Bearing device

Abstract

To provide a bearing device capable of accurately detecting an abnormality of a bearing that supports a rotary shaft in a drive unit of an electric vertical landing machine and realizing stable flight.SOLUTION: A bearing device 6 comprises a plurality of drive units 3A-3D each of which includes a rotary vane and a motor for rotating the rotary vane; roller bearings 7A-7D that are mounted on an electric vertical landing machine 1 that flies by means of rotation of the rotary vanes and that support rotary shafts of the drive units 3A-3D; sensors 8A-8D that are provided inside or outside the roller bearings and that acquire indexes indicating the states of the roller bearings; a storage device that stores the indexes; an abnormality determination unit 10 that determines abnormalities of the roller bearings on the basis of the indexes; and a control unit 11 that controls the drive units 3A-3D.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a bearing device mounted on an electric vertical take-off and landing aircraft that flies by rotating multiple rotors. [Background technology]

[0002] With the development of road networks, automobiles are now widely used as a means of transportation worldwide. However, in many countries, including Japan, populations are concentrating in urban areas, and traffic congestion caused by automobiles has become a serious social problem in overcrowded urban areas. It is said that such traffic congestion is causing a huge loss of labor force.

[0003] Although the road network has developed in recent years, there are still many areas in mountainous and depopulated regions where roads are not adequately maintained. Furthermore, future population decline is seen as a problem in Japan, and road development in rural areas will become an issue in the future. Meanwhile, roads can be cut off in the event of natural disasters such as earthquakes, making travel by car difficult.

[0004] Due to these various circumstances, there is a growing demand for a new, sustainable means of transportation to replace automobiles. In recent years, flying cars, or cars that can fly, have been attracting attention as a means of transportation. Flying cars are expected to solve the above social problems and are expected to be used in a variety of situations, including intra-regional travel, inter-regional travel, tourism and leisure, emergency medical care, and disaster relief. In Japan, the "Public-Private Council for the Air Mobility Revolution" was held, and in 2018 a roadmap for realizing flying cars was compiled, and studies are underway to make them a reality.

[0005] Vertical take-off and landing aircraft (VTOL) are attracting attention as flying cars. VTOLs can ascend and descend vertically between the sky and takeoff and landing sites, eliminating the need for runways and offering great convenience. In particular, in recent years, due to societal demands for reducing CO2 emissions, electric vertical take-off and landing aircraft (eVTOL), which fly using batteries and motors, have become the mainstream of development.

[0006] Electric vertical take-off and landing aircraft are broadly divided into multicopter and fixed-wing types. Multicopter types are suitable for short-distance flights and are characterized by their compact size and small number of parts. A multicopter primarily comprises multiple drive units with rotors and motors that rotate the rotors, and a main body on which the occupants ride (see, for example, Patent Document 1). Multicopters lift using the lift generated by the rotation of the rotors, and balance and control their flight attitude by controlling the rotation speed of the multiple rotors. On the other hand, fixed-wing types are said to be useful not only for short-distance flights but also for medium-distance flights, but it is said that multicopter types, which have lower development and certification costs, will be the first to be implemented in society. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2020-132098 Summary of the Invention [Problem to be solved by the invention]

[0008] Electric vertical take-off and landing aircraft are classified as aircraft under the Aviation Act. As such, they must meet the safety standards set forth by the Act, and extremely high levels of safety are required. In addition to stable flight performance, fail-safe functions that allow the aircraft to continue flying safely even if a component malfunctions are also important.

[0009] In particular, multicopters do not have fixed wings and obtain propulsion solely through the rotation of their rotors. Therefore, if a malfunction occurs in the rotation of one of the rotors, it may become difficult to maintain flight attitude. Therefore, the role of bearings that support the rotating shaft in the drive unit is important, and accurate detection of bearing abnormalities is required. Furthermore, when a multicopter moves horizontally, it tilts its flight attitude by converting part of the lift used for lift into horizontal movement force. Because the rotors are also used to control flight attitude, bearings play a major role in achieving more agile and accurate attitude control.

[0010] The present invention has been made in consideration of the above circumstances, and aims to provide a bearing device that can accurately detect abnormalities in bearings that support a rotating shaft in a drive unit of an electric vertical take-off and landing aircraft, thereby achieving stable flight. [Means for solving the problem]

[0011] The bearing device of the present invention is a bearing device mounted on an electric vertical take-off and landing aircraft that flies by rotation of a rotor and a plurality of drive units each having a rotor and a motor for rotating the rotor, the bearing device comprising: a rolling bearing that supports a rotating shaft in the drive unit; a sensor provided inside or outside the rolling bearing and that acquires an index indicating the state of the rolling bearing; a storage device that stores the index; an abnormality determination unit that determines an abnormality in the rolling bearing based on the index; and a control unit that controls the drive unit, wherein the index includes at least vibration of the rolling bearing; the abnormality determination unit determines an abnormality in the rolling bearing on a weekly or monthly basis based on the progress of the index accumulated and stored in the storage device; and when the abnormality determination unit determines that at least one of the plurality of rolling bearings is abnormal, the control unit controls the drive unit on which the rolling bearing is mounted to alleviate the state of the rolling bearing determined to be abnormal, while controlling the other drive units to continue flight.

[0012] The control unit adjusts the rotation speed of the motor of the drive unit when the abnormality determination unit determines that an abnormality has occurred.

[0013] The bearing device of the present invention is a bearing device that is mounted on an electric vertical take-off and landing aircraft that flies by rotation of a rotor and a plurality of drive units each having a rotor and a motor that rotates the rotor, and the bearing device comprises a rolling bearing that supports a rotating shaft in the drive unit, a sensor that is provided inside or outside the rolling bearing and obtains an index that indicates the state of the rolling bearing, a storage device that stores the index, an abnormality determination unit that determines an abnormality in the rolling bearing based on the index, and a control unit that controls the drive unit, wherein the index includes at least vibration of the rolling bearing, the abnormality determination unit determines an abnormality in the rolling bearing on a weekly or monthly basis based on the progress of the index accumulated and stored in the storage device, and the control unit adjusts the rotation speed of the motor in the drive unit if an abnormality is determined by the abnormality determination unit.

