EP0857253A1

EP0857253A1 - Internal combustion engine fuel injection system

Info

Publication number: EP0857253A1
Application number: EP96934907A
Authority: EP
Inventors: Cornel Stan; Jean-Louis Lefebvre
Original assignee: Peugeot Motocycles SA
Current assignee: Peugeot Motocycles SA
Priority date: 1995-10-24
Filing date: 1996-10-14
Publication date: 1998-08-12
Also published as: WO1997015756A1; AU7304796A; FR2740178A1; FR2740178B1

Abstract

A system comprising a fuel tank (20), pressurised fuel accumulation means (21), means (26) for connecting the accumulation means to means (27) for injecting fuel into the engine, and a control valve (29) positioned between the connecting means (26) and the tank (20) and connected to control means (30) for opening and closing the valve to generate a fuel pressure wave by means of a surge effect in the connecting means up to the injection means, and thereby inject fuel into the engine. Said system further comprises means (30) for controlling the fuel pressure in the accumulation means (21) to enable adjustment of the fuel pressure wave amplitude in the injection means (27) and thus also of the amount of fuel injected into the engine, in accordance with the operating conditions thereof.

Description

Fuel injection system in an internal combustion engine.

The present invention relates to a fuel injection system in an internal combustion engine.

The entry into force of increasingly stringent anti-pollution standards has led vehicle engine manufacturers to develop new fuel supply systems for internal combustion engines.

These fuel supply systems include, for example, so-called indirect injection systems, in which the fuel is injected into the air supply duct or ducts of the engine or direct injection, in which the fuel is injected directly into the combustion chamber (s) of the engine. In the latter case, these systems also make it possible to considerably reduce the basic polluting emissions of two-stroke engines with sweeping by crankcase pump and powered by carburetor.

Thus, for example, air-assisted fuel injection systems or liquid fuel injection systems such as, for example, water hammer effect systems have been developed in the state of the art.

For a detailed explanation of the operation of these different systems, reference may be made to the documents "FISITA 865040", entitled "EIN UNKONVENTIONELLES EINSPRITTZSYSTEM FUR KLEINE SCHELLAUFENDE DIESEL MOTOREN" pages 1293-1296, XXI FISITA CONGRESS, BELGRADE 1986 and "SAE 950269", entitled "RAM-TUNED AND AIR-ASSISTED DIRECT FUEL INJECTION SYSTEMS APPLIED to a SI TWO-STROKE ENGINE", pages 43-52 - International Congress and Exposition- Detroit, Michigan, February 27 - March 2, 1995.

More particularly, the invention relates to a fuel injection system by water hammer effect. As described in the documents previously mentioned, such a fuel injection system includes a fuel tank, means for accumulating under fuel pressure, means for connecting means for accumulating under pressure to fuel. means for injecting fuel into the engine and a control valve located between the connection means and the fuel tank and connected to means for controlling the latter on opening and closing, to generate by effect water hammer, a fuel pressure wave in the connection means to the injection means, making it possible to inject fuel into the engine.

It will then be understood that these control means manage the opening and closing of this control valve during the engine operating cycle, so that the opening of the valve causes a flow of fuel from the means accumulation towards the tank, while the closing thereof causes water hammer, a pressure wave in the connection means, allowing fuel to be injected into the engine via the means of injection.

As indicated in the documents mentioned above, the quantity of fuel injected into the engine depends on the amplitude of the fuel pressure wave in the connection and injection means, this amplitude depending itself on the speed of the fuel in the connection means. However, this speed is controlled in the prior art, by the duration of opening of the control valve.

In fact, the greater the duration of opening of the valve, the higher the speed of the fuel in the connection means at the time of closing of the valve is high, the greater the amplitude of the pressure wave in the connection means and the greater the amount of fuel injected into the engine, and vice versa. It will be noted that the instant of injection into the engine operating cycle is also controlled by the control means which make it possible to control the opening time of the valve and therefore, for example, to anticipate this opening instant. in the valve operating cycle as the quantity of fuel to be injected increases, to obtain a fixed injection instant in the engine operating cycle.

