JP6306218B2 - Torque detection device - Google Patents

Description

  The present invention relates to a torque detection device.

  In recent years, various devices for detecting torque generated in a rotating shaft used in an automobile have been developed. For example, the torque detection device described in Patent Document 1 employs a structure in which a flat plate-like attachment that converts the torque of the rotational drive shaft into a planar strain is fixed to the outer peripheral surface of the rotational drive shaft. A surface acoustic wave sensor is attached to the flat portion of the attachment.

  As a sensor for detecting strain generated in a shaft when torque is applied, for example, a semiconductor strain sensor described in Patent Document 2 is known. A semiconductor strain sensor is a device that utilizes a semiconductor piezoresistor formed by doping a semiconductor such as silicon (Si) with an impurity. 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. Furthermore, since the resistance change of the semiconductor strain sensor is large, the obtained electric signal can be used without using an external amplifier.

JP 2013-174562 A JP 2006-220574 A

  By the way, when a sensor is mounted on a flat attachment, by mounting the sensor at a position where the strain sensitivity is high, the amount of strain generated when a rated torque requiring measurement is applied can be increased, and the measurement accuracy can be improved. However, when a semiconductor strain sensor is used, the fracture strength of silicon, which is a sensor member, is smaller than the fracture strength of the steel material used for the shaft material, so there is a risk that the sensor will break if a strain greater than the rating occurs. there were.

A torque detection device according to an aspect of the present invention includes a flat plate that extends in the axial direction of the shaft and has both ends fixed to the outer peripheral surface of the shaft, and bends in the front-back direction as the shaft is twisted. A strain sensor that is mounted on the front surface or the back surface and detects strain of the flat plate; and a limiting portion that limits the amount of bending of the flat plate when the twist of the shaft is equal to or greater than a predetermined amount . The flat plate is provided on the outer peripheral surface so as to be separated from the flat plate in the direction of twisting the shaft. The strain sensor is disposed on the one end side with respect to a position where the restriction portion contacts .
A torque detection device according to another aspect of the present invention includes a flat plate that extends in the axial direction of the shaft and has both ends fixed to the outer peripheral surface of the shaft, and bends in the front-back direction as the shaft is twisted. A strain sensor that is mounted on the front surface or the back surface of the flat plate and detects the strain of the flat plate; and a limiting portion that limits the amount of bending of the flat plate when the twist of the shaft is equal to or greater than a predetermined amount. Is provided on the one end side of the flat plate and fixed to the outer peripheral surface, and extends from the first fixed portion toward the other end side of the flat plate and is spaced apart from the outer peripheral surface. A first arm portion, a second fixing portion fixed to the outer peripheral surface on the other end side of the flat plate, and the outer peripheral surface extending from the second fixing portion toward one end side of the flat plate. A second arm portion provided at a distance from the second arm portion. The first arm and the second arm are in contact with each other in the shaft twist direction, and one end of the flat plate is fixed to the first fixing portion. And / or at least one of the fixed parts to which the other end is fixed to the second fixed part and the flat plate is fixed via an elastic member having a smaller elastic modulus than the fixed part and the arm part. And is fixed to the outer peripheral surface of the shaft.

  According to the present invention, it is possible to prevent an excessive strain from being generated in the strain sensor.

FIG. 1 is a perspective view of a shaft provided with a torque detection device. FIG. 2 is a plan view of the torque detection device. FIG. 3 is a perspective view when the protrusion has a ring shape. FIG. 4 is a plan view when the protrusion is ring-shaped. FIG. 5 is a diagram showing a strain sensor provided on a flat plate. FIG. 6A is a plan view of the strain sensor. FIG. 6B is a side view of the strain sensor. FIG. 7 is a plan view showing another example of the strain sensor. FIG. 8 is a schematic diagram showing the amount of torsional deformation on the outer peripheral surface of the shaft. FIG. 9 is a side view of the torque detection device before torque application. FIG. 10 is a schematic diagram illustrating a state of the torque detection device when torque is applied. FIG. 11A is a diagram showing a portion on the left side from the center S in FIG. 10 and shows a state when the stopper comes into contact. FIG. 11B is a diagram showing a portion on the left side from the center S in FIG. 10 and shows a state in which the stopper is twisted by ΔR from the time of contact. FIG. 12 is a diagram illustrating the relationship between the load torque and the distortion generated at the sensor mounting position. FIG. 13 is a diagram for explaining the relationship between load torque and generated distortion in the conventional case. FIG. 14 is a diagram illustrating the predetermined position. FIG. 15 is a diagram when the constraint condition at the contact point P is assumed to be complete constraint. FIG. 16 is a diagram illustrating the relationship between the load torque when the strain sensor is shifted from a predetermined position and the strain generated at the sensor mounting position. FIG. 17 is a diagram illustrating a first modification. FIG. 18 is a diagram illustrating a second modification. FIG. 19 is a diagram illustrating a third modification. FIG. 20 is a perspective view of the torque detection device according to the second embodiment. FIG. 21 is a plan view of the torque detection device according to the second embodiment. 22 is a cross-sectional view taken along line A1-A1 of FIG. FIG. 23 is a perspective view of a torque detector according to the third embodiment. FIG. 24 is a plan view of the torque detection device according to the third embodiment. 25 is a cross-sectional view taken along line A2-A2 of FIG. FIG. 26 is a diagram illustrating a fourth modification.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
-First embodiment-
1 and 2 are diagrams for explaining a first embodiment of a torque detection device according to the present invention. FIG. 1 is a perspective view of a shaft 1 provided with a torque detection device, and FIG. 2 is a plan view. As shown in FIGS. 1 and 2, the torque detection device includes a flat plate 4, a strain sensor 5, a circuit unit 11, and a wireless communication unit 12. 1, illustration of the wiring part 10, the circuit part 11, and the radio | wireless communication part 12 was abbreviate | omitted.

