Cooling system for a rearward portion of a vehicle and method of cooling

A cooling system dedicated to cooling the vehicle components located in the rearward portion of a vehicle is provided. The rear-dedicated cooling system operates independently of any cooling systems located in a frontward portion of the vehicle. The rear-dedicated cooling system may be subdivided into high temperature and low temperature cooling circuits. A method of cooling a vehicle is also provided.

TECHNICAL FIELD

The invention relates to cooling systems for cooling vehicle components.

BACKGROUND OF THE INVENTION

Numerous components on a vehicle generate heat in performing their intended functions. Accordingly, cooling systems are provided that typically include a liquid coolant directed past the heat-generating components to transfer the excess heat to a heat-dissipating component, such as a radiator. Outside air is then directed over the radiator to lower the coolant temperature and the coolant is then re-directed to the heat-generating component, creating a cooling circuit. Cooling systems are typically designed with a single radiator, centrally located in a frontward portion of the vehicle.

SUMMARY OF THE INVENTION

A cooling system is provided that is dedicated to cooling vehicle components located in a rearward portion of the vehicle and operates independently of one or more separate cooling systems that cool vehicle components located in a frontward portion of the vehicle. The rear-dedicated cooling system is especially beneficial on vehicles that have rear traction system propulsion motors (e.g., wheel motors), power electronic devices, and/or batteries located in the rearward portion of the vehicle.

Accordingly, a cooling system for a vehicle includes a heat-generating component and a heat-dissipating component mounted in a normally rearward or downwind portion of the vehicle. As used herein, “normally rearward portion” means a portion of the vehicle disposed toward the rear when the vehicle is in forward drive mode (i.e., rearward of a transverse centerline of the vehicle such that it is nearer a rear end of the vehicle than a front end of the vehicle). Because it is rearward, this portion is also generally “downwind” during forward motion of the vehicle. Preferably, the heat-generating component and the heat dissipating component are located substantially rearward of rear wheels on the vehicle. “Normally frontward or forward portion” means a portion normally disposed toward the front as the vehicle is in forward drive mode.) The normally frontward portion is forward of the transverse centerline of the vehicle. Coolant is circulated through coolant flow passages, such as hoses, to transfer heat between the heat-generating component and the heat-dissipating component. An air inlet in series air flow relationship with the heat-dissipating component provides outside air to the heat-dissipating component in order to cool it. Notably, the coolant flow passages and the air inlet are also in the rearward portion of the vehicle. The proximity of the coolant flow passages and air inlet (as well as any associated coolant temperature sensors, coolant reservoirs and air flow ducts) to the heat-generating components to be cooled may enable improved cooling performance, as the rear-dedicated heat-dissipating component may be “customized” in size and position for optimal cooling of the rearward components. Additionally, the closer proximity may permit shorter flow passages and a smaller radiator than one designed to cool all (both front and rear) vehicle components, both of which may enable vehicle mass reduction. Finally, because separate radiators are used for front and rear components (rather than one radiator to cool all components), the radiators may be smaller in size than a single radiator design, thus enabling greater packaging flexibility.

In one aspect of the invention, the heat-dissipating component is a radiator that is disposed generally horizontally. Horizontal packaging of the radiator enables additional placement options, such as beneath the floor of the vehicle.

In yet another aspect of the invention, the heat-dissipating component is a radiator module having a first radiator and a second radiator. The first radiator dissipates heat from relatively low temperature coolant that is transferred from a relatively low temperature heat-generating component such as a battery. The second radiator dissipates heat from relatively high temperature coolant that is transferred from a relatively high temperature heat-generating component such as a rear traction motor. The radiator module further includes at least one fan that pulls outside air through the air inlet onto the first and second radiators. Optionally, the first and second radiators are generally horizontally stacked above the fan.

In still another aspect of the invention, the rear-mounted heat-generating component may be one or more of a rear traction motor, a battery for buffering fuel cell output and capturing regenerative energy, a power module interfacing with the battery to provide the battery power to the rear traction motor, a power inverter module for inverting battery power between direct current and alternating current, or a distribution unit for distributing power to the rear traction motor.

