EP2971641A1

EP2971641A1 - Method for controlling the progress of an operating cycle of an internal combustion engine with an extended expansion phase

Info

Publication number: EP2971641A1
Application number: EP14720177.6A
Authority: EP
Inventors: Stephane Venturi; Jean-Marc Zaccardi; Xavier Gautrot
Original assignee: IFP Energies Nouvelles IFPEN
Current assignee: IFP Energies Nouvelles IFPEN
Priority date: 2013-03-14
Filing date: 2014-03-13
Publication date: 2016-01-20
Also published as: FR3003299A1; WO2014140497A1; FR3003299B1

Abstract

The present invention concerns a method for controlling the progress of an operating cycle of an internal combustion engine comprising at least one cylinder (14) inside which a piston (10) slides between top (PMH) and bottom (PMB) end positions, a link mechanism (18) linking the piston to two crankshafts (16a, 16b) of rotational direction (R), a distribution system (36) for at least one inlet valve (38) and at least one exhaust valve (40), said cycle comprising an inlet phase with a piston stroke (A1) according to an inlet crankshaft angle interval (VA1), a compression phase with a piston stroke (C1) within a compression crankshaft angle interval (VC1), an expansion phase with a piston stroke (D1) greater than that (C1) of the compression phase according to an expansion crankshaft angle interval (VD1) greater than that of the compression phase. According to the invention, the method consists of reducing the expansion crankshaft angle interval (VD1) and of obtaining an increase in the expansion speed of said piston after the top end position of the expansion stroke.

Description

A method of controlling the progress of an operating cycle of an internal combustion engine with a prolonged expansion phase.

The present invention relates to a method for controlling the progress of an operating cycle of an internal combustion engine.

It concerns indifferently engines with direct or indirect injection with controlled ignition or compression ignition and comprising at least one cylinder with a combustion chamber inside which is placed a piston connected to a connecting rod system (s) -manivelle ( s) and which moves in an alternative translational motion.

As is widely known, the conventional cycle of operation of this type of engine on two turns of the crankshaft is decomposed into four stages, or phases, with an intake phase during which air or a mixture of air and fuel is introduced into the combustion chamber, a compression phase is compression of air, in which is injected fuel, or the fuel mixture contained in the combustion chamber, a combustion / expansion phase during which the fuel mixture, after having been ignited either by a controlled ignition, such as a spark plug, or by auto-ignition, burns and the combustion gases relax, then a final exhaust phase where the flue gas resulting from the combustion / expansion phase are evacuated out of the combustion chamber.

As shown in Figure 1 representative of an example of the prior art, this is reflected in the strong line curve which illustrates the path of the piston (P) depending on the rotation angle of the crankshaft (° V ).

Thus, for a conventional engine, the piston follows a path during which it carries out four identical races A0, C0, DO and E0 during two crankshaft revolutions (720 °) with four identical angular intervals between them (180 °) which correspond to the four phases of the cycle: admission with stroke A0 (0 ° - 180 °), compression with stroke C0 (180 ° -360 °), stroke D0 for expansion (360 ° -540 °) and exhaust with stroke E0 (540 ° -720 °). Thus, during the relaxation phase between a crankshaft angle of 360 ° to 540, the piston performs a stroke D0 which starts at the position 0 of the extreme high position of the piston (High Dead Point - TDC - at 360 °) for end at position P0 at 540 ° corresponding to an extreme low position (Low Dead Point - PMB) with the producing an expansion volume during an expansion crankshaft angle interval of VDO (180 °).

