Bearing system

Abstract

To provide a bearing system that can accurately achieve both ensuring the load capacity of the sliding bearing and reducing friction without complicating the control system. [Solution] The sliding bearing 15 of the bearing system 200 has two grooves 15a formed on its sliding surface that extend radially and circumferentially, and these grooves 15a divide the sliding surface of the sliding bearing 15 into a plurality of divided sections R1 to R3 in the axial direction. The sliding bearing 15 also has a discharge hole 15b formed in the groove 15a for discharging fluid from the sliding bearing 15, and a plurality of supply holes 15c1 to 15c4 for supplying fluid to the divided sections R1 to R3 divided by the grooves 15a. Furthermore, the sliding bearing 15 is configured to supply oil and refrigerant (CO2 refrigerant) of different viscosities, respectively, to one of the divided sections R2 in the plurality of divided sections R1 to R3 from supply holes 15c2 and 15c4.

Description

Technical Field

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[0001] The present invention relates to a bearing system that supports a rotating shaft by a sliding bearing lubricated with a fluid.

Background Art

[0002] Conventionally, a sliding bearing configured to perform lubrication with a fluid (working fluid) such as oil and support a rotating shaft is known. This type of technology is described in, for example, Patent Document 1. Specifically, Patent Document 1 describes a technique in which an auxiliary bearing as a rolling bearing is made to function as a sliding bearing (fluid bearing) by supplying a refrigerant (fluid) into the gap between its inner ring and the rotating shaft, thereby mitigating the influence of frictional heat generated between the auxiliary bearing and the rotating shaft.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, the inventors of the present case have considered applying a sliding bearing to a rotating shaft of a motor (for example, a motor of an electric vehicle) that can rotate at a high rotational speed, and have obtained the following findings in the process of developing this sliding bearing.

[0005] First, when the rotational speed of the rotating shaft is relatively low, the load capacity of the sliding bearing tends to be low. However, when the rotational speed of the rotating shaft is relatively high, the load capacity of the sliding bearing increases due to the wedge effect and throttling effect, while losses due to fluid resistance (friction loss) tend to increase. Therefore, it is desirable to ensure the load capacity of the sliding bearing in the low rotational speed range of the rotating shaft, and to suppress the load capacity of the sliding bearing and reduce friction loss in the high rotational speed range of the rotating shaft. Accordingly, the inventors of this invention considered preparing multiple fluids with different viscosities, mixing these multiple fluids, supplying the resulting fluid to the sliding bearing, and adjusting the mixing ratio of the multiple fluids according to the rotational speed of the rotating shaft. In other words, they considered controlling the load capacity of the sliding bearing by changing the viscosity of the fluid by adjusting the mixing ratio. In this case, in the low rotational speed range of the rotating shaft, the mixing ratio should be adjusted to increase the viscosity of the fluid supplied to the sliding bearing, and in the high rotational speed range of the rotating shaft, the mixing ratio should be adjusted to decrease the viscosity of the fluid supplied to the sliding bearing. This makes it possible to achieve both ensuring the load capacity of the sliding bearing and reducing friction.

[0006] However, through diligent research by the inventors, it was found that the viscosity of the fluid changes due to the effects of temperature changes and pressure fluctuations, making it difficult to adjust the mixing ratio as described above to set the fluid supplied to the sliding bearing to the desired viscosity. In particular, in extremely hot or extremely cold environments, viscosity variations become large, making it easy for the fluid to deviate from the desired viscosity (fluid viscosity tends to decrease in extremely hot conditions). As a result, it becomes impossible to accurately control the load capacity of the sliding bearing. One method to accurately set the fluid to the desired viscosity is to continuously measure the fluid's pressure, temperature, and viscosity, and then finely control the mixing ratio of the fluid according to the measurement results. However, this method complicates the system configuration and control configuration.

[0007] The present invention was made to solve the problems of the prior art described above, and aims to provide a bearing system that can accurately achieve both securing the load capacity of the sliding bearing and reducing friction without complicating the control. [Means for solving the problem]

[0008] To achieve the above objective, the present invention provides a bearing system that supports a rotating shaft by a sliding bearing lubricated by a fluid, wherein the sliding bearing has grooves formed on its sliding surface that extend radially and circumferentially, and the grooves are configured to divide the sliding surface into a plurality of sections in the axial direction; a discharge hole formed in the groove for discharging fluid from the sliding bearing; and a plurality of supply holes for supplying fluid to each of the plurality of sections divided by the groove, wherein the sliding bearing is configured to supply each of a plurality of fluids with different viscosities from the supply holes to one or more predetermined sections in the plurality of sections.

[0009] According to the present invention configured in this manner, the sliding bearing divides the sliding surface into multiple sections (hereinafter referred to as "divided sections" as appropriate) in the axial direction by grooves, and supplies multiple fluids with different viscosities separately to one or more predetermined divided sections, thereby allowing the viscosity of the fluids in the predetermined divided sections to be appropriately changed. As a result, the average viscosity of the fluid in the sliding bearing can be changed, making it possible to control the load on the sliding bearing. In particular, in the present invention, multiple divided sections are formed by grooves, and discharge holes are provided in these grooves, so the fluid in each divided section flows out through the grooves defining each divided section and from the discharge holes, preventing the fluids from mixing in adjacent divided sections. Therefore, since the viscosity does not fluctuate in each divided section due to the mixing of multiple fluids, the viscosity of each fluid in each divided section can be accurately adjusted, making it possible to achieve a desired average viscosity in the sliding bearing. Therefore, according to the present invention, the load on the sliding bearing can be precisely controlled, and compared to the configuration described above, which changes the viscosity of the fluid by adjusting the mixing ratio of multiple fluids, it is possible to accurately achieve both securing the load capacity of the sliding bearing and reducing friction without complicating the control configuration.

[0010] In the present invention, preferably, the sliding bearing is configured such that fluids of different viscosities are supplied to each of the multiple supply holes. According to the present invention configured in this way, the viscosity of the fluid can be made different for each segment in a sliding bearing.

[0011] In the present invention, preferably, the groove portion of the sliding bearing is provided with two or more such grooves that form three or more sections. According to the present invention configured in this way, by using a number of divided sections, it is possible to increase the variation in the average viscosity of the fluid in the sliding bearing, and to switch the load applied by the sliding bearing in multiple stages.

