WO2013143676A1

WO2013143676A1 - Method for reducing pressure spikes in a cylinder of a reciprocating internal combustion engine, and piston for a reciprocating internal combustion engine

Info

Publication number: WO2013143676A1
Application number: PCT/EP2013/000883
Authority: WO
Inventors: Peter Kreuter
Original assignee: Peter Kreuter
Priority date: 2012-03-26
Filing date: 2013-03-22
Publication date: 2013-10-03
Also published as: DE102012005922B4; DE102012005922A1

Abstract

The invention relates to a piston (4) for a reciprocating internal combustion engine, containing a piston body with an upper face, containing a bearing shaft, which is arranged at a distance from the upper face, for supporting a connecting rod (6) that can be connected to a crankshaft, containing a hollow chamber (45) with an adjustable volume, containing a feed channel (46) which connects the upper face of the piston to the hollow chamber and in which a non-return valve (48) that releases a fluid flow from the upper face of the piston to the hollow chamber is arranged, and containing a spring (44) which pushes the upper face in a direction such that the distance between the upper face and the bearing shaft increases. A force which acts on the upper face of the piston is transmitted to the bearing shaft via the pressure acting in the hollow chamber and the force of the spring. The volume of the hollow chamber decreases in the event of a pressure increase, thereby reducing the distance between at least one part of the upper face of the piston and the bearing shaft.

Description

A method for reducing pressure peaks in a cylinder of a reciprocating internal combustion engine and piston for a reciprocating internal combustion engine

The invention relates to a method for reducing pressure peaks in a cylinder of a reciprocating internal combustion engine and a piston for a reciprocating internal combustion engine.

In the combustion of fuels in the combustion chamber of a cylinder of an internal combustion engine pressure peaks occur in the region of the top dead center of the piston, leading for example to increased formation of nitrogen oxides, inhomogeneous combustion with soot formation and high mechanical loads of the internal combustion engine.

The invention has for its object to provide a remedy for the aforementioned problem.

A first solution of this object is achieved by a method according to claim 1, which is further developed with the features of claim 2.

Another solution of the invention task is achieved with a piston according to claim 3, which is further developed with the features of claims 4 to 10 in an advantageous manner.

One aspect of the invention is to design the piston of an internal combustion engine in such a way that at least a portion of the surface of the piston facing the combustion chamber moves relative to the articulation of the piston on a connecting rod such that the volume of the combustion chamber increases and thereby the pressure in the combustion chamber does not rise to a value which it would assume in conventional design of the piston.

The invention can be applied to any type of internal combustion engine, gasoline engines, diesel engines, gas engines u. s. w.

The invention is explained below with reference to schematic drawings, for example, and with further details. In the figures represent:

Fig. 1 shows a central section through a part of a cylinder with pistons therein, cut perpendicular to a piston pin and

Fig. 2 shows a central section through the piston of FIG. 1, cut parallel to the piston pin.

1 operates in a cylinder 2 of a single or multi-cylinder piston internal combustion engine a piston designated generally by 4. The piston is connected via a connecting rod 6 in a conventional manner with a crankshaft of the internal combustion engine. In the upwardly through a cylinder head 8 and down through the piston 4 finished working chamber 10 opens in a conventional manner, an inlet channel 12 and an outlet 14. The connection between the inlet channel 12 and the working chamber 10 by means of an inlet valve 16 can be opened and closed. The connection between the outlet channel 14 and the working chamber 10 can be opened and closed by means of an outlet valve 18.

The piston 4 has a multi-part construction and has an annular part 20, the outer circumferential surface of which can be moved in a manner known per se along the inner circumferential surface of the cylinder 2 while being sealed by means of piston rings (not shown).

The ring member 20 includes a preferably coaxial to its outer peripheral surface passage opening whose diameter decreases in a step 24.

In the formed with a larger diameter lower portion of the through hole 22, a support member 26 of the piston 4 is received, which is fixed by means of a piston pin 28, which penetrates the support member and the ring member 20, rigidly on the ring member 20.

In the illustrated embodiment, the support member 26 has a cylindrical outer wall whose outer diameter corresponds to the inner diameter of the lower portion of the through hole 22, wherein between the outer wall 30 and the ring member 20, a sealing ring 32 is arranged. The outer wall 30 merges via a bottom wall 34 into a pot-like projection 36 projecting upwards according to the figure, in which the piston pin 28 projecting through the projection 36 is arranged, on which the connecting rod 6 is mounted.

In the upper end region of the passage opening 22 according to the FIGURE, an upper part 38 is accommodated which, in the example shown, is designed with a combustion chamber trough 40 open to the working chamber 10. The upper part 38 has a step 42 complementary to step 42, so that the relative to the ring member 20 axially displaceable upper part 38 abuts in its uppermost position according to the figure with the step 42 on the step 24 of the through hole 22.

