EP0037296B1 - Apparatus for metering an injected fuel quantity in a fuel-injection engine - Google Patents

Description

The invention relates to fuel injection systems for internal combustion engines. More specifically, it relates to a device intended to measure the volume of fuel introduced into the engine each time an injector is opened.

Knowing the precise volume of fuel introduced at each opening of an injector is particularly useful for acting on the engine supply, with a view to obtaining optimum efficiency and reducing the quantity of polluting gases contained in the exhaust gases. .

This action on the supply can be done by modulating the quantity of exhaust gas recycled as a function of the volume of fuel injected and / or by correcting the volume injected as a function of the quantity of air admitted so as to maintain the richness of the mixing between very narrow limits.

It has already been proposed in patent GB-A-2017,205 to measure the volume of fuel injected by means of a device constituted by a movable shuttle in a bore interposed in the supply circuit, said shuttle being associated with a sensor of displacement. In this known arrangement, the measuring device is placed on the fuel supply to the injection pump, which has the following disadvantages in particular: firstly, the measurement is not very precise, since the device does not hold account of internal leaks from the injection pump; secondly, this device is only applicable to intake metering pumps, that is to say pumps for which the pumped volume is determined by the admitted volume; finally, this device does not make it possible to know the moment of the start of the injection.

The object of the invention is to provide a more precise measuring device, which takes into account the volume of fuel actually discharged by the pump, which indicates the instant of the start of injection and which is also applicable to all types of injection pumps.

Furthermore, patent FR-A-1 319 872 describes a distributor injection pump comprising a body delimiting a cylinder in which is mounted a rotor comprising a “pump part formed by a bore arranged radially relative to the axis of the rotor and in which are received opposite free pistons located in line with a fixed annular cam, and a "distributor" part. This pump comprises a device for adjusting the quantity of fuel to be injected, formed by a bore formed in the body and extending radially with respect to the axis of the rotor, and in which is received a piston whose angular position and axial can be adjusted. This piston cooperates with a discharge conduit opening into an intermediate part of the bore to determine the start and end of the injection phase. Given this cooperation with a discharge conduit and its adjustable axial position, such a piston cannot be used in a measuring device making it possible to solve the problem posed.

The patent FR-A-1 207501 describes a dispensing injection pump provided with a device for self-regulation of the quantity of fuel injected. This device, placed between the discharge chamber of the pump and the distributor, comprises a bore in which an auxiliary piston is received, cooperating with a discharge conduit opening into an intermediate part of the bore to determine the end of the phase of injection. The position of the auxiliary piston at the time of the start of the injection phase varies according to the engine speed and it is this variation which determines the quantity of fuel injected. In this prior arrangement, the self-regulating device is supplied from the delivery chamber of the pump, which results in a relatively complex arrangement.

The subject of the invention is therefore a device for injecting fuel into a heat engine, comprising a distributing injection pump connected to a source of low pressure fuel and comprising, on the one hand, a part forming a pump proper comprising a delivery chamber and a device for adjusting the quantity of fuel to be injected, and, on the other hand, a portion forming a distributor in the direction of several injectors, and a device for measuring the amount of fuel injected, of the type comprising a shuttle movable in a bore formed in a fixed part of the injection pump and a sensor sensitive to the movements of this shuttle, characterized in that the bore of the measuring device has a first end hydraulically connected to the delivery chamber of the part forming a pump, at least during the delivery phase of this part forming a pump, and an opposite end, connected only and successively by the in intermediate part of the distributor part, on the one hand, at the low pressure fuel source and, on the other hand, at the injectors, the shuttle being biased by a spring towards said first end of the bore to its initial position .

• La pompe étant du type comprenant un corps délimitant deux alésages sécants et s'étendant à angle droit l'un par rapport à l'autre, le premier alésage contenant un piston d'injection monté coulissant et le second contenant un distributeur entraîné en rotation par un arbre qui porte une came d'actionnement du piston coulissant, l'alésage du dispositif de mesure est délimité dans le corps et est relié, à une extrémité par un conduit à la chambre de refoulement de la pompe et, à son autre extrémité, par deux conduits à deux zones du distributeurs reliées elles-mêmes, respectivement, aux injecteurs et à la source de carburant sous basse pression.

According to three embodiments:

• The pump being of the type comprising a body delimiting two intersecting bores and extending at right angles to each other, the first bore containing an injection piston mounted to slide and the second containing a distributor driven in rotation by a shaft which carries a cam for actuating the sliding piston, the bore of the measuring device is delimited in the body and is connected, at one end by a conduit to the discharge chamber of the pump and, at its other end, by two conduits to two zones of the distributor connected themselves, respectively, to the injectors and to the fuel source under low pressure.

