EP3844379A1 - Piston assembly for an internal combustion engine - Google Patents

Piston assembly for an internal combustion engine

Info

Publication number
EP3844379A1
EP3844379A1 EP19762359.8A EP19762359A EP3844379A1 EP 3844379 A1 EP3844379 A1 EP 3844379A1 EP 19762359 A EP19762359 A EP 19762359A EP 3844379 A1 EP3844379 A1 EP 3844379A1
Authority
EP
European Patent Office
Prior art keywords
pin
bore
piston
obstructing member
disposed
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP19762359.8A
Other languages
German (de)
French (fr)
Inventor
Alexander Zauner
Markus Doppelbauer
Heinz Kusel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BRP Rotax GmbH and Co KG
Original Assignee
BRP Rotax GmbH and Co KG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by BRP Rotax GmbH and Co KG filed Critical BRP Rotax GmbH and Co KG
Publication of EP3844379A1 publication Critical patent/EP3844379A1/en
Pending legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F3/00—Pistons 
    • F02F3/24—Pistons  having means for guiding gases in cylinders, e.g. for guiding scavenging charge in two-stroke engines

Definitions

  • the present technology relates to piston assemblies for internal combustion engines.
  • an internal combustion engine includes: a crankcase; a crankshaft disposed at least in part in the crankcase; a cylinder block connected to the crankcase; a cylinder defined in the cylinder block and having a cylinder axis; and a piston movably disposed within the cylinder and being operatively connected to the crankshaft.
  • the piston includes a piston head, a piston skirt extending from the piston head, and first and second pin bosses.
  • the first pin boss defines a first pin bore having a first bore end.
  • the first bore end opens in an outer surface of the piston skirt.
  • the second pin boss defines a second pin bore having a second bore end.
  • the second bore end opens in the outer surface of the piston skirt opposite the first bore end.
  • the first and second pin bores are aligned with each other.
  • the engine also includes a pin, first and second obstructing members, and a connecting rod.
  • the pin is disposed in the first and second pin bores.
  • the pin has a first pin end and a second pin end.
  • the first obstructing member is disposed within the first pin bore between the first bore end and the first pin end for blocking passage through the first pin bore.
  • the second obstructing member is disposed within the second pin bore between the second bore end and the second pin end for blocking passage through the second pin bore.
  • the connecting rod connects the pin to the crankshaft.
  • the connecting rod has a first rod end connected to the pin and a second rod end connected to the crankshaft. The first rod end is disposed between the first and second pin bosses.
  • the first obstructing member seals a first portion of the first pin bore from a second portion of the first pin bore.
  • the first portion of the first pin bore is defined between the first bore end and the first obstructing member.
  • the second portion of the first pin bore is defined on an opposite side of the first obstructing member from the first portion of the first pin bore.
  • the second obstructing member seals a first portion of the second pin bore from a second portion of the second pin bore.
  • the first portion of the second pin bore is defined between the second bore end and the second obstructing member.
  • the second portion of the second pin bore is defined on an opposite side of the second obstructing member from the first portion of the second pin bore.
  • the first obstructing member abuts the first pin end and the second obstructing member abuts the second pin end.
  • the first obstructing member is a first disc and the second obstructing member is a second disc.
  • Each of the first and second discs has opposite circular surfaces. The first and second discs are positioned such that the circular surfaces of the first and second discs are normal to a center axis of the pin bores.
  • the pin has a pin diameter and at least one of the first and second discs has a disc diameter that is greater than the pin diameter.
  • the first and second obstructing members are made of aluminum and have an anodized coating.
  • a first groove is defined about the first pin bore and a second groove is defined about the second pin bore.
  • the first groove is located between the first pin end and the first bore end.
  • the first obstructing member is inserted in the first groove.
  • the second groove is located between the second pin end and the second bore end. The second obstructing member is inserted in the second groove.
  • the engine also includes a first retaining ring and a second retaining ring.
  • the first retaining ring is disposed between the first obstructing member and the first bore end.
  • the first retaining ring retains the first obstructing member in place.
  • the second retaining ring is disposed between the second obstructing member and the second bore end. The second retaining ring retains the second obstructing member in place.
  • the first and second pin bores define at least in part a radially- extending groove.
  • each of the first and second pin bosses defines at least one drain bore.
  • the at least one drain bore extends generally transversally to a corresponding one of the first and second pin bores and fluidly connects the corresponding one of the first and second pin bores to the crankcase.
  • the at least one drain bore is disposed radially inward of a corresponding one of the first and second obstructing members.
  • the engine also includes: an upper piston ring located above the first and second pin bores; a first lower piston ring located below the first and second pin bores; and a second lower piston ring located below the first lower piston ring.
  • the first rod end and the pin define a plain bearing.
  • the first obstructing member is spaced from the first pin end and the second obstructing member is spaced from the second pin end.
  • the cylinder has a cylinder wall defining an intake port for feeding air into the cylinder and an exhaust port for discharging exhaust fluids therethrough. Reciprocating motion of the piston along the cylinder axis opens and closes the intake and exhaust ports.
  • the first obstructing member has a greater diameter than the first pin bore at a location aligned with the first pin end.
  • the second obstructing member has a greater diameter than the second pin bore at a location aligned with the second pin end.
  • a piston assembly for an internal combustion engine.
  • the piston assembly includes a piston, a first obstructing member and a second obstructing member.
  • the piston includes a piston head, a piston skirt extending from the piston head, and first and second pin bosses.
  • the first pin boss defines a first pin bore having a first bore end.
  • the first bore end opens in an outer surface of the piston skirt.
  • the second pin boss defining a second pin bore having a second bore end.
  • the second bore end opens in the outer surface of the piston skirt opposite the first bore end.
  • the first and second pin bores are aligned with each other.
  • the first obstructing member is disposed within the first pin bore radially inwardly of the first bore end for blocking passage through the first pin bore.
  • the second obstructing member is disposed within the second pin bore radially inwardly of the second bore end for blocking passage through the second pin bore.
  • the piston assembly also includes a pin disposed in the first and second pin bores.
  • the pin has a first pin end and a second pin end.
  • the first obstructing member is disposed between the first bore end and the first pin end.
  • the second obstructing member is disposed between the second bore end and the second pin end.
  • the piston assembly also includes a connecting rod having a first rod end connected to the pin and a second rod end for connecting to a crankshaft. The first rod end is disposed between the first and second pin bosses.
  • an internal combustion engine includes the piston assembly.
  • an internal combustion engine includes: a crankcase; a crankshaft disposed at least in part in the crankcase; a cylinder block connected to the crankcase; a cylinder defined in the cylinder block and having a cylinder axis; and a piston movably disposed within the cylinder and being operatively connected to the crankshaft.
  • the piston includes a piston head, a piston skirt extending from the piston head, and first and second pin bosses.
  • the first pin boss defines a first pin bore having a first bore end.
  • the first bore end opens in an outer surface of the piston skirt.
  • the second pin boss defines a second pin bore having a second bore end.
  • the first and second pin bores are aligned with each other.
  • the engine also includes a pin, an obstructing member, and a connecting rod.
  • the pin is disposed in the first and second pin bores.
  • the pin has a first pin end and a second pin end.
  • the obstructing member is disposed within the first pin bore between the first bore end and the first pin end.
  • the obstructing member seals a first portion of the first pin bore from a second portion of the first pin bore.
  • the first portion of the first pin bore is defined between the first bore end and the obstructing member.
  • the second portion of the first pin bore is defined on an opposite side of the obstructing member from the first portion of the first pin bore.
  • the connecting rod connects the pin to the crankshaft.
  • the connecting rod has a first rod end connected to the pin and a second rod end connected to the crankshaft. The first rod end is disposed between the first and second pin bosses.
  • Embodiments of the present technology each have at least one of the above- mentioned object and/or aspects, but do not necessarily have all of them. It should be understood that some aspects of the present technology that have resulted from attempting to attain the above-mentioned object may not satisfy this object and/or may satisfy other objects not specifically recited herein.
  • Figure 1A is a front cross-sectional view of a two-stroke internal combustion engine
  • Figure 1B is a rear cross-sectional view of the engine of Fig. 1A;
  • Figure 2 is a schematic illustration of components of the engine of Fig. 1A and of associated components thereof;
  • Figure 3 is a perspective view, taken from a bottom right side, of a piston of the engine of Fig. 1A;
  • Figure 4 is a front cross-sectional view of a piston assembly including the piston of Fig. 3, a pin positioned in the piston and a connecting rod connected to the pin;
  • Figure 5 is a top cross-sectional view of the piston of Fig. 3;
  • Figure 6 is a perspective view, taken from a left side, of a cross-section of the piston of Fig. 3, with the pin and the connecting rod removed to expose the underlying structure of the piston;
  • Figure 7 is a left side cross-sectional view of the piston and components of Fig. 4, showing a lubrication device for lubricating an interface between the pin and connecting rod;
  • Figure 8 is a top cross-sectional view of the pin positioned in the piston in accordance with an alternative embodiment in which inner retaining rings are provided;
  • Figure 9 is a front cross-sectional view of the piston assembly in accordance with another embodiment.
