Torque measurement device, torque measurement system, and torque measurement method

Abstract

To measure output torque of an electric motor of a drive unit in which the electric motor and a gear mechanism are accommodated within a housing.SOLUTION: An input shaft 12 of a gear mechanism of a drive unit 1 is removed, and instead, a measurement input shaft unit 3 which functions as a first power transmission shaft of the gear mechanism is coupled to a rotor shaft 111 of an electric motor 11, similarly to the input shaft 12. The measurement input shaft unit 3 has a length such that its end portion protrudes outside through a through-hole 107 of a housing 10, and an external interface board 32 that performs wireless transmission of a detection value of a strain gauge attached to the measurement input shaft unit 3 and receives wireless power supply is coupled to the end portion.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a technique for measuring torque in a drive unit of an electric vehicle. [Background technology]

[0002] Known technologies related to measuring the torque of a drive unit of an electric vehicle include a technology that measures the output current of an inverter that drives the electric motor of an electric vehicle and estimates the output torque of the electric motor from the measured value (for example, Patent Document 1), and a technology that connects a dynamometer to the output shaft of an electric motor for an electric vehicle and measures the torque acting between the output shaft of the electric motor and the dynamometer with a torque meter (for example, Patent Document 2).

[0003] Also, as a technology related to the present invention, a drive unit for an electric vehicle is known in which an electric motor and a gear mechanism such as a transaxle (reduction gear and differential gear) are housed in a single housing (case) (for example, Patent Document 3). As a technique related to the present invention, a measuring device shown in FIG. 7 is known as a retrofittable measuring device for detecting torque of a rotating shaft (for example, Patent Document 4). Figure 7a shows the configuration of the measuring device as seen in a direction perpendicular to the axial direction of the rotation axis, and Figure 7b shows the configuration of the measuring device as seen in the axial direction of the rotation axis (as seen from the right side of Figure 7a). This measuring device comprises a first mounting base 713 consisting of two halves, a first upper base 711 and a first lower base 712, which clamp the rotating shaft 700, a second mounting base 723 consisting of two halves, a second upper base 721 and a second lower base 722, which clamp the rotating shaft 700 at a position a predetermined distance axially away from the clamping surface of the first mounting base 713, a beam-shaped strain-flexing part 730 whose both ends are fixed to the first mounting base 713 and the second mounting base 723, respectively, and a strain gauge 731 attached to the middle part of the side of the strain-flexing part 730, and the torque of the rotating shaft 700 is measured from the amount of strain detected by the strain gauge 731. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-219843 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-91410 [Patent Document 3] JP 2018-35824 A [Patent Document 4] Publication No. 3029548 Summary of the Invention [Problem to be solved by the invention]

[0005] A drive unit called an eAxle, which houses an electric motor and a gear mechanism such as a transaxle within a single housing, is becoming popular. Furthermore, if it were possible to measure the output torque of the electric motor within the drive unit while keeping the drive unit in the same state as when it is in operation, it would be useful for evaluating the drive unit, as it would enable the power and energy loss of the entire drive unit to be broken down into losses in the electric motor and the gear mechanism. However, the space inside the housing of the drive unit may be narrow, making it impossible to detect the amount of strain by retrofitting a measuring device such as that shown in Fig. 7 to the output shaft of the electric motor. It is also difficult to stably measure the amount of strain detected inside the closed housing from outside the housing.

[0006] Therefore, an object of the present invention is to make it possible to stably measure the output torque of an electric motor within a drive unit, even when the space within the housing of the drive unit, which houses an electric motor and a gear mechanism within a single housing, is narrow. [Means for solving the problem]

