Motor system

Abstract

To provide a motor system with improved wear resistance of the bearing portion during rotational starting and stopping. [Solution] The motor system S includes a control device 10 configured to adjust the mixing ratio Rmix of CO2 fluid and lubricating oil by a flow control valve 87 according to the rotation speed r of the rotating shaft 13 detected by a rotation sensor 17. The control device 10 controls the flow control valve 87 to supply both CO2 fluid and lubricating oil to the sliding bearing 20 in the start-stop section R1 where the rotation speed r is less than a predetermined set rotation speed rs.

Description

Technical Field

[0001] The present invention relates to a motor system, and particularly to a motor system having a sliding bearing.

Background Art

[0002] Conventionally, a sliding bearing that supports a rotating shaft and lubricates using lubricating oil reduces the sliding resistance between the rotating shaft and the sliding bearing by means of a lubricating film (oil film) formed by the lubricating oil. In such a bearing structure, particularly, a sliding bearing for suppressing an increase in sliding resistance in a low-temperature environment has been proposed (see, for example, Patent Document 1).

[0003] In the sliding bearing of Patent Document 1, the surface structure (the structure of the sliding surface) of the sliding bearing is configured so as to suppress the conduction of frictional heat generated by the sliding between the rotating shaft and the sliding bearing at the start-up to the rotating shaft body. Therefore, in the sliding bearing of Patent Document 1, since it is possible to lower the viscosity of the lubricating oil by frictional heat, a reduction in sliding resistance at the start-up is expected.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the present inventor has found that when a sliding bearing such as that of Patent Document 1 is applied to the rotor rotating shaft of an electric motor, a lubricating film of sufficient thickness is not formed between the rotating shaft and the sliding bearing at the start-stop of the electric motor (particularly in the extremely low speed range), and there is a risk that the rotating shaft and the sliding bearing come into contact and the bearing portion wears.

[0006] Such wear leads to increased bearing clearance, the generation of abnormal noise, and a decrease in electromagnetic efficiency. To suppress such wear, it is conceivable to supply a large amount of lubricating oil to the sliding bearing from an external source. However, if configured in this way, the lubricating oil will scatter from the bearing into the motor, resulting in an increased stirring resistance during motor operation.

[0007] This invention was made to solve the problems of the prior art described above, and aims to provide a motor system that improves the wear resistance of the bearing portion during rotational starting and stopping. [Means for solving the problem]

[0008] To achieve the above objective, the motor system of the present invention comprises a sliding bearing that supports the rotating shaft of a rotating body; a rotation sensor for detecting the rotational speed of the rotating shaft; a supply unit that supplies CO2 fluid and lubricating oil constituting a refrigerant to the sliding bearing, respectively; a flow control valve having a first control valve provided in a first flow passage that supplies CO2 fluid from the supply unit to the sliding bearing, and a second control valve provided in a second flow passage that supplies lubricating oil from the supply unit to the sliding bearing; and a control device configured to adjust the mixing ratio of CO2 fluid and lubricating oil by the flow control valve according to the rotational speed of the rotating shaft detected by the rotation sensor, wherein the control device controls the flow control valve to supply both CO2 fluid and lubricating oil to the sliding bearing in a start-stop section where the rotational speed is less than a predetermined set rotational speed.

[0009] In the present invention configured as described above, both CO2 fluid and lubricating oil are supplied to the sliding bearing during the extremely low-speed range when the rotating shaft starts and stops (specifically, the start-stop interval where the rotational speed is less than the set rotational speed). This configuration promotes the formation of a wear-resistant chemical reaction film on the sliding surfaces of the rotating shaft and / or sliding bearing through surface reactions caused by friction, thereby improving the wear resistance of the rotating shaft and sliding bearing, which are the bearing parts, especially in the low-speed range.

[0010] Furthermore, in the present invention, preferably, the set rotational speed corresponds to the rotational speed at which the sliding bearing and the rotating shaft begin to make direct contact as the rotational speed of the rotating shaft decreases while lubricating oil is supplied. With the present invention configured in this way, the formation of a chemical reaction film can be promoted in the rotational speed range in which direct contact between the sliding bearing and the rotating shaft can occur.

