Wireless sensor system for motors

Abstract

This wireless sensor system comprises a reception antenna and a transmission antenna disposed inside a housing that covers a motor. When the larger one between the coil diameter of the transmission antenna and the coil diameter of the reception antenna is defined as an antenna diameter, the distance from the transmission antenna and the reception antenna to a metal positioned closest to the transmission antenna and the reception antenna is defined as a metal distance, the ratio of the metal distance to the antenna diameter is defined as an M / D ratio, and the signal-to-noise ratio of the output of the reception antenna is defined as an S / N ratio, the S / N ratio has a characteristic of being maximum when the M / D ratio is a prescribed value. The M / D ratio is set to a value that makes the S / N ratio greater than a predetermined reference value.

Description

Wireless Sensor System for Motor

[0001] The present disclosure relates to a wireless sensor system for a motor.

[0002] Japanese Patent Application Laid-Open No. 2015-2618 (Patent Document 1) discloses a motor including a wireless sensor system that transmits and receives detection results by a sensor in a non-contact (wireless) manner. This wireless sensor system includes a transmission antenna and a reception antenna disposed inside a housing that covers the motor. The transmission antenna transmits a signal indicating a detection result by a temperature detection element. The reception antenna receives the signal from the transmission antenna in a non-contact manner.

[0003] Japanese Patent Application Laid-Open No. 2015-2618

[0004] As described above, the wireless sensor system (transmission antenna and reception antenna) disclosed in Japanese Patent Application Laid-Open No. 2015-2618 (Patent Document 1) is disposed inside the housing of the motor. In order to perform wireless communication between the transmission antenna and the reception antenna inside the housing of the motor, it is necessary to dispose the transmission antenna and the reception antenna away from surrounding metal parts. However, conventionally, no consideration has been given to how the distance between the transmission antenna and the reception antenna and surrounding metal parts affects the signal-to-noise ratio (hereinafter also referred to as "S / N ratio") of the output of the reception antenna.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to appropriately set the distance between a transmission antenna and a reception antenna and surrounding metal parts to a value that enables or improves communication between the transmission antenna and the reception antenna in a wireless sensor system including the transmission antenna and the reception antenna disposed inside a housing that covers a motor. [[ID=十六]] [[ID=十七]]

[0006] The wireless sensor system according to this disclosure is a wireless sensor system for a motor, comprising a transmitting antenna including a coil disposed inside a housing covering the motor, and a receiving antenna including a coil disposed inside the housing covering the motor at a predetermined distance from the transmitting antenna and capable of receiving signals from the transmitting antenna non-contact. The larger of the coil diameter of the transmitting antenna and the coil diameter of the receiving antenna is defined as the antenna diameter, the distance from the transmitting antenna and the receiving antenna to the metal located closest to them is defined as the metal distance, the ratio of the metal distance to the antenna diameter is defined as the M / D ratio, and the signal-to-noise ratio of the output of the receiving antenna is defined as the S / N ratio. The S / N ratio has the characteristic of being maximum when the M / D ratio is a predetermined value, and decreasing as the M / D ratio moves away from the predetermined value. The M / D ratio is set to a value in which the S / N ratio is greater than a predetermined reference value.

[0007] According to this disclosure, in a wireless sensor system comprising a transmitting antenna and a receiving antenna located inside a housing covering a motor, the distance between the transmitting antenna and the receiving antenna and surrounding metal parts can be appropriately set to a value that enables or improves communication between the transmitting antenna and the receiving antenna.

[0008] This is a partial perspective view (1) of a motor equipped with a wireless sensor system. This is a partial perspective view (2) of a motor equipped with a wireless sensor system. This figure shows the parameters that affect communication in the wireless sensor system and the assumed range of each parameter. This is a graph showing an example of the correspondence between the G / D ratio and the S / N ratio. This is a graph showing an example of the correspondence between the M / D ratio and the S / N ratio. This figure shows the communication area and the communication good area. This is a partial cross-sectional view (3) of a motor equipped with a wireless sensor system. This is a perspective view of the transmitting antenna and the receiving antenna.

[0009] The embodiments of this disclosure will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0010] (Basic configuration of the motor) Figure 1 is a partially transparent view of the motor 1 equipped with the wireless sensor system according to this embodiment, viewed from an oblique direction. Figure 2 is a partially transparent view of the motor 1 from a different oblique direction than that shown in Figure 1.

