WO2014074430A1

WO2014074430A1 - Thermal system cold start layout circuit with egr

Info

Publication number: WO2014074430A1
Application number: PCT/US2013/068215
Authority: WO
Inventors: John Shutty; Michael Becker; Wolfgang Wenzel
Original assignee: BorgWarner Inc
Current assignee: BorgWarner Inc
Priority date: 2012-11-07
Filing date: 2013-11-04
Publication date: 2014-05-15
Anticipated expiration: 2015-05-07

Abstract

A thermal system layout circuit adapted for use in a vehicle engine cold start situation. A valve is positioned to prevent flow from the cooling pump to the engine or radiator. An exhaust heat exchanger and/or an EGR heat exchanger is used to warm up one or more secondary devices, such as the transmission oil, heater core for the passenger cabin heater system and the rear axle oil.

Description

THERMAL SYSTEM COLD START LAYOUT CIRCUIT WITH EGR

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Patent Application No. 61/723,768 filed on November 7, 2012, which is related to U.S. Patent Application Serial No. 61/691,180, entitled "Thermal System Cold Start Layout Circuit," filed on August 20, 2012, now PCT/US2013/054079 filed on August 8, 2013.

TECHNICAL FIELD

The present invention relates to the efficiency of internal combustion engines, and more particularly to unique thermal system layout circuits and systems to improve the speed and efficiency of vehicles, particularly in cold start situations.

BACKGROUND OF THE INVENTION

One of the ways to improve the efficiency of internal combustion engines is to accelerate the warm-up during cold starts. A method for performing this acceleration is to initially prevent the coolant pump from operating until key areas of the engine and oil reach a certain temperature. This isolates the large quantity of coolant in the radiator and the engine which are at the cold start temperature. Significant time and energy are typically needed to bring these large quantities of coolant up to a desired temperature.

Another way to improve the efficiency of internal combustion engines via accelerated initial heating of the engines and other vehicle components is to circulate coolant through exhaust-to-coolant heat exchangers. This approach, however, requires operating the coolant pump at medium to high speeds. It may also require heating a large volume of coolant including the quantity in the radiator and/or in the engine.

These two approaches to efficiency improvement lead to a conflict relative to the operation of the coolant pump.

It is an object of the present invention to provide layout circuits and systems which improve the efficiency of internal combustion engines particularly during initial warm-up of the engines and vehicle components from a cold start. It is another object to provide systems for simultaneously heating the engine and other components, such as the passenger compartments, rear axle fluids, transmission fluids and the like from a cold start, and doing so in a faster and more efficient manner.

SUMMARY OF THE INVENTION

The present invention meets the above objectives by providing layout circuit systems and methods which provide faster and simultaneous warm-ups from cold starts of both the internal combustion engines and the other vehicle components and systems. The invention, in particular, improves the speed and efficiency of the engines during cold starts, but also can be utilized to maintain the temperatures of vehicle fluids and components within acceptable temperature ranges.

In preferred embodiments of the invention, thermal system layout circuits are provided which have unique routing layouts for the engine coolant system with unique valving systems and programmed control systems. In one embodiment, valves in the coolant routing layout allow the coolant pump to run coolant to exhaust heat exchangers and/or exhaust gas recirculation heat exchangers and then to various vehicle components, such as the passenger compartment heater core, the transmission fluid, and the rear axle fluids, while coolant flow is prevented to the engine and radiator. The volume of coolant fluids that need to be warmed by the engine and heat exchangers are significantly reduced.

The unique layout circuits provide smaller volumes of coolant to be warmed and routed to one or more of the vehicle components and heating systems. This allows the vehicle oil and other fluids to be initially heated in a faster manner which in turn allows the vehicles to be more efficient.

In a further embodiment, a multifunction valve can be utilized in the layout circuit as the vehicle thermostat component and it can be internally programmed to prevent operation of the vehicle engine cooling system through the radiator, or allow partial or full passage of coolant to the radiator, as necessary or programmed to do so. It can also prevent flow to the engine or allow partial or full flow to the engine. The multifunction valve can be operated by a programmed electronic system through data supplied by various sensors.

