Indian Patents. 272686:METHOD AND APPARATUS FOR MONITORING A THERMAL MANAGEMENT SYSTEM OF AN ELECTRO-MECHANICAL TRANSMISSION

Title of Invention	METHOD AND APPARATUS FOR MONITORING A THERMAL MANAGEMENT SYSTEM OF AN ELECTRO-MECHANICAL TRANSMISSION
Abstract	Temperature of an electric power device of a hybrid transmission is managed based upon device temperatures and power flow, ambient temperature, and a cooling circuit flow rate.

Full Text	METHOD AND APPARATUS FOR MONITORING A THERMAL MANAGEMENT SYSTEM OF AN ELECTRO-MECHANICAL TRANSMISSION TECHNICAL FIELD [0001] This disclosure is related to control systems for electro-mechanical transmissions, and thermal management systems therefor. BACKGROUND [0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. [0003] Powertrain architectures comprise torque-generative devices, including internal combustion engines and electric machines, which transmit torque through a transmission device to an output. One exemplary transmission is a two-mode, compound-split, electro-mechanical transmission which utilizes an input member for receiving motive torque from a prime mover power source, for example an internal combustion engine, and an output member for delivering motive torque from the transmission to a vehicle driveline. Electric machines, operable as motors or generators, generate a torque input to the transmission, independently of a torque input from the internal combustion engine. The electric machines may transform vehicle kinetic energy, transmitted through the vehicle driveline, to electrical energy potential that is storable in the electrical energy storage device. A control system monitors various inputs from the vehicle and the operator and provides operational control of the powertrain system, including controlling transmission operating state and gear shifting, controlling the torque- generative devices, and regulating the electrical power interchange between the electrical energy storage device and the electric machines. [0004] During operation of the electric machines, heat is generated in the various electric power devices, including the electric machines, power inverters, and electrical energy storage devices, e.g., high voltage batteries. Heat transfer devices, including heat sinks, heat exchangers, and cooling systems may be incorporated to manage waste heat in the system. Systems include closed-circuit cooling systems which flow liquid coolant over heat sinks and pump the coolant through a heat exchanger to remove the waste heat. Other systems include fan devices which pass air over the heat sink devices to remove heat therefrom. SUMMARY [0005] A method for thermal management of an electric power device includes monitoring temperature of the electric power device and an ambient temperature and determining an electric power flow through the electric power device. A temperature gradient across the electric power device based upon the monitored temperature of the electric power device is determined. A flow rate through the heat transfer circuit is estimated and compared to a threshold flow rate based upon the temperature gradient, the ambient temperature, and the electric power flow. BRIEF DESCRIPTION OF THE DRAWINGS [0006] One or more embodiments will now be described, by way of example, with reference to the accompanying drawings, in which: [0007] Fig. 1 is a schematic diagram of an exemplary powertrain, in accordance with the present disclosure; and [0008] Figs. 2 and 3 are algorithmic flowcharts, in accordance with the present disclosure. DETAILED DESCRIPTION [0009] Referring now to the drawings, wherein the showings are for the purpose of illustrating certain exemplary embodiments only and not for the purpose of limiting the same, Fig. 1 depicts a vehicle system 12 which has been constructed in accordance with an embodiment of the present disclosure. The vehicle system 12 comprises an internal combustion engine 14, electro- mechanical transmission 10, and driveline 92 adapted to transmit tractive torque to vehicle wheels 90. An electric power system comprises electric power components or devices including respective first and second electric machines 56 and 72, an electrical energy storage device ('ESD') 74, and power electronics circuit 19. The electric machines 56 and 72 comprise motor/generators, each of which converts electric power to mechanical torque via the power electronics circuit 19. The ESD 74 comprises a high-voltage battery system adapted to store electrical energy and transmit electrical power to the electric machines 56 and 72 via the power electronics circuit 19. The ESD 74 and electric machines 56 and 72 are electrically-operatively coupled for electric power flow therebetween. The engine 14, electric machines 56, 72, and the electro-mechanical transmission 10 are mechanically-operatively coupled to transmit mechanical power therebetween to transmit motive torque to the driveline 92 and vehicle wheels 90 via output shaft 64, and to transmit mechanical power to one of the electric machines 56 and 72 for electric power generation via a power splitting device 16. A distributed control module ('CM') 4 is adapted to monitor inputs from a plurality of sensing devices (not shown) and execute predetermined algorithms stored therein to control actuators of the various devices to achieve an operator torque request and meet other parameters related to performance, fuel economy, and emissions, among others. The exemplary hybrid powertrain system is configured to execute the control schemes depicted hereinbelow with reference to Figs. 2 and 3, among various others required for operation of the vehicle system 12. [0010] The exemplary engine 14 comprises a multi-cylinder internal combustion engine selectively operative in several states to transmit torque to the transmission 10, and can be either a spark-ignition or a compression- ignition engine. The transmission 10 comprises an electro-mechanical torque- transmitting device. The exemplary electro-mechanical transmission 10 operates in one of several operating range states comprising fixed gear operation and continuously variable operation. [0011] The first and second electric machines 56 and 72 comprise three- phase AC machines and include a stator, a rotor, and a resolver assembly, all not shown. The motor stator for each machine is grounded to an outer portion of the transmission case, and includes a stator core with coiled electrical windings extending therefrom. Each resolver assembly comprises a variable reluctance device including a resolver stator, operatively connected to the [0014] A heat transfer circuit 96 preferably comprises a closed fluidic circuit including a heat transfer or fluid/air radiator device 95 that is preferably separate from a main vehicle radiator 34 used for cooling the engine 14. However those skilled in the art will recognize that the fluid air radiator device 95 may be incorporated within the main vehicle radiator 34 while remaining within the scope of that which is claimed. The fluid/air radiator device 95 is fluidly connected to, and forms a fluid circuit with, a thermal interface