FORM 2
THE PATENT ACT, 1970
(39 of l970)
&
THE PATENTES RULES, 2005
COMPLETE SPECIFICATION
(See section 10, rule 13)
V. TITLE OF THE INVENTION
"Cooling System for Hybrid Electric Vehicles"
2. APPLICANT(S)
a) Name ; MAHINDRA & MAHINDRA LIMITED
b) Nationality : Indian Company registered under the provisions
of the Companies Act, 1956
c) Address : R&D Center, Automotive Sector,
89, M.I.D.C., Satpur, Nashik - 422 007 Maharashtra State, India
3. PREAMBLE OF THE DESCRIPTION
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

Cooling System for Hybrid Electric Vehicles
Field of the invention
The present invention relates in general, to a field of power electronics in hybrid electric vehicles and more particularly, to a cooling system for power electronics
module in hybrid electric vehicles.
Background of the invention
The rapid decrease in available fossil fuel levels along with the extensive time required for their formation has brought about a major change in the human mentality towards automobile technology. Automotive research has branched into conventionally powered vehicles and the relatively novel electric vehicles. The immense reduction in emission levels is another major factor for increasing the preference of electric vehicles over the petrol/diesel vehicles. However, the . electric vehicles have limited range, limited power capabilities and need substantial time to recharge their batteries. These drawbacks can be addressed by combining an Internal Combustion Engine (ICE) propulsion system and an electric propulsion system into one vehicle, a Hybrid Electric Vehicle (HEV). The presence of the electric power train is intended to achieve either better fuel economy or better performance or both.
The major components in an HEV which require cooling, in order to maintain an optimum operating range to achieve longevity and performance, are engine block, cylinder head, electric motor, exhaust gas re-circulator, high voltage battery and power electronics module. In the existing cooling systems, either all the components are cooled using one single system or a separate system is used to cool all the electric components, i.e. electric motor, HV battery and power electronics module.

Cooling Systems are required to maintain each individual component within a desired temperature operation range. Maintaining a component within its defined operational range ascertains optimum performance and life of the component. The power electronics (PE) contains an inverter and an AC/DC converter. It is of paramount importance that both these components are maintained within the desired temperature range so that the performance is not de-rated. As the power electronics operates at significantly lower temperature compared to the engine cooling circuit, it is proposed to have a dedicated low temperature cooling architecture to maintain the temperature of the system below a threshold temperature.
Efforts are being made for cooling of power electronics in Hybrid Electric Vehicles. For example, US patent 6450275 Bl discloses the concept of coolant in a single closed circuit which is responsible for the cooling of all components, in the ICE system as well as the electric propulsion system of which power electronics is one component. Moreover this idea suggests that the fan speed be regulated by a controller monitoring individual component temperatures and not the coolant temperature.
Another US patent 8276694 B2 discloses the cooling system for the transmission which is used for temporary cooling of power electronics whenever required, especially during peak loads. The opposite is also true, meaning the power electronics cooling system can support with temporary transmission cooling when required. This is achieved by shaping the power electronics unit as a plate, where the biggest cross sectional area is extended to enter one side of the transmission housing.
Reference may be made to power electronics coolant loop design that uses a high flow 12-volt electric pump to create and control the coolant flow which passes through (in order); the plug-in battery charger assembly, the radiator, the power inverter module (PIM), and then back to the pump. Also, the power

electronics cooling system radiator is the upper half section of a dual radiator assembly that is common with the high voltage battery cooling system. Moreover, the same coolant loop is responsible for cooling the Plug-in Charger Assembly whenever a PHEV is in "plug-in" charging.
Accordingly, there is a need of a cooling system in hybrid electric vehicles for providing a dedicated low temperature cooling which overcomes the drawbacks
of the prior art.
Object of the invention
An object of the present invention is to use a dedicated low temperature cooling system for a power electronics module in hybrid electric vehicles (HEV).
Summary of the invention
Accordingly, the present invention provides a cooling system for hybrid electric vehicles. The cooling system is a closed coolant loop system. The cooling system comprises a power electronics module, a pump, a first radiator, a second radiator, a sensor and a controller. The power electronics module is capable of absorbing dissipated heat from each component of the hybrid electric vehicles. The pump is operably connected to the power electronics module and capable of circulating a coolant through each component of the hybrid electric vehicles. The first radiator is operably connected to the pump and capable of venting heat received from the power electronics module. The sensor is mounted on an outlet of the first radiator and measures temperature of the coolant. The second radiator is used for cooling of a high temperature cooling loop. The radiator fan is positioned adjacent to the second radiator. The radiator fan is capable of creating an air flow for dissipation to an outside environment.
The controller is operably connected to the power electronics module. The

