WO2020137703A1 - Cooling system - Google Patents

Abstract

This cooling system for cooling a to-be-cooled object (2) in which electricity flows is provided with a coolant (12) that cools the to-be-cooled object, and a radiator (18) that causes the coolant to radiate heat. The coolant has electric insulation properties, and contains: a liquid base material containing water; and an orthosilicate ester compatible with the base material.

Description

Cooling system Cross-reference to related application

This application is based on Japanese Patent Application No. 2018-243352 filed on December 26, 2018 and Japanese Patent Application No. 2019-227007 filed on December 17, 2019, where Its description is incorporated by reference.

The present disclosure relates to a cooling system.

There is a cooling system disclosed in Patent Document 1 as a cooling system that cools an object to be cooled through which electricity flows with an electrically insulating cooling liquid. In the cooling system of Patent Document 1, the cooling target is immersed in the cooling liquid, and the cooling target is directly cooled by the cooling liquid. Further, as another cooling system, there is one in which an object to be cooled is indirectly cooled by a cooling liquid via a heat transfer member. In these cooling systems, silicone oil or fluorine-based inert liquid is used as the cooling liquid.

JP, 2008-125363, A

The above-mentioned conventional electrically insulating coolant has a low heat transfer property. Therefore, in the case of directly cooling the cooling target with the cooling liquid, the size of the pump for sending the cooling liquid and the size of the radiator for releasing the heat of the cooling liquid are increased so that the cooling target is sufficiently cooled. Was needed. This is because the size of the pump increases and the flow rate of the cooling liquid increases, so that the amount of heat input from the cooling target to the cooling liquid increases. In addition, as the radiator becomes larger, the amount of heat released from the coolant increases.

Further, in the case of indirectly cooling the cooling target with the cooling liquid, it is necessary to increase the size of the cooler including the heat transfer member and the size of the radiator so that the cooling target is sufficiently cooled. This is because the size of the cooler and the size of the heat radiator increase the amount of heat input from the object to be cooled to the cooling liquid and the amount of heat radiation from the cooling liquid.
As described above, in the conventional cooling system, it is necessary to increase the size of the components that make up the cooling system. As a result, the entire cooling system is large.

The present disclosure aims to provide a cooling system capable of downsizing the entire system.

In order to achieve the above object, according to one aspect of the present disclosure,
A cooling system that cools a cooling object that flows electricity
A cooling liquid for cooling the object to be cooled,
With a radiator that releases the heat of the cooling liquid,
The cooling liquid contains a liquid base material containing water and an orthosilicate ester compatible with the base material, and has electrical insulation properties.

According to this, the cooling liquid has a function of rust prevention because the cooling liquid contains orthosilicate ester. Therefore, it is possible to reduce the amount of the ionic rust preventive contained in the cooling liquid as compared with the cooling liquid containing the ionic rust preventive for rust prevention. That is, the conductivity of the cooling liquid can be lowered as compared with the cooling liquid containing an ionic anticorrosive agent for rust prevention. As a result, the cooling liquid can be provided with electrical insulation.

Furthermore, the base material of this cooling liquid contains water, which has a higher heat transfer property than the conventional cooling liquid described above. Therefore, the heat transfer property of this cooling liquid can be made higher than that of the conventional cooling liquid described above. By using a cooling liquid having a heat transfer property higher than that of the conventional cooling liquid, the components of the cooling system can be downsized as compared with the conventional cooling system. Therefore, the entire cooling system can be downsized.

Further, in order to achieve the above object, according to another viewpoint,
A cooling system that cools a cooling object that flows electricity
A cooling liquid for cooling the object to be cooled,
With a radiator that releases the heat of the cooling liquid,
The cooling liquid contains a liquid base material containing water and an orthosilicate ester compatible with the base material, and does not contain an ionic rust preventive agent.

According to this, the cooling liquid has a function of rust prevention because the cooling liquid contains orthosilicate ester. Therefore, the cooling liquid does not have to include the ionic rust inhibitor. Since the cooling liquid does not contain an ionic anticorrosive agent, this cooling liquid has a low electric conductivity and a high electric insulation property as compared with the case of containing an ionic anticorrosive agent.

Furthermore, the base material of this cooling liquid contains water, which has a higher heat transfer property than the conventional cooling liquid described above. Therefore, the heat transfer property of this cooling liquid can be made higher than that of the conventional cooling liquid described above. By using a cooling liquid having a higher heat transfer property than the conventional cooling liquid, it is possible to downsize the components of the cooling system as compared with the conventional cooling system. Therefore, the entire cooling system can be downsized.