The injection pump being of the type comprising a body, a fixed cylinder delimiting a delivery chamber in which a piston simultaneously forming a distributor moves in a continuous rotational movement and in an alternating axial movement, there is provided a head attached to the body in the extension of the cylinder and delimiting said the bore receiving the shuttle, this bore communicating directly at one end with the delivery chamber and communicating by its other end, selectively, with the fuel source and with at least one injector, via the distributor that constitutes the piston of the injection pump.

The injection pump being of the type comprising a body delimiting a cylinder in which is rotatably mounted a rotor comprising a pump part formed by a bore arranged radially relative to the axis of the rotor and in which are received opposite free pistons located at the right of a fixed annular cam, a distributor part, and an axial channel, the bore receiving the shuttle is formed at least partly in the body and extends radially with respect to the axis of the rotor, the axial channel is interrupted and separated into two sections connected respectively one to the pump part and the other to the distributor part and a series of channels extend from each section and open at the periphery of the rotor to cooperate with two channels formed in the body and each connected to a respective end of the bore in which the shuttle is received, the relative arrangement of the channels of the rotor and of the channels formed in the body being such that during the rotation of the rotor the two sections They are periodically and simultaneously placed in communication with the ends of the bore containing the shuttle.

• la figure 1 représente, schématiquement, une pompe distributrice à distributeur séparé, agencée selon l'invention ;
• la figure 2 représente une application à une pompe distributrice à distributeur intégré ;
• la figure 3 est une coupe axiale schématique d'une pompe à réglage d'admission, aménagée selon l'invention, le rotor occupant une position correspondant à une phase d'injection ;
• la figure 4 est une section partielle selon la ligne 4-4 de la figure 3 ;
• la figure 5 est une section partielle selon la ligne 5-5 de la figure 3 ;
• les figures 6 et 7 sont deux coupes axiales partielles de la pompe de la figure 3 pour deux autres positions du rotor par rapport au corps de la pompe.

Three exemplary embodiments are the subject of the following description, with reference to the accompanying drawings, in which:

• Figure 1 shows, schematically, a distributor pump with separate distributor, arranged according to the invention;
• FIG. 2 represents an application to a dispensing pump with an integrated dispenser;
• Figure 3 is a schematic axial section of an intake control pump, arranged according to the invention, the rotor occupying a position corresponding to an injection phase;
• Figure 4 is a partial section along line 4-4 of Figure 3;
• Figure 5 is a partial section along line 5-5 of Figure 3;
• Figures 6 and 7 are two partial axial sections of the pump of Figure 3 for two other positions of the rotor relative to the pump body.

Referring to FIG. 1, a pump body 1 contains an injection piston 2 sliding in a bore 3 and a distributor 4 rotating in a bore 5.

A shaft 6, carried by two bearings 7, carries a cam 8 which, by means of a roller 9 and a pusher 10, drives the piston 2 in a reciprocating linear movement. A spring 11 permanently maintains the piston 2, the pusher 10, the roller 9 and the cam 8 in contact with one another. The shaft 6 has a polygonal axial housing 12 which cooperates with a conjugate finger 13 of the distributor 4 to drive the latter in rotation, in synchronism with the reciprocating movement of the piston 2.

The end of the piston 2 forms, in the bottom of the bore 3 a chamber 14. The latter communicates, by a longitudinal channel 15 and a transverse channel 16 with an annular chamber 17 formed with the bore 3 by a narrowed part of the piston 2. The annular chamber 17 is limited, on one side, by a helical ramp 18 of the piston 2.

This chamber 17 comes into communication with a discharge orifice 19 when, in the discharge movement of the piston 2, the ramp 18 reaches the level of the orifice 19. The communication of the chamber 17 with the orifice 19, which corresponds to the end of the injection, intervenes for a variable delivery stroke of the piston 2, depending on its angular position.

The angular position of the piston 2 is defined by a rack 20 acting on a pinion 21 integral in rotation but not in sliding, with the piston 2, thanks to a flat 22.

