Motor system

Abstract

To provide a motor system that can reduce the possibility of stator insulation failure. [Solution] The motor system 100 of this disclosure comprises a case 2, a circulation path 3, a cooling mechanism 4, and a moisture removal mechanism 5. The case 2 houses the stator 11 of the motor 1. The case 2 is filled with cooling oil so as to submerge the stator 11. The circulation path 3 connects an outlet 21 and an inlet 22 provided in the case 2 and circulates the cooling oil. The cooling mechanism 4 is located in the middle of the circulation path 3 and cools the circulating cooling oil. The moisture removal mechanism 5 is located in the middle of the circulation path 3, either downstream of the cooling position of the cooling mechanism 4 or at the same position as the cooling position of the cooling mechanism 4, and removes moisture from the cooling oil that has been cooled or is being cooled by the cooling mechanism 4.

Description

Technical Field

[0001] The present disclosure relates to a motor system.

Background Art

[0002] In Patent Document 1, an annular oil chamber is formed by hermetically sealing both ends of a cylindrical stator of a motor in the circumferential direction. The oil chamber is connected to an oil cooler so that cooling oil can be supplied and replenished. For example, by supplying the cooling oil cooled by the oil cooler to the oil chamber, the stator and the like are directly cooled, and the cooling efficiency is improved.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technology according to Patent Document 1, when moisture enters the cooling oil, there is a problem that the moisture adheres to the stator, and the stator may cause insulation failure.

[0005] In view of such problems, an object of the present disclosure is to provide a motor system capable of reducing the possibility of the stator causing insulation failure.

Means for Solving the Problems

[0006] The motor system of the present disclosure comprises: a case housing a motor stator and filled with cooling oil so as to submerge the stator; a circulation path connecting an outlet and an inlet provided in the case for circulating the cooling oil; a cooling mechanism positioned in the middle of the circulation path for cooling the cooling oil circulating in the circulation path; and a moisture removal mechanism positioned in the middle of the circulation path, either downstream of the cooling position of the cooling mechanism or at the same position as the cooling position of the cooling mechanism, for removing moisture from the cooling oil that has been cooled or is being cooled by the cooling mechanism.

[0007] With the above configuration, by removing moisture from the cooling oil, it is possible to suppress moisture from adhering to the stator and reduce the possibility of the stator experiencing insulation failure.

[0008] In other embodiments of the present disclosure, the motor system includes a water removal mechanism comprising: a tank that temporarily stores a certain amount of coolant circulating in the circulation path and is further filled with a gas capable of receiving water vapor evaporated from the stored coolant; and a relief valve that, in accordance with the internal pressure of the tank, can exchange the gas filled in the tank with gas from outside the tank.

[0009] With the above configuration, water can be efficiently removed from the coolant.

[0010] In other embodiments of the present disclosure, the water removal mechanism further comprises a membrane permeable only to water vapor, which is arranged to surround the hollow portion of the tank, and the membrane is positioned at a height greater than or equal to the liquid level of the cooling oil stored in the tank.

[0011] The above configuration allows for more efficient removal of moisture from the cooling oil. [Effects of the Invention]

[0012] This disclosure provides a motor system that can reduce the possibility of stator insulation failure. [Brief explanation of the drawing]

[0013] [Figure 1] This figure shows an example of the configuration of the motor system 100 according to the first embodiment. [Figure 2] This figure shows an example of the structure and arrangement of the moisture removal mechanism 5 of the motor system 100 according to the first embodiment. [Figure 3] This graph shows the relationship between temperature and the saturation moisture absorption capacity of the coolant. [Figure 4] This figure shows the configurations of motor system R1 according to the first comparative example and motor system R2 according to the second comparative example. [Figure 5] This figure shows the results of a verification experiment to determine the presence or absence of water droplets in the cooling oil after cooling to 25°C in the motor system 100 according to the first embodiment. [Figure 6] This figure shows the results of a verification experiment of the dielectric breakdown voltage of the cooling oil after cooling to 25°C in the motor system 100 according to the first embodiment. [Modes for carrying out the invention]

[0014] In the following, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. In each drawing, the same elements are denoted by the same reference numerals, and redundant explanations will be omitted where necessary for clarity.

