WO2014039287A1

WO2014039287A1 - Thermal system transmission cooler

Info

Publication number: WO2014039287A1
Application number: PCT/US2013/056355
Authority: WO
Inventors: John Shutty; Dan E. HORNBACK
Original assignee: Borgwarner Inc.
Priority date: 2012-09-05
Filing date: 2013-08-23
Publication date: 2014-03-13

Abstract

A system and method for cooling or heating fluid in a transmission or other secondary/auxiliary device. For cooling, an air cooled heat exchanger is provided for the engine coolant to assist in cooling the transmission fluid. The heat exchanger can be a tubular device. For heating, gill shutters prevent air flow to the heat exchanger and a bypass valve prevents coolant flow through the radiator.

Description

THERMAL SYSTEM TRANSMISSION COOLER

TECHNICAL FIELD

An improved system and method for improving the efficiency of internal combustion engines, and more particularly for maintaining transmission fluid in a vehicle within acceptable temperature limits.

BACKGROUND OF THE INVENTION

Automatic transmissions create a significant amount of heat during operation. Most of this heat is caused by friction: friction of the fluid churning inside the torque converter, friction created when the clutch plates engage, and friction created by the gears and bearings carrying their normal load.

Automatic transmission fluid ("ATF") heats up quickly once the vehicle is in motion. Normal driving will raise fluid temperatures to about 175° F, which is the usual temperature range at which most fluids are designed to operate. If the ATF temperatures are maintained within their normal range they can last up to 100,000 miles or more. However, if the fluid temperature goes much higher, the life of the fluid can drop significantly, along with the seals and even the clutches in extreme situations.

At elevated operating temperatures, the ATF can oxidize, turn colors and create a different odor. The heat can destroy the lubricating qualities and friction characteristics, which interferes with the operation of the transmission. If the temperate gets to 250°F or higher, rubber seals can harden which leads to leaks and pressure losses. At higher temperatures, the transmission plates can slip. Eventually the clutches can burn out and the transmission can fail.

In order to attempt to keep the temperature of the transmission fluid within acceptable temperature limits, it is known today to use the engine coolant to help cool the transmission fluid. However, in some situations, such as a heavy load on the engine or elevated atmospheric temperatures, it is still possible that the temperature of the transmission fluid can be elevated to undesirable levels. Also, even normal driving can raise the fluid temperatures beyond safe limits. The elevated fluid temperatures can cause premature degrading of the integrity and effectiveness of the fluid, leading to significant reductions in the life of the fluid and, if not discovered, lead to costly transmission repairs and even replacement of the transmission.

Thus, it is an object of the present invention to provide a unique system and method for maintaining the temperature of transmission fluid in a vehicle within acceptable limits.

SUMMARY OF THE INVENTION

The present invention meets the above objects by providing a system and method which provides additional cooling to the transmission fluid. Prior to the time that the engine coolant is used to reduce the temperature of the transmission fluid, the engine coolant is subjected to further cooling by the air. A tubular heat exchanger is positioned in the air flow entering or passing through the vehicle and used to lower the temperature of the engine coolant before it is used to remove heat from the transmission fluid.

The additional heat exchanger can be of any conventional design, such as a tube with fins, an elongated or twisted tube, or another tube construction, that enhances heat rejection from the coolant to the air. The heat exchanger can be positioned adjacent the engine cooling fan.

For cold start situations, gill shutters could be used to prevent air flow over the tubular heat exchanger. Alternatively, the heat exchanger could be placed in an alternate area where air flow is restricted during cold start.

Other benefits, features, and advantages of the present invention will become apparent from the following description of the invention, when viewed together with the accompanying drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 schematically depicts a known system for heating and cooling an auxiliary device, such as a transmission.

FIGURE 2 schematically depicts an embodiment of the invention.

FIGURE 3 depicts an alternate embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Attention is being directed today in one manner to find ways to prevent the fluid in the transmission or other secondary devices from overheating. In another manner, attention is being directed to improve the speed and efficiency of cold start-up of engines. This can be achieved by assisting in the heating of the transmission fluid or secondary devices. In each situation, the overall object is to improve the efficiency and durability of internal combustion engines.

