Engine system

Abstract

[Problem] A motor system is provided that improves the wear resistance of a bearing unit during starting and stopping of rotation. [Means of solution] A motor system S with a control device 10 configured to set a mixing ratio Rmix of a CO2 fluid and a lubricating oil by means of a flow control valve 87 according to a rotational speed r of a rotating shaft 13 detected by a rotation sensor 17, wherein the control device 10 controls the flow control valve 87 such that both the CO2 fluid and the lubricating oil are supplied to a plain bearing 20 in a start / stop interval R1 in which the rotational speed r is less than a predetermined set rotational speed rs.

Description

[Technical field]

[0001] The present invention relates to a motor system, in particular a motor system with a plain bearing. [State of the art]

[0002] Conventionally, a plain bearing supporting a rotating shaft and lubricated with lubricating oil reduces the sliding resistance between the rotating shaft and the plain bearing by means of a lubricating film (oil film) formed by the lubricating oil. Plain bearings have been proposed that reduce the increase in sliding resistance in such a bearing design, particularly under low-temperature conditions (see, for example, patent literature 1).

[0003] In the plain bearing described in patent literature 1, a surface structure of the plain bearing (a structure of a sliding surface) is configured to prevent frictional heat, caused by sliding between the rotating shaft and the plain bearing at the start of movement, from being conducted to the main body of the rotating shaft. Therefore, in the plain bearing described in patent literature 1, the viscosity of the lubricating oil can be reduced by the frictional heat, which is expected to reduce the sliding resistance at the start of movement. [List of oppositions][Patent literature]

[0004] [Patent Literature 1] Japanese Unexamined Patent Publication No. 2021-8914 [Brief description of the invention][Problems to be solved by the invention]

[0005] However, the inventor has determined that in a case where such a plain bearing from patent literature 1 is applied to the rotating shaft of a rotor of an electric motor, there is a risk that when starting and stopping the electric motor (especially in an extremely low speed range) no lubricating film of sufficient thickness is formed between the rotating shaft and the plain bearing and the rotating shaft and the plain bearing come into contact with each other, which can lead to wear of the bearing unit.

[0006] Such wear leads to an increase in bearing clearance, the generation of abnormal noise, and a reduction in electromagnetic efficiency. To reduce this wear, a large quantity of lubricating oil can be introduced into the plain bearing from the outside. However, if the plain bearing is configured in this way, problems arise due to the lubricating oil splashing from the bearing assembly into the interior of the motor and an increase in stirring resistance during motor operation.

[0007] The present invention was developed to solve the problems of the prior art, and one object of the present invention is to provide a motor system that improves the wear resistance of a bearing unit during starting and stopping of rotation. [Means of solving the problems]

[0008] To solve this problem, a motor system of the present invention is characterized in that it comprises: a plain bearing that supports a rotating shaft of a rotating body; a rotation sensor for detecting the rotational speed of the rotating shaft; a supply unit that supplies a CO2 fluid and a lubricating oil, forming a refrigerant, to the plain bearing; a flow control valve comprising a first control valve provided in a first flow channel for supplying the CO2 fluid from the supply unit to the plain bearing, and a second control valve provided in a second flow channel for supplying the lubricating oil from the supply unit to the plain bearing;and a control device configured to adjust the mixing ratio of the CO2 fluid and the lubricating oil via the flow control valve according to the rotational speed of the rotating shaft detected by the speed sensor, wherein the control device controls the flow control valve such that both the CO2 fluid and the lubricating oil are supplied to the plain bearing in a start / stop interval in which the rotational speed is below a predetermined set speed.

[0009] According to the present invention, configured as follows, both the CO2 fluid and the lubricating oil are supplied to the plain bearing at extremely low speeds when the rotation of the rotating shaft is started and stopped (particularly during a start / stop interval where the rotational speed is below the set speed). In this configuration, the formation of a wear-resistant chemical reaction film on a sliding surface of the rotating shaft and / or the plain bearing is facilitated by a surface reaction caused by friction, thereby improving the wear resistance of the rotating shaft and the plain bearing, which serve as a bearing unit, especially at low speeds.

[0010] Furthermore, the set rotational speed in the present invention corresponds to a speed at which the plain bearing and the rotating shaft come into direct contact with each other when the rotational speed of the rotating shaft decreases in a state where lubricating oil is supplied. According to the present invention, configured in this way, the formation of the chemical reaction film can be facilitated in a speed range where direct contact between the plain bearing and the rotating shaft can occur.

