Patent Description:
Hybrid vehicles may be powered by an electric power unit in combination with some other form power unit such as a combustion engine. The electric power unit may comprises an electric machine which alternately works as motor and generator, an electric energy storage for storing of electrical energy and power electronics for controlling the flow of electrical energy between the electrical energy store and the electric machine. The power electronics may include a DC converter and inverter for conducting electrical energy between the electrical energy storage and the electric machine. The electrical energy storage and power electronics are designed to operate within a specific temperature range. The electrical energy storage and the power electronics are heated during operation. A certain type of electrical energy storage should, for example, not be heated to a temperature above a maximum temperature of <NUM> ° C. The power electronics can be heated to a somewhat higher temperature. Consequently, it is important to cool the electrical energy storage and the power electronics during operation. Furthermore, the efficiency of the electrical energy storage and the efficiency of the power electronics are reduced than they have a too low temperature. Thus, it is also suitable to heat the electrical energy storage and the power electronics when they have a too low temperature.

<CIT> shows a vehicle powered by an electric motor. A low-temperature cooling circuit is used to cool a battery device supplying electric power to the electric motor. A high-temperature cooling circuit cools power electronics controlling the power supply to the electric motor. The low temperature cooling circuit is, via a heat exchanger, connectable to an AC circuit.

<CIT> is disclosing (<FIG>) a cooling arrangement for an electric power unit in a vehicle with two cooling systems and two radiator fans.

The object of the present invention is to provide a cooling arrangement providing an efficient temperature control of an electric energy storage and power electronics in a vehicle. A further object is to provide a cooling arrangement which can be modified in a simple manner. A further object is to provide a cooling arrangement operating in an energy efficient manner.

The above mentioned object is achieved by the arrangement according to the characterized part of claim <NUM>. The power electronics is cooled by a first cooling system and the electric energy storage is cooled by a second cooling system. The use of two different cooling systems makes it easy to provide an individual cooling of the electric energy storage and the power electronics. The cooling arrangement comprises two radiator fans providing a first cooling air flow and a second air flow. The first cooling system and the second cooling system comprise radiators and the refrigeration system comprises a condenser which can be arranged in said two cooling air flows in different combinations. This possibility makes it possible to modify the cooling arrangement in a simple manner and adapt it to different types of vehicles and climate where the vehicle is to be used. Furthermore, it is possible to distribute the required cooling of the electric energy storage on the second cooling system and the refrigeration system in a variable manner. The cooling effect of the second cooling system is defined by the input energy to the radiator fan. The cooling effect of the refrigeration system is defined by the input energy to a compressor of the refrigeration system. The arrangement makes it possible to select an appropriate distribution of the required cooling effect on the second cooling system and the refrigeration system. Preferably, the most energy efficient distribution is selected at which the total supply of input energy to the second cooling system and the refrigeration system is minimized.

According to an embodiment of the invention, the first cooling system comprises a single radiator having a first part cold by the first air flow and a second part cooled by the second coolant air flow. In this case, the different parts of the radiator may be cooled with different air flows rates from the two radiator fans. Alternatively, the first cooling system may comprises a first radiator cold by the first air flow and a second radiator cold by the second air flow. In some cases, it is more favorable to use two smaller radiators in the first cooling system instead of one large radiator.

According to an embodiment of the invention, the first cooling system comprises at least one bypass valve and a bypass line allowing a coolant flow past at least one radiator of the first cooling system. In this case, the first coolant will not be cooled in any radiator at all, in one of two radiators or in two of two radiators. In this manner, it is possible to vary the cooling of the first coolant and provide an adjusted cooling of the power electronics. The second cooling system also may comprise a bypass valve and a bypass line allowing a coolant flow past the radiator of the second cooling system. It is possible to circulate the second coolant in the second coolant system without cooling in the radiator when, for example, the electric energy storage has a too low temperature.