  • Figure 10 is a perspective view of an obstructing member of the piston assembly of Figure 9; and [0042] Figure 11 is a cross-sectional view of the obstructing member of Figure 10 taken along line 11-11 in Figure 10.
  • the present technology will be described below with respect to a direct fuel injection, two-stroke, inline, two-cylinder internal combustion engine. It is contemplated that at least some aspects of the present technology could be provided on a two-stroke internal combustion engine that is carbureted or has semi-direct injection, that has cylinders arranged in a V-type or other arrangement, and/or that has only one or more than two cylinders. It is also contemplated that at least some aspects of the present technology could be provided on a four-stroke internal combustion engine or a diesel engine.
  • Figs. 1A and 1B illustrate an internal combustion engine 10.
  • the engine 10 operates on a two-stroke engine cycle such that the engine 10 completes a power cycle with two strokes (an upstroke and a downstroke) of the engine’s pistons 34.
  • the engine 10 can thus be referred to as a two-stroke engine.
  • the engine 10 has a crankcase 12, a cylinder block 14 connected on top of the crankcase 12 and a cylinder head 16 connected on top of the cylinder block 14.
  • the crankcase 12 rotationally supports a crankshaft 18.
  • An output shaft 20 is rotationally supported by the crankcase 12 and driven by the crankshaft 18.
  • the output shaft 20 is coaxial with the crankshaft 18. In other embodiments, the output shaft 20 could be offset from the crankshaft 18.
  • the output shaft 20 protrudes from the crankcase 12 and is connected to a transmission of a vehicle or another mechanical component to be driven by the engine 10. As such, the side of the engine 10 from which the output shaft 20 protrudes is referred to herein as the power take-off side of the engine 10. It is contemplated that the engine 10 may omit the output shaft 20 and that instead a portion of the crankshaft 18 protrudes from the crankcase 12 to be connected to the mechanical component to be driven by the engine 10.
  • a generator 25 is connected to the side of the crankcase 12 opposite the power take-off side.
  • the generator 25 uses power produced by the engine 10 to generate electrical energy for storage in a battery (not shown).
  • a generator housing 27 encloses the generator 25 therein.
  • An electric starter motor (not shown) is also connected to the side of the crankcase 12. The starter motor selectively engages the crankshaft 18 via gears (not shown) to cause the crankshaft 18 to turn before the engine 10 can run on its own as a result of the internal combustion process in order to start the engine 10.
  • a mechanically driven oil pump 23 (schematically shown in Fig. 2) is fluidly connected to various parts of the engine 10 to circulate oil through the engine 10.
  • the oil pump 23 pumps oil from an oil reservoir 28 connected to a bottom of the crankcase 12.
  • the oil pumped by the oil pump 23 is distributed to the various components of the engine 10 that need lubrication.
  • the oil then falls back by gravity inside the oil reservoir 28.
  • the cylinder block 14 defines two cylinders 30 adjacent to one another in a lateral direction of the engine 10. Each cylinder 30 defines a cylinder axis 32 along which the cylinder 30 extends.
  • the engine 10 has two pistons 34 each of which is disposed within a corresponding one of the cylinders 30.
  • each piston 34 moves along the cylinder axis 32 of its corresponding cylinder 30 in a reciprocating motion including an upstroke (whereby the piston 34 moves toward an upper end of the cylinder 30) and a downstroke (whereby the piston 34 moves away from the upper end of the cylinder 30).
  • each piston 34 is connected to the crankshaft 18 by a connecting rod 36 so as to rotate the crankshaft 18 during the upstroke and downstroke of the piston 34.
  • each cylinder 30 has a cylinder wall 31 defining an intake port 33 and an exhaust port 35.
  • the intake port 33 When the intake port 33 is open, air is fed through the intake port 33 into a combustion chamber defined in part by the cylinder 30.
  • the exhaust port 35 When the exhaust port 35 is open, exhaust fluids are discharged from the combustion chamber therethrough.
  • the reciprocating motion of the corresponding piston 34 along the cylinder axis 32 opens and closes the intake and exhaust ports 33, 35 in a controlled manner to provide efficient fuel combustion in the combustion chamber.
  • the cylinder block 14 defines part of an air chamber 22 (i.e., a plenum) to which the intake port 33 is fluidly connected.
  • a supercharger (not shown) feeds the air chamber 22 with compressed air.
  • the cylinder block 14 also defines part of an exhaust passage (not shown) for each cylinder 30 extending from a corresponding one of the exhaust ports 35.
  • An exhaust manifold (not shown) is connected to the cylinder block 14 at the exhaust passages. Notably, the exhaust manifold has two inlets in alignment with the two exhaust passages and a single outlet.
  • the cylinder head 16 closes the tops of the cylinders 30 such that for each cylinder 30 a variable volume combustion chamber is defined between the cylinder 30, its corresponding piston 34 and the cylinder head 16.
  • Two fuel injectors 68 (not shown in Figs. 1A and 1B, schematically illustrated in Fig. 2) and two spark plugs 70 (one of each per cylinder 30) are connected to the cylinder head 16.
  • the fuel injectors 68 inject fuel directly in the combustion chambers.
  • the spark plugs 70 ignite the fuel-air mixture in the combustion chambers.
  • the operation of the fuel injectors 68, the spark plugs 70, the starter motor and the oil pump is controlled by an electronic control unit (ECU) 72 that is schematically illustrated in Fig. 2.
  • the ECU 72 controls these components based on signals received from various sensors and components, some of which are illustrated schematically in Fig. 2.
  • An engine speed sensor 74 senses a speed of rotation of the crankshaft 18 and sends a signal representative of engine speed to the ECU 72.
  • a throttle valve position sensor 76 senses the position of a throttle valve 48 associated with the cylinders 30 and configured to regulate the flow of air into the engine 10. It is contemplated that the engine 10 could include more than one throttle valve 48 in alternative implementations.
  • the throttle valve position sensor 76 sends a signal representative of the position of the throttle valve 48 to the ECU 72.
  • a start/stop switch 78 sends a signal to the ECU 72 to start the engine 10 when the engine 10 is stopped and to stop the engine 10 when the engine 10 is running. It is contemplated that the start/stop switch 78 could be separated into a start switch and a separate stop switch. It is contemplated that the start/stop switch 78 could be incorporated into an ignition key assembly or could be a separate button.
  • a coolant temperature sensor 125 senses a temperature of a coolant flowing in a cooling jacket of the engine 10 and sends a signal representative of the coolant temperature to the ECU 72.
  • ECU 72 Although a single ECU 72 is illustrated, it is contemplated that the various functions of the ECU 72 could be split between two or more control units/controllers and that at least some of these control units could communicate with each other.
  • pistons 34 will now be described with reference to Figs. 3 to 6. Both pistons 34 are identical and therefore a single one of the pistons 34 will be described below in relation to its associated cylinder 30 and related structure. It is noted that the spatial orientation of the components associated with the piston 34 will be described in relation to a cylindrical coordinate system defined by the piston 34. Therefore, the use of the term “radially” refers to the radial direction defined by the piston 34.
  • the piston 34 has a piston head 38 defining an upper end of the piston 34, and a piston skirt 40 extending from the piston head 38 and defining a lower end of the piston 34.
  • the lower end of the piston 34 is open, notably defining a bottom opening 24 in which, as will be described in more detail below, the connecting rod 36 extends.
  • the piston 34 has two pin bosses 42L, 42R that are spaced apart from one another.
  • the pin bosses 42L, 42R define respective pin bores 44L, 44R which are aligned with each other such as to define a center axis 55 (Figs. 5, 6). As shown in Fig.
  • each of the pin bores 44L, 44R has an outer bore end 46 opening in an outer surface 41 of the piston skirt 40 and an inner bore end 47 opposite the outer bore end 46 and opening into an interior of the piston 34.
  • the outer bore end 46 of the pin bore 44L opens in the outer surface of the piston skirt 40 opposite the outer bore end 46 of the pin bore 44R (i.e., the outer bore ends 46 of the pin bores 44L, 44R are at diametrically opposite locations of the outer surface of the piston skirt 40).
  • the piston skirt 40 also defines recesses 105 (Figs. 3, 4) above the pin bores 44L, 44R for reducing the weight of the piston 34.
  • the piston skirt 40 also defines three ring lands for receiving therein respective piston rings 50, 52, 54.
  • the piston rings 50, 52, 54 include an upper piston ring 50 adjacent the upper end of the piston 34 and two lower piston rings 52, 54 adjacent the lower end of the piston 34.
  • the upper piston ring 50 is located above the pin bores 44L, 44R while the first and second lower piston rings 52, 54 are located below the pin bores 44L, 44R.
  • the second lower piston ring 54 is positioned below the first lower piston ring 52 and is thus closer to the lower end of the piston 34 than the first lower piston ring 52.
  • the upper piston ring 50 is a semi-trapeze ring
  • the first lower piston ring 52 is a taper-faced Napier ring
  • the second lower piston ring 54 is an oil control ring which collects and directs oil through radially-extending openings 56 defined in the piston skirt 40 to the interior of the piston 34.
  • oil collected by the second lower piston ring 54 is returned to the crankcase 12 via the openings 56.
  • the piston 34 cyclically opens and closes the intake port 33.
  • the second lower piston ring 54 is positioned below the intake port 33 such that the piston skirt 40 of the piston 34 blocks the intake port 33 (see piston 34 on right-hand side of Fig. 1A)
  • a pin 60 extends radially within the piston 34 and connects the connecting rod 36 to the piston 34.
  • the pin 60 is generally cylindrical and hollow.
  • the pin 60 is disposed in the pin bores 44L, 44R such that each of the two opposite ends 61, 63 of the pin 60 is located in a respective one of the pin bores 44L, 44R.
  • the connecting rod 36 is connected to the pin 60 in a space 45 between the pin bosses 42L, 42R. More specifically, a small end 64 of the connecting rod 36 is pivotably connected to the pin 60 between the pin bosses 42L, 42R. A bushing 66 is disposed between the small end 64 of the connecting rod 36 and the pin 60 such that a plain bearing is defined between the small end 64 of the connecting rod 36 and the pin 60. As best seen in Figs. 1 A and 1B, the opposite bigger end 69 of the connecting rod 36 is coupled to the crankshaft 18 such that the reciprocating motion of the piston 34 along the cylinder axis 32 causes the connecting rod 36 to rotate the crankshaft 18.
  • a lubricating device 26 is disposed in the cylinder block 14 and is operable to lubricate the interior of the piston 34, notably including the connection between the pin 60 and the connecting rod 36, and to cool the piston head 38.