[0011] Furthermore, in the present invention, the control device preferably controls the flow control valve such that the mixing ratio of the CO2 fluid in the refrigerant is reduced with increasing rotational speed in a transition interval between a first rotational speed and the set rotational speed, in which the rotational speed is greater than zero and less than the set rotational speed. According to the present invention, configured in this way, it is possible to reduce the risk of inhibiting the formation of the chemical reaction film by gradually changing the mixing ratio in the transition interval.

[0012] Furthermore, the control device according to the present invention preferably controls the flow control valve to set the mixing ratio of the CO2 fluid in the refrigerant to zero when the rotational speed equals the set rotational speed. According to the present invention, configured in this way, it is possible to reduce the wear of the bearing unit by means of an oil film formed by the lubricating oil, at least in a condition where the rotational speed equals the set rotational speed.

[0013] Furthermore, in the present invention, the control device preferably controls the flow control valve such that the mixing ratio of the CO2 fluid in the refrigerant is increased with increasing rotational speed during an operating interval in which the rotational speed is greater than the set speed. According to the present invention configured in this way, when the rotational speed is greater than the set speed and after a transition from the start / stop state to the operating state, the plain bearing is lubricated by the CO2 fluid instead of the lubricating oil. Consequently, the present invention makes it possible to maintain good lubrication while simultaneously reducing the stirring resistance caused by the scattering of the lubricating oil on the rotating body.

[0014] Furthermore, the control device in the present invention preferably maintains the mixing ratio of the CO2 fluid in the refrigerant at zero during a low-speed interval, in which the speed lies between the set speed and a second speed that is greater than the set speed. According to the present invention, when configured, it is possible in the low-speed range to reduce the wear of the bearing unit by means of an oil film formed by the lubricating oil.

[0015] Furthermore, in the present embodiment, the first flow channel and the second flow channel are preferably configured such that they merge before reaching the sliding bearing and supply the CO2 fluid and the lubricating oil to the sliding bearing. According to the present invention configured in this way, it is possible to supply the refrigerant to the sliding bearing in a state in which the CO2 fluid and the lubricating oil are mixed in a predetermined mixing ratio.

[0016] Furthermore, in the present invention, the first flow channel and the second flow channel are preferably configured such that they supply the CO2 fluid and the lubricating oil to the sliding bearing independently of one another. According to the present invention in this configuration, the CO2 fluid and the lubricating oil can be mixed within the sliding bearing after the CO2 fluid and the lubricating oil have been supplied individually to the sliding bearing 20.

[0017] In addition, in the present invention, the rotating body is preferably a rotor of an electric motor. According to the present invention configured in this way, the refrigerant can lubricate the sliding bearing of the electric motor and cool the interior of the electric motor, which generates heat during operation. [Advantageous effects of the invention]

[0018] According to the motor system of the present invention, a motor system can be provided which reduces the increase in stirring resistance and improves the wear resistance of the bearing unit during starting and stopping of the rotation. [Brief description of the drawings] Fig. Figure 1 is a schematic configuration diagram of a motor system according to an embodiment of the present invention. Fig. Figure 2 is an electrical block diagram of the motor system according to the embodiment of the present invention. Fig. Figure 3 is a diagram showing the mixing ratio of a CO2 fluid according to the embodiment of the present invention. Fig. Figure 4 is an illustrative view of a lubricating coating according to the embodiment of the present invention. Fig. Figure 5 is an explanatory view showing the relationship between the relative velocity and the oil film thickness according to the embodiment of the present invention. Fig. Figure 6 is a diagram showing the relationship between the rotational speed and the oil film thickness in a sliding section according to the embodiment of the present invention. Fig. 7 is a control sequence of the motor system according to the embodiment of the present invention. Fig. Figure 8 is a partial configuration diagram of a motor system according to a further embodiment of the present invention. [Version]

[0019] A motor system according to an embodiment of the present invention is described below with reference to the accompanying drawings. [Overall configuration]

[0020] First, with reference to Fig. 1. A complete configuration of a motor system (bearing device) according to the present embodiment is described. Fig. Figure 1 is a schematic configuration diagram of the engine system according to the present embodiment. A diagram in Fig. For example, the motor system S shown is attached to a vehicle such as an electric car and can provide a rotary drive force for the vehicle.

