EP1255040A1 - Starting device for internal combustion engines - Google Patents

Abstract

The motor vehicle internal combustion engine start up fuel feed (1) has a pressurized fuel feed (3) with a fuel accumulator (2) and an injector (5). The feed has an energy storage sprung piston (4) in the fuel accumulator. The piston spring is pretensioned by the stored fuel pressure. Upon starting, the spring is released to cause a larger increase in fuel feed pressure.

Description

The invention relates to a starting device for engines with a common fuel injection rail.

Nowadays, car manufacturers are looking for technologies that would allow them to design vehicles less polluting cars. First of all because vehicle drivers are more sensitive than ever to ecology but especially because the standards on discharges coming into force are becoming more and more severe.

One of the solutions envisaged by the manufacturers for reducing polluting emissions consists in stopping the engine when it is not requested, such as for example Red fire. This technique is more generally called "stop and start". Indeed, stopping the engine will allow lower fuel consumption and therefore decrease polluting discharges. This drop in releases is significant especially in cities where the high concentration of signs road forces to stop regularly and where it forms often traffic jams.

This "stop and start" technique is easily applied with engines whose injection into each cylinder is piloted individually. However, this is not the case with engines with a common rail (or "common rail") which manages the injection of several cylinders at the same time time. Indeed, the current starting of these "common" engines rail "with high pressure fuel jet is too" slow "for the "stop and start" is applicable to them. This slowness is induced by the time required for the high pressure pump to compress the fuel in the common rail up to the minimum pressure necessary for the operation of the injectors. So, for common rail engines can operate in "stop and start", it is necessary to shorten their start-up time.

Patent application US5839413 discloses a system which reduces the starting time of an engine "common rail". The principle of this system consists in making communicate the common rail not only to a pump high pressure but also to a low pressure circuit thanks to two calibrated non-return valves (a first bass pressure and a second high pressure). The low circuit pressure has a low pressure accumulator which allows maintain a stable pressure lower than that delivered when the high pressure pump is at full load. So at starting while the high pressure pump is on running, the low pressure circuit is already compressing the fuel in the common rail. Then when the high pressure pump exerts a pressure higher than that prevailing in the circuit low pressure, the low pressure valve, which let through until then the low pressure flow will close in favor of second valve. The common rail is finally set up pressure only by the high pressure pump.

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

The purpose of the present invention is to overcome all or some of the drawbacks encountered in the prior art. So, the invention proposes a device for starting up a constitution simple for internal combustion engine, which can be integrated by causing few modifications to the engine and which allows to shorten the start-up time so as to allow the adaptation of these engines to "stop and start".

To this end, the invention provides a starting device for internal combustion engine comprising means pressurized fuel accumulator, means pressurized fuel supply and at least one injection means supplied with fuel by the means accumulator characterized in that it additionally comprises a energy storage device powered by pressure prevailing in said accumulator means and in that the energy storage device is able to supply at startup said energy stored so as to provide a second fuel compression means allowing said engine to start faster

This invention thus avoids modifications heavy structural, not having to provide too much energy additional to that currently required and to provide the injectors with sufficient pressure to initiate the engine until the high pressure pump takes over relay.

According to the invention, the fuel supply means advantageously have a high pump pressure supplying fuel to said accumulator means and a non-return valve allowing a direction of circulation of the fuel only from said pump to said means accumulator. This system allows, upon release of said energy, that the pressure is confined in the means accumulator and thus provides the minimum pressure required injection means.

Advantageously, said energy storage means is, according to the invention, located at one of the two ends of said means accumulator and includes a piston, a spring located between said piston and said end, at least a first stop static and at least one second movable stop allowing to limit the stroke of said piston. This simple device therefore allows to easily adapt the motors to "stop and start" existing.

According to one aspect of the invention, said first stop static is advantageously able to accommodate said piston in order to limit the spring stress.

Advantageously, said second stops include control means allowing, during the engine operation, to prevent movement of the piston from said end towards the inside of said means accumulator and, during startup, to authorize this same movement. This simple pair of stops allows you to release or to keep the piston-spring assembly under stress.

Advantageously according to the invention, the means of control are electromagnetic for compactness and optimal tool precision.

According to a second variant, the storage means of energy, advantageously, comprises a piston, a means elastic located between said piston and said end and a locking system to selectively release the piston.

