Bearing system

Abstract

This invention provides a bearing system that can ensure load capacity without increasing resistance for sliding bearings using high-viscosity and low-viscosity fluids. [Solution] The bearing system 200 is lubricated by oil and refrigerant (CO2 refrigerant) and includes a sliding bearing 15 that supports the rotating shaft 13, oil passages 27a and 27b for supplying oil to a first region of the sliding surface of the sliding bearing 15, and a refrigerant passage 22b provided spaced apart from the oil passages 27a and 27b in the axial direction and for supplying refrigerant to a second region of the sliding surface that is different from the first region, and the sliding bearing 15 is configured such that the inner diameter of the second region is smaller than the inner diameter of the first region.

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 lubricate with a fluid (working fluid) such as oil and support a rotating shaft has been known. This type of technology is described in, for example, Patent Document 1. This Patent Document 1 describes a technique for making an auxiliary bearing as a rolling bearing function as a sliding bearing (fluid bearing) by supplying a refrigerant (fluid) to the gap between its inner ring and the rotating shaft, thereby reducing the influence of frictional heat generated between the auxiliary bearing and the rotating shaft.

[0003] ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​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 using a high-viscosity fluid and a low-viscosity fluid, applying the high-viscosity fluid mainly to the sliding bearing in the low rotational speed range of the rotating shaft, and applying the low-viscosity fluid mainly to the sliding bearing in the high rotational speed range of the rotating shaft.

[0007] However, when considering the use of high-viscosity fluids in sliding bearings, if the gap between the sliding surface of the sliding bearing and the rotating shaft is too small, significant resistance will be generated, so it is desirable to increase the gap to a certain extent. Conversely, when considering the use of low-viscosity fluids in sliding bearings, if the gap between the sliding surface and the rotating shaft is increased in this way, the load capacity of the sliding bearing will not be ensured, so it is desirable to decrease the gap. If the load capacity is not ensured, the rotating shaft may wobble radially, which can create new resistance.

[0008] The present invention was made to solve the problems of the prior art described above, and aims to provide a bearing system that can ensure load capacity without increasing resistance for sliding bearings using high-viscosity fluids and low-viscosity fluids. [Means for solving the problem]

[0009] To achieve the above objective, the present invention provides a bearing system comprising: a sliding bearing that supports a rotating shaft and is lubricated by a first fluid and a second fluid having a lower viscosity than the first fluid; a first passage for supplying the first fluid to a first region of the sliding surface of the sliding bearing; and a second passage provided spaced apart from the first passage in the axial direction for supplying the second fluid to a second region of the sliding surface that is different from the first region, wherein the sliding bearing is configured such that the inner diameter of the second region is smaller than the inner diameter of the first region.

[0010] According to the present invention configured in this way, in a sliding bearing, the inner diameter of the second region to which a relatively low-viscosity second fluid is supplied is smaller than the inner diameter of the first region to which a relatively high-viscosity first fluid is supplied. As a result, the gap between the sliding surface of the sliding bearing and the outer surface of the rotating shaft is smaller in the second region than in the first region. Consequently, because the gap in the second region to which the second fluid is supplied is relatively small, the load capacity provided by the second fluid in this second region can be secured, while because the gap in the first region to which the first fluid is supplied is relatively large, the increase in resistance provided by the first fluid in this first region can be suppressed. Therefore, according to the present invention, in a sliding bearing using first and second fluids with different viscosities, load capacity can be secured without increasing resistance. Thus, when a relatively low-viscosity second fluid is applied, the rotating shaft can wobble radially, preventing unnecessary increases in resistance.

[0011] In the present invention, preferably, the sliding bearing is configured such that the inner diameter of the sliding surface changes continuously along the axial direction such that the inner diameter of the second region is smaller than the inner diameter of the first region. According to the present invention configured in this way, the gap between the sliding surface of the sliding bearing and the outer surface of the rotating shaft changes continuously along the axial direction, so that the surface pressure applied to the sliding surface can be made uniform.

[0012] In the present invention, preferably, the sliding bearing has a cross-section of the sliding surface, viewed along the axial direction, that is arc-shaped. According to the present invention configured in this manner, the surface pressure applied to the sliding surface can be effectively made uniform.