[0007] To achieve the above object, the present invention provides a torque measurement device for measuring the output torque of an electric motor of a drive unit that houses an electric motor and a gear mechanism that transmits the power of the electric motor within a housing. The torque measurement device includes a measurement input shaft unit including a shaft portion connected to the rotor shaft of the drive unit when the input shaft of the gear mechanism connected to the rotor shaft of the electric motor is removed, and a transmission unit. The shaft portion has a connecting portion connected to the rotor shaft, a gear portion that meshes with a gear driven by the gear of the input shaft when the input shaft of the gear mechanism is not removed, and a strain-flexing portion that is part of the shaft portion located between the connecting portion and the gear portion. A strain gauge is attached to the strain-flexing portion of the shaft portion to detect strain in the strain-flexing portion. The transmission unit transmits a detection value detected by the strain gauge from the position of the transmission unit to the outside of the housing. Here, this torque measuring device may be configured so that the tip of the shaft, which is the end of the shaft that is not connected to the rotor shaft, protrudes outside the housing through a hole that passes through the housing, the transmission unit is fixed to the tip of the shaft outside the housing, and the detection value detected in the transmission unit using the strain gauge is transmitted from the position of the transmission unit to the outside.

[0008] In this case, in the torque measuring device, the transmission section may transmit the detection value detected by the strain gauge by wireless communication. Alternatively, the transmission unit may include a rotary connector having a fixed part and a rotating part rotatable relative to the fixed part, wherein the rotating part is fixed to the tip of the shaft outside the housing, and the rotary connector transmits a signal representing the detection value detected by the strain gauge.

[0009] Furthermore, in the torque measuring device described above, a passage may be provided inside the shaft portion, which is a hollow cavity that passes through between the opening of the strain-flexing portion and the opening at the tip of the shaft portion, and the transmission portion and the strain gauge may be connected by wire via an electric wire that passes through the passage. Furthermore, when the transmission unit transmits the detected value by wireless communication, the measurement input shaft unit may be provided with an external interface panel that is a plate-shaped member fixed to the tip of the shaft and perpendicular to the axis of the shaft outside the housing, and this external interface panel may be equipped with the transmission unit, a receiving coil that receives AC power by wireless power supply, and a rectifier that generates DC power to be supplied to the transmission unit and the strain gauge from the AC power received by the receiving coil. Here, at least the wireless communication antenna of the transmission unit and the receiving coil are disposed on the outer surface of the external interface panel, which is the surface opposite to the drive unit side.

[0010] In the torque measuring device described above, the gear mechanism of the drive unit may include a gear mechanism that functions as a reducer and a differential gear. The present invention also provides a torque measurement system equipped with the torque measurement device described above, which includes a mark fixed to the peripheral surface of the tip of the shaft portion and a rotation measurement device that detects the mark without contact and measures the rotation speed of the rotor shaft from the detection period of the mark.

[0011] Furthermore, the present invention also provides a torque measurement system including the torque measurement device, which includes a dynamometer arranged outside the housing and connected to the output shaft of the gear mechanism of the drive unit. Furthermore, there is also provided a torque measurement system including a torque measurement device having the above-described power receiving coil, the torque measurement system including a power feeding / receiving unit having an inner surface facing the outer surface of the external interface panel in a position close to the outer surface of the external interface panel outside the housing, wherein a power transmitting coil arranged coaxially with the power receiving coil and an antenna for wireless communication with the transmission unit are mounted on the inner surface of the power feeding / receiving unit.

[0012] The present invention also provides a torque measurement method for measuring the output torque of an electric motor of a drive unit that houses an electric motor and a gear mechanism that transmits the power of the electric motor within a housing, the method comprising: a first step of opening the housing of the drive unit and removing the input shaft of the gear mechanism that is connected to the rotor shaft of the electric motor; a second step of incorporating into the drive unit the shaft of a measurement input shaft unit, which has a shaft portion having a connecting portion and a gear portion and a transmission portion, in a form in which the connecting portion of the shaft portion is connected to the rotor shaft and the gear portion meshes with a gear that would be driven by the gear of the input shaft if the input shaft of the gear mechanism were not removed; and a third step of closing the housing so that the tip of the shaft portion, which is the end of the shaft portion that is not connected to the rotor shaft, protrudes outside the housing through a hole that passes through the housing. The shaft portion has a strain-flexing portion that is a part of the shaft portion located between the connecting portion and the gear portion, and a strain gauge used to detect strain in the strain-flexing portion is attached to the strain-flexing portion of the shaft portion. The transmission portion is fixed to the tip end of the shaft portion outside the housing, and transmits detection values detected using the strain gauge from the position of the transmission portion to the outside.