However, it is understood that such a system has a number of drawbacks.

In fact, the choice of the value of the pressure in the accumulation means is guided by the maximum quantity of fuel to be injected into the engine and by the operating frequency thereof, which taking into account the uniqueness of the parameter for controlling the quantity injected, indicated previously, leads to a limitation of the possible operating range of the motor on the one hand, by an imprecision of the control times relative to the response times of the system on the small quantities injected and d on the other hand, by the impossibility of supplying the energy necessary to create this pressure when the engine is operating on points of low power.

Furthermore, it is also difficult to precisely control the amount of fuel injected into the engine over a wide operating speed range of the latter.

To limit these drawbacks, specific solutions have been developed and are the subject of the following patents: - WPF02D / 172393 N ° 106216 dated 20/7/73 (KLUJ Olaf, IH ZWICKAU, RDA),

- WPF02D / 3093078 N ^β 266384 of 23/11/87 (STAN Cornel, HOFFMANN Werner, IH ZWICKAU, RDA), - PCT / EP91 / 01902 N ° W092 / 14925 of 26/2/91

(HEIMBERG Wolfgang, FICHT Gmbh, D).

In the first of these patents, a system for controlling an electric pump is described which is part of means for accumulating pressurized fuel for supplying fuel to an injection system and which makes it possible to obtain a pressure. constant in the means of accumulation.

This control system, usable in injection systems operating by water hammer effect, relates to a pump energy supply based on the combination of a constant current and a variable voltage whose value is a function of the pres ¬ sion in the means of accumulation. To obtain a constant pressure, a pressure sensor connected to the accumulation means delivers the pressure information necessary for a computer for the correction of the supply voltage values of the pump.

Although this solution limits the flow of fuel to the quantity strictly necessary for the operation of the system and of the engine, it does not solve the problems of adjustment and energy consumption mentioned previously.

The second patent describes, within the framework of a water hammer injection system, a device which allows a finer adaptation between on the one hand, the fuel flow control means and on the other hand, the fuel speed obtained by the opening time and the operating frequency of the control valve. This device actually controls the flow of fuel through a control unit that manages the control valve and a flow control valve. This combined control provides finer adjustment of the system than in the previous cases, but results in a large quantity of fuel being pumped directly from the regulating valve to the tank.

The last cited patent describes an injection system similar to a system based on the effect of water hammer and whose fuel flow control means to accelerate, are replaced by an intermittent electromagnetic piston pump.

This pump which ensures the flow of fuel to be accelerated and the control valve which brakes the fuel to achieve the water hammer effect, are connected to a common control unit, with the aim of achieving an adaptation between the fuel flow and the opening time of the valve.

This solution has drawbacks from the hydrodynamic point of view and does not make it possible to obtain engine operating ranges without energetic losses and significant technical complications.

Thus, the replacement of a flow rate and a fuel pressure with stable values for a duration of opening of the control valve - obtained by a continuous flow pump - by a flow rate and a fuel pressure with variable values due discontinuous pumping performed only during the opening of the control valve, leads to variations in flow, pressure and hydraulic losses in the connection means. The effect of these variations results in an unstable characteristic of the fuel speed which changes with the duration of opening and the operating frequency of the control valve. The relationship between the valve opening time and the means of generating the electric force tromagnetic in the magnet of the piston pump becomes a very complex and difficult to manage function over the entire operating range of the engine.

The object of the invention is therefore to solve these problems.

Document DE-A-42 06 817 in the name of FICHT, also relates to the field of fuel injection in an internal combustion engine and describes a fuel injection device in which a piston pump is associated with means for temporarily storing a certain volume of fuel.