[0013] In the present invention, preferably, a pair of sliding bearings are provided to support a rotating shaft, and each of the pair of sliding bearings is configured to have a first region at one or both of its axial ends and a second region in the intermediate portion between the axial ends. In the present invention configured as described above, a first fluid with relatively high viscosity is supplied to one or both of the axial ends, while a second fluid with relatively low viscosity is supplied to the intermediate portion (typically the central portion) in the axial direction. This effectively ensures the load capacity of the sliding bearing, particularly the load capacity provided by the second fluid.

[0014] In the present invention, preferably, the bearing system further comprises a third passage for supplying a second fluid to a first region, a first valve and a second valve provided in the first passage and the third passage, respectively, 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 the first region between the first fluid and the second fluid. In the present invention configured in this way, the bearing system is configured to selectively supply a second fluid to a first region instead of a first fluid. This makes it possible to effectively suppress the increase in resistance caused by applying the first fluid in a sliding bearing.

[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 in order to supply a first fluid to a first region, and a control that closes a first valve and opens a second valve in order to supply a second fluid to a first region. According to the present invention configured in this manner, by switching the fluid supplied to the first region between the first fluid and the second fluid based on the rotational speed of the rotating shaft, it is possible to accurately achieve both securing load capacity in the low rotational speed range and reducing resistance in the high rotational speed range.

[0016] In the present invention, preferably, the sliding bearing is a groove portion formed on the sliding surface and extending in the radial direction and the circumferential direction, and the groove portion is configured to divide the sliding surface into a plurality of sections (hereinafter, appropriately referred to as "divided sections") in the axial direction. The groove portion further has discharge holes formed in the groove portion for discharging the first and second fluids from the sliding bearing. Each of the first region and the second region is defined by a section divided by the groove portion. In the present invention configured as described above, each of the fluids (first fluid or second fluid) within each divided section flows out from the discharge hole through the groove portion defining each divided section, thereby preventing the fluids from mixing in adjacent divided sections. Therefore, it is possible to prevent the fluids from mixing between the first region and the second region defined by the divided sections. Thus, according to the present invention, it is possible to effectively ensure the load capacity and reduce the resistance in the sliding bearing.

[0017] In a preferred example of the present invention, the first fluid is oil and the second fluid is CO2. In this case, in a more preferred example, the bearing system is configured to support the rotating shaft of the motor by the sliding bearing.

Advantages of the Invention

[0018] According to the bearing system of the present invention, for a sliding bearing using a high-viscosity fluid and a low-viscosity fluid, it is possible to ensure the load capacity without increasing the resistance.

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] FIGS. 4(a) and (b) are schematic configuration diagrams of a bearing system according to an embodiment of the present invention. [Figure 5] Figs. 5(a), 5(b), and 5(c) are explanatory diagrams regarding the switching between oil and refrigerant in a low rotation range, a medium rotation range, and a high rotation range in a bearing system according to an embodiment of the present invention. [Figure 6] It is a block diagram showing an electrical configuration of a bearing system according to an embodiment of the present invention. [Figure 7] It is a time chart showing control according to an embodiment of the present invention. [Figure 8] It is a flowchart showing control according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

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

[0021] [Overall Configuration] First, referring to FIG. 1, it is a schematic configuration diagram of a vehicle to which a bearing system according to the present embodiment is applied.

[0022] As shown in FIG. 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 (electric motor) 1 that generates power for driving the vehicle 300, a compressor (compressor) 3 that compresses the refrigerant supplied to the motor 1, and a heat exchanger (condenser) 5 that includes a condenser, a fan, etc. and cools 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 with respect to the rotor 11 in the axial direction. Each of these sliding bearings 15 is supplied with oil from two oil passages 27 (27a, 27b) and refrigerant from three refrigerant passages 22 (22a, 22b, 22c). These refrigerant and oil are supplied to the gap between the inner surface of the sliding bearing 15 and the outer 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.