[0013] According to the torque measurement device, torque measurement system, and torque measurement method described above, the input shaft of the gear mechanism of a drive unit in which the electric motor and gear mechanism are housed in a single housing is replaced with a shaft portion to which a strain gauge is attached, and torque is measured using the strain gauge, so that the output torque of the electric motor in the drive unit can be measured even when the space inside the housing is narrow.In addition, since the detected value detected using the strain gauge is transmitted from a transmission unit fixed outside the housing to the end of the shaft portion exposed outside the housing, the detected value can be stably obtained outside the housing. [Effects of the Invention]

[0014] As described above, according to the present invention, even when the space inside the housing of a drive unit in which an electric motor and a gear mechanism are housed in a single housing is narrow, the output torque of the electric motor inside the drive unit can be measured stably. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a diagram illustrating a drive unit to be measured in an embodiment of the present invention; [Figure 2] FIG. 2 is a diagram showing an input shaft of a drive unit that is a measurement target in an embodiment of the present invention. [Figure 3] FIG. 2 is a diagram showing a measurement input shaft unit according to an embodiment of the present invention. [Figure 4] 5A to 5C are diagrams illustrating an assembly procedure for the measurement input shaft unit according to the embodiment of the present invention. [Figure 5] FIG. 10 is a diagram showing a state during torque measurement according to an embodiment of the present invention. [Figure 6] FIG. 10 is a diagram illustrating another configuration example of an embodiment of the present invention. [Figure 7] FIG. 1 is a diagram showing the configuration of a known measuring device. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described. This embodiment relates to measurement of the output torque of an electric motor in a drive unit of an electric vehicle in which the electric motor and gear mechanism are housed in a single housing. The following explanation will be given using an example where the measurement target is a drive unit in which a transaxle (reduction gear and differential gear) as a gear mechanism is housed in the same housing as an electric motor. First, FIG. 1 shows an outline of a drive unit that is the object of measurement in this embodiment. 1a shows the top surface of the drive unit 1, FIG. 1b shows the left side surface of the drive unit 1, and FIG. 1c shows the right side surface of the drive unit 1. FIG. As shown in the figure, the drive unit 1 includes a housing 10. The housing 10 is configured by connecting four separable housing parts indicated by P1, P2, P3, and P4 in Fig. 1a. An inverter is connected to the top surface of the housing 10 and is integrated with the housing 10 as part of the drive unit 1, but the inverter is not shown here to avoid complication. Next, FIG. 1d shows a schematic view of the mechanism of the drive unit 1 seen from above through the housing 10. As shown in the figure, an electric motor 11, an input shaft 12, a transmission gear 13, and a differential gear 14 are housed inside a housing 10, and the differential gear 14 is made up of a ring gear 141 and a differential case 142. One end of the input shaft 12 is connected by spline fitting to the rotor shaft 111 of the electric motor 11. The other end of the input shaft 12 is supported by a bearing 101, and a portion of the input shaft 12 near the connection point with the rotor shaft 111 is supported by a bearing provided in an input shaft mounting portion 112 of the electric motor 11. A helical gear is formed in the middle portion of the input shaft 12. The rotating shaft of the transmission gear 13 is supported at both ends by bearings 102 and 103. The transmission gear 13 is a two-stage gear and includes a large-diameter counter driven gear that meshes with the helical gear of the input shaft 12, and a small-diameter counter drive gear that meshes with a ring gear 141. Here, the ring gear 141 is a gear with a larger diameter than the counter driven gear of the transmission gear 13.

[0017] The rotating shaft of the differential gear 14 is supported at both ends by bearings 104 and 105. A gear mechanism is housed inside a differential case 142 of the differential gear 14, and this gear mechanism is connected to the left and right drive shafts 2 of the automobile and, together with a ring gear 141, realizes differential rotation of the left and right drive shafts 2.

