FR2689180A1 - IC engine supercharging system with centrifugal and mechanical compressors - has mechanical compressor driven from engine or auxiliary electric motor with clutch to engage or disengage it - Google Patents

Abstract

The system comprises at least one turbo-compressor (2) and at least one mechanical air compressor (3), driven by the engine (1), and situated in parallel in the engine feed circuit, and with the mechanical air compressor operated through an electromagnetic clutch (11) which has a response time of under 0.1 seconds. The mechanical air compressor can be either volumetric or centrifugal, and can be driven by the engine itself or by an auxiliary motor, preferably electric. The electric motor is preferably equipped with a speed regulator and powered by an engine auxiliary. The mechanical air compressor can be electronically controlled according to one or more engine parameters, and the engine is preferably of compression-ignition type. ADVANTAGE - Improved engine performance and lower exhaust pollution.

Description

The present invention relates to a supercharging device of an internal combustion engine comprising a mechanically driven air compressor and a turbo-compressor whose turbine is actuated by the exhaust gases of the engine, said compressors being connected to the circuit of power to this engine.

In the majority of the supercharging devices currently used on internal combustion engines, the compressor is constituted in the form of a turbocharger, the turbine of which is driven by the exhaust gases of the engine, and the compressor of which supplies air engine suction.

In the engine operating zones corresponding to a high power and a high rotation speed, and according to the adaptations, the energy available in the exhaust gases makes it possible to drive the turbocharger turbine at a sufficient speed to sufficiently supercharging the engine and allow sudden acceleration.

On the other hand, at low speed and / or at low engine load, the energy available in the exhaust gases is insufficient to allow sudden accelerations.

This results in a limitation of the available power and a delay in acceleration. In addition, in the particular case of compression ignition engines, this relative lack of air, at low speed or at low load, results in a greatly increased emission of gaseous pollutants and also of solid or soot particles from combustion. .

Furthermore, it is known and described, for example in patent application GB-A-144322, to supercharging an internal combustion engine by a device comprising an air compressor which is driven by the output shaft of the engine and the discharge conduit of which is connected to the supply circuit of said motor. Such a system comprising a mechanical compressor driven by the engine itself does not have the drawbacks described above, in the case of the use of a turbocharger, but on the other hand, taking into account the energy withdrawn permanently on the motor shaft by the compressor, the performance of the assembly will necessarily be less favorable than the device according to the invention.

 I1 is also known and described, for example in French patent FR-B-2491996 in the name of the applicant, of supercharging an internal combustion engine and with ignition controlled by a system allowing sudden acceleration in particular at low revs. This system comprises a mechanical compressor associated with a turbo-compressor, said mechanical system allowing an additional energy supply to the turbine of the turbo-compressor, this energy being available to ensure the operation of the turbo-compressor at a sufficient speed to allow in principle of sudden accelerations. However, such a system would not be able to correctly resolve, in the case of a compression-ignition engine, the pollution problems mentioned above. In addition, this system almost constantly consumes the energy taken from the engine, which decreases the performance of the whole.

The present invention relates to a supercharging device, of an internal combustion engine, which allows, in particular in its preferred embodiment, and this both in the case of its use in connection with a spark ignition engine, as in that of its implementation in conjunction with a compression-ignition engine, largely avoiding the drawbacks associated with the use of the systems described and implemented previously. This device is particularly applicable to compression ignition engines of the Diesel type.

To this end, the subject of the invention is a device for supercharging an internal combustion engine equipped with at least one turbo-compressor and at least one mechanical air compressor driven by motor means, said compressors being each connected to the supply circuit of said engine characterized in that said turbo-compressors and said mechanical compressors are arranged in parallel on the supply circuit, and in that the mechanical compressor is put into service by means of a clutch-disengageable system.

The mechanical compressor used in the context of the device of the invention is most often chosen from the group formed by positive displacement compressors and centrifugal compressors. This mechanical compressor is usually driven by a motor means chosen from the group formed by the motor itself, an auxiliary rotary member of the motor and an auxiliary motor, preferably electric. The rotating member of the engine may for example be a shaft driven by the distribution of the engine. In the case of the use of an electric auxiliary motor, this will preferably include means for adjusting the speed of rotation of the mechanical compressor and will preferably be supplied with energy by auxiliary elements associated with the motor.