Advantageously, the locking system, according to this second variant, comprises at least three rods provided at each of their ends with rollers and pivotally mounted on a disc, a shaft connecting the piston and the disc, elastic means connecting the links together and control means allowing according to the commands transmitted to the steering means to selectively block the links between said control means and the end of the medium accumulator.

Steering means, advantageously according to the second variant, comprise a stop substantially in truncated cone shape, a sensitive T-shaped piece of which the base extends said stop and the body of which is piloted in translation by electromagnetic means allowing the said first rollers to follow the surface of the stop for selectively block or unblock the second rollers of the end of the accumulator means.

• la figure 1 est une vue schématique du dispositif de démarrage selon une première variante ;
• la figure 2 est une vue schématique du moyen stockeur d'énergie selon une deuxième variante.

Other features and advantages will appear on reading the description which is given below, by way of indication and in no way limitative, with reference to the accompanying drawings, in which:

• Figure 1 is a schematic view of the starting device according to a first variant;
• Figure 2 is a schematic view of the energy storage means according to a second variant.

In the example illustrated in Figure 1, we can see that the central element of the starting device shown generally in 1 is the fuel accumulator means 2 or common rail. Significantly cylindrical in shape, it is connected to fuel supply means 3, to a means energy store 4 and injection means 5.

The fuel supply means 3, first of all, include, in the example illustrated, a high pressure pump 6 allowing the fuel present in the accumulator means 2, a duct 7, comprising a valve non-return 8, which provides the connection between the pump 6 and the means accumulator 2. The valve 8, in the example illustrated, authorizes direction of fuel flow only from pump high pressure 6 to the accumulator means 2.

Then, the injection means 5 in the example illustrated consist of pipes 9 and injectors 10. In addition in this example, it is a common rail motor managing the injection of four cylinders. As such, there are four lines 9 for transporting fuel under pressure of accumulator 2 towards the four injectors 10. Each of the injectors distributes the fuel under pressure in each combustion chamber (not shown).

Finally in the example illustrated in FIG. 1, the device 1 includes an energy storage means 4 cooperating with the fuel accumulator means 2. Said storage means energy consists mainly of a piston 11, a spring 12 and two sets of stops 13, 14.

The piston 11 is movable inside the means pressurized fuel accumulator 2. Displacement piston 11 is sealed by means of a connecting means 15, like an annular seal or segment, contained at its periphery.

The spring 12 previously cited, preferably of helical type, is connected in the example illustrated between the end of the accumulator means 2b, opposite the end 2a to which the duct 7 and the piston 11 are connected.

Finally, the energy storage means 4 has two stop series 13, 14. The first series, formed by a single stop 13, is static and annular in shape. She is secured inside the accumulator means 2 between its end 2b and the piston 11. In the example illustrated, the second series, composed of two stops 14, is movable by so as to be able to cooperate with the piston 11 to make this last 11 stationary in ramp 2. This cooperation can be carried out for example using an attachment of the type tenon 14 - mortise 11. Thus, this second series of stops 14 sometimes authorizes sometimes prevents the passage of piston 11 to its proximity. Preferably, the control command for these two movable stops is of the electromagnetic type.

When the common rail engine is started for the first time comprising the invention, the piston 11 of the storage means energy 4 is in the rest position (corresponding to the spring -12- in equilibrium) and the second series of stops 14 authorizes the passage of the piston 11 near it. The piston is therefore in the position furthest from the end 2b. This first starting is therefore carried out as for a conventional engine. The high pressure pump 6 will supply fuel under pressure the accumulator means 2 through the conduit 7. When the pressure, arriving at the injectors 10 via the lines 9, is sufficient to activate them, the engine is started.

It was during this first start-up of the engine and during its operation that the energy storage means 4 will be activated. Indeed thanks to the high pressure prevailing in the accumulator means 2, the piston 11 will be moved from the interior of said accumulator towards its end 2b thus compressing the spring 12. The calibration of the spring 12 is such with respect to the pressure in the accumulator means 2 that the piston 11 will very quickly be pushed into region 2b where the single stop 13 is located. The two movable stops 14 go then be activated so as to block the movement of the piston 11. Thus, when the engine stops, the piston 11 will remain substantially in its position so as to store energy retaining the spring 12 under stress.

