GB1600033A

GB1600033A - Cooling systems for vehicle engines in combination with heating systems for vehicle passenger compartments

Info

Publication number: GB1600033A
Application number: GB22904/77A
Authority: GB
Original assignee: METRO CAMMELL WEYMANN Ltd
Current assignee: METRO CAMMELL WEYMANN Ltd
Priority date: 1977-05-31
Filing date: 1977-05-31
Publication date: 1981-10-14
Also published as: AU3661278A; ZA783022B

Description

(54) IMPROVEMENTS IN OR RELATING TO COOLING SYSTEMS FOR VEHICLE ENGINES IN COMBINATION WITH HEATING SYSTEMS FOR VEHICLE PASSENGER COMPARTMENTS (71) We, METRO-CAMMELL WEYMANN LIMITED, a British Company of P.O. Box 248, Leigh Road, Washwood Heath, Birmingham B8 2YJ, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a combined cooling system for a vehicle engine and heating system for a vehicle passenger compartment, and in particular, though not exclusively, to such a system for a public service vehicle such as a bus.

A cooling system for any vehicle engine usually performs two functions. Firstly, it cools the engine to prevent overheating and, secondly it provides the heat source for the heating system of the vehicle. The conventional cooling system conveniently comprises a single coolant circuit including a radiator, coolant circulating pump, engine cylinder block and the heating system. Coolant from the radiator is passed through the engine cylinder block to cool the engine and the hot coolant is returned to the radiator either directly or indirectly through the heating system. The hot coolant flowing through the heating system is used to heat air in the vehicle interior by any suitable arrangement and the heating system can be by-passed when not required, for example in the summer, or there may be thermostatic control.

The passenger accommodation in a bus is much greater than a car and the heating system includes an extensive circuit since the hot coolant leaving the engine must be supplied to all parts of the bus including the driver's cab.

Consequently the circuit includes many pipe joints, for example there can be up to 130 joints in the bus circuit, and the majority of these are in the heating system where the pipes are built into the body structure. As a result a great many of the joints are not easily accessible and often such a joint can leak quite a considerable volume of coolant without it being apparent. Any loss of coolant from the coolant system is undesirable and it is not unknown in certain engine arrangements for a loss of 'A gallon of coolant from the minimum coolant volume to cause the pump to stop circulating coolant. When this occurs the engine overheats and causes pick-up of metal between the pistons and their cylinder liners, which results either in a seized engine or excessive oil consumption, both of which are undesirable.Thus regular checks must be made on all the joints in the circuit and on the level of coolant to ensure that it does not fall below the minimum acceptable level. Since a check on most of the joints can only be carried out when the bus is taken out of service regular checks reduce the amount of use which can be made of the bus and add to the overall running cost. Furthermore since the cooling system comprises a single circuit of necessarily large volume it is not uncommon when filling the system from a hose-pipe for blow-backs to occur as a result of air being expelled from the system and these can be mistaken as an indication that the system is full. As a result a bus can be sent out with an incompletely filled system which has the undesirable results already mentioned.Additionally, in the known single circuit cooling system, as the engine wears, gaseous emission and deposits from the engine produce, dependent on the type of coolant used, a hard brown sludge which fouls the system, in particular the radiator and the heating system.

It is an object of the present invention to provide a cooling system for a vehicle engine which substantially overcomes the above described disadvantages of the known single circuit cooling systems.

According to the present invention we provide a combined cooling system for a vehicle engine and heating circuit for the vehicle passenger compartment comprising a primary circuit arranged for the passage of a first coolant the primary circuit comprising a jacket around the vehicle engine and one path of a heat exchanger and a secondary circuit separate from the primary circuit, for the passage of a second coolant and comprising a second path through the said heat exchanger in heat exchange relationship with the path of the first coolant, the secondary circuit comprising a passenger compartment heating system including at least one coolant/air heat exchanger adapted to heat air in the passenger compartment by convection.

Both the primary circuit and the secondary circuit preferably include respective coolant circulating pumps and header tanks and can be operated either in an unpressurised or a pressurised condition.

The secondary circuit may also include a radiator for cooling the coolant in the secondary circuit and a thermostatically controlled bypass for controlling the supply of coolant to the radiator or to a pipe by-passing the radiator.

Where the heating system includes more than one heat exchanger they can be connected in series or in parallel. Preferably valve means comprising a manually operable valve is provided for shutting-off the heating system from the secondary circuit.

