Rotation measuring device

Abstract

To detect a physical quantity correlated with angular acceleration of a rotating shaft using a retrofittable rotation measuring device.SOLUTION: A sub-base 12 is bound to a main base 11 in which a rotating shaft 500 is inserted into a hollow section 111, and a rotation detector 1 is fixed to the rotating shaft 500. A first acceleration sensor 161 and a second acceleration sensor 162 that respectively detect acceleration in a tangential direction of a circle centered on a set axis C passing through the positions with a direction heading to a same rotational direction as a positive direction are provided at the two positions on the main base 11 which are line-symmetrical with respect to the set axis C overlapping with a rotational center axis of the rotating shaft 500 in the time of fixation. 1 / 2 of an addition value of the output of the first acceleration sensor 161 and the second acceleration sensor 162 is detected as tangential acceleration due to angular acceleration of the rotating shaft 500.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a technique for detecting a physical quantity correlated with the angular acceleration of a rotating shaft.

Background Art

[0002] As a technique for detecting the angular acceleration of a rotating shaft, a technique for detecting the angular acceleration of an electric motor of an electric vehicle by differentiating the rotation speed of the electric motor is known (for example, Patent Document 1). In addition, a technique for detecting the rotation speed of an electric motor of an electric vehicle using an encoder that outputs a pulse for each predetermined rotation angle is known (for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The electric motor of an electric vehicle has better response than an internal combustion engine. When detecting the angular acceleration by differentiating the rotation speed detected by a general rotation sensor provided in the electric motor, the time resolution may not be sufficient for applications such as measurement for tests and performance evaluations. Also, when the above-described encoder is used as a rotation sensor, etc., the time interval of the pulse output may become extremely large during low-speed driving (low rotation speed) of several km / h or less, and the rotation speed itself may not be correctly detected.

[0005] Therefore, for such an electric vehicle, it is desired that a retrofittable rotation detection device can measure a physical quantity correlated with the angular acceleration within the required time resolution and measurement range. Therefore, the object of the present invention is to provide a retrofittable rotation measuring device that can detect a physical quantity correlated with the angular acceleration of a rotating shaft even at low rotational speeds with high temporal resolution. [Means for solving the problem]

[0006] To achieve the above objective, the present invention provides a rotation measuring device for measuring the rotation of a rotating shaft, comprising a main base, a sub-base that can be fastened to the main base, a first acceleration sensor fixed to the main base, and a second acceleration sensor fixed to the main base. Here, the main base and the sub-base are fastened together such that the setting axis, whose relative position to the main base is fixedly determined, coincides with the rotational center axis of the rotating shaft.

[0007] Furthermore, this rotation measuring device may have one or more first clamping members attached to the main base, each having an end that contacts the outer circumferential surface of the rotating shaft by fastening the main base and the sub-base, and one or more second clamping members attached to the sub-base, each having an end that contacts the outer circumferential surface of the rotating shaft by fastening the main base and the sub-base. Here, the main base and the sub-base clamp the rotating shaft in the radial direction by the contact between the end of the first clamping member and the outer circumferential surface of the rotating shaft, and by the contact between the end of the second clamping member and the outer circumferential surface of the rotating shaft. Furthermore, the first clamping member is interchangeably mounted on the main base, and the distance from the end of the first clamping member to the setting axis can be changed by replacing the first clamping member, and the second clamping member is interchangeably mounted on the sub-base, and the distance from the end of the second clamping member to the setting axis when the main base and the sub-base are fastened together can be changed by replacing the second clamping member.

[0008] Furthermore, the rotation measuring device described above has a main base that has a rotating shaft housing space formed by a recess perpendicular to the setting axis, which contains the setting axis, and the recess includes positions on both sides of the recess that are symmetrical with respect to the setting axis, where the first acceleration sensor and the second acceleration sensor are arranged. The sub-base may be fastened to the main base so as to cover the opening of the rotating shaft housing space of the main base while the rotating shaft is housed within the rotating shaft housing space of the main base.

[0009] In this case, the first clamping member described above may be mounted such that its end protrudes from the surface of the main base facing the rotating shaft housing space, and the second clamping member may be mounted such that its end protrudes from the surface of the main base facing the rotating shaft housing space when the main base and the sub-base are fastened together.

[0010] Furthermore, the rotation measuring device may be provided with a rotation detection means. In this case, the second acceleration sensor detects the acceleration in the same circumferential direction as the first tangential acceleration in the direction of the tangential line passing through the second acceleration sensor of the circle, and the rotation detection means calculates the detected tangential acceleration by adding the first tangential acceleration and the second tangential acceleration.

[0011] Alternatively, the rotation measuring device may be provided with an adjustment means, an adjustment amount setting means, and a rotation detection means. In this case, the second acceleration sensor detects the acceleration in the same circumferential direction as the first tangential acceleration, where the sign of the tangential line passing through the second acceleration sensor of the circle is the same. The adjustment means adjusts at least one of the first tangential acceleration and the second tangential acceleration with a set gain and offset and outputs it. The adjustment amount setting means sets the gain and offset so that the sum of the first tangential acceleration and the second tangential acceleration output from the adjustment means is zero when the angular acceleration of the rotating shaft is zero. The rotation detection means calculates the detected tangential acceleration as the acceleration obtained by adding the first tangential acceleration and the second tangential acceleration output from the adjustment means.

[0012] Furthermore, the rotation detection means may calculate the angular acceleration of the rotating shaft by dividing the detected tangential acceleration by the radius of the circle. In the rotation measuring device described above, a first acceleration sensor and a second acceleration sensor are fixed to a single main base. Furthermore, the first and second acceleration sensors are positioned symmetrically with respect to a set axis that coincides with the rotation center axis of the rotating shaft when the main base and sub-base are fastened together and fixed to the rotating shaft.

