GB2030214A

GB2030214A - Intake air heating systems for turbo- charged compression-ignition internal combustion engines

Info

Publication number: GB2030214A
Application number: GB7837670A
Authority: GB
Original assignee: Vauxhall Motors Ltd
Current assignee: Vauxhall Motors Ltd
Priority date: 1978-09-21
Filing date: 1978-09-21
Publication date: 1980-04-02

Abstract

The space above the fuel 2 in the tank 1 supplying the heater 6 downstream of the compressor 4 is connected to the intake 3 via a solenoid valve 14 energised with the engine starter 33. The valve 14 has lands 25,26 closing fuel supply and return passages 19, 17 when energised. <IMAGE>

Description

SPECIFICATION Starting systems for turbo-charged compressionignition engines This invention relates to sta rting systems for tu rbocharged compression-ignition internal combustion engines, and in particularto systems in which, during a starting operation, fuel is delivered into the engine inlet manifold and is ignited therein by the energization of a glow plug or like heater and igniter element. Such systems are well known under the trade name "Thermostart".

A difficulty which arises with such starting systems in turbo-charged compression-ignition engines, especially in cold conditions, is that the turbo-charger, which comes into operation upon the initiation of the starting operation, may cause the burning fuel in the inlet manifold to be extinguished, may prevent ignition of the fuel, or may cause the fuel to be forced back into the vessel from which it is delivered.

In a starting system for a turbo-charged compress- ion-ignition internal combustion engine according to the present invention, upon the initiation of a starting operation, and during such operation, fuel from an auxiliary reservoir is delivered into the engine intake manifold; an electric heater element in said manifold is energized to effect combustion of said fuel in the manifold; and a normally closed conduit between said manifold and the space above the fuel in said auxiliary reservoir is opened so as to maintain said space at a pressure at least equal to that in said manifold.

The said conduit is preferably opened, as by a solenoid valve, upon the closure of an electric circuit which actuates said heater element upon the initiation of the starting operation.

The fuel from the auxiliary reservoir is delivered to the inlet manifold, in known manner, by the operation of a valve in a conduit from the base of the auxiliary reservoirto the inlet manifold upon the energization of the heater element therein when the starting operation for the engine is initiated.

The auxiliary fuel tank is preferably maintained supplied with fuel by means of an inlet thereto, which is connected to the fuel return line of the engine fuel supply system, and an outlet which is connected to the engine fuel tank, the connections to said inlet and outlet of the auxiliary reservoir respectively having therein valves which are normally open but which are arranged to be closed upon the initiation of the starting operation. This is preferably effected by providing solenoid valves which are operated in conjunction with the aforesaid solenoid valve in the conduit between the manifold and the auxiliary reservoir.

The three valves may conveniently be formed as a single unit comprising a valve housing integral with said auxiliary reservoir and a piston-form or spool valve member which is slidable in a cylindrical bore in the valve housing, the bore having in the wall thereof openings providing communication between the space above the fuel in said auxiliary reservoir and the conduit between the reservoir and the engine inlet manifold and further openings which respectively provide communication between the interior of the auxiliary reservoir and connections to the engine fuel supply return line and to the engine fuel tank, the valve member being spring biased so as normally to close the conduit to the inlet manifold and open the connections to the fuel return line and to the engine fuel tank, and having formations thereon arranged so that, upon the energization of a solenoid operatively connected to said spool valve member the passage between the auxiliary reservoir and the engine inlet manifold is opened, and the passages between the auxiliary reservoir and the engine fuel supply return line and between the auxiliary reservoir and the engine fuel tank are closed.

The arrangement described above ensures that the space in the auxiliary fuel tank above the fuel therein will, during an engine starting operation, be at a pressure at least equal to that in the engine inlet manifold so that the fuel ignited in the inlet manifold during the starting operation will not therefore be extinguished by the high pressure air from the tu rbo-charger, no r wi l l the starter fuel be forced back into the auxiliary reservoir by the increased pressure in the inlet manifold.

In the operation of a "Thermostart" system a switch is moved from an OFF to an ON position in which the heater and igniter element is connected to an electrical supply and, after a delay of, say, 10 seconds, the switch is moved to STARTER position in which the engine starter motor is brought into operation. This brings into operation the fuel pump and, as the engine is cranked, also brings into operation the turbo-charger, which is operated by the gases under pressure which are discharged from the engine exhaust manifold.In the use of the starting system according to the present invention, the operation of the switch to energize the engine starter motor is arranged so as also to energize the solenoid valve which effect the opening of the passage between the auxiliary fuel reservoir and the engine inlet manifold, and close the passages between the auxiliary reservoir and the fuel return line and fuel tank.

One preferred embodiment of the system according to the invention is shown in the accompanying diagrammatic drawings, in which: Figure 1 shows the system with the switch in the ON position, only the heater and igniter element being energized; and Figure 2 shows the system in the STARTING mode, with the heater and ignites, the starter motor and the solenoid valve energized.

