FR2709516A1 - Fuel supply circuit for an internal combustion engine and device forming a fuel flow regulator which can be used in such a supply circuit - Google Patents

Abstract

The present invention relates to a fuel supply circuit for an internal combustion engine as well as to a device forming a fuel flow regulator forming part of the supply circuit. The supply circuit in accordance with the invention is characterised in that the means (12) for regulating the fuel flow rate is placed on a supply pipe (4) between a feed pump (2) and an injector set (5) conveying fuel to injectors (6) and operates continuously so as to vary the fuel flow rate to the injector set (5), reducing it to a minimum when the engine is at idle and letting through a maximum fuel flow rate from the pump (2) when the engine is operating under high load. The invention finds application in fuel-injected engines of motor vehicles.

Description

 The present invention relates to a fuel supply circuit for an internal combustion engine, in particular a motor vehicle injection engine.

 It also relates to a device forming a fuel flow regulator which can be used in such a supply circuit.

 FIG. 1 represents a known supply circuit making it possible to supply fuel to an injection engine 3 and comprising a fuel tank 1, a high pressure pump 2 for supplying fuel to the engine 3, a supply line 4 connecting the pump 2 has an injection manifold S leading the fuel to injectors 6 electrically controlled by a suitable circuit known per se (not shown) and in this case four in number for a four-cylinder engine.

 The supply circuit also includes a fuel pressure regulator 7 in the injection manifold 5 and connected on the one hand to the tank 1 by a line 8 for returning fuel to the tank 1 and on the other hand to a pipe d intake 9 by an air line 10 at a connection point to the manifold 9 located downstream of the intake throttle 11 and upstream of the intake valves (not shown) of the engine 3. For simplicity, the three other air-fuel intake pipes associated respectively with the other three injectors are not shown and are each symbolized by a dashed line. The pressure in the area located at the connection point of line 10 to the intake manifold 9 is transmitted by line 10 to the regulator 7 to modulate the fuel pressure in the injection manifold 5 so that the quantity of fuel passing through the injectors 6 is only linked to their opening time.

 The arrangement of the above-mentioned supply circuit has the major drawback of conveying to and onto the engine 3 all the fuel coming from the feed pump 2, with the consequence that the fuel heats up, which gives off vapor and saturation. of the absorber (not shown) intended to collect the vapors emitted by the tank 1, particularly in the engine idling phases or during traffic jams in hot weather of the vehicle whose engine heats up considerably.

 The object of the present invention is to eliminate the above known drawback of the supply circuit by proposing a supply circuit which effectively regulates the supply of fuel to an injection heat engine, thereby reducing the production of steam from the fuel. fuel tank.

 To this end, the fuel supply circuit of an internal combustion engine, such as a motor vehicle injection engine, of the type comprising a fuel tank connected by a supply line to an injection rail. leading the fuel to injectors, a supply pump provided on the supply line, a fuel return line connecting the injection rail to the tank, and means for regulating the flow of fuel arriving at the rail injection, is characterized in that the regulating means is placed on the supply line between the supply pump and the injection rail and operates continuously so as to vary the flow of fuel to the injection rail by reducing it to a minimum during the engine idling phase and by allowing a maximum flow of fuel from the supply pump to pass during the engine's high load phase.

 Advantageously, the supply circuit also comprises a static pressure regulator connected between the supply line downstream of the supply pump and the fuel return line so as to stabilize and limit the pressure of the fuel sent to the engine. regardless of fuel flow.

 Preferably, the fuel flow regulation means is pneumatically controlled.

 The fuel flow regulation means is connected by an air line to an intake manifold at a location downstream of the intake throttle so as to be controlled by the vacuum prevailing in the intake manifold.

 According to an alternative embodiment, the supply circuit comprises an absorber connected on the one hand to the reservoir and on the other hand to an intake manifold and the regulating means is connected to the pipe connecting the absorber to the manifold d 'admission so as to be controlled by the vacuum prevailing in this connecting pipe.