  • the lubricating device 26 is fluidly connected to the oil pump 23 and has a nozzle 88 which, when the piston 34 is close to its bottom dead center position (i.e., closest to the crankshaft 18 and furthest from the cylinder head 16), enters the bottom opening 24 of the piston 34 and sprays a jet of oil 90 upwardly into the interior of the piston 34.
  • the small end 64 of the connecting rod 36 has openings 92 extending from an outer surface 94 to an inner surface 96 of the small end 64 to guide oil into the plain bearing defined between the small end 64 of the connecting rod 36 and the pin 60. It is contemplated that the lubricating device 26 could be positioned in a part of the engine 10 other than the cylinder block 14, for example in the crankcase 12, and that the nozzle 88 does not enter the bottom opening 24 of the piston 34.
  • each of the pin bores 44L, 44R defines a radially-extending groove 102.
  • Each of the grooves 102 extends radially outwardly from the inner bore end 47 of the corresponding one of the pin bores 44L, 44R.
  • the radially-extending groove 102 accommodates momentary deformation of the pin 60 which occurs in operation.
  • the pin 60 is generally cylindrical when at rest, the pin 60 has a tendency to deform and acquire an oval shape due to the pressures acting on the pin 60 when the engine 10 is running.
  • the radially-extending groove 102 can be helpful to circulate oil within the pin bores 44L, 44R.
  • each of the pin bosses 42L, 42R also defines a drain bore 104 for draining oil from the pin bores 44L, 44R.
  • each of the drain bores 104 fluidly connects a corresponding pin bore 44L, 44R to the crankcase 12.
  • the drain bores 104 extend generally transversally to the pin bores 44L, 44R (i.e., generally transversally to the center axis 55). As such, oil used for lubricating the connection between the pin 60 and the connecting rod 36 is drained from the pin bores 44L, 44R and returns to the crankcase 12. It is contemplated that, in certain embodiments, no drain bores 104 may be defined by the pin bosses 42L, 42R.
  • Two obstructing members 62L, 62R flank the pin 60 at each end thereof such that the pin 60 is disposed between both obstructing members 62L, 62R. More specifically, a left obstructing member 62L is disposed in the pin bore 44L between the outer bore end 46 thereof and the end 61 of the pin 60, while a right obstructing member 62R is disposed in the pin bore 44R between the outer bore end 46 thereof and the end 63 of the pin 60.
  • the obstructing members 62L, 62R block passage through the corresponding pin bores 44L, 44R such as to limit or otherwise prevent oil from flowing from within the pin bores 44L, 44R to the outer surface 41 of the piston skirt 40. This can therefore eliminate or reduce the amount of oil that is discharged from the pin bores 44L, 44R into the intake port 33 and/or the exhaust port 35 of the cylinder 30, which in turn can reduce harmful emissions being discharged through the exhaust passages of the engine 10.
  • the obstructing members 62L, 62R seal parts of each of the pin bores 44L, 44R from one another. For instance, as best seen in Fig. 6, each of the obstructing members 62L, 62R seals an outer portion 80 of a corresponding one of the pin bores 44L, 44R from an inner portion 82 of that pin bore 44L, 44R.
  • the outer portion 80 of the pin bore 44L is defined between the outer bore end 46 thereof and the obstructing member 62L, while the inner portion 82 is defined on a side of the obstructing member 62L opposite from the outer portion 80 (i.e., between the inner bore end 47 of the pin bore 44L and the obstructing member 62L).
  • the obstructing member 62R seals the outer portion 80 of the pin bore 44R from the inner portion 82 of the pin bore 44R.
  • the obstructing members 62L, 62R are identical and therefore only the left obstructing member 62L will be described below in relation to the pin bore 44L. It is to be understood that the right obstructing member 62R is also positioned in the same manner in relation to the pin bore 44R and has a same configuration relative thereto (e.g., sizing).
  • the obstructing member 62L is a disc having opposite outer and inner circular surfaces 84, 86.
  • the circular surfaces 84, 86 of the obstructing member 62L are normal to the center axis 55, with the outer circular surface 84 facing the outer bore end 46 of the pin bore 44L and the inner circular surface 86 facing the inner bore end 47 of the pin bore 44L.
  • the obstructing member 62L has a disc diameter that is greater than the diameter of the pin 60.
  • the disc diameter of the obstructing member 62L is greater than the diameter of the pin bore 44L at a location aligned with the end 61.
  • the obstructing member 62L could have any other suitable shape.
  • the outer and inner surfaces 84, 86 may not be circular.
  • an alternative embodiment of the obstructing member 62L will be described below with respect to Figs. 9 to 11.
  • the obstructing member 62L is made of aluminum and has an anodized coating.
  • the anodized coating of the obstructing member 62L provides protection from wear caused by movement of the pin 60 in the pin bores 44L, 44R.
  • the obstructing member 62L could be made of steel. In such embodiments, the anodized coating may be omitted given the higher strength of steel.
  • the obstructing member 62L is positioned radially outwardly of the end 61 of the pin 60. To that end, as shown in Fig. 5, a groove 98 is defined about the pin bore 44L (i.e., concentric with the pin bore 44L) at a location between the end 61 of the pin 60 and the outer bore end 46.
  • the obstructing member 62L is inserted in the groove 98 which is sized for accommodating the obstructing member 62L therein. More specifically, in this embodiment, the groove 98 defines a shoulder facing radially outwardly.
  • the inner circular surface 86 of the obstructing member 62L is in contact with the shoulder of the groove 98 such that the shoulder restricts movement of the obstructing member 62L radially inwardly within the pin bore 44L.
  • an identical groove 98 is defined about the pin bore 44R to position the obstructing member 62R therein, radially outwardly of the end 63 of the pin 60 and such as to abut the end 63 of the pin 60.
  • the obstructing member 62R is therefore positioned in the pin bore 44R in a mirror image to that which has been described in relation to the obstructing member 62L and the pin bore 44L. The positioning of the obstructing member 62R will thus not be described further here.
  • Retaining rings 110L, 11 OR are provided to retain the obstructing members 62L, 62R and the pin 60 in place.
  • the retaining rings 110L, 11 OR will be referred to as“outer” retaining rings in that they are positioned radially outwardly of the corresponding obstructing members 62L, 62R. More specifically, the outer retaining ring 110L is disposed between the obstructing member 62L and the outer bore end 46 of the pin bore 44L, while the outer retaining ring 11 OR is disposed between the obstructing member 62R and the outer bore end 46 of the pin bore 44R. Respective grooves 114 (Fig.
  • the outer retaining rings 110L, 110R are circlips which are snapped into place in the grooves 114.
  • the outer retaining rings 110L, 11 OR thus restrict movement of the obstructing members 62L, 62R radially outwardly within their respective pin bores 44L, 44R such that, in collaboration with the grooves 98, radial movement of the obstructing members 62L, 62R and the pin 60 is restricted.
  • inner retaining rings 120L, 120R are provided between the ends 61, 63 of the pin 60 and the adjacent obstructing members 62L, 62R.
  • the inner retaining rings 120L, 120R are “inner” in that they are positioned radially inwardly of the corresponding obstructing members 62L, 62R. More specifically, the inner retaining ring 120L is disposed between the end 61 of the pin 60 and the left obstructing member 62L, while the inner retaining ring 120R is disposed between the end 63 of the pin 60 and the right obstructing member 62R.
  • Respective ring-locating grooves 122 are defined about the pin bores 44L, 44R to position the inner retaining rings 120L, 120R therein.
  • the ends 61, 63 of the pin 60 are spaced apart from the corresponding obstructing members 62L, 62R. Consequently, the obstructing members 62L, 62R could also omit the anodized coating described above since contact between the pin 60 and the obstructing members 62L, 62R is prevented by the spacing therebetween.
  • retaining rings similar to the outer retaining rings 110L, 11 OR could be provided radially inwardly of the obstructing members 62L, 62R to retain the pin 60 in place.
  • a press fit between the pin bosses 42L, 42R and the obstructing members 62L, 62R restricts movement of the obstructing members 62L, 62R radially outwardly within the pin bores 44L, 44R while the retaining rings restrict radial movement of the pin 60 within the pin bores 44L, 44R.
  • piston assembly could be provided on its own including the piston 34 and the obstructing members 62L, 62R.
  • the piston assembly could also include the pin 60 and/or the connecting rod 36.
  • the obstructing members are shaped differently than that described above.
  • obstructing members 62L’, 62R’ are provided and are not disc shaped like the obstructing members 62L, 62R.
  • the obstructing members 62L’, 62R’ are identical and therefore only the left obstructing member 62L’ will be described below in relation to the pin bore 44L.
  • the right obstructing member 62R’ is also positioned in the same manner in relation to the pin bore 44R and has a same configuration relative thereto (e.g., sizing).
  • the obstructing member 62L’ is circular and generally cup-shaped.
  • a side 200 of the obstructing member 62L’ has offset surfaces 204, 206 normal to a central axis of the obstructing member 62L’, while an opposite side 202 of the obstructing member 62L’ has a circular surface 208.
  • the surfaces 204, 206 are axially offset from one another.
  • the surface 206 is an annular surface and the surface 204 is a circular surface.
  • the surfaces 204, 206, 208 of the obstructing member 62L’ are normal to the center axis 55, with the outer surface 208 facing the outer bore end 46 of the pin bore 44L and the inner surfaces 204, 206 facing the inner bore end 47 of the pin bore 44L. Moreover, when in position, the annular surface 206 abuts the end 61 of the pin 60.
  • the obstructing member 62L’ has an outer diameter that is greater than the diameter of the pin 60. Moreover, the outer diameter of the obstructing member 62L’ is greater than the diameter of the pin bore 44L at a location aligned with the end 61.
  • This configuration of the obstructing member 62L’ may increase a radial contact area between the obstructing member 62L’ and the pin boss 42L thus reducing contact pressure therebetween which in turn may reduce wear of the contact area between the obstructing member 62L’ and the pin boss 42L. Moreover, the shape of the obstructing member 62L’ does not significantly increase its weight relative to the obstructing member 62L described above. [0079] Modifications and improvements to the above-described embodiments of the present technology may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting. The scope of the present technology is therefore intended to be limited solely by the scope of the appended claims.

