FR2832462A1 - Motor vehicle fuel injection feed, has temporary storage of fuel in stop and start driving for extra fuel feed on starting - Google Patents

Abstract

The motor vehicle fuel injection system (1) has injectors (5) with a pressure feed (2) for fuel and an accumulator (3) common for each injector. Between the accumulator and each injector is a fuel storage holder (4) to hold fuel under pressure. On starting, the store feeds extra fuel to the respective injector.

Description

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Injection system
The invention relates to an injection system for an internal combustion engine provided with a common fuel injection rail.

 Nowadays, car manufacturers are looking for technologies that would allow them to design less polluting motor vehicles. First of all because the drivers of vehicles are more sensitive than ever to the environment, but above all because the standards on discharges coming into force are becoming more stringent.

 One of the solutions envisaged by manufacturers to reduce polluting emissions consists in stopping the engine when it is not used, such as at a red light. This technique is more generally called "stop and start". In fact, stopping the engine will make it possible to lower fuel consumption and therefore to reduce polluting emissions. This drop in discharges is significant, especially in cities where the high concentration of road signs means that stops have to be made regularly and traffic jams are often formed.

 This "stop and start" technique is easily applied with engines whose injection into each cylinder is controlled individually. However, this is not the case with engines equipped with a common rail (or "common rail") which manages the injection of several cylinders at the same time.

 Indeed, the current starting of these engines fitted with a common high pressure fuel jet rail is too "slow" for the "stop and start" to be applicable to them. This slowness is induced by the time required for the high pressure pump to compress the fuel present in the common rail to the minimum pressure necessary for the operation of the injectors. So, for the motors to

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 common rail can operate in "stop and start", it is necessary to shorten their start time.

 Patent application US5839413 discloses a system which makes it possible to reduce the starting time of a common rail motor. The principle of this system consists in making the common rail communicate not only with a high pressure pump but also with a low pressure circuit thanks to two calibrated non-return valves (a first low pressure and a second high pressure). The low pressure circuit has a low pressure accumulator which allows to maintain a stable pressure lower than that delivered when the high pressure pump is at full load.

 Thus at start-up while the high pressure pump is started, the low pressure circuit already compresses the fuel in the common rail. Then, when the high pressure pump exerts a pressure higher than that prevailing in the low pressure circuit, the low pressure valve, which previously allowed the low pressure flow to pass, will close in favor of the second valve. The common rail is finally pressurized only by the high pressure pump.

 The pressure build-up time thanks to this system is therefore reduced. However, this technique is not satisfactory on the one hand because it is too complex to implement and on the other hand because it is not fast enough for its application to "stop and start" to be pleasant. in use.

 The object of the present invention is to overcome all or part of the drawbacks encountered in the prior art. Thus, the invention proposes an injection system of simple constitution for an internal combustion engine making it possible to shorten the starting time in order to adapt these engines to "stop and start".

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 To this end, the invention relates to an injection system for an internal combustion engine comprising at least one injection means, means for supplying fuel under pressure, an accumulator common to each injection means containing pressurized fuel supplied by said supply means, characterized in that it further comprises, between each injection means and said accumulator, a pressurized fuel storage device supplied by said accumulator, said storage device being suitable for starting releasing said stored pressurized fuel to its associated injection means in order to supply pressurized fuel more quickly than with said supply means alone. This system makes it possible to keep the existing structure and to adapt it stop and start by shortening the start-up time.

 Advantageously, each pressurized fuel storage device according to the invention comprises a first channel which, connecting said accumulator and one of said injection means, comprises at least one reservoir and at least two controlled opening means respectively located between the accumulator and the tank and between the tank and said injection means to selectively allow the tank to be filled with pressurized fuel from said accumulator or to empty the tank to supply said injection means. This configuration has the advantage of not having to install an additional compression source to recover pressurized fuel from the accumulator.

 Advantageously, said controlled opening means, according to the invention, are solenoid valves.

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 Each pressurized fuel storage device according to the invention advantageously comprises in addition a second channel which, in parallel with the first, only allows, thanks to a non-return valve, the passage of fuel from said accumulator to said means d injection to allow the injection means to be supplied directly by said accumulator. This allows, after the starting phases, that the injection is carried out normally, that is to say that each injection means is supplied by the same pressurized fuel accumulator.

 Other particularities and advantages will appear on reading the description below made with reference to the single figure showing a simplified diagram of the injection system according to the invention.

 In the example illustrated in Figure 1, one can see an injection system 1, according to the invention, intended for use in an internal combustion engine. It mainly consists of a high pressure pump 2, a common rail 3, a storage device 4 and an injector 5.

A single injector 5 is visible, but of course, the common rail 3 can, for example, supply as many injectors 5 as there are cylinders present in the engine.

 The high pressure pump 2 supplies the common rail 3 with pressurized fuel. This widely used and well-known configuration will not be described in more detail in this patent.

 In the example illustrated, it can be seen that the storage device 4 connects the common rail 3 and the injector 5 by two channels 6, 7 joining before arriving at the injector 5.