Additional objects, features, and benefits of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiments when taken in conjunction with the attached drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 schematically depicts a preferred embodiment of the present invention. FIGURE 2 is a graph depicting the use of a preferred embodiment of the invention. FIGURE 3 schematically depicts another preferred embodiment of the present invention.

FIGURE 4 depicts another embodiment of the invention which includes a multifunction valve.

FIGURES 5 A, 5B and 5C schematically illustrate multifunction valves which can be used with the present invention.

FIGURE 6 schematically depicts methods of use of preferred embodiments of the invention.

FIGURE 7 schematically depicts another preferred embodiment of the present invention.

FIGURE 8 schematically depicts another preferred embodiment of the present invention.

FIGURE 9 schematically depicts several other alternate embodiments of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention is described herein with respect to certain embodiments for use with vehicles, such as automobiles and trucks. It is to be understood, however, that the embodiments described herein are only representative embodiments and that other embodiments and variations thereof will be apparent from the following descriptions to persons of ordinary skill in the art. These additional embodiments and variations are to be included within the scope of the invention if they are set forth within the scope, definition and meaning of the claims.

In addition, although the invention is described herein with respect to its use in vehicles, it is to be understood that the invention can be utilized in other systems and environments, such as, for example, industrial engines and industrial systems. These other uses are also to be included within the scope and meaning of the present invention and defined by any claims which are not limited to vehicles. In the drawings, the components of the various layouts, systems and methods, which are the same from Figure to Figure are referred to by the same reference numbers. Thus, a description or discussion of the structure or a portion of a particular component or system will be the same from layout to layout unless otherwise indicated.

One preferred embodiment of the layout circuit and process invention are shown in

Figure 1 and referred to generally by the reference numeral 10. The layout circuit includes a vehicle internal combustion engine 12, a cooling fan 14, a radiator 16, a coolant pump 18, a thermostat 20 and a mixing valve 22 in a fluid coolant layout circuit. The vehicle can be any of the known vehicles today, such as an automobile or truck, which use internal combustion engines. The engine also can be any of the conventional internal combustion engines in use today, such as spark ignited, diesel, natural gas, electronics, or other.

The system also includes an electronic control unit (ECU) which is in use in one form or another in most vehicles today, such as ECU 24 shown in Figure 1. The ECU accumulates data from a number of sensors or sources in order to operate and regulate the various systems of the engine and vehicle. The sensors can be used to measure temperatures of fluids or components, pressures, speeds (e.g. RPM), and the like. In the layout circuit shown in Figure 1, only representative temperature sensors 26 and 28 are shown for clarity. Not all of the various sensors in use in vehicles today, or which can be used with the present invention, are included.

A system which is relatively conventional today is included in the dashed box 30 in

Figure 1. At start up, the coolant pump 18 circulates coolant through lines 32 and 34 to the engine 12. After circulating through the engine, the coolant passes through line 36 from the engine to the thermostat 20 and then through line 38 to the radiator 16 and back to the pump through line 40. When the engine is cold, the thermostat may route the coolant from the engine through bypass line 42 and mixing valve 22 back to the pump 18. When the engine and coolant are warmer, the thermostat routes the coolant through line 38 to the radiator where it is recirculated through the engine by the coolant pump.

In one cold-start system and process, the coolant pump is kept in an inoperative condition (by the ECU) and the engine is used to heat up the coolant and oil which have remained in the engine block when the engine coolant pump was turned off. When the temperature of the coolant in the engine reaches a desired temperature, such as by being sensed by temperature sensor 28, the coolant pump is turned on and coolant stored in the radiator and the rest of the coolant system is circulated through the engine. With the engine heating up more quickly, the engine and engine oil are also heated up more quickly which acts to reduce the amount of undesirable exhaust materials to be vented to the atmosphere through the exhaust system of the vehicle. In addition, a faster warm-up of the engine allows the catalytic converter in the vehicle (through which the engine exhaust passes) to also be heated more quickly. This also acts to reduce the amount of undesirable materials to be exhausted into the atmosphere. The faster warm up of the oil allows warmer oil to be circulated more quickly to the engine and vehicle components which utilize the oil. This reduces friction and improves fuel consumption.