Another problem arises from the fact that the heat output from the engine is relied on for the heating system and in certain conditions this is insufficient to obtain and maintain an acceptable temperature in the passenger compartment.

To this end in a preferred arrangement the heat output of the gearbox and the exhaust system is employed to boost the heating of the secondary circuit. Accordingly, the secondary circuit preferably includes heat exchange means through which the gearbox oil flows and a jacket surrounding the exhaust manifold to further heat the coolant prior to its returning to the radiator or to its flowing to the heating system.

The cooling system according to the invention is particularly suited in its application to vehicles such as buses. The primary circuit need include only two flexible connections, which can be easily inspected for any leakage. Thus it is unlikely that any gradual leakage resulting in failure of the pump to circulate the coolant in the primary circuit would go undetected. Although the secondary circuit still includes a large number of connections a gradual leak from any one which was undetected would first result in failure of the pump to circulate the coolant in the secondary circuit. The pump for circulating the coolant in the primary circuit would be unaffected so that the temperature of the coolant in the primary circuit would then only increase gradually and this increase would be detected by the driver before any permanent damage was done to the engine.Furthermore it will be appreciated that in the cooling system of the present invention any gaseous emission and engine deposits are confined to the primary circuit and, as a result, the secondary circuit including the radiator and heating system is less likely to become fouled than is the single circuit of the known cooling systems.

A preferred embodiment of the invention will now be described with reference to the accompanying drawing which schematically shows a cooling system suitable for a bus.

Referring to the drawing the cooling system comprises a primary coolant circuit 1 for cooling a vehicle engine 2 and a secondary coolant circuit 3 for cooling the coolant flowing in the primary circuit and adapted for heating convection air flowing to the interior of the bus. The primary coolant circuit 1 comprises a header tank 4 connected to a pump 5 which in turn is connected to the coolant inlet 6 of the cylinder block 7 of the engine. The coolant outlet 8 from the cylinder block 7 is connected to a heat exchanger 9 which in turn is connected to the pump 5 thus completing a full flow system in which coolant is circulated in the direction of the arrows by the pump 5.

The secondary coolant circuit 3 comprises a header tank 10 connected to the inlet 11 to a radiator 12 having cooling fins 13 over which air is passed by a hydraulically or electrically driven fan 14. The outlet 15 from the radiator is connected to a pump 16 which in turn is connected to an oil cooler comprising a heat exchanger 17 through which the gearbox oil is circulated in a network of pipes 18. The heat exchanger 17 is connected to the inlet 19 to a network of pipes 20 connected in parallel and extending longitudinally through the heat exchanger 9 of the primary circuit. The outlet 21 from the pipes is connected to a thermostatically controlled valve 22 for controlling the passage of coolant to the inlet 11 to the radiator or to a by-pass pipe 23 connected to the outlet 15 from the radiator.Also connected to the secondary circuit 3 is the heating system 24 of the bus comprising a first heat exchanger 25 for heating convection air flowing to the driver's cab connected in series to second and third heat exchangers 26 and 27 respectively connected in parallel. The second and third heat exchangers 26,27 are situated at any appropriate part of the bus for heating convection air flowing to the interior of the bus. The outlet 28 from the first heat exchanger and the outlet 29 from the second and thir heat exchangers are connected to the secondary circuit 3 downstream of the outlet 15 from the radiator. A shut-off valve 30 is provided for stopping the flow of coolant to the heating system if required.

Dependent on the positions of the thermostatically controlled valve and the shut-off valve the coolant is circulated in the direction of the arrows by the pump 16.

Additionally the secondary circuit 3 has a by-pass line 31 including ajacket 32 surrounding the exhaust manifold 33 and means 34, for example a manually operable valve, for controlling the flow of coolant through the jacket 32. The valve is adjustable through a range of positions between a fully open position and a fully closed position so that when the heating system 24 is connected to the secondary circuit 3 the coolant canbe further heated by adjusting the valve to control the flow of coolant through the by-pass line 31 where it is heated by the exhaust gases flowing through the manifold 33.

In this way a more rapid and efficient heating of the convection air is obtained.