[0021] According to the present embodiment, in an extremely low speed range (start / stop interval R1, see Fig. 3) When a motor is started and stopped, a reaction film is formed on a sliding surface of a rotor shaft to improve wear resistance. In particular, in the present embodiment, a coating film (such as a carbonate film) with wear resistance is formed on the sliding surface by supplying CO2 fluid and lubricating oil to a bearing unit, utilizing a surface reaction caused by friction.

[0022] The motor system S comprises an electric motor (motor) 1, a refrigerant circulation system 8, and a control device 10. The electric motor 1 provides rotary drive power for the vehicle. The refrigerant circulation system 8 is configured to circulate a refrigerant R in a cooling circuit to cool the electric motor 1. Specifically, this cooling circuit includes an expansion stroke and an evaporation stroke of the refrigerant R in the electric motor 1, and a compression stroke and a condensation stroke of the refrigerant R in the refrigerant circulation system 8.

[0023] In the present embodiment, the electric motor 1 is an ultra-high-speed rotary motor that can be operated at a high speed of, for example, more than 30,000 rpm and is configured such that it operates in a high-speed rotation interval RH during normal operation (see Fig. 3) operates. Although the refrigerant R is a mixture of CO2 fluid, a natural refrigerant, and lubricating oil (for example, PAG oil), a bearing 20 is configured such that it is lubricated only by the CO2 fluid during the high-speed rotation interval RH. [Configuration of the refrigerant circulation system]

[0024] The refrigerant circulation system 8 comprises: a compressor 81 for compressing the refrigerant R; a heat exchanger (condenser) 83, including a condenser and a 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 fluid (lubricating oil); a flow control valve 87 (first control valve V1, second control valve V2) for adjusting the flow rates of the CO2 fluid and the lubricating oil, respectively; and a flow channel 88 connecting these valves. The flow channel 88 branches downstream of the gas-liquid separator 85 into two channels (a first flow channel 88a in which the first control valve V1 is located, and a second flow channel 88b in which the second control valve V2 is located), and each of the channels is connected to the electric motor 1.The electric motor 1 is integrated into the refrigerant circulation system 8. In the present embodiment, the compressor 81, the heat exchanger 83 and the gas-liquid separator 85 form a supply unit 80 for the refrigerant R. [Engine configuration]

[0025] The electric motor 1 according to the present embodiment comprises: a rotor (rotating body) 11; a stator 12; a rotor shaft 13, which is attached to the rotor 11 and extends in the axial direction; a pair of bearings (plain bearings) 20, which rotatably support the rotor shaft 13; a housing 15, which accommodates and supports the rotor 11, the stator 12, the rotor shaft 13, the bearings 20, etc.; a sealing element 16, which seals between the housing 15 and the rotor shaft 13 and prevents the refrigerant R from escaping from the interior of the housing 15; and a rotation sensor 17, which detects the rotational speed of the rotor shaft 13. One end of the rotor shaft 13 is connected to a gearbox (not shown) or the like of the vehicle.

[0026] The stator 12, which has a substantially cylindrical shape, is constructed by winding a coil 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 attached 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] The electric motor 1 further comprises: coolant supply flow channels 18a, 18b for supplying the coolant R supplied by the coolant circuit system 8 to the bearings 20; and a coolant outlet channel 19 for returning the coolant R from the interior of the electric motor 1 to the coolant circuit system 8. The coolant supply channels 18a, 18b are sections of the first channel 88a and the second channel 88b, respectively.

[0028] In particular, the refrigerant supply channels 18a, 18b supply the gap between the rotor shaft 13 and each bearing 20 with the CO2 fluid and the lubricating oil, respectively. Consequently, the refrigerant R is supplied to lubricate the sliding surfaces of the rotor shaft 13 and each bearing 20. In the present embodiment, the CO2 fluid supplied to each bearing 20 is a high-pressure gas or a supercritical fluid. The CO2 fluid and the lubricating oil, which are used as lubricants, leave each bearing 20, enter the housing 15, exchange heat with motor components, and then return to the refrigerant circulation system 8 via the refrigerant outlet channel 19. [Refrigerant refrigeration cycle]

