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 a cooling system.

Background Art

[0002] Various technologies have been proposed regarding cooling systems as disclosed in Patent Documents 1 to 5.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0004] For a cooling system of a secondary battery (battery), insulation of the coolant is required. Also, in electric vehicles with intense cost competition, cost reduction is required for the cooling system. Furthermore, in electric vehicles where heat-generating devices (secondary batteries, inverters, converters, generators, motors, etc.) are mounted at high density, a cooling system that can efficiently cool even when the flow path of the coolant is made narrow (small cross-sectional area) is required. With conventional coolants, it is difficult to achieve both cooling performance and compatibility with low-cost nitrile rubber.

[0005] The present disclosure has been made in view of the above circumstances, and the main object thereof is to provide a cooling system with low cost and high cooling efficiency.

Means for Solving the Problems

[0006] In other words, this disclosure includes the following aspects: <1> A cooling system for cooling heat-generating equipment in an electric vehicle, The cooling system comprises a coolant, a flow path for the coolant, and a pump for circulating the coolant within the flow path. The aforementioned flow channel includes a portion of the flow channel wall containing nitrile rubber, The cooling system is characterized by a coolant containing 95% by mass or more of mineral oil and having an aniline point of 80°C to 105°C.

[0007] <2> The coolant has a kinematic viscosity of 5 mm at 40°C. 2 The above is less than or equal to / s. <1> The cooling system described above.

[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 described above.

[0009] <4> The coolant contains an additive, The additive is at least one selected from the group consisting of defoaming agents, antioxidants, rust inhibitors, pour point depressants, dispersants, surfactants, and flow antistatic agents. <1> The cooling system described above. [Effects of the Invention]

[0010] The cooling system described herein is low-cost and highly efficient. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram of the test machine used to evaluate the cooling performance of the coolant. [Modes for carrying out the invention]

[0012] Embodiments of this disclosure are described below. Matters other than those specifically mentioned herein but necessary for the implementation of this disclosure (e.g., general configurations and manufacturing processes of cooling systems not characterizing this disclosure) can be understood as design matters for those skilled in the art based on prior art. This disclosure can be implemented based on the content disclosed herein and common technical knowledge in the art. Furthermore, the dimensions (length, width, thickness, etc.) shown in the diagram do not necessarily reflect the actual dimensions.

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

[0014] Traditionally, cooling components have been made with an insulating structure, and water-based coolants with low insulating properties have been used. However, adding an insulating structure to the cooling component means that a material with poor heat transfer properties is sandwiched between the part to be cooled and the coolant, thus reducing cooling performance. Commonly used water-based coolants (ethylene glycol-based) have low insulating properties. On the other hand, mineral oils, which have excellent insulating properties, also require consideration of their compatibility with rubber materials used in hoses and other applications. A common indicator used to determine rubber compatibility is the aniline point. A low aniline point generally indicates a greater swelling effect on the rubber, requiring caution regarding leakage. Conversely, an excessively high aniline point causes the rubber to shrink, also raising concerns about leakage. Traditionally, in applications involving lubricants, acrylic rubber, which is heat-resistant and operates at relatively high temperatures, has been used. Therefore, rubber compatibility is defined as aniline point specification relative to acrylic rubber compatibility. On the one hand, in the present disclosure, it is limited to cooling applications such as batteries in electric vehicles, and due to the use temperature being lower than before, although there is heat resistance like acrylic rubber, it is difficult to apply rubber that is expensive and has low oil resistance, and the application of nitrile rubber with higher oil resistance and lower cost is assumed. Since the optimal aniline point on the corresponding oil side varies depending on the rubber type, the aniline point suitable for nitrile rubber is defined in the present disclosure.

[0015] The present disclosure determines a coolant (non-aqueous) with high insulation properties for heat-generating devices such as batteries, inverters, converters, generators, motors, radiators, and oil coolers in electric vehicles, which has compatibility with nitrile rubber when applied. The cooling system of the present disclosure includes a coolant that can ensure the airtightness of the piping even when low-cost nitrile rubber is used in the coolant piping, and has a small pressure loss even when the flow path of the coolant has a small diameter. By providing the coolant of the present disclosure, even when nitrile rubber is used in the flow path piping, the swelling property can be controlled, and as a result, the airtightness of the flow path piping can be ensured. At the same time, the kinematic viscosity of the coolant can be reduced, and the pressure loss can be reduced even in a cooling system where heat-generating devices are densified and the cross-sectional area of the coolant 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 electric vehicles. An electric vehicle is a vehicle that runs by driving a motor. An electric vehicle includes a cooling system, heat-generating devices, etc.