[0018] The input shaft 12, the speed change gear 13, and the differential gear 14 described above constitute a gear mechanism that functions as a transaxle. The bearings 101-105 are fixed to the corresponding housing parts P1 / P2. 1a, for ease of manufacturing and maintenance and to ensure expandability, a through hole 107 covered with a removable cover 106 is provided on an extension of the rotational axis of the input shaft 12 of the housing part P1 on the opposite side of the housing 10 from the electric motor 11. Similarly, a through hole 109 covered with a removable cover 108 is provided on an extension of the rotational axis of the transmission gear 13 of the housing part P1.

[0019] Next, FIG. 2 shows the input shaft 12 of the drive unit 1 that is the object of measurement shown in FIG. As shown in the figure, the input shaft 12 has a rotor fitting portion 121 with an external spline formed at the end on the electric motor 11 side, and the input shaft 12 and the rotor shaft 111 are connected by inserting the rotor fitting portion 121 into a hole with an internal spline formed in the rotor shaft 111 of the electric motor 11 and spline-fitting it.

[0020] In addition, the input shaft 12 has a housing side supported portion 122 that is supported by a bearing 101 at the end on the housing 10 side opposite the electric motor 11 side, and also has a rotor side supported portion 123 that is supported by a bearing in the input shaft mounting portion 112 of the electric motor 11, slightly closer to the housing 10 than the rotor fitting portion 121.

[0021] The input shaft 12 is provided with a gear portion 125 in which the above-mentioned helical gear is formed in an intermediate portion 124 between the housing side supported portion 122 and the rotor side supported portion 123 . The drive unit 1 that is the object of measurement in this embodiment has been described above. Measurement of the torque of the output shaft of the electric motor 11 of the drive unit 1 according to this embodiment will be described below. The torque of the output shaft of the electric motor 11 of the drive unit 1 is measured in a form in which the input shaft 12 of the drive unit 1 shown in Fig. 2 is replaced with the measurement input shaft unit 3 shown in Fig. 3. In other words, the input shaft 12 is removed from the drive unit 1, and the measurement input shaft unit 3 is attached to the drive unit 1 instead for measurement.

[0022] Figures 3a and 3b show the measurement input shaft unit 3 as viewed from two directions that are perpendicular to the axial direction of the measurement input shaft unit 3 and are mutually perpendicular, and Figure 3c shows the cross-sectional shape along the cutting line AA in Figure 3a. As shown in the figure, the measurement input shaft unit 3 includes a shaft portion 31 and an external interface board 32. The shaft portion 31 has a rotor fitting portion 311 having an external spline formed thereon, a housing side supported portion 312, a rotor side supported portion 313, and an intermediate portion 314 which is the portion between the housing side supported portion 312 and the rotor side supported portion 213, and a gear portion 315 having a helical gear formed thereon is provided in the intermediate portion 314. The relative positions of the rotor fitting portion 311, housing side supported portion 312, rotor side supported portion 313, and gear portion 315 are the same as those of the input shaft 12 shown in Figure 2, with the rotor fitting portion 311 connected to the rotor shaft 111 by spline fitting, the helical gear of the gear portion 315 meshing with the large-diameter counter driven gear of the speed change gear 13, the housing side supported portion 312 being supported by bearing 101, and the rotor side supported portion 313 being supported by a bearing within the electric motor 11.

[0023] On the other hand, unlike the input shaft 12 shown in Figure 2, a strain-generating portion 316 is provided between the rotor-side supported portion 313 and the gear portion 315 of the intermediate portion 314 of the shaft portion 31, as shown in Figure 3c, and is formed to be thin so that part of the outer surface is flat. In addition, the shaft portion 31 is an extension of the input shaft 12 on the side opposite the electric motor 11, and the length of the shaft portion 31 is such that, when assembled to the drive unit 1, the end of the shaft portion 31 opposite the electric motor 11 protrudes outside the housing 10 through the through hole 107 when the cover 106 in Figure 1b is removed.