[0013] Therefore, in a configuration that can be retrofitted to a rotating shaft, the first acceleration sensor and the second acceleration sensor can be precisely fixed at positions symmetrical with respect to the rotational axis of the rotating shaft. Here, from the accelerations at two positions that are symmetrical with respect to the rotational axis, physical quantities correlated with the angular acceleration of the rotating shaft, such as tangential acceleration due to angular acceleration, can be calculated. By precisely fixing the first and second acceleration sensors at these symmetrical positions, accurate measurement of physical quantities correlated with angular acceleration can be performed.

[0014] For example, if a rotation detection means is provided as described above, and the acceleration obtained by adding the first tangential acceleration detected using the first acceleration sensor and the second tangential acceleration detected using the second acceleration sensor is calculated as the detected tangential acceleration, the tangential acceleration due to the angular acceleration of the rotating shaft can be accurately measured, excluding the effects of gravity and external forces. Furthermore, the effect of the deviation of the rotating shaft from the rotation center axis of the set axis can also be eliminated.

[0015] Furthermore, if the rotation detection means calculates the angular acceleration of the rotating shaft by dividing the detected tangential acceleration by the radius of the circle, it is possible to accurately measure the angular acceleration of the rotating shaft while eliminating the influence of gravity and external forces. Furthermore, by detecting tangential acceleration and angular acceleration due to the angular acceleration of the rotating shaft from the tangential acceleration in this way, it is possible to detect physical quantities correlated with the angular acceleration of the rotating shaft even at low rotational speeds with higher temporal resolution compared to detecting angular acceleration by differentiating the rotational speed detected by the rotation sensor.

[0016] Furthermore, if the first clamping member of the main base and the second clamping member of the sub-base are made interchangeable, the rotation measuring device can be applied to rotating shafts of different diameters. Next, in order to achieve the above objective, the present invention provides a rotation measuring device for measuring the rotation of a rotating shaft, which includes a base that is detachably fixed to the rotating shaft so as to rotate together with the rotating shaft, a first acceleration sensor fixed to the base, a second acceleration sensor fixed to the base, and a rotation detection means. The base is fixed to the rotating shaft such that a setting axis, whose relative position to the base is fixedly determined, coincides with the rotation center axis of the rotating shaft, and the first acceleration sensor and the second acceleration sensor are positioned symmetrically with respect to the setting axis. Furthermore, the first acceleration sensor detects the acceleration in the tangential direction of a circle centered on the setting axis that passes through the first acceleration sensor as the first tangential acceleration, and also detects the acceleration in the radial direction of the circle that passes through the first acceleration sensor as the first radial acceleration, and the second acceleration sensor detects the acceleration in the radial direction of the circle that passes through the second acceleration sensor, where the sign of the acceleration toward the center of the circle is the same as the first radial acceleration as the second radial acceleration. Furthermore, the rotation detection means, with the base fixed to the rotating shaft, performs a correction according to the ratio of the first radial acceleration to the second radial acceleration to remove the influence of the deviation of the rotation center axis of the rotating shaft from the set axis on the tangential acceleration component due to the angular acceleration of the rotating shaft included in the first tangential acceleration.

[0017] Here, the rotation measuring device is configured such that the second acceleration sensor detects as the second tangential acceleration the acceleration in the same circumferential direction, where the positive and negative sign of the tangential line passing through the second acceleration sensor of the circle is the same as the first tangential acceleration, and the rotation detection means determines the tangential acceleration a due to the angular acceleration of the rotating shaft, with the first tangential acceleration being SA, the second tangential acceleration being SB, the first radial acceleration being DA, the second radial acceleration being DB, the radius of the circle being r, the tangential acceleration component due to the angular acceleration of the rotating shaft in the first tangential acceleration SA being aA, and the tangential acceleration a due to the angular acceleration of the rotating shaft in the first tangential acceleration SB being aB, KD = DA / DB dx = {(1-KD)·r} / (1+KD) KA = r / (r - dx) KB = r / (r + dx) As aA = (SA + SB) / {(1 / KD)+1)} aB = (SA + SB) / (1 + KD) a = {(KA·aA)+(KB·aB)} / 2 Or a = {(KA·SA)+(KB·SB)} / 2 It may be calculated by

[0018] Even with such a rotation measuring device, it is possible to perform measurement that removes the influence of the deviation of the rotation center axis of the rotating shaft from the set axis. In addition, in such a rotation measuring device, in the rotation detecting means, the angular acceleration of the rotating shaft may be calculated by dividing the tangential acceleration a by the radius of the circle.

Advantages of the Invention

[0019] As described above, according to the present invention, it is possible to provide a retrofittable rotation measuring device that can detect a physical quantity correlated with the angular acceleration of a rotating shaft even at a low rotation speed with high time resolution.

Brief Description of the Drawings

[0020] [Figure 1] It is a diagram showing the configuration of a rotation detector according to an embodiment of the present invention. [Figure 2] It is a diagram showing a fixing method of a rotation detector according to an embodiment of the present invention. [Figure 3] It is a diagram showing a method of dealing with differences in the diameter of the rotating shaft of a rotation detector according to an embodiment of the present invention. [Figure 4] It is a diagram showing the configuration of a rotation measurement system using a rotation detector according to an embodiment of the present invention. [Figure 5] It is a diagram showing the acceleration detected by an acceleration sensor according to an embodiment of the present invention. [Figure 6] It is a diagram showing another configuration example of a rotation measurement system using a rotation detector according to an embodiment of the present invention. [Figure 7] This figure shows another example configuration of a rotation detector according to an embodiment of the present invention. [Figure 8] This figure shows another example configuration of a rotation detector according to an embodiment of the present invention. [Figure 9] This figure shows another example configuration of a rotation detector according to an embodiment of the present invention. [Modes for carrying out the invention]

[0021] Embodiments of the present invention will be described below. First, let me describe the first embodiment. Figures 1a-f show the configuration of the rotation detector. For convenience, the front, back, top, bottom, left, and right directions of the rotation detector 1 are defined as shown in the figures. Figure 1a shows the top surface of the rotation detector 1, Figure 1b shows the front surface of the rotation detector 1, Figure 1c shows the left side of the rotation detector 1, Figure 1d shows the right side of the rotation detector 1, Figure 1e shows the bottom surface of the rotation detector 1, and Figure 1f shows a perspective view of the rotation detector 1. The rear surface of the rotation detector 1 is shown symmetrically to the front surface.

