CN104376166A - Method for analyzing engine valve impact force peak value - Google Patents

Abstract

The invention discloses a method for analyzing an engine valve impact force peak value. According to the method, in the collision process of a valve and a valve seat ring, through collision analysis of the engine valve and the valve seat ring, on the basis of energy conservation, the contact force expression is combined, and a force index n is determined; finally an analysis calculation method of the valve impact force peak valve is provided. The calculation process becomes simple and feasible. The method can be applied to analysis of valve impact force peak value calculation in the field of engines.

Description

A kind of engine valve is taken a seat the analytic method of power peak value

Technical field

The present invention relates to engine design field, be specifically related to a kind of engine valve and take a seat the analytic method of power peak value.

Background technology

The reliability of quality to complete machine of engine valve actuating mechanism dynamic property has a significant impact, and wherein the working condition of valve is the final performance reflecting whole valve actuating mechanism quality.The design of valve actuating mechanism is except will meeting engine breathing process entails, and this has enough serviceable life to friction pair also to need to ensure valve and valve retainer.And power of the taking a seat size affected when this is exactly air valve drop to a key factor in friction pair serviceable life between valve and valve retainer suffered by surface in contact, and valve exit flow field simultaneously or the important driving source of engine structure vibration and noise.Power of taking a seat suffered between valve and valve retainer is less, and the Valve-valve seat circle life-span is longer, and engine structure vibration and noise is less.

At present, valve exit flow field numerical value can be calculated by large-scale numerical simulation software (as ABAQUES software), but this type of software price is expensive, and carries out the emulation of nonlinear collision process and need specialty analysis personnel to operate, be unfavorable for the use of project planner.At present, those skilled in the art also not yet propose the analytic expression of valve exit flow field peak value.

The research of a large amount of contact-impact models shows, in nonlinear relationship between contact force and deformation, consider Damping work, contact force F expression formula is such as formula shown in (1):

$F=K{\mathrm{\δ}}^n[1+\frac{3(1-e^2)}{4}\frac{\stackrel{\·}{\mathrm{\δ}}}{{\stackrel{\·}{\mathrm{\δ}}}^{-}}]---\left(1\right)$

Wherein, K is contact stiffness between collision object, and δ is the deformation in contact process, and n is the power index distributing relevant with contact geometry and contact force F, and its size is in contact with it geometric analysis by material therefor and draws, e is the recovery factor, for speed of deformation, for contacting the relative velocity of initial time.

But the parameters such as the contact stiffness K in contact force F expression formula (1) and power index n only have clear and definite calculating formula or numerical value for the collision of the simple geometry body such as spherical, can't be directly used in the crash analysis of engine valve and valve retainer.

Contact force F in the contact force F expression formula (1) mentioned in background technology be consider impact contact force and distortion between nonlinear relationship and Damping work draw, contact force F can be considered as two parts form, a part is size is K δ ⁿelastic contact force, to be size be another part damping force.

And in the present invention, because the collision time between valve and valve retainer is short, the Damping work energy that its damping force produces is very little relative to the total kinetic energy of collision, therefore ignore.Therefore contact force F expression formula is reduced to F _m=K δ _m ⁿ.

Because Damping work energy is very little, the total kinetic energy therefore during air valve drop just can think that all conversion is in order to deformation energy, namely

${\∫}_0^{{\mathrm{\δ}}_m}{\mathrm{K\δ}}^n\mathrm{d\δ}=\frac{1}{2}m{\left({\stackrel{\·}{\mathrm{\δ}}}^{-}\right)}^2---\left(\text{2}\right)$

Wherein, K is the contact stiffness between valve and valve retainer, δ _mfor the Maximum Contact deformation in valve and valve retainer contact process, for the relative velocity of valve and valve retainer initial time in contact process, m is valve quality.

Maximum Contact distortion δ can be drawn thus _mfor:

${\mathrm{\δ}}_m={\left(\frac{n+1}{2K}m{\left({\stackrel{\·}{\mathrm{\δ}}}^{-}\right)}^2\right)}^{1/n+1}---\left(3\right)$

In the Maximum Contact distortion moment, juxtaposition metamorphose speed so known by expression formula (1), now produced damping force is 0, and then can by valve exit flow field peak F _mcomputing formula be reduced to:

$F_m={{\mathrm{K\δ}}_m}^n=K^{\frac{1}{n+1}}{\left(\frac{n+1}{2}m{\left({\stackrel{\·}{\mathrm{\δ}}}^{-}\right)}^2\right)}^{\frac{n}{n+1}}---\left(4\right)$