[0015] (First Embodiment) First, the configuration of the motor system 100 according to the first embodiment will be described using Figure 1.

[0016] Figure 1 shows an example of the configuration of a motor system 100 according to the first embodiment. As shown in Figure 1, the motor system 100 comprises a motor 1, a case 2, a circulation path 3, a cooling mechanism 4, a moisture removal mechanism 5, a TA case 6, and a relief valve 7. Motor 1 comprises a stator 11 and a rotor 12.

[0017] Case 2 houses the stator 11 and rotor 12 of the motor 1. The case 2 is filled with cooling oil so as to submerge the stator 11 and rotor 12 of the motor 1 (that is, to fill the space part of the case 2, stator 11 and rotor 12). The cooling oil is the oil for cooling the stator 11. For example, the cooling oil has the role of absorbing the heat generated from the stator 11 and preventing overheating of the stator 11.

[0018] The circulation path 3 connects the outlet 21 and the inlet 22 provided in the case 2 and is a path for circulating the cooling oil from the outlet 21 to the inlet 22. Note that the circulation of the cooling oil is performed by a pump (not shown).

[0019] The cooling mechanism 4 is arranged in the middle of the circulation path 3. The cooling mechanism 4 cools the cooling oil circulating in the circulation path 3. The cooling mechanism 4 is, for example, a radiator or a water jacket.

[0020] The moisture removal mechanism 5 is arranged at a position downstream of the cooling position of the cooling mechanism 4 or at the same position as the cooling position of the cooling mechanism 4 in the middle of the circulation path 3. The moisture removal mechanism 5 removes moisture from the cooling oil cooled by the cooling mechanism 4 or during cooling.

[0021] The TA (Transmission Actuator) case 6 is a case that houses the case 2. The relief valve 7 is a valve for adjusting the internal pressure of the TA case 6.

[0022] Subsequently, with reference to FIG. 2, a structural example and an arrangement example of the moisture removal mechanism 5 of the motor system 100 according to the first embodiment will be described.

[0023] FIG. 2 is a diagram showing a structural example and an arrangement example of the moisture removal mechanism 5 of the motor system 100 according to the first embodiment.

[0024] <Structural example of the moisture removal mechanism 5> Figure 2(A) shows a first structural example of the moisture removal mechanism 5. Similarly, Figure 1 (mentioned above) also shows a first structural example. As shown in Figure 2(A), the moisture removal mechanism 5 includes a tank 51 and a relief valve 52.

[0025] Tank 51 temporarily stores a fixed amount of coolant circulating in the circulation path 3. The inlet (In) of Tank 51 is connected to the outlet 21 of Case 2 via the circulation path 3. As a result, the coolant discharged from the outlet 21 of Case 2 flows into the interior of Tank 51. The outlet (Out) of Tank 51 is connected to the inlet 22 of Case 2 via the circulation path 3. As a result, the coolant inside Tank 51 is discharged from Tank 51 toward the inlet 22 of Case 2.

[0026] Furthermore, the inside of the tank 51 is filled with a gas capable of receiving water vapor evaporated from the stored coolant. The gas is, for example, air. By doing so, the motor system 100 can remove moisture from the coolant circulating in the circulation path 3. Note that the gas is not limited to air; any gas capable of receiving water vapor evaporated from the stored coolant may be used, such as argon gas.

[0027] Furthermore, it is preferable that the outlet of the tank 51 be installed at a position lower than the liquid level of the stored coolant. This prevents gas from flowing into the coolant being discharged from the tank 51. The location of the inlet of the tank 51 is not a concern.

[0028] The relief valve 52 is a valve that can exchange the gas stored inside the tank 51 with the gas outside the tank 51, depending on the internal pressure of the tank 51. By exchanging the gas, the motor system 100 can prevent a situation where it is unable to receive water vapor evaporated from the coolant in which the gas is stored.

[0029] On the other hand, Figure 2(B) shows a second structural example of the moisture removal mechanism 5. As shown in Figure 2(B), the moisture removal mechanism 5 includes a tank 51 and a relief valve 52, as well as a membrane 53.