device 94 of the power electronics circuit 19 via coolant lines 93. A pump device 91, such as an electrically actuated pump, pumps or circulates fluid, e.g., an ethylene glycol based coolant, within the heat transfer circuit 96. The pump device 91 preferably comprises a variable flow device having a flow rate controlled via a pulsewidth-modulated electric circuit. Operation of the pump device 91, and therefore pump flow rate, is preferably controlled via a pulsewidth-modulated (PWM) signal output from the control module 4 as a function of operating conditions, e.g., temperature measured at the inverter, ambient temperature and electrical load. The high-voltage ESD 74 and the stators of the electric machines 56 and 72 include the thermal interface device 94 that connects to the heat transfer circuit 96, or, alternatively, are on separate cooling circuits. The thermal interface device 94 preferably comprises a heat exchange device thermally connected to a coolant manifold (not shown). The power electronics circuit 19 includes a multi-sectioned housing (not shown in detail) having an electrical connection for feedthrough of power, control and data cables in a first section 21, and a fluidic connection for feedthrough of liquid coolant to the coolant manifold of the thermal interface device 94 in a second section. The first section 21 of the housing contains the plurality of semiconductor power switching devices (e.g., the IGBTs), not shown. Each of the semiconductor power switching devices is thermally coupled to the thermal interface device 94. The thermal interface device 94 preferably comprises a fin-type radiant heat exchanger located in the housing in a manner that the fins are exposed in the coolant manifold of the second section, while the power switching devices are fluidly sealed therefrom, preventing exposing the power switching devices to the coolant fluid. There are other electronic devices in the housing, including a plurality of temperature sensing devices 97 and 97' and electrical current sensing devices. The temperature sensors 97 and 97' each monitor one of the plurality of semiconductor power switching devices to determine temperature states thereof, referred to hereinbelow as TNJGBT> with N indicating the specific semiconductor power switching devices. Signal outputs of the temperature sensors 97 and 97' are input to the control module 4 for analysis. The second section of the housing comprises the thermal interface device 94, consisting of the fin-type radiant heat exchanger and the coolant manifold fluidly sealed in the second section of the housing. The second section of the housing includes a fluidic inlet and outlet, and the coolant manifold comprises a fluidic passage which exposes the fin- type radiant heat exchanger to coolant fluid. [0015] The volume and frontal area of the fluid/air radiator device 95 and the flow capacity of the pump device 91 are determined based upon the amount of heat rejection from the power electronics circuit 19 through the thermal interface device 94. The fluid/air radiator device 95 is sized such that the heat generation of the power electronics circuit 19 operating at a low electrical efficiency point is less than system heat rejection through the fluid/air radiator device 95 at a maximum ambient temperature, e.g., 35-40°C. [0016J The control module 4 comprises a distributed control module architecture which provides coordinated system control of the powertrain system described herein, and is a subset of an overall vehicle control architecture. The control module 4 synthesizes pertinent information and inputs, and executes algorithms to control various actuators to achieve control targets, including such parameters as fuel economy, emissions, performance, driveability, and protection of hardwaie, including batteries contained within the ESD 74 and the first and second electric machines 56 and 72. The distributed architecture preferably includes an engine control module, transmission control module, battery pack control module, the power electronics circuit 19, and a hybrid control module, which provides supervisory control and coordination ofthe aforementioned control modules. A user interface, not shown, is operatively connected to a plurality of devices through which a vehicle operator typically controls or directs operation ofthe powertrain including the transmission 10. Such operator driven control signals may include an operator torque request and operator brake. Exemplary input devices to the user interface include an accelerator pedal, a brake pedal, a transmission gear selector, and a vehicle speed cruise control, all of which are not shown. Each of the aforementioned control modules communicates with other control modules, sensors, and actuators via a local area network which allows for structured communication of control parameters and commands between the various control modules. [0017] Each of the control modules is preferably a general-purpose digital computer generally comprising a microprocessor or central processing unit, storage mediums comprising read only memory (ROM), random access memory (RAM), electrically programmable read only memory (EPROM), high speed clock, analog to digital (A/D) and digital to analog (D/A) circuitry, and input/output circuitry and devices (I/O) and appropriate signal conditioning and buffer circuitry. Each control module has a set of control algorithms, comprising resident program instructions and calibrations stored in ROM and executed to provide the respective functions of each computer. Information transfer between the various computers is preferably accomplished using a local area network communications bus. Algorithms for control and state estimation in each of the control modules are typically executed during preset loop cycles such that each algorithm is executed at least once each loop cycle. Algorithms stored in the non-volatile memory devices are executed by one of the central processing units and are operable to monitor inputs from the sensing devices and execute control and diagnostic routines to control operation of the respective device, using preset calibrations. Loop cycles are typically executed at regular intervals, for example each 3.125, 6.25, 12.5, 25 and 100 milliseconds during ongoing engine and vehicle operation. Alternatively, algorithms may be executed in response to occurrence of an event. [0018J A computer program is executed in the control module 4 to monitor the temperature sensing devices 97 and 97', ambient temperature, and electric power flow through one or more electric power components or devices. The electric power devices comprise one of the power electronics circuit 19 (having temperature TIGBT_N for N temperature sensors), the motor stator of one of the electric machines 56 and 72, and the ESD 74. A temperature gradient across the electric power component is determined based upon input from the monitored temperature sensing devices. A flow rate through the heat transfer circuit 96 is estimated based upon the temperature gradient, the ambient temperature, and the electric power flow. The