Operation of the system is as follows:hot coolant leaving the engine cylinder block 7 is cooled in the heat exchanger 9 by the relatively cold coolant flowing through the heat exchanger in the network of pipes 20 and is then returned to the cylinder block 7. The heated coolant leaving the network of pipes 20 flows through the secondary circuit ot the thermostatically controlled valve 22. If the shut-off valve 30 is closed so that the coolant cannot flow to the heating system the coolant either flows through the radiator 12 or through the by-pass pipe 23. Initially when the temperature of the coolant is low, the engine not having yet reached its operating temperature, there is no need for the coolant to flow through the radiator 12 so the thermostatically controlled valve 22 closes the inlet 11 to the radiator and the coolant flows through the by-pass pipe 23.

As the temperature of the engine increases and the temperature of the coolant in the secondary circuit increases the thermostatically controlled valve 22 opens the inlet 11 to the radiator and closes the by-pass pipe 23 so that the coolant flows through the radiator 12 and is effectively cooled. When the shut-off valve 30 is open the coolant also flows through the heating system 24 where convection air circulating around the heat exchangers 25, 26 and 27 is warmed prior to flowing to the interior of the bus. In addition to the heating of the coolant obtained by heat exchanger 9, the coolant is also heated by passage through the heat exchanger 17 and through the jacket 32, the driver controlling the flow of coolant through the jacket to obtain the desired temperature in the heating system.

The above described cooling system may be modified in a number of ways, for example the oil cooler and the by-pass line 31 may be omitted or one only may be included in the secondary circuit. Furthermore the oil cooler may be located downstream of the heat exchanger 9 so that the rate of cooling of the coolant flowing in the primary circuit is increased while the rate of cooling of the gearbox oil is reduced. The position of the oil cooler, i.e. upstream or downstream of the heat exchanger 9, depends on the thermal balance and transfer in the engine and is selected accordingly.

Another modification comprises the provision or means for selectively controlling the flow of coolant to the heat exchangers 25, 26 and 27 of the heating system. Such means may comprise a manually operable valve adjustable through a range of positions between an open position and a closed position so that the temperature of the convection air provided by each heat exchanger can be controlled.

In yet another modification the coolant leaving the heat exchangers 25, 26 and 27 of the heating system is returned to the secondary circuit upstream of the inlet 11 to the radiator so that the coolant which is already relatively cool is further cooled by passage through the radiator.

It will be appreciated that the heat exchangers may be of any appropriate type while the design and lay-out of the flow lines and valves may be selected to suit the type of vehicle to which the system is fitted, for example the valves for controlling the supply of coolant to the heating system, for selectively controlling the supply of coolant to the heat exchangers of the heating system and for controlling the supply of coolant to the jacket surrounding the engine manifold are conveniently operable through suitable controls located near to the vehicle driver's seat.

WHAT WE CLAIM IS: 1. A combined vehicle engine cooling system and passenger compartment heating system comprising a primary circuit for the passage of a first coolant, the primary circuit comprising a jacket around the vehicle engine and one path of a heat exchanger, and a secondary circuit separate from the primary circuit, for the passage of a second coolant, and comprising a second path through the said heat exchanger in heat exchange relationship with the path of the first coolant, the secondary circuit comprising a passenger compartment heating system including at least one coolant/air heat exchanger adapted to heat air in the passenger compartment by convection.

2. A combined system according to claim 1 wherein the secondary circuit includes a radiator.

3. A combined system according to claim 2 wherein the secondary circuit includes a thermostatically controlled by-pass for controlling the supply of coolant to the radiator or to a pipe by-passing the radiator.

4. A combined system according to claim 2 or claim 3 wherein the second coolant leaving the passenger compartment heating system is returned to the secondary circuit downstream of the radiator.

5. A combined system according to claim 2 or claim 3 wherein the second coolant leaving the passenger compartment heating system is returned to the secondary circuit upstream of the radiator.

6. A combined system according to any one of claims 1 to 5 wherein the passenger compartment heating system comprises a plurality of coolant air heat exchangers connected in series or in parallel and flow control means for selectively controlling the flow of the second coolant to the heating system.

7. A combined system according to claim 6 wherein the flow control means is adjustable through a range of positions between an open position and a closed position whereby the temperature of the air provided by each coolant! air heat exchanger can be controlled.

8. A combined system according to any one of claims 1 to 6, wherein the passenger compartment heating system has a manually operable shut-off valve for controlling the supply of the second coolant to the heating system.