[0022] As shown in the figure, the rotation detector 1 has a rigid, integrated main base 11 and a sub-base 12 connected to the lower part of the main base 11. The main base 11 and the sub-base 12 are connected by a hinge 13 located at the lower right end of the main base 11, which rotatably connects the right end of the sub-base 12, and by a screw 14 located at the lower left end of the main base 11, which vertically connects the left end of the sub-base 12. The main base 11 has an inner surface that forms a hollow portion 111 (recess) with a downward-opening opening that penetrates in the front-to-back direction. The shape of the inner surface of the main base 11 is such that the width of the hollow portion 111 in the left-to-right direction is equally maximum in the range from at least the lowest position where the opening is located to the position of the set axis height, which is set at a predetermined height in the vertical direction of the hollow portion 111. In addition, the shape of the left and right inner surfaces of the main base 11 in the range above the position of the set axis height or a position slightly above the position of the set axis height is tapered, narrowing towards the center in the left-to-right direction.

[0023] The tapered portions on the left and right inner surfaces of the main base 11 are provided with first mounting grooves 112 extending in the front-to-back direction. Each first mounting groove 112 is detachably fitted with a clamping block 15, such that the clamping block 15 protrudes inward from the inner surface. The upper surface of the sub-base 12 is provided with a second mounting groove 121 extending in the front-to-back direction. Each second mounting groove 121 is detachably fitted with a clamping block 15, such that the clamping block 15 protrudes upward from the upper surface.

[0024] Here, a setting axis C is pre-set for the rotation detector 1, with the front-rear direction as the axial direction. The setting axis C is the axis that is equidistant from the inward-facing surface of the hollow portion 111 of each clamping block 15 when the sub-base 12 is fastened to the main base 11 with screws 14. The vertical height of the setting axis C is the setting axis height described above.

[0025] Next, the first acceleration sensor 161 and the second acceleration sensor 162 are fixed at the setting axis height positions on the left and right sides of the main base 11 outside the hollow section 111, such that their distances to the setting axis C are equal. Therefore, the first acceleration sensor 161 and the second acceleration sensor 162 are positioned symmetrically with respect to the setting axis C (point-symmetrically with respect to the setting axis C when viewed in the axial direction).

[0026] Next, the rotation detector 1 is used by fixing it to the rotating shaft to be measured. The rotating shaft is secured by opening the hinge 13 as shown in Figure 2a, inserting the hollow portion 111 of the main base 11 onto the rotating shaft 500, then closing the hinge 13 as shown in Figure 2b to fasten the sub-base 12 to the main base 11 with screws 14, and finally clamping the rotating shaft 500 with the three clamping blocks 15 as shown in Figures 2c and 2d.

[0027] In this state, with the rotation detector 1 fixed to the rotating shaft 500, the rotational axis of the rotating shaft 500 is equidistant from the inward-facing surface of the hollow portion 111 of each clamping block 15, and coincides with the setting axis C described above. Next, as described above, the three clamping blocks 15 are detachably attached to the main base 11 and the sub-base 12. Furthermore, as shown in Figures 3a, b, and c, by replacing the clamping block 15 with one of a different length in the direction toward the setting axis C to match the diameter of the rotating shaft 500, the rotation detector 1 can be fixed and used on a rotating shaft 500 of a different diameter. Next, we will describe a rotation measurement system configured using such a rotation detector 1. Figure 4 shows the functional configuration of the signal processing system of the rotation measurement system. As shown in the figure, the rotation measurement system comprises a rotation detector 1 and a calculation device 2. In addition to the first acceleration sensor 161 and the second acceleration sensor 162 described above, the rotation detector 1 includes a gain / offset adjustment unit 101, an adder 102, an analog-to-digital converter 103 (A / D), and a wireless interface 104 (wireless IF), which are not shown in Figure 1-3. The gain / offset adjustment unit 101 adjusts the gain and offset of the output of the first acceleration sensor 161 and outputs it to the adder unit 102. The adder unit 102 adds the output of the gain / offset adjustment unit 101 and the output of the second acceleration sensor 162 and transmits it to the analog-to-digital converter 103. The analog-to-digital converter 103 converts the output of the adder unit 102 into a digital signal, and the wireless interface 104 wirelessly transmits the output of the analog-to-digital converter 103 as detection data to the arithmetic unit 2.

[0028] Next, the arithmetic unit 2 includes a wireless communication unit 201, an arithmetic processing unit 202, a digital-to-analog converter 203 (D / A), and a control unit 204 that controls the entire rotation measurement system. The wireless communication unit 201 receives detection data from the rotation detector 1 via wireless communication and sends it to the arithmetic processing unit 202. The arithmetic processing unit 202 performs predetermined calculations on the detection data sent from the wireless communication unit 201 to generate digital measurement data. The details of the calculations performed by the arithmetic processing unit 202 will be described later.

[0029] The arithmetic processing unit 202 then outputs the generated digital measurement data as a digital measurement signal DO to an external device of the arithmetic unit 2. The digital-to-analog converter 203 converts the digital measurement data generated by the arithmetic processing unit 202 into an analog signal and outputs it as an analog measurement signal AO to an external device of the arithmetic unit 2.