controller regulates speed of the radiator fan and the pump. The controller monitors the component temperature and the coolant temperature. The controller operates the radiator fan via an engine management system (EMS).The controller comprises a logic of a low temperature cooling architecture. The logic is an open loop control algorithm having the coolant circuit temperature and the component temperature as inputs for the system. The logic comprises a Trigger 1, a Trigger 2 and a plurality of trigger definitions. When the Trigger 1 is set then the pump control signal is set to follow the component temperature based control and the request to set the radiator fan signal to high is turned OFF. When the Trigger 1 is not set then the pump control signal is set to follow the coolant temperature based control.
The power electronics module sends an actual component temperature to the controller over a Controller Area Network (CAN). The controller sends the fan control request to the EMS over the CAN. The EMS after receiving a radiator fan request from the controller sets a fan speed signal to any one of a low speed operation and a high speed operation then the logic is run within the controller to determine the pump speed in a Pulse Width Modulation for controlling the pump and the radiator fan request, the pump on receiving a Pulse Width Modulation signal from the controller sets a required coolant flow rate and sends a feedback signal to the controller thereby ensuring that the required temperature is maintained.
Brief description of the drawings
Figure 1 illustrates a schematic representation of a cooling system for hybrid electric vehicles, in accordance with the present invention;
Figure 2 illustrates a schematic representation of a logic of a low temperature cooling architecture of the present invention; and

Figure 3 illustrates a schematic representation of a trigger definition of the logic for the low temperature cooling architecture of figure 2.
Detailed description of the embodiments
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.
The present invention provides a cooling system for hybrid electric vehicles (hereinafter "HEV"). The system for a low temperature component of the HEV is required to ensure that components are being operated within the defined temperature limit to have better operating efficiency and also to avoid thermal run-away and hence failure of the components. The components requiring cooling, for the HEV, are both related to a conventional power train (ICE) and additional electric drive component. The electric drive system includes a generator motor (not shown), traction motor (not shown), a DC-DC converter (not shown) and an inverter (not shown). The present invention segregates the cooling system based on the thermal operating boundaries and focus on the low temperature cooling circuit to ensure operating efficiency is maintained.
The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description.
Referring to figure 1, a cooling system (200) for the HEV in accordance with the present invention is shown. Specifically, the cooling system (200) is designed to provide a dedicated low temperature cooling circuit/architecture and is a closed coolant loop system.

The cooling system (200) comprises a heat generation source/power electronics module (10), a first radiator (20), a second radiator (30), a radiator fan (40), a pump (50), a sensor (60) and a controller (100).
The power electronics module (10) combines a DC-DC converter (not shown) and an inverter (not shown). The power electronics module (10) absorbs dissipated heat from each component of the HEV. The power electronics module (10) sends an actual component temperature to the controller (100) over a Controller Area Network (herein after CAN).
The pump (50) is operably connected to the power electronics module (10). The pump (50) is used to circulate a coolant through the each component of the HEV. The first radiator (20) is operably connected to the pump (50) and vents the heat received from the power electronics module (10). The second radiator (30) is used as a heat exchanger for a high temperature cooling circuit (not shown). Both the radiators (20, 30) share the same radiator fan (40) which is in close proximity of the second radiator (30).
The sensor (60) is a coolant temperature sensor. The sensor (60) is mounted on an outlet (not numbered) of the first radiator (20). The sensor (60) measures coolant temperature and sends to the controller (90). The radiator fan (40) is positioned adjacent to the second radiator (30) and used for ICE cooling. The radiator fan (40) is a shared fan for both the low temperature cooling circuit and a high temperature cooling circuit. The radiator fan (40) is used to create an air flow for dissipation of the heat to an outside environment.
The controller (100) is operably connected to the power electronics module (10). The controller (100) includes a logic (90) of the low temperature cooling architecture. The controller (100) operates the radiator fan (40) via an engine management system (EMS) (not shown). The controller (90) monitors the component temperature and the coolant temperature thereby ensures efficient operation of the cooling system (200) and based on the system temperature