This type of motor has the disadvantage of having a thermodynamic efficiency imperfect compared to the theoretical yield possible. Indeed, the energy released during the expansion phase is not fully recovered at the crankshaft and pumping losses are generated during the intake phase. It has been proposed by document FR 2 828 910 or by document

US 20070125326 other types of engine that increase the piston stroke during the expansion phase so as to recover a greater amount of energy generated by the expansion of the combustion gases. An example of this type of engine of the prior art whose constitution and operation is described in more detail in application FR 2 828 910 is illustrated schematically in FIG. 2. This engine comprises a piston 10 animated with a movement of alternative translation in the combustion chamber 12 of the cylinder 14 and which is connected to two crankshafts 16a, 16b driven by a conventional rotational movement R by a linkage 18 with three connecting rods. The crankshafts are driven in the opposite direction (or counter-rotating) relative to each other with a speed of rotation of N / 2 for the crankshaft 16a with respect to the crankshaft 16b whose rotation speed is N. This linkage comprises a connecting rod 20 connected to the pivot axis 22 of the piston, another connecting rod 24 connected to a crankpin 26 of the crankshaft 16a and a last connecting rod 28 connected to a crankpin 30 of the other crankshaft 16b, the free ends of these three rods articulating by a pivot 32 to a connecting rod node 34.

The cylinder of this engine also comprises a distribution system 36 comprising at least one intake valve 38 and at least one exhaust valve 40. This distribution system also comprises any control means 42, such as a camshaft, for selectively open / close the valves. The two crankshafts each carry a toothed wheel 44a and 44b connected by a mechanism 46, such as a gear train, for driving the crankshafts in a reverse direction with different speeds of rotation.

This mechanism also makes it possible to achieve an angular phase shift of one crankshaft relative to the other, in particular by driving a crankshaft gear by a series of gears and bars, as is better described in FIG. document FR 2 828 910.

Although extended, this phase shift can be achieved by any means known as a phase shifter placed between the ring gear and the axis of the crankshaft.

Thus, thanks to this linkage system and returning to the purely illustrative example of FIG. 1 (dashed line curve), the stroke A1 of the piston for the intake phase starts in the vicinity of the position 0 (extreme high position - TDC admission) with a crankshaft angle of 0 ° and terminates substantially at the position P0 of this piston at a crankshaft angle V1 close to 180 ° with an intake crank angle angle VA1. The compression stroke C1, substantially symmetrical with the intake stroke, starts from the position P0 (extreme low position - PMB compression) and ends in the vicinity of the position 0 at a crankshaft angle V2 of less than 360 ° and greater than 180 ° with a crank angle of compression crankshaft VC1. The piston stroke D1 for the extended expansion phase starts at the crankshaft angle V2 in the vicinity of the position 0 (high end position - TDC relaxation) and then ends at the position P1 (extreme low position - exhaust PMB), in below the position P0 (PMB compression), and at a crankshaft angle V3 close to 540 °. This race D1 is larger than the compression stroke C1 and takes place at an interval of expansion crankshaft angle of expansion VD1.

Thus, the piston stroke, in the expansion phase of the engine of FIG. 2, is longer than that of the expansion stroke of the conventional engine (D1> D0) and that of the compression stroke which precedes it (D1 > C1). This stroke is also of longer duration with a VD1 extended expansion crankshaft angle interval that is larger than that of VD0 range of this conventional engine and with a slower piston speed at the 0 position. than that of the motor curve with four identical phases. Finally, the exhaust stroke E1 (escape angular interval VE1) starts from the position P1 and ends in the vicinity of the position 0 at a crank angle of 720 °.

By this, energy recovery during the cycle is done with better performance.

However, the Applicant has noticed that a long and slow relaxation phase is not beneficial to recover the maximum energy and to promote an increase in yield.

Indeed, this type of relaxation phase is conducive to the increase in thermal losses to the walls, which can only adversely affect the efficiency of the engine.

In addition, a slow piston speed from position 0 is a factor which increases the sensitivity to rattling in the case of a spark ignition engine.

In addition and as is generally accepted, the maximum efficiency can be achieved by isochoric combustion, which requires a very slow relaxation after the 0 position to minimize the change in volume during combustion. This has the disadvantage of causing high pressures and high temperatures in the chamber at the time of combustion, which introduces not only a penalty related to losses to the walls but also a constraint on the thermomechanical behavior of the cylinder head.