  The shaft 1 rotates about a rotation axis (axial core) 8. Torque is applied to the shaft 1 in the direction of arrow 6. In the present embodiment, the shaft 1 is a hollow shaft, but is not limited to a hollow shaft, and can also be applied to a solid shaft. A pair of protrusions 3a and 3b are provided on the outer peripheral surface of the shaft 1 to be measured so as to be separated in the shaft axial direction.

  One end of the flat plate 4 is fixed to the protrusion 3a, and the other end is fixed to the protrusion 3b. As shown in FIG. 2, the flat plate 4 has a longitudinal direction substantially parallel to the rotation axis 8 of the shaft 1, and the front surface 4 a and the back surface 4 b of the flat plate 4 are substantially perpendicular to the circumferential direction of the shaft 1. Thus, it is being fixed to protrusion 3a, 3b. That is, the flat plate 4 is arranged on a straight line extending in the 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 front and back surfaces 4 a and 4 b are in the straight line. It is parallel. The strain sensor 5 is provided on the surface 4 a of the flat plate 4. The strain sensor 5 is connected to the circuit unit 11 via a wiring unit 10 (for example, a flexible wiring board or a glass epoxy substrate).

  A stopper 32 is provided at a position facing the back surface 4 b of the flat plate 4 with a gap having a dimension G. That is, the stopper 32 is provided on the outer peripheral surface of the shaft 1 at a position separated from the flat plate 4 with respect to the twisting direction of the shaft 1 due to load torque. An R is formed in the tip end region in the circumferential direction of the stopper 32, and a region closest to the back surface 4b of the flat plate 4 is the tip end portion of the R. Thereby, the contact between the flat plate 4 and the stopper 32 becomes a linear contact (line contact in the shaft radial direction), and the contact position is stable even if the deflection of the flat plate 4 changes due to an increase in load torque.

  The flat plate 4 is fixed to the protrusions 3a and 3b by screwing or welding. In the example shown in FIGS. 1 and 2, the flat plate 4 and the protrusions 3 a and 3 b are separated from each other, but the shaft 1, the protrusions 3 a and 3 b, and the flat plate 4 may be integrally formed by, for example, cutting. . The material of the shaft 1, the protrusions 3a and 3b, and the flat plate 4 is not particularly specified, but a metal material such as steel for machine structure is often used. Moreover, it is desirable that the shaft 1, the protrusions 3a and 3b, and the flat plate 4 are made of the same material. This is because in the case of different materials, thermal strain due to the difference in linear expansion coefficient between the two members occurs, and the strain measurement accuracy at the time of torque detection decreases.

  In the example shown in FIGS. 1 and 2, the hill-like projections 3a and 3b are formed to fix the flat plate 4 to the shaft 1, but the ring-like projections 30a and 30b as shown in FIGS. You may do it. Since the ring-shaped protrusions 30 a and 30 b are formed over the entire outer periphery of the shaft 1, the ring-shaped protrusions 30 a and 30 b are excellent in terms of the rotation balance of the shaft 1. In the following description, the shaft 1 on which the ring-shaped protrusions 30a and 30b are formed will be described as an example.

  FIG. 5 is a view showing the strain sensor 5 provided on the surface 4 a of the flat plate 4. The wiring unit 10 includes a plurality of wirings that are electrically connected to the plurality of electrode pads 9 of the strain sensor 5. For example, the wiring part 10 is configured by sealing a wiring made of a plurality of metal patterns in a resin film. In the opening provided in a part of the resin film, a part of the plurality of wirings is exposed, and this exposed part constitutes the plurality of terminals 10a. The portion of the wiring portion 10 provided with the terminal 10 a is fixed to the surface 4 a of the flat plate 4.

  The plurality of electrode pads 9 of the strain sensor 5 and the plurality of terminals 10a of the wiring part 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 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.

  The other end of the wiring part 10 is connected to the circuit part 11. The circuit part 11 is provided with a board component on which a strain measurement circuit is mounted, and the wiring part 10 is connected to the board part. For connection to the board component, a connector may be used, or the wiring part 10 may be directly connected to the board component.

  In FIG. 5, 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 an input / output current between the distortion sensor 5 and the external apparatus which is not shown in figure, and is not limited to the aspect shown in FIG.

  The strain measurement value measured by the strain sensor 5 is transmitted to an external measurement system unit (not shown) by the wireless communication unit 12 shown in FIG. In the above-described embodiment, the circuit unit 11 includes a battery. However, it is possible to use wireless power feeding by an electromagnetic induction method or a magnetic resonance method without mounting the battery.