estimated flow rate through the heat transfer circuit 96 is compared to a threshold flow rate. Embodiments of this are now described in detail with reference to Figs. 2 and 3 and with continued reference to Fig. 1. [0019] Fig. 2 depicts a first embodiment, comprising control scheme 200, executable as program code in the control module 4 preferably during one of the loop cycles. Temperature(s) of one of the electric power devices is monitored. In the present embodiment of Fig. 2, the electric power device monitored is the power electronics circuit 19 which is preferably monitored in a plurality of locations using temperature sensors 97 and 97'. The motor stator of one of the electric machines 56 and 72, and the ESD 74 may be similarly monitored. A device temperature (TDEv) is determined to be the maximum of the plurality of monitored temperatures, or, alternatively, some calculated average of the plurality of monitored temperature (Step 202). [0020] The temperature of the device (TDEV) is compared to a predetermined upper threshold temperature (TJHD) (Step 204). When the temperature of the device is less than the predetermined upper threshold temperature, inputs from the coolant circuit are monitored (Step 206), including electric power to the pump 91 (PPUMP)5 typically the commanded PWM duty cycle, the ambient temperature (TAMB) and the electrical load (LOAD). A temperature gradient across the electric power device is also determined (ATDEV), comprising a temperature difference between a maximum output from one of the temperature sensors 97 or 97' on the device and a minimum output from one of the temperature sensors 97 or 97' on the device, at a given point in time. A first coolant flow rate is estimated, comprising a precalibrated coolant flow rate determined based upon the temperature gradient across the device, depicted as CFREST. A calibration array for the first precalibrated coolant flow rate CFREST is preferably generated during testing of the system described, and stored as an array in one of the memory devices of the control module 4. A second, threshold coolant flow rate is determined, referred to as CFRTHR, arid comprises a precalibrated flow which is determined based upon the electric power to the pump 91 (PPUMP), the ambient temperature (TAMB), and the electrical load (LOAD) (step 207). The first and second flow rates CFREST and CFRTHR, respectively, are compared (Step 208). When the first and second flow rates, CFREST and CFRTHR, are substantially the same, with allowance for measurement errors and other sources of variation, operation of the system continues (Step 210). When the first and second flow rates, CFREST and CFRTHR, vary by an amount greater than allowable measurement error (Step 208), or the temperature of the electric power device TDEV is less than the predetermined upper threshold temperature TTHD (from Step 204), a fault counter is incremented (Step 212). A fault code is set when there are X faults out of Y observations, i.e., executions of the algorithm in the loop cycle (Step 216). Depending upon the conditions and requirements, the operator of the vehicle is notified of the presence of a fault in the heat transfer circuit 96, and the control module 4 executes a mitigating action to prevent further harm or damage to the hardware. The mitigating action may include adjusting the PWM control signal to the coolant pump 91 and limiting power output from the electric machines 56 and 72. [0021] Fig. 3 depicts a second embodiment, comprising control scheme 300 executable as program code in the control module 4 during one of the loop cycles. Temperatures are monitored in the electric power component being cooled, which comprises the power electronics circuit 19 in this embodiment. The power electronics circuit 19 is monitored in N locations to determine temperatures thereof, via temperature sensors 97, 97' located at or near the IGBTs of the power electronics circuit 19. Load (LOAD) and ambient temperature (TAMB) are monitored, with load consisting of the power conducted through the power electronics circuit, typically measured as current (I) (Step 302). A temperature gradient across the electric power device (+/- ∆TDEV) is calculated, including both a magnitude and a direction of the gradient (Step 304). The temperature gradient across the electric power device is normalized (+/- ∆TDEV(Load, TAMB)), based upon the load and the ambient temperature (Step 306). The normalization removes influences in the temperature gradient that are based upon system load and ambient temperature. An estimate of coolant flow rate (CFREST) is determined based upon the normalized temperature gradient (Step 308). The estimated coolant flow rate is preferably determined based upon two predetermined calibrations. The predetermined calibrations comprise a first calibration when the temperature gradient (+∆TDEV) across the power electronics circuit is positive, and a second calibration when the temperature gradient (-∆TDEV) across the power electronics circuit is negative. Each of the predetermined calibrations comprises an array of flow rates (CFREST) corresponding to normalized temperature gradient (+/- ∆TDEV(Load, TVMB) determined during system development and testing. The estimated flow rate, CFREST, is compared to a normalized threshold flow rate, CFRTHR.NORMAL (Step 310). The normalized threshold flow rate, CFRTHR_NORMAL, preferably comprises a scalar value determined during calibration based upon the PWM control signal to the coolant pump 91. When the estimated flow rate, CFREST, exceeds the normalized threshold flow rate, CFRTHR NORMAL, the control scheme 300 determines the heat transfer circuit 96 is operating as intended. When the estimated flow rate, CFREST, does not exceed the normalized threshold flow rate, CFRTHR_NORMAL, the control scheme 300 determines the heat transfer circuit 96 is not operating as intended. A fault counter is incremented, and when X faults occur in Y observations, or loops (Step 312), a fault code is set (Step 314). Depending upon the conditions and requirements, the operator of the vehicle is notified of the presence of the fault, and the control module 4 executes mitigating action to prevent further harm or damage to the hardware. The mitigating action may include adjusting the PWM control signal to the coolant pump 91 and limiting power output from the electric machines 56 and 72. In operation, the control system monitors operation of the heat transfer circuit 96 to identify faults therein and mitigate damage to system components. [0022] The system set forth hereinabove described a heat transfer circuit 96 related to the power electronics circuit 19; however, one skilled in the art will readily apply the concepts of the disclosure to monitoring one of the electric machines 56 and 72, or the high-voltage ESD 74. [0023] The disclosure has described certain preferred embodiments and modifications thereto. Further modifications and alterations may occur to others upon reading and understanding the specification. Therefore, it is intended that the disclosure not be limited to the particular embodiment(s) disclosed as the best mode contemplated for carrying out this disclosure, but that the disclosure will include all embodiments falling within the scope of the appended claims. CLAIMS 1. Method for thermal management of an electric power device, the method comprising: monitoring temperature of the electric power device and an ambient temperature; determining an electric power flow through the electric power device; determining a temperature gradient across the electric power device based upon the monitored temperature of the electric power device; and, estimating a flow rate through the heat transfer circuit and comparing the flow rate to a threshold flow rate based upon the temperature gradient, the ambient temperature, and the electric power flow. 2. The method of claim 1, further comprising estimating the flow rate based upon the temperature gradient across the electric power device. 