Bearing system

Abstract

Provided is a bearing system capable of securing load capacity without increasing resistance for a sliding bearing using a high-viscosity fluid and a low-viscosity fluid. A bearing system (200) is provided with: a sliding bearing (15) that is lubricated by oil and a refrigerant (CO2 refrigerant) and that supports a rotating shaft (13); oil passages (27a, 27b) for supplying oil to a first region of a sliding surface of the sliding bearing (15); and a refrigerant passage (22b) that is provided so as to be separated from the oil passages (27a, 27b) in the axial direction, and that supplies a refrigerant to a second region of the sliding surface, which is different from the first region. 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

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

[0002] Conventionally, it is known that sliding bearings are configured to be lubricated by a fluid such as oil (working fluid) and support a rotating shaft. Such technology is described, for example, in Patent Document 1. Patent Document 1 describes a technique in which a refrigerant (fluid) is supplied to the gap between the inner wheel of the auxiliary bearing, which functions as a rolling bearing, and the rotating shaft, thereby enabling the auxiliary bearing to function as a sliding bearing (fluid bearing) and mitigating the effects of frictional heat generated between the auxiliary bearing and the rotating shaft.

[0003] Furthermore, for example, Patent Document 2 describes a technique related to the present invention. Patent Document 2 describes a method for suppressing unilateral collision between the sliding bearing and the rotating shaft by forming the sliding surface of the sliding bearing into a convex shape composed of inclined surfaces.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent document 1: Japanese Patent Application Publication No. 2022-155811.

[0007] Patent Document 2: International Publication No. 2010 / 038588.

[0008] The technical problem that the invention aims to solve

[0009] Here, the inventors of the present invention have studied the application of sliding bearings to the rotating shafts of motors (such as electric motors for electric vehicles) capable of rotating at high speeds, and in the process of developing such sliding bearings, they have obtained the following insights.

[0010] First, at relatively low rotational speeds of the rotating shaft, the load capacity of the sliding bearing tends to decrease. However, at relatively high rotational speeds, due to wedge and throttling effects, the load capacity of the sliding bearing increases. On the other hand, losses caused by fluid resistance (friction losses) tend to increase. Therefore, it can be said that in the low-speed rotation region of the rotating shaft, it is desirable to ensure the load capacity of the sliding bearing, while in the high-speed rotation region, it is desirable to suppress the load capacity of the sliding bearing and reduce friction losses. Therefore, the inventors of this invention considered using both high-viscosity and low-viscosity fluids. In the low-speed rotation region of the rotating shaft, the high-viscosity fluid is mainly used in the sliding bearing, while in the high-speed rotation region, the low-viscosity fluid is mainly used.

[0011] However, when considering the use of high-viscosity fluids in sliding bearings, if the clearance between the sliding surface of the bearing and the rotating shaft is too small, significant resistance will be generated. Therefore, it is desirable to increase the clearance to a certain extent. Conversely, when considering the use of low-viscosity fluids in sliding bearings, increasing the clearance in this way would compromise the load-bearing capacity of the bearing. Therefore, it is desirable to reduce the clearance. If the load-bearing capacity cannot be guaranteed, the rotating shaft will wobble radially, generating new resistance. Summary of the Invention

[0012] The present invention was made to solve the problems of the prior art mentioned above, and its object is to provide a bearing system that can ensure load capacity without increasing resistance for sliding bearings using high-viscosity fluids and low-viscosity fluids.

[0013] Technical means for solving technical problems

[0014] To achieve the above objectives, the present invention provides a bearing system comprising: a sliding bearing that is lubricated by a first fluid and a second fluid with a lower viscosity than the first fluid, and supports a rotating shaft; a first passage for supplying the first fluid to a first region of a sliding surface of the sliding bearing; and a second passage that is axially separated from the first passage for supplying the second fluid to a second region on 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.

[0015] According to the present invention, in a sliding bearing, the inner diameter of the second region supplied with a second fluid of relatively low viscosity is smaller than the inner diameter of the first region supplied with a first fluid of relatively high viscosity. Therefore, the clearance between the sliding surface of the sliding bearing and the outer circumferential surface of the rotating shaft is smaller in the second region than in the first region. As a result, since the clearance in the second region supplied with the second fluid is smaller, the load-bearing capacity of the second fluid in that region can be ensured. On the other hand, since the clearance in the first region supplied with the first fluid is larger, the increase in resistance of the first fluid in that region can be suppressed. Therefore, according to the present invention, in a sliding bearing using a first fluid and a second fluid of different viscosities, load-bearing capacity can be ensured without increasing resistance. Therefore, when a second fluid of relatively low viscosity is used, radial wobbling of the rotating shaft, which increases useless resistance, can be prevented.

[0016] In this invention, it is preferred that the sliding bearing is configured such that the inner diameter of the sliding surface continuously varies axially in such a way that the inner diameter of the second region is smaller than the inner diameter of the first region.

[0017] According to the present invention configured in this way, since the gap between the sliding surface of the sliding bearing and the outer peripheral surface of the rotating shaft changes continuously along the axial direction, the surface pressure applied to the sliding surface can be made uniform.

[0018] In this invention, it is preferred that the cross-section of the sliding surface of the sliding bearing, viewed along the axial direction, is formed in an arc shape.

[0019] According to the present invention configured in this way, the surface pressure applied to the sliding surface can be effectively made uniform.