One of the known approaches is to use the same coolant flow lines to both warm and cool the transmission or other auxiliary device. Figure 1 schematically depicts a known system 20 for heating and cooling an auxiliary device such as a transmission. The engine coolant is circulated by the coolant pump 12 into the engine 14 and also to a heat exchanger 16 in the transmission. In the transmission, which also could be any of the other auxiliary devices in a vehicle, such as the heater core or rear axle, the heat exchanger 16 is used to remove heat from the transmission fluid. This keeps the transmission fluid at a lower temperature.

After the engine coolant leaves the engine and transmission, it flows to the thermostat 18 which also is preferably a three-way valve. The coolant then proceeds either into and through the radiator 20, or through a bypass line 22. In cold start situations when it is desired to heat-up the transmission fluid, the thermostat bypass valve 18 flows the coolant around the radiator. This prevents the large quantity of cool coolant in the radiator from preventing the coolant from heating up quickly.

When it is necessary to cool the transmission fluid, the bypass valve 18 directs the coolant into and through the radiator. This allows the cooler coolant to be used in the heat exchanger 16 to draw heat from the hotter transmission fluid.

Figure 2 schematically depicts an example (embodiment) 30 of the invention. In this system, the engine coolant is pumped by a coolant pump 32 through line 34 to the engine 36 and then to a three-way valve thermostat 38. The thermostat valve is used to either send coolant through the radiator 40 or through a bypass line 42 depending on whether the transmission needs to be warmed or cooled. This portion of the invention is similar to the system described above with respect to Figure 1.

In the embodiment of the invention shown in Figure 2, however, the coolant being pumped to the transmission heat exchanger 44 is first passed through another heat exchanger 46 which is located in a position to be cooled by air being forced or drawn into the engine compartment. In the example shown, the air, which is indicated by the arrow 50, passes through the radiator and is increased in velocity by the cooling fan 52. The air is then passed over the heat exchanger 46 which acts to cool the temperature of the coolant in the line 54 before it is introduced into the transmission heat exchanger 44.

The cooled coolant passing through the transmission heat exchanger 44 is used to draw heat from the transmission fluid. This assists in keeping the temperature of the transmission fluid within its normal ranges. The heat exchanger 46 cools the engine coolant and prevents very hot engine coolant from either not cooling the transmission fluid sufficiently, or, in extreme cases, from not adding heat to the transmission fluid.

The heat exchanger 46 can be positioned in a number of locations and does not have to be positioned between the cooling fan 52 and the engine 36. For example, as shown in dashed lines in Figure 2, the heat exchanger could be located at position 46' which is between the radiator 40 and the cooling fan 52. Since there are wide variations in the positions of the radiator and cooling fans in vehicles today, the heat exchanger could be positioned at other locations in different vehicles and still achieve the purposes and benefits of the invention.

The type, size and configuration of the heat exchanger 46 can be varied in accordance with the knowledge and experience of persons skilled in the art. The heat exchanger 46 can be an elongated or twisted tube as shown in Figure 2, or it can be a heat exchanger with cooling fins or another type altogether, so long as it can meet the objects and purposes of the present invention. For purposes of the description however, the heat exchanger 46 will be referred to generally as a tubular heat exchanger.

The amount of reduction of the temperature of the coolant and in turn the amount of reduction of the temperature the transmission fluid is dependent on the size or length of the tubular heat exchange 46 and, of course, the temperature of the air 50 and the temperature of the coolant passing through the coolant pump 32.

During cold start situations, that is, when the engine is started after being turned off for a while, or overnight, or in cold environments, the invention also provides a system which is used to warm up the transmission fluid. For this purpose, a set of gill shutters 60 are provided in the vehicle which can be used to block the flow of air to the radiator and vehicle. The gill shutters are activated by the engine computer mode ("ECU") in a conventional manner.

In cold starts with the system layout 30 as shown in Figure 2, the gill shutters 60 are closed, and the thermostat 38 directs the coolant through the bypass passageway 42. This prevents the tubular heat exchanger 46 from cooling the coolant, and also prevents the cooled quantity of coolant in the radiator from preventing the coolant from quickly becoming warmer. Since vehicle engines heat up relatively quickly, the coolant pumped by the coolant pump 32 into the engine also heats-up quickly. As a result, the coolant passing through the tubular heat exchanger 46 does not change its temperature significantly, and warm coolant is introduced into the heat exchanger 44 in the transmission. This causes the transmission fluid to be heated up more quickly.

