FR2938880A1 - Engine i.e. internal combustion engine, for vehicle, has positioning unit utilized such that transferring valve discharges exhaust gas during exhaust phase and allows exhaust gas to cylinders during compression phase - Google Patents

Abstract

The engine (10) has cylinders (12) provided with a transferring valve, and a positioning unit for placing the transferring valve in an opening/closing position. The positioning unit is arranged such that the transferring valve discharges exhaust gas during an exhaust phase and allows exhaust gas in the cylinder during a compression phase. The cylinders are connected together by an exhaust gas storage pipe (32) that is arranged in a cylinder head.

Description

The present invention relates to an engine and a vehicle comprising the engine. [0002] Improving the efficiency of the thermodynamic cycles of internal combustion engines has always been a concern of motorists to reduce consumption. Thus, it is known to use the exhaust gas recirculation technique (called the EGR acronym for Exhaust Gas Recirculation). Exhaust gas recirculation is a system introduced in the 1970s that involves redirecting part of the exhaust from internal combustion engines to the intake. Recirculation reduces the combustion temperature. Indeed, the exhaust gases are rich in nitrogen (N2) and carbon dioxide (CO2) and dilute the fuel load. The combustion is thus slowed down and cooled. However, the formation of NOx in the combustion chamber is favored by the temperature. The reduction of the combustion temperature therefore leads to a reduction in the production of quantity of NOx produced at the source. In order to increase the efficiency of the recirculation on NOx reduction, the exhaust gases can be cooled before introduction into the engine intake. But, no recovery of the energy contained in the exhaust gas is then achieved. Indeed, at the end of relaxation, at the opening of the exhaust valve, the gases released into the atmosphere have a significant internal energy that is generally lost. Different concepts can be used to exploit lost energy. The document EP-B-1 054 143 describes a process for internal reintroduction of the exhaust gases in a multi-cylinder internal combustion engine, according to which, for certain predetermined operating states, a part of the exhaust gases is reintroduced. 'exhaust. By opening a first exhaust of a first cylinder, which is at the end of an expansion time, a pressure wave is formed which develops in the common exhaust pipe during the opening of the first exhaust, a second exhaust of a second cylinder which is in the suction phase or in an earlier phase of a compression time, is kept open beyond the opening time required for the exchange of gases as such, and the pressure wave back through the second escapement kept open, exhaust gases to the second cylinder. [0006] EP-A-0 705 383 discloses an internal combustion engine comprising a valve mechanism provided with at least one intake valve and at least one exhaust valve in each cylinder, and for each cylinder at least two rockers machined on a rocker shaft to control said valves. The engine also comprises means for recycling the exhaust gas into the cylinder during the normal drive mode of the engine, said means for recycling the exhaust gas during the normal drive mode of the engine comprising cooperating transmission means with the valve mechanism for selectively opening the exhaust valve during the engine intake stroke to drive the exhaust gas into the cylinder during the intake stroke. [0007] WO-A-01/96728 discloses an exhaust gas recirculation system for an internal combustion engine having a plurality of cylinders, each of the cylinders defining a combustion chamber and having an exhaust valve and an intake valve. The exhaust system includes exhaust manifold means for receiving exhaust gases from each of said cylinders through exhaust lines respectively connected to exhaust valves of said cylinders. The system also includes an exhaust flow control valve associated with at least one of said cylinders, said exhaust flow control valve controlling the supply of a portion of the exhaust gas of each cycle of at least one of said cylinders to another of the cylinders through the exhaust gas recirculation passage, bypassing said exhaust manifold, an exhaust stroke of a piston within a cylinder for pumping the exhaust gas through said exhaust flow control valve into said other cylinder. US-A-5 782 226 discloses a method of reducing harmful emissions of a multi-cylinder internal combustion engine comprising, for each cylinder arranged in a cylinder head at least one intake passage, a valve of intake, an exhaust gas passage with an exhaust valve and an exhaust gas recirculation passage extending between an exhaust passage and the interior of a cylinder or its passage. intake, an exhaust gas recirculation valve. Said method comprises the steps of opening the exhaust gas recirculation valve associated with a first cylinder during the cycle of admission of the first cylinder at the beginning of the exhaust cycle of a second cylinder associated with the first cylinder. cylinder and closing the exhaust gas recirculation valve when the exhaust gas pressure in the exhaust gas recirculation passage of said first cylinder falls below the pressure in the combustion chamber of the first cylinder or a pressure of the intake air in its passage and when a predetermined amount of exhaust gas