CN110848044A

CN110848044A - Reciprocating piston internal combustion engine and reciprocating piston for reciprocating piston internal combustion engine

Info

Publication number: CN110848044A
Application number: CN201910772439.9A
Authority: CN
Inventors: P.I.U.托雷斯; M.比尔; A.莱嫩; H.罗根坎普
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 2018-08-21
Filing date: 2019-08-21
Publication date: 2020-02-28
Also published as: DE102018214130A1

Abstract

The invention relates to a reciprocating piston internal combustion engine and a reciprocating piston for a reciprocating piston internal combustion engine, in particular to a reciprocating piston internal combustion engine with at least one cylinder (42) and at least one reciprocating piston (10), wherein the reciprocating piston (10) reciprocates in an axial direction along a cylinder axis (Z) during operation of the reciprocating piston internal combustion engine (12), wherein the reciprocating piston (10) has a base body (14) with a piston crown (16) and a piston underside (18) formed on the rear side of the piston crown (16), and wherein the reciprocating piston (10) is connected to a connecting rod via a piston pin, wherein at least one means for generating an annular fluid flow (38) is provided, wherein the annular fluid flow (52) extends annularly around the piston crown and flows through a region between the piston underside (18) and the piston pin. The invention also relates to a reciprocating piston (10) for a reciprocating piston internal combustion engine (12).

Description

Reciprocating piston internal combustion engine and reciprocating piston for reciprocating piston internal combustion engine

Technical Field

The present invention relates to a reciprocating piston internal combustion engine and a reciprocating piston for a reciprocating piston internal combustion engine.

Background

DE 19616474 a1 discloses a piston with a ring assembly for a reciprocating piston internal combustion engine, wherein the piston comprises a plurality of grooves and piston rings arranged therein. An oil scraper ring is arranged in the groove facing away from the piston crown. An oil drain hole leading into the interior of the piston is provided in this groove. In addition, the adjacent intermediate ring grooves likewise have oil drainage bores which lead into the interior of the piston. The oil drain hole in the middle ring groove is to be designed radially or radially inclined. As will be pointed out below, four oil drainage holes in the middle ring groove are formed distributed over the circumference of the piston. By this arrangement of the oil discharge hole, the oil consumption of the internal combustion engine should be minimized.

Disclosure of Invention

The object of the invention is to provide a reciprocating piston internal combustion engine and a reciprocating piston, by means of which an efficient cooling of the underside (kolbenneterseite) of the piston can be achieved.

According to the invention, this object is achieved by the features of the independent claims. Further practical embodiments and advantages of the invention are described in connection with the dependent claims.

The reciprocating piston internal combustion engine according to the invention comprises at least one cylinder and at least one reciprocating piston, wherein the reciprocating piston reciprocates in an axial direction along a cylinder axis during operation of the reciprocating piston internal combustion engine, the reciprocating piston has a piston crown directed toward a combustion chamber of the reciprocating piston internal combustion engine and a base body configured on a back side of the piston crown, a piston underside faces away from the combustion chamber and is directed in the direction of a crankshaft, furthermore, the reciprocating piston is connected with a connecting rod via a gudgeon pin (Kolbenbolzen), in order to cool the piston underside, in the case of the reciprocating piston internal combustion engine according to the invention, at least one means for generating an annular fluid flow (Ring-Fluidströmung) is provided, wherein the annular fluid flow extends annularly around the gudgeon pin and flows through a region between the piston underside and the gudgeon pin.

During operation of a reciprocating piston internal combustion engine, the piston crown facing the combustion chamber and the piston underside facing away from the combustion chamber are heated by the temperature prevailing in the combustion chamber, the temperature of the fluid in the crankcase space (Kurbelgehäuser, sometimes referred to as the crankcase chamber) below the reciprocating piston then builds up in the region of the piston underside, which likewise rises and heats up during operation.