During subsequent starts, the storage medium of energy 4 being under stress, the motor will be able start much faster and so will make it possible to make it work in "stop and start". So during starting, the pump 6 is put into action. She will provide a low pressure at the start then will gradually increase in intensity through the conduit 7 through the valve 8.

From a threshold pressure, the two movable stops 14 in the example illustrated will authorize the movement again of the piston 11. This freedom of the piston 11 will make it possible to release spring 12 from the stress at which it was submitted. This release will propel the piston 11 towards inside the accumulator means 2 causing a strong fuel overpressure in said accumulator means.

The valve 8, because the pressure at the outlet of the pump high pressure 6 (not yet fully loaded) is less than that of the accumulator means 2, will then close and therefore temporarily condemn the conduit 7. Thanks to this valve 8, the pressure generated by the activation of the storage means of energy 4 (sufficient to start the engine) is confined in the accumulator means 2. The first injection can therefore take place.

Following this first injection, the engine will be launched before the pump 6 has reached full load. The pump 6 being partially supplied with energy by the shaft engine (not shown), the start of the latter will have an accelerating effect on the pressure rise of the pump 6. The shortening of the start will therefore be increased tenfold.

After a certain time, the pump 11 will provide a pressure higher than that prevailing in the medium accumulator 2. The non-return valve 8 will then open under the effect of the pressure coming out of the pump 6 and therefore will do communicate, through line 7, the high pump pressure 6 with the fuel accumulator means 2. The normal fuel delivery and injection cycle can then take place.

Again during this cycle, the piston 11 of the means storage device 4 will be actuated so as to compress its spring 12 associated so as to be able to provide energy sufficient to shorten the next start.

The cycle cited and repeated several times allows, thanks to this starting device, to a common rail motor of operate in "stop and start". Preferably, the overpressure provided by the energy storage means 4 is tared so that two injections can be given before that the high pressure pump 6 take over.

According to a second variant illustrated in an example to Figure 2, we can see that the energy storage means 104 mainly comprises a piston assembly 101, an assembly rods 102 and a steering assembly 103.

The piston assembly 101 includes a piston 111, a spring 112, a piston end collar 113 and a shaft 114. The piston 111 slides tightly along the internal diameter of the accumulator means 2 thanks for example to an O-ring 115 along its periphery. Spring 112 is interposed between one of the ends 2a, 2b of the means accumulator and said piston 111. Finally the shaft 114, fixed substantially along the axis of translation of the piston 111, passes successively in the interior space formed by the turns of spring 112 and through a hole drilled on said end 2a, 2b where said piston assembly 101 is installed. This shaft 114 is partially covered along its length by the collar 113 which limits the output length of the shaft 114 relative to the common rail 2.

The rod assembly 102 preferably comprises at minus three links, two of which 105a, 105b are visible on the Figure 2, a disc 107, at least three springs, only one of which 108 is visible in FIG. 2, and rollers 109, 110.

In the example illustrated in Figure 2, the rods 105 are pivotally mounted relative to the disc 107. By therefore, the latter must have as many grooves as of rods which, preferably distributed equidistantly each other, each partially framing one of the rods. The disc 107 is fixed substantially perpendicular to the shaft 114 which implies for the rods 105 a positioning substantially parallel to the shaft 114.

In the example illustrated in FIG. 2, each link 105 has at each of its two ends a roller 109, 110. The first rollers 109a and 109b are intended to come correspond respectively with a notch 121a, 121b hollowed out on the surface of the end of the accumulator means 2. The second rollers 110a and 110b are in permanent contact with the control assembly 103. Thus in the example illustrated, for n links, there will be n disc grooves 107, 2n rollers, n notches and n springs.

In the example illustrated in Figure 2, all of piloting 103 mainly consists of a stop 116, a T-element 117 and an electromagnetic element 118. The stop 116 is in the form of a truncated cone whose surface inclined serves as a ramp for said second rollers 110a and 110b.

The element substantially in T 117 comprises a base of discoid shape 119 of diameter substantially identical to larger diameter of said cone so as to extend it and a rod 120 mechanically connecting the stop to the element electromagnetic 118. The latter is capable of translating said rod substantially along the axis of the shaft 114. Thus, the electromagnetic element 118 can control the approximation or spacing of the stop 116 relative to the disc 107.