regulates the speed of the pump (50) and the radiator fan (40).
Referring to figure 2, a flowchart of the logic (90) of the low temperature cooling architecture of the controller is shown. The logic includes a Trigger 1 (not numbered) and a Trigger 2 (not numbered). In an embodiment, the logic (90) is an open loop control algorithm having coolant circuit temperature and component temperature as inputs for the cooling system (200).
The logic (90) starts at step (72). The cooling system (200) determines whether the Trigger 1 or the Trigger 2 of the logic (90) of the controller (100) is to be set. At step (74), if the Trigger 2 is set, the pump (50) runs at a predefined speed and the pump control signal is set to a predefined value (step 76). At the same time, a request to set a radiator fan signal/speed to high is sent via the CAN to the EMS.
If the Trigger 2 is not set then at step (78), the cooling system (200) determines whether the Trigger 1 is set (step 80). If Trigger 1 is set, then at step (82), the pump control signal is set to follow the component temperature based control and the request to set the radiator fan (40) signal to high is turned OFF. If the Trigger 1 is not set (step 84), then at step (86) the pump control signal is set to follow the coolant temperature based control.
Referring now to figure 3, a plurality of trigger definitions (not numbered) for the low temperature cooling architecture of the present invention is shown. The Trigger 1 is given if the sensor (60) fails or if the component temperature exceeds the predefined value. The Trigger 2 is given if a Pulse Width Modulation (herein after PWM) pump control exceeds the predefined value for a predefined delay time, or if the sensor (60) fails and the component temperature exceeds the predefined value, or if the component de-rating flag is set to high.
Referring to figures 2 and 3, in operation, the open loop control algorithm has

the coolant circuit temperature and the component temperature as inputs for the cooling system (200). The PWM pump control signal varies based on the coolant temperature measured by the sensor (60). If the sensor (60) fails or if the coolant temperature exceeds a preset value, the PWM signal varies with the component temperature. If the component de-rating status is set, the pump (50) runs at a predefined speed. The algorithm also sends a request to the EMS via the CAN to increase the radiator fan (40) speed if the PWM pump control signal is above a threshold for more than a predefined time, or if the sensor (60) fails and the component temperature exceeds a predefined value, or if the component de-rating status is set to high.
The logic (90) also controls the radiator fan (40) speed. The radiator fan (40) is normally operated in a low speed that is a default speed. The logic (90) sets the radiator fan (40) speed to high based on the following conditions:
• The PWM pump control signal is above the threshold for more than a predefined time.
• Component temperature based de-rating status.
• In case of the sensor (60) failure and the component temperature is above the predefined value.
The radiator fan (40) request signal is sent to the controller (100) for varying the radiator fan (40) speed for maintaining the temperature of the cooling system (200) below a specified temperature limit.
In accordance with the present invention, the low temperature control
architecture is achieved using the following signals:
Coolant circuit temperature: This signal refers to the temperature in a low
temperature cooling circuit. The sensor (60) is used to measure the coolant
circuit temperature. This part of the control architecture is an open loop control
where the PWM pump control signal request varies based on the circuit coolant
temperature.