[0012] In the present invention, preferably, the grooves of the sliding bearing are arranged such that the lengths of each of the multiple sections along the axial direction are different. According to the present invention configured in this way, a desired average viscosity can be achieved in a sliding bearing by appropriately setting the length of each of the multiple divided sections along the axial direction.

[0013] In the present invention, preferably, the sliding bearing is provided with two supply holes in a predetermined section, and is configured to supply a first fluid and a second fluid having a lower viscosity than the first fluid as a plurality of fluids from these two supply holes. According to the present invention configured in this way, the viscosity of a predetermined divided section can be reliably switched in two stages.

[0014] In the present invention, preferably, the bearing system further comprises a first passage and a second passage communicating with each of two supply holes for supplying a first fluid and a second fluid, respectively; a first valve and a second valve provided in each of the first and second passages; and a control device configured to control the opening and closing of the first valve and the second valve, respectively, so as to switch the fluid supplied to a predetermined section between the first fluid and the second fluid. According to the present invention configured in this way, the control device can reliably switch the viscosity of a predetermined divided section by controlling the opening and closing of the first and second valves, respectively.

[0015] In the present invention, preferably, the control device is configured to selectively perform, based on the rotational speed of the rotating shaft, a control that opens a first valve and closes a second valve to supply a first fluid to a predetermined section, and a control that closes a first valve and opens a second valve to supply a second fluid to a predetermined section. According to the present invention configured in this manner, by switching the supply of the first and second fluids to predetermined divided sections according to the rotational speed of the rotating shaft, it is possible to accurately achieve both securing the load capacity of the sliding bearing and reducing friction.

[0016] In the present invention, preferably, the control device is configured to perform control to open the first valve and close the second valve in order to supply the first fluid to a predetermined section, then to close the first valve and open the second valve in order to supply the second fluid to a predetermined section, and after this control, to close the first and second valves in order to stop supplying the first and second fluids to the predetermined section. According to the present invention configured in this way, after stopping the supply of a relatively high-viscosity first fluid to a predetermined divided section, a relatively low-viscosity second fluid can be supplied to the predetermined divided section to wash away the first fluid remaining in the predetermined divided section with the second fluid. This suppresses resistance caused by the dragging of the first fluid. Furthermore, according to the present invention, since the supply of the second fluid to the predetermined divided section is stopped after washing away the first fluid remaining in the predetermined divided section with the second fluid, unnecessary energy consumption for preparing the second fluid can be suppressed.

[0017] In a preferred example of the present invention, the bearing system is configured to use oil and CO2 (CO2 refrigerant) as multiple fluids. In this case, a more preferable example is that the bearing system is configured to support the motor's rotating shaft with sliding bearings. [Effects of the Invention]

[0018] According to the bearing system of the present invention, both ensuring the load capacity of the sliding bearing and reducing friction can be accurately achieved without complicating the control.

Brief Description of the Drawings

[0019] [Figure 1] It is a schematic configuration diagram of a vehicle to which the bearing system according to an embodiment of the present invention is applied. [Figure 2] It is a schematic configuration diagram of a refrigerant circulation system according to an embodiment of the present invention. [Figure 3] It is a schematic configuration diagram of a motor or the like according to an embodiment of the present invention. [Figure 4] Figures 4(a) and (b) are schematic configuration diagrams of a bearing system according to an embodiment of the present invention. [Figure 5] Figures 5(a) and (b) are explanatory diagrams of the load load realized by the bearing system according to an embodiment of the present invention. [Figure 6] It is a block diagram showing the electrical configuration of the bearing system according to an embodiment of the present invention. [Figure 7] It is a time chart showing the control according to an embodiment of the present invention. [Figure 8] It is a flowchart showing the control according to an embodiment of the present invention. [Figure 9] It is an explanatory diagram of the control according to Modification Example 1 of an embodiment of the present invention. [Figure 10] It is a time chart showing the control according to Modification Example 1 of an embodiment of the present invention. [Figure 11] It is a flowchart showing the control according to Modification Example 1 of an embodiment of the present invention. [Figure 12] It is a schematic configuration diagram of a bearing system according to Modification Example 2 of an embodiment of the present invention. [Figure 13] It is an explanatory diagram of the control according to Modification Example 2 of an embodiment of the present invention. [Figure 14] It is an explanatory diagram of the load load realized by Modification Example 2 of an embodiment of the present invention.

Modes for Carrying Out the Invention

[0020] Hereinafter, an embodiment of the bearing system according to the present invention will be described with reference to the attached drawings.

[0021] [Overall structure] First, referring to Figure 1, this is a schematic diagram of a vehicle to which the bearing system according to this embodiment is applied.

[0022] As shown in Figure 1, the vehicle 300 is, for example, an electric vehicle and has a refrigerant circulation system 100 that circulates a refrigerant in a refrigeration cycle. This refrigerant circulation system 100 mainly includes a motor 1 that generates power to drive the vehicle 300, a compressor 3 that compresses the refrigerant supplied to the motor 1, and a heat exchanger (condenser) 5 that includes a condenser and a fan, etc., for cooling the refrigerant compressed by the compressor 3.

[0023] The refrigerant circulation system 100 circulates a CO2 refrigerant (hereinafter sometimes simply referred to as "refrigerant") as a natural refrigerant. This CO2 refrigerant may contain not only CO2 but also refrigerant oils such as PAG and additives. Because such a CO2 refrigerant is used, the compressor 3 is configured to compress the refrigerant to a very high pressure. The motor 1 uses the refrigerant thus compressed by the compressor 3 (typically in a supercritical state) for lubrication of the sliding bearings supporting the rotating shaft and for cooling the rotor and stator. In this case, the motor 1 is configured to function as an evaporator in the refrigeration cycle. For example, in the refrigerant circulation system 100, high-temperature liquid refrigerant is supplied from the compressor 3 to the heat exchanger 5, low-temperature liquefied refrigerant is supplied from the heat exchanger 5 to the motor 1, and high-temperature gaseous refrigerant is supplied from the motor 1 to the compressor 3. The refrigerant compressed by the compressor 3 may also be used for air conditioning in an air conditioner or for cooling a battery.