 The first channel 6 is provided with a non-return valve 8, preventing the flow of fuel from passing from the injector 5 to the common rail 3 but allowing the reverse flow. The second channel 7 comprises a reservoir 9, a pressure sensor 10 and two solenoid valves 11,12. In the example illustrated in Figure 1, the latter 11,12, located

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 respectively on either side of the reservoir 9, selectively and independently of one another open part of the channel 7. The sensor 10 detects the pressure prevailing in the reservoir 9.

 When the engine is started for the first time, the tank 9 being empty, the sensor 10 indicates that there is no pressure. The solenoid valve 10 is then put in its open position and the second 11 in its closed position. When the high pressure pump 2 supplies the common rail 3 with pressurized fuel, fuel will pass through the channel 6 and the channel 7 of each storage device 4 associated with an injector 5.

 The solenoid valve 10 being open, the fuel will then be introduced into the tank 9 without being able to go any further, the solenoid valve 11 being closed. The fuel which is in the channel 6 passes through the non-return valve 8 and thus feeds the injector 5.

 The high pressure pump 2 will gradually increase the pressure to provide, after a moment, a pressure high enough to reach the minimum operating pressure of the injectors 5. A pressure sensor (not shown) located in each injector 5 makes it possible to determine said minimum pressure and then controls the injection. The engine can then be started.

 The sensor 10 of the storage device 4 in the same way detects whether the necessary pressure in the tank 9 (which may be much higher than that mentioned in the previous paragraph) is reached. The solenoid valve 10 at this time will be put in its closed position and will therefore trap pressurized fuel in the tank 9. The engine is now ready to operate in stop and start mode.

 When the start control is actuated again and the sensor 10 detects pressure, the solenoid valve 12 is placed in the open position and therefore releases the pressurized fuel to its associated injector 5. In

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 Indeed, the non-return valve 8 prevents this fuel from going up along the channel 6 towards the common rail 3.

 This released pressure being greater than the minimum operating pressure of its associated injector 5, the injection can take place more quickly than if it had been necessary to wait for the high pressure pump 2 to supply said minimum pressure alone. The engine can therefore be started earlier.

 The high pressure pump 2 being partially supplied with energy by the engine timing belt (not shown), the starting of the latter will have an accelerating effect on the rise in pressure of the high pressure pump 2. The shortening of the starting will therefore to be further multiplied.

 After a certain time, the high pressure pump 2 will supply a higher pressure in the common rail 3 compared to that prevailing at the inlet of the injector 5. The non-return valve 8 will then let the fuel s '' flow through the channel 6 to the injector 5. At this time, the solenoid valve 12 is returned to the closed position and then the solenoid valve 11 is reopened. The normal fuel injection cycle can then take place. As previously specified, when the necessary pressure, detected by the sensor 10, is reached in the tank 9, the solenoid valve 11 closes and traps fuel under pressure in the tank 9 again.

 The restart cycle cited and repeated several times allows, thanks to this injection system, a motor with a common rail to operate in "stop and start". The fact that there is a storage device 4 for each injector 5 allows a small volume of reservoir 9 compared to that of the common rail 3. The reservoir 9 will preferably be dimensioned so that two injections can be carried out before the pump high pressure 2 takes over.

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 Of course, the present invention is not limited to the example illustrated but is capable of various variants and modifications which will appear to those skilled in the art. In particular, configurations of channel 7 with a single solenoid valve or a technology different from the solenoid valves can be envisaged. Also, the strategy of the first start may be different, for example by filling the reservoir 9 only after a few injections.

Claims (4)

CLAIMS 1. Injection system (1) for an internal combustion engine comprising at least one injection means (5), pressurized fuel supply means (2), an accumulator (3) common to each means d injection (5) containing pressurized fuel supplied by said supply means characterized in that it further comprises, between each injection means (5) and said accumulator, a pressurized fuel storage device (4) supplied by said accumulator, said storage device being able to release said fuel under pressure stored towards its associated injection means during starting in order to supply it with fuel under sufficient pressure more quickly than with said supply means alone. 2. Injection system (1) according to claim 1, characterized in that each pressurized fuel storage device (4) comprises a first channel (7) which, connecting said accumulator and one of said injection means, comprises at at least one reservoir (9) and at least two controlled opening means (11,12) respectively located between the accumulator (3) and the reservoir (9) and between the reservoir (9) and said injection means to allow selectively fill the fuel tank under pressure (9) from said accumulator or empty the tank (9) to supply said injection means. 3. Injection system (1) according to claim 2, characterized in that said controlled opening means are solenoid valves. <Desc / Clms Page number 9> 4. Injection system (1) according to claim 2 or 3, characterized in that each pressurized fuel storage device (4) further comprises a second channel (6) which, in parallel with the first (7), allows only, thanks to a non-return valve (8), the passage of fuel from said accumulator to said injection means in order to allow the supply of injection means (5) directly by said accumulator.