FR2783019A1 - Fuel feed for motor vehicle internal combustion engine has main pump feeding distribution tank connected to cylinder injectors - Google Patents

Abstract

The invention proposes a circuit (10) for supplying liquid fuel to a combustion engine of a motor vehicle, in particular a gasoline direct injection engine, of the type comprising at least a first pump (14) which draws the fuel. fuel in a tank (12) and which delivers it to a fuel distribution network (18, 26, 28) towards the various combustion chambers of the engine, characterized in that it comprises an automatic purge device (38) gases contained in the fuel which is arranged in parallel to the distribution network and which is located vertically above the highest point (40) of the network.

Description

FUEL SUPPLY CIRCUIT

FOR INTERNAL COMBUSTION ENGINE

  The present invention relates to a fuel supply circuit for an internal combustion engine intended in particular for equipping a vehicle.

automobile or road.

  The invention relates more particularly to a high pressure fuel supply circuit,

  1o in particular in petrol, of a direct injection engine.

  According to a known general design, the supply circuit comprises at least a first pump which draws fuel from a fuel tank and which discharges it into a fuel distribution network in the direction of the different

combustion of the engine.

  When the fuel supply circuit, in particular for petrol, is a high pressure circuit, it may include a first low pressure supply pump which delivers the fuel towards the inlet of a second high pressure pump, the outlet of which delivers the fuel into a supply chamber which is for example an internal supply chamber common to different injectors of

  fuel and which is formed in an injection manifold.

  The regulation of the injection pressure is generally ensured at the level of the injection rail and thus all the flow of liquid fuel coming from the tank "sweeps" the bubbles of gas, and in particular of air, contained in the circuit before return to the tank. When the engine is started for the first time, or after a breakdown requiring intervention on the fuel supply circuit, and when the regulation is mechanical regulation, the pressure build-up in the injector rail supply circuit may take several tens of seconds, that is to say the time to compress all the air contained in the circuit. When the circuit is equipped with electronic regulation, a time delay can then be activated to allow the air contained in the fuel supply circuit to be purged, and

  especially in the high pressure part of the circuit.

  In general, any presence of air or gas trapped in the fuel supply circuit is harmful, especially if we consider the generalization of the supply circuits without return to the tank in order to avoid otherwise warming up

fuel in the tank.

  If we suppress the return of fuel to the tank, it becomes impossible to evacuate the purged air to the tank and the rise time in

  pressure is further increased.

  The object of the invention is to remedy the drawbacks which have just been mentioned by proposing a liquid fuel supply circuit of the type defined above, characterized in that it comprises an automatic device for purging the gases contained in the fuel which is arranged in parallel to the distribution network and which is located vertically

  above the highest point of the network.

  According to other characteristics of the invention - the distribution network comprises a supply ramp for several fuel injectors which delimits a common internal supply chamber, and the highest point of the network is the highest point of the feed chamber; the automatic purge device has an inlet opening for the fuel-gas mixture which is connected to the highest point of the network and an outlet opening for the purged gases which is connected to the fuel tank or to a device for filtering the purged gases ; the automatic purge device comprises a body which delimits a control cylinder in which a control piston is slidably mounted in order to delimit in leaktight manner a main rear control chamber which is connected directly to the inlet port of the device and a auxiliary front control chamber which is connected to the inlet orifice of the device by a purge duct of reduced passage cross section, the inlet of which is connected to the inlet of the device and the outlet of which is connected to the auxiliary control chamber which has an outlet orifice connected to the outlet orifice of the device and which is capable of being closed by a closure member carried by the piston when the latter slides from back to front, against a tared elastic return force, under the action of a positive pressure difference between the main and auxiliary control chambers; The closing member is a needle coaxial with the piston, the free front end of which is capable of cooperating with a seat formed by the outlet orifice formed in the transverse face of the front end of the cylinder; The elastic return force of the piston is applied to the latter by a helical compression spring interposed between the front face of the piston and the transverse face of the front end of the cylinder; - The axis of the cylinder of the automatic purge device is arranged substantially vertically; the first pump is a low pressure pump which delivers fuel to a second high pressure pump which supplies fuel

in the feed ramp.

  Other features and benefits of

  The invention will appear on reading the description

  detailed below for the understanding of which reference will be made to the accompanying drawings in which: - Figure 1 is a schematic view of the main components of a fuel supply circuit of a combustion engine with direct injection of petrol for motor vehicle produced in accordance with the teachings of the invention; - Figure 2 is a schematic view on a large scale and in axial section of the automatic device for purging the supply circuit according to the invention which is illustrated in the gas purge position; and - Figure 3 is a view similar to that of Figure 2 in which the automatic purge device is illustrated in the closed position, that is to say after the

  bleeding of the gases contained in the fuel.

  In a known manner, the fuel supply circuit 10 of a direct petrol injection engine (not shown) comprises a reservoir 12 from which a first pump is drawn.

  low pressure 14 driven by a motor 16.

  A pipe 18 connects the discharge port of the low pressure pump 14 to the inlet port of a

second high pressure pump 17.

  1s A filter 20 is interposed in the line 18 and a line 22, arranged as a bypass on the line 18, makes it possible to regulate the low pressure value of the fuel by means of a

  regulator 24 of known general design.

  The high pressure pump 17 is rotated to discharge high pressure fuel inside a common supply chamber 26 which, in known manner, is formed inside a

fuel rail 28.

  Chamber 26 is connected to injectors 30, here four in number, which are illustrated

schematically in the figure.

  The regulation of the high pressure fuel value is ensured by means of a regulator 32, of known general design, which is associated with a pressure sensor 34 and which is mounted in a return line 36 which opens into the main line d supply 18 downstream of the filter 20 and upstream of the high pressure pump 17. In accordance with the teachings of the invention, the circuit 10 comprises a device 38 which is an automatic device for purging gases, in particular the air contained in the fuel circulating in the circuit 10. According to a characteristic of the invention, the automatic purge device 38 is arranged vertically above the highest point of the network 28, 30 for distributing fuel to the combustion chambers of the engine which, in the preferred embodiment of the invention illustrated in the figures,

  is the highest point 40 of the injection manifold 28.

  Thus, this point 40 is connected to an orifice 42 of the automatic purge device 38 and to the pipe

  return 36 downstream from regulator 32.

  The automatic purge device 38 will now be described in more detail with reference to FIGS. 2 and 3. The automatic purge device 38 illustrated diagrammatically in FIGS. 2 and 3 is essentially constituted by a body 44 inside which is formed a control cylinder 46 which is preferably

  oriented with its X-X axis vertically.

  The cylinder 46 is delimited vertically downwards by a transverse rear end face 48 and vertically upwards by a transverse face

front end 50.

  A piston 52 is slidably mounted in the cylinder 46 to delimit there a rear main control chamber 54 and an auxiliary front chamber

56.

  The main control chamber 54 is connected to the orifice 42 for the arrival of the fuel-gas mixture by an axial duct 58 which opens into the face

  transverse rear end 48 of cylinder 46.

  The upper end 60 of the conduit 58 constitutes the inlet orifice of the rear main chamber of

i5 command 54.

  The body 44 comprises an axial duct 62 whose upper end 64 constitutes the orifice for the departure of the purged gases and which is connected by a pipe 66 to the fuel tank, or to a filtration device also called a "canister" before rejecting purged gases

towards the atmosphere.

  The lower end 68 of the conduit 62 opens axially in the transverse front end face of the cylinder 46 and it constitutes the outlet orifice of

  the auxiliary control chamber 56.

  The body 44 also includes a purge duct whose inlet end 72 is connected to the inlet orifice 60 of the main control chamber 48, that is to say to the latter, and whose outlet 74 opens radially into the auxiliary chamber of

command 56.

  The piston 52 is biased elastically, here vertically downwards, by a helical compression spring 76 which is interposed between the front transverse face 78 of the piston 52 and the transverse front end face 50 of the auxiliary control chamber 56, of so as to apply a calibrated elastic restoring force of the piston 52 to its lo rest position, which is also the purge position, in which its rear transverse face 80 is in axial abutment against the transverse end face

rear 48 of cylinder 46.

  The piston 52 carries a member for closing the outlet orifice 68 which here is a needle 82 coaxial with the piston 52, the conical front free end 84

  extends opposite the outlet orifice 68.

  In the rest position illustrated in Figure 2, the outlet port 68 is open, that is to say that the outlet end 74 of the purge duct 70 communicates with the duct 62 through the auxiliary chamber of control 56 while, in the closed position illustrated in FIG. 3, the outlet 68 is closed, thus preventing any communication between

  the auxiliary control chamber 56 and the conduit 62.

  The automatic purge device 38 is designed to operate as a function of the positive pressure difference existing between the main control chamber 48 and the auxiliary control chamber 56 taking into account the density difference existing between the liquid fuel on the one hand and the gases contained in it, that is to say

especially the air.

  s In order to take account of this difference in density, the purge duct 70 has a reduced passage section and it preferably comprises a throttling device 90 interposed in the duct

purge 70.

  o0 We will now describe the functioning of the

automatic purge device 38.

  The operating principle of the device consists in letting the gases, and in particular the air, pass, and

block the fuel.

  When the engine is started, the low pressure pump 14 is started and the air possibly contained in the circuit 10 is "pushed" by the fuel to the orifice 42 for the arrival of the fuel-gas mixture. , then through the purge duct 70

  up to the orifice 64 for the start of the purged air.

  The air discharged in the direction of the device 38 naturally acts on the rear face 80 of the piston 52 and it passes through the throttling device 90. Due to the low density of the air, the difference in pressure on the part and other of the throttle device 90 is very reduced and the net force exerted on the piston 52 by the air is insufficient to overcome the tared return force exerted by the spring 76 which maintains the piston 42 in its position rest illustrated in Figure 2, that is to say in a position allowing the evacuation of the purged air

  through the auxiliary chamber 56 and the conduit 62.

  After having expelled and purged the air, when the fuel arrives at the inlet orifice 42 of the automatic purge device 38, it circulates in the duct 70 and through the throttle device 90 which, due to the density liquid fuel, causes a significant pressure difference between the main chamber 80 and the auxiliary control chamber 56. This pressure difference applied to the piston 52 is greater than the calibrated restoring force applied by the spring 76 and it occurs then a vertical displacement of the piston 52 up to its position illustrated in FIG. 3 in which the conical end 84 of the needle 82 closes the outlet orifice 68, thus avoiding

  any fuel escaping through line 62.

he

Claims (8)

  1. Circuit (10) for supplying liquid fuel to a combustion engine of a motor vehicle, in particular to a direct gasoline injection engine, of the type comprising at least a first pump (14) which draws fuel from a tank (12) and which discharges it into a network (18, 26, 28) for distributing the fuel in the direction of the different combustion chambers of the engine, characterized in that it comprises o an automatic device (38) for purging gases contained in the fuel which is arranged in parallel to the distribution network and which is located vertically   above the highest point (40) of the network.   2. Circuit according to the preceding claim, is characterized in that the distribution network comprises a ramp (28) for supplying several fuel injectors (30) which delimits an internal supply chamber (26), and in that that the highest point (40) of the network is the highest point of the supply chamber (26).   3. Circuit according to any one of   previous claims, characterized in that the   automatic purge device (38) comprises an opening (42) for the fuel-gas mixture which is connected to the highest point of the network and an orifice (64) for the departure of purged gases which is connected to the fuel tank   or to a device for filtering the purged gases.   4. Circuit according to the preceding claim, characterized in that the automatic purge device (38) comprises a body (44) which delimits a control cylinder (46) in which a control piston (52) is slidably mounted to delimit a rear main control chamber (54) which is directly connected to the inlet port (42) of the device (38) and an auxiliary front control chamber (56) which is connected to the inlet port (42) of the device (38) by a purge duct (70) of reduced passage cross-section, the inlet (72) of which is connected to the inlet orifice (42) of the device and the outlet (74) of which is connected to the auxiliary control chamber (56) which has an outlet orifice (68) connected to the starting orifice (64) of the device (38) and which is capable of being closed by a closing member (82, 84) carried by the piston (52) when the latter slides from rear to front, against a calibrated elastic force of ra ppel (76), under the action of a positive pressure difference between the chambers   main (54) and auxiliary (56) control.   5. Circuit according to the preceding claim, characterized in that the closing member (82) is a needle coaxial with the piston (52) whose free front end (84) is capable of cooperating with a seat formed by the orifice outlet (68) formed in the face   transverse front end (50) of the cylinder (46).   6. Circuit according to any one of   claims 4 or 5, characterized in that the effort   elastic return piston (52) is applied to the latter by a helical compression spring (76) interposed between the front face (78) of the piston and the face   transverse front end (50) of the cylinder (46).   7. Circuit according to any one of   Claims 4 to 6, characterized in that the axis (X-X)   of the cylinder of the automatic purge device (38) is arranged substantially vertically.   8. Circuit according to claim 2, characterized in that the first pump (14) is a low pressure pump which discharges the fuel towards a second high pressure pump (17) which discharges the   fuel in the fuel rail (26, 28).