WO2001063107A1

WO2001063107A1 - Internal combustion engines

Info

Publication number: WO2001063107A1
Application number: PCT/GB2001/000678
Authority: WO
Inventors: Richard Alan Bastable
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-02-23
Filing date: 2001-02-20
Publication date: 2001-08-30
Anticipated expiration: 2002-08-23
Also published as: GB2359589A; GB0004271D0; GB0104104D0; GB2359589B8; GB2359589B; GB2359589A8; AU3388701A

Abstract

An internal combustion engine has an inlet air manifold (24), at least one cylinder (16) having a combustion chamber, spark ignitor (26) and a fuel injector (21), a cylinder head (14) including an inlet valve connecting the inlet air manifold to the or each combustion chamber, and a pressure relief valve (26) connecting the combustion chamber to the manifold (24) and operable to pass to the manifold part of the air/fuel mixture in the combustion chamber if the pressure in the combustion chamber during compression exceeds a maximum desired pressure.

Description

INTERNAL COMBUSTION ENGINES

This invention is concerned with improvements in and relating to internal combustion engines, especially gas injection engincd, and is also concerned with a cylinder head for such engines.

Gas injection engines using liquid petroleum gas (LPG) or compressed natural gas (CNG) are not as thermally efficient as other internal combustion engines as they must have a lower compression ratio and the gas/air mixture in the combustion chamber bums more slowly than does the fuel/air mixture in a petrol or diesel engine. Moreover, gas powered engines have poor cold starting characteristics. However, a major advantage of a gas powered engine is that it is environmentally clean with low pollution exhaust emissions.

It is an object of the present invention to obviate or mitigate these disadvantages while maintaining the low pollution exhaust emissions.

The present invention is an internal combustion engine having an inlet air manifold, at least one cylinder having a combustion chamber, spark ignitor and a fuel injector, a cylinder head including an inlet valve connecting the inlet air manifold to the or each combustion chamber, and a pressure relief valve connecting the combustion chamber to the manifold and operable to pass to the manifold part of the air/fuel mixture in the combustion chamber if the pressure in the combustion chamber during compression exceeds a maximum desired pressure.

The engine may be a gas injection engine. -?-

The spark ignitor and the injector may be mounted in an injector plate intermediate the engine cylinder block and the cylinder head.

The present invention is also a cylinder head for use in an internal combustion engine as defined in either of the last two preceding paragraphs, the cylinder head partly defining at least one combustion chamber and including an inlet valve connecting an air inlet manifold to the or each combustion chamber, and a pressure relief valve connecting the combustion chamber to the manifold and operable to pass to the manifold part of the air/fuel mixture in the combustion chamber if the pressure in the cylinder during compression exceeds a maximum desired pressure.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings, in which:-

Fig. 1 is a partially exploded perspective view of a cylinder head on a cylinder block of an engine according to the present invention; and Fig. 2 is a cross sectional elevation of a gas injector/pressure relief valve.

Referring now to Fig. 1 , a gas injection engine according to the present invention comprises a cylinder block 10 on which is mounted an intermediate injection plate 12 and a cylinder head 14.

The cylinder block 10 is conventional and defines six cylinders in line, though these are not visible in Fig.1. and the cylinder head 14 at least partly defines a combustion chamber at the -

top of each cylinder. The injection plate 12 has six holes 16 aligned with respect e cylinders in the cylinder block, the holes 16 lengthening or forming extensions of the combustion chambers.

At one side of the plate 12 are six solenoid controlled valves 18, one for each cylinder. The valves 18 receive the pressurised liquid fuel, which may be either liquid petroleum gas (LPG) or compressed natural gas (CNG), from a line 19 and it passes from each valve 18 to a respective injector 20 for each combustion chamber at an appropriate point in the cycle of that cylinder. The amount of gas injected into the cylinders and the timing of the injection is controlled by conventional engine control means in accordance with the required engine speed and power.

