Vehicular cooling system

A series-hybrid vehicle includes an internal combustion engine for electric power generation and a motor generator for travelling. The internal combustion engine is cooled by a second coolant water circuit that has a main radiator. A first coolant water circuit having a sub radiator is used to cool a front wheel-side power train cooling part, a rear wheel-side power train cooling part, a water-cooled condenser, and a low temperature-side intercooler. When the vehicle is accelerating, an electrical compressor for an air conditioner comes to a stop, and the circulation of refrigerant to the water-cooled condenser is brought to a halt.

TECHNICAL FIELD

The present invention relates to a vehicular cooling system structured to dissipate heat of a vehicle interior air conditioner via a radiator in a cooling water circuit, wherein the vehicle interior air conditioner includes a water-cooled condenser.

BACKGROUND ART

In general, a vehicle includes a vehicle interior air conditioner utilizing a refrigeration cycle of coolant, for cooling of a vehicle interior. In most cases, a vehicle employing an internal combustion engine as a drive source for traveling includes a compressor mechanically driven by the internal combustion engine, and an air-cooled condenser structured to perform heat exchange with outside air.

Patent Document 1 discloses an art for a vehicle including a vehicle interior air conditioner and an internal combustion engine as a traveling drive source, which serves to improve the vehicle in acceleration performance by releasing an electromagnetic clutch between an output shaft and a compressor of the internal combustion engine in order to reduce a load on the internal combustion engine, during acceleration due to depression of an accelerator pedal.

However, this art does not pay attention to a water temperature and a heat quantity in a cooling water circuit in case of employing a water-cooled condenser.

PRIOR ART DOCUMENT(S)

Patent Document 1: JP 2006-298042 A

SUMMARY OF THE INVENTION

Problem(s) to be Solved by the Invention

According to one aspect of the present invention, a vehicular cooling system for a vehicle includes: a cooling device of water-cooled type structured to contribute to cooling of a drive source of the vehicle; a water-cooled condenser structured to cool coolant of a vehicle interior air conditioner of the vehicle; a first cooling-water circuit including the cooling device and the water-cooled condenser; a first radiator structured to perform heat exchange between outside air and first cooling water circulating in the first cooling-water circuit; and a control unit configured to suspend a flow of the coolant in the water-cooled condenser, in response to satisfaction of a predetermined vehicle acceleration condition.

The cooling device may be one such as a cooling system for an internal combustion engine serving as a vehicle drive source, a cooling system for a motor and an inverter of an electric vehicle, or a water-cooled intercooler for a supercharge engine.

The configuration to suspend the coolant flow in the water-cooled condenser in response to satisfaction of the predetermined vehicle acceleration condition serves to reduce an amount of heat transferred from the water-cooled condenser to the first cooling water in the first cooling-water circuit. This decreases a temperature of the first cooling water flowing into the cooling device, and improves a cooling efficiency of the cooling device, and thereby temporarily enhance an output of the drive source.

In case that the cooling device is a cooling system for an internal combustion engine, the decrease in temperature of the first cooling water contributes to reduction of knockings, lowering of an intake air temperature, etc., and thereby serves to improve the output. In case that the cooling device is a cooling system for a motor and an inverter of an electric vehicle, the decrease in temperature of the first cooling water serves to improve the motor in output. In case that the cooling device is a water-cooled intercooler for a supercharge engine, the decrease in temperature of the first cooling water serves to lower a temperature of intake air, and improve the output. Thus, the cooling device described above widely includes devices structured to produce beneficial effects on the output of the vehicle drive source by cooling effect.

MODE(S) FOR CARRYING OUT THE INVENTION

The following details an embodiment of the present invention with reference to the drawings. The following embodiment exemplifies a case of applying the present invention to a series hybrid vehicle: in particular, a series hybrid vehicle of four-wheel drive type structured to separately drive front wheels and rear wheels.

FIG.1shows a drive system of the series hybrid vehicle according to the embodiment. The series hybrid vehicle includes: a power-generation motor generator1that operates mainly as an electric power generator; an internal combustion engine2that operates as a power-generation internal combustion engine for driving the power-generation motor generator1in response to a request for electric power; a front wheel motor generator5that operates mainly as a motor, and drives front wheels3; a rear wheel motor generator6that operates mainly as a motor, and drives rear wheels4; and a battery7structured to temporarily store the generated electric power. The motor generators1,5, and6are respectively provided with inverter units8,9, and10each of which is structured to perform electric power conversion with battery7. Each of the inverter units8,9, and10is substantially united with a corresponding one of the motor generators1,5, and6. Internal combustion engine2is connected to power-generation motor generator1via a gear train11. Front wheel motor generator5is structured to drive the front wheels3via a gear train12including a differential gear. Rear wheel motor generator6is structured to drive the rear wheels4via a gear train13including a differential gear. Battery7stores, via inverter unit8, the electric power generated by power-generation motor generator1driven by internal combustion engine2. Front wheel motor generator5and rear wheel motor generator6are driven with the electric power from battery7, via inverter units9and10respectively. Battery7stores also electric power generated due to regeneration in front wheel motor generator5and rear wheel motor generator6, via inverter units9and10.