(Description of strain sensor 5)
In the present embodiment, a semiconductor strain sensor is used as the strain sensor 5. 6A, 6B, and 7 are diagrams illustrating a semiconductor strain sensor. FIG. 6A is a plan view schematically showing the configuration of the front surface side of the strain sensor 5, and FIG. 6B is a diagram schematically showing the side surface of the strain sensor 5.

  As shown in FIG. 6A, the strain sensor (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 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 a metal film on the back surface 5b of the 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). In the example shown in FIG. 6A, for example, a square having a side length of about 2 mm to 5 mm is formed. The strain sensor 5 includes a plurality of resistance elements 15 (piezoresistive elements) formed in the sensor region 14 located at the center on the surface 5a side. The plurality of electrode pads 9 are electrically connected to a plurality of resistance elements 15 (piezoresistance 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 strain sensor 5 includes a Wheatstone bridge circuit (detection 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 strain sensor 5. The input / output terminals include, for example, a terminal Vcc that supplies a power supply potential (first power supply potential) to the sensor chip, a terminal GND that supplies a reference potential (second power supply potential), 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. 6A, but the following configuration is adopted in the present embodiment. That is, when a semiconductor substrate (for example, a silicon substrate made of silicon (Si)) included in the 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 ) Coincides with the <110> direction or <100> direction of a semiconductor substrate having a (100) plane.

  In the example shown in FIG. 6A, the semiconductor substrate (silicon substrate) included in the strain sensor 5 is aligned along the 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. 6A). Four p-type diffusion regions (regions doped with impurities whose conductivity type is p-type) are formed so that current flows. In other words, in the semiconductor strain sensor, 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. .

  Further, as in the example shown in FIG. 7, n-type impurities are doped at four locations so as to extend along the crystal orientation in the <100> direction of the silicon single crystal of the silicon substrate, and the four resistance elements 15 are formed. It may be formed. In this case, in the semiconductor substrate (silicon substrate), four n so that current flows along the crystal orientation of the <100> direction of the silicon single crystal (the X direction and the Y direction orthogonal to the X direction in FIG. 7). A type diffusion region (a region doped with an n-type impurity) is formed.

  As shown in FIGS. 6A and 7, the semiconductor strain in which the extending directions of the plurality of resistance elements 15 constituting the detection circuit coincide with the <110> direction or the <100> direction of the semiconductor substrate having the (100) plane, respectively. For example, the sensor can output the difference between the strain in the X direction and the strain in the Y direction shown in FIGS. 6A and 7. 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. 6A and 7. 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 strain sensor 5.

  As shown in FIG. 5, the strain sensor 5 is mounted on an object to be measured which is a flat plate 4. Therefore, when the measurement environment temperature changes, thermal strain due to the difference in linear expansion coefficient between the flat plate 4 and the strain sensor 5 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.

  On the other hand, as shown in FIGS. 6A and 7, when the planar shape of the strain sensor 5 is a square, the influence of the 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 strain sensor 5 as shown in FIG. 6A and FIG. 7 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 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.

  The bonding material for attaching the strain sensor 5 to the flat plate 4 is provided so as to cover the entire back surface 5b of the strain sensor 5 and a part of the side surface of the strain sensor 5. In other words, the peripheral edge of the bonding material may extend to the outside of the side surface of the strain sensor 5 to form a fillet. From the viewpoint of fixing the strain sensor 5 and the flat plate 4, the bonding material is not limited to a metal material, and for example, a resin adhesive such as a thermosetting resin can also be used.

  Next, the feature point of the torque detection device of the present embodiment, that is, the function of the stopper 32 will be described. FIG. 8 schematically shows the amount of torsional deformation on the outer peripheral surface of the shaft with an arrow R when the right end 17 of the shaft is completely fixed and a torque as shown by the arrow 6 is applied to the left end 18 of the shaft 1. It is. The torsional deformation amount R increases in proportion to the axial distance from the shaft right end portion 17 which is a fixed end.

  FIG. 9 shows a side view of the torque detection device before torque application. As described above, the stopper 32 is formed on the outer peripheral surface of the shaft at a position facing the back surface 4 b of the flat plate 4. In the state before the torque application, a gap with a dimension G is formed between the stopper 32 and the back surface 4b.

  FIG. 10 is a schematic diagram illustrating a state of the torque detection device when torque is applied. FIG. 10 shows a case where the ring-shaped protrusion 30a is a fixed end and the ring-shaped protrusion 30b is rotated in the direction of the arrow 6 by torsional deformation. At this time, the flat plate 4 is deformed downward in a region on the left side of the center S, and is deformed in a convex shape in a region on the right side of the center, and is deformed into an S shape as a whole. This is because when bending deformation occurs in the flat plate 4 due to the applied torque, both end portions of the flat plate 4 are completely restrained by the protrusions 30a and 30b, so that the bending deflection angle at both end portions of the flat plate 4 becomes 0 °. to cause.

  As a result, on the surface 4a side of the flat plate 4 on which the strain sensor 5 is mounted, a compressive strain is generated on the left side from the center S, which is a downward convex deformation. On the other hand, tensile strain occurs in the region on the right side from the center S, which is an upward convex deformation. Since the strain on the surface 4a continuously changes from the compressive strain to the tensile strain, there is always a portion where the strain becomes zero between the protrusion 30a and the protrusion 30b. If the S-shape is point-symmetric with respect to the center S, the distortion is zero at the center S.

