FR2727159A1 - Fuel injection and supply circuit for Diesel IC engine - Google Patents

Abstract

A first pump (10) draws fuel from a tank (40) and delivers it to a loop circuit (100) which passes it through an injection system (120). A second pump (110) is located within the loop circuit to maintain circulation of the fuel at a constant temperature and flow consistency.The first pump is electrically-driven, and the second pump is a venturi-effect or jet pump. The loop circuit is additionally connected to the tank via a return conduit (130) incorporating a pressure regulator (14). A water trap (60) is located between the first pump and the loop circuit.

Description

 The present invention relates to the field of fuel supply systems for an internal combustion engine, in particular self-ignition or diesel.

 Many fuel supply systems for internal combustion engines have already been proposed.

 In particular, a new concept of diesel fuel supply and metering system has been proposed recently. This new system has a fuel supply circuit, part of which passes through the cylinder head or the engine rocker cover. This concept has the advantage of simplifying the structure of the supply circuit compared to many known prior structures.

 However, this concept poses a specific problem: the circuit thus formed at the level of the cylinder head of the engine causes the fuel to heat up and risks creating a significant temperature gradient between the injectors located at the entry of the circuit and those located at the exit. of the last.

 The present invention now aims to improve the previously known fuel supply systems.

 An important aim of the present invention is to propose a new supply system which makes it possible to limit the heating of the fuel.

 Another important object of the invention is to limit the temperature gradient between two separate zones of the supply circuit, in particular at the level of the injectors.

 These aims are achieved according to the present invention thanks to a fuel supply system for an internal combustion engine, in particular of the diesel type, characterized in that it comprises: - a first pump adapted to suck fuel located in a tank , - a loop circuit which communicates on the one hand, with the output of the first pump to receive fuel from that <: i, and which communicates on the other hand, with an operating site, and - a second pump placed on the loop circuit and adapted to put the fuel in circulation in it in order to avoid excessive heating of the fuel and guarantee good temperature uniformity of the latter.

 The present invention thus makes it possible to obtain, using simple means, a high flow rate in the loop circuit, and consequently to limit the heating of the fuel, as well as in particular to avoid large temperature differences between the nearby injectors. from the entrance to the circuit and those located at the exit of it.

 According to other advantageous features of the present invention, the first pump is an electric pump, while the second pump is a so-called venturi or jet pump.

 According to another advantageous characteristic of the invention, the loop circuit is connected to the reservoir by a return duct preferably equipped with a pressure regulator.

 Other characteristics, objects and advantages of the present invention will appear on reading the detailed description which follows, and with reference to the appended drawings given by way of non-limiting example and in which - Figure 1 shows a schematic view in perspective of the assembly of a supply system according to the present invention, and - Figure 2 shows a schematic sectional view of a pressure regulator capable of being used in the context of the invention.

 As indicated above, the supply system according to the present invention mainly comprises: a first pump 10, a loop circuit 100 and a second pump 110.

 The first pump 10 is adapted to draw fuel from a tank 40.

 The loop circuit 100 communicates, on the one hand with the output of the first pump 10, to receive fuel from the latter and communicates, on the other hand with an operating site 120, for example a ramp d 'injectors.

 The second pump 110 is placed on the loop circuit 100.

It is suitable for putting the fuel in circulation in that.

 The first pump 10 is preferably an electric pump.

 It is provided in a manner known per se with an upstream filter 11.

 Preferably, as illustrated in the appended FIG. 1, the pump 10 pumps the fuel into a bowl 20 supplied with fuel by any suitable means. The bowl 20 can be supplied for example using a return conduit 160, which will be described later. The bowl 20 can also be supplied by any other suitable means, such as for example using a booster pump, or a pump such as a jet pump, or even using a non-return valve. adapted to allow the penetration of fuel from the tank 40 to the bowl 20 when the fuel level in the tank 40 is higher than that of the fuel in the bowl 20, while on the contrary preventing the flow of fuel from the bowl 20 to the tank 40.

 The inlet of the pump 10 which coincides with the upstream filter 11 is preferably placed near the bottom of the bowl 20.

 Preferably, the pump 10 and the bowl 20 are also permanently urged against the lower wall 42 of the reservoir 40, in order to ensure optimum supply of the circuit, whatever the possible deformations of the reservoir 40.

 By way of nonlimiting example, the pump 10 can be adapted to supply a flow rate of the order of 50 I / h, under a pressure of the order of 6 bars, in its outlet pipe 50.

