SU957773A3 - Distribution cam for internal combustion engine - Google Patents

Abstract

Known cams for controlling the valves of a piston engine, by means of which the valve is opened by way of a sliding tappet (2) with plane base (3), exhibit high wear. In order to achieve optimum lubricating conditions in the area of the cam tip, the area of critical lubricating film formation, the cam (1) is formed so that the quotient <IMAGE> has either the value 0.15 </= gamma </= 0.25 or the value gamma >/= 0.6, where rN is the cam radius of curvature, rG is the base-circle radius of the cam and z is the cam lift. <IMAGE>

Description

0.) 957773

Union of Soviet Socialist Republics

DESCRIPTION OF THE INVENTION

TO THE PATENT (61) Additional to the patent _

State Committee

USSR for inventions and discoveries (22) Declared 09.06.78 (23) Priority - (31) p 2726073.7 (21) 2629398 / 25-06 (32) 10.06.77 (33) frg

Published about 7.09.82. Bulletin No. 33 (51) M. Cl ^E

F 01 L 1/08 (53) UDC621.43-231.2 (088.8)

Date of publication of the description 07.09.82 (72) Authors of the invention (71) Applicant

Foreigners

Gerhard Deschler, Hans Gebhardt and DietDrey? Ttman_ .. '(Germany) |

Foreign company = ‘

Machinenfabrik Augsburg-Nuremberg AG; -j (Germany)) (54) DISTRIBUTION FIST OF THE INTERNAL COMBUSTION ENGINE

The invention relates to mechanical engineering and can be used, for example, in gas distribution mechanisms of an internal combustion engine.

Known distribution cams of an internal combustion engine, coupled with a sliding pusher having a flat bottom, [Containing a curved protrusion and a cylindrical occipital part £ 1}.

However, in gas distribution mechanisms with such cams, the contacting valve and pusher are poorly lubricated, which leads to rapid wear of the cams and pushers.

The purpose of the invention is to improve the lubrication of the contacting surfaces of the valve and pusher.

To achieve the goal, the radius of curvature of the protrusion and the radius of curvature of the cylindrical occipital part are related by the relation _{ ^ .. _{r =} o, ₁₅ °, 25 where rz is the radius of curvature of the protrusion;

G. - radius of curvature of the cylindrical occipital, part;

Z is the amount of cam lift.

ts

Figure 1 shows the contact circuit of the cam and the pusher; figure 2 is a graph of the relative thickness of the oil film from the hydrodynamic coefficient of assessment J.

The distribution cam 1 ^{T is} in contact with the plunger 2 with a flat bottom 3. The distance of the center 4 of the radius of curvature g * from the center 5 of the radius of curvature of the cylindrical occipital part is equal to a, and this is the distance measured in the direction of movement of the plunger 2 depending on the position of the cam 1. The cam lift Ζ represents the distance from the radius of the main circle r _e to. bottom 3. Cam 1 rotates with an angular speed w in the direction of the arrow 6. Sliding speed on the cam 1 U _H »r'W. Sliding speed along the pusher (in the center of the pusher), 0; ”- a ka.

Sliding speed between cam and pusher U = (l / 2)> (U ^ Ui) »(1/2)» (r _N · ω-a-οϋ) = (1/2) · (r _N -a) w.

Since the distance a = r _N - (r "♦ Z), then" * (1/2). "B> £ 2r4, - (r _a + Z)]

Using the Dawson and Higkinson formula to calculate the minimum thickness h _m ^ _{n of a} lubricating film ^: = 5 _? go * ChmG7, ....., where H is the viscosity;

U is the sliding velocity; 5 ψ is the theoretical contact radius, and replacing the theoretical contact radius by the radius of curvature of the cam '/ μ. we obtain for a minimum thickness of 10 lubricating film _g -------- st—.

where cons t “5/10 ^ -1 - ^ - ^ - '

fifteen

The solution to this equation has'

Howl (limit Г), since in this case, the resulting wear and tear, followed by a shift in the hydrodynamic coefficient of estimation $ towards 0.5, initially improves and, after exceeding the maximum, worsens the formation of an oil film that can withstand the load. Within $> 0.5 (limit AND), wear, on the contrary, is an advantage for the formation of an oil film.

I It was established that this limit is reached very rarely, for example, in round cams.