In a further aspect of the invention, heat-generating components that create relatively high temperature coolant flow may be separated from other rearward portion heat-generating components that create relatively low temperature coolant flow. In that case, a second heat-dissipating component may be mounted in the normally rearward portion of the vehicle and additional structure defining separate coolant flow passages operable for transferring heat from the relatively higher temperature heat-generating components may be fluidly connected to the second heat-dissipating component. Preferably, the coolant flow passages for the lower temperature heat-generating components are interconnected with the coolant flow passages for the relatively higher temperature heat-generating components only via a common coolant flow reservoir. This minimizes coolant flow mixing between the two sets of coolant flow passages. Separating the relatively higher temperature heat-generating components from the relatively lower temperature heat-generating components in this manner effectively creates two separate rear-dedicated cooling circuits. Notably, the same air inlet may be operable to provide outside air to both of the heat-dissipating components provided for the two separate rear-dedicated circuits. The air inlet may be formed by body structure such as a vehicle rear quarter panel, a rear panel or the vehicle roof. A duct may extend from the air inlet to the heat-dissipating component to direct cooling air over the heat-dissipating component. A second duct may extend from the radiator module to an air exit.

In a still further aspect of the invention, a frontward or forward portion cooling circuit includes a heat-generating component and a heat-dissipating component, both mounted in the frontward portion of the vehicle, as well as structure defining coolant flow passages also located in the frontward portion and operable to transfer heat between the frontward mounted heat-generating component and heat-dissipating component. Structure located in the normally frontward portion defines another air inlet to provide outside cooling air to the frontward portion heat-dissipating component for cooling thereof. The frontward or forward portion air inlet may be formed by a front grille disposed on a forward face of the vehicle. The frontward or forward portion cooling circuit is not in substantial (i.e., thermally significant) coolant flow communication with the rearward portion cooling circuit. As used herein, substantial or thermally significant coolant flow communication means that more than 10% of coolant mass flow per unit of time is shared between the frontward portion and rearward portion cooling circuits. Preferably, coolant mixing between the two circuits is near zero.

In another aspect of the invention, the vehicle may be a fuel cell powered vehicle or a hybrid electro-mechanical powered vehicle; in this instance, the heat-generating component located in the frontward portion may be a fuel cell or an internal combustion engine, respectively.

A method of cooling vehicle components on a vehicle characterized by a frontward portion and a rearward portion is provided. The method includes installing at least one heat-dissipating component in the rearward or downwind portion. The method further includes fluidly connecting the rearward portion heat-generating component with at least one heat-dissipating component located in the rearward portion to establish a first coolant flow circuit. The method further includes providing a first air inlet formed by rear vehicle structure that is operable to deliver outside air to the rearward portion heat-dissipating component for cooling thereof.

In one aspect of the invention, the method includes categorizing at least two rearward portion (also referred to herein as downwind) located heat-generating components into a first group characterized by heat generation causing the coolant flow to be a relatively low temperature and a second group characterized by heat generation causing the coolant flow to be a relatively high temperature. Preferably, the heat-dissipating components installed in the rearward portion include at least two radiators. The method may further include fluidly connecting the first group of heat-generating component(s) to a first of the radiators via first flow passages. The method may further include fluidly connecting the second group of heat-generating component(s) to a second of the radiators via second flow passages.

