Method for determining the deterioration of foil bearings

Abstract

This method for determining deterioration in a foil bearing that supports a rotor shaft of an electric compressor device comprises: a torque under determination acquisition step for acquiring a torque under determination, which is the torque of the rotor shaft at a startup time or a stopping time; a torque determination step for determining whether the torque under determination is less than or equal to a torque threshold value; and a deterioration determination step for determining that the foil bearing has deteriorated when it has been determined that the torque under determination is less than or equal to the torque threshold value.

Description

[Technical Field]

[0001] This disclosure relates to a method for determining the deterioration of a foil bearing that supports the rotor shaft of an electric compressor device. [Background technology]

[0002] Conventionally, devices for determining the degree of deterioration of foil bearings supporting a rotating shaft are known. For example, the deterioration diagnostic device disclosed in Patent Document 1 comprises the outer circumferential surface of a rotating body and a sensor provided opposite the outer circumferential surface. The sensor is configured to measure the distance to the outer circumferential surface, and the size of the gap between the rotating body and the foil bearing is estimated based on the results measured sequentially by the sensor while the rotating body is rotating. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-127541 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, with the estimation method described above, error factors such as misalignment of the rotating shaft or vibrations that occur during rotation are reflected in the sensor's measurement results, making it difficult to accurately determine whether the foil bearing is deteriorating.

[0005] The purpose of this disclosure is to provide a method for determining the deterioration of a foil bearing that can accurately determine whether the foil bearing is deteriorated. [Means for solving the problem]

[0006] A method for determining the deterioration of a foil bearing according to at least one embodiment of the present disclosure is: A method for determining the deterioration of a foil bearing that supports the rotor shaft of an electric compressor, A process for acquiring a target torque, which is the torque of the rotor shaft during startup or shutdown, A torque determination step of determining whether the torque to be determined is less than or equal to a torque threshold, If the torque to be determined is determined to be less than or equal to the torque threshold, a deterioration determination step is performed to determine that the foil bearing is deteriorated. It is equipped with. [Effects of the Invention]

[0007] According to this disclosure, a method for determining whether a foil bearing is deteriorating can be provided that can accurately determine whether the foil bearing is deteriorating. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic cross-sectional view of a turbocharger device according to one embodiment. [Figure 2] This is a schematic cross-sectional view of a foil bearing according to one embodiment. [Figure 3] This is a schematic cross-sectional view of a foil bearing that has deteriorated over time according to one embodiment. [Figure 4] This is a schematic graph showing the relationship between the radial clearance length and the rotor shaft starting torque. [Figure 5] This is a schematic graph showing the relationship between the radial gap length and starting torque in multiple turbocharger devices. [Figure 6] This flowchart shows an example of a method for determining the deterioration of a foil bearing according to the first embodiment. [Figure 7] This is a schematic graph showing the changes in rotor shaft rotation speed and output torque over time. [Figure 8] This is a schematic graph showing the relationship between the radial gap length and the starting output torque in multiple turbocharger devices. [Figure 9] This flowchart shows an example of a method for determining the deterioration of a foil bearing according to the second embodiment. [Modes for carrying out the invention]

[0009] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements and the like of components described in the embodiments or illustrated in the drawings are not intended to limit the scope of the present disclosure, and are merely illustrative examples. For example, expressions indicating relative or absolute arrangements such as "in a direction", "along a direction", "parallel", "perpendicular", "central", "concentric" or "coaxial" not only strictly indicate such an arrangement, but also indicate a state of relative displacement with tolerances or angles and distances that allow the same function to be obtained. For example, expressions indicating that things are in an equal state such as "identical", "equal" and "homogeneous" not only strictly represent an equal state, but also represent a state where there are tolerances or differences to an extent that the same function can be obtained. For example, expressions representing shapes such as a quadrangular shape or a cylindrical shape not only represent shapes such as a quadrangular shape or a cylindrical shape in a strictly geometric sense, but also represent shapes including uneven portions, chamfered portions and the like within a range where the same effect can be obtained. On the other hand, the expressions "comprising", "including" or "having" one component are not exclusive expressions that exclude the presence of other components. In addition, the same reference numerals are given to similar configurations, and the description thereof may be omitted.

[0010] <Overall Configuration of Turbocharger Device 1> As an example of the electric compressor device of the present disclosure, an electric turbocharger device (hereinafter referred to as turbocharger device 1) will be described. FIG. 1 is a schematic cross-sectional view of a turbocharger device 1 according to an embodiment of the present disclosure. The turbocharger device 1 is, for example, mounted on an automobile engine. The turbocharger device 1 includes a turbine 3 that rotates under the flow of exhaust gas, a compressor 5 that takes in and compresses air by the rotation of the turbine 3, and a motor unit 80 for assisting the rotation of the compressor 5.

[0011] The turbine 3 includes a turbine housing 31 and a turbine impeller 33 rotatably accommodated in the turbine housing 31, and the compressor 5 includes a compressor housing 51 and a compressor impeller 53 rotatably accommodated in the compressor housing 51. The turbine impeller 33 and the compressor impeller 53 are connected via a rotor shaft 9 which is a component of the turbocharger device 1.