  In FIG. 10, a broken line 35 indicates a case where the protrusion 30a and the protrusion 30b are connected by a straight line. As can be seen from FIG. 8, this corresponds to the torsional deformation amount R on the outer periphery of the shaft. The torsional deformation amount R on the outer periphery of the shaft increases in proportion to the axial distance from the protrusion 30a corresponding to the fixed end. That is, on the right side from the center S, the amount of deflection in the rotational direction of the flat plate 4 (the amount of deflection based on the protrusion 30a) is smaller than the amount of torsional deformation R of the outer peripheral surface of the shaft. Conversely, on the left side from the center S, the amount of deflection in the rotational direction of the flat plate 4 is larger than the torsional deformation amount R of the outer peripheral surface of the shaft.

  The stopper 32 provided on the outer peripheral surface of the shaft moves in the rotational direction along with the torsional deformation of the outer peripheral surface of the shaft. In FIG. 10, since the stopper 32 is provided on the left side of the center S of the flat plate 4, the amount of movement of the stopper 32 in the rotational direction due to the twist of the shaft 1 is smaller than the amount of deflection of the flat plate 4. Therefore, as the shaft 1 is twisted, the gap between the stopper 32 and the flat plate 4 is gradually reduced. A gap dimension G shown in FIG. 10 indicates a gap dimension before loading.

  When a certain torque value is reached, the back surface 4b of the flat plate 4 comes into contact with the stopper 32 as shown in FIG. After the stopper 32 contacts the back surface 4b of the flat plate 4, the contact point becomes a new restraint fulcrum, so that the deformation mode of the flat plate 4 changes.

  Next, with reference to FIG. 11A and 11B, the deformation | transformation state after the flat plate 4 and the stopper 32 contact is demonstrated. 11A is a diagram showing a portion on the left side of the center S in FIG. That is, the state at the moment when the back surface of the flat plate 4 contacts the stopper 32 is shown. As shown in FIG. 11A, until the flat plate 4 comes into contact with the stopper 32, the region on the left side from the center S of the surface 4a on which the strain sensor 5 is mounted has a compressive strain.

  On the other hand, FIG. 11B shows a case where the torsional deformation amount of the protrusion 30a is increased by ΔR from the state of FIG. 11A. As shown in FIG. 11B, after the flat plate 4 and the stopper 32 come into contact, the flat plate 4 undergoes bending deformation with the contact point P as a fulcrum. As a result, a point where the distortion does not change even when the shaft 1 is further twisted as in ΔR occurs between the contact point P and the protrusion 30b. Here, the position of the point is referred to as a predetermined position 41.

  In the present embodiment, the strain sensor 5 is mounted so that the center position of the sensor is arranged at the predetermined position 41. FIG. 12 is a diagram for explaining the relationship between the load torque and the strain generated at the mounting position (predetermined position 41) of the strain sensor 5. In FIG. The allowable value shown on the vertical axis is a distortion value allowed for the strain sensor 5, and it is necessary to suppress the distortion generated at the mounting position (predetermined position 41) below this value. The rated torque shown on the horizontal axis indicates a torque value that needs to be measured as a torque detector. Further, the maximum torque indicates the maximum load torque applied to the shaft 1.

  In the present embodiment, the size of the gap dimension G in FIG. 9 is set so that the stopper 32 contacts the flat plate 4 when the load torque reaches the rated torque. Until the stopper 32 comes into contact with the flat plate 4 (that is, up to the rated torque), as shown in FIG. 11A, a compressive strain is generated at the predetermined position 41, and the magnitude of the strain increases as the load torque increases. Therefore, the generated distortion line L1 is a line that rises to the right. When the load torque reaches the rated torque, the stopper 32 comes into contact with the flat plate 4, and the strain at the predetermined position 41 remains constant even when the load torque increases.

  By the way, in the conventional configuration in which the stopper 32 is not provided, the distortion at the sensor mounting position continues to increase even after the load torque reaches the rated torque. Therefore, the strain at the mounting position of the strain sensor 5 further increases as shown by a line L2 in FIG. By the way, in the case of a semiconductor strain sensor formed of Si, brittle fracture is likely to occur when a large strain occurs. Therefore, it is necessary to design so that the amount of strain generated in the strain sensor when the maximum torque is applied is within a predetermined allowable strain value (for example, ± 1000 με). For example, when the amount of strain at the sensor mounting position exceeds the allowable value as in the line L2, the strain sensor 5 may be destroyed.

  In order to avoid such sensor destruction, it is necessary to mount the strain sensor 5 at a position where the strain sensitivity is smaller as indicated by the line L3. Here, the strain sensitivity represents the amount of strain generated when a constant torque is applied. For example, in the case of the deformed flat plate 4 as shown in FIG. 10, the strain sensitivity is low when mounted near the center S, and the strain sensitivity is increased when mounted near the protrusion 30b. In the case of strain sensitivity like the line L3, the amount of strain generated when the maximum torque is applied can be adjusted within the allowable strain value of the strain sensor 5, so that the sensor can be prevented from being destroyed. However, since the amount of strain generated when the rated torque is applied becomes small, there arises a problem that the measurement accuracy within the rated torque value is lowered.