[0029] In the present embodiment, the compressor 81 takes in the high-temperature, low-pressure refrigerant R from the electric motor 1, compresses the refrigerant R, and discharges the high-temperature, high-pressure refrigerant R. Next, the heat exchanger 83 exchanges heat between the high-temperature, high-pressure refrigerant R and the external environment (cold air, cooling water, etc.) to produce the medium-temperature, high-pressure refrigerant R. The medium-temperature, high-pressure refrigerant R is supplied to the bearings 20 of the electric motor 1 and lubricates them. Upon entering an interior space of the housing 15, the lubricated refrigerant R expands and becomes the cold, low-pressure refrigerant R.Furthermore, the low-temperature, low-pressure refrigerant R exchanges heat with a high-temperature section of the electric motor 1 in the housing 15 and becomes a high-temperature, low-pressure refrigerant R. This high-temperature, low-pressure refrigerant R is returned to the compressor 81. [Warehouse structure]

[0030] The bearings 20 rotatably support the ends of the rotor shaft 13. Each bearing 20 has a generally cylindrical main body section containing a metallic material such as iron and comprises a sliding surface, which is an inner circumferential surface of the main body, and an outer circumferential surface of the main body. The sliding surface supports the rotor shaft 13. The main body section also has a through-hole that penetrates a side face of the outer circumferential surface and communicates with the sliding surface. The through-hole communicates with each refrigerant supply flow channel 18a, 18b and forms a section of each refrigerant supply flow channel 18a, 18b. [Electrical block diagram]

[0031] Fig. Figure 2 is an electrical block diagram of the motor system. The control device 10 is a computer comprising a processor, memory, etc., which receives a rotation signal from the rotation sensor 17 provided in the motor system S and outputs a valve opening signal to the flow control valve 87. In particular, the control device 10 outputs a valve opening signal corresponding to a rotational speed r (rpm) of the electric motor 1 and adjusts the valve opening of each of the first control valves V1 and the second control valves V2 to control a mixing ratio Rmix and the flow rates of the CO2 fluid and the lubricating oil in the refrigerant R supplied to the bearings 20.

[0032] The control device 10 can also 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 component devices of the refrigerant circulation system 8, a solenoid valve, an electromagnet (electromagnetic solenoid valve), etc. [Overview of the flow rate adjustment control]

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

[0034] In the present embodiment, the electric motor 1 is configured to operate within a speed range that includes the start / stop interval R1 (0 to rs) and an operating interval R2 (from r2 onwards). In the present embodiment, the mixing ratio of the CO2 fluid in the refrigerant R supplied to the bearings 20 is controlled to change according to the speed.

[0035] In particular, within a high-speed rotational range RH from a third rotational speed r3 (for example, 10,000 rpm) to a fourth rotational speed r4 (for example, 30,000 rpm or higher) within the operating range R2, the CO2 fluid mixture ratio is set to 100%. In other words, the electric motor 1 of the present embodiment is a motor configured such that the bearings 20 are lubricated only by the CO2 fluid within a predetermined rotational speed range (high-speed rotational interval RH).

[0036] Within a predetermined medium speed range RM, from a second speed r2 (for example, 200 to 800 rpm) to the third speed r3 within the operating range R2, the mixing ratio of the CO2 fluid in the refrigerant R decreases as the speed r decreases, reaching 0% at the second speed r2. In the present embodiment, the medium speed range RM is a transitional range until the speed r of the electric motor 1 reaches the high speed range RH.

[0037] Furthermore, in a low-speed range RL from the set speed rs (for example, 100 rpm) up to the second speed r2 (r2 > rs) within the operating range R2, the mixing ratio of the CO2 fluid in the refrigerant R is kept at 0%, and only the lubricating oil is supplied to the bearings 20.

[0038] Note that in the low-speed rotation interval RL, the mixing ratio of the CO2 fluid in the refrigerant R is preferably 0%; however, this is not a limitation and it can be set to a low mixing ratio within a range of, for example, 0% to 20%. If the mixing ratio is greater than 0%, the set rotational speed rs, which corresponds to 3σ, will be adjusted as described in [reference to...]. Fig. 6 described, set to a larger value.