As for the first variant 4, the purpose of the means energy store 104 is to release the piston at start-up 111 so as to provide a temporary means of compression fuel in the common rail until this the latter is supplied by the high pressure pump 6. From the same way, the second variant 104 also uses the stabilized pressure prevailing in the common rail for prestressing the storage means 104.

So when the pressure in the common rail 2 will be stronger than the setting of the spring 112, the piston 111 is pushed towards the end of said ramp to the stop 113 and therefore compresses the spring 112. This movement of the piston 111 forces the shaft 114 to come out of the common rail 2. this movement printed by tree 114 results in bring the disc 107 closer to the stop 116 and thereby make the second rollers 110 "climb" along the cone to the discoid base 119.

As the rollers 110 rise, the springs 108 are more and more spread apart to impose a quasi-horizontality of the rods 105 which obliges each first roller to hang in its associated notch 121 as illustrated in FIG. 2. The storage means is then ready to operate for "stop and start".

At the next start, the electromagnetic means 118 retracts the rod 120. This movement forces the second rollers 110 to descend along the cone of the stop 116 which induced, under the combined forces of the contraction of springs between the links 108 and the rebound of the spring 112 contained in the common rail 2, the unlocking of the rollers 109 of their respective notches 121 and a translation of the piston 111 towards the interior of the common rail 2. This translation, like the first variant 4, allows you to start faster the internal combustion engine. The movement described above is repeated to allow the adaptation of said engine to "stop and start".

Of course, the invention cannot be limited to the examples set out in this patent. So, the means of piloting of the electromagnetic type can be of another type. Of even, the tenon-mortise connection cited as an example between the movable stops 14 and the piston 11 may be different.

Finally, the overpressure in said accumulator means can be carried out using a pre-stressed elastic mechanical device passive trigger. Piloting this system which can for example be carried out using a pressure (10 - 20 bar) supplied by the HP pump. This pressure commands then the deindexing of the pre-constrained organ which, by relaxing, provides said overpressure.

Claims (9)

Starting device (1) for an internal combustion engine comprising pressurized fuel supply means (3), pressurized fuel accumulator means (2), at least one injection means (5) supplied with fuel by the accumulator means (2), an energy storage device (4) supplied by the pressure prevailing in said accumulator means characterized in that said accumulator means is located at one (2b) of the two ends of said fuel accumulator means so as to offer a second fuel compression means allowing said engine to start more quickly. Device according to claim 1, characterized in that the supply means (3) comprise a high pressure pump (6) supplying fuel to said accumulator means and a non-return valve (8) allowing a direction of circulation of the fuel only from said pump towards said accumulator means. Device according to claim 1 or 2, characterized in that the energy storage means (4) comprises a piston (11), a spring (12) located between said piston and said end, at least a first static stop (13) and at least one second movable stop (14) for limiting the stroke of said piston. Device according to claim 3, characterized in that said first static stop is able to receive said piston in order to limit the stress of the spring (12). Device according to claim 3 or 4, characterized in that said second movable stops (14) comprise control means making it possible, during the operation of the engine, to prevent movement of the piston (11) from said end towards the inside of said accumulator means and, during start-up, to authorize this same movement. Device according to claim 5, characterized in that the control means are of the electromagnetic type. Device according to claim 1 or 2, characterized in that the energy storage means (104) comprises a piston (111), an elastic means (112) located between said piston and said end and a locking system (102, 103 ) to selectively release the piston (111). Device according to claim 7, characterized in that the locking system (102, 103) comprises at least three links (105) provided at each of their ends with rollers (109, 110) and pivotally mounted on a disc (107), a shaft (114) connecting the piston (111) and the disc (107), elastic means (108) connecting between them the rods (105) and control means (103) allowing, according to the commands transmitted to the control means ( 103) to selectively block the links (105) between said control means and the end of the accumulator means (2). Device according to claim 8, characterized in that the control means (103) comprise a stop (116) substantially in the form of a truncated cone, a sensitive part (117) in the form of a T, the base (119) of which extends said stop ( 116) and the body (120) of which is driven in translation by electromagnetic means (118) allowing said first rollers (110) to follow the surface of the stop (116) to selectively block or unblock the second rollers (109) from the end of the accumulator means (2).

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