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  • Chemical & Material Sciences (AREA)
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  • General Engineering & Computer Science (AREA)
  • Pistons, Piston Rings, And Cylinders (AREA)

Abstract

An internal combustion engine includes a crankcase, a crankshaft disposed at least in part in the crankcase, and acylinder block connected to the crankcase. A piston is movably disposed within acylinder of the cylinder block and isoperatively connected to the crankshaft. Afirst pin bossof the pistondefinesa first pin bore having a first bore end opening in an outer surface of apiston skirtof the piston. Asecond pin boss of the piston definesa second pin bore having a second bore end opening in the outer surface of the piston skirt opposite the first bore end.A pin is disposed in the first and second pin bores. Obstructing members are disposed within the first and second pin bores respectively for blocking passage through the firstand secondpin bores.Aconnecting rod connects the pin to the crankshaft.

Description

PISTON ASSEMBLY FOR AN INTERNAL COMBUSTION ENGINE
CROSS-REFERENCE
[0001] The present application claims priority to U.S. Provisional Patent Application No. 62/724,935, filed on August 30, 2018, the entirety of which is incorporated herein by reference.
FIELD OF TECHNOLOGY
[0002] The present technology relates to piston assemblies for internal combustion engines.
BACKGROUND [0003] Internal combustion engines, and in particular two-stroke internal combustion engines, are known to release harmful emissions as a by-product of the combustion occurring within the engine’s cylinder(s). While certain improvements have been made to provide cleaner engines, it is nevertheless desirable to reduce the emissions of an engine as much as possible. [0004] This is particularly true for two-stroke internal combustion engines which are generally considered to be more polluting than their four-stroke counterparts. Notably, since the intake and exhaust ports of a cylinder of a two-stroke internal combustion engine are blocked only momentarily by a corresponding piston moving within the cylinder, unwanted transmission of oil and/or fuel to the exhaust ports of the cylinder will typically occur and cause the engine to discharge harmful emissions. This can be especially apparent when oil is sprayed inside the piston skirt of the piston in order to lubricate a connection between the piston and a connecting rod that couples the piston to the engine’s crankshaft. Notably, the sprayed oil can find its way outside of the piston and into the intake and exhaust ports of the cylinder as described above. [0005] There is therefore a desire for an internal combustion engine with reduced emissions. SUMMARY
[0006] It is an object of the present technology to ameliorate at least some of the inconveniences present in the prior art.
[0007] According to one aspect of the present technology, there is provided an internal combustion engine. The engine includes: a crankcase; a crankshaft disposed at least in part in the crankcase; a cylinder block connected to the crankcase; a cylinder defined in the cylinder block and having a cylinder axis; and a piston movably disposed within the cylinder and being operatively connected to the crankshaft. The piston includes a piston head, a piston skirt extending from the piston head, and first and second pin bosses. The first pin boss defines a first pin bore having a first bore end. The first bore end opens in an outer surface of the piston skirt. The second pin boss defines a second pin bore having a second bore end. The second bore end opens in the outer surface of the piston skirt opposite the first bore end. The first and second pin bores are aligned with each other. The engine also includes a pin, first and second obstructing members, and a connecting rod. The pin is disposed in the first and second pin bores. The pin has a first pin end and a second pin end. The first obstructing member is disposed within the first pin bore between the first bore end and the first pin end for blocking passage through the first pin bore. The second obstructing member is disposed within the second pin bore between the second bore end and the second pin end for blocking passage through the second pin bore. The connecting rod connects the pin to the crankshaft. The connecting rod has a first rod end connected to the pin and a second rod end connected to the crankshaft. The first rod end is disposed between the first and second pin bosses.
[000S] In some embodiments, the first obstructing member seals a first portion of the first pin bore from a second portion of the first pin bore. The first portion of the first pin bore is defined between the first bore end and the first obstructing member. The second portion of the first pin bore is defined on an opposite side of the first obstructing member from the first portion of the first pin bore. The second obstructing member seals a first portion of the second pin bore from a second portion of the second pin bore. The first portion of the second pin bore is defined between the second bore end and the second obstructing member. The second portion of the second pin bore is defined on an opposite side of the second obstructing member from the first portion of the second pin bore. [0009] In some embodiments, the first obstructing member abuts the first pin end and the second obstructing member abuts the second pin end.
[0010] In some embodiments, the first obstructing member is a first disc and the second obstructing member is a second disc. Each of the first and second discs has opposite circular surfaces. The first and second discs are positioned such that the circular surfaces of the first and second discs are normal to a center axis of the pin bores.
[0011] In some embodiments, the pin has a pin diameter and at least one of the first and second discs has a disc diameter that is greater than the pin diameter.
[0012] In some embodiments, the first and second obstructing members are made of aluminum and have an anodized coating.
[0013] In some embodiments, a first groove is defined about the first pin bore and a second groove is defined about the second pin bore. The first groove is located between the first pin end and the first bore end. The first obstructing member is inserted in the first groove. The second groove is located between the second pin end and the second bore end. The second obstructing member is inserted in the second groove.
[0014] In some embodiments, the engine also includes a first retaining ring and a second retaining ring. The first retaining ring is disposed between the first obstructing member and the first bore end. The first retaining ring retains the first obstructing member in place. The second retaining ring is disposed between the second obstructing member and the second bore end. The second retaining ring retains the second obstructing member in place.
[0015] In some embodiments, the first and second pin bores define at least in part a radially- extending groove.
[0016] In some embodiments, each of the first and second pin bosses defines at least one drain bore. The at least one drain bore extends generally transversally to a corresponding one of the first and second pin bores and fluidly connects the corresponding one of the first and second pin bores to the crankcase.
[0017] In some embodiments, the at least one drain bore is disposed radially inward of a corresponding one of the first and second obstructing members. [0018] In some embodiments, the engine also includes: an upper piston ring located above the first and second pin bores; a first lower piston ring located below the first and second pin bores; and a second lower piston ring located below the first lower piston ring.
[0019] In some embodiments, the first rod end and the pin define a plain bearing. [0020] In some embodiments, the first obstructing member is spaced from the first pin end and the second obstructing member is spaced from the second pin end.
[0021] In some embodiments, the cylinder has a cylinder wall defining an intake port for feeding air into the cylinder and an exhaust port for discharging exhaust fluids therethrough. Reciprocating motion of the piston along the cylinder axis opens and closes the intake and exhaust ports.
[0022] In some embodiments, the first obstructing member has a greater diameter than the first pin bore at a location aligned with the first pin end. The second obstructing member has a greater diameter than the second pin bore at a location aligned with the second pin end.
[0023] According to another aspect of the present technology, there is provided a piston assembly for an internal combustion engine. The piston assembly includes a piston, a first obstructing member and a second obstructing member. The piston includes a piston head, a piston skirt extending from the piston head, and first and second pin bosses. The first pin boss defines a first pin bore having a first bore end. The first bore end opens in an outer surface of the piston skirt. The second pin boss defining a second pin bore having a second bore end. The second bore end opens in the outer surface of the piston skirt opposite the first bore end. The first and second pin bores are aligned with each other. The first obstructing member is disposed within the first pin bore radially inwardly of the first bore end for blocking passage through the first pin bore. The second obstructing member is disposed within the second pin bore radially inwardly of the second bore end for blocking passage through the second pin bore.