According to an embodiment of the invention, the arrangement comprises a heat exchanger providing heat transfer between the first coolant in the first cooling system and the second coolant in the second cooling system. In this case, it is possible to equalize the temperatures of the coolants in a position of the cooling systems. The existence of such a heat exchanger makes it possible to increase or decrease the temperature of the coolants in the both systems by supplying heat or cold to the coolant in one of the cooling systems. Said heat exchanger may be provided to transfer energy between the first coolant in a radiator outlet line of the first cooling system and the second coolant in a radiator outlet line of the second cooling system. In this position, the first coolant may be cooled to a relatively low temperature by the second coolant before it enters the power electronics. The second coolant can be cooled by the refrigeration system to a lower temperature than the first coolant by the refrigeration system before it enters the electrical energy storage. Furthermore, the radiator outlets line of the first cooling system and the second cooling systems are usually arranged close to each other in this position which facilitate the arrangement of the heat exchanger.

According to an embodiment of the invention, a radiator or a part of a radiator of the first cooling system is arranged in a downstream position of the radiator of the second cooling system with respect to the direction of the first air flow. In this case, the second coolant in the second cooling system will be cooled to a lower temperature than the first coolant in the first cooling system. Such a temperature difference between the first coolant and the second coolant is many times advantageous since the electric energy storage, which is cooled by the second coolant, usually needs to be cooled to a lower temperature than the power electronics, which is cooled by the first coolant.

According to an alternative embodiment of the invention, a radiator or a part of a radiator of the first cooling system is arranged in an upstream position of the radiator of the second cooling system with respect to the direction of the first air flow. When ambient air has a high temperature, the cooling effect of the ambient air is low. In this case, it is many times advantageous to use the first air flow to cool the first coolant in the first cooling system in order to ensure the cooling of the power electronics. In any event, the second coolant can be cooled by the refrigeration system in order to allow a suitable low temperature before it enters the electrical energy storage. On the other hand, when ambient air has a low temperature, the cooling efficiency of the ambient air is high. In this case, it is usually enough to cool the first coolant in the radiator by the second air flow. The radiator in the first air flow can be bypassed. As a consequence, the second coolant obtains a cooling in the downstream located radiator by air of ambient temperature.

According to an embodiment of the invention, a radiator or a part of a radiator of the first cooling system is arranged in a downstream position of the condenser of the refrigeration system with respect to the direction of the first air flow. Such an arrangement of the condenser and the radiator of the first cooling system is advantageous since the refrigerant usually needs to be cooled by air of a lower temperature than the first coolant in the first cooling system.

According to an embodiment of the invention, each radiator fans may be driven by an electric motor. The speed of an electric motor is easily adjustable and thus the speed of the radiator fans and the cooling air flow rates through the radiators and the condenser. The speed of the radiator fans may be controlled by a control unit. The control unit may receive information about the temperature of the an electric energy storage and power electronics and control the radiator fans in order to continuously maintain a suitable operating temperature of the electric energy storage and power electronics.

According to an embodiment of the invention, the first cooling system comprises a heat exchanger by which it is possible to heat the first coolant by an external heating source. During certain operating condition such after a cold start in a cold environment, the power electronics may have a too low temperature. In this case, a hot medium can be directed to the heat exchanger and to heat first coolant from a heating source. The first coolant heats in its turn the temperature of the power electronics to a suitable temperature level. A coolant cooling a heating source in the form of the electric machine may be used to heat the first coolant and the power electronics. The second cooling system may comprise a heat exchanger by which it is possible to heat the second coolant by a heating source. Thereby, it is possible to provide a quick heating of the electric energy storage in case it has a lower temperature than a minimum temperature. A coolant cooling a heating source in the form of a combustion engine may be used to heat the second coolant and the electric energy storage to a suitable temperature level.