[0020] In this invention, preferably, a pair of sliding bearings are provided to support a rotating shaft, and the pair of sliding bearings are respectively configured such that one or both of the two end portions in the axial direction have a first region, and the middle portion between the two end portions in the axial direction has a second region.

[0021] According to the present invention configured in this way, a first fluid with a relatively high viscosity is supplied to one or both ends in the axial direction, while a second fluid with a relatively low viscosity is supplied to the middle portion (typically the central portion) in the axial direction. This effectively ensures the load-bearing capacity of the sliding bearing, especially the load-bearing capacity of the second fluid.

[0022] In this 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 respectively disposed in the first passage and the third passage; and a control device configured to control the opening and closing of the first valve and the second valve respectively to switch the fluid supplied to the first region between the first fluid and the second fluid.

[0023] In this invention, the bearing system is configured to selectively supply a second fluid to a first region instead of the first fluid. This effectively suppresses the increase in resistance caused by the application of the first fluid in the sliding bearing.

[0024] In this invention, it is preferred that the control device is configured to selectively control the following based on the rotational speed of the rotating shaft: control to open the first valve and close the second valve to supply a first fluid to a first region; and control to close the first valve and open the second valve to supply a second fluid to the first region.

[0025] According to the present invention configured in this way, by switching the fluid supplied to the first region between a first fluid and a second fluid based on the rotational speed of the rotating shaft, it is possible to reliably ensure both the load capacity in the low-speed rotation region and the resistance reduction in the high-speed rotation region.

[0026] In this invention, preferably, the sliding bearing further comprises: a groove formed on the sliding surface and extending radially and circumferentially, configured to divide the sliding surface axially into a plurality of intervals (hereinafter appropriately referred to as "divided intervals"); and a discharge hole formed in the groove for discharging a first fluid and a second fluid from the sliding bearing, the first region and the second region being respectively defined by the intervals divided by the groove.

[0027] In this invention, the fluid (first fluid or second fluid) within each segmented section flows out from the discharge port via a groove defining each segment, thereby preventing the fluid from mixing in adjacent segments. Therefore, mixing of fluids between the first and second regions defined by the segmented sections can be prevented. Thus, according to the invention, the load-bearing capacity and resistance reduction in the sliding bearing can be effectively achieved.

[0028] In this invention, in a preferred embodiment, the first fluid is oil and the second fluid is CO2.

[0029] In this case, in a further preferred example, the bearing system is configured to support the rotating shaft of the motor via a sliding bearing.

[0030] The effects of the invention

[0031] According to the bearing system of the present invention, load capacity can be ensured without increasing resistance for sliding bearings using high-viscosity fluids and low-viscosity fluids. Attached Figure Description

[0032] Figure 1 This is a schematic structural diagram of a vehicle using a bearing system according to an embodiment of the present invention.

[0033] Figure 2 This is a schematic structural diagram of the refrigerant circulation system according to an embodiment of the present invention.

[0034] Figure 3 This is a schematic structural diagram of an electric motor or the like according to an embodiment of the present invention.

[0035] Figure 4 (a) and (b) are schematic structural diagrams of the bearing system according to an embodiment of the present invention.

[0036] Figure 5 (a), (b), and (c) are explanatory diagrams of the switching of oil and refrigerant in the low-speed rotation region, medium-speed rotation region, and high-speed rotation region of the bearing system according to an embodiment of the present invention.

[0037] Figure 6 This is a block diagram illustrating the electrical structure of a bearing system according to an embodiment of the present invention.

[0038] Figure 7 This is a timing diagram illustrating the control of an embodiment of the present invention.

[0039] Figure 8 This is a flowchart illustrating the control process of an embodiment of the present invention.

[0040] Symbol Explanation

[0041] 1 motor

[0042] 3 compressors

[0043] 5 heat exchangers

[0044] 6 fuel tanks

[0045] 11 rotors

[0046] 12 stators

[0047] 13 rotating axes

[0048] 15 sliding bearings

[0049] 15a groove section

[0050] 15b discharge port

[0051] 15c1~15c5 supply holes

[0052] 21-26 Refrigerant passages

[0053] 27 and 28 oil passages

[0054] 29 Mixed Fluid Path

[0055] 80 control device

[0056] 100 refrigerant cycle system

[0057] 200 bearing system

[0058] 300 vehicles

[0059] The interval is divided into R1 and R3. Detailed Implementation

[0060] Hereinafter, the bearing system according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0061] [Overall Structure]

[0062] First, refer to Figure 1 This is a schematic structural diagram of a vehicle using the bearing system of this embodiment.

[0063] like Figure 1As shown, the vehicle 300 is, for example, an electric vehicle, and has a refrigerant circulation system 100 that circulates 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 5 that includes a condenser, a fan, etc., for cooling the refrigerant compressed by the compressor 3.

[0064] The refrigerant circulation system 100 circulates CO2 refrigerant (hereinafter sometimes simply referred to as "refrigerant"), which is a natural refrigerant. This CO2 refrigerant may contain not only CO2 but also refrigeration oils such as PAG, additives, etc. Because of the use of such a CO2 refrigerant, the compressor 3 is configured to compress the refrigerant to a very high pressure. The motor 1 uses the refrigerant compressed by the compressor 3 (typically a supercritical refrigerant) for lubrication of the sliding bearings supporting the rotating shaft; and for cooling the rotor and stator. In this case, the motor 1 functions 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. Furthermore, the refrigerant compressed by the compressor 3 can also be used for air conditioning in air conditioners, battery cooling, etc.