The present invention proposes to overcome the above drawbacks by means of a method of controlling the running of the operating cycle of the engine which makes it possible to obtain a better efficiency of the engine without requiring complex and expensive devices.

To this end, the present invention relates to a method for controlling the progress of an operating cycle of an internal combustion engine comprising at least one cylinder inside which slides a piston between extreme high and low positions, a crankshaft connecting the piston to two crankshafts R direction of rotation, a distribution system for at least one intake valve and at least one exhaust valve, this cycle comprising an intake phase with a piston stroke at an inlet crank angle, a compression phase with a piston stroke in a crank angle of compression, a stretcher with a stroke piston greater than that of the compression phase at a larger crankshaft angle than the compression phase, characterized in that the method consists in reducing the expansion crankshaft angle interval. and to obtain an increase in the expansion speed of said piston after the extreme high position of the expansion stroke.

The method may include varying the intake stroke to control the intake displacement.

The method may include altering the motor setting to reduce the expansion crankshaft angle interval.

The method may include driving the crankshafts in a reverse rotation direction -R. The method may include changing the drive direction of the motor starter to drive the crankshafts in a reverse direction of rotation -R.

The method may include controlling the dispensing system to accommodate the reversal of the direction of rotation.

The method may consist in phase shifting one of the crankshafts relative to the other and in controlling the timing and phasing distribution system to adapt it to a variable phase shift between the two crankshafts. The method may include controlling a variable timing system at least in calibration. The other features and advantages of the invention will now appear on reading the following description, given solely by way of illustration and not limitation, and to which are appended:

FIG. 3 which illustrates the path of the piston (P) as a function of the rotation angle of the crankshaft (° V) according to a known method of a two crankshaft engine of the prior art (curve 1) and according to FIG. invention (curve 2),

FIG. 4, which is a graph illustrating the various lifting laws (L) of the intake and exhaust valves of the cylinder according to the engine with two crankshafts of the prior art (curve 1) and according to the invention (curve 2), - Figure 5 which shows the path of the piston (P) depending on the rotation angle of the crankshaft (° V) according to the invention (curve 2) and according to a variant of the invention (curve 2 ' ) and

- Figure 6 which is a graph illustrating the different laws of emergence (L) of the intake and exhaust valves of the cylinder according to the invention (curve 2) and according to a variant of the invention (curve 2 ').

Reference is now made to Figures 2 and 3 to further develop the invention.

In FIG. 3, provided for purely illustrative purposes, the curve 1 of the piston path of a two-crankshaft engine according to the prior art is broken down as described above into an intake stroke A1, a compression stroke C1, a relaxation stroke D1 and an exhaust stroke E1.

In order to be able to obtain a relaxation phase with a prolonged expansion stroke, called the extended expansion phase, which is faster at TDC and shorter than that illustrated by curve 1, it is planned to modify the engine parameters, such as the length ratios. between the connecting rods, the speed ratio between the crankshafts, the direction of rotation of the crankshafts, ...

Thus, by way of example only to illustrate the invention, it is provided that the control method of the unfolding of the operating cycle of the motor makes it possible to carry out the rotation of the two crankshafts in a rotational movement -R in the opposite direction to that conventional rotational movement (see Figure 2). This can be achieved by any means, such as a starter whose the driving direction of the starting ring connected to the crankshaft is contrary to the conventional sense R.

This reversal of the direction makes it possible to obtain a relaxation phase which has not only a higher volumetric ratio than the compression phase, but also a higher piston displacement speed in the vicinity of the 0 position and a longer VD2 expansion time. short that VD1 of the trigger illustrated by the curve 1 of Figure 3 and / or that VDO illustrated in Figure 1. This inversion of the crankshaft rotation direction is associated with a distribution of the valves, such as by a camshaft, which makes it possible to obtain a relaxation phase which is at the same time more important than compression in terms of volume while being and shorter and faster, especially in the vicinity of the 0 position.