[0024] In some embodiments, the piston assembly also includes a pin disposed in the first and second pin bores. The pin has a first pin end and a second pin end. The first obstructing member is disposed between the first bore end and the first pin end. The second obstructing member is disposed between the second bore end and the second pin end. [0025] In some embodiments, the piston assembly also includes a connecting rod having a first rod end connected to the pin and a second rod end for connecting to a crankshaft. The first rod end is disposed between the first and second pin bosses.
[0026] In some embodiments, an internal combustion engine includes the piston assembly.
[0027] According to another aspect of the present technology, there is provided an internal combustion engine. The engine includes: a crankcase; a crankshaft disposed at least in part in the crankcase; a cylinder block connected to the crankcase; a cylinder defined in the cylinder block and having a cylinder axis; and a piston movably disposed within the cylinder and being operatively connected to the crankshaft. The piston includes a piston head, a piston skirt extending from the piston head, and first and second pin bosses. The first pin boss defines a first pin bore having a first bore end. The first bore end opens in an outer surface of the piston skirt. The second pin boss defines a second pin bore having a second bore end. The first and second pin bores are aligned with each other. The engine also includes a pin, an obstructing member, and a connecting rod. The pin is disposed in the first and second pin bores. The pin has a first pin end and a second pin end. The obstructing member is disposed within the first pin bore between the first bore end and the first pin end. The obstructing member seals a first portion of the first pin bore from a second portion of the first pin bore. The first portion of the first pin bore is defined between the first bore end and the obstructing member. The second portion of the first pin bore is defined on an opposite side of the obstructing member from the first portion of the first pin bore. The connecting rod connects the pin to the crankshaft. The connecting rod has a first rod end connected to the pin and a second rod end connected to the crankshaft. The first rod end is disposed between the first and second pin bosses.
[0028] Embodiments of the present technology each have at least one of the above- mentioned object and/or aspects, but do not necessarily have all of them. It should be understood that some aspects of the present technology that have resulted from attempting to attain the above-mentioned object may not satisfy this object and/or may satisfy other objects not specifically recited herein.
[0029] Additional and/or alternative features, aspects and advantages of embodiments of the present technology will become apparent from the following description, the accompanying drawings and the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] For a better understanding of the present technology, as well as other aspects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where: [0031] Figure 1A is a front cross-sectional view of a two-stroke internal combustion engine;
[0032] Figure 1B is a rear cross-sectional view of the engine of Fig. 1A;
[0033] Figure 2 is a schematic illustration of components of the engine of Fig. 1A and of associated components thereof; [0034] Figure 3 is a perspective view, taken from a bottom right side, of a piston of the engine of Fig. 1A;
[0035] Figure 4 is a front cross-sectional view of a piston assembly including the piston of Fig. 3, a pin positioned in the piston and a connecting rod connected to the pin;
[0036] Figure 5 is a top cross-sectional view of the piston of Fig. 3; [0037] Figure 6 is a perspective view, taken from a left side, of a cross-section of the piston of Fig. 3, with the pin and the connecting rod removed to expose the underlying structure of the piston;
[0038] Figure 7 is a left side cross-sectional view of the piston and components of Fig. 4, showing a lubrication device for lubricating an interface between the pin and connecting rod; [0039] Figure 8 is a top cross-sectional view of the pin positioned in the piston in accordance with an alternative embodiment in which inner retaining rings are provided;
[0040] Figure 9 is a front cross-sectional view of the piston assembly in accordance with another embodiment;
[0041] Figure 10 is a perspective view of an obstructing member of the piston assembly of Figure 9; and [0042] Figure 11 is a cross-sectional view of the obstructing member of Figure 10 taken along line 11-11 in Figure 10.
DETAILED DESCRIPTION
[0043] The present technology will be described below with respect to a direct fuel injection, two-stroke, inline, two-cylinder internal combustion engine. It is contemplated that at least some aspects of the present technology could be provided on a two-stroke internal combustion engine that is carbureted or has semi-direct injection, that has cylinders arranged in a V-type or other arrangement, and/or that has only one or more than two cylinders. It is also contemplated that at least some aspects of the present technology could be provided on a four-stroke internal combustion engine or a diesel engine.
[0044] Figs. 1A and 1B illustrate an internal combustion engine 10. The engine 10 operates on a two-stroke engine cycle such that the engine 10 completes a power cycle with two strokes (an upstroke and a downstroke) of the engine’s pistons 34. The engine 10 can thus be referred to as a two-stroke engine. The engine 10 has a crankcase 12, a cylinder block 14 connected on top of the crankcase 12 and a cylinder head 16 connected on top of the cylinder block 14.
[0045] The crankcase 12 rotationally supports a crankshaft 18. An output shaft 20 is rotationally supported by the crankcase 12 and driven by the crankshaft 18. The output shaft 20 is coaxial with the crankshaft 18. In other embodiments, the output shaft 20 could be offset from the crankshaft 18. The output shaft 20 protrudes from the crankcase 12 and is connected to a transmission of a vehicle or another mechanical component to be driven by the engine 10. As such, the side of the engine 10 from which the output shaft 20 protrudes is referred to herein as the power take-off side of the engine 10. It is contemplated that the engine 10 may omit the output shaft 20 and that instead a portion of the crankshaft 18 protrudes from the crankcase 12 to be connected to the mechanical component to be driven by the engine 10.
[0046] A generator 25 is connected to the side of the crankcase 12 opposite the power take-off side. The generator 25 uses power produced by the engine 10 to generate electrical energy for storage in a battery (not shown). A generator housing 27 encloses the generator 25 therein. An electric starter motor (not shown) is also connected to the side of the crankcase 12. The starter motor selectively engages the crankshaft 18 via gears (not shown) to cause the crankshaft 18 to turn before the engine 10 can run on its own as a result of the internal combustion process in order to start the engine 10.
[0047] A mechanically driven oil pump 23 (schematically shown in Fig. 2) is fluidly connected to various parts of the engine 10 to circulate oil through the engine 10. The oil pump 23 pumps oil from an oil reservoir 28 connected to a bottom of the crankcase 12. The oil pumped by the oil pump 23 is distributed to the various components of the engine 10 that need lubrication. The oil then falls back by gravity inside the oil reservoir 28.
[0048] The cylinder block 14 defines two cylinders 30 adjacent to one another in a lateral direction of the engine 10. Each cylinder 30 defines a cylinder axis 32 along which the cylinder 30 extends. The engine 10 has two pistons 34 each of which is disposed within a corresponding one of the cylinders 30. During operation of the engine 10, each piston 34 moves along the cylinder axis 32 of its corresponding cylinder 30 in a reciprocating motion including an upstroke (whereby the piston 34 moves toward an upper end of the cylinder 30) and a downstroke (whereby the piston 34 moves away from the upper end of the cylinder 30). As will be discussed in greater detail below, each piston 34 is connected to the crankshaft 18 by a connecting rod 36 so as to rotate the crankshaft 18 during the upstroke and downstroke of the piston 34.
[0049] As shown in Fig. 1B, each cylinder 30 has a cylinder wall 31 defining an intake port 33 and an exhaust port 35. When the intake port 33 is open, air is fed through the intake port 33 into a combustion chamber defined in part by the cylinder 30. When the exhaust port 35 is open, exhaust fluids are discharged from the combustion chamber therethrough. The reciprocating motion of the corresponding piston 34 along the cylinder axis 32 opens and closes the intake and exhaust ports 33, 35 in a controlled manner to provide efficient fuel combustion in the combustion chamber.
[0050] The cylinder block 14 defines part of an air chamber 22 (i.e., a plenum) to which the intake port 33 is fluidly connected. A supercharger (not shown) feeds the air chamber 22 with compressed air. The cylinder block 14 also defines part of an exhaust passage (not shown) for each cylinder 30 extending from a corresponding one of the exhaust ports 35. An exhaust manifold (not shown) is connected to the cylinder block 14 at the exhaust passages. Notably, the exhaust manifold has two inlets in alignment with the two exhaust passages and a single outlet. [0051] The cylinder head 16 closes the tops of the cylinders 30 such that for each cylinder 30 a variable volume combustion chamber is defined between the cylinder 30, its corresponding piston 34 and the cylinder head 16. Two fuel injectors 68 (not shown in Figs. 1A and 1B, schematically illustrated in Fig. 2) and two spark plugs 70 (one of each per cylinder 30) are connected to the cylinder head 16. The fuel injectors 68 inject fuel directly in the combustion chambers. The spark plugs 70 ignite the fuel-air mixture in the combustion chambers.
