JPH0329979B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a piston ring for an internal combustion engine, and particularly to an oil ring with a coil expander for scraping excess oil from the inner wall of a cylinder. Piston rings are placed between the piston and the inner peripheral wall of the cylinder, and in the case of automobile engines in particular, one or two piston rings are placed for each piston.
Usually, several oil scraping rings are provided. The oil ring needs to be pressed against the cylinder inner wall at all times for its oil scraping function.
Therefore, an annular coil expander is provided on the inner periphery of the oil ring to press the oil ring against the inner wall of the cylinder. Such an oil ring generally consists of upper and lower side rails and a web connecting these side rails. An outer circumferential groove is formed on the outside of the side rail and the web to receive scraped oil. On the other hand, an inner circumferential groove for fitting the coil expander is formed on the inner circumferential side thereof. Several elongated oil holes are formed in the web to allow the scraped oil to escape from the outer circumferential groove to the inner circumferential groove. The oil that has reached the inner circumferential groove of the oil ring is brought into the piston through an oil drain provided in the piston ring, and from there is finally returned to the oil pan of the engine. Conventionally, in the piston ring as described above, the oil ring was generally made of cast iron, and the shape of the inner circumferential groove thereof was an arc shape corresponding to the circular cross-sectional shape of the coil expander. That is, the coil expander is held tightly in the inner circumferential groove of the oil ring over a portion of its arcuate cross section, for example, approximately half the circumference. However, if the coil expander and the oil ring come into surface contact over a large area in this way, most of the oil holes formed in the web of the oil ring will be blocked. This makes it difficult for the scraped oil to escape from the outer circumferential groove of the oil ring to the inner circumferential groove through the oil hole, and as a result, the oil hole is sometimes completely blocked by oil sludge. In this case, the oil ring can no longer be expected to have much of an oil scraping effect. As a result, oil consumption increased. Furthermore, in conventional cast iron oil rings, it is necessary to increase the web thickness to some extent in order to ensure the necessary strength, which goes against the demand for lighter piston rings.
Furthermore, in the case of cast iron oil rings as mentioned above, when used for a long time, the coil expander easily scratches or wears the inner circumference of the oil ring, resulting in the coil expander digging into the oil ring as a whole. This could easily lead to a decrease in the tension of the coil expander. The object of the present invention is to eliminate the above-mentioned drawbacks. Therefore, according to the present invention, the inner peripheral portion of the steel oil ring has a square shape instead of a rounded arc shape as in the conventional oil ring. Therefore, the coil expander disposed on the inner periphery of the oil ring is held in contact with the oil ring at only two points when viewed in cross section, and is furthermore slightly separated from the web. By making such a two-point contact, even if the coil expander has a different size, the contact point only moves, so that coil expanders of various sizes (diameters) can be applied. Conventionally, the inner circumference of the oil ring and the coil expander were in close contact over a considerable area as mentioned above, so the coil expander and oil ring corresponded one-to-one, and the diameters of the oil rings were different. I had to prepare a corresponding coil expander. The oil ring according to the present invention has a generally I-shaped cross section similar to a railway rail. However, the two-point contact system between the oil ring and the coil expander as described above will accelerate the wear of the oil ring compared to the conventional surface contact over a considerable area. This is because the contact pressure of the coil expander acting on the oil ring is inversely proportional to the contact area between them. In order to prevent such increased wear on the oil ring, according to the present invention, the oil ring is made of steel instead of conventional cast iron. Further preferably, the surface of the coil expander and the surface of the oil ring in contact therewith are subjected to anti-wear treatment. Preferably, the part of the coil expander that contacts the inner circumference of the oil ring is provided with a flat surface part for the purpose of ensuring a contact area, thereby suppressing wear of the oil ring and allowing the coil expander to contact the inner circumference of the oil ring. Make sure not to dig into it. Further, since a steel oil ring has much greater strength than a cast iron oil ring, the required strength can be obtained even if the web thickness is made considerably thinner. Being able to reduce the thickness of the web means that the flexibility of the entire oil ring or the ability to follow the inner wall of the cylinder can be increased, so that a high oil scraping effect can be achieved. Since the upper and lower side rails themselves are formed as rigid blocks, deformation of the oil ring can be prevented and a predetermined pressing force against the cylinder inner wall can be ensured. Other features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings. Figures 1 and 2 show a coil expander 40 and an oil ring 1 of the present invention used in a diesel engine.
is shown. This oil ring 1 is placed in a sill circumferential groove 51 of a piston 50 of an engine. The piston 50 reciprocates within the cylinder bore 63 of the cylinder 60. Oil ring 1 is integrally molded,
It has upper and lower side rails 3A, 3B and a web 5 that connects these both side rails. The side rails are rigid blocks, while the webs are fairly thin-walled and preferably straight. As a result, the oil ring according to the present invention is approximately I as shown in the figure.
take on a form. The side rails 3A, 3B have protruding peripheral sliding surface portions 7A, 7B that slide against the inner wall 61 of the cylinder 60 when the piston 50 reciprocates. These sliding surface portions 7A, 7B preferably have a wear-resistant layer 9.