  On the other hand, in the present embodiment, since the stopper 32 is provided, the distortion at the mounting position does not change from the rated torque to the maximum torque as shown in FIG. As a result, even when the maximum load torque is applied, the generated strain can be reduced to an allowable value or less, and the strain sensor 5 can be prevented from being broken. In addition, since the strain does not change from the rated torque to the maximum torque, the strain sensor 5 can be mounted at a mounting position with a large strain sensitivity so that the strain becomes an allowable value at the rated torque. As a result, torque measurement accuracy can be improved. That is, in this embodiment, it is possible to improve measurement accuracy while preventing sensor destruction.

14 and 15 are diagrams illustrating the predetermined position 41. FIG. In the case of the present embodiment, as shown in FIG. 14, when the distance from the protrusion 30b to the stopper 32 is L and the distance from the protrusion 30b to the predetermined position 41 is x, x is expressed by the following equation (1). Fulfill.
L / 2 <x <L (1)

  As described above, after the stopper 32 comes into contact with the flat plate 4, the flat plate 4 is deformed as shown in FIG. 11B. In this case, the constraint condition at the contact point P is rotation free. Here, let us consider a case where the constraint condition at the contact point P is assumed to be a completely non-rotatable constraint as shown in FIG. In this case, the position xa where the change in distortion becomes zero is xa = L / 2 because of the left-right symmetric structure.

  On the other hand, in the case where the stopper 32 is in contact with the flat plate 4, the contact point P is a rotation-free restraint condition. Therefore, the bending moment is reduced as compared with the case of complete restraint, and the tensile strain generated on the mounting surface. Decrease. Therefore, the position x where the change in distortion is zero is on the right side of the position where xa = L / 2.

  When the positions of the strain sensor 5 and the stopper 32 are set so that the generated strain at the sensor mounting position is the line L1 shown in FIG. 12, the strain sensitivity is zero when a load torque exceeding the rated torque is applied. . Therefore, when a load torque from the rated torque to the maximum torque is applied, the torque value cannot be estimated from the sensor output. Therefore, when it is desired to measure a torque value equal to or higher than the rated torque, the strain sensor 5 may be installed with a slight shift in a direction where the strain sensitivity is smaller than the predetermined position 41.

  As a result, the relationship between the load torque and the distortion is as shown by a line L4 in FIG. Since the sensor mounting position is shifted in a direction in which the distortion sensitivity is smaller than the predetermined position 41, the distortion at the rated torque is smaller than that in the case of FIG. Furthermore, when the load torque is increased from the rated torque by shifting from the predetermined position 41, the distortion also increases. That is, the distortion sensitivity slightly increases from zero.

(Modification 1)
FIG. 17 is a diagram illustrating a first modification. In the embodiment described above, as shown in FIG. 10, the strain sensor 5 is mounted on the front surface 4a of the flat plate 4 on the protrusion 30b side from the center S, and the stopper 32 is provided at a position corresponding to the back surface 4b via a gap having a gap size G. However, it may be arranged as shown in FIG. In FIG. 17, the strain sensor 5 is mounted on the back surface 4b on the protrusion 30a side from the center S, and the stopper 32 is disposed on the front surface 4a side. The configuration shown in FIG. 17 is point-symmetric with respect to the configuration shown in FIG. 10 with respect to the center S of the flat plate 4, and therefore the relationship between the load torque and the generated strain is the same as in FIG.

(Modification 2)
FIG. 18 is a diagram illustrating a second modification. In the configuration shown in FIG. 10, until the stopper 32 comes into contact with the back surface 4b of the flat plate 4, compressive strain is generated from the center S of the front surface 4a of the flat plate 4 to the projection 30b side, and tensile is generated from the central S to the projection 30a side. Distortion has occurred. On the contrary, on the back surface 4b of the flat plate 4, tensile strain is generated from the center S to the projection 30b side, and compressive strain is generated from the center S to the projection 30a side.

  As shown in FIG. 18, when the stopper 32 abuts on the back surface 4b, the tensile strain at the predetermined position 42 on the back surface 4b does not change after the abutment. Therefore, in the second modification, the strain sensor 5 is mounted at the predetermined position 42. The change of the strain with respect to the load torque shows the same change as the line L1 in FIG. 12 except that the strain is a tensile strain. Further, by shifting the mounting position of the strain sensor 5 from the predetermined position 42 toward the smaller strain sensitivity, a line L4 similar to FIG. 16 can be obtained.

(Modification 3)
FIG. 19 is a diagram showing a third modification, in which a strain sensor 5 is mounted at a predetermined position 41 on the surface 4 a of the flat plate 4. FIG. 19 shows a case where a load torque is applied in the direction of the arrow 7. In this case, tensile strain is detected by the strain sensor 5, and when the stopper 32B contacts the surface 4a, the change in strain detected by the strain sensor 5 becomes zero. This is the same as in the configuration shown in FIG. Conversely, when a load torque acts in the direction opposite to the arrow 7, the flat plate 4 is deformed into an S shape as shown by a two-dot chain line. In this case, the strain (compression strain) detected by the strain sensor 5 is the same as in the configuration shown in FIGS. 11A and 11B. Thus, by providing the stopper 32B that contacts the front surface 4a of the flat plate 4 and the stopper 32A that contacts the back surface 4b, it is possible to detect load torque in both forward and reverse directions with a single strain sensor.

