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 
  • F02F3/16—Pistons  having cooling means
  • F02F3/20—Pistons  having cooling means the means being a fluid flowing through or along piston
  • F02F3/22—Pistons  having cooling means the means being a fluid flowing through or along piston the fluid being liquid

Definitions

• the present invention refers to a piston for an internal combustion engine and, more particularly, to a piston of this type comprising a refrigeration gallery, which is circumferentially and internally located in relation to the ring zone and which is provided with an oil inlet orifice, to receive an oil ⁇ et from an injection nozzle, and with an oil outlet orifice .
• One of the problems which arises in the construction of this type of piston refers to the necessity of taking a certain adequate amount of oil to the inside of the refrigeration gallery, from an oil let, which has a direction inclined m relation to the longitudinal displacement of the piston and substantially parallel to the articulating axis of the piston to the connecting rod, and which comes from an injection nozzle mounted inside the engine.
• Another important aspect to be considered in the construction of these pistons is that the adequate filling of the refrigeration gallery should be optimized without impairing the structural resistance of said pistons in those applications in which they are submitted to severe efforts .
• the refrigeration gallery is provided with an oil inlet orifice comprising an upper end, which is opened towards the bottom of the gallery and a lower end, which is opened towards the inner surface of the skirt and under the combustion chamber of the piston, the shape of the inlet orifice, between its upper and lower opposite ends, being such as to define a funnel, with its reduced opening being opened towards the inside of the refrigeration gallery .
• the upper end of the oil inlet orifice is shaped, as previously discussed in document SU-973900, in order to present a longitudinal extension along a certain circumferential extension of the refriqeration gallery which, in the case of this last cited document, corresponds to the circumferential distance between the piston bosses.
• the constructive arrangement cited above is intended to follow the elongated circumferential shape of the upper end of the oil inlet orifice, in order to still maintain a high degree of direct reception of the oblique oil jet, but increasing the structural resistance of the piston in relation to the solution known up to that time.
• the oil outlet orifice is dimensioned so as to have a smaller cross section in its circular contour.
• the desired higher cross section for oil passage in the elongated circumferential shape is limited to the longitudinal extension of the upper end of the oil inlet orifice and it cannot be increased, without the risk of impairing the structural resistance of a piston using the prior art solution. It has been observed that the shape of the cross section of the upper end of the prior art oil inlet orifice herein considered imparts a severe restriction to increasing the structural resistance of the piston, avoiding its application in certain operational conditions. It should be also observed that the circumferential shape of the oil inlet orifice fragilizes the piston structure in a region which is subject to higher impact efforts during the operation of the piston. Disclosure of the Invention
• the object of the invention is to provide a piston of the type considered herein, but having an oil inlet orifice which is constructed so as to allow a more adequate oil filling in the refrigeration gallery of the piston, leading to a higher refrigeration of the latter with an increased structural resistance.
• Another object of the invention is to provide an oil inlet orifice with a construction which may be also used to define the oil outlet orifice of the refrigeration gallery in a symmetrical position in relation to the oil inlet orifice.
• the upper end of the oil inlet orifice has a contour with the largest dimensions, in the radial and circumferential directions, being at maximum equal to the radial width of the gallery, the lower end of the oil inlet orifice having a widened contour, which is tangent to the inner surface of the piston skirt and v ⁇ hich is dimensioned to allow the direct reception therewithin of the oil jet in any operational position of the piston .
• the minimum radial spacing of the lower end contour of the oil inlet orifice to the piston center is determined by simultaneously obtaining the least possible reciprocating mass with the minimum required structural resistance.
• the contour of the upper and lower ends of the oil inlet orifice takes the polygonal form with the vertices and radial sides being rounded, more particularly with the approximate form of an isosceles triangle with the sides being rounded and matching with a central common vertex which is radially external and markedly rounded, and with the base substantially rectilinear and defining the radially innermost side of the contour .
• the new constructive form further allows the oil inlet and oil outlet orifices to be identically and symmetrically constructed in relation to a diameter which is orthogonal to the articulating pin axis of the connecting rod, making easy the construction and the assembly of these pistons.
• the pistons comprising the combustion chamber axially centered may be mounted at either side of the piston in relation to the injection nozzle, the radial widening of the lower end of the oil inlet orifice allowing less strict mounting tolerances for adjusting the oil injector in the direction of the oscillating plane of the connecting rod.
