EP1255040B1 - 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, automakers are looking for technologies that would allow them to design cleaner vehicles. First of all because the drivers of the vehicles are more sensitive than ever to the ecology but especially because the standards on the rejections coming into force are more and more severe.

One of the solutions considered by manufacturers to reduce pollutant emissions is to stop the engine when it is not requested, such as at a red light. This technique is more generally called "stop and start". Indeed, stopping the engine will help lower fuel consumption and thus reduce pollutant emissions. This decline in emissions is significant especially in the city where the high concentration of road signs requires regular stops and where plugs often form.

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 motors with a common rail (or "common rail") which, it manages the injection of several cylinders at the same time. Indeed, the current start of these "common rail" high pressure fuel jet engines is too "slow" for the "stop and start" to be applicable. 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. Thus, for the common-rail motors to operate in "stop and start", it is necessary to shorten their startup time.

Patent application US5839413 discloses a system that reduces the startup time of a common rail engine. The principle of this system is to communicate the common rail not only to a high pressure pump but also to a low pressure circuit with two calibrated check valves (a first low pressure and a second high pressure). The low pressure circuit has a low pressure accumulator which makes it possible to maintain a stable pressure lower than that delivered when the high pressure pump is at full load. Thus at startup while the high pressure pump is turned on, the low pressure circuit already compresses the fuel in the common rail. Then, when the high pressure pump exerts a pressure greater than that prevailing in the low pressure circuit, the low pressure valve, which previously let the low pressure flow, will close in favor of the second valve. The common rail is finally put under pressure only by the high pressure pump.

The pressure rise time with this system is thus shortened. However this technique is unsatisfactory 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" is pleasant in use.

JP 10 274130 A shows a starting device according to the preamble of claim 1.

The object of the present invention is to overcome all or part of the disadvantages encountered in the prior art. Thus, the invention proposes a start-up device with a simple constitution for an internal combustion engine, which can be integrated by causing few modifications to the engine and which makes it possible to shorten the start-up time so as to allow the adaptation of these engines. at the "stop and start".

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

This invention thus makes it possible to avoid heavy structural modifications, to avoid having to supply too much additional energy compared to that currently required and to provide the injectors with sufficient pressure to start the engine until the high pressure pump take over.

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

Advantageously, said energy storage means is, according to the invention, located at one of the two ends of said accumulator means and comprises a piston, a spring located between said piston and said end, at least a first static stop and at least a second mobile stop for limiting the stroke of said piston. This simple device therefore makes it easy to adapt the existing engines to "stop and start".

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

Advantageously, said second stops comprise control means allowing, during operation of the motor, to prevent movement of the piston of said end towards the inside of said accumulator means and, during start-up, to allow this same movement. This simple pair of stops makes it possible to release or keep in constraint the piston - spring assembly.

Advantageously according to the invention, the control means are of the electromagnetic type for compactness and optimum precision tools.

According to a second variant, the energy storage means, advantageously, comprises a piston, a resilient means situated between said piston and said end and a locking system for selectively releasing 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 linking together the connecting rods and control means allowing according to the commands transmitted to the control means to selectively block the links between said control means and the end of the accumulator means.

The control means, advantageously according to the second variant, comprise an abutment substantially in the shape of a truncated cone, a sensitive piece in the shape of a T whose base extends said abutment and whose body is controlled in translation by electromagnetic means allowing said first rollers to follow the surface of the stop to selectively lock or unlock 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 particularities and advantages will appear on reading the description which is given below, as a indicative and in no way limiting, 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, it can be seen that the central element of the starting device generally represented in 1 is the fuel accumulator means 2 or common rail. Substantially cylindrical in shape, it is connected to fuel supply means 3, energy storage means 4 and injection means 5.

The fuel supply means 3, first of all, comprise, in the illustrated example, a high pressure pump 6 for compressing the fuel present in the accumulator means 2, a conduit 7, comprising a non-return valve 8, which is connected between the pump 6 and the accumulator means 2. The valve 8, in the illustrated example, allows the direction of circulation of the fuel only from the high pressure pump 6 to the accumulator means 2.

Then, the injection means 5 in the illustrated example consist of pipes 9 and injectors 10. Moreover, in this example, it is a common rail engine managing the injection of four cylinders. As such, there are four pipes 9 for transporting the pressurized fuel accumulator means 2 to 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 comprises an energy storage means 4 cooperating with the fuel accumulator means 2. Said energy storage means consists mainly of a piston 11, a spring 12 and two series of abutment 13, 14.

