RU104636U1 - CYLINDER PISTON GROUP - Google Patents

Abstract

 A piston-piston group containing a piston with piston rings placed on it, in contact with the cylinder, having a microrelief on the working surface in the form of uniformly alternating fragments located along helical lines, each of which consists of a groove associated with a section parallel to the cylinder axis, characterized in that that the grooves are made with a depth equal to the radial clearance of the piston ring in the cylinder, the lengths of the microrelief sections with positive, zero and negative angles of attack make up one third microrelief step portion, and the step microrelief is commensurate with the axial height of the piston ring.

Description

The utility model relates to mechanical engineering and can be used in reciprocating machines, in particular internal combustion engines.

An analogue of the proposed utility model is a device [US Patent 2292662, F02F 1/20, publ. 1942], on the rubbing surface of the cylinder of which there are two counter-directed helical grooves filled with an alloy of non-ferrous metals.

The disadvantages of this device include the location of the grooves in the most heated zone of the cylinder (top dead center), which, due to a significantly different (almost twice) coefficient of linear expansion of the materials of the cylinder and alloy in the grooves, will lead to a violation of the adhesion of these materials, and In addition, it will cause an increase in oil consumption for waste.

The closest in technical essence to the claimed object can be recognized as a device [RF Patent 2186234, F02F 1/20, publ. 2002], which is a cylinder-piston group (CPG) containing a piston with rings in a cylinder having two counter-made helical grooves filled with non-ferrous metal on the working surface, and the angle of elevation (angle of attack) of the sides of the grooves ranges from 15 to 60 °, and the step size does not exceed the distance between the upper compression and lower oil scraper rings.

The specified device has several disadvantages:

1. Filling the grooves with a non-ferrous metal alloy leads to complete or partial (as the alloy is consumed) loss of the main hydrodynamic property of the groove, for the formation of which it is intended, namely: the creation of a reserve hydrodynamic bearing capacity (HPS) of the lubricant in the piston-cylinder interface ”And mainly“ piston ring-cylinder ”. In the case of internal combustion engines, the presence and wear (presence of wear particles) of non-ferrous metals in engine oil additionally increases the ash content of the latter.

2. The values of the angle of attack of the sides of the groove, even the minimum equal to 15 °, as shown by the study of the function of the hydrodynamic bearing capacity to a maximum, are very (two times) more than the optimal values (6 ... 8 °); the maximum angle value of 60 ° additionally leads to an unjustified increase in the depth of the groove, which provokes an increase in oil consumption for waste.

3. The microrelief step is unreasonably overestimated: the recommended upper limit of not more than the height of the annular zone of the piston does not take into account the number of rings on the piston, which, for example, for low-speed engines can reach 6. The estimates given below show that with an incomparably large relative to the axial height single ring pitch microrelief, the hydrodynamic bearing capacity of the latter drops sharply.

The technical task of the utility model is to increase the wear resistance of the piston ring-cylinder interface by increasing the hydrodynamic bearing capacity of the cylinder ..

The stated technical problem is achieved in that in a cylinder-piston group containing a piston with piston rings placed on it in contact with a cylinder having a microrelief on the working surface in the form of uniformly alternating fragments located along helical lines, each of which consists of a groove associated with flat, parallel to the cylinder axis, section, the depth of the groove is equal to the radial clearance of the piston ring in the cylinder, and the lengths of the sections of the microrelief with positive, zero and negative lnym attack angles constitute the third step portion of the microrelief, wherein step microrelief is commensurate with the axial height of the piston ring.

The originality of the utility model lies in the fact that, unlike the prototype, the microrelief grooves are not filled with non-ferrous metal alloy, but rather have clear geometric shapes, while the values of the step-height parameters of the microrelief are aligned with the dimensions of the piston ring in such a way that contribute to maximizing GNS.

The utility model is illustrated by drawings, in which Fig. 1 shows a contact scheme of a single piston ring (for example, a compression ring) with a microrelief fragment on the working surface of the cylinder.

The device (Fig. 1) consists of a cylinder l, on the working surface of which a microrelief of step L is made, consisting of alternating fragments in the form of a triangular groove 2 of depth ΔН, paired with a section 3 parallel to the cylinder axis and facing the axle height of the piston ring 4 S located in the piston groove 5. The piston ring-cylinder mating clearance is filled with a viscous incompressible lubricant (for example, engine oil) with a dynamic viscosity µ. The ring 4 together with the piston 5 moves reciprocatingly with a speed ν. A section of a groove of length l ₁ with a gap tapering in the direction of the velocity vector ν has a positive angle of attack γ and, according to the hydrodynamic theory of lubrication, creates a positive GNS, which increases due to the conjugated section of length l ₂ with a zero angle of attack γ (due to the parallelism of this section of the ring surface 4 ), a section of length l ₃ with a negative angle of attack creates a negative GNS. As can be seen from figure 2, which shows the calculated distribution of the hydrodynamic pressure p (x) along the mating gap “piston ring-microrelief”, the positive part of the plot prevails over the negative, which causes the emergence of GNS (geometrically interpreted as the area of the positive plot of the hydrodynamic pressure ), opposing the approach and contact (wear) of surfaces in operation.

When changing the direction of movement, the picture is repeated with the difference that the sections l ₃ and l ₂ become load-bearing _.