Note that the reference numerals in parentheses attached to the respective components and the like indicate an example of a correspondence relationship between the components and the like and specific components and the like described in the embodiments described later.

It is a schematic diagram which shows the whole structure of the cooling system in 1st Embodiment. It is sectional drawing of the cooler in 1st Embodiment. It is sectional drawing of the cooler in 2nd Embodiment. It is sectional drawing of the electrically conductive member in 3rd Embodiment.

Hereinafter, an embodiment of the present disclosure will be described based on the drawings. In each of the following embodiments, the same or equivalent portions will be denoted by the same reference numerals for description.

(First embodiment)
The cooling system 10 shown in FIG. 1 is mounted on an electric vehicle. An electric vehicle obtains a driving force for traveling the vehicle from an electric motor for traveling. Examples of the electric vehicle include an electric vehicle, a plug-in hybrid vehicle, and an electric two-wheel vehicle. The number of wheels of the electric vehicle and the vehicle application are not limited. An electric vehicle is equipped with a traveling electric motor as an on-vehicle device, a battery 2, an inverter, and the like.

The electric motor for traveling is a motor generator that converts the electric power supplied from the battery 2 into power for traveling the vehicle and also converts the power of the vehicle into electrical power during deceleration. The traveling electric motor generates heat as power and electric power are converted.

The battery 2 is a battery for running the vehicle that supplies electric power to the electric motor for running. The battery 2 charges the electric power supplied from the traveling electric motor when the vehicle is decelerated. The battery 2 can be charged with electric power supplied from an external power source (that is, a commercial power source) when the vehicle is stopped. The battery 2 generates heat as it is charged and discharged.

The inverter is a power conversion device that converts the power supplied from the battery 2 to the electric motor for traveling from DC to AC. Further, the inverter converts the electric power charged from the traveling electric motor into the battery 2 from AC to DC. The inverter generates heat as power is converted.

The cooling system 10 includes a battery 2 that is an object to be cooled, a cooling liquid 12 that cools the battery 2, and a cooling circuit 14 in which the cooling liquid 12 flows.

The cooling liquid 12 transports the heat received from the battery 2. The cooling liquid 12 contains a liquid base material containing water and an orthosilicate ester, and does not contain an ionic rust preventive agent.

The base material is a material that becomes the base of the cooling liquid 12. The liquid base material means that it is in a liquid state in use. The base material contains a freezing point depressant in addition to water. Water is used because it has a large heat capacity, is inexpensive, and has low viscosity. The freezing point depressant is used to ensure the liquid state even when the environmental temperature is below freezing. The freezing point depressant dissolves in water and lowers the freezing point of water. As the freezing point depressant, an organic alcohol such as alkylene glycol or its derivative is used. As the alkylene glycol, for example, monoethylene glycol, monopropylene glycol, polyglycol, glycol ether and glycerin are used alone or as a mixture. The freezing point depressant is not limited to organic alcohols, and inorganic salts and the like may be used.

Orthosilicate ester is compatible with the base material. The orthosilicate ester is a compound for giving the cooling liquid 12 a function of rust prevention.

As the orthosilicate ester, a compound represented by the general formula (I) is used.

In the general formula (I), the substituents R ¹ to R ⁴ are the same or different and are an alkyl substituent having 1 to 20 carbon atoms, an alkenyl substituent having 2 to 20 carbon atoms, and a hydroxyalkyl having 1 to 20 carbon atoms. It represents a substituent, a substituted or unsubstituted aryl substituent having 6 to 12 carbon atoms and/or a glycol ether-substituent of the formula —(CH ₂ —CH ₂ —O)nR ⁵ . R ⁵ represents hydrogen or alkyl having 1 to 5 carbons. n represents a number of 1 to 5.

Typical examples of orthosilicates are pure tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetra(n-propoxy)silane, tetra(isopropoxy)silane, tetra(n-butoxy)silane, tetra. (T-butoxy)silane, tetra(2-ethylbutoxy)silane, or tetra(2-ethylhexoxy)silane, and further tetraphenoxysilane, tetra(2-methylphenoxy)silane, tetravinyloxysilane, tetraallyloxysilane, Tetra(2-hydroxyethoxy)silane, tetra(2-ethoxyethoxy)silane, tetra(2-butoxyethoxy)silane, tetra(1-methoxy-2-propoxy)silane, tetra(2-methoxyethoxy)silane or tetra[2-methoxyethoxy)silane 2-[2-(2-methoxyethoxy)ethoxy]ethoxy]silane.