[0024] [Refrigerant circulation system configuration] Next, with reference to Figure 2, the refrigerant circulation system 100 according to this embodiment will be described in detail. Figure 2 is a schematic diagram of the refrigerant circulation system 100 according to this embodiment.

[0025] As shown in Figure 2, the refrigerant circulation system 100 mainly includes, in addition to the motor 1, compressor 3, and heat exchanger 5 described above, a bearing system 200 equipped with a pair of sliding bearings 15 supporting the rotating shaft 13 of the motor 1, an oil tank 6 for storing oil used for lubricating the sliding bearings 15, refrigerant passages 21-26 through which the refrigerant (CO2 refrigerant) flows, oil passages 27 and 28 through which the oil flows, and a mixed fluid passage 29 through which a mixed fluid of refrigerant and oil passes. For example, the oil is refrigerant oil such as PAG.

[0026] The refrigerant passage 21 is a passage for supplying refrigerant from the compressor 3 to the motor 1, etc., via the heat exchanger 5, and branches into refrigerant passage 22 and refrigerant passage 23 downstream of the heat exchanger 5. The refrigerant passage 21 is equipped with a refrigerant temperature sensor 51 for detecting the temperature of the refrigerant and a refrigerant pressure sensor 52 for detecting the pressure of the refrigerant.

[0027] Refrigerant passage 22 is a passage for supplying refrigerant into the sliding bearing 15, and refrigerant passage 23 is a passage for supplying refrigerant into the motor 1. These refrigerant passages 22 and 23 supply liquid (typically supercritical) refrigerant to the sliding bearing 15 and the motor 1, respectively. The refrigerant supplied to the sliding bearing 15 is used for lubrication of the sliding bearing 15, and the refrigerant supplied to the motor 1 is used for cooling the motor 1. In addition, a flow control valve 30 is provided in refrigerant passage 23 to adjust the flow rate of the refrigerant.

[0028] The refrigerant passage 24 is a passage for supplying the refrigerant discharged from the motor 1 to the compressor 3. A refrigerant passage 25 is connected to the refrigerant passage 24. One end of the refrigerant passage 25 is connected to the refrigerant passage 21 downstream of the heat exchanger 5, and the other end is connected to the refrigerant passage 24. It functions to return the refrigerant from the heat exchanger 5 to the compressor 3 without passing through the motor 1 or the sliding bearing 15. Check valves 41 and 42 are provided in the refrigerant passages 24 and 25, respectively.

[0029] The oil passage 27 is a passage for supplying oil stored in the oil tank 6 to the sliding bearing 15. The oil supplied to the sliding bearing 15 is used for lubrication of the sliding bearing 15 together with the refrigerant mentioned above. The oil passage 27 is equipped with an oil pump 38 for pumping the oil, an oil temperature sensor 54 for detecting the oil temperature, and an oil pressure sensor 55 for detecting the oil pressure. An oil passage 28 is also connected to the oil passage 27 for returning the oil in the passage 27 to the oil tank 6. A check valve 44 is provided in this oil passage 28.

[0030] The mixed fluid passage 29 is a passage for supplying the mixed fluid of refrigerant and oil discharged from the sliding bearing 15 to the oil tank 6. The oil tank 6 is configured to separate the oil from the mixed fluid supplied from this mixed fluid passage 29 (gas-liquid separation), store the separated oil, and supply the remaining refrigerant (which also contains a small amount of oil) from the refrigerant passage 26 to the refrigerant passage 24. A check valve 43 is provided in this refrigerant passage 26. The oil tank 6 is also equipped with an oil level sensor 53 for detecting the level of the stored oil.

[0031] [Bearing system configuration] Next, the configuration of the bearing system 200 according to this embodiment will be specifically described with reference to Figures 3 to 5.

[0032] First, Figure 3 is a schematic diagram of the motor 1 and bearing system 200 according to this embodiment. Specifically, Figure 3 is a cross-sectional view of the motor 1 and bearing system 200 along the axial direction. Note that in Figure 3, the vertical positions of the refrigerant passage 22 and oil passage 27 are shown in reverse compared to Figure 2 (the same applies to the figures described later).

[0033] As shown in Figure 3, the motor 1 mainly consists of a rotor 11 and a stator 12, a rotating shaft 13 connected to the rotor 11 and one end of which is connected to the transaxle (not shown) of the vehicle 300, and a housing 14 that houses the rotor 11, stator 12, and rotating shaft 13, and the bearing system 200 mainly consists of a pair of sliding bearings 15 that support the rotating shaft 13 of the motor 1. The pair of sliding bearings 15 are also housed within the housing 14 of the motor 1.

[0034] As described above, in motor 1, refrigerant (liquefied refrigerant) is supplied to the rotor 11 and stator 12 from the refrigerant passage 23. The refrigerant supplied to motor 1 in this way is used to cool the rotor 11 and stator 12, in particular the coils (not shown) inside the stator 12. In this case, the refrigerant exchanges heat with the relatively high temperature of the stator 12, etc. (at this time the refrigerant evaporates in the coils of the stator 12), thus realizing the function of an evaporator in a refrigeration cycle. The refrigerant used for cooling in motor 1 is then discharged from the refrigerant passage 24.

[0035] Next, the pair of sliding bearings 15 are arranged symmetrically (left-right symmetrically) opposite each other in the axial direction, with the rotor 11 in between. Each of these sliding bearings 15 is supplied with oil from multiple (three) oil passages 27 (27a, 27b, 27c), and with refrigerant supplied from one refrigerant passage 22. This refrigerant and oil are supplied to the gap between the inner circumferential surface of the sliding bearing 15 and the outer circumferential surface of the rotating shaft 13 of the motor 1, and are used to lubricate the sliding bearing 15 when it supports the rotating shaft 13. The refrigerant and oil used to lubricate the sliding bearings 15 are discharged together as a mixed fluid from the mixed fluid passage 29. In addition, the refrigerant used to lubricate the sliding bearings 15, especially the refrigerant used at the end of the sliding bearing 15 on the rotor 11 side, flows into the space in the housing 14 where the rotor 11 and stator 12 are housed, and is discharged together with the refrigerant used to cool the motor 1 from the refrigerant passage 24.