As shown inFIG.1, the vehicle includes a vehicle interior air conditioner including an electric compressor14that is a compressor used in a refrigeration cycle. Electric compressor14is driven with the electric power from battery7, via an inverter unit15.

According to the embodiment ofFIG.1, front wheel motor generator5and rear wheel motor generator6serve as drive sources that directly drive the vehicle. Internal combustion engine2serves as an indirect drive source of the vehicle, because battery7is relatively small in capacity, and, in most situations, maximum outputs of front wheel motor generator5and rear wheel motor generator6depend on a generation amount of internal combustion engine2and power-generation motor generator1. Internal combustion engine2includes a supercharger16such as a turbocharger or a mechanical supercharger.

The series hybrid vehicle according to the embodiment includes a cooling system using cooling water. The cooling system is composed of a first cooling-water circuit21shown inFIG.2and a second cooling-water circuit22shown inFIG.3. Cooling water in first cooling-water circuit21(namely, first cooling water) is controlled to be basically lower in temperature than cooling water in second cooling-water circuit22(namely, second cooling water).

As shown inFIG.2, first cooling-water circuit21includes electric water pumps23and24arranged in two tiers. Electric water pumps23and24circulate the cooling water as shown by an arrow inFIG.2. First cooling-water circuit21further includes an auxiliary radiator25, a bypass valve26, and a reservoir tank27. Auxiliary radiator25is a heat dissipater disposed downstream with respect to electric water pumps23and24, and performs heat exchange with outside air. Bypass valve26is disposed adjacently to an outlet (or an inlet) of auxiliary radiator25. This allows the cooling water to bypass the auxiliary radiator25, in case that the temperature of the cooling water is lower than a preset temperature (i.e., a preset temperature for first cooling-water circuit21). Reservoir tank27is disposed upstream with respect to electric water pumps23and24.

First cooling-water circuit21includes, as objects to be cooled, a front wheel powertrain cooler31, a rear wheel powertrain cooler32, a water-cooled condenser33, and a low-temperature-side water-cooled intercooler34. Front wheel powertrain cooler31is structured for cooling of front wheel motor generator5and inverter unit9accompanying it. Rear wheel powertrain cooler32is structured for cooling of rear wheel motor generator6and inverter unit10accompanying it. Water-cooled condenser33is structured to condense coolant in the refrigeration cycle of the vehicle interior air conditioner. Low-temperature-side water-cooled intercooler34is disposed in an intake system of internal combustion engine2. Each of front wheel powertrain cooler31and rear wheel powertrain cooler32is configured as, for example, a cooling water passage running inside a housing containing the motor generator and the inverter unit.

Water-cooled condenser33is composed of, for example, a housing in which the cooling water flows and a core in which the coolant flows, wherein the core is contained in the housing, and the coolant is cooled due to heat exchange between the coolant in gas phase and the cooling water. Water-cooled condenser33includes a liquid tank (not shown) for temporary storing of the condensed coolant in liquid phase. Low-temperature-side water-cooled intercooler34is disposed in an intake passage between internal combustion engine2and supercharger16, and is structured to perform heat exchange between the cooling water and supercharge intake air and thereby cool the supercharge intake air.

As shown inFIG.2, the cooling water in first cooling-water circuit21flows in parallel in three passages: i.e., front wheel powertrain cooler31, water-cooled condenser33, and rear wheel powertrain cooler32. Low-temperature-side water-cooled intercooler34is disposed downstream with respect to rear wheel powertrain cooler32, so as to be connected to rear wheel powertrain cooler32in series in view of the flow of the cooling water. In other words, a flow passage36for water-cooled condenser33and a flow passage37for rear wheel powertrain cooler32, which are in parallel, diverge at a bifurcation point38and converge at a confluence point39, wherein low-temperature-side water-cooled intercooler34is disposed between rear wheel powertrain cooler32and confluence point39. In the actual vehicle, rear wheel powertrain cooler32is disposed in a rear part of the vehicle, while auxiliary radiator25and front wheel powertrain cooler31are disposed in a front part of the vehicle. Accordingly, flow passage37extends toward the vehicle rear part, and passes low-temperature-side water-cooled intercooler34in the vehicle front part again, and then joins confluence point39.