 Preferably, the means for regulating the fuel flow comprises a regulating membrane sensitive to the vacuum prevailing in the intake manifold or in the abovementioned connection pipe and a bulging needle which can move in translation in the body of the means of regulation under the control of the regulation membrane so that the bulge of the needle cooperates with a fixed seat of the body of shape substantially conjugate with the bulge to decrease or increase the cross-section of fuel passage from the supply pump to the boom injection depending on the vacuum prevailing in the intake manifold or in the connecting pipe.

 The regulating means also comprises a spring pushing one end of the needle against the regulating membrane maintained in equilibrium by a balancing spring housed in the chamber delimited in the body of the regulating means by the regulating membrane and communicating with the air line above so that a high vacuum in the intake manifold or in the connecting line moves the control diaphragm and the needle by compressing the balancing spring so as to bring the bulge closer to the needle from its seat to reduce the fuel passage section and thus allow a low flow of fuel to pass and that a low vacuum in said tube or said connecting pipe brings the regulation membrane, under the action of the balancing spring, pushing the needle against the return force of the thrust spring so as to move the bulge of the needle away from its seat to increase the fuel passage section and thus allow a large flow of fuel to pass.

 The needle is guided in its translational movement in the body of the regulating means by guide fins fixed respectively in the vicinity of the two ends of the needle and the needle pushing spring against the regulating membrane is mounted coaxially with the needle between a shoulder of the body of the regulating means and the guide fins opposite to those adjacent to the regulating membrane.

 The invention also relates to a device forming a flow regulator for a fluid, such as fuel arriving in an injection manifold leading the fuel to injectors of an injection engine of a motor vehicle and which is characterized in that it includes a body comprising a regulation membrane sensitive to the pressure of a control fluid, such as air, arriving in the chamber delimited between the regulation membrane and said body, and a bulging needle kinematically linked to the regulation membrane to be moved in translation in the body by the membrane so that the bulge of the needle cooperates with a fixed seat of the body of shape substantially conjugated with the bulge to decrease or increase the section of fuel passage defined between the seat and the bulge and therefore the flow of fuel flowing through the regulator.

 The regulator device also comprises a spring mounted in the aforementioned body coaxially with the needle to constantly push one end of the latter against the regulating membrane which is held in an equilibrium position by a balancing spring mounted in the chamber above between the regulating membrane and the regulator body.

The invention will be better understood and other objects, characteristics, details and advantages thereof will appear more clearly during the explanatory description which follows, made with reference to the appended schematic drawings given solely by way of example illustrating two modes. of the invention and in which:
- Figure 1 shows a known fuel supply circuit of an internal combustion engine of the motor vehicle injection type;
- Figure 2 shows an embodiment of the supply circuit according to the invention;
- Figure 3 shows in section the means of regulating the fuel flow used in the supply circuit of Figure 2; and
- Figure 4 shows another embodiment of the supply circuit of the invention.

 The supply circuit according to the invention which will be described with reference to FIGS. 2 to 4 comprises structural and operating components identical to those of the components of the supply circuit in FIG. 1 and thus bear the same references.

 The supply circuit as described in FIG. 2 comprises a fuel tank 1, a high pressure pump 2 making it possible to supply fuel to the injection engine 3 of the motor vehicle via a supply line 4, an injection manifold 5 leading the fuel coming from the feed pump 2 to electrically controlled fuel injectors 6, four in number and only one of which is shown for simplicity, a fuel pressure regulator 7 in the manifold injection 5 connected on the one hand to the tank 1 by a line 8 for returning fuel to the tank 1 and on the other hand to an air-fuel intake pipe 9 by an air pipe 10 opening into the pipe 9 at a point located downstream of the intake throttle 11 and upstream of the intake valves (not shown) of the engine 3. As already explained with reference to the supply circuit of FIG. 1, the pressure in the portion of the t intake manifold 9 located downstream of the throttle valve and upstream of the intake valves is transmitted through line 10 to regulator 7 to modulate the fuel pressure in the injection manifold 5 so that the quantity of fuel passing through the injectors 6 is only related to their opening time.