[0011] The configuration of the motor 1 will be described with reference to Figures 1 and 2. The motor 1 comprises a stator 10, a rotor 20, a shaft 30, a housing 40, a transmitting antenna 50, a receiving antenna 60, spacers 51 and 61, and a sensor 70. The spacers 51 and 61 are insulators that do not conduct electricity (for example, resin). In this embodiment, the components other than the spacers 51 and 61 will be described as metal parts that include metal in at least part.

[0012] The stator 10 and rotor 20 are arranged inside the housing 40. The stator 10 is installed so as to surround the rotor 20. The stator 10 is fixed to the housing 40. The rotor 20 is supported so as to be rotatable relative to the stator 10.

[0013] One end of the shaft 30 is fixed to the rotor 20, and the other end of the shaft 30 protrudes outside the housing 40. The shaft 30 rotates integrally with the rotor 20 as the rotor 20 rotates.

[0014] The wireless sensor system according to this embodiment consists of a transmitting antenna 50 and a receiving antenna 60. Both the transmitting antenna 50 and the receiving antenna 60 are located inside the housing 40.

[0015] The sensor 70 is fixed to the rotor 20 inside the housing 40 and detects physical quantities of the rotor 20. The physical quantities detected by the sensor 70 may be, for example, the temperature of the rotor 20, the strain of the rotor 20, or the acceleration of the rotor 20. If the sensor 70 is a temperature-sensing element, for example, a temperature sensing element disclosed in Japanese Patent No. 5983854 can be used. Specifically, a quartz crystal oscillator or other resonant devices (such as a SAW (Surface Acoustic Wave) resonator or a MEMS (Micro Electro Mechanical Systems) resonator) can be used as the sensor 70. Alternatively, the sensor 70 may be an IC tag with a temperature sensor function (RFID; Radio Frequency Identification) that detects and stores the temperature of the rotor 20.

[0016] The transmitting antenna 50 is located inside the housing 40 that covers the motor 1. The transmitting antenna 50 is wired to the sensor 70 and includes a coil that transmits a signal indicating the detection result of the sensor 70 to the receiving antenna 60 without contact.

[0017] A circular groove is formed on the surface of the spacer 51 facing the receiving antenna 60, and the transmitting antenna 50 is fitted into this groove. The transmitting antenna 50 is fixed to the rotor 20 and shaft 30 via the insulated spacer 51. As a result, the transmitting antenna 50 rotates integrally with the rotor 20 and shaft 30 without contacting surrounding metal parts.

[0018] The receiving antenna 60, like the transmitting antenna 50, is also located inside the housing 40 that covers the motor 1. The receiving antenna 60 includes a coil capable of receiving signals from the transmitting antenna 50 without contact.

[0019] The axis of the coil of the receiving antenna 60, the axis of the coil of the transmitting antenna 50, the axis of rotation of the shaft 30, and the axis of rotation of the rotor 20 are approximately the same. Hereafter, the direction of the coil axis of the receiving antenna 60, the direction of the coil axis of the transmitting antenna 50, the direction of rotation of the shaft 30, and the direction of rotation of the rotor 20 will all be referred to as the "axial direction" without distinction.

[0020] A circular groove is formed on the surface of the spacer 61 facing the transmitting antenna 50, and the receiving antenna 60 is fitted into this groove. The receiving antenna 60 is fixed to the inner wall of the housing 40, which is located in the axial direction, via the insulated spacer 61. As a result, the receiving antenna 60 is fixed to the inner wall of the housing 40 without contacting any surrounding metal parts.

[0021] The receiving antenna 60 is positioned along the axial direction at a predetermined distance from the transmitting antenna 50. Note that Figures 1 and 2 are merely schematic representations of the arrangement of the transmitting antenna 50 and the receiving antenna 60, and the distance between the transmitting antenna 50 and the receiving antenna 60 is not limited to the distance shown in Figures 1 and 2.

[0022] In this embodiment, the coil diameter of the receiving antenna 60 is approximately the same as the coil diameter of the transmitting antenna 50. Also, the number of coil turns of the receiving antenna 60 is the same as the number of coil turns of the transmitting antenna 50.

[0023] The receiving antenna 60 outputs the signal received non-contact from the transmitting antenna 50 to the outside of the motor 1. The output of the receiving antenna 60 is transmitted to the outside of the motor 1 via a signal line (not shown).

[0024] (Parameters affecting communication of the wireless sensor system) As described above, the wireless sensor system according to this embodiment (transmitting antenna 50 and receiving antenna 60) is arranged inside the housing 40 that covers the motor 1.