As shown in Figure 1, the coolant forced by the coolant pump 18 into line 32 is also forced into line 50 into and through an exhaust-to-coolant heat exchanger 52. A valve 54 can be used to selectively open and close line 50 to the heat exchanger 52. Another valve 56 can be used to selectively create a by-pass of line 50 around the heat exchanger 52. The valve 56 also could be a proportioning type valve which allows full, partial, or no flow to the bypass. In this manner, the change of the flow from the heat exchanger to the bypass could be over a period of time.

Once the coolant in line 50 is heated (warmed-up) by the exhaust-to-coolant heat exchanger 52, it then can be used to heat (warm-up) other components and systems in the vehicle, such as the heat exchanger 58 (heater core) for the passenger cabin heater system, the heat exchanger for the fluid in transmission 60, the heat exchanger for the oil in the rear axle 62 and/or heat exchangers for other vehicle components and systems 64 and 66. (As indicated below in the descriptions relative to Figures 7-9, the "other" heat exchanger 64 can be or can include an exhaust gas recirculation system.) Optional shut-off valves A, B, C and D can be controlled by the ECU to selectively allow the warmed fluid from line 50 to selectively pass through one or more of the heat exchangers 58, 60, 62, 64 and/or 66.

The heat exchangers that are warmed by the heated fluid in line 50 can be positioned in series or in parallel. As shown in Figure 1, heat exchangers 58, 60, 62 and 64 are in series, while heat exchangers 62 and 66 are arranged in parallel. Any combination of series or parallel arrangements can be provided.

The fluids passing through heat exchangers 58, 60, 62, 64 and 66 are directed back to the mixing valve 22 through lines 70, 72, 74, 76 and 78. This can be accomplished in any desired manner; the system shown in Figure 1 sets forth only one manner in which this can be accomplished. The inventive layout circuit embodiment and process shown in Figure 1 also includes a shut-off valve 80 positioned in line 34. The valve 80 is positioned between the pump 18 and the engine 12 and is controlled by the ECU or another control member (not shown) in the vehicle.

In one preferred method of cold-start of an engine using the layout circuit as shown in

Figure 1, the valve 80 is initially closed, valve 54 is open and bypass valve 56 is initially closed. Since there is no flow of coolant circulated through the engine block, the relatively small amount of coolant in the engine heats up more rapidly, along with engine oil. This improves the efficiency of the combustion of fuel in the engine and helps minimize the exhaust of undesirable materials into the atmosphere.

At the same time in the initial cold-start process, in accordance with the invention, the system simultaneously circulates an amount of coolant through the exhaust heat exchanger where it is separately warmed up. The heated fluid is then returned to the pump through one or more of lines 70, 72, 74 and 76, allowing it to warm the engine compartment (on cold days), the transmission fluid, the rear axle fluid and/or other components as desired. The heated fluid can be circulated through whatever component is desired at the time, depending on the temperature of the environment and other conditions, such as the temperature of the initial coolant and other fluids. Valves A, B, C and D can be selectively opened or closed for this purpose.

Once the coolant in the engine reaches a predetermined temperature, the valve 80 is opened allowing the coolant to be pumped and circulated through the engine in a normal manner.

Similarly, once the temperature of the coolant in line 50 downstream of the exhaust heat exchanger 52 reaches a predetermined temperature, the bypass valve 56 is opened allowing coolant to bypass the exhaust heat exchanger 52. This prevents the coolant from becoming too hot.

The valve 56 can be a proportional valve which regulates the amount of fluid passing through it, rather than a simple ON-OFF valve. This allows the amount of coolant passing through the exhaust heat exchanger to be diminished gradually over time until the valve 56 is fully open.

Valve 54 is an optional valve. If provided, it is left opened during cold start situations in order to allow coolant to flow to the exhaust-to-coolant heat exchanger. Once the secondary (auxiliary) devices, such as 58, 60, 62 and 64 are warmed to their normal operations temperatures, the valve 54 can be closed or left opened. If the temperature of any the auxiliary devices get too high, then valve 54, if closed, can be reopened, along with bypass valve 56 and appropriate valves 58, 60, 62 and/or 64, in order to allow coolant to reduce or moderate the temperature of the fluid in the auxiliary device.

