JP2000054911A - Piston for reciprocating piston internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a piston so as to elongate its service life even under a relatively high ignition pressure with a simple means at a low cost. SOLUTION: In this reciprocating piston internal combustion engine, especially a piston for a large engine comprises at least one piston ring groove 3 having a plurality of flanks 4 provided for a piston ring 4 and protected against abrasion. In the piston, a surface of at least one flank is provided with an outer end peripheral region 7 formed of a curing material and an inner region 8 adjacent to the outer end peripheral region 7 and almost made of chromium, whereby a service life of the piston can be elongated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a reciprocating piston internal combustion engine, in particular a large engine, provided with at least one piston ring groove provided for a piston ring and having a plurality of flanks protected against wear. Related to the piston.

[0002]

2. Description of the Prior Art It is known to harden a ring groove flank on the top of a piston made of hardenable steel for the purpose of wear protection. However, this measure is still insufficient above a predetermined ignition pressure. That is, the flank load increases excessively as the ignition pressure increases. In this connection, recently proposed low lubrication rates are also not preferred. As a result, the hardened flanks also wear rapidly. This is especially true for the edge region. It is, according to experience, very heavy.

Attempts have also been made to increase the resistance of the ring groove flank by means of a chromium coating. However, chromium is harder than hardened steel in the low temperature range, but wear resistance decreases at high temperatures. As the ignition pressure increases, the surface pressure and surface friction increase, thereby increasing the material temperature. Thus, at ignition pressures above 160 bar, as required today, the chromium coatings described above do not improve.

[0004]

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide a piston of the type mentioned at the beginning with a simple and inexpensive means of achieving a long service life under relatively high ignition pressures. Is to improve it.

[0005]

According to the invention, it is provided according to the invention that the surface of at least one flank comprises an outer edge region formed by a hardening material and an inner region consisting essentially of chromium adjacent thereto. Achieved by

[0006] Experience has shown that the highest surface pressures occur in the edge region and therefore also the highest material heating. This area is therefore protected by the chrome. However, chromium has reduced wear resistance at high temperatures. In this region, a hardening material having higher resistance than chromium at high temperature is provided. The effect of the chromium reinforcement extends to the interior, where the material heating is not so intense that the chromium loses its resistance. During operation, first of all, a large load on the edge area causes an initial wear of the hardened material in the edge area. First, when the micro layer of this material is removed, the load shifts in the depth direction of the groove, and the original chromium acts. Thereby, the peak load present in the edge region is first removed and the load shifts inward. As a result, the load area value is kept constant. Correspondingly, a relatively balanced support pattern results, which leads to a long service life.

[0007] Preferred configurations and modifications of the present invention are described in claim 2 and the following. For example, within at least one flank region, there is provided a curing zone formed over the entire flank width and formed by a stiffening material, wherein the stiffening zone has a thickness remote from the outer edge and less than the thickness of the stiffening zone. A fitting part consisting essentially of chrome can be fitted. The protection of the chrome inset over the entire width by the hardening material in the adjacent edge region preferably results in a step or discontinuous pattern, which better resists peeling or removal of the inset. be able to.

The inset may be constructed as a conductively made filling of a receiving pocket provided in the region of the curing zone. This provides a particularly simple and low-cost manufacturing method and gives good fixation of chromium.

Another advantageous measure is to provide 15% to 20% of the width of the flank, provided that the width of the edge region is at least 1.5 mm. This measure provides certain protection against edge area flaking.

The thickness of the fitting portion is 3/10 mm to 1
It can be in the range of 0/10 mm.
In this way, a sufficient load capacity can be obtained despite a small material consumption.

Another preferred measure is to expand the fitting into a conical shape with respect to the support surface in the outer edge region. By doing so, a seam inclined with respect to the piston axis is formed between the fitting portion and the hardening material.
Chromium adheres to the hardened material in the joint region, and it is possible to prevent the shearing action in the joint region, that is, the occurrence of a cut.

In the simple case, it is sufficient if at least the flank remote from the combustion chamber is constructed according to the invention. This is because these flanks are the most wear-resistant. However, both flanks of the ring groove may be constructed according to the invention. This is because a similar load pattern is applied to the opposite side. On the other hand, the required expenses are relatively low.

Another advantageous configuration is that at least one flank of the piston ring, preferably both flank,
An outer peripheral edge formed by a hardening material and an inner region substantially made of chromium adjacent thereto are provided.
This provides the same material pair in the contact area, which has a favorable effect on preventing corrosion.