[0036] Specifically, oil passages 27a and 27b supply oil to two different locations along the axial direction of the sliding bearing 15, while refrigerant passages 22a, 22b, and 22c supply refrigerant to three different locations along the axial direction of the sliding bearing 15. More specifically, oil passage 27a is configured to supply oil to one side end portion of the sliding bearing 15 in the axial direction (opposite to the rotor 11), and oil passage 27b is configured to supply oil to the other side end portion of the sliding bearing 15 in the axial direction (towards the rotor 11). Additionally, refrigerant passage 22a is configured to supply refrigerant to one side end portion of the sliding bearing 15 in the axial direction (opposite to the rotor 11), refrigerant passage 22b is configured to supply refrigerant to the central portion of the sliding bearing 15 in the axial direction, and refrigerant passage 22c is configured to supply refrigerant to the other side end portion of the sliding bearing 15 in the axial direction (towards the rotor 11). In this case, the oil passage 27a and the refrigerant passage 22a, as well as the oil passage 27b and the refrigerant passage 22c, supply oil and refrigerant to approximately the same locations in the axial direction. That is, the locations where oil passage 27a supplies oil and where refrigerant passage 22a supplies refrigerant are approximately the same in the axial direction, and the locations where oil passage 27b supplies oil and where refrigerant passage 22c supplies refrigerant are approximately the same in the axial direction. On the other hand, oil is not supplied to the locations where refrigerant passage 22b supplies refrigerant in the axial direction.

[0037] Furthermore, the bearing system 200 has oil bearing valves 31a and 31b provided in the oil passages 27a and 27b, respectively, which can switch between supplying and shutting off oil by opening and closing them, and refrigerant bearing valves 32a and 32b provided in the refrigerant passages 22a and 22c, respectively, which can switch between supplying and shutting off refrigerant by opening and closing them.

[0038] 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.

[0039] 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, oil passages 27a and 27b correspond to the "first passage" in this invention, refrigerant passage 22b corresponds to the "second passage" in this invention, and refrigerant passages 22a and 22c correspond to the "third passage" in this invention. In addition, oil bearing valves 31a and 31b and refrigerant bearing valves 32a and 32b correspond to the "first valve" and "second valve" in this invention, respectively.

[0040] 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.

[0041] 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.

[0042] Furthermore, the sliding bearing 15 has a discharge hole 15b formed in each of the two grooves 15a for discharging refrigerant and oil from the sliding bearing 15, supply holes 15c1 and 15c2 for supplying oil to the divided sections R1 and R3 respectively, and supply holes 15c3, 15c4 and 15c5 for supplying refrigerant to the divided sections R1, R2 and R3 respectively. The discharge hole 15b is in communication with the mixed fluid passage 29, the supply holes 15c1 and 15c2 are in communication with the oil passages 27a and 27b respectively, and the supply holes 15c3, 15c4 and 15c5 are in communication with the refrigerant passages 22a, 22b and 22c. In this case, the oil passage 27a is configured to supply oil to section R1, which is located at the end of section R1 to R3 that is opposite the rotor 11 in the axial direction, and the oil passage 27b is configured to supply oil to section R3, which is located at the end of section R1 to R3 that is on the rotor 11 side in the axial direction. Furthermore, the refrigerant passage 22a is configured to supply refrigerant to section R1, which is located at the end of section R1 to R3 that is opposite the rotor 11 in the axial direction, the refrigerant passage 22b is configured to supply refrigerant to section R2, which is located in the central part of section R1 to R3 in the axial direction, and the refrigerant passage 22c is configured to supply refrigerant to section R3, which is located at the end of section R1 to R3 that is on the rotor 11 side in the axial direction. Note that two or more discharge holes 15b may be provided on the same groove 15a.

[0043] 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.

[0044] Here, in the divided section R2, only refrigerant is supplied via the refrigerant passage 22b and the supply hole 15c4. In contrast, in the divided section R1, oil is supplied via the oil passage 27a and the supply hole 15c1, and refrigerant is supplied via the refrigerant passage 22a and the supply hole 15c3. In addition, in the divided section R3, oil is supplied via the oil passage 27b and the supply hole 15c2, and refrigerant is supplied via the refrigerant passage 22c and the supply hole 15c5. As described above (Figure 3), the oil passage 27a and the refrigerant passage 22a applied to the divided section R1 are provided with an oil bearing valve 31a and a refrigerant bearing valve 32a, respectively, and the oil passage 27b and the refrigerant passage 22c applied to the divided section R3 are provided with an oil bearing valve 31b and a refrigerant bearing valve 32b, respectively. In this embodiment, by opening one of the oil bearing valves 31a, 31b and the refrigerant bearing valves 32a, 32b and closing the other, only oil or refrigerant is supplied to each of the divided sections R1 and R3 (i.e., both oil and refrigerant are not supplied simultaneously). By changing the open / closed state of these oil bearing valves 31a, 31b and refrigerant bearing valves 32a, 32b, the fluid supplied to each of the divided sections R1 and R3 is switched between oil and refrigerant.

