Component system for flex-fuel internal combustion engines

Abstract

The present invention relates to the field of internal combustion engines / components for internal combustion engines. The present invention more specifically relates to a combination of components for flex-fuel internal combustion engines so as to provide high energy parity between ethanol and gasoline. The component system for flex-fuel internal combustion engines comprises a piston housed within an engine cylinder, a plurality of piston rings and at least one engine exhaust valve, wherein the piston is provided with a circular body (10) defining a top portion (11), a ring region (12) having circumferential grooves housing the plurality of piston rings, and a cooling gallery (13); the plurality of piston rings comprises at least two groove rings having outer faces (17, 20) that contact the cylinder wall and are coated with a layer (P, J) of diamond-like carbon (DLC); and the at least one exhaust valve (21) is provided with a stem (22) and a head (23), wherein the stem (22) comprises a hollow internal region (24) filled with sodium.

Description

"SYSTEM OF COMPONENTS FOR BI-FUEL INTERNAL COMBUSTION ENGINES" Field of invention

[0001] The present invention relates to the field of internal combustion engines / components for internal combustion engines. Specifically, the present invention relates to a combination of components for dual-fuel (flex-fuel) internal combustion engines in order to provide high energy parity between ethanol and gasoline. Description of the State of the Art

[0002] Following global efforts to reduce greenhouse gas (GHG) emissions, the Brazilian government has been encouraging the use of ethanol as fuel for passenger vehicles, since this fuel is produced from renewable sources that promote the capture of CO2 from its combustion.

[0003] One way to encourage ethanol consumption among the population is to increase the efficiency of flex-fuel internal combustion engines when this fuel is used, so that a financial benefit is perceived as a result of choosing it instead of gasoline.

[0004] Flex-fuel internal combustion engines are designed as a compromise solution to run on both gasoline and ethanol.

[0005] During the engine cycles (intake, compression, combustion, and exhaust), the pistons, piston rings, and valves work in sync.

[0006] The pistons move within the cylinder while the rings ensure sealing and oil film control, and the valves control the air / fuel and exhaust gas flows.

[0007] The efficient interaction of these components is essential for engine performance, fuel economy, and durability.

[0008] However, the efficiency and peak performance of these engines with gasoline or ethanol are compromised, since this compromise solution does not represent the optimal configuration for either fuel.

[0009] In this regard, the efficiency of flex-fuel internal combustion engines using ethanol can be increased by altering the design of their components (pistons, valves, rings, etc.) in order to prioritize an optimal configuration, which includes an increase in the engine's compression ratio.

[0010] The geometric compression ratio in an internal combustion engine represents the ratio between the volumes of the combustion chamber at bottom dead center and at top dead center of the piston stroke. This parameter directly influences the thermal efficiency of engines, such that an increase in the compression ratio leads to a reduction in fuel consumption.

[0011] However, an increase in the compression ratio introduces drawbacks to engine operation, especially when using gasoline, such as increased component temperature and a propensity for auto-ignition (knocking), which can limit maximum engine performance, impair durability, and affect vehicle drivability.

[0012] Nevertheless, the viscosity of lubricating oil in modern engines has been drastically reduced to reduce fuel consumption. This reduction poses challenges to engine components due to the increased tribological conditions of moving systems, especially with the use of ethanol, since the dilution of this fuel in the lubricating oil further reduces its viscosity, in addition to creating a potential for oxidation of parts bathed in the oil. Objective of the Invention

[0013] The present invention, therefore, aims at a combination of components for dual-fuel internal combustion engines, aiming to increase energy efficiency when fueled with ethanol, while maintaining the viability of operation with gasoline, resulting in increased energy parity between ethanol and gasoline. Brief Description of the Invention

[0014] To that end, the present invention relates to a system of components for dual-fuel internal combustion engines comprising a piston housed within an engine cylinder, a plurality of piston rings and at least one engine exhaust valve, wherein the piston is provided with a circular body defining a top portion, a region of rings with circumferential grooves that house the plurality of piston rings, and a cooling gallery; the plurality of piston rings comprising at least two groove rings with outer faces in contact with the cylinder wall coated with a layer of DLC (Diamond Like Carbon), and at least one exhaust valve being provided with a stem and a head, wherein the stem comprises a hollow inner region filled with sodium.

[0015] In one embodiment, the top portion comprises a central elevation corresponding to an orientation perpendicular to the direction of the piston pin hole.

