JP4417481B2 - Reciprocating piston Piston for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The invention relates to a reciprocating piston internal combustion engine, in particular a piston for a large engine, provided with at least one piston ring groove provided for the piston ring and having a plurality of flank protected against wear.
[0002]
[Prior art]
For the purpose of wear protection, it is known to harden the ring groove flank at the top of the piston made of hardenable steel. However, this measure is still insufficient above a predetermined ignition pressure. That is, as the ignition pressure increases, the load on the flank increases excessively. The proposal of a low lubrication rate recently proposed in connection with this is not preferable. As a result, the cured flank also wears rapidly. This is especially true for the edge region. There is an extremely large load according to experience.
[0003]
Attempts have already been made to increase the resistance of ring groove flank by chromium coating. However, chromium is harder than hardened steel in the low temperature region, 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, the chromium coating described above does not improve under ignition pressures above 160 bar as required today.
[0004]
[Problems to be solved by the invention]
In view of the above circumstances, it is an object of the present invention to improve a piston of the type described at the outset so that a long life can be achieved with relatively simple ignition costs under relatively high ignition pressures.
[0005]
[Means for Solving the Problems]
This object is achieved according to the invention by the fact that the surface of at least one flank comprises an outer edge region formed by a hardener and an inner region consisting essentially of chromium adjacent to it.
[0006]
Experience has shown that the highest surface pressure occurs in the edge region and therefore also the highest material heating. This area is therefore protected by chromium. However, chromium has low wear resistance at high temperatures. This region is provided with a hardener having a higher resistance than chromium at high temperatures. The effect of chromium reinforcement is also internal, where the material heating is not so intense that chromium loses its resistance. During operation, first of all, when a large load is applied to the edge region, initial wear of the hardened material occurs in the edge region. First, when the microlayer of this material is extracted, 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 life.
[0007]
Preferred configurations and modifications of the present invention are described in claims 2 and the following. For example, in at least one flank region, there is provided a curing zone extending over the entire flank width and formed by a curing material, wherein the curing zone has a thickness less than the thickness of the curing zone, spaced from the outer edge. It is possible to fit an inset made of chrome. The entire width of the chrome indentation is protected by a hardener in the adjacent edge region, preferably resulting in a stepped or discontinuous pattern, thereby better resisting the removal or removal of the inset. be able to.
[0008]
The inset may be configured as a filling made with the conductivity of a receiving pocket provided in the region of the curing zone. This gives a particularly simple and low-cost manufacturing method and gives good adhesion of the chromium.
[0009]
Another advantageous measure is 15% to 20% of the flank width, provided that the width of the edge region is at least 1.5 mm. This measure provides a certain protection against peeling off of the edge area.
[0010]
The thickness of the inset may be in the range of 3/10 mm to 10/10 mm. By doing so, a sufficient load capacity can be obtained despite a small material consumption.
[0011]
Another preferred measure is to extend the inset in 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 shaft is formed between the fitting portion and the hardened material. Chromium adheres closely to the hardened material in the joint region, and shearing in the joint region, that is, generation of breaks can be prevented.
[0012]
In simple cases, it is sufficient to construct at least the flank spaced from the combustion chamber according to the invention. This is because these flanks have the highest wear resistance. However, both flank of the ring groove may be configured according to the present invention. This is because a similar load pattern is given to the opposite side. On the other side, the required expenses are relatively low.
[0013]
Another advantageous configuration is that at least one flank of the piston ring, preferably both flank, is provided with an outer peripheral edge formed by a hardened material and an adjacent inner region consisting essentially of chromium. In this way, the same material pair is provided in the contact area, which has a favorable effect on preventing corrosion.
[0014]
Other preferred configurations of the invention are described in the dependent claims and will become apparent from the description of the embodiments described below 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, are well known and therefore their detailed description is omitted here. A cylinder liner 1 is shown in FIGS. 1 and 2, and a piston 2 that reciprocates, in this case, moves up and down, is disposed in the cylinder liner 1. The piston 2 defines a combustion chamber that can be expanded and contracted, and operates with the crankshaft. Preferably, a plurality of piston ring grooves 3 that run in the circumferential direction are provided in the upper part of the piston 2 that is removably incorporated in the lower part of the piston 2, and each receives a radial force therein, A piston ring 4 that is in contact with the cylinder liner 1 on the outer periphery thereof is provided.