If the specifications and characteristics of a particular engine are known, it is possible for the various steps in the Figure 1 process to be time dependent rather than temperature dependent. Thus, rather than opening valves 80 and 56, based on reaching certain fluid or component temperatures, the operation of these valves could be based on time. It is also possible to operate the system with a combination of time and temperature.

Figure 2 depicts a graph 100 showing the warming of the engine and the coolant relative to time. This graph depicts generally the process that transpires by utilizing the layout circuit embodiment set forth in Figure 1. The graph also could be used to conduct the steps in the warm-up process based on time.

As shown in Figure 2, the first portion of time 102 exists where there is no flow to the engine. Valve 80 is closed. This is the starting point of a cold start for the engine. The temperature 104 of the engine heats up rapidly. At point 106, the valve 80 is opened and coolant flow is started through line 32, 34 to the engine. The coolant fluid heats up in the engine until it reaches a maximum flow 110. At point in time 112, the valve 20 starts to divert the flow from the bypass line 42 to the radiator.

The flow of the coolant reaches point 116 where it stays constant for a period of time as the flow of fluid through the bypass line 42 and radiator line 38 stays constant. At time 118, the valve 20 further restricts the flow of coolant until it all flows to the radiator. At point 120, full flow is passing through the radiator.

Meanwhile, the temperature 124 of the engine reaches a maximum constant temperature 126. After this, the engine and coolant are maintained at their normal operating temperatures, or temperature ranges. Under certain extreme conditions, however, the temperature of the engine can increase 128.

A simpler layout circuit is shown in Figure 3 and designed by the reference number 10'. Components which are the same as those shown in Figure 1 and described above have the same reference numbers. Through the routing of the coolant in a similar manner as set forth in Figure 1 and with the use of shut-off valve 80, the pump 18 can be run allowing coolant to flow to the exhaust heat exchanger 52 while coolant flow to the engine is cut-off. Since there is no flow of coolant circulated through the engine block, the volume of fluid that needs to be warmed by the heat exchanger is significantly reduced.

When the vehicle engine is cold-started, the pump 18 flows coolant fluid through lines 32 and 50 where the fluid is heated by the exhaust heat exchanger 52. The fluid is then routed only through the transmission heat exchanger 60 to warm the transmission fluid and the systems of one or more other components 61 before being cycled back to the pump 18 through valve 22. After a certain time, or once the engine (or coolant in it) reaches a certain temperature, the shut-off valve 80 is opened and fluid is allowed to flow through the engine and bypass line 42. When the coolant reaches a higher temperature, the valve 20 allows coolant to flow through line 38 to the radiator. The coolant in the radiator is then circulated through the engine in a normal manner.

With the present invention, rapid coolant warm-up is achieved along with accelerated block and engine oil warm-up, as well as warm-up of selected secondary devices (a/k/a "auxiliary" devices), such as the transmission oil, rear axle oil, passenger cabin heating, etc. By excluding the volumes of cold coolant in the engine block and radiator, the exhaust heat exchangers act on a smaller volume of coolant. This allows faster heating of the devices that are being warmed, while simultaneously allowing the engine to be warmed internally.

In another embodiment, the thermostat valve 20 shown in the systems of Figures 1 and 3 is replaced with a multifunction valve 21 which is operated by changes in the temperature of the coolant flowing into it from engine 12. This embodiment is shown in Figure 4. In this embodiment, another shut-off valve 23 is positioned in line 36 between the engine and the multifunction valve. The valve 23 is operated by the ECU. In an alternate embodiment, the valve 23 can be included in the valve 20.

A schematic drawing of a basic valve 21, which is a three-way valve, is shown in Figure 5 A. Coolant flow through line 36 is passed to the valve 21 where it is directed either to line 42 or to line 38.

The valve 21 can be any type of conventional multifunction valve that will perform the function explained above. Solenoid valves which are controlled electronically can be used. The actuator can be in the form of a plunger or pivoted armature, often against the action of a spring or other biasing member. It can be electrically energized or de-energized and returned to its normal position by the biasing action.