According to an embodiment of the invention, the first radiator fan and the second radiator fan are positioned in the vehicle such that they provide first air flow and a second air flow which are adjacent, parallel and in the same direction. In this case, the radiator fans are arranged relatively close to each other at a surface of the vehicle. Preferably, the radiator fans are arranged at a front surface of the vehicle. In this position, the ram air will assist the radiator fans to provide the first air flow and the second air flow.

In the following preferred embodiments of the invention are described, as examples, and with reference to the attached drawings, in which:.

<FIG> shows a cooling arrangement for a schematically indicated hybrid vehicle <NUM>. The hybrid vehicle <NUM> is a powered by an electric machine <NUM> and a combustion engine <NUM>. The electric machine works alternately as motor and generator. The hybrid vehicle <NUM> comprises an electric energy storage <NUM> for storing of electrical energy and power electronics <NUM> for controlling the flow of electrical energy between the electrical energy storage 4and the electric machine <NUM>. The electrical energy storage <NUM> and the power electronics <NUM> are design to work within a respective specific temperature range. The electrical energy storage <NUM> and the power electronics <NUM> are heated during operation. Thus, the electrical energy storage <NUM> and the power electronics <NUM> need to be cooled during operation. The power electronics <NUM> is designed to have a somewhat higher temperature than the electrical energy storage <NUM>. During certain operating conditions such as after a cold start, the temperature of the electrical energy storage <NUM> and the power electronics <NUM> can be too low. In this case, it is suitable to heat the electrical energy storage <NUM> and the power electronics <NUM>.

The hybrid vehicle <NUM> comprises a first cooling system <NUM> with a first circulating coolant. The first cooling system <NUM> comprises an expansion tank <NUM>. The first coolant further comprises a radiator <NUM> where it is cooled. The first coolant enters the radiator <NUM> via a radiator inlet line 8a and leaves the radiator via a radiator outlet line 8b. The radiator outlet line 8b directs the first coolant to a pump <NUM>. The pump <NUM> circulated the first coolant in the first cooling system <NUM>. The pump <NUM> directs the first coolant to a heat exchanger <NUM> where the first coolant can be heated. In this case, a circuit <NUM>, which is a part of a cooling system cooling which cools the electric machine <NUM>, is used to heat the first coolant. A control unit <NUM> regulates the medium flow to the heat exchanger <NUM> by means of a control valve <NUM>. Alternatively, an electric heater can be used to heat the first coolant. The first coolant leaving the heat exchanger <NUM> enters the power electronics <NUM>. Primary, the first coolant is used to cool the power electronics <NUM> but it can also be used to heat the power electronics <NUM>. A temperature sensor <NUM> measures the temperature of the first coolant leaving the heat exchanger <NUM>. Finally, the first coolant is returned to the radiator <NUM>.

The hybrid vehicle <NUM> comprises a second cooling system <NUM> with a second circulating coolant. The second cooling system <NUM> comprises an expansion tank <NUM>. The second cooling system <NUM> further comprises a radiator <NUM> where it is cooled in a first step. The second coolant enters the radiator <NUM> via a radiator inlet line 17a and leaves the radiator <NUM> via a radiator outlet line 17b. The radiator inlet line 17a comprises a bypass valve <NUM>. The bypass valve <NUM> can direct the second coolant to the radiator <NUM> or to a radiator bypass line 17c directing the second coolant past the radiator <NUM> and to the radiator outlet line 17b. The radiator outlet line 17b directs the second coolant to a pump <NUM>. The pump <NUM> circulates the second coolant in the second cooling system <NUM>.