 The supply circuit according to the invention further comprises a means 12 for regulating the flow of fuel arriving at the injection rail 5 placed on the supply line 4 upstream of the rail 5 and connected to the line d 10 and therefore to the intake manifold 9 via a connecting pipe 13.

 The supply circuit further comprises a static pressure regulator 14, known per se, intended to stabilize and limit the pressure of the fuel sent to the engine by the pump 2, regardless of the fuel flow rate. The static regulator 14 is connected by two connecting lines 15 and 16 respectively to the supply line 4 between the outlet of the pump 2 and the fuel inlet into the regulating means 12 and to the return line 8.

 The purpose of the regulating means 12 is to vary the flow of fuel to the injection manifold 5 by linking this flow to the depression prevailing in the intake manifold 9. Thus, when the depression in the manifold 9 is high, as is the case in the engine idling phase 3, the regulating means 12 reduces the flow of fuel passing therethrough to the minimum necessary for the correct operation of the pressure regulator 7 to ensure the so-called "low" pressure in the injection manifold 5. Taking into account the characteristics of the feed pump 2, this low flow would cause a very high fuel pressure making its safety valve work, which is not designed to operate continuously under these conditions. The static regulator 14 is calibrated at a determined pressure, for example around 4 bars, to allow the excess fuel to be discharged to the tank 1 without transporting it to the hot zone of the engine 3. Only the very low flow of fuel passing through the injection manifold 5 is heated and contributes to the formation of steam at idle.

When the vacuum in the intake manifold 9 is low, as is the case in the heavy load phase of the engine 3, the regulating means 12 lets through all the fuel flow from the pump 2, flow which is not limited only by the characteristic of the pump 2 and the so-called "high" back pressure in the injection manifold 5 by the pressure regulator 7. The thermal power of the engine heating the fuel in the tank is important, but the speed of movement of the vehicle easily cools it and the engine's capacity to absorb the vapors produced by burning them is maximum.

 FIG. 3 shows in detail the regulating means 12 making it possible to modulate the fuel flow rate by the vacuum prevailing in the intake manifold 9.

 The regulating means 12 comprises a body 15 comprising an end piece 16 to which the connection line 13 is connected, a end piece 17 to which the supply line 4 is connected and an end piece 18 to which the injection rail 5 is connected. The means regulator 12 also comprises a regulating membrane 19 delimiting in the body 15 a first chamber 20 into which opens the connection endpiece 16 and a second chamber 21 and a needle 22 with bulge 23 which can move in rectilinear translation in the body 15 under the control of the regulating membrane 19. For this purpose, the needle 22 comprises, in the vicinity of its two ends respectively, guide fins 24 and 25 guiding the needle 22 in the body 15 while allowing the passage of fuel between the needle and the body 15 and a spring 26 mounted between a shoulder 27 of the body 15 and the guide fins 25 opposite the end of the needle 22 held in abutment p ermanent on the reinforced central portion of the regulating membrane 9 by the thrust action exerted to the left relative to FIG. 3 by the spring 26. The bulge 23 of the needle 22 cooperates with a seat of conjugate shape 28 produced in the body 15 of the regulating means 12 so as to reduce or increase the fuel passage section defined between the bulge 23 and the seat 28 as a function of the value of the vacuum in the intake manifold 9 and therefore in the chamber 20 which comprises a spring 29 for balancing the regulation membrane 19 mounted coaxially with the needle 22 between the reinforced central part of the membrane 19 and the end wall of the body 15 closing the chamber 20.

 The combination of the bulge 23 and the seat 28 thus makes it possible to modulate the flow of fuel as a function of the position of the needle 22, therefore of the vacuum in the intake manifold 9, while the pressure regulator 7 located downstream of the injection manifold 5 regulates the pressure in the manifold 5 by the vacuum in the pipe 9 by producing a variable pressure drop with a constant flow rate.