3. The method of claim 2, wherein the threshold flow rate through the heat transfer circuit is determined based upon the electric power flow through the electric power device. 4. The method of claim 1, further comprising identifying a fault in the heat transfer circuit when the estimated flow rate through the heat transfer circuit is not substantially the same as the threshold flow rate. 5. The method of claim 4, further comprising identifying the fault in the heat transfer circuit when the estimated flow rate through the heat transfer circuit is not substantially the same as the threshold flow rate in X out of Y observations. 6. The method of claim 1, wherein estimating the flow rate through the heat transfer circuit comprises: normalizing the temperature gradient across the electric power device based upon the ambient temperature and the electric power flow; and determining a flow rate from a precalibrated array based upon the normalized temperature gradient. 7. The method of claim 6, wherein the temperature gradient comprises a magnitude and a direction of the temperature gradient determined based upon the monitored temperature of the electric power device. 8. The method of claim 7, further comprising identifying a fault in the heat transfer circuit when the estimated flow rate through the heat transfer circuit is less than the threshold flow rate. 9. The method of claim 8, further comprising identifying the fault in the heat transfer circuit when the estimated flow rate through the heat transfer circuit is less than the threshold flow rate X out of Y observations. 10. The method of claim 1, wherein the electric power device comprises a power electronics circuit operative to control the electric power flow. 11. The method of claim 10, wherein the power electronics circuit further comprises a thermal interface device thermally connected to the electric power device and fluidly sealed therefrom. 12. The method of claim 11, wherein the thermal interface device comprises a housing comprising a heat transfer element incorporated into the heat transfer circuit. 13. Article of manufacture, comprising a storage medium having a machine- executable program encoded therein to monitor a closed fluidic heat transfer circuit for an electric power device of an electro-mechanical transmission system, the program comprising: code to monitor temperature of the electric power device and an ambient temperature; code to determine an electric power flow through the electro-mechanical transmission system; code to determine a temperature gradient of the electric power device based upon the monitored temperature of the electric power device; and code to estimate and compare a flow rate through the heat transfer circuit to a threshold flow rate based upon the temperature gradient, the ambient temperature, and the electric power flow through the electro-mechanical transmission system. 14. The article of claim 13, further comprising: code to estimate the flow rate based upon the temperature gradient of the electric power device; and code to determine the threshold tlow rate through the heat transfer circuit based upon the electric power flow through the electric power device. 15. The article of claim 14, wherein the code to estimate the flow rate through the heat transfer circuit further comprises: code to normalize the temperature gradient across the electric power device based upon the ambient temperature and the electric power flow; and code to determine a flow rate from a precalibrated array based upon the normalized temperature gradient. 16. The article of claim 15, further comprising code to identify a fault in the heat transfer circuit when the estimated flow rate through the heat transfer circuit is not substantially the same as the threshold flow rate. 17. The article of claim 13, wherein the electric power device comprises an electric machine of the electro-mechanical transmission. 18. Electro-mechanical transmission system, comprising: an electro-mechanical transmission mechanically-operatively coupled to an internal combustion engine and an electric machine to transmit mechanical power flow to an output shaft; an electric power system comprising an energy storage device electrically-operatively coupled to the electric machine via a power electronics circuit, said electric power system including a thermal interface device; a plurality of temperature sensors operative to monitor temperature of an electric power device and ambient temperature; a heat transfer circuit, fluidly connected to the thermal interface device and operative to manage heat transfer therewith; and a control module, signally connected to the temperature sensors and having a machine-executable program encoded therein, the program comprising: code to monitor temperature of the electric power device and an ambient temperature; code to determine an electric power flow through the electro- mechanical transmission system; code to determine a temperature gradient of the electric power device based upon the monitored temperature of the electric power device; code to estimate and compare a flow rate through the heat transfer circuit to a threshold flow rate based upon the temperature gradient, the ambient temperature, and the electric power flow through the electro-mechanical transmission system; and code to identify a fault in the heat transfer circuit when the estimated flow rate through the heat transfer circuit is not substantially the same as the threshold flow rate. 19. The electro-mechanical transmission system of claim 18, wherein the program further comprises: code to estimate the flow rate based upon the temperature gradient of the electric power device; and code to determine the threshold flow rate through the heat transfer circuit based upon the electric power flow through the electric power device. 20. The electro-mechanical transmission system of claim 18, wherein the heat transfer circuit comprises a fluidly closed circuit including the thermal interface device, a pump, and a heat transfer device. Temperature of an electric power device of a hybrid transmission is managed based upon device temperatures and power flow, ambient temperature, and a cooling circuit flow rate.