[0039] Furthermore, in the present embodiment, during the start / stop interval R1, the refrigerant R, which contains both the CO2 fluid and the lubricating oil, is supplied to the bearings 20. Specifically, during a predetermined transition interval RT from a first rotational speed r1 to the set rotational speed rs (r1 < rs) within the start / stop interval R1, the mixing ratio of the CO2 fluid in the refrigerant R increases as the rotational speed r decreases, and the mixing ratio reaches a predetermined set mixing ratio Ra (for example, 50%) at the first rotational speed r1. Moreover, the set mixing ratio Ra is maintained during a reaction film formation interval RF from zero to the first rotational speed r1 within the start / stop interval R1.Thus, in the present embodiment, both the lubricating oil and the CO2 fluid as refrigerant R are supplied to the bearings 20 during the start / stop interval R1, in which the rotational speed is very low, immediately after the electric motor 1 is started and immediately before the electric motor 1 is stopped. It should be noted that, in order to achieve a smooth transition of the mixing ratio between the set mixing ratio Ra and zero during the transition interval RT, the initial rotational speed r1 is set to the set rotational speed rs multiplied by a coefficient of 0.6 to 0.9. [Lubricating coating]

[0040] Next, with reference to the Fig. 4 to Fig. 6 describes a lubricating coating film (oil film) that is formed between two solid elements. Fig. Figure 4 shows a state in which an oil film M of lubricating oil with a thickness h is formed between the sliding surfaces of two solid elements (in the present embodiment, the rotor shaft 13 and each bearing 20). Each of the sliding surfaces has a predetermined surface roughness. Fig. Figure 4 schematically shows normal probability density distributions of surface roughness, and the standard deviations of the surface roughness are σ 1 and σ 2 respectively.

[0041] Fig. 5 shows based on Fig. 4. The relationship between the lubricating film M formed between the two solid elements and a relative velocity VL of the two solid elements. As in Fig. 4 are also in Fig. 5 the normal probability density distributions of surface roughness are shown. Fig. Figure 5(a) shows a dry friction condition that occurs when the relative velocity is very low and in which the solid elements come into contact with each other without the presence of a fluid (lubricating oil) on the friction surfaces (sliding surfaces) and the coefficient of friction is high. Next, Figure 5(a) shows a dry friction condition that occurs when the relative velocity is very low and in which the solid elements come into contact with each other without the presence of a fluid (lubricating oil) on the friction surfaces (sliding surfaces) and the coefficient of friction is high. Fig. 5(b) a boundary lubrication condition which occurs when the relative velocity is low and in which a small amount of fluid is present on the friction surfaces and the coefficient of friction is still high.

[0042] Next, show Fig. 5(c) a mixed lubrication condition that occurs when the relative speed is relatively low and a certain amount of fluid is present on the friction surfaces and the coefficient of friction is low. Next, it shows Fig. 5(d) A fluid lubrication condition occurs when the relative velocity is sufficiently high and the friction surfaces are filled with the fluid, the solid elements do not touch, and the coefficient of friction is low. Thus, when the relative velocity is high, an oil film M of sufficient thickness forms, preventing direct contact between the solid elements. Conversely, when the relative velocity is low, no oil film M of sufficient thickness forms, and the solid elements come into contact with each other.

[0043] It is generally known that the film thickness h is inversely proportional to the load W and proportional to the velocity U and the viscosity G, which is mathematically expressed, for example, by the Dowson-Higginson equation 1. The mathematical equation can, for example, be written as follows: h=2.922W−0.166U0.692G0.470

[0044] Fig. Figure 6 shows the relationship between the rotational speed r (rpm) and the film thickness h of the lubricating film coating formed between the rotor shaft 13 and the bearings 20, which is calculated on the basis of Equation 1 to correspond to the present embodiment. Fig. Figure 6 shows the relationship for each case when the mixing ratio of the CO2 fluid in the refrigerant R is changed (when the CO2 fluid is 0%, 20%, 40%, 60%, and 80%). When the CO2 fluid is 0%, the proportion of lubricating oil is 100%. As shown in Fig. As shown in Figure 6, the film thickness h of the oil film increases with increasing rotational speed.

[0045] The inventor has determined that, considering the surface roughness of two solid elements (the rotor shaft 13 and each bearing 20), the point in time at which the film thickness h of the oil film is three times a composite standard deviation σ of the surface roughness of the two solid elements corresponds to a transition interval from the fluid lubrication state to the mixed lubrication state. In other words, when the film thickness h is less than 3σ, the coefficient of friction between the two solid elements begins to change from a low state to a high state (that is, the two solid elements begin to come into direct contact with each other).

[0046] If the standard deviations of the surface roughness of the two solid elements are σ1 and σ2 respectively, the composite standard deviation σ is expressed as follows: σ=σ12+σ22.