[0065] [Structure of the refrigerant cycle system]

[0066] Next, refer to Figure 2 The refrigerant circulation system 100 of this embodiment will be described in detail. Figure 2 This is a schematic structural diagram of the refrigerant circulation system 100 of this embodiment.

[0067] like Figure 2 As shown, the refrigerant circulation system 100, in addition to the aforementioned motor 1, compressor 3, and heat exchanger 5, mainly includes: a bearing system 200 having a pair of sliding bearings 15 supporting the rotating shaft 13 of the motor 1; an oil tank 6 storing oil for lubrication of the sliding bearings 15; refrigerant passages 21-26 for refrigerant (CO2 refrigerant) flow; oil passages 27 and 28 for oil flow; and a mixed fluid passage 29 for a mixture of refrigerant and oil. For example, the oil is a refrigeration oil such as PAG.

[0068] Refrigerant passage 21 is a passage for supplying refrigerant from compressor 3 to motor 1 and the like via heat exchanger 5. It branches into refrigerant passage 22 and refrigerant passage 23 downstream of heat exchanger 5. 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 are provided in refrigerant passage 21.

[0069] Refrigerant passage 22 is for supplying refrigerant to the sliding bearing 15, and refrigerant passage 23 is for supplying refrigerant to 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, and the refrigerant supplied to the motor 1 is used for cooling. Additionally, a flow regulating valve 30 for adjusting the refrigerant flow rate is provided in refrigerant passage 23.

[0070] Refrigerant passage 24 is used to supply refrigerant discharged from motor 1 to compressor 3. Additionally, refrigerant passage 25 is connected to refrigerant passage 24. One end of refrigerant passage 25 is connected to refrigerant passage 21 downstream of heat exchanger 5, and the other end is connected to refrigerant passage 24, preventing refrigerant from heat exchanger 5 from returning to compressor 3 via motor 1, sliding bearing 15, etc. Furthermore, check valves 41 and 42 are respectively provided in refrigerant passages 24 and 25.

[0071] Oil passage 27 is a passage for supplying oil stored in oil tank 6 to sliding bearing 15. The oil supplied to sliding bearing 15, together with the aforementioned refrigerant, is used for lubrication of sliding bearing 15. Oil passage 27 is equipped with an oil pump 38 for pressurizing oil, an oil temperature sensor 54 for detecting oil temperature, and an oil pressure sensor 55 for detecting oil pressure. Additionally, oil passage 28 is connected to oil passage 27 for returning oil in passage 27 to oil tank 6. A check valve 44 is installed in oil passage 28.

[0072] The mixing fluid passage 29 is a passage for supplying a mixture of refrigerant and oil discharged from the sliding bearing 15 to the oil tank 6. The oil tank 6 is configured to separate (gas-liquid separation) the oil from the mixture supplied from the mixing fluid passage 29 and store the separated oil. On the other hand, the remaining refrigerant (which also contains a small amount of oil) is supplied from the refrigerant passage 26 to the aforementioned refrigerant passage 24. A check valve 43 is provided in the refrigerant passage 26. Additionally, an oil level sensor 53 is provided in the oil tank 6 to detect the level of the stored oil.

[0073] [Structure of the bearing system]

[0074] Next, refer to Figures 3 to 5The structure of the bearing system 200 in this embodiment will be described in detail.

[0075] first, Figure 3 This is a schematic structural diagram of the motor 1 and bearing system 200 according to this embodiment. Specifically, Figure 3 This is a cross-sectional view of the motor 1 and bearing system 200 viewed along the axial direction. Furthermore, Figure 3 and Figure 2 Conversely, the vertical positions of refrigerant passage 22 and oil passage 27 are indicated (the same applies to the diagrams described later).

[0076] like Figure 3 As shown, the motor 1 mainly includes: a rotor 11 and a stator 12; a rotating shaft 13 connected to the rotor 11 and one end connected to the transmission drive axle (not shown) of the vehicle 300; and a housing 14 that houses the rotor 11, stator 12, and rotating shaft 13, etc. The bearing system 200 mainly includes a pair of sliding bearings 15 supporting 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.

[0077] As described above, in the motor 1, refrigerant (liquefied refrigerant) is supplied to the rotor 11 and stator 12 through the refrigerant passage 23. The refrigerant supplied to the motor 1 is used for cooling the rotor 11 and stator 12, especially the coils (not shown) inside the stator 12. In this case, since the refrigerant exchanges heat with the relatively high-temperature stator 12 (whereby the refrigerant evaporates in the coils of the stator 12), the function of the evaporator in the refrigeration cycle is realized. Furthermore, the refrigerant used for cooling the motor 1 is discharged through the refrigerant passage 24.

[0078] Next, a pair of sliding bearings 15 are symmetrically (left-right symmetrically) arranged axially across the rotor 11. Oil is supplied to the pair of sliding bearings 15 from two oil passages 27 (27a, 27b), and refrigerant is supplied to the pair of sliding bearings 15 from three refrigerant passages 22 (22a, 22b, 22c). 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, thereby providing lubrication for the sliding bearings 15 supporting the rotating shaft 13. The refrigerant and oil used for lubricating the sliding bearings 15 are discharged together as a mixed fluid from the mixed fluid passage 29.