The pump <NUM> directs the second coolant to a chiller <NUM> where the second coolant can be cooled in a second step. Thereafter the second coolant enters a heat exchanger <NUM> where the second coolant can be heated. In this case, a circuit <NUM>, which is a part of a cooling system which cools the combustion engine <NUM>, is used to heat the second coolant. The control unit <NUM> regulates the coolant flow to the heat exchanger <NUM> by means of a control valve <NUM>. Alternatively, an electric heater can be used to heat the second coolant. The second coolant leaving the heat exchanger <NUM> enters the electrical energy storage <NUM>. Primary, the second coolant is used to cool the electrical energy storage <NUM> but it can also be used to heat the electrical energy storage <NUM>. A temperature sensor <NUM> measures the temperature of the second coolant when it leaves the electrical energy storage <NUM>. Finally, the second coolant is returned to the radiator <NUM>.

The hybrid vehicle <NUM> comprises a refrigeration system <NUM> with a circulating refrigerant.

The refrigeration system <NUM> comprises a condenser <NUM> where the refrigerant condenses. The liquefied refrigerant is directed to an expansion valve <NUM> where it experiences a pressure drop and a significantly lower temperature. Thereafter, the refrigerant enters an evaporator in the form of the chiller <NUM> of the second cooling system. The refrigerant is heated by the second coolant in the chiller <NUM> such that it vaporizes. The vaporized refrigerant is directed to a compressor <NUM>. The compressor <NUM> provides a compression of the refrigerant. The refrigerant leaving the compressor <NUM> and entering the condenser <NUM> has an increased pressure and an increased temperature.

The hybrid vehicle <NUM> comprises a radiator fan <NUM> driven by an electric motor <NUM>. The control unit <NUM> controls the electric motor <NUM> and the speed of the radiator fan <NUM>. The radiator fan <NUM> provides a first air flow <NUM> through a half of the radiator <NUM> of the first cooling system and the radiator <NUM> of the second cooling system. The radiator <NUM> of the second cooling system is arranged in an upstream position of the half of the radiator <NUM> of the first cooling system <NUM> with respect to the flow direction of the first air flow <NUM>. Thus, the second coolant is cooled to a lower temperature in the radiator <NUM> than the first coolant in the radiator <NUM>. The hybrid vehicle <NUM> comprises a second radiator fan <NUM> driven by an electric motor <NUM>. The control unit <NUM> controls the electric motor <NUM> and the speed of the second radiator fan <NUM>. The second radiator fan <NUM> provides a second air flow <NUM> through a remaining half of radiator <NUM> of the first cooling system and the condenser <NUM> of the refrigeration system. The condenser <NUM> of the refrigerant system <NUM> is arranged in an upstream position of the half of the radiator <NUM> of the first cooling system <NUM> with respect to the flow direction of the second air flow <NUM>. Usually, the refrigerant is cooled to a lower temperature in the condenser <NUM> than the first coolant in the radiator <NUM> but it depends on condenser load, condenser- and radiator performance.

During operation of the hybrid vehicle <NUM>, the control unit <NUM> receives information about the temperature of the first coolant from the first temperature sensor <NUM> and information about the temperature of the second coolant from the second temperature sensor <NUM>. The temperatures of the coolants are related to the temperatures of the electrical energy storage <NUM> and the power electronics <NUM>. Alternatively, temperature sensors may be used which directly measures the temperatures of the electrical energy storage <NUM> and the power electronics <NUM>. The control unit <NUM> controls the speed of the first radiator fan <NUM> and the second radiator fan <NUM> and thus the cooling of the first coolant in the radiator <NUM>. The first coolant is cooled in the radiator <NUM> to a temperature at which it cools the power electronics <NUM>. The control unit <NUM> controls by the speed of the second radiator fan <NUM> and the temperature of the second coolant leaving the radiator <NUM>. The second coolant is cooled in a first step in the radiator <NUM> and in a second step in the chiller <NUM> before it cools the electrical energy storage <NUM>.