[0052] The operation of the fuel injectors 68, the spark plugs 70, the starter motor and the oil pump is controlled by an electronic control unit (ECU) 72 that is schematically illustrated in Fig. 2. The ECU 72 controls these components based on signals received from various sensors and components, some of which are illustrated schematically in Fig. 2. An engine speed sensor 74 senses a speed of rotation of the crankshaft 18 and sends a signal representative of engine speed to the ECU 72. A throttle valve position sensor 76 senses the position of a throttle valve 48 associated with the cylinders 30 and configured to regulate the flow of air into the engine 10. It is contemplated that the engine 10 could include more than one throttle valve 48 in alternative implementations. The throttle valve position sensor 76 sends a signal representative of the position of the throttle valve 48 to the ECU 72. A start/stop switch 78 sends a signal to the ECU 72 to start the engine 10 when the engine 10 is stopped and to stop the engine 10 when the engine 10 is running. It is contemplated that the start/stop switch 78 could be separated into a start switch and a separate stop switch. It is contemplated that the start/stop switch 78 could be incorporated into an ignition key assembly or could be a separate button. A coolant temperature sensor 125 senses a temperature of a coolant flowing in a cooling jacket of the engine 10 and sends a signal representative of the coolant temperature to the ECU 72.
[0053] Although a single ECU 72 is illustrated, it is contemplated that the various functions of the ECU 72 could be split between two or more control units/controllers and that at least some of these control units could communicate with each other.
[0054] The pistons 34 will now be described with reference to Figs. 3 to 6. Both pistons 34 are identical and therefore a single one of the pistons 34 will be described below in relation to its associated cylinder 30 and related structure. It is noted that the spatial orientation of the components associated with the piston 34 will be described in relation to a cylindrical coordinate system defined by the piston 34. Therefore, the use of the term “radially” refers to the radial direction defined by the piston 34.
[0055] The piston 34 has a piston head 38 defining an upper end of the piston 34, and a piston skirt 40 extending from the piston head 38 and defining a lower end of the piston 34. The lower end of the piston 34 is open, notably defining a bottom opening 24 in which, as will be described in more detail below, the connecting rod 36 extends. The piston 34 has two pin bosses 42L, 42R that are spaced apart from one another. The pin bosses 42L, 42R define respective pin bores 44L, 44R which are aligned with each other such as to define a center axis 55 (Figs. 5, 6). As shown in Fig. 6, each of the pin bores 44L, 44R has an outer bore end 46 opening in an outer surface 41 of the piston skirt 40 and an inner bore end 47 opposite the outer bore end 46 and opening into an interior of the piston 34. The outer bore end 46 of the pin bore 44L opens in the outer surface of the piston skirt 40 opposite the outer bore end 46 of the pin bore 44R (i.e., the outer bore ends 46 of the pin bores 44L, 44R are at diametrically opposite locations of the outer surface of the piston skirt 40). The piston skirt 40 also defines recesses 105 (Figs. 3, 4) above the pin bores 44L, 44R for reducing the weight of the piston 34.
[0056] Furthermore, the piston skirt 40 also defines three ring lands for receiving therein respective piston rings 50, 52, 54. The piston rings 50, 52, 54 include an upper piston ring 50 adjacent the upper end of the piston 34 and two lower piston rings 52, 54 adjacent the lower end of the piston 34. The upper piston ring 50 is located above the pin bores 44L, 44R while the first and second lower piston rings 52, 54 are located below the pin bores 44L, 44R. The second lower piston ring 54 is positioned below the first lower piston ring 52 and is thus closer to the lower end of the piston 34 than the first lower piston ring 52. In this embodiment, the upper piston ring 50 is a semi-trapeze ring, the first lower piston ring 52 is a taper-faced Napier ring, and the second lower piston ring 54 is an oil control ring which collects and directs oil through radially-extending openings 56 defined in the piston skirt 40 to the interior of the piston 34. Thus, oil collected by the second lower piston ring 54 is returned to the crankcase 12 via the openings 56.
[0057] The piston 34 cyclically opens and closes the intake port 33. At a top dead center position of the piston 34 (i.e., a position in which the piston 34 is closest to the cylinder head 16), the second lower piston ring 54 is positioned below the intake port 33 such that the piston skirt 40 of the piston 34 blocks the intake port 33 (see piston 34 on right-hand side of Fig. 1A)
[0058] A pin 60 extends radially within the piston 34 and connects the connecting rod 36 to the piston 34. The pin 60 is generally cylindrical and hollow. The pin 60 is disposed in the pin bores 44L, 44R such that each of the two opposite ends 61, 63 of the pin 60 is located in a respective one of the pin bores 44L, 44R.
[0059] The connecting rod 36 is connected to the pin 60 in a space 45 between the pin bosses 42L, 42R. More specifically, a small end 64 of the connecting rod 36 is pivotably connected to the pin 60 between the pin bosses 42L, 42R. A bushing 66 is disposed between the small end 64 of the connecting rod 36 and the pin 60 such that a plain bearing is defined between the small end 64 of the connecting rod 36 and the pin 60. As best seen in Figs. 1 A and 1B, the opposite bigger end 69 of the connecting rod 36 is coupled to the crankshaft 18 such that the reciprocating motion of the piston 34 along the cylinder axis 32 causes the connecting rod 36 to rotate the crankshaft 18.
[0060] As shown in Fig. 7, a lubricating device 26 is disposed in the cylinder block 14 and is operable to lubricate the interior of the piston 34, notably including the connection between the pin 60 and the connecting rod 36, and to cool the piston head 38. To that end, the lubricating device 26 is fluidly connected to the oil pump 23 and has a nozzle 88 which, when the piston 34 is close to its bottom dead center position (i.e., closest to the crankshaft 18 and furthest from the cylinder head 16), enters the bottom opening 24 of the piston 34 and sprays a jet of oil 90 upwardly into the interior of the piston 34. In order to facilitate lubrication of the interface between the connecting rod 36 and the pin 60, the small end 64 of the connecting rod 36 has openings 92 extending from an outer surface 94 to an inner surface 96 of the small end 64 to guide oil into the plain bearing defined between the small end 64 of the connecting rod 36 and the pin 60. It is contemplated that the lubricating device 26 could be positioned in a part of the engine 10 other than the cylinder block 14, for example in the crankcase 12, and that the nozzle 88 does not enter the bottom opening 24 of the piston 34.
[0061] As best seen in Fig. 6, each of the pin bores 44L, 44R defines a radially-extending groove 102. Each of the grooves 102 extends radially outwardly from the inner bore end 47 of the corresponding one of the pin bores 44L, 44R. The radially-extending groove 102 accommodates momentary deformation of the pin 60 which occurs in operation. Notably, while the pin 60 is generally cylindrical when at rest, the pin 60 has a tendency to deform and acquire an oval shape due to the pressures acting on the pin 60 when the engine 10 is running. In addition, the radially-extending groove 102 can be helpful to circulate oil within the pin bores 44L, 44R.
[0062] As best seen in Figs. 4 and 6, each of the pin bosses 42L, 42R also defines a drain bore 104 for draining oil from the pin bores 44L, 44R. To that end, each of the drain bores 104 fluidly connects a corresponding pin bore 44L, 44R to the crankcase 12. The drain bores 104 extend generally transversally to the pin bores 44L, 44R (i.e., generally transversally to the center axis 55). As such, oil used for lubricating the connection between the pin 60 and the connecting rod 36 is drained from the pin bores 44L, 44R and returns to the crankcase 12. It is contemplated that, in certain embodiments, no drain bores 104 may be defined by the pin bosses 42L, 42R.
[0063] Two obstructing members 62L, 62R flank the pin 60 at each end thereof such that the pin 60 is disposed between both obstructing members 62L, 62R. More specifically, a left obstructing member 62L is disposed in the pin bore 44L between the outer bore end 46 thereof and the end 61 of the pin 60, while a right obstructing member 62R is disposed in the pin bore 44R between the outer bore end 46 thereof and the end 63 of the pin 60. The obstructing members 62L, 62R block passage through the corresponding pin bores 44L, 44R such as to limit or otherwise prevent oil from flowing from within the pin bores 44L, 44R to the outer surface 41 of the piston skirt 40. This can therefore eliminate or reduce the amount of oil that is discharged from the pin bores 44L, 44R into the intake port 33 and/or the exhaust port 35 of the cylinder 30, which in turn can reduce harmful emissions being discharged through the exhaust passages of the engine 10.