By this, the different phases of the motor are reversed as illustrated by way of example of embodiment in FIG. 3 with the curve in dashed lines carrying the shaded arrows and this in association with FIG. 4 showing the various opening / closing the valves.

Thus, the phase (a), which corresponds to a prolonged expansion phase, with a piston stroke from the vicinity of the 0 position to a crank angle of 720 ° to the position P1 (V3 angle) with the maintenance in closing of the intake and exhaust valves 40, the phase (b), which corresponds to an exhaust phase, with a piston stroke going from the piston position P1 to the vicinity of the position 0 ( angle V2) with a maintenance in closing of the intake valve 38 and an opening / closing sequence of the exhaust valve 40 between the crankshaft angles V3-V2, the phase (c), corresponding to a phase of intake, which starts from the vicinity of position 0 (angle V2) to position P0 (angle V1) with the holding in closing of the exhaust valve and a sequence of opening / closing of the intake valve 38 and the phase (d) of compression of the position P0 to the vicinity of the position 0.

The curve thus obtained according to these different races was recaled according to the curve 2 (dotted curve) with the white arrows, in order to better correspond to the profile of curve 1 using the same reference system, namely with an admission phase starting from position 0.

Thus, the phase (c ') between the crankshaft angles of 0 ° to V1 - the admission phase of the curve 2 - corresponds to the phase (c) of the curve 1, the compression phase (d') of the curve 2 between the crankshaft angles of V1 to V2 corresponds to the phase (d), the expansion phase (a ') between the crankshaft angles of V2 to V4, the angle V4 being greater than V2 and less than V3 corresponds in phase (a), and the exhaust phase (b ') between the crankshaft angles of V4 at 720 ° in phase (b).

For this resetting (see FIG. 4), the intake valve 38 (curve 2) follows an opening / closing sequence during phase (c ') and the exhaust valve 40 (curve 2) follows a sequence of opening / closing during the exhaust phase (b ') between the crankshaft angles of V4 at 720 °.

Therefore, the stroke D2 of the piston in the expansion phase (a ') has substantially the same elongation as that of the expansion stroke D1 of the two crankshaft motor of curve 1 but is shorter with a corner angle crankshaft VD2 which is smaller than that of VD1 range of the motor curve 1. The average speed of this expansion during the stroke D2 is therefore higher and the expansion speed of the piston in the vicinity of the position 0 is greater than that illustrated by the stroke D1 of the curve 1.

By this, energy recovery during the cycle is done with better performance.

The engine as described above also offers the possibility, as is better described in the document FR 2,828,910, to be able to vary the volumetric compression ratio.

This is achieved by changing the angular phasing between the two crankshafts. The variation of this phasing makes it possible to modify the displacement of the connecting rod connected to the piston and to change the volumes reached at the different extreme positions of the piston stroke.

In Figure 5, the curve 2 with a phasing 01 is that of Figure 3 and the curve 2 'is a variant of the curve 2 with another phase shift 02 between the two crankshafts. The applicant has been able to show that variations in the phase shift between the crankshafts have an impact not only for the volumes reached at the different extreme positions (PMH and PMB), but also for the crankshaft angles at which these extreme positions are reached.

As illustrated by the curve 2 '(curve in mixed lines), this variation of the phase shift makes it possible in particular to vary the quantity of air admitted to the intake (intake cylinder) by performing an intake stroke A3 between the position 0 and the position P3 (angle V6) of the piston in the crankshaft angle interval VA3 (V5-V6) which is larger than the intake stroke A2 of the curve 2 in the crankshaft angle interval VA2 ( 0 ° -V1).

This variation also makes it possible to vary the expansion stroke D3 in the crankshaft angle interval VD3 (V7-V8).