[0036] More specifically, the oil passages 27a, 27b, and 27c supply oil to three different locations along the axial direction of the sliding bearing 15, while the refrigerant passage 22 supplies refrigerant to the same locations along the axial direction as the locations where the oil passages 27b supply oil. In this case, refrigerant is not supplied to the locations where the oil passages 27a and 27c supply oil. Furthermore, the oil passage 27b is provided with an oil bearing valve 31 that can switch between supplying and shutting off oil by opening and closing it, and the refrigerant passage 22 is provided with a refrigerant bearing valve 32 that can switch between supplying and shutting off refrigerant by opening and closing it.

[0037] On the other hand, the housing 14 of the motor 1 is provided with a sealing member 18 to seal the side of the rotating shaft 13 that is connected to the transaxle, etc. (the side where the sliding bearing 15 shown on the left in Figure 3 is provided). This sealing member 18 is provided to prevent fluid leakage from the gap between the portion of the rotating shaft 13 that extends from the housing 14 to the outside and the housing 14. The sealing member 18 is configured as a mechanical seal that prevents fluid leakage by using oil supplied from an oil passage 27d connected to the oil passage 27a mentioned above.

[0038] Furthermore, oil corresponds to an example of the "first fluid" in this invention, and refrigerant (CO2 refrigerant) corresponds to an example of the "second fluid" in this invention. Also, the oil passage 27b and the refrigerant passage 22 correspond to the "first passage" and the "second passage," respectively, in this invention, and the oil bearing valve 31 and the refrigerant bearing valve 32 correspond to the "first valve" and the "second valve," respectively, in this invention.

[0039] Next, Figure 4 is a schematic diagram illustrating the bearing system 200 according to this embodiment in more detail. Specifically, Figure 4(a) is a perspective view of one of the pair of sliding bearings 15 in the bearing system 200 (the sliding bearing 15 shown on the left in Figure 3, that is, the sliding bearing 15 on the side where the sealing member 18 is provided), and Figure 4(b) is a cross-sectional view of this sliding bearing 15 along the axial direction.

[0040] As shown in Figures 4(a) and (b), and especially in Figure 4(b), the sliding bearing 15 (as described above, one of a pair of sliding bearings 15; the same applies hereinafter) has two annular grooves 15a formed on its sliding surface (inner circumferential surface) that extend radially and around the entire circumference in the circumferential direction. The sliding surface of the sliding bearing 15 is divided into three sections (divided sections) R1 to R3 in the axial direction by these two grooves 15a. The divided sections R1 and R3 at both ends have approximately the same length along the axial direction, but the divided section R2, located in the middle between divided sections R1 and R3, has a longer length along the axial direction than divided sections R1 and R3.

[0041] Furthermore, the sliding bearing 15 has, in each of the two grooves 15a, a discharge hole 15b for discharging refrigerant and oil from the sliding bearing 15, supply holes 15c1, 15c2, and 15c3 for supplying oil to the divided sections R1, R2, and R3 respectively, and a supply hole 15c4 for supplying refrigerant to the divided section R2. The discharge hole 15b communicates with the mixed fluid passage 29, the supply holes 15c1, 15c2, and 15c3 communicate with the oil passages 27a, 27b, and 27c respectively, and the supply hole 15c4 communicates with the refrigerant passage 22. Note that two or more discharge holes 15b may be provided on the same groove 15a.

[0042] With this type of sliding bearing 15, two grooves 15a form three axially divided sections R1 to R3, and discharge holes 15b are provided in these grooves 15a. As a result, the fluid (oil or refrigerant) in each divided section R1 to R3 flows out through the grooves 15a that define each divided section R1 to R3 and out through the discharge holes 15b. This prevents the fluid from moving back and forth between adjacent divided sections R1 to R3 and mixing of the fluids in each divided section R1 to R3. This is because the size of the grooves 15a (e.g., on the order of millimeters) is much larger than the gap between the rotating shaft 13 of the motor 1 and the sliding bearing 15 (e.g., on the order of micrometers), so the fluid in each divided section R1 to R3 flows into the grooves 15a rather than passing through them to adjacent divided sections.

[0043] In this configuration, only oil is supplied to the divided section R1 via the oil passage 27a and the supply hole 15c1, and only oil is supplied to the divided section R3 via the oil passage 27c and the supply hole 15c3. In contrast, oil is supplied to the divided section R2 via the oil passage 27b and the supply hole 15c2, and refrigerant is supplied via the refrigerant passage 22 and the supply hole 15c4. As described above, the oil passage 27b and the refrigerant passage 22 applied to the divided section R2 are provided with an oil bearing valve 31 and a refrigerant bearing valve 32, respectively (Figure 3). In this embodiment, by opening one of the oil bearing valve 31 and the refrigerant bearing valve 32 and closing the other, only oil or refrigerant is supplied to the divided section R2 (i.e., both oil and refrigerant are not supplied simultaneously), and by changing the open / closed state of the oil bearing valve 31 and the refrigerant bearing valve 32, the fluid supplied to the divided section R2 is switched between oil and refrigerant.

[0044] Next, Figure 5 is an explanatory diagram of the load load realized by the bearing system 200 according to this embodiment. Specifically, the top of Figures 5(a) and (b) shows the supply state of oil or refrigerant in one of the pair of sliding bearings 15 (the sliding bearing 15 shown on the left in Figure 3, i.e., the sliding bearing 15 on the side where the seal member 18 is provided), and the bottom of Figures 5(a) and (b) shows the viscosity distribution of the fluid in the gap between the rotating shaft 13 of the motor 1 and the sliding bearing 15. In Figures 5(a) and (b), the viscosity of the fluid is represented by the intensity of the color (high viscosity oil is represented by a dark color, and low viscosity refrigerant is represented by a light color), and "↑" or "↓" indicates the supply of the corresponding fluid, and "×" indicates the cessation of the supply of the corresponding fluid. The same notation will be used in the figures described later.

[0045] Figure 5(a) shows the case where oil is supplied to all of the divided sections R1 to R3. In this case, oil is used as the fluid supplied to divided section R2, rather than a refrigerant (the fluid supplied to divided sections R1 and R3 is fixed as oil). In this case, the oil bearing valve 31 of the oil passage 27b is opened, while the refrigerant bearing valve 32 of the refrigerant passage 22 is closed. As shown in Figure 5(a), when oil is supplied to all of the divided sections R1 to R3, the viscosity distribution in the gap between the rotating shaft 13 of the motor 1 and the sliding bearing 15 becomes uniform in the axial direction. In this case, the load on the sliding bearing 15 becomes relatively large.