[0014] The index is characterized by including one selected from the heat flux of the rolling bearing, the temperature of the rolling bearing, the load of the rolling bearing, and the absolute angle of the rolling bearing.

[0015] The abnormality determination unit determines abnormality in the rolling bearing at intervals that are m times (m is an integer) the interval at which the index of the sensor is acquired.

[0016] The bearing device is characterized by having a notification unit that notifies the abnormality when the abnormality determination unit determines that an abnormality has occurred.

[0017] The abnormality determination unit determines an abnormality based on the index at a preset threshold value, in which the threshold value is set in a plurality of stages, the abnormality determination unit determines the level of abnormality of the rolling bearing based on the threshold value, and the notification unit changes the notification mode depending on the level of abnormality determined by the abnormality determination unit. [Effects of the Invention]

[0018] The bearing device of the present invention is mounted on an electric vertical take-off and landing aircraft and comprises a rolling bearing that supports a rotating shaft in a drive unit, a sensor provided inside or outside the rolling bearing and that acquires an index indicating the condition of the rolling bearing, a storage device that stores the index, an abnormality determination unit that determines an abnormality in the rolling bearing based on the index, and a control unit that controls the drive unit, the index including at least vibration of the rolling bearing, and the abnormality determination unit determining an abnormality in the rolling bearing on a weekly or monthly basis based on trends in the index accumulated and stored in the storage device, thereby enabling trend management through long-term condition monitoring, which results in a reduction in the frequency of maintenance and a lighter workload.

[0019] Furthermore, if the abnormality determination unit determines that at least one of the multiple rolling bearings is abnormal, the control unit controls the drive unit on which the rolling bearing determined to be abnormal is mounted to alleviate the condition of that rolling bearing, while controlling the other drive units to continue flight.In this configuration, even if an abnormality occurs in a rolling bearing, flight can be continued safely and a fail-safe function can be achieved.

[0020] Furthermore, in a configuration in which the control unit adjusts the rotation speed of the motor of the drive unit when an abnormality is determined by the abnormality determination unit, the control unit can, for example, reduce the rotation speed of the motor of the drive unit to reliably reduce the load on the rolling bearing determined to be abnormal, while adjusting the rotation speed of the motors of the other drive units to allow flight to continue.

[0021] The above index is an index that combines one or more selected from the heat flux of the rolling bearing, the temperature of the rolling bearing, the load on the rolling bearing, and the absolute angle of the rolling bearing, and therefore allows for a more accurate understanding of the condition of the rolling bearing, leading to improved accuracy in detecting abnormalities.

[0022] The abnormality determination unit determines whether an abnormality has occurred in the rolling bearing at intervals that are m times (m is an integer) the interval at which the sensor index is acquired, making it possible to reduce the frequency of determination depending on the load on the abnormality determination unit and control unit.

[0023] By providing a notification unit that notifies the abnormality when the abnormality determination unit determines that an abnormality has occurred, it is possible to quickly make the crew and people outside the aircraft aware of an abnormality in the aircraft (abnormality in the bearings).

[0024] Furthermore, by determining the level of abnormality in the rolling bearing based on threshold values ​​set in multiple stages and changing the notification method depending on the level of abnormality, the abnormal condition can be made known to the crew and people outside the aircraft in stages. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a perspective view of an electric vertical take-off and landing aircraft on which a bearing device of the present invention is mounted. [Figure 2] 1 is a schematic diagram of the overall configuration of a bearing device according to the present invention; [Figure 3] FIG. 1 is a partial cross-sectional view of a motor in a drive unit of an electric vertical take-off and landing aircraft. [Figure 4] FIG. 4 is an enlarged cross-sectional view of the rolling bearing of FIG. 3. [Figure 5] 10A and 10B are cross-sectional views of other examples of rolling bearings. [Figure 6] FIG. 2 is a block diagram showing details of the sensor and control device. [Figure 7] FIG. 10 is a diagram showing the relationship between heat flux, temperature, and vibration and rotation speed. [Figure 8] Graphs showing changes in effective vibration values ​​over time are given. [Figure 9] 4 is a flowchart illustrating a process executed by a control device. [Figure 10] FIG. 10 is a diagram illustrating an example of control by the control unit in an abnormal mode. [Figure 11] FIG. 10 is a diagram illustrating another example of control by the control unit in the abnormal mode. DETAILED DESCRIPTION OF THE INVENTION

[0026] An electric vertical take-off and landing aircraft on which a bearing device of the present invention is mounted will be described with reference to Fig. 1. The electric vertical take-off and landing aircraft 1 shown in Fig. 1 is a multicopter having a main body 2 located in the center of the aircraft and four drive units 3 arranged on the front, rear, left and right sides. The drive units 3 are devices that generate lift and thrust for the electric vertical take-off and landing aircraft 1, and the electric vertical take-off and landing aircraft 1 flies when driven by the drive units 3. The electric vertical take-off and landing aircraft 1 may have multiple drive units 3, and is not limited to four.

[0027] The main body 2 has a living space large enough to accommodate a crew member (for example, one to two people). This living space is equipped with an operating system for determining the direction of travel and altitude, and instruments for indicating altitude, speed, flight position, etc. Four arms 2a extend from the main body 2, and a drive unit 3 is attached to the tip of each arm 2a. In FIG. 1, each arm 2a is integrally provided with a ring-shaped portion that covers the rotating periphery of the rotor 4 to protect it. In addition, a skid 2b that supports the aircraft during landing is attached to the bottom of the main body 2.

[0028] The drive unit 3 has a rotor 4 and a motor 5 that rotates the rotor 4. In the drive unit 3, a pair of rotors 4 are provided on both axial sides of the motor 5. Each rotor 4 has two blades extending radially outward. Note that the rotor 4 is not limited to a blade-type rotor, but may also be a spiral rotor.