[0016]
The upper part of the piston 2 is made of heat-treated alloy steel, which is hardened in the region of the upper flank and lower flank of the piston ring groove 3 so as to form a hardening zone 5 extending over the support region of the flank width. Yes. This is shown in FIG. 1 and FIG. 2 by hatched decorative lines. The thickness of the curing zone 5 gradually decreases from the outside to the inside. The hardening zone 5 consists of martensite. Accordingly, the curing process is performed such that the austenite structure is converted to a martensite structure. The curing step can be performed by an induction method, and as a result, it is possible to easily perform a temperature treatment necessary for performing a desired tissue transformation. The piston ring 4 is also made of alloy steel.
[0017]
The hardened material in the hardened zone 5 is fitted with a fitting portion 6 made of chromium or a chromium alloy. The inset portion 6 extends from a region separated from the outer groove edge to the inner end of each curing zone 5, and the thickness thereof is thinner than the minimum thickness of the curing zone 5. Therefore, the surface of the ring groove flank facing the piston ring 4 has an edge region 7 made of hardened material, here martensite, and an inner region 8 made of almost chromium adjacent thereto.
[0018]
The inset 6 is preferably constructed as a filling made electrically in the receiving pocket 9 formed by a suitable recess of the hardened material in the corresponding hardened zone 5 according to the hardened chrome plating method. The receiving pocket 9 can be made by turning or polishing hardened material. This treatment step is preferably performed after the curing step. The surface should be polished again after being mounted by chromium plating.
[0019]
The width of the edge region 7 is preferably in the range of 15% to 20% of the groove depth. However, its width must be at least 1.5 mm to ensure sufficient stability. The thickness of the chromium inset can be 3/10 to 1 mm. In the illustrated example, the outer edge of the fitting portion 6 is expanded conically with respect to the support surface, and as a result, a protective surface 10 inclined with respect to the piston shaft is formed. For this reason, a vertical supporting force is applied in the region of the inclined protective surface 10, thereby effectively preventing a cut pattern or a stepped pattern. The inclination angle of the protective surface 10 can be 45 °.
[0020]
In a simple case, the chromium fitting portion 6 may be provided only in the ring groove flank region separated from the combustion chamber, usually in the lower ring groove flank region. In the illustrated example, chromium fittings 6 are provided in the region of both ring groove flank, which guarantees a high degree of wear resistance for the ring groove flank near the combustion chamber.
[0021]
The embodiment shown in FIG. 2 is different from the embodiment shown in FIG. 1 in that a chrome fitting portion 11 is additionally provided in both flank regions of the piston ring 4, and the chrome fitting portion 11 is provided in the piston ring 4. It is different in that it is not provided up to the outer edge of the substrate but is separated from the outer edge so that the edge region 12 made of the substrate remains. The edge region 12 effectively has a steel-to-steel and chrome-to-chromium material pair in the equipment area of the opposing piston ring 4 and piston ring groove 3, thereby preventing battery action and thus A high degree of corrosion resistance can be achieved. In the illustrated example, the outer peripheral surface of the piston ring 4 is provided with an additional reinforcing portion 13, for example, a plasma layer or a ceramic layer.
