GB2054034A

GB2054034A - Liquid-cooled internal combustion engine

Info

Publication number: GB2054034A
Application number: GB8020675A
Authority: GB
Original assignee: Audi NSU Auto Union AG; Audi AG
Current assignee: Audi AG
Priority date: 1979-07-13
Filing date: 1980-06-24
Publication date: 1981-02-11
Also published as: IT8023284A0; DE2928298A1; JPS5652519A; SE8004892L; FR2461100A1; IT1141005B

Abstract

The cylinder head jacket (5) has inflow and return connections (6, 7) for pumped coolant circulation, and the cylinder block jacket (4) is in communication with the head jacket (5) solely through orifices (8) at the interface between block and head, exchanging its coolant with that in the pumped circulation channel by thermo-syphoning. A thermostatic valve (12) responsive to the coolant can bypass a radiator (10) at low temperatures to achieve rapid warm- up. <IMAGE>

Description

SPECIFICATION Liquid-cooled internal combustion engine The invention relates to liquid-cooled internal combustion engines. It is concerned with the type of engine having a cylinder block and a cylinder head, each with cavities to form jackets for the coolant liquid (hereafter for convenience generally referred to as water), and a pumped water circulation system with inflow and return connections to the cylinder head jacket.

In one such internal combustion engine, water jackets in the cylinder head and in the cylinder block are separate from each other, both having inflow and return connections, and each being in communication with an individual cooling system.

With this arrangement, the intention is to be able to adjust the cooling of the cylinder head and cylinder block independently, each to its own optimum, and therefore to obtain improved overall cooling. This separate control requires a separate circulating pump, radiator and thermostatic control valve to be provided for each cooling system, which is costly. Moreover, it is difficult to make the two cooling systems compatible with each other, and adapt them to the cooling requirements of those parts of the engine which are thermally highly stressed. Too abrupt or too slight a cooling of one of the two main parts of the engine tends to produce a temperature incorrect for the sequence of combustion and to give rise to wear and tear.Finally, in the event of breakdown or malfunction of the control of one of the two cooling systems, there is the danger of considerable overheating of the associated engine part without the other cooling system being able to compensate. This leads to lime deposits in the water jackets and to distortion.

It is also known for the cylinder head jacket to be divided and its parts to be in communication via the cylinder block jacket. This series connection produces a constant cooling of the cylinder block and makes individual cooling of the cylinder block and cylinder head impossible.

The aim therefore is to produce a simply constructed liquid cooled internal combustion engine which allows rapid heating of the engine at start-up, and at the same time ensures reliable cooling.

According to the present invention there is provided a liquid-cooled internal combustion engine having a cylinder block and a cylinder head, each formed with jackets for coolant liquid and the cylinder head jacket having inflow and return connections for pumped circulation of liquid, wherein the jackets are in communication at the interface of the cylinder head and block via orifices in said head and block, whereby circulation of liquid through the cylinder block jacket is by thermo-syphon action.

Thus, only the cylinder head jacket will be in the direct forced circulation path of the cooling liquid or water. As water circulation through the cylinder block jacket takes place merely by thermo-syphon action, there is no such circulation initially, after a cold start. The engine therefore quickly reaches its running temperature. This can be helped by arranging for the water in the warm-up phase to be conveyed around a circuit by-passing the radiator, and thus containing only a small quantity of water.

Although no direct through-flow of the cylinder block occurs, there will be no overheating leading to distortion or lime deposits at running temperature, as a constant exchange of water takes place between the cylinder block and cylinder head jackets by thermo-syphon action.

Any vapour bubbles which may be formed in the cylinder block jacket rise upwards into the cylinder head jacket and reach the direct water circulation channel.

During coasting or partial load running normally a substantial drop in temperature as compared with fuli load running can occur. However, the water which is in the cylinder block and does not participate directly in the cooling circuit through the cylinder head is always strongly heated even in those easy running conditions, and therefore the water temperature of the entire cooling circuit is fully maintained.

As a result of the rapid heating and constant maintenance of the running temperature which can be achieved with this system, not only can the friction losses occurring during a cold start be very rapidly reduced and cold wear and tear be largely prevented, but with changing load states the temperature of the lubricant in the cylinders is kept constant, so that the friction losses of the engine as a whole can be reduced.

In order to ensure that the water flows completely through the cylinder head jacket, the inflow and return connections in the cylinder head are preferably located facing each other. In the case of a liquid cooled internal combustion engine with several cylinders located in series it is advantageous if the inflow connection is located close to the first cylinder and the return connection close to the last cylinder of the line.

For a better understanding of the invention, one embodiment will now be described, by way of example, with reference to the accompanying drawing, in which the single figure is a diagrammatic longitudinal section of a watercooled internal combustion engine, and its associated water circulation system.

The internal combustion engine 1 has a cylinder block 2 and a cylinder head 3. The cylinder block 2 is formed with in-line cylinders in which pistons (not shown) reciprocate, and a water jacket 4 shaped in the normal way. The cylinder head 3 is formed wi.th combustion chambers and valve ports (not shown) and has its own water jacket 5 with an inlet 6 at one end close to the first cylinder and an outlet 7 at the opposite end close to the last cylinder of the line. The jackets 4 and 5 are in co,mmunication with each other through several orifices 8 at the interface between the cylinder block 2 and the cylinder head 3.

A return pipe 9 leads from outlet 7 to a radiator 10, and a further pipe 11 leads from the radiator to one inlet of a thermostatic valve 12. A by-pass 13 branches off pipe 9 and leads to an ther inlet of the valve 12. A circulating pump 14 draws water from the valve 12 and forces it into inlet 6.

The cooling system of the engine operates in the following way: After a cold start, the water circulated by the pump 14 passes through the jacket 5 of the cylinder head 3 and is directed via the pipe 9, bypass 1 3 and thermostatic valve 1 2 back to the pump 14. The thermostatic valve 12 is responsive to the water temperature and at a cold start it blocks the return pipe 11 from radiator 10. The water in the jacket 4 of the cylinder block 2 remains generally stationary and does not penetrate into the jacket 5, which forms part of a direct cooling circuit. During this initial running phase very rapid heating of the cylinder walls occurs so that friction losses are very rapidly overcome and cold wear and tear is reduced to a minimum.Also during this initial phase, the water which flows through the jacket 5 does not include that which is contained in the radiator 10 and pipe 11. Since it is of low volume, the water in this bypass circuit is correspondingly rapidly heated, and therefore so is the cylinder head 3.

As the temperature rises water is passed to an increasing extent from the pipe 11 through the thermostatic valve 12. Finally, when the running temperature is reached, the bypass 13 is blocked and all the water has to flow through the radiator 10 and pipe 11. Overheating of the water in the jacket 4 of the cylinder block 2 is precluded, since that water rises up through the orifices 8 into the jacket 5 and thus penetrates into the direct cooling circuit. Relatively cooler water in the jacket 5 passes down through the orifices 8 into the jacket, the exchange being by thermo-syphon action.

Claims

1. A liquid-cooled internal combustion engine having a cylinder block and a cylinder head, each formed with jackets for coolant liquid and the cylinder head jacket having inflow and return connections for pumped circulation of liquid, wherein the jackets are in communication at the interface of the cylinder head and block via orifices in said head and block, whereby circulation of liquid through the cylinder block jacket is by thermo-syphon action.

2. A liquid-cooled combustion engine as claimed in claim 1, wherein the inflow and return connections are arranged facing each other.

3. A liquid-cooled internal combustion engine as claimed in claim 2, wherein the block has cylinders in line and the inflow connection is adjacent one end and the outflow connection is adjacent the other end of said line.

4. A liquid-cooled internal combustion engine as claimed in claim 1, 2 or 3, in combination with a circulation system including a pump, a radiator and a thermostatic valve responsive to the temperature of liquid in the engine, the valve being arranged to direct the liquid through the pump and cylinder head jacket but not the radiator at low temperatures and progressively to include the radiator in the circulation channel as the temperature rises.

5. A liquid-cooled internal combustion engine substantially as hereinbefore described with reference to the accompanying drawing.