During a first phase of operation of this device, the pump piston moves along a so-called "dead" stroke, during which this piston encounters a very low displacement resistance, insofar as the volume corresponding fuel is transferred to the storage means.

This then allows the piston to reach a certain speed of movement and acquire a certain kinetic energy, useful during a second phase of operation of this device, when the storage means are filled, to generate a pressure wave of fuel in the injection device, to allow fuel to be injected into the engine. In fact, this injection device is based on the use of a phenomenon other than the water hammer phenomenon as described in the present application, insofar as in this prior document, the pressure pulse is generated in the fuel by dissipation of the kinetic energy of the piston of the pump, whereas in the system according to the invention, the pressure wave is created by dissipation of the kinetic energy of the fuel, this kinetic energy of the fuel being obtained by piloting the valve. 7/15756 PO7FR96 / 01601

The subject of the invention is therefore a system for injecting fuel into an internal combustion engine, of the type comprising:

- a fuel tank, - fuel pressure accumulation means,

- means for connecting the fuel pressurization means to fuel injection means in the engine, and - a control valve located between the connection means and the fuel tank and connected to control means of the latter on opening and closing, to generate by water hammer effect, a fuel pressure wave in the connection means to the injection means, making it possible to inject fuel in the engine, characterized in that it further comprises means for controlling the fuel pressure in the accumulation means to allow adjustment of the amplitude of the fuel pressure wave in the means of injec¬ tion and therefore the amount of fuel injected into the engine, depending on the operating conditions thereof.

Advantageously, the control means of the control valve are adapted to control the instant and the duration of opening of the latter.

Advantageously also, the operating conditions of the engine further include the operating regime and the load thereof. The invention will be better understood on reading the description which follows, given solely by way of example and made with reference to the appended drawings, in which:

- Fig.l shows a block diagram illustrating the structure of an injection system, by water hammer, fuel in an internal combustion engine, state of the art;

- Fig.2 illustrates the operation of such a system, - Fig.3 shows a block diagram illustrating the structure of an embodiment of a system of injection, by water hammer effect, of fuel in an internal combustion engine according to the invention; and - Fig.4 illustrates the operation of such a system.

As can be seen in FIG. 1, a system of fuel injection by water hammer effect, in an internal combustion engine, conventionally comprises a fuel tank designated by the general reference 1 in this figure. .

This fuel tank is connected to means for accumulating fuel under pressure designated by the general reference 2, these means for accumulating fuel under pressure comprising for example an accumulator designated by the general reference 3 in this figure, a fuel pump 4, a filter 5 and pressure regulating means 6, connected in parallel between the outlet of the fuel pump 4 and the tank 1. Furthermore, connection means designated by the general reference 7 in this figure, are also provided between the means 2 for accumulating fuel under pressure and means for injecting carbu¬ rant into the engine, designated by the general reference 8 in this figure.

These connection means generally comprise a fuel acceleration duct into which a member such as a damping valve designated by the general reference 9 can be integrated. Finally, a control valve designated by the general reference 10 in this figure, is also connected between these connection means 7 and the fuel reser¬ see 1. The operation of this control valve 10 is controlled at the opening and at closing by control means generally designated by the reference 11 in this figure, to generate by water hammer effect, a fuel pressure wave in the connection means to the injection means 8, allowing d '' inject fuel into the engine.

These control means comprise an information processing unit 12 based on a microcontroller for example, associated with means 13 for storing an injection map of conventional type.

The processing unit receives information relating to the operating conditions of the engine, such as for example the speed and the operating load of the latter. As illustrated in FIG. 2, the fuel pressure in the fuel tank 1 is designated by Pr, while the fuel pressure in the fuel pressure accumulation means 2 is designated by PO. This pressure PO in the accumulation means is obtained thanks to the fuel pump 4 and to the pressure regulation means 6.