Three-way valves typically have three port connections and two valve seats. One valve seal remains open and the other closed in the de-energized mode. When the solenoid coil is energized, the mode reverses. Rotating actuators with a spool inside a cylinder are common.

A schematic representation of another multifunction valve 90 which can be utilized with the present invention is shown in Figure 5B. Three valves A, B and C are included and each one allows the fluid flow to be varied or throttled from zero flow to maximum flow. The valves are operated by the ECU or separate electronic control system. The fluid flow through valve A can be regulated to supply the desired amount of coolant flow. The "input" into valve A then is directed either to "output 1" or "output 2," or both, as desired by the system. Also, the amount of fluid passing through valves B and C can be regulated as indicated.

Another multifunction valve 150 which can be utilized with the present invention is shown in Figure 5C. The valve has a central housing or mixing chamber 152 and an inlet line A. The valve apportions the coolant flow in line A to flow to either lines B or C, or partially to both lines B or C. The valve can also prevent flow to both lines B and C.

The sequence of operation of the valve 150 from O⁰ rotation (a) to 60° rotation (f), and at various stages in-between, (b), (c), (d) and (e), is shown in Figure 5C. The rotation of the valve members 154 and 156 either clockwise ("CW") or counterclockwise ("CCW") through 10°-60° rotations are depicted.

As indicated above with reference to Figure 1, the "other" heat exchanger 64, can be an exhaust gas recirculation ("EGR") system. The EGR system can be utilized as a secondary exhaust heat exchanger which captures heat from the exhaust gases from the engine and then can be utilized to warm up the engine coolant and/or assist in warming up the other vehicle components or fluids. The EGR system could be used in place of the exhaust heat exchanger 52 and be the principal system for quickly adding heat to the coolant in a cold start situation.

If the EGR system is used as the sole coolant warming system, or only as a secondary source, it is also necessary to position it in the vehicle such that it is always in operation when the engine is operating. EGR systems are used in principal part to recirculate the engine exhaust gases and to assist in reducing the amount of toxic materials that are exhausted into the atmosphere. In the layout circuit, however, it is also preferred to position a bypass line around the EGR system and heat exchanger so that it does not continue to add heat to the coolant where it is no longer desired. (An optional gas side bypass may also be included for this purpose.) Typical engines today have 0-2 EGR systems. Thus, when EGR systems are included in a layout circuit in accordance with the present invention, more than one EGR system could be utilized in the circuit. It is also possible to position the EGR systems at different locations in a layout circuit and still achieve the benefits and advantages of the present invention.

Figure 7 depicts an alternate layout circuit 63 which includes an EGR system in the circuit of Figure 1. The EGR heat exchanger 65 is positioned in the layout circuit in place of the Other" heat exchanger 64 in Figure 1. An optional bypass line 67 is also included which can be utilized when it is not necessary or desirable to use the EGR heat exchanger in the system. A bypass valve 69, which is controlled by the ECU of the vehicle, is used to control the use of the bypass.

Figure 8 depicts another alternate layout circuit 90 which includes an EGR system 92 with a heat exchanger. The EGR system 92 can be used solely or concurrently with the exhaust heat exchanger 52 in order to heat up the engine coolant following a cold start situation. Valve 94, which preferably is a three-way valve, is controlled by the vehicle ECU and is used to direct all or a portion of the coolant in line 50 to line 96. (With the layout circuit 90, the valves 54 and 56 may be unnecessary).

A bypass line 98 controlled by valve 99 is used to bypass the EGR system heat exchanger 92 when desired or when the EGR is not needed to warm up the engine coolant. The bypass line 98 may also be unnecessary since the flow of coolant to the EGR heat exchanger can be prevented by operation of valve 94.

Figure 9 depicts still another alternate layout circuit 130 which includes an EGR system heat exchanger 132. Figure 4 illustrates that the EGR heat exchanger can be positioned at various locations in the cold start layout circuit. For example, the EGR system heat exchanger could be positioned alternatively at 162.

The EGR system heat exchanger 132 is fed by line 134 and has bypass line 136.

Three way valve 138 facilitates flow into or around the EGR heat exchanger. The valve 138 is controlled by the vehicle ECU.