[0046] Figure 5(b) shows the case where oil is supplied to divided sections R1 and R3, while refrigerant is supplied to divided section R2. In this case, the oil bearing valve 31 of the oil passage 27b is closed, while the refrigerant bearing valve 32 of the refrigerant passage 22 is open. In the case shown in Figure 5(b), the viscosity distribution in the gap between the rotating shaft 13 of the motor 1 and the sliding bearing 15 is not uniform in the axial direction, and the viscosity in the divided section R2 (viscosity of the refrigerant) is lower than the viscosity in the divided sections R1 and R3 (viscosity of the oil). In this case, if the average viscosity of the viscosity distribution is calculated (bottom right of Figure 5(b)), this average viscosity will be lower than the viscosity in Figure 5(a). As a result, the load on the sliding bearing 15 becomes relatively small. For example, the load in the case shown in Figure 5(b) is half the load in the case shown in Figure 5(a).

[0047] In this embodiment, the load applied by the sliding bearing 15 can be switched by switching the fluid supplied to the divided section R2 between oil and refrigerant. This makes it possible to apply a relatively large load, as shown in Figure 5(a), in the low rotation range of the motor shaft 13, and a relatively small load, as shown in Figure 5(b), in the high rotation range of the motor shaft 13. In this embodiment, as described above, by forming divided sections R1 to R3 with the groove 15a, it is possible to prevent the fluids from mixing in adjacent divided sections R1 to R3. Therefore, when both oil and refrigerant are applied as shown in Figure 5(b), the oil and refrigerant do not mix in adjacent divided sections R1 to R3, so that the viscosity of the fluid in each divided section R1 to R3 remains almost constant (in other words, the viscosity in each divided section R1 to R3 does not fluctuate due to mixing of oil and refrigerant), and the desired average viscosity can be reliably achieved. As a result, according to this embodiment, it is possible to accurately control the load applied by the sliding bearing 15.

[0048] As shown in Figure 5(b), the average viscosity within the sliding bearing 15 when both oil and refrigerant are applied varies depending on the axial length of the divided sections R1 to R3. Specifically, the average viscosity changes depending on the relationship (ratio) between the sum of the axial lengths of the divided sections R1 and R3 where oil is applied and the axial length of the divided section R2 where refrigerant is applied. Therefore, the axial lengths of each of the divided sections R1 to R3 should be set according to the desired average viscosity to be achieved.

[0049] [Electrical configuration] Next, the electrical configuration of the bearing system 200 according to this embodiment will be described with reference to Figure 6. Figure 6 is a block diagram showing the electrical configuration of the bearing system 200 according to this embodiment.

[0050] As shown in Figure 6, the bearing system 200 has a control device 80 configured to perform various controls in the system. The control device 80 is composed of a computer comprising one or more processors 80a (typically a CPU) and memory 80b such as ROM or RAM for storing various programs (including basic control programs such as an OS and application programs launched on the OS to realize specific functions) and various data that are interpreted and executed on the processors 80a.

[0051] In addition to the sensors 51 to 55 described above (see Figure 2), the bearing system 200 also includes a motor speed sensor 56 for detecting the motor speed of the motor 1 (the rotational speed of the rotor 11 and the rotating shaft 13, which is synonymous with rotational speed), a vehicle speed sensor 57 for detecting the speed of the vehicle 300, an accelerator opening sensor 58 for detecting the accelerator opening corresponding to the amount the accelerator pedal is pressed in the vehicle 300, and a brake sensor 59 for detecting the operation of the brake pedal in the vehicle 300.

[0052] The control device 80 supplies control signals to the motor 1, compressor 3, flow control valve 30, oil bearing valve 31, refrigerant bearing valve 32, oil pump 38, and oil level warning light 39 based on the detection signals from these sensors 51 to 59. The oil level warning light 39 is a lamp that warns when the level of oil stored in the oil tank 6 (detected by the oil level sensor 53) is below a predetermined value.

[0053] In this embodiment, the control device 80 primarily controls the opening and closing of the oil bearing valve 31 and the refrigerant bearing valve 32, respectively, in order to switch the fluid supplied to the divided section R2 of the sliding bearing 15 between oil and refrigerant, based on the motor rotation speed detected by the motor rotation speed sensor 56. Specifically, the control device 80 selectively performs two actions based on the motor rotation speed: one that opens the oil bearing valve 31 and closes the refrigerant bearing valve 32 to supply oil to the divided section R2, and another that closes the oil bearing valve 31 and opens the refrigerant bearing valve 32 to supply refrigerant to the divided section R2.

[0054] [Control Method] Next, the control performed by the control device 80 of the bearing system 200 in this embodiment will be specifically described. First, with reference to Figure 7, the flow of control performed by the control device 80 in this embodiment will be described. Figure 7 is a time chart showing the control according to this embodiment. From top to bottom, Figure 7 shows the time changes of the motor rotation speed, the load by the sliding bearing 15 (corresponding to the viscosity of the fluid in the sliding bearing 15), the opening and closing of the refrigerant bearing valve 32, and the opening and closing of the oil bearing valve 31.

[0055] As shown in Figure 7, the motor speed increases at time t11. This reduces the load that the sliding bearing 15 must provide (hereinafter referred to as the "required load"), which is determined according to the motor speed. Therefore, at time t11, in order to reduce the load on the sliding bearing 15, the control device 80 controls the oil bearing valve 31 to close while opening the refrigerant bearing valve 32, thereby switching the fluid supplied to the divided section R2 of the sliding bearing 15 from oil to refrigerant.

[0056] Next, with reference to Figure 8, a flowchart illustrating the specific control according to this embodiment will be described. This flow is repeatedly executed by the control device 80 at predetermined intervals. Specifically, the processor 80a within the control device 80 reads a program stored in memory 80b and executes the program, thereby realizing the control related to this flow.

[0057] First, in step S10, the control device 80 acquires various information, such as the detected values, from the sensors 51 to 59 (Figure 6) described above. Then, the control device 80 proceeds to step S11 and determines whether the oil level detected by the oil level sensor 53 is above a predetermined value. If the control device 80 does not determine that the oil level is above a predetermined value (step S11: No), that is, if the oil level is below a predetermined value, it proceeds to step S12 and illuminates the oil level warning light 39.