[0012] Each of the turbine housing 31 and the compressor housing 51 is fixed to a bearing housing 71 that accommodates a pair of foil bearings 6 described later. The turbine impeller 33 is rotated by, for example, exhaust gas discharged from an automobile engine, whereby the compressor impeller 53 is rotated via the rotor shaft 9, so that supply air to be fed to the automobile engine is compressed.

[0013] The turbine housing 31 of the present example includes a cylindrical portion 31A that accommodates the turbine impeller 33, and a scroll portion 31B that surrounds a portion of the cylindrical portion 31A on the bearing housing 71 side. The scroll portion 31B has an exhaust gas inlet (not shown) and communicates with the cylindrical portion 31A via a throat portion 31C. An exhaust gas outlet 31D is formed in an opening of the cylindrical portion 31A on a side opposite to the bearing housing 71.

[0014] An end wall 75 of the bearing housing 71 is fitted into an opening of the turbine housing 31 on the bearing housing 71 side. The end wall 75 of the bearing housing 71 is fastened to one end of a cylindrically formed peripheral wall 73 by a fastening member, and constitutes a part of the bearing housing 71. A seal portion 751 is provided in a through hole of the end wall 75, and the rotor shaft 9 is inserted through the seal portion 751.

[0015] The compressor housing 51 in this example includes a cylindrical portion 51A that houses the compressor impeller 53 and a scroll portion 51B that surrounds the portion of the cylindrical portion 51A that faces the bearing housing 71. The scroll portion 51B has an air intake outlet (not shown) and communicates with the cylindrical portion 51A via a diffuser portion 51C. The opening of the cylindrical portion 51A on the side opposite the bearing housing 71 is an air intake inlet 51D.

[0016] The end wall 77 of the bearing housing 71 is fitted into the opening of the compressor housing 51 on the bearing housing 71 side. The end wall 77 of the bearing housing 71 is fastened to the other end of the peripheral wall 73 by a fastening member and constitutes a part of the bearing housing 71. A seal portion 771 is provided in the through hole of the end wall 77, and the rotor shaft 9 is inserted through the seal portion 771.

[0017] A pair of bearing portions 76 are provided on each of the end walls 75 and 77, and a bearing hole 761 is formed in each of the pair of bearing portions 76. A pair of foil bearings 6, which function as radial bearings, are arranged in each of the pair of bearing holes 761. The pair of foil bearings 6 rotatably support the rotor shaft 9.

[0018] The motor unit 80 includes a rotor unit 81 provided on the rotor shaft 9 between a pair of foil bearings 6, and a stator unit 85 facing the rotor unit 81. The rotor unit 81 has permanent magnets and a rotor core that supports the permanent magnets, and the stator unit 85 has a stator core 851 supported by a peripheral wall 73 and a stator coil 853 provided on the stator core 851. In this example, a rotational force acts on the permanent magnets of the rotor unit 81 due to the rotating magnetic field generated when current flows through the stator coil 853. This rotational force allows the motor unit 80 to assist the rotation of the rotor shaft 9.

[0019] The energization control of the stator coil 853 is performed by a motor controller 100, which is a component of the turbocharger device 1. The motor controller 100 is a computer and comprises a processor, memory (storage medium), and an external communication interface. The processor is a CPU, GPU, MPU, DSP, or a combination thereof. In other embodiments, the processor may be implemented by an integrated circuit such as a PLD, ASIC, FPGA, or MCU. The memory is configured to store various data temporarily or non-temporarily and is implemented by, for example, at least one of RAM, ROM, or flash memory. The motor controller 100 in this example is equipped with a motor driver for controlling the motor unit 80.

[0020] <Foil bearing 6> Figure 2 is a schematic cross-sectional view of a foil bearing 6 according to one embodiment of the present disclosure. Each foil bearing 6 includes a housing 11, a back spring 15, a top foil 13, and a pair of snap rings 17.

[0021] The housing 11 is formed inside the bearing portion 76 (see Figure 1) described above. The back spring 15 is provided inside the housing 11 so as to surround the rotor shaft 9. The back spring 15 is elastically deformable in the radial direction of the rotor shaft 9. The top foil 13 is a substantially cylindrical member that surrounds the rotor shaft 9 inside the back spring 15. The inner circumferential surface 13A of the top foil 13 is coated with resin, and when the turbocharger device 1 is stopped, the inner circumferential surface 13A is in contact with the outer circumferential surface of the rotor shaft 9.

[0022] A pair of snap rings 17 are arranged with the back spring 15 and top foil 13 in between, and each snap ring 17 is attached to the outer surface of the rotor shaft 9. Furthermore, the axial movement of each snap ring 17 on the rotor shaft 9 is restricted by the housing 11. Therefore, the axial movement of the back spring 15 and top foil 13 is restricted by the pair of snap rings 17.