As shown inFIG.3, second cooling-water circuit22includes a mechanical or electric water pump41driven with an output from internal combustion engine2. Water pump41circulates the cooling water (i.e., the second cooling water) as shown by an arrow inFIG.3. Second cooling-water circuit22further includes a main radiator42, a bypass valve43, and a reservoir tank44. Main radiator42is a heat dissipater disposed upstream with respect to water pump41, and performs heat exchange with outside air. Bypass valve43is disposed adjacently to an outlet (or an inlet) of main radiator42. This allows the cooling water to bypass the main radiator42, in case that the temperature of the cooling water is lower than a preset temperature (i.e., a preset temperature for second cooling-water circuit22). Reservoir tank44is disposed upstream with respect to main radiator42.

As described above, first cooling-water circuit21and second cooling-water circuit22are different from each other in cooling water temperature, and the cooling water in first cooling-water circuit21is lower in temperature than the cooling water in second cooling-water circuit22. For example, the first cooling water flowing in first cooling-water circuit21is controlled to have a temperature of approximately 50 to 55° C. at the outlet of auxiliary radiator25, while the second cooling water flowing in second cooling-water circuit22is controlled to have a temperature of approximately 70 to 90° C. under a target temperature of 80° C. at the outlet of main radiator42.

As shown inFIG.3, second cooling-water circuit22includes, as objects to be cooled, the internal combustion engine2and a high-temperature-side water-cooled intercooler45disposed in the intake system of internal combustion engine2. Internal combustion engine2includes a water jacket for the cooling water, and is cooled mainly by the cooling water flowing in the water jacket.

High-temperature-side water-cooled intercooler45is disposed in the intake passage between internal combustion engine2and supercharger16, adjacently to low-temperature-side water-cooled intercooler34, and is structured to perform heat exchange between the cooling water and the supercharge intake air and thereby cool the supercharge intake air. In view of a flow direction of intake air in the intake passage, high-temperature-side water-cooled intercooler45is positioned relatively upstream, while low-temperature-side water-cooled intercooler34is positioned relatively downstream. For example, high-temperature-side water-cooled intercooler45and low-temperature-side water-cooled intercooler34may be configured as two cores arranged in series inside a housing in which the intake air flows, wherein the first cooling water and the second cooling water respectively flow in a corresponding one of the cores. For another example, each of high-temperature-side water-cooled intercooler45and low-temperature-side water-cooled intercooler34may be provided with an individual housing, independently from each other.

As described above, the second cooling water relatively high in temperature flows in high-temperature-side water-cooled intercooler45, while the first cooling water maintained relatively low in temperature flows in low-temperature-side water-cooled intercooler34. Accordingly, the supercharge intake air raised in temperature due to supercharging is cooled to a certain extent in high-temperature-side water-cooled intercooler45positioned upstream, and is further cooled in low-temperature-side water-cooled intercooler34positioned downstream. Thus, high-temperature-side water-cooled intercooler45and low-temperature-side water-cooled intercooler34compose a two-stage water-cooled intercooler. The first cooling water and the second cooling water may be same with each other or different from each other in components, concentration, etc. As one example, the first cooling water and the second cooling water may be ethylene glycol aqueous solutions containing appropriate additives.

FIG.4schematically shows a coolant circuit for the vehicle interior air conditioner. The vehicle interior air conditioner includes the electric compressor14, a condenser51, and an evaporator52. Electric compressor14described above is structured to compress the gas phase coolant. Condenser51is structured to cool and condense the gas phase coolant that has been raised in temperature and pressure due to the compression. Evaporator52includes an expansion valve structured to expand the liquefied coolant for cooling of the vehicle interior etc.

According to the embodiment, condenser51is composed of a combination of water-cooled condenser33described above and an air-cooled condenser53structured to perform heat exchange with outside air. In view of a flow of the coolant, water-cooled condenser33is disposed relatively upstream, where the compression of the coolant is performed mainly in water-cooled condenser33. Air-cooled condenser53is disposed relatively downstream, where air-cooled condenser53serves as a subcooler for further subcooling of the liquefied coolant. Thus, air-cooled condenser53may be relatively small in size, because water-cooled condenser33bears a major part of a heat exchange amount required in condenser51.