[0058] In response, if the control device 80 determines in step S11 that the oil level is above a predetermined value (step S11: Yes), it proceeds to step S13. In step S13, the control device 80 determines whether motor 1 is stopped or not based on the motor rotation speed detected by the motor rotation speed sensor 56. If the control device 80 determines that motor 1 is stopped (step S13: Yes), it proceeds to step S14 and determines whether there is a motor start request or not based on the start switch of the vehicle 300 and the accelerator opening detected by the accelerator opening sensor 58. If the control device 80 determines that there is a motor start request (step S14: Yes), it proceeds to step S15, while if it does not determine that there is a motor start request (step S14: No), it terminates the control related to this flow.

[0059] In step S15, before starting the motor 1, the control device 80 opens the oil bearing valve 31 and closes the refrigerant bearing valve 32 to supply oil to the divided section R2 of the sliding bearing 15 in order to ensure the load on the sliding bearing 15. Then, the control device 80 proceeds to step S16 to start the motor 1, and after that, proceeds to step S17 to perform control to adjust the rotational speed of the compressor 3.

[0060] On the other hand, if the control device 80 does not determine in step S13 that the motor 1 is stopped (step S13: No), that is, if the motor 1 is already operating, it proceeds to step S18. In step S18, the control device 80 determines the target motor rotation speed based on the accelerator opening detected by the accelerator opening sensor 58, and determines whether or not this target motor rotation speed has changed. As a result, if the control device 80 determines that the target motor rotation speed has changed (step S18: Yes), it proceeds to step S19. On the other hand, if it does not determine that the target motor rotation speed has changed (step S18: No), it proceeds to step S17 as described above without performing the processes in steps S19 to S21.

[0061] In step S19, the control device 80 determines the required load on the sliding bearing 15 based on the motor rotation speed detected by the motor rotation speed sensor 56, and determines whether this required load has decreased. In this case, the required load tends to decrease as the motor rotation speed increases. If the control device 80 determines that the required load has decreased as a result of step 19 (step S19: Yes), it proceeds to step S20. In this case, since the motor rotation speed increases, the control device 80 closes the oil bearing valve 31 and opens the refrigerant bearing valve 32 to supply refrigerant to the divided section R2 of the sliding bearing 15 in order to reduce the load on the sliding bearing 15. Then, the control device 80 proceeds to step S17 as described above.

[0062] On the other hand, if the control device 80 does not determine in step S19 that the required load has decreased (step S19: No), that is, if the required load has increased, it proceeds to step S21. In this case, since the motor rotation speed will decrease, the control device 80 opens the oil bearing valve 31 and closes the refrigerant bearing valve 32 to supply oil to the divided section R2 of the sliding bearing 15 in order to ensure the load on the sliding bearing 15. Then, the control device 80 proceeds to step S17 as described above.

[0063] In step S19, the control device 80 determined whether the required load on the sliding bearing 15 had decreased. However, in other examples, instead of making this determination, it may determine whether the motor rotation speed is above a predetermined value.

[0064] [Mechanism of Action and Effects] Next, the operation and effects of the bearing system 200 according to this embodiment will be described.

[0065] In this embodiment, the sliding bearing 15 of the bearing system 200 has two grooves 15a formed on its sliding surface, extending radially and circumferentially, which divide the sliding surface of the sliding bearing 15 into a plurality of divided sections R1 to R3 in the axial direction. The sliding bearing 15 also has a discharge hole 15b formed in the groove 15a for discharging fluid from the sliding bearing 15, and a plurality of supply holes 15c1 to 15c4 for supplying fluid to the divided sections R1 to R3 divided by the grooves 15a. Furthermore, the sliding bearing 15 is configured to supply oil and refrigerant (CO2 refrigerant) of different viscosities, respectively, to one of the divided sections R2 in the plurality of divided sections R1 to R3 from supply holes 15c2 and 15c4.

[0066] In this embodiment, the two grooves 15a form three axially divided sections R1 to R3, and oil and refrigerant are supplied separately to divided section R2 from supply holes 15c2 and 15c4, so that the viscosity of divided section R2 can be appropriately changed. As a result, the average viscosity of the fluid in the sliding bearing 15 can be changed, and the load on the sliding bearing 15 can be controlled. In particular, in this embodiment, the grooves 15a form divided sections R1 to R3, and a discharge hole 15b is provided in the grooves 15a, so that the fluid in each divided section R1 to R3 flows out from the discharge hole 15b through the grooves 15a that define each divided section R1 to R3, thus preventing the fluids in adjacent divided sections R1 to R3 from mixing. Therefore, since the viscosity in each divided section R1 to R3 does not fluctuate due to mixing of oil and refrigerant, the viscosity of each fluid in each divided section R1 to R3 can be accurately adjusted, so that a desired average viscosity can be achieved in the sliding bearing 15. Therefore, according to this embodiment, the load on the sliding bearing 15 can be precisely controlled. Compared to the configuration described above, which changes the viscosity of the fluid by adjusting the mixing ratio of multiple fluids, this embodiment makes it possible to accurately achieve both the load capacity of the sliding bearing 15 and friction reduction without complicating the control configuration.

[0067] Furthermore, according to this embodiment, the control device 80 selectively performs two types of control based on the motor rotation speed (including the required load set based on the motor rotation speed): one that opens the oil bearing valve 31 and closes the refrigerant bearing valve 32 to supply oil to the divided section R2, and another that closes the oil bearing valve 31 and opens the refrigerant bearing valve 32 to supply refrigerant to the divided section R2. This ensures that the load capacity of the sliding bearing 15 is secured in the low rotation range, while reducing friction (reducing lubrication resistance) of the sliding bearing 15 in the high rotation range.

[0068] Furthermore, according to this embodiment, the two grooves 15a of the sliding bearing 15 are arranged so that their lengths along the axial direction of each of the multiple divided sections R1 to R3 are different. This makes it possible to achieve the desired average viscosity when both oil and refrigerant are applied to the sliding bearing 15 by appropriately setting the lengths along the axial direction of each of the divided sections R1 to R3.

[0069] [Differentiation] The following describes modifications of the embodiments described above.

