DE7509408U - Piston ring - Google Patents

Description

^ PATENT AGENCIES

> Dlpl-lng. P. WIRTH Dr. V. SCHMIED-KOWARZIK J

Dipi.-lng. G. DANNENBERG Dr. P. WcINHOLD Dr. D. GUDEL

281) 34 β FRANKFURT AM MAIN /

TELEPHONE (0611) 1

2870H OR. ESCHENHEIMER 8TRA86B 3

73 M 298

March 24, 1975

Koppers Company, Inc. Pittsburgh, Pennsylvania United States of America

Piston ring

The invention relates, generally speaking, to piston rings for internal combustion engines and in particular to a piston ring which has a chrome-plated running surface .

Piston rings plated with chrome are known in the prior art. However, there have been difficulties in making and using chrome plated piston rings. For example, British PS 526 states that when a layer of chrome deposited on the ring is ground to produce the final outer diameter of the ring, small and very small pieces of the layer will break off. In the British PS it is proposed to remedy this deficiency by making indentations in the length of the ring and depositing the chromium in these indentations . In US-PS 2,380,654 one seeks to solve the problem, and thereby also to break in the ring

make it easier for the chrome to be deposited in a concave surface of the ring «and the outer ends of the Rings as sharp lines of the base metal to scrape off the cylinder wall and oil in the recessed or concave and to hold it in place with chrome plated part of the ring. U.S. Patent 3,573,874 has advanced the practice by that a plurality of axially spaced, circumferentially extending and spaced apart Ridges and ridges are provided in the chrome plated surface to collect and hold the oil.

In general, chrome plated rings have been used successfully in common diesel engines. However, the working conditions that exist in some modern high-revving and high-powered diesel engines cause piston ring breakage, which can occur even during the warranty period of the engine. In one of these engines, the stresses exerted on the compression rings caused such a high degree of fatigue cracking in the rings that continued production of the engine was called into question. Before production of the engine was actually discontinued, an emergency test program called the "Accelerated Test of Ring Break ¹¹ " was initiated to screen new ring constructions. This accelerated test was accomplished by eliminating the margin between the The upper compression and the piston groove were increased from nominally 0.101 mm to 0.432 mm. This change increased the fiber tension on the ring by giving the ring a more pronounced curve in the hat, as shown by the hia In addition, major changes in the load and in the heat circuit of the engine were caused by the speed of the engine periodically alternating between idle speed for a period of 10 seconds and subsequent acceleration of the speed about 25 pounds over the hem speed was changed and this

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Maintain speed for a period of 20 seconds became. Such periods of work were repeated over a period of 100 hours. Since the chrome plating of the Base ring makes it possible to produce the base ring from materials of various types that have high strength because the hard chromium absorbs the wear load was investigated by examining the use of various base ferrous metals for aimed at the body of the piston ring, the wear resistance, maintain the corrosion resistance and low coefficient of friction of the chrome plating. A large number of ferrous metals, including martensitic ductile iron species, cold formable irons, stainless steel, shotpeened rings were tested; but in all cases came dia rings break in periods smaller than those provided 100 hours were.

It has been found that the chrome plating reduces the endurance limit stresses (endurance lim '?; - fatigue life) and that by creating a chrome-free base metal surface on each side of the chrome plating, the chrome is removed from the area of maximum stress xaiL rings are created, which have greatly increased fatigue limit stresses, especially when the ratio of the width of the exposed base metal surface to the width of the chrome plating is kept between 5 and 30 # of the ring width. According to the invention, a piston ring is thus provided which has a solid, provided with a gap body made of ferrous metal, which has a groove in its outer circumferential surface, whose side flanks diverge in the radial direction and which extends completely around the circumference of the running surface around; The hat has a length which corresponds to the length of the circumference of the circumferential surface, but has a width which is less than the width of the circumferential surface, so that the hat lies between plateau areas ^ _{β β} "of the base metal. Pie groove is filled with electrolytically precipitated chromium.

Embodiments of the invention are described below, for example with reference to the drawings, namely show:

1 is a perspective view of a ring made according to the invention;

Fig. 2 shows on a larger scale a cross section along the line II-II of the ring according to Figure 1;

3 shows, on a larger scale, a cross-section of an embodiment in which the circumferential surface is ab, 2: is inclined (in the range from 1/2 to 4 °);

4 shows, on a larger scale, a cross-section of an embodiment, referred to as the Keystone Ring;

5 shows, on a larger scale, a cross-section of an embodiment, in which a spherical peripheral surface is provided;

6 shows, on a larger scale, a cross-section of an embodiment with a spherical peripheral surface and a chamfered Plateau area, and

Fig. 7 is a diagram in which the bends of the ring are shown as a function of the number of load changes (cycles) »

According to the drawings, the piston ring according to the invention is produced from a conventional metal piston ring blank 10, which is an angular ring member provided with a gap. Any conventional piston ring material can be used for this blank, for example cast iron, steel grades and stainless steels} As FIG. 2 shows, there is an angled groove λ2 on the circumference or on the outer circumferential surface or running surface of the piston ring blank 10 by machining

manufactured.