In the illustrated example, the expansion stroke D3 of the curve 2 'starts from a piston position P4 (extreme high position - TDC relaxation) below the position 0 (crankshaft angle V7) to a position P5 (crankshaft angle V8) located at a position lower than that P2 of the piston of the curve 2 in a crankshaft angle interval VD3 (V5-V6) similar to the interval VD2. Since the stroke D3 is greater than the stroke C3 and the stroke C2 is greater than the stroke C2, the two cases of operation illustrated by the curves 2 and 2 'correspond to cases of prolonged relaxation with variable intake cylinders since the race admission varies between A2 and A3.

It follows therefore that a fixed distribution (stall and / or spreading and / or lifting) can not be perfectly optimized for different values of the phase shift between the two crankshafts.

In this context, the applicant has planned to associate a Variable Valve Timing (VVA) or Variable Valve Timing (VVT) to the intake and exhaust valves to vary the phasing of the lifting laws of these valves. and independently of one another or in an associated manner thereby being able to adequately synchronize the opening / closing sequences of the intake and exhaust valves with the variations of the piston stroke.

In Figure 5, the curve 2 'is a curve representative of the path of the piston with a phase shift 02 between the two crankshafts. According to this curve 2 ', the intake phase starts at position 0 at a crankshaft angle V5 offset by an angle α (of approximately 60 °) with respect to the beginning of the admission phase of curve 2. This phase of admission of the curve 2 'ends at a crank angle V6 larger by a value β (about 55 °) than the angle V1. The compression phase starts from the angle V6 to arrive at the angle V7 which is larger than the angle V2 by a value δ (about 35 °). The expansion phase starts from the angle V7 and ends at the angle V8 which is larger than the angle V4 by a value Θ (about 40 °). This expansion phase is continued by an exhaust phase which starts from position V8 and ends in the vicinity of position 0 at angle V5.

Thus, with reference to FIG. 6, the control system of the intake and exhaust valves 40 and 40 is a variable control system for adapting the opening / closing sequences of these valves to the variation of the opening angles. and closing the valves depending on the phasing between the crankshafts.

The distribution system is controlled in duration and phasing to adapt to the variable phase difference between the two crankshafts.

Claims

1) A method for controlling the progress of an operating cycle of an internal combustion engine comprising at least one cylinder (14) inside which slides a piston (10) between extreme high positions (PMH) and low positions ( PMB), an assembly (18) connecting the piston to two crankshafts (16a, 16b) of direction of rotation (R), a distribution system (36) for at least one intake valve (38) and at least one valve exhaust (40), this cycle comprising an intake phase with a stroke (A1) of the piston at an intake crank angle (VA1), a compression phase with a stroke (C1) of the piston in a compression crankshaft angle interval (VC1), an expansion phase with a piston stroke (D1) greater than that (C1) of the compression phase at an expansion crankshaft angle (VD1 ) greater than that of the compression phase, characterized in that the method consists in reducing e the expansion crankshaft angle (VD1) and to obtain an increase in the expansion speed of said piston after the extreme high position of the expansion stroke.

2) Process according to claim 1, characterized in that it consists in varying the intake stroke (A3) to control the intake displacement.

3) Process according to claim 1 or 2, characterized in that it consists in modifying the engine parameterization to reduce the expansion crankshaft angle interval (VD1).

4) Method according to claim 3, characterized in that it consists in driving the crankshafts in a reverse direction of rotation (-R).

5) Method according to claim 4, characterized in that it consists in modifying the drive direction of the motor starter to drive the crankshafts in a reverse direction of rotation (-R).

6) Method according to one of the preceding claims, characterized in that it consists in controlling the distribution system (36) to adapt to the reversal of the direction of rotation. 7) Method according to one of the preceding claims, characterized in that it consists of phase shifting one of the crankshafts relative to the other and control the distribution system in duration and phasing to adapt to a phase shift variable between the two crankshafts.

8) Method according to claim 7, characterized in that it consists in controlling a variable distribution system at least in wedging.