[0070] (Variation 1) Referring to Figure 9, the control according to Modification 1 of this embodiment will be described. Figure 9, like Figure 5, shows the supply state of oil or refrigerant in one of the pair of sliding bearings 15 (the sliding bearing 15 shown on the left in Figure 3, that is, the sliding bearing 15 on the side where the sealing member 18 is provided).

[0071] The left side of Figure 9 shows a situation where oil is supplied to the divided section R2 of the sliding bearing 15 to ensure the load capacity of the sliding bearing 15, because the motor rotation speed is relatively low. From this situation, when the motor rotation speed becomes relatively high, in the above embodiment, the control device 80 stops supplying oil to the divided section R2 and supplies refrigerant to the divided section R2 in order to reduce friction by oil in the sliding bearing 15 (reduction of lubrication resistance) (Figures 7 and 8). However, even if refrigerant is supplied to the divided section R2 in this way, it can be said that the effect of the refrigerant on the load capacity is almost negligible (because the load capacity of the refrigerant is low). In this case, it can be said that the load capacity can be sufficiently ensured with the oil supplied to the divided sections R1 and R3. On the other hand, preparing refrigerant to supply to the divided section R2 results in wasted energy consumption. From the above, it can be said that it is not necessary to supply refrigerant to the divided section R2 when the motor rotation speed is relatively high. This can be said because the sliding bearing 15 is designed primarily on the premise of oil lubrication. Specifically, the gap between the rotating shaft 13 of the motor 1 and the sliding bearing 15 is designed to be wide for oil lubrication, meaning the gap is too wide to generate load capacity using a coolant.

[0072] Therefore, in Modification 1, after stopping the supply of oil to the divided section R2, the supply of refrigerant to the divided section R2 is stopped. In this case, after stopping the supply of oil to the divided section R2, oil remains in the divided section R2, which causes drag resistance. Therefore, in Modification 1, after stopping the supply of oil to the divided section R2, the control device 80 supplies refrigerant to the divided section R2 for a predetermined time, as shown in the center of Figure 9, to wash away the oil remaining in the divided section R2 with the refrigerant (i.e., wash the oil-lubricated surface). Then, in Modification 1, after supplying refrigerant to the divided section R2 for a predetermined time, the control device 80 stops the supply of refrigerant to the divided section R2, as shown in the right of Figure 9.

[0073] Next, with reference to Figure 10, the control flow performed by the control device 80 in Modified Example 1 will be explained. Figure 10 is a time chart showing the control according to Modified Example 1. From top to bottom, Figure 10 shows the time changes of the motor rotation speed, the load by the sliding bearing 15 (corresponding to the viscosity of the fluid in the sliding bearing 15), the opening and closing of the refrigerant bearing valve 32, and the opening and closing of the oil bearing valve 31.

[0074] As shown in Figure 10, at time t21, the motor speed increases. As a result, the required load, which is determined according to the motor speed, decreases. Therefore, at time t21, the control device 80 controls the oil bearing valve 31 to close the supply of oil to the divided section R2 of the sliding bearing 15 in order to reduce the load on the sliding bearing 15. At the same time, the control device 80 controls the refrigerant bearing valve 32 to open the refrigerant bearing valve 32 in order to supply refrigerant to the divided section R2 in order to wash away any oil remaining in the divided section R2 with refrigerant. After this, at time t22, when a predetermined time T2 has elapsed from time t21, the control device 80 controls the refrigerant bearing valve 32 to close the supply of refrigerant to the divided section R2.

[0075] Next, with reference to Figure 11, a flowchart illustrating the specific control according to Modification 1 will be described. This flow is also repeatedly executed by the control device 80 at predetermined intervals. More specifically, the processor 80a within the control device 80 reads the program stored in memory 80b and executes the program, thereby realizing the control related to this flow.

[0076] Steps S30 to S41 in Figure 11 are identical to steps S10 to S21 in Figure 8, respectively, so their explanations will be omitted, and step S42 will be explained here. Step S42 is performed after step S40. In step S40, the control device 80 closes the oil bearing valve 31 while opening the refrigerant bearing valve 32 in order to supply refrigerant to the divided section R2 of the sliding bearing 15 in order to wash away the oil remaining in the divided section R2 with refrigerant. After a predetermined time T2 has elapsed since this control, the control device 80 proceeds to step S42 and closes the refrigerant bearing valve 32 while keeping the oil bearing valve 31 closed in order to stop the supply of refrigerant to the divided section R2.

[0077] According to this modified example 1, after stopping the supply of oil to the divided section R2 of the sliding bearing 15, refrigerant is supplied to the divided section R2 to wash away the oil remaining in the divided section R2 with the refrigerant (i.e., wash the oil-lubricated surface), thereby suppressing resistance due to oil drag. Furthermore, according to this modified example 1, after washing away the oil remaining in the divided section R2 with the refrigerant, the supply of refrigerant to the divided section R2 is stopped, thus suppressing the wasted energy consumption of preparing refrigerant for the divided section R2.

[0078] (Modification 2) Referring to Figure 12, the configuration of the bearing system 200x according to Modification 2 of this embodiment will be described. Figure 12 is a cross-sectional view along the axial direction of one of the pair of sliding bearings 15x in the bearing system 200x according to Modification 2, similar to Figure 4(b).

[0079] As shown in Figure 12, the sliding bearing 15x according to the modified example 2 has four grooves 15a, each containing a discharge hole 15b, and these four grooves 15a divide the sliding surface of the sliding bearing 15x into five axial sections R21 to R25. For example, the ratio of the lengths of the axial sections R21, R22, R23, R24, and R25 is 6.25:25:50:12.5:6.25. The sliding bearing 15 also has supply holes 15d1 to 15d5 that communicate with oil passages 27d to 27h for supplying oil to each of the axial sections R21 to R25, and supply holes 15d6 to 15d8 that communicate with refrigerant passages 22a to 22c for supplying refrigerant to each of the axial sections R22 to R24. In this case, only oil is supplied to the divided sections R21 and R25, while either oil or refrigerant is selectively supplied to the divided sections R22 to R24.

[0080] Next, with reference to Figure 13, the control of the bearing system 200x according to Modification 2 will be described. Figures 13(a) to (d) show the oil or coolant supply state to one of the pair of sliding bearings 15x, similar to Figure 5.