[0079] Specifically, oil passages 27a and 27b supply oil to different axial locations (two locations) of the sliding bearing 15, and refrigerant passages 22a, 22b, and 22c supply refrigerant to different axial locations (three locations) of the sliding bearing 15. More specifically, oil passage 27a is configured to supply oil to one side of the axially inclined sliding bearing 15 (the side opposite to the rotor 11), and oil passage 27b is configured to supply oil to the other side of the axially inclined sliding bearing 15 (the rotor 11 side). Furthermore, refrigerant passage 22a is configured to supply refrigerant to one side of the axially inclined sliding bearing 15 (the side opposite to the rotor 11), refrigerant passage 22b is configured to supply refrigerant to the central portion of the axially inclined sliding bearing 15, and refrigerant passage 22c is configured to supply refrigerant to the other side of the axially inclined sliding bearing 15 (the rotor 11 side). In this case, oil passage 27a and refrigerant passage 22a, as well as oil passage 27b and refrigerant passage 22c, supply oil and refrigerant to approximately the same locations in the axial direction, respectively. That is, the location where oil is supplied in oil passage 27a and the location where refrigerant is supplied in refrigerant passage 22a are approximately the same in the axial direction, and the location where oil is supplied in oil passage 27b and the location where refrigerant is supplied in refrigerant passage 22c are approximately the same in the axial direction. On the other hand, no oil is supplied to the location where refrigerant is supplied in refrigerant passage 22b in the axial direction.

[0080] In addition, the bearing system 200 has oil bearing valves 31a and 31b respectively provided in oil passages 27a and 27b, which can switch the supply / cut-off of oil by opening and closing, and refrigerant bearing valves 32a and 32b respectively provided in refrigerant passages 22a and 22c, which can switch the supply / cut-off of refrigerant by opening and closing.

[0081] On the other hand, a side of the rotating shaft 13 connected to the transmission drive axle, etc., is provided in the housing 14 of the motor 1. Figure 3 The sealing member 18 (shown on the left side, where the sliding bearing 15 is located) is configured to prevent leakage of fluid from the gap between the portion of the rotating shaft 13 extending outward from the housing 14 and the housing 14. The sealing member 18 is configured as a mechanical seal that is supplied with oil from the oil passage 27d connected to the aforementioned oil passage 27a, thereby preventing fluid leakage.

[0082] 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. Additionally, 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. Furthermore, 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.

[0083] then, Figure 4 This is a schematic structural diagram illustrating the bearing system 200 of this embodiment in more detail. Specifically, Figure 4 (a) is one of a pair of sliding bearings 15 in the bearing system 200. Figure 3 The left side shows a perspective view of the sliding bearing 15 (i.e., the sliding bearing 15 located on the side where the sealing member 18 is provided). Figure 4 (b) is a cross-sectional view of the sliding bearing 15 on this side viewed along the axial direction.

[0084] like Figure 4 (a) and (b), especially Figure 4 As shown in (b), the sliding bearing 15 (as described above, is one of a pair of sliding bearings 15. The same applies below.) has two annular grooves 15a formed on its sliding surface (inner circumferential surface) and extending radially and circumferentially. The sliding bearing 15 divides its sliding surface into three sections (segmented sections) R1 to R3 in the axial direction through these two grooves 15a. The segmented sections R1 and R3 located at the two ends have approximately the same length along the axial direction, but the segmented section R2 located in the middle part sandwiched between these segmented sections R1 and R3 has a longer length along the axial direction than the segmented sections R1 and R3.

[0085] In addition, the sliding bearing 15 also includes: discharge holes 15b formed in two grooves 15a for discharging refrigerant and oil from the sliding bearing 15; supply holes 15c1 and 15c2 for supplying oil to the segmented sections R1 and R3 respectively; and supply holes 15c3, 15c4, and 15c5 for supplying refrigerant to the segmented sections R1, R2, and R3 respectively. The discharge hole 15b communicates with the mixed fluid passage 29, the supply holes 15c1 and 15c2 communicate with the oil passages 27a and 27b respectively, and the supply holes 15c3, 15c4, and 15c5 communicate with the refrigerant passages 22a, 22b, and 22c. In this case, the oil passage 27a is configured to supply oil to the segmented section R1, which is located on the opposite side of the rotor 11 in the axial direction among the segmented sections R1 to R3, and the oil passage 27b is configured to supply oil to the segmented section R3, which is located on the rotor 11 side in the axial direction among the segmented sections R1 to R3. Furthermore, refrigerant passage 22a is configured to supply refrigerant to segment R1, which is located axially on the opposite side of rotor 11 among the segmented segments R1 to R3; refrigerant passage 22b is configured to supply refrigerant to segment R2, which is located axially in the central part of segmented segments R1 to R3; and refrigerant passage 22c is configured to supply refrigerant to segment R3, which is located axially on the rotor 11 side among the segmented segments R1 to R3. Additionally, two or more discharge holes 15b may be provided on the same groove 15a.

[0086] According to this sliding bearing 15, since three axially segmented sections R1 to R3 are formed by two grooves 15a, and discharge holes 15b are provided in these grooves 15a, the fluid (oil or refrigerant) in each segmented section R1 to R3 flows out from the discharge hole 15b through the groove 15a that defines each segmented section R1 to R3. This prevents the fluid from reciprocating between adjacent segmented sections R1 to R3 and mixing within those sections. This is because the size of the grooves 15a (e.g., in the mm range) is much larger than the clearance (e.g., in the μm range) between the rotating shaft 13 of the motor 1 and the sliding bearing 15, so the fluid in each segmented section R1 to R3 does not flow through the grooves 15a to adjacent segmented sections but flows into the grooves 15a.