[0045] Furthermore, in this embodiment, as shown in Figure 4(b), the sliding bearing 15 is configured such that the inner diameter of the divided section R2, to which only refrigerant is supplied on the sliding surface, is smaller than the inner diameters of the divided sections R1 and R3, to which oil is supplied on the sliding surface. In other words, the inner diameter of the intermediate portion (central portion) of the sliding bearing 15 in the axial direction is smaller than the inner diameters of the portions at both ends of the sliding bearing 15 in the axial direction. Note that the divided sections R1 and R3 correspond to the "first region" in the present invention, and the divided section R2 corresponds to the "second region" in the present invention. That is, the "first region" and the "second region" in the present invention are defined by the divided sections R1, R3 and R2, respectively.

[0046] Furthermore, the sliding bearing 15 is configured such that the inner diameter of the sliding surface changes continuously along the axial direction, such that the inner diameter of the divided section R2 is smaller than the inner diameters of the divided sections R1 and R3. In particular, the cross-section of the sliding surface of the sliding bearing 15, when viewed along the axial direction, is formed in an arc shape, in other words, it is formed in a so-called crowning type. Specifically, in the cross-section when viewed along the axial direction, the middle portion of the sliding surface (divided section R2) protrudes radially inward, while the portions at both ends of the sliding surface (divided sections R1 and R3) recede radially outward, thus the cross-section of the sliding surface of the sliding bearing 15 is formed in an arc shape.

[0047] With this type of sliding bearing 15, the inner diameter of section R2 is smaller than the inner diameters of sections R1 and R3. As a result, the gap between the sliding surface of the sliding bearing 15 and the rotating shaft 13 of the motor 1 is smaller in section R2 than in sections R1 and R3. Consequently, the gap in section R2, where the refrigerant is supplied, is relatively small, ensuring sufficient load capacity from the refrigerant in section R2. On the other hand, the gaps in sections R1 and R3, where oil is supplied, are relatively large, suppressing the increase in resistance due to the oil in sections R1 and R3.

[0048] Note that, for the sake of clarity, Figure 3, shown above, does not depict the cross-sectional shape (arc shape, crowning type) of the sliding surface of the sliding bearing 15 as described above.

[0049] Next, referring to Figure 5, the switching of oil and refrigerant supplied to the divided sections R1 and R3 in the bearing system 200 according to this embodiment, which is performed according to the motor rotation speed, will be explained. Figures 5(a), (b), and (c) show 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) in the low rotation range, medium rotation range, and high rotation range, respectively. In Figures 5(a), (b), and (c), 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.

[0050] First, as shown in Figure 5(a), in the low-speed range of the motor rotation, refrigerant is supplied to the divided section R2, while oil is supplied to both divided sections R1 and R3. In this way, the load capacity of the sliding bearing 15 is ensured by the oil supplied to divided sections R1 and R3 in the low-speed range. In this case, the oil bearing valves 31a and 31b provided in the oil passages 27a and 27b are opened so that oil is supplied to both divided sections R1 and R3, while the refrigerant bearing valves 32a and 32b provided in the refrigerant passages 22a and 22c are closed.

[0051] Next, as shown in Figure 5(b), in the medium motor speed range, while refrigerant is supplied to section R2, oil is supplied to section R1, and refrigerant is supplied to section R3. In this way, in the medium speed range, the oil supplied to section R1 ensures a certain level of load capacity for the sliding bearing 15, while supplying refrigerant to section R3 instead of oil suppresses the increase in resistance at the sliding bearing 15. In this case, the oil bearing valve 31a provided in the oil passage 27a is opened so that oil is supplied to section R1, while the refrigerant bearing valve 32a provided in the refrigerant passage 22a is closed. Also, the oil bearing valve 31b provided in the oil passage 27b is closed so that oil is supplied to section R3, while the refrigerant bearing valve 32b provided in the refrigerant passage 22c is opened.

[0052] Next, as shown in Figure 5(c), in the high-speed range of the motor (especially when the motor speed is very high), refrigerant is supplied to both R1 and R2 while refrigerant remains supplied to R2. In this way, by supplying refrigerant to all of R1 to R3 in the high-speed range, the increase in resistance at the sliding bearing 15 is effectively suppressed. In this case, the oil bearing valves 31a and 31b provided in the oil passages 27a and 27b are closed, while the refrigerant bearing valves 32a and 32b provided in the refrigerant passages 22a and 22c are opened so that refrigerant is supplied to both R1 and R2.