7509408 27.0177

was

The groove is fairly flat and has a flat bottom or groove 13. The side flanks of the groove are outwardly in inclined at an angle A of 35 to 80 °, preferably by about 55 °. The thickness W of the base metal, which in the area of the circumferential surface " remains after the groove has been made, is 5 to 30 # of the thickness B of the ring, preferably about 27 $.

When the ring is made, it will be

brought to its exact outer diameter and the desired profile, after which the groove 12 is made in the ring. Groove depths of 0.228 to 0.748 mm (0.009 to 0.0295 inches) allow gradual finishing after plating such that a finish of 0.0508 to 0.508 mm (0.002 to 0.020 inches) is obtained. A number of these pieces are placed concentrically with one another on a plating spindle and are closed in such a way that only their running surfaces are exposed to the plating bath. The chromium filling 17 is then electrolytically deposited until the precipitation is a few thousandths of an inch (a few hundredths of a mm) greater than the depth of the groove. The plating can be done in the usual way . An example of a typical composition of the plating bath is given by the following numbers: chromic acid - 90 g / l to 560 g / l (12 to 75 οζ per gal.), Sulphate - 75 g to 450 g / l (10 to 60 oz per gal.) gal.); The operating parameters include a bath temperature of - 32.5 to 60 ⁰ C (90 to 14O ⁰ P) and current density - 0.465 to 0.775 A / cm ² (3 * 0 to 5 _t 0 asi.). The plating of the chrome is continued for a period of time sufficient to obtain the desired thickness of the layer. The Plattierspindel is then removed from the bath, and the ring is ground such that the Srundmetall auberefcn§zw as a Plat _e. one on each side of the deposited chromium layer 17 is exposed. Grinding removes surface roughness and chrome nodules so that the surface becomes smooth and the fatigue limit or fatigue strength is increased. Grinding frees the chrome from tensile stresses (chrome has low tensile strength), namely

7509408 27.0177

·> ··· ■ * ti "n ¹

- 6-

this appears due to the fact that the chrome of cten highly stressed '

"* Vi *

Part 15 of the ring is removed. _f

The rings produced according to the invention show in operation surprising properties. On the first try with one Engine that ran in FiJ. Ϊ shown ring 400 hours without to fail. On a retry attempt using new rings, these 2 hours ran without any problems. In the case of wear-and-tear on the totor (in such tests If fine dust is continuously introduced into the cylinder through the intake pipe) the engine ran for more than 200 hours without that rupture of the rings occurred, and the rupture did not occur until after abrasion of 25 # the radial wall thickness · Some engines have reached more than 160 * 000 km in actual operation without the rings breaking.

A standard compression ring or piston ring (FIGS. 1 and 2) has a simple rectangular cross-section and is used in all cases used in which dfe working conditions do not require a special design of the rings.

A beveled ring according to FIG. 3 has a bevel of 1/2 to 4 ° on its outer circumferential surface, which depends on the size of the ring. The bevel has the advantage that the ring runs in faster than any other normal piston ring. This advantage makes the beveled ring particularly useful for use with hardened cylinders. With cylinders that are out of round or warped, the ability of the beveled ring to break in quickly prevents blow-through from occurring.

The trapezoidal ring according to Pig. 4 is similar to the piston rings similar to gt _p with the difference that its end faces _. are bevelled or drafted towards the inside. The groove in the piston into which this ring is inserted must be the same

have quietly bevelled side surfaces,

Ill 111!

I I > III

whose bevel angle is the same as that of the ring is used. This construction allows the piston to be designed in such a way that the webs between the grooves of the piston are reinforced. While the engine is working, the

. " _En relative movement between the ring and piston causes the formation / of carbon, so that the trapezoidal ring tends to prevent the piston ring from sticking together."

Pig's ring. 5 has a spherical circumferential surface.

Pig's ring. 6 has a spherical peripheral surface and a chamfered edge area.

A piston ring is described above which has the good wear properties of a ring plated with chrome. Tests with conventional rings with a chrome-plated circumferential surface, in which Bru> h occurred, show that the break results from fatigue on the upper or lower outer edge ^; the ring enters; these edges are evidently the places of greatest concentration of space. In the case of conventional rings, this area is provided with a chrome coating. The chrome plating of a conventional ring reduces the fatigue limit stress on the piston ring (this limit stress is the highest stress that the metal can absorb without fatigue failure occurring) By maintaining the chrome plating on part of the running surface of the ring according to the invention, but outer ring shoulders made of the base metal

exist, 'it is possible to place a higher load on the ring without causing fatigue cracks. When comparing a conventional, chrome-plated ring with a ring made according to the invention, test results show that if both rings are of the same size, the ring according to the invention has a fatigue limit stress that is 27 $> higher than the conventional ring, as shown in FIG Pig. 7 is shown »

7509408 27.0177

Electrolytically precipitated chromium has strong residuals Residual stresses. According to the invention, it has been shown that these high residual stresses cause fatigue cracks or fractures causing premature breakage of the usual chrome plated piston rings, which include the entire Peripheral surface is electrolytically coated with chrome. According to of the invention is enhanced by the omission of the chrome plating the service life of the

\ Rings without reducing the wear properties of the ring

be set.