[0023] The operation of the foil bearing 6 is as follows: When the turbocharger device 1 starts driving, the previously stationary rotor shaft 9 begins to rotate. During the acceleration of the rotor shaft 9, gas flows in between the rotor shaft 9 and the top foil 13. Eventually, the gas film formed between the rotor shaft 9 and the top foil 13 separates the rotor shaft 9 and the top foil 13 from each other. Subsequently, the rotational speed of the rotor shaft 9 reaches the rated rotational speed, and a steady gap GA is formed between the rotor shaft 9 and the top foil 13. Then, when the turbocharger device 1 starts its drive stop operation, the rotor shaft 9, which was rotating at the rated rotational speed, begins to decelerate, and the gas film formed between the rotor shaft 9 and the top foil 13 disappears. After the rotor shaft 9 contacts the top foil 13, the rotor shaft 9 decelerates further and eventually stops.

[0024] Figure 3 is a schematic cross-sectional view of a foil bearing 6 that has deteriorated over time according to one embodiment of the present disclosure. As the cumulative operating time of the turbocharger device 1 increases, the deterioration of the foil bearing 6 progresses. More specifically, the inner circumferential surface 13A of the top foil 13 wears down, creating a gap M between the rotor shaft 9 and the inner circumferential surface 13A even when the turbocharger device 1 is stopped. When the radial length of the gap M in the radial direction of the rotor shaft 9 exceeds the allowable limit, failures that make it difficult to continue operating the turbocharger device 1 may occur, such as excessive vibration of the rotor shaft 9 or damage to the foil bearing 6. Note that the allowable limit of the gap M is smaller than the radial length of the steady-state gap GA (dimension Lg in Figure 2) mentioned above.

[0025] If the radial gap length of the turbocharger device 1 used by a user in the market exceeds the permissible limit, it is preferable to perform maintenance such as replacing the foil bearing 6, based on the determination that the foil bearing 6 has deteriorated. However, since the degree of wear progression of the top foil 13 varies depending on the various conditions under which the user uses the turbocharger device 1, it is difficult to accurately determine whether the foil bearing 6 has deteriorated based solely on the cumulative operating time of the turbocharger device 1.

[0026] Faced with the aforementioned challenges, the inventors of this invention discovered that as the radial gap length increases due to the progression of wear on the top foil 13, the area of ​​the outer circumferential surface of the rotor shaft 9 in contact with the top foil 13 decreases, resulting in a decrease in the torque of the rotor shaft 9 during startup or shutdown. They then discovered that by determining whether the torque during startup or shutdown, as determined by measurement, is below the torque at the allowable limit of the radial gap length, it is possible to accurately determine whether the foil bearing 6 is deteriorating. Below, the method for determining the deterioration of the foil bearing 6, embodied by the inventors based on this idea, will be described in two embodiments.

[0027] The rotor shaft 9 startup period refers to the period from when the stationary rotor shaft 9 starts rotating until its rotational speed reaches the rated speed. In other words, the rotor shaft 9 startup period includes the period of speed increase. To put it another way, the rotor shaft 9 startup period includes the period during which the outer surface of the rotor shaft 9 and the inner surface 13A of the top foil 13 are in contact with each other. The rotor shaft 9 stop period refers to the period from when the rotor shaft 9, which was rotating at the rated speed, starts to decelerate until it stops. The rotor shaft 9 stop period includes the period during which the outer surface of the rotor shaft 9 and the inner surface 13A of the top foil 13 are in contact with each other.

[0028] <Method for determining deterioration of foil bearing 6 according to the first embodiment> In the first embodiment, the starting torque, which is the torque required at the moment when a stationary rotor shaft 9 begins to rotate, is used to determine whether or not the foil bearing 6 is deteriorated. The starting torque is one specific example of the torque of the rotor shaft 9 at startup as described above, and is measured by an operator operating a torque driver 90 (see Figure 3). More specifically, the operator applies a force circumferentially to the rotor shaft 9 via the torque driver 90 connected to the stationary rotor shaft 9. As the applied force gradually increases, the stationary rotor shaft 9 eventually begins to rotate. The torque at the moment the rotor shaft 9 begins to rotate is measured by the torque driver 90 as the starting torque.

[0029] In this example, the torque driver 90 measures the starting torque while connected to the fastening member 25 (see Figure 1) that fastens the compressor impeller 53 to the rotor shaft 9. When performing such a measurement, piping (not shown) connected to the inlet 51D (see Figure 1) of the turbocharger device 1 may be temporarily removed.

[0030] Figure 4 is a schematic graph showing the relationship between the radial gap length and the starting torque of the rotor shaft 9. The radial gap length, shown on the horizontal axis of the graph, is the dimension of the smallest region of the gap M shown in Figure 3. The range on the horizontal axis of the graph where the value of the radial gap length is negative indicates not only that no gap M is formed, but also that the back spring 15 is elastically deformed toward the housing 11 (a negative value of the radial gap length represents the amount of deformation of the most elastically deformed part of the back spring 15). Although the amount of elastic deformation of the back spring 15 is strictly a different physical quantity (i.e., concept) from the radial gap length of the gap M, adopting the idea that the amount of elastic deformation is included in the radial gap length allows for a clearer understanding of the relationship between the radial gap length and the starting torque.