[0029] The main body 2 is provided with a battery (not shown) and a control device 9 (see FIG. 2). The control device is also called a flight controller. The electric vertical take-off and landing aircraft 1 is controlled by the control device, for example, as follows: The control device outputs a command to change the rotation speed of the motor 5, which should adjust lift based on the difference between the current attitude and the target attitude. Based on this command, an amplifier provided in the motor 5 adjusts the amount of power sent from the battery to the motor 5, changing the rotation speed of the motor 5 (and the rotor 4). Furthermore, adjustment of the rotation speed of multiple motors 5 is performed simultaneously, which determines the attitude of the aircraft. Thus, control of the rotating shaft in the drive unit is important for the aircraft's flight attitude, and to achieve a safe and comfortable flight, it is necessary to accurately detect abnormalities in the rolling bearings that support the rotating shaft.

[0030] Fig. 2 is a schematic diagram of the overall configuration of the bearing device of the present invention. In Fig. 2, the four drive units are labeled with the letters A to D to distinguish them from one another. The rolling bearings and sensors provided in each drive unit are also labeled with the letters A to D. The same applies to Figs. 6, 10, and 11, which will be described later.

[0031] As shown in Figure 2, the bearing device 6 includes rolling bearings 7A-7D that support the rotating shafts of the drive units 3A-3D, sensors 8A-8D that acquire indicators indicating the condition of the rolling bearings 7A-7D, and a control device 9 that is communicatively connected to the sensors 8A-8D via wired or wireless communication. The control device 9 is primarily configured using a microcomputer that includes a known CPU, ROM, RAM, and the like. The control device 9 also includes an abnormality determination unit 10 that determines abnormalities in the rolling bearings 7A-7D based on the indicators acquired by the sensors 8A-8D, and a control unit 11 that controls the drive units 3A-3D. This configuration makes it possible to detect abnormalities in the rolling bearings of each drive unit, and to control each drive unit based on the detection results.

[0032] The bearing device of the present invention will be described in detail below. Fig. 3 shows a partial cross section of a motor in an arbitrary drive unit (e.g., 3A). In Fig. 3, the above-mentioned rotor is attached to one end (upper side of the figure) of the rotating shaft 13 of the motor 5, and a rotor is attached to the other end (lower side of the figure). The rotor is disposed opposite a stator fixed to a housing and is rotatable relative to the stator. The motor 5 can be configured as an outer rotor brushless motor or an inner rotor brushless motor.

[0033] In FIG. 3, the motor 5 includes a housing 12, a rotor (not shown), a stator (not shown), an amplifier 29 (see FIG. 6), two angular contact ball bearings 7a and 7b as the rolling bearing 7A, and two sensor units 8a and 8b as the sensor 8A. The housing 12 has an outer cylinder 12a and an inner cylinder 12b, and a coolant flow path 12c is provided between them. By flowing a coolant through this flow path 12c, excessive temperature rise can be prevented. The angular contact ball bearings 7a and 7b rotatably support a rotating shaft 13 within the inner cylinder 12b. An inner ring spacer 14 and an outer ring spacer 15 are inserted between the angular contact ball bearings 7a and 7b, and a preload is applied.

[0034] 4, angular contact ball bearing 7a includes inner ring 21 having a raceway surface on its outer peripheral surface, outer ring 22 having a raceway surface on its inner peripheral surface, balls 23 that roll between the raceway surfaces of inner ring 21 and outer ring 22, and cage 24 that rollably holds balls 23. Inner ring 21, outer ring 22, and balls 23 are in contact with each other at a predetermined angle θ (contact angle) relative to the radial center line, and can bear radial loads and unidirectional axial loads.

[0035] In the angular contact ball bearing 7a, both the inner ring 21 and the outer ring 22 are made of steel. Any material commonly used as a bearing material can be used for the steel. For example, high-carbon chromium bearing steel (SUJ1, SUJ2, SUJ3, SUJ4, SUJ5, etc.; JIS G 4805), carburized steel (SCr420, SCM420, etc.; JIS G 4053), stainless steel (SUS440C, etc.; JIS G 4303), cold-rolled steel, etc. can be used. The balls 23 can be made of the above steel or ceramic materials. The angular contact ball bearing 7b has a similar structure.

[0036] In Figure 3, two angular contact ball bearings 7a, 7b are installed in a back-to-back (DB) configuration, but this is not limiting and a face-to-face (DF) configuration is also possible. Furthermore, in addition to angular contact ball bearings, deep groove ball bearings, tapered roller bearings, self-aligning roller bearings, needle roller bearings, etc. can also be used. Furthermore, the number of rolling bearings in motor 5 is not particularly limited and may be one, two, or more.

[0037] As shown in Figure 3, the outer ring spacer 15 is provided with nozzle members 16, 16 for injecting lubricating oil to cool and lubricate the angular contact ball bearings 7a, 7b. The nozzle member 16 has an internal lubricating oil flow path that guides air-oil supplied from an external lubricating oil supply device (not shown) into the bearing space. The lubricating oil flow path consists of a nozzle hole whose tip opens toward the bearing space and an inlet hole that communicates with this nozzle hole. The lubricating oil supply device mixes lubricating oil with compressed air and sends out the air-oil.

[0038] When the angular contact ball bearings 7a and 7b rotate, a predetermined amount of air oil (for example, 0.01 to 0.03 mm) is supplied from the lubricating oil supply device at predetermined intervals. 3 / 3 to 10 min). Air oil enters the inlet hole of the nozzle member 16 from the lubricating oil supply passage in the housing 12 and is sprayed from the nozzle hole toward the raceway surface of the inner ring 21. As a result, the raceway surface of the inner ring 21 and the raceway surface of the outer ring 22 are lubricated. The lubrication method is not limited to air-oil lubrication, and oil mist lubrication may also be used. In oil mist lubrication, a lubricating gas mixture (oil mist) made by mixing atomized lubricating oil with compressed air is supplied to the bearing to lubricate it.

[0039] 3, sensor units 8a and 8b are fixed near angular contact ball bearings 7a and 7b, which are sources of heat generation and vibration. The types of sensors constituting sensor units 8a and 8b are not particularly limited as long as they acquire indicators that indicate the state of each bearing 7a and 7b. The acquired indicators are preferably one or a combination of two or more selected from bearing heat flux, bearing temperature, bearing vibration, bearing load, and bearing absolute angle, and more preferably a combination of two or more.