[0016] In one embodiment, the cooling gallery is located behind the ring region towards the center of the piston and below its top, and comprises an annular and hollow shape, having at least one engine lubricating oil inlet and at least one engine lubricating oil outlet.

[0017] In one embodiment, the at least two groove rings comprise an upper groove ring, closer to the top of the piston, having an annular shape defining an inner face, facing the groove of the ring region, an upper face, facing the combustion chamber, a lower face opposite the upper face, and the outer face in contact with the cylinder wall.

[0018] In one embodiment, the at least two groove rings comprise a lower groove ring, further from the top of the piston, consisting of an expander with the inner face facing the groove of the ring region and two segments defining the outer face in contact with the cylinder wall.

[0019] In one embodiment, the plurality of piston rings comprises a central groove ring, disposed in the ring region between at least two groove rings.

[0020] In one embodiment, the stem and head of at least one exhaust valve comprise a cylindrical shape. Brief description of the drawings

[0021] The details and functionalities of the present invention can be better understood from the following detailed description in conjunction with the attached figures, where: Figure 1 illustrates a cross-section of the piston component of the present invention. Figure 2 illustrates a perspective view of the upper channel ring component of the present invention. Figure 3 illustrates a cross-section of the lower channel ring component of the present invention. Figure 4 illustrates a cross-section of the exhaust valve component of the present invention. Detailed Description of the Invention

[0022] First, it should be noted that the term "preferred" used here refers to a particular embodiment of the invention among the multiple possible embodiments. The term "preferred" should not be understood as limiting the possible embodiments of the present invention, that is, it should not be understood as "imperative" or "mandatory" for the realization of the present invention. Furthermore, the term "component system" of the present invention should be interpreted as a specific set of elements applicable to existing biofuel internal combustion systems.

[0023] As shown in the figures, the component system for a dual-fuel internal combustion engine comprises a piston housed within an engine cylinder, a plurality of piston rings, and at least one engine exhaust valve, wherein the piston is provided with a substantially circular body 10 defining a top portion 11, a ring region 12 with circumferential grooves housing the plurality of piston rings, and a cooling gallery 13.

[0024] The plurality of piston rings comprises at least two groove rings with outer faces 17, 20 in contact with the cylinder wall, said faces being coated with a layer P, J of DLC.

[0025] Furthermore, at least one exhaust valve 21 is provided with a stem 22 and a head 23, wherein the stem 22 comprises a hollow inner region 24 filled with sodium.

[0026] Notably, in biofuel internal combustion engines, the piston moves inside the engine cylinder and its main function is to convert the energy released in the combustion of the air-fuel mixture into mechanical motion. This motion is transmitted to the crankshaft via the connecting rods, generating the torque necessary to move the vehicle.

[0027] Similarly, the piston design is fundamental to determining the engine's compression ratio. Geometrically, the compression ratio is defined as the ratio between the volumes of the cylinder with the piston in the bottom dead center and top dead center positions.

[0028] It is well known that increasing the compression ratio improves the engine's thermal efficiency; however, lower octane fuels (such as gasoline) can suffer from auto-ignition at high compression ratios, which compromises engine durability.

[0029] The present invention, therefore, provides a distinctive and inventive configuration of a piston for dual-fuel internal combustion engines, by combining a substantially circular body 10 defining a top portion 11 designed to reduce the volume of the combustion chamber at the top dead center position of the stroke and to confer an increase in the compression ratio, together with a cooling gallery 13 and an exhaust valve 21 provided with a hollow internal region 24 filled with sodium.

[0030] It should be noted that valves are moving components that control the entry, in the case of intake valves, and the exit, in the case of exhaust valves, of gases in the engine.

[0031] Its main functions are to ensure the correct flow of gases at the appropriate time, according to the engine cycle, and to help seal the combustion chamber during compression and combustion, preventing pressure loss.

[0032] The functioning of the exhaust valves is particularly critical due to their exposure to high-temperature exhaust gas flow during the engine's exhaust cycle. Excessive heating of this component must be avoided to prevent compromising its durability and to avoid the creation of surface hot spots that could lead to fuel auto-ignition.

[0033] Thus, in a relevant manner, aiming to increase the efficiency of the combustion engine using ethanol, the system proposed by the present invention is composed of a piston that promotes an increase in the compression ratio above the values ​​traditionally found in turbocharged dual-fuel internal combustion engines of the state of the art, while mitigating the temperature rise, by means of a cooling gallery 13 through which engine lubricating oil circulates, promoting a reduction in surface temperature of up to 25°C, as well as an exhaust valve 21 filled with sodium exhibiting a lower surface temperature.