[0024] The external interface board 32 is detachably connected to the end of the shaft portion 31 opposite to the electric motor 11. As shown in Fig. 3d, which shows the external interface board 32 as viewed in the axial direction from the opposite side to the shaft portion 31, the external interface board 32 has a disk-shaped base 321, and this base 321 is connected to the end of the shaft portion 31 opposite to the electric motor 11 in such a manner as to form a flange of the shaft portion 31. The base 321 is also provided with a central hole 3211 that penetrates in the axial direction. 3a, one or more strain gauges 401, one or more temperature gauges 402, and one or more thermocouples 403 are fixed by adhesive or the like to the flat outer surface of strain-flexing portion 316 of shaft 31. In addition, a reflective mark 404 for rotation detection is fixed by adhesive or the like to the side surface of the end of shaft 31 that will protrude outside housing 10 when assembled to drive unit 1.

[0025] 3d, a power receiving coil 322 wound in an annular shape around the edge of the base 321, a rectifier 323, and a wireless communication unit 324 are mounted on the surface of the base 321 of the external interface board 32 opposite the shaft 31. However, the rectifier 323 does not necessarily have to be provided on the surface of the base 321 opposite the shaft 31. Furthermore, if a separate antenna for wireless communication is used as the wireless communication unit 324, it is sufficient that at least the antenna is provided on the surface of the base 321 opposite the shaft 31.

[0026] Now, the power receiving coil 322 of the external interface board 32 outputs the AC power wirelessly fed via the magnetic field to the rectifier 323, and the rectifier 323 converts the AC power into DC power and supplies it to each part such as the wireless communication unit 324. The wireless communication unit 324 is connected by wire to the strain gauges 401, temperature gauges 402, and thermocouples 403 of the strain-flexing part 316, and converts the strain of the strain-flexing part 316 detected by the strain gauges 401, the temperature detected by the temperature gauges 402, and the temperature detected by the thermocouples 403 into digital values and transmits them wirelessly. This wireless transmission is performed, for example, by Bluetooth (registered trademark) or the like. The detection of strain using the strain gauges 401 can be performed using a bridge circuit of the strain gauges 401 using a four-gauge method or the like. Similarly, the detection of temperature using the temperature gauges 402 can be performed using a bridge circuit of the temperature gauges 402. In these cases, the bridge circuit may be formed in the strain-flexing part 316. In this case, DC power is supplied from the rectifier 323 to the bridge circuit of the strain-flexing part 316.

[0027] 3a and 3b, the wired connection between the wireless communication unit 324 and the strain gauge 401, temperature gauge 402, and thermocouple 403 is achieved by providing a passage 33 in the shaft 31, which is a cavity that runs from the opening in the strain-flexing part 316 of the shaft 31 to the opening at the end of the shaft 31 on the external interface panel 32 side, and connecting a cable that passes through the passage 33 and the central hole 3211 in the base 321 of the external interface panel 32. Furthermore, when a bridge circuit is provided in the strain-flexing part 316, a cable for supplying DC power to the bridge circuit is also connected through this passage 33.

[0028] An example of a procedure for measuring the output shaft torque of the electric motor 11 using such a measurement input shaft unit 3 will now be described. First, as shown in FIG. 4a, the housing 10 of the drive unit 1 to be measured is opened to a necessary extent, and the input shaft 12 is removed from the drive unit 1. Next, as shown in Figure 4b, the shaft 31 of the measurement input shaft unit 3 is attached to the drive unit 1 in place of the input shaft 12, and the housing 10 is returned to its original position. However, the lid 106 of the housing part P1 is removed, and the end of the shaft 31 on the external interface panel 32 side protrudes outside the housing 10 through the through-hole 107 that was covered by the lid 106. In addition, the cables of the strain gauge 401, temperature gauge 402, and thermocouple 403 are pulled out to the outside of the end of the shaft 31 on the external interface panel 32 side.

[0029] An oil seal is then installed to seal the gap between shaft 31 and through-hole 107. As shown in Fig. 4c, the cables for strain gauge 401, temperature gauge 402, and thermocouple 403 are passed through central hole 3211 of base 321 at the end of shaft 31 protruding from housing 10, and then base 321 of external interface panel 32 is connected, and the cables connecting strain gauge 401, temperature gauge 402, and thermocouple 403 are connected as required to wireless communication unit 324 and rectifier 323.