In case the power electronics <NUM> has a too high temperature, the control unit <NUM> can increase the speed of the first fan <NUM> and/or the speed of the second fan <NUM> such that the first coolant is cooled to a lower temperature in the radiator <NUM>. In case the power electronics <NUM> has a too low, or unnecessarily low temperature, the control unit <NUM> can reduce the actual speed of the radiator fan <NUM> and/or the actual speed of the second fan <NUM> such that the first coolant leaving the radiator is cooled to a somewhat higher temperature. Alternatively or in combination, the control unit <NUM> may open the valve <NUM> such that the medium cooling the electric machine <NUM> heats the first coolant before it reaches the power electronics <NUM>.

In case the electrical energy storage <NUM> has a too high temperature, the control unit <NUM> can increase the speed of the first fan <NUM> such that the second coolant is cooled to a lower temperature in the radiator <NUM>. Alternately or in combination, the control unit <NUM> can activate the compressor <NUM> and provide a cooling of the second coolant in a second step in the chiller <NUM> before it enters the electrical energy storage <NUM>. In order to further increase the cooling of the second coolant, the control unit <NUM> can increase the actual speed of the radiator fan <NUM> such that the refrigerant receives a lower condensation temperature in the condenser <NUM> resulting in an increased cooling of the second coolant in the chiller <NUM>. In case the electrical energy storage <NUM> has a too low temperature, the control unit <NUM> can reduce the actual speed of the first radiator fan <NUM> and the cooling of the second coolant the radiator <NUM>. Alternatively, the control unit <NUM> can reduce the actual speed of the second radiator fan <NUM> and reduce the cooling of the refrigerant in the condenser <NUM>. Furthermore, the control unit <NUM> can set the bypass valve <NUM> in a bypass position in which it directs the flow of the second coolant to the bypass line <NUM> and past the radiator <NUM>. The control unit <NUM> also can shut off the compressor <NUM> of the compressor refrigeration system <NUM>. As a result, the second coolant receives no cooling in the chiller <NUM>. Finally, the control unit <NUM> may open the valve <NUM> such that the coolant cooling the combustion engine <NUM> heats the second coolant in the heat exchanger 21before it enters the electrical energy storage <NUM>.

Consequently, the control unit <NUM> has a lot of options to regulate the temperatures of the first coolant and the second coolant before they cool the electrical energy storage <NUM> and the power electronics <NUM>. The control unit <NUM> has access to information about the most energy efficient option during different temperatures of the electrical energy storage <NUM> and the power electronics <NUM>. The control unit <NUM> selects the most energy efficient option to maintain or adjust the actual temperatures of the electrical energy storage <NUM> and the power electronics <NUM>. The most energy efficient can be defined as a minimum supply of electric energy to the radiator fans <NUM>, <NUM> and to the compressor <NUM> of the refrigeration system <NUM>.

<FIG> shows an alternative embodiment of the cooling arrangement. In this case, the radiator <NUM> has been divided into a two smaller radiators <NUM><NUM>, <NUM><NUM>. It is usually easier to find space for two smaller radiators <NUM><NUM>, <NUM><NUM> than for a single large radiator <NUM>.

Furthermore, the first cooling system comprises a bypass line <NUM>, a first bypass valve <NUM> and a second bypass valve <NUM>. The control unit <NUM> may set the first bypass valve <NUM> in a non- bypass position in which it directs the first coolant flow to the radiator <NUM><NUM> cooled by the second air flow <NUM> or in a bypass position in which it directs the first coolant flow past the radiator <NUM><NUM>, <NUM><NUM>. The control unit <NUM> may set the second bypass valve <NUM> in a non- bypass position in which it directs the first coolant flow to the radiator <NUM><NUM> cooled by the first air flow <NUM> or in a bypass position in which it directs the first coolant flow past the radiator <NUM><NUM> cooled by the first air flow <NUM>. In this case, the control unit <NUM> achieves further option to regulate the temperature of the first coolant and the cooling/heating of the power electronics <NUM>.