[0040] 3, in order to obtain multiple indicators indicating the state of the angular contact ball bearings 7a, 7b, the sensor units 8a, 8b are equipped with a heat flow sensor 17, a temperature sensor 18, a vibration sensor 19, and a load sensor 20. Although these sensors are provided outside the respective bearings, some or all of them may be provided inside the bearings.

[0041] The heat flow sensor 17 is fixed to the inner diameter surface of the outer ring spacer 15 and faces the outer diameter surface of the inner ring spacer 14. More specifically, the heat flow sensors 17 are fixed to both axial ends of the inner diameter surface of the outer ring spacer 15. By installing the heat flow sensors 17 near each bearing 7a, 7b, the heat flux flowing between the inner and outer rings of the bearings can be directly detected. Heat flux is the amount of heat passing through a unit area per unit time. The heat flow sensor converts heat flow into an electrical signal using the Seebeck effect, and an output voltage is generated from the slight temperature difference between the front and back of the sensor. Compared to the temperature sensor described below, the heat flow sensor is more sensitive to changes in heat inside the bearing and can track these changes in a timely manner. This allows it to quickly detect sudden temperature increases in the bearing.

[0042] 3, the heat flow sensors 17 are installed at both axial ends of the inner diameter surface of the outer ring spacer 15, but the heat flow sensors 17 may also be installed near the axial center portion of the inner diameter surface of the outer ring spacer 15. The heat flow sensors 17 may also be installed inside each bearing (for example, on the inner peripheral surface of the outer ring).

[0043] Temperature sensor 18 is fixed to both axial end faces of outer ring spacer 15 and detects the temperature of outer ring spacer 15 or outer ring 22. Temperature sensor 18 may be a non-contact temperature sensor, a thermocouple, a thermistor, or the like. The installation location of temperature sensor 18 is not limited to the installation location shown in FIG. 3 . A sensor installation space facing the outer peripheral surface of the outer ring may be formed in the fitting hole of inner cylinder 12b, and the temperature sensor may be installed in this sensor installation space to detect the temperature of outer ring 22. Alternatively, the temperature sensor may be installed on the inner peripheral surface of the inner ring so as to detect the temperature of inner ring 21.

[0044] During operation, the vibration sensor 19 measures vibrations of the angular contact ball bearings 7a, 7b caused by surface roughness, peeling, indentations, etc. on the bearing raceway surface. The vibration sensor 19 is fixed, for example, to both axial end faces of the outer ring spacer 15. It is also possible to install the vibration sensor 19 on the outer peripheral surface of the housing 12, but it is preferable to incorporate the vibration sensor 19 into the outer ring spacer 15 adjacent to the angular contact ball bearings 7a, 7b, in order to detect with good sensitivity even the early stages of abnormalities and conditions with small vibration levels.

[0045] Load sensor 20 is installed, for example, between angular contact ball bearings 7a, 7b and outer ring spacer 15 to detect bearing preload and external load. For example, the preload applied to angular contact ball bearings 7a, 7b fluctuates due to heat generation and centrifugal force caused by high-speed operation. If the preload increases, there is a risk that the amount of heat generated will increase due to frictional forces caused by oil film breakdown.

[0046] The bearing configuration in the drive unit is not limited to the configuration shown in FIG. 3. In FIG. 3, the motor's rotating shaft and the impeller's rotating shaft are the same rotating shaft, but the motor's rotating shaft and the impeller's rotating shaft may be connected via a transmission mechanism. In this case, the rolling bearing supporting the rotating shaft in the drive unit may be the rolling bearing supporting the motor's rotating shaft, or the rolling bearing supporting the impeller's rotating shaft. Furthermore, for example, if the drive unit has a mechanism for controlling the pitch angle of the impeller, the rolling bearing supporting the rotating shaft in the drive unit also includes a rolling bearing supporting the rotating shaft that controls the pitch angle of the impeller.

[0047] In the present invention, an absolute angle may be acquired as an indicator of the bearing condition. FIG. 5 shows a configuration for acquiring the absolute angle of the inner ring (rotating shaft) relative to the outer ring, for example. As shown in FIG. 5(a), deep groove ball bearing 7A' is provided with angle sensor 25 for acquiring the absolute angle. Angle sensor 25 is composed of detection circuit 26 fixed to sensor housing 28 and magnetic encoder 27 fixed to inner ring 21. Magnetic encoder 27 generates a physical signal that uniquely indicates the absolute angle, and this physical signal is detected by detection circuit 26. Here, the absolute angle is information indicating the angle from an origin determined at a single point in the circumferential direction, such as an angle value. Note that angle sensor 25 is not limited to a magnetic sensor, and an optical sensor may also be used.

[0048] The magnetic encoder 27 is formed by pressing a magnetic plate, such as a rolled steel plate or a magnetic stainless steel plate, into a circular ring shape with an L-shaped cross section, and a cylindrical magnetic rubber 27b vulcanized and bonded to the metal core 27a. The magnetic encoder 27 is fixed to the inner ring 21 by press-fitting the inner periphery of the metal core 27a into the inner circumferential surface of the inner ring 21. The magnetic rubber 27b is formed by kneading a synthetic rubber, such as nitrile rubber (NBR), as a binder with an appropriate blend of magnetic powder, such as ferrite, and forming it into a string. The string-shaped molded body and the metal core 27a, which is coated with an adhesive, are placed in a mold and vulcanized to bond it to the metal core 27a. The magnetic rubber 27b is then magnetized into a predetermined pattern. The magnetic tracks on the magnetic rubber 27b are magnetized in multiple rows so that the phases are shifted relative to each other by 360° (one cycle) per rotation (360°).

[0049] FIG. 5(b) shows a plan view of the cylindrical magnetic rubber 27b as seen from the outer peripheral surface side. Each of the magnetic tracks T1 and T2 is configured with alternating north and south poles arranged in the circumferential direction. In FIG. 5(b), the magnetic rubber 27b has multiple magnetic tracks T1 and T2 with different numbers of magnetic poles. Specifically, the number of magnetic pole pairs in the magnetic track T1 is greater than the number of magnetic pole pairs in the magnetic track T2. In this case, the circumferential pitch (circumferential length) of the magnetic poles in the magnetic track T1 is shorter than the circumferential pitch (circumferential length) of the magnetic poles in the magnetic track T2. The magnetic rubber 27b has an origin P set at only one location in the circumferential direction. At the origin P, one side of the circumferential end of the magnetic pole face of the magnetic track T1 and one side of the circumferential end of the magnetic pole face of the magnetic track T2 are aligned on the same straight line in the axial direction.

