DE2336861A1 - CAM OF A CONTROL MECHANISM FOR COMBUSTION POWER MACHINES - Google Patents

Description

Automobilove zävody, närodni podnik 293 60 Mladä Boleslav (CSSR)

Cam of a control mechanism for internal combustion engines

The invention relates to the design of the cam of a control mechanism for internal combustion engines with continuous connection of the start-up, lift and stop acceleration curves.

With cams previously used to control internal combustion engines with a sudden change in acceleration at the end of the run-up and at the beginning of the The run-out leads to shocks, which are undesirable dynamic phenomena in the control environment which in turn lead to increased control noise, more frequent malfunctions and a shorter service life to lead.

-J3833) -SdIs

409886/0167

A method for solving this problem is already known, at the beginning and at the end of the cam lift the third derivative of the cam lift is zero. This cam section where the condition third Derivation = * 0 is supposed to be fulfilled, however, is so tiny that it is difficult to determine from a manufacturing point of view can.

The object of the invention is to eliminate these disadvantages of the prior art and to provide a cam to create, which causes a more uniform ram stroke or run-up and in which the mass production unavoidable manufacturing inaccuracies do not have a detrimental effect on the slide movement.

This object is achieved according to the invention in that the surface area of the cam stop part is formed _{by a puncture P n} = N ₁ ^{-X- 5} HN ₂ . Χ ^ + Ν, .Χ ⁵ + ^. Χ is formed, the acceleration curve F "in the area where the plunger touches the cam, falling between two points A and B and decreasing to negative values. The surface area of the cam lifting part is determined by a polynomial of the type P ₂ -K ₁ . X ^P + K ₂ .X ^q -f + K, .X ^r + K ^ .X ^s + K ₅ .X ^Z formed and the acceleration curves of the starting and lifting part of the cam follow one another at the points of the starting point of the stroke that they have a common tangent t _N , the rise tg ^ _{N of which} lies in the interval 0 <tg ^ _N <+ © O.

The area of the surface of the cam run-out part is formed by a puncture Py-V ₁ -X ⁵ + V ₂ -X * + V ^ .X ⁵ + V ^ .X ⁶ and the acceleration curves of the lift and run-out part of the cam close at the points

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of the end of the stroke and the start of the run-out so that they have a common tangent ty, the rise of which tg >> 6 _v lies in the interval 0 "^ C.

The cam start and the cam lift part are formed by the punctures P _n and F ", whose acceleration steepness at the end and start of the stroke is determined by the relationship F _n * '= 35F" _N + k, in which the constant k is between -10 and + 10. A similar relationship also applies to the cam run-out part:

-35F _V + ic

In the case of the cam design according to the invention, the acceleration curve mentioned is low Values of the touchdown speeds achieved at the start of the approach and the start of the run-out. As a result, no shocks occur in the control mechanism of internal combustion engines, thereby extending their life and reducing the noise of the mechanism.

In the drawing, the accelerations occurring with cams designed according to the invention are shown. E ₃ show:

1 shows the mutual dependence of the acceleration of a cam according to the invention and the cam rotation angle,

Fig. 2 shows the mutual dependence of the acceleration and the angle of rotation of the cam stop part for two different acceleration rates.

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The area of the surface of the cam stop part A control mechanism for internal combustion engines can generally be represented mathematically by a polynomial of the

_{σ MY} 3 _MY 4 ^ _MY i>, _ _{KT Y} 6, _n

Γ, _τ —Γ *, .Λ + JM ^ «Λ + JM - ^ · Λ + IM ι, · A ................ I l · I

N 1 2 3 ^

be expressed, where

X moves in the range from 0 to 1 and the constants N to N _{4 are determined} from four selected boundary conditions:

1) The stroke at the start-up is selected F "

2) The end-of-run speed is chosen Fj,

3) The acceleration at the end of the run-up is selected F "

4) The acceleration steepness at the end of the start-up

is elected FJI '

Substituting these conditions into equation (1) one obtains four equations with four unknowns, the solution of which gives _{the constants N 1 to N 4.} The constants N ₁ to N _{4 obtained} are reinserted into equation (1) and by multiplying the entire equation by the maximum stroke, the corresponding stroke sizes are obtained for the individual relative values X, which enable the cam surface shape to be designed.