In addition to cooling components located in the rearward or downwind portion via the method described above, the method may also involve the cooling of components located in the frontward or forward portion. For instance, the method may include installing at least one heat-dissipating component in the frontward or forward portion. The method may further include fluidly connecting at least one heat-generating component located in the frontward portion with the frontward portion heat-dissipating component to establish a second (i.e., frontward portion) coolant flow circuit. Preferably, the frontward portion coolant flow circuit and the rearward portion coolant flow circuit or circuits are not in thermally significant coolant flow communication with one another. The method may further include providing a second air inlet formed by front vehicle structure that is operable for delivering outside air to the frontward portion heat-dissipating component for cooling thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, wherein like reference numbers refer to like components,FIG. 1shows a vehicle10formed by frame structure12. The vehicle10is represented by a generally frontward portion14and a generally rearward portion16distinguishable from one another by an imaginary, generally centrally located transverse dividing line A. Both the frontward portion and the rearward portion include a variety of heat-generating components as well as heat-dissipating components, all of which are supported by vehicle structure such as the frame structure12. For instance, the rearward portion16includes electric traction wheel motors18A and18B. A traction battery20which may be nickel metal hydride (NIMH), lithium ion (LiIon) or another type of battery, is also located in the generally rearward portion16and is used for buffering fuel cell output (if the vehicle10is a fuel cell vehicle) and for capturing regenerative energy. A distribution unit22, a pair of power inverter modules24A and24B as well as a pair of auxiliary power modules26A and26B are operatively connected to the traction battery20and to the distribution unit22and are used in selectively powering the traction wheel motors18A and18B. As will be readily understood by those skilled in the art, the distribution unit22distributes power from the battery20to other vehicle systems. The power inverter modules24A and24B convert the DC current (DC) provided by the battery20into alternating current (AC). The accessory power modules26A,26B contain a power supply that interfaces with the battery20to energize various vehicle components such as the traction wheel motors18A and18B. Importantly, the rearward portion16also includes a heat-dissipating component in the form of radiator module30which acts to dissipate the heat generated by the heat-generating components, namely the rear motors18A,18B, the traction battery20, the distribution unit22, the power inverter modules24A,24B and the auxiliary power modules26A,26B.

Like the rearward portion16, the frontward portion14includes a variety of heat-generating components such as a vehicle powering component34which may be, for example, an internal combustion engine, a hybrid electro-mechanical internal combustion engine and electric motor assembly, or a fuel cell stack. A variety of other forward portion heat-generating components are located on the vehicle10, such as an air compressor motor36, a stack compressor controller38, a coolant heater40, an electric traction system controller (ETSC)42for front traction, a front electric traction system (ETS)44operable for converting electrical power providing the powering component34into rotary motion for driving front wheels55C,55D, a charge air cooler (CAC)46for cooling air used by the vehicle powering component34, as well as a power distribution and control module (PDCM)48. Those skilled in the art will readily understand the function of such components. A variety of heat-dissipating components including a central stack radiator50and left and right radiators52,54are also mounted in the frontward portion14and are operable for cooling the heat-generating components34-48of the frontward portion14.

Rear-Dedicated Cooling System

Referring toFIG. 2A, vehicle10is supported by wheels55A-D. Wheels55A and55B are operatively connected to electric traction wheel motors18A and18B, respectively. The vehicle10includes a rear-dedicated cooling system56operable to cool the rearward portion heat-generating components18A,18B,20,22,24A,24B,26A and26B. The rear-dedicated cooling system56includes low temperature coolant flow passages58which circulate coolant between the traction battery20and the radiator module30. A battery coolant pump60maintains appropriate coolant flow through the low temperature coolant flow passages58.

Referring toFIG. 2B, the radiator module30is composed of a battery radiator62as well as a rear traction radiator64. Each of the radiators has a core of winding coolant tubes arranged to create an inlet face and an outlet face, as will be well understood by those skilled in the art. The battery radiator62is stacked with respect to a rear traction radiator64. The radiator module30also includes at least one and preferably two radiator module cooling fans66A and66B (shown inFIG. 1) that pull cooling air across or through the battery radiator62and the rear traction radiator64for dissipating heat from the coolant flowing therethrough. An inlet face of the battery radiator62receives the outside cooling air. The fans66A,66B pull the air through the radiator core of coolant tubes to an outlet face which is adjacent an inlet face of the rear traction battery64. The fans66A,66B then pull the air through the radiator core of coolant tubes of radiator64to an outlet face of radiator64, to be exhausted below the module30(i.e., below the vehicle10). Alternatively, the fans may be located above the radiators62,64to push air across the radiators62,64. Referring again toFIG. 2A, an air inlet which may be a side air inlet80A or80B formed in the left rear quarter panel76A or right rear quarter panel76B, respectively, or a rear air inlet82formed in rear panel78permits outside air to flow across or through the radiator module30for cooling thereof. As used herein “rear quarter panel” means side body structure located generally between a vehicle side door and a rear face of the vehicle. “Rear panel” includes any vehicle body structure establishing a generally rearward facing surface on the vehicle. Those skilled in the art readily understand the meaning of the terms “rear quarter panel” and “rear panel.” Referring again toFIG. 1, radiator module fans66A and66B direct the air flow through the air inlet and across the radiators62and64and then exhaust the air below the vehicle10. By exhausting air at the relatively low pressure area beneath the vehicle, requisite air flow may be accomplished with smaller fans than would be necessary if the air flow was exhausted at a higher pressure area. The relative low pressure region may be enhanced with an air dam or other aerodynamic device, which further reduces pressure when the vehicle is moving.