[0053] [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.

[0054] 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.

[0055] 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.

[0056] The control device 80 supplies control signals to the motor 1, compressor 3, flow control valve 30, oil bearing valves 31a, 31b, refrigerant bearing valves 32a, 32b, 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.

[0057] In this embodiment, the control device 80 primarily controls the opening and closing of the oil bearing valves 31a, 31b and the refrigerant bearing valves 32a, 32b, respectively, in order to switch the fluid supplied to the divided sections R1 and R3 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 the following actions based on the motor rotation speed: opening the oil bearing valve 31a and closing the refrigerant bearing valve 32a to supply oil to divided section R1, and closing the oil bearing valve 31a and opening the refrigerant bearing valve 32a to supply refrigerant to divided section R1. Furthermore, based on the motor rotation speed, the control device 80 selectively performs the following actions: opening the oil bearing valve 31b and closing the refrigerant bearing valve 32b to supply oil to divided section R3, and closing the oil bearing valve 31b and opening the refrigerant bearing valve 32b to supply refrigerant to divided section R3.

[0058] [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 32a, the opening and closing of the refrigerant bearing valve 32b, the opening and closing of the oil bearing valve 31a, and the opening and closing of the oil bearing valve 31b.

[0059] As shown in Figure 7, at time t11, the motor speed increases. As a result, the load that the sliding bearing 15 must achieve (hereinafter referred to as the "required load"), which is determined according to the motor speed, decreases from a high load to a medium load. Therefore, at time t11, in order to suppress the load on the sliding bearing 15, the control device 80 closes the oil bearing valve 31b while opening the refrigerant bearing valve 32b, thereby switching the fluid supplied to the divided section R3 of the sliding bearing 15 from oil to refrigerant.

[0060] Subsequently, at time t12, the motor speed increases further, causing the required load to decrease from a medium load to a low load. Therefore, at time t12, in order to further reduce the load on the sliding bearing 15, the control device 80 closes the oil bearing valve 31a while opening the refrigerant bearing valve 32a, thereby switching the fluid supplied to the divided section R1 of the sliding bearing 15 from oil to refrigerant.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] In step S15, the control device 80 opens the oil bearing valves 31a and 31b and closes the refrigerant bearing valves 32a and 32b to supply oil to both the divided sections R1 and R3 of the sliding bearing 15 in order to ensure the load on the sliding bearing 15 before starting the motor 1. 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.

[0065] 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 S23.

[0066] In step S19, the control device 80 determines the required load for the sliding bearing 15 based on the motor rotation speed detected by the motor rotation speed sensor 56, and determines whether this required load is low. In this case, if the motor rotation speed is in the high rotation range (especially when the motor rotation speed is very high), the required load will be low. If, as a result of step 19, the control device 80 determines that the required load is low (step S19: Yes), it proceeds to step S20. In this case, the control device 80 closes the oil bearing valves 31a and 31b while opening the refrigerant bearing valves 32a and 32b to supply refrigerant to both the divided sections R1 and R3 of the sliding bearing 15. Then, the control device 80 proceeds to step S17 as described above.

[0067] In response to this, if the control device 80 does not determine in step S19 that the requested load is a low load (step S19: No), it proceeds to step S21. In step S21, the control device 80 determines whether the requested load is a medium load. In this case, if the motor speed is in the medium speed range, the requested load becomes a medium load. If, as a result of step S21, the control device 80 determines that the requested load is a medium load (step S21: Yes), it proceeds to step S22. In this case, the control device 80 opens the oil bearing valve 31a to supply oil to the divided section R1 of the sliding bearing 15, while closing the refrigerant bearing valve 32a, and closes the oil bearing valve 31b to supply refrigerant to the divided section R3 of the sliding bearing 15, while opening the refrigerant bearing valve 32b. Then, the control device 80 proceeds to step S17 as described above.

[0068] In response to this, if the control device 80 does not determine in step S21 that the requested load is a medium load (step S21: No), that is, if the requested load is a high load, it proceeds to step S23. When the motor rotation speed is in the low rotation range, the requested load becomes a high load. In this case, the control device 80 opens the oil bearing valves 31a and 31b to supply oil to both the divided sections R1 and R3 of the sliding bearing 15, while closing the refrigerant bearing valves 32a and 32b. Then, the control device 80 proceeds to step S17 as described above.