Electric compressor14is driven under control of an air conditioner controller54that is a part of a control unit55. Air conditioner controller54is connected to an HEV controller (not shown) controlling a drive system for the entire vehicle and an engine controller (not shown) controlling the internal combustion engine2, via communication such as CAN communication. As detailed below, air conditioner controller54is configured to suspend electric compressor14in response to a compressor suspension command sent from the HEV controller when the vehicle detects a predetermined acceleration request. In addition, also the HEV controller and the engine controller not shown are parts of the control unit55.

Evaporator52is a so-called cold storage evaporator employing a cold storage material disposed adjacently to a coolant tube, and is structured to supply cold air to the vehicle interior for a certain time even after the suspension of electric compressor14.

Each of auxiliary radiator25, main radiator42, and air-cooled condenser53for heat exchange with outside air is disposed in the front part of the vehicle, so as to receive wind due to vehicle traveling.FIG.5shows how the three heat exchangers (i.e., main radiator42, auxiliary radiator25, and air-cooled condenser53) are arranged in vehicle body61. Vehicle body61includes a grille opening63disposed above a bumper62and a bumper opening64disposed below bumper62, both for introduction of the vehicle traveling wind. Main radiator42is disposed behind both of grille opening63and bumper opening64, so as to receive the vehicle traveling wind from both of these two openings63and64. Air-cooled condenser53is disposed in front of main radiator42, overlapping with a lower region of main radiator42, so as to receive the vehicle traveling wind mainly from bumper opening64. Auxiliary radiator25is disposed in front of main radiator42, overlapping with an upper region of main radiator42, so as to receive the vehicle traveling wind mainly from grille opening63. Auxiliary radiator25and air-cooled condenser53are arranged in a vertical direction, along a plane parallel with main radiator42. It is allowed to dispose auxiliary radiator25at a lower position and dispose air-cooled condenser53at an upper position. Behind main radiator42, an electric fan66is disposed with a shroud67. Electric fan66is structured to forcibly generate cooling wind in case of being insufficient in the vehicle traveling wind, such as a case of a low vehicle speed.

The following describes operation of the cooling system according to the above embodiment, with reference to time charts inFIGS.6A to6H and6J.FIG.6Ashows behavior and change of an accelerator opening degree of the vehicle (i.e., a depression amount of the accelerator pedal).FIG.6Bshows behavior and change of a ratio in driving force exerted on front wheels3.FIG.6Cshows behavior and change of a ratio in driving force exerted on rear wheels4.FIG.6Dshows behavior and change of a water temperature at the inlet of low-temperature-side water-cooled intercooler34.FIG.6Eshows behavior and change of an intake air temperature at an intake air inlet of internal combustion engine2.FIG.6Fshows behavior and change of ON/OFF state of electric compressor14.FIG.6Gshows behavior and change of a cold storage amount of evaporator52.FIG.6Hshows behavior and change of a blowout air temperature at an outlet of the vehicle interior air conditioner in the vehicle interior.

FIG.6Jat the top schematically shows how the vehicle travels, in which a subject vehicle101overtakes a preceding vehicle102on a two-lane road such as an express way. Preceding vehicle102travels relatively slowly in a traveling lane104, while towing a towed vehicle103. Each of reference numerals101a,101b,101c,101d, and101erepresents subject vehicle101, which shows change in relative position of subject vehicle101with respect to preceding vehicle102. Subject vehicle101(101a) that has been traveling behind preceding vehicle102moves to an overtaking lane105while accelerating due to depression of the accelerator pedal in order to overtake preceding vehicle102, and then travels at a constant vehicle speed from around a timing of catch up with preceding vehicle102, and overtakes preceding vehicle102. Thereafter, subject vehicle101returns to the traveling lane104while decelerating. Thus, in view of positions of the subject vehicle shown inFIG.6J, the subject vehicle is in an acceleration period at positions of101ato101c, and is in a constant speed period at positions of101cto101d, and is in a deceleration period at positions of101dto101e.

Such acceleration, overtaking, and deceleration of the vehicle are reflected in the behavior and the change shown inFIGS.6A to6H. In steady traveling at the initial stage, electric compressor14is ON, and the cold storage amount of evaporator52is at the maximum due to traveling so far. The driving force is borne by front wheels3and rear wheels4at an allotment ratio of, for example, 50:50.