! It has been found desirable prior to implementation

! of experiments in a diesel engine, the various piston ring

Evaluate execution types by means of a fatigue test in order to achieve the

\ Determine fatigue limit stress. The fatigue limit

\ stress is defined as the maximum stress that a

\ Material can be subjected to an infinite number of times without breaking

\ is caused. It was found that good interchangeability

■ relationship between the fatigue limit stress and the working method of the piston ring in the engine. The fatigue limit stress values is obtained by plotting the voltage as a function of the number of load changes (cycles) in the form

j of curves commonly referred to as S-N curves.

It is known in principle that a metal stressed in the elastic range assumes its original dimensions again after the stress has been removed, provided that sufficient time has passed. D5, however, it is not the pail if the metal is stressed in the elastic range with high repetition speed. Depending on the load applied, the metal finally breaks " due to fatigue" within a certain time interval.

L Before testing a piston ring on a fatigue testing machine

or endurance testing machine becomes an attempt to plague

7509408 27.0177

Loading as a function of the bend or bend on each ring is carried out by looking at the compression The receiving surface of the ring applies a compressive load and measures the amount of deflection. For each Differential of the bend, the load (F ~) is recorded and the load curve is drawn up as a function of the bend. The tension in kp / cm is then either measured or for different bends according to the next formula calculated:

6F _D (Dd) (2a + b)

S =

d ² (a ² + 4? -b + b ² )

whereby:

S = tension, kp / cm
FQ = load, kp

d = ring wall, cm
b = ring thickness, cm
a = b-2d tg O ^

Ot = wedge or trapezoidal angle of the piston ring cross section.

The ring is then put into the fatigue or endurance test machine installed, in which one end of the gap is fixed and the other end is bent or bent so that in the the outer fibers of the ring create a high tension. If the tests are started with a high voltage level, sin occurs Fatigue failure after a small number of load changes. The test results are recorded for each stress level, and then the tension level is lowered and the process is repeated. If the ring has over 10 million load changes. was bent without breaking, a horizontal line is drawn in the diagram that shows the bend as a function of on the number of load changes (or the voltage as a function of the number of load changes). The horizontal line

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- 10 -

represents the fatigue limit stress of the material. Another line is drawn through the points at which each of the tested stress levels fracture occurred at the minimum of load changes. The falling line denotes the fatigue limit stress values of the material with a low number of load changes · This is how the diagram according to Pig · 7 was developed Apez ring, which is plated with chrome over its entire circumferential surface The s is the standard version ► The line labeled B shows the results for a ring which is designed according to the embodiment according to Pig.

The Ermtidungsversuche comparative show that the produced according to the invention, significantly better with chrome-plated ring values gives as an embodiment of the ring, the chromium plating extends in the entire outer circumferential surface of the ring. Tests with engines not only confirmed the improved fatigue test results, but also showed that the superior wear properties of the chrome plating were not impaired by the fact that the chrome was placed in a groove according to the invention.

Claims (1)

Da / Kt G 75 09 408.5 April 26, 1976 Koppers Company, Inc. 73 M 298 Protection requirements: 1. Piston ring with a solid body made of ferrous metal, one gap and one with chrome in the circumferential surface has filled groove, characterized in that the groove (12) provided with a flat groove base (13) has side flanks (14) which are inclined outwards by an angle (A) of 35-80 °, that the groove is one of the length of the! start of the The circumferential surface has a corresponding length, but a width that is smaller than the width of the circumferential surface, with the groove between the flateaus (15) of the ferrous metal body, which is: Width (W) 5 - 30 % of the width (B) of the circumferential surface * is, and that the groove is filled with electrolytically deposited chromium (17). 2. piston ring according to claim 1, characterized, that the angle of inclination (A) of the side flanks (14) of the Groove (12) is about 55 °. 3. Piston ring according to claim 1 or 2, characterized, that the width (W) of the plateaus is about 27 % of the width (B) of the ring. 4 piston ring according to one of claims 1-3, characterized in that the outer surface of the chrome filling (17) is convex (Figs. 5 and 6). - Claim 5 - 7509488 27.0177 5. Piston ring according to one of claims 1-3, characterized in that the circumferential surface is beveled 1/2 - 4 ° (Fig. 3) 6. piston ring according to claim 4, d & characterized in that the outer parts of the ring are chamfered (Fig.4-6). 7. Piston ring according to one of the preceding claims, characterized in that; that the end faces of the »ring (10) are bevelled inwards (Fig.4). sentafiwalt: -7- η Dannenberg & 7509408 01/27/77