[0069] In steps S19 and S21, the control device 80 determined the required load for the sliding bearing 15, but in other examples, the motor rotation speed may be determined instead of the required load.

[0070] [Mechanism of Action and Effects] Next, the operation and effects of the bearing system 200 according to this embodiment will be described.

[0071] In this embodiment, the bearing system 200 is lubricated by oil and refrigerant (CO2 refrigerant) and includes a sliding bearing 15 that supports the rotating shaft 13, oil passages 27a and 27b for supplying oil to a first region of the sliding surface of the sliding bearing 15, and a refrigerant passage 22b provided spaced apart from the oil passages 27a and 27b in the axial direction for supplying refrigerant to a second region of the sliding surface that is different from the first region, and the sliding bearing 15 is configured such that the inner diameter of the second region is smaller than the inner diameter of the first region.

[0072] In this embodiment, the inner diameter of the second region to which low-viscosity refrigerant is supplied in the sliding bearing 15 is smaller than the inner diameter of the first region to which high-viscosity oil is supplied. As a result, the gap between the sliding surface of the sliding bearing 15 and the rotating shaft 13 of the motor 1 is smaller in the second region than in the first region. Consequently, because the gap in the second region to which refrigerant is supplied is relatively small, the load capacity provided by the refrigerant in this second region can be ensured, while the gap in the first region to which oil is supplied is relatively large, thus suppressing the increase in resistance due to the oil in this first region. Therefore, in this embodiment, load capacity can be ensured in a sliding bearing 15 using high-viscosity oil and low-viscosity refrigerant without increasing resistance. Thus, when a low-viscosity refrigerant is applied, the rotating shaft 13 can wobble radially, preventing unnecessary increases in resistance.

[0073] Furthermore, according to this embodiment, the sliding bearing 15 is configured such that the inner diameter of the sliding surface changes continuously along the axial direction, such that the inner diameter of the second region becomes smaller than the inner diameter of the first region. As a result, the gap between the sliding surface of the sliding bearing 15 and the rotating shaft 13 of the motor 1 changes continuously along the axial direction, making it possible to make the surface pressure applied to the sliding surface uniform.

[0074] In particular, according to this embodiment, since the cross-section of the sliding surface of the sliding bearing 15, when viewed along the axial direction, is formed in an arc shape (i.e., it is formed in a crowning type), the surface pressure applied to the sliding surface can be effectively made uniform.

[0075] Furthermore, according to this embodiment, a pair of sliding bearings 15 are provided to support the rotating shaft 13, and each of the pair of sliding bearings 15 is configured to have a first region at both ends in the axial direction and a second region in the intermediate portion (particularly the central portion) between the two ends in the axial direction. In other words, in this embodiment, high-viscosity oil is supplied to both ends in the axial direction, while low-viscosity refrigerant is supplied to the intermediate portion in the axial direction. By allocating the supply of high-viscosity oil and low-viscosity refrigerant to the sliding bearings 15 in this way, the load capacity of the sliding bearings 15 (particularly the load capacity due to the refrigerant) can be effectively ensured.

[0076] Furthermore, according to this embodiment, the bearing system 200 further includes refrigerant passages 22a and 22c for supplying refrigerant to a first region, oil bearing valves 31a and 31b and refrigerant bearing valves 32a and 32b provided in the oil passages 27a and 27b and the refrigerant passages 22a and 22c, respectively, and a control device 80 configured to control the opening and closing of the oil bearing valves 31a and 31b and the refrigerant bearing valves 32a and 32b, respectively, so as to switch the fluid supplied to the first region between oil and refrigerant. This makes it possible to selectively supply refrigerant instead of oil to the first region, thereby effectively suppressing the increase in resistance caused by applying oil in the sliding bearing 15.

[0077] Furthermore, according to this embodiment, the control device 80 is configured to selectively perform the following actions based on the motor rotation speed: control to open the oil bearing valve 31a and close the refrigerant bearing valve 32a to supply oil to the first region, and / or control to open the oil bearing valve 31b and close the refrigerant bearing valve 32b; and control to close the oil bearing valve 31a and open the refrigerant bearing valve 32a to supply refrigerant to the first region, and / or control to close the oil bearing valve 31b and open the refrigerant bearing valve 32b. As a result, by switching the fluid supplied to the first region between oil and refrigerant based on the motor rotation speed, it is possible to accurately achieve both load capacity at low rotation speeds and resistance reduction at high rotation speeds.