In its preferred embodiment, the invention makes it possible to minimize the drawbacks inherent in each of the two compression systems. Although all clutch-disengageable systems can be used, it is most often preferred to use as clutch-disengageable system an electromagnetic clutch preferably having a response time of less than about 0.1 seconds. This clutch is usually electrically controlled, which allows easy control by an electronic control unit. The electromagnetic type clutch is preferably chosen for its compactness, its ease of control, its very short response time and its service life.

Thus, the putting into service of the mechanical compressor by means of the clutch-disengageable system can be controlled electronically by a programmable system from the acquisition of at least one engine parameter preferably chosen from the group formed by the engine speed. , the variation of the engine acceleration control and the variation of the engine boost pressure.

Other details and advantages of the present invention will appear better on reading the description which follows, with reference to the appended drawings according to which: - Figure 1 schematically shows an example of a combustion engine
internal equipped with the supercharging device of the present invention.

- Figure 2 shows curves defined by the engine torque as a function of
engine speed, for different types of speed.

According to FIG. 1, the engine 1 comprises four cylinders A, B, C and D and its supply of oxidizer to the engine 1 is ensured from an intake pipe 8 through a filter 6: - on the one hand via a pipe 17, a turbo-compressor 2 and a pipe 19 in
downstream of the turbo-compressor 2, the pipe 19 possibly comprising a check valve
return 9, - and secondly via a line 18, a mechanical compressor 3 and a line
20 at the outlet of the compressor 3, the line 20 possibly comprising a check valve
back 10.

The pipes 19 and 20 meet to form a common pipe 21 upstream of the intake manifold 5 from which the different intake pipes 16a, 16b, 16c and 16d of each of the cylinders leave.

The compressor 3 is driven by means of a clutch 11 connected to the shaft 12 of the engine 1 by a transmission comprising a pulley 14 connected to the pulley 13 fixed to the shaft 12 by a transmission belt 22.

According to the embodiment of the invention shown in Figure 1, the engine 1 comprises four fuel injectors 4a, 4b, 4c and 4d opening directly into each of the cylinders. I1 also includes on each cylinder an exhaust pipe l5a, 15b, 15c and l5d each connected to an exhaust manifold 24 then to the turbo-compressor 2 and to the general exhaust 23. Three systems are shown diagrammatically in FIG. 1 7a, 7b and 7c for cooling the oxidant before it is admitted to the intake manifold 5. A first cooling system 7a can be placed on the line 19, a second system 7b can be placed on the line 20, while a third system 7c can equip the common pipe 21. These systems can be present simultaneously or not.

We can therefore have zero, one, two or three cooling systems.

A diagrammatic diagram of a spark ignition and fuel injection engine using the supercharging device of the present invention would be identical to FIG. 1 except for the position of the fuel injectors 4a, 4b, 4c and 4d which would open out not in the cylinders but in the intake pipes 16a, 16b, 16c and 16d of each of the cylinders.

In the context of the use of the device according to the invention, the mechanical compressor is usually put into service, either when it is desired to increase the engine power while keeping the oxidant / fuel ratio substantially constant, or when it is desired modify the oxidant / fuel ratio, in particular with a view to improving combustion.

Thus, the mechanical compressor 3 can be engaged very quickly as soon as an acceleration is requested, then disengaged as soon as the speed is stabilized or the intake pressure sufficient.

According to another use in accordance with the invention, the mechanical compressor 3 can also be permanently engaged at low speed, which will make it possible to use the turbo-compressor 2 better suited to high speed.

In particular, two examples of use of the invention are now given, in relation to FIG. 2. As has been stated, in this figure appear curves defined by the maximum engine torque CO as a function of the speed Re.

According to a first example, a diesel engine supercharged by turbo compressor 2 has a curve A (shown in solid lines) of maximum torque Cg as a function of the rotation speed Re, from the idling speed R1 to a nominal speed
R3 through an R2 regime of maximum torque. This curve A is performed in a stabilized regime. On the other hand, when a rapid acceleration of the engine speed is requested, taking into account the response time of the turbo-compressor, the maximum torque curve that can be reached by the engine is curve B shown in dotted lines. The purpose of adopting a mechanical compressor 3 according to the present invention is to make curve B coincide as much as possible on curve A.

