PISTON PIN WITH EMERGENCY GUIDING CAPABILITY Technical Field

The present disclosure generally relates to internal combustion engines, and more particularly to piston pins configured to connect connecting rods and pistons of an internal combustion engine.

Background

A known technique for connecting a piston to an associated connecting rod are piston pin. Said piston pin allow delivery of power between a rotating crankshaft and a reciprocating piston. The piston, the piston pin, the connecting rod and the crankshaft together facilitate conversion in both directions between linear motion of the piston and rotational movement of the crankshaft.

For example, EP 1 227 269 A2 discloses a piston connected to a connecting rod via a piston pin. The piston pin may comprise spherical end surfaces axially securing the piston pin in the piston as they may come into contact with a combustion cylinder during operation of the engine.

The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of prior systems.

Summary of the Disclosure

In another aspect of the present disclosure, a piston pin for connecting a connecting rod and a piston is disclosed. The piston pin may be integrally formed with a main body section with a main body diameter and extending between two opposite ends. The piston pin may be further integrally formed with, extending from the opposite ends, a first outer guiding section and a second outer guiding section. The first outer guiding section may include a first guiding section diameter and the second outer guiding section may include a second guiding section diameter. The main body diameter may be greater than the first guiding section diameter and the second guiding section diameter. The piston pin may be configured to be axially fixed in the piston via a first circlip and a second circlip.

[06] In another aspect of the present disclosure, a piston pin may be configured to connect a connecting rod and a piston arranged within a cylinder having an inner cylinder wall. The piston pin may be integrally formed with a first emergency guiding outer wall facing the inner cylinder wall and a second emergency guiding outer wall on an opposite side of the piston pin with respect to the first emergency guiding outer wall, the second emergency guiding outer wall facing the inner cylinder wall. Piston pin may be dimensioned to contact the inner cylinder wall with the first emergency guiding outer wall and the second emergency guiding outer wall only in case of a demolition of the piston.

[07] In another aspect of the present disclosure, a piston assembly may be configured to be arranged in a cylinder, may comprise a piston configured to be reciprocatingly arranged within the cylinder, a connecting rod, and a piston pin as exemplary disclosed herein. The piston pin may connect the connecting rod and the piston. The piston assembly may further comprise a first circlip and a second circlip. The first circlip and the second circlip may be arranged to axially fix the piston pin in the piston.

[08] In a further aspect of the present disclosure, a cylinder assembly of an internal combustion engine is disclosed. The cylinder assembly may comprise a cylinder including an inner cylinder wall with an inner cylinder diameter, and a piston reciprocatingly arranged within the cylinder. The cylinder assembly may further comprise a connecting rod, a piston pin as exemplary disclosed herein and connecting the connecting rod and the piston, and a first circlip and a second circlip arranged to axially fix the piston pin in the piston.

[09] In yet another aspect of the present disclosure, a method for

providing an emergency guidance of a connecting rod with a piston pin in a cylinder only in case of a piston demolition may comprise providing a fixed gap between each end of the piston pin and the inner cylinder wall within the range from 0.1 % to 5 % of an inner cylinder diameter.

[10] Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.

Brief Description of the Drawings

[1 1] Fig. 1 shows a sectional view of an exemplary piston assembly arranged within a cylinder of an internal combustion engine;

Fig. 2 shows a sectional view of an exemplary piston pin; and Fig. 3 shows another sectional view of an exemplary piston pin.

Detailed Description

[12] The following is a detailed description of exemplary embodiments of the present disclosure. The exemplary embodiments described therein and illustrated in the drawings are intended to teach the principles of the present disclosure, enabling those of ordinary skill in the art to implement and use the present disclosure in many different environments and for many different applications. Therefore, the exemplary embodiments are not intended to be, and should not be considered as, a limiting description of the scope of patent protection. Rather, the scope of patent protection shall be defined by the appended claims.

[13] The present disclosure may be based in part on the realization that in case of a piston demolition, a connecting rod may cause considerable damage to the cylinder liner as the connecting rod may reciprocate within the cylinder in an unguided state for several times within before the engine stops.

[14] Accordingly, a piston pin having emergency guidance capabilities is disclosed. Emergency guiding outer walls of the piston pin may facilitate guidance of the connecting rod only in case of a piston demolition.

[15] Referring now to Fig. 1 , a piston arranged in a cylinder of an

internal combustion engine is shown.

[16] A cylinder 2 of an internal combustion engine (not shown) extends along a central axis 9 includes an inner cylinder wall 4. Cylinder 2 is covered by a cylinder head 5, which accommodates various components such as inlet valves(s) and port(s), outlet valve(s) and port(s) and a spark plug.

[17] A piston 6 is reciprocatingly arranged along central axis 9 within cylinder 2. Piston 6 is connected via a piston pin 10 to a connecting rod 8 which in turn is connected to a crankshaft 12. Piston 6 comprises a piston skirt 7 facing inner cylinder wall 4.