At the other side of the plate 12 are provided, for each cylinder, an electrical connection

21 for a spark plug or other spark ignitor. the timing of the spark at each plug again being controlled by the engine control means.

The cylinder head 14 has an inlet air manifold 24 which receives air through an inlet pipe

22 and is connected to the combustion chambers through conventional valves 26 which open under the control of the engine control means at the start of the induction stroke.

Each valve 26, as seen in Fig. 2, has a body 30 on which is mounted a head 31 and in which are defined an outlet passage 34. The outlet passage 34 contains a relief valve 42 which is operated by electrical means to open during the compression stroke if the pressure in the cylinder exceeds a predetermined value corresponding to the maximum desired compression ratio in the cylinder, but is held shut during the ignition stroke. When the valve 42 is open during the compression stroke, excess air/fuel mixture is bled from the cylinder and passes through a one way valve and a cryocooler to the inlet manifold where it mixes mixed with fresh incoming air. The cryocooler is effectively a heat exchanger in which the hot excess mixture from the combustion chamber is cooled by. and inturn heats, the fuel gas before it passes through the line 19 to the valves 18. Instead of electrical means operating the valves 42, mechanical means could also be employed.

It can thus be seen that the compression ratio in the cylinders can be controlled by the engine control means operating the valves 42, and this control, in addition to the normal controls of mixture richness and timing allows the engine to be operated veiy efficiently.

The engine described may be a petrol engine, or more especially a diesel engine, modified to use gas as its fuel by having the cylinder head and the injection plate mounted on the original cylinder block; the added control of the compression ratio provided by the present invention allows the ratio to be reduced to the appropriate value without having to make to the engine more fundamental changes such as altering the stroke of the pistons. Control of the compression ratio may be exercised continuously if the valves 42 are operated electrically, or may be fixed for a given set-up if the control of the valves is mechanical. This flexibility allows an engine to be modified for use with iiferent fueis requiring uinerent optimum compression ratios. Tn m Λrϋ" ir»αtι nn nf Axπt i αnrl t t >

cylinder head is provided with spark ignitors in a conventional fashion. In this case the valve 26 of Fig. 2 has. in addition to the outlet passage 34 previously described, an inlet passage 32 through which fuel gas, which may be in a liquid or gaseous state, is passed to the combustion chamber through a valve 40 controlled, in this modification, by a solenoid 34. The inlet passage 32 is surrounded by an annular insulating space 33 which is preferably a vacuum.

The engine may have any number of cylinders and the various valves may be of any suitable type and may be controlled by any appropriate control means or system. It should also be understood that references to fuel being "gas" include the petroleum or natural gas in a liquid state.

Claims

l . AΠ internal comoustion engine naving an liuet air mannoiα. at least one cyunαer naving a combustion chamber, spanc ignitor anu a luei injector, a c linder head including an inlet vαive connecting tne iniet air niiOiu to mc or eacn con uustion Cuαn uer, nu a pressure f i o/iliiαcfi i vfuliivrαvy t

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combustion chamber during compression exceeds a maximum desired rtressure.

2. An engine as claimed in claim 1. in which the engine is a gas injection engine.

3. An engine as claimed in claim 1 or claim 2, in which the spark ignitor and the injector are mounted in a plate intermediate the engine cylinder block and the cylinder head.

4. An engine as claimed in claim 2 or claim 3. in which the plate includes a valve connecting a fuel line to each respective injector.

5. An engine as claimed in any preceding claim, in which the cylinder head includes a cryocooler in which hot gas from the pressure relief valve is cooled by fuel gas.

6. A σas in'ection en^gine substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

7. A cylinder head for use in a gas injection engine as defined in either of the last two preceding paragraphs, the cylinder head partly defining at least one combustion chamber and including an inlet valve connecting an air inlet manifold to the or each combustion chamber, and a pressure relief valve connecting the combustion chamber to the manifold and operable to pass to the manifold part of the air/gas mixture in the combustion chamber if the pressure in the cylinder during compression exceeds a maximum desired pressure.