For this, the mechanical compressor 3 is engaged as soon as a request for acceleration of the engine speed is detected by an appropriate sensor, for example a speed sensor or a sensor on the acceleration control. The mechanical compressor 3 then supplies the engine with the necessary amount of air in place of the turbo compressor 2. In this case, combustion takes place with an air / fuel ratio comparable to that of a stabilized state, with two consequences: greater torque and a significant reduction in gaseous pollutants, particles, and smoke. This is particularly advantageous when the engine is used for the traction of a vehicle, in particular, of heavy goods vehicle for which the European regulations as regards pollution are severe.

When the acceleration is complete, or the pressure reached by the turbo compressor 2 is equal to that supplied by the mechanical compressor 3, then the control system (not shown) disengages the mechanical compressor 3 so as not to deteriorate the efficiency of the motor.

As shown in Figure 2, between the R1 and R2 regimes, the torque curve is limited by the curve A in stabilized regime. This limit is usually due to a lack of air at low speed and therefore an insufficient air / fuel ratio (<18), which leads to excessive pollution.

The present invention overcomes this drawback by the presence of the compressor 3 which in particular performs at low speed an immediate and sufficient air addition.

Thus, according to a second example of use of the invention, the adoption of a mechanical compressor makes it possible to improve the curve A up to the curve C. For this it suffices to engage the mechanical compressor 3 at low speed or for example when the engine speed is equal to the value R1, and adjusting the injection system, so as to provide the corresponding fuel flow. Curve C is thus obtained in dashed lines, with a maximum torque obtained at the speed R'2 lower than the speed R2 corresponding to the maximum torque obtained in stabilized operation (curve A). This feature improves the handling of the vehicle.

In addition, in the case of a cold start of the engine, it is possible, during the starting phase, to put the mechanical compressor into service in order to heat the combustion air and thus facilitate the starting of the engine and reduce gaseous pollutants and the solid particles emitted from the exhaust during this phase.

Of course, other additions and / or modifications may be made, by a person skilled in the art, to the device described above without departing from the scope of the present invention.

Claims (11)

1- Supercharging device of an internal combustion engine (1) equipped with at least one turbo-compressor (2) and at least one mechanical air compressor (3) driven by motor means, said compressors being each connected to the supply circuit of said engine characterized in that said turbo-compressors and said mechanical compressors are arranged in parallel on the supply circuit, and in that the mechanical compressor is put into service by means of a clutch-disengageable system (11). 2- Device according to claim 1 wherein the mechanical compressor is put into service via an electromagnetic clutch (11). 3- Device according to claim 1 or 2 wherein the disengageable disengageable system is a system having a response time less than about 0.1 second. 4- Device according to one of claims 1 to 3 wherein the mechanical compressor is selected from the group formed by positive displacement compressors and centrifugal compressors. 5- Device according to one of claims 1 to 4 wherein the motor means driving the mechanical compressor is chosen from the group formed by the motor (1) itself, an auxiliary rotary member of the motor (1) and an auxiliary motor preferably electric. 6- Device according to one of claims 1 to 5 wherein the motor means is an electric auxiliary motor comprising means for adjusting the speed of rotation of the mechanical compressor and supplied with energy by auxiliary elements associated with the motor (I). 7- Device according to one of claims 1 to 6 wherein the mechanical compressor is engaged when it is desired to increase the engine power by keeping the oxidant / fuel ratio substantially constant. 8- Device according to one of claims 1 to 6 wherein the mechanical compressor is engaged when one wishes to change the oxidant / fuel ratio in particular to improve combustion. 9- Device according to one of claims 1 to 6 wherein the mechanical compressor is engaged during the start-up phase. 10- Device according to one of claims 1 to 9 wherein the commissioning of the mechanical compressor, through the clutch-disengageable system, is controlled electrically by a programmable electronic system from the acquisition of at least an engine parameter preferably chosen from the group formed by the engine speed, the variation of the engine acceleration control and the variation of the engine boost pressure. 11- Device according to any one of the preceding claims characterized in that it is used in a compression ignition engine.