WO2012128772A1

WO2012128772A1 - Vehicle electrical system with cooling

Info

Publication number: WO2012128772A1
Application number: PCT/US2011/029784
Authority: WO
Inventors: Jay E. BISSONTZ
Original assignee: International Truck Intellectual Property Company, Llc
Priority date: 2011-03-24
Filing date: 2011-03-24
Publication date: 2012-09-27

Abstract

In a vehicle electrical system comprising an electrical power source, at least a first load for energization from the electrical power source and a resistive load which may be interposed between the electrical power source and the first load to prevent current inrush upon initialization, a cooling system for the resistive load is provided. Isolation contactors provide for the selective connection of the at least first load to the electrical power source in energization circuits, the electrical contactors allowing interposing and removing the resistive load from the energization circuit from particular energization circuits to suppress inrush currents. A cooling system provides for directing forced gas toward the resistive load during initialization of the first loads. An electrical system controller controls the electrical contactors and turns on and off means for directing the forced gas.

Description

VEHICLE ELECTRICAL SYSTEM WITH COOLING

BACKGROUND

[001] Technical Field:

[002] The technical field relates generally to motor vehicle electrical systems and, more particularly, to cooling high voltage system pre-charge circuits.

[003] Description of the Technical Field:

[004] Hybrid electric vehicles typically use a high voltage, direct current (DC) electrical power storage and distribution architecture in which a plurality of high voltage DC storage devices/traction battery packs are arranged in series. The vehicle traction system receives power from and supplies power to the storage and distribution system at the maximum DC voltage. The traction battery packs may be individually tapped to support electrical loads at lower voltages. A possible arrangement uses two battery packs which can supply power at 350 volts on accessory buses and which in series supply power to the vehicle electric traction system at 700 volts DC.

[005] The loads attached to accessory buses can include electrical motors, controllers, inverters and the like. The vehicle traction system is usually connected across the two traction packs in series and includes an inverter for converting 700 volt DC to three phase alternating current (AC). When the vehicle is initially turned on, some of these devices exhibit minimal impedance and have no voltage across their input terminals. Application of 350 or 700 volts DC can result in a brief, but relatively unimpeded flow of current into the devices. Such surges can have detrimental effects on the life, functionality and efficiency of the various electrical components.

[006] In order to control inrush surges electrical distribution systems are equipped with "pre-charge circuits," which comprise electrical resistors which can be cycled into and out of the connection circuit between the electrical supply and the loads. A pre-charge cycle can occur upon the initialization of the vehicle for starting and is generall turning the in-cab ignition key switch to "ON." The pre-charge cycle is sustained long enough to gradually equalize the electrical potentials between the high and low potential components within the same electrical architecture in order to avoid damage to the loads at the lower electrical potential. The process of gradually pre-charging a hybrid electric vehicle's electrical system/s generally involves the vehicle's battery/s, or an external electrical power sources, providing electrical energy through the pre-charge circuit until the lower potential components within the system are within an acceptable level with relationship to the high potential source. During this process of electrical potential equalization the pre-charge circuit will dissipate electrical energy as heat.

[007] The heat produced by the pre-charge circuits has been rejected in the prior art by use of solid metallic heat sinks, glycol filled (circulated liquid cooled) heat sinks, pusher/puller fans to reject heat from the pre-charge resistors and combinations of these elements. Metallic heat sinks (including radiating blades) and circulated liquid cooled heat sinks are in physical contact with the pre-charge resistors and may generally be referred to as planars. The heat generated from the pre-charge circuit can become problematic if the number of vehicle initializations increases relative to the interval of time between initializations which result in the heat sink temperature rising above a critical level beyond the ability of fans to reject the heat to the environment.

SUMMARY

[008] A vehicle electrical system comprises an electrical power source, at least a first load for energization from the electrical power source and a resistive load which may be interposed between the electrical power source and the first load to prevent current inrush upon initialization. Isolation contactors provide the selective connection of the at least first load to the electrical power source in energization circuits through or without the resistive load. Cooling of the resistive load is enhanced by directing forced gas toward the resistive load, either in response to current flow through the resistive load or in response to resistive load temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[009] Fig. 1 is a side elevation of a truck and trailer system which may be equipped with a hybrid drive train.