[0087] Here, only refrigerant is supplied to the segmented section R2 via refrigerant passage 22b and supply port 15c4. In contrast, oil is supplied to the segmented section R1 via oil passage 27a and supply port 15c1, and refrigerant is supplied to the segmented section R1 via refrigerant passage 22a and supply port 15c3. Furthermore, oil is supplied to the segmented section R3 via oil passage 27b and supply port 15c2, and refrigerant is supplied to the segmented section R3 via refrigerant passage 22c and supply port 15c5. As described above ( Figure 3In this embodiment, an oil bearing valve 31a and a refrigerant bearing valve 32a are respectively installed in the oil passage 27a and refrigerant passage 22a applied to the segmented interval R1, and an oil bearing valve 31b and a refrigerant bearing valve 32b are respectively installed in the oil passage 27b and refrigerant passage 22c applied to the segmented interval R3. In this embodiment, by opening one of the oil bearing valves 31a and 31b and the refrigerant bearing valves 32a and 32b and closing the other, only one of oil and refrigerant is supplied to the segmented intervals R1 and R3 (i.e., neither oil nor refrigerant is supplied simultaneously). Furthermore, by changing the opening and closing states of these oil bearing valves 31a and 31b and the refrigerant bearing valves 32a and 32b, the fluid supplied to the segmented intervals R1 and R3 is switched between oil and refrigerant.

[0088] Furthermore, in this embodiment, such as Figure 4 As shown in (b), the sliding bearing 15 is configured such that the inner diameter of the segment R2, on the sliding surface where only refrigerant is supplied, is smaller than the inner diameter of the segment R1 and R3, on the sliding surface where oil is supplied. That is, the inner diameter of the middle portion (central portion) of the sliding bearing 15 in the axial direction is smaller than the inner diameter of the two end portions of the sliding bearing 15 in the axial direction. Furthermore, the segment R1 and R3 correspond to the "first region" in this invention, and the segment R2 corresponds to the "second region" in this invention. That is, the "first region" and "second region" of this invention are defined by the segment R1, R3, and segment R2, respectively.

[0089] Furthermore, the sliding bearing 15 is configured such that the inner diameter of the sliding surface continuously varies along the axial direction, so that the inner diameter of the segmented interval R2 is smaller than the inner diameters of the segmented intervals 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 convex shape. Specifically, in the cross-section viewed along the axial direction, the middle portion of the sliding surface (segmented interval R2) protrudes radially inward, while the cross-section of the sliding surface of the sliding bearing 15 is formed in an arc shape such that the two ends of the sliding surface (segmented intervals R1 and R3) are radially outward.

[0090] According to this sliding bearing 15, since the inner diameter of the segmented section R2 is smaller than the inner diameters of the segmented sections R1 and R3, the clearance between the sliding surface of the sliding bearing 15 and the rotating shaft 13 of the motor 1 is smaller in segmented section R2 than in segmented sections R1 and R3. As a result, since the clearance in segmented section R2 where refrigerant is supplied is smaller, the refrigerant load capacity in segmented section R2 can be ensured. On the other hand, since the clearance in segmented sections R1 and R3 where oil is supplied is larger, the increase in oil resistance in segmented sections R1 and R3 can be suppressed.

[0091] Furthermore, in the above Figure 3For ease of explanation, the cross-sectional shape (circular arc shape, convex surface type) of the sliding surface of the sliding bearing 15 described above is not shown in the figure.

[0092] Next, refer to Figure 5 The switching of oil and refrigerant supplied to the segmented intervals R1 and R3 according to the motor speed in the bearing system 200 of this embodiment will be described. Figure 5 (a), (b), and (c) represent one of a pair of sliding bearings 15 in the low-speed rotation region, the medium-speed rotation region, and the high-speed rotation region, respectively. Figure 3 The oil or refrigerant supply status within the sliding bearing 15 shown on the left (i.e., the sliding bearing 15 on the side where the sealing member 18 is provided). Furthermore, in Figure 5 In (a), (b), and (c), the color intensity indicates the viscosity of the fluid (high-viscosity oil is represented by a dark color, and low-viscosity refrigerant is represented by a light color). In addition, "↑" or "↓" indicates that the corresponding fluid is supplied, and "×" indicates that the corresponding fluid supply is stopped.

[0093] First, such as Figure 5 As shown in (a), in the low-speed rotation region of the motor, refrigerant is supplied to the segmented section R2, while oil is supplied to both segmented sections R1 and R3. Thus, in the low-speed rotation region, the load capacity of the sliding bearing 15 is ensured by the oil supplied to segmented sections R1 and R3. In this case, the oil bearing valves 31a and 31b provided in the oil passages 27a and 27b are opened, while the refrigerant bearing valves 32a and 32b provided in the refrigerant passages 22a and 22c are closed to supply oil to both segmented sections R1 and R3.