The reciprocating piston internal combustion engine according to the invention solves this problem by providing one or more means which bring about an efficient cooling of the piston underside by generating an annular fluid flow, wherein the annular fluid flow flows annularly around the piston pin and therefore likewise has a component in the axial direction, which results in that the heated fluid is conveyed by the region immediately adjacent to or between the piston underside and the piston pin downwards in the direction of the crankshaft and at the same time the cooler fluid flows back in the direction of the crankshaft (nachsrömen, sometimes referred to as reflow or flushing).

As a means for generating the annular fluid flow, in particular, a through-opening is provided in the base body of the piston, as is explained in more detail below. Alternatively or additionally, at least one ventilation device and/or a blower (or a plurality of ventilation devices or blowers) can be arranged in the region of the crankcase or the at least one cylinder, which conveys the colder fluid from the region below the reciprocating piston in the direction of the piston underside in such a way that an annular fluid flow occurs. Likewise, one or more pumps can alternatively be provided, by means of which the fluid which has become hot is pumped out of the region between the underside of the piston and the piston pin. Here, the drive of the ventilation device or blower can be effected via an external energy source and/or by the reciprocating movement of the reciprocating piston.

In a particularly advantageous embodiment of the reciprocating piston internal combustion engine according to the invention, at least one piston ring groove is formed on the outer circumference of the basic body of the reciprocating piston, and at least one through-opening in the basic body is formed as a means for generating an annular fluid flow. The at least one through-opening extends from at least one piston ring groove or, if several piston ring grooves are formed, the piston ring groove having the greatest distance from the piston crown to the inside of the piston. In this context, the piston inner side is understood to mean the entire inner surface of the reciprocating piston, which includes not only the piston underside but also the inner circumferential wall. In other words, the at least one through-hole is formed, for the case in which a plurality of piston ring grooves are formed at the base body of the reciprocating piston, starting from the lowermost piston ring groove in the installation position of the reciprocating piston. Typically, an oil scraper ring is disposed in the piston ring groove.

During operation of a reciprocating piston internal combustion engine, Blow-by Gas (sometimes referred to as Blow-by Gas) formed in the combustion chamber flows along the outer periphery of the reciprocating piston in the direction of the crankcase space. In this case, the blow-by gas likewise reaches through at least one through-hole in the one piston ring groove or in the piston ring groove at the greatest distance from the piston crown in the direction of the inside of the piston. The piston ring groove or grooves configured above the lowermost piston ring groove are typically used to seal the crankcase volume from the combustion chamber in order to reduce or avoid blow-by gas leakage from the combustion chamber.

In particular, an additional structural element, such as, for example, an oil spray nozzle, can be omitted, onto which oil for cooling the underside of the piston is sprayed, when a cooling channel is formed or arranged in the reciprocating piston, which cooling channel can be kept unchanged despite the formation of the passage opening, additionally causes an oil return (Ölr ü ckf ü hrun, sometimes referred to as oil return) of the oil mist in the direction of the crankcase space and thus counteracts the flow of the oil mist in the direction of the combustion chamber.

In particular, the main flow direction (also referred to below as the outflow angle) of the outflow opening of the at least one through opening is inclined to the horizontal in such a way that it points away from the piston head or is directed away from it. In the case of a through-hole designed as a bore or in a straight-line configuration, when the combustion chamber is located axially above the piston, the section of the through-hole pointing opposite the piston ring groove is then arranged axially above the section of the through-hole pointing opposite the inside of the piston, as viewed in the axial direction. In other words, the through-hole in this case is inclined downward (that is to say at least partially oriented in the direction of gravity) as viewed in the flow direction of the blow-by gas. Horizontal here means a plane perpendicular to the cylinder axis. By the inclination of the at least one through opening, the fluid in the region of the piston underside is accelerated or conveyed at least partially in the axial direction in the direction of the crankshaft. By forcibly returning the fluid, an annular fluid flow thus occurs.

Preferably, the inclination of at least one through-hole with respect to the horizontal is at least 10 °, preferably at least 20 °, further preferably at least 30 ° and particularly preferably at least 45 °. The steeper the inclination of the at least one through opening relative to the horizontal, the more efficiently the heated fluid is conveyed from the region between the underside of the piston and the piston pin in the direction of the crankshaft or downwards in the crankcase space. Correspondingly, the colder fluid likewise flows back in the direction of the piston underside.