[18] Piston pin 10 is disposed in piston bosses 14 and 16. Specifically, piston pin 10 is arranged in a first piston boss 14 and a second piston boss 16. ■ Axially fixation of piston pin 10 is achieved by first circlip 22 arranged in a circlip groove 26 in first piston boss 14, and second circlip 24 arranged in a circlip groove 28 in second piston boss 16. Thus, piston pin 10 is axially secured between first circlip 22 and second circlip 24. In the shown configuration, piston pin 10 is formed as hollow piston pin and configured to connect connecting rod 8 and piston 6 arranged within cylinder 2 of an internal combustion engine.

[19] Piston pin 10 comprises a main body section 1 1 extending

between main body section ends 18, 20, and emergency guiding sections 30, 31 extend towards inner cylinder wall 4 from main' body section ends 18, 20 without contacting the same.

[20] Piston 6, connecting rod 8, piston pin 10, and circlips 22, 24

together form a piston assembly 33. [21] Fig. 2 gives a more detailed view of first emergency guiding section 30 extending from main body section 1 1 of piston pin 10 at first main body section end 18 in a sectional view. However, the hereinafter given description similarly relates to second emergency guiding section 31 extending from second main body section end 20 towards inner cylinder wall 4.

[22] Due to structural limitations caused by the axial fixation of piston pin 10 by circlip 22 in circlip groove 26, first main body section end 18 of piston pin 10 is spaced apart with its main body piston pin outer wall 32 from inner cylinder wall 4 in a distance A. In practice, distance A may be typically within a range from 5 % to 10 % of an inner cylinder diameter B.

[23] Emergency guiding section 30 is configured to set distance C

between an integrally formed emergency guiding outer wall 34 and inner cylinder wall 4 within a range from 0.1 % to 5 %, preferably within a range from 0.1 % to 4.5 %, of inner cylinder diameter B. Therefore, emergency guiding section 30 may extend more or less along a piston pin axis 36, said extend depending on several boundary conditions defined by, for example, position of circlip groove 26, length of piston pin 10, and diameter of piston skirt 7.

[24] Although shown in Fig. 2, emergency guiding section 30 may not necessarily extend beyond piston skirt 7. That is, depending on a desired distance C within a range from 0.1 % to 5 %, for example 1 %, of an inner cylinder diameter B and a distance between piston skirt 7 and inner cylinder wall 4 depending on the specific piston used, emergency guiding outer wall 34 may extend beyond piston skirt 7, may extend until piston skirt 7, or may extend within the confines of piston skirt 7.

[25] To facilitate arrangement of circlip 22, an emergency guiding section diameter E of emergency guiding section 30 is less than a main body diameter D of main body section 11 of piston pin 10. Accordingly, piston pin 10 is configured to be axially fixed along piston pin axis 36 via circlips, namely circlip 22 and circlip 24 (shown in Fig. 1) [26] Piston pin 10 may be made of, for example, aluminum or steel.

[27] Additionally, emergency guiding outer wall 34 may be coated with a sliding coating, for example, a polyamideimide based coating with added lubricant and hard particle enhancements.

[28] Turning to Fig. 3, a sectional view of an exemplary piston pin 10 is shown. Sectional view of Fig. 3 lies in a plane of piston pin axis 36 and perpendicular to central axis 9. For purpose of clarity, only piston pin 10 and cylinder 2 with inner cylinder wall 4 are shown.

[29] As can be seen, emergency guiding outer wall 34 has a curved shape. Some sections of said curved shape may be adapted to a shape of inner cylinder wall 4. For example, emergency guiding outer wall 34 may be at least partially shaped as a spherical cap, a spherical segment, and/or a cylindrical surface segment.

[30] At opposite ends 18, 20, the main body section 11 transitions steplike into first outer guiding section 30 and second outer guiding section 31 , respectively. Thereby, main body piston pin outer walls 32 act as contact faces for first circlip 22 and second circlip 24, respectively. Said contact faces extend substantially perpendicular to a longitudinal axis of piston pin 10. In an assembled state, in which piston pin 10 is mounted in piston 6, said contact faces abut against first and second circlips 22, 24, or at least limit the movement of piston pin 10 within boundaries defined by first and second circlips 22, 24.

[31 ] First outer guiding section 30 comprises first emergency outer guiding wall 34, which faces axially away from piston pin 10, thus, facing inner cylinder wall 4 in the mounted state. Similarly, second outer guiding section 31 comprises a second emergency outer guiding wall 34, which faces axially away from piston pin 10, thus, facing inner cylinder wall 4 in the mounted state.

[32] As indicated in the cross-sectional views, main body piston pin outer walls 32 as well as first and second emergency outer guiding walls 34 are in the exemplary embodiment circular rings. Industrial Applicability

In the following, operation and functionality of exemplary disclosed emergency guiding elements 30 is described with reference to Figs. 1 and 2.

During operation of the internal combustion engine, piston 6 reciprocates within cylinder 2. In doing so, piston pin 10 is axially secured along piston pin axis 36 due to the presence of circlips 22 and 24. As emergency guiding sections 30 and 31 are configured set a minimum distance C between emergency guiding outer wall 34 and inner cylinder wall 4 within a range from 0.1 % to 5 % of the inner cylinder diameter B, emergency guiding sections 30 and 31 do not come into contact with inner cylinder wall 4.