[0050] The number of magnetic pole pairs in each track is not particularly limited, but for example, the number of magnetic pole pairs in magnetic track T1 can be 64 (64 north and 64 south poles), and the number of magnetic pole pairs in magnetic track T2 can be 63 (63 north and 63 south poles). In this case, by dividing one period of magnetic track T1 into a maximum of 16,384, a maximum resolution of 1,048,576 divisions (20 bits) can be obtained per rotation.

[0051] In the configuration of Figure 5, phase outputs (first track phase P1 and second track phase P2) are obtained from detection circuits 26 facing the two magnetic tracks T1 and T2. By calculating the phase difference between these phases, a signal of 360 degrees per rotation is obtained, and the absolute angle is obtained based on this. For example, if deep groove ball bearing 7A' is a bearing that supports the rotating shaft of the rotor, this absolute angle is obtained as the rotation angle of the rotating shaft. Also, if deep groove ball bearing 7A' is a bearing that supports the rotating shaft that controls the pitch angle of the rotor, it is obtained as the pitch angle of the rotor.

[0052] The configuration for acquiring the absolute angle is not limited to the configuration in Fig. 5. For example, the number of rows of magnetic tracks in magnetic encoder 27 is not limited to two, and may be one row, three rows, or more. Also, in Fig. 5, a radial type magnetic encoder in which magnetic tracks are formed around the entire outer periphery of the cylindrical core metal 27a is used as magnetic encoder 27, but an axial type magnetic encoder may also be used.

[0053] Next, Figure 6 shows a block diagram of an example of a configuration for determining anomalies based on indicators obtained from sensors. Figure 6(a) shows a case where anomaly detection is primarily performed through real-time monitoring to lead to flight stabilization control during operation. Figure 6(b) shows a case where anomaly detection is performed through medium- to long-term monitoring to determine whether maintenance is necessary. The interval (sampling period) at which indicators are acquired by sensors is not particularly limited. To enable real-time anomaly detection, an interval of 1 second or less is preferable, and an interval of 100 milliseconds or less is even acceptable, as long as the minimum interval obtainable within the specifications of the sensor. Furthermore, if the purpose is only medium- to long-term monitoring, the interval may be the same as that for real-time monitoring, or a longer interval, such as every few minutes, several hours, or every startup. Note that it is desirable to use a combination of real-time monitoring and medium- to long-term monitoring as appropriate.

[0054] The real-time monitoring and control shown in FIG. 6(a) will now be described. The bearing device includes a plurality of rolling bearings 7A-7D (see FIG. 2), sensors 8A-8D corresponding to these rolling bearings, and a control device 9. The specific configurations of the rolling bearings and sensors are as described above. Although not shown in FIG. 6, sensors 8B-8D also have the same sensor configuration as sensor 8A. Similarly to drive unit 3A, drive units 3B-3D also have an amplifier and a lubricant supply device. In addition to the abnormality determination unit 10 and control unit 11 described above, the control device 9 also has a storage device 9a that stores indicators and a notification unit 9b that notifies of abnormal conditions. The abnormality determination unit 10 determines whether or not there is an abnormality in the rolling bearings 7A-7D based on the indicators acquired by the sensors 8A-8D. The control unit 11 controls the drive units and other components based on the results of this abnormality determination.

[0055] The storage device 9a stores, as needed, indicators acquired by, for example, the sensors 8A to 8D. The notification unit 9b has a function of notifying an abnormal state. The notification means is not particularly limited, and may be one or a combination of the following means: displaying the abnormal state on a monitor for the crew, notifying them by sound or voice, notifying them by communication to the outside of the aircraft, notifying them by lamp display or sound, etc.

[0056] In the case of FIG. 6(a), the abnormality determination unit determines abnormalities in the rolling bearing at intervals that are, for example, m times (m is an integer) the interval at which the sensor index is acquired (for example, the minimum acquisition interval). m is, for example, 1 to 100. The value of m can be set appropriately taking into consideration the load on the abnormality determination unit or control unit. In the case of real-time monitoring, by setting the index acquisition interval to a very short interval, for example, at nanosecond intervals, abnormalities can be determined instantaneously, making it possible to respond to sudden abnormalities.

[0057] The medium- to long-term monitoring shown in Figure 6(b) will now be described. The control device 9 has an abnormality determination unit 10, a storage device 9a, and an alarm unit 9b. The specific configurations of the rolling bearing, sensor, storage device, and alarm unit are the same as those in FIG. 6(a). The data (indexes, thresholds, etc.) stored in the storage device may be different depending on the abnormality determination method, etc. Furthermore, for medium- to long-term monitoring, a control unit may be provided as needed to perform automatic control in cooperation with the abnormality determination unit.

[0058] In the case of FIG. 6(b), the abnormality determination unit determines whether an abnormality exists in the rolling bearing at intervals that are n times (n is an integer) the interval at which the sensor index is acquired (for example, the minimum acquisition interval). n is a value greater than the above-mentioned m, for example, 1000 to 10000. The abnormality determination interval may also be determined independently of the interval at which the sensor index is acquired. For example, the sensor index itself may be stored in the storage device 9a at very short intervals (for example, within one second), and an abnormality may be determined at predetermined intervals, such as every few hours, every day, or every month, based on the trends in the index accumulated and stored in the storage device 9a. Such medium- to long-term condition monitoring makes it possible to determine whether maintenance is necessary.

[0059] A specific method for determining whether the rolling bearing 7A is abnormal will be described below, but abnormality determination for other rolling bearings can also be performed in the same manner.