[0011] Furthermore, in the present invention, preferably, the control device controls the flow control valve in the transition interval between a first rotational speed (where the rotational speed is greater than zero and less than the set rotational speed) and the set rotational speed, such that the mixing ratio of the CO2 fluid in the refrigerant decreases as the rotational speed increases. With the present invention configured in this way, the risk of inhibiting the formation of a chemical reaction film can be reduced by gradually changing the mixing ratio in the transition interval.

[0012] Furthermore, in the present invention, preferably, the control device controls the flow control valve to set the mixing ratio of CO2 fluid in the refrigerant to zero when the rotational speed is set to a set rotational speed. With the present invention configured in this way, wear of the bearing can be suppressed by the oil film of lubricating oil, at least when the rotational speed is set to a set rotational speed.

[0013] Furthermore, in the present invention, preferably, the control device controls the flow control valve such that, in the operating section where the rotational speed is greater than the set rotational speed, the mixing ratio of CO2 fluid in the refrigerant increases as the rotational speed increases. With the present invention configured in this way, once the rotational speed is greater than the set rotational speed and the system transitions from the start / stop state to the operating state, the sliding bearings are lubricated by the CO2 fluid rather than the lubricating oil. As a result, the present invention can maintain good lubrication while suppressing stirring resistance caused by the scattering of lubricating oil onto the rotating body.

[0014] Furthermore, in the present invention, preferably, the control device maintains the mixing ratio of CO2 fluid in the refrigerant to zero in the low-speed rotation section between the set rotation speed and a second rotation speed greater than the set rotation speed. With the present invention configured in this way, wear of the bearing can be suppressed in the low-speed rotation section by the oil film of the lubricating oil.

[0015] Furthermore, in the present invention, preferably, the first and second flow passages merge before reaching the sliding bearing, supplying CO2 fluid and lubricating oil to the sliding bearing. With the present invention configured in this way, the refrigerant can be supplied to the sliding bearing in a state where the CO2 fluid and lubricating oil are mixed in a predetermined mixing ratio.

[0016] Furthermore, in the present invention, preferably, the first and second flow passages are configured to supply CO2 fluid and lubricating oil independently to the sliding bearing, respectively. With the present invention configured in this way, after supplying the CO2 fluid and lubricating oil separately to the sliding bearing 20, the CO2 fluid and lubricating oil can be mixed within the sliding bearing.

[0017] Furthermore, in the present invention, the rotating body is preferably the rotor of an electric motor. With the present invention configured in this way, it is possible to lubricate the sliding bearings of the electric motor with a coolant and to cool the inside of the electric motor, which generates heat during operation. [Effects of the Invention]

[0018] According to the motor system of the present invention, it is possible to provide a motor system that suppresses the increase in stirring resistance and improves the wear resistance of the bearing portion during rotational starting and stopping. [Brief explanation of the drawing]

[0019] [Figure 1] This is a schematic diagram of a motor system according to an embodiment of the present invention. [Figure 2] This is a diagram showing the electrical block configuration of a motor system according to an embodiment of the present invention. [Figure 3]A graph showing the mixing ratio of the CO2 fluid according to an embodiment of the present invention. [Figure 4] An explanatory diagram of the lubricating coating according to an embodiment of the present invention. [Figure 5] An explanatory diagram showing the relationship between the relative speed and the oil film thickness according to an embodiment of the present invention. [Figure 6] A graph showing the relationship between the rotational speed and the oil film thickness in the sliding part according to an embodiment of the present invention. [Figure 7] A control flow of the motor system according to an embodiment of the present invention. [Figure 8] A partial configuration diagram of the motor system according to another embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0020] Hereinafter, a motor system according to an embodiment of the present invention will be described with reference to the accompanying drawings. [Overall Configuration] First, referring to FIG. 1, the overall configuration of the motor system (bearing device) according to the present embodiment will be described. FIG. 1 is a schematic configuration diagram of the motor system according to the present embodiment. The motor system S shown in FIG. 1 is mounted on a vehicle such as an electric vehicle, for example, and can provide a rotational driving force to the vehicle.

[0021] In the present embodiment, in the extremely low-speed rotation range (start-stop section R1; see FIG. 3) at the start and stop of the motor, a reaction film is formed on the sliding surface of the rotor shaft to improve wear resistance. That is, in the present embodiment, in addition to lubricating oil, a CO2 fluid is supplied to the bearing portion, and a film (such as a carbonate film) having wear resistance is formed on the sliding surface by utilizing the surface reaction due to friction.