[0031] In the graph of Fig. 4, in the initial state where the turbocharger device 1 is in a state where the top foil 13 can be considered not worn, the radial length of the gap is -L1 (L1>0). This indicates that the gap M is not formed, and the amount of elastic deformation of the back spring 15 is L1. According to the inventor's findings, as wear progresses on the inner peripheral surface 13A of the top foil 13, the amount of elastic deformation of the back spring 15 gradually decreases, and the radial length of the gap increases from -L1. Eventually, the elastic deformation of the back spring 15 disappears, and the radial length of the gap becomes 0. When wear of the inner peripheral surface 13A of the top foil 13 progresses further, the gap M is formed, and the radial length of the gap becomes a value larger than 0. Then, the radial length of the gap exceeds L2 which corresponds to the allowable limit value. In the process where the radial length of the gap changes from -L1 to L2, the measured value of starting torque decreases continuously. In the first embodiment, when the starting torque measured by the torque driver 90 falls below the starting torque (Ta) corresponding to L2, which is the allowable limit value, it is determined that the foil bearing 6 has deteriorated.

[0032] Note that various means can be employed to specify the radial length of the gap. For example, L1, which is the radial length of the gap, can be obtained by the following equation (1). L1 = ((D A -(d1+H f )×2)-D x ) / 2 ···Equation (1) In Equation (1), D A is the inner diameter of the housing 11, d1 is the thickness (radial dimension) of the top foil 13, and H f is the radial dimension of the convex portion of the back spring 15 in a free state, and D x is the outer diameter of the rotor shaft 9. These four parameters are exemplified in Fig. 3. D A , H f , D x are specified as fixed values (design values), and d1 is obtained by a measuring instrument such as a vernier caliper, for example. Then, the minimum value of d1 obtained by measurement is D A , H f , D xBy substituting this into equation (1), we can identify L1.

[0033] The graph shown in Figure 4 illustrates the relationship between the radial gap length and starting torque in a single turbocharger unit 1. However, this relationship inevitably varies among multiple turbocharger units 1. Therefore, in the first embodiment, the relationship between the measured radial gap length and the measured starting torque is measured in multiple turbocharger units 1, allowing for a more accurate determination of the starting torque corresponding to the allowable limit.

[0034] Figure 5 is a schematic graph showing the relationship between the radial gap length and starting torque in several turbocharger units 1 prepared as samples. The figure illustrates the measured values ​​of the radial gap length and starting torque for three turbocharger units 1 prepared as test samples.

[0035] As shown in Figure 5, the measured values ​​of the radial gap length measured at each turbocharger device 1 and the measured values ​​of the starting torque at the timing when the radial gap length is measured are plotted on a single graph, and an approximate curve AC is obtained using, for example, the least squares method. The approximate curve AC is expressed as a functional equation. Then, the starting torque (Tb) corresponding to the allowable limit value (L2) which has already been determined by design calculations before measurement is calculated based on the approximate curve AC. Since this starting torque is a torque identified based on the results measured at multiple turbocharger devices 1, it can serve as a more accurate threshold (i.e., the torque threshold described later) for determining the deterioration of the foil bearing 6.

[0036] For the sake of clarity, Figure 5 shows three samples of turbocharger device 1, but a larger sample size is preferable. Furthermore, plotting the measurement results on a graph is not essential to obtain the approximate curve AC. If the relationship between the measured gap radial length and the measured starting torque for multiple turbocharger devices 1 is aggregated as measurement results, it is possible to obtain the approximate curve AC as a functional equation without plotting a graph.

[0037] The method for determining the deterioration of the foil bearing 6 according to the first embodiment described above will be explained in detail with reference to Figure 6. Figure 6 is a flowchart showing an example of the method for determining the deterioration of the foil bearing 6 according to the first embodiment. In the following description, "step" may be abbreviated as "S".

[0038] First, a first measurement result acquisition step (S11) is performed to obtain measurement results collected from multiple turbocharger devices 1, which show the relationship between the measured value of the gap radial length and the measured value of the starting torque. In S11 of this example, the gap radial length is measured for each of the multiple turbocharger devices 1 prepared as test samples, and the starting torque at the time of measuring the gap radial length is also measured. After both measurements are completed, the turbocharger device 1 is driven for a certain period of time, and then the same measurements are performed. By repeating the measurement and the driving of the turbocharger device 1 alternately, measurement results as shown in Figure 5 are obtained from multiple turbocharger devices 1.

[0039] Next, a torque threshold acquisition step (S13) is performed to acquire a torque threshold from the measurement results obtained in the first measurement result acquisition step (S11). In S13 of this example, the operator inputs the measurement results obtained in S11 into a personal computer (PC), and the PC outputs a function equation showing the approximate curve AC. The operator then calculates the starting torque corresponding to the allowable limit value based on this function equation. The calculated starting torque is treated as the torque threshold. Note that the process of calculating the starting torque based on the function equation and the allowable limit value may be performed by the PC, or the operator may perform the calculation using another calculator.