In the initial state, the control valve 10 is closed. If at the instant you open the control valve 10 via the information processing unit 12 described above, the fuel pressure in the connection means 7 therefore drops to a value close to Pr as a function of the pressure losses of the circuit, but the speed of the fuel circulating in these means gradually increase to a speed V01 as illustrated.

If the control valve 10 is closed at time t03 via the information processing unit 12, the kinetic energy stored by the fuel flow causes a fuel pressure wave in the connection means described above, this pressure wave having, as illustrated, an amplitude greater than the setting pressure PM of the injection means, which makes it possible to inject fuel into the engine.

As described in the documents previously mentioned, the quantity of fuel injected into the engine is a function of the amplitude of this pressure wave and it is known that it is possible to adjust this amplitude by controlling the speed of the fuel in the connection means 7 before the valve 10 closes.

This is achieved by controlling the opening time of the control valve 10 as illustrated in this FIG. 2, where it can be seen that the longer the opening time of the valve 10, the greater the speed of the the higher the fuel, the higher the amplitude of the fuel pressure wave in the injection means.

It is therefore understandable that by varying the instant and the duration of opening of this control valve 10, for example between TOI and T02, a fuel speed is obtained in the connection means 7 which varies between V01 and V02 at the instant T03 and therefore an amplitude of the fuel pressure wave in the connection means, which varies between Pmaxl and Pmax2, which makes it possible to vary the quantity of fuel injected into the engine. As indicated above, this has a number of drawbacks.

The object of the invention is to solve these problems thanks to the structure illustrated by way of example in FIG. 3.

We recognize in this figure 3, a fuel tank, designated by the general reference 20, fuel pressure accumulation means, designated by the general reference 21, comprising an accumulator 22, a fuel pump 23, a filter 24 and pressure regulating means 25 connected in parallel between the outlet of the fuel pump 23 and the fuel tank 20.

Furthermore, connection means designated by the general reference 26, constituted for example by a fuel acceleration duct, are also interposed between the accumulation means 21 and means for injecting fuel into the engine designated by the general reference 27. A member such as a damping valve 28 can also be interposed in these connection means 26.

A control valve designated by the general reference 29 is also interposed between the connection means 26 and the fuel tank 20.

This control valve is connected to control means generally designated by the reference 30 in this figure, making it possible to control the latter on opening and closing, to generate by water hammer effect, a wave of fuel pressure in the connection means 26, which makes it possible to inject fuel into the engine, thanks to the injection means 27.

These control means 30 comprise, as described above, an information processing unit designated by the general reference 31 for example at micro-controller base, associated with storage means 32 of an injection map.

According to the invention, the injection system also comprises means for controlling the fuel pressure in the accumulation means 21, to allow adjustment of the amplitude of the fuel pressure wave in the connection means 26 and therefore the amount of fuel injected into the engine, depending on the operating conditions of the latter. These engine operating conditions may, for example, include engine speed and operating load information.

In this case, the information processing unit 31 described above is conventionally connected to means for determining the speed and the operating load of the engine, these means possibly having any suitable structure known in the state of the art.

This information processing unit 31 can then be connected through conventional interface means to the fuel pump 23 to control the operation thereof, in order to control the fuel pressure in the accumulation means 21 and more particularly in the accumulator 22. This control of the operation of the pump can for example be ensured in open loop or in closed loop and in the latter case, the processing unit information 31 receives pressure information from a pressure sensor, for example 33, associated with the accumulator 22.

Such a pump control is in itself conventional, for example in current and / or in voltage to obtain a determined fuel outlet pressure.

This pump can be constituted for example by a conventional positive displacement pump actuated by a motor electric whose power supply is controlled by current and voltage as indicated above.

Other parameters relating to the operating conditions of the engine, such as for example the external temperature and pressure, can be used in a conventional manner to make corrections to the control described above, in order to optimize the quantities injected. for the different points and the different operating conditions of this engine. It can then be seen, as can be seen in FIG. 4, that the information processing unit 31 is adapted to control the operation of the fuel pump 23 in order to adjust the fuel pressure in the accumulator 22 so as to control this between a pressure at least equal to the pressure Pr prevailing in the fuel tank and a maximum pressure P01.

If, for example, the pressure in the fuel accumulation means is controlled, for instants and durations of opening of the control valve 29 identical, one obtains in the connection means 26, different fuel speeds V01 and V02. In fact, the higher the fuel pressure in the accumulation means, the higher the speed of the fuel in the connection means. When controlling the closing of the control valve 29 at time t03, the amplitudes of the corresponding generated pressure waves will also be different, for example Pmaxl and Pmax2.

The control of the fuel pressure in the accumulation means then also makes it possible to adjust the quantity of fuel injected into the engine.

It goes without saying of course that the information processing unit 31 mentioned above and the storage means 32 of the injection map can be adapted to control in a coordinated manner, the fuel pressure in the accumulation means 21 and the instant and the duration of opening of the control valve 29.

The different parameters defining this mapping is determined for each point of _f onc _¬ tioning of the motor in order to optimize the operation.

It will be noted, for example, that for a low engine operating speed, it may be advantageous to establish in the accumulation means 21 a relatively low pressure, since this will require lower energy consumption at the engine level and will allow the opening time of the control valve 29 to be extended sufficiently to achieve the desired precision on the quantities of fuel injected. This is also made possible since the engine operating speed is low, the time available for the injection cycle is important.

It is therefore conceivable in fact that the fuel injection system according to the invention is based on a modulation of the fuel pressure in the accumulation means, which may or may not be associated with a modulation of the instant and the duration of the opening of the control valve and this to allow optimum adjustment of the quantity of fuel injected into the engine for each operating point thereof, by controlling the amplitude of the pressure wave created by water hammer during the operation of this control valve.

Each engine operating point can then be characterized by optimum operating parameters corresponding to a determined pressure in the accumulation means, a determined duration of opening of the control valve and a determined instant of triggering of the opening thereof, these various parameters being able to be determined beforehand by calculation and / or experimentation as a function of the desired operating characteristics of the engine and of the characteristics characteristic thereof.

These different parameter values then constitute the injection map stored conventionally in the storage means 32 associated with the information processing unit 31, which controls the control valve 29 and for example the fuel pump. 23. It goes without saying of course that the fuel pressure in the accumulation means can be adjusted by action on a means other than the fuel pump such as for example the accumulator.

Claims

1. Fuel injection system in an internal combustion engine, of the type comprising:

- a fuel tank (20), - means (21) for accumulating fuel under pressure,

- means (26) for connecting the means for accumulating fuel under pressure to means (27) for injecting fuel into the engine, and - a control valve (29) located between the connection means (26) and the fuel tank (20) and connected to control means (30) thereof on opening and closing, to generate by water hammer effect, a fuel pressure wave in the means of connection to the injection means, making it possible to inject fuel into the engine, characterized in that it further comprises means (30) for controlling the fuel pressure in the accumulation means (21) for allow adjustment of the amplitude of the fuel pressure wave in the injection means (27) and therefore of the quantity of fuel injected into the engine, as a function of the operating conditions thereof.

2. System according to claim 1, characterized in that the control means (30) of the control valve (29) are adapted to control the time and the duration of opening thereof.

3. System according to claim 1 or 2, characterized in that the engine operating conditions further include information relating to the speed and the engine operating load.

4. System according to any one of the preceding claims, characterized in that the control means (30) comprise an information processing unit (31) connected to storage means (32) of a injection mapping and means for determining the engine speed and operating load.

5. System according to any one of the preceding claims, characterized in that the accumulation means (21) comprise an accumulator (22), and a fuel pump (23) and in that the means (30) Pressure control valves are adapted to control the operation of the fuel pump (23) to control the fuel pressure in the accumulator (22).