[0025] In order for the transmitting antenna 50 and the receiving antenna 60 to communicate with each other, the transmitting antenna 50 and the receiving antenna 60 must be positioned away from surrounding metal parts. To this end, in this embodiment, the transmitting antenna 50 is fixed to the rotor 20 and shaft 30 (metal parts) via an insulated spacer 51, and the receiving antenna 60 is fixed to the housing 40 (metal parts) via an insulated spacer 61. As a result, the transmitting antenna 50 and the receiving antenna 60 do not come into contact with surrounding metal parts, enabling communication between the transmitting antenna 50 and the receiving antenna 60.

[0026] On the other hand, conventionally, no consideration was given to how the distance between the transmitting antenna 50 and the receiving antenna 60 and the surrounding metal parts affects the signal-to-noise ratio (S / N ratio) of the output of the receiving antenna 60.

[0027] Therefore, the inventors of the present invention decided to verify, through experiments and other means, how the distance between the transmitting antenna 50 and the receiving antenna 60 and the surrounding metal parts affects the signal-to-noise ratio, and to set various parameters that affect communication based on the results.

[0028] Figure 3 shows the parameters that affect communication in the wireless sensor system and the assumed ranges for each parameter. The upper part of Figure 3 shows a partial cross-sectional view of motor 1, and the lower part of Figure 3 shows the four parameters that affect communication and their assumed ranges.

[0029] The inventors of this application have defined four parameters that affect communication: communication distance G, antenna diameter D, coil turn count n, and metal distance M. Communication distance G is the shortest distance between the transmitting antenna 50 and the receiving antenna 60. Antenna diameter D is the larger of the coil diameter of the transmitting antenna 50 and the coil diameter of the receiving antenna 60. Coil turn count n is the number of coil turns of the transmitting antenna 50 and the receiving antenna 60, respectively. Metal distance M is the distance from the transmitting antenna 50 and the receiving antenna 60 to the metal object located closest to them.

[0030] In this embodiment, since the transmitting antenna 50 and the receiving antenna 60 are arranged side by side in the axial direction, the communication distance G is the axial distance between the transmitting antenna 50 and the receiving antenna 60. Also, since the coil diameter of the transmitting antenna 50 and the coil diameter of the receiving antenna 60 are approximately the same, the antenna diameter D is the coil diameter of either the transmitting antenna 50 or the coil diameter of the receiving antenna 60.

[0031] Furthermore, in the example shown in Figure 3, the metal closest to the transmitting antenna 50 and the receiving antenna 60 is the shaft 30, so the metal distance M is the distance from the transmitting antenna 50 and the receiving antenna 60 to the shaft 30.

[0032] The communication distance G is a parameter that affects whether communication is possible between the transmitting antenna 50 and the receiving antenna 60. The antenna diameter D and the number of coil turns n are parameters that affect the coupling coefficient between the transmitting antenna 50 and the receiving antenna 60. The metal distance M is a parameter that affects the signal-to-noise ratio.

[0033] The inventors of this application assume that the communication distance G is in the range of 0 to 250 mm, the antenna diameter D is in the range of 5 to 300 mm, the number of coil turns n is in the range of 1 to 20 turns, and the metal distance M is in the range of 0.5 to 40 mm.

[0034] The inventors of the present invention conducted experiments assuming that each parameter was within the range shown in Figure 3, and verified the correspondence between the ratio of the communication distance G to the antenna diameter D (hereinafter also referred to as the "G / D ratio") and the S / N ratio, and the correspondence between the ratio of the metal distance M to the antenna diameter D (hereinafter also referred to as the "M / D ratio") and the S / N ratio.

[0035] Figure 4 is a graph showing an example of the correspondence between the G / D ratio and the S / N ratio obtained through experiments. As shown in Figure 4, it can be seen that the S / N ratio decreases as the G / D ratio increases.

[0036] Here, if the lower limit of the signal-to-noise ratio (S / N ratio) at which communication between the transmitting antenna 50 and the receiving antenna 60 is possible (hereinafter also referred to as the "first reference value") is set to "1.5", it can be seen that by setting the G / D ratio to a value within the range of 0 to 1.5, the S / N ratio can be made greater than the first reference value "1.5", and communication becomes possible.

[0037] Furthermore, if the lower limit of the signal-to-noise ratio (S / N ratio) at which communication between the transmitting antenna 50 and the receiving antenna 60 is good (hereinafter also referred to as the "second reference value") is set to "3", it can be seen that by setting the G / D ratio to a value within the range of 0 to 0.5, the S / N ratio can be made greater than the second reference value "3", resulting in good communication.