[0040] Next, the starting torque of the rotor shaft 9 of the turbocharger unit 1 to be maintained is acquired as the torque to be determined (S15). The turbocharger unit 1 to be maintained is a different unit from the test turbocharger unit 1 used in S11, and is a unit used by a user in the market. In this example, S15 is performed by a customer engineer at the timing when it is estimated that the cumulative rotational speed of the rotor shaft 9 of the turbocharger unit 1 to be maintained has reached tens of thousands of revolutions. This timing may be the timing when a specified period has elapsed since the turbocharger unit 1 was delivered to the user, or when the cumulative operating time of the turbocharger unit 1 has elapsed to a specified time. Also, the customer engineer who performs S15 may be the same as or different from the worker who performs S11 and S13.

[0041] Next, a step is performed to determine whether the target torque acquired in S15 is below the torque threshold (S17). S17 is performed by the customer engineer as described above. If it is determined that the target torque exceeds the torque threshold (S17: NO), the foil bearing 6 deterioration determination method is terminated. On the other hand, if it is determined that the target torque is below the torque threshold (S17: YES), the foil bearing 6 is determined to be deteriorated (S19), and the foil bearing 6 deterioration determination method is terminated thereafter. At this point, the customer engineer continues to perform maintenance such as replacing the foil bearing 6.

[0042] According to the above configuration, if the torque to be judged is determined to be below the torque threshold (S17: YES), it is determined that the foil bearing 6 is deteriorated (S19), so it is possible to accurately determine whether the foil bearing 6 is deteriorated. In particular, the starting torque required when the rotor shaft 9 starts to rotate is greater than the dynamic torque required by the rotor shaft 9 after rotation has started, and the amount of change in the starting torque is large as the wear of the top foil 13 of the foil bearing 6 progresses. Therefore, according to the embodiment in which the starting torque is treated as the torque to be judged, it is possible to accurately determine whether the foil bearing 6 is deteriorated.

[0043] Furthermore, in a configuration in which the first measurement result acquisition process (S11) and the first torque threshold acquisition process (S13) are performed, the relationship between the gap radial length and the starting torque is measured in multiple turbocharger devices 1. As a result, the relationship between the gap radial length and the starting torque, which is independent of differences between the turbocharger devices 1, can be obtained as a measurement result. This allows for accurate determination of the starting torque at the permissible limit, and since the determined starting torque is treated as the torque threshold, it is possible to accurately determine whether the foil bearing 6 is deteriorating.

[0044] The first embodiment is not limited to the above description. In S11, not only is the relationship between the gap radial length and the starting torque obtained from multiple turbocharger devices 1, but a single turbocharger device 1 whose starting torque measurement has been completed may be disassembled and reassembled, and the starting torque of the reassembled turbocharger device 1 may be measured again. Such measurement is equivalent to measuring the starting torque from each of two turbocharger devices 1 having the same gap radial length, and the number of sample measurements collected in S11 can be substantially increased. As a result, in S13, a more accurate starting torque corresponding to the permissible limit can be obtained as the torque threshold.

[0045] <Method for determining deterioration of foil bearing 6 according to the second embodiment> In the second embodiment, the foil bearing 6 is determined to be deteriorated based on the output torque output by the rotating rotor shaft 9 during startup or shutdown. The second embodiment differs from the first embodiment in that the torque used as the basis for the determination is the output torque, which is classified as dynamic torque, rather than the starting torque, which is classified as static torque. Furthermore, as will be described later, the second embodiment also differs from the first embodiment in that the motor controller 100, rather than a customer engineer, performs the determination of whether the foil bearing 6 is deteriorated.

[0046] The principle of the determination method according to the second embodiment will now be explained. Figure 7 is a schematic graph showing the change in rotational speed of the rotor shaft 9 over time and the change in output torque over time. The period from time 0 to t1 is the start-up period of the rotor shaft 9, and the period from time t2 to t3 is the stop-down period of the rotor shaft 9. In the graph, the solid line shows the rotational speed of the rotor shaft 9, the dashed line shows the output torque of the rotor shaft 9 when the turbocharger device 1 is in its initial state, and the dashed line shows the output torque of the rotor shaft 9 when the clearance radial length is at the allowable limit value. As can be seen from the figure, the output torque during start-up and stop-down decreases continuously during the wear of the top foil 13. This is because the area of ​​the outer surface of the rotor shaft 9 that contacts the top foil 13 decreases as the wear of the top foil 13 progresses.

[0047] Furthermore, the reason why the output torque is relatively small during the period from time t1 to t2 in the same graph is that the rotor shaft 9 moves away from the top foil 13, and the dynamic torque required for the rotor shaft 9 to rotate at the rated speed is relatively small. During this period, the value of the current flowing through the stator coil 853 is relatively small.