The drawings show an auxiliary or header tank 1 arranged in the position required to give a gravita tional flow of the fuel 2 therein to the intake manifold 3 of a compression-ignition engine which is adapted to be turbo-charged by an engine exhaust-driven turbo-charger 4 which delivers air under pressure into the manifold 3.

A pipe 5 delivers fuel from the bottom of the tank 1 to a "Thermostart" device 6 having a heater and ignition coil 7 around a thermo-expansive tubular valve housing 8 carrying a central valve stem 9 the end of which normally holds a ball or like valve member 10 on its seat 11. Upon the expansion of the tube 8 when heated by the coil 7, the valve member 10 is unseated to allow fuel to flow from the pipe 5 into the manifold 3 and be heated and ignited therein by the heater and ignition coil 7.

Formed integrai with the tank lisa housing 12 of a solenoid operated spool valve 14. The valve housing 12 is formed with a longitudinal bore 15 which intersects a first lateral passage 16 in the housing which opens into the tank 1 above the intended fuel level therein. A second transverse passage 17 intersected by the bore 15 opens at one end into the tank 1 at the intended level of fuel therein and at its other end is adapted to be connected to a pipe 18 connected to the vehicle fuel tank. A third transverse passage 19 opens at one end into the tank 1 below the intended level of fuel therein and at its other end is adapted to be connected to the fuel return line of the engine fuel supply circuit.The end wall of the bore 15 has therein a passage 21 the other end of which is adapted to be connected to a balance pipe 22 which opens into the inlet manifold 3 intermediate the turbo-charger 4 and the "Thermostart" device 6.

Slidably mounted in the valve bore 15 is a valve spool 23 which is axially biased by a spring 24 into the position shown in Figure 1 in which lands 25, 26 on the valve spool permit communication between the passages 17, 19 and the pipes 18,20 respectively, while a washer 27 seated in a recess in the upper end face of the spool 23 engages the passage 21 and closes communication between the balance pipe 22 and the passage 16.

Surrounding the lower end of the valve spool 23 is a solenoid coil 30 which, when energized draws the spool 23 downwards into the position shown in Figure 2, in which communication between the balance pipe 22 and the passage 16 is opened, and that between the passages 17 and 19 and the pipes 18 and 20 is closed.

Figure 1 shows a switch 31 in the ON position, in which the heater and igniter coil 7 is energized from a battery 32, but the solenoid valve 14 and starter motor 33 are inoperative, and the balance pipe 22 is closed by the washer 27. Passages 17-18 and 19-20 are open.

Figure 2 shows the switch 31 in the STARTER position in which the passages 17-18 and 19-20 are closed by the energization of the solenoid valve 14, the starter motor is energized, and the balance pipe 22 is opened to equalize the pressure in the manifold 3 and above the fuel 2.

Claims

1. A starting system for a turbo-charged compression ignition engine, in which upon the initiation of a starting operation and during such operation, fuel from an auxiliary reservoir is delivered into the engine intake manifold; an electric heater element in said manifold is energized to effect combustion of said fuel in the manifold; and a normally closed conduit between said manifold and the space above the fuel in said auxiliary reservoir is opened so as to maintain said space at a pressure at least equal to that in said manifold.

2. An engine starting system according to claim 1, in which said conduit is opened by a solenoid valve, upon the closure of an electric circuit which actuates said heater element upon the initiation of the starting operation.

3. An engine starting system according to claim 1 or 2, in which the auxiliary fuel tank is maintained supplied with fuel by means of an inlet thereto which is connected to the fuel return line of the engine fuel supply system, and an outlet which is connected to the engine fuel tank, the connections to said inlet and outlet of the auxiliary reservoir respectively having therein valves which are normally opened but which are arranged to be closed upon the initiation of the starting operation.

4. An engine starting system according to claim 3, in which said valves are solenoid valves operated in conjunction with said solenoid valve in the conduit between the manifold and the auxiliary reservoir.

5. An engine starting system according to claim 4, in which said three valves are formed as a single unit comprising a valve housing integral with said auxiliary reservoir and a piston-form or spool valve member which is slidable in a cylindrical bore in the valve housing, the bore having in the wall thereof openings providing communication between the space above the fuel in said auxiliary reservoir and the conduit between the reservoir and the engine inlet manifold and further openings which respectively provide communication between the interior of the auxiliary reservoir and connections to the engine fuel supply return line and to the engine fuel tank, the valve member being spring biased so as normally to close the conduit to the inlet manifold and open the connections to the fuel return line and to the engine fuel tank, and having formations thereon arranged so that, upon the energization of a solenoid operatively connected to said spool valve member the passage between the auxiliary reservoir and the engine inlet manifold is opened, and the passages between the auxiliary reservoir and the engine fuel supply return line and between the auxiliary reservoir and the engine fuel tank are closed.

6. A starting system for a turbo-charged compression ignition engine, constructed and adapted to operate substantially as hereinbefore described with reference to and as shown in the accompanying drawings.