The chamber 14 communicates by a channel 23 with a bore 24 in which slides, without play, a shuttle 25 pushed by a spring 26 towards the bottom of the bore 24 where the channel 23 opens. The shuttle thus delimits in the bore 24 two rooms 24 ° and 24 ^b . From the other end of the bore 24, that is to say of the chamber 24 ^b , leaves a channel 27 which terminates in the bore 5 facing a groove 28 formed in the distributor 4. The groove 28 is in permanent communication with a longitudinal groove 29 of the distributor 4, groove which passes successively, during the rotation of the distributor 4, in front of starting orifices 30 towards injectors 31 of which only one is shown.

The dispenser 4 further comprises longitudinal grooves 32 connected together by transverse channels 33 and located at the level of the three channels 34, 35 and 36. Through the channel 34 comes fuel under low pressure, coming from a transfer pump, not shown. Channel 35 ends in chamber 14.

Around the bore 24, facing the shuttle 25, is arranged a displacement sensor 37 which can, for example, be a capacitive sensor and which is connected to appropriate means (not shown) for processing and exploiting the information which are supplied by the sensor 37 as well as on the various operating parameters of the engine: speed, load temperature.

• Pendant la phase d'aspiration du piston 2, du carburant provenant du canal 34 est envoyé, à travers les rainures 32, les canaux 33, 35 et 36 vers la chambre 14 et dans l'alésage 24.

The operation of the assembly described is as follows:

• During the suction phase of the piston 2, fuel from the channel 34 is sent, through the grooves 32, the channels 33, 35 and 36 to the chamber 14 and into the bore 24.

During the delivery phase of piston 2, the channels 35 and 36 are closed by the distributor 4 and the fuel discharged by the piston 2 pushes the shuttle 25, which in turn discharges fuel, through the channel 27, towards that of the injectors 31 connected to the orifice 30 which communicates with the groove 29 of the distributor 4. The end of the delivery, which determines the quantity of fuel injected, occurs when the annular chamber 17 of the piston 2 is placed in communication with the discharge orifice 19.

It can therefore be seen that the sensor 37 makes it possible to know on the one hand, the precise instant of the start of the injection, corresponding to the start of the movement of the shuttle 25, and the volume of fuel injected, corresponding to the travel of the shuttle. 25.

From this information and other available information, it is possible to act by known means on the flow rate of recycled exhaust gases and / or on the volume of fuel injected and / or on the start of injection of so as to maintain optimal feeding conditions.

Since the measurement is carried out on the delivery path from piston 2 to the injectors, it is not distorted by internal leaks from the pump or by the development, over time, of internal clearances and this constitutes a decisive advantage as regards the accuracy of the measurement and its fidelity over time.

In the example of FIG. 2, a pump body 40 contains a fixed cylinder 41 in a bore 42 of which is mounted a piston 43. The latter is driven, in a known manner, from a motor, not shown, in a continuous rotary movement and according to a reciprocating axial movement.

In the extension of the cylinder 41, a head 44 is attached, blocked by a screw 45.

The piston 43 has longitudinal grooves 46 which open into a chamber 47 formed, in the bore 42, between the end of the piston 43 and the head 44. During the rotation of the piston 43, these grooves 46 pass in front of an orifice supply 48 and in front of orifices 49 connected by channels 50 to a bore 51 formed in the head 44.

In the bore 51 slides, without play, a shuttle 52 pushed by a spring 53 against the bottom of the bore in which is formed a passage 54 for communication with the chamber 47. The spring 53 is supported on a plug 55 which closes the bore 51. as before, it can be considered that the shuttle 52 divides the bore 51 into two chambers 51 °, ^51b.

One of the channels 50 is extended by a channel 56 to a transverse passage 57 which opens into the bore 42 facing a groove 58. of the piston 43. From this groove leaves a longitudinal groove 59 which passes successively, during of the rotation of the piston 43, in front of the starting orifices 60 towards the injectors, not shown.

The piston 43 also comprises a central channel 61 connecting the chamber 47 to a transverse passage 62 closed by a ring 63 but opening to the atmosphere, outside the ring 63, from a certain delivery stroke of the piston 43.

The venting of passage 62 corresponds to the end of the injection. It operates for a variable stroke of the piston 43, as a function of the position of the ring 63 determined by an eccentric control 64.

In the head 44, around the bore 51, facing the shuttle 52, is arranged a displacement sensor 65 which plays the same role as that of the first example described.

• Pendant la phase d'aspiration du piston 43, du carburant, introduit par le canal 48, remplit la chambre 47 et la chambre 51^b de l'alésage 51.

The operation of this second example is as follows:

• During the suction phase of the piston 43, the fuel, introduced by the channel 48, fills the chamber 47 and the chamber 51 ^b of the bore 51.