The outer contour of the upper part 38 corresponds to the inner contour of the through hole 22, wherein for sealing in the outer periphery of the upper part 38, one or more piston rings are arranged, which are formed as sealing rings 39 itself.

The height of the upper part 38 is preferably such that, when the upper part 38 is in contact with the step 24, its upper side is flush with the upper side of the annular part 20.

Between the upper part 38 and the support part 26, a compression spring 44 is arranged, which urges the upper part 38 away from the support part 26.

In the illustrated position, in which the upper part 38 abuts against the step 24, the volume of a cavity or space 45 between the upper part 38 and the support part 26 is maximum.

From the working chamber 10 leads through the ring member 20, a supply channel 46 into the intermediate space 45. In the supply channel 46, a check valve 48 is arranged, which allows a flow from the working chamber 10 into the intermediate space 45 and blocks in the opposite direction. From the intermediate space 45, a discharge channel 50 leads through the ring part 20 into a crank chamber 51. A safety valve 52 is arranged in the discharge channel 50 and opens in the intermediate space 45 at an unacceptably high pressure.

The assembly of the described multi-part piston is as follows: In the channels 46 and 50, the valves 48 and 52, which may also be known per se in their construction, installed in a conventional manner.

The upper part 38 is inserted from below into the passage opening 22. Subsequently, the compression spring 44 is introduced and the support member 30 is inserted. The support member 30 is rigidly secured by inserting the piston pin 28 through the ring member 20 and the support member 26 through the ring member 20, wherein thereby the connecting rod 6 is mounted on the piston pin 28.

The function of the described multi-part piston is as follows:

The volume of the intermediate space 45 is initially maximum as a result of the compression spring 44, wherein the intermediate space 45 can fill with fluid when the check valve 48 is open. The compression spring 44 is preferably dimensioned such that the upper part 38 does not move in the direction of the support part 26 as a result of inertia forces occurring during the up and down movement of the piston.

When the piston 4 moves downwards in an intake stroke and an open intake valve 16, the volume of the gap 45 remains maximum. In a subsequent compression stroke, the pressure in the working chamber increases, so that the upper part 38 moves against the force of the compression spring 44 while reducing the volume of the intermediate space 45 in the direction of the support member 26, since the average cross section of the inlet channel 46 is relatively small, even with the check valve 48 open is and forms a throttle, so that a balance of the pressures in the working chamber 10 and the gap 45 due to a fluid flow from the working chamber into the gap can be delayed. Upon further, in particular rapid pressure increase in the region of the top dead center of the piston or thereafter as a result of the combustion of the fresh charge this pressure increase leads to a further reduction of the volume of the gap 45, whereby occurring in the working chamber pressure peaks are reduced.

In the case of an equilibrium of forces at the upper part 38 which is not adjacent to the step 24, the following applies: p _A × F = p _z × F + K (d), where: PA ⁼ pressure in the working chamber,

F = surface of the upper part 38 adjoining the intermediate space 45, pz = pressure in the intermediate space 45,

K = force of the compression spring 44 depending on the distance d between the upper part 38 and the support member 26th

Thus:

PA - Pz ⁼ K (d) / F. The pressure PA in the working chamber is as long as the upper part 38 can move and does not abut the step 24, that is in principle greater than the pressure pz in the intermediate space, the difference being due to the force of Compression spring 44 is determined.

Because of the throttling effect of the supply channel 46 thus takes place during an increase in pressure in the working chamber 10 at most a restricted inflow of fluid from the working chamber 10 into the space 45. As soon as the pressure in the working chamber 10 decreases, the upper 38 moves under appropriate pressure decrease in the space 45 toward a system at the stage 24, wherein a restricted inflow of fluid from the working chamber takes place in the intermediate space. Once the top 38 abuts the step 24, the volume of the gap 45 in adaptation to the possibly further decreasing pressure in the working chamber 10 does not increase further, so that the pressure in the gap 45, the pressure in the working chamber 10 increasingly exceeds and Check valve 48 closes, so that the pressure in the gap 45 is maintained.

Overall, the described multi-part design of the piston causes that in the space 45 as a result of the compression spring 44 and the already opening at low differential pressure check valve 48 builds a pressure at befindlichem in contact with the stage 24 upper part 38 as a result of unavoidable leakage losses under the The peak pressure occurring during combustion remains, so that pressure peaks occurring during the combustion are reduced and the energy stored by the increase in pressure in the intermediate space 45 and the pressure spring 44 in the subsequent pressure drop in the working chamber. is recovered. The geometric compression ratio is not changed since the upper part 38 remains in contact with the step 24 after only a few work cycles in the TDC of the piston 4 or before the beginning of the combustion.