[0022] The motor system S comprises an electric motor 1, a refrigerant circulation system 8, and a control device 10. The electric motor 1 provides rotational driving force to the vehicle. The refrigerant circulation system 8 is configured to circulate refrigerant R in a refrigeration cycle and cool the electric motor 1. In other words, in this refrigeration cycle, the expansion and evaporation strokes of refrigerant R are performed in the electric motor 1, and the compression and condensation strokes of refrigerant R are performed in the refrigerant circulation system 8.

[0023] In this embodiment, the electric motor 1 is an ultra-high-speed rotating motor capable of operating at high rotational speeds exceeding, for example, 30,000 rpm, and is configured to operate in the high-speed rotation section RH (see Figure 3) during normal operation. The refrigerant R is a mixture of a natural refrigerant CO2 fluid and a lubricating oil (e.g., PAG oil), but in the high-speed rotation section RH, the bearing 20 is configured to be lubricated only by the CO2 fluid.

[0024] [Refrigerant circulation system configuration] The refrigerant circulation system 8 includes a compressor 81 for compressing the refrigerant R, a heat exchanger (condenser) 83 including a condenser and fan for cooling the refrigerant R compressed by the compressor 81, a gas-liquid separator 85 for separating the refrigerant R discharged from the heat exchanger 83 into gas (CO2 fluid) and liquid (lubricating oil), flow control valves 87 (first control valve V1, second control valve V2) for adjusting the flow rates of the CO2 fluid and lubricating oil respectively, and a flow passage 88 connecting these. Downstream of the gas-liquid separator 85, the flow passage 88 divides into two passages (first flow passage 88a where the first control valve V1 is located, and second flow passage 88b where the second control valve V2 is located), and each is connected to an electric motor 1. The electric motor 1 is incorporated into the refrigerant circulation system 8. In this embodiment, the compressor 81, heat exchanger 83, and gas-liquid separator 85 constitute the refrigerant R supply section 80.

[0025] [Motor Configuration] The electric motor 1 according to this embodiment includes a rotor (rotating body) 11, a stator 12, a rotor shaft (rotating shaft) 13 fixed to the rotor 11 and extending in the axial direction, a pair of bearings (sliding bearings) 20 that rotatably support the rotor shaft 13, a housing 15 that houses and supports the rotor 11, stator 12, rotor shaft 13, and bearings 20, a sealing member 16 that seals the space between the housing 15 and the rotor shaft 13 and prevents leakage of refrigerant R from the inside of the housing 15 to the outside, and a rotation sensor 17 that detects the rotational speed of the rotor shaft 13. One end of the rotor shaft 13 is connected to a vehicle transaxle (not shown) or the like.

[0026] The roughly cylindrical stator 12 is constructed by winding coils around a stator core. The rotor 11 has a rotor core and a plurality of permanent magnets attached to the rotor core. The rotor shaft 13 is fixed to the rotor core. The rotor 11 is configured to rotate within the stator 12 with the rotor shaft 13 as its axis of rotation.

[0027] Furthermore, the electric motor 1 also has refrigerant supply passages 18a and 18b that supply refrigerant R supplied from the refrigerant circulation system 8 to the bearing 20, and a refrigerant discharge passage 19 that returns the refrigerant R from inside the electric motor 1 to the refrigerant circulation system 8. The refrigerant supply passages 18a and 18b are parts of the first passage 88a and the second passage 88b, respectively.

[0028] In detail, the refrigerant supply passages 18a and 18b supply CO2 fluid and lubricating oil, respectively, to the gap between the rotor shaft 13 and the bearing 20. This supplies the refrigerant R to the sliding surfaces of the rotor shaft 13 and the bearing 20 for lubrication. In this embodiment, the CO2 fluid supplied to the bearing 20 is a high-pressure gas or supercritical fluid. The CO2 fluid and lubricating oil used as lubricants exit the bearing 20, enter the housing 15, exchange heat with the motor components, and then return to the refrigerant circulation system 8 through the refrigerant discharge passage 19.