At time instant t1, the acceleration starts due to increase in accelerator opening degree. After the start of the acceleration, at time instant t2at which the accelerator opening degree exceeds a predetermined threshold, electric compressor14is turned OFF because a predetermined vehicle acceleration condition is determined to be satisfied. Electric compressor14is maintained OFF until time instant t5at which the accelerator opening degree falls below the predetermined threshold after a start of the deceleration (i.e., decrease in accelerator opening degree) at time instant t4. At time instant t5, electric compressor14is turned ON again. In another manner, it is allowed to control the driving of electric compressor14to be restarted after a certain time period or a certain travel distance after the start of the acceleration.

In response to this suspension of electric compressor14, the circulation of the coolant for the vehicle interior air conditioner is suspended: i.e., the coolant stops flowing in water-cooled condenser33. This reduces an amount of heat provided from water-cooled condenser33to the first cooling water, while reducing also an amount of heat radiation from air-cooled condenser53.

Thus, the suspension of the coolant circulation causes the refrigeration cycle to be substantially suspended. However, evaporator52being the cold storage evaporator serves to suppress the vehicle interior from rising in temperature as shown inFIG.6H, by utilizing coldness stored in evaporator52. Accordingly, the cold storage amount of evaporator52gradually decreases during the suspension of electric compressor14. Thereafter, the cold storage is replenished again in response to the driving restart of electric compressor14at time instant t5.

As shown inFIG.6D, the water temperature at the inlet of low-temperature-side water-cooled intercooler34in first cooling-water circuit21decreases due to the suspension of electric compressor14and the decrease in amount of heat dissipated from water-cooled condenser33to the first cooling water. Furthermore, the acceleration of the vehicle (i.e., increase in vehicle speed) increases the vehicle traveling wind, and thereby increases an amount of heat radiation from auxiliary radiator25. This is another factor to decrease the water temperature at the inlet of low-temperature-side water-cooled intercooler34.

As shown inFIG.6E, the intake air temperature introduced to internal combustion engine2decreases with decrease in water temperature at the inlet of low-temperature-side water-cooled intercooler34. This increases the output of internal combustion engine2, and increases the amount of generation in power-generation motor generator1, and thereby raises front wheel motor generator5and rear wheel motor generator6in acceleration performance.

The decrease in temperature of the first cooling water in first cooling-water circuit21serves to enhance front wheel powertrain cooler31and rear wheel powertrain cooler32in cooling performance, which contributes to improvement of front wheel motor generator5and rear wheel motor generator6in output. This serves to enhance the acceleration performance.

In view of electric power consumption, the suspension of electric compressor14serves to ensure electric power for front wheel motor generator5and rear wheel motor generator6, and thereby improve them in output. This contributes to the enhancement of the acceleration performance.

In the example shown in the drawings, the allotment ratio of the driving force between front wheels3and rear wheels4is changed upon the acceleration, by the HEV controller that belongs to the control unit55. Specifically, front wheels3increases and rear wheels4decreases in allotment ratio of the driving force in response to the acceleration, in order to reduce a heat load exerted on rear wheel powertrain cooler32that is disposed adjacently to and upstream with respect to low-temperature-side water-cooled intercooler34in first cooling-water circuit21. In the example of the drawing, the allotment ratio is permitted to vary up to 90:10. Front wheels3gradually increases in allotment ratio of the driving force from 50% with increase in accelerator opening degree, while rear wheels4gradually decreases in allotment ratio of the driving force from 50%. The allotment ratio becomes 90:10 at time instant t3at which the acceleration stops.

Such relative decrease in driving force borne by rear wheels4reduces an amount of heat dissipated from rear wheel powertrain cooler32to the first cooling water in first cooling-water circuit21. This serves to suppress the water temperature at the inlet of low-temperature-side water-cooled intercooler34from rising in temperature, and contributes to the enhancement of the acceleration performance via the enhancement of the output of internal combustion engine2. If the heat dissipation amount from rear wheel powertrain cooler32increased in response to the acceleration, the low-temperature-side water-cooled intercooler34would be deteriorated in cooling performance for the supercharge intake air due to rise in temperature of the first cooling water flowing into low-temperature-side water-cooled intercooler34, because rear wheel powertrain cooler32is disposed immediately before low-temperature-side water-cooled intercooler34in first cooling-water circuit21.

After the start of the deceleration (i.e., decrease in accelerator opening degree), the allotment ratio of the driving force between front wheels3and rear wheels4starts to gradually change toward 50:50 that is a default value for steady state.

Although the embodiment above exemplifies a case of applying the present invention to the four-wheel drive type series hybrid vehicle, the present invention is not limited to that, but may be variously modified.