[0034] In addition to preventing the formation of hot spots on the piston surface that can lead to auto-ignition (knocking) when using gasoline, the temperature reduction provided by the invention advantageously increases the durability of the components.

[0035] In a preferred embodiment, the top portion 11 of the piston is designed as a central elevation corresponding to the orientation perpendicular to the direction of the piston pin bore, in a substantially cylindrical shape, and may also include recesses and recesses to avoid impact with the valves, spark plug, or other protrusions or elements in the cylinder head. Furthermore, the piston of the system is composed of a body 10 made of aluminum. The configuration of a central projection perpendicular to the direction of the pin bore results in an increase in the compression ratio to up to 13:1, considering turbocharged engines, or up to 16:1, considering naturally aspirated engines.

[0036] Accordingly, the cooling gallery 13 is arranged behind the ring region 12 towards the center of the piston and below its top, and comprises an annular and hollow shape, having one or more engine lubricating oil inlets and one or more engine lubricating oil outlets to promote heat removal.

[0037] The stem 22 and head 23 of the exhaust valve 21 are cylindrical in shape. Inside the stem there is a hollow region 24 filled with sodium, which serves to absorb heat from the combustion chamber and reduce the surface temperature of the valve, especially the head 23.

[0038] Advantageously, the combination of these characteristics results in greater thermal efficiency of the engine when using ethanol and mitigates the occurrence of auto-ignition (knocking) with gasoline when increasing the compression ratio.

[0039] Nevertheless, the proposed system comprises a plurality of piston rings housed in a ring region 12 of the piston, wherein the outer faces 17, 20 of at least two rings are coated with a hydrogen-free (H-free) DLC layer P, J by means of DLC deposition methods known in the prior art. Importantly, the DLC rings of the present invention advantageously fit into the system, providing greater strength under severe mechanical loading conditions.

[0040] It should be noted that piston rings are metal components mounted in grooves on the outside of pistons. They play a crucial role in sealing between the piston and the cylinder wall.

[0041] Its main functions are to prevent combustion gases from escaping into the crankcase, maintaining the necessary pressure inside the cylinder, regulating the amount of oil that lubricates the cylinder walls, reducing friction and wear, and also transferring heat from the piston to the cylinder wall, preventing overheating.

[0042] Thus, and importantly, the piston rings of the proposed system are designed to withstand severe tribological conditions and maintain their basic functions throughout the vehicle's lifespan, considering the dilution of ethanol in the low-viscosity lubricating oil used in modern flex-fuel internal combustion engines.

[0043] In a preferred embodiment, the at least two groove rings comprise an upper groove ring, closer to the top of the piston, having an annular shape defining an inner face 14, facing the groove of the ring region 12, an upper face 15, facing the combustion chamber, a lower face 16 opposite the upper face 15, and the outer face 17 in contact with the cylinder wall.

[0044] A DLC (Diamond Like Carbon) coating, 5 µm to 30 µm thick, is applied to the entire surface of the outer face 17 in contact with the cylinder wall. This coating advantageously provides greater wear resistance and increased resistance to seizing, which is especially important when working under severe tribological conditions, such as high temperatures, ethanol dilution in the oil, and low viscosity lubricants.

[0045] In a preferred embodiment, the at least two groove rings comprise a lower groove ring, further from the top of the piston, consisting of an expander 18 with the inner face 19 facing the groove of the ring region 12 and two segments 19 defining the outer face 20 in contact with the cylinder wall. Detailed information about the expander is described in patent document US12117085B2.

[0046] A coating J of DLC, with a thickness of 5 µm to 30 µm, is applied to the entire surface of the outer face 20 where segments 19 contact the cylinder wall, which advantageously provides greater wear resistance and greater resistance to seizing.

[0047] In a preferred embodiment, the plurality of piston rings comprises a central groove ring, disposed in the ring region 12, between at least two groove rings. Notably, the ring region 12 comprises three circumferential grooves that house the three piston rings, upper, lower and central.

[0048] The central groove ring advantageously features a substantially annular shape with a differentiated profile on the contact face in order to promote the scraping of oil from the cylinder wall. Performing tests

[0049] Engine dynamometer tests were performed where the specific fuel consumption of the engine was measured using ethanol and gasoline in the reference configuration, with a compression ratio of 10.5:1, and in the proposed condition with a compression ratio of 12:1 using the components described above.