 In FIG. 1, the electrical supply wires for the pump 10 are shown diagrammatically under the reference 12.

 Preferably, the tank 40, more precisely the bowl 20, is provided with a system for gauging the fuel level in the tank 40.

 Such a gauging system can be the subject of numerous embodiments known to those skilled in the art.

 Such a gauging device 30 equipping the pumping assembly can be in accordance with the arrangements known and marketed today and essentially comprising a box 32 fixed to a wall of the tank 40 or to the bowl 20, a resistive track placed in this box, a float 34 able to follow changes in the fuel level and a cursor linked directly to the float or linked to the latter by means of a pivoting lever 36, which cursor moves on the resistive track as a function of the evolutions of the float 34. The gauge 30 can also be formed from any other known structure. I1 can be for example a capacitive gauge.

 The outlet pipe 50 of the pump 10 is directed towards the loop circuit 100.

 More specifically, the conduit 50 which communicates with the outlet of the pump 10, is connected to the inlet of the second pump 110 preferably made up of a venturi or jet pump.

 The outlet pipe 50 can be connected directly to the inlet of the second pump 110. However, preferably, the outlet pipe 50 of the first electric pump 10 is connected to the inlet of the jet pump 110 by the through a water separator 60 and a fine filter 70 connected in cascade, that is to say in series.

 Such water separator 60 and fine filter 70 are well known to those skilled in the art and will therefore not be described in more detail below.

 The loop circuit 100 can be the subject of numerous variant embodiments. Preferably, it comprises at least one part passing through the cylinder head of the engine.

 This loop circuit 100 communicates on the one hand, with the site of use 120, preferably a ramp of injectors, as shown schematically in Figure 1. However, alternatively, the site of use can be formed by any equivalent means.

 In addition, the loop circuit 100 communicates with the output of the first pump 10 via the second pump 110.

 Preferably, this second pump 110 is a venturi or jet pump.

 This second pump 110 shown diagrammatically in FIG. 1 comprises a chamber 112 formed in series on the loop circuit 100. The chamber 112 has an inlet 113 and an outlet 114.

 The chamber 112 houses a coaxial tube 116 whose inlet 117 communicates with the outlet of the filter 70.

 The outlet of the tubing 116 has a convergent 118 directed towards the outlet 114.

 In a manner known per se, the jet pump 110 works by a venturi effect. The injection of fuel into the pipe 116, by the electric pump 10, causes a vacuum in the chamber 112. And this vacuum sucks fuel from the inlet 113 towards the outlet 114. Thus, the jet pump 110 ensures a setting circulating fuel in the loop circuit 100.

 According to an advantageous embodiment, the jet pump 110 is placed at the inlet of the loop circuit 100 in the cylinder head of the engine.

 As a preferred and nonlimiting example, the jet pump 110 is adapted to ensure a minimum fuel flow rate of the order of 3 to 4 times the maximum fuel consumption of the engine, i.e. for example 180 l / h under a pressure of 4 bars.

 The loop circuit 100 is also connected via a return duct 130, 160 with the reservoir 40.

 More precisely, preferably, a return duct 130 is connected in derivation of the loop circuit 100, immediately downstream of the injector manifold 120.

 This conduit 130 communicates with the inlet of a pressure regulator 140, calibrated for example at 4 bars, the outlet of which communicates with the aforementioned conduit 160, which opens out above the reserve bowl 20 into which the pump 10 sucks.

 The pressure regulator 140 can be the subject of numerous embodiments.

 Preferably, it is a regulator with coaxial input / output, for example of the type illustrated in FIG. 2.

 The pressure regulation function is obtained using the regulator 140, by a bypass flow, regulated by a membrane subjected to the combined action of the liquid whose pressure is regulated, and a calibration spring.

 We will now describe, by way of non-limiting example, the structure of the regulator 140 shown diagrammatically in FIG. 2 appended.

 According to the representation, the regulator 140 comprises a body 141, generally cylindrical of revolution about a vertical axis 142.

The body 141 is provided with a collar 143 or rib projecting from its outer surface, substantially halfway up. The body 141 is divided into two chambers 144, 145 by a flexible membrane 146, transverse to the axis 142.

 The external periphery of the membrane 146 is sealed in a sealed manner on the internal surface of the body 141. To this end, preferably, the external periphery of the membrane 146 is pinched by the body 141 at the flange 143.