[0064] In this embodiment, the obstructing members 62L, 62R seal parts of each of the pin bores 44L, 44R from one another. For instance, as best seen in Fig. 6, each of the obstructing members 62L, 62R seals an outer portion 80 of a corresponding one of the pin bores 44L, 44R from an inner portion 82 of that pin bore 44L, 44R. The outer portion 80 of the pin bore 44L is defined between the outer bore end 46 thereof and the obstructing member 62L, while the inner portion 82 is defined on a side of the obstructing member 62L opposite from the outer portion 80 (i.e., between the inner bore end 47 of the pin bore 44L and the obstructing member 62L). In the same manner, the obstructing member 62R seals the outer portion 80 of the pin bore 44R from the inner portion 82 of the pin bore 44R. [0065] The obstructing members 62L, 62R will now be described with particular reference to Figs. 4 to 6. The obstructing members 62L, 62R are identical and therefore only the left obstructing member 62L will be described below in relation to the pin bore 44L. It is to be understood that the right obstructing member 62R is also positioned in the same manner in relation to the pin bore 44R and has a same configuration relative thereto (e.g., sizing).
[0066] As best seen in Figs. 3 and 6, the obstructing member 62L is a disc having opposite outer and inner circular surfaces 84, 86. When the obstructing member 62L is positioned in the pin bore 44L, the circular surfaces 84, 86 of the obstructing member 62L are normal to the center axis 55, with the outer circular surface 84 facing the outer bore end 46 of the pin bore 44L and the inner circular surface 86 facing the inner bore end 47 of the pin bore 44L. The obstructing member 62L has a disc diameter that is greater than the diameter of the pin 60. Moreover, the disc diameter of the obstructing member 62L is greater than the diameter of the pin bore 44L at a location aligned with the end 61.
[0067] It is contemplated that, in alternative embodiments, the obstructing member 62L could have any other suitable shape. In such embodiments, the outer and inner surfaces 84, 86 may not be circular. For instance, an alternative embodiment of the obstructing member 62L will be described below with respect to Figs. 9 to 11.
[0068] In this embodiment, the obstructing member 62L is made of aluminum and has an anodized coating. The anodized coating of the obstructing member 62L provides protection from wear caused by movement of the pin 60 in the pin bores 44L, 44R. In alternative embodiments, the obstructing member 62L could be made of steel. In such embodiments, the anodized coating may be omitted given the higher strength of steel.
[0069] The obstructing member 62L is positioned radially outwardly of the end 61 of the pin 60. To that end, as shown in Fig. 5, a groove 98 is defined about the pin bore 44L (i.e., concentric with the pin bore 44L) at a location between the end 61 of the pin 60 and the outer bore end 46. The obstructing member 62L is inserted in the groove 98 which is sized for accommodating the obstructing member 62L therein. More specifically, in this embodiment, the groove 98 defines a shoulder facing radially outwardly. The inner circular surface 86 of the obstructing member 62L is in contact with the shoulder of the groove 98 such that the shoulder restricts movement of the obstructing member 62L radially inwardly within the pin bore 44L. When the obstructing member 62L is inserted in the groove 98, the obstructing member 62L abuts the end 61 of the pin 60 and the drain bore 104 of the pin bore 44L is positioned radially inwardly of the obstructing member 62L.
[0070] As will be appreciated, an identical groove 98 is defined about the pin bore 44R to position the obstructing member 62R therein, radially outwardly of the end 63 of the pin 60 and such as to abut the end 63 of the pin 60. The obstructing member 62R is therefore positioned in the pin bore 44R in a mirror image to that which has been described in relation to the obstructing member 62L and the pin bore 44L. The positioning of the obstructing member 62R will thus not be described further here.
[0071] Retaining rings 110L, 11 OR are provided to retain the obstructing members 62L, 62R and the pin 60 in place. The retaining rings 110L, 11 OR will be referred to as“outer” retaining rings in that they are positioned radially outwardly of the corresponding obstructing members 62L, 62R. More specifically, the outer retaining ring 110L is disposed between the obstructing member 62L and the outer bore end 46 of the pin bore 44L, while the outer retaining ring 11 OR is disposed between the obstructing member 62R and the outer bore end 46 of the pin bore 44R. Respective grooves 114 (Fig. 5) are defined about the pin bores 44L, 44R to position the outer retaining rings 110L, 11 OR therein. In this embodiment, the outer retaining rings 110L, 110R are circlips which are snapped into place in the grooves 114. The outer retaining rings 110L, 11 OR thus restrict movement of the obstructing members 62L, 62R radially outwardly within their respective pin bores 44L, 44R such that, in collaboration with the grooves 98, radial movement of the obstructing members 62L, 62R and the pin 60 is restricted.
[0072] In an alternative embodiment, as shown in Fig. 8, in addition to the outer retaining rings 110L, 11 OR, inner retaining rings 120L, 120R are provided between the ends 61, 63 of the pin 60 and the adjacent obstructing members 62L, 62R. The inner retaining rings 120L, 120R are “inner” in that they are positioned radially inwardly of the corresponding obstructing members 62L, 62R. More specifically, the inner retaining ring 120L is disposed between the end 61 of the pin 60 and the left obstructing member 62L, while the inner retaining ring 120R is disposed between the end 63 of the pin 60 and the right obstructing member 62R. Respective ring-locating grooves 122 are defined about the pin bores 44L, 44R to position the inner retaining rings 120L, 120R therein. As such, in this alternative embodiment, the ends 61, 63 of the pin 60 are spaced apart from the corresponding obstructing members 62L, 62R. Consequently, the obstructing members 62L, 62R could also omit the anodized coating described above since contact between the pin 60 and the obstructing members 62L, 62R is prevented by the spacing therebetween.
[0073] In another alternative embodiment, rather than being positioned radially outwardly of the corresponding obstructing members 62L, 62R, retaining rings similar to the outer retaining rings 110L, 11 OR could be provided radially inwardly of the obstructing members 62L, 62R to retain the pin 60 in place. For instance, in such embodiments, a press fit between the pin bosses 42L, 42R and the obstructing members 62L, 62R restricts movement of the obstructing members 62L, 62R radially outwardly within the pin bores 44L, 44R while the retaining rings restrict radial movement of the pin 60 within the pin bores 44L, 44R.
[0074] While the connection between the piston 34 and the connecting rod 36 has been described in relation to an entirety of the engine 10, it is contemplated that a piston assembly could be provided on its own including the piston 34 and the obstructing members 62L, 62R. Optionally, the piston assembly could also include the pin 60 and/or the connecting rod 36.
[0075] With reference to Figs. 9 to 11, in an alternative embodiment, the obstructing members are shaped differently than that described above. Notably, obstructing members 62L’, 62R’ are provided and are not disc shaped like the obstructing members 62L, 62R. The obstructing members 62L’, 62R’ are identical and therefore only the left obstructing member 62L’ will be described below in relation to the pin bore 44L. It is to be understood that the right obstructing member 62R’ is also positioned in the same manner in relation to the pin bore 44R and has a same configuration relative thereto (e.g., sizing).
[0076] As best seen in Figs. 10 and 11, the obstructing member 62L’ is circular and generally cup-shaped. Notably, a side 200 of the obstructing member 62L’ has offset surfaces 204, 206 normal to a central axis of the obstructing member 62L’, while an opposite side 202 of the obstructing member 62L’ has a circular surface 208. The surfaces 204, 206 are axially offset from one another. The surface 206 is an annular surface and the surface 204 is a circular surface.
[0077] As shown in Fig. 9, when the obstructing member 62L’ is positioned in the pin bore 44L, the surfaces 204, 206, 208 of the obstructing member 62L’ are normal to the center axis 55, with the outer surface 208 facing the outer bore end 46 of the pin bore 44L and the inner surfaces 204, 206 facing the inner bore end 47 of the pin bore 44L. Moreover, when in position, the annular surface 206 abuts the end 61 of the pin 60. The obstructing member 62L’ has an outer diameter that is greater than the diameter of the pin 60. Moreover, the outer diameter of the obstructing member 62L’ is greater than the diameter of the pin bore 44L at a location aligned with the end 61.
[0078] This configuration of the obstructing member 62L’ may increase a radial contact area between the obstructing member 62L’ and the pin boss 42L thus reducing contact pressure therebetween which in turn may reduce wear of the contact area between the obstructing member 62L’ and the pin boss 42L. Moreover, the shape of the obstructing member 62L’ does not significantly increase its weight relative to the obstructing member 62L described above. [0079] Modifications and improvements to the above-described embodiments of the present technology may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting. The scope of the present technology is therefore intended to be limited solely by the scope of the appended claims.