This process also results in increasing the efficiency of the engine. This in turn acts to increase the gas mileage of the vehicle and to reduce the exhaust of undesirable emissions into the atmosphere.

Once the engine achieves a certain temperature, the gill shutters 60 are opened and the bypass thermostat valve 38 directs the coolant into and through the radiator 40. The cooling fan 52, which typically is connected to a viscous clutch or the like, is also allowed to operate and pass cooling air to the engine 36. Then, during normal and warm driving, the open shutters and/or fan operation would provide the air flow over the tubular heat exchanger 46 thus cooling the coolant on its way to the transmission.

It is to be understood that although the present embodiment of the invention disclosed above discusses the invention with respect to its use to heat or cool the transmission fluid, the invention can be used with any of the secondary (a/k/a "auxiliary") devices in a vehicle which need to be cooled, or which need to be heated in a cold start situation. These other secondary devices could be, for example, the rear axle, the heater core for the passenger compartment, or the like.

It is also possible to locate the heat exchanger 46 in an alternate area where air flow is restricted during cold starts. This area could be, for example, the belly flaps of a vehicle. The heat exchanger could also be placed in an area where air flow is not controlled, since vehicle speeds during start up typically are low. This may still provide a decent trade -off between transmission fluid warm up and transmission fluid cooling.

Figure 3 illustrates an alternate embodiment 100 of the invention. Coolant from the coolant pump 102 is pumped into the engine 104 and through an air cooled heat exchanger 106 to the transmission heat exchanger 108. The air cooled heat exchanger 106 is positioned between the cooling fan 110 and the engine. The heat exchanger 106 alternatively could be positioned between the fan and the radiator 112 as described above with respect to Figure 2. The heat exchanger 106 also is preferably a tube-type heat exchanger as described above, although it can be any of the other conventional air cooled heat exchanger.

The coolant from the engine flows through thermostat 114 which preferably is a three-way valve. The valve 114 directs the coolant either to the radiator 1 12 or a bypass line 116. In an alternate embodiment, the valve 114 could be a proportioning valve and also allow partial flows to either the radiator 112 or bypass 116, as well as full flow to either one. A mixing or directing valve 118 is positioned at the intersection of the flows from the radiator or bypass valve and the transmission heat exchanger.

Gill shutters 120 are positioned upstream of the radiator and are controlled to selectively close off air flow to the radiator and fan when desired in cold start situations. The fan 110 is preferably a viscous clutch fan assembly which allows use of the fan only when needed and only to the extent needed to cool the engine and coolant. Any of the viscous clutch assemblies known in the art can be used for this purpose.

In use, the layout circuit embodiment 100 can be used to either heat the transmission fluid or to cool it. In order to assist in cooling the transmission fluid, the engine coolant is pumped through the air cooled heat exchanger 106 where it is cooled by the air flow before it is directed to the transmission heat exchanger 108. This aids in cooling the transmission fluid and assists in maintaining the transmission fluid within its acceptable temperature range. At the same time, the gill shutters are open to allow the full amount of cooling air through the radiator and to the heat exchanger 106.

In order to warm (heat up) the transmission fluid from a cold start situation, the gill shutter are closed to cut off the cooling air, the thermostat three-way valve is set to direct all of the coolant to the bypass line 116, and the fan is either not rotating or rotating at a slow speed. In this manner, the coolant is heated up in the engine and is passed along directly to the transmission heat exchanger 108. This warms the transmission fluid. This system and method also isolates the large volume or quantity of coolant in the radiator which is at a cooler temperature.

Although the embodiment shown in Figure 3 is directed to a secondary device for the vehicle which is the transmission, persons or ordinary skill in the art will understand that the system and method discussed herein can alternative be used for other secondary devices which need to be heated or cooled, such as the rear axle fluid and the heater core for the passenger compartment. 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 assisting in cooling fluid in a secondary device for a vehicle, said thermal system comprising:

an engine;

a cooling fan in operative association with the engine;

a radiator;

a coolant pump;

a first heat exchanger in the secondary device; and

an air cooled heat exchanger;

wherein engine coolant directed to said first heat exchanger in said secondary device is first cooled by said air-cooled heat exchanger.