Further preferred embodiments of the invention are described in the dependent claims and will become apparent from the following description of embodiments with reference to the drawings.

[0015]

DETAILED DESCRIPTION OF THE INVENTION The basic structure and operation of a reciprocating piston internal combustion engine, for example a large diesel engine, is known.
Therefore, detailed description thereof is omitted here. FIGS. 1 and 2 show a cylinder liner 1 in which a piston 2 that reciprocates, here moves up and down, is arranged. The piston 2 defines a combustion chamber that can expand and contract, and operates together with the crankshaft. Preferably, a plurality of circumferentially running piston ring grooves 3 are provided in the upper part of the piston 2 which is detachably incorporated in the lower part of the piston 2, and each receives a radial force therein. Piston ring 4 that abuts cylinder liner 1 on its outer periphery
Is provided.

The upper part of the piston 2 is made of a heat-treated alloy steel, so that in the region of the upper and lower flank of the piston ring groove 3 a hardening zone 5 is formed which extends over the support region of the flank width. Has been cured. This is indicated in FIGS. 1 and 2 by a hatched decorative line. The thickness of the curing zone 5 gradually decreases from the outside to the inside. Curing zone 5
Consists of martensite. Accordingly, the hardening step is performed such that the austenitic structure is converted to a martensitic structure. The curing step can be performed by an induction method, and as a result, it is possible to easily perform the temperature treatment necessary for performing the desired tissue conversion. The piston ring 4 is also made of alloy steel.

Into the hardening material of the hardening zone 5, a fitting 6 made of chromium or a chromium alloy is fitted. The inset 6 extends from a region remote from the outer groove edge to the inner end of each curing zone 5, the thickness of which is less than the minimum thickness of the curing zone 5. To this end, the surface of the ring groove flank facing the piston ring 4 has an edge region 7 consisting of a hardening material, here martensite, and an inner region 8 consisting essentially of chromium adjacent thereto.

The inset 6 may be configured as a hardened chromium plating method and may be configured as an electrically created fill in a receiving pocket 9 formed by a suitable recess in the hardening material of the corresponding hardening zone 5. The receiving pocket 9 can be made by lathing or polishing a hardened material.
This processing step is preferably performed after the curing step. The surface is preferably polished again after mounting by chrome plating.

The width of the edge region 7 is 15% to 20% of the groove depth.
%. However, its width must be at least 1.5 mm to guarantee sufficient stability. The thickness of the chrome fitting is 3/10 to 1
mm. The outer edge of the fitting portion 6
In the example shown, the support surface 10 is conically enlarged with respect to the support surface, so that a support surface 10 inclined with respect to the piston axis is formed. Therefore, a vertical support force is applied in the region of the inclined support surface 10, thereby effectively preventing a cut pattern or a step-like pattern. The tilt angle of the support surface 10 can be 45 °.

In a simple case, the chrome fitting 6 may be provided only in the region of the ring groove flank remote from the combustion chamber, usually in the region of the lower ring groove flank. In the example shown, a chrome insert 6 is provided in the region of both ring groove flanks, which ensures a high degree of wear resistance of the ring groove flanks near the combustion chamber.

The embodiment shown in FIG. 2 is different from the embodiment shown in FIG. 1 in that chrome fitting portions 11 are additionally provided in both flank regions of the piston ring 4, and the chrome fitting portions 11 are not provided. The difference is that the piston ring 4 is not provided up to the outer edge but is separated from the outer edge so that the edge region 12 made of the base material remains. The edge region 12 is, in effect, a steel-to-steel and chromium-to-chromium material pair in the installation area of the opposing piston ring 4 and the piston ring groove 3,
Thereby, battery action is prevented and a high degree of corrosion resistance can be achieved. In the example shown, the outer peripheral surface of the piston ring 4 is provided with an additional reinforcing part 13, for example a plasma layer or a ceramic layer.