[0048] In the second embodiment, if the output torque measured during startup or shutdown is less than or equal to the output torque shown by the dashed line, the foil bearing 6 is determined to be deteriorated. The measured output torque may be either the output torque of the rotor shaft 9 during startup or the output torque of the rotor shaft 9 during shutdown, but below we will illustrate an embodiment in which the output torque during startup is measured. Hereinafter, the output torque during startup may be referred to as "startup output torque".

[0049] The starting output torque of the rotor shaft 9 is measured by measuring the current flowing through the stator coil 853 of the turbocharger device 1. The current flowing through the stator coil 853 is measured by a motor driver mounted on the motor controller 100, and the processor mounted on the motor controller 100 calculates the output torque based on the measurement results. Data representing the relationship between the current value and the output torque is used to calculate the output torque. This data may be a functional expression showing the relationship between the current value and the output torque, and is stored in the memory of the motor controller 100. In this case, the processor can read the functional expression from memory and use it for calculations. The starting output torque calculated in this way can be considered a measured value.

[0050] The output torque shown by the dashed line in the graph of Figure 7 represents the output torque of a single turbocharger unit 1. However, the output torque when the clearance radial length reaches the allowable limit will inevitably vary among multiple turbocharger units 1. Therefore, in the second embodiment, the relationship between the measured value of the clearance radial length and the measured value of the output torque at startup is measured for multiple turbocharger units 1, and the startup output torque corresponding to the allowable limit can be determined more accurately.

[0051] Figure 8 is a schematic graph showing the relationship between the radial gap length and the starting output torque in several turbocharger devices 1 prepared as samples. The figure illustrates the measured values ​​of the radial gap length and the starting output torque in three turbocharger devices 1 prepared as test samples.

[0052] As shown in Figure 8, the measured values ​​of the radial gap length and the measured values ​​of the starting output torque measured at each turbocharger device 1 are plotted on a single graph, and an approximate curve BD is obtained using, for example, the least squares method. The approximate curve BD is expressed as a functional equation. Then, the starting output torque corresponding to the allowable limit value (L2), which has already been determined as a design value before measurement, is calculated based on the approximate curve BD. Since this starting output torque (Tc) is a torque determined based on the results measured at multiple turbocharger devices 1, it can serve as a more accurate threshold (torque threshold) for determining the deterioration of the foil bearing 6.

[0053] For the sake of clarity, Figure 8 shows three samples for the turbocharger device 1, but a larger sample size is preferable. Furthermore, plotting the measurement results on a graph is not essential to obtain the approximate curve BD. If the relationship between the measured values ​​of the gap radial length and the measured values ​​of the starting output torque for multiple turbocharger devices 1 is aggregated, it is possible to obtain the approximate curve BD as a functional equation without plotting a graph.

[0054] The method for determining the deterioration of the foil bearing 6 according to the second embodiment described above will be explained in detail with reference to Figure 9. Figure 9 is a flowchart showing an example of the method for determining the deterioration of the foil bearing 6 according to the second embodiment.

[0055] First, a second measurement result acquisition step (S31) is performed to acquire measurement results collected from multiple turbocharger devices 1 regarding the relationship between the measured value of the gap radial length and the measured value of the starting output torque. In S31 of this example, the gap radial length is measured in each of the multiple turbocharger devices 1 prepared as test samples, and the starting output torque at the time of measuring the gap radial length is also measured. The measurement of the starting output torque is performed, for example, by measuring the value of the peak current flowing through the stator coil 853 during the startup period. The starting output torque, which is determined based on this current value and the relationship formula described above, is output from the motor controller 100 of each turbocharger device 1 to an external computing device such as a personal computer. An operator operating the external computing device can acquire the starting output torque as a measurement result. After the gap radial length and starting output torque have been measured, the turbocharger device 1 is driven for a certain period of time, and then the gap radial length and starting output torque are measured again using the same procedure. By repeatedly performing measurements and driving the turbocharger device 1 alternately, measurement results like those shown in Figure 8 can be obtained from multiple turbocharger devices 1.

[0056] Next, a torque threshold acquisition process (S33) is performed to acquire a torque threshold from the measurement results obtained in the second measurement result acquisition process (S31). In S33 of this example, the operator inputs the measurement results obtained in S31 into a personal computer (PC), and the PC outputs a function equation showing the approximate curve BD. The operator then calculates the starting output torque corresponding to the allowable limit value based on this function equation. The calculated starting output torque is treated as the torque threshold. Note that the process of calculating the output torque based on the function equation and the allowable limit value may be performed by the PC, or the operator may perform the calculation using other external computing equipment. In this example, the torque threshold obtained in S33 is stored in the memory of the motor controller 100 of the turbocharger device 1 that will be shipped as a product.

[0057] Next, the starting output torque of the rotor shaft 9 of the turbocharger unit 1 to be maintained is acquired as the torque to be judged (S35). The turbocharger unit 1 to be maintained is a different unit from the test turbocharger unit 1 used in S31, and is a unit used by users in the market. S35 in this example is performed periodically by the controller of the turbocharger unit 1 to be maintained. The method for acquiring the starting output torque to be judged is as previously described.