Similarly, the alternate EGR system heat exchanger 162 is fed by line 164 and has bypass line 166. Three way valves 168 and 170 are used, respectively, to direct coolant flow to the EGR system, or to bypass the EGR heat exchanger.

Similarly, the EGR heat exchanger could also be positioned in a location that allows flow when the valve 20 is closed. The operation of the alternate cold start layout circuits shown in Figure 7-9 are basically the same as that described above with respect to the system 10 depicted and described above, with the additional feature of possible inclusion of an EGR heat exchanger.

Another alternate system is also shown in Figure 9. This system includes valve 180 in coolant line 42. (Valve 180 is shown in dashed lines.) Valve 180 could be closed during warm-up of the engine and vehicle from a cold-start, and valve 20 would be a normal thermostat.

FIGURE 6 depicts a cold-start process 200 for a vehicle engine in accordance with a preferred embodiment of the invention. The process 200 begins by the operator starting the engine 202. The temperatures of the engine block, engine coolant, engine oil, and other vehicle engine related components and systems are sensed 204 by appropriate sensors. It is also possible to sense the temperatures of the fluids and other components, such as the transmission fluid, passenger heater core, rear axle oil, etc. The temperature data is sent to the ECU or other electronic control which then decides by an appropriate look-up table or the like, the desired steps to take subsequently.

For example, the operating indicia could be to determine if one or more of the temperatures are below certain values and a cold start process is needed. (If the temperatures are all at or above prespecified values, a cold start process may not be desired and the vehicle engine, coolant and components are allowed to heat up in a normal manner.

In a cold start process in accordance with a preferred embodiment of the invention, a valve, such as valve 80 in Figure 1, is closed 206. This blocks the coolant pumped by the coolant pump from circulating through the engine. This heats up the engine block and engine oil quickly. As indicated above, the valve 80 is opened 208 after a prespecified period of time or after the engine has reached a certain temperature.

Also, in a cold start, the coolant from the pump flows through the exhaust to coolant heat exchanger 206. The engine exhaust system heats up the coolant rapidly.

When the exhaust system gets too hot and could cause the coolant to overheat (i.e. it reaches a prespecified temperature), a bypass valve, such as valve 56 in Figure 1, is opened 208. This allows the fluid to bypass the exhaust heat exchanger and maintain a more even temperature.

The heated coolant then passes into heat exchangers in one or more of the secondary (auxiliary) devices, to allow them also to be warmed-up. As stated above, the secondary devices could be the transmission, the passenger compartment, the rear axle, the EGR system, and the like.

To complete the circulation circuit, the coolant fluid returns to the coolant pump where the cycle is repeated until the appropriate temperatures are reached or the appropriate time transpires.

Also, as discussed above with reference to Figure 7-9, the heat exchanger could be the heat exchanger which is part of the EGR system and it could be used in combination with, or as an alternate to, the exhaust heat exchanger.

When the coolant in the engine is allowed to flow and circulate toward the radiator, it may not be appropriate to allow the heated engine coolant to immediately pass through and get chilled by the large volume of coolant still in the radiator. For this reason, the valve positioned between the engine and the radiator, such as a thermostat valve or multifunction valve, can direct some or all of the heated engine coolant through a bypass line where it is circulated by the coolant pump. This is shown at 210. The coolant could be proportioned between the bypass line and radiator until the temperature of the entire coolant achieves the desired temperature or temperature range.

When the engine, the vehicle fluids and the secondary devices and systems reach their desired temperatures and ranges, the vehicle engine and systems are allowed to run normally 212.

With this process, the engine and secondary device can be all warmed-up more quickly in a cold start situation. This improves the efficiency of the engine in many ways, such as increasing fuel economy and decreasing toxic emissions.

While preferred embodiments of the present invention have been shown and described herein, numerous variations and alternative embodiments will occur to those skilled in the art. Accordingly, it is intended that the invention is not limited to the preferred embodiments described herein but instead limited to the terms of the appended claims.