 When the engine 3 is running at low load, the significant vacuum in the intake manifold 9 transmitted by the line 13 in the chamber 20 displaces the membrane 19 and the needle 22 in the direction approaching the bulge 23 of the seat 28 so as not to leave that a reduced section of fuel passage from line 4 to line 5 through the body 15 of the regulating means 12 and which, under the pressure difference prevailing between the lines 4 and 5, allows a low flow of fuel to pass , of the order of 10 to 15 liters per hour.

 When the engine load increases, the vacuum in the intake manifold 9 decreases and the membrane 19 under the action of the spring 29 pushes the needle 22 to the right with respect to FIG. 3 and therefore removes the bulge 23 from the seat 28 to give a larger section of fuel passage, increasing the flow of fuel to the injection rail 5. At full engine load, the regulating means 12 behaves like a tube with very low pressure drop and lets through all the fuel necessary for the engine, corresponding to a flow rate for example of the order of 120 liters per hour.

 It is thus understood that the shape of the bulge 23 of the needle 22 is combined with that of the seat 28 to create a variable section with the displacement of the membrane 19 and this section leads to gradually putting the fuel threads in speed gradually along the needle 22 so as to reach, whatever the cross-section, a substantially constant speed depending only on the pressure difference existing between the lines 4 and 5.

 For injection engines absorbing high fuel flows at high speed and low load, it may be advantageous to introduce, for the control of the regulating means 12, the parameter relating to the engine rotation speed by carrying out the embodiment of the supply circuit shown in FIG. 4 comprising an absorber 30 intended to collect vapors emitted by the fuel tank 1 while being connected to the latter by a line 31 and a valve 32 for draining the absorber 30 connected to it ci by a pipe 33 and also connected to an intake manifold 9 by a connecting pipe 34 defining the regeneration circuit of the absorber 30. The regulating means 12, identical to that of FIGS. 2 and 3, is connected by a pipe 35 to the connecting pipe 34.

 The regulating means 12 is thus controlled by the vacuum prevailing in the connection line 34 at the level of the purge valve 32 of the absorber 30. A computer (not shown) controlling the valve 32 gives an order to open it. ci as soon as the engine speed exceeds a certain value, much higher than the engine idling speed. Thus, the vacuum between the purge valve 32 and the manifold 9 depends both on the engine load and its speed of rotation.

 An adjustment of the lengths and of the relative sections of the lines 33 and 34 must be carried out in order to respect both the purge law of the absorber 30 and the control of the means for regulating the fuel flow 12.

 The supply circuit of the invention therefore makes it possible to modulate the flow of fuel flowing to the injection engine by controlling the means for regulating the fuel flow by the vacuum prevailing in the intake manifold or in the connection line. from the absorber to the intake manifold and the addition of a static pressure regulator at the supply pump. The specially profiled needle regulating means alone controls the flow of fuel to the injection engine, from a minimum value essential for the proper functioning and longevity of the pressure regulator to the maximum absorbed by the engine.

Claims (10)