For this contact-impact process of air valve drop, known valve crash speed V, as shown in Figure 1, considers the angle theta between the Valve-valve seat circle contact conical surface and valve end face, the normal direction relative velocity of contact initial time valve and valve retainer surface of contact

${\stackrel{\·}{\mathrm{\δ}}}^{-}=V\cos \mathrm{\θ}---\left(5\right)$

Then formula (5) is substituted in formula (4), obtains:

$F_m=K^{\frac{1}{n+1}}{\left(\frac{n+1}{2}m{\left(V\cos \mathrm{\θ}\right)}^2\right)}^{\frac{n}{n+1}}---\left(6\right)$

In this formula, the value of n is unknown, for the problems of value of power index n in formula, the present invention adopts finite element method, modeling is carried out to the material of conventional valve and valve retainer and contact geometry, adopts the contact stiffness K that the analysis of static(al) contact FEA obtains between corresponding valve and valve retainer; And then adopt display dynamic analysis method, when not considering damping, with different this process of seating velocity collision seat ring, dynamic analysis is carried out to valve, draw corresponding Maximum Contact force value, under the condition that contact stiffness K is known, formula (6) is adopted to carry out matching, the value of index of must exerting oneself.

In the present embodiment, determine that the detailed process of contact stiffness K is:

1. the material of conventional valve and valve retainer and contact geometry thereof is adopted to set up the contact FEA grid model of valve and valve retainer, definition size of mesh opening, general, fine and closely woven in the surface of contact grid place size of valve and valve retainer, to ensure precision.

2. fixed constraint is applied at valve retainer outside surface.For plane-plane contact retrains between setting valve and valve retainer.

3. multiple distributed load F perpendicular to valve is applied at valve end face _n, its size is determined according to the material of valve and valve retainer and size, valve and valve retainer size larger, then applied distributed load F _nlarger; Preferably, distributed load F _nsize is 1000N ~ 5000N, in case the contact deformation between air-stop gate and valve retainer is excessive thus cause distortion.

4. the emulation of static(al) contact FEA grid model is adopted to obtain the corresponding contact deformation δ of each distributed load _n, calculate contact stiffness K between valve and valve retainer according to formula (7) and average and finally obtain contact stiffness K between valve and valve retainer.

K＝F _Ncosθ/δ _N(7)

Wherein, θ is angle between the Valve-valve seat circle contact conical surface and surface level.

In the present embodiment, based on determined contact stiffness K, the detailed process of deterministic force index n is:

1. owing to being out of shape the moment at Maximum Contact, juxtaposition metamorphose speed so known by expression formula (1), now produced damping force is 0, and by this moment Maximum Contact distortion δ _mnamely formula (3) substitutes into, then:

2. owing to being out of shape the moment at Maximum Contact, juxtaposition metamorphose speed namely, when ignoring damping force, with this process of different seating velocities collision seat ring, display dynamic analysis being adopted to valve, is drawn the valve exit flow field peak F under friction speed by simulation software _m, contact stiffness K between the valve calculated in conjunction with formula (7) and valve retainer, matching draws the power index n of formula (6).

Through above-mentioned fit procedure, power index is got 1.1 proper.

Consider and act on laterostigmatal valve spring pretightning force F all the time ₀, just can show that the computing formula of maximum unilateral force and valve exit flow field peak value is by formula (6):

$F_m={{{\mathrm{K\δ}}_m}^n=K}^{\frac{1}{n+1}}{\left(\frac{n+1}{2}m{\left(V\cos \mathrm{\θ}\right)}^2\right)}^{\frac{n}{n+1}}+F_0---\left(8\right)$

N=1.1 is adopted to substitute into above formula (8) and arrange, just can obtain a kind of preferred valve exit flow field peak value expression formula, this valve exit flow field peak value is Valve-valve seat circle contact stiffness K, valve quality m, valve crash speed V, angle theta and valve spring pretightning force F between the Valve-valve seat circle contact conical surface and valve end face ₀function, shown in (9):

F _m＝1.03K ^0.476m ^0.524(Vcosθ) ^1.05+F ₀(9)

The present invention proposes the analytic method of valve exit flow field peak value on the basis of this formula (9), and first the method should determine m, θ, K, F ₀and V, then substitute into formula (9) and just can resolve and obtain valve exit flow field peak F _m.

In formula (9), the determination mode of each parameter is as follows:

(1) m is determined: weigh the valve quality m for calculating this valve exit flow field peak value.