[0022]
According to experience, an extremely high load is generated in the region of the outer peripheral edge of the ring groove flank. In that case, the hardened material in the edge region 7 first bears the full load at the start of operation. In that case, a load pattern as shown by the characteristic line 14 in FIG. This load pattern indicates that a large peak load is generated on the edge side. As soon as the micro-layer of the hardened material in the edge region 7 is peeled off, the peak load is shifted in the depth direction of the groove, and the chromium material in the chromium fitting 6 is now loaded. Accordingly, the peak load in the edge region is removed, and the load increases inward as shown by the load pattern of the characteristic line 15 in FIG. This shift is performed so that the integrated values are equal under the load pattern indicated by the characteristic lines 14 and 15. Comparison of load patterns by both characteristic lines 14 and 15 shows that the structure of the present invention performs load balancing and each material is properly applied. Here, only hardened steel is provided, but the peak load is removed. On the other hand, the load of high load resistance chromium is increased below the critical temperature, and the surface integral value is kept constant. At the same time, chromium is kept from being involved in the region where the highest material heating is expected. Therefore, a particularly long life can be expected by this optimization.
[0023]
【The invention's effect】
According to the present invention, it is possible to provide a piston having a long life even under a relatively high ignition pressure, with 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 is provided with a chromium inset provided in both groove edge regions.
FIG. 2 is a longitudinal sectional view showing another configuration example according to the present invention corresponding to FIG. 1, which is provided with a chromium fitting portion in the region of both groove flank and piston ring flank opposite to the groove flank.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cylinder liner 2 Piston 3 Piston ring groove 4 Piston ring 5 Hardening zone 6 Insertion part 7 Edge area 8 Inner area 9 Receiving pocket 10 Protective surface 11 Chrome insertion part 12 Edge area 13 Reinforcement part 14 Characteristic line 15 Characteristic line

Claims (13)

Provided for the piston ring (4), a piston for reciprocating piston internal combustion institutions having at least one piston ring groove (3) having a plurality of flanks protected against wear, at least one flank in those surface is provided with formed by curing material, an outer edge region (7) and an inner region consisting substantially chromium adjacent thereto (8),
In at least one flank region, there is provided a curing zone (5) extending over the entire flank width and formed by a curing material, said curing zone (5) being spaced from the outer edge in this curing zone (5). A piston for a reciprocating piston internal combustion engine, characterized in that a fitting portion (6) made of substantially chrome having a thickness smaller than the thickness of the reciprocating piston is fitted . At least one piston ring groove (3) made of a hardenable steel material, the piston ring groove (3) being at least in the flank region, over the entire flank width and deeper than the thickness of the fitting (6). 2. Piston according to claim 1, characterized in that it comprises a receiving pocket (9) that is hardened and corresponds to the inset (6) . The fitting portion (6), according to claim 1, characterized in that it is configured as the electrical-made packings of hardening zone (5) receiving pocket provided in the region of (9) piston. 3. Piston according to claim 2 , characterized in that the receiving pocket (9) is configured as a cut-out part . 5. 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 . piston. The piston according to claim 1, wherein the thickness of the fitting portion (6) is within the range of 3/10 mm to 1 mm. Wherein the outer edge of the fitting portion (6), the piston of claim 1, wherein the protective surface inclined with respect to the piston shaft (10) is formed. The piston according to the inner region consisting of chromium (8) is any one of claims 1, characterized in that continuously from the edge region (7) to the flank ends of the radially inner 7. The flank at least separated from the combustion chamber of the piston ring groove (3) has an outer edge region (7) formed of a hardened material and an inner region (8) made of substantially chromium adjacent thereto . The piston according to any one of claims 1 to 8, wherein: 2. Both flank of said piston ring groove (3) are provided with an outer edge region (7) formed of a hardened material and an inner region (8) made of substantially chromium adjacent thereto. The piston as described in any one of thru | or 9. The piston ring (4) is at least one flank area, that it comprises a surface having an inner region (11) comprising a substantially chromium adjacent to the outer edge region (12) and that which was formed of an alloy steel The piston according to any one of claims 1 to 10, wherein: The flank spaced from the combustion chamber of the piston ring (4) has a surface having an outer edge region (12) formed of alloy steel and an inner region (11) consisting essentially of chromium adjacent thereto. The piston according to any one of claims 1 to 11, characterized in that: Both flanks of the piston ring (4) are each provided with a surface having an outer edge region (12) made of alloy steel and an inner region (11) consisting essentially of chromium adjacent thereto. Item 13. The piston according to any one of Items 1 to 12.

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