[0081] Figure 13(a) shows the case where oil is supplied to all of the divided sections R21 to R25. In this case, the ratio of oil to refrigerant in the sliding bearing 15x is "100:0" (oil ratio is 100%). Figure 13(b) shows the case where oil is supplied to divided sections R21, R22, R24, and R25, and refrigerant is supplied to divided section R23. In this case, based on the relationship of the lengths along the axial direction of each of the divided sections R21 to R25 described above, the ratio of oil to refrigerant in the sliding bearing 15x is "50:50" (oil ratio is 50%). Figure 13(c) shows the case where oil is supplied to divided sections R21, R24, and R25, and refrigerant is supplied to divided sections R22 and R23. In this case, the ratio of oil to refrigerant in the sliding bearing 15x is "25:75" (oil ratio is 25%). Figure 13(d) shows the case where oil is supplied to divided sections R21 and R25, and refrigerant is supplied to divided sections R22, R23, and R24. In this case, the ratio of oil to refrigerant in the sliding bearing 15x is "12.5:87.5" (oil ratio is 12.5%).

[0082] Next, with reference to Figure 14, the load capacity of the sliding bearing 15x realized by Modification 2 will be explained. In Figure 14, graph G1 (dashed line) shows the oil ratios (100%, 50%, 25%, 12.5%) that are achieved in stages by switching the oil and refrigerant supplied to each of the divided sections R22 to R24. Graph G2 (solid line) shows the load capacity of the sliding bearing 15x achieved when these oil ratios are set. Thus, according to Modification 2, the load capacity of the sliding bearing 15x can be switched in multiple stages by using a number of divided sections R21 to R25. As a result, according to Modification 2, the load capacity of the sliding bearing 15 can be secured in the low rotation range, while the friction (lubrication resistance) of the sliding bearing 15 can be effectively reduced in the high rotation range.

[0083] (Other variations) In the embodiment described above, oil and refrigerant were supplied to section R2 of the three divided sections R1 to R3 in the sliding bearing 15. However, in a modified example, oil and refrigerant may be supplied to sections R1 and R3 instead of section R2. In a further modified example, oil and refrigerant may be supplied to sections R1 and R3 in addition to section R2. In other words, it is not limited to supplying oil and refrigerant only to section R2 of the divided sections R1 to R3, and in a modified example, oil and refrigerant may be supplied to all of sections R1 to R3.

[0084] Furthermore, in the above-described embodiment, two supply holes 15c2 and 15c4 were used to switch the viscosity of the fluid supplied to the divided section R2 of the sliding bearing 15, that is, to switch the supplied fluid between oil and refrigerant. However, in a modified example, only one supply hole may be used. In this case, the fluid supplied to the single supply hole can be switched between oil and refrigerant upstream of the supply hole.

[0085] Furthermore, in the embodiment described above, the sliding bearing 15 had two grooves 15a forming three divided sections R1 to R3, and in the modified example 2 described above, the sliding bearing 15x had four grooves 15a forming five divided sections R21 to R25. However, in the modified example, one groove 15a may form two divided sections, or five or more grooves 15a may form six or more divided sections.

[0086] Furthermore, in the embodiments described above, oil and CO2 (CO2 refrigerant) were used as fluids with different viscosities, but various fluids other than oil and CO2 may be used, or three or more fluids with different viscosities may be used. [Explanation of symbols]

[0087] 1 motor 3 Compressors 5 Heat exchanger 6 Oil tank 11 rotors 12 staters 13 Rotation axis 15, 15x plain bearings 15a Groove 15b Discharge hole 15c1~15c4 Supply hole 21-26 Refrigerant passage 27, 28 Oil passages 29 Mixed fluid passage 80 Control device 100 Refrigerant Circulation System 200, 200x bearing system 300 vehicles R1-R3, R21-R25 divided sections

Claims

1. A bearing system that supports a rotating shaft with a sliding bearing lubricated by a fluid, The aforementioned sliding bearing is A groove formed on the sliding surface of the sliding bearing, extending radially and circumferentially, wherein the groove is configured to divide the sliding surface into a plurality of sections in the axial direction, A drain hole is formed in the groove for discharging the fluid from the sliding bearing, A plurality of supply holes for supplying the fluid to each of the plurality of sections divided by the groove, It has, The bearing system is characterized in that the sliding bearing is configured to be able to supply each of the multiple fluids with different viscosities from the supply hole to one or more predetermined sections in the multiple sections.

2. The bearing system according to claim 1, wherein the sliding bearing is configured such that fluids of different viscosities are supplied to each of the plurality of supply holes.

3. The bearing system according to claim 1, wherein two or more grooves are provided in the sliding bearing so as to form three or more sections.

4. The bearing system according to claim 1, wherein the grooves of the sliding bearing are arranged such that the lengths of each of the plurality of sections along the axial direction are different.

5. The bearing system according to claim 1, wherein the sliding bearing is provided with two supply holes in the predetermined section, and a first fluid and a second fluid having a lower viscosity than the first fluid are supplied from these two supply holes as a plurality of fluids.

6. A first passage and a second passage, which communicate with each of the two supply holes and supply the first fluid and the second fluid respectively, A first valve and a second valve are provided in the first passage and the second passage, respectively. A control device configured to control the opening and closing of the first valve and the second valve, respectively, so as to switch the fluid supplied to the predetermined section between the first fluid and the second fluid, The bearing system according to claim 5, further comprising:

7. The bearing system according to claim 6, wherein the control device is configured to selectively perform, based on the rotational speed of the rotating shaft, control to open the first valve and close the second valve in order to supply the first fluid to the predetermined section, and control to close the first valve and open the second valve in order to supply the second fluid to the predetermined section.

8. The bearing system according to claim 6, wherein the control device is configured to perform control to open the first valve and close the second valve in order to supply the first fluid to the predetermined section, then to perform control to close the first valve and open the second valve in order to supply the second fluid to the predetermined section, and after this control, to perform control to close the first and second valves in order to stop supplying the first and second fluids to the predetermined section.

9. Multiple fluids include oil and CO 2 A bearing system according to any one of claims 1 to 8, configured to apply the following:

10. The bearing system according to claim 9, wherein the sliding bearing is configured to support the rotating shaft of the motor.

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