Full Text

METHOD AND APPARATUS FOR MONITORING A THERMAL
MANAGEMENT SYSTEM OF AN ELECTRO-MECHANICAL
TRANSMISSION
TECHNICAL FIELD
[0001] This disclosure is related to control systems for electro-mechanical
transmissions, and thermal management systems therefor.
BACKGROUND
[0002] The statements in this section merely provide background
information related to the present disclosure and may not constitute prior art.
[0003] Powertrain architectures comprise torque-generative devices,
including internal combustion engines and electric machines, which transmit
torque through a transmission device to an output. One exemplary
transmission is a two-mode, compound-split, electro-mechanical transmission
which utilizes an input member for receiving motive torque from a prime
mover power source, for example an internal combustion engine, and an
output member for delivering motive torque from the transmission to a vehicle
driveline. Electric machines, operable as motors or generators, generate a
torque input to the transmission, independently of a torque input from the
internal combustion engine. The electric machines may transform vehicle
kinetic energy, transmitted through the vehicle driveline, to electrical energy
potential that is storable in the electrical energy storage device. A control
system monitors various inputs from the vehicle and the operator and provides
operational control of the powertrain system, including controlling

transmission operating state and gear shifting, controlling the torque-
generative devices, and regulating the electrical power interchange between
the electrical energy storage device and the electric machines.
[0004] During operation of the electric machines, heat is generated in the
various electric power devices, including the electric machines, power
inverters, and electrical energy storage devices, e.g., high voltage batteries.
Heat transfer devices, including heat sinks, heat exchangers, and cooling
systems may be incorporated to manage waste heat in the system. Systems
include closed-circuit cooling systems which flow liquid coolant over heat
sinks and pump the coolant through a heat exchanger to remove the waste
heat. Other systems include fan devices which pass air over the heat sink
devices to remove heat therefrom.
SUMMARY
[0005] A method for thermal management of an electric power device
includes monitoring temperature of the electric power device and an ambient
temperature and determining an electric power flow through the electric power
device. A temperature gradient across the electric power device based upon
the monitored temperature of the electric power device is determined. A flow
rate through the heat transfer circuit is estimated and compared to a threshold
flow rate based upon the temperature gradient, the ambient temperature, and
the electric power flow.

BRIEF DESCRIPTION OF THE DRAWINGS
[0006] One or more embodiments will now be described, by way of
example, with reference to the accompanying drawings, in which:
[0007] Fig. 1 is a schematic diagram of an exemplary powertrain, in
accordance with the present disclosure; and
[0008] Figs. 2 and 3 are algorithmic flowcharts, in accordance with the
present disclosure.
DETAILED DESCRIPTION
[0009] Referring now to the drawings, wherein the showings are for the
purpose of illustrating certain exemplary embodiments only and not for the
purpose of limiting the same, Fig. 1 depicts a vehicle system 12 which has
been constructed in accordance with an embodiment of the present disclosure.
The vehicle system 12 comprises an internal combustion engine 14, electro-
mechanical transmission 10, and driveline 92 adapted to transmit tractive
torque to vehicle wheels 90. An electric power system comprises electric
power components or devices including respective first and second electric
machines 56 and 72, an electrical energy storage device ('ESD') 74, and
power electronics circuit 19. The electric machines 56 and 72 comprise
motor/generators, each of which converts electric power to mechanical torque
via the power electronics circuit 19. The ESD 74 comprises a high-voltage
battery system adapted to store electrical energy and transmit electrical power
to the electric machines 56 and 72 via the power electronics circuit 19. The
ESD 74 and electric machines 56 and 72 are electrically-operatively coupled
for electric power flow therebetween. The engine 14, electric machines 56,

72, and the electro-mechanical transmission 10 are mechanically-operatively
coupled to transmit mechanical power therebetween to transmit motive torque
to the driveline 92 and vehicle wheels 90 via output shaft 64, and to transmit
mechanical power to one of the electric machines 56 and 72 for electric power
generation via a power splitting device 16. A distributed control module
('CM') 4 is adapted to monitor inputs from a plurality of sensing devices (not
shown) and execute predetermined algorithms stored therein to control
actuators of the various devices to achieve an operator torque request and meet
other parameters related to performance, fuel economy, and emissions, among
others. The exemplary hybrid powertrain system is configured to execute the
control schemes depicted hereinbelow with reference to Figs. 2 and 3, among
various others required for operation of the vehicle system 12.
[0010] The exemplary engine 14 comprises a multi-cylinder internal
combustion engine selectively operative in several states to transmit torque to
the transmission 10, and can be either a spark-ignition or a compression-
ignition engine. The transmission 10 comprises an electro-mechanical torque-
transmitting device. The exemplary electro-mechanical transmission 10
operates in one of several operating range states comprising fixed gear
operation and continuously variable operation.
[0011] The first and second electric machines 56 and 72 comprise three-
phase AC machines and include a stator, a rotor, and a resolver assembly, all
not shown. The motor stator for each machine is grounded to an outer portion
of the transmission case, and includes a stator core with coiled electrical
windings extending therefrom. Each resolver assembly comprises a variable
reluctance device including a resolver stator, operatively connected to the

[0014] A heat transfer circuit 96 preferably comprises a closed fluidic circuit
including a heat transfer or fluid/air radiator device 95 that is preferably
separate from a main vehicle radiator 34 used for cooling the engine 14.
However those skilled in the art will recognize that the fluid air radiator device
95 may be incorporated within the main vehicle radiator 34 while remaining
within the scope of that which is claimed. The fluid/air radiator device 95 is
fluidly connected to, and forms a fluid circuit with, a thermal interface device
94 of the power electronics circuit 19 via coolant lines 93. A pump device 91,
such as an electrically actuated pump, pumps or circulates fluid, e.g., an
ethylene glycol based coolant, within the heat transfer circuit 96. The pump
device 91 preferably comprises a variable flow device having a flow rate
controlled via a pulsewidth-modulated electric circuit. Operation of the pump
device 91, and therefore pump flow rate, is preferably controlled via a
pulsewidth-modulated (PWM) signal output from the control module 4 as a
function of operating conditions, e.g., temperature measured at the inverter,
ambient temperature and electrical load. The high-voltage ESD 74 and the
stators of the electric machines 56 and 72 include the thermal interface device
94 that connects to the heat transfer circuit 96, or, alternatively, are on separate
cooling circuits. The thermal interface device 94 preferably comprises a heat
exchange device thermally connected to a coolant manifold (not shown). The
power electronics circuit 19 includes a multi-sectioned housing (not shown in
detail) having an electrical connection for feedthrough of power, control and
data cables in a first section 21, and a fluidic connection for feedthrough of
liquid coolant to the coolant manifold of the thermal interface device 94 in a
second section. The first section 21 of the housing contains the plurality of