[0030] Next, as shown in FIG. 5a, the drive unit 1 is fixed to a test stand, and a dynamometer 5 is connected to the drive unit 1 in place of the left and right drive shafts 2. In addition, a power supply receiving panel 6 is arranged so as to face the external interface panel 32 located outside the housing 10 of the measurement input shaft unit 3, and a power supply device 7 and a measuring device 8 are connected to the power supply receiving panel 6. Here, the power supply receiving panel 6 has a disk-shaped base 61, as shown in Figure 5b when the power supply receiving panel 6 is viewed in the axial direction of the measurement input shaft unit 3 when facing the external interface panel 32, and is equipped with a power transmission coil 62 and one or more wireless receiving antennas 63 on the surface of the base 61 facing the external interface panel 32.

[0031] The power transmission coil 62 is a coil wound so as to be coaxial with the power receiving coil 322 of the external interface panel 32 when the power supply receiving panel 6 is placed directly opposite the external interface panel 32, and is driven by AC power from the power supply unit 7 to wirelessly supply power to the power receiving coil 322 via a magnetic field.

[0032] The wireless receiving antenna 63 receives the wireless transmission signal from the wireless communication unit 324 of the external interface board 32 and sends it to the measuring device 8. When multiple wireless receiving antennas 63 are provided, they are installed at positions directly facing the positions of the wireless communication units 324 when the external interface board 32 is at different rotation angles (for example, at rotation angles of 180 degrees, 120 degrees, or 90 degrees) so that the wireless transmission signal can be received well regardless of the rotation angle of the external interface board 32.

[0033] In addition, a rotation detector 9 is positioned so that light such as red visible light is irradiated onto the position where a reflective mark 404 fixed to the side of the end of the shaft portion 31 of the measurement input shaft unit 3 passes as the shaft portion 31 rotates, and the reflected light is detected. The rotation detector 9 outputs the detection timing of the reflected light to the measuring device 8 . Then, the measuring device 8 demodulates the wireless transmission signal received by the wireless receiving antenna 63 to obtain each detection value detected using the strain gauge 401, temperature gauge 402, and thermocouple 403, and measures the output torque of the electric motor 11 of the drive unit 1 from the amount of strain of the strain-generating part 316 of the measurement input shaft unit 3 represented by the detection value detected using the strain gauge 401, while performing temperature correction using the temperature detection value detected using the temperature gauge 402 and thermocouple 403.

[0034] The measuring device 8 also performs processing such as measuring the rotation speed of the rotor shaft 111 of the electric motor 11 from the detection period of the reflected light in the rotation detector 9. The embodiments of the present invention have been described above. As described above, in this embodiment, the input shaft 12 of the gear mechanism of the drive unit 1, which houses the electric motor 11 and gear mechanism in one housing 10, is replaced with a shaft portion to which a strain gauge 401 is attached, and torque is measured using the strain gauge 401, so that the output torque of the electric motor 11 in the drive unit 1 can be measured even when the space inside the housing 10 is narrow. Furthermore, since the detection value detected using the strain gauge 401 is transmitted from the wireless communication unit 324 fixed outside the housing 10 to the end of the shaft portion 31 exposed outside the housing 10, the detection value can be stably obtained outside the housing 10.