Component temperature: This signal refers to a component internal temperature that is available from the component. If the sensor (60) fails or component temperature exceeds a set-point temperature limit then the control output switch to the component temperature based control algorithm. Component temperature is a redundant part of the controller (100) for increasing the cooling system (200) robustness in case of sensor (60) failure.
If the component temperature de-rating status is set then the control output switch to a fixed control (control signal set to the pre-defined value). The output PWM pump control signal request is a filtered value for providing smoothing ramping to avoid possible NVH issues.
Referring again to figures 1-3. in an operation, the cooling system (200) maintains the component temperature by moving the coolant through the closed cooling loop. As coolant pass through each component of the system, the power electronics module (10) absorbs the dissipated heat and traverse the absorbed heat through the pump (50) and then venting the heat out of the cooling system (200) from the first radiator (20) with the help of the radiator fan (40). The flow of the pump (50) and the radiator fan (40) speed is controlled based on temperature of the cooling system (200).
The controller (100) sends the fan control request to the EMS over the CAN. The request is any one from a high speed request ON and a high speed request OFF. The EMS after receiving the radiator fan (40) request from the controller (100) sets the radiator fan (40) speed signal to any one of a low speed operation and a high speed operation.
Next, the cooling system (200) runs the logic (90) within the controller (100) to determine the pump (50) speed in Pulse Width Modulation (hereafter "Pump PWM signal") for controlling the pump (50) and the radiator fan (40) request. The pump (50) on receiving the Pump PWM signal from the controller (100) set

the required coolant flow rate in the cooling system (200) to ensure that cooling system (200) is maintained within defined operating temperature boundaries. The pump (50) sends a feedback signal to the controller (100) to ensure that the cooling system (200) temperature is maintained within temperature limits in case of any system error related to the pump (50).
Advantages of the invention
1. The present invention provides an independent, low temperature, dedicated cooling system (200) for power electronics.
2. Two redundancies incorporated for thermal control that makes the cooling system (200) more robust and fault-proof.
3. In the present invention, the first radiator (20) is used for power electronics module (10) and the radiator fan (40) speed high request is sent by the power electronics module (10) via CAN to the EMS.
4. The present invention also uses a component de-rating based concept.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light , of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.

We Claim:
1. A cooling system for hybrid electric vehicles, the cooling system comprising:
a power electronics module being capable of absorbing dissipated heat from each component of the hybrid electric vehicles;
a pump operably connected to the power electronics module, the pump being capable of circulating a coolant through each component of the hybrid electric vehicles;
a first radiator operably connected to the pump, the first radiator being capable of venting heat received from the power electronics module;
a sensor mounted on an outlet of the first radiator, the sensor being capable of measuring temperature of the coolant;
a second radiator used for cooling of a high temperature cooling loop;
a radiator fan positioned adjacent to the second radiator, the radiator fan being capable of creating an air flow for dissipation to an outside environment; and
a controller operably connected to the power electronics module, the controller being capable of regulating speed of the radiator fan and the pump and monitoring the component temperature and the coolant temperature, the controller having a logic of a low temperature cooling architecture, the logic having a Trigger 1. a Trigger 2 and a plurality of trigger definitions,
wherein, an engine management system after receiving a radiator fan request from the controller sets a fan speed signal to any one of a low speed operation and a high speed operation then the logic is run within the controller to determine the pump speed in a Pulse Width Modulation for controlling the pump and the radiator fan request, the pump on receiving a Pulse Width Modulation signal from the controller sets a required coolant flow rate and sends a feedback signal to the controller thereby ensuring that the required temperature is maintained.

2. The cooling system as claimed in claim 1 is a closed coolant loop system.
3. The cooling system as claimed in claim 1, wherein the power electronics module sends an actual component temperature to the controller over a Controller Area Network (CAN).
4. The cooling system as claimed in claim 1, wherein the controller sends the fan control request to the engine management system over the Controller Area Network (CAN).
5. The cooling system as claimed in claim 1, wherein the controller operates the radiator fan via the engine management system.
6. The cooling system as claimed in claim 1, wherein the logic is an open loop control algorithm having the coolant circuit temperature and the component temperature as inputs for the system.
7. The cooling system as claimed in claim 1, wherein when the Trigger 1 is set then the pump control signal is set to follow the component temperature based control and the request to set the radiator fan signal to high is turned OFF.
8. The cooling system as claimed in claim 1, wherein when the Trigger 1 is not set then the pump control signal is set to follow the coolant temperature based control.