[0094] Next, as Figure 5 As shown in (b), in the medium-speed rotation region of the motor, refrigerant is supplied to the segmented section R2, oil is supplied to the segmented section R1, and refrigerant is supplied to the segmented section R3. Thus, in the medium-speed rotation region, the oil supplied to the segmented section R1 ensures the load capacity of the sliding bearing 15 to a certain extent, while the refrigerant supplied to the segmented section R3 instead of oil suppresses the increase in resistance in the sliding bearing 15. In this case, the oil bearing valve 31a provided in the oil passage 27a is opened, and the refrigerant bearing valve 32a provided in the refrigerant passage 22a is closed to supply oil to the segmented section R1. Furthermore, the oil bearing valve 31b provided in the oil passage 27b is closed, and the refrigerant bearing valve 32b provided in the refrigerant passage 22c is opened to supply refrigerant to the segmented section R3.

[0095] Next, as Figure 5As shown in (c), in the high-speed rotation region of the motor (especially when the motor speed is very high), refrigerant is supplied to the segmented section R2, and refrigerant is supplied to both segmented sections R1 and R2. Therefore, in the high-speed rotation region, by supplying refrigerant to all segmented sections R1 to R3, the increase in resistance of 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 to supply refrigerant to both segmented sections R1 and R2.

[0096] [Electrical Structure]

[0097] Next, refer to Figure 6 The electrical structure of the bearing system 200 of this embodiment will be described. Figure 6 This is a block diagram showing the electrical structure of the bearing system 200 in this embodiment.

[0098] like Figure 6 As shown, the bearing system 200 has a control device 80 configured to perform various controls within the system. The control device 80 is a computer equipped with one or more processors 80a (typically a CPU) and memory 80b such as ROM and RAM. The memory 80b stores various programs (including basic control programs such as the OS, and application programs that start on the OS and perform specific functions) and various data that are interpreted and executed on the processor 80a.

[0099] In addition, the bearing system 200 includes the aforementioned sensors 51-55 (see reference). Figure 2 In addition to the motor speed sensor 56, which detects the motor speed of the motor 1 (which is the speed of the rotor 11 and the rotating shaft 13, and is synonymous with rotational speed), the vehicle speed sensor 57, which detects the speed of the vehicle 300, the throttle opening sensor 58, which detects the throttle opening corresponding to the amount of accelerator pedal depressing in the vehicle 300, and the brake sensor 59, which detects the operation of the brake pedal in the vehicle 300.

[0100] The control device 80 supplies control signals to the motor 1, compressor 3, flow regulating valve 30, oil bearing valves 31a and 31b, refrigerant bearing valves 32a and 32b, oil pump 38, and oil level warning light 39 based on the detection signals from these sensors 51 to 59. Furthermore, the oil level warning light 39 is used to warn of situations where the oil level (detected by oil level sensor 53) stored in the oil tank 6 is below a specified value.

[0101] In this embodiment, the control device 80 mainly controls the opening and closing of the oil bearing valves 31a and 31b and the refrigerant bearing valves 32a and 32b based on the motor speed detected by the motor speed sensor 56, so as to switch the fluid supplied to the divided intervals R1 and R3 of the sliding bearing 15 between oil and refrigerant. Specifically, the control device 80 selectively performs the following control based on the motor speed: opening the oil bearing valve 31a and closing the refrigerant bearing valve 32a to supply oil to the divided interval R1; closing the oil bearing valve 31a and opening the refrigerant bearing valve 32a to supply refrigerant to the divided interval R1, and selectively performs the following control based on the motor speed: opening the oil bearing valve 31b and closing the refrigerant bearing valve 32b to supply oil to the divided interval R3; closing the oil bearing valve 31b and opening the refrigerant bearing valve 32b to supply refrigerant to the divided interval R3.

[0102] [Control Methods]

[0103] Next, the control performed by the control device 80 of the bearing system 200 in this embodiment will be described in detail. First, refer to... Figure 7 The control process performed by the control device 80 in this embodiment will be explained. Figure 7 This is a timing diagram illustrating the control in this embodiment. Figure 7 In the middle, from top to bottom, the following parameters are represented: motor speed, load based on sliding bearing 15 (equivalent to the viscosity of the fluid inside sliding bearing 15), opening and closing of refrigerant bearing valve 32a, opening and closing of refrigerant bearing valve 32b, opening and closing of oil bearing valve 31a, and time variation of opening and closing of oil bearing valve 31b.

[0104] like Figure 7 As shown, at time t11, the motor speed increases. Consequently, the load that the sliding bearing 15 should bear (hereinafter referred to as the "required load"), determined by the motor speed, decreases from a high load to a medium load. Therefore, at such time t11, in order to suppress the load on the sliding bearing 15, the control device 80 controls the oil bearing valve 31b to close, and on the other hand, opens the refrigerant bearing valve 32b, so that the fluid supplied to the segmented section R3 of the sliding bearing 15 is switched from oil to refrigerant.

[0105] Subsequently, at time t12, the motor speed increases further, thus requiring the load to decrease from medium load to low load. Therefore, at such time t12, in order to further suppress the load on the sliding bearing 15, the control device 80 controls the oil bearing valve 31a to close, and on the other hand, opens the refrigerant bearing valve 32a to switch the fluid supplied to the segmented section R1 of the sliding bearing 15 from oil to refrigerant.

[0106] Next, refer to Figure 8 A flowchart illustrating the specific control process of this embodiment will be described. This process is repeatedly executed by the control device 80 at a predetermined cycle. Specifically, the processor 80a within the control device 80 reads and executes a program stored in the memory 80b, thereby implementing the control involved in this process.

