RU2238445C1 - Crankshaft for internal combustion engine - Google Patents

Abstract

FIELD: mechanical engineering.

SUBSTANCE: crankshaft has crank pins 2, main journal 1 and webs 3 which go from crank pin to main journal and interconnect them. The spherical surface is conjugated with main journal 1 over the radius with two planes whose intersection is in the plane of the crankpin at axis 7 of the crank pin 2, and their angle of inclination is determined form the formula α=90^o-arctg(R_cr-R_cp)/(B/2), where R_cr is the radius of the crank of the crankshaft, R_cp is the radius of the crankpin, and B is the width of the web.

EFFECT: strengthened crankshaft.

2 cl, 1 tbl

Description

The invention relates to mechanical engineering and can be used in the production of crankshafts of internal combustion engines.

There is a known crankshaft containing connecting rod journals, root necks and cheeks, while the transition from the connecting rod neck to the root neck on the outside of the cheek is made in the form of a plane with an angle to the axis of the crankshaft of about 60 ° (see “KAMAZ 6x4 vehicles”, Manual manual 5320-3902004RE, M., Engineering, 1994, p. 40, Fig. 29).

The disadvantage of this crankshaft is the presence in the transition from the connecting rod neck to the root neck on the outside of the cheek material, which is practically not loaded. This leads to a heavier crankshaft, and, consequently, the entire engine, increased consumption of material and to a deterioration in the balance of the crankshaft.

The closest set of essential features to the claimed technical solution is a one-piece crankshaft for reciprocating engines, containing a connecting rod and root neck connected by mutual overlap with the cheek, which thickens on the outside in the direction from the connecting rod neck to the root to a maximum thickness of “a” in the overlap zone, while the degree of overlap is determined by the size “b”. The transition along the outer side of the cheek from the connecting rod to the main neck is made along the sphere and is determined by the curve y = (x / 2) ⁿ and the exponent n = loga / 2b. The starting point of the curve “y” from the side of the connecting rod neck is the thickness of the cheek x = 2 (0.2r) ^{l / n} , where r is the radius of the connecting rod neck (see application DE No. 3614722 Al, F 16 C 3/06, publ. 11/05/87).

A disadvantage of the known crankshaft is its weakening in the most loaded section, passing through the centers of the fillets of the connecting rod and root neck perpendicular to the plane of the crank.

The task was to increase the strength of the crankshaft, while ensuring a decrease in its mass and improved balancing.

The problem is solved due to the fact that in the crankshaft of an internal combustion engine containing connecting rod journals, root necks and connecting their cheeks with the transition from the connecting rod to the root neck along the outer side of the cheek, made on a sphere, in the middle part the spherical transition surface is conjugated to the side of the radical neck along the radius with two planes, the intersection of which is in the plane of the crank on the axis of the connecting rod neck, and their angle of inclination α in the plane perpendicular to the plane of the crank is determined by the formula

α ° = 90 ° -arctg (R _cr -R _c.sh ) / (B / 2),

where R _cr - the radius of the crankshaft;

R _K.Sh - radius of the radical neck;

B is the width of the cheek.

Analysis of known technical solutions for scientific, technical and patent documentation showed that the set of essential features of the proposed solution were not previously known, therefore, it meets the patentability condition of “novelty”.

The claimed technical solution is not obvious to qualified specialists in this field, since it resolved a seemingly insoluble contradiction, namely

- on the one hand, to reduce the mass and improve the balance of the crankshaft, it is necessary to remove material at the transition from the connecting rod neck to the root neck on the outside of the cheek, on the other hand, material removal can lead to a decrease in the strength and rigidity of the crankshaft, which is unacceptable. The transition from the connecting rod neck to the root neck along the sphere is followed by its conjugation towards the root neck along the radius with two planes, the intersection of which is in the plane of the crank on the axis of the connecting rod neck, and their angle of inclination α in the plane perpendicular to the plane of the crank is determined by the formula

α ° = 90 ° -arctg (R _cr -R _c.sh ) / (B / 2),

where R _cr - the radius of the crankshaft;

R _K.Sh - radius of the radical neck;

B is the width of the cheek.

allowed to increase the strength of the crankshaft with a simultaneous decrease in its mass and improved balance, and thus resolved the above contradiction, which is evidence of the conformity of the claimed solution to the criterion of "inventive step". The claimed technical solution is illustrated by drawings, where figure 1 shows a fragment of the crank of the crankshaft of the internal combustion engine; figure 2 is a section aa in figure 1.

