GB2433585A

GB2433585A - Engine Coolant System

Info

Publication number: GB2433585A
Application number: GB0526008A
Authority: GB
Inventors: Antonis Dris; John Caine; Harald Kaufeld
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2005-12-22
Filing date: 2005-12-22
Publication date: 2007-06-27
Anticipated expiration: 2025-12-22
Also published as: GB2433585B; GB0526008D0

Abstract

A coolant circuit for a motor vehicle comprising an internal combustion engine, 14' a pump, 12' a heater matrix , 16' an engine oil/coolant heat exchanger 20' and a valve 24' for selectively bypassing the engine oil/coolant heat exchanger characterised in that the heater matrix is located in parallel with the oil/coolant heat exchanger, the valve having a first position to cause the coolant to flow only through the heater matrix and a second position to cause the coolant to flow only through the oil/coolant heat exchanger.

Description

Engine Coolant System This invention relates to thermal management

systems for internal combustion engines, and more particularly to increasing the operating efficiency of such systems.

The purpose of a vehicle thermal management system (TMS) is to coordinate the thermal energy in the engine, the cooling system and the cabin, through the control of cooling system actuators such as valves.

Conventional thermal management systems utilise a pumped coolant circuit. Coolant flows through and removes heat from an internal combustion engine. The coolant then flows through a heater matrix which may be used to heat up the passenger compartment if required. A valve located downstream of the heater matrix determines if coolant flows through an engine oil/coolant heat exchanger (OCHE) or through a bypass channel. The purpose of the OCHE is to impart heat from the coolant to the oil to aid in oil warm-up as the coolant tends to heat up more quickly. It further acts as an oil cooler to prevent over heating of the oil. It is important to heat the oil as quickly as possible in order to optimise its lubricating properties and hence increase fuel economy.

A disadvantage with the above arrangement is that when fuel economy is a priority of the thermal management system, the function of the heater matrix component is not required, yet the system suffers in terms of warm-up speed due to the coolant volume, thermal mass and pressure loss associated with this component.

With a view to mitigating the above disadvantage, the present invention provides a coolant circuit for a motor vehicle comprising an internal combustion engine, a pump, a heater matrix, an engine oil/coolant heat exchanger and a valve for selectively bypassing the engine oil/coolant heat exchanger characterised in that the heater matrix is located in parallel with the oil/coolant heat exchanger, and in that the valve serves as a diverter valve to vary the relative proportions of the total flow passing the heater matrix and the oil/coolant heat exchanger.

Preferably the valve has a first end position to cause the coolant to flow only through the heater matrix and a second end position to cause the coolant to flow only through the oil/coolant heat exchanger.

Advantageously the relative proportions of the total flow are continuously variable.

Preferably a radiator is connected in parallel with the internal combustion engine and the pump in order to cool the coolant.

It is further preferable to provide a thermostat for selectively closing the branch of the coolant circuit containing the radiator in dependence upon the temperature of the coolant.

The invention will now be described further by way of example with reference to the accompanying drawings in which Figure 1 is a cooling circuit according to the prior art showing a coolant flow path prioritising fuel economy during warm-up, Figure 2 is a cooling circuit according to the prior art showing a coolant flow path prioritising cabin heating during warm-up, Figure 3 is a cooling circuit according to the present invention showing a coolant flow path prioritisirig fuel economy during warm-up, and Figure 4 is a cooling circuit according to the present invention showing a coolant flow path prioritising cabin heating during warm-up.

Figure 1 shows a conventional thermal management system in a vehicle. The solid lines indicate the coolant flow path, whereas the dotted lines indicate a selectively by-passable section of the coolant circuit.

The coolant system 10 is a series circuit consisting of a pump 12, which may be driven by the engine 14, or by an external electrical power supply, such as an alternator or battery of the vehicle. The coolant is pumped through chambers within the engine block and cylinder heads where it absorbs heat, and thereby cools the engine 14. The pumped coolant then flows into a heater matrix 16, which is an air/water heat exchanger. When warm air is required in the cabin of the vehicle, air is heated by passing over the matrix 16.