Claims

What is claimed:
1. An internal combustion engine comprising:
a crankcase;
a crankshaft disposed at least in part in the crankcase;
a cylinder block connected to the crankcase;
a cylinder defined in the cylinder block and having a cylinder axis;
a piston movably disposed within the cylinder and being operatively connected to the crankshaft, the piston comprising:
a piston head;
a piston skirt extending from the piston head;
a first pin boss defining a first pin bore having a first bore end, the first bore end opening in an outer surface of the piston skirt; and
a second pin boss defining a second pin bore having a second bore end, the second bore end opening in the outer surface of the piston skirt opposite the first bore end, the first and second pin bores being aligned with each other;
a pin disposed in the first and second pin bores, the pin having a first pin end and a second pin end;
a first obstructing member disposed within the first pin bore between the first bore end and the first pin end for blocking passage through the first pin bore; and
a second obstructing member disposed within the second pin bore between the second bore end and the second pin end for blocking passage through the second pin bore; and
a connecting rod connecting the pin to the crankshaft, the connecting rod having a first rod end connected to the pin and a second rod end connected to the crankshaft, the first rod end being disposed between the first and second pin bosses.
2. The engine of claim 1, wherein:
the first obstructing member seals a first portion of the first pin bore from a second portion of the first pin bore;
the first portion of the first pin bore being defined between the first bore end and the first obstructing member;
the second portion of the first pin bore being defined on an opposite side of the first obstructing member from the first portion of the first pin bore; the second obstructing member seals a first portion of the second pin bore from a second portion of the second pin bore;
the first portion of the second pin bore being defined between the second bore end and the second obstructing member;
the second portion of the second pin bore being defined on an opposite side of the second obstructing member from the first portion of the second pin bore.
3. The engine of claim 1, wherein:
the first obstructing member abuts the first pin end; and
the second obstructing member abuts the second pin end.
4. The engine of claim 1, wherein:
the first obstructing member is a first disc;
the second obstructing member is a second disc;
each of the first and second discs has opposite circular surfaces; and
the first and second discs are positioned such that the circular surfaces of the first and second discs are normal to a center axis of the pin bores.
5. The engine of claim 4, wherein:
the pin has a pin diameter; and
at least one of the first and second discs has a disc diameter that is greater than the pin diameter.
6. The engine of claim 1, wherein the first and second obstructing members are made of aluminum and have an anodized coating.
7. The engine of claim 1, wherein:
a first groove is defined about the first pin bore, the first groove being located between the first pin end and the first bore end, the first obstructing member being inserted in the first groove; and
a second groove is defined about the second pin bore, the second groove being located between the second pin end and the second bore end, the second obstructing member being inserted in the second groove.
8. The engine of claim 1, further comprising:
a first retaining ring disposed between the first obstructing member and the first bore end, the first retaining ring retaining the first obstructing member in place; and
a second retaining ring disposed between the second obstructing member and the second bore end, the second retaining ring retaining the second obstructing member in place.
9. The engine of claim 1, wherein the first and second pin bores define at least in part a radially- extending groove.
10. The engine of claim 1, wherein each of the first and second pin bosses defines at least one drain bore, the at least one drain bore extending generally transversally to a corresponding one of the first and second pin bores and fluidly connecting the corresponding one of the first and second pin bores to the crankcase.
11. The engine of claim 10, wherein the at least one drain bore is disposed radially inward of a corresponding one of the first and second obstructing members.
12. The engine of claim 1, further comprising:
an upper piston ring located above the first and second pin bores;
a first lower piston ring located below the first and second pin bores; and
a second lower piston ring located below the first lower piston ring.
13. The engine of claim 1, wherein the first rod end and the pin define a plain bearing.
14. The engine of claim 1, wherein:
the first obstructing member is spaced from the first pin end; and
the second obstructing member is spaced from the second pin end.
15. The engine of claim 1, wherein:
the cylinder has a cylinder wall defining an intake port for feeding air into the cylinder and an exhaust port for discharging exhaust fluids therethrough; and
reciprocating motion of the piston along the cylinder axis opens and closes the intake and exhaust ports.
16. The engine of any one of claims 1 to 15, wherein:
the first obstructing member has a greater diameter than the first pin bore at a location aligned with the first pin end; and
the second obstructing member has a greater diameter than the second pin bore at a location aligned with the second pin end.
17. A piston assembly for an internal combustion engine, the piston assembly comprising: a piston comprising:
a piston head;
a piston skirt extending from the piston head;
a first pin boss defining a first pin bore having a first bore end, the first bore end opening in an outer surface of the piston skirt; and
a second pin boss defining a second pin bore having a second bore end, the second bore end opening in the outer surface of the piston skirt opposite the first bore end, the first and second pin bores being aligned with each other;
a first obstructing member disposed within the first pin bore radially inwardly of the first bore end for blocking passage through the first pin bore; and
a second obstructing member disposed within the second pin bore radially inwardly of the second bore end for blocking passage through the second pin bore.
18. The piston assembly of claim 17, further comprising:
a pin disposed in the first and second pin bores, the pin having a first pin end and a second pin end,
the first obstructing member being disposed between the first bore end and the first pin end, and
the second obstructing member being disposed between the second bore end and the second pin end.
19. The piston assembly of claim 18, further comprising:
a connecting rod having a first rod end connected to the pin and a second rod end for connecting to a crankshaft, the first rod end being disposed between the first and second pin bosses.
20. An internal combustion engine comprising the piston assembly of any one of claims 17 to 19.
21. An internal combustion engine comprising:
a crankcase
a crankshaft disposed at least in part in the crankcase;
a cylinder block connected to the crankcase;
a cylinder defined in the cylinder block and having a cylinder axis;
a piston movably disposed within the cylinder and being operatively connected to the crankshaft, the piston comprising:
a piston head;
a piston skirt extending from the piston head;
a first pin boss defining a first pin bore having a first bore end, the first bore end opening in an outer surface of the piston skirt; and
a second pin boss defining a second pin bore having a second bore end, the first and second pin bores being aligned with each other;
a pin disposed in the first and second pin bores, the pin having a first pin end and a second pin end;
an obstructing member disposed within the first pin bore between the first bore end and the first pin end, the obstructing member sealing a first portion of the first pin bore from a second portion of the first pin bore,
the first portion of the first pin bore being defined between the first bore end and the obstructing member,
the second portion of the first pin bore being defined on an opposite side of the obstructing member from the first portion of the first pin bore;
and
a connecting rod connecting the pin to the crankshaft, the connecting rod having a first rod end connected to the pin and a second rod end connected to the crankshaft, the first rod end being disposed between the first and second pin bosses.
EP19762359.8A 2018-08-30 2019-08-30 Piston assembly for an internal combustion engine Pending EP3844379A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US201862724935P 2018-08-30 2018-08-30
PCT/EP2019/073219 WO2020043881A1 (en) 2018-08-30 2019-08-30 Piston assembly for an internal combustion engine

Publications (1)

Publication Number Publication Date
EP3844379A1 true EP3844379A1 (en) 2021-07-07

Family

ID=67841061

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Application Number Title Priority Date Filing Date
EP19762359.8A Pending EP3844379A1 (en) 2018-08-30 2019-08-30 Piston assembly for an internal combustion engine

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EP (1) EP3844379A1 (en)
WO (1) WO2020043881A1 (en)

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2282085A (en) * 1941-08-13 1942-05-05 American Locomotive Co Piston
US2742883A (en) * 1953-07-15 1956-04-24 Frank J Smith Oil cooled piston structure
DE1729910U (en) * 1955-10-13 1956-09-13 Schmidt Gmbh Karl SEALING THE PISTON PIN IN COMBUSTION MACHINERY.
US4050360A (en) * 1975-09-19 1977-09-27 Caterpillar Tractor Co. Oil damped piston
US4945864A (en) * 1989-06-21 1990-08-07 General Motors Corporation Two cycle engine piston lubrication
JP2000027993A (en) * 1998-07-08 2000-01-25 Yamaha Motor Co Ltd Piston for internal combustion engine and surface treating method therefor
US20080271597A1 (en) * 2006-03-31 2008-11-06 Soul David F Methods and apparatus for operating an internal combustion engine
CN103557087A (en) * 2013-11-14 2014-02-05 安徽中鼎动力有限公司 Connecting rod structure for piston

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