The crankshaft crank contains a root neck 1, a connecting rod neck 2, a cheek 3, a fillet 4 on a root neck and a fillet 5 on a crank neck. The transition of the cheek 3 from the connecting rod neck 2 to the main neck 1 on the outside in the middle part is made in the form of a sphere 6, radius R _cf. , which is mated with a radius r with two planes Ф-Ф and NN, the intersection line of which is on the axis 7 of the connecting rod journal 2. The plane П-П determines the dangerous section of the crankshaft passing through the line К-К, drawn through the middle of the fillets 4 and 5, perpendicular to the plane of the crank. The geometric characteristics of this section (area, torsion and bending moment) during optimization of the crank cheeks must remain unchanged, otherwise the voltage in the crankshaft elements increases sharply, which is unacceptable. The introduction of two planes with the intersection line on the axis 7 and the angle of inclination α to the crank plane into the composition of the structure of the cheek 3 3 solves this problem. In this case, the angle is considered optimal at which the points T1 and T2 of the intersection of the П-П plane with the Ф-Ф and NN planes are located on the edge of the cheek 3 along the end 8 facing the root neck 1 and determined by the maximum size B along the width of the cheek 3. Based on of this, the optimal angle is determined by the formula

α ° = 90 ° -arctg (R _cr - _Rc.sh ) / (B / 2),

where R _cr - the radius of the crankshaft;

R _K.Sh - radius of the radical neck;

B is the width of the cheek.

The design of the inventive crankshaft was tested on the example of the crankshaft of the engine of a KAMAZ automobile having the following parameters

R _cr = 60 mm - radius of the crank of the crankshaft;

R _K.sh = 47.5 mm - radius of the radical neck;

B = 130 is the width of the cheek.

The angle α determined by the formula

α ° = 90 ° -arctg (R _cr -R _c.sh ) / (B / 2),

with these parameters it is equal to 79 °.

The studies were carried out using the finite element method with the refinement of the result when conducting fatigue-free engine tests of natural crankshafts. The initial stage of this work was the development of an electronic model of the crankshaft using the CADDS-5 volumetric parametric modeling package. Next, the model was calculated, and in order to accelerate the results, a split circuit was used - an electronic model of an individual knee. The calculation was carried out in the ANSYS, v.5.4 environment using the finite element method. As the main loading of the knee was taken joint load - bending with torsion.

The calculation results are summarized in the table in which

1. - a crank with relief on the cheeks made on a spherical surface and the absence of additional elements in the form of planes from the side of the root neck (α ° = 0);

2. - a crank made in accordance with the claimed technical solution (α ° = 79 °);

3. - a crank, made with relief on the cheeks with a spherical surface and the presence of additional elements in the form of planes from the side of the main neck with their angle of inclination α ° equal to 90 °.

4. - the crank of the serial crankshaft, in which the transition from the connecting rod to the main shaft on the outside of the cheek is made in the form of a plane with an angle of inclination to the axis of the crankshaft of about 60 °.

The analysis shows that the maximum stresses occur in the regions of the fillet of the connecting rod and root neck in the P-P plane and their values are different for different design of the connecting rod journal cheeks.

The most loaded crank according to claim 1 (α = 0 °). Cranks according to claim 2 (α = 79 °), claim 3 (α = 90 °) and claim 4 (serial crankshaft) in terms of maximum stresses, geometric characteristics of the dangerous section in the PP plane are almost identical, but at the same time crank mass reduced by 12.8% and 10.1%. Thus, the design with α = 79 ° is optimal, where the voltage in the hazardous section is almost the same as the serial design, but there is a weight reduction of 12.8%. This result was confirmed by fatigue tests, which showed the same values of safety margin for both a serial crankshaft and a crankshaft made in accordance with the claimed technical solution.

Using the inventive design of the crankshaft at KamAZ will reduce the weight of the finished part by 2 kg, while maintaining the strength of the crankshaft and virtually eliminate manual labor during the operation of balancing the crankshaft in an automatic line.

The claimed technical solution meets the requirement of industrial applicability and is possible for implementation on standard technological equipment using modern technologies.

Claims (1)

The crankshaft of an internal combustion engine containing connecting rod necks, root necks and connecting cheeks with a transition from the connecting rod to the root neck along the outer side of the cheek, made in a sphere, characterized in that in the middle part the spherical transition surface is conjugated to the side of the radical neck in radius c two planes, the intersection of which is in the plane of the crank on the axis of the crank pin, and the angle of inclination α in the plane perpendicular to the plane of the crank is determined by the formula:

where R _cr - the radius of the crankshaft; R _K.Sh - radius of the radical neck; B is the width of the cheek.

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