[0058] Next, it is determined in S37 whether the target torque acquired in S35 is less than or equal to the torque threshold acquired in S33. In S37 of this example, the motor controller 100 compares the torque threshold read from memory with the target torque acquired in S35. If the motor controller 100 determines that the target torque exceeds the torque threshold (S37: NO), the foil bearing 6 deterioration determination method is terminated. On the other hand, if it is determined that the target torque is less than or equal to the torque threshold (S37: YES), the motor controller 100 determines that the foil bearing 6 is deteriorated (S39), and then the foil bearing 6 deterioration determination method is terminated. At this time, the motor controller 100 may output a signal to a predetermined external computing device indicating that maintenance such as replacement of the foil bearing 6 is necessary, or it may execute a process to forcibly stop the turbocharger device 1.

[0059] According to the above configuration, if the torque to be judged is determined to be below the torque threshold (S37: YES), it is determined that the foil bearing 6 is deteriorated (S39), thus allowing for accurate determination of whether the foil bearing 6 is deteriorated. In particular, the starting output torque of the rotor shaft 9 has a relatively large peak, and the amount of change in the starting output torque is large as the wear of the top foil 13 of the foil bearing 6 progresses. Therefore, according to the embodiment in which the starting output torque is treated as the torque to be judged, it is possible to accurately determine whether the foil bearing 6 is deteriorated.

[0060] Furthermore, in a configuration in which the second measurement result acquisition process (S31) and the second torque threshold acquisition process (S33) are performed, the relationship between the gap radial length and the starting output torque is measured in multiple turbocharger devices 1. As a result, the relationship between the gap radial length and the starting output torque, which is independent of differences between the turbocharger devices 1, can be obtained as a measurement result. This allows for accurate determination of the starting output torque at the permissible limit, and since the determined starting output torque is treated as the torque threshold, it is possible to accurately determine whether the foil bearing 6 is deteriorating.

[0061] In the flowchart shown in Figure 9, an example is given where the starting output torque is the torque to be judged, but the second embodiment is not limited to this. For example, there is no problem if the output torque at stopping is used as the torque to be judged. The method for obtaining the output torque at stopping is the same as the method for obtaining the starting output torque. The output torque at stopping also has a relatively large peak, similar to the starting output torque (see Figure 7), and decreases significantly as the wear of the foil bearing 6 progresses. Therefore, even in embodiments where the output torque at stopping is used as the torque to be judged and the torque threshold, it is possible to accurately determine whether the foil bearing 6 is deteriorating.

[0062] <Other variations> The above description has described an embodiment in which the electric compressor device is a turbocharger device 1, but the disclosure is not limited thereto. For example, the disclosure may be applied to an electric compressor that does not include a turbine 3. The electric compressor may be a single-stage electric compressor in which a compressor impeller 53 is provided only at one end of the rotor shaft 9, or a two-stage electric compressor in which a pair of compressor impellers 53 are provided at both ends of the rotor shaft 9.

[0063] <Summary> The contents described in some of the embodiments above can be understood, for example, as follows:

[0064] 1) A method for determining the deterioration of a foil bearing (6) according to at least one embodiment of the present disclosure is: A method for determining the deterioration of a foil bearing that supports the rotor shaft of an electric compressor device (turbocharger device 1), A process to acquire a target torque (S15, S35) to acquire a target torque, which is the torque of the rotor shaft at startup or shutdown, A torque determination step (S17, S37) for determining whether the torque to be determined is below a torque threshold, If the torque to be judged is determined to be less than or equal to the torque threshold, a deterioration determination step (S19, S39) is performed in which it is determined that the foil bearing is deteriorated. It is equipped with.

[0065] The inventors of this invention have found that as wear of the foil bearing progresses, the torque to be judged decreases. According to the configuration of 1) above, if the torque to be judged is below the torque threshold, it is determined that the foil bearing is deteriorated, so it is possible to accurately determine whether the foil bearing is deteriorated.

[0066] 2) In some embodiments, the method for determining deterioration of a foil bearing as described in 1) above, In the process of acquiring the torque to be judged, the measured value of the starting torque required for the rotor shaft to start rotating at startup is acquired as the torque to be judged.

[0067] The starting torque required when the rotor shaft begins to rotate is greater than the dynamic torque required by the rotor shaft after rotation has started, and the amount of change in the starting torque is large as the wear of the foil bearing progresses. With the configuration described in 2) above, the starting torque is obtained as the torque to be judged, so it is possible to accurately determine whether the foil bearing is deteriorating.