A valve 18 is located downstream of the heater matrix 16 and selectively diverts the coolant through an oil/coolant heat exchanger (OCHE) 20 or through a bypass channel 22 in parallel with the OCHE 20. Returning the coolant through a thermostat 24 back to the pump 12 completes the coolant system 10. In the event that the coolant exceeds a predetermined temperature, the thermostat 24 opens to allow the coolant through a radiator 26, usually placed in the airflow created by the movement of the vehicle. This serves to remove heat from the coolant until it falls below the opening temperature of the thermostat 24.

Figure 1 shows the coolant system when the priority is fuel economy. In this situation, the valve 18 is set to divert all the flow of coolant through the OCHE 20 so as to accelerate heating of the engine oil. This is possible since, in use, the engine coolant is heated faster than the engine oil. When flowing through the OCHE, heat is lost from the coolant to the oil, reducing the oil's viscosity, which leads to reduced engine friction and therefore increased fuel economy.

In Figure 2, the priority of the coolant system is cabin heating. The 3-way valve 18 is therefore set to bypass the OCHE 20 via bypass channel 22. This ensures that as little heat as possible is lost from the coolant system to the lubricating oil in order that the temperature of the heater matrix is as high possible. This ensures that the cabin heating is more effective.

The arrangement of Figures 1 and 2 above is flawed in that the coolant is forced to circulate through the heater matrix regardless of whether the priority of the thermal management system is to heat the lubricating oil or not. The heater matrix is a large capacity heat exchanger and so dramatically increases the volume of coolant and the pressure loss of the system. Further disadvantages come from the increased thermal mass in the system and also the heat lost from the matrix to the air. The combination of these factors leads to increased engine oil warm up time and hence reduced fuel economy.

In addition, though less severe in impact, when cabin heating is the priority of the coolant system, there is an associated loss of heat due to the volume, thermal mass and pressure loss associated with bypass channel 22.

A system of the present invention is shown in Figures 3 and 4 in which the common features are marked with a prime to distinguish them from those in the prior art circuit. The present invention relocates the heater matrix 16' to the bypass channel 22' so that the heater matrix 16' is located in parallel with the OCHE 22'. In this arrangement, when either the OCHE or the heater matrix is intended as the main heat loss of the coolant system, the other may be totally isolated from the circuit using valve 18'. This ensures that energy is not lost in heating an unnecessary mass of metal and coolant and through an excessive pressure drop across redundant components in the coolant flow path.

Figures 3 and 4 show the two different modes of operation. Again, the dotted line indicates when no coolant is flowing along a branch of the circuit. The solid line as in Figures 1 and 2 indicating the coolant flow path. In the preferred embodiment, the valve 18' is a three way valve which allows for coolant to flow through the OCHE 22', the matrix 16' or both. The same valve allows for the proportion of coolant through each component to be determined in dependence upon the need to heat the engine oil or the passenger compartment.

At the same time, a conventional thermostat 24' is utilised in each of Figures 1 to 4 to remove excess heat from the coolant system to the atmosphere through a radiator 26'. The thermostat is a conventional valve that allows coolant to flow through the radiator when the temperature of the coolant exceeds a predetermined level.

Claims

Claims 1. A coolant circuit for a motor vehicle comprising: an internal

combustion engine, a pump, a heater matrix, an engine oil/coolant heat exchanger and a valve for selectively bypassing the engine oil/coolant heat exchanger characterised in that the heater matrix is located in parallel with the oil/coolant heat exchanger, and in that the valve serves as a diverter valve to vary the relative proportions of the total flow passing the heater matrix and the oil/coolant heat exchanger.

2. A coolant circuit as claimed in claim 1, wherein the valve has a first end position to cause the coolant to flow only through the heater matrix and a second end position to cause the coolant to flow only through the oil/coolant heat exchanger.

3. A coolant circuit as claimed in claim 1 or 2, wherein the relative proportions of the total flow are Continuously variable.

4. A coolant circuit as claimed in any preceding claim, wherein a radiator is connected across with the series combination of the pump and the engine in order to cool the coolant.

5. A coolant circuit as claimed in claim 4, wherein a thermostat is provided for selectively closing the branch of the coolant circuit containing the radiator in dependence upon the temperature of the coolant.

6. A coolant circuit for a motor vehicle substantially as herein described with reference to and as illustrated in the accompanying drawings.