[0029] [Refrigerant refrigeration cycle] In this embodiment, the compressor 81 receives high-temperature, low-pressure refrigerant R from the electric motor 1, compresses the received refrigerant R, and discharges high-temperature, high-pressure refrigerant R. Next, the heat exchanger 83 performs heat exchange between the high-temperature, high-pressure refrigerant R and the external environment (cold air, cooling water, etc.) to generate medium-temperature, high-pressure refrigerant R. The medium-temperature, high-pressure refrigerant R is supplied to the bearing 20 of the electric motor 1 and lubricates the bearing 20. The refrigerant R that has lubricated the bearing 20 expands as it enters the internal space of the housing 15, becoming low-temperature, low-pressure refrigerant R. Furthermore, the low-temperature, low-pressure refrigerant R exchanges heat with the high-temperature part of the electric motor 1 within the housing 15, becoming high-temperature, low-pressure refrigerant R. This high-temperature, low-pressure refrigerant R is returned to the compressor 81.

[0030] [Bearing structure] The bearing 20 rotatably supports the end of the rotor shaft 13. The bearing 20 has a substantially cylindrical body made of a metal material such as iron, and comprises a sliding surface which is the inner circumferential surface of the body and an outer circumferential surface of the body. The sliding surface supports the rotor shaft 13. The body also has through holes formed therein that penetrate the side wall from the outer circumferential surface and communicate with the sliding surface. The through holes communicate with the refrigerant supply flow passages 18a and 18b, respectively, and form part of the refrigerant supply flow passages 18a and 18b.

[0031] [Electrical Block Diagram] Figure 2 is an electrical block diagram of the motor system. The control device 10 is a computer equipped with a processor, memory, etc. It receives a rotation signal from the rotation sensor 17 installed in the motor system S and outputs a valve opening signal to the flow control valve 87. Specifically, the control device 10 outputs a valve opening signal according to the rotation speed r (rpm) of the electric motor 1 and adjusts the valve openings of the first control valve V1 and the second control valve V2 to control the mixing ratio Rmix of CO2 fluid and lubricating oil in the refrigerant R supplied to the bearing 20, as well as the flow rate.

[0032] Furthermore, the control device 10 can be configured to receive signals (such as refrigerant temperature, refrigerant pressure, refrigerant flow rate, and stator temperature) from other sensors (not shown) provided in the motor system S, and to output operating signals to each component of the refrigerant circulation system 8, as well as to solenoid valves, electromagnets, etc.

[0033] [Outline of flow rate control] Next, the flow rate adjustment control by the control device 10 will be described with reference to Figure 3. Figure 3 shows the relationship between the rotational speed r and the mixing ratio Rmix of the CO2 fluid in the refrigerant R. In this embodiment, the control device 10 stores the flow rate adjustment data shown in Figure 3 in its memory. Based on this data, the control device 10 is configured to adjust the mixing ratio Rmix (e.g., weight ratio) of the CO2 fluid in the refrigerant R supplied to the bearing 20 according to the rotational speed r.

[0034] In this embodiment, the electric motor 1 is configured to operate within a rotational speed range that includes a start-stop section R1 (0 to rs) and an operating section R2 (r2 onwards). In this embodiment, the mixing ratio of the CO2 fluid in the refrigerant R supplied to the bearing 20 is controlled to differ depending on the rotational speed.

[0035] Within the operating section R2, particularly in the high-speed rotation section RH from the third rotational speed r3 (e.g., 10,000 rpm) to the fourth rotational speed r4 (e.g., 30,000 rpm or higher), the mixing ratio of CO2 fluid is set to 100%. In other words, the electric motor 1 of this embodiment is configured such that the bearing 20 is lubricated only with CO2 fluid in a predetermined rotational speed range (high-speed rotation section RH).

[0036] Furthermore, within the operating section R2, in the medium-speed rotation section RM from a predetermined second rotational speed r2 (for example, 200-800 rpm) to the third rotational speed r3, the lower the rotational speed r, the smaller the mixing ratio of CO2 fluid in the refrigerant R becomes, reaching 0% at the second rotational speed r2. In this embodiment, the medium-speed rotation section RM is the transition section until the rotational speed r of the electric motor 1 reaches the high-speed rotation section RH.

[0037] Furthermore, within the operating section R2, in the low-speed rotation section RL from the set rotational speed rs (e.g., 100 rpm) to the second rotational speed r2 (r2 > rs), the mixing ratio of CO2 fluid in the refrigerant R is maintained at 0%, and only lubricating oil is supplied to the bearing 20.