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

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

Finally, the energy storage means 4 has two series of stops 13, 14. The first series, formed by a single stop 13, is static and annular. It is secured inside the accumulator means 2 between its end 2b and the piston 11. In the illustrated example, the second series, composed of two stops 14, is movable so as to cooperate with the piston 11 to make the latter 11 immobile in the ramp 2. This cooperation can be achieved for example by means of a fastening type tenon 14 - mortise 11. Thus, this second series of abutment 14 sometimes authorizes sometimes prevents the passage of the piston 11 to its proximity. Preferably, the piloting control of these two mobile stops is of the electromagnetic type.

At the first start of the "common rail" motor comprising the invention, the piston 11 of the energy storage means 4 is in the rest position (corresponding to the spring -12- in equilibrium) and the second series of stops 14 allows the passage of the piston 11 in its vicinity. The piston is therefore in the furthest position from the end 2b. This first start is performed as for a conventional engine. The high-pressure pump 6 will supply pressurized fuel to the accumulator means 2 via the duct 7. When the pressure, arriving at the injectors 10 via the ducts 9, is sufficient to actuate them, the engine is started.

It is during this first start-up of the engine and during its operation that the average energy storage 4 will be activated. Indeed, thanks to the high pressure prevailing in the accumulator means 2, the piston 11 will be moved from the inside 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 the region 2b where the single stop 13 is located. The two mobile stops 14 will then be activated so as to block the movement of the piston 11. Thus, when the engine is stopped, the piston 11 will remain substantially in its position so as to store energy by holding the spring 12 under duress.

During subsequent starts, the energy storing means 4 being under stress, the engine will be able to start much faster and thus will make it possible to operate it in "stop and start" mode. Thus during startup, the pump 6 is actuated. It will provide a low pressure at the beginning and then gradually increase in intensity through the conduit 7 through the valve 8.

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

The valve 8, because the pressure at the outlet of the high pressure pump 6 (not yet at full load) is lower than that of the accumulator means 2, will then close and thus condemn the conduit temporarily 7. With this valve 8, the pressure generated by the activation of the energy storage means 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 arrived at full load. The pump 6 is partially powered by the motor shaft (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 greater than that prevailing in the accumulator means 2. The non-return valve 8 will then open under the effect of the pressure exiting the pump 6 and therefore will do communicating, through the conduit 7, the high pressure pump 6 with the fuel accumulator means 2. The normal cycle of dispensing and fuel injection can then take place.

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

The cycle mentioned and repeated several times makes it possible, thanks to this starting device, for a common-rail motor to operate in "stop and start" mode. Preferably, the overpressure provided by the energy storage means 4 is calibrated so that two injections can be performed before the high pressure pump 6 takes over.

According to a second variant illustrated in an example in FIG. 2, it can be seen that the energy storage means 104 mainly comprises a piston assembly 101, a link assembly 102 and a steering assembly 103.

The piston assembly 101 comprises a piston 111, a spring 112, an end-of-stroke collar of the piston 113 and a shaft 114. The piston 111 slides sealingly along the inside diameter of the accumulator means 2, for example by means of a seal ring 115 along its periphery. The spring 112 is interposed between one of the ends 2a, 2b of the accumulator means and said piston 111. Finally the shaft 114, fixed substantially along the axis of translation of the piston 111, passes successively into the interior space formed by the turns of the spring 112 and by a hole drilled on said end 2a, 2b where said piston assembly 101 is installed. This shaft 114 is partially covered over its length by the collar 113 which makes it possible to limit the output length of the shaft 114 relative to the common rail 2.

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

In the example illustrated in FIG. 2, the links 105 are pivotally mounted with respect to the disk 107. Consequently, the latter must comprise as many grooves as rods which, preferentially distributed at equidistance from each other, frame each in part. one of the links. The disk 107 is fixed substantially perpendicular to the shaft 114 which implies for the rods 105 a substantially parallel positioning relative to the shaft 114.

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

In the example illustrated in FIG. 2, the driving assembly 103 consists mainly of a stop 116, a T-shaped element 117 and an electromagnetic element 118. The abutment 116 is in the form of a truncated cone of which the inclined surface serves as a ramp for said second rollers 110a and 110b.