[0078] Furthermore, according to this embodiment, the sliding bearing 15 has grooves 15a formed on its sliding surface that extend radially and circumferentially, and the 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 grooves 15a for discharging fluid from the sliding bearing 15, and the first and second regions are defined by the divided sections R1 to R3 divided by the grooves 15a.

[0079] In this embodiment, the fluid (oil or refrigerant) within each divided section R1 to R3 flows out through the groove 15a defining each divided section R1 to R3 and out through the discharge hole 15b, thereby preventing the fluids from mixing in adjacent divided sections R1 to R3. Therefore, it is possible to prevent the fluids from mixing between the first region and the second region defined by the divided sections R1 to R3. Accordingly, according to this embodiment, it is possible to effectively secure the load capacity and reduce resistance in the sliding bearing 15.

[0080] [Differentiation] In the embodiment described above, the sliding bearing 15 had a first region to which oil was supplied at both ends in the axial direction (corresponding to the divided sections R1 and R3). However, in a modified example, the first region may be located at one of the ends in the axial direction (either of the divided sections R1 or R3).

[0081] Furthermore, in the embodiment described above, the sliding bearing 15 had three divided sections R1 to R3 formed by two grooves 15a, but in a modified example, one groove 15a may form two divided sections, or three or more grooves 15a may form four or more divided sections.

[0082] Furthermore, in the above-described embodiment, oil and CO2 (CO2 refrigerant) were used as fluids with different viscosities (first and second fluids), but various fluids other than oil and CO2 may be used. [Explanation of Symbols]

[0083] 1 motor 3 Compressors 5 Heat exchanger 6 Oil tank 11 rotors 12 staters 13 Rotation axis 15 Plain bearings 15a Groove 15b Discharge hole 15c1~15c5 Supply hole 21-26 Refrigerant passage 27, 28 Oil passages 29 Mixed fluid passage 80 Control device 100 Refrigerant Circulation System 200 Bearing System 300 vehicles R1~R3 ​​Divided Section

Claims

1. A bearing system, Lubrication is provided by a first fluid and a second fluid having a lower viscosity than the first fluid, and a sliding bearing supports the rotating shaft. A first passage for supplying the first fluid to a first region of the sliding surface of the sliding bearing, A second passage is provided spaced apart from the first passage in the axial direction, and is for supplying the second fluid to a second region on the sliding surface that is different from the first region, It has, The bearing system is characterized in that the sliding bearing is configured such that the inner diameter of the second region is smaller than the inner diameter of the first region.

2. The bearing system according to claim 1, wherein the sliding bearing is configured such that the inner diameter of the sliding surface changes continuously along the axial direction such that the inner diameter of the second region becomes smaller than the inner diameter of the first region.

3. The bearing system according to claim 2, wherein the cross-section of the sliding surface of the sliding bearing, viewed along the axial direction, is formed in an arc shape.

4. The bearing system according to claim 1, wherein a pair of sliding bearings are provided to support the rotating shaft, and each of the pair of sliding bearings is configured to have the first region in one or both of the axial ends and the second region in the intermediate portion between the axial ends.

5. The bearing system is A third passage for supplying the second fluid to the first region, A first valve and a second valve are provided in the first passage and the third 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 first region between the first fluid and the second fluid, The bearing system according to claim 1, further comprising the following:

6. The bearing system according to claim 5, 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 first region, and control to close the first valve and open the second valve in order to supply the second fluid to the first region.

7. The aforementioned sliding bearing is A groove formed on the sliding surface, extending radially and circumferentially, wherein the groove is configured to divide the sliding surface into a plurality of sections in the axial direction, The groove portion is formed with a discharge hole for discharging the first and second fluids from the sliding bearing, It further possesses, Each of the first and second regions is defined by the section divided by the groove. The bearing system according to claim 1.

8. The first fluid is oil, and the second fluid is CO 2 The bearing system according to any one of claims 1 to 7.

9. The bearing system according to claim 8, wherein the sliding bearing is configured to support the rotating shaft of the motor.

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