During the discharge phase of the piston 43, the orifices 48 and 49 are closed by the piston 43. The fuel discharged by the latter repels the shuttle 52, which, in turn, repels fuel through the channel 56 towards that of the connected injectors at the orifice 60 which communicates with the groove 59 of the piston 43. The end of the delivery, which determines the quantity of fuel injected, occurs when the passage 62 opens out from the ring 63.

As in the first example, the sensor 65 makes it possible to detect the precise instant of the start of the injection, corresponding to the start of the movement of the shuttle 52, and to determine the volume of fuel injected, corresponding to the stroke of the shuttle 52 The same advantages are therefore obtained, with a different type of pump.

The pump shown in Figs. 3 to 7 comprises a body 101 containing a fixed cylinder 102 in a bore 103 from which rotates a rotor 104, driven in a known manner by a heat engine, not shown. The rotor 104 comprises a pump part 105 and a distributor part 106. The axis of the cylinder and of the rotor is designated by the reference X-X.

In the pump part 105, a radial bore 107 contains two free pistons 108 whose outer faces are in contact with pads 109 carrying rollers 110 situated at the right of a fixed annular cam 111. The central part of the bore 107 forms, between the two pistons 108, a chamber 112 from which an axial channel 113 leading to radial channels 114, the number of which corresponds to the number of engine cylinders.

In line with the radial channels 114, that is to say in the same plane perpendicular to the axis XX of the rotor, the fixed cylinder 102 has a radial channel 115 which opens into a chamber 116 located opposite a bore 117 formed in the body 101. In this bore slides, without play, a shuttle 118 provided with a flange 119. The latter limits the displacement of the shuttle 118 towards the chamber 116 by abutting against a radial bearing surface 120. It cooperates also with a displacement sensor 121 mounted in a plug 122 screwed into the body 101 concentrically with the bore 117. A spring 123, disposed between the plug 122 and the shuttle 118 tends to push the latter until the stop of the flange 119 on the surface 120. The plug 122 and shuttle 118 delimit a chamber 124 from which a channel 125 pierced in the body 101 and the fixed cylinder 102 starts.

The part of the distributor 106 of the rotor 104 has an axial channel 126 connecting radial channels 127 to a single radial channel 128. The channels 127 are located to the right of the channel 125. The number and the angular position of the channels 127 and of the channels 114 are the same. The channel 128 passes successively, during the rotation of the rotor 104, in front of the starting channels 129 to the injectors, not shown.

The rotor 104 also comprises longitudinal grooves 130 located between the outlets of the channels 114 and 127 intended to connect, intermittently, the channels 115 and 125.

Low pressure fuel, coming from a transfer pump, not shown, arrives via a duct 131 with two channels 132, 133. The channel 132 is located at the right of the radial channels 127. The channel 133, on the path of which is interposed a member 134 for adjusting the flow rate, known per se, is situated in line with the radial channels 114.

• L'admission de carburant se produit lorsque l'un des canaux 114 coïncide avec le canal 133. Le carburant introduit, dont la quantité dépend de la position de l'organe de réglage 134, repousse les pistons 108 radialement vers l'extérieur. Simultanément l'un des canaux 127 coïncide avec le canal 132, ce qui permet de ramener l'ensemble des canaux 126,127 et 128 du distributeur à la pression de la pompe de transfert.

The pump which has just been described operates as follows:

• The fuel intake occurs when one of the channels 114 coincides with the channel 133. The fuel introduced, the amount of which depends on the position of the adjusting member 134, pushes the pistons 108 radially outward. Simultaneously one of the channels 127 coincides with the channel 132, which allows all the channels 126, 127 and 128 of the distributor to be brought back to the pressure of the transfer pump.

At about the same time, the grooves 130 provide the connection between the channels 115 and 125 which balances the pressures in the chambers 116 and 124 located on either side of the shuttle 118. Under the action of the spring 123, the shuttle 118 is then pushed until its flange 119 comes into abutment against the surface 120.

The fuel is returned by bringing the pistons 108 together under the action of the cam 111. This delivery occurs when one of the channels 114 coincides with the channel 115 and one of the channels 127 coincides with the channel 125 , while the channel 128 coincides with one of the channels 129 from the start to an injector.

The fuel discharged by the pistons 108, the quantity of which has been determined, during admission, by the regulating member 134, displaces the shuttle 118 which, in turn, discharges the fuel towards one of the injectors.