[0035] In the above embodiment, power is supplied to the measurement input shaft unit 3 and detection values detected by the measurement input shaft unit 3 using the strain gauge 401, temperature gauge 402, and thermocouple 403 are acquired wirelessly. However, as shown in FIG. 6a, for example, instead of the external interface board and power supply receiving panel 6, a multi-stage rotary connector 600 such as a multi-stage slip ring or a multi-stage rotary connector that connects the end of the shaft portion 31 of the measurement input shaft unit 3 to the power supply device 7 and the measurement device 8 may be provided, and power may be supplied and detection values may be acquired via the rotary connector 600. The rotating portion of the rotary connector 600 is fixed to the end of the shaft portion 31 so as to rotate together with the end, and the fixed portion of the rotary connector 600 is fixed to a support or the like provided outside the housing 10 and connected to the power supply device 7 and the measurement device 8. Furthermore, in the above embodiment, the end of the shaft portion 31 of the measurement input shaft unit 3 and the external interface panel 32 are exposed to the outside of the housing 10. However, when applied to a drive unit 1 that is capable of communication and power supply inside and outside the housing 10, the measurement input shaft unit 3 may not be exposed to the outside of the housing 10. That is, without providing the external interface panel 32, the length of the shaft portion 31 may be reduced so that the entire shaft portion 31 is housed inside the housing 10, and a communication unit that performs communication inside and outside the housing 10 and a power receiving unit that receives power from outside the housing 10 may be provided inside the housing 10, and the power received by the power receiving unit may be supplied to the strain gauge 401, the temperature gauge 402, the thermocouple 403, and the communication unit, and each detected value may be transmitted from the communication unit to the outside of the housing 10.

[0036] Furthermore, by using the measurement input shaft unit 3 as described above, a dynamometer 5 may be connected to the end of the shaft portion 31 of the measurement input shaft unit 3 via a coupling 610, as shown in Figure 6b, to measure the output torque of the electric motor 11. In addition, in the above embodiment, a through hole 107 is provided in the drive unit 1 to be measured to allow the end of the shaft portion 31 of the measurement input shaft unit 3 to protrude outside the housing 10, but if such a through hole 107 does not exist in the drive unit 1 to be measured, a through hole may be formed by processing and this embodiment may be applied.

[0037] The above embodiment can also be applied to the case where the drive unit 1 is mounted on an automobile and measurements are taken of the electric motor 11 in an operating state. In this case, the left and right drive shafts 2 of the automobile are connected to the drive unit 1, and the power supply receiving panel 6 and rotation detector 9 are placed in the motor room together with the drive unit 1. [Explanation of symbols]

[0038] 1...drive unit, 2...drive shaft, 3...measurement input shaft unit, 5...dynamometer, 6...power supply receiving panel, 7...power supply device, 8...measuring device, 9...rotation detector, 10...housing, 11...electric motor, 12...input shaft, 13...transmission gear, 14...differential gear, 31...shaft portion, 32...external interface panel, 33...passage, 61...base, 62...power transmission coil, 63...wireless receiving antenna, 101-105...bearing, 106...lid, 107...through hole, 108...lid, 109...through hole, 111...rotor shaft, 112...input shaft mounting portion, 121...rotor fitting portion, 122...housing side supported portion, 123...rotor side supported portion, 124...center Intermediate portion, 125...gear portion, 141...ring gear, 142...differential case, 311...rotor fitting portion, 312...housing side supported portion, 313...rotor side supported portion, 314...intermediate portion, 315...gear portion, 316...strain-flexing portion, 321...base, 322...receiving coil, 323...rectifier, 324...wireless communication unit, 401...strain gauge, 402...temperature gauge, 403...thermocouple, 404...reflective mark, 600...rotary connection connector, 610...coupling, 711...first upper base, 712...first lower base, 713...first mounting base, 721...second upper base, 722...second lower base, 723...second mounting base, 730...strain-flexing portion, 731...strain gauge, 3211...central hole.

Claims

1. A torque measuring device for measuring an output torque of an electric motor of a drive unit in which an electric motor and a gear mechanism for transmitting power of the electric motor are housed in a housing, a measurement input shaft unit including a shaft portion connected to the rotor shaft of the drive unit from which the input shaft of the gear mechanism connected to the rotor shaft of the electric motor has been removed, and a transmission portion; the shaft portion has a connecting portion connected to the rotor shaft, a gear portion that meshes with a gear that is driven by a gear of the input shaft when the input shaft of the gear mechanism is not removed, and a strain-flexing portion that is a part of the shaft portion and is located between the connecting portion and the gear portion; a strain gauge used to detect strain in the strain-flexible portion is attached to the strain-flexible portion of the shaft portion; The torque measuring device is characterized in that the transmission unit transmits the detection value detected by the strain gauge to the outside of the housing.