• Figure 1 is a partial longitudinal sectional view of a piston of the type used in the present invention
• Figure 2 is a bottom view of the piston of figure 1;
• Figure 3 is a sectional view similar to that of figure
• the piston of the present invention is provided with a combustion chamber 10 in its upper face and a refrigeration gallery 20 circumferentially located on the piston head, internally to the ring mounting region (not illustrated) .
• the refrigeration chamber 20 is provided with an oil inlet orifice 30 and with an oil outlet orifice 40, which are the only openings of the refrigeration chamber 20 to the inside of the region of the piston skirt 50.
• the oil inlet orifice 30 has an upper end 31 and a widened lower end 32, which is opened to the inside of the region of the piston skirt 50, under the combustion chamber 10, the snape of the croos section of the oil inlet orifice 30, between its opposite ends, being such as to define a funnel, with its smaller opening being defined at the upper end 31 opened to the refrigeration gallery 30.
• the introduction of the refrigerating oil into the refrigeration gallery 30 is achieved by an oil jet, produced by an injector (not illustrated), which is mounted inside the engine and which is directed towards the oil inlet orifice 30
• the oil jet has a direction, which is inclined in relation to the longitudinal displacement of the piston and vvhich is usually substantially parallel to the articulating pin axis of the connecting rod.
• the upper end 31 of the oil inlet orifice 30 has a polygonal contour, with the vertices being rounded and matching with sides which may be also either totally or partially rounded or convexely bent
• the contour of said upper end 31 takes the approximate form of an isosceles triangle as described above, with its central common vertex being cut and markedly rounded and with a substantially rectilinear base matching, through rounded lateral vertices, with a pair or sides which are also rounded and matching with the common central vertex, giving to this approximately triangular contour a "D" shape, with the radially innermost side being usuallv disposed in a direction which is substantially parallel to the oil jet and oblique to the articulating pin axis of the connecting rod.
• the contour of the upper end 31 of the oil inlet orifice 3C should have its larger dimensions, both in the radial and circumferential dimensions, at maximum equal to the width of the refrigeration gallery 20.
• the contour of the lower end 32 of the oil inlet orifice 30 is widened, usually similar to that of the upper end 31 and dimensioned to be tangent to the inner surface of the piston skirt 50 and to receive the oil jet directly into its inside in any operational position of the piston.
• the oil jet is then most of its part directed against the tapered lateral surface of the oil inlet orifice 30, therefrom it is deflected to the inside of the refrigeration gallery 20. Only a small part of the oil jet is conducted directly to the inside of the refrigeration gallery 20, without falling agaisnt the tapered lateral surface of the oil inlet orifice 30.
• the construction with a reduced contour of the upper end 31 of the oil inlet orifice 30 acts m order not to avoid the oil from arriving to the refrigeration gallery 20 and to maintain said oil inside said refrigeration gallery 20, preventing the oil that is thrown against the top of the gallery from returning to the engine crankcase through the same orifice without providing the desired refrigeration effect.
• the widened contour of the lower end 32 of the oil inlet orifice 30 is designed so as to be tangent to the inner surface of the piston skirt 50, avoiding any step or obstacle to the reception and upward sliding of the oil jet, said contour being dimensioned in order to receive directly therein the oil jet, whatever the operational position of the piston during its reciprocating travel.
• the contour of the lower end 32 of the oil inlet orifice 30 should also be maintained at a minimum radial distance from the piston center, determined by the requirement of having the least possible reciprocating piston mass with the minimum structural resistance required for the intended application. As a whole, this minimum spacing is around 35% of the diameter value of the piston constructed with the presently known alloys, without the risk of negatively affecting the structural resistance of said piston. Due to constructive requirements, the lower end 32 of the oil inlet orifice 30 is usually defined at an inner surface portion of the piston head which matches with the inner surface of the piston skirt 50.
• Another advantage of the construction proposed herein is due to the possibility of the oil outlet orifice 40 having its upper and lower ends 41, 42 identical to the ends of the oil inlet orifice 30, said oil outlet orifice 40 being symmetrical to the oil inlet orifice 30 in relation to a diameter orthogonal to the articulating pin axis of the connecting rod.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Pistons, Piston Rings, And Cylinders (AREA)

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• 1996
  • 1996-06-20 BR BR9601862A patent/BR9601862A/pt not_active IP Right Cessation
• 1997
  • 1997-06-20 EP EP97935386A patent/EP0906502B1/de not_active Expired - Lifetime
  • 1997-06-20 WO PCT/BR1997/000032 patent/WO1997048896A1/en active IP Right Grant
  • 1997-06-20 DE DE69702059T patent/DE69702059T2/de not_active Expired - Fee Related

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