A and 9B are applied. The wear-resistant layers 9A and 9B are, for example, chromium plating, nickel in which borides, carbides, nitrides, ceramics, etc. are dispersed, composite plating mainly composed of nickel-phosphorous, chromium, or iron, or molybdenum, self-melting. It is formed by a single or mixed sprayed layer (plasma sprayed) of alloy, stainless steel, ferrochrome alloy, etc. When applying plasma spraying, pre-coat with nickel aluminide,
It is also possible to provide a base layer such as a molybdenum-nickel alloy. Apart from this, the wear-resistant layers 9A and 9B may be subjected to hardening (laser, high frequency), nitriding (nitriding, soft nitriding using a gas or salt bath), or perosulfitriding. Furthermore, instead of the wear-resistant layers 9A and 9B shown in FIG. 1, circumferential grooves 30A and 30B are formed in the sliding surfaces 7A and 7B as shown in FIG. 4, and the grooves are filled with a wear-resistant material. You can also do this. The filling material is the wear-resistant layer 9 described above.
The same material as A and 9B may be used. The sliding surface portions 7A, 7B preferably have a trapezoidal shape as shown in FIG. This trapezoidal part has a cylinder wall 61
Narrow flat bearing surfaces 8A, 8B are formed with sharp edges to ensure scraping of the oil on top. In the present invention, since the web thickness is considerably thinner than in the past, the flexibility of the oil ring is increased, and therefore, the necessary surface pressure can be ensured even if the surface area of the bearing surfaces 8A, 8B is considerably reduced. Furthermore, the surface pressure acts uniformly on the cylinder wall surface due to the high flexibility of the oil ring. Of course, if a wear-resistant layer 9A, 9B is applied, the bearing surfaces 8A, 8B are provided on this wear-resistant layer. The oil ring 1 has an outer circumferential groove 15 formed by the side rails 3A, 3B and the web 5,
The oil scraped off by the sliding surfaces 7A and 7B is received in this outer circumferential groove. Further, an inner circumferential groove 17 formed by the side rails 3A, 3B and the web 5 is formed on the inner circumferential side of the oil ring 1. Side rails 3A, 3 forming inner circumferential groove 17
The inner facing walls of B are formed as inclined flat surfaces 11A and 11B. The angle formed by these inclined flat surfaces is 60° to 120°, preferably 90°. Inclined flat surface 11
Since the coil expander 40 is rubbed on A and 11B, it is preferable to apply wear-resistant treatment layers 13A and 11B.
13B is provided. The wear-resistant layer may be, for example, a chromium plating layer or a nitrided (including persulphur-nitrided) layer. The web 5 of the oil ring 1 preferably has a third
As shown in the figure, a large number of small rectangular, oval, or circular oil holes 21 are arranged along the circumferential direction. In the case of a steel oil ring, the strength is greater than that of a cast iron oil ring, so the number of oil holes 21 can be considerably increased. The oil hole 21 connects the inner circumferential groove 17 and the outer circumferential groove 15 of the oil ring, and the scraped oil flows into the inner circumferential side of the oil ring through the oil hole 21. Therefore, being able to increase the number of oil holes 21 means that smooth passage of oil can be guaranteed. Note that the oil that has come inside the oil ring passes between the windings of the coil expander 40 and is further brought into the piston through an oil relief hole (not shown) provided in the piston 50. The oil ring is the circumferential center line L of the web 5.
It is symmetrical with respect to (Figure 3). The coil expander 40 is as shown in FIG.
Preferably, a wire 43 having a cross-section with a partially cut out circle is wound into a coil, and the cutout forms a flat contact surface portion 45 . That is, the coil expander 40 makes surface contact with the inclined flat surfaces 11A and 11B of the oil ring at two points through the flat contact surface portion 45. The flat contact surface 45 is provided by:
The purpose is to reduce the pressure acting on the oil ring at two points by increasing the contact surface area. The cross-sectional shape of the wire 43 is not limited to a circle, but may be rectangular, square, or other shapes. The coil expander 40 is placed within the inner circumferential groove 17 of the oil ring 1 and presses the oil ring against the cylinder wall. According to the present invention, the coil expander 40 does not come into surface contact with the inner periphery of the oil ring over a considerable area as in the prior art, but instead comes into contact with the inclined flat surfaces 11A and 11B of the side rail at 2 in cross-sectional view. Only the points touch. That is,
According to the invention, the coil expander 40 does not come into contact with the web 5 of the oil ring 1, but is separated by a small gap 19. The web 5 is preferably provided with a recess 18 having rounded corners 18' for forming a gap 19. Round corners 18' are preferred over square corners, which are more prone to cracking due to internal stress concentrations. The outer periphery of the coil expander 40, that is, the wire 43 is marked with
It is desirable to provide a wear-resistant layer such as chromium plating or nitriding (including persulphur-nitriding) as shown in FIG. If the gap 19 were not provided as in the prior art, most of the oil hole 21 would be blocked by the coil expander, making it difficult for oil to pass through.However, according to the present invention, this drawback is eliminated. The oil ring of the present invention meets, for example, JIS standards.
