WO1997048896A1

WO1997048896A1 - A piston for an internal combustion engine

Info

Publication number: WO1997048896A1
Application number: PCT/BR1997/000032
Authority: WO
Inventors: José NARDI; Armando Alcaraz Rodes; Luis Miguel Valdes Lopez
Original assignee: Metal Leve S.A. Indústria E Comércio
Priority date: 1996-06-20
Filing date: 1997-06-20
Publication date: 1997-12-24
Also published as: DE69702059D1; EP0906502B1; DE69702059T2; EP0906502A1; BR9601862A

Abstract

A piston for an internal combustion engine, of the type comprising a refrigeration gallery (20), which is provided with an oil inlet orifice (30) and an oil outlet orifice (40). The upper end (31) of the oil inlet orifice (30), which is opened to the inside of the refrigeration gallery (20), has a contour with the largest dimensions, at the radial and circumferential directions, at maximum equal to the radial width of the refrigeration gallery (20), the lower end (32) of the oil inlet orifice (30) having a widened contour, which is tangent to the inner surface of the piston skirt (50) and which is dimensioned in order to receive directly therewithin an oil jet, which is inclined in relation to the longitudinal displacement of the piston in any operational position of said piston.

Description

A PISTON FOR AN INTERNAL COMBUSTION ENGINE

Field of the Invention

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 .

Background of the Invention

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 .

In a known constructive solution, described in Patent Application PCT DE94/01375, 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 .

In this prior art construction, 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.

With the aim of increasing the structural lesistance of the piston constructed as described above, the solution presented in document PCT DE94/01375 proposes reducing the circumferential longitudinal extension of the upper end of the oil inlet orifice to a value which is equal or lower than two thirds of the circumferetial distance between the piston bosses and also slightly lower than it would be required to directly receive the oil jet in all positions of the piston displacement.

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. In order to improve the refrigeration conditions of the oil inside the refrigeration gallery, the oil outlet orifice is dimensioned so as to have a smaller cross section in its circular contour.

Independently from the efficiency of the refrigeration obtained with the prior art solution, it is desirable to obtain the highest possible degree of direct reception of the oil jet within a certain acceptable result in terms of structural resistance. Thus, the circumferential elongated shape was maintained, aiming a more direct oil reception, and the upper end longitudinal extension of the oil inlet orifice was adjusted, in order to obtain a possible structural resistance for the piston. In this solution, it is given to the tapered lateral wall of the oil inlet orifice the function of directing to the inside of the refrigeration gallery the oil jet portion that will fall on said wall, considering that the shape and dimensioning of the cross section of the upper end of the oil inlet orifice are intended to provide a higher direct reception of the oil jet. Nevertheless, 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

In function of the difficulties mentioned above, 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.

It has been observed, according to the invention, that a new construction and a new dimensioning of the cross section of the upper end of the oil inlet orifice opened to the inside of the refrigeration gallery allows to maintain a high refπqeration degree for the piston, through the necessary oil circulation within the refrigeration gallery, even when a substantial part of the oil jet falls on the lateral wall of the tapered oil inlet orifice. The dimensioning of the upper end contour of the oil inlet orifice may be achieved in order to allow the oil that is falling against the tapered wall of the oil inlet orifice to be conducted into the inside of the refrigeration gallery, thereby assuring the adequate refrigeration of the piston head.

In function of the above observations, a new construction for the oil inlet orifice has been provided, which shape allows to obtain an improved structural resistance for the piston together with a higher refrigeration degree provided by the oil circulation through the refrigeration gallery. According to the invention, 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 .

Also according to the present invention, 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. In a particular form of the invention, 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 . With the constructive arrangement now proposed, there is maintained a cross sectional area for oil passage, which is sufficient to allow the adequate filling of the refrigeration gallery with the oil that is thrown, in great part, against the tapered lateral walls of the oil inlet orifice, wherefrom it penetrates into the refrigeration gallery, as well as to simultaneously obtain a substantial increase in the structural resistance of the piston in function of the new contour given to the oil inlet orifice. The weakening of a circumferential portion of the piston is substituted by a much less relevant radial weakening of said piston.

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.

Brief Description of the Drawings

The invention will be described below, /.ith reference to the attached drawings, in which.

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; and

Figure 3 is a sectional view similar to that of figure

1, taken according to line III- III of figure 2. Best Mode for Carrying Out the Invention

According to the above cited illustrations, 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 In the constructions considered by the invention, 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. According to the constructive form as illustrated, 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 In the illustrated embodiment, 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.

In order to achieve the highest refrigeration results, it has been observed that 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.

With this construction, said larger dimensions are usually substantially equal. On the other hand, 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. On the other hand, 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.

With the condition above being observed, 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.

Claims

1. A piston for an internal combustion engine, of the type comprising a refrigeration gallery (20), which is circumferentially and internally located in relation to a ring zone of the piston and which is provided with an oil inlet orifice (30) to recei^ve an oil jet which is inclined in relation to the longitudinal displacement of the piston, and with an oil outlet orifice (40), said oil inlet and outlet orifices having an upper end (31, 41) opened to the inside of the refrigeration gallery (20) and a lower end (32, 42) opened to the inside of the region of the piston skirt (50), characterized in that the upper end (31) of the oil inlet orifice (30) nas a contour with the largest dimensions, at the radial and circumferential directions, at maximum equal to the radial width of the gallery, the lower end (32) of the oil inlet orifice (30) having a widened contour, which is tangent to the inner surface of the piston skirt (50) and which is dimensioned in order to receive directly therewithm the oil jet in any operational position of the piston.

2. Piston, as in claim 1, characterized in that the contour of the lower end (32) of the oil inlet orifice

(30) maintains a minimum radial spacing from the center of the piston, determined by a requirement of having the least possible reciprocating mass with the minimum required structural resistance.

3. Piston, as in claim 2, characterized in that said minimum radial spacing is of about 35% of the value of the piston diameter.

4. Piston, as in claim 1, characterized in that the larger dimensions at both the radial and circumferential directions of the contour of the upper end (31) of the oil inlet orifice (30) are substantially equal.

5 Piston, as in claim 1, characterized in that the contour of the upper end (31) of the oil inlet orifice (30) is polygonal, with the vertices and at least the radial sides being rounded.

6. Piston, as in claim 5, characterized in that the contour of the lower end (32) of the oil inlet orifice (30) is similar to the contour of the upper end (31) of this same orifice.

7 Piston, as in claim 6, characterized in that the polygonal contour of the upper end (31) and lower end (32) of the oil inlet orifice (30) takes the approximate form of an isosceles triangle with the rounded sides matching with a central common vertex, which is radially external and markedly rounded and with the base being substantially rectilinear, defining the radially innermost side of the contour.

8. Piston, as in claim 7 , characterized in that the radially innermost side of said isosceles triangular contour is arranged in a direction which is substan^¬ tially parallel to the direction of the oil jet.

9 Piston, as in claim 8, characterized m that the direction of the radially innermost side of said isosceles triangular contour is oblique to the articulating pin axis of the connecting rod.

10. Piston, as in claim 1, characterized in that the lower end (32) of the oil inlet orifice (30) is defined in a piston head surface portion which matches with the inner surface of the piston skirt (50) .

11. Piston, as in any of the preceding claims, characterized in that the oix inlet orifice (40) is identical to the oil inlet orifice (30) and symmetrical to the latter in relation to a diameter which is orthogonal to the articulating pin axis of the connecting rod.