[0060] (Method 1 for detecting abnormalities) The abnormality determination unit 10 determines that the rolling bearing 7A is abnormal when an index acquired by at least one of the heat flow sensor 17, the temperature sensor 18, the vibration sensor 19, and the load sensor 20 exceeds a predetermined threshold. The index may be the output value (Q) of the heat flow sensor, the output value (T) of the temperature sensor, the output value (V) of the vibration sensor, or the output value (L) of the load sensor, as well as the amount of change over time of each output value (for example, the amount of change over time of the output value of the heat flow sensor (ΔQ / Δt), the amount of change over time of the output value of the temperature sensor (ΔT / Δt), or the amount of change over time of the output value of the load sensor (ΔL / Δt)), the maximum value of the power spectrum after frequency analysis of the vibration sensor, or the integral value (Vf) in a specific frequency range.

[0061] The threshold values ​​to be compared with the above indexes are set in advance according to the rotational speed, etc. For example, in a test in which a test machine having the bearing configuration shown in Figure 3 was rotated from the low speed range to the ultra-high speed range (dmn value 1.44 million) under the following test conditions, it was found that the temperature and heat flux increased in a predetermined relationship as the rotational speed increased, as shown in Figure 7. Note that each graph in Figure 7 is a simplified diagram showing the overall trend. <Test conditions> Test bearing: φ70 x φ110 x 20, equivalent to 5S-2LA-HSE014 (Ultra-high speed angular contact ball bearing with ceramic balls) Preload method: Fixed position preload (post-assembly preload 750N) Rotation speed: 0 to 16,000 min -1 Lubrication method: Air-oil lubrication Oil supply amount: 0.03mL / 10min Lubricating oil: ISO VG32 Lubrication air flow rate: 30NL / min Outer cylinder cooling: Yes, room temperature synchronization Axis orientation: Horizontal axis

[0062] Based on the trends shown in FIG. 7, when using the output value (Q) of the heat flow sensor or the output value (T) of the temperature sensor as the index, it is preferable to set multiple thresholds according to the rotational speed range. For example, when using the output value (Q) of the heat flow sensor, the following thresholds can be set in advance: Q_th1 corresponding to a rotational speed N<2000 (1 / min), Q_th2 corresponding to a rotational speed 2000≦N<4000 (1 / min), Q_th3 corresponding to a rotational speed 4000≦N<6000 (1 / min), Q_th4 corresponding to a rotational speed 6000≦N<8000 (1 / min), Q_th5 corresponding to a rotational speed 8000≦N<10000 (1 / min), and Q_th6 corresponding to a rotational speed N≧10000 (1 / min). The thresholds for the output value (T) of the temperature sensor can also be set in a similar manner. The rotational speed is acquired by a rotation sensor provided inside the motor.

[0063] The threshold value is stored in the storage device 9a of the abnormality determination unit 10. In addition, the storage device 9a stores indices acquired by various sensors as needed, and is capable of storing indices acquired over a long period of time.

[0064] Here, the cause of the bearing abnormality can be inferred by appropriately combining the indicators. For example, if an excessive load is applied to a rolling bearing, the contact pressure between the rolling elements and the inner and outer rings increases, causing heat generation. If an abnormality is determined based on such an event using a combination of indicators from the heat flow sensor and indicators from the load sensor, it can be inferred that the abnormal heat generation is due to an excessive load.

[0065] Furthermore, surface roughness can occur on the raceway surface due to poor lubrication of the rolling bearing or the inclusion of foreign matter. As the surface roughness progresses, the raceway surface is damaged and heat is generated. If an abnormality is determined based on such an event using a combination of indicators from the heat flow sensor and vibration sensor, it can be assumed that the abnormal heat generation is due to damage to the raceway surface.

[0066] Vibration sensors can also be used to estimate bearing damage and damaged locations. Depending on their installation location, vibration sensors can distinguish between various disturbance vibrations and noises and extract only the vibration values ​​caused by bearings. For example, by installing a high-frequency vibration sensor on the outer surface of the outer ring of a rolling bearing to measure radial vibrations, bearing damage can be detected from the acquired effective values. By installing a low-frequency vibration sensor to measure radial vibrations, unbalance can be detected from the acquired primary, secondary, and tertiary rotational frequency components. By installing a low-frequency vibration sensor to measure axial vibrations, misalignment can be detected from the acquired primary, secondary, and tertiary rotational frequency components.

[0067] Figure 8(a) is a graph showing an example of the change over time in the vibration value of a rolling bearing. The vertical axis of the graph shows the effective value, and the horizontal axis shows the date. As shown in Figure 8(a), it can be seen that the effective value rises gradually over time. In this case, if the effective value exceeds a predetermined threshold, it can be determined to be an abnormality. Furthermore, Figure 8(b) shows the envelope spectrum at measurement point A, and Figure 8(c) shows the envelope spectrum at measurement point B. In other words, Figures 8(b) and (c) show the vibration acceleration for each frequency.

[0068] Here, the frequencies include the frequency that occurs when the outer ring is damaged (outer ring damage frequency fo), the frequency that occurs when the inner ring is damaged (inner ring damage frequency fi), and the frequency that occurs when the rolling elements are damaged (rolling element damage frequency fb), and these can be calculated in advance using the following equations (1) to (3). fo=(fr / 2)×(1-(d / D)×cosθ)×z...(1) fi=(fr / 2)×(1+(d / D)×cosθ)×z...(2) fb=(fr / 2)×(D / d)(1-(d / D) 2 ×cos 2 θ) (3) In the above formulas (1) to (3), fr is the rotational frequency (Hz), d is the diameter of the rolling element (mm), D is the pitch circle diameter (mm), θ is the contact angle, and z is the number of rolling elements. The nth-order (n is a natural number) damage frequency can be calculated using n×fo, n×fi, and n×fb, respectively.

[0069] In Figure 8(b), the peak of the bearing's inner ring damage frequency fi and sidebands of the rotational frequency modulation components (fi±fr, 2fi±fr) are observed on either side. From this result, it can be inferred that there is damage to the inner ring of the bearing. In Figure 8(c), which is taken approximately 12 months after Figure 8(b), it can be seen that the sidebands of the inner ring damage frequency fi and its modulation components (fi±fr, 2fi±fr) are observed more strongly than in Figure 8(b). From this result, it can be inferred that the damage that occurred in the inner ring of the bearing has progressed.