[0038] In addition, in the low-speed rotation range RL, the mixing ratio of the CO2 fluid in the refrigerant R is preferably 0%, but is not limited thereto. For example, it may be set to a low mixing ratio within the range of 0% to 20%. When the mixing ratio is greater than 0%, as described with reference to FIG. 6, the set rotation speed rs corresponding to 3σ is set to a larger value.

[0039] Further, in the present embodiment, in the start-stop interval R1, the refrigerant R containing the CO2 fluid in addition to the lubricating oil is supplied to the bearing 20. Specifically, in the transition interval RT from a predetermined first rotation speed r1 to the set rotation speed rs (r1 < rs) in the start-stop interval R1, as the rotation speed r is lower, the mixing ratio of the CO2 fluid in the refrigerant R becomes larger, and becomes a predetermined set mixing ratio Ra (for example, 50%) at the first rotation speed r1. Further, in the reaction film formation interval RF from zero to the first rotation speed r1 in the start-stop interval R1, the set mixing ratio Ra is maintained. Thus, in the present embodiment, in the start-stop interval R1 of extremely low rotation speeds immediately after starting and immediately before stopping of the electric motor 1, both the lubricating oil and the CO2 fluid are supplied to the bearing 20 as the refrigerant R. In the present embodiment, in order to smoothly transition the mixing ratio between the set mixing ratio Ra and zero in the transition interval RT, the first rotation speed r1 is set to a value obtained by multiplying the set rotation speed rs by a coefficient of 0.6 to 0.9.

[0040] [Lubricating coating] Next, referring to FIGS. 4 to 6, the lubricating film (oil film) formed between two solid elements will be described. FIG. 4 shows a state in which an oil film M with a film thickness h of lubricating oil is formed between the sliding surfaces of two solid elements (in the present embodiment, the rotor shaft 13 and the bearing 20). These sliding surfaces each have a predetermined surface roughness. FIG. 4 schematically shows the normal probability density distribution of these surface roughnesses, and the standard deviations of the surface roughnesses are σ1 and σ2, respectively.

[0041] Figure 5, based on Figure 4, shows the relationship between the lubricating film M formed between two solid elements and the relative velocity VL between the two solid elements. Similar to Figure 4, Figure 5 also shows the normal probability density distribution of surface roughness. Figure 5(a) shows the dry friction state that occurs at extremely low relative velocities, where there is no fluid (lubricant) on the friction surface (sliding surface), contact occurs between the solid elements, and the coefficient of friction is high. Next, Figure 5(b) shows the boundary lubrication state that occurs at low relative velocities, where a small amount of fluid is present on the friction surface, and the coefficient of friction remains high.

[0042] Next, Figure 5(c) shows the mixed lubrication state that occurs at relatively low relative velocities, where a certain amount of fluid is present on the friction surface and the coefficient of friction is low. Next, Figure 5(d) shows the fluid lubrication state that occurs at sufficiently high relative velocities, where the friction surface is filled with fluid, there is no contact between solid elements, and the coefficient of friction is low. Thus, at high relative velocities, an oil film M with sufficient thickness is formed, preventing direct contact between solid elements. On the other hand, at low relative velocities, an oil film M with sufficient thickness is not formed, and contact between solid elements occurs.

[0043] Generally, it is known that film thickness h is inversely proportional to load W and proportional to velocity U and viscosity G, which can be expressed mathematically, for example, by Dowson-Higginson equation 1. This equation can be expressed, for example, h=2.922W -0.166 U 0.692 G 0.470 (Formula 1) It can be done this way.

[0044] Figure 6 shows the relationship between the thickness h of the lubricating film formed between the rotor shaft 13 and the bearing 20 and the rotational speed r (rpm), calculated to suit this embodiment based on Equation 1 above. Figure 6 shows the relationship for different mixing ratios of CO2 fluid in the refrigerant R (when the CO2 fluid is 0%, 20%, 40%, 60%, and 80%). When the CO2 fluid is 0%, the lubricating oil is 100%. As shown in Figure 6, the thickness h of the oil film increases with increasing rotational speed.

[0045] The inventors have found that, considering the surface roughness of the two solid elements (rotor shaft 13 and bearing 20), the transition interval from fluid lubrication to mixed lubrication corresponds when the oil film thickness h is three times the combined standard deviation σ of the surface roughness of the two solid elements. That is, when the film thickness h becomes less than 3σ, the friction coefficient between the two solid elements begins to shift from a low state to a high state (i.e., the two solid elements begin to come into direct contact).