[0038] Figure 5 is a graph showing an example of the correspondence between the M / D ratio and the S / N ratio obtained through experiments. As shown in Figure 5, the S / N ratio has the characteristic of being maximum when the M / D ratio is at a predetermined value, and decreasing as the M / D ratio deviates from the predetermined value. This experimental result shows that, when the antenna diameter D is kept constant, the S / N ratio decreases if the M / D ratio is too small or too large. From this result, it can be seen that, when the antenna diameter D is kept constant, the S / N ratio decreases if the metal distance M is too small or too large, so the metal distance M should be set to an appropriate value.

[0039] As shown in Figure 5, the results indicate that by setting the M / D ratio to a value within the range of 0.03 to 4, the S / N ratio can be made greater than the first reference value of "1.5," enabling communication.

[0040] Furthermore, the results shown in Figure 5 indicate that by setting the M / D ratio to a value within the range of 0.03 to 0.1, the S / N ratio can be made greater than the second reference value "3," resulting in good communication.

[0041] Figure 6 shows areas where the signal-to-noise ratio (S / N ratio) is greater than the first reference value "1.5" (communication-enabled areas) and areas where the S / N ratio is greater than the second reference value "3" (good communication areas), using the G / D ratio and M / D ratio as parameters.

[0042] As shown in Figure 6, the communication area is the area where the G / D ratio is in the range of 0 to 1.5 and the M / D ratio is in the range of 0.03 to 4. Therefore, if we want to enable communication between the transmitting antenna 50 and the receiving antenna 60, the G / D ratio is set to a value within the range of 0 to 1.5 and the M / D ratio is set to a value within the range of 0.03 to 4. This enables communication between the transmitting antenna 50 and the receiving antenna 60 (communication where the S / N ratio is equal to or greater than the first reference value).

[0043] Also, as shown in FIG. 6, the communication good area is an area where the G / D ratio is in the range of 0 to 0.5 and the M / D ratio is in the range of 0.03 to 0.1. Therefore, when it is desired to improve the communication between the transmission antenna 50 and the reception antenna 60, the G / D ratio is set to a value within the range of 0 to 0.5, and the M / D ratio is set to a value within the range of 0.03 to 0.1. Thereby, good communication (communication with an S / N ratio equal to or higher than the second reference value) between the transmission antenna 50 and the reception antenna 60 becomes possible.

[0044] As described above, in the wireless sensor system according to the present embodiment, considering the characteristic that the S / N ratio decreases when the M / D ratio is too small or too large as shown in FIG. 5, the M / D ratio is set to a value larger than the first reference value (1.5) or the second reference value (3). Thereby, the metal distance M can be appropriately set to a value that enables or improves communication with the transmission antenna 50 and the reception antenna 60.

[0045] Also, in the wireless sensor system according to the present embodiment, considering the characteristic that the S / N ratio decreases as the G / D ratio increases as shown in FIG. 4, the G / D ratio is set to a value larger than the first reference value (1.5) or the second reference value (3). Thereby, the communication distance G can be appropriately set to a value that enables or improves communication with the transmission antenna 50 and the reception antenna 60.

[0046] <Modification Example 1> In FIG. 1 described above, an example in which the transmission antenna 50 and the reception antenna 60 are arranged side by side in the axial direction is shown. However, the transmission antenna 50 and the reception antenna 60 may be arranged side by side in a direction orthogonal to the axial direction (coil diameter direction).

[0047] FIG. 7 is a partial cross-sectional view of a motor 1A including the wireless sensor system according to this Modification Example 1.

[0048] The motor 1A shown in FIG. 7 is obtained by changing the transmission antenna 50, the reception antenna 60, and the spacers 51 and 61 of the motor 1 shown in FIG. 1 described above to a transmission antenna 50A, a reception antenna 60A, and spacers 51A and 61A, respectively.

[0049] The wireless sensor system according to the first modification example is composed of a transmission antenna 50A and a reception antenna 60A.

[0050] The transmission antenna 50A is fixed to the shaft 30 via a spacer 51A which is a non-conductor.

[0051] The reception antenna 60 is arranged at a predetermined distance from the transmission antenna 50A in the coil diameter direction (the direction orthogonal to the axial direction) of the transmission antenna 50. The reception antenna 60 is fixed to the inner wall located in the coil diameter direction of the housing 40 via a spacer 61A which is a non-conductor. Note that the axis of the coil of the reception antenna 60A substantially coincides with the axis of the coil of the transmission antenna 50A.

[0052] As described above, the reception antenna 60A may be arranged at a predetermined distance from the transmission antenna 50A in the coil diameter direction of the transmission antenna 50A.