[0030] Furthermore, the control unit 204 controls the execution of calibration operations for adjusting the gain and offset in the gain / offset adjustment unit 101, as well as other control operations, via the wireless communication unit 201 and the wireless interface 104 of the rotation detector 1. The following describes the details of the signal processing operation of such a rotation measurement system. First, the first acceleration sensor 161 and the second acceleration sensor 162 are uniaxial acceleration sensors, and capacitive MEMS sensors can be used as such uniaxial acceleration sensors. Generally, capacitive acceleration sensors can also detect DC component acceleration. However, the first acceleration sensor 161 and the second acceleration sensor 162 may be other types of acceleration sensors depending on the measurement application. For example, in applications requiring high resolution of acceleration magnitude, piezoelectric acceleration sensors may be used. Next, as shown in Figure 5a, the first acceleration sensor 161 is positioned to detect acceleration SA in the direction of the detection axis, with the axis tangential to the circle passing through the first acceleration sensor 161 and centered on the setting axis C as the detection axis, and the second acceleration sensor 162 is positioned to detect acceleration SB applied in the direction of the detection axis, with the axis tangential to the circle passing through the second acceleration sensor 162 and centered on the setting axis C as the detection axis.

[0031] In this state, with the rotation detector 1 fixed to the rotating shaft 500 as described above, the rotational axis of the rotating shaft 500 coincides with the set axis C. Therefore, with the rotation detector 1 fixed to the rotating shaft 500, the positions of the first acceleration sensor 161 and the second acceleration sensor 162 are symmetrical with respect to the rotational axis of the rotating shaft 500, and the angular difference between the first acceleration sensor 161 and the second acceleration sensor 162 in the direction of rotation of the rotating shaft 500 as seen from the rotational axis of the rotating shaft 500 is 180°. The first acceleration sensor 161 and the second acceleration sensor 162 then detect acceleration in the tangential direction of the same circle centered on the rotational axis of the rotating shaft 500.

[0032] Furthermore, as shown in Figure 5a with the arrows marked with "+" indicating the positive direction, the positive direction of acceleration SA detected by the first acceleration sensor 161 and the positive direction of acceleration SB detected by the second acceleration sensor 162 are set to be in the direction of tangential lines pointing in the same circumferential direction, and are in opposite directions from the perspective of a stationary system, which is a system fixed to the Earth and does not rotate with the rotating shaft 500.

[0033] Furthermore, as shown in Figure 5b, if we denote the tangential acceleration applied to the first acceleration sensor 161 and the second acceleration sensor 162 by the angular acceleration of the rotating shaft 500 as a, the acceleration due to gravity as g, the acceleration applied to the rotating shaft 500 by disturbance in a direction perpendicular to the rotational axis of the rotating shaft 500 as b, and if we denote the component of the acceleration due to gravity g in the positive direction of the detection axis of the first acceleration sensor 161 as gx, and the component of the acceleration due to disturbance b in the positive direction of the detection axis of the first acceleration sensor 161 as bx, then, when the rotating shaft 500 has rotated θ from an angle where the left-right direction of the rotation detector 1 is in the horizontal direction of the fixed system (perpendicular to the acceleration due to gravity) as viewed from the fixed system, the acceleration SA detected by the first acceleration sensor 161 and the acceleration SB detected by the second acceleration sensor 162 can be expressed by the following equation when the gain and offset of the first acceleration sensor 161 and the second acceleration sensor 162 are equal.

[0034] SA = a + gx + bx SB = a - gx - bx Therefore, SA + SB = 2a, and the tangential acceleration a is, a can be found using the formula a = (SA + SB) / 2.

[0035] Now, prior to starting the measurement, the operator instructs the control unit 204 of the calculation unit 2 to perform calibration while the angular velocity of the rotating shaft 500 is constant, preferably while the rotating shaft 500 is stationary. The control unit 204, having been instructed to perform calibration, instructs the gain / offset adjustment unit 101 to perform a calibration operation to adjust the gain and offset via the wireless communication unit 201 and the wireless interface 104 of the rotation detector 1. Upon receiving the instruction, the gain / offset adjustment unit 101 performs a calibration operation and sets the gain and offset adjustment values ​​to be applied to the first acceleration sensor 161 so that the sum signal output by the adder unit 102, which is the sum of the output of the gain / offset adjustment unit 101 and the output of the second acceleration sensor 162, becomes 0.

[0036] Here, when the angular velocity of the rotating shaft 500 is constant or the rotating shaft 500 is stationary, the angular acceleration of the rotating shaft 500 becomes 0, the tangential acceleration a applied to the first acceleration sensor 161 and the second acceleration sensor 162 becomes 0, and when the gain and offset of the first acceleration sensor 161 and the second acceleration sensor 162 are equal, the sum signal SA+SB obtained by adding the acceleration SA detected by the first acceleration sensor 161 and the acceleration SB detected by the second acceleration sensor 162 is, SA + SB = (gx + bx) + (-gx - bx) = 0.

[0037] Furthermore, even when acceleration b is absent, SA + SB = (gx) + (-gx) = 0. Therefore, by setting the gain and offset adjustment values ​​applied to the first acceleration sensor 161 so that the summing signal output by the summing unit 102 becomes 0, the output of the gain / offset adjustment unit 101 can be adjusted to the signal that the first acceleration sensor 161 would output if the gain and offset of the first acceleration sensor 161 were equal to those of the second acceleration sensor 162. As a result, with the output of the gain / offset adjustment unit 101 as SA and the output of the second acceleration sensor 162 as SB, the above-mentioned SA+SB=2a and a=(SA+SB) / 2 hold true.

[0038] Now, once the gain / offset adjustment unit 101 has set the gain and offset adjustment values ​​applied to the output of the first acceleration sensor 161 so that the sum signal becomes 0, it completes the calibration operation and thereafter adjusts the gain and offset of the output of the first acceleration sensor 161 using the set adjustment values.

[0039] Furthermore, once the gain / offset adjustment unit 101 has completed the calibration operation, it notifies the control unit 204 of the calibration completion via the wireless interface 104 and the wireless communication unit 201 of the calculation unit 2. Upon receiving the notification, the control unit 204 indicates to the operator that measurement preparation is complete via display output, audio output, etc., and instructs the calculation processing unit 202 to start the measurement.