The solid curve 7 was obtained using the simplified formula of Dawson and Higginson, and the dashed curve 8 was obtained using the full form’le.

two roots ¹ __Е1_ = о j and _ between which the maximum value of the function is located

If the dimensionless geometric quantity r ^ + 2, by means of which the profile is calculated by the angle of rotation of the cam rot, is designated as the hydrodynamic coefficient of estimation y and the minimum film thickness bm _< ' _n be attributed to the optimal value h _oft , which lies in the range 0 χ 4- 0.5, then we obtain the relative thickness of the lubricating film ΐ _hnvn · [2 ft ΐ- 'θ'' ^_ h ~~ _t Ί 0? 125' ^C Thus, the relative thickness of the oil film depends on cooT-j35 wearing sizes r _N ! (r _Q + Z)., and its on ·; · \ is the maximum; its value is established experimentally and lies within

---- * = = 0.15 - 0.25 Γς * Z

In Fig.2, the relative thickness of the oil film is presented depending on the hydrodynamic coefficient of evaluation $.

Due to the fact that the hydrodynamic estimation coefficient consists of the geometrical values of cam 1, of which the cam lift Ζ and the radius of curvature of the occipital part g # change due to wear, the optimal performance of the cam profile within the wear 0 X 0..5 can only be achieved if the case when $ is located.

During the rotation of the cam shaft, it slides along the flat bottom of the pusher, due to viscosity, the oil is drawn into the gap between the pusher and the cam, providing liquid lubrication with a certain thickness of the oil film.

The proposed device provides the most favorable size of the oil film between the contacting surfaces of the pusher and the cam.

Claims (1)

Using the formula of Dawson and Hiaginson to calculate the minimum thickness of the lubricant tn 5a &amp; -lPyG7, where H - viscosity; U - slip speed | heed p is the theoretical radius of the contact, and the replacement is the theoretical contact radius of the cam curvature radius. for the minimum thickness of the lubricating film, we obtain: tg-g- ((where cons t "5 x10- | - | -., The solution of this equation has. two roots; between which there is -MaKCimene function If the dimensionless geometric value (.- f2, by means of which the profile is calculated by cam rotation, designate the hydrodynamic coefficient coefficient jf as the hydrodynamic coefficient and refer the minimum film thickness H (; to the optimal hgpt value which lies within O 4 0.5, then the resulting film thickness hm .nf: -h - t 1 | 07125- Thus, from The relative thickness of the oil film depends on the COOT of the wearing of the dimensions r, / (r i-Z), and its optimum value has been experimentally determined and lies within the limits of G 0 - O 25. In Fig. 2, the relative thickness of the oil film is shown depending on the hydrodynamic estimation coefficient jf. For the reason that the hydrodynamic estimation coefficient consists of the geometrical values of cam 1 of which cam rise Z and radius of curvature of the occipital part D vary due to wear, the cam profile is optimally within wear range O , 5 could be achieved only in the case when Jj is located on the left .. maximum of the CRE 9OI (limit D),, since in this case the resulting wear with subsequent displacement of the hydrodynamic coefficient of estimation towards 0.5 first improves, and after exceeding the maximum affects the formation of an oil film capable of withstanding the load. Within 0.5 (P limit), wear, on the contrary, is advantageous for the formation of an oil film. It has been established that this limit is reached very rarely, for example, round cams. The solid curve 7 was obtained using the simplified Dawson and Higinson formula, and the dashed lines 8 - using the full formula. As the shaft rotates, the cam slides along the flat bottom of the pusher, as a result of viscosity, the oil is drawn into the gap between the pusher and the cam, providing a liquid lubricant with a certain thickness of oil film. The proposed device provides the most favorable amount of oil film between the contacting surfaces of the pusher and the cam. Claims of an Inner-Combustion Engine Cam, mated to a sliding pusher having a flat bottom, containing a curved protrusion and a cylindrical occipital portion, characterized in that, in order to improve lubrication, the radius of curvature of the protrusion and the radius of curvature of the cylindrical occipital portion are related by a ratio of "(G (., - n2) 0.15-0.25, where Hz is the radius of curvature of the protrusion; g is the radius of curvature of the cylindrical occipital part; Z is the amount of cam lift. Sources of information taken into account in the examination see 1. Automobile and tractor engines (theories, power systems, designs and calculation). Edited by Professor I.M. Lenin. M., 1969, School 1969, p.586, Fig.416.