This annular fluid flow is particularly pronounced and therefore the cooling of the underside of the piston is particularly efficient if at least two through-openings, which have correspondingly different inclination angles with respect to the horizontal, are provided at a distance from one another in the circumferential direction, in particular approximately opposite one another. For example, one through-hole may be disposed on a pressure side of the piston and another through-hole may be disposed on an opposite pressure side (sometimes referred to as a counter pressure side) of the piston. It is likewise possible that one or more through-holes are arranged on one side with a gentle inclination and one or more through-holes are arranged on the opposite side with a steeper inclination, respectively. Such asymmetrically formed through-openings, which are inclined relative to the horizontal, can be matched to one another in particular in such a way that the blow-by gas flows correspondingly through the through-openings in such a way that the formation of an annular fluid flow is achieved. A more steeply formed through opening is understood to mean an outflow opening with an angle of at least 20 °, preferably at least 30 °, and particularly preferably at least 40 ° relative to the horizontal. A gently configured through hole represents an outflow opening enclosing a smaller angle relative to the horizontal than the angle of the other through holes. Preferably, the angle between the horizontal and the outflow opening of the gently configured through-hole is at most 30 °, preferably at most 20 °, particularly preferably at most 10 °. The gently formed outlet opening can likewise be formed horizontally or inclined in the direction of the piston crown, i.e. a negative angle is set. The blow-by gas, which is supplied into the interior of the piston via the gently formed through-hole, supplies the air or the fluid present there in the direction of the cylinder axis in the radial direction. On the opposite side, the more steeply formed passage opening then produces a blow-by fluid flow in the direction of the crankshaft, whereby the fluid is conveyed in a direction away from the piston crown, preferably mainly in the axial direction.

In particular, the at least one through-hole is arranged on the pressure side of the base body and/or on the opposite pressure side of the base body. If only one through-hole is constructed, it can be arranged at the pressure side or at the opposite pressure side. In the case of a plurality of through-holes, not only possibly all through-holes can be arranged on the pressure side or on the opposite pressure side. It is considered to be particularly advantageous when the at least one through-opening is configured on the pressure side and the opposite pressure side, respectively. The side of the reciprocating piston on which the reciprocating piston is pressed against the cylinder wall during the expansion phase in the operation of the reciprocating piston internal combustion engine is referred to as the pressure side. The opposite pressure side is the side of the reciprocating piston opposite the pressure side. The arrangement on the pressure side and/or on the opposite pressure side is particularly well adapted in design, since the material thickness of the base body in these regions is smaller here and the formation of the through-opening is thereby simplified, for example by means of drilling.

In order to obtain different flow directions of the blow-by gas flowing through the through holes in the direction of the lower side of the piston, a plurality of through holes may be provided, which are distributed over the circumference of the base body. In particular, the plurality of through-holes are distributed such that they are respectively arranged equidistantly on the pressure side and on the opposite pressure side. Preferably, the through-holes are arranged mirror-imaged on the pressure side and the opposite pressure side, wherein the cylinder axes form a mirror plane. In particular, 2, 3 or 4 through-holes are provided on the pressure side and the opposite pressure side, respectively.

The diameter or the maximum cross-sectional extension of the at least one through-opening is in particular at least 1mm, preferably at least 1.5mm and particularly preferably at least 2 mm.

The simulation has shown that the cooling of the underside of the piston is particularly strongly pronounced when the at least one first through-hole is arranged on the opposite pressure side of the base body and the at least one second through-hole is arranged on the pressure side of the base body, wherein the at least one second through-hole is less inclined to the horizontal than the at least one first through-hole.