-Second Embodiment-
A second embodiment of the torque detection device will be described with reference to FIGS. 20 is a perspective view of the shaft 1 provided with the torque detection device, FIG. 21 is a plan view, and FIG. 22 is a cross-sectional view taken along line A1-A1 of FIG. 20-22, illustration of the wiring part 10, the circuit part 11, and the radio | wireless communication part 12 was abbreviate | omitted. The basic configuration is the same as the configuration shown in FIGS. 3 and 4 of the first embodiment, but the configuration of the stopper 32 is different in the second embodiment.

  The stopper 32 includes an arm portion 321 fixed to the protrusion 30 a and an abutting portion 322 provided at the tip of the arm portion 321. The arm portion 321 is formed so as to extend in the shaft axial direction from the side surface of the protrusion 30a, and is provided apart from the outer peripheral surface of the shaft 1 (see FIG. 22). The contact portion 322 protrudes from the arm portion 321 in the direction of the flat plate 4, and a gap with a dimension G <b> 1 (see FIG. 21) is formed between the tip thereof and the back surface 4 b of the flat plate 4. The tip region of the contact portion 322 has an R shape, and G1 is the distance between the R shape tip and the back surface 4b. The position of the contact portion 322 in the shaft axial direction and the mounting position of the strain sensor 5 on the surface 4a of the flat plate 4 are set in the same manner as that shown in FIGS. 3 and 4 of the first embodiment.

As shown in FIGS. 3 and 4 of the first embodiment, when the stopper 32 is formed on the outer peripheral surface of the shaft 1, the circumferential movement amount of the stopper 32 when the shaft 1 is twisted is the shaft outer periphery at that position. It is equal to the torsional deformation amount R (see FIG. 8) of the surface. On the other hand, since the stopper 32 of the second embodiment is fixed to the protrusion 30a that is a fixed end, the circumferential movement amount of the stopper 32 is zero even if the shaft 1 is twisted. Therefore, in order for the stopper 32 to come into contact with the back surface 4b of the flat plate 4 at the same load torque as in FIGS. 3 and 4, the gap dimension G1 may be set as the following equation (2). The deformation behavior of the flat plate 4 after the contact is the same as that in the first embodiment, and the description thereof is omitted.
G1 = G + R (2)

  As described above, in the second embodiment, the stopper 32 as the restricting portion includes the protrusion 30 a fixed to the outer peripheral surface on one end side of the flat plate 4, the arm portion 321 provided on the protrusion 30 a, and the arm portion 321. And an abutting portion 322 provided at the tip portion. The arm portion 321 is provided apart from the outer peripheral surface so as to extend from the protrusion 30a toward the other end side of the flat plate 4, and the abutting portion 322 is provided on the flat plate 4 when the twist of the shaft 1 is a predetermined amount or more. It abuts at a position biased to one end side from the center in the shaft axial direction.

  Since the stopper 32 is fixed to the protrusion 30a, the rate of decrease in the distance between the abutting portion 322 and the back surface 4b when a load torque is applied is larger than in the configuration shown in FIGS. As a result, in the second embodiment, as shown in Expression (2), the no-load gap dimension G1 can be set larger than the dimension G in the case of FIGS. Since the gap dimension G1 can be set larger, the processing accuracy and assembly accuracy of the stopper 32 can be relaxed.

-Third embodiment-
23 to 25 are diagrams illustrating a third embodiment of the torque detection device. 23 is a perspective view of the shaft 1 provided with the torque detection device, FIG. 24 is a side view, and FIG. 25 is a cross-sectional view taken along line A2-A2 of FIG. 23 to 25, the wiring unit 10, the circuit unit 11, and the wireless communication unit 12 are not shown.

  Unlike the above-described first and second embodiments, the configuration of the present embodiment is not provided with the stopper 32 that contacts the flat plate 4. Instead of the stopper 32, an arm portion 301 extending from the protrusion 30a toward the protrusion 30b in the shaft axial direction and an arm portion 302 extending from the protrusion 30b toward the protrusion 30a in the shaft axial direction are provided. The arm portions 301 and 302 are spaced apart from the outer peripheral surface of the shaft 1. Other configurations are the same as those of the first and second embodiments, and the strain sensor 5 is mounted on one surface of the flat plate 4 whose both ends are fixed to the protrusions 30a and 30b.

  In the first and second embodiments, the stopper 32 abuts against the flat plate 4 when the load torque exceeds the allowable torque, thereby reducing the amount of strain at the portion (predetermined position) where the strain sensor 5 is mounted. It functions as a restriction. In the present embodiment, when the load torque exceeds the allowable torque, the arm portion 301 and the arm portion 302 are in contact with each other in the circumferential direction, thereby limiting the distortion amount of the portion where the strain sensor 5 is mounted. .