As in the examples described in Figs. 1 and 2, the control of the movements of the shuttle 118 by the sensor 121 makes it possible to know with great precision the start of the delivery and the quantity of fuel delivered.

Claims (9)

1. A device for injecting fuel into a heat engine, comprising a distributing injection pump (1-5; 40-43 ; 101, 106) connected to a low-pressure fuel source and including, on one hand, a part constituting a pump proper comprising a discharge chamber (14 ; 47; 112) and a device (18-21 ; 62-64 ; 134) for regulating the quantity of fuel to be injected, and, on the other hand, a part constituting a distributor toward a plurality of injectors, and a device for measuring the quantity of fuel injected, of the type comprising a shuttle member (25 ; 52; 118) movable in a bore (24; 51 ; 117) provided in a fixed part of the injection pump and a sensor (37 ; 65 ; 121) responsive to the displacements of this shuttle member (25; 52 ; 118), characterised in that the bore (24 ; 51 ; 117) of the measuring device comprises a first end (24a ; 51a ; 116) hydraulically connected to the discharge chamber (14 ; 47 ; 112) of the part constituting a pump, at least during the discharge stage of this part constituting a pump, and an opposite end (24b ; 51 b ; 124) solely and successively connected through the part constituting a distributor, on one hand, to the low-pressure fuel source and, on the other hand, to the injectors, the shuttle member being biased by a spring (26 ; 53 ; 123) toward said first end of the bore to its initial position.

2. A device according to claim 1, characterised in that the pump is of the type comprising a body (1) defining two intersecting bores (3, 5) extending at a right angle to each other, the first bore (3) containing a slidably mounted injection piston (2) and the second containing a distributor (4) driven in rotation by a shaft (6) which carries a cam for actuating the slidable piston, the bore (24) of the measuring device is defined in the body (1) and is connected, at one end (24a), through a conduit (23) to the discharge chamber of the pump and, at its other end, through two conduits (27 ; 36) to two regions of the distributor which are connected respectively to the injector (31) and to the low-pressure fuel source (34).

3. A device according to claim 1, characterised in that the injection pump is of the type comprising a body (40), a fixed cylinder (41) defining a discharge chamber (47) in which a piston (43) constituting simultaneously a distributor is movable in a continuous movement of rotation and in a reciprocating axial movement, and there is provided a head (44) mounted on the body in the extension of the cylinder (41) and defining said bore (51) receiving the shuttle member (52), this bore communicating directly at one end (at 54) with the discharge chamber (47) and communicating through its other end selectively with the fuel source and with at least one injector, through the distributor which constitutes the piston (43) of the injection pump.

4. A device according to claim 3, characterised in that the piston (43) includes longitudinal grooves (46) opening into the discharge chamber (47) and cooperating with orifices (49) provided in the cylinder and connected to said other end of the bore (51) through conduits (49, 50) respectively provided in the head (44) and in the fixed cylinder (41).

5. A device according to claim 1, characterised in that the injection pump is of the type comprising a body (101) defining a cylinder (103) in which is rotatively mounted a rotor (104) including a pump part (105) formed by a bore disposed radially relative to the axis of the rotor and in which are received opposed free pistons located in alignment with a fixed annular cam, a distributor part (106) and an axial passageway, and the bore (117) receiving the shuttle member (118) is provided at least partly in the body (101) and extends radially with respect to the axis of the rotor, the axial passage is interrupted and divided into two sections (113, 126), one of which is connected to the pump part (105) while the other is connected to the distributor part (106), and a series of passageways (114, 127) extend from each section and open out on the periphery of the rotor so as to cooperate with two passageways (115, 125) provided in the body and each connected to one respective end of the bore (117) in which the shuttle member (118) is received, the relative arrangement of the passageways (114, 127) of the rotor and the passageways (115, 125) provided in the body being such that, when the rotor rotates, the two sections (113, 126) are periodically and simultaneously put in communication with the ends of the bore (117) containing the shuttle member.

6. A device according to claim 5, characterised in that said series of passageways (114 ; 127) are connected to the same fuel supply source.

7. A device according to claim 5, characterised in that the number and the angular position of the passageways (114, 127) of said series are the same.

8. A device according to claim 5, characterised in that the passageways (115, 125) provided in the body and each connected to one end of the bore (117) containing the shuttle member (118) are periodically interconnected through axial grooves (130) provided on the periphery of the rotor.

9. A device according to claim 5, characterised in that the sensor (121) is carried by a plug (122) screwed into the body (101).

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