[0030] The membrane 53 is a membrane that allows only water vapor to pass through. The membrane 53 is installed so as to surround the hollow portion of the tank 51. For example, the outer periphery of the membrane 53 is installed along the inner wall of the tank 51. The membrane 53 is installed at a height greater than or equal to the liquid level of the coolant stored in the tank 51. Alternatively, the outer periphery of the membrane 53 may not be installed along the inner wall of the tank 51, but rather float on the surface of the coolant stored in the tank 51, surrounding the liquid level of the coolant.

[0031] <Example of arrangement of moisture removal mechanism 5> Figure 2(C) shows a first example of the arrangement of the moisture removal mechanism 5. In Figure 2(C), a radiator 4a is used in the cooling mechanism 4. The moisture removal mechanism 5 is positioned downstream of the cooling position of the radiator 4a. In this case, the moisture removal mechanism 5 removes moisture from the coolant cooled by the cooling mechanism 4.

[0032] On the other hand, Figure 2(D) shows a second example of the arrangement of the moisture removal mechanism 5. In Figure 2(D), a water jacket 4b is used for the cooling mechanism 4. The moisture removal mechanism 5 is positioned at the same location as the cooling position of the water jacket 4b. In this case, the moisture removal mechanism 5 removes moisture from the cooling oil being cooled by the cooling mechanism 4.

[0033] Figure 3 is a graph showing the relationship between temperature and the saturation moisture absorption capacity of the coolant. As shown in Figure 3, the saturation moisture absorption capacity of the coolant is high at high temperatures and low at low temperatures. When coolant that has absorbed water at a high temperature is cooled, the amount of water exceeding the saturation moisture absorption capacity is released from the coolant. For example, if water is absorbed at 80°C and cooled to 40°C, 500 ppm of water will be released from the coolant. Therefore, in order to efficiently remove water from the coolant, it is necessary to remove the water after or during the cooling of the coolant. In this embodiment, after the coolant is heated by the stator 11, water can be efficiently removed from the coolant by removing it at a timing after the coolant has cooled (shown in Figure 2(C)) or during the cooling (shown in Figure 2(D)).

[0034] Next, using Figures 4 to 6, we will explain the comparison results of the motor system 100 according to the first embodiment, the motor system R1 according to the first comparative example, and the motor system R2 according to the second comparative example.

[0035] Figure 4 shows the configurations of motor system R1 according to the first comparative example and motor system R2 according to the second comparative example.

[0036] Figure 4(A) shows the configuration of motor system R1 according to the first comparative example. Motor system R1 is a system that employs a cooling method in which cooling oil is dripped onto the motor stator to cool the stator.

[0037] On the other hand, Figure 4(B) shows the configuration of motor system R2 according to the second comparative example. Motor system R2 is a system that employs a cooling method in which the stator is cooled by submerging the stator in cooling oil. Here, motor system R2 is also the stator cooling method disclosed in Patent Document 1. Furthermore, the cooling method in which the stator is cooled by submerging the stator in cooling oil is also employed in motor system 100 according to the first embodiment. By employing this cooling method, motor system R2 improves the cooling efficiency of the stator compared to motor system R1.

[0038] Table 1 below shows the comparison results for motor system 100, motor system R1, and motor system R2. The items compared are: "cooling method," "cooling efficiency," "water absorption of cooling oil at 85°C and 85% humidity," "presence or absence of a water removal mechanism," "presence or absence of water droplets in the cooling oil after cooling to 25°C," "dielectric breakdown voltage of the cooling oil after cooling to 25°C," and "insulation reliability."

[0039] [Table 1]

[0040] The following is supplementary information for Table 1. (*1) The "water absorption of coolant at 85°C and 85% RH" was determined as follows: The maximum water absorption under actual operating conditions was assumed, and the amount of water absorbed when the coolant was exposed to an 85°C, 85% RH environment for 6 hours was determined. As shown in Figure 3, the saturated water absorption at 85°C is 660 ppm.