[0010] Fig. 2 is a high level block diagram of a control system and electrical power storage and distribution system for the truck of Fig. 1.

[0011] Fig. 3 is a block diagram of pneumatic supply system adapted to provide compressed gas cooling of a pre-charge circuit.

[0012] Fig. 4 is a graph illustrating change in power dissipation over time through a pre- charge resistor.

DETAILED DESCRIPTION

[0013] In the following detailed description, like reference numerals and characters may be used to designate identical, corresponding, or similar components in differing drawing figures. Furthermore, example sizes/models/values/ranges may be given with respect to specific embodiments but are not to be considered generally limiting. In circuit diagrams well-known power and ground connections, waveguide terminating impedances and similar well-known elements, may be omitted for the sake of simplicity of illustration.

[0014] Referring now to the figures and in particular to FIG. 1, a truck/trailer combination 10 comprising a truck 12 and trailer 14 attached to one another along the axis of a fifth wheel is shown. Truck 12 includes drive wheels 18 which are operatively connected to a hybrid drive train 20. The rotation of wheels drive wheels 18 can be retarded by using them to back drive the hybrid drive train 20 to generate electricity. While the embodiment described here relates to a hybrid electric drive train it is not limited to hybrid electric drive train applications. [0015] Referring to Fig. 2, hybrid truck 12 may be equipped with a hybrid electric drive train 20 having a dual mode electrical machine 16 and an internal combustion engine (ICE) 22. Dual mode electrical machine 16 can function in a generator mode for regenerative braking or in a traction motor mode. Depending upon the mode assumed by electrical machine 16, it can supply power to or draw power from 350 volt high voltage (traction) battery packs 38, 39. Power transfer occurs indirectly through a high voltage distribution system (HVDS) 21 and a hybrid system inverter/controller 17. HVDS 21 supplies 700 volt DC power to hybrid inverter/controller 17 where typically it is converted to three phase alternating current for application to the electrical machine 16.

[0016] Battery packs 38, 39 are connected in series along series connection 41 from the positive output of battery pack 38 to the negative terminal of battery pack 39 to supply power at 700 volts DC, or at what is termed herein as the "traction voltage level." The positive terminals of both battery packs 38, 39 are connected to an isolation contactor sub-system 34 in HVDS 21. During truck 12 operation dual mode electrical machine 16 and 350 volt traction batteries 38, 39 alternate as the major sources of power through the HVDS 21.

[0017] Usually one or more chassis batteries 61, 65 are provided on a truck 12 to supply power to and stabilize voltage on a low (12 volt) voltage electrical power distribution system 19. Twelve volt systems have been common on motor vehicles for decades and a large variety of electrical appliances and lighting exist for 12 volt systems. In addition the 12 volt low voltage distribution system 19 may be used to support relatively low noise electrical power to the on-board vehicle management computers, including hybrid control unit (HCU) 51, gauge controller 53, engine control unit (ECU) 45, anti-lock brake system (ABS) controller 43, electronic system controller (ESC) 40, accessory motor controller 29, compressor motor controller 31 and remote power module (RPM) 36. Usually the chassis batteries 61, 65 of the 12 volt system are kept charged by power from the high voltage system and the batteries (and their power distribution systems) are connected to the HVDS 21 by at least two bi-directional DC-DC converters 62, 63, respectively. Because the DC-DC converters 62, 63 are bi-directional the pc exists for the 12 volt system to supply power to the HVDS 21. Other electrical power sources may be available, such as external power.

[0018] HVDS 21 provides first and second internal DC buses, namely first and second high voltage accessory buses 44, 50, which may be used to supply power to accessory motors and other loads at voltage levels intermediate the traction voltage level and the voltage level on the low voltage distribution system 19. Usually, the intermediate voltage levels are both 350 volts DC. Power is supplied to buses 44, 50 through a particular configuration of isolation contactors 34 from traction battery packs 38, 39 or from the hybrid inverter/controller 17 (at 700 volts DC). Isolation contactors 34 can also be configured to transfer power between hybrid inverter 17 and the traction battery packs 38, 39. Power on first HV accessory bus 44 is drawn primarily from battery pack 38 and power on second HV accessory bus 50 is drawn primarily from traction battery pack 39 at 700 volts on line 35. Bus 44 may be taken as embodying a 350 volt to chassis ground system while bus 50 carries a 350 volt difference based on a 700 volt to 350 volt difference.