[0046] When the standard deviations of the surface roughness of two solid elements are σ1 and σ2, respectively, their combined standard deviation σ is: It is represented as JPEG2026077148000002.jpg1135.

[0047] Therefore, in this embodiment, the rotational speed at which h=3σ in the graph of Figure 6 is set to the set rotational speed rs. As shown in Figure 3, in the low-speed rotation section RL (rs~r2), the refrigerant R supplied to the bearing 20 contains only lubricating oil, but since the film thickness h is at least 3σ or greater (h>3σ), wear is unlikely to occur between the rotor shaft 13 and the bearing 20. In addition, in this embodiment, even in the other sections RM and RH within the operating section R2, the refrigerant R contains CO2 fluid, but wear is unlikely to occur. On the other hand, in the start-stop section R1 (0~rs), the film thickness h is less than 3σ, so there is a risk of wear occurring due to direct contact between solid elements.

[0048] Furthermore, the set rotational speed rs may be set experimentally, not limited to the above. In this case, for example, the set rotational speed rs may be set to the rotational speed at which the rotational resistance increases as the rotational speed of the rotor shaft 13 is decreased. Alternatively, the physical contact between the rotor shaft 13 and the bearing 20 may be observed, and the set rotational speed rs may be set to the rotational speed at which physical contact begins to occur.

[0049] Thus, contact between solid elements can occur in the start-stop section R1. However, the inventors have found that it is possible to impart wear resistance to solid elements (rotor shaft 13 and / or bearing 20) by utilizing a chemical reaction film. This chemical reaction film (e.g., tribo-reaction film) is a strong film (e.g., iron carbonate FeCO3) that is formed on the surface of various materials (steel, etc.) due to interactions such as friction in the presence of a CO2 fluid and lubricating oil. For the formation of the chemical reaction film, it is preferable that lubricating oil is present in addition to the CO2 fluid. At least one of the rotor shaft 13 and the bearing 20 contains a material (Fe, etc.) that is a component of the chemical reaction film.

[0050] Therefore, in this embodiment, in the start-stop section R1, in the reaction film formation section RF (0~r1), a refrigerant R containing CO2 fluid in a set mixing ratio Ra in addition to lubricating oil is supplied to the bearing 20 to form a chemical reaction film on the sliding surfaces of the two solid elements, thereby improving wear resistance. In other words, in this embodiment, in the range of rotational speeds in which contact between solid elements can occur, wear of the solid elements can be suppressed by bringing the solid elements into contact via the chemical reaction film.

[0051] Furthermore, in this embodiment, in the transition section RT (r1 to rs), the larger the rotational speed r, the lower the mixing ratio Rmix of the CO2 fluid, and at the set rotational speed rs, a refrigerant R consisting only of lubricating oil is supplied to the bearing 20. A chemical reaction film is also formed in this transition section RT.

[0052] In this embodiment, the set mixing ratio Ra is selected to promote the formation of a chemical reaction film in the start-stop section R1. That is, supplying more CO2 fluid to the sliding surface is advantageous for the formation of a chemical reaction film, but if CO2 fluid that cannot dissolve in the lubricating oil is supplied to the sliding surface, the formation of the chemical reaction film may be inhibited. For this reason, the set mixing ratio Ra of lubricating oil and CO2 fluid is determined based on the set supply temperature of the refrigerant R, using known data such as a predetermined Daniel chart or a two-phase separation temperature diagram, so as to be a miscible mixing ratio.

[0053] [Processing flow] Next, the processing flow of the motor system S will be explained with reference to Figure 7. When the electric motor 1 is operating, the control device 10 continuously repeats the processing shown in Figure 7. When processing begins, the control device 10 detects the rotational speed (rpm) of the rotor shaft 13 based on the rotational signal received from the rotation sensor 17 (S1). Next, based on the detected rotational speed, the control device 10 uses the flow rate adjustment data stored in memory (see Figure 3) to determine the mixing ratio Rmix of the refrigerant R CO2 fluid, and determines the valve opening degree of the flow control valve 87 to achieve this mixing ratio (S2). Specifically, the valve opening degrees of the first control valve V1 and the second control valve V2 are set to achieve the determined mixing ratio Rmix.