(2) θ is determined: determine angle theta between the Valve-valve seat circle contact conical surface and surface level according to the design of Valve-valve seat circle

(3) K is determined: the valve used according to reality and the material of valve retainer, by applying direction perpendicular to valve end face to valve end face, the distributed load F varied in size _n, and calculate contact stiffness K between valve and valve retainer by formula (7) after adopting static(al) contact FEA grid model to emulate the contact deformation δ obtained; And the contact stiffness calculating under the different loads obtained is averaged.

(4) F is determined ₀: measure valve spring pretightning force F ₀.

(5) determine V: as shown in Figure 2, valve crash speed V is obtained by valve lift curve and corresponding cam rotating speed analysis, and its size equals the product of valve lift curve at the slope of taking a seat a little and geometry speed and cam rotating speed, namely

V＝V _αω (8)

Wherein V _αbe valve in geometry speed a little of taking a seat, ω is cam rotating speed.The valve lift curve that general design provides describes with the valve stroke table that different cam angle degree discrete point is corresponding, and therefore valve lift curve can be taken a seat a little and before taking a seat, the simple difference method of the data application in 1 to 2 moment calculates according to corresponding in valve stroke table in the slope of taking a seat a little and geometry speed.

Summary of the invention

In view of this, the invention provides a kind of engine valve to take a seat the analytic method of power peak value, compared with obtaining the mode of valve exit flow field peak value with the large-scale numerical simulation software emulation of employing, can by the mode of analytical Calculation, obtain engine valve more easily to take a seat power peak value, and the valve exit flow field peak value obtained is comparatively accurate, the limitation avoided needing specialty analysis personnel to carry out Operations Analyst and bring, the Dynamic Property Design improving valve actuating mechanism for reducing valve exit flow field provides foundation.

Engine valve is taken a seat the analytic method of power peak value, and concrete steps are as follows:

Step one, by analyzing the collision characteristic of valve and valve retainer, the damping force in the contact force expression formula of routine being ignored and be 0 in Maximum Contact deformation moment juxtaposition metamorphose speed, the normal direction relative velocity of foundation valve and valve retainer surface of contact and the relation V between valve crash speed, derives valve exit flow field peak F during Maximum Contact deformation _mexpression formula:

$F_m={{\mathrm{K\δ}}_m}^n=K^{\frac{1}{n+1}}{\left(\frac{n+1}{2}m{\left(V\cos \mathrm{\θ}\right)}^2\right)}^{\frac{n}{n+1}}---(1-1)$

Wherein, m is valve quality, and K is valve and valve retainer Contact rigidity, and n is power index, δ _mfor the Maximum Contact deformation of valve and valve retainer;

Step 2, method by matching, determine power index n unknown in formula (1-1);

Step 3, the numerical value of power index n step 2 determined substitute into formula (1-1), and consider to act on laterostigmatal valve spring pretightning force F all the time ₀, obtain valve exit flow field peak F _mangle theta and valve spring pretightning force F between the conical surface and valve end face is contacted with valve retainer Contact stiffness K, valve quality m, valve crash speed V, Valve-valve seat circle about valve ₀analytical relation (1-2):

$F_m=K^{\frac{1}{n+1}}{\left(\frac{n+1}{2}m{\left(V\cos \mathrm{\θ}\right)}^2\right)}^{\frac{n}{n+1}}+F_0---(1-2)$

Step 4, resolve valve exit flow field peak value time, obtain K, m, V, θ and F ₀, substitute into above formula (1-2) and obtain valve exit flow field peak value.

Especially, described step 2 is specially:

Material and the contact geometry thereof of step 21, the conventional valve of employing and valve retainer carry out modeling, and the analysis of employing static(al) contact FEA obtains the contact stiffness K between corresponding valve and valve retainer;

Step 22, employing display dynamic analysis method, when ignoring damping force, carrying out dynamic analysis to valve with this process of different seating velocities collision seat ring, drawing the valve exit flow field peak F under different seating velocity V _m;

Step 23, when contact stiffness K is certain, by step 22 adopt different seating velocity V and a series of Fs corresponding with it _m, adopt formula (1-3) to carry out matching, obtain power index n;

$F_m=K^{\frac{1}{n+1}}{\left(\frac{n+1}{2}m{\left(V\cos \mathrm{\θ}\right)}^2\right)}^{\frac{n}{n+1}}---(1-3).$

Especially, described step 21 specifically comprises:

Adopt the material of conventional valve and valve retainer and contact geometry thereof to set up the contact FEA grid model of valve and valve retainer, apply fixed constraint at valve retainer outside surface, for plane-plane contact retrains between setting valve and valve retainer;

The distributed load F perpendicular to valve is applied at valve end face _n, calculate the contact deformation δ of corresponding valve and valve retainer _n, (1-4) calculates contact stiffness K according to the following formula:

K＝F _Ncosθ/δ _N(1-4)。

Especially, described contact stiffness K, according to its corresponding valve and valve retainer, adopts the analysis of static(al) contact FEA to obtain; The valve of different materials, size and valve retainer, contact stiffness K is different.

