor 5 is mounted is separate from the shaft 1.

  As shown in FIGS. 13 and 14, the protruding portion 2 formed on the shaft 1 is composed of only the connecting portion 3. Further, a gap portion 24 is formed in the connection portion 3. FIG. 15 shows a metal plate 23 on which the semiconductor strain sensor 5 is mounted. The metal plate 23 is a member for constituting the flat plate portion 4 of each embodiment described above. Note that FIG. 15 does not show other parts such as wiring parts, wires, and sealing resin. In this embodiment, the metal plate 23 is inserted into the gap portion 24 and both ends of the metal plate 23 are fixed. Various methods such as adhesion, welding, and bolting are conceivable as the fixing method. In FIGS. 13 to 15, assuming that bolting is performed, round holes 23 a are processed at both ends of the metal plate 23. The connecting portion 3 is processed with a round hole 3a and a screw portion 3b. That is, in the two portions 3A and 3B that are opposed to each other through the gap 24, a circular hole 3a is formed in one portion 3A, and a screw portion 3b is formed in the other portion 3B.

  As described above, when the metal plate 23 on which the semiconductor strain sensor 5 is mounted and the shaft 1 are separated, the following effects can be considered. First, the process of connecting the semiconductor strain sensor 5 to the metal plate 23 is often heated at a high temperature by a heater or a high-temperature bath, but when mounted on the metal plate 23 having a small size, the temperature rise of the metal plate is rapid. You can save time. Moreover, since only the connection part 3 needs to be additionally processed in the shaft 1, the processing of the shaft 1 can be simplified.

  In addition, in the present Example, although the connection part 3 and the shaft 1 were the same members, both members are good also as a different body. By making the connecting portion 3 and the shaft 1 separate, the manufacturing time of the shaft 1 can be shortened and the material cost can be reduced. On the other hand, when the connection portion 3 and the shaft 1 are integrally formed, the shaft 1 and the connection portion 3 can be designed in consideration of the rotation balance, and rotation imbalance due to an attachment error or the like hardly occurs.

  The linear expansion coefficient (α) of the materials used for the shaft 1, the connection portion 3, and the metal plate 23 are all the same. In this case, even if the use environment temperature changes, thermal strain due to the difference in linear expansion coefficient does not occur, and the fluctuation of the output of the semiconductor strain sensor becomes small. That is, the torque estimation accuracy can be improved.

  In each of the above-described embodiments according to the present invention, the bending strain is zero on the center line (center line) 21 of the flat plate portion 4. Accordingly, the strain sensor 5 is disposed so as to be biased toward the connecting portions 3, 3 </ b> A, 3 </ b> B, avoiding the center line (center line) 21. For this reason, the length dimension in which at least one strain sensor 5 is accommodated on both sides of the center line (center line) 21 in the direction of the rotation axis 8 is required. That is, the length of the flat plate portion 4 in the direction of the rotation shaft 8 needs to be at least two lengths of the strain sensor 5. Further, in the vicinity of the center line (center line) 21, the bending strain becomes a very small value. In order to arrange the strain sensor 5 while avoiding the region where the bending strain is small, a sensor mounting portion having a length dimension that fits at least two strain sensors 5 on both sides of the center line (center line) 21 in the direction of the rotation axis 8. It is desirable to provide In this case, the length of the flat plate portion 4 in the direction of the rotation axis 8 needs to be at least the length of four strain sensors 5. In the embodiment described above, the five strain sensors 5 are arranged on one side of the center line (center line) 21 so that the magnitude of the bending strain received by the strain sensor 5 can be reliably changed and adjusted. The total length of 10 pieces is secured.

  In addition, you may apply the structure which concerns on protrusion part 2A, 2B of a present Example to Example 1- Example 3. FIG.

  In addition, this invention is not limited to each above-mentioned Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  DESCRIPTION OF SYMBOLS 1 ... Shaft, 2, 2A, 2B ... Projection part, 3, 3A, 3B ... Connection part, 3a ... Round hole, 3b ... Screw part, 4 ... Flat plate part, 4a ... Side along the longitudinal direction of a flat plate part, 5, 5A, 5B ... Semiconductor strain sensor, 5a ... Front surface of semiconductor strain sensor, 5b ... Back surface of semiconductor strain sensor, 6 ... Load torque, 7 ... Sensor mounting surface, 8 ... Shaft rotating shaft, 9 ... Electrode pad, 10 ... Wiring part DESCRIPTION OF SYMBOLS 10a ... Terminal of wiring part, 11 ... Battery, 12 ... Wireless communication component, 13 ... Wire, 14 ... Sensor area | region, 15 ... Resistance element (piezoresistive element), 16 ... Sealing resin, 17 ... Shaft fixing | fixed part (FIG. Middle right end), 18 ... shaft load portion (left end in the figure), 19 ... fixed side of plate 4 (right half side in the figure), 19a ... upper surface of fixed side 19, 19b ... lower surface of fixed side 19, 20: Torque load side of the flat plate portion 4 (left half in the figure) ), The upper surface of 20a ... torque load side 20, the lower surface of the 20b ... torque load side 20, 21 ... flat plate portion 4 of the center line, 22 ... bending deformation, 23 ... metal plate, 23a ... round hole, 24 ... clearance.

Claims (8)

A projection provided on the outer peripheral surface of the shaft member to be subjected to torque measurement, and a strain sensor for measuring strain mounted on the projection, wherein the projection mounts the strain sensor; and The connecting portion is composed of two connecting portions for connecting and fixing the both end portions of the mounting portion to the outer peripheral surface of the shaft member at two locations separated in the axial direction of the shaft member, and the mounting portion is separated from the outer peripheral surface of the shaft member. In the torque detection device provided
The strain sensor is arranged so as to be biased from the center of the mounting portion in the axial direction toward one connecting portion ,
The strain sensor is a semiconductor strain sensor in which a Wheatstone bridge circuit is formed on one semiconductor substrate,
The two semiconductor strain sensors are arranged so as to be point-symmetrical with respect to the rotation axis of the shaft member, and the output values of the two Wheatstone bridge circuits of the two semiconductor strain sensors are added. A torque detector characterized by the above. The torque detection device according to claim 1,
The mounting portion has a flat plate shape having a longitudinal direction, the longitudinal direction is disposed substantially parallel to the shaft rotation axis, and the surface on which the strain sensor is mounted is disposed substantially perpendicular to the circumferential direction of the shaft member. A torque detector characterized by the above. The torque detection device according to claim 2,
A torque detecting device, wherein another strain sensor is disposed at a position symmetrical to the position where the sensor is disposed with respect to the center of the mounting portion. The torque detection device according to claim 1,
The torque detector according to claim 1, wherein the connecting portion is formed integrally with the shaft member. The torque detector according to claim 4, wherein
The mounting portion is made of a metal plate separate from the connection portion, and is joined to the connection portion. The torque detection device according to claim 1,
The strain sensor is a semiconductor strain sensor in which a piezoresistive element is formed on a surface of a semiconductor substrate. The torque detection device according to claim 1,
The torque detection device, wherein the protrusion and the strain sensor are arranged symmetrically with respect to a rotation axis of the shaft member. The torque detection device according to claim 5,
The torque detector according to claim 1, wherein a linear expansion coefficient of a material of the shaft member and the connecting portion is equal to a linear expansion coefficient of a material of the metal plate.

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