[0047] Therefore, in the present embodiment, a rotational speed at which h = 3σ is referred to as the set rotational speed rs in the diagram of Fig. 6 specified. As in Fig. As shown in Figure 3, the refrigerant R supplied to the bearings 20 contains only the lubricating oil in the low-speed range RL (rs to r2). However, since the film thickness h is at least 3σ or greater (h > 3σ), wear between the rotor shaft 13 and the bearings 20 is unlikely. Furthermore, in the present embodiment, wear is unlikely in other intervals RM and RH within the operating interval R2, even though the refrigerant R contains the CO2 fluid. On the other hand, in the start / stop interval R1 (0 to rs), since the film thickness h is less than 3σ, there is a risk of wear due to direct contact between the solid elements.

[0048] Note that the set speed rs is not limited to what is mentioned above and can be set experimentally. In this case, for example, if the speed of the rotor shaft 13 is reduced, a speed at which the rotational resistance increases can be set as the set speed rs. Furthermore, the physical contact between the rotor shaft 13 and each bearing 20 can be observed, and a speed at which physical contact begins can be set as the set speed rs.

[0049] Thus, contact between the solid elements can occur during the start / stop interval R1. However, the inventor has determined that it is possible to impart wear resistance to the solid elements (rotor shaft 13 and / or bearing 20) by using a chemical reaction layer. The chemical reaction film (for example, tribo-reaction film) is a thick film (for example, iron carbonate FeCO3) that forms on the surfaces of various materials (such as steel) due to an interaction, such as friction, in the presence of the CO2 fluid and the lubricating oil. The presence of the lubricating oil and the CO2 fluid is preferential for the formation of the chemical reaction film. It is noted that at least one of the rotor shafts 13 and the bearing 20 contains a material (such as Fe) that is a component of the chemical reaction film.

[0050] Therefore, in the present embodiment, during the reaction film formation interval RF (0 to r1) within the start / stop interval R1, the refrigerant R, which contains only the set mixing ratio Ra of the CO2 fluid in addition to the lubricating oil, is supplied to each bearing 20 to form the chemical reaction film on the sliding surfaces of the two solid elements and thereby improve wear resistance. In other words, in the present embodiment, in a speed range where contact between the solid elements can occur, the wear of the solid elements can be reduced by bringing the solid elements into contact with each other via the chemical reaction film.

[0051] Furthermore, in the present embodiment, during the transition interval RT (r1 to rs), the mixing ratio Rmix of the CO2 fluid is reduced with increasing rotational speed r, and at the set rotational speed rs, each bearing 20 is supplied with the refrigerant R, consisting solely of the lubricating oil. A chemical reaction film is also formed during this transition interval RT.

[0052] In the present embodiment, during the start / stop interval R1, the set mixing ratio Ra is selected to facilitate the formation of the chemical reaction film. In other words, supplying a larger quantity of the CO2 fluid to the sliding surfaces is advantageous for the formation of the chemical reaction film, but if the CO2 fluid is supplied to the sliding surfaces in a state where it is not dissolved in the lubricating oil, it can, conversely, inhibit the formation of the chemical reaction film. Therefore, using known data, such as a predetermined Daniel diagram or a two-layer temperature diagram, the set mixing ratio Ra of the lubricating oil and the CO2 fluid is determined based on a temperature R specified for the supply of the refrigerant, such that the mixing ratio ensures miscibility. [Process flow]

[0053] Next, with reference to Fig. 7 describes a process sequence of the motor system S. The control device 10 executes the process of Fig. 7 continuously and repeatedly when the electric motor 1 is operated. When the process is started, the control device 10 detects the rotational speed (rpm) of the rotor shaft 13 (S1) based on a rotational signal received from the rotation sensor 17. Next, the control device 10 determines the flow rate adjustment data stored in memory based on the detected rotational speed and using the flow rate adjustment data stored in memory (see Fig. 3) The mixing ratio Rmix of the CO2 fluid in the refrigerant R is determined, and an opening degree of the flow control valve 87 is set to achieve this mixing ratio (S2). In particular, the opening degrees of the respective first control valve V1 and the second control valve V2 are set so that the determined mixing ratio Rmix is ​​achieved.