The invention also relates to a reciprocating piston for a reciprocating piston internal combustion engine, in particular for a reciprocating piston internal combustion engine as described before. The reciprocating piston according to the invention in particular likewise has one or more of the features explained above in connection with the reciprocating piston. The reciprocating piston has a base body with a piston crown and a piston underside formed on the rear side of the piston crown and can be connected to a connecting rod via a piston pin. At least one piston ring groove is formed on the outer circumference of the basic body of the reciprocating piston, wherein, starting from the at least one piston ring groove or, if a plurality of piston ring grooves are formed, from the piston ring groove which has the greatest distance from the piston crown, at least one first through opening extends to the inside of the piston at an outflow angle of more than 10 ° relative to the horizontal. By means of the at least one through-hole, an annular fluid flow for cooling the underside of the piston is generated as explained before.

In particular, in addition to the at least one first through-opening, the at least one further second through-opening extends from at least one piston ring groove or, if several piston ring grooves are formed, from the piston ring groove with the greatest distance from the piston crown to the inside of the piston. In this case, the outflow angle of at least one second through opening encloses a smaller angle with the horizontal than the first through opening. This likewise includes variants in which the second through-opening extends purely horizontally or the outflow opening is inclined in the direction of the piston crown and the combustion chamber, i.e. the angle is negative. With regard to the advantages of this asymmetric arrangement of the first and second through holes, reference is made to the previous description.

Drawings

Further practical embodiments of the invention are described below in connection with the figures. Wherein:

figure 1 shows in cross-section a reciprocating piston according to the invention,

figure 2 shows the reciprocating piston from figure 1 in a perspective view,

figure 3 shows the reciprocating piston from figures 1 and 2 in a side view according to arrow III in figures 1 and 2,

figure 4 shows the reciprocating piston from figure 1 in a side view up to the arrow IV according to figure 1,

fig. 5 shows a part of a reciprocating piston internal combustion engine according to the invention in schematic illustration with a reciprocating piston according to fig. 1 to 4.

List of reference numerals

10 reciprocating piston

12 reciprocating piston type internal combustion engine

14 base body

16 piston top

18 piston underside

20 piston pin hub (Kolbenbolzennab)

22a,22b piston skirt (Kolbenhem)

24 relative pressure side

26 pressure side

28 side wall

30 opening

32 inside of piston

34 inner peripheral wall

36a,36b,36c piston ring grooves

38 device for generating an annular fluid flow

40a,40b through hole

42 air cylinder

44 cylinder wall

46 combustion chamber

48 crankcase

50 crankcase space

52 annular fluid flow.

Detailed Description

In fig. 1 to 4, a reciprocating piston 10 according to the invention for a reciprocating piston internal combustion engine 12 is shown. The reciprocating piston 10 comprises a main body 14 with a piston crown 16 which, during operation of the reciprocating piston internal combustion engine 12, points in the direction of the combustion chamber (see fig. 5). Furthermore, the base body 14 has a piston underside 18 which is formed on the rear side of the piston crown 16. The piston underside 18 points in the direction of the crankshaft in the installed position of the reciprocating piston 10. Furthermore, the reciprocating piston 10 has a piston pin (not shown) guided by a piston pin boss 20, which can be connected with a connecting rod (not shown). In addition, the base 14 of the reciprocating piston 10 includes a first piston skirt 22a disposed on an opposite pressure side 24 of the reciprocating piston 10 (on the right side of the reciprocating piston 10 in fig. 1 and 5), and a second piston skirt 22b disposed on a pressure side 26 of the reciprocating piston 10 (on the left side of the reciprocating piston 10 in fig. 1 and 5). Between the first piston skirt 22a and the second piston skirt 22b, a side wall 28 (see fig. 2) extends in each case. The piston pin bosses 20 provide openings 30 for receiving piston pins, not shown. The reciprocating piston 10 has a piston inner side 32 which comprises not only the piston underside 18 but also an inner peripheral wall 34.

At the outer periphery of the base body 14 of the reciprocating piston 10, three

piston ring grooves

36a,36b,36c are formed. The lowermost ring groove 36c, which has the greatest distance from the piston crown 16, serves to accommodate a scraper ring (not shown). The two

piston ring grooves

36a,36b formed above them serve to accommodate sealing rings (not shown), by means of which the crankcase space is sealed off from the combustion chamber, so that as little blow-by gas as possible reaches the crankcase space from the combustion chamber.

