Cooling system

Abstract

To provide a cooling system of low cost and high cooling efficiency.SOLUTION: A cooling system for cooling a heating device in an electric vehicle, comprises a cooling liquid, a channel for the cooling liquid, and a pump for circulating the cooling liquid in the channel, the channel has a portion containing nitrile rubber in the channel wall, and the cooling liquid contains 95 mass% or more mineral oil and has an aniline point of 80°C to 105°C.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to cooling systems. [Background technology]

[0002] Various techniques have been proposed for cooling systems as disclosed in Patent Documents 1-5. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-146320 A [Patent Document 2] Patent Publication No. 2021-068838 [Patent Document 3] JP 2017-091801 A [Patent Document 4] JP 2016-190953 A [Patent Document 5] JP 2011-252100 A Summary of the Invention [Problem to be solved by the invention]

[0004] Cooling systems for secondary batteries require insulating coolant. In addition, in electric vehicles where cost competition is fierce, there is a demand for low-cost cooling systems. Furthermore, electric vehicles, which are densely equipped with heat-generating devices (secondary batteries, inverters, converters, generators, motors, etc.), require cooling systems that can efficiently cool even when the coolant flow path is narrowed (reduced cross-sectional area). With conventional coolants, it is difficult to achieve both cooling properties and compatibility with low-cost nitrile rubber.

[0005] The present disclosure has been made in consideration of the above-described circumstances, and has a primary object to provide a cooling system that is low-cost and has high cooling efficiency. [Means for solving the problem]

[0006] That is, the present disclosure includes the following aspects. <1> A cooling system for cooling a heat-generating device in an electric vehicle, The cooling system includes a coolant, a flow path for the coolant, and a pump for circulating the coolant within the flow path; The flow path has a portion including nitrile rubber in a flow path wall, The cooling system, wherein the coolant contains 95% by mass or more of mineral oil and has an aniline point of 80°C to 105°C.

[0007] <2> The cooling liquid has a kinetic viscosity of 5 mm at 40°C. 2 / s or less, <1> The cooling system according to claim 1 .

[0008] <3> The heat generating device is at least one selected from the group consisting of an inverter, a converter, a generator, a motor, and a battery. <1> The cooling system according to claim 1 .

[0009] <4> the coolant comprises an additive; The additive is at least one selected from the group consisting of an antifoaming agent, an antioxidant, a rust inhibitor, a pour point depressant, a dispersant, a surfactant, and a flow antistatic agent. <1> The cooling system according to claim 1 . Effect of the Invention

[0010] The cooling system of the present disclosure has low cost and high cooling efficiency. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a schematic diagram of a test machine used to evaluate the cooling performance of a coolant. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present disclosure will be described. Note that matters other than those specifically mentioned in this specification and necessary for implementing the present disclosure (for example, the general configuration and manufacturing process of a cooling system that does not characterize the present disclosure) can be understood as design matters of a person skilled in the art based on the prior art in the field. The present disclosure can be implemented based on the contents disclosed in this specification and the technical common sense in the field. Furthermore, the dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect the actual dimensional relationships.

[0013] The present disclosure provides a cooling system for cooling heat-generating equipment in an electric vehicle, The cooling system includes a coolant, a flow path for the coolant, and a pump for circulating the coolant within the flow path; The flow path has a portion including nitrile rubber in a flow path wall, The cooling system includes a cooling liquid containing 95% by mass or more of mineral oil and having an aniline point of 80°C to 105°C.

[0014] Conventionally, the cooling component side has been made to have an insulating structure, and a water-based coolant with low insulating properties has been used as the coolant. However, adding an insulating structure to the cooling component side means that a material with poor thermal conductivity is sandwiched between the part to be cooled and the coolant, which reduces cooling performance. Commonly used water-based coolants (ethylene glycol-based) have low insulating properties. On the other hand, even with mineral oils, which have excellent insulating properties, it is necessary to consider their compatibility with rubber materials used in hoses, etc. Aniline point is a common indicator of rubber compatibility. A low aniline point generally has a greater effect on swelling the rubber, so care must be taken to prevent leakage. If the aniline point is too high, the rubber will shrink, which can also lead to leakage. Conventionally, in cases where lubricants are used, acrylic rubber, which has a relatively high operating temperature and is heat resistant, has been used, so rubber compatibility = aniline point standard for acrylic rubber compatibility. On the other hand, in the present disclosure, the application is limited to cooling applications such as batteries in electric vehicles, and since the operating temperature is lower than conventional ones, it is difficult to apply rubber such as acrylic rubber, which has heat resistance but is expensive and has low oil resistance, and it is assumed that nitrile rubber, which has higher oil resistance and is inexpensive, will be applied. Since the optimal aniline point of the corresponding oil side varies depending on the type of rubber, the present disclosure specifies the aniline point suitable for nitrile rubber.

[0015] This disclosure specifies a coolant that is compatible with nitrile rubber when used as a highly insulating coolant (non-aqueous) for heat-generating equipment such as batteries, inverters, converters, generators, motors, radiators, and oil coolers for electric vehicles. The cooling system of the present disclosure is provided with a coolant that can ensure airtightness of the piping even when low-cost nitrile rubber is used for the coolant piping, and that has small pressure loss even when the coolant flow path has a small diameter. By using the cooling liquid of the present disclosure, even if nitrile rubber is used in the flow path piping, the swelling can be controlled, and as a result, the airtightness of the flow path piping can be ensured. At the same time, the kinetic viscosity of the cooling liquid can be reduced, and pressure loss can be reduced even in a cooling system in which the heat generating devices are highly dense and the cross-sectional area of ​​the cooling liquid flow path is small. As a result, a low-cost and highly efficient cooling system can be achieved.