[0017] Examples of heat-generating devices include inverters, converters, generators, motors, batteries, radiators, oil coolers, etc., and among them, inverters, converters, generators, motors, batteries, etc. may be used. [[ID=二十一]] [[ID=二十二]]The heat-generating device may have a power card. The power card may be physically in contact with the coolant. The type of battery (secondary battery) is not particularly limited, but examples include nickel-metal hydride secondary batteries and lithium-ion secondary batteries. The secondary battery may be a liquid-type secondary battery using an electrolyte solution, or a solid-state secondary battery using a solid electrolyte solution.

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

[0019] The flow path only needs to have a portion of the flow path wall containing nitrile rubber, and the flow path may be made of nitrile rubber.

[0020] The coolant contains 95% or more by mass of mineral oil and has an aniline point of 80°C to 105°C. The coolant has a kinematic viscosity of 5 mm at 40°C. 2 It may be less than / s. The coolant may contain additives. Examples of additives include defoaming agents, antioxidants, rust inhibitors, pour point depressants, dispersants, surfactants, and flow antistatic agents, and may contain one or more of these. The coolant may contain 95% or more by mass of mineral oil, or 97% or more by mass. The coolant may contain additives in an amount of 5% by mass or less, or in an amount of 3% by mass or less.

[0021] Mineral oil may contain a first hydrocarbon comprising at least one of naphthenic hydrocarbons and aromatic hydrocarbons, and a second hydrocarbon comprising at least one of paraffinic hydrocarbons and olefinic hydrocarbons. The proportion of the second hydrocarbon can be higher than that of the first hydrocarbon. To improve nitrile rubber compatibility, the aniline point can be adjusted to 80-105°C by reducing the proportion of naphthenic and aromatic hydrocarbons that cause rubber swelling and increasing the proportion of paraffinic and olefinic hydrocarbons. [Examples]

[0022] The parameters in the examples were measured and calculated using the following methods. (1) Aniline point Aniline was placed in a beaker, and an equal amount of the sample to be measured was added (aniline:sample = 5:5). The solution of aniline and the sample was cooled, and the temperature at which separation occurred was defined as the aniline point. (2) Rubber compatibility Sheet-shaped nitrile rubber pieces were immersed in a 100°C sample for 200 hours. The rubber volume swelling rate after the test was measured according to JIS standard (K6258). (3)Kinematic viscosity at 40℃ The kinematic viscosity of the sample was measured using an Ubbelohde viscometer placed in a tank maintained at 40°C, according to JIS standard (Z8803). (4) Flash point Measurements were taken using the Pennsky-Haltens sealed method according to JIS standard (K 2265-3:2007). (5) Pour point Measurements were taken according to JIS standard (K2269). (6) Cooling performance Figure 1 is a schematic diagram of the test machine used to evaluate the cooling performance of the coolant. The cooling performance Qw (W / K) of the sample was measured using the test machine shown in Figure 1, according to the following formula and evaluation conditions. <Evaluation Criteria> Desk fan airflow: 4.5 m / sec Temperature difference: 40°C (Ambient air: 25°C, Coolant: 65°C) Vw: Coolant flow rate (10 L / min) γw: Density of the coolant Cpw: Specific heat of coolant tw1: Coolant temperature upstream of the radiator tw2: Coolant temperature downstream of the radiator

[0023]

number

[0024] (Examples 1-3, Comparative Examples 1-5) 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. Furthermore, 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, where a polar base such as ethyl octanoate, as seen in conventional technology, is applied, nitrile rubber is unsuitable. Furthermore, as shown in Comparative Examples 1 to 4, when the aniline point falls outside the specified range of this disclosure, the suitability of the nitrile rubber tends to deviate from the preferred value. On the other hand, as shown in Examples 1 to 3, if the aniline point is within the specified range of this disclosure, the suitability of the nitrile rubber will be within a favorable numerical range and the desired cooling performance will be ensured.

Claims

1. A cooling system for cooling heat-generating equipment in an electric vehicle, The cooling system comprises a coolant, a flow path for the coolant, and a pump for circulating the coolant within the flow path. The aforementioned flow channel includes a portion of the flow channel wall containing nitrile rubber, The cooling system is characterized by a coolant containing 95% by mass or more of mineral oil and having an aniline point of 80°C to 105°C.

2. The coolant has a kinematic viscosity of 5 mm at 40°C. ２ The cooling system according to claim 1, wherein the speed is less than or equal to / s.

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 contains an additive, The cooling system according to claim 1, wherein the additive is at least one selected from the group consisting of defoaming agents, antioxidants, rust inhibitors, pour point depressants, dispersants, surfactants, and flow antistatic agents.

5. The cooling system according to claim 1, wherein the coolant contains 95% by mass or more and 97% by mass or less of the mineral oil and has an aniline point of 80°C to 105°C.

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