Especially, different distributed load F is applied at valve end face _n, the contact stiffness calculated value obtained under different loads is averaged the contact stiffness K be between described valve and valve retainer.

Preferably, described distributed load F _nspan be 1000N ~ 5000N.

Especially, the valve crash speed V in described step 4 is obtained by valve lift curve and corresponding cam rotating speed analysis, and its size equals valve lift curve at the slope of taking a seat a little and valve at the geometry speed V a little that takes a seat _αwith the product of cam rotational speed omega, namely

V＝V _αω (1-5)。

Preferably, described power index n=1.1.

Beneficial effect:

1, in the collision process of valve and valve retainer, because collision time is shorter, therefore its Damping work energy is less relative to the total kinetic energy of collision, can ignore at this.So, total kinetic energy during air valve drop will be considered as the deformation energy being all converted into valve and valve retainer, show that Maximum Contact is out of shape thus, and finally obtains the analytic expression of valve exit flow field peak value.

The present invention adopts the peak value expression formula of contact force F and carries out matching by the peak value of contact forces that large artificial software obtains and obtains power index n, then peak value expression formula power index n being substituted into contact force F just finally obtains the analytical formula of valve exit flow field peak value.Adopt the analytical formula of this valve exit flow field peak value to significantly reduce to assess the cost, just can calculate valve exit flow field peak value according to underlying parameter, the Dynamic Property Design simultaneously also improving valve actuating mechanism further for reducing valve exit flow field provides foundation.

For during by the crash analysis of expression formula (1) for engine valve and valve retainer, power index n this how value does not have people to propose solution.

2, the present invention take energy conservation as foundation, and in conjunction with contact force F expression formula (1), the final analytical formula proposing valve exit flow field peak value, makes computation process become simple, feasible.

Accompanying drawing explanation

Fig. 1 is the schematic diagram of valve crash speed and contact load component.

Fig. 2 is valve lift diagram.

The geometric model of Fig. 3 Valve Gear of Diesel valve and valve retainer.

Fig. 4 is the finite element grid model of certain Valve Gear of Diesel valve and valve retainer contact analysis.

The Finite element analysis results of valve and valve retainer juxtaposition metamorphose when Fig. 5 is imposed load 2000N on valve.

Fig. 6 is the finite element Explicit Dynamics result of calculation of certain Valve Gear of Diesel valve impulsive force.

Embodiment

To develop simultaneously embodiment below in conjunction with accompanying drawing, describe the present invention.

Embodiment:

As shown in Figure 3, angle theta=30 ° between the Valve-valve seat circle contact conical surface and valve end face, density of material is 7800kg/m to the geometric model of certain Valve Gear of Diesel valve and valve retainer ³, elastic modulus is 210GPa, and Poisson ratio is 0.3, can calculate valve quality m=0.128kg by geometric model, known valve spring pretightning force F ₀=200N.

In ABAQUES software, adopt hexahedral element to carry out stress and strain model to valve and valve retainer assembly geometric model, size of mesh opening is defined as: contact area is about 0.3mm, be about 1mm near contact area, the valve stem away from contact area is 5mm, and the grid model obtained as shown in Figure 4.Apply fixed constraint at valve retainer outside surface, define plane-plane contact constraint between valve and seat ring, applying direction perpendicular to valve end face, size at valve end face is F _nthe distributed load of=2000N, obtains the distortion distribution of assembly as shown in Figure 5 by analysis.Load F _nwhen being taken as 1000N, 1500N, 2000N, 2500N respectively, the contact total deformation of the valve obtained and seat ring is δ _nas shown in table 1:

Table 1 valve and raceway contacts are out of shape result of calculation:

Contact stiffness is calculated according to formula (7):

K＝F _Ncosθ/δ _N(7)

Be averaged by contact stiffness calculated value under the different loads obtained and be valve and raceway contacts rigidity, its value is K=3.4 × 10 ⁹n/m.