  As shown in FIG. 25, the cross-sectional shape of the arm portions 301 and 302 is a substantially semicircular shape, and the circumferential end surfaces 301a and 301b of the arm portion 301 are spaced from the circumferential end surfaces 302a of the arm portion 302 via a gap. , 302b. When load torque is applied to the protrusion 30b side and the shaft 1 is twisted in the direction of arrow 6, the protrusion 30b on which the arm portion 302 is formed rotates in the direction of arrow 6. The arm portion 302 also rotates integrally with the protrusion 30b as indicated by the broken line, and the end surface 302b of the arm portion 302 and the end surface 301b of the arm portion 301 come into contact with each other. The gap between the end surface 302b and the end surface 301b is substantially parallel as shown in FIG. 25, and when the end surface 302b and the end surface 301b abut, the entire surface of the end surface 302b and the entire surface of the end surface 301b are in contact with each other. It is formed as follows.

  On the other hand, when a load torque in the direction opposite to that of the arrow 6 is applied, the protrusion 30b and the arm portion 302 rotate in the direction opposite to that in the case of FIG. And the end surface 302a and the end surface 301a contact | abut. The gap between the end surface 302a and the end surface 301a is also substantially parallel as shown in FIG. 24. When the end surface 302a and the end surface 301a come into contact with each other, the entire end surface 302a and the entire end surface 301a come into contact with each other. It is formed as follows.

  In the present embodiment, the dimension of the gap G2 is set so that the end surfaces of the arm part 301 and the arm part 302 come into contact with each other when the rated torque is applied. Therefore, the relationship between the load torque and the generated distortion is the same as that of the line L4 shown in FIG. That is, when the rated torque is applied and the end surfaces of the arm portions 301 and 302 come into contact with each other, a part of the torque applied to the shaft 1 is transmitted to the arm portions 301 and 302. As a result, the torsional rigidity of the shaft 1 increases, and the strain sensitivity decreases. That is, when the load torque exceeds the rated torque, the slope of the line L4 becomes small.

  Thus, also in 3rd Embodiment, there can exist an effect similar to 1st and 2nd embodiment mentioned above.

(Modification 4)
FIG. 26 is a diagram illustrating a modification (fourth modification) in the third embodiment. FIG. 26 is a cross-sectional view corresponding to the cross section A3-A3 of FIG. 24, and shows a cross section of the protrusion 30a. In the above-described third embodiment, the protrusion 30 a is formed integrally with the shaft 1 or is directly fixed to the outer peripheral surface of the shaft 1. On the other hand, in the modified example 4, the annular protrusion 30a is fixed to the shaft 1 via the annular member 46 having a small elastic modulus. Such a triple structure is employed in at least one of the protrusion 30a and the protrusion 30b. In addition, only one of the ring-shaped protrusions 30a and 30b having a triple structure (for example, the protrusion 30a) is provided, and one end of the flat plate 4 fixed to the protrusion 30b is fixed to the shaft 1 and fixed to the protrusion 30b. Alternatively, the arm portion 302 may be fixed to the shaft 1.

  The elastic modulus of the annular member 46 is set to be smaller than that of the shaft 1, the protrusions 30a and 30b, and the arm portions 301 and 302. Therefore, until the end surfaces of the arm portions 301 and 302 come into contact with each other, that is, until the load torque reaches the rated torque, the load torque is transmitted only to the shaft 1, and the generated distortion changes in the same manner as the line L4 in FIG. .

  On the other hand, after the end surfaces of the arm portions 301 and 302 come into contact with each other, a force 44 as indicated by an arrow is generated on the annular member 46 and the protrusion 30a through the contact portion. The elastic modulus of the annular member 46 is set to be smaller than the elastic modulus of the protrusion 30a and the arm portion 301, and the rigidity is small, so that the torsional deformation 45 occurs in the annular member 46.

  That is, after the end surfaces of the arm portions 301 and 302 are in contact with each other, even if the torsional deformation of the shaft 1 is increased by the torque applied to the shaft 1, the annular member 46 is torsionally deformed 45 as shown in FIG. Therefore, the protrusion 30a rotates integrally with the protrusion 30b, so that the rotation deviation of the protrusion 30b with respect to the protrusion 30a hardly occurs. As a result, the bending of the flat plate 4 hardly changes and the amount of strain detected by the strain sensor 5 hardly increases. Since the elastic modulus of the annular member 46 is smaller than the elastic modulus of the arm portions 301 and 302, when the load torque exceeds the rated torque, a line L4 in FIG. 16 is obtained.

  As described above, the torque detection device includes the flat plate 4 that extends in the axial direction of the shaft 1, has both ends fixed to the outer peripheral surface of the shaft 1, and bends in the front-back direction as the shaft 1 is twisted. A strain sensor 5 that is mounted on the front surface 4a or the back surface 4b and detects the strain of the flat plate 4, and a stopper 32 that is a limiting portion that limits the amount of bending of the flat plate 4 when the twist of the shaft 1 is a predetermined amount or more. Arms 301 and 302 are provided. When the amount of twist when the rated torque is applied as the predetermined amount is selected, even when a load torque exceeding the rated torque is applied, the amount of bending of the flat plate 4 is limited, and an excessive torque is applied to the strain sensor 5. Can be prevented. Therefore, when a semiconductor strain sensor is used for the strain sensor 5, it is possible to prevent the sensor from being destroyed due to excessive strain.