By tuning the compression spring 44, the required for the opening of the check valve 48 pressure difference at the check valve 48, the surface of the stage 24 (as a result of which caused by the pressure in the working chamber 10, the upper part 38 downwardly urging force when the upper part 38 at the Step 24 decreases suddenly) and the possibly existing leaks from the gap 45 out can be achieved that sets in the space 45 when the upper part of the stage 24, for example, a pressure about the end of the compression stroke or before the start of combustion in the working chamber 10 prevailing pressure corresponds.

The safety valve 52 is dimensioned such that at impermissibly high pressure in the intermediate space 45, for example at a pressure which approaches the combustion peak pressure as a result of very high tightness of the intermediate space 45 relative to the working chamber 10 or the crank chamber opens, so that the pressure in the Interspace 45 is limited to a predetermined maximum pressure.

The exemplified piston can be modified in many ways.

For example, the upper part 38 can be rigidly connected to the ring part 20 and the support part 26 can be displaceable relative to the ring part 20. The upper part then forms a piston body together with the ring part. Alternatively, both the supporting part and the upper part can be displaceable relative to the ring part.

The upper part 38 does not necessarily have to be formed with a combustion bowl 40, which forms the combustion chamber together with the working chamber. A combustion bowl 40 is particularly advantageous for diesel engines.

The discharge channel 50 with the safety valve 52 may be missing and the safety valve 52 may also be designed as a bypass to the check valve 48. The channels can go through the top. The discharge channel can open into the working chamber 10. The support member may be fixed independently of the piston pin on the ring member or in one piece with the Ring member be formed, wherein the upper part is inserted from above into the ring member and is held for example by means of a screwed into the ring member socket as a stop in the ring member.

List of reference cylinders

piston

pleuel

cylinder head

working chamber

inlet channel

exhaust port

intake valve

outlet valve

ring part

Through opening

step

supporting part

piston pin

outer wall

seal

bottom wall

head Start

top

seal

Combustion bowl

step

compression spring

gap

supply channel

check valve

discharge channel

1 crank room

safety valve

Claims

claims

A method of reducing pressure spikes in a combustion chamber (10, 40) of a cylinder (2) of a reciprocating internal combustion engine by use of a piston (4) mounted on a connecting rod (6) connected to a crankshaft which adjusts its position relative to the bearing axis of the connecting rod a pressure increase in the combustion chamber changes such that the volume of the combustion chamber increases.

2. The method of claim 1, wherein the piston (4) is constructed such that a part of its the combustion chamber (10,40) facing surface with pressure increase in the combustion chamber so relative to the other part of the combustion chamber facing surface of the piston shifts, that the combustion chamber volume increases.

3. Piston (4) for a reciprocating internal combustion engine, comprising a piston body with an upper side, a bearing axle arranged at a distance from the upper side for supporting a connecting rod (6) which can be connected to a crankshaft,

a variable volume cavity (45),

a feed passage (46) connecting the top of the piston to the cavity and having a check valve (48) releasing fluid flow from the top of the piston to the cavity, and

a spring (44) urging the upper side in the direction of enlarging the distance between the upper side and the bearing axis, wherein

acting on the top of the piston force is transmitted through effective in the cavity pressure and the force of the spring on the bearing axis and reduces the volume of the cavity at a pressure increase while reducing the distance between at least a portion of the top of the piston and the bearing axis.

4. Piston according to claim 3, having a cylindrical annular part (20) having an axial passage opening (22), in the sealing under the wall of the passage opening with the connecting rod (6) connectable support member (26) and at least a part of Upper part forming the upper part (38) are received, wherein the support member and / or the upper part are displaceable in the axial direction relative to the ring member, a cavity defining the cavity disposed between the support member (26) and the top (38) and connected to the top of the piston via the supply channel (46), the spring (44) being disposed between the top and the support member; pushes the support member away from the upper part and the maximum distance between the support member and upper part is limited.

5. Piston according to claim 4, wherein the support member (26) is axially rigidly connected to the ring member (20).

6. Piston according to claim 4 or 5 wherein the diameter of the upper part (38) is reduced in a step (42) to the working chamber (10) towards the maximum distance between the upper part (38) and support member (26) at a complementary stage (24) of the passage opening (22) is present.

7. Piston according to one of claims 4 to 6, wherein the side facing away from the support part (26) of the upper part (38) is formed with a combustion chamber trough (40).

8. Piston according to one of claims 4 to 7, wherein the intermediate space (45) via a discharge channel (50) with a space outside of the piston (4) is connected and in the discharge channel, a safety valve (52) is arranged, which at one over threshold pressure in the space (45) releases gas flow from the space into the space outside the piston.

9. Piston according to claim 8, wherein the supply channel through the ring member (20) leads.

10. Piston according to one of claims 3 to 9, wherein a bolt (28) for supporting the connecting rod (6) holds the support member (26) rigidly on the ring member (20).