In the piston ring groove 36c, which is furthest away from the piston crown 16, two through

openings

40a,40b are formed as means for generating the annular fluid flow 38. In fig. 1, a first through-opening 40a is formed on the right side (opposite pressure side 24) of the reciprocating piston 10, which extends from the lowermost piston ring groove 36c to the piston inner side 32. The first through-hole 40a is now inclined with respect to the horizontal H and encloses an angle of 65 ° with the horizontal H. A second through-opening 40b is formed on the left side (pressure side 26) shown in fig. 1, which likewise extends from the lowermost piston ring groove 36c to the piston inner side 32. The second through hole 40b shown here extends in the horizontal direction.

The opposite pressure side 24 of the reciprocating piston 10 according to the present invention with the first through hole 40a is well recognizable in fig. 2 and 3. Fig. 4 shows the reciprocating piston 10 according to the invention in a view towards the pressure side 26, wherein the second through hole 40b extends horizontally in the direction of the piston inner side 32.

In fig. 5 a part of a reciprocating piston internal combustion engine 12 according to the invention with a reciprocating piston 10 according to the invention is shown. The reciprocating piston internal combustion engine 12 has a cylinder 42 with a cylinder wall 44 surrounding a combustion chamber 46. Within the cylinder 42, the reciprocating piston 10 reciprocates in an axial direction along a cylinder axis Z during operation of the reciprocating piston internal combustion engine 12. At the lower end of the cylinder wall 44, a crankcase 48 is coupled, which encloses a crankcase space 50 and in which a crankshaft (not shown) is arranged.

During operation of the reciprocating piston internal combustion engine 12, the piston crown 16 and likewise the piston underside 18, which face the combustion chamber 46, become hot. Likewise, a temperature gradient, schematically indicated by means of arrow T, results in the crankcase space 50, wherein a higher temperature in the direction of the crankshaft exists in the crankcase space 50 in the region between the piston underside 18 and the piston pin bosses 20 than further below.

The following describes how the means for generating the annular fluid flow 38 generates the annular fluid flow 52 for cooling the piston underside 18. By the reciprocating movement of the reciprocating piston 10 along the cylinder axis Z, the compression and combustion process caused thereby, which causes a pressure difference between the combustion chamber 46 and the crankcase space 50, blow-by gases follow from the combustion chamber 46 in the direction of the crankcase space 50 between the basic body 14 and the cylinder wall 44. The blow-by gas arrives from the lowermost ring groove 36c in the direction of the piston inner side 32 through the through

holes

40a,40 b. Through the second through-openings 40b arranged on the pressure side 26, the fluid present in the region of the pressure side 26 and in the region between the piston underside 18 and the piston pin bosses 20 is conveyed in the direction of the opposite pressure side 24. The blow-by gas flowing through the first through hole 40a (which has an axial component due to the inclination of the first through hole 40a) conveys the fluid that heats up below the piston underside 18 downward in the direction of the crankshaft. At the same time, the cooler fluid spaced from the piston underside 18 flows back on the pressure side 26. An annular fluid flow 52 is thus formed, which flows through the region between the piston underside 18 and the piston pin bosses 20 and causes a fluid exchange there.

The features of the invention disclosed in the description, in the drawing and in the claims can be essential both individually and in any desired combination for the realization of the invention in its various embodiments. The invention may be varied within the scope of the claims and taking into account the knowledge of the person skilled in the art in charge.

Claims

1. A reciprocating piston internal combustion engine with at least one cylinder (42) and at least one reciprocating piston (10), wherein the reciprocating piston (10) reciprocates in the axial direction along the cylinder axis (Z) during operation of the reciprocating piston internal combustion engine (12), wherein the reciprocating piston (10) has a basic body (14) with a piston crown (16) and a piston underside (18) configured on the back side of the piston crown (16), and wherein the reciprocating piston (10) is connected with a connecting rod via a piston pin, characterized in that at least one means for generating an annular fluid flow (38) is provided, wherein the annular fluid flow (52) extends annularly around the piston pin and flows through the region between the piston underside (18) and the piston pin.