  The strain sensitivity value representing the strain detection value of the strain sensor 5 with respect to the applied torque is set so that the case where the twist of the shaft 1 is greater than the predetermined amount is smaller than the case where the twist is less than the predetermined amount. Thereby, it is possible to prevent excessive distortion from occurring in the strain sensor 5. Further, by setting the strain sensitivity to be zero when the twist of the shaft 1 is greater than or equal to a predetermined amount, the strain sensor can be reliably prevented from being broken.

  For example, a stopper 32 as shown in FIGS. The stopper 32 is provided on the outer peripheral surface so as to be spaced apart from the flat plate 4 in the shaft twist direction. When the twist of the shaft 1 is a predetermined amount or more as shown in FIG. It arrange | positions so that it may contact | abut to the position biased to the side. The strain sensor 5 is disposed on the one end side from the position where the stopper 32 abuts.

  As described above, in the configuration in which the stopper 32 that is the limiting portion is in contact with the flat plate 4, the distance x from one end of the flat plate 4 to the mounting position of the strain sensor 5, and the distance L from one end of the flat plate 4 to the contact position. However, it is desirable to set so as to satisfy the expression “L / 2 <x <L”.

  Further, as shown in FIGS. 23 to 25, as a restricting portion, a protrusion 30 a fixed to the outer peripheral surface on one end side of the flat plate 4, and extends from the protrusion 30 a toward the other end side of the flat plate 4 and is separated from the outer peripheral surface. Provided on the other end side of the flat plate 4, the projection 30 b fixed to the outer peripheral surface, the projection 30 b extending toward the one end side of the flat plate 4, and provided away from the outer peripheral surface. It is good also as a structure provided with the arm part 302. FIG. When the twist of the shaft 1 is greater than or equal to a predetermined amount, the arm portion 301 and the arm portion 302 abut against each other in the shaft twist direction, so that the bending of the flat plate 4 is limited even when the load torque further increases.

  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.

  3a, 3b, 30a, 30b ... projection, 4 ... flat plate, 5, 5A, 5B ... strain sensor, 10 ... wiring part, 11 ... circuit part, 12 ... wireless communication part, 32, 32A, 32B ... stopper, 46 ... circle Ring member, 301, 302, 321 ... arm part, 322 ... contact part

Claims (6)

A flat plate that extends in the axial direction of the shaft and both ends are fixed to the outer peripheral surface of the shaft, and bends in the front-back direction as the shaft is twisted;
A strain sensor that is mounted on the front or back surface of the flat plate and detects the strain of the flat plate;
When the twist of the shaft is greater than or equal to a predetermined amount, a limiting portion that limits the amount of bending of the flat plate ,
The restricting portion is provided on the outer peripheral surface so as to be spaced apart from the flat plate in the shaft twist direction, and is biased to one end side with respect to the shaft axial direction center of the flat plate when the shaft twist is a predetermined amount or more. Abut the position,
The said strain sensor is a torque detection apparatus arrange | positioned in the said one end side rather than the position where the said limitation part contact | abuts . The torque detection device according to claim 1 ,
The restriction unit is
A fixing portion fixed to the outer peripheral surface on one end side of the flat plate;
An arm portion extending from the fixed portion toward the other end of the flat plate and spaced from the outer peripheral surface;
A torque detecting device provided at a tip portion of the arm portion, and abutting portion that abuts at a position biased to one end side with respect to a shaft axial direction center of the flat plate when the shaft is twisted by a predetermined amount or more. . The torque detection device according to claim 1 or 2 ,
A torque detection device in which a distance x from one end of the flat plate to a mounting position of the strain sensor and a distance L from one end of the flat plate to a position where the limiting portion abuts satisfy the following expression (a): .
L / 2 <x <L (a) A flat plate that extends in the axial direction of the shaft and both ends are fixed to the outer peripheral surface of the shaft, and bends in the front-back direction as the shaft is twisted;
A strain sensor that is mounted on the front or back surface of the flat plate and detects the strain of the flat plate;
When the twist of the shaft is greater than or equal to a predetermined amount, a limiting portion that limits the amount of bending of the flat plate,
The restriction unit is
A first fixing portion fixed to the outer peripheral surface on one end side of the flat plate;
A first arm portion extending from the first fixed portion toward the other end of the flat plate and spaced from the outer peripheral surface;
A second fixing portion fixed to the outer peripheral surface on the other end side of the flat plate;
A second arm portion extending from the second fixing portion toward one end side of the flat plate and spaced apart from the outer peripheral surface,
When torsion of the shaft is greater than a predetermined amount, and said first arm portion and the second arm portions are abutted against each other in the shaft torsional direction,
The flat plate has one end fixed to the first fixing portion and / or the other end fixed to the second fixing portion,
The torque detection device , wherein at least one of the fixing portions to which the flat plate is fixed is fixed to an outer peripheral surface of the shaft via an elastic member having an elastic modulus smaller than that of the fixing portion and the arm portion . In the torque detection device according to claim 1 or 4 ,
A torque detection device wherein a strain sensitivity value representing a strain detection value of the strain sensor with respect to an applied torque is smaller when the shaft twist is a predetermined amount or more than when the shaft twist is less than a predetermined amount. The torque detection device according to claim 5 ,
A torque detection device in which the distortion sensitivity becomes zero when the twist of the shaft is equal to or greater than a predetermined amount.

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