[0040] Next, when measurement begins, the arithmetic processing unit 202 starts processing the summation signal SA+SB, which is input to the arithmetic processing unit 202 via the analog-to-digital converter 103, wireless interface 104, and wireless communication unit 201. The summation unit 102 adds the output of the gain / offset adjustment unit 101 and the output of the second acceleration sensor 162, and outputs the calculation result as the digital measurement signal DO and the analog measurement signal AO.

[0041] The calculation processing performed by the calculation processing unit 202 is as follows when the tangential acceleration a is to be measured: a = (SA + SB) / 2 Perform the following calculation. Here, tangential acceleration = radius × angular acceleration, and since tangential acceleration is proportional to angular acceleration, even if tangential acceleration a is the target of measurement, the behavior and characteristics of the angular acceleration of the rotating shaft 500 can be evaluated from tangential acceleration a. However, the angular acceleration ω' of the rotating shaft 500 may also be the measurement target, in which case the calculation processing unit 202 will: a = (SA + SB) / 2, ω'=a / r The calculation is performed. However, r is the distance (radius of rotation) from the setting axis C, which has been set in the calculation processing unit 202 in advance, to the first acceleration sensor 161 or the second acceleration sensor 162.

[0042] Furthermore, the arithmetic processing unit 202 may perform calculations on other physical quantities related to the rotation of the rotating shaft 500, such as integrating the angular acceleration ω' to calculate the angular velocity ω of the rotating shaft 500. As described above, in this embodiment, the tangential acceleration due to the angular acceleration of the rotating shaft 500 and the angular acceleration of the rotating shaft 500 are measured from the tangential acceleration detected by the first acceleration sensor 161 and the second acceleration sensor 162, which are installed on the rotation detector 1 that is retrofitted and fixed to the rotating shaft 500.

[0043] Therefore, according to this embodiment, compared to the case where angular acceleration is detected by differentiating the rotational speed detected by the rotation sensor, physical quantities correlated with angular acceleration, such as tangential acceleration and angular acceleration of the rotating shaft 500, can be detected with high temporal resolution even at low rotational speeds by a rotation measurement system that can be retrofitted to the rotating shaft 500.

[0044] Furthermore, in this embodiment, the first acceleration sensor 161 and the second acceleration sensor 162 are fixed in positions symmetrical with respect to the setting axis C of a rigid, integrated main base 11. In addition, the rotation detector 1 has a structure in which the setting axis C coincides with the rotation center axis of the rotation shaft 500 due to the clamping of the rotation shaft 500 by fastening the main base 11 and the sub-base 12.

[0045] Therefore, the first acceleration sensor 161 and the second acceleration sensor 162 can be precisely fixed at positions symmetrical with respect to the rotational axis of the rotating shaft 500, and measurements can be performed. As a result, accurate measurements without mounting errors are achieved. Furthermore, since the clamping block 15, which is the part that directly clamps the rotating shaft 500, is made replaceable, the rotation detector 1 can be applied to rotating shafts 500 of different diameters. In the above embodiment, as shown in Figure 4, the gain and offset of the output of the first acceleration sensor 161 were adjusted on the rotation detector 1 side, and the output of the first acceleration sensor 161 after the adjustment was added to the output of the second acceleration sensor 162. However, these adjustments and additions may be performed on the arithmetic unit 2 side.

[0046] In other words, in this case, as shown in Figure 6, the signal processing system of the rotation detector 1 is composed of a first acceleration sensor 161, a second acceleration sensor 162, a first analog-to-digital converter 61, a second analog-to-digital converter 62, a first wireless interface 63, and a second wireless interface 64.

[0047] Then, the output of the first acceleration sensor 161 is converted into a digital signal by the first analog-to-digital converter 61 and wirelessly transmitted to the computing device 2 via the first wireless interface 63, and the output of the second acceleration sensor 162 is converted into a digital signal by the second analog-to-digital converter 62 and wirelessly transmitted to the computing device 2 via the second wireless interface 64.

[0048] Furthermore, the wireless communication unit 201 of the arithmetic unit 2 is configured to be capable of receiving 2 channels of wireless signals. The arithmetic processing unit 202 adjusts the gain and offset of the digital signals of the output of the first acceleration sensor 161 and the output of the second acceleration sensor 162 received via the wireless communication unit 201, as described above, and adds the adjusted output of the first acceleration sensor 161 and the output of the second acceleration sensor 162 as a preprocessing step for the arithmetic processing described above.

[0049] Furthermore, in the above embodiment, two-axis or three-axis acceleration sensors may be used as the first acceleration sensor 161 and the second acceleration sensor 162. As shown in Figure 7a, the first acceleration sensor 161 may detect not only the tangential acceleration SA of a circle centered on the setting axis C and passing through the first acceleration sensor 161, but also the radial acceleration DA of a circle centered on the setting axis C and passing through the first acceleration sensor 161. The second acceleration sensor 162 may detect not only the tangential acceleration SB of a circle centered on the setting axis C and passing through the second acceleration sensor 162, but also the radial acceleration DB of a circle centered on the setting axis C and passing through the first acceleration sensor 161. The acceleration DA and acceleration DB may be used to correct for the effect of the deviation of the rotation center axis of the rotating shaft 500 from the setting axis C.