[0053] <Modification Example 2> In the above-described embodiment, an example in which the transmission antenna 50 and the reception antenna 60 are fitted into the groove portion of the spacer is shown. However, the transmission antenna 50 and the reception antenna 60 are not necessarily limited to being fitted into the groove portion of the spacer.

[0054] FIG. 8 is a perspective view of the transmission antenna 50B and the reception antenna 60B according to the second modification example. In FIG. 8, the configuration of the transmission antenna 50B is shown as a representative.

[0055] The spacer 51B according to the second modification example is an insulating substrate, and the coil of the transmission antenna 50B is constituted by a metal pattern formed on the surface of the spacer 51B. The spacer 61B according to the second modification example is an insulating substrate, and the coil of the reception antenna 60B is constituted by a metal pattern formed on the surface of the spacer 61B.

[0056] As described above, the coils of the transmission antenna 50B and the reception antenna 60B may be constituted by metal patterns formed on the surfaces of insulating substrates.

[0057] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope of the claims are intended to be included.

[0058] 1, 1A motor, 10 stator, 20 rotor, 30 shaft, 40 housing, 50, 50A, 50B transmitting antenna, 51, 51A, 51B, 61, 61A, 61B spacer, 60, 60A, 60B receiving antenna, 70 sensor.

Claims

1. A wireless sensor system for a motor, comprising: a transmitting antenna including a coil disposed inside a housing covering the motor; and a receiving antenna including a coil disposed inside the housing covering the motor at a predetermined distance from the transmitting antenna and capable of receiving signals from the transmitting antenna without contact, wherein the larger of the coil diameter of the transmitting antenna and the coil diameter of the receiving antenna is defined as the antenna diameter, the distance from the transmitting antenna and the receiving antenna to the metal located closest to the transmitting antenna and the receiving antenna is defined as the metal-to-distance ratio (M / D ratio), and the signal-to-noise ratio of the output of the receiving antenna is defined as the signal-to-noise ratio (S / N ratio), wherein the S / N ratio is maximized when the M / D ratio is a predetermined value and decreases as the M / D ratio moves away from the predetermined value, and the M / D ratio is set to a value such that the S / N ratio is greater than a predetermined reference value.

2. The wireless sensor system according to claim 1, wherein the shortest distance between the transmitting antenna and the receiving antenna is defined as the communication distance, and the ratio of the communication distance to the antenna diameter is defined as the G / D ratio, the S / N ratio has the characteristic of decreasing as the G / D ratio increases, and the G / D ratio is set to a value such that the S / N ratio is greater than the reference value.

3. The wireless sensor system according to claim 2, wherein the communication distance is in the range of 0 to 250 mm, the antenna diameter is in the range of 5 to 300 mm, the number of coil turns of the transmitting antenna and the receiving antenna are in the range of 1 to 20, the metal distance is in the range of 0.5 to 40 mm, and the reference value is 1.5, the M / D ratio is set to a value in the range of 0.03 to 4, and the G / D ratio is set to a value in the range of 0 to 1.

5.

4. The wireless sensor system according to claim 2, wherein the communication distance is in the range of 0 to 250 mm, the antenna diameter is in the range of 5 to 300 mm, the number of coil turns of the transmitting antenna and the receiving antenna are in the range of 1 to 20, the metal distance is in the range of 0.5 to 40 mm, and the reference value is 3, the M / D ratio is set to a value in the range of 0.03 to 0.1, and the G / D ratio is set to a value in the range of 0 to 0.

5.

5. The wireless sensor system according to any one of claims 1 to 4, wherein the axis of the coil of the receiving antenna and the axis of the coil of the transmitting antenna substantially coincide, and the receiving antenna is positioned at a predetermined distance from the transmitting antenna in a direction along the axis of the coil of the transmitting antenna.

6. The wireless sensor system according to any one of claims 1 to 4, wherein the axis of the coil of the receiving antenna and the axis of the coil of the transmitting antenna substantially coincide, and the receiving antenna is positioned at a predetermined distance from the transmitting antenna in the radial direction of the coil of the transmitting antenna.

7. The wireless sensor system according to any one of claims 1 to 6, wherein the transmitting antenna is fixed to the rotor of the motor via a first non-conductive spacer, and the receiving antenna is fixed to the inner wall of the housing of the motor via a second non-conductive spacer.

8. The wireless sensor system according to claim 7, wherein the first spacer and the second spacer are insulating substrates, the coil of the transmitting antenna is composed of a metal pattern formed on the surface of the first spacer, and the coil of the receiving antenna is composed of a metal pattern formed on the surface of the second spacer.

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