has been recirculated. EP-BO 426 320 discloses an alcohol engine with recombustion control means, comprising a block of cylinders with a cylinder, a cylinder head fixed to said cylinder block, pistons to come and go in said cylinders of said cylinder block, intake ducts and exhaust ducts formed in said cylinder head, for each cylinder, and intake valves and exhaust valves disposed in said intake ducts and said exhaust ducts respectively and adapted to be selectively actuated sequentially in a four-stroke cycle of admission, compression, expansion and exhaust. The recombustion control means comprise combustion gas conduits formed in said cylinder head, for each cylinder, control valves disposed in said flue gas ducts and a flue gas passageway communicating between said gas ducts. combustion. The control means further comprises valve control means for actuating said intake, exhaust and control valves to open and close the valves by means of an electromagnetic force. Said control means can be actuated so that the alcohol fuel is burned with the air introduced via said intake ducts of the selected cylinders, the combustion gas of said selected cylinders is unloaded only in said passage of combustion gas by opening said control valves during an exhaust time, said exhaust valves of the selected cylinders remaining closed when the flue gas is transferred via said flue gas passage during said exhaust time, the flue gas is distributed in the other cylinders of said flue gas passage during the opening of said control valves of said other cylinders during an admission time, said intake valves of said other cylinders remaining closed while the combustion gas is transferred to them , said combustion gas thus distributed is re-burnt in said other cylinders es, and the combustion gas resulting from this recombustion is then discharged to the outside during the opening of said exhaust valves of said other cylinders during an exhaust time. EP-B-0 643 804 discloses an engine comprising a plurality of combustion chambers, an intake port and an exhaust port. The engine also includes a piston that can move back and forth in each of the combustion chambers, between a top dead center position and a bottom dead center position to form an intake stroke during which the air is introduced into the combustion chamber through the inlet port, between the bottom dead position and the top dead center position to form a compression stroke during which the air in the combustion chamber is compressed to a defined temperature range, with fuel being introduced at or before top of the dead center, and during which there appears an ignition delay time before combustion, and between the bottom dead position and the stitch position dead high to form an exhaust stroke during which the exhaust gas is expelled from the combustion chamber through the exhaust port. The engine has an apparatus comprising a flow control means comprising an intake valve operatively mounted in each of the intake ports to selectively pass air into the combustion chambers during the intake stroke. and an exhaust valve operatively mounted in each of the exhaust ports for selectively passing exhaust gas out of the combustion chamber during the exhaust stroke. The engine further includes means for operating the intake valve and the exhaust valve independently in response to a control signal. An electronic control means responds to detected operating parameters to provide the control signal, and is arranged to allow a controlled volume of exhaust gas to enter any preselected combustion chamber by opening its control valve. exhaust during its intake stroke, after the start of its intake stroke, and close its exhaust valve before its intake stroke is completed, to raise the temperature of the compressed air in the pre-selected combustion chamber the exhaust valve thus being open in the range of crankshaft angles approximately between 390 ° and 455 °. US-B-6,868,842 discloses a cylinder head comprising a body, said body being configured to receive at least one intake valve, said body defining at least one orifice. The cylinder head further comprises at least one recirculation chamber in communication with said at least one orifice, said recirculation chamber being spaced from said at least one intake valve. The cylinder head comprises a flow control system, said flow control system having a flow input position and a flow output position, said flow control system being positioned between said at least one orifice and said flow control system. at least one recirculation chamber. However, none of the aforementioned documents recover the energy of the exhaust gas during the compression phase. Part of the energy of the exhaust gas is not recovered. There is therefore a need for an engine for efficiently recovering the energy of the exhaust gas. For this, the invention provides an engine comprising at least one cylinder with at least one transfer valve and a positioning means for placing said valve in the open or closed position, characterized in that said positioning means is such that said transfer valve escapes exhaust gas during an exhaust phase and admits exhaust gas into the cylinder during a compression phase. In a variant, the engine further comprises an exhaust gas storage pipe, at least a portion of the exhaust gas admitted into the cylinder from the storage pipe.

In a variant, the engine comprises a plurality of cylinders each with a transfer valve.