[0050] That is, as shown in Figure 7b, in a plane perpendicular to the axial direction of the rotating shaft 500, the direction connecting the first acceleration sensor 161 and the second acceleration sensor 162 is the X direction, the direction perpendicular to the X direction is the Y direction, and an XY coordinate system is set with the coordinates of the setting axis C as the origin. The rotation center axis C' of the rotating shaft 500 is offset by dx in the X direction and dy in the Y direction from the setting axis C, and the coordinates of the rotation center axis C' are assumed to be (dx, dy). Furthermore, if the distance from the setting axis C to the first acceleration sensor 161 and the distance from the setting axis C to the second acceleration sensor 162 is r, the distance from the rotation center axis C' to the first acceleration sensor 161 is rA, the distance from the rotation center axis C' to the second acceleration sensor 162 is rB, the inclination of the line connecting the rotation center axis C' and the first acceleration sensor 161 with respect to the X axis is θA, and the inclination of the line connecting the rotation center axis C' and the second acceleration sensor 162 with respect to the X axis is θB, then the following equations 1 and 2 hold.

[0051] cosθA = (r - dx) / rA ... Equation 1 cosθB = (r+dx) / rB ... Equation 2 Furthermore, if the angular velocity of the rotating shaft 500 is ω, then the radial acceleration DA detected by the first acceleration sensor 161 is the X-component of the centrifugal acceleration rA·ω² around the rotational axis C', and the radial acceleration DB detected by the second acceleration sensor 162 is the X-component of the centrifugal acceleration rB·ω² around the rotational axis C', and the following equations 3 and 4 hold true.

[0052] DA = rA·ω²·COSθA...Equation 3 DB = rB·ω²·COSθB...Equation 4 Substitute equations 1 and 2 into equations 3 and 4, DA=(rA·ω2)·{(r-dx) / rA}=ω2·(r-dx) DB=(rB·ω2)·{(r+dx) / rB}=ω2·(r+dx) Therefore, equation 5 holds true.

[0053] DA / DB=ω2·(r-dx) / ω2·(r+dx)=(r-dx) / (r+dx)...Equation 5 r is the design value, and DA / DB is obtained by dividing the value detected by the first acceleration sensor 161 by the value detected by the second acceleration sensor 162. Assuming KD = DA / DB, dx = {(1-KD)·r} / (1+KD)...Equation 6 Thus, dx can be calculated using Equation 6. That is, dx can be calculated from the radial acceleration DA detected by the first acceleration sensor 161 and the radial acceleration DB detected by the second acceleration sensor 162.

[0054] Next, if we let ω' be the angular acceleration of the rotating shaft 500, then the tangential acceleration component aA due to the angular acceleration of the rotating shaft 500, which is included in the tangential acceleration SA detected by the first acceleration sensor 161, becomes the Y-direction component of the tangential acceleration rA·ω' around the rotational axis C', and the tangential acceleration component aB due to the angular acceleration of the rotating shaft 500, which is included in the tangential acceleration SB detected by the second acceleration sensor 162, becomes the Y-direction component of the tangential acceleration rB·ω' around the rotational axis C', and their magnitudes are shown by the following equations 7 and 8.

[0055] aA = rA·ω'·COSθA...Equation 7 aB = rB·ω'·COSθB...Equation 8 Here, from equations 1 and 2, aA=rA·ω'·COSθA=ω'·(r-dx)...Equation 9 aB=rB·ω'·COSθB=ω'·(r+dx)...Equation 10 Therefore, by setting a = r·ω' and applying the obtained dx, we set the first correction coefficient KA and the second correction coefficient KB according to equations 9 and 10.

[0056] KA=a / aA=(r·ω') / (rA·ω'·COSθA)=r / (r-dx)...Equation 11 KB=a / aB=(r·ω') / (rB·ω'·COSθB)=r / (r+dx)...Equation 12 Using KA and KB set in this way, KA·aA=a=r·ω'...Equation 13 KB·aB=a=r·ω'...Equation 14 This is the result.

[0057] Now, the detection axes for the acceleration components due to gravity and external forces of the tangential acceleration SA detected by the first acceleration sensor 161 and the tangential acceleration SB detected by the second acceleration sensor 162 are always in opposite directions in a fixed system. SA+SB=(aA+gx+bx)+(aB-gx-bx)=aA+aB This is the result.

[0058] Here, as shown in equations 9 and 10, aA=ω'·(r-dx) aB = ω'·(r+dx) Therefore, SA+SB=aA+aB=ω'·2r As a result, SA+SB eliminates the effect of the deviation of the rotation center axis C' from the set axis C.

[0059] On the other hand, it is also possible to eliminate the effect of deviation from the set axis C of the rotation center axis C' by calculating the tangential acceleration a while taking into account the DA and DB information. That is, from equations 9 and 10, aA / aB = (r-dx) / (r+dx), and from equation 5, aA / aB = DA / DB. And if we set DA / DB = aA / aB = KD, SA+SB=aA+aB=aA+(1 / KD)·aA={(1 / KD)+1)}·aA Next We can find aA by setting aA = (SA + SB) / {(1 / KD) + 1)}.

[0060] Also, SA + SB = aA + aB = (KD·aB) + aB = (1 + KD)aB, so We can find aB by setting aB = (SA + SB) / (1 + KD). Then, using KA and KB from equations 13 and 14, a=r·ω'=(KA·aA+KB·aB) / 2 The tangential acceleration a is detected by this method. Furthermore, if the rotation axis is vertical, or if the situation is in a zero-gravity environment, and the acceleration due to gravity (g) can be ignored, and acceleration (b) is not considered, a = {(KA·SA) + (KB·SB)} / 2 a=KA·SA a=KB·SB The tangential acceleration a may be detected by this method. By doing so, the effect of the deviation of the rotation center axis C' from the set axis C, which cannot be eliminated when only a single acceleration sensor is provided, can be eliminated.

[0061] Furthermore, when calculating the tangential acceleration a using a=KA·SA, it is not necessary to detect the tangential acceleration SB with the second acceleration sensor 162, and when calculating the tangential acceleration a using a=KB·SB, it is not necessary to detect the tangential acceleration SA with the first acceleration sensor 161. Therefore, the rotation detector 1 is equipped with a detection unit that calculates the tangential acceleration a as described above, and transmits the detected tangential acceleration a to the calculation device 2. In addition, the calculation processing unit 202 of the calculation device 2 may perform calculations of other physical quantities related to the rotation of the rotating shaft 500, such as the calculation of angular acceleration ω' using ω'=a / r, and the calculation of the angular velocity ω of the rotating shaft 500 by integrating the angular acceleration ω'.

[0062] However, such calculation and evaluation functions may be performed in cooperation between the rotation detector 1 and the calculation device 2 with an arbitrary division of functions. For example, the SA and DA detected by the first acceleration sensor 161 and the SB and DB detected by the second acceleration sensor 162 may be wirelessly transmitted to the calculation device 2, and the calculation processing unit 202 of the calculation device 2 may perform calculations such as tangential acceleration a and angular acceleration ω' in the manner described above.

[0063] Alternatively, the arithmetic unit 2 may acquire the aforementioned SA, SB, DA, DB, KD, dx, aA, aB, etc., from the rotation detector 1, and perform analysis to evaluate the deviation of the rotation center axis C' from the set axis C based on the acquired values. Next, the connection between the main base 11 and the sub-base 12 of the rotation detector 1 in the above embodiment may be done without using a hinge 13, as shown in Figures 8a1 and a2, by using a screw 14 that connects the left end of the sub-base 12 vertically to the lower left end of the main base 11, and a screw 14 that connects the right end of the sub-base 12 vertically to the lower right end of the main base 11. Alternatively, the connection may be done by any other mechanism or structure that can mechanically fasten the main base 11 and the sub-base 12.

[0064] Furthermore, in the above embodiment, the rotation detector 1 was fixed to the rotating shaft 500 using a clamping block 15, but this can be done by other mechanisms or structures as long as the rotation detector 1 can be fixed to the rotating shaft 500 so that the setting axis C coincides with the rotational center axis of the rotating shaft 500.

[0065] For example, as shown in Figures 8b1, b2, and b3, the rotation detector 1 may be fixed to the rotating shaft 500 using three clamping screws 800 instead of the clamping block 15. As shown in the figures, the rotation detector 1 is fixed to the rotation shaft 500 as shown in Figure 8b3 by opening the hinge 13 as shown in Figure 8b1, inserting the hollow portion 111 of the main base 11 onto the rotation shaft 500, and then closing the hinge 13 as shown in Figure 8b2, thereby fastening the sub-base 12 to the main base 11 with screws 14.

[0066] As shown in Figure 8b3, when the sub-base 12 is fastened to the main base 11 with screws 14, the main base 11 has two screw holes that penetrate from the outer circumference to the hollow portion 111, and the sub-base has one screw hole. Using these three screw holes, three clamping screws 800 can be attached so that their tips protrude into the hollow portion 111.

[0067] The three screw holes are arranged such that, when the main base 11 and the sub-base 12 are fastened together with screws 14, the orientation of the three clamping screws 800 differs by 120 degrees around the setting axis C. The rotation detector 1 is fixed to the rotation shaft 500 by clamping the rotation shaft 500 from 120-degree different directions with the tips of these three clamping screws 800.

[0068] Furthermore, the length of each clamping screw 8000 is set such that when the rotating shaft 500 is clamped by the three clamping screws 8000 that are fully screwed into the screw holes, the setting axis C coincides with the rotational axis of the rotating shaft 500. Furthermore, by replacing the clamping screw 800 attached to the rotation detector 1 with a clamping screw 800 of a different length, the rotation detector 1 can be fixed and used on a rotating shaft 500 of a different diameter. Furthermore, by changing the screw-in depth of each clamping screw 800, adjustments can be made to align the setting axis C with the rotational center axis of the rotating shaft 500. As shown in the left side view of Figure 8c1 and the right side view of Figure 8c2, the three clamping screws 800, the first acceleration sensor 161, and the second acceleration sensor 162 are positioned so that no unwanted moments are generated. Furthermore, even when clamping the rotating shaft 500 using the clamping screws 800 in this manner, the connection between the main base 11 and the sub-base 12 of the rotation detector 1 may be made without using the hinge 13, as shown in Figure 8d, by using a screw 14 that connects the left end of the sub-base 12 vertically to the lower left end of the main base 11, and a screw 14 that connects the right end of the sub-base 12 vertically to the lower right end of the main base 11. Alternatively, the connection between the main base 11 and the sub-base 12 may be made by any other mechanism or structure that can mechanically fasten them together.

[0069] Herein, the rotation measurement system described above is applicable to various rotating shafts 500. For example, as shown in Figure 9a, if the left and right drive shafts 900 of an electric vehicle are used as rotating shafts 500 and the rotation detector 1 is fixed to them, the angular velocity of the left and right drive shafts 900, the tangential acceleration proportional to the angular velocity, and other parameters such as angular acceleration and angular velocity can be measured. Furthermore, when applied to a transmission shaft that transmits torque, such as a drive shaft 900, it is preferable to also provide the rotation detector 1 with a function to measure the torque of the rotating shaft 500. In this case, for example, as shown in Figure 9b1, a composite detector is configured in which a rotation detector 1 and a fixing device 910 that can be fixed to the rotating shaft 500 by a mechanism similar to that of the rotation detector 1 are connected in the axial direction of the rotating shaft 500 by a beam-shaped strain generating section 912 to which a strain gauge 911 is attached. The strain generated in the strain generating section 912 in response to the torque transmitted by the rotating shaft 500 is detected by the strain gauge 911, the detected strain is wirelessly transmitted to the calculation device 2, and the amount of strain is converted into torque in the calculation device 2.

[0070] Alternatively, as shown in Figure 9b2, two rotation detectors 1 connected in the axial direction of the setting axis C by a beam-shaped elastic body 921 are fixed to the rotating shaft 500, and the moment of inertia of the two rotation detectors 1 connected by the elastic body 921 and the rotating shaft 500 is I, the distance from the setting axis C to the first acceleration sensor 161 and the second acceleration sensor 162 is r, and the difference between the tangential acceleration a measured using one rotation detector 1 and the tangential acceleration a measured using the other rotation detector 1 is Δa, and the torque T is, T = I × Δa / r It may also be calculated by this method.