[0068] 3) In some embodiments, the foil bearing deterioration determination method described in 2) above, Before executing the torque acquisition step described above, a first measurement result acquisition step (S11) is performed to acquire the relationship between the measured value of the gap dimension between the foil bearing and the rotor shaft and the measured value of the starting torque, by acquiring measurement results collected from multiple electric compressor devices. A first torque threshold acquisition step (S13) is performed in which the starting torque corresponding to the allowable limit value of the gap dimension is calculated from the measurement results obtained in the first measurement result acquisition step, and the calculated starting torque is acquired as the torque threshold. To further prepare.

[0069] According to the configuration described in 3) above, the relationship between the gap dimension and the starting torque is measured for multiple electric compressor units, so that the relationship between the gap dimension and the starting torque, which is independent of differences between the electric compressor units, can be obtained as a measurement result. As a result, the starting torque at the permissible limit can be accurately determined, and the determined starting torque is treated as a torque threshold, so that it is possible to accurately determine whether the foil bearing is deteriorating.

[0070] 4) In some embodiments, the foil bearing deterioration determination method described in 1) above, In the process of acquiring the torque to be judged, the output torque that is output when the rotor shaft is started or stopped is calculated based on the measured value of the current flowing through the electric compressor device, and the calculated torque is acquired as the torque to be judged.

[0071] During startup and shutdown, the rotor shaft is in contact with the foil bearing, and the output torque changes significantly depending on whether the foil bearing is worn. According to the configuration in 4) above, this output torque is acquired as the torque to be judged, so it is possible to accurately determine whether the foil bearing is deteriorating.

[0072] 5) In some embodiments, the foil bearing deterioration determination method described in 4) above, Before executing the torque acquisition step described above, a second measurement result acquisition step (S31) is performed to acquire measurement results collected from multiple electric compressor devices, which determine the relationship between the measured value of the gap dimension between the foil bearing and the rotor shaft and the measured value of the output torque. A second torque threshold acquisition step (S33) is performed, in which the output torque corresponding to the allowable limit value of the gap dimension is calculated from the measurement results obtained in the second measurement result acquisition step, and the calculated output torque is acquired as the torque threshold. To further prepare.

[0073] According to the configuration described in 5) above, the relationship between the gap dimension and the output torque is measured in multiple electric compressor units, so that the relationship between the gap dimension and the output torque, which is independent of the differences between the electric compressor units, can be obtained as a measurement result. As a result, the output torque at the permissible limit can be accurately determined, and the determined output torque is treated as a torque threshold, so that it can be accurately determined whether the foil bearing is deteriorating. [Explanation of Symbols]

[0074] 1: Turbocharger device 3: Turbine 5: Compressor 6: Foil bearings 9: Rotor shaft 11: Housing 13: Top Foil 13A: Inner surface 15: Backspring 17: Snap ring 25: Fastening member 31: Turbine Housing 33: Turbine impeller 51: Compressor Housing 53: Compressor propeller 71: Bearing housing 73: Surrounding wall 75,77: End wall 80: Motor section 81: Rotor section 85: Stator section 90: Torque driver 100: Motor Controller 851: Stator core 853: Stator coil AC,BD:Approximate curve GA: Steady-state gap M: Gap

Claims

1. A method for determining the deterioration of a foil bearing that supports the rotor shaft of an electric compressor, A process for acquiring a target torque, which is the torque of the rotor shaft during startup or shutdown, A torque determination step of determining whether the torque to be determined is less than or equal to a torque threshold, If the torque to be determined is determined to be less than or equal to the torque threshold, a deterioration determination step is performed to determine that the foil bearing is deteriorated. A method for determining the deterioration of a foil bearing, comprising the following features.

2. In the process of acquiring the torque to be judged, the measured value of the starting torque required for the rotor shaft to start rotating at startup is acquired as the torque to be judged. A method for determining the deterioration of a foil bearing according to claim 1.

3. Before executing the torque acquisition step for determination, a first measurement result acquisition step is performed to acquire the relationship between the measured value of the gap dimension between the foil bearing and the rotor shaft and the measured value of the starting torque, by acquiring measurement results collected from multiple electric compressor devices. A first torque threshold acquisition step is performed, in which the starting torque corresponding to the allowable limit value of the gap dimension is calculated from the measurement results obtained in the first measurement result acquisition step, and the calculated starting torque is acquired as the torque threshold. Furthermore, it is equipped with A method for determining the deterioration of a foil bearing according to claim 2.

4. In the process of acquiring the torque to be determined, the output torque that is output when the rotor shaft is started or stopped is calculated based on the measured value of the current flowing through the electric compressor device, and the calculated torque is acquired as the torque to be determined. A method for determining the deterioration of a foil bearing according to claim 1.

5. Before executing the torque acquisition step for determination, a second measurement result acquisition step is performed to acquire measurement results collected from multiple electric compressor devices, which determine the relationship between the measured value of the gap dimension between the foil bearing and the rotor shaft and the measured value of the output torque. A second torque threshold acquisition step is performed, in which the output torque corresponding to the allowable limit value of the gap dimension is calculated from the measurement results obtained in the second measurement result acquisition step, and the calculated output torque is acquired as the torque threshold. To further enhance A method for determining the deterioration of a foil bearing according to claim 4.

Images