According to experience, a very high load is generated in the region of the outer peripheral edge of the ring groove flank. In that case,
At the start of operation, the hardened material in the edge region 7 initially bears the full load. In that case, a load pattern occurs as shown by the characteristic line 14 in FIG. This load pattern indicates that a large peak load occurs on the edge side. As soon as the micro-layer of hardening material in the edge region 7 is peeled off, the peak load shifts in the depth of the groove, and the chromium material of the chrome insert 6 now bears the load. Correspondingly, the peak load in the edge region is removed and the load increases on the inside, as shown by the load pattern of characteristic line 15 in FIG. This shift is performed so that the integrated values become equal under the load patterns shown by the characteristic lines 14 and 15. The comparison of the load patterns by the two characteristic lines 14 and 15 shows that in the configuration of the present invention, the load balancing action is performed, and that each material is appropriately applied. Here, only hardened steel is provided, but the peak load has been eliminated. On the other hand, below the critical temperature, the load of the high load-resistant chromium is increased, and the surface integral value is kept constant. At the same time, chromium is kept free from areas where the highest material heating is expected. Therefore, particularly long life can be expected by this optimization.

[0023]

According to the present invention, it is possible to provide a piston which has a long life even under a relatively high ignition pressure by means of simple and low-cost means.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a main part of a piston according to the present invention, which has a chrome fitting portion provided in both groove edge regions.

FIG. 2 shows a chromium fitting in the region of the two groove flanks and the piston ring flanks opposed thereto.
FIG. 7 is a longitudinal sectional view showing another configuration example according to the present invention corresponding to FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder liner 2 Piston 3 Piston ring groove 4 Piston ring 5 Hardening zone 6 Fitting part 7 Edge area 8 Inner area 9 Receiving pocket 10 Protection surface 11 Chrome fitting part 12 Edge area 13 Reinforcement part 14 Characteristic line 15 Characteristic line

Claims (14)

[Claims] 1. A reciprocating piston internal combustion engine having at least one piston ring groove (3) provided for a piston ring (4) and having a plurality of flanks protected against wear, especially for large engines. In the piston,
For a reciprocating piston internal combustion engine, characterized in that the surface of at least one flank comprises an outer edge region (7) formed by a hardening material and an inner region (8) consisting essentially of chromium adjacent thereto. piston. 2. In at least one flank region there is provided a curing zone (5) formed over the entire flank width and formed by a stiffening material, in said stiffening zone (5) spaced apart from an outer edge; The piston according to claim 1, characterized in that a fitting (6) consisting essentially of chromium having a thickness smaller than the thickness of the hardening zone (5) is fitted. 3. A piston ring groove (3) made of a hardenable steel material, said piston ring groove (3) spanning the entire flank width, at least in the region of the flank, and said fitting (6). 3. Receiving pocket (9) which is hardened to a depth exceeding the thickness of the fitting and which corresponds to the fitting (6).
The described piston. 4. The fitting (6) is characterized in that it is configured as a conductively produced filling of a receiving pocket (9) provided in the region of the curing zone (5). The piston according to claim 2. 5. The piston according to claim 2, wherein the receiving pocket is configured as a hollow. 6. The width of the edge region (7) corresponds to 15% to 20% of the width of the flank and is at least 1.5 mm. The piston according to one. 7. The fitting part (6) has a thickness of 3/10.
A piston according to any one of claims 2 to 6, characterized in that it is in the range from mm to 1 mm. 8. The piston according to claim 2, wherein the fitting (6) extends conically in the outer region with respect to the support surface. 9. The chromium inner region (8) is continuous from the edge region (7) to the radially inner flank end.
The piston described in one of the above. 10. The flank of said piston ring groove (3), at least spaced from the combustion chamber, has an outer edge region (7) formed by hardened material and an inner region (8) consisting essentially of chromium adjacent thereto. The piston according to any one of claims 1 to 9, further comprising: 11. The flank of the piston ring groove (3) has an outer edge region (7) formed by a hardening material.
And an inner region (8) consisting essentially of chromium adjacent thereto.
0. The piston according to any one of 0. 12. The piston ring (4) has a surface in at least one flank region having an outer edge region (12) formed by alloy steel and an inner region (11) consisting essentially of chromium adjacent thereto. The piston according to any one of claims 1 to 11, further comprising: 13. The flank of the piston ring (4) remote from the combustion chamber has a surface with an outer edge region (12) formed by alloy steel and an inner region (11) consisting essentially of chromium adjacent thereto. The piston according to any one of claims 1 to 12, wherein the piston is provided. 14. The flank of the piston ring (4) has a surface having an outer edge region (12) formed by an alloy steel and an inner region (11) of substantially chromium adjacent thereto. The piston according to any one of claims 1 to 13, characterized in that: