FR2796988A1 - IMPROVED SUPPLY CIRCUIT - Google Patents

Abstract

The invention proposes a circuit (10) for supplying an engine comprising an air injection circuit (14) and a fuel injection circuit (12) (26) which comprises at least, in series of upstream downstream, a tank (16), a low pressure pump (18), a filter (20) and at least one fuel injector (22), of the type in which the air injection circuit (14) comprises , in series from upstream to downstream, a filter (30), an air compressor (32) and an air injector (34), and of the type in which a member (38) for limiting the fuel pressure (26) interposed between the filter (20) and the injector (22) can regulate the flow of fuel (26) when its pressure reaches a determined maximum value, characterized in that the member (38) for limiting the pressure valve has a valve (70) which is controlled by the air pressure downstream of the compressor (32) so as to stop the flow of fuel (26) when the fuel pressure (26) passing through the valve (70) ) reaches the determined maximum value.

Description

B530 "Improved supply circuit" The invention relates to a circuit

supply in

  fuel mixture for a motor vehicle engine.

  The invention relates more particularly to a fuel mixture supply circuit of a motor vehicle engine, of the type which includes a fuel injection circuit and of an air injection circuit, of the mixed type in which the circuit fuel injection system comprises at least, mounted in series from upstream to downstream, a tank, a low pressure fuel io pump, a filter and at least one fuel injector, of the type in which the fuel injection circuit air comprises at least, mounted in series from upstream to downstream, a filter, an air compressor and an air injector, and of the type in which a member for limiting the fuel pressure, which is interposed between the filter and the injector, is capable of regulating the flow of fuel when the pressure of the latter reaches a determined maximum value, which corresponds to the value of the air pressure downstream of the compressor, increased

  of a determined constant differential pressure.

  We know many examples of circuits

fuel injection.

  Conventionally, these are circuits in which a liquid fuel circulates which is sent under a determined pressure into an injection manifold which supplies injectors associated with each of the combustion chambers of the engine. The injection manifold comprises means for regulating the fuel pressure which allow excess fuel to return to a vehicle storage tank. Some of these circuits are mixed circuits which also include an air injection system in order to improve the atomization of the fuel in the combustion chambers B530 of the engine. In such circuits, the fuel injectors inject the fuel into air injectors which are supplied by an air compressor and which, in turn, inject

  the fuel mixture in the combustion chamber of the engine.

  In supply circuits of this type, the air pressure is regulated according to a pressure of constant value, and the value of the fuel pressure corresponds to the value of the air pressure downstream of the compressor, increased by a

  determined differential constant pressure.

  io To regulate the fuel pressure, use has hitherto been of organs for limiting the fuel pressure, that is to say organs for limiting the pressure difference between the air and the fuel, which are interposed in the fuel supply circuit between the

filter and injector rail.

  Such a fuel pressure limiting device is capable of diverting part of the fuel, which circulates from the filter to the injector in the fuel injection circuit, in the direction of the vehicle's fuel storage tank when the value of fuel pressure may exceed that of the air pressure downstream of the compressor

  increased by the determined constant differential pressure.

  The disadvantage of such a supply circuit is to include a fuel return circuit to the tank of the

vehicle.

  Indeed, the heating of fuel under pressure in return tends to favor its evaporation and requires the installation of an activated carbon filter, or "canister", which is intended to ensure the recovery of residual fuel vapors. In certain embodiments of this solution, the fuel is returned to the air intake of the engine during restart. This solution has the disadvantage of B530. require a large volume canister, since the volume of gas recovered is generally large. This makes the canister of an inappropriate size for its compact layout

in a private vehicle.

  In addition, the return of fuel requires the installation under the vehicle of costly and bulky return lines. To overcome these drawbacks, the invention proposes a supply circuit without a return circuit from

io fuel.

  To this end, the invention proposes a supply circuit

  tion in a fuel mixture of the type described above, characterized in that the fuel pressure limiting member comprises a valve which is interposed between the is filter and the injector and which is controlled by the air pressure downstream of the compressor so as to interrupt the flow of fuel when the fuel pressure passing through the

  valve reaches the determined maximum value.

  According to other characteristics of the invention - the valve is controlled by a substantially axial pressure housing which comprises a first axial pressure chamber supplied with air and a second axial pressure chamber supplied with fuel which are delimited by the walls of the housing pressure and by a common transverse movable wall of which a first face, facing the first air pressure chamber, is supported on an axial elastic element linked to a wall of the first air pressure chamber to oppose at the fuel pressure, and of which a second face, facing the second chamber of

  fuel pressure, has an axial actuation rod

  valve, B530 - the axial elastic element is a spring which bears on a transverse bottom of the first air pressure chamber of the pressure box, and which is calibrated according to a stiffness corresponding to the determined constant differential pressure , - the valve comprises the second pressure chamber inside which the fuel circulates, - the second fuel pressure chamber comprises a fuel inlet orifice, which is capable of being closed by a valve controlled by the axial valve actuation rod, and a fuel outlet pipe, - the shut-off valve of the fuel inlet orifice is arranged outside the pressure box, - the axial rod of actuation of the valve protrudes from the pressure box to control the shut-off valve of the fuel inlet port, - the fuel inlet port coincides with a fuel outlet port of a box ier axial cylindrical shutter which is fixed externally to the pressure box, a first wall of which comprises the fuel inlet duct connected to the fuel circuit downstream of the filter to allow the admission of fuel, and of which a second frustoconical wall comprises the fuel fuel outlet orifice of the housing, which is crossed by the axial actuating rod of the valve, a ball of a diameter substantially equal to an average diameter of the frustoconical wall being biased on the one hand resiliently against it and, on the other hand, pressing on the free end of the axial valve actuating rod to constitute the shut-off valve of the fuel inlet orifice of the housing, B530 - the pressure air is regulated downstream of the compressor

  by an independent pressure regulator.

  Other characteristics and advantages of the invention

  will appear on reading the detailed description which follows

  for the understanding of which reference will be made to the accompanying drawings in which: - Figure 1 is a schematic view of a supply circuit according to the state of the art; - Figure 2 is a schematic sectional view of a fuel pressure limiting member for a supply circuit according to Figure 1; - Figure 3 is a schematic view of a supply circuit according to the invention; - Figure 4 is a schematic sectional view of an i5 fuel pressure limiting member for a fuel system, according to the invention, according to Figure 3, shown in the position in which it allows the circulation of fuel; and - Figure 5 is a schematic sectional view of a fuel pressure limiting member for a fuel system, according to the invention, according to Figure 3, shown in the position in which it interrupts the

fuel circulation.

  In the description which follows, figures of

  identical reference designates identical parts or having

similar functions.

  FIG. 1 shows a conventional circuit 10 for supplying a fuel mixture for a vehicle engine.

automobile (not shown).

  In known manner, the circuit 10 for supplying a fuel mixture comprises a circuit 12 for injecting

  fuel and an air injection circuit 14.

  B3530 The fuel injection circuit 12 comprises at least, mounted in series from upstream to downstream, a fuel tank 16 inside which is arranged a low pressure pump 18, a filter 20 which is connected to an outlet of the low pressure pump 18, and at least one fuel injector 22. In known manner, such a fuel injection circuit 12 adapted to a heat engine comprising several combustion chambers (not shown), in particular comprises a ramp 24 for supplying the injectors 22 of

0o fuel.

  The low pressure pump 18 of the fuel storage tank 16 is in particular a pump 18 which is immersed in the fuel 26 and which comprises a member 28 for regulating its outlet pressure. The member 28 of regulating the outlet pressure of the pump 18 may in particular be a valve arranged at the outlet of the low pressure pump 18 and which is capable of opening when the pressure at the outlet of the low pressure pump 18 exceeds a

threshold value determined.

  The air injection circuit 14 comprises, mounted in series from upstream to downstream, a filter 30 which is intended to filter the intake air. The intake air is then compressed in a

  compressor 32 which supplies at least one air injector 34.

  Preferably, the vehicle engine has as many

  air injectors 34 than fuel injectors 22.

  Obtaining the fuel mixture intended to allow the engine of the vehicle to operate can be obtained from

different ways.

  According to a first design, it is known to have a fuel injector 22 and an air injector 34 in each combustion chamber of the engine so that the fuel mixture takes place directly in the combustion chamber. According to another design (not shown), it is also known to inject the fuel, by means of the fuel injectors 22, into the air circuit 14 upstream of the air injectors 34. each combustion chamber of the engine comprising only an air injector 34 which directly injects the fuel mixture into the combustion chamber. In a known manner, the pressure of the air leaving the compressor 32 is regulated by a member 36 for limiting the air pressure. This member 36 may for example consist of a valve which is resiliently biased against its seat and whose elastic return means are calibrated so that it opens at a determined threshold value of the air pressure, and then causes the air to escape from the air injection circuit. The air pressure is therefore

  constant at the outlet of the air injectors 34.

  In known manner, the fuel injection circuit 12 comprises a member 38 for limiting the fuel pressure, which is interposed between the filter 20 and the ramp 24 for supplying the fuel injectors 22. The fuel pressure limiting member 38 is capable of regulating the fuel flow 26 so as to drop the fuel pressure when it reaches a determined maximum value, which corresponds to the value of the air pressure in downstream of compressor 32, increased by a pressure

  constant differential determined.

  As illustrated in FIG. 2, such a member 38 for limiting the fuel pressure comprises a substantially axial housing 40 which comprises a first chamber 52 for air pressure and a second chamber 54 for B530 fuel pressure isolated from one another. the other. The second fuel pressure chamber 54 has a fuel inlet duct 42 which is connected to the outlet of the filter 20 described above, a fuel outlet duct 44 to which the injector manifold 24 is connected, and a valve 46 return pipe which is connected to the fuel storage tank 16 26 via a return pipe 48 shown in FIG. 1. The device 38 for limiting the fuel pressure io is capable of diverting the circulation fuel 26 when the fuel pressure passing through the valve 46 reaches the determined maximum value corresponding to the value of the air pressure downstream of the compressor 32, that is to say the air pressure prevailing in the chamber of air pressure 52, increased by the determined constant differential pressure. In known manner, the valve 46 is integrated into the housing 40 of the member 38 for limiting the fuel pressure. To this end, the fuel return valve 46 comprises a movable membrane 50, which separates the interior volume of the housing 40 according to the first air pressure chamber 52 and the second fuel pressure chamber 54. The movable diaphragm 50 has a first face 58, facing the air pressure chamber 52, which is resiliently biased against the pressure forces of the fuel flowing in the opposite fuel pressure chamber 54, and a second face 56, facing the second fuel pressure chamber 54 which is susceptible

  shut off the fuel return line 48 to the tank.

  In particular, a spring 62 exerts on the first face 58 of the membrane 50 the elastic return action corresponding to the value of the differential pressure which one B530 wishes to maintain between the air pressure and the fuel pressure. So that the fuel line 48 can be closed by the membrane 50, the latter is arranged substantially coaxially with the housing 40 and penetrates inside the second fuel pressure chamber 54 so that its end 64 is flush with the second face 56 of the membrane when the latter is in the rest position, as shown

in Figure 2.

  o0 The first air pressure chamber 52 is supplied with air by an air inlet duct 60 which is supplied by pressurized air taken downstream from the compressor 32, and the fuel inlet duct 42 and the fuel outlet pipe 44 and the second fuel pressure chamber 54 both open into the second chamber 54 of

fuel pressure.

  In this way, as long as the fuel pressure 26 which circulates in the second fuel pressure chamber 54 is less than the joint pressures exerted by the spring 62 and by the air pressure within the first pressure chamber 52 d air on the first face 58 of the membrane, the latter is in a rest position and seals the end 64 of the fuel return duct 48. The fuel then circulates normally in the second fuel pressure chamber 54, from the inlet duct 42 to the outlet duct 44. When the fuel pressure 26 which circulates in the second fuel pressure chamber 54 and which is exerted on the second face 56 of the membrane 50 tends to be greater than the joint pressures exerted by the spring 62 and by the pressure of the air on the first face 58 of the membrane 50, the fuel pressure 26 pushes the -B530 membrane 50 towards the first air pressure chamber 52, and thus takes it off from the upper opening 64

  of the fuel return line 48.

  Part of the fuel 26 which circulates in the second fuel pressure chamber 54 is then deflected in this fuel return conduit 48, which has the effect of instantly causing the fuel pressure to drop in the second fuel pressure chamber 54 and again cause a plugging of the end 64 of the conduit 48 of

  io return of fuel through the membrane 50.

  The drawback of such a circuit 10 for supplying a fuel mixture mainly resides in the existence of the conduit 48 for returning fuel to the tank 16 which is on the one hand bulky, and which on the other hand entails, during the manufacture of the vehicle comprising such a circuit 10, an additional cost

Manufacturing.

  To overcome this drawback, the invention provides a circuit 10 for supplying a fuel mixture such as

shown in Figure 3.

  The circuit 10 for supplying a fuel mixture according to the invention is analogous to that described above with reference to FIG. 1, except that it does not include a fuel return conduit similar to the conduit 48 previously described, and in which it comprises a fuel pressure limiting member 38 which is intended to interrupt the circulation of fuel 26 between the filter 20 and the injector supply manifold 22 when the fuel pressure 26 which passes through it reaches the maximum value

previously determined.

  In this way, it is possible to prevent fuel overpressure 26 from prevailing in the injector supply ramp 24 by interrupting the circulation of fuel g530 II 26 in the fuel injection circuit 12, without calling upon to a fuel diversion through any

  fuel return, fuel pressure 26 dropping

  even as the fuel 26 is consumed by the fuel injectors 22. As illustrated in FIGS. 4 and 5, the fuel pressure limiting device 38 produced in accordance with the invention comprises, in a similar manner to the fuel pressure limiting device 38 previously described, the o0 substantially axial pressure housing 40 which includes the first axial air pressure chamber 52 divided by the membrane 50 along the first air pressure chamber 52

  52 and the second fuel pressure chamber 54.

  The first axial air pressure chamber 52 is delimited by the first face 58 of the membrane 50 and by the walls of the pressure housing 40, and the second axial fuel pressure chamber 54 is delimited by the second face 56 of the membrane 50 and through the walls of the housing

pressure 40.

  The first face 58 of the membrane 50, turned towards the side of the first axial air pressure chamber 52, is supported on one end of the spring 62 which is also supported on a bottom wall 66 of the first air pressure chamber 52 and the second face 56 of the membrane 50, turned towards the side of the second fuel pressure chamber 54 is rigidly linked to a rod 68 for actuating a valve 70 for interrupting the circulation of the fuel whose operation will be described later, which is external to the housing 40 and which feeds the second chamber

  54 fuel pressure thereof.

  The air inlet duct 60 opens into the bottom wall 66 of the first air pressure chamber 52, B530 coaxial therewith. The fuel inlet duct 42 is arranged at the inlet of the valve 70 opposite its part which opens into the second fuel pressure chamber 54. In this way, as will be seen later, the actuation of the valve 70 selectively allows the passage of the fuel or the interruption of the circulation of the fuel. In a manner analogous to the design of the state of the art, the spring 62 is calibrated according to a corresponding stiffness io at a determined constant differential pressure which must be maintained between the air pressure which prevails in the pressure chamber d 52 and the fuel pressure prevailing in the second pressure chamber 54

fuel.

  In the preferred embodiment of the invention, and without limitation thereof, the valve 70 is coaxial with the housing 40 and a port 72 for the fuel outlet of the valve coincides with a port 74 for the fuel inlet of the second fuel pressure chamber 54. The fuel inlet orifice 74 can be closed by the valve 70 in response to a movement of the rod 68

actuating valve 70.

  In fact, the valve 70 comprises a cylindrical axial shutter housing 71 which is mounted coaxially with the housing 40. The rod 68 for actuating the valve 70 is also coaxial with the housing 40 and passes through the inlet orifices 74 of the second chamber 54 for fuel pressure and outlet 72 of the valve 70 to penetrate inside the axial cylindrical shutter box 71. The rod 68 controls the actuation of a valve 76 which is arranged inside the element.

valve 70.

  B530. The valve 76 inside the valve 70 consists of a ball 78 which is capable of closing the orifice 72 at the outlet of the shutter housing 71. To this end, one end of the shutter housing 71 which comprises the orifice 72 has an inner frustoconical bearing 82 with a diameter substantially corresponding to that of the ball 78, the end diameter of which coincides with the orifice 72 of outlet from the shutter box. The ball 78 can be resiliently biased against the frustoconical bearing 82 by a spring 1o 84, which bears on the ball 78 and on an inner wall 86 opposite an opposite end 88 of the housing 71. This opposite end 88 of the housing 71 comprises the fuel inlet duct 42. The ball 78 can be pushed back against the spring 84 by the free end of the rod 68 for actuating the valve 70 which passes through the outlet orifice

  72 and therefore the frustoconical bearing 82.

  In this way as illustrated in FIG. 5, when the fuel pressure reaches the determined maximum value, this pressure pushes the diaphragm 50 towards the air pressure chamber 52 against the spring 62 inside said first chamber 52 of air pressure, which has the effect of retracting the actuating rod 68 in the second fuel pressure chamber 54 and of allowing the spring 84 to push the ball 78 against the frustoconical bearing 82 by closing the orifice 72 exit

shutter housing 71.

  Fuel circulation is then interrupted in

valve 70.

  However, the fuel contained in the second fuel pressure chamber 54 being consumed by the injectors 22 as the vehicle engine operates, the closing of the valve 70 has the consequence of causing B530 to drop the fuel pressure to inside the second

  fuel pressure chamber 54.

  In this way, as illustrated in FIG. 4, when the fuel pressure has dropped sufficiently inside the second fuel pressure chamber 54, the air pressure inside the first pressure chamber 52 air, combined with the action of the return spring 62 pushes the membrane 58 towards its rest position and pushes the actuating rod 68 so that the ball 78 is again 1o detached from the frustoconical bearing 82. The valve 76 is then opened again and the flow of fuel through the valve 70 resumes from the fuel inlet duct 42 to the

fuel outlet line 44.

  Thus, the invention makes it possible to have a circuit 10 i for supplying a fuel mixture which has simple and inexpensive regulation of the fuel pressure.

26 upstream of the injectors 22.

B530

Claims (9)

  1. Circuit (10) for supplying a fuel mixture to a motor vehicle engine, of the type which comprises a fuel injection circuit (12) (26) and an air injection circuit (14), of the mixed type in which the fuel injection circuit (12) comprises at least, mounted in series from upstream to downstream, a tank (16), a low pressure fuel pump (18), a filter (20) and at least one fuel injector (22), of the type in which the air injection circuit (14) comprises at least, mounted in series from upstream to downstream, a filter (30), a compressor (32) of air and an air injector (34), and of the type in which a member (38) for limiting the fuel pressure (26), which is interposed between the filter (20) and the injector (22) , is capable of regulating the fuel flow (26) when the pressure of the latter reaches a determined maximum value, which corresponds to the value of the air pressure downstream of the compressor (32), increased by a pressure determined constant differential, characterized in that the member (38) for limiting the fuel pressure comprises a valve (70), which is interposed between the filter (20) and the injector (22), and which is controlled by the air pressure downstream of the compressor (32) so as to interrupt the flow of fuel (26) when the fuel pressure (26) passing through the valve   (70) reaches the determined maximum value.   2. Supply circuit (10) according to the preceding claim, characterized in that the valve (70) is controlled by a housing (40) of substantially axial pressure which comprises a first chamber (52) of axial pressure supplied with air and a second axial pressure chamber (54) supplied with fuel (26) which are delimited by the B530 walls of the pressure housing (40) and by a common transverse movable wall (50) including a first face (58), facing the first air pressure chamber (52), is supported on an axial elastic element linked to a wall of the first air pressure chamber (52) to oppose the fuel pressure (26), and whose a second face (56), facing the second fuel pressure chamber (54), has a   axial rod (68) for actuating the valve (70).   3. Supply circuit (10) according to claim 0o preceding, characterized in that the axial elastic element is a spring (62) which bears on a transverse bottom of the first air pressure chamber (52) of the pressure housing (40) which is calibrated according to a stiffness corresponding to the   constant differential pressure determined.   4. Supply circuit (10) according to one of   claims 2 or 3, characterized in that the valve (70)   has the second pressure chamber (54) inside   from which the fuel circulates (26).   5. The supply circuit (10) according to claim 4, characterized in that the second fuel pressure chamber (54) has a fuel inlet orifice (74) which is capable of being closed by a valve. (76) controlled by the axial actuating rod (68) of the valve   (70), and a fuel outlet conduit (44).   6. Circuit (10) supply according to the preceding claim characterized in that the valve (76) for closing the orifice (74) of fuel inlet is arranged outside pressure housing (40).   7. Supply circuit (10) according to claim 6, characterized in that the axial rod (68) for actuating the valve (70) protrudes from the pressure housing (40) for B533 controlling the valve (76 ) closing the orifice (74) fuel inlet.   8. Fuel supply circuit (10) according to claim 7, characterized in that the fuel inlet orifice (74) coincides with a fuel outlet orifice (72) of an axial housing (71) cylindrical shutter which is fixed externally to the pressure housing (40), a first wall of which comprises the fuel inlet conduit (42) connected to the fuel circuit (12) downstream of the filter (20) to allow io l fuel inlet (26), and a second frustoconical wall (82) of which has the fuel fuel outlet orifice (72) from the housing (71), which is crossed by the axial rod (68) for actuating the valve (70), a ball (78) of a diameter substantially equal to an average diameter of the frustoconical wall (82) being biased on the one hand elastically against the latter and being on the other hand resting on the free end of the axial actuating rod (68) of the valve (70) to form the valve (76) for closing the orifice this   fuel inlet (74) from the housing (40).   9. Fuel supply circuit (10) according to one   any one of the preceding claims, characterized in   that the air pressure is regulated downstream of the compressor (32)   by an independent pressure regulator (36).