However, in the case of a piston demolition which constitutes in piston 6 braking away from piston pin 10, emergency guiding outer wall 34 of emergency guiding section 30 comes into contact with inner cylinder wall 4. Thus, piston pin 10 is dimensioned to contact inner cylinder wall 4 with first and second emergency guiding outer wall 34 only in case of a demolition of piston 6.

Said contact between emergency guiding outer wall 34 and inner cylinder wall 4 in case of said piston demolition facilitates an emergency guidance of connecting rod 8 until the internal combustion engine finally stops. That is, piston pin 10 comprises an emergency guidance capability. The emergency guidance of connecting rod 8 may reduce damage of connecting rod 8 reciprocating in cylinder 2 after demolition of piston 6.

Furthermore, a tilting tendency of piston pin 6 in case of a demolition of the piston 6 may be reduced by providing emergency guiding outer wall 34 with a height. Height as used herein means an extend of contact face 34 along an axis parallel to central axis 9 (for example, as can be seen in Fig. 2). Thereby, more than one potential emergency guiding contact point on emergency guiding outer wall 34 may be provided. In other words, each of the first and second emergency guiding outer wall 34 may be configured to provide two emergency guiding contact points to contact inner cylinder wall 4 only in case of a demolition of piston 6. The two emergency guiding contact points being spaced apart from each other in a direction of central axis 9 of cylinder 2. This may be achieved, for example, by forming emergency guiding outer wall 34 as a cylindrical surface segment (which may have an annular shape due to the tubular nature of piston pin 10). A reduced tilting tendency may further lead to an improved emergency guidance of connecting rod 8.

[38] On the contrary, in prior art solutions, a piston pin may be spaced apart with its outer wall at each end from an inner cylinder wall in a distance being typically within a range from 5 % to 10 % of an inner cylinder diameter, or greater, as already described. If a piston demolition occurs in such configurations, the clearance between the outer wall of the piston pin and the inner cylinder wall is too large resulting in an unguided reciprocation of a connecting rod attached to the piston pin for the next few strokes of the internal combustion engine until the engine finally stops. The unguided connecting rod may cause considerable damage to the cylinder wall, the cylinder as well as the entire engine, which may lead to a complete engine write-off.

[39] Accordingly, emergency guiding sections 30 and 31 may reduce damages occurring after a piston demolition, which may allow a repair of the piston demolition (for example, by replacement) in a cost effective manner as a complete engine write-off due to an unguided connecting rod considerably increasing the damage may be prevented.

[40] As emergency guiding sections 30 and 31 are not in contact with inner cylinder wall 4 during normal operation of the internal combustion engine, no friction between emergency guiding sections 30 and 31 and inner cylinder wall 4 occurs, which could reduce efficiency of the internal combustion engine.

[41] The present disclosure further relates to a method for providing an emergency guidance of a connecting rod with a piston pin in a cylinder only in case of a demolition of the piston. [42] The method comprises providing a fixed gap between each end of piston pin 10 and inner cylinder wall 4 within the range from 0.1 % to 5 %, preferably 0.1 % to 4.5 % of an inner cylinder diameter B. For example, this may be achieved by providing emergency guiding sections 30, 31 as exemplary disclosed herein at each end of piston pin 10, thereby, said fixed gap may be provided between emergency guiding section outer wall 34 and inner cylinder wall 4.

[43] Additionally, the method may comprise releasing the fixed gap only in case of a demolition of the piston. In other words, the method may comprise the step of guiding the piston pin 10 only in case of a piston demolition. For instance, emergency guiding sections 30, 31 of piston pin 10 may be configured to come into contact with inner cylinder wall 4 only in case of a demolition of piston 6 as piston pin 10 is axially secured along piston axis 36 during operation of the internal combustion engine.

The method may further comprise reducing tilting of the piston pin 10 by providing two emergency guiding contact points at opposing sides of the piston pin 10 for contacting the inner cylinder wall 4 if guiding the piston pin 10 in the case of a piston demolition as already described in detail.

Generally, exemplary disclosed piston pin 10 having an

emergency guiding capability may be applicable in internal combustion engines including a piston connected to a connecting rod via a piston pin. Said internal combustion engine may include features not shown, such as air systems, cooling systems, peripheries, drivetrain components, etc. Furthermore, internal combustion engine may be of any size, with any number of cylinders, and in any configuration (e.g., "V," in-line, radial, etc.). Additionally, internal combustion engine may be used to power any machine or other device, including, but not limited to, locomotive applications, on-highway trucks or vehicles, off-highway trucks or machines, earth moving equipment, generators, aerospace applications, marine applications, offshore applications, pumps, stationary equipment, or other engine powered applications.

[46] Furthermore, exemplary disclosed piston pin 10 with emergency guiding capability may be applicable in any piston machine including, but not limited to, piston compressors and piston pumps, to reduce damages caused by a piston demolition.

[47] Although the preferred embodiments of this invention have been described herein, improvements and modifications may be incorporated without departing from the scope of the following claims.