The proposed device operates as follows. It is well known that maximizing GNS allows you to reduce the intensity and contact time of the interface, which are the main causes of wear of surfaces in normal (non-abrasive) operation. To maximize GNS, the device implements optimization of step-height parameters of the microrelief based on the provisions of the hydrodynamic theory of lubrication. The essence of hydrodynamic analysis is described below.

Derived by solving the Reynolds equation, the GNS function for the gap form shown in Fig. 1 has the form:

Here g (δ, λ) is a dimensionless function that depends only on the step-height parameters of the microrelief:

Where - the relative length of the inclined section of the microrelief (step parameter);

- the relative height difference of the microrelief (altitude parameter).

Assuming that the geometric parameters included in expression (1) are unchanged, the solution to the problem is reduced to finding values (or relations) for the step-height parameters of the microrelief λ and δ that maximize the dimensionless function g (δ, λ) defined by expression (2).

Given the geometry of the microrelief fragment in figure 1, the region of existence of the values of the relative length of the inclined section λ: 0≤λ≤0.5. For the relative height difference of the microrelief based on the analysis of the topography parameters of the completed structures, the area of existence can be defined as 0≤δ≤5. The analytical method of finding the global maximum of the function of two variables g (δ, λ) is very laborious, therefore, a graphic technique was used (Fig. 3).

The resulting rational values of the parameters δ and λ, as well as the associated global maximum of the function g (δ, λ), were:

δ ₀ = 1.121; λ ₀ = 0.344; g (δ ₀ , λ ₀ ) = 0.011. (3)

From the definition of the relative height difference it follows that the depth of the groove is equal to the product of the relative height difference and the minimum clearance:

ΔH = δ · H ₁ .

Substituting in (4) the maximal GNS (rational) value of the relative height difference parameter, we obtained the rational value of the groove depth:

ΔH = δ ₀ · H ₁ = 1,121 · H ₁ .

From (5) it follows that, taking into account the smallness of the factor 1.121 compared to unity, the rational groove depth ΔН can be taken as a first approximation equal to the minimum clearance in the piston ring-cylinder mating H ₁ . Actually, the minimum clearance of the indicated interface is determined from the design of the CPG as the radial clearance of the piston ring within the range of the gap selection σ

H ₁ = σ / 2π≈σ / 6.28. (6)

The parameter H ₁ according to expression (6) is a hydrodynamically justified altitude parameter of the microrelief of the proposed device and is determined by the structurally set, known value, namely: the value of the gap in the lock of the piston ring σ.

Since for a symmetrical groove

L = 2l _1,3 + l ₂ , then, taking into account (3), the rational values of the step parameters (lengths of characteristic sections) of the microrelief at a given value of the microrelief step L will be:

l _1.3 = 0.344 L;

l ₂ = 0.312L

or, using the simplifying replacement of the factors 0.344 and 0.312 by a single factor 0.333,

l _1,2,3 = 0,3331 L.

From relation (7) we obtain that the rational values of the lengths of the sections of the microrelief fragment with positive, negative, and zero angles of attack should be one third of the microrelief step.

Obviously, with the axial height of the piston ring S, the following main options for choosing the microrelief pitch L are possible:

1. A commensurate step (L≈S);

2. The increased step (L> S);

3. Reduced pitch (L <S).

In the first embodiment, within the length of the piston ring is one fragment of the microrelief; in the second, a certain part of it; in the third, on the contrary, several fragments. In the prototype device, a variant of the increased microrelief pitch is applied with respect to a single piston ring.

In order to substantiate the choice of the microrelief step, GNS calculations were performed according to formula (1), the results of which are given in the table.

As follows from the table, the maximum GNS, ceteris paribus, provides a microrelief with a step commensurate with the given length of the piston ring. The decrease in GNS during the transition from a commensurate step to an increased one was 37%, to a reduced one - 58%.

Thus, in a first approximation, the rational value of the microrelief pitch L should be set based on the axial height of the piston ring S, which is a known structural parameter, while the rational value of L should be comparable (i.e. approximately equal) to S.

The technical and economic advantage of the claimed utility model is to increase the reliability and durability of reciprocating machines by reducing wear, friction and oil consumption for waste, as well as saving expensive non-ferrous metals, the introduction of which is not required in the groove or on the plane of the microrelief. The absence of wear products of non-ferrous metals in the lubricant will also reduce the ash content of the latter. The application of the recommended microrelief with rational step-altitude parameters does not entail any refinement of the existing technology, for example, roller rolling during surface plastic deformation. The binding of the choice of rational step-height parameters to the axial height of the piston ring is the most generalized and, therefore, applicable to the widest range of dimensions of piston machines.

Table GNS calculation results for microrelief fragments with various step options: 1 - commensurate; 2 - enlarged; 3 - reduced Option δ λ P, (× µν) N / m Absolute value Relative difference,% one 1,0 0.333 0.613 0 2 0.5 0.167 0.384 -37 3 0.5 0.333 0.258 -58

Claims (1)

A piston-piston group containing a piston with piston rings placed on it, in contact with the cylinder, having a microrelief on the working surface in the form of uniformly alternating fragments located along helical lines, each of which consists of a groove associated with a section parallel to the cylinder axis, characterized in that that the grooves are made with a depth equal to the radial clearance of the piston ring in the cylinder, the lengths of the microrelief sections with positive, zero and negative angles of attack are one third microrelief step portion, and the step microrelief is commensurate with the axial height of the piston ring.