[0054] Next, the control device 10 outputs valve opening signals to the first control valve V1 and the second control valve V2, respectively, so that the valve opening is determined (S3), and then terminates the process. As a result, the first control valve V1 and the second control valve V2 supply CO2 fluid and lubricating oil to the bearing 20 at a flow rate corresponding to the desired valve opening.

[0055] In the above embodiment, the refrigerant supply passage 18a from the first control valve V1 and the refrigerant supply passage 18b from the second control valve V2 are each connected to the through-hole of the bearing 20. However, they may also be configured as shown in Figure 8. That is, the first passage 88a and the second passage 88b (or the refrigerant supply passage 18a and the refrigerant supply passage 18b) can merge, and the merged refrigerant supply passage 18c can then be connected to the through-hole provided in the bearing 20.

[0056] [Mechanism of Action and Effects] Next, the operation and effects of the motor system S according to this embodiment will be described. The motor system S according to this embodiment comprises a sliding bearing 20 supporting the rotating shaft 13 of a rotating body 11, a rotation sensor 17 for detecting the rotational speed r of the rotating shaft 13, a supply unit 80 that supplies CO2 fluid and lubricating oil constituting the refrigerant R to the sliding bearing 20, a flow control valve 87 having a first control valve V1 provided in a first flow passage 88a that supplies CO2 fluid from the supply unit 80 to the sliding bearing 20, and a second control valve V2 provided in a second flow passage 88b that supplies lubricating oil from the supply unit 80 to the sliding bearing 20, and a control device 10 configured to adjust the mixing ratio Rmix of CO2 fluid and lubricating oil by the flow control valve 87 according to the rotational speed r of the rotating shaft 13 detected by the rotation sensor 17, wherein the control device 10 controls the flow control valve 87 to supply both CO2 fluid and lubricating oil to the sliding bearing 20 in a start-stop section R1 where the rotational speed r is less than a predetermined set rotational speed rs.

[0057] In this embodiment, both CO2 fluid and lubricating oil are supplied to the sliding bearing 20 during the extremely low-speed range when the rotating shaft 13 starts and stops rotating (specifically, the start-stop interval R1 where the rotational speed r is less than the set rotational speed rs). This configuration promotes the formation of a wear-resistant chemical reaction film on the sliding surfaces of the rotating shaft 13 and / or the sliding bearing 20 through surface reactions caused by friction, thereby improving the wear resistance of the bearing portion, the rotating shaft 13 and the sliding bearing 20, especially in the low-speed range.

[0058] Furthermore, according to this embodiment, the set rotational speed rs corresponds to the rotational speed at which the sliding bearing 20 and the rotating shaft 13 begin to make direct contact as the rotational speed r of the rotating shaft 13 decreases while lubricating oil is supplied. In this embodiment, the formation of a chemical reaction film can be promoted in the rotational speed range in which direct contact between the sliding bearing 20 and the rotating shaft 13 can occur.

[0059] Furthermore, according to this embodiment, in the transition interval RT between a first rotational speed r1, where the rotational speed r is greater than zero and less than the set rotational speed rs, and the set rotational speed rs, the control device 10 controls the flow control valve 87 so that the greater the rotational speed r, the lower the mixing ratio Rmix of the CO2 fluid in the refrigerant R. In this embodiment, by gradually changing the mixing ratio Rmix in the transition interval RT, the risk of inhibiting the formation of a chemical reaction film can be reduced.

[0060] Furthermore, according to this embodiment, the control device 10 controls the flow control valve 87 to set the mixing ratio Rmix of CO2 fluid in the refrigerant R to zero when the rotational speed r is set to the set rotational speed rs. In this embodiment, at least when the rotational speed r is set to the set rotational speed rs, wear of the bearing can be suppressed by the oil film of lubricating oil.

[0061] Furthermore, according to this embodiment, in the operating section R2 where the rotational speed r is greater than the set rotational speed rs, the control device 10 controls the flow control valve 87 so that the greater the rotational speed r, the greater the mixing ratio Rmix of CO2 fluid in the refrigerant R. In this embodiment, once the rotational speed r is greater than the set rotational speed rs and the system transitions from the start / stop state to the operating state, the sliding bearing 20 is lubricated by the CO2 fluid rather than the lubricating oil. As a result, in this embodiment, good lubrication can be maintained while suppressing stirring resistance caused by the scattering of lubricating oil onto the rotating body 11.