[0041] (*2) The presence or absence of water droplets in the coolant after cooling to 25°C was determined as follows. Figure 5 shows the results of a verification experiment to determine the presence or absence of water droplets in the coolant after cooling to 25°C in the motor system 100 according to the first embodiment. As shown in Figure 5, after the coolant was cooled to 25°C after absorbing moisture in an 85°C 85%RH environment, the presence or absence of water droplets in the coolant was visually confirmed. Here, a sample was prepared in which the coolant was sealed in a container that allowed water vapor to pass through only one side, corresponding to the motor system 100 according to the first embodiment (the sample with an open container in this figure). In addition, a sample was prepared in which the coolant was sealed in a container that did not allow water vapor to pass through, corresponding to the motor system R2 according to the second comparative example (the sample with a closed container in this figure). As shown in this figure, it was confirmed that there were no water droplets in the coolant after cooling to 25°C in the sample with an open container. On the other hand, it was confirmed that there were water droplets in the coolant after cooling to 25°C in the sample with a closed container.

[0042] (*3) The dielectric breakdown voltage of the coolant after cooling to 25°C was determined as follows. Figure 6 shows the results of a verification experiment of the dielectric breakdown voltage of the coolant after cooling to 25°C in the motor system 100 according to the first embodiment. As shown in Figure 6(A), electrodes were inserted into the coolant after cooling to 25°C, and the distance between the electrodes was set to 0.5 mm. Furthermore, a voltage of up to 5 kV was applied using a dielectric strength tester, and the voltage at which dielectric breakdown occurs between the electrodes (dielectric breakdown voltage) was measured. Here, as shown in Figure 6(B), when there were no water droplets between the electrodes, dielectric breakdown did not occur even when a voltage of 5 kV was applied. On the other hand, as shown in Figure 6(C), when there were water droplets between the electrodes, dielectric breakdown occurred at 1.5 kV. This is because the presence of water droplets at the location where the electric field is applied reduces the insulation distance, and thus the dielectric breakdown voltage decreases.

[0043] (*4) "Insulation reliability" was determined as follows: If the insulation design value (rated voltage × 2 + 1kV) was 2.3kV or higher, the "insulation reliability" was judged to be high. For example, the rated voltage was set to 650V.

[0044] As described above, the motor system 100 employs a cooling method in which the stator 11 is cooled by submerging it in cooling oil, thus increasing the cooling efficiency of the stator 11. The motor system 100 is equipped with a moisture removal mechanism 5, which removes water droplets from the cooling oil after it has cooled from 85°C to 25°C. In the motor system 100, since the moisture is removed from the cooling oil after it has cooled to 25°C, the dielectric breakdown voltage of the cooling oil after it has cooled to 25°C is high, and the insulation reliability is also high. Therefore, the motor system 100 can reduce the possibility of the stator 11 experiencing insulation failure.

[0045] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention. [Explanation of Symbols]

[0046] 1 Motor, 2 Case, 3 Circulation path, 4 Cooling mechanism, 4a Radiator, 4b Water jacket, 5 Moisture removal mechanism, 6 TA case, 7 Relief valve, 11 Stator, 12 Rotor, 21 Outlet, 22 Inlet, 51 Tank, 52 Relief valve, 53 Membrane, 100 Motor system

Claims

1. A case in which the motor stator is housed and which is filled with cooling oil so as to submerge the stator, A circulation path is provided in the case, connecting the outlet and inlet, and circulating the cooling oil. A cooling mechanism is positioned in the middle of the circulation path and cools the cooling oil circulating in the circulation path, The circulation path includes a moisture removal mechanism positioned downstream of the cooling position of the cooling mechanism or at the same position as the cooling position of the cooling mechanism, which removes moisture from the cooling oil that has been cooled or is being cooled by the cooling mechanism. Motor system.

2. The aforementioned moisture removal mechanism is A tank that temporarily stores a certain amount of cooling oil circulating in the aforementioned circulation path, and is further filled with a gas capable of receiving water vapor evaporated from the stored cooling oil, The tank is equipped with a relief valve that can exchange the gas filled in the tank with gas from outside the tank, depending on the internal pressure of the tank. The motor system according to claim 1.

3. The aforementioned moisture removal mechanism is The tank further comprises a membrane that is permeable only to water vapor and is positioned to surround the hollow portion of the tank. The aforementioned film is It is positioned at a height greater than the liquid level of the coolant stored in the aforementioned tank. The motor system according to claim 2.

Images