[0071] However, the two rotation detectors 1 do not necessarily need to be connected by an elastic body 921; the two rotation detectors 1 can be fixed at positions separated by a predetermined distance in the axial direction of the rotating shaft 500, and the above formula T = I × Δa / r Torque T may be calculated by this method. [Explanation of symbols]

[0072] 1...Rotation detector, 2...Calculation unit, 11...Main base, 12...Sub base, 13...Hinge, 14...Screw, 15...Clamping block, 61...First analog-to-digital converter, 62...Second analog-to-digital converter, 63...First wireless interface, 64...Second wireless interface, 101...Gain / offset adjustment unit, 102...Addition unit, 103...Analog-to-digital converter, 104...Wireless interface, 111...Hollow section, 112...First mounting groove, 121...Second mounting groove, 161...First acceleration sensor, 162...Second acceleration sensor, 201...Wireless communication unit, 202...Calculation processing unit, 203...Digital-to-analog converter, 204...Control unit, 500...Rotation shaft, 800...Clamping screw, 900...Drive shaft, 910...Fixing device, 911...Strain gauge, 912...Strain generating section, 921...Elastic body.

Claims

1. A rotation measuring device for measuring the rotation of a rotating shaft, Main base and, A sub-base that can be fastened to the main base, A first acceleration sensor fixed to the main base, It has a second acceleration sensor fixed to the main base, The main base and the sub-base are fastened together such that they clamp the rotating shaft in the radial direction of the rotating shaft, so that the setting axis, whose relative position to the main base is fixed, coincides with the rotational axis of the rotating shaft, and the main base and the sub-base have such a shape. The main base comprises a rotating shaft housing space which contains the setting axis, formed by a recess which is a hollow portion having an opening in a direction perpendicular to the setting axis, and a first clamping member which protrudes toward the rotating shaft housing space, and has a shape which includes positions on both sides of the recess that are symmetrical with respect to the setting axis, where the first acceleration sensor and the second acceleration sensor are arranged. The sub-base is provided with a second clamping member that protrudes toward the rotating shaft housing space when the main base and the sub-base are fastened together. With the rotating shaft housed within the rotating shaft housing space of the main base, the main base and the sub-base are fastened together so as to cover the opening of the rotating shaft housing space, and the first clamping member and the second clamping member are configured to clamp the rotating shaft. The first acceleration sensor and the second acceleration sensor are positioned symmetrically with respect to the setting axis of the main base. A rotation measuring device characterized in that the first acceleration sensor detects the acceleration in the direction of the tangential line of a circle centered on the setting axis that passes through the first acceleration sensor as the first tangential acceleration, and the second acceleration sensor detects the acceleration in the direction of the tangential line of the circle that passes through the second acceleration sensor as the second tangential acceleration.

2. A rotation measuring device according to claim 1, The main base has one or more first clamping members attached to the main base, each having an end that contacts the outer surface of the rotating shaft through fastening between the main base and the sub-base. The sub-base has one or more second clamping members attached to the sub-base, each having an end that contacts the outer surface of the rotating shaft through fastening between the main base and the sub-base. The main base and the sub-base clamp the rotating shaft in the radial direction by the contact between the end of the first clamping member and the outer circumferential surface of the rotating shaft, and by the contact between the end of the second clamping member and the outer circumferential surface of the rotating shaft. The first clamping member is interchangeably mounted on the main base, and by replacing the first clamping member, the distance from the end of the first clamping member to the setting axis can be changed. The rotation measuring device is characterized in that the second clamping member is interchangeably mounted on the sub-base, and by replacing the second clamping member, the distance from the end of the second clamping member to the setting axis when the main base and the sub-base are fastened together can be changed.

3. A rotation measuring device according to claim 2, A rotation measuring device characterized in that the first clamping member is mounted such that its end protrudes from the surface of the main base facing the rotating shaft housing space, and the second clamping member is mounted such that its end protrudes from the surface of the main base facing the rotating shaft housing space when the main base and the sub-base are fastened together.

4. A rotation measuring device according to any one of claims 1 to 3, Having rotation detection means, The second acceleration sensor detects the acceleration in the same circumferential direction, where the positive and negative sign of the tangential line passing through the second acceleration sensor of the circle is the same as the first tangential acceleration, and this is defined as the second tangential acceleration. The rotation detection means is a rotation measuring device characterized by calculating the acceleration obtained by adding the first tangential acceleration and the second tangential acceleration as the detected tangential acceleration.

5. A rotation measuring device according to claim 4, The rotation detection means is a rotation measuring device characterized by calculating the angular acceleration of the rotating shaft by dividing the detected tangential acceleration by the radius of the circle.

6. A rotation measuring device according to any one of claims 1 to 3, Adjustment means, means for setting the adjustment amount, Having rotation detection means, The second acceleration sensor detects the acceleration in the same circumferential direction, where the positive and negative sign of the tangential line passing through the second acceleration sensor of the circle is the same as the first tangential acceleration, and this is defined as the second tangential acceleration. The adjustment means adjusts and outputs at least one of the first tangential acceleration and the second tangential acceleration with a set gain and offset. The adjustment amount setting means sets the gain and offset such that when the angular acceleration of the rotating shaft is 0, the sum of the first tangential acceleration and the second tangential acceleration output from the adjustment means becomes 0. The rotation detection means is characterized in that it calculates the acceleration obtained by adding the first tangential acceleration and the second tangential acceleration output from the adjustment means as the detected tangential acceleration.

7. A rotation measuring device according to claim 6, The rotation detection means is a rotation measuring device characterized by calculating the angular acceleration of the rotating shaft by dividing the detected tangential acceleration by the radius of the circle.

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