<FIG> shows a further alternative embodiment of the cooling arrangement. In this case, a heat exchanger <NUM> is used to conduct heat energy between the first coolant in a radiator outlet line 8b and the second coolant in the radiator outlet line 17b. In this case, the temperature difference between the first coolant and the second coolant can be substantially eliminated. During operating conditions, when the electric machine <NUM> heats the first coolant in the heat exchanger <NUM>, it is possible to heat the second coolant by the first coolant in the heat exchanger <NUM> and the electrical energy storage <NUM>.

During operating conditions, when the electric machine <NUM> heats the second coolant in the heat exchanger <NUM>, it is possible to heat the first coolant by the second coolant in the heat exchanger <NUM> and the power electronics <NUM>.

<FIG> shows a further alternative embodiment of the cooling arrangement. In this case, the radiators <NUM><NUM>, <NUM> in the first air flow <NUM> have changed positions. As a consequence, the radiator <NUM> in the second cooling system <NUM> is arranged downstream of the radiator <NUM><NUM> in the first cooling system <NUM> with respect to the flow direction of the first air flow <NUM>. When ambient air has a high temperature, the first air flow <NUM> provides an effective cooling of the first coolant in the upstream located radiator <NUM><NUM>. However, there is in this case a risk that the first air flow heats the second coolant in the downstream located radiator <NUM>. When such a risk exists, the second coolant is directed to the bypass line 17c and past the radiator <NUM>. In this case, the second coolant is cooled to a low temperature in the chiller <NUM> by the refrigerant system. When the ambient air has a low temperature, the bypass valve <NUM> may direct the first coolant to the bypass line <NUM> and thus past the radiator <NUM><NUM>. In this case, first coolant achieves necessary cooling in the radiator <NUM><NUM> by the second air flow <NUM>. The first air flow <NUM> enters the downstream located radiator <NUM> at ambient air temperature and provide an effective cooling of the second coolant in the second cooling system <NUM>.

The above mention embodiments of the cooling arrangement can be designed with relatively small changes from a base structure including two independently controlled cooling air flows <NUM>, <NUM>. Thus, it is relatively uncomplicated to arrange the radiators <NUM>, <NUM><NUM>, <NUM><NUM>, <NUM> of the cooling systems <NUM>, <NUM> and the condenser <NUM> of the refrigerant system in different positions in relation to each other in the first air flow <NUM> and the second air flow <NUM>. Furthermore, it is easy to selectively arrange a heat exchanger <NUM> to the radiator outlet lines 8b, 17b which provides heat transfer between the coolants in the two cooling systems. Finally, it is possible to arrange a heat exchanger <NUM>, 21or other kinds of heating element in the respective cooling system which heats the coolant.

Claim 1:
Cooling arrangement for an electric power unit in a vehicle (<NUM>), wherein electric power unit comprises an electric machine (<NUM>), an electric energy storage (<NUM>) for storing of electrical energy and power electronics (<NUM>) for controlling the flow of electrical energy between the electrical energy store (<NUM>) and the electric machine (<NUM>), and wherein the cooling arrangement comprises a first cooling system (<NUM>) with a circulating first coolant cooling the power electronics (<NUM>) , a second cooling system (<NUM>) with a circulating second coolant cooling electric energy storage (<NUM>) and a refrigeration system (<NUM>) configured to cool the second coolant in the second cooling system (<NUM>) in a chiller (<NUM>) wherein said refrigeration system (<NUM>) comprises a condenser (<NUM>), characterized in that the cooling arrangement comprises a first radiator fan (<NUM>) configured to provide a first air flow (<NUM>) both through at least a part of a radiator (<NUM>, <NUM><NUM>) of the first cooling system (<NUM>) and through a radiator (<NUM>) of the second cooling system (<NUM>) but not through said condenser (<NUM>), and a second radiator fan (<NUM>) configured to provide a second air flow (<NUM>) both through at least a part of the radiator (<NUM>, <NUM><NUM>) of the first cooling system (<NUM>) and through said condenser (<NUM>), but not through said radiator (<NUM>) of the second cooling system.