[0054] Next, the control device outputs 10 valve opening degree signals to the first control valve V1 and the second control valve V2 to achieve the determined valve opening degrees (S3), and then terminates the process. Consequently, the first control valve V1 and the second control valve V2 supply the CO2 fluid and the lubricating oil to each bearing 20 at flow rates corresponding to the desired valve opening degrees.

[0055] It is noted that in the above embodiment, although the refrigerant supply channel 18a from the first control valve V1 and the refrigerant supply channel 18b from the second control valve V2 are each connected to the through-hole of each bearing 20, the refrigerant supply channels are, however, as in Fig.8 shown can be configured. In other words, after the first flow channel 88a and the second flow channel 88b (or the refrigerant supply flow channel 18a and the refrigerant supply flow channel 18b) merge, the resulting merged refrigerant supply flow channel 18c can be connected to the through-hole provided in each bearing 20. [Functions and effects]

[0056] Next, the functions and effects of the motor system S of the present embodiment will be described.

[0057] The motor system S according to the present embodiment is characterized in that it comprises: a plain bearing 20 which supports a rotary shaft 13 of a rotating body 11; a rotation sensor 17 for detecting a rotational speed r of the rotary shaft 13; a supply unit 80 which supplies a CO2 fluid and a lubricating oil, forming a refrigerant R, to the plain bearing 20; a flow control valve 87 which comprises a first control valve V1, which is provided in a first flow channel 88a to supply the CO2 fluid from the supply unit 80 to the plain bearing 20, and a second control valve V2, which is provided in a second flow channel 88b to supply the lubricating oil from the supply unit 80 to the plain bearing 20;and a control device 10 configured to adjust the mixing ratio Rmix of the CO2 fluid and the lubricating oil by the flow control valve 87 according to the rotational speed r of the rotating shaft 13 detected by the speed sensor 17, wherein the control device 10 controls the flow control valve 87 such that both the CO2 fluid and the lubricating oil are supplied to the sliding bearing 20 in a start / stop interval R1 in which the rotational speed r is less than a predetermined set rotational speed rs.

[0058] In such an embodiment, at extremely low speeds, when the rotation of the rotating shaft 13 is started and stopped (particularly during the start / stop interval R1, where the rotational speed r is less than the set rotational speed rs), both the CO2 fluid and the lubricating oil are supplied to the plain bearing 20. In this configuration, the formation of a wear-resistant chemical reaction film on the sliding surface of the rotating shaft 13 and / or the plain bearing 20 is facilitated by a surface reaction caused by friction, and, especially at low speeds, the wear resistance of the rotating shaft 13 and the plain bearing 20, which serve as a bearing unit, can be improved.

[0059] Furthermore, according to the present embodiment, the set rotational speed rs corresponds to a speed at which the plain bearing 20 and the rotating shaft 13 come into direct contact with each other when the rotational speed r of the rotating shaft 13 decreases in a state in which the lubricating oil is supplied. In such an embodiment, the formation of the chemical reaction film can be facilitated in a speed range in which direct contact between the plain bearing 20 and the rotating shaft 13 can occur.

[0060] Furthermore, according to the present embodiment, the control device 10 controls the flow control valve 87 such that the mixing ratio Rmix of the CO2 fluid in the refrigerant R is reduced with increasing rotational speed r in a transition interval RT between an initial rotational speed r1 and the set rotational speed rs, in which the rotational speed r is greater than zero and less than the set rotational speed rs. In such an embodiment, the risk of inhibition of the formation of the chemical reaction film can be reduced by gradually changing the mixing ratio Rmix in the transition interval RT.

[0061] Furthermore, according to the present embodiment, the control device 10 controls the flow control valve 87 to set the mixing ratio Rmix of the CO2 fluid in the refrigerant R to zero when the rotational speed r equals the set rotational speed rs. In such an embodiment, it is possible, in a state where at least the rotational speed r equals the set rotational speed rs, to reduce the wear of the bearing unit by means of an oil film formed by the lubricating oil.

[0062] Furthermore, according to the present embodiment, the control device 10 controls the flow control valve 87 such that the mixing ratio Rmix of the CO2 fluid in the refrigerant R is increased with increasing rotational speed r during an operating interval R2 in which the rotational speed r is greater than the set rotational speed rs. In such an embodiment, when the rotational speed r is greater than the set rotational speed rs and after a transition from the start / stop state to the operating state, the plain bearing 20 is lubricated by the CO2 fluid instead of the lubricating oil. Consequently, in the present embodiment, it is possible to maintain good lubrication while simultaneously reducing the stirring resistance caused by the scattering of the lubricating oil on the rotating body 11.