2. The thermal system layout circuit as described in claim 1 wherein said secondary device is a transmission.

3. The thermal system layout circuit as described in claim 1 wherein said secondary device is selected from the group comprising a rear axle and a heater core.

4. The thermal system layout circuit as described in claim 1 wherein said air-cooled heat exchanger is positioned between the cooling fan and the engine.

5. A thermal system layout circuit for assisting in warming fluid in a secondary device for a vehicle in a cold start situation, said thermal system comprising: an engine;

a cooling fan in operative association with the engine

a radiator;

a coolant pump;

a bypass valve and circuitry for bypassing the radiator;

a first heat exchanger in the secondary device;

an air-cooled heat exchanger; and

gill shutters;

wherein engine coolant directed to the engine bypasses the radiator and is directed to the first heat exchanger; and

wherein the gill shutters can selectively prevent air flow to the radiator.

6. The thermal system layout circuit as described in claim 5 wherein said secondary device is a transmission.

7. The thermal system layout circuit as described in claim 5 wherein said secondary device is selected from the group comprising a rear axle and a heater core.

8. The thermal system layout circuit as described in claim 5 wherein said air-cooled heat exchanger is positioned between the cooling fan and the engine.

9. A thermal system layout circuit for alternatively assisting in either heating or cooling the fluid in a secondary device in a vehicle, said thermal system comprising: an engine;

a cooling fan in operative association with the engine;

a radiator;

a coolant pump;

a first heat exchanger in said secondary device;

an air-cooled heat exchanger;

gill shutters; and

a bypass valve and coolant circuitry for bypassing the radiator;

wherein for cooling the fluid in the secondary device, the engine coolant directed to said first heat exchanger in said secondary device is first cooled by said air cooled heat exchanger;

wherein for heating the fluid in the secondary device, the gill shutters are closed preventing air flow to the radiator and the engine coolant is directed by the bypass valve to bypass the radiator.

10. The thermal system layout circuit as described in claim 9 wherein said secondary device is a transmission.

11. The thermal system layout circuit as described in claim 9 wherein said secondary device is selected from the group comprising a rear axle and a heater core.

12. The thermal system layout circuit as described in claim 9 wherein said air-cooled heat exchanger is positioned between said cooling fan and said engine.

13. A method for assisting the cooling of fluid in a secondary device in a vehicle, the vehicle having an engine, a cooling fan, a radiator, a coolant pump, a first heat exchanger in the secondary device, and an air-cooled heat exchanger, said method comprising the steps of:

providing a coolant circuit in the vehicle wherein the coolant fluid is circulated by the coolant pump through the engine, through the radiator and through the first heat exchanger in the secondary device; positioning the air-cooled heat exchanger in the coolant circuit adjacent the cooling fan and between the radiator and the first heat exchanger in the secondary device; and

cooling the coolant in the coolant circuit by an air-cooled heat exchanger before the coolant is circulated through the first heat exchanger.

14. The method as set forth in claim 13 wherein said secondary device is a transmission.

15. The method as set forth in claim 13 wherein said secondary device is selected from the group comprising a rear axle and a heater core.

16. The method as set forth in claim 13 further comprising positioning the air- cooled heat exchanger between the coating fan and the engine.

17. A method for assisting in the warming of fluid in a secondary device in a vehicle, the vehicle having an engine, a cooling fan, a radiator, a coolant pump, a first heat exchanger in the secondary device, a bypass valve and circuitry for bypassing the radiator with the engine coolant, an air cooled heat exchanger, and gill shutter members, said method comprising the steps of:

providing a coolant circuit in the vehicle wherein the coolant fluid is circulated by the coolant pump through the engine, through the radiator and through the first heat exchanger in the secondary device;

operating the bypass valve to prevent coolant from circulating through the radiator;

closing the gill shutter members to prevent air flow to the air-cooled heat exchanger;

heating the coolant by pumping it through the engine by the coolant pump; and circulating the heated coolant to the secondary device to assist in warming the fluid in the secondary device.

18. The method as described in claim 17 wherein said secondary device is a transmission.

19. The method as described in claim 17 wherein said secondary device is selected from the group comprising a rear axle and a heater core.

20. The method as described in claim 17 further comprising the step of positioning the air-cooled heat exchanger between the cooling fan and the engine.