The stroke function F can also be represented by a polynomial with -n terms of the type

ρ _ ν yP, v- _Y q, ν- _Y 5, v-5 _Y ^z

Δι ι. C- ι)

The values ρ to ζ are selectable constants ranging from 2 to 50. Four of the η necessary constants of the polynomial must

98 86/0 167

from the above-mentioned boundary conditions of the cam start-up and outlet can be calculated. Because of the For extensive calculations, it is recommended that you run the solution on a computer.

From Fig. 1 it can be seen that the acceleration curves of the cam start and the cam lift part _{connect to each other at a point T n} , in which they have a common tangent t ″, which form _{an angle N with the axis χ.} The increase “ _& · ^ lies in the interval

The acceleration curve is in the area where the lifter touches the cam, i.e. in the area between points A and B, a descending course that leads to negative acceleration values sinks. For the right choice of the acceleration gradient at the end of the approach and at the beginning of the stroke and their Greatness is the relationship

+ k where the constant k lies in the interval ^ C-IO, +10 / ".

The ratio of the maximum positive acceleration is also important for the design of an optimal cam at point A and the minimum negative acceleration at point B. The positive acceleration value in point A should be approx. 2 to 3 times greater than the negative acceleration value in point B. If it is fulfilled of these conditions is a minimum amplitude of the positive and negative acceleration wave and one

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minimum size of the negative acceleration value guaranteed. Examples of the course of two curves with different acceleration rates at the end of the cam approach are shown in FIG. The curve a corresponds to a smaller increase in acceleration at point T ^ des Starting curve and the dashed curve b of a greater acceleration gradient.

The same procedure can also be used when designing the area of the surface of the cam run-out part of a control mechanism of an internal combustion engine, formed by function

F _v = V ₁ -X ⁵ +

The cam run-out part can be identical to the cam run-up part or, in special cases given by specific requirements, sometimes also different. The acceleration curves at the end of the lifting part and at the beginning of the cam run-out part adjoin one another at point Ty, where they have a common tangent t "which includes an angle" with the axis χ. The increase tg * C lies in the interval 0 ^> tg * C y - the same relationship also applies to the acceleration gradient of the cam run-out part

where Fy. Acceleration value at the start of the run-out

Fit 'acceleration steepness at the start of the run-out

k lies in the interval <C -10; 10 / *

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The inventive design of the cam stop and outlet part is particularly suitable for the design of cams in control mechanisms of high-speed engines and internal combustion engines.

409886/0187

Claims (5)

_ ₈ _ 2336867 Claims Cam of a control mechanism for internal combustion engines with an area of the surface of the starting part formed by the function F _n = N ₁ -X- ⁵ + N ₂ -X ⁴ + Ν, .Χ ⁵ + N ₄ -X , .Χ + N ₄ characterized in that its acceleration curve (F ") in the area where the lifter touches the cam, between two points (A) and (B) is falling and goes down to negative values 2. Cam according to claim 1 with a region of the surface of the lifting part formed by a polynomial of the type characterized in that the acceleration curves of the cam start and lift part connect to each other at the points of the start end and the start of the stroke in such a way that they have a common tangent (t ") whose rise (tg-C) in the interval 0 <tgoC _N <+ Ό lies. 3- cam according to claim 1 and 2. with a region of the surface of the run-off part formed by the function F _v = V ₁ -X ³ + V ^ .X ⁴ + V - X ^ + V ₄ -X ⁶ characterized in that the acceleration curves of the Nockenhub- and -auslaufteils in the points of 409886/0167 of the end of the stroke and the start of the run-out are connected to one another in such a way that they have a common tangent (t _T. ), the increase of which (tg.C _u ) in the interval _v y 4. Cam according to claim 1 to ρ with areas of the surfaces of the starting and lifting part formed by functions P _n and F, characterized in that the acceleration rate at the starting end and at the Hubbe ^ inn is determined by the relationship + k where the constant (k) lies in the interval <^ -10, + 10 / ^. 5. cam according to claim 1 to 4 with areas of the Surface of the lifting and discharge part formed by functions F "and P", characterized in that the acceleration gradient at the end of the stroke and at the start of the run-out is determined by the relationship where the constant (k) is in the interval <C -10, +! 409886/0167