Alternatively, the engine is such that the cylinders are interconnected by an exhaust gas storage pipe, at least a portion of the exhaust gas admitted into a first cylinder by a transfer valve during a compression phase of this first cylinder are escaped into the storage pipe by a transfer valve of a second cylinder during an exhaust phase of the second cylinder.

In a variant, the engine further comprises a cylinder head in which is placed the conduit.

In a variant, the positioning means comprises a cam with two bosses.

In a variant, the engine further comprises a camshaft with single boss cams and two bosses, single boss cams controlling the exhaust valves and cams with two bosses controlling the valves of the engine. transfer.

In a variant, the positioning means comprises an electromechanical or hydraulic control.

[0024] In a variant, each cylinder of the engine further comprises an exhaust gas discharge valve.

In a variant, the engine is such that the duration and the height of the lift of the transfer valve 18 can be adjusted according to the operating conditions of the engine, said operating conditions including including the regime, the load and the temperature of an engine intake or exhaust fluid.

In a variant, the exhaust gas storage duct is thermally insulated from the rest of the cylinder head in order to reduce the losses of thermal energies of the stored gases.

The invention also relates to a vehicle equipped with a motor as described above. Other features and advantages of the invention will appear on reading the following detailed description of the embodiments of the invention, given by way of example only and with reference to the drawings which show: FIG. 1 a schematic top view of an exemplary motor; • Figure 2, a schematic sectional view of the engine example; • Figure 3, a schematic sectional view of the engine example; • Figure 4, a schematic view of a cam with two bosses; • Figure 5, a diagram showing the valve lifts on a motor cycle time; • Figure 6, a top view of another example of an engine. It is proposed an engine comprising at least one cylinder with at least one transfer valve. The transfer valve escapes exhaust gas during an exhaust phase and admits exhaust gases into the cylinder during a compression phase. The internal energy contained in the gas during the exhaust can be injected into another engine cycle during the compression phase. Thermal energy and pressure energy are thus recovered by losing only the transfer energy. The recovery of the energy of the exhaust gas is therefore effective. Such recovery generates a significant gain in engine efficiency. Figure 1 illustrates a schematic top view of an engine example 10. The engine 10 comprises at least one cylinder 12 (in this case illustrated, the engine has 4 cylinders). A piston 14 (Figures 2 and 3) slides in each cylinder 12 and is connected to a crankshaft not visible in Figure 1. Each cylinder 12 is further closed by a cylinder head provided with a number of orifices closed by valves as will be detailed later, the internal volume of the cylinder between the piston and the cylinder head forming a combustion chamber. Each combustion cycle operated in a cylinder comprises at least one intake phase, a compression phase, a combustion phase and an exhaust phase. The intake phase corresponds to a phase in which gases are admitted into the cylinder 12. A compression phase corresponds to a phase in which the piston 14 compresses the admitted gases. A combustion phase is a phase in which the gases are burned. An exhaust phase is a phase in which the gases escape from the cylinder 12. [0033] In the particular case of the engine 10 operating at four times, the four phases take place successively resulting in a rotation of two turns of the crankshaft. The time of the four phases can therefore be defined crank angle.

The intake phase takes place while the crankshaft is between 0 ° and 180 ° while the compression phase corresponds to a crankshaft angle of 180 ° to 360 °. When the angle of the crankshaft is at the top dead center at 360 ° the combustion phase takes place, then between 360 ° and 540 ° is the expansion phase, while the exhaust and discharge phase corresponds to an angle crankshaft between 540 ° and 720 °. The cylinder 12 comprises at least one transfer valve 16 with a transfer port 18. The transfer valve 16 closes the transfer port 18. The transfer valve 16 escapes exhaust gas during an exhaust phase and admits exhaust gas into the cylinder during a compression phase. This makes it possible to recover the internal energy contained in the escaped gases. The internal energy of the gases comprises the thermal energy and the pressure energy resulting from the combustion in the cylinder 12. Only the transfer energy is not recovered. The recovery of the energy of the exhaust gas is therefore effective, which generates a significant gain in engine efficiency 10. Each cylinder 12 may furthermore comprise an exhaust exhaust valve 20 and an orifice 22 exhaust. The exhaust valve 20 closes the exhaust port 22. An exhaust valve serves only to push the gases out via an exhaust line. FIG. 5 illustrates the different phases, positioning with respect to a conventional opening diagram of the exhaust valve SE (discharge phase) and of the intake valve SA (intake phase). , the ordinate axis corresponding to a lift height of the valves, and the abscissa axis to the crankshaft rotation degrees. During the expansion phase, before opening the exhaust valve, the transfer valve is opened to store exhaust gas in the conduit (Sto), a stored gas that is destocked by a new valve opening. transfer (Defect) during the compression phase. The motor 10 may further comprise a plurality of cylinders 12 each with a transfer valve 16. According to the example of Figure 1, the engine 10 20 comprises four cylinders 12. As explained above, this allows in the case of a motor operating at four times, each cylinder 12 being in a different phase. This ensures that at any time, one of the cylinders 12 is in a combustion phase and relaxation, and thus drive the crankshaft. According to the example of FIG. 1, each cylinder 12 comprises four orifices: two inlet orifices 26 placed on the left side of the cylinder 12, an exhaust port 22 and a transfer orifice 18 placed on the right side. of the cylinder 12. Inlet valves 28 are used for closing the inlet orifices 26. The engine 10 further comprises a conduit 32 for storing exhaust gases. This duct 32 makes it possible to connect the transfer ducts 18. In the intake phase, the fresh gases are admitted into the cylinder 12, the two inlet valves 28 being open. In the compression phase, the transfer valve 16 is open for a short time typically a few crankshaft degrees to allow the pressurized exhaust gas from the transfer chamber 32 to be transferred into the cylinder 12. In the of combustion, the transfer valve 16 is closed. At the end of the expansion phase, the transfer valve 16 is opened for a few crankshaft degrees to allow the pressurized exhaust gas to be transferred into the storage chamber 32 and, when the transfer valve 16 is closed, the Exhaust valve 20 is open to allow the discharge of the exhaust gas without pressure to the outside. Such a mode of operation is only given for illustrative purposes and does not constitute a limitation. In particular, it is possible that at admission only one of the two intake valves 28 are opened to create a swirling movement also called swirl movement. Such a swirl effect can also be advantageously obtained by inclining the storage duct relative to the transfer duct, which then induces a stratification of the gases in the combustion chamber at the end of compression, with fresh gases essentially concentrated. in the center of this room, and surrounded by a halo of exhaust fumes. In the case of a motor 10 comprising several cylinders 12 as in the example of Figure 1, the cylinders 12 may be interconnected by the conduit 32 for storing the exhaust gas. The duct 32 thus makes it possible to connect the various transfer valves 16 in a manner that is simple to implement. At least a portion of the exhaust gas admitted into a first cylinder 12 by a transfer valve 16 during a compression phase of this first cylinder 12 are escaped into the storage pipe by a valve 16 for transferring a second cylinder 12 during an exhaust phase of this second cylinder 12. FIGS. 2 and 3, which are cross-section views of the engine 10 of FIG. 1 respectively in directions AA and BB, show the position of the duct 32. In Figures 2 and 3, an inlet port 26 closed by an inlet valve 28 is shown on the left. The piston 14 is in the top of the cylinder 12. For FIG. 3, the section in the direction AA is made at an exhaust orifice 22 closed by an exhaust valve 20 which is situated on the right of the cylinder. 12. The exhaust port 22 is connected to the exhaust line 24. Below line 24 is the exhaust pipe 32. For Figure 2, the section in the direction BB is made at a transfer port 18 located on the right and closed by a transfer valve 16. The transfer port 18 is connected to the duct 32. [0043] The engine 10 may further comprise a cylinder head. The conduit 32 is in the cylinder head, the cylinder head thus serving as protection for the conduit 32. In addition, such a positioning of the conduit 32 makes it possible to place the conduit 32 very close to the transfer valves 16. The duct 32 can thus be made as short as possible. The path taken by the exhaust gas in the duct 32 is thus minimized, which makes it possible to reduce the energy losses associated with the transfer of the gases in the duct 32. [0044] The two lift laws used for the valves 16 of transfer determine the efficiency of exhaust energy recovery. The laws of emergence determine the times during which the valves 16 are open and in particular the times when the valves 16 must open or close. The optimal lifting laws to ensure the most efficient energy recovery possible depend on a number of parameters. The speed of rotation and the load of the motor are some of the parameters influencing the choice of the laws of emergence. The realization of the lifting laws can be carried out in several different ways. Each transfer valve 16 can thus be actuated by an electromechanical or hydraulic control. By way of illustration, a piezoelectric element can be used to achieve electromechanical control of a transfer valve 16. A piezoelectric element is an element that converts an electric current into motion. Each transfer valve 16 can also be controlled by a cam 36 with two bosses as shown in Figure 4 which is a schematic view of a cam with two bosses. A cam with two bosses makes it possible to create two levee laws on a valve. The cam 36 comprises two bosses 40 mounted on a camshaft 38. The angle between the two bosses 40 is chosen to allow the two lifts of the valve 16 at the desired times to effectively recover the internal energy of the gases. A cam with two bosses being a simple piece to achieve, such a solution allows implementation of the actuation of transfer valves relatively easy. For the case of a control valves 16 transfer by a cam 36 with two bosses, the camshaft 38 with single boss cams and cams 36 with two bosses can be used. The single boss cams serve to control the engine exhaust valves 10 while the dual boss cams control the transfer valves. The camshaft 38 may for example comprise an alternation of cams with a single boss and cams with two bosses. Such camshaft 38 may be used to operate a motor 10 as shown in FIG. 1. In a variant of the invention particularly illustrated in FIG. 6, the storage and transfer conduit 32 may be placed in communication with the exhaust ducts 24 or more precisely with a manifold 41 in which the set of exhaust ducts 24 open, using an orifice 42 means such as a valve 43 allowing control this setting in communication. Such a variant makes it possible to take advantage of the two exhaust valves for better evacuation of the exhaust gas at full load. In the proposed embodiments, each cylinder is provided with two intake valves, an exhaust valve and a transfer valve. Those skilled in the art will understand that alternative embodiments may also be used without departing from the scope of the invention. Thus, the two intake valves can be replaced by a single valve with then means for precisely controlling its opening time and its opening time, for example an electromechanical control mechanism. Conversely, it is also possible to provide more than one exhaust valve per cylinder. Moreover, not all the cylinders of the engine are necessarily identical. Thus, when the cylinder bank has an odd number of cylinders (typically three for a 3-cylinder engine or 6, arranged for example in V), it may be advantageous to provide transfer valves only for the cylinders to the cylinder. end of the bench.