 The upper chamber 144 delimited in the body 141 by the membrane 146 receives a calibration spring 147.

 The lower chamber 145 located on the other side of the membrane 146 receives a projecting tube 148, centered on the axis 142. This tube 148 extends on the outside of the body 141, towards the outlet tube 160, in the form a tip 149.

 The tube 148 is tightly connected to the body 141. The top 150 of the internal tube 148 is located near the membrane 146, more precisely opposite a shutter 151 supported by the latter.

Those skilled in the art will understand that thus the spring 147 pushes the shutter 151 against the top of the tube 148, to close the latter.

 In addition, the lower chamber 145 is connected to the return pipe 130 by through passages 152 formed in the body 141, at the base thereof, around the end piece 149.

 Preferably, several evenly-spaced through passages are thus provided around the axis 142.

 When the pressure of the fuel supplied to the lower chamber 145, via the passages 152, and coming from the return line 130, is lower than the calibration pressure of the spring 147, the shutter 151 is pressed against the top of the tube 148. Thus, the fuel cannot flow from the lower chamber 145 to the bowl 20, via the return duct 160.

 On the other hand, when the fuel pressure in the chamber 145 becomes higher than the setting pressure of the spring 147, the membrane 146 and the shutter 151 are spaced from the top of the tube 148. The fuel can then flow from the lower chamber 145 towards the end piece 149, and from there join via the return duct 160, the reserve bowl 20.

 The pressure regulator 140 therefore makes it possible to maintain a constant pressure, corresponding to the setting pressure of the spring 147, in the loop circuit 100.

 According to an alternative embodiment, instead of being closed, so that the regulator works with a constant absolute reference pressure, the upper chamber 144 of the regulator 140, which houses the spring 147, can have at least one through passage 153 by through which the chamber 144 communicates with an auxiliary pressure reference. I1 can be for example the pressure prevailing in an intake manifold, or an intake manifold.

 The supply system according to the present invention offers numerous advantages over known prior systems.

 The present invention makes it possible in particular to obtain in the loop circuit 100 a high flow rate, therefore good temperature uniformity of the fuel circulating in this circuit, as well as a working pressure corresponding precisely to the set value ensuring proper operation. of the motor.

 In addition, the system according to the present invention proves to be particularly economical, in its structure, compared to certain systems previously proposed, in particular systems comprising several electric fuel pumps.

 Of course the present invention is not limited to the particular embodiments which have just been described but extends to any variant in accordance with its spirit.

Claims (12)

 1. Fuel supply system for an internal combustion engine, in particular of the diesel type, characterized in that it comprises: - a first pump (10) adapted to draw fuel located in a tank (40), - a loop circuit (100) which communicates, on the one hand with the output of the first pump (10) to receive fuel from the latter and which communicates, on the other hand with an operating site (120) , and - a second pump (110) placed on the loop circuit (100) and adapted to put the fuel in circulation in it in order to avoid excessive heating of the fuel and guarantee good temperature uniformity of the latter .  2. System according to claim 1, characterized in that the first pump (10) is an electric pump.  3. System according to one of claims 1 or 2, characterized in that the second pump is a venturi or jet pump (110).  4. System according to one of claims 1 to 3, characterized in that the loop circuit (100) is connected to the reservoir (40) via a return duct (130, 160).  5. System according to claim 4, characterized in that the return duct (130, 160) is equipped with a pressure regulator (140).  6. System according to one of claims 1 to 5, characterized in that the first pump (10) is adapted to deliver the order of 50 l / h of fuel under a pressure of the order of 6 bars.  7. System according to one of claims 1 to 6, characterized in that a water separator (60) is interposed between the outlet of the first pump (10) and the inlet of the second pump (110) .  8. System according to one of claims 1 to 7, characterized in that a fine filter (70) is interposed between the outlet of the first pump (10) and the inlet of the second pump (110).  9. System according to one of claims 1 to 8, characterized in that the loop system (100) comprises at least one part formed in the cylinder head of the engine.  10. System according to one of claims 1 to 9, characterized in that the loop circuit (100) communicates with a rail of injectors (120).  11. System according to one of claims 1 to 10, characterized in that the second pump (110) is designed for a fuel flow of at least 3 to 4 times the maximum fuel consumption of the engine, ie for example at least 180 l / h.  12. System according to one of claims 1 to 11, characterized in that means (140) are provided capable of regulating the pressure in the loop circuit (100) at a pressure of the order of 4 bars .