9. A combined system according to any one of the preceding claims wherein the secondary circuit includes an oil cooler in heat-exchange relationship with the engine gearbox oil where

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. cold coolant flowing through the heat exchanger in the network of pipes 20 and is then returned to the cylinder block 7. The heated coolant leaving the network of pipes 20 flows through the secondary circuit ot the thermostatically controlled valve 22. If the shut-off valve 30 is closed so that the coolant cannot flow to the heating system the coolant either flows through the radiator 12 or through the by-pass pipe 23. Initially when the temperature of the coolant is low, the engine not having yet reached its operating temperature, there is no need for the coolant to flow through the radiator 12 so the thermostatically controlled valve 22 closes the inlet 11 to the radiator and the coolant flows through the by-pass pipe 23. As the temperature of the engine increases and the temperature of the coolant in the secondary circuit increases the thermostatically controlled valve 22 opens the inlet 11 to the radiator and closes the by-pass pipe 23 so that the coolant flows through the radiator 12 and is effectively cooled. When the shut-off valve 30 is open the coolant also flows through the heating system 24 where convection air circulating around the heat exchangers 25, 26 and 27 is warmed prior to flowing to the interior of the bus. In addition to the heating of the coolant obtained by heat exchanger 9, the coolant is also heated by passage through the heat exchanger 17 and through the jacket 32, the driver controlling the flow of coolant through the jacket to obtain the desired temperature in the heating system. The above described cooling system may be modified in a number of ways, for example the oil cooler and the by-pass line 31 may be omitted or one only may be included in the secondary circuit. Furthermore the oil cooler may be located downstream of the heat exchanger 9 so that the rate of cooling of the coolant flowing in the primary circuit is increased while the rate of cooling of the gearbox oil is reduced. The position of the oil cooler, i.e. upstream or downstream of the heat exchanger 9, depends on the thermal balance and transfer in the engine and is selected accordingly. Another modification comprises the provision or means for selectively controlling the flow of coolant to the heat exchangers 25, 26 and 27 of the heating system. Such means may comprise a manually operable valve adjustable through a range of positions between an open position and a closed position so that the temperature of the convection air provided by each heat exchanger can be controlled. In yet another modification the coolant leaving the heat exchangers 25, 26 and 27 of the heating system is returned to the secondary circuit upstream of the inlet 11 to the radiator so that the coolant which is already relatively cool is further cooled by passage through the radiator. It will be appreciated that the heat exchangers may be of any appropriate type while the design and lay-out of the flow lines and valves may be selected to suit the type of vehicle to which the system is fitted, for example the valves for controlling the supply of coolant to the heating system, for selectively controlling the supply of coolant to the heat exchangers of the heating system and for controlling the supply of coolant to the jacket surrounding the engine manifold are conveniently operable through suitable controls located near to the vehicle driver's seat. WHAT WE CLAIM IS:

1. A combined vehicle engine cooling system and passenger compartment heating system comprising a primary circuit for the passage of a first coolant, the primary circuit comprising a jacket around the vehicle engine and one path of a heat exchanger, and a secondary circuit separate from the primary circuit, for the passage of a second coolant, and comprising a second path through the said heat exchanger in heat exchange relationship with the path of the first coolant, the secondary circuit comprising a passenger compartment heating system including at least one coolant/air heat exchanger adapted to heat air in the passenger compartment by convection.

by to cool that oil.

10. A combined system according to claim 9 wherein the oil cooler in the secondary circuit is upstream of the first-mentioned heat exchanger.

11. A combined system according to claim 9 wherein the oil cooler in the secondary circuit is downstream of the first-mentioned heat exchanger.

12. A combined system according to any one of the preceding claims wherein the secondary circuit includes a by-pass line arranged and adapted to heat the second coolant by heat exchange with exhaust gases from the engine.

13. A combined system according to claim 12 wherein the by-pass line has a jacket arranged and adapted to surround the exhaust manifold of the engine.

14. A combined system according to claim 12 or claim 13 wherein the by-pass line has means for controlling the flow of the second coolant through the by-pass line.

15. A combined system according to claim 14 wherein said means comprises a manually operable valve adjustable through a range of positions between a fully open and a fully closed position.

16. A combined system according to any one of the preceding claims wherein the primary and secondary circuits each have a respective coolant circulating pump and header tank.

17. A combined system according to any one of the preceding claims adapted to operate in either a pressurised or an unpressurised condition.

18. A combined vehicle engine cooling system and passenger compartment heating system as hereinbefore described with reference to the accompanying drawing.

19. A vehicle having a combined cooling system and heating system as claimed in any one of the preceding claims.