semiconductor power switching devices (e.g., the IGBTs), not shown. Each of
the semiconductor power switching devices is thermally coupled to the
thermal interface device 94. The thermal interface device 94 preferably
comprises a fin-type radiant heat exchanger located in the housing in a manner
that the fins are exposed in the coolant manifold of the second section, while
the power switching devices are fluidly sealed therefrom, preventing exposing
the power switching devices to the coolant fluid. There are other electronic
devices in the housing, including a plurality of temperature sensing devices 97
and 97' and electrical current sensing devices. The temperature sensors 97
and 97' each monitor one of the plurality of semiconductor power switching
devices to determine temperature states thereof, referred to hereinbelow as
TNJGBT> with N indicating the specific semiconductor power switching
devices. Signal outputs of the temperature sensors 97 and 97' are input to the
control module 4 for analysis. The second section of the housing comprises
the thermal interface device 94, consisting of the fin-type radiant heat
exchanger and the coolant manifold fluidly sealed in the second section of the
housing. The second section of the housing includes a fluidic inlet and outlet,
and the coolant manifold comprises a fluidic passage which exposes the fin-
type radiant heat exchanger to coolant fluid.
[0015] The volume and frontal area of the fluid/air radiator device 95 and
the flow capacity of the pump device 91 are determined based upon the
amount of heat rejection from the power electronics circuit 19 through the
thermal interface device 94. The fluid/air radiator device 95 is sized such that
the heat generation of the power electronics circuit 19 operating at a low

electrical efficiency point is less than system heat rejection through the
fluid/air radiator device 95 at a maximum ambient temperature, e.g., 35-40°C.
[0016J The control module 4 comprises a distributed control module
architecture which provides coordinated system control of the powertrain
system described herein, and is a subset of an overall vehicle control
architecture. The control module 4 synthesizes pertinent information and
inputs, and executes algorithms to control various actuators to achieve control
targets, including such parameters as fuel economy, emissions, performance,
driveability, and protection of hardwaie, including batteries contained within
the ESD 74 and the first and second electric machines 56 and 72. The
distributed architecture preferably includes an engine control module,
transmission control module, battery pack control module, the power
electronics circuit 19, and a hybrid control module, which provides
supervisory control and coordination ofthe aforementioned control modules.
A user interface, not shown, is operatively connected to a plurality of devices
through which a vehicle operator typically controls or directs operation ofthe
powertrain including the transmission 10. Such operator driven control
signals may include an operator torque request and operator brake. Exemplary
input devices to the user interface include an accelerator pedal, a brake pedal,
a transmission gear selector, and a vehicle speed cruise control, all of which
are not shown. Each of the aforementioned control modules communicates
with other control modules, sensors, and actuators via a local area network
which allows for structured communication of control parameters and
commands between the various control modules.

[0017] Each of the control modules is preferably a general-purpose digital
computer generally comprising a microprocessor or central processing unit,
storage mediums comprising read only memory (ROM), random access
memory (RAM), electrically programmable read only memory (EPROM),
high speed clock, analog to digital (A/D) and digital to analog (D/A) circuitry,
and input/output circuitry and devices (I/O) and appropriate signal
conditioning and buffer circuitry. Each control module has a set of control
algorithms, comprising resident program instructions and calibrations stored in
ROM and executed to provide the respective functions of each computer.
Information transfer between the various computers is preferably
accomplished using a local area network communications bus. Algorithms for
control and state estimation in each of the control modules are typically
executed during preset loop cycles such that each algorithm is executed at
least once each loop cycle. Algorithms stored in the non-volatile memory
devices are executed by one of the central processing units and are operable to
monitor inputs from the sensing devices and execute control and diagnostic
routines to control operation of the respective device, using preset calibrations.
Loop cycles are typically executed at regular intervals, for example each
3.125, 6.25, 12.5, 25 and 100 milliseconds during ongoing engine and vehicle
operation. Alternatively, algorithms may be executed in response to
occurrence of an event.
[0018J A computer program is executed in the control module 4 to monitor
the temperature sensing devices 97 and 97', ambient temperature, and electric
power flow through one or more electric power components or devices. The
electric power devices comprise one of the power electronics circuit 19

(having temperature TIGBT_N for N temperature sensors), the motor stator of
one of the electric machines 56 and 72, and the ESD 74. A temperature
gradient across the electric power component is determined based upon input
from the monitored temperature sensing devices. A flow rate through the heat
transfer circuit 96 is estimated based upon the temperature gradient, the
ambient temperature, and the electric power flow. The estimated flow rate
through the heat transfer circuit 96 is compared to a threshold flow rate.
Embodiments of this are now described in detail with reference to Figs. 2 and
3 and with continued reference to Fig. 1.
[0019] Fig. 2 depicts a first embodiment, comprising control scheme 200,
executable as program code in the control module 4 preferably during one of
the loop cycles. Temperature(s) of one of the electric power devices is
monitored. In the present embodiment of Fig. 2, the electric power device
monitored is the power electronics circuit 19 which is preferably monitored in
a plurality of locations using temperature sensors 97 and 97'. The motor stator
of one of the electric machines 56 and 72, and the ESD 74 may be similarly
monitored. A device temperature (TDEv) is determined to be the maximum of
the plurality of monitored temperatures, or, alternatively, some calculated
average of the plurality of monitored temperature (Step 202).
[0020] The temperature of the device (TDEV) is compared to a predetermined
upper threshold temperature (TJHD) (Step 204). When the temperature of the
device is less than the predetermined upper threshold temperature, inputs from
the coolant circuit are monitored (Step 206), including electric power to the
pump 91 (PPUMP)5 typically the commanded PWM duty cycle, the ambient
temperature (TAMB) and the electrical load (LOAD). A temperature gradient