As the orthosilicate ester, in the general formula (I), the substituents R ¹ to R ⁴ are the same, and an alkyl substituent having 1 to 4 carbon atoms or a formula —(CH ₂ —CH ₂ —O)n It is preferable to use a compound which represents a glycol ether substituent of —R ⁵ , R ⁵ represents hydrogen, methyl or ethyl, and n represents a number of 1, 2 or 3.

The orthosilicate ester is contained in the cooling liquid 12 so that the concentration of silicon with respect to the entire cooling liquid 12 is 1 to 10000 mass ppm. The concentration of this silicon is preferably 1 mass ppm or more and 2000 mass ppm or less. The concentration of this silicon is preferably higher than 2000 mass ppm and 10000 mass ppm or less. The above-mentioned orthosilicic acid esters are commercially available or can be prepared by simply transesterifying 1 equivalent of tetramethoxysilane with 4 equivalents of the corresponding long-chain alcohol or phenol and distilling off the methanol.

Since the cooling liquid 12 does not contain an ionic rust inhibitor, the conductivity of the cooling liquid 12 is lower than that when the cooling liquid 12 contains an ionic rust inhibitor. The conductivity of the cooling liquid 12 is 50 μS/cm or less, preferably 1 μS/cm or more and 5 μS/cm or less. As a reference, a cooling liquid containing a liquid base material containing water and an ionic rust preventive agent is engine cooling water used for cooling a vehicle engine. The conductivity of engine cooling water is 4000 μS/cm or more. As described above, the cooling liquid containing an ionic anticorrosive agent for rust prevention has high electric conductivity and does not have electric insulation.

The cooling liquid 12 may contain an azole derivative as a rust preventive agent in addition to the orthosilicate ester.

The cooling circuit 14 includes a cooler 16, a radiator 18, a pump 20, and a hose 22.

The cooler 16 cools the battery 2 by transferring heat from the battery 2 to the cooling liquid 12 by heat exchange between the battery 2 and the cooling liquid 12. As shown in FIG. 2, the cooler 16 has a flow path forming member 17 and the like that internally forms a flow path through which the cooling liquid 12 flows. The flow path forming member 17 is a heat transfer member. The cooler 16 cools the battery 2 by heat exchange between the cooling liquid 12 and the battery 2 via the flow path forming member 17. In this way, the cooler 16 indirectly cools the battery 2 with the cooling liquid 12.

The radiator 18 is a heat exchanger that radiates the heat of the cooling liquid 12 by exchanging heat with the air outside the vehicle. Air is supplied to the radiator 18 by the operation of a blower (not shown). The pump 20 is a fluid machine that sends the cooling liquid 12. The hose 22 is a flow path forming member that forms a flow path through which the cooling liquid 12 flows. The cooler 16, the radiator 18, and the pump 20 are connected by a hose 22. Thereby, the cooling circuit 14 in which the cooling liquid 12 circulates and flows is formed.

By operating the pump 20, the cooling liquid 12 circulates between the cooler 16 and the radiator 18. At this time, the cooling liquid 12 receives heat from the battery 2 in the cooler 16. In the radiator 18, the cooling liquid 12 releases heat to the air outside the vehicle. Thereby, the battery 2 is cooled.

As described above, the cooling system 10 of this embodiment includes the cooling liquid 12 and the radiator 18. The cooling liquid 12 contains a liquid base material containing water and an orthosilicate ester, and does not contain an ionic rust preventive agent.

The cooling liquid 12 has a function of rust prevention because the cooling liquid 12 contains an orthosilicate ester. Therefore, the cooling liquid 12 may not include the ionic rust preventive agent. Since the cooling liquid 12 does not contain an ion rust preventive, the cooling liquid 12 has a lower electric conductivity and a higher electric insulating property than a cooling liquid containing an ion rust preventive.

Further, the base material of the cooling liquid 12 contains water having a higher heat transfer property than the conventional cooling liquid described above. Therefore, the heat transfer property of the cooling liquid 12 can be made higher than that of the conventional cooling liquid described above.

Here, Table 1 shows the thermal conductivity of the cooling liquid 12 of the present embodiment, the conventional cooling liquid such as silicone oil, and the fluorine-based inert liquid.

The cooling liquid 12 of the first embodiment in Table 1 contains water and ethylene glycol as base materials. The cooling liquid 12 contains tetraethoxysilane as an orthosilicate ester. The mass ratio of water to ethylene glycol is 1:1. The silicone oils in Table 1 are KF-96 series silicone oils manufactured by Shin-Etsu Silicone. The fluorine-based inert liquid in Table 1 is a high-performance liquid of the Novec 7000 series manufactured by 3M Company. The thermal conductivity in Table 1 is a value at 25°C.

As shown in Table 1, the thermal conductivity of the cooling liquid 12 of the present embodiment is 0.4 W/mK, and the thermal conductivity of the conventional cooling liquid is 0.1 W/mK and 0.07 W/mK. Is also high. This is because the thermal conductivity of the base material containing water is higher than 0.1 W/mK.

There is a relationship between the heat conductivity and the heat transfer coefficient that the higher the heat conductivity, the higher the heat transfer coefficient. Therefore, the heat transfer coefficient of the cooling liquid 12 of this embodiment is higher than the heat transfer coefficient of the conventional cooling liquid. That is, the heat transferability of the cooling liquid 12 of this embodiment is higher than the heat transferability of the conventional cooling liquid.

According to the cooling system 10 of the present embodiment, by using the cooling liquid 12 having a higher heat transfer property than that of the conventional cooling liquid, each of the cooler 16 and the radiator 18 is smaller than the conventional cooling system. Is possible. Therefore, the entire cooling system 10 can be downsized.

(Second embodiment)
In the present embodiment, the cooling circuit 14 includes a cooler 24 shown in FIG. 3 instead of the cooler 16 of the first embodiment. The cooler 24 directly cools the battery 2 with the cooling liquid 12. Specifically, the cooler 24 has a container 26 that stores the cooling liquid 12. The battery 2 is immersed in the cooling liquid 12 inside the container 26. The cooler 24 directly transfers heat from the battery 2 to the cooling liquid 12 by heat exchange between the battery 2 and the cooling liquid 12 to cool the battery 2.

The other configuration of the cooling system 10 is the same as that of the first embodiment. Also in this embodiment, the same effect as that of the first embodiment can be obtained.

(Third Embodiment)
As shown in FIG. 4, in the present embodiment, the battery 2 has a conductive member 30. An electrically insulating coating layer 32 that covers the surface of the conductive member 30 is formed on the conductive member 30. That is, the battery 2 has the coating layer 32. The coating layer 32 is composed of an organic compound, an inorganic compound, or a mixture thereof.

The conductive member 30 may be an electrode of the battery 2, a case, or the like. For example, when the conductive member 30 is the electrode of the battery 2, the coating layer 32 is formed on the surface of the electrode. Further, for example, when the conductive member 30 is a case forming the outer shape of the battery 2, the coating layer 32 is formed on the entire surface of the case. In this way, the coating layer 32 is formed on the surface of part or all of the battery 2.

According to this embodiment, even if the conductivity of the cooling liquid 12 rises for some reason and the cooling liquid 12 touches the battery 2, it is possible to prevent a liquid junction from occurring in the battery 2. it can.

(Other embodiments)
(1) In each of the above-described embodiments, the battery 2 is an object to be cooled. However, other in-vehicle devices such as a motor generator, an inverter, and a computer mounted in a vehicle in which electricity flows may be the object to be cooled. Further, the object to be cooled may be one that is not mounted on the vehicle as long as electricity flows. Examples of such an object to be cooled include an electric device such as an inverter included in a stationary charging station that charges a battery of an electric vehicle. Further, a large-scale computer for stationary use can be mentioned.

(2) In each of the above-described embodiments, the cooling liquid 12 does not include an ionic rust preventive agent. However, if the cooling liquid 12 has electrical insulation, the cooling liquid 12 may contain an ionic rust preventive agent. Examples of the ionic rust preventive agent include nitrite, molybdate, chromate, phosphonate, phosphate, sebacic acid, and triazole compound. The phrase "the cooling liquid 12 has electrical insulation" as used herein means that the conductivity of the cooling liquid 12 is 500 μS/cm or less. This conductivity is a measured value at room temperature, for example, 25°C. According to the experimental results of the present inventor, the conductivity of the cooling liquid is 500 μS/cm or less, and thus it is possible to suppress the occurrence of the liquid junction in the cooling target. In order to suppress the liquid junction, the conductivity of the cooling liquid 12 is preferably 100 μS/cm or less, and more preferably 10 μS/cm or less.

Even in this case, the cooling liquid has a function of rust prevention by containing the orthosilicate ester in the cooling liquid. Therefore, it is possible to reduce the amount of the ionic rust preventive agent contained in the cooling liquid as compared with the cooling liquid containing the ionic rust preventive agent (for example, engine cooling water) for rust prevention. That is, the conductivity of the cooling liquid can be lowered as compared with the cooling liquid containing an ionic anticorrosive agent for rust prevention. As a result, the cooling liquid can be provided with electrical insulation.

(3) The present disclosure is not limited to the above-described embodiment, can be modified as appropriate, and includes various modifications and modifications within the equivalent range. Further, the above embodiments are not unrelated to each other, and can be appropriately combined unless a combination is obviously impossible. Further, in each of the above-mentioned embodiments, it is needless to say that the elements constituting the embodiment are not necessarily indispensable except when explicitly specified as being indispensable and when it is considered to be indispensable in principle. Yes. Further, in each of the above-mentioned embodiments, when numerical values such as the number of components of the embodiment, numerical values, amounts, ranges, etc. are mentioned, it is clearly limited to a particular number and in principle limited to a specific number. It is not limited to the specific number, except in the case of being performed. Further, in each of the above-mentioned embodiments, when referring to materials, shapes, positional relationships, etc. of constituent elements, etc., unless specifically stated or in principle limited to specific materials, shapes, positional relationships, etc. However, the material, shape, positional relationship, etc. are not limited.

(Summary)
According to the first aspect shown in part or all of each of the above-described embodiments, the cooling system that cools the cooling object through which electricity flows releases the cooling liquid that cools the cooling object and the heat of the cooling liquid. The cooling liquid, which includes a heat radiator, includes a liquid base material containing water and an orthosilicate ester compatible with the base material, and has electrical insulation.

According to the second aspect, the cooling system that cools the cooling object through which electricity flows includes a cooling liquid that cools the cooling object and a radiator that releases the heat of the cooling liquid. The cooling liquid contains a liquid base material containing water and an orthosilicate ester compatible with the base material, and does not contain an ionic rust inhibitor.

Also, according to the third aspect, the conductivity of the cooling liquid is 500 μS/cm or less. As described above, the cooling liquid has an electric insulating property with an electric conductivity of 500 μS/cm or less. As a result, it is possible to suppress the occurrence of a liquid junction in the object to be cooled.

According to the fourth aspect, the cooling system further includes a cooler. The cooler has a flow path forming member that forms a flow path through which the cooling liquid flows. The cooler cools the object to be cooled by heat exchange between the cooling liquid and the object to be cooled via the flow path forming member.

The configurations of the fourth aspect can be adopted from the first to third aspects. According to this, by using the cooling liquid having a higher heat transfer property than the conventional cooling liquid, it is possible to downsize the cooler as compared with the conventional cooling system. Therefore, the cooling system can be downsized.

Further, according to the fifth aspect, the cooling system further includes an object to be cooled. The cooling target has a conductive member and an electrically insulating coating layer that covers the surface of the conductive member. According to this, even if the conductivity of the cooling liquid rises for some reason, it is possible to avoid the occurrence of a liquid junction in the object to be cooled.

Claims (5)

A cooling system for cooling a cooling object (2) through which electricity flows,
A cooling liquid (12) for cooling the cooling target;
A radiator (18) for releasing the heat of the cooling liquid,
A cooling system in which the cooling liquid includes a liquid base material containing water and an orthosilicate ester compatible with the base material, and has electrical insulation. A cooling system for cooling a cooling object (2) through which electricity flows,
A cooling liquid (12) for cooling the cooling target;
A radiator (18) for releasing the heat of the cooling liquid,
A cooling system in which the cooling liquid contains a liquid base material containing water and an orthosilicate ester compatible with the base material, and does not contain an ionic rust inhibitor. The cooling system according to claim 1 or 2, wherein the conductivity of the cooling liquid is 500 µS/cm or less. Cooling that has a flow path forming member (17) that forms a flow path through which the cooling liquid flows, and cools the cooling target object by heat exchange between the cooling liquid and the cooling target object via the flow path forming member. Cooling system according to any one of claims 1 to 3, further comprising a vessel (16). Further comprising the cooling object,
The cooling system according to any one of claims 1 to 4, wherein the object to be cooled has a conductive member (30) and an electrically insulating coating layer (32) covering a surface of the conductive member.

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