[0050] The variation in specific fuel consumption was observed, where, using ethanol, a reduction of 1% to 5% in specific fuel consumption was evident, depending on the engine operating conditions. With gasoline, although some high load conditions showed an increase of up to 8% in specific consumption, points with up to 3% reduction were observed under lower load and engine speed conditions, which are the most significant regimes during the execution of vehicle homologation cycles.

[0051] Based on this data, numerical simulations were performed to estimate the expected variation in fuel consumption and energy parity in the official vehicle homologation cycle (ABNT NBR 7024).

[0052] As a simulated result, a 1.5% reduction in specific fuel consumption was observed with ethanol and 0.7% with gasoline. Consequently, the simulation shows a 0.7% improvement in energy parity.

[0053] Additionally, to demonstrate the improved cooling of the piston configuration of the present invention with the cooling gallery 13, an engine test was performed on a dynamometer to measure the component's temperature.

[0054] A temperature reduction was observed near the top of the piston under full load (maximum performance) conditions across all engine speeds from 1250 to 5750 rpm. A 30°C reduction was noted under high engine speed conditions, i.e., under the most critical conditions in terms of thermal load.

[0055] In accordance with all that has been presented, the present invention advantageously provides a combination of components for dual-fuel internal combustion engines that results in increased energy efficiency when fueled with ethanol, while maintaining the viability of operation with gasoline, resulting in increased energy parity between ethanol and gasoline. Distinctly, the system proposed by the present invention is composed of a piston that, through a top portion configuration 11, promotes an increase in compression ratio above the values ​​traditionally found in prior art turbocharged dual-fuel internal combustion engines, while mitigating temperature rise by means of a cooling gallery 13 through which engine lubricating oil circulates, promoting a reduction in surface temperature of up to 25°C, as well as a sodium-filled exhaust valve 21 exhibiting a lower surface temperature.The system also consists of a plurality of piston rings that advantageously fit into the system, providing greater resistance under severe mechanical loading conditions.

[0056] Notably, the combination of components for biofuel internal combustion engines of the present invention advantageously provides high ethanol / gasoline energy parity.

[0057] Having described an example of a preferred embodiment, it should be understood that the scope of the present invention encompasses other possible variations, being limited only by the content of the claims alone, including possible equivalents.

Claims

CLAIMS 1. A system of components for a dual-fuel internal combustion engine, characterized by comprising a piston housed within an engine cylinder, a plurality of piston rings, and at least one engine exhaust valve, wherein the piston is provided with a circular body (10) defining a top portion (11), a ring region (12) with circumferential grooves that house the plurality of piston rings, and a cooling gallery (13); wherein the plurality of piston rings comprises at least two groove rings with outer faces (17, 20) in contact with the cylinder wall being coated with a layer (P, J) of DLC (Diamond Like Carbon, or diamond-like carbon arrangement) and at least one exhaust valve (21) having a stem (22) and a head (23), wherein the stem (22) comprises a hollow inner region (24) filled with sodium.

2. System of components for dual-fuel internal combustion engines according to claim 1, characterized in that the top portion of the piston (11) comprises a central elevation corresponding to an orientation perpendicular to the direction of the piston pin bore which confers an increase in the geometric compression ratio of the engine.

3. System of components for dual-fuel internal combustion engines according to claim 1, characterized in that the piston cooling gallery (13) is arranged behind the ring region (12) towards the center of the piston and below its top, and comprising an annular and hollow shape, having at least one engine lubricating oil inlet and at least one engine lubricating oil outlet.

4. System of components for dual-fuel internal combustion engines according to claim 1, characterized in that the at least two groove rings comprise an upper groove ring, closer to the top of the piston, having an annular shape defining an inner face (14), facing the groove of the ring region (12), an upper face (15), facing the combustion chamber, a lower face (16) opposite the upper face (15), and the outer face (17) in contact with the cylinder wall.

5. System of components for dual-fuel internal combustion engines according to claim 1, characterized in that the at least two groove rings comprise a lower groove ring, further from the top of the piston, composed of an expander (18) with the inner face (19) facing the groove of the ring region (12) and two segments (19) defining the outer face (20) in contact with the cylinder wall.

6. System of components for dual-fuel internal combustion engines according to claim 1, characterized in that the plurality of piston rings comprises a central groove ring, disposed in the ring region (12) between at least two groove rings.

7. System of components for dual-fuel internal combustion engines according to claim 1, characterized in that the stem (22) and the head (23) of at least one exhaust valve (21) comprise a cylindrical shape.

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