There are K, m, θ and F ₀occurrence, according to the seating velocity V of valve under different cam rotating speed, using formula (10) can calculate the valve exit flow field peak value under different seating velocity.Fig. 6 adopts ABAQUES/Explicit to carry out the impulsive force time history along valve motion direction when valve crash speed that finite element explicit dynamical Epidemiological Analysis obtains is respectively 0.05m/s, 0.06m/s, 0.07m/s, 0.08m/s, 0.09m/s and 0.1m/s to this diesel engine spiracle process of taking a seat, and table 2 is valve exit flow field peak values of using Analytic Calculation Method of the present invention to obtain along the contrast of valve motion durection component and finite element explicit dynamical Epidemiological Analysis acquired results:

Table 2 take a seat power peak value contrast

In sum, these are only preferred embodiment of the present invention, be not intended to limit protection scope of the present invention.Within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (8)

1. engine valve is taken a seat an analytic method for power peak value, and it is characterized in that, concrete steps are as follows:

Step one, by analyzing the collision characteristic of valve and valve retainer, the damping force in the contact force expression formula of routine being ignored and be 0 in Maximum Contact deformation moment juxtaposition metamorphose speed, the normal direction relative velocity of foundation valve and valve retainer surface of contact and the relation V between valve crash speed, derives valve exit flow field peak F during Maximum Contact deformation _mexpression formula:

$F_m={{\mathrm{K\δ}}_m}^n=K^{\frac{1}{n+1}}{\left(\frac{n+1}{2}m{\left(V\cos \mathrm{\θ}\right)}^2\right)}^{\frac{n}{n+1}}---(1-1)$

Wherein, m is valve quality, and K is valve and valve retainer Contact rigidity, and n is power index, δ _mfor the Maximum Contact deformation of valve and valve retainer;

Step 2, method by matching, determine power index n unknown in formula (1-1);

Step 3, the numerical value of power index n step 2 determined substitute into formula (1-1), and consider to act on laterostigmatal valve spring pretightning force F all the time ₀, obtain valve exit flow field peak F _mangle theta and valve spring pretightning force F between the conical surface and valve end face is contacted with valve retainer Contact stiffness K, valve quality m, valve crash speed V, Valve-valve seat circle about valve ₀analytical relation (1-2):

$F_m=K^{\frac{1}{n+1}}{\left(\frac{n+1}{2}m{\left(V\cos \mathrm{\θ}\right)}^2\right)}^{\frac{n}{n+1}}+F_0---(1-2)$

Step 4, resolve valve exit flow field peak value time, obtain K, m, V, θ and F ₀, substitute into above formula (1-2) and obtain valve exit flow field peak value.

2. the method for claim 1, is characterized in that, described step 2 is specially:

Material and the contact geometry thereof of step 21, the conventional valve of employing and valve retainer carry out modeling, and the analysis of employing static(al) contact FEA obtains the contact stiffness K between corresponding valve and valve retainer;

Step 22, employing display dynamic analysis method, when ignoring damping force, carrying out dynamic analysis to valve with this process of different seating velocities collision seat ring, drawing the valve exit flow field peak F under different seating velocity V _m;

Step 23, when contact stiffness K is certain, by step 22 adopt different seating velocity V and a series of Fs corresponding with it _m, adopt formula (1-3) to carry out matching, obtain power index n;

$F_m=K^{\frac{1}{n+1}}{\left(\frac{n+1}{2}m{\left(V\cos \mathrm{\θ}\right)}^2\right)}^{\frac{n}{n+1}}---(1-3).$

3. method as claimed in claim 2, it is characterized in that, described step 21 specifically comprises:

Adopt the material of conventional valve and valve retainer and contact geometry thereof to set up the contact FEA grid model of valve and valve retainer, apply fixed constraint at valve retainer outside surface, for plane-plane contact retrains between setting valve and valve retainer;

The distributed load F perpendicular to valve is applied at valve end face _n, calculate the contact deformation δ of corresponding valve and valve retainer _n, (1-4) calculates contact stiffness K according to the following formula:

K＝F _Ncosθ/δ _N(1-4)。

4. method as claimed in claim 3, is characterized in that, described contact stiffness K, according to its corresponding valve and valve retainer, adopts the analysis of static(al) contact FEA to obtain; The valve of different materials, size and valve retainer, contact stiffness K is different.

5. method as claimed in claim 3, is characterized in that, apply different distributed load F at valve end face _n, the contact stiffness calculated value obtained under different loads is averaged the contact stiffness K be between described valve and valve retainer.

6. the method as described in claim 3 or 4, is characterized in that, described distributed load F _nspan be 1000N ~ 5000N.

7. the method for claim 1, is characterized in that, the valve crash speed V in step 4 is obtained by valve lift curve and corresponding cam rotating speed analysis, and its size equals valve lift curve at the slope of taking a seat a little and valve at the geometry speed V a little that takes a seat _αwith the product of cam rotational speed omega, namely

V＝V _αω (1-5)。

8. method as claimed in claim 2, is characterized in that, described power index n=1.1.