Substantially Separate Low Temperature and High Temperature Cooling Circuits

Referring again toFIGS. 2A-2B, the rear-dedicated cooling system56is sub-divided into two separate cooling circuits, a low temperature cooling circuit68and a high temperature cooling circuit70. The low temperature cooling circuit68includes the coolant flow passages58, the battery coolant pump60, the traction battery20and the battery radiator62. The high temperature cooling circuit70includes a high temperature coolant pump72operable for maintaining appropriate coolant flow in high temperature coolant flow passages74which route coolant in the high temperature cooling system or circuit70. The high temperature cooling circuit70further includes the distribution unit22, the power inverter modules24A,24B, the auxiliary power modules26A,26B, the electric traction wheel motors18A,18B and the rear traction radiator64as well as, the high temperature coolant flow passages74. Both the low temperature cooling circuit68and the high temperature cooling circuit70also include the air inlet which may be formed in the left or right rear quarter panel76A,76B, respectively, or in the rear panel78. For example, air inlet80A may be formed in the left rear quarter panel and/or air inlet80B may be formed in the right rear quarter panel76B, respectively. Alternatively or in addition, rear panel air inlet82may be formed in the rear panel78. An air inlet may also be formed in the vehicle roof (not shown) and routed through pillar structure to the radiator module30. Regardless of which air inlet (e.g.,80A,80B or82) is selected, the same air inlet may be used to provide cooling air flow to cool the battery radiator62and the rear traction radiator64of the high temperature and low temperature cooling circuits68,70, respectively. Location of the air inlet in any of these rear locations may improve vehicle aerodynamic drag by keeping the slipstream attached to the vehicle longer, thereby improving airflow separation characteristics and reducing drag.

FromFIG. 2A, it is apparent that the high temperature cooling circuit70and the low temperature cooling circuit68maintain separate coolant flow passages58,74. A coolant flow reservoir84is in fluid communication with both the low temperature coolant flow passages58as well as the high temperature coolant flow passages74as indicated by the dashed connection passages86. Although the reservoir84is in fluid communication with both the low temperature and high temperature coolant flow passages58,74, respectively, intermixing of the relatively low temperature coolant flow through low temperature coolant flow passages58with the relatively high temperature coolant flowing through high temperature coolant flow passages74is minimized in that minimal flow passes through the reservoir84. By substantially separating the high temperature cooling circuit70from the low temperature cooling circuit68, the battery radiator62and the rear traction radiator64may be optimally sized for appropriate and efficient cooling of heat-generating components in the low temperature and high temperature circuits68,70, respectively.

Front-Dedicated Cooling System

A separate front-dedicated cooling system90is also employed on the vehicle10for cooling of the heat-generating components located in the frontward portion14discussed with respect toFIG. 1above. Like the rear-dedicated cooling system56, the front dedicated cooling system90may include a separate high temperature frontward cooling circuit92and low temperature frontward cooling circuit94(having flow passages indicated by heavier lines than the flow passages of the high temperature circuit92). A front structure air inlet96is formed in a front face98of the vehicle10. A grille100represented by dashed lines in the front structure air inlet96may be employed. Air flow through the air inlet96is across or through the stack radiator50for cooling thereof via a stack radiator fan99A. Air naturally forced through the air inlet96during forward motion of the vehicle also aids in cooling. Left and right radiators52,54are preferably cooled via separate air flow fans99B,99C than that used to cool the central stack radiator50(i.e., the left and right radiators52,54are preferably not provided with cooling air flow via the air inlet96) but rather have their own separate cooling air paths to maximize thermal efficiency. The speed of each of the fans66A,66B,99A,99B and99C may be individually controlled to provide optimal cooling based upon overall vehicle conditions (such as vehicle load) or upon conditions specific to the cooling circuit and components affected by each fan.

Separate high temperature and low temperature front cooling system reservoirs91,93may be employed to insure separation of coolant flow in the high temperature frontward cooling circuit92and the low temperature frontward cooling circuit94, respectively. Additionally, a high temperature coolant pump95and a low temperature coolant pump97are employed to maintain appropriate coolant flow in the high temperature and low temperature frontward cooling circuits92,94, respectively.

Preferably, the front-dedicated cooling system90is not in fluid communication with the rear-dedicated cooling system56. That is, there is no significant shared coolant or cooling air flow between the two systems. By providing a radiator module30in the rearward portion16and structuring the coolant flow passages58and74so that they are in thermally significant flow communication only with rearward-located heat-generating components, as well as by providing a rearward air inlet (80A,80B or82), a self-contained rear-dedicated cooling system56that enables flexible placement of the radiator module30in close packaging arrangement with the rearward portion heat-generating components is provided. Thus, travel distances for coolant flow in coolant flow passages as well as for air flow over the heat-dissipating components are minimized, thus, decreasing component size and minimizing overall addition to vehicle weight.

Rear Air Duct

Referring toFIG. 3, a duct101having a duct opening102cooperates with the air inlet80B formed in the left rear quarter panel76B to receive airflow indicated by arrows A. Support frame103is also visible. An alternate duct opening102′ may be employed. The alternate duct opening102′ receives air from an alternate inlet (not shown) in a rear face of the vehicle, as indicated by arrows B. Alternatively, the duct opening102may function independently of an air inlet formed in vehicle body structure. For instance, if the rear quarter panel76B was not formed with air inlet80B, the duct opening102may extend below the rear quarter panel76B and take in outside air from that location. Also alternatively, the duct inlet may be forward-facing. Outside air is pulled through the duct101by the cooling fans66A,66B of the radiator module30(fans shown inFIG. 1) to flow from a duct outlet105through the radiator module30for cooling thereof. The air is exhausted to the relatively low pressure space below the vehicle (as shown by phantom arrow(s) C extending below the radiator module30). Preferably, a second symmetrical duct (not shown) functions similarly to cool the right portion of the radiator module30. Location of the air path in a low pressure region beneath the vehicle improves cooling airflow potential.

Method of Cooling

Referring now toFIG. 4, a method of cooling vehicle components200is provided by the vehicle10described above. The method includes installing202at least one heat-dissipating component in the rearward portion of the vehicle. The method further includes fluidly connecting204at least one rearward portion heat-generating component with the rearward portion heat-dissipating component(s). The fluid connection is accomplished by coolant flow passages such as passages58and74described with respect toFIG. 2A. The method200optionally allows for the creation of separate high temperature and low temperature cooling flow circuits within a rear-dedicated cooling flow system. For instance, step204may include optionally categorizing heat-generating components206into high and low temperature heat generation groups. After the categorizing step206, step204optionally includes fluidly connecting the first, low temperature group to a first radiator208via first flow passages. Similarly, step204optionally includes fluidly connecting the second, high temperature group to a second radiator210via second flow passages. By performing the categorizing step206as well as the fluid connecting steps208and210, separate low temperature and high temperature cooling circuits such as cooling circuits68and70described with respect toFIG. 2Aare created.

The method200further includes providing a rear structure first air inlet212. The first air inlet cools the rearward portion heat-dissipating component(s). The method200optionally includes installing at least one heat-dissipating component in a frontward portion of the vehicle214. Also optionally, the method200may further include fluidly connecting at least one frontward portion heat-generating component with the frontward portion heat-dissipating component(s)216. If optional steps214and216are carried out, then the method200may further include providing a front structure second air inlet218. The front structure second air inlet cools the frontward portion heat-dissipating component(s). The separate frontward portion heat-dissipating components, heat-generating components and air inlets described with respect toFIG. 2Aillustrate steps214,216and218of the method200. Within the scope of the invention, the steps of method200need not be performed in the order shown inFIG. 4.

In summary, a rear-dedicated cooling system is provided that enables efficient cooling of rearward located heat-generating components. The rear-dedicated system may be subdivided into high temperature and low temperature cooling circuits for further optimization of the cooling system design. Preferably, the rearward dedicated cooling system is not in fluid communication with any frontward portion heat-generating components or frontward portion heat-dissipating components. Also preferably, a separate rearward located cooling air inlet is provided.