[0062] Furthermore, according to this embodiment, the control device 10 maintains the mixing ratio Rmix of CO2 fluid in the refrigerant R at zero during the low-speed rotation section RL between the set rotation speed rs and a second rotation speed r2 which is greater than the set rotation speed rs. In this embodiment, wear of the bearing can be suppressed in the low-speed rotation section RL by the oil film of lubricating oil.

[0063] Furthermore, according to this embodiment, the first flow passage 88a and the second flow passage 88b merge before reaching the sliding bearing 20, and are configured to supply CO2 fluid and lubricating oil to the sliding bearing 20. In this embodiment, the refrigerant R can be supplied to the sliding bearing 20 in a state in which the CO2 fluid and lubricating oil are mixed in a predetermined mixing ratio.

[0064] Furthermore, according to this embodiment, the first flow passage 88a and the second flow passage 88b are configured to supply CO2 fluid and lubricating oil to the sliding bearing 20 independently, respectively. In this embodiment, after supplying the CO2 fluid and lubricating oil separately to the sliding bearing 20, the CO2 fluid and lubricating oil can be mixed within the sliding bearing 20.

[0065] Furthermore, according to this embodiment, the rotating body 11 is the rotor of the electric motor 1. In this embodiment, the coolant R can lubricate the sliding bearing 20 of the electric motor 1 and cool the inside of the electric motor 1, which generates heat during operation. [Explanation of Symbols]

[0066] 1 Electric motor 8. Refrigerant circulation system 10 Control device 11. Rotor (rotating body) 13. Rotor shaft (rotating axis) 20 Plain bearings 80 Supply section 85 Gas-liquid separator 87 Flow control valve V1 First control valve V2 Second control valve R refrigerant S Motor System

Claims

1. A motor system, A sliding bearing that supports the rotating shaft of a rotating body, A rotation sensor for detecting the rotation speed of the aforementioned rotating shaft, Towards the aforementioned sliding bearing, CO, which constitutes the refrigerant 2 A supply unit that supplies fluid and lubricating oil, From the supply unit to the sliding bearing the CO 2 A flow control valve having a first control valve provided in a first flow passage for supplying fluid, and a second control valve provided in a second flow passage for supplying the lubricating oil from the supply unit to the sliding bearing, According to the rotation speed of the rotating shaft detected by the rotation sensor, the flow control valve controls the CO 2 The system comprises a control device configured to adjust the mixing ratio of the fluid and the lubricating oil, The control device, in the start-stop section where the rotational speed is less than a predetermined set rotational speed, the CO 2 A motor system that controls the flow control valve to supply both the fluid and the lubricating oil to the sliding bearing.

2. The motor system according to claim 1, wherein the set rotational speed corresponds to the rotational speed at which the sliding bearing and the rotating shaft begin to make direct contact as the rotational speed of the rotating shaft decreases while the lubricating oil is supplied.

3. The control device, in the transition interval between a first rotational speed, which is greater than zero and less than the set rotational speed, and the set rotational speed, the greater the rotational speed, the greater the CO in the refrigerant. 2 The motor system according to claim 1, wherein the flow control valve is controlled to reduce the mixing ratio of the fluid.

4. The control device, when the rotation speed is set to the set rotation speed, the CO in the refrigerant 2 The motor system according to claim 1, wherein the flow control valve is controlled to set the fluid mixing ratio to zero.

5. The control device, in an operating section where the rotational speed is greater than the set rotational speed, increases the amount of CO in the refrigerant as the rotational speed increases. 2 The motor system according to claim 3, wherein the flow control valve is controlled to increase the mixing ratio of the fluid.

6. The control device, in the low-speed rotation section between the set rotation speed and a second rotation speed greater than the set rotation speed, controls the CO in the refrigerant. 2 The motor system according to claim 5, which maintains a fluid mixing ratio of zero.

7. The first flow path and the second flow path merge before reaching the sliding bearing, and supply the CO 2 fluid and the lubricating oil to the sliding bearing. The motor system according to claim 1, which is configured to do so.

8. The first and second flow passages are independently connected to the sliding bearings, respectively, and the CO 2 The motor system according to claim 1, configured to supply a fluid and the lubricating oil.

9. The motor system according to claim 1, wherein the rotating body is the rotor of an electric motor.

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