[0107] First, in step S10, the control device 80 acquires data from the aforementioned sensors 51 to 59. Figure 6 The system detects various information, including the detected values. Then, the control device 80 proceeds to step S11 to determine whether the oil level detected by the oil level sensor 53 is above the specified value. As a result, if the control device 80 does not determine that the oil level is above the specified value (step S11: no), that is, if the oil level is below the specified value, the system proceeds to step S12 and illuminates the oil level warning light 39.

[0108] In contrast, if the control device 80 determines in step S11 that the oil level is above a specified value (step S11: Yes), it proceeds to step S13. In step S13, the control device 80 determines whether the motor 1 is stopped based on the motor speed detected by the motor speed sensor 56, etc. As a result, if the control device 80 determines that the motor 1 is stopped (step S13: Yes), it proceeds to step S14, and determines whether there is a motor starting requirement based on the throttle opening detected by the vehicle 300's start switch, throttle opening sensor 58, etc. As a result, if the control device 80 determines that there is a motor starting requirement (step S14: Yes), it proceeds to step S15; on the other hand, if it does not determine that there is a motor starting requirement (step S14: No), the control involved in this process ends.

[0109] In step S15, to ensure the load on the sliding bearing 15 before starting the motor 1, 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 the divided sections R1 and R3 of the sliding bearing 15. Then, the control device 80 proceeds to step S16 to start the motor 1, and then proceeds to step S17 to control the speed of the compressor 3.

[0110] On the other hand, in step S13, if the control device 80 does not determine that the motor 1 is stopped (step S13: No), that is, if the motor 1 is already working, it proceeds to step S18. In step S18, the control device 80 calculates the target motor speed based on the throttle opening detected by the throttle opening sensor 58, and determines whether the target motor speed has changed. As a result, if the control device 80 determines that the target motor speed has changed (step S18: Yes), it proceeds to step S19; otherwise, if it does not determine that the target motor speed has changed (step S18: No), it does not perform the processing of steps S19 to S23 and proceeds to the aforementioned step S17.

[0111] In step S19, the control device 80 calculates the required load of the sliding bearing 15 based on the motor speed detected by the motor speed sensor 56, and determines whether the required load is a low load. In this case, when the motor speed is in the high-speed rotation range (especially when the motor speed is very high), the required load is a low load. As a result of step S19, if the control device 80 determines that the required load is a low load (step S19: Yes), it proceeds to step S20. In this case, the control device 80 closes the oil bearing valves 31a and 31b, and on the other hand, opens 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.

[0112] In contrast, if the control device 80 does not determine in step S19 that the required load is a low load (step S19: No), it proceeds to step S21. In step S21, the control device 80 determines whether the required load is a medium load. In this case, when the motor speed is in the medium speed rotation range, the required load is a medium load. As a result of step S21, if the control device 80 determines that the required 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 and closes the refrigerant bearing valve 32a to supply oil to the segmented section R1 of the sliding bearing 15. Additionally, it closes the oil bearing valve 31b and opens the refrigerant bearing valve 32b to supply refrigerant to the segmented section R3 of the sliding bearing 15. Then, the control device 80 proceeds to step S17 as described above.

[0113] In contrast, if the control device 80 does not determine in step S21 that a medium load is required (step S21: No), that is, a high load is required, it proceeds to step S23. When the motor speed is in the low-speed rotation range, a high load is required. In this case, 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. Then, the control device 80 proceeds to step S17 as described above.

[0114] In addition, in steps S19 and S21, the control device 80 determines the required load of the sliding bearing 15, but in other examples, the motor speed can be determined instead of the required load.

[0115] [Functions and Effects]

[0116] Next, the function and effects of the bearing system 200 in this embodiment will be explained.

[0117] In this embodiment, the bearing system 200 includes: a sliding bearing 15, which is lubricated by oil and refrigerant (CO2 refrigerant) and supports a 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, which is axially separated from the oil passages 27a and 27b and is used to supply refrigerant to a second region of the sliding surface that is different from the first region, wherein 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.

[0118] According to this embodiment, in the sliding bearing 15, the inner diameter of the second region supplying low-viscosity refrigerant is smaller than the inner diameter of the first region supplying high-viscosity oil. Therefore, the clearance 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. As a result, since the clearance in the second region where refrigerant is supplied is smaller, the load-bearing capacity of the refrigerant in the second region can be ensured. On the other hand, since the clearance in the first region where oil is supplied is larger, the increase in oil resistance in the first region can be suppressed. Therefore, according to this embodiment, in the sliding bearing 15 using high-viscosity oil and low-viscosity refrigerant, load-bearing capacity can be ensured without increasing resistance. Therefore, when using low-viscosity refrigerant, it is possible to prevent the rotating shaft 13 from wobbling radially and increasing useless resistance.

[0119] Furthermore, according to this embodiment, the sliding bearing 15 is configured such that the inner diameter of the sliding surface continuously varies axially in such a way that the inner diameter of the second region is smaller than the inner diameter of the first region. Therefore, the gap between the sliding surface of the sliding bearing 15 and the rotating shaft 13 of the motor 1 continuously varies axially, thus enabling uniform surface pressure applied to the sliding surface.

[0120] In particular, according to this embodiment, since the cross-section of the sliding surface of the sliding bearing 15 viewed along the axial direction is formed as an arc (i.e. formed as a convex surface), the surface pressure applied to the sliding surface can be effectively made uniform.