Claims (12)

Revendications1. A motor (10) comprising at least one cylinder (12) with at least one transfer valve (16) and positioning means for placing said valve in an open or closed position, characterized in that said positioning means is such that said transfer valve (16) escapes exhaust gas during an exhaust phase and admits exhaust gas into the cylinder (12) during a compression phase. 2. The engine (10) according to claim 1, characterized in that it further comprises an exhaust gas storage pipe (32), at least a portion of the exhaust gas admitted into the cylinder (12). from the storage conduit (32). 3. The engine (10) according to one of claims 1 to 2, characterized in that it comprises a plurality of cylinders (12) each with a valve (16) for transfer. 4. The engine (10) according to claim 3, characterized in that the cylinders (12) are interconnected by an exhaust gas storage duct (32), at least a portion of the exhaust gas admitted into the engine. a first cylinder (12) by a transfer valve (16) during a compression phase of this first cylinder (12) are escaped into the storage pipe (32) by a valve (16) for transferring a second cylinder ( 12) during an exhaust phase of this second cylinder (12). 5. The engine (10) according to any one of claims 2 or 4, characterized in that it further comprises a yoke, the conduit (32) being in the cylinder head. 6. The motor (10) according to any one of claims 1 to 5, characterized in that said positioning means comprises a cam (36) with two bosses. 7. The engine (10) according to any one of claims 1 to 6, characterized in that it further comprises a camshaft (38) with cams with a single boss and two bosses, the cams to a only one boss boss of the exhaust valves (20) and the two boss cams controlling the transfer valves (16). 8. The engine (10) according to any one of claims 1 to 7, characterized in that said positioning means comprises an electromechanical or hydraulic drive. 9. The engine (10) according to any one of claims 1 to 8, characterized in that each cylinder (12) further comprises a valve (20) of exhaust gas discharge. The engine (10) according to any one of claims 1 to 9, wherein the duration and height of the lift of the transfer valve (16) can be adjusted according to the operating conditions of the engine. 11. The engine (10) according to any one of claims 2 to 10, characterized in that the storage duct (32) is thermally insulated from the rest of the cylinder head 12. Vehicle comprising the engine (10) according to one of claims 1 to 11.