Claims

What is claimed is:

1. A thermal system layout circuit for a cold start for a vehicle engine comprising:

an internal combustion engine having a cooling fan and a radiator;

a coolant pump to circulate coolant through the engine and radiator;

a first valve member positioned between the coolant pump and the engine and adapted to prevent flow of coolant to the engine;

an exhaust heat exchanger for heating coolant pumped through it by said coolant pump;

a bypass valve for routing coolant to bypass said exhaust heat exchanger;

at least one vehicle secondary device having a heat exchanger;

wherein coolant pumped by said coolant pump through said exhaust heat exchanger is also pumped to said heat exchanger of said at least one vehicle secondary device;

wherein when said first valve member prevents flow of coolant to said engine, said engine heats up quickly in a cold start situation and said exhaust heat exchanger heats up said coolant before it flows to said heat exchanger of said at least one secondary device.

2. The thermal system layout circuit as set forth in claim 1 further comprising a second valve member positioned upstream of said exhaust heat exchanger and adapted to prevent flow of coolant thereto.

3. The thermal system layout circuit as described in claim 1 wherein at least two secondary devices are provided, each with a heat exchanger and each adapted to be warmed- up by the coolant downstream of said exhaust heat exchanger.

4. The thermal system layout circuit as described in claim 3 wherein said two secondary devices are positioned in a series arrangement.

5. The thermal system layout circuit as described in claim 3 wherein said two secondary devices are positioned in a parallel arrangement.

6. The thermal system layout circuit as described in claim 1 in which said at least one secondary device is selected from the group comprising a transmission, a passenger cabin heater core, a rear axle, and an EGR system.

7. The thermal system layout circuit as described in claim 1 wherein said bypass valve is a proportion-type valve which allows full, partial or no flow of coolant.

8. The thermal system layout circuit as described in claim 1 further comprising a multifunction thermostat valve positioned between the engine and the radiator.

9. A thermal system layout circuit for a cold start for a vehicle engine comprising:

an internal combustion engine having a cooling fan and a radiator;

a coolant pump to circulate coolant through the engine and radiator;

a first valve member positioned between the engine and the radiator and adapted to prevent flow of coolant to the radiator;

a bypass valve for routing coolant to bypass said exhaust heat exchanger;

at least one vehicle secondary device having a heat exchanger;

10. The thermal system layout circuit as set forth in claim 9 further comprising a second valve member positioned upstream of said exhaust heat exchanger and adapted to prevent flow of coolant thereto.

11. The thermal system layout circuit as described in claim 9 wherein at least two secondary devices are provided, each with a heat exchanger and each adapted to be warmed- up by the coolant downstream of said exhaust heat exchanger.

12. The thermal system layout circuit as described in claim 11 wherein said two secondary devices are positioned in a series arrangement.

13. The thermal system layout circuit as described in claim 11 wherein said two secondary devices are positioned in a parallel arrangement.

14. The thermal system layout circuit as described in claim 9 in which said at least one secondary device is selected from the group comprising a transmission, a passenger cabin heater core, and a rear axle.

15. The thermal system layout circuit as described in claim 9 wherein said bypass valve is a proportion-type valve which allows full, partial or no flow of coolant.

16. The thermal system layout circuit as described in claim 9 further comprising a multifunction thermostat valve positioned between the engine and the radiator.

17. The thermal system layout circuit as described in claim 1 further comprising an EGR heat exchanger.

18. A thermal system layout circuit for a cold start for a vehicle engine comprising:

an internal combustion engine having a cooling fan and a radiator;

a coolant pump to circulate coolant through the engine and radiator;

an EGR heat exchanger for heating coolant pumped through it by said coolant pump; at least one vehicle secondary device having a heat exchanger;

wherein coolant pumped by said coolant pump through said EGR heat exchanger is also pumped to said heat exchanger of said at least one vehicle secondary device;

wherein when said first valve member prevents flow of coolant to said engine, said engine heats up quickly in a cold start situation and said EGR heat exchanger heats up said coolant before it flows to said heat exchanger of said at least one secondary device.

19. The thermal system layout circuit as claimed in claim 18 comprising an exhaust heat exchanger.

20. The thermal system layout circuit as recited in claim 18 further comprising a bypass valve for routing coolant to bypass said EGR heat exchanger;