[0063] Furthermore, according to the present embodiment, the control device 10 maintains the mixing ratio Rmix of the CO2 fluid in the refrigerant R at zero during a low-speed interval RL, in which the rotational speed r lies between the set rotational speed rs and a second rotational speed r2, which is greater than the set rotational speed rs. In such an embodiment, it is possible to reduce the wear of the bearing unit by the oil film formed by the lubricating oil during the low-speed rotational interval RL.

[0064] Furthermore, according to the present embodiment, the first flow channel 88a and the second flow channel 88b are configured such that they merge before reaching the sliding bearing 20 and supply the CO2 fluid and the lubricating oil to the sliding bearing 20. In such an embodiment, it is possible to supply the refrigerant R to the sliding bearing 20 in a state in which the CO2 fluid and the lubricating oil are mixed in a predetermined mixing ratio.

[0065] Furthermore, according to the present embodiment, the first flow channel 88a and the second flow channel 88b are configured such that they supply the CO2 fluid and the lubricating oil to the sliding bearing 20 independently of one another. In such an embodiment, the CO2 fluid and the lubricating oil, after each having been supplied individually to the sliding bearing 20, can be mixed within the sliding bearing 20.

[0066] Additionally, according to the present embodiment, the rotating body 11 is a rotor of the electric motor 1. In such an embodiment, the refrigerant R can lubricate the sliding bearing 20 of the electric motor 1 and cool the interior of the electric motor 1, which generates heat during operation. [List of reference symbols] 1 electric motor 8 Refrigerant circulation system 10 Control device 11 Rotor (rotating body) 13 Rotor shaft (rotating shaft) 20 plain bearings 80 feed unit 85 Gas-Liquid Separators 87 Flow control valve V1 first control valve V2 second control valve R Refrigerant S engine system QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2021-8914

[0004]

Claims

[1] Engine system which features: a plain bearing that supports a rotating shaft of a rotating body; a rotation sensor for detecting the rotational speed of the rotating shaft; a supply unit that supplies the plain bearing with a CO2 fluid and a lubricating oil, which together form a refrigerant; a flow control valve comprising a first control valve provided in a first flow channel for supplying the CO2 fluid from the supply unit to the sliding bearing, and a second control valve provided in a second flow channel for supplying the lubricating oil from the supply unit to the sliding bearing; and a control device configured to adjust the mixing ratio of the CO2 fluid and the lubricating oil via the flow control valve according to the rotational speed of the rotating shaft detected by the speed sensor, wherein the control device controls the flow control valve in such a way that both the CO2 fluid and the lubricating oil are supplied to the plain bearing in a start / stop interval in which the rotational speed is below a predetermined speed. [2] Motor system according to claim 1, wherein the set speed corresponds to a speed at which the plain bearing and the rotating shaft begin to come into direct contact with each other when the speed of the rotating shaft decreases in a state in which the lubricating oil is supplied. [3] Motor system according to claim 1, wherein the control device controls the flow control valve such that the mixing ratio of the CO2 fluid in the refrigerant is reduced with increasing rotational speed in a transition interval between a first rotational speed and the set rotational speed, in which the rotational speed is greater than zero and less than the set rotational speed. [4] Motor system according to claim 1, wherein the control device controls the flow control valve such that the mixing ratio of the CO2 fluid in the refrigerant is set to zero when the rotational speed is equal to the set rotational speed. [5] Motor system according to claim 3, wherein the control device controls the flow control valve such that the mixing ratio of the CO2 fluid in the refrigerant is increased with increasing rotational speed in an operating interval in which the rotational speed is greater than the set rotational speed. [6] Motor system according to claim 5, wherein the control device maintains the mixing ratio of the CO2 fluid in the refrigerant at zero in a low-speed range in which the speed is between the set speed and a second speed which is greater than the set speed. [7] Motor system according to claim 1, wherein the first flow channel and the second flow channel are configured such that they merge before reaching the sliding bearing and supply the CO2 fluid and the lubricating oil to the sliding bearing. [8] Motor system according to claim 1, wherein the first flow channel and the second flow channel are configured such that they supply the CO2 fluid and the lubricating oil to the sliding bearing independently of each other. [9] Motor system according to claim 1, wherein the rotating body is a rotor of an electric motor.

Images