[0121] Furthermore, according to this embodiment, a pair of sliding bearings 15 are provided to support the rotating shaft 13. Each pair of sliding bearings 15 is configured such that it has a first region at both ends in the axial direction and a second region in the middle portion (especially the central portion) between the two ends in the axial direction. That is, in this embodiment, high-viscosity oil is supplied to the two ends in the axial direction, while low-viscosity refrigerant is supplied to the middle portion in the axial direction. In this way, by distributing the portions supplying high-viscosity oil and low-viscosity refrigerant in the axial direction of the sliding bearings 15, the load capacity (especially the refrigerant load capacity) of the sliding bearings 15 can be effectively ensured.

[0122] 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 respectively disposed in oil passages 27a and 27b and refrigerant passages 22a and 22c; 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 to switch the fluid supplied to the first region between oil and refrigerant. Thus, by selectively supplying refrigerant to the first region instead of oil, the increase in resistance caused by the application of oil in the sliding bearing 15 can be effectively suppressed.

[0123] Furthermore, according to this embodiment, the control device 80 is configured to selectively control the following based on the motor speed: opening the oil bearing valve 31a and closing the refrigerant bearing valve 32a, and / or opening the oil bearing valve 31b and closing the refrigerant bearing valve 32b, to supply oil to the first region; closing the oil bearing valve 31a and opening the refrigerant bearing valve 32a, and / or closing the oil bearing valve 31b and opening the refrigerant bearing valve 32b, to supply refrigerant to the first region. Thus, by switching the fluid supplied to the first region between oil and refrigerant based on the motor speed, both ensuring load capacity in the low-speed rotation region and reducing resistance in the high-speed rotation region can be reliably achieved.

[0124] Furthermore, according to this embodiment, the sliding bearing 15 has a groove 15a formed on the sliding surface and extending radially and circumferentially. The sliding surface of the sliding bearing 15 is divided into a plurality of segmented intervals R1 to R3 in the axial direction by the groove 15a. In addition, the sliding bearing 15 also has a discharge hole 15b formed on the groove 15a for discharging fluid from the sliding bearing 15. The first region and the second region are defined by the segmented intervals R1 to R3 divided by the groove 15a.

[0125] In this embodiment, the fluid (oil or refrigerant) within each segmented section R1 to R3 flows out from the discharge port 15b via the groove 15a that defines each segmented section R1 to R3, thereby preventing the fluid from mixing in adjacent segmented sections R1 to R3. Therefore, mixing of the fluid between the first and second regions defined by the segmented sections R1 to R3 can be prevented. Thus, according to this embodiment, the load capacity of the sliding bearing 15 can be effectively ensured and resistance reduced.

[0126] [Variation Example]

[0127] In the above embodiment, both ends of the sliding bearing 15 in the axial direction (corresponding to the segmented intervals R1 and R3) have a first region where oil is supplied. However, in a modified embodiment, only one of the two ends in the axial direction (either of the segmented intervals R1 and R3) may have a first region.

[0128] In addition, in the above embodiment, three segmented intervals R1 to R3 are formed by two grooves 15a in the sliding bearing 15. However, in the modified example, two segmented intervals may be formed by one groove 15a, or four or more segmented intervals may be formed by three or more grooves 15a.

[0129] In addition, in the above embodiments, oil and CO2 (CO2 refrigerant) were used as fluids with different viscosities (first fluid and second fluid), but various fluids other than oil and CO2 can also be used.

Claims

1. A bearing system, characterized by have: A sliding bearing, which is lubricated by a first fluid and a second fluid with a lower viscosity than the first fluid, and supports a rotating shaft; A first passage is provided for supplying the first fluid to a first region of the sliding surface of the sliding bearing; as well as A second passage, which is axially separated from the first passage, is used to supply the second fluid to a second region on the sliding surface that is different from the first region. 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, characterized in that, The sliding bearing is configured such that the inner diameter of the sliding surface continuously varies axially in such a way that the inner diameter of the second region is smaller than the inner diameter of the first region.

3. The bearing system according to claim 2, characterized in that, The cross-section of the sliding surface of the sliding bearing, viewed axially, is arc-shaped.

4. The bearing system according to claim 1, characterized in that, The sliding bearings are provided in a pair to support the rotating shaft. Each pair of sliding bearings is configured such that one or both of the two end portions in the axial direction have the first region, and the middle portion between the two end portions in the axial direction has the second region.

5. The bearing system according to claim 1, characterized in that, The bearing system also has: A third passage is used to supply the second fluid to the first region; A first valve and a second valve are respectively disposed in the first passage and the third passage; as well as 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.

6. The bearing system according to claim 5, characterized in that, The control device is configured to selectively control, based on the rotational speed of the rotating shaft, the following: opening the first valve and closing the second valve to supply the first fluid to the first region; and closing the first valve and opening the second valve to supply the second fluid to the first region.

7. The bearing system according to claim 1, characterized in that, The sliding bearing also has: A groove is formed on the sliding surface and extends radially and circumferentially, and is configured to divide the sliding surface into multiple sections in the axial direction through the groove; as well as A discharge port, formed in the groove, is provided for discharging the first fluid and the second fluid from the sliding bearing. The first region and the second region are respectively defined by the intervals cut out by the groove.

8. The bearing system according to any one of claims 1 to 7, characterized in that, The first fluid is oil, and the second fluid is CO2.

9. The bearing system according to claim 8, characterized in that, It is configured such that the rotating shaft of the motor is supported by the sliding bearing.

Images