SWRS, SWRH, SWOSC, SWOCV, SK,
It can be formed from steel materials such as SUP and SUS. Further, the oil ring of the present invention can be easily manufactured from a rod-shaped, wire-shaped or band-shaped steel material having a uniform cross section by a conventional drawing or rolling method. The material drawn or rolled into the cross-sectional shape shown in FIG. 1 is hardened by heat treatment, but the oil holes 21 are generally punched before the hardening process. However, in the present invention, the thickness of the web is so thin that it is even possible to punch the oil holes 21 after the curing process. After punching the oil holes, roll the material into a coil, cut it to a predetermined length, insert a pin into the abutment, and abut the abutments to obtain an annular coil expander. In the case of conventional cast iron oil rings, punching is not possible, so the oil holes had to be milled. However, as is well known, when a hole is drilled by milling, burrs tend to form on the edge of the hole, and the wall thickness near the hole is thicker than other parts, resulting in a uniform oil ring width (see Figure 5). ) and flatness could not be obtained.
The burrs come off while the engine is running and get stuck between the piston ring and the cylinder wall, causing engine trouble. Punching the oil holes will eliminate all these types of problems. Other main advantages of the oil ring according to the invention are summarized as follows. 1. By using a thin web, the weight of the oil ring as a whole can be reduced. 2. The thin web improves the oil ring's ability to follow the cylinder wall. 3. The diameter of the coil expander can be increased by the two-point contact between the oil ring and the coil expander and by using a thin web. As the diameter of the coil expander increases, its spring constant decreases, and therefore the tension in the coil expander decreases less during use. 4. Increased resistance to deformation or strain of the oil ring when it is assembled into a piston and during use. This is because internal stress is reduced by forming the oil holes by punching instead of milling. 5 By punching the oil holes and using a thin web, it is possible to easily obtain the roundness of the oil ring and the flatness of the upper and lower surfaces of the upper and lower side rails, which were difficult to achieve with milling in cast iron oil rings. It will be done. This also reduces the overall amount of wear and improves the sealing performance of the upper and lower surfaces, leading to a reduction in oil consumption. 6. By manufacturing a steel oil ring by drawing or rolling, an oil ring with a precise contour can be easily obtained. 7. A predetermined surface pressure against the cylinder wall can be obtained by the small area of the side rail sliding surface. 8. Since the oil ring can be made smaller overall, the scope of application is expanded, and it can even be used for small pistons for two-wheeled vehicles such as motorcycles, which was impossible with conventional cast iron oil rings. 9 Since the oil ring has high rigidity, thinner rings can be manufactured, which reduces the wear resistance (friction loss) of the oil ring against the cylinder bore.
can be made smaller. 10 Since the overall oil ring can be made smaller, the piston group into which it is fitted can be made smaller, which in turn leads to smaller and lighter pistons. In the present invention, a so-called "equal pressure spring" such as a wave spring may be used instead of the coil expander. In that case, the portions of the oil ring that come into contact with the inclined flat surfaces 11A and 11B may be made flat surfaces. The table below shows three exemplary dimensions of piston ring parts in accordance with the present invention for use in gasoline, diesel, or other multi-purpose engines.

【table】
〓Unit: mm〓
The meanings of the letters and symbols in the table are as follows. D ₁ =...Outer diameter of the oil ring B...Width of the oil ring T...Radial thickness of the oil ring in cross section b...Width of the outermost bearing surface of the side rail t...Thickness of the web D ₁ =...Coil expander Outer diameter x...Length of the bottom of the trapezoid of the side rail y...Length of the bottom of the inclined flat surface Generally, the thickness of the web of a cast iron oil ring is
It was not possible to make it smaller than 0.8mm. According to the present invention, the thickness t of all webs is 0.8 mm or less, and therefore, as described above, the followability to the cylinder wall is improved. However, in view of strength, it is desirable that the lower limit of the web thickness t is 0.3 mm or more. That is, it has been experimentally confirmed that 0.3 mm≦t≦0.8 mm is desirable. Furthermore, the relationships between x and b and y and t are each 2.5≦
It has also been experimentally confirmed that the range of x/b≦8.0 and 2.0≦y/t≦5.5 is the most preferable for reducing the amount of wear on the side rail bearing surface and therefore reducing oil consumption. ing. Figures 6 and 7 show experimental results regarding the amount of wear on the outer periphery of the oil ring and the amount of oil consumed.