The substantially T-shaped element 117 comprises a disc-shaped base 119 of diameter substantially identical to the largest diameter of said cone so as to extend it and a rod 120 mechanically connecting the stop to the electromagnetic element 118. The latter is able to translate said rod substantially along the axis of the shaft 114. Thus, the electromagnetic element 118 can control the approximation or the separation of the abutment 116 relative to the disk 107.

As for the first variant 4, the purpose of the energy storing means 104 is to release the piston 111 at start-up so as to offer a means of temporarily compressing the fuel in the common rail until the latter is fed by the In the same way, the second variant 104 also uses the stabilized pressure prevailing in the common rail for prestressing the storage means 104.

Thus when the pressure in the common rail 2 is greater 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 requires the shaft 114 to exit the common ramp 2. this movement printed by the shaft 114 has the effect of bringing the disc 107 of the abutment 116 and thereby to "up" the second rollers 110 along the cone until at the discoid base 119.

As this rise of the rollers 110 increases, the springs 108 are more and more spaced apart to impose a quasi-horizontality of the links 105 which forces each first roller to lock in its associated notch 121 as illustrated in FIG. 2. The storage medium is then ready for "stop and start" operation.

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 the springs between the rods 108 and the expansion of the spring 112 contained in the common rail 2, the release of the rollers 109 of their respective notches 121 and a translation of the piston 111 inwardly of the common rail 2. This translation, like the first variant 4, makes it possible to start the internal combustion engine more quickly. The movement described above is repeated to allow the adaptation of said motor to "stop and start".

Of course, the invention can not be limited to the examples set forth in this patent. Thus, the control means of the electromagnetic type may be of another type. Similarly, the mortise and tenon 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 achieved by means of a pre-stressed elastic mechanical device with passive tripping. The control of this device can for example be achieved using a pressure (10 - 20 bar) provided by the HP pump. This pressure then controls the deindexing of the pre-constrained member which, by relaxing, provides said overpressure.

Claims (7)

1. Starting device (1) for an internal combustion engine comprising means (3) for supplying pressurised fuel, a means (2) for accumulating pressurised fuel, at least one injection means (5) provided with fuel by the accumulator means (2), an energy storage device (4, 104) that is supplied by means of the pressure prevailing in said accumulator means (2) characterised in that said energy store (4) is located at one (2b) of the two ends of said fuel accumulator means (2) and comprises a piston (11, 111), the piston being mobile within the fuel accumulator means, a spring (12, 112) located between said piston and said end (26), at least a first static stop (13, 113) making it possible to limit the travel of said piston (11, 111) and at least some means (14, 109) for locking the piston in the compressed position, and means for controlling said locking means (14, 109) so that, when the engine starts initially, the piston is in a rest position, the furthest away from the end (2b), that it is pushed back towards the end (2b) against the first static stop (13, 113) when the pressure rises in the accumulator means (2), locked in this second position by the locking means (14, 109) until a command to release the piston is sent at the time of restarting.
2. Device according to Claim 1, characterised in that the supply means (3) comprise a high-pressure pump (6) supplying said accumulator means with fuel and a non-return valve (8) permitting fuel to flow solely from said pump towards said accumulator means.
3. Device according to Claim 1 or 2, characterised in that said first stop (13) is a static stop capable of accommodating said piston so as to limit the compression of the spring (12).
4. Device according to one of the preceding claims, characterised in that the control means are of electromagnetic type.
5. Device according to Claim 1 or 2, characterised in that the energy storage means (104) comprises a resilient means (112) located between the piston (111) and said end (2b) and a locking system (102, 103) making it possible to release the piston (111) selectively.
6. Device according to Claim 5, characterised in that the locking system (102, 103) comprises at least three connecting rods (105) provided at each of their ends with rollers (108, 110) and mounted so as to pivot on a disc (107), a shaft (114) connecting the piston (111) and the disc (107), resilient means (108) linking together the connecting rods (105) and control means (103) making it possible, depending on the commands transmitted to the control means (103), to lock the connecting rods (105) selectively between said control means and the end of the accumulator means (2).
7. Device according to Claim 6, characterised in that the control means (103) comprise a stop (116) substantially in the shape of truncated cone, a substantially T-shaped part (117), the base (119) of which extends said stop (116) and the body (120) of which is controlled in translation by electromagnetic means (118) allowing said first rollers (110) to follow the surface of the stop (116) in order to lock or unlock selectively the second rollers (109) of the end of the accumulator means (2).

Images