2. 2. The torque measuring device according to claim 1, a shaft tip end portion, which is an end portion of the shaft portion that is not connected to the rotor shaft, protruding to the outside of the housing through a hole that penetrates the housing; A torque measuring device characterized in that the transmission unit is fixed to the tip of the shaft outside the housing, and the transmission unit transmits the detection value detected using the strain gauge from the position of the transmission unit to the outside.

3. 3. The torque measuring device according to claim 2, The torque measuring device is characterized in that the transmission unit transmits the detection value detected using the strain gauge by transmitting it via wireless communication.

4. 3. The torque measuring device according to claim 2, the transmission unit includes a rotary connector having a fixed portion and a rotary portion rotatable relative to the fixed portion; A torque measuring device characterized in that the rotating part is fixed to the tip of the shaft part outside the housing, and the rotary connection connector transmits a signal representing the detection value detected using the strain gauge.

5. 3. The torque measuring device according to claim 2, The shaft portion has a passage therein that is a cavity penetrating between the opening of the strain-flexing portion and the opening of the tip end of the shaft portion, The torque measuring device is characterized in that the transmission unit and the strain gauge are connected by wire via an electric wire passing through the passage.

6. 4. The torque measuring device according to claim 3, The measurement input shaft unit has an external interface board, which is a plate-like member fixed to the tip of the shaft portion and perpendicular to the axis of the shaft portion, outside the housing, The torque measurement device is characterized in that the external interface panel is equipped with the transmission unit, a receiving coil that receives AC power via wireless power supply, and a rectifier that generates DC power from the AC power received by the receiving coil to be supplied to the transmission unit and the strain gauge, and at least the antenna for wireless communication of the transmission unit and the receiving coil are arranged on the outer surface of the external interface panel, which is the surface opposite to the drive unit side.

7. 7. A torque measuring device according to claim 1, 2, 3, 4, 5 or 6, A torque measuring device characterized in that the gear mechanism of the drive unit includes a gear mechanism that functions as a reducer and a differential gear.

8. A torque measurement system including the torque measurement device according to claim 2, 3, 4, 5 or 6, a mark fixed to the peripheral surface of the tip of the shaft portion; A torque measurement system comprising a rotation measurement device that detects the marks without contact and measures the rotation speed of the rotor shaft from the detection period of the marks.

9. A torque measurement system including the torque measurement device according to claim 2, 3, 4, 5 or 6, A torque measurement system comprising a dynamometer arranged outside the housing and connected to the output shaft of the gear mechanism of the drive unit.

10. A torque measurement system including the torque measurement device according to claim 6, a power supply receiving unit having an inner surface facing the outer surface of the external interface board without contacting the outer surface, the power supply receiving unit being located at a position close to the outer surface of the external interface board outside the housing; a power transmission coil arranged coaxially with the power receiving coil and an antenna for wireless communication with the transmission unit, mounted on the inner surface of the power supply / receiving unit.

11. A torque measurement method for measuring an output torque of an electric motor of a drive unit in which an electric motor and a gear mechanism that transmits power of the electric motor are housed in a housing, comprising: a first step of opening a housing of the drive unit and removing an input shaft of the gear mechanism connected to a rotor shaft of the electric motor; a second step of incorporating the shaft portion of a measurement input shaft unit, which includes a connecting portion, a gear portion, and a transmission portion, into a drive unit in such a manner that the connecting portion of the shaft portion is connected to the rotor shaft and the gear portion is engaged with a gear that is driven by the gear of the input shaft when the input shaft of the gear mechanism is not removed; a third step of closing the housing so that a shaft tip, which is an end of the shaft that is not connected to the rotor shaft, protrudes to the outside of the housing through a hole that penetrates the housing; the shaft portion has a strain-flexing portion that is a part of the shaft portion and is located between the connecting portion and the gear portion, and a strain gauge used to detect strain in the strain-flexing portion is attached to the strain-flexing portion of the shaft portion, A torque measurement method characterized in that the transmission part is fixed to the tip of the shaft part outside the housing, and the detection value detected using the strain gauge is transmitted from the position of the transmission part to the outside.

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