[0070] As shown in Figure 8, by performing frequency analysis of vibration data from vibration values ​​caused by bearings, it is possible to estimate which part of the bearing (rolling element, inner ring, outer ring, etc.) each frequency is caused by. Furthermore, the extent of damage can be estimated from the vibration values. In addition, by correcting for the effect of rotational speed (the magnitude of vibration values), it is also possible to extract the bearing vibration spectrum, which is useful for determining abnormalities.

[0071] (Method 2 for determining abnormalities) Furthermore, the abnormality determination unit 10 may substitute the indices acquired by the various sensors into a predetermined calculation formula and perform the abnormality determination using the calculated value. In this case, if the calculated value exceeds a predetermined threshold, it is determined that the rolling bearing 7A is abnormal. The indices may be those based on the output values ​​of the various sensors described above (Q, T, V, ΔQ / Δt, etc.).

[0072] When using a formula, each index may be weighted. For example, a coefficient may be set for each index, and the sum of the values ​​obtained by multiplying each index by the coefficient may be compared with a predetermined threshold value to determine whether an abnormality has occurred. The coefficient and threshold value are preferably set according to the rotation speed.

[0073] Returning to Fig. 6, the control unit 11 controls the drive units 3A to 3D based on the determination result of the abnormality determination unit 10. If the abnormality determination unit 10 determines that all of the rolling bearings 7A to 7D are normal, the control unit 11 performs control in normal mode. In normal mode, the control unit 11 outputs a command to change the rotation speed to the amplifier 29 of the motor that should adjust the lift based on the difference between the current attitude and the target attitude of the aircraft. Then, based on the command, the amount of power is adjusted by the amplifier 29, and the rotation speed of the motor (and the rotor blades) is controlled.

[0074] On the other hand, if the abnormality determination unit 10 determines that at least one of the rolling bearings 7A to 7D is abnormal, the control unit 11 performs control in abnormal mode. For example, if the rolling bearing 7A is determined to be abnormal, the control unit 11 controls the drive unit 3A on which the rolling bearing 7A is mounted to alleviate the condition of the rolling bearing 7A, while controlling the other drive units 3B to 3D to continue flight. Specifically, by controlling the amplifiers 29 of the drive units 3A to 3D, the motor rotation speed is adjusted to maintain the flight attitude, or by controlling the lubricating oil supply device 30, the amount of lubricating oil supplied is increased to resolve issues such as oil film shortage.

[0075] 9 is a flowchart showing the procedure for determining abnormality and controlling the drive unit, which is executed by the control device. The process from start to end in FIG. 9 is repeated at predetermined time intervals.

[0076] First, the control device inputs the indices acquired by the sensors (step S11). The indices include indices based on the output values ​​of the various sensors described above (Q, T, V, ΔQ / Δt, etc.). In the following step S12, the acquired indices are substituted into a predetermined calculation formula to calculate a calculated value (determined value).

[0077] In step S13, the abnormality determination unit performs abnormality determination for the rolling bearings. The abnormality determination is performed for each rolling bearing mounted in each drive unit. For example, in the configuration of FIG. 2, abnormality determination is performed for each of the rolling bearings 7A to 7D. Furthermore, if each of the rolling bearings 7A to 7D is made up of multiple rolling bearings, abnormality determination is performed for one or all of these rolling bearings. As described above, abnormality determination is performed by comparing the magnitude of a predetermined threshold value with the value calculated in step S12.

[0078] In the flowchart of FIG. 9, the abnormality determination (method 2 above) is performed using the calculated value calculated in step S12, but step S12 may be omitted and the abnormality determination (method 1 above) may be performed using the index acquired in step S11 as the determination value.

[0079] If the result of the abnormality determination in step S13 is that all bearings are normal (step S14: Yes), control is performed in normal mode (step S15).On the other hand, if all bearings are not normal (step S14: No), that is, if at least one of the bearings is abnormal, control is performed in abnormal mode (step S16).

[0080] A specific example of control in the abnormality mode is shown in Figures 10 and 11. Figures 10 and 11 assume that rolling bearing 7A supporting the rotating shaft in drive unit 3A is determined to be abnormal. More specifically, the type of abnormality is assumed to be abnormal heat generation due to bearing damage in Figure 10, and abnormal heat generation due to oil film shortage in Figure 11.

[0081] 10, the control unit 11 outputs commands to the amplifiers of the drive units 3A to 3D. In this case, since the rolling bearing 7A is determined to be abnormal (bearing damage), the control unit 11 reduces or stops the rotation speed of the motor of the drive unit 3A via the amplifier. This reduces the load on the rolling bearing 7A and alleviates the condition of the bearing.

[0082] On the other hand, as the rotation speed of the rotor of drive unit 3A decreases as the motor rotation speed decreases, there is a risk that the lift on the front right side of the aircraft will decrease and the lift balance will be disrupted. However, control unit 11 stabilizes the flight attitude by adjusting the rotation speed of the motors of the other drive units 3B to 3D via the amplifier. For example, it is thought that the lift balance can be maintained and the aircraft can be kept horizontal by increasing the rotation speed of the motors of drive units 3B and 3C and decreasing the rotation speed of the motor of drive unit 3D, which is located diagonally across from drive unit 3A across main body 2.

[0083] In FIG. 11, the control unit 11 outputs a command to each lubricant supplying device of the drive units 3A to 3D. In this case, since the rolling bearing 7A is determined to be abnormal (oil film shortage), the control unit 11 outputs a command to the lubricant supplying device of the drive unit 3A to increase the amount of oil supplied to the rolling bearing 7A per time to more than a specified amount. Note that the amount of oil supplied may be increased by increasing the frequency of oil supply. This improves the lubricated state of the rolling bearing 7A and alleviates the abnormal state. Note that the control unit 11 controls the lubricant supplying devices of the other drive units 3B to 3D to maintain the amount of oil supplied (supplying the specified amount).

[0084] Note that the control by the control unit 11 in the abnormality mode is not limited to these. For example, the adjustment amount of the motor rotation speed or oil supply amount may be changed depending on the type and severity of the abnormality in the rolling bearing. For example, if a serious abnormality such as bearing damage is determined, the drive of the corresponding drive unit can be stopped, that is, the motor rotation speed can be set to zero.