2. A reciprocating piston internal combustion engine according to the preceding claim, characterized in that at least one piston ring groove (36a,36b,36c) is configured at the outer periphery of the basic body (14) of the reciprocating piston (10), and at least one through-hole (40a,40b) is configured in the basic body (14) as a means for generating the annular fluid flow (38), which extends from the at least one piston ring groove (36a,36b,36c) or, if a plurality of piston ring grooves (36a,36b,36c) is configured, from that piston ring groove (36c) having the greatest spacing from the piston crown (16) up to an outflow opening in the region of the piston inside (32).

3. A reciprocating piston internal combustion engine according to the preceding claim, characterized in that the main flow direction of the outflow opening of the at least one through hole (40a) is inclined with respect to the horizontal (H) in such a way that it is directed away from the piston crown (16).

4. A reciprocating piston internal combustion engine according to any one of the two preceding claims, characterised in that the at least one through hole (40a) has an inclination of at least 10 ° in relation to the horizontal (H).

5. A reciprocating piston internal combustion engine according to any one of the three preceding claims, characterised in that at least two through-holes (40a,40b) are provided spaced from each other in the circumferential direction, which in each case have different inclinations relative to the horizontal (H).

6. A reciprocating piston internal combustion engine according to any one of the four preceding claims,

a) at least one through-hole (40a) is arranged on the pressure side (26) of the base body (14) of the reciprocating piston (10) and at least one through-hole (40b) is arranged on the opposite pressure side (24) of the base body (14) of the reciprocating piston (10), and/or

b) A plurality of through-holes (40a,40b) are distributed over the circumference of the base body (14).

7. A reciprocating piston internal combustion engine according to any one of the five preceding claims, characterized in that at least one first through hole (40a) is arranged on the opposite pressure side (24) of the basic body (14) and at least one second through hole (40b) is arranged on the pressure side (24) of the basic body (14), wherein the at least one second through hole (40b) is less inclined to the horizontal (H) than the at least one first through hole (40 a).

8. A reciprocating piston internal combustion engine according to any one of the preceding claims, characterised in as means for generating an annular fluid flow (38)

a) At least one ventilation device and/or a blower is arranged in the region of the crankcase (48) or the at least one cylinder (42), which conveys a cooler fluid from the region below the reciprocating piston (10) in the direction of the piston underside (18) in such a way that an annular fluid flow (52) occurs and/or

b) One or more pumps are provided by means of which the fluid that has become heated is pumped out of the region between the underside of the piston and the piston pin.

9. A reciprocating piston for a reciprocating piston internal combustion engine (12), wherein the reciprocating piston (10) has a basic body (14) with a piston crown (16) and a piston underside (18) which is formed on the rear side of the piston crown (16), and wherein the reciprocating piston (10) can be connected to a connecting rod via a piston pin, wherein at least one piston ring groove (36a,36b,36c) is formed at the outer circumference of the base body (14) of the reciprocating piston (10), characterized in that, starting from the at least one piston ring groove (36a,36b,36c) or, if several piston ring grooves (36a,36b,36c) are formed, from the piston ring groove (36c) having the greatest distance from the piston crown (16), at least one first through opening (40a) extends up to the piston inner side (32) at an outflow angle of more than 10 ° relative to the horizontal (H).

10. The reciprocating piston as claimed in the preceding claim, wherein, in addition to the at least one first passage opening (40a), at least one second passage opening (40b) extends from the at least one piston ring groove (36a,36b,36c) or, if a plurality of piston ring grooves (36a,36b,36c) are formed, from the piston ring groove (36c) having the greatest distance from the piston crown (16) to the piston inner side (32), wherein the second passage opening (40b) encloses a smaller outflow angle with the horizontal (H) than the first passage opening (40 a).