 1. Fuel supply circuit of an internal combustion engine (3), such as a motor vehicle injection engine, comprising a fuel tank (1) connected by a supply line (4) to a injection rail (5) leading the fuel to injectors (6), a supply pump (2) provided on the supply line (4), a fuel return line (8) connecting the rail injection (5) to the tank (1) and a means (12) for regulating the flow of fuel arriving at the injection rail (5), characterized in that the regulating means (12) is placed on the supply line supply (4) between the supply pump (2) and the injection rail (5) and operates continuously so as to vary the flow of fuel to the injection rail (5) by reducing it to a minimum when the engine is idling and allowing a maximum flow of fuel from the feed pump (2) to pass during the high engine load phase ur.  2. Circuit according to claim 1, characterized in that it also comprises a static pressure regulator (14) connected between the supply line (4) downstream of the supply pump (2) and the return line fuel (8) so as to stabilize and limit the pressure of the fuel to be sent to the engine (3) regardless of the fuel flow.  3. Circuit according to claim I or 2, characterized in that the means for regulating the fuel flow (12) is pneumatically controlled.  4. Circuit according to claim 3, characterized in that the fuel flow regulation means (12) is connected by a line (13) to an intake manifold (9) at a location located downstream of the throttle valve intake (11) so as to be controlled by the vacuum prevailing in the intake manifold (9).  5. Circuit according to claim 3, characterized in that it comprises an absorber (30) connected on the one hand to the tank (1) and on the other hand to an intake manifold (9) and in that the means regulator (12) is connected to the pipe (34) connecting the absorber (30) to the intake manifold (9) so as to be controlled by the vacuum prevailing in this connecting pipe (34).  6. Circuit according to one of the preceding claims, characterized in that the means for regulating the fuel flow (12) comprises a regulating membrane (19) sensitive to the vacuum prevailing in the intake manifold (9) or in the aforesaid connecting pipe (34) and a bulging needle (22) (23) which can move in translation in the body (15) of the regulating means (12) under the control of the regulating membrane (19) so that the bulge (23) of the needle (22) cooperates with a fixed seat (28) of shape substantially conjugate with the bulge (23) to decrease or increase the fuel passage section of the feed pump (2) to the injection manifold (5) as a function of the vacuum prevailing in the intake manifold (9) or in the connecting pipe (34).  7. Circuit according to claim 6, characterized in that the regulating means (12) comprises a spring (26) pushing one end of the needle (22) against the regulating membrane (19) kept in equilibrium by a spring d balancing (29) housed in a chamber (20) delimited in the body (15) of the regulating means (12) by the regulating membrane (19) and communicating with the aforementioned air line (10, 13) so that a high vacuum in the intake manifold (9) or in the connection line (34) moves the regulating diaphragm (19) and the needle (22) by compressing the balancing spring (29) so bringing the bulge (23) of the needle (22) closer to its seat (28) in order to reduce the fuel passage section and thus allow a low flow of fuel and a low vacuum to pass through said tube (9) or said connecting pipe (34) brings the regulation membrane (19), under the action of the balancing spring age (29), pushing the needle (22) back against the return force of the thrust spring (26), so as to move the bulge (23) of the needle (22) away from its seat (28) to increase the fuel passage section and thus allow a large flow of fuel to pass.  8. Circuit according to claim 6 or 7, characterized in that the needle (22) is guided in its translational movement in the body (15) of the regulating means (12) by guide fins (24, 25) fixed respectively in the vicinity of the two ends of the needle (22) and in that the thrust spring (26) of the needle (22) against the control membrane (19) is mounted coaxially with the needle (22) between a shoulder (27) of the body (15) of the regulating means (12) and the guide fins (25) opposite those (24) adjacent to the regulating membrane (19).  9. Device forming a flow regulator for a fluid, such as fuel arriving in an injection manifold (5) leading the fuel to injectors (6) of a motor vehicle injection engine, characterized in that it comprises a body (15) comprising a regulation membrane (19) sensitive to the pressure of a control fluid, such as air, arriving in the chamber (20) delimited between the regulation membrane (19) and the body (in), and a needle (22) with bulge (23) kinematically linked to the regulation membrane (19) to be moved in translation in the body (15) by the membrane (19) so that the bulge ( 23) of the needle (22) cooperates with a fixed seat (28) of the body (15) of shape substantially conjugated with the bulge (23) to reduce or increase the fuel passage section defined between the seat (28) and the bulge (23) and thus decrease or increase the flow rate of the fuel circulating through the regulate eur.  10. Device according to claim 9, characterized in that it comprises a spring (26) mounted in the aforementioned body (15) coaxially with the needle (22) to constantly push one end of the latter against the regulating membrane ( 19) which is held in an equilibrium position by a balancing spring (29) mounted in the aforementioned chamber (20) between the regulating membrane (19) and the body (15) of the regulator.