[0085] In the present invention, the threshold value used by the abnormality determination unit may be set in multiple stages, and the abnormality determination unit may determine the level of abnormality of the rolling bearing based on these threshold values. For example, a first threshold value (e.g., a caution threshold value) and a second threshold value (e.g., a warning threshold value) set higher than the caution threshold value may be set, and an abnormality of the first level (caution level) may be determined when the caution threshold value is exceeded but is equal to or less than the warning threshold value, and an abnormality of the second level (warning level) may be determined when the warning threshold value is exceeded. Note that three or more threshold values ​​may be set. In this case, the manner of control (for example, notification) may be changed depending on the level of the determined abnormality. For example, if the determined value based on the index exceeds a first-stage threshold, an alarm lamp may be turned on or the allowable rotation speed of the motor of the drive unit may be limited. Furthermore, if a second-stage threshold is exceeded, an alarm buzzer may be sounded or an abnormality may be notified via communication outside the machine. As a result, inspection, etc., may be prompted. Furthermore, in the flowchart shown in FIG. 9, the abnormality determination unit determines whether or not there is an abnormality in the rolling bearing, but the abnormality determination unit may also determine whether or not there is a sign of an abnormality.

[0086] As described above, the bearing device of the present invention can sense rolling bearings in real time during a single flight to detect sudden abnormalities (real-time monitoring). Furthermore, by acquiring indicators over long periods, such as weekly or monthly periods, the bearing device of the present invention can detect abnormalities or signs of abnormalities in the rolling bearings from their trends (medium- to long-term monitoring). For example, as shown in Figure 8, it is possible to manage long-term trends based on indicators acquired by various sensors and perform control and response based on these trends. It is expected that many electric vertical take-off and landing aircraft will fly in the future, raising concerns about an accompanying increase in the maintenance burden. However, trend management based on such long-term condition monitoring can also help reduce the workload. [Industrial Applicability]

[0087] The bearing device of the present invention can accurately detect abnormalities in the bearings that support the rotating shaft in the drive unit of an electric vertical take-off and landing aircraft, enabling stable flight, and therefore can be widely used as a bearing device to be installed in electric vertical take-off and landing aircraft. [Explanation of symbols]

[0088] 1 Electric vertical take-off and landing aircraft 2 Main body 3, 3A, 3B, 3C, 3D drive unit 4 rotor blades 5 motors 6 Bearing device 7A, 7B, 7C, 7D Rolling bearings 7a, 7b Angular contact ball bearings 7a' deep groove ball bearing 8A, 8B, 8C, 8D sensors 9 Control Device 9a Storage device 9b Notification Department 10 Abnormality determination section 11 Control section 12 Housing 13 Rotation axis 14 Inner ring spacer 15 Outer ring spacer 16 Nozzle member 17 Heat flow sensor 18 Temperature Sensor 19 Vibration Sensor 20 Load Sensor 21 Inner Circle 22 outer ring 23 balls 24 Cage 25 Rotation Sensor 26 Detection circuit 27 Magnetic Encoder 28 Sensor housing 29 Amplifier 30 Lubricating oil supply device

Claims

1. A bearing device mounted on an electric vertical take-off and landing aircraft that flies by rotation of a rotor and includes a plurality of drive units each having a motor that rotates the rotor, the bearing device comprising: The bearing device includes a rolling bearing that supports a rotating shaft in the drive unit, a sensor that is provided inside or outside the rolling bearing and that acquires an index that indicates the state of the rolling bearing, a storage device that stores the index, an abnormality determination unit that determines an abnormality in the rolling bearing based on the index, and a control unit that controls the drive unit, the indicator is an indicator including at least vibration of the rolling bearing, the abnormality determination unit determines an abnormality in the rolling bearing on a weekly or monthly basis based on the transition of the indexes accumulated and stored in the storage device, A bearing device characterized in that, when the abnormality determination unit determines that at least one of the plurality of rolling bearings is abnormal, the control unit controls the drive unit on which the rolling bearing determined to be abnormal is mounted to alleviate the condition of the rolling bearing determined to be abnormal, while controlling the other drive units to continue flight.

2. 2. The bearing device according to claim 1, wherein the control unit adjusts the rotation speed of the motor of the drive unit when the abnormality determination unit determines that an abnormality has occurred.

3. A bearing device mounted on an electric vertical take-off and landing aircraft that flies by rotation of a rotor and includes a plurality of drive units each having a motor that rotates the rotor, the bearing device comprising: The bearing device includes a rolling bearing that supports a rotating shaft in the drive unit, a sensor that is provided inside or outside the rolling bearing and that acquires an index that indicates the state of the rolling bearing, a storage device that stores the index, an abnormality determination unit that determines an abnormality in the rolling bearing based on the index, and a control unit that controls the drive unit, the indicator is an indicator including at least vibration of the rolling bearing, the abnormality determination unit determines an abnormality in the rolling bearing on a weekly or monthly basis based on the transition of the indexes accumulated and stored in the storage device, The control unit adjusts the rotation speed of the motor of the drive unit when the abnormality determination unit determines that an abnormality has occurred.

4. 4. The bearing device according to claim 1, wherein the indicator is an indicator including one selected from the group consisting of a heat flux of the rolling bearing, a temperature of the rolling bearing, a load of the rolling bearing, and an absolute angle of the rolling bearing.

5. 5. The bearing device according to claim 1, wherein the abnormality determination unit determines abnormality in the rolling bearing at intervals that are m times (m is an integer) the interval at which the index of the sensor is acquired.

6. 6. The bearing device according to claim 1, further comprising a notification unit that notifies the user of an abnormality when the abnormality determination unit determines that an abnormality has occurred.

7. 7. The bearing device according to claim 1, wherein the abnormality determination unit determines an abnormality based on the index when a preset threshold value is reached.

8. a notification unit that notifies the abnormality when the abnormality determination unit determines that an abnormality has occurred; The threshold value is set in a plurality of stages, and the abnormality determination unit determines the level of abnormality of the rolling bearing based on the threshold value, 8. The bearing device according to claim 7, wherein the notification unit changes the notification mode depending on the level of the abnormality determined by the abnormality determination unit.

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