In FIG. 6, the prior art uses a cast iron oil ring having an arcuate circumferential groove in which the coil expander is in close contact. Further, the second example in the above table was used as the one of the present invention. As is clear from FIG. 6, the amount of wear is reduced in the present invention compared to the prior art. In the experiment shown in FIG. 7, a piston ring combination consisting of first and second compression rings and one oil ring was used in order to see the oil consumption of the piston ring as a whole. Naturally, the same first and second compression rings were used in both the present invention and the prior art. Regarding the oil ring, please refer to the 6th section.
The same experiment as in the figure was used. Note that the measured values in FIG. 7 are average values. The specifications of the engine used are as follows. 4-cycle diesel engine with a displacement of 2188 c.c. Cylinder bore...(90〓(mm)) x Stroke (86
mm) Horsepower...72PS As is clear from FIG. 7, the oil consumption in the present invention is smaller than that in the prior art. Figures 8A and 8B show the same experimental results as Figure 7 under different conditions. As shown in A and B. In FIGS. 8, 9, and 10, A indicates the prior art and B indicates the present invention, respectively. In the experiment, a 500-hour durability test was conducted after 2 hours of break-in operation.
95φmm×stroke 110mm・6 cylinder displacement
A 4700 c.c. diesel engine was used under identical operating conditions. The test condition is the 8th
As shown in the figure. As is clear from these experimental results, the steel oil ring according to the present invention consumes about one quarter of the amount of oil compared to the conventional cast iron oil ring.
Furthermore, it was confirmed that the amount of wear on the outer peripheral surface of the ring was 17.7μ, which was much smaller than that of the conventional cast iron oil ring, which was 24.9μ. Figure 11 shows surface pressure and oil consumption (L, O, C)
The specifications of the diesel engine used in this experiment are as follows. Diesel engine used: Diameter 119φmm x Stroke 135mm x V-type 8-cylinder engine Displacement: 12010c.c. 280ps/2400rpm Equipped with turbo charger Also, the experiment was (2400rpm x Fully open throttle x
12hr) and (1800rpm x full throttle x
Each test was repeated twice under the following conditions: 12 hours). As is clear from Fig. 11, the oil consumption varies slightly depending on changes in the surface pressure in each oil ring, but in any case, the oil consumption in the present invention is smaller than in the conventional one. ing.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of an oil ring with a coil expander according to the present invention placed between a piston and a cylinder wall, and FIG. 2 is a main part of an oil ring with a coil expander shown in FIG. Part perspective view,
3A is a perspective view showing only the oil ring shown in FIG. 1, FIG. 3B is an enlarged view of part A in FIG. 3A,
FIG. 4 is a cross-sectional view showing another embodiment of the oil ring, FIG. 5 is a view showing the dimensional relationship between each part of the coil expander and oil ring according to the present invention, and FIG.
The figure is a diagram showing the amount of wear of the oil ring with a coil expander according to the present invention in comparison with the prior art, and Figure 7 is a diagram showing the amount of oil consumption of the oil ring with a coil expander according to the present invention in comparison with the prior art. Figures 8A and 8B are diagrams of experimental results showing the difference in oil consumption between the conventional technology and the present invention, with A representing the prior art and B representing the present invention.
B and FIG. 10A and B show the ring specifications and cross-sectional shape of the oil scraping ring used in the experiment shown in FIGS. 8A and B, respectively, where A shows the conventional technology, B shows the present invention, and FIG. is a line showing the experimental results regarding the relationship between surface pressure and oil consumption. 1... Oil ring, 3A, 3B... Side rail, 5... Web, 19... Gap, 21... Oil hole, 40... Coil expander.

Claims (1)

[Claims] 1. Regarding the oil ring with a coil expander, the width of the outermost bearing surface of the side rail is b, the bottom length of the trapezoid of the side rail is x, the bottom length of the inclined flat surface of the side rail is y, and the length of the web is When the thickness is t, 2.5<x/b<8.0 and 2.0<y/t/
Steel with a roughly I-shaped cross section, consisting of upper and lower side rails that are rigid blocks that satisfy the relationship 5.5, and a thin web with a diameter of 0.3 mm or more and 0.8 mm or less, which is equipped with a large number of oil holes that connect these side rails. A circumferential groove is formed on the outer periphery of the oil scraping ring to receive the scraped oil, and a circumferential groove is formed on the inner periphery for accommodating the annular coil expander. The coil expander is in contact with the upper and lower side rails at only two points when viewed in cross section, and in areas other than these contact points, the coil expander is separated from the web and there is a small gap between the coil expander and the web. An oil ring with a coil expander that is characterized by a gap formed therein.