[0019] There are several electrical power loads to which HVDS 21 can deliver power. Implicitly, the traction battery packs 38, 39 alternate with dual mode electrical machine 16 as loads. The 12 volt power distribution system is usually a load on HVDS 21 but one which may be supported from bus 44, bus 50, or both power buses at independent rates. In addition, truck 12 may be equipped with high voltage accessory motors such as accessory motor 28 and accessory/compressor motor 30. High voltage (350 volt) accessory motors 28, 30 may be substituted for more common 12 volt motors as a weight saving measure. Accessory motor 28 may be mechanically coupled to a mechanical load such as air conditioning compressors, hydraulic pumps and the like. Accessory/compressor motor 30 is mechanically coupled to a pneumatic compressor 32 which supplied compressed air to a pneumatic supply system 33. [0020] Upon truck 12 initialization/start up the input terminals of various high loads may be at ground which can result in 350 volts DC or 700 volts DC being applied across the input terminals upon system initialization. In order to suppress in rush currents on system initialization to vehicle loads such as hybrid inverter/controller 17 or to bidirectional DC-DC converters 62, 63, HVDS 21 is equipped with a plurality of pre- charge resistors 11 (shown in Fig. 3) which are in thermally conductive contact with a heat sinking planar 37. Electrical power from traction battery packs 38, 39 is routed by isolation contactors 34, which are under the control of remote power module 36, through the pre-charge resistors 11 upon truck 12 initialization (circuit connections to the pre- charge resistors are omitted for sake of clarity).

[0021] Management of truck 12 initialization is handled by a control system pertinent aspects of which are illustrated in Fig. 2. Contemporary vehicle management is typically based on networks connecting microcontrollers for major systems. The ABS controller 43, ECU 45, gauge controller and ESC 40 communicate over an SAE J1939 compliant bus/data link 23 to implement a drive train controller area network (CAN). The HCU 51, ESC 40, an accessory motor controller 29 and compressor motor controller 31 communicate over a second data link 25 to implement a hybrid CAN. RPM 36 is one node of the hybrid CAN connected to data link 25 to function as an extension of ESC 40 and controls the configuration of the isolation contactors 34. The key input which begins system initialization is typically a direct input to the ESC 40.

[0022] Conventionally the pneumatic supply system 33 supports operation of the truck's service brakes (not shown). Pneumatic supply system 33 is usually under the control of ESC 40 to implement this functionality. Here the pneumatic supply system 33 is also used by ESC 40 to supplement cooling of the heat sinking planar 37 providing pre-charge resistors 11.

[0023] The pneumatic supply system 33 is illustrated in greater detail in Fig. 3. Compressed air is delivered from the pneumatic compressor 32 to an air dryer 52 and from air dryer 52 to a supply tank 54 for distribution to the primary and secondary air tanks 55, 56. Secondary air tank 56 is connected to supply air to primary air tanl optional auxiliary gas supply 58 may also be provided. The auxiliary gas supply 58 may be used for cryogenic storage of a source material used to pre-charge resistor cooling. Such materials may be liquid carbon dioxide or liquid nitrogen. Alternatively the auxiliary gas supply 58 may contain air compressed by the pneumatic compressor 32 but isolated from the remaining elements of the pneumatic supply system 33 to assure availability upon vehicle electronic system initialization. Pneumatic connections to allow employment as a secondary source of compressed air are shown including a manifold 60 connected to the supply air tank 54, outlets and inlets from manifold 60 to the auxiliary gas supply 58 and solenoid valve controllers 64, 66 for controlling air flow through the manifold and out of the auxiliary gas supply.

[0024] Compressed air and gas flow from the pneumatic supply system 33 to various consumers is controlled by a multi-solenoid valve assembly (MSVA) 57 which is under the control of the ESC 40. Primary air tank 55 and manifold 60 are connected to directly supply the MSVA 57 which directs high pressure gas or air to vehicle components such as service brakes or through an air filter 59 and inlet 67 into the sealed HVDS 21 for pre- charge resistor cooling applications. Inlet 67 is connected to an air distribution manifold 13 which divides the flow among a plurality of jets 15. The jets 15 are aimed at pre- charge resistors 11, or against cooling fins (not shown), to direct a flow of forced gas against the resistors or cooling fins to enhance heat rejection from the resistors or from the heat sinking planar 37. Heating sinking planar 37 may be located isolated within HVDS 21 or abutting one wall of HVDS to enhance conduction of heat outside of the HVDS. HVDS is conventionally sealed to avoid moisture intrusion. Air is extracted from HVDS 21 by an outlet 68 and returned to MSVA 57 for discharge to the atmosphere.

[0025] The present pre-charge resistor cooling system employs reconfigurable software lodged in the ESC 40 and a conventional electrical hardware architecture to control the delivery of gas under pressure originating from a compressed air or gas source, for example primary air tank 55 or auxiliary gas supply 58. A high pressure gas flow derived from these sources is triggered by a vehicle initialization event and returns the resistors to a maximum allowed temperature. The endurance of the gas flow may be times o on cut off by a temperature sensor (not shown).

[0026] Operation of the system begins upon initialization of truck 12's electrical system. Initialization of the electrical system typically begins with the activation of an operator control such as the "turning on" a key switch. Vehicle electrical system initialization includes establishing the flow of electrical energy flow through an electrical isolation device (commonly an IGBT or discrete isolation contactors 34) to a vehicle integrated electrical pre-charge circuit generally comprising of at least one electro resistive device/s typified by a plurality of pre-charge resistors 11 installed on a heat sinking planar 37. The pre-charge resistors 11 limit the flow of electrical energy to portions of the hybrid electric vehicle's electrical architecture which would be susceptible to damage from the otherwise free flow of electrical energy when included in the energization circuit for a load from the traction battery packs 38, 39. Once the vehicle's electrical architecture has been brought up to operating voltages at least one main high voltage isolation contactor/s 34 and, or isolated gate bi-polar transistor/s (IBGT) type device/s will transition and cut out the pre-charge circuit allowing the vehicle to operate at the full electrical energy levels.

[0027] A by-product of the pre-charge resistors 11 limiting current flow to elements of the vehicle electrical architecture is that energy is dissipated by the pre-charge resistors 11 as heat. If heat is not rejected from the HVDS 21, and subsequent initializations of the vehicle electrical system occur in a compressed time interval, it is possible that the pre- charge resistors 11 could degrade in performance or fail altogether due to heat build up. For this reason a body computer such as the ESC 40 will send control signals over data link 25 to the MSVA 57 to direct high pressure gas flow into the HVDS 21 and over the pre-charge resistors 11.

[0028] Pneumatic supply system 33 is conventionally applied to supply pneumatic systems such as pneumatic brakes, suspensions, fifth wheel slides and seats. Consequently the pneumatic supply system 33 may be subject to leakage when the vehicle is not initialized without the possibility of repressurization. It is poss compressed air stored in the primary and secondary air tanks 55, 56 may be unavailable to extract heat from the pre-charge resistive devices immediately upon the initialization. For this reason once the pre-charge system and subsequent vehicle systems are initialized, the compressed gases may be delivered at an increasing rate as the available supply builds. An auxiliary gas supply 58 may take one of several forms, such as a compressed gas reservoir or cryogenic storage vessel. The auxiliary gas supply 58 is isolated from the remaining vehicle pneumatic supply system 33 assures that pressurized gas flow is available when needed in the event that the vehicle's common pneumatic storage system is unavailable at the needed pressure and flow rates for extracting heat. The ESC 40 controls the out flow of gas from auxiliary gas supply 58 and its charging if it used to store compressed air from the pneumatic supply system 33.

[0029] Latent heat level associated with heat sinking planar 37 can be sensed using a temperature sensor 42 and reported to ESC 40. ESC 40 may continue to direct the rejection of heat during and after the truck 12's operation has been suspended. The duration and manner of injection of cooling gas may be based on temperature measurements taken at or near the pre-charge resistors 11 or it may be programmed to occur automatically at times when the pre-charge resistors 11 are likely to reached a maximum allowed level of heat saturation. Gases introduced to the sealed environment of the HVDS 21 have a maximum allowable moisture content to the presence of high voltage components. The time intervals provided for cooling events may be calculated to take into account operation of the air dryer 52 (and air filter 59 if adapted for moisture extraction).

[0030] Outlet 68 (an outlet check valve or purge valve) and the MSVA 57 provide for pressure relief from HVDS 21 so that the internal pressure inside the HVDS 21 does not substantially exceed ambient atmospheric pressure. Pressure relief prevents external particulate matter and moisture from entering the HVDS 21. Outlet 68 is controlled by the ESC 40 through MSVA 57. Feedback data may be displayed on an in-cab driver's display under the control of gauge controller 53 indicating the state, performs status of the pre-charge resistors 11 and of systems relating to the rejection of heat.

[0031] Fig. 4 is a graph illustrated heat produced by a representative pre-charge resistor upon vehicle initialization. Initially power consumption in terms of heat production can easily exceed a kilowatt, falling off to less than 200 watts after about one half second and a few tens of watts after one second. It is easy to see that for a given application several hundred watt-seconds of energy may have to be sunk, particularly if the system is subjected to repeated initializations during a short period of time.

Claims

What is claimed is:

A vehicle electrical system comprising:

an electrical power source;

at least a first load for energization from the electrical power source;

a resistive load;

isolation contactors for selective connection of the at least first load to the electrical power source in energization circuits, the isolation contactors allowing inclusion and exclusion of the resistive load from particular energization circuits; means for directing forced gas toward the resistive load; and

an electrical system controller for configuring the isolation contactors and for turning on and off the means for directing forced gas.

A vehicle electrical system as set forth in claim 1, further comprising:

the electrical system controller being responsive to an operator action for initializing the at least first load by selecting a particular energization circuit including the resistive load during an initialization period and upon completion of initialization for reselecting the isolation contactors to provide a particular energization circuit without the resistive load.

A vehicle electrical system as set forth in claim 2, further comprising:

the electrical system controller being responsive to inclusion of the resistive load in an energization circuit for activating the means for directed forced gas.

A vehicle electrical system as set forth in claim 3, further comprising:

the resistive load being in thermally conductive contact with a heat sink.

A vehicle electrical system as set forth in claim 3, further comprising:

a temperature sensor in thermal contact with the resistive load.

6. A vehicle electrical system as set forth in claim 3, further comprising: the means for directing forced gas including a pneumatic supply system having a compressor and air supply tanks.

7. A vehicle electrical system as set forth in claim 3, further comprising:

the pneumatic supply system further including an auxiliary supply dedicated to supplying gas for cooling the resistive load.

8. A vehicle electrical system as set forth in claim 3, the resistive load being a pre- charge resistor.

9. A vehicle electrical system including a cooling system, the cooling system

comprising:

an ambient air compressor;

a compressed air storage system connected to the ambient air compressor;

a plurality of jets directed toward heat generating elements of the electrical power distribution system;

a valve system for connecting the plurality of jets with the compressed air storage system; and

a controller for the valve system responsive to initialization of the electrical power distribution system for opening the valve system to allow forced air to be released from the plurality of jets.

10. A vehicle electrical system including a cooling system as claimed in claim 9, further comprising:

the electrical power distribution system is a direct current system and the heat generating elements are pre-charge resistors.

11. A vehicle electrical system including a cooling system as claimed in c further comprising:

a heat sinking planar in contact with the pre-charge resistors; and

a thermal sensor in thermal contact with the heat sinking planar or the pre-charge resistors.

12. A vehicle electrical system including a cooling system as claimed in claim 10, further comprising:

a sealed enclosure in which the pre-charge resistors are located.

13. A vehicle electrical system including a cooling system as claimed in claim 12, further comprising:

an outlet from the enclosure.

14. A vehicle electrical system including a cooling system as claimed in claim 9, further comprising:

an auxiliary gas supply connectable to the plurality of jets.

15. A vehicle electrical system including a cooling system as claimed in claim 14, further comprising:

the auxiliary gas supply being charged with an inert gas.