[0016] The cooling system of the present disclosure cools heat-generating devices in an electric vehicle. An electric vehicle is a vehicle that runs by being driven by a motor. Electric vehicles are equipped with cooling systems, heat-generating equipment, etc.

[0017] Examples of the heat-generating device include an inverter, a converter, a generator, a motor, a battery, a radiator, and an oil cooler. Among them, the heat-generating device may be an inverter, a converter, a generator, a motor, a battery, or the like. The heat generating device may have a power card, which may be in physical contact with the cooling fluid. The type of battery (secondary battery) is not particularly limited, but examples include nickel-metal hydride secondary batteries, lithium-ion secondary batteries, etc. The secondary battery may be a liquid secondary battery that uses an electrolytic solution as the electrolyte, or a solid secondary battery that uses a solid electrolyte as the electrolyte.

[0018] The cooling system includes a coolant, a flow path for the coolant, and a pump for circulating the coolant through the flow path.

[0019] The flow path may be made of nitrile rubber as long as the flow path has a portion including nitrile rubber in the flow path wall.

[0020] The coolant contains 95% by mass or more of mineral oil and has an aniline point of 80°C to 105°C. The coolant has a kinetic viscosity of 5mm at 40°C. 2 / s or less. The coolant may contain additives. The additives include antifoaming agents, antioxidants, rust inhibitors, pour point depressants, dispersants, surfactants, and flow antistatic agents, and the like, and the composition may contain one or more of these. The coolant may contain 95% by mass or more of mineral oil, and may contain 97% by mass or more. The coolant may contain up to 5% by mass of the additive, or may contain up to 3% by mass of the additive.

[0021] The mineral oil may include a first hydrocarbon including at least one of naphthenic hydrocarbons and aromatic hydrocarbons, and a second hydrocarbon including at least one of paraffinic hydrocarbons and olefinic hydrocarbons. The blending ratio of the second hydrocarbon may be higher than that of the first hydrocarbon. To improve compatibility with nitrile rubber, the aniline point can be adjusted to 80-105°C by reducing the ratio of naphthenic and aromatic hydrocarbons that swell the rubber and increasing the ratio of paraffinic and olefinic hydrocarbons. EXAMPLES

[0022] The parameters in the examples were measured and calculated by the following methods. (1) Aniline point Aniline was placed in a beaker, and the same amount of the measurement sample was added (aniline: measurement sample = 5:5). The solution containing aniline and the measurement sample was cooled, and the temperature at which they separated was taken as the aniline point. (2) Rubber compatibility A sheet-shaped nitrile rubber piece was immersed for 200 hours in the measurement sample at 100°C. After the test, the rubber volume swelling rate was measured according to JIS standard (K6258). (3)Kinematic viscosity at 40℃ The Ubbelohde viscometer was placed in a tank controlled at 40°C, and the kinetic viscosity of the measurement sample was measured according to the JIS standard (Z8803). (4) Flash point Measurements were taken using the Pensky-Martens closed-cell method according to JIS standard (K 2265-3:2007). (5) Pour point Measurements were taken according to JIS standard (K2269). (6) Cooling performance FIG. 1 is a schematic diagram of a testing machine used to evaluate the cooling performance of a coolant. The cooling performance Qw (W / K) of the measurement sample was measured using the tester shown in FIG. 1 according to the following formula and evaluation conditions. <Evaluation conditions> Desk fan airflow: 4.5m / sec Temperature difference: 40℃ (outside air: 25℃, coolant: 65℃) Vw: Coolant flow rate (10L / min) γw: Density of the coolant Cpw: Specific heat of the coolant tw1: Coolant temperature upstream of the radiator tw2: Coolant temperature downstream of the radiator

[0023]

number

[0024] (Examples 1 to 3, Comparative Examples 1 to 5) Coolants containing the components shown in Table 1 were prepared and the performance of each coolant was evaluated. The results are shown in Table 1. The physical properties of mineral oils 1 to 6 shown in Table 1 are shown in Table 2.

[0025] [Table 1]

[0026] [Table 2]

[0027] In Comparative Example 5, which uses a polar base such as ethyl octanoate found in the prior art, there is no compatibility with nitrile rubber. Furthermore, as shown in Comparative Examples 1 to 4, when the aniline point is outside the range specified in the present disclosure, the compatibility of the nitrile rubber tends to deviate from the preferred values. On the other hand, as shown in Examples 1 to 3, if the aniline point is within the range specified in the present disclosure, the compatibility of the nitrile rubber falls within a preferred numerical range and the desired cooling performance is ensured.

Claims

1. A cooling system for cooling a heat-generating device in an electric vehicle, The cooling system includes a coolant, a flow path for the coolant, and a pump for circulating the coolant within the flow path; The flow path has a portion including nitrile rubber in a flow path wall, The cooling system, wherein the coolant contains 95% by mass or more of mineral oil and has an aniline point of 80°C to 105°C.

2. The cooling liquid has a kinetic viscosity of 5 mm at 40°C. ２ The cooling system of claim 1 , wherein the cooling system has a maximum flow rate of 100 rpm.

3. The cooling system according to claim 1 , wherein the heat-generating device is at least one selected from the group consisting of an inverter, a converter, a generator, a motor, and a battery.

4. the coolant comprises an additive; 2. The cooling system according to claim 1, wherein the additive is at least one selected from the group consisting of an antifoaming agent, an antioxidant, a rust inhibitor, a pour point depressant, a dispersant, a surfactant, and a flow antistatic agent.

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