across the electric power device is also determined (ATDEV), comprising a
temperature difference between a maximum output from one of the
temperature sensors 97 or 97' on the device and a minimum output from one
of the temperature sensors 97 or 97' on the device, at a given point in time. A
first coolant flow rate is estimated, comprising a precalibrated coolant flow
rate determined based upon the temperature gradient across the device,
depicted as CFREST. A calibration array for the first precalibrated coolant flow
rate CFREST is preferably generated during testing of the system described, and
stored as an array in one of the memory devices of the control module 4. A
second, threshold coolant flow rate is determined, referred to as CFRTHR, arid
comprises a precalibrated flow which is determined based upon the electric
power to the pump 91 (PPUMP), the ambient temperature (TAMB), and the
electrical load (LOAD) (step 207). The first and second flow rates CFREST
and CFRTHR, respectively, are compared (Step 208). When the first and
second flow rates, CFREST and CFRTHR, are substantially the same, with
allowance for measurement errors and other sources of variation, operation of
the system continues (Step 210). When the first and second flow rates,
CFREST and CFRTHR, vary by an amount greater than allowable measurement
error (Step 208), or the temperature of the electric power device TDEV is less
than the predetermined upper threshold temperature TTHD (from Step 204), a
fault counter is incremented (Step 212). A fault code is set when there are X
faults out of Y observations, i.e., executions of the algorithm in the loop cycle
(Step 216). Depending upon the conditions and requirements, the operator of
the vehicle is notified of the presence of a fault in the heat transfer circuit 96,
and the control module 4 executes a mitigating action to prevent further harm

or damage to the hardware. The mitigating action may include adjusting the
PWM control signal to the coolant pump 91 and limiting power output from
the electric machines 56 and 72.
[0021] Fig. 3 depicts a second embodiment, comprising control scheme 300
executable as program code in the control module 4 during one of the loop
cycles. Temperatures are monitored in the electric power component being
cooled, which comprises the power electronics circuit 19 in this embodiment.
The power electronics circuit 19 is monitored in N locations to determine
temperatures thereof, via temperature sensors 97, 97' located at or near the
IGBTs of the power electronics circuit 19. Load (LOAD) and ambient
temperature (TAMB) are monitored, with load consisting of the power
conducted through the power electronics circuit, typically measured as current
(I) (Step 302). A temperature gradient across the electric power device (+/-
∆TDEV) is calculated, including both a magnitude and a direction of the
gradient (Step 304). The temperature gradient across the electric power device
is normalized (+/- ∆TDEV(Load, TAMB)), based upon the load and the ambient
temperature (Step 306). The normalization removes influences in the
temperature gradient that are based upon system load and ambient
temperature. An estimate of coolant flow rate (CFREST) is determined based
upon the normalized temperature gradient (Step 308). The estimated coolant
flow rate is preferably determined based upon two predetermined calibrations.
The predetermined calibrations comprise a first calibration when the
temperature gradient (+∆TDEV) across the power electronics circuit is positive,
and a second calibration when the temperature gradient (-∆TDEV) across the
power electronics circuit is negative. Each of the predetermined calibrations

comprises an array of flow rates (CFREST) corresponding to normalized
temperature gradient (+/- ∆TDEV(Load, TVMB) determined during system
development and testing. The estimated flow rate, CFREST, is compared to a
normalized threshold flow rate, CFRTHR.NORMAL (Step 310). The normalized
threshold flow rate, CFRTHR_NORMAL, preferably comprises a scalar value
determined during calibration based upon the PWM control signal to the
coolant pump 91. When the estimated flow rate, CFREST, exceeds the
normalized threshold flow rate, CFRTHR NORMAL, the control scheme 300
determines the heat transfer circuit 96 is operating as intended. When the
estimated flow rate, CFREST, does not exceed the normalized threshold flow
rate, CFRTHR_NORMAL, the control scheme 300 determines the heat transfer
circuit 96 is not operating as intended. A fault counter is incremented, and
when X faults occur in Y observations, or loops (Step 312), a fault code is set
(Step 314). Depending upon the conditions and requirements, the operator of
the vehicle is notified of the presence of the fault, and the control module 4
executes mitigating action to prevent further harm or damage to the hardware.
The mitigating action may include adjusting the PWM control signal to the
coolant pump 91 and limiting power output from the electric machines 56 and
72. In operation, the control system monitors operation of the heat transfer
circuit 96 to identify faults therein and mitigate damage to system
components.
[0022] The system set forth hereinabove described a heat transfer circuit 96
related to the power electronics circuit 19; however, one skilled in the art will
readily apply the concepts of the disclosure to monitoring one of the electric
machines 56 and 72, or the high-voltage ESD 74.

[0023] The disclosure has described certain preferred embodiments and
modifications thereto. Further modifications and alterations may occur to
others upon reading and understanding the specification. Therefore, it is
intended that the disclosure not be limited to the particular embodiment(s)
disclosed as the best mode contemplated for carrying out this disclosure, but
that the disclosure will include all embodiments falling within the scope of the
appended claims.

CLAIMS
1. Method for thermal management of an electric power device, the method
comprising:
monitoring temperature of the electric power device and an ambient
temperature;
determining an electric power flow through the electric power device;
determining a temperature gradient across the electric power device
based upon the monitored temperature of the electric power device;
and,
estimating a flow rate through the heat transfer circuit and comparing the
flow rate to a threshold flow rate based upon the temperature
gradient, the ambient temperature, and the electric power flow.
2. The method of claim 1, further comprising estimating the flow rate based
upon the temperature gradient across the electric power device.
3. The method of claim 2, wherein the threshold flow rate through the heat
transfer circuit is determined based upon the electric power flow through
the electric power device.
4. The method of claim 1, further comprising identifying a fault in the heat
transfer circuit when the estimated flow rate through the heat transfer
circuit is not substantially the same as the threshold flow rate.

5. The method of claim 4, further comprising identifying the fault in the
heat transfer circuit when the estimated flow rate through the heat
transfer circuit is not substantially the same as the threshold flow rate in
X out of Y observations.
6. The method of claim 1, wherein estimating the flow rate through the heat
transfer circuit comprises:
normalizing the temperature gradient across the electric power device
based upon the ambient temperature and the electric power flow;
and
determining a flow rate from a precalibrated array based upon the
normalized temperature gradient.
7. The method of claim 6, wherein the temperature gradient comprises a
magnitude and a direction of the temperature gradient determined based
upon the monitored temperature of the electric power device.
8. The method of claim 7, further comprising identifying a fault in the heat
transfer circuit when the estimated flow rate through the heat transfer
circuit is less than the threshold flow rate.
9. The method of claim 8, further comprising identifying the fault in the
heat transfer circuit when the estimated flow rate through the heat
transfer circuit is less than the threshold flow rate X out of Y
observations.

10. The method of claim 1, wherein the electric power device comprises a
power electronics circuit operative to control the electric power flow.
11. The method of claim 10, wherein the power electronics circuit further
comprises a thermal interface device thermally connected to the electric
power device and fluidly sealed therefrom.
12. The method of claim 11, wherein the thermal interface device comprises
a housing comprising a heat transfer element incorporated into the heat
transfer circuit.
13. Article of manufacture, comprising a storage medium having a machine-
executable program encoded therein to monitor a closed fluidic heat
transfer circuit for an electric power device of an electro-mechanical
transmission system, the program comprising:
code to monitor temperature of the electric power device and an ambient
temperature;
code to determine an electric power flow through the electro-mechanical
transmission system;
code to determine a temperature gradient of the electric power device
based upon the monitored temperature of the electric power device;
and
code to estimate and compare a flow rate through the heat transfer circuit
to a threshold flow rate based upon the temperature gradient, the

ambient temperature, and the electric power flow through the
electro-mechanical transmission system.
14. The article of claim 13, further comprising:
code to estimate the flow rate based upon the temperature gradient of the
electric power device; and
code to determine the threshold tlow rate through the heat transfer circuit
based upon the electric power flow through the electric power
device.
15. The article of claim 14, wherein the code to estimate the flow rate
through the heat transfer circuit further comprises:
code to normalize the temperature gradient across the electric power
device based upon the ambient temperature and the electric power
flow; and
code to determine a flow rate from a precalibrated array based upon the
normalized temperature gradient.
16. The article of claim 15, further comprising code to identify a fault in the
heat transfer circuit when the estimated flow rate through the heat
transfer circuit is not substantially the same as the threshold flow rate.
17. The article of claim 13, wherein the electric power device comprises an
electric machine of the electro-mechanical transmission.

18. Electro-mechanical transmission system, comprising:
an electro-mechanical transmission mechanically-operatively coupled to
an internal combustion engine and an electric machine to transmit
mechanical power flow to an output shaft;
an electric power system comprising an energy storage device
electrically-operatively coupled to the electric machine via a power
electronics circuit, said electric power system including a thermal
interface device;
a plurality of temperature sensors operative to monitor temperature of an
electric power device and ambient temperature;
a heat transfer circuit, fluidly connected to the thermal interface device
and operative to manage heat transfer therewith; and
a control module, signally connected to the temperature sensors and
having a machine-executable program encoded therein, the
program comprising:
code to monitor temperature of the electric power device and an
ambient temperature;
code to determine an electric power flow through the electro-
mechanical transmission system;
code to determine a temperature gradient of the electric power
device based upon the monitored temperature of the electric
power device;
code to estimate and compare a flow rate through the heat transfer
circuit to a threshold flow rate based upon the temperature

gradient, the ambient temperature, and the electric power
flow through the electro-mechanical transmission system; and
code to identify a fault in the heat transfer circuit when the
estimated flow rate through the heat transfer circuit is not
substantially the same as the threshold flow rate.
19. The electro-mechanical transmission system of claim 18, wherein the
program further comprises:
code to estimate the flow rate based upon the temperature gradient of the
electric power device; and
code to determine the threshold flow rate through the heat transfer circuit
based upon the electric power flow through the electric power
device.
20. The electro-mechanical transmission system of claim 18, wherein the
heat transfer circuit comprises a fluidly closed circuit including the
thermal interface device, a pump, and a heat transfer device.

Temperature of an electric power device of a hybrid transmission is
managed based upon device temperatures and power flow, ambient
temperature, and a cooling circuit flow rate.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=0JFDCyQjDfmoPn4zYdkVkQ==&loc=wDBSZCsAt7zoiVrqcFJsRw==

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Patent Number

272686

Indian Patent Application Number

154/KOL/2009

PG Journal Number

17/2016

Publication Date

22-Apr-2016

Grant Date

19-Apr-2016

Date of Filing

28-Jan-2009

Name of Patentee

GM GLOBAL TECHNOLOGY OPERATIONS, INC.

Applicant Address

300 GM RENAISSANCE CENTER DETROIT, MICHIGAN

Inventors:

#	Inventor's Name	Inventor's Address
1	ANDREW M. ZETTEL	1839 MICHELLE COURT ANN ARBOR, MICHIGAN 48105
2	PETER E. WU	5230 RED FOX DRIVE BRIGHTO, MICHIGAN 48114
3	RAYN D MARTINI	412 E. KENILWORTH AVE. ROYAL OAK, MICHIGAN 48067
4	WEI D. WANG	1526 CHARLEVOIS DR. TROY, MICHIGAN 48085
5	STEPHEN T. WEST	11705 NORTH SHELBY 700 W. NEW PALESTINE, INDIANA 46163
6	CHARLES J VAN